Inorganic Gate Dielectrics

The Penn State group has employed an ion-beam sputter process for silicon dioxide. This process deposits a dielectric film at low temperatures (80 °C) and is suitable for deposition on glass and flexible substrates [2, 29, 30]. With this ion- 

Material Preparation method Deposition temperature [°C] Dielectric constant Refs 

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Different layers deposited by low pressure chemical vapour deposition (LPCVD) or by plasma enhanced chemical vapour deposition (PECVD) were examined as further inorganic gate dielectrics. Insulating layers of tetraethylor-thosilicate (TEOS) oxide, deposited by the thermal pyrolysis of the vapour... 

Additionally, low-temperature oxides (LTO) were examined. The deposition process uses triethylsilane and oxygen at 550 °C. Table 18.1 gives an overview of the different inorganic gate dielectrics, their deposition temperatures, the deposited layer thicknesses and their permittivities. 

Polymer electronics on foils require mechanically flexible gate dielectric layers. Unfortunately, inorganic insulating films suffer from high deposition temperatures and a lack of mechanical elasticity. In a first step the inorganic gate dielectric is substituted by a polymer film, still using a silicon substrate because of their smooth and well-known surface. 

There have been few studies of either phenomenon in OTFTs [8-10]. In general, the bias-stress instability of OTFTs fabricated on inorganic gate dielectrics behaves as follows The primary effect of positive gate bias is to shift the threshold voltage to more positive voltages, and the primary effect of negative bias is to shift the... 

In summary, the electrical strength of the LTO oxide was not sufficient for use as the gate dielectric in organic circuits. Therefore, another inorganic insulator of a better electrical quality is necessary, which can be deposited at lower process temperatures. 

Mabakal, A. et al., Inorganic oxide core, polymer shell nanocomposite as a high K gate dielectric for flexible electronics applications, J. Am. Chem. Soc. Ill (42), 14655-14662, 2005. 

Figure 12.5. Photograph of microdispensing system depositing an inorganic dielectric dispersion onto a patterned, metallized polyester film. The pattern is of a transistor gate electrode array. The microdispensing head atomizes the dispersion, generating a liquid spray much like a dual orifice atomizer found on an airbrush.

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