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Details of Grant 

EPSRC Reference: GR/J47071/01
Title: BURIED METALLIC LAYERS IN SILICON SUBSTRATES
Principal Investigator: Armstrong, Dr B M
Other Investigators:
Mitchell, Dr NSJ Gamble, Professor H Armstrong, Professor G A
Researcher Co-Investigators:
Project Partners:
Department: Sch of Electronics, Elec Eng & Comp Sci
Organisation: Queen's University of Belfast
Scheme: Standard Research (Pre-FEC)
Starts: 01 March 1994 Ends: 30 June 1997 Value (£): 196,131
EPSRC Research Topic Classifications:
EPSRC Industrial Sector Classifications:
Related Grants:
Panel History:  
Summary on Grant Application Form
The project will investigate the main processes necessary to obtain buried metal layers in silicon structures. An LPCVD system will be constructed to deposit tungsten layers from WF6 Micromachining techniques in combination with direct wafer bonding will be used to produce buried tunnels. In-situ plasma clean followed by selective deposition on tunnel walls will produce the buried metallic layers. A demonstrator device e.g. a power bipolar transistor, will be manufactured.Progress:This grant application was only part funded. The manpower was reduced by 50% and therefore the original objectives have had to be scaled down.The initial phase of the project was concerned with the building of a CVD system suitable for the selective deposition of tungsten. This can best be achieved with a rapid thermal processor which is loadlocked to eliminate moisture contamination during wafer loading. Originally it was intended to upgrade a QUB designed and built reactor, but a previously used Varian 5101 CVD system became available. This system had been specifically designed for tungsten deposition and possessed all the required features for the present work. It was therefore decided to install and refurbish the Varian system so that it was capable of selective tungsten deposition by RTCVD. A turbo pump is being fitted to allow evacuation to a base pressure of approximately 10-8 torr. This is particularly important as tungsten hexafluoride is readily hydrolysed by moisture. It also enables the entire system to be pumped with the turbo via the loadlock to eliminate moisture before initial start up and also the use of Residual Gas Analysis to check chamber environment. The rotary and roots pumps have been built into a frame and positioned in a service corridor close to the system. The main roots pump is connected to the chamber via a 100 mm diameter pipe to ensure high conductance. Nitrogen purge gas has been plumbed to all the pumps to ensure dilution of the hazardous gases. A safety interlock system prevents processing should the purge flows fall below a suitable level. The gas control box on the system has been connected to an exhaust purge and the necessary process gases are being connected via welded stainless steel pipes. The WF6 requires the installation of a new gas bottle cabinet with associated control regulators. This line is required to be heated to prevent condensation of the WF6. A gas monitor has been purchased to warn against any WF6 leaks.Water cooling supplies have been provided to the system and electrical installation is complete. The on board computer has been installed and the control of basic functions verified. The installation of the system is nearing completion and trial runs will commence in April 1995.
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Organisation Website: http://www.qub.ac.uk