Thin Wafer Mirror Polishing via Liquid Adsorption and Support Substrate
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Solution Overview
Problem
The challenge lies in producing thin piezoelectric oxide single crystal wafers with a thickness of 100 microns or less for SAW devices while maintaining high mechanical strength to prevent breakage during lapping and mirror polishing, and ensuring manufacturing yield and accuracy equivalent to thicker wafers.
Innovation Solution
A method involving lapping and mirror polishing of thin wafers using a support substrate, where the wafer is laminated with a support substrate of similar material and polarized surfaces, and held in place using a liquid adsorption force or adhesive, to enhance mechanical strength and maintain surface accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wafer thickness is reduced to 100 microns or less, then the device profile is reduced and productivity is improved, but the mechanical strength decreases causing increased breakage during lapping and mirror polishing
Solution Approach 1:
A support substrate is introduced as an intermediary element during the lapping and mirror polishing processes. The thin wafer is bonded to this support substrate, which provides the necessary mechanical strength to prevent breakage during processing. The support substrate acts as a temporary carrier that enables processing of ultra-thin wafers that would otherwise be too fragile to handle.
Solution Approach 2:
The invention creates a composite structure by bonding the thin piezoelectric oxide single crystal wafer to a support substrate. This composite allows the thin wafer to gain the mechanical strength of the support substrate during processing, enabling ultra-thin wafers (100 microns or less) to undergo lapping and mirror polishing without breaking.
2Length of moving object
If the wafer thickness is reduced to 100 microns or less, then the device size is reduced, but the manufacturing yield decreases due to increased susceptibility to failure during processing
Solution Approach 1:
The support substrate serves as a mediator that protects the thin wafer during manufacturing processes. By bonding the ultra-thin wafer to the support substrate before lapping and mirror polishing, the wafer is protected from mechanical failures that would otherwise occur due to its thinness, thereby maintaining high manufacturing yield.
Solution Approach 2:
The support substrate provides beforehand cushioning or protection to the thin wafer during critical processing steps. This pre-protection measure ensures that the wafer can withstand the mechanical stresses of lapping and mirror polishing without breaking, thus preserving manufacturing yield.
3Device complexity
If the wafer is processed without a support substrate, then the process is simpler, but the flatness and parallelism accuracy deteriorate due to wafer deformation
Solution Approach 1:
The support substrate acts as a mediator that maintains wafer flatness and parallelism during lapping and mirror polishing. The rigid support substrate prevents deformation of the thin wafer, ensuring that the processed surfaces achieve the required flatness and parallelism accuracy that would be impossible to obtain by processing the thin wafer alone.
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 consistent production of thin wafers with high flatness and parallelism comparable to thicker wafers, reducing breakage and maintaining yield, while eliminating the need for subsequent surface grinding steps.
Implementation Method 1
feeding a liquid onto the plate side surface of the wafer substrate so that the wafer substrate is directly held to the plate by the adsorption force of the liquid
Data Source
AI summary
A wafer substrate is polished by disposing the wafer substrate between an abrasive cloth on a polishing platen and a plate, and relatively rotating the polishing platen and the plate for mirror polishing the surface of the wafer substrate with the abrasive cloth. A liquid is fed onto the plate side surface of the wafer substrate so that the wafer substrate is directly held to the plate by the adsorption force of the liquid, while performing the mirror polishing.