Characterizing kernel function in photolithography based on photoresist pattern

• US 6,647,137 B1
• Filed: 07/10/2000
• Issued: 11/11/2003
• Est. Priority Date: 07/10/2000
• Status: Expired due to Fees

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Lu, Ning
• Primary Examiner(s): Johns, Andrew W.
• Assistant Examiner(s): NAKHJAVAN, SHERVIN K
• Application Number:
  US09/612,887
• Time in Patent Office: 1,219 Days
• Field of Search: 382/100, 382/112, 382/144, 382/212, 382/213, 382/214, 382/283, 382/286, 382/287, 430/302, 430/949, 349/4, 378/34, 378/35
• US Class Current: 382/144
• CPC Class Codes: G03F 7/705 Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
• CPC Class Codes: G03F 7/7065 Defects, e.g. optical inspection of patterned layer for defects
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/60 Analysis of geometric attributes

Abstract

A method and structure for determining a range and a shape of a kernel function of a lithographic system which includes exposing, in the lithographic system, a photosensitive layer on a top surface of a substrate through a mask having a mask image, the mask image being of sufficient width to ensure a transferred image will not exhibit foreshortening but will exhibit corner rounding; developing the photosensitive layer to form the transferred image in the photosensitive layer; measuring a distance from an intersection of projected extensions of edges of the transferred image to a point along one edge where corner rounding starts; and defining the range of the kernel function as the measured distance. The projected extension edges are an unaltered version of the mask image overlaid on the transferred image and the foreshortening is a reduction in length of transferred images when compared to the mask image. Corner rounding occurs as a result of light diffraction and photosensitive layer development processes. The measuring simultaneously accommodates for the light diffraction and photosensitive layer development effects.

Claims

1. A method of determining a range of a kernel function of a lithographic system comprising:

exposing, in said lithographic system, a photosensitive layer on a top surface of a substrate through a mask having a mask image, said mask image being of sufficient width to ensure a transferred image will not exhibit foreshortening but will exhibit corner rounding;

developing said photosensitive layer to form said transferred image in said photosensitive layer;

measuring a distance from an intersection of projected extensions of edges of said transferred image to a point along one edge where corner rounding starts; and

defining said range of said kernel function as said measured distance.

2. The method in claim 1, wherein said projected extension edges comprise an unaltered version of said mask image overlaid on said transferred image.

3. The method in claim 1, wherein said foreshortening comprises a reduction in length of transferred image when compared to said mask image.

4. The method in claim 1, wherein said corner rounding occurs as a result of light diffraction and photosensitive layer development processes.

5. The method in claim 4, wherein said measuring simultaneously accommodates for said light diffraction and photosensitive layer development effects.

6. A method of determining a range of a kernel function of a lithographic system comprising:

exposing, in said lithographic system, a photosensitive layer on a top surface of a substrate through a mask having a plurality of mask images of decreasing widths;

developing said photosensitive layer to form a plurality of corresponding transferred images in said photosensitive layer;

comparing widths of said transferred images with widths of corresponding mask images; and

defining said range of said kernel function as a smallest transferred image width that equals a corresponding mask image width.

7. The method in claim 6, wherein said comparing includes overlaying unaltered versions of said mask images on corresponding ones of said transferred images.

8. The method in claim 6, wherein all transferred images having widths below said range of said kernel function are smaller than corresponding mask images.

9. The method in claim 6, wherein a difference between a mask image width and a corresponding transferred image width occurs as a result of light diffraction and photosensitive layer development processes.

10. The method in claim 9, wherein comparing simultaneously accommodates for said light diffraction and photosensitive layer development effects.

11. A method of determining a shape of an integral of a kernel function of a lithographic system comprising:

exposing, in said lithographic system, a photosensitive layer on a top surface of a substrate through a mask having a mask image, said mask image being of sufficient width to ensure a transferred image will not exhibit foreshortening but will exhibit corner rounding in a region at a corner of said transferred image;

developing said photosensitive layer to form said transferred image in said photosensitive coating;

defining a reference point as an intersection of projected extensions of the edges of said transferred image; and

measuring x and y distances from said reference point to a plurality of points along said transferred image in said region of corner rounding to form a set value numerical evaluation of said integral of said kernel function.

