Session EMP4 - Poster Session: Deposition.
POSTER session, Monday afternoon, October 19
Haku/Pikake Room, Aston Wailea

[EMP4.01] The deposition of SiOF film with low dielectric constant in a helicon plasma source

SiOF films deposited by a helicon wave plasma chemical vapor deposition method has been characterized using Fourier transform infrared spectroscopy and ellipsometry. High density plasma of 10^12 cm^-3 can be obtained on a substrate at low pressure(,10 mTorr) with rf power >400 W with a helicon plasma source. A gas mixture of SiF_4, O_2, and Ar was used to deposit SiOF films on 5 in. Si(100) wafers not intentionally heated. Optical emission spectroscopy was used to study the relation between the relative densities of the radicals and the deposition mechanism. It was found that the addition of Ar gas to the SiOF/O2 mixture greatly increased the F concentration in the SiOF film. Discharge conditions such as gas composition, sheath potential, and the relative densities of the radicals affect the properties of the film. The dielectric constant of the SiOF film deposited using the helicon plasma source was 3.1, a value lower than that of the oxide film by other methods.

[EMP4.02] Plasma Copolymerization of Fluorocarbon Sources and Hexamethyldisiloxane for the Application to Low Dielectric Constant Interlayer Dielectric Films

The plasma copolymerization of tetrafluoroethyelene (TFE) and hexamethyldisiloxane (HMDSO) was investigated for the purpose of application to low dielectric constant interlayer dielectric films. The films were prepared by using a conventional capacitively coupled RF (13.56 MHz) plasma enhanced chemical vapor deposition method.

Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy on the films have revealed that the film composition can be controlled gradually by changing the proportions of TFE/HMDSO. The dielectric constant of the films has ranged from 2 for the pure TFE films and 4 for the pure HMDSO films. Thermal treatment on the films has revealed that IR absorption peak intensity for C-H and C-H_2 decreases by the treatment, and dielectric constant of the films increases at the same time.

Film deposition mechanisms are also discussed with the aid of in situ FT-IR gas-phase absorption spectroscopy on the plasma during film deposition.

The results obtained for TFE/HMDSO gas are compared to those for commercially available C_4F_8/HMDSO gas.

[EMP4.03] Sputter Deposition of Carbon Nitride Films by Reactive High-Density Plasmas with Excitation of m=0 Mode Helicon Wave

Studies on the synthesis of carbon nitride (\beta-C_3N_4) films have attracted great interests due to the theoretically-predicted extreme properties similar or even superior to those of diamond. Motivated by the desire to establish a nitridation environment with extremely high reactivity for the synthesis of this metastable covalent material, we have developed a sputtering deposition system with installation of high-density helicon wave-excited plasma source to supply high concentration of atomic nitrogen. Carbon nitride films have been deposited on Si and WC substrates using reactive sputtering of carbon in N_2 and Ar mixture gas around 0.1 Pa. High-density plasmas of 10^12-10^13 /cm^3 were produced even in pure N_2 using a helical antenna, where the excitation of m=0 mode helicon wave was verified to propagate. The composition, structure and bonding states of the films were characterized by XPS and FTIR. The nitrogen to carbon (N/C) ratio in the films was found to be controlled up to 0.9. The XPS analysis suggested the formation of sp^3 bonding, which consistently correlated with the film microhardness.

[EMP4.04] RF-Compensated Langmuir Probe Measurements in an IPVD System

The experimental apparatus consists of a commercial-scale magnetron with an RF coil between the target and substrate holder. This coil creates a secondary inductive plasma that ionizes a significant portion of the sputter flux en route from target to substrate. In order to understand and predict the ionization of the sputter flux arriving at the substrate, Langmuir probe measurements of this secondary inductive plasma were made under various combinations of powers (magnetron and RF), pressures, and working gas mixtures. The probe apparatus is RF-compensated in order to keep the voltage difference between the probe tip and plasma constant throughout the RF cycle. In order to yield accurate measurements in the dirty depositing environment of the IPVD system, the back of probe tip is recessed in a small ceramic tube, preventing shorting. Further, the potential on the probe tip is kept low except during the data-collecting voltage sweeps in order to continuously clean it and maintain stable electrical characterisitics.

