Coating and Developing System for Immersion Exposure Resist Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing photolithography processes for semiconductor device fabrication and LCD production face challenges in maintaining consistent resist film properties due to variations in contact angles and moisture content across substrates, leading to defects in resist pattern formation during immersion exposure.
Innovation Solution
A coating and developing system that includes a cleaning unit, a carrying mechanism, and a controller to manage the time interval between substrate wetting and exposure, ensuring the contact angle drop rate is significantly reduced before immersion exposure, and a buffer unit to adjust the time interval between heating and cleaning processes to standardize moisture content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is cleaned with cleaning liquid before immersion exposure, then particles adhering to the substrate surface are removed, but the contact angle between the cleaning liquid and substrate surface changes over time, causing variations in resist film properties
Solution Approach 1:
The invention applies preliminary action by controlling the timing of the cleaning process and introducing a waiting period after cleaning to allow the contact angle to stabilize before forming the resist film. This ensures that the substrate surface reaches a stable state with consistent contact angle properties before the resist is applied, thereby resolving the contradiction between removing particles and maintaining contact angle stability.
2Productivity
If the contact angle drop rate is not controlled before immersion exposure, then the immersion exposure process can proceed quickly, but line width variations occur in the resist patterns due to inconsistent resist film permeability
Solution Approach 1:
The invention implements feedback control by monitoring the contact angle drop rate and using this information to control the timing of the immersion exposure process. The system waits until the contact angle drop rate falls below a predetermined threshold before proceeding with exposure, ensuring that the substrate surface has reached a stable state. This feedback mechanism resolves the contradiction by automatically adjusting the process timing based on actual surface conditions.
3Productivity
If substrates are processed at different times after cleaning, then the production flow can be maintained, but the moisture content and contact angle vary across substrates, affecting resist film uniformity
Solution Approach 1:
The invention applies preliminary action by establishing a standardized waiting period after cleaning for all substrates before they undergo immersion exposure. This predetermined time interval ensures that all substrates reach a consistent stable state regarding contact angle and moisture content, regardless of when they were cleaned. This approach maintains production flow while ensuring uniformity across all substrates.
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 system ensures consistent resist film properties across substrates, reducing line width variations in resist patterns and maintaining uniformity in resist film permeability, thereby enhancing the reliability of the immersion exposure process.
Implementation Method 1
When pure water, namely, the cleaning liquid, wets and penetrates the protective film formed on the surface of the wafer W
Implementation Method 2
The penetration degree (penetration distance I) at which pure water penetrates the protective film is expressed by Expression (1), namely, Lucas-Washburn formula. I=(d·y·cos θ/2η)1/2·t
Implementation Method 3
a buffer unit to adjust the time interval between heating and cleaning processes to standardize moisture content
Data Source
AI summary
A coating and developing system for forming a resist film on a substrate by coating the substrate with a liquid resist and developing the resist film after the resist film has been processed by immersion exposure that forms a liquid layer on the surface of the substrate is capable of reducing difference in property among resist films formed on substrates. The coating and developing system includes: a cleaning unit; a carrying means; and a controller. A set time interval is determined such that the substrate is subjected to the immersion exposure process after contact angle drop rate at which contact angle between the cleaning liquid and a surface of the substrate drops has dropped from an initial level at the wetting time point when the surface of the substrate is wetted with the cleaning liquid to a level far lower than the initial level.