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New challenges to the modelling and electrical characterisation of ohmic contacts for ULSI devices

Microelectronics Reliability
Publication Date
DOI: 10.1016/s0026-2714(00)00006-8


Abstract Continuing developments in semiconductor process and materials technology have enabled significant reductions to be achieved in the contact resistance R c of devices. This reduction is commonly assessed in terms of the specific contact resistance (SCR) parameter ρ c (Ω cm 2) of the metal–semiconductor interface. Such a reduction in SCR is essential, for as device dimensions decrease, then so also must ρ c and the corresponding contact resistance in order not to compromise the down-scaled ULSI device performance. Thus the ability to accurately model contacts and measure ρ c is essential to ohmic contact development. The cross kelvin resistor (CKR) test structure is commonly used to experimentally measure the Kelvin resistance of an ohmic contact and obtain the specific contact resistance ρ c. The error correction curves generated from computer modelling of the CKR test structure are used to compensate for the semiconductor parasitic resistance, thus giving the SCR value. In this paper the increased difficulty in measuring lower ρ c values, due to trends in technology, is discussed. The challenges presented by the presence of two interfaces in silicided contacts (metal-silicide–silicon) is also discussed. Experimental values of the SCR of an aluminium–titanium silicide interface is determined using multiple CKR test structures.

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