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Temperature-dependent emission current–voltage measurements were carried out for nitrogen (N)-doped nanocrystalline diamond (NCD) films grown on n-type Si substrates by microwave plasma-assisted chemical vapor deposition (MP-CVD). Low threshold temperature (~ 260 °C) and low threshold electric field (~ 5 × 10− 5 V/µm) were observed. Both the temperature dependence and the electric field dependence have shown that the obtained emission current was based on electron thermionic emission from N-doped NCD films. We have also studied the relation between nitrogen concentration and the saturation emission current. The saturation current obtained was as high as 1.4 mA at 5.6 × 10− 3 V/µm at 670 °C when the nitrogen concentration was 2.4 × 1020 cm− 3. Low value of effective work function (1.99 eV) and relatively high value of Richardson constant (~ 70) were estimated by well fitting to Richardson–Dushman equation. The results of smaller φ and larger A′ suggest that N-doped NCD has great possibility of being a highly efficient thermionic emitter material.

We have fabricated the stacked interconnects of multi-layer graphene (MLG) and nickel (Ni) at the line width from 30 to 1000 nm in 300 mm wafer. MLG, which was grown by CVD process, was selectively deposited on Ni damascene interconnects by the catalytic reaction of Ni. MLG grown from C 2 H 2 was composed of approximately 20 layers of graphene sheets and covered the overall surface of Ni interconnects. Two processes, one with the gas mixture of C 2 H 2 /Ar and the other with only Ar gas, were compared and short failure was observed at the comb structure specifically by the usage of C 2 H 2 gas. Along with the failure analysis, this short failure was suggested to be caused by the unintended growth of carbon material from the Ni nanoparticle on the interconnects. An addition of ashing process improved the electrical performance with the minimum damage to MLG. At last, crystalline analysis of MLG suggests a necessity of a continuous process optimization of CVD process for positive influence on resistivity of the interconnects.

Electrical characteristics of n-type diamond Schottky diodes and metal/diamond interfaces have been systematically investigated for phosphorus (P)-doped homoepitaxial diamond layers. The current-voltage (I-V) characteristics of the Ni/n-type diamond Schottky diode show excellent rectification properties from 297 K to 773 K. The ideality factor and the rectification ratio were 1.0 and ∼10 6 at +10 V at 573 K, respectively. The rectifying properties deteriorated with increasing P concentration in the diamond layers. Temperature-dependent capacitance-frequency (C-f) and conductance-frequency (G-f) measurements on the Schottky diodes have shown that the capacitance is reduced at high frequency due to the inability of deep centers to maintain an equilibrium ionization state under a high-frequency modulation. C- V measurements deduced that the P electrical activity (the ratio of the net donor concentration to the P concentration) was nearly 1 from low concentration (1.6 x 10 16 cm -3 ) to high concentration (2.7 x 10 18 cm -3 ) of P. The Schottky barrier height was found to be almost constant at ∼4.3 eV independent of the metal work function (Ni, Pt, Al and Ti).

Generation and recombination processes of electrons through phosphorus (P) donor are analyzed by admittance spectroscopy for a Ni/Au Schottky contact on an n-diamond epilayer. The dependence of capacitance and conductance frequency on temperature is interpreted by Shockley–Read–Hall statistics. The thermal ionization energy and capture cross-section of P donor are evaluated to be 0.54 ± 0.02 eV and (4.5 ± 2.0) × 10 − 17 cm 2 , respectively. Broadening of the conductance–frequency curve is observed, which is believed to be evidence of a long Debye tail of electron distribution at the depletion layer edge.

