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Synthesis of thin coatings by plasma-assisted chemical vapour deposition using metallo-organic compounds as precursors
Surface and Coatings Technology, 59 (1993) 202—206
202
Synthesis of thin coatings by plasma-assisted chemical vapour deposition using metallo-organic compounds as precursors K.-T. Rie, J. Wöhle and A. Gebauer Inst itutfür Oberflachentechnik und Plasmatechnische Werkstoffentwicklung, TU Braunschweig, Bienroder Weg 53, W-3300 Braunschweig (Germany)
Abstract The pulsed d.c. plasma-assisted chemical vapour deposition process using four metallo-organic compounds as precursors (MOPACVD) was investigated. The compounds contain titanium or zirconium as metal to deposit Ti(C,N) or Zr(C,N) layers on steel substrates or hard metals. The influence of experimental parameters such as gas pressure, coating temperature and precursor evaporation temperature on the layer properties has been examined. For in-situ process control optical emission spectroscopy was used. It is shown that it is possible to decrease the coating temperature to 300 °Cand to deposit chlorine-free layers by MO-PACYD.
1. Introduction The nitrides and carbides of the group IV, V and VI transition metals are very important for the deposition of thin hard coatings in industrial applications. Chemical vapour deposition (CVD) techniques for the preparation of these hard coatings are based on chlorides as precursors. However, for several applications the coating temperatures are still too high and the chlorine from the metal donor causes undesired side effects on the layer quality [1] and the deposition furnace. Thus in this work the use of non-chlorinated metallo-organic compounds as precursors was investigated to avoid the harmful effects of chlorine on the layers and the plasma-assisted CVD (PACVD) equipment and to reduce the deposition temperature via the higher reactivity of these compounds [2].
with a diode array (optical multichannel analyser (OMA)) and a photomultiplier tube (PMT) (Fig. 1). Details are described elsewhere [3].
3. Metallo-organic compounds One critical factor in the CVD process is the selection of a precursor with suitable properties [4]. Since most metallo-organic compounds are sensitive to oxygen and moisture, special precautions in handling and deposition are necessary. Here as metal donor the organometallics tetrakis(dialkylamido)metal were used (Fig. 2). Methyl (Me) and/or ethyl (Et) are the alkyls and titanium or zirconium the metal (Table I). Up to now a deficiency exists in the vapour pressure diagrams of these metalloorganic compounds. Some volatility data are reported in Table 2.
2. Apparatus The PACVD equipment used in this study is shown schematically in Fig. 1. The reactor consists of a steel chamber as anode with a cathodic substrate holder and parallel-placed anodic gas admission. The power supply generates pulsed d.c. power up to 900 V and 50 kHz. Thus the plasma exists between the cathode and the anode. An additional heating facility located inside the reactor allows independent adjustment of the substrate temperature and plasma parameters. Pure N2, H2 and Ar gases are fed into the reactor via pressure-reducing valves and mass flow controllers. The liquid metal donor used was evaporated and introduced into the reaction chamber via a carrier gas (H2). The emitted spectra of the discharge were recorded using a monochromator
0257—8972/93/$6.00
~~tr0~iiIHfl
~.iuc
:
carrier
reac~tor
evaporator ~uxIUory heating
L. H~ :
..V~igi,twovegulde
II
Ii II~
/
~—~—lmonoch~omatoj--
I
1
PMT
DMA
pressure
vacuum
control
pump
L supply
e
set
temperature control Fig. 1. Experimental set-up of PACVD and OES equipment.
©
1993
—
Elsevier Sequoia. All rights reserved
/
K.-T. Rie et al.
R1
R2
I
N— Ri \
—
N
M
/
/\
R2
203
measurements, scratch tests, light- and electron-optical microscopy and X-ray diffraction. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical bonding of the layers.
I
R 2— N
R1
MO-PACVD of thin coajings
N— R 2
5. Results and discussion
Ri
5.1. Microstructure and layer properties
Fig. 2. Structure of metallo-organic compounds used (M RI Me,Et; R2 Me,Et).
