JP2014084483A - Sputtering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-frequency sputtering apparatus which can effectively suppress discharge leakage from a gap between deposition preventing plates even if partial pressure of sputtering gas is increased when high-frequency power is input to a target for performing sputtering.SOLUTION: A high-frequency sputtering apparatus SM according to the invention includes: a vacuum chamber 1 to which a target 2 is freely installed and removed; a stage 5 which is disposed facing the target in the vacuum chamber, and holds a processing object; and deposition preventing means 9 which prevents sputtered particles from being deposited on the internal wall surface of the vacuum chamber by surrounding space between the target and the stage. The deposition preventing means is constructed of a plurality of deposition preventing plates 91 to 93 arranged vertically. The adjacent deposition preventing plates are arranged by overlapping one another over a predetermined length with a gap of 3 mm or less in the plate thickness direction.

Description

  The present invention relates to a sputtering apparatus, and more particularly to an apparatus having an adhesion preventing means for preventing adhesion of sputtered particles to an inner wall surface of a vacuum chamber by surrounding a space between a target and a stage.

  Conventionally, for example, an insulator made of an oxide such as alumina or a nitride such as silicon nitride is used as a target, and an insulating film such as an oxide or nitride is formed on the surface facing the target of the substrate to be processed by sputtering. When forming a film, it is widely known to use a high-frequency sputtering apparatus having a high-frequency power source for supplying high-frequency (alternating current) power to and from the ground (see, for example, Patent Document 1). In the case of film formation with such a high-frequency sputtering apparatus, in order to obtain a higher film formation rate, the AC power input to the target is increased, or the partial pressure of sputtering gas such as argon gas in the vacuum chamber during sputtering ( For example, it is generally known to form a film by increasing the total pressure in the vacuum chamber to 10 Pa).

  By the way, in a general high-frequency sputtering apparatus, a space between a target arranged opposite to each other in a vacuum chamber and a stage holding a processing object is surrounded to prevent adhesion of sputtered particles to the inner wall surface of the vacuum chamber. An adhesion prevention means is provided. In this case, the adhesion prevention means is generally configured by arranging a plurality of adhesion prevention plates in the vertical direction in consideration of maintainability and delivery / reception of the substrate to the stage. For example, in order to allow the passage of gas from the space, a gap is provided between the adhesion preventing plates.

  However, it has been found that when sputtering is performed with the partial pressure of the sputtering gas increased, the sputtering rate is lowered and the productivity is impaired. This is because the gap provided between the protective plates is not properly managed, and the plasma leaks through the gap to the inner wall surface of the earth-grounded vacuum chamber. This is considered to be due to the fact that the electric power discharged to the target is relatively reduced and the electric power supplied to the target is relatively lowered. Further, if the plasma leaks and is discharged, it can be a source of particles.

JP 2002-4042 A

  In view of the above points, the present invention effectively suppresses discharge leakage from the gap between the deposition preventing plates even when the partial pressure of the sputtering gas is increased when sputtering is performed by applying high-frequency power to the target. An object of the present invention is to provide a high-frequency sputtering apparatus that can be used.

  In order to solve the above-described problems, a high-frequency sputtering device according to the present invention includes a vacuum chamber in which a target is detachably attached, a stage that is disposed facing the target in the vacuum chamber and holds a processing object, and a target and a stage. And an adhesion preventing means for preventing the adhesion of sputtered particles to the inner wall surface of the vacuum chamber, with the direction from the stage toward the target facing up, and the adhesion preventing means being arranged in parallel in the vertical direction. Each of the adhering plates adjacent to each other is arranged to overlap with each other over a predetermined length with a gap of 3 mm or less in the plate thickness direction. It is characterized by.

  According to the present invention, since each of the adhesion prevention plates adjacent to each other overlaps with a predetermined length and with a gap of 3 mm or less in the thickness direction, for example, in the vacuum chamber Even if sputtering is performed by applying high-frequency power to the target in a state where the partial pressure of the sputtering gas is increased so that the total pressure becomes 10 Pa or more, discharge leakage from the gaps between the protective plates can be effectively suppressed. Was confirmed. Thereby, the fall of the amplitude voltage Vpp of the high frequency alternating current component applied to the target is suppressed, and the sputtering rate can be increased and the productivity can be improved. In addition, if the length which overlaps each of an adhesion prevention board shall be 10 mm or more, an electric discharge leak can be suppressed reliably.

