Method for Controlling Semiconductor Film Thickness

Abstract

In one embodiment, a method for processing a semiconductor substrate includes depositing a resin film on a substrate having micro-fabricated structures defining recesses. The resin film fills the recesses and covers the micro-fabricated structures. The method includes performing localized removal of the resin film using a photo-acid generator (PAG)-based process to remove the resin film to a first depth in each of the recesses, where at least two of the first depths are different depths. The method includes repeatedly performing uniform removal of remaining portions of the resin film using a thermal acid generator (TAG)-based process until a predetermined condition is met to remove the resin film to a substantially uniform depth within the recesses.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 073,047, filed on September 1, 2020, and U.S. Non - Provisional Patent Application No. 17 / 125,609, filed on December 17, 2020, which are incorporated herein by reference.

[0002] This disclosure generally relates to semiconductor manufacturing, and in certain embodiments, to methods for controlling semiconductor film thickness.

Background Art

[0003] Constructing an electrical circuit involves depositing multiple layers of material across various features or structures, similar to patterning, etching, and filling processes. As design innovations for next - generation transistors shift towards smaller dimensions and vertical architectures, the demand for techniques to precisely control film thickness within a die and across a wafer is increasing. The etching process can be time - adjusted to remove a portion of the film without an endpoint, but such processes have insufficient position control and high variability.

Summary of the Invention

Means for Solving the Problems

[0004] In one embodiment, a method for processing a semiconductor substrate includes receiving a substrate having a microfabrication structure that defines a recess, and depositing a resin film on the substrate. The resin film fills the recess, covers the microfabrication structure, and is initially resistant to development with a solvent. The method includes depositing a first overcoat film on the substrate. The first overcoat film includes a first agent-generating component that reacts to actinic radiation to generate a first solubility modifier. The method includes exposing the first overcoat film to a first actinic radiation sufficient to generate the first solubility modifier within the first overcoat film. The method includes diffusing the first solubility modifier to a first predetermined depth within the resin film to render a first portion of the resin film soluble in a first solvent, and developing the first overcoat film and the first portion of the resin film with the first solvent. The method includes depositing a second overcoat film on the substrate. The second overcoat film includes a first agent-generating component that reacts to actinic radiation to generate a first solubility modifier. The method includes exposing the second overcoat film to a second actinic radiation sufficient to generate the first solubility modifier within the second overcoat film. The method includes diffusing the first solubility modifier to a second predetermined depth within the resin film to render a second portion of the resin film soluble in a first solvent, and developing the second overcoat film and the second portion of the resin film with the first solvent such that the resin film is embedded to a respective first bonded depth of the recesses.

[0005] In one embodiment, a method for processing a semiconductor substrate includes receiving a substrate having a microfabrication structure defining a recess, and depositing a resin film on the substrate. The resin film fills the recess, covers the microfabrication structure, and is initially resistant to development with a first solvent. The method includes depositing a first overcoat film on the substrate. The first overcoat film includes a first agent generating component that reacts to actinic radiation to generate a first solubility modifier. The method includes exposing the first overcoat film to actinic radiation sufficient to generate the first solubility modifier within the first overcoat film. The method includes diffusing the first solubility modifier to a first predetermined depth within the resin film to render a first portion of the resin film soluble in the first solvent, and developing the first portion of the resin film using the first solvent. The method includes depositing a second overcoat film on the substrate. The second overcoat film includes a second agent generating component that reacts to heating of the substrate to generate a second solubility modifier. The method includes baking the substrate sufficiently to generate the second solubility modifier within the second overcoat film and diffusing the second solubility modifier to a second predetermined depth within the resin film to render a second portion of the resin film soluble in the first solvent. The method includes developing the second portion of the resin film using the first solvent such that the resin film is embedded to the respective combined depth of the recesses.

[0006] In one embodiment, a method for processing a semiconductor substrate includes depositing a resin film on a substrate having a microfabrication structure defining a recess. The resin film fills the recess and covers the microfabrication structure. The method includes performing local removal of the resin film using a photoacid generator (PAG)-based process to remove the resin film to a respective first depth of each recess, wherein at least two depths of the respective first depths are different depths. The method includes repeatedly performing uniform removal of the remaining portion of the resin film using a thermal acid generator (TAG)-based process until a predetermined condition is met to remove the resin film having a substantially uniform depth within the recess.

[0007] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings.

Brief Description of the Drawings

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Best Mode for Carrying Out the Invention

[0009] Throughout the deposition, patterning, and removal processes associated with forming semiconductor devices, it may be desirable to control the height of films deposited for various reasons. For example, it may be desirable to remove a portion of the deposited film (e.g., in a trench) to achieve a certain height of the film deposited in the trench. Conventional removal processes such as time-regulated wet or dry etching processes for removing a portion of the deposited layer are difficult to control and are often plagued by other problems such as planarization issues. These problems are becoming even more common as feature sizes continue to shrink or vary across the surface of the semiconductor wafer being processed.

[0010] Embodiments of the present disclosure provide a technique for controlling the film thickness for a semiconductor substrate. The substrate may have pre-patterned features, for example, including a structure that defines a recess. The film being controlled may be a filler such as a polymer resin that is deposited over the pre-patterned features, fills the recess, and covers the structure. It may be desirable to precisely and repeatedly reduce the filler within the recesses to a specific target height (thickness) across the semiconductor wafer including the substrate, and those target heights may vary between recesses. Certain embodiments achieve this film thickness control without using an etch stop layer or other time-regulated etching process that is used with conventional etching techniques where film height control is desired.

[0011] The filler may initially be resistant to removal (e.g., development) by a solvent (e.g., developer) used to remove a portion of the filler. Certain embodiments use a cyclic process that includes depositing an overcoat film that includes a chemical generating agent that generates a chemical in response to a stimulus. The chemical is then diffused into the filler to a predetermined depth to render a portion of the filler deprotected (removable / developable) with respect to the solvent. The overcoat film and the deprotected portion of the filler are then removed using the solvent. This process may be repeated until the filler within the recesses reaches one or more corresponding target heights.

