Semiconductor Wafer Nanotopography Improvement via Segmented Grinding
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Solution Overview
Problem
Existing semiconductor wafer machining processes fail to adequately address nanotopography issues, leading to insufficient surface quality after mirror polishing, and cause significant processing damage with fixed abrasive grain wire saws, resulting in large waviness and poor nanotopography.
Innovation Solution
A machining process involving repeated application of a curable material and surface grinding, where the first surface is coated after slicing, followed by grinding and using the second surface as a reference, with reduced stock removal in subsequent steps to improve nanotopography quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single resin application and grinding step is performed, then the process is simple and fast, but the nanotopography quality is insufficient
Solution Approach 1:
The single resin application and grinding step is divided into multiple sequential steps (first resin application, first grinding, first resin removal, second resin application, second grinding, second resin removal). Each step removes a portion of the waviness, with the total stock removal being the sum of individual step removals. This segmentation allows the process to achieve superior nanotopography quality (PV value of 0.05 μm or less) while maintaining reasonable process complexity through systematic multi-stage processing.
2Manufacturing precision
If fixed abrasive grain wire saw is used for slicing, then the slicing process is stable and controllable, but significant processing damage occurs causing large waviness
Solution Approach 1:
The processing damage and large waviness generated by the fixed abrasive grain wire saw are not treated as defects to be avoided, but as the starting condition that the resin application and grinding process is designed to correct. The curable material is applied to the damaged surface, and through controlled grinding steps, the damage layer is removed systematically. The multi-step approach converts the harmful effect (large initial waviness) into a manageable starting point that can be progressively improved.
3Manufacturing precision
If large stock removal is used in single grinding step, then all waviness and warp are absorbed, but the nanotopography quality remains insufficient
Solution Approach 1:
The total stock removal is segmented across multiple grinding steps. The first grinding step removes a first portion of the waviness with a first stock removal amount, and the second grinding step removes a second portion with a second stock removal amount. The sum of these portions equals the total waviness and warp. This segmentation allows each grinding step to work on a progressively improved surface, achieving superior nanotopography quality while minimizing the total material removed compared to a single aggressive grinding step.
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 process significantly reduces waviness and improves nanotopography quality, even with large-diameter wafers and those sliced using fixed abrasive grain wire saws, achieving superior surface flattening with minimal total stock removal.
Implementation Method 1
a first application layer forming step of applying a curable material to one entire surface of the wafer after the slicing step to form a flat application layer
Implementation Method 2
a first surface grinding step of mounting the wafer on a table of a grinding apparatus in such a manner that one surface of the flattened wafer abuts on a reference surface of the table, and then performing surface grinding with respect to the other surface of the wafer with the use of the grinding apparatus
Data Source
AI summary
A surface of a semiconductor wafer is subjected to high flattening processing.A resin application and grinding step is repeatedly carried out, the step including determining as a reference surface a flat surface obtained by applying a curable material to one entire surface of a wafer sliced out from a semiconductor single crystal ingot with the use of a wire saw apparatus and performing surface grinding with respect to the other surface of the wafer, and determining as a reference surface the other surface of the wafer subjected to the surface grinding and performing the surface grinding with respect to the one surface of the wafer.