Papers by Author: Li Bo Zhou

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Authors: Y.B. Tian, Li Bo Zhou, Jun Shimizu, H. Sato, Ren Ke Kang
Abstract: The demand for extremely-thin Si wafers is expanding. Current manufacturing technologies are meeting great challenges with the continuous decrease in Si wafer thickness. In this study, a novel single step thinning process for extremely thin Si wafers was put forward by use of an integrated cup grinding wheel (ICGW) in which diamond segments and chemo-mechanical grinding (CMG) segments are alternately allocated along the wheel periphery. The basic machining principle and key technologies were introduced in detail. Grinding experiments were performed on 8-in. Si wafers with a developed ICGW to explore the minimal wafer thickness and grinding performance. The experimental results indicate that the proposed grinding process with the ICGW is an available thinning approach for extremely thin Si wafer down to 15μm
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Authors: Teppei Onuki, Ryusuke Ono, Akira Suzuki, Hirotaka Ojima, Jun Shimizu, Li Bo Zhou
Abstract: In this study, measurable thickness range was improved by re-customized components of the thickness measurement system using the method of Fabry-Perot interference signature analyzing. A Fourier transform near infrared (FT-NIR) spectrometer with indium gallium arsenide was used in the developed system. As a result of the sensitiveness in the whole near infrared band and high spectral resolution united with high signal noise ratio of the FT-NIR spectrometer, the maximum measurable thickness is improved to 88μm while sub-micron order of the minimum measurable thickness is also improved.
549
Authors: Li Bo Zhou, Jun Shimizu, Hiroshi Eda
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Authors: Hirotaka Ojima, Kazutaka Nonomura, Li Bo Zhou, Jun Shimizu, Teppei Onuki
Abstract: In the semiconductor industry, high resolution and high accuracy measurement is needed for the geometric evaluation of Si wafers. The flatness parameters are important to evaluate the wafer profile and are required to be the same level as the design rule of IC, and the tolerance for flatness is very tight. According to SEMI (Semiconductor Equipment and Materials International) standards, the required wafer flatness will be 22 nanometres by the year 2016. However, to obtain a higher resolution for sensors, the uncertainty becomes very large compared to the resolution and influences the measured data when the noise is increased. High resolution instruments always incorporate a certain degree of noise. In the presence of noise, form parameters are normally biased. Correction and compensation need a large population of measurements to analytically estimate both bias and uncertainty. The estimation is still far from perfect because of the nature of noise. Another approach is to extract a true profile by filtering noise from the measured data. For the purpose of noise reduction, low-pass filters by Gaussian smoothing and Fourier transform are often used. The noise is normally considered to be a component of small deviation (amplitude) with high frequency which also takes a normal distribution around zero. However these conventional filters can remove the noise in the spatial frequency domain only. So, it is essential to design a filter capable of removing the noise both in the spatial frequency domain and the amplitude component. Thus, we have designed and developed new type of digital filter for denoising. We introduce two new digital filters. One is wavelet transform capable of denoising in the spatial frequency domain and amplitude component, and the other is total variation that can be applied to discontinuous signals without introducing artificial Gibbs Effects.
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Authors: Kazutaka Nonomura, Masashi Ono, Li Bo Zhou, Jun Shimizu, Hirotaka Ojima
Abstract: Recently in semiconductor industry, production of ever flatter, thinner and larger silicon wafers are required to fulfill the demands of high-density packaging and cost reduction. In geometric evaluation of Si wafers, according to SEMI (Semiconductor Equipment and Materials International) standards, the required wafer flatness approaches to the 22 nanometers by year 2016 [1]. For such application, uncertainty of measured data is encountered as a severe problem because the requirement has met the limit of available instrument in terms of resolution and reliability. In order to precisely evaluate the wafer profile, it is essential to remove the noise from the measured data. Described in this paper is design and development of digital filters for denoising. In previous paper, digital filters for denoising with Haar wavelet transform are described. In this paper, the new filters by use of 2nd generation wavelet transform (lifting scheme) are proposed and show better performance of decomposition in the spatial frequency domain and amplitude domain.
