JP5464800B2 - Sputtering apparatus and film forming method - Google Patents

Description

  The present invention relates to a sputtering apparatus for forming a film on the surface of a workpiece.

  2. Description of the Related Art A sputtering apparatus that forms an optical thin film such as an antireflection film on a workpiece to be formed is known. In the sputtering apparatus, the vacuum chamber is filled with a thin sputtering gas, and glow discharge is performed in the vacuum chamber using the target as one electrode. Then, the positive ions of the plasma generated by the glow discharge collide with the target, so that sputtered particles (atoms, molecules) are knocked out of the target, and the sputtered particles are deposited on the work surface to form a thin film. Also known is reactive sputtering in which a reactive gas such as oxygen gas or nitrogen gas is introduced into a vacuum chamber in addition to the sputtering gas to form a compound thin film.

  By the way, although the above-described sputtering apparatus can obtain a certain degree of uniformity in film formation, it cannot be said that the uniformity is sufficiently high in forming an optical thin film. This is because the sputtered particles knocked out from the surface of the target scatter with a fairly high linearity and have a high adhesion probability. As one of measures for improving such film formation, it is conceivable to increase the film formation pressure to scatter the sputtered particles. However, even in this case, the film thickness increases at a position where many sputtered particles are scattered, and it is difficult to obtain a thin film with satisfactory uniformity. Further, since the sputtered particles are scattered with a fairly high linearity, there is a problem that a film cannot be formed on a portion other than the surface facing the target, or only a very thin film is formed.

  The present invention has been made to solve the above-described problems, and can form a film on a workpiece having various shapes with good uniformity. It is an object of the present invention to provide a sputtering apparatus capable of performing the above.

In order to achieve the above object, according to the present invention, in the sputtering apparatus according to claim 1, the ionization means for ionizing the sputtered particles scattered from the target toward the workpiece and the workpiece or the back side of the workpiece are provided close to each other. a bias electrode plate having conductivity as well as negatively biased, limits a bias power source for supplying electrons to electrically neutralize the sputtered particles positive ions into the work, the number of electrons supplied to the workpiece from a bias power source And a limiting means for delaying the electrical neutralization of the sputtered particles of positive ions adhering to the workpiece .

  In the sputtering apparatus according to the second aspect, the ionization means is composed of a high-frequency coil disposed between the target and the work, and a high-frequency power source for supplying high-frequency power to the high-frequency coil.

  In the sputtering apparatus according to claim 3, the high-frequency coil is disposed at a position closer to the workpiece than the target.

  According to another aspect of the present invention, the ionization means is a thermoelectron generator that emits thermoelectrons between the target and the workpiece.

  In the sputtering apparatus according to claim 5, the ionization means is an ion gun that irradiates ions between the target and the workpiece.

In the sputtering apparatus according to claim 6, the bias electrode plate has a shape substantially similar to the surface shape on the back side of the work, and is arranged along the surface on the back side of the work. In the sputtering apparatus according to the seventh aspect, the bias electrode is provided integrally with the holding member that holds the workpiece.

In the film-forming method of Claim 8, it discharges in the atmosphere which introduce | transduced sputtering gas using the target distribute | arranged in the vacuum chamber as an electrode, sputter | spatter particles are spattered from the target to the workpiece | work of film-forming, In the meantime, the scattered sputtered particles are ionized into positive ions, the work or the vicinity of the back of the work is negatively biased, and the ionized sputtered particles are deposited on the work surface to form a thin film and biased. In the meantime, electrons that electrically neutralize the positive ion sputtered particles are supplied to the workpiece, and by limiting the number of electrons supplied, the positive ion sputtered particles adhering to the workpiece are electrically neutralized. It is something that delays.

