SiC Trench Plasma Etching for Taper Angle Control
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Solution Overview
Problem
Conventional plasma etching methods for silicon carbide (SiC) substrates struggle to achieve a well-defined taper in trenches without reducing etch rate, often resulting in a re-entrant profile due to the use of fluorine-based chemistries, which limits the process window and affects electrical performance.
Innovation Solution
A method involving a plasma etch process using a gas mixture comprising fluorine-containing components like SF6 and SiF4, combined with chlorine gas, and an oxygen-containing component, allowing for fine tuning of the taper angle while maintaining etch rate and selectivity by adjusting the F:Cl 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°) which worsens the trench profile
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 (85-90° taper) while preserving the high etch rate capability of fluorine-based chemistries, thereby resolving the contradiction between productivity and manufacturing precision.
2Manufacturing precision
If etch mixtures of SF6 with BCl3 or HCl are used to improve trench profile, then taper control is improved, but etch rate decreases
Solution Approach 1:
The patent optimizes the concentration ratios of fluorine-containing to chlorine-containing gases in the etch mixture. By carefully controlling these parameter ratios, the process achieves both improved trench profile (85-90° taper) and maintains high etch rates (600-1000 nm/min), thereby resolving the contradiction between manufacturing precision and productivity that plagued previous attempts.
3Productivity
If high power and low pressure are used to break SiC bonds and prevent micro-trenching, then material removal efficiency is improved, but re-entrant profile is worsened
Solution Approach 1:
The patent creates a composite etch chemistry system that combines fluorine-containing gases (for high etch rate and material removal efficiency) with chlorine-containing gases (for vertical sidewall profile control). This composite chemical system resolves the contradiction by allowing both high power/low pressure operation for efficient material removal and controlled sidewall etching for precise profile formation.
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 precise control of the taper angle in SiC trenches, reducing field-bunching and maintaining high etch rate and selectivity, resulting in smooth and uniform features suitable for high-power, high-frequency applications.
Implementation Method 1
performing a plasma etch step to anisotropically etch the substrate through the opening to produce a feature. The plasma etch step comprises generating a plasma from an etchant gas mixture comprising at least one fluorine-containing component and chlorine gas
Implementation Method 2
generating a plasma from an etchant gas mixture comprising at least one fluorine-containing component and chlorine gas
Data Source
AI summary
A plasma etch step anisotropically etches a silicon carbide semiconductor substrate through an opening to produce a feature. The plasma etch step generates a plasma from an etchant gas mixture that includes at least one fluorine-containing component and chlorine gas. The etchant gas mixture can further include SiCl4, an oxygen-containing component, and/or inert gas component.