CHEMICAL MECHANICAL POLISHING SHIELDING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application claims the benefit of priority to U.S. Provisional Application No. 63/673,604, filed on Jul. 19, 2024, the contents of which are hereby incorporated by reference.

TECHNICAL FIELD

[0002]The present disclosure relates to chemical mechanical polishing, and more particularly to shielding components in chemical mechanical polishing system.

BACKGROUND

[0003]An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive, or insulative layers on a silicon wafer. One fabrication step involves depositing a filler layer over a non-planar surface and planarizing the filler layer. For certain applications, a conductive filler layer is planarized until the top surface of a patterned layer is exposed. For other applications, such as oxide polishing, the filler layer is planarized until a predetermined thickness is left over the non-planar surface. In addition, planarization of the substrate surface is usually required for photolithography.

[0004]Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is typically placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to push it against the polishing pad. A polishing liquid, e.g., an abrasive slurry, is typically supplied to the surface of the polishing pad.

SUMMARY

[0005]In one aspect, a polishing system includes a housing having sidewalls and a ceiling to form a polishing chamber, a platen located in the chamber to support a polishing pad, a carrier head located in the chamber to hold a substrate, a motor to generate relative motion between the platen and the carrier head, a polishing liquid dispenser having a polishing liquid supply line in fluid communication with a reservoir positioned outside the housing, and a shield positioned inside the chamber and adjacent a sidewall of the housing. The shield has a backing plate having a flat inner surface facing the platen, and a laminate of a plurality of individually peelable layers attached to the inner surface of the backing plate.

[0006]In another aspect, a polishing system includes a housing having sidewalls and a ceiling to form a polishing chamber, a platen located in the chamber to support a polishing pad, a carrier head located in the chamber to hold a substrate, a motor to generate relative motion between the platen and the carrier head, a polishing liquid dispenser having a polishing liquid supply line in fluid communication with a reservoir positioned outside the housing, and a shield positioned inside the chamber and horizontally over one or more components in the chamber. The shield has a backing plate having a flat inner surface facing the ceiling, and a laminate of a plurality of individually peelable layers attached to the inner surface of the backing plate.

[0007]In another aspect, a method of cleaning a polishing system includes disposing a shield inside a chamber of the polishing system, the shield having a backing plate and plurality of individually peelable layers laminated on the backing plate, and peeling a layer of a plurality of layers off the shield positioned in a polishing chamber.

[0008]Implementations may optionally include, but are not limited to, one or more of the following advantages. Contaminants that accumulate on an inner surface of a polishing chamber can be easily and quickly removed, thereby reducing the risk of defects. Less water may be required than conventional cleaning techniques. A shield can be re-laminated, permitting reuse.

[0009]The details of one or more implementations are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a schematic cross-sectional view of a polishing system.

[0011]FIG. 2 is a schematic top view of various components of the polishing system.

[0012]FIG. 3 is a schematic cross-sectional side view of a shield.

[0013]Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0014]Surfaces inside a chemical mechanical polishing chamber can accumulate contaminants, e.g., dried slurry particles, polishing by-products, polishing pad debris, or pad cleaning chemistry. For example, a polishing liquid, e.g., an abrasive slurry, is typically supplied to the surface of the polishing pad. However, some amount of the abrasive slurry can be flung off the polishing pad due to centrifugal forces or droplets of slurry can be reflected, eventually landing on other surfaces. In general, contaminants on surfaces in the polishing chamber can become airborne again or otherwise increase the presence of airborne particles, and thus increase the risk of defects, e.g., particles on the wafer, scratches, etc.

[0015]A current approach is to rinse the polishing pad, e.g., with a high-pressure rinse of deionized water, and to rinse wafer itself, e.g., at a wafer transfer station. In addition, other exposed surface in the polishing chamber, e.g., sidewalls of the chamber, outer surfaces of tubing or valves, motor casings, and the like, can be manually wiped down, e.g., with a damp sponge, during periodic maintenance. However, manual cleaning is time-consuming and reduces usable tool-time, thus impacting cost of ownership. In addition, the outer surfaces of many parts inside the polishing chamber, e.g., tubing or valves, motor casings, mechanical fasteners holding the struts or other components in place, can have cornered recesses which are difficult to clean manually.

