Terabit/sec 48-channel fiber-coupled optical module based on holey CMOS transceiver IC

Abstract

A compact optical transceiver module providing 0.48 Tb/s transmitter plus 0.48 Tb/s receiver throughput has been demonstrated using a second-generation single-chip holey CMOS transceiver IC. The single-chip CMOS transceiver IC designed in standard 90nm IBM CMOS has 24 receiver and 24 laser driver circuits each with a corresponding through-substrate optical via (hole). The forty-eight 150-um diameter optical vias are fabricated using a wafer-scale deep Si RIE process followed by substrate thinning to 150um thickness. Direct flip-chip attachment of custom-designed 24-channel 850-nm VCSEL and PD arrays to the IC using AuSn solder provides a compact 48-channel Optochip measuring only 5.2mm x 5.8mm. The 48 optical vias enable optical access to the 24 VCSELs and 24 PDs and are arranged in a 4 x 12 array on 250um x 250um pitch to facilitate direct fiber-coupling to a standard 4 x 12 fiber array. The Optochips are packaged into complete modules by flip-chip soldering to high-density, high-speed organic carriers using eutectic PbSn solder. The organic carrier measures 17mm x 17mm with C4 pads on the top surface for Optochip attachment and typical ball grid array (BGA) pads on 0.8mm pitch on the bottom surface to permit attachment to a larger printed circuit board, i.e. system motherboard. Due to the exclusive use of flip-chip soldering throughout the assembly process, the holey Optochips and transceiver modules offer the potential of unprecedented highspeed performance and I/O density. Optical modules have been fabricated and DC optical measurement verified good bond yield for the OE arrays to IC and the IC to organic carrier. High-speed characterization of the complete module attached to a test motherboard demonstrated 24 transmitter channels operating up to 20 Gb/s/ch. Receiver characterization was carried out as full transmitter-to-receiver link - the output of a reference transmitter channel was coupled into a MMF and directed to 24 receiver channels within a module. The transmitter-to-receiver measurements also operated up to 20 Gb/s/ch. At 20 Gb/s/ch, the 48-channel module delivers an unprecedented off-card I/O bandwidth of 0.96 Tb/s. © 2012 IEEE.