Search

In this study, we demonstrated a TSV wafer with hybrid via with fine pitch of 6 μm and 9 μm. An effective finite element analysis (FEA) modeling methodology was developed for warpage and stress analysis by considering both silicon and Cu via effect. Based on the effective model, parametric studies were conducted for wafer warpage, including wafer annealing temperature, reticle size, via depth and TSV design. FEA simulation results show that critical parameters are annealing temperature and TSV density. Several stress analysis models were also discussed and compared. TSV stress is independent of TSV location on wafer. Parametric study was also conducted for stress analysis using the simplified TSV array model. In addition, thinning process affecting on stress was also investigated.

The high-temperature requirement of Al-Ge eutectic bonding stands as a major obstacle to its wider acceptance for hermetic sealing application in the microelectromechanical systems packaging industry, in particular for temperature-sensitive devices. It has been demonstrated that a reduction in bonding temperature is feasible without compromising the hermeticity. The change in the mode of bonding from eutectic to solid-state diffusion did not have a dramatic impact on the bonding quality. However, this resulted in a substantial increase in bonding time. The shear strength also deteriorated as a result of the decrease in thickness of the reaction interface. However, the shear strength still complied with military standards. It has been confirmed that a hermetic seal could still be achieved without any solidification occurring at the interface. This is feasible since the interdiffusion coefficients of Al in (Ge) phase and Ge in (Al) phase are closer and are comparable to diffusion between solid-solution phases of identical metals such as in Au-Au, Cu-Cu, and Si-Si bonding, which are generally used for such hermetic sealing application. An appropriate stacking mechanism for Al-Ge diffusion bonding is identified to overcome the limitations with respect to surface topography.

This paper presents the design considerations for thin-film magnetic power inductors for integrated voltage regulator (IVR). Optimum design parameters for solenoid inductors are arrived at that maximize key performance metrics such as quality factor, inductor efficiency, inductance density, and operation frequency. A fabrication approach to integrate the solenoid inductor with thin-film magnetic material is presented. Finally, electrical characterization of a set of test inductors that were fabricated is carried out and the results such as inductance, quality factor, DC resistance are presented.

Cu-Cu is a prefer choice of interconnects as it offered lower electrical resistance, no risk of shorting between the bump and higher reliability as compared to Cu-Solder Bump. However, Cu-Cu interconnect requests stringent condition such as Cu bump surface topography, flatness, uniformity of pillar array heights and clean bonding surface. From throughput point of view, Cu-Cu bonding is challenging as bonding profile involves long heating duration and high temperature. In this paper, we explore the method to improve the bonding throughput and improve interconnect formation. A novel Cu pillar structure is proposed with center core Cu pillar surrounded by side-wall layer solder. Such Cu pillar array is bonded on a bottom wafer with Cu pads through chip-to-wafer (C2W) method. Study shows the solder located at side-wall offers an assist of temporary tacking the chip on the wafer. Then the entire interconnect forms joint through the use of gang bonder. As the side-wall solder seals individual Cu pillar to corresponding bond pad, it helps to prevent non-contact or void interconnection in pillar array. With the tacking and gang bonding process, a higher throughput process can be realized and actively adopted by industry as it offers lower cost of assembly.

In this study, it is shown that temporary tacking (without flux and temporary tack materials) is feasible to temporary tack Cu/SnAg or SnAg sealing ring onto Cu sealing ring at the bottom wafer. The temporary tacked samples were reflowed in a formic acid environment and this allowed the removal of the native oxide of solder. The removal of oxide provides a good solder joints formation during reflow [4]. Vacuum reflow with formic acid and load of 20g per unit showed good sealing results. Helium leak test for chip on silicon substrate was carried out. The results indicated the leak rate at the level of ≤ 5×10−8 atm cc/s Helium can be achieved. Chip on wafer (CoW) bonding with hermetic sealing was demonstrated on 8″ wafer with cavity.

