JPH02294473A - Method and apparatus for thin film formation - Google Patents

Abstract

PURPOSE:To form a thin uniform film free from contamination with impurities on the internal surface of a material body by initiating electric discharge in electrodes provided in a space inside a material body having an opening and sputtering respective surfaces of the above electrodes. CONSTITUTION:In an evacuated chamber 4, a material body 1 having an opening is disposed and electrodes 2, 3 are inserted and disposed in a space enclosed by the surfacer to be coated with thin film, of the material body 1. This material body 1 is moved or rotated along the electrodes 2, 3 via a holder 6 by means of a drive mechanism 8 and a controller 9. Subsequently, a voltage is impressed on the above electrodes 2, 3 by means of an electric power source 5 to initiate electric discharge. By means of sputtering applied to respective surfaces of the electrodes 2, 3 attendant upon the above electric discharge, a thin film is formed on the internal surface of the above material body 1. At this time, it is preferable to monitor, e.g. the thickness of the thin film, the state of electric discharge, the position of the material body 1 and to control impressed voltage, the above movement, electric discharge gas pressure, etc. By this method, thin superior film can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to thin film formation, and more particularly to a thin film formation method and apparatus capable of forming a good thin film on the inner surface of an object having an opening. (Conventional technology) Currently, for the purpose of microanalysis, the development of condensing reflectors for light in the vacuum ultraviolet to soft X-ray/X-ray range is underway in various places. For the purpose of increasing reflectance, a thin film of gold, platinum, etc. (reflection 1!I!) is usually coated.The coating method for this purpose (WI film formation method) is as follows.
There are representative methods described below. (1) Vapor deposition method: The film material is heated and evaporated in a vacuum to form a reflective thin film on the reflective surface of a reflecting mirror placed opposite the vapor deposition source. (2) Subatsuta method: A target is made of a thin film material, and charged particles (e.g. Ar◆ ions, etc.) are generated by discharge.
By sputtering this target, a reflective thin film is formed on the reflective surface of a reflective mirror placed opposite the target. (3) Plating method: The reflective surface is placed in a plating solution, and a thin metal film is plated electrolessly or electrolytically on the reflective surface. [Problems to be solved by the invention] - The reflective surface on which a thin film can be formed by the conventional method described above is a flat surface or a curved surface having a shape close to a flat surface. On the other hand, Walter-type reflectors and tandem-type reflectors have recently attracted attention as reflectors for light in the vacuum ultraviolet to soft X-ray/X-ray region. These reflecting mirrors have a reflecting surface around an axis of rotational symmetry, so to speak, and the reflecting surface is the inner surface of a pipe-shaped object (with a continuously changing inner diameter). In many cases, the aperture diameter of these reflecting mirrors is approximately 10 to 30 m at most (Sadao Aoki, Optics, Vol. 13, p. 18, 1984), and the length of the reflecting mirror (40 to 70 m). , Sadao Aoki (cited above), and Hiroshi Tachibanagi et al., Journal of the Japan Society for Precision Engineering, No. 54
volume, p. 299, 1988). It is difficult to form a reflective thin film on the reflective surface of such a reflective mirror using conventional methods for the following reasons. In evaporation and sputtering methods, the solid angle of the reflection surface from the evaporation source or sputtering source is extremely small. For this reason, the evaporated or sputtered atoms and particles do not reach the reflective surface, making it difficult to form a reflective thin film. Furthermore, even if it were possible to form a thin film, vapor f! The thin film formation rate is faster in areas closer to the spatter source, making it impossible to obtain a uniform reflective film. In the plating method, there is a possibility of impurity contamination of the formed thin film. Generally, a plating solution contains several dozen types of elements. These elements mix into the thin film and cause a decrease in reflectance. The above explanation uses