Hot Spots In Integrated Circuits Research Articles

Surface wetting to enhance thermoreflectance characterization of integrated circuits.

Thermoreflectance (TR) imaging enables non-contact thermal imaging of devices and integrated circuits (ICs) with sub-µm spatial resolution. TR coefficient of most metals and semiconductors in visible wavelengths is in the 10-5 to 10-3K-1 range, which gives a temperature resolution of 0.1-0.5 °C with a few minutes of averaging. Here, we show that surface wetting with various solvents, such as water, methanol, as well as Fluorinert, which is a commonly used coolant for high-power ICs, can enhance the TR coefficient by up to 19 times. Systematic characterizations as a function of the heating power, illumination-wavelength, liquid layer thickness, sample's tilt, and objective lens's numerical aperture are presented. TR images are distorted due to interference in the liquid layer, but this technique could be used for fast detection of small temperature variations and hot spots in ICs.

Hot spot analysis in integrated circuit substrates by laser mirage effect

This work shows an analytical and experimental technique for characterizing radial heat flow present in integrated circuits (ICs) when power is dissipated by integrated devices. The analytical model comes from the resolution of the Fermat equation for the trajectory of rays and supposing a spherical heat source dissipating a time-periodic power. An application example is presented; hence demonstrating how hot spots and heat transfer phenomena in the IC substrate can be characterized. The developed method may become a practical alternative to usual off-chip techniques for inspecting hot spots in ICs and to experimentally characterize heat flow in the semiconductor substrate.

Location of hot spots in integrated circuits by monitoring the substrate thermal-phase lag with the mirage effect

This Letter presents a solution for locating hot spots in active integrated circuits (IC) and devices. This method is based on sensing the phase lag between the power periodically dissipated by a device integrated in an IC (hot spot) and its corresponding thermal gradient into the chip substrate by monitoring the heat-induced refractive index gradient with a laser beam. The experimental results show a high accuracy and prove the suitability of this technique to locate and characterize devices behaving as hot spots in current IC technologies.

A heterodyne method for the thermal observation of the electrical behavior of high-frequency integrated circuits

The observation of spectral components of the power dissipated by devices and circuits in integrated circuits (IC) by temperature measurements is limited by the bandwidth of either the temperature transducer or the intrinsic cut-off frequency provided by the thermal coupling inside the chip. In this paper, we use a heterodyne method to observe the high-frequency behavior of circuits and devices by means of low-frequency lock-in temperature measurements. As experimental results, two applications of the technique are presented: detection of hot spots in ICs activated by high-frequency electrical signals and the observation of the frequency response of an integrated resistor through temperature measurements. The heterodyne method has been used in this paper with four different measurement techniques: embedded differential BiCMOS temperature sensor, laser reflectometer, laser interferometer and internal IR laser deflection meter.