EUV Mask Absorber Sidewall Angle and Reflective Layers
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Solution Overview
Problem
Extreme Ultraviolet (EUV) lithography faces Line Edge Roughness (LER) issues due to photoresist chemistry and low photon generation, leading to random pattern variations that affect the Critical Dimension (CD) and electrical performance, necessitating increased exposure doses which reduce manufacturing throughput.
Innovation Solution
An EUV mask absorber with a sidewall angle less than 90 degrees and layers of reflective materials like Ruthenium and Tantalum Oxynitride is used to enhance reflectivity and phase shift EUV light, improving image contrast and reducing shot noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If exposure dose is increased to reduce LER, then manufacturing precision is improved, but productivity deteriorates
Solution Approach 1:
The patent changes the geometric parameters of the absorber structure by forming sidewalls at angles between 80-90 degrees instead of vertical walls. This geometric parameter modification optimizes the interaction between EUV light and the absorber material, improving image contrast and reducing LER without requiring increased exposure dose, thereby maintaining high wafer throughput
Solution Approach 2:
The patent employs composite material structures including absorber layers (molybdenum, ruthenium, tantalum), capping layers (silicon oxide, silicon nitride), and mandrel materials. These composite structures work synergistically to enhance the absorber's effectiveness in improving image contrast and reducing shot noise, allowing lower exposure doses while maintaining precision
2Manufacturing precision
If exposure dose is increased to reduce shot noise, then manufacturing precision is improved, but energy consumption increases
Solution Approach 1:
The patent modifies the absorber sidewall angle parameter to between 80-90 degrees, which optimizes light absorption and phase shift effects. This parameter change enhances image contrast and reduces shot noise intrinsically, eliminating the need for increased exposure dose and thereby reducing energy consumption in the lithography process
Solution Approach 2:
The patent performs preliminary structuring of the absorber with optimized sidewall angles and composite material compositions before exposure. This preliminary optimization of the mask structure pre-establishes conditions for reduced shot noise and improved image contrast, allowing the exposure process to proceed at lower energy levels
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 enhances image contrast by 10% to 15%, reducing LER and lowering the exposure dose, thereby increasing wafer throughput and maintaining manufacturing efficiency.
Implementation Method 1
The sidewall includes a layer of reflective material
Implementation Method 2
the EUV mask absorber is adapted to shift a phase of the EUV light passing therethrough
Data Source
AI summary
An EUV mask absorber formed on a semiconductor structure, includes, in part a sidewall forming am angle relative to a surface of the semiconductor structure that is less than 90 degrees. The sidewall includes a layer of reflective material. The semiconductor structure may include, in part, a multitude of layers. The semiconductor structure may be disposed on a glass substrate, a silicon substrate, or the like. The EUV mask absorber is adapted to shift a phase of the EUV light passing therethrough. The EUV mask absorber may further include, in part, a layer of Ruthenium near a bottom surface of the absorber structure. The EUV mask absorber may further includes, in part, a layer of reflective material near a top surface of the absorber structure. The EUV mask absorber may further include, in part, Tantalum Oxynitride.