Backside film deposition to correct for overlay error

Abstract

One disclosed example provides a method of mitigating substrate warpage. The method comprises depositing, on a warped substrate, a backside film having a controlled, variable thickness profile. The method further comprises chucking the warped substrate on a chuck. Chucking the warped substrate flattens the backside film against the chuck, thereby bending the warped substrate to mitigate the substrate warpage.

Description

BACKSIDE FILM DEPOSITION TO CORRECT FOR OVERLAY ERRORBACKGROUND

[0001] Semiconductor device manufacturing involves a series of processes to deposit and pattern structures on a substrate. As the complexity and / or non-uniformity of the structure and / or materials on or across the wafer increase, stress applied to the substrate by films of materials formed and patterned on the substrate can cause substrate deformation (e.g., bowing, twisting, etc.). Such deformation can impact various aspects of device fabrication.SUMMARY

[0002] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

[0003] One disclosed example provides a method of mitigating substrate warpage. The method comprises depositing, on a warped substrate, a backside film having a controlled, variable thickness profile. The method further comprises chucking the warped substrate on a chuck, wherein chucking the warped substrate flattens the backside film against the chuck, thereby bending the warped substrate to mitigate the substrate warpage.

[0004] In some such examples, the method further comprises performing sub strate-to- substrate bonding while the warped substrate is chucked.

[0005] Alternatively or additionally, in some such examples, the method further comprises performing lithography on the warped substrate while the warped substrate is chucked.

[0006] Alternatively or additionally, in some such examples, a stress of the backside film is between -2 GPa and 2 GPa.

[0007] Alternatively or additionally, in some such examples, the backside film is deposited using a showerhead pedestal.

[0008] Alternatively or additionally, in some such examples, the warped substrate has an asymmetrical warpage, and the method comprises performing a first backside deposition phase with a first concentration gradient of reactant gas to diluent gas as a function of an x-axis location on the warped substrate, rotating the substrate, and then performing a second backside deposition phase with a second concentration gradient of reactant gas to diluent gas as a function of y-axis location on the warped substrate.

[0009] Alternatively or additionally, in some such examples, the backside film comprises a parabolic film profile.

[0010] Alternatively or additionally, in some such examples, the backside film comprises a hyperbolic paraboloid film profile.

[0011] Alternatively or additionally, in some such examples, the backside film comprises one of a dielectric film or a metal film.

[0012] Alternatively or additionally, in some such examples, the backside film comprises one or more of silicon oxide, silicon nitride, silicon oxynitride, aluminum, or tungsten.

[0013] Another example provides a showerhead pedestal for depositing a film having a controlled, variable thickness profile. The showerhead pedestal comprises a plurality of first processing gas channels in fluid connection with a first processing gas inlet, each first processing gas channel comprising a plurality of first processing gas outlet holes. The showerhead pedestal further comprises a plurality of second processing gas channels in fluid connection with a second processing gas inlet, each second processing gas channel comprising a plurality of second processing gas outlet holes. An arrangement of first processing gas outlet holes and second processing gas outlet holes is configured to provide a concentration gradient of a first processing gas to a second processing gas along one or more of an x-axis or y-axis direction of the showerhead pedestal.

[0014] In some such examples, one or more of the plurality of first processing gas channels are interlaced with one or more of the plurality of second processing gas channels.

[0015] Alternatively or additionally, in some such examples, the first processing gas outlet holes comprise vertical holes at a center of the showerhead pedestal and slanted outlet holes at other regions of the showerhead pedestal.

[0016] Alternatively or additionally, in some such examples, the second processing gas outlet holes comprise vertical holes at an edge of the showerhead pedestal and slanted outlet holes at other regions of the showerhead pedestal.

[0017] Another example provides a processing tool for depositing a shaped backside film for mitigating substrate warpage, the processing tool comprises a processing chamber. The processing tool further comprises a substrate support configured to hold a substrate. The processing tool further comprises a showerhead pedestal configured for flowing precursor gas and diluent gas to a backside of a substrate disposed on the substrate support, the showerhead pedestal further configured to provide a concentration gradient of precursor gas to diluent gas along at least one of an x-axis or y-axis direction of the showerhead pedestal. The processing tool further comprises a controller configured to control the processing tool to perform backside film deposition on the substrate disposed on the substrate support. The controller is configured to cause the processing tool to flow a processing gas and a diluent gas to the showerhead pedestal under conditions configured to form a backside film on the backside of the substrate, the backside film having a controlled, variable thickness profile.

