JP4151000B2 - Surface treatment method and apparatus for workpiece - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a workpiece surface treatment method and apparatus capable of uniformly modifying the surface of a long workpiece.
[0002]
[Prior art]
There is a known modification treatment technology that improves the hardness, surface smoothness, wear resistance, and corrosion resistance of materials by forming thin films such as diamond-like carbon films and titanium-based compound films on the surface of the workpiece. Yes.
[0003]
A thin film such as a diamond-like carbon film can be formed by converting the material gas into plasma and irradiating the surface of the workpiece with ions or radicals in the plasma. In some cases, an inductively coupled plasma apparatus is used to turn the source gas into plasma. The inductively coupled plasma apparatus has an internal pressure of about 1 Pa in the vacuum chamber, and high frequency power is supplied to the raw material gas via an antenna installed in the vacuum chamber, and the raw material gas is turned into plasma to irradiate the workpiece with ions or radicals in the plasma. In addition, a thin film can be formed on the surface of the workpiece. In the vacuum chamber, the antenna is installed above the work on a suitable table, and the source gas is introduced into the vicinity of the work, diffused around the work, and turned into plasma by the high-frequency power from the antenna.
[0004]
[Problems to be solved by the invention]
According to such a conventional technique, the high-frequency power from the antenna only converts the raw material gas in the vicinity of the workpiece into plasma, so even if it is a small workpiece, it cannot be applied to a long workpiece. There is a problem that it is extremely difficult to uniformly modify the surface of the long workpiece over the entire length.
[0005]
Therefore, in view of the problems of the prior art, the object of the present invention is to uniformly modify the surface of a long workpiece by supplying high-frequency power to a loop antenna arranged in a plurality of upper and lower stages in a vertically long vacuum chamber. An object of the present invention is to provide a surface treatment method of a workpiece that can be treated and an apparatus therefor.
[0006]
[Means for Solving the Problems]
The structure of the first invention according to this application for achieving the above object is to supply a source gas from the upper part of a vertically long cylindrical vacuum tank when surface-treating a long work housed in the vacuum tank. High-frequency power from the power supply means through a matching circuit that connects the loop antennas that are arranged at equal intervals in the upper and lower stages in the axial direction in the vacuum chamber in parallel, and equalizes the ground voltage at both ends of the loop antenna evenly. Is supplied to the loop antenna to convert the raw material gas into plasma, suspended from the top of the vacuum chamber, and subjected to a modification treatment over the entire length of the work surface disposed around the loop antenna.
[0007]
A plurality of workpieces may be arranged around the loop antenna in a concentric circle coaxial with the loop antenna, or the workpieces may be rotated.
[0008]
The configuration of the second invention consists of a vertically long cylindrical vacuum chamber, a gas supply means for supplying a raw material gas to the upper portion of the vacuum chamber, and a parallel connection by being arranged at equal intervals in the upper and lower stages in the axial direction of the vacuum chamber. Loop antenna, power supply means for supplying high-frequency power to the loop antenna through a matching circuit, and a hanger that hangs a long workpiece from the upper part of the vacuum chamber and is arranged around the loop antenna. The matching circuit evenly distributes the ground voltage at both ends of the loop antenna, and the vacuum chamber discharges the source gas from the lower part and turns the source gas into plasma by the high frequency power from the loop antenna to cover the entire surface of the workpiece. The gist is to perform the modification treatment.
[0009]
A bias voltage can be applied to the work suspended from the hanger, and a grid is provided in the vacuum chamber between the loop antenna and the work to maintain the ground potential. As a result, the electromagnetic field from the loop antenna can be prevented from reaching the workpiece as an electromagnetic shield.
[0010]
Moreover, the power supply means can supply high-frequency power intermittently.
[0011]
[Action]
According to the configuration of the first invention, the workpiece is suspended from the upper part of the vertically long vacuum chamber and is disposed around the loop antenna. On the other hand, the raw material gas supplied from the upper part of the vacuum chamber is turned into plasma by the high-frequency power from the loop antennas arranged in multiple upper and lower stages, and the bulk of the plasma density is uniform in the height direction of the vacuum chamber, that is, in the longitudinal direction of the workpiece. A plasma volume is formed, and the workpiece can be uniformly modified by irradiating the surface of the workpiece with ions or radicals in the plasma. In addition, each loop antenna in the vacuum chamber is arranged coaxially with the vacuum chamber, and, for example, a one-turn loop antenna having a diameter of about 200 to 400 mm with respect to the inner diameter of 800 mm of the vacuum chamber reduces the high frequency resistance. The transmission efficiency of the high frequency power with respect to the source gas can be improved. Note that the plasma density in the longitudinal direction of the workpiece can be made substantially uniform by setting the interval between the loop antennas of each stage to be about 1.2 to 1.5 times or less the diameter of the loop antenna. The frequency of the high frequency power is on the order of MHz where the discharge start voltage starts to decrease, and 13.56 MHz or 27.12 MHz is preferable. However, even if it exceeds 30 MHz, it does not contribute to the improvement of the plasma density.
