Ohmic contacts on n-type and p-type cubic silicon carbide (3C-SiC) grown on silicon

Abstract

This paper is a report on Ohmic contacts on n-type and p-type type cubic silicon carbide (3C-SiC) layers grown on silicon substrates. In particular, the morphological, electrical and structural properties of annealed Ni and Ti/Al/Ni contacts has been studied employing several characterization techniques. Ni films annealed at 950°C form Ohmic contacts on moderately n-type doped 3C-SiC (ND ~ 1×10 17 cm -3 ), with a specific contact resistance of 3.7×10 -3 Ωcm 2 . The main phase formed upon annealing in this contact was nickel silicide (Ni2Si), with randomly dispersed carbon in the reacted layer. In the case of a p-type 3C-SiC with a high doping level (NA ~ 5×10 19 cm -3 ), Ti/Al/Ni contacts were preferable to Ni ones, as they gave much lower values of the specific contact resistance (1.8 ×10 -5 Ωcm 2 ). Here, an Al3Ni2 layer was formed in the uppermost part of the contact, while TiC was detected at the interface. For this system, a temperature dependent electrical characterization allowed to establish that the thermionic field emission rules the current transport at the interface. All these results can be useful for the further development of a devices technology based on the 3C-SiC polytype.

Impact of Stacking Faults and Domain Boundaries on the Electronic Transport in Cubic Silicon Carbide Probed by Conductive Atomic Force Microscopy

“…Arrays of Pt Schottky diodes with variable size were fabricated on the 3C‐SiC surface as follows. First, a ohmic contact, consisting of a Ni 2 Si frame on the sample front side, was obtained by Ni sputtering and lift‐off, followed by thermal annealing at 950 °C for the silicide formation . Afterward, Pt contacts with circular shape and radius ranging from 5 to 25 µm were fabricated inside this frame by Pt sputtering and lift‐off.…”

Status and Prospects of Cubic Silicon Carbide Power Electronics Device Technology

“…As with 4H-SiC, Al based alloys are most commonly used for p-type ohmic contact since very often Al is also the doping species. A Ti interlayer is often applied not only to improve the adhesion, but the TiC product after PMA also helps to reduce the contact resistance [ 36 , 66 ].…”

“…Among the very limited data, the lowest specific contact resistances (10 −5 –10 −4 Ωcm 2 ) are obtained from trials made on p-type epilayers [ 66 , 67 ], which eliminates the issue of acceptor activation. However, when fabricating power devices such as MOSFETs, it is crucial to obtain ohmic contacts on selective highly doped, mostly implanted p+ regions.…”

“…Until recently, however, fabricating 3C-SiC PiN diodes has been difficult, not only because of the high defect density within 3C-SiC epilayers caused by the lattice mismatch with Si [ 21 ], but also due to the lateral nature of structures necessary to avoid the 3C-SiC/Si heterojunction. While there are several reports on achieving n-type conduction in 3C-SiC epi/implanted layers [ 42 , 48 , 66 ], and p-type conduction in Al doped epilayers [ 66 , 89 ], it remains an obstacle for p-type implanted layers. This is mainly due to the post implantation anneal temperature, which was limited to the Si melting point, 1414 °C, which is not sufficient to activate the deep level Al dopants, even if hot implantation was applied.…”

A study on free-standing 3C-SiC bipolar power diodes

“…Low voltage lateral p-n junction diodes were previously demonstrated by forming implanted regions in 3C-SiC epilayers grown on Si substrates [10,11]. Furthermore, while there were several reports achieving p-type conduction in Al doped 3C-SiC epilayers [12][13][14], it remains an obstacle for implanted layers, which is often required in edge termination and JBS designs. This is mainly due to the post implantation anneal temperature, which is limited to the 1414 °C (melting point of Si), thus not sufficient to activate the deep level Al dopants.…”