US5764363A — Apparatus for observing a surface using polarized…

Claim 1

Independent Claim 170 words

An observation apparatus comprising: a light source for generating light; a separating optical system which splits the light emitted from said light source into two different polarized light beams; a condenser optical system which converges the two polarized light beams emitted from said separating optical system so as to respectively form light spots on two different positions on a sample object; a polarization selecting means, which has a predetermined analyzer angles, for selecting a specific polarized light component from composite light made of the two polarized light beams reflected by or transmitted through said sample object; light detecting means for detecting the polarized light component selected by said polarization selecting means; and phase difference adjustment means for adjusting a phase difference between the two polarized light beams reflected by or transmitted through said sample object to provide a circularly polarized light by composing the two polarized light beams to said polarization selecting means, when said sample object does not modulate both the phase and amplitude of the light incident thereon.

Claim 2

Dependent Claim 170 words

An observation apparatus comprising: a light source for generating light; a separating optical system which splits the light emitted from said light source into two different polarized light beams; a condenser optical system which converges the two polarized light beams emitted from said separating optical system so as to respectively form light spots on two different positions on a sample object; a polarization selecting means, which has a predetermined analyzer angles, for selecting a specific polarized light component from composite light made of the two polarized light beams reflected by or transmitted through said sample object; light detecting means for detecting the polarized light component selected by said polarization selecting means; and phase difference adjustment means for adjusting a phase difference between the two polarized light beams reflected by or transmitted through said sample object to provide a circularly polarized light by composing the two polarized light beams to said polarization selecting means, when said sample object does not modulate both the phase and amplitude of the light incident thereon.

Claim 3

Dependent Claim 49 words

An observation apparatus according to claim 1, further comprising a scanning device for scanning said sample object with the two light spots thereon which are split by said separating optical system, wherein said light source generates spatially coherent light and guides thus generated light to said separating optical system.

Claim 4

Dependent Claim 110 words

An observation apparatus according to claim 2, wherein said light source generates linearly polarized light having a predetermined direction of polarization; wherein, when said sample object is a light reflecting member having a mirror surface, said phase difference adjustment means imparts a phase difference of π multiplied by an integer to the two polarized light beams split by said separating optical system and then reflected by said sample object, as said two polarized light beams travel through said separating optical system to-and-fro, and wherein said phase difference adjustment means includes a 1/4-wavelength plate which converts the linearly polarized light emitted from said separating optical system into the circularly polarized light.

Claim 5

Dependent Claim 84 words

An observation apparatus according to claim 2, wherein said light source generates linearly polarized light having a predetermined direction of polarization; and wherein, when said sample object is a light reflecting member having a mirror surface, said phase difference adjustment means imparts a phase difference of π/2 multiplied by an odd number to the two polarized light beams split by said separating optical system and then reflected by said sample object, as said two polarized light beams travel through said separating optical system to-and-fro.

Claim 6

Dependent Claim 119 words

An observation apparatus according to claim 2, further comprising a synthesizing optical system which combines the two polarized light beams transmitted through said sample object and guides the composite light to said polarization selecting means, wherein said light source generates linearly polarized light having a predetermined direction of polarization; wherein, when said sample object is optically flat, said phase difference adjustment means imparts a phase difference of π multiplied by an integer to the two polarized light beams split by said separating optical system and then transmitted through said sample object, and wherein said phase difference adjustment means includes a 1/4-wavelength plate which converts the linearly polarized light emitted from said synthesizing optical system into the circularly polarized light.

Claim 7

Dependent Claim 93 words

An observation apparatus according to claim 2, further comprising a synthesizing optical system which combines the two polarized light beams transmitted through said sample object and guides the composite light to said polarization selecting means, wherein said light source generates linearly polarized light having a predetermined direction of polarization; and wherein, when said sample object is optically flat, said phase difference adjustment means imparts a phase difference of π/2 multiplied by an odd number to the two polarized light beams split by said separating optical system and then transmitted through said sample object.

Claim 8

Dependent Claim 72 words

An observation apparatus according to claim 1, further comprising an illumination optical system which is disposed between said light source and said separating optical system and illuminates said sample object with the light thereon emitted from said light source by way of said separating optical system, wherein said light detecting means is constituted by a two-dimensional image sensor disposed on at least one of respective focal planes of said condenser optical system.

Claim 9

Dependent Claim 31 words

An observation apparatus according to claim 7, wherein said illumination optical system includes a wavelength selecting means for selecting a specific wavelength component from the light emitted from said light source.

Claim 10

Dependent Claim 34 words

An observation apparatus according to claim 7, wherein said illumination optical system includes a polarized light selecting means for selecting a specific linear polarized light component from the light emitted from said light source.

Claim 11

Dependent Claim 96 words

An observation apparatus according to claim 9, wherein, when said sample object is a light reflecting member having a mirror surface, said phase difference adjustment means imparts a phase difference of π multiplied by an integer to the two polarized light beams split by said separating optical system and then reflected by said sample object, as said two polarized light beams travel through said separating optical system to-and-fro, and wherein said phase difference adjustment means includes a 1/4-wavelength plate which converts the linearly polarized light emitted from said separating optical system into the circularly polarized light.

