Double-Side Grinding Thin Wafers Using Carrier Support
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Solution Overview
Problem
Existing methods for machining very thin workpieces, such as semiconductor wafers, face challenges in precision and stability due to their flexibility, leading to discontinuities and material removal issues when processed in conventional grinding machines.
Innovation Solution
A double-sided processing machine with planetary kinematics is used, where workpieces are attached to carriers with through-going recesses, allowing for precise material removal without carrier contact, using different working surfaces for the workpieces and carriers to minimize material removal from the carriers, and employing optical measurement methods for accurate thickness monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If very thin workpieces are processed in conventional grinding machines, then material removal can be achieved, but the workpieces cannot be processed due to their flexibility and lack of stability
Solution Approach 1:
A carrier serves as an intermediary support structure that holds the thin workpiece during machining. The carrier provides the necessary stability and rigidity, allowing the flexible thin workpiece to be processed without deformation or vibration. The workpiece is mounted on the carrier, which acts as a mediator between the workpiece and the machining system.
Solution Approach 2:
The workpiece itself is a thin, flexible component that requires special handling. By mounting it on a rigid carrier, the flexible nature of the workpiece is accommodated while the carrier provides the structural support needed for stable machining operations.
2Productivity
If the carrier is machined along with the workpiece, then continuous material removal can occur, but significant material is removed from the carrier reducing its lifespan
Solution Approach 1:
Different working surfaces are used with different properties: one surface is designed for aggressive material removal from the workpiece, while the other surface is designed for minimal material removal from the carrier. This local differentiation of surface qualities allows continuous machining while preserving the carrier.
Solution Approach 2:
The machining parameters are changed between the two working surfaces. One surface uses parameters optimized for high material removal rate (for the workpiece), while the other surface uses parameters optimized for minimal material removal (for the carrier), thereby extending carrier lifespan.
3Device complexity
If the same working surface is used for both workpiece and carrier, then simpler machine design is achieved, but equal material removal rates cause carrier degradation
Solution Approach 1:
The machine is equipped with two working surfaces having different local qualities: one surface with properties optimized for workpiece machining and another surface with properties optimized for carrier machining. This allows differential material removal rates while maintaining a relatively simple overall machine structure.
4Device complexity
If thin workpieces are processed without carriers, then simpler processing setup is achieved, but discontinuities form in the middle of the machined surface
Solution Approach 1:
The carrier acts as an intermediary support that prevents discontinuities in the machined surface. By providing continuous support across the workpiece, the carrier eliminates mid-surface discontinuities that would otherwise occur during machining of unsupported thin workpieces.
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 enables precise and continuous machining of workpieces with thicknesses below 100 μm, avoiding discontinuities and allowing for multiple uses of carriers, while ensuring accurate thickness control and high precision in material removal.
Implementation Method 1
at least the working surface of the machine assigned to the workpieces has a working covering, in particular a grinding or polishing covering, and thus leads to material removal
Implementation Method 2
the working surface assigned to the surfaces of the workpieces is provided with an abrasive coating and the working surface assigned to the surfaces of the carrier is provided with a polishing coating
Data Source
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AI summary
The invention relates to a method for the grinding or polishing machining of very flat work pieces (38) that are releaseably fastened on flat carriers (28). The work pieces (38) are inserted together with the carriers (28) into the recesses (23) of at least one rotor disc (22) of a double side grinding machine (10) and are moved along cycloid paths between the working surfaces of the double side grinding machine (10). The removal rate on the working surfaces of the double side grinding machine (10) is either the same, or the removal rate on one working surface is substantially less than the removal rate on the opposite working surface, or no material removal is carried out on one of the working surfaces. In an embodiment, two work pieces (38) are releaseably fastened on a carrier (28), that is to say on the top side and the bottom side.