Polymer Hybrid SiPh poised to save the data center
The advent of hybrid silicon photonics (SiPh) technology has fueled an exciting breakthrough in price/performance for fiber optics. But it requires revolutionary advances in wafer-level testing.
Hybrid SiPh chips present a test challenge: on both the transmitter and receiver sides, the chip must interface with light sources in the outside world. These input and output ports require extremely accurate fiber positioning to both propagate and capture the light going in and out of the silicon photonics device.
Moving Silicon Photonics from the Lab to the Fab
The first wave of the Hybrid SiPh revolution stands poised to roll over data centers around the world with optical interconnects that breach the barriers set by copper wire. End user benefits might include an HD movie or 100 hours of music downloaded in a single second. Bandwidths of a terabit per second now come within practical reach.
In essence, silicon photonics merges two technologies-integrated circuits and optical communications, which have evolved along parallel but separate paths. Each offers distinct advantages. Silicon-based IC fabrication now integrates literally billions of transistors onto a single substrate. Laser-based optical communications produce very high bandwidths and low-loss signal transmission over long distances. When combined via hybrid SiPh, they offer new possibilities in transmission speed, scalability, energy efficiency and cost reduction.
Optical fibers must be precisely aligned to couple light in and out of a wafer without physical contact. Hybrid SiPh permits both logical and optical components to coexist on the same wafer. Optical devices such as lasers, waveguide structures, detectors, multiplexers and others could interface directly with classic logic components or can be combined as separate ICs through advanced 2.5D and 3D integration techniques. This new level of integration permits the fabrication of hybrid devices that can be mass produced and interconnected via optical fiber cabling at very low cost while yielding substantial performance gains.
Moving to a New Paradigm in Wafer Test
Typically, hybrid SiPh includes on-chip I/O devices in the form of etched diffraction gratings, which route the light from off-chip optical fibers to waveguides within the chip, where operations such as filtering and conversion to digital data streams are performed.
This addition of optical I/O, along with electrical, adds an entirely new dimension to wafer test methodologies. The need to capture and insert modulated beams of light requires the development of novel probing strategies that accommodate a new set of mechanical requirements. The classic problem of maintaining accurate physical probe contact with pads on the wafer surface gives way to a new paradigm when optical fibers must be precisely aligned to couple light in and out of a wafer without physical contact.
Alliances Hold the Key to SiPh Test Solutions
Developing successful approaches to SiPh wafer test devices requires partnerships between key suppliers of test technology that play on each contributor’s individual strengths.