  In the present invention, it is preferable that the deposition preventing plates are overlapped so that the gap extends in the vertical direction. According to this, compared with the case where each of the deposition preventing plates is overlapped so that the end of the gap faces the plasma formed in the vacuum chamber, the discharge leakage can be suppressed more reliably. .

  By the way, when arrange | positioning so that the space between a target and a stage may be enclosed, and each adhesion prevention board may be provided so that the space further isolated in the vacuum chamber may be defined, any one adhesion prevention board Must be configured to be able to move relative to other deposition prevention plates, for example, so that the substrate can be transferred / received to / from the stage by a transfer robot. In this case, the drive shaft of the drive means for moving the one deposition plate up and down is connected to the one deposition plate. Even in such a case, it is necessary to configure so as to effectively suppress discharge leakage from the gaps between the adhesion preventing plates. Therefore, the end of the other deposition plate is bent in an L shape toward the inside of the vacuum chamber, and the end of the other deposition plate on the deposition plate side Is bent at right angles toward the inside of the vacuum chamber, and a space is preferably filled in a space defined by the end portions of the two protection plates to form the gap.

The schematic diagram of the high frequency sputtering device of the present invention. Sectional drawing which expands and demonstrates the principal part of the high frequency sputtering device of FIG.

  Hereinafter, with reference to the drawings, a high-frequency sputtering apparatus according to an embodiment of the present invention will be described by taking as an example a case where an insulating film is formed on the surface of a substrate W such as a silicon wafer or a sapphire substrate using an insulator.

  With reference to FIG.1 and FIG.2, SM is the high frequency sputtering device of this embodiment. The high-frequency sputtering device SM includes a vacuum chamber 1 that defines a vacuum processing chamber 1a, and a cathode unit C is detachably attached to a ceiling portion of the vacuum chamber 1. In the following description, in FIG. 1, the direction facing the ceiling portion side of the vacuum chamber 1 is referred to as “up” and the direction facing the bottom portion side is described as “down”.

  The cathode unit C includes a target 2 and a magnet unit 3 disposed above the target 2. The target 2 is made of an insulator such as alumina, silicon nitride, or silicon carbide, and is formed in a circular shape or a rectangular shape in plan view by a known method according to the contour of the substrate W. The target 2 is attached to the upper portion of the vacuum chamber 1 via the first insulator 41 provided on the upper wall of the vacuum chamber 1 with the sputtering surface 22 facing downward while being mounted on the backing plate 21. The target 2 is connected to a high-frequency power source E having a known structure, and high-frequency (alternating current) power having a predetermined frequency (for example, 13.56 MHz) is supplied between the target 2 and the ground during sputtering. The magnet unit 3 disposed above the target 2 generates a magnetic field in the space below the sputtering surface 22 of the target 2, captures electrons etc. ionized below the sputtering surface 22 during sputtering, and sputters from the target 2. It has a known closed magnetic field or cusp magnetic field structure for efficiently ionizing particles, and detailed description thereof is omitted here.

  A stage 5 is disposed in the center of the bottom of the vacuum chamber 1 so as to face the target 2. The stage 5 includes a metal base 51 having a cylindrical outline, for example, and a chuck plate 52 bonded to the upper surface of the base 51. The chuck plate 52 has an outer diameter that is slightly smaller than the upper surface of the base 51, and is embedded with electrodes 52a and 52b for electrostatic chuck, so that a voltage is applied from a chuck power source (not shown). In this case, the chuck plate 52 is detachably attached to the upper surface of the base 51 by a ring-shaped first attachment plate 53. In this case, the first deposition preventing plate 53 is attached to the upper surface of the base 51 via the second insulator 42 in order to reduce the bias potential generated in the substrate W during sputtering. In addition, about the structure of an electrostatic chuck, since well-known things, such as a monopolar type and a bipolar type, can be utilized, detailed description is abbreviate | omitted here.