[0012]
For example, high frequency power is preferably intermittently supplied to the loop antenna at a repetition frequency of 0.1 to 10 kHz. If high-frequency power is intermittently supplied, the plasma temperature can be kept high while lowering the plasma potential by lowering the electron temperature in the plasma. Concentration of ions on the edges and sharp edges of the workpiece, side etching, etc. It is possible to improve the throwing power of the film and to prevent local abnormal heating of the work, thereby preventing a decrease in the adhesion of the film and a deterioration in the film quality. The electron temperature in the plasma decreases rapidly when high-frequency power is lost, while ions and radicals last longer than the lifetime of the excited molecule, increasing the time-average plasma density and keeping the plasma potential low. Because you can. The plasma potential can be further reduced by reducing the high-frequency resistance of the loop antenna and making the ground voltage at both ends of the loop antenna equal.
[0013]
By introducing the raw material gas from the upper part of the vacuum chamber and discharging it from the lower portion, the source gas is uniformly diffused into the vacuum chamber by gravity, and the plasma density in the vacuum chamber can be made uniform. Moreover, there is no possibility that the workpiece will be bent or deformed due to gravity by being suspended in the vacuum chamber.
[0014]
If a plurality of workpieces are arranged around the loop antenna, the plurality of workpieces can be reformed at once. However, the workpieces at this time are arranged in concentric circles coaxial with the loop antenna.
[0015]
If the workpiece is rotated, the entire surface of the workpiece can be made to uniformly face the loop antenna, and the surface of the workpiece can be uniformly modified.
[0016]
According to the configuration of the second invention, the gas supply means supplies the raw material gas to the vacuum chamber, and the power supply means supplies the high frequency power to the loop antenna to convert the raw material gas into a plasma with a uniform plasma density. The entire surface of the work suspended in the vacuum chamber through the hanger can be uniformly modified.
[0017]
The power supply means can increase the plasma density and lower the plasma potential by intermittently supplying high-frequency power to the loop antenna.
[0018]
The grid provided in the vacuum chamber is interposed between the loop antenna and the workpiece, traps electrons with high electron temperature in the plasma reaching the workpiece, lowers the substantial plasma potential in the vicinity of the workpiece, As an electromagnetic shield, it is possible to prevent the electromagnetic field from the antenna from reaching the workpiece and improve the throwing power. The grid should be kept at the ground potential together with the vacuum chamber. In addition to using a conductive mesh material or a metal plate having a slit, etc., any grid such as a large number of metal rods arranged in a fence at regular intervals may be used. Can be formed into a form. However, the grid is concentrically formed coaxially with the loop antenna and is incorporated in the vacuum chamber.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
The workpiece surface treatment apparatus includes a vertically long vacuum chamber 11, gas supply means 20 for supplying a raw material gas to the vacuum chamber 11, loop antennas 31, 31... Arranged in a plurality of stages in the vacuum chamber 11, and a matching circuit. Are provided with power supply means 35 for supplying high-frequency power to the loop antennas 31, 31..., And hangers 41, 41. (FIGS. 1 and 2).
[0021]
The vacuum chamber 11 is formed in a vertically long sealed cylindrical shape. A vacuum pump 14 is connected to the lower part of the vacuum chamber 11 via, for example, a conductance valve type throttle valve 12 and an on-off valve 13. Therefore, the vacuum chamber 11 can exhaust the inside to a sufficient degree of vacuum by opening the throttle valve 12 and the on-off valve 13 and operating the vacuum pump 14. That is, the throttle valve 12, the on-off valve 13, and the vacuum pump 14 form an exhaust system of the vacuum chamber 11.
[0022]
The loop antennas 31, 31... Are each formed in a one-turn loop shape. The loop antennas 31, 31... Are connected in parallel by arranging them at equal intervals in the axial direction of the vacuum chamber 11, for example, with an inner diameter d = 800 mm of the vacuum chamber 11 and a diameter D = 250 mm and a vertical interval L = 300 mm. Has been. In the vacuum chamber 11, a conductive grid 16 is incorporated so as to surround the outer periphery of the loop antennas 31, 31..., And the grid 16 is kept at a ground potential together with the vacuum chamber 11.
