Real time measurement of etch rate during a chemical etching process

• US 5,500,073 A
• Filed: 05/08/1995
• Issued: 03/19/1996
• Est. Priority Date: 06/30/1994
• Status: Expired due to Fees

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Barbee, Steven G., Hsiao, Yiping, Wong, Justin W., Li, Leping, Ratzlaff, Eugene H., Heinz, Tony F.
• Primary Examiner(s): POWELL, WILLIAM A
• Application Number:
  US08/435,059
• Time in Patent Office: 316 Days
• Field of Search: 156/345, 156/627.1, 156/345 M, 156/345 C, 156/345 L, 216/84, 216/86, 324/671
• US Class Current: 156/345.16
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: G01N 2291/0231 Composite or layered materials
• CPC Class Codes: G01N 2291/2694 Wings or other aircraft parts
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 29/42 by frequency filtering or by tuning to resonant frequency
• CPC Class Codes: G03F 7/3028 characterised by means for on-wafer monitoring of the processing
• 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
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A contactless method and apparatus for real-time in-situ monitoring of a chemical etching process during etching of at least one wafer in a wet chemical etchant bath are disclosed. The method comprises the steps of providing two conductive electrodes in the wet chemical bath, wherein the two electrodes are proximate to but not in contact with a wafer; monitoring an electrical characteristic between the two electrodes as a function of time in the etchant bath of the at least one wafer, wherein a prescribed change in the electrical characteristic is indicative of a prescribed condition of the etching process; and recording a plurality of values of the electrical characteristic as a function of time during etching. From the plurality of recorded values and corresponding times, instantaneous etch rates, average etch rates, and etching end points may be determined. Such a method and the apparatus therefor are particularly useful in a wet chemical etch station.

Claims

1. A contactless real-time in-situ chemical etch monitor for providing an indication of a condition of an etching process during etching of at least one wafer in a wet chemical etchant bath, said monitor comprising:

a) two conductive electrodes;

b) a means for positioning said two conductive electrodes inside the wet chemical etchant bath proximate to but not in contact with the at least one wafer;

c) a means for monitoring an electrical characteristic between the two electrodes as a function of time in the etchant bath of the at least one wafer, wherein a change in the electrical characteristic is indicative of a state of the etching process; and

d) a means for recording a plurality of values of said electrical characteristic as a function of time during etching.

2. The monitor of claim 1, wherein the monitoring means comprises an impedance monitor and further wherein the change in the electrical characteristic comprises a change in impedance.

3. The monitor of claim 2, wherein the monitoring means comprises an impedance monitor and further wherein the change in the electrical characteristic comprises a change in a component of impedance, wherein said component is selected from the group consisting of admittance, reactance, resistance, capacitance, and inductance.

4. The monitor of claim 1, further comprising a means for determining an instantaneous etch rate in real time from at least two of the recorded plurality of values.

5. The monitor of claim 4, further comprising a means for controlling the etching process in response to the instantaneous etch rate, wherein the instantaneous etch rate is determined in real time.

6. The monitor of claim 4, further comprising a means for determining an average etch rate in real time from at least two of the recorded plurality of values.

7. The monitor of claim 6, further comprising a means for controlling the etching process in response to the average etch rate, wherein the average etch rate is determined in real time.

8. The monitor of claim 1, further comprising a means for determining an etching end point in real time from at least two of the recorded plurality of values.

9. The monitor of claim 8, further comprising a means for controlling the etching process in response to the determined etching end point, wherein the end point is determined in real time.

10. An etch station having contactless real-time in-situ control of an etching process during etching of at least one wafer in a wet chemical etchant bath, said etch station comprising:

a) two conductive electrodes;

b) a means for positioning said two conductive electrodes inside the wet chemical etchant bath proximate to but not in contact with the at least one wafer;

c) a means for monitoring an electrical characteristic between the two electrodes as a function of time in the etchant bath of the at least one wafer, wherein a change in the electrical characteristic is indicative of a state of the etching process;

d) a means for recording a plurality of values of said electrical characteristic as a function of time during etching; and

e) a means for controlling the etching process in response to the monitoring of the change in the electrical characteristic.

11. The etch station of claim 10, wherein the monitoring means comprises an impedance monitor and further wherein the change in the electrical characteristic comprises a change in impedance.

12. The etch station of claim 11, wherein the monitoring means comprises an impedance monitor and further wherein the change in the electrical characteristic comprises a change in a component of impedance, wherein said component is selected from the group consisting of admittance, reactance, resistance, capacitance, and inductance.

13. The etch station of claim 10, further comprising a means for determining an instantaneous etch rate in real time from at least two of the recorded plurality of values.

14. The etch station of claim 10, further comprising a means for determining an average etch rate in real time from at least two of the recorded plurality of values.

15. The etch station of claim 10, further comprising a means for determining an etching end point in real time from at least two of the recorded plurality of values.