JP2004250784A - Sputtering system, mixed film produced by the system, and multilayer film including the mixed film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering system for producing a mixed film having a stoichiometrically perfect composition and a refractive index matched with a set value without reducing a film deposition rate, to provide a mixed film produced by the sputtering system, and to provide a multilayer film including the mixed film. <P>SOLUTION: The sputtering system 100 has a rotatably supported cylindrical substrate holder 9, and a substrate 10 mounted on the outer circumferential face of the substrate holder 9 at the inside of a vacuum tank 1. The inside of the vacuum tank 1 is provided with a first film deposition area A and a second film deposition area B. The first film deposition area A is provided with a first sputtering source 35 and a first plasma generator 51. The second film deposition area B is provided with a second sputtering source 36 and a second plasma generator 52. The first sputtering source 35 and the first plasma generator 51 are physically separated. Also, the second sputtering source 36 and the second plasma generator 52 are physically separated. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a sputtering apparatus mainly used for manufacturing a dielectric thin film for an optical element, a mixed film manufactured by the sputtering apparatus, and a multilayer film including the mixed film.

  Conventionally, electron beam evaporation has been widely used as a method for producing a multilayer film used for a dielectric thin film for an optical element. Recently, there is an increasing use of sputtering methods with high accuracy of film thickness control and stable film formation.

As the material for the multilayer film, oxides such as SiO ₂ , Ta ₂ O ₅ , and TiO ₂ are widely used. However, in the conventional sputtering method, the sputtering yield of these oxides is small and the film formation rate is low. Therefore, there was a problem that productivity was low. In addition, since the oxide target is insulative, it is necessary to use a high-frequency sputtering method. However, the high-frequency sputtering method has problems that the apparatus cost is high and the productivity is low because the film forming speed is low.

  In order to increase the deposition rate, it is conceivable to use a direct current (DC) sputtering method having a high sputtering rate. In order to form an oxide film, from the viewpoint of film formation speed, DC is formed using a metal target or an incomplete oxide target (a target in which oxygen is lost from the stoichiometric ratio) and oxygen gas. Reactive sputtering can be used. However, in this case, the target surface is oxidized by oxygen gas during the film formation to become an insulator, and the film formation speed is greatly reduced or the discharge becomes unstable. It was necessary to keep the surface constant.

  In order to solve the above-mentioned problem, a discharge voltage is alternately supplied to a pair of cathodes using a direct current (AC) power source to prevent charge accumulation on the target, thereby stabilizing discharge and increasing the sputtering rate. A double magnetron sputtering method and a twin magnetron sputtering method are disclosed (for example, refer to Patent Document 1).

  In addition, a method of forming an oxide film using plasma instead of oxygen gas is also disclosed (see, for example, Patent Document 2). However, in the method described in Patent Document 2, since the target unit and the plasma supply unit are not partitioned from each other and the discharge is combined, the target surface is insulated by oxygen gas during film formation. The problem that the film forming speed is greatly reduced cannot be completely solved.

  Further, recent optical elements, in particular, various filters and light emitting elements used for optical communication, are required to have higher functions than conventional ones. For example, in a thin-film interference filter, generally, a high-refractive index film and a low-refractive index film alternately stacked are mainly used, but only a high-refractive index film and a low-refractive index film are stacked alternately. The problem is that ripples occur in the filter characteristics (for example, the wavelength dependence of the refractive index). In order to solve this problem, it has been proposed to stack a plurality of intermediate layers having a refractive index intermediate between the refractive index of the high refractive index film and the refractive index of the low refractive index film in the multilayer film. By providing this intermediate layer, it is possible to significantly reduce ripples and reduce the total number of layers. However, in order to manufacture the intermediate layer, it is necessary to use a third material having a refractive index different from that of the high refractive index film and the low refractive index film as a target, and from the necessity of attaching three types of targets, The size of the apparatus becomes large, and cost increases become a problem.

  In order to solve the above problem, if a mixed film in which a high refractive index material and a low refractive index material are mixed can be formed so as to exhibit a desired refractive index as an intermediate layer, a target for forming the intermediate layer Can be eliminated, and the cost can be reduced. Further, by laminating a plurality of the intermediate layers, a multilayer film having advanced optical characteristics required with a small number of layers can be manufactured, and productivity is improved.

  For example, as a method for forming the mixed film, a so-called co-sputtering method is known in which appropriate two types of targets are discharged simultaneously in a limited region and the two types of materials are mixed to form a mixed film. (For example, see Non-Patent Document 1). However, if a mixture film is formed by simultaneously discharging both targets with different refractive indexes by the co-sputtering method, there is a problem that the reproducibility of the film composition is deteriorated due to cross-contamination between the two targets. However, it cannot be said that there is always a common condition for carrying out stable and high-speed sputtering for both target materials, and there has been a problem in mass production in terms of discharge stability and yield.

  In addition, a co-sputtering method using a double magnetron sputtering method or a twin magnetron sputtering method can also be used in order to stabilize the discharge and increase the deposition rate. However, even in this co-sputtering method, it is necessary to realize a stable discharge condition and a high film formation rate for a plurality of different material targets in the same vacuum chamber at the same time, but such a condition does not necessarily exist. However, it is difficult to form a film with good reproducibility because it is not optimal for each target.

