JP6871068B2 - Sputtering equipment - Google Patents

Description

The present invention relates to a sputtering apparatus, and more particularly to an apparatus for forming a carbon film on the surface of an object to be filmed.

Conventionally, this type of sputtering apparatus has been used to form a carbon film as an electrode film for a device such as a non-volatile memory (see, for example, Patent Document 1). This includes a vacuum chamber provided with a carbon target, a vacuum pump that evacuates the vacuum chamber, and a stage that is arranged in the vacuum chamber so as to face the target and holds an object to be formed. Further, the vacuum chamber is provided with a shield plate which is installed with a gap from the inner wall thereof and surrounds the film formation space between the target and the stage. Then, the inside of the vacuum chamber is evacuated to a predetermined pressure by a vacuum pump, and then the target is sputtered to form a carbon film on the surface of the object to be formed.

Here, when a carbon target is sputtered to form a film on the surface of the film-forming object, fine particles may adhere to the surface of the film-forming object immediately after the film formation. Since such adhesion of particles causes a decrease in product yield, it is necessary to suppress the adhesion of particles to the surface of the film-forming object as much as possible. Therefore, the present inventors have conducted extensive research and have come to find that the carbon particles floating in the vacuum chamber are attached to the surface of the film-forming object immediately after the film-forming as fine particles. That is, when the carbon target is sputtered, the carbon particles scattered from the target adhere and accumulate not only on the film-forming object but also on the surface of the parts and the shield plate existing around the target. It is considered that the particles are re-disengaged for some reason, and the re-disengaged carbon particles are suspended in the vacuum chamber without being evacuated.

International Publication No. 2015/122159

The present invention has been made based on the above findings, and an object of the present invention is to provide a sputtering apparatus capable of reducing the number of particles adhering to the surface of a film-forming object as much as possible. ..

In order to solve the above problems, a vacuum chamber provided with a carbon target, a vacuum pump that evacuates the vacuum chamber, a stage that holds an object to be formed in the vacuum chamber, and a gap from the inner wall surface of the vacuum chamber. It is provided with a shield plate that surrounds the film formation space between the target and the stage, and the inside of the vacuum chamber is evacuated to a predetermined pressure by a vacuum pump, and then the target is evacuated to form a film. The sputtering apparatus of the present invention for forming a carbon film on the surface of an object further includes an adsorbent whose surface is cooled to a temperature of 123 K or less, and the adsorbent is in a vacuum chamber in which radiation to the object to be formed is prevented. It is characterized in that a gap is provided in the outer surface portion of the shield plate at a predetermined position.

According to the present invention, once the carbon particles suspended in the vacuum chamber are adsorbed on the adsorbent, the surface of the adsorbent is cooled to a temperature of 123 K or less, so that re-separation is prevented. As a result, by reducing the amount of carbon particles suspended in the vacuum chamber, the number of particles adhering to the surface of the film-forming object can be reduced as much as possible. In this case, since the adsorbent is arranged at a predetermined position in the vacuum chamber where radiation to the film-forming object is prevented, there is a problem that the film quality is changed and the film-forming process for the film-forming object is adversely affected. Does not occur. Furthermore, the shield plate itself is cooled to a predetermined temperature by radiation from the adsorbent, so that the shield plate itself plays a role as an adsorbent, and carbon particles are adsorbed by the shield plate that defines the film formation space. However, by retaining the particles, the amount of suspended carbon particles can be further reduced, which is advantageous.

In the present invention, the target and the stage are arranged to face each other, and an exhaust space portion is provided that is locally expanded in a direction orthogonal to an extension line connecting the two, and an exhaust port is provided in the exhaust space portion. It said vacuum pump to be connected to is preferred.

In this case, it is preferable that the outer surface portion of the shield plate is in a range facing the exhaust gas inflow port of the exhaust space portion. According to this, the presence of the adsorbent in the exhaust path of the exhaust gas leading from the film forming space in the vacuum chamber to the exhaust space portion makes it easier to adsorb carbon particles, which is advantageous.

The schematic cross-sectional view which shows the sputtering apparatus of embodiment of this invention. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. The figure which shows the modification of this embodiment.

Hereinafter, referring to the drawings, the object to be filmed is a silicon wafer (hereinafter, simply referred to as “substrate W”), a carbon target for sputtering is provided above the vacuum chamber, and a stage on which the substrate W is installed is provided below the target. An embodiment of the sputtering apparatus of the present invention will be described by taking the above-mentioned one as an example.

With reference to FIGS. 1 and 2, the 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 part of the vacuum chamber 1. The cathode unit Cu is composed of a carbon target 2 and a magnet unit 3 arranged above the target 2.

