- Email: [email protected]
TiN coating and ion implantation of materials with three-dimensional topology in metal DC plasma-based ion implantation
Surface and Coatings Technology 136 Ž2001. 168᎐171
TiN coating and ion implantation of materials with three-dimensional topology in metal DC plasma-based ion implantation M. Sano a , T. Teramoto a , K. Yukimuraa,U , T. Maruyamab a
Department of Electrical Engineering, Doshisha Uni¨ ersity, 1-3,Tatara-Miyakodani, Kyotanabe, Kyoto 610-0321, Japan b Department of Chemical Engineering, Kyoto Uni¨ ersity, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
Abstract Titanium ions were implanted into silicon substrates which adhered to the material of three-dimensional shapes, such as trench and sphere, and the titanium nitride films were deposited on the substrate by plasma-based ion implantation using a titanium vacuum arc in nitrogen gas. The pulse voltage applied formed a nearly uniform implanted layer of titanium and nitrogen ions all over the surface of the materials of three-dimensional shape. The variation in thickness of the implanted layer with position was small compared to that of the deposited layer. For the parallel trench with a width of 16 mm, the maximum ratio of the thickness of the implanted layer was 2.5, whereas that of the deposited layer amounted to 10. For the perpendicular trench, the thickness of the deposited and implanted layers on the inner sidewall and bottom of the trench were not as small as those of the back and inner sidewall for the parallel trench. The thickness of the deposited and implanted layers on the central partition of the double trench was not influenced by the existence of side partitions. 䊚 2001 Elsevier Science B.V. All rights reserved. Keywords: TiN coating; Ion implantation; Three-dimensional; Trench
1. Introduction Plasma-based ion implantation ŽPBII. is a promising method for modifying the surface properties of materials of three-dimensional topology in order to improve wear resistance and hardness in engineering fields w1᎐4x. Although the PBII technique shows some similarities to ion-assisted coating and ion-beam mixing, PBII has the advantages of easy handling, large area and low-cost treatment for materials of complicated shape. Recently, titanium and nitrogen ions have been implanted using a titanium arc source in nitrogen gas w5x. The PBII facility for obtaining metal ions includes a metal plasma source in the same vacuum chamber as
U
Corresponding author. Tel.: q81-774-65-6266; fax: q81-774-656816. E-mail address: [email protected] ŽK. Yukimura..
the substrate. This facility has the advantages that the ion implantation and film preparation are carried out simultaneously, and that it is possible to be applied to objects with three-dimensional shapes without using vacuum manipulation in order to obtain uniform doses. The preparation of TiN films on a flat substrate has been reported by Treglio et al. w6x. This paper describes the PBII process applied to materials of three-dimensional shapes, such as trench and sphere.
2. Experimental A schematic diagram of the experimental facility is shown in Fig. 1. The inner dimensions of the width, depth and height of the vacuum chamber are 340, 550 and 380 mm, respectively. A pulse voltage of negative polarity was applied to the substrate via a feedthrough
0257-8972r01r$ - see front matter 䊚 2001 Elsevier Science B.V. All rights reserved. PII: S 0 2 5 7 - 8 9 7 2 Ž 0 0 . 0 1 0 4 9 - 5
M. Sano et al. r Surface and Coatings Technology 136 (2001) 168᎐171
169
Fig. 3. Dimensions of the single trench-shaped substrate holder and positions of the substrate. Trenches are placed Ža. parallel and Žb. perpendicular to the direction of ion emission. Fig. 1. Schematic diagram of the experimental facility.
