NANOSTRUCTURES BY CVD ASSISTED METHODS USING INORGANIC PRECURSORS

摘要

Due to particularly well adapted precursors, and improved technologies local nanometric size deposition (dots, lines and bridges) by CVD (Chemical Vapor Deposition) finds a new youth. These deposition techniques are STM (scanning tunneling microscopy) assisted CVD (STM-CVD) and electron-beam induced deposition (EBID). The precursors investigated in this paper are inorganic rhodium and gold volatile transition metal complexes. The complexes, (RhCl(PF_3)_2)_2 and AuCl(PF_3), are solids at room temperature with a moderate partial pressure (5.5xl0~(-2) Torr for (RhCl(PF_3)_2)_2). The latter compound decomposes in the 130-200°C temperature range into pure metal, as analyzed by ESCA of the obtained rhodium film. Besides dots and lines, EBID can produce nanosized high aspect ratio supertips and sophisticated 3D structures which can be used as sensing tips and bridging of broken contacts in microelectronic circuits. High metal content EBID with [RhCl(PF_3)_2]_2 was achieved. Energy dispersive X-ray spectroscopy (EDXS) with TEM revealed a Rh/P ratio of 4:1 and Auger electron analysis shows that the deposited lines contain up to 60%at Rh. High resolution TEM images and diffraction patterns reveal Rh-nanocrystals of about 5-10 nm in diameter. Application are local X-ray mask repair, electrical repair in microelectronics and supertips for scanning probe microscopy. Using local CVD in the tip-sample gap of a scanning tunneling microscope, we demonstrate the controlled deposition of noble metal dots and lines. 3nm-diameter rhodium or gold dots have been patterned by local decomposition of these inorganic precursors. Deposition is obtained on gold surfaces by applying a series of negative voltage pulses on the sample exceeding a voltage threshold of around 2V. In a second step, the deposition process has been applied on hydrogenated silicon (100) surfaces. The influence of kinetics parameters (pulse duration, number of pulses and voltage amplitude, as well as the effect of gas pressure) are presented. The difference in the deposition processes observed in both cases is discussed.