ADVANCED THIN FILM LABORATORY

Director: Dr. Aurangzeb Khan

The Excimer laser is an electronically excited molecular gas laser, which emits high intensity, short duration pulses of ultraviolet energy. By using different gas combinations in the laser cavity, emission can be made to occur at any of several ultraviolet wavelengths. The system used in this lab is optimized for fluorine-based gasses, hence limited to three wavelengths; ArF 193-nm, KrF 248-nm and XeF 352-nm.

Currently all the work (deposition) in the Advanced Thin Film Laboratory of USA is being conducted with KrF 248-nm wavelength. The output energy can be as high as 550-mJ/pulse with a frequency of pulses at 30 Hz.

OPTICS: Excimer Laser system produces a laser beam, which consists of several wavelengths. The dielectric mirror, which is coated to split the incoming UV spectrum into two beams. It reflects 248-nm wavelength energy and transmits the remaining energy to rectify all non-required wavelengths. This reflected energy beam of 248-nm wavelength is then directed to the deposition chamber to evaporate target material.

Deposition Chamber. The six-way cross-vacuum deposition chamber at Advanced Thin Film Laboratory of USA is custom designed and is used for growth of epitaxial thin films by laser-induced physical vapor deposition from solid sources. A vacuum as high as 10^-7 Torr is achieved.

Mass Flow Controller. A four channel (MKS # 1159B-00100SV) supply/readout (MKS #247C) mass flow controller is installed at USA’s Advanced Thin Film Laboratory to control the flow of gases to attain a predetermined pressure of certain gases in vacuum chamber.

Temperature Controller: Deposition system at USA Advance Thin Film Laboratory is recently equipped (added) with a Neocera 2" substrate heater assembly and Eurotherm Programmable temperature controller (2408). Heater is designed for maximum temperature of 950⁰ C for vacuum to oxygen environment.

Chemical Vapor Deposition (CVD),

In Chemical Vapor Deposition solids are deposited from gaseous precursor onto a substrate with high deposition rate (approx. 10um/hr). Hot filament CVD uses tungsten wire as hot filament. Mixture of CH4 and H2 is fed into the chamber through a single line. A mass flow ratio of approx. 100:1 is maintained. The main purpose of hot filament is to dissociate molecular hydrogen into atomic hydrogen. This atomic hydrogen reacts with CH4 and deposit solid Carbon on the substrate.

RT66A Standardized ferroelectric Test System

The RT66A Standardized Ferroelectric Test System is specifically designed to perform the tests required for characterizing non-linear ferroelectric thin films or specific bulk ceramic devices. It combines the features of a function generator, an electrometer and a digital oscilloscope in a single package. The tester is controlled from a IBM PC or compatible. The user specifies the operations, which the tester is to perform from a menu driven interface. The RT66A software then executes the appropriate hardware commands, collects and processes the data, and then displays the results on the user's screen.

The RT66A has following software:

• CHARGE: Allows the user to perform hysteresis, pulse response, and bipolar resistively measurements. From hysteresis data, the program can compute capacitance vs. voltage and normalized capacitance vs. voltage data.
• FATIGUE: Allows the user to measure the effects of fatigue on a ferroelectric capacitor. After each fatigue period a pulse polarization measurement is performed on the test sample. The fatigue pulses may either be internally generated by the RT66A test unit or provided externally by the user.
• MANUAL: Allows the user to perform the same measurement as the CHARGE program while allowing the user greater flexibility in defining the drive profile used in the tests.
• RESIST: Allows the user to measure changes in the resistivity of a ferroelectric capacitor due to long term DC bias.
• RETAIN:Allows the user to measure retention loss of a ferroelectric capacitor.

The RT66A is equipped with following hardware accessories:

• High Voltage Interface (HVI): The HVI is a unique accessory unit designed to expand the capabilities of the RT66A to high voltage and large capacitor value testing of nonlinear ceramic devices.
• Multiplexer (MUX): The 24:1 Mux expands the number of controllable outputs for the RT66A, allowing the user to connect up to 24 samples simultaneously to the tester.

4192A LF IMPEDANCE ANALYZER

The HP Model LF Impedance Analyzer is a fully automatic , high performance test instrument designed to measure a wide range of impedance parameters as well as gain, phase, and grooup delay. The 4192A improves efficiency and quality in development and production of many types of complex components, semiconductors, and materials. Complete network analysis of devices such as filters, crystals and audio and vedio equipment, plus evaluation of the impedance characterestics of their circuit components, csn be performed.

Keithley Model 617 Programmable Electrometer

The Keithley Model 617 Programmable Electrometer is a highly sensitive instrument designed to measure voltage, current, charge, and resistance. Two forms of resistance measurements are included in the standard configuration: a constant current method, and a constant voltage method that uses a built in voltage source for greater sensitivity. The measuring range of the Model 617 is between 10m V and 200V for voltage measurements, 0.1fA to 20mA in the current mode, 0.1W and 200W G (up to 10^16W using the built in voltage source), and 10fC and 20nC in the Coulombs mode. The very high input impedance and extremely low input offset current allow accurate measurement in the situations where many other instruments would have detrimental effects on the circuit being measured. A 4 1/2 digit display and IEEE-488 interface give the user easy to access to the instrument data.