  According to the present invention, the sputter particles scattered from the target toward the workpiece are ionized, and a negative bias is applied to the conductive bias electrode plate provided close to the workpiece or the back side of the workpiece by a bias power source, Since the sputtered particles are adsorbed on the surface of the workpiece, the sputtered particles can be efficiently attached not only to the surface facing the target of the workpiece but also to other surfaces to achieve uniform film formation. At the same time, the current flowing to the bias power source is limited so as to be smaller than the current corresponding to the charge amount of the positive ion sputtered particles generated by the ionization means, so that the sputtered particles are uniformly adhered and deposited on the workpiece. Thus, it is possible to perform film formation with high uniformity of film thickness.

  FIG. 1 shows a configuration of a sputtering apparatus 2 in which the present invention is implemented. The vacuum chamber 3 is made of, for example, stainless steel and has a substantially cylindrical shape. A cylindrical carousel 4 is disposed inside the vacuum chamber 3. The carousel 4 is rotatable about a rotating shaft 4a perpendicular to the vacuum chamber 3, and is rotated at a predetermined speed by a motor (not shown).

  A vacuum pump 5 is connected to the vacuum chamber 3 and is adjusted so that the inside of the vacuum layer 3 has a degree of vacuum necessary for sputtering during film formation. Note that the carousel 4 may be rotated about a horizontal rotation axis. Further, the vacuum chamber 3 can be opened by a well-known structure after leaking to atmospheric pressure for work such as loading and unloading the workpiece W, replacement of the target described later, and inspection and maintenance.

  On the outer peripheral surface of the carousel 4, a number of work holders 8 for holding the work W to be deposited are provided. For example, a plurality of work holders 8 are arranged at a constant pitch in each of the vertical direction and the circumferential direction of the carousel 4. The workpiece W attached to the workpiece holder 8 rotates around the rotation shaft 4 a together with the carousel 4.

  A target unit 10 is arranged on the outer periphery of the carousel 4 in the vacuum chamber 3. The target unit 10 includes a cylindrical target 11 whose axis is parallel to the rotating shaft 4a, a magnet 12 for performing magnetron sputtering, a jacket 13 covering the peripheral surface of the target 11, a shutter plate 14, and the like.

  The target 11 is formed into a cylindrical shape by, for example, forming a layer of a material to be deposited on a workpiece W such as aluminum, titanium, silicon, or the like on the outer peripheral surface of a cylindrical support cylinder (not shown) by spraying or the like. The target 11 is rotated at a predetermined speed around the rotation shaft 11a. The jacket 13 is disposed with a gap having an appropriate width between the jacket 13 and an opening 13 a that exposes the target 11 on the carousel 4 side. The shutter plate 14 is movable between a closed position where the opening 13a is closed and an open position where the target 11 is exposed by retreating from the front surface of the opening 13a.

  The magnet 12 is arranged in a hollow tube (not shown) provided inside the above-described support cylinder, and generates a magnetic field near the surface of the target 11 exposed from the opening 13a. Thereby, sputtering is performed with high efficiency using the surface of the target 11 exposed from the opening 13a as a sputtering surface.

  The drive unit 16 supplies sputtering gas to the target unit 10, supplies cooling water, rotates the target 11, and opens / closes the shutter plate 14. The sputtering gas is introduced into the gap between the target 11 and the jacket 13. For example, argon gas is supplied as the sputtering gas. When reactive sputtering is performed, a reactive gas such as oxygen gas or nitrogen gas is supplied in addition to the sputtering gas. Further, the cooling water is passed between the support cylinder in which the target 11 is formed and the hollow tube in which the magnet 12 is disposed, thereby preventing the target unit 10 from becoming high temperature.

  The sputtering power supply 21 supplies power necessary for sputtering to the target unit 10. The sputtering power source 21 is a direct current power source or a direct current pulse power source, and its negative electrode is connected to a rotating shaft 11a having conductivity and electrically connected to the target 11, and the positive electrode is connected to a shutter plate. , Connected to the jacket and grounded. The rotating shaft 11a and the vacuum layer 3 are insulated.

