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The two-step implantation of argon precursor ion (Ar+) followed by boron ion (B+) in single crystalline silicon at room temperature is discussed to activate boron implanted region by post heating at 300 followed by 400°C. The implantation of Ar+ at a dose of 6.0 × 1013 cm-2 at 70 keV with a projected range Rp(Ar) of 80 nm followed by B+ at 1.0 × 1015 cm-2 and 15 keV with Rp(B) of 62 nm caused crystalline disordered states with the effective disordered amorphous depth Aeff of 32 nm, while the post heating of 300°C for 90 min followed by 400°C for 30 min markedly decreased Aeff to 1.8 nm. The effective recrystallization by the post heating promoted activation of doped region associated with decrease in the sheet resistivity to 189 Ω/sq by the post heating. The activation ratio was estimated as 0.33 under the assumption of a hole mobility of 50 cm2/Vs in the boron implanted region.

We report a microwave heating system with a carbon heating tube (CHT) which was made by a 4-mm diameter quartz tube filled with carbon particles and Ar gas at 1400 Pa. A 60-mm-long CHT was set in a cavity in which 2.45-GHz microwave was introduced. Via nearly complete absorption of a microwave power of 200 W by carbon in the CHT during multi-reflection of the microwave in the cavity, the CHT was effectively heated to 1279 °C at 33 s after the microwave initiation, which was observed by the radiation-type thermometer. Moreover, the control of the CHT temperature was demonstrated with a home-made proportional–integral–differential feedback circuit which regulated the magnetron power source using a signal of the thermometer. The control of temperature at 1100 °C was successfully realized. Crystallization of a 58-nm-thick amorphous silicon thin film formed on the glass substrate was demonstrated by mechanically moving the silicon sample just below the heated CHT. A high crystalline volume ratio of 0.92 was achieved. Furthermore, heating of 500- $\mu \text{m}$ -thick-n-type silicon substrate implanted with $1.0\times 10^{15}$ cm−2 phosphorus and boron atoms with the CHT resulted in activation of the doped regions. Rectified diode characteristics were achieved.

We report a microwave heating system with a carbon heating tube (CHT) made by a 4-mm diameter quartz tube filled carbon particles and Ar gas at 1400 Pa. 2.45-GHz microwave at 200 W was introduced to a 300-dimameter metal cavity, in which 60-mm-long CHT was set at the central position. The numerical simulation with a finite element moment method resulted in the standing wave of the electric field caused by three dimensional Fresnel interference effect with low high electric field intensity ranging from from 1 to 6 kV/m because of effective absorption of microwave power by the CHT. The lowest average electrical field intensity of 5 kV/m in the cavity space was given by the electrical conductivity of carbon ranging from 10 to 55 S/m. The CHT with 55 S/m heated to 1200oC by microwave irradiation at 200 W. This heating method was applied to activate 1.0x1015-cm-2 boron and phosphorus implanted regions in n-type crystalline silicon substrate to fabricate pn junction and solar cells. The CHT heating at 1200oC realized decrease in the sheet resistivity to 146 Ω/sq, decrease in the density of defect states to 1.3x1011 and 9.2x1010 cm-2 for boron (p+) and phosphorus (n+) implanted surfaces, and solar cell characteristic with a conversion efficiency of 15% under illumination of air mass 1.5 at 0.1 W/cm2.

We report formation of low resistivity n-type doped silicon region at 300°C by the method of two-step ion implantation. Phosphorus ions with a dose of 2×1014 cm−2 at 70 keV followed by hydrogen ions with 1×1016 cm−2 at 8 keV were implanted at RT to the both surfaces of single crystalline silicon substrates. Post heating at 300°C for 90 min decreased the sheet resistivity to 417 Ω/sq. The activation ratio was estimated as 75% under the assumption of electron mobility of 50 cm2/Vs in the doped region. Moreover, the minority carrier effective lifetime (τ eff ) was also increased to 253 μs. This indicates a low density of surface recombination defect states of 6.4×1010 cm−2. In contrast, a high sheet resistivity of 8×104 Ω/sq and a low τ eff of 64 μs resulted from a single phosphorus ion implantation with 2×1014 cm−2 at 70 keV followed by 300°C heating for 90 min. The hydrogen ion implantation probably decreased the silicon bonding energy to easily move phosphorus atoms in the silicon lattice sites at 300°C and passivated the doped region by terminating silicon dangling bonds.

We report 2.45-GHz microwave heating system with a carbon heating tube (CHT) made by a 4-mm-diameter and 60-mm-long-quartz tube filled with conductive carbon particles and Ar gas at 1400 Pa set in a 300-mm-diameter-sized metal cavity. The three-dimensional finite element numerical simulation method resulted in the most effective electrical conductivity of CHT ranged from 10 to 55 S/m to absorb the microwave power. A proportional-integral-differential feedback CHT temperature control system was used to activate 1.0×1015-cm−2-boron and phosphorus implanted regions in n-type crystalline silicon substrate from 1000 to 1200°C. The CHT heating at 1200°C realized decrease in the sheet resistivity to 146 Ω/sq, decrease in the density of defect states to 1.3×1011 and 9.2×1010 cm−2 for boron (p+) and phosphorus (n+) implanted surfaces, and solar cell characteristic with a conversion efficiency of 15% under illumination of air mass 1.5 at 0.1 W/cm2.

We experimentally studied the Si surface orientation dependence of SiC nano-dot formation in a hot-C+-ion implanted bulk-Si substrate (C+-bulk Si), to analyze the effects of Si atom surface density on SiC nano-dot formation in Si and the photoluminescence (PL) property. We successfully demonstrated SiC dot formation even in (110) and (111) C+-bulk Si, too. SiC dot size and density of (110) C+-bulk Si is larger than those of (100) C+-bulk Si. The photoluminescence (PL) properties of C+-bulk Si strongly depend on the Si surface orientation, and the PL intensity is the minimum in (110) C+-bulk Si with lowest Si atom surface density.

