Cycloidal Grinding of Semiconductor Wafers for Thickness Uniformity
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Solution Overview
Problem
Existing semiconductor wafer grinding methods result in convex thickness profiles, edge roll-off, excessive surface roughness, and strain-induced warpage, making them unsuitable for demanding applications, and suffer from high wear of carrier materials and frequent tool changes, leading to economic inefficiencies.
Innovation Solution
The method involves simultaneous double-side grinding of semiconductor wafers on cycloidal trajectories between bonded-abrasive coated ring-shaped working disks, with controlled working gap geometry and carrier materials that minimize interaction with the abrasive, ensuring uniform material removal and reduced wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional grinding methods are used to machine semiconductor wafers, then material removal is achieved, but convex thickness profiles and edge roll-off are produced
Solution Approach 1:
The patent applies cycloidal trajectory motion where carriers move in curved paths between working disks, creating uniform material removal across the wafer surface. The cycloidal path ensures that all regions of the wafer (center and edge) experience equivalent grinding conditions, eliminating the convex thickness profile and edge roll-off that occur with conventional linear or radial grinding methods.
Solution Approach 2:
The invention uses dynamic motion of carriers on cycloidal trajectories rather than static positioning. The carriers are continuously moved along curved paths during grinding, which dynamically distributes the grinding force uniformly across the wafer surface. This dynamic approach prevents localized over-grinding at edges or center that causes thickness profile defects.
2Manufacturing precision
If conventional grinding methods are used, then material removal is achieved, but excessive surface roughness and strain-induced warpage occur
Solution Approach 1:
The cycloidal trajectory creates a curved grinding path that uniformly distributes mechanical stress across the wafer. This prevents strain concentration that leads to warpage and reduces surface damage by avoiding repeated passes over the same locations. The curved motion pattern ensures gentle, uniform material removal that preserves surface integrity.
3Manufacturing precision
If frequent tool changes are made to maintain grinding quality, then manufacturing precision is maintained, but productivity decreases
Solution Approach 1:
The cycloidal grinding method enables continuous operation with extended tool life. The uniform distribution of grinding forces and reduced peak stresses allow working disks to maintain quality standards for longer periods without requiring frequent changes or maintenance, thus preserving productivity while sustaining manufacturing precision.
Solution Approach 2:
The invention changes the motion parameters from conventional linear/radial paths to cycloidal trajectories. This parameter change fundamentally alters the grinding mechanics, distributing wear more evenly across the working disk surface and reducing the rate of tool degradation, thereby extending tool life and reducing change frequency.
4Duration of action of stationary object
If carrier materials with high wear resistance are used, then carrier lifespan is extended, but interaction with bonded abrasive increases reducing grinding efficiency
Solution Approach 1:
The patent applies different material properties to different parts of the carrier system. The carrier body uses wear-resistant materials for longevity, while the contact surfaces interact with the cycloidal motion pattern to minimize abrasive engagement. This local differentiation allows high wear resistance without sacrificing grinding efficiency, as the abrasive interaction is optimized by the motion pattern rather than material composition.
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 produces semiconductor wafers with improved flatness, reduced surface damage, and extended carrier lifespan, enabling the production of components with small linewidths and reducing the need for frequent tool replacements, thus enhancing economic viability.
Implementation Method 1
each working disk comprises a working layer containing bonded abrasive
Implementation Method 2
each semiconductor wafer lies such that it is freely moveable in a cutout of one of a plurality of carriers caused to rotate by means of a rolling apparatus and is thereby moved on a cycloidal trajectory
Data Source
AI summary
Simultaneous double-side grinding of a plurality of semiconductor wafers involves positioning each wafer freely in a cutout of one of plural carriers which rotate on a cycloidal trajectory, wherein the wafers are machined between two rotating ring-shaped working disks, each disk having a working layer of bonded abrasive, wherein the form of the working gap between working layers is determined during grinding and the form of the working area of at least one disk is altered such that the gap has a predetermined form. The wafers, during machining, may temporarily overhang the gap. The carrier is optionally composed only of a first material, or is completely or partly coated with the first material such that during machining only the first material contacts the working layer, and the first material does not reduce the machining ability of the working layer.