Silicon solution processing

Shimoda, T. Matsuki, Y. Furusawa, M. Aoki, T. Yudasaka, I. Tanaka, H. Iwasawa, H. Wang, D. Miyasaka, M. Takeuchi, M. 2006. Solution-processed silicon films and transistors. Nature 440 783-786. 

FABRICATION OF A TFT USING A SOLUTION-PROCESSED SILICON FILM... 

Figure 5.5. Raman spectroscopy of laser crystallized solution-processed silicon films. The plot shows laser intensity versus Raman shift of the film. The crystallinity is estimated from the intensity and width of the crystalline peak at 520 cm-1. [Reproduced with permission from Ref. 11. Copyright 2006 The Japan Society of Applied Physics.]...

Figure 5.14. The transfer characteristics of LTPS TFTs prepared using a solution-processed gate dielectric, underlayer dielectric, and channel silicon (TFT-4, n-ch, solid line TFT-5, p-ch, dashed line), respectively. TFT-6 (n-ch, broken line) is a reference TFT prepared using solution processing only for the channel silicon. [Reproduced with permission from Ref. 24. Copyright 2007 Society for Information Display.]...

Next, we fabricated TFTs whose ULD, channel Si, and gate dielectric were all solution-processed. The fabricated TFTs (TFT-4, 5, and 6) have similar solution-processed 50-nm-thick silicon films,1011 the details of which are described in Section 5.4. In addition, TFT-4 (n-channel) and TFT-5 (p-channel) have the SP-Si02 as both ULD and gate dielectric, which are fabricated using... 

TABLE 5.4. Characteristics of TFTs with Solution-Processed Gate Dielectric, Underlayer Dielectric, and Channel Silicon... 

Figure 5.14 and Table 5.4 show the electrical characteristics of the fabricated TFTs (W/L = lOpm/lOpm). TFT-4 and 5 (Gox, UDL and channel Si are solution-processed) have the mobility values, 23,0cm2/Vs and 9.9cm2/Vs, respectively. They are lower than that of TFT-6 (only the channel silicon was solution-processed). In this experiment, however, the mobility of the reference TFT (TFT-6) is also relatively poor, as expected, because the laser power and other conditions under which the channel silicon was solution-processed were not optimized. Thus, the mobilities of TFT-4 and TFT-5 were also affected by the channel silicon and were much lower than the mobilities of TFT-1 and TFT-2. With optimization of the conditions under which the channel silicon is deposited, we believe that higher mobility values can be achieved in the devices with solution-processed Gox, UDL, and channel Si. 

The solution-processed doped silicon films described above (baked at 500 °C for 2 hr) exhibited high electrical resistivity (greater than 300 Qcm), which is the measurement limit of the instrument we used. To lower the resistivity, we tried an additional rapid thermal annealing (RTA) of the film prepared from the copolymerized solution with 1 wt% phosphorus concentration. In this RTA, the SiC plate on which the sample was placed was irradiated with infrared (IR) light from a 1-kW IR lamp. The RTA conditions were 600 °C for 2 hr, 650 °C for 20 min, 700 °C for 5 min, and 750 °C for 5 min these temperatures were that of the SiC plate, and the temperature of the Si film is estimated to be several dozens of degrees lower than that. 

Finally, silicon-based polymers, especially with hydrogen lateral groups, are very interesting, but they are not yet explored sufficiently. There are many unknown properties in these materials, including the details of the photopolymerization process and a-Si formation from polysilane. Additional academic work in this field is expected and necessary to make the solution processing of silicon devices more convenient and reliable. 

Shimoda, T. et al. 2006. Solution-processed silicon films and transistors. Nature 440 783-786. 

Compounds 818-820 are kinetically labile and undergo epimerization in solution. The rates of these epimerization processes were determined by kinetic measurements. Owing to the hydrolytic sensitivity of compounds 821 and 822, a conceivable role of bidentate amino acid ligands in the silicon biomineralization process has been denied.821... 

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