We experimentally studied the material structure and photoluminescence (PL) properties of SiC quantum-dots (QD) in SiO2 layer (Si+/C+–OX) fabricated by double hot-Si+/C+ ion implantation into SiO2 and the post N2 annealing, comparing with those of SiC-dots by single hot-C+ ion implanted oxide (C+–OX) and crystal-Si layers (C+–Si). X-ray photoemission spectroscopy for Si+/C+–OX confirmed Si–C bonds even in SiO2, which is the direct verification of SiC formation in SiO2. Moreover, transmission electron microscope analyzes showed that 2 nm diameter SiC-dots with a clear lattice spots were successfully formed in Si+/C+–OX. After N2 annealing, we demonstrated strong PL emission from Si+/C+–OX, and the PL intensity I PL of Si+/C+–OX is approximately 2.6 and 12 times larger than those of C+–Si and C+–OX, respectively. The stronger I PL of Si+/C+–OX is possibly attributable to QD-induced PL-efficiency enhancement in Si+/C+–OX. Moreover, PL photon energy at the peak I PL of Si+/C+–OX rapidly increases to approximately 2.4 eV after N2 annealing.

The H+ or Ar+ precursor implantation at room temperature (RT) was proposed to activate boron atoms subsequently implanted in single crystalline silicon by post heating at a low temperature. The two-step ion implantation of 1.5×1016 cm−2 H+ at 8 keV followed by 1.0×1015 cm−2 B+ at 40 keV for both surfaces of silicon and 1.0×1014 cm−2 Ar+ at 70 keV followed by 1.0×1015 cm−2 B+ at 40 keV resulted in low sheet resistivities of 520 and 890 Ω/sq, respectively by post heating at 300°C for 30 min. Their activation ratios were estimated as 22 and 13%. The optimization of the projected ranges of 79 nm for 6×1013 cm−2 Ar+ at 70 keV and of 46 nm for B+ at 10 keV further decreased the sheet resistivity to 392 Ω/sq and increased the activation ratio to 29.5%. The activation of B+ implanted region at 300°C probably resulted from a decrease in the activation energy induced by a decrease in the silicon bonding energy promoted by the first H+ or Ar+ precursor implantation.

Ion implantation of 1.5xl016-cm−2 H+ at 8 keV or 1.0xl014-cm−2 Ar+ at 70 keV was carried out at room temperature (RT) to crystalline silicon in advance of ion implantation of 1.0×10-15-cm−2B+ at RT. Decrease in the crystalline volume ratio and generation of crystalline defects were promoted by the first H+ or Ar+ implantation. Subsequently post heating at 300°C for 30 min decreased the sheet resistivity to 520 and 890 Ω/sq in the cases of the H+ and Ar+ implantation, respectively. The decreases in the sheet resistivity by 300°C post annealing is interpreted that formation of crystalline defects by the first H+ or Ar+ implantation decreased the activation energy for moving boron atoms from the interstitial to lattice sites and achieved carrier generation at the low temperature.

13.56 MHz capacitance coupled Ar plasma irradiation at 50 W for 120 s caused serious damage at SiO2/Si interfaces for n-type 500-μm-thick silicon substrates. The 635-nm-light induced minority carrier effective lifetime (τeff) was decreased from 1.7 × 10−3 (initial) to 1.0 × 10−5 s by Ar plasma irradiation. Moreover, the capacitance response at 1 MHz alternative voltage as a function of the bias voltage (C–V) was changed to hysteresis characteristic associated with the density of charge injection type interface traps at the mid gap (Dit) at 9.1 × 1011 cm−2 eV−1. Subsequent 940-nm laser annealing at 3.7 × 104 W/cm2 for 4.0 × 10−3 s markedly increased τeff to 1.7 × 10−3 s and decreased Dit to 2.1 × 1010 cm−2 eV−1. The hysteresis phenomenon was reduced in C–V characteristics. Laser annealing effectively decreased the density of plasma induced carrier recombination and trap states. However, laser annealing with a high power intensity of 4.0 × 104 W/cm2 seriously caused a thermal damage associated with a low τeff and a high Dit with no hysteresis characteristic.

We report effective passivation of silicon surfaces by heating single crystalline silicon substrates in liquid water at 110°C for 1 h. High values of photo-induced effective minority carrier lifetime τeff in the range from 1.9x10-4 to 1.8x10-3 s were obtained for the n-type samples with resistivity in the range from 1.7 to 18.1 Ωcm. τeff ranged from 8.3x10-4 to 3.1x10-3 s and from 1.2x10-4 to 6.0x10-4 s over the area of 4 inch sized 17.0 Ωcm n- and 15.0 Ωcm p-type samples, respectively. The heat treatment in liquid water at 110°C for 1 h resulted in low surface recombination velocities ranging from 7 to 34 cm/s and from 49 to 250 cm/s for those 4 inch sized n- and p-type samples, respectively. The thickness of the passivation layer was estimated to be approximate only 0.7 nm. Metal-insulator-semiconductor type solar cell was demonstrated with Al and Au metal formation on the passivated surface. Rectified current voltage and solar cell characteristics were observed. Open circuit voltage of 0.47 V was obtained under AM 1.5 light illumination at 100 mW/cm2.

