Tantalum Nitride Thin Films Synthesized by Pulsed Nd:YAG Laser Deposition Method
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TANTALUM NITRIDE THIN FILMS SYNTHESIZED BY PULSED Nd:YAG LASER DEPOSITION METHOD Hiroharu Kawasaki, Kazuya Doi. Jun Namba and Yoshiaki Suda Department of Electrical Engineering. Sasebo National College of Technolog~i, O)kishin 1-i, Saseho. Nagasaki. 857-1 193, Japan ABSTRACT Tantalum nitride (TAN) films have been deposited on silicon substrates by using a pulsed Nd:YAG laser deposition method. Experimental results suggest that the substrate temperature is one of the most important parameters to prepare crystalline tantalum nitride thin films. Glancing-angle X-ray diffraction patterns show that the films deposited at Ts < 300 °C are almost amorphous. and crystalline Ta6 N2 .57 films are obtained at Ts > 500 °C. Grain size of the film increases with increasing substrate temperature. INTRODUCTION Tantalum nitride (TAN) has been extensiv'ely used in many applications due to some interesting properties, such as high hardness and high temperature stability' 2 . In the silicon technology, copper (Cu) has drawn much attention recently as a new interconnecting material for deep submicron integrated circuits as a replacement for aluminium (Al) and its alloys. I Iowever, Cu is known to diffuse into either Si or SiO2 layers during processing, and this problem is addressed by employing a suitable diffusion barrier layer betwteen the copper overlayer and the silicon substrate. In this direction, TaN and Ta2 N compounds have been investigated and found to be promising materials to serve as a diffusion barrier because TaN-based materials canl withstand high temperatures3 •6 . As these properties, TaN films have been deposited by several physical and chemical vapor deposition techniques. However, high quality TaN films for the diffusion barrier layer have not been prepared. Pulsed Nd:YAG laser deposition (PLD) method is a widely used technique for the deposition of thin films. due to the advantages of a simple system setup, wide ranging deposition conditions, wider range choice of materials and higher instantaneous deposition rate. Because of this versatility, we have developed several kinds of functional thin films, such as tungsten carbide 7 8 , silicon carbide 9 , chromium carbide 10 , cubic boron nitride'', carbon nitride' 2 and silicon nitride' 3 using the PLD method. In this paper, we describe the fundamental characteristics of the tantalum nitride (TaNx) films prepared using the PI.D method as well as the conditions required to fabricate crystalline and amorphous tantalum nitride thin films. EXPERIM4ENTAL The schematic of the experimental apparatus is shown in Fig. 1. A deposition chamber was fabricated of stainless steel with a diameter of 400 mm and a length of 370 mm. The chamber was evacuated to a base pressure (below 4.0×10.4 Pa) using a turbo molecular pump and a rotary,
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i
pump. A pulsed Nd:YAG laser (Lumonics YM600; wavelengthF-of 532 nm, pulse duration of 6.5
I lamp
ns, maximum output energy of 340 mJ) was used to irradiate TahN 2.57 (purity > 99 %) targets. Their radiated area was 2 maintained at 2.8 I
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