(Ta2O5)1-X-(TiO2)X介電薄膜研究與微波被動元件製作

Abstract

本論文為利用反應式射頻磁控濺鍍法製備(Ta2O5)1-X-(TiO2)X介電薄膜，並探討在低頻與微波下之特性。在低頻方面，分別以IrOX與Al為下上電極，將薄膜製作成MIM電容結構，做物性與電性分析。非晶質薄膜的初始厚度小於300埃。利用快速退火製程使薄膜結晶，探討不同退火溫度、時間、OMR與薄膜成分下，薄膜之結晶性、電性與表面型態之特性與關係。發現薄膜的退火溫度須大於650℃才會結晶，薄膜中TiO2佔8.8mole%時有最大介電常數，退火溫度越高介電常數與漏電流越高。其漏電流機制在高電場下主要為普勒-法蘭克發射(Poole-Frenkel emission)。 以此介電薄膜做成之微波濾波器是以CPW方式量測其高頻下之S參數，量測結果與Sonnet模擬比對，發現共振頻率偏移模擬值，其原因為介電層厚度及介電常數偏移設計值所致。

Amorphous (Ta2O5)1-X-(TiO2)X films were fabricated by rf magnetron co-sputtering and annealed through a rapid thermal processing(RTP). The film thickness was controlled within 300A. The film was sandwiched between IrO2 and Al as the bottom and top electrode in order to study its electrical and physical properties. The relationships among surface roughness, annealing temperature, annealing time, leakage current and dielectric constant was discussed. The highest dielectric constant was obtained for a film of composition at TiO2/Ta2O5 ratio equal to 9.65%. The film crystallized at temperature larger than 650oC and its leakage current increased with RTP temperature. The leakage current mechanism is identified to be Pool-Frenkel emission. The S parameters of microwave filter fabricated by the dielectric film were measured by CPW method. The result was compared with Sonnet simulation. The discrepancy between the experimental central resonant frequency and the simulated one is found due to the deviation of dielectric constant and film thickness the preset one.