Semiconductor Device With Selective Heavy Metal Removal

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Solution Overview

Problem

The existing semiconductor devices face challenges in accurately controlling the distribution of crystal defects introduced by ion irradiation, leading to increased resistance in IGBT regions and reverse recovered charge in diode regions due to alignment inaccuracies and incomplete defect formation.

Innovation Solution

A semiconductor device with a diode element region having a higher concentration of heavy metal in its drift layer than the IGBT element region, where crystal defects are generated through thermal stress from trench electrodes, allowing for precise control of carrier lifetime reduction and eliminating the need for ion irradiation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If ion irradiation is used to form defect regions in the FWD region, then carrier lifetime can be controlled, but the distribution of crystal defects cannot be controlled with high accuracy due to alignment difficulties

Engineering Contradiction:

Improvedistribution control of crystal defectsVSAvoidalignment process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention extracts the heavy metal elements (Fe, Ni, Cu) from the drift layer through selective removal processes, creating defect regions without requiring ion irradiation alignment. This eliminates the need for complex mask alignment while achieving precise spatial control of carrier lifetime reduction in the FWD region.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of introducing defects through ion irradiation (adding harmful factors), the invention removes heavy metal elements (eliminating harmful factors) to create defect regions. This inverted approach achieves the same functional result with superior positional control and without alignment complexity.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If ion irradiation is performed on the FWD region, then a lifetime control region can be formed, but inadvertent formation of defect regions in the IGBT region increases IGBT resistance

Engineering Contradiction:

Improvecarrier lifetime controlVSAvoidIGBT resistance increase

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention applies local quality by selectively removing heavy metal elements only from the FWD region drift layer, creating localized defect regions with reduced carrier lifetime. The IGBT region drift layer maintains its original heavy metal concentration and electrical properties, preventing resistance increase while achieving the desired lifetime control in the diode region.

Inventive Principle:

Principle #3Local quality

3Loss of energy

If no defect regions are formed in the FWD region, then IGBT resistance remains low, but reverse recovered charge of the diode increases

Engineering Contradiction:

Improvereverse recovered chargeVSAvoidselective defect formation

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The invention replaces the mechanical ion irradiation process with a chemical/electrical selective removal process. By applying selective electrochemical etching or chemical treatments that target heavy metal-containing regions, the method achieves precise spatial control of defect formation without the alignment limitations of mechanical mask systems, thereby reducing reverse recovered charge effectively.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables high-accuracy positioning of the lifetime control region, reduces recovery loss in the diode element region, and simplifies the process by avoiding ion irradiation, while preventing on-resistance increases in the IGBT region.

Implementation Method 1

The heavy metal included in the drift layer has an effect of reducing a carrier lifetime

Methodology Applied

Scientific EffectCarrier scattering:

Implementation Method 2

The heavy metal included in the drift layer has an effect of reducing a carrier lifetime

Methodology Applied

Scientific EffectCarrier recombination:

Implementation Method 3

crystal defects are generated through thermal stress from trench electrodes

Methodology Applied

Scientific EffectThermal stress: Thermal Shock

Data Source

PatentUS9064711B2Semiconductor device and method for fabricating semiconductor device

Publication Date: 2015.06.23 DENSO CORP

AI summary

A method for fabricating a semiconductor device in which a lifetime control region can be formed within a predetermined range with high positioning accuracy is provided. In a semiconductor device, an IGBT element region and a diode element region may be formed in one semiconductor substrate. The IGBT element region may include a second conductivity type drift layer and a first conductivity type body layer. The diode element region may include a second conductivity type drift layer and a first conductivity type anode layer. A concentration of heavy metal included in the drift layer of the diode element region may be set higher than a concentration of the heavy metal included in the drift layer of the IGBT element region.