| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 93 === Abstract
To improve the speed, packing density and performance of integrated circuits, the dimension of devices has been continuously scaled down, it has pushed the structure of conventional MOS devices to its physical limits. Because the thickness of gate dioxide has only a few atom layers, the leakage current resulting from direct tunneling mechanism increases drastically, thus it leads to a power dissipation too large to be accepted, or even worse resulting in the malfunction of devices. Therefore, the search for novel high k materials to serve as alternatives of silicon dioxide as the gate insulator has been very urgent for today’s VLSI technology.
In this thesis, aluminum nitride (AlN) thin film deposited by using RF magnetron sputtering is proposed as an alternative for silicon dioxide. Both Al/AlN/Si and capacitor and field effect transistor have been successfully fabricated. The essential structures and electrical properties of AlN thin film are investigated. XRD, ESCA, AES, and EDS analysis are used to confirm the composition of the AlN film. Results obtained form SEM and TEM cross-section images show that the interface between Si and AlN is in good condition. TEM image is also used to estimate the physical thickness of AlN thin film. AlN films prepared under different sputtering conditions are characterized and analyzed. According to C-V measurement together with the TEM image, it is found that the relative dielectric constant of the sputtered ALN films is of about 10.
The IG-VG, ID-VD and ID–VG characteristics of MISFET are measured. The gate leakage current density of the transistor is about 5×10-5 A/cm2 at 1V. The driving current is at the range of several milliampere. From the ID–VG curve, several parameters have been extracted. The threshold voltage and subthreshold swing are -0.18 V and 214 mV/dec, respectively, the ION/IOFF ratio is about 104, and the channel mobility is about 218 cm2/V�泅ec. These results show that the AlN film is with the same good performances as compared to other high κ materials like HfO2. The reliability of the AlN film is also examined. Experimental results reveal that the maximum voltage of operation for a 10-year-lifetime is around 2.4 V, which is good enough for practical applications. Based on experimental studies conducted in this thesis, it is concluded that both the electrical and physical properties of the sputtered AlN films is suitable for serving a new gate insulator for advanced FETs and and DRAMs.
|
|---|