[EMP4.05] Characterization and Performance of a High-Current-Density Ion Implanter with Magnetized Hollow-Cathode Plasma Source

In a collaboration between the Institute of Electrophysics (IEP) and the Los Alamos National Laboratory (LANL), the IEP has developed an industrial scalable, high-power, large-area ion source for the surface modification of materials. The plasma source of the ion beam source can be described as a pulsed glow discharge with a cold, hollow-cathode in a weak magnetic field. Extraction and focusing of positive ions by an acceleration and ion-optical plate system renders the generation of a homogeneous, large-area ion beam with an averaged total ion current of up to 50 mA at acceleration voltages of up to 50 kV. The principle set-up of the ion beam source as well as some electrical characteristics (gas discharge current and the extracted ion beam current) are presented for a lab-scale prototype. Measurements of the radial ion current density profiles within the ion beam for various discharge parameters, as well as results on surface modification by ion implantation of nitrogen into aluminum and chromium are presented. Finally, a comparison of the applied ion dose with the retained ion doses is given.

[EMP4.06] Deposition of a-SiC:H Films on Si Substrate by 50Hz Plasma CVD using Hexamethyldisilane + H2

Hydrogenated amorphous silicon carbide (a-SiC:H) films have been deposited on Si substrates by 50Hz plasma using Hexamethyldisilane [((CH3)3Si2(CH3)3):HMDS] + H2 gas mixtures. Hexamethyldisilane has nonpyrophoric and nontoxic nature, and the plasma CVD method using HMDS is a safe process of SiC film deposition. Deposition rate, refractive index, Vickers hardness and IR spectrum of the deposited a-SiC:H films have been measured for various deposition temperature Tsub with a constant gas flow rates of the HMDS and H2 (12.5sccm and 250sccm). As Tsub increases, the deposition rate of the a-SiC:H films decreases, and becomes constant value of about 100nm/h at above Tsub =350^oC. The refractive index of the films was 2.4 for Tsub =350^oC, while the Vickers hardness was 2200Hv for Tsub =350^oC. The infrared transmission measurement shows that the films contain both Si-C and Si-CH3 bonds. The composition of deposited a-SiC:H films was measured by XPS method. It was found that Si, C and O atom were contained in the deposited a-SiC:H films. From these results, it seems that high quality a-SiC:H films was obtained with above Tsub =350^oC using HMDS+H2 gas mixture by 50Hz plasma CVD.

[EMP4.07] Plasma Parameter Control of the Spatially Afterglow Plasma for the Gr owth of 3C-SiC Epitaxial Films by Triode Plasma CVD

To grow epitaxial SiC films at low temperature, plasma parameters in the afterglow plasma region of hydrogen gas were extensively controlled using rf triode plasma CVD. Under negative grid biases, the discharge region was effectively confined between cathode and grid. The average sheath potential of anode surface drastically decreased from 60V at positive grid bias of 50V to about 1V at negative grid bias of -50V. The electron temperature in the afterglow plasma region also decreased to less than 1eV. The reduction of the rf plasma potential fluctuation was also investigated by the addition of bypass condensers between grid and grounded chamber. The amplitude of the potential fluctuation in afterglow plasma region decreased from several tens volts to less than 2V at grid bias of -100V with the bypass condenser. At the same time, the electron temperature decreased to less than 0.2eV. Using dimethylsilane diluted with hydrogen as the source gas, 3C-SiC films were epitaxially grown on hydrogen terminated Si substrates placed on the anode at 1000^oC under the above plasma conditions.

[EMP4.08] Preparation of ZnO thin films by remote plasma enhanced CVD method

Highly transparent ZnO films were successfully prepared by remote plasma enhanced CVD of Zn(C_2H_5)_2 and carbon dioxide. Zn(C_2H_5)_2 contained in a temperature-controlled bath was bubbled with H_2. Carbon dioxide flowed through a coaxial low-frequency discharge chamber, and then into a reactor. The Zn(C_2H_5)_2-H_2 mixture was introduced to the reactor separately. The flow rates of H_2 and carbon dioxide were set to 10 sccm and 100 sccm, respectively. The pressure in the chamber was kept at 3.75 Torr. Plasma excitation in carbon dioxide was critical in being able to deposit transparent films. The films deposited on glass substrates at temperature around 450 ^oC show polycrystalline nature with (0002) preferred orientation. Measurement by the X-ray Photoelectron spectroscopy (XPS) indicates that the deposited films are free from carbon contamination. The resistivity of the films is 10^6 Ømega\cdotcm range and high photosensitivity in near ultraviolet radiation.

In addition, we found that ZnO was epitaxially grown on sapphire single crystal substrate using this simple system. Reflection high-energy electron diffraction (RHEED) and X-ray diffraction patterns show that ZnO (11øverline20) plain is formed on a sapphire (1øverline102) plain.

