Time-Resolved and Post-Irradiation Studies of the Interaction of High-Power Pulsed Microwave Radiation with Silicon
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TIME-RESOLVED AND POST-IRRADIATION STUDIES OF THE INTERACTION OF HIGH-POWER PULSED MICROWAVE RADIATION WITH SILICON
R. B. JAMES , P. R. BOLTON , R. A. ALVAREZ , R. E. VALIGA+, and W. H. ýHRISTIE+ **Sandia National Laboratories, Livermore, CA 94550 Lawrence Livermore National Laboratory, Livermore, CA 94550 + Analytical Chemistry Division, Oak Ridge National Lab, Oak Ridge, TN 37831
Abstract We have measured the microwave-induced damage to the near-surface region of silicon for 1.9-ps pulses at a frequency of 2.856 GHz and a pulse power of up to 7.2 MW. Rectangular samples were irradiated in a test section of WR-284 waveguide that was filled with freon to a pressure of 30 psig. Incident, transmitted and reflected powers were monitored with directional couplers and fast diodes. The results of the time-resolved optical measurements show that the onset of surface damage is accompanied by a large increase in the reflected power. Examination of the irradiated surfaces shows that the degree of damage is greatest near the edges of the samples. Using secondary ion mass spectrometry to profile the implanted As, we find that the microwave pulses can melt the near-surface region of the material for pulse powers exceeding a threshold value. Introduction There is considerable interest in the use of directed-energy sources to process electronic materials.[lJ Most of these reports have concentrated on the use of pulsed lasers to appropriately modify the electrical and/or structural properties of the material. The goal of this work is to understand the mechanisms of energy deposition due to high-power pulsed microwaves and to determine if
microwave radiation can be used to process the near-surface re-
gion of silicon. In this paper we present the first results of time-resolved in situ and post-irradiation studies of the interaction of high-power pulsed microwave radiation with ion-implanted silicon. Initial measurements were conducted on silicon due to the large amount of information presently available on the absorption of pulsed laser radiation in this material and because of the technological significance of the material for the fabrication of electronic devices. Experiment The experiments were performed using a modulator and high-power pulsed klystron at the LLNL 100-MeV electron linac. The microwave pulses have a frequency of 2.856 GHz and a maximum peak power of 20 MW. By gating the rf drive, the pulse duration was varied between about 100 ns and 2 Ps. A schematic diagram of the experimental setup is shown in Fig. 1. The output of a highly stable cw master oscillator is gated by a PIN diode that provides a variable-length 500-mW drive pulse to a driver klystron, which in turn produces a 100-2000 ns drive pulse for the high-power klystron. The output pulse from the klystron passes through a high-power circulator, which then feeds into a WR-284 copper waveguide. The waveguide is terminated with an impedancematched, water-cooled load to minimize reflections and ensure that the sample is irradiated by a single-pass, TE0 1 tra
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