Method and apparatus for slope to threshold conversion for process state monitoring and endpoint detection

• US 20040117054A1
• Filed: 12/13/2002
• Published: 06/17/2004
• Est. Priority Date: 12/13/2002
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Kistler, Rodney, Gotkis, Yehiel, Hemker, David, Bright, Nicolas J., Katz, Vladimir
• Granted Patent: US 6,859,765 B2
• Time in Patent Office: Days
• US Class Current: 700/121
• CPC Class Codes: G05B 23/0254 based on a quantitative model, e.g. mathematical relationships between inputs and outputs; functions: observer, Kalman filter, residual calculation, Neural Networks
• CPC Class Codes: H01L 22/26 Acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection, in-situ thickness measurement endpoint detection arrangements in CMP apparatus B24B37/013, in discharge apparatus H01J37/32

Abstract

A method for converting a slope based detection task to a threshold based detection task is provided. The method initiates with defining an approximation equation for a set of points corresponding to values of a process being monitored. Then, an expected value at a current point of the process being monitored is predicted. Next, a difference between a measured value at the current point of the process being monitored and the corresponding expected value is calculated. Then, the difference is monitored for successive points to detect a deviation value between the measured value and the expected value. Next, a transition point for the process being monitored is identified based on the detection of the deviation value. A processing system configured to provide real time data for a slope based transition and a computer readable media are also provided.

Claims

1. A method for converting a slope based detection task to a threshold based detection task, comprising:

defining an approximation equation for a set of points corresponding to values of a process being monitored;

predicting an expected value at a current point of the process being monitored;

calculating a difference between a measured value at the current point of the process being monitored and the corresponding expected value;

monitoring the difference to detect a deviation value between the measured value and the expected value; and

identifying a transition point for the process being monitored based on the detection of the deviation value.

2. The method of claim 1, wherein the approximation equation is a polynomial equation.

3. The method of claim 1, wherein the process being monitored is a semiconductor process selected from the group consisting of a chemical mechanical planarization process and an etch, deposition or surface modification process.

4. The method of claim 1, wherein the measured value is generated by a sensor configured to detect a property associated with process being monitored.

5. The method of claim 1 further comprising:

tracing the difference between the measured value and the corresponding expected value; and

defining a corridor of noise, the corridor of noise providing a boundary, wherein which the deviation value falls outside of the boundary.

6. The method of claim 1, wherein the method operation of identifying a transition point for the process being monitored based on the detection of the deviation value includes,

identifying more than one consecutive points in which the deviation value associated with each of the at least two consecutive points is outside a corridor of noise

7. The method of claim 1, wherein the approximation equations derives the expected value from an interval of past data generated by a sensor associated with the process being monitored.

8. The method of claim 1, further comprising:

in response to identifying the transition point, triggering an end of the processing being monitored.

9. A method for detecting a transition point of a slope based change through a threshold detection, comprising

monitoring a parameter associated with a transition point;

calculating a predicted value of the parameter from past values of the monitored parameter, the predicted value corresponding to a current value of the parameter being monitored;

defining a threshold value;

tracking a difference between the current value and the predicted value; and

identifying the transition point when the difference exceeds the threshold value.

10. The method of claim 9, wherein the threshold value is outside an offset, the offset configured to substantially eliminate background noise from interfering with identification of the transition point.

11. The method of claim 9, wherein the method operation of identifying a transition point when the difference exceeds the threshold value includes,

identifying at least two points when the difference exceeds the threshold value.

12. The method of claim 9 further comprising:

tracing the difference between the current value and the corresponding predicted value; and

defining a corridor of noise, the corridor of noise providing a boundary, wherein which the threshold value falls outside of the boundary.

13. The method of claim 9, wherein the parameter is capable of being monitored by a sensor configured to detect a composition change or a state change associated with an object being processed.

14. A semiconductor processing system capable of detecting a transition point for slope change transitions through a threshold determination in real time, comprising:

a processing module configured to process a semiconductor wafer until a defined parameter associated with the semiconductor wafer being processed is obtained, the processing system including;

a sensor configured to monitor a process parameter associated with a process operation;

a detector in communication with the sensor, the detector configured to compare measured values to predicted values, the measured values indicating a transition point through a slope change, the predicted values being derived from previously measured values, the detector further configured to track a difference between the measured values and the corresponding predicted values to enhance a change at the transition point to enable a threshold deviation value to be defined, the threshold deviation value indicating the transition point associated with the process operation.

15. The system of claim 14, wherein the detector is configured to initiate a transition associated with the processing system when a difference between the measured values and the predicted values for at least two consecutive time points exceeds the threshold deviation value.

16. The system of claim 14, wherein the processing module is selected from the group consisting of a chemical mechanical planarization module and an etch module.

17. The system of claim 14, wherein the sensor is sensitive to variation of the process parameter, the process parameter varying as one of a composition and a state changes, the composition and the state changes associated with one of the semiconductor wafer and a component of the processing module.

18. The system of claim 14, wherein the sensor is selected from the group consisting of an eddy current sensor, an infrared sensor, a vibration sensor and a sensor configured to detect reflected spectra.

19. The system of claim 14, wherein the detector is configured to associate an offset configured to substantially eliminate background noise from interfering with the threshold determination.

20. The system of claim 14, wherein the threshold deviation value occurs at a time point corresponding to a slope transition associated with a trace of the measured values.

21. A computer readable media having program instructions for converting a slope based detection task to a threshold based detection task, comprising:

program instructions for defining an approximation equation for a set of points corresponding to values of a process being monitored;

program instructions for predicting an expected value at a current point of the process being monitored;

program instructions for calculating a difference between a measured value at the current point of the process being monitored and the corresponding expected value;

program instructions for monitoring the difference to detect a deviation value between the measured value and the expected value; and

program instructions for identifying a transition point for the process being monitored based on the detection of the deviation value.

22. The computer readable media of claim 21, wherein the approximation equation is a polynomial equation.

23. The computer readable media of claim 21, further comprising:

program instructions for tracing the difference between the measured value and the corresponding expected value; and

program instructions for defining a corridor of noise, the corridor of noise providing a boundary, wherein which the deviation value falls outside of the boundary.