Halftone Phase Shift Mask Blank Light Resistance
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Solution Overview
Problem
Halftone phase shift masks used in semiconductor fabrication are prone to damage from repeated exposure to high-energy light, leading to deviations in phase difference and transmittance, which affect pattern accuracy and yield.
Innovation Solution
A halftone phase shift mask blank with a halftone phase shift film composed of metal, silicon, and optionally oxygen and nitrogen, deposited by sputtering under low gas pressure, exhibits minimal changes in phase shift and transmittance when exposed to high-energy light, such as ArF or F2 laser beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If halftone phase shift masks are used to achieve fine pattern transfer, then resolution and focal depth are improved, but the masks are damaged by repeated exposure to high-energy light
Solution Approach 1:
The patent changes the material composition parameters of the phase shift film by incorporating specific metal elements (Mo, Zr, Ta, W) in controlled ratios with silicon and oxygen/nitrogen. This compositional parameter adjustment optimizes both the optical properties for pattern transfer and the resistance to exposure light damage
Solution Approach 2:
The patent creates a composite phase shift film material combining metal elements, silicon, and oxygen/nitrogen. This composite structure provides both the required phase shift functionality for fine pattern transfer and enhanced durability against repeated high-energy light exposure
2Use of energy by moving object
If the phase shift film is made transparent to exposure light for full transmission type masks, then light transmittance is maximized, but phase shift effect is reduced
Solution Approach 1:
The patent precisely controls the composition ratios of metal elements, silicon, and oxygen/nitrogen in the phase shift film to achieve optimal balance between light transmittance and phase shift effect. By adjusting these material parameters, the film maintains sufficient transparency while generating the required 180° phase difference for effective pattern transfer
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
The halftone phase shift mask blank demonstrates excellent resistance to exposure light, maintaining phase difference and transmittance stability even after repeated exposure, ensuring high productivity in imagewise exposure processes.
Implementation Method 1
deposited by sputtering under low gas pressure
Implementation Method 2
Due to light interference at the pattern boundary, the light intensity at the interfering boundary becomes zero, improving the contrast of a transferred image
Data Source
AI summary
In a halftone phase shift mask blank comprising a halftone phase shift film on a substrate which is transparent to exposure light, the halftone phase shift film comprises a metal, silicon, and optionally oxygen and nitrogen. The halftone phase shift film experiences a phase difference change of up to 1 deg. and a transmittance change of up to 0.2% before and after it is exposed to light in a cumulative dose of 1 kJ/cm2. The halftone phase shift film has excellent resistance to exposure light, specifically high-energy exposure light of short wavelength such as ArF or F2 laser beam (193 or 157 nm).