Do dopant diffusion and drift decide semiconductor device degradation and dimension Limits?

We explore chemical and physical limits to semiconductor device miniaturiza tion. Minimal sizes for space charge-based devices can be estimated from De bye screening lengths of the materials used. Because a doped semiconductor can be viewed as a mixed electronic-ionic conductor, with the dopants as mo bile ions, dopant intermixing across a p/n junction presents a chemical lim it. Given a desired lifetime, simple relations can be derived between size and dopant intermixing for reverse- or forward-biased devices. Mostly, cond itions for significant dopant mobility are far from those where the materia l is used. Thus, it is generally held that elemental and III-V-based p-n ju nctions are immune to this problem and persist because of kinetic stability . Indeed, we find this to be so for Si in the foreseeable future, but not f or III-V- and II-VI-based ones. The limitation is more severe in structures with very thin undoped layers sandwiched between doped ones or vice versa, where even 1% intermixing can be critical. This decreases lifetime nearly 100 times. For example, for structures containing a 10 nm critical dimensio n, none of the components can have an average diffusion coefficient higher than 10(-24) cm(2)/s for a 3 year lifetime. Ways to overcome or mitigate th is limitation are indicated. (C) 2000 Elsevier Science B.V. All rights rese rved.