Automated ellipsometer and the like systems

• US 7,746,472 B1
• Filed: 08/29/2008
• Issued: 06/29/2010
• Est. Priority Date: 01/16/2001
• Status: Expired due to Term

• Current Assignee: J.A. Woollam Co., Inc.
• Original Assignee: J.A. Woollam Co., Inc.
• Inventors: Goeden, Christopher A., Liphardt, Martin M., He, Ping, Johs, Blaine D., Welch, James D., Woollam, John A.
• Primary Examiner(s): Pham; Hoa Q
• Application Number:
  US12/231,074
• Time in Patent Office: 669 Days
• Field of Search: 356364-369, 356399-401, 250/225
• US Class Current: 356/369
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0278 Control or determination of height or angle information for sensors or receivers
• CPC Class Codes: G01N 2021/151 Gas blown
• CPC Class Codes: G01N 2021/212 Arrangement with total internal reflection
• CPC Class Codes: G01N 2021/214 Variangle incidence arrangement
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G01N 2201/021 Special mounting in general
• CPC Class Codes: G01N 2201/0693 Battery powered circuitry

Abstract

Systems and methodology for orienting the tip/tilt and vertical height of samples, preferably automated, as applied in ellipsometer and the like systems.

Claims

1. A system comprising:

source of a beam of spectroscopic electromagnetic radiation;

stage for supporting a sample;

data detector of spectroscopic electromagnetic radiation;

said system further comprising, between said source and stage, means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof and providing it to a surface of a sample on said stage at any of at least two angles-of-incidence with respect to said surface, with at least one of said angles-of-incidence being available as a focused, and as a non-focused, beam onto said sample surface;

said source of a beam of spectroscopic electromagnetic radiation, data detector of spectroscopic electromagnetic radiation, and means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof and providing it to a surface of a sample on said stage at any of at least two angles-of-incidence with respect to said surface, being functionally mounted so as to enable movement as a unit;

said system further comprising means for detecting the direction in which a normal to a sample surface projects and means for detecting the angle and plane of incidence of a beam of electromagnetic radiation provided by said source of a beam of spectroscopic electromagnetic radiation, and providing signals which are representative thereof;

said system further comprising actuator means for receiving said representative signals and in response automatically controlling the separation between;

as a unit, said source, data detector, and means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof and providing it to a sample on said stage; and

the surface of a sample on said stage;

said system further comprising actuator means for receiving said representative signals and in response automatically controlling the effective tip/tilt between said beam of electromagnetic radiation provided by said source of a beam of spectroscopic electromagnetic radiation with respect to said sample surface, and therefor the orientation of the angle and plane of incidence of said spectroscopic beam of electromagnetic radiation provided by said source of a beam of spectroscopic electromagnetic radiation with respect to said sample surface; and

optionally, means for causing rotation of said sample about a normal to said surface thereof.

2. A system as in claim 1, which further comprises between said stage and detector, means for receiving a beam of spectroscopic electromagnetic radiation reflected from said sample and providing it to said detector in any of at least two angles-of-incidence with respect to said surface, with at least one of said angles-of-incidence being available as a focused, and as a non-focused, beam onto said sample surface.

3. A system as in claim 1, which further comprises a polarizer between said source of a beam of spectroscopic electromagnetic radiation said stage, and an analyzer between said stage and said detector, and in which said system is an ellipsometer or polarimeter.

4. A system as in claim 1, in which actuator action causes a normal to the sample surface at the point at which said beam of spectroscopic electromagnetic radiation impinges, to project substantially vertically upward in laboratory coordinates.

5. A system comprising:

source of a beam of spectroscopic electromagnetic radiation;

stage for supporting a sample;

data detector of spectroscopic electromagnetic radiation;

said system further comprising, between said source and stage, means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof and providing it to the surface of a sample on said stage at any of at least two angles-of-incidence with respect to said surface, with at least one of said angles-of-incidence being available as a focused, and as a non-focused, beam onto said sample surface;

said system being characterized by at least one selection from the group consisting of;

a) said stage for supporting said sample comprises means for moving said sample in two orthogonal directions in a plane substantially parallel to said sample surface and/or in a direction substantially perpendicular thereto; and

b) the presence of means for moving, as a group, said source;

data detector; and

means for receiving a beam of

spectroscopic electromagnetic radiation from said source thereof and providing it to a sample on said stage;

in two orthogonal directions in a plane substantially parallel to said sample surface and/or in a direction substantially perpendicular thereto;

said system further comprising;

means for controlling stage tip/tilt and therefor the orientation of the plane in which said sample surface is present; and

optional means for causing rotation of said sample.

