Enhancement-Mode HEMT Barrier Layout for Flat Isolation Regions
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Solution Overview
Problem
Conventional high electron mobility transistors (HEMTs) require complex photolithographic and etching processes, leading to increased complexity and non-flat interconnection issues due to recessed isolation regions, which need to be improved.
Innovation Solution
The design includes a semiconductor device with an enhancement mode HEMT featuring a group III-V body layer and barrier layer with varying thicknesses in the active and isolation regions, along with a passivation layer and etch mask, allowing for the formation of specific 2D electron gas regions and recesses to simplify the fabrication process and enhance flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple photolithographic and etching processes are used to define source/drain regions and isolation regions, then the HEMT can be fabricated with proper region definition, but the overall process complexity increases
Solution Approach 1:
The patent combines the definition of source/drain regions and isolation regions into a single photolithographic and etching process step. By designing the etch mask pattern to simultaneously define both region types in one exposure and etch cycle, the method eliminates the need for separate process steps, thereby reducing overall process complexity while maintaining precise region definition.
Solution Approach 2:
The etch mask layer is designed to serve multiple functions: it defines both the source/drain regions and the isolation regions in a single pattern. This multi-functional mask design allows one photolithographic and etching process to accomplish what would traditionally require multiple separate processes, simplifying the fabrication workflow.
2Reliability
If the isolation region is made more recessed than surrounding regions, then the HEMT can be properly isolated, but the flatness of interconnection in the isolation region deteriorates
Solution Approach 1:
The patent applies different thickness characteristics of the group III-V barrier layer to different regions: the isolation region has a thinner portion while the active region has thicker portions. This local variation in layer thickness allows the isolation region to be properly recessed for effective isolation while the thicker portions in the active region maintain the necessary structural integrity and flatness for interconnections.
Solution Approach 2:
Instead of achieving isolation solely through vertical recessing that compromises flatness, the patent introduces thickness variation as an additional dimensional parameter. By controlling the barrier layer thickness to be thinner in the isolation region and thicker in the active region, the solution addresses both isolation requirements and flatness requirements simultaneously through dimensional variation.
Data Source
AI summary
A semiconductor device includes an enhancement mode high electron mobility transistor (HEMT) with an active region and an isolation region. The HEMT includes a substrate, a group III-V body layer, a group III-V barrier layer, a first recess, a second recess, a passivation layer, and an etch mask layer. The group III-V barrier layer includes a thinner portion, a first thicker portion and a second thicker portion in the active region, the thinner portion surrounds the first thicker portion, and the second thicker portion surrounds the thinner portion. The first recess is disposed in the group III-V barrier layer in the active region. The second recess is disposed in the group III-V barrier layer in the isolation region.