  The base 51 is held by a third insulator 43 that is airtightly attached to an opening provided on the bottom surface of the vacuum chamber 1, and is separated from the grounded vacuum chamber 1 and is electrically floating. There is no restriction | limiting in particular as a material of each 1st-3rd insulator 41,42,43, A glass-containing fluororesin (polytetrafluoroethylene), a glass-filled epoxy resin, etc. can be used. Further, the stage 5 is connected to a potential switching means 54 for switching the base 51 between a floating state and a ground potential. During sputtering, the potential of the stage 5 is set to a floating state, and positive ions in the plasma are drawn into the substrate W. Therefore, the amount taken into the film is greatly reduced. The potential switching means 54 includes a wiring 54a connected to the base 51. The wiring 54a is positioned outside the vacuum processing chamber 1a, and a resistor 54b and a switching element 54c are interposed and grounded. . In this case, the resistor 54b stops the voltage application from the chuck power supply and shorts to the ground to release the adsorption of the substrate W. When the resistor 54b switches the switching element 54c in synchronization with this to ground the stage 5 to the ground. This is to prevent an overcurrent from flowing (for example, 1 MΩ). The base 51 incorporates a refrigerant circulation passage 55a and a heater 55b so that the substrate W can be controlled to a predetermined temperature during sputtering.

  Further, a gas pipe 6 serving as a gas introducing means for introducing sputtering gas is connected to the side wall of the vacuum chamber 1, and this gas pipe 6 communicates with a gas source (not shown) via a mass flow controller 6a. The sputtering gas includes not only a rare gas such as an argon gas introduced when forming plasma in the vacuum processing chamber 1a but also a reactive gas such as an oxygen gas or a nitrogen gas. The side surface of the vacuum chamber 1 is also connected to an exhaust pipe 7 leading to a vacuum pump P constituted by a turbo molecular pump, a rotary pump, or the like so that the vacuum processing chamber 1a can be evacuated at a constant speed and maintained at a predetermined pressure. I have to.

  Around the stage 5 in the vacuum chamber 1, an annular second adhesion-preventing plate 8 is provided as a ground electrode. The second adhesion-preventing plate 8 is formed so as to incline downward radially outward from the inner peripheral edge thereof. Although not specifically illustrated and described, a plurality of through holes penetrating in the vertical direction may be formed in the second deposition preventing plate 8. And the 2nd adhesion prevention board 8 is installed in the bottom face of the vacuum chamber 1 of earth ground, and plays a role as earth at the time of sputtering. In the vacuum chamber 1, a third deposition plate 9 that surrounds the space between the target 2 and the substrate W is disposed in order to prevent sputter particles from adhering to the inner wall surface of the vacuum chamber 1. The 3rd adhesion prevention board 9 constitutes the adhesion prevention means of this embodiment.

  Referring also to FIG. 2, the third deposition preventive plate 9 is made of a well-known material such as alumina or stainless steel, and the upper deposition preventive plate 91 suspended from the upper wall of the vacuum chamber 1 and the vacuum chamber 1. Between the lower deposition plate 92 erected on the bottom surface, the upper deposition plate 91 and the lower deposition plate 92, both the deposition plates 91, 92 are provided inside the vacuum chamber 1, and the upper deposition plate 91 and the lower deposition plate 91 are disposed below. It is comprised by the adhesion prevention board 92 and the movable adhesion prevention board 93 which overlaps in an up-down direction. The upper protection plate 91 is formed by bending one side of a plate-like member substantially at a right angle, forming a circular shape in this state, and joining both free ends so as to have a ring-like contour. The lower prevention plate 92 is also formed by bending one side of the plate-like member substantially at a right angle, forming a circular shape in this state, and joining both free ends so as to have a ring-shaped contour. Is installed so as to extend inward of the vacuum chamber 1. The upper deposition preventing plate 91 and the lower deposition preventing plate 92 can also be configured by dividing a plurality of components in the circumferential direction of the vacuum chamber 1. The movable deposition plate 93 provided between the upper deposition plate 91 and the lower deposition plate 92 is bent at substantially right angles on both sides of the plate-shaped member alternately, and is formed into a circular shape in this state, thereby forming a ring-shaped contour. Both free ends are joined so as to have.