In this paper we have demonstrated the 12 inch (300 mm) wafer level fabrication and characterization of a laminated CoZrTa-based magnetic thin film stack with excellent magnetic and electrical properties. Clear magnetic anisotropy with low coercivity (∼0.3 Oe) and high permeability (∼500) were achieved. High resistivity (∼92.8 μΩ·cm) was also obtained for a four-fold lamination stack. Adhesive properties of the CoZrTa film were improved by inserting a proper adhesion layer. The film properties fully satisfy the requirements of a magnetic core for the embedded inductor integration. The superior wafer level uniformity of the film indicates it is ready for manufacturing the Integrated Voltage Regulator system.

Ultra-fine pitch (6μm) interconnects are essential for high-end application-products that demands high speed and high bandwidth inter-chip communication. Achieving Cu-Cu bonding with such a fine pitch is challenging since bond time is too long and bond interface gets easily oxidized. Throughput issue associated with long-bonding time is solved by using 2-step bonding procedure where first step is a temporary bonding and second step is a permanent bonding using a gang bonder. Gaseous formic acid is used to remove surface oxide on Cu surface and wafer level pre applied underfill is used as a tacking material in temporary bonding. Bonding is carried out with dies having 500,000 interconnects and the results show excellent bonding and electrical properties.

Present study focuses on various thin wafer handling issues associated with via-last TSV fabrication integration schemes. Thin wafer handling methodology play very key role in any successful TSV interposer fabrication. Zonebond TBDB method is selected for this evaluation and critically analysed issues encountered in various fabrication steps like PECVD, PVD, etching, curing and CMP processes. Thin TSV wafer fabrication is always challenging as thin wafers are instable and more prone to failures in various fabrication environments. Hence it is timely to establish robust thin wafer handling schemes that promote seamless TSV interposer wafer fabrication. Extensive TBDB and process integration DOE has been conducted to mitigate these issues.

For ultra-fine pitch and high density Cu pillar low temperature bonding (200°C), the surface contact between substrate and Cu pillar array is the key. Therefore, the fabrication quality of copper bump array affects severely the bonding results. The qualitative factors include (1) Cu pillar array height uniformity, (2) free of copper oxide layer, (3) Cu material property (e.g. elastic modulus, grain size), (4) certain levels of roughness and (5) even the Cu pillar with or without TSV in the wafer. In this paper, test vehicle with dia3um and pitch 6um TSV 20um thin wafer are design and fabricated. The test vehicle is used to study above major bonding contributors. Solid Cu-Cu interconnects are demonstrated with both Chip to chip (C2C) and Chip to wafer (C2W) process. The developed process is promising for high density I/O (

Throughput issue is limiting the adoption of 3D IC stacking process although 3D IC has many advantages in shorter communication lines, lower electrical parasitic and lower package footprint. Local thermal compression bond on each chip stack incurs enormous process time if there is a need to have multi-chip stack and it will be further complicated with the enormous number of chip stack on one 12" wafer. With the proposed temporary stack and final gang bonding process, the time to complete one wafer with multi-chip stack is tremendously reduced to a stage that is very attractive to be implemented in production. Pre-applied wafer level underfill is used as a temporary tacking medium during chip stacking. For the first time, gas pressure gang bonder is used to perform wafer level gang bonding. The high pressure gas in chamber provides uniform bonding pressure to each chip regardless their height. The temporary tacking medium ensures the chip edge is properly sealed, so that no gas leaks into bonding interface. The gas pressure is isotropic, which ensure no risk of chip shifting. The process of using the pre-applied underfill has to be carefully plan and execute to avoid issues of underfill voids, smears and poor bonding. In this paper, high throughput thermal compression bonding on 20µm pitch 10µm diameter micro-pillar array is demonstrated by using the developed two-step bonding method.

A wafer level under-fill (WLUF) process for ultra-fine Cu-Cu bonding is developed. Under-fill is applied as pre-applied under-fill then planarized the surface. The methodology used for surface planarization (bit grinding) and surface treatment (H2 plasma) are fond to be important in the surface preparation and activation. Underfill material needs to have sufficient hardness and adhesion to the wafer to survive during bit grinding process. Again, it must not get cured during plasma treatments before bonding is carried out. DOE is carried out with four different WLUF materials and one capillary under-fill material. Tests were carried out with a test vehicle having 5 um diameter and 10 um pitch. Results showed only one material could pass through all those requirements.

