Method for adjusting wafer shape using a multi-directional actuating membrane

Abstract

The technology herein includes methods for coating a single layer actuator film or a multi-layer actuator film on the backside of a wafer. The actuator film includes one or more chemical actuators. Chemical actuators are various molecules, crystals, chemical compounds, and other chemical compositions that can exert a directional stress in response to the application of an external stimulus to the chemical actuator. The external stimulus can include a particular wavelength of light or polarization of light, or heat (or directional infrared), or a load that can include load-responsive actuation or pressure-responsive actuation.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This disclosure claims the benefit of U.S. Provisional Patent Application No. 63 / 219,414, filed July 8, 2021, and U.S. Provisional Patent Application No. 17 / 684,473, filed March 2, 2022, the entireties of which are incorporated by reference herein.

[0002] The present disclosure relates to semiconductor manufacturing methods, and more particularly to wafer shape optimization. [Background technology]

[0003] The background description provided herein is intended to generally present the context of the present disclosure. The inventors' work to the extent described in this background section, and aspects of the description that would not otherwise qualify as prior art at the time of filing, are not expressly or implicitly admitted as prior art to the present disclosure.

[0004] Semiconductor manufacturing involves several different steps and processes. One typical manufacturing process is known as photolithography (also known as microlithography). Photolithography uses radiation, such as ultraviolet or visible light, to create fine patterns in the design of semiconductor devices. Semiconductor manufacturing techniques, such as photolithography, etching, film deposition, surface cleaning, and metallization, can be used to construct various semiconductor devices, such as diodes, transistors, and integrated circuits. All of these processing techniques can affect the stress on and within the wafer.

[0005] Photolithography techniques are implemented using exposure systems (also called exposure tools). Exposure systems typically include an illumination system, a reticle (also called photomask) or spatial light modulator (SLM) that creates the circuit pattern, a projection system, and a wafer alignment stage that aligns a semiconductor wafer covered with a photosensitive resist. The illumination system illuminates an area of ​​the reticle or SLM with a (preferably) rectangular slot illumination field. The projection system projects an image of the illuminated area of ​​the reticle pattern onto the wafer. For the projection to be accurate, it is important to expose the wafer to the light pattern, which is relatively flat or planar, preferably with a height deviation of less than 10 microns. Therefore, a method for optimizing the wafer shape is desired. Summary of the Invention

[0006] The present disclosure relates to a method of processing a substrate comprising forming an actuator membrane on a first surface of a wafer, the wafer including the first surface and a second surface opposite the first surface, the actuator membrane including an actuator material, the actuator membrane being responsive to a predetermined activation stimulus, the actuator membrane being configured to undergo a position change in response to activation of the actuator material; and activating the actuator material in the actuator membrane via the predetermined activation stimulus at a position along the first surface of the wafer to induce a stress in the actuator membrane, the stress modifying a shape of the wafer.

[0007] Additionally, the present disclosure relates to a method of processing a substrate, the method comprising: receiving a wafer including a first structure on a first surface of the wafer, the wafer including a shape; generating a shape deformation stress map of the wafer to determine stress at the location of the first structure; forming an actuator membrane on the first structure, the actuator membrane including an actuator material, the actuator membrane being responsive to a predetermined activation stimulus, the actuator membrane being configured to undergo a position change in response to activation of the actuator material; activating the actuator material in the actuator membrane via the predetermined activation stimulus at the location of the first structure to induce stress in the actuator membrane, the induced stress in the actuator membrane relaxing the stress at the location of the first structure; and removing the first structure with the activated actuator membrane formed thereon from the first surface of the wafer.

[0008] It should be noted that this Summary section does not specify all embodiments and / or inherently novel aspects of the invention described in this disclosure or claims. Instead, the Summary of the Invention only provides a preliminary discussion of different embodiments and corresponding points of novelty. For further details and / or anticipated aspects of the invention and embodiments, the reader is directed to the Detailed Description of the Invention section of this disclosure and corresponding figures, discussed further below. [Brief description of the drawings]

[0009] Various embodiments of the present disclosure, proposed by way of example, will now be described in detail with reference to the following figures, in which like numbers refer to like elements, and in which:

