• PDF / 1,493,103 Bytes
• 6 Pages / 414.72 x 648 pts Page_size
• 92 Downloads / 269 Views

DOWNLOAD

REPORT

---

ABSTRACT A new bias-enhanced nucleation method based on an AC-bias step to form highly oriented diamond (HOD) nuclei on silicon substrates is presented. The uniformity of the nucleated film and the bias time strongly depended on the substrate temperature and the substrate holder. In our case the shortest bias time and highest nucleation densities were achieved at - 850'C while using a graphite susceptor. Following this nucleation enhancement step the diamond films were grown out using conditions employing an (a-parameter slightly greater than 2. This ultimately leads to extremely smooth and well-faceted (100) textured HOD films which could be used as substrates for the fabrication of electronic devices. Schottky diodes with high rectification ratios and high breakdown voltages have been fabricated for the first time via selective growth of the active boron doped diamond layers on these HOD films. Results of the growth procedure and diode performance will be given.

INTRODUCTION Synthetic diamond is readily used for tribology purposes; however, this unique material also holds promise for commercial application in the microelectronics arena. Although significant progress has been made in the fabrication of diamond over the past decades, the development of large area single crystals has not yet been achieved. Further improvements in diamond synthesis are essential in order for diamond to realize its full potential. The recent development of a nucleation enhancement process, termed biasenhanced nucleation (BEN), which is performed in situ during microwave plasma chemical vapor deposition led to the discovery of obtaining broad area highly oriented diamond (HOD) on P3-SiC1 and Si(100) 2 ,3 . The microelectronic character of these films was first investigated by Stoner et al.4 . Later work by Fox et al.5 revealed carrier mobilities approaching that of devices fabricated via homoepitaxial diamond growth. 63 Mat. Res. Soc. Symp. Proc. Vol. 423 01996 Materials Research Society

The purpose of this paper is to discuss the application of BEN utilizing an AC bias rather than the conventional DC bias source used in previous works1 -5 . It has been observed that a carburization treatment prior to BEN is essential for growing oriented diamond on silicon 3 . Alternating current bias-enhanced nucleation (AC BEN) was observed to form HOD without this additional carburization pretreatment. Subsequent to AC BEN, diamond growth was carried out to form a (100) textured HOD film. Au-Schottky diodes were then fabricated on these surfaces. The fabrication and rectifying character of these devices will be discussed.

EXPERIMENTAL Diamond deposition was undertaken in an ASTeXTM microwave plasma chemical vapor deposition (MP CVD) chamber using methane and hydrogen as source gases. This growth system has been modified so that a bias potential may be applied to the substrate. One pole of a 50Hz voltage source is connected to the metal casing of the thermocouple which is situated in the graphite susceptor containing the substrate and the other