Metal Bonding Layer for Semiconductor Substrate Stress Reduction

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Solution Overview

Problem

Semiconductor devices based on nitride compound semiconductors bonded to silicon substrates experience significant thermal stress due to differing expansion coefficients, leading to substrate bowing and detachment issues when using direct bonding with silicon oxide layers.

Innovation Solution

The method involves applying a silicon oxide layer and a metal layer (such as gold) on the semiconductor layer sequence and silicon substrate, respectively, and bonding them at elevated temperatures (150° C. to 400° C.) to form a metal bonding layer, which reduces thermal stress and enhances adhesion, allowing for the detachment of the growth substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If direct bonding with silicon oxide layers is used to bond the semiconductor body to the silicon substrate, then adhesion is achieved, but significant stress occurs due to different thermal expansion coefficients causing substrate bowing

Engineering Contradiction:

ImproveadhesionVSAvoidthermal stress

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

A metal intermediate layer (such as gold, silver, copper, or aluminum) is introduced between the silicon oxide layer and the silicon substrate. This intermediate metal layer serves as a stress buffer that compensates for the thermal expansion coefficient mismatch between gallium nitride and silicon, thereby reducing substrate bowing while maintaining bonding strength

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The bonding structure is formed as a composite system consisting of multiple layers: silicon oxide layer, metal intermediate layer, and silicon substrate. This composite structure combines the adhesion properties of silicon oxide with the stress-buffering properties of the metal layer, achieving both strong bonding and reduced thermal stress

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If direct bonding with silicon oxide layers is used, then bonding is achieved, but the silicon substrate exhibits bow after bonding and detaching the growth substrate

Engineering Contradiction:

Improvebonding stabilityVSAvoidsubstrate bowing

Core Design Contradiction:

Stability of the object's compositionVSShape

Solution Approach 1:

The metal intermediate layer acts as a mediator that decouples the thermal expansion mismatch between the semiconductor body and silicon substrate, allowing stable bonding to be achieved without significant substrate bowing

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The thermal expansion parameters of the bonding structure are modified by introducing a metal layer with intermediate thermal expansion properties between silicon oxide and silicon, thereby changing the overall thermal response of the bonded structure to reduce bowing

Inventive Principle:

Principle #35Parameter changes

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 achieves a strong, stress-reduced bond between the semiconductor layer sequence and the silicon substrate, enabling efficient reuse of the growth substrate and minimizing substrate bowing, with improved adhesion compared to direct SiO2 bonding.

Implementation Method 1

bonding the semiconductor layer sequence to the silicon substrate by direct bonding of the first metal layer to the second metal layer

Methodology Applied

Scientific EffectDirect bonding:

Implementation Method 2

bonding them at elevated temperatures (150° C. to 400° C.) to form a metal bonding layer, which reduces thermal stress and enhances adhesion

Methodology Applied

Scientific EffectThermal stress reduction:

Implementation Method 3

The silicon oxide layers can, for example, be applied to the semiconductor body and the carrier substrate before direct bonding

Methodology Applied

Scientific EffectSilicon oxide layer deposition:

Data Source

PatentUS11557691B2Method of manufacturing a semiconductor device and semiconductor device

Publication Date: 2023.01.17 AMS OSRAM INT GMBH

AI summary

In an embodiment a method includes forming a semiconductor layer sequence on a growth substrate, applying a silicon oxide layer to a surface of the semiconductor layer sequence facing away from the growth substrate, applying a first metal layer to the silicon oxide layer, wherein the first metal layer includes gold, platinum, copper or silver, providing a silicon substrate and applying a second metal layer formed of the same material as the first metal layer to the silicon substrate, bonding the semiconductor layer sequence to the silicon substrate by direct bonding of the first metal layer to the second metal layer, wherein the first metal layer and the second metal layer are brought into contact at a temperature in a range of 150° C. to 400° C. so that they form a metal bonding layer and detaching the growth substrate from the semiconductor layer sequence.