The present invention is directed toward methods and apparatuses for cleaning the surface of a microelectronic substrate.
During processing of substrates and substrate assemblies used to form microelectronic devices, the surfaces of the substrates and substrate assemblies can become contaminated with particulate matter. The contaminants must generally be removed to prevent interference with subsequent processing steps and/or to prevent improper formation or operation of the microelectronic devices. Accordingly, several conventional tools can rinse the surfaces of the microelectronic substrates between processing steps to remove the contaminants.
FIG. 1 is a partially schematic, front isometric view of a conventional apparatus 10 (such as a model AS-2000, available from Dai Nippon Screen of Hikone, Japan) having a substrate support 20 that supports a substrate 12 having an upper surface 14 and a lower surface 16 facing opposite the upper surface 14. The substrate support 20 can include a plurality of rollers 21, each having an outer surface 22 engaged with an outer rim 18 of the substrate 12. Each roller 21 is rotatable about a roller axis 23, as indicated by arrow A. As the rollers 21 rotate about the roller axes 23, they rotate the substrate 12 about a substrate rotation axis 13, as indicated by arrow B.
The apparatus 10 can further include two brush assemblies 30, one proximate to the upper surface 14 of the substrate 12 and the other proximate to the lower surface 16. Each brush assembly 30 overhangs the outer rim 18 of the substrate 12, and is intersected by the substrate rotation axis 13. Accordingly, the entire area of the upper and lower surfaces 14, 16 can contact the brush assemblies 30 as the substrate 12 rotates about the substrate rotation axis 13.
Each brush assembly 30 can include a brush support 40 having a first flange 41 secured to a second flange 42 with screws 46 to clamp a brush 50 therebetween. The brush 50 includes a flat, cross-shaped base 53 having four contact portions 51 projecting toward the substrate 12. Each contact portion 51 has a pair of edges 52 that bear against the substrate 12. The brush support 40 has a central opening 44 and the base 53 of the brush 50 has a base opening 55 aligned with the central opening 44.
Each brush support 40 is removably coupled to a chuck 80 which is in turn coupled to a drive mechanism 31 (shown schematically in FIG. 1) to rotate the brush support 40 about a brush rotation axis 33, as indicated by arrow C. Each brush support 40 is also coupled to a fluid supply conduit 32 (shown chematically in FIG. 1) which is in turn coupled to a source of cleaning liquid (not shown), such as de-ionized water. The fluid supply conduit 32 directs liquid through the base opening 55 in the base 53 and the central opening 44 of the brush support 40. The liquid passes through the central opening 44 directly to the surface of the substrate 12. When the liquid reaches the surface of the substrate 12, the rotational motion of the brushes 50 about the brush rotation axes 33 and the rotational motion of the substrate 12 about the substrate rotation axis 13 together distribute the liquid over the surfaces 14, 16 of the substrate 12. The liquid entrains contaminants on the substrate 12, and the contact portions 51 of the brushes 50 sweep the liquid and the entrained contaminants from the substrate 12.
One drawback with some conventional substrate cleaning devices of the type shown in FIG. 1 is that the devices may not uniformly distribute the cleaning liquid over the surfaces 14, 16 of the substrate 12. As a result, residual contaminants may remain on some portions of the substrate 12. The residual contaminants can interfere with subsequent substrate processing steps or with the operation of the microelectronic device formed on the substrate 12.
Another drawback is that the brushes 50 can dry out and damage the substrate 12. For example, if the cleaning liquid is not uniformly distributed over the surfaces 14, 16 of the substrate 12, portions of the brushes 50 can dry out. Alternatively, the brushes 50 can dry out between cleaning cycles. In either case, the dry brush portions can become rigid and/or abrasive and can scratch the substrate 12, potentially damaging the substrate 12.
Another drawback with the apparatus 10 shown in FIG. 1 is that the contact portions 51 of the brushes 50 may entrap the contaminants entrained by the liquid as the brushes 50 and the substrate 12 move relative to each other. The contact portions 51 can press the entrapped contaminants against the surfaces of the substrate 12 and scratch or otherwise damage the substrate 12.
Another conventional device, described in U.S. Pat. No. 5,729,856 to Jang et al., includes a bristle brush having a U-shaped cross-section to clean the edge of a semiconductor wafer mounted on a chuck. A rinsing solution is injected through spaces in the body of the brush to flow along the bristles toward the wafer. One drawback with this device is that it does not clean the entire surface of the wafer, but rather cleans only the edge of the wafer. A further drawback is that the chuck engages the center of the wafer so that the center is not accessible to the brush for cleaning.
Still another conventional device, described in U.S. Pat. No. 5,858,109 to Hymes et al., and U.S. Pat. No. 5,806,126 to de Larios et al., includes an elongated roller brush that rotates about an axis perpendicular to the axis about which the semiconductor wafer rotates. Liquid is supplied to a hollow core of the brush and is then distributed through slots or holes to the brush itself. One drawback with devices of this type is that the elongated roller brush can be relatively large and therefore expensive to manufacture. A further drawback is that it can be difficult to supply the liquid to the brush at a high flow rate because the liquid may leak from the interface between the core and the brush. Furthermore, at high liquid pressures, the liquid may be more likely to pass through portions of the brush that do not contact the wafer rather than those that do contact the wafer because the brush portions that do not contact the wafer have a low fluid flow resistance. Accordingly, the fluid may not be delivered to the wafer at the point of contact between the wafer and the brush, reducing the cleaning effectiveness of the brush.
The present invention is directed to methods and apparatuses for treating one or more surfaces of a microelectronic substrate as the substrate rotates about a substrate axis. The apparatus can include a support member having an entrance port coupled to a source of liquid and in fluid communication with at least one exit aperture. The apparatus can further include an engagement element, such as a porous pad, coupled to the support member and having at least one contact portion positioned against the exit aperture of the support member to receive liquid directly from the exit aperture. The support member and the engagement element are positionable relative to the microelectronic substrate in a contact position with the contact portion against the surface of the microelectronic substrate as the microelectronic substrate rotates relative to the support member.
In one aspect of the invention, the support member can be rotatable about a support member axis generally parallel to the substrate axis, and can include a manifold in fluid communication with the entrance port and coupled to a channel extending radially away from the support member axis. A first region of the contact portion of the engagement element can be aligned with the channel and a second region, positioned radially outwardly from the first region, can be spaced apart from the channel. Accordingly, the liquid can pass from the manifold, through the channel, into the first region of the contact portion, through the contact portion to the second region, and outwardly to the substrate surface.
In another aspect of the invention, the engagement element and support member can form part of an assembly for both cleaning and planarizing the microelectronic substrate. The assembly can also include a carrier configured to support the microelectronic substrate and a polishing pad proximate to the carrier. The polishing pad can have a planarizing surface configured to press against the microelectronic substrate and at least one of the polishing pad and the carrier can be movable relative to the other to remove material from the microelectronic substrate.
In a method in accordance with an aspect of the invention, at least one contact portion of an engagement element is pressed against the surface of the microelectronic substrate and the microelectronic substrate is rotated about a substrate axis. Liquid is supplied through pores of the contact portion to the surface of the microelectronic substrate. The liquid can be supplied at a rate sufficient to remove particulates and other contaminants from an outer surface of the contact portion and/or the liquid can be supplied to the contact portion after the contact portion has been disengaged from the microelectronic substrate to keep the contact portion moist. The contact portion can be rotated relative to the microelectronic substrate about an axis generally parallel to the substrate axis.