[0018] In some such examples, the showerhead pedestal comprises a plurality of first processing gas channels in fluid connection with a first processing gas inlet, each first processing gas channel comprising a plurality of first processing gas outlet holes, and a plurality of second processing gas channels in fluid connection with a second processing gas inlet, each second processing gas channel comprising a plurality of second processing gas outlet holes, wherein an arrangement of first processing gas outlet holes and second processing gas outlet holes is configured to provide the concentration gradient of precursor gas to diluent gas along the at least one of an x-axis or y-axis direction of the showerhead pedestal.

[0019] Alternatively or additionally, in some such examples, the controller further is configured to cause the processing tool to provide a selected concentration gradient of the precursor gas to the diluent gas along the x-axis direction of the showerhead pedestal to deposit the backside film, the backside film comprising a parabolic film profile.

[0020] Alternatively or additionally, in some such examples, the processing tool is configured to rotate the substrate 90 degrees, and wherein the controller further is configured to cause the processing tool to deposit the backside film on the backsideof the substrate by performing a first backside deposition phase with a first concentration gradient of precursor gas to diluent gas as a function of an x-axis direction on the substrate, rotating the substrate 90 degrees, and then performing a second backside deposition phase with a second concentration gradient of precursor gas to diluent gas as a function of a y-axis direction location on the substrate.

[0021] Alternatively or additionally, in some such examples, the controller is configured to cause the processing tool to deposit one or more of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, an aluminum film, or a tungsten film.

[0022] Alternatively or additionally, in some such examples, the processing tool further comprises a chuck, and the controller is configured to, after depositing the backside film, chuck the substrate on the chuck to flatten the backside film against the chuck, thereby bending the substrate to mitigate substrate warpage.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 A schematically shows an example substrate on which a backside film with a variable thickness profile has been deposited.

[0024] FIG. IB schematically illustrates a flattening of the backside film of FIG. 1 A against a chuck.

[0025] FIG. 2 shows an example substrate profile that illustrates a saddle- shaped warpage.

[0026] FIG. 3 shows a graphical depiction of a magnitude and direction of overlay error as a function of location on a substrate having the substrate profile of FIG.2.

[0027] FIG. 4 shows a graphical depiction of a magnitude and direction of overlay error as a function of location on the substrate of FIG. 3 after depositing a backside film with a variable thickness profile and chucking the substrate.

[0028] FIG. 5 shows a graphical depiction of the thickness profile of a backside film applied to the substrate of FIG. 2 to achieve the overlay error correction illustrated in FIG. 4 compared to FIG. 3.

[0029] FIG. 6A shows a sectional view of an example showerhead pedestal suitable for use to form a backside film having a variable thickness profile.

[0030] FIGS. 6B-6D schematically show additional views of the showerhead pedestal of FIG. 6 A.

[0031] FIG. 7 shows an overhead sectional view of another example showerhead pedestal suitable for use to form a backside film having a variable thickness profile.

[0032] FIG. 8 schematically shows an example processing tool that includes a showerhead pedestal for backside film deposition.

[0033] FIG. 9 shows a flow diagram of an example method for mitigating substrate warpage.DETAILED DESCRIPTION

[0034] Some integrated circuit fabrication processes involve performing sub strate-to- substrate bonding. Substrate-to-substrate bonding involves bonding a first substrate and a second substrate together in a face-to-face manner to connect electrical features of integrated circuits formed on the first substrate with electrical features of integrated circuits formed on the second substrate. However, circuit performance issues can arise when electrical features on the first substrate and second substrate are not properly aligned when bonded. Misalignment of electrical features on the first and second substrates is referred to as overlay error. Overlay error can lead to various problems. For example, the electrical resistance of an interface between an integrated circuit of the first substrate and an integrated circuit of the second substrate can increase with increasing overlay error. This can result in greater heat dissipation and power consumption at the interface, which can harm device performance.

[0035] Overlay error can arise from various sources. One source of overlay error is positional misalignment of the first substrate with respect to the second substrate. Such misalignment can be translational and / or rotational. Positional misalignment of first and second substrates can be addressed relatively easily by, prior to bonding, moving one or both substrates using an apparatus that holds the substrates during the substrate-to-substrate bonding process.

[0036] Another source of overlay error is distortion of a substrate. Substrate warpage is one example of distortion that can lead to overlay error. As mentioned above, stress applied to a substrate by films of materials formed and patterned on the substrate can cause substrate warpage. Warpage can cause features on a substrate surface to move closer together or farther apart upon chucking. Such positional changes of features on the substrate surface can generate overlay errors when bonded to another substrate. For example, a symmetrically bowed substrate can cause wafer size to scaleisotopically. The magnitude of overlay error in such a substrate can increase isotropically from a center of the substrate to an edge of the substrate.