  The driving shaft Cr of the cylinder Cy provided through the bottom surface of the vacuum chamber 1 at 90 ° intervals in the circumferential direction is connected to the outer surface of the movable protection plate 93 and supported by each driving shaft Cr. Then, the cylinder Cy is used to move the lower adhesion position (position shown in FIG. 1) to prevent the sputter particles from adhering to the inner wall surface of the vacuum chamber 1 and the movable adhesion prevention plate 93 by moving to the upper adhesion prevention plate 91 side. A gap is formed between the lower protection plate 92 and the upper moving position where the substrate W can be carried out and carried into the stage 5 through a through hole To for opening and closing by a gate valve (not shown). The movable adhesion preventing plate 93 is movable.

Here, at the downward movement position of the movable deposition plate 93, the upper end portion extending in the vertical direction of the movable deposition plate 93 and the lower end portion extending in the vertical direction of the movable deposition plate 93 extend over a predetermined length l ₁ . and a gap d ₁ between the upper and lower ends are overlapped so that less than 3mm. In this case, the length l ₁ may be 10 mm or more. On the other hand, when the movable deposition plate 93 and the lower deposition plate 92 are formed as described above, an annular space is formed between the horizontal upper end portion of the lower deposition plate 92 and the movable deposition plate 93. Is done. For this reason, the gap d ₂ between the horizontal upper end of the lower anti-adhesion plate 92 and the horizontal upper end of the lower anti-adhesion plate 92 is 3 mm or less below the horizontal portion of the movable anti-adhesion plate 93 over a predetermined length l _2. Thus, the overlapping spacer 94 was fixed. In this case, as the spacer 94, a glass-containing fluororesin (polytetrafluoroethylene) or a glass-containing epoxy resin that is integrally formed in a ring shape can be used.

  Below, the film-forming process by the said high frequency sputtering device SM is demonstrated. An unillustrated vacuum transfer robot unloads the substrate W onto the stage 5 through the transfer through hole To to the vacuum processing chamber 1a in the vacuum atmosphere at the upward movement position of the movable protection plate 93, and the stage 5 The substrate W is placed on the upper surface of the chuck plate 52. When the vacuum transfer robot is retracted, it moves to the lower position of the movable adhesion preventing plate 93 so that the sputtered particles do not adhere to the inner wall surface of the vacuum chamber 1. The switching element 54c of the potential switching means 54 is off, and the stage 5 is in a floating state. When a predetermined voltage is applied from the chuck power source to the electrostatic chuck electrodes 52a and 52b, the substrate W is electrostatically attracted.

Next, when the inside of the vacuum processing chamber 1a is evacuated to a predetermined pressure (for example, 10 ⁻⁵ Pa), an argon gas as a sputter gas is supplied at a constant flow rate (for example, an argon partial pressure of 1 through the gas introduction means). In addition to this, predetermined high-frequency power (for example, 1 to 5 kW) is input from the high-frequency power source E to the target 2. Thereby, plasma is formed in the vacuum processing chamber 1a, the target 2 is sputtered by ions of argon gas in the plasma, and the sputtered particles from the target 2 adhere to and deposit on the substrate W to form a silicon nitride film, an alumina film, etc. An insulating film is formed. In this case, a high-frequency current flows to the ground through the plasma. However, in this embodiment, the stage 5 and the first deposition plate 53 around the substrate are in an electrically floating state, and therefore flow to the substrate W. The film is formed in a state where the high-frequency current is limited and the bias potential is not applied to the substrate W.

