FLEXIBLE WAFER LEVELING DESIGN FOR VARIOUS ORIENTATION OF LINE/TRENCH

• US 20140362359A1
• Filed: 06/10/2013
• Published: 12/11/2014
• Est. Priority Date: 06/10/2013
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Liu, Heng-Hsin, Peng, Jui-Chun, Chao, Kuo-Hung
• Granted Patent: US 9,228,827 B2
• Time in Patent Office: Days
• US Class Current: 355/67
• CPC Class Codes: G01B 11/0608 Height gauges
• CPC Class Codes: G03F 9/7026 Focusing
• CPC Class Codes: G03F 9/7034 Leveling

Abstract

The present disclosure relates to a photolithography system having an ambulatory projection and/or detection gratings that provide for high quality height measurements without the use of an air gauge. In some embodiments, the photolithography system has a level sensor having a projection source that generates a measurement beam that is provided to a semiconductor substrate via a projection grating. A detector is positioned to receive a measurement beam reflected from the semiconductor substrate via a detection grating. An ambulatory element selectively varies an orientation of the projection grating and/or the detection grating to improve the measurement of the level sensor. By selectively varying an orientation of the projection and/or detection gratings, erroneous measurements of the level sensor can be eliminated.

Claims

1. A photolithography system, comprising:

a lithographic exposure element configured to selectively expose a semiconductor substrate to electromagnetic radiation;

a level sensor configured to measure a height of a semiconductor substrate at different points over a top surface of the semiconductor substrate, comprising;

a projection source configured to generate a measurement beam that is provided to a semiconductor substrate via a projection grating;

a detector configured to receive a measurement beam that is reflected off of a semiconductor substrate via a detection grating and to measure an intensity of the reflected measurement beam corresponding to a height of the semiconductor substrate; and

an ambulatory element configured to selectively adjust an orientation of detection grating or the projection grating.

2. The photolithography system of claim 1, wherein the ambulatory element is configured to compare a detected intensity level of the reflected measurement beam to a threshold value and to adjust an orientation of the detection grating or the projection grating if the detected intensity level violates the threshold value.

3. The photolithography system of claim 1, wherein the ambulatory element is configured to adjust an orientation of the detection grating or the projection grating to match an orientation of lines on the semiconductor substrate.

4. The photolithography system of claim 1, wherein the ambulatory element is configured to adjust the orientation of the projection grating and the detection grating to have a same orientation.

5. The photolithography system of claim 4, wherein the electromagnetic radiation comprises extreme ultraviolet electromagnetic radiation.

6. The photolithography system of claim 1,

wherein the projection grating is positioned between the projection source and a first level sensing lens;

and

wherein the detection grating is positioned between a second level sensing lens and the detector.

7. The photolithography system of claim 1,

wherein the semiconductor substrate comprises a photoresist layer overlying a bottom antireflective coating (BARC) layer;

and

wherein the level sensor is configured to measure a height of the BARC layer at different points over a top surface of the semiconductor substrate.

8. The photolithography system of claim 1, wherein the detection grating comprises a plurality of segments configured to act as a filter on a received reflected measurement beam.

9. The photolithography system of claim 8, wherein a sum of a width and spacing of the plurality of segments is equal to a range of between 20 microns and 40 microns.

10. A level sensor configured to measure a height of a semiconductor substrate at different points over a top surface of the semiconductor substrate, comprising:

a projection source configured to generate a measurement beam that is reflected off of a semiconductor substrate;

a detector configured to receive the measurement beam reflected off of the semiconductor substrate and to measure an intensity of the reflected measurement beam corresponding to a height of the semiconductor substrate;

a detection grating positioned between the semiconductor substrate and the detector; and

an ambulatory element configured to selectively rotate the detection grating.

11. The level sensor of claim 10, further comprising:

a projection grating positioned between the projection source and the semiconductor substrate, wherein the projection grating is configured to filter the measurement beam output from the projection source.

12. The level sensor of claim 11, wherein the ambulatory element is configured to compare a detected intensity level to a threshold value and to rotate the detection grating or the projection grating if the detected intensity level violates the threshold value.

13. The level sensor of claim 11, wherein the ambulatory element is configured to adjust an orientation of the detection grating or the projection grating to match an orientation of lines on the semiconductor substrate.

14. The level sensor of claim 11,

wherein the projection grating is positioned between the projection source and a first level sensing lens;

and

wherein the detection grating is positioned between a second level sensing lens and the detector.

15. The level sensor of claim 11, wherein the detection grating comprises a plurality of segments configured to act as a filter on a received reflected measurement beam.

16. The level sensor of claim 15, wherein a sum of a width and spacing of the plurality of segments is equal to a range of between 20 microns and 40 microns.

17. A method of determining a height of a semiconductor substrate for a photolithography process, comprising:

providing a semiconductor substrate into a photolithography tool with an ambulatory projection grating or an ambulatory detection grating;

operating a level sensor to generate a measurement beam along a path that passes through the projection grating or the detection grating;

measuring an intensity level of the reflected measurement beam passing through the detection grating; and

selectively adjusting an orientation of the projection grating or the detection grating based upon the detected intensity level.

18. The method of claim 17, further comprising:

comparing the intensity level to a threshold value, wherein if the intensity level violates the threshold value the orientation of the projection grating or the detection grating is adjusted.

19. The method of claim 18, wherein adjusting the orientation of the projection grating or the detection grating comprises rotating an angle of the projection grating or the detection grating to match an orientation of lines on the semiconductor substrate.

20. The method of claim 19, wherein adjusting the orientation of the projection grating or the detection grating comprises adjusting the orientation of the projection grating and the detection grating to have a same orientation.