placed at the end of the chamber, opposite to the cathode of the arc source. A water-cooled titanium cathode was mounted with a trigger electrode at the other end of the chamber. The vacuum chamber was grounded to make an anode. Both cathode and trigger electrodes were connected to a DC power source. The DC arc current and voltage were 100 A Žmaximum. and 20 V, respectively. A trigger discharge was ignited to generate a DC metal-arc between the cathode and the grounded chamber by disconnecting the trigger electrode from the cathode. The resistance R in Fig. 1 suppressed the trigger-discharge current after the main arc ignition. The pulse modulator was used to apply a pulse voltage of y40 kV with a width of 20 s. The repetition rate was 400 Hz. Deposition occurred during the DC arc between pulses. The process time was 2 min. The pumping system consisted of a turbo-molecular pump and two rotary pumps, which were connected to the vacuum chamber at the sidewall. The nitrogen pressure was 0.27 Pa. A silicon substrate Ž p-type, Ž111., 0.626 mm in thickness. was used for the X-ray photoelectron spectroscopy ŽXPS. measurements and a carbon substrate for the Rutherford backscattering spectrometry ŽRBS.
Fig. 2. Schematic representations of the sphere holder.
measurements. The details of the XPS and RBS measurements are described in a recent paper w7x. The substrates were positioned at 150 and 400 mm from the cathode. The six substrates were placed on the sphere-shaped substrate holder as shown in Fig. 2. The diameter of sphere is 40 mm. The directions of the trench-shaped substrate holder and substrate positions are shown in Fig. 3a,b. The bottom or the outer sidewall was placed opposite to the arc source. The substrates were placed on the bottom, inner side, outer side and back wall of the trench. The depth and width of the trench is 16 mm. The dimensions of the double-trench-shaped substrate holder and substrate positions are shown in Fig. 4. The substrates were placed on the bottom and sidewalls Žof the side and central partition., and top Žof the side and central partition. of the trench. The depth and width of the trench is 32 and 16 mm, respectively.
3. Results and discussion 3.1. Structure of TiN film and implanted layer Fig. 5 shows the XPS depth profile for the TiN film
Fig. 4. Dimensions of the double-trench-shaped substrate holder and positions of the substrate.
170
M. Sano et al. r Surface and Coatings Technology 136 (2001) 168᎐171
Fig. 5. XPS depth profile for the film deposited on a flat substrate.
deposited on the flat substrate at a nitrogen pressure of 0.27 Pa and a longitudinal distance of 400 mm. The etch rate was approximately 0.4 nmrmin. The profiles at etch times of 0᎐150 min show the deposited TiN film. The atomic concentration of titanium in the film is almost equal to that of nitrogen. The profiles at etch times of 150᎐180 min show the surface of the Si substrate, and the profiles at etch times above 180 min show that the titanium and nitrogen ions are implanted into the substrate. Thus, the implanted layer is formed by the implantation of titanium and nitrogen ions accelerated by the high-voltage pulse applied to the substrate. 3.2. Implantation to sphere The thickness of deposited and implanted layers was obtained from the XPS depth profiles similar to those in Fig. 5. The results are shown in Fig. 6 as a function of the tilt angle of the substrate. At a tilt angle in the range 30᎐90⬚, the TiN film thickness is nearly proportional to sin, which is the fraction of the substrate surface area where the substrate is projected to the plane opposite to the arc source. This fact indicates a strong directivity of the metallic arc. It is noted that the TiN film is deposited on the back of the sphere. On the other hand, the thickness of the implanted layer is independent of the tilt angle of substrate. The Ti ions are implanted through the coated layer into the Si substrate. Therefore, the implantation depth in Si substrate for each pulse decreases with increasing coating
Fig. 6. Thickness of the deposited and implanted layers on a sphere as a function of the tilt angle of the substrate.
Fig. 7. Number of titanium atoms on the sphere as a function of the tilt angle of the substrate.