a reflector as an example. However, there are many requests to form a thin film not only on the reflective mirror but also on its inner surface. An example is the lens barrel of an electron microscope. An object of the present invention is to relate to a thin film forming method and apparatus capable of forming a good thin film on the inner surface of an object having an opening, such as a reflecting mirror. [Means for solving the problem] In order to achieve the above object, an object whose inner surface is a thin film forming surface is installed in a vacuum chamber, and the space surrounded by the thin film forming surface of this object (i.e., the space surrounded by the inner surface) is The electrode is inserted into the opening (hereinafter referred to as the inner space) through the opening (see Figure 1). Next, by introducing a gas such as a rare gas into the vacuum chamber and applying a voltage to this electrode, it is possible to Generate a discharge near the e1 pole. Furthermore, means for rotating the object having the surface on which the thin film is to be formed around the electrodes, or means for moving the object up and down along the horizontal direction of the electrodes is provided. [Operation] The disadvantage of the conventional sputtering method is that the sputtering source is located outside the object whose inner surface is the surface on which the thin film is to be formed. The problem was that it was difficult to reach the surface on which the thin film was formed. This drawback can be solved by installing a sputtering source in the space (inner space) surrounded by the surface of the object on which the thin film is to be formed. Moreover, since the particle size of the thin film formed by sputtering is smaller than that of other methods such as vapor deposition, if the present invention is used for reflective AM production, it will be possible to form a reflective thin film with small roughness, which is necessary for the reflective mirror. We can expect the formation of In fact, experiments have confirmed that it is possible to form a thin film with a surface roughness of approximately 0.01 μm at R■8. The electrode inserted into the inner space through the opening described in the previous section plays the role of the splatter source. Due to the voltage applied to this electrode, a discharge of the gas introduced into the vacuum chamber occurs in the inner space of the object, and the electrode surface is sputtered by charged particles generated during the discharge. Sputtered atoms and particles reach the thin film formation surface,
It adheres and a thin film is formed. Here, it is desirable that the entire electrode or its surface be made of the same (or similar composition) material as the thin film to be formed. Alternatively, the thin film formed must be made of a material that does not cause problems with impurity contamination. In addition, the means for rotating the object and moving it up and down as described in the previous section are as follows:
This is a means to improve the uniformity of the thin film formed. As described above, by using the present invention, it is possible to efficiently and uniformly form a thin film free from impurity contamination on the inner surface of an object having an opening, such as a reflecting mirror. , one embodiment of the present invention will be specifically explained. <Example 1> A basic embodiment of the present invention was shown in Part 1. In Fig. 1, an object 1 (object The inner diameter of 1 is
It may change continuously as shown in Figure 1, or it may be uniform throughout. ) is fixed to the holding stand 6. The holding stand 6 is attached to a drive mechanism 8 via an arm 7. As a result, object 1 moves up and down with respect to electrodes 2 and 3.
and rotational movement around the electrodes 2, 3 is possible. These movements, and therefore the drive mechanism 8, are controlled by a controller 9. Electrodes 2 and 3 are inserted into the inner space of object 1 through the opening. A voltage (several 100 volts) is applied to the electrode 2.3 by the power source 5.
~ several KV) is applied. The power supply 5 may be a DC power supply or an AC power supply. It is also possible to use a pulse power source. According to experiments, discharge in the inner space of object 1 is more likely to occur when an AC power source is used than when a DC power source is used. The object 1, electrodes 2, 3, etc. are stored in a chamber 4,