We report rapid laser-induced passivation of the silicon surface. When the top surfaces of n-type 500-µm-thick silicon substrates with surfaces coated with 100 nm thermally grown SiO2 layers (initial samples) were irradiated with Ar plasma at 50 W for 120 s, the 635-nm-light induced minority carrier effective lifetime τeff decreased from 1.7x10 -3 (initial) to 1.7x10 -5 s because Ar plasma caused substantial carrier recombination defect states at the silicon surfaces. τeff was markedly increased to 1.7x10 -3 s by 940-nm-semiconductor laser irradiation at 3.57x10 4 W/cm 2 for 4 ms. Laser heating effectively decreased the density of plasma induced carrier recombination defect. However, laser heating of the initial sample at 4.0x10 4 W/cm 2 decreased τeff from 2.2x10 -3 (initial) to 1.7x10 -4 s. Additional laser heating at 3.70x10 4 W/cm 2 increased τeff to 3.9x10 -4 s and it partially cured laser in

We report connection conductivity ( $$C_{\rm c}$$ ) of adhesive which including $$\hbox {In}_2\hbox {O}_3$$ – $$\hbox {SnO}_2$$ (ITO) particles developed for fabrication of stacked-type-multi-junction solar cells. The commercial 20- $$\upmu $$ m sized ITO particles were heated in vacuum at temperature ranging from 800 to 1,300 $$^{\circ }{\rm C}$$ for 10 min to increase $$C_{\rm c}$$ . 6.2 wt% ITO particles were dispersed in commercial Cemedine adhesive gel to form 100 samples structured with n-type Si/adhesive/n-type Si (n-Si sample) and p-type Si/adhesive/p-type Si (p-Si sample). Current density as a function of voltage (J–V) characteristics gave $$C_{\rm c}$$ . It ranged from 4.3 to 1.0 S/cm $$^2$$ for the n-Si sample with 800 $$^{\circ }{\rm C}$$ heat-treated ITO particles. Its standard deviation was 0.59 S/cm $$^2$$ . On the other hand, it ranged from 2.0 to 0.6 S/cm $$^2$$ for the p-Si sample with 800 $$^{\circ }{\rm C}$$ heat-treated ITO particles. Its standard deviation was 0.22 S/cm $$^2$$ . The distribution of $$C_{\rm c}$$ mainly resulted from contact efficiency of ITO particles to substrate. We theoretically estimated that present $$C_{\rm c}$$ achieved a low loss of the power conversion efficiency ( $$E_{\rm ff}$$ ) lower than 0.3 % in the application of fabrication of multi-junction solar cell with an intrinsic $$E_{\rm ff}$$ of 30 % and an open circuit voltage above 1.9 V.

We experimentally studied SiC nanodot formation in an amorphous-Si (a-Si) and poly-Si on quartz substrates, using a hot-C+-ion implantation technique and post-N2 annealing, compared with SiC-dots in a (100) crystal-Si (c-Si) on insulator substrate. Even in the poor crystal quality substrates of the C+-ion implanted in a-Si and poly-Si layers, we experimentally verified 3C-SiC dot formation by transmission electron microscopy, and the strong photoluminescence (PL) intensity in the near-UV-vis regions, because a-Si is partially poly-crystallized by the high-temperature processes of hot-C+-ion implantation and post-N2 annealing. The PL spectral line shape strongly depends on the Si crystal structures, but the peak PL intensity after N2 annealing is almost independent of the Si crystal structures. Moreover, the PL spectrum can be explained by the sum of PL emissions from different cubic and hexagonal polytypes of SiC. We clarified that the three Si crystal structures have a different contribution ratio of PL components of SiC polytypes.

We report diffusing boron and phosphorus dopant atoms in silicon with impurity sources of BOx and POx layers formed on the top surfaces of n- and p-type crystalline silicon substrates. The silicon samples with impurity sources were subsequently covered with carbon powders to effectively absorb 2.45 GHz microwave power. Microwave irradiation at 1000 W for 27 s rapidly heated the carbon powders to 1265°C. The sheet resistivity of the samples decreased to 29 and 16 Ω/sq because of boron and phosphorus doping by 29-s-microwave heating. The photo-induced minority carrier lifetime increased to 2.0×10−5 and 3.5×10−5 s by 20- and 14-s-microwave heating for the boron- and phosphorus-doped samples. Boron atoms with a concentration above 1020 cm−3 diffused 150 nm deep by 26-s-microwave heating. Achievements of diode rectified characteristics and photovoltaic effect demonstrate pn junction formation at the top surface region by the present doping method.

A high photo-induced effective minority carrier lifetime τ eff of crystalline silicon was achieved by simple heat treatment in liquid water. τ eff was 2.8×10−3 s for 15-Ωcm n-type crystalline silicon heat treated in liquid water at 120°C for 1.5 h. The τ eff for the sample treated at 90°C increased from 1.0×10−4 s (just after the treatment) to 1.7×10−3 s by keeping the sample in the air atmosphere for 700 h. τ eff maintained high values up to 1800 h. The metal-insulator-semiconductor type diodes were formed by forming Al and Au metals on the 0.7-nm-thick passivated layers. Rectified current characteristics were observed in the dark field because of the difference of the work function between Al and Au. Capacitance response with the bias voltage suggested low density of interface traps. Short circuit current density of 24.3 mA/cm2 and open circuit voltage of 0.36 V were observed in the MIS-type solar cell under the light illumination of AM 1.5 at 100 mW/cm2 to the rear surface.

A combination of the carbon-powder absorber with microwave irradiation is proposed as a rapid heat method. 2-μm-diameter carbon powders with a packing density of 0.08 effectively absorbed 2.45 GHz 1000-W-microwave and heated themselves to 1163 °C for 26 s. The present heat treatment recrystallized n-type crystalline silicon surfaces implanted with $$1.0 \times 10^{15}\hbox {-cm}^{-2}$$ -boron and phosphorus atoms with crystalline volume ratios of 0.99 and 0.93, respectively, by microwave irradiation at 1000 W for 20 s. Activation and carrier generation were simultaneously achieved with a sheet resistivity of $$62\, \Omega / \hbox {sq}$$ . A high photo-induced-carrier effective lifetime of $$1.0 \times 10^{-4}$$ s was also achieved. Typical electrical current-rectified characteristic and solar cell characteristic with an efficiency of 12.1 % under $$100\hbox{-mW/cm}^{2}\hbox{-air-mass-}1.5$$ illumination were obtained. Moreover, heat treatment with microwave irradiation at 1000 W for 22 s successfully crystallized silicon thin films with thicknesses ranging from 2.4 to 50 nm formed on quartz substrates. Nano-crystalline cluster structure with a high volume ratio of 50 % was formed in the 1.8-nm (initial 2.4-nm)-thick silicon films. Photoluminescence around 1.77 eV was observed for the 1.8-nm-thick silicon films annealed at 260 °C in $$1.3 \times 10^{6}$$ -Pa-H2O-vapor for 3 h after the microwave heating.