thickness. However, the deepest implantation in Si substrate occurs at the first pulse, where the effect of coating on the implantation is least. The implantation depth at the first pulse is solely determined by the pulsed voltage. Thus, the thickness of the implanted layer in Si substrate is independent of the substrate angle. Fig. 7 shows the number of titanium atoms on the sphere as a function of the tilt angle of substrate. At 30 F F 90, the number is nearly proportional to sin. The sinusoidal change of the number of titanium atoms is similar to the thickness of the deposited layer for the tilted substrate at 30 F F 90. It is also noted that the titanium atoms are implanted or deposited even on the back of the sphere. Thus, PBII carries out the simultaneous implantation of titanium and nitrogen ions through the TiN film coating into the substrate. 3.3. Implantation to single trench Fig. 8 show the thickness of the deposited and implanted layers on each wall of the trench placed parallel to the direction of the ion emission. The ratio of the thickness of the deposited layer between different walls amounts to 10. The thickness at the bottom wall is largest, due to the strong directivity of the metallic arc. In the meantime, the thickness of the implanted layer is in the range 8᎐20 nm, and consequently, the ratio of
Fig. 8. Thickness of the deposited and implanted layers on each wall of the single trench placed parallel to the direction of ion emission.
M. Sano et al. r Surface and Coatings Technology 136 (2001) 168᎐171
171
trench was affected by the existence of two side partitions. However, the thickness of the layers on the top and inner sidewall of the central partition is similar to those of the side partition. The thickness of the deposited layer on the bottom of the double trench is smaller than that of the single trench. It is attributable to the smaller angle of vision from the bottom compared to that for the single trench, because the depthrwidth ratio of the double trench is twice that for the single trench. Fig. 9. Thickness of the deposited and implanted layers on each wall of the single trench placed perpendicular to the direction of ion emission.
4. Conclusions 2.5 is smaller than that of the deposition thickness. The thickness of the implanted layer is larger at the bottom and outer sidewall than on other walls, and at the outer side and back walls it is larger than the deposition thickness. It is characteristic that the ions are implanted even in the back wall. These facts indicate that a number of ions diffuse to the back of the material and that the pulse voltage application promotes a uniform distribution of the ions along the outer walls of the material. Fig. 9 shows the thickness of the deposited and implanted layers for the trench placed perpendicular to the direction of the ion emission. The thickness is smaller at the bottom and inner sidewall 1 and 2 than that at the outer sidewall. The deposited or implanted layer on the inner sidewalls and bottoms are not as small as those of the back and inner sidewall for the parallel trench.
The applied pulse voltage forms a nearly uniform implanted layer of titanium and nitrogen ions all over the surface of materials of three-dimensional shape. The variation in thickness of the implanted layer with position is small compared to that of the deposited layer. For a parallel trench with a width of 16 mm, the maximum ratio of the thickness of the implanted layer is 2.5, whereas that of the deposited layer amounts to 10. For a perpendicular trench, the thickness of the deposited and implanted layers on the inner sidewall and bottom of the trench is not as small as that of the back and inner sidewall for the parallel trench. The thickness of both the deposited and implanted layers on the central partition of the double trench is not influenced by the existence of the side partitions.
3.4. Implantation to double trench
Acknowledgements
Fig. 10 shows the thickness of the deposited and implanted layers on each wall of the double trench. It was inferred that the thickness of deposited and implanted layers on the central partition of the double
This work was supported by the Proposed Based Advanced Industrial Technology R& D program from the New Energy and Industrial Technology Development Organization under Contract No. A-454. References
Fig. 10. Thickness of the deposited and implanted layers on each wall of the double trench.
w1x R.J. Adler, S.T. Picraux, Nucl. Instrum. Methods Phys. Res. B 6 Ž1985. 123. w2x J.R. Conrad, J.L. Radtke, R.A. Dodd, F.J. Worzala, J. Appl. Phys. 62 Ž1987. 4591. w3x A. Anders, S. Anders, I.G. Brown, M.R. Dickinson, R.A. MacGill, J. Vac. Sci. Technol. B12 Ž1994. 815. w4x G.A. Collins, R. Hutchings, K.T. Short, J. Tendys, C.H. Van Der Valk, Surf. Coat. Technol. 84 Ž1996. 537. w5x M. Sano, K. Yukimura, T. Maruyama et al., Nucl. Instrum. Methods Phys. Res. B 148 Ž1999. 37. w6x A.J. Perry, J.R. Treglio, A.F. Tian, Surf. Coat. Technol. 76r77 Ž1995. 815. w7x K. Yukimura, K. Ohno, M. Koto et al., Surf. Coat. Technol. 103r104 Ž1998. 252.
