Opto-mechanical automatic focusing system and method

Claim 2

Apparatus comprising: a particle beam system comprising: particle beam generating means for forming a beam of electrons, ions or other particles, and for directing said beam along a predetermined axis of a focal point; and object support means for supporting an object on said axis with said focal point on a surface of said object; and in an autofocusing system for maintaining the relative positions of said beam generating means and said object support means along said particle beam axis, an optical beam system comprising: means for developing an optical beam; means for directing said optical beam transversely to said particle beam axis and at an acute angle to said object surface and for forming an optical beam first focus on a surface of said object; and a spherical mirror with its center of curvature on said object surface at said first focus for collecting radiation from said optical beam first focus and for forming a beam second focus in the vicinity of said beam first focus such that a change in the height or vertical position of said object surface along said axis produces a change in the position of said second focus indicative of said object surface height or position change.

Claim 3

The apparatus defined by claim 1 wherein said object support means includes Z-motion stage means for making adjustments in the operating distance between said particle beam generating means and said object surface along said axis, and wherein said means for directing said beam and for forming a first optical beam focus substantially on a surface of said object includes means for adjusting the optical path length of the optical beam to accommodate gross adjustments in said operating distance without substantially altering the angle of incidence of said optical beam on said object surface.

Claim 4

The apparatus defined by claim 1 wherein said object support means includes Z-motion stage means for making gross and fine adjustments in the operating distance between said particles beam generating means and said object surface along said axis, and wherein said apparatus includes means for mechanically coupling said spherical mirror to said object support means to move therewith to maintain said second focus on said surface as gross or fine adjustments in the position of said object are made.

Claim 5

The apparatus defined by claim 1 wherein said object support means includes Z-motion stage means for making gross and fine adjustments in the operating distance between said particle beam generating means and said object surface along said axis, and wherein said apparatus includes mirror support means for supporting said spherical mirror means independently of said object support means.

Claim 6

The apparatus defined by claim 1 wherein said object support means includes Z-motion stage means for making adjustments in the operating distance between said particle beam generating means and said object surface along said axis, wherein said apparatus includes means for supporting said spherical mirror for Z-axis movement in coordination with said operating distance adjustments, and wherein said means for directing said optical beam and for forming a first optical beam focus on a surface of said object includes means for adjusting the optical path length of the optical beam, whereby adjustments of the operating distance are accommodated without significantly altering the geometrical inter-relationship of said optical beam, said spherical mirror, and said object.

Claim 7

Apparatus comprising: a particle beam system comprising: particle beam generating means for forming a base of electrons, ions or other particles, and for directing said beam along a predetermined axis to a focal point; and object support means for supporting an object on said axis with said focal point on a surface of said object; and in an autofocusing system coupled to said object support means for adjusting the position of said object support means along said particle beam axis, an optical beam system comprising: means for developing an optical beam; means for directing said beam transversely to said particle beam axis and at an acute angle to said object surface and for forming an optical beam first focus on a surface of said object; object image forming and reflecting means for collecting radiation from said optical beam first focus and for forming a second focus in the vicinity of said beam first focus such that a change in the height or vertical position of said object surface along said axis produces a change in the position of said second focus indicative of said object surface height or position change; and said object support means including means for making adjustments in the operating distance between said particle beam generating means and said surface along said axis, and wherein said apparatus includes means for mechanically coupling said image-forming and reflecting means to said object support means to move therewith to maintain said second focus on said surface as any adjustments in the position of said object surface are made.

Claim 8

Apparatus comprising: a particle beam system comprising: particle beam generating means for forming a base of electrons, ions or other particles, and for directing said beam along a predetermined axis to a focal point; and object support means for supporting an object on said axis with said focal point on a surface of said object; and in an autofocusing system coupled to said object support means for adjusting the position of said object support means along said particle beam axis, an optical beam system comprising: means for developing an optical beam; means for directing said beam transversely to said particle beam axis and at an acute angle to said object surface and for forming an optical beam first focus on a surface of said object; object image forming and reflecting means for collecting radiation from said optical beam first focus and for forming a second focus in the vicinity of said beam first focus such that a change in the height or vertical position of said object surface along said axis produces a change in the position of said second focus indicative of said object surface height or position change; and said object support means including means for making adjustments in the operating distance between said particle beam generating means and said surface along said axis, and wherein said apparatus includes means for mechanically coupling said image-forming and reflecting means to said object support means to move therewith to maintain said second focus on said surface as any adjustments in the position of said object surface are made.

Claim 9

The apparatus defined by claim 6 wherein said image-forming means is a spherical mirror having a center of curvature on said object surface at said first focus.

