GaN Contact Layer Selective Growth via Nitrogen Carrier Gas
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Solution Overview
Problem
Nitride semiconductor devices, such as high electron mobility transistors (HEMTs), face challenges in achieving uniform thickness of the GaN layer due to source material migration during selective epitaxial growth, leading to uneven distribution and increased contact resistance.
Innovation Solution
A process involving the sequential growth of a semiconductor stack with a channel and barrier layer, followed by patterning a mask and etching to form recesses, where a contact layer is selectively grown using nitrogen as a carrier gas at 1000°C, ensuring homogeneous thickness and reduced contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If selective epitaxial growth is performed using a non-crystallized mask, then the GaN layer is grown in the desired pattern, but the source materials migrate and collect near the mask, causing uneven thickness distribution
Solution Approach 1:
The patent changes the temperature parameter during selective epitaxial growth to suppress source material migration. By controlling the growth temperature within a specific range (below 1000°C), the migration length of gallium and nitrogen sources is reduced, preventing their collection near the mask edge and achieving uniform GaN layer thickness.
Solution Approach 2:
The patent uses an inert gas atmosphere (such as nitrogen or hydrogen) during the selective epitaxial growth process to prevent unwanted chemical reactions and control the migration behavior of source materials. The inert environment helps maintain uniform thickness by controlling the transport and deposition of gallium and nitrogen species.
2Reliability
If the GaN layer thickness is increased to reduce contact resistance, then contact resistance decreases, but the layer becomes too thick and causes other performance degradation
Solution Approach 1:
The patent optimizes the growth temperature parameter to achieve uniform GaN layer thickness with precise control. By maintaining temperature below 1000°C during selective growth, the process achieves both low contact resistance (through sufficient thickness) and uniform thickness distribution (through suppressed material migration), resolving the contradiction between these two requirements.
3Stability of the object's composition
If higher growth temperature is used to improve crystal quality, then crystal quality improves, but source material migration increases causing uneven thickness
Solution Approach 1:
The patent identifies and controls the growth temperature parameter within an optimal range (below 1000°C) that balances crystal quality and thickness uniformity. This temperature constraint prevents excessive source material migration while still allowing sufficient atomic mobility for high-quality crystal formation, thus resolving the contradiction between these two competing requirements.
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 process results in a nitride semiconductor device with reduced contact and access resistance, enhancing the high-frequency performance of HEMTs by maintaining a uniform GaN layer thickness and improving crystal quality.
Implementation Method 1
growing a contact layer selectively within the recess using nitrogen (N2) as a carrier gas
Implementation Method 2
selectively grown within the recesses, 21 and 22
Implementation Method 3
growing a contact layer selectively within the recess using nitrogen (N2) as a carrier gas at a temperature of 1000° C. at highest
Data Source
AI summary
A process of forming a semiconductor device primarily made of nitride semiconductor materials is disclosed. The process includes steps of: (a) growing a semiconductor stack including a channel layer and a barrier layer sequentially on a substrate, where the channel layer is made of gallium nitride (GaN); (b) patterning a mask on the barrier layer; (c) etching a portion of the barrier layer and a portion of the channel layer with the mask to form a recess in the semiconductor stack; and (d) growing a contact layer selectively within the recess with nitrogen (N2) used as a carrier gas at a maximum temperature of 1000° C.