  After the film formation is completed, the application of high-frequency power to the target 2 and the introduction of gas are stopped, the voltage application from the chuck power supply is stopped, the short circuit to the ground is released, the adsorption of the substrate W is released, and the switching element 54c is turned on. And the stage 5 is grounded. Then, the film-formed substrate W on the stage 5 is unloaded from the vacuum processing chamber 1a through a through hole To for transporting to the vacuum processing chamber 1a by a vacuum transfer robot (not shown).

  According to the above embodiment, the upper and lower protective plates 91 and 92 and the movable protective plate 93 are vertically moved with a gap of 3 mm or less in the thickness direction over a predetermined length. Since they are overlapped so as to extend in the direction, for example, sputtering is performed by applying high-frequency power to the target 2 in a state where the partial pressure of the sputtering gas is increased so that the total pressure in the vacuum chamber 1 is 10 Pa or more. Moreover, the discharge leakage from the clearance gap between the adhesion prevention plates 91, 92, and 93 is effectively suppressed. Thereby, the fall of the amplitude voltage Vpp of the high frequency alternating current component applied to the target 2 is suppressed, and the sputtering rate can be increased and the productivity can be improved.

Next, in order to confirm the above effects, the following experiment was performed using the high-frequency sputtering apparatus SM shown in FIG. In this experiment, the substrate W was a silicon wafer. Then, alumina was used as the target 2 and an alumina film was formed on the silicon wafer surface. As the sputtering conditions, the distance between the target 2 and the substrate W was set to 70 mm, the input power was set to 1 kW by the high frequency power source E, and the sputtering time was set to 90 sec. Further, the adhesion preventing means 9 is provided so that l ₁ and l ₂ are 10 mm each, and d ₁ and d ₂ are 3 mm each. In this experiment, argon gas was used as the sputtering gas. During sputtering, the partial pressure of the sputtering gas was changed in the range of about 1 to 10 Pa and the input high frequency power from the high frequency power source E was changed in the range of 0.5 kW to 5 kW. And the presence or absence of the discharge leakage was confirmed from the viewport. According to this, no discharge leakage from the deposition preventing plate could be confirmed in the pressure range and input power range.

  As mentioned above, although embodiment of this invention was described, this invention is not limited above. Although the description has been given of the example in which the anti-adhesion means 9 is configured by the upper anti-adhesion plate 91, the lower anti-adhesion plate 92 and the movable anti-adhesion plate 93, the anti-adhesion means 9 is not limited to this, The present invention can be applied to a case where a plurality of deposition prevention plates are used regardless of whether the deposition prevention plate is movable.

SM ... high frequency sputtering apparatus, 1 ... vacuum chamber, 1a ... vacuum processing chamber, 2 ... target, 5 ... stage, 6 ... gas pipe (gas introduction means), 9 ... third deposition plate (protection means), 91 ... Upper protective plate, 92 ... Lower protective plate, 93 ... Movable protective plate, 94 ... Spacer, C ... Cathode unit, E ... High frequency power supply, W ... Substrate.

Claims (3)

A vacuum chamber in which the target is detachably attached, a stage that is disposed opposite to the target in the vacuum chamber and holds the object to be processed, and surrounds a space between the target and the inner wall of the vacuum chamber. An adhesion preventing means for preventing adhesion of sputtered particles,
The direction from the stage toward the target is the top, and the adhesion prevention means is composed of a plurality of adhesion prevention plates arranged in parallel in the vertical direction, each of the adhesion prevention plates adjacent to each other over a predetermined length, and A sputtering apparatus characterized by being disposed so as to overlap with a gap of 3 mm or less in the thickness direction.   The sputtering apparatus according to claim 1, wherein the adhesion preventing plates are overlapped so that the gap extends in the vertical direction. The sputtering apparatus according to claim 1 or 2, wherein a driving shaft of a driving means for moving the one deposition preventing plate up and down is connected to any one deposition preventing plate. In those that can move up and down with respect to the other deposition plate located on the upper side or the lower side
The end of the other plate is bent in an L shape toward the inside of the vacuum chamber, and the end of the other plate is closed A sputtering apparatus, wherein the gap is formed by bending at a right angle toward the inside of the chamber and providing a spacer in a space defined by the end portions of both deposition preventing plates.

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