EUV Reflection Mask Phase Reversing Layer Shadow Effect
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional EUV photolithography reflection masks suffer from a 'shadow effect' due to the large height of absorption material patterns, leading to discrepancies between the intended and actual photoresist patterns on silicon wafers, as well as incomplete absorption of EUV light, resulting in inaccurate pattern formation during the etching process.
Innovation Solution
A reflection mask for EUV photolithography is developed, featuring a phase reversing layer between the lower and upper reflection layers, which causes destructive interference of unnecessary EUV light, allowing for precise patterning of the photoresist layer by forming a multi-layer structure using materials like molybdenum and silicon, and employing sputtering methods for layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional reflection mask with absorption material pattern is used, then the mask structure is simple, but the shadow effect occurs causing pattern dimension discrepancy between mask and photoresist
Solution Approach 1:
The reflection mask is divided into multiple functional layers: a lower reflection layer, an upper reflection layer, and a phase reversing layer positioned between them. This segmentation allows each layer to perform its specific function - the reflection layers provide EUV light reflection while the phase reversing layer creates destructive interference to eliminate the shadow effect, thereby achieving both structural feasibility and high pattern dimension accuracy
Solution Approach 2:
The phase reversing layer acts as an intermediary between the lower and upper reflection layers. It receives EUV light from the lower reflection layer, reverses its phase, and combines it with light reflected from the upper reflection layer to create destructive interference. This intermediary layer eliminates the harmful shadow effect without requiring changes to the fundamental reflection mask structure
2Ease of manufacture
If absorption material pattern with large height is used, then the mask can be fabricated, but shadow effect occurs leading to incomplete photoresist exposure
Solution Approach 1:
Instead of trying to eliminate the shadow effect by reducing the absorption material height (which would compromise manufacturability), the invention converts the harmful shadow effect into a beneficial outcome. By introducing the phase reversing layer that creates destructive interference, the shadow effect is neutralized and actually improves pattern accuracy. This allows the absorption material to maintain its necessary height for easy fabrication while eliminating its harmful effects
Solution Approach 2:
The invention changes the optical parameter (phase) of the EUV light by introducing the phase reversing layer. This layer shifts the phase of reflected light by 180 degrees, transforming constructive interference into destructive interference. This parameter change eliminates the shadow effect and ensures complete and accurate photoresist exposure without altering the physical dimensions or manufacturability of the mask structure
3Device complexity
If a single reflection layer is used, then the mask structure is simple, but EUV light absorption is incomplete causing pattern distortion
Solution Approach 1:
The single reflection layer is segmented into two separate reflection layers (lower and upper) with a phase reversing layer in between. This segmentation allows the system to achieve complete EUV light absorption through destructive interference, eliminating pattern distortion while maintaining a relatively simple overall structure that can be fabricated using standard processes
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 solution eliminates the shadow effect and ensures that the photoresist pattern on the silicon wafer is formed with the same dimensions as the mask pattern, enhancing the precision and accuracy of the photolithography process by effectively canceling out unwanted EUV light through destructive interference.
Implementation Method 1
a phase reversing layer formed in a predetermined pattern between the lower reflection layer and the upper reflection layer and causing destructive interference between reflection light from the upper reflection layer and reflection light from the lower reflection layer
Implementation Method 2
a lower reflection layer formed in a multi-layer structure on the substrate and including a material that can reflect EUV light; an upper reflection layer formed in a multi-layer structure on the lower reflection layer and capable of reflecting EUV light
Implementation Method 3
employing sputtering methods for layer formation
Data Source
AI summary
A reflection mask for extreme ultraviolet (EUV) photolithography and a method of fabricating the same, in which the reflection mask includes a substrate, a lower reflection layer formed in a multi-layer structure on the substrate and including a material reflecting EUV light, an upper reflection layer formed in a multi-layer structure on the lower reflection layer and reflecting EUV light, and a phase reversing layer formed between the lower reflection layer and the upper reflection layer in a certain pattern and causing destructive interference between reflection light from the upper reflection layer and reflection light from the lower reflection layer. An incidence of a shadow effect can be reduced and unnecessary EUV light can be eliminated, so that a pattern on the reflection mask can be projected precisely on a silicon wafer. Since the phase reversing layer includes the same material as the reflection layer and an absorption layer, mask fabrication processes can be handled easily.