TiN coating and ion implantation of materials with three-dimensional topology in metal DC plasma-based ion implantation M. Sano a , T. Teramoto a , K. Yukimuraa,U , T. Maruyamab a
Department of Electrical Engineering, Doshisha Uni¨ ersity, 1-3,Tatara-Miyakodani, Kyotanabe, Kyoto 610-0321, Japan b Department of Chemical Engineering, Kyoto Uni¨ ersity, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
Abstract Titanium ions were implanted into silicon substrates which adhered to the material of three-dimensional shapes, such as trench and sphere, and the titanium nitride films were deposited on the substrate by plasma-based ion implantation using a titanium vacuum arc in nitrogen gas. The pulse voltage applied formed a nearly uniform implanted layer of titanium and nitrogen ions all over the surface of the materials of three-dimensional shape. The variation in thickness of the implanted layer with position was small compared to that of the deposited layer. For the parallel trench with a width of 16 mm, the maximum ratio of the thickness of the implanted layer was 2.5, whereas that of the deposited layer amounted to 10. For the perpendicular trench, the thickness of the deposited and implanted layers on the inner sidewall and bottom of the trench were not as small as those of the back and inner sidewall for the parallel trench. The thickness of the deposited and implanted layers on the central partition of the double trench was not influenced by the existence of side partitions. 䊚 2001 Elsevier Science B.V. All rights reserved. Keywords: TiN coating; Ion implantation; Three-dimensional; Trench
1. Introduction Plasma-based ion implantation ŽPBII. is a promising method for modifying the surface properties of materials of three-dimensional topology in order to improve wear resistance and hardness in engineering fields w1᎐4x. Although the PBII technique shows some similarities to ion-assisted coating and ion-beam mixing, PBII has the advantages of easy handling, large area and low-cost treatment for materials of complicated shape. Recently, titanium and nitrogen ions have been implanted using a titanium arc source in nitrogen gas w5x. The PBII facility for obtaining metal ions includes a metal plasma source in the same vacuum chamber as
U
Corresponding author. Tel.: q81-774-65-6266; fax: q81-774-656816. E-mail address: [email protected] ŽK. Yukimura..
the substrate. This facility has the advantages that the ion implantation and film preparation are carried out simultaneously, and that it is possible to be applied to objects with three-dimensional shapes without using vacuum manipulation in order to obtain uniform doses. The preparation of TiN films on a flat substrate has been reported by Treglio et al. w6x. This paper describes the PBII process applied to materials of three-dimensional shapes, such as trench and sphere.
2. Experimental A schematic diagram of the experimental facility is shown in Fig. 1. The inner dimensions of the width, depth and height of the vacuum chamber are 340, 550 and 380 mm, respectively. A pulse voltage of negative polarity was applied to the substrate via a feedthrough
0257-8972r01r$ - see front matter 䊚 2001 Elsevier Science B.V. All rights reserved. PII: S 0 2 5 7 - 8 9 7 2 Ž 0 0 . 0 1 0 4 9 - 5
M. Sano et al. r Surface and Coatings Technology 136 (2001) 168᎐171
169
Fig. 3. Dimensions of the single trench-shaped substrate holder and positions of the substrate. Trenches are placed Ža. parallel and Žb. perpendicular to the direction of ion emission. Fig. 1. Schematic diagram of the experimental facility.
placed at the end of the chamber, opposite to the cathode of the arc source. A water-cooled titanium cathode was mounted with a trigger electrode at the other end of the chamber. The vacuum chamber was grounded to make an anode. Both cathode and trigger electrodes were connected to a DC power source. The DC arc current and voltage were 100 A Žmaximum. and 20 V, respectively. A trigger discharge was ignited to generate a DC metal-arc between the cathode and the grounded chamber by disconnecting the trigger electrode from the cathode. The resistance R in Fig. 1 suppressed the trigger-discharge current after the main arc ignition. The pulse modulator was used to apply a pulse voltage of y40 kV with a width of 20 s. The repetition rate was 400 Hz. Deposition occurred during the DC arc between pulses. The process time was 2 min. The pumping system consisted of a turbo-molecular pump and two rotary pumps, which were connected to the vacuum chamber at the sidewall. The nitrogen pressure was 0.27 Pa. A silicon substrate Ž p-type, Ž111., 0.626 mm in thickness. was used for the X-ray photoelectron spectroscopy ŽXPS. measurements and a carbon substrate for the Rutherford backscattering spectrometry ŽRBS.
