Silicon Substrate Cleaning via SPM Solution for Plasma Doping
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Solution Overview
Problem
Current methods for cleaning silicon substrates after impurity introduction, such as plasma doping, often result in metal contamination and loss of dopant particles at shallow depths, leading to reduced yield rates in semiconductor devices. The existing cleaning processes, including hydrogen fluoride, are ineffective in maintaining the introduced particles, especially when the impurity depth is less than 15 nm, causing undesirable sheet resistance and contamination levels.
Innovation Solution
A cleaning method using a mixed solution of sulfuric acid and hydrogen peroxide water, combined with a plasma-doping apparatus with a coated inner wall, effectively cleans the substrate without removing the introduced particles. This method forms an oxide layer and reduces contamination, ensuring the dopant particles remain intact before the anneal process, thereby maintaining the desired yield rate of semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If hydrogen fluoride or conventional cleaning solutions are used to clean the silicon substrate after plasma doping, then metal contamination is reduced, but the introduced dopant particles at shallow depths are removed
Solution Approach 1:
The patent changes the chemical parameters of the cleaning solution by using a mixed solution of sulfuric acid and hydrogen peroxide (SPM) with specific concentration ratios and temperatures, rather than conventional hydrogen fluoride solutions. This parameter change allows effective metal contamination removal while preserving shallow dopant particles through selective chemical etching that spares silicon-dopant bonds.
Solution Approach 2:
The patent employs a composite cleaning approach by combining sulfuric acid and hydrogen peroxide in specific proportions to create a synergistic cleaning solution. This composite solution provides both strong oxidation capability for removing metal contaminants and controlled etching properties that preserve the shallow dopant profile, achieving dual functionality that single solutions cannot provide.
2Use of energy by moving object
If plasma doping is used to introduce particles into the substrate, then ultra-low energy doping is achieved, but metal contamination from the chamber increases
Solution Approach 1:
The patent converts the harmful effect of plasma exposure (which causes metal contamination) into a beneficial cleaning opportunity. By implementing a targeted cleaning process using SPM solution after plasma doping, the method removes metal contaminants deposited during plasma exposure while preserving the doping benefits, effectively turning the contamination problem into a manageable step in the overall process.
Solution Approach 2:
The patent applies a preliminary cleaning action using the SPM solution immediately after plasma doping and before annealing. This preliminary cleaning removes metal contaminants that would otherwise be activated or embedded during subsequent high-temperature annealing processes, preventing contamination-related device failures before they can occur.
3Object-affected harmful factors
If the cleaning time is extended to remove more contamination, then metal contamination level decreases, but more dopant particles are washed away
Solution Approach 1:
The patent optimizes cleaning parameters including solution concentration (e.g., 3:1 or 4:1 ratio of sulfuric acid to hydrogen peroxide), temperature (heating to enhance cleaning efficiency), and contact time. These parameter changes create a cleaning window where sufficient contamination removal occurs while dopant particle loss is minimized, achieving effective cleaning without excessive doping loss.
Solution Approach 2:
The cleaning solution exhibits local quality differences in its chemical reactivity - it strongly attacks metal contaminants while having minimal effect on silicon-dopant bonds at the optimized parameters. This selective local reactivity allows differential cleaning where the same solution removes unwanted metals from certain regions while preserving the dopant profile in the silicon 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
The proposed method effectively cleans silicon substrates without reducing the introduced dopant particles, achieving a contamination level comparable to ion implantation and ensuring the electrical activation of dopants, thus maintaining the yield rate of semiconductor devices.
Implementation Method 1
A cleaning method using a mixed solution of sulfuric acid and hydrogen peroxide water, combined with a plasma-doping apparatus with a coated inner wall, effectively cleans the substrate without removing the introduced particles
Implementation Method 2
Hydrogen fluoride has higher cleaning power than the mixed solution of sulfuric acid and hydrogen peroxide water, so that solution including hydrogen fluoride is often used for cleaning silicon substrates after the ion implantation
Implementation Method 3
plasma-doping is a promising method to be used in the next generation for introducing particles into substrates efficiently with ultra-low energy
Implementation Method 4
Ion implantation is used as a method for introducing particles into silicon substrates
Implementation Method 5
the plasma doping does not use the analytical electromagnet and exposes the silicon substrate directly to plasma. In other words, the chamber inner wall is exposed to plasma, and the silicon substrate is exposed to the same plasma, so that metal contamination caused by the chamber tends to occur
Implementation Method 6
This method forms an oxide layer and reduces contamination, ensuring the dopant particles remain intact before the anneal process
Data Source
AI summary
A method of forming an impurity-introduced layer is disclosed. The method includes at least a step of forming a resist pattern on a principal face of a solid substrate such as a silicon substrate (S27); a step of introducing impurity into the solid substrate through plasma-doping in ion mode (S23), a step of removing a resist (S28), a step of cleaning metal contamination and particles attached to a surface of the solid substrate (S25a); a step of anneal (S26). The step of removing a resist (S28) irradiates the resist with oxygen-plasma or brings mixed solution of sulfuric acid and hydrogen peroxide water, or mixed solution of NH4OH, H2O2 and H2O into contact with the resist. The step of cleaning (S25a) brings mixed solution of sulfuric acid and hydrogen peroxide water, or mixed solution of NH4OH, H2O2 and H2O into contact with the principal face of the solid substrate. The step of removing a resist (S28) and the step of cleaning (S25a) can be conducted simultaneously by bringing mixed solution of sulfuric acid and hydrogen peroxide water, or mixed solution of NH4OH, H2O2 and H2O into contact with the principal face of the solid substrate.