Sacrificial Layer for Oxygen-Resistant Semiconductor Die Sintering

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Solution Overview

Problem

Sintering processes in the semiconductor industry cause microstructural degradation and delamination or corrosion issues in Ag thin films used in semiconductor die backside metallization stacks due to exposure to oxygen at elevated temperatures.

Innovation Solution

A sacrificial layer with a material that decomposes or becomes volatile between 100° and 400° C is applied on the protection layer of the semiconductor die, preventing oxygen ingress and facilitating reliable decomposition during sintering, thereby protecting the die backside metallization stack.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If sintering is performed at elevated temperatures in oxygen environment, then reliable sintering and interconnect formation are achieved, but microstructural degradation and corrosion occur in Ag thin films

Engineering Contradiction:

Improvesintering reliabilityVSAvoidoxygen corrosion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A sacrificial layer is introduced as an intermediary between the oxygen-containing sintering environment and the Ag protection layer. This sacrificial layer preferentially reacts with oxygen during sintering, preventing oxygen from reaching and corroding the Ag thin film, thus resolving the contradiction between achieving reliable sintering and preventing oxygen-induced degradation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The sacrificial layer is designed as a consumable, short-lived protective element that is intentionally sacrificed during the sintering process. It performs its protective function temporarily during elevated temperature processing and is subsequently removed or decomposed, allowing the Ag layer to remain intact for long-term device operation

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If Ag thin films are used as protection layer, then good electrical conductivity and protection are provided, but microstructural degradation occurs at elevated temperatures

Engineering Contradiction:

Improveprotection layer functionalityVSAvoidAg layer microstructural stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The sacrificial layer is applied in advance on top of the Ag protection layer before the sintering process. This preliminary action creates a protective barrier that prevents oxygen from attacking the Ag layer during the subsequent high-temperature sintering, thereby maintaining the Ag layer's microstructural stability while preserving its electrical conductivity and protection functions

Inventive Principle:

Principle #10Preliminary action

3Productivity

If conventional sintering process is used, then electronic devices can be mounted onto carriers, but delamination and corrosion issues arise in backside metallization

Engineering Contradiction:

Improvedevice mounting capabilityVSAvoidmetallization stack integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The sacrificial layer serves as a mediator between the sintering environment and the backside metallization stack. During the sintering process that enables device mounting, the sacrificial layer absorbs oxygen and prevents it from reaching the metallization layers, thereby preventing delamination and corrosion while maintaining productivity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The sacrificial layer is a temporary, consumable component designed to be present only during the sintering process. It sacrifices itself to protect the metallization stack during the critical mounting operation, after which it decomposes or is removed, leaving the metallization intact for reliable long-term operation

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 sacrificial layer effectively prevents oxygen adsorption and corrosion, ensuring reliable sintering and interconnect formation by controlling the decomposition process, thus enhancing the thermal and mechanical performance of semiconductor devices.

Implementation Method 1

a sacrificial layer disposed on the protection layer, wherein the sacrificial layer comprises a material which decomposes or becomes volatile at a temperature between 100° and 400° C.

Methodology Applied

Scientific EffectDecomposition: Decomposition (biological)

Implementation Method 2

a sacrificial layer disposed on the protection layer, wherein the sacrificial layer comprises a material which decomposes or becomes volatile at a temperature between 100° and 400° C.

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

The sacrificial layer effectively prevents oxygen adsorption and corrosion

Methodology Applied

Scientific EffectAdsorption: Adsorption

Data Source

PatentUS11581194B2Sintering method using a sacrificial layer on the backside metallization of a semiconductor die

Publication Date: 2023.02.14 INFINEON TECHNOLOGIES AG

AI summary

An electronic device comprises a semiconductor die, a layer stack disposed on the semiconductor die and comprising one or more functional layers, wherein the layer stack comprises a protection layer which is an outermost functional layer of the layer stack, and a sacrificial layer disposed on the protection layer, wherein the sacrificial layer comprises a material which decomposes or becomes volatile at a temperature between 100° and 400° C.