Claim 10

Apparatus comprising: a particle beam system comprising: particle beam means for forming a beam of electrons, ions or other particles, and for directing said beam along a predetermined axis to a focal point; and object support means for supporting an object on said axis with said focal point on a surface of said object; and in an autofocusing system coupled to said object support means for adjusting the position of said object support means along said particle beam axis, an optical beam system comprising: means for developing an optical beam; means for directing said beam transversely to said particle beam axis and at an acute angle to said object surface and for forming a first optical beam focus on a surface of said object; optical image forming and reflecting means for collecting radiation from said optical beam first focus and for forming a second focus in the vicinity of said beam focus such that a change in the height or vertical position of said object surface along said axis produces a change in the position of said second focus indicative of said object surface height or position change; and said object support means including means for making adjustments in the operating distance between said particle beam means and said object surface measured along said axis, and wherein means for directing said beam and for forming a first optical beam focus on a surface of said object includes means for adjusting the optical path length of the optical beam to accommodate gross adjustments in said operating distance without substantially altering the angle of incidence of said optical beam on said surface.

Claim 11

Apparatus comprising: a particle beam system comprising: particle beam means for forming a beam of electrons, ions or other particles, and for directing said beam along a predetermined axis to a focal point; and object support means for supporting an object on said axis with said focal point on a surface of said object; and in an autofocusing system coupled to said object support means for adjusting the position of said object support means along said particle beam axis, an optical beam system comprising: means for developing an optical beam; means for directing said beam transversely to said particle beam axis and at an acute angle to said object surface and for forming a first optical beam focus on a surface of said object; optical image forming and reflecting means for collecting radiation from said optical beam first focus and for forming a second focus in the vicinity of said beam focus such that a change in the height or vertical position of said object surface along said axis produces a change in the position of said second focus indicative of said object surface height or position change; and said object support means including means for making adjustments in the operating distance between said particle beam means and said object surface measured along said axis, and wherein means for directing said beam and for forming a first optical beam focus on a surface of said object includes means for adjusting the optical path length of the optical beam to accommodate gross adjustments in said operating distance without substantially altering the angle of incidence of said optical beam on said surface.

Claim 12

The apparatus defined by claim 8 wherein said apparatus includes means for mechanically coupling said image-forming and reflecting mirror means to said object support means, and wherein said means for directing said beam and for forming a first optical beam and for forming a first optical beam focus on a surface of said object includes optical telescope means for adjusting the optical path length of the beam, whereby adjustments of the operating distance are accommodated without significantly altering the geometrical inter-relationship of said optical beam, said image-forming mirror means, and said object.

Claim 13

The apparatus defined by claim 9 wherein said image-forming and reflecting means is a spherical mirror with its center of curvature substantially on said object surface at said first focus.

Claim 14

The apparatus defined by claim 8 wherein said image-forming means is a spherical mirror with a center of curvature on said object surface of said first focus.

Claim 17

The apparatus defined by claim 12 wherein said optical image-forming means is a spherical mirror.

Claim 18

Apparatus comprising: a particle beam system comprising: particle beam generating means for forming a beam of electrons, ions or other particles, and for directing said beam along a predetermined axis to a focal point; and object support means for supporting an object on said axis with said focal point on a surface of said object; and in an autofocusing system for maintaining the relative positions of said beam generating means and said object support means along said particle beam axis, an optical beam system comprising: means for developing an optical beam; means for directing said optical beam transversely to said particle beam axis and at an acute angle to said object surface and for forming an optical beam first focus on a surface of said object; and optical image forming and reflecting means for collecting radiation from said optical beam first focus and for reflectively forming a beam second focus in the vicinity of said beam first focus such that a change in the height or vertical position of said object surface along said axis produces a change in the position of said second focus indicative of said object surface height or position change, said object support means including Z-motion stage means for making gross or fine adjustments in the operating distance between said particle beam generating means and said object surface along said axis, said apparatus including second support means for supporting said image-forming and reflecting means independently of said object support means, and adapted to move said image-forming and reflecting means in coordination with adjustments of said operating distance so as to maintain said second focus on said surface as gross or fine adjustments in the position of said object are made.

Claim 19

Apparatus comprising: a particle beam system comprising: particle beam generating means for forming a beam of electrons, ions or other particles, and for directing said beam along a predetermined axis to a focal point; and object support means for supporting an object on said axis with said focal point on a surface of said object; and in an autofocusing system for maintaining the relative positions of said beam generating means and said object support means along said particle beam axis, an optical beam system comprising: means for developing an optical beam; means for directing said optical beam transversely to said particle beam axis and at an acute angle to said object surface and for forming an optical beam first focus on a surface of said object; and optical image forming and reflecting means for collecting radiation from said optical beam first focus and for reflectively forming a beam second focus in the vicinity of said beam first focus such that a change in the height or vertical position of said object surface along said axis produces a change in the position of said second focus indicative of said object surface height or position change, said object support means including Z-motion stage means for making gross or fine adjustments in the operating distance between said particle beam generating means and said object surface along said axis, said apparatus including second support means for supporting said image-forming and reflecting means independently of said object support means, and adapted to move said image-forming and reflecting means in coordination with adjustments of said operating distance so as to maintain said second focus on said surface as gross or fine adjustments in the position of said object are made.

Claim 20

The apparatus defined by claim 14 wherein said image-forming and reflecting means is a spherical mirror with its center of curvature on said object surface substantially at said first focus.

