Substrate Cleaning Method Preventing Liquid Stream Cutting
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Solution Overview
Problem
Conventional substrate cleaning methods, such as spin cleaning, are ineffective in removing dissolved products between high aspect ratio circuit patterns on semiconductor wafers, leading to pattern damage and defects due to incomplete cleaning and stress imbalances caused by centrifugal forces.
Innovation Solution
A substrate cleaning method involving a liquid film formation on the entire substrate surface, followed by a first drying process using gas discharge to form a drying region, and a second drying process where the residual liquid is removed by moving a residual liquid removing position in a diametrical direction, ensuring the liquid is not cut and minimizing stress on the circuit patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wafer is rotated at high speed to remove cleaning liquid by centrifugal force, then the cleaning liquid can be removed from the surface, but the liquid stream becomes cut at the peripheral portion and dissolved products remain between circuit patterns
Solution Approach 1:
The patent applies dynamics by varying the rotation speed of the wafer during different stages of the cleaning process. Initially, the wafer is rotated at a first rotation speed to form a liquid film and remove loose contaminants. Then, the rotation speed is reduced to a second rotation speed (lower than the first) to prevent the liquid stream from being cut at the peripheral portion, allowing the cleaning liquid to flow continuously and remove dissolved products from between high aspect ratio circuit patterns effectively.
2Stability of the object's composition
If the supply of cleaning liquid is stopped to prevent stream cutoff, then rotation can continue, but dissolved products and cleaning liquid remain between circuit patterns
Solution Approach 1:
The patent ensures continuity of useful action by maintaining the supply of cleaning liquid throughout the entire cleaning process, even when the rotation speed is reduced. The cleaning liquid is supplied continuously at both the first and second rotation speeds, ensuring that the liquid stream never cuts off at the peripheral portion. This continuous supply allows the cleaning liquid to constantly flow over the circuit patterns and remove dissolved products effectively, preventing any residual liquid from remaining between the patterns.
3Stability of the object's composition
If surface tension of cleaning liquid between circuit patterns is high, then liquid holds together, but pattern damage occurs due to stress balance
Solution Approach 1:
The patent applies parameter changes by modifying the rotation speed parameter during the cleaning process. By reducing the rotation speed from the first rotation speed to the second rotation speed (which is lower), the centrifugal force acting on the cleaning liquid is reduced. This parameter change allows the cleaning liquid to exert gentler pressure on the circuit patterns while still maintaining effective flow and cleaning action, thereby preventing pattern damage caused by excessive surface tension stress on high aspect ratio structures.
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 prevents liquid stream cutting and pattern damage by ensuring thorough removal of cleaning liquid between circuit patterns, improving cleaning efficiency and reducing development defects.
Implementation Method 1
a liquid film of the cleaning liquid L is formed by a centrifugal force
Implementation Method 2
by discharging a gas G toward the central portion of the wafer W from a gas nozzle 70, a drying region is formed on the wafer W
Implementation Method 3
the wafer W is rotated about a vertical axis thereof while being held horizontally
Data Source
AI summary
A substrate cleaning method is capable of preventing a liquid stream on a substrate from being cut and circuit patterns thereon from being damaged. The substrate cleaning method includes a liquid film forming process that forms a liquid film on an entire substrate surface by supplying a cleaning liquid L from a central portion of the substrate W toward a peripheral portion thereof while rotating the substrate; a drying region forming process that discharges a gas G on the substrate surface and removes the cleaning liquid on the substrate surface; and a residual liquid removing process that removes the cleaning liquid remaining between the circuit patterns by discharging a gas G while moving in a diametrical direction of the substrate.