[0023]
.. Are mounted on the upper part of the vacuum chamber 11. However, in FIG. 1, only two hangers 41, 41... Are shown. Each hanger 41 penetrates the upper surface of the vacuum chamber 11 through an insulating sealing material 42 so as to be rotatable and airtight, and is connected to the motor M outside the vacuum chamber 11. Each hanger 41 is connected to the output of the power supply device 50 via a slip ring (not shown), for example. Therefore, each hanger 41 suspends a long workpiece W from the upper part of the vacuum chamber 11 in the vacuum chamber 11 and arranges the workpiece W around the loop antennas 31, 31. The workpiece W can be rotated via M (in the direction of each arrow in FIG. 2). Further, a positive or negative bias voltage V from the power supply device 50 can be applied to the workpiece W suspended from each hanger 41. Note that each hanger 41 may be rotated alternately one or more times in the forward and reverse directions regardless of FIG.
[0024]
In the gas supply means 20, a mass flow controller 22 is connected to a source gas cylinder 21, and an outlet side of the mass flow controller 22 is connected to an upper portion of the vacuum chamber 11 via an on-off valve 23 and a supply pipe 24. Yes. Therefore, the gas supply means 20 can supply the source gas from the cylinder 21 to the upper part of the vacuum chamber 11 by opening the on-off valve 23 and operating the mass flow controller 22. That is, the vacuum chamber 11 can introduce the raw material gas from the gas supply means 20 from the upper part and discharge it from the lower part through the throttle valve 12, the on-off valve 13, and the vacuum pump 14.
[0025]
The power supply means 35 is configured by attaching a pulse signal generator 35b to a high frequency generator 35a. The output of the high frequency generator 35 a is connected in parallel to the loop antennas 31, 31... In the vacuum chamber 11 through the matching circuit 36. The output of the high-frequency generator 35a is connected to the matching circuit 36 via a coaxial cable, for example, and the matching circuit 36 is housed in a shield box 36a that is connected to the ground potential integrally with the vacuum chamber 11.
[0026]
The matching circuit 36 is constructed by adding capacitors C3 on the return side of the loop antennas 31, 31... To an inverted L-type impedance matching circuit composed of coils L1 and capacitors C1 and C2. That is, the matching circuit 36 performs impedance matching of the high frequency generator 35a and the loop antennas 31, 31 through the coil L1, capacitors C1, C2, and both ends of the loop antennas 31, 31 through the capacitors C1, C3. The ground voltage can be evenly aligned. On the other hand, the power supply means 35 intermittently operates the high frequency generator 35a by the pulse signal generator 35b, intermittently supplies the high frequency power to the loop antennas 31, 31,. Turn into plasma.
[0027]
The source gas in the vacuum chamber 11 is supplied with high frequency power at intervals L by the loop antennas 31, 31..., And can achieve a uniform plasma density n with respect to the height direction H of the vacuum chamber 11 ( Curve 2 in FIG. However, in FIG. 3, curves 1 and 1 indicate the plasma density n by the upper and lower loop antennas 31 and 31 separated by an interval L, and curve 2 indicates the plasma density n corresponding to the sum of the curves 1 and 1. ing. The loop antennas 31, 31... Are each made into a one-turn loop antenna to reduce the high-frequency resistance, and the ground voltages at both ends are made uniform through the capacitors C1 and C3 of the matching circuit 36 so as to be evenly aligned. The plasma potential of the plasma in the vacuum chamber 11 can be kept low. Note that the grid 16 in the vacuum chamber 11 can capture electrons in the plasma and further lower the plasma potential in the vicinity of the workpieces W, W.
[0028]
For example, the power supply means 35 intermittently supplies high-frequency power to the loop antenna every intermittent period T (repetition frequency 1 / T≈0.1 to 10 kHz) with an operation period Ta = 0.25T and a stop period Tb = 0.75T. Are supplied to 31, 31... (FIG. 4). The operation period Ta is set so that the plasma potential does not become excessive, and the stop period Tb is set shorter than the annihilation time of ions in the plasma and longer than the annihilation time of electrons in the plasma.
[0029]
Such a workpiece surface treatment apparatus operates, for example, as follows.
