GaN Plasma Etching With In-Situ Passivation for Rounded Trenches
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Solution Overview
Problem
Current dry etching methods for GaN trenches produce sharp corners leading to charge leakage and limited breakdown voltage, while wet etching methods are time-consuming and environmentally unfriendly, disrupting existing process flows.
Innovation Solution
A two-step plasma etching process using chlorine-based etchants with a fluorocarbon-based passivation material precursor to deposit material on the trench walls, controlling the etch profile to achieve rounded corners without additional wet etching steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dry etching is used to etch GaN trenches, then the etching speed and process integration are improved, but the trench corners become sharp leading to charge leakage
Solution Approach 1:
The patent applies preliminary action by depositing a passivation material layer on the trench walls before completing the etching process. This pre-protection of the trench corners during the etching process prevents the formation of sharp corners, thereby eliminating charge leakage issues while maintaining the high etching speed of dry etching processes.
Solution Approach 2:
The patent introduces a passivation material as an intermediary substance between the etching plasma and the trench corners. This intermediary layer selectively protects the corner regions from excessive etching, rounding the corners and preventing charge accumulation while allowing the main trench etching to proceed at high speed.
2Reliability
If wet etching is used to round trench corners, then charge leakage is reduced, but the process time and environmental impact increase
Solution Approach 1:
The patent merges the corner rounding function with the existing dry etching process by integrating passivation material deposition into the same process chamber and sequence. This combination eliminates the need for separate wet etching steps, reducing total process time while achieving the same charge leakage reduction effect.
Solution Approach 2:
The patent substitutes wet chemical etching with a plasma-based dry etching process combined with in-situ passivation deposition. This replacement eliminates the use of environmentally harmful wet chemicals and reduces process time while achieving comparable or superior corner rounding and charge leakage prevention.
3Reliability
If wet etching is used to round trench corners, then charge leakage is reduced, but the process complexity and chemical handling increase
Solution Approach 1:
The patent combines multiple functions (trench etching, corner rounding, and passivation deposition) into a single integrated dry etching process sequence. This merging simplifies the overall process flow by eliminating separate wet etching steps and associated chemical handling requirements, while still achieving effective corner rounding to prevent charge leakage.
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
Produces GaN etch features with curved corners, reducing charge leakage and increasing breakdown voltage, compatible with existing process flows and environmentally friendly.
Implementation Method 1
performing a first plasma etch step to anisotropically etch the at least one GaN or GaN alloy layer through the opening
Implementation Method 2
the first plasma etch step uses an etch recipe comprising a chlorine-based etchant
Implementation Method 3
depositing a passivation material onto the walls, wherein the deposition of the passivation material within the feature causes an attenuation in etching of the peripheral region
Data Source
Figure 1(a)~2
Figure 3(a)~4
AI summary
According to the invention there is provided a method of plasma etching a substrate comprising at least one GaN or GaN alloy layer to form a feature, the method comprising the steps of: (a) providing a substrate with a mask formed thereon, the mask having an opening, wherein the substrate comprises at least one GaN or GaN layer; (b) performing a first plasma etch step to anisotropically etch the at least one GaN or GaN alloy layer through the opening to produce a partially formed feature having one or more side walls and a bottom surface comprising a peripheral region, wherein the first plasma etch step uses an etch recipe comprising a chlorine-based etchant; and (c) performing a second plasma etch step to anisotropically etch the bottom surface of the partially formed feature through the opening while depositing a passivation material onto the walls, wherein the second plasma etch step uses an etch recipe comprising a chlorine-based etchant and a fluorocarbon-based passivation material precursor and wherein the deposition of the passivation material within the feature causes an attenuation in etching of the peripheral region thereby producing a fully formed feature having a bottom surface comprising a central region and an edge region, wherein the edge region is curved and the central region is deeper than the edge region of the bottom surface of the fully formed feature.