Electrical properties of phosphorus (P)-related donors have been investigated for P-doped homoepitaxial diamond layers grown by microwave plasma CVD. Temperature-dependent current–voltage (I–V), capacitance–voltage (C–V) measurements and frequency-dependent C–V measurements have been carried out with lateral dot-and-plane (with ring-shaped gap) Schottky barrier diodes. N-type Schottky junction properties were obtained. The ideality factor and the rectification ratio of the Schottky junction were obtained to be 1.9 and 1.7×105 at ±10 V and 473 K, respectively. Frequency-dependent measurements on these Schottky barrier diodes have shown that the capacitance is reduced at high frequency, most likely due to the inability of deep centers to maintain an equilibrium ionization state under a high-frequency modulation. C–V measurements deduced that the net donor concentration was 6.2×1017 cm−3 and the corresponding built-in potential was 4.0 eV, when the P concentration was 8.3×1017 cm−3. Phosphorus electrical activity was 0.75 in the P-doped diamond layer. The carrier thermal activation energy (the donor level) was evaluated to be 0.6 eV from the relation between the net donor concentration and the carrier concentration.

Electrical properties of B-related acceptor associated with B doping have been studied by current–voltage ( I – V ) measurements, frequency-dependent capacitance–voltage ( C – V ) measurements, Hall effect measurements and secondary ion mass spectroscopy measurements in B-doped homoepitaxial diamond layers grown by microwave plasma CVD. Lateral dot-and-plane (with ring-shaped gap) Schottky barrier diodes using Au/Ni and Au/Pt/Ti were fabricated. These diodes have been considered to be nearly ideal Schottky junctions, in which the ideality factor n was 1.04 at 300 K. Frequency-dependent measurements on these Schottky barrier diodes have shown that capacitance is reduced at a high-frequency, most probably due to the inability of a deep center to maintain an equilibrium ionization state under a high-frequency modulation. We have shown the relation between doped B concentration, net acceptor concentration and hole concentration at 300 K. B electrical activity, which means ratio of net acceptor concentration to B concentration, was found to be almost unity in the B concentration range from 5×10 16 to 6×10 17 cm −3 . It was considered that the background (or compensating) donor concentration is quite low in comparison with the net acceptor concentration in B-doped homoepitaxial diamond layer in this work.

R&D activities on diamond chemical vapor deposition (CVD) and field emission in the Frontier Carbon Technology Project are presented. The topics are (1) morphology control of diamond films grown by a 60-kW, 915-MHz microwave plasma CVD reactor, (2) growth technology of large single crystal diamond with a low density of defects, (3) heteroepitaxial growth technology of diamond films on Pt, (4) fabrication of sharp emitter tips on single crystal diamond, (5) field emission study from diamond particles, and (6) intense field emission from ion implanted homoepitaxial diamond layer. Research results of field emission obtained by Kyoto University and North Carolina State University are also described.

We have developed a CMP process providing a short polishing time and sufficient uniformity that is applicable to 300 mm scale carbon nanotube (CNT) via integration. To achieve our target, we have developed a new CMP process to make selectively grown CNT in a via hole. Spin on carbon (SOC)film was coated to protect nickel (Ni) catalyst and titanium nitride (TiN) film inside the via hole during SOC-CMP. The SOC-CMP process was used to perform two-step polishing to remove Ni catalyst and TiN film from the field area. CNT-CMP polishing time was reduced from 1690 sec to 200 sec and the yield ratio improved to 100%. CNT-CMP performance improved to a level usable for practical use by selectively growing CNT only from the via. We also evaluated the behavior of CNT-CMP during polishing using a damascene pattern wafer. Step height (Step height means a step between the wiring area and field area) occurred when CNT-SOG (spin-on glass) composite film was appeared upper the via hole but was reduced by concentrating the polishing pressure to project the CNT-SOG composite film. This result indicates that CNT-SOG composite film was polished by mechanical force.

