Hot Chemical Buffer Tank Venting for Bubble-Free Wafer Cleaning
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Solution Overview
Problem
High temperature chemical solutions like SC1 generate gas bubbles during the cleaning process, leading to malfunctioning of pumps, heaters, and ultrasonic devices due to dissociation of chemicals under low pressure suction and mechanical agitation, which complicates the cleaning of semiconductor substrates.
Innovation Solution
A high temperature chemical solution supply system comprising a solution tank, a buffer tank with a vent line and needle valve, and two pumps, where the buffer tank vents gas bubbles out, maintaining a controlled pressure to minimize bubble formation and ensure effective cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high temperature chemical solution is heated to more than 80°C to effectively remove particles, then cleaning effectiveness is improved, but gas bubbles are generated due to dissociation of chemicals
Solution Approach 1:
The system performs preliminary heating of the chemical solution to a temperature between 40°C to 80°C before the substrate cleaning process. This pre-heating action reduces the temperature differential during cleaning, thereby minimizing thermal dissociation of chemicals into gas bubbles while still maintaining effective cleaning capability.
Solution Approach 2:
The invention changes the temperature parameter from exceeding 80°C to a controlled range of 40°C to 80°C. This parameter optimization maintains particle removal effectiveness while significantly reducing the dissociation of H2O2 and NH4OH into oxygen and ammonia gas bubbles.
2Quantity of substance
If low pressure suction is applied to deliver chemical solution, then solution delivery is achieved, but gas bubbles are generated due to pressure reduction
Solution Approach 1:
The invention introduces a buffer tank as an intermediary component between the chemical solution reservoir and the substrate cleaning chamber. The buffer tank serves as a pressure stabilization zone where gas bubbles can separate from the liquid phase before the solution is delivered to the substrate, preventing bubble-related malfunctions in pumps and heating elements.
Solution Approach 2:
The system segments the chemical solution delivery process into multiple stages: storage in reservoir, temperature control and bubble separation in buffer tank, and final delivery to substrate. This segmentation allows each stage to be optimized independently, with the buffer tank specifically addressing the gas bubble issue.
3Stability of the object's composition
If mechanical agitation is used to mix chemical solution, then solution mixing is improved, but gas bubbles are generated through chemical dissociation
Solution Approach 1:
The invention replaces intensive mechanical agitation with a gentler mixing approach in the buffer tank. The chemical solution components (H2O2, NH4OH, and water) are mixed to achieve the required SC1 composition, but the mixing intensity and temperature are controlled to minimize dissociation into gas bubbles, unlike conventional vigorous agitation methods.
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 system effectively reduces gas bubbles in high temperature chemical solutions, preventing equipment malfunction and enhancing the cleaning process by maintaining a stable pressure and flow rate, thus improving the efficiency of substrate cleaning.
Implementation Method 1
The needle valve is adjusted to reach a flow rate to vent gas bubbles inside of the high temperature chemical solution out of the buffer tank through the vent line
Implementation Method 2
vent gas bubbles inside of the high temperature chemical solution out of the buffer tank
Implementation Method 3
apparatus for cleaning substrates having an ultrasonic device
Data Source
AI summary
A method for cleaning substrates includes rotating a substrate; delivering deionized water on a surface of the substrate for pre wetting the surface of the substrate; delivering chemical solution with high temperature on the surface of the substrate for cleaning the surface of the substrate; changing the rotation speed of the substrate to a low rotation speed, and moving a ultra/mega sonic device. The method further includes turning on the ultra/mega sonic device and supplying a constant or pulse working power in a first cleaning cycle; turning off the ultra/mega sonic device, and delivering a high temperature chemical solution or deionized water. The method further includes turning on the ultra/mega sonic device and supplying a constant or pulse working power in a second cleaning cycle; turning off the ultra/mega sonic device, and delivering rinse chemical solution or deionized water on the surface of the substrate; and drying the substrate.