Method and apparatus for contactless real-time in-situ monitoring of a chemical etching process

• US 5,456,788 A
• Filed: 03/31/1995
• Issued: 10/10/1995
• Est. Priority Date: 06/30/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Barbee, Steven G., Datta, Madhav, Li, Leping, Shenoy, Ravindra V., Ratzlaff, Eugene H., Heinz, Tony F.
• Primary Examiner(s): Breneman, R. Bruce
• Assistant Examiner(s): CHANG, JONI YUK YING
• Application Number:
  US08/414,404
• Time in Patent Office: 193 Days
• Field of Search: 156/626, 156/627, 156/345, 156/637, 156/639, 156/638, 156/642, 156/635
• US Class Current: 156/345.16
• CPC Class Codes: H01L 21/32135 by vapour etching only

Abstract

A contactless method and apparatus for in-situ chemical etch monitoring of an etching process during etching of a workpiece with a wet chemical etchant are disclosed. The method comprises steps of providing a base member having a reference surface; releasably securing the workpiece to the base member; providing at least two sensors disposed on the base member to be proximate to but not in contact with the outer perimeter of the workpiece surface; and monitoring an electrical characteristic between said at least two sensors, wherein a prescribed change in the electrical characteristic is indicative of a prescribed condition of the etching process.

Claims

1. A contactless in-situ chemical etch monitor for providing an indication of a prescribed condition of an etching process during etching of a workpiece with a wet chemical etchant, the workpiece characterized by a workpiece surface with side edge portions along an outer perimeter thereof, said monitor comprising:

a) a base member having a reference surface;

b) means for releasably securing the workpiece to said base member, wherein the workpiece surface is substantially flush with the reference surface;

c) at least two sensors disposed on said base member to be proximate to but not in contact with the outer perimeter of the workpiece surface, said at least two sensors further being substantially flush with the reference surface and positioned on opposite side edge portions of the workpiece surface; and

d) means for monitoring an electrical characteristic between said at least two sensors, wherein a prescribed change in the electrical characteristic is indicative of the prescribed condition of the etching process.

2. The monitor of claim 1, wherein:

said base member further includes a recess formed in the reference surface thereof, the recess being of a prescribed dimension for receiving the workpiece therein; and

said means for releasably securing the workpiece to said base member comprises a prescribed vacuum source, the vacuum source for releasably securing the workpiece in the recess.

3. The monitor of claim 1, wherein the at least two sensors comprise chemically inert conductive wires imbedded in the reference surface of said base member, the inert wires having respective exposed surfaces thereof, the exposed surfaces being in substantially the same plane as that of the workpiece surface.

4. The monitor of claim 1, wherein the at least two sensors comprise two sensors.

5. The monitor of claim 1, wherein the monitoring means comprises an impedance monitor and further wherein the prescribed change comprises a prescribed change in impedance.

6. An etch station having contactless in-situ control of an etching process during etching of a workpiece with a wet chemical etchant, the workpiece characterized by a workpiece surface with side edge portions along an outer perimeter thereof, said etch station comprising:

a) a base member having a reference surface;

b) means for releasably securing the workpiece to said base member, wherein the workpiece surface is substantially flush with the reference surface;

c) at least two sensors disposed on said base member to be proximate to but not in contact with the outer perimeter of the workpiece surface, said at least two sensors further being substantially flush with the reference surface and positioned on opposite side edge portions of the workpiece surface;

d) means for monitoring an electrical characteristic between said at least two sensors, wherein a prescribed change in the electrical characteristic is indicative of a prescribed condition of the etching process; and

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

7. The etch station of claim 6, wherein:

said base member further includes a recess formed in the reference surface thereof, the recess being of a prescribed dimension for receiving the workpiece therein; and

said means for releasably securing the workpiece to said base member comprises a prescribed vacuum source, the vacuum source for releasably securing the workpiece in the recess.

8. The etch station of claim 6, wherein the at least two sensors comprise chemically inert conductive wires imbedded in the reference surface of said base member, the inert wires having respective exposed surfaces thereof, the exposed surfaces being in substantially the same plane as that of the workpiece surface.

9. The etch station of claim 6, wherein the at least two sensors comprise two sensors.

10. The etch station of claim 6, wherein the monitoring means comprises an impedance monitor and further wherein the prescribed change comprises a prescribed change in impedance.