  When film formation is performed, power is supplied from the sputtering power source 21 with the sputtering gas supplied, and glow discharge is performed using the target 11 as a cathode. By causing the positive ions of the sputtering gas plasma generated by the glow discharge to collide with the target 11, sputtered particles (atoms and molecules) are knocked out and scattered from the target 11. A film is formed by the scattered sputtered particles adhering to and depositing on the surface of the workpiece W. By rotating the carousel 4, each workpiece W repeatedly faces the target 11, thereby forming a thin film having a necessary thickness on the surface of the workpiece W.

  The configuration of the target unit 10 is not limited to the above. For example, a flat target may be used, and it may not be magnetron sputtering. In this example, one target unit 10 is incorporated, but the number of film forming stages and the number of target units are appropriately increased or decreased according to the type of film to be formed, the number of stacked layers, the arrangement of workpieces, and the like. be able to.

  An RF coil (high frequency coil) 23 is disposed between the target unit 10 and the carousel 4. The RF coil 23, together with the RF power source (high frequency power source) 24 and the matching circuit 25, constitutes ionization means for ionizing sputtered particles scattered from the target 11 toward the workpiece W.

  The RF coil 23 is connected to the RF power source 24 via the matching circuit 25. By applying an appropriate high frequency, for example, 13.56 MHz high frequency power, from the RF power source to the RF coil 23, plasma containing sputtered particles ionized into positive ions is generated in the space surrounded by the RF coil 23. As the ionization of the sputtered particles, when the sputtered particles themselves are ionized by being excited by the high frequency magnetic field generated by the RF coil 23, or the sputtered particles are exchanged between the sputtered gas excited by the high frequency magnetic field and the sputtered particles. May be ionized.

  In order to ionize the sputtered particles scattered toward each workpiece W, as shown in FIG. 2, the workpiece W is mounted on the carousel 4 via the workpiece holder 8 and surrounds the workpiece W arranged to face the target 11. The RF coil 23 is arranged.

  The bias power source 26 is for applying a bias to the work W or the work holder 8 and uses a DC power source. The bias power supply 26 has its plus electrode grounded and connected to the vacuum layer 3, and its minus electrode is connected to the rotating shaft 4a via a current limiting circuit 27 described later. The carousel 4, the rotating shaft 4a, and the work holder 8 are all electrically conductive and electrically connected to each other. By connecting the bias power supply 26 in this way, a negative bias is applied to the work W or the work holder 8 so that the sputtered particles ionized by the RF coil 23 are attracted to the work W.

  The RF coil 23 is provided at a position closer to the workpiece W than the target 10 so that the ionized sputtered particles do not return to the target 11, and is arranged as close to the workpiece W as possible, that is, at a position away from the target unit 10. It is good to do. In this example, a negative bias is applied to the work W or the work holder 8 on the assumption that the sputtered particles are positive ions. However, when the sputtered particles are negative ions, the work W or the work holder 8 is applied to the work W or the work holder 8. What is necessary is just to give a positive bias voltage.

  The current limiting circuit 27 is provided to perform uniform film formation on the workpiece W, and suppresses the current flowing through the bias power source 26, that is, the number of electrons supplied to the positive sputtered particles attached to the workpiece W. . This current limiting circuit 27 is a current that is sufficiently smaller than a current corresponding to the amount of positive ions of sputtered particles generated in the RF coil 23 per unit time, that is, a current that is sufficiently smaller than that required to neutralize the positive charges. The impedance is adjusted so that current flows.

  The current limiting circuit 27 is an impedance composed of a resistor, an inductance, a capacitor and the like, and is variable so that the impedance can be adjusted. The reason why the inductance and the capacitor are included is to prevent the high-frequency current from flowing for the operation of the RF coil 23 and to maintain the plasma in the RF coil 23.

  The work holder 8 is a member for applying a bias to the work W by connecting the negative electrode of the bias power source 26 to the work W made of metal. On the other hand, for a work W made of, for example, resin having an insulating property, when a surface facing the target 11 of the work W is a front surface, the bias electrode plate is provided close to the back side of the work W. .