  In addition, in order to increase the deposition rate, a thin film of about one atomic layer of metal is first formed by sputtering, and this is efficiently oxidized by physically separated oxygen gas plasma to form an oxide. A high-speed mixed film manufacturing method called a so-called metamode method or radical assist sputtering method is disclosed (see, for example, Patent Document 3 or 5).

  A sputtering apparatus in the case of using this meta mode method or radical assist sputtering method will be described with reference to FIG. FIG. 3 is a schematic plan view showing the configuration of the sputtering apparatus described in Patent Document 3. This sputtering apparatus 300 is provided in a vacuum chamber 101 with a cylindrical substrate holder 109 and an outer peripheral surface of the substrate holder 109. And each substrate 110 is supported so as to be rotatable about the central axis of the substrate holder 109.

  Inside the vacuum chamber 101, the first sputtering source 135 including the first cathode 121 and the first target 131 installed before the first cathode 121, and the second cathode 122 and the second cathode 122 are installed inside. A second sputter source 136 composed of the second target 132 and a plasma generator 151 are provided apart from both sputter sources 135 and 136. Further, a first shutter 141 and a first shutter 142 for starting and stopping the film formation are provided in the film forming directions of the first sputtering source 135 and the second sputtering source 136. Furthermore, in the vacuum chamber 101, partition plates (shielding plates) 171 and 172 for separating each sputtering source and the plasma generator are provided.

  When the mixed film is formed by the sputtering apparatus 300 of FIG. 3, a film in which metal is mixed by the first sputtering source 135 and the second sputtering source 136 is formed on the substrate and then formed by the plasma generator 51. It is necessary to form an oxide film by reacting a reactive gas such as oxygen radical with a film in which this metal is mixed.

  However, the degree of oxidation of the metal largely depends on the reactivity of the metal material. When an oxide mixed film is produced by oxidizing two kinds of metals that are greatly different in reactivity with the reactive gas, There are large restrictions on selection. That is, a highly reactive metal is sufficiently oxidized to become a complete oxide having a stoichiometric ratio, while a less reactive metal is not sufficiently oxidized and remains partially reduced. At the same time, it was difficult to obtain an oxide mixed film having a stoichiometrically complete composition. For this reason, the formed oxide mixed film becomes an absorption film having a large extinction coefficient, the refractive index expected from the mixing ratio is large and deviates from the design value, or both metals are completely oxidized. There has been a problem that the film formation rate is reduced.

  In addition, an apparatus is disclosed in which a substrate is installed around a drum-type rotating cylinder, and an oxide multilayer film is formed using two targets and one oxidation source while rotating the drum (for example, a patent). Reference 4). However, even in this method, compared to the method described in Patent Document 3, although there is a difference that ions are mainly used for the oxidation reaction, there is a difference in reactivity between the two target materials. 3 has the same problem as the method described in 3.

JP-A-4-325680 Japanese National Patent Publication No. 8-511830 JP-A-11-256327 JP-A-3-229870 JP-A-11-279758 R. Laird and one other, “Cosputered films of mixed TiO 2 / SiO 2”, J. Am. Vac. Sci. Technol. 1992, A10 (4), p. 1908-1912

  The present invention is manufactured from a sputtering apparatus for manufacturing a mixed film having a stoichiometrically perfect composition and a refractive index that matches a design value without reducing the film forming speed, and the sputtering apparatus. It is an object of the present invention to provide a mixed film and a multilayer film including the mixed film and having characteristics matching a design value, for example, reflection performance.

  The present invention is a sputtering apparatus having a cylindrical substrate holder rotatably supported in a vacuum chamber, and a substrate mounted on an outer peripheral surface of the substrate holder, wherein the vacuum chamber includes the There are a first film formation area and a second film formation area for forming a film on a substrate, and the first film formation area includes a first cathode and a first cathode held by the first cathode. A first sputtering source composed of one target and a first plasma generator adjacent to the first sputtering source. The second film formation area includes a second cathode and the second sputtering source. And a second plasma generator adjacent to the second sputtering source, the first sputtering source, and the first sputtering source. The second generator is physically separated from the plasma generator and is To provide a sputtering device, characterized in that Tsu is data source and said second plasma generators are physically separated.

  Further, the present invention is a sputtering apparatus having a disk-shaped substrate holder rotatably supported in a vacuum chamber, and a substrate mounted on the disk of the substrate holder, the vacuum chamber, A first film formation area and a second film formation area for forming a film on the substrate are provided, and the first film formation area is held by the first cathode and the first cathode. A first sputtering source including a first target; and a first plasma generator adjacent to the first sputtering source. The second deposition area includes a second cathode and the first sputtering source. A second sputtering source comprising a second target held by two cathodes, and a second plasma generator adjacent to the second sputtering source, the first sputtering source and the first sputtering source. Physically separated from the plasma generator and the second That is physically separated from the sputtering source and said second plasma generator to provide a sputtering apparatus according to claim.

