Mask quality measurements by fourier space analysis

• US 6,187,483 B1
• Filed: 05/28/1999
• Issued: 02/13/2001
• Est. Priority Date: 05/28/1999
• Status: Expired due to Term

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Spence, Christopher A., Capodieci, Luigi
• Primary Examiner(s): Rosasco, S.
• Application Number:
  US09/322,546
• Time in Patent Office: 627 Days
• Field of Search: 430/5, 430/322, 355/53, 716/20, 395/500.2, 395/500.21
• US Class Current: 430/5
• CPC Class Codes: G03F 1/36 Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes

Abstract

A method (200) of determining an optimal mask fabrication process includes fabricating (202) a first mask pattern (220) on a mask using a first mask fabrication process and a second mask pattern (222) on a mask using a second mask fabrication process, wherein each mask pattern approximates an ideal pattern. The method (200) further includes performing a mathematical transform on the first and second mask patterns (230), wherein the mathematical transform provides a representation of the first and second mask patterns as sums of functions. A metric is then obtained for the transformed mask patterns (220, 222), wherein the metric is based upon a capability of a pattern transfer system which will utilize the masks employing the first and second mask patterns one of the first and second mask fabrication processes is selected (236) based upon an application of the metric to the first and second sum of orthogonal functions, thereby selecting the one of the first or second mask fabrication processes that provides for a better mask pattern which most closely approximates the ideal mask pattern.

Claims

1. A method of determining an optimal mask fabrication process, comprising the steps of:

fabricating a first mask pattern on a mask using a first mask fabrication process, wherein the first mask pattern provides a pattern on a substrate which approximates an ideal pattern;

performing a mathematical transform on the first mask pattern, wherein the mathematical transform provides a representation of the first mask pattern as a first sum or product of functions;

fabricating a second mask pattern on a mask using a second mask fabrication process, wherein the second mask pattern provides a pattern on a substrate which approximates the ideal pattern;

performing a mathematical transform on the second mask pattern, wherein the mathematical transform provides a representation of the second mask pattern as a second sum or product of functions;

obtaining a metric for the transformed mask patterns, wherein the metric is based upon a capability of a pattern transfer system which will utilize the masks employing the first and second mask patterns, respectively; and

selecting the first mask fabrication process or the second mask fabrication process based upon an application of the metric to the first and second sum or product of functions, thereby selecting the one of the first or second mask fabrication process that provides for a better mask pattern which most closely approximates the ideal mask pattern.

2. The method of claim 1, wherein the mathematical transform comprises a Fourier transform which transforms the first and second mask patterns into two-dimensional mappings which represent a distribution of energy over a plurality of spatial frequencies in Fourier space.

3. The method of claim 2, wherein the metric comprises an area on the two-dimensional mappings which correspond to a predetermined range of spatial frequencies, and wherein the energy within the area represents the energy within the predetermined range of spatial frequencies which will be transmitted through the pattern transfer system.

4. The method of claim 3, wherein applying the metric comprises integrating the Fourier transforms of the first feature and the second feature over the area.

5. The method of claim 1, wherein the selecting of one of the first mask fabrication process or the second mask fabrication process comprises applying the metric to the transformed first and second mask patterns to generate first and second values, and selecting the mask fabrication process which has a larger value than the other, wherein the larger value represents a more efficient transfer of energy by the pattern transfer system to the substrate.

6. The method of claim 1, wherein the mathematical transform comprises a Wavelet transform which transforms the first and second mask patterns into a finite sum or product of translated and/or scaled functions.

7. The method of claim 6, wherein the metric comprises a function of one or more coefficients of the functions obtained by the Wavelet transforms of the first and second mask patterns, respectively.

8. The method of claim 7, wherein the selecting of one of the first mask fabrication process or the second mask fabrication process comprises comparing a value of the metric function of the first and second transformed mask patterns, and selecting the first mask fabrication process or the second mask fabrication process using the value based on a predetermined criteria.

