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Titanium nitride films prepared by ion implantation
L91
Thin Solid Films, 81 (1981) L91 L92
Letter
Titanium nitride films prepared by ion implantation P. A. CHEN
Chung Shah Institute ~f Science and Technology, P.O. Box No. 1-3-7, Lungtan ( Taiwan ) T. T. YANG hzstitute ()[ Nuclear Energy Research, P.O. Box No. 3, Lungtan (Taiwan) (Received March 17, 1981 : accepted April 3, 1981)
Because of its refractoriness, good wear resistance and golden lustre, TiN has found many applications in industry. The preparation of TiN by the conventional chemical vapour deposition method requires high temperature facilities, and the materials used as the substrate for TiN coating must be able to withstand a high temperature. However, with the advance of ion implantation technology, a great number of new materials or devices have been developed by direct implantation of selected elements into the surface of the base material (see for example ref. 1). The process has usually been carried out at room temperature. Similarly, films deposited by sputtering can also be prepared at room temperature and the films thus produced show good bonding with most substrate materials. Therefore the preparation of TiN film by direct nitrogen implantation into a sputtered titanium film is technically feasible. For convenience in subsequent experiments, we started from a tantalum-coated silicon wafer, because tantalum can serve as a marker in the helium ion backscattering spectrum. After a titanium film about 1200 A thick had been deposited, nitrogen was implanted, first at a beam energy of 50 keV with fluences of 3 x 1015 cm 2 and then at a beam energy of 80 keV with fluences of 9 x 1016 c m - 2 . The surface of the sample assumed a light golden colour which indicated that the composition of the surface layer had been modified. For further investigation, 2.5 MeV helium ion backscattering experiments were conducted on the Ti/Ta/Si multilayer structure. Scattering spectra of the film both before and after nitrogen implantation are shown in Fig. 1. The difference in the slopes of the titanium peaks with and without nitrogen implants contrasts with the nearly parallel slopes of the tantalum and silicon peaks. From the depleted portion in the post-implantation titanium peak, we estimated z that about 1000 A of TiN was formed. X-ray diffraction results of the film gave a broad peak at d = 2.427 A. This corresponds to the (111) orientation of cubic TiN. The lattice constant calculated from the d value is 4.27. In comparison with the lattice constant of bulk crystalline TiN (4.24 A), this implies that about 0.7~, distortion was induced in the implanted TiN film. Uniformity in film thickness was checked by ellipsometric measurements. Over a surface of diameter 2 in, thickness variations were less than 2 A in thickness readings of 1370 A measured at the centre. The refractive index n obtained for TiN was 1.525. Since no similar measurements have been made on TiN to our 0040-6090/81/0000-0000/S02.50
~:~)~Elsevier Sequoia/Printed in The Netherlands
L92
LETTERS
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Ti/Ta/Si:
- -
, before nitrogen implantation;
after nitrogen implantation.
knowledge, we cannot say anything further about the film quality; however, excellent film uniformity can be reported. In conclusion, we demonstrated a method of preparing TiN film by direct nitrogen implantation into a sputtered titanium film. In principle, this method can be applied to any material that can be put into a sputtering system for titanium coating. G o o d thickness uniformity and reproducibility can easily be obtained by monitoring the implantation parameters with methods which have been well established in the semiconductor industry. 1 T. Hussain et al., Appl. Phys. Lett., 37 (1980) 298. 2 T.T. Yang and J. C. Chou, Nucl. lnstrum. Methods, 158 (1979) 493.
Thin Solid Films, 81 (1981) L91 L92
Letter
Titanium nitride films prepared by ion implantation P. A. CHEN
Chung Shah Institute ~f Science and Technology, P.O. Box No. 1-3-7, Lungtan ( Taiwan ) T. T. YANG hzstitute ()[ Nuclear Energy Research, P.O. Box No. 3, Lungtan (Taiwan) (Received March 17, 1981 : accepted April 3, 1981)
Because of its refractoriness, good wear resistance and golden lustre, TiN has found many applications in industry. The preparation of TiN by the conventional chemical vapour deposition method requires high temperature facilities, and the materials used as the substrate for TiN coating must be able to withstand a high temperature. However, with the advance of ion implantation technology, a great number of new materials or devices have been developed by direct implantation of selected elements into the surface of the base material (see for example ref. 1). The process has usually been carried out at room temperature. Similarly, films deposited by sputtering can also be prepared at room temperature and the films thus produced show good bonding with most substrate materials. Therefore the preparation of TiN film by direct nitrogen implantation into a sputtered titanium film is technically feasible. For convenience in subsequent experiments, we started from a tantalum-coated silicon wafer, because tantalum can serve as a marker in the helium ion backscattering spectrum. After a titanium film about 1200 A thick had been deposited, nitrogen was implanted, first at a beam energy of 50 keV with fluences of 3 x 1015 cm 2 and then at a beam energy of 80 keV with fluences of 9 x 1016 c m - 2 . The surface of the sample assumed a light golden colour which indicated that the composition of the surface layer had been modified. For further investigation, 2.5 MeV helium ion backscattering experiments were conducted on the Ti/Ta/Si multilayer structure. Scattering spectra of the film both before and after nitrogen implantation are shown in Fig. 1. The difference in the slopes of the titanium peaks with and without nitrogen implants contrasts with the nearly parallel slopes of the tantalum and silicon peaks. From the depleted portion in the post-implantation titanium peak, we estimated z that about 1000 A of TiN was formed. X-ray diffraction results of the film gave a broad peak at d = 2.427 A. This corresponds to the (111) orientation of cubic TiN. The lattice constant calculated from the d value is 4.27. In comparison with the lattice constant of bulk crystalline TiN (4.24 A), this implies that about 0.7~, distortion was induced in the implanted TiN film. Uniformity in film thickness was checked by ellipsometric measurements. Over a surface of diameter 2 in, thickness variations were less than 2 A in thickness readings of 1370 A measured at the centre. The refractive index n obtained for TiN was 1.525. Since no similar measurements have been made on TiN to our 0040-6090/81/0000-0000/S02.50
~:~)~Elsevier Sequoia/Printed in The Netherlands
L92
LETTERS
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C h . NO.
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N2 N2
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No.
F i g . 1. B a c k s c a t t e r i n g s p e c t r a o f n i t r o g e n - i m p l a n t e d
Ti/Ta/Si:
- -
, before nitrogen implantation;
after nitrogen implantation.
knowledge, we cannot say anything further about the film quality; however, excellent film uniformity can be reported. In conclusion, we demonstrated a method of preparing TiN film by direct nitrogen implantation into a sputtered titanium film. In principle, this method can be applied to any material that can be put into a sputtering system for titanium coating. G o o d thickness uniformity and reproducibility can easily be obtained by monitoring the implantation parameters with methods which have been well established in the semiconductor industry. 1 T. Hussain et al., Appl. Phys. Lett., 37 (1980) 298. 2 T.T. Yang and J. C. Chou, Nucl. lnstrum. Methods, 158 (1979) 493.