Moreover, this invention provides the mixed film manufactured by repeating the following operation on the said board | substrate using the said sputtering device.
In the first film formation area, a conductive material that is the first target material is formed by sputtering in the first sputtering source, and the formed film is reacted by the first plasma generator, Next, in the second film formation area, a conductive material as the second target material is formed by sputtering in the second sputtering source, and the formed film is reacted by the second plasma generator. about.

  The present invention also provides a multilayer film including the mixed film.

  By using the sputtering apparatus of the present invention, a mixed film having a stoichiometrically complete composition and a refractive index that matches the design value can be formed without reducing the film formation speed. By laminating the films, it is possible to produce a high-performance multilayer film, particularly an optical multilayer film, having characteristics that match the design values.

  Hereinafter, preferred embodiments of a sputtering apparatus of the present invention, a mixed film produced by the sputtering apparatus, and a multilayer film including the mixed film will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic plan view showing a configuration of a sputtering apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic plan view showing a configuration of a sputtering apparatus according to another embodiment of the present invention.

  A sputtering apparatus 100 shown in FIG. 1 has a cylindrical substrate holder 9 and a substrate 10 provided on the outer peripheral surface of the substrate holder 9 in the vacuum chamber 1, and each substrate 10 is the center of the substrate holder 9. This is a sputtering apparatus having a structure that is rotatably supported around an axis.

  A vacuum chamber 1 serving as a reaction chamber is connected to an exhaust pump (not shown), and a low pressure necessary for sputtering can be obtained by sucking the vacuum chamber 1 with an exhaust pump. Further, the vacuum chamber 1 is provided with a gas supply means for supplying a sputtering gas (not shown) and a loading door.

  As shown in FIG. 1, the substrate holder 9 is rotated in the direction of the arrow at a constant speed (for example, 100 rpm) by a rotation driving device (not shown). Inside the vacuum chamber 1, there are a first film formation area A and a second film formation area B so that different types of films can be formed on the substrate 10 by rotating the substrate holder 9. It has become. For example, a low refractive index film can be formed in the first film formation area A, and a high refractive index film can be formed in the second film formation area B.

  In the first film-forming area A, a first sputtering source 35 including a first cathode 21 and a first target 31 held by the first cathode 21, and a first sputtering source 35 are adjacent to each other. A first plasma generator 51 driven by microwave power is installed. The first cathode 21 is a so-called AC power source or DC pulse power source that alternately supplies a discharge voltage to a pair of cathodes to prevent charge accumulation on the target, thereby stabilizing discharge and increasing the sputtering rate. It may be a double magnetron cathode. In addition, as microwave discharge for plasma generation used in the plasma generator, ECR discharge which is microwave discharge having high discharge density is used, or dielectric coupling or capacitive coupling type high frequency is used instead of microwave discharge. Discharge can be used.

  In the first film formation area A, the substrate holder 9 is rotated so that the material of the first target 31 is first formed on the substrate by the first sputtering source 35 and then the film is formed. The film is reacted by the adjacent first plasma generator 51 to form a dielectric film.

  Although the first sputter source 35 and the first plasma generator 51 are adjacent to each other, they need to be physically separated (separated) from each other. Adjacent does not mean that they are completely adjacent to each other, but means that no apparatus that affects film formation is installed between them. The physical separation means that the reactive gas generated from the first plasma generator 51 is not diffused so much as to affect the discharge of the first target 31, and stable sputter deposition is possible. Means that they are placed apart. For this purpose, it is preferable to provide separation means such as a partition plate 61, an atmosphere separation cover 71, and an exhaust port 81 as will be described later.

  A partition plate 61 is installed between the first sputtering source 35 and the first plasma generator 51, and the reactive gas decomposed and generated by the first plasma generator 51 is on the surface of the first target 31. This prevents contamination and insulation. Further, an atmosphere separation cover 71 is installed between the first plasma generator 51 and the vacuum chamber 1, and contamination in the vacuum chamber 1 due to the reactive gas decomposed and generated by the first plasma generator 51 is prevented. It is preventing. In addition, an exhaust port 81 is provided at the rear part of the first plasma generator 51, and the reactive gas decomposed and generated from the first plasma generator 51 is effectively exhausted to contaminate the vacuum chamber 1. Is preventing. Further, the partition plate 61 and the atmosphere separation cover 71 also have an effect of suppressing instability of discharge due to electrical interference between the sputter discharge and the plasma discharge.

  In FIG. 1, a second film formation area B is installed at a position away from the first film formation area A in the vacuum chamber 1, and the second film formation area A is the same as the first film formation area A. A second sputtering source 36 comprising a cathode 22 and a second target 32, a second shutter 42, a second plasma generator 52, a partition plate 62, an atmosphere separation cover 72, and an exhaust port 82 are installed. Similarly to the first sputtering source 35, the second sputtering source 36 and the second plasma generator 52 need to be partitioned from each other.

  FIG. 1 shows an example in which a plurality of substrates 10 are mounted on the outer periphery of a substrate holder 9 having a cylindrical shape. However, when a large substrate having a substrate diameter or side length exceeding 6 inches (152.4 mm) is used, a disk-shaped substrate holder 9 as shown in FIG. It is preferable to mount it on the disk from the viewpoint of the film thickness of the formed film and the stability of the film quality.