Graphene is a promising material to replace copper interconnect metallization under 10 nm in width. We report a method for evaluating graphene interconnect wiring structure by conductive atomic force microscopy (C-AFM), which enables direct measurement of the 2D-resistance distribution and coverage evaluation of multilayer graphene (MLG) grown on Ni interconnects using a 300 mm damascene process. It is demonstrated that the coverage of MLG upon Ni can be estimated more precisely by C-AFM than that by back-scattered electron scanning electron microscopy (BSE-SEM) observation. We also measured the resistance of the MLG/Ni conductor and confirmed conduction paths of the MLG/Ni interconnect. Process dependence of MLG shows that lower local resistance corresponds to higher G band and D band intensity ratio (G/D ratio) in Raman spectra. C-AFM is demonstrated to be a potential technique for local conductance evaluation of next generation interconnects.

We fabricated a carbon nanotube (CNT) via structure on a 300-mm wafer. We investigated the CNT chemical-mechanical polishing (CNT-CMP) behavior in an actual via pattern structure and clarified the technical issues of the CNT-CMP process. We developed a fabrication process of CNT via structures using selective CNT growth, which has a high potential for applying CNTs to high aspect ratio via structures.

The process conditions for improving the electrical properties of carbon nanotubes (CNTs) were investigated by using a blanket-structure method for quantifying CNT resistance independently. The growth mechanism of CNTs formed with two different gas precursors was investigated from the viewpoint of crystallinity, growth-length uniformity, and resistance. Although the formed CNTs still require further improvements to obtain a ballistic transport property, it was found that the resistance of CNTs is reduced by using a two-step growth method that produces a multi-wall CNT structure and a uniform micrometer-order growth length.

A cold cathode fluorescent lamp (CCFL) is a gas discharge light source widely used for liquid crystal display (LCD) backlighting. We proposed applying diamond as a new cathode material to reduce the power consumption of the CCFL. In this work, we show stable and low (less than 50% of metal) cathode-fall voltage for a glass discharge tube.

The present work investigated the possibility of the formation of graphene interconnects and studied the behavior of graphene growth in wiring structure. Graphene nucleated on the facet of catalytic metal, and multi layer graphene grew along the terrace surface of catalytic metal. Selective graphene growth served the stacked interconnects structure of graphene / Ni catalytic metal.

Temperature-dependent current–voltage (I–V), capacitance–voltage (C–V) measurements, and frequency-dependent C–V measurements have been carried out to investigate electrical properties of phosphorus (P)-doped n-type homoepitaxial diamond layers. We have fabricated lateral dot-and-plane (with ring-shaped-gap) Schottky barrier diodes. Frequency-dependent capacitance measurements revealed the existence of a deep donor level. C–V measurements deduced that the net donor concentration was 6.2×1017 cm−3 and the corresponding built-in potential was 4.0 eV, when the P concentration was 8.3×1017 cm−3. Phosphorus electrical activity was 0.75 in the P-doped diamond layer. The carrier thermal activation energy (the donor level) was evaluated to be 0.6 eV from the relation between the net donor concentration and the carrier concentration.

A 2/3-in 400-k pixel-stack-CCD (charge coupled device) image sensor that has bias charge injection into the a-Si layer is described. Because the bias charges fill the deep level traps in advance, image sticking is reduced to imperceptible levels 0.3 s after 10000*standard incident light is turned off. This device has the frame interline transfer architecture; the V-CCD (vertical-CCD) registers are used not only as signal charge transfer paths in the vertical-blanking period, but also as blooming drains in the signal-charge-integration period. The equivalent circuit of the stack-CCD sensor is shown along with a cross-section view of the unit pixel in the stack-CCD sensor. >

We have succeeded in fabricating ultrafine carbon nanotube (CNT) via interconnects with SiOC interlayer dielectrics. High-quality multiwalled CNTs are grown in via holes with a diameter of 70 nm using pulse-exited remote plasma-enhanced chemical vapor deposition at 450 °C. The resistance of a 70-nm-diameter CNT via is 52 Ω, which is the lowest ever reported for CNT via interconnects. The CNT via interconnect has the capability to sustain current density as high as 1×108 A/cm2.

