Quality factor enhancement in polycrystalline diamond MEMS resonators by post-deposition plasma treatment

Although many researchers have studied boron-doped diamond thin films in the past several years, there have been few reports on the effects of doping CVD-grown diamond films with phosphorous. For this work, polycrystalline diamond thin films were grown by hot filament chemical vapor deposition (HFCVD) on p-type silicon substrates. Phosphorous was introduced into the reaction chamber as an in situ dopant during the growth. The quality and orientation of the diamond thin films were monitored by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Current-voltage (I-V) data as a function of temperature for golddiamond film-silicon-aluminum structures were measured. The activation energy of the phosphorous dopants was calculated to be approximately 0.29 eV.

Enhanced terahertz (THz) absorption of NiCr film deposited on a dielectric substrate has been proven by applying a reactive ion etching (RIE) treatment to the dielectric film. Nano – scale nickel – chromium (NiCr) thin films are deposited on RIE treated silicon dioxide (SiO 2 ) dielectric substrates to study the transmission and reflection characteristics. Experimental results suggest that both transmission and reflection of NiCr film are weakened by the RIE treatment. The most significant decrease of transmission is observed in 1 ~ 4 THz while that of reflection occurs in 1.7 ~ 2.5 THz band. The decrease of both transmission and reflection is more significant for NiCr film with higher thickness. The RIE treatment, which induces nano – scale surface structures and increases the effective surface area of NiCr film, enhances the absorption and weakens the transmission and reflection of THz radiation. DOI: http://dx.doi.org/10.5755/j01.ms.21.2.6131

Polycrystalline diamond and diamond-like carbon (DLC) thin films are becoming attractive candidates for protective coatings, and, as dielectric materials. They may also find application areas in construction of spacecraft components. However, the space environment is very harsh, and survivability of these materials in that environment has not been clearly understood. In this work, the authors present experimental results identifying some surface flashover characteristics of polycrystalline diamond and diamond-like carbon (DLC) thin films in space vacuum conditions. The polycrystalline diamond and DLC samples used in the experiments are produced by a microwave plasma deposition technique. The diamond films were polished to optical-quality before the experiments. The electrode material was copper, and a dc voltage was applied between the electrodes. When surface flashover occurred between the electrodes, it only occurred on the surface of the diamond or DLC samples. Surface flashover voltage characteristics and breakdown voltage-wave forms of polished polycrystalline diamond and DLC thin film samples were determined.

The chemical vapor deposition (CVD) diamond and diamond-like carbon (DLC) films are deposited on the cobalt cemented tungsten carbide (WC-Co) cutting tools respectively using the hot filament chemical vapor deposition (HFCVD) technique and the vacuum arc discharge with a graphite cathode. The scanning electron microscope (SEM), optical interferometer profiler and Raman spectroscopy were adopted to characterize the as-deposited diamond and DLC films. The cutting performance of as-fabricated CVD diamond and DLC coated milling tools is evaluated in dry milling SiC particulate reinforced Al-metal matrix composite material (Al/SiC-MMCs), comparing with the uncoated WC-Co milling tool. The milling results demonstrate that the uncoated WC-Co milling tool suffers severest wear in its circumferential cutting edge, while the wear of DLC coated milling tool is slightly lower. Comparatively, the CVD diamond coated milling tool exhibits much stronger wear resistance. The wear on its circumferential cutting edge is less than 0.07 mm at the end of milling test, only a half of that of DLC coated milling tool. This result is attributed to the extremely high hardness and strong adhesive strength of CVD diamond film covered on the WC-Co milling tool.

Scribing wheel (SW) is an important tool for separating glass panels in thin-film transistor liquid crystal display industry. In this study, unlike the traditional SW completely made of polycrystalline diamond (PCD) or cemented tungsten carbide (c-WC), an alternative partially taking advantage of chemical vapor deposition diamond (CVDD) was newly developed. The fabrication of such unique sandwich-like CVDD-SW combined hot filament chemical vapor deposition (HFCVD), welding, and other machining processes. Both hard CVDD scribing edge and tough c-WC supporting layers contributed to SW structure. CVDD was prepared by adjusting the concentration of methane fed into HFCVD chamber. Morphological observation confirmed the reproducibility of microcrystal diamond (MCD), submicrocrystal diamond (SMCD), and nanocrystal diamond (NCD) diamond. Besides grain size, the existence of columnar structure, the nondiamond carbon content, the residual stress, and I(220)/I(111) ratio of CVDD films were characterized by scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. Based on results, SMCD was predicted as the optimized CVDD for making a scribing edge. After three CVDD films were respectively integrated into SW, this prediction was supported by preliminary scribing test. Selecting Corning-1737 as the cutting object, among three CVDD-SWs and one self-made PCD-SW, only the scribing edge of SMCD-SW kept almost undamaged. The outperformance of our design was thus confirmed.

