Line Beam Research Articles

The design philosophy for a 200 kV industrial high current ion implanter

A third generation industrial high current ion implanter, Series III, has been produced for the uniform implantation of milliampere-beams with total acceleration voltages up to 200 kV. Magnetic analysis of the beam with initial acceleration voltages variable up to 40 kV is carried out in the accelerator terminal followed by post-acceleration across a single gap up to a maximum total acceleration voltage of 200 kV into a grounded processor chamber. The ion source is a Freeman type capable of delivering milliampere beams of most elements. The source feed materials for the three main ion species required by the semiconductor industry, i.e. B, P and As, can all be pumped by surfaces with temperatures down to liquid nitrogen temperature. Consequently large liquid nitrogen cryopump/traps are used as the primary pumping system with diffusion pumps having a secondary role for non-cryopumpable gases. Three stages of differential pumping are provided in the accelerator together with a 12″ pumping system for the processor. The large processor takes a maximum load of 108 2″ silicon wafers or 54 3″ silicon wafers. Mechanical scanning is used because of the need to maintain space charge neutralisation in the beam which rules out electrostatic scanning and also because of the need to distribute the heat dissipation over a large number of wafers in order to prevent an excessive temperature rise in the wafers during high dose implants (>10 15 ions/ cm 2). The carousel which carries the wafers is shaped so that the wafers pass through the beam in a straight line and at a constant speed. A stepper motor driven vane unit in the terminal controls the ion beam current. In order to achieve high implantation uniformities the processor dose control system controls the ratio ion current/carousel speed and therefore any small non-uniformities in the carousel rotation speed can be compensated by the vane unit. The various functions in the terminal are controlled from ground potential using fibre optics. The system is highly automated and unskilled operators can be used.

High power CO2 laser energy detector

A CO2 laser energy detector is described which uses the pressure rise generated in a vaccum cell by gaseous infrared absorption to provide linear energy detection over many decades, good responsivity, wide aperture, and in−line beam monitoring. Nonadiabatic pressure measurements resulting when the beam size is less than the cell aperture are discussed.

Picosecond Beam Monitor

A coaxial transmission line beam monitor with a risetime of approximately 18 psec is described. This monitor was used to examine the fine structure of the electron beam from an L-band linear accelerator.

LASER ACTION FROM TERBIUM TRIFLUOROACETYLACETONATE IN p-DIOXANE AND ACETONITRILE AT ROOM TEMPERATURE

Laser activity has been obtained from terbium tris (1, 1, 1-trifluoroacetylacetonate) at room temperature in a liquid solution in acetonitrile and in p-dioxane. Threshold pumping energy is about 1700 J. Characteristic line narrowing, spiking and beam collimation was exhibited.

PERFORMANCE OF A VIBRATIONAL H2-STOKES OSCILLATOR

A H2-Stokes Raman oscillator was constructed operating at 9755 Å, and its performance was found to be as expected of laser oscillators. No beam instability was developed (beam trapping), confirming earlier measurements. A significant beam brightness enhancement (in terms of line width and beam divergence) over that of the Q-switched ruby laser resulted.

A Note on Filter-Type Traveling-Wave Amplifiers

A small-signal analysis of systems in which an electron beam interacts with a circuit composed of discrete filter elements is given here. The effects of a line beam interacting with a series of gaps, which are capacitive elements of a filter structure, are calculated, and it is shown that an admittance can be introduced which arises from the presence of the electrons. This admittance is in parallel with the gap capacitance, and thus will alter the propagation factor of the filter circuit. It is shown that traveling-wave solutions exist for the combination of electron beam and filter circuit, and that there is a solution which has a positive real part, indicating that gain will be exhibited.