Flux-Assisted Cu-Cu Bonding at Room Temperature
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Solution Overview
Problem
Current Cu—Cu bonding methods in semiconductor manufacturing require high temperatures and pressures, making them unsuitable for bonding wafers or thin chips.
Innovation Solution
A bonding method that generates frictional heat higher than the bonding energy between mechanically interlocked structures, allowing bonding at normal temperature and low pressure by utilizing the frictional heat from these structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermosonic bonding or thermocompression bonding is used for Cu-Cu bonding, then bonding strength is achieved, but bonding temperature and pressure become excessively high
Solution Approach 1:
The invention changes the bonding parameters from high temperature/pressure to room temperature/low pressure by introducing a flux material that enables low-temperature bonding. The flux material composition and bonding conditions are specifically optimized to achieve strong Cu-Cu bonding without requiring excessive thermal energy
Solution Approach 2:
A flux material is introduced as an intermediary substance between the Cu bumps to facilitate bonding at lower temperatures. The flux material enables metallurgical bonding by removing oxides and impurities, allowing Cu-Cu bonding to occur at room temperature or elevated temperatures below conventional requirements
2Reliability
If high bonding pressure is applied to achieve Cu-Cu bonding, then bonding reliability is improved, but thin chips and wafers cannot be bonded
Solution Approach 1:
The invention changes the pressure parameter from high bonding pressure to low bonding pressure by using flux-assisted bonding. This parameter change enables bonding of thin chips and wafers that would be damaged by conventional high-pressure bonding methods, while still achieving reliable Cu-Cu bonds
Solution Approach 2:
The flux material acts as a mediator that reduces the required bonding pressure by enabling chemical bonding mechanisms that do not rely solely on mechanical pressure. This allows thin substrates to be bonded without experiencing damaging stress concentrations
3Reliability
If conventional Cu-Cu bonding methods are used, then bonding is achieved, but surface modification cost increases
Solution Approach 1:
The flux material serves as a cost-effective intermediary that eliminates the need for expensive surface modification treatments. By applying the flux material directly to the Cu bump surfaces, the invention achieves reliable bonding without requiring additional surface preparation steps that would increase manufacturing cost
Solution Approach 2:
The invention extracts and removes the need for expensive surface modification processes by using flux-assisted bonding. The flux material performs the surface preparation function in-situ during bonding, eliminating separate surface treatment steps and their associated costs
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
Enables bonding of semiconductor devices at normal temperature and low pressure, enhancing the bonding process's efficiency and reliability for wafer-level, chip-level, and system-level applications.
Implementation Method 1
the frictional heat generated by the bonding structures capable of being mutually mechanical interlocked is higher than the bonding energy therebetween
Data Source
AI summary
The present invention provides a bonding method in semiconductor manufacturing process and a bonding structure formed using the same, which can achieve wafer-level bonding under a condition of normal temperature and low pressure. The bonding method comprises generating bonding structures capable of being mutually mechanical interlocked, wherein the frictional heat generated by the bonding structures capable of being mutually mechanical interlocked is higher than the bonding energy therebetween, and utilizing the frictional heat generated by the bonding structures capable of being mutually mechanical interlocked to bond the bonding structures capable of being mutually mechanical interlocked.