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MICRO-CRYSTALLINE SILICON INIMAGE SENSOR B.W.Park, J.I.Choi, C.W.Hur, T.K.Oh, I.K.Kang Advanced Research Lab. 3. GoldStar Central Research Laboratory, Seocho-Gu, Seoul, 137-140 Korea.

16 Woomyeon-Dong,

ABSTRACT Amorphous semiconductors play a major role in the field of electronic imaging. The function of an image sensor is to generate an electrical signal corresponding to the light distribution in the optical image. The photodiodes convert light Into electrical signal. We investigated the linear image sensor driven by thin film transistor as an switching element, with each photodiode connected to the corresponding thin film transistor. The photo/dark conductivity of photodiode are compared in the case of amorphous silicon and microcrystalline. The influences in contact resistance between microcrystalline n* layer and the source/drain metal electrode, electron mobility, threshold voltage, and on-off current ratio of thin film transistor with intrinsic microcrystalline silicon channel layer were also investigated. I.

Introduction

Recently, microcrystalline silicon has attracted increasing attention as a new potential material for thin film device applications. The preparation of thin films of microcrystalline silicon via chemical transport in a hydrogen plasma was first reported in 1968 Veprek and Marecek.[1] More recently, it has been reported by several groups that microcrystalline silicon is obtained via deposition from the glow discharge of silane diluted in hydrogen at a higher power level[2-10]. Microcrystalline silicon deposited from the silane-mixture gas has been characterized by a structure of amorphous microcrystalline mixed-phase including a few atomic % of H[4-8]. In this sense, the material should be represented by hydrogenated microcrystalline silicon, which is essentially different from the conventional polycrystalline silicon. However a detailed structure and morphology as well as the optical and electronic properties of microcrystalline silicon have not yet been well characterized. ff. Experiments After searching for the deposition donditions that formed the microcrystalline. applied to the TF1'and photodiode with optimum condition, respectively. The films described in this paper were prepared by the 13.56 MHz rf glow discharge decomposition of silane and hydrogen gas mixture in a plasma-enhanced CVD chamber down type. Some examples of the different experimental deposition conditions are given in Table 1(a) and (b). Taguchi method, which is one of the economical and statistical approach to find out the optimum precedure as shown in Tablel(b) with the preliminary experiment as in Table 1(a). The value in 1(b) means the multiple value of in Table 1(a). Above experimental methods consist of various levels and factors determined by empirical sense. For example, condition No.2 means that deposition

Mat. Res. Soc. Symp. Proc. Vol. 283. 01993 Materials Research Society

610

temperature, r.f. power, process chamber pressure, and H2 flow rate are 250"C, 150 watts, 0.8 Torr, and 1500 SC04, respectively