[EMP4.09] Growth and Characterization of Polycrystalline Ge_1-xC_x Thin Films

Polycrystalline Ge_1-xC_x thin films have been prepared by ECR reactive plasmas. Systematic investigations were made into how deposition parameters affected the material properties of the resulting films. The films were grown from 300 to 500^oC, pressures between 5 and 25 mT, and microwave powers between 100 and 200 W. The substrates were glass, stainless steel, and [100] oriented Si wafers. The optical properties were measured by UV/VIS/NIR photospectroscopy and Photoreflectance Spectroscopy, the lattice parameters were measured by X-Ray Diffraction, the crystallinity was characterized by Raman Spectroscopy, and the atomic percent C in the films was measured by X-Ray Photoelectron Spectroscopy. The films displayed excellent crystallinity, approximately 0 to 3 at. percent C, and the values of the bandgap and lattice dimensions could be varied continuously with the amount of C alloyed in the films. Ge_1-xC_x films are of particular interest to the microelectronics industry because they offer a new option for the design of Group IV heterojunction devices.

[EMP4.10] Trench Filling and Deposition of High Quality Cu Thin Films Using CVD Plasma Reactor with H Radical Source

Effects of H radicals on removing impurities in Cu thin films during plasma enhanced metal organic chemical vapor deposition (PEMOCVD) are studied using in-situ FT-IR method which is employed for measuring relative impurity concentration in the films. The results show that H radicals are very effective for removing impurities in the film as well as on its surface. Based on such knowledge regarding the roles of H radicals, a PEMOCVD reactor equipped with an H radical source is developed to control both densities of H radicals and Cu-contained radicals independently. High purity (\approx100%) Cu films of a low resistivity of 2 \mu Ømegacm can be deposited for a H_2 dilution rate of 50-67% by using the H radical source, while the high purity films were obtained only for a very high dilution rate above about 90% for the reactor with no radical source as reported previously. This feature opens up a new possibility of deposition of high quality Cu films at a high rate using the reactor equipped with the H radical source, since a concentration of Cu metal organic material can be increased by more than 5 times. In addition, when using the plasma CVD reactor with H radical source, high quality Cu films can be deposited in trench of 0.7 \mum width and 3 \mum depth with good step coverage.

[EMP4.11] Formation of diamond films by intermittent DC plasma chemical vapor deposition using sub-electrode

When diamond film was formed by intermittent DC plasma chemical vapor deposition (CVD) from methane-hydrogen gas mixture, wherein the waveform of the power supply was half-wave-recrified, it was found that the crystalline quality of the film became superior with increasing the distance between the electrodes. However, the discharge at longer electrode distance became unstable or impossible because the voltage to start the discharge became very high. Then, to perform stable discharge at longer electrode distance, sub-electrode having short distance to the cathode was laid, and the substrate (anode) was biased with another DC power supply. The crystalline quality of the films deposited on Si substrate became superior when the electrode distance was about 20 to 25 mm, in comparison with those when the electrode distance was 10 and 30 mm. This method was also effective to change the discharge current widely and to perform the stable discharge at very low discharge current.

[EMP4.12] The Relationship between C_60 Mass Spectrum Intensity and C_2 Vibrational Temperature in Microwave Helium Plasmas

The soot containing C_60 and C_70 was synthesized in helium plasmas generated in a quartz tube by microwave discharge. We used reticulated vitreous carbon (RVC) that was heated by electric field of TE_10 mode microwave and the plasma. During soot deposition, optical emission of plasmas was observed with a monochromator. The soot deposited on the quartz tube was analyzed by the laser desorption time-of-flight mass-spectroscopy (LD-TOF-MS). Up to the present, the most intense C_60 mass spectrum intensity was obtained for the condition of absorbed microwave power 200W and pressure 100Torr, where C_2 vibrational temperature was about 5500K.

[EMP4.13] Characteristics of Scanning Mirror-type Magnetic Field Coaxial ECR Plasma for Inner Coating of Slender Tubes

We have developed an inner coating system by using scanning coaxial electron cyclotron resonance (ECR) plasma. In this system, plasma was generated inside the coaxial metallic or insulated tubes by ECR method that was possible to discharge at low pressure and narrow gap. ECR plasma was transported along the tube axis using the control system for applied magnetic field that consists of a computer, switching regulator and five solenoid coils. The coils were set around a long process chamber at equal spaces apart. Low pressure discharge with mirror-type magnetic field were realized in the tube of 30 mm in inner diameter at the pressures of 3\times10^-5 Torr even for less than 150 W microwave power. Increases of the electron density and the deposition rate were achieved by generating mirror-type magnetic field. Using the developed plasma source, it could be coated by titanium nitride (TiN) thin films on inner wall of tube with use of a reactive sputtering.

