Ordered polymer-based spin-on dopants

Abstract

Conventional doping of crystalline Si via ion implantation results in a stochastic distribution of doped regions in the x-y plane along with relatively poor control over penetration depth of dopant atoms. As the gate dimensions get to 10 nm, the related device parameters also need to be scaled down to maintain electrical activity. Thus highly doped abrupt, ultra-shallow junctions are imperative for source-drain contacts to realize sub-10 nm transistors. Uniform ultra-shallow junctions can be achieved via monolayer doping, wherein thermal diffusion of a self-limiting monolayer of dopant atomcontaining organic on Si surface yields sub-5 nm junctions. We have extended the use of organic dopant molecules in the monolayer doping technique to introduce a new class of spin-on polymer dopants. In effect, these new spin-on dopants offer a hybrid between the monolayer doping technique and traditional inorganic spin-on dopants. We have been able to uniformly introduce p- and n-type dopants with doping efficiencies comparable to the monolayer doping technique. Control over junction depth can be easily achieved via optimizing annealing temperature and time. Concurrently, sequestering the dopant precursors within the cores of block copolymer micelles allows us to achieve precise control over the spatial positions of dopant atoms in all three dimensions owing to the high periodicity of block copolymer domains on the 10-100 nm length scale.