Stainless Steel Chamber Passivation for Manganese Contamination Control
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Solution Overview
Problem
The challenge in heat treatment processes for semiconductor wafers is metal contamination due to manganese precipitation on the inner surfaces of stainless steel chambers, which can occur despite the corrosion-resistant chromium passive film, especially at damaged joints and welds.
Innovation Solution
A method involving the introduction of an oxidizing gas into the chamber to form a passive film on the stainless steel surfaces, which suppresses manganese precipitation, and a heat treatment apparatus with a gas supply and exhaust system to seal and heat the oxidizing gas for efficient passive film formation, ensuring safety through nitrogen discharge in case of abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stainless steel is used for the chamber inner wall, then corrosion resistance and heat resistance are improved, but manganese precipitation occurs causing metal contamination
Solution Approach 1:
A passive film is formed on the inner surface of the stainless steel chamber before substrate processing by introducing an oxidizing atmosphere and heating to 50-150°C. This preliminary passivation treatment creates a protective chromium oxide layer that prevents manganese precipitation during subsequent high-temperature processing
Solution Approach 2:
The surface chemistry of the stainless steel is changed by controlling the oxidation state through temperature (50-150°C) and oxidizing atmosphere (oxygen concentration 1-100%). This parameter change transforms the surface from a manganese-prone state to a passivated chromium oxide state that resists contamination
2Reliability
If the chamber is heated to form a passive film, then manganese precipitation is suppressed, but processing time increases
Solution Approach 1:
By optimizing the heating temperature range to 50-150°C and controlling oxidizing atmosphere concentration (1-100%), the passive film forms efficiently within a short time period. This parameter optimization balances film quality with processing speed
Solution Approach 2:
The passivation process is designed to proceed continuously without interruption by maintaining stable heating and oxidizing atmosphere conditions, ensuring complete and uniform film formation across the entire chamber surface in minimal time
3Reliability
If oxidizing gas is continuously supplied, then passive film formation is maintained, but gas consumption increases
Solution Approach 1:
Instead of continuous oxidizing gas supply, the system uses periodic or controlled atmosphere maintenance. The passive film, once formed, provides ongoing protection without requiring constant oxidizing gas flow, significantly reducing gas consumption while maintaining film stability
Solution Approach 2:
The formed passive film serves as a self-maintaining protective layer that continues to prevent manganese precipitation without requiring ongoing external intervention or continuous gas supply, making the system self-sustaining after initial formation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The passive film effectively prevents manganese precipitation, reducing metal contamination of substrates and optimizing the process by minimizing oxidizing gas consumption and shortening the formation time of the passive film.
Implementation Method 1
forming a passive film on an inner surface of the chamber by means of the oxidizing gas
Implementation Method 2
a heat treatment apparatus which irradiates a substrate with light to heat the substrate
Data Source
AI summary
A chamber in a heat treatment apparatus is made of stainless steel. After pressure in the chamber is reduced, ozone is introduced into the chamber, and is sealed in the chamber by stopping the supply and exhaust of gas to and from the chamber. The ozone is kept sealed in the chamber for a waiting time period that is not greater than the half-life of ozone. The ozone having an extremely strong oxidizing power acts on an inner surface of the chamber made of stainless steel, whereby an inert passive film is formed on the inner surface. This inert passive film suppresses the precipitation of manganese from the chamber made of stainless steel. This prevents metal contamination of a semiconductor wafer from the chamber even when the semiconductor wafer is subjected to heating treatment in the chamber.