Scott Balster

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

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.

The effects of radiation on 1/f noise in complementary (npn+pnp) SiGe HBTs

We present the first study of the effects of radiation on low-frequency noise in a novel complementary (npn+pnp) silicon-germanium (SiGe) HBT BiCMOS technology. In order to manipulate the physical noise sources in these complementary SiGe HBTs, 63.3 MeV protons were used to generate additional (potentially noise-sensitive) trap states. The base currents of both the npn and pnp SiGe HBTs degrade with increasing proton fluence, as expected, although in general more strongly for the npn transistors than for the pnp transistors, particularly in inverse mode. For the pnp SiGe HBTs, irradiation has almost no effect on the 1/f noise to proton fluence as high as 5.0/spl times/10/sup 13/ p/cm/sup 2/, while the npn SiGe HBTs show substantial radiation-induced excess noise. In addition, unlike for the pnp devices, which maintain an I/sub B//sup 2/ bias dependence, the 1/f noise of the post-irradiated npn SiGe HBTs change to a near-linear dependence on I/sub B/ at low base currents following radiation. That suggests a fundamental difference in the noise physics between the two types of devices.

The Effects of Proton and X-Ray Irradiation on the DC and AC Performance of Complementary (npn + pnp) SiGe HBTs on Thick-Film SOI

The impact of 63.3 MeV proton and 10 keV X-ray irradiation on the DC and AC performance of complementary SiGe HBTs on thick-film SOI is investigated. Proton and X-ray induced changes in the forward and inverse Gummel characteristics, the output characteristics, and avalanche multiplication are reported for both npn and pnp SiGe HBTs, at both room temperature (300 K) and at cryogenic temperatures (down to 30 K). Comparison of room temperature and cryogenic data suggests interface trap formation at two distinct physical locations in the transistors. Experimental data and calibrated TCAD simulations are used to compare the radiation response of both thick-film SOI devices and thin-film SOI SiGe HBTs.

An investigation of low-frequency noise in complementary SiGe HBTs

We present a comprehensive investigation of low-frequency noise behavior in complementary (n-p-n + p-n-p) SiGe heterojunction bipolar transistors (HBTs). The low-frequency noise of p-n-p devices is higher than that of n-p-n devices. Noise data from different geometry devices show that n-p-n transistors have an increased size dependence when compared with p-n-p transistors. The 1/f noise of p-n-p SiGe HBTs was found to have an exponential dependence on the (intentionally introduced) interfacial oxide (IFO) thickness at the polysilicon-to-monosilicon interface. Temperature measurements as well as ionizing radiation were used to probe the physics of 1/f noise in n-p-n and p-n-p SiGe HBTs. A weak temperature dependence (nearly a 1/T dependence) of 1/f noise is found in both n-p-n and p-n-p devices with cooling. In most cases, the magnitude of 1/f noise is proportional to I/sub B//sup 2/. The only exception in our study is for noise in the post-radiation n-p-n transistor biased at a low base current, which exhibits a near-linear dependence on I/sub B/. In addition, in proton radiation experiments, the 1/f noise of p-n-p devices was found to have higher radiation tolerance than that of n-p-n devices. A two-step tunneling model and a carrier random-walk model are both used to explain the observed behavior. The first model suggests that 1/f noise may be caused by a trapping-detrapping process occurring at traps located inside IFO, while the second one indicates that noise may be originating from the emitting-recapturing process occurring in states located at the monosilicon-IFO interface.

Modeling of broadband noise in complementary (npn + pnp) SiGe HBTs

We present the first comprehensive investigation of broadband noise in a complementary (npn + pnp) SiGe (C-SiGe) HBT BiCMOS technology. A base-transit time based simple noise model with its origins in linear noisy two-port theory is presented, which takes into account the fundamental base and collector shot noise in a bipolar transistor, and their cross-correlation. The minimum noise figure of the npn and the pnp SiGe HBT in this technology at 2.0 GHz is measured to be 1.0 dB and 1.4 dB, respectively. This noise model is compared with the conventional SPICE noise model and the measured differences in the noise behavior of the npn and pnp SiGe HBTs are analyzed.