Germanium n-type shallow junction activation dependences

Abstract

A few of the recent unsatisfactory germanium n-channel metal-oxide-semiconductor field-effect transistor MOSFET experimentations are believed to stem from the poor source and drain n+-p junction formations. In order to explain the primary cause and suggest rectifying solutions, we have examined the activation of common n-type dopants in germanium and the related dependences. These dependences include thermal anneal budget, impurity species, and implantation dosage. Low thermal budgets are generally preferred to activate shallow junctions to simultaneously annihilate defects and suppress fast dopant diffusion. Injecting dopants over the solid-solubility limitation into shallow junctions would only generate more implantation damage but could not however lower the junction sheet resistance.

Frustrated incomplete donor ionization in ultra-low resistivity germanium films

“…Since the highest Si concentration in the samples shown in Fig. 3 is x ¼ 0.012 by SIMS, we can safely combine data from samples doped with P(SiH 3 ) 3 or P(GeH 3 ) 3 . We see that the standard theory predicts a very significant level of incomplete ionization for N d > 5 Â 10 17 cm…”

“…For growth of the doped layer on the same reactor, the Ge-buffered samples were subjected to a brief in situ annealing step at 650 C for 3 min. The n-type layers, with thicknesses ranging between 180 nm and 430 nm, were then grown at the same temperature as the buffer using gaseous mixtures of H 2 , Ge 4 H 10 , and varying amounts of P(MH 3 ) 3 . For UHV-CVD growth, the buffer layers were removed from the GSME reactor and cleaved into 45 mm  45 mm pieces.…”

“…The relationship between carrier concentration and donor atomic concentration has been determined in n-type Ge films doped with P. The samples were carefully engineered to minimize non-active dopant incorporation by using specially designed P(SiH 3 ) 3 and P(GeH 3 ) 3 hydride precursors. The in situ nature of the doping and the growth at low temperatures, facilitated by the Ge 3 H 8 and Ge 4 H 10 Ge sources, promote the creation of ultra-low resistivity films with flat doping profiles that help reduce the errors in the concentration measurements.…”

The formation, stability, and suitability of n-type junctions in germanium formed by solid phase epitaxial recrystallization

“…[6][7][8][9] Quantifying the expected diffusion is difficult as available diffusivity values were either extracted under intrinsic conditions, or at higher temperatures than studied here. 1 However, extrapolating diffusivity values from Chui et al, 6 which are accurate for high concentrations, only a few nanometers of diffusion could be expected for the highest thermal budgets in this work.…”

“…n-type dopants in germanium have proven to be problematic, and are now a key bottleneck in the realization of advanced n-type MOS ͑NMOS͒ device performance and scaling. 5 In short, phosphorus ͑P͒ and arsenic ͑As͒ are relatively difficult to activate and diffuse quickly, [6][7][8][9] leading to high resistances and limited capability to reduce the device dimensions.…”