Chamber 4 is evacuated. A discharge gas such as a rare gas is introduced into the chamber 4 through a valve 10. Introducing pressure is 10 Tarr or less. After introducing the above gas. When a voltage is applied between the electrodes 2 and 3 using the m source 5, a discharge occurs at the electrodes 2 and 3 and in their vicinity. The surface of the electrode 2 or 3 is sputtered by the charged particles generated during this discharge, and a thin film is formed on the inner surface of the object 1. Uniform film formation is possible by vertically and rotationally moving the object 1 during discharge using the drive device [8]. Although there are two electrodes in Figure 1, only one electrode may be inserted as long as discharge is possible. According to this embodiment, it is possible to efficiently and uniformly form a thin film free from impurity contamination on the inner surface of the object l. Example 2 In the example shown in FIG. 2, compared to the example shown in FIG.
The shape of the electrode is different. In Example 1, one of electrodes 2 and 3 is a ground electrode. According to experiments, fI1
If poles 2 and 3 are in the inner space of object 1, (in general)
Discharge occurs more easily when the surface area of the ground electrode is larger. For this reason, in this embodiment, the surface area of the electrode l2 on the ground side is increased. In this way, depending on the surface area of the ground side electrode, the surface area of the other electrode facing the ground side electrode, the ratio of the surface areas of both electrodes, and furthermore the electrode spacing between the two electrodes,
The ease with which discharge occurs varies. In all Examples described below, including this Example and Example 1,
Electrode surface area and surface area ratio. The fl pole spacing is variable to obtain the optimum discharge. A portion of the electrode 11 is covered with a sleeve l3 made of an insulator. This is to adjust the surface area of the electrode l1 mentioned earlier. Moreover, this cover allows voltage to be efficiently applied to the exposed portion of the electrode 11 (portion close to the electrode 12), and discharge in the inner space of the object 1 can be more easily performed. Furthermore, since the discharge becomes more localized, the uniform V of thin film formation is improved. Other details are the same as in Example 1. According to this embodiment, it is possible to adjust the electrode surface area, surface area ratio, or electrode spacing, so that an optimal discharge for forming a thin film can be obtained. Furthermore, by covering the electrode with a sleeve, it is possible to efficiently apply voltage to the tip of the electrode. As a result of the above, the optimal discharge for thin film formation can be easily performed, and a better and more uniform thin film can be formed on the surface on which the thin film is to be formed. <Example 3> Depending on the purpose of thin film formation, it is necessary to accurately monitor and control the thickness of the thin film formed. For example, when using a multilayer film as a reflective thin film, the film thickness is 10-4.
It must be controlled in μm units. An example of implementation in such a case is shown in Figure 3. In Figure 3, monitors 14 to 19 are placed around object 1. In this case, monitors 14 and 17, monitors 15 and 18,
Monitors 16 and 19 each work in pairs. For example, the monitor 14 is a light source (e.g., a semiconductor laser) having a specific wavelength (e.g., the wavelength of light that is specifically absorbed by the thin film being formed), and the monitor 17 is a light detector having that wavelength. (For example, photodiode, etc.)
That's fine. In this case, the film thickness and its changes can be determined from the light that passes through the yeast membrane. Monitor 14~
19 is controlled by a controller 2o. In particular, the film thickness is calculated by the controller 20 based on the detection signals from the monitors 17 to 19, and the calculation results are fed back to the power source 5 and the controller 9. As a result, the voltage applied to the electrode 12 or 13 is controlled, and the discharge state or sputtering rate of atoms/particles from the electrode 12 or 13 is controlled. Also, the vertical movement of object 1,
The speed of rotational movement is also adjusted. In this embodiment, the feedback destinations from the controller 20 are both the power source 5 and the controller 9, but the feedback may be sent to only one of them. Further, the type and number of film thickness monitors and their positions are also arbitrary.