Ti,Zr;
The investigation of the microstructure and morphology of the layers shows a domed appearance typical of PACVD coatings and already described elsewhere [4].
TABLE 1. Chemical composition of metallo-organic compounds used Metal
Alkyl
Formula
MmTi
Rl mR2mMe
Ti(NMe
Mm Ti MmTj MmZr
Ri mEt, R2 Me Rl mR2mEt RlmR2mEt
2)4 Ti(NEtMe)4 Ti(NEt2)4 Zr(NEt2)4
Code designation TMT TEMT TET TEZ
TABLE 2. Precursor volatility data Precursor
Boiling point (°C)/pressure(Pa)
Ti(NMe2)4 Ti(NEtMe)4 Ti(NEt2)4 Zr(NEt2)4
56—58/l00~ 95/bOb l04/l00~ I l5—120/lO0~
c~HERAEUS, Hanau, Germany, Safety Specifications, 1991; bG. Erker and C. Sarter, Organisch-Chemisches Institut, WestfálischeWilhelms-Universität, MUnster, Germany, Safety Specifications 1992.
a~y
m (a)
4. Experimental details In this study the process parameters were varied to investigate the formation of layers using organometallics. Table 3 summarizes the variable process parameters. The treatment gas was composed of Ar, H2 and N2. H2 was the carrier gas. Flat samples were used for the tests. The layers were produced on tempered steel 1.1181 (Ck 35), cold-worked steel 1.2379 (X 155 CrVMo 12 1) and hard metal P 30. The layer composition was determined by energy- and wavelength-dispersive X-ray (EDX and WDX) analysis. The microstructure and properties of the surface layers were investigated by means of hardness TABLE 3. Variable process parameters Evaporation temperature Substrate temperature Gas pressure Plasma parameters voltage pulse/current pause Coating duration
Dependent on precursor 250—550 °C 50—350 Pa 400—600 V 1/12—15 1.5—3 h
(b) Fig. 3. Surface topography of Ti(C,N) layers, precursor Ti(NMe2)4, pressure 250 Pa, temperature (a) 450 °C,(b) 550 °C.
204
K.-T. Rie et al.
/
MO-PACVD
Studies of the layer structure demonstrate parallelism with the Thornton model [5]. Thus it is possible to realize a smooth fine-domed surface or a relatively rough surface by varying the process parameters such as pressure and temperature. The process parameters led to coatings in zone 1 or the transition zone of the model. Coatings obtained at low coating temperature or higher gas pressure tend to a relatively rough surface (Fig. 3). According to Thornton, higher gas pressures move the zone boundaries to higher temperatures. The surface topography results from the characteristics of layer growth. A more columnar structure increases the surface roughness. Figure 4 shows an example of a fracture cross-section with recognizable columnar structure. The determination of grain size is not a simple
of thin coatings
_______________
_____ ______
________________________________________________
L
problem [6]. Chatterjee-Fischer and Mayr [6] postulate a growth model of CVD coatings. The grain size increases with increasing layer thickness because of a preferred growth of some grains. By varying the coating time and therefore increasing the layer thickness, similar effects can be noticed (Fig. 5).
(a)
The microhardness measurements were performed on polished samples. Knoop hardness values of about 1100—1500 HK for Zr(C,N) with Zr(NEt2)4, 1200— 2000 HK for Ti(C,N) with Ti(NMe2)4 or Ti(NEtMe)4 and 1200—2200 HK for Ti(C,N) with Ti(NEt2)4 as precur-
sor were obtained. The hardness increased with increasing deposition temperature and decreasing deposition rate. Scratch tests showed critical loads of up to 40—50 N by light-optical microscopy interpretation of the scratch track. 5.2. Chemical element and bonding analysis The chemical composition was examined. The layers
are composed of metal (Ti or Zr), carbon, nitrogen and -
(b) Fig. 5. Surface topography of Ti(C,N) layers, precursor Ti(NEt2)4, (a) coating time 2 h, layer thickness about 2 ~m, (b) coating time 3 h, layer thickness about 3 .tm.
small amounts of oxygen. Oxygen incorporation probably results from traces of 02 and/or H20 in the carrier gas or absorbed in the walls of the reactor. Especially at the surface of the layer a remarkable contamination
~ ___________
can be noticed (Fig. 6). Generally Ti(NR2)4 and Zr(NR2)4 led to the same bonding structure of the deposited layers. As an example the XPS analysis of a Zr(C,N) layer is given showing the existence of Zr—N and Zr—C bond structure (Fig. 7).