  4 and 5 are schematic plan views showing the configuration of the sputtering apparatus according to another embodiment of the present invention of FIGS. 1 and 2, respectively. 4 and 5, the partition plates 61 and 62 in FIGS. 1 and 2 are the partition spaces 63 and 64, respectively. With such a configuration, the first sputter source 35 and the first plasma generator 51 can be more reliably partitioned from each other, and the second sputter source 36 and the second plasma generation can be separated. It is possible to partition the container 52 from each other.

Next, a case where a dielectric film having a relatively low refractive index (hereinafter referred to as an L film) is formed using the film forming apparatus of FIG. 1 or FIG. Here, the dielectric film means an oxide film, a nitride film, an oxynitride film, a fluoride film, or the like. Specific examples of the L film include SiO ₂ and SiN _x O _y (x <y). Further, it is preferable to use a conductive material capable of DC sputtering as a target material for sputtering film formation from the viewpoint of film formation speed, and specifically, Si or SiO _x which is an oxygen deficient material can be used. . Here, first description will be given of a case where the SiO ₂ film by using the sputtering apparatus 100 of FIG. 1 in a single layer forming the L film.

In FIG. 1, a Si (B-doped conductive crystal) target is set on a first target 31. The substrate 10 is mounted on the substrate holder 9 and the inside of the vacuum chamber 1 is evacuated to a high vacuum of 10 ⁻⁴ Pa or less. Next, the substrate holder 9 is held at a predetermined rotational speed, for example, 100 rpm, Ar gas is introduced while the first shutter 41 is closed, DC power is supplied to the first cathode 21, and the first target 31 Start pre-sputtering. The number of revolutions is preferably as high as possible from the viewpoint of film formation speed, but is preferably 100 to 300 rpm from the viewpoint of mechanical reliability. Next, oxygen gas is introduced into the first plasma generator 51 while the first shutter 41 is closed, oxygen gas plasma is generated by ECR discharge which is a kind of microwave discharge, and then the first shutter 41 is closed. And oxygen gas plasma is diffused on the substrate 10. With these preparations, it is possible to simultaneously condition the surface of the Si target (cleaning and stabilization) and clean the substrate with a reactive gas (mainly removal of organic substances).

When the discharge current and voltage of the Si target are constant and the target surface is stabilized, the first shutter 41 is opened while the substrate holder 9 is rotated in the direction of the arrow in FIG. Start the membrane. First, a Si metal film, which is a first target material, is formed by sputtering, and then the Si metal film is oxidized by oxygen gas plasma generated from the first plasma generator 51, and the film formation and oxidation are alternately performed. As a result, a SiO ₂ film, which is an L film, is laminated on the substrate 10. When the thickness of the SiO ₂ film reaches a predetermined thickness, the shutter 41 is closed and film formation is stopped.

The thickness of the Si metal layer formed by sputtering at a time (one rotation) is approximately 1 atomic layer or less from the viewpoint of allowing the oxidation reaction in the first plasma generator 51 to proceed completely. The electric power supplied to the cathode 21 and the rotation speed of the substrate holder 9 are set. For example, in the case of a Si metal film, one atomic layer has a thickness of about 1.5 angstroms, and the power supplied to the first cathode 21 is 1 to 10 (W / cm ² ). At this time, the density of the oxygen plasma generated by the first plasma generator 51 is preferably high in order to obtain an oxide film having a stoichiometrically complete composition by causing the oxidation reaction to proceed completely. However, in order to prevent the reactive gas (oxygen) contamination on the surface of the adjacent first target 21 and to obtain a stable sputter discharge, it is better to keep it low. Therefore, it is preferable to experimentally determine the oxygen gas flow rate to be used and the microwave and high-frequency power for generating plasma based on the balance between the film quality and the film formation speed.

  In the present invention, as a method for suppressing insulation of an adjacent target surface due to diffusion / contamination of a reactive gas such as excited oxygen decomposed and generated in the plasma generator and instability of the resulting discharge, A method of partitioning between the first plasma source 35 and the first plasma generator 51 by a partition plate 61 is used. Further, an atmosphere separation cover 71 is installed between the first plasma generator 51 and the vacuum chamber 1 to prevent diffusion of the reactive gas decomposed and generated by the first plasma generator 51. Further, an exhaust port 81 is provided at the rear of the first plasma generator 51, and the reactive gas decomposed and generated from the first plasma generator 51 is effectively exhausted to diffuse the reactive gas. It is preventing. Further, by using the so-called double magnetron method or twin magnetron method using AC discharge, it is possible to minimize the influence of the diffusion of the reactive gas.

  Examples of the reactive gas include oxygen, nitrogen, carbon dioxide, and nitrogen dioxide in that oxidation and nitridation can be performed efficiently and accurately, and the optical characteristics of the dielectric formed by the reaction can be improved. , Ammonia, water, hydrogen and the like are preferably used.

