JP2539990B2 - Method for forming titanium compound film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a titanium compound coating film by a plasma CVD method.

[0002]

2. Description of the Related Art In a film forming method using various low temperature plasmas, for example, a physical vapor deposition method (PVD method) such as an ion plating method, a chemical vapor deposition method (CVD method) is used.
It is possible to form a ceramic thin film such as a titanium compound film at a low temperature as compared with the above. However,
The PVD method has a problem that the covering power of the coating film on the three-dimensional base material is low. In particular, in the case of a large-sized complex three-dimensionally shaped substrate, the throwing power is markedly reduced, so that it is practically difficult to apply the PVD method.

Therefore, the good throwing power of the CVD method and P
A plasma CVD method which has both advantages of forming a thin film at a low temperature in the VD method is being developed. This plasma CVD method uses the thermal energy required for the chemical reaction of the source gas.
It is possible to form a thin film at low temperature by substituting a part or all of the above with electric energy by plasma. In such a plasma CVD method, a raw material gas in a vacuum chamber is supplied through a nozzle, and direct current or high frequency is applied to a three-dimensional base material arranged in the chamber to cause glow discharge to generate plasma. At this time, the source gas supplied into the chamber becomes active excited species such as ions, radicals, atoms and molecules when passing through the plasma. It is considered that these excited species are capable of forming a thin film on the three-dimensionally shaped substrate at a low temperature because the reaction proceeds at a low temperature. Therefore, the plasma CVD method can form a thin film having good throwing power on a three-dimensional substrate at a low temperature.

By the way, conventionally, in order to form a titanium compound film such as a titanium nitride film or a titanium carbide film by a plasma CVD method, a film forming experiment was conducted by changing many film forming parameters, and the characteristics of the formed film were The empirical method of setting the optimum film-forming conditions by investigating is adopted.

[0005]

However, the above-mentioned research requires a large amount of experiments, which requires a lot of time, cost, and cost.
It takes effort. Furthermore, the optimum film forming conditions vary greatly due to various factors. For example, the pressure in the film formation reaction tank, the power supplied to the plasma, the plasma generation method, the raw material gas mixing ratio, the raw material gas species, the shape of the nozzle for supplying the raw material gas, the speed of the raw material gas, the shape of the reaction tank. And material, the shape and material of the substrate on which the film is formed, the temperature of the substrate, and the like, which greatly vary. Therefore, the optimum film forming condition obtained for a certain base material under a certain condition by a certain plasma CVD apparatus also changes if the shape or material of the base material changes.
In addition, if the apparatus is different, various controllable film forming parameters are not necessarily the same even if they are controlled to be the same as the previously obtained conditions. As a result, it becomes necessary to newly investigate the optimum film forming conditions. Even if the film formation is repeated in the same apparatus under the same film forming conditions, the reproducibility of various film forming parameters is not always obtained. It can be seen that the state changes. These are plasma CVD
Controllability and reproducibility of film formation by the
Further, it impedes the application and development of the plasma CVD method.

The present invention was made in order to solve the above-mentioned conventional problems, and by developing a method for easily finding the optimum plasma CVD film forming conditions, the easiness of film formation, applicability, and further An object of the present invention is to provide a method for forming a titanium compound coating film by a plasma CVD method with improved controllability and reproducibility.

[0007]

The present invention is a plasma CV.
A method of forming a titanium compound film on a substrate by Process D, is measured a plasma CVD film forming condition dependence of the emission intensity of Ti ⁺ ions in advance the substrate surface near or plasma space, emission intensity of the Ti ⁺ ions Point that starts to deviate from the linearity when increasing linearly ( hereinafter, the bending point
Is called ) and the plasma C is calculated based on the bending point.
It is a method of forming a titanium compound film, which is characterized by setting optimum film forming conditions of the VD method.

[0008]

The inventors of the present invention can easily find the optimum plasma CVD film forming conditions by a simple method based on the knowledge described below, and easily form a titanium compound film by the plasma CVD method with good controllability and reproducibility. Invented a possible method.

