Die-to-Wafer Stacking with Electrostatic Chuck Batch Bonding
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Solution Overview
Problem
Current die-to-wafer stacking techniques face challenges such as copper oxidation, prolonged waiting times leading to activation loss, and inefficiency in bonding dies of different sizes, which hinder mass production applications.
Innovation Solution
A method involving pre-arrangement of dies on an electrostatic chuck followed by collective bonding to a wafer, including plasma activation and the use of a metal antioxidant to prevent oxidation, and applying thermal and mechanical loads for atomic bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If bumpless bonding with direct copper-to-copper bonding is used to achieve smaller interconnect size and higher connection density, then interconnect size is reduced and connection density is improved, but copper oxidation occurs and activation is easily lost during waiting time
Solution Approach 1:
The invention applies preliminary plasma activation to the bonding surfaces of dies before they are arranged on the electrostatic chuck. This pre-activation creates a reactive state on the copper surfaces that remains stable during the subsequent arrangement and bonding processes, preventing oxidation and activation loss that plagues conventional bumpless bonding approaches.
Solution Approach 2:
The invention introduces an electrostatic chuck as an intermediary device to hold and position multiple activated dies simultaneously. The chuck provides a controlled environment that maintains the activated state of bonding surfaces while allowing precise positioning, acting as a mediator between the activated dies and the final bonding process.
2Manufacturing precision
If dies are bonded one by one after activation, then bonding precision can be maintained, but waiting time increases and activation is easily lost
Solution Approach 1:
The invention merges multiple individual bonding operations into a single collective bonding process. Multiple activated dies are arranged on the electrostatic chuck simultaneously and bonded to the target wafer in one step, eliminating the sequential waiting time between individual bonding operations while maintaining precision through the chuck's positioning capabilities.
Solution Approach 2:
The electrostatic chuck performs preliminary positioning and holding of multiple dies in their final positions before bonding occurs. This pre-positioning allows all dies to be arranged and held in place simultaneously, eliminating the need for sequential positioning and reducing total process time while maintaining bonding precision.
3Ease of manufacture
If conventional micro-bump packaging with lower filler is used, then manufacturing simplicity is maintained, but heat dissipation performance deteriorates
Solution Approach 1:
The invention replaces the conventional micro-bump mechanical interconnection system with a direct copper-to-copper bonding system. This substitution eliminates the need for bump structures and lower filler materials, creating direct thermal pathways between dies and the substrate that significantly improve heat dissipation while maintaining manufacturing simplicity through the collective bonding process.
4Adaptability or versatility
If dies of different sizes are densely bonded, then integration flexibility is improved, but bonding efficiency deteriorates due to lack of standardized processes
Solution Approach 1:
The electrostatic chuck provides a universal platform that can accommodate dies of different sizes, shapes, and configurations through its adjustable and programmable positioning capabilities. The same chuck and bonding process can handle various die formats, enabling flexible heterogeneous integration while maintaining high efficiency through standardized collective bonding operations.
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 significantly reduces the risk of activation loss and enhances efficiency by shortening waiting times and improving bonding quality, allowing for flexible integration of dies of varying sizes and functions.
Implementation Method 1
arranging the dies to be bonded on an electrostatic chuck
Implementation Method 2
subjecting a bonding surface of the wafer to be bonded and/or bonding surfaces of the arranged dies to plasma activation
Implementation Method 3
bonding the dies pre-arranged on the electrostatic chuck, as a whole, to a wafer to be bonded
Implementation Method 4
direct copper-to-copper bonding achievable by hybrid bonding
Data Source
AI summary
A die-to-wafer stacking method includes: providing a wafer to be processed, including a substrate, a dielectric layer on the substrate and a metal layer embedded in the dielectric layer; forming a bonding layer covering the dielectric layer; picking up dies to be bonded from the wafer to be processed and arranging the dies to be bonded on an electrostatic chuck; and bonding the dies arranged on the electrostatic chuck, as a whole, to a wafer to be bonded. Pre-arranging all the dies to be bonded on the electrostatic chuck and then bonding the dies on the electrostatic chuck, as a whole, to the wafer to be bonded can greatly shorten post-activation waiting times of dies before they are bonded to the wafer and thus reduce the risk of loss of activation.