[0030]
A work W made of a mild steel material having a length of 1 m is hung on the hangers 41, 41... In the vacuum chamber 11, and argon (Ar), tetramethylsilane (Si (CH ₃ ) ₄ , TMS) from the gas supply means 20 is suspended. Acetylene (C ₂ H ₂ ) is switched and introduced into the vacuum chamber 11 as a source gas (FIG. 5). However, the period for introducing argon, the period for introducing only tetramethylsilane, the period for switching tetramethylsilane to acetylene, and the period for introducing only acetylene are the first step S1, the second step S2, the third step S3, the third step, respectively. Let 4 step S4. In the first step S1 to the fourth step S4, the ultimate vacuum of the vacuum chamber 11 is 1.0 × 10 ⁻³ Pa, the high frequency power is 100 W from the power supply means 35, the intermittent period T = 0.1 ms (repetition frequency 1). / T = 10 kHz) and the bias voltage V from the power supply device 50 = −2.5 kV. Each workpiece W is continuously rotated via the corresponding hanger 41.
[0031]
In the first step S1, 40 sccm of argon is introduced into the vacuum chamber 11 as a raw material gas, and when the internal pressure of the vacuum chamber 11 is maintained at 0.3 Pa, the argon is turned into plasma in the vacuum chamber 11, and the workpiece W is formed by argon ion bombardment. It is possible to remove the corrosive layer and the like on the surface of the workpiece W and perform degassing of the workpiece W by heating.
[0032]
In the second step S2, when the raw material gas introduced into the vacuum chamber 11 is changed to tetrascylsilane 30 sccm and the internal pressure of the vacuum chamber 11 is 0.3 Pa, an SiC intermediate layer F1 is formed on the surface of the workpiece W. (FIG. 6).
[0033]
In the third step S3, tetramethylsilane is gradually switched to acetylene. However, tetramethylsilane is decreased by 5 sccm, for example, every minute, and acetylene is increased by 15 sccm, and finally tetramethylsilane is 0 sccm and acetylene is 90 sccm. Tetramethylsilane and acetylene may be continuously decreased and increased, respectively. At this time, a dislocation layer F2 in which the silicon composition ratio Si / C gradually decreases can be formed on the intermediate layer F1 of the workpiece W.
[0034]
In the fourth step S4, when acetylene 150 sccm is introduced into the vacuum chamber 11 and the internal pressure of the vacuum chamber 11 is 0.4 Pa, an amorphous diamond-like carbon film F3 can be formed on the dislocation layer F2 of the workpiece W. .
[0035]
As described above, through the first step S1 to the fourth step S4, the thin film F composed of the intermediate layer F1, the dislocation layer F2, and the diamond-like carbon film F3 can be formed on the surface of the work W. An example of the quality of the thin film F is shown in FIG. That is, in the longitudinal direction of the workpiece W, the difference in film thickness of the thin film F is 15% or less (FIG. 7A), and there is almost no deviation in the hardness of the thin film F (FIG. 7B). A uniform thin film F could be formed over the entire length. However, in the same figure, the i-th axis (i = 1, 2,...) Refers to each hanger 41 in FIG.
[0036]
In the first step S1, if the bias voltage V> 0, the workpiece W can be cleaned and degassed by electron irradiation instead of argon ion bombardment. However, the bias voltage V at this time can be improved by pulsing instead of direct current to improve the electron irradiation effect.
[0037]
[Other embodiments]
The vacuum chamber 11 accommodates a large number of loop antennas 31, 31... In an upper and lower multistage at intervals L ≦ 1.2 to 1.5D, thereby arbitrarily increasing the overall length to correspond to a longer work W. (FIG. 8). At this time, in addition to the lower exhaust system composed of the upper source gas supply line 24, the throttle valve 12, the on-off valve 13, and the vacuum pump 14, these sets have an intermediate height. By adding also to the position, the uniformity of the plasma density in the height direction of the vacuum chamber 11, that is, in the longitudinal direction of the workpiece W can be improved. Further, the loop antennas 31, 31... Are preferably grouped so as to satisfy a group of maximum distances Lm = (a−1) L ≦ λ / 10 and correspond to individual matching circuits 36. This is because when the maximum distance Lm> λ / 10, it is difficult to make the excitation phases of the loop antennas 31 connected in parallel to the common matching circuit 36 substantially the same. In the above equation, a is the number of groups of loop antennas 31, 31... Connected in parallel, λ is the wavelength of the high frequency power from the power supply means 35, and FIG. 8 is illustrated as a = 6. Yes.
[0038]
In FIG. 8, the power supply means 35 is provided with a high frequency generator 35 a for each matching circuit 36. The high frequency generators 35a and 35a detect the phase difference δ on the output side of the matching circuits 36 and 36 via the phase difference detection circuit 35c, thereby generating the high frequency power generated so that the phase difference δ = 0. Phase matching control is performed.
