Besides cryogenic electronics, CoolSPICE also includes circuit elements for niche electronics applications. SPICE models for silicon carbide device models are currently being developed for use in power electronics simulations. The silicon carbide power library includes MOSFETs, JFETs, and diodes, along with simplified power switches and passives.

CoolSPICE also includes libraries for components for simulating photodetector circuits with elements such rectennas and avalanche photodiodes.

Click on the CoolSPICE page to download the student version!

We develop Verilog-A models for various devices that cannot be found in standard SPICE libraries or devices operating in extreme environments that are not well modeled with standard device model sets. For example, cryogenic operation of CMOS devices are modeled with a modified BSIM equation set and coded into a Verilog-A for enabling simulation of cryogenic circuit operation in commercial SPICE simulators. (These Verilog-A libraries are similar to those coded in CoolSPICE using the C-programming language.) However we note that C-programming based codes have inherently faster running times than similar Verilog-A libraries. But Verilog-A libraries offer flexibility in terms of simulator choice and easy access to the device parameter set as well as device equations.

For CMOS technologies, we design, lay out and have fabricated SPICE model extraction test chips. Using the test structures, we then extract SPICE models using measurements. We have applied this method to some CMOS technologies, and have developed SPICE models for an extreme temperature range and also for under radiation operation for this technologies. More specifically, our SPICE models predict n- and p-channel MOSFET operation for all width and length devices from 4K up to 300K for the technologies listed below:

- IBM 8RF
- IBM 10LP
- Jazz CA18
- Peregrine 5FC
- AMI/ON C5

**SPICE Models for Silicon Carbide Power Devices: **
We design and develop a comprehensive Silicon Carbide Power System CAD
tool to address the need for improved methodologies for developing next
generation high efficiency power electronics using Silicon Carbide power
devices. To this end, we have developed SPICE models for SiC MOSFETs,
JFETs and diodes. More specifically, we have developed SPICE models for
CREE power MOSFETs valid from room temperature up to 200 C. We are also
developing models for SiC diodes, and JFETs. These models are currently being
incorporated into CoolSPICE-PS (CoolSPICE-Power System), and are coupled
with a three-dimensional thermal simulator for resolving electrical as
well as thermal characteristics for power modules.

**SPICE Models for Niche Components: **We develop SPICE
models for niche devices such as MIM diodes, rectennas, and avalanche photodiodes.
We can develop models for your various applications!

First we draw power module or circuit board in a three-dimensional CAD program. During the creation of the mesh, the geometry can be divided up into different "bodies", which can be associated with different generated heat. Additionally, each face of the surface can be associated with a different boundary condition: temperature is fixed; derivative of the temperature is fixed with various heat conductivities and thermal radiation coefficients. We then use the SPICE engine to determine the power consumed by the circuit components, and use the thermal engine to calculate the temperature of these components for given power consumption levels. We iterate electrical performance and heating figures until they both agree.

We specifically apply coupled thermal-electrical simulations to silicon carbide power devices and circuits. As silicon carbide components are generally aimed for high power applications, they are prone to heating that is experienced by all high power switches. For example, even for a highly efficient 5 kW system, with a few power switches only consuming 2% of total power, 100W of Joule heating will give rise to significant elevated temperatures at the switch level. This will in turn affect the electrical performance, since changes in temperature alter electrical performance characteristics, and it may even provide a positive feedback between temperature rise and power consumption, leading to excessive heating and reduced system efficiency.

CoolSPICE-PS is capable of incorporating temperature variations at the device level into circuit simulations, unlike the standard SPICE that forces the entire circuit operate at one ambient temperature. Even though there are efforts to incorporate some temperature variations into key circuit elements by using voltage and current controlled sources to provide feedback to electrical operation, these efforts often result in convergence problems in circuits with more than few parts, and also cannot resolve heat coupling between components.

Our drift-diffusion based simulator solves for Poisson equation coupled with electron and hole current continuity equations to obtain two and one dimensional profiles of electron concentration, hole concentration and electrostatic potential, as well as terminal currents for given doping profiles and physical device layout.

Here we show calculated and measured current-voltage curves of a 0.6 μm long n-channel MOSFET. We also show doping profile for this MOSFET, calculated using an incomplete ionization model.

We perform self-consistent simulations of two-dimensional devices in conjunction with SPICE circuit elements. At the detailed device level, drift-diffusion equations that include electron and hole current continuity equations as well as Poisson equation are self-consistently solved for to calculate terminal currents and to obtain electron concentration, hole concentration and electrostatic potential profiles. At the circuit level, we solve for nodal equations to determine branch currents and voltages.

As an example, we show a boost converter circuit with the switching element modeled using TCAD, along with the simulated inductor current and output voltage. We also show an inverter circuit with NMOS and PMOS modeled using TCAD.

A. Akturk, M. Holloway, S. Potbhare, D. Gundlach, B. Li, N. Goldsman, M. Peckerar, K. P. Cheung, "Compact and distributed modeling of cryogenic bulk mosfet operation ," IEEE Transactions on Electron Devices 57(6), 1334-1342 (2010).

A. Akturk, S. Potbhare, J. Booz, N. Goldsman, D. Gundlach, R. Nandwana, K. Mayaram, "CoolSPICE: SPICE for Extreme Temperature Range Integrated Circuit Design and Modeling," Proceedings of Int. Conf. on Simulation of Semiconductor Processes and Devices (SISPAD), (5-7 Sept. 2012).

A. Akturk, M. Peckerar, K. Eng, J. Hamlet, S. Potbhare, E. Longoria, R. Young, T. Gurrieri, M. S. Carroll, N. Goldsman, "Compact modeling of 0.35μm SOI CMOS technology node for 4K dc operation using Verilog-A," Microelectronic Engineering 87(12), 2518-2524 (2010).

S. Potbhare, A. Akturk, N. Goldsman, M. Peckerar, J. M. McGarrity, A. Agarwal, "Modeling and design of high temperature silicon carbide DMOSFET based medium power DC-DC converter," Proceedings of Int. Conf. on High Temperature Electronics (HiTEC), (11-13 May 2010).

A. Akturk, N. Goldsman, G. Metze, "Self-consistent modeling of heating and mosfet performance in three-dimensional integrated circuits," IEEE Transactions on Electron Devices 52(11), 2395-2403 (2005).

A. Akturk, N. Goldsman, L. Parker, G. Metze, "Mixed-mode temperature modeling of full-chip based on individual non-isothermal device operations," Solid-State Electronics49(7), 1127–1134 (2005).

Z. Dilli, A. Akturk, N. Goldsman, G. Metze, "Controlled on-chip heat transfer for directed heating and temperature reduction," Solid State Electronics 53(6), 590–598 (2009).