Jeffrey A. Babcock

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.

Precision electrical trimming of very low TCR poly-SiGe resistors

Precision electrical trimming of stacked Si/SiGe polycrystalline resistors available from the extrinsic base structure of a SiGe BiCMOS technology has been demonstrated for the first time. It is shown that pulse current trimming techniques can be used to trim the poly-SiGe resistors by up to 50% from their original values with accuracy better than /spl plusmn/0.5%. The temperature coefficient of resistance (TCR) is shown to be linearly proportional to the percent change in electrically trimmed poly-SiGe resistance. Finally, we demonstrate resistance cycling using an electrical trim/recovery sequence, indicating that the technique is reversible and is governed by dopant segregation/diffusion mechanisms. The results are consistent with those obtained on conventional polysilicon resistors suggesting that the introduction of a strained SiGe layer does not adversely affect the electrical trim properties of these resistors.

Comparative low frequency noise analysis of bipolar and MOS transistors using an advanced complementary BiCMOS technology

In this paper, for the first time we compare 1/f noise in both complementary bipolar and complementary MOSFET transistors fabricated on thick film bonded SOI with full dielectric isolation capability. For MOS devices, a new relationship for 1/f noise is given which allows intuitive insight when comparing technologies. Both bipolar and MOS transistors show agreement to a number fluctuation model for noise mechanisms. A factor of 2 lower 1/f noise is determined for the PNP in comparison to NPN transistors. For this technology generation, bipolar transistors indicate an order of magnitude lower noise level when compared to MOSFETs under similar drive currents and effective area conditions. Finally, we discuss generation recombination noise, which can be observed in some of the devices.

Total Ionizing Dose Effects on a High-Voltage (>30V) Complementary SiGe on SOI Technology

Total ionizing dose (TID) effects are evaluated for a high-voltage (>30 V) complementary SiGe on SOI technology. Devices are irradiated with 10-keV X-rays at doses up to 5 Mrad(SiO2). The results depend strongly on collector-to-emitter bias, in both forward- and inverse-mode. An anomalous reduction in current gain at high injection in forward-mode operation is observed at doses >500 krad(SiO2). Calibrated 2-D TCAD simulations suggest that this high injection phenomenon is primarily due to interface traps near the STI/Si interface, which is exhibited as a collector resistance increase in the forward Gummel characteristics. Additionally, a strong collector doping dependence is observed, which indicates that this is primarily driven by the thick and lightly doped collector used in this technology. These results illustrate, that high concentrations of interface traps at the STI can have a strong impact on the forward-mode TID response of SiGe HBTs.