Semiconductor Electrode Buffer Layer for Low-Resistance Bonding
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Solution Overview
Problem
Semiconductor devices face damage and increased resistance issues due to foreign matter during external wiring connection, leading to reduced breakdown voltage and device failure, as existing solutions like insulating layers between wiring and electrodes increase wiring resistance and do not adequately prevent semiconductor layer damage.
Innovation Solution
A semiconductor device design featuring a buffer layer with higher Vickers hardness than the electrode, having openings that satisfy specific width conditions, which reduces resistance between external wiring and the semiconductor layer and minimizes foreign matter-induced damage by preventing foreign matter from reaching the semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating layer is disposed immediately below the external wiring to separate the wiring region from the electrode-semiconductor contact region, then the semiconductor layer is protected from damage, but wiring resistance increases due to the distance from the external wiring to the semiconductor layer
Solution Approach 1:
A buffer layer made of semiconductor material with higher hardness than the electrode is introduced as an intermediary between the electrode and the external wiring. This buffer layer has at least one opening that allows external wiring to contact the second semiconductor layer directly, thereby reducing wiring resistance while the buffer layer itself protects the semiconductor layer from damage by foreign matter pushed during wiring connection.
2Loss of energy
If the anode layer is made thinner or has lower impurity concentration to reduce recovery loss, then the recovery current is reduced, but the breakdown voltage is reduced and the depletion layer may reach the anode electrode causing device breakdown
Solution Approach 1:
The invention uses a composite structure with a first semiconductor layer (drift layer) and a second semiconductor layer (anode layer) with different conductivity types, where the second semiconductor layer has higher hardness than the electrode. This composite structure allows the anode layer to be made thinner with lower impurity concentration to reduce recovery loss, while the harder second semiconductor layer prevents foreign matter from reaching the semiconductor layer and causing premature breakdown.
3Ease of manufacture
If foreign matter is present on or inside the anode electrode, then the foreign matter is pushed into the anode electrode during joining of external wiring, damaging the semiconductor layer
Solution Approach 1:
The buffer layer made of semiconductor material with higher hardness than the electrode is prepared in advance and disposed on the front surface of the second semiconductor layer. This buffer layer acts as a protective cushion that stops foreign matter before it can reach and damage the semiconductor layer during the external wiring joining process, while still allowing the wiring to be connected through the openings in the buffer layer.
Data Source
AI summary
According to one aspect, a semiconductor device includes: a buffer layer disposed on a front surface of a second semiconductor layer, and having at least one opening in plan view; and an electrode disposed over the second semiconductor layer and the buffer layer, and being in contact with the second semiconductor layer through the at least one opening, wherein the buffer layer has a higher Vickers hardness than the electrode, and a width w of each of the at least one opening satisfies w<Wth, where s is a thickness of the buffer layer, t is a thickness of the electrode, and Wth=2×(s×t−s2)0.5 holds true.