Papers by Keyword: Planarization

Abstract: Catalyst-referred etching (CARE) is an abrasive-free and damage-free polishing method that involves applying a catalytic reaction at the contact point of the catalyst surface and workpiece in a chemical solution. An atomically flat silicon carbide (SiC) wafer surface can be obtained by the CARE process. Recently, it was found that water can be used as a chemical solution, even in the case of SiC polishing. However, its current removal rate of 4H-SiC (0001) 4°off-axis substrate is only 2 nm/h and is expected to increase. In this study, the use of photoelectrochemical oxidation in combination with the CARE process using water was investigated, successfully increasing the removal rate up to approximately 100 nm/h.

Abstract: Catalyst-referred etching (CARE) is a planarization method based on the chemical etching reaction, which does not need abrasives. In this paper, CARE was applied to the planarization of 6-inch silicon carbide (SiC) wafers, and removal properties were investigated. The etching rate was about 20nm/h, which is almost equal to that of 2-inch SiC wafer (16 nm/h). The rms roughness was reduced along with the removal depth, and step-terrace structure was observed in whole area of the on-axis wafer surface.

Abstract: In this work, we present a planarization concept for epitaxial SiC trench structures involving reactive ion etching (RIE) and inductive coupled plasma (ICP) dry etching. The general idea is to transfer the flat surface from spun-on BCB/photo-resist layers to deposited silicon dioxide and finally to bulk SiC by applying process conditions with the same etch rate for the different materials. In this way several microns of unwanted material can be removed and planar SiC surfaces are obtained. With this method trench structures filled by epitaxial re-growth can be planarized with smooth surfaces and good homogeneity over the wafer. Cost-efficient device manufacturing can be achieved by using standard semiconductor process equipment. This technology makes it possible to manufacture advanced epitaxial SiC material structures for devices such as trench JBS diodes and double-gate trench JFETs.

Abstract: In order to obtain ultrasmooth polymer films, in combination with sacrificial layer a variety of impending structures in MEMS devices can be easily prepared. Two methods using polymer concentration control and spin speed adjustment to planarize polymer surface are presented. The influence of polymer concentration and spin speed on the effect of photoresist planarization is studied on. Through a large number of experiments, optimized process parameters are collected. It is found that the roughness was reduced effectively when the spin high speed was 5000rpm for 50 seconds under the condition of volume dilution ratio of 1:5. This process is able to produce a smooth surface structure.

Abstract: This work reports about effect of SiC epitaxial-wafer surface planarization by chemo-mechanical polishing (CMP) treatment on electrical properties of SiC-MOS capacitor. We have observed the surface morphology of 4H-SiC epitaxial layer planarized by CMP treatment using a confocal differential interference microscope, and evaluated the reliability of gate oxides on this surface using constant current time-dependent dielectric breakdown (CC-TDDB) and current-voltage (I-V) characteristics. Surface roughness such as step bunching deteriorates drastically the reliability of gate oxide, while the epitaxial-surface planarization by CMP treatment improved oxide reliability due to the high uniformity of the oxide film thickness.

Abstract: The appropriate planarization layer is the foundation for realization of ion beam deposition correction polishing technology, the significant difference between ion beam deposition correction polishing technology and ordinary ion beam polishing, is using spin or methods of ion beam sputtering deposition, forming sediments which has planarization effect on the processing surface to reduce intermediate frequency error, coupled with ion beam polishing, removing the high-frequency processing error, the typical error is cut marks by single point diamond turning left on the component surface.

Abstract: A submicron InGaAs/InP DHBT fabricated using triple mesa structure and BCB planarization technology is presented. All processes are on 3-inch wafers. The DHBT with emitter area of 0.7×10μm2 exhibits a current cutoff frequency ft and a maximum oscillation frequency fmax both of 280GHz. The breakdown voltage is more than 4V. The high speed InGaAs/InP DHBT with comparable high breakdown voltage is promising for voltage controlled oscillator (VCO) and mixer applications at W band or even higher frequencies.

Abstract: The properties of abrasives have great influences on the surface qualities of glass substrate, hard disk, etc^[1], during the chemical mechanical planarization (CMP) process. α-Al₂O₃ particles, as one of the most widely used abrasives in CMP slurries, often cause great surface defects because of its high hardness and unfeasible control of agglomeration during the synthesizing process ^[2,3]. In this paper, spherical nanocomposite alumina powders with particle sizes of 10-50 nm were prepared, via a homogeneous precipitation method. The structures and surface morphologies of the alumina nanopowders were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic force microscope (AFM). The results showed that the nanopowders composed of both alpha and theta phase alumina, which had a small particle size and narrow size distributions. The CMP investigations performed on glass substrate showed that the nanocomposite alumina abrasives exhibited a better surface planarization performance than the pure single alpha phase Al2O3 nanopowders, with lower surface roughnesses and less scratches after CMP process. The results indicated that the current processing for the synthesis of nanocomposite Al₂O₃ powders were of great potentials for practical applications of Al₂O₃ based abrasives.

Abstract: We have developed a chemical process for atomic planarization of gallium nitride (GaN) using a platinum catalyst and ultraviolet (UV) light irradiation. The process is mediated by a hydrolysis reaction catalyzed by platinum as a solid catalyst. Because the reaction occurs selectively from the step edges, a flat surface composed of a straight step-and-terrace structure is obtained. In the absence of UV light, owing to the low step edge density, the removal rate is quite slow, approximately 1 nm/h. In contrast, under UV light, etch pits are formed on the terraces by photo-electrochemical etching causing an increase in the step edge density. We achieved surface planarization with a removal rate of 9.6 nm/h assisted by irradiation with UV light.

Abstract: Chemical-mechanical polishing (CMP)-a perspective technology in fabrication of micro-and nanoelectronics elements, devices and systems. The development of models of CMP processes remains to be the actual problem. It is pointed out that known CMP models do not account for the features of chemical and mechanical mechanisms of interaction of active fluid and particles with a polished surface as well as an interaction of a viscoelastic pad with the surface. A description of the elementary acts of such interaction are absent in the available models. On the base of the analytical review of the current state of the theory and problems of (CMP) modeling some approaches were suggested to the problem accounting for the complex of the phenomena of different scales determining the polishing rate such as diffusion of slurry into the surface layer and restriction of time of chemical treatment of the surface by a rough pad being under the action of a mechanical load. A model of the CMP process was developed. Within the framework of this model a dependence of the polishing rate on the loading parameters was derived. The dependence generalizes the empirical Preston law.