Initial Interaction of Crystalline Al/Amorphous Si Bilayer during Annealing
- PDF / 1,040,484 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 6 Downloads / 199 Views
A4.23.1
Initial Interaction of Crystalline Al/Amorphous Si Bilayer during Annealing Yonghao Zhao1,2, Jiangyong Wang1 and Eric J. Mittemeijer1 Max Planck Institute for Metals Research, Heisenbergstr. 3, D-70569 Stuttgart, Germany 2 Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM-87545, U.S.A. 1
ABSTRACT Initial interaction of a magnetron sputter deposited Al(100 nm, {111} fibre textured)/Si(150 nm, amorphous) bilayer, induced by isothermally annealing at 523 K for 60 min in a vacuum of 2.0×10-4 Pa, was studied by X-ray diffraction, Auger electron microscopy and focused-ion beam imaging techniques. Upon annealing, the crystalline Si had grown into the grain boundaries of the Al layer with a {111} texture, a crystallite size of approximate 12 nm and a tensile stress of +138 MPa. Simultaneously, the Al grains had grown into the Si layer from the original interface of the a-Si and Al sublayers with the lateral grain growth. The stress parallel to the surface of the Al layer had changed from +27 MPa to +232 MPa after annealing. INTRODUCTION In the last decades, interdiffusion and/or reactions between semiconductor and metal systems have been paid increasing attention not only in view of the practical applications in the microelectronic industry [1−3], but also because of great scientific interest. Si/Al system is an interesting example, because according to the thermodynamics for bulk materials, Si and Al do not form compounds and are rather immiscible [5]. For Si (amorphous)/Al (crystalline) bilayers, further written as a-Si/Al, various studies showed that the presence of Al layer lowers the crystallization temperature of a-Si significantly as compared to bulk a-Si [6-8]. In situ transmission electron microscopy observation on an a-Si/Al multilayer showed that, during annealing at 493 K, c-Si nucleates within the Al layers and penetrates the Al as the c-Si grows [9]. Annealing an a-Si/Al bilayer (623-773 K) showed that c-Si nucleates at the Si/Al interface and grows further into the Al layer until, finally, a continuous c-Si film has formed at the initial Al layer, resulting in a layer exchange [10]. More recently, we found that the layer exchange can occur at even lower annealing temperature (523 K) accompanied with the crystallization of amorphous Si [11]. An extensive analysis indicated that the largest gain in energy upon transformation is due to the crystallization of the amorphous Si [11]. However, this driving force contribution cannot explain why layer exchange occurs. The objective of this investigation is to study the initial interaction of the Al/Si bilayer. EXPERIMENTAL DETAILS The thermally oxidized, single crystalline Si wafers were used as substrates. Prior to deposition, the chamber was pumped down to 10-7 Pa, the substrate and the Al, Si targets (with purities of 99.999 wt.%) were cleaned by argon ion sputtering. Then, the direct current magnetron sputter deposition of Al(100 nm)/Si(150 nm) bilayer was carried out at room temperature under an input power of 100
Data Loading...
