(Invited) Issues with n-type Dopants in Germanium

Abstract

The last decade has seen considerable experimental and theoretical work towards the use of germanium for high-speed low-power electronics. Despite the demonstration of high performance p-channel Ge transistors in planar and non-planar device technology, fabrication of n-channel Ge transistors faces a number of scientific and technological challenges, which hinder the development of CMOS logic circuits based entirely on Ge. Major challenge constitutes the control of fast n-type dopant (out-/in-)diffusion in Ge, which prevents the formation of ultra-shallow and highly activated n+/p junctions necessary for n-channel Ge MOSFET’s enhanced performance. The paper focuses on parameters affecting n-type dopant diffusion in Ge and the attempts to suppress it, with particular emphasis on the action of nitrogen as phosphorous diffusion blocker.

Investigation of recrystallization and stress relaxation in nanosecond laser annealed Si1−xGex/Si epilayers

“…Similar surface structures have already been observed at the early stages of melting induced by NLA of Si and Ge [32,33] or millisecond Flash Lamp Annealing of Si, Ge and SiC [34][35][36]. Similarly to our case, these structures have also been interpreted as the consequence of a local melt of the material at the beginning of the melting process.…”

Post-metallization annealing and photolithography effects in p-type Ge/Al2O3/Al MOS structures

“…(According to this scheme the alumina layer is reduced by the deposited aluminum forming an AlO x interfacial layer, while the released aluminum from the Al 2 O 3 layer diffused towards the Ge substrate to form the AlGeO interfacial layer at the Ge interface). 8 The composition of the Al 2 O 3 /Ge interface of both samples was studied using ex situ XPS measurements. The presence of the Al 2 O 3 film is verified by the Al2p spectrum (not shown) with an expected peak binding energy at 74.6 eV.…”

“…[1][2][3][4][5][6] These studies showed that although Ge is CMOS compatible, it exhibits quite different behavior raising processing issues related to critical fabrication steps of the MOS device. 7,8 The formation of a good quality interface between the gate insulator and the Ge substrate remains a challenge. Among the methods available to fabricate a well passivated Ge interface there is the formation of a relatively thick GeO x or AlGeO interfacial layer between the dielectric and the Ge substrate.…”

Phosphorus diffusion and activation in fluorine co-implanted germanium after excimer laser annealing

“…Besides, the n-type doping level as high as 1×10 20 cm −3 activation concentration with low diffusion is usually necessary for a downscaling beyond 15 nm. However, it is hard to fulfill the high level n-type doping in Ge because of low solid solubility and large diffusion coefficient of V-group impurity, [6] which will restrict its applications to some extent. In order to obtain heavy n-type doping in Ge, the combination of ion implantation and post-annealing process is frequently utilized.…”