6. A system as in claim 5, in which the stage for supporting a sample is comprised of two sections:

the first section being comprised of means for adjusting a sample location in two dimensions substantially parallel to the surface of said sample, and

the second section being comprised of means for moving the first section in a direction to place said first section closer to or further away from said source, data detector and said means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof and providing it to a sample on said stage, and for adjusting tip/tilt of the surface of said sample;

such that in use the first section of said stage can be applied to position a spot on a surface of a sample placed on said stage in a plane which is parallel to that of a plane formed by the two dimensions in which said first section can cause movement, and the second section of said stage can be applied to orient said surface of a sample placed on the first section with respect to a beam of spectroscopic electromagnetic radiation provided by said source thereof via adjustment of the location of a surface of a sample along a direction generally perpendicular to said sample surface, and to control the tip/tilt orientation of the plane in which said first section of said stage causes movement of said sample, such that the plane in which the first section causes the surface of a sample to move with respect to an electromagnetic beam from said source thereof can orient the plane of incidence, which includes both a perpendicular to the sample surface and the locus of said spectroscopic electromagnetic, so that both project substantially perpendicular to the sample surface.

7. A system as in claim 5, which further comprises a polarizer between said source of electromagnetic radiation and said stage, and an analyzer between said stage and said data detector and in which said system is an ellipsometer or polarimeter.

8. A system as in claim 5, which further comprises means for providing an alignment beam of electromagnetic radiation provided by said source of a beam of spectroscopic electromagnetic radiation or an alternative source, and an alignment detector, said alignment detector being positioned to detect when said sample is oriented so that said alignment beam approaches said sample surface so that, at the point of reflection therefrom, it reflects directly back along its incident locus, the purpose being to enable align said sample surface in a known orientation.

9. A system as in claim 5, which further comprises a beam modulator which modulates at least one selection from the group consisting of:

said spectroscopic electromagnetic beam; and

said alignment beam;

to distinguish said at least one selection from external light, thereby enabling use in rooms illuminated by non-modulated light.

10. A system as in claim 5, which further comprises between said stage and detector, means for receiving a beam of spectroscopic electromagnetic radiation reflected from said sample and providing it to said detector in any of at least two angles-of-incidence with respect to said surface, with at least one of said angles-of-incidence being available as a focused, and as a non-focused, beam onto said sample surface.

11. A method of aligning a beam of electromagnetic radiation onto a sample surface comprising:

a) causing a beam of electromagnetic radiation to impinge upon a sample surface at an oblique angle of incidence such that it reflects into a data detector, said reflected beam optionally passing through a central hole in a multiple element alignment detector or being partially reflected via beam splitter means onto a multiple element alignment detector;

b) causing said sample to be tilted/tipped to realize a selection from the group consisting of;

the data detector signal is maximized; and

the signals from the multiple elements of a multiple element alignment detector through which said beam is caused to pass or is reflected onto are essentially equal;

c) at the same oblique angle of incidence, placing focusing and recollimating lenses into the pathway of said electromagnetic beam before and after said sample, respectively, and causing said sample to be raised or lowered such that a selection from the group consisting of;

the data detector signal is maximized; and

the signals from the multiple elements of a multiple element detector through which said beam is caused to pass or is reflected onto are essentially equal.

12. A method as in claim 11, in which steps b and c are itteratively repeated a plurality of times at a selection from the group consisting of:

the same location on the sample surface; and

a plurality of locations on the sample surface;

to improve alignment.

13. A method as in claim 11, wherein said system further comprises feedback/actuator means;

said feedback means being applied to receive at least one signal from at least one selection from the group consisting of;

said data detector; and

said alignment detector;

and wherein said actuator means effects sample tilt/tip and/or sample raising or lowering in steps b and c by automatic response to said received at least one signal.

14. A method as in claim 11, which further comprises the step of:

d) removing the focusing lenses from the pathway of said beam of electromagnetic radiation and acquiring sample describing data from said data detector.

