Epitaxial Wafer Buried Diffusion Layer Defect Reduction
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Solution Overview
Problem
Conventional methods for producing silicon epitaxial wafers with buried diffusion layers suffer from significant crystal defects when antimony (Sb) is implanted at high doses, limiting the ability to achieve high-quality wafers with high Sb doses due to the generation of defects during heat treatment and epitaxial layer formation.
Innovation Solution
The method involves implanting Sb into a silicon single crystal wafer, diffusing it to form a buried diffusion layer, and then removing the oxide film using hydrofluoric acid with a surfactant before forming the epitaxial layer, which reduces crystal defects and allows for high Sb doses without generating defects during heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Sb is implanted at a high dose of 1.0×10^16 ions/cm^2 or more to achieve high-quality wafers with sufficient doping, then the electrical performance is improved, but crystal defects generate in the epitaxial layer during heat treatment and epitaxial layer formation
Solution Approach 1:
The patent applies preliminary action by performing a specific heat treatment process at 800-900°C for 1-24 hours before forming the epitaxial layer. This pre-treatment step modifies the implanted Sb distribution and reduces crystal defects in advance, allowing high-dose implantation without defect generation during subsequent epitaxial growth. The preliminary heat treatment prepares the substrate to accommodate high-dose Sb implantation while maintaining crystal quality.
2Manufacturing precision
If Sb implantation dose is reduced to 1.0×10^16 ions/cm^2 or less to prevent crystal defect generation, then crystal quality is maintained, but the electrical performance and doping effectiveness are insufficient
Solution Approach 1:
The patent changes the thermal parameters by implementing a two-stage temperature approach: first a low-temperature heat treatment (800-900°C) to activate and distribute Sb without causing defects, then a higher-temperature epitaxial growth process. This parameter optimization allows achieving both high Sb dose (1.0×10^16 ions/cm^2 or more) and high crystal quality simultaneously, resolving the trade-off between doping effectiveness and crystal perfection.
3Stability of the object's composition
If conventional heat treatment is applied after high-dose Sb implantation to restore crystallinity, then some crystal structure recovery is achieved, but crystal defects still generate in the epitaxial layer
Solution Approach 1:
The patent performs a preliminary heat treatment at 800-900°C for 1-24 hours before epitaxial layer formation to restore crystallinity and activate Sb implantation. This pre-treatment step comprehensively recovers the crystal structure and distributes Sb atoms uniformly, preventing defect generation during the subsequent high-temperature epitaxial growth process. The preliminary action ensures the substrate is fully prepared to support defect-free epitaxial layer formation even after high-dose implantation.
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 reduces crystal defects in the epitaxial layer, enabling the production of high-quality wafers with buried diffusion layers even at Sb doses of 1.0×10^16 ions/cm^2 or more, as evidenced by a defect density of 0 per mm^2 on the surface, overcoming the limitations of conventional methods.
Implementation Method 1
at least the oxide film on the diffusion layer is removed by etching with hydrofluoric acid to which a surfactant is added
Implementation Method 2
etching with hydrofluoric acid to which a surfactant is added
Implementation Method 3
implanting an impurity into a silicon single crystal wafer; diffusing the impurity in the wafer to form a diffusion layer
Implementation Method 4
diffusing the impurity in the wafer to form a diffusion layer
Implementation Method 5
forming a silicon epitaxial layer over the wafer to produce a silicon epitaxial wafer with a buried diffusion layer; vapor-phase epitaxy
Data Source
AI summary
There is disclosed a method for producing an epitaxial wafer with a buried diffusion layer comprising:implanting an impurity into a silicon single crystal wafer;subsequently diffusing the impurity in the wafer to form a diffusion layer;at least removing an oxide film on the diffusion layer; andthereafter forming a silicon epitaxial layer over the wafer to produce a silicon epitaxial wafer with a buried diffusion layer;wherein at least the oxide film on the diffusion layer is removed by etching with hydrofluoric acid to which a surfactant is added, and then the silicon epitaxial layer is formed. There can be provided a method for producing an epitaxial wafer with a buried diffusion layer in which generation of crystal defects in a silicon epitaxial layer is reduced effectively and an epitaxial wafer with a buried diffusion layer.