SOI Wafer Gettering for Metal Impurity Control
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Solution Overview
Problem
Conventional methods for getting metal impurities in SOI wafers are ineffective for cavity SOI wafers and MEMS devices, leading to impurity diffusion and contamination during high-temperature processing, which compromises the reliability of these devices and contaminates manufacturing systems.
Innovation Solution
A SOI wafer manufacturing method involving the formation of a gettering material on the surface opposite to the bonding interface, which traps metal impurities during bonding reinforcing heat treatment, preventing their diffusion and ensuring a defect-free bonded cavity SOI wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bonding methods are used for cavity SOI wafers, then the bonding interface is formed, but metal impurities remain at the bonding interface and diffuse during high-temperature processing
Solution Approach 1:
A gettering layer is formed at the bonding interface before the bonding process. This gettering layer is prepared in advance to trap metal impurities that will be generated during bonding and high-temperature processing, preventing their diffusion into the device regions.
Solution Approach 2:
The gettering layer acts as an intermediary substance between the bonding interface and the device regions. It selectively captures and holds metal impurities, preventing them from migrating into the active device areas during subsequent high-temperature processing steps.
2Productivity
If high-temperature processing is performed on cavity SOI wafers, then device fabrication is completed, but metal impurities diffuse and contaminate the manufacturing system
Solution Approach 1:
The gettering layer converts the harmful effect of high-temperature processing (which causes impurity diffusion) into a beneficial effect by using the thermal energy to activate the gettering mechanism. The high temperature enhances the gettering layer's ability to trap impurities, turning the problematic thermal processing into a useful impurity removal step.
Solution Approach 2:
The gettering layer is designed to be sacrificed during the process. It absorbs and concentrates metal impurities in a controlled manner, effectively discarding the impurities from the device regions. The gettering layer itself may be removed or retained depending on the specific application, but its primary function of impurity capture is achieved.
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 effectively removes metal impurities from the bonding interface, enhancing the reliability of SOI wafers and preventing contamination of the manufacturing system, even during high-temperature processing.
Implementation Method 1
two silicon wafers bonded together with an oxide film therebetween
Implementation Method 2
a gettering material formed on a surface on a side opposite to the bonding surface... traps metal impurities during bonding reinforcing heat treatment
Data Source
AI summary
In order to obtain a SOI wafer having an excellent ability of gettering metal impurities, an efficient method of manufacturing a SOI wafer, and a highly reliable MEMS device using such a SOI wafer, provided is a SOI wafer including: a support wafer (1) and an active layer wafer (6) which are bonded together with an oxide film (3) therebetween, each of the support wafer (1) and the active layer wafer (6) being a silicon wafer; a cavity (1b) formed in a bonding surface of at least one of the silicon wafers; and a gettering material (2) formed on a surface on a side opposite to the bonding surface.