Semiconductor Substrate Cleaning via Ozone and Acid-Base Mixtures
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Solution Overview
Problem
Conventional wafer cleaning processes in semiconductor fabrication require large volumes of chemicals, leading to increased costs and environmental impact, and existing methods are not entirely satisfactory for all aspects of particle and metal ion removal.
Innovation Solution
A method and apparatus using a cleaning solution comprising ozone, de-ionized water, and either an acid or a base, such as hydrofluoric acid or ammonium hydroxide, which is sprayed onto a heated semiconductor substrate, followed by a rinse process, to effectively remove impurities and reduce chemical usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cleaning processes (SC1, SC2) are used to remove particles and metal ions, then cleaning effectiveness is achieved, but large volumes of chemicals are consumed leading to increased costs and environmental impact
Solution Approach 1:
The patent changes the chemical composition parameters by replacing conventional cleaning solutions with a specific formulation containing ozone (50-500 ppm), hydrofluoric acid (0.1-5%), and deionized water. This parameter change achieves effective particle and metal ion removal while reducing overall chemical volume consumption and environmental impact.
Solution Approach 2:
The patent substitutes chemical cleaning mechanisms with a combination of ozone oxidation and controlled etching. The ozone provides oxidative cleaning power while the hydrofluoric acid selectively removes metal ions, replacing the need for larger volumes of conventional cleaning chemicals.
2Productivity
If ozone is used in cleaning processes to improve cleaning efficiency, then impurity removal rates increase, but ozone loss increases leading to reduced efficiency
Solution Approach 1:
The patent applies local quality by using hydrofluoric acid as a selective etching agent that targets specific metal ions and contaminants. This localized chemical action works synergistically with ozone oxidation, allowing effective impurity removal at lower ozone concentrations and reducing ozone loss while maintaining high cleaning efficiency.
Solution Approach 2:
The cleaning solution is a composite formulation combining ozone, hydrofluoric acid, and deionized water. This composite approach leverages the oxidative power of ozone combined with the selective etching capability of hydrofluoric acid, achieving enhanced impurity removal efficiency while optimizing ozone utilization and minimizing loss.
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 reduces the amount of ozone lost and increases impurity removal rates, offering cost savings and a lower environmental impact by optimizing chemical usage and improving cleaning efficiency.
Implementation Method 1
cleaning the semiconductor substrate with a mixture of ozone and at least one of an acid and a base
Implementation Method 2
at least one of an acid and a base, such as hydrofluoric acid or ammonium hydroxide
Implementation Method 3
at least one of an acid and a base, such as hydrofluoric acid or ammonium hydroxide
Implementation Method 4
sprayed onto a heated semiconductor substrate
Data Source
AI summary
A method of cleaning a substrate such as semiconductor substrate for IC fabrication is described that includes cleaning the semiconductor substrate with a first mixture of ozone and one of an acid and a base, followed by a second mixture of ozone and the other one of the acid and the base. The cleaning mixtures may further include de-ionized water. In an embodiment, the mixture is sprayed onto a heated substrate surface. The acid may be HF; the base may be NH4OH.