[0016]Hypothetically various other exposed surfaces (e.g., besides the polishing surface) inside the polishing chamber could be sprayed with water from a rinsing manifold. However, such automatic rinsing adds significant water usage to the polishing system, and is limited by the possible positions for the manifold. Moreover, if the flow rate of the rinse water is sufficiently high to reliably remove contaminants, there is danger of splashing of the contaminants onto even more surfaces.

[0017]A technique to address these issues is to place one or more removable shields over various components in the polishing chamber, e.g., tubing or valves, motor casings. A removable shield can have a flat outer surface, and a multi-layer plastic sheet can be laminated onto the shield. To clean the shield, the outermost layer of the laminate is peeled off, leaving a fresh and clean surface. As such, maintenance time can be reduced and water usage for cleaning can be avoided. After a certain number of sheets have been used, the shield can be removed and swapped with a fresh laminated shield. The used shield can be re-laminated, and installed at a later time.

[0018]FIG. 1 illustrates a polishing system 20 to polish a substrate 10. The polishing system includes a housing 40 with sidewalls 42 and a ceiling 44, e.g., of a hard plastic, that enclose a polishing chamber 46. The housing 40 can include a floor 48, or the housing can sit on the floor 48 of the fab facility. One or more openable and closable ports 49, e.g., slit valves, provide access through a sidewall 42 of the housing 40 for transfer of the substrate into the polishing system 20. For example, a substrate transfer robot 30 can include a horizontally movable arm 32 with an end effector 34 to hold the substrate, e.g., using a vacuum chuck or an edge gripper.

[0019]Located inside the chamber 46 is a substrate transfer station 50. The transfer station 50 includes a substrate support 52 to hold the substrate 10. For example, the substrate support 52 can include a ring or pins positioned to contact the beveled edge of the substrate. The support 52 can be vertically movable, e.g., by an actuator 54. In operation, the substrate transfer robot 30 can move a substrate 10 through the port 49 and deposit the substrate on the support 52 at the transfer station 50, or pick a substrate up from the transfer station 50 and remove the substrate through the port 49.

[0020]Also located inside the chamber 46 is a rotatable platen 60, on which a polishing pad 70 is situated. The platen 60 is operable to rotate about an axis 62. For example, a motor 64 can turn a drive shaft 66 to rotate the platen 60. The polishing pad 70 can be a two-layer polishing pad with an outer polishing layer 72 having a polishing surface 76 and a softer backing layer 74. Grooves 78 can be formed in the polishing surface, e.g., to carry polishing liquid.

[0021]The polishing system 20 includes a carrier head 80 operable to hold the substrate 10 against the polishing pad 70. The carrier head 80 can include a flexible membrane 82 having a substrate mounting surface to contact the back side of the substrate 10, and a plurality of pressurizable chambers 84 to apply different pressures to different zones, e.g., different radial zones, on the substrate 10. A retaining ring 86 is secured to the carrier head 80 to surround and retain the substrate 10 below the pressurizable chambers 84.

[0022]The carrier head 80 is suspended from a support structure 90, for example, a swing arm, carousel, or track, and is connected by a carrier drive shaft 92 to a carrier head rotation motor 94 so that the carrier head can rotate about an axis 96. In addition, the carrier head 70 can oscillate laterally across the polishing pad 70, e.g., by moving in a radial slot in the arm or carousel as driven by an actuator, by rotation of the arm or carousel as driven by a motor, or movement back and forth along the track as driven by an actuator. In operation, the platen 60 is rotated about its central axis 62 (shown by arrow A in FIG. 2), and the carrier head 80 is rotated about its central axis 96 (shown by arrow B in FIG. 2) and oscillated laterally across the top surface of the polishing pad 70 (shown by arrow C in FIG. 2).