[0010] [Figure 1A] FIG. 2 is a schematic perspective view of layers in a wafer in which a defect has been introduced into one of the layers. [Figure 1B] 1 is a schematic representation of various types and degrees of resulting wafer bow. [Figure 2A]1A-1C are schematic diagrams of chemical structures and optical images of actuator membrane properties from said chemical structures according to one embodiment of the present disclosure. [Figure 2B] FIG. 2 is a schematic diagram of entangled polymer chains, according to one embodiment of the present disclosure. [Figure 2C] 1 is an optical image of the peeling of an azopolymer film from a substrate according to one embodiment of the present disclosure. [Figure 2D] 1 is a schematic diagram and accompanying optical images of bending a film of azopolymer P1-100k, according to one embodiment of the present disclosure. [Figure 2E] 1 is a schematic diagram and accompanying optical images of bending a film of azopolymer P1-100k, according to one embodiment of the present disclosure. [Figure 3A] 1 is a schematic diagram of a single-walled carbon nanotube (CNT) and a multi-walled CNT, according to one embodiment of the present disclosure. [Figure 3B] 1 is a schematic diagram of fullerene C60 (left) and fullerene C70 (right), according to one embodiment of the present disclosure. [Figure 3C] FIG. 1 is a schematic diagram of single layer graphene and graphene oxide according to one embodiment of the present disclosure. [Figure 4A] 1 is an optical image of a multi-directional actuator incorporating carbon material along with PDMS and chitosan, according to one embodiment of the present disclosure. [Figure 4B] 1 is a graph of actuator material curvature as a function of time, according to one embodiment of the present disclosure. [Figure 4C] 1 is a graph of various characteristics of an actuator according to one embodiment of the present disclosure. [Figure 5A] FIG. 5A is a schematic diagram of a CNT-boron nitride (BN) bilayer actuator responsive to Joule heating, according to one embodiment of the present disclosure. [Figure 5B] 1 is an optical image of a temperature responsive CNT-BN bilayer actuator according to one embodiment of the present disclosure. [Figure 6A] 1 is a schematic diagram and formula for the deflection of a CNT-BN bilayer actuator, according to one embodiment of the present disclosure. [Figure 6B]1 is a series of schematics and images showing the fabrication and characterization of a CNT-BN bilayer film according to one embodiment of the present disclosure. [Figure 7] 1 is a graph of the optical properties of a single-walled CNT-polymer bilayer actuator and images of various solutions of single-walled CNTs (SWCNTs), according to one embodiment of the present disclosure. [Figure 8] FIG. 1 is a schematic diagram of wafer shape optimization according to one embodiment of the present disclosure. [Figure 9A] 1 is a cross-sectional view of a substrate segment showing structures or devices formed on the surface according to one embodiment of the present disclosure. [Figure 9B] FIG. 1 is a cross-sectional view of a substrate segment showing a warp modified actuator membrane formed on the backside of the wafer according to one embodiment of the present disclosure. [Figure 9C] 11 is a cross-sectional segment of a wafer 1105 during direct-write laser projection according to one embodiment of the present disclosure. [Figure 10] 1 is a flowchart of a method for manufacturing a semiconductor device according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The following disclosure shows various embodiments or examples for implementing various features of the presented subject matter. To simplify the disclosure, specific examples of components and configurations are described below. It should be understood that these are merely examples and are not intended to be limiting. For example, the formation of a first feature above or on a second feature in the following description may include embodiments in which the first feature and the second feature are formed in direct contact with each other, and may also include embodiments in which an additional feature may be formed between the first feature and the second feature such that the first feature and the second feature may not be in direct contact with each other. In addition, the present disclosure may repeat reference numbers and / or letters in various examples. This repetition is for the purposes of brevity and clarity and does not in itself address the relationship between the various embodiments and / or configurations discussed. Furthermore, for ease of explanation, spatially relative terms such as "top", "bottom", "lower", "below", "lower", "upper", "above" and the like may be used herein to describe the relationship of one element or feature to another element or feature as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the figures: the device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein similarly interpreted accordingly.

[0012] The order of description of the different steps described herein is shown for the sake of clarity. In general, these steps can be performed in any suitable order. In addition, although different features, techniques, configurations, etc. herein may each be referred to in different places in this disclosure, it is understood that each concept can be performed independently of each other or in combination with each other. Thus, the present invention can be embodied and viewed in many different ways.

[0013] In the fabrication of 3D NAND memory devices, device structures may extend vertically from the wafer's work surface. The use of larger wafers (e.g., 5 / 6 inch, 100 mm, 150 mm, 200 mm, 300 mm, and 450 mm, etc.) and the increasing number of layers required to fabricate leading-edge integrated circuits often results in significant deformation of the wafer shape. As 3D NAND incorporates more vertical layers, the devices are also heavier. FIG. 1A is a schematic perspective view of layers in a wafer where a defect has been introduced in one of the layers. For example, a 3D NAND device on a 300 mm wafer may use 128 layers. As shown, defects in an underlying previous layer may propagate to cause severe bowing in the subsequent layers. FIG. 1B shows that systematically increasing the number of layers in the front-side 3D NAND stack further deforms the wafer shape, increasing the severity of the problem. This can cause problems including non-uniformity, non-planarity, overlay mismatch for lithography or other processes, and poor wafer handling. Wafer shape distortion is particularly undesirable in overlay mismatch because these problems can occur early in the manufacturing process and carry over to subsequent steps, causing further problems in device performance and yield.

[0014] It is desirable to find a preferably simple means to precisely optimize the wafer shape. Some mitigation strategies include, for example, depositing a silicon nitride (SiN) film on the backside of the wafer by chemical vapor deposition (CVD), which can impose significant stress on the wafer and devices. That is, the SiN film stresses the wafer when deposited. This counter stress can be mitigated and the bow controlled positionally by lithographic patterning. That is, a given portion of the silicon nitride can be imaged, irradiated, or exposed and then removed to relieve stress at a particular point on the wafer, which can reshape the wafer in a different way. The problem posed by the silicon nitride film method is that it requires a different tool, which may mean that it may not be compatible with simple track-based processes, so the wafer must be loaded into an entirely different tool, which can be expensive and reduce throughput. Furthermore, this method can also take time to get the desired amount of silicon nitride on the backside of the wafer. In addition, this method is generally a very complicated process of imaging and adjusting the pattern in the silicon nitride film to mitigate water warping, and throughput may be a concern for mass production.

[0015] Described herein is a method to control and optimize wafer shape and overlay using a high throughput process. Throughput can be improved in part because the techniques herein can be embodied as or within a track tool or coater-developer tool module. In addition to the efficiency achieved by using a track tool, the techniques herein can modify stress in the wafer immediately after patterning. Thus, there is no need to perform a separate etching process to release or create stress from the patterned film.