Next, a method of forming a dielectric film (hereinafter referred to as “H film”) having a relatively high refractive index using the film forming apparatus of FIG. 1 or FIG. 2 will be described. Specific examples of the H film include TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₃ , Hf ₂ O ₅ , ZrO ₂ , Y ₂ O ₃ , ZnO, and CeO ₂ . In addition, it is preferable to use a conductive material as a target material to be sputtered to form the dielectric film from the viewpoint of film formation speed. Specifically, Ti, Ta, Nb, Hf, Zr, Y, Examples thereof include Zn, Ce, and TiO _x which is an oxygen-deficient material. The TiO ₂ film can be formed as a single layer using the same method as that for the SiO ₂ film as described above.

That is, in FIG. 1, a metal Ti target is installed on the second target 32. The substrate 10 is mounted on the substrate holder 9 and the inside of the vacuum chamber 1 is evacuated to a high vacuum of 10 ⁻⁴ Pa or less. The substrate holder 9 is held at a predetermined rotational speed, for example, 100 rpm, Ar gas is introduced with the second shutter 42 closed, DC power is supplied to the second cathode 22, and the pre-sputtering of the second target 32 is performed. To start. The number of rotations is preferably as high as possible from the viewpoint of film formation speed, but is preferably 100 to 300 rpm from the viewpoint of mechanical reliability. Next, oxygen gas is introduced into the second plasma generator 52 while the second shutter 42 is closed, then microwave power is applied to generate oxygen gas plasma, the second shutter 42 is opened, and the substrate 10 is exposed. To diffuse oxygen gas plasma. With these preparations, the surface of the Ti target can be conditioned (cleaning and stabilization) and the substrate can be cleaned with a reactive gas (mainly removal of organic substances) at the same time.

When the discharge current and voltage of the Ti target are constant and the target surface is stabilized, the second shutter 42 is opened while the substrate holder 9 is rotated in the direction of the arrow in FIG. Start the membrane. First, a Ti metal film, which is the second target material, is formed by sputtering, and thereafter, an oxidation reaction of the Ti metal film proceeds by oxygen gas plasma generated from the second plasma generator 52, and the film formation and oxidation are alternately performed. As a result, a TiO ₂ film that is an H film is laminated on the substrate 10. When the thickness of the TiO ₂ film reaches a predetermined thickness, the second shutter 42 is closed and the film formation is stopped.

Even in the case of the H film, the thickness of the metal Ti layer formed by sputtering once (one rotation) so that the oxidation reaction in the second plasma generator 52 can proceed completely as in the case of the L film. Sets the electric power supplied to the second cathode 22 and the rotational speed of the rotary holder 9 so that it is within about one atomic layer. For example, in the case of metal Ti, one atomic layer is about 1 angstrom, and the power supplied to the first cathode 21 is 0.5 to 5 (W / cm ² ).

Further, a case where a SiO ₂ —TiO ₂ mixed film that is a mixed film of an L film and an H film (hereinafter referred to as an M film) is formed using the film forming apparatus of FIG. 1 or FIG. 2 will be described. First, an Si (B-doped conductive crystal) metal target that is an L film material is installed on the first target 31, and a Ti metal target that is an H film material is installed on the second target 32. The substrate 10 is mounted on the substrate holder 9 and the inside of the vacuum chamber 1 is evacuated to a high vacuum of 10 ⁻⁴ Pa or less. Next, the substrate holder 9 is held at a predetermined rotational speed, for example, 100 rpm, Ar gas is introduced with the first shutter 41 and the second shutter 42 closed, and the first cathode 21 and the second cathode 22 are introduced. Supply power and start pre-sputtering. Next, oxygen gas is introduced into the first plasma generator 51 and the second plasma generator 52 with the first shutter 41 and the second shutter 42 closed, and then microwave power is applied to generate oxygen gas plasma. Generated and diffused onto the substrate 10.

When the discharge current and voltage of both targets are constant and the surfaces of both targets are stabilized, the first shutter 41 and the second shutter 42 are simultaneously moved while the substrate holder 9 is rotated in the direction of the arrow in FIG. Open and start sputter deposition on the substrate 10. In order to prevent a shift in the composition ratio of the mixed film immediately after the start of film formation, it is preferable that the shutters 41 and 42 are opened simultaneously, and the two shutters are integrally moved. The two shutters are preferably opened and closed with the same opening with respect to the first cathode and the second cathode. When the two shutters are opened and film formation is started in this manner, first, a Si metal film as a first target material is formed by sputtering, and thereafter, the Si metal film is oxidized by the first plasma generator 51, and the substrate One layer of an SiO ₂ film, which is an L film, is formed on 10. At this time, the plasma density is adjusted so that the Si metal is completely oxidized by the oxidation reaction in the first plasma generator 51. Subsequently, a Ti metal film as a second target material is formed by sputtering, and then the Ti metal film is oxidized by the second plasma generator 52, and one layer of TiO ₂ film as an H film is formed on the SiO ₂ film. A film is formed. At this time, the plasma density is adjusted so that the Ti metal is completely oxidized by the oxidation reaction in the second plasma generator 51. The film formation / oxidation of the SiO ₂ film and the film formation / oxidation of the TiO ₂ film are alternately performed by the rotation of the substrate holder 9, whereby two kinds of oxides are mixed, and an SiO film that is an M film is formed on the substrate 10. _{A 2-} TiO ₂ mixed film is formed. At this time, since the thickness of one layer of each of the TiO ₂ film and the SiO ₂ film is much thinner than the wavelength of light in question, has a thickness of about 1 atomic layer, a TiO ₂ film and SiO SiO ₂ —TiO ₂ mixture in which TiO ₂ atoms and SiO ₂ atoms are evenly mixed by stacking _two films, and oxides having _two stoichiometrically complete compositions uniform at the atomic level are mixed A film is formed. Further, the refractive index of this mixed film substantially coincides with a value determined by the mixing ratio (composition ratio) of both.

