GB2210062A

GB2210062A - Chemical vapour deposition apparatus incorporating demountable filter

Info

Publication number: GB2210062A
Application number: GB8722081A
Authority: GB
Inventors: Edward John Thrush; Joseph Mark Trigg
Original assignee: STC PLC
Current assignee: STC PLC
Priority date: 1987-09-19
Filing date: 1987-09-19
Publication date: 1989-06-01
Also published as: GB8722081D0

Abstract

An apparatus for the chemical vapour deposition of metal/phosphorus semiconductor alloys is provided with a demountable filter 20 for the removal and subsequent disposal of excess, highly pyrophoric, white phosphorus. Filter 20 comprises a stainless steel cartridge packed with activated charcoal 21. The cartridge can be removed under nitrogen without the risk of fire and the contents rendered safe by a controlled burn-off procedure or by immersion in water. <IMAGE>

Description

SEMICONDUCTOR DEPOSITION APPARATUS This invention relates to apparatus for the MOCVD deposition (metal - organic chemical vapour deposition) of alloy semiconductors and in particular to a filter construction for the removal of reaction products in such apparatus.

The MOCVD growth of semiconductor metal/phosphorus alloys, particularly Indium Phosphide (InP)involves a number of problems. The most difficult problem is a considerable fire risk arising from the highly pyrophoric nature of the yellow phophorus byproduct. To minimise the risk, conventional deposition systems require cumbersome arrangements of air locks.

This results in difficulties in wafer handling and relatively low through put.

The object of the invention is to minimise or to overcome this disadvantage.

According to the invention there is provided an apparatus for the deposition of metal/phophorus semiconductor alloys, the apparatus including a demountable cartridge containing an absorbent material whereby, in use, phosphorus generated as a byproduct from the deposition process may be concentrated.

An embodiment of the invention will now be described with reference to the accompanying drawing in which the single figure is a schematic cross-sectional view of a MOCVD apparatus provided with a demountable cartridge filter.

Referring to the drawing, the apparatus includes a reaction chamber 11 having an inner chamber or work tube 12 in which a susceptor 13 is mounted for receiving a substrate workpiece 14. The work tube 12 has a demoutable section 12a. Hydrogen is supplied to the outer chamber 11 via inlet 15 and a mixture of Hydrogen and reactants is supplied to the inner chamber 12 via inlet tube 16. Radio frequency heating of the susceptor and workpiece is supplied via coil 17.

The system incorporates a removable stainless steel filter cartridge, generally indicated as 20, packed with activated charcoal 21. Unlike previous pipeline mounted charcoal filter assemblies there are no exposed internal surfaces between the cartridge and the removable worktube 12a to be contaminated. The charcoal is held in place by two stainless steel gauzes 22, 23 which are compressed by threaded pressure ring 24 and a set of Bellville washers (not shown). An adapter plate 25 provided with a cut-out to match the worktube 12a is used to couple the tube to the cartridge. As the demoutable section 12a of the worktube and the entire cartridge assembly can be changed om a run-to-run basis, no significant phosphorus contamination is retain between runs and the reactor is returned to a standard condition at the start of each run. The cartridge filter has been found to be extremely effective proventing the passage of phosphorus byproducts into the exhaust line 26 whilst imposing no perceptible increase in back pressure even after process runs of up to six hours in duration have been carried out. The cartridge can be removed under a Nitrogen ambient without the risk of fire and the contents rendered safe either by a controlled burn-off procedure effected by passing a Nitrogen/Oxygen mixture through it, or by immersion in water. The cartridge can then be dismantled and cleaned in Nitric acid prior to re-packing with a fresh charcoal charge.

Claims

CLAIMS.

1. An apparatus for the deposition of metal/phophorus semiconductor alloys, the apparatus including a demountable cartridge containing an absorbent material whereby, in use, phosphorus generated as a byproduct from the deposition process may be concentrated.

2. An apparatus for the deposition of metal/phosphorus semiconductor alloys, the apparatus including a reaction chamber wherein, in use, chemical vapour deposition of volatile metal and phosphorus compounds is effected, and a demountable filter assembly in communication with said reaction chamber whereby excess phosphorus is removed therefrom, and wherein said filter comprises a body of activated charcoal disposed in a housing detachable from the reaction chamber and retained in said housing between first and second gauze members.

3. An apparatus for the deposition of metal/phosphorus semiconductor alloys substantially as described herein with reference to and as shown in the accompanying drawing.