Spin rinse dryer with improved drying characteristics

Abstract

To provide a low-profile spin rinse dryer capable of high density vertical stacking, with a reduced risk of contamination of a wafer after cleaning and drying.SOLUTION: A spin rinse dryer for treating a substrate has: an enclosure; a rotatable support 23 for supporting the substrate; a rotatable member 27 located within the enclosure above the rotatable support 23, the rotatable member 27 having a continuous lower surface; and a drive device for rotating the rotatable member 27. During cleaning of a wafer, liquid that splashes up from the wafer strikes the rotatable member 27, rather than an upper wall of the enclosure, and forms droplets on the rotatable member 27.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to spin rinse dryers, and more particularly to spin rinse dryers provided with means to reduce the possibility of unwanted contamination. [Background technology]

[0002] Spin rinse dryers (SRDs) are commonly used in the semiconductor and related industries to clean substrates. SRDs can be used as stand-alone units or integrated into larger systems that include additional systems to perform other functions (e.g., wet etching systems, photoresist systems, or electrochemical deposition systems).

[0003] A common function of an SRD is the cleaning and drying of (typically circular) workpieces or wafer substrates (particularly in the semiconductor industry). During the cleaning process, a cleaning fluid (typically an aqueous solution) is sprayed onto the wafer while the wafer is rotated in a horizontal plane at a relatively slow speed (typically 50-200 rpm). This is usually done within a chamber or enclosure, which prevents leakage of the liquid spray and ensures that the wafer is maintained in a controlled environment. The processing volume is typically purged with an inert gas (such as N2) from above the wafer, promoting fluid flow within the chamber. Once the cleaning fluid has removed contaminants from the wafer, the fluid flow is stopped and the wafer is rotated at a high speed (up to approximately 2000-2500 rpm) to promote drying of the wafer, after which it is brought to a rest and collected, ready for further processing.

[0004] For several critical processing steps, such as the final cleaning before returning to the cassette or front-opening unified pod (FOUP), it is essential that the wafers are not only thoroughly cleaned by this "clean and dry" process, but also completely dry when removed from the SRD chamber. The presence of water droplets on the wafer surface can lead to damage to the devices on the substrate; for example, if the layer being cleaned is a metal such as copper, the water droplets can cause corrosion or excessive oxidation of the substrate's surface. This is undesirable as it can lead to reduced yield.

[0005] Integrating several processing steps into a single automated system has several advantages, including cost, productivity, and yield. In the case of an electrochemical deposition system, the process sequence may include a pre-cleaning step, followed by several metal deposition steps, and several post-deposition wafer cleaning steps before returning to the wafer cassette or FOUP.

[0006] For example, if bump metallization requires a relatively thick (several microns) metal deposition step, a relatively large number of modules (more than 10 deposition stations) is required to make the production system cost-effective. Because cleanroom space is expensive and therefore the tool footprint is a major contributor to the tool's overall cost of ownership, minimizing footprint is important in the context of semiconductor capital equipment. This has led to the practice of "stacking" process modules vertically to increase productivity while minimizing cleanroom footprint. For example, U.S. Pat. No. 9,421,617 shows a configuration in which one SRD module is positioned above a second SRD module (in FIG. 2 of this document).

[0007] 1a and 1b show schematic diagrams of a conventional bowl-type SRD similar to the type shown in U.S. Pat. No. 6,497,241. In FIG. 1a, the top of chamber 1 is open, allowing wafers 3 to be inserted into and removed from chamber 1 from above. In FIG. 1b, chamber 1 has a flat lid 7 to provide an enclosure. Wafers 3 may be inserted into and removed from chamber 1 through a slit in the sidewall, or the lid 7 may be removed, allowing wafers 3 to be inserted and removed in a manner similar to the configuration shown in FIG. 1a.

[0008] Chamber 1 is typically made from a polymeric material such as high-density polyethylene (HDPE), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), or polyvinyl chloride (PVC). The choice of material depends largely on the properties of the cleaning fluid used to process the wafer. Some cleaning fluids are incompatible with traditional polymeric materials, and when using these fluids, the chamber may be constructed using stainless steel or another metal.

[0009] The chamber has a rotor assembly 2 that holds a wafer 3 and can be controlled to rotate at speeds up to about 3000 rpm. A spray nozzle or series of spray nozzles 4a is positioned above the plane of the wafer 3 and is aimed at the front side of the wafer. Similarly, a spray nozzle or series of spray nozzles 4b is positioned below the plane of the wafer 3 and is aimed at the back side of the wafer.

