Modified mask method

Photostructuring Using the Modified Mask Method Principle... 

The modified mask method and the protection layer technology enable the simultaneous fabrication of geometrical structures of different depth, such as holes or slits and sack holes or trenches with predefined depths, in a single... 

The best photostructuring technology for the fabrication of complicated and complex structures is the modified mask method. This process enables the production of three dimensional geometrical structures (without undercut) in single processing step. Unfortunately the masks are very expensive. The produced devices are suitable for many microtechnology applications. 

If we attempt to modify the method to make it less sensitive to batch-to-batch differences, it is worthwhile to try to understand the source of the differences. In the case of silica-based bonded phases, differences in surface coverage or silanol activity are the most likely culprit. Often, the silanol activity can be masked by the addition of mobile-phase modifiers. See the respective chapters for more information. 

Noise allocation followed by scalar quantization and Huffman coding. In this method, no explicit bit allocation is performed. Instead, an amount of allowed noise equal to the estimated masked threshold is calculated for each scalefactor band. The scalefactors are used to perform a coloration of the quantization noise (i.e. they modify the quantization step size for all values within a scalefactor band) and are not the result of a normalization procedure. The quantized values are coded using Huffman coding. The whole process is normally controlled by one or more nested iteration loops. The technique is known as analysis-by-synthesis quantization control. It was first introduced for OCF [Brandenburg, 1987], PXFM [Johnston, 1989b] and ASPEC [Brandenburg et al., 1991], In a practical application, the following computation steps are performed in an iterative fashion ... 

Figure 18 UV photopatterning method. The molecular structure of a photocleavable SAM formed on glass surfaces. UV irradiation through masks placed on top of SAM-modified microchannels leads to the production of hydrophilic carboxylate groups in the irradiated regions (Zhao et al, 2001).

The sodium flame masks that of other elements, e.g, that of potassium. Mixtures can be readily detected with the direct vision spectroscope (see Fig. II.4). A less delicate method is to view the flame through two thicknesses of cobalt blue glass, whereby the yellow colour due to sodium is masked or absorbed, and the other colours are modified as listed in Table V.3. 

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