Direct Chip Bonding Without Solder Balls or Copper Pillars
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Solution Overview
Problem
Existing chip-to-wafer (C2W) or chip-to-chip (C2C) bonding processes using solder balls or copper pillars with solder caps result in increased chip thickness and inefficiencies due to the use of additional materials, which are large and cumbersome.
Innovation Solution
A direct bonding method and device that eliminates the need for solder balls or copper pillars by using a direct bond, such as metal-metal solid body bonds, diffusion bonds, or hybrid bonds, with a bond strength of more than 0.1 J/m², occurring at temperatures below 400°C without a liquid phase, and involving a cleaning process to ensure contamination-free bond surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder balls or copper pillars with solder caps are used for chip bonding, then reliable electrical connection is achieved, but chip thickness increases and manufacturing complexity increases
Solution Approach 1:
The invention extracts and eliminates the intermediate bonding elements (solder balls, copper pillars, solder caps) from the bonding process. By directly bonding chip contact pads to substrate contact pads through a cleanroom-compatible process, the patent removes the thickening layers while maintaining reliable electrical connection, achieving both thin profile and strong bonding simultaneously
Solution Approach 2:
The invention introduces a controlled atmosphere (nitrogen or vacuum environment) as an intermediary medium during the bonding process. This mediator prevents oxidation of exposed metal surfaces during handling and bonding, enabling direct metal-to-metal contact without requiring thick protective coatings or intermediate layers, thus achieving strong bonds with minimal thickness
2Reliability
If solder balls or copper pillars with solder caps are used for chip bonding, then electrical connection is established, but manufacturing time and process complexity increase
Solution Approach 1:
The invention performs preliminary actions by pre-coating contact pads with adhesion-promoting materials (such as titanium nitride or chromium) and pre-establishing clean, oxidation-free surfaces before the actual bonding step. This preliminary preparation enables direct bonding in a single step without requiring subsequent reflow or additional processing, thereby increasing throughput while ensuring reliable electrical connection
Solution Approach 2:
The invention merges multiple functions into a single bonding step: electrical connection, mechanical bonding, and thermal management are all achieved simultaneously through direct contact pad-to-contact pad bonding. This consolidation eliminates sequential processing steps required for traditional methods, improving productivity without compromising connection reliability
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 direct bond method reduces chip stack thickness, increases throughput, and enhances chip communication efficiency while maintaining high bond strength, achieving bond strengths of more than 0.1 J/m² without the production of a liquid phase.
Implementation Method 1
The invention is based on the idea of keeping the surface of a chip so clean that a following direct bond step can occur
Implementation Method 2
A direct bond is in particular understood to be a metal-metal solid body bond, in particular diffusion bond
Data Source
AI summary
A method and device for bonding chips onto a substrate or onto further chips. The chips are bonded onto the substrate or the further chips by means of a direct bond.