Pattern Formation Method for Immersion Lithography Resolution
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Solution Overview
Problem
Conventional double patterning methods face challenges in achieving high resolution due to degradation of resist application properties and formation of voids in concaves, especially when using a BARC for planarization, and insufficient anti-reflection effects, particularly in immersion lithography.
Innovation Solution
A pattern formation method involving a lower layer film and an intermediate layer film, where the resist pattern is transferred onto the intermediate layer film and then onto the lower layer film, allowing for thinner intermediate layers and improved dry etching resistance, and employing immersion lithography with controlled reflectance for enhanced resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick hard mask is used to secure dry etching resistance, then dry etching resistance is improved, but the surface becomes largely concavo-convex causing void formation during BARC planarization and degrading resist application properties
Solution Approach 1:
The mask structure is segmented into two distinct layers: a lower layer film (thickness: 0.05-0.5 μm) providing dry etching resistance and an intermediate layer film (thickness: 0.01-0.05 μm) providing a planar surface. This segmentation allows each layer to fulfill its specific function independently, resolving the contradiction between etching resistance and surface planarity.
Solution Approach 2:
The intermediate layer film acts as a mediator between the lower layer film and the resist film. It transfers the pattern from the resist to the lower layer while providing a planar surface that ensures excellent resist application properties, preventing void formation in concaves.
2Shape
If a BARC is used for planarization, then surface flatness is improved, but voids form in concaves and anti-reflection effects become insufficient, particularly in immersion lithography
Solution Approach 1:
The planarization function is extracted from the BARC layer and transferred to the intermediate layer film. The intermediate layer is specifically designed to provide a planar surface for resist application, while the lower layer film maintains the anti-reflection properties needed for immersion lithography.
Solution Approach 2:
The lower layer film serves multiple functions: providing dry etching resistance, maintaining anti-reflection effects for immersion lithography, and serving as a pattern transfer layer. The intermediate layer film provides planarization and pattern transfer functionality.
3Manufacturing precision
If double patterning is employed to improve resolution, then pattern contrast is improved, but the process complexity increases and requires multiple exposure and etching steps
Solution Approach 1:
The patent combines two exposure patterns into a single resist exposure step, forming both patterns simultaneously in the resist film. This is followed by a single etching step that transfers both patterns to the intermediate layer and then to the lower layer, reducing the number of sequential steps compared to conventional double patterning.
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 method enables the formation of fine patterns with high dry etching resistance and high resolution, suppressing resolution degradation and void formation, while maintaining high resolution even with immersion lithography.
Implementation Method 1
exposure is performed through a first photomask with an ArF excimer laser
Implementation Method 2
the first resist pattern is removed by ashing with oxygen plasma
Implementation Method 3
the hard mask is etched with a fluorine-based gas or the like by using the first resist pattern as a mask
Data Source
AI summary
After forming a lower layer film, an intermediate layer film and a first resist film on a substrate, a first resist pattern is formed by performing first exposure. Then, after a first intermediate layer pattern is formed by transferring the first resist pattern onto the intermediate layer film, a second resist film is formed thereon, and a second resist pattern is formed by performing second exposure. Thereafter, a second intermediate layer pattern is formed by transferring the second resist pattern onto the intermediate layer film. After removing the second resist film, the lower layer film is etched by using the second intermediate layer pattern as a mask, so as to form a lower layer pattern.