With the continuous dimensional scaling down of Si based devices has called for using high-k dielectrics to replace SiO2 or nitrided SiO2 as the gate oxide in CMOS devices. However, the untrollability of flatband voltage (VFB) is still a crucial issue for CMOS devices with high-k gate dielectrics. This undesirably flatband voltage shift is highly related to the interfacial defects, such as interface defect density, fixed charge density and oxygen vacancy. Therefore, it is significant to understanding the physical and chemical properties of the interface regions.

To grow thin films with excellent properties, plasma-enhanced atomic layer deposition (ALD) has been widely used as a thin film deposition method. PEALD commonly produces better quality of films at lower growth temperatures than dose thermal ALD because the required activation energy is provided by a plasma source. Some processes require the presence of radicals to enhance chemical reactions without having to use ion bombardment, as it can cause plasma-induced damage. Remote plasma ALD (RPALD), wherein the plasma is created in a remote chamber using RF power, was developed to meet these processing demands. The radicals generated in the plasma enter into the process chamber for deposition.

 In order to understand the interfacial influence on the VFBshift in high-k based MOS structure, it is need to investigate the dependence of the VFB shift on the properties of interfacial layer. In this paper, to modify the Si surface, N2 plasma was treated on Si surface at RF powers of 100 W, 200 W and 300 W. The Al2O3 was deposited by remote plasma ALD at 250oC. The Pt/Al2O3/Si MOS structure was fabricated to investigate the impact of interfacial layer between Al2O3 and Si substrate on change in VFB. In addition, plasma was monitored by optical emission spectroscopy (OES). The physical and chemical properties of high-k dielectric films and interfacial layer were examined by XPS and AES.

 We found that the nitrogen content at Si substrate increased during N2 plasma pre-treatment at high RF power which results in a negative shift of VFB. Therefore, the properties of the interfacail layer which are critical in determining the VFB are affected by N2 plasma pre-treatment.