Two-Layer Phase Shift Mask Blank for Fine ArF Patterning
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Solution Overview
Problem
Existing phase shift masks struggle to achieve high transmittance and control film thickness to form fine patterns with favorable optical performance, especially with the transition to ArF excimer lasers, limiting pattern miniaturization and resolution.
Innovation Solution
A mask blank with a phase shift film comprising a lower layer of hafnium and oxygen and an upper layer of silicon, oxygen, and nitrogen, with specific atomic content ratios, allowing for a two-layer structure that enhances transmittance and controls film thickness to 60 nm or less, ensuring a phase shift effect and optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional single-layer phase shift film is used, then the manufacturing process is simple, but the transmittance is insufficient and fine pattern formation is difficult
Solution Approach 1:
The phase shift film is divided into two distinct layers: a lower layer (containing silicon and nitrogen) and an upper layer (containing hafnium and oxygen). This segmentation allows each layer to be optimized for different functions - the lower layer provides phase shift effect while the upper layer enhances transmittance and enables fine pattern formation through controlled etching characteristics.
Solution Approach 2:
The invention uses a composite two-layer structure combining materials with different optical and etching properties. The lower layer uses silicon-nitrogen-based material for phase shift, while the upper layer uses hafnium-oxygen-based material for enhanced transmittance. This composite structure resolves the contradiction by integrating multiple material advantages.
2Reliability
If the phase shift film thickness is increased to enhance phase shift effect, then the phase shift effect is improved, but the film thickness cannot be controlled to form fine patterns
Solution Approach 1:
By segmenting the phase shift film into two layers with different thicknesses and compositions, the invention achieves both sufficient phase shift effect and fine pattern formation. The lower layer provides the necessary phase shift while the thinner upper layer enables precise thickness control for fine patterns.
Solution Approach 2:
Different regions of the phase shift film have different properties - the lower layer has higher nitrogen content for phase shift effect, while the upper layer has higher hafnium content for transmittance and thickness control. This local quality differentiation resolves the contradiction between phase shift effect and thickness control.
3Manufacturing precision
If a phase shift film with high nitrogen content is used, then the etching selectivity is improved, but the transmittance decreases
Solution Approach 1:
The invention segments the film structure so that high nitrogen content is concentrated in the lower layer for etching selectivity, while the upper layer has low nitrogen content for high transmittance. This spatial segmentation resolves the contradiction between etching selectivity and transmittance.
Solution Approach 2:
Different nitrogen concentrations are applied locally - high nitrogen in the lower layer for etching control and low nitrogen in the upper layer for light transmission. This local quality approach allows simultaneous optimization of both contradictory properties.
4Manufacturing precision
If the phase shift film thickness is reduced to form fine patterns, then the pattern resolution is improved, but the phase shift effect is weakened
Solution Approach 1:
The composite two-layer structure allows the total film thickness to be reduced for fine pattern formation while the lower layer maintains sufficient thickness for phase shift effect. The upper layer's thin structure enables fine patterns while the lower layer's optimized composition compensates for the reduced overall thickness.
Solution Approach 2:
The lower layer is designed with specific composition and thickness to provide adequate phase shift effect even when the total film thickness is reduced. This local quality optimization in the lower layer compensates for the reduced overall thickness, maintaining phase shift effect while enabling fine patterns.
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 enables increased transmittance and controlled film thickness, enabling the formation of fine patterns with enhanced phase shift effects and improved optical performance, suitable for semiconductor manufacturing.
Implementation Method 1
a phase shift film formed on the light-transmissive substrate, in which the phase shift film includes a lower layer containing hafnium and oxygen and an upper layer formed on the lower layer and containing silicon, oxygen, and nitrogen
Data Source
AI summary
A mask blank comprises: a light-transmissive substrate; and a phase shift film formed on the light-transmissive substrate, in which the phase shift film includes a lower layer containing hafnium and oxygen and an upper layer formed on the lower layer and containing silicon, oxygen, and nitrogen, a total content of hafnium and oxygen in the lower layer is 95 atom % or more, and a content of nitrogen in the upper layer is 15 atom % or more.