JP3511089B2 - Control method of solid surface treatment by low temperature plasma - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment such as carburization, an etching treatment, or a dissociation in plasma, which positively utilizes the interaction between plasma generated by molecular gas discharge and a solid surface. During the surface treatment of solids using low-temperature plasma, such as thin film formation that uses the adhesion of the products of the reaction to the solid surface, control the treatment conditions to obtain the surface with the best physical properties based on the emission intensity of the plasma. For a new method for

[0002]

2. Description of the Related Art Up to now, it has been known that, in a method of treating a solid substance using plasma, the state of plasma in a reaction zone is diagnosed by an emission spectroscopic analysis method, an electron probe method, a laser spectroscopic method, a mass spectrometric method and the like. There is. For example, when using silicon as a target and argon, hydrogen, helium, or neon as a sputtering gas to form an amorphous SiH-based thin film, a plasma state should be diagnosed by an optical emission spectroscopy method , Volume 44,
139 (1980)], in the production of titanium nitride by evaporating metallic titanium with an electron gun in a nitrogen atmosphere, T
Obtaining the emission intensity of the i and N ₂ emission lines and estimating the film composition from the emission intensity ratio and the Ti—N composition ratio of the film [Journal of the Japan Institute of Metals, vol. 57, p. 926 (199).
3)] and the like are known.

According to these methods, the emission lines of a plurality of chemical species that are theoretically related by the constituent elements of the film, the reaction mechanism, etc. are monitored according to the type of the film to be formed, and their strength and film composition are monitored. I investigated the relationship, but SiH
Has a drawback in that it is not possible to easily detect light emission with a weak emission line, and the emission intensity ratio between the emission lines of Ti and N ₂ has a drawback that the error increases with increasing nitrogen pressure. Has not been done.

In addition, as in the reactive sputtering method for producing chromium oxycarbide composed of three kinds of elements in a mixed gas atmosphere of argon, carbon dioxide and methane by using metallic chromium as a target, the emission lines of chromium and argon are strong and carbon When the emission lines of oxygen and carbon dioxide are weak, it is difficult to detect all of the main elements that make up the film, and plasma diagnosis cannot be put to practical use.

[0005]

DISCLOSURE OF THE INVENTION The present invention is directed to a reaction spatter.
Forming Chromium Oxycarbide Thin Film by Tulling Method
In this case, there is no relation to the intensity of the emission line due to the type of element present, and based on the result of diagnosing the plasma state,
The object of the present invention is to provide a solid surface treatment control method capable of adjusting treatment conditions so as to obtain the best surface properties.

[0006]

SUMMARY OF THE INVENTION The inventors of the present invention have found that when a low temperature plasma is used to form a thin film on a solid surface, the present invention is intended to always maintain the processing conditions that give the best results regarding desired physical properties. As a result of extensive research to develop a control method, the plasma during processing is subjected to emission spectroscopy, and two or three emission lines of a specific element with high emission intensity are selected from the obtained emission spectra, and the emission intensity is determined. The inventors have found that the processing conditions can be easily and accurately controlled by using the ratio as a parameter for monitoring, and have completed the present invention.

That is, the present invention is directed to reactive sputtering.
Method for forming chromium oxycarbide thin film
, Chromium as a target, and C as a reaction gas
Using O ₂ and CH ₄ , the emission spectrum of the plasma is measured over time, and two or three emission lines of chromium at different wavelengths with large emission intensity are selected from the obtained emission spectra, and the emission intensity ratio is monitored. The method for controlling the solid surface treatment by low temperature plasma is characterized by maintaining the treatment conditions within the range where the desired physical property value of the treated surface is maximized while ringing, and chromium oxide by the reactive sputtering method.
When forming a carbide thin film , (a) chromium as a target and a reaction gas
CO ₂ and CH ₄ are used, ( b ) emission spectrum of plasma is obtained over time to obtain an emission spectrum, and ( c ) two or three emission spectra having different emission wavelengths from the emission spectrum. (2) Next, the relative ratio of the emission intensity is determined, and ( d ) the physical properties are measured while changing the processing conditions for the desired physical properties of the thin film to be formed. Determining the relationship with the value, and ( e ) monitoring the emission intensity relative ratio,
It is intended to provide a method for controlling a solid surface treatment by low-temperature plasma, which is characterized in that the treatment condition is adjusted so that a desired measured value of physical property is maximized.

