本文採用430型不銹鋼(SUS430)取替Pt電極與矽晶片基板，搭配CO2低溫雷射退火製程，以改善傳統爐管之退火中導致元件產生介面擴散與氧化等問題，使得PZT鐵電薄膜與LSMO氧化物電極能成功鍍製於SUS430基材。
SUS430中添加元素以Cr元素佔有最高成份比例，一般Cr金屬在元件中主要是作為黏結層，本實驗討論以Cr作為金屬電極，並使用傳統爐管退火與CO2雷射退火製程比較對Cr金屬氧化的情形。X-ray繞射圖顯示純Cr金屬電極鍍製於矽晶片基板時，當爐管退火溫度超過350℃時開始有Cr2O3與CrO2氧化物產生，當改用CO2雷射退火製程， Cr金屬電極仍會形成Cr2O3氧化物，使得底電極電阻率增加，造成元件之驅動電壓耗損，對鐵電特性影響極大，因此測得PZT薄膜其殘留極化值為11.94 μC/cm2 ，矯頑電場高達358.2 kV/cm，漏電流密度較未退火處理時1×10-8增加至1×10-4 A/cm2。因此本研究採用SUS430取替Cr金屬電極與矽晶片基板，研究CO2雷射退火是否能抑制SUS430的氧化，維持底電極的導電性，以得到良好的電性。
研究中發現，PZT厚度為0.2 μm鍍製於非結晶LSMO氧化物電極上，PZT/LSMO/SUS430元件結構進行CO2雷射退火後，發現薄膜中形成Cr2O3氧化物與Fe-Cr-Mn spinel，導致PZT表面微觀結構膜裂嚴重，且無法測得出典型的電滯曲線，漏電流密度為1×10-3 A/cm2。改良熱處理製程將PZT與LSMO分段進行CO2雷射退火，首先以退火條件為雷射功率與照射時間467 W/cm2_70 s進行LSMO 結晶化處理，接著旋鍍上PZT薄膜，再以雷射功率267 W/cm2_55 s與334 W/cm2_35 s對PZT進行退火處理，獲得PZT殘留極化值分別17.20 μC/cm2與18.08 μC/cm2，漏電流密度為1×10-5 A/cm2，由此可知，藉由分段CO2雷射退火處理LSMO氧化物電極與PZT鐵電薄膜，將能抑制Cr2O3的產生與降低Fe-Cr-Mn spinel形成，同時LSMO可做為緩衝層以改善PZT 與SUS430基板介面特性，以獲得緻密PZT膜層組織，且有效減少元素互相擴散問題，改善元件的鐵電特性。研究中同時探討不同PZT薄膜厚度，PZT厚度為0.1 μm時其殘留極化最高值僅為6.07 μC/cm2，漏電流密度為1×10-5 A/cm2；PZT厚度為0.4 μm時其殘留極化最高值為 24.01 μC/cm2，且漏電流密度可維持在1×10-9 A/cm2內，因此以CO2雷射退火製程可以實現0.4 μm膜厚PZT/不銹鋼材元件製作的可能性。

In order to lower cost of processing and increase applications of ferroelectric devices, we substitute Cr and SUS430 for Pt on Si as an electrode material and substrate. In this work, we evaluate the possibility of applying as SUS430 to be the electrode and substrate for ferroelectric devices using a continuous wave CO2 laser annealing technique. We investigated microstructures, electrical properties and conductivity mechanism of Cr thin films and SUS430 substrates through different laser annealing conditions.

The Cr electrode oxidizes easily after furnace annealing at temperature higher than 350℃, so the devices structure of PZT/LSMO/Cr/SiO2/Si was annealed by CO2 laser at the present work, but the Cr electrode still oxidized, which deteriorate electrical properties of specimens. The PZT films deposited on LSMO/Cr/SiO2/Si substrate crystallize well by CO2 laser annealing, the SEM images of PZT thin films are also smooth and without cracks. However, the remanent polarization (Pr) of PZT is 11.94 μC/cm2, and the coercive field (Ec) is 358.2 kV/cm. This result represents that Cr bottom electrode oxidized, and high resistivity as well as high leakage current deteriorate ferroelectric properties of PZT thin films.

The coefficient of thermal expansion of SUS430 was close to the (La0.7Sr0.3)MnO3. The LSMO thin films (0.2 μm) sputtered on SUS430 substrate without crystallization and spin-coated PZT films (0.2 μm) by laser annealed at 334 W/cm2 for 35 s. SEM images show that PZT thin films crack seriously, Fe-Cr-Mn spinel appeared at the interfaces due to the reaction of LSMO and SUS430. So the leakage current increases badly when LSMO was amorphous. To resolve this problem, the LSMO oxide electrode crystallized after sputtering using laser annealing at 467 W/cm2 for 70 s, and then the PZT thin films was coated and annealed at 267 and 334 W/cm2. SEM images show that PZT thin films are smooth and crack-free. The specimens exhibit remanent polarization of PZT (0.2 μm) from 17.20 μC/cm2 to 18.08 μC/cm2, and the leakage current is 1×10-6 A/cm2.
To compare effect of thickness of PZT thin films, we prepared the PZT thin films of 0.1 μm and 0.4 μm. The remanent polarizations and leakage currents of PZT thin films of 0.1 μm is 6.07 μC/cm2 and 1×10-5 A/cm2. On the other hand, those of 0.4 μm specimens is 24.01 μC/cm2 and 1×10-9 A/cm2. CO2 laser annealing not only improves ferroelectric and electric leakage properties of PZT films, but also avoids inter-diffusion of elements in electrode and ferroelectrics. Moreover, laser annealing decreases oxidation of SUS430 and enhances the electrical performance of materials.

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