擴散阻礙層對銅閘極金氧半結構之熱穩定性的德響

Abstract

Copyright (c) 1990, Microsoft Corp 本論文以介電質劣化,電容-電 壓測量法及加溫偏壓法,來探討擴散阻礙層對銅閘極金氧半結構之熱穩定 性的影響. 首先,在鋁/二氧化矽/矽結構中我們設計了二氧化矽在高溫 氧化形成之後經氮氣退火處理與未經氮氣退火處理的兩樣樣本.我們測量 整個結構的介電質劣化情形,與介面能階密度,高頻曲線的變化,來觀察此 結構之熱穩定性.我們觀察到整個結構在金屬濺鍍沉積過程中與其結構中 的二氧化矽在高溫氧化形成之後若不經氮氣退火處理皆會破壞氧化層,因 而影響到其結構之熱穩定性. 我們又利用擴散阻礙層對銅閘極金氧半結 構經爐管熱處理後,觀察其高頻曲線在經加溫偏壓法前後的變化.了解得知 此結構於不加擴散阻礙層時經400 ℃ 30分爐管熱處理後,電性便生劣化, 其劣化程度隨熱處理溫度升高而加劇.劣化原因可能來自熱處理過程中,帶 正電的銅離子在二氧化矽層中的快速移動.置入一層50nm的氮化鈦或氮化 鉭可成功地阻礙銅在二氧化矽或二氧化矽/矽介面中的擴散,如氮化鉭擴散 阻礙層的樣本在最佳條件下在熱處理溫度中可提高到700 ℃, 仍然具備有 效的擴散阻止能力.另外,我們也作了一些氟玻璃矽化物的研究來探討氟玻 璃矽化物的一些基本特性. Copyright (c) 1990, Microsoft Corp Abstract This thesis studies the thermal stability of Cu/ SiO2/Si system with and without diffusion barrier. Ti-series and Ta-series nitrides were studied withrespect to their barrier capacity against Cu permeation and migration in the oxide layer. We used C-V measurements and the dielectric breakdown field (Ebd) to characterize the thermal stability of Metal/SiO2/Si system and use the technique of bias-temperature stress to characterize the thermal stability of the Cu/Barrier/SiO2/Si system with and without diffusion barrier. For the Cu/SiO2/Si MOS capacitors annealed at temperature below 400 ℃, theDit decreased, the Vfb shifted in the positive voltage direction, and the Ebd improved, all with the increase of annealing temperature. This is presumablybecause that with the increase of annealing temperature, the dangling bondsand sputter induced oxide damage were repaired. On the other hand, annealingof the capacitors at temperatures above 400 ℃ resulted in increase of theDit, negative shift of Vfb, and degradation of Ebd; this observation is obvious particularly for the Cu/SiO2/Si samples. Cu ion migration in the metal-gated MOS capacitor is presumably the major reason. Form BTS experiments, we can demonstrate that the barrier layer is useful against Cu ion. TaN (12:3)(500 □ barrier layer is the better one amoung those barriercadidates with various nitrogen contents. The structure with barrier layer TaN (12:3)(500 □ is still stable at heat treatment 700 ℃. The FSG film was found to have index of refraction lower than various oxides presently used in microelectronic processing. However, the index of FSG filmwith Cu gate will become larger at the elevated temperature. Without proper diffusion barrier, it seems difficult to combine the low dielectric FSG and low resistivity Cu together.