Method and apparatus for monitoring and controlling wafer fabrication process

• US 6,632,321 B2
• Filed: 01/05/1999
• Issued: 10/14/2003
• Est. Priority Date: 01/06/1998
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Mui, David, Grimbergen, Michael, Lill, Thorsten
• Primary Examiner(s): LUND, JEFFRIE ROBERT
• Application Number:
  US09/225,825
• Publication Number:
  US 20030029834A1
• Time in Patent Office: 1,743 Days
• Field of Search: 156/345, 156/345-4-3
• US Class Current: 156/345.24
• CPC Class Codes: H01J 2237/3348 control of ion bombardment energy
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring
• 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 and apparatus for monitoring, measuring and/or controlling the etch rate in a dry etch semiconductor wafer processing system. The wafer processing system has a monitoring assembly which comprises an electromagnetic radiation source and detector which interferometrically measures the etch rate. The actual rate of change of the etch as it progresses is measures by this technique and is compared to a model of a desired rate of change in a controller. The error between the actual rate of change and the desired rate of change is then used to vary at least one of the process parameters of the system in a direction tending to null the difference.

Claims

1. Apparatus for controlling a wafer processing system having a chamber and a pedestal within said chamber, the apparatus comprising:

an interferometer for generating a signal indicative of a rate of an aspect ratio dependent etch (ARDE) occurring within said chamber; and

a controller coupled to said interferometer and said wafer processing system, for varying one or more process parameters of said wafer processing system in response to said signal, wherein the controller comprises a memory and an etch rate processing routine to control the rate of the aspect ratio dependent etch, the etch rate processing routine being capable of executing the steps of;

retrieving a predetermined etch rate schedule from the memory of the controller, the predetermined etch rate schedule comprising a function of desired aspect ratio dependent etch rate over time;

mesuring an actual aspect ratio dependent etch rate by measuring the elapsed time between two conjugate maxima or minima points of the signal generated by the interferometer;

comparing the actual aspect ratio dependent etch rate to the desired aspect ratio dependent etch rate in the retrieved predetermined etch rate schedule; and

varying one or more of the process parameters of the wafer processing system to change the actual aspect ratio dependent etch rate occurring in the chamber to substantially follow the desired aspect ratio dependent etch rate.

2. The apparatus of claim 1 wherein said interferometer comprises:

an optical fiber, coupled between a light source, a lens coupled to the light source, and a detector.

3. The apparatus of claim 1 further comprising:

a pressure sensor coupled to said chamber and said controller for measuring a pressure within said chamber.

4. The apparatus of claim 1 further comprising a cathode and a temperature sensor coupled to said cathode and said controller.

5. The apparatus of claim 1 wherein the etch rate processing routine is capable of executing the step of:

comparing said actual aspect ratio dependent etch rate to said desired aspect ratio dependent etch rate to determine an etch rate error.

6. An apparatus according to claim 5 wherein the controller is adapted to either increment a process parameter which lowers the aspect ratio dependent etch rate or decrement a process parameter that increases the aspect ratio dependent etch rate when the actual aspect ratio dependent etch rate is greater than the desired aspect ratio dependent etch rate.

7. An apparatus according to claim 5 wherein the controller is adapted to either increment a process parameter which increases the aspect ratio dependent etch rate or decrement a process parameter that lowers the aspect ratio dependent etch rate when the actual aspect ratio dependent etch rate is less than the desired aspect ratio dependent etch rate.

8. The apparatus of claim 1 wherein the controller is adapted to vary a process parameter comprising an RF power supplied to a gas in the chamber, a flow rate of a gas flowing into the chamber, a pressure in the chamber, or a temperature in the chamber.

9. An apparatus according to claim 1 wherein the controller is adapted to vary the process parameters to maintain the aspect ratio dependent etch rate at a constant etch rate.

10. An apparatus for controlling a wafer processing system having a chamber comprising a pedestal to support a substrate for the etching of features on the substrate, the apparatus comprising:

an interferometer capable of generating a signal indicative of an etch rate that is dependent upon an aspect ratio of a feature being etched on the substrate; and

a controller coupled to the interferometer and the wafer processing system, the controller being adapted to vary one or more process pararmeters of the wafer processing system in response to the signal, the process parameters comprising one or more of an RF power supplied to a gas in the chamber, a flow rate of a gas flowing into the chamber, a pressure in the chamber, and a temperature in the chamber, wherein the controller comprises a memory and an etch rate processing routine to control the etch rate, the etch rate processing routine being capable of executing the steps of;

retrieving a predetermined etch rate schedule from the memory of the controller, the predetermined etch rate schedule comprising a function of desired aspect ratio dependent etch rate over time;

measuring an actual aspect ratio dependent etch rate by measuring the elapsed time between two conjugate maxima or minima points of the signal generated by the interferometer;

comparing the actual aspect ratio dependent etch rate to the desired aspect ratio dependent etch rate in the retrieved predetermined etch rate schedule; and

varying one or more of the process parameters to change the actual aspect ratio dependent etch rate to substantially follow the desired aspect ratio dependent etch rate.

