Stepped Wafer Curved Surface Resist Removal
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Solution Overview
Problem
Stepped semiconductor wafers with steep portions face issues during lithography and dicing processes due to residual resist after development, leading to contamination and reduced yields.
Innovation Solution
A stepped wafer design with a curved surface having a radius of curvature ranging from 300 μm to 1800 μm, preventing resist from remaining after development by improving resist flow and application uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If steep stepped portions are formed on the wafer, then warpage and deflection are reduced, but resist remains after development causing contamination and yield reduction
Solution Approach 1:
The patent applies curvature to the stepped portions of the wafer by forming a curved surface with a specific radius of curvature (300 μm to 1800 μm) instead of a steep angled surface. This curved transition region allows resist to flow smoothly during spin coating and prevents resist from pooling or remaining after development, while still providing the thickness variation needed to reduce wafer warpage and deflection.
2Ease of operation
If conventional sloped surfaces are used instead of steep steps, then lithography and dicing processes are improved, but resist still remains in the stepped portion after development
Solution Approach 1:
The patent changes the geometric parameters of the stepped portion by specifying a radius of curvature between 300 μm and 1800 μm. This parameter optimization ensures that the curved surface is gentle enough to allow complete resist removal during development, yet maintains sufficient thickness variation for wafer stability. The specific radius range balances resist flow characteristics with structural requirements.
Data Source
AI summary
The present invention has an object of providing a stepped wafer that can prevent a resist from remaining after development, and a method for manufacturing the stepped wafer. The stepped wafer according to the present invention is a stepped wafer having a step and whose main surface is thinner in a center portion and is thicker in an outer periphery. The step includes a curved surface with a radius of curvature ranging from 300 μm to 1800 μm.