  The work W has a property as a dielectric when it is made of an insulator. When a dielectric is placed in the electric field, the lines of electric force pass through the dielectric, so that ionized sputtered particles are adsorbed on the surface of the dielectric. Therefore, when the bias electrode plate is provided close to the back side of the workpiece W, and the workpiece W made of an insulator such as a resin is a film formation target, the effect of adsorbing the ionized sputtered particles by applying a bias is obtained. obtain.

  Further, the bias electrode plate has a shape substantially similar to the shape of the back side of the workpiece W, and is arranged along the back side of the workpiece W, so that the effect of adsorbing the ionized sputtered particles can be improved. It can be obtained effectively on the surface.

  The shape of the work holder 8 used in this example and the work holder 8 having a function as a bias electrode plate is shown in FIG. The workpiece W has a rectangular parallelepiped shape with a concave portion on the back side, or a rectangular dish shape obtained by bending the periphery of a plate-like member. 31f is a film formation target. The work W has a recess 32 formed on the back side. On the other hand, as such a workpiece W, the workpiece holder 8 includes a holding portion 8a and a support shaft 8b in which the holding portion 8a and the carousel 4 are connected.

  The holding portion 8a holds the workpiece W and functions as a bias electrode plate. The holding portion 8 a has a close contact surface 34 formed in a surface shape substantially similar to the inner wall surface 33 of the recess 32 that is a back surface, and when the work W is attached to the work holder 8, the close contact surface 34 is in close contact with the inner wall surface 33. As a result, the work W is held by the holding portion 8a, and the holding portion 8a as a bias electrode plate is arranged along the inner wall surface 33. In addition to the front surface 31a, the upper surface 31b, the lower surface 31c, and the side surfaces 31d and 31e are also provided. The ionized sputtered particles are adsorbed by a bias.

  Further, the rear edge 31f protrudes behind the holding portion 8a as a bias electrode plate, so that the effect of the bias that adsorbs the ionized sputtered particles can be obtained with respect to the rear edge 31f. The film is also formed on the rear edge 31f.

  In this example, as a form in which the bias electrode plate is arranged along the surface on the back side of the workpiece, the holding portion 8a is in close contact with the inner wall surface 33, but the bias electrode plate is arranged away from the surface on the back side of the workpiece. May be. Further, the shape of the workpiece W is not limited to the above, including the shape of the back side. For example, the surface shape of the back side of the workpiece W can be various, such as a flat shape, a spherical shape, a shape with projections, and a shape with projections and depressions, and the surface shape of the bias electrode can be adapted accordingly. Can be determined as appropriate.

  Furthermore, in this example, as a form in which the bias electrode plate is integrally provided on the holding member that holds the workpiece, the work holder 8 has the function of the bias electrode plate. A conductive bias electrode plate may be integrally attached. Further, the holding member and the bias electrode plate may be provided separately.

  If the workpiece W is made of metal, the workpiece W only needs to be electrically connected and biased, so the negative electrode of the bias electrode is electrically connected at any part other than the surface to be deposited. It only has to be adapted.

  Next, the operation of the above configuration will be described. The vacuum chamber 3 is opened and the work W is attached to the work holder 8. Thereafter, the vacuum chamber 3 is closed, and the vacuum pump 5 is operated to bring the inside of the vacuum chamber 3 to a predetermined degree of vacuum necessary for sputtering. And after starting rotation of the carousel 4, a sputtering process is started. In addition, when the workpiece | work W is metal, after starting rotation of the carousel 4, you may heat each workpiece | work W with the heater provided in the vacuum chamber 3. FIG.

  In the sputtering process, first, a sputtering gas is supplied from the drive unit 16 between the target 11 and the jacket 13. As a result, the peripheral surface of the target 11 is placed in an atmosphere rich in sputtering gas. Further, the rotation of the target 11 is started by the driving unit 16.

  After confirming that the shutter plate 14 is in the closed position, power is supplied to the target unit 10 by the sputtering power source 21. Thereby, discharge is started between the jacket 13 and the shutter plate 14, and the target 11, and plasma of sputtering gas is generated.