The formulated organic solvent cleaners for aluminum (Al) post etch residues removal have been available on the market for many years. They are used in large quantities in the fabrication of integrated circuits with aluminum interconnects. However, the effectiveness of these chemistries on the aluminum MEMS structures is less well known. In this study, we compared the effectiveness of four different formulated organic solvent chemistries for Al post etch residues removal for certain types of aluminum MEMS structures. The four different formulated solvent clean chemistries evaluated in this study were ST250 from Advanced Technology Materials Incorporated (ATMI), NE14 and ACT690S from Air Products (AP), and EKC265 from DuPont. Both ST250 and NE14 were implemented in a single wafer cleaner as they are typically used in a single wafer cleaning environment. ACT690S and EKC265 were implemented in a tank on a wet bench as they were formulated to work in total immersion environment. Short loop wafers of Al MEMS structures of several microns in sizes were etched in a DPS (Decoupled Plasma Source) metal etch chamber using Cl 2 /BCl 3 plasma followed by H 2 O-based plasma photoresist strip in an ASP (Advanced Strip and Passivation) chamber on the Centura etch platform. These wafers were then cleaned in one of the four different solvent chemistries for comparison. We found that each organic solvent cleaner has its own advantages and disadvantages in cleaning efficiency, cost, as well as the post etch metal corrosion. For each and every organic solvent cleaner, the process conditions during cleaning must be optimized in order to achieve the best results for residues removal and corrosion prevention.

Remote hydrogen and remote oxygen plasma chemical vapor depositions (RHP−CVD and ROP−CVD, respectively) of amorphous hydrogenated silicon−carbon (a-Si:C:H) and amorphous silica (a-SiO2) films, respectively, from organosilicon source compounds were selected as model processes for the mechanistic study. Hexamethyldisilane (HMDS) and trimethylsilane (TrMS) source compounds were used for RHP−CVD, whereas tetraethoxysilane (TEOS) was a source compound for ROP−CVD. The reactivity of HMDS and TrMS with atomic hydrogen and TEOS with atomic oxygen was characterized by determining the rate constants of RHP−CVD and ROP−CVD, respectively. On the basis of the values of the rate constants, the identified low-molecular-weight and oligomeric products collected from the gas phase, and the chemistry involved in their formation, the mechanisms of the precursors formation step are proposed. The results provide strong evidence for the gas-phase conversion of HMDS and TrMS to 1,1-dimethylsilene, Me2SiCH2, and TEOS to diethoxys...

The step coverage of a Cu seed layer is one of critical factors to be controlled in order to achieve void-free TSV for 2.5D and 3D IC. The step coverage of a Cu seed layer can be changed by aging of the Cu seed layer with time and there are two mechanisms in its aging. The one was the oxidation of a Cu seed layer which can change the step coverage by changing the actual thickness of the Cu seed layer. The other was the self-annealing of a Cu seed layer which can change the step coverage by changing the electrical resistivity due to its grain growth. Both of them can result in higher terminal effect causing the failure of void-free TSV Cu filling.

A low temperature

Amorphous hydrogenated silicon-carbon (a-Si:C:H) films were produced by atomic hydrogen-induced (AH) CVD using hexamethyldisilane (HMDS) as a single-source precursor. Radio frequency (rf) hydrogen plasma was the source of atomic hydrogen. The effect of substrate temperature (T s ) on the chemical structure, composition, surface morphology, mechanical properties (dynamic hardness, total stress), and optical properties (refractive index, optical bandgap) of a-Si:C:H film has been examined. Fourier transform infrared (FTIR) spectroscopy and Auger electron spectroscopy (AES) data revealed a drastic drop in hydrogen content in the film, and a rise of the atomic concentration ratio Si/C with increasing T s , thus accounting for the elimination of organic moieties from the film and the formation of a Si-carbidic structure. In the light of scanning electron microscopy (SEM) and atomic force microscopy (AFM) examinations, the films were found to be morphologically homogeneous materials with a maximum size of surface roughness not exceeding 2 nm at T s = 300 °C. Both hardness and stress (tensile in nature) are strongly affected by the film composition, their values increasing with rising atomic ratio Si/C. The investigated optical properties of a-Si:C:H film, i.e., refractive index (n) and optical bandgap (E 0 ). can be controlled by the atomic ratio Si/C for a wide range of values: n = 1.58-2.02 and E 0 = 2.3-3.2 eV.