The reactive ion etching (RIE) procedures were applied for mechanically polished {111} diamond substrates surfaces using oxygen and hydrogen gas sources to improve the crystalline quality of chemical vapor deposited (CVD) n‐type diamond layers. The growth of phosphorus‐doped films was performed on RIE treated diamond substrates by microwave plasma‐assisted CVD using phosphine (PH3) as a doping source. Cathodoluminescence (CL) measurements of the epilayer clearly revealed a significant decrease of the intensity of band‐A emission for samples with RIE pre‐treatment. The Hall mobility was also improved reproducibly for all the RIE pre‐treated samples. It was found that the RIE treatment of diamond {111} substrate is effective to obtain high quality n‐type diamond thin films reproducibly. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Diamond thin films can be, at a relatively low-cost, prepared with a high-density of light-emitting negatively charged silicon vacancy (SiV) centers, which opens up the possibility of their application in photonics or sensing. The films are composed of diamond grains with both the SiV centers and sp2-carbon phase, the ratio of these two components being dependent on the preparation conditions. The grain surface and the sp2-related defects might act as traps for the carriers excited within the SiV centers, consequently decreasing their internal photoluminescence (PL) quantum efficiency. Here, we show that in a 300 nm thick polycrystalline diamond film on a quartz substrate, the SiV centers in the diamond grains possess similar temperature-dependent (13-300 K) PL decay dynamics as the SiV centers in monocrystalline diamond, which suggests that most of the SiV centers are not directly interconnected with the defects of the diamond thin films, i.e. that the carriers excited within the centers do not leak into the defects of the film. The activation energy ΔE = 54 meV and the attempt frequency α = 2.6 were extracted from the measured data. These values corresponded very well with the published values for SiV centers in monocrystalline diamond. We support this claim by measuring the transient absorption via a pump and probe technique, where we separated the nanosecond recombination dynamics of carriers in SiV centers from the picosecond decay dynamics of polycrystalline diamond defects. Our results show that PL emission properties of SiV centers in polycrystalline diamond thin films prepared via chemical vapor deposition are very similar to those in monocrystalline diamond thereby opening the door for their application in diamond photonics and sensing.

Synthesizing thin diamond films by chemical vapor deposition (CVD) is the most recent and technologically important development in the thin-film field. Thin diamond films are useful in many applications because of their unique physical, chemical, optical, and electronic properties.To assess thin diamond films’ suitability for support membranes in X-ray lithography, X-ray diffraction was used to characterize the crystal structure and orientation of these films deposited on silicon wafers by hot-filament assisted CVD. X-ray transmission properties of free-standing thin diamond films prepared by selectively etching silicon substrates were characterized by X-ray fluorescence in short and long wavelength regions.This paper discusses conventional and grazing incidence diffraction techniques used to study the crystal structure of thin diamond films and compares the results with film morphology. It also describes X-ray transmission properties of these films in terms of Beer's Law, the mass absorption coefficient, and the wavelength of attenuated radiation. Finally, it reveals the long wavelength regions for optimum X-ray lithography operations using polycrystalline diamond (PCD) film.

Electron field emission has been observed from carbon thin films at relatively low electric fields. These films range from amorphous carbon to polycrystalline diamond films. There are many models that attempt to account for the electron field emission process observed in these films. The initial models that were based on the emission due purely to a negative electron affinity have now been modified. The emission from diamond like carbon (DLC) films, although following a Fowler–Nordheim type curve, do not give realistic values for the emission areas or barriers purely based on a tunneling mechanism. Therefore, a model based on space charge band bending at the back junction is proposed to account for the electron emission at low electric fields from DLC. In this “space charge interlayer” model the real cathode is the substrate, from which hot electrons are created due to the fully depleted DLC film the electrons encounter before reaching the front surface of the film. In this article we extend the model to incorporate the emission of electrons from polycrystalline diamond thin films.

