Wafer plane

Ld.2 image formation. The lens is the most important part of a projection system. It is a device constructed of transparent material and whose whose function is to collect the light emitted from an object (such as a mask) and focus or image this light at the wafer plane (25). Figure 11 illustrates a simple lens that images an object (O) onto the wafer plane (I)... 

Modifications to Electron Beam System. The retarding potential field was introduced into our vector scan system by attaching a O-to-20 KV, 2 mAmp external power supply to the wafer holder. This is shown diagrammatically in Figure 2. Whereas the wafer is at ground potential in the standard system, in our modified system the net potential at the wafer can vary from 0 to 20 KV. Thus, the electrons are accelerated down the column at a standard operating potential, exit the final lens and are retarded by the variable electrostatic field near the wafer plane. 

Although this method of generating a retarding field at the wafer plane is straightforward and requires minimal modifications, it does introduce a few... 

In this approach, the excellent stability of the external power supply minimizes aberrations within the field near the wafer plane. However, the final field size at the wafer will vary with the net acceleration potential. The specific field size was determined by measuring the distance between four gold marks (using the laser controlled stage) at each landing energy. This value was then compared to the distance obsei ved when the bias on the wafer holder was zero. 

Figure 2.10. This plot shows the flux at the wafer plane as a function of wavelength for the Ferkin-Elmer Micralign 500. The ratio of the flux available in the DUV (C7V-2) region compared to that in the near-UV UV-4) region is approximately the ratio of the indicated areas under this curve.

Figure 3.8. Optical output at wafer plane of Perkin-Elmer Micralign 500. Courtesy of Perkin-Elmer.)...

Figure 3.14. Free space image at the wafer plane for 1.0-, 1.5, and2- im lines and spaces at NA = 0.167y partial coherence 0.71, and X = 313 nm. (Repro-duced with permission from r erence 30.)...

Wet bulk micromachining is restricted to very specific crystallographic orientations, obviously not offering freedom to create any desired shape in the wafer plane, i.e. the x-y plane. There are strong incentives to move away from wet etchants, as environmental concerns about their disposal have grown and demands for improved process control on finer features have increased. In dry bulk micromachining, one can freely create any desired shape in the x-y plane with large dimensions perpendicular to the wafer, i.e. in the z direction in mechanically superior crystalline materials. 

Periodic structures of deep narrow grooves with vertical walls were prepared by liquid anisotropic etching of silicon. It was shown experimentally that the obtained media possesses the properties of a negative uniaxial crystal with its optical axis lying in the wafer plane. These structures display a large optical anisotropy in the middle IR range of spectrum. The difference in the effective refractive indices of the ordinary and the extraordinary rays An 1.5. 

The product of the pupil function and the diffraction pattern describes the light entering the objective lens. A combination of the pupil function with the inverse Fourier transform of the diffraction pattern gives an expression for the electric field at the wafer plane as... 

The aerial image is the intensity distribution at the wafer plane and is the square of the magnitude of the electric field. ... 

As mentioned above, the SCALPEL mask is uniformly illuminated hy a parallel beam of 100-keV electrons. In the SCALPEL exposure tool, a reduction-projection optic in a telecentric doublet arrangement produces a 4 1 demagnified image of the mask at the wafer plane. Given that the features to be printed are much larger than the wavelength of the electrons (X. 3.7 pm) used, the full benefits of the... 

In principle, aU molecules within the illuminated volume of the solution contribute to Abuik. However, the collection efficiency of scattered photons from molecules in each plane of the solution varies with confocal depth, that is, the distance deviated from the ideally focal plane, where z equals zero and molecules therein contribute the most to the overall intensity, the integrated intensity of which is defined to be /max- Experimentally, a single crystal silicon vrafer immersed in a solution can be used to provide the confocal depth profile. The integrated intensity of the strongest band for Si at 520.6 cm was measured as the Si wafer plane was moved up and down vertically, while the confocal position was kept stationary. Fig. 29(c) presents the intensity-distance profile that simulated the confocal depth profile, see the solid line. It shows an abrupt decrease at both sides of the ideally focused plane. 

Fig. 4. Ellipsometrie cartography of the thin precursor film zone, for a drop deposited on a grafted wafer, a) cos A as a function of the position (x ) in the wafer plane b) Equal cos A lines (i.e., equal thickness lines), displaying an overall axial symmetry, plus strong fluctuations, related to the inhomogeneities of the grafted silane monolayer. For a better visualization, the carto- raphy is truncated at A = - 0.7, i.e., thicknesses of order 250... 

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