[0008]

METHOD OF THE PREFERRED EMBODIMENTS The present invention is reactive sputtering phosphorus
A thin film of chromium oxycarbide to a solid surface can be used to be <br/> formed by grayed method.

In the method of the present invention, the plasma in the treatment or reaction zone is subjected to emission spectroscopy over time according to a conventional method, and the emission intensity is high in the plasma emission spectrum.
Two or three emission lines of a specific element that can be easily detected are arbitrarily selected, and the intensity ratio of the emission lines is used as a parameter to determine the optimum treatment conditions in relation to the physical properties of the solid surface.

[0010] In the present invention, the bright line having a high emission intensity JP
It can be arbitrarily selected from the constant elements , that is, irrespective of the emission line of the chemical species that is theoretically related to the constituent elements and reaction mechanism of the film in which the emission line is manufactured. And, it is necessary to use the emission line in which the intensity ratio between the emission lines clearly changes in accordance with the change in the physical properties of the solid surface, but many emission lines have their strength in accordance with the change in the physical properties of the solid surface. The ratio changes. The bright line corresponds to the transition between the electron energy levels of elements, molecules, ions, and radicals, but when the electrons accelerated in the plasma collide with the source gas and ionization, excitation, dissociation, etc. occur, the electron energy state Distribution depends on time and space. In the case of film formation, the distribution of electron energy states in plasma is also considered to depend on film formation conditions such as gas type, ratio, substrate temperature, and substrate bias. Although the detailed mechanism of the dependence is not clarified at present, the change of the emission intensity ratio is used as a parameter for controlling the film formation directly and in situ from the film formation reaction field, instead of the conventional film formation parameter. be able to.

Basically, the number of bright lines selected in the method of the present invention may be two for each physical property, but since the relative comparison of the intensities among the bright lines may not be possible, it may be inaccurate. It is preferable to select three. These bright lines are preferably the strongest bright lines commonly used for normalization.

As the plasma emission spectroscopy in the method of the present invention, for example, emission spectroscopy analysis of low temperature plasma by an instant multi-photometer using a photodiode array is used. An instantaneous multi-photometer using a photodiode array can measure a plasma spectrum relatively easily in a short time, and is therefore preferable for controlling the plasma in situ. Optical emission spectroscopy is one of the viewing windows of plasma processing equipment.
This is done by guiding the light from a light collector attached to one to a multi-channel photodetector controlled by a personal computer with an optical cable. Maximum measurement wavelength range is 38
It is sufficient if the visible range can be monitored at once from 0 to 780 nm. Smaller wavelength resolution is desirable, but 1 nm
It doesn't matter if it's rough. Before measurement, it is desirable to calibrate the wavelength using a mercury / neon mixed light source.

In the method of the present invention, in order to arbitrarily select a bright line having a high emission intensity from the emission spectrum and determine the optimum plasma state for the treatment, the relative intensity ratio between the selected bright lines and the physical properties of the solid surface are determined. The relative intensity ratio (optimal intensity ratio) of several kinds of bright lines under the optimum processing conditions is determined by investigating the relationship. For example, if there are three bright lines selected with the substrate bias as a parameter of the film forming conditions,
A plot of the relative intensity ratio, peak 2 / peak 1, peak 3 / peak 1 on the XY plane shows the optimum intensity ratio on the XY plane according to changes in the physical properties of the solid surface. Since the locus is drawn with this, the value of the substrate bias as a parameter may be feedback-controlled according to the deviation from the optimum intensity ratio measured in situ. Similarly, the emission line selected with the reaction gas flow rate ratio as the film forming parameter is set to 3
In other words, by using the relative intensity ratio, peak 2 '/ peak 1', peak 3 '/ peak 1', the reaction gas flow rate ratio can be feedback-controlled in situ. Bright lines 1 ', 2', 3
A part of ′ may overlap the bright lines 1, 2, and 3. This is because even if the bright lines that do not overlap are selected, the respective bright line intensities are related to each other and do not change completely independently.

