TiB 2 as a Diffusion Barrier for Cu/<si> Metallization
- PDF / 1,013,580 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 77 Downloads / 231 Views
INTRODUCTION For the current sub-micron integrated circuit technology, diffusion barriers have become a critical component for improving the reliability of metallization system and the whole circuit. Due to their high chemical inertness, the interstitial compounds of refractory metals, including nitrides, borides and carbides, have been considered as candidates for diffusion barriers [1]. Although titanium nitride (TIN) is currently the most popular material for diffusion barriers [2],
the columnar grain structure of sputtered TiN is in fact inadequate since the grain boundaries offer fast diffusion paths. Titanium boride (TiB,) is an interesting material for diffusion barriers since that TiB, has a high melting point (32250 C) and a low bulk resistivity (10-30 110-cm) [3]. Shappirio et al. [4] have reported that the contact stability of GaAs devices was significantly improved by applying a TiB diffusion barrier. For Si system, Choi et al. [5] have examined the applicability of chemical vapor deposited amorphous TiB, as the diffusion barrier for Al and Cu metallizations. No significant reaction took place between Al and TiB1up to 600'C, and TiB, did not react with Cu up to 750'C. It is also reported that sputtered TiB, from a Ti and a B target served as a diffusion barrier against Cu penetration up to 680'C, when TiB2 is in an amorphous form [6]. Regarding to the reaction between Cu and TiB2, no interface mixing occurred in a TiB 2 /Cu multilayered structure when irradiated with a 400 keV He" ion beam up to a dose of 12xl10" ions/cm 2 [7]. In this work, TiB1 films are synthesized by co-sputtering from a boron and a TiB, target and their potential use as the diffusion barrier for Cu/ metallization is investigated by characterizing the thermal reaction of the Cu/TiB2/ stacks annealing at 400-700'C. EXPERIMENT (100) n-type silicon wafers were used as substrates in this study.
The substrates were
33 Mat. Res. Soc. Symp. Proc. Vol. 563 ©1999 Materials Research Society
degreased in organic baths and chemically etched with diluted HF solution just prior to loading into the deposition chamber. Thin films of TiB 2 were deposited on silicon substrates by cosputtering from a titanium diboride target and a boron target. Both targets are 5 cm in diameter and the target-to-substrate distance is about 10 cm. The TiB 2 target was sputtered with a dc power supply and the boron target was powered by a RF generator. All sputterings were carried out in pure Ar atmosphere with a base pressure of 3 X 10.6 Torr and an operation pressure of 7 mTorr. The thickness of the sputtered Ti-B films was 100 nm. Chemical compositions of the Ti-B films were examined by Auger electron spectroscopy, while the crystal structures were characterized by x-ray diffraction using a glancing incident angle of 5 degrees. The film resistivity was determined based on the film thickness measured by a Tencor a-step profilometer and the sheet resistance measured by a four-point probe. To test the thermal stability of the TiB2 barriers, copper films of 180 nm t
Data Loading...
