Dongha Shim

A 410GHz CMOS Push-Push Oscillator with an On-Chip Patch Antenna

The uses of terahertz systems (300 GHz to 3 THz) in radars, remote sensing, advanced imaging, and bio-agent and chemical detection have been extensively studied. A compact and low-cost signal source is a key circuit block of terahertz systems. Traditionally, the circuits have been built using highly optimized III-V technologies. With the advances of CMOS, it has become realistic to consider terahertz circuits in CMOS. This paper reports a signal source operating near 410 GHz that is fabricated using low-leakage transistors in a 6 M 45 nm digital CMOS technology.

Progress and Challenges Towards Terahertz CMOS Integrated Circuits

Key components of systems operating at high millimeter wave and sub-millimeter wave/terahertz frequencies, a 140-GHz fundamental mode voltage controlled oscillator (VCO) in 90-nm CMOS, a 410-GHz push-push VCO with an on-chip patch antenna in 45-nm CMOS, and a 125-GHz Schottky diode frequency doubler, a 50-GHz phase-locked loop with a frequency doubled output at 100 GHz, a 180-GHz Schottky diode detector and a 700-GHz plasma wave detector in 130-nm CMOS are demonstrated. Based on these, and the performance trends of nMOS transistors and Schottky diodes fabricated in CMOS, paths to terahertz CMOS circuits and systems including key challenges that must be addressed are suggested. The terahertz CMOS is a new opportunity for the silicon integrated circuits community.

Towards terahertz operation of CMOS

The electromagnetic spectrum between 300GHz and 3THz is broadly referred as terahertz [1]. The utility of this portion of spectrum for detection of chemicals and bio agents, for imaging of concealed weapons, cancer cells and manufacturing defects [1, 2], and for studying chemical species using electron paramagnetic resonance, as well as, in short range radars and secured high data rate communications has been demonstrated. However, high cost and low level of integration for III–V devices needed for the systems have limited their wide use. The improvements in the high frequency capability of CMOS have made it possible to consider CMOS as a lower cost alternative for realizing the systems that can greatly expand the use of this spectrum range.

Complementary Antiparallel Schottky Barrier Diode Pair in a 0.13-

A shunt-connected complementary antiparallel diode pair (C-APDP) using n- and p-type Schottky barrier diodes (SBDs) in a 0.13-mum CMOS logic process is demonstrated. The structure eliminates the deleterious effects of parasitic capacitance to substrate and reduces the substrate resistance effects. The extrapolated cutoff frequency of C-APDP is above 470 GHz, which demonstrates the potential as a millimeter-wave frequency component. The harmonic power measurements indicate that C-APDPs can generate more than 25 dB higher third harmonic powers than n-type SBDs. The C-APDPs can be integrated with the other devices in CMOS technologies to enable generation and processing of millimeter- and submillimeter-wave signals.

\mu \hbox{m}

The first complementary anti-parallel Schottky diode frequency tripler in CMOS is demonstrated. The tripler exhibits ~34-dB minimum conversion loss, -24-dBm maximum output power at 150 GHz, and 3 db output frequency range of ~10 GHz.

Logic CMOS Technology

A 140-GHz fundamental mode VCO in 90-nm CMOS and a 410-GHz push-push VCO in 45-nm CMOS, and a 125-GHz Schottky diode frequency doubler, a 50-GHz phase locked loop with a frequency doubled output at 100 GHz, a 180-GHz Schottky diode detector and a 700-GHz plasma wave detector in 130-nm CMOS have been demonstrated. Based on these, paths to terahertz CMOS circuits are suggested.

150 GHz Complementary Anti-Parallel Diode Frequency Tripler in 130 nm CMOS

Components for generating and phase locking 390-GHz signal are demonstrated using low leakage transistors in 45-nm CMOS. An integrated chain of circuits composed of an 195-GHz oscillator with frequency doubled output at ~390 GHz followed by two cascaded ÷2 injection locked frequency dividers with output frequency of ~49 GHz is demonstrated. The peak power radiated at ~390 GHz by an on-chip antenna is ~2 μW. The oscillator and frequency divider consumes 21 and 6 mW, respectively.

Paths to terahertz CMOS integrated circuits

A symmetric varactor (SVAR) in 130-nm digital complementary metal-oxide-semiconductor (CMOS) for frequency multiplier applications with the maximum cutoff frequency of ~320 GHz and a dynamic cutoff frequency of ~125 GHz is demonstrated. To demonstrate the generation of odd-order harmonics and suppression of even-order ones, an SVAR was measured at the pumping frequency of 900 MHz. The measured third-order harmonic power is more than 25 dB higher than that for the second order. Harmonic balance simulations showed that the SVAR pumped by a 50-GHz signal source can generate a 150-GHz third-harmonic output signal with 15.8-dB minimum conversion loss at the input power of 7.8 dBm. The SVAR can be integrated with other (CMOS) components to generate millimeter-wave signals.

Components for generating and phase locking 390-GHz signal in 45-nm CMOS

High volume millimeter wave applications are emerging. With the speed improvement of CMOS, sub-millimeter wave operation of CMOS circuits appears to be possible. in traditional millimeter and sub-millimeter wave systems, discrete Schottky diodes are widely utilized. This paper reviews the high frequency performance of junction and Schottky diodes fabricated in CMOS without any process modification, and circuits using the diodes, as well as suggesting approaches that can improve their performance.

Symmetric Varactor in 130-nm CMOS for Frequency Multiplier Applications

A Colpitts oscillator that generates signal at 589 GHz using both phase superposition and nonlinearities of components is demonstrated in a 0.12 m SiGe BiCMOS process. This approach increases the ratio between fourth and second order harmonic power levels by more than 2 dB compared to that obtained using only linear phase superposition. The output power of this circuit with the highest operating frequency for transistor based signal generators is -37.7 dBm.