That is, the inventors of the present invention conducted a research on the formation mechanism of a titanium compound film by a plasma CVD method using a direct current glow discharge or a high frequency glow discharge by plasma diagnosis, and a study on the dependence of various film formation characteristics on various film formation parameters. It was As a result, Ti ⁺ formed by decomposing and ionizing the source gas of the titanium source in the plasma space, especially in the sheath portion near the surface of the substrate It has been revealed that ions are plasma species that play an important role in the film formation reaction process. The raw material gas of the titanium source, for example, titanium tetrachloride gas, is easily decomposed in plasma to become Ti atoms and further ionized. Further, the energy state of plasma generally used in the plasma CVD method is various P
Lower than that in the VD method, many titanium atoms are 2
Is not ionized up to trivalent and trivalent, most of which is monovalent Ti ⁺ Become an ion. It is considered that this plays an important role in the assumption of the film formation reaction. It is presumed that active plasma species are present in each of the formed compounds, both of which form precursor molecules or ions of the coating film, and the precursors carry out the coating film forming reaction on the substrate surface. Furthermore, the plasma CVD film forming conditions capable of producing the optimum precursor formation state are presumed to be the film forming conditions capable of forming the optimum titanium compound film.

The optimum precursor formation state is Ti ⁺ which exists in the plasma space particularly near the surface of the substrate. It is considered that the formation amount of each active plasma species existing in each of the ions and the target compound, that is, the density is optimized. Moreover, when various film forming parameters capable of controlling the film forming state are changed, the densities of those plasma species are changed, and as a result, the film forming characteristics are changed. In particular, when the density of the plasma species used as the raw material of the compound to be formed becomes excessive, the state of precursor formation rapidly deteriorates, resulting in the formation of fine powder due to a uniform gas phase reaction,
It adheres to the coating, and the corrosion resistance of the coating is greatly deteriorated, which adversely affects the characteristics of the coating. Furthermore, the throwing power of the coating is greatly reduced.

However, when the characteristics of the film formed by changing various parameters are examined and the results of the film forming characteristics are defined by various film forming parameters and classified, the most excellent film forming condition region is the excellent film. It has been clarified that, among the film forming condition regions in which the film is formed, it exists particularly near the boundary line with the unfavorable film forming condition region where fine powder is generated by the uniform gas phase reaction.

From the above, when the dependence of the emission intensity of Ti ⁺ ions on the film formation parameter is measured, the emission intensity of Ti ⁺ ions is found to be at the boundary between the optimum film formation condition region and the undesirable film formation condition region. that starts to deviate from linearity (Orikyokuten) is found when the linearly increasing, the folding
Based on the points , it was possible to find the most excellent film forming condition of the plasma CVD method. Furthermore, it was possible to estimate the most excellent film forming condition region by sequentially changing each film forming parameter and performing the same measurement.

Of the many factors involved in the film formation conditions by the plasma CVD method, the factors related to the apparatus itself used and the factors related to the control using the apparatus, that is, the film formation parameters can be divided. . When a certain device is used, it is mainly necessary to optimize the latter film forming parameter. Generally, in the film formation by the plasma CVD method, controllable film formation parameters are power supply to plasma, pressure of reaction tank, flow rate of each source gas, substrate temperature during film formation, and the like.

A titanium compound film is formed on a base material having a predetermined shape by using a predetermined plasma CVD apparatus. At this time, two kinds of film forming parameters A and B that most affect the film forming characteristics are selected, other film forming parameters are fixed, and further the film forming parameter A is fixed to a certain value.
The film formation parameter B is changed, and the bending point of the emission intensity of Ti ⁺ ions at that time is obtained by the method described above. Then, by further changing the film formation parameter A, the dependence of the emission intensity of Ti ⁺ ions at that time on the film formation parameter is measured, and the bending point under each condition is measured. It is possible to find the boundary line between the optimum film forming condition and the undesirable film forming condition region defined by B. As a result, the most excellent film forming condition region can be obtained in advance. Further, under the above conditions, a target titanium compound film is formed on a substrate similar to the substrate used for the preliminary measurement to form a film having excellent properties on the substrate with good throwing power. It will be possible.

Conventionally, the optimum film forming conditions for forming a film by the plasma CVD method have been empirically obtained by conducting film forming experiments by changing various film forming parameters.
For that purpose, great expense, labor, and time were required.
In addition, the optimum film forming conditions greatly change when the substrate and the device are different. Further, the obtained optimum film forming conditions gradually change due to various factors, but there is no drastic means for detecting this.

