Chemically Amplified Resist Film Uniformity via Solvent Mixture
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Solution Overview
Problem
The challenge is to achieve improved line edge roughness (LER) and high resolution in patterning processes, particularly for feature sizes of 50 nm or less, where conventional solvent systems fail to form uniform resist films due to non-uniform distribution of components and increased domain sizes, especially when resist film thickness is reduced.
Innovation Solution
A chemically amplified resist composition using a solvent mixture with propylene glycol monomethyl ether acetate (PGMEA) and ethyl lactate, combined with a high-boiling solvent such as γ-butyrolactone, is applied, followed by post-development heat treatment to sinter the resist film, ensuring uniformity and minimizing LER.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional solvent system is used to form a resist film, then the coating process is simple, but the resist film exhibits non-uniform distribution of components and increased domain sizes, resulting in poor line edge roughness (LER) and resolution
Solution Approach 1:
The patent employs a composite solvent system consisting of multiple components: propylene glycol monomethyl ether acetate (PGMEA) as the primary solvent, ethyl lactate (EL) as a secondary solvent, and γ-butyrolactone (GBL) as a high-boiling solvent. This composite solvent mixture creates a uniform resist film with controlled evaporation rates, eliminating non-uniform component distribution and reducing domain sizes, thereby improving LER and resolution without requiring complex additional equipment
Solution Approach 2:
The patent utilizes the different boiling points of the solvent components to control the evaporation process. PGMEA (lower boiling point) evaporates first during prebaking, EL evaporates second, and GBL (higher boiling point) remains as a high-boiling solvent component. This parameter-based control of evaporation rates ensures uniform film formation and prevents premature solvent loss that would cause non-uniformity and increased LER
2Manufacturing precision
If the resist film thickness is reduced to achieve finer feature sizes, then the resolution improves, but the uniformity of the resist film deteriorates due to increased domain sizes
Solution Approach 1:
The patent changes the physical parameters of the solvent system by introducing a high-boiling solvent (γ-butyrolactone) with a boiling point significantly higher than PGMEA and EL. This parameter change allows the resist film to maintain uniform composition even at reduced thicknesses (50 nm or less) because the high-boiling solvent prevents premature evaporation and maintains homogeneous distribution of resist components throughout the film, eliminating domain formation that would occur with conventional solvent systems
3Manufacturing precision
If additional system components are added to improve LER through solvent gas exposure, then the LER improves, but the system complexity and cost increase
Solution Approach 1:
The patent applies the self-service principle by using the resist composition's own solvent components to achieve LER improvement. The high-boiling solvent (γ-butyrolactone) within the resist film itself serves the dual function of maintaining film uniformity during formation and providing the necessary solvent vapor during post-development heat treatment to smooth the resist surface. This eliminates the need for external solvent gas delivery systems, reducing device complexity and cost while maintaining improved LER
Solution Approach 2:
The patent recovers and utilizes the high-boiling solvent component (γ-butyrolactone) that would otherwise be discarded or require separate handling. This solvent is retained in the resist film during prebaking and post-exposure baking, then evaporated controllably during post-development heat treatment to provide the necessary surface smoothing effect. This approach converts a potential waste product into a functional element that improves LER without requiring additional system components
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 results in a resist pattern with minimized LER and improved resolution, maintaining pattern profile integrity even at reduced film thicknesses, without requiring additional system components for solvent gas exposure.
Implementation Method 1
heat treating to form a resist pattern... when the resist film is sintered by the post-development heat treatment
Implementation Method 2
the high-boiling solvent remains in the resist film after pattern formation... effects uniformization of roughness
Data Source
AI summary
In a chemically amplified resist composition comprising a base resin, an acid generator, and a solvent, 1,400-5,000 pbw of the solvent is present per 100 pbw of the base resin, and the solvent comprises at least 60 wt% of PGMEA and ethyl lactate, and 0.2-20 wt% of a high-boiling solvent. A resist pattern is formed by coating the resist composition on a substrate, prebaking, patternwise exposure, post-exposure baking, development, and heat treatment.