The simple passivation method of heat treatment in liquid water is discussed. Photo-induced effective minority carrier lifetime τ eff increased to 3.3 × 10−3 s above 110 °C for 1 h for 17-Ωcm n-type crystalline silicon. Increase in τ eff was observed ranging from 3.5 × 10−4 to 3.7 × 10−3 s for n-type silicon with resistivity ranging from 2 to 17 Ωcm. τ eff maintained high values ranging from 1.5 × 10−4 to 1.4 × 10−3 s for 1270 h. The metal-insulator-semiconductor-type diodes were formed on the top surfaces of the n-type and p-type substrates by forming Al and Au metals on the 0.7-nm-thin passivated layers. Rectified and Fowler–Nordheim current characteristics were observed in the dark field because of the difference of the work function between Al and Au. High photo-induced current density of 31.1 mA/cm2 and photovoltaic effect were observed in case of light illumination of AM 1.5 at 100 mW/cm2 to the rear surface. The recombination velocity in the regions under the metal electrode in the MIS structure was determined by lateral diffusion of photo-induced carriers. They were 1000 and 11,000 cm/s under Al and Au, respectively, in the n-type Si substrate.

Buried void layer formation in silicon substrates was achieved by hydrogen ion implantation followed by 940-nm infrared laser rapid heating. P-type silicon substrates coated with 100-nm-thick thermally grown SiO2 layers were implanted with hydrogen atoms at 5x10 15 and 3x10 16 cm -2 at 60 keV. Structural investigation with analysis of optical reflectivity spectra revealed that 3x10 16 cm -2 implantation caused a void layer with a void ratio of 0.04 at a depth of 250 nm close to the position of hydrogen peak concentration. Laser irradiation at 4.2x10 4 W/cm 2 increased the void ratio to 0.12. No void layer was observed at ion implantation stage for sample with 5x10 15 cm -2 -hydrogen atoms. Laser irradiation at 4.9x10 4 W/cm 2 formed a void layer with a void ratio of 0.013 at a depth of 255 nm.

We report formation of thin aluminum oxide AlOx films on the silicon surface by a simple method of Al metal evaporation in oxygen gas atmosphere. 520 μm thick 30-Ωcm p-type-silicon substrates with a top bare surface and a rear surface coated with 100 nm thick thermally grown SiO2 layers were prepared. AlOx films were formed on the top surfaces by Al metal evaporation up to 20 s in oxygen gas atmosphere at 0.8 Pa with a flow rate of 3 sccm. Samples were subsequently annealed with 9.0x105 Pa H2O vapor at 260°C for 3 h. Measurement of capacitance response to a modulation voltage at 500 kHz as a function of bias gate voltages C-V revealed that AlOx films had the effective oxide thickness ranging from 2.0 and 2.6 nm were formed. C-V measurements also revealed that negative fixed charges were accumulated with a density of 5x1012 cm-2 in AlOx films. Photo-induced carrier microwave absorption measurement resulted in a high minority carrier effective lifetime τeff of 3.6x10-4 s comparable to that of 4.1x10-4 s for thermally grown SiO2 passivation. Field effect passivation was probably caused by negative charges in AlOx so that the surface recombination velocity decreased to 70 cm/s. X-ray reflectivity analysis indicated that the interfacial layer like SiOx was formed between AlOx and Si substrate. High pressure H2O vapor heat annealing caused increase in the density and decrease in the thickness of AlOx layers, although it increased the density and thickness of the interfacial SiOx layer thickness. H2O vapor treatment is effective to improve the quality of nanometer thick AlOxlayer.

Change in the light-induced minority carrier effective lifetime τeff of crystalline silicon caused by rapid laser heating is reported. The top surface of n- and p-type silicon substrates with thicknesses of 520 μm coated with thermally grown SiO2 layers were heated by a 940 nm semiconductor laser for 4 ms. τeff was measured by a method of microwave absorption caused by carriers induced by 620 nm light illumination at 1.5 mW/cm2. τeff for light illumination of the top surfaces was decreased to 1.0x10-5 and 4.8x10-6 s by laser heating at 5.0x104 W/cm2 for n- and ptype 520-μm-thick silicon substrates, respectively. The decrease in τeff resulted from the generation of defect states associated with the carrier recombination velocity at the top surface region, Stop. Laser heating increased Stop to 6000 and 10000 cm/s for n- and p-type silicon samples, respectively. Heat treatment at 400oC for 4h markedly decreased Stop to 21 and 120 cm/s, respectively, for n- and p-type silicon samples heated at 5.0x104 W/cm2. Laser heating at 4.0x104 W/cm2 for 4 ms was also applied to samples treated with Ar plasma irradiation at 50 W for 60 s, which decreased τeff (top) to 2.0x10-5 s and 3.9x10-6 s for n- and p-type silicon samples, respectively. Laser heating successfully increased τeff (top) to 2.8x10-3 and 4.1x10-4 s for n- and p-type samples, respectively. Laser irradiation at 4x104 W/cm2played a role of curing recombination defect sites.

We report formation of thin silicon oxide films on the silicon surfaces by combination of oxygen radical and high pressure H2O vapor heat treatment for passivation of silicon surfaces at a low temperature. Oxygen plasma was generated by 13.56 MHz radio frequency induction-coupled remote plasma with mixed gases of O2 and Ar at 2 sccm, 2x10-2 Pa and at a power of 50 W. Oxygen radical was produced from the plasma via a metal mesh closing plasma in the reactor. The top surfaces of 20 Wcm n-type silicon substrates with the rear surface coated by thermally grown SiO2 layers were exposed by oxygen radical from 1 to 5 min to oxidize the silicon surface. The samples were subsequently annealed with 9.0x105 Pa H2O vapor heat treatment at 260oC for 3 h. The effective minority carrier lifetime estimated using photo-induced carrier microwave absorption system in the case of 635 nm light illumination at 1.5 mW/cm2 to the top surface increased from 1.3x10-4 to 5.1x10-4s as the oxygen radical treatment duration increased from 1 to 5 min. The recombination velocity decreased from 380 to 90 cm/s. 500 kHz capacitance response with bias gate voltages characteristics of metal oxide semiconductor structure resulted in the effective oxide thicknesses (EOT) ranging from 1.3 to 1.7 nm. These results indicate a capability of thin oxide formation and effective passivation of silicon surfaces at a low temperature.

