Browse Prior Art Database

Photoconductive Switch

IP.com Disclosure Number: IPCOM000062488D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Brady, MJ: AUTHOR [+3]

Abstract

A fast photoconductive switch useful as a source of pulses in semiconductor testing is constructed using a device quality layer over an insulator layer on a substrate. The device is constructed using single crystal silicon (100) that is masked using a heavy metal with high temperature properties, i.e., tungsten. This heavy metal mask allows for selective implantation within the crystal and is capable of high temperature annealing (1200ŒC) to generate a buried dielectric of either silicon dioxide or silicon nitride, as illustrated in Fig. 1. The device may be constructed on the kerf of a wafer. The tungsten metal is removed following annealing, and the silicon wafer is then processed further to place circuitry elsewhere on the wafer.

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Photoconductive Switch

A fast photoconductive switch useful as a source of pulses in semiconductor testing is constructed using a device quality layer over an insulator layer on a substrate. The device is constructed using single crystal silicon (100) that is masked using a heavy metal with high temperature properties, i.e., tungsten. This heavy metal mask allows for selective implantation within the crystal and is capable of high temperature annealing (1200OEC) to generate a buried dielectric of either silicon dioxide or silicon nitride, as illustrated in Fig. 1. The device may be constructed on the kerf of a wafer. The tungsten metal is removed following annealing, and the silicon wafer is then processed further to place circuitry elsewhere on the wafer. High speed photoconductive switches for fast electrical pulse generation and detection are fabricated over the buried insulator regions by doping these regions heavily to shorten the carrier lifetime and running electrical leads to the regions, leaving small gaps to be shorted by light pulses. The switching gaps can be narrow and well controlled in depth to provide specified increases in conductivity upon radiation from the external laser, as illustrated in Fig. 2. Transmission of optical pulses through the device grade silicon and buried insulator is facilitated by the addition of the following processing steps. The buried insulator of silicon dioxide or silicon nitride is used as an etch stop for preferential...