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The effect of ion species on bombardment induced topography during ion etching of silicon
1004
World Abstracts on Microelectronics and ReliabiliD
Some mechanisms of sputtered negative ion production. M. C. UNDERWOOD. Vacuum 34, 1 2, 153 (1984). Sputtered negative ion spectra from a carbon target under 12 keV, H~ and D f b o m b a r d m e n t were investigated at 300 K and elevated temperature. At 300 K the absolute yield of ~zC~ was measured and the ionization probability determined. The ionization probability is shown to be in good agreement with that predicted from the calculated survival probability of an affinity level in an atom leaving the surface. The yield of ion clusters, ~2Cf and IzC 3 was determined and are consistent with the existence of clusters as contiguous atoms on the surface prior to sputtering. A cluster formation process whereby sputtered atoms re-combine away from the target surface is shown to be highly improbable. At elevated temperature the yield of ~2C- and ~2C2 increased and this is attributed to two mechanisms, i.e. a changing surface adsorbate coverage and changes in surface topography. Both of these processes can result in a surface work function change and so influence ion yield. Oxygen distributions in synthesized SiO 2 layers formed by high dose O + implantation into silicon. P. L. F. HEMMENT,E. MAYDELL-ONDRUSZ, K. G. STEVENS, J. A. KILNER and J. BUTCHER. Vacuum 34 (1-2), 203 (1984). Oxygen depth distributions have been determined, in silicon on insulator (SOI) structures formed by implantation of 200keV oxygen ions into (100) silicon wafers. The implanted layers have been studied by RBS, SIMS and cross-sectional T E M and a computer model has been developed which enables the evolution of the oxygen distribution to be followed. Processing conditions, to form SOI substrates for fabrication of VLSI devices in the top silicon layer, are implantation energy 200keV, dose 1.8× 10 TM O c m 2 and implantation temperature 500°C. An anneal at 1150°C for 2 h is required to form a thin single crystal layer, which is depleted of oxygen. The dielectric properties of the stoichiometric SiO 2 are improved by this thermal processing. Ion beam etching GaAs for integrated optical applications. A. P. WEBB and C. D. W. WILKINSON Vacuum 34 (1-2), 159 (1984). Stripe waveguides fabricated in the II1 V semiconductors are required if the possibility of monolithic integration of optical devices and components is to be realized. A technique that is able to define micron and sub-micron features is essential to produce low loss waveguides. Ion beam etching has been demonstrated to be a possible method for the fabrication of guides with good wall edges. A comparison of etch rates, using argon and freon 12 has been made, as a function of the beam energy. Ion beam etching of GaAs grown on AlxGa~ As layers has been examined for utilization in integrated optical applications. Results of etch rates, edge definition and wall profiles are presented. The influence of beam angle relative to the sample surface is reported and problems relating to the use of photoresist masks are also discussed. Rib type waveguides have been fabricated and light guiding demonstrated at 1.15 p.m. Damage effects in silicon and MNOS structures caused by beams of ionized and neutral argon atoms with energies below 5keV. U. BANGERT, C. JEYNES, P. GOODHEW and f. H. WILSON. Vacuum 34 (1 2), 163 (1984). Low energy ion and/or atom beams (2 5 keV) produced by saddle field ion sources have been used to study the damage effects of ion/atom beam milling on single crystal silicon wafers either uncoated or with both thermal oxide and deposited silicon nitride layers on the surface. MeV ion channelling techniques and transmission electron microscopy have been applied to assess the total disorder, argon retention and microstructure of the damage in the uncoated wafers before and after annealing. Capacitance voltage measurements (1.3 M H z and quasi-static) have been made on M N O S structures after ion and atom beam milling. Specimens bombarded with atoms
show smaller flatbed shifts than those bombarded with io~s of the same energy and dose. The results are interpreted in terms of field assisted injection of charge carriers during bombardment and preferential removal of positive space charge (holes) during low temperature annealing.
