複晶薄膜電晶體之遮光層光電特性之分析

Abstract

中文摘要 複晶矽薄膜電晶體應用主動式液晶顯示器時，會受到背光源的影響產生漏電流，導致畫素電壓之下降的增加。因此本論文主要探討複晶矽薄膜電晶體在照光狀態下的元件特性與遮光層結構來抑制光漏電現象。此外，運用C-V(capacitance-voltage)的分析去觀察複晶矽薄膜電晶體的特性，藉由改變量測頻率與照光特性以及比較結構上的差異對於C-V曲線的變化。目前研究上，複晶矽薄膜電晶體光漏電主要在汲極空乏區產生，光子能量被矽膜吸收後，激發價帶電子躍遷到傳導帶形電子與電洞對，此電子與電洞對在空乏區內建電場影響下，會分開相反方向移動形成光電流。為了增進複晶矽薄膜電晶體特性，對光吸收較佳的非晶矽薄膜為遮光層，探討元件特性與光漏電流效應在C-V之照光與無照光量測.。

Abstract Since poly-Si TFTs are widely used in active-matrix liquid crystal display (AMLCD), they usually will be exposed to the scattered light from the backlight system. In this paper, The Poly-Si TFTs with light shielding in order to suppress photo-leakage currents, which is essential to realize a high contrast ratio in display images. The C-V (capacitance-voltage) analysis observer poly-Si TFTs characteristics, which adjust measure frequency and compare structure differences. Today studies, the photon energy will be absorbed by the silicon film to excite the generation of electron-hole pairs. Under certain electric field such as the built-in electric field in the depletion regions, the electron and the hole will move toward the opposite direction and from the current. Compared to the generation current from the depletion in the dark environment, the light caused current is much larger and cause pronounced leakage current problem. We use the well-absorbing a-Si silicon film (amorphous silicon film) to be the light-shielding layer. The variation in the C-V result allows us to identify the degradation mechanism in the dark and illumination circumstance.