Abstract:
Embodiments of the present invention provide systems, apparatus, and methods for chemical polishing a substrate using a fluid network platen assembly that includes a pad having a plurality of fluid openings; a network of a plurality of fluid channels, each channel in fluid communication with at least one fluid opening; a plurality of inlets, each inlet coupled to a different fluid channel; and an outlet coupled to one of the fluid channels not coupled to an inlet. Numerous additional aspects are disclosed.

Description:
RELATED APPLICATION 
       [0001]    The present application claims priority to U.S. Provisional Patent Application No. 62/292,850, filed on Feb. 8, 2016, and entitled “SYSTEMS, APPARATUS, AND METHODS FOR CHEMICAL POLISHING” (Docket No. 23560/L), which is hereby incorporated herein by reference in its entirety for all purposes. 
     
    
     FIELD 
       [0002]    The present invention relates to substrate polishing, and more specifically to systems, apparatus, and methods for chemical polishing. 
       BACKGROUND 
       [0003]    Existing chemical mechanical polishing (CMP) material removal methods use mechanical down force to generate friction between a substrate and a polishing pad. Material removal is conventionally performed at a rate on the order of 1500 nm per minute down to 400 nm per minute. However, reducing the material removal rate below 20 nm per minute is beyond the capability of existing CMP tools primarily due to the minimum down force required to be applied to the substrate to effect any material removal. Improved device formation technologies that allow creation of ever smaller devices would benefit from the enhanced control that lower removal rates would allow but are not possible with existing CMP tools. Thus, what is needed are methods and apparatus for chemical polishing that do not rely on mechanical down force. 
       SUMMARY 
       [0004]    In some embodiments, the present invention provides a fluid network platen assembly that includes a pad having a plurality of fluid openings; a network of a plurality of fluid channels, each channel in fluid communication with at least one fluid opening; a plurality of inlets, each inlet coupled to a different fluid channel; and an outlet coupled to one of the fluid channels not coupled to an inlet. 
         [0005]    In other embodiments, the present invention provides a chemical polishing system for polishing substrates. The system includes a polishing head; an orbital actuator; and a fluid network platen assembly coupled to the orbital actuator and disposed below the polishing head, wherein the fluid network platen assembly includes a pad having a plurality of fluid openings; a network of a plurality of fluid channels, each channel in fluid communication with at least one fluid opening; a plurality of inlets, each inlet coupled to a different fluid channel; and an outlet coupled to one of the fluid channels not coupled to an inlet. 
         [0006]    In still other embodiments, the present invention provides a method of polishing a substrate. The method includes providing a chemical polishing system including a fluid network platen assembly having a network of a plurality of fluid channels, each channel in fluid communication with at least one fluid opening in a pad coupled to the fluid network platen assembly; exposing a substrate to a thin film of a first chemical solution via the fluid network platen assembly; rinsing the substrate using a first thin film of deionized water via the fluid network platen assembly; exposing the substrate to a thin film of a second chemical solution via the fluid network platen assembly; and rinsing the substrate using a second thin film of deionized water via the fluid network platen assembly. 
         [0007]    Other features, aspects, and advantages of the present invention will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawings by illustrating a number of exemplary embodiments and implementations, including the best mode contemplated for carrying out the present invention. Embodiments of the present invention may also be capable of other and different applications, and its several details may be modified in various respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. The drawings are not necessarily drawn to scale. The description is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view depicting an example embodiment of a chemical polishing system according to embodiments of the present invention. 
           [0009]      FIGS. 2A-2C  are top, front, and composite cross-sectional views of the example embodiment of  FIG. 1  according to embodiments of the present invention. 
           [0010]      FIG. 3  is an exploded top perspective view of the example embodiment of  FIG. 1  according to embodiments of the present invention. 
           [0011]      FIG. 4  is an exploded bottom perspective view of the example embodiment of  FIG. 1  according to embodiments of the present invention. 
           [0012]      FIG. 5  is a perspective view of a pad of the example embodiment of  FIG. 1  according to embodiments of the present invention. 
           [0013]      FIGS. 6A-6C  are top, front and perspective views of a top deck plate of the example embodiment of  FIG. 1  according to embodiments of the present invention. 
           [0014]      FIGS. 7A-7C  are top, front and perspective views of a middle deck plate of the example embodiment of  FIG. 1  according to embodiments of the present invention. 
