Selective ALD Contact Bonding for Fine-Pitch 3D IC Stacks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current 3D chip integration technologies face challenges with solder bumps shorting and forming unfavorable intermetallic compounds at fine pitches, and existing Cu-Cu direct bonding methods require high temperatures, extreme planarity, and mechanical forces, making them difficult to implement for densely connected IC stacks.
Innovation Solution
A method using selective thermal atomic layer deposition (ALD) to fill gaps between conductive contacts with a metal layer, such as Cobalt, to create seamless interconnections without the need for mechanical forces or extreme surface planarity, allowing for low-temperature bonding at pitches less than 1 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder bumps are used for flip-chip bonding at fine pitches, then bonding can be achieved, but the bumps easily short with adjacent bumps during bonding due to melting
Solution Approach 1:
The patent introduces an intermediary material layer between the solder bumps and the substrate to prevent direct contact and shorting. This intermediary layer acts as a barrier that maintains electrical isolation while allowing thermal and mechanical coupling during the bonding process.
Solution Approach 2:
The patent replaces the traditional mechanical compression and heating system with a chemical vapor deposition-based bonding approach. Instead of relying on mechanical forces to hold and bond components, the system uses controlled chemical reactions and vapor-phase material deposition to create bonds, thereby eliminating the harmful mechanical effects that cause bump shorting.
2Reliability
If Cu-Cu direct bonding is performed using thermo-compression methods, then bonding can be achieved, but high temperatures, extreme surface planarity, and large mechanical forces are required
Solution Approach 1:
The patent replaces complex mechanical compression and heating systems with a chemical vapor deposition-based bonding process. This substitution eliminates the need for extreme surface planarity and large mechanical forces, significantly simplifying the bonding process while maintaining reliable Cu-Cu direct bonding.
Solution Approach 2:
The patent changes the bonding parameters from high temperature and high pressure to low temperature and atmospheric pressure conditions. By using chemical vapor deposition, the bonding process occurs at temperatures below 400°C and ambient pressure, fundamentally altering the process parameters to reduce complexity and enable bonding of temperature-sensitive materials.
3Productivity
If hybrid bonding is performed with sub-10 μm pitch, then dense bonding can be achieved, but sophisticated CMP processes and tight alignment specifications are required
Solution Approach 1:
The patent replaces sophisticated mechanical CMP processes with a chemical vapor deposition-based approach. This substitution eliminates the need for complex mechanical polishing and alignment systems, enabling dense bonding at sub-10 μm pitch while significantly improving ease of manufacture.
Solution Approach 2:
The patent employs self-aligned bonding features and self-organizing material properties that automatically position components during the bonding process. This self-service mechanism eliminates the need for tight alignment specifications and complex alignment systems, enabling high-density bonding with simplified manufacturing processes.
4Reliability
If conventional bonding methods are used, then bonding can be achieved, but die or wafer cracking can occur due to thermal-mechanical stress
Solution Approach 1:
The patent replaces thermal-compression bonding with chemical vapor deposition-based bonding, eliminating the high thermal-mechanical stress that causes die and wafer cracking. The new method uses controlled chemical reactions at low temperatures to create bonds without the harmful thermal and mechanical effects of conventional methods.
Solution Approach 2:
The patent fundamentally changes the bonding parameters from high temperature and high pressure to low temperature and atmospheric pressure conditions. This parameter change eliminates the thermal-mechanical stress that causes cracking, enabling reliable bonding of temperature-sensitive and mechanically fragile components.
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 approach enables high-density Cu-Cu interconnect bonding with over 90% yield, providing thermal-mechanical stability and preventing die or wafer cracking, while allowing for bonding of multi-diameter and multi-pitch contacts simultaneously.
Implementation Method 1
depositing a layer of selective metal on the lower surface of the second electrical contact and on the upper surface of the first electrical contact by a thermal Atomic Layer Deposition (ALD) process
Data Source
AI summary
Methods of bonding and structures with such bonding are disclosed. One such method includes providing a first substrate with a first electrical contact; providing a second substrate with a second electrical contact above the first electrical contact, wherein an upper surface of the first electrical contact is spaced apart from a lower surface of the second electrical contact by a gap; and depositing a layer of selective metal on the lower surface of the second electrical contact and on the upper surface of the first electrical contact by a thermal Atomic Layer Deposition (ALD) process until the gap is filled to create a bond between the first electrical contact and the second electrical contact.