In the method of the present invention, the physical properties of the solid surface having a correlation with the relative intensity ratio of the bright lines are, for example, hardness of the surface or thin film, tensile strength, flexural strength, compressive strength, flexural modulus, Mechanical strength such as elongation and interlaminar shear force, physical and electrical properties such as thermal expansion coefficient, thermal conductivity, conductivity, density and film thickness, and chemical properties such as oxidation resistance and chemical resistance. Can be mentioned.

In this way, for example, the plasma state during the production of the chromium oxycarbide coating consisting of three elements by reactive sputtering is monitored, and the relationship between the emission spectrum and the physical properties of the solid surface is examined for chromium oxycarbide. Of the constituent elements Cr, C, and O, only the emission line of chromium CrI, which has the highest emission intensity, is used, and the three emission intensities that are the strongest are detected from the emission lines of CrI, and the intensity ratios thereof are used as the gas flow rate ratio, substrate temperature, and substrate bias. The optimum film forming conditions can be determined by plotting on the diagram as a function of various processing condition factors such as electric potential. The optimum film forming condition, that is, the optimum processing condition, appears as the same emission intensity ratio regardless of which bright line is selected.

[0016]

EXAMPLES The present invention will be described in more detail with reference to examples.

Reference Example 1 A chromium compound was formed on a SUS304 substrate under various film forming conditions by using chromium as a planar magnetron type target electrode by the RF activation reaction sputtering method.
The device used is a deposition up type device in which the substrate is placed above the target electrode.
An RF electrode consisting of a three-turn coil capable of generating plasma independently of the sputter electrode at a radio frequency of Hz was used. The processing conditions were as follows. Vacuum pressure: 0.5 Pa sputtering power source output: 0.7 kW substrate temperature: 673 K RF Output: 40W substrate bias: -250 V gas flow _{rate: Ar = 14sccm, CO 2 =} 6sccm,
CH ₄ = 0.5 sccm Treatment time: 60 minutes The chromium compound thin film thus obtained has a black metallic luster, a film thickness of 1.93 μm and a Vickers hardness of 2
A high value of 280 kg / mm ² was exhibited. The film forming conditions used in this example are the standard processing conditions.

Reference Example 2 FIGS. 1 to 3 show the Vickers hardness and the film thickness of the obtained thin film when only one of the film forming conditions in Reference Example 1 was changed to form a film. 1 maintains a sum of CO ₂ flow rate and Ar flow rate at a constant value of 20 sccm, CO ₂ flow rate of CO ₂ flow rate and the ratio of the Ar flow rate [CO ₂ / (CO ₂ + A
r)] shows the changes in Vickers hardness and film forming rate. ○ and ● CH ₄ flow rate 0.5s at the same time
In the case of introducing into a vacuum chamber with ccm, □ and ■ are cases in which CH ₄ is not introduced. CH ₄ flowed at 0.5 sccm, C
Ar / CO ₂ / CH ₄ = 14 sccm / 6 sccm / under standard processing conditions with an O ₂ / (CO ₂ + Ar) ratio of 0.3
The highest hardness was obtained at 0.5 sccm. The film formation rate increased as the CO ₂ / (CO ₂ + Ar) ratio decreased, regardless of the CH ₄ flow rate. When the substrate temperature is changed, the Vickers hardness is 623 to 723K and is 2 as shown in FIG.
The value was 000 kg / cm ² or more. The maximum film thickness per hour of film formation was 673 K, which was 1.93 μm. When the substrate bias during film formation was changed, the highest Vickers hardness was obtained at -250V as shown in FIG. The film thickness is 1.9μ in the range of 0 to -350V bias.
No significant change was observed above m.