[0012] Certain embodiments use a PAG-based process to reduce at least a portion of the height of a resin film within a recess of a substrate. For example, the chemical generating agent within the overcoat film may be a photoactivator generating agent (e.g., PAG) that is activated in response to actinic radiation. This PAG-based process may be repeated a suitable number of times until a target film height (e.g., within the recess) is achieved.

[0013] One embodiment uses a TAG-based process to reduce at least a portion of the height of a resin film within a recess of a substrate. For example, the agent generator within the overcoat film may be a heat-activated agent generator (e.g., TAG) that reacts to heat and becomes activated. This TAG-based process may be repeated an appropriate number of times until a target film height (e.g., within the recess) is achieved.

[0014] One embodiment combines one or more repetitions of a PAG-based process with one or more repetitions of a TAG-based process to establish a change in the height of a resin film and further uniformly reduce the thickness of the film height until a target film height (e.g., within the recess) is achieved.

[0015] That is, embodiments provide adjustment of film thickness and profile across a wafer by generation and diffusion of acid from an overcoat to an acid-deprotectable resin, followed by development. The depth of acid deprotection into the resin film can be defined by the amount of acid produced in and diffused from the overlying overcoat. Positional height control can be achieved using a photoacid and / or thermoacid generator-containing overcoat. Embodiments can be used with backside overlay control techniques, similar to the position-based critical dimension optimizer platform for frontside processing.

[0016] One embodiment also results in improved flatness. For example, certain conventional etching techniques cause or exacerbate planarization problems, especially when the pitch between or the width of structures on a substrate varies. Certain embodiments of the present disclosure are capable of controlling the removal of a filler to a target height with little or no impact from the changing topography of the substrate.

[0017] Figures 1A - 1J show cross - sectional and plan views of an exemplary semiconductor substrate 100 during an exemplary process 102 for processing a substrate 100, according to an embodiment. Process 102 includes steps 104a - 104j, although process 102 may include more or fewer steps if necessary. Substrate 100 may be part of a larger semiconductor device, such as part of a larger semiconductor wafer. In certain embodiments, process 102 includes repeatedly performing a PAG - based process to remove a filler material from a recess in substrate 100 until the filler material reaches a predetermined height within the recess.

[0018] As shown in FIG. 1A, in step 104a, substrate 100 includes a base 106 and a microfabricated structure 108 formed on base 106. Structure 108 defines a recess 110. The present disclosure contemplates a structure 108 patterned with any suitable features. For example, although the present disclosure primarily describes "recesses", other suitable features, including (regardless of whether "recesses" are considered) lines, holes, trenches, vias, and / or other suitable structures, may be formed in or on a semiconductor substrate using conventional lithography processes and / or other suitable deposition and etching processes. Structure 108 and recess 110 may be formed using conventional lithography processes and / or other suitable deposition and etching processes. Base 106 and structure 108 may include the same or different materials (or combinations of materials) as necessary.

[0019] The substrate 100 generally refers to a workpiece to be processed in accordance with an embodiment of the present disclosure. The substrate 100 may include any material portion or structure of a device, particularly a semiconductor or other electronic device, such as a base substrate structure like a semiconductor wafer, a reticle, or a layer on a base substrate structure such as a thin film or a layer overlapping the base substrate structure. Thus, the substrate 100 is not limited to any particular base structure, underlying layer or upper layer, whether patterned or not, but rather may include any such layer or base structure, as well as any combination of layers and / or base structures. The substrate 100 may be a bulk substrate such as a bulk silicon substrate, a silicon-on-insulator substrate, or various other semiconductor substrates.

[0020] The structures 108 each have a respective upper surface 112, and the recesses 110 have a bottom surface 113. In certain embodiments, the structures 108 and the recesses 110 have different heights relative to each other. For example, in certain embodiments, the recess has a height 114 (in the z-direction from the bottom of the base 106 to the bottom surface 113 of the recess 110), and the structure 108 has a second height 116 (in the z-direction from the bottom of the base 106 to the upper surface 112 of the structure 108). In certain embodiments, the difference in height between the structures 108 and the recesses 110 relative to each other can be from 10 nm to 100 nm (e.g., greater than 50 nm). In other embodiments, the difference in height can be greater than 5 microns, for example, in the case of a deep opening / trench. The structures 108 are separated by a gap (e.g., defined by the recesses 110), and the gap can have any suitable width 118 for a given application.

[0021] As shown in FIG. 1B, in step 104b, the filler 120 is deposited on the substrate 100. The filler 120 can be deposited in any suitable manner. For example, the filler 120 can be deposited using spin-on deposition (or spin coating), spray coating, roll coating, chemical vapor deposition (CVD), or any other suitable deposition technique. The filler 120 fills the recess 110 and covers the structure 108. In a subsequent photolithography step, it may be desirable to embed the filler 120 in the recess 110 such that the filler 120 has a specific height within the recess 110 by photolithographic development techniques.

[0022] In certain embodiments, the filler 120 is a resin film such as a polymer resin. The filler 120 may have photo-deprotectable properties and, when deposited, may exhibit resistance to dissolution by a given solvent (which may also be referred to as a developer). However, as described in a later step, after exposure to a specific acid, the filler 120 may experience a change in solubility, and thereafter, the filler 120 (or a portion thereof) is no longer protected from the solvent and dissolves in the solvent. For example, in certain embodiments, the filler 120 is an acid-deprotectable polymer, and a portion of the polymer reacts with a certain species (e.g., an acid) to decompose to convert the solubility of the filler 120 such that the filler 120 dissolves or is washed away when the filler 120 is deprotected in a specific manner. As a specific example, the filler 120 may be a copolymer or terpolymer composed of multiple types of monomers having at least one monomer that is decomposable in the presence of a strong acid to create more polar groups such as carboxylic acid end groups, thereby rendering the filler 120 more soluble in an aqueous medium. As a specific example, the filler 120 may include multiple monomer species including acid-sensitive monomers such as tert-butyl acrylic acid or methyl adamantyl methacrylate.

[0023] In one embodiment, the filler 120 includes a photosensitive material such as a positive-type, negative-type, or hybrid-tone photoresist. In one example, the filler 120 includes a phenolic formaldehyde resin or a diazonaphthoquinone-based resin. In one embodiment, the filler 120 may include a chemically amplified resist. In other embodiments, the filler 120 may include a non-chemically amplified resist material such as polymethyl methacrylate (PMMA) or hydrogen silsesquioxanes (HSQ).

