Hard Mask Pattern Transfer for EUV Resist Scum Defects
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Solution Overview
Problem
At semiconductor technology nodes of 7 nm or smaller, line-and-space patterning requires pitch resolution in optical lithography smaller than about 32 nm, which is challenging even with extreme ultra violet (EUV) lithography, leading to issues like resist scum defects and low throughput.
Innovation Solution
A method involving the formation of a hard mask pattern over a patterned photoresist layer with scums, using a dielectric or conductive material to conceal the scums, followed by planarization and etching to pattern underlying layers, thereby improving etching selectivity and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If EUV lithography is employed to achieve smaller pitch resolution, then the resolution capability is improved, but resist scum defects and low throughput occur
Solution Approach 1:
A hard mask layer is introduced as an intermediary between the photo resist pattern and the underlying layer. This hard mask layer conceals the resist scum defects that form during EUV lithography, allowing the pattern transfer to proceed without the defects affecting the final structure. The hard mask layer acts as a mediator that separates the problematic photo resist from the target layer, enabling continued use of EUV lithography for high-resolution patterning while eliminating the harmful effect of resist scum.
2Manufacturing precision
If EUV lithography is employed to achieve smaller pitch resolution, then the resolution capability is improved, but throughput decreases
Solution Approach 1:
The patterning process is segmented into distinct stages: first forming the photo resist pattern with EUV lithography to achieve high resolution, then adding a separate hard mask layer for pattern transfer. This segmentation allows each stage to be optimized independently - the photo resist stage for resolution and the hard mask stage for efficient pattern transfer - thereby maintaining high throughput while achieving the required pitch resolution.
3Device complexity
If photo resist pattern is directly used for etching, then the process is simple, but etching selectivity is poor
Solution Approach 1:
The solution uses a composite structure consisting of the photo resist pattern combined with a hard mask layer. The photo resist provides the initial pattern definition, while the hard mask layer provides the necessary etching selectivity and structural support. This composite approach combines the advantages of both materials - the patternability of photo resist and the etching resistance of hard mask materials - achieving both good etching selectivity and manageable process 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 pattern defects and enhances etching selectivity, allowing for finer patterns without defects and improving the throughput of the lithography process.
Implementation Method 1
a photo resist layer is exposed to an actinic radiation carrying pattern information from a photo mask
Implementation Method 2
a hard mask layer is formed over the developed resist pattern
Data Source
AI summary
In a method of forming a pattern, a first pattern is formed over an underlying layer, the first pattern including main patterns and a lateral protrusion having a thickness of less than 25% of a thickness of the main patterns, a hard mask layer is formed over the first pattern, a planarization operation is performed to expose the first pattern without exposing the lateral protrusion, a hard mask pattern is formed by removing the first pattern while the lateral protrusion being covered by the hard mask layer, and the underlying layer is patterned using the hard mask pattern as an etching mask.