[0037] Overlay error from symmetric bowing can be corrected by bending the substrate to an appropriate degree during substrate-to-substrate bonding. Such bending can be accomplished, for example, using an actuated chuck to hold the substrate during substrate-to-substrate bonding. The actuated chuck can mechanically deform the substrate to a desired degree by applying mechanical force to the substrate to reduce or avoid overlay errors with another substrate.

[0038] However, an asymmetrically bowed wafer (aka saddle shape wafer) can cause substrate surface features to move closer together along one direction (e.g. X) and farther apart another direction (e.g. Y). Such overlay error can be difficult to correct, as it can be difficult to bend a substrate asymmetrically using an actuated chuck.

[0039] Accordingly, examples are disclosed that relate to depositing a backside film with a controlled shape profile to cause a substrate to automatically bend to a desired shape when the substrate is chucked to a flat chuck surface. For example, to correct for a bowed substrate, the backside film can have a thickness profile that varies from a center of a substrate toward the edges of the substrate in a radially (e.g. circularly) symmetric manner. As another example, to correct for a saddle-shaped substrate, the backside film can be deposited to have a hyperbolic paraboloid film profile. By bending the substrate to mitigate substrate warpage, the disclosed examples can help to reduce overlay error in various integrated circuit fabrication processes, such as substrate-to-substrate bonding and lithography.

[0040] FIG. 1 A schematically shows an example substrate 100 with a backside film 102 having a variable profile deposited to cause a substrate to bend in a manner to mitigate overlay errors. The overlay errors can arise from stress from films deposited on the substrate frontside 104 (films not shown). The substrate 100 and backside film 102 are not shown to scale, but rather are shown with exaggerated features for clarity.

[0041] As depicted, the backside film 102 has a variable thickness profile, with a thicker profile at the center of the substrate 100 and a thinner profile at the edge of the substrate 100. For a substrate with symmetrical warpage, this film profile can be radially symmetric. Such a radially symmetric backside film 102 can help to correct for cup-shaped bowing of the substrate. Other film profiles can be used to correct for other types of substrate warpage, as described below.

[0042] FIG. IB schematically shows the substrate after being positioned on a chuck 106, such as for bonding to another substrate. The chuck 106 can comprise an electrostatic chuck that electrostatically attracts the substrate 100, or a vacuum chuck that secures the substrate using pressure differential. The attraction of the substrate 100 to the chuck 106 flattens the backside film 102 against the chuck 106. This results in the substrate 100 being bent by the variable thickness profile of the backside film 102. As indicated by arrows over the frontside 104, the frontside 104 is stretched, thereby moving features on the frontside 104 farther apart. This can help to correct overlay error between the substrate 100 and another substrate (not shown) in a substrate-to-substrate bonding process. This also can be used to correct substrate alignment in a lithographic process, and / or in any other suitable process in which the substrate is chucked and in which overlay errors can cause issues.

[0043] A backside film with a controlled thickness profile also can be used to mitigate overlay error for a substrate with symmetric warpage or asymmetric warpage such as saddle-shaped warpage and / or other complex, asymmetric warpages. FIG. 2 shows a graphical depiction of modeling results indicating a profile of an example substrate having saddle-shaped warpage. The substrate has a first pair of opposite sides 200 A, 200B that are raised with respect to a substrate center, and a second pair of opposite sides 202A, 202B, rotationally shifted ninety degrees from the first pair of opposite sides, that are lowered with respect to a substrate center. As indicated by dotted contour lines in FIG. 2, region 204A comprises a displacement between -30.0 pm and -22.5 pm. Region 204B comprises a displacement between -22.5 pm and -12.5 pm. Region 204C comprises a displacement between -12.5 pm and -5.0 pm. Region 204D comprises a displacement between -5.0 pm and 5.0 pm. Region 204E comprises a displacement between 5.0 pm and 12.5 pm. Region 204F comprises a displacement between 12.5 pm and 22.5 pm. Region 204G comprises a displacement between 22.5 pm and 30.0 pm.

[0044] FIG. 3 includes arrows that illustrate directions and magnitudes of overlay error as a function of location on the substrate of FIG. 2. The length of each arrow indicates and approximate magnitude of overlay error, ranging from 0 nm to 50 nm. The arrows along a line 300 extending from the center horizontally to the left and right edges are inwardly directed toward the center, with increasing magnitude from the center to the edge of the substrate. This indicates that features at those locations of the substrate would be compressed together relative to ideal positions of the features.Conversely, the arrows along a line 302 extending from the center to the top and bottom edges (with reference to the orientation of FIG. 3) are directed outwardly toward the substrate edges. This indicates that features at those locations of the substrate would be stretched apart relative to ideal locations of those features. The arrows at other locations on the substrate show directions transverse to each of these two lines, and magnitudes that are a function of radial distance from the substrate center. The x-direction overlay (mean + 3 sigma) is 72.27 nm and the y-direction overlay also is 72.27 nm.