Claim 12

Dependent Claim 69 words

An observation apparatus according to claim 9, wherein, when said sample object is a light reflecting member having a mirror surface, said phase difference adjustment means imparts a phase difference of π/2 multiplied by an odd number to the two polarized light beams split by said separating optical system and then reflected by said sample object, as said two polarized light beams travel through said separating optical system to-and-fro.

Claim 13

Dependent Claim 104 words

An observation apparatus according to claim 9, further comprising a synthesizing optical system which combines the two polarized light beams transmitted through said sample object and guides the composite light to said polarization selecting means, wherein, when said sample object is optically flat, said phase difference adjustment means imparts a phase difference of π multiplied by an integer to the two polarized light beams split by said separating optical system and then transmitted through said sample object, and wherein said polarization selecting means includes a 1/4-wavelength plate which converts the linearly polarized light emitted from said synthesizing optical system into the circularly polarized light.

Claim 14

Dependent Claim 78 words

An observation apparatus according to claim 9, further comprising a synthesizing optical system which combines the two polarized light beams transmitted through said sample object and guides the composite light to said polarization selecting means, wherein, when said sample object is optically flat, said phase difference adjustment means imparts a phase difference of π/2 multiplied by an odd number to the two polarized light beams split by said separating optical system and then transmitted through said sample object.

Claim 15

Dependent Claim 75 words

An observation apparatus according to claim 1, wherein said condenser optical system is arranged so as to serve as an objective optical system which collects the two polarized light beams reflected by said sample object, and said separating optical system is arranged so as to serve as a synthesizing optical system which combines the two polarized light beams again exited from said condenser optical system and guides the composite light to said polarization selecting means.

Claim 16

Dependent Claim 16 words

An observation apparatus according to claim 14, wherein said separating optical system includes a birefringence prism.

Claim 17

Dependent Claim 44 words

An observation apparatus according to claim 14, wherein said separating optical system includes a prism having two reflecting surfaces non-parallel to each other, and a polarizing beam splitter surface disposed between said two reflecting surfaces and parallel to either of said two reflecting surfaces.

Claim 18

Dependent Claim 49 words

An observation apparatus according to claim 14, wherein said separating optical system includes two mirrors having respective reflecting surfaces non-parallel to each other, and two prisms disposed between said two mirrors and having respective polarizing beam splitter surfaces parallel to either of said reflecting surfaces of two reflecting mirrors.

Claim 19

Dependent Claim 24 words

An observation apparatus according to claim 14, wherein said phase difference adjustment means comprises a driving member capable of moving said separating optical system.

Claim 20

Dependent Claim 53 words

An observation apparatus according to claim 1, further comprising an objective optical system which collects the two polarized light beams transmitted through said sample object, and a synthesizing optical system which combines the two polarized light beams exited from said objective optical system and guides the composite light to said polarization selecting means.

Claim 21

Dependent Claim 25 words

An observation apparatus according to claim 19, wherein at least one of said separating optical system and said synthesizing optical system includes a birefringence prism.

Claim 22

Dependent Claim 53 words

An observation apparatus according to claim 19, wherein at least one of said separating optical system and said synthesizing optical system includes a prism having two reflecting surfaces non-parallel to each other, and a polarizing beam splitter surface disposed between said two reflecting surfaces and parallel to either of said two reflecting surfaces.

Claim 23

Dependent Claim 58 words

An observation apparatus according to claim 19, wherein at least one of said separating optical system and said synthesizing optical system includes two mirrors having respective reflecting surfaces non-parallel to each other, and two prisms disposed between said two mirrors and having respective polarizing beam splitter surfaces parallel to either of said reflecting surfaces of two reflecting mirrors.

Claim 24

Dependent Claim 33 words

An observation apparatus according to claim 19, wherein said phase difference adjustment means comprises a driving member capable of moving at least one of said separating optical system and said synthesizing optical system.

Claim 25

Dependent Claim 173 words

An observation apparatus according to claim 1, further comprising a measuring means for quantitatively measuring, based on an output of said light detecting means, a level difference on said sample object; wherein said polarization selecting means includes a polarizing beam splitter which splits the composite light composed of the two polarized light beams emitted from said sample object into two different directions; wherein said light detecting means includes a first photodetector for detecting the polarized light transmitted through said polarizing beam splitter and a second photodetector for detecting the polarized light reflected by said polarizing beam splitter; wherein said measuring means measures the level difference of said sample object based on a relationship which is established between an output difference in said first and second photodetectors for the level difference of said sample object and a phase difference in the two polarized light beams caused by the level difference of said sample object, while depending on change in an amplitude reflectance between two regions holding the level difference of said sample object therebetween.

Claim 26

Dependent Claim 35 words

An observation apparatus according to claim 24, wherein the analyzer angle of said polarization selecting means is set to nπ/4 as the analyzer angle of said polarizing beam splitter wherein n is an odd number.

Claim 27

Dependent Claim 150 words

An observation apparatus according to claim 24, wherein said measuring means measures the level difference of said object sample based on a phase difference Ψ between the two polarized light beams calculated by the following relationship: sin Ψ=D·S/(W.sub.a.sup.1/2 ·W.sub.b.sup.1/2) wherein Ψ is the phase difference between the two polarized light beams caused by the level difference of said sample object, S is an output difference between said first and second photodetectors, W a is an output sum of said first and second photodetectors for one of two regions holding the level difference of said sample object therebetween reflecting amplitude reflectance of said region, W b is an output sum of said first and second photodetectors for the other of the two regions holding the level difference of said sample object therebetween reflecting amplitude reflectance of said other region, and D is a constant depending on said apparatus as a whole.

