High performance n+/p and p+/n germanium diodes at low-temperature activation annealing (original) (raw)
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Thermal annealing behaviour of platinum, nickel and titanium Schottky barrier diodes on n-Ge (100)
Journal of Alloys and Compounds, 2010
Platinum (Pt) and titanium (Ti) Schottky barrier diodes were fabricated on bulk grown (1 0 0) Sb-doped ntype germanium using the electron beam whereas nickel (Ni) contacts were fabricated using the resistive evaporation system. Electrical characterization of these contacts using current-voltage (I-V) measurements was performed under various annealing conditions. The variation of the electrical properties of these Schottky diodes can be attributed to combined effects of interfacial reaction and phase transformation during the annealing process. The results have also revealed that Pt Schottky contacts are of a high quality, with low reverse currents in the order of (10 −5 to 10 −6 ) A and as-deposited ideality factors as low as 1.09. Furthermore, the samples microstructural characterization was performed by scanning electron microscopy (SEM) at different annealing temperatures. From the results, it can be concluded that the onset temperature in 30 nm Ni-and Pt/n-Ge (1 0 0) systems occurs at 500-600 • C and 600-700 • C, respectively.
Impact of germanium surface passivation on the leakage current of shallow planar p–n junctions
Materials Science in Semiconductor Processing, 2006
One of the challenges in the development of CMOS on Ge is the fabrication of low-leakage shallow junctions. Like in the case of silicon technology, one aims to achieve this goal by ion-implantation of the dopants followed by a thermal activation step. The thermal budget should be low enough to minimize excessive diffusion but at the same time sufficient to remove the lattice damage and activate the dopants. However, as will be shown, for the planar junctions fabricated in germanium substrates, another factor dominates the leakage current, namely the surface generation current in the peripheral regions surrounding the diode. This emphasizes the role of adequate surface passivation. Results will be presented for diodes fabricated in 100 mm diameter p-and n-type Ge wafers, using different dielectrics as surface passivation layer, namely 20 nm Si 3 N 4 deposited by CVD and GeON/HfO 2 (4 nm) deposited by MBE. A difference of up to five decades between forward and reverse current has been achieved. Analysis of the area/perimeter scaling of the reverse current demonstrates that even for these junctions, the surface generation current is dominant. It will also be pointed out that the substrate doping density plays an important role.
Laser annealing for n+/p junction formation in germanium
Materials Science in Semiconductor Processing, 2006
In the present work we focus our study on laser annealing of implanted with high phosphorus dose p-type germanium wafers using an Nd-YAG laser at 355 nm. Dopant profiles as monitored by SIMS measurements demonstrate dopant profile movement less than 15 nm at junction depth. Germanium (Ge) structural defects were observed by TEM measurements and the roughness of the surface was measured by AFM. The above analysis shows the efficiency of laser annealing in recrystallizing the Ge substrates at lower energy fluences compared to Si and without substantial dopant loss and diffusion. r
Germanium n-type shallow junction activation dependences
Applied Physics Letters, 2005
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.
IEEE Transactions on Electron Devices, 2000
This paper presents an analysis of junction leakage in heavily doped p+/n germanium junctions, targeted for short-channel transistor fabrication. There exists an optimal p+/n junction condition, with a doping concentration of 1 × 10 17 -5 × 10 17 cm −3 , where the area-leakage-current density is minimal. Use of a halo-implant condition optimized for our 125-nm gate-length pMOS devices shows less than one decade higher area leakage than the optimal p+/n junction. For even higher doping levels, the leakage density increases strongly. Therefore, careful optimization of p+/n junctions is needed for decananometer germanium transistors. The junction leakage shows good agreement with electrical simulations, although for some implant conditions, more adequate implant models are required. Finally, it is shown that the area-junction static-power consumption for the best junctions remains below the power-density specifications for high-performance applications.