Browsing by Author "Liu, YW"

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Calibrations of phase modulation amplitude of photoelastic modulator
(2004-02-01)
Wang, MW
;
Chao, YF
;
Leou, KC
;
Tsai, FH
;
Lin, TL
A multiple harmonic intensity ratio technique is proposed for calibrating the modulation amplitude (Delta(0)) of a photoelastic modulator (PEM). A data acquisition system is utilized to investigate the frequency response of this technique. Delta(0) determined by this technique is independent of frequency, which is proved using the reflection and transmission setups. In addition to confirm our calibration using the digitized oscilloscope waveform, we also obtain a set of ellipsometric parameters under various values of Delta(0) before and after calibration. We also introduce a correction factor to correct the effect caused by the shift of the modulation amplitude in the process of etching. An optical thick film is used to calibrate Delta(0) using PEM ellipsometry, and its refractive index and extinction coefficient are also obtained in etching. Finally, we suggest the use of the traces of the ellipsometric parameters under various thicknesses for monitoring instead of calculating the thickness in real time.
Data transformation in SPC for semiconductor machinery control: A case of monitoring particles
(2005-07-01)
Chen, MC
;
Su, CT
;
Hsu, CC
;
Liu, YW
;
工業工程與管理學系
Yield is an important indicator of productivity in semiconductor manufacturing. In the complex manufacturing process, the particles on wafers inevitably cause defects, which may result in chip failure and thus reduce yield. Semiconductor manufacturers initially use wafer testing to control the machine for the number of particles. This machinery control procedure aims to detect any unusual condition of machines, reduce defects in actual wafer production and thus improve yield. In practice, the distribution of particles does not usually follow a Poisson distribution, which causes an overly high rate of false alarms in applying the c-chart. Consequently, the semiconductor machinery cannot be appropriately controlled by the number of particles on machines. This paper primarily combines data transformation with the control chart based on a Neyman type- A distribution to develop a machinery control procedure applicable to semiconductor machinery. The proposed approach monitors the number of particles on the testing wafer of machines. A semiconductor company in Taiwan in the Hsinchu Science Based Industrial Park demonstrated the feasibility of the proposed method through the implementation of several machines. The implementation results indicated that the occurrence of false alarms declined extensively from 20% to 4%.
Effects of glass additions on microstructure and microwave dielectric properties of La4Ti9O24 ceramics
(2005-07-15)
Liu, YW
;
Lin, P
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Two commercially available glasses, PbO-B2O3-SiO2 (GA-9) and ZnO-B2O3-SiO2 (GP-032), were used to improve the sintering property of La4Ti9O24 ceramics. Above 20 vol.% of respective GA-9/GP-032 addition, La4Ti9O24 ceramics with similar to 95% of the theoretical density were obtained at a relatively low temperature of similar to 1000 degrees C, compared to the sintering temperature, similar to 1350 degrees C, for preparing pure La4Ti9O24 bulks with a similar density. The interaction between GA-9 and La4Ti9O24 results in the formation of a secondary phase La2/3TiO3. Further investigations indicated that La2/3TiO3 has a strong influence on the microwave dielectric property of La4Ti9O24 ceramics with GA-9 addition. (c) 2005 Elsevier B.V. All rights reserved.
Effects of glass additions on microstructure and microwave dielectric properties of La4Ti9O24 ceramics
(2005-07-15)
Liu, YW
;
Lin, P
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Two commercially available glasses, PbO-B2O3-SiO2 (GA-9) and ZnO-B2O3-SiO2 (GP-032), were used to improve the sintering property of La4Ti9O24 ceramics. Above 20 vol.% of respective GA-9/GP-032 addition, La4Ti9O24 ceramics with similar to 95% of the theoretical density were obtained at a relatively low temperature of similar to 1000 degrees C, compared to the sintering temperature, similar to 1350 degrees C, for preparing pure La4Ti9O24 bulks with a similar density. The interaction between GA-9 and La4Ti9O24 results in the formation of a secondary phase La2/3TiO3. Further investigations indicated that La2/3TiO3 has a strong influence on the microwave dielectric property of La4Ti9O24 ceramics with GA-9 addition. (c) 2005 Elsevier B.V. All rights reserved.
First-ply failure strength of laminated composite pressure vessels
(1997-05-01)
Kam, TY
;
Liu, YW
;
Lee, FT
;
機械工程學系
;
Department of Mechanical Engineering
Strengths of laminated composite pressure vessels are studied via both analytical and experimental approaches. Experimental techniques are presented to determine the first-ply failure and burst strengths of laminated composite pressure vessels with different lamination arrangements. Different analytical methods, together with various failure criteria, are used to predict the first-ply failure strengths of the laminated pressure vessels. The accuracy of the theoretical prediction of first-ply failure strength is verified by the test data. The suitability of the failure criteria, as well as the limitations of the analytical methods are discussed. (C) 1997 Elsevier Science Ltd.