[0024] It may be desirable to remove a portion of the filler 120 including within the recess 110 such that the filler has a predetermined target height 121 within the recess 110. In this example, the target height 121 is shown as being measured from the bottom surface 113 of the recess 110, although the target height of the filler 120 within the recess 110 may be measured from any suitable location such as the bottom of the base 106. The target height 121 may also be considered the target thickness of the filler 120. The filler 120 is initially resistant to development by one or more solvents used to remove a portion of the filler 120 in subsequent processes.

[0025] As shown in FIG. 1C, in step 104c, an overcoat film 122 is deposited on the substrate 100. The overcoat film 122 may be deposited in any suitable manner including spin-on deposition (or spin coating), spray coating, roll coating, CVD, or any other suitable deposition technique. The overcoat film 122 includes a photoactivator generator that generates a solubility modifier in response to actinic radiation to modify the solubility of another material (e.g., the material of the overcoat film 122 and / or the filler 120) to be soluble in one or more solvents used in subsequent removal processes. In one embodiment, the photoactivator generator is a PAG and the solubility modifier is an acid.

[0026] In addition to the photoactivator generator, the overcoat film 122 may or may not contain the same material or a similar material as the filler 120. In certain embodiments, the overcoat film 122 may contain, in addition to the photoactivator generator, a polymer resin having solubility in a solvent similar to the solubility of the deprotected filler 120 in a solvent (to be used later to remove the deprotected portion of the filler 120 within the recess 110), such that the deprotected portion of the filler 120 and the overcoat film 122 can be removed in one step. In certain embodiments, the photoactivator generator of the overcoat film 122 is pre-formulated in the material (e.g., resin) of the overcoat film 122.

[0027] As shown in FIG. 1D, in step 104d, the overcoat film 122 is exposed to actinic radiation 124 for an appropriate period of time. In particular, such that the overcoat film 122 here contains the solubility modifier 126, the overcoat film 122 is exposed to actinic radiation 124 sufficient for the photoactivator generator (e.g., PAG) within the overcoat film 122 to generate the solubility modifier 126 (e.g., an acid) within the overcoat film 122. The solubility modifier 126 solubilizes the overcoat film 122 such that the overcoat film 122 is soluble in one or more solvents used in subsequent removal processes here.

[0028] The actinic radiation 124 may include light of an appropriate wavelength having other appropriate characteristics for activating a photoactivator generator (e.g., PAG) within the overcoat film 122 such that the photoactivator generator within the overcoat film 122 generates a solubility modifier 126 (e.g., an acid) within the overcoat film 122. The characteristics of the actinic radiation 124 that can affect whether (and the amount by which) the photoactivator generator within the overcoat film 122 is activated to generate the solubility modifier 126 within the overcoat film 122 include the content of the overcoat film 122, the type of photoactivator generator, the wavelength of the actinic radiation 124, the period during which the overcoat film 122 is exposed to the actinic radiation 124, and other appropriate factors.

[0029] A predetermined photoactivator generator (e.g., PAG) is sensitive to a predetermined wavelength or a predetermined wavelength range, enabling the use of various exposure light sources. As just one example, the wavelength of actinic ray 124 may be in the range of about 170 nm to about 405 nm, and the exposure time may be from about 10 seconds to about 1 minute (for the wafer, the portions shown in FIGS. 1A - 1J are part of it). The polymer of the filler and the overcoat film 122 may be transparent or substantially transparent to a predetermined wavelength.

[0030] However, it should be understood that the values and actinic ray sources are provided as merely examples. In one embodiment, as will be described later with reference to FIGS. 4B and 4F, the substrate 100 is part of a larger substrate, and the actinic ray 124 is part of a larger pattern of actinic rays directed at an overcoat film (of which the overcoat film 122 is part) on the larger substrate. Exposure to actinic rays (e.g., light) can be performed, as just a few examples, using mask - based exposure, or by a direct - write exposure step or flood exposure. Physical lithographic exposure steppers or scanners can be used as well. In another example, a relatively simple scanning laser system that can spatially vary the exposure energy across the surface of the wafer may be used. The specific wavelength of the actinic ray 124 and the exposure time to the actinic ray 124 appropriate for a given embodiment can be affected by the tool used, including the laser intensity.

[0031] As shown in FIG. 1E, in step 104e, a solubility modifier 126 is diffused into the filler 120 to modify at least a part of the filler 120 so that it is soluble in a solvent used in a subsequent removal process, making a part (deprotected portion 120a) of the filler 120 soluble in the solvent used in the subsequent removal process. The deprotected portion 120a is generally shown as the portion of the filler 120 into which the solubility modifier 126 has diffused. The diffusion of the solubility modifier 126 into the filler 120 results in a solubility modification reaction within the filler 120 to a depth (e.g., a predetermined depth) into which the solubility modifier 126 diffuses into the filler 120, resulting in the deprotected portion 120a. The deprotected portion 120a of the filler 120 then becomes soluble in one or more specific solvents, which may also be referred to as developers. The deprotection reaction (resulting in the generation of the deprotected portion 120a) resulting from the diffusion of the solubility modifier 126 into a part of the filler 120 may be a depolymerization reaction within a part of the filler 120. A similar reaction may occur within the overcoat film 122 to solubilize the overcoat film 122.

[0032] The solubility modifier 126 can be diffused into the filler 120 using any suitable process. In one embodiment, a thermal process (e.g., heat 127) is used to diffuse the solubility modifier 126 into at least a part of the filler 120. For example, the substrate 100 may be baked to apply the heat 127, and the solubility modifier 126 diffuses into at least a part of the filler 120 due to the heat associated with baking the substrate 100. The substrate 100 can be baked by a substrate plate of a suitable tool, by the ambient heat in a substrate processing chamber of a suitable tool, by a combination of these, or in any other suitable manner.

[0033] In one embodiment, the solubility modifier 126 diffuses to a predetermined depth of the filler 120 to modify the solubility of the filler 120 to the predetermined depth. The predetermined depth may or may not be sufficient to reach the target height 121 of the filler 120 within the recess 110. In the illustrated example, the predetermined depth of step 104e is insufficient to embed the filler 120 to the target height 121 of the filler 120 within the recess 110.

