Cr-N Diffusion Barrier for Cr/Au Electrode Bonding

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Solution Overview

Problem

Existing electronic devices with a Cr/Au layer configuration face issues with bonding strength due to Cr diffusion into the Au layer during production, leading to peeling and complex configurations requiring additional layers or difficult nitrogen plasma treatments.

Innovation Solution

A metal film structure with a Cr-N layer having 20-100% nitrogen atoms, sandwiched between a base material and a gold layer, formed by sputtering in a nitrogen-containing atmosphere to enhance bonding strength and prevent Cr diffusion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a Cr layer and Au layer are laminated to form an electrode, then the electrode can be formed with simple structure, but Cr diffuses into the Au layer during production and decreases bonding strength

Engineering Contradiction:

Improveelectrode configurationVSAvoidbonding strength between Cr layer and Au layer

Core Design Contradiction:

Device complexityVSStrength

Solution Approach 1:

The patent introduces a nitrogen-containing atmosphere during the sputtering process as an intermediary medium. This nitrogen atmosphere modifies the deposition environment to form a Cr-N compound layer that prevents Cr diffusion into the Au layer, thereby maintaining bonding strength without adding extra protective layers.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical composition parameters of the Cr layer by controlling the nitrogen content during sputtering. By adjusting the nitrogen partial pressure and sputtering conditions, a Cr-N compound layer with specific stoichiometry is formed, which provides both diffusion barrier functionality and bonding strength.

Inventive Principle:

Principle #35Parameter changes

2Strength

If a Ni layer or Ni-W layer is added between Cr layer and Au layer to prevent Cr diffusion, then bonding strength is improved, but the electrode configuration and production steps become complicated

Engineering Contradiction:

Improvebonding strength between metal layersVSAvoidelectrode configuration and production steps

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent merges the functions of the Cr layer (adhesion promoter) and the diffusion barrier layer into a single Cr-N compound layer. This eliminates the need for separate Ni or Ni-W intermediate layers, simplifying the electrode structure to just Cr-N/Au while maintaining both adhesion and diffusion prevention functions.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The nitrogen-containing atmosphere acts as an intermediary that transforms the Cr layer into a Cr-N compound during deposition. This in-situ transformation provides diffusion barrier functionality without requiring additional material layers or production steps.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If nitrogen plasma treatment is applied to Cr layer surface to form CrN layer, then Cr diffusion is prevented, but nitrogen plasma treatment is difficult to control and bonding strength may decrease

Engineering Contradiction:

Improvebonding strength between CrN layer and Au layerVSAvoidcontrol of nitrogen plasma treatment

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent replaces the plasma treatment process (chemical/physical surface modification) with a controlled sputtering process in nitrogen-containing atmosphere. This substitution provides more precise control over nitrogen incorporation by adjusting sputtering power, gas flow rates, and pressure, eliminating the controllability issues of plasma treatment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent incorporates nitrogen into the Cr layer during the deposition process itself, before the Au layer is formed. This preliminary nitrogen incorporation ensures uniform Cr-N compound formation throughout the Cr layer thickness, providing consistent diffusion barrier properties and bonding strength without requiring subsequent plasma treatment steps.

Inventive Principle:

Principle #10Preliminary 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

The configuration significantly increases bonding strength between the metal films and the base material, reduces peeling, and simplifies production while maintaining high mechanical strength and reliability.

Implementation Method 1

a first metal film disposed on the first surface and containing nitrogen and chromium... The first metal film includes a region in which the number of nitrogen atoms in the first metal film is 20% or more and 100% or less of the number of chromium atoms

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 2

formed by sputtering in a nitrogen-containing atmosphere

Methodology Applied

Scientific EffectSputtering: Sputtering

Data Source

PatentUS10340440B2Electronic device, method for producing electronic device, electronic apparatus, and moving object

Publication Date: 2019.07.02 SEIKO EPSON CORP

AI summary

An electronic device includes a base material, a first metal film disposed on the base material and containing nitrogen and chromium, and a second metal film disposed on the first metal film and containing gold. In the first metal film, the number of nitrogen atoms may be between 20% to 100% of the number of chromium atoms. Further, the distribution of nitrogen atoms in the first metal film is larger in a third region sandwiched between a first region on the base material side of the first metal film and a second region on the second metal film side than in the first region and in the second region.