           [0015]      FIGS. 8A-8C  are top, front and perspective views of a bottom deck plate of the example embodiment of  FIG. 1  according to embodiments of the present invention. 
           [0016]      FIG. 9  is a composite perspective view of internal fluid channel networks of the example embodiment of  FIG. 1  according to embodiments of the present invention. 
           [0017]      FIG. 10A  is a top view of the example embodiment of  FIG. 1  according to embodiments of the present invention. 
           [0018]      FIG. 10B  is a cross-sectional view taken alone line BB in  FIG. 10A  according to embodiments of the present invention. 
           [0019]      FIG. 10C  is a magnified cross-sectional detail view of encircled portion C′ of  FIG. 10B  according to embodiments of the present invention. 
           [0020]      FIG. 10D  is a magnified cross-sectional detail view of encircled portion D of  FIG. 10B  according to embodiments of the present invention. 
           [0021]      FIG. 10E  is a cross-sectional view taken alone line EE in  FIG. 10A  according to embodiments of the present invention. 
           [0022]      FIG. 1OF  is a magnified cross-sectional detail view of encircled portion F of  FIG. 10E  according to embodiments of the present invention. 
           [0023]      FIG. 11A  is a top view of the example embodiment of  FIG. 1  with a substrate represented according to embodiments of the present invention. 
           [0024]      FIG. 11B  is a side view of the example embodiment of  FIG. 1  with a substrate, a polishing head, and an orbital actuator represented according to embodiments of the present invention. 
           [0025]      FIG. 12  is a flowchart depicting an example method of chemical polishing according to embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    Embodiments of the present invention provide systems, apparatus, and methods for chemical polishing (e.g., nano-scale devices) that are adapted to achieve a removal rate of less that 20 nm per minute to support next generation device technologies. By polishing substrates using an exposure-based chemical etching process without applying any mechanical down force from a polishing pad, precise material removal rates can be achieved. Improved process control to within  2 nm to  4 nm, desirable for next generation devices, can be achieved with embodiments of the present invention. In other words, the height of devices on a substrate can be controlled to be within  2 nm to  4 nm using embodiments of the present invention. Example applications for such control include polishing FinFET technology devices including gate height control and lower interconnect levels where within-die (WID) control of 2 nm to 4 nm is desired. 
         [0027]    Chemical polishing with removal rates of substantially less than 20 nm per min to achieve WID control of 2 nm to 4 nm can be realized with embodiments of the present invention using a fluid network platen assembly that exposes the substrate to an example sequence of exposures: (1) a thin film of chemical A fluid, (2) a deionized (DI) water rinse, and then (3) a thin film of chemical B fluid in a cyclic manner without any applied mechanical force. The duration of exposure of the chemicals (e.g., chemicals A and B) and the rate of change over of fluids controls the material removal rate to achieve a degree of process control to within a range of approximately 2 nm to approximately 4 nm. Example embodiments of a platen assemble with a fluid network for delivering the chemicals and water is described below with respect to the drawings. 
         [0028]    Turning now to  FIG. 1 , a perspective view of an example embodiment of a fluid network platen assembly  100  for a chemical polishing system is shown. In some embodiments, the fluid network platen assembly  100  includes a pad  102  with an array of fluid channel openings  104 . In some embodiments, the fluid channel openings  104  are arranged in evenly spaced rows and columns to form a circular pattern of openings with a diameter larger than a substrate (e.g., a 360 mm diameter semiconductor wafer) to be polished. For example, in some embodiments, the circular pattern of fluid channel openings  104  can have a diameter in the range of approximately 400 mm+/ 31  10 mm to approximately 520 mm+/−10 mm or, in some embodiments, the diameter can be approximately 460 mm+/−10 mm. Other diameters can be used. The pad  102  sits upon and can be removably coupled to a top deck plate  106 , which sits upon and can be permanently bonded to or removably coupled to a middle deck plate  108 , which sits upon and can be permanently bonded to or removably coupled to a bottom deck plate  110 . In some embodiments, the deck plates can be constructed from a plastic polymer such as polyvinyl chloride (PVC) or any other practicable material that is non-reactive with the chemical solutions to be used for chemical polishing. 
