JP2018204060A - Sputtering equipment - Google Patents

Abstract

Provided is a sputtering apparatus capable of forming a predetermined thin film with a more uniform thickness distribution in a substrate surface. A sputtering apparatus (SM) according to the present invention is provided in a cylindrical vacuum chamber (1) in which a sputtering target (2) is installed, and is provided at a position facing the target in the vacuum chamber to enable installation of a film-forming target. And a shield plate 5 which is provided with a gap from the inner wall surface 1a of the vacuum chamber and surrounds a film formation space between the target and the stage. An exhaust space portion 11 locally bulged in a direction orthogonal to the extension line Cl to be connected is provided, and the inside of a vacuum chamber including the film formation space 1b is driven by a vacuum pump Vp through an exhaust port 11a opened in the exhaust space portion. Is evacuated, and a cover plate 7 is provided to cover the outer surface portion of the shield plate facing the exhaust gas inlet 11b in the exhaust space with a gap. [Selection diagram] Fig. 1

Description

  The present invention relates to a sputtering apparatus, and more particularly to an apparatus having a structure capable of improving the film thickness distribution.

  This type of sputtering apparatus is known from Patent Document 1, for example. In this apparatus, a cylindrical vacuum chamber having a sputtering target is provided on the upper portion, and a silicon wafer, a glass substrate, or the like (hereinafter simply referred to as “film formation target”) is formed in the lower portion of the vacuum chamber so as to face the target. A stage on which a “substrate” is installed is provided. In addition, in order to prevent film deposition on the inner wall surface of the vacuum chamber during deposition by sputtering of the target, a film deposition space between the target and the stage is disposed close to the inner wall surface of the vacuum chamber with a gap. A shield plate is provided in the vacuum chamber.

  Here, on the upper side of the target, for example, various components such as a magnet unit that applies a leakage magnetic field to the sputtering surface side of the target are provided. On the other hand, various parts such as a heating / cooling mechanism and an electrostatic chuck mechanism for efficiently heating and cooling the substrate are provided below the stage. For this reason, in order to evacuate the vacuum chamber including the film formation space, an exhaust port to which the exhaust pipe from the vacuum pump is connected and an exhaust pipe connected to the exhaust port are provided on an extension line connecting the target and the stage. Is virtually impossible. Therefore, in this type of sputtering apparatus, an exhaust space portion that is locally expanded in a direction perpendicular to the extension line is provided at the lower portion of the vacuum chamber, and vacuum is provided through an exhaust port opened in the exhaust space portion. In general, a vacuum chamber is designed so that a vacuum chamber including a deposition space is evacuated by a pump. In this case, the outer surface portion of the shield plate facing the exhaust gas inflow port of the exhaust space portion has a structure in which the inner wall surface of the vacuum chamber is not in close proximity.

  By the way, for example, in the manufacturing process of a semiconductor device such as a nonvolatile memory or a flash memory, when a predetermined thin film is formed on the substrate surface using the sputtering apparatus, the uniformity of the film thickness distribution in the substrate surface is In recent years, it has been required to be within a range of several% (for example, ± 5%). As one of the methods for satisfying such requirements, a gas introduction path to the film formation space for the sputtering gas is appropriately designed, and the film formation space defined by the shield plate is formed during film formation by sputtering of the target. It is considered to make the pressure distribution of the same throughout. However, even if the pressure distribution in the film formation space is made equal throughout, the portion of the substrate located in the direction of the exhaust space (particularly the outer peripheral portion of the substrate) where the film thickness is located in another direction. It turned out that there exists a tendency which becomes thin easily compared with. If there is a portion where the film thickness is likely to be locally reduced in this manner, it becomes an obstacle to obtaining a more uniform film thickness distribution in the substrate surface.

  Thus, the inventors of the present invention have conducted extensive research and have come to know the following. That is, in the sputtering apparatus, a part of the sputtering gas introduced into the film formation space becomes an exhaust gas during film formation, and the shield plate has a gap between the shield plate and the gap between the shield plate and the target or stage. It flows from the exhaust gas inlet to the exhaust space through a gap between the outer surface and the inner wall surface of the vacuum chamber, and is evacuated to a vacuum pump through the exhaust port. At this time, the flow rate of the exhaust gas that has reached the vicinity of the exhaust gas inlet of the exhaust space is extremely lower than when it flows through the gap between the outer surface of the shield plate and the inner wall surface of the vacuum chamber. In other words, there is a region where the flow rate of the exhaust gas is locally low around the shield plate that defines the film formation space. If a region where the flow rate of exhaust gas is low is present around the shield plate in this way, it is considered that the film thickness tends to be thin at the portion of the substrate located in the direction of the region.

