MoSiON Etching Mask for Sub-40nm Photomask Resolution
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Solution Overview
Problem
Conventional etching mask technologies for photomasks are insufficient for achieving the required resolution and pattern precision in DRAM hp32 nm and subsequent generations, particularly due to limitations in resist film thickness, line edge roughness, and etching mask durability, which hinder the formation of fine auxiliary patterns and lead to pattern collapse.
Innovation Solution
A photomask blank comprising a transparent substrate with a molybdenum and silicon light-shielding film and a chromium-based etching mask film, where the etching mask film has a chromium content of 45 at % or less and a sheet resistance value of 3.0 kΩ/square or less, and is processed to maintain the mask pattern during etching, ensuring high etching selectivity and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the light-shielding film is reduced to improve resolution, then the resolution when mask pattern is transferred to the light-shielding film is improved, but the OD value (optical density) decreases
Solution Approach 1:
The patent changes the material composition parameters of the light-shielding film by incorporating tungsten (5-30 at%) in addition to molybdenum and silicon. This compositional parameter change allows achieving both high resolution and high optical density simultaneously, resolving the contradiction between reducing film thickness for resolution and maintaining OD value.
Solution Approach 2:
The patent uses a composite light-shielding film containing multiple elements (Mo, Si, W) with specific compositional ratios. This composite material approach enables the film to achieve both high etching selectivity and high optical density, allowing thin film formation without sacrificing light-shielding performance.
2Manufacturing precision
If a Cr-based etching mask film is used to reduce resist load, then the resolution when mask pattern is transferred to the etching mask film is improved, but the etching mask film durability and pattern precision are insufficient for sub-40 nm nodes
Solution Approach 1:
The patent changes the material composition of the etching mask film from conventional Cr-based to a novel MoSiON-based film with specific compositional ratios (SiO2: 30-70 wt%, MoO3: 10-30 wt%, Nb2O5: 10-30 wt%). This parameter change provides both sufficient etching selectivity and enhanced durability for sub-40 nm pattern transfer.
Solution Approach 2:
The patent introduces a specific intermediate layer structure between the resist and the light-shielding film. The MoSiON-based etching mask film acts as an intermediary that provides both the necessary etching selectivity and the mechanical durability required for high-resolution patterning at advanced nodes.
3Productivity
If the chromium content of the etching mask film is reduced to 45 at % or less to improve etching selectivity, then the etching performance is improved, but the conductivity and sheet resistance control become more difficult
Solution Approach 1:
The patent changes the compositional parameters of the etching mask film by incorporating specific ratios of SiO2, MoO3, and Nb2O5. This compositional adjustment allows achieving low chromium content (45 at% or less) for improved etching selectivity while maintaining controllable sheet resistance through the synergistic effects of the oxide components.
Data Source
AI summary
[Object] A photomask blank for use in producing a photomask for exposure with an ArF excimer laser. The photomask blank is intended to be applied to the 32-nm DRAM half-pitch (hp) and succeeding generations in the semiconductor design rule.[Solution] The photomask blank is for use in producing a photomask to which an exposure light having a wavelength not longer than 200 nm is applied. The photomask blank is characterized by comprising a transparent substrate, a light-shielding film formed on the transparent substrate and containing molybdenum and silicon, and an etching mask film formed directly on the light-shielding film and containing chromium. The photomask blank is further characterized in that the light-shielding film comprises a light-shielding layer and an antireflection layer which have been disposed in this order from the transparent substrate side, the light-shielding layer having a molybdenum content of 9-40 at %, and that the etching mask film has a chromium content of 45 at % or lower.