A feasibility study in the development of a large area high-density plasma source with a higher radial plasma uniformity for large area wafer processing was carried out. Experiments were performed for 200 mm diameter wafers using parallel plate capacitively coupled plasma excited by 60 MHz radio frequency current. Point-cusp magnetic fields that can be easily expanded for 300 mm diameter wafer processing reactors without any technical difficulties are applied to the upper electrode. The point-cusp magnetic fields are generated by arranging 115 permanent magnets on a 266 mm diameter upper electrode with alternate polarity and equal distance. This arrangement of magnets produces a strong magnetic field at the surface of upper electrode and almost a magnetic field-free environment at around 40 mm below the upper electrode. This magnetic field also causes no polarization of the plasma due to the E×B drift of electrons where E and B are the direct current electric and magnetic field strengths, respectively. Application of the point-cusp magnetic field increases the plasma density by a factor of 2 and decreases the radial nonuniformity by a factor >1.5. The radial nonuniformity of the plasma at 58 mm below the upper electrode is further reduced to ±3.5% across the central 200 mm region by the application of a bucket magnetic field to the reactor sidewall and removing 16 magnets from the central region of the upper electrode. This latter change, however, slightly reduces the earlier explained plasma density increment. The radial uniformity of large area plasmas can be controlled with considerable ease by removing selected magnets from the central region of the upper electrode or reducing the magnetic field strength at the central region.

Atomic oxygen-induced chemical vapor deposition (AOCVD), using tetraethoxysilane (TEOS) as single-source compound, was investigated to get insight into the mechanism of silica film growth. In particular, an effort was made to elucidate the chemical nature of silica film-forming precursors. AOCVD, selected as a model process suitable for mechanistic study, has been examined in terms of the effects of atomic oxygen concentration, of the contents of the ground and excited state oxygen atoms in atomic oxygen fraction, and of thermal activation. The growth rate of silica film does not depend on the composition of the atomic oxygen fraction, but is proportional to the total concentration of atomic oxygen fed into the CVD reactor. In the light of the apparent activation energy (E a ) values calculated from the Arrhenius plots of the substrate temperature dependencies of film growth rate, the mechanism of AOCVD is related to the concentration of atomic oxygen. The near zero E a value found at low concentration of atomic oxygen (1.5 × 10 1 cm -3 ) implies that AOCVD is not a thermally activated process; diffusion of the precursors from the gas phase to the substrate seems to be the ratelimiting factor of AOCVD under these conditions. Apparently negative E a values observed for high concentrations of atomic oxygen(≥9.7 × 10 14 cm -3 ) indicate that the adsorption of the precursors onto the growth surface is the main factor controlling the rate of AOCVD. Reaction products of the gas-phase conversion of TEOS, investigated by high-resolution gas chromatography/mass spectrometry, revealed the presence of linear and cyclic siloxane oligomers, containing the -(EtO) 2 SiO- repeating unit. The structure O identified oligomers, results of the study of TEOS reactions with atomic oxygen, the structure of the deposited film, chemiluminescence spectra of the gas-phase products in the CVD reactor, and the results of step coverage tests, point to diethoxysilanone (a high reactivity intermediate) and hexaethoxydisiloxane (a high surface mobility, low reactivity intermediate) as the major precursors of silica film growth.