JP 2014-148703 A

  The present invention has been made on the basis of the above knowledge, and it is an object of the present invention to provide a sputtering apparatus capable of depositing a predetermined thin film with a more uniform film thickness distribution within the substrate surface. It is what.

  In order to solve the above-described problems, a sputtering apparatus according to the present invention includes a cylindrical vacuum chamber in which a sputtering target is installed, and a film-forming target installed in a position facing the target in the vacuum chamber. An extension stage that connects the target and the stage to the vacuum chamber, and includes a stage that can be installed and a shield plate that is installed with a gap from the inner wall surface of the vacuum chamber and surrounds the film formation space between the target and the stage. An exhaust space portion that is locally expanded in a direction perpendicular to the line is provided, and the inside of the vacuum chamber including the film formation space is evacuated by a vacuum pump through an exhaust port opened in the exhaust space portion. A cover plate is provided to cover the outer surface portion of the shield plate facing the exhaust gas inlet of the portion with a gap.

  According to the present invention, the region where the exhaust gas flow rate is low around the shield plate that defines the film formation space becomes as small as possible, in other words, the exhaust gas flow rate around the shield plate is substantially equal. Thus, it is possible to form a thin film having a more uniform film thickness distribution (for example, ± 3%) in the substrate surface.

  In the present invention, the cover plate is composed of a fixed plate portion erected on the bottom wall surface that defines the exhaust space portion, and a movable plate portion that is movable forward and backward with respect to the fixed plate portion by an elevating mechanism, It is preferable that the fixed plate portion and the movable plate portion are curved so as to have the same curvature on the inner wall surface of the vacuum chamber 1. According to this, it is possible to adjust the flow rate of the exhaust gas around the shield plate to be substantially uniform for each sputtering apparatus, which is advantageous.

Sectional drawing which shows typically the sputtering device of embodiment of this invention. Sectional drawing which follows the II-II line | wire of FIG. Sectional drawing of the sputtering device of the prior art example corresponding to FIG.

  Hereinafter, with reference to the drawings, a film formation target is a silicon wafer (hereinafter simply referred to as “substrate W”), a sputtering target is provided at the top of the vacuum chamber, and a stage on which the substrate W is installed is provided below the sputtering target. An embodiment of the sputtering apparatus of the present invention will be described by taking as an example.

  Referring to FIGS. 1 and 2, SM is a magnetron type sputtering apparatus of the present embodiment. The sputtering apparatus SM includes a vacuum chamber 1, and a cathode unit Cu is detachably attached to the upper portion of the vacuum chamber 1. The cathode unit Cu is composed of a sputtering target 2 and a magnet unit 3 disposed above the target 2.

  The composition of the target 2 is appropriately selected according to the thin film to be formed on the substrate W, and is formed in a circular shape in plan view according to the outline of the substrate W. The target 2 is attached to the upper portion of the vacuum chamber 1 via an insulator Ib 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. Further, a sputtering power source E having a known structure is connected to the target 2, and at the time of film formation by sputtering, the target 2 has a predetermined frequency (for example, 13.56 MHz) between a DC power having a negative potential and the ground. High frequency power can be input. 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 closed magnetic field or cusp magnetic field structure that ionizes particles efficiently. Since a known unit can be used as the magnet unit 3 itself, further explanation is omitted.

  At the center of the bottom of the vacuum chamber 1, a stage 4 is disposed via another insulator Ib so as to face the target 2. Although not specifically illustrated and described, the stage 4 includes, for example, a metal base having a cylindrical outline and a chuck plate bonded to the upper surface of the base, and adsorbs the substrate W during film formation. It can be held. As the structure of the electrostatic chuck, known ones such as a monopolar type and a bipolar type can be used, and thus further detailed description is omitted. Further, the base may include a refrigerant circulation passage and a heater so that the substrate W can be controlled to a predetermined temperature during film formation.

  Further, the vacuum chamber 1 is provided with a shield plate 5 that is installed with a gap from the inner wall surface 1 a to surround the film formation space 1 b between the target 2 and the stage 4. The shield plate 5 surrounds the periphery of the target 2 and extends substantially below the vacuum chamber 1. The shield plate 5 surrounds the periphery of the stage 4 and the stage 4, and extends approximately above the vacuum chamber 1. It has a cylindrical lower plate portion 52, and the lower end of the upper plate portion 51 and the upper end of the lower plate portion 52 are overlapped with a gap in the circumferential direction. Note that the upper plate portion 51 and the lower plate portion 52 may be integrally formed, or may be divided into a plurality of portions in the circumferential direction and combined.

