Growth and Characterisation of 4H-SiC MESFET structures grown by Hot-Wall CVD
- PDF / 279,103 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 93 Downloads / 201 Views
Growth and Characterisation of 4H-SiC MESFET structures grown by Hot-Wall CVD U. Forsberg, A. Henry, Ö. Danielsson, N. Rorsman1, J. Eriksson1, Q. Wahab, L. Storasta, M.K. Linnarsson2 and E. Janzén Department of Physics and Measurement Technology, Linköping University SE-681 83 Linköping, Sweden 1 Department of Microelectronics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden 2 Solid State Electronics, Royal Institute of Technology, SE-164 40 Kista, Sweden
ABSTRACT Metal semiconductor field effect transistor, MESFET, structures have been grown in a hot-wall CVD reactor. Using trimethylaluminium and nitrogen as dopant sources, p- and n-type epitaxial layers were grown on semi insulating substrates. A comprehensive characterization study of thickness and doping of these structures has been performed by using scanning electron microscopy, secondary ion mass spectrometry, capacitance-voltage measurements. Each technique is discussed concerning its advantage and disadvantage. Some transistor properties of MESFETs processed on the grown material are presented.
INTRODUCTION A Metal semiconductor field effect transistor (MESFET) structure comprises several different (both n- and p-type) epitaxial layers and the total thickness is usually less than 2 µm. The transitions between each epilayer are requested to be very abrupt and the doping and thickness uniformity on a wafer is very important to obtain a high device yield and uniformity. A MESFET structure is considered as a relatively simple transistor structure but there is still a lot of work to be done in growing these structures and to develop reliable routine characterisation methods. No real investigation has been made on the growth of MESFET structures in a hot-wall CVD reactor. The challenge with abrupt interfaces and sharp doping profiles will be presented. Results from different characterisation techniques for doping and thickness will be presented as well as electrical properties and device performance.
EXPERIMENTAL 1
GROWTH SYSTEM
The reactor used in this work is a commercial hot-wall CVD reactor. The reactor has been modified “in house” to fulfil our demands of intentional nitrogen and aluminium doping. The precursors were silane (5 % in H2 N60) and propane (5 % in H2 N60). Palladium diffused hydrogen was used as carrier gas. Nitrogen (N60) was used for n-type doping and H2.3.1
trimethylaluminium (TMA) for p-type. The SiC coated graphite susceptor was inductively heated by an RF generator. The temperature was measured by a two-colours pyrometer and was focused on a drilled hole on the backside of the susceptor, giving an approximation of a black body. Silicon melting was performed to calibrate the temperature inside the susceptor with an accuracy of ± 6 °C. The base pressure in the reactor chamber before growth was always lower than 2⋅10-6 mbar. A hydrogen flow of 13 l/min, 21 ml/min of propane, 18 ml/min of silane, a C/Si =3.5 and a growth rate of 2.5 µm/h (≈7 Å/s) were used. All growth runs were performed at atmospheric pressure at a growth
Data Loading...
