Basic OFET fabrication

This section discussed the basic unit operations and process flows for OFET fabrication. Several example processes were presented which integrate these process flows into a system capable of producing an integrated circuit. The next section will explain some additional strategies for improving the performance of these devices. 

Most of the interest in OFETs stems from the low thermal budget required to fabricate these devices and their high degree of mechanical flexibility. These characteristics follow from two basic properties of organic semiconductors ... 

Fig. 4.12. The basic idealized OFET strucure in a bottom gate top and bottom contact configuration. In the processes presented in this section, all four of these layers are patterned. Many, but not all, organic semiconductors can also be fabricated in a top gate configuration.

In principle, the choice of materials used to develop both the electrodes and the insulator of an OFET-based sensor should be basically the same as for OFETs developed for other applications. Similarly, the design of the device should follow the same rules. However, there are some unique aspects that are intrinsic to sensors and deserve special attention. For instance, the sensing area of the device this is the area where the external stimulus (chemical or physical) must be applied to the device without affecting its integrity and/or robustness. The first example of an ISOFET reported in the literature [13] was fabricated on silicon and the only organic component of it was the semiconductor employed as the active layer. In order to develop this structure, it is necessary to etch the highly doped silicon from the back side of the device... 

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