UV LED Photoelectrochemical Etching of SiC for Low TTV
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Solution Overview
Problem
Traditional photoelectrochemical etching methods using mercury lamps result in non-uniform light intensity, leading to uneven etching rates and high Total Thickness Variation (TTV) in silicon carbide layers, and the use of hydrofluoric acid poses safety hazards.
Innovation Solution
Employing LED lamps emitting UV light with a wavelength of 300 nm or less, combined with an electrolyte solution of potassium hydroxide, sodium hydroxide, or lithium hydroxide, to achieve uniform etching rates and eliminate the need for hydrofluoric acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mercury lamps are used for photoelectrochemical etching, then etching can be performed, but non-uniform light intensity causes uneven etching rates and high Total Thickness Variation
Solution Approach 1:
The patent changes the wavelength parameter of the light source from broad-spectrum mercury lamp to narrow-band UV LED (265-285 nm), and adjusts the geometric parameters of the LED array configuration to achieve uniform light distribution across the wafer surface, thereby improving etching uniformity and reducing TTV
Solution Approach 2:
The patent uses multiple UV LED light sources arranged in an array to replicate and distribute uniform UV illumination across the entire wafer surface, replacing the single-point source mercury lamp and achieving homogeneous light intensity distribution
2Manufacturing precision
If mercury lamps are used, then etching process can be performed, but wide wavelength range causes unwanted heating and non-uniform etching
Solution Approach 1:
The patent narrows the wavelength range from broad-spectrum mercury lamp (including visible and infrared) to specific UV band (265-285 nm) using UV LED, ensuring that only the wavelengths effective for SiC etching are used, thereby eliminating wasteful energy consumption in non-effective wavelength ranges and preventing unwanted heating
Solution Approach 2:
The patent extracts only the useful UV wavelength component (265-285 nm) from the broad spectrum and eliminates the ineffective visible and infrared components, achieving energy-efficient etching by using only the wavelengths that contribute to the photoelectrochemical reaction
3Productivity
If hydrofluoric acid is used as electrolyte, then etching process can be performed, but safety hazards arise due to corrosive nature
Solution Approach 1:
The patent replaces the harmful hydrofluoric acid with safer alternatives (potassium hydroxide, sodium hydroxide, or lithium hydroxide solutions), converting a dangerous process into a safe one while maintaining effective etching performance through the photoelectrochemical mechanism
Solution Approach 2:
The patent uses commercially available, non-toxic, and easily handled hydroxide solutions instead of expensive and dangerous hydrofluoric acid, making the process safer and more accessible while achieving comparable etching results
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 method ensures consistent etching rates and reduces TTV, while providing a safer and more efficient etching process for silicon carbide and silicon carbide on insulator, using environmentally safer electrolytes.
Implementation Method 1
As the UV light irradiates the substrate's surface, an oxidation reaction forms oxide (e.g., SiO2) on the surface
Implementation Method 2
The oxide is subsequently dissolved by the electrolyte solution
Data Source
AI summary
A method for etching a substrate using a light emitting diode (LED) lamp includes placing the substrate in an etching chamber equipped with the LED lamp configured to emit ultra-violet (UV) having a selected wavelength. The method includes submerging the substrate in an electrolyte solution within the etching chamber and applying a bias voltage between the substrate and the electrolyte solution. The method includes illuminating the substrate with the UV light to irradiate the substrate's surface. The method includes removing the substrate from the electrolyte solution once a desired etch depth is achieved.