Shadow mask layer

Fig. 2 (a) Edwards E308 evaporator. One quartz-crystal thickness monitor is pointed towards the Au source to monitor Au vapor deposition on chamber walls the other monitors Au deposited through the shadow mask atop the organic layer. In the cold Au deposition, a small amount of Ar gas is added to the chamber to cool the Au atoms to room temperature before they physisorb atop the cryocooled organic monolayer, (b) Geometry of an Au I monolayer I Au pad sandwich, with electrical connections made using a Ga/In eutectic... 

FIGURE 7.3 Schematic representation of the basic steps required in fabricating a vapor-deposited OLED test pixel, (a) anode patterning via lithography, (b) deposition of the organic, and (c) metal cathode layers through shadow masks. 

The metal cathode is deposited onto the organic layers through a shadow mask (see Figure 7.3c). For active-matrix OLED (AMOLED) displays, a single unbroken cathode is often used over the entire display area. 

A silicon wafer with anisotropically KOH-etched openings was used as shadow mask. The shadow mask is accurately positioned with the help of an optical microscope and fixed using a custom-made wafer holder. A 50-nm-thick TiW-film is deposited by sputtering through the shadow mask. This film serves as adhesion layer and diffusion barrier and covers the rough surface of the CMOS-Al-metallization. A Pt-layer with a thickness of 100 nm was sputtered on top of this TiW-layer. 

In order to establish good electrical contact to the sensitive layer, it was necessary to coat the electrodes with a metal stack of Ti/W (diffusion barrier and adhesion layer) and Pt. The usage of a shadow mask during the metal deposition ensures full compatibility with other MEMS processing steps so that it is possible to fabricate various CMOS-MEMS devices on the same wafer. 

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.)...

Figure 5.9. Functionalization of GaN using the UV-photoinduced reaction with alkenes. Using a shadow mask for the irradiation allows for patterned functionalization. In this study, the alkyl terminated layer was later functionalized with DNA. Figure reproduced with permission from Ref. [152]. Copyright...

The first step in sample preparation is the deposition of a thin metal film on an insulating substrate (e.g. a glass microscope slide). This base electrode is deposited by conventional vacuum deposition techniques with the electrode geometry defined by a shadow mask. Next, this electrode is oxidized either by exposing the film to room air or oxygen, or by establishing an oxygen plasma within the vacuum chamber. In the case of Al-electrodes, a remarkably uniform oxide layer is formed, typically 1-2 nm thick. The oxide film may then be dosed with the compound of interest this is achieved in one of three ways. 

Several transparent electrode materials were tried, including indium-tin oxide, or 5-nm-thick layers of Cr or Nb. Although the thin-metal films have an optical density of 0.2 - 0.3, they produce less debris on the surface during laser writing. The opposite electrode was typically a 20-30-nm-thick film of Cr or Nb deposited by evaporation or ion-beam deposition, respectively. For test purposes, this layer was patterned with a shadow mask in 3.5-mm-diameter circles that could be connected independently to the voltage source. 

The photoconductor is a 1.8- m-thick film of reactively sputtered a-Si H. This film was deposited under the same condition as described in the preceding section. The second conductor layer was deposited through a shadow mask to produce 3.5-mm-diameter circles that could be connected independently to the voltage source. Finally, a 1.5-/im-thick layer of positive photoresist (Shipley 1350J) was applied by spinning at 6000 rpm for 30 sec. This polymer film was baked for 30 min at 70 °C. Small contact areas were opened by conventional exposure and development process, and the sample was again backed for 30 min at 70°C. 

Fig. VII-1 shows a schematic of the structure of a polymer LED and a picture of a thin film flexible polymer LED seven-segment display. The bottom electrode of this display was made by spin-cas ting a layer of metallic polyaniline onto a flexible plastic substrate [69]. Polyaniline was chosen as the electrode material because it is flexible, conducts current, and is transparent to visible light. The emissive layer of the display was fo med by spin casting a layer of MEH-PPV over the polyaniline. The top electrodes were formed by evaporating calcium through a patterned shadow mask. Since the conductivity of undoped emissive polymers is relatively low, it was not necessary to pattern the polymer or the bottom electrode to prevent current spreading between neighboring pixels.

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