Kiichiro Kamata

Conductive indium-doped zinc oxide films prepared by atmospheric-pressure chemical vapour deposition

Abstracts are not published in this journal

PREPARATION OF NITROGEN CONTAINING CARBON FILMS USING CHEMICAL VAPOR DEPOSITION ENHANCED BY ELECTRON CYCLOTRON RESONANCE PLASMA

A chemical vapor deposition apparatus enhanced by electron cyclotron resonance plasma was employed to deposit nitrogen containing carbon films. In the apparatus, negative dc bias voltage was applied to the substrate for acceleration of positive ions toward the substrate. The deposition rate and nitrogen content of the film was found to be mainly dependent upon the deposition conditions. Although a large N2 flow rate and bias voltage contribute to inhibit film growth through surface sputtering of the substrate, an optimum [N2]/([CH4]+[N2]) flow rate of 0.67 and a bias voltage of 50 V promote nitrogen implantation into the growing films through possible nitrogen ion bombardment.

Rapid formation of TiO2 films by a conventional CVD method

TiO2 is attractive as a dielectric material in integrated electronic applications [1], semiconductor devices in photo-catalytic reactions [2], gas sensors [3], and so on. The authors have already reported on the deposition of various ceramic thin films such as ZnO [4], MgO [5], Y203 [6] and ZrO2 [6] by a conventional chemical vapour deposition (CVD) method. Following this, a rapid formation of TiO2 films by the CVD process will be described in this report. Assuming that a homogeneous CVD reaction occurs in the gas phase, it is claimed that powder formation is negligible at low temperatures and predominates over film formation at higher temperatures [7]. This reaction model can explain a large body of experimental evidence and indicates the existence of an upper limit on the growth rate of films [7]. Several papers on the formation of TiO2 films by the CVD method have reported generally low growth rates of 0.1 to 7 .0nmsec l (e.g. 7 n m s e c t [8]). Recently, Komiyama et al. [9] succeeded in the rapid formation of porous and amorphous TiO2 films at around 30 nmsec ~ by the CVD method associated with thermophoretic precipitation [9]. However, the rapid formation of TiO2 films can be realized by the conventional CVD method without the adoption of the thermophoretic effect. This report demonstrates a rapid formation of TiO 2 films, and refers to some factors affecting the growth rate of films such as substrate temperatures, distance between the substrate and the nozzle head, vaporizing temperature, flow rate of gases and water vapour content. Concomitantly, the activation energy for the formation of TiO 2 films will be estimated. Fig. 1 shows the assembly used for the formation of TiO2 films. Dried N 2 gas (6 cm 3 sec 1) passed through CaC12 and P205 columns was bubbled through a flask containing titanium tetraisopropoxide, Ti(OC3H7)4, (TTI) held at 80 to 130 ° C. In addition, 02 gas (3 to 12 cm 3 secl ) was bubbled, if necessary, though a flask containing water held at room temperature ( ~ 68 ° C), then introduced into the reagent-containing N 2 gas near the top of a nozzle with an outlet diameter of 3 ram. The distance between the nozzle and the substrate was 5 to 25 ram. The nozzle and other parts of the apparatus were warmed by ribbon-type heaters in order to avoid the condensation of TTI. The mixed gas stream was injected with a linear velocity of 127cmsec i on to the crown glass substrate, which rested on a hotplate maintained at the desired temperature (300 to 500 ° C). The reaction conditions are summarized in Table I. The thickness of the TiO2 films obtained was measured by a roughness meter with a diamond probe. Adhesive TiO2 films were obtained above ca. 300 ° C substrate temperature (T~). Fig. 2 shows the relationship between Ts and the growth rate of the TiO2 film under the conditions of a vaporizing temperature (T~) of 80 and 100 °C. The growth rate increases with increasing T~, and beyond 100 nm sec i. X-ray diffraction patterns of the TiO2 films obtained above T~ = 400°C indicated the preferred orientation of (1 0 1), (20 0), (2 1 1) and (220) planes ofanatase TiO2

Effect of negative dc bias voltage on mechanical property of a‐C:H films deposited in electron cyclotron resonance plasma

Amorphous C:H films were deposited with CH4‐Ar‐H2 using a chemical vapor deposition apparatus assisted by electron cyclotron resonance plasma. The effects of applying negative dc bias voltage on the mechanical property and the microstructure of the films were examined. The microhardness of the films increased rapidly at a threshold value of the bias voltage at each gas ratio, [Ar]/([Ar]+[H2]). The results obtained from Raman spectroscopy suggest that the films contain diamondlike structure added to polymer structure over the threshold value on the negative dc bias voltage. Although the dc bias voltage required to form diamondlike carbon (DLC) becomes stronger with the increase in the H2 flow rate, the approximate volume fraction of DLC in the films rapidly increases, implying that hydrogen is more effective to synthesize DLC films.Amorphous C:H films were deposited with CH4‐Ar‐H2 using a chemical vapor deposition apparatus assisted by electron cyclotron resonance plasma. The effects of applying negative dc bias voltage on the mechanical property and the microstructure of the films were examined. The microhardness of the films increased rapidly at a threshold value of the bias voltage at each gas ratio, [Ar]/([Ar]+[H2]). The results obtained from Raman spectroscopy suggest that the films contain diamondlike structure added to polymer structure over the threshold value on the negative dc bias voltage. Although the dc bias voltage required to form diamondlike carbon (DLC) becomes stronger with the increase in the H2 flow rate, the approximate volume fraction of DLC in the films rapidly increases, implying that hydrogen is more effective to synthesize DLC films.