The applicability of modified magnetron-type plasma source for SiO2 etching was investigated. The plasma source is comprised of a cylindrical shaped rf electrode with two magnetic rings attached to its outer surface, and an electrically isolated top plate made of Al. The substrate holder lies parallel to the top plate. This basic configuration was slightly modified twice by placing two punched-plates at the height of substrate as a plasma shield at one time and by connecting an LC circuit to the top plate at the other time in order to confine the plasma between the top plate and the substrate. Variations of plasma density, uniformity and etching rates of thermally grown SiO2 for the above different configurations were observed. When the plasma shield is attached, the plasma can be confined between the substrate and the top plate by changing the value of the capacitor of the LC circuit. The plasma generated with this configuration yields a higher plasma density (9.8 × 1010 cm-3) and a higher etch rate (506 nm/min) at 9.1 Pa.

Amorphous hydrogenated silicon-carbon films (a-Si:C:H) were produced by atomic hydrogen-induced chemical vapor deposition (CVD) using hexamethyldisilane (HMDS) and tetrakis(trimethylsilyl)silane (TMSS) as a single-source compounds. The CVD process has been examined in terms of the mechanism of the activation step. The susceptibility of particular bonds in the source compounds towards reaction with atomic hydrogen is characterized. The effect of substrate temperature (Ts) on the deposition rate, chemical structure, composition, surface morphology, as well as optical properties of the films, such as refractive index, optical band gap and photoluminescence, has been investigated. The increase of Ts from 30 to 400 °C causes the elimination of organic moieties from the film and the formation of compositionally and morphologically homogeneous inorganic material of Sicarbidic structure. The investigated optical properties of the film can be controlled by its stoichiometry or deposition temperature.

The chemistry in depositing a-SiO 2 using tetraethoxysilane, Si(OC 2 H 5 ) 4 , (TEOS) and tetraisocyanatesilane, Si(NCO) 4 , (TICS) with an oxidant is comparatively studied. In both cases, absorption and desorption reactions of intermediate precursors are seen to be dominant. TEOS O 2 chemistry, where there is no N atom in the source gas, yields conformal step coverage over patterned surfaces. The precursor or precursors generated in TICS O 2 chemistry are expected to contain N atom or atoms and have no surface migration property. The N atom in the precursor is believed to limit the surface migration property. This results in an uneven step coverage over patterned surfaces similar to that of SiH 4 O 2 chemistry.

ZnSe epitaxial films were grown by the low pressure metal organic chemical vapor deposition (MOCVD) technique using diethylzinc and selenium hydride as the source materials. When H radicals generated by a rf glow discharge are introduced into the reaction site, the growth rate of the ZnSe film was increased by a factor of 10. The reactivity between source materials and H radicals was investigated for different pressures, substrate temperatures as well as for different concentrations of H radicals and source materials. With the assistance of H radicals, epitaxial growth of ZnSe films on Si substrates was realized at substrate temperatures above 400°C. If the plasma is produced by N 2 gas, ZnSe films could be obtained similar to that of the H 2 plasma environment. This method is seen to be a promising technique in doping nitrogen into ZnSe in producing p-ZnSe films.

The amorphous hydrogenated silicon carbide (a-SiC:H) films were produced by the remote hydrogen plasma chemical vapor deposition (CVD) using tetrakis(trimethylsilyl)silane (TMSS) molecular cluster as a novel single-source precursor. The remote plasma CVD process has been examined in terms of mechanism of the activation step. The determined temperature dependence of the film deposition rate suggests that the examined remote hydrogen plasma CVD is a non-thermally activated process. The susceptibility of particular bonds in TMSS molecule to the activation step has been characterized using suitable model source compounds. The films have been characterized by ellipsometry, Auger electron spectroscopy, scanning electron microscopy, and reflection high energy electron diffraction analysis. There is reported the effect of substrate temperature (T s ) on such properties of the film as the compositional uniformity, surface morphology, and refractive index. The films exhibit an excellent morphological homogeneity, outstanding compositional uniformity and stoichiometry near pure silicon carbide at T s = 300–400°C. The refractive index alters from 1.5 to 2.4 with rising T s in the range of 30–400°C.