A highly sensitive 2-million-pixel high-definition charge-coupled device (CCD) image sensor was developed that features an overlaid amorphous silicon photoconversion layer on an interline transfer-type CCD scanner. The device is adapted to the 16:9 aspect ratio. 1125 scanning lines and 2:1 interlace high-definition TV system. A dual-channel horizontal CCD register is used to reduce the operating frequency to one half of the 74.25-MHz readout frequency. A horizontal period signal storage memory (1H line memory) is provided between the vertical CCD register and the horizontal CCD register to provide the signal distribution from the vertical CCD to the horizontal CCD register during the 3.77- mu s short horizontal blanking interval. This device realized a 1000 TV line horizontal limiting resolution 210 nA/1x high sensitivity. Total random noise was found to be 52 electrons RMS and a 72-dB dynamic range was achieved. >

Simultaneous surface topography and conductivity/potential measurements were carried out on low-field-emission (1 V/μm) carbon films by combining conductive atomic force microscopy and Kelvin probe force microscopy. The current image showed that highly conducting sites and nonconducting regions coexisted on a micro- and/or nanoscale. Further, in situ I–V characteristics of both regions demonstrated that the conducting sites have an Ohmic property, whereas nonconducting regions have a degenerated Schottky property. When combined with the current image, the contact potential difference image showed that the conducting sites have a highest contact potential difference of 0.5 V, which implies the existence of a graphite phase. It is revealed that the conducting channels play an important role in the low-field-emission process. It is also suggested that the combination of conductivity and surface-potential measurements is an effective method for investigating complex-phase nanostructural surfaces.

Multiwalled carbon nanotubes (CNTs) have been grown by remote plasma-enhanced chemical vapor deposition at temperatures as low as 400 °C. In via formation, the selective growth of CNT bundles in via holes at 430 °C and chemical mechanical polishing for planarization have been performed. The electrical evaluation of CNT single vias with various diameters reveals that the via resistance is inversely proportional to the via area. This result indicates that the CNTs are grown with uniform quality and density in the via holes with various diameters and stable contact formations are obtained. Moreover, the resistances of single vias are approximately equivalent to the via resistances estimated from the resistances of via chains, demonstrating the via-to-via uniformity of the CNT vias obtained by the remote plasma-enhanced chemical vapor deposition.

Graphene is a promising material to replace Cu-interconnect metallization under a width of 10 nm. We report a method for evaluating the graphene interconnect wiring structure by conductive atomic force microscopy (C-AFM), which enables the direct measurement of the two-dimensional (2D) resistance distribution and the coverage evaluation of multilayer graphene (MLG) grown on Ni interconnects using a 300 mm damascene process. The resistivity of exfoliated two-layer graphene was measured and a reasonable value of 30 µΩcm was obtained. We also measured the resistance of the MLG/Ni stack of 350 nm L/S patterns and confirmed the conduction paths of the MLG/Ni stack. It is demonstrated that the coverage of MLG on Ni interconnects can be estimated more precisely by C-AFM than by backscattered electron scanning electron microscopy (BSE-SEM) observation. C-AFM is demonstrated to be a potential technique for the local conductance evaluation of next-generation interconnects.

Shrinking pixel size in conventional CCD imagers degrades device performance. Unsatisfactory smear noise of -90 dB is attained in a 2/3-inch 2M pixel CCD imager. The STACK-CCD imager has a great advantage regarding this problem. A 100% aperture ratio and low smear noise are maintained regardless of future pixel shrinking, because CCD scanning circuits are overlaid with an amorphous silicon (a-Si) photoconversion layer. >

An Hg-sensitized photochemical vapor deposition method has been developed which has enabled the hydrogenated amorphous silicon photoconversion layer to be overlaid on a CCD (charge coupled device) imaging device, without requiring the pixel separation structure. The a-Si:H photoconversion layer prepared by the Hg-sensitized photo-CVD method has several advantages, including high resistivity, coverage conformable to an uneven substrate, few line defects grown between adjacent image pixels, low SiH/sub 2/ bond content without missing the high resistivity, and few dust fragments generated. This CVD method has been used to realize imaging devices with high sensitivity and high resolution for high definition TV. >

