Photo-etching process

Laser-Etching Process. In certain photo-etching processes, a laser pointed at a target area rg causes an emission of surface atoms with a gaussian distribution in velocities, i.e., we have the initial state for the single atom distribution function as (see Fig. 2.4)... 

As stated in the introduction, wet etching processes may proceed either with or without external current flow. In the former case, the semiconductor crystal is incorporated as an electrode in an electrochemical cell and polarized anodically under illumination or in darkness for n- and p-type samples, respectively, leading to dissolution of the sample (see Sec. 2). This is referred to as the (photo)anodic etching process. 

In summary, the interpretation of the morphology of electroless etching processes at GaP is analogous to the proposed interpretation of (photo)anodic etching. In electroless etching, though, the potential is not applied by an external source, but it is imposed as a rest potential through addition of Fe(CN) to the solution. 

Semiconductor electrochemistry has various important applications, such as solar energy conversion by photoelectrochemical cells, photo-detoxification of organic waste, etching processes in semiconductor technology and device fabrication, photoplating and photography. In particular, the first-mentioned application provided a great impetus to research in the field of semiconductor electrochemistry. 

HGURE 31.6 Formation of fineline conductors by etching process results in undesirable, nonrectangular conductor cross section. (Photo courtesy of Ibiden Co., Ltd.)... 

Drilling Punching Laser drilling Plasma etching Chemical etching Photo polymer process... 

Feed forward control/feed backward control (FF/FB) considers dependencies along the process sequence. For example, the layer thickness of the photo resistor after the lithography process can affect the subsequent reactive ion etch process (Ruegsegger et al. 1998). An FF model holds the information, how the reactive ion etch process recipe has to be adjusted for compensation of pho-toresistant thickness. FB can be understood similarly to R2R with the only difference that not the immediately last process step but the setup of another one in the process history is adjusted. 

Very fine holes or slots in flat sheets can be made by electrolytic processes, although the open areas are also small for the finer sizes of perforation. The processes involve either photo-etching or electroforming. Photo-etching involves the removal of metal from a continuous sheet on which a photomask has been deposited to protect some areas and allow others to be eroded, while electroforming creates the perforated sheet by building up a layer of metal by depositing it upon a similarly patterned substrate. 

Illumination generates holes within the material of PS and causes photo corrosion of PS that is much faster than that in the dark. Depending on illumination intensity and time, the pore walls in a PS can be thinned to various extents by the photo induced corrosion. This corrosion process is responsible for the etched crater between the initial surface and the surface of PS as illustrated in Figure 28. It is also responsible for the fractal structure of the micro PS formed under illumination. 

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