Photolithography Mask Cleaning via Vacuum Thermal Sublimation
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Solution Overview
Problem
Current methods for cleaning photolithography masks in the electronics industry, which involve aqueous solutions containing sulfates, lead to contamination in clean rooms due to gas residues and require external processing, increasing manufacturing costs and risking defects in electronic circuits.
Innovation Solution
A method involving thermal treatment under reduced pressure and temperature, below 100°C, to sublimate salts on the mask surface, combined with gas pumping and neutral gas reintroduction to maintain a clean environment, using a controlled equipment system for efficient salt removal without aqueous solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If aqueous solutions containing sulfates are used for cleaning masks, then cleaning effectiveness is improved, but gas residues remain and cause salt deposition on masks
Solution Approach 1:
The invention changes the cleaning approach from chemical (aqueous sulfate solutions) to physical (thermal treatment under vacuum). By modifying the parameters of the cleaning process - using temperature and pressure control instead of chemical agents - the method achieves effective cleaning while avoiding the generation of harmful gas residues and salt deposition that plague chemical cleaning methods
Solution Approach 2:
The invention employs a vacuum environment (inert atmosphere without oxygen and moisture) during thermal treatment. This inert environment prevents oxidation and chemical reactions that would otherwise generate harmful residues. The vacuum conditions ensure that no contaminants are introduced during the cleaning process, addressing the problem of gas residues and salt formation
2Ease of manufacture
If masks are transported outside clean room for cleaning, then cleaning can be performed, but controlled atmosphere is disrupted and contamination risk increases
Solution Approach 1:
The invention makes the cleaning system universal by integrating it directly into the clean room environment. The thermal treatment chamber can be positioned within or adjacent to the clean room, allowing masks to be cleaned in-situ without leaving the controlled atmosphere. This multi-functional approach combines cleaning capabilities with clean room maintenance, eliminating the need for external cleaning facilities
Solution Approach 2:
The invention introduces a vacuum chamber as an intermediary between the mask and the cleaning process. This intermediary environment allows the mask to remain protected within the clean room while undergoing thermal treatment. The vacuum chamber acts as a mediator that isolates the mask from uncontrolled atmospheric conditions during cleaning, preventing contamination while enabling effective cleaning
3Manufacturing precision
If thermal treatment is performed at high temperature to remove salts, then cleaning effectiveness is improved, but mask damage may occur
Solution Approach 1:
The invention optimizes the temperature parameter within a safe range (below 100°C) that is sufficient to sublimate salt deposits but too low to damage the mask structure. By carefully controlling this parameter along with pressure conditions, the method achieves effective salt removal while preserving mask integrity, resolving the contradiction between cleaning effectiveness and component safety
Solution Approach 2:
The invention exploits the phase transition (sublimation) of salt deposits at controlled temperatures and vacuum conditions. By operating in the vacuum environment, salts can be removed via sublimation at lower temperatures than would be required at atmospheric pressure. This phase transition mechanism enables effective cleaning at temperatures that do not compromise mask reliability
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 method effectively removes salts from masks within the clean room environment, preventing contamination and reducing manufacturing costs by eliminating the need for external processing and ensuring high-quality circuit production.
Implementation Method 1
thermal treatment under pumping at a pressure lower than the atmospheric pressure and at a temperature greater than the ambient temperature
Implementation Method 2
thermal treatment under pumping at a pressure lower than the atmospheric pressure
Implementation Method 3
the thermal treatment is obtained by a radiation focused on the surface to be cleaned
Data Source
AI summary
A method and an equipment for cleaning masks used for photolithography steps, including at least one step of thermal treatment under pumping at a pressure lower than the atmospheric pressure and at a temperature greater than the ambient temperature.