[0016] The methods described herein include coating a single layer actuator film or a multi-layer actuator film on the backside of the wafer. The actuator film includes one or more chemical actuators. Chemical actuators are various molecules, crystals, chemical compounds, and other chemical compositions that can apply directional stress in response to applying an external stimulus to the chemical actuator. The external stimulus can include a "load" that can include a specific wavelength of light or polarization of light, or heat (or directional infrared), or even load-responsive actuation or pressure-responsive actuation. Thus, there are several different external stimuli that can be applied. The activation stimulus can also be applied at a specific location on the wafer film, for example, according to a wafer shape correction map of the wafer. Herein, actuation can be programmable or patternable according to what is needed to relax the global and / or local shape or bow from a wafer stress map from front-side bow measurements. Such chemical actuators can be "shape memory" in nature, in that the stress generated remains after the stimulus. The actuators can be reversible or multi-directional. Herein, direct write exposure can be used, such as using a laser scanned across the actuator film.

[0017] The embodiments herein include depositing a chemical actuator film and activating at least one chemical actuator by applying a location-specific stimulus that causes a modification of the wafer topography, all performed in a coater-developer tool. Although a stand-alone tool can be used to perform the techniques herein, there are significant advantages to performing the techniques herein on a track tool. The track tool can be connected to a scanner and stepper and can be used for several processing steps such as coating a photoresist film on the wafer, developing the wafer, and cleaning the wafer. Scanners and steppers, or other photolithography tools, benefit greatly from having a relatively flat wafer, i.e., a wafer without curvature and bowing. Thus, correcting such wafer topography deformations before exposure of the lithography pattern means better and more accurate patterning.

[0018] Additionally, the methods described herein include reversible adjustment of the force applied to the wafer. Thus, wafer shape correction herein has adaptive capabilities not present in wafer shape correction achieved solely by patternable polymer crosslinking. Preferably, the chemical actuator film is deposited on the backside of the wafer, although embodiments can include depositing the chemical actuator material on the frontside as well.

[0019] The backside (or frontside) formation process of the actuator membrane may vary depending on the type of actuator platform being formed. In general, however, the chemical actuator membrane may be formed on the backside of the wafer before, after, or at any stage in between full wafer processing. For wafer shape correction, a stress map of global and / or local bowing may be used to program a stress correction pattern, which may be a counter stress pattern imposed by the backside actuator membrane upon actuation. The techniques herein may be embodied in a stand-alone tool or as one or more modules in a track (coater-developer) tool or other semiconductor system.

[0020] Chemical actuators are molecules or compounds or other materials that change physical position or orientation in response to a stimulus. In other words, chemical actuator materials can stretch, contract, bend, change crystal orientation or chemical arrangement, or undergo other physical changes that modify internal stresses. Some chemical actuators can perform radical rearrangements. One advantage of chemical actuators is that it is the function of some actuators to reverse stresses or physical changes. This is beneficial compared to crosslinking, since crosslinked membranes are difficult to unbind. The availability of reversible actuators and / or step changes allows a single actuator membrane to be activated multiple times to modify internal stresses. This can be very useful, since as structures are patterned and layers are added to the wafer, the wafer surface can become increasingly warped and curved. Furthermore, stresses across the wafer are often non-uniform. The actuator membranes herein are versatile, addressing both local and global wafer (whole wafer) distortions.

[0021] In one embodiment, the wafer can include a first surface and a second surface. The first surface can be a working surface and the second surface can be a backside of the wafer. An actuator membrane can be deposited on the backside of the wafer and after an initial set of manufacturing steps are performed (such as shallow trench isolation, doping, initial channel formation, etc.), the wafer can be measured to identify bowing. In one embodiment, a wafer stress map can be generated that correlates to the degree of deformation of the wafer shape at a position along the wafer. For example, the wafer stress map can indicate a relaxation stress value across coordinate positions along the first surface of the wafer. A wafer shape correction image or pattern based on the wafer stress map can be exposed onto the actuator membrane. This exposure can cause a physical position change of the actuators in the actuator membrane. This physical change can then modify the internal stresses in the actuator membrane, which can then exert stresses on the wafer. These stresses can flatten the initial bow of the wafer or reduce the bowing to within a desired threshold. Once the wafer is flattened, additional processing steps can be performed. A planarized wafer improves overlay, especially in photolithographic patterning. As fabrication continues with the deposition and removal and modification of additional material, stresses again build up in the wafer, causing bowing beyond the desired amount. At this point, the wafer bow can be measured again, a second wafer shape correction pattern calculated, and the actuator membrane then exposed to the second wafer shape correction pattern. The second wafer shape correction pattern can account for the first exposure that an additional exposure is required. Depending on the actuator membrane, this may mean that the strength or duration of the activation stimulus is added.

[0022] In one embodiment, the actuator membrane can be reset. The method of resetting or reversing the actuator membrane can vary depending on the type of actuator used. For example, some actuators can reverse the physical change to an initial state by applying heat or a specific wavelength of light. Thus, instead of changing the actuator membrane stepwise, the actuator membrane can be reset first each time it is activated. The change in the actuator membrane can be reversed, such as by applying heat. The wafer is then measured to determine the deformation of the wafer shape and a second wafer shape correction pattern is calculated to be applied to the actuator membrane. A corresponding stimulus can then be used to apply the second wafer shape correction pattern to the actuator membrane. It is noted that the wafer shape correction pattern may appear visually as an inversion of the wafer shape deformation pattern or may appear different, such as by an optical proximity correction pattern. The particular wafer shape correction pattern will vary depending on the amount of stress required, the direction of the stress required, the type of actuator membrane, and the materials or devices to be stacked on the wafer.