12. The method in claim 11, wherein said projected extension edges comprise an unaltered version of said mask image overlaid on said transferred image.

13. The method in claim 11, wherein said foreshortening comprises a reduction in length of transferred image when compared to said mask image.

14. The method in claim 11, wherein said corner rounding occurs as a result of light diffraction and photosensitive layer development processes.

15. The method in claim 14, wherein said measuring simultaneously accommodates for said light diffraction and photosensitive layer development effects.

16. A method of determining a shape of an integral of a kernel function of a lithographic system comprising:

exposing, in said lithographic system, a photosensitive layer on a top surface of a substrate through a mask having a plurality of mask images of decreasing widths;

developing said photosensitive layer to form a plurality of corresponding transferred images in said photosensitive layer;

comparing widths of said transferred images with widths of corresponding mask images to determine line width narrowing; and

forming a set value numerical evaluation of said integral of said kernel function based on said line width narrowing.

17. The method in claim 16, wherein said comparing includes overlaying unaltered versions of said mask images on corresponding ones of said transferred images.

18. The method in claim 16, wherein all transferred images having widths below said range of said kernel function are smaller than corresponding mask images.

19. The method in claim 16, wherein said line width narrowing occurs as a result of light diffraction and photosensitive layer development processes.

20. The method in claim 19, wherein comparing simultaneously accommodates for said light diffraction and photosensitive layer development effects.

21. A method of determining a shape of an integral of a kernel function of a lithographic system comprising:

exposing, in said lithographic system, a photosensitive layer on a top surface of a substrate through a mask having a plurality of mask images of decreasing widths, said mask image being of sufficient width to ensure first transferred images will not exhibit foreshortening but will exhibit corner rounding in a region at a corner of said transferred image;

developing said photosensitive layer to form said transferred image in said photosensitive coating;

defining a reference point as an intersection of projected extensions of the edges of said first transferred images;

measuring x and y distances from said reference point to a plurality of points along said first transferred images in said region of corner rounding;

comparing widths of second transferred images with widths of corresponding mask images to determine line width narrowing; and

forming a set value numerical evaluation of said integral of said kernel function based on said line width narrowing and said measuring.

22. The method in claim 21, wherein said projected extension edges comprise an unaltered version of said mask image overlaid on said first transferred images.

23. The method in claim 21, wherein said foreshortening comprises a reduction in length of first transferred images when compared to said mask image.

24. The method in claim 21, wherein said comparing includes overlaying unaltered versions of said mask images on corresponding ones of said second transferred images.

25. The method in claim 21, wherein all of said second transferred images having widths below said range of said kernel function are smaller than corresponding mask images.

26. The method in claim 21, wherein said corner rounding and said line width narrowing occurs as a result of light diffraction and photosensitive layer development processes.

27. The method in claim 24, wherein said comparing and said measuring simultaneously accommodates for said light diffraction and photosensitive layer development effects.

28. A method of determining a range of a kernel function of a lithographic system comprising:

exposing, in said lithographic system, a photosensitive layer on a top surface of a substrate through a mask having a plurality of mask images of decreasing widths;

developing said photosensitive layer to form a plurality of corresponding transferred images in said photosensitive layer;

comparing widths of said transferred images with widths of corresponding mask images; and

defining said range of said kernel function as half of a smallest transferred image width before line-end foreshortening occurs.

29. The method in claim 28, wherein said comparing includes overlaying unaltered versions of said mask images on corresponding ones of said transferred images.

30. The method in claim 28, wherein all transferred images having widths below said range of said kernel function exhibit line-end foreshortening.

31. The method in claim 28, wherein said line-end foreshortening occurs as a result of light diffraction and photosensitive layer development processes.

32. The method in claim 31, wherein comparing simultaneously accommodates for said light diffraction and photosensitive layer development effects.