[0045] FIG. 4 graphically shows modeling results of the substrate of FIG. 2 after deposition of a backside film having a thickness profile shown in FIG. 5, and after being chucked. Referring to FIG. 5, the film thickness is illustrated with dotted contour lines. Region 504A comprises a thickness between 0 and 3 pm. Region 504B comprises a thickness between 3 and 6 pm. Region 504C comprises a thickness between 6 and 9 pm. Region 504D comprises a thickness between 9 and 12 pm. Region 504E comprises a thickness between 12 and 15 pm. Region 504F comprises a thickness between 15 and 18 pm. Region 504G comprises a thickness between 18 and 20 pm.

[0046] Referring again to FIG. 4, by depositing a film having the thickness profile of FIG. 5, the overlay error of the substrate has been corrected. The x-direction overlay (mean + 3 sigma) is 3.06 nm and the y-direction overlay is 3.54 nm. As such, depositing a film having a controlled, variable profile can be used to correct substrate warpage and resulting overlay error when performing substrate-to-substrate bonding.

[0047] Backside films can be deposited with any suitable film profile. Examples include parabolic film profiles and hyperbolic paraboloid film profiles. In some examples, a hyperbolic paraboloid film profile can comprise different amount of curvature in the x-axis and y-axis directions.

[0048] Any suitable type of film can be deposited as a backside film to correct for overlay error. Some illustrative examples include silicon oxide, silicon nitride, silicon oxynitride, other dielectric films, aluminum, tungsten, and other metallic films. In some examples, film stress in the backside film can be from -2 gigapascals (GPa) to 2 GPa. Having a film stress close to zero can help reduce the impact of film stress on substrate shape, and thereby avoid complicating the overlay correction. In other examples, a backside film with a desired tensile or compressive stress can be used to help bend the substrate. In some examples, the backside film stress can vary with location.

[0049] According to various examples, a thickness profile of a deposited film is modulated by controlling concentrations of precursor and diluent gases adjacent to a substrate during material deposition. This concentration of precursor and diluent gas may be controlled by varying how much precursor and diluent gas is flowed from a gas distributor, such as a showerhead or showerhead pedestal, along at least one of the x- axis and y-axis directions of the showerhead or showerhead pedestal. Structural components of the gas distributor can be configured to vary precursor and / or diluent gas distribution therefrom. The precursor and diluent gas distribution profile adjacent to the substrate may match (or substantially match) a desired thickness profile of material deposited on a substrate. In some implementations, precursor and diluent gas output may be divided into multiple zones in order to produce a particular thickness profile. In various examples, precursor and diluent gas output may be interlaced, alternated, or otherwise integrated within one or more other zones to further control, e.g., smoothen a desired profile within and / or between one or more zones, etc.) to further produce a particular thickness profile. In some examples, to deposit a film comprising a hyperbolic paraboloid profile, a film can be deposited with a parabolic film profile for a first thickness. Then, the substrate is rotated 90 degrees, and a parabolic film profile is deposited for a second thickness. The first thickness and second thickness can be varied based on a desired overlay compensation for the x-axis and y- axis directions.

[0050] FIG. 6A shows a sectional view of an example showerhead pedestal 600 suitable for use in depositing a backside film having a controlled variable thickness to help mitigate overlay error. The view of FIG. 6A is sectioned along both an x-z plane and a y-z plane, referring to the coordinate axes shown in FIG. 6A. As shown, the showerhead pedestal 600 comprises a first zone (Zone 1) and a second zone (Zone 2). Zone 1 and Zone 2 comprise interlaced, alternating processing gas channels, examples of which are shown at 602A for Zone 1 and 602B for Zone 2.

[0051] Each processing gas channel 602A of Zone 1 is connected to a Zone 1 processing gas inlet 604A by a corresponding spoke 606A. Likewise, each processing gas conduit 602B of Zone 2 is connected to a Zone 2 processing gas inlet 604B by a corresponding spoke 606B (shown in FIG. 6D). The spokes for Zone 1 are configured to form different flows of processing gases into different processing gas channels of Zone 1. Likewise, the spokes for Zone 2 are configured to form different flows of processing gases into different processing gas channels of Zone 2. As a more specificexample, flows of processing gases from the different processing gas channels of Zone 1 can decrease from center to edge of the showerhead pedestal. Conversely, flows of processing gases from the different processing gas channels of Zone 2 can increase from center to edge of the showerhead pedestal. Each processing gas channel of each of Zone 1 and Zone 2 is fluidly connected to a series of gas outlet holes 608, examples of which are respectively shown a processing gas outlet holes 608A and processing gas outlet holes 608B, to output processing gases toward a backside of a substrate positioned on showerhead pedestal 600.

