TaBNH Absorbing Layer for EUV Mask Blank Charge-Up
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Solution Overview
Problem
Conventional EUV mask blanks face challenges in achieving a balance between low reflectivity for EUV light and pattern inspection light, while maintaining stable film deposition rates and controlling B content in the absorbing layer, particularly with TaBN and TaBNO films, which can lead to charge-up issues and productivity losses.
Innovation Solution
A reflective mask blank with an absorbing layer composed of TaBNH, containing tantalum (Ta), boron (B), nitrogen (N), and hydrogen (H), with specific atomic ratios and film thickness, and a low reflective layer with Ta, B, O, or N, and H, to achieve amorphous structure and low reflectivity, enhancing etching characteristics and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the O content of the absorbing layer is increased to improve insulation property, then charge-up occurs during electron-beam-writing, but if the O content is decreased, then insulation property deteriorates
Solution Approach 1:
The patent changes the compositional parameters of the absorbing layer by incorporating hydrogen (0.1-5 at%) in addition to controlling oxygen content (1-20 at%). This parameter change allows the layer to maintain insulation properties while reducing charge-up through the specific compositional ratio of Ta-B-O-H elements
Solution Approach 2:
The patent creates a composite absorbing layer material comprising Ta-B-O-H system with specific compositional ranges. This composite material combines the benefits of oxygen for insulation with hydrogen for charge-up suppression, achieving both requirements simultaneously
2Shape
If the B content in the absorbing layer is increased to achieve amorphous structure, then surface smoothness improves, but film deposition rate decreases and productivity is reduced
Solution Approach 1:
The patent optimizes the B content parameter to a specific range (1-20 at%) rather than using high B content. This parameter optimization achieves amorphous structure formation while maintaining acceptable deposition rates, resolving the contradiction between surface quality and productivity
Solution Approach 2:
The patent uses a composite Ta-B-O-H material system where the interaction of multiple elements facilitates amorphous structure formation at lower B content levels. The presence of O and H elements assists in achieving surface smoothness without requiring excessive B, thus maintaining higher deposition rates
3Ease of manufacture
If a TaBN or TaBNO film is used for the absorbing layer to achieve high EUV absorption, then low reflectivity for EUV light is obtained, but charge-up occurs during electron-beam-writing
Solution Approach 1:
The patent develops a composite absorbing layer material in the Ta-B-O-H system with specific compositional ratios. This composite material maintains high EUV absorption capability while the hydrogen component specifically addresses the charge-up issue, achieving both low EUV reflectivity and charge-up suppression
4Productivity
If the film deposition rate is increased to improve productivity, then B content control becomes difficult and film quality deteriorates, but if deposition rate is decreased, then manufacturing efficiency is reduced
Solution Approach 1:
The patent establishes specific parameter ranges for B (1-20 at%), O (1-20 at%), and H (0.1-5 at%) content that enable reliable film quality within acceptable deposition rates. These parameter specifications provide clear manufacturing targets that balance productivity and precision
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 proposed solution provides a stable and controllable EUV mask blank with low reflectivity for EUV light and pattern inspection light, reducing the risk of charge-up and improving productivity by maintaining a B content below 5 at%, ensuring excellent etching and optical characteristics.
Implementation Method 1
a material having a high absorbing coefficient to EUV light, specifically, a material having Cr or Ta as major component, is used
Implementation Method 2
a multilayered reflective film which is formed by laminating alternately a layer of high refractive index and a layer of low refractive index whereby the reflectance of light is increased when EUV light is irradiated to the layer surface
Data Source
AI summary
A reflective mask blank for EUV lithography having an absorbing layer which has a low reflectivity with respect to wavelength regions of EUV light and pattern inspection light, and which is easily controllable to obtain desired film composition and film thickness.The reflective mask blank for EUV lithography having a reflective layer for reflecting EUV light and an absorbing layer for absorbing EUV light which are formed in this order on a substrate, wherein the absorbing layer contains at least tantalum (Ta), boron (B), nitrogen (N) and hydrogen (H), andthe absorbing layer has a B content that is 1 at % or greater but less than 5 at %, an H content that is between 0.1 and 5 at %, a Ta+N total content that is between 90 and 98.9%, and a Ta:N composition ratio (Ta:N) that is between 8:1 and 1:1.