  As described above, by generating plasma with the shutter plate 14 closed, the surface of the target 11 is cleaned with the plasma. After the cleaning is completed, high frequency power is supplied from the RF power source 24 to the RF coil 23 via the matching circuit 25, and a negative bias is applied to the work W or the work holder 8 from the bias power source 26 via the current limiting circuit 27. After starting, the shutter plate 14 is set to the open position, and film formation by sputtering is started.

  When the shutter plate 14 is in the open position, the sputtered particles sputtered from the surface of the target 11 by the sputtering gas plasma are scattered toward the workpiece W. The sputtered particles heading toward the workpiece W are ionized into positive ions when passing through the space surrounded by the RF coil 23. Then, the ionized sputtered particles adhere to the workpiece W.

  Since the workpiece W or the workpiece holder 8 is biased, the ionized sputtered particles P adhere to each surface of the workpiece W as shown in FIG. Therefore, not only the front surface 31a facing the target of the workpiece W but also the upper surface 31b and the lower surface 31c, or the side surfaces 31d and 31e, the rear side edge 31f, etc. are incident and adhered substantially vertically, Film formation is performed. Of course, even when the workpiece W has irregularities, the sputtered particles P adhere to each surface of the irregularities and film formation is performed.

  The effect by the bias can be similarly obtained as described above not only when the workpiece W is made of metal but also when it is made of an insulator. Moreover, since the work holder 8 is arranged in the recess 32 on the back side of the work W as described above, a bias effect can be obtained on each surface of the work W made of an insulator.

  The sputtered particles adhering to the workpiece W are electrically neutralized by supplying electrons through the workpiece W. In this way, film formation is performed on the workpiece W made up of a large number of sputtered particles. The current flowing through the bias power source 26 is increased by the current limiting circuit 27 plus sputtered particles generated by the RF coil 23 per unit time. Is sufficiently smaller than the current required to neutralize the amount of charge. For this reason, the ionized sputtered particles adhere to the work W to such an extent that the work W is kept electrically neutral by the current flowing through the bias power source 26, and the adhering sputtered particles are electrically neutral. And not immediately.

  As described above, while the sputtered particles adhering to the workpiece W are not electrically neutral, the electric field is affected by the electric charge of the sputtered particles in the vicinity of the portion where the sputtered particles are adhered. Distorted. Therefore, as shown in FIG. 5, the sputtered particles P <b> 2 heading to the vicinity of the sputtered particles P <b> 1 that are attached to the workpiece W but are not electrically neutralized are arranged to avoid the attached sputtered particles P <b> 1. The course turns and adheres to the workpiece W.

  As a result, the sputtered particles that are scattered toward the workpiece W one after another come to adhere to the surface of the workpiece W different from the sputtered particles that are not electrically neutralized, so that the film thickness is highly uniform. A film can be formed.

  In the above embodiment, one RF coil is used. However, a plurality of RF coils may be arranged side by side so as to divide a space in which plasma is to be generated, and the sputtered particles may be ionized. In this way, uniform plasma can be generated in a space where plasma should be generated, and film formation can be made uniform. For example, in the example of FIG. 6, three RF coils 23 arranged in the vertical direction are arranged to cover each workpiece W facing the target 11. The RF coil 23 is connected in parallel to the RF power source 24, and a matching circuit 25 is connected to each of the RF coils 23.

  In the above description, the RF coil and its RF power source are used as the ionization means for ionizing the sputtered particles. However, the ionization means is not limited to this, and various ionization means can be used.

  For example, as shown in FIGS. 7 and 8, an ion gun 36 that irradiates ions by applying power from a power source 35 may be used as the ionization means. Then, the sputtered particles are ionized by the ions irradiated from the ion gun 36.

  In this case, as shown in FIG. 8, the ions from the ion gun 36 are irradiated to the space between the target 11 and the workpiece W, and the sputtering from the target 11 toward each workpiece W is performed. It is preferable to irradiate the entire space where the particles are scattered. In the example of FIG. 7, the ion gun 36 is arranged so that the ion irradiation region becomes longer in the vertical direction in response to the workpieces W facing the target 11 being arranged in the vertical direction at the same time.

