Molecular Beam Epitaxy (MBE) and Thin-Film Growth Facilities
1. An integrated, hybrid, gas-source MBE (GS-MBE)/solid source MBE (SS-MBE) facility (see Figure 1). The growth system, which was made by Vacuum Generators (VG Scientific), consists of four interconnected sections:
a. two MBE/GS-MBE chambers fitted with three electron beam evaporators and effusion cells,
b. analysis, and
c. two load-lock chambers (only one is shown in the Figure 1.).
A third deposition chamber equipped with two electron beam evaporators, an analysis chamber, and a load-lock chamber with 10 sample magazine will be added to the system during the coming year. The cluster facility will be capable of loading 30 samples at a time.
This configuration combines the advantages of SS-MBE and GS-MBE (materials choice, temperature consideration, conformal growth, etc.). The SS-MBE growth chambers, which are shielded by a liquid nitrogen shroud, contain electron beam evaporators and provisions for up to four effusion cells, gas-source or solid-source low-energy ion guns. Each electron gun, made by Airco Temscal, is provided with a dual quartz microbalance for thickness measurements and deposition control, a pneumatic shutter, and an independent view port with shutter assembly to prevent deposition on the window. The chambers are also equipped for mass-spectrometry and provisions for reflection high energy electron diffraction (RHEED). The chambers have many additional ports that allow expansion of the system and the addition of other surface processing and characterization techniques. The facility is pumped by a combination of turbo pump, Cryo and titanium sublimation pumps unit while roughing is accomplished by using a root/mechanical pumping station. The Deposition chamber I, which is also cooled by a LN2 shroud, equipped for up to eight materials delivery sources and provisions for RHEED, mass-spectrometry, and thickness monitor. In addition, it can accommodate a 40cc or two smaller electron guns. The analysis chambers contain provisions for Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED). AES utilizes a CLAM2 hemispherical analyzer made by VG which is also capable of XPS/UPS measurements. An ion source is also available for surface cleaning and AES depth profiling. The computerized CCD-LEED/RHEED vision and profiling system will provide a detailed correlation of diffraction spots’ profiles versus the surface domain sizes, roughness and reconstruction. The three load-locks, which are pumped independently, can handle sample magazines with up to ten samples at each load-lock station.
The system base pressure is ~ 5×10-11 Torr. The facility can handle up to 3″ wafers in two of the deposition chambers and up to 4″ in the third chamber. Also, it can be modified to handle up to 6″ wafers. The substrate heater assembly is equipped with movable ion gauge to monitor the incident flux prior or during deposition.