[0023] In one embodiment, an actuator membrane that includes two or more layers of actuator membranes, or multiple actuators, can be used. Using multiple actuators and / or membranes allows for additional functionality. For example, a given actuator can have different types of physical changes and different activation stimuli. Thus, in one embodiment, a first actuator can be activated with a first predetermined wavelength of actinic radiation or light, while a second actuator can be activated with a second predetermined wavelength of actinic radiation. As will be appreciated, the first actuator or the second actuator can be activated individually by separate application of the first predetermined wavelength of actinic radiation or the second predetermined wavelength of actinic radiation. In one example, the first actuator can expand upon activation, while the second actuator can contract. Since both expansion and contraction are available in the actuator membrane, either compressive or tensile stresses can be induced simultaneously, thereby further controlling the stress modification of the membrane. For example, the first actuator can provide a compressive stress, while the second actuator can provide a tensile stress. For example, a first actuator can provide a compressive stress while a second actuator can also provide a compressive stress. For example, a first actuator can provide a tensile stress while a second actuator can also provide a compressive stress. For example, a first actuator can provide a tensile stress while a second actuator can also provide a tensile stress. The bilayer membrane can have different thermal expansion coefficients, which can be used to further control the stress in the membrane.

[0024] The actuator films herein can be deposited in a variety of ways, including typical deposition methods in the semiconductor industry. For example, deposition can be achieved by spin-on deposition. The track tool module can be configured to dispense a liquid formulation that includes the actuator. The wafer can be spun with the liquid dispensed on the wafer surface, and then a bake can be performed to harden the film or remove the solvent. It can also be understood that deposition can be achieved by spray coating, vapor deposition, and other techniques.

[0025] This specification describes actuator materials that can be selected for use in wafer shape optimization. Preferred actuator materials for wafer shape optimization include, but are not limited to, liquid crystal elastomers, shape memory polymers, and electrothermal / photothermal bilayer actuators, or composites of these platforms. The application of encapsulated or shielded ionic electroactive polymers or polymer / inorganic piezoelectrics is also contemplated herein. The range of materials used to mitigate actuator warpage can be broad, as long as the selected material can be deposited on the surface of the wafer and protected. These actuator materials can be combined with other membrane materials to facilitate layering. Additionally, some actuator materials can bend in different directions in response to different wavelengths or polarizations of actinic radiation or light.

[0026] In one embodiment, liquid crystal elastomers or thiolene polymers have low glass transition temperatures (Tg) and low use temperatures and can be used as actuator materials. However, composite systems and the inclusion of higher Tg acrylate materials may improve thermal stability and film integrity. Examples of photoactivated liquid crystal elastomers are shown in Figures 2A-4B. These are all relatively soft materials and may not be stable at high temperatures.

[0027] 2A is a schematic diagram of a chemical structure according to one embodiment of the present disclosure, and an optical image of the actuator film properties from the aforementioned chemical structure. In one embodiment, the actuator film includes an azopolymer P1 that can undergo photoisomerization. Photoisomerization can induce a solid-to-liquid transition of P1 powder (e.g., by UV light), healing of scratches in a film formed with the azopolymer P1, and bending of a free-standing film formed with the azopolymer P1 (see Chen, M., et al., Entangled Azobenzene-Containing Polymers with Photoinduced Reversible Solid-to-Liquid Transitions for Healable and Reprocessable Photoactuators. Adv. Funct. Mater. 2020, 30, 1906752. https: / / doi.org / 10.1002 / adfm.201906752).

[0028] 2B is a schematic diagram of entangled polymer chains according to one embodiment of the present disclosure. In one embodiment, the polymer chains of the low molecular weight azopolymer P1 can hardly entangle, while the polymer chains of the high molecular weight azopolymer P1 can entangle.

[0029] 2C is an optical image of the peeling of an azopolymer film from a substrate according to one embodiment of the present disclosure.In one embodiment, the film of azopolymer P1 with a molar mass of 100 kg / mol can be peeled and stretched more easily than the film of azopolymer P1 with a molar mass of 10 kg / mol.Free-standing films of azopolymer P1-100k can be obtained, but free-standing films of azopolymer P1-10k may not be obtained because the polymer chains may lack entanglement, which may make them hard and brittle.

[0030] 2D and 2E are schematic illustrations and accompanying optical images of bending of a film of azopolymer P1-100k, according to one embodiment of the present disclosure. In one embodiment, the bending can be photoinduced and reversible. UV light (e.g., 365 nm, 51 mW cm) induces a first photomechanical response.-2 Over a first duration (e.g., 10 min) of exposure to actinic radiation such as 470 nm, 9 mW cm, the film of azopolymer P1-100k can bend or curl. Blue light (e.g., 470 nm, 9 mW cm) induces a second photomechanical response. -2 Over a second duration (e.g., 50 seconds) of exposure to actinic radiation such as UV light, the film of azopolymer P1-100k can bend or curl in the opposite direction compared to UV exposure. Thus, the film can be reversibly photomechanically actuated. In FIG. 2D, the film of azopolymer P1-100k can be stretched prior to exposure. In FIG. 2E, the film of azopolymer P1-100k can be unstretched prior to exposure.