On the other hand, according to the present invention, the most excellent film forming condition region can be found easily in a very short time by the above-mentioned method, and it is also utilized as a monitor of the required optimum film forming condition. be able to. Therefore, the controllability and reproducibility of the titanium compound film formation by the plasma CVD method can be improved, and the applicability can be greatly expanded.

[0017]

Embodiments of the present invention will now be described in detail with reference to FIG.

FIG. 1 is a schematic diagram showing a DC plasma CVD apparatus used in this embodiment. Reference numeral 1 in the drawing is a vacuum chamber. A DC electrode 2 having a rotating mechanism is installed in the lower part of the vacuum chamber 1. A DC power supply 3 is connected to the DC electrode 2. An exhaust pipe 4 is provided near the lower portion of the vacuum chamber 1. A pressure control valve 5 and a vacuum pump 6 are sequentially connected to the exhaust pipe 4 from the vacuum chamber 1 side.

On the outer wall of the vacuum chamber 1, there is provided a heater 7 for uniformly heating the large three-dimensional base material placed on the DC electrode 2. Gas supply nozzles 8a to 8d are provided on the side wall of the vacuum chamber 1, and the raw material gas supplied from the gas supply nozzles 8a to 8d is sprayed onto the entire large three-dimensional base material installed on the DC electrode 2. It is designed to be used. The other end of each of the gas supply nozzles 8 a to 8 d penetrates a side wall of the vacuum chamber 1 and extends to the outside, and is connected to a gas introduction pipe 9. The gas introducing pipe 9 includes gas branch pipes 10 a to 1 a.
0c is connected. Each of the gas branch pipes 10a to 10
Valves 11a to 11c are respectively provided in c. Gas branch pipe 1 on the rear end side of the valves 11a to 11c
0a to 10c include mass flow controllers 12a to 1
2c are respectively interposed. Each of the mass flow controllers 12a to 12c includes titanium tetrachloride (TiCl4).
₄ ) Gas, nitrogen (N ₂ ) gas, and hydrogen (H ₂ ) gas supply lines are connected.

In the vacuum chamber 1, the DC electrode 2
An emission spectroscopic analysis system 13 for measuring the emission of plasma in the vicinity of a large three-dimensional base material installed above or in a plasma space is arranged. The emission spectroscopic analysis system 13 includes a condenser lens 15 made of quartz glass for concentrating the emitted light of the plasma through a window 14 made of quartz glass arranged on the side wall of the vacuum chamber 1. The condenser lens 15 is connected to a spectroscope 17 through an optical fiber 16. The spectroscope 17 is provided with a photomultiplier tube 18 for receiving and sensitizing the spectrally separated light. The photomultiplier tube 18 is connected to a recorder 19 for recording the plasma emission as a spectrum. Example A thin film forming method will be described using the above-described DC plasma CVD apparatus.

First, a large three-dimensional base material 20 made of SKH51 was placed on the DC electrode 2 in the vacuum chamber 1. Subsequently, the vacuum pump 6 was operated to exhaust the gas in the vacuum chamber 1 through the exhaust pipe 4. Continuing, 150scc whose flow rate was adjusted by the mass flow controller 12a
m of TiCl ₄ gas, 500 sccm of N ₂ gas whose flow rate was adjusted by the mass flow controller 12b, and 8000 sc whose flow rate was adjusted by the mass flow controller 12c.
cm gas mixture gas consisting of H ₂ gas, gas supply nozzle 8
It was supplied into the vacuum chamber 1 through a to 8d. At this time, the pressure in the vacuum chamber 1 was kept at 0.43 Torr by the pressure control valve 5, and the large-sized three-dimensional substrate 20 was kept at 550 ° C. by the heater 7. At the same time, a DC voltage of −400 V was applied from the DC power supply 3 to the DC electrode 2 to generate DC plasma in the chamber 1. Next, the plasma emission in the vicinity of the surface of the large-sized three-dimensional base material 20 is condensed by the condensing lens 15 of the emission spectroscopic analysis system 13 and guided to the spectroscope 17 through the optical fiber 16, and the photomultiplier tube 18 and the recorder 19 are collected. To obtain a plasma emission spectrum.

