Characteristics of Pulsed-Laser Deposition (Pb0.6Sr0.4)TiO3 Thin Films with Low Thermal Budget Post Treatment
|關鍵字:||鐵電材料;準分子雷射退火;鈦酸鍶鉛;薄膜;Ferroelectric Material;Excimer Laser Annealing (ELA);PST;Thin Film|
我們使用沈積於Pt/Ti/Ox/Si基底結構上之低結晶溫度(Pb,Sr)TiO3 (PST) 鐵電材料作為電容式1T-FeRAM之探討。此PST薄膜在低溫下採用雷射剝鍍方法於基版溫度200度下製備。首先，我們從傳統的後續熱處理方法（快速退火（RTA），爐管退火（FA））的結果得知，較大的熱應力造成表面龜裂及介面掀起。
除此之外，ELA及RTA熱處理方法的結合可以大大改善整層薄膜的結晶性及鐵電性。在經過可靠度包括Fatigue, Imprint, TDDB的測試之後，經ELA及RTA結合熱處理的PST薄膜有著不錯的可靠度特質。最後，我們成功的利用低溫後續熱處理達到整層較好的結晶特性及鐵電特性，此一特性使之成為電容式1T-FeRAM的最佳選擇。|
Since high temperature post-annealing for ferroelectric materials was usually required to get the fine crystallinity and ferroelectric characteristics. But many trouble issues was induced by the high thermal budget, such as the inter-diffusion of ferroelectric and substrate, and the deformation of junction profile etc. Therefore it is essential for the reduction of post-annealing temperature in order to make the ferroelectric material compatible the Si-base fabrication process. In this these, low temperature and low thermal budget for fabrication and post-annealing methods are introduced in this thesis. The (Pb,Sr)TiO3 (PST) ferroelectric material with low crystallization temperature was deposited onto the Pt/Ti/Ox/Si substrate for the research of capacitor type 1T-FeRAM. The PST thin film was fabricated by pulse-laser-deposition (PLD) method at low substrate temperature 200oC. At first, the results of conventional post annealing methods (Rapid Thermal Annealing (RTA), Furnace Annealing (FA) were acquired, witch surface cracks and interface lift were found by lager thermal stress. Therefore, novel post-treatment for Excimer Laser Annealing (ELA) method was introduced to suppress the above troubles. The PST thin films were irradiated with conditions of different laser energy density and shot number at low substrate temperature 300oC. The improvement of ferroelectric characteristic was apparently observed from electrical measurement and physical analysis, and it is further inferred that the crystallization phenomenon was occurred only on the surface region. The better improvement for crystallinity was found by appropriate control of laser energy density and shot number. Besides the larger improvement on crystallinity and characteristic of whole thin film were obtained with the combination of ELA and RTA post-treatment. The fine reliability properties for PST thin film with treatment of combination of ELA and RTA method were acquired after Fatigue, Imprint, and TDDB tests. Finally, the better crystallization and ferroelectric characteristic of the whole PST thin film treatments had been successfully achieved under low temperature post-treatment, and it is excellent for the most promising candidate in capacitor type 1T-FeRAM applications.