JP2005290417A - Method and apparatus for capturing droplet in physical film forming method - Google Patents

Abstract

[PROBLEMS] To collect and collect droplets that have accumulated on a rotating filter plate over time to enable continuous operation over a long period of time and eliminate the need to remove the rotating filter plate for cleaning the droplets. To do.
[Structure] Droplets generated from a target are captured by a loplet capturing means having a rotating filter plate attached between the substrate and the target, and flowed around the rotating shaft of the rotating filter plate by a centripetal force and recovered. A method and an apparatus for capturing droplets in a physical film forming method.
[Selection] Figure 6

Description

  The present invention relates to a method and an apparatus for selectively capturing coarse particles called droplets accompanying fine particles flying from a target in a physical film forming method such as a laser ablation method, a sputtering method, or an arc discharge method. .

  As a conventional droplet capturing technique in the laser ablation film forming method, there is a rotating filter method such as a method using a rotating filter disk (Patent Document 1) and a method using a rotating blade (Patent Document 2). In the former, the laser is pulsed and needs to be synchronized with the filter, and the speed range to be selected is limited. In the latter, since the blade has an angle, the blade reflects without capturing the droplet. Therefore, it is necessary to increase the thickness of the filter in the particle flight direction because the design of the blade for capturing the low speed component is extremely severe and it is difficult to install a large number of blades. As a result, the distance between the target and the substrate has to be increased, and there is a problem that it is difficult to obtain a high-quality film. Further, both of them are expensive because a very advanced technique is required for manufacturing the filter, and there is a drawback that the droplets once captured are likely to be re-released.

  In order to overcome these drawbacks, the inventor has filed a patent application for an invention relating to a method of rotating a plurality of blades perpendicularly to a rotating surface and rotating them at high speed (Patent Document 3). Further, a method using a fine particle passage area control plate provided with a mesh, lattice, or spiral gap is also considered (Patent Document 4). However, in any case, collection of droplets adhering to the filter was not considered, and when a large amount of droplets accumulated on the filter, the filter was removed and overhauled or replaced.

Japanese Patent Laid-Open No. 10-30168 Japanese Patent Laid-Open No. 10-30169 Japanese Patent Laid-Open No. 2003-49262 Japanese Patent Laid-Open No.8-176805

  The present invention collects and collects droplets accumulated in the rotating filter plate over time, enabling continuous operation over a long period of time and eliminating the need to remove the rotating filter plate for cleaning the droplets. The problem is to do.

  In order to solve the above problems, the present invention provides blades that vortex outward from the periphery of the rotation center of the rotary filter plate and spread radially outward, and fine particles fly between the blades. By using the fact that the droplet trapped in the gap without passing through the gap due to rotation of the filter plate receives the centripetal force due to rotation of the filter plate and flows to the center part of the filter plate It collect | recovers.

When the rotary filter plate having the above structure is used, the gap between the blades in the rotation direction on the surface of the filter plate on the target side is X, and the distance from the filter plate rotation axis center to the middle point of X is R. The maximum velocity Vmax (unit = mm / second) of the fine particles that can be captured by the filter plate is given by Vmax = (1/2) h ω / tan ⁻¹ (X / 2R). Where h is the thickness h (unit = mm) of the filter plate in the particle flight direction, ω is the angular velocity of the filter (unit = radians / second), and the gap X between the blades is the front and back of the filter plate. Identical. In the case where the maximum capture speed is unified between the outer side and the inner side of the filter plate surface, the gap between the inner blades needs to be small and the gap between the outer blades needs to be large. On the other hand, by changing the gap between the blades at the position of the filter plate, the capture characteristics of the filter plate can be flexibly changed depending on the position.

  In order to prevent the droplets once trapped from being re-emitted, the front side in the rotational direction has a concave shape with a concave surface when viewed in the thickness direction of the rotating filter plate of each blade and in the thickness direction of the blade. To do. The droplets captured on the inner surface on the front side when viewed in the direction of rotation of each blade are not re-released along the concave portion of the inner surface of the blade, and receive the centripetal force in the direction of the rotation axis due to the rotation of the filter plate. Gathers in the middle part of Accordingly, the droplets accumulated on the inner surface of the blades of the filter plate can be collected in the central portion of the filter plate while the droplet is captured.

 A droplet collection box is installed below the central portion of the filter plate where the droplets gather. This makes it possible to collect the captured droplets while operating the filter plate without releasing the vacuum. In order to allow the captured droplets to flow easily towards the periphery of the axis of rotation, the vanes are at least wettable with respect to the droplet material on which the front side in the rotational direction is captured. Manufactured or coated with a bad material, that is, a material that does not adhere easily. For example, a fluororesin such as polytetrafluoroethylene is effective for most target materials such as metals, oxides, and carbon. In addition, TiN is effective when heat resistance is required.