[0023]In addition, the support structure 90 can be movable to carry the carrier head 80 from a position over the platen 60 for polishing to a position over the substrate transfer station 50 for the substrate 10 to be loaded from the support 52 into the carrier head 80, or unloaded from the carrier head 80 onto the support 52.

[0024]The polishing system 20 includes a dispenser 100 to apply polishing liquid 120, e.g., an abrasive slurry, to the polishing pad 70 at a controllable flow rate. The dispenser 100 includes a supply port 102, e.g., at the end of a slurry supply arm 104. The arm 104 can extend over the platen 60 to the center of polishing pad 70, to or at least near the center (e.g., within 5% of the total radius of the polishing pad 70). The arm 104 can be supported by a base 106 that includes one or more actuators 108, e.g., a linear actuator to raise or lower the arm 104, and/or a rotational actuator to swing the arm 104 laterally over the platen 60. The base 106 can be supported on the same floor 48 as supports the platen 60, motor 64, substrate transfer station 50, etc.

[0025]A variety of components can couple an external polishing liquid reservoir 110 to the supply port 102, such as tubing 112, a pump 114, one or more control valves 116, or one or more passages 118 through the base 106 and arm 104. At least some of these components, e.g., the tubing 112, pump 114 and/or valve 116, can be located inside the chamber 46, off to a side of the platen 60.

[0026]In some implementations, multiple polishing fluids are combined or mixed, e.g., an abrasive slurry can be combined with deionized wafer as a diluent, with other chemistry to control pH or concentration of oxidants. In addition, air or steam can be injected into the abrasive slurry to increase the temperature and aerosolize the slurry. Each of these additional fluids can require additional tubing, pumps, valves, etc.

[0027]Referring to FIG. 2, the polishing system can also include a conditioner system 130 to maintain the polishing pad in a consistent state of roughness on a wafer-to-wafer basis. The conditioner system 130 can include a conditioner head 132 that holds a conditioner disk at the end of a swing arm 134 supported by a base 136.

[0028]Other components in the polishing system can include a rinse liquid dispenser 140 and a heating or cooling fluid dispenser 150. The rinse liquid dispenser 140 can include an arm 142 that extends over the platen 60 with a plurality of ports 144 to dispense a rinse liquid, e.g., deionized water, onto the polishing pad 70 to wash away slurry and polishing by-products. Tubing 146 can connect the ports 144 to an external rinse liquid supply 148, e.g., a reservoir. Similarly, the heating or cooling fluid dispenser 150 can include an arm 152 that extends over the platen 60 with a plurality of ports 154 to dispense a heating or cooling fluid onto the polishing pad 70 to increase or decrease the temperature of the polishing pad. In the case of heating, the fluid can be hot deionized water or steam. In the case of heating, the fluid can be cold water or a cold water aerosol. Tubing 156 can connect the ports 154 to an external heating or cooling fluid supply 158, e.g., a boiler in the case of steam, or a refrigerated reservoir in the case of a cold liquid. Similar to the polishing liquid dispenser 100, the rinse liquid dispenser 140 and a heating or cooling fluid dispenser 150 can also include pumps, valves, and the like between the dispenser arm and the external supply, and some of these elements can be positioned inside the chamber 46.

[0029]Referring to FIGS. 1 and 2, in some implementations, a cylindrical baffle 160 surrounds the platen 60. The baffle 160 extends above the top surface of the platen 60 such that slurry 120 that is centrifugally flung off the polishing pad 70 due to rotation of the platen 60 will be blocked. The blocked slurry can run down the inside of the baffle 160 and be captured in a basin below the platen 60.

