Reducing Ga Diffusion in GaN Semiconductor Devices
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Summary
Problems
The formation of conductive layers in silicon substrates during the growth of GaN-based semiconductor devices leads to increased parasitic capacitance and signal loss, deteriorating the characteristics of high-frequency semiconductor devices, particularly due to the diffusion of Ga impurities from the MOCVD apparatus.
Innovation solutions
The method involves separating the steps of forming the AlN buffer layer and the GaN-based semiconductor layers, with thorough cleaning of the MOCVD apparatus to minimize Ga impurity retention, ensuring the AlN layer has a Ga impurity concentration of 2×10^18 atoms/cm^3 or less, thereby preventing Ga diffusion into the silicon substrate.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If the MOCVD method is used to grow GaN-based semiconductor layers on silicon substrates, then the device can operate at high frequencies and use inexpensive substrates, but Ga diffuses into the silicon substrate forming conductive layers that increase parasitic capacitance and degrade device characteristics
Why choose this principle:
The patent segments the layer formation process into distinct stages: first forming a Ga-free nitride semiconductor layer (AlN or AlGaN) as a barrier layer, then separately forming the Ga-containing GaN-based semiconductor layer. This segmentation prevents Ga diffusion into the silicon substrate by isolating the Ga source from the substrate through the Ga-free barrier layer, thereby resolving the contradiction between achieving high-frequency operation and preventing harmful Ga diffusion.
Principle concept:
If the MOCVD method is used to grow GaN-based semiconductor layers on silicon substrates, then the device can operate at high frequencies and use inexpensive substrates, but Ga diffuses into the silicon substrate forming conductive layers that increase parasitic capacitance and degrade device characteristics
Why choose this principle:
The Ga-free nitride semiconductor layer acts as an intermediary barrier between the silicon substrate and the Ga-containing GaN layer. This intermediate layer prevents direct contact and diffusion between Ga and the silicon substrate, allowing the device to maintain high-frequency characteristics without the harmful effects of Ga-induced conductive layers forming in the substrate.
Application Domain
Data Source
AI summary:
The method involves separating the steps of forming the AlN buffer layer and the GaN-based semiconductor layers, with thorough cleaning of the MOCVD apparatus to minimize Ga impurity retention, ensuring the AlN layer has a Ga impurity concentration of 2×10^18 atoms/cm^3 or less, thereby preventing Ga diffusion into the silicon substrate.
Abstract
A method for fabricating a semiconductor device including: cleaning an apparatus used to grow a layer including Ga; performing a first step of forming a first layer on a substrate made of silicon by using the apparatus, the first layer including a nitride semiconductor that does not include Ga as a composition element and has a Ga impurity concentration of 2×10 18 atoms/cm 3 or less; and performing a second step of forming a second layer on the first layer by using the apparatus after the first step is repeatedly carried out multiple times, the second layer including a nitride semiconductor including Ga.