Phase Shift Lithography Mask With Etch Stop Layer Precision
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the inability to precisely define small feature sizes due to insufficient contrast in aerial images and photoresist profiles, leading to critical dimension variation and placement errors, particularly when using phase shifting masks, which are affected by unwanted etching of the substrate during mask formation.
Innovation Solution
Incorporation of an etch stop layer that is semi-transmissive to lithography light and resistant to etchants, protecting the substrate from etching during phase shifting mask fabrication, thereby maintaining precise phase shifts and preventing substrate alteration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If phase shifting masks are used to improve image contrast and reduce critical dimension variation, then manufacturing precision is improved, but the substrate becomes susceptible to unwanted etching during mask formation
Solution Approach 1:
An etch stop layer is introduced as an intermediary between the substrate and the phase shifting mask layers. This intermediate layer protects the substrate from etching during mask fabrication while allowing the phase shifting functionality to be maintained. The etch stop layer acts as a mediator that prevents direct contact between etchants and the substrate.
Solution Approach 2:
The mask structure is segmented into multiple functional layers: the substrate, the etch stop layer, and the phase shifting mask layers. This segmentation allows each layer to perform its specific function independently - the etch stop layer handles substrate protection while the phase shifting layers handle image contrast enhancement.
2Object-affected harmful factors
If the etch stop layer is made highly transmissive to protect substrate, then substrate protection is improved, but phase shift accuracy deteriorates due to insufficient phase modulation
Solution Approach 1:
The etch stop layer is designed with composite properties - it is semi-transmissive rather than fully transmissive or opaque. This semi-transmissive characteristic allows it to provide both substrate protection and maintain adequate phase shift accuracy by allowing sufficient light transmission while still performing the etching protection function.
Solution Approach 2:
The transmissivity parameter of the etch stop layer is optimized to a specific range that balances two competing requirements: high enough to protect the substrate from etching, and low enough to maintain sufficient phase modulation for accurate patterning. This parameter optimization resolves the contradiction between protection and accuracy.
3Productivity
If feature size is reduced to increase functional density, then productivity is improved, but image contrast and placement precision deteriorate
Solution Approach 1:
The patent replaces conventional opaque mask patterns with phase shifting mask technology that uses optical phase modulation instead of simple absorption. This substitution enables better image contrast and placement precision at reduced feature sizes, allowing higher functional density without sacrificing manufacturing precision.
Solution Approach 2:
The invention changes the optical parameters of the mask by introducing phase shifting functionality. This parameter change in the mask design enables improved image contrast and placement precision even as feature sizes are reduced to increase functional density.
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 etch stop layer ensures accurate phase shifts and reduces substrate etching, enhancing the precision and reproducibility of pattern projection onto silicon wafers, improving the quality of photoresist patterns and reducing imaging aberrations.
Implementation Method 1
a phase shift layer 204, 214 disposed over a front surface of the substrate 202, 212
Implementation Method 2
an etch stop layer 206, 216 between the substrate 202, 212 and the phase shift layer 204, 214
Data Source
AI summary
A lithography mask including a substrate, a phase shift layer on the substrate and an etch stop layer is provided. The phase shift layer is patterned and the substrate is protected from etching by the etch stop layer. The etch stop layer can be a material that is semi-transmissive to light used in photolithography processes or it can be transmissive to light used in photolithography processes.