Fig. 4. Fracture cross-section of a Ti(C,N) layer, precursor Ti(NEt2)4.
Furthermore, it can be seen that the carbon is both Zr bound and organic (Fig. 7(a)). Further studies are needed
K.-T. Rie et al. 100
I
/
MO-PACVD of thin coatings a—Fe
I
•
205 a—Fe
(111) (200)
80
(220)
Zr(C,N) 350°C
0, C
~
~
_____
______________
3000C
C
~
0
•
I
I
20
30
•
0
10
A
40
distance from surface / nm
_________________________________________________
CC
L
A
-
30
Fig. 6. Depth profile of elemental analysis of a Ti(C,N) bayer with oxygen contamination, precursor Ti(NEt 2)4, 260 °C,500 V, 150 Pa.
C—H
.
80 2
e
—~
Fig. 8. X-Ray diffraction pattern (Cu Ks) ofZr(C,N) layers on Ck 35, precursor Zr(NEt2)4, 550 V, 250 Pa.
temperature. For PACVD with TiCl4 as precursor Oguri et a!. [7] observed similar results influenced by the ratio
Zr-C
of the precursor and reactive gases. They have made a classification of their results in terms of (200)- and (111)I
I
I
I
287.5
279.5
oriented coatings.
Binding Energy 1eV)
5.4. Optical emission spectroscopy Optical emission spectroscopy (OES) is a powerful tool for controlling the coating process and for optimiz-
Zr-N
ing both the layer properties and the coating process.
Here OES was used as a qualitative in situ diagnostic I’,
0
U
I
I
398.5
Binding Energy 1eV) Fig. 7. XPS analysis of a Zr(C,N) layer, precursor Zr(NEt2)4, 300 °C, 600 V, 250 Pa, (a) carbon bonds, (b) nitrogen bonds.
method. By measuring the intensity of the spectral lines, it is possible to identify the density of each excited state. The OES results have to be correlated with the layer properties. One example is given in Fig. 9 which shows a small part of the emission spectrum from a coating process at 300 °C, 250 Pa and 600 V on varying the
evaporation temperature of the precursor Ti(NEtMe)4. Several Ti + lines occurred in the discharge, e.g. at wavelengths of 323.4, 323.6, 323.9 and 334.9 nm. In this
to verify or disprove the statement that with increasing C—C bonds the hardness of Zr(C,N) and Ti(C,N) layers decreases.
I
Figure 8 shows an example of an X-ray diffraction analysis of a Zr(C,N) layer on Ck 35. In the same way the presence of Ti(C,N) was proved using the titanium
amides as precursors. Additional to the peaks of cubic Zr(C,N) of the layer one can see the peaks of eL-Fe of the base material (Fig. 8). The preferred orientation
changed with increasing coating temperature. At low
temperature the peak of the (200) plane dominates. The peak of the (111) plane exceeds all other Zr(C,N) peaks at higher temperatures. The ratio of the (ill) and (200) peaks altered from 0.66 to 1.32, indicating a change in preferred growth orientation dependent on the coating
N 337,Thm “336,Onm
24
5.3. X-Ray diffraction
I
334 gnm
—a c
o 18
~ ~
~
_______________
-75CC 12 C
c
•=85°C
-~
___________________
6
________________________________________
334
340.8
347.6
354.4
3612
308
wavelength / Fig. 9. Optical emission spectrum, precursor Ti(NEtMe)4, 300 °C, 250 Pa, 600 V, evaporation temperature ç.
206
K.-T. Rie et al.
