A 4H-SiC Bipolar Technology for High-Temperature Integrated Circuits

Abstract

AbstractÀA 4H-SiC bipolar technology suitable for hightemperature integrated circuits is tested with two interconnect systems based on aluminum and platinum. Successful operation of low-voltage bipolar transistors and digital integrated circuits based on emitter coupled logic (ECL) is reported from 278C up to 5008C for both the metallization systems. When operated on 215 V supply voltage, aluminum and platinum interconnect OR-NOR gates showed stable noise margins of about 1 V and asymmetric propagation delays of about 200 and 700 ns in the whole temperature range for both OR and NOR output. The performance of aluminum and platinum interconnects was evaluated by performing accelerated electromigration tests at 3008C with current density of about 1 MA/cm 2 on contact chains consisting of 10 integrated resistors. Although in both cases the contact chains failed after less than one hour, different failure mechanisms were observed for the two metallization systems: electromigration for the aluminum system and poor step coverage and via filling for the platinum system.

A 500 °C Active Down-Conversion Mixer in Silicon Carbide Bipolar Technology

“…After 3 hours of continuous operation, CG dropped by almost 1.4 dB as compared to its initial value. This performance degradation was permanent and persisted even when the mixer was cooled back to 25 • C. The onset of failure mechanism, due to the accelerated electromigration in the Al-based metallization system [18], is believed to be the cause of permanent performance degradation with time at 500 • C. The electromigration manifests as a permanent increase in the access and contact resistances of the BJT with time, which not only degrades g m but also increase the mismatch losses, therefore leading to a CG degradation. Consequently, the long-term reliability of the in-house SiC BJT based circuits at elevated temperatures requires stable metallization systems e.g.…”

Lateral depletion-mode 4H-SiC n-channel junction field-effect transistors operational at 400 °C*

“…Compared with the reported light n-type layer sheet resistance data, [18] R SH.n in our work is effectively reduced by optimization of the dose of light nitrogen implants. As temperature increases to 400 • C, the higher the doping concentration, the lower the dopant activation, and the ionized dopant concentration increase is compensated for by the mobility lowering, [19] therefore R SH.n gradually increases to 9.44 kΩ/ while R SH.n + swings to 0.48 kΩ/ . to 0.89%, which is dominated by the increase of R S/D .…”

Towards Silicon Carbide VLSI Circuits for Extreme Environment Applications

“…Reliability testing for the 11-stage ring-oscillator (RO) using SiC TTL PDK indicated that the RO frequency of oscillation decreased 16% after HT characterization [17]. The degradation in DC and transient measurements was permanent, due to the accelerated electro-migration in the Al-based metalization system [26]. The long-term reliability of the SiC ICs at elevated temperatures require stable metalization as reported in [27].…”