SOI Wafer Ionization Deposition for Gettering and Resistivity
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Solution Overview
Problem
The existing SOI wafer manufacturing process using thermal oxidization methods results in insufficient gettering ability, non-uniform resistivity distribution, and low productivity due to the disappearance of ion implantation layers and significant resistance variance at the oxide film interface, leading to leak currents and device characteristic deterioration.
Innovation Solution
A process involving ionization deposition of oxide films by accelerating and emitting ionized silicon and oxygen at high temperatures, combined with normal-temperature vacuum bonding to prevent dopant diffusion and maintain the ion implantation layer, ensuring high gettering ability and reduced resistance variance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If thermal oxidization method is used to form oxide film, then oxide film can be formed, but ion implantation layer disappears and gettering ability is lost
Solution Approach 1:
The patent changes the formation method parameter from thermal oxidization to ionization deposition. This parameter change allows oxide film formation without the consumption of silicon from the substrate, thereby preserving the ion implantation layer and maintaining gettering ability while achieving the required oxide film thickness.
Solution Approach 2:
The patent replaces the chemical thermal oxidization process with a physical ionization deposition process. In this process, ionized silicon and oxygen are accelerated and deposited onto the substrate, forming oxide film without consuming silicon from the substrate surface, thus preserving the ion implantation layer.
2Reliability
If thermal oxidization method is used to form thick oxide film, then leak current prevention is improved, but manufacturing time increases to 1 month or more
Solution Approach 1:
The patent replaces the slow thermal oxidization process with ionization deposition, which is a physical process that can rapidly deposit oxide material. This substitution enables thick oxide films (5-10 μm) to be formed in a fraction of the time required by thermal oxidization, dramatically improving productivity while maintaining leak current prevention capability.
Solution Approach 2:
The patent performs preliminary ionization of silicon and oxygen before deposition, creating a ready-to-deposit plasma state. This preliminary preparation allows the oxide film formation to proceed rapidly once the ionized materials are accelerated onto the substrate, reducing the overall manufacturing time compared to waiting for slow thermal oxidation to occur.
3Strength
If bonding thermal processing is used, then substrate bonding is achieved, but dopant diffusion occurs causing resistance variance
Solution Approach 1:
The patent changes the bonding temperature parameter from high temperature (approximately 1200°C) to normal temperature. This parameter change prevents dopant diffusion that would otherwise occur during high-temperature bonding, thereby maintaining uniform resistivity distribution in the active layer while still achieving adequate bonding strength through the ionization deposition process.
4Reliability
If ion implantation layer is formed in superficial portion, then gettering sites are created, but thermal oxidization consumes this layer reducing gettering ability
Solution Approach 1:
The patent replaces thermal oxidization with ionization deposition, changing from a chemical process that consumes substrate silicon to a physical deposition process. This substitution eliminates the consumption of the ion implantation layer while still forming the necessary oxide film, thereby preserving the gettering sites and maintaining gettering ability.
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 process achieves high gettering ability, minimal resistance variance, and increased productivity by forming high-quality oxide films without consuming silicon and creating variable resistance regions, thus enhancing the quality and efficiency of SOI wafer production.
Implementation Method 1
an oxide film is formed by accelerating and emitting ionized Si and oxygen to a substrate on which the oxide film is to be formed while heating the substrate
Implementation Method 2
implanting light element ions to a surface of at least one of a first substrate made of silicon single crystal and a second substrate made of silicon single crystal to form, in the at least one of the first substrate and the second substrate, a modified layer in which the light element ions are present in solid solution
Implementation Method 3
accelerating and emitting ionized Si and oxygen to a substrate on which the oxide film is to be formed while heating the substrate
Implementation Method 4
bonding the first substrate and the second substrate at a normal temperature by emitting an ion beam or a neutral atomic beam to surfaces to be bonded of the first substrate and the second substrate under vacuum to activate the surfaces and subsequently by contacting the surfaces to be bonded with each other under vacuum
Data Source
AI summary
Provided is an SOI wafer manufacturing method that allows production of an SOI wafer having a high gettering ability and a small resistance variance in a thickness direction of an active layer, at high productivity. The SOI wafer manufacturing method includes a first step of implanting light element ions to a surface of at least one of a first substrate and a second substrate to form, on the at least one of the first substrate and the second substrate, a modified layer in which the light element ions are present in solid solution, a second step of forming an oxide film on a surface of at least one of the first substrate and the second substrate, a third step of bonding the first substrate and the second substrate according to a normal-temperature vacuum bonding method, and a fourth step of obtaining an active layer by thinning the first substrate.