System and method for controlling semiconductor wafer processing

• US 5,526,293 A
• Filed: 12/17/1993
• Issued: 06/11/1996
• Est. Priority Date: 12/17/1993
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Barna, Gabe G., Mozumder, Purnendu K.
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US08/169,865
• Time in Patent Office: 907 Days
• Field of Search: 364/468, 364/550, 364/552, 364/488, 364/489, 364/490, 364/491, 364/148, 364/149, 364/150, 364/151, 364/500
• US Class Current: 700/109
• CPC Class Codes: G05B 13/042 in which a parameter or coefficient is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 17/02 electric

Abstract

A system (10) for run-to-run control of semiconductor wafer processing is provided. An input/output device (12) receives a desired quality characteristic for a particular semiconductor fabrication process. A generating circuit (22) uses a model to generate appropriate process parameters for a processing unit (20) and an expected quality characteristic. An adjusting circuit (16) functions to adjust process parameter inputs of the processing unit (20). In-situ sensor (18) functions to measure a quality characteristic of the process in the processing unit (20) on a real-time basis. A comparing circuit (24) functions to compare the measured quality characteristic with the expected quality characteristic. A model adjusting circuit (26) may adjust the model of the generating circuit (22) if the measured quality characteristic varies from the expected quality characteristic by more than a predetermined statistical amount.

Claims

1. A system for run-to-run control of a semiconductor processing unit, comprising:

a generator operable to generate process parameters using a model which provides a transfer function from said progress parameters to a quality characteristic provided by a user;

circuitry responsive to said generator and operable to adjust selected inputs of the processing unit to process a semiconductor wafer using said generated process parameters;

an in-situ sensor comprising an optical device operable on a single wavelength to generate a signal proportional to the concentration of a predetermined chemical species present during processing of the wafer for measuring a quality characteristic of said process in real-time during said process;

a comparator responsive to said sensor and said generator and operable to compare said measured quality characteristic with said quality characteristic; and

circuitry responsive to said comparator and operable to adjust said model if said measured quality characteristic varies from said expected quality characteristic by more than a predetermined statistical amount.

2. The system of claim 1, and further comprising an input/output device for receiving said quality characteristic from the user.

3. The system of claim 1, wherein said adjusting circuitry comprises a plurality of actuating devices operable to adjust selected process parameter inputs of the processing unit.

4. The system of claim 1, wherein said comparator subtracts said expected quality characteristic from said measured quality characteristic to generate a difference value and averages said difference value with between two to eight difference values from previous wafers.

5. The system of claim 1, wherein said model adjusting circuitry comprises circuitry operable to adjust a constant term of said model if said measured quality characteristic varies from said expected quality characteristic by more than a predetermined statistical amount.

6. The system of claim 1, wherein said model adjusting circuitry weights the difference between said measured quality characteristic and said expected quality characteristic for the current wafer with said difference for up to twenty-five previous wafers to adjust a constant term of said model.

7. A system for run-to-run control of a semiconductor processing unit, comprising:

a generator operable to generate process parameters and an expected quality characteristic using a model and a desired quality characteristic provided by a user;

circuitry responsive to said generator and operable to adjust selected inputs of the processing unit to process a semiconductor wafer using said generated process parameters;

a real-time, in -situ sensor comprising optical device operable on a single wavelength to generate a signal proportional to the concentration of a predetermined chemical species present during processing of the wafer for measuring a quality characteristic of said process, wherein said sensor comprises;

a monochromator operable to generate said signal proportional to the concentration of a predetermined chemical species present during processing of the wafer;

a storage responsive to said monochromator and operable to store a value of said signal at predetermined intervals during the processing to generate data representative of an optical emission trace; and

circuitry responsive to said storage and operable to use a function to convert a slope at an end-point of said optical emission trace to a quality characteristic for the process;

a comparator responsive to said sensor and said generator and operatable to compare said measured quality characteristic with said expected quality characteristic; and

circuitry responsive to said comparator and operable to adjust said model if said measured quality characteristic varies from said expected quality characteristic by more than a predetermined statistical amount.

8. A system for run-to-run control of a semiconductor processing unit, comprising:

a generator operable to generate process parameters using a plurality of models each of which provides a transfer function from said process parameters to at least one of a plurality of quality characteristics at least one of said characteristics being unmeasurable after said process is complete;

circuitry responsive to said generator and operable to adjust selected inputs of the processing unit to process a semiconductor wafer using said generated process parameters;

an in-situ sensor for measuring a quality characteristic of said process in real-time during said process;

a comparator responsive to said sensor and said generator and operable to compare the measured quality characteristics with the expected quality characteristics; and

circuitry responsive to said comparator and operable to adjust the model if the measured quality characteristics vary from the expected quality characteristics by more than a predetermined statistical amount.

