... first an overview
Where and what is the CIMD lab? The CIMD laboratory is dedicated to the synthesis of new materials and occupies a 400 square feet clean-room of class 100, located inside the IBeAM Facility of the basement of the Goldwater Center at ASU. This feature provides the CIMD lab with next door access to analysis for the new materials grown in the CIMD lab.
The IBeAM Facility houses a 1.7 MeV Tandem ion accelerator for RBS/Ion Channeling used extensively to characterize the composition and structure of the thin films and interfaces grown in the clean room. The IBeAM is shared by Profs. Culbertson, Mayer and Herbots, and overseen by AP B. Wilkens. The IBeAM can be seen through the windows of the clean-room.
Class 100 means than less than 100 particulates larger than 0.3 microns fall per cubic feet per minute in the room. The containment outfits worn by the researchers shown in the lab, and all the surface materials in the clean-room are all selected to minimize particulate shedding. The CIMD laboratory contains several class 10 laminar flow hoods for sample preparation and storage, and used as workbenches for ultra-high-vacuum components, which are discussed and shown in pictures here below.
What is it for? Nicole Herbots and her group of students research low temperature methods of synthesis and processing of new semiconductor thin films such as SiGeO2, epitaxial silicon dioxides, SiGe, SiGeC, SiGeC oxides, and GaAs Oxides. The synthesis methods used include CIMD (US Patent 4,800,200, N. Herbots et al) which combines molecular beams, ion beam deposition, and IBO (Ion Beam Oxidation), and new low temperature surface processing techniques to produce templates for epitaxy
THE PICTURE: The view shows the ultra-high-vacuum chamber used for CIMD deposition on the right, with a graduate student in Physics, Joan Xiang , seated and examining the carbon deposition source through a small window Kurt Daley, a graduate student in Science and Engineering of Materials stands next to the small loadlock chamber of the CIMD system. He holds a 4 inch silicon wafer that he poised to insert into the loadlock. The orange transfer rod on the left enables the transfer of the wafer from the loadlock to the vacuum system.
A smaller, intermediate vacuum chamber is attached on the left hand side, and acts as a buffer between the loadlock where wafers are loaded from atmosphere and the deposition CIMD deposition chamber whose base pressure is 5 x 10-10 Torr.
The larger, cylindrical vacuum chamber houses deposition hardware for various materials, such as Si and Ge (on the largest side flange on the right).
It also supports different oil-free vacuum pumps to maintain the base pressure, such as cryopumps, ion pumps and sublimation pumps (one of the cryopumps can be partially seen on the far right )
Several monitoring devices control the species and the rate of deposition via a feedback loop connected to the deposition hardware. They include a quartz monitor, Electron Induced Electroluminescence Spectroscopy (EIES) sensors (above the large source flange), ion gauges (not seen), and Reflective High Energy Electron Diffraction (RHEED). The camera used to capture RHEED diffraction patterns is seen on the far right just above the cryopump.
Many items..
For example:
Key elements of the CIMD system are commercial electron beam evaporators (called e-guns) used to produce the molecular beams.
Shown here at left are the Si and Ge electron beam evaporation units pulled out of the chamber for much needed maintenance. Debris of previous deposition can be seen littering the copper blocks forming the e-guns..
The copper blocks, which are water-cooled during operation, each contain a 40 cc hearth where the either Si and Ge solid charges are inserted. The Si e-gun on the left is almost empty. The Ge e-gun on the left has Ge material recessed in the earth.
The electrical connections isolated by a string of cylindrical ceramic beads are seen on the right hand side.
After careful cleaning and loading of new Si and Ge material, the e-guns are ready to be inserted back into the system.
The shroud is a double-walled stainless steel "box" which can be cooled with water or liquid nitrogen. Shutters are seen above the holes in the shroud giving access to the molecular hearths allow for the formation of alternating layers. The hole in the shutter allows sampling of the molecular beam by the sensors while the shutter is shut. The evaporation rate can thus be adjusted prior for the deposition to commence.
THE PICTURE: Suresh Chandrasekaran (Graduate Student in Electrical Engineering) and Sean Hearne (Graduate Student in Physics) finish rinsing a silicon wafer with 18 MegOhms deionized water after chemical surface processing in the chemical laminar flow hood.
Many of the specialized research apparatus was designed and built by Prof. Herbots and her students with the Physics Department machine shop.
Many of the specialized research apparatus was designed and built by Prof. Herbots and her students with the Physics Departement machine shop.
This box was designed by Vasu Atluri during his Ph.D. thesis in Materials Engineering.
A smaller controlled atmosphere loadlock, also designed by Vasu Atluri, limits the introduction of atmospheric contaminants when loading wafers in the vacuum loadlock below.
Suresh Chandrasekaran (on the left), one of Prof. Herbots 's Graduate Student in Electrical Engineering, examines a compact deposition chamber that he designed. The chamber was then built by the Physics Machnine Shop at ASU.
