The frequency dependence of PECVD nitride and LPCVD oxide metal-insulator-metal (MIM) capacitors is investigated with special attention for precision analog applications. At measurement frequencies of 1.0 MHz, nitride MIM capacitors show capacitance linearity close to that of oxide MIM capacitors, indicating potential for precision analog circuit applications. Due to dispersion effects, however, nitride MIM capacitors show significant degradation in capacitor linearity as the frequency is reduced, which leads to accuracy limitations for precision analog circuits. Oxide MIM capacitors are essentially independent of frequency.

Analog characteristics of metal-insulator-metal capacitors using PECVD nitride dielectrics

Metal-insulator-metal (MIM) capacitors with PECVD nitride exhibit trap-induced dispersive behavior, which leads to degradation in capacitor linearity at low frequencies, limiting the accuracy in precision analog circuits. While LPCVD oxide results in nondispersive behavior, the high deposition temperature excludes the use of LPCVD dielectrics for MIM capacitors using the standard back-end metal layers as capacitor bottom plates. The latter is preferred in view of the low substrate coupling needed for RF applications. In this work, alternative PECVD dielectrics have been investigated with respect to frequency dependence of voltage linearity, hysteresis, matching, and leakage characteristics. It will be shown that ONO stacks offer a combination of good voltage linearity, absence of dispersive behavior and hysteresis, excellent matching, and low leakage.

Investigation of PECVD dielectrics for nondispersive metal-insulator-metal capacitors

Gate slow transient (or gate lag) in GaAs MESFETs were investigated and found to be responsible for pulse narrowing and loss of transmitted pulses in long inverter chains Gate transients are caused by surface states near the edges of the gate Gate transients can be drastically reduced in recessed gate MESFETs by controlling the gate trough geometry so that gates fit tightly in the bottom of the trough Doping level and passivation also affect gate lag, although they are of less importance than trough geometry Isolation technique and subchannel material structure do not strongly affect gate lag Dispersion of FET output conductance is also found to be independent of gate lag >

Gate slow transients in GaAs MESFETs-causes, cures, and impact on circuits

X-parameters are the mathematically correct supersets of S-parameters valid for nonlinear (and linear) components under large-signal (and small-signal) conditions. This paper compares a PHD model generated from arbitrary load-dependent measured X-parameters and a measurement-based non-quasi-static device model and validates them against tuned-load measurements. CW, IMD, and ACPR swept-power measurements are compared. The models agree on the simulated device behavior and compare well to validation measurements..

Nonlinear validation of arbitrary load X-parameter and measurement-based device models

A monolithic 0.5-50-GHz distributed amplifier has been developed using a MODFET IC process to demonstrate a gain of 6.5 dB+or-0.5 dB across the frequency range. Input and output return losses were better than 12 dB. The noise figure of this amplifier was 4.8 dB+or-0.4 dB measured up to 26.5 GHz. The output power at the 1-dB compression point was 12 dBm at 40 GHz. >

http://ieeexplore.ieee.org/iel2/827/2443/00069301.pdf

A monolithic 0.5 to 50 GHz MODFET distributed amplifier with 6 dB gain

A 26 GHz MMIC technology has been developed to manufacture high performance integrated circuits for microwave instrumentation. The fabrication process features an MBE active layer, a 0.4 mu m gate patterned by DUV contact lithography, Ta/sub 2/N thin-film resistors, Si/sub 3/N/sub 4/ MIM capacitors and dry-etched backside vias. The completed MESFET has a nominal f/sub t/ of 23 GHz and a f/sub max/ of 55 GHz. Two standard products are currently being manufactured. The first is a 2-26.5 GHz travelling wave amplifier (TWA) which routinely achieves 8.7 dB+or-0.5 dB gain across the band with 21 dBm saturated output power and a noise figure of better than 8 dB at 18 GHz. RF yield to a gain spec of 7 dB at 26.5 GHz and 10 dB input and output return loss is 40%. The second product is a DC-50 GHz variable attenuator which achieves 72% yield to a 26.5 GHz spec of 2.4 dB minimum insertion loss, 27 dB maximum attenuation and greater than 8 dB input and output return loss. >

E.H. Wong

Papers

A manufacturable, 26 GHz GaAs MMIC technology