[0031] FIG. 3A is a schematic diagram of a single-walled carbon nanotube (CNT) and a multi-walled CNT according to one embodiment of the present disclosure. FIG. 3B is a schematic diagram of a fullerene C according to one embodiment of the present disclosure. 60 (Left) and fullerene C 70 (Right) is a schematic diagram of a graphene nanotube (Ge) and a graphene oxide (Ge) according to one embodiment of the present disclosure. In one embodiment, a class of actuators that exhibit improved thermal stability and the potential for both thermal (IR / NIR) and photothermal actuation are those that include carbon nanotubes or graphene (see Figures 3A-3C). Most carbon materials are photothermally active, have broadband optical absorption that absorbs light at various wavelengths, and most have high photothermal conversion rates. These actuators can be either composites (i.e., carbon type + other liquid crystal elastomers in the same layer) (see Figures 4A-4C), or photothermal bilayers (see Figures 5A-5B) where carbon nanotubes can be stacked with other materials with significantly different coefficients of thermal expansion (CTE), such as carbon nanotubes and boron nitride. Significant advances have been made in the technology for processing carbon nanotubes and graphene (graphene oxide), making these materials not only solution processable (see Figures 6A-6B), but also tunable to specific wavelengths of light based on the chirality of single-walled carbon nanotubes (see Figure 7).

[0032] 4A is an optical image of a multidirectional actuator incorporating carbon materials with PDMS and chitosan, according to one embodiment of the present disclosure. In one embodiment, the optical and infrared images (inset) show light-driven actuation of the PDMS-CNT / chitosan actuator with different irradiation times (see Xu, H., et al., (2019), An Ultra-large Deformation Bidirectional Actuator Based on a Carbon Nanotube / PDMS Composite and a Chitosan Film. J. Mater. Chem. B, 7, 7558-7565. https: / / doi.org / 10.1039 / C9TB01841G).

[0033] 4B is a graph of actuator material curvature as a function of time, according to one embodiment of the present disclosure, in one embodiment, the graph on the left shows one actuation and recovery cycle of a PDMS-CNT actuator, while the graph on the right shows a repeatability test of a light-driven PDMS-CNT actuator.

[0034] FIG. 4C is a graph of various properties of an actuator according to one embodiment of the present disclosure. In one embodiment, the top left graph shows axial force measurements of a PDMS-CNT / chitosan actuator for different light power densities, the top right graph shows the change in electrical conductivity of a PDMS-CNT / chitosan actuator (15% CNT) with temperature, and the bottom graph shows the curvature of a PDMS-CNT / chitosan actuator with time subjected to a light-humidity-light-driven actuation switch. In particular, the insets are optical images of the PDMS-CNT / chitosan actuator at different actuation times. Positive values ​​indicate bending towards the PDMS-CNT side and negative values ​​indicate bending towards the chitosan side.

[0035] FIG. 5A is a schematic diagram of a CNT-boron nitride (BN) bilayer actuator responding to Joule heating according to one embodiment of the present disclosure. In one embodiment, via selective Joule heating, for example, a free-standing U-shaped CNT thin film with a thickness of 10 μm can be heated to 2000 K within 100 ms, at which time the actuator bends towards the BN side (see Wang, C., et al., (2016), A Solution-Processed High-Temperature, Flexible, Thin-Film Actuator. Adv. Mater., 28:8618-8624. https: / / doi.org / 10.1002 / adma.201602777). When the current is removed, the actuator can be rapidly cooled to room temperature by radiation and thermal conduction. The large surface area and high thermal conductivity of the CNT thin film enable rapid cooling.

[0036] 5B is an optical image of a CNT-BN bilayer actuator responsive to temperature, according to one embodiment of the present disclosure. In one embodiment, time-lapse images of the bilayer actuator show the response to applied heat during heating and cooling cycles and possible fast response windows. In particular, the CNT-BN actuator can be stable up to high temperatures (e.g., 1726° C.), is thin and flexible, has fast switching (e.g., 100 ms response time), and is durable for over 10,000 cycles.

[0037] 6A is a schematic diagram and equation for the deflection of a CNT-BN bilayer actuator according to one embodiment of the present disclosure. In one embodiment, the CNT-BN bilayer actuator can be characterized after high temperature actuation as shown by the equation and accompanying illustration (left) and stress-strain measurements of the CNT and CNT-BN bilayer films (right) (see Wang, C. et al., (2016), A Solution-Processed High-Temperature, Flexible, Thin-Film Actuator. Adv. Mater., 28:8618-8624. https: / / doi.org / 10.1002 / adma.201602777).

[0038] FIG. 6B is a series of schematics and images showing the fabrication and characterization of a CNT-BN bilayer film according to one embodiment of the present disclosure. In one embodiment, the fabrication can include the use of stable, homogeneous BN and CNT solutions. Both CNTs and BN nanosheets can be suspended in a solvent to form a stable ink, so that a bilayer thin film can be fabricated by a two-step vacuum filtration process. Optical and scanning electron microscope images show the film topology of the CNT-BN bilayer film.