/
MO-PACVD of thin coatings
study the Ti~line at 334.9 nm proved most important
as the main indicator determining the layer properties
(4) M—N and M—C bonds as well as C—C bonds have been detected,
during the coating process. Good layer properties were achieved only for evaporation temperatures between 65 and 70°Cin the described experimental set-up. At lower temperatures the growth rate is very low and tends to
(5) correlation of the intensity of the Ti + line with the layer properties is possible.
zero. At higher temperatures, in contrast, the growth
Acknowledgments
rate is too high. The C—C bonds in the layer increase,
the hardness decreases and spalling may occur. Thus the importance of the Ti + line (2 = 334.9 nm) is proved for
We are grateful to the BMFT (Bundesministerium für
the correlation with the layer properties in our study.
Forschung und Technologie) for support of this work (13N5793). The authors wish to thank Dr. H. Hantsche, BAM, Berlin for performing the XPS measurements.
6. Conclusions
References
In
this study the
usefulness of titanium- and
zirconium-tetrakisdialkylamide has been demonstrated for Ti(C,N) and Zr(C,N) coatings respectively, since (1) the substrate temperature can be reduced to below 300 °C, (2) the formation of chlorine-free layers can be achieved, (3) the surface topography can be altered from relatively rough to a smooth fine-domed surface by process parameter variation,
I N. Kikuchi, Y. Oosawa and A. Nishiyama, Proc. 9th mt. Conf. on CVD, Pennington, NJ, 1984, Electrochemical Society, Pennington, NJ, 1984, p. 728. 2 Th. Kruck, in H. Dimigen, K. Hieber, K.-T. Rie and G. Wahl (eds.), Proc. Workshop ISPC 10, Bochum, 1991, p. 84. 3 K.-T. Rie and J. Wdhle, Mater. Sci. Eng. A, 139 (1991) 37. 4 K.-T. Rie, J. Wöhle and A. Gebauer, J. Phys. (Paris) II, Colloq. C2. 1(1991)397. 5 J. A. Thornton, J. Vac. Sci. Technol., 11 (1974) 666. 6 R. Chatterjee-Fischer and P. Mayr, Harterei-Technische Mitteilungen. 41 (1986) 113. 7 K. Oguri, H. Fujita and T. Arai, Thin Solid Films, 195 (1991) 77.
202
Synthesis of thin coatings by plasma-assisted chemical vapour deposition using metallo-organic compounds as precursors K.-T. Rie, J. Wöhle and A. Gebauer Inst itutfür Oberflachentechnik und Plasmatechnische Werkstoffentwicklung, TU Braunschweig, Bienroder Weg 53, W-3300 Braunschweig (Germany)
Abstract The pulsed d.c. plasma-assisted chemical vapour deposition process using four metallo-organic compounds as precursors (MOPACVD) was investigated. The compounds contain titanium or zirconium as metal to deposit Ti(C,N) or Zr(C,N) layers on steel substrates or hard metals. The influence of experimental parameters such as gas pressure, coating temperature and precursor evaporation temperature on the layer properties has been examined. For in-situ process control optical emission spectroscopy was used. It is shown that it is possible to decrease the coating temperature to 300 °Cand to deposit chlorine-free layers by MO-PACYD.
1. Introduction The nitrides and carbides of the group IV, V and VI transition metals are very important for the deposition of thin hard coatings in industrial applications. Chemical vapour deposition (CVD) techniques for the preparation of these hard coatings are based on chlorides as precursors. However, for several applications the coating temperatures are still too high and the chlorine from the metal donor causes undesired side effects on the layer quality [1] and the deposition furnace. Thus in this work the use of non-chlorinated metallo-organic compounds as precursors was investigated to avoid the harmful effects of chlorine on the layers and the plasma-assisted CVD (PACVD) equipment and to reduce the deposition temperature via the higher reactivity of these compounds [2].
with a diode array (optical multichannel analyser (OMA)) and a photomultiplier tube (PMT) (Fig. 1). Details are described elsewhere [3].