Total photoyield spectroscopy (TPYS) measurement is applied to boron (B)-doped polycrystalline diamond, which shows an extremely low cathode fall voltage (Vc) in glow discharge operation. The B-doped diamond film grown on a molybdenum (Mo) substrate shows Vc of about 43 V after hydrogenation with a small amount of hydrogen added to argon (Ar + 0.03% H2). This Vc value is almost 1/3 that of the Mo substrate without diamond. The TPY spectrum of the diamond after hydrogenation in microwave hydrogen plasma shows obvious onset at 4.5 eV, which is below the band-gap energy of diamond (5.47 eV). This is attributed to the negative electron affinity (NEA), which results in an electron affinity of −1.0 eV. Vc and TPY spectra are also measured for acid treatment condition and Mo. From these experiments, the low Vc values of B-doped polycrystalline diamond depending on the surface treatment correlate to the difference between electron affinities derived from the TPYS measurements.

Multilayer graphene (MLG) is expected to be a low-resistance and high-reliability interconnect material replacing copper (Cu) in nanoscale interconnects. To achieve low-resistance interconnect with MLG, carrier doping is necessary since the carrier concentrations in pristine MLGs are low. In this work, the effects of bromine (Br) doping by intercalation on the carrier concentration and sheet resistance of exfoliated highly oriented pyrolytic graphite (HOPG) were investigated by measuring the Fermi level shift using ultraviolet photoelectron spectroscopy (UPS) and the four-terminal method, respectively. The Fermi level was shifted downward up to 0.63 eV, and the sheet resistance was reduced to less than 10% of that of the pristine HOPG by increasing the Br concentration. A similar Fermi level shift was observed for the commercially available CVD-MLG. Br doping is thus promising for low-resistance MLG interconnects from the perspective of carrier doping.

Low-resistance metal contacts for CVD-nanocarbon (NC)/cobalt (Co) interconnects have been investigated among contact metals such as Ni, Ti, Au, and Cu. Contact resistivity was independent of contact area owing to low-resistance NC/Co interconnect structure. The lowest contact resistivity and superior adhesion were obtained from Ni. Although the factors for the low contact resistivity were not clear enough from the comparison of work-function difference and adhesion strength for the contact metals, Ni is a promising low-resistivity contact metal for CVD-NC interconnects in the future.

Multilayer graphene (MLG) is expected to be a low-resistance and high-reliability interconnect material replacing copper (Cu) in nanoscale interconnects. Chemical vapor deposition (CVD) on catalytic metals is expected as a practical method for MLG deposition. To obtain high-quality MLG films without catalyst agglomeration by CVD, heat-resistant Co–W catalytic metals were investigated. The agglomeration of the Co–W catalytic metals was suppressed by increasing the W composition; however, MLG deposition was suppressed at the same time. The effects of W addition on the MLG growth were discussed from the viewpoints of the crystallographic change of the Co–W catalysts and chemical reactions. It was found that the Co grain size was reduced and the fcc Co formation was suppressed by W addition. In addition, graphite formation was supposed to be suppressed by W addition owing to the formation of phases other than fcc Co according to the Co–W–C phase diagram. With the optimum W concentration, MLG crystallinity was improved by high-temperature CVD using the heat-resistant Co–W catalytic metals (0.7 at. %) without agglomeration, compared with that in the case of using pure-Co catalysts.

In order to realize a high conductive carbon nanotube (CNT) via structure, an accurate evaluation of electrical properties of CNTs and their metal contacts is essential. We succeeded in evaluating the resistance of CNTs and their contacts individually by using our proposed test method and test structure. The contact resistance of CNTs to metals was dependent on the types of contacting metals, which can be explained by the Gibbs energy of oxide formation and differences in work functions of each metal with CNTs and adhesion property. Ti and Pd had common chemical and mechanical characteristics and showed the lowest contact resistance with CNTs among contact metals we used.