While gradually increasing the DC voltage applied to the DC electrode 2, the emission spectrum was measured by the same operation as described above using the emission spectrum analysis system 13. The obtained emission spectrum, in particular titanium monovalent ions (Ti ⁺ Focusing on the emission of ions), Ti ⁺ The DC voltage dependence of the emission intensity of ions was investigated. The result is shown in FIG.

As is apparent from FIG. 2, the emission intensity of Ti ⁺ ions increases linearly with an increase in the applied DC voltage, and at 1800 V, there appears a bending point which starts to deviate from the linearity. The emission intensity of Ti ⁺ ions reaches a maximum value at around −2200 V, and starts to decrease when the DC voltage is further increased. In addition, the direct current voltage dependence of the film forming rate under the above film forming conditions and the index (Di) showing the throwing power of the film represented by the following equation was examined. The result is shown in FIG. Di = [absolute value of (maximum displacement value from average film thickness−average film thickness value)] / average film thickness × 100 (%)

As is apparent from FIG. 3, a TiN coating film which exhibits gold color from the region (WG) where a coating film of gold white and slightly less in hardness than the TiN coating film is formed as the applied voltage is increased and which has excellent characteristics is obtained. The transition to the optimum film forming condition region (G) is formed, and further, it exhibits a reddish gold color or brown, and the fine powder generated by the uniform gas phase reaction is attached,
It changes into a uniform gas phase reaction generation condition region (RG) where a film having poor corrosion resistance is formed. The film formation rate increases linearly with an increase in the DC applied voltage, but reaches the maximum value in the RG region. Further, the Di value is low in the G region, and it can be seen that the excellent throwing power of the TiN film is achieved.

From FIG. 2 and FIG. 3, the voltage at the bending point seen in the DC voltage dependence of the emission intensity of Ti ⁺ ions is the same as the optimum film forming condition region (G) in which an excellent TiN film is formed. The applied voltage is the same as the applied voltage of the boundary line of the uniform gas phase reaction generation condition region (RG), that is, -1800V. In this way, the boundary applied voltage is obtained from the bending point seen in the direct current voltage dependence of the emission intensity of Ti ⁺ ions, so that the optimum applied voltage at the time of forming the TiN film is actually subjected to many film forming experiments. Can be easily estimated without.

For example, when the TiN film is formed, the boundary applied voltage (-1800V) is 50V lower by -17.
When the applied voltage is set to 50 V, the film formation rate can be increased, and the large three-dimensional base material 20 has good throwing power and has a high Vickers hardness of 2200 Hv and a stoichiometric atomic ratio (N / Ti). = About 1), a TiN film with low residual chlorine (1 wt% or less) could be formed.

On the other hand, the obtained boundary applied voltage greatly changes due to changes in many film forming parameters. For example, when only the N ₂ gas flow rate is changed under the film forming conditions used in the above-described measurement and the same measurement is performed to examine the DC voltage dependence of the emission intensity of Ti ⁺ ions, the results shown in FIG. 4 are obtained. can get. From FIG. 4, the applied voltage at which the bending point of the emission intensity of Ti ⁺ ions appears as the N ₂ gas flow rate increases,
That is, it is understood that the boundary applied voltage shifts to the low current applied voltage side. Based on FIG. 4, the DC applied voltage at which the bending point of the emission intensity of Ti ⁺ ions at each N ₂ gas flow rate appears is obtained, and when the points are connected, the result is as shown in FIG. The line shown in FIG. 5 shows the estimation result of the boundary line between the optimum film forming condition region (G) defined by the N ₂ gas flow rate and the DC voltage and the uniform gas phase reaction generation region (RG). Become.

In order to show that the above estimation is correct, a TiN film forming experiment was actually conducted at each N ₂ gas flow rate and each applied voltage, and the characteristics of the obtained film were measured. The results shown in FIG. 6 were obtained. . As is clear from FIG. 6, the boundary line between the optimum condition region (G) and the uniform gas phase reaction generation condition region (RG) obtained by the characteristics of the film actually formed is the optimum condition of FIG. It can be seen that the result agrees with the estimation result of the boundary line between the condition region (G) and the uniform gas phase reaction generation condition region (RG).

