Microscale Heat Conduction in Integrated Circuits and Their Constituent Films

Miniaturization of circuit elements has played an essential role in improving the performance, capacity, and functionality of semiconductor integrated circuits. Transistors with shorter channel lengths can switch faster. The capability to integrate a larger number of devices generally translates into enhanced capacity and functionality. For these reasons, the semiconductor industry is expected to continue its miniaturization efforts in the coming decades. Indeed, minimum feature sizes of integrated circuit components are projected to reach the sub-0.1 /un regime during the first decade of the 21st century. A recent study (Timp et al., 1997) demonstrated the operation of field-effect transistors with 61 nm gate width.

There has been considerable progress in recent years in thermometry techniques that characterize microdevices and their constituent materials. Some of these techniques are applicable for both device and material characterization while others are suitable only for device thermometry. This chapter reviews thermometry techniques for microdevices and microstructures. The techniques are categorized depending on whether they employ electrical or optical signals.

The preceding chapter provides an overview of thermometry techniques applicable for microdevices and microstructures. The present research realizes the potential for high temporal and spatial resolution of the thermoreflectance technique thermoreflectance technique by developing an experimental setup that combines diffraction limited optics with a high speed electrical probing facility. Quantitative as opposed to qualitative temperature distributions can be obtained using calibration methods developed in the present study. The setup is employed for the thermal characterization of microdevices subjected to brief electrical stresses and for the determination of thermal transport properties of thin films. The present chapter provides details of the technique and its application for microdevices. Subsequent chapters describe thermal characterization of thin films.

The present chapter is concerned with the thermal transport properties of dielectric thin films. The thermometry techniques discussed in Chapter 3 form the basis of the techniques that measure the in- and out-of-plane thermal conductivity thermal conductivity and volumetric heat capacity heat capacity of thin dielectric films. The characterization capability is applied to the study of process-dependent thermal properties of silicon dioxide, which serves as a model amorphous solid.

The nature of heat transport in crystalline non-metallic solids is very different from that in their amorphous counterparts. This yields drastic differences in the magnitude and temperature dependence of the thermal conductivities of the two types of materials. The short mean free paths of heat carriers in amorphous materials permit the use of the heat diffusion equation to describe thermal phenomena at typical operating temperatures of microdevices. The validity of this approximation in crystalline silicon regions of compact semiconductor devices is the central question of this chapter.

The present research develops high temporal and spatial resolution thermometry techniques and applies them for the thermal characterization of integrated circuit elements and thin films. An experimental setup is constructed that integrates high resolution scanning optical thermometry capability into an electrical probing facility. Spatial resolution near 500 nm and temporal resolution better than 100 ns have been demonstrated using high voltage transistors and interconnects subjected to brief electrical stresses. The two step temperature calibration method developed here is well suited for microdevices and can be easily extended to other types of optical thermometry techniques. The thermometry technique also plays a key role in the extraction of the thermal transport properties of thin films. Simultaneous measurements of thermal conductivity anisotropy and volumetric heat capacity can be performed. Data on CVD silicon dioxide indicate that degree of disorder in atomic arrangements affect the thermal conductivity of amorphous solids. The experimental capability and physical understanding will help characterize and design new dielectric passivation layers.