An attempt has been made to improve the electrical and metallurgical stability of Au-Be alloyed contacts to moderately doped p-type InP by minimizing the thickness of the Au-Be contacts layer and using an Ru layer as a new, more effective diffusion barrier between the Au-Be and a thick Au top layer. It was found that the Au-Be contact layer only 40-50 nm thick is sufficient to give excellent ohmic contacts with specific contact resistance values as low as 2x10-8 and 7x10-8 Ω m2 (for NA-ND=(2-4)x1024 and (0.8-1)x1024 m-3 respectively). When subjected to an aging test at 280°C for 50 h in N2 gas, the 50 nm Au-B2/50 nm Ru/300 nm Au contacts alloyed at an optimum temperature of about 425°C exhibit good thermal stability and no substantial increase in the specific contact resistance. The remarkable metallurgical stability of such contacts was confirmed by secondary neutral mass spectroscopy (SNMS) in-depth profile measurements. A comparison with the previously investigated diffusion barrier metals (such as Cr, Ti, Pt, etc) shows that the Ru layer is much better barrier against the migration of Au into the InP substrate and, at the same time, it suppresses the out-diffusion of in and P from the semiconductor.
Au-Be/Ru/Au Multiplayer Metallization as Stable Ohmic Contact Scheme to P-type InP
Micheli, Victor;
1996-01-01
Abstract
An attempt has been made to improve the electrical and metallurgical stability of Au-Be alloyed contacts to moderately doped p-type InP by minimizing the thickness of the Au-Be contacts layer and using an Ru layer as a new, more effective diffusion barrier between the Au-Be and a thick Au top layer. It was found that the Au-Be contact layer only 40-50 nm thick is sufficient to give excellent ohmic contacts with specific contact resistance values as low as 2x10-8 and 7x10-8 Ω m2 (for NA-ND=(2-4)x1024 and (0.8-1)x1024 m-3 respectively). When subjected to an aging test at 280°C for 50 h in N2 gas, the 50 nm Au-B2/50 nm Ru/300 nm Au contacts alloyed at an optimum temperature of about 425°C exhibit good thermal stability and no substantial increase in the specific contact resistance. The remarkable metallurgical stability of such contacts was confirmed by secondary neutral mass spectroscopy (SNMS) in-depth profile measurements. A comparison with the previously investigated diffusion barrier metals (such as Cr, Ti, Pt, etc) shows that the Ru layer is much better barrier against the migration of Au into the InP substrate and, at the same time, it suppresses the out-diffusion of in and P from the semiconductor.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
