Microdosimetry theory for microelectronics applications

Abstract

Although classical microdosimetry theory was originally intended for radiation biology applications, understanding the effect of ionizing radiations on small target volumes has become an important consideration in a number of research areas. In this paper we review the application of microdosimetry to radiation effects problems in microelectronics, with emphasis on large arrays of devices such as optical imagers and memories. A brief historical background of the evolution of microdosimetry theory for microelectronics is presented. An overview of some of the theory is given, with emphasis on compound Poisson process theory. An important consideration is how to evaluate the fundamental distributions that contribute to ionization fluctuations – the incident radiation linear energy transfer (LET) spectrum, the path lengths of primary charged particles in the microvolume, and the energy-loss straggling distribution. Methods of accomplishing this for microelectronics applications are discussed. The rapid evolution of microelectronics to smaller dimensions, larger arrays and new materials has presented challenges that have led to the development of approaches not found in classical microdosimetry. Two such developments are discussed. The first is a versatile and analytic approach for describing dose fluctuations induced by ions in microvolumes. It accounts for both ion (direct) events and electron (indirect) events, and is called the two component model. The second is the use of extreme value theory in conjunction with microdosimetry theory to assess the threshold dose at which a large array of devices begins to fail.