[0039] FIG. 7 is a graph of the optical properties of a single-walled CNT-polymer bilayer actuator and images of different solutions of single-walled CNTs (SWCNTs) according to one embodiment of the present disclosure. In one embodiment, three types of SWCNTs can be used to tailor the optical absorption properties: i) high-pressure carbon monoxide disproportionated (HiPCO) SWCNTs, ii) metallic nanotubes with a single absorption peak at about 700 nm, and iii) single chirality nanotubes with characteristic absorption peaks at about 560 and 970 nm. Depending on the type, SWCNTs can act as excellent optical absorbers and wavelength-sensitive media. This special optical property has enabled actuators with monochromatic optical actuation capabilities (see Wang, T., et al., (2017), Maximizing the Performance of Photothermal Actuators by Combining Smart Materials with Supplementary Advantages. Sci. Adv. 3, e1602697. DOI: 10.1126 / sciadv.1602697).

[0040] The technology herein encompasses multiple aspects of warpage mitigation that can combine the fabrication process with material selection and activation to achieve backside actuation or stress correction. Similar materials and processes can be used for frontside warpage mitigation. The technology herein includes reversible or multi-directional actuation materials to correct both global and local warpage. It also allows for in-situ wafer shape correction and can correct or compensate for warpage as it occurs throughout the fabrication process. For example, a backside actuator membrane that "moves" with the wafer during processing can be used to adjust the wafer shape deformation as needed. The external stimuli can be applied at different stages or times as desired, corresponding to the type of actuator material. Thus, the same actuator membrane can enable multiple stress corrections throughout the fabrication process, with the stress fixed or adjusted in stages as needed. For light-activated stimuli, a module in a direct write tool or coater-developer tool can be used to activate the actuator by coordinate position. For example, a scanning laser beam can be used that can adjust the light intensity by coordinate position.

[0041] Actuation of the carbon nanotube bilayer allows for "through-wafer" bow mitigation and patterning using an IR light source that is known to activate carbon-based actuator devices. Thus, the wafer can remain backside down on a wafer holder while IR light from above can be shone onto or through the wafer. In particular, silicon is nearly transparent to IR wavelengths. Thus, through-wafer patterning can reduce the number of times the wafer needs to be flipped during processing.

[0042] Extending the application of actuator material to the front side of the wafer allows for a variety of process options. In one embodiment, a force can be applied to the edge of each die to roughly correct the bow on a die by die basis. Custom reticles can incorporate areas for activating actuators at the edge of each die, allowing the scanner to both print the pattern and perform wafer shape corrections, thus improving throughput. In one embodiment, the actuator material can be embedded into the device itself. In one embodiment, the actuator film can be applied at the end of front side processing on top of the device itself during packaging to minimize impact on the manufactured device.

[0043] 8 is a schematic diagram of wafer shape optimization according to one embodiment of the present disclosure. In one embodiment, a wafer distortion map can be generated and then a wafer shape correction pattern can be applied, resulting in a corrected or planar wafer Z height measurement.

[0044] 9A is a cross-sectional substrate segment showing structures or devices 1199 formed on a surface according to one embodiment of the disclosure. In one embodiment, a wafer 305 includes a first surface 1110 and a second surface 1115. For example, the first surface 1110 of the wafer can be a processing surface where target devices are fabricated, and the second surface 1115 can be a backside of the wafer. The devices 1199 formed on the processing surface 1110 can be active devices or structures, such as transistors or memory cells, or partially formed active devices or structures. The wafer 1105 can be received at a coating module of a coater-developer tool or other track-based tool.

[0045] FIG. 9B is a cross-sectional substrate segment showing a warp-modified actuator membrane 1125 (referred to herein as "actuator membrane 1125") formed on the backside 1115 of the wafer 1105, according to one embodiment of the present disclosure. In one embodiment, the wafer 1105 can be flipped to form the actuator membrane 1125 on the backside 1115, but the wafer 1105 need not be flipped. For example, the tool can include a system for vertical upward coating, spraying, or deposition. That is, the wafer 1105 can move on a track and the tool can form the actuator membrane 1115 on the backside 1115 of the wafer by spray coating. In either case, the actuator membrane 1125 can be formed on the backside 1115, and the actuator membrane 1125 can include one or more actuators that respond to light, temperature, current, chemicals, etc., as previously described with reference to the actuators in FIGS. 2A-7. For devices 1199 disposed on the work surface 1110, a protective fill or film may be deposited or a carrier wafer may be attached to facilitate handling of the wafer 1105.

[0046] FIG. 9C is a cross-sectional segment of a wafer 1105 during direct-write laser projection according to one embodiment of the present disclosure. In one embodiment, the actuator membrane 1125 can be activated by direct-write laser projection on the backside 1115 of the wafer 1105, for example, while the wafer 1105 is still on a track in the tool. Based on the generated wafer shape deformation stress map of the wafer 1105, a wafer shape correction pattern can be projected using a digital light processing chip, a laser galvanometer, or the like. A scanning laser beam can also be used. It should also be noted that the wafer 1105 can be flipped to activate the actuator membrane 1115, but does not need to be flipped. Advantageously, as previously described, the backside 1115 of the wafer 1105 can be coated with the actuator membrane 1125 on the track, and the actuator membrane 1125 can also be activated without moving or flipping the wafer 1105 on the track.

[0047] The exposure can cause a physical position change of the actuators in the actuator membrane 1125. This physical change can then modify the internal stresses in the actuator membrane 1125, which can then stress the wafer 1105. These stresses can flatten the wafer 1105 from its initial bow or reduce the bow to within a desired threshold. As the processing of the wafer 1105 progresses, the bow of the wafer 1105 can be measured again, a second wafer shape correction pattern can be calculated, and the actuator membrane 1125 can then be exposed to the second wafer shape correction pattern. The second wafer shape correction pattern can account for the first exposure that an additional exposure is required. Depending on the actuator membrane 1125, this can mean an additional strength or duration of the activation stimulus.