The effect of hydrogen content in dielectric a‐SiC:H films, fabricated in remote H2 plasma using tetrakis(trimethylsilyl)silane as the source gas, on the optical energy gap Eopt and the photoluminescence (PL) was investigated. The amount of hydrogen bonded to C in the fabricated a‐SiC:H films was three orders of magnitude higher than that bonded to Si. The total hydrogen content of the films decreased with an increase of substrate temperature maintained during the deposition. Maximum Eopt, 3.2 eV, was observed for the sample prepared at room temperature in which the hydrogen content was about 7.2×1022 cm−3. This sample shows blue‐white PL with the peak energy at 475 nm. After this sample was annealed at 400 °C, the PL peak energy shifted to 425 nm with an improved chromaticity, even though the hydrogen concentration was reduced by about 14%. Further reduction of hydrogen after annealing at 600 °C resulted in a decrease of Eopt. The variation of Eopt is observed to depend on the density of unoccupied dangl...

High purity and low resistive copper films are in high demand for ultralarge scale integrated process technology. By remote plasma-enhanced chemical vapor deposition, high purity Cu films can be prepared using copper(II) acetylacetonate [Cu(acac) 2 ] as a source material. Depositions were carried out with three types of flow tubes in order to study the reaction steps of the film formation. It is found that Cu films could be deposited only upon reaction of atomic hydrogen (H * ), but not with ultraviolet radiation. Hydrogen remote plasma method makes Cu films damage free from ion impacts and free from contaminants of carbon, oxygen, and others. The resistivities of Cu film measured are about 1.8 μΩ cm which is close to the intrinsic value (1.72 μΩ cm) of bulk copper

Characterization of films deposited by hexamethyldisilane (HMDS) in remote hydrogen plasma is carried out and a reaction model for film deposition is presented. The Si/C ratio increases from 0.6 to 1.3 while the optical bandgap decreases from 3.3 to 2.1 eV with an increase in substrate temperature from 30 to 600°C. When the chemical aspect of the deposition process is concerned it was found that atomic H decomposes the HMDS molecule via a chemical reaction. UV radiation appears to be inactive during the deposition process. It is proposed that the most susceptible bond for the initial breakup is the Si—Si bond in the HMDS molecule. We assume that the other possible bond for the initial break up is C—H. A reaction model for the deposition of is presented by considering as the film‐forming precursor.

The remote hydrogen plasma chemical vapor deposition (CVD) using tetrakis(trimethylsilyl)silane (TMSS) as a source compound has been examined in terms of the mechanism of the activation step. The deposition experiments performed for different configurations of the afterglow tube (straight, with a light trap, and with a hydrogen‐radical annihilator) prove that the TMSS molecules are exclusively activated by the reactions with the hydrogen radicals. The determined temperature dependence of the film deposition rate suggests that the examined remote hydrogen plasma CVD is a nonthermally activated process. Susceptibility of particular bonds in TMSS molecule to the activation step has been characterized using suitable model source compounds. Mechanisms of the most important elementary reactions contributing to the activation step have been proposed.

High purity and low resistive copper films are in high demand for ultralarge scale integrated process technology. By remote plasma-enhanced chemical vapor deposition, high purity Cu films can be prepared using copper(II) acetylacetonate [Cu(acac) 2 ] as a source material. Depositions were carried out with three types of flow tubes in order to study the reaction steps of the film formation. It is found that Cu films could be deposited only upon reaction of atomic hydrogen (H * ), but not with ultraviolet radiation. Hydrogen remote plasma method makes Cu films damage free from ion impacts and free from contaminants of carbon, oxygen, and others. The resistivities of Cu film measured are about 1.8 μΩ cm which is close to the intrinsic value (1.72 μΩ cm) of bulk copper

The wall recombination coefficient (γ) of several materials for atomic oxygen was measured introducing a new method based on the NO*2 continuum in a discharge‐flow system. This method has many advantages, such as the ability of measuring γ under different pressures, nonessentiality of measuring absolute atom concentrations, simplicity of experimental technique, etc. over the previous methods. Investigated materials in this work were selected specially considering the feasibility of industrial applications of plasmas. Although a few metals show slight differences, most of the calculated values of γ are in agreement with the literature values. Observed γ for Al and Al based materials were in the order of 10−3. The highest and lowest γ measured were of Cu and teflon, as 2.6×10−2 and 7.3×10−5 , respectively.