Claim 28

Dependent Claim 149 words

An observation apparatus according to claim 1, further comprising a measuring means for quantitatively measuring, based on an output of said light detecting means, a level difference on said sample object; wherein said polarization selecting means variably sets the analyzer angle with respect to the composite light composed of the two polarized light beams reflected by or transmitted through said sample object; wherein said measuring means measures the level difference of the sample object based on a relationship which is established between an output difference in said light detecting means for the level difference of said sample object when two different analyzer angles for said polarization selecting means are respectively set and a phase difference in the two polarized light beams caused by the level difference of said sample object, while depending on change in amplitude reflectance between two regions holding the level difference of said sample object therebetween.

Claim 29

Dependent Claim 32 words

An observation apparatus according to claim 27, said polarization selecting means includes a polarizing plate which is disposed so as to be rotatable around an optical axis of said condenser optical system.

Claim 30

Dependent Claim 32 words

An observation apparatus according to claim 27, wherein said polarization selecting means includes a liquid crystal polarizer which changes a refractive index distribution thereof based on a voltage signal externally applied thereto.

Claim 31

Dependent Claim 30 words

An observation apparatus according to claim 27, wherein the analyzer angles of said polarization selecting means are set to nπ/4 and (n/4+m/2)π, respectively, wherein n and m are odd numbers.

Claim 32

Dependent Claim 158 words

An observation apparatus according to claim 27, wherein said measuring means measures a level difference of the object surface based on a phase difference Ψ between the two polarized light beams calculated by the following relationship: sin Ψ=D·S/(W.sub.a.sup.1/2 ·W.sub.b.sup.1/2) wherein Ψ is the phase difference between the two polarized light beams caused by the level difference of said sample object, S is an output difference in said light detecting means when two analyzer angles for said polarization selecting means are set, W a is an output sum of said light detecting means for one of two regions holding the level difference of said sample object therebetween reflecting amplitude reflectance of this region, W b is an output sum of said light detecting means for the other of the two regions holding the level difference of said sample object therebetween reflecting amplitude reflectance of said other region, and D is a constant depending on said apparatus as a whole.

Claim 33

Dependent Claim 152 words

An observation apparatus according to claim 1, further comprising a measuring means for quantitatively measuring, based on an output of said light detecting means, a level difference on said sample object; wherein said polarization selecting means variably sets the analyzer angle with respect to the composite light composed of the two polarized light beams reflected by or transmitted through said sample object and includes a polarizing beam splitter which splits said composite light into two different directions; wherein said light detecting means includes a first photodetector for detecting light transmitted through said polarizing beam splitter and a second photodetector for detecting light reflected by said polarizing beam splitter; and wherein said measuring means measures the level difference of said sample object based on the analyzer angle which is set so as to maximize or minimize the output difference between said first and second photodetectors for the level difference of said sample object.

Claim 34

Dependent Claim 52 words

An observation apparatus according to claim 32, wherein said polarizing beam splitter is fixed around an optical axis of said condenser optical system and wherein said polarization selecting means includes an azimuth rotator disposed on an inlet side of said polarizing beam splitter, said azimuth rotator having a variable polarization rotational angle.

Claim 35

Dependent Claim 32 words

An observation apparatus according to claim 33, wherein said azimuth rotator is constituted by a 1/2-wavelength plate disposed so as to be rotatable around the optical axis of said condenser optical system.

Claim 36

Dependent Claim 35 words

An observation apparatus according to claim 32, wherein each of said polarizing beam splitter and said first and second photodetectors is disposed so as to be rotatable around the optical axis of said condenser lens.

Claim 37

Dependent Claim 81 words

An observation apparatus according to claim 32, wherein an analyzer angle φ min of said polarization selecting means when the output difference between said first and second photodetectors for the level difference of said sample object is minimum, coincides with φ max +nπ/4, wherein φ max is an analyzer angle of said polarization selecting means when the output difference between said first and second photodetectors for the level difference of said sample object is maximum, and n is an odd number.

Claim 38

Dependent Claim 158 words

An observation apparatus according to claim 32, wherein said measuring means measures a level difference of said object sample based on a phase difference Ψ between the two polarized light beams calculated by the following relationship: tan 2φ=-2a·b·sin Ψ/(a.sup.2 -b.sup.2) wherein φ is the analyzer angle of said polarization selecting means when the output difference between said first and second photodetectors for the level difference of said sample object is maximum, Ψ is the phase difference between the two polarized light beams caused by the level difference of said sample object, a is an amplitude reflectance of one of two regions holding the level difference of said sample object therebetween incorporated in an output sum of said light detecting means for said region, and b is an amplitude reflectance of the other of two regions holding the level difference of said sample object therebetween incorporated in an output sum of said light detecting means for said other region.

Claim 39

Dependent Claim 106 words

An observation apparatus according to claim 1, further comprising a measuring means for quantitatively measuring, based on an output of said light detecting means, a level difference on said sample object; wherein said polarization selecting means variably sets the analyzer angle with respect to the composite light composed of the two polarized light beams reflected by or transmitted through said sample object and wherein said measuring means measures the level difference of said sample object based on two different analyzer angles which are set so as to maximize or minimize the output difference between said light detecting means for the level difference of said sample object.

