Negative Photoresist Coating Uniformity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current negative photoresists used in semiconductor encapsulation processes face challenges with high viscosity, leading to non-uniform coating and increased film thickness differences across wafers, which affect copper electroplating quality and manufacturing costs.
Innovation Solution
A negative photoresist formulation comprising 40-65 wt % modified epoxy acrylate, 3-6 wt % photosensitizer, and 100-1000 ppm leveling agent, with a polydimethylsiloxane copolymer as the leveling agent, is used to achieve improved coating uniformity and thickness control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the solid content of photoresist is increased to meet high film thickness requirements, then the film thickness can be increased, but the viscosity increases continuously making pump extraction difficult and increasing extraction amount
Solution Approach 1:
The patent changes the chemical composition parameters of the photoresist by using modified epoxy acrylate with specific molecular weight (80,000-140,000) and molecular weight distribution (2.0-4.0), along with specific photosensitizers and leveling agents, to achieve high film thickness while controlling viscosity for pumpable extraction
Solution Approach 2:
The patent creates a composite photoresist formulation combining modified epoxy acrylate, specific photosensitizers (mixture of sulfonium salt and diazo compound), and leveling agents (polydimethylsiloxane copolymer and propylene glycol monomethyl ether acetate) to simultaneously achieve high film thickness, controlled viscosity, and coating uniformity
2Length of stationary object
If the viscosity of photoresist is increased to achieve high film thickness, then the film thickness can be increased, but the coating uniformity deteriorates with large thickness difference between center and edge
Solution Approach 1:
The patent introduces leveling agents with specific parameters (polydimethylsiloxane copolymer with molecular weight 3000-6000, mixed with propylene glycol monomethyl ether acetate in 7:3 mass ratio) to modify the flow characteristics and reduce thickness variation during coating
Solution Approach 2:
The leveling agents are pre-added to the photoresist formulation before coating to proactively prevent thickness non-uniformity from occurring during the coating process, rather than correcting it afterward
3Length of stationary object
If the viscosity of photoresist is increased to achieve high film thickness, then the film thickness can be increased, but the exposure amount and electroplated copper thickness become non-uniform
Solution Approach 1:
The patent optimizes the photoresist composition parameters including modified epoxy acrylate molecular weight and distribution, photosensitizer ratios (3:7 mixture), and leveling agent concentrations (300-500 ppm) to ensure uniform exposure characteristics and subsequent electroplating uniformity
Solution Approach 2:
The patent establishes a formulation system where the interaction between photosensitizers and leveling agents provides feedback control on film thickness uniformity, which in turn ensures uniform exposure and electroplating results
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 formulation ensures coating uniformity below 5% and consistent copper electroplating thickness, reducing manufacturing costs and improving process quality.
Implementation Method 1
The negative photoresist, upon exposure to ultraviolet light, forms crosslinks at the exposed portion
Implementation Method 2
The leveling agent is a solution of polydimethylsiloxane copolymer having a molecular weight of 3000-6000 and propylene glycol monomethyl ether acetate mixed with a mass ratio of 7:3
Data Source
AI summary
Provided is a negative photoresist used for a semiconductor encapsulation process, belonging to the technical field of semiconductor processing. A negative photoresist formulation includes 40-65 wt % of modified epoxy acrylate, 3-6 wt % of photosensitizer, 100-1000 ppm of leveling agent, and the remainder of solvent; the leveling agent is a solution of a 7:3 mass ratio of polydimethylsiloxane copolymer having a molecular weight of 3000-6000 and propylene glycol monomethyl ether acetate. If the negative photoresist is coated at a thickness of about 50 um, the coating uniformity can be controlled to below 5%, ensuring the quality of exposure such that the thickness of electroplated copper meets requirements.