Optical monitoring system for III-V wafer processing

• US 6,075,909 A
• Filed: 06/26/1998
• Issued: 06/13/2000
• Est. Priority Date: 06/26/1998
• Status: Expired due to Term

• Current Assignee: Bell Semiconductor, LLC (Hilco Inc. (d/b/a Hilco Global))
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Ressl, Michael G.
• Primary Examiner(s): Ullah, Akm E.
• Application Number:
  US09/105,712
• Time in Patent Office: 718 Days
• Field of Search: 385/72, 385/80, 385/88-90, 385/147, 356/236.7
• US Class Current: 385/14
• CPC Class Codes: G02B 6/12 of the integrated circuit kind electric integrated circuits H01L27/00
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring
• CPC Class Codes: H01L 22/34 Circuits for electrically characterising or monitoring manufacturing processes, e. g. whole test die, wafers filled with test structures, on-board-devices incorporated on each die, process control monitors or pad structures thereof, devices in scribe line switching, multiplexing, gating devices G01R19/25; process control with lithography, e.g. dose control, G03F7/20; structures for alignment control by optical means G03F7/70633

Abstract

An optical monitoring system for III-V integrated circuit wafers utilizes an optical transmitter/receiver assembly formed in the wafer at an early stage in the fabrication process. The optical transmitter is then activated and the optical output signal is monitored during subsequent processing steps, such as ion implantation and layer deposition to assess the quality of the process. In one embodiment, the monitoring system is useful as an endpoint detection process.

Claims

1. An optical monitoring system for a semiconductor wafer, said system comprising

an optical transmitter fabricated within a top surface of semiconductor wafer;

an optical waveguide formed in a surface region of said semiconductor wafer and coupled to said optical transmitter to support the propagation of an optical output signal from said transmitter;

an optical receiver fabricated within said top surface of said semiconductor wafer and coupled to said optical waveguide for receiving the optical output signal from said transmitter; and

a monitoring device coupled to said optical receiver for measuring the output signal and evaluating predetermined process parameters of said semiconductor wafer as a function of the output signal.

2. An optical monitoring system as defined in claim 1 wherein the predetermined process parameters include dopant concentration of said semiconductor wafer and thickness of deposited layers on the top surface of the semiconductor wafer.

3. An optical monitoring system as defined in claim 1 wherein the optical transmitter is biased by an externally applied electrical signal to generate the optical output signal.

4. An optical monitoring system as defined in claim 1 wherein the optical receiver includes a photodiode for converting the received optical signal into an electrical equivalent.

5. An optical monitoring system as defined in claim 1 wherein the optical waveguide is disposed in a arcuate pattern around the edge periphery of the semiconductor wafer.

6. An optical monitoring system as defined in claim 1 wherein the optical waveguide comprises a linear waveguide disposed between the optical transmitter and the optical receiver.

7. An optical monitoring system as defined in claim 1 wherein the optical waveguide comprises a circular waveguide.

8. An optical monitoring system as defined in claim 1 wherein the optical waveguide comprises a plurality of linear sections including a reflector disposed at the intersection between adjacent sections.

9. An optical monitoring system as defined in claim 1 wherein the optical transmitter includes optical pump means for exciting the optical transmitter.

10. An optical monitoring system as defined in claim 1 wherein the optical receiver includes an optical probe for propagating a polarized signal through said semiconductor wafer and monitoring changes in optical polarization state as a function of the physical characteristics of said semiconductor wafer.

11. An optical monitoring system as defined in claim 1 wherein the optical transmitter comprises a plurality of MQW devices.