Method and apparatus for measuring properties of thin materials

Claim 3

The method as claimed in Claim 1, wherein said first and second polarized components are at right angles to each other and define S and P beam components, respectively.

Claim 4

The method as claimed in Claim 1, wherein: said step of varying includes alternately passing the source beam through two different optical paths and altering the polarization angle of the beam as it passes along at least one of the paths to produce said first and second beam components, and merging the two beam components into a single beam path, prior to said directing steps.

Claim 5

The method as claimed in Claim 1, wherein said varying step includes alternately inserting into the path of said source beam, first and second polarization plates having their directions of polarization at right angles with respect to each other.

Claim 6

The method as claimed in Claim 1, including, prior to said directing steps, the steps of: splitting the source beam into two separate source sub-beams and issuing said sub-beams along separate paths; and converging said sub-beams so as to meet at the point of impingement upon said sample, thereby automatically carrying out said first and second-mentioned directing steps.

Claim 7

The method as claimed in Claim 1, wherein: said providing step includes providing a polarizer in the path of said source beam to produce a source of linearly polarized laser light, and passing said linearly polarized laser light through a one-quarter wave plate to convert the beam source to one of circularly polarized light;and said varying step includes rotating the polarizer at a prescribed rate of rotation.

Claim 8

The method as claimed in Claim 6, wherein said providing step includes passing the circularly polarized light source alternately through two polarizing plates oriented at right angles with respect to each other to produce said first and second polarized components.

Claim 9

The method as claimed in Claim 6, wherein said detecting step includes passing the circularly polarized reflected light beam alternately through two polarizing plates oriented at right angles with respect to each other prior to determining said relative amplitudes.

Claim 12

The method as claimed in Claim 9, wherein said two polarized components are at right angles to each other and define S and P beam components respectively.

Claim 13

The method as claimed in Claim 9, including the steps of: providing a main source beam of radiant energy; alternately passing the single main source beam through two different optical paths and altering the polarization angle of the beam as it passes along at least one of the paths to produce said pair of angularly displaced beam components; and merging the two beam components into a single beam path, prior to said directing step.

Claim 14

The method as claimed in Claim 9, including, prior to said directing step, providing a main source beam of radiant energy; and alternately inserting into the path of said main source beam, first and second polarization plates having their directions of polarization at right angles with respect to each other.

Claim 15

The method as claimed in Claim 9, including, prior to said directing steps, the steps of: providing a main source beam of radiant energy; splitting the source beam into two separate source sub-beams and issuing said sub-beams along separate paths; and converging said sub-beams so as to meet at the point of impingement upon said sample, thereby automatically carrying out said directing step.

Claim 16

The method as claimed in Claim 9, including, prior to said directing step, the step of: providing a source of laser light; passing said laser light through a polarizer to produce a linearly polarized light source; passing said linearly polarized laser light through a one-quarter wave plate to convert the beam source to one of circularly polarized light; and rotating the polarizer at a prescribed rate of rotation.

Claim 17

The method as claimed in Claim 14, wherein said providing step includes passing the circularly polarized light source alternately through two polarizing plates oriented at right angles with respect to each other to produce said pair of polarized components.

Claim 18

The method as claimed in Claim 14, wherein said detecting step includes passing the circularly polarized reflected light beam alternately through two polarizing plates oriented at right angles with respect to each other prior to determining said relative peak amplitudes.

Claim 19

Apparatus for measuring the thickness of a thin material sample having a transmission efficiency of greater than zero for an impinging beam of radiant energy, said apparatus comprising: a radiant energy beam source providing a beam of radiant energy of a single given wavelength and polarized in a predetermined direction, said sample having a given index of refraction at said given wavelength; means for varying the polarization direction of the beam to produce, in time shared relationship, a first polarized component of the beam polarized in a first direction, and a second polarized component of the beam polarized in a second direction angularly displaced from the first direction; means for directing the polarization-varying beam onto an entry surface of the thin material sample at a first predetermined angle with respect thereto; means for detecting and analyzing the beam reflected by the sample at said first predetermined angle to determine the relative peak amplitudes of reflected first and second polarized components; means for directing the polarization-varying beam onto the entry surface of the thin material sample at a second predetermined angle with respect thereto; means for detecting and analyzing the beam reflected by the sample at said second predetermined angle to determine the respective peak amplitudes of reflected first and second polarized components; a comparator for comparing the ratio of first-to-second component peak amplitudes at said first predetermined angle with the ratio of first-to-second component peak amplitudes at said second predetermined angle; and processor means for determining the thickness of said sample from a mathematical model equating material thickness to a relationship between said given wavelength of the source beam, the angular values of -said first and second predetermined angles and said first and second component peak amplitude ratio comparisons.

