Stress Migration Bonding for Semiconductor Substrates
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Solution Overview
Problem
Bonding semiconductor elements and substrates using high-temperature soldering often results in thermal stress-induced damage or voids at the bonding interface, making it difficult to achieve reliable bonding, especially with materials having different thermal expansion coefficients.
Innovation Solution
A bonding structure utilizing a metal film with a higher thermal expansion coefficient than the substrate and semiconductor element, where stress migration occurs to diffuse metal and fill interface gaps, allowing bonding at low temperatures (100°C to 400°C) without the need for high-temperature sintering or specialized equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-temperature soldering is used to bond semiconductor element and substrate, then bonding strength is improved, but thermal stress damage and void formation occur
Solution Approach 1:
The patent changes the bonding temperature parameter from high temperature (conventional soldering) to low temperature (100-400°C), and changes the bonding mechanism parameter from diffusion bonding to stress migration. This allows achieving adequate bonding strength while avoiding thermal stress damage and void formation associated with high-temperature processing.
Solution Approach 2:
The patent introduces a metal film as an intermediary bonding layer between the semiconductor element and substrate. This metal film undergoes stress migration to fill interface gaps and create reliable bonding, mediating the connection without requiring direct high-temperature contact between the semiconductor elements and substrate that would cause thermal stress damage.
2Reliability
If high-temperature sintering is used for bonding, then bonding reliability is improved, but equipment complexity and processing cost increase
Solution Approach 1:
The patent changes the processing temperature parameter from high temperature sintering to low temperature stress migration bonding (100-400°C). This eliminates the need for complex high-temperature sintering equipment while maintaining bonding reliability through the stress migration mechanism that fills interface gaps and creates strong metallurgical bonds.
3Adaptability or versatility
If materials with different thermal expansion coefficients are bonded, then design flexibility is improved, but thermal stress and bonding reliability deteriorate
Solution Approach 1:
The patent introduces a metal film as an intermediary layer between materials with different thermal expansion coefficients. This metal film undergoes stress migration to fill interface gaps and create a reliable bonding interface, accommodating the thermal expansion differences without causing bonding failure, thus maintaining design flexibility while ensuring bonding reliability.
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 enables reliable bonding of semiconductor elements and substrates at lower temperatures, reducing the risk of thermal stress damage and void formation, while using cost-effective materials and simplifying the bonding process.
Implementation Method 1
The metal film contains a metal diffused mainly through stress migration
Implementation Method 2
the bonding with the metal film proceeds through a redox reaction occurring on a surface before the bonding
Data Source
AI summary
A bonding structure (100) of the present invention includes a substrate (110), a metal film (120), a semiconductor element (130). The substrate (110), the metal film (120), and the semiconductor element (130) are laminated in order just mentioned. The metal film (120) contains a metal diffused through stress migration, and the substrate (110) and the semiconductor element (130) are bonded together with the metal film (120) therebetween.