矽化鎳接觸淺接面二極體之研製

Abstract

本論文主要探討以離子植入矽化鎳(NiSi)的技術來製作NiSi/p+n以及NiSi/n+p淺接面二極體。經適當能量的BF2+離子佈植使得NiSi/n-Si界面處具有較高硼（B）和氟（F）離子濃度的矽化鎳薄膜可減緩薄膜結塊的發生，高溫穩定性可達到750℃，此乃由於聚集在矽化鎳晶界的硼離子以及矽化鎳薄膜中的氟離子效應有效阻礙了結塊的發生。較高的BF2+離子佈植劑量在接面處形成較高的參雜濃度，可以得到電特性較佳的NiSi/p+n淺接面二極體。其中，以35keV能量將5×1015cm-2劑量的BF2+離子植入NiSi(310Å)/n-Si，並在氮氣爐管中作650℃的退火處理30分鐘所得到的NiSi/p+n淺接面二極體，其接面深度(自初始矽基板高度算起) 約為87nm，反偏壓（5伏）漏電流密度約為1nA/cm2，正向理想參數為1.01。此接面二極體之反偏壓電流的活化能約為1.07eV，顯示反偏壓電流的主要成份為擴散電流(diffusion current)。對反偏壓電流成分的分析結果顯示，就面積為1×10-4cm2的接面二極體而言，漏電主要來自二極體的周邊，而非底部。 在NiSi/n+p接面二極體方面，以P+離子植入並經後續退火所得到的NiSi/n+p接面二極體，具有優於以As+離子植入所製得之接面二極體的電特性。其中，以35keV能量將5×1015cm-2劑量的P+離子植入NiSi(760Å)/p-Si，並在氮氣爐管中作600℃的退火處理30分鐘所得到的NiSi/n+p接面二極體，其反偏壓電流密度約為60 nA/cm2，正向理想參數約為1.20，接面深度（自初始矽基板高度算起）約為80nm。此接面二極體之反偏壓電流在低溫(40~100℃)之活化能約為0.6eV，顯示反偏壓電流的主要成份為產生電流(generation current )；在高溫(120~200℃)之活化能約為0.94eV，顯示其電流成份含有擴散電流和產生電流。

This thesis studies the formation, using the technique of implant into/through silicide (ITS), and the characterization of NiSi/p+n and NiSi/n+p shallow junctions. It is found that a NiSi film which is implanted with BF2+ at a proper energy and dose and has high concentration of dopant at the NiSi/Si interface will have a better resistance to the NiSi film agglomeration up to a temperature of about 750℃ due to the segregation of dopant atom at the NiSi grain boundaries and the effect of fluorine atom in the NiSi film. As for the electrical characteristics of the NiSi/p+n junction diodes, higher dose implantation results in better junction characteristics because of higher dopant concentration at the junction. For the p+n junction diodes fabricated using the ITS scheme, BF2+ implantation at 35keV to a dose of 5×1015cm-2 into the NiSi(310Å)/n-Si structure, followed by a furnace annealing at 650℃ for 30min resulted in NiSi/p+n shallow junctions with a junction depth of about 87nm, a reverse bias leakage current density of about 1nA/cm2 and a forward ideality factor of nearly unity. It is found that diffusion current is the predominant component of the reverse bias leakage current, which is mainly contributed by the peripheral leakage for the NiSi/p+n junctions with a size of 1×10-4cm2. The NiSi film implanted with As+ and P+, separately, at higher energy and to a larger dose resulted in worse resistance to the agglomeration of Ni-silicide and NiSi2 was formed at lower annealing temperature, owing to the increase in surface energy of NiSi film. The NiSi/n+p junction diodes with a reverse bias leakage current about 60 nA/cm-2 and a forward ideality factor of about 1.20 were obtained by P+ implantation at 35 keV to a dose of 5×1015 cm-2 into the structure of NiSi(760Å)/p-Si, followed by a furnace annealing at 600℃ for 30min. The junction depth is determined to be about 80nm. It is found that the generation current is the predominant component of the reverse bias leakage current of the NiSi/n+p shallow junction at temperatures below 100℃ presumably because the recoiled Ni atom in and/or near the n+p junction plays a role of generation center.