EXAMPLE FIG. 4 shows a plasma emission spectrum observed when a chromium compound was formed into a film under the standard treatment conditions of Reference Example 1. The main peaks of brightness are 426 nm, 434 nm and 519n
recognized by m. These peaks and the small peak at 464 nm are estimated to be the emission from CrI. 700 ~
A small group of peaks seen at 800 nm is light emission from Ar. 5 to 7 show emission spectra under various film forming conditions. These spectra are similar to those of FIG. 4, but there is a change in the intensity ratio of the major peaks. FIG. 5 shows that when only Ar was used at a flow rate of 20 sccm as the gas to be introduced into the reaction tank under the standard processing conditions (a), the CH ₄ flow rate was kept at 0.5 sccm,
Ar, flow ratio of CO _2, the Ar / CO ₂ 18 / 2,14 /
It is [(b), (c) and (d)] when produced as 6 and 10/10 (sccm / sccm). (C),
Although many small peaks are observed in 400 to 600 nm in (d), these become prominent when CO ₂ is introduced, so it is presumed that the emission is from C, O or CO ₂ . FIG. 6 shows the case where the substrate temperature is changed under the standard processing conditions, and FIG. 7 shows the case where the substrate bias is changed under the standard processing conditions. The main peak intensities observed at 434 nm and 519 nm (peak 2 and peak 3) and 751 n relative to the intensity of the emission peak at 426 nm (peak 1).
Table 1 shows the emission intensity (peak 4) ratio of Ar observed in m.

[0020]

[Table 1]

FIG. 8 shows the emission intensity ratio (peak 2 / peak 1).
Is the x-axis and the emission intensity ratio (peak 3 / peak 1) is the y-axis. It should be noted that the peak intensity ratio greatly changes with the change in the parameters of the film forming conditions. Is. Moreover, all of these peaks are CrI emission lines. If the parameters of the film forming conditions are narrowed down so that the change in the peak intensity ratio is small, the plasma state can be controlled more precisely by linear approximation. The reference processing condition with the highest Vickers intensity is located in the lower right.
The numbers in the figure are the numbers in the figure, and 5, 6 and 7 correspond to the case where the film forming conditions are changed with the gas flow rate ratio, the substrate temperature and the substrate bias as film forming parameters. This means that the plasma emission intensity ratio (peak 2 / peak 1) and the plasma emission intensity ratio (peak 3 / peak 1) are monitored in situ in the RF activation reactive sputtering method, and the ratio is under the standard processing conditions of FIG. It is shown that it is technically possible to maintain the film forming condition with the highest Vickers hardness by controlling the flow rate of the reaction gas, the substrate temperature, and the substrate bias so that the emission intensity ratio is at the position (lower right).

Similarly, in FIG. 9, the emission intensity ratio (peak 2 / peak 1) is plotted on the X-axis, and the emission intensity ratio (peak 4 / peak 1) is plotted on the y-axis.
It is organized for the axis. Only peak 4 is a bright line from Ar. In this case, the reference processing condition with the highest Vickers intensity is located in the upper right. This is because in the RF activated reactive sputtering method, the plasma emission intensity ratio (peak 2 / peak 1) and the plasma emission intensity ratio (peak 4 / peak 1) are monitored in situ, and the ratio is the standard processing condition of FIG. It is shown that the film forming conditions with the highest Vickers hardness can be maintained by controlling the flow rate of the reaction gas, the substrate temperature, and the substrate bias so that the emission intensity ratio is in the position.

Emission intensity ratio (peak 2 / peak 1) to emission intensity ratio (peak 3 / peak 1) and emission intensity ratio (peak 2 / peak 1) to emission intensity ratio (peak 4) shown in FIGS. 8 and 9. Based on the locus of / peak 1), it is possible to control the parameters of the two film forming conditions so that the optimum film forming conditions are obtained. In this case, since the emission intensity ratio (peak 2 / peak 1) is commonly used for the X axis, it is considered that more effective control can be performed by using the intensity ratio of other plasma emission lines.

In this way, when the Vickers hardness is selected as the desired physical property for the thin film and the film forming conditions in which it exhibits the highest value are to be maintained, the emission intensity ratio (peak 2 / peak 1) or ( Each parameter of the film-forming conditions may be adjusted while monitoring peak 3 / peak 1) or both.