At this time, the mixing ratio (composition ratio) of both can be controlled by relatively changing the ratio of the power supplied to the first cathode 21 and the second cathode 22. Further, an M film having an arbitrary refractive index can be formed by changing the mixing ratio of the two. For example, the L film is a SiO ₂ film (refractive index: 1.46), the H film is a TiO ₂ film (refractive index: 2.36), and the M film is a SiO ₂ —TiO ₂ mixed film, When the installation conditions in the tank 1 are the same in the first film formation area A and the second film formation area B, the power supplied to the first cathode 21 (Si) and the second cathode 22 (Ti) The power ratio is 1: 1 (the power ratio does not mean the ratio of the absolute values of power, but represents the power ratio when the power for forming a single film is set to 1; the same applies hereinafter). By adjusting the thickness, a film having a refractive index of 1.91 can be formed. In addition, a film having a refractive index of 1.69 can be formed by setting the ratio of power supplied to the first cathode 21 (Si) and the second cathode 22 (Ti) to about 3: 1. The power ratio is determined experimentally from the characteristics of the device.

  In addition, a multilayer film including a mixed film having desired optical characteristics can be formed by stacking the H film, the L film, and the M film on the substrate. By providing the M film as the intermediate layer in the multilayer film in which the H film and the L film are alternately stacked, the ripple can be eliminated or the total number of layers can be reduced. Further, if an M film in which a high refractive index material and a low refractive index material are mixed can be formed so as to exhibit a desired refractive index as an intermediate layer, a target for forming the intermediate layer becomes unnecessary, and the work The complexity is reduced and the cost can be reduced. Further, by laminating a plurality of the intermediate layers, it is possible to manufacture a multilayer film having advanced optical characteristics required with a small number of layers, and a significant improvement in productivity can be realized.

  The sputtering apparatus of the present invention has two sputtering areas each having a plasma source and a plasma generator. The number of the sputter areas is not limited to two, but may be three or more, and a sputter apparatus having three or more sputter areas and a mixed film manufactured using the apparatus are also included in the present invention. included.

Since the film formed by the method of the present invention has a stoichiometrically complete composition, it is easy to produce a multilayer film as designed having desired performance. For example, M ₁ film on a glass substrate, M ₂ film (The M _n film (n = natural number),. That show different intermediate film refractive index), H film or rugate filters laminated on L film and the forward A specific example of a multilayer film having a mixed film is given.

  The substrate used in the present invention is not particularly limited, and a glass substrate, a quartz substrate and the like are preferably used. The thickness of the glass substrate is preferably 0.5 to 2 mm in terms of strength. In addition, when the sputtering apparatus of the present invention is used, productivity can be improved by optimizing the shape of the substrate holder with a substrate having a large area and a substrate having a small area. In the case of a substrate having a large area, the substrate holder is preferably a flat type as shown in FIG. The material to be deposited on the substrate may have a film quality anisotropy depending on the flying direction, but a plane type is preferable because such anisotropy can be avoided. When the substrate is circular, the area of the substrate is preferably 127 to 203.2 mm in diameter.

  The substrate with a multilayer film (multilayer film element) in the present invention is a low reflection film, edge filter (infrared reflection filter, ultraviolet reflection filter, red, etc.) used for applications such as displays, projectors, lighting equipment, and various camera lens components. It is useful for external ultraviolet reflection filters, visible light reflection filters, etc.), polarizing filters, and the like. In particular, the rugate filter exhibits a smooth and steep frequency dependence with little ripple, and has a high degree of freedom in design, so that it is useful as an optical multilayer interference filter capable of selecting the wavelength of transmitted light or reflected light.

In addition, according to the present invention, as the mixed film, a crystalline double oxide film that requires a high temperature of 900 ° C. or higher in a normal sputtering apparatus can be formed at a low temperature and with good crystallinity. Examples of using two kinds of metals as the double oxide material include LiNbO ₄ and BaTiO _4. These have a structure in which the constituent metal elements are alternately arranged. Therefore, by using the sputtering apparatus of the present invention in which very thin layers of about one atomic layer are stacked one by one, a film having good crystallinity with few defects can be formed at a low temperature.

Further, according to the present invention, as an example of using three types of the metal as a complex oxide _{material, YBa 2 Cu 3 O x (} X = 6~7.) And the like. Although this material is useful for high-temperature superconducting films, this high-temperature superconducting film can also be formed at a low temperature by using the sputtering apparatus of the present invention, and a film with a composition ratio between elements aligned as designed. Can be formed.

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to this.
A four-layer AR film having the following structure is formed by a method described later and evaluated.