Embedded capacitor technology is an essential method for miniaturization and high performance of electronic package systems. High dielectric constant epoxy/ceramic composites have been of great interest as embedded capacitor materials because they have good processability, compatibility with printed wiring boards (PWB), and high dielectric constant. In previous works, epoxy/BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> composite embedded capacitor films (ECFs) were successfully fabricated and the properties of the capacitors using newly developed ECFs were characterized. The ECFs were mainly composed of epoxy based polymer resin and barium titanate powder. The ECFs were B-stage films and tacky before curing, and coated on a releasing film. ECFs can be easily detached from the releasing film, and transferred to the surface of interlayer within multi-layered organic substrates. In this study, using ECFs and test vehicles specially designed for correcting stray effect around the capacitors, the dielectric constant and dielectric loss can be measured by the reflection coefficient measured with a network analyzer. For fabricating of test vehicles, ECFs patterning process, investigated in previous work, was applied. ECFs were coated on a releasing film with 10~15 mum thickness. Then, ECFs were laminated and cured on Cu coated a 4 inch Si wafer, and Cu was sputtered on ECFs. The sputtered Cu foil was patterned, which was used as a mask for ECFs patterning and also used as top electrodes. For forming vias, plasma etching which is one of the useful methods for removing the cured epoxy based polymer resin was used. Using O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> mixed gases, the epoxy based polymer resin of epoxy/BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> composite ECFs was removed by RIE (reactive ion etching) treatment. After RIE treatment, the agglomeration of BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> powders with residue of epoxy based polymer resin was removed by a ultrasonic cleaning treatment. The eliminated space by RIE & ultrasonic cleaning was electro-plated with Cu. Finally, top Cu was patterned for top electrodes. Then, using these test vehicles, the high-frequency characteristics are consistent with low frequency characteristics measured with an LCR bridge. The relative error between the high-frequency and the low frequency is estimated to be within 10%. The method is a practical way to obtain the characteristics of ECFs accurately and quickly in a final form.

The effects of chemical, plasma, and reactive ion etching (RIE) treatments on the adhesion of Cu and Cr/Cu to the multifunctional polymer were investigated. The adhesion was measured with the newly developed pull test. The polymer surfaces were characterized by the x-ray photoelectron spectroscopy, atomic force microscopy, and surface free energy measurement. The failure modes were examined with the scanning electron microscopy and energy-dispersive spectroscopy. It was found that the adhesion of Cu and Cr/Cu to the highly functional photoresist was poor, regardless of the chemical, plasma, and reactive ion etching treatment with either O2 or CF4 used. However, the RIE pretreatment with the gas mixture (O2+CF4) of the photoresist surface increased the adhesion of sputtered Cr/Cu to the photoresist remarkably, and the failure mode was cohesive within the photoresist. Furthermore, the RIE pretreatment with pure oxygen gave rise to the needle-like surface together with virtually no introduced reactive functional groups, whereas the RIE with O2-rich gas mixture of O2+CF4 resulted in the relative smooth polymer surfaces and the newly formed C=O/O–C–O and O–C=O functionalities were incorporated on the treated surface with the increased polar surface free energy. The adhesion mechanism based on the experimental adhesion results and the surface characterizations of the polymer is proposed and discussed.

Effect of argon and substrate bias on diamond thin film surface morphology

Reactive Ion Etch (RIE) has been an important process in the world of microelectronic fabrication. Focus of this preliminary study is on how RIE affects the grain size of aluminum film which is fabricated on substrates. RIE parameters are varied to obtain 16 different recipes which are done using Design of Experiment. Grain size of the samples is recorded for all 16 samples before and after RIE treatment. This produces results that can be compared to obtain the effect of RIE on the aluminum film. Results show that RIE affects the mean grain size of the aluminum film as it increases after RIE treatment.

Diamond is known to be an excellent electrical insulator and also an exceptional thermal conductor material. Because of these properties of diamond, polycrystalline diamond thin films are becoming attractive candidates for protective coatings, and, as insulating material for high voltage systems. They are also being examined for use in the construction of spacecraft components. In this work, experimental results of surface flashover of polycrystalline diamond thin films operated in space vacuum conditions are presented. The polycrystalline diamond samples used in the experiments were produced by a microwave plasma CVD deposition technique, and the diamond films were polished to optical quality before the experiments. The electrode material was copper, and a DC voltage was applied between the electrodes. Two copper electrodes were placed on the diamond film surface at a discrete distance from one another. The sample/electrode assembly was placed in a high vacuum chamber and the surface flashover occurred between the electrodes but on the surface of the diamond surface in vacuum. Surface flashover voltage characteristics and breakdown voltage-wave forms of polished diamond thin film samples were determined. These results were compared with the surface flashover characteristics of quartz and optical quality diamond-like carbon (DLC) thin film samples.

Summary form only given. Polycrystalline diamond and diamond-like carbon (DLC) thin films are becoming attractive candidates for protective coatings and as dielectric materials in the space environment because they are excellent electrical insulators, exceptional thermal conductor materials, and are also highly resistive to chemical attacks. Therefore, the design and development of devices using diamond in vacuum requires a sound understanding of surface flashover phenomena across solid insulators supporting the high voltage electrodes. In this work, the authors present experimental results identifying some surface flashover characteristics of polycrystalline diamond and DLC thin films deposited on different dielectric materials such as quartz, silicon nitride, and cubic boron nitride in space vacuum conditions. These samples were produced by a microwave plasma deposition technique, the electrodes were copper, and a dc was applied between the electrodes.