*** We report the crystallization of 40-nm-thick hydrogenated amorphous silicon films using 940nm continuous wave infrared semiconductor laser with 200 nm diameter carbon particles as photo absorption. The laser beam was focused to 100 μm diameter at the surface of carbon particles. Laser irradiation at 25 W heated the carbon surface region to about 3430 K, which was estimated by analysis of spectra of light emission caused by laser irradiation when quartz substrates were placed on the surface of carbon particles. The silicon films coated with SiO2 films were crystallized by laser irradiation for 170 μs at 25 W. The crystallization volume ratio was 0.53. Crystallization over 1.1 mm area was also demonstrated by laser irradiation at 25 W.

The quantity of hysteresis phenomena in capacitance response for metal–oxide–semiconductor (MOS) capacitors with 100-nm-thick SiO2 films formed by the sputtering method was reduced by remote oxygen plasma treatment followed by high-pressure H2O vapor heat treatment at 150 °C. In order to determine the quantity of hysteresis phenomena in capacitance response, we defined hysteresis charge as the difference in fixed oxide charge density for round bias voltage application. As-fabricated MOS capacitor samples had a high density of hysteresis charges of 1.0×1012 cm-2. The density of hysteresis charge was not decreased by 4.7×105-Pa-H2O-vapor heat treatment at 150 °C for 3 h. On the other hand, it was markedly reduced to 1.0×1011 cm-2 by 13.56-MHz-radio frequency remote oxygen plasma treatment at 300 W and 150 °C followed by 4.7×105-Pa-H2O-vapor heat treatment at 150 °C for 3 h. Hysteresis phenomena are probably caused by a temporal electron charging up of SiO2 films.

We activated silicon implanted with phosphorus atoms by infrared semiconductor laser annealing with a diamond-like carbon (DLC) optical absorption layer. The silicon samples implanted with phosphorus atoms at 10 and 70 keV with concentrations of 5×1014, 1×1015, and 2×1015 cm-2 were coated with 200-nm-thick DLC films. The samples were annealed by irradiation with a 940 nm continuous wave laser at 70 kW/cm2 with a beam diameter of 180 µm. The laser beam was scanned using a moving stage at 3–20 cm/s, which gave an effective dwell time of 0.9–6.0 ms. The amorphized surface regions were recrystallized by laser annealing longer than 1.2 ms. The in-depth profile of phosphorus concentration hardly changed within 5 nm for laser annealing for 2.6 ms. The sheet resistance markedly decreased to 106 and 46 Ω/sq for the samples implanted with phosphorus atoms at 10 and 70 keV by laser annealing at a dwell time of 2.6 ms, respectively. Phosphorus atoms were effectively activated with a carrier density near the phosphorus concentration for implantation at 70 keV. A low carrier generation rate was observed for implantation at 2×1015 cm-2 and 10 keV. An intermediate SiO2 layer effectively blocked carbon incorporation to a level below 1017 cm-3.

We investigated defect reduction in laser crystallized polycrystalline silicon (poly-Si) films by heat treatment with 1.3×106 Pa H2O vapor. The H2O vapor heat treatment at 260 °C for 6 h reduced the spin density in laser crystallized poly-Si films from 2.0×1018 (initial) to 6.5×1016 cm-3. The activation energy of the reaction for defect reduction was 0.26 eV. Photoconductivity under 532 nm light illumination at 100 mW/cm2 was increased from 2.7×10-6 (initial) to 3.3×10-5 S/cm by heat treatment for 1 h. The oxygen concentration in the silicon films was increased by 1.1×1019 cm-3 by heat treatment, although the hydrogen concentration was decreased by 1.4×1020 cm-3. This suggests that oxygen atoms have an important role in defect state reduction in polycrystalline silicon films.

We report the crystallization of silicon thin films using a continuous wave (CW) infrared semiconductor laser with the assistance of diamond-like carbon (DLC) as a photoabsorption layer. A beam of a 940-nm-wavelength CW semiconductor laser was irradiated to samples of 400-nm-thick DLC/50-nm-thick Si/glass with a laser power density of 7.4–24.7 kW/cm2. The beam was scanned on the samples at a speed of 15–100 cm/s. The DLC layer was heated to a temperature above the melting point of silicon by effective absorption of laser light. Thus, the underlying 50-nm-thick silicon films were crystallized by the heat defused from DLC. It was found that the threshold energy density for the crystallization of silicon films decreased as the laser power density increased. The maximum crystallinity factors estimated from Raman scattering spectral data of silicon films were 1 and 0.78 for laser power densities of 24.7 and 7.8 kW/cm2, respectively. Electron backscattering diffraction pattern (EBSD) measurements revealed that crystalline grains were randomly oriented with an average size of 3 µm.