[0010] Fluid from nozzles 4a, 4b impinges on wafer 3, is thrown off wafer 3, strikes the sidewalls of chamber 1, and is removed through an exhaust port (not shown) at the base of the chamber, much like in a centrifuge. After the cleaning step, an inert purge gas (such as N2) can be directed at wafer 3 to help dry it. However, even after drying wafer 3, some fluid may remain on the walls of chamber 1, and in the configuration of FIG. 1b, droplets 6 may form on the underside of chamber lid 7. These droplets may fall onto wafer 3 during removal from chamber 1 and contaminate it.

[0011] The configuration in Figure 1a obviously does not have this problem as there is no lid on which droplets can form. However, the configuration in Figure 1a is not compatible with the design of low profile SRD modules and when several SRDs as shown in Figure 1a are stacked vertically, a large gap between the modules is required to avoid droplets forming on the underside of the top module.

[0012] Alternative approaches have been proposed to address the problem of droplet formation on the underside of the lid. For example, U.S. Patent No. 9,421,617 shows a configuration in which the lid 10 is formed in a conical shape, so that droplets tend to flow downward and radially outward, away from the wafer (schematically shown in FIG. 2a). This effect can be enhanced by forming the underside of the lid as a hydrophobic surface. FIG. 2b shows a configuration in which the lid 12 is formed as a dome, which can also have a hydrophobic underside. A purge gas nozzle can be provided on top of the dome 12 to direct an inert purge gas (such as N2) along the inner surface of the dome 12, pushing droplets radially outward and away from the wafer.

[0013] However, both of these configurations require significant vertical space above the wafer and are therefore not well suited to high density vertical chamber stacking. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] U.S. Patent No. 6,497,241 [Patent Document 2] U.S. Patent No. 9,421,617 Summary of the Invention [Problem to be solved by the invention]

[0015] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a thin spin rinse dryer that allows for high density vertical stacking with reduced risk of wafer contamination after cleaning and drying. [Means for solving the problem]

[0016] According to a first aspect of the present invention, there is provided a spin rinse dryer for processing a substrate, comprising an enclosure, a rotatable support for supporting a substrate, a rotatable member located within the enclosure above the rotatable support, the rotatable member having a continuous underside, and a drive for rotating the rotatable member.

[0017] During wafer cleaning, liquid splashed from the wafer may strike the underside of the rotatable member rather than the upper wall of the enclosure, forming droplets on the rotatable member. After the flow of cleaning liquid stops, the drive may rotate the rotatable member at a high speed, which tends to cause droplets to fly off the underside of the rotatable member due to centrifugal force. The liquid then flows down the wall of the enclosure, away from the wafer, thereby significantly reducing the chance of contamination of the cleaned wafer.

[0018] An advantage of the present invention is that the spin rinse dryer can be provided as a low profile spin rinse dryer, which can have a vertical height of 300 mm or less, which is particularly suitable for applications where modules are stacked vertically.

[0019] The lower surface of the rotatable member may be positioned to be substantially parallel to the upper surface of the substrate when the substrate is supported by the rotatable support.

[0020] The rotatable support may be connected to the rotatable member such that the rotatable support and the rotatable member rotate together. Several arms may extend downward from the rotatable member, and prongs may extend radially inward from the lower end of each arm, the prongs acting as rotatable supports. There may be three arms equally spaced circumferentially.

[0021] A drive may be located laterally of the enclosure and may be connected to the rotatable member and the rotatable support so as to drive them to rotate.

[0022] The rotatable support and the rotatable member may be unconnected to each other and may rotate independently. The rotatable support and the rotatable member may be arranged to rotate about a common axis. A single drive may be located next to the enclosure and may be connected to and drive to rotate both the rotatable member and the rotatable support. The drive may be connected to the rotatable member and the rotatable support via a telescoping shaft. In another configuration, two drive units may be located next to the enclosure, a first of the drive units connected to and drive to rotate the rotatable member, and a second of the drive units connected to and drive to rotate the rotatable support.

[0023] Both the enclosure and the rotatable member may be circular in plan view. The diameter of the rotatable member may be slightly smaller than the inner diameter of the enclosure. The diameter of the rotatable member may be larger than the diameter of the substrate to be processed.

