The effect of wafer thinning and thermal capacitance on chip temperature of SiC Schottky diodes during surge currents

Abstract

Due to superior material properties of SiC for high-voltage devices, SiC Schottky diodes are used in energy-conversion systems such as solar-cell inverters, battery chargers, and power modules for electric cars and unmanned aerial vehicles. The reliable operation of these systems requires the chip temperature of SiC Schottky diodes to be maintained within the limit set by the device package. This is especially crucial during surge-current events that dissipate heat within the device. As a thermal-management method, manufactures of commercial SiC Schottky diodes have introduced wafer thinning practices to reduce the thickness of the SiC chip and, consequently, to reduce its thermal resistance. However, this also leads to a reduction in the thermal capacitance. In this paper, we present experimental data and theoretical analysis to demonstrate that the reduced thermal capacitance has a much larger adverse effect in comparison to the beneficial reduction of the thermal resistance. An implication of the presented results is that, contrary to the adopted wafer thinning practices, SiC Schottky diodes fabricated without wafer thinning have superior surge-current capability.

Comparative Analysis of Thermal Properties in Molybdenum Substrate to Silicon and Glass for a System-on-Foil Integration

“…sine wave in order to prevent any switching signal discontinuities on the monitoring signals, which follows a similar approach as Damcevska et al [5]. For each substrate, signals were applied with peak powers of 1 W, 2 W, and 2.7 W-corresponding to 1.13 W/mm 2 , 2.26 W/mm 2 , and 3.05 W/mm 2 respectively, for pulses of 5, 10, 20, 50, and 100 ms.…”

“…The thermal response to heat pulses of different frequencies and power was studied for the three different substrates. The applied power was introduced as a ½ sine wave in order to prevent any switching signal discontinuities on the monitoring signals, which follows a similar approach as Damcevska et al [5]. For each substrate, signals were applied with peak powers of 1 W, 2 W, and 2.7 W-corresponding to 1.13 W/mm 2 , 2.26 W/mm 2 , and 3.05 W/mm 2 respectively, for pulses of 5, 10, 20, 50, and 100 ms. As described in the methods section, the resistance of both the heat and sense resistors were calculated by measuring their voltage drop and the current flowing through a control resistor, which was in series with the resistors measured and was kept at room temperature.…”

“…The applied power was introduced as a squared ried Pulse and Power Temperature Measurements e thermal response to heat pulses of different frequencies and power was studied three different substrates. The applied power was introduced as a ½ sine wave in to prevent any switching signal discontinuities on the monitoring signals, which s a similar approach as Damcevska et al [5]. For each substrate, signals were d with peak powers of 1 W, 2 W, and 2.7 W-corresponding to 1.13 W/mm 2 , 2.26 2 , and 3.05 W/mm 2 respectively, for pulses of 5, 10, 20, 50, and 100 ms.…”

“…The data presented in this work demonstrate the feasibility of the proposed systemon-foil technology as an advanced packaging solution for improved heat management and device operation. Metal-based substrates, such as molybdenum, with much higher thermal conductivities, provide lower maximum operating temperatures and can be made thinner than traditional substrates for a lower thermal resistance [5]. Glass substrates, with a much lower thermal conductivity, are much slower to reach maximum steady-state temperatures and can be used to thermally isolate specific areas of a chip.…”

“…One of the main motivations for thinned substrates is to reduce electrical resistance, which then allows for more efficient heat removal from active circuitry to a heat sink or other heating solutions [3,4]. Measuring the thermal conductivity of thin electronic substrates has previously been studied using SiC Schottky diodes, which, in their most basic form, are metal-semiconductor junctions, creating an electron barrier [5].…”