Pulsed Laser Deposition and Characterization of Novel Cu/TiN/Si(100) Heterostructures Grown VIA Domain Epitaxy
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t. Res. Soc. Symp. Proc. Vol. 355 0 1995 Materials Research Society
TiN giving rise to 4.0% and 0.6% misfits respectively, providing a domain matched epitaxy in such large lattice mismatch systems. EXPERIMENTAL PROCEDURE A pulsed KrF excimer laser ( X = 248 nm, and c = 25 ns) was used to ablate titanium nitride and copper from a stoichiometric TiN pellet and a polycrystalline Cu target, respectively. The substrate-to-target distance mounted in parallel was kept at 4 cm. The laser beam was focused onto the target to obtain an energy density of - 4-10 J cm- 2 at a 450 angle of incidence. The laser plume is forward directed, the extent of which depends upon the laser spot size. The target was rotated continuously and as well as the laser beam was translated in the x -y direction periodically to obtain uniform films. The laser and target parameters were optimized to obtain particle-free films. The Si(100) substrates were cleaned prior to introduction in the vacuum chamber by ultrasonically degreasing in acetone for 5 tninutes, and then in methanol for another 5 minutes, followed by oxide-removal in 5% HF solution for 2 minutes. The TiN films were deposited at 600"C at the optimized conditions discussed elsewhere[5]. The Cu depositions were performed at different substrate temperatures ranging from room temperature to 600'C in a chamber maintained at a base pressure of 1x0-7 torr. The films were deposited at repetition rates of 15 and 30 Hz. Detailed XRD analysis was done which ascertained the crystalline quality of the films in a nondestructive way. The crystalline quality of the films was further determined by RBS channeling. Cross-sectional and planar HRTEM analyses were performed in detail by employing a TOPCON 002B microscope operated at 200kV to investigate film growth characteristics and the defect structures in copper films. RESULTS AND DISCUSSION The XRD pattern of Cu/TiN/Si heterostructures where Cu was deposited at 15 Hz, indicates that the Cu films deposited at 25°C is polycrystalline. The films deposited at 150°C is highly textured along [100] orientation and a small fraction of the film has [111] orientation. The texturing improves above 200*C with Cu IITiN IISi. Figure 1 shows the XRD patterns of Cu/TiN/Si(100) heterostructures, where TiN was deposited at 600°C, and Cu was deposited at 15 Hz and at substrate temperatures of (a) 25'C, (b) 150*C, and (c) 175°C. Figure 2 shows the XRD pattern of a Cu/TiN/Si heterostructure where Cu was deposited at 600'C and 30 (a)
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Figure 2. XRD pattern of Cu/TiN/Si(100) heterostructure at 30 Hz and 200 *C.
Figure 1. XRD patterns of Cu/TiN/Si(100) heterostructures at 15 Hz and at (a) 25"C, (b) 150'C, and (c) 175"C.
40
Hz. The pattern shows only (200) and (400) peaks of Cu along with (200) and (400) reflections of TiN and (400) reflection of Si. This result establishes Cu IITiN IISi . Table I indicates the
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