Phase Shift Film Stacked Structure for ArF Light Fastness
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the difficulty in producing a phase shift mask with longer life due to the low ArF light fastness of conventional MoSi-based materials, which leads to significant critical dimension changes and increased manufacturing costs, especially with the miniaturization of transfer patterns and the need for multiple patterning techniques.
Innovation Solution
A mask blank with a phase shift film on a transparent substrate, featuring a stacked structure of a lower layer made from silicon or silicon with nonmetallic elements and an upper layer of silicon and nitrogen, optimized for refractive index and extinction coefficient properties to enhance ArF light fastness, allowing for reduced film thickness and improved transmittance and phase difference while suppressing photoexcitation of silicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MoSi-based material is used for phase shift film, then phase shift function is achieved, but ArF light fastness deteriorates and critical dimension changes significantly
Solution Approach 1:
The patent employs a composite phase shift film structure consisting of a MoSi-based lower layer and a SiN-based upper layer. The MoSi layer provides the necessary phase shift function while the SiN layer protects against photoexcitation and oxidation during ArF exposure, thereby improving light fastness and maintaining critical dimension stability.
Solution Approach 2:
The patent applies different material properties to different regions of the phase shift film. The lower layer uses MoSi material with specific optical properties for phase shifting, while the upper layer uses SiN material with high resistance to photoexcitation. This local differentiation of material quality resolves the contradiction between achieving phase shift function and maintaining light fastness.
2Reliability
If phase shift film thickness is increased to improve phase difference, then phase shift function is enhanced, but transmittance deteriorates and exposure efficiency decreases
Solution Approach 1:
The composite structure allows optimization of each layer's thickness independently. The MoSi layer can be made thinner to maintain transmittance while the SiN layer compensates for phase difference, achieving both adequate phase shift and sufficient light transmittance for efficient exposure.
Solution Approach 2:
The patent changes the material composition parameters of the phase shift film, transitioning from a single-material thick film to a multi-material structure with optimized thickness ratios. This parameter change enables simultaneous achievement of adequate phase difference and acceptable transmittance.
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 solution significantly reduces critical dimension changes and enhances ArF light fastness, enabling the production of phase shift masks with improved durability and reduced manufacturing time and costs, while maintaining high precision in semiconductor device patterning.
Implementation Method 1
the phase shift film has a function to generate a phase difference of 150 degrees or more and 180 degrees or less between the exposure light that transmitted through the phase shift film and the exposure light that transmitted through air
Implementation Method 2
the lower layer has refractive index n of less than 1.8 and extinction coefficient k of 2.0 or more
Data Source
AI summary
Provided is a mask blank with a phase shift film having a function to transmit ArF exposure light at a predetermined transmittance and a function to generate a predetermined phase difference to the transmitting ArF exposure light, and having high ArF light fastness. The phase shift film has a function to transmit ArF exposure light at 2% or more transmittance and a function to generate a phase difference of 150 degrees or more and 180 degrees or less to the transmitting ArF exposure light; a lower layer and an upper layer are stacked from a substrate side; the lower layer is formed from silicon or silicon containing one or more elements selected from nonmetallic elements other than oxygen and semimetal elements; the upper layer other than a surface layer is formed from silicon and nitrogen or a material consisting of silicon, nitrogen and one or more elements selected from nonmetallic elements excluding oxygen and semimetal elements; the lower layer has refractive index n of less than 1.8 and extinction coefficient k of 2.0 or more; the upper layer has refractive index n of 2.3 or more and extinction coefficient k of 1.0 or less; and the upper layer has more thickness than the lower layer.