15. A method as in claim 11, wherein electromagnetic radiation is entered to the data detector is via a fiber optic, thereby providing a relatively small target for the focused electromagnetic beam in step c.

16. A method as in claim 11, in which an alignment beam of electromagnetic radiation provided by a selection from the group consisting of:

said source of a beam of spectroscopic electromagnetic radiation; and

an alternative source a beam of electromagnetic radiation;

and an alignment detector are present with said alignment detector being positioned to detect when said sample is oriented so that said alignment beam approaches said sample surface so that, at the point of reflection therefrom, it reflects directly back along its incident trajectory, the purpose being to enable orienting said sample surface in a known orientation.

17. A method as in claim 16 in which a beam modulator modulates at least one selection from the group consisting of:

said spectroscopic electromagnetic beam; and

said alignment beam;

to distinguish said at least one selection from external light, thereby enabling use in rooms illuminated by non-modulated light, in which the electromagnetic beam is modulated to distinguish it from external light, to enable use in lit rooms.

18. A method of aligning a beam of electromagnetic radiation onto a sample comprising:

a) providing a system comprising;

a source of a beam of spectroscopic electromagnetic radiation;

a stage for supporting a sample;

a data detector of spectroscopic electromagnetic radiation;

said system further comprising, between said source and stage, means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof and providing it to a surface of a sample on said stage at any of at least two oblique angles-of-incidence to said surface, with at least one of said oblique angles-of-incidence being available as a focused and as a non-focused beam onto said sample surface;

said system being further characterized by at least one selection from the group consisting of;

said stage for supporting said sample comprises means for moving said sample in two orthogonal directions in a plane parallel to said sample surface; and

the presence of means for moving as a group, said source, data detector and means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof and providing it to a sample on said stage, in two orthogonal directions in a plane substantially parallel to said sample surface;

said system further comprising;

means for changing the distance between the sample and, as a group, said source, data

detector, and said means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof along a loccus substantially perpendicular to a normal to said sample surface;

said system further comprising means for controlling stage tip/tilt and therefor the orientation of the plane in which said sample surface is present;

said system further comprising means for providing an alignment beam of electromagnetic radiation provided by a selection from the group consisting of;

said source of a beam of spectroscopic electromagnetic radiation; and

an alternative source a beam of electromagnetic radiation;

and an alignment detector, said alignment beam and alignment detector being oriented and positioned to detect when said sample is oriented with a normal to its surface projecting such that when said alignment beam approaches said sample surface, at the point of reflection therefrom, it reflects directly back upward along its incident trajectory; and

said system optionally comprising a second alignment detector positioned and oriented to monitor spectroscopic electromagnetic radiation reflected from said sample surface at an oblique angle;

b) placing a sample on said stage and causing an alignment beam of electromagnetic radiation to impinge upon a sample at a substantially normal angle to a surface of said sample, such that it reflects from said sample surface into said alignment detector, and causing said stage to cause said sample surface to be tilted/tipped such that the signals from the alignment detector indicate that said alignment beam of electromagnetic radiation caused to impinge upon the surface of said sample reflects therefrom along a normal angle to said sample surface;

c) causing a beam of spectroscopic electromagnetic radiation to approach the surface of said sample at an oblique angle thereto, and placing focusing lenses before and after said sample into the pathway of said spectroscopic beam of electromagnetic radiation, then causing said sample and/or, as a group, said source, data detector, and said means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof, and providing it to a sample on said stage, to be moved along a locus substantially perpendicular to a normal to said sample surface, such that a selection from the group consisting of;

the data detector signal strength is maximized; and

signals from said optional second alignment detector indicate that the reflected beam is directed to substantially maximize data detector signal strength.

19. A method as in claim 18, in which steps b and c are itteratively repeated a plurality of times at a selection from the group consisting of:

the same location on the sample surface; and

a plurality of locations on the sample surface;

to improve alignment of said spectroscopic electromagnetic beam.

20. A method as in claim 18, wherein effecting tilt/tip and changing the distance between the sample and as a group, said source, data detector, and said means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof, and providing it to a sample on said stage, in steps b and c, respectively, are effected by automatic systems which utilize feedback from said data detector and/or optionally, said alignment detectors.

