Controlled Nanoscale Doping of Semiconductors via Molecular Monolayers
Ali Javey, Johnny Ho, Roie Yerushalmi, Zachery Jacobson, Zhiyong Fan and Robert Alley
One of the major challenges towards scaling down of the electronic devices to the nm-regime is attaining controlled doping of semiconductor materials with atomic accuracy. At such small scales, the various existing technologies suffer from a number of setbacks, including an inability to achieve junction abruptness down to nm range, stochastic distribution of the dopant atoms, crystal damage, and incompatibility with nanomaterials. In this work, we present a novel strategy for controlled, nanoscale doping of semiconductor materials by taking advantage of the crystalline nature of silicon and its rich, self-limiting surface reaction properties. Our method relies on the formation of highly uniform and covalently bonded monolayer of dopant containing molecules which allows for deterministic positioning of dopant atoms on the Si surfaces.
Figure 1: Monolayer doping process for Si substrates. The native silicon oxide layer is first removed by the HF etching followed by a reaction with dopant containing molecules to form a covalently bonded monolayer. A silicon dioxide capping layer (~50 nm thick) is then formed followed by rapid thermal annealing for dopant diffusion. Finally, the capping layer is removed by HF etching.
- Nature Materials (to appear).