[0025]

According to the method of the present invention, when a chromium oxycarbide thin film is formed on a solid surface using low temperature plasma, the plasma state can be easily controlled, and the thin film formation can be performed in an optimum state. Can be controlled. In addition, a computer can reflect changes in the intensity ratio of emission lines in parameters that influence film forming conditions such as gas flow rate, gas species ratio, substrate temperature, and substrate bias. It can be widely applied to parts industry, chemical industry and machine industry.

[Brief description of drawings]

FIG. 1 is a graph showing changes in the film thickness and Vickers hardness of a thin film when the ratio of CO ₂ flow rate to Ar flow rate was changed in Reference Example 2.

FIG. 2 is a graph showing changes in film thickness and Vickers hardness of a thin film when the substrate temperature is changed in Reference Example 2.

FIG. 3 is a graph showing changes in film thickness and Vickers hardness of a thin film when the substrate bias is changed in Reference Example 2.

FIG. 4 is a plasma emission spectrum of a thin film formed under the standard processing conditions of the example.

FIG. 5 is a plasma emission spectrum of a thin film obtained when a film is formed by changing the Ar flow rate and the CO ₂ flow rate in the example.

FIG. 6 is a plasma emission spectrum of a thin film obtained when the film was formed by changing the substrate temperature in the example.

FIG. 7 is a plasma emission spectrum of a thin film obtained when a film is formed by changing the substrate bias in the example.

FIG. 8 is a graph showing the relationship between the emission intensity ratio (peak 2 / peak 1) and the emission intensity ratio (peak 3 / peak 1).

FIG. 9 is a graph showing the relationship between the emission intensity ratio (peak 2 / peak 1) and the emission intensity ratio (peak 4 / peak 1).

─────────────────────────────────────────────────── ───Continued from the front page (56) Reference JP-A-10-81965 (JP, A) JP-A-7-331432 (JP, A) JP-A-11-61391 (JP, A) JP-A-2- 194175 (JP, A) JP-A-61-216415 (JP, A) JP-A-62-180070 (JP, A) Tetsuo Kado, Preparation of chromium oxycarbide film by RF assisted magnetros sputtering method, 49th Proceedings of the Joint Lecture on Applied Physics, March 2002, No. 2, p. 605, 27p-YB-17 T.I. KADO, Q. FAN, Chromium Oxycardide Thin Films prepared by Inductively Coupled Radio-Frequency Plasma-Assisted J. Am. Ceram. Soc, 2001, Vol. 84, p. 1763-1766 (58) Fields surveyed (Int.Cl. ⁷ , DB name) C23C 14/00-14/58 JISST file (JOIS)

Claims (2)

(57) [Claims] 1. A chrome tree by a reactive sputtering method.
As a target for forming a thin film of carbide
Chromium and using CO ₂ and CH ₄ as reaction gases ,
The emission spectrum of the plasma is analyzed over time, and the emission spectrum obtained has a large emission intensity at different wavelengths.
Solid surface treatment with low-temperature plasma, characterized in that two or three chromium emission lines are selected and the emission intensity ratio is monitored while maintaining the treatment conditions within the range where the desired physical properties of the treated surface are maximized. Control method. 2. A chrome tree by a reactive sputtering method.
Per in forming the sheet carbide thin film, chromium as (i) the target, and as a reaction gas
CO ₂ and CH ₄ are used, ( b ) emission spectrum of plasma is obtained over time to obtain an emission spectrum, and ( c ) two or three emission spectra having different emission wavelengths from the emission spectrum. (2) Next, the relative ratio of the emission intensity is determined, and ( d ) the physical properties are measured while changing the processing conditions for the desired physical properties of the thin film to be formed. Determining the relationship with the value, and ( e ) monitoring the relative ratio of the emission intensity,
A method for controlling a solid surface treatment by low-temperature plasma, which comprises adjusting treatment conditions so that a measured value of desired physical properties becomes maximum .