21. A method as in claim 18, which further comprises the step of:

d) removing the focusing lenses from the pathway of said beam of electromagnetic radiation and acquiring sample describing data from said data detector.

22. A method as in claim 18, wherein electromagnetic radiation is entered to the data detector is via a fiber optic, thereby providing a relatively small target for the focused electromagnetic beam in step c.

23. A method as in claim 18 in which there is a known relationship between the loci of said alignment and said beam of spectroscopic electromagnetic radiation from said source thereof which is provided to said surface of a sample on said stage.

24. A method as in claim 18 in which:

said at least two oblique angles-of-incidence of said beam of spectroscopic electromagnetic radiation from said source thereof to said surface of said sample, of which at least one of said oblique angles-of-incidence is available as a focused and as a non-focused beam,

are made available sequentially.

25. A method of aligning a beam of electromagnetic radiation onto a sample comprising

a) providing a system comprising:

source of a beam of spectroscopic electromagnetic radiation;

stage for supporting a sample;

data detector of spectroscopic electromagnetic radiation;

said system further comprising, between said source and stage, means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof and providing it to the surface of a sample on said stage at any of at least two angles-of-incidence to said surface, with at least one of said angles-of-incidence being available as a focused and as a non-focused beam onto said sample surface;

said system being characterized by at least one selection from the group consisting of;

said stage for supporting said sample comprises means for moving said sample in two orthogonal directions in a plane parallel to said sample surface; and

the presence of means for moving as a group, said source, data detector and means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof and providing it to a sample on said stage, in two orthogonal directions in a plane substantially parallel to said sample surface;

the presence of means for moving the sample in a direction to place it closer to or further away from said source, data detector, and said means for receiving a beam of spectroscopic electromagnetic radiation from said source thereof, and providing it to a sample on said stage;

said system further comprising means for controlling stage tip/tilt and therefor the orientation of the plane in which said sample surface is present, and

said system optionally further comprising means for causing rotation of said sample;

said system further comprising means for providing an alignment beam of electromagnetic radiation provided by a selection from the group consisting of;

said source of a beam of spectroscopic electromagnetic radiation; and

an alternative source a beam of electromagnetic radiation;

and an alignment detector, said alignment beam and detector being oriented and positioned to detect when said sample is oriented and with a normal to its surface projecting such that said alignment beam approaches said sample surface and, at the point of reflection therefrom, reflects directly back upward along its incident trajectory, there being a known relationship between the loci of said alignment and said beam of spectroscopic electromagnetic radiation;

b) placing a sample on said stage and causing an alignment beam of electromagnetic radiation to impinge upon a sample at a substantially normal angle to a surface of said sample, such that it reflects from said sample surface into said alignment detector, and causing said stage to cause said sample surface to be tilted/tipped such that the signals from the alignment detector indicate that said alignment beam of electromagnetic radiation caused to impinge upon the surface of said sample reflects therefrom along a normal angle to said sample surface;

c) causing a beam of spectroscopic electromagnetic radiation to approach the surface of said sample at an oblique angle thereto, and placing focusing lenses before and after said sample into the pathway of said spectroscopic beam of electromagnetic, and optionally placing and orienting a second alignment detector to monitor reflected spectroscopic electromagnetic radiation from said sample surface, then causing said sample to be moved along a locus substantially perpendicular to a normal to said sample surface, such that a selection from the group consisting of;

the data detector signal strength is maximized; and

signals from said second alignment detector indicate that the reflected beam is directed to substantially maximize data detector signal strength.

26. A method as in claim 25, in which steps b and c are itteratively repeated a plurality of times at a selection from the group consisting of:

the same location on the sample surface; and

a plurality of locations on the sample surface;

to improve alignment of said spectroscopic electromagnetic beam.

27. A method as in claim 25, wherein effecting tilt/tip and sample raising or lowering in steps b and c are effected by automatic systems which utilize feedback from said data detector and/or optionally, said alignment detectors.

28. A method as in claim 25, which further comprises the step of:

d) removing the focusing lenses from the pathway of said beam of electromagnetic radiation and acquiring sample describing data from said data detector.

29. A method as in claim 25, wherein electromagnetic radiation is entered to the data detector is via a fiber optic, thereby providing a relatively small target for the focused electromagnetic beam in step c.