We fabricate planarized carbon nanotube (CNT) via interconnects using chemical mechanical polishing (CMP). The selective growth of CNT bundles in via holes and the filling of spin-on-glass into the space among the CNTs are performed, followed by a CMP process. The via resistance is reduced by post-CMP treatment and post-annealing due to the improvement in the top contact formation. The measured CNT via resistance is higher than the CNT bundle resistance estimated from the measured resistance of an individual CNT. This indicates that contact resistance is higher than the CNT resistance in the CNT via interconnect.

We explored the characteristic behavior of low-temperature graphene growth on catalytic metal films. The results suggested that graphene growth originates from the crystalline facets with specific angles with respect to the crystalline orientation of the catalytic metals at low temperatures, which is different from the conventional growth models. The G/D ratio of the Raman spectrum of the graphene film was affected by both the number of specific facets and the width of the terrace. Because of this behavior, it is important to prepare the surface conditions with a smaller number of facets and a wider terrace for high-quality graphene growth at low temperatures.

We report on the electrical properties of carbon nanotube (CNT) via interconnects with improvement in contact formations between the CNT via and metal electrodes. For the improvement of the bottom contact formation, a TiN/TaN multilayer on a Cu bottom wiring layer is applied to suppress formation of a highly resistive oxide layer on the TaN barrier layer. The top electrode formation with good coverage on CNTs reduces contact resistance. The current–voltage characteristics of ultrafine CNT via interconnects exhibit ohmic behavior. The resistance of the CNT via interconnect is inversely proportional to the via area, indicating that the CNT bundles are grown with uniform quality and density in various-diameter via holes.

We report a synthesis of a closely packed multi-walled carbon nanotube (MWCNT) forest by a multi-step growth method, including a new approach to immobilize catalytic nanoparticles, using plasma-based chemical vapor deposition. The CNT packing density reaches one-half of the theoretical value, where the space of 30–40% is filled with MWCNTs. This value is approximately one order of magnitude larger than that of as-grown CNT forest synthesized using conventional methods. The method is applicable even at a spatially restricted region, for example, in trench or via hole, and is available at the growth temperature as low as 450 °C.

Carbon nanotubes (CNTs) have been grown by surface-wave plasma-enhanced chemical vapor deposition (CVD) using size-classified Co nanoparticles at low temperatures. A mesh grid is used in the remote plasma-enhanced CVD system for the suppression of ion bombardment damage from plasma. The control of the electric field distribution using a mesh grid with a narrower opening is effective for the CNT growth. Multiwalled CNTs are obtained at a low temperature of 400 °C under low ion-density conditions. No significant difference in the microscopic structure of the CNTs grown at temperatures between 400 and 500 °C is observed.

Carbon nanotube (CNT) growth at temperatures below 400 °C by pulse-excited remote plasma chemical vapor deposition was demonstrated. Reduction of plasma power was carried out in order to decrease the amount of all particles, ions, electrons, and radicals. In addition, a biased plate-type screening electrode was introduced to removal of charged particles, ions, and electrons. The negative bias below 50 V was most effective for growth rate. High-quality CNT growth with the growth rate of 98 nm/min was successfully obtained at 400 °C. The results suggest that both removal of charged particles and control of the amount of radicals are important for high-quality CNT growth at temperatures below 400 °C.

The ratio of Si-H2 bonds to hydrogen content in hydrogenated amorphous silicon films, prepared by mercury-sensitized photochemical vapor deposition, depends on the deposition conditions, in particular on the distance between the substrate and the light-transparent window.The ratio is reduced from 20 % to 8 % by decreasing the distance from 30 mm to 8 mm. On the other hand, the hydrogen content remains constant at 15 at.%. Decreasing the distance has been found to be almost equivalent to increasing the light intensity, especially 254 nm-light intensity.

