Silicon Wafer Defect Removal via Rapid Thermal Processing
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Solution Overview
Problem
Existing methods for producing silicon wafers using the Czochralski method result in crystal defects such as crystal-originated particles (COPs) and dislocation clusters, which degrade semiconductor device characteristics, and current defect removal techniques are costly and inefficient, especially in reducing latent defects like plate-like oxygen precipitates and oxygen precipitate nuclei.
Innovation Solution
A method involving the growth of single crystal silicon ingots by the Czochralski method with controlled V/G ratio, followed by rapid thermal processing (RTP) at 1,250°C or higher in an oxidizing atmosphere to reduce or eliminate grown-in defects, including silicon oxides, and subsequent removal of these defects from the wafer surface layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a faster pulling rate is employed to increase V/G for improving productivity, then productivity is improved, but crystal defects (COPs) are introduced into the single crystal
Solution Approach 1:
The patent applies preliminary action by performing rapid thermal processing (RTP) in an oxidizing atmosphere before final wafer fabrication. This pre-treatment oxidizes and removes COPs and other crystal defects that were inevitably introduced during high-speed single crystal growth, thereby resolving the contradiction between high pulling rate and low defect density
Solution Approach 2:
The patent converts the harmful effect of COPs introduced during fast growth into a beneficial process by using controlled oxidation. The RTP treatment transforms COPs into oxidized regions that can be selectively removed through chemical etching, turning the unavoidable growth defects into removable byproducts that improve final wafer quality
2Reliability
If conventional heat treatment is used to remove COPs, then COPs are reduced, but production cost increases and latent defects remain
Solution Approach 1:
The patent fundamentally changes the parameters of heat treatment by using rapid thermal processing (RTP) at very high temperatures (1000-1400°C) for extremely short durations (1-60 seconds). This parameter change enables effective COP removal through oxidation while minimizing wafer deformation and reducing production costs compared to conventional slow heat treatment methods
Solution Approach 2:
The patent applies the skipping principle by using extremely short RTP treatment times (1-60 seconds) to achieve COP removal. This rushes through the heat treatment process, preventing excessive oxygen diffusion that would cause wafer deformation while still effectively oxidizing and removing COPs, thereby reducing production costs and improving manufacturing efficiency
3Reliability
If high temperature heat treatment is applied to remove defects, then defect density is reduced, but wafer deformation occurs
Solution Approach 1:
The patent applies skipping by using extremely short RTP treatment times (1-60 seconds) at very high temperatures. This rapid processing allows the wafer to reach high temperatures for defect removal and then quickly cool down, preventing excessive thermal stress and deformation while still achieving effective COP and latent defect removal
Solution Approach 2:
The patent uses periodic action through the rapid heating and cooling cycles of RTP treatment. The wafer is rapidly heated to high temperature for defect removal, then quickly cooled, creating a controlled thermal cycle that achieves defect reduction while minimizing cumulative thermal stress and wafer deformation
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 produces silicon wafers with significantly reduced crystal defects, improving mechanical strength and device characteristics by effectively vanishing or reducing latent defects, thereby enhancing the quality and yield of semiconductor devices.
Implementation Method 1
a single crystal silicon ingot which is grown by the Czochralski method
Implementation Method 2
subjecting the silicon wafer to an RTP at 1,250° C. or more for 10 seconds or more in an oxidizing atmosphere
Implementation Method 3
rapid thermal processing (RTP) at 1,250°C or higher
Data Source
AI summary
It is possible to provide a silicon wafer that as well as being free of COPs and dislocation clusters, has defects (grown-in defects including silicon oxides), which are not overt in an as-grown state, such as OSF nuclei and oxygen precipitate nuclei existing in the PV region, to be vanished or reduced, by adopting a method for producing a silicon wafer, the method comprising the steps of: growing a single crystal silicon ingot by the Czochralski method; cutting a silicon wafer out of the ingot; subjecting the wafer to an RTP at 1,250° C. or more for 10 seconds or more in an oxidizing atmosphere; and removing a grown-in defect region including silicon oxides in the vicinity of wafer surface layer after the RTP.