EUV Mask Buffer Layer Exposure for Etching Uniformity
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Solution Overview
Problem
Defects in photolithography masks used in extreme ultraviolet photolithography processes can lead to defects in semiconductor devices, resulting in resource wastage due to improper functioning, as these defects propagate from the mask to the fabrication processes.
Innovation Solution
A photolithography mask is fabricated with a substrate, a reflective multilayer, a buffer layer, and an absorption layer, where the absorption layer is patterned to expose an outer portion of the buffer layer, allowing photoresist to cover lateral surfaces, thereby stabilizing the surface voltage during plasma etching and ensuring consistent etching rates across the mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the absorption layer is fully covered by photoresist, then the mask structure is simple, but the surface voltage becomes unstable during plasma etching causing site-to-site differences
Solution Approach 1:
The patent applies local quality by creating a peripheral region where the buffer layer is exposed at the edges of the mask, while the central region maintains full photoresist coverage. This localized exposure of the buffer layer specifically at the periphery stabilizes the surface voltage during plasma etching without affecting the overall mask structure or requiring changes to the absorption layer pattern. The solution addresses the voltage stability issue only where needed, maintaining simplicity in the majority of the mask structure.
2Manufacturing precision
If the absorption layer is patterned to expose buffer layer, then surface voltage stabilizes during plasma etching, but the mask fabrication process becomes more complex
Solution Approach 1:
The patent implements preliminary action by pre-patterning the buffer layer exposure during the absorption layer formation process. The buffer layer is exposed at the periphery before the plasma etching step, so that when etching occurs, the surface voltage is already stabilized. This advance preparation ensures uniform etching rates without requiring additional process steps during the actual etching operation, thereby maintaining ease of manufacture while achieving manufacturing precision.
3Reliability
If photoresist covers lateral surfaces of absorption layer, then etching rate becomes consistent, but the mask structure requires additional layers
Solution Approach 1:
The patent applies universality by making the buffer layer serve multiple functions: it acts as both a protective layer during fabrication and as a voltage stabilization layer during plasma etching. The buffer layer's exposure at the periphery provides electrical isolation that stabilizes surface voltage, while its presence in the central region continues to protect the absorption layer. This multi-functionality achieves etching rate consistency without requiring additional dedicated layers, thereby minimizing the increase in mask structure complexity.
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 reduces defects in semiconductor devices by maintaining consistent etching rates and preventing site-to-site differences, ensuring proper functioning and reducing resource wastage.
Implementation Method 1
a reflective multilayer positioned on the substrate and configured to reflect ultraviolet radiation during extreme ultraviolet photolithography processes
Implementation Method 2
an absorption layer positioned on the buffer layer and configured to absorb ultraviolet light during extreme ultraviolet photolithography processes
Implementation Method 3
allowing photoresist to cover lateral surfaces, thereby stabilizing the surface voltage during plasma etching
Data Source
AI summary
A method for forming an extreme ultraviolet photolithography mask includes forming a reflective multilayer, forming a buffer layer on the reflective multilayer, and forming an absorption layer on the reflective multilayer. Prior to patterning the absorption layer, an outer portion of the absorption layer is removed. Photoresist is then deposited on the top surface of the absorption layer and on sidewalls of the absorption layer. The photoresist is then patterned, and the absorption layer is etched with a plasma etching process in the presence of the patterned photoresist. The presence of the photoresist on the sidewalls of the absorption layer during the plasma etching process helps to improve uniformity in the etching of the absorption layer during the plasma etching process.