CVD Reactors

Introduction

CVD Reactor Configurations

Tube Reactors

Tube Reactor Overview
Transport in Tube Reactors
Tube Reactor Conclusions

Showerhead Reactor

Showerhead Overview
Flow and Mass Transport
Wafer Heat Transport
Showerhead Conclusions

High Density Plasma Reactor

HDP Deposition Overview
HDP Reactor Design Issues
Transport in HDP Reactors
Wafer Chucks for HDP
HDP Conclusions

Linear Injector Atmospheric Pressure Reactor

APCVD Reactor Overview
Transport in APCVD Reactors
APCVD Reactor Conclusions


CVD Reactor Conclusions


Special topic: Vapor delivery

Bubbler Overview
How Much Goes Out?
Bubbler Problems
Direct Liquid Injection
Vapor Concentration Monitoring

Vapor Concentration Monitoring

Problems with vapor delivery are often sporadic, appearing only for certain parameter settings and resulting in time-varying vapor delivery. It is difficult to diagnose such problems by examining deposition results.

It is possible to use non-invasive techniques to monitor vapor concentration in the gas flow. One method is to measure the speed of sound in the gas. A schematic of the test setup is shown below:




Recall that the velocity of sound is proportional to the square root of (1/M) where M is the molecular mass. Adding heavy vapor molecules slows the sound velocity and thus lengthens the transit time in the cell. Shawn Murphy of ASM Thermal Systems has reported that 1% resolution for TEOS concentration in N₂ is achievable. The availability of real time measurements of vapor concentration is a powerful tool for diagnosing and correcting vapor delivery problems.

A commercial sensor based on this principle, the Piezocon vapor sensor, is available from Veeco (http://www.veeco.com/technologies-and-products/gas-and-vapor-delivery-systems).



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