Makyoh topography is an optical tool for the flatness testing of specular surfaces, based on the defocused detection of a
collimated light beam reflected from the tested surface. The reflection image is related to the relief pattern of the tested
surface due to the focusing/defocusing action of the surface irregularities. The main application of the method is
semiconductor technology. In this contribution, the effects of the coherence of the illumination on the Makyoh imaging
is analyzed. It is shown that coherence effects are expected even for white-light illumination because of the small source
size. Under optimum imaging conditions, coherence is manifested as diffraction patterns around isolated defects and at
sample edges, and as speckle due to surface roughness. These phenomena are analyzed as a function of surface
roughness, illumination coherency and wavelength, light source size and instrumental geometrical parameters. The
findings are illustrated with experimental images of various semiconductor samples.
Makyoh topography is an optical tool for the flatness testing of specular surfaces, based on the defocused detection of a
collimated light beam reflected from the tested surface. The reflection image is related somehow to the surface relief
pattern of the surface due to the focusing/defocusing action of the surface irregularities. The main application of the
method is the assessment of the polishing quality of wafers in semiconductor technology. In this contribution, the
imaging properties of periodic and quasiperiodic surfaces is analysed through analytic calculations and ray-tracing
simulations for surfaces of various spectral properties. General imaging properties are established. Practical implications
in the semiquantitative inspection of surface morphology/texture are pointed out, and experimental results are shown to
illustrate the main points of the presented analysis.
Makyoh topography (MT) is an optical characterisation tool for flatness testing of mirror-like surfaces. In MT, the
surface is illuminated by a collimated light beam, and the reflected image is detected on a screen placed some distance
away from the sample. Because of the focussing/defocussing action of the surface undulaations, the image shows
intensity variations related to the sample morphology. In its original form, MT is qualitative only. By inserting a
structured mask (e.g., a grid) into the path of the illuminating beam, the surface topography can be calculated by the
integration of the gradients obtained by the determination of the displacements of the grid node positions, compared to a
reference flat, similarly to a wavefront sensor. A DMD provides an easy and verstile way of realisation of such a
structured mask. In this paper, we report on a quantitative MT set-up using a programmed DMD. Possibilities of the
realisation of different mask patterns are analysed. The results are compared to interferometry.
Makyoh topography is an optical surface defect and flatness characterization tool. Its operation principle is based on the whole-field reflection of a collimated beam and defocused detection. This paper reviews the history, the basic principles and applications of the method. The problem of quantitativity is discussed in detail and the solutions are described. The accuracy limits are discussed. Application examples are shown from semiconductor wafer processing and MEMS technology. Comparison is made to related optical and other topographic techniques.
A quantitative approach to the Makyoh-topography image formation mechanism is presented. General relations are given on the optical settings. Then, optical ray-tracing simulations of an isolated defect (hillock or depression) and a periodic (sinusoidal) surface are presented for different optical settings. Optimum working conditions are established, and general features of the imaging are pointed out. Supporting experimental images of semiconductor samples are shown.
Interdigitated planar photodetector structures were fabricated on semi-insulating GaAs material using ohmic-ohmic and Schottky-Schottky contacts. The dc and pulse response performance of the devices indicate that the devices with Schottky contacts are more suitable for high-speed photodetection and pulse generation. The differences between the two types of devices are interpreted with the difference in contact type, trapping mechanisms, and contact resistance effects.
A closed-form analytical expression is given for the bandwidth of p-i-n avalanche photodiodes in a normalized form. The formula simultaneously describes the effect of the time constant of the RC network formed by the load resistor and junction capacitance and the finite gain- bandwidth product of the avalanche multiplication process. An optimum choice of the depletion layer width resulting in maximum bandwidth is also given.
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