  Further, the vacuum chamber 1 is provided with gas introduction means 6 for introducing a predetermined gas. The gas includes not only a rare gas such as an argon gas introduced when forming plasma in the film formation space 1b but also a reactive gas such as an oxygen gas and a nitrogen gas that are appropriately introduced according to the film formation. The gas introduction means 6 has a gas ring 61 provided on the outer periphery of the upper plate portion 51 and a gas pipe 62 that is connected to the gas ring 61 and penetrates the side wall of the vacuum chamber 1. It communicates with a gas source (not shown) via a controller 63. In this case, although the detailed illustration is omitted, the gas ring 61 is provided with a gas diffusion portion, and the sputter gas from the gas pipe 62 is diffused by the gas diffusion portion and perforated in the circumferential direction in the gas ring 61 at equal intervals. Sputtering gas is injected at an equal flow rate from the provided gas injection port 61a. Then, the sputtering gas injected from the gas injection port 61a is introduced into the film formation space 1b from a gas hole (not shown) formed in the upper plate portion 51 at a predetermined flow rate, and during the film formation, the film formation space 1b. The pressure distribution inside is made equal throughout. In addition, the method for making the pressure distribution in the film-forming space 1b equal throughout is not limited to this, and other known methods can be appropriately employed.

  Further, the vacuum chamber 1 is provided with an exhaust space portion 11 that is locally expanded in a direction orthogonal to a center line (extension line) Cl connecting the target 2 and the stage 4. An exhaust port 11a is opened in the bottom wall surface that divides. A vacuum pump Vp such as a cryopump or a turbo molecular pump is connected to the exhaust port 11a through an exhaust pipe. During film formation, part of the sputtering gas introduced into the film formation space 1b becomes exhaust gas, and the outside of the shield plate 5 is removed from the joint between the shield plate 5 and the gap between the shield plate 5 and the target 2 or the stage 4. The gas flows from the exhaust gas inlet 11b to the exhaust space 11 through the gap between the surface and the inner wall surface 1a of the vacuum chamber 1, and is evacuated to the vacuum pump Vp through the exhaust port 11a. At this time, a pressure difference of about several Pa is generated between the film formation space 1b and the exhaust space 11.

When a predetermined thin film is formed on the substrate W, the substrate W is loaded onto the stage 4 by a vacuum transfer robot (not shown), and the substrate W is placed on the upper surface of the chuck plate of the stage 4 (in this case, the substrate W). The upper surface of the film is the film formation surface) Then, while retracting the vacuum transfer robot, a predetermined voltage is applied to the electrode for the electrostatic chuck from the chuck power source to electrostatically attract the substrate W onto the upper surface of the chuck plate. Next, when the inside of the vacuum chamber 1 is evacuated to a predetermined pressure (for example, 1 × 10 ⁻⁵ Pa), argon gas as a sputtering gas is introduced at a constant flow rate through the gas introduction means 6. At the same time, a predetermined power is supplied to the target 2 from the sputtering power source E. As a result, plasma is formed in the film formation space 1b, the target is sputtered by argon gas ions in the plasma, and sputtered particles from the target 2 adhere to and deposit on the upper surface of the substrate W to form a predetermined thin film. Is done. When the target 2 is thus sputtered to form a film, even if the pressure distribution in the film formation space 1b is made equal throughout, the portion of the substrate W positioned in the direction of the exhaust space 11 (particularly, It has been found that the film thickness tends to be thinner at the outer end side in the radial direction of the substrate W than the portion located in other directions.

  Here, as shown in FIG. 3, in the sputtering apparatus of the conventional example, the outer surface portion 52 a of the lower plate portion 52 of the shield plate 5 facing the exhaust gas inlet 11 b of the exhaust space portion 11 is the inner wall surface of the vacuum chamber 1. The structure is not close to 1a. Therefore, when the exhaust gas flows from the exhaust gas inlet 11b to the exhaust space 11 through the gap Gp between the outer surface of the shield plate 5 and the inner wall surface 1a of the vacuum chamber 1, the exhaust gas inlet 11b The flow rate of the exhaust gas that has reached the vicinity is extremely lower than when flowing through the gap Gp (in FIG. 3, the arrow indicates the flow rate of the exhaust gas, and the shorter the flow rate, the slower the flow rate). . In other words, there is a region where the flow rate of the exhaust gas is locally low around the shield plate 5 that defines the film formation space 1b. If a region where the flow rate of the exhaust gas is slow exists around the shield plate 5 in this way, it is considered that the film thickness tends to be thin at the portion of the substrate W located in the direction of the region.