Claim 40

Dependent Claim 33 words

An observation apparatus according to claim 38, wherein said polarization selecting means includes a polarizing plate which is disposed so as to be rotatable around the optical axis of said condenser optical system.

Claim 41

Dependent Claim 32 words

An observation apparatus according to claim 38, wherein said polarization selecting means includes a liquid crystal polarizer which changes a refractive index distribution thereof based on a voltage signal externally applied thereto.

Claim 42

Dependent Claim 30 words

An observation apparatus according to claim 38, wherein a difference in the two analyzer angles of said polarization selecting means is set to nπ/4, wherein n is an odd number.

Claim 43

Dependent Claim 215 words

An observation apparatus according to claim 38, wherein said measuring means measures a level difference of said object sample based on a phase difference Ψ between the two polarized light beams calculated by the following relationship: tan 2φ=-2a·b·sin Ψ/(a.sup.2 -b.sup.2) wherein φ is the analyzer angle of said polarization selecting means when Ψ is the phase difference between the two polarized light beams caused by the level difference of said sample object, a is an amplitude reflectance of one of two regions holding the level difference of said sample object therebetween incorporated in an output sum of said light detecting means for said region and b is an amplitude reflectance of the other of the two regions holding the level difference of said sample object therebetween incorporated in an output sum of said light detecting means for said other region when the two analyzer angles for said polarization selecting means are respectively set to φ and φ+π/2 so that the output difference between said light detecting means for the level difference of said sample object is maximum, or when the two analyzer angles for said polarization selecting means are respectively set to φ+π/4 and φ+3π/4 so that the output difference between said light detecting means for the level difference of said sample object is minimum.

Claim 44

Dependent Claim 156 words

An observation apparatus according to claim 1, further comprising an image forming means which forms a differential interference image of said sample object based on an output of said light detecting means; wherein said polarization selecting means variably sets the analyzer angle with respect to the composite light composed of the two polarized light beams reflected by or transmitted through said sample object and includes a polarizing beam splitter which splits said composite light into two different directions; wherein said light detecting means includes a first photodetector for detecting light transmitted through said polarizing beam splitter and a second photodetector for detecting light reflected by said polarizing beam splitter; and wherein said image forming means generates, based on an output difference between said first and second photodetectors for the level difference of said sample object, a contrast corresponding to the analyzer angle of said polarization selecting means for the differential interference image of said sample object.

Claim 45

Dependent Claim 54 words

An observation apparatus according to claim 43, wherein said polarizing beam splitter is fixed around an optical axis of said condenser optical system and wherein said polarization selecting means includes an azimuth rotator which is disposed on an inlet side of said polarizing beam splitter, said azimuth rotator having a variable polarization rotational angle.

Claim 46

Dependent Claim 32 words

An observation apparatus according to claim 44, wherein said azimuth rotator is constituted by a 1/2-wavelength plate disposed so as to be rotatable around the optical axis of said condenser optical system.

Claim 47

Dependent Claim 36 words

An observation apparatus according to claim 43, wherein each of said polarizing beam splitter and said first and second photodetectors is disposed so as to be rotatable around the optical axis of said condenser optical system.

Claim 48

Dependent Claim 26 words

An observation apparatus according to claim 43, wherein the analyzer angle of said polarization selecting means is set to nπ/4 wherein n is an odd number.

Claim 49

Dependent Claim 121 words

An observation apparatus according to claim 1, further comprising an image forming means which forms a differential interference image of said sample object based on an output of said light detecting means; wherein said polarization selecting means variably sets the analyzer angle with respect to the composite light composed of the two polarized light beams reflected by or transmitted through said sample object; wherein said image forming means generates, based on an output difference in said light detecting means for the level difference of said sample object when two different analyzer angles for said polarization selecting means are respectively set, a contrast corresponding to the analyzer angle of said polarization selecting means for the differential interference image of said sample object.

Claim 50

Dependent Claim 33 words

An observation apparatus according to claim 48, wherein said polarization selecting means includes a polarizing plate which is disposed so as to be rotatable around the optical axis of said condenser optical system.

Claim 51

Dependent Claim 32 words

An observation apparatus according to claim 48, wherein said polarization selecting means includes a liquid crystal polarizer which changes a refractive index distribution thereof based on a voltage signal externally applied thereto.

Claim 52

Dependent Claim 30 words

An observation apparatus according to claim 48, wherein a difference in the two analyzer angles of said polarization selecting means is set to nπ/4, wherein n is an odd number.

Claim 53

Dependent Claim 153 words

An observation apparatus according to claim 1, further comprising a defect detection system which detects the defect formed on a substrate being said sample object on the basis of an output from said light detecting means, wherein said polarization selecting means variably sets the analyzer angle with respect to the composite light composed of the two polarized light beams emitted from said sample object and includes a polarizing beam splitter which splits said composite light into two different directions; wherein said light detecting means includes a first photodetector for detecting light transmitted through said polarizing beam splitter and a second photodetector for detecting light reflected by said polarizing beam splitter, and wherein said defect detecting means shows the defects as the differential interference image of said sample object generated with a contrast corresponding to the analyzer angle of said polarization selecting means, based on an output difference between said first and second photodetectors.

