Thermoreflectance imaging of current dynamics in high power SiGe heterojunction bipolar transistors

Abstract

By generating high resolution two dimensional temperature images of electronic devices and linking heat dissipation to electrical current, the authors demonstrate that thermoreflectance measurements employing a charge-coupled device can provide a useful and nondestructive method for profiling current density in electronic devices. Here they apply this method to high power SiGe heterojunction bipolar transistors (HBTs) integrated in a commercial SiGe bipolar complementary metal-oxide-semiconductor platform, measuring the current carried by each subcell and quantifying current collapse under high-bias operation. They show that current hogging for a HBT with two emitter subcells can lead to one subcell carrying 81% of the total current.

CCD-based thermoreflectance microscopy: principles and applications

“…5.3.1. Transistors. Utilizing the link between current density and temperature, high-resolution thermal microscopy has been used as a non-destructive tool to image current density in high power heterojunction bipolar transistors (HBTs) [48]. As shown in figure 5, this technique can be used to quantify effects such as current hogging in subcells of multifinger power transistors, a primary cause of reduced overall gain and device failure.…”

“…Profiling current density in high-power transistors: normalized thermoreflectance images ( R/R) of a SiGe HBT at increasing V CE bias with V BE held constant at 1.52 V. The thermal images result from about an hour total accumulation time. (Reprinted with permission from[48]. Copyright 2006 American Institute of Physics.…”

Thermal characterization of organic light emitting devices

“…4,5,6 The detailed experimental setup has been discussed elesewhere and will not be repeated here. 7,8 The fundametnal operating principle of the TR method is to evalualte the temperature variation of the device by measureing the changes in the normalized reflectivitiy of the surface.…”

The Intrinsic Thermoreflectance Property of 4H-SiC

“…Localized hot spots often determine the peak operating temperature of a power transistor, even though the average die temperature may be significantly lower. 7 Thermal measurement of devices is therefore very important. There are several thermal measurement techniques used to measure microelectronic devices, e.g.…”