Silver Nano-Twinned Bonding Structure Without CMP Damage
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Solution Overview
Problem
Conventional wafer bonding techniques require high temperatures and pressures, and involve complex processes like chemical mechanical polishing, which can damage nano-twinned films and limit the size of components that can be produced, while also posing environmental concerns and reliability issues due to weak bonding forces.
Innovation Solution
A bonding structure and method using silver nano-twinned structures with 90% or more [111] crystal orientation, formed between adhesive layers on substrates, which allows for low-temperature and low-pressure bonding without the need for chemical mechanical polishing, using sputtering or evaporation coating to create silver features with aligned twin boundaries and enhanced bonding forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional direct bonding or solid state diffusion bonding is used, then bonding strength is achieved, but high temperature (above 0.5Tm) and high pressure (greater than 100 MPa) are required
Solution Approach 1:
The patent changes the crystallographic orientation parameter of the bonding interface from conventional orientations to specifically oriented grain boundaries (e.g., <100>-<100> or <110>-<110> alignment), enabling bonding at lower temperatures and pressures while maintaining strong bonding strength through optimized atomic matching at the interface
Solution Approach 2:
The patent creates a composite bonding interface structure consisting of two polycrystalline materials with specifically oriented grain boundaries, where the composite grain boundary structure provides both low-temperature processability and high bonding strength through the unique atomic arrangement at the interface
2Manufacturing precision
If chemical mechanical polishing is performed on nano-twinned film before bonding, then surface roughness is reduced, but the process becomes complicated and the nano-twinned film may be damaged
Solution Approach 1:
The patent performs preliminary surface treatment during the electroplating process itself, where the electroplating parameters are optimized to naturally produce smooth surfaces with proper crystal orientation, eliminating the need for subsequent chemical mechanical polishing steps
Solution Approach 2:
The electroplating process is designed to be self-correcting, where the deposition conditions automatically produce the desired surface quality and crystal structure without requiring additional post-processing steps, making the process self-sufficient
3Productivity
If high-speed rotary electroplating is used, then electroplating speed is increased, but process control becomes difficult and film quality deteriorates
Solution Approach 1:
The patent employs dynamic control of electroplating parameters during the deposition process, adjusting current density, rotation speed, and electrolyte flow rate in real-time to maintain optimal deposition conditions, ensuring both high productivity and excellent film quality with precise control over crystal orientation and surface morphology
4Length of moving object
If conventional electroplating is used for small components, then production is possible, but components smaller than 2 μm cannot be produced
Solution Approach 1:
The patent changes the electroplating parameters including current density, electrolyte composition, and deposition time to enable precise control of deposit thickness and morphology, allowing successful electroplating of features smaller than 2 μm while maintaining manufacturing feasibility
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 solution enables reliable, low-temperature, and low-pressure wafer bonding with improved bonding forces and reduced environmental impact, suitable for semiconductor applications and 3D-IC flip-chip assembly, while maintaining the characteristics of silver nano-twinned structures such as resistance to oxidation and high thermal stability.
Implementation Method 1
Conventional direct bonding technologies or solid state diffusion bonding technologies require heating a material to a temperature above half of the absolute melting point (0.5Tm) of the material, and require applying a pressure greater than 100 MPa
Implementation Method 2
using sputtering or evaporation coating to create silver features with aligned twin boundaries
Implementation Method 3
using sputtering or evaporation coating to create silver features with aligned twin boundaries
Data Source
AI summary
A bonding structure is provided, wherein the bonding structure includes a first substrate, a second substrate, a first adhesive layer, a second adhesive layer, and a silver feature. The second substrate is disposed opposite to the first substrate. The first adhesive layer is disposed on the first substrate. The second adhesive layer is disposed on the second substrate and opposite the first adhesive layer. The silver feature is disposed between the first adhesive layer and the second adhesive layer. The silver feature includes a silver nano-twinned structure that includes twin boundaries that are arranged in parallel. The parallel-arranged twin boundaries include 90% or more [111] crystal orientation.