1) Structure of 4-layer AR film Structure of 4-layer AR film: Glass substrate / M ₁ film / M ₂ film / H film / L film Here, glass substrate, M ₁ film, M ₂ film, H film, L film Is as follows, and the film thickness indicates the optical film thickness.
(A) Glass substrate: BK7 (trade name: borosilicate glass), refractive index: = 1.52, size: diameter 125 mm × thickness 0.525 mm
(B) M ₁ film: mixed film of SiO ₂ and TiO ₂ , refractive index = 1.69, film thickness = 106 nm
(C) M ₂ film: mixed film of SiO ₂ and TiO ₂ , refractive index = 1.91, film thickness = 95 nm
(D) H film: TiO ₂ film, refractive index = 2.36, film thickness = 122 nm
(E) L film: SiO ₂ film, refractive index = 1.46, film thickness = 94 nm
In addition, the antireflection film having the above structure has a reflectance within 0.5% over the entire visible light wavelength range of 450 to 700 nm based on optical calculation if each film is a stoichiometrically perfect oxide. I know that

2) Example 1 (Example)
A four-layer AR film is formed using the sputtering apparatus shown in FIG. First, a Si (B-doped conductive crystal) target is installed on the first target 31, and a metal Ti target is installed on the second target 32. A glass substrate 10 is mounted on the substrate holder 9 and the inside of the vacuum chamber 1 is evacuated to 5 × 10 ⁻⁵ Pa at a high vacuum. Next, the substrate holder 9 is rotated at 100 rpm, Ar gas is introduced at 50 sccm while the first shutter 41 and the second shutter 42 are closed, and pre-sputtering is started (ratio of power supplied to the Si target and Ti target). Is 3: 1.) Next, after introducing 100 sccm of oxygen gas into the first plasma generator 51 and the second plasma generator 52 with the first shutter 41 and the second shutter 42 closed, the first plasma generator 51 and Microwave power is applied to the second plasma generator 52 to generate oxygen gas plasma and diffuse it on the substrate 10. The pressure in the vacuum chamber 1 at this time is 0.3 Pa.

When the discharge current and voltage of both targets are constant and the surfaces of both targets are stabilized, the first shutter 41 and the second shutter 42 are opened while the substrate holder 9 is rotated in the direction of the arrow in FIG. Sputter deposition is started on the top. First, Si metal, which is the first target material, is formed by sputtering on the substrate, and then the Si metal is oxidized in the first plasma generator 51 to form an SiO ₂ film, which is an L film, on the glass substrate. . Subsequently, Ti metal as a second target material is formed by sputtering, and then Ti metal is oxidized in the second plasma generator 52, and a TiO ₂ film as an H film is laminated on the SiO ₂ film. At this time, since the thickness of each film is a very thin film of about one atomic layer, it is possible to form a SiO ₂ —TiO ₂ mixed film composed of two oxides that are uniform at the atomic level. Sputter film formation is continued until the film thickness reaches 106 nm. When the film thickness reaches 106 nm, the first shutter 41 and the second shutter 42 are closed, and the film formation of the M ₁ film is stopped.

Next, the power of the first cathode 21 and the power of the second cathode 22 are changed (the ratio of power supplied to the Si target and Ti target is 1: 1), and the first shutter 41 and the second shutter 42 are changed. To start forming the M ₂ film. Even in the case of the M ₂ film, similarly to the M ₁ film, the film thickness of each film is a very thin film of about one atomic layer, and therefore, SiO ₂ —TiO ₂ mixture composed of two oxides which are uniform at the atomic level. A film can be formed. When the film thickness reaches 95 nm, the first shutter 41 and the second shutter 42 are closed, and the film formation of the M ₂ film is stopped.

  Next, the second shutter 42 is opened while the first shutter 41 is closed, and the film formation of the H film is started. When the film thickness reaches 122 nm, the second shutter 42 is closed and the film formation of the H film is stopped.

  Finally, with the second shutter 42 closed, the first shutter 41 is opened and the film formation of the L film is started. When the film thickness reaches 94 nm, the first shutter 41 is closed and the film formation of the L film is stopped. A four-layer AR film is manufactured by the above method.

3) Example 2 (comparative example)
A four-layer AR film is formed using the sputtering apparatus shown in FIG. First, a Si (B-doped conductive crystal) target is installed on the first target 131, and a metal Ti target is installed on the second target 132. The glass substrate 110 is mounted on the substrate holder 109, and the inside of the vacuum chamber 101 is evacuated to 10 ⁻⁵ Pa at a high vacuum. Next, the substrate holder 109 is rotated at 100 rpm, and pre-sputtering is started with the first shutter 141 and the second shutter 142 closed (the ratio of power supplied to the Si target and Ti target is 3: 1). Next, microwave power is applied to the plasma generator 151 while the first shutter 141 and the second shutter 142 are closed, and oxygen gas plasma is generated by ECR discharge and diffused on the substrate 110.

When the discharge current and voltage of both targets become constant and the surfaces of both targets become constant, the first shutter 141 and the second shutter 142 are opened while the substrate holder 109 is rotated in the direction of the arrow in FIG. Sputter deposition is started on the glass substrate 110. First, Si metal as a first target material is sputter-deposited on a substrate, then Ti metal as a second target material is sputter-deposited, and then Si metal and Ti metal are oxidized in a plasma generator, A SiO ₂ —TiO ₂ mixed film is formed. When the film thickness reaches 106 nm, the first shutter 141 and the second shutter 142 are closed, and the film formation of the M ₁ film is stopped.

