Papers by Keyword: Silicon Wafer

Abstract: Bi-based perovskite-type oxide materials such as BiFeO₃ (BFO) and Bi (Zn_1/2Ti_1/2)O₃ and the related compounds receive much attention and have been developed actively as important candidates for Pb-free ferroelectric materials instead of toxic Pb-based perovskite oxide materials. Recently, many researches have been reported for thin films of Bi-based materials by various film-deposition techniques for actual application of semiconductive devices, microactuators, etc. In this study, we tried preferential crystal growth of BFZT films on semiconductive silicon substrates using uniaxial-(100)-oriented LaNiO₃ (LNO) buffer layer. BFO films were fabricated via chemical solution deposition (CSD) technique on platinized silicon wafer [(111)Pt/TiO₂/(100)S and (100)LNO-coated platinized silicon [(100)LNO/(111)Pt/TiO₂/(100)S substrates. XRD analysis indicated that the films fabricated on (111)Pt/TiO₂/(100)Si substrate consisted of randomly-oriented BFZT crystal with lower crystallinity. On the other hand, the films on (100)LNO/(111)Pt/TiO₂/(100)Si consisted of uniaxial-one-oriented BFZT crystal with higher crystallinity. The crystallization temperature these films were 500°C, respectively. These results suggest that the BFZT crystal was grown successfully on uniaxial oriented (100)LNO plane which also had perovskite-type crystal structure. Consequently, one-oriented BFZT films were prepared on Si substrate successfully using (100)LNO buffer layer.

Abstract: In this paper, a novel lapping method based on regulating the position of carrier centroid is proposed to modify interfacial normal pressure uniformity. Eight special points are selected to represent carrier weight. This lapping process can be divided into initial stage, regulated stage and stable stage. The purpose of initial stage is calculating the position of carrier centroid according to the equivalent mass of eight points. The regulated stage is to decrease total thickness variation (TTV) by regulating the position of weight. Finally, the stable stage will keep uniformity of material removal rate (MRR) uniform at each point. A 3-inch and 400 μm thickness silicon wafer is lapped to demonstrate the feasibility of this method. We can find that TTV of this wafer decreases from initial stage 20 μm to 3 μm and remain constant. Therefore, the uniformity of MRR has been greatly improved by this novel lapping method.

Abstract: Doping can lead to residual strain and change of elastic properties in silicon. Residual strain makes silicon wafer exhibit curvature, which are used for fabricate MEMS structure. The boron doping profile is not uniform through depth, which makes doped silicon become a inhomogeneous material or Functionally Graded Material. For boron-doped circular single crystal silicon wafer, a analytical method which based on functionally graded plate mechanics theory, is proposed to calculate its curvature. Example was used to verify the analytical method through 3D finite element simulation.

Abstract: For the final finishing of the substrate surface, Chemo-mechanical polishing (CMP) is often utilized. Those processes are able to offer a great sur-face roughness, but sacrifice profile accuracy. On the other hand, Chemo-mechanical grinding (CMG) is potentially emerging defect-free machining process which combines the advantages of CMP. In order to simultaneously achieve high surface quality and high profile accuracy, CMG process has been applied into machining of large size quartz glass substrates for photomask use. In this paper, based on the characteristics of higher machining efficiency and higher surface quality of ultrasonic vibration machining, a new ultrasonic vibration assisted CMG of silicon wafer hybrid technique is achieved by designing elliptical vibrator with longitudinal mode and bending mode. The experimental results show that under the elliptic ultrasonic vibration assistance, the surface roughness is decreased significantly, the surface quality is improved obviously, and moreover caused little or even doesn’t lead to the surface damage.

Abstract: Laser molten cutting silicon wafer was focused more recently, but this method has the material loss disadvantage. So this paper indicates the finite element simulation and experiments of cutting silicon wafer with YAG laser induced thermal-crack propagation. A theoretical model of a thermal laser shock method for separation of the silicon wafer is developed, and the fracture propagation mechanism is studied by the stress fields using finite element software ABAQUS. Optical microscope and laser scan confocal microscope (LSCM) photographs of the separation surface and path are obtained to examine the cutting quality. The impact of technological parameters on the cutting quality is studied and the optimum processing parameters are presented in the paper.

Abstract: The design ideas of intelligent control and the influence mechanism of process parameters on chemical mechanical polishing (CMP) are combined to develop the CMP intelligent monitoring system, which has the function of learning, inference and memory. The system can be used in many kinds of CMP facilities, the process parameter from the system can be used to control each unit of the CMP facility. And compared with the past way of processing by virtue of experience, the system has friendly operating interface and is easy to operate. The volume production of silicon wafers can be achieved by the total CMP intelligent monitoring. The efficiency of production can be improved highly on condition that the quality can be ensured.

Abstract: Several chelating agents in silicon polishing slurries were studied about their effects on copper adhesion to the surface of silicon wafer. The copper contamination level on the Si wafer surface was measured with GFAAS. The results indicate that PAA and HEDP for acid slurries can reduce 80% copper contamination with respect to the situation of without chelating agent. EDTA, the most common chelating agent for alkaline slurries, has no predominant compared with FA/O and AEEA. The copper contamination on Si wafer surface can reduce nearly 50% by adding EDTA while the addition of FA/O or AEEA in the same concentration for alkaline slurries can reach more than 70% reduction of copper contamination level.

Abstract: Fixed diamond wire saw has the advantages such as higher cutting rate and clearer operating environment over the slurry wire saw in wafering. However, the higher cost and poor sliced wafer surface are still the obstacles for the diamond wire saw to totally replace slurry wire saw. In this study, the distribution of diamond grits on the wire was investigated by numerical simulation. The results show that there is a critical value of the abrasive interval to transfer the machining mechanism from plastic plowing to brittle indentation cracking for the material removal. The value depends on both the wire tension and bow angle during the operation.

Abstract: This study presents design of an ultra-precision wafer grinder which incorporates state-of-the-art automatic supervision and control system. The wafer grinder is characterized by wafer surface shape control, grinding forces and wafer thickness monitoring systems. The design provides a totally integrated solution to the ultra-precision grinder that is capable of grinding silicon wafers with surface roughness Ra<3 nm and total thickness variation<2µm/300mm.

Abstract: Grinding force is strongly related to grinding process, and the application of dynamometer for its measurement during machining is essential for investigating, monitoring and optimizing the grinding process. This paper presents an innovative dynamometer for triaxial grinding force measurement, specifically designed for an ultra-precision grinder. Two different kinds of spatial arrangements are discussed, including lozenge and square arrangement. The mathematical model is established and calculated. Furthermore, a series of static calibration tests have been conducted for the dynamometer, and static properties of the grinding area are also measured and analyzed. Eventually, on-line static tests of the dynamometer installed in silicon wafer grinder are performed. The results show that the grinding dynamometer has excellent properties, which reach the CIRP standards and meet the working requirements of the ultra-precision grinder.