Silicon-Germanium Bonding with Buffer Layers to Reduce Shear Stress
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Solution Overview
Problem
Current bonding methods for silicon and germanium parts face challenges such as high manufacturing costs, material loss, and thermal limitations, along with contamination and mechanical weakness due to the use of elastomers and metallic bonding agents, which restrict their application in semiconductor processing systems.
Innovation Solution
A method involving a bonding process where a first part and a second part made of silicon or germanium are bonded using a different material as a bonding agent, with a predetermined temperature and solidification period, creating a bonding layer with buffer layers and a eutectic layer to manage thermal expansion and reduce stress, while controlling pressure and heating rates to form a strong and durable bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If elastomers are used to bond silicon parts, then bonding is achieved, but tensile strength is weak and working temperature is limited to about 185°C
Solution Approach 1:
The bonding method changes the temperature parameter by heating to a predetermined temperature greater than 1.5 times the eutectic temperature of the Si-bonding material alloy, enabling the bonding material to melt and form strong bonds while eliminating the temperature limitation of elastomers
Solution Approach 2:
A bonding material layer is introduced as an intermediary between silicon parts, composed of a eutectic layer and buffer layers. This intermediary enables strong bonding at high temperatures while managing thermal expansion differences through the buffer layers
2Strength
If liquid phase bonding with aluminum or gold is used, then strong bonds are achieved, but maximum application temperature is limited by eutectic temperature (580°C for Si-Al, 363°C for Si-Au)
Solution Approach 1:
The method changes the bonding temperature parameter by heating to a predetermined temperature greater than 1.5 times the eutectic temperature but less than the melting temperature of silicon, enabling application temperatures exceeding 580°C for Si-Al bonds and 363°C for Si-Au bonds
Solution Approach 2:
The bonding material is preliminarily arranged between the silicon parts before heating, and the parts are heated to a predetermined temperature for a predetermined period to melt the bonding material and form strong bonds before cooling and solidification
3Strength
If bonding agents are used to bond silicon parts, then bonding is achieved, but metallic contamination and non-volatile particles are generated
Solution Approach 1:
The bonding process is performed in a controlled environment that prevents contamination, and the bonding material is selected and processed to minimize metallic contamination and non-volatile particle generation during subsequent use in substrate processing systems
Solution Approach 2:
The bonding material is consumed during the bonding process to form the bonding layer, and its composition is optimized to minimize contamination while providing strong bonds
4Strength
If bonding material is used between silicon parts, then CTE mismatch causes shear stress in silicon and weakens mechanical strength
Solution Approach 1:
The bonding layer is structured with different regions having different properties: a eutectic layer for bonding and buffer layers with intermediate CTE values adjacent to the silicon parts. This local quality variation allows the buffer layers to accommodate CTE mismatch and reduce shear stress in the silicon parts
Solution Approach 2:
The bonding layer is composed of a composite structure with a eutectic layer and buffer layers, where each layer has different CTE values. This composite structure manages thermal expansion differences and reduces stress in the bonded assembly
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 results in a bonded part with improved mechanical strength and thermal stability, reducing material loss and manufacturing costs, and eliminating micro-cracks and contamination issues, enabling higher temperature applications in semiconductor processing.
Implementation Method 1
The predetermined temperature is greater than 1.5 times a eutectic temperature of an alloy including the first material and the second material
Implementation Method 2
followed by a predetermined solidification period
Implementation Method 3
The first buffer layer and the second buffer layer have a higher concentration of the first material than the eutectic layer
Data Source
AI summary
A method includes providing a first part, a second part and a bonding material between the first part and the second part. The first part and the second part are made of a first material selected from a group consisting of silicon and germanium. The bonding material includes a second material that is different than the first material. The method includes arranging the first part, the bonding material, and the second part in a furnace; and creating a bonded part by heating the first part, the second part and the bonding material to a predetermined temperature for a predetermined period followed by a predetermined solidification period. The predetermined temperature is greater than 1.5 times a eutectic temperature of an alloy including the first material and the second material and less than a melting temperature of the first material.