[0052] FIGS. 6B and 6C show example configurations for processing gas channels 602A, 602B. FIG. 6B shows a processing gas channel comprising slanted gas outlet holes 612. FIG. 6C shows a processing gas channel comprising vertical gas outlet holes 614. Returning to FIG. 6A, showerhead pedestal 600 comprises vertical Zone 1 gas outlet holes 614A at the center and vertical Zone 2 gas outlet holes 614B towards the edge of showerhead pedestal 600. Further, the showerhead pedestal comprises slanted gas outlet holes in the region between the center and edge. Additionally, rows of gas outlet holes between adjacent processing gas channels 602A, 602B can comprise slanted Zone 1 gas outlet holes 612A alternating with slanted Zone 2 gas outlet holes 612B. In other examples, a showerhead pedestal can comprise a different configuration for processing gas channels and processing gas outlet holes.

[0053] FIG. 6D shows an overhead schematic view of the configuration of spokes in showerhead 600. As shown, a plurality of Zone 1 spokes 606A extend radially to provide gas to an end of corresponding Zone 1 processing gas channels 602A. Additionally, a plurality of Zone 2 spokes 606B extend radially to provide gas to an end of corresponding Zone 2 processing gas channels 602B. In some examples, the spokes, processing gas channels, and gas outlet holes are configured to provide a concentration gradient of processing gas(es) as a function of at least one of the x-axis or y-axis direction of the substrate pedestal. In FIG. 6D, portions of processing gas channels 602 A, 602B are shown in dotted lines for clarity.

[0054] With such a configuration, if one or more reactant gases for forming a backside film are introduced into Zone 1, and one or more diluent gases are introduced into Zone 2, the relative concentration of reactant gas(es) output by the showerhead pedestal compared to inert diluent gas(es) will be higher at a center of the showerhead pedestal than closer to an edge of the showerhead pedestal. Conversely, if the one or more reactant gases for forming the backside film are introduced into Zone 2, and oneor more inert diluent gases are introduced into Zone 2, then the relative concentration of reactant gas(es) compared to diluent gas(es) will be higher toward an edge of the showerhead pedestal than at the center.

[0055] Using showerhead pedestal 600, the film profile of FIG. 4 can be achieved by performing a first deposition phase in which the one or more reactant gases are introduced into Zone 1 while one or more diluent gases are introduced into Zone 2, and performing a second deposition phase in which the substrate is rotated ninety degrees compared to the first deposition phase, and in which the one or more reactant gases are introduced into Zone 2 while the one or more diluent gases are introduced into Zone 1. The thickness of the backside films deposited in the first deposition phase and the second deposition phase can be adjusted based upon how much overlay compensation is needed for each corresponding direction.

[0056] In the example of FIG. 6A, the processing gas outlet holes 608A for Zone 1 are oriented vertically at a center region of the showerhead pedestal 600 (as indicated at 614A), and are slanted between the center and edge regions of the showerhead pedestal 600 (as indicated at 612A). Likewise, processing gas outlet holes 608B for Zone 2 are oriented vertically at an edge region of the showerhead pedestal 600 (as indicated at 614B), and are slanted between the edge and center regions of the showerhead pedestal (as indicated at 612B). This can help to achieve a desired concentration gradient of the ratio of processing gas(es) to inert diluent gas(es). In other examples, the gas outlet holes for Zone 1 and Zone 2 can have any other suitable configuration than that shown.

[0057] FIG. 7 shows a schematic overhead view of another example showerhead pedestal 700 comprising multiple zones to allow a thickness profile of a film deposited on a substrate backside to be controllably varied to mitigate overlay error when the substrate is chucked. Showerhead pedestal 700 comprises a plurality of Zone 1 spokes 706A extending radially to provide gas to an end of corresponding Zone 1 processing gas channels 702A. Additionally, a plurality of Zone 2 spokes 706B extend radially to provide gas to an end of corresponding Zone 2 processing gas channels 702B. As such, showerhead pedestal 700 comprises a Zone 1 towards the center of the showerhead pedestal and a Zone 2 at the edge of the showerhead pedestal. However, in contrast to showerhead pedestal 600 of FIGS. 6A-6D, showerhead pedestal 700 does not have alternating Zone 1 / Zone 2 processing gas channels.

[0058] The disclosed examples are not limited to wafer bonding, but also to any other suitable use context where a substrate is chucked. Another example includes lithography.

[0059] Other examples of suitable gas distribution hardware for depositing backside films having controlled, variable profiles to compensate for substrate warpage when performing sub strate-to- substrate bonding are described in U.S. Provisional Patent Application Serial No. 63 / 578,289, the disclosure of which is hereby incorporated by reference.