Claim 20

Apparatus for measuring the thickness of a thin material sample having a transmission efficiency of greater than zero for an impinging beam of radiant energy, said apparatus comprising: a radiant energy beam source providing a beam of radiant energy of a single given wavelength and polarized in a predetermined direction, said sample having a given index of refraction at said given wavelength; means for varying the polarization direction of the beam to produce, in time shared relationship, a first polarized component of the beam polarized in a first direction, and a second polarized component of the beam polarized in a second direction angularly displaced from the first direction; means for directing the polarization-varying beam onto an entry surface of the thin material sample at a first predetermined angle with respect thereto; means for detecting and analyzing the beam reflected by the sample at said first predetermined angle to determine the relative peak amplitudes of reflected first and second polarized components; means for directing the polarization-varying beam onto the entry surface of the thin material sample at a second predetermined angle with respect thereto; means for detecting and analyzing the beam reflected by the sample at said second predetermined angle to determine the respective peak amplitudes of reflected first and second polarized components; a comparator for comparing the ratio of first-to-second component peak amplitudes at said first predetermined angle with the ratio of first-to-second component peak amplitudes at said second predetermined angle; and processor means for determining the thickness of said sample from a mathematical model equating material thickness to a relationship between said given wavelength of the source beam, the angular values of -said first and second predetermined angles and said first and second component peak amplitude ratio comparisons.

Claim 21

The apparatus as claimed in Claim 17, wherein said first and second polarized components are at right angles to each other and define S and P beam components respectively.

Claim 22

The apparatus as claimed in Claim 17, wherein: said means for varying includes: means for alternately passing the source beam through two different optical paths; means for altering the polarization angle of the beam as it passes along at least one of the paths to produce said first and second beam components;and means for merging the two beam components into a single beam path, prior to reaching said material sample.

Claim 23

The apparatus as claimed in Claim 17, including first and second polarization plates, and wherein said means for varying includes means for alternately inserting into the path of said source beam, said first and second polarization plates with their directions of polarization at right angles with respect to each other.

Claim 24

The apparatus as claimed in Claim 17, including: means for splitting the source beam into two separate source sub-beams and issuing said sub-beams along parallel paths; and . means for converging said sub-beams so as to meet at the point of impingement upon said sample.

Claim 25

The apparatus as claimed in Claim 17, wherein: said radiant energy beam source is a beam source of linearly polarized laser light, and said apparatus includes a one-quarter wave plate through which said linearly polarized laser light is passed to covert the linearly polarized light; and said means for varying includes means for rotating the one-quarter wave plate at a prescribed rate of rotation.

Claim 26

The apparatus as claimed in Claim 22, including a pair of polarizing plates having their angles of polarization orientated angularly with respect to each other, and wherein said radiant energy beam source includes means for passing the circularly polarized light source alternately through said two polarizing plates to produce said first and second polarized components.

Claim 27

2 4 . The apparatus as claimed in Claim 22, including a pair of polarizing plates, and wherein said detecting means includes means for passing the reflected light beam alternately through two polarizing plates oriented at right angles with respect to each other prior to the reflected beam reaching the detector.

Claim 28

Apparatus for measuring the thickness of a thin material sample having a transmission efficiency of greater than zero for an impinging beam of radiant energy, comprising: means for generating a pair of single wavelength radiant energy beams; means for directing the pair of radiant energy beams onto an entry surface of the material sample, said sample having a given index of refraction at said wavelength, each beam having two components of different angles of polarization with respect to each other, said directing means directing the two beams at different respective angles of incidence to said entry surface; means for detecting and analyzing the two beams reflected by the sample to determine the ratio of reflected energy for the two components of each beam; and - means for determining the thickness of said sample from a mathematical model equating material thickness to a relationship between said wavelength of the source beams, said given index of refraction, the angular values of said different angles of incidence, and the ratio comparisons of the amplitudes of said two beam components.

Claim 29

Apparatus for measuring the thickness of a thin material sample having a transmission efficiency of greater than zero for an impinging beam of radiant energy, comprising: means for generating a pair of single wavelength radiant energy beams; means for directing the pair of radiant energy beams onto an entry surface of the material sample, said sample having a given index of refraction at said wavelength, each beam having two components of different angles of polarization with respect to each other, said directing means directing the two beams at different respective angles of incidence to said entry surface; means for detecting and analyzing the two beams reflected by the sample to determine the ratio of reflected energy for the two components of each beam; and - means for determining the thickness of said sample from a mathematical model equating material thickness to a relationship between said wavelength of the source beams, said given index of refraction, the angular values of said different angles of incidence, and the ratio comparisons of the amplitudes of said two beam components.

Claim 36

The method as claimed in Claim 28, wherein: said providing step includes the step of continuously varying the polarization angle of the source beam; and said detecting and analyzing step includes the step of determining the peak amplitudes of said first and second polarized components of the beam leaving the sample.

Claim 39

The apparatus as claimed in Claim 30, wherein: said providing means comprises means for continuously varying the polarization angle of the source beam; and said detecting and analyzing means includes means for determining the peak amplitudes of said first and second polarized components of the beam leaving the sample.