Hybridization between Si3N4 and SiC films by plasma CVD

Preparation de films homogenes Si 3 N 4 -SiC par depot chimique en phase vapeur. Observation des films par microscopies electroniques a balayage et a transmission

Mechanical properties of SiNxCx ceramic films prepared by plasma CVD

The mechanical properties of Si3N4-SiC, SiNx and SiCy films prepared at a low temperature of 400 °C by plasma chemical vapour deposition are reported. Microhardness, internal stress of the film and adhesive strength between the film and glass or stainless steel substrate were evaluated as principal mechanical properties. Microhardness was measured to be about 10 to 20 G Pa dependent on the film composition in each system. Internal stress of the films on borosilicate glass substrates extensively varied from tensile to compressive with the film composition change from Si3N4 to SiC. Adhesive strength, as ascertained by the scratch test, was about 580 to 800 MPa for crown glass substrates, and about 210 to 310 M Pa for 316 stainless steel substrates. It is pointed out that tensile stress in these films brought about more abrupt decreases of the adhesive strength than did compressive stress.

Positive and negative direct current bias effects on the microstructures and physical properties of hydrogenated amorphous carbon films prepared by radio frequency plasma chemical vapor deposition

Positive and negative direct current (dc) bias effects were investigated for the synthesis of hydrogenated amorphous carbon films in radio frequency plasma chemical vapor deposition at 0.025 Torr and 200 °C. The applied bias ranged from +250 to −500 V. Both the positive and negative dc bias effects are discussed on the basis of surface and cross‐sectional morphology by scanning electron microscopy, deposition rate, threshold energy for photoelectron emission, contact angle, and adhesive strength of these films. For a negative bias, the surface of the film is very flat. The surface of the film deposited with no bias is somewhat pebbly while that of the film deposited with a positive bias is very rough and shows the presence of pores in the cross section. A negative bias substantially increases the deposition rate, refractive index, wettability, and adhesive strength. With no bias (ground potential), as compared to with a positive bias, there is a little increase in the wettability and adhesive force. The n...

Physical properties of diamondlike carbon films deposited in mixed atmospheres of C2H4–Ar, C2H4–H2, and C2H4–N2

Diamondlike carbon films were deposited in a pure C2H4 atmosphere and in mixed atmospheres of C2H4–Ar, C2H4–H2, and C2H4–N2 by radio frequency plasma chemical vapor deposition. The partial pressures of Ar, H2, and N2 were 25%, 50%, and 66.7%, respectively. The films were deposited with a high negative bias of −610 V. The hardness, the density, and the internal stress of the films decrease and the amount of gas evolution increases with increasing partial pressures of N2 and H2, while they do not depend on the partial pressure of Ar. These results show that N2 and H2 react with carbon in the films and decrease the degree of the crosslinking in the network structure, while Ar does not change the degree of crosslinking. The surface is very flat and the roughness (Rmax) is below 1 nm. The hardness is 40 GPa for the films deposited in atmospheres of pure C2H4 and mixed C2H4–Ar with a bias of −610 V.

Preparation of Zinc Oxide Films by Low-Pressure Chemical Vapor Deposition Method

ZnO and Al-doped ZnO films prepared using a low-pressure chemical vapor deposition (LP-CVD) method were studied. The films were prepared on fused quartz substrates using bis(2,4-pentanedionato)zinc and tris(2,4-pentanedionato)aluminum which are inexpensive and stable source materials. The highly c-axis oriented ZnO films were grown on the substrates above 500°C. The minimum electrical resistivity of ρ=6.5×10 −5 Ωm was obtained for the ZnO film, and of ρ = 3.5×10 −5 Ωm was obtained for the ZnO:Al film.

High Strength, Electrically Conductive Pore-free TiO 2 Ceramics made by Hot Isostatic Pressing

A high-purity, single-phase TiO 2 ceramic with high density, strength, and electrical conduction was developed as a key structural material for the production equipment of semiconductors. Green bodies were made of high purity rutile TiO 2 of very fine powder. They were sintered in air at 1200 °C for 2 h and then were hot isostatically pressed (HIPed) in argon at 1000 °C, 150 MPa for 2 h. HIPed TiO 2 ceramics were found to be electrically conductive and pore free. Their relative density, specific resistance, and bending strength were 100%, 1 Ω ·cm, and 300 MPa, respectively. No strength degradation was found to the temperature up to 1000 °C. This material has high potential for use as electrically conductive structure materials in the semiconductor industry.