Core Concepts
This work presents the design and implementation of low-loss and broadband chip-to-package transitions for mm-Wave and sub-THz communication systems, addressing the challenges of high-frequency signal transitions between integrated circuits and packaging.
Abstract
The key highlights and insights from the content are:
Motivation and Technology Choice:
The mm-Wave and sub-THz frequency bands offer large available bandwidths for future communications and sensing systems, but the transition of signals from integrated circuits (ICs) to printed circuit boards (PCBs) becomes increasingly difficult and costly at these high frequencies.
CMOS technology is an attractive choice due to its high yield, low cost, and high integration density, despite the higher fT/fmax of III-V material-based technologies.
Antenna-integrated packages offer higher gain and radiation efficiency, while supporting the large integration needs of massive transceiver arrays.
Organic substrate packages provide a cost-effective alternative to other packaging options, such as low-temperature co-fired ceramic (LTCC) or silicon-based technologies.
Limitations of Conventional GSG Transitions:
The standard coplanar ground-signal-ground (GSG) transition structure becomes very lossy above 100 GHz due to the mismatch between the signal and return current paths, leading to the excitation of parasitic modes and radiation losses.
Analytical modeling and simulations are used to identify the key loss mechanisms, including parallel-plate propagation modes and parasitic loop antenna resonances.
Alternative Transition Structures:
Several modified transition structures are explored, including half-shielded, rectangular shield, fully shielded, reverse microstrip, and stripline designs.
The stripline transition is identified as the most promising solution, providing a practical signal escape and superior performance compared to other practical options.
The limitations of the stripline structure, such as the excitation of substrate-integrated waveguide modes, are analyzed and addressed through design considerations.
Transition Designs and Measurements:
Two chip-to-package transitions are designed and implemented using the stripline approach, one in a 28 nm Bulk CMOS technology with an organic substrate interposer, and the other in a 16 nm FinFET CMOS technology with a different organic substrate interposer.
The 28 nm Bulk CMOS design achieves 1.03 dB loss with an 85 GHz 3 dB bandwidth, while the 16 nm FinFET CMOS design achieves 0.41 dB loss with a 339 GHz 3 dB bandwidth.
Measurement results of the 28 nm Bulk CMOS design validate the analysis and simulation, demonstrating the effectiveness of the proposed transition structures.
Stats
The transition from the 28 nm Bulk CMOS technology to the organic substrate interposer has a measured insertion loss of 1.03 dB with an 85 GHz 3 dB bandwidth.
The transition from the 16 nm FinFET CMOS technology to the organic substrate interposer has a measured insertion loss of 0.41 dB with a 339 GHz 3 dB bandwidth.
Quotes
"The transition of signal from an integrated circuit (IC) to printed circuit board (PCB) becomes increasingly difficult and costly as the signal frequency increases."
"With the trend towards large phased arrays or massive multiple-input multiple-output (MIMO) antenna arrays to compensate for high frequency path losses, the integration of transceivers with antenna elements becomes a challenge."
"While on-chip antennas eliminate the need to transition from the IC to the PCB, due to the excitation of substrate waves and ohmic losses, radiation efficiency and gain remain low."