Wafer Chamfered Edge Shape Uniformity via Alkali Etching
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Solution Overview
Problem
Alkali etching in semiconductor wafer manufacturing causes variations in the chamfered cross-sectional shape due to differing etching speeds based on crystal orientation, leading to non-uniformity in the circumferential direction.
Innovation Solution
A method involving chamfering with smaller radii of curvature (R1 and R2) followed by mirror-polishing to ensure these values are within target ranges, using an alkaline aqueous solution for etching to maintain flatness and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If alkali etching is used to maintain wafer flatness, then wafer flatness is improved, but variation in chamfered cross-sectional shape in circumferential direction increases
Solution Approach 1:
The invention applies preliminary action by performing a first chamfering step before etching to create a chamfered portion with specific geometric features (first and second arc portions with radii R1 and R2). This preliminary chamfering establishes a foundation that compensates for the non-uniform etching that will occur later, ensuring that the final chamfered cross-sectional shape maintains uniformity in the circumferential direction even after alkali etching creates variations.
2Productivity
If acid etching is used to achieve high etching rate, then etching efficiency is improved, but wafer flatness deteriorates
Solution Approach 1:
The invention applies parameter changes by switching from acid etching to alkali etching, fundamentally changing the chemical parameters of the etching process. This parameter change allows the process to achieve both acceptable etching rates and improved wafer flatness, though it introduces the challenge of non-uniform chamfered shape that is then addressed through the preliminary chamfering action.
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 results in a wafer with a uniform chamfered cross-sectional shape in the circumferential direction, effectively addressing the non-uniformity issues caused by alkali etching and maintaining the required specifications.
Implementation Method 1
alkali etching using an alkali such as sodium hydroxide or potassium hydroxide
Implementation Method 2
grinding and chamfering a circumferential edge portion of a wafer sliced from a single crystal ingot; lapping or double-side grinding main surfaces of the chamfered wafer
Implementation Method 3
one-side or double-side mirror-polishing main surfaces of the etched wafer; mirror-polishing a chamfered portion of the mirror-polished wafer
Data Source
AI summary
A method for manufacturing a wafer product, including the steps of: chamfering a circumferential edge portion of a wafer; lapping or double-side grinding main surfaces thereof; etching; mirror-polishing the main surface; and mirror-polishing the chamfered portion. The chamfered portion has a cross-sectional shape including: a first inclined portion continuous from the first main surface; a first arc portion continuous from the first inclined portion and having a radius of curvature; a second inclined portion continuous from the second main surface; a second arc portion continuous from the second inclined portion and having a radius of curvature; and an end portion connecting the first arc portion to the second arc portion. This provides a method for manufacturing a wafer by which a variation in a chamfered cross-sectional shape in a circumferential direction caused by etching can be suppressed.