Victor M. Benveniste

Low energy ion beam transport

The need for ultra-shallow junction formation in advanced devices makes the development of high throughput ion implantation solutions at very low (sub-keV) energies increasingly more important. The fundamental challenges confronting the implant tool designer tasked with delivering these high throughput solutions are examined in this paper. A discussion of space charge and its implications for low energy beam transport is presented. The origins behind the shape of the classic beam current versus energy curve are detailed and the historical evolution of this curve is shown. Demonstration of the effects of space charge is made via consideration of beam current density and beam potential profiles under a variety of space charge conditions and highlights the importance of efficient space charge neutralization in the generation and transport of low energy beams. Issues resulting from space charge effects and related to the control of beam size, shape, and stability are outlined in the context of their importance to high productivity high current tool design. Improvements to ion source and beam extraction efficiency, and to overall beamline acceptance, have been the dominant historical paths leading to incremental improvements in low energy beam current performance. The adoption into production-worthy tools of deceleration mode and, more recently, molecular implantation for n-type dopants has further expanded the usable energy range of these leading edge tools. Most recently, significant developments to actively neutralize space charge have enabled even more substantial low energy beam current improvements. Performance details underlying this newest technology are presented.

Negative ions for heavy ion fusion and semiconductor manufacturing applications

Radio frequency driven multicusp source was set up to run chlorine plasma and the source performance was compared between positive and negative chlorine ion production. A maximum Cl− current density of 45 mA/cm2 was achieved at 2.2 kW of rf power with electron to negative ion ratio of 7 and positive to negative ion ratio of 1.3. 99.8% of the total negative chlorine beam was atomic Cl−. To produce negative boron ions for semiconductor manufacturing applications, a noncesiated, sputtering-type surface production ion source was constructed. An external rf antenna geometry and large LaB6 converter were implemented in the source design. Maximum B2− ion current density of 1 mA/cm2 was achieved at 800 W of rf power and −600 V converter voltage. Total B2− ion current was 1.8 mA.

Particle trapping and annihilation within the extraction system of ion sources

Many applications of ion sources (e.g., ion implantation in the semiconductor industry) are very sensitive to particles and have tight specifications on allowable particle number and size. Among the sources of particles are the ion source itself (due to either nucleation in the plasma, or ion bombardment of the surfaces), and the extraction electrodes (due to ion bombardment). This article investigates the processes to which such particles are subjected during their flight through the extraction electrodes. They travel at much lower velocity than the accelerated ions due to their much larger mass, and so are bombarded by these increasingly energetic ions. The processes considered during the trajectory of the particle are: charging, acceleration in the electrode fields, entrapment within the suppression gap, heating from ion bombardment, radiation cooling, melting, vaporization, and Coulomb explosion. These processes are all modeled simultaneously as the trajectory of the particle is followed. A general co...