3. Metallo-organic compounds One critical factor in the CVD process is the selection of a precursor with suitable properties [4]. Since most metallo-organic compounds are sensitive to oxygen and moisture, special precautions in handling and deposition are necessary. Here as metal donor the organometallics tetrakis(dialkylamido)metal were used (Fig. 2). Methyl (Me) and/or ethyl (Et) are the alkyls and titanium or zirconium the metal (Table I). Up to now a deficiency exists in the vapour pressure diagrams of these metalloorganic compounds. Some volatility data are reported in Table 2.
2. Apparatus The PACVD equipment used in this study is shown schematically in Fig. 1. The reactor consists of a steel chamber as anode with a cathodic substrate holder and parallel-placed anodic gas admission. The power supply generates pulsed d.c. power up to 900 V and 50 kHz. Thus the plasma exists between the cathode and the anode. An additional heating facility located inside the reactor allows independent adjustment of the substrate temperature and plasma parameters. Pure N2, H2 and Ar gases are fed into the reactor via pressure-reducing valves and mass flow controllers. The liquid metal donor used was evaporated and introduced into the reaction chamber via a carrier gas (H2). The emitted spectra of the discharge were recorded using a monochromator
0257—8972/93/$6.00
~~tr0~iiIHfl
~.iuc
:
carrier
reac~tor
evaporator ~uxIUory heating
L. H~ :
..V~igi,twovegulde
II
Ii II~
/
~—~—lmonoch~omatoj--
I
1
PMT
DMA
pressure
vacuum
control
pump
L supply
e
set
temperature control Fig. 1. Experimental set-up of PACVD and OES equipment.
©
1993
—
Elsevier Sequoia. All rights reserved
/
K.-T. Rie et al.
R1
R2
I
N— Ri \
—
N
M
/
/\
R2
203
measurements, scratch tests, light- and electron-optical microscopy and X-ray diffraction. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical bonding of the layers.
I
R 2— N
R1
MO-PACVD of thin coajings
N— R 2
5. Results and discussion
Ri
5.1. Microstructure and layer properties
Fig. 2. Structure of metallo-organic compounds used (M RI Me,Et; R2 Me,Et).
Ti,Zr;
The investigation of the microstructure and morphology of the layers shows a domed appearance typical of PACVD coatings and already described elsewhere [4].
TABLE 1. Chemical composition of metallo-organic compounds used Metal
Alkyl
Formula
MmTi
Rl mR2mMe
Ti(NMe
Mm Ti MmTj MmZr
Ri mEt, R2 Me Rl mR2mEt RlmR2mEt
2)4 Ti(NEtMe)4 Ti(NEt2)4 Zr(NEt2)4
Code designation TMT TEMT TET TEZ
TABLE 2. Precursor volatility data Precursor
Boiling point (°C)/pressure(Pa)
Ti(NMe2)4 Ti(NEtMe)4 Ti(NEt2)4 Zr(NEt2)4
56—58/l00~ 95/bOb l04/l00~ I l5—120/lO0~
c~HERAEUS, Hanau, Germany, Safety Specifications, 1991; bG. Erker and C. Sarter, Organisch-Chemisches Institut, WestfálischeWilhelms-Universität, MUnster, Germany, Safety Specifications 1992.
a~y
m (a)
4. Experimental details In this study the process parameters were varied to investigate the formation of layers using organometallics. Table 3 summarizes the variable process parameters. The treatment gas was composed of Ar, H2 and N2. H2 was the carrier gas. Flat samples were used for the tests. The layers were produced on tempered steel 1.1181 (Ck 35), cold-worked steel 1.2379 (X 155 CrVMo 12 1) and hard metal P 30. The layer composition was determined by energy- and wavelength-dispersive X-ray (EDX and WDX) analysis. The microstructure and properties of the surface layers were investigated by means of hardness TABLE 3. Variable process parameters Evaporation temperature Substrate temperature Gas pressure Plasma parameters voltage pulse/current pause Coating duration
Dependent on precursor 250—550 °C 50—350 Pa 400—600 V 1/12—15 1.5—3 h
(b) Fig. 3. Surface topography of Ti(C,N) layers, precursor Ti(NMe2)4, pressure 250 Pa, temperature (a) 450 °C,(b) 550 °C.
204
K.-T. Rie et al.
