Ultrasonic Bonding of Semiconductor Elements with Frangible Coatings
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Solution Overview
Problem
Advanced semiconductor packaging technologies face limitations, particularly in achieving reliable and efficient bonding of semiconductor elements, such as those related to oxidation issues and the infancy of some methods, which hinder the development of robust interconnections.
Innovation Solution
The method involves ultrasonically bonding semiconductor elements with conductive structures coated in a frangible layer, such as silicon nitride or rare earth metal complexes, to protect against oxidation and facilitate metal-to-metal contact, allowing for room temperature bonding without the need for solder or heat reflow, using an ultrasonic bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional die attach and wire bonding processes are used, then the bonding process is well-established and reliable, but the process complexity and manufacturing steps are increased
Solution Approach 1:
The patent extracts and eliminates intermediate bonding materials (such as solder, epoxy, or flux) from the bonding process. By using ultrasonic bonding with a frangible coating, the process directly bonds conductive structures without requiring traditional die attach materials or wire bonding procedures, thereby reducing process complexity while maintaining reliability
Solution Approach 2:
The patent replaces thermal-mechanical bonding systems (solder reflow, hot press bonding) with an ultrasonic mechanical bonding system. The ultrasonic vibration provides the necessary energy for bonding through mechanical means, eliminating the need for high-temperature thermal processes and complex material layers
2Reliability
If thermo-compression bonding is used to form interconnections, then heat and pressure are applied to bond semiconductor elements, but oxidation issues and material degradation occur at high temperatures
Solution Approach 1:
The patent changes the bonding parameters from high-temperature thermal processes to room-temperature ultrasonic processes. By using ultrasonic vibration energy instead of thermal energy, the bonding occurs at or near room temperature, preventing oxidation and material degradation that would occur during high-temperature thermo-compression bonding
Solution Approach 2:
The patent introduces a frangible coating as a temporary intermediary layer on the conductive structures. This coating protects the underlying metal from oxidation during handling and storage, then breaks down under ultrasonic bonding conditions to enable direct metal-to-metal contact, thus preventing oxidation without requiring high-temperature processing
3Reliability
If copper conductive structures are used, then electrical conductivity is improved, but oxidation resistance deteriorates
Solution Approach 1:
The patent uses a frangible coating as a protective intermediary layer on copper conductive structures. This coating prevents oxidation of the copper surface during handling, storage, and assembly, while being thin and brittle enough to break under ultrasonic bonding conditions, allowing direct copper-to-copper electrical contact with superior conductivity and no oxidation barrier
Solution Approach 2:
The patent applies the frangible coating to the copper conductive structures in advance, before bonding. This preliminary protective action prevents oxidation from occurring during subsequent processing steps, and the coating is designed to automatically break during the ultrasonic bonding process, providing oxidation protection when needed without compromising electrical conductivity
4Reliability
If fluxing is used in bonding processes, then bonding adhesion is improved, but process complexity and environmental concerns increase
Solution Approach 1:
The patent extracts and eliminates flux from the bonding process entirely. By using ultrasonic bonding with a frangible coating, the process achieves reliable bonding adhesion through direct metal-to-metal contact and ultrasonic energy, without requiring flux application, activation, or cleanup steps that would increase process complexity and create environmental concerns
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 enhances the reliability and efficiency of semiconductor bonding by preventing oxidation, enabling robust interconnections and reducing the complexity of the bonding process, while allowing for the use of aluminum interconnects in a lead-free and room temperature environment.
Implementation Method 1
a bonding surface of at least one of the first conductive structures and the second conductive structures includes a frangible coating
Implementation Method 2
ultrasonically bonding ones of the first conductive structures to respective ones of the second conductive structures
Data Source
AI summary
A method of ultrasonically bonding semiconductor elements includes the steps of: (a) aligning surfaces of a plurality of first conductive structures of a first semiconductor element to respective surfaces of a plurality of second conductive structures of a second semiconductor element; and (b) ultrasonically bonding ones of the first conductive structures to respective ones of the second conductive structures. A bonding surface of at least one of the first conductive structures and the second conductive structures includes a frangible coating.