  In place of the above-described embodiment, vanes that vortex outward from the periphery of the rotation center of the rotary filter plate and spread radially outward are provided, and a gap through which fine particles fly and pass is provided between the vanes. By attaching a plate with a large number of through holes so as to partially mask the gaps between the blades on the upper and lower surfaces of the rotary filter plate, and by allowing the fine particles to fly through the through holes, It is possible to more strongly prevent the re-release of the droplets flying in the gap and trapped on the inner surface on the front side when viewed in the rotation direction of each blade. The captured droplets receive a centripetal force in the direction of the rotation axis due to the rotation of the filter plate as in the above-described aspect, and gather at the center of rotation of the filter plate.

  In this case, compared to the above embodiment, the area ratio of the portion occupied by the through holes through which the fine particles fly is reduced with respect to the total surface area of the rotating filter plate, and the deposition rate of the generated film is reduced. It is not always necessary to form the concave structure as described above in the spiral blade, and the filter plate can be manufactured at low cost.

  The cross-sectional shape of the through hole may be any of a circle, an ellipse, and a polygon. The capturing characteristics of the droplet can be adjusted by the shape of the through hole. The simplest and preferred method is to attach a plate having many through holes to the front and back surfaces of a spiral blade filter plate.

  As described above, according to the method and apparatus of the present invention, it is possible to collect the captured droplets while operating the rotary filter plate, and long-term continuous operation in film formation using the rotary filter plate. Is possible. The maintenance of the rotating filter plate can also be greatly reduced compared to the conventional method.

Hereinafter, the method and apparatus of the present invention will be specifically described with reference to the drawings. When used for capturing a droplet of the laser ablation method, as shown in FIG. 1, a focused laser beam 3 is irradiated on a target 5 installed in a target holder 4 by a lens 2 inside a reaction chamber 1. Then, the fine particles generated from the target 5 are adhered to the substrate 8 placed on the substrate holder 7. The target holder 4 and the substrate holder 7 are rotated by rotating shafts 41 and 71, respectively. An atmospheric gas is appropriately supplied into the reaction chamber 1. A rotary filter plate 10 is installed on a rotary shaft 11 so as to be able to rotate at a high speed so as to shield the flight path of fine particles from the target 5 to the substrate 8. A droplet collection box 12 is provided outside the reaction chamber 1 below the rotary shaft 11 of the rotary filter plate 10.

  FIG. 2 shows a schematic plan view of the rotary filter plate 10 as viewed from above. The blades B of the rotary filter plate are swirled from the periphery of the rotation center of the filter plate and formed radially outward to the outer peripheral plate P, and a gap S is formed between adjacent blades. The maximum speed of the captured droplet is the distance R from the center of the rotation axis 11 of the filter plate to the middle point between the gaps X and X of the gap S between the blades in the rotation direction on the surface of the filter plate on the target side, and the filter It depends on the number of rotations of the plate as described above.

  FIG. 3 shows a cross-sectional view in which the two blades B1 and B2 adjacent to each other in the filter plate are focused and viewed in the blade thickness direction parallel to the filter plate thickness direction. The blades B1 and B2 are designed so that the front side in the rotational direction is concave and the thickness is reduced toward the inside in the depth direction. As a result, as shown in FIG. 3, the droplets captured on the inner surface I on the front side in the rotational direction are collected near the center of the concave portion on the inner surface of the blade and are difficult to re-release.

  FIG. 4 shows blades B that vortex from the periphery of the center of rotation of the filter plate and spread radially outward to the outer peripheral annular plate P, respectively, on the upper and lower surfaces of the filter plate. The schematic plan view which looked at the filter board which mounted | wore with the board | plate with many circular through-holes H in the clearance gap S between blades was seen from the top is shown. The radial vanes inside the filter plate are indicated by dotted lines. The through hole H is formed between two blades as shown in FIG. Actually, the through hole H is formed over the entire area of the filter plate.

  FIG. 5 shows a cross-sectional view focusing on one through hole H in the filter plate. The through holes are formed by mounting plates 13 and 14 having through holes H on the upper and lower surfaces of the gap between the spiral blades B1 and B2. If the leftward direction is the rotational direction, the holes H are formed more to the left than the center between the blades B1 and B2, so that the particles once captured are less likely to be released again. The droplets captured on the inner surface on the front side in the rotational direction of the blade B2 receive a centripetal force in the direction of the rotational axis and flow and collect along the inner surface of the blade B2 near the center of the filter plate.

  FIG. 6 shows a conceptual diagram of the vicinity of the collection box when the rotary filter plate as shown in FIGS. 2 and 3 is used. In order to move the droplet that has flowed to the center portion of the filter plate to the recovery box 12, the cross-sectional structure of the blades surrounded by the dotted line portion is sharpened from the concave structure B in the direction of the recovery box 12. Change to structure B ′. As a result, in this dotted area, the collected droplets D drop toward the collection box 12. Stopper rings 14 are mounted on both sides of the dotted line area so as not to spill from the gap to the collection box 12. Further, since the amount of droplets gathered at the central portion increases, a cap plate 15 is attached to prevent upward spillage.

