Adjusting Charge Carrier Lifetime in Bipolar Semiconductor Devices

Solution Overview

Problem

Bipolar power semiconductor devices face challenges in adjusting charge carrier lifetime to minimize switching losses and achieve soft switching behavior, as existing methods either increase conduction losses or result in steep reverse recovery currents.

Innovation Solution

The method involves implanting recombination center atoms into a semiconductor body and causing them to diffuse, creating a specific distribution of recombination centers that adjust the minority charge carrier lifetime, thereby optimizing charge carrier reservoirs for reduced switching losses and soft switching behavior.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the charge carrier lifetime is decreased to achieve low switching losses, then switching losses are reduced, but the reverse recovery current slope becomes steeper

Engineering Contradiction:

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

Solution Approach 1:

The patent implements local quality by selectively distributing recombination centers in specific regions. High recombination center concentrations are placed in the emitter regions to control overall charge carrier lifetime and reduce switching losses, while the base region near the depletion zone maintains lower recombination center concentration. This gradient distribution ensures that charge carriers are removed at a controlled rate during reverse recovery, producing a softer current slope while still achieving low switching losses.

Inventive Principle:

Principle #3Local quality

2Duration of action of moving object

If recombination centers are uniformly distributed throughout the semiconductor body, then charge carrier lifetime is reduced, but conduction losses increase and switching behavior deteriorates

Engineering Contradiction:

Core Design Contradiction:

Duration of action of moving objectVSLoss of energy

Solution Approach 1:

The patent explicitly avoids uniform distribution of recombination centers and instead implements a non-uniform, localized distribution. Recombination centers are concentrated in the emitter regions where they most effectively reduce charge carrier lifetime and switching losses, while the base region maintains lower recombination center density to preserve charge carriers necessary for low conduction losses. This targeted spatial distribution optimizes the balance between charge carrier lifetime reduction and maintaining device performance.

Inventive Principle:

Principle #3Local quality

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 reduces switching losses and achieves a soft switching behavior by controlling the charge carrier lifetime, leading to improved performance in bipolar power semiconductor devices.

Implementation Method 1

causing the implanted recombination center atoms to diffuse in the semiconductor body in a first diffusion process

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

adjusting the minority charge carrier lifetime, which is the average time it takes for a minority charge carrier to recombine

Methodology Applied

Scientific EffectRecombination:

Data Source

PatentUS9349799B2Adjusting the charge carrier lifetime in a bipolar semiconductor device

Publication Date: 2016.05.24

AI summary

Disclosed are a method and a semiconductor device. The method includes implanting recombination center atoms via a first surface into a semiconductor body, and causing the implanted recombination center atoms to diffuse in the semiconductor body in a first diffusion process.