[0060] FIG. 8 shows a schematic view of an example processing tool 800 that can implement deposition of a backside film having a controlled variable thickness according to the disclosed examples. Processing tool 800 is described in the context of a chemical vapor deposition (CVD) tool, including plasma-enhanced CVD (“PECVD”) tool. However, backside film deposition according to the disclosed examples may be performed in other types of processing tools, such as atomic layer deposition (ALD) tools.

[0061] Processing tool 800 is configured to perform a deposition process on a substrate 802. Example substrates include semiconductor substrates, such as silicon wafers. Processing tool 800 comprises a processing station 804 at which a substrate 802 may be processed. Processing station 804 is positioned within a processing chamber 806. In some examples, two or more processing stations 804 may be in a same processing chamber 806. This is illustrated in FIG. 8 by additional processing station(s) 807. Each additional processing station(s) 807 is positioned within the processing chamber 806.

[0062] Processing tool 800 is configured to allow processing to be selectively performed on a substrate frontside or a substrate backside. As such, processing tool 800 comprises a showerhead pedestal 808 configured to distribute processing chemicals (for example, reactive precursors, and / or diluent gases) toward a substrate backside. Showerhead pedestal 600 and showerhead pedestal 700 are examples of showerhead pedestal 808.

[0063] Processing tool 800 further comprises a showerhead 810 positioned facing the showerhead pedestal 808. Showerhead 810 is configured to distribute processing chemicals (for example, reactive precursors and / or inert gases) toward a substrate frontside, depending upon a process being performed. In some examples, showerhead 810 is electrically coupled to a radio frequency (RF) power supply 812with an RF matching network 815. RF power supply 812 may be controlled by a controller 820. In other examples, RF power may be provided to showerhead pedestal 808 instead of showerhead 810. In this example, RF power supply 812, RF matching network 815, showerhead 810, and showerhead pedestal 808 comprise a plasma generator configured to form a capacitively coupled plasma between showerhead pedestal 808 and showerhead 810. In other examples, a plasma generator may be configured to form an inductively coupled plasma. In yet further examples, a plasma generator may be configured to form a plasma at a location remote from the processing station 804 and additional processing stations 807. In such examples, flow control hardware may be used to deliver reactive species generated in the remote plasma to processing chamber 806. In still further examples, both showerhead 810 and showerhead pedestal 808 may be connected to RF power. In some such examples, more than one RF power supply / matching network may be used.

[0064] Substrate 802 is positioned on a substrate support 824. Substrate support 824 takes the form of a carrier ring that may be mechanically rotated and / or moved to other process stations. In FIG. 8, substrate 802 is positioned for backside processing. As such, substrate support 824 is positioned on supports 826 that are configured to hold substrate 802 a selected distance above showerhead pedestal 808. In this configuration, precursors and / or diluent gases may be distributed toward a backside of substrate 802 using showerhead pedestal 808, while inert gases may be distributed toward a frontside of substrate 802 using showerhead 810 (e.g., to prevent precursors directed to the backside from reaching the frontside).

[0065] When the frontside of substrate 802 is being processed, substrate 802 is positioned on showerhead pedestal 808, and substrate support 824 rests on a carrier ring support region 827 of the showerhead pedestal 808. An end effector (not shown) may be used to place the substrate 802 and substrate support 824 on showerhead pedestal 808 for frontside processing, or on supports 826 for backside processing.

[0066] In some examples, at least a portion of processing station 804 may move relative to processing chamber 806. For example, processing tool 800 may comprise a motor-driven bellows (not shown) to move showerhead pedestal 808 (together with the substrate 802) vertically. The movement of showerhead pedestal 808 may be facilitated by one or more flexible gas lines (not shown) that are coupled to gas flow path components leading to showerhead pedestal 808.

[0067] The processing tool 800 further comprises a processing gas source 832. Processing gas source 832 comprise reactive precursor gas(es) and / or inert gas(es). Controller 820 controls the delivery of processing gas from processing gas source 832 to showerhead 810 through flow path 833. As a specific example, when deposition is targeted for the backside of substrate 802, an inert gas flow is directed over the frontside of substrate 802 with the showerhead 810. The inert gas flow may prevent precursors entering the space between the showerhead 810 and the substrate front side and / or push precursors away from the substrate frontside, protecting frontside from unwanted processing during backside processing.

[0068] In various examples, processing chemicals may be premixed before introduction into processing chamber 806 or introduced separately into processing chamber 806. Process gases exit processing chamber 806 through one or more outlets. For example, an exhaust system 817 is employed to draw process gases out and maintain a suitable pressure within the reactor.