         [0029]      FIGS. 2A-2C  illustrate top, front, and composite cross-sectional views of the fluid network platen assembly  100 .  FIG. 2C  is a composite cross-section of the fluid network platen assembly  100  taken along the width of line CC in  FIG. 2A . A network of fluid channels within the fluid network platen assembly  100  can be seen in  FIG. 2C  wherein individual nozzles are aligned with the fluid channel openings  104  in the pad  102 . As shown, the rows of fluid channel openings  104  correspond to alternate fluid channels within the fluid network platen assembly  100 . Thus, the fluid channels are spaced apart by a distance H in one direction and by a distance W in a perpendicular direction. In some embodiments, H can be in the range of approximately 15 mm+/−2 mm to approximately 35 mm+/−2 mm or, in some embodiments, approximately 25 mm+/−2 mm. In some embodiments, W can be in the range of approximately 15 mm+/−2 mm to approximately 35 mm+/−2 mm or, in some embodiments, approximately 25 mm+/−2 mm. Other dimensions are possible. In some embodiments, H and W can be approximately equal and in others, H and W can be different. The dimensions given are selected to allow even, consistent, and uniform application of a thin film of one or more chemical solutions to the major surface of a substrate being processed. 
         [0030]      FIGS. 3 and 4  are exploded perspective views of the fluid network platen assembly  100 .  FIG. 3  is a top view and  FIG. 4  is a bottom view. As can be seen, the bottom deck  110  includes a mounting disk  402  that is used to couple the fluid network platen assembly  100  to an orbital motion actuator (not shown in  FIG. 4  but see  FIG. 11B  described below). Also as can be seen, the top deck plate  106 , middle deck plate  108 , and bottom deck plate  110  each include an array of aligned channels that collectively form the network of fluid channels within the fluid network platen assembly  100  when the various plates are coupled or bonded together. 
         [0031]      FIG. 5  is a perspective view of the pad  102  upon which the substrate is placed for processing.  FIGS. 6A-6C  are top, front and perspective views respectively of an example of the top deck plate  106  of the fluid network platen assembly  100 .  FIGS. 7A-7C  are top, front and perspective views of an example of the middle deck plate  108  of the fluid network platen assembly  100 .  FIGS. 8A-8C  are top, front and perspective views of an example of the bottom deck plate  110  of the fluid network platen assembly  100 .  FIG. 9  depicts a perspective view of the fluid network  900  that is formed by the collective arrays of aligned channels within the fluid network platen assembly  100 . Note the four connectors for adding fluid to, or removing fluid from, the fluid network platen assembly  100 . The drain channel outlet connector  902  can be coupled to a flexible vacuum line for drawing fluid down from the pad  102  and out of the fluid network platen assembly  100 . Chemistry A channel inlet connector  908  can be coupled to a flexible chemical A supply line (not shown). Likewise, Chemistry B channel inlet connector  904  can be coupled to a flexible chemical B supply line (not shown). Rinse channel inlet connector  906  can be coupled to a flexible deionized water (DIW) supply line. 
         [0032]    Turning now to  FIGS. 10A-10F , details of the fluid network platen assembly  100  are further illustrated.  FIG. 10B  is a cross-sectional view of the fluid network platen assembly  100  taken at line BB in  FIG. 10A .  FIG. 10C  depicts a magnified cross-sectional detail view of an example chemical A or B fluid channel  1002  within the encircled portion C′ of  FIG. 10B . In some embodiments, all or part of the fluid channel  1002  can be formed by a removable tubular insert  1004  that is replaceable. 
         [0033]    Thus, if the fluid channel  1002  becomes clogged, the clog can easily be eliminated by simply replacing the removable tubular insert  1004 . In some embodiments, the removable tubular insert  1004  has a diameter of approximately 0.5 mm. Other diameters can be used.  FIG. 10D  depicts a magnified cross-sectional detail view of an example drain channel  1006  within the encircled portion D of  FIG. 10B .  FIG. 10E  is a cross-sectional view of the fluid network platen assembly  100  taken at line EE in  FIG. 10A .  FIG. 1OF  depicts a magnified cross-sectional detail view of an example DIW fluid channel  1008  within the encircled portion F of  FIG. 10E . In some embodiments, the DIW fluid channel  1008  has a diameter of approximately 0.5 mm. Other diameters can be used. 