[0048] In one embodiment, the actuator membrane 1125 can be reset as described above. For example, some actuators can reverse the physical changes to an initial state by applying heat or a specific wavelength of light. Thus, instead of incrementally changing the actuator membrane 1125, the actuator membrane 1125 can be reset first each time it is activated. The changes in the actuator membrane 1125 can be reversed, such as by applying heat. The wafer 1105 can then be measured to determine the deformation of the wafer shape and a second wafer shape correction pattern can be calculated to apply to the actuator membrane 1125. The second wafer shape correction pattern can then be applied to the actuator membrane 1125 using a corresponding stimulus, for example while still on the track in the tool.

[0049] In one embodiment, as previously described, two or more layers of actuator film 1125, or actuator film 1125 including multiple actuators, can be used. Using multiple actuators and / or films 1125 allows for additional functionality. For example, a given actuator can have different types of physical changes and different activation stimuli. Thus, in one embodiment, a first actuator in a first layer of actuator film 1125 can be activated with a first predetermined wavelength of light, while a second actuator in a second layer of actuator film 1125 can be activated with a second predetermined wavelength of light. As will be appreciated, the first actuator or the second actuator can be activated individually by separate application of the first predetermined wavelength of light or the second predetermined wavelength of light. Furthermore, in one embodiment, each layer of actuator film 1125 can correspond to a different wafer shape compensation pattern. For example, a first wafer shape compensation pattern can be used during exposure of a first layer of actuator film 1125, while a second wafer shape compensation pattern can be used during exposure of a second layer of actuator film 1125. The multiple layers of the actuator membrane 1125 provide additional flexibility to accommodate stress in multiple directions in multiple ways. That is, a blanket actuator membrane 1125 can accommodate global bending (i.e., 1D) characteristics, while a multi-directional actuator membrane 1125 can accommodate local bending (i.e., 2D+) strains. For example, a first layer of a first actuator material is prestressed along a first direction and a second layer of a second actuator material is prestressed along a second direction, where the first and second directions are aligned. For example, a first layer of a first actuator material is prestressed along a first direction and a second layer of a second actuator material is prestressed along a second direction, where the first and second directions are not aligned, e.g., the first and second directions are orthogonal to each other.

[0050] Again, multiple layers of actuator membrane 1125 can be applied to the work surface 1110 rather than the backside 1115. Backside integration of membranes can lead to trade-offs that may impact device yield. Using co-optimization of design techniques where multi-directional front-side integration is planned, the benefits of this method may be realized without the trade-offs. In one embodiment, selective application / removal of the multi-directional actuation membrane 1125 can be controlled such that the multi-directional actuation membrane 1125 is only present at the streets (areas between devices 1199) on the wafer 1105. In one embodiment, the actuator membrane 1125 can be formed along the periphery of the wafer. Then, by applying forces to the periphery of the wafer 1105, the shape of the wafer 1105 local to the die can be controlled.

[0051] In one embodiment, the entire wafer 1105 can attenuate / filter stresses that affect the chiplets prior to singulation. Once diced, the chiplets may pop / break upon release because the bulk wafer 1105 may not be filtering the stresses. Thus, a multi-directional actuation membrane 1125 can be deposited on top of the chiplets prior to release to counteract the expected stresses per chip.

[0052] In one embodiment, the actuator membrane 1125 can provide for in situ warpage relaxation or correction that can compensate for warpage that occurs or is formed during the manufacturing process, i.e., the stress responsive actuators can be activated during the formation of a bend such that the actuator membrane 1125 relieves stresses that are applied during the formation of the bend.

[0053] In one embodiment, the actuator membrane 1125 can be deactivated via a predetermined deactivation stimulus at a location along the first surface of the wafer to remove stress in the actuator membrane 1125.

[0054] In one embodiment, the first surface includes the fully formed devices and is opposite the back surface, and actuator membranes are formed on each of the fully formed devices, and each membrane of actuator membranes 1125 is separated from the others and localized to a respective one of said respective fully formed devices.

[0055] FIG. 10 is a flow chart of a method 1000 for processing a substrate according to one embodiment of the present disclosure.

[0056] In step 1005, a wafer 1105 is received by the tool, and the wafer 1105 may include a first surface 1110 (working side 1110) and a second surface 1115 (backside 1115).

[0057] In step 1010, an actuator membrane 1125 can be formed on the first surface 1110 or the second surface 1115. The actuator membrane 1125 can include an actuator, where the actuator membrane 1125 is configured to undergo a position change in response to activation of an actuator material.

[0058] In step 1015, the actuator material in the actuator membrane can be activated via an activation stimulus at a location along the first surface of the wafer, inducing a stress in the actuator membrane that modifies the warp of the wafer.

[0059] In one embodiment, a structure in a wafer on which an actuator membrane is formed may be removed from the surface of the wafer.

[0060] In the above description, specific details have been described, such as the specific geometry of the processing system and a description of the various components and processes used. However, it should be understood that the technology herein may be implemented in other embodiments that deviate from these specific details, and that such details are for illustrative purposes and are not intended to be limiting. Several embodiments disclosed herein have been described with reference to the accompanying drawings. Similarly, for illustrative purposes, specific numbers, materials, and configurations have been shown to ensure thorough understanding. However, several embodiments may be implemented without such specific details. Components having substantially the same functional structure are designated by similar reference numerals, and redundant descriptions may be omitted.