[EMP4.14] Extended Anode Effect in Coaxial Magnetron Pulsed Plasmas for Inner Coating of Narrow Tubes

For coating thin films onto inner walls of narrow tubes, we developed a coaxial magnetron pulsed plasma (CMPP) device. The most advantage of this device is that deposited conductive films play the role of an anode. As a result, the plasma position shifts away from an anode set at the tube end and the distribution of film thickness spreads with increasing deposition time. We call this extended anode effect. The moving velocity of the plasma position is dependent on film materials, i.e. sputtering yields and film resistivities. In order to reveal this phenomenon, we deposited films which are different in these, such as titanium, tangsten and gold films onto inner walls of narrow insulated glass tubes.

[EMP4.15] Electromagnetic Acceleration Plasma Spraying Applied to Ceramic Coating

Electromagnetic acceleration plasma generators, which are called Magneto-Plasma-Dynamic (MPD) arcjet generators, can produce higher-velocity, higher-temperature and higher-density plasmas than those of conventional thermal plasma torches, because MPD arcjet plasma is efficiently accelerated by electromagnetic body forces in MW-class input power operation. For applications of MPD arcjet generators to ceramic spray coatings, an MPD arcjet generator that has a continuous supply mechanism of ceramic materials was developed. In the present study, calcia-stabilized zirconia (CSZ) and titanium nitride (TiN) are sprayed onto steel substrates. At CSZ spraying, argon was used as working gas. However at TiN spraying, nitrogen gas and titanium rod were used as working gas and cathode, respectively. The phase structure and the composition of the coating were analyzed by means of x-ray diffraction and scanning electron microscopy. The results showed that the MPD arcjet generator could successfully prepare a dense ceramic coating. Consequently, the MPD arcjet generator was found to have a high potential for ceramic spray coatings.

[EMP4.16] Effect of ion bombardment on the initial growth in low temperature poly-Si formation

Recently, poly-Si films have attracted much attention in the application for TFT of LCD. PECVD is a candidate for the low temperature poly-Si formation. However, the films with good crystallinity are hard to be obtained at lower temperatures (< 300 \! ^\circ \! \! C). In this study, firstly, in ECR SiH_4/H_2 plasma CVD, poly-Si films were deposited by removing the charged species by using permanent magnets to clarify the effect of ion bombardment. The crystalline fraction of films without charged species was about twice as high as that with charged species from Raman spectra. Moreover, poly-Si films were successfully formed on plastic substrates at a low temperature (150 \! ^\circ \! \! C) by eliminating charged species. Furthermore, two step growth method was performed to evaluate the effect of the ion bombardment at the initial stage on the film quality. For the first step, the seed layer was formed without charged species, and the growth layer was formed on the seed layer with charged species. The surface roughness and the crystalline fraction were improved to be 2.5nm and 73% with almost the same deposition rate as that of the conventional ECR PECVD. These results indicate that the ion bombardment prevents the growth of nuclei at the initial stage and affect the roughness and crystallinity of the films.

[EMP4.17] Photo Luminescence from Si Films fabricated by Double Tubed Coaxial Line Type Microwave Plasma CVD Apparatus

In this study, we used a double tubed coaxial line type microwave plasma CVD apparatus. Under the low gas pressure (\sim\backslashmtorr), a-Si:H film is fabricated and photo luminescence (PL) is not observed at room temperature. However, under the high gas pressure (\sim\backslash100mtorr), a-Si:H nanoball film is fabricated and PL is observed at room temperture. The diameter of a-Si:H nanoball is about 20nm. It is judged by X-ray diffractmeter that there are nanocrystal Si (nc-Si) in this a-Si:H nanoball. The diameter of nc-Si is about several nm. In this work, we fabricated the a-Si:H nanoball films varying the substrate DC bias voltage from -80V to +40V, the substrate temperture during deposition from R.T. to 400^oC and the gas flow rate of SiH_4 per total gas flow (which consists of SiH_4 and Ar) from 7% to 36%. When the films are oxidized at 80^oC for more than the several hours, the PL (\sim\backslash800nm) is observed at R.T.. We discuss how the deposition circumstances affect the property and the film characteristics. The result will be presented at the meeting.