FIG. 7 shows a conceptual diagram of the vicinity of the collection box when the filter plate as shown in FIGS. 4 and 5 is used. In order to move the droplets D collected in the central portion of the filter plate to the collection box 12, there is no lower surface plate 14 in the region surrounded by the dotted line portion. In the dotted line region, the collected droplets D fall toward the collection box 12. Stopper rings 14 are attached to both sides of the dotted line area so that the droplets do not fall out from the gap to the collection box 12. In addition, since the amount of droplets gathered at the center of the filter plate increases, a through hole is not formed in the upper surface plate 13 in the dotted line region so as not to spill upward.

ArF excimer laser (wavelength 193 nm, FWHM = 20 ns) is irradiated to Si target at an incident angle of 45 ° in a vacuum chamber of 5 × 10 ^-7 Torr or less evacuated by a turbo molecular pump, facing 50 mm away Film deposition was performed on a glass substrate. Between the target and the substrate, a rotating filter plate capable of high-speed rotation was installed to capture droplets.

  Stainless steel was used as the blade material, and the surface thereof was coated with a fluoroethylene resin. The size of the filter plate was 200 mm in diameter and 10 mm in thickness, and the thickness of the concave blades was 0.3 mm at the thinnest portion of the central thickness, and 0.8 mm at the maximum thickness portions on the outer sides.

FIG. 8 shows the relationship between the rotation speed of the designed filter plate and the maximum speed that can be captured. The area ratio of the blade portion occupying the surface of the filter plate was about 90%, and the area of the gap portion was 10%. The fluence F of the laser pulse was 4 J / cm ² , the repetition frequency was 10 Hz, and the substrate temperature was room temperature. The degree of adhesion of fine particles in the produced silicon thin film was evaluated using a scanning electron microscope (SEM).

  FIG. 9 shows a SEM image of the film surface of a silicon thin film produced at a rotation speed of 0 (a) and 3,500 rpm (b) of the filter plate and a film formation time of 60 minutes. It can be seen that the droplets are completely captured at 3,000 rpm and above. No re-emission of droplets once trapped from the filter plate was observed.

  FIG. 10 shows an SEM image of the droplets collected in the collection box after 1000 hours. Many droplets around 10mm in diameter were observed. The amount of recovered droplets was about 50 mg.

The schematic diagram of the apparatus which shows an example in the case of using the rotating filter board for droplet capture | acquisition for the thin film preparation by laser ablation. FIG. 3 is a schematic plan view of a rotating filter plate having radial blades that vortex from the periphery of the rotation center of the filter plate and spread radially outward. Sectional drawing parallel to the thickness direction of a blade | wing filter board shown in FIG. 2, and the thickness direction of a blade | wing. A plate having a plurality of circular through holes on the upper and lower surfaces of the rotating filter plate is provided between the blades. The conceptual top view of the rotation filter board with which the clearance gap was partially masked. The expanded sectional view of the through-hole part vicinity of the rotation filter board shown in FIG. The conceptual diagram of the periphery of a collection box at the time of using the rotation filter board shown in FIG. The conceptual diagram of the collection box vicinity in the case of using the rotation filter board shown in FIG. The graph which shows the relationship between the rotational speed of a rotation filter board, and the maximum speed which can be captured. The drawing substitute photograph which shows the film | membrane surface SEM image of the silicon thin film produced at the rotation speed 0 (a) and 3,500 rpm (b) of the rotation filter board. The drawing substitute photograph which shows the SEM image of the droplet collect | recovered by the collection box.

Claims (7)

Capturing droplets generated from the target with a droplet capturing means equipped with a rotating filter plate attached between the substrate and the target, and collecting the droplets around the rotation axis of the rotating filter plate by centripetal force. A method for capturing droplets in the physical film forming method. In a droplet trapping device of a film forming apparatus that captures droplets generated from a target with a rotating filter plate attached between the substrate and the target, the rotating filter plate winds around the rotation center axis and radiates outward. Fine particles fly in the gap formed by the blades spreading toward the front, and the droplets captured on the front side of the inner surface of the blade in the rotational direction flow by the centripetal force in the rotational axis direction of the rotary filter plate. A droplet trapping device for a physical film-forming apparatus, characterized in that: 3. The drop according to claim 2, wherein the rotary filter plate has a concave shape having a concave surface on the front side in the rotational direction when viewed in the thickness direction of the rotary filter plate of each blade and a cross section in the blade thickness direction. Let trapping device. The rotary filter plate is equipped with a plate with a large number of circular through-holes on the upper and lower surfaces so as to mask the gaps between the blades, so that fine particles can fly through the through-holes. The droplet capturing device according to claim 2. 3. A droplet trapping according to claim 2, wherein the blade is made of or coated with a material having poor wettability with respect to the droplet material to be trapped at least in the rotational direction. apparatus. 6. The droplet capturing device according to claim 2, further comprising means for dropping the droplet that has flowed to the central portion of the rotary filter plate. The droplet trapping device according to claim 6, further comprising a droplet collection container at a lower portion of a central portion of the rotary filter plate.

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