[0030]The polishing system 20 includes a controller 190 (see FIG. 2), e.g., a programmable computer with a central processing unit, non-transitory computer readable media that store a computer program with instructions to control the polishing system 20. However, portions of the controller can be implemented as firmware or electronic hardware. The controller is in electrical connection with the various controllable components of the polishing system 20, e.g., the motors (e.g., motors 64 and 94), the actuators (e.g., actuators 54 and 108), the pumps or valves (e.g., pump 114 and valve 116), etc., in order to control movement of the various components as well as the flow rate of various fluids onto the polishing pad 70. Although unillustrated, this typically involves a variety of wires and conduits that extend from the controller 190 through the sidewalls 42 and through the polishing chamber 46 to the respective components.

[0031]Although the baffle 160 can catch a significant portion of the polishing liquid that is centrifugally expelled from the polishing pad 70, some polishing liquid can still be flung over the baffle 160. Moreover, there may need to be apertures or gaps in the baffle 160 to accommodate the various arms, e.g., the conditioner arm 134, polishing liquid dispenser arm 104, etc., as well as the movement of the carrier head 80, and polishing liquid can be expelled through those gaps. In addition, the spray of other liquids onto the polishing pad, e.g., the high-pressure rinse or the steam or cold liquid of the temperature control system, can be reflected off the polishing surface and carry particulates.

[0032]In short, a variety of effects can result in contaminants, e.g., slurry particles, polishing by-products, polishing pad debris, or pad cleaning chemistry, becoming airborne and then accumulating on the various exposed surfaces within the chamber, e.g., the interior surfaces of the sidewalls 42, the floor 48, and exposed surfaces of other parts inside the chamber, e.g., tubing such as tubing 112, 146 or 146, or pumps or valves such as pump 114 or valve 116. Such contaminants can dry or agglomerate on the surfaces in the polishing chamber, resulting in larger particles that, if they become dislodged or airborne again, can reach the substrate and cause defects.

[0033]In addition, the outer surfaces of many parts inside the polishing chamber, e.g., tubing or valves, motor casings, mechanical fasteners holding the struts or other components in place, can have cornered recesses which are difficult to clean manually.

[0034]Although the exposed surfaces can be manually wiped down during periodic maintenance of the polishing system, this is time consuming. In particular, the polishing chamber typically includes irregular surfaces that have protrusions, recesses, or ridges. For example, the chamber walls can include flanges that are screwed together to connect the individual wall components. The bases that support the various arms can have flanges that are screwed to the chamber floor. Wires and conduits can extend along the chamber walls or chamber floor. Even for drawings that illustrate chamber walls as linear, e.g., in a patent application, it would be generally understood that the interior surfaces of the chamber walls would include such protrusions and more complex surfaces. All of these situations provide opportunity for contaminants to accumulate in locations that are difficult to clean manually.

[0035]Still referring to FIGS. 1 and 2, one or more removable shields 200 can be installed within the chamber 46 to cover various components or surfaces in the polishing chamber. As shown in FIG. 3, each shield 200 includes a backing plate 210 with a flat and smooth front surface 212 positioned to face the interior of the chamber from which the contaminants will be emitted. The backing plate can be a metal, e.g., stainless steel, or a hard plastic, e.g., acrylonitrile butadiene styrene (ABS), polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), or glass. The back side 214 of the backing plate 210 need not be flat, and can have various projections or recesses 214 to permit attachment of shield 200 to the sidewalls 42, floor 48, or any support struts or bracing within the chamber 46.

[0036]The front surface 212 of the backing plate 210 is covered by a multi-layer peelable laminate 220. Individual layers 222 of the laminate 220 can be a plastic material, e.g., a polyvinyl chloride (PCV) film. A polytetrafluoroethylene (PTFE) film can be used if it will adhere due to static charge or a thermoplastic adhesive is added. Other possibilities include polyethylene terephthalate glycol (PETG), polyethylene terephthalate (PET), polyimide, polyethylene (PE), or polypropylene (PP). The laminate can have at least 10 layers, e.g., 10 to 100 layers.