50-nm-thick amorphous Si films doped with 4.3 x 10^17 cm-3 phosphorus atoms were crystallized by thermal plasma jet (TPJ) irradiation. The electrical conductivity (sigma) of the crystallized films ranges from 1.2 x 10^-5 - 1.7 x 10^-2 S/cm, while Si films crystallized by excimer laser annealing (ELA) show much smaller sigma of 1.6 - 4.5 x 10^-6 S/cm regardless of laser fluence. This result can be interpreted that the defect density in the TPJ crystallized films is much smaller than that in ELA Si films. By treating the films with hydrogen plasma for 60 s at 250oC, sigma of TPJ crystallized films increased to 1.4 x 10^-2 - 1.1 S/cm, while it was 3.0 x 10^-6 - 6.5 x 10^-3 S/cm in the case of films crystallized by ELA. This result indicates that a short period hydrogenation is effective to improve the electrical characteristics of TPJ crystallized Si films., 論文

We report effective passivation of silicon surfaces by heating single crystalline silicon substrates in liquid water at 110°C for 1 h. High values of photo-induced effective minority carrier lifetime τ eff were obtained ranging from 8.3×10−4 to 3.1×10−3 s and from 1.2×10−4 to 6.0×10−4 s over the area of 4 inch sized n- and p-type samples, respectively, while values of τ eff of initial bare samples were lower than 1.2×10−5 s. The heat treatment in liquid water at 110°C for 1 h resulted in low surface recombination velocities ranging from 7 to 34 cm/s and from 49 to 250 cm/s for those 4 inch sized n- and p-type samples, respectively. The thickness of the passivation layer was estimated to be approximate only 0.7 nm. Metal-insulator-semiconductor type solar cell was demonstrated with Al and Au metal formation on the passivated surface. Rectified current voltage and solar cell characteristics were observed. Open circuit voltage of 0.49 V was obtained under AM 1.5 light illumination at 100 mW/cm2.

Excimer laser induced melting and solidification of Ge films on Si have been investigated using in-situ measurement of transient conductance of the films. 35-nm-thick Ge films are partially melted by irradiating them with laser energies higher than 114 mJ/cm 2 and are completely melted at 191 mJ/cm 2 . The crystalline growth of Ge irradiated with laser energies lower than 191 mJ/cm 2 proceeds independently of the underlying Si film, however, by irradiating at a higher energy, the diffusion of Si atoms into molten Ge and the formation of Si x Ge 1− x layer result. The electrical conductivity of the Si x Ge 1− x film decreases with Si composition until x = 0.16, and then increases and peaks at around x = 0.25 to 0.3, presumably due to defected and/or strained bonds in the film induced by underlying Si layer.

The 30 ns pulsed XeCl excimer laser annealing of silicon films with an average thickness of 2.2 nm formed on quartz substrates is reported. Crystallization occurred at laser energies between 150 and 170 mJ/cm2. Raman scattering spectra revealed the mixed states of small crystalline grains, and nanocrystalline and disordered amorphous regions. The amorphization of the silicon films was observed for laser irradiation above 180 mJ/cm2. Photoluminescence was observed around at approximately 3 and 2 eV from 18 to 130 K for the films annealed at 260 °C for 3 h in 1.3 ×106 Pa H2O vapor after laser irradiation at 170 mJ/cm2.

We report 308-nm-pulsed-XeCl-excimer laser annealing of 2.2-nm-thick silicon films formed on quartz substrates. Crystallization occurred at laser energy of 150∼170 mJ/cm 2 . Raman scattering spectra revealed mixed states of small crystalline grains and disordered amorphous regions. Broad optical extinction coefficient was obtained for wavelength from 250 to 400 nm, although it was similar to that of crystalline silicon for wavelength longer than 400 nm. Blue-green photoluminescence was observed for the films annealed at 260 °C for 3 h in 1.3×10 6 Pa H 2 O vapor after crystallization.

Electrical and structural properties of polycrystalline silicon germanium (poly-SiGe) films fabricated by pulsed-laser annealing were investigated. Observation of laser-induced melt-regrowth of SiGe films using transient conductance measurement revealed that the melt depth and the crystallization velocity increased as Ge concentration increased. The increase of the crystallization velocity resulted in increase of the average size of crystalline grains from 66 to 120 nm at the laser energy density of 360 mJ/cm2 with increasing Ge concentration from 0 to 60%. The crystalline volume ratio obtained by reflectivity spectra in the ultraviolet region also increased from 0.83 to 1.0. Numerical analysis revealed that the density of electrically active defects decreased from 3.5×1018 to 1.1×1018 cm−3 as Ge concentration increased from 0 to 80%. The density of defect states of Si0.8Ge0.2 films were reduced from 3.5×1018 to 1.9×1018 cm−3 by 13.56-MHz hydrogen plasma treatment at 250 °C, 30 W, and 130 Pa for 30 s. How...

Analyses of free-carrier optical absorption and Hall-effect current measurements indicated in high carrier mobilities of 32 cm2/Vs and 30 cm2/Vs, respectively, and low carrier densities of 5.0×1019 cm-3 and 3.8×1019 cm-3, respectively, for 1.1×1020 cm-3-phosphorus-doped solid-phase crystallized polycrystalline silicon films fabricated at 600 °C for 48 h. The silicon films had good crystalline properties of the crystalline grains and a low crystalline volume fraction of 0.43. A XeCl excimer laser anneal at 500 mJ/cm2 effectively increased the carrier density to 1.1×1020 cm-3, and also increased the crystalline volume fraction to 0.93. Moreover, H2O-vapor heat treatment at 1.3×106 Pa for 3 h at 260 °C reduced the density of the defect states from 6.2×1018 cm-3 to 2.6×1018 cm-3.

We analyzed the rapid heating properties of 50-nm-thick silicon films via 250-nm-thick SiO2 intermediate layers by heat diffusion from joule heating induced by electrical current flow in chromium strips. Numerical heat-flow simulation resulted in that the silicon films were heated to the melting point by a joule-heating intensity above 1 MW/cm2. A marked increase in electrical conductance associated with silicon melting was experimentally detected. Taper-shaped chromium strips detected the temperature gradient in the lateral direction caused by the spatial distribution of the joule-heating intensity. Crystallization occurred according to the temperature gradient. A 2–4-μm lateral crystalline grain growth was demonstrated for the silicon films.

Fabrication of n-channel polycrystalline silicon thin-film transistors (poly-Si TFTs) at a low temperature is reported. 13.56 MHz-oxygen plasma at a 100 W, 130 Pa at 250/spl deg/C for 5 min, and heat treatment at 260/spl deg/C with 1.3/spl times/10/sup 6/-Pa-H/sub 2/O vapor for 3 h were applied to reduction of the density of defect states in 25-nm-thick silicon films crystallized by irradiation of a 30 ns-pulsed XeCl excimer laser. Defect reduction was numerically analyzed. Those treatments resulted in a high carrier mobility of 830 cm/sup 2//Vs and a low threshold voltage of 1.5 V at a laser crystallization energy density of 285 mJ/cm/sup 2/.