When a film is formed in the optimum film forming condition region (G) near the boundary line estimated by the method as described above, a TiN film excellent in film forming rate, throwing power, and other Sesuma section characteristics and film quality is formed. It became clear that it could be done.

As described above, Ti ⁺ When the bending point of the emission intensity of the ions was obtained, it was obtained by the dependence of the emission intensity on the DC applied voltage. However, the DC applied voltage was fixed to an arbitrary value and N
₂ Change the gas flow rate and change Ti ⁺ By obtaining the bending point of the emission intensity of the ions, the boundary line between the optimum condition region (G) and the uniform gas phase reaction generation condition region (RG) can be similarly estimated.

Further, the method of estimating the optimum film forming condition region is such that a different source gas species, for example, N ₂ gas instead of ammonia is used under a pressure different from that in the above embodiment or when a similar TiN film is formed. It was clarified that it can be carried out very accurately even when gas is used. Moreover, it can be carried out sufficiently accurately even when forming a titanium compound coating other than TiN, for example, a titanium carbide (TiC) coating.

Therefore, when the desired titanium compound film is to be formed by the plasma CVD method, it is possible to easily optimize the film forming conditions by the above-mentioned method, and under the condition, the desired titanium compound film is formed. When formed, it becomes possible to easily form a film having excellent film forming characteristics and excellent film quality. Further, by confirming the optimum film forming conditions as needed by the above method, it becomes possible to always form the titanium compound film under the optimum film forming conditions.

[0033]

As described above in detail, according to the present invention, when the titanium compound film is to be formed by the plasma CVD method, the plasma CVD film is formed in advance near the surface of the substrate or in the plasma space with the emission intensity of Ti ⁺ ions. The condition dependence is measured, and a point (a bending point) at which the emission intensity of the Ti ⁺ ions starts to deviate from the linearity is linearly determined, and based on the bending point , the optimum composition of the plasma CVD method is determined. By setting the film conditions, the film forming conditions can be optimized in a reasonable and short time, and if the target titanium compound film is formed under these conditions, excellent film quality can be obtained under excellent film forming characteristics. The coating can be easily formed. Furthermore, by constantly checking the change in the optimum film forming conditions by the above method, it becomes possible to always form the titanium compound film under the optimum film forming conditions. Therefore, it is possible to improve the easiness, applicability, controllability, and reproducibility of the titanium compound film formation by the plasma CVD method.

[Brief description of drawings]

FIG. 1 is a DC plasma CVD used in an embodiment of the present invention.
Schematic which shows an apparatus.

FIG. 2 is a characteristic diagram showing the direct current voltage dependence of the emission intensity of Ti ⁺ ions obtained by an example of the present invention.

FIG. 3 is a characteristic diagram showing the DC voltage dependency of an index (Di) showing the film forming rate and the throwing power of the film, which were obtained by an example of the present invention.

FIG. 4 is a characteristic diagram showing the direct current voltage dependence of the emission intensity of Ti ⁺ ions under each N ₂ gas flow rate, which is obtained by an example of the present invention.

5 is a graph showing the flow rate of each N ₂ gas obtained from the results of FIG.
The characteristic view which shows the direct-current applied voltage in which a bending point appears.

FIG. 6 is a characteristic diagram showing characteristics of a film when a film is formed by changing a N ₂ gas flow rate and a DC applied voltage.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber, 2 ... DC electrode, 4 ... Exhaust pipe, 8a ...
8d ... Gas supply nozzle, 13 ... Emission spectroscopic analysis system.
15 ... Condensing lens, 17 ... Spectrometer, 20 ... Large three-dimensional base material.

Claims (1)

(57) [Claims] 1. A method of forming a titanium compound film on a substrate by a plasma CVD method, wherein the dependence of the emission intensity of Ti ⁺ ions on the plasma CVD film forming conditions in the vicinity of the surface of the substrate or in the plasma space is measured in advance to obtain the Ti compound film.
^A point at which the emission intensity of ⁺ ions linearly increases is found, and a point at which the ion intensity starts to deviate from the linearity is obtained.
A method for forming a titanium compound film, which comprises setting an optimum film forming condition of a VD method.