Reduction of phosphorus diffusion in germanium by fluorine implantation

Abstract

The control of phosphorus (P) diffusion in germanium (Ge) is essential for the realisation of ultrashallow n-type junctions in Ge. This work reports a detailed study of the effect of fluorine (F) co-implantation on P diffusion in Ge. P and F profiles were characterized by secondary ion mass spectroscopy. The ion implantation damage was investigated using cross sectional transmission electron microscopy. It is shown that F co-implantation reduces the implanted P profile width and reduces both intrinsic and extrinsic P diffusion in Ge. A defect mediated mechanism for the strong influence of F co-implantation on P diffusion in Ge is proposed and invokes the formation of FnVm clusters in the F-amorphized Ge layer. A fraction of these FnVm clusters decorate the interstitial type end-of-range defects in the re-grown Ge layer and the rest react during re-growth with interstitial germanium atoms diffusing back from the amorphous crystalline interface. The Ge vacancies are then annihilated and mobile interstitial F is released and out diffuses from the surface. This results in a re-grown Ge layer which has a low vacancy concentration and in which the P diffusion rate is reduced. These results open the way to the realization of enhanced Ge n-type devices.

Strong Diffusion Suppression of Low Energy-Implanted Phosphorous in Germanium by N2 Co-Implantation

“…The presented results are very encouraging taking into account the implantation conditions and the proximity of P distribution to the Ge surface. A comparison between the presented results to the recently reported on fluorine impact on P diffusion in Ge, 9 suggests that nitrogen is probably more effective in suppressing P diffusion as compared to fluorine. This could be attributed to the different way each element acts (fluorine reduces vacancy concentration by formation of F n V m clusters while the most probable mechanism for nitrogen action is the formation of P-N complexes) in combination to slower out-diffusion trend of N as compared to F. 14,9 The method offers great flexibility in terms of implantation (energy and dose) and subsequent annealing (flash or spike annealing) conditions towards the formation of more abrupt and highly active n + /p junctions.…”

“…14), this is also supported by the studies of arsenic and phosphorous diffusion when co-implanted with fluorine in Ge. 9,18 In the later works the formation of FI clusters in the presence of an interstitial P50 ECS Solid State Letters, 4 (6) P47-P50 (2015) supersaturation at the EOR region has been verified experimentally as well as by theoretical calculations.…”

“…2 Consequently significant research efforts have been focused to the study of P macroscopic diffusion behavior as a function of the implantation and annealing conditions, as well as the nature of a capping layer (CL) on the Ge surface. [3][4][5][6][7] In parallel, techniques which could suppress P diffusion and/or enhance its activation level have been pursuit, most representative of which are co-implants with carbon or fluorine, 8,9 co-doping with other n-type dopants (such as arsenic and antimony) 10,11 and low temperature metal-induced dopant activation. 12 Nitrogen constitutes a significant element, which has been used in silicon front-end processes.…”

Processing of germanium for integrated circuits

“…• C temperature range [88]. Furthermore, it was shown experimentally that F co-implants can affect the diffusion of low-dose As implants [89].…”

Phosphorous Diffusion in N2+-Implanted Germanium during Flash Lamp Annealing: Influence of Nitrogen on Ge Substrate Damage and Capping Layer Engineering

“…1,4 Consequently, a variety of approaches has been followed to suppress P fast diffusion in Ge, and to increase in parallel its activation levels. These can be divided in specific categories, the most representative being: (a) co-implants with impurities such as carbon, 1,4 fluorine 5,6 or nitrogen, 7,8 (b) co-doping with other n-type dopants such as arsenic or antimony, 9,10 (c) non-conventional approaches such as low temperature metal-induced dopant activation, 11 and bulk interstitial injection by GeOx clusters disolution. 12 The majority of these approaches have been recently summarized and reviewed by Simoen et al 1 The diffusion of n-type dopants in Ge is highly influenced by the following three experimental parameters.…”