Amorphous Silicon Film Formation Using Dual Gas Segmentation
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Solution Overview
Problem
Conventional substrate processing methods for forming amorphous silicon films on monocrystalline substrates with insulating films face challenges in maintaining film thickness uniformity while achieving a desired film forming rate, particularly due to the generation of fine crystalline grains at the interface between amorphous silicon and the insulating film.
Innovation Solution
A substrate processing method and apparatus that involves forming first and second amorphous silicon films using different gases, where the first gas is a higher-order gas than the second gas, with the first gas used at a lower process temperature to suppress fine crystalline grain generation and the second gas used at a higher temperature to increase film thickness uniformly, ensuring improved thickness uniformity without reducing the film forming rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a low-temperature process is used to suppress fine crystalline grain generation, then film thickness uniformity is improved, but the film forming rate decreases
Solution Approach 1:
The film formation process is divided into two distinct stages: first forming a thin initial film at low temperature to ensure uniformity and suppress crystalline grain generation, then forming the remaining film thickness at higher temperature to achieve high forming rate. This segmentation allows each stage to optimize for its specific purpose without compromising the other.
Solution Approach 2:
A preliminary thin film is formed at low temperature before the main film formation process. This preliminary film acts as a foundation that prevents fine crystalline grain generation at the interface, enabling subsequent high-temperature processing to proceed without uniformity issues while maintaining high productivity.
2Productivity
If highly reactive gas is used to increase film forming rate, then productivity is improved, but film thickness uniformity deteriorates
Solution Approach 1:
The gas supply process is segmented into two phases: first using a reactive gas to establish rapid film growth, then switching to a less reactive gas to complete the film formation with improved uniformity. This temporal segmentation of gas types allows the system to capture the advantages of both reactive and non-reactive gases.
Solution Approach 2:
The chemical reactivity parameter of the process gas is dynamically changed during the film formation process. By transitioning from a highly reactive gas to a less reactive gas, the system adjusts the deposition kinetics to achieve both high initial growth rate and improved final uniformity, resolving the contradiction between productivity and precision.
3Reliability
If heat treatment is performed for monocrystallization of Si, then crystal quality is improved, but fine crystalline grains grow and make monocrystallization difficult
Solution Approach 1:
A low-temperature film formation step is performed beforehand to create a uniform amorphous silicon layer that prevents fine crystalline grain generation at the interface. This preliminary action counteracts the potential harmful effect of grain growth during subsequent heat treatment, allowing monocrystallization to proceed successfully.
Solution Approach 2:
The interface between the silicon film and insulating film is prepared in advance by forming a uniform thin film at low temperature, which suppresses the nucleation of fine crystalline grains. This preliminary preparation ensures that subsequent heat treatment for monocrystallization can proceed without the complication of grain growth, maintaining composition stability.
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
This approach effectively prevents the deterioration of film thickness uniformity while maintaining a high film forming rate, achieving in-plane film thickness uniformity within ±2% and maintaining a growing rate of up to 6 nm/min, compared to ±5% with previous methods.
Implementation Method 1
forming first amorphous silicon films to a predetermined thickness by heating at least the substrates and supplying first gas
Implementation Method 2
forming first amorphous silicon films to a predetermined thickness by heating at least the substrates and supplying first gas
Data Source
AI summary
There are provided a substrate processing method and apparatus adapted to prevent deterioration of film thickness uniformity while maintaining the film forming rate. The substrate processing method comprises: (a) accommodating a plurality of substrates in a process chamber by carrying and stacking the substrates in the process chamber, (b) forming first amorphous silicon films to a predetermined thickness by heating at least the substrates and supplying first gas, and (c) forming second amorphous silicon films to a predetermined thickness by heating at least the substrates and supplying second gas different from the first gas. The first gas is higher order gas than the second gas.