/
MO-PACVD
Studies of the layer structure demonstrate parallelism with the Thornton model [5]. Thus it is possible to realize a smooth fine-domed surface or a relatively rough surface by varying the process parameters such as pressure and temperature. The process parameters led to coatings in zone 1 or the transition zone of the model. Coatings obtained at low coating temperature or higher gas pressure tend to a relatively rough surface (Fig. 3). According to Thornton, higher gas pressures move the zone boundaries to higher temperatures. The surface topography results from the characteristics of layer growth. A more columnar structure increases the surface roughness. Figure 4 shows an example of a fracture cross-section with recognizable columnar structure. The determination of grain size is not a simple
of thin coatings
_______________
_____ ______
________________________________________________
L
problem [6]. Chatterjee-Fischer and Mayr [6] postulate a growth model of CVD coatings. The grain size increases with increasing layer thickness because of a preferred growth of some grains. By varying the coating time and therefore increasing the layer thickness, similar effects can be noticed (Fig. 5).
(a)
The microhardness measurements were performed on polished samples. Knoop hardness values of about 1100—1500 HK for Zr(C,N) with Zr(NEt2)4, 1200— 2000 HK for Ti(C,N) with Ti(NMe2)4 or Ti(NEtMe)4 and 1200—2200 HK for Ti(C,N) with Ti(NEt2)4 as precur-
sor were obtained. The hardness increased with increasing deposition temperature and decreasing deposition rate. Scratch tests showed critical loads of up to 40—50 N by light-optical microscopy interpretation of the scratch track. 5.2. Chemical element and bonding analysis The chemical composition was examined. The layers
are composed of metal (Ti or Zr), carbon, nitrogen and -
(b) Fig. 5. Surface topography of Ti(C,N) layers, precursor Ti(NEt2)4, (a) coating time 2 h, layer thickness about 2 ~m, (b) coating time 3 h, layer thickness about 3 .tm.
small amounts of oxygen. Oxygen incorporation probably results from traces of 02 and/or H20 in the carrier gas or absorbed in the walls of the reactor. Especially at the surface of the layer a remarkable contamination
~ ___________
can be noticed (Fig. 6). Generally Ti(NR2)4 and Zr(NR2)4 led to the same bonding structure of the deposited layers. As an example the XPS analysis of a Zr(C,N) layer is given showing the existence of Zr—N and Zr—C bond structure (Fig. 7).
Fig. 4. Fracture cross-section of a Ti(C,N) layer, precursor Ti(NEt2)4.
Furthermore, it can be seen that the carbon is both Zr bound and organic (Fig. 7(a)). Further studies are needed
K.-T. Rie et al. 100
I
/
MO-PACVD of thin coatings a—Fe
I
•
205 a—Fe
(111) (200)
80
(220)
Zr(C,N) 350°C
0, C
~
~
_____
______________
3000C
C
~
0
•
I
I
20
30
•
0
10
A
40
distance from surface / nm
_________________________________________________
CC
L
A
-
30
Fig. 6. Depth profile of elemental analysis of a Ti(C,N) bayer with oxygen contamination, precursor Ti(NEt 2)4, 260 °C,500 V, 150 Pa.
C—H
.
80 2
e
—~
Fig. 8. X-Ray diffraction pattern (Cu Ks) ofZr(C,N) layers on Ck 35, precursor Zr(NEt2)4, 550 V, 250 Pa.
temperature. For PACVD with TiCl4 as precursor Oguri et a!. [7] observed similar results influenced by the ratio
Zr-C
of the precursor and reactive gases. They have made a classification of their results in terms of (200)- and (111)I
I
I
I
287.5
279.5
oriented coatings.
Binding Energy 1eV)
5.4. Optical emission spectroscopy Optical emission spectroscopy (OES) is a powerful tool for controlling the coating process and for optimiz-
Zr-N
ing both the layer properties and the coating process.
