Chemically Amplified Resist Composition for Thick Film Patterning
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Solution Overview
Problem
Chemically amplified positive resist compositions face challenges in forming thick films with high sensitivity, vertical profile, and crack resistance during electroplating or electroless plating, particularly for solder bump formation, where long development times and pattern deformation issues arise due to the use of conventional acid labile groups like acetal and tertiary alkyl esters.
Innovation Solution
A chemically amplified positive resist composition comprising an organic solvent, a base resin with specific recurring units, an acid generator, and a benzotriazole compound, which allows for high sensitivity, short development time, and resistance to cracking during plating, by optimizing the molecular weight and structure of the base resin and incorporating a benzotriazole compound to prevent footing or undercut profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a thick resist film (5 to 100 μm) is formed to enable solder bump pattern formation, then the height requirement for solder bumps is satisfied, but the development time becomes excessively long and sensitivity is reduced
Solution Approach 1:
The patent modifies the chemical structure of the base resin by introducing specific recurring units with formula (1) containing ester groups and hydroxyl groups, along with controlling molecular weight (1,000 to 500,000). These parameter changes in resin composition enable thick film formation while maintaining fast development speed and high sensitivity, resolving the contradiction between film thickness and development time
Solution Approach 2:
The patent creates a composite resist system combining the specific base resin (with recurring units of formula 1) and polyvinyl ether (formula 2) in a defined weight ratio (95:5 to 5:95). This composite material approach allows the resist to achieve both thick film capability and rapid development, overcoming the limitations of single-material systems
2Productivity
If a chemically amplified positive resist composition containing certain acid generator is used to form patterns on metal substrates, then sensitivity is improved, but footing or undercut phenomenon occurs degrading the pattern profile
Solution Approach 1:
The patent introduces a benzotriazole compound as an intermediary substance that mediates between the acid generator and the metal substrate. This compound prevents the direct harmful interaction that causes footing or undercut, while allowing the chemically amplified system to maintain its high sensitivity. The benzotriazole acts as a protective intermediary layer during the patterning process
Solution Approach 2:
The patent converts the potentially harmful acid diffusion that causes footing into a beneficial effect by using the benzotriazole compound to control and direct the acid action. The acid that would normally degrade the pattern profile is instead channeled to effectively dissolve the exposed resist while the benzotriazole prevents unwanted side reactions with the metal substrate, transforming a harmful phenomenon into a useful one
3Ease of manufacture
If conventional acid labile groups like acetal and tertiary alkyl esters are used in the resist composition, then the resist can be developed, but the pattern deforms during electroplating or electroless plating
Solution Approach 1:
The patent fundamentally changes the chemical parameters of the acid labile group by replacing conventional acetal and tertiary alkyl ester groups with the specific recurring unit structure of formula (1). This new structure contains ester groups and hydroxyl groups in specific configurations that provide both developability and resistance to deformation during plating, eliminating the reliability issue while maintaining ease of manufacture
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 composition enables the formation of thick resist films with high sensitivity and vertical profiles, reducing development time and preventing cracking and deformation during electroplating or electroless plating, thereby improving the efficiency and quality of solder bump formation.
Implementation Method 1
a photoacid generator and a benzotriazole compound... (C) an acid generator
Implementation Method 2
incorporating a benzotriazole compound to prevent footing or undercut profiles
Data Source
Figure 1
AI summary
A chemically amplified positive resist composition is provided comprising a substantially alkali-insoluble polymer having an acid labile group-protected acidic functional group, a poly(meth)acrylate polymer having Mw of 1,000-500,000, and an acid generator in a solvent. The composition forms on a substrate a resist film of 5-100 µm thick which can be briefly developed to form a pattern at a high sensitivity and a high degree of removal or dissolution to bottom.