Pre-coated silicon fixtures used in a high temperature process

Abstract

A silicon-based wafer support tower particularly useful for batch-mode thermal chemical vapor deposition and other high-temperature processes, especially reflow of silicate glass at above 1200° C. The surfaces of the silicon tower are bead blasted to introduce sub-surface damage, which produces pits and cracks in the surface, which anchor subsequently deposited layer of, for example, silicon nitride, thereby inhibiting peeling of the nitride film. Wafer support portions of the tower are preferably composed of virgin polysilicon. The invention can be applied to other silicon parts in a deposition or other substrate processing reactor, such as tubular sleeves and reactor walls. Tubular silicon members are advantageously formed by extrusion from a silicon melt or by fixing together silicon staves in a barrel shape. The tower parts are preferably pre-coated with silicon nitride or polysilicon prior to chemical vapor deposition of these materials, or with silicon nitride prior to reflow of silica.

Description

[0001] This application is a continuation in part of Ser. No. 09 / 860,392, filed May 18, 2001.[0002] 1. Field of the Invention[0003] The invention relates generally to semiconductor processing. In particular, the invention relates to wafer support fixtures and reactor tubes used in batch-mode processing such as chemical vapor deposition and high temperature annealing.[0004] 2. Background Art[0005] The fabrication of silicon integrated circuits typically involves one or more steps of chemical vapor deposition (CVD). Many advanced deposition processes use plasma enhanced CVD to activate the chemical reaction resulting in the deposition of the film from a precursor gas. The plasma process allows low temperature deposition. On the other hand, thermal CVD is performed at elevated temperatures to thermally activate the chemical reaction resulting in the deposition of the film from a precursor gas. The temperatures associated with thermal CVD tend to be much higher than those for plasma enh...

AI Technical Summary

Problems solved by technology

However, thermal CVD tends to coat all surfaces exposed in the furnace.

However, as the feature sizes on integrated circuits has decreased to 0.18 .mu.m and even smaller, quartz support towers have nonetheless experienced substantial problems because of their tendency to produce particles.

These particulates fall on the wafer and can significantly reduce the yield of operable integrated circuit dies obtained from the wafer.

However, after some number of runs, the number of particles greatly increases to a totally unacceptable level.

It is believed that the origin of the problem is that the silicon nitride is also depositing on the quartz tower.

Although quartz towers are relatively inexpensive, such short life greatly increases the cost of ownership (COO) when measured per wafer.

Also, the necessity of changing out towers and cleaning towers complicates the work flow and reduces productivity.

Both factors reduce the yield of operable dice obtained from the wafers.

Quartz tubes are also often replaced after a finite number of batches although the problem being addressed is often fracturing of the quartz tube.

However, the CVD silicon carbide film is fragile, and a single pin hole through the film ruins the protective coating resulting in the necessity that the tower be scrapped.

Entire towers of CVD silicon carbide can be made, but they are very expensive.

Their tower fabrication is believed to still be weak.

Further, when silicon towers are used to support wafer preformed with a silica glass that requires reflowing at high temperature, the wafers have been observed to stick to the tower after reflow.

Forcefully removing the stuck wafer may result in the tower becoming chipped.

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