Flexible Semiconductor Devices Based On A-IGZO Thin Film Materials

The world’s electronic industry develop fast, so the electronic components industry which is the foundation of electronic information industry also develop very fast. Due to the key role in the display, the thin film transistor (TFT) has traditionally been the laboratory and the research emphasis of the enterprise. However, with the development of the society, the traditional semiconductor devices can’t adapt to the new requirements, such as shape extendable, flexible and transparent, in this case, the flexible semiconductor devices get more and more people’s attention.For flexible semiconductor device, the selection of substrate is the key. After comprehensive literature research, this paper chose kapton (PI) from the several kinds of the most common and most widely application of flexible substrate materials. The PI is peeled on the surface of silicon which is coated with a layer of 300 nm silicon dioxide and called silicon for short. Comprehensive considering the performance of the device and the stability of the test, this paper chose the bottom gate and top contact as the structure of TFT. This paper chose the amorphous indium gallium zinc oxide (a-IGZO) as the active layer. The most important reason is that it has high mobility, high stability, easy preparation, high light transmittance and low temperature made. Because the sample needs to be bent, insulation layer choose the coated PI solution to replace traditional SiO2 and Si3N4 material.In the process of preparation of flexible a-IGZO TFT, which by changing the metal electrodes and increasing buffer layer between the insulation PI and active layer, gradually created the TFT devices which have certain characteristics. Then the device chose different annealing temperature and test ID-VD and ID-VD curve, selecting the best annealing temperature is 200℃ at last. Though adjusting the IGZO film thickness to change the performance of the device, which find 90 W,3 min, pure Ar (20 sccm) cases that has the best performance. Again by improving buffer layer to get the most excellent device, which make its migration rate of 3.49 cm2/Vs, the threshold swing of 3.45 V/decade, current switch ratio of 3.5 e+6 A.PI tape whose adhesion is higher and has higher vacuum production process, which makes it very difficult to strip. So this paper chose coating a layer of poly methyl methacrylate (PMMA). Because PMMA is mixed with impurities, which makes PI tape fluctuate in the back of the heating process and then the device becomes bad. After stripping the migration rate is 0.30 cm2/Vs, the threshold swing is 4.65 V/decade and current switch ratio is 4.6 E+5 A.New device select coating PMMA solution to form film on silicon substrate, then coating PI solution to form a thin film as a flexible substrate, that at last making TFT device on the surface. When the device is put in acetone, the PMMA thin film is dissolved and the device floats in the acetone with PI as a substrate. This paper successfully produced thin flexible device whose thickness only has several micron. The performance of the device basically remains unchanged before and after floating, so this way to make flexible device is successful.