News: Suppliers
23 October 2024
Toray develops high-speed mounting of III-V chips on silicon for silicon photonics
Toray Industries Inc of Tokyo, Japan has developed materials and technologies for mounting indium phosphide (InP) and other optical semiconductors used in silicon photonics on silicon substrates.
Artificial intelligence (AI)-driven demand for high-speed communications is fueling the construction of more data centers, raising concerns about their heavy power demands. This has accelerated the development of optical communications, whose energy losses are lower than those of conventional systems, for long-distance transmission and short-range (less than 1m) communications within data centers.
This has led to the use of silicon photonic optical circuits on silicon substrates. The challenge is that this setup requires mounting optical semiconductors made from indium phosphide and other III-V compounds onto silicon. Mass transfer technology (which shifts a large number of chips to a substrate at once and accurately positions them) is essential to do this swiftly and in large quantities.
Toray has hence worked with subsidiary Toray Engineering Co Ltd to develop a material for fast laser transfers of indium phosphide and other optical semiconductors. They also worked on a material to catch transferred chips and bond them directly to silicon substrates and a related mounting process technology.
Picture: Toray’s high-speed mounting process for optical semiconductors.
Toray Engineering has semiconductor bonding and laser mass transfer technologies. The work with Toray has boosted optical semiconductor bonding speed to 6000 units per minute (according to Toray research, compared with about 4 units per minute with conventional flip-chip bonders). This is expected to accelerate the application of optical communications within data centers. The two companies will keep collaborating to establish technologies with actual devices by 2025 with a view to early mass production.
Developed materials and technology details
1. Transfer materials (impact resistance control)
Toray previously innovated transfer materials for micro-LEDs. In this case, the InP-based optical semiconductors are 640μm long and 90μm wide and less than 3μm thick. While longer and wider than general micro-LEDs, the chips are also extremely thin. Toray developed a new material that enables transfer with a single laser irradiation without damaging chips, which should improve yields and throughput.
2. Catch material offering improved thermal and chemical resistance
The catch material must not only capture fast-flying chips but also withstand the subsequent direct bonding of these chips to the silicon substrate after chemical cleaning and activating the bonding surface with plasma, pressurizing under high temperature more than 200°C. Release must thereafter be easy. Toray says that it employed years of expertise in designing heat-resistant polymers and controlling adhesive properties to develop a new catch material that makes this possible.
3. Process technology (demonstrating laser transfer to direct bonding)
Toray used the developed materials to collaborate with Toray Engineering in developing and demonstrating the entire process, from laser transfer to direct bonding on a silicon substrate. The company has confirmed a post-bonding positional accuracy of ±2μm and a rotational deviation of ±1°.
Toray aims to verify chip operation and use actual devices to establish its technology. It intends to enhance positional accuracy and broaden technology applications to include mass transfer of chips made from other different materials and millimeter-scale chips.
Toray developed part of this technology with a grant for the New Energy and Industrial Technology Development Organization’s JPNP 20017 project, which aims to solidify the foundations of post-5G information and communications systems.
