Copper Bond Pad Grain Orientation for Direct Wire Bonding

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Solution Overview

Problem

Existing semiconductor device packaging technologies face challenges in reducing costs and improving reliability due to issues with bond pad oxidation and intermetallic compound formation, which affect the bonding of copper bond wires.

Innovation Solution

A bond pad structure with a top surface layer of copper having a specific grain orientation (Cu) is formed, allowing direct attachment of copper bond wires without additional processing steps, minimizing oxide growth and eliminating intermetallic compound formation and associated corrosion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional bond pad structures are used, then manufacturing processes are simpler, but oxidation and intermetallic compound formation occur affecting bonding reliability

Engineering Contradiction:

Improvebonding reliabilityVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the grain orientation parameter of the copper top surface layer to the <100> orientation, which fundamentally alters the oxidation resistance properties of the copper surface. This parameter change enables direct copper-to-copper bonding without additional protective layers or processing steps, thereby improving bonding reliability while maintaining manufacturing simplicity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The bond pad structure uses a composite material approach with a multi-layer configuration: a copper base layer combined with a copper top surface layer having specific <100> grain orientation. This composite structure combines the electrical conductivity of copper with the oxidation resistance provided by the specific crystal orientation, eliminating intermetallic compound formation while simplifying the manufacturing process

Inventive Principle:

Principle #40Composite materials

2Reliability

If additional processing steps are added to prevent oxidation, then bonding reliability improves, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvebonding reliabilityVSAvoidprocessing steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The copper top surface layer with <100> grain orientation provides self-protection against oxidation without requiring external protective layers or additional processing steps. The specific crystal orientation inherently resists oxidation and prevents intermetallic compound formation, allowing the material to serve its own protective function and enabling direct bonding to copper bond wires

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

By changing the grain orientation parameter to <100>, the copper surface inherently gains oxidation resistance and compatibility with copper bond wires. This single parameter change eliminates the need for multiple processing steps such as applying protective coatings or performing complex surface treatments, thereby reducing device complexity while improving bonding reliability

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If copper bond wires are directly bonded on conventional bond pads, then costs are reduced, but oxidation and intermetallic compound formation occur

Engineering Contradiction:

Improvemanufacturing costVSAvoidoxidation and corrosion

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent changes the grain orientation parameter of the copper top surface layer to <100>, which fundamentally alters the chemical properties of the copper surface. This parameter change eliminates oxidation and intermetallic compound formation, enabling direct copper-to-copper bonding without harmful reactions while maintaining cost effectiveness

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Inventive Principle:

Principle #40Composite materials

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 enhances conductivity while reducing costs and improving reliability by enabling direct bonding of copper bond wires on copper bond pads, eliminating oxidation and corrosion susceptibility.

Implementation Method 1

The Cu top surface layer has minimal oxide growth due to the grain density and allows for direct bonding with a copper bond wire

Methodology Applied

Scientific EffectOxidation resistance: Oxidation

Implementation Method 2

The Cu top surface layer may be formed by deposition or plating

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS10147697B1Bond pad structure for semiconductor device packaging

Publication Date: 2018.12.04 NXP USA INC

AI summary

A semiconductor device includes a leadframe having a flag and a plurality of bond terminals. A semiconductor die is attached to the leadframe at the flag. A bond pad is formed on the semiconductor die. A top surface layer of the bond pad includes copper having a predetermined grain orientation. A bond wire includes a first end and a second end. The bond wire is attached to the bond pad at the first end and attached to one of the bond terminals in the plurality at the second end.