Bonded Wafer Dopant Diffusion Control
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Solution Overview
Problem
The ion implantation delamination method for manufacturing bonded wafers faces challenges in achieving high film thickness uniformity and maintaining dopant concentration, particularly for thick-film SOI wafers, due to surface roughness and dopant profile changes during heat treatment, which affects the quality of silicon thin films and epitaxial layers.
Innovation Solution
A method involving the implantation of hydrogen and rare gas ions into a bond wafer, followed by bonding and delamination, with a flattening heat treatment under a hydrogen or hydrogen chloride atmosphere containing a dopant gas of the same conductivity type as the silicon thin film, to suppress dopant diffusion and improve surface roughness, allowing for high uniformity and desired dopant concentration, enabling the growth of high-quality epitaxial layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a flattening heat treatment is performed under hydrogen or hydrogen chloride atmosphere to improve surface roughness, then surface quality is improved, but dopant concentration changes due to outward diffusion
Solution Approach 1:
A dopant gas is introduced as an intermediary substance into the heat treatment atmosphere. The dopant gas molecules act as mediators that fill the spaces around existing dopants in the silicon thin film, preventing their outward diffusion while allowing the heat treatment to proceed for surface flattening. This intermediary gas layer maintains dopant concentration stability during the necessary thermal processing.
Solution Approach 2:
The composition of the heat treatment atmosphere is changed by adding dopant gas to the hydrogen or hydrogen chloride atmosphere. This parameter change (atmospheric composition) enables simultaneous achievement of surface flattening and dopant concentration maintenance, transforming the heat treatment process from one that causes dopant diffusion to one that preserves dopant profile while improving surface quality.
2Manufacturing precision
If ion implantation is used to create thin silicon films with high uniformity, then film thickness uniformity is improved, but surface roughness increases making epitaxial growth difficult
Solution Approach 1:
The useful action of heat treatment is made continuous by performing surface flattening in the same processing step where dopant concentration is being maintained. Instead of separate processes that would interrupt the film structure, the dopant-containing atmosphere enables continuous thermal processing that simultaneously flattens the surface and preserves dopant profile, maintaining the integrity of the ion-implanted film throughout the process.
Solution Approach 2:
The atmospheric parameters are changed by introducing dopant gas, which enables the heat treatment to produce beneficial surface flattening without the harmful side effect of dopant diffusion. This parameter modification transforms the heat treatment from a damaging process to a beneficial one that improves surface quality while preserving film characteristics.
3Strength
If high temperature heat treatment is performed to strengthen bonding, then bonding strength is improved, but dopant diffusion occurs and film uniformity deteriorates
Solution Approach 1:
The atmospheric composition parameter is changed by adding dopant gas to create a dopant-saturated environment. This prevents dopant out-diffusion during high-temperature bonding heat treatment, allowing the temperature to be raised sufficiently for strong bonding without sacrificing film uniformity or dopant concentration profile.
Solution Approach 2:
The dopant gas acts as an intermediary that protects the dopant atoms in the silicon thin film during high-temperature bonding. The dopant gas molecules in the atmosphere prevent the outward diffusion of dopants from the film, enabling high-temperature processing necessary for strong bonding while maintaining film quality.
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 method effectively maintains high film thickness uniformity and desired dopant concentration, resulting in a flat silicon thin film suitable for thick-film SOI wafer production with improved epitaxial layer quality and reduced defects.
Implementation Method 1
at least one gas ion of a hydrogen ion and a rare gas ion is implanted into a bond wafer from a surface thereof to form an ion-implanted layer
Implementation Method 2
a dopant gas is added into the atmosphere of the flattening heat treatment to perform the heat treatment, wherein the dopant gas having the same conductivity type as a dopant contained in the silicon thin film
Implementation Method 3
performing a flattening heat treatment on the bonded wafer under an atmosphere containing hydrogen or hydrogen chloride
Data Source
AI summary
A method for manufacturing a bonded wafer including the steps of: implanting at least one gas ion of a hydrogen ion and a rare gas ion into a bond wafer from a surface thereof to form an ion-implanted layer; bonding the ion-implanted surface of the bond wafer to a surface of a base wafer directly or through an oxide film; thereafter delaminating the bond wafer at the ion-implanted layer to prepare the bonded wafer having a silicon thin film formed on the base wafer; and performing a flattening heat treatment on the bonded wafer under an atmosphere containing hydrogen or hydrogen chloride, wherein a dopant gas is added into the atmosphere of the flattening heat treatment to perform the heat treatment, the dopant gas having the same conductivity type as a dopant contained in the silicon thin film.