Sequencing, chemical, silicon-wafer

Figure 17.10 shows the process sequence of the hydrophilic overlayer (HOL) process. First, a chemically amplified or non-chemically amplified positive-tone photoresist comprising hydrophobic polymer and appropriate PAG is coated to a nominal thickness on an appropriate substrate such as a silicon wafer, followed by a soft bake to dry out the nonaqueous solvent. Next, the photoresist film is exposed to radiation of appropriate wavelength to generate photoacid from the PAG. Then the exposed film is again baked (called PEB) at the standard temperature to enhance the diffusion of the photoacid and thermolysis of the acid-labile protecting groups of the polymers. 

Figure 1. Chemical structures of functional sequences of the methacrylate polymers and copolymers employed to equip anodically oxidized and roughed aluminium surfaces, glass and smooth silicon wafers to control their wetting behavior tert-hvXy methacrylate sequence (a), methyl methacrylate sequence (b), 2-(methacryloyloxy)ethyl acetoacetate sequence (c), 2-hydroxy ethyl methacrylate sequence (d), and Zonyl TM sequence (e).

A second example concerns another common processing step - chemical passivation of porous silicon surfaces, in particles or patterned wafers. There are three dedicated reviews in the handbook that deal with this Oxidation of mesoporous silicon, Silicon-Carbon Bond Formation for Porous Silicon, and Photoluminescent Nanoparticle Derivatization for Porous Silicon. It can be important to perform these passivation treatments after the particle sizing or patterning process otherwise freshly fractured or patterned porous silicon surfaces will not be passivated. Note that for some applications one can also choose to derivatize the pore walls during anodization (Mattei and Valentini 2003) rather than the more common sequence to derivatize after, or even both during and after anodization to get specific surface chemistries and spatially selective functionalization (Valentini et al. 2007). 

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