Crystallization of silicon films formed on glass substrates was achieved by rapid-joule heating of Cr strips adjacently formed via 200-nm-thick SiO 2 intermediate layers. 3-μs-pulsed voltages applied to the Cr strips caused a high joule heating intensity about 1×10 6 W / cm 2 . Transmission electron microscopy measurements confirmed a crystalline grain size of 50–100 nm. 1-μm-long crystalline grain growth was observed just beneath of the edge of Cr strips. The activation of phosphorus atoms according to crystallization was also achieved.

Improvement of characteristics of polycrystalline silicon thin film transistors (poly-Si TFTs) was achieved by defect reduction methods of oxygen plasma at 250 ° C and at 30 W and 1.25×106-Pa high-pressure H2O vapor heat treatments at 270 ° C . Numerical analysis of transfer characteristics revealed that the combination of oxygen plasma for 40 min with the high-pressure H2O vapor annealing for 3 h effectively reduced the densities of deep level states from 1.4×1018 (as crystallized) to 1.6×10 17 cm −3 and the densities of tail states from 9.2×1018 (as crystallized) to 2.7×10 18 cm −3 , respectively. The threshold voltage of transfer characteristics was reduced from 4.1 to 1.3 V through the defect reduction.

We experimentally studied the material structures of two-/three-dimensional (2D/3D) silicon carbon layers Si1− Y C Y with Y ≤ 0.25 and 5 ≤ N L ≤ 162 [N L is the atomic layer number of Si1− Y C Y )] on buried oxide (BOX), which were fabricated by hot-C+-ion implantation into a (100) silicon-on-insulator (SOI) substrate before an oxidation process. A 2D Si layer was also fabricated as a reference. The C 1s spectrum obtained by X-ray photoemission spectroscopy shows that the implanted C atoms segregate at the oxide interface. Using a scanning transmission electron microscope and a high-resolution scanning transmission electron microscope to observe cross sections of Si0.75C0.25 layers, 2-nm-thick 3C-SiC layers were found be partially formed in the C segregation layer near the BOX interface. At Y > 0.1 and 5 ≤ N L ≤ 162, we observed very strong photoluminescence (PL) emission in the UV/visible regions from a 3C-SiC area and a Si1− Y C Y area in the C segregation layer, whereas a 2D Si emitted weak PL photons only at N L < 10. Thus, the silicon carbon technique is very promising for Si photonics and bandgap engineering in CMOS.

We report passivation on the silicon surfaces by combination of oxygen radical and high pressure H 2 O vapor heat treatment. The top bear surface of 20 Ωcm n-type silicon substrates with the rear surface coated by 100 nm thermally grown SiO 2 layers were treated by oxygen radical generated from oxygen plasma via a metal mesh closing the plasma induced by 13.56 MHz radio frequency induction-coupled remote plasma with mixed gases of O 2 and Ar at 10 sccm, 1.0 Pa and at a power of 100 W. The samples were subsequently annealed with 1.3×10 6 Pa H 2 O vapor heat treatment at 260°C for 3 h. A high effective minority carrier lifetime of 1.1×10 -3 s was achieved in the case of 635 nm light illumination on the top surface in the case of the oxygen radical treatment for 3 min. Metal-insulator-semiconductor-type solar cells were formed by formation Al and Au metal strips with a gap length of 17 μm on the passivated surfaces. When airmass 1.5 at 100 mW/cm 2 were illuminated on the rear surface with 100 nm thermally grown SiO 2 layers, solar cell characteristics were observed by applying voltage between Al and Au electrodes. The open circuit voltage and efficiency were obtained as 0.51 V and 6.4 %.

We report crystallization of amorphous silicon (a-Si) thin films and improvement of thin film transistors (TFTs) characteristics using 2.45 GHz microwave heating assisted with carbon powders. Undoped 50-nm-thick a-Si films were formed on quartz substrates and heated by microwave irradiation for 2, 3, and 4 min. Raman scattering spectra revealed that the crystalline volume ratio increased to 0.42 for the 4-min heated sample. The dark and photo electrical conductivities measured by Air mass 1.5 at 100 mW/cm2 were 2.6x10-6 and 5.2x10-6 S/cm in the case of 4-min microwave heating followed by 1.3x106-Pa-H2O vapor heat treatment at 260°C for 3 h. N channel polycrystalline silicon TFTs characteristics were improved by the combination of microwave heating with high-pressure H2O vapor heat treatment. The threshold voltage decreased from 5.3 to 4.2 V and the effective carrier mobility increased from 18 to 25 cm2/Vs.

50-nm thick amorphous silicon films formed on glass substrates were crystallized by rapid Joule heating induced by an electrical current flowing in 100-nm-thick Cr strips formed adjacently to 200-nm-thick SiO2 intermediate layers. 3-μs-pulsed voltages were applied to the Cr strips. Melting of the Cr strips caused a high Joule heating intensity of about 1×106 W/cm2. Raman scattering measurements revealed complete crystallization of the silicon films at a Joule heating energy of 1.9 J/cm2 via the SiO2 intermediate layer. Transmission electron microscopy measurements confirmed a crystalline grain size of 50–100 nm. 1-μm-long crystalline grain growth was also observed just beneath the edge of the Cr strips. The electrical conductivity increased from 10-5 S/cm to 0.3 S/cm for 7×1017-cm-3-phosphorus-doped silicon films because of activation of the phosphorus atoms because of crystallization. The numerical analysis showed a density of localized defect states at the mid gap of 8.0×1017 cm-3. Oxygen plasma treatment at 250 °C and 100 W for 5 min reduced the density of the defect states to 2.7×1017 cm-3.

