Cu3Sn Via Metallization for Low-Temperature Hybrid Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional 3D-integrated electrical devices face challenges with high-temperature annealing requirements for reliable interconnect formation, which can degrade temperature-sensitive materials and cause cracking due to thermal expansion differences between materials used in the devices.
Innovation Solution
The use of a copper-tin intermetallic compound, Cu3Sn, for forming interconnect structures that enables low-temperature hybrid bond processing, allowing for reliable fusion bonding at temperatures below 200°C, and is compatible with conventional IC fabrication processes, including the use of temperature-sensitive materials like HgCdTe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional high-temperature annealing (excess of 300°C) is used for fusion bonding of vertical metal interconnects, then reliable electrical connection is achieved, but temperature-sensitive materials (such as HgCdTe) are degraded and cracking occurs due to thermal expansion differences
Solution Approach 1:
The patent changes the bonding temperature parameter from conventional high temperatures (excess of 300°C) to low temperatures (200°C or less). This is achieved by using Cu3Sn intermetallic compound interconnects that can form reliable fusion bonds at reduced temperatures, thereby preventing degradation of temperature-sensitive materials like HgCdTe while avoiding thermal expansion-induced cracking
Solution Approach 2:
The patent employs Cu3Sn intermetallic compound as a composite material system that combines copper and tin in specific proportions. This intermetallic compound provides both the necessary electrical conductivity and the low-temperature bonding capability, resolving the contradiction between achieving reliable electrical connections and protecting temperature-sensitive materials
2Object-affected harmful factors
If low-temperature bonding (200°C or less) is used for hybrid bond processing, then temperature-sensitive materials are preserved and thermal expansion cracking is avoided, but reliable fusion bonding of vertical metal interconnects becomes difficult to achieve
Solution Approach 1:
The patent modifies the material composition parameter of the interconnects by using Cu3Sn intermetallic compound instead of conventional pure metals. This compositional change enables the interconnects to form reliable fusion bonds at low temperatures (200°C or less) through solid-state diffusion, thereby achieving both material protection and reliable electrical connections
Solution Approach 2:
The patent utilizes solid-state diffusion as a phase transition mechanism to achieve fusion bonding of Cu3Sn interconnects at low temperatures. The controlled diffusion process allows atoms to migrate and form reliable electrical connections without requiring high-temperature melting or liquid-phase bonding, thus preserving temperature-sensitive materials
3Reliability
If conventional interconnect materials (such as nickel or copper) are used, then electrical conductivity is achieved, but high-temperature annealing (excess of 300°C) is required for fusion bonding
Solution Approach 1:
The patent uses Cu3Sn intermetallic compound as a composite material that maintains good electrical conductivity while enabling low-temperature bonding. The specific stoichiometric composition of Cu3Sn provides both the necessary electrical properties and the reduced bonding temperature requirement, eliminating the need for high-temperature annealing
Solution Approach 2:
The patent changes the material composition parameter from conventional copper or nickel to Cu3Sn intermetallic compound. This compositional modification fundamentally alters the bonding behavior, allowing fusion bonding to occur at temperatures of 200°C or less while maintaining adequate electrical conductivity for interconnect functionality
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
Cu3Sn interconnects provide reliable electrical conductivity, high corrosion resistance, and a higher coefficient of thermal expansion, facilitating low-temperature thermo-compressive bonding, thus enabling the integration of a wider variety of materials and devices, such as infrared detectors, without the need for high-temperature annealing.
Implementation Method 1
heating the Sn layer and the Cu layer such that the Sn and Cu layers diffuse together to form a Cu3Sn interconnect in the via hole
Implementation Method 2
the fusion bonding of the respective vertical metal interconnect structures (e.g., nickel or copper) often requires a high-temperature anneal in excess of 300° C. to establish a reliable electrical connection
Implementation Method 3
the high-temperature fusion bond process may cause cracking and bond failures between electrical devices having varying coefficients of thermal expansion between the different materials utilized in such devices
Data Source
AI summary
A Cu3Sn electrical interconnect and method of making same in an electrical device, such as for hybrid bond 3D-integration of the electrical device with one or more other electrical devices. The method of forming the Cu3Sn electrical interconnect includes: depositing a Sn layer in the via hole; depositing a Cu layer atop and in contact with the Sn layer; and heating the Sn layer and the Cu layer such that the Sn and Cu layers diffuse together to form a Cu3Sn interconnect in the via hole. During the heating, a diffusion front between the Sn and Cu layers moves in a direction toward the Cu layer as initially deposited, such that any remaining Cu layer or any voids formed during the diffusion are at an upper region of the formed Cu3Sn interconnect in the via hole, thereby allowing such voids or remaining material to be easily removed.