[0024] The rotatable member may be formed from a hydrophobic material such as polycarbonate.

[0025] The rotatable member may be formed as a single piece.

[0026] The rotatable member may be formed with reinforcing features such as ribs.

[0027] The spin rinse dryer may be provided with nozzles located above and below the rotatable support for directing liquid toward a substrate positioned on the rotatable support.

[0028] The spin rinse dryer may be capable of operating at sub-atmospheric pressure.

[0029] The spin rinse dryer may have a vertical height of less than about 300 mm.

[0030] The present invention also extends to an apparatus for processing substrates comprising a stack of substrate processing modules, at least one of the modules being a spin rinse dryer as described above.

[0031] According to a further aspect of the present invention, there is provided a method of processing a substrate, the method comprising the steps of supporting the substrate on a rotatable support in an enclosure below a rotatable member, directing liquid from nozzles above and below the rotatable support at the substrate to clean the substrate, rotating the rotatable support to remove the liquid from the substrate, rotating the rotatable member to remove the liquid from the rotatable member, and removing the substrate from the enclosure.

[0032] The substrate may be a semiconductor substrate, such as a semiconductor wafer.

[0033] The invention has been described above, but the invention extends to any combination of the features set out above or set out in the following description, drawings and claims. For example, any feature disclosed in connection with one aspect of the invention may be combined with any feature disclosed in connection with any other aspect of the invention.

[0034] Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0035] [Figure 1a] 1 is a schematic diagram of a prior art spin rinse dryer. [Figure 1b] 1 is a schematic diagram of a prior art spin rinse dryer. [Figure 2a] 1 is a schematic diagram of a prior art spin rinse dryer including means intended to reduce contamination of cleaned wafers; [Figure 2b] 1 is a schematic diagram of a prior art spin rinse dryer including means intended to reduce contamination of cleaned wafers; [Figure 3] 1 is a schematic cross-sectional view of a first embodiment of a spin rinse dryer according to the present invention. [Figure 4] FIG. 1 is a side view of a spin rinse dryer according to the present invention. [Figure 5a] FIG. 4 is a schematic cross-sectional view similar to FIG. 3, showing an alternative drive means. [Figure 5b] FIG. 4 is a schematic cross-sectional view similar to FIG. 3, showing an alternative drive means. DETAILED DESCRIPTION OF THE INVENTION

[0036] Figure 3 illustrates a first embodiment of the present invention. The spin-rinse dryer of Figure 3 includes an enclosure formed by a body 21 and a lid 22, with a rotatable support 23 for a wafer 29. Located above the wafer 29 and below the enclosure lid 22 is a rotatable member 27 in the form of a disk having a continuous underside. During cleaning, liquid splashed from the wafer 29 strikes the underside of the rotatable member 27 rather than the enclosure lid 22, causing droplets to form on the rotatable member 27 instead of the lid 22. The rotatable member 27 can then be rotated to remove the droplets from the underside via centrifugal force.

[0037] In the particular version shown in FIG. 3, the rotatable support 23 for the wafer 29 and the rotatable member 27 are integrally formed. Three circumferentially equally spaced arms extend downward from the rotatable member 27, and the wafer 29 is supported on three prongs extending radially inward from the lower ends of the arms. The rotatable member 27, and thus the arms and prongs, are rotated by a central shaft 25 that extends vertically through the enclosure lid 22. The central shaft 25 is powered to rotate by a motor 28 located on one side of the chamber, whose shaft extends vertically and is connected to the central shaft 25 by a belt drive 26. Locating the drive means to the side of the enclosure allows for a reduced overall height of the spin rinse dryer.

[0038] During wafer cleaning, the rotatable member 27 and the rotatable support 23 for the wafer 29 are rotated (typically at 50 to 200 rpm) while cleaning fluid is sprayed from the nozzles 24a and 24b. All interior surfaces of the chamber are wetted with the scattered spray, which can cause the formation of hanging droplets (similar to those shown in FIG. 1b) that can fall onto the wafer 29.

[0039] Once the wafer 29 is cleaned, the fluid supply is stopped, and the wafer 29 is dried by spinning at high speed (typically 2000-2500 rpm). An inert, dry purge gas, such as nitrogen, can also be used. During this high-speed spinning, not only is the wafer 29 dried (by centrifugal forces that move water radially away from the wafer 29), but the rotatable member 27 located directly above the wafer 29 is also dried. Any droplets that form on the rotatable member 27 are dispersed by centrifugal forces. When the spinning is terminated, there should be no droplets above the wafer 29, and therefore there should be no risk of liquid dripping onto the wafer 29. Furthermore, this is accomplished in a low-profile package (i.e., with minimal vertical height).

