於VLSI上AlSiCu/TiN/Ti之接觸系統

Abstract

在本論文中,我們主要研究將AlSiCu/TiN/Ti多層金屬接觸系統實際應用 在1毫米下的互補式金氧半導體製程中.電性研究包含了接觸電阻及PN接面 的反偏壓電流特性.我們發現鈦金屬在約500C退火過程中開始矽化作用.對 AlSiCu/TiN/Ti接觸系統來說,由於硼在矽化鈦回火過程中,會擴散至矽化 鈦,為了降低及穩定P+接觸電阻,在蝕刻接觸窗後,便加入了BF2植入.為了 節省黃光製程,BF2是全面植入,這使N+接觸窗被反摻雜.因而引致N+接觸電 阻隨著退火溫度增加而增加,從N+及P+接面反偏壓電流溫度特性,經過換算 之活化能數據比較,AlSiCu及AlSiCu/TiN/Ti接觸系統不管其測試圖型有相 同之反偏壓電流機制.從SIMS分析,在退火過程中摻雜元素包括砷,磷及硼 均會部分擴散至矽化物裡,同時,磷及砷更堆積在矽基底的介面,使N+接觸 電阻降低.因為有較好的覆蓋度,較高的耐熱穩定性,較低的N+接觸電阻,及 相當的漏電流表現,AlSiCu/TiN/Ti接觸系統適用於1毫米下互補式金氧半 導體製程.在另一方面,如果接觸窗的高與寬比例降低,AlSiCu亦可能適用 於1毫米的接觸系統中. This thesis is to realize AlSiCu/TiN/Ti multilayed contact system on the CMOSprocess below one-micron. Electrical properties including contact resistivityand reverse bias junction leakage current have been studied. Silicidation oftitanium appears to start at about 500 C sintering. For AlSiCu/TiN/Ti contactsystem, since boron atoms can outdiffuse into silicide during the annealing period, BF2 implant is required after contact opening to reduce and stablize the p+ contact resistivity. However, for reducing a photo step, BF2 is implanted without mask, leading to the n+ contact being counterdoped. It makes the n+ contact resistivity increase as the sintering temperature rises.Comparing the activation energies extracted from the temperature dependence of n+/p- and p+/n- reverse bias junction current, both AlSiCu and AlSiCu/TiN/ Ti contact system have the same leakage mechanism independent oftest pattern. From the SIMS analysis, boron, phosphorus partially segregate into silicise, whereas, arsenic and phosphorus pile up at the interfacebetween silicide and silicon substrate during TiN/Ti sintering cycle. This makes the n+ contact resistivity be lower. Having better contact step coverage, higher thermal stability, lower n+ contact resistivity and comparable leakage current performance, AlSiCu/TiN/Ti contact system is applicable on the CMOS process below one- micron. On the other hand, if theaspect ratio of contact is reduced, AlSiCu can be probably used in the one-micron contact system.