The target 2 is formed in a circular shape in a plan view according to the contour of the substrate W. The target 2 is attached to the upper part 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 attached to the backing plate 21. Further, a sputtering power source E having a known structure is connected to the target 2 so that DC power having a negative potential can be applied during film formation by sputtering. The magnet unit 3 arranged above the target 2 generates a magnetic field in the space below the sputter surface 22 of the target 2, captures ions and the like ionized below the sputter surface 22 during sputter, and scatters the spatter from the target 2. It has a closed magnetic field or cusp magnetic field structure that efficiently ionizes particles. Since a known magnet unit itself can be used, further description will be omitted.

At the center of the bottom of the vacuum chamber 1, a stage 4 is arranged so as to face the target 2 via another insulator Ib. Although not particularly illustrated, the stage 4 is composed of, for example, a metal base having a tubular contour and a chuck plate adhered to the upper surface of the base, and adsorbs the substrate W during film formation. I am trying to hold it. As for the structure of the electrostatic chuck, known ones such as a unipolar type and a bipolar type can be used, so further detailed description thereof will be omitted. Further, the base may include a passage for circulating a refrigerant 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 which is installed with a gap from the inner wall surface 1a and surrounds the film formation space 1b between the target 2 and the stage 4. The shield plate 5 surrounds the periphery of the target 2 and extends below the vacuum chamber 1 with a substantially tubular upper plate portion 51, and surrounds the periphery of the stage 4 and extends above the vacuum chamber 1. It has a tubular 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. 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 a gas introducing means 6 for introducing a predetermined gas. The gas includes not only a rare gas such as argon gas introduced when forming plasma in the film forming space 1b, but also a reaction gas such as oxygen gas and nitrogen gas appropriately introduced according to the film forming. The gas introducing means 6 has a gas ring 61 provided on the outer periphery of the upper plate portion 51 and a gas pipe 62 connected to the gas ring 61 and penetrating the side wall of the vacuum chamber 1, and the gas pipe 62 is a mass flow controller. It communicates with a gas source (not shown) via a controller 63. In this case, although detailed illustration is omitted, a gas diffusion portion is attached to the gas ring 61, and the sputter gas from the gas pipe 62 is diffused by the gas diffusion portion to perforate the gas ring 61 at equal intervals in the circumferential direction. Sputter gas is injected at the same flow rate from the provided gas injection port 61a. Then, the sputter gas injected from the gas injection port 61a is introduced into the film forming space 1b from a gas hole (not shown) formed in the upper plate portion 51 at a predetermined flow rate, and is introduced into the film forming space 1b at a predetermined flow rate, and is introduced into the film forming space 1b during the film forming process. The pressure distribution inside is made equal throughout. The method for making the pressure distribution in the film formation space 1b equal throughout the film formation space 1b is not limited to this, and other known methods can be appropriately adopted.

Further, the vacuum chamber 1 is provided with an exhaust space portion 11 locally expanded in a direction orthogonal to the center line (extension line) Cl connecting the target 2 and the stage 4, and the exhaust space portion 11 is provided. An exhaust port 11a is provided on the bottom wall surface for partitioning. A vacuum pump Vp such as a cryopump or a turbo molecular pump is connected to the exhaust port 11a via an exhaust pipe. During film formation, a part of the sputter gas introduced into the film formation space 1b becomes exhaust gas, and is outside the shield plate 5 through the seam of the shield plate 5 or the gap between the shield plate 5 and the target 2 or the stage 4. It flows from the exhaust gas inflow port 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 forming space 1b and the exhaust space portion 11.

When forming a predetermined thin film on the substrate W, the substrate W is carried onto the stage 4 by a vacuum transfer robot (not shown), and the substrate W is installed 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, the vacuum transfer robot is retracted, and a predetermined voltage is applied from the chuck power supply to the electrode for the electrostatic chuck to electrostatically attract the substrate W to 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 introducing means 6 and into the vacuum chamber 1. At the same time, a predetermined power is applied 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 the ions of argon gas in the plasma, and the sputtered particles (carbon particles) from the target 2 adhere to and deposit on the upper surface of the substrate W to form a carbon film. Is formed. When the target 2 is sputtered to form a carbon film in this way, it is found that the carbon particles floating in the vacuum chamber 1 are attached to the surface of the film-forming object immediately after the film formation as fine particles. It came to. This is because the carbon particles scattered from the target adhere and accumulate not only on the substrate W but also on the parts existing around the target 2 and the surface of the shield plate 5, but the carbon particles adhered in this way re-separate for some reason. However, it is considered that the carbon particles that have re-emerged are suspended in the vacuum chamber 1 without being evacuated.

