Embedded Electrode Phosphorus Control for IGBT Gate Leakage
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Solution Overview
Problem
Insulated-gate bipolar transistors (IGBTs) with trench gate electrodes and embedded electrodes experience increased hysteresis of gate leakage due to phosphorus segregation at the interface between the embedded electrodes and the gate trench insulating films, caused by heat treatment processes, leading to higher switching losses and ON voltage.
Innovation Solution
A semiconductor device structure with a semiconductor substrate, including a carrier storage layer, base layer, emitter layer, and active trench gate, where the embedded electrode has a lower phosphorus concentration than the gate trench electrode, and is made of doped polysilicon with a non-doped polysilicon surface layer to prevent phosphorus segregation, reducing hysteresis of gate leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment processes are applied to embedded electrodes to activate phosphorus doping, then electrical conductivity is improved, but phosphorus segregates at the interface with gate trench insulating films causing increased gate leakage hysteresis
Solution Approach 1:
The patent applies preliminary action by forming the gate trench insulating film before applying heat treatment to the embedded electrode. This sequence prevents phosphorus segregation because the insulating film is already in place to act as a barrier during the heat treatment process that activates the phosphorus doping in the embedded electrode.
Solution Approach 2:
The gate trench insulating film serves as an intermediary layer between the embedded electrode and the gate trench electrode. This intermediate film prevents direct contact between phosphorus-doped regions, thereby preventing phosphorus segregation at the interface while still allowing the heat treatment process to effectively activate the phosphorus doping in the embedded electrode.
2Reliability
If phosphorus is heavily doped in embedded electrodes to reduce resistance, then electrical conductivity increases, but phosphorus segregation at interfaces increases causing higher gate leakage hysteresis
Solution Approach 1:
The gate trench insulating film is formed in advance before phosphorus doping and heat treatment of the embedded electrode. This preliminary formation of the insulating film creates a protective barrier that prevents phosphorus segregation during subsequent heat treatment, allowing heavy phosphorus doping to be applied without causing interface contamination and gate leakage hysteresis.
Solution Approach 2:
The gate trench insulating film acts as an intermediary barrier that allows the embedded electrode to maintain high phosphorus concentration for low resistance while preventing phosphorus migration to the interface. This mediator enables the system to achieve both low electrical resistance and low gate leakage hysteresis simultaneously.
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 reduced phosphorus concentration in the embedded electrodes minimizes phosphorus segregation, thereby decreasing hysteresis of gate leakage, leading to lower switching losses and ON voltage in IGBTs.
Implementation Method 1
When phosphorus segregates at an interface between each of the gate trench electrodes and the embedded electrodes and an insulating film (a gate trench insulating film) formed on the surface of the gate trench electrodes and the embedded electrodes
Data Source
AI summary
Hysteresis of gate leakage is reduced in a semiconductor device with a structure including embedded electrodes below gate trench electrodes. A semiconductor device includes an active trench gate formed in a trench coming in contact with an emitter layer, a base layer, and a carrier storage layer to reach a drift layer. The active trench gate includes: a gate trench insulating film formed on an inner wall of the trench; and a gate trench electrode, and an embedded electrode below the gate trench electrode, the gate trench electrode and the embedded electrode being formed on the gate trench insulating film in the trench and being insulated from each other. The embedded electrode is lower in phosphorus concentration than the gate trench electrode.