Silicon Surface Preparation with Dilute HF and Surfactant
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Solution Overview
Problem
Current methods for preparing clean and stable silicon surfaces are inefficient, time-consuming, and costly, with the APM clean requiring expensive equipment and potentially introducing contaminants, leading to rapid native oxide re-growth and particle contamination.
Innovation Solution
A method involving a dilute hydrofluoric acid treatment with anionic surfactant, followed by in-situ rinsing and drying using ultrapure water and heated, ionized gas, or hydrogen gasified water with megasonic energy, to achieve a stable hydrogen-terminated silicon surface without the need for an APM clean.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If APM clean is used to prepare silicon surface, then cleaning effectiveness is improved, but equipment cost and complexity increase
Solution Approach 1:
The patent replaces expensive, complex APM clean equipment with simple, inexpensive dilute HF acid solution that can be easily prepared and disposed of. The dilute HF acid (1-10% HF in water) serves as a disposable cleaning agent that achieves effective silicon surface cleaning without requiring costly specialized equipment.
2Reliability
If APM clean is used to prepare silicon surface, then cleaning effectiveness is improved, but contamination risk increases
Solution Approach 1:
The patent extracts and removes the harmful APM clean process and replaces it with a simpler dilute HF acid treatment. This extraction eliminates the sources of contamination associated with APM clean while maintaining effective cleaning through the selective action of dilute HF acid on silicon oxide surfaces.
Solution Approach 2:
The patent creates a cleaner, more inert cleaning environment by using dilute HF acid solution that does not introduce the same contamination risks as APM clean. The simplified chemistry of dilute HF acid provides a more controlled and less contaminating atmosphere during the cleaning process.
3Reliability
If HF last treatment is used to remove oxide layer, then oxide removal is improved, but particle contamination increases
Solution Approach 1:
The patent changes the concentration parameter of HF acid from standard concentrations to dilute concentrations (1-10% HF in water). This parameter change allows effective oxide removal while reducing the generation of particle contamination that occurs with more concentrated HF treatments.
4Stability of the object's composition
If multiple cleaning steps are used to achieve stable surface, then surface stability is improved, but processing time increases
Solution Approach 1:
The patent merges multiple cleaning steps into a single dilute HF acid treatment step. This combination achieves both oxide removal and surface stabilization in one process, eliminating the need for separate cleaning steps and reducing total processing time while maintaining surface stability.
Solution Approach 2:
The dilute HF acid treatment performs preliminary oxide removal that prepares the surface for subsequent processing without requiring additional stabilization steps. The treatment leaves the surface in a stable state ready for immediate use, eliminating waiting time between cleaning and processing.
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 achieves a particle removal efficiency of 35%-95% and limits native oxide growth to less than 1 Å for over 5 days, reducing capital costs and environmental hazards while maintaining surface stability.
Implementation Method 1
The anionic surfactant reduces the surface energy of the silicon wafer and the zeta potential of particles, causing particles to repel each other and be easily removed
Implementation Method 2
The anionic surfactant reduces the surface energy of the silicon wafer
Implementation Method 3
treating the silicon surface with dilute hydrofluoric acid... to etch away the native oxide layer
Implementation Method 4
rinsing and drying the silicon surface... using heated, ionized gas, or hydrogen gasified water
Implementation Method 5
drying the surface... using heated, ionized gas
Implementation Method 6
hydrogen gasified water with megasonic energy
Data Source
AI summary
Methods are provided for producing a pristine hydrogen-terminated silicon wafer surface with high stability against oxidation. The silicon wafer is treated with high purity, heated dilute hydrofluoric acid with anionic surfactant, rinsed in-situ with ultrapure water at room temperature, and dried. Alternatively, the silicon wafer is treated with dilute hydrofluoric acid, rinsed with hydrogen gasified water, and dried. The silicon wafer produced by the method is stable in a normal clean room environment for greater than 3 days and has been demonstrated to last without significant oxide regrowth for greater than 8 days.