Formation and electrical properties of Hf Si2 grown thermally from evaporated Hf and Si films

Abstract

MeV4 He+ backscattering spectrometry and x-ray diffraction have been used to study HfSi 2 formed by thermal annealing of a Hf Si film on evaporated Si (Si•) at temperatures between 575 and 650 ·c. A laterally uniform layer of Hf Si 2 forms and its thickness is proportional to the square root of time at a fixed temperature. The activation energy of this reaction is found to be 3.5 ± 0.3 eV. This transport-limited process differs from that observed on single crystal Si, where Hf Si 2 forms at temperatures above 700 ·c by a process believed to be nucleation controlled. Fourpoint probe measurements of resistivity and Hall coefficient at room temperature on samples with both Hf Si and Hf Si 2 were used to determine that both Hf Si and Hf Si 2 are electron conductors.For HfSi 2 , the electron concentration is 2.9 ± 0.2X 10

Diffusion Rates of Components in Metal-Silicides Depending on Atomic Number of Refractory Metal Component

“…The same phenomena are reported in this system also. The monosilicide phase HfSi is reported to grow first before the growth of the disilicide phase HfSi 2 at the interface of Si/HfSi 2 interface by nucleating on HfSi [23,27]. The phase is found to grow parabolically with time indicating the diffusion controlled process [27].…”

“…They also reported Si as the faster-diffusing component. So et al [27] studied the and calculated the activation energy as 3.5±0.3 eV. (337±29 kJ/mol).…”

“…The monosilicide phase HfSi is reported to grow first before the growth of the disilicide phase HfSi 2 at the interface of Si/HfSi 2 interface by nucleating on HfSi [23,27]. The phase is found to grow parabolically with time indicating the diffusion controlled process [27]. Ziegler et al [23] reported the activation energy for growth of the HfSi 2 phase as 2.5 eV (241 kJ/mol).…”

Hafnium silicide formation onSi(001)

“…The Hf/Si system has been investigated previously in the hope of forming silicide device interconnects having low sheet resistance and contact resistivity [6,7,8]. In these works, Hf was deposited on Si substrates, and the kinetics of the reaction to form HfSi and then HfSi 2 were monitored.…”

“…Si was found to be the dominant diffusing species. For a film of Hf on crystalline Si, HfSi would form in a layer-wise fashion between the Si substrate and the unreacted Hf, but the formation of HfSi 2 would nucleate heterogeneously [7] unless excess Si was supplied in the form of an amorphous Si capping layer [8]. Later work focused on the thin (~12 nm) amorphous hafnium silicide layer that is formed at the Hf/Si interface at annealing temperatures of 400-500˚C [9,10,11].…”