EUV Reflective Mask Blank Anti-Diffusion Layer
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Solution Overview
Problem
EUV exposure machines face challenges in achieving high throughput due to variations in reflectance caused by thermal diffusion between the protective film and phase-shift film in reflective masks, leading to reduced contrast and functionality when the power of the exposure light source increases.
Innovation Solution
A reflective mask blank is designed with a substrate, a multilayer reflective film, a ruthenium-based protective film, a tantalum-based phase-shift film, and an anti-diffusion layer comprising ruthenium and oxygen to inhibit counter diffusion, ensuring stable reflectance even with high-power exposure light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the power of the exposure light source is increased to achieve high throughput, then productivity is improved, but thermal diffusion between the protective film and phase-shift film increases causing reflectance variation
Solution Approach 1:
An anti-diffusion layer is introduced as an intermediary barrier between the protective film and the phase-shift film. This layer prevents thermal diffusion and counter diffusion between the two films when high-power exposure light is applied, thereby maintaining reflectance stability while enabling high throughput manufacturing
2Productivity
If high-power exposure light is applied to increase throughput, then productivity is improved, but counter diffusion between protective film and phase-shift film occurs reducing mask functionality
Solution Approach 1:
The anti-diffusion layer serves as a protective barrier that prevents counter diffusion between the protective film and phase-shift film. This maintains the compositional stability of both films even when high-power exposure light is applied for extended periods, ensuring the mask remains functional
3Productivity
If the exposure time is extended to achieve high throughput, then productivity is improved, but thermal diffusion increases causing phase-shift effect reduction
Solution Approach 1:
The anti-diffusion layer acts as a thermal barrier that prevents heat transfer between the protective film and phase-shift film during extended exposure periods. This allows the mask to withstand prolonged exposure to high-power light sources without experiencing thermal diffusion that would reduce the phase-shift effect
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 effectively reduces thermal diffusion and maintains reflectance stability, preventing a reduction in phase-shift effect, thus enhancing the performance and longevity of reflective masks in EUV lithography.
Implementation Method 1
thermal diffusion due to the heat causes counter diffusion between the protective film and a material of the adjacent phase-shift film pattern
Implementation Method 2
a heating value per unit time in the reflective mask upon the exposure (pattern transfer) is increased (since the energy of light absorbed by the phase-shift film is converted into heat), and thus, thermal diffusion due to the heat causes counter diffusion
Implementation Method 3
a reflective mask, in which a multilayer reflective film for reflecting exposure light is formed on a substrate
Implementation Method 4
The light incident on the reflective mask mounted on an exposure machine (pattern transfer apparatus) is absorbed at a region where the phase-shift film pattern exists
Implementation Method 5
some of the incident exposure light is reflected with a phase difference of about 180 degrees with respect to the light reflected by the multilayer reflective film (phase shift), thereby achieving the contrast
Data Source
AI summary
A reflective mask blank that comprises a multilayer reflective film 13, protective film 14, and phase-shift film 16 for shifting a phase of the EUV light, which are formed in said order on a substrate 12. The protective film 14 is made of a material containing ruthenium as a main component, and an anti-diffusion layer 15 which is an oxidized layer containing ruthenium as a main component is formed on a surface of the protective film 14, or as a part of the protective film 14 on a side adjacent to the phase-shift layer 16, so as to inhibit counter diffusion in relation to the phase-shift film 16, thereby inhibiting the thermal diffusion between the protective film 14 and the material of the phase-shift film pattern. Also, a reflective mask and method of manufacture.