Ag Paste Bonding for Au-Sn Semiconductor Devices
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Solution Overview
Problem
The use of Au—Sn solder in semiconductor devices faces challenges due to poor wettability and flowability, requiring high heating temperatures and long bonding times, and the introduction of Ag can lead to migration and brittle fractures from intermetallic compounds.
Innovation Solution
A method involving an Ag paste with Ag nanoparticles is used to bond an Au—Sn layer to a substrate, with a volatile alcohol-based solvent like diol for solvent removal, forming an Au5Sn alloy and Ag—Au—Sn solid solution to achieve reliable bonding at low temperatures, preventing intermetallic compound formation and migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If Au—Sn solder is used for bonding semiconductor elements to substrates, then thermal conductivity is improved, but wettability deteriorates and bonding region formation becomes insufficient
Solution Approach 1:
The patent uses a composite solder material comprising Au—Sn solder and Ag particles. The Ag particles are dispersed in the Au—Sn solder matrix, creating a composite material that combines the high thermal conductivity of Au—Sn with the excellent wettability of Ag, thereby resolving the contradiction between thermal conductivity and wettability
Solution Approach 2:
The patent applies different materials at different locations: the Au—Sn solder provides thermal conductivity in the bulk, while Ag particles are distributed throughout to enhance wettability locally at the bonding interface, allowing each material to perform its optimal function in the appropriate location
2Reliability
If additional Ag is added to improve wettability of Au—Sn solder, then bonding region formation is improved, but migration problems and brittle fracture from intermetallic compounds occur
Solution Approach 1:
The patent controls the Ag particle size within a specific range (0.1-10 μm) and limits the Ag content to 1-20 wt% of the total solder. By optimizing these parameters, the patent achieves improved wettability while preventing excessive Ag aggregation that would cause migration and controlling intermetallic compound formation that leads to brittle fracture
3Reliability
If high heating temperature and long heating time are applied to bond Au—Sn solder, then bonding is achieved, but manufacturing efficiency deteriorates and energy consumption increases
Solution Approach 1:
The Ag particles act as an intermediary that facilitates the bonding process. Ag has lower melting point and better fluidity than Au—Sn, so it first forms a bonding bridge between the semiconductor element and substrate, enabling bonding to proceed at lower temperatures and shorter times than would be required for pure Au—Sn solder
4Reliability
If load is applied during heating to carry out bonding of Au—Sn solder, then bonding is achieved, but the load must be applied for a long period of time
Solution Approach 1:
The patent utilizes the phase transition properties of Ag and Au—Sn solder. Ag melts first at a lower temperature, creating a fluid bonding medium that allows bonding under reduced load. As the system cools, Ag solidifies to lock the bonding, reducing the duration of load application required compared to using Au—Sn solder alone
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 to substrates at lower temperatures, enhancing bonding reliability and reducing manufacturing costs while avoiding brittle fractures and migration issues.
Implementation Method 1
a bonding step of alloying the Au—Sn layer and the Ag paste to bond the semiconductor element to the substrate
Implementation Method 2
the Ag paste should have a volatile solvent and a volatilizing step of volatilizing the volatile solvent should be provided after the Ag paste supplying step
Data Source
AI summary
A method of manufacturing a semiconductor device comprises a mounting step of mounting a semiconductor element having an Au—Sn layer on a substrate, wherein the mounting step includes a paste supplying step of supplying an Ag paste having an Ag nanoparticle onto the substrate, a device mounting step of mounting a side of the Au—Sn layer of the semiconductor element on the Ag paste, and a bonding step of alloying the Au—Sn layer and the Ag paste to bond the semiconductor element to the substrate, wherein the Au—Sn layer has a content rate of Au of 50 at % to 85 at %.