The essence of this embodiment is that when forming a thin film on the inner surface of the object 1, the film thickness is monitored and feedback is applied to the forming means to control the film thickness. The other parts are the same as the previous embodiment. According to this embodiment, since it is possible to form a thin film by accurately controlling the film thickness, it is possible to easily form a thin film such as a multilayer film that requires highly accurate film thickness control. <Example 4> It was confirmed through experiments that when object 1 has a small opening, the state of discharge changes rapidly at the opening.
This rapid change in the discharge state may affect the uniformity and surface roughness of the thin film formed on the inner surface of the object 1 near the opening. This example is an example for reducing such an influence. Figure 4 shows an example. In order to clarify the essence of the example, only the parts directly related to the aforementioned impact reduction are illustrated. Although the power supply for generating electric discharge, the upper and lower parts of the object l, the rotational movement mechanism, the gas introduction mechanism, etc. are not shown in FIG. 4, they are of course included in this embodiment. In FIG. 4, dummy pipes 21, 22 are added to object 1 in forming a thin film on the inner surface of object 1. As a result, the area near the opening of object 1 (object 1 and dummy pipe 2)
This prevents sudden changes in the discharge state near the seams (see 1.22), making it possible to form thin films with excellent uniformity and surface roughness. Example 5 Figure 5 shows another example. In place of the dummy pipe shown in Fig. 4, a cover 23 is provided in this embodiment. By using the cover 23, the same effect as in the fourth embodiment can be obtained. The shapes of the dummy pipes 21, 22 and the cover 23 shown in FIGS. 4 and 5 are arbitrary. The rapid change in discharge state that occurs near the opening of object l is caused by the energized electrode (eg, electrode 11) seeing a larger ground plane outside object l. Therefore, in order to prevent this change in the discharge state, it is best to make the external ground plane difficult to see. If the configuration makes it difficult to see the external ground plane near the opening of object l, the fourth
Means other than the dummy pipes 21, 22 and cover 23 shown in FIG. 5 are also included in the present invention. <Example 6> When the electrode is located inside the object 1, discharge is less likely to occur than when it is outside. In such cases, creating a magnetic field in the discharge region facilitates discharge due to electron cyclotron motion. In addition, by creating a magnetic field, the discharge can be performed at a lower gas pressure, and the quality of the thin film formed can be expected to improve. Figure 6 shows an example of the magnetic field formation method.
Discharge area (between electrodes 11.12) by coils 24.25
A magnetic field is formed. A permanent magnet may be used instead of a coil. Further, although the coils 24 and 25 are shown outside the vacuum in FIG. 6, these coils and permanent magnets may be installed inside the vacuum (inside the chamber 1). The other parts are the same as the other embodiments. <Example 7> In Examples 1 to 6, object 1 had two openings, but it is also possible to form a thin film on the inner surface of objects having other shapes using the present invention. ．． An example of this is shown in Figure 7. In FIG. 7, object 26 is a pipe-like object with one end closed. By inserting the electrodes 3 and 11 from the other end of the object 26 and applying a high voltage between the electrodes 3 and 11, a discharge is generated in the inner space of the object 26. During this discharge, the electrode 3 or 11 is sputtered, and the object 26
A thin film is formed on the inner surface of the The object 26 is the electrode 3,1l
Needless to say, it is possible to move up and down against the electrodes and rotate around these electrodes. The other parts are the same as the previous embodiment. As is clear from the examples described so far, if an electrode can be inserted into the inner part of an object having a surface on which a thin film is formed,
It goes without saying that the present invention can be used to form capsules on the inner surface of an object, regardless of its shape. Example 8 When forming a thin film on the inner surface of an object whose inner diameter changes continuously, it may be better to vary the discharge voltage or discharge gas pressure depending on the location. 8th
An example is shown in the figure. In FIG. 8, a sensor 27 is a sensor that monitors the discharge state (for example, the brightness of the discharge). The detection signal from this sensor is analyzed by the controller 28 and the power supply 5 is controlled. For example, the minimum voltage required to generate a discharge at each location is applied to the electrodes 11 or 12. Alternatively, if the sensor 27 is a position sensor, the discharge voltage corresponding to each position is transmitted to the controller 28.
The controller 28 controls the power supply 5 based on the detection signal from the sensor 27. The same thing can be said about discharge gas pressure control. Generally, the smaller the inner diameter, the higher the discharge gas pressure required. Therefore, the discharge state and the position of the object are monitored by the sensor 27, and based on the detected signal, the controller 28 controls the valve 10 to achieve the optimum discharge gas pressure. Although FIG. 8 shows that the power source 5 and the valve 10 are controlled simultaneously, it is also possible to control only one of them. According to this embodiment, since the sputtering speed can be adjusted not only by film thickness control but also by voltage control or discharge gas pressure control, it is possible to form a thin film with good film quality. (For example, monitors 14-19 shown in FIG. 3 can be used in all embodiments.)

