Low-Temperature Silicon Epitaxy via PECVD Gas Dilution
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Solution Overview
Problem
Conventional selective epitaxial growth methods for silicon require high temperatures above 600°C, limiting their applications and failing to achieve selective growth on predetermined areas, especially where crystalline silicon is exposed.
Innovation Solution
A low-temperature epitaxial growth process using plasma enhanced chemical vapor deposition (PECVD) with a hydrogen dilution ratio of [H2]/[SiH4] less than 1000, allowing silicon deposition at temperatures below 500°C, and subsequent plasma etching to achieve selective epitaxial growth on exposed areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional high temperature processing (>600°C) is used for selective epitaxial growth of silicon, then epitaxial growth can be achieved, but the process temperature is too high which limits device integration and causes excessive thermal budget
Solution Approach 1:
The patent changes the temperature parameter from conventional >600°C to low temperature <500°C range, and adjusts the gas composition parameter by using silane (SiH4) as source gas with specific flow rates. This parameter change enables epitaxial growth to occur at lower temperatures while maintaining growth quality, thereby resolving the contradiction between growth quality and processing temperature.
Solution Approach 2:
The patent employs a composite approach by combining silane source gas with oxygen-containing gas (such as O2, N2O, or air) in a specific ratio. This gas mixture creates a chemical environment that enables low-temperature epitaxial growth by facilitating silicon deposition through a different mechanism than conventional high-temperature processes, thus resolving the temperature-quality contradiction.
2Manufacturing precision
If conventional high temperature deposition is used, then silicon can be deposited, but selective growth on predetermined areas (where c-Si is exposed) cannot be achieved
Solution Approach 1:
The patent changes the temperature parameter to below 500°C and adjusts the gas composition ratio (silane to oxygen-containing gas ratio between 0.01 to 10). These parameter changes enable the deposition process to be selective to crystalline silicon surfaces, as the low-temperature process with specific gas composition preferentially deposits silicon on c-Si areas while avoiding amorphous regions, thus achieving manufacturing precision without requiring high temperature.
3Manufacturing precision
If low temperature deposition (<500°C) is used with high dilution gas ratio, then selective epitaxial growth can be achieved, but the deposition rate becomes too slow for practical manufacturing
Solution Approach 1:
The patent optimizes the gas composition parameter by using silane as source gas and controlling the silane to oxygen-containing gas ratio between 0.01 to 10, along with adjusting absolute flow rates. This parameter optimization achieves a balance where sufficient deposition rate is maintained while preserving selective growth capability at low temperatures, resolving the contradiction between selectivity and productivity.
Solution Approach 2:
The patent employs periodic alternation between deposition steps and etching steps in a cyclic manner. During deposition, silicon is deposited on exposed c-Si areas; during etching, non-selectively deposited silicon on insulator surfaces is removed. This periodic action enhances overall productivity by allowing faster deposition rates while maintaining selectivity through the etching cycle, effectively resolving the deposition rate limitation.
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
Enables high dopant activation and selective epitaxial growth of silicon at low temperatures, suitable for applications like 3D integration and raised source/drain regions, with improved silicon quality and reduced defects.
Implementation Method 1
Silicon is epitaxially deposited on the substrate material in a low temperature process wherein a deposition temperature is less than 500 degrees Celsius
Implementation Method 2
A low-temperature epitaxial growth process using plasma enhanced chemical vapor deposition (PECVD)
Implementation Method 3
A source gas is diluted with a dilution gas with a gas ratio of dilution gas to source gas of less than 1000
Implementation Method 4
etching the non-epitaxial silicon using a plasma to further epitaxial deposition of silicon over the exposed areas
Data Source
AI summary
An epitaxy method includes providing an exposed crystalline region of a substrate material. Silicon is epitaxially deposited on the substrate material in a low temperature process wherein a deposition temperature is less than 500 degrees Celsius. A source gas is diluted with a dilution gas with a gas ratio of dilution gas to source gas of less than 1000.