Application of a-Si Diodes to Liquid Crystal Display Panels
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APPLICATION OF a-Si DIODES TO LIQUID CRYSTAL DISPLAY PANELS HIROSHI SAKAI, MICHINARI KAMIYAMA AND EIZO TANABE Fuji Electric Co. Research and Development, Ltd. 2-2-1 Nagasaka, Yokosuka, Kanagawa 240-01, Japan ABSTRACT An integrated a-Si:H p-i-n thin film diode (TFD) substrate having an ring structure has been developed for driving active matrix liquid crystal display (LCD) panels. The TFD sub-trate (240x480) for a 5.5" LCD panel with 115,200 developed is pixels. A series of technical data on the fabrication process and the electrical properties of the a-Si TFD are presented. It has been shown that the forward bias characteristics of TFD were mainly dominated by the carrier recombination in the i layer near the p/i interface, and control of the plasma etching condition for the a-Si TFD patterning was very important to reduce the leak current and to improve the production yield. INTRODUCTION of valency control was found in Since an exsistence films deposited by silicon (a-Si:H) hydrogenated amorphous plasma CVD, various electronic devices composed of a-Si:H films a-Si:H device, In 1980, the first have been developed (1]. solar cell, was industrialized as a power source for pocket and the production amount for this application calculators, 1987. Another important application of reached 10MW/year in for liquid crystal a-Si:H films is the switching element especially active matrix LCD panels. The LCD, display (LCD) having the switching element, has been studied for pocket size televisions and full size portable terminals. Both thin' film have been (TFD) and thin film diodes transistors (TFT) developed for the switching element of the active matrix LCD for the The advantage to use the a-Si:H materials (2,3]. switching element is as follows: (1)a-Si:H films deposited by plasma CVD can be formed on a large area substrate. (2)Plasma CVD used for the fabrication of a-Si:H devices is a low temperature process. (3)Well developed fine patterning techniques are applicable to the fabrication of switching element matrix. The a-Si TFD has some advantages as compared with the a-Si TFT; the fabrication process is simpler and the operation is more stable and controllable than those of the TFT. In the TFD, as a are used characteristics current-voltage nonlinear threshold for the on and off states. Thus, it was said that the switching characteristics of the TFD were inferior to those of which the on and off states were completely the TFT in controlled by the gate voltage. However, it becomes clear that a better contrast is obtained in the TFD by contriving the drive signal system [4]. From these reasons, we have considered that the a-Si TFD is one of excellent switching elements for the active matrix LCD. In this paper, we will present and discuss the fabrication process and the characteristics, especially the current-voltage characteristics, of the a-Si TFD.
Mat. Res. Soc. Symp. Proc. Vol. 118. e1988 Materials Research Society
376
A
Glass substrate
Pixel (ITO) etalM---
Data Line LC
Am
Pixel DoeRing
a-Si (pin)
Insulating layer
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