Claim 54

Dependent Claim 62 words

An observation apparatus according to claim 52, wherein said light source emits a linearly polarized light beam having a wavelength of light for which a phase shift of π multiplied by an integer is caused by a transparent substance constituting a predetermined pattern on said substrate or a wavelength substantially equal to a wavelength of light used to expose said predetermined pattern.

Claim 55

Dependent Claim 94 words

An observation apparatus according to claim 52, wherein said defect detection system comprises a differential circuit which generates a difference signal as the difference of two output signals respectively input from said first and second photodetectors, corresponding the two different polarized light beams selected by said polarization selecting means, a binaring circuit which compares the difference signal from said differential circuit with a predetermined threshold value thereby generating a binary signal, and a judging circuit which detects the defects formed on the substrate on the basis of the binary signal from said binaring circuit.

Claim 56

Dependent Claim 54 words

An observation apparatus according to claim 52, wherein said polarizing beam splitter is fixed around an optical axis of said condenser optical system and wherein said polarization selecting means includes an azimuth rotator which is disposed on an inlet side of said polarizing beam splitter, said azimuth rotator having a variable polarization rotational angle.

Claim 57

Dependent Claim 32 words

An observation apparatus according to claim 55, wherein said azimuth rotator is constituted by a 1/2-wavelength plate disposed so as to be rotatable around the optical axis of said condenser optical system.

Claim 58

Dependent Claim 36 words

An observation apparatus according to claim 52, wherein each of said polarizing beam splitter and said first and second photodetectors is disposed so as to be rotatable around the optical axis of said condenser optical system.

Claim 59

Dependent Claim 26 words

An observation apparatus according to claim 52, wherein the analyzer angle of said polarization selecting means is set to nπ/4 wherein n is an odd number.

Claim 60

Dependent Claim 119 words

An observation apparatus according to claim 1, further comprising a defect detection system which detects the defect formed on a substrate being said sample object on the basis of an output from said light detecting means, wherein said polarization selecting means variably sets the analyzer angle with respect to the composite light composed of the two polarized light beams emitted from said sample object, and wherein said defect detecting means shows the defects as the differential interference image of said sample object generated with a contrast corresponding to the analyzer angle of said polarization selecting means, based on an output difference in said light detecting means when two different analyzer angles for said polarization selecting means are respectively set.

Claim 61

Dependent Claim 62 words

An observation apparatus according to claim 59, wherein said light source emits a linearly polarized light beam having a wavelength of light for which a phase shift of π multiplied by an integer is caused by a transparent substance constituting a predetermined pattern on said substrate or a wavelength substantially equal to a wavelength of light used to expose said predetermined pattern.

Claim 62

Dependent Claim 106 words

An observation apparatus according to claim 59, wherein said defect detection system comprises a differential circuit which generates a difference signal as the difference of two output signals sequentially input from said light detecting means, corresponding the two different polarized light beams selected by said polarization selecting means when two different analyzer angles for said polarization selecting means are respectively set, a binaring circuit which compares the difference signal from said differential circuit with a predetermined threshold value thereby generating a binary signal, and a judging circuit which detects the defects formed on the substrate on the basis of the binary signal from said binaring circuit.

Claim 63

Dependent Claim 25 words

An observation apparatus according to claim 59, wherein said polarization selecting means comprises an analyzer rotatable about an optical axis of said condenser optical system.

Claim 64

Dependent Claim 29 words

An observation apparatus according to claim 62, further comprising an azimuth rotator which is disposed between said light source and said substrate, and having a variable polarization rotational angle.

Claim 65

Dependent Claim 32 words

An observation apparatus according to claim 63, wherein said azimuth rotator is constituted by a 1/2-wavelength plate disposed so as to be rotatable around the optical axis of said condenser optical system.

Claim 66

Dependent Claim 52 words

An observation apparatus according to claim 66, further comprising an actuator which rotates said azimuth rotator around the optical axis of said condenser optical system, wherein said actuator changes an azimuth of said azimuth rotator by 45° when said polarization selecting means changes selecting either of the two different polarized light components.

Claim 67

Dependent Claim 30 words

An observation apparatus according to claim 62, further comprising a polarizer which is disposed between said light source and is rotatable about the optical axis of said condenser optical system.

Claim 68

Dependent Claim 50 words

An observation apparatus according to claim 63, further comprising an actuator which rotates said polarizer around the optical axis of said condenser optical system, wherein said actuator changes an azimuth of said polarizer by 90° when said polarization selecting means changes selecting either of the two different polarized light components.

Claim 69

Dependent Claim 31 words

An observation apparatus according to claim 61, wherein the two analyzer angles of said polarization selecting means are set to nπ/4 and (n/4+m/2)π, respectively, wherein n and m are odd numbers.

Claim 70

Dependent Claim 184 words

An observation apparatus comprising: a light source for generating light; a separating optical system which splits the light emitted from said light source into two different polarized light beams; a condenser optical system which converges the two polarized light beams emitted from said separating optical system so as to respectively form light spots on two different positions on a sample object; a polarization selecting means, which includes an azimuth rotator having a variable polarization rotational angle, for variably setting an analyzer angle by said azimuth rotator and selecting a specific polarized light component from composite light made of the two polarized light beams reflected by or transmitted through said sample object; light detecting means for detecting the polarized light component selected by said polarization selecting means; and phase difference adjustment means for adjusting a phase difference between the two polarized light beams reflected by or transmitted through said sample object to provide a circularly polarized light by composing the two polarized light beams to said polarization selecting means, when said sample object does not modulate both phase and amplitude of the light incident thereon.