[0034] The depth to which the solubility modifier 126 diffuses into the filler 120 is the content of the overcoat film 122 (including the type of photoactivator generator in the overcoat film 122, other components of the overcoat film 122, and the concentration of the photoactivator generator in the overcoat film 122), the characteristics of the actinic ray 124 (for example, those used in step 104d or later steps), the content of the filler 120, the width 118 with respect to the difference between the heights 116 and 114 (which may also be referred to as the aspect ratio of the recess 110, and in particular, when the filler 120 is embedded in the recess 110 at a later step, it can affect the ability of the actinic ray 124 to activate the photoactivator generator to generate the solubility modifier 126), the exposure amount of the actinic ray 124, the heating (for example, baking) time and temperature, and can be affected by various factors including any of a variety of other factors, and / or can be controlled using a variety of factors.

[0035] As shown in FIG. 1F, in step 104f, the overcoat film 122 and the deprotected portion 120a of the filler 120 are removed. In one embodiment, the overcoat film 122 and the deprotected portion 120a of the filler 120 are developed using a solvent 128, and the overcoat film 122 and the deprotected portion 120a of the filler 120 are removed from the substrate 100.

[0036] The present disclosure contemplates a solvent 128 that includes any suitable substance for removing the overcoat film 122 and the deprotected portion 120a of the filler 120. As just one example, the solvent 128 may include an aqueous solution of tetramethylammonium hydroxide that is capable of solubilizing an acid deprotected resin (for example, the deprotected portion 120a of the filler 120). The solvent 128 may also be referred to as a developer.

[0037] By removing the overcoat film 122 and the deprotected portion 120a of the filler 120, a change in the height of the filler 120 in the recess 110 corresponding to the exposure amount (for example, the depth of diffusion of the solubility modifier 126 into the filler 120 or the depth of the deprotected portion 120a of the filler 120) occurs.

[0038] This process of depositing the overcoat film 122 (step 104c), exposing to actinic rays 124 (step 104d), diffusing by baking for a certain period (step 104e), and developing the deprotected portion of the filler 120 (step 104f) can be repeated until the cumulative depth of deprotection and development (removal) of the filler 120 reaches the target height 121 so that the remaining filler 120 in the recess 110 becomes approximately the target height 121. For example, FIGS. 1G to 1J show the second iteration of this cyclic process, which is sufficient to achieve the target height 121 of the filler 120 in the recess 110 in this embodiment.

[0039] In particular, FIG. 1G shows step 104g in which the overcoat film 122 is deposited again on the substrate 100. The overcoat film 122 contains a photoactivator generator (for example, PAG) that reacts with actinic rays to generate a solubility modifier (for example, an acid) in order to change the solubility of the overcoat film 122 and / or the material of the filler 120 so that it can be dissolved in one or more solvents used in subsequent removal processes.

[0040] FIG. 1H shows step 104h in which the overcoat film 122 is exposed to actinic rays 124, and the photoactivator generator in the overcoat film 122 generates the solubility modifier 126 in the overcoat film 122 so that the overcoat film 122 contains the solubility modifier 126 here and solubilizes the overcoat film 122 (makes it soluble in one or more solvents used in subsequent removal processes).

[0041] FIG. 1I shows stage 104i where the solubility modifier 126 diffuses into the filler 120 to solubilize a further portion of the filler 120 (deprotected portion 120b) in a solvent (e.g., solvent 128). The deprotected portion 120b is generally shown as the portion of the filler 120 into which the solubility modifier 126 has diffused. As described above, the solubility modifier 126 can be diffused into the filler 120 using a thermal process (e.g., baking of the substrate 100). In certain embodiments, the solubility modifier 126 is diffused to a predetermined depth within the filler 120 to modify the solubility of the filler 120 to the predetermined depth. In this example, the predetermined depth is sufficient to deprotect the filler 120 to the target height 121.

[0042] FIG. 1J shows stage 104j where the overcoat film 122 and the deprotected portion 120b of the filler 120 have been removed. In certain embodiments, the overcoat film 122 and the deprotected portion 120a of the filler 120 are developed using the solvent 128 such that the overcoat film 122 and the deprotected portion 120a of the filler 120 are removed from the substrate 100. In this example, removal of the overcoat film 122 and the deprotected portion 120b of the filler 120 results in a change in the height of the filler 120 within the recess 110 such that the remaining filler 120 within the recess 110 is substantially at the target height 121.

[0043] In the illustrated embodiment, two repetitions of the circulation process are sufficient to achieve the target height 121 of the filler 120 within the recess 110. However, the present disclosure contemplates any suitable number of repetitions sufficient to reach the target height 121 for a given application. For example, more than two repetitions may be suitable to remove sufficient filler 120 to reach the target height 121 of the filler within the recess 110. In another embodiment, a single repetition (e.g., of steps 104b - 104f) may be suitable to remove sufficient filler 120 to reach the target height 121 of the filler within the recess 110. Further, the predetermined depth of diffusion of the solubility modifier 126 into the filler 120 and subsequent removal of the deprotected portion of the filler 120 may be the same from one repetition to the next (and potentially over all repetitions) according to specific needs, or may vary from one repetition to the next (and potentially over all repetitions).

[0044] Subsequent processing can then be performed on the semiconductor substrate 100. For example, process 102 may be integrated into a process for forming semiconductor devices using various deposition and etching processes.

[0045] Figures 2A - 2I show cross-sectional and plan views of the substrate 100 during a process 202 as an example for processing the substrate 100 according to an embodiment. In particular, process 202 includes one or more repetitions of the use of a PAG-based process (e.g., process 102) for positional deprotection of a portion of the filler 120, and one or more subsequent repetitions of a TAG-based process for deprotection of a portion of the filler 120.

