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The author first applied a chemical mechanical polishing (CMP) process to fabricate a ferroelectric Pb(Zr,Ti)O3 (PZT) capacitor instead of using a plasma etching process for the vertical profile without plasma damage in their previous study. The post-CMP cleaning process was very important in this CMP process. In this study, they investigated the effects of the post-CMP cleaning process on the ferroelectric properties of a PZT thin film capacitor. They proposed an optimized post-CMP cleaning process that uses a SC-1 chemical, diluted HF treatment, and an ultrasonic cleaning process. The slurry residues on the surface of the PZT thin films were removed. The polarization-voltage (P-V) characteristics showed the typical hysteresis loop of PZT thin films after a post-CMP cleaning process with the optimized conditions, while the ferroelectric characteristics could not be observed in the specimen without the post-CMP cleaning process. The remanent polarization (Pr) and coercive voltage (Vc) of the PZT thin films after the post-CMP process with the optimized condition were 17.092μC∕cm2 and 3.252V, respectively.

-Chalcopyrite CuInSe 2 (CIS) thin films were prepared without Se-/ S-containing gas by co-sputtering using CuSe 2 and InSe 2 selenide-targets and rapid thermal annealing. The grain size increased to a maximum of 54.68 nm with a predominant (112) plane. The tetragonal distortion parameter η decreased and the inter-planar spacing d (112) increased in the RTA-treated CIS thin films annealed at a 400°C, which indicates better crystal quality. The increased carrier concentration of RTA-treated p-type CIS thin films led to a decrease in resistivity due to an increase in Cu composition at annealing temperatures ≥ 350°C. The optical band gap energy (E g ) of CIS thin films decreased to 1.127 eV in RTA-treated CIS thin films annealed at 400°C due to the improved crystallinity, elevated carrier concentration and decreased In composition.

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The 20.9% conversion efficiency of I-III-VI chalcopyrite-based solar cells, the highest in the world, makes them promising candidates for high-efficiency thin film solar cells. However, Ga is one of the most expensive rare materials with the critical degradation in device efficiency. Cu(ln(1-X)Al(X))Se2 (CIAS) is considered an alternative to Cu(ln(1-X)Ga(X))Se2 because of its good structural suitability and the low cost of Al. CIAS thin films were formed using triple targets of CuSe2/ln/Al in a co-sputtering system to control the composition ratio, x = [Al]/([ln]+[Al), by varying each RF power for In/Al with rapid thermal annealing. The chalcopyrite peaks shifted toward higher 2theta as x increased. The CIAS thin films had 74.24-86.81% absorption with band gap, Eg, of 2.28-2.50 eV in the 400-1600 nm range. A low resistivity of 1.1 x 10(-2) omega(-cm) was obtained in the CIAS thin films with x of 0.74.