Compound Semiconductor Plasma Etching With Pulsed Bias Control
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Solution Overview
Problem
Current plasma etch technologies for compound semiconductor substrates face challenges in reducing microtrench formation without compromising etch rate and etch selectivity, and existing methods that use hydrogen gas can lead to undesirable byproducts and surface properties.
Innovation Solution
A method of plasma etching a compound semiconductor substrate using a pulsed electrical bias power with a frequency of less than or equal to 160 Hz and a duty cycle of less than or equal to 50%, which reduces microtrench formation and enhances etch selectivity without using hydrogen gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous electrical bias power is applied during plasma etching, then etch rate is maintained, but microtrench formation increases due to excessive ion bombardment at feature bottom edges
Solution Approach 1:
The patent applies pulsed electrical bias power instead of continuous power, creating periodic cycles of high power (for etching) and low power (for relaxation). This periodic modulation reduces cumulative ion bombardment at feature bottom edges while maintaining adequate average etch rate, directly resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The patent dynamically adjusts the electrical bias power between high and low states during the etching process. By making the power application dynamic rather than static, the system can control ion bombardment intensity in real-time, preventing microtrench formation while preserving etch rate through optimized pulse parameters
2Manufacturing precision
If hydrogen gas is used as process gas, then microtrench formation is suppressed, but undesirable byproducts (PH3 and AsH3) are generated and surface properties deteriorate
Solution Approach 1:
The patent changes the electrical bias power parameter from continuous to pulsed mode, which fundamentally alters the etching mechanism. This parameter change enables microtrench suppression without requiring hydrogen gas, thereby eliminating the generation of harmful byproducts while maintaining manufacturing precision
Solution Approach 2:
The patent extracts the microtrench suppression function from the chemical mechanism (hydrogen gas) and implements it through a physical mechanism (pulsed electrical bias). This extraction eliminates the need for hydrogen gas and its associated harmful byproducts while achieving the same manufacturing precision benefit
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 effectively reduces microtrench formation while maintaining a high etch rate and improved etch selectivity, and it avoids the use of hydrogen gas, which can lead to undesirable byproducts and surface properties.
Implementation Method 1
sustaining a plasma of the etchant gas or gas mixture within the chamber to plasma etch the compound semiconductor material
Implementation Method 2
it is believed that microtrenches are formed due to excessive ion bombardment at the bottom edges of the feature
Implementation Method 3
applying a pulsed electrical bias power to the substrate support whilst the plasma is being sustained
Data Source
AI summary
Plasma etching a compound semiconductor substrate includes providing a substrate that includes a compound semiconductor material on a substrate support within a chamber. An etchant gas or gas mixture is introduced into the chamber. A plasma of the etchant gas or gas mixture is sustained within the chamber to plasma etch the compound semiconductor material. A pulsed electrical bias power is applied to the substrate support whilst the plasma is being sustained. The pulsed electrical bias power has a pulse frequency of less than or equal to about 160 Hz and a duty cycle of less than or equal to about 50%.