SOI Hybrid Substrate Bonding via Terrace Structure and Consolidation
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Solution Overview
Problem
Existing methods for producing silicon-on-insulator (SOI) hybrid substrates face challenges such as defects from hydrogen ion implantation, thermal expansion issues, and irregular film thickness due to high-temperature treatments, leading to delamination and peripheral defects during bonding of substrates with different thermal expansion coefficients.
Innovation Solution
A method involving bonding an SOI substrate to a support substrate with a different thermal expansion coefficient, where the SOI substrate has a terrace portion to prevent peripheral peeling, and using consolidation heat treatments and grinding to enhance bond strength without trimming, utilizing a first silicon oxide layer as an etch stop and controlling the thickness of the silicon active layer for precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature heat treatment is applied to increase bond strength between substrates with different thermal expansion coefficients, then bonding reliability is improved, but thermal stress and defects increase due to thermal expansion mismatch
Solution Approach 1:
The patent changes the temperature parameter from high-temperature heat treatment to low-temperature consolidation treatment, achieving sufficient bond strength without inducing thermal stress and defects caused by thermal expansion mismatch between substrates
Solution Approach 2:
The patent replaces thermal bonding mechanism with mechanical pressing and consolidation treatment, eliminating the need for high-temperature heat treatment while achieving reliable bonding between substrates
2Productivity
If the silicon substrate is ground to achieve thin film, then material removal efficiency is improved, but film thickness uniformity deteriorates due to lack of etch stop layer
Solution Approach 1:
The patent forms an oxide film on the silicon substrate before grinding, which serves as an etch stop layer that prevents excessive material removal and ensures uniform film thickness, while still allowing efficient material removal during grinding
3Reliability
If trimming is performed before grinding to remove peripheral portion, then peripheral defect prevention is improved, but process complexity increases due to additional trimming step
Solution Approach 1:
The patent extracts the oxide film formation step to serve as a functional layer that prevents peripheral defects during grinding, eliminating the need for separate trimming operations while maintaining process simplicity
4Productivity
If hydrogen ion implantation is used to create separation layer, then separation efficiency is improved, but defect density increases due to ion damage and hydrogen diffusion
Solution Approach 1:
The patent converts the potentially harmful oxide film formation process into a beneficial etch stop layer that prevents excessive grinding and ensures uniform film thickness, while avoiding the defects caused by hydrogen ion 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 method effectively increases bond strength between the SOI and support substrates, prevents delamination, and allows for precise control of silicon active layer thickness, eliminating the need for trimming and reducing defects, resulting in a high-quality hybrid substrate with improved manufacturing accuracy.
Implementation Method 1
utilizing a first silicon oxide layer as an etch stop and controlling the thickness of the silicon active layer for precision
Implementation Method 2
grinding the silicon substrate to a predetermined thickness
Implementation Method 3
using consolidation heat treatments and grinding to enhance bond strength
Data Source
Figure 1(a)~2
Figure 3~4
AI summary
A hybrid substrate which has an SOI structure having a good silicon active layer, and which is free from defects such as partial separation of the silicon active layer at the outer peripheral portion of the substrate is obtained without trimming the outer periphery of the substrate by: preparing an SOI substrate which is obtained by sequentially laminating a first silicon oxide film and a silicon active layer in this order on a silicon substrate, and wherein a terrace portion that does not have the silicon active layer is formed in the outer peripheral portion of the silicon substrate surface; forming a second silicon oxide film on the silicon active layer surface of the SOI substrate; subjecting the bonding surfaces of the SOI substrate and a supporting substrate that has a thermal expansion coefficient different from that of the SOI substrate to an activation treatment; bonding the SOI substrate and the supporting substrate with the second silicon oxide film being interposed therebetween at a temperature higher than room temperature; then repeating at least twice a combination of a bonding heat treatment for increasing the bonding strength between the SOI substrate and the supporting substrate in the bonded substrate and a grinding/thinning process for grinding and thinning the silicon substrate under predetermined heat treatment temperature conditions and plate thickness thinning conditions; exposing the first silicon oxide film by removing the thinned silicon substrate by means of etching; and removing the first silicon oxide film by means of etching.