[0069] FIG. 8 also shows various processing chemical sources. Diluent gas source 834 is configured to provide one or more diluent gases to showerhead pedestal 808 through flow path 835. Example diluent gases include helium, neon, argon, krypton, and nitrogen.

[0070] Precursor source 836 is configured to provide one or more reactive precursor gases to showerhead pedestal 808 through flow path 837. Example precursors include precursors for forming silicon oxide, silicon nitride, silicon oxynitride, and other dielectric films. Further examples include precursors for forming aluminum, tungsten, and other metallic films.

[0071] As mentioned above, in some implementations, precursor and diluent gas output may be divided into multiple zones in a showerhead pedestal in order to produce a particular thickness profile of a backside film. As such, in some examples, reactive precursor gases and diluent gases can be flowed to two or more processing gas inlets of showerhead pedestal 808 for delivery to two or more zones. Referring to FIGS. 6A-6D, in examples where showerhead pedestal 600 is used, reactive precursor gas can be flowed to processing gas inlet 604A for outputting the reactive precursor gas to Zone 1. Likewise, diluent gas can be flowed to processing gas inlet 604B for outputting the diluent gas to Zone 2. In some examples, showerhead pedestal 700 can be used for dividing processing gases into multiple zones. In some examples, a gas mixture comprising a first concentration of precursor gas is flowed to Zone 1, and a gas mixturecomprising a second concentration of precursor gas different from the first concentration is flowed to Zone 2.

[0072] Flow paths 833, 835, and 839 each may comprise any suitable flow control hardware to allow the selective delivery of processing chemicals to processing chamber 806 and additional processing station(s) 807. Examples include valves and mass flow controllers.

[0073] Additional processing station(s) 807 further may receive power from RF power supply 812 through RF matching network 815. Additional processing station(s) 807 also may be controlled by controller 820. In some examples, different RF power supplies / matching networks and / or different processing chemical sources may be applied to different stations so that processing at each separate processing station may be controlled independently.

[0074] In some examples, processing tool 800 comprises a chuck such that substrate 802 can be chucked to flatten a deposited backside film against the chuck. As described above, forming a backside film comprising a controlled, variable thickness on substrate 802 and then chucking the substrate on the chuck to flatten the backside film against the chuck can help mitigate substrate warpage. After chucking, additional processing can be performed on substrate 802, e.g., at additional processing station(s) 807. Example processes include sub strate-to- substrate bonding and lithography. In some examples, such processes can be performed at processing tool separate from processing tool 800.

[0075] FIG. 9 shows a flow diagram of an example method 900 for mitigating substrate warpage in a warped substrate. At 902, method 900 comprises depositing, on a warped substrate, a backside film having a controlled, variable thickness. In some examples, at 904, method 900 comprises depositing the backside film using a showerhead pedestal (e.g., showerhead pedestal 600 or 700). In some examples, at 906, the backside film comprises a parabolic profile. In some examples, at 908, the backside film comprises a hyperbolic paraboloid profile. In some examples, at 910, a stress of the backside film is between -2 GPa to 2 GPa.

[0076] In some examples, at 912, depositing the backside film comprises performing a first backside deposition phase with a first concentration gradient of reactant gas to diluent gas as a function of an x-axis direction on the warped substrate. Step 912 further comprises rotating the substrate (e.g., 90 degrees) and performing asecond backside deposition phase with a second concentration gradient of reactant gas to diluent gas as a function of a y-axis direction on the warped substrate.

[0077] Any suitable film can be deposited on the backside of the warped substrate. In some examples, at 914, method 900 comprises depositing a dielectric film or a metal film. In some more specific examples, at 916, the method comprises depositing one of silicon oxide, silicon nitride, silicon oxynitride, aluminum, or tungsten.

[0078] Continuing, at 918, method 900 further comprises chucking the warped substrate on a chuck to flatten the backside film against the chuck. This bends the warped substrate to mitigate the substrate warpage. In some examples, at 920, method 900 further comprises performing substrate-to-substrate bonding while the warped substrate is chucked. In some examples, at 922, method 900 comprises performing lithography on the warped substrate while the warped substrate is chucked. By using a backside film with controlled variable thickness to mitigate substrate warpage, the disclosed examples can help to reduce overlay error in various substrate processes, such as substrate-to-substrate bonding and lithography.

[0079] The subject matter of the present disclosure includes all novel and non- obvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts, and / or properties disclosed herein, as well as any and all equivalents thereof.

Claims

CLAIMS:

1. A method of mitigating substrate warpage, comprising: depositing, on a warped substrate, a backside film having a controlled, variable thickness profile; and chucking the warped substrate on a chuck, wherein chucking the warped substrate flattens the backside film against the chuck, thereby bending the warped substrate to mitigate the substrate warpage.