[0046] Figures 2A-2F generally correspond to Figures 1A-1F, and the details described above with respect to non-repeated Figures 1A-1F are incorporated by reference. Generally, Figures 2A-2F show the repetition of receiving the substrate 100 (step 204a), depositing the filler 120 on the substrate 100 (the filler 120 fills the recess 110, covers the structure 108, and the filler 120 is initially resistant to development by the solvent 128) (step 204b), depositing an overcoat film 122 (including a photoactivator generator (e.g., PAG) that reacts with the actinic ray 124 to generate a solubility modifier 126 (e.g., an acid)) on the substrate 100 (step 204c), exposing the overcoat film 122 to the actinic ray 124 to generate the solubility modifier 126 in the overcoat film 122 (step 204d), diffusing the solubility modifier 126 to a predetermined depth within the filler 120 (e.g., by exposing the substrate 100 to heat) to make a part of the filler 120 (e.g., the deprotected portion 120a) soluble in the solvent 128 (step 204e), and developing the overcoat film 122 and the deprotected portion 120a of the filler 120 using the solvent 128 to remove the overcoat film 122 and the deprotected portion 120a of the filler 120 from the substrate 100 (step 204f). That is, Figures 2A-2F show the repetition of a PAG-based process for removing a part of the filler 120 within the recess 110.

[0047] Figures 2G to 2I illustrate a TAG-based process, which can be performed one or more times to remove additional portions of the filler 120 within the recess 110 until the target height 121 is reached. As shown in Figure 2G, at step 204g, an overcoat film 222 is deposited on the substrate 100. The overcoat film 222 can be deposited in any suitable manner, including spin-on deposition (or spin coating), spray coating, roll coating, CVD, or any other suitable deposition technique. The overcoat film 222 includes a thermal activator generator that generates a solubility modifier by reacting with heat to make the solubility of another material (e.g., the material of the overcoat film 222 and / or the filler 120) soluble in one or more solvents used in subsequent removal processes. In certain embodiments, the thermal activator generator is a TAG and the solubility modifier is an acid.

[0048] In addition to the thermal activator generator, the overcoat film 222 may or may not include the same or a similar material as the filler 120. In certain embodiments, the overcoat film 222 may include a polymer resin that, in addition to a photoactivator generator, has a solubility in a solvent similar to the solubility of the deprotected filler 120 in a solvent (to be used subsequently to remove the deprotected portion of the filler 120), such that the deprotected portion of the filler 120 and the overcoat film 222 can be removed in one step. In certain embodiments, the thermal activator generator of the overcoat film 222 is pre-formulated in the resin of the overcoat film 222.

[0049] As shown in FIG. 2H, in step 204h, the overcoat film 222 is exposed to heat 127 for a suitable period of time. In particular, such that the overcoat film 222 here contains the solubility modifier 226, the overcoat film 222 is exposed to heat 127 sufficient for a heat-activated agent generator (e.g., TAG) within the overcoat film 222 to generate the solubility modifier 226 (e.g., an acid) within the overcoat film 222. The solubility modifier 226 solubilizes the overcoat film 222 such that the overcoat film 222 is soluble in one or more solvents used in subsequent removal processes here. In certain embodiments, a thermal process (e.g., heat 127) is used to activate the heat-activated agent generator within the overcoat film 222. For example, the substrate 100 may be baked to apply heat 127, and the heat associated with baking the substrate 100 causes the heat-activated agent generator to generate the solubility modifier 226 within the overcoat film 222. The substrate 100 can be baked by an appropriate tool's substrate plate, by the ambient heat in an appropriate tool's substrate processing chamber, by a combination of these, or by any other appropriate method.

[0050] Continuing with step 204h of FIG. 2H, in addition to the heat activator generator in the overcoat film 222 generating the solubility modifier 226 within the overcoat film 222, the thermal process (e.g., heating) applied to the substrate 100 also diffuses the solubility modifier 226 to a predetermined depth within the filler 120. By the diffusion of the solubility modifier 226 into the filler 120, at least a portion (the deprotected portion 220a) of the filler 120 is modified to be soluble in the solvent used in a subsequent removal process. The deprotected portion 220a is generally shown as the portion of the filler 120 into which the solubility modifier 226 has diffused. The diffusion of the solubility modifier 226 into the filler 120 results in a solubility modification reaction within the filler 120 to the depth (e.g., a predetermined depth) to which the solubility modifier 226 diffuses into the filler 120, resulting in the deprotected portion 220a. The deprotected portion 220a of the filler 120 then becomes soluble in one or more specific solvents, which may also be referred to as developers. The deprotection reaction (resulting in the generation of the deprotected portion 220a) resulting from the diffusion of the solubility modifier 226 into a portion of the filler 120 may be a crosslink cleavage reaction within a portion of the filler 120. A similar reaction may occur within the overcoat film 222 to solubilize the overcoat film 222.

[0051] In certain embodiments, the solubility modifier 226 is diffused to a predetermined depth within the filler 120 to modify the solubility of the filler 120 to that depth. The predetermined depth may or may not be sufficient to reach the target height 121 for the filler 120 within the recess 110. In the illustrated example, the predetermined depth of step 204h is insufficient to fill the filler 120 up to the target height 121 of the filler 120 within the recess 110. In embodiments where the predetermined depth of step 204h is insufficient to fill the film material 120 up to the target height 121 of the filler 120 within the recess 110, one or more additional iterations of steps 204g - 204i may be performed.

[0052] The depth to which the solubility modifier 226 diffuses into the filler 120 is affected by and / or can be controlled using various factors, including any of the contents of the overcoat film 222 (including the type of heat-activated agent generator in the overcoat film 222, other components of the overcoat film 222, and the concentration of the heat-activated agent generator in the overcoat film 222), the temperature of the heat 127, the length of time the substrate 100 is exposed to the heat 127 (e.g., the baking period), the contents of the filler 120, and various other factors.

[0053] In certain embodiments, as described below with reference to FIGS. 5A-5C, the substrate 100 is part of a larger substrate and the heat 127 is applied across multiple (and potentially all) portions of the larger substrate. Exposure to the heat 127 can result in a substantially uniform amount of the solubility modifier 226 being generated within the overcoat film 222. Further, exposure to the heat 127 can result in a substantially uniform depth of diffusion of the solubility modifier 226 into the filler 120.

[0054] As shown in FIG. 2I, in step 204i, the unprotected portions 220a of the overcoat film 222 and the filler 120 have been removed. In certain embodiments, the unprotected portions 220a of the overcoat film 222 and the filler 120 are developed using a solvent 228 such that the unprotected portions 220a of the overcoat film 222 and the filler 120 are removed from the substrate 100.

