Multi-variable statistical process controller for discrete manufacturing

• US 5,408,405 A
• Filed: 09/20/1993
• Issued: 04/18/1995
• Est. Priority Date: 09/20/1993
• Status: Expired due to Fees

• Current Assignee: Adventa Control Technologies, Inc. (Onto Innovation Inc.)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Pu, William W., Saxena, Sharad, Mozumder, Purnendu K.
• Primary Examiner(s): Gordon, Paul P.
• Application Number:
  US08/124,083
• Time in Patent Office: 575 Days
• Field of Search: 364/151, 364/468, 364/552, 364/149, 364/551.01, 364/554, 364/578
• US Class Current: 700/31
• CPC Class Codes: G05B 21/02 electric

Abstract

A method and system for controlling a plurality of process control variables for processing discrete products is described. The method comprising: utilizing process models relating a plurality of product quality parameters to the plurality of process control variables; measuring the plurality of product quality parameters on a first plurality of products; exercising statistical quality control tests on the plurality of product quality parameters of the first plurality of products; continuing processing if statistical quality control tests are successful; otherwise measuring the plurality of product quality parameters on a second plurality of products; tuning the process models to create tuned process models using the plurality of product quality parameters from the second plurality of products, wherein the tuning estimates a changed state of the processing; estimating new values for the plurality of process control variables from the tuned models; processing a third plurality of products at the new values of the plurality of process control variables; measuring the plurality of product quality parameters on the third plurality of products; repeating the tuning of the process models and the estimating new values for the plurality of process control variables if the quality control parameters from the third plurality of products are not acceptable; otherwise continuing processing products with the new values of the plurality of process control variables if the quality control parameters from the third plurality of products are acceptable.

Claims

1. An automated system for controlling fabrication of a product, wherein said system includes a plurality of process control variables, said system comprising:

a. sensors for measuring a plurality of quality parameters of said product;

b. a memory for storing said plurality of quality parameters;

c. means for administering statistical quality control tests on said plurality of quality parameters of said product;

d. means for creating process models relating said plurality of quality parameters to said plurality of process control variables;

e. means for analyzing said process models;

f. means for tuning said process models so that said process models indicate which of said plurality of process control variables are in error;

g. means for calculating new values of said plurality of process control variables by sequentially optimizing for a process goal; and

h. means for resetting said plurality of process control variables with said new values.

2. The system of claim 1, wherein said sensors include internal sensors.

3. The system of claim 1, wherein said sensors include external sensors.

4. The system of claim 1, wherein said system includes a means for calculating new values by sequential optimization of said process models.

5. The system of claim 1, wherein said system includes a means for indicating a preference for the order in which the process control variables are to be adjusted.

6. The system of claim 1, wherein said plurality of quality parameters are weighted corresponding to their relative importance.

7. The system of claim 1, wherein said process models are tuned using process observations made at operating points determined by a local experiment design.

8. A method of controlling a plurality of process control variables in processing discrete products, said method comprising:

a. utilizing process models relating a plurality of product quality parameters to said plurality of process control variables;

b. measuring said plurality of product quality parameters on a first plurality of products;

c. exercising statistical quality control tests on said plurality of product quality parameters of said first plurality of products;

d. continuing processing if statistical quality control tests are successful;

otherwise

e. measuring said plurality of product quality parameters on a second plurality of products;

f. tuning said process models to create tuned process models using said plurality of product quality parameters from said first and said second plurality of products, wherein said tuning estimates a changed state of said processing;

g. estimating new values for said plurality of process control variables from said tuned models;

h. processing a third plurality of products at said new values of said plurality of process control variables;

i. measuring said plurality of product quality parameters on said third plurality of products;

j. repeating said tuning of said process models and said estimating new values for said plurality of process control variables if said quality control parameters from said third plurality of products are not acceptable;

otherwise

k. continuing processing products with said new values of said plurality of process control variables if said quality control parameters from said third plurality of products are acceptable.

9. The method of claim 8, wherein said tuning process models includes local experiment design.

10. The method of claim 8, wherein said estimating new values further includes optimizing said plurality of product quality parameters.

11. The method of claim 10, wherein said optimizing includes weighting said plurality of product quality parameters corresponding to their relative importance.

12. The method of claim 8, wherein said optimizing includes indicating a preference for the order in which the process control variables are to be adjusted.

13. The method of claim 8, wherein said measuring said parameters utilizes external sensors.

14. The method of claim 8, wherein said measuring said parameters utilizes internal sensors.

15. A method of controlling a plurality of process control variables in semiconductor wafer processing, said method comprising:

a. utilizing process models relating a plurality of product quality parameters to said plurality of process control variables;

b. measuring said plurality of product quality parameters on a first plurality of wafers;

c. exercising statistical quality control tests on said plurality of product quality parameters of said first plurality of wafers;

d. continuing processing if statistical quality control tests are successful;

otherwise

e. measuring said plurality of product quality parameters on a second plurality of wafers;

f. tuning said process models to create tuned process models using said plurality of product quality parameters from said first and said second plurality of wafers, wherein said tuning estimates a changed state of said semiconductor wafer processing;

g. estimating new values for said plurality of process control variables from said tuned models to optimize said plurality of product quality parameters;

h. processing a third plurality of wafers at said new values of said plurality of process control variables;

i. measuring said plurality of product quality parameters on said third plurality of wafers;

j. repeating said tuning of said process models and said estimating new values for said plurality of process control variables if said quality control parameters from said third plurality of wafers are not acceptable;

otherwise

k. continuing processing wafers with said new values of said plurality of process control variables if said quality control parameters from said third plurality of wafers are acceptable.

16. The method of claim 15, wherein said measuring utilizes external sensors.

17. The method of claim 15, wherein said measuring utilizes internal sensors.

18. The method of claim 15, wherein said optimizing includes indicating different combinations of said plurality of process control variables according to preference of adjustment.

19. The method of claim 15, wherein said optimizing includes weighting said plurality of product quality parameters corresponding to their relative importance.

20. The method of claim 15, wherein said tuning uses process observations made at operating points determined by a local experiment design.