9. The method of claim 1, further comprising the steps of:

(a) performing a mathematical transform on another mask pattern formed using another mask fabrication process;

(b) applying the metric to the transformed another mask pattern to thereby generate a value corresponding to the another transformed mask pattern;

(c) comparing the value of the another transformed mask pattern to the value of the previously selected mask fabrication process;

(d) selecting the another mask fabrication process or the previously selected mask fabrication process using the values based on the predetermined criteria;

(e) repeating steps (a)-(d) until all the mask fabrication processes of interest have been characterized, and wherein the mask fabrication process selected in step (d) provides a best mask pattern transfer compared to the other mask fabrication processes.

10. The method of claim 1, wherein the mask fabrication processes include an etch variable which may be varied.

11. The method of claim 1, wherein the mask fabrication processes include a resist-type variable which may be varied.

12. A system for determining an optimal mask fabrication process, comprising:

an input device which receives input data corresponding to a plurality of mask patterns that each approximate an ideal mask pattern, wherein the mask patterns are formed by different mask fabrication processes, and wherein the input device transmits the input data to the system, and wherein the input data represents a two-dimensional data representation of the plurality of mask patterns;

a processor coupled to the input device, wherein the processor receives the input data from the input device and performs a Fourier transform thereon, and wherein the Fourier transform provides a two-dimensional mapping of spatial frequencies for each of the plurality of mask patterns; and

a memory coupled to the processor, wherein the memory stores a metric which is based upon a capability of a pattern transfer system which will utilize one or more masks employing the plurality of mask patterns thereon, and wherein the processor accesses the memory to utilize the metric in evaluating the plurality of transformed mask patterns, wherein the metric represents a selected range of spatial frequencies which the pattern transfer system is capable of transmitting therethrough, and wherein the processor is programmed to apply the metric to the two-dimensional mapping of spatial frequencies for the plurality of mask features by integrating the two-dimensional mappings of the mask patterns over the selected range of spatial frequencies, and wherein the result of the integration is a value which indicates an amount of energy associated with the respective mask pattern which is transmitted through the pattern transfer system to the substrate, and

wherein the processor selects one of the mask fabrication processes by selecting its associated mask pattern using the metric based upon a predetermined criteria, wherein using the metric comprises selecting the mask fabrication process associated with the mask pattern having the largest amount of energy within the selected range of spatial frequencies.

13. The system of claim 12, further comprising an output device coupled to the processor, wherein the output device receives output data from the processor and provides a representation of the output data for review and analysis.

14. The system of claim 13, wherein the output device comprises a printer and/or a display.

15. The system of claim 13, wherein the output data comprises one or more of the selection of one of the mask fabrication processes, a representation of the transformed mask patterns, a representation of the metric applied to the representation of the transformed mask patterns, and a value associated with the application of the metric to the transformed mask patterns.

16. The system of claim 15, wherein the representation of the transformed mask patterns and the representation of the metric are graphical representations.

17. The system of claim 12, wherein the input device comprises a keyboard or mouse for data entry or a disk drive for transmitting the input data from a portable storage media to the processor.

18. A system for determining an optimal mask fabrication process, comprising;

an input device which receives input data corresponding to a plurality of mask patterns that each approximate an ideal mask pattern, wherein the mask patterns are formed by different mask fabrication processes, and wherein the input device transmits the input data to the system, and wherein the input data represents a two-dimensional data representation of the plurality of mask patterns;

a processor coupled to the input device wherein the processor is programmed to perform a Wavelet transform on the input data to form a sum or product of finite, scaled and translated functions for each of the plurality of mask patterns; and

a memory coupled to the processor, wherein the memory stores a metric which is based upon a capability of a pattern transfer system which will utilize one or more masks employing the plurality of mask patterns thereon, and wherein the processor accesses the memory to utilize the metric in evaluating the plurality of transformed mask patterns,

wherein the processor selects one of the mask fabrication processes by selecting its associated mask pattern using the metric based upon a predetermined criteria.

19. The system of claim 18, wherein the metric represents a predetermined function of one or more coefficients of the transformed mask patterns, and wherein the processor is programmed to apply the metric to the transformed mask patterns to generate a value associated with each of the mask patterns, and wherein the processor is programmed to select one of the mask patterns and its associated mask fabrication process using the value based upon a predetermined criteria.