Semiconductor Electrode Thickness for Alpha Ray Shielding

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Solution Overview

Problem

Semiconductor devices, particularly MOSFETs, face reliability issues due to α rays generated from solder penetrating the gate insulating film, causing electron-positive hole pairs to form, with positive holes remaining and altering the threshold voltage to a more negative side, leading to performance degradation.

Innovation Solution

The semiconductor device incorporates electrodes with specific metal materials having a film thickness greater than or equal to (65 [g·μm·cm−3])/(density of the metal material [g·cm−3]) to suppress α ray penetration, ensuring the electrodes' higher density absorbs the energy and prevents α rays from reaching the MOSFET, thereby maintaining the threshold voltage stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electrodes containing Cu or the like are used to connect source/gate/drain electrodes, then electrical connection is achieved, but α rays generated from solder penetrate the gate insulating film causing threshold voltage shift

Engineering Contradiction:

Improvethreshold voltage stabilityVSAvoidα ray penetration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a specific electrode structure with Cu electrodes having controlled thickness (≥65[g·μm·cm−3]/density) as an intermediary layer between the solder and the MOSFET gate insulating film. This intermediary electrode structure absorbs the α rays generated from the solder, preventing them from penetrating into the gate insulating film and causing threshold voltage shifts, while still maintaining the electrical connection function.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the physical parameters of the electrode, specifically controlling the Cu electrode thickness to be greater than or equal to (65[g·μm·cm−3])/density of the metal material. This parameter change ensures the electrode has sufficient stopping power to absorb α rays while maintaining electrical conductivity, thus resolving the contradiction between electrical connection and α ray shielding.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If solder is used to connect electrodes, then electrical connection is established, but α rays are generated from solder causing electron-positive hole pairs in gate insulating film

Engineering Contradiction:

Improveelectrode connectionVSAvoidα ray generation

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful effect of α ray generation from solder into a beneficial shielding mechanism. By designing the Cu electrode with specific thickness (≥65[g·μm·cm−3])/density), the electrode that would normally be vulnerable to α ray damage instead becomes an effective shield that absorbs the α rays, transforming the potential harm into a protective function.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If positive holes remain in gate insulating film, then electron-positive hole pairs are formed, but threshold voltage shifts to more negative side causing performance degradation

Engineering Contradiction:

Improvedevice performanceVSAvoidthreshold voltage

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary anti-action by pre-establishing the Cu electrode structure with adequate thickness (≥65[g·μm·cm−3])/density before the α rays can penetrate and cause damage. This preventive electrode structure blocks the α rays in advance, preventing the formation of electron-positive hole pairs and the subsequent threshold voltage shift, thus maintaining device performance and electrical characteristics.

Inventive Principle:

Principle #9Preliminary anti-action

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 solution effectively suppresses α ray penetration, enhancing the reliability of the semiconductor device by maintaining the threshold voltage stability and preventing performance degradation, thus ensuring high reliability.

Implementation Method 1

electrodes with specific metal materials having a film thickness greater than or equal to (65 [g·μm·cm−3])/(density of the metal material [g·cm−3]) to suppress α ray penetration, ensuring the electrodes' higher density absorbs the energy

Methodology Applied

Scientific EffectAlpha ray absorption: Absorption (EM radiation)

Data Source

PatentUS10998437B2Semiconductor device

Publication Date: 2021.05.04 KK TOSHIBA

AI summary

A semiconductor device according to an embodiment includes a semiconductor substrate having a first plane and a second plane, a semiconductor element provided in the semiconductor substrate, the semiconductor element including a gate insulating film provided in the first plane, a first electrode provided on the first plane, a second electrode provided on the first electrode, the second electrode including a first metal material, the second electrode having a film thickness of (65 [g·μm·cm−3])/(density of the first metal material [g·cm−3]) or more, a first solder portion provided on the second electrode, a third electrode provided on the first solder portion, a fourth electrode provided on the first plane, a fifth electrode provided on the fourth electrode, the fifth electrode including a second metal material, the fifth electrode having a film thickness of (65 [g·μm·cm−3])/(density of the second metal material [g·cm−3]) or more, a second solder portion provided on the fifth electrode, and a sixth electrode provided on the second solder portion.