EUV Phase Shift Mask With Nitrogen-Chromium Absorber
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Solution Overview
Problem
Extreme ultraviolet (EUV) lithography faces challenges in achieving high-resolution images due to the absorption of EUV light by refractive optical materials, necessitating the use of reflective systems, and requires improved productivity in semiconductor device manufacturing.
Innovation Solution
A phase shift mask for EUV lithography is designed with a substrate, a reflective layer, a capping layer, a buffer pattern, and an absorber pattern that includes nitrogen and chromium, where the absorber pattern has a refractive index less than the buffer pattern and a thickness greater than the capping layer, allowing for etch selectivity and optimized EUV light reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a reflective optical system is used for EUV lithography, then light absorption by refractive materials is avoided, but manufacturing precision and image resolution are difficult to achieve
Solution Approach 1:
The mask is divided into multiple functional layers: a reflective layer for EUV light reflection, a phase shift layer for phase modulation, and an absorber layer for amplitude modulation. Each layer performs a specific function to collectively achieve high-resolution patterning while minimizing light absorption losses.
Solution Approach 2:
The mask uses composite material structures including metal layers (e.g., molybdenum, silicon) for reflection, compound semiconductor layers for phase shifting, and nitrogen-containing absorber materials. These composite structures enable simultaneous optimization of reflectivity, phase control, and absorption characteristics for EUV lithography.
2Productivity
If conventional lithography processes are used, then existing manufacturing methods can be maintained, but productivity and patterning quality are limited
Solution Approach 1:
The invention utilizes changes in optical parameters (refractive index, absorption coefficient) of mask materials at EUV wavelengths to achieve superior patterning. By optimizing layer thicknesses and material compositions, the mask enables higher resolution and better process control compared to conventional lithography, thereby improving both productivity and patterning quality.
3Loss of energy
If the absorber pattern thickness is increased to improve EUV light absorption, then phase shift control is enhanced, but etch selectivity and pattern fidelity deteriorate
Solution Approach 1:
The absorber layer is designed with specific local properties: nitrogen-containing materials with controlled thickness (e.g., 20-50 nm) and composition gradients. This local optimization ensures sufficient EUV absorption while maintaining etch selectivity and pattern fidelity through precise control of material properties at the pattern level.
Solution Approach 2:
The phase shift layer acts as an intermediary between the reflective layer and absorber layer, enabling phase modulation with thinner absorber materials. This intermediate layer allows adequate EUV absorption without requiring excessive absorber thickness, thereby preserving pattern fidelity and etch selectivity.
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 phase shift mask enables high-resolution image formation by controlling EUV light reflection and absorption, improving productivity in semiconductor device manufacturing by reducing process defects and enhancing patterning quality.
Implementation Method 1
the extreme ultraviolet light may be absorbed into most of the refractive optical materials commonly used in other lithography processes, and thus the EUV lithography process may generally use a reflective optical system, instead of a refractive optical system
Implementation Method 2
an absorber pattern on the buffer pattern, the absorber pattern including a refractive index less than a refractive index of the buffer pattern
Implementation Method 3
phase shift mask for extreme ultraviolet lithography... capable of realizing a high-resolution image
Implementation Method 4
phase shift mask... enabling high-resolution image formation by controlling EUV light reflection and absorption
Data Source
AI summary
A phase shift mask for extreme ultraviolet lithography includes a substrate, a reflective layer on the substrate, a capping layer on the reflective layer, a buffer pattern on the capping layer, the buffer pattern including an opening exposing a surface of the capping layer, and an absorber pattern on the buffer pattern, the absorber pattern including a refractive index less than a refractive index of the buffer pattern and a thickness greater than a thickness of the buffer pattern. The buffer pattern includes a material having an etch selectivity with respect to the absorber pattern and the capping layer.