嵌入圖案化的奈米磁鐵FePt的磁化作用在MIM結構上的特性

Abstract

磁性物質的研究與應用相當的廣泛，因此我們將磁性物質加入半導體製程中以探討新的物理現象。選用的磁性物質為FePt，其具有相當大的晶格異相性、飽和磁化量以及熱穩定性。本研究主要目的是嵌入不同圖案安排的奈米磁鐵FePt，使其在奈米尺度空間中產生內建磁場，研究發生磁電效應的最佳條件，諸如電流-電壓、電容-電壓、電容-頻率等。 本論文內容主要分成兩個部分，第一部分為MIM結構的製程以及FePt奈米磁鐵的圖案設計安排，不同的磁化條件以及不同的奈米磁鐵圖案安排會影響磁場在空間中的分布。第二部分為探討磁性FePt MIM結構的磁性與電性，磁退火製程後有提升的殘磁化量與飽和磁化量，根據張俊彥教授的理論預測，電子在磁場下的穿隧機率會降低，電子在磁場下的平均自由路徑會減少，使磁性FePt MIM結構的漏電流減少，產生高崩潰電壓，而長寬比例大的圖案在這方面結果明顯。

Recently, there are a lot of researches and applications about magnetic material. Therefore, to investigate new physical phenomenon, we introduce magnetic material into semiconductor process. FePt is selected since magnetocrystalline anisotropy and saturated magnetization of it is larger than other magnetic materials and chemical stability is better than others. The purpose of this research is to produce build-in magnetic field in the MIM device of nanometer scale by embedding patterned FePt nano-magnets into the device, and to study optimal condition for measurements of magneto-electric coupling effect on current-voltage, capacitance-voltage and capacitance-frequency. There are two parts in this thesis. First part is the process of MIM structure and the design of arrangement of patterns for FePt nano-magnets. Arrangement of the pattern and magnetizing condition both affect distribution of magnetic field in the space. In the second part we analyze magnetic and electrical characteristics of FePt nano-magnets embedded MIM structure. Magnetization annealing process enhances remanent magnetization and saturated magnetization of device. According to theoretical predictions of Prof. Chun-Yen Chang, reduction of leakage current and higher breakdown field can be obtained since decrease of tunneling probability of electron under magnetic field is observed and reduction of mean free path of electron under magnetic field is also studied. In this research we find the phenomenon is obvious with patterns of large ratio of the length to width.