Applications of a Continuous Wave Incoherent Light Source (CWILS) to Semiconductor Processing
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APPLICATIONS OF A CONTINUOUS WAVE INCOHERENT LIGHT SOURCE (CWILS) CONDUCTOR PROCESSING
TO SEMI-
H.B. HARRISON, S.T. JOHNSON, B. CORNISH, F.M. ADAMS, K.T. SHORT and J.S. WILLIAMS. J.M.R.C. Faculty of Engineering, Royal Melbourne Institute of Technology, Melbourne, 3000, Australia
ABSTRACT We present results which highlight applications of a continuous wave incoherent light source in the processing of semiconductor devices. In particular, damage removal and activation of ion implanted gallium arsenide is demonstrated for both capless and capped annealing of low dose implants at temperatures of > 8000C for times < 10 s. For gallium arsenide FET applications, we demonstrate that it is possible to simultaneously carry out activation, contacting and interconnection steps by utilizing thermomigration processes which are not available with conventional furnace processing. In silicon we demonstrate that shallow multi layer bipolar structures can be successfully fabricated with anneal cycles that lead to supersaturation effects and negligible diffusion.
INTRODUCTION Rapid bulk heating of semiconductor structures using a continuous wave incoherent light source (CWILS) offers an attractive alternative to both conventional furnace annealing and other more rapid and local forms of transient processing using pulsed lasers, CW lasers and electron beams. For example, the technique potentially offers high throughput for processing of wafers, compatability with other device processing steps and controllable alloying of metals to semiconductors for contacting applications [1]. For the annealing of ion implanted layers in semiconductors, we have already demonstrated that it is a decided advantage to be able to achieve dopant activation at high temperatures (typically 800-1100°C) in a time regime (Z 3-10s) that can prohibit dopant redistribution and often provide supersaturated solid solutions [1]. In this paper, we further explore the applications of CWILS in semiconductor device processing. In particular, we concentrate our attention on i) the thermal processing of ion implanted GaAs and Si, and ii) intriguing thermomigration processes in GaAs which result from a finite temperature gradient across the wafer. ANNEALING DETAILS Details of the CWILS apparatus employed in the present study have been described in detail elsewhere [1]. Basically, radiant light from a 500 W quartz-iodide lamp is focussed to a 2 cm diameter spot onto the front surface of a semiconductor sample by means of an aluminium bowl reflector. The apparatus is mounted in a bell jar to permit annealing in vacuum or under a desired gaseous environment. Mat. Res. Soc. Syrp. Proc. Vol. 13 (1983) @Elsevier Science Publishing Co.,
Inc.
394 Our particular CWILS annealing situation is depicted in Figure 1 and operates in an isothermal mode. Radiant light is absorbed by the front surface of the sample and emitted from the back. The sample is thermally isolated from its surrounds and thus attains thermal equilibrium rapidly, in times of the order of 1-10 s depending on th
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