9. The system of claim 8, wherein said adjusting circuitry comprises a plurality of actuating devices operable to adjust selected process parameter inputs of the processing unit during the processing of the semiconductor wafer.

10. The system of claim 8, wherein said comparing circuitry subtracts said expected quality characteristic from said measured quality characteristic to generate a difference value and averages said difference value with between two to eight difference values from previous wafers.

11. The system of claim 8, wherein said model adjusting circuitry comprises circuitry operable to adjust a constant term of said model if said measured quality characteristic varies from said expected quality characteristic by more than a predetermined statistical amount.

12. The system of claim 8, wherein said model adjusting circuitry weights the difference between said measured quality characteristic and said expected quality characteristic for the current wafer with said difference for up to twenty-five previous wafers to adjust a constant term of said model.

13. A system for run-to-run control of a semiconductor processing unit, comprising:

a generator operable to generate process parameters and a plurality of expected quality characteristics using a plurality of models and desired quality characteristics;

circuitry responsive to said generator and operable to adjust selected inputs of the processing unit to process the semiconductor wafer using said generated process parameters;

a real-time, in-situ sensor for measuring a quality characteristic of said process wherein said sensor comprises;

a monochromator operable to generate a signal proportional to the concentration of a predetermined chemical species present during processing of the wafer;

a storage responsive to said monochromator and operable to store a value of a signal at predetermined intervals during the processing to generate data representative of an optical emission trace; and

circuitry responsive to said storage and operable to use a function to convert a slope at an end-point of said optical emission trace to a quality characteristic for the process;

a comparator responsive to said sensor and said generator and operable to compare the measured quality characteristics with the expected quality characteristics;

circuitry responsive to said comparator and operable to adjust the model if the measured quality characteristics varies from the expected quality characteristics by more than a predetermined statistical amount.

14. A system for run-to-run control of a semiconductor processing unit, comprising:

a generator operable to generate process parameters and an expected quality characteristic using a model and a desired quality characteristic provided by a user;

circuitry responsive to said generating circuitry and operable to adjust selected inputs of the processing unit to process a semiconductor wafer using said generated process parameters;

a real-time, in-situ sensor for measuring a signal correlated to a quality characteristic of said process which is not measurable after the process is complete;

a comparator responsive to said sensor and said generator and operable to compare said measured quality characteristic with said expected quality characteristic;

circuitry responsive to said comparator and operable to adjust said model if said measured quality characteristic varies from said expected quality characteristic by more than a predetermined statistical amount.

15. The system of claim 14, and further comprising an input/output device for receiving said quality characteristic from the user.

16. The system of claim 14, wherein said adjusting circuitry comprises a plurality of actuating devices operable to adjust selected process parameter inputs of the processing unit.

17. The system of claim 14, wherein said comparator subtracts said expected quality characteristic from said measured quality characteristic to generate a difference value and averages said difference value with between two to eight difference values from previous wafers.

18. The system of claim 14, wherein said model adjusting circuitry comprises circuitry operable to adjust a constant term of said model if said measured quality characteristic varies from said expected quality characteristic by more than a predetermined statistical amount.

19. The system of claim 14, wherein said model adjusting circuitry weights the difference between said measured quality characteristic and said expected quality characteristic for the current wafer with said difference for up to twenty-five previous waters to adjust a constant term of said model.

20. A system for run-to-run control of a semiconductor processing unit, comprising:

a generator operable to generate process parameters and an expected quality characteristic using a model and a desired quality characteristic provided by a user;

circuitry responsive to said generator and operable to adjust selected inputs of the processing unit to process a semiconductor wafer using said generated process parameters;

a real-time, in-situ sensor for measuring a signal correlated to a non-directly observable quality characteristic of said process wherein said sensor comprises;

a monochromator operable to generate a signal proportional to the concentration of a predetermined chemical species present during processing of the wafer;

a storage responsive to said monochromator and operable to store a value of a signal at predetermined intervals during the processing to generate data representative of an optical emission trace; and

circuitry responsive to said storage and operable to use a function to convert a slope at an end-point of said optical emission trace to a quality characteristic for the process;

a comparator responsive to said sensor and said generator and operable to compare said measured quality characteristic with said expected quality characteristic;

circuitry responsive to said comparator and operable to adjust said model if said measured quality characteristic varies from said expected quality characteristic by more than a predetermined statistical amount.