Bonded Wafer Terrace Machining with Segmented Chamfering
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Solution Overview
Problem
The prior art machining method for forming a terrace portion on bonded wafers results in poorly machined shapes due to high wear resistance of insulating films, leading to breakage or excessive machining strain, and subsequent etching causes anisotropy issues.
Innovation Solution
A method involving a chamfering wheel with a multistage structure using a low grit number grinding stone for coarse chamfering and a high grit number grinding stone for finish chamfering, followed by strain removal through etching, to stabilize the machining process and prevent anisotropy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single high grit number grinding stone is used for finish chamfering of the insulating film, then machining precision is improved, but the grinding stone breaks or wears excessively due to high wear resistance of the insulating film
Solution Approach 1:
The chamfering process is segmented into two distinct stages: coarse chamfering using a low grit number grinding stone to remove material and prevent breakage, followed by finish chamfering using a high grit number grinding stone to achieve precise machining. This segmentation allows each grinding stone to perform its optimal function without suffering from the limitations of the other.
2Strength
If a low grit number grinding stone is used for coarse chamfering, then grinding stone breakage is prevented, but excessive machining strain is generated causing anisotropy
Solution Approach 1:
The chamfering process is divided into coarse chamfering (low grit number) and finish chamfering (high grit number) stages. The coarse stage removes material with minimal strain, while the finish stage eliminates the remaining strain and achieves precise machining, preventing anisotropy.
Solution Approach 2:
Coarse chamfering is performed as a preliminary action before finish chamfering. This preliminary removal of material reduces the workload for the subsequent finish chamfering step, preventing excessive strain accumulation that would lead to anisotropy.
3Manufacturing precision
If much etching is performed to remove machining strain, then strain removal is improved, but anisotropy becomes evident due to different etching rates among active layer, insulating film, and support substrate
Solution Approach 1:
Instead of performing much etching to remove all strain, the patent applies partial action by using a high grit number grinding stone for finish chamfering that removes only the necessary amount of strain. This minimizes the etching required and prevents anisotropy from becoming evident.
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 allows for the stable manufacture of bonded wafers with a terrace surface on the support substrate, preventing breakage and anisotropy, and ensuring accurate machining without excessive strain or surface roughening.
Implementation Method 1
coarse chamfering of the insulating film and the support substrate wafer, using a low grit number grinding stone
Implementation Method 2
finish chamfering of a machined surface obtained from the coarse chamfering step, using a high grit number grinding stone
Implementation Method 3
a strain removing step of removing a strained region generated by the terrace forming step
Data Source
AI summary
Disclosed is a method of manufacturing a bonded wafer, wherein a terrace forming step is carried out using a chamfering wheel which comprise a low grit number grinding stone and a high grit number grinding stone having a higher grit number than the low grit number grinding stone, and wherein the terrace forming step comprises: a coarse chamfering step of chamfering, after chamfering the active layer wafer, the insulating film from the active layer wafer side and further chamfering the support substrate wafer, using the low grit number grinding stone; and a finish chamfering step of finish chamfering, after the coarse chamfering step, a machined surface obtained from the coarse chamfering step, using the high grit number grinding stone.