Therefore, in the present embodiment, the adsorbent 7 whose surface is cooled to a temperature of 123 K or less is provided at a predetermined position in the vacuum chamber 1 in which radiation to the film-forming object W is prevented. In this case, the adsorbent 7 is provided with a gap in the outer surface portion 52a of the lower plate portion 52 of the shield plate 5, and the surface is cooled to the above temperature by a cooling mechanism such as a refrigerator (not shown). Since a known cooling mechanism can be used, detailed description thereof will be omitted here. Although the adsorbent 7 is configured to be movable in the vertical direction by an elevating mechanism 7a such as a motor, it may be erected on the bottom wall surface of the vacuum chamber 1.

According to the above, once the carbon particles floating in the vacuum chamber 1 are adsorbed on the adsorbent 7, the surface of the adsorbent 7 is cooled to a temperature of 123 K or less, so that re-separation is prevented. .. As a result, by reducing the amount of carbon particles suspended in the vacuum chamber 1, the number of particles adhering to the surface of the substrate W can be reduced as much as possible. In this case, since the adsorbent 7 is arranged at a predetermined position in the vacuum chamber where radiation to the substrate W is prevented, there is no problem that the film quality is changed or the film forming process on the substrate W is adversely affected. Further, when the shield plate 5 itself is cooled to a temperature of 123 K or less by the radiation from the adsorbent 7, the shield plate 5 itself plays a role as an adsorbent, and the shield defining the film formation space 1b. By adsorbing and holding the carbon particles on the plate 5, the amount of floating carbon particles can be further reduced, which is advantageous. In this case, the substrate W and the shield plate 5 may be separated by 10 mm or more so that the substrate W is not cooled by the radiation from the cooled shield plate 5.

Next, in order to confirm the effect of the present invention, the following invention experiment was carried out. That is, the substrate W was made of a silicon wafer having a diameter of 300 mm and the target 2 was made of carbon having a diameter of 400 mm, and a carbon 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. Argon gas was used as the sputtering gas, and the partial pressure of the sputtering gas was set to 0.1 Pa during sputtering. Further, as a comparative experiment, the adsorbent 7 was removed from the sputtering apparatus SM, and a film was formed under the same conditions.

The number of particles of 0.1 μm or more adhering to the substrate W before and after the film formation was measured, and the number of particles adhering to the substrate W during the film formation was determined. According to this, the number of particles was 84 in the invention experiment, but it was 145 in the comparative experiment, and it was found that the number of particles can be reduced by providing the adsorbent 7.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above. In the above embodiment, the adsorbent 7 is provided so as to cover the outer surface portion 52a of the lower plate portion 52 of the shield plate 5 in the range facing the exhaust gas inflow port 11b of the exhaust space portion 11 with a gap. As shown in FIG. 3, both ends of the adsorbent 7 may be provided so as to extend further to the gap between the inner wall surface 1a of the vacuum chamber 1 and the lower plate portion 52 of the shield plate 5. In FIG. 3, the arrow indicates the flow of exhaust gas. According to this, the shield plate 5 can be efficiently cooled, and the carbon particles in the exhaust gas flow into the film forming space 1b by efficiently adsorbing and holding the carbon particles contained in the exhaust gas. It is advantageous because it can suppress the adhesion to the substrate W.

In the above embodiment, the case where the shield plate 5 is cooled by the adsorbent 7 has been described as an example, but the present invention can also be applied to the case where the components other than the shield plate 5 to which carbon particles are attached are cooled. it can.

SM ... Sputtering device, Vp ... Vacuum pump, W ... Substrate (object to be deposited), 1 ... Vacuum chamber, 1a ... Inner wall surface of vacuum chamber 1, 11 ... Exhaust space, 11a ... Exhaust port, 2 ... Target, 4 ... stage, 5 ... shield plate, 7 ... adsorbent.

Claims (3)

A vacuum chamber provided with a carbon target, a vacuum pump that evacuates the vacuum chamber, a stage that holds the object to be formed in the vacuum chamber, and a target that is installed with a gap from the inner wall surface of the vacuum chamber. It is equipped with a shield plate that surrounds the film formation space between the film and the stage, and after vacuuming the inside of the vacuum chamber to a predetermined pressure with a vacuum pump, the target is sputtered to form a carbon film on the surface of the film formation target. In a film sputtering device
Further provided with an adsorbent whose surface is cooled to a temperature of 123 K or less, the adsorbent has a gap in the outer surface portion of the shield plate at a predetermined position in the vacuum chamber where radiation to the film-forming object is prevented. sputtering system, characterized by being provided. Te claim 1, wherein the sputtering apparatus odor, the target and the direction in which the stage and is orthogonal to the extension line connecting the two together are opposed is provided an exhaust space portion locally swelled, exhaust space portions A sputtering apparatus characterized in that the vacuum pump is connected to an exhaust port opened in. The sputtering apparatus according to claim 2, wherein the outer surface portion of the shield plate is set to a range facing the exhaust gas inflow port of the exhaust space portion.

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