GaN Semiconductor Fabrication Ga Diffusion Control
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Solution Overview
Problem
High growth temperatures during the fabrication of GaN-based semiconductor devices on silicon substrates lead to Ga diffusion, forming conductive layers that increase parasitic capacitance and signal loss, deteriorating the characteristics of the semiconductor devices.
Innovation Solution
Separating the steps of forming the AlN layer and the GaN-based semiconductor layers, and thoroughly cleaning the MOCVD apparatus to prevent Ga impurities from remaining and diffusing into the silicon substrate, thereby reducing the formation of conductive layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high growth temperature (900°C or more) is used to grow GaN-based semiconductor on silicon substrate, then the GaN layer can be successfully formed, but Ga diffuses into the silicon substrate forming conductive layers that increase parasitic capacitance and signal loss
Solution Approach 1:
An AlN buffer layer is introduced as an intermediary between the silicon substrate and the GaN-based semiconductor layer. This buffer layer acts as a barrier to prevent Ga diffusion into the silicon substrate while still allowing the GaN layer to be grown successfully at high temperatures. The AlN layer has appropriate crystal structure and thermal properties that facilitate this intermediary function.
Solution Approach 2:
The semiconductor structure is segmented into distinct layers: a silicon substrate, an AlN buffer layer, and a GaN-based semiconductor layer. This segmentation separates the functions of substrate support, diffusion barrier, and active semiconductor functionality, allowing each layer to be optimized for its specific purpose.
2Productivity
If AlN layer and GaN-based semiconductor layers are formed in sequence without cleaning, then production efficiency is maintained, but Ga impurities from previous GaN growth remain and diffuse into subsequent AlN layers forming unwanted conductive layers
Solution Approach 1:
A cleaning step is performed as a preliminary action between the formation of GaN-based semiconductor layers and AlN layers. This cleaning removes Ga impurities from the reaction chamber and equipment surfaces before the AlN layer growth begins, preventing contamination while maintaining efficient production through a standardized process sequence.
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 effectively prevents the formation of conductive layers in the silicon substrate, maintaining high-frequency signal integrity and improving the overall characteristics of the semiconductor devices by minimizing Ga diffusion and parasitic capacitance.
Implementation Method 1
a first layer including a nitride semiconductor that does not include Ga as a composition element is formed on a plurality of substrates made of silicon by using an apparatus
Implementation Method 2
cleaning the apparatus includes performing a process of heating the interior of the apparatus to a temperature of 1,000° C. or more in a nitrogen atmosphere and performing a process of oxidizing the interior of the apparatus
Implementation Method 3
performing a process of oxidizing the interior of the apparatus
Implementation Method 4
performing a process of heating the interior of the apparatus to a temperature of 1,000° C. or more in a nitrogen atmosphere
Data Source
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AI summary
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 x 1018 atoms/cm3 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.