Solvent Pre-wetting and Distillation for Resist Coating
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Solution Overview
Problem
In semiconductor manufacturing, the spin coating method for resist liquids results in high wastage and challenges in removing infinitesimal foreign matter, such as particles and ionized metals, which affects yield as circuit patterns are miniaturized, and existing filters have limitations in mesh size and ion removal.
Innovation Solution
A liquid processing apparatus that includes a substrate holding unit, a processing liquid nozzle, an evaporating unit to convert the processing liquid into vapor, a cooling unit to liquefy the vapor, and a storage tank, with a filter unit in the flow line to remove foreign matter, and a solvent pre-wetting process to enhance resist liquid spread uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a filter with a mesh body is used to remove foreign matter from the processing liquid, then particles can be filtered out, but ionized metals cannot be removed and the mesh size cannot be miniaturized further
Solution Approach 1:
The patent changes the physical state of the processing liquid from liquid to vapor and back to liquid through controlled temperature changes. This phase transition enables removal of foreign matter including ionized metals that cannot be filtered by traditional mesh filters, as the vaporization process separates all particulate and ionic contaminants from the processing liquid.
Solution Approach 2:
The patent utilizes phase transitions of the processing liquid (liquid → vapor → liquid) to achieve foreign matter removal. The evaporating unit vaporizes the processing liquid, and the cooling unit condenses it back, leaving all foreign matter including particles and ionized metals behind in the vapor phase or as residues, thus purifying the processing liquid without requiring miniaturized mesh filters.
2Manufacturing precision
If the spin coating method is used to coat resist liquid on the wafer, then the resist liquid spreads uniformly, but most of the resist liquid is thrown out and wasted
Solution Approach 1:
The patent applies preliminary action by coating a processing liquid (solvent) on the wafer surface before resist liquid coating. This pre-wetting treatment modifies the wafer surface to enhance resist liquid spreadability and uniformity, allowing for reduced resist liquid supply量 while maintaining high in-plane uniformity, thus reducing wastage without compromising coating quality.
3Manufacturing precision
If the mesh of filters is miniaturized to remove smaller foreign matter, then particle removal improves, but it becomes difficult to remove ionized metals and the filter structure reaches its limit
Solution Approach 1:
The patent changes the temperature parameter of the processing liquid, transitioning it from liquid state to vapor state and back. This temperature-induced phase change effectively removes all types of foreign matter including ionized metals, which cannot be removed by mechanical filtration regardless of mesh size, thereby achieving comprehensive purification without structural filter limitations.
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 apparatus effectively reduces foreign matter on the substrate, improving yield by suppressing the entry of particles and ionized metals, ensuring continuous, high-quality semiconductor device production with reduced solvent wastage and improved resist liquid distribution.
Implementation Method 1
an evaporating unit configured to evaporate the processing liquid supplied from the processing liquid supply source to obtain vapor
Implementation Method 2
a cooling unit configured to cool and liquefy the vapor of the processing liquid obtained from the evaporating unit
Data Source
AI summary
A solvent such as PGMEA is coated on a wafer in advance to easily spread resist liquid onto the wafer on a spin chuck. Before coating, the solvent supplied from a solvent supply source is stored in a distill tank first, the solvent is heated by a heating unit to be evaporated, and the evaporated solvent is cooled by a cooler, thereby performing the purification of the solvent by distillation. Therefore, particles among the solvent are removed. The purified solvent is stored in a storage tank first, and then supplied to a solvent nozzle above the spin chuck from a solvent supplying line. And then, the solvent is coated on the wafer by ejecting the solvent from the solvent nozzle to the wafer. Further, the distill tank is cleaned periodically to suppress the increase of the concentration of the particles in the solvent.