Apparatus and method for detection and measurement of environmental parameters

• US 6,700,385 B2
• Filed: 10/22/2002
• Issued: 03/02/2004
• Est. Priority Date: 06/06/2001
• Status: Active Grant

• Current Assignee: Desco Industries Incorporated
• Original Assignee: Credence Technologies, Inc. (3M Company)
• Inventors: Kraz, Vladimir
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): KERVEROS, JAMES C
• Application Number:
  US10/278,589
• Publication Number:
  US 20030048107A1
• Time in Patent Office: 497 Days
• Field of Search: 324/457, 324/458, 324/452, 324/72, 324/72.5, 343/701, 343/703, 375/219, 375/220, 438/275, 438/14, 438/19
• US Class Current: 324/457
• CPC Class Codes: G01R 29/12 Measuring electrostatic fields or voltage-potential
• CPC Class Codes: G03F 1/44 Testing or measuring features, e.g. grid patterns, focus monitors, sawtooth scales or notched scales
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring

Abstract

The present invention provides a device for in-situ measurement and recording of various environmental parameters in a semiconductor fabrication process. The device comprises sensors for detecting the parameters and converting them to sensor outputs; and a data logger coupled to the sensors for receiving the sensor outputs and logging them in a file. The device may also comprise an analog to digital converter to convert the sensor outputs to digital data and a communication module to communicate the digital data with other devices. When applied to reticles used in a semiconductor fabrication process comprising a plurality of stages, the device may be used to monitor electrostatic field and electrostatic discharge activities on and around the reticle, convert the monitored parameters into data, and log the data along with a timestamp and an identification of each individual stage. Logged data can be retrieved and analyzed to determine the time and location of detrimental activities such as electrostatic discharge on reticles.

Claims

1. A method for localizing electrostatic discharges (ESD) by detecting electrostatic discharges and electrostatic field, the method comprising:

detecting an electrostatic discharge and converting it into a first output;

detecting said electrostatic field and converting it into a second output;

determining a valid local electrostatic discharge based on said first and second outputs; and

correlating the valid local electrostatic discharge with a stage of a fabrication process to create a log of electrostatic discharges occurring at different stages of the fabrication process.

2. The method of claim 1 wherein said determining comprises determining said valid local electrostatic discharge when said electrostatic discharge is combined with said electrostatic field having a magnitude that exceeds a predetermined value.

3. The method of claim 2 further comprising converting said first and second outputs to first and second digital data, respectively.

4. A device for localizing electrostatic discharges affecting a unit by detecting an electrostatic discharge and electrostatic field, the device comprising:

an electrostatic sensor for detecting said electrostatic field affecting said unit and generating a first output;

an ESD sensor for detecting said electrostatic discharge affecting said unit and generating a second output; and

a means for correlating a process stage with the electrostatic discharge to create a log of electrostatic discharge occurring at different stages of a fabrication process.

5. The device of claim 4 further comprising:

an analog comparator coupled to said first output for generating a comparator output when said electrostatic field has a magnitude exceeding a predetermined value.

6. The device of claim 5 further comprising:

a circuit coupled to said analog comparator and to said ESD sensor for receiving said comparator output and said second output, said circuit configured to generate a valid ESD signal when said comparator output and said second output are detected.

7. The device of claim 4 further comprising:

an analog to digital converter (ADC) coupled to said electrostatic sensor and said ESD sensor for converting said first and second outputs to first and second digital data, respectively.

8. The device of claim 7 further comprising:

a digital comparator coupled to said first data and generating a comparator output when said electrostatic field has a magnitude exceeding a predetermined value.

9. The device of claim 8 further comprising:

a circuit coupled to said digital comparator and to said ADC for receiving said comparator output and said second data, said circuit configured to generate a valid ESD signal when said comparator output and said second data are detected.

10. The device of claim 9 wherein said circuit is an AND gate.

11. The device of claim 10 further comprising:

a data logger comprising a timestamping module for logging said first and second digital data.

12. The device of claim 11 further comprising an RF (radio frequency) communication module coupled to said data logger.

13. A method for localizing electrostatic discharges (ESD) by detecting electrostatic discharges and electrostatic field, the method comprising:

detecting an electrostatic discharge and converting it into a first output;

detecting a change in said electrostatic field and converting it into a second output;

determining a valid local electrostatic discharge based on said first and second outputs; and

correlating the valid local electrostatic discharge with a stage of a fabrication process to create a log of electrostatic discharges occurring at different stages of the fabrication process.

14. The method of claim 13 wherein said determining comprises determining said valid local electrostatic discharge when said electrostatic discharge is combined with said electrostatic field changing at a rate that exceeds a predetermined value.

15. The method of claim 14 further comprising converting said first and second outputs to first and second digital data, respectively.

16. A device for localizing electrostatic discharges affecting a unit, the device comprising:

an electrostatic sensor for detecting a change in said electrostatic field and generating a first output;

an ESD sensor for detecting said electrostatic discharge and generating a second output; and

a means for correlating a process stage with the electrostatic discharge to create a log of electrostatic discharge occurring at different stages of a fabrication process.

17. The device of claim 16 further comprising:

a high pass filter coupled to said first output for generating a high pass filter output when said electrostatic field changes at a rate exceeding a predetermined value.

18. The device of claim 17 further comprising:

a circuit coupled to said high pass filter and to said ESD sensor for receiving said high pass filter output and said second output, said circuit configured to generate a valid ESD signal when said high pass filter output and said second output are detected.

19. The device of claim 18 further comprising:

an analog to digital converter (ADC) coupled to said electrostatic sensor and said ESD sensor for converting said first and second outputs to first and second digital data, respectively.

20. The device of claim 19 further comprising:

a high pass filter coupled to said first data for generating a high pass filter output when said electrostatic field changes at a rate exceeding a predetermined value.

21. The device of claim 20 wherein said high pass filter comprises software codes executable by a microprocessor.

22. The device of claim 20 further comprising:

a circuit coupled to said high pass filter and to said ADC for receiving said high pass filter output and said second data, said circuit configured to generate a valid ESD signal when said high pass filter output and said second data are detected.

23. The device of claim 22 wherein said circuit is an AND gate.

24. The device of claim 23 further comprising:

a data logger comprising a timestamping module for logging said first and second digital data.

25. The device of claim 24 further comprising an RF (radio frequency) communication module coupled to said data logger.