2. The method of claim 1, further comprising performing substrate-to- substrate bonding while the warped substrate is chucked.

3. The method of claim 1, further comprising performing lithography on the warped substrate while the warped substrate is chucked.

4. The method of claim 1, wherein a stress of the backside film is between -2 GPa and 2 GPa.

5. The method of claim 1, wherein the backside film is deposited using a showerhead pedestal.

6. The method of claim 1, wherein the warped substrate has an asymmetrical warpage, and wherein the method comprises performing a first backside deposition phase with a first concentration gradient of reactant gas to diluent gas as a function of an x-axis location on the warped substrate, rotating the warped substrate, and then performing a second backside deposition phase with a second concentration gradient of reactant gas to diluent gas as a function of y-axis location on the warped substrate.

7. The method of claim 1, wherein the backside film comprises a parabolic film profile.

8. The method of claim 1, wherein the backside film comprises a hyperbolic paraboloid film profile.

9. The method of claim 1, wherein the backside film comprises one of a dielectric film or a metal film.

10. The method of claim 9, wherein the backside film comprises one of silicon oxide, silicon nitride, silicon oxynitride, aluminum, or tungsten.

11. A showerhead pedestal for depositing a film having a controlled, variable thickness profile, the showerhead pedestal comprising: a plurality of first processing gas channels in fluid connection with a first processing gas inlet, each first processing gas channel comprising a plurality of first processing gas outlet holes; and a plurality of second processing gas channels in fluid connection with a second processing gas inlet, each second processing gas channel comprising a plurality of second processing gas outlet holes, wherein an arrangement of first processing gas outlet holes and second processing gas outlet holes is configured to provide a concentration gradient of a first processing gas to a second processing gas along one or more of an x-axis or y-axis direction of the showerhead pedestal.

12. The showerhead pedestal of claim 11, wherein one or more of the plurality of first processing gas channels are interlaced with one or more of the plurality of second processing gas channels.

13. The showerhead pedestal of claim 11, wherein the first processing gas outlet holes comprise vertical holes at a center of the showerhead pedestal and slanted outlet holes at other regions of the showerhead pedestal.

14. The showerhead pedestal of claim 13, wherein the second processing gas outlet holes comprise vertical holes at an edge of the showerhead pedestal and slanted outlet holes at other regions of the showerhead pedestal.

15. A processing tool for depositing a shaped backside film for mitigating substrate warpage, the processing tool comprising: a processing chamber;a substrate support configured to hold a substrate; a showerhead pedestal configured for flowing precursor gas and diluent gas to a backside of a substrate disposed on the substrate support, the showerhead pedestal further configured to provide a concentration gradient of precursor gas to diluent gas along at least one of an x-axis or y-axis direction of the showerhead pedestal; and a controller configured to control the processing tool to perform backside film deposition on the substrate disposed on the substrate support, the controller configured to cause the processing tool to flow a processing gas and a diluent gas to the showerhead pedestal under conditions configured to form a backside film on the backside of the substrate, the backside film having a controlled, variable thickness profile.

16. The processing tool of claim 15, wherein the showerhead pedestal comprises: a plurality of first processing gas channels in fluid connection with a first processing gas inlet, each first processing gas channel comprising a plurality of first processing gas outlet holes; and a plurality of second processing gas channels in fluid connection with a second processing gas inlet, each second processing gas channel comprising a plurality of second processing gas outlet holes, wherein an arrangement of first processing gas outlet holes and second processing gas outlet holes is configured to provide the concentration gradient of precursor gas to diluent gas along the at least one of an x-axis or y-axis direction of the showerhead pedestal.

17. The processing tool of claim 15, wherein the controller further is configured to cause the processing tool to provide a selected concentration gradient of the precursor gas to the diluent gas along the x-axis direction of the showerhead pedestal to deposit the backside film, the backside film comprising a parabolic film profile.

18. The processing tool of claim 15, wherein the processing tool is configured to rotate the substrate 90 degrees, and wherein the controller further isconfigured to cause the processing tool to deposit the backside film on the backside of the substrate by performing a first backside deposition phase with a first concentration gradient of precursor gas to diluent gas as a function of an x-axis direction on the substrate, rotating the substrate 90 degrees, and then performing a second backside deposition phase with a second concentration gradient of precursor gas to diluent gas as a function of a y-axis direction location on the substrate.

19. The processing tool of claim 15, wherein the controller is configured to cause the processing tool to deposit one or more of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, an aluminum film, or a tungsten film.

20. The processing tool of claim 15, further comprising a chuck, and wherein the controller is configured to, after depositing the backside film, chuck the substrate on the chuck to flatten the backside film against the chuck, thereby bending the substrate to mitigate substrate warpage.

Images