Polycrystalline Diamond Wafer Bonding With Bow Compensation
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Solution Overview
Problem
Wafer-bow induced by mismatched coefficients of thermal expansion between silicon and polycrystalline diamond layers is not effectively addressed in existing technologies, leading to undesirable deflection in wafer structures.
Innovation Solution
A wafer structure is developed with a polycrystalline diamond layer on one side and a bow-compensation layer on the other, along with surface preparation techniques such as chemical-mechanical polishing and plasma activation to create dangling bonds for contact bonding, reducing wafer-bow to less than 50 microns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polycrystalline diamond layer is deposited on a silicon-containing layer, then the hardness and thermal conductivity are improved, but wafer-bow increases due to mismatched coefficients of thermal expansion
Solution Approach 1:
A bow-compensation layer is deposited on the back side of the silicon-containing layer before the diamond layer is deposited. This layer is specifically designed to counteract the wafer-bow that will be induced by the thermal expansion mismatch between the diamond and silicon layers, thereby preventing the shape distortion while maintaining the hardness improvement
2Shape
If a bow-compensation layer is added to reduce wafer-bow, then the shape stability is improved, but the device complexity increases
Solution Approach 1:
The bow-compensation layer is applied only on the back side of the silicon-containing layer, specifically where needed to counteract the thermal stress, rather than modifying the entire wafer structure uniformly. This localized approach reduces the overall complexity while achieving the shape stabilization
3Manufacturing precision
If surface preparation techniques such as chemical-mechanical polishing are used to reduce surface roughness, then the bonding quality is improved, but the manufacturing time increases
Solution Approach 1:
Surface preparation techniques including chemical-mechanical polishing are performed on the bonding surfaces before the actual bonding process. By preparing the surfaces in advance to achieve the required roughness reduction, the actual bonding step can proceed quickly and efficiently, overall reducing the total manufacturing time
4Strength
If plasma activation is used to create dangling bonds for contact bonding, then the bonding strength is improved, but the energy consumption increases
Solution Approach 1:
The plasma activation process parameters such as power, pressure, and gas flow are optimized to achieve the required dangling bond density with minimal energy input. By carefully controlling these parameters, strong bonding is achieved while reducing unnecessary energy consumption
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 solution effectively reduces wafer-bow to minimal levels, enabling precise bonding and device fabrication by compensating for thermal expansion mismatches and facilitating low-temperature bonding processes.
Implementation Method 1
performing an activation process on a surface of a first substrate, to create dangling bonds on at least that surface, and then contact bonding the surface of the first substrate to a surface of a second substrate. The activation process may be, for example, a plasma activation process.
Implementation Method 2
The wafer-bow that is reduced or eliminated can be induced by a mis-match between the coefficients of thermal expansion of the respective materials of the layer containing silicon and the layer of polycrystalline diamond.
Implementation Method 3
Contact bonding of the substrates may be initially established by Van der Waals forces.
Data Source
AI summary
A wafer has a layer containing silicon, a layer of polycrystalline diamond deposited on the silicon-containing layer, and a bow-compensation layer on the other side of the silicon-containing layer for reducing wafer-bow. A method of making a bonded structure includes an activation process for creating dangling bonds on the surface of one substrate, followed by contact-bonding the surface to a second substrate at low temperature. A bonded structure may include two substrates contact bonded to each other, one substrate including a layer containing silicon, a layer of polycrystalline diamond, a bow-compensation layer for reducing wafer-bow of the first substrate, and the other substrate including gallium nitride, silicon carbide, lithium niobate, lithium tantalate, gallium arsenide, indium phosphide, or another suitable material other than diamond.