[0040] Typically, the rotatable member 27 has a larger diameter than the wafer 29; for example, if the wafer 29 has a diameter of 300 mm, the rotatable member 27 has a diameter of 320 mm. Furthermore, the rotatable member 27 should extend as close as possible to the chamber wall, preferably within a maximum of 10 mm from the chamber wall. This further reduces the risk of liquid dripping from the underside of the chamber lid 22 onto the wafer 29. A drain path for the fluid can be located near the chamber wall. Additionally, the top of the rotatable member 27 should be located near the underside of the chamber lid 22 (to reduce the risk of spray from the nozzle hitting the underside of the chamber lid 22), preferably within 3 mm of the underside of the chamber lid 22.

[0041] Figure 4 shows a low-profile spin rinse dryer with the chamber open to allow for wafer loading or unloading. In this case, the lower chamber portion 31 moves away from the fixed upper portion 32. However, it is also possible for the lower chamber portion 31 to be fixed and the upper chamber portion 32 to move. This opening and closing movement can be accomplished using an electric motor or a pneumatic or hydraulic piston.

[0042] When the chamber is open, wafers 39 can be inserted into or removed from the rotatable support 33. The inner diameter between the holding arms must be larger than the diameter of the wafer 39 so that the wafer 39 can be placed into the chamber and on the rotatable support 33. Furthermore, if notch alignment is required, the position of the wafer 39 on the rotatable support 33 must be rotationally aligned before any wafer loading or unloading can occur. This is achieved by a central lift pillar 40, which lifts the wafer 39 from the rotatable support 33 and allows the notch or flat on the wafer 39 to be aligned with a defined orientation on the rotatable support before the unload step.

[0043] The particular version of the chamber of Figure 4 has a maximum height of about 215mm when open, which allows the chambers to be stacked on a pitch of about 225mm, resulting in efficient use of space.

[0044] The present invention is not limited to the specific drive configuration shown in FIG. 3. FIG. 5a shows a variant in which the rotatable support 53 and the rotatable member 54 are separate bodies arranged to rotate about a common axis. The rotatable support 53 for the wafer supports the wafer from below, thereby simplifying the wafer loading and unloading procedures. The rotatable support 53 and the rotatable member 54 are driven by a single motor 51 and connected to it via a telescopic shaft coupling 52 (the telescopic aspect is necessary to allow the upper and lower parts of the chamber to move away from each other to open the chamber). FIG. 5b shows an alternative version in which the rotatable support 63 and the rotatable member 64 are provided with separate motors 61, 62, also arranged to rotate about a common axis. As with the embodiment shown in FIG. 3, the motors 61, 62 are located on the sides of the chamber to keep the overall height as low as possible.

[0045] By forming the rotatable support and rotatable member as two separate entities, the overall size of the rotor assembly can be reduced, resulting in a chamber with a smaller diameter. The configuration shown in Figures 5a and 5b also allows the rotatable support and rotatable member to rotate at different speeds, thereby increasing the flexibility of the process for cleaning and drying the wafer. Furthermore, the configuration shown in Figure 5b allows the rotatable support and rotatable member to rotate independently of each other.

[0046] When operated with two drive assemblies, the rotatable member typically has a maximum speed lower than that of the wafer (approximately 1000 rpm or less) because it does not contain surface features that need to be dried and only requires the removal of relatively large droplets. If the process uses deionized water rinsing, the rotatable member can be made from a hydrophobic plastic material such as polycarbonate, although the choice of material will of course depend on compatibility with the process chemistry.

[0047] The rotatable member is typically machined or molded as a single piece to ensure mechanical robustness, and may also be formed with ribs or similar stiffening features radiating from a center to increase its stiffness.

[0048] Figures 3, 5a, and 5b show only a limited number of wetting nozzles. In practice, spin-rinse dryers are equipped with several wetting nozzles that can access both the top and bottom (front and back) surfaces of the wafer. Depending on the process requirements, different nozzle flow rates, drive pressures, and spray shapes can be used. Common choices for spray shapes are fan and solid cone. A typical nozzle flow rate is 1 liter per minute at 35 psi (approximately 240 kPa); therefore, a spin-rinse dryer using four fluid nozzles operates at 4 liters per minute.