[EMP4.18] Plasma Dynamics in a Large Area, Rectangular, Inductive Reactor for CVD

An advanced plasma reactor for chemical vapor deposition of diamond films over large flat areas (\sim1/3 m^2) is discussed. The reactor essentially is a single strap coil surrounding a metal box with slots running perpendicular to the current in the coil. The plasma within the box is coupled inductively by the magnetic flux penetrating through the slots while the interior surface of the box is the growth substrate. Typical operating conditions are \sim20 W/cm^2 surface power density and \sim1 Torr pressure. The discharge objective is a large uniform plasma so that constant deposition will occur throughout the chamber. In the present paper a global discharge model for the reactor is developed to demonstrate that classical resistivity holds for the plasma and the gas flow is diffusion dominated. Using these conditions a 2-D model is presented which self-consistently treats the electromagnetic coupling, plasma diffusion, and non-equilibrium hydrogen gas dynamics. Results are compared with experimental data on the plasma length electron and gas temperature profiles, and hydrogen dissociation fraction. The observed trends in the first three of these quantities are reproduced by the model.

[EMP4.19] The influence of uncontrolled carbon sources on diamond nucleation and synthesis using magneto-active microwave plasma CVD

It is found that carbon films substantially deposited on reactor walls significantly influence on diamond nucleation and growth using magneto-active microwave plasma CVD, indicating that carbon-related sources originated from the unintentionally deposited materials on the chamber wall and substrate holder make an important effect to nucleation density and growth rate and quality of diamond films. In order to clarify the effect,

a reproducible cleaning process of the growth equipment used should first be required. In the present study, the dependences of etching rate of the carbon films on treatment time, working pressure, microwave power, and substrate holder bias voltage have been examined using magneto-active microwave oxygen plasma as well as a mechanical cleaning method. On the other hand, the time dependences of various molecular species have been investigated using mass spectroscopy, infrared laser absorption spectroscopy, and plasma optical emission spectroscopy. The gas phase synthesis using additional solid sources of nanometer-sized carbon materials beside the source gas usually employed have brought forth an additional information about the influence of the uncontrolled carbon-related sources, especially the particle-related effect, in the plasma CVD growth chamber.

[EMP4.20] Dependence of the TiN hard coating properties on the substrate position

TiN coatings were deposited by hollow cathode discharge deposition process on samples mounted in various positions within the deposition chamber. Some microchemical, mechanical and tribological characteristics of the layers were investigated by Rutherford backscattering spectroscopy (RBS), spectroscopic ellipsometry (SE), X-ray diffraction analysis, thickness and microhardness measurements and tribological tests. The observed differences between the film properties for the substrates differently positioned can be accounted for by variations both of the coating flux arrival rate and of the ion bombardment intensity on the substrates.

[EMP4.21] Silicon Nitride Ultra Thin Film Formation by Electron Cyclotron Resonance Plasma and its Application to Gate-Insulator

The silicon nitride film attracts much attention as scaled gate dielectric films, because of low gate leakage current. In this study, we have investigated the properties of the silicon nitride ultra thin films produced by ECR-PECVD method employing SiH_4 and N_2 gases, and ECR N_2 plasma nitridation on silicon substrates. The silicon nitride films were formed by ECR plasma nitridation on silicon substrates at 300W, 0.5Pa, a N_2 flow of 100sccm. The bias and temperature of the substrate were floating and 350 degree C. The film properties were studied by Fourier Transform Infrared Spectroscopy(FT-IR), ellipsometry and in-situ X-ray Photoelectron Spectroscopy(XPS). In-situ XPS analysis showed that the peaks of Si2p and N1s were saturated in 60 min. N_2 plasma duration. The silicon nitride layer was 3.5nm in thickness and the stoichiometric composition(Si_3N_4) without hydrogen content. The films synthesized by ECR-PECVD indicated the nearly stoichiometric composition(SiN_1) without hydrogen content. These results suggest that those nitride films are applicable for the gate insulator in next generations ULSI.

[EMP4.22] Ellipsometric Monitoring of First Stages of Diamond Nucleation in a Bias-Enhanced Microwave Plasma

Appropriate negative bias to a substrate in plasma chemical vapor deposition enhances diamond nucleation, i. e., increases the nucleation density and enables highly oriented diamond growth, scattered heteroepitaxy. In order to improve the method into complete heteroepitaxy, the mechanism should be analyzed. However the analysis has hardly been performed because of the difficulty of in-process monitoring in a microwave plasma. We have developed a new diamond synthesis system of surface wave-excited microwave plasma with a slotted antenna, in which an ellipsometric monitor is installed. The first stages of diamond nucleation in a bias-enhanced CH4/H2 plasma were monitored with the use of the monitor, and carbonization, incubation, nucleation, and nuclei growth stages have been able to be distinguished from the changes of the ellipsometric parameters. Ellipsometric monitoring is a useful method for the control of diamond nucleation stages in a bias-enhanced plasma process.

Part E of program listing