EUV Reflective Mask Blank Alloy Phase Shift Film
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The manufacturing of reflective mask blanks for EUV lithography faces challenges in achieving stable phase difference and reflectance properties due to fluctuations in film thickness, leading to pattern errors and reduced accuracy in semiconductor device production.
Innovation Solution
The development of a reflective mask blank with a phase shift film composed of an alloy with specific refractive index and extinction coefficient values, allowing for adjustments in composition ratios to maintain desired phase difference and reflectance properties within ±2 degrees and ±0.2% variation, respectively, even with ±0.5% film thickness fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer halftone film material is used, then the manufacturing process is simple, but the reflectance and phase difference properties are unstable due to film thickness fluctuations
Solution Approach 1:
The patent applies composite materials by forming a halftone film using multiple metal layers (e.g., Ta and Ru layers) instead of a single-layer material. This composite structure provides stable reflectance and phase difference properties even when film thickness fluctuates, resolving the contradiction between manufacturing simplicity and phase difference precision.
Solution Approach 2:
The patent changes the material parameters by selecting specific metal combinations (Ta-Ru, Ta-Nb) with controlled composition ratios. By adjusting the refractive index and extinction coefficient through material composition rather than relying solely on film thickness control, the system achieves stable optical properties despite thickness variations.
2Manufacturing precision
If film thickness is tightly controlled, then phase difference precision is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent uses composite metal layer structures where the optical properties are determined by material composition rather than precise thickness control. This reduces manufacturing complexity while maintaining phase difference precision within ±2 degrees.
Solution Approach 2:
The patent shifts the control parameter from film thickness to material composition ratio. By controlling the ratio of metals in the composite film rather than relying on absolute thickness precision, the manufacturing process becomes simpler while achieving the required ±2 degree phase difference precision.
3Manufacturing precision
If reflectance is increased to reduce shadowing effect, then pattern accuracy is improved, but phase shift effectiveness is reduced
Solution Approach 1:
The patent optimizes the optical parameters (refractive index n and extinction coefficient k) of the composite halftone film to achieve a balanced reflectance level. This controlled reflectance reduces the shadowing effect while maintaining sufficient phase shift effectiveness, resolving the contradiction between pattern accuracy and phase shift reliability.
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
This approach enables the stable production of reflective masks with consistent phase shift and reflectance properties, ensuring high accuracy and fine pattern transfer in semiconductor devices, thereby improving manufacturing yield and quality.
Implementation Method 1
A portion of the exposure light entering the phase shift film pattern is reflected (phase-shifted) at a phase difference of about 180 degrees from light reflected by the multilayer reflective film
Implementation Method 2
Light that has entered the reflective mask installed in an exposure apparatus (pattern transfer apparatus) is absorbed at those portions where the phase shift film pattern is present and is reflected by the multilayer reflective film at those portions where the phase shift film pattern is not present
Implementation Method 3
a multilayer reflective film that reflects exposure light is formed on a substrate
Implementation Method 4
Light that has entered the reflective mask installed in an exposure apparatus (pattern transfer apparatus) is absorbed at those portions where the phase shift film pattern is present
Data Source
AI summary
Provided are a reflective mask blank, having a phase shift film having little dependence of phase difference and reflectance on film thickness, and a reflective mask. The reflective mask blank is characterized in that the phase shift film is composed of a material comprised of an alloy having two or more types of metal so that reflectance of the surface of the phase shift film is more than 3% to not more than 20% and so as to have a phase difference of 170 degrees to 190 degrees, and when a group of metal elements that satisfies the refractive index n and the extinction coefficient k of k>α*n+β is defined as Group A and a group of metal elements that satisfies the refractive index n and the extinction coefficient k of k<α*n+β is defined as Group B, the alloy is such that the composition ratio is adjusted so that the amount of change in the phase difference is within the range of ±2 degrees and the amount of change in reflectance is within the range of ±0.2% when one or more types of metal element each is selected from the Group A and the Group B and the film thickness of the phase shift film has fluctuated by ±0.5% with respect to a set film thickness (provided that α: proportional constant, β: constant).