- 學位論文
熱處理對低介電材料電性及可靠度影響
Effect of Thermal Treatment on Physical, Electrical Properties, and Reliability of Porous Low-k Dielectrics
摘要
本論文研究主要可分為兩部分，第一部分主要研究低介電質材料 (low-k) 經不同熱容積 (退火溫度與退火時間) 後，探討其對薄膜特性,電性, 及可靠度之影響。實驗結果顯示，未摻雜孔洞 (porogen) 的 low-k 薄膜在機械強度或電性分析上都比摻雜 porogen 的 low-k 薄膜好，且薄膜特性受熱容積影響較小，但會擁有較高的親水性及介電常數；同時，摻雜 porogen 的 low-k 薄膜經紫外光 (UV) 照射產生孔洞降低薄膜密度，達到最低的介電常數。當退火溫度為400℃時，退火時間增加至30 min，三種 low-k 薄膜其材料結構及電性沒有明顯的變化。當退火溫度增加至600℃，隨著退火時間增加，經 UV 光處理的 low-k 薄膜保有較多的 Si-CH3 鍵，同時，產生較多的網狀結構 (network)，因此有較穩定的機械結構與電性。另一方面，摻雜 porogen 未經 UV 光的 low-k 薄膜，隨著退火時間增加，介電常數持續下降，但仍大於經 UV 光處理的 low-k 薄膜，且其機械強度較差；同時，薄膜電性在退火1 min 內受到 porogen 揮發影響，其漏電流大幅上升，並且崩潰電場明顯下降。但隨著退火時間增加，薄膜內 network 鍵增加使得漏電流緩慢下降。在可靠度壽命之分析，三種 low-k 薄膜在退火溫度400℃時，退火時間對其崩潰時間沒有明顯變化。然而，當退火溫度升至600℃後，摻雜 porogen 的 low-k 薄膜之崩潰時間在退火時間1 min 時會下降，其中以未經 UV 光處理的 low-k 薄膜下降幅度較為明顯。當退火時間增加至30 min，摻雜 porogen 的 low-k 薄膜，其崩潰時間反而會增加，其中又以經過 UV 光處理的 low-k 薄膜增加幅度較大。 論文第二部分主要探討銅 (Cu) 導線金屬與低介電材料薄膜經不同熱容積後，兩者之間的交互作用,電性, 及可靠度之影響。實驗結果可發現，不論是否含有孔洞的 low-k 薄膜，隨著退火溫度及退火時間增加，Cu 擴散到 low-k 薄膜的現象會變得更加嚴重；對於含有孔洞的 low-k 薄膜，Cu 在其擴散速率較快，因此介電常數有較高的增加率，此結果顯示 Cu 原子易透過孔洞擴散至 low-k 薄膜中。當 Cu 擴散現象發生，容易在 low-k 薄膜中形成陷阱 (trap)，並且此數量會隨著 Cu 擴散量的增加而增多，亦即隨著退火溫度與退火時間的上升，trap 的數量也將顯著的增加。因此，含有孔洞的 low-k 薄膜，由於這些不斷增加數量的 trap，將增強 low-k 的薄膜中電子的傳導，使薄膜漏電流上升。對於可靠度之影響，當兩種 low-k 薄膜同時施加相同的電場 (4.7 MV/cm)，可發現含有孔洞的 low-k 薄膜壽命時間小於未含有孔洞的 low-k 薄膜將近兩個級數以上。且兩種 low-k 薄膜其壽命時間經過不同熱容積影響，隨著退火溫度及退火時間增加而持續下降，其中又以含有孔洞的 low-k 薄膜下降幅度較大。
並列摘要
This thesis consists of two parts. The first part focuses on the effects of thermal annealing on the physical, electrical properties, and reliability of low-k films. The results reveal that mechanical structure and electrical properties of low-k films without porogen are better than those with porogen, but they have a higher dielectric constant and hydrophilicity. Moreover, the porogen-free low-k film, which the porogen re-moved by UV curing, has the lowest dielectric constant. At an annealing temperature of 400℃, the material structure and the electrical properties did not change significantly for three low-k films studied here as the annealing time up to 30 min. At an annealing temperature of 600℃, the porogen-free low-k film retains more Si-CH3 bonds than others even as the annealing time up to 30 min. Additionally, this annealing treatment can produce network bonds in the low-k film, leading to the more stable mechanical structure and electrical properties. Compared with the porogen-free low-k film, the dielectric constant of porogen-containing low-k films decreases significantly. However, the dielectric constant of porogen-containing low-k films is still higher than the porogen-free low-k film. Additionally, the mechanical strength of the porogen-containing low-k film is weaker than the porogen-free low-k film. In the annealing time of 1 min, the leakage current increases and the breakdown field decreases for porogen-containing low-k film due to the removal of the porogen. As the annealing time further increases ( >1 min), the leakage current decreases due to the formation of network bonds in the low-k film. In case of reliability lifetime evaluation, the lifetimes of the three low-k films are not affected by the annealing time at an annealing temperature of 400℃. However, at an annealing temperature of 600℃, the lifetimes of the low-k films with porogen decrease for 1 min annealing and increases for 30 min annealing. For the same annealing time, the lifetime of porogen-free low-k film is still longer than porogen-containing low-k film. The second part of this thesis studies the effects of thermal annealing on the interaction between the copper film with low dielectric material, electrical properties, and reliability performance. The experimental results showed that copper diffusion depth increased with the annealing temperature and annealing time increasing in the both low-k films. However, the copper diffusion rate in the porous low-k films is faster, so that a higher increase in the dielectric constant was observed. This result implies that copper atoms diffuse easily through the void within the low-k films. The diffused copper atoms within the low-k films formed the traps. The number of traps significantly increased with the annealing temperature and annealing time in both low-k films, resulting to an increased leakage current. Moreover, the lifetime of the porous low-k film is shorter than the non-porous low-k film by about two orders when stressed under the electric field of 4.7 MV/cm. Moreover, the lifetimes decreased with annealing temperature and annealing time for both low-k films. Especially, the lifetime of porous low-k film decreases significantly.