SC-2 Wafer Cleaning With Segmented HCl Concentration
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Solution Overview
Problem
The existing RCA cleaning method for semiconductor wafers faces challenges in SC-2 cleaning, where the acidic nature of the solution can lead to higher particle adhesion due to uneven electrostatic charges, and increasing HCl concentration or cleaning time degrades the metal impurity removal efficiency.
Innovation Solution
A method utilizing multiple chemical tanks for SC-2 cleaning, where the HCl concentration is progressively lowered in subsequent tanks to minimize particle adhesion while maintaining effective metal impurity removal, with the final tank having the lowest HCl concentration to prevent particle adherence and ensure thorough cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If HCl concentration in SC-2 solution is increased or cleaning time is extended, then metal impurity removal effect is improved, but particle adhesion to wafer surface increases
Solution Approach 1:
The SC-2 cleaning process is divided into multiple sequential tanks with progressively decreasing HCl concentrations. The first tank uses higher HCl concentration (e.g., 1-6%) for effective metal impurity removal, while subsequent tanks use lower HCl concentrations (e.g., 0.1-1% in the second tank, and 0.01-0.1% in the third tank) to minimize particle adhesion. This segmentation allows each tank to perform its specific function optimally without compromising the other requirement.
2Object-affected harmful factors
If HCl concentration in SC-2 solution is lowered to reduce particle adhesion, then particle level degradation is suppressed, but metal removal effect is decreased
Solution Approach 1:
The cleaning process performs metal impurity removal in advance using the first SC-2 tank with higher HCl concentration before the wafer enters subsequent tanks with lower HCl concentrations. This preliminary action ensures that the majority of metal impurities are removed when the cleaning agent is most effective, allowing later tanks to focus on preventing particle adhesion without compromising overall metal removal performance.
3Manufacturing precision
If SC-2 cleaning time is extended to improve metal removal, then metal impurity level is improved, but particle adhesion increases
Solution Approach 1:
The extended cleaning time is segmented across multiple tanks rather than using a single long exposure in one tank. The first tank provides intensive metal removal for a shorter duration with high HCl concentration, while subsequent tanks provide additional cleaning time with low HCl concentration to prevent particle adhesion. This temporal and functional segmentation resolves the contradiction between cleaning time and particle adhesion.
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 approach effectively reduces particle adhesion and maintains metal impurity removal efficiency, improving the overall cleaning quality without degrading the semiconductor wafer surface.
Implementation Method 1
The SC-2 solution is an aqueous solution of hydrochloric acid and hydrogen peroxide, and plays a role in removing metal impurities
Implementation Method 2
Since the SC-1 solution is an alkaline solution, the wafer surface and the surfaces of various particles are both negatively charged at the time of SC-1 cleaning. Hence, the electrostatic repulsion therebetween suppresses the adhesion of the particles
Data Source
AI summary
A method for cleaning a semiconductor wafer by using a chemical tank containing an SC-2 solution including, a plurality of the chemical tanks are used, and among SC-2 solutions contained in the plurality of chemical tanks, an HCl concentration in an SC-2 solution contained in a chemical tank to be finally used is lowered to the lowest to clean the semiconductor wafer. The method for cleaning a semiconductor wafer thus provided can improve the particle level in SC-2 cleaning for a semiconductor wafer without degrading the metal impurity level on the semiconductor wafer surface.