選擇性鎢沈積法製備之鎢接觸P+N接面二極體研究

Abstract

本論文主要探討鎢接觸p+n接面二極體，而此鎢膜係以矽烷(SiH4)還原六 氟化鎢(WF6)方式選擇性地成長在該接觸窗內。對於具300nm厚度鎢接觸之 Cu/W/p+n二極體而言，該元件無法承受30分鐘的600℃熱處理，如此將造 成元件特性之劣化。藉由在化學氣相沈積成長的鎢膜上作氮氣電漿處理以 形成自動對準的WNx薄膜，可以成功的阻礙銅和矽的交互擴散，使元件特 性的劣化在650℃以下都不致發現。此外，以快速退火方法於氨氣中形成 的WNx薄膜亦具備有效的擴散障礙特性，以阻止銅的穿透。雖然WNx的形成 使接觸電阻增加，但是在矽基表面形成一薄層的鈦矽化物將可有效的降低 接觸電阻。再者，防止銅穿透保護層將是達成高可靠度製程的重要關鍵， 氮化保護層將能阻礙銅的滲透直到600℃。總而言之，氮化處理不僅能有 效的增進鎢膜的擴散障礙能力亦能壓制銅滲透進入保護層。 This thesis studies the W contacted p+n junction diode with the W film deposited using the selective W-CVD technique. For the Cu/W/p+n junction diode with a W layer of 300 nm, a thermal treatment at 600 C for 30 min caused slight degradation to the devices characteristics. With formation of a self-aligned WNx layer on the W surface by post CVD-W in situ N2 plasma treatment, the device remained stable after annealing at 600 C for 30 min. However, degradation occurred after 650 C anneal for 30 min, presumably due to the permeation of Cu into TEOS oxide. For the Cu/WNx/W/p+n junction diode with the Cu layer covering the barrier only, the device was able to sustain a 30 min thermal treatment up to 650 C without causing degradation. The WNx layer formed by RTA treatment in NH3 ambient was found to possess a similar barrier capacity against Cu penetration. Although WNx layer formation increased the contact resistance, application of a Ti silicide layer on the Si surface could reduce the resistance effectively. Copper permeates into the TEOS oxide passivation layer easily. The nitrogenized passivation layer could retard the Cu permeation up to 600 C. In a word, the nitridation treatment not only improved the barrier capacity of W layer but also suppressed the permeation of Cu into the passivation layer.