ion-beam system resolves patterns of 0.5 micrometer..lolls, GOSCH. Electronics 73 (February 1984). Step-and-repeal system handles up to 6-in. wafers with an alignment accuracy of better than + 0.1 p.m. Recoil profiles produced by ion implantation through dielectric layers. R. T. BLUNT, R. SWEDA and I. R. SANDERS. Vacuum 34 (1 2), 281 (1984). An investigation of the recoil effects of implantation into GaAs through dielectric layers using secondary ion mass spectroscopy, SIMS, is described. Implants of boron, phosphorus and selenium were made into Si3N 4 and SiO 2 dielectric films deposited on GaAs to determine the effects of dielectric type, thickness, implant species, energy and dose on silicon recoils in GaAs. Data on both atomic profiles and total recoil yields is presented and compared with published theoretical calculations. CORDIS--an improved high-current ion source for gases. R. KELLER, F. N()HMAYER.P. SPADTKEand M-H. SCH(JNENBIq~,G. Vacuum 34 (1-2), 31 (1984). The multipole/reflex discharge ion source ELSIRE delivered high-current heavy ion beams (20-50mA) of low emittance, but with poor power- and gas-efficiencies. Therefore, a new version of the source, CORDIS, was constructed, based on the same discharge principle. The diameter of the discharge chamber was doubled, compared to ELSIRE, thus allowing enlarged extraction areas. At the same time, a modified magnetic multipole field leads to enhanced electron confinement, while a shift of the extraction plane increases the effective plasma density. The measurements show a reduction of discharge power and gas pressure by a factor of ten. Thus reliability and life-time are much improved and d.c. operation has also become possible. With 1.3kW d.c. discharge power, the source life-time exceeds 80 h. Several test runs with singleand multi-aperture extraction systems will be discussed. The most prominent result a m o u n t s to 71 mA for xenon ions or 814 (mA) normalized current (proton equivalent ). Process and film characterization of PECVD borophosphosilieate films for VLSI applications. JERRY E. TONG, KURT SCHERTENLEIB and RONALD A. CARPIO. Solid St. Technol. 161 (January 1984). Borophosphosilicate glass (BPSG) films have been deposited in a Plasma Enhanced Chemical Vapor Deposition (PECVD) system. The thickness uniformity was better than + 5 % and the dopant variation was better than + 0 . 5 w t ~o over a deposition zone capable of holding 70 wafers (100mm). The deposition rate was 200 300A/min with conformal step coverage. New analytical techniques for dopant analysis which utilize ion chromatography are outlined, as are rapid nondestructive analytical techniques using more conventional instrumentation. Low reflow temperatures for various dopant levels are also shown as a function of reflow angle. The effect of ion species on bombardment induced topography during ion etching of silicon. G. CARTER,G. W. LEWIS,M. J. NOBES, J. C o x and W. BEGEMANN. Vacuum 34 (3 4), 445 (1984). The topography induced by 7 keV particle bombardment of Si substrates has been measured dynamically as a function of particle fluence with a B11 source coupled into a scanning electron microscope. Distinctive differences are observed according to particle species used (Ar, Kr or O) and flux incidence angle to the surface. Strategies for morphology development minimization are discussed and the relevance of the study to sputter profiling and lithographic etching outlined.
World Abstracts on Microelectronics and ReliabiliD
Some mechanisms of sputtered negative ion production. M. C. UNDERWOOD. Vacuum 34, 1 2, 153 (1984). Sputtered negative ion spectra from a carbon target under 12 keV, H~ and D f b o m b a r d m e n t were investigated at 300 K and elevated temperature. At 300 K the absolute yield of ~zC~ was measured and the ionization probability determined. The ionization probability is shown to be in good agreement with that predicted from the calculated survival probability of an affinity level in an atom leaving the surface. The yield of ion clusters, ~2Cf and IzC 3 was determined and are consistent with the existence of clusters as contiguous atoms on the surface prior to sputtering. A cluster formation process whereby sputtered atoms re-combine away from the target surface is shown to be highly improbable. At elevated temperature the yield of ~2C- and ~2C2 increased and this is attributed to two mechanisms, i.e. a changing surface adsorbate coverage and changes in surface topography. Both of these processes can result in a surface work function change and so influence ion yield. Oxygen distributions in synthesized SiO 2 layers formed by high dose O + implantation into silicon. P. L. F. HEMMENT,E. MAYDELL-ONDRUSZ, K. G. STEVENS, J. A. KILNER and J. BUTCHER. Vacuum 34 (1-2), 203 (1984). Oxygen depth distributions have been determined, in silicon on insulator (SOI) structures formed by implantation of 200keV oxygen ions into (100) silicon wafers. The implanted layers have been studied by RBS, SIMS and cross-sectional T E M and a computer model has been developed which enables the evolution of the oxygen distribution to be followed. Processing conditions, to form SOI substrates for fabrication of VLSI devices in the top silicon layer, are implantation energy 200keV, dose 1.8× 10 TM O c m 2 and implantation temperature 500°C. An anneal at 1150°C for 2 h is required to form a thin single crystal layer, which is depleted of oxygen. The dielectric properties of the stoichiometric SiO 2 are improved by this thermal processing. Ion beam etching GaAs for integrated optical