Melt-regrowth properties of 60-nm-thick silicon films were characterized in the case of electrical-current-induced joule heating. The electrical energy accumulated at a capacitance caused melting of the silicon films via joule heating with a maximum intensity at 1.5×106 W/cm2. The melt-regrowth duration increased from 6 to 75 μs as the capacitance increased to 0.05–1.5 μF. Crystalline properties of the silicon films were also investigated. 7 μm long crystalline grains with the (110) preferential crystalline orientation were observed using a transmission electron microscope. The tensile stress at 3.4×108 Pa remained in the films. The analysis of electrical conductivity resulted in a density of defect states of 3.5×1016 cm−3 in the films. The product of the generation efficiency, the carrier mobility and the average carrier lifetime was estimated to be ∼10−3 cm2/V.

The analysis of free-carrier optical absorption was applied to investigation of electrical properties for doped microcrystalline silicon "lms formed at 100}1803C by the RF-plasmaenhanced chemical vapor deposition method. The analysis gave in-depth characteristics of the carrier mobility and the carrier density. The electron mobility was 8 cm2/Vs (phosphorous doped) and 6 cm2/Vs (boron doped) at the surface region and it decreased to & 1c m2/Vs at bottom "lm/substrate interfaces. The carrier mobility and density were much higher than those obtained by Hall e!ect current measurements. It shows the existence of substantial nonactivated and disordered regions among crystalline grains. ( 2001 Elsevier Science B.V. All rights reserved.

We report epitaxial growth of polycrystalline silicon films using microwave-induced PECVD from initial laser crystallized silicon formed on glass substrates. Undoped silicon was first crystallized by a method of pulsed laser-induced rapid melt-regrowth. Crystalline volume ratio of 100 nm thick microcrystalline silicon layer subsequently deposited on the bottom laser crystallized layer increased from 0.2 to 0.37 as the ratio of the bottom layer increased from 0.69 to 0.8. Epitaxial growth ratio was determined as 0.45 for the present CVD method. The electrical conductivity of doped microcrystalline silicon top layer also increased because of increase crystalline volume ratio.

We report dependences of electrical properties on SiH 4 /H 2 dilution rate and film thickness for microcrystalline silicon films formed by a hydrogen radical-induced chemical vapor deposition (HRCVD) method. The electrical conductivity of the films at SiH 4 18 sccm /H 2 120 sccm was markedly increased to 10 −3 S/cm as film thickness increased above 100 nm. Crystalline grains with (2 2 0) orientation were formed. Theoretical analysis revealed that grain boundaries among (2 2 0) grains had a low defect density of 1×10 12 cm −2 so that the high conductivity was achieved.

An improvement of electrical properties of pulsed laser crystalllized silicon"lms was achieved by simple heat treatment with high-pressure H 2 O vapor. The electrical conductivity of 7.4]1017 cm~3 phosphorus-doped 50-nm-thick pulsed laser crystallized silicon "lms was markedly increased from 1.6]10~5 S/cm (as crystallized) to 2 S/cm by heat treatment at 2703C for 3 h with 1.25]106 Pa H 2 O vapor because of reduction of density of defect states localized at grain boundaries. Spin density was reduced from 1.7]1018 cm~3 (as crystallized) to 1.2]1017 cm~3 by heat treatment at 3103C for 3 h with 1.25]106 Pa H 2 O vapor. ( 2001 Elsevier Science B.V. All rights reserved.

High-pressure H 2 O vapor heating was applied to oxidation of SiO x (x < 2) films formed on silicon substrates at room temperature by thermal evaporation in vacuum, in order to improve properties of SiO x /Si interfaces for passivation of silicon surfaces. The SiO x films were oxidized with an activation energy of 0.035 eV. The spin density of unpaired electron decreased from 2.3 × 10 17 to 1.4 × 10 15 cm -3 by the heat treatment at 260°C with 2.1 x 106 Pa H 2 O vapor for 3 h. The surface recombination velocity for excess carriers decreased from 405 (as deposited SiO x film) to 13 cm/s. There was no change in the surface recombination velocity after keeping the samples at an atmospheric pressure and at room temperature for 8000 h. Suitable passivation of silicon surface was achieved by simple heating with high-pressure H 2 O vapor at low temperature.

We investigated a simple field effect passivation of the silicon surfaces using the high-pressure H 2 O vapor heating. Heat treatment with 2.1 x 10 6 Pa H 2 O vapor at 260°C for 3 h reduced the surface recombination velocity from 405cm/s (before the heat treatment) to 38cm/s for the thermally evaporated SiO x film/Si. Additional deposition of 140 nm-SiO x films (x < 2) with a high density of fixed positive charges on the SiO 2 /Si samples further decreased the surface recombination velocity to 22 cm/s. We also demonstrated the field effect passivation for n-type silicon wafer coated with thermally grown SiO 2 . Additional deposition of 210 nm SiO x films on both the front and rear surfaces increased the effective lifetime from 1.4 to 4.6 ms. Combination of thermal evaporation of SiO x film and the heat treatment with high-pressure H 2 O vapor is effective for low-temperature passivation of the silicon surface.

Carrier transport properties were investigated for polycrystalline silicon (poly-Si:H:F) films fabricated at 300 °C by 100 MHz plasma enhanced chemical vapor deposition from gaseous mixture of SiF4 and H2. Analysis of free carrier optical absorption (FCA) revealed that 1 μm thick (400) oriented phosphorus-doped poly-Si:H:F films with a carrier concentration of 5×1019 cm−3 had the average electron mobility in crystalline grains at 40 cm2/V s, while the electron mobility of the (220) oriented phosphorus-doped poly-Si:H:F films was only 12 cm2/V s. These results indicated that (400) oriented poly-Si:H:F films had excellent quality crystalline grains. Analyses of the FCA combined with Hall effect current measurements revealed that the electrical conductivity at grain boundaries of top doped films increased as the underlying film thickness increased from 0 to 280 nm for (400) oriented phosphorus-doped/undoped double layered samples, but grain boundaries still acted as large resistive regions limiting the effec...