Silsesquioxane Resin Systems with Base Additives
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Solution Overview
Problem
The development of silicon-containing resins for bilayer resist compositions in photolithographic applications faces challenges such as low thermal stability, pattern collapse, and outgassing issues, particularly at 193 nm and 157 nm wavelengths, which affect etch resistance, sensitivity, and shelf life.
Innovation Solution
Silsesquioxane-based compositions with acid dissociable groups and organic base additives, such as bulky tertiary amines, are used to enhance the thermal stability and etch resistance of the resins, minimizing outgassing and improving shelf life, while maintaining high transparency and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high silicon content is incorporated into the polymer to increase etch resistance, then etch resistance is improved, but outgassing of silicon-containing components occurs during exposure
Solution Approach 1:
The patent incorporates silicon-containing groups specifically at the terminal ends of polymer chains rather than throughout the backbone. This localized placement provides etch resistance at the film surface while minimizing bulk outgassing during exposure, resolving the contradiction between etch resistance and outgassing.
Solution Approach 2:
The patent uses a composite polymer structure combining silicon-containing terminal groups with a non-silicon polymer backbone. This composite approach allows the silicon-containing groups to provide etch resistance while the main backbone minimizes outgassing, simultaneously achieving both desired properties.
2Strength
If silsesquioxane-based resins are used to provide etch resistance, then etch resistance is improved, but thermal stability remains low
Solution Approach 1:
The patent combines silsesquioxane-based resin components with other polymer materials to create a composite resist system. This composite structure allows the silsesquioxane to provide etch resistance while the additional components contribute thermal stability, resolving the contradiction between etch resistance and thermal stability.
Solution Approach 2:
The patent modifies the chemical composition and structural parameters of the resist system by incorporating specific silicon-containing terminal groups and adjusting the polymer architecture. These parameter changes enable simultaneous achievement of high etch resistance and improved thermal stability beyond what single-component silsesquioxane resins provide.
3Device complexity
If conventional single-layer resist is used, then process simplicity is maintained, but pattern collapse occurs during pattern transfer
Solution Approach 1:
The patent applies a thin silicon-containing top layer specifically at the patterned regions where etching occurs. This localized silicon layer provides etch resistance and pattern collapse prevention only where needed, while the rest of the resist structure maintains the simplicity of conventional single-layer processing.
Solution Approach 2:
The patent uses a thin top layer rather than a full multi-layer structure. This partial approach provides sufficient etch resistance and pattern collapse prevention without requiring complete multi-layer complexity, achieving a balance between simplicity and reliability.
4Reliability
If multi-layer process is used to prevent pattern collapse, then pattern collapse resistance is improved, but process complexity and cost increase
Solution Approach 1:
The patent extracts the essential function of the silicon-containing etch-resistant layer from a full multi-layer structure and applies it as a thin top layer on a conventional resist. This extraction provides pattern collapse resistance without requiring the complete complexity of multi-layer processes.
Solution Approach 2:
The patent uses a thin top layer approach that provides sufficient pattern collapse resistance without implementing full multi-layer complexity. This partial solution achieves the necessary reliability improvement while minimizing additional process complexity and cost.
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
The silsesquioxane-based compositions provide superior etch resistance, thermal stability, and extended shelf life, along with improved resolution and process latitude, addressing the limitations of existing silicon-containing resins in photolithographic applications.
Implementation Method 1
The organic base additive stabilizes the silsesquioxane resin resulting in extended shelf life
Implementation Method 2
a good chemically amplified photoresist must meet all of the stringent requirements for microlithography at a given wavelength such as transparent, chemically amplifiable, and soluble in industry standard developer (e.g. tetramethyl ammonium hydroxide—TMAH), resistance to plasma etching
Implementation Method 3
193 nm immersion lithography is rapidly emerging as a viable technology
Implementation Method 4
most silsesquioxane-based resins have low thermal stability (i.e., low Tg), it is challenging to obtain high resolution, high sensitivity and a high process latitude
Data Source
AI summary
Silsesquioxane-based compositions that contain (a) silsesquioxane resins that contain HSiO3/2 units and RSiO3/2 units wherein; R is an acid dissociable group, and (b) least one organic base additive selected from bulky tertiary amines, imides, amides and the polymeric amines wherein the organic base additive contains an electron-attracting group with the provision that the organic base additive is not 7-diethylamino-4-methylcoumarin. The silsesquioxane-based compositions are useful as positive resist compositions in forming patterned features on substrate, particularly useful for multi-layer layer (i.e. bilayer) 193 nm & 157 nm photolithographic applications.