Electrical evaluation of the crystallization characteristics of excimer laser annealed polycrystalline silicon active layer

We showed that the crystallinity of polycrystalline silicon (poly-Si) active layer of low temperature poly silicon (LTPS) devices can be comparatively analyzed through conventional electrical methods. We fabricated the MOS capcitors and the thin film transistors (TFT) with different excimer laser annealing (ELA) crystallization conditions. Through the capcitance-time (C-t) method and the frequency variable capacitance-votage (C-V) method, we detected the influence of grain boundaries of poly-Si. The generation lifetime (τg) and the number of border traps (Nbt) calculated by these methods could detect tiny crystallinity differences related to energy density differences about 10-15 mJ/cm2 during the recrystallization. The field effect mobility (μFE) and off current (Ioff) measured with the TFTs also showed the same tendency. The results of this study show that the measurements using MOS capacitor are sufficiently reliable and suitable for obseving property changes of the poly-Si active layer.