AVS 45th International Symposium
    Manufacturing Science and Technology Group Thursday Sessions
       Session MS-ThM

Paper MS-ThM4
Advances in Broadband RF Sensing for Real-time Control of Plasma-Based Semiconductor Processing

Thursday, November 5, 1998, 9:20 am, Room 317

Session: Sensors and Support Technology
Presenter: C. Garvin, The University of Michigan
Authors: C. Garvin, The University of Michigan
D.S. Grimard, The University of Michigan
J.W. Grizzle, The University of Michigan
Correspondent: Click to Email
Ever shrinking geometries are putting heavy pressure on sensor systems to provide adequate process knowledge for control and diagnostics. Plasma processing specialists in industry and academia have recognized that a substantial amount of information about the plasma state should be contained in the RF signal (13.56 MHz) and its harmonics. On the surface, making measurements for control purposes should be straightforward, and the real work should lie in making the connections (mathematical models) between measurements and key plasma quantities. Unfortunately, this is not the case. Work reported in this area from major University and Government research facilities, as well both US and Japanese chip manufacturers, has shown disappointing results and revealed that the RF sensing problem itself is non-trivial. An approach which has shown promise is `broadband sensing', a novel sening method based on the Resonance Probe used in ionospheric physics. The goal of the broad band RF work is to create a diagnostic with much greater signal to noise ratio, and much higher sensitivity to the plasma state and its environment than standard RF sensing. The idea is to scan the plasma with a very low wattage, broad band RF signal from 100 MHz to 1 GHz, measuring the reflected signal. In a typical scan, the large amount of data taken over a wide range of frequencies provides redundancy and enhances the signal to noise ratio of the sensor. Preliminary work has shown this sensor to have favorable performance when compared to standard RF sensing. We will present novel results of a non-intrusive implementation of the sensor.