Fig. 2. Schematic representations of the sphere holder.
measurements. The details of the XPS and RBS measurements are described in a recent paper w7x. The substrates were positioned at 150 and 400 mm from the cathode. The six substrates were placed on the sphere-shaped substrate holder as shown in Fig. 2. The diameter of sphere is 40 mm. The directions of the trench-shaped substrate holder and substrate positions are shown in Fig. 3a,b. The bottom or the outer sidewall was placed opposite to the arc source. The substrates were placed on the bottom, inner side, outer side and back wall of the trench. The depth and width of the trench is 16 mm. The dimensions of the double-trench-shaped substrate holder and substrate positions are shown in Fig. 4. The substrates were placed on the bottom and sidewalls Žof the side and central partition., and top Žof the side and central partition. of the trench. The depth and width of the trench is 32 and 16 mm, respectively.
3. Results and discussion 3.1. Structure of TiN film and implanted layer Fig. 5 shows the XPS depth profile for the TiN film
Fig. 4. Dimensions of the double-trench-shaped substrate holder and positions of the substrate.
170
M. Sano et al. r Surface and Coatings Technology 136 (2001) 168᎐171
Fig. 5. XPS depth profile for the film deposited on a flat substrate.
deposited on the flat substrate at a nitrogen pressure of 0.27 Pa and a longitudinal distance of 400 mm. The etch rate was approximately 0.4 nmrmin. The profiles at etch times of 0᎐150 min show the deposited TiN film. The atomic concentration of titanium in the film is almost equal to that of nitrogen. The profiles at etch times of 150᎐180 min show the surface of the Si substrate, and the profiles at etch times above 180 min show that the titanium and nitrogen ions are implanted into the substrate. Thus, the implanted layer is formed by the implantation of titanium and nitrogen ions accelerated by the high-voltage pulse applied to the substrate. 3.2. Implantation to sphere The thickness of deposited and implanted layers was obtained from the XPS depth profiles similar to those in Fig. 5. The results are shown in Fig. 6 as a function of the tilt angle of the substrate. At a tilt angle in the range 30᎐90⬚, the TiN film thickness is nearly proportional to sin, which is the fraction of the substrate surface area where the substrate is projected to the plane opposite to the arc source. This fact indicates a strong directivity of the metallic arc. It is noted that the TiN film is deposited on the back of the sphere. On the other hand, the thickness of the implanted layer is independent of the tilt angle of substrate. The Ti ions are implanted through the coated layer into the Si substrate. Therefore, the implantation depth in Si substrate for each pulse decreases with increasing coating
Fig. 6. Thickness of the deposited and implanted layers on a sphere as a function of the tilt angle of the substrate.
Fig. 7. Number of titanium atoms on the sphere as a function of the tilt angle of the substrate.
thickness. However, the deepest implantation in Si substrate occurs at the first pulse, where the effect of coating on the implantation is least. The implantation depth at the first pulse is solely determined by the pulsed voltage. Thus, the thickness of the implanted layer in Si substrate is independent of the substrate angle. Fig. 7 shows the number of titanium atoms on the sphere as a function of the tilt angle of substrate. At 30 F F 90, the number is nearly proportional to sin. The sinusoidal change of the number of titanium atoms is similar to the thickness of the deposited layer for the tilted substrate at 30 F F 90. It is also noted that the titanium atoms are implanted or deposited even on the back of the sphere. Thus, PBII carries out the simultaneous implantation of titanium and nitrogen ions through the TiN film coating into the substrate. 3.3. Implantation to single trench Fig. 8 show the thickness of the deposited and implanted layers on each wall of the trench placed parallel to the direction of the ion emission. The ratio of the thickness of the deposited layer between different walls amounts to 10. The thickness at the bottom wall is largest, due to the strong directivity of the metallic arc. In the meantime, the thickness of the implanted layer is in the range 8᎐20 nm, and consequently, the ratio of
Fig. 8. Thickness of the deposited and implanted layers on each wall of the single trench placed parallel to the direction of ion emission.