[0049] The chamber may be sealed while the water is supplied, allowing the wafers to be processed at pressures below atmospheric pressure, typically 10-100 Torr (about 133-1330 Pa).

[0050] While only certain embodiments of the present invention have been described, those skilled in the art will understand that the invention is not limited to these embodiments and that modifications may be made within the scope of the appended claims. [Explanation of symbols]

[0051] 1 chamber, 2 rotor assembly, 3 wafer, 4a nozzle, 4b nozzle, 6 droplet, 7 lid, 10 lid, 12 dome, 21 body, 22 lid, 23 support, 24a nozzle, 24b nozzle, 25 central shaft, 26 belt drive, 27 member, 28 motor, 29 wafer, 31 lower part, 32 upper part, 33 support, 39 wafer, 40 central lift pillar, 51 motor, 52 telescopic shaft coupling, 53 support, 54 member, 61 motor, 62 motor, 63 support, 64 member.

Claims

1. 1. A spin rinse dryer for processing a substrate, comprising: an enclosure formed by a body and a lid; a rotatable support located within the enclosure for supporting the substrate; a rotatable member located within the enclosure above the rotatable support, the rotatable member having a continuous lower surface and an apex, the apex being located adjacent the lower surface of the lid; a drive for rotating the rotatable member; A spin rinse dryer comprising:

2. 2. The spin rinse dryer of claim 1, wherein the lower surface of the rotatable member is oriented substantially parallel to an upper surface of the substrate when the substrate is supported by the rotatable support.

3. 3. The spin rinse dryer of claim 1 or 2, wherein the rotatable support is connected to the rotatable member such that the rotatable support and the rotatable member rotate together.

4. 4. The spin rinse dryer of claim 3, wherein several arms extend downwardly from the rotatable member and a prong extends radially inward from a lower end of each arm, the prongs serving as the rotatable supports.

5. 5. A spin rinse dryer as claimed in claim 3 or 4, wherein the drive is located laterally of the enclosure and is connected to the rotatable member and the rotatable support to drive them to rotate.

6. 2. The spin rinse dryer of claim 1, wherein the rotatable support and the rotatable member are not connected to each other and rotate independently.

7. 7. The spin rinse dryer of claim 6, wherein a single drive is located laterally of the enclosure and is connected to both the rotatable member and the rotatable support to drive them to rotate.

8. 8. The spin rinse dryer of claim 7, wherein the drive is connected to the rotatable member and the rotatable support via a telescoping shaft.

9. 7. The spin rinse dryer of claim 6, wherein two drives are located laterally of the enclosure, a first of the drives being connected to and driving to rotate the rotatable member, and a second of the drives being connected to and driving to rotate the rotatable support.

10. 10. A spin rinse dryer according to any one of claims 1 to 9, wherein the enclosure and the rotatable member are both circular in plan view, and / or the diameter of the rotatable member is smaller than the inner diameter of the enclosure, and / or the diameter of the rotatable member is larger than the diameter of the substrate being processed.

11. 11. A spin rinse dryer according to any one of claims 1 to 10, wherein the rotatable member is formed from a hydrophobic material such as polycarbonate, and / or the rotatable member is formed as a single piece, and / or the rotatable member is formed with reinforcing features such as ribs, and / or the spin rinse dryer is provided with nozzles located above and below the rotatable support for directing liquid towards a substrate positioned on the rotatable support.

12. 12. A spin rinse dryer according to any one of claims 1 to 11, characterized in that it is capable of operating at sub-atmospheric pressure.

13. 13. The spin rinse dryer of any one of claims 1 to 12, wherein the vertical height of the spin rinse dryer is less than about 300 mm.

14. 14. An apparatus for processing substrates, comprising a stack of substrate processing modules, at least one of said modules being a spin rinse dryer according to any one of claims 1 to 13.

15. 1. A method of processing a substrate, comprising: supporting a substrate on a rotatable support in an enclosure formed by a body and a lid, the rotatable support having a continuous lower surface and a top, the top being located below a rotatable member located near the lower surface of the lid; directing a liquid onto the substrate from nozzles above and below the rotatable support to clean the substrate; rotating the rotatable support to remove liquid from the substrate; rotating the rotatable member to remove liquid from the rotatable member; removing the substrate from the enclosure; A method comprising:

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