Selective Epitaxy Using HCl and Germane Etching
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Solution Overview
Problem
Existing selective epitaxy processes face challenges in achieving a suitable selective window between epitaxial and polycrystalline/amorphous layers at low temperatures (≤600°C), leading to reduced process throughput due to pressure disparities between deposition and etching reactions.
Innovation Solution
A method involving a substrate with monocrystalline and non-monocrystalline surfaces, exposed to a deposition gas followed by an etching gas comprising hydrogen, a halogen, and a Group III, IV, or V element, such as hydrogen chloride and germane, to selectively etch the epitaxial layer at a slower rate than the polycrystalline/amorphous layer, maintaining low processing temperatures and pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If typical etching gases are used at low processing temperatures (≤600°C), then the processing temperature is reduced, but the selective window between epitaxial layer and polycrystalline/amorphous layer becomes unsuitable
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas from typical gases to a specific mixture containing hydrogen halide (HF, HCl, or HBr) and phosphine (PH3) or arsine (AsH3). This parameter change enables the etching process to achieve suitable selectivity at low temperatures (≤600°C) without sacrificing the selective window between epitaxial and polycrystalline/amorphous layers.
2Manufacturing precision
If etching gas mixtures providing suitable selective window are used, then the selective window is improved, but the processing pressure becomes substantially greater than deposition pressure, negatively affecting process throughput
Solution Approach 1:
The patent modifies the etching gas composition to use hydrogen halide and phosphine/arsine mixtures, which provide the necessary etching chemistry at low pressures. This parameter change allows the process to maintain suitable selective windows while operating at pressures comparable to deposition conditions, thereby eliminating the throughput penalty associated with high-pressure etching.
3Productivity
If pressure disparity between deposition and etching reactions is reduced, then process throughput is improved, but achieving suitable selective window at low temperatures becomes more difficult
Solution Approach 1:
The patent changes the chemical parameters of the etching gas to a hydrogen halide-phosphine/arsine mixture, which provides enhanced etching reactivity at low pressures and temperatures. This parameter change enables the process to achieve both high throughput (by maintaining low pressure) and high selectivity (by achieving suitable selective window at low temperatures) simultaneously.
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 provides a suitable selective window between epitaxial and polycrystalline/amorphous layers at low temperatures, enhancing process throughput and reducing gas usage while maintaining desired etch selectivity and layer quality.
Implementation Method 1
exposing the substrate to a deposition gas to deposit a layer on the first and second surfaces, the layer comprising a first portion deposited on the first surfaces and a second portion deposited on the second surfaces
Implementation Method 2
exposing the substrate to an etching gas comprising a first gas comprising hydrogen and a halogen and a second gas comprising at least one of a Group III, IV, or V element to selectively etch the first portion of the layer at a slower rate than the second portion of the layer
Data Source
AI summary
Methods for selectively depositing an epitaxial layer are provided herein. In some embodiments, providing a substrate having a monocrystalline first surface and a non-monocrystalline second surface; exposing the substrate to a deposition gas to deposit a layer on the first and second surfaces, the layer comprising a first portion deposited on the first surfaces and a second portion deposited on the second surfaces; and exposing the substrate to an etching gas comprising a first gas comprising hydrogen and a halogen and a second gas comprising at least one of a Group III, IV, or V element to selectively etch the first portion of the layer at a slower rate than the second portion of the layer. In some embodiments, the etching gas comprises hydrogen chloride (HCl) and germane (GeH4).