M. Sano et al. r Surface and Coatings Technology 136 (2001) 168᎐171
171
trench was affected by the existence of two side partitions. However, the thickness of the layers on the top and inner sidewall of the central partition is similar to those of the side partition. The thickness of the deposited layer on the bottom of the double trench is smaller than that of the single trench. It is attributable to the smaller angle of vision from the bottom compared to that for the single trench, because the depthrwidth ratio of the double trench is twice that for the single trench. Fig. 9. Thickness of the deposited and implanted layers on each wall of the single trench placed perpendicular to the direction of ion emission.
4. Conclusions 2.5 is smaller than that of the deposition thickness. The thickness of the implanted layer is larger at the bottom and outer sidewall than on other walls, and at the outer side and back walls it is larger than the deposition thickness. It is characteristic that the ions are implanted even in the back wall. These facts indicate that a number of ions diffuse to the back of the material and that the pulse voltage application promotes a uniform distribution of the ions along the outer walls of the material. Fig. 9 shows the thickness of the deposited and implanted layers for the trench placed perpendicular to the direction of the ion emission. The thickness is smaller at the bottom and inner sidewall 1 and 2 than that at the outer sidewall. The deposited or implanted layer on the inner sidewalls and bottoms are not as small as those of the back and inner sidewall for the parallel trench.
The applied pulse voltage forms a nearly uniform implanted layer of titanium and nitrogen ions all over the surface of materials of three-dimensional shape. The variation in thickness of the implanted layer with position is small compared to that of the deposited layer. For a parallel trench with a width of 16 mm, the maximum ratio of the thickness of the implanted layer is 2.5, whereas that of the deposited layer amounts to 10. For a perpendicular trench, the thickness of the deposited and implanted layers on the inner sidewall and bottom of the trench is not as small as that of the back and inner sidewall for the parallel trench. The thickness of both the deposited and implanted layers on the central partition of the double trench is not influenced by the existence of the side partitions.
3.4. Implantation to double trench
Acknowledgements
Fig. 10 shows the thickness of the deposited and implanted layers on each wall of the double trench. It was inferred that the thickness of deposited and implanted layers on the central partition of the double
This work was supported by the Proposed Based Advanced Industrial Technology R& D program from the New Energy and Industrial Technology Development Organization under Contract No. A-454. References
Fig. 10. Thickness of the deposited and implanted layers on each wall of the double trench.
w1x R.J. Adler, S.T. Picraux, Nucl. Instrum. Methods Phys. Res. B 6 Ž1985. 123. w2x J.R. Conrad, J.L. Radtke, R.A. Dodd, F.J. Worzala, J. Appl. Phys. 62 Ž1987. 4591. w3x A. Anders, S. Anders, I.G. Brown, M.R. Dickinson, R.A. MacGill, J. Vac. Sci. Technol. B12 Ž1994. 815. w4x G.A. Collins, R. Hutchings, K.T. Short, J. Tendys, C.H. Van Der Valk, Surf. Coat. Technol. 84 Ž1996. 537. w5x M. Sano, K. Yukimura, T. Maruyama et al., Nucl. Instrum. Methods Phys. Res. B 148 Ž1999. 37. w6x A.J. Perry, J.R. Treglio, A.F. Tian, Surf. Coat. Technol. 76r77 Ž1995. 815. w7x K. Yukimura, K. Ohno, M. Koto et al., Surf. Coat. Technol. 103r104 Ž1998. 252.