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The infrared phase shift polariscope (IR-PSP) is a full-field optical technique for stress analysis in Silicon wafers. Phase shift polariscope is preferred to a conventional polariscope, as it can provide quantitative information ...
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The infrared phase shift polariscope (IR-PSP) is a full-field optical technique for stress analysis in Silicon wafers. Phase shift polariscope is preferred to a conventional polariscope, as it can provide quantitative information of the normal stress difference and the shear stress in the specimen. The method is based on the principles of photoelasticity, in which stresses induces temporary birefringence in materials which can be quantitatively analyzed using a phase shift polariscope. Compared to other stress analysis techniques such as x-ray diffraction or laser scanning, infrared photoelastic stress analysis provides full-field information with high resolution and in near real time. As the semiconductor fabrication is advancing, larger wafers, thinner films and more compact packages are being manufactured. This results in a growing demand of process control. Residual stress exist in silicon during semiconductor fabrication and these stresses may make cell processing difficult or even cause the failure of the silicon. Reducing these stresses would improve manufacturability and reliability. Therefore stress analysis is essential to trace the root cause of the stresses. The polariscope images are processed using MATLAB and four-step phase shifting method to provide quantitative as well as qualitative information regarding the residual stress of the sample. The system is calibrated using four-point bend specimen and then the residual stress distribution in a MEMS sample is shown.
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Power converters deals with high input power as well as high output power. Pulse Width Modulation (PWM) is mostly used technique to control the power converters. A combination of several power converters like in multiphase convert...
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Power converters deals with high input power as well as high output power. Pulse Width Modulation (PWM) is mostly used technique to control the power converters. A combination of several power converters like in multiphase converter are used to obtain a high efficiency output with decreased current ripple and voltage ripple. In this paper phase shifted PWM signals for open loop control and phase shifted saw tooth signals for closed loop control are generated utilizing FPGA in order to control the combination of power converters. In this dissertation two 180° phase shifted PWM and two 180° sawtooth signal of frequency 50 KHz are generated.
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Multiple synthetic aperture imaging can enlarge pupil diameter of optical systems, and increase system resolution. Multiple synthetic aperture imaging is a cutting-edge topic and research focus in recent years, which is prospectiv...
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Multiple synthetic aperture imaging can enlarge pupil diameter of optical systems, and increase system resolution. Multiple synthetic aperture imaging is a cutting-edge topic and research focus in recent years, which is prospectively widely applied in fields like astronomical observations and aerospace remote sensing. In order to achieve good imaging quality, synthetic aperture imaging system requires phase extraction of each sub-aperture and co-phasing of whole aperture. In the project, an in-depth study about basic principles and methods of segments phase extraction was done. The study includes: application of sinusoidal extreme strip light irradiation phase shift method to extract the central dividing line to get segment phase extraction information, and the use of interference measurement to get the aperture phase extraction calibration coefficients of spherical surface. Study about influence of sinusoidal extreme strip phase shift on phase extraction, and based on sinusoidal stripe phase shift from multiple linear light sources of the illumination reflected image, to carry out the phase shift error for inhibiting the effect in the phase extracted frame.
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摘要 :
Multiple synthetic aperture imaging can enlarge pupil diameter of optical systems, and increase system resolution. Multiple synthetic aperture imaging is a cutting-edge topic and research focus in recent years, which is prospectiv...
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Multiple synthetic aperture imaging can enlarge pupil diameter of optical systems, and increase system resolution. Multiple synthetic aperture imaging is a cutting-edge topic and research focus in recent years, which is prospectively widely applied in fields like astronomical observations and aerospace remote sensing. In order to achieve good imaging quality, synthetic aperture imaging system requires phase extraction of each sub-aperture and co-phasing of whole aperture. In the project, an in-depth study about basic principles and methods of segments phase extraction was done. The study includes: application of sinusoidal extreme strip light irradiation phase shift method to extract the central dividing line to get segment phase extraction information, and the use of interference measurement to get the aperture phase extraction calibration coefficients of spherical surface. Study about influence of sinusoidal extreme strip phase shift on phase extraction, and based on sinusoidal stripe phase shift from multiple linear light sources of the illumination reflected image, to carry out the phase shift error for inhibiting the effect in the phase extracted frame.
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The visible light polariscope has been developed to provide high-resolution, full field, stress visualization and analysis in transparent materials. The polariscope images are processed using a four-step phase shifting algorithm t...
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The visible light polariscope has been developed to provide high-resolution, full field, stress visualization and analysis in transparent materials. The polariscope images are processed using a four-step phase shifting algorithm to provide qualitative information. The system is calibrated using a disk under compression and then applied to detect the laser induced damage. The capability of the system to locate laser induced damage induced by different power and scanning speed are explored and compared to that using conventional transmission imaging. From the thermal stress, the preliminary information of the laser power and the scanning speed can be obtained.
