METHODS FOR HIGH-RESOLUTION, STABLE MEASUREMENT OF PITCH AND ORIENTATION IN OPTICAL GRATINGS

20230314126

18/118269

March 07, 2023

Embodiments described herein provide for a measurement system having an aperture filtering component and methods of utilizing the measurement system. The measurement system described herein includes a measurement arm and a stage. The measurement arm projects a light beam to a top surface of an optical device structure. Multi-reflection beams resulting from reflections and diffraction off other surfaces of a non-opaque substrate leads to interference. The measurement arm includes an aperture (e.g., an aperture filtering component) that filters the multi-reflection beams from being relayed to the detector. As such, only images of the light beam are relayed to the detector.

1. A measurement system, comprising: a light source, the light source configured to project a light beam to a substrate disposed below the light source; a first lens disposed between the substrate and the light source, the first lens configured to focus the light beam to the substrate; a first beam splitter disposed between the first lens and the light source; a second lens disposed adjacent to the first beam splitter, the first beam splitter configured to direct the light beam to the second lens, the second lens configured to direct the light beam to a mirror; an aperture disposed in front of the mirror; a second beam splitter, the second beam splitter configured to direct the light beam to a third lens from the mirror; and a detector, wherein the light beam is projected to the detector by the third lens.

2. The measurement system of claim 1, wherein the first lens is a focusing lens.

3. The measurement system of claim 1, wherein the third lens is configured to relay an original image of the light beam at a Fourier plane to the detector, wherein the Fourier plan is formed adjacent to the second lens.

4. The measurement system of claim 1, wherein the aperture has an aperture size between about 50 μm to about 1 mm.

5. The measurement system of claim 1, further comprising a reticle disposed between the first beam splitter and the light source.

6. The measurement system of claim 5, wherein the reticle includes a marker thereon, wherein the marker is a cross, circular, or triangular.

7. The measurement system of claim 1, wherein the detector is a charge-coupled device (CCD) array or an active-pixel sensor (CMOS array).

8. A measurement system, comprising: a stage having a substrate support surface, the stage coupled to a stage actuator configured to move the stage in a scanning path and rotate the stage about an axis; and a measurement arm disposed above the stage, the measurement arm configured to direct a light beam to a substrate disposed on the substrate support surface, the measurement arm including: a light source, the light source configured to project the light beam to the substrate disposed below the light source; a first lens disposed between the substrate and the light source, the first lens configured to focus the light beam to the substrate; a first beam splitter disposed between the first lens and the light source; a second lens disposed adjacent to the first beam splitter, the first beam splitter configured to direct the light beam to the second lens; an aperture, the second lens configured to direct the light beam through the aperture; a third lens; and a detector, wherein the light beam is projected to the detector by the third lens.

9. The measurement system of claim 8, wherein the first lens is a focusing lens.

10. The measurement system of claim 8, wherein the third lens is configured to relay an original image of the light beam at a Fourier plane to the detector, wherein the Fourier plan is disposed adjacent to the second lens.

11. The measurement system of claim 8, wherein the measurement arm is coupled to an arm actuator configured to scan the measurement arm and rotate the measurement arm about the axis.

12. The measurement system of claim 8, wherein the measurement arm further comprises: a first linear polarizer disposed adjacent to the light source; a second linear polarizer disposed between the beam splitter and the third lens; a first waveplate disposed between the beam splitter and the first lens; and a second waveplate disposed between the second lens and the beam splitter.

13. The measurement system of claim 8, wherein the detector is a charge-coupled device (CCD) array or an active-pixel sensor (CMOS array).

14. The measurement system of claim 8, further comprising a reflection arm disposed above the stage.

15. The measurement system of claim 14, wherein the reflection arm is coupled to an arm actuator configured to scan the measurement arm and rotate the measurement arm about the axis.

16. The measurement system of claim 15, wherein the reflection arm comprises: a first reflection arm lens; a second reflection arm lens adjacent to the first reflection arm lens; a third reflection arm lens; a reflection arm aperture disposed between the second reflection arm lens and the third reflection arm lens; and a reflection arm detector, wherein the third reflection arm lens directs a reflection beam to the reflection arm detector.

17. The measurement system of claim 8, wherein the aperture is disposed at an aperture angle, wherein the aperture angle is non-perpendicular relative to a projection direction of the light beam.

18. A method, comprising: projecting a light beam to a first optical device structure from a measurement arm, the light beam diffracting off a top surface of the first optical device structure of a substrate, the substrate disposed on a stage; projecting the light beam through an aperture disposed in front of a mirror in the measurement arm, the aperture operable to allow only the light beam to contact the mirror; relaying a first original image of the light beam to a detector in the measurement arm; moving the stage along a scanning path and projecting the light beam to a second optical device structure, wherein a second original image is relayed to the detector; and forming a high resolution map of a pitch and orientation angle of at least the first optical device structure and the second optical device structure.

19. The method of claim 18, wherein multi-reflection beams formed from the light beam reflecting from at least a bottom surface of the substrate are filtered by the aperture.

20. The method of claim 18, further comprising determining an aperture position of the aperture, wherein the aperture position is determined to align the first original image in an X-Y plane on the substrate.

01; 02; 02; 02

edspap.20230314126