Wafer Drying via Supercritical Solvent Substitution
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Solution Overview
Problem
The challenge in semiconductor device manufacturing is the pattern collapse phenomenon during the removal of liquids from wafer surfaces, which occurs when using supercritical high-pressure fluids, as existing methods fail to effectively prevent surface tension-related issues.
Innovation Solution
A substrate processing method involving a sequence of fluorine-containing organic solvents, starting with IPA substitution, followed by a first and second fluorine-containing organic solvent substitution, and finally using a supercritical processing fluorine-containing organic solvent, all while maintaining a low-humidity gas atmosphere to prevent moisture absorption and subsequent pattern collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a supercritical high-pressure fluid is used to remove liquid from the wafer surface, then the liquid extraction performance is improved and viscosity is reduced, but pattern collapse still occurs due to surface tension effects
Solution Approach 1:
The patent applies preliminary action by performing multiple substitution steps with fluorine-containing organic solvents before the final supercritical drying step. The liquid is first substituted with IPA, then with a first fluorine-containing organic solvent, and finally with a second fluorine-containing organic solvent that has lower surface tension. This preliminary substitution sequence prepares the wafer surface for supercritical processing by progressively replacing high surface tension liquids with low surface tension fluids, thereby preventing pattern collapse during the final drying step.
Solution Approach 2:
The patent applies parameter changes by systematically varying the surface tension parameter of the processing fluid through the substitution sequence. Each fluorine-containing organic solvent has progressively lower surface tension than the previous fluid. By changing the surface tension parameter from high (water/IPA) to low (fluorine-containing organic solvents), the patent eliminates capillary forces that cause pattern collapse while maintaining effective liquid extraction performance during supercritical processing.
2Manufacturing precision
If multiple substitution steps with fluorine-containing organic solvents are performed, then pattern collapse is prevented, but the processing time and process complexity increase
Solution Approach 1:
The patent applies segmentation by dividing the liquid substitution process into distinct sequential steps: IPA substitution, first fluorine-containing organic solvent substitution, and second fluorine-containing organic solvent substitution. Each step targets a specific aspect of surface tension reduction. This segmented approach allows systematic control of the substitution process, ensuring complete replacement of high surface tension liquids while maintaining manageable processing time through optimized step duration.
3Quantity of substance
If IPA is used to substitute moisture on the workpiece, then moisture removal is achieved, but moisture absorption from the environment can occur leading to pattern collapse
Solution Approach 1:
The patent applies inert atmosphere by conducting the entire multi-step substitution process in an environment controlled to prevent moisture absorption from the surrounding air. By creating a protected processing environment, the patent prevents re-absorption of moisture during the transition between substitution steps, ensuring that the IPA and subsequent fluorine-containing organic solvents effectively remove moisture without being contaminated by ambient humidity, thereby preventing pattern collapse.
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 liquids from wafer surfaces without causing pattern collapse by using a controlled sequence of fluorine-containing solvents and low-humidity conditions, ensuring the surface remains stable during the supercritical processing.
Implementation Method 1
a method of using a supercritical high-pressure fluid is known. The supercritical high-pressure fluid has a low viscosity compared to a liquid, and also has a high performance of extracting the liquid
Implementation Method 2
when the liquid attached to the surface of the wafer is substituted with the supercritical high-pressure fluid and then the supercritical high-pressure fluid is changed into a gas state, the liquid may be dried
Implementation Method 3
A low-humidity gas is supplied into the liquid processing unit chamber at least during the supply of the IPA
Data Source
AI summary
Disclosed is a substrate processing method. The method includes: supplying a rinse liquid, IPA, a first fluorine-containing organic solvent, a second fluorine-containing organic solvent to a wafer within an outer chamber of a liquid processing unit; conveying the wafer to a supercritical processing unit container; and supplying a supercritical processing fluorine-containing organic solvent in a supercritical high-pressure fluid state to the wafer within the supercritical processing unit container. At least during the supply of the IPA, a low-humidity N2 gas is supplied into the outer chamber so that the inside of the outer chamber is formed as a low-humidity N2 gas atmosphere, and thus moisture absorption into the IPA is prevented.