Design for Manufacturing in IC Fabrication: Mask Cost, Circuit Performance and Convergence

Ph.DDOCTOR OF PHILOSOPH

Characterization and Performance Comparison of Low-Voltage, High-Speed, Push-Pull and traveling-wave Silicon Mach-Zehnder Modulators

The well-known power and memory walls are recognized as the current bottlenecks in computing performance, and with the increasing computational load of commonly run applications, it is necessary to nd ways to alleviate the issues presented by the aforementioned bottlenecks. It is therefore necessary to not focus solely on extracting performance improvement by way of changes to the processing architecture, but rather by holistically improving the computing platform, namely the communications backbone. This work focuses on the characterization and performance comparison of two families of optical data modulators, both fundamentally Mach{Zehnder modulators (MZMs); namely, a modulator with a Push-Pull (PP) modulation scheme, and another modulator with a Traveling-Wave Electrode (TWE) design, prioritizing the effects on high-speed performance. A number of operating conditions temperature, wavelength, bias voltage, and bit rate were varied to determine effects of modulator performance, measured in terms of DC performance characterization, bit error rate, electrical bandwidth, and power-penalty. Custom xtures were designed and fabricated to achieve long-term experimental stability, and software was written to accomplish long term experimentation; the con uence of the two resulted in a wealth of data for use in performance comparison. Despite the use of a push-pull modulation scheme, the devices using a traveling-wave electrode outperformed the push- pull modulators in almost all metrics, even at what was assumed to be a relatively low bit rate of 3 Gbps. This work then accentuates the importance of velocity and impedance matching, even at presumably low data rates, in spite of increased device fabrication complexity