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The visible light polariscope has been developed to provide high-resolution, full field, stress visualization and analysis intransparent materials. The polariscope images are processed using a four-step phase shifting algorithm to...
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The visible light polariscope has been developed to provide high-resolution, full field, stress visualization and analysis intransparent materials. The polariscope images are processed using a four-step phase shifting algorithm to providequalitative information. The system is calibrated using a disk under compression and then applied to detect the laserinduced damage. The capability of the system to locate laser induced damage induced by different power and scanningspeed are explored and compared to that using conventional transmission imaging. From the thermal stress, thepreliminary information of the laser power and the scanning speed can be obtained.
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A two-step iterative algorithm (TSIA) immune to tilt shifts is proposed for phase extraction in phase-shifting interferometry (PSI). The TSIA constructs a model of the least-squares iteration of the phase distribution and the tilt...
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A two-step iterative algorithm (TSIA) immune to tilt shifts is proposed for phase extraction in phase-shifting interferometry (PSI). The TSIA constructs a model of the least-squares iteration of the phase distribution and the tilt shifts based on parametric decoupling. Finally, the phase distribution is extracted via the least-squares method. The experimental results show that the PTI has high accuracy and fast iterative convergence speed for the conditions of the large amplitude of tilt shifts, closed fringes, nonuniform background and modulation.
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This paper presents a method of phase-shift control in two-beam laser interference lithography. In the method, a PZT actuator is used to push a mirror and introduce phase shifts in a He-Ne laser interference lithography simulation...
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This paper presents a method of phase-shift control in two-beam laser interference lithography. In the method, a PZT actuator is used to push a mirror and introduce phase shifts in a He-Ne laser interference lithography simulation system. When different voltages are applied to the PZT actuator, fringe positions are changed accordingly, and the phase shifts are introduced. The phase shifts can be determined by fringe pattern correlation with subpixel accuracy. This method is useful in two-beam laser interference lithography for the control of phase shifts and fringe positions in interference patterns for multi-exposure patterning applications.
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This paper presents a method of phase-shift control in two-beam laser interference lithography. In the method, a PZT actuator is used to push a mirror and introduce phase shifts in a He-Ne laser interference lithography simulation...
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This paper presents a method of phase-shift control in two-beam laser interference lithography. In the method, a PZT actuator is used to push a mirror and introduce phase shifts in a He-Ne laser interference lithography simulation system. When different voltages are applied to the PZT actuator, fringe positions are changed accordingly, and the phase shifts are introduced. The phase shifts can be determined by fringe pattern correlation with subpixel accuracy. This method is useful in two-beam laser interference lithography for the control of phase shifts and fringe positions in interference patterns for multi-exposure patterning applications.
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Phase Shift Masks (PSMs) for Extreme Ultraviolet Lithography (EUVL) have the potential for extending the lithographic capability of EUVL to at least the 22-nm node. Typical PSM structures, such as for attenuated PSMs (Att-PSMs), a...
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Phase Shift Masks (PSMs) for Extreme Ultraviolet Lithography (EUVL) have the potential for extending the lithographic capability of EUVL to at least the 22-nm node. Typical PSM structures, such as for attenuated PSMs (Att-PSMs), are similar to those of binary masks in the sense that patterned structures of one or more layers of phase shifter are deposited on the EUV multilayer mirror to provide the correct amount of attenuation and phase shift. However, another type of PSM implemented by etching into the Mo/Si multilayer, rather than by adding lithographic structures on top of the Mo/Si multilayer (additive approach), can also provide the required phase shift for both attenuated and hard PSMs. One of anticipated technical challenges, i.e. terminating etching at a specific depth with good surface uniformity can be solved by employing an etch stop layer (ESL) embedded at a target depth inside the multilayer. In designing PSMs using this subtractive fabrication technique, the position and thickness of the ESL should be optimized, so that optical function of the multilayer substrate with embedded ESL should be same or close to when it does not have any embedded layer. According to simulation, the print bias for PSMs by etching into the multilayer stack to create the phase shift is smallest and near ideal compared to other types of PSMs or binary masks fabricated by conventional methods. The increase of depth of focus by 25-75% for contacts using an attenuated PSM and by 50-100% for lines using an ideal hard PSM is another lithographic advantage as well. The design and method of fabricating PSMs by etching into the multilayers is described, which include the optimization of the thickness and depth of the embedded layer. Experimental results of the multilayer etch process demonstrate initial feasibility of the subtractive approach to fabricating EUV PSMs.
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