Papers by Keyword: Profile Measurement

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.

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.

Abstract: The inflatable space antenna is gradually used in various spacecrafts because it is portable and foldaway. It is usually made of thin-film materials and has a flexible surface, so that measuring force is not tolerable in measurement process. Close-range photogrammetry is considered as an optimal solution because of its advantages of non-contact operation and fast data acquisition. To improve measuring precision, a method combining bundle adjustment algorithm and the distance constraint is presented in the paper. Two experiments under different conditions are accomplished and experiment results are compared. One experiment is completed with the distance constraint and another without. The experiment results are compared by two parameters: tightness and residuals. The measured object is an inflatable antenna with a 3.5-m diameter.

Abstract: A wide-range laser auto-collimation method to measure the surface profiles of targets with steep slopes has been proposed. This method employs a deflecting optical system to enlarge the measurement range of the angle sensor. However, this optical system also changes the sensitivity property of the angle sensor. Therefore, we propose a new in-situ self-calibration method that includes the geometrical designed data of the target and can be applied to wide-range laser auto-collimation method. In the proposed method, the calibration sensitivities at each measurement point are obtained with two sets of measured data, which are acquired before and after performing minute rotation or translation with respect to the measured target, and the simulated shift of the normal angle at each point. The present paper describes the calibration procedure and specific calculation method used in the proposed method.

Abstract: A novel scanning probe measurement system has been developed to achieve precise profile measurements of micro-aspheric surfaces. The system consists of a scanning stage (a spindle and a linear slide) and a sensor unit. The sensor unit consists of a ring artifact, two capacitance sensors and a contact-mode displacement sensor. The two capacitance sensors scan the surface of the ring artifact to measure and compensate the error motions of the scanning stage while the contact-mode displacement sensor scans the surface of a micro-aspheric. In this paper, a new contact-mode displacement sensor that has a small contact force of less than 2.3 mN and a stable output has been developed. After investigating the fundamental performance of the contact-mode displacement sensor, the sensor has been applied to the micro-aspheric surface profile measurement system. The effectiveness of the measurement system has been verified by the measurement results.

Abstract: Focus detection method is one of non-contact profile measurement methods. However, the measurement accuracy of current focus detection method is limited by voice coil motor adopted by it. In this paper, based on an improved Foucault focus detection method, a new non-contact displacement sensor with diffraction grating metrology system is presented. Driven by a piezoelectric actuator instead of a voice coil motor, and a diffraction grating metrology system being with it, the sensor has high measurement accuracy. During surface profile sampling, according to focusing deviation signal, the focusing lens was driven to move vertically by the piezoelectric actuator so that its focus was always located on the workpiece surface, synchronously the vertical displacement of the focusing lens was obtained by the diffraction grating metrology system as the profile height of sampling points. The displacements of all sampling points gave the whole profile of the measured surface, which can be processed by a characterization software to obtain the measurement result. The resolution of the non-contact displacement sensor was 10 nm.