Che-Hoo Ng

Charge control in a ribbon beam high current ion implanter

Wafer charge control has evolved from systems that add gas to the beam or extract electrons from an external source to systems that respond directly to beam potential and current density via an externally coupled plasma. The capability of a plasma to add low energy electrons to an ion beam greatly exceeds the ability of any extracted electron system due to space charge effects. However, even plasma coupled charge neutralization systems still show that effective charge control is more difficult as the beam current density increases. Further improvements have often been obtained by controlling the beam current density by deliberately increasing beam size. This can result in a loss of throughput and can result in possible contamination problems. An alternative approach to further improve charge control is to use a large area ribbon beam, which offers a very low beam current density during high current implantation. This paper presents results for wafer charging on a ribbon beam implanter, the Varian VIISta 80, incorporating a Plasma Flood Gun for charge control. These results are based on sensitive antenna structures using thin oxides with antenna ratios up to 100,000:1 and EEPROM devices.

Effects of pre-amorphization on junction characteristics and damage behavior in low energy boron implantation

One of the major challenges of meeting the source/drain extension requirements for high performance scaled devices is to achieve low series resistance with shallow junctions. Pre-amorphization has been used to suppress implant channeling and to enhance dopant activation during solid phase crystal re-growth. In this paper the effects of Ge premorphization on the activation of 1 keV boron implants under various thermal treatments have been investigated. The wafers were pre-amorphized with 5 keV 1/spl times/10/sup 15/ cm/sup -2/ Ge/sup +/ implant. Subsequent anneals on some samples were performed in a furnace at temperatures ranging from 500/spl deg/C to 750/spl deg/C for 30 min and some were processed by RTA at 800/spl deg/C to 1050/spl deg/C under various soak times. While the activation behavior above 700/spl deg/C for the crystalline and preaamorphized samples was similar, distinctly different behavior was observed at lower temperatures in the two cases. Lower sheet resistance was obtained In pre-amorphized samples below 300/spl deg/C but reverse annealing is observed when the temperature is increased. Spreading resistance and SIMS analysis were used to generate junction profiles. In addition, TEM analysis was done to understand the physics of the observed phenomenon and to investigate the merits and demerits of preamorphization from a process integration standpoint.

Material study of indium implant under channel doping conditions

In this paper we investigate the material characteristics of implanted indium under channel doping conditions. Indium was implanted into CZ silicon at an energy of 200 keV and doses of 2e12/cm2 to 1e14/cm2. Subsequent rapid thermal annealing was conducted at 950 degrees Celsius to 1050 degrees Celsius between 10 sec and 30 sec. The diffusion of indium was studied by means of Secondary Ion Mass Spectroscopy (SIMS). Up to a dose of 1e13/cm2, the diffusion of indium was in- significant. The activation of indium was studied by means of Spreading Resistance Profiling (SRP). It was found that at a concentration of about 2e17/cm3, the electrical solubility is reached above which no more activation can be achieved. Damage due to indium implant was studied by Transmission Electron Microscopy (TEM). Dislocation loops remain stable after high temperature anneal for higher dose implants and dissolve for lower dose implants.