[0037]Returning to FIGS. 1 and 2, one or more shields 200 can be positioned in various locations in the chamber 46, and in particular to cover surfaces that would otherwise be difficult to manually clean.

[0038]For example, one or more shields 200 can be attached in a vertical orientation to one or more sidewalls 42 by mechanical fasteners, with each shield extending parallel to the respective sidewall 42. In some implementations, a shield 200 is attached to just one sidewall 42 (see FIG. 1). In some implementations, there is a shield 200 for each sidewall 42 (see FIG. 2). For shields 200, attached to the side walls 42, the shield 200 can extends along the sidewall sufficiently that a lower edge 230 of the shield is lower than the top surface of the platen 60 (see FIG. 1). On the other hand, shields 200 need not extend entirely to the floor, as some components such as wires or tubing for fluids may need a gap near the floor before running along the sidewall behind the shield 200 to a sealed exit port 49a (see FIG. 1). As noted above, the sidewalls of the chamber often have other components, e.g., tubing or wires that runs along the sidewall, flanges to permit parts of the wall to fastened to each other, screws and bolts to secure components in place, and the like. Placing the shield 200 in front of the side wall permits contaminants to accumulate on the interior surface of the shield 200 rather than on the more difficult to clean surfaces.

[0039]For the sidewall 42 with the port 49, the shield 200 can be a unitary body having an aperture therethrough that is aligned with the port 49, or multiple shields can be placed adjacent the wall while leaving a gap that is aligned with the port 49. Alternatively, the port 49 can be positioned in a lower section of the polishing, e.g., below the shield 200. An example port is a slit valve.

[0040]As another example, one or more shields 200a, 200b can be secured in a horizontal orientation to cover various components within the chamber 46. In some implementations, a shield 200a is placed over components of the polishing fluid delivery system, e.g., over the tubing 112, pump 114 and/or valve 116 (the shield is shown in phantom in FIG. 2). Such a shield could be adjacent the baffle 124. The same shield 200a or a different shield 200b can be positioned over the tubing, pumps, valves and the like of the other fluid delivery systems, e.g., of the rinse liquid dispenser 140, or the heating or cooling fluid dispenser 150.

[0041]To clean a shield during periodic maintenance, the outermost layer 222a (see FIG. 3) of the laminate 220 is peeled off, leaving a fresh and clean surface. Because the surface 212 of the backing plate is smooth, the layer 222a should be easy to remove. In addition, the smooth surface can be easily wiped down, e.g., with a damp sponge or cloth. As such maintenance time can be reduced, and cleaning can be performed without requiring significant water usage.

[0042]After a certain number of layers have been used, e.g., one or two layers remain, the shield 200 can be removed from the polishing chamber 46 and swapped with a fresh laminated shield. The used shield can be re-laminated, and installed at a later time. The shield can be manually removable, i.e., detachable by use of conventional hand tools such as screwdriver or hex wrench and without damage to the shield itself or chamber.

[0043]As used in the instant specification, the term substrate can include, for example, a product substrate (e.g., which includes multiple memory or processor dies), a test substrate, a bare substrate, and a gating substrate. The substrate can be at various stages of integrated circuit fabrication, e.g., the substrate can be a bare wafer, or it can include one or more deposited and/or patterned layers. The term substrate can include circular disks and rectangular sheets.

[0044]As an alternative implementation, rather than a peel-off film, the backing plate of the shield can be coated with a hydrophobic layer, e.g., a single hydrophobic layer. Techniques to apply a hydrophobic layer include spray coating, liquid coating, and wipe on coating. The hydrophobic coating permits the shield to be easily manually wiped down, e.g., with a damp rag or sponge.

[0045]The shield can be periodically removed from the chamber, and the hydrophobic coating can be reapplied. For example for each ten times that the shield is manually wiped down, the shield could be removed.

[0046]A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other embodiments are within the scope of the following claims.