[0039]
In the above description, the source gas can be arbitrarily selected depending on the content of the reforming process applied to the workpiece W. That is, the present invention can be applied to any film thickness and film quality coating treatment for a long workpiece W, as well as any modification treatment including nitriding, carburizing, etc., regardless of the surface shape of the workpiece W. A uniform reforming process can be realized over the entire length of the workpiece W.
[0040]
When the grid 16 in the vacuum chamber 11 is able to obtain a sufficiently high plasma density and a small plasma potential by intermittently supplying high frequency power from the power supply means 35 to the loop antennas 31, 31,. This can be omitted. The same applies to the pair of the source gas supply pipe 24 and the exhaust system at the intermediate height position in FIG. 8, and a part or all of them can be omitted.
[0041]
Moreover, since this invention can suppress the temperature rise of the workpiece | work W in process extremely, it is very suitable also for the modification | reformation process of a mild steel material or a stainless steel material.
[0042]
【The invention's effect】
As described above, according to the first invention of this application, the high-frequency power is supplied to the loop antenna arranged in a plurality of upper and lower stages in the vertically long vacuum chamber, and the source gas supplied from the upper portion of the vacuum chamber is converted into plasma. By modifying the workpiece suspended from the upper part of the vacuum chamber, the plasma density in the height direction in the vacuum chamber can be made uniform, so the surface of the long workpiece is made uniform over the entire length. There is an excellent effect that it can be modified.
[0043]
According to the second invention, the first invention is easily implemented by providing a vertically long vacuum chamber, a gas supply means, a plurality of loop antennas, a power supply means, and a hanger that suspends a workpiece. Can do.
[Brief description of the drawings]
1 is a schematic system diagram of the overall configuration. FIG. 2 is a cross-sectional view of the main part of FIG. 1. FIG. 3 is an operation explanatory diagram (1).
[Fig. 4] Operation explanatory diagram (2)
FIG. 5 is an operation explanatory diagram (3).
6 is a cross-sectional view of the structure of the thin film. FIG. 7 is a table of quality data of the thin film. FIG. 8 is a diagram corresponding to FIG.
W ... Work 11 ... Vacuum chamber 16 ... Grid 20 ... Gas supply means 31 ... Loop antenna 35 ... Power supply means 36 ... Matching circuit 41 ... Hanger

Claims (7)

When surface-treating a long workpiece housed in a vacuum chamber, source gas is supplied from the top of a vertically long cylindrical vacuum chamber and discharged from the bottom , and is equidistantly spaced vertically in multiple stages in the axial direction of the vacuum chamber. The loop antennas to be arranged are connected in parallel, and the high-frequency power from the power supply means is supplied to the loop antenna through a matching circuit that uniformly equalizes the ground voltage at both ends of the loop antenna, and the raw material gas is turned into plasma from the upper part of the vacuum chamber A surface treatment method for a workpiece, characterized in that the surface of the workpiece to be suspended and disposed around the loop antenna is subjected to a modification treatment over the entire length . The surface treatment method of a work according to claim 1, wherein placing the multiple workpieces to the loop antenna and coaxial concentric around the loop antenna.   The work surface treatment method according to claim 1, wherein the work is rotated. A vertically long cylindrical vacuum chamber, a gas supply means for supplying a raw material gas to the upper portion of the vacuum chamber, a loop antenna arranged in parallel at equal intervals in the upper and lower stages in the axial direction in the vacuum chamber, it comprises a power supply means for supplying high frequency power to the loop antenna through the matching circuit, and a hanger to place around the loop antenna from the top of the vacuum tank suspended from the workpiece long, the The matching circuit uniformly equalizes the ground voltage at both ends of the loop antenna, and the vacuum chamber discharges the source gas from the lower part, and the source gas is turned into plasma by the high-frequency power from the loop antenna, so that the surface of the workpiece is lengthened. A surface treatment apparatus for a workpiece, characterized by performing a reforming treatment over the entire surface. The workpiece surface treatment apparatus according to claim 4, wherein a bias voltage is applied to the workpiece suspended from the hanger. In the vacuum chamber, a grid is provided between the loop antenna and the workpiece to keep the ground potential , and the grid traps electrons in the plasma reaching the workpiece and also serves as an electromagnetic shield for the loop. electromagnetic field surface treatment device of a work according to claim 5, wherein that you prevent spanning the workpiece from the antenna. It said power supply means, for 4 to claim, characterized in that by intermittently supplying the high frequency power surface treatment device of a work according to claim 6.

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