         [0034]    In some embodiments, the DIW fluid channel  1008  can be in fluid communication with approximately  412  fluid channel openings  104 . These openings  104  can be approximately 1 mm in diameter. The flow rate through each of these individual openings  104  can be less than or equal to approximately 8 ml per minute. The fluid pressure at the rinse channel inlet connector  906  can be in the range of approximately 10 psi+/−5 psi to approximately 60 psi+/−5 psi. The total in-flow at the inlet of the rinse channel inlet connector  906  can be approximately 3000 ml per minute. 
         [0035]    In some embodiments, the Chemistry A channel inlet connector  908  can be in fluid communication with approximately  92  channel openings  104 . These openings  104  can be approximately 1 mm in diameter. The flow rate through each of these individual openings  104  can be less than or equal to approximately 32.5 ml per minute. The fluid pressure at the Chemistry A channel inlet connector  908  can be in the range of approximately 10 psi+/−5 psi to approximately 60 psi+/−5 psi. The total in-flow at the inlet of the Chemistry A channel inlet connector  908  can be approximately 3000 ml per minute. 
         [0036]    In some embodiments, the Chemistry B channel inlet connector  904  can be in fluid communication with approximately  108  channel openings  104 . These openings  104  can be approximately 1 mm in diameter. The flow rate through each of these individual openings  104  can be less than or equal to approximately 27.5 ml per minute. The fluid pressure at the Chemistry B channel inlet connector  904  can be in the range of approximately 10 psi+/−5 psi to approximately 60 psi+/−5 psi. The total in-flow at the inlet of the Chemistry B channel inlet connector  904  can be approximately 3000 ml per minute. 
         [0037]    In some embodiments, the drain channel outlet connector  902  can be in fluid communication with approximately  184  channel openings  104 . These openings  104  can be approximately 1 mm in diameter. The flow rate through each of these individual openings  104  can be less than or equal to approximately 30 ml per minute. The pump pressure drawing in fluid from the pad  102  can be in the range of approximately 10 psi+/−5 psi to approximately 60 psi+/−5 psi. The total discharge rate at the drain outlet of the drain channel outlet connector  902  can be approximately less than or equal to 5000 ml per minute. 
         [0038]      FIG. 11A  is a top view of the example fluid network platen assembly  100  with a substrate  1102  represented on the pad  102 .  FIG. 11B  is a side view of a chemical polishing system  1100  including the fluid network platen assembly  100 , a polishing head  1104 , and an orbital actuator  1108  coupled to the fluid network platen assembly  100  via a mounting disk  402  and a linkage  1106 . As shown in  FIG. 11A , the substrate  1102  is positioned with its center offset from the center of the pad  102 . In some embodiments, the center of the substrate  1102  is offset approximately 50 mm+/−10 mm from the center of the pad  102 . Other offset amounts can be used. 
         [0039]    In operation, the substrate  1102  is held securely and rotated by the polishing head  1104  in close proximity to the pad  102  without applying down force against the pad  102 . While the fluid network platen assembly  100  is moved in an orbital motion (without rotation) by the orbital actuator  1108 , a predefined sequence of chemical solutions and DIW are sequentially output and removed from the pad  102  and the surface of the substrate  1102 . A thin film of fluid is formed between the pad  102  and the substrate  1102  such that the substrate need not contact the pad  102  to contact the fluid film. 
         [0040]    In some embodiments, the polishing head  1104  rotates in the range of approximately 0+/−5 revolutions per minute to approximately 500+/−5 revolutions per minute. Other rotation rates can be used. In some embodiments, the fluid network platen assembly  100  is orbited within a frequency range of approximately 0+/−5 cycles per minute to approximately 500+/−5 cycles per minute. Other orbit frequencies can be used. In some embodiments, the polishing head  1104  and the fluid network platen assembly  100  move in opposing directions while in other embodiments, they move in non-opposing directions. In some embodiments, the amount of offset between the center of the polishing head  1104  and the center of the fluid network platen assembly  100  can be variable and/or adjustable before or during processing. For example, the fluid network platen assembly  100  can be configured to be offset from the center of the polishing head  1104  within the range of approximately 0+/−0.5 inches to approximately 2+/−0.5 inches. Other offset values can be used. In some embodiments, the offset can be configured to be adjustable in discrete increments (e.g., eight) within the specified range. In some embodiments, the offset can be configured to be infinitely adjustable within the specified range. The switching time period (e.g., the length of exposure) of the chemical solutions and DIW to the substrate  1102  can vary in the range of approximately 0+/−2 seconds to approximate 60+/−2 seconds. Other exposure time periods can be used. 