Claim 71

Dependent Claim 184 words

An observation apparatus comprising: a light source for generating light; a separating optical system which splits the light emitted from said light source into two different polarized light beams; a condenser optical system which converges the two polarized light beams emitted from said separating optical system so as to respectively form light spots on two different positions on a sample object; a polarization selecting means, which includes an azimuth rotator having a variable polarization rotational angle, for variably setting an analyzer angle by said azimuth rotator and selecting a specific polarized light component from composite light made of the two polarized light beams reflected by or transmitted through said sample object; light detecting means for detecting the polarized light component selected by said polarization selecting means; and phase difference adjustment means for adjusting a phase difference between the two polarized light beams reflected by or transmitted through said sample object to provide a circularly polarized light by composing the two polarized light beams to said polarization selecting means, when said sample object does not modulate both phase and amplitude of the light incident thereon.

Claim 72

Dependent Claim 49 words

An observation apparatus according to claim 69, further comprising a scanning device for scanning said sample object with the two light spots thereon which are split by said separating optical system, wherein said light source generates spatially coherent light and guides thus generated light to said separating optical system.

Claim 73

Dependent Claim 110 words

An observation apparatus according to claim 70, wherein said light source generates linearly polarized light having a predetermined direction of polarization; wherein, when said sample object is a light reflecting member having a mirror surface, said phase difference adjustment means imparts a phase difference of π multiplied by an integer to the two polarized light beams split by said separating optical system and then reflected by said sample object, as said two polarized light beams travel through said separating optical system to-and-fro, and wherein said phase difference adjustment means includes a 1/4-wavelength plate which converts the linearly polarized light emitted from said separating optical system into the circularly polarized light.

Claim 74

Dependent Claim 84 words

An observation apparatus according to claim 70, wherein said light source generates linearly polarized light having a predetermined direction of polarization; and wherein, when said sample object is a light reflecting member having a mirror surface, said phase difference adjustment means imparts a phase difference of π/2 multiplied by an odd number to the two polarized light beams split by said separating optical system and then reflected by said sample object, as said two polarized light beams travel through said separating optical system to-and-fro.

Claim 75

Dependent Claim 119 words

An observation apparatus according to claim 70, further comprising a synthesizing optical system which combines the two polarized light beams transmitted through said sample object and guides the composite light to said polarization selecting means, wherein said light source generates linearly polarized light having a predetermined direction of polarization; wherein, when said sample object is optically flat, said phase difference adjustment means imparts a phase difference of π multiplied by an integer to the two polarized light beams split by said separating optical system and then transmitted through said sample object, and wherein said phase difference adjustment means includes a 1/4-wavelength plate which converts the linearly polarized light emitted from said synthesizing optical system into the circularly polarized light.

Claim 76

Dependent Claim 93 words

An observation apparatus according to claim 70, further comprising a synthesizing optical system which combines the two polarized light beams transmitted through said sample object and guides the composite light to said polarization selecting means, wherein said light source generates linearly polarized light having a predetermined direction of polarization; and wherein, when said sample object is optically flat, said phase difference adjustment means imparts a phase difference of π/2 multiplied by an odd number to the two polarized light beams split by said separating optical system and then transmitted through said sample object.

Claim 77

Dependent Claim 72 words

An observation apparatus according to claim 69, further comprising an illumination optical system which is disposed between said light source and said separating optical system and illuminates said sample object with the light thereon emitted from said light source by way of said separating optical system, wherein said light detecting means is constituted by a two-dimensional image sensor disposed on at least one of respective focal planes of said condenser optical system.

Claim 78

Dependent Claim 31 words

An observation apparatus according to claim 75, wherein said illumination optical system includes a wavelength selecting means for selecting a specific wavelength component from the light emitted from said light source.

Claim 79

Dependent Claim 34 words

An observation apparatus according to claim 75, wherein said illumination optical system includes a polarized light selecting means for selecting a specific linear polarized light component from the light emitted from said light source.

Claim 80

Dependent Claim 96 words

An observation apparatus according to claim 77, wherein, when said sample object is a light reflecting member having a mirror surface, said phase difference adjustment means imparts a phase difference of π multiplied by an integer to the two polarized light beams split by said separating optical system and then reflected by said sample object, as said two polarized light beams travel through said separating optical system to-and-fro, and wherein said phase difference adjustment means includes a 1/4-wavelength plate which converts the linearly polarized light emitted from said separating optical system into the circularly polarized light.

Claim 81

Dependent Claim 69 words

An observation apparatus according to claim 77, wherein, when said sample object is a light reflecting member having a mirror surface, said phase difference adjustment means imparts a phase difference of π/2 multiplied by an odd number to the two polarized light beams split by said separating optical system and then reflected by said sample object, as said two polarized light beams travel through said separating optical system to-and-fro.

Claim 82

Dependent Claim 104 words

An observation apparatus according to claim 77, further comprising a synthesizing optical system which combines the two polarized light beams transmitted through said sample object and guides the composite light to said polarization selecting means, wherein, when said sample object is optically flat, said phase difference adjustment means imparts a phase difference of π multiplied by an integer to the two polarized light beams split by said separating optical system and then transmitted through said sample object, and wherein said polarization selecting means includes a 1/4-wavelength plate which converts the linearly polarized light emitted from said synthesizing optical system into the circularly polarized light.

