Calibration Substrate Cleaning via UV Photodissociation
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Solution Overview
Problem
Calibration substrates in semiconductor fabrication face contamination issues due to hydrocarbon deposits and high-energy metrology tool interactions, leading to inaccurate measurements and premature substrate degradation, as conventional cleaning methods can modify the substrate and induce oxide growth.
Innovation Solution
A cleaning system utilizing ultraviolet light at 185-254 nm wavelengths to remove molecular airborne contaminants without raising the substrate temperature above 50°C, minimizing oxide formation and maintaining calibration substrate integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional cleaning systems (solvent-based or thermal) are used to remove contamination from calibration substrates, then contamination is reduced, but the substrate properties are modified (residue left or oxide growth induced)
Solution Approach 1:
The patent replaces conventional mechanical/thermal cleaning systems with a photochemical cleaning system using UV light at 185-254 nm. This substitution eliminates the need for solvents and high-temperature thermal processes that modify substrate properties, while still effectively removing hydrocarbon contamination through photodissociation of contaminant molecules.
Solution Approach 2:
The patent changes the cleaning mechanism from thermal/chemical to optical/photochemical by using specific UV wavelengths (185-254 nm). This parameter change allows contamination removal at low temperatures that do not induce oxide growth, thereby preserving substrate properties while achieving cleaning effectiveness.
2Reliability
If high energy optical sources (lasers) are used for measurement or contamination removal, then measurement capability or cleaning effectiveness is improved, but substrate temperature increases causing accelerated oxide growth
Solution Approach 1:
The patent applies UV cleaning light in a controlled manner that targets only the contamination layers on the substrate surface without excessive energy deposition into the bulk substrate. This localized energy application removes contaminants while maintaining substrate temperature below 50°C, preventing thermally-induced oxide growth.
Solution Approach 2:
The cleaning system uses periodic or pulsed UV irradiation rather than continuous high-energy exposure. This periodic action allows heat dissipation between pulses, maintaining substrate temperature at acceptable levels while still achieving effective contamination removal over time.
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
Effectively cleans calibration substrates to maintain accurate correlations with product substrates, reducing the need for frequent replacements and ensuring precise metrology tool calibration without adverse effects on the substrate.
Implementation Method 1
directing ultraviolet (UV) light at a wavelength of between approximately 185 nm and 254 nm to the surface of the calibration substrate at a power sufficient to remove substantially all molecular airborne contaminants from the surface of the calibration substrate
Data Source
AI summary
A method of cleaning calibration and other substrates that improves the correlation of measurements from calibration and product substrates and increases the useful life of the calibration substrates is herein disclosed. By exposing a calibration substrate to ultraviolet light, a reaction is triggered that results in the cleaning of the contaminants from the calibration substrate. For instance, monatomic oxygen is introduced to contaminants on the surface of a calibration substrate to remove the contaminants without inducing modifications in the substrate itself. Through the cleaning process, the temperature of the calibration substrate may be controlled to limit adverse effects caused by the overheating of the calibration substrate.