Photolithography 2- mask process

The depth of structure achieved will depend on the processing time. The aspect ratio is 2-3, and the smallest structure that can be created is 50 pm. The masks are created with photolithography. The process permits both very fine tolerances of shape and position and also allows as many lateral structures/side by side as desired, densely packed. The mechanical nature of the procedure means that the chemical composition of the material is unimportant. As the items are not exposed to heat, there is no distortion. One disadvantage is the angle of the abraded contours to the surface of the substrate. It will be 70° to 85°, depending on the depth sought. Deeper... 

Photolithography - A process by which a mask pattern is transferred to a wafer, usually using a stepper. ... 

Figure 1.1 The semiconductor fabrication process, (a) Thin-film deposition (yellow), (b) photoresist deposition (blue), (c) photolithography (mask clear and opaque red arrows), (d) photoresist development, and (e) etching to transfer the pattern in the photoresist into the thin film. See color plate section.

The minimum size of the monochrome pixels (we consider color in Section 13.7.3) that can be fabricated using OLEDs is dictated primarily by the ability to pattern the electrode which is deposited on top. OLEDs are not sufficiently robust to withstand the normal processes of photolithography. Among the schemes which have been suggested for high resolution patterning is one in which the substrate is pne-pattemed to provide its own shadow mask [1911. By this means, pixel sizes down to 300 p have been demonstrated, and a lower limit of about 100 p is estimated. 

Schematic of the Si-nMEA fabrication process (a) sputter Au layer on double-side polished wafer (b) pattern Au layer with liftoff process (c) spincoat and cure a polyimide layer (d) perform the double-sided photolithography to pattern etch pits (e) etch Si in ICP-DRIE to form Au/Si electrode (f) dice the wafer into a single die (g) RIE etch the polyimide layer with a shadow mask to expose current collecting region (h) electroplate Pt black on Au layer (i) sandwich both electrodes with Nafion 112 in a hot-press bonder. (Reprinted from J. Yeom et al. Sensors Actuators B107 (2005) 882-891. With permission from Elsevier.)...

The basic steps of the lithographic process are shown schematically in Figure 1. The example shown corresponds to photolithography in which the photosensitive resist or photoresist is applied as a thin film to the substrate (Si02 on Si) and subsequently exposed in an image-wise fashion through a mask. The mask contains clear and opaque features that define the circuit pattern. The areas in the photoresist that are exposed to light are made either... 

The Si substrate was micromachined based on photolithography see Figure 2.1 for the process steps of a standard one-mask Si-micromachining process [3]. After photolithography, the exposed portions of photoresist were dissolved by a developer, and the remaining unexposed areas were hardened by heating (baking). The exposed areas of the Si substrate were etched subsequently. 

---