  Therefore, in the present embodiment, as shown in FIGS. 1 and 2, the outer surface portion 52a of the lower plate portion 52 of the shield plate 5 facing the exhaust gas inlet port 11b of the exhaust space portion 11 is covered with a gap. The cover plate 7 was provided. In this case, the cover plate 7 includes a fixed plate portion 71 erected on the bottom wall surface that defines the exhaust space portion 11, and a movable plate portion that is movable up and down with respect to the fixed plate portion 71 by a lifting mechanism 72a such as a motor. 72. The fixed plate portion 71 and the movable plate portion 72 are curved so as to have a curvature that substantially matches the inner wall surface 1 a of the vacuum chamber 1, and the movable plate portion 72 passes through the inner wall surface 1 a of the vacuum chamber 1. It arrange | positions so that it may be located substantially on 72b. On the other hand, the height of the movable plate portion 72 is such that when the movable plate portion 72 is moved to the upward movement position with respect to the fixed plate portion 71 by the elevating mechanism 72a, the lower end of the movable plate portion 72 is the upper end of the fixed plate portion 71. It overlaps in the radial direction and is set so that the upper end of the movable plate portion 72 can come into contact with the inner wall surface portion 11c of the vacuum chamber that defines the exhaust gas inlet port 11b.

  According to the above, as shown in FIG. 2, the region where the flow rate of the exhaust gas is slow around the shield plate 5 that defines the film formation space 1 b becomes as small as possible. The flow rate of the exhaust gas in the surroundings becomes substantially uniform. As a result, a thin film having a more uniform film thickness distribution (for example, ± 3%) in the substrate surface can be formed. In addition, if the cover plate 7 is configured by the fixed plate portion 71 and the movable plate portion 72, the flow rate of the exhaust gas around the shield plate 5 can be adjusted to be substantially uniform for each sputtering apparatus, which is advantageous. It is. In addition, by adjusting the height position of the movable plate portion 72 with respect to the fixed plate portion 71, fine adjustment of the film thickness distribution in the substrate surface can be performed.

Next, in order to confirm the effect of the present invention, the substrate W was made of a silicon wafer, the sputtering target 2 was made of Al ₂ O ₃ , and an Al ₂ O ₃ film was formed on the substrate W using the sputtering apparatus SM. As the sputtering conditions, the distance between the target 2 and the substrate W was set to 60 mm, the input power from the sputtering power source E was set to 2 kW, and the sputtering time was set to 120 sec. Moreover, argon gas was used as sputtering gas, and the partial pressure of sputtering gas was set to 0.1 Pa during sputtering. As a comparative experiment, the cover plate 7 was removed from the sputtering apparatus SM, and a film was formed under the same conditions. The film thickness distribution in the radial direction of the substrate W of the Al ₂ O ₃ film was measured using a known measuring instrument. According to this, in the comparative experiment corresponding to the conventional example, the film thickness distribution was 1.8%, whereas in the present embodiment, the film thickness distribution was 0.8%. .

  As mentioned above, although embodiment of this invention was described, this invention is not limited above. In the above embodiment, the cover plate is configured by the fixed plate portion 71 and the movable plate portion 72 as an example, but a single cover plate may be installed in the exhaust space portion.

  SM ... Sputtering device, Vp ... Vacuum pump, W ... Substrate (film formation target), 1 ... Vacuum chamber, 1a ... Inner wall surface of vacuum chamber 1, 1b ... Film formation space, 11 ... Exhaust space, 11a ... Exhaust port 11b ... exhaust gas inlet, 2 ... sputtering target, 4 ... stage, 5 ... shield plate, 7 ... cover plate, 71 ... fixed plate portion, 72 ... movable plate portion.

Claims (2)

There is a gap between the cylindrical vacuum chamber in which the sputtering target is installed, a stage in the vacuum chamber facing the target that allows the deposition target to be installed, and the inner wall surface of the vacuum chamber. A sputtering apparatus comprising a shield plate installed and surrounding a film formation space between the target and the stage,
The vacuum chamber is provided with an exhaust space portion that is locally expanded in a direction orthogonal to the extension line connecting the target and the stage, and the film formation space is formed by a vacuum pump through an exhaust port opened in the exhaust space portion. In the vacuum chamber containing the evacuated,
A sputtering apparatus comprising a cover plate that covers an outer surface portion of a shield plate facing an exhaust gas inlet of an exhaust space portion with a gap.   The cover plate is composed of a fixed plate portion standing on the bottom wall surface that defines the exhaust space portion, and a movable plate portion that is movable up and down with respect to the fixed plate portion by an elevating mechanism. The sputtering apparatus according to claim 1, wherein the plate portion is curved so as to have an equivalent curvature on the inner wall surface of the vacuum chamber 1.

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