  Further, as shown in FIG. 9, for example, a thermoelectron generator 38 that emits thermoelectrons from a filament 38a may be provided as ionization means, and the sputtered particles may be ionized by an electron ionization method. Also in this case, it is preferable to arrange the thermoelectron generator 38 so that ions are emitted to the entire space where the sputtered particles traveling from the target 11 toward each workpiece W are scattered.

  In the above description, an example is described in which film formation is performed by repeatedly moving the workpiece W against the target while rotating the workpiece W with the carousel. The present invention can also be used when forming a film without moving the film.

It is explanatory drawing which shows the structure of the sputtering device which implemented this invention. It is explanatory drawing which shows the arrangement | positioning relationship between RF coil and a workpiece | work. It is a perspective view which fractures | ruptures and shows the shape of a workpiece | work and a workpiece holder. It is explanatory drawing which shows typically the state by which the ionized sputtered particle is adsorb | sucked to a workpiece | work. It is explanatory drawing which shows typically the path | route of the other sputtered particle in the state in which the sputtered particle adhering to the workpiece | work is not electrically neutralized. It is explanatory drawing which shows the example which ionizes sputtered particle using a some RF coil. It is explanatory drawing which shows the structure of the sputtering device which has arranged the ion gun which ionizes sputtered particles. It is explanatory drawing which shows arrangement | positioning of an ion gun. It is explanatory drawing which shows the example which arranged the thermoelectron generator which ionizes sputtered particle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Sputtering device 3 Vacuum chamber 8 Work holder 8a Holding part 10 Target unit 11 Target 23 RF coil 24 High frequency power supply 26 Bias power supply W Workpiece

Claims (8)

Target is placed in a vacuum chamber, by the row Ukoto discharge in an atmosphere obtained by introducing a sputtering gas, the sputtering particles are scattered from the target, the film is formed by depositing the scattered sputtered particles word over click In sputtering equipment,
Ionizing means for ionizing sputtered particles scattered from the target toward the workpiece into positive ions ;
With biasing the bias electrode plate having conductivity provided close to the rear side of the workpiece or the workpiece to the negative, and a bias power source for supplying electrons to electrically neutralize the sputtered particles positive ions to the workpiece ,
A sputtering apparatus comprising: limiting means for limiting the number of electrons supplied from the bias power source to the workpiece and delaying electrical neutralization of the sputtered particles of positive ions adhering to the workpiece .   The sputtering apparatus according to claim 1, wherein the ionization unit includes a high-frequency coil disposed between the target and the workpiece, and a high-frequency power source that supplies high-frequency power to the high-frequency coil.   The sputtering apparatus according to claim 2, wherein the high-frequency coil is disposed at a position closer to the workpiece than the target.   The sputtering apparatus according to claim 1, wherein the ionization means is a thermoelectron generator that emits thermoelectrons between the target and the workpiece.   The sputtering apparatus according to claim 1, wherein the ionization means is an ion gun that irradiates ions between the target and the workpiece.   6. The bias electrode plate according to claim 1, wherein the bias electrode plate has a shape substantially similar to a shape of the back side of the workpiece, and is arranged along a surface of the back side of the workpiece. The sputtering apparatus as described.   The sputtering apparatus according to claim 1, wherein the bias electrode is provided integrally with a holding member that holds the workpiece. Discharge in an atmosphere where a sputtering gas is introduced using the target placed in the vacuum chamber as an electrode, and sputter particles are scattered from the target to the workpiece to be deposited,
Ionized spatter particles scattered between the target and the workpiece into positive ions,
Biasing the work or the vicinity of the back of the work negatively, depositing ionized sputtered particles on the work surface to form a thin film,
During biasing, electrons that electrically neutralize the positive ion sputtered particles are supplied to the workpiece, and by limiting the number of electrons supplied, the electric ions of the positive ion sputtered particles adhering to the workpiece are supplied. A film forming method characterized by delaying proper neutralization.

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