Capture and emission processes of electron at phosphorus (P) donor in a n-diamond epilayer are analyzed by admittance spectroscopy. Dependence of temperatures on capacitance and conductance-frequency curves is well explained by Shockley-Read-Hall statistics. Thermal ionization energy and capture cross section of P donor are evaluated to be 0.54±0.02eV and (4.5±2.0)×10−17cm2, respectively. Broadening of the conductance-frequency curve is observed, which is believed to be due to a large Debye tail of electron distribution at a depletion layer edge.

Conductive scanning probe microscopy (SPM) was applied to field-emission carbon films. The microstructures, conductivity and surface potential properties of carbon films were investigated by conductive atomic force microscopy (AFM) and Kelvin probe force microscopy (KFM), as well as a combination of the two techniques. SPM was proven to be very effective for the study of materials with multiple phases and complex structures, and in clarifying the low-field-emission mechanism.

Transfer mold type field emitter arrays which integrate a novel self-aligned Si gate have been fabricated. Applying the self-limiting Si etching technique, a part of the Si-mold substrate was preserved for the gate structure to simplify the gate fabrication process and to improve the gate aperture shape reproducibility. The gate aperture (Dg) was precisely controlled and a minimum Dg of 0.15 μm was achieved with conventional photolithography techniques. Also, Dg could be widely varied by changing only the size of the emitter mold, and the relationship between Dg and the emission threshold gate voltage (Vth) under identical emitter tip conditions was studied.

An Hg-sensitized photochemical vapor deposition method has been developed which has enabled a hydrogenated amorphous silicon photoconversion layer to be overlaid on a charge coupled device (CCD) imager, without a pixel separation structure. This chemical vapor deposition (CVD) method has been used to realize imaging devices with high sensitivity and high resolution for high-definition TV.

The relations between the photocurrent transient after the end of steady-state illumination for hydrogenated amorphous silicon photodiodes and the related film properties for undoped hydrogenated amorphous silicon prepared by mercury-sensitized photochemical vapor deposition are investigated. The photocurrent transient characteristic indicates significant correlations with the film properties, such as electron drift mobility ( mu /sub d/), silicon dangling bond density (N/sub s/), a minimum in the density of states near the Fermi level (N/sub min/), and space-charge density (N/sub i/). The photocurrent transient decay decreases with increasing mu /sub d/ and with decreasing N/sub s/, M/sub min/, and N/sub i/. This result was confirmed by a model analysis. >

Hydrogenated amorphous silicon (a-Si:H) films were prepared by mercury photosensitized decomposition of silane using a low-pressure mercury lamp. The deposition rate showed an activation type for substrate temperature (the activation energy: 0.13 eV), because the deposition rate would be determined by the rate of hydrogen elimination from the hydrogen saturated surface. Moreover, the relationship was found between the Si-H2 bond density in a- Si:H films and the gas phase reactions.

An etching study for undoped a-Si:H films and c-Si has been carried out by using Hg-sensitized H radicals in H2 gas under UV-light irradiation with a low pressure mercury lamp. It has been found that the etch rate of undoped a-Si:H increases with decreasing substrate temperature and H2 flow rate, as well as with increasing UV-light intensity. Concerning H2 gas pressure dependence, a maximum etch rate was observed at around 0.1 Torr. An adsorbed layer, composed of H2 molecules, H radicals, Hg atoms and photoexcited Hg atoms, can be considered to be formed on the surface. The adsorbed layer irradiated with UV light may supply a sufficient number of H radicals near the surface to rapidly cut off the Si network, leading to the formation of volatile SiH x .

The correlation between Si-H2 bond density and electron drift mobility in a-Si:H films has been investigated by using the dependence of the film properties on the silane gas pressure in mercury-sensitized photochemical vapor deposition. It was found that the electron drift mobility decreased with increasing the Si-H2 bond density, when the hydrogen contents were about the same amount.