New Paper: Test-Station for Flexible Semi-Automatic Wafer-Level Silicon Photonics Testing

As the need for data links with ever greater bandwidth continues to grow, optical interconnects are becoming an attractive alternative to electrical links. The cost and performance of optical transceivers are key elements that determine the economic viability of optical interconnects. Imec is addressing these two elements by developing an active silicon photonics platform that leverages existing CMOS infrastructure and processing techniques to provide a wide range of passive and active optical devices on silicon wafers. Developing the specific process modules for this photonics platform, as well as establishing a component library with predictable, stable, and reliable device performance requires efficient wafer-level testing capabilities to provide accurate feedback regarding device performance to process engineers and optical component and circuit designers.

Wafer-level photonics testing hardware is, just like the silicon photonics technology itself, a newly emerging application for manufacturers of test equipment. Die-level testing has been enabled by the use of edge coupling on separated die, as used in I/O front-end test stations. The use of diffractive gratings for coupling photonic waveguides with single-mode fibers (SMF) is becoming an established technique that enables photonic circuit testing at wafer-level. In this paper, we present a highly flexible test setup that is based on a Cascade Microtech 300mm probe station for semiconductor characterization. Motorized fiber manipulators allow measurement of any combination of optical and electrical ports of photonics circuits with highly customized layouts as schematically depicted in the figure below.

The test station allows characterization of both passive and active photonics devices. For passive devices such as fiber grating couplers (FGC), waveguides and filters, the optical transmission spectrum can be measured in the O- (1260-1360nm), C- (1530-1565nm), and L- (1565-1625nm) bands. For active devices such as photodiodes and modulators, electrical and electro-optical parameters can be measured as well. Electrical measurements can be performed at DC (IV measurement, photocurrent measurement, diode responsivity) as well as at RF frequencies (e.g. detector and modulator bandwidth). In addition, an optical calibration method has been developed and the repeatability of measurement data can be actively monitored.

Download this paper to learn more about the test application.