〔Effect of the invention〕

According to the present invention, it is possible to form a thin film uniformly and without impurity contamination on the inner surface of an object having an opening, such as a reflecting mirror. Thereby, for example, the reflectance of the reflecting mirror can be significantly improved.

[Brief explanation of drawings]

1 to 8 are all schematic illustrations of an embodiment of the present invention. 1...object, 2...electrode, 3...electrode, 4...
Chamber, 5... Power supply, 6... Holding stand, 7... Arm, 8... Drive mechanism, 9... Controller, 1o
...Bulb, 11...Electrode, 12...Electrode 213
...cover, 14,15,16, 1 roller, 124 sensor, 2 7,18.19...monitor, 20...control 21.
22...Dummy pipe, 23...Hippo, 25...
Coil, 26...Object, 27...Se8...Controller. Collection ￥3 2 -4′. Kokukei ■ Millet b Figure S Ki δ Carp 1re

Claims (1)

[Claims] 1. In forming a thin film on the inner surface of an object having an opening, an electrode is provided in a space surrounded by a surface on which the thin film is to be formed, and a thin film is formed by sputtering the surface of the electrode as a result of electric discharge. A method for forming thin films. 2. In forming a thin film on the inner surface of an object having an opening, an electrode is inserted into the space inside the object, and a thin film is formed by sputtering the electrode surface due to the discharge generated by applying a voltage to the electrode. Formation method. 3. The method for forming a thin film according to item 1 or 2, wherein the thin film is formed while moving the object along the electrode, or rotating it around the electrode, or while performing both movements. 4. The thin film according to item 3, wherein the thickness of the formed thin film is monitored and, based on the monitoring results, any one or more of the voltage applied to the electrode, the movement, and the discharge gas pressure is controlled. Formation method. 5. The thin film forming method according to item 3, wherein the discharge state is monitored and, based on the monitoring result, any one or more of the voltage applied to the electrode, the movement, and the discharge gas pressure is controlled. 6. The method for forming a thin film according to item 3, wherein the position of the object is monitored, and one or more of the voltage applied to the electrode, the movement, and the discharge gas pressure are controlled based on the monitoring result. 7. The thin film forming method according to any one of items 3 to 6, wherein the thin film is formed by forming a magnetic field near the electrode. 8. The thin film forming method according to any one of items 3 to 6, wherein the thin film is formed while preventing a sudden change in the discharge state near the opening of the object. 9. A thin film forming apparatus for forming a thin film by sputtering, characterized in that a sputtering source is provided in a space surrounded by a surface on which a thin film is to be formed. 10. A thin film forming apparatus for forming a thin film by sputtering, characterized in that an electrode is provided through an opening in a space surrounded by a surface on which a thin film is to be formed, and means for applying a voltage to this electrode is provided. Thin film forming equipment. 11. Thin film formation according to item 10, further comprising means for moving the object having the thin film formation surface along the electrode, or means for rotating the object around the electrode, or both means. Device. 12. A means for monitoring the thickness of the thin film to be formed, and controlling any one or more of the voltage applied to the electrode, the movement, rotational movement, and discharge gas pressure for sputtering based on the output signal from this monitoring means. 12. The thin film forming apparatus according to item 11, further comprising means for. 13. Monitoring means for the discharge state; based on the output signal from the monitoring means, any one of the voltage applied to the electrode, the movement, rotational movement, and sputtering discharge gas pressure;
12. The thin film forming apparatus according to claim 11, further comprising means for controlling one or more of the following. 14. Monitoring means for the position of the object; means for controlling any one or more of the voltage applied to the electrode, the movement, rotational movement, and sputtering discharge gas pressure based on the output signal from the monitoring means; 12. The thin film forming apparatus according to item 11, further comprising: 15. Eleventh device provided with means for forming a magnetic field near the electrode
The thin film forming apparatus according to any one of Items 1 to 14. 16. The thin film forming apparatus according to any one of items 11 to 14, further comprising means for reducing changes in discharge state near the opening of the object. 17. A reflecting mirror made by the thin film forming method described in items 1 to 8.