11. The apparatus of claim 10 wherein the interferometer comprises:

an optical fiber coupled between a light source, a lens coupled to the light source, and a detector.

12. The apparatus of claim 10 wherein the etch rate processing routine is capable of executing the step of:

comparing the actual aspect ratio dependent etch rate to a desired aspect ratio dependent etch rate to determine an etch rate error.

13. An apparatus according to claim 12 wherein the controller is adapted to either increment a process parameter which lowers the aspect ratio dependent etch rate or decrement a process parameter that increases the aspect ratio dependent etch rate when the actual aspect ratio dependent etch rate is greater than the desired aspect ratio dependent etch rate.

14. An apparatus according to claim 12 wherein the controller is adapted to either increment a process parameter which increases the aspect ratio dependent etch rate or decrement a process parameter that lowers the aspect ratio dependent etch rate when the actual aspect ratio dependent etch rate is less than the desired aspect ratio dependent etch rate.

15. An apparatus according to claim 10 wherein the controller is adapted to maintain aspect ratio dependent the etch rate at a constant etch rate.

16. A wafer processing system comprising the apparatus of claim 10.

17. An apparatus for etching a substrate, the apparatus comprising:

a chamber comprising a pedestal capable of supporting a substrate;

a reactive gas source for delivering a reactive gas to the chamber and an excitation source capable of energizing the reactive gas to etch the substrate;

an interferometer capable of generating a signal indicative of an actual aspect ratio dependent etch rate of the features being etched on the substrate; and

a controller coupled to the interferometer, the controller being adapted to vary one or more process parameters in response to the signal, wherein the controller comprises a memory and an etch rate processing routine to control the actual aspect ratio dependent etch rate, the etch rate processing routine capable of executing the steps of;

retrieving a predetermined etch rate schedule from the memory of the controller, the predetermined etch rate schedule comprising a function of desired aspect ratio dependent etch rate over time;

comparing the actual aspect ratio dependent etch rate to the desired aspect ratio dependent etch rate in the predetermined etch rate schedule that is stored in a memory of the controller; and

varying one or more process parameters of the wafer processing system to change the actual aspect ratio dependent etch rate occurring in the chamber to substantially follow the desired aspect ratio dependent etch rate.

18. An apparatus for etching a substrate, the apparatus comprising:

a chamber comprising a pedestal capable of supporting a substrate;

a reactive gas source for delivering a reactive gas to the chamber and an excitation source capable of energizing the reactive gas to etch the substrate;

an interferometer to monitor features being etched in the substrate and generate a signal indicative of an actual aspect ratio dependent etch rate of the features being etched on the substrate; and

a controller coupled to the interferometer, the controller comprising a memory and an etch rate processing routine capable of;

receiving the signal from the interferometer;

evaluating the signal to determine the actual aspect ratio dependent etch rate;

during the processing of a first substrate, monitoring the actual aspect ratio dependent etch rate to generate an actual aspect ratio dependent etch rate profile and storing the actual aspect ratio dependent etch rate profile in the memory of the controller;

retrieving a desired aspect ratio dependent etch rate profile from the memory of the controller;

comparing the actual aspect ratio dependent etch rate profile to the desired aspect ratio dependent etch rate profile to generate an etch rate error; and

during the processing of a second substrate, varying one or more process parameters of the wafer processing system in relation to the etch rate error.

19. An apparatus for etching a substrate, the apparatus comprising:

a chamber comprising a pedestal capable of supporting a substrate;

a reactive gas source for delivering a reactive gas to the chamber and an excitation source capable of energizing the reactive gas to etch the substrate;

an interferometer to monitor features being etched in the substrate and generate a signal indicative of an actual etch rate of the features being etched on the substrate; and

a controller coupled to the interferometer, the controller comprising a memory and an etch rate processing routine capable of;

receiving the signal from the interferometer;

evaluating the signal to determine a rate of change of the actual etch rate;

comparing the rate of change of the actual etch rate to a desirable rate of change of an etch rate; and

varying one or more process parameters to change the rate of change of the actual etch rate of the features being etched in the substrate.

20. An apparatus according to claim 19 wherein the controller comprises an etch rate processing routine capable of measuring a rate of change of the actual etch rate that is dependent on the aspect ratio of the features being etched on the substrate.

21. An apparatus according to claim 19 wherein the controller comprises an etch rate processing routine capable of varying one or more process pararmeters to change the rate of change of the actual etch rate to substantially follow the desired rate of change of the etch rate.