Driven by the need to reduce the power consumption of mobile devices, and servers/data centers, and yet continue to deliver improved performance and experience by the end consumer of digital data, the semiconductor industry is looking for new technologies for manufacturing integrated circuits (ICs). In this quest, power consumed in transferring data over copper interconnects is a sizeable portion that needs to be addressed now and continuing over the next few decades. 2.5D Through-Si-Interposer (TSI) is a strong candidate to deliver improved performance while consuming lower power than in previous generations of servers/data centers and mobile devices. These low-power/high-performance advantages are realized through achievement of high interconnect densities on the TSI (higher than ever seen on Printed Circuit Boards (PCBs) or organic substrates), and enabling heterogeneous integration on the TSI platform where individual ICs are assembled at close proximity (

The higher reactivity and density of thermodynamically non‐equilibrium high‐temperature plasmas than that of glow‐discharge plasmas are confirmed by the observation of atomic oxygen concentration and the population densities of the O(3P), O(1D), and O(1S) energy states. At 60 cm from the plasma exit, the downstream flow mainly consisted of the O(1D) state. This flow is about 95% O(1D) at 1000 W and the fraction of O(1D) state slightly decreases with increasing power due to the production of O+ ions. The flow is about 55% 0(1D) for 200‐W glow‐discharge plasmas, which also give a low atomic oxygen concentration.

SiO2 thin films were deposited on automobile plastics at low temperatures using a microwave activated ECR plasma. Oxygen was used as the plasma gas while tetraethoxysilane (TEOS) was used as the source gas which was introduced into the downstream. In the present investigation high quality SiO2 films were deposited on polycarbonate (PC) and polypropylene (PP) substrates with and without a mesh and the characteristics of hard coating films were studied. The film growth rate increases with the decrease of substrate temperature when a mesh is inserted into the plasma. The irregularities of polymer surfaces could be planarized by the deposition of 1.0 μm thick SiO2 film. The dynamic hardness of PC and PP are increased by the deposition of SiO2 film, however, films deposited on PP is seen to be cracked while that of on PC is crack-free.

A study of laser annealing of a-SiC:H films was carried out in order to obtain poly-SiC films. First, a-SiC:H films were fabricated at temperatures ranging from 30 to 400 °C. All these films show amorphous structure before the annealing process. After annealing by a single pulse of 248 nm laser, films show poly-SiC structure. The pulse energies used for these anneals varied from 30 to 300 mJ/pulse. After exposing to a laser pulse, the a-SiC:H films melt and recrystallize forming poly-SiC structure. In addition to this process, a fraction of the film is observed to be vaporized. This vaporized fraction depends on the original film composition, hardness and the laser pulse-energy. Electrical resistivity of the films before the annealing process lies in the region of 1015 Ωcm. This resistivity drops drastically after the annealing process.

SiO2 thin firms were fabricated in a remote electron cyclotron resonance (ECR) plasma by tctraethoxysilane (TEOS) as the silicon source. Oxygen was used as the plasma gas. A mesh was placed between the TEOS gas outlet and the substrate. In the present investigation a-SiO2 films were deposited with and without the mesh and film properties were studied comparatively. The deposition rate increased when the mesh was attached. The optimum deposition rate is observed when the mesh voltage was zero, that is the mesh was grounded. The deposition rates of both methods were also dependnt on the TEOS flow rate, applied microwave power and the substrate temperature. These three parameters have significant roles in controlling the film quality. Good quality SiO2 films can be obtained with a higher deposition rate when a mesh is attached.

detailed study was carried out in investigating the chemical reaction scheme involved with the deposition of a-SiC:H films by carbosilane sources in a remote hydrogen plasma. As the carbosilane sources, tetramethylsilane (TMS), hexamethyldisilane (HMDS) and tetrakis(trimethylsilyl)silane (TMSS) were used. Depositions were performed in the presence and absence of both UV radiation and H radicals. UV radiation activates only the TMS molecules out of the above three types of molecules in depositing a-SiC:H films. Other two monomers are seen to be activated by hydrogen radicals. It is proposed that the most susceptible bond to be broken at first by hydrogen radical is the Si-Si bond. A reaction model for the formation of a- SiC:H films was presented by considering the Me2Si=CH2 as the film forming precursor.