Claim 21

Apparatus comprising: a particle beam system comprising: particle beam generating means for forming a beam of electrons, ions or other particles, and for directing said beam along a predetermined axis to a focal point; and object support means for supporting an object on said axis with said focal point on a surface of said object; and in an autofocusing system for maintaining the relative positions of said beam generating means and said object support means along said particle beam axis, an optical beam system comprising: means for developing an optical beam; means for directing said optical beam transversely to said particle beam axis and at an acute angle to said object surface and for forming an optical beam first focus on a surface of said object; and optical image-forming and reflecting means for collecting radiation from said optical beam first focus and for reflectively forming a beam second focus in the vicinity of said beam first focus such that a change in the height or vertical position of said object surface along said axis produces a change in the position of said second focus indicative of said object surface height or position change, said object support means including cradle means adapted to tilt about a tilt axis passing substantially along said object surface and through said particle beam focal point, and wherein said image-forming and reflecting means is mechanically coupled to said object support means to tilt therewith.

Claim 22

Apparatus comprising: a particle beam system comprising: particle beam generating means for forming a beam of electrons, ions or other particles, and for directing said beam along a predetermined axis to a focal point; and object support means for supporting an object on said axis with said focal point on a surface of said object; and in an autofocusing system for maintaining the relative positions of said beam generating means and said object support means along said particle beam axis, an optical beam system comprising: means for developing an optical beam; means for directing said optical beam transversely to said particle beam axis and at an acute angle to said object surface and for forming an optical beam first focus on a surface of said object; and optical image-forming and reflecting means for collecting radiation from said optical beam first focus and for reflectively forming a beam second focus in the vicinity of said beam first focus such that a change in the height or vertical position of said object surface along said axis produces a change in the position of said second focus indicative of said object surface height or position change, said object support means including cradle means adapted to tilt about a tilt axis passing substantially along said object surface and through said particle beam focal point, and wherein said image-forming and reflecting means is mechanically coupled to said object support means to tilt therewith.

Claim 23

The apparatus defined by claim 16 wherein said image-forming and reflecting means is a spherical mirror with its center of curvature substantially on said object surface at said first focus.

Claim 24

The apparatus defined by claim 17 wherein said spherical mirror is angularly asymmetric with respect to a plane defined by incident and reflected optical beams and favors the direction of tilt of said mirror.

Claim 25

The apparatus defined by claim 18 wherein said mirror comprises a sector of approximately 90 degrees with about 75 degrees on the favored side of said plane.

Claim 26

The apparatus defined by claim 16 wherein said object support means further includes means for making gross and fine adjustments in the operating distance between said particle beam means and said object surface along said axis, and wherein said apparatus includes means for mounting said image-forming and reflecting means on said cradle means such that when adjustments are made in said operating distance, said image forming and reflecting means moves with said cradle means to maintain said second focus on said surface.

Claim 27

The apparatus defined by claim 20 wherein said image-forming and reflecting means is a spherical mirror with its center of curvature substantially on said object surface at said first focus.

Claim 28

The apparatus defined by claim 21 wherein said spherical mirror is angularly asymmetric with respect to a plane defined by incident and reflected optical beams and favors the direction of tilt of said mirror.

Claim 29

The apparatus defined by claim 22 wherein said mirror comprises a sector of approximately 90 degrees with about 75 degrees on the favored side of said plane.

Claim 30

The apparatus defined by claim 20 wherein said means for directing said beam and for forming a first optical beam focus on said surface of said object includes means for adjusting the optical path length of the beam to accommodate adjustments in said operating distance without substantially altering the angle of incidence of said optical beam on said surface.

Claim 31

An optical beam surface inspection system comprising: means for developing an optical beam; means for directing said optical beam at an acute angle to a surface of an object and for forming a first optical beam focus on said surface of said object; and optical image-forming mirror means for collecting radiation from said optical beam first focus and for forming a beam second focus in the vicinity of said beam first focus such that a change in the height or vertical position of said object surface along said axis produces a change in the position of said second focus indicative of said object surface height or position change, said system including cradle means supporting said object and adapted to tilt about a tilt axis passing substantially along said object surface, said image-forming mirror means being mechanically coupled to said cradle to tilt therewith.

Claim 32

An optical beam surface inspection system comprising: means for developing an optical beam; means for directing said optical beam at an acute angle to a surface of an object and for forming a first optical beam focus on said surface of said object; and optical image-forming mirror means for collecting radiation from said optical beam first focus and for forming a beam second focus in the vicinity of said beam first focus such that a change in the height or vertical position of said object surface along said axis produces a change in the position of said second focus indicative of said object surface height or position change, said system including cradle means supporting said object and adapted to tilt about a tilt axis passing substantially along said object surface, said image-forming mirror means being mechanically coupled to said cradle to tilt therewith.

Claim 33

The apparatus defined by claim 25 wherein said image-forming mirror means is a spherical mirror with its center of curvature on said object surface substantially at said first focus.

Claim 34

The apparatus defined by claim 26 wherein said mirror comprises a sector of approximately 90 degrees with about 75 degrees on the favored side of said plane.