Papers by Keyword: Surface Measurement

Abstract: This paper proposes a sphere-based calibration method for the structured light system with unconstrained one projector & one camera, regardless of pattern codification. A 1-pose example of such a method is also proposed and tested. In comparison with a traditional plane translation method of 15 poses, we note an increase in the consistency of more than 10% while the calibration time shrinks to 6% and the calibration accessory is reduced to the size of a flash-light. This method suits well for applications where mobility, speed and ease-of-use are important criteria.

Abstract: Chemical mechanical polishing (CMP) is the best global planarization technology of GLSI process. After CMP process, there may appear large roughness, micro scratch, dishing pit, erosion pit, with-in-wafer-non-uniformity (WIWNU), organic contamination, particles and metal ions pollution on wafer with copper interconnects. Surface measurement of CMP process on the wafer mainly involves the test of roughness, defects and the contaminations. Atomic force profiler (AFP) combined with the resolution of the AFM and long-range-scan ability of the steps instrument (100 mm), is suitable for CMP process which needs to measure both the planarization of long-range scanning and tungsten plug and copper interconnects with high resolution imaging. Optical detection technology combined with the advantages of dark and bright view detection is suitable for detection of particles, crystal originated pits (COP), defects, etc. The time-of-flight static secondary ion mass spectrometry (TOF-SIMS) and total reflection X-ray fluorescence (TXRF) are applicable to detect metal ions. The selection and use of advanced data analysis theory and method can help to improve the speed of analysis and to find the main factors of influence surface quality. Pareto diagram analysis is very beneficial for study polishing effects and the main reason of the surface state for Cu-CMP wafer. Nine sampling method and five sampling method fit to analysis the uniform surface distribution, on the contrast isometric sampling can reflect the distribution of the surface state along the radius difference.

Abstract: The 3D surface measurement methods are described based on the single and multi-frame fringe projection principles, respectively. The key algorithm  phase reconstructing (PR) is conducted by means of two different concepts; one is the single-frequency spatial phase reconstructing method and the other is the multi-frequency temporal one. On the side of spatial PR, a few typical methods are carried out, among which the most robust one could be achieved. The described spatial methods are implemented under the guide of the suggested modulation gradient variance (MGV) map. Moreover, the network programming (NP) method is also conducted to compare with them. The tested results show that the weighted least square (WLS) is the most robust one among the spatial PR methods. At the same time, the temporal PR method is introduced based on the multi-frequency fringes, and the result proves that it features the better noise immunity and robustness than spatial ones, but needs many different frequencies of fringes that would be more time-consuming. Lastly, the surfaces are reconstructed in reverse engineering (RE) software.

Abstract: The point diffraction interferometer (PDI), which generates the nearly ideal spherical wavefront with the pinhole method, is realized the absolute interferometric measurement without the use of reference surface. But it is hard to detect the diameter of the pinhole and hard for use of phase shifting interferometers in PDI. However the advanced fiber point diffraction interferometer (FPDI) not only replaces the pinhole with the fiber, but also makes it possible to implement phase shifting and maintain advantage of traditional PDI. In this paper, the different methods of measuring surface are proposed according to different experimental conditions and different targets (such as concave spherical surface, convex spherical surface, flat surface) with the fiber point diffraction interferometer built in the laboratory. Base on these experiments, there are several key factors in the measurement process such as measurement configuration, laser source, polarization beamsplitter, optical fiber. And these factors, affecting the experiment accuracy, were analyzed seriously.

Abstract: The fiber point diffraction technology has been used in fiber point diffraction interferometer (FPDI) to measure optical surface with high precision. The wavefront diffracted from the single mode fiber with microns core diameter can be considered as an ideal spherical wave and used as the referenced wave in interferometer. The absolute accuracy of the diffraction wavefront can not be directly measured in experiment. To estimate its quality, the vector diffraction method must be introduced because conventional scalar diffraction theory is unsuitable when the fiber core size is comparable to wavelength. The transfer mode feature which includes single-mode transmission condition and mode field distribution is analyzed at first. Then vector the model of fiber point diffraction is established. Finally, the diffraction wavefront is analyzed with numerical method based on vector theory, and the difference between scalar and vector method is discussed. The results show that vector model can achieve rigorous wavefront analysis for fiber point diffraction and provide important help for PFDI design.

Abstract: Metrology plays an important role in the development and commercialisation of micro and nanotechnology. For calibrating versatile micro- and nanoscale standards, a dimensional metrology instrument coupled with multi sensor heads including atomic force microscope (AFM), tactile stylus, laser focus sensor and assembled cantilever probes (ACPs) has been developed. Two kinds of ACPs are highlighted in the paper. One is fabricated by gluing a vertical AFM cantilever to a horizontal AFM cantilever using micro assembling techniques. It is applicable for direct and non-destructive measurements of sidewall surfaces. The other is an ACP ball probe designed for true 3D measurements of micro structures. It is realised by gluing a tungsten wire with a probing sphere ball, 40 ... 120 µm in diameter, to a horizontal AFM cantilever. The ACP ball probe has advantages such as small probing forces (<1µN) and high probing sensitivity. Some typical calibrations on micro and nano structures such as step height, grating and sphere calotte artefact are introduced.

Abstract: With the development of modern industry, the consciousness of quality monitoring increases rapidly. The requirements to the dimensional control and profile monitoring of the products including the mechanical, optical and electric ones become higher and higher. New, non-contact and convenient instruments are needed to enable people to evaluate their products. A new type of dynamic active confocal probe is developed in this paper. The key point of this new method is that the displacement measurement of the vibrating lens located on the tuning fork is converted to time difference measurement, which is much simpler and assures higher accuracy in measurement. System structure and improvement, electric circuit and signal processing system are discussed. Experimental studies of the probe performance and analyses of the experimental results are presented.