Next, the power of the first cathode 121 and the power of the second cathode 122 are changed (the ratio of power supplied to the Si target and Ti target is 1: 1), and the first shutter 141 and the second shutter 142 are changed. To start forming the M ₂ film. When the film thickness reaches 95 nm, the first shutter 141 and the second shutter 142 are closed, and the film formation of the M ₂ film is stopped.

  Next, with the first shutter 141 closed, the second shutter 142 is opened, and deposition of the H film is started. When the film thickness reaches 122 nm, the second shutter 142 is closed and film formation of the H film is stopped.

  Finally, with the second shutter 142 closed, the first shutter 141 is opened, and film formation of the L film is started. When the film thickness reaches 94 nm, the first shutter 141 is closed and the film formation of the L film is stopped. A four-layer AR film is manufactured by the above method.

4) Four-layer AR film evaluation The reflectance of the glass substrate with the four-layer AR film produced in Example 1 and Example 2 is measured with a spectrophotometer (manufactured by Hitachi, Ltd .: U4000).

  As a result, the visible light reflectance of the glass substrate with the 4-layer AR film of Example 1 is 0.4%, which is equivalent to the design value, whereas the visible light reflectance of the glass substrate with the 4-layer AR film of Example 2 is Since the oxidation is inadequate and the film is an absorption film, there is a large difference from the design value, and it is confirmed that the AR film as designed is not manufactured.

  Since the sputtering apparatus of the present invention can form a mixed film having a stoichiometrically complete composition and a refractive index that matches the design value without reducing the film formation rate, a Lugate filter, etc. It is useful for the formation of

The plane schematic diagram which shows the structure of the sputtering device which concerns on embodiment of this invention. The plane schematic diagram which shows the structure of the sputtering device which concerns on another embodiment of this invention. The plane schematic diagram which shows the structure of the conventional sputtering device. The plane schematic diagram which shows the structure of the sputtering device which concerns on another embodiment of this invention. The plane schematic diagram which shows the structure of the sputtering device which concerns on another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101: Vacuum tank 9, 109: Substrate holder 10, 110: Substrate 21, 121: 1st cathode 22, 122: 2nd cathode 31, 131: 1st target 32, 132: 2nd target 35 135: first sputter source 36, 136: second sputter source 41, 141: first shutter 42, 142: second shutter 51: first plasma generator 52: second plasma generator 151 : Plasma generator 61, 62: Partition plate 63, 64: Partition space 71, 72, 171, 172: Atmosphere separation cover 81, 82, 83, 84, 181, 182: Exhaust port A: First film formation area B : Second film formation area 100, 200, 300, 400, 500: Sputtering apparatus

Claims (7)

A sputtering apparatus having a cylindrical substrate holder rotatably supported in a vacuum chamber, and a substrate mounted on the outer peripheral surface of the substrate holder,
The vacuum chamber has a first film formation area and a second film formation area for forming a film on the substrate, and the first film formation area includes a first cathode and a first cathode held by the first cathode. A first sputtering source composed of one target and a first plasma generator adjacent to the first sputtering source, and the second film formation area includes a second cathode and a second target held by the second cathode. A second sputtering source, and a second plasma generator adjacent to the second sputtering source,
A sputtering apparatus, wherein the first sputtering source and the first plasma generator are partitioned from each other, and the second sputtering source and the second plasma generator are partitioned from each other. A sputtering apparatus having a disk-shaped substrate holder rotatably supported in a vacuum chamber, and a substrate mounted on the disk of the substrate holder,
The vacuum chamber has a first film formation area and a second film formation area for forming a film on the substrate, and the first film formation area includes a first cathode and a first cathode held by the first cathode. A first sputtering source composed of one target and a first plasma generator adjacent to the first sputtering source, and the second film formation area includes a second cathode and a second target held by the second cathode. A second sputtering source, and a second plasma generator adjacent to the second sputtering source,
A sputtering apparatus, wherein the first sputtering source and the first plasma generator are partitioned from each other, and the second sputtering source and the second plasma generator are partitioned from each other.   The sputtering apparatus according to claim 1 or 2, wherein the first cathode and / or the second cathode are a pair of cathodes to which a discharge voltage is alternately supplied by an AC power source or a DC pulse power source. 4. The sputtering apparatus according to claim 1, further comprising a shutter mechanism that opens and closes at the same opening degree with respect to the first cathode and the second cathode.   The first plasma generator and / or the second plasma generator is a plasma generator for generating plasma by microwave discharge or by dielectric coupling type or capacitive coupling type high frequency discharge. The sputtering apparatus according to item. A mixed film produced by repeating the following operation on the substrate using the sputtering apparatus according to claim 1.
A conductive material, which is a material constituting the first target, is formed by sputtering in the first sputtering source, the formed film is reacted by the first plasma generator, and then the second target material is applied in the second sputtering source. A conductive material to be latticed is formed by sputtering, and the formed film is reacted by the second plasma generator. A multilayer film comprising the mixed film according to claim 6.

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