Multi-Layer Photomask Shading Structure for Defect Reduction
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Solution Overview
Problem
The miniaturization of semiconductor circuit patterns poses challenges in forming precise patterns due to defects caused by particles during the etching process, which can lead to scratching and damage, especially when forming right-angle edges, and existing photomasks with single-layer shading structures are inadequate in controlling these defects.
Innovation Solution
A photomask blank and photomask design featuring a multi-layer shading structure with a first and second shading layer, where the second shading layer has a lower hardness and Young's modulus than the first, strategically positioned to reduce particle occurrence and scratching, with specific hardness and Young's modulus ratios optimized for reduced particle formation and improved etching characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer shading structure is used in the photomask, then the device complexity is reduced, but particle formation and scratching defects increase during the etching process
Solution Approach 1:
The single-layer shading structure is segmented into multiple layers with different hardness values. The patent applies this by creating a first shading layer with higher hardness and a second shading layer with lower hardness, allowing each layer to serve specific functions in preventing particle formation while maintaining structural integrity during etching processes
Solution Approach 2:
The patent uses composite material principles by combining materials with different hardness properties in the shading layers. The first shading layer uses a harder material to prevent particle formation, while the second shading layer uses a softer material to reduce scratching defects, creating a composite structure that addresses multiple defects simultaneously
2Object-affected harmful factors
If the shading layer hardness is increased to prevent particle formation, then particle occurrence is reduced, but scratching and damage during etching increases
Solution Approach 1:
The patent applies local quality by assigning different hardness characteristics to different regions (layers) of the shading structure. The first shading layer has higher hardness locally to prevent particle formation, while the second shading layer has lower hardness locally to prevent scratching, allowing each region to address specific harmful factors without causing adverse effects
3Reliability
If a multi-layer shading structure is implemented to reduce particle formation, then particle occurrence and scratching defects are suppressed, but the device complexity increases
Solution Approach 1:
The shading structure is segmented into functional layers with distinct hardness characteristics. This segmentation allows the system to address multiple defect mechanisms (particle formation and scratching) simultaneously, improving reliability while the modular layer structure keeps the complexity manageable through clear functional differentiation
Data Source
AI summary
A photomask blank includes a light-transmitting substrate, and a shading layer part disposed on the light-transmitting substrate, the shading layer part including a first shading layer having a first hardness and a second shading layer having a second hardness. The first shading layer is disposed closer to the light-transmitting substrate than the second shading layer, and a value of the first hardness is larger that a value of the second hardness.