Recessed Germanium Layer in Eutectic Bonding
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Solution Overview
Problem
In existing eutectic bonding methods for semiconductor substrates, the eutectic alloy formed from germanium and aluminum layers can protrude from the bonding surface, leading to defective devices and reduced productivity due to undesirable conduction to electrodes.
Innovation Solution
A method where the outer end of the germanium layer is recessed inward relative to the aluminum containing layer, preventing the eutectic alloy from protruding, and controlling the heating and pressurization to ensure accurate alloy formation, with the aluminum and germanium layers being film-formed in specific patterns to enhance bonding strength and sealing characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the germanium layer and aluminum containing layer are film-formed on a whole bonding surface, then the eutectic bonding area is increased, but the eutectic alloy is pressed out from the bonding surface causing device defects
Solution Approach 1:
The patent applies local quality by creating a non-uniform germanium layer structure where the outer end is receded inward relative to the aluminum containing layer. This localized modification ensures that eutectic alloy formation is confined to a specific region, preventing press-out while maintaining adequate bonding strength in the bonding area.
2Reliability
If the germanium layer outer end is receded inward, then the eutectic alloy press-out is prevented, but the bonding area is reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the receded distance between the germanium layer outer end and aluminum containing layer outer end to be 20 μm or less. This parameter optimization ensures that the bonding area is sufficiently large to maintain bonding strength while the receded structure effectively prevents eutectic alloy press-out.
3Force
If the eutectic alloy spreads to the outside during pressurization, then the bonding pressure is distributed, but the alloy conducts to electrodes causing defects
Solution Approach 1:
The patent applies the taking out principle by extracting or removing the germanium layer material from the outer peripheral region, creating a receded structure. This removal prevents the eutectic alloy from forming and conducting to electrodes in the outer regions, while still allowing adequate pressure distribution through the bonding interface.
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 approach prevents eutectic alloy protrusion, avoids undesirable conduction, and improves device productivity by maintaining high sealing and bonding strength, allowing for precise packaging of MEMS devices.
Implementation Method 1
a first semiconductor substrate is bonded with a second semiconductor substrate by eutectic bonding with pressurization and heating, an aluminum containing layer primarily made of aluminum and a germanium layer in an overlaid state being interposed between a bonding surface of the first semiconductor substrate and a bonding surface of the second semiconductor substrate
Implementation Method 2
The method has a step of receding an outer end of the germanium layer inward with respect to an outer end of the aluminum containing layer as to the aluminum containing layer and the germanium layer in the overlaid state
Data Source
AI summary
A method of bonding a semiconductor substrate has a step of pressurizing and heating to bond a substrate 11 with a substrate 12 by eutectic bonding in a state that an aluminum containing layer 31 and a germanium layer 32 between a bonding section 30a of the substrate 11 and a bonding section 30b of the substrate 21 are overlaid and an outer end 32a of the germanium layer 32 is receded inward with respect to an outer end 31a of the aluminum containing layer 31.