SiC Substrate Via Formation for Nitride Semiconductor Source Inductance
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Solution Overview
Problem
In nitride-based semiconductor devices, forming a via immediately below the source electrode is challenging due to the etching of Al source electrodes by chlorine-based gases, which complicates the miniaturization of semiconductor components and affects high-frequency characteristics.
Innovation Solution
A method involving the formation of a metal via by etching the SiC substrate using a fluorine-based gas and the nitride semiconductor layer using a chlorine-based gas, with intermittent radiation of fluorine and chlorine ions, and a laminated structure including a Ni and Au layer, allowing for the creation of a metal via continuous with the first metal film from the back surface, facilitating the formation of a metal via below the source finger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chlorine-based gas is used for etching the nitride semiconductor layer, then the etching process can proceed effectively, but the Al source electrode is etched simultaneously which complicates via formation
Solution Approach 1:
The etching process is segmented into two distinct steps: first etching the SiC substrate using fluorine-based gas, then etching the nitride semiconductor layer using chlorine-based gas. This segmentation allows selective removal of materials without unwanted side effects, solving the problem of Al electrode etching while maintaining etching efficiency.
Solution Approach 2:
The SiC substrate is etched in advance using fluorine-based gas before the nitride semiconductor layer etching step. This preliminary action creates a through-hole in the substrate that stops at the metal via, preventing the subsequent chlorine-based gas from reaching and etching the Al source electrode, thus enabling easy via formation.
2Reliability
If a via is formed immediately below the source electrode, then high-frequency characteristics are improved, but the Al source electrode is etched by chlorine-based gases making the process complex
Solution Approach 1:
The etching process is divided into two separate steps with different gases: fluorine-based gas for SiC substrate etching, and chlorine-based gas for nitride semiconductor layer etching. This segmentation enables via formation below the source electrode without etching the Al electrode, improving high-frequency characteristics while keeping the process manageable.
Solution Approach 2:
The metal via structure acts as an intermediary that stops the fluorine-based gas etching process, preventing it from reaching the Al source electrode. This allows the via to be formed immediately below the source electrode for improved high-frequency characteristics while avoiding the complexity of Al electrode etching.
3Length of moving object
If miniaturization of semiconductor components is pursued, then device size is reduced, but via formation becomes more difficult due to Al electrode etching
Solution Approach 1:
The etching process is segmented into two steps using different gases, allowing precise control over which layers are removed. This enables miniaturization of semiconductor components while maintaining easy via formation below the source electrode without unwanted Al electrode etching.
Solution Approach 2:
The SiC substrate is etched in advance to create a through-hole that stops at the metal via layer. This preliminary action establishes a controlled etching path that prevents subsequent chlorine-based gas from etching the Al source electrode, facilitating miniaturization while maintaining via formation ease.
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
Enables the easy formation of a via below the source finger, improving high-frequency characteristics by reducing source inductance and stabilizing gain, while using the Ni layer as an etching stop film to manage the etching process effectively.
Implementation Method 1
forming a hole being continuous with the first metal film from a back surface of the SiC substrate
Implementation Method 2
forming a hole being continuous with the first metal film from a back surface of the SiC substrate
Implementation Method 3
using the Ni layer as an etching stop film to manage the etching process effectively
Data Source
AI summary
Disclosure is a method for manufacturing a semiconductor device. The method includes forming a source electrode and a drain electrode on a nitride semiconductor layer formed on a main surface of a SiC substrate, forming a gate electrode having a laminated structure including a Ni layer and an Au layer on the Ni layer between the source electrode and the drain electrode on the nitride semiconductor layer and forming a first metal film having the same laminated structure as the gate electrode in a region adjacent to the source electrode with an interval therebetween, forming a second metal film to contact with the source electrode and the first metal film, forming a hole being continuous with the first metal film from a back surface of the SiC substrate, and forming a metal via being continuous with the first metal film from the back surface in the hole.