單晶及複晶矽上的LPD Oxide之電性探討

Abstract

本論文主要探討室溫液相沉積二氧化矽膜(LPD)的膜質特性,並開發其 可可行之處.首先,我們提出其漏電流機制,結果發現對於較薄的膜或在較 低溫度下,其主要導電機制是Fowler-Nordheim 穿透,而在較高溫度下或對 於較厚膜,將會有 Poole-Frenkel 的導電機制.而經過熱處理,其導電機制 亦會改變.經由這些改變,我們發現 LPD 二氧化矽膜中的SiOH 鍵會主導其 導電機制.開發具有良好電特性的 LPD SiO2 膜,其漏電流約為 10nA/cm2 (在4MV/cm),崩潰電場約為 7 ~ 8 MV/cm.為求進一步擴大 LPD SiO2 的應 用範圍與價值,必須沈機高品質且較薄之 LPD SiO2 膜.因而我們開發一新 的沈積系統及製程方法以沈積高品質 LPD SiO2 薄膜. For the growth of silicon dioxide using the traditional thermal furnacetube, the interface damges caused by high temperature process such as ther-mal stress and dislocation growth will degrade the performance of the deviceand the integrated ciecuit. In paticular, the junction redistribution results from the high temperayure process will become more significant for smalll geometric devices. Therefore, the deduction of process temperature is nece-ssary for the growth of SiO2 in future. In order to reduce the process temperature , various CVD techniques withlow temperature are developed to substitute for thermal oxidation. The CVD oxide films have better breakdown characteristics than thermal oxides. Ingeneral, the as-deposited oxide film exhibits a higher interface state dens-ity. This drawback can reduced by further development. Neverthless, the conventional CVD oxide films produced from SiH4 and O2 and N2O contain NH, SiH, SiN and OH groups in the film create deeep traps or recombination centersin the oxide film from the infraded absorption spectrum. These chemical con- tainments act as defects. HOwever, the CVD oxidess without SiH, SiN and OHgroups can be obtained using He-diluted or ECR microwave plasma. These methodrequired high temperature(350C) process and expensive equipments. In addition, it has been reported that the fluroine incorpration in gate oxide can evidently reduce the interface trap density and increase immunity to hot-carrier-induced stress. We are interested in liquid-phase deposition method which can depositeoxide film without chemical containments as described above and obtain fluorine-contained oxide film without additional process. Moreever, the equipment of this method is inexpensive and easy to operate. The oxide film with perfact unifimity can be obtained by LPD method. The LPD has sucessful applied in gate insulator of MOSFET and polysilicon thin filmtransistor for LCD. However, few studies have been reported on electrical pro- perties of LPD oxide films, especially their leakage conduction mechanism. In order to improve the oxide quality, it is essential to clarify the leakage current conduction mechanism. In this studies, we will describe the and verifythe various leakage conducton mechanisms before and after thermal and RTPambient annealing. In addition, we also distinguish the difference of LPD oxidebetween the two kinds of substrates (single-Si and polysilicon. Finally, we use the previous results to deposite the LPD oxides companying with various annealing conditions. The deposited LPD oxide films shows better quality than before.