[0061] To aid in understanding various embodiments, various techniques have been described as multiple operations. The order of description should not be construed as though the operations are necessarily order dependent. In fact, the operations need not be performed in the order presented. The operations described may be performed in a different order than in the described embodiments. Various additional operations may be performed and / or the operations described may be omitted in additional embodiments.

[0062] As used herein, "substrate" or "target substrate" refers generally to an object to be processed according to the present invention. The substrate may include any material portion or structure of a device, particularly a semiconductor device or other electronic device, and may be, for example, a base substrate structure such as a semiconductor wafer, a reticle, or a layer on or overlying the base substrate structure, such as a thin film. Thus, the substrate is not limited to any particular base structure, underlying layer, or overlying layer, whether patterned or not, but rather is intended to include any such layer or base structure, and any combination of layers and / or base structures. Although the description may refer to a particular type of substrate, this is for illustrative purposes only.

[0063] Those skilled in the art will also appreciate that many variations can be made to the operation of the techniques described above and still achieve the same objectives of the invention. Such variations are intended to be encompassed within the scope of the present disclosure. Accordingly, the above description of embodiments of the invention are not intended to be limiting. Rather, limitations to embodiments of the invention are presented in the following claims.

Claims

1. A method for processing a substrate, the method comprising: forming an actuator film on a first surface of a wafer, the wafer including the first surface and a second surface opposite the first surface, the actuator film including an actuator material, the actuator film being responsive to a predetermined activation stimulus, and the actuator film being configured to undergo a position change in response to activation of the actuator material; activating the actuator material in the actuator film via the predetermined activation stimulus at a position along the first surface of the wafer to generate a stress in the actuator film, the stress modifying the shape of the wafer, and the stress generated in the actuator film relieving a determined deformation stress at a position of a first structure on the first surface.

2. The method of claim 1, wherein the first surface is a back surface of the wafer and the second surface includes at least partially formed structures.

3. The method of claim 1, wherein the first surface includes at least partially formed structures and is on the side opposite the back surface.

4. The method of claim 3, wherein the actuator film is formed between each of the at least partially formed structures.

5. The method of claim 3, wherein the actuator film is formed along the periphery of a region including the at least partially formed structures.

6. The method of claim 1, wherein activating the actuator in the actuator film generates a compressive stress in the actuator film.

7. The method of claim 1, wherein activating the actuator material in the actuator film generates a tensile stress in the actuator film.

8. The method of claim 1, wherein the actuator film includes a first layer of a first actuator material and a second layer of a second actuator material.

9. The method of claim 8, wherein the first layer of the first actuator material responds to a predetermined activation stimulus different from that of the second layer of the second actuator material.

10. The method according to claim 8, wherein the first layer of the first actuator material applies a compressive stress and the second layer of the second actuator material applies a tensile stress.

11. The method according to claim 1, wherein the actuator film comprises a first actuator material and a second actuator material, and the first actuator material responds to a predetermined activation stimulus different from that of the second actuator material.

12. The method according to claim 1, wherein the step of activating the actuator material in the actuator film includes exposing the first surface to a pattern of light using a direct writing system.

13. The step of forming an actuator film on the first surface of the wafer comprises depositing a first layer of a first actuator material on the first surface of the wafer, the first layer of the first actuator material responding to a first predetermined activation stimulus, and depositing a second layer of a second actuator material on the first layer of the first actuator material, the second layer of the second actuator material responding to a second predetermined activation stimulus, the first predetermined activation stimulus being different from the second predetermined activation stimulus. The method according to claim 1 further includes.

14. The step of activating the actuator material in the actuator film comprises activating the first layer of the first actuator material using the first predetermined activation stimulus, and activating the second layer of the second actuator material using the second predetermined activation stimulus. The method according to claim 13 further includes.

15. The first layer of the first actuator material is prestressed along a first direction, and the second layer of the second actuator material is prestressed along a second direction. The first direction and the second direction are not aligned. The method according to claim 13.

16. The method according to claim 1 further includes deactivating the actuator material in the actuator film via a predetermined deactivation stimulus at a position along the first surface of the wafer, and removing the stress in the actuator film.

17. The first surface includes the fully formed device and is on the opposite side of the back surface, The actuator film includes a plurality of portions, The actuator film is formed on each of the fully formed devices, and each portion of the plurality of portions is separated from each other and localized on each of the fully formed devices. The method according to claim 1.

18. The step of activating the actuator material in the actuator film via the predetermined activation stimulus at the position along the first surface of the wafer is based on the wafer shape deformation stress map of the wafer. The method according to claim 1.

19. The wafer shape deformation stress map shows stress values that relax across positions along the first surface of the wafer. The method according to claim 18.

20. A method of processing a substrate, the method comprising: Receiving the wafer including the first structure on the first surface of the wafer, the wafer including a shape; Generating a wafer shape deformation stress map of the wafer and determining a first stress at the position of the first structure; Forming an actuator film on the first structure, the actuator film including an actuator material, the actuator film being reactive to a predetermined activation stimulus, and the actuator film being configured to undergo a position change in response to activation of the actuator material; Activating the actuator material in the actuator film via the predetermined activation stimulus at the position of the first structure, generating a second stress in the actuator film, and the second stress generated in the actuator film relaxes the first stress at the position of the first structure; Removing the first structure on which the activated actuator film is formed from the first surface of the wafer. A method of processing a substrate.

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