Tantalum Seed Layer for Indium Electroplating Stability

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Solution Overview

Problem

In semiconductor device manufacturing, alloy formation between indium and other materials during heat exposure can lead to signal amplitude and timing variations, as well as structural integrity degradation, resulting in degraded performance and shortened device life.

Innovation Solution

A method involving physical vapor deposition to form a tantalum-nitride film and a tantalum layer on a substrate, followed by electroplating indium onto the tantalum layer, avoiding alloy formation with indium by using tantalum as the seed metal instead of materials like tin.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional seed metals like tin are used for indium electroplating, then the electroplating process can proceed normally, but alloy formation occurs at elevated temperatures causing signal variations and structural degradation

Engineering Contradiction:

Improvedevice performanceVSAvoidalloy formation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

Tantalum is introduced as an intermediary seed metal layer between the substrate and indium electroplating layer. This intermediary prevents direct alloy formation between indium and traditional seed metals like tin, while still enabling successful electroplating. The tantalum layer acts as a barrier that eliminates harmful alloying reactions at elevated temperatures, thereby resolving the contradiction between enabling electroplating and preventing alloy formation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the material parameter of the seed metal from traditional tin or nickel to tantalum. This parameter change fundamentally alters the chemical interaction behavior at elevated temperatures, preventing alloy formation while maintaining electroplating capability. The specific choice of tantalum with its unique properties (electrical conductivity, chemical stability) resolves the contradiction by changing the material composition parameter.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If alloy formation is prevented by using tantalum seed metal, then structural integrity is maintained, but the manufacturing process becomes more complex

Engineering Contradiction:

Improvestructural integrityVSAvoidmanufacturing process

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent combines physical vapor deposition (PVD) and electroplating processes in a single manufacturing flow, where tantalum is deposited via PVD and indium is deposited via electroplating on the same substrate. This merging of processes, while adding a tantalum layer, streamlines the overall manufacturing by creating a unified structure that prevents alloy formation without requiring separate protective layers or complex post-processing steps.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If indium is electroplated directly on traditional seed metals, then the electroplating process is simpler, but signal amplitude and timing variations occur due to alloy formation

Engineering Contradiction:

Improveelectroplating processVSAvoidsignal characteristics

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

Tantalum serves as an intermediary layer that enables electroplating to proceed easily while simultaneously preventing alloy formation that would cause signal variations. The intermediary layer maintains the simplicity of the electroplating process (indium deposits well on tantalum) while eliminating the harmful side effects (alloy formation) that would degrade signal characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Prevents alloy formation with indium even at elevated temperatures, maintaining electrical characteristics and structural integrity, thus enhancing the performance and longevity of semiconductor devices.

Implementation Method 1

forming a tantalum-nitride film on a substrate of the wafer stack using physical vapor deposition, forming a tantalum layer on the tantalum-nitride film using physical vapor deposition

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Implementation Method 2

depositing indium on the tantalum layer using electroplating

Methodology Applied

Scientific EffectElectroplating: Electroplating

Data Source

PatentUS11753736B2Indium electroplating on physical vapor deposition tantalum

Publication Date: 2023.09.12 RAYTHEON CO

AI summary

A method for fabricating a wafer stack. The method includes forming a tantalum-nitride film on a substrate of the wafer stack using physical vapor deposition, forming a tantalum layer on the tantalum-nitride film using physical vapor deposition, and depositing indium on the tantalum layer using electroplating.