Ion implanters: chemical and radiation safety

Classified abstracts 6913-6922 SiH4/NH3 with a variable N20 flow-rate is controlled by the addition of the N20 gas. As the oxygen content in the film is increased a corresponding shift in the Si-N IR peak frequency takes place to higher wavenumbers. Also the ratio of Si H / N H bonds is changed such that the N - H bonds are favoured for increased oxygen content. The mechanical stress in the film is related to the Si/N ratio. The oxynitride wet etch rate is determined by the film stress and Si/N ratio. The dry etch rate using C H F 3 + O 2 is influenced by the film density and the Si H / N H bond ratio. S P Speakman et ul, Vacuum, 38, 1988, 183 188. 23 6913. Deposition of hard carbon films by the r.f. glow discharge method Hard carbon films were produced by the r.f. glow discharge plasma decomposition of the hydrocarbon gases CH4 and C2H4 diluted with H2. Optical emission spectra and ionic densities in the plasmas were measured during the deposition of the carbon films, and a correlation between the carbon film's properties and the plasma's condition was established. From these results, ionic species were concluded to be very important for the formation of hard carbon films. The films were examined by transmission electron microscopy, and the growth of diamond particles was observed in the hard films. The CH3 radicals were suggested to promote the growth of diamond. The hard films obtained had about half the hardness of diamond. Several properties of the hard carbon films were also examined. Kenji Kobayashi et al, Thin Solid Film, 158, 1988, 233-238. 23 6914. The deposition rate dependence of plasma polymerization on the radius of curvature of the substrate In the plasma polymerization deposition of CHx onto microspherical inertial fusion targets we have found that the coating rate varies with substrate diameter. Spherical shells ranging in diameter from I00 to 1000/~ were coated with several microns of plasma polymerized trans-2-butene under identical conditions and their coating thicknesses measured interferometrically. We found that the coating rate variation with shell radius could be described by an equation having the form dr/dt = A/(R + r) 4- B, where dr/dt is the coating rate, R the initial sphere radius, r the coating thickness, and A and B parameters related to the plasma conditions. We also found that there exists a functional relationship between the parameters A and B which is dependent on the rfpower density. A model has been developed to show how this observed rate dependence relates to the buildup of an electrical charge on the nonconducting substrate surface. The electric field which arises is dependent on the radius of curvature of the substrate and in turn affects the contribution to the film growth by the ionized species impinging upon the surface. Neutral species arriving at the surface are not affected and thus lead to the B term in the empirical form of the rate dependence. H K Lintz et al, J Vac Sci Technol, A6, 1988, 1869-1871. 23 6915. Growth of AI and AI nitride films in Nz-Ne and N 2 - ( N e + A r ) discharges : construction of a ternary gas phase diagram An A1 target was sputtered in N2, N2-Ne and 5% N 2 ( N e + A r ) discharges. The resulting films were studied by X-ray diffraction, Rutherford backscattering spectroscopy and resistivity measurements. The results were combined with data previously obtained for the N2-Ar system. A three-gas composition diagram was constructed onto which phase evolution in the films was mapped. In general, phase evolution proceeded as follows : A1 ---,microcrystalline cermet --* microcrystalline A1N-* multiorientation A1N ~ single basal orientation A1N. For the same nominal discharge N2 content, the use of Ne in place of Ar as the rare-gas component of the discharge suppressed the formation of the A1, cermet, and microcrystalline A1N phases, and enlarged the region over which basal orientation A1N was formed. In situ optical emission spectroscopy data suggested that this result is related to an increased N+/A1 ° flux in the discharge when Ne rather than Ar gas was used. James R Siettmann and Carolyn Rubin Aita, J Vac Sci Technol, A6, 1988, 1712-1716.

III. Particle beam technology and processing of materials 30. PARTICLE BEAMS A N D SOURCES 30 6916. Uhv linear actuators for N S L S beam lines Linear actuators used for beam line operations in the National Synchro982

tron Light Source are described. The standard model, many of which are built and in use, is outlined. Details are given of some more recent developments in this field. T Oversluizen, Vacuum, 38, 1988, 27-30. 30 6917. New microwave ion source for multiply charged ion beam production To obtain high-current beams of rather lower-charge-state multiply charged ions, a new microwave ion source is designed. Ion beams of a few mA are extracted from the plasma and mass-analysed. The extracted beams have large quantities of multiply charged Ar ions at relatively lower gas pressures of 10 4-10 3 Pa. In addition, these quantities tend to effectively increase with microwave power. The microwave power necessary for mA-class implantation current of low-charge-state ions is estimated to be from 3-5 kW. K Tokiguehi et al, Vacuum, 38, 1988, 487~490. 30 6918. The development and use of a time-of-flight system to analyse energy spectra produced by a fast atom beam source This paper describes the development of pulsing, time-of-flight and data acquisition and processing systems and their use in order to generate and analyse energy spectra for beams containing a high proportion of fast atoms. The systems were employed in the study of beams produced by an Ion Tech FAB I 1 saddle-field fast atom beam source and results are presented of mean energies, energy spread and resolution, neutral content and proportion of doubly charged species in the beam. S O Stied et al, Vacuum, 38, 1988, 469-473. 30 6919. Optimisation of the properties of a microfocuscd ion beam system The chromatic aberration of optical columns used to produce microfocused ion beams is examined in detail. Numerical solution of Poisson's equation and optimisation algorithms are used to ascertain the best possible design. The results show that, if the ultimate resolution of the column is limited by chromatic aberration, then microfocused spots o f less than 20 nm diameter should be achievable with acceptable current densities for a number of technological applications. R J Amos et al, J Phys E: Sci Instrum, 21, 1988, 8(~91. 30 6920. Ion implanters : chemical and radiation safety Recommendations to reduce chemical and radiation hazards for ion implanters are described along with pertinent regulations. Data are presented on production and maintenance operations. Routine chemical and radiation exposures during production operations are at least an order of magnitude below allowable limits. Airborne exposures during maintenance operations can be easily controlled by local exhaust ventilation and by keeping residues wet during cleaning operations. Without these controls, excessive exposure to airborne arsenic can occur, particularly when personnel clean source housing chambers of solid source arsenic implanters. David G Baldwin et al, Solid State Technol, 31, 1988, 99-105. 30 6921. Broad ion beam modeling for extraction optics optimization and etching process simulation A r 3del for calculating the ion~current density distribution of a broadbeam ion source at the target level is proposed. Three model parameters related to a single beamlet such as the beam divergence, the maximum ion-current density in the beamlet center, and a possible misalignment between the different grids are needed to describe the overall extraction performance. These parameters were determined partially with the AXCEL simulation code or experimentally via etch tests. In this work the model parameters have been determined for a capacitively coupled filamentless 13.56 MHz rf source operated with argon at low power levels ranging from 20-100 W and low acceleration voltages (100-1000 V). However, the model proposed is applicable also for other types of ion sources, for different extraction grid sets with varying geometry and a wide range of working conditions. Intensity profiles predicted by the above model show good agreement with experimental results. D Korzec et al, J Vac Sci Technol, B6, 1988, 263 267. 3O 6922. Microbeam line with 1.5 MeV helium ions and protons at Osaka A microprobe for Rutherford backscattering (RBS) and particle-induced X-ray emission (PIXE) measurements has been realized by focusing 1.5