Sacrificial Layer Detachment for Solder Bump Manufacturing

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Solution Overview

Problem

In the manufacturing of metal structures for semiconductor substrates, the existing wet-etching methods often result in under-etching of solder bumps due to lateral attack on the galvanic starting layer, leading to detachment issues with small solder bumps, which compromises the reliability of the electrical connection.

Innovation Solution

A method involving the deposition and structuring of an auxiliary layer on the substrate, followed by the deposition of a galvanic starting layer and a lithography layer, where the auxiliary layer is expanded using light to physically detach the galvanic starting layer after metal structure deposition, eliminating the need for chemical wet-etching and ensuring secure attachment of small metal structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If wet-etching method is used to remove the galvanic starting layer, then the galvanic starting layer can be removed, but lateral attack occurs on the galvanic starting layer at the end-face of the solder contact causing under-etching and detachment of small solder bumps

Engineering Contradiction:

Improveremoval of galvanic starting layerVSAvoidattachment of solder bumps

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

A sacrificial layer is introduced as an intermediary between the substrate and the galvanic starting layer. This sacrificial layer serves as a protective mediator that prevents the etching agent from directly contacting and laterally attacking the galvanic starting layer at the solder bump end-faces, thereby eliminating under-etching while still allowing removal of the galvanic starting layer where not covered by solder bumps

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The sacrificial layer is deposited beforehand (before the galvanic starting layer) to create a protective foundation. This preliminary action ensures that when etching occurs, the sacrificial layer is already in place to protect the galvanic starting layer from lateral attack, preventing detachment issues before they can occur

Inventive Principle:

Principle #10Preliminary action

2Length of moving object

If the dimensions of solder contacts are reduced, then fine-pitch connections are achieved, but the risk of under-etching and detachment increases due to lateral attack on the galvanic starting layer

Engineering Contradiction:

Improvedimension of solder contactsVSAvoidattachment of solder bumps

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The sacrificial layer acts as a protective intermediary that is particularly crucial for small-dimensional solder contacts. By placing this intermediate protective layer between the etching agent and the galvanic starting layer, the invention enables reliable manufacturing of fine-pitch connections without the lateral attack problems that plague traditional direct-etching methods

Inventive Principle:

Principle #24Intermediary (Mediator)

3Area of stationary object

If the galvanic starting layer extends over a large surface of the substrate, then complete coverage is achieved, but short-circuiting between different solder bumps occurs

Engineering Contradiction:

Improvecoverage area of galvanic starting layerVSAvoidelectrical connection

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The sacrificial layer is selectively removed (taken out) from specific regions where it is not needed. By removing the sacrificial layer in areas between solder bumps, the galvanic starting layer can be cleanly exposed and removed in those regions, preventing short-circuits while maintaining complete coverage under the solder bumps where the sacrificial layer remains protective

Inventive Principle:

Principle #2Taking out (Extraction)

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 method ensures reliable fastening of solder bumps on the substrate by preventing under-etching and detachment, maintaining a secure connection even for small metal structures without chemical etching, thereby enhancing the reliability of the electrical connection.

Implementation Method 1

the auxiliary layer is expanded using light

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 2

the auxiliary layer is expanded using light to physically detach the galvanic starting layer

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10074608B2Method for manufacturing a contact bump by thermal expansion of a patterned sacrificial layer underneath a galvanic layer

Publication Date: 2018.09.11 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

A method for manufacturing metal structures for the electrical connection of components comprises the following steps: depositing an auxiliary layer on a substrate; structuring the auxiliary layer in a manner such that the substrate is exposed at least one environment which is envisaged for the metal structures; depositing a galvanic starting layer on the structured auxiliary layer; depositing a lithography layer on the galvanic starting layer and structuring the lithography layer in a manner such that the galvanic starting layer is exposed at least one location envisaged for the metal structure; galvanically depositing the at least one metal structure at the at least one exposed location; removing the structured auxiliary layer. An electronic component is also described.