Claim 83

Dependent Claim 78 words

An observation apparatus according to claim 77, further comprising a synthesizing optical system which combines the two polarized light beams transmitted through said sample object and guides the composite light to said polarization selecting means, wherein, when said sample object is optically flat, said phase difference adjustment means imparts a phase difference of π/2 multiplied by an odd number to the two polarized light beams split by said separating optical system and then transmitted through said sample object.

Claim 84

Dependent Claim 75 words

An observation apparatus according to claim 69, wherein said condenser optical system is arranged so as to serve as an objective optical system which collects the two polarized light beams reflected by said sample object, and said separating optical system is arranged so as to serve as a synthesizing optical system which combines the two polarized light beams again exited from said condenser optical system and guides the composite light to said polarization selecting means.

Claim 85

Dependent Claim 16 words

An observation apparatus according to claim 82, wherein said separating optical system includes a birefringence prism.

Claim 86

Dependent Claim 44 words

An observation apparatus according to claim 82, wherein said separating optical system includes a prism having two reflecting surfaces non-parallel to each other, and a polarizing beam splitter surface disposed between said two reflecting surfaces and parallel to either of said two reflecting surfaces.

Claim 87

Dependent Claim 48 words

An observation apparatus according to claim 82, wherein said separating optical system includes mirrors having respective reflecting surfaces non-parallel to each other, and two prisms disposed between said two mirrors and having respective polarizing beam splitter surfaces parallel to either of said reflecting surfaces of two reflecting mirrors.

Claim 88

Dependent Claim 24 words

An observation apparatus according to claim 82, wherein said phase difference adjustment means comprises a driving member capable of moving said separating optical system.

Claim 89

Dependent Claim 53 words

An observation apparatus according to claim 69, further comprising an objective optical system which collects the two polarized light beams transmitted through said sample object, and a synthesizing optical system which combines the two polarized light beams exited from said objective optical system and guides the composite light to said polarization selecting means.

Claim 90

Dependent Claim 25 words

An observation apparatus according to claim 87, wherein at least one of said separating optical system and said synthesizing optical system includes a birefringence prism.

Claim 91

Dependent Claim 53 words

An observation apparatus according to claim 87, wherein at least one of said separating optical system and said synthesizing optical system includes a prism having two reflecting surfaces non-parallel to each other, and a polarizing beam splitter surface disposed between said two reflecting surfaces and parallel to either of said two reflecting surfaces.

Claim 92

Dependent Claim 58 words

An observation apparatus according to claim 87, wherein at least one of said separating optical system and said synthesizing optical system includes two mirrors having respective reflecting surfaces non-parallel to each other, and two prisms disposed between said two mirrors and having respective polarizing beam splitter surfaces parallel to either of said reflecting surfaces of two reflecting mirrors.

Claim 93

Dependent Claim 33 words

An observation apparatus according to claim 87, wherein said phase difference adjustment means comprises a driving member capable of moving at least one of said separating optical system and said synthesizing optical system.

Claim 94

Dependent Claim 85 words

An observation apparatus according to claim 69, wherein said polarization selecting means variably sets the analyzer angle with respect to the composite light composed of the two polarized light beams reflected by or transmitted through said sample object and includes a polarizing beam splitter which splits said composite light into two different directions; and wherein said light detecting means includes a first photodetector for detecting light transmitted through said polarizing beam splitter and a second photodetector for detecting light reflected by said polarizing beam splitter.

Claim 95

Dependent Claim 39 words

An observation apparatus according to claim 92, wherein said polarizing beam splitter is fixed around an optical axis of said condenser optical system and wherein said azimuth rotator is disposed on an inlet side of said polarizing beam splitter.

Claim 96

Dependent Claim 32 words

An observation apparatus according to claim 92, wherein said azimuth rotator is constituted by a 1/2-wavelength plate disposed so as to be rotatable around the optical axis of said condenser optical system.

Claim 97

Dependent Claim 36 words

An observation apparatus according to claim 92, wherein each of said polarizing beam splitter and said first and second photodetectors is disposed so as to be rotatable around the optical axis of said condenser optical system.

Claim 98

Dependent Claim 81 words

An observation apparatus according to claim 92, wherein an analyzer angle φ min of said polarization selecting means when the output difference between said first and second photodetectors for the level difference of said sample object is minimum, coincides with φ max +nπ/4, wherein φ max is an analyzer angle of said polarization selecting means when the output difference between said first and second photodetectors for the level difference of said sample object is maximum, and n is an odd number.

Claim 99

Dependent Claim 74 words

An observation apparatus according to claim 92, further comprising a measuring means for quantitatively measuring, based on an output of said light detecting means, a level difference on said sample object, wherein said measuring means measures the level difference of said sample object based on the analyzer angle which is set so as to maximize or minimize the output difference between said first and second photodetectors for the level difference of said sample object.