         [0041]    In some embodiments, the processing of the substrate can include a sequence of exposures each intended to effect a functional and/or structural change to the substrate. For example, in a first exposure to a chemical solution, formation of metal oxide using H 2 0 2  can be followed by formation of a reinforced film by an inhibitor. In a second exposure, removal of the reinforced film from relatively high spots by erosive action can be effected. In a third exposure, dissolution of oxide film by complexing can be effected and reformation of a reinforced film can also be effected. In a forth exposure, global planarization and material removal can be effected. 
         [0042]    Turning now to  FIG. 12 , a flowchart depicting an example method  1200  of chemical polishing according to embodiments of the present invention is provided. A chemical polishing system including a fluid network platen assembly and a polishing head is provided ( 1202 ). A substrate is secured by the polishing head and brought proximate to the fluid network platen ( 1204 ). A thin film of a first chemistry (Chemistry A) is formed by the fluid network platen between the substrate and the fluid network platen in contact with the substrate for a predefined exposure time period ( 1206 ). The polishing head is rotated ( 1208 ). The fluid network platen is orbited about a point offset from the center of the substrate ( 1210 ). A thin film of DIW is formed by the fluid network platen between the substrate and the fluid network platen in contact with the substrate for a predefined exposure time period ( 1212 ). A thin film of a second chemistry (Chemistry B) is formed by the fluid network platen between the substrate and the fluid network platen in contact with the substrate for a predefined exposure time period ( 1214 ). A thin film of DIW is formed by the fluid network platen between the substrate and the fluid network platen in contact with the substrate for a predefined exposure time period ( 1216 ). A determination is made if the polishing endpoint has been reached ( 1218 ). If yes, processing completes and if not, flow loops back to performing the Chemistry A exposure  1206 . 
         [0043]    In some embodiments, the chemistry exposures can be thought of as pulses that are applied to the substrate. For example, an oxidation pulse using a first chemistry can be applied for a specific time increment, and then after a rinse pulse (e.g., with DIW) is applied, an abrasive pulse can be applied to the substrate for a specific time increment. The oxidation pulse can be, for example, a concentration in the range of approximately 0.1% to approximately 1% (or approximately 0.25%) of H 2 O 2  and/or a concentration in the range of 0.001% to approximately 0.1% (or approximately 0.05%) of benzotriazole (BTA). In some embodiments, tetradecylthioacetic acid (TTA) can be used instead of BTA. The abrasive pulse can be a concentration of SiO 2  in the range of approximately 0.005 wt % to approximately 0.05 wt % (or approximately 0.01 wt %) and approximately 0.05 wt % to approximately 0.5 wt % (or approximately 0.1 wt %) of ammonium citrate or other carboxylic acids such as oxalic acid, etc., can be used. 
         [0044]    Numerous embodiments are described in this disclosure, and are presented for illustrative purposes only. The described embodiments are not, and are not intended to be, limiting in any sense. The presently disclosed invention embodiments are widely applicable to numerous implementations, as is readily apparent from the disclosure. One of ordinary skill in the art will recognize that the disclosed embodiments may be practiced with various modifications and alterations, such as structural, logical, software, and electrical modifications. Although particular features of the disclosed embodiments may be described with reference to one or more particular configurations and/or drawings, it should be understood that such features are not limited to usage in the one or more particular embodiments or drawings with reference to which they are described, unless expressly specified otherwise. 
         [0045]    The present disclosure is neither a literal description of all embodiments nor a listing of features of the invention that must be present in all embodiments. The Title (set forth at the beginning of the first page of this disclosure) is not to be taken as limiting in any way as the scope of the disclosed embodiments of the inventions. 
         [0046]    The present disclosure provides, to one of ordinary skill in the art, an enabling description of several embodiments and/or inventions. Some of these embodiments and/or inventions may not be claimed in the present application, but may nevertheless be claimed in one or more continuing applications that claim the benefit of priority of the present application. 
         [0047]    The foregoing description discloses only example embodiments of the invention. Modifications of the above-disclosed apparatus, systems and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. 
         [0048]    Accordingly, while the present invention has been disclosed in connection with exemplary embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.