SOI Wafer Defect Removal via Chemical Etching
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Solution Overview
Problem
Current methods for manufacturing thin SOI wafers with ion implantation peeling methods result in ion-implanted defect layers and surface roughness issues, making it difficult to achieve in-plane uniformity and increasing manufacturing costs and complexity.
Innovation Solution
Immersion of post-peeling SOI wafers in an aqueous ammonia-hydrogen peroxide solution to etch and remove the damaged layer, followed by annealing or CMP polishing to achieve uniformity and reduce surface roughness, allowing for lower temperature and shorter heat treatment times, and batch processing for cost reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion implantation peeling method is used to manufacture thin SOI wafers, then film transfer is achieved, but ion-implanted defect layers and surface roughness are introduced
Solution Approach 1:
The patent extracts and removes the harmful ion-implanted defect layer through chemical etching using aqueous ammonia-hydrogen peroxide solution. The etching process selectively removes the damaged amorphous silicon layer while preserving the underlying crystalline silicon, thereby eliminating the defect layer and smoothing the surface without compromising the film transfer quality.
Solution Approach 2:
The patent changes the chemical parameters by using a specific aqueous ammonia-hydrogen peroxide solution composition and controlling etching conditions (temperature, time, concentration) to selectively remove the ion-implanted defect layer. This parameter control enables precise removal of damaged material while maintaining the integrity of the transferred film.
2Object-affected harmful factors
If polishing is performed to remove ion-implanted defect layer, then surface is smoothed, but in-plane uniformity in thickness is compromised
Solution Approach 1:
The patent replaces the mechanical polishing process with a chemical etching process using aqueous ammonia-hydrogen peroxide solution. This chemical approach provides more uniform material removal across the wafer surface, achieving surface smoothing while maintaining better in-plane thickness uniformity compared to mechanical polishing methods.
3Stability of the object's composition
If high temperature heat treatment is applied to recover crystallinity, then damaged layer is repaired, but metal contamination and warpage increase
Solution Approach 1:
The patent reduces the heat treatment temperature and optimizes treatment parameters to achieve crystallinity recovery with minimal contamination and warpage. By carefully controlling temperature, time, and atmosphere conditions, the patent recovers the crystalline structure while minimizing adverse effects.
Solution Approach 2:
The patent uses hydrogen or nitrogen atmosphere during heat treatment to prevent metal contamination, creating a clean environment that avoids introducing harmful contaminants while still achieving the desired crystallinity recovery.
4Object-affected harmful factors
If hydrogen gas etching is used to smooth surface, then asperity is eliminated, but thickness uniformity deteriorates
Solution Approach 1:
The patent uses a composite chemical system of aqueous ammonia and hydrogen peroxide instead of pure hydrogen gas. This composite etchant provides controlled, uniform etching that removes surface asperities while maintaining thickness uniformity through synergistic chemical action.
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
The method ensures in-plane thickness uniformity, reduces metal contamination and warpage, and enhances throughput by effectively removing ion-implanted defects and smoothing the surface, while allowing the use of low-melting-point materials as handle wafers.
Implementation Method 1
immersing the post-peeling SOI wafer in an aqueous ammonia-hydrogen peroxide solution and etching the post-peeling SOI wafer
Implementation Method 2
the crystallinity of a damaged layer is recovered by a high temperature heat treatment
Implementation Method 3
the surface is subjected to polishing by several tens of nm, called 'touch polishing'
Data Source
Figure 1(a)~1(d)
Figure 2(a)~2(b)
Figure 3~4
AI summary
Provided is a method for manufacturing an SOI wafer, which is capable of: efficiently removing an ion-implanted defect layer existing in an ion implanted layer in the vicinity of a peeled surface peeled by an ion implantation peeling method; ensuring the in-plane uniformity of a substrate; and also achieving cost reduction and higher throughput. The method for manufacturing an SOI wafer comprises at least the steps of: bonding a silicon wafer with or without an oxide film onto a handle wafer to prepare a bonded substrate, wherein the silicon wafer has an ion implanted layer formed by implanting hydrogen ions and/or rare gas ions into the silicon wafer; peeling the silicon wafer along the ion implanted layer, thereby transferring the silicon wafer onto the handle wafer to produce a post-peeling SOI wafer; immersing the post-peeling SOI wafer in an aqueous ammonia-hydrogen peroxide solution; and performing a heat treatment at a temperature of 900°C or higher on the immersed post-peeling SOI wafer, and/or polishing a silicon film layer of the immersed post-peeling SOI wafer, through CMP polishing by 10 to 50 nm.