Substrate Cleaning via Aqueous Film Freezing and Thawing
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Solution Overview
Problem
Conventional substrate cleaning methods, such as ultrasonic cleaning and chemical etching, often result in pattern damage or excessive etching, which can lead to device defects due to the fragile nature of modern semiconductor patterns and the need for precise control over particle removal and etching thickness.
Innovation Solution
A substrate processing method involving the rotation of a substrate to adjust an aqueous film thickness, freezing the film, and then thawing and removing it to gently dislodge particles without damaging the substrate, utilizing a rotator, freezer, and thawing/removing unit to manage the aqueous film effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ultrasonic vibrations are applied to remove particles from substrate surface, then particle removal efficiency is improved, but patterns on substrate surface may collapse due to vibration stress
Solution Approach 1:
The invention utilizes phase transition of water (freezing and thawing) to remove particles. Water is frozen to form ice that adheres to particles, then thawed to release particles from substrate surface without applying direct mechanical vibration stress to fragile patterns, thus resolving the contradiction between particle removal efficiency and pattern integrity
Solution Approach 2:
The invention introduces ice as an intermediary substance between the cleaning mechanism and the substrate. Ice forms during freezing and acts as a gentle mediator that lifts particles away during thawing, avoiding direct contact between ultrasonic vibrations and the substrate surface, thereby protecting patterns while maintaining cleaning effectiveness
2Productivity
If chemical solution such as SC1 is used to etch and remove particles, then particle removal is achieved, but excessive etching of substrate surface occurs
Solution Approach 1:
The invention replaces chemical etching with physical phase transition (freezing/thawing of water). This eliminates the need for chemical solutions like SC1 that cause excessive etching, while still achieving effective particle removal through the mechanical action of ice formation and thawing, thus maintaining substrate surface precision
Solution Approach 2:
The invention substitutes chemical action with physical mechanical action. Instead of using chemical solutions to dissolve and remove particles, the system uses the mechanical force generated by water freezing and thawing to physically lift and remove particles, avoiding chemical etching damage to the substrate surface
3Productivity
If ice film is peeled off from substrate to remove particles, then particle removal is achieved, but considerable physical force may damage the device
Solution Approach 1:
The invention utilizes the phase transition of water to ice and back to liquid water to create a gentle particle removal mechanism. The freezing process forms ice that adheres to particles, and the subsequent thawing process naturally releases particles with minimal force, avoiding the need for aggressive ice peeling that could damage the substrate
Solution Approach 2:
The invention applies preliminary freezing action to prepare particles for removal. By freezing water onto particles first, the system prepares a gentle removal mechanism where particles are already attached to ice crystals, allowing for easy removal during thawing without applying considerable physical force to the substrate
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 significantly improves particle removal rates while minimizing substrate damage, ensuring precise control over etching and preventing defects by weakening the adhesion between particles and the substrate through the expansion of the frozen aqueous film, allowing for effective removal without excessive physical force or etching.
Implementation Method 1
a second step of freezing the aqueous film after the first step
Implementation Method 2
the expansion of the frozen aqueous film
Implementation Method 3
a third step of thawing the aqueous film thus frozen and removing the aqueous film from the surface of the substrate
Data Source
AI summary
A substrate immersed in pure water held inside a processing bath disposed to a cleaning unit 1 and accordingly washed, as it bears an aqueous film on its surface, is transported by a substrate transportation mechanism 3 to a spin-processing unit 2. The substrate rotates in the spin-processing unit 2, thereby adjusting the thickness of the aqueous film on the substrate surface. As the aqueous film is then frozen, the volume of the aqueous film expands, adhesion between the substrates and particles adhering to the substrate surface becomes weak, or further the particles are separated from the substrate surface. The substrate transportation mechanism 3 transports thus frozen substrate to the cleaning unit 1 from the spin-processing unit 2, and the substrate is immersed in a processing liquid held inside the processing bath. The overflowing processing liquid thaws and removes the aqueous film, and particles on the substrate surface are discharged outside the substrate.