鈦酸鍶鋇在金屬-絕緣層-金屬結構中之磁電耦合特性

Abstract

在主流的半導體領域裡，通常將重點放在矽半導體、高介電值材料、三五族化合物半導體等研究。鮮少看見有人將磁性材料應用在標準的矽半導體製程上。然而從文獻上可知，電子元件在磁場下會影響其載子的傳輸現象。所以我們大膽的利用磁性材料內建磁場在電子元件中，並進而研究、觀察其電子元件不管在電性、光性甚至機械等效應。這裡我們將FePt奈米磁鐵內建到奈米尺度大小的鈦酸鍶鋇MIM (Metal-Insulator-Metal)結構裡並觀察其磁電耦合特性。 本論文主要內容分為三部分，第一部分為磁性鈦酸鍶鋇MIM電容結構的設計與製作以及FePt奈米磁鐵的圖案設計。磁性鈦酸鍶鋇MIM電容包含Bottom_Ti與Bottom_Pt，(詳見第三章)。第二部分為介紹用來控制FePt中磁矩方向的磁退火爐與磁退火方法(詳見第幾四章)。最後一部分為奈米磁鐵FePt作用於磁性鈦酸鍶鋇MIM電容的電性與磁性探討。由於我們使用的的絕緣層為高介電係數的多鐵性材料鈦酸鍶鋇(BaSrTiO3)，我們期待其鐵電性與鐵磁性在奈米磁鐵的磁場下能展現不同的元件特性，諸如低漏電流、高崩潰電場、高介電常數等。磁退火步驟後確實有提升元件殘磁化量與飽和磁化量。此外，元件的漏電流(在0.1 MV/cm)有明顯的減少，也得到更高的介電強度(在10-6 A/cm2)與崩潰電場。

In the semiconductor domain, the mainstream research is always focusing on Si-based semiconductor, high-κ material, III-V compound semiconductor etc. It is rare to see magnetic materials which be used in standard Si process. According to literatures, there are some phenomena had been observed that carriers transport in electronic device under magnetic field. So we take adventure to apply magnetic materials into semiconductor process and investigate new phenomena no matter on electricity, optics and even mechanism. Here, we introduce FePt nano-magnets into the nano-space BaSrTiO3 metal-insulator-metal (MIM) structure and observe their magnetoelectric coupling properties. The thesis is divided into three parts. The first part is about design and fabrication process of magnetic BaSrTiO3 MIM capacitor and design of FePt nano-magnets array. There are two magnetic BaSrTiO3 MIM capacitors here, the Bottom_Ti and Bottom_Pt structure (see chapter 3). The second part introduces magnetic annealing process and equipments which control the magnetized directions of magnetic dipoles in FePt (see chapter 4). The last part investigates the electrical and characteristics of magnetic BaSrTiO3 MIM capacitor which is affected by FePt nano-magnets. Because the insulator layer we use is high-κ and multi-ferroic material: barium strontium titanate (BaSrTiO3, BST). We look forward to its ferroelectricity and ferromagnetism under magnetic field by nano-magnets can show different device characteristics, such as low leakage current, high breakdown voltage and high dielectric constant, etc. Magnetic annealing process indeed enhances remanent magnetization and saturated magnetization of devices. In addition, their leakage current (at 0.1 MV/cm) is obviously reduced and higher dielectric strength (at 10-6 A/cm2) and breakdown field can be obtained.