Masao Naito

Activation of Silicon Implanted with Phosphorus and Boron Atoms by Infrared Semiconductor Laser Rapid Annealing

We report the activation of silicon implanted with phosphorus and boron atoms by infrared semiconductor laser annealing using carbon films as an optical absorption layer. 2-µm surface region was heated above 1000 °C longer than 22 µs by scanning the laser beam for a dwell time of 40 µs. We carried out implantations of 1 ×1015 cm-2 phosphorus atoms at 100, 300, and 500 keV, and boron clusters with a boron concentration of 1 ×1015 cm-2 at 6 keV. Laser irradiation at 375 kW/cm2 was conducted to activate impurities. Secondary ion mass spectrometry measurement revealed that laser annealing caused no substantial change in the phosphorus and boron atom profiles. Laser-induced recrystallization of surface amorphized regions caused by the ion implantation was analyzed using the optical reflectivity spectra ranging from 250 to 1000 nm. The free carrier absorption analyses indicated that the phosphorus and boron atoms were effectively activated by laser annealing.

Mass Filtering Function of Magnetic Boundaries in Multi-Cusp Ion Source

In a multi‐cusp ion source, magnetic boundaries, together with the difference between plasma potential and plasma chamber potential, functioned as a mass filter which filters out heavier ions in multi‐component plasmas. This method was applied to mixed inert gas plasmas and hydrogen plasmas and found to be very effective for general purposes which require to decrease unwanted heavier ions. Using this method to the ion source of iG4, target boron current above 80 mA and proton current above 120 mA were obtained.

Increase of Beam Current Mass‐Separated by Long Gap Dipole Sector Magnet for S/D Process in FPD manufacturing

A mass analyzing ion implantation system (called Ion Doping iG4) was developed for FPD manufacturing. One of most important concept of iG4 is to transport a sheet ion beam maintaining its current density profile from the ion source to the target, which leads good mass resolution and simple control of the beam profile. The system has a bucket type ion source which provides a sheet ion beam whose longer dimension of the cross section is 800 mm the 4th generation FPD glass substrate generally sized 730mm × 920mm. The sheet ion beam is mass‐analyzed with a dipole sector magnet with a long pole gap. In order to enhance through‐put for Source Drain implantation processes, we modified the ion source to increase high beam currents and obtained 300μA/cm for Boron ion beams and 500μA/cm for Phosphorus ion beams. Better uniformity and higher mass resolution were achieved by optimizing shape of the analyzing magnet pole faces.

NISSIN iG5 implantation tool for generation 5.5 in the flat panel display industry

We have developed a new implantation tool for the generation 5.5 glass. 150 cm high ion beams, which are bigger than the glass height, are extracted from the ion source. After being bent by the mass separation magnet, the beams reach the glass which is standing upright. The new tool exhibits high throughput in high dose applications because of high beam current capability. To cut down on time and workload of maintenance, dedicated kits were designed. A new cleaning method developed to extend the ion source lifetime showed excellent performance of reduction in the beam glitches.

Increase of Boron Ion Beam Current Extracted from a Multi‐Cusp Ion Source in an Ion Doping System with Mass Separation

A multi‐cusp ion source with large area extraction area has a capacity to extract high current ion beams. However it is difficult to obtain high current boron ion beams from boron trifluoride plasma as input power density is low and BF2+ is a main ion species. It was found that fluoride ion currents were selectively decreased by applying positive potential to a plasma electrode with respect to a plasma chamber. Using this method to a multi‐cusp ion source with adequate magnet configuration, high current boron ion beams of 500 μA/cm were obtained.

Ion sources for large area processing (invited)

Large area ion sources have been used in ion doping systems in the field of LCD production. In these ion sources good uniformity and wide dynamic range in beam current are both required to achieve the good dose uniformity in wide dose range. A new ion source which uses dc arc discharge with three filaments, each of which is controlled individually, is now in the production lines instead of the conventional rf discharge type. Better than 5% of beam uniformity across 600 mm is achieved by an automated feedback control using beam profile data taken by a built-in beam profiler in less than 10 s from arc ignition. Another emerging requirement is high beam purity, for the ion beams from these ion sources are used without mass analysis. The hydrogen ion fraction was successfully reduced by magnetically retarding the hydrogen ions to less than 5%. A large area ion source having a newly designed mass separating structure is developed. The structure is comprised of a permanent magnet array and a beamlet scanner jus...

Formation of Shallow PN Junction by Cluster Boron Implantation and Rapid Annealing Using Infrared Semiconductor Laser

We report shallow PN junctions and analysis of their electrical characteristics. Infrared semiconductor laser annealing using carbon films as optical absorption layer was adapted to the activation of silicon implanted with boron cluster ions. We carried out implantations of boron clusters at 6 keV with an equivalent boron concentration of 1.0×1015 cm−2. Laser irradiation at 375 kW/cm2 was conducted to activate impurities. Secondary ion mass spectroscopy revealed that boron atoms with a concentration of 6.0×1014 cm−2 were incorporated into silicon surface within a 10 nm depth. The free carrier absorption analyses and current‐voltage characteristics of the PN junction diode indicated that the boron atoms were effectively activated by laser annealing.

Doping Process and Tool for Surface Treatment Using Large-Area Ion Beams

Ion doping tools which have ability to process large size glass substrate with high productivity are briefly described. Such tools might develop new fields that utilize ion implantation technology. So far we tried several applications. In this study, three applications for which large area treatment will be essential to commercial production are reported.

Multi-cusp ion source for doping process of flat panel display manufacturing

We developed a multi-cusp ion source for Nissin ion doping system iG5 which is used in low temperature poly-crystalline silicon processes for flat panel display (FPD) manufacturing. In this ion source, BF3 or PH3 diluted H2 plasmas are produced and large area ribbon ion beams are extracted. In general, ion ratio of B(+) in BF3 plasma is much smaller than BF2 (+) in multi-cusp ion sources. We developed a new method to increase B(+) ratio and obtained mass analyzed B(+) target current of 130 mA. We employed newly improved multi-slot type electrodes for the beam extraction system and obtained stable beams with the uniformity of below 3%. In BF3 plasmas, several undesirable metal fluorides are produced in the plasma chamber and deposited on the electrode system, which cause glitches and poor beam uniformity. We introduce several cleaning methods.

Instability in low energy beams extracted from BF 3 plasma

Ion beam instabilities on a wide ribbon beam which cross-section is 150 cm × 10 cm are discussed. At low energy conditions, we detected two kinds of instabilities on the ion beam extracted from BF₃ plasmas. One kind of the instabilities is that onset of the instability is dependent on the extraction current from the ion source. This instability occurred when the extraction current exceeded 300 - 350 mA at the energy of 15keV. Another is that the onset is dependent on the BF₂⁺ beam current. The BF₂⁺ beam current became unstable when it exceeded about 20 μA/cm² at 15keV. Energy dependence of these instabilities is also discussed.