SiC Plasma Etch Chemistry for Precise Trench Taper Control
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Solution Overview
Problem
Conventional plasma etching methods for silicon carbide (SiC) substrates face challenges in achieving a well-defined taper of 85-90° while maintaining high etch rates, as fluorine-based etch chemistries often result in re-entrant profiles and reduced etch rates when attempting to fine-tune the taper.
Innovation Solution
A method involving a plasma etch process using a gas mixture comprising fluorine-containing components, such as SF6 and SiF4, combined with chlorine gas, and an oxygen-containing component, which allows for fine-tuning of the taper angle without sacrificing etch rate or selectivity, by adjusting the flow rates of these gases to control the fluorine-to-chlorine ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluorine-based etch chemistries (SF6) are used to achieve high etch rates, then etch rate is improved, but the sidewall profile becomes re-entrant (taper > 90°) and manufacturing precision deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the etch gas mixture by adding chlorine-containing gases (BCl3, HCl, or Cl2) to the fluorine-based chemistry. This parameter change modifies the etch mechanism to produce a more vertical sidewall profile while maintaining high etch rates, resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The patent uses a composite etch chemistry system combining fluorine-containing gases (SF6, SiF4) with chlorine-containing gases (BCl3, HCl, or Cl2). This composite chemical system leverages the high etch rate capability of fluorine chemistry while the chlorine component suppresses re-entrant profiling, achieving both high productivity and precise taper control.
2Manufacturing precision
If fluorine-based etch chemistries are used to fine-tune taper, then manufacturing precision is improved, but etch rate deteriorates
Solution Approach 1:
The patent adjusts the ratio parameters of fluorine-to-chlorine gases in the etch mixture to independently control taper angle and etch rate. By varying these composition parameters, the process achieves fine-tuned taper control without sacrificing productivity, as the chlorine component enables vertical profiling while fluorine maintains high etch velocity.
3Reliability
If high power and low pressure are used to break SiC bonds and prevent micro-trenching, then reliability is improved, but the sidewall profile becomes re-entrant and manufacturing precision deteriorates
Solution Approach 1:
The patent employs a composite gas chemistry system where fluorine-containing gases provide the necessary reactivity to break strong SiC bonds at high power/low pressure conditions, while the chlorine-containing component modifies the etch mechanism to prevent re-entrant profiling. This composite approach maintains reliability by preventing micro-trenching while improving sidewall profile precision.
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 approach enables the formation of silicon carbide features with precise taper angles and maintains high etch rates and selectivity, reducing field-bunching and improving the electrical performance of SiC devices.
Implementation Method 1
performing a plasma etch step to anisotropically etch the substrate through the opening to produce a feature
Implementation Method 2
performing a plasma etch step to anisotropically etch the substrate
Implementation Method 3
Sulfur Hexafluoride (SF6) is the main gas used to plasma etch SiC at high etch rates
Implementation Method 4
the plasma etch step comprises generating a plasma from an etchant gas mixture comprising at least one fluorine-containing component
Implementation Method 5
the plasma etch step comprises generating a plasma from an etchant gas mixture comprising at least one fluorine-containing component and chlorine gas
Data Source
Figure 1A~1B
Figure 2~3
AI summary
A method of plasma etching silicon carbide semiconductor substrate and plasma etch apparatus for plasma etching a silicon carbide semiconductor substrate are provided.