Barrier height engineering of CoSi₂ Schottky contacts on n-type and p-type Si(100)

Shao-Pin Chiu^1*, Bai-Chen Lee¹

¹Department of Physics, Fu Jen Catholic University, New Taipei City, Taiwan

* Presenter:Shao-Pin Chiu, email:fluentbb@gmail.com

Cobalt disilicide (CoSi₂) has been used for many years as interlinks and Ohmic contacts in silicon integrated circuits. The superconducting temperature of CoSi₂ is close to that of aluminum (≈ 1.5 K). It can exhibit unconventional superconductivity induced by heterostructures. A lateral CoSi₂/Si/CoSi₂ structure on a Si substrate can serve as a quantum dot device because CoSi₂/Si Schottky barriers naturally form and serve as potential barriers for confining the charge carriers in the middle Si part which is the dot area. Therefore, studying the properties of the CoSi₂/Si Schottky interface at low temperatures is crucial. We use thermal evaporation to in situ deposit a silicon layer and then a cobalt layer on n-type or p-type Si(100) substrates, and then use high-vacuum annealing to transform the deposited film into CoSi₂/Si Schottky contacts. We use a closed-cycle refrigerator (base T ~ 8 K) and a Keithley 2401 SourceMeter to measure the I-V characteristics of CoSi2/Si contacts at temperatures between 300 and 8 K. After analysis with thermionic emission theory, we extract Schottky barrier height (Φ_Bp) for lightly p-type Si substrates to be about 0.45 eV at room temperature. Φ_Bp decreases with decreasing temperature. It's down to ≈ 0.2 eV at 80 K. We found that the doping level and dopant types (n- or p-type) are important to the temperature behavior of Φ_Bp. The Φ_Bp below 80 K is still under study.

Keywords: Cobalt disilicide, CoSi2/Si contact, Schottky barrier height