Integrated Circuit Design for Radiation Environments

3 Radiation Effects in Semiconductor Materials

3.1 Introduction

Particles and photons interact with matter, and this chapter provides the introductory physics behind these interactions. An understanding of the basic effects in semiconductor materials caused by particles and photons (e.g. X‐rays and gamma rays) will lead to a better understanding of more complex or higher‐order effects on devices and circuits, for example the change in beta of a bipolar transistor or the dependence of operational amplifier open‐loop gain on total dose of radiation accumulated.

An understanding of the interaction of radiation on semiconductor materials and structures also guides semiconductor process development, whether specifically aimed at designing radiation hardened processes or used during the development of conventional foundry processes. The ion implantation process used to form doped regions in semiconductor wafers is a good example of a conventional process step where the effects of a radiation source (ionized boron, phosphorous, arsenic, etc.) are finely calculated. The energy of the ionized specie and the dose of ions are chosen to achieve a desired distribution of dopant in the semiconductor wafer. The implant angle is chosen to avoid channeling effects along certain crystal lattice directions. Lattice damage caused by the ion implant step is repaired using a high‐temperature anneal (>700 °C).

While analogous to an ion implantation processing step, the incident conditions ...