[0055] The present disclosure contemplates a solvent 228 that includes any suitable material for removing the unprotected portions 220a of the overcoat film 222 and the filler 120. As just one example, the solvent 228 can include an aqueous solution of tetramethylammonium hydroxide that is capable of solubilizing an acid-deprotecting resin (e.g., the unprotected portion 220a of the filler 120). In certain embodiments, it may be possible to use an organic solvent as the solvent 228 if the resin (e.g., the filler 120) is designed to interact with a solubility modifier other than an acid generator. The solvent 228 may or may not be the same as the solvent 128. The solvent 228 may also be referred to as a developer.

[0056] By removing the overcoat film 222 and the deprotected portion 220a of the filler 120, a change occurs in the height of the filler 120 within the recess 110 corresponding to the exposure amount (for example, the depth of diffusion of the solubility modifier 226 into the filler 120, or the depth of the deprotected portion 220a of the filler 120). In this embodiment, a change in the height of the filler 120 within the recess 110 occurs by removing the overcoat film 122 and the deprotected portion 120b such that the remaining filler 120 within the recess 110 is substantially at the target height 121.

[0057] This process of depositing the overcoat film 222 (step 204g), heating the substrate 100 (step 204h), and subsequent development of the deprotected portion 120a of the filler 120 (step 204i) is repeated until the cumulative depth of deprotection and development of the filler 120 reaches the target height 121. For example, FIGS. 2G - 2I illustrate the first iteration of this cycle TAG - based process, which in this embodiment is sufficient to achieve the target height 121 of the filler 120 within the recess 110. In other embodiments, additional iterations of the TAG - based process may be used to remove sufficient filler 120 to reach the target height 121 of the filler within the recess 110.

[0058] In the illustrated embodiment of FIGS. 2A - 2I, a single iteration (PAG - based process) using a photo - activatable solubility modifier generating component is illustrated and described. However, the present disclosure contemplates a process 202 that includes multiple iterations of the use of a photo - activatable solubility modifier generating component prior to one or more iterations of the use of a thermo - activatable agent generating agent (TAG - based process) to achieve the target height 121 of the filler 120 within the recess 110 according to specific needs. Further, regardless of whether a PAG - based process or a TAG - based process is considered, the predetermined depth of diffusion of the solubility modifier 126 / 226 into the filler 120 and subsequent removal of the deprotected portion of the filler 120 may be the same from one iteration to the next (and potentially over all iterations) according to specific needs, or may vary from one iteration to the next (and potentially over all iterations).

[0059] Subsequent processing can then be performed on the semiconductor substrate 100. For example, process 202 may be integrated into a process for forming semiconductor devices using various deposition and etching processes.

[0060] FIG. 3 shows, as an example of the change in the depth of the change in the diffusion of the solubility modifier 126 / 226 within the filler 120, the effect according to an embodiment. Generally, FIG. 3 shows that, according to an embodiment, as the depth of the diffusion of the solubility modifier 126 / 226 (e.g., an acid) into the filler 120 increases, the amount of the filler 120 removed during a subsequent development process increases, thereby reducing the height of the filler 120 after development within the recess 110. The portion of the filler 120 into which the solubility modifier 126 / 226 (e.g., an acid) has diffused becomes soluble in the solvent 128 / 228, such that when the filler 120 is developed using the solvent 128 / 228, the solvent 128 / 228 can remove those portions of the filler 120. The exemplary embodiment controls the film height by position through the diffusion of an acid into an acid-soluble-modifiable resin layer, where a greater degree of acid diffusion results in a greater change in film thickness per overcoat cycle. Thus, by controlling the depth of the diffusion of the solubility modifier 126 / 226 into the filler 120, the amount of the filler 120 removed (e.g., the deprotected portions 120a / 120b / 220a) in a subsequent removal process can be controlled. The factors that potentially affect the depth of diffusion have been described above.

[0061] Figures 4A - 4H show cross - sectional views of substrate portions 400a - 400d, having pre - patterned features, during process 102 (described above with reference to FIGS. 1A - 1J) as an example for processing substrate portions 400a - 400d according to an embodiment. For ease of reference, substrate portions 400a - 400d may be referred to collectively as substrate 400. Substrate portions 400a - 400d may be part of the same substrate 400 or part of different substrates 400. Substrate 400 may be part of a larger semiconductor device, such as part of a larger semiconductor wafer. Further, substrate portions 400a - 400d may be part of the same semiconductor wafer or one or more different semiconductor wafers. In one embodiment, process 102 includes repeatedly performing a PAG - based process to remove the fill material from recesses 110 of substrate 400 until the fill material reaches a predetermined height within recesses 110. To the extent not repeated, details regarding substrate 100 and process 102 described with reference to FIGS. 1A - 1J (or elsewhere) are incorporated by reference.

[0062] As shown in FIG. 4A, in addition to base 106, substrate 400 includes a plurality of structures 108 that define a plurality of recesses 110. Structures 108 are shown to generally have the same shape, height, and pitch, but structures 108 may have any suitable shape, height, and / or pitch, including varying shapes, heights, and / or pitches. Additionally, recesses 110 are shown to generally have the same shape and depth, but recesses 110 may have any suitable shape and / or depth, including varying shapes and / or depths. The present disclosure contemplates structures 108 patterned with any suitable features.

[0063] As shown in FIG. 4A (corresponding to stage 104c), the filler 120 is deposited on the substrate 400. The filler 120 fills the recess 110 and covers the structure 108, and the overcoat film 122 is deposited on the substrate 400. In subsequent photolithography steps, it may be desirable to embed the filler 120 into the recess 110 by photolithographic development techniques so that the filler 120 has a specific height within the recess 110. The target height 121 for embedding the filler 120 into the recess 110 is indicated for each recess 110. In this embodiment, different target heights 121 are desired for each recess 110, and for the recess 110 at the right end of FIG. 4A, little or no embedding of the filler 120 is desired. However, the present disclosure contemplates that the same target height 121 may be desired for two or more (and potentially all) of the recesses 110.