applications. A. P. WEBB and C. D. W. WILKINSON Vacuum 34 (1-2), 159 (1984). Stripe waveguides fabricated in the II1 V semiconductors are required if the possibility of monolithic integration of optical devices and components is to be realized. A technique that is able to define micron and sub-micron features is essential to produce low loss waveguides. Ion beam etching has been demonstrated to be a possible method for the fabrication of guides with good wall edges. A comparison of etch rates, using argon and freon 12 has been made, as a function of the beam energy. Ion beam etching of GaAs grown on AlxGa~ As layers has been examined for utilization in integrated optical applications. Results of etch rates, edge definition and wall profiles are presented. The influence of beam angle relative to the sample surface is reported and problems relating to the use of photoresist masks are also discussed. Rib type waveguides have been fabricated and light guiding demonstrated at 1.15 p.m. Damage effects in silicon and MNOS structures caused by beams of ionized and neutral argon atoms with energies below 5keV. U. BANGERT, C. JEYNES, P. GOODHEW and f. H. WILSON. Vacuum 34 (1 2), 163 (1984). Low energy ion and/or atom beams (2 5 keV) produced by saddle field ion sources have been used to study the damage effects of ion/atom beam milling on single crystal silicon wafers either uncoated or with both thermal oxide and deposited silicon nitride layers on the surface. MeV ion channelling techniques and transmission electron microscopy have been applied to assess the total disorder, argon retention and microstructure of the damage in the uncoated wafers before and after annealing. Capacitance voltage measurements (1.3 M H z and quasi-static) have been made on M N O S structures after ion and atom beam milling. Specimens bombarded with atoms
show smaller flatbed shifts than those bombarded with io~s of the same energy and dose. The results are interpreted in terms of field assisted injection of charge carriers during bombardment and preferential removal of positive space charge (holes) during low temperature annealing.
ion-beam system resolves patterns of 0.5 micrometer..lolls, GOSCH. Electronics 73 (February 1984). Step-and-repeal system handles up to 6-in. wafers with an alignment accuracy of better than + 0.1 p.m. Recoil profiles produced by ion implantation through dielectric layers. R. T. BLUNT, R. SWEDA and I. R. SANDERS. Vacuum 34 (1 2), 281 (1984). An investigation of the recoil effects of implantation into GaAs through dielectric layers using secondary ion mass spectroscopy, SIMS, is described. Implants of boron, phosphorus and selenium were made into Si3N 4 and SiO 2 dielectric films deposited on GaAs to determine the effects of dielectric type, thickness, implant species, energy and dose on silicon recoils in GaAs. Data on both atomic profiles and total recoil yields is presented and compared with published theoretical calculations. CORDIS--an improved high-current ion source for gases. R. KELLER, F. N()HMAYER.P. SPADTKEand M-H. SCH(JNENBIq~,G. Vacuum 34 (1-2), 31 (1984). The multipole/reflex discharge ion source ELSIRE delivered high-current heavy ion beams (20-50mA) of low emittance, but with poor power- and gas-efficiencies. Therefore, a new version of the source, CORDIS, was constructed, based on the same discharge principle. The diameter of the discharge chamber was doubled, compared to ELSIRE, thus allowing enlarged extraction areas. At the same time, a modified magnetic multipole field leads to enhanced electron confinement, while a shift of the extraction plane increases the effective plasma density. The measurements show a reduction of discharge power and gas pressure by a factor of ten. Thus reliability and life-time are much improved and d.c. operation has also become possible. With 1.3kW d.c. discharge power, the source life-time exceeds 80 h. Several test runs with singleand multi-aperture extraction systems will be discussed. The most prominent result a m o u n t s to 71 mA for xenon ions or 814 (mA) normalized current (proton equivalent ). Process and film characterization of PECVD borophosphosilieate films for VLSI applications. JERRY E. TONG, KURT SCHERTENLEIB and RONALD A. CARPIO. Solid St. Technol. 161 (January 1984). Borophosphosilicate glass (BPSG) films have been deposited in a Plasma Enhanced Chemical Vapor Deposition (PECVD) system. The thickness uniformity was better than + 5 % and the dopant variation was better than + 0 . 5 w t ~o over a deposition zone capable of holding 70 wafers (100mm). The deposition rate was 200 300A/min with conformal step coverage. New analytical techniques for dopant analysis which utilize ion chromatography are outlined, as are rapid nondestructive analytical techniques using more conventional instrumentation. Low reflow temperatures for various dopant levels are also shown as a function of reflow angle. The effect of ion species on bombardment induced topography during ion etching of silicon. G. CARTER,G. W. LEWIS,M. J. NOBES, J. C o x and W. BEGEMANN. Vacuum 34 (3 4), 445 (1984). The topography induced by 7 keV particle bombardment of Si substrates has been measured dynamically as a function of particle fluence with a B11 source coupled into a scanning electron microscope. Distinctive differences are observed according to particle species used (Ar, Kr or O) and flux incidence angle to the surface. Strategies for morphology development minimization are discussed and the relevance of the study to sputter profiling and lithographic etching outlined.