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Authors: Masashi Ono, Kazutaka Nonomura, Li Bo Zhou, Jun Shimizu
Abstract: Recently in semiconductor industry, production of ever flatter, thinner and larger silicon wafers are required to fulfill the demands of high-density packaging and cost reduction. In geometric evaluation of Si wafers, according to SEMI (Semiconductor Equipment and Materials International) standards, the required wafer flatness approaches to the 22 nanometers by year 2016 [1]. For such application, uncertainty of measured data is encountered as a severe problem because high resolution instrument always incorporate a certain degree of noise. In order to precisely evaluate the wafer profile, it is essential to remove the noise from the measured data. Described in this paper is design and development of digital filters for denoising. Compared to the conventional low-pass filters, the developed filter by use of wavelet transform not only provides better performance of decomposition in the spatial frequency domain, but also offers the new capability of denoising in amplitude domain.
544
Authors: Li Bo Zhou, Yuta Yaguchi, Tsutomu Fujii, Jun Shimizu, Hiroshi Eda
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Authors: Yuki Mikami, Li Bo Zhou, Jun Shimizu, Hirotaka Ojima, Yoshiaki Tashiro, Sumio Kamiya
Abstract: In recent semiconductor industry, production of ever flatter, thinner and larger Si wafer are required to fulfill the demands in high integration and cost reduction. A severe problem encountered in wafer thinning process is the warp and distortion of wafer induced by the residual stress and subsurface damage. Chemo-mechanical grinding (CMG) process is emerging process which combines the advantages of fixed abrasive machining and chemical mechanical polishing (CMP), offers a potential alternative for stress relief. This paper studies the influence of the wheel manufacturing process on the wheel physical properties. Three-factor two-level full factorial designs of experiment are employed to reveal the main effects and interacted effects of mixing method and filtration of raw materials on the bending strength and elastic modulus of CMG wheel. The difference in wheel properties is discussed by association with CMG performance including wheel wear, grinding force and surface roughness.
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Authors: Jun Shimizu, Takeyuki Yamamoto, Li Bo Zhou, Teppei Onuki, Hirotaka Ojima
Abstract: It is known that the TiO2 has some photocatalytic functions, even though they are relatively weak and their further enhancements are necessary for wider practical usages. On the other hand, improving materials surface functions by introducing microtextures is of great interest in various fields. Under such circumstances, the present study is aiming at developing a high-functional photocatalytic surface by earning the real surface area and reducing the light reflection and so on with the support of microtexturing technique. In this work, a pure Ti plate surface, which was covered with numerous micro impressions and micro pile-ups formed by the vibration-assisted microscratching, was anodized in order to obtain a regularly microtextured TiO2 film on the uppermost surface of Ti plate, and its wettabilty was evaluated in order to investigate its potential as the photocatalyst. As a result, it was found that the wettability of the TiO2 film surface regularly microtextured by the vibration-assisted microscratching was superior to those of the mirror finished one under the irradiation environment by the ultraviolet rays.
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Authors: Tomohiro Inada, Li Bo Zhou, Jun Shimizu, Hirotaka Ojima, Takuya Ito
Abstract: The phenomenon that bubbles or particles are suspended at the node position of a standing wave of sound is known as acoustic levitation and has recently been applied in the fields of semiconductors, aerospace, and biology [1-3]. By using this phenomenon in this study, a new classification method has been proposed, and a device has been developed to sort objects in accordance with their densities. Unlike the conventional methods as such as centrifugal particle separation or magnetic separation, this method can separate fine particles both of metal and non-metal and without contact easily only using acoustic power. First, we derived the acoustic radiation pressure to be applied to the object from King’s theory, and then we designed and developed a twin-transducer system to apply the required levitation force. The distributions of sound pressure and particle velocity were then visualized. Finally, a series of experiments was conducted to show the capability of classifying the fine abrasive SiO2 particles and fine iron particles (φ = 50 μm).
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