Study of HfAlOx Films Deposited by Layer-by-Layer Growth for CMOS High-k Gate Dielectrics
- PDF / 514,881 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 84 Downloads / 318 Views
E2.5.1
Study of HfAlOx Films Deposited by Layer-by-Layer Growth for CMOS High-k Gate Dielectrics
Akira Toriumi1,2, Toshihide Nabatame3 and Tsuyoshi Horikawa2 1 Department of Materials Science, The University of Tokyo, Tokyo 113-8656, Japan 2 MIRAI, Advanced Semiconductor Research Center (ASRC), National Institute of Advanced Industrial Science and Technologies (AIST), Tsukuba 305-8569, Japan 3 MIRAI, Association of Super-Advanced Electronics Technologies (ASET), Tsukuba 305-8569, Japan ABSTARCT We have investigated ternary metal oxide films for high-k gate dielectrics by using a layer-by-layer deposition & annealing method so as to keep the dielectric constant of the film high with no crystallization. HfAlOx films have been prepared by alternating deposition of HfO2 and Al2O3 layers, where it is a key for the improvement of the film quality to understand the intermixing process between two layers by thermal treatments. So, we first discuss the atomic diffusion and structural change of the HfO2/Al2O3 “superlattice” film as a function of the annealing temperature by changing the Hf/Al ratio. In a typical case of the film with HfOx/AlOx=3Å/9Å cycle, a clear superlattice peak is observed below 750 ºC by XRD. Above 850 ºC, a different type of crystalline structure with no superlattice peaks is observed. These results indicate that the intermixing in HfO2/Al2O3 (3Å/9Å) films occurs between 750 and 850 ºC. The intermixing onset temperature increases with increasing Al content in Hf/Al ratio. To further increase the crystallization temperature, nitrogen incorporation into the film is considered, and effects of the nitrogen incorporation into HfAlOx films are studied from the structural and electrical viewpoints. The results indicate that there is a tradeoff between crystallization restriction and leakage current degradation for the nitrogen incorporation into HfAlOx films. INTRODUCTION A new method for high-k film growth, which is called as Layer-by-Layer Deposition & Annealing (LL-D&A), has been proposed for the improvement of high-k films [1]. A key concept of this method is to reduce impurities incorporated into the film through decomposition of precursors, to densify the deposited films effectively, and to achieve a good uniformity of a targeted thickness film, as schematically shown in Fig.1. We have demonstrated better qualities
E2.5.2
Deposition
Annealing
Deposition
Annealing
Si
Fig.1. A schematic description for LL-D&A method. Annealing process for very thin deposited film is important for improving the film quality. It is typically performed in a diluted O2 or NH3 at 130 Pa and 650 °C. of HfAlOx film grown by the LL-D&A method in MOSCAPs and MOSFETs [2], when both physical and electrical properties are compared between LL-D&A and conventional ALD+PDA. The conventional high-k fabrication process consists of the film deposition and subsequent PDA, resulting in insufficient removal of impurities, most likely because the impurity desorption rate from the deeper layer is basically very low. In case of the LL-D
Data Loading...