A magnetron-type plasma source of parallel plate configuration has been developed for large-area wafer processing in the semiconductor industry. In this plasma source there are 80 equally separated magnets arranged with alternative polarities on a 40-cm-diameter top rf electrode. These magnets generate magnetic field cusps below the top rf electrode. Since electrons that lie in the magnetic field cusps are confined, a lower self-bias voltage of the top rf electrode results. With this magnet arrangement, the E×B drifts of charged particles are limited to smaller localized areas and canceled out in macro-scale. Therefore, the radial uniformity of the plasma does not differ much from that of a nonmagnetic parallel plate capacitively coupled plasma source. The plasma density of this magnetron-type plasma source monitored at 1.3 Pa is above 1011 cm-3 for rf powers over 1000 W. The plasma nonuniformity over φ300 mm area is

The power absorption of a modified magnetron-type discharge that has a cylindrical shaped rf electrode is estimated using two different independent methods. The experiment was carried out for the rf power up to 500 W at a frequency of 13.56 MHz and for the pressure region of 0.5 mTorr to 10 mTorr. This magnetron-type plasma shows a higher power transfer efficiency (η) around 75% in the pressure region of 0.5 mTorr to 10 mTorr. With an increase of the pressure or applied rf power, the η tends to drop. For comparison, the η in the absence of the magnetic field is also estimated and reported. In the absence of the magnetic field, the η of the plasma source drops to about 30% at 2 mTorr.

Thin films of SiO2are deposited using tetraethoxysilane (TEOS) as the source gas in remote rf (13.56 MHz) and microwave plasmas. Depositions were carried out using atomic and molecular radicals of different reactivities generated in O2, N2, H2, Ar and He plasmas. SiO2films could be fabricated only in the downstreams of O2, N2and Ar plasmas with the reaction of TEOS. SiO2was not produced by TEOS with the reaction of downstream of H2or He plasma. SiO2deposited with Ar plasma contains a small amount of C. The activation energy of film growth rate varies depending on the partially decomposed TEOS precursor density. Furthermore, the quality of SiO2films deposited with energetically different ground-state ( O(3P)) and excited-state ( O(1D)) atomic oxygen environments was comparatively studied. Films deposited in an excess O(1D) environment show better physical and electrical properties, though the yield of SiO2is independent of the state of the atom.

The downstream gas temperature variation of radio frequency (13.56 MHz) electrodeless discharges is measured as a function of power, gas flow rate and pressure. The gas temperature is seen to increase linearly with power but shows a drastic drop at the point where glow discharge plasma shifts to the plasmoid state. The drop in temperature is assumed to be due to the dissipation of energy which leaves the localized plasmoid. The variation of gas temperature is found to follow a relationship similar to that of the gas residence time in the discharge region with changing flow rate and pressure.

The wall recombination coefficient (γ) of atomic oxygen on a pyrex surface and O(1D) concentration in the downstream flow were measured in a radio-frequency (13.56 MHz) oxygen discharge in the applied power region of 200 W-2500 W. The NO2 * continuum intensity was used to monitor the atomic oxygen. The γ varies from 1.1×10-4 to 6.1×10-5, having a minimum value of 5.1×10-5 at 700 W, at which point the glow discharge plasma changes to an arclike plasma. The mechanism of the transition of glow discharge plasma to arclike plasma and possible reasons for the inconstant γ are discussed in light of electron density, O(1D) concentration in the downstream flow, and the gas temperature.

Cuprous thiocyanate (a p-type semiconductor) was found to photo-oxidize water in the presence of sacrificial electron acceptors more readily than most materials generally used for this purpose. Photocatalytic properties of p-CuCNS are compared with those of n-TiO2.