Claim 100

Dependent Claim 158 words

An observation apparatus according to claim 97, wherein said measuring means measures a level difference of said object sample based on a phase difference Ψ between the two polarized light beams calculated by the following relationship: tan 2φ=-2a·b·sin Ψ/(a.sup.2 -b.sup.2) wherein φ is the analyzer angle of said polarization selecting means when the output difference between said first and second photodetectors for the level difference of said sample object is maximum, Ψ is the phase difference between the two polarized light beams caused by the level difference of said sample object, a is an amplitude reflectance of one of two regions holding the level difference of said sample object therebetween incorporated in an output sum of said light detecting means for said region, and b is an amplitude reflectance of the other of two regions holding the level difference of said sample object therebetween incorporated in an output sum of said light detecting means for said other region.

Claim 101

Dependent Claim 78 words

An observation apparatus according to claim 92, further comprising an image forming means which forms a differential interference image of said sample object based on an output of said light detecting means, wherein said image forming means generates, based on an output difference between said first and second photodetectors for the level difference of said sample object, a contrast corresponding to the analyzer angle of said polarization selecting means for the differential interference image of said sample object.

Claim 102

Dependent Claim 78 words

An observation apparatus according to claim 92, further comprising a defect detection system which detects the defect formed on a substrate being said sample object on the basis of an output from said light detecting means, wherein said defect detecting means shows the defects as the differential interference image of said sample object generated with a contrast corresponding to the analyzer angle of said polarization selecting means, based on an output difference between said first and second photodetectors.

Claim 103

Dependent Claim 62 words

An observation apparatus according to claim 100, wherein said light source emits a linearly polarized light beam having a wavelength of light for which a phase shift of π multiplied by an integer is caused by a transparent substance constituting a predetermined pattern on said substrate or a wavelength substantially equal to a wavelength of light used to expose said predetermined pattern.

Claim 104

Dependent Claim 94 words

An observation apparatus according to claim 100, wherein said defect detection system comprises a differential circuit which generates a difference signal as the difference of two output signals respectively input from said first and second photodetectors, corresponding the two different polarized light beams selected by said polarization selecting means, a binaring circuit which compares the difference signal from said differential circuit with a predetermined threshold value thereby generating a binary signal, and a judging circuit which detects the defects formed on the substrate on the basis of the binary signal from said binaring circuit.

Claim 105

Dependent Claim 168 words

An observation apparatus comprising: a light source for generating light; a separating optical system for splitting the light emitted from the light source into two different polarized light beams; a condenser optical system for converging the two polarized light beams emitted from the separating optical system so as to respectively form light spots on two different positions on a sample object; a polarization selecting means having a predetermined analyzer angle for selecting a specific polarized light component from composite light made of the two polarized light beams reflected by or transmitted through the sample object; light detecting means for detecting the polarized light component selected by the polarization selecting means; and phase difference setting means for setting a phase difference between the two polarized light beams reflected by or transmitted through the sample object to provide a circularly polarized light by composing the two polarized light beams to the polarization selecting means, when the sample object does not modulate both phase and amplitude of the light incident thereon.

Claim 106

Dependent Claim 168 words

An observation apparatus comprising: a light source for generating light; a separating optical system for splitting the light emitted from the light source into two different polarized light beams; a condenser optical system for converging the two polarized light beams emitted from the separating optical system so as to respectively form light spots on two different positions on a sample object; a polarization selecting means having a predetermined analyzer angle for selecting a specific polarized light component from composite light made of the two polarized light beams reflected by or transmitted through the sample object; light detecting means for detecting the polarized light component selected by the polarization selecting means; and phase difference setting means for setting a phase difference between the two polarized light beams reflected by or transmitted through the sample object to provide a circularly polarized light by composing the two polarized light beams to the polarization selecting means, when the sample object does not modulate both phase and amplitude of the light incident thereon.

Claim 107

Dependent Claim 179 words

An observation apparatus comprising: a light source for generating light; a separating optical system for splitting the light emitted from the light source into two different polarized light beams; a condenser optical system for converging the two polarized light beams emitted from the separating optical system so as to respectively form light spots on two different positions on a sample object; a polarization selecting means, including an azimuth rotator having a variable polarization rotational angle, for variably setting an analyzer angle and selecting a specific polarized light component from composite light made of the two polarized light beams reflected by or transmitted through the sample object; light detecting means for detecting the polarized light component selected by the polarization selecting means; and phase difference setting means for setting a phase difference between the two polarized light beams reflected by or transmitted through the sample object to provide a circularly polarized light by composing the two polarized light beams to the polarization selecting means, when the sample object does not modulate both phase and amplitude of the light incident thereon.

Claim 108

Dependent Claim 179 words

An observation apparatus comprising: a light source for generating light; a separating optical system for splitting the light emitted from the light source into two different polarized light beams; a condenser optical system for converging the two polarized light beams emitted from the separating optical system so as to respectively form light spots on two different positions on a sample object; a polarization selecting means, including an azimuth rotator having a variable polarization rotational angle, for variably setting an analyzer angle and selecting a specific polarized light component from composite light made of the two polarized light beams reflected by or transmitted through the sample object; light detecting means for detecting the polarized light component selected by the polarization selecting means; and phase difference setting means for setting a phase difference between the two polarized light beams reflected by or transmitted through the sample object to provide a circularly polarized light by composing the two polarized light beams to the polarization selecting means, when the sample object does not modulate both phase and amplitude of the light incident thereon.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2001-06-08	2001-12-08	2002-06-09	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2005-06-08	2005-12-08	2006-06-09	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2009-06-08	2009-12-08	2010-06-09	$7700.00	Window Closed / Lapsed

Apparatus for observing a surface using polarized light

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