CompoundTek and STAr Technologies Co-Develop Advanced Silicon Photonics (SiPh) Wafer Test Solution

Posted  by GoPhotonics


CompoundTek, a global foundry service provider in emerging silicon photonics (SiPh) solutions, and STAr Technologies (STAr), one of the leading providers for semiconductor test solutions, have announced that they have successfully developed a groundbreaking Silicon Photonics (SiPh) Wafer Test Solution with automatic fiber array block edge coupling.

This breakthrough will help to address the need from SiPh product companies and manufacturers to be able to test the wafer as per how the light is coupled into the SiPh product in the end application, thus expanding the test coverage capability of the wafer test. This is possibly the only SiPh tester with the capability for edge coupling fiber array automatically to SiPh ICs with trench width smaller than 100µm, which is of high repeatability and efficiency.

CompoundTek’s Chief Executive Officer, Raj Kumar, explained, “Testing the die using vertical grating coupler will compromise the test coverage of the wafer testing, as the test condition is not the same as per what it is going to be used in the field. Furthermore, designers will have to allocate space in the prime die for this vertical grating coupler and their test structure, increasing the die size as a result, while lowering gross die per wafer.”

“Skipping the wafer test totally will drive up the overall cost of products, as companies cannot identify SiPh known good dies before assembling with other dies, resulting in overall high costs and material wastage if a defective SiPh is assembled,” he added.

SiPh today is a technology that is not only used to displace traditional electrical interconnects, but also used in a broad range of applications, including lidar, quantum computing, and bio-sensing. However, the integration of optical components on a chip creates a host of new engineering and high-volume manufacturing challenges in wafer-level testing of SiPh devices as most of the products use an edge coupler to couple the light in and out of the chip. To go around the challenges of the edge coupler, most product companies either use vertical grating coupler during wafer test or choose to skip wafer test and only test after the SiPh test is assembled and packaged.

CompoundTek and STAr enable this technology with very precise positioning of fiber array block with accuracy and repeatability down to 0.1um, in a narrow trench of typically less than 100µm wide. The test fibers can deflect the light at about 90 degrees into the edge coupler with low optical power insertion loss and extremely low light reflection. This is enabled through patent-pending fiber alignment test kits and pattern recognition software that applies to all SiPh devices for both optical-optical and electro-optical tests.

STAr’s CEO and Founder, Dr. Choon Leong said, “The jointly developed tester managed to address the technical challenges required for wafer-level efficient edge coupling testing with up to 50 percent reduction in setup and alignment test time while keeping test system cost as low as 40 percent lower than that of others available in the market. This partnership marks a new milestone for SiPh testing that successfully meets the market's present and future needs for a reliable and cost-efficient test system for both vertical and edge coupling, especially for high-volume testing. We believe that our test solution has hit the sweet spot in terms of meeting performance and cost requirements.”

The technology shift in the form of SiPh demonstrates the potential for measurable gains in speed, power efficiency, and density. The first wave of the SiPh revolution is poised to roll over data centers around the world with optical interconnects that break the barriers set by copper wire. In parallel, the development of SiPh transceivers has resulted in increased demand for cost-effective wafer test solutions, enabling the industry to improve its quality control coverage at the wafer level, potentially driving down product costs due to failures after packaging.

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