[0064] As described above, the overcoat film 122 includes a photoactivator generator (e.g., PAG) that reacts to the actinic ray 124 to generate a solubility modifier 126 (e.g., an acid) in order to modify the overcoat film 122 so that the overcoat film 122 and / or the filler 120 is soluble in one or more solvents (e.g., solvent 128) used in subsequent removal processes.

[0065] As shown in FIG. 4B (corresponding to stage 104d), the overcoat film 122 is exposed to sufficient actinic rays 124 for a sufficient period of time so that the overcoat film 122 now contains the solubility modifier 126, such that the photoactivator generator (e.g., PAG) within the overcoat film 122 generates the solubility modifier 126 (e.g., an acid) within the overcoat film 122, if desired. In the embodiment of FIG. 4B, the actinic ray 124 is a patterned actinic ray directed at the overcoat film 122.

[0066] As described above, the characteristics of the actinic ray 124 affect the amount of photoactivator generator in the overcoat film 122 that is activated. That is, the actinic ray 124 having certain characteristics activates a greater amount of photoactivator generator in the overcoat film 122, resulting in a greater amount of solubility modifier 126 being generated in those regions of the overcoat film 122. The actinic ray 124 having certain other characteristics activates a smaller amount of photoactivator generator in the overcoat film 122, resulting in a smaller amount of solubility modifier 126 being generated in those regions of the overcoat film 122. The amount of solubility modifier 126 in a particular region of the overcoat film 122 affects how much of the solubility modifier 126 is available for diffusion into the filler 120 in a subsequent heating step.

[0067] Accordingly, in the overcoat film 122 over the regions of the filler 120 where greater depth of diffusion of the solubility modifier 126 and ultimate removal of the filler are desired, the pattern of the actinic ray 124 can be adapted to activate a greater amount of photoactivator generator, and in the overcoat film 122 over the regions of the filler 120 where smaller depth of diffusion of the solubility modifier 126 and ultimate removal of the filler are desired, the pattern of the actinic ray 124 can be adapted to activate a smaller amount of photoactivator generator. Although the use of the pattern of the actinic ray 124 to vary the depth of diffusion of the solubility modifier 126 and ultimate removal of the filler 120 has been described, when the target heights 121 for the filler 120 in the recesses 110 under one or more portions of the overcoat film 122 are substantially equal, for example, the pattern of the actinic ray 124 can be designed such that the photoactivator generator in the overcoat film 122 generates substantially equal amounts of the solubility modifier 126 in one or more portions of the overcoat film 122.

[0068] In the embodiment shown in FIG. 4B, the pattern of the actinic ray 124 is designed such that the photoactivator generator in the overcoat film 122 generates an amount of the solubility modifier 126 that decreases from the overcoat film 122 on the substrate portion 400a (the left side in FIG. 4A) to the overcoat film 122 on the substrate portion 400d (the right side in FIG. 4A). (Since no actinic ray 124 is applied on the substrate portion 400d,) little or no solubility modifier 126 is generated on the recess 110 of the substrate portion 400d. In certain embodiments, the ability to control the activation and subsequent diffusion of the photoactivator generator in the overcoat film 122 (e.g., by adjusting the exposure amount of the actinic ray 124) may be affected by the resolution limit of the exposure tool.

[0069] As shown in FIG. 4C (corresponding to step 104e), in order to modify at least a part of the filler 120 to be soluble in the solvent 128, the solubility modifier 126 is diffused into the filler 120 to make a part of the filler 120 (the deprotected portion 420a) soluble in the solvent 128. The deprotected portion 420a is generally shown as the portion of the filler 120 into which the solubility modifier 126 has diffused. In certain embodiments, the solubility modifier 126 is diffused into at least a part of the filler 120 (to generate the deprotected portion 420a) using a thermal process (e.g., application of heat 127 for a suitable period). In the embodiment shown in FIG. 4C, the solubility modifier 126 is diffused into the recess 110 at a varying predetermined depth. Additionally, the predetermined depth in this embodiment is insufficient to fill the filler 120 up to the target height 121 of the filler 120 within the recess 110.

[0070] As shown in FIG. 4D (corresponding to step 104f), the deprotected portions 420a of the overcoat film 122 and the filler 120 are removed. In certain embodiments, the deprotected portions 420a of the overcoat film 122 and the filler 120 are developed using a solvent 128 such that the deprotected portions 420a of the overcoat film 122 and the filler 120 are removed from the substrate 400. Removal of the deprotected portions 420a of the overcoat film 122 and the filler 120 results in a change in the height of the filler 120 within the recess 110 corresponding to the exposure amount (e.g., the depth of diffusion of the solubility modifier 126 into the filler 120, or the depth of the deprotected portion 420a of the filler 120).

[0071] This process of deposition of the overcoat film 122, exposure to the actinic radiation 124, diffusion by baking for a certain period of time, and subsequent development of the deprotected portion 120a of the filler 120 is repeated until the cumulative depth of deprotection and development of the filler 120 within each recess 110 reaches the corresponding target height 121. For example, FIGS. 4E-4H illustrate a second iteration of this cyclic process, which in this example is sufficient to achieve the target height 121 of the filler 120 within the recess 110. In certain embodiments, additional or fewer iterations may be appropriate to remove sufficient filler 120 to reach the target height 121 of the filler within the recess 110. Further, the predetermined depth of diffusion of the solubility modifier 126 into the filler 120 and subsequent removal of the deprotected portion of the filler 120 may be the same from one iteration to the next (and potentially over all iterations) or may vary from one iteration to the next (and potentially over all iterations) according to specific needs.

[0072] In particular, as shown in FIG. 4E (corresponding to step 104g), the overcoat film 122 is deposited again on the substrate 400. The overcoat film 122 contains a photoactivator generator (e.g., PAG) that reacts with the actinic radiation 124 to generate a solubility modifier 126 (e.g., an acid) to change the solubility of the material of the overcoat film 122 and / or the filler 120 again to be soluble in the solvent 128.

[0073] (Corresponding to step 104h) As shown in FIG. 4F, the overcoat film 122 is exposed to actinic rays 124 of a certain pattern, and a photoactivator generator in the overcoat film 122 generates a solubility modifier 126 in the overcoat film 122 so that the overcoat film 122 contains the solubility modifier 126 here, solubilizing (making soluble in the solvent 128) the overcoat film 122. It should be understood that the pattern of the actinic rays 124 used in FIG. 4F may or may not be the same as the pattern of the actinic rays 124 used in FIG. 4B, depending on the desired predetermined depth of diffusion of the solubility modifier 126 into the filler 120 in subsequent processing steps.

