Selective vapor-liquid-solid epitaxial growth of micro-Si probe electrode arrays with on-chip MOSFETs on Si (111) substrates

This paper reports on a fabrication technique for realizing micro-Si probe arrays with MOSFETs on the same Si substrate. Micro-Si probe arrays have been successfully fabricated on Si (111) substrates by selective vapor-liquid-solid (VLS) growth using catalytic Au dot arrays and Si₂H₆ used as the gas source for a molecular-beam-epitaxy. The Si probes can be grown at temperatures ranging from 500°C to 700°C. In this paper, MOSFETs were fabricated on Si (111) substrates and Au dots were placed at the drain regions of the MOSFETs in order to grow the Si probes. VLS growth at 700°C for 2 h was carried out on these substrates. Consequently, the MOSFETs can be used in on-chip circuits for the VLS-Si probe array. The electrical characteristics of the MOSFETs were measured before and after the VLS process. After the VLS process, no changes in the MOSFET characteristics were observed due to the effects of Au-diffusion, and the results confirmed that VLS growth at a temperature of 700°C allows fabrication of micro-Si probes without deterioration of the MOSFETs. VLS-Si probes with controlled conductance were realized. The as-grown Si probes were of high resistance, but could be changed to various conductivities by impurity diffusion.