Here OES was used as a qualitative in situ diagnostic I’,
0
U
I
I
398.5
Binding Energy 1eV) Fig. 7. XPS analysis of a Zr(C,N) layer, precursor Zr(NEt2)4, 300 °C, 600 V, 250 Pa, (a) carbon bonds, (b) nitrogen bonds.
method. By measuring the intensity of the spectral lines, it is possible to identify the density of each excited state. The OES results have to be correlated with the layer properties. One example is given in Fig. 9 which shows a small part of the emission spectrum from a coating process at 300 °C, 250 Pa and 600 V on varying the
evaporation temperature of the precursor Ti(NEtMe)4. Several Ti + lines occurred in the discharge, e.g. at wavelengths of 323.4, 323.6, 323.9 and 334.9 nm. In this
to verify or disprove the statement that with increasing C—C bonds the hardness of Zr(C,N) and Ti(C,N) layers decreases.
I
Figure 8 shows an example of an X-ray diffraction analysis of a Zr(C,N) layer on Ck 35. In the same way the presence of Ti(C,N) was proved using the titanium
amides as precursors. Additional to the peaks of cubic Zr(C,N) of the layer one can see the peaks of eL-Fe of the base material (Fig. 8). The preferred orientation
changed with increasing coating temperature. At low
temperature the peak of the (200) plane dominates. The peak of the (111) plane exceeds all other Zr(C,N) peaks at higher temperatures. The ratio of the (ill) and (200) peaks altered from 0.66 to 1.32, indicating a change in preferred growth orientation dependent on the coating
N 337,Thm “336,Onm
24
5.3. X-Ray diffraction
I
334 gnm
—a c
o 18
~ ~
~
_______________
-75CC 12 C
c
•=85°C
-~
___________________
6
________________________________________
334
340.8
347.6
354.4
3612
308
wavelength / Fig. 9. Optical emission spectrum, precursor Ti(NEtMe)4, 300 °C, 250 Pa, 600 V, evaporation temperature ç.
206
K.-T. Rie et al.
/
MO-PACVD of thin coatings
study the Ti~line at 334.9 nm proved most important
as the main indicator determining the layer properties
(4) M—N and M—C bonds as well as C—C bonds have been detected,
during the coating process. Good layer properties were achieved only for evaporation temperatures between 65 and 70°Cin the described experimental set-up. At lower temperatures the growth rate is very low and tends to
(5) correlation of the intensity of the Ti + line with the layer properties is possible.
zero. At higher temperatures, in contrast, the growth
Acknowledgments
rate is too high. The C—C bonds in the layer increase,
the hardness decreases and spalling may occur. Thus the importance of the Ti + line (2 = 334.9 nm) is proved for
We are grateful to the BMFT (Bundesministerium für
the correlation with the layer properties in our study.
Forschung und Technologie) for support of this work (13N5793). The authors wish to thank Dr. H. Hantsche, BAM, Berlin for performing the XPS measurements.
6. Conclusions
References
In
this study the
usefulness of titanium- and
zirconium-tetrakisdialkylamide has been demonstrated for Ti(C,N) and Zr(C,N) coatings respectively, since (1) the substrate temperature can be reduced to below 300 °C, (2) the formation of chlorine-free layers can be achieved, (3) the surface topography can be altered from relatively rough to a smooth fine-domed surface by process parameter variation,
I N. Kikuchi, Y. Oosawa and A. Nishiyama, Proc. 9th mt. Conf. on CVD, Pennington, NJ, 1984, Electrochemical Society, Pennington, NJ, 1984, p. 728. 2 Th. Kruck, in H. Dimigen, K. Hieber, K.-T. Rie and G. Wahl (eds.), Proc. Workshop ISPC 10, Bochum, 1991, p. 84. 3 K.-T. Rie and J. Wdhle, Mater. Sci. Eng. A, 139 (1991) 37. 4 K.-T. Rie, J. Wöhle and A. Gebauer, J. Phys. (Paris) II, Colloq. C2. 1(1991)397. 5 J. A. Thornton, J. Vac. Sci. Technol., 11 (1974) 666. 6 R. Chatterjee-Fischer and P. Mayr, Harterei-Technische Mitteilungen. 41 (1986) 113. 7 K. Oguri, H. Fujita and T. Arai, Thin Solid Films, 195 (1991) 77.