[0074] (Corresponding to step 104i) As shown in FIG. 4G, the solubility modifier 126 diffuses into the filler 120, making a further portion of the filler 120 (the deprotected portion 420b) soluble in the solvent 128. The deprotected portion 420b is generally shown as the portion of the filler 120 into which the solubility modifier 126 has diffused. As described above, the solubility modifier 126 can be diffused into the filler 120 using a thermal process (e.g., baking of the substrate 400). In certain embodiments, the solubility modifier 126 is diffused to a predetermined depth within the filler 120 to modify the solubility of the filler 120 to that predetermined depth, which in this example is sufficient to deprotect the filler 120 up to the target height 121 of the recess 110.

[0075] (Corresponding to step 104j) As shown in FIG. 4H, the overcoat film 122 and the deprotected portion 420a of the filler 120 have been removed. In certain embodiments, the overcoat film 122 and the deprotected portion 420a of the filler 120 are developed using the solvent 128, and the deprotected portion 420a of the overcoat film 122 and the filler 120 is removed from the substrate 400. In this example, removal of the deprotected portion 120b of the overcoat film 122 and the filler 120 causes a change in the height of the filler 120 within the recess 110 such that the remaining filler 120 within the recess 110 is substantially at the target height 121.

[0076] Subsequent processing can then be performed on semiconductor substrate 400. For example, process 102 may be integrated into a process for forming semiconductor devices using various deposition and etching processes.

[0077] Process 102 can provide one or more technical advantages. For example, removing the filler 120 by generating a solubility modifier 126 generated from a photoactivator in the overcoat film 122 to create a deprotected portion of the filler 120 can provide a precise method for changing the height of the filler 120. As another example, the ability to direct a pattern of actinic radiation 124 towards the overcoat film 122 enables the filler 120 to be removed at different precise depths within one or more of the recesses 110 and ultimately reach different target heights 121.

[0078] Figures 5A - 5C show cross - sectional views of substrate portions 400a - 400d having pre - patterned features during a portion of process 202 (described above with reference to FIGS. 2A - 1I) as an example for processing substrate portions 400a - 400d according to an embodiment. In one embodiment, process 202 includes one or more iterations of performing a PAG - based process to establish a potentially varying height of the filler 120 (by removing the filler 120 to varying depths of the recesses 110) on various substrate portions 400a - 400d, and one or more subsequent iterations of performing a TAG - based process to potentially uniformly remove a portion of the filler 120 on various substrate portions 400a - 400d. To the extent not repeated, details regarding the substrate 100, process 202, and substrate portions 400a - 400d / substrate 400 described with reference to FIGS. 2A - 2I and / or FIGS. 4A - 4H (or elsewhere) are incorporated by reference.

[0079] Figure 5A begins not at the beginning of stage 202a of process 202, but in a step similar to stage 204g of Figure 2G. That is, Figure 5A shows the substrate 400 after at least one iteration of the PAG-based process to remove a portion of the filler 120 to a varying predetermined depth within the recess 110 and set different relative heights of the remaining filler 120 within the recess 110. For example, immediately prior to the state of the substrate 400 shown in Figure 5A, the substrate 400 may be in a state corresponding to Figure 4D. Figures 5A - 5C show a TAG-based process, which may be performed one or more times to remove additional portions of the filler 120 within the recess 110 until the target height 121 is reached.

[0080] As shown in Figure 5A (corresponding to stage 204g), an overcoat film 222 is deposited on the substrate 400. The overcoat film 222 contains a thermal activator generator (e.g., TAG) that reacts to heat to generate a solubility modifier 226 (e.g., an acid) to modify the solubility of another material (e.g., the material of the overcoat film 222 and / or the filler 120) to be soluble in a solvent 228 used in a subsequent removal process.

[0081] As shown in Figure 5B (corresponding to stage 204h), the overcoat film 222 is exposed to sufficient heat 127 for a sufficient period such that the overcoat film 222 now contains the solubility modifier 226, and the thermal activator generator (e.g., TAG) within the overcoat film 222 generates the solubility modifier 226 (e.g., an acid) within the overcoat film 222. By a thermal process (e.g., heating) applied to the substrate 400, the solubility modifier 226 also diffuses to a predetermined depth within the filler 120. By the diffusion of the solubility modifier 226 into the filler 120, at least a portion (deprotected portion 520a) of the filler 120 is modified to be soluble in the solvent 228. The deprotected portion 520a is generally shown as the portion of the filler 120 into which the solubility modifier 226 has diffused.

[0082] In one embodiment, the solubility modifier 226 diffuses to a predetermined depth within the filler 120 to modify the solubility of the filler 120 to the predetermined depth. The predetermined depth may or may not be sufficient to reach the target height 121 of the filler 120 within the recess 110. In the illustrated example, the predetermined depth is insufficient to embed the filler 120 up to the target height 121 of the filler 120 within the recess 110. In embodiments where the predetermined depth is insufficient to embed the membrane material 120 up to the target height 121 within the recess 110, one or more additional iterations of the process shown in FIGS. 5A - 5C may be performed.

[0083] In one embodiment, heat 127 is applied across the substrate 400, and exposure to the heat 127 can cause a substantially uniform amount of the solubility modifier 226 to be generated within the overcoat film 222. Further, exposure to the heat 127 can cause a substantially uniform depth diffusion of the solubility modifier 226 into the filler 120.

[0084] As shown in FIG. 5C (corresponding to step 204i), the overcoat film 222 and the deprotected portion 420a of the filler 120 are removed. In one embodiment, the overcoat film 222 and the deprotected portion 420a of the filler 120 are developed using a solvent 228, and the deprotected portion 420a of the overcoat film 222 and the filler 120 is removed from the substrate 400. In this example, removal of the overcoat film 122 and the deprotected portion 120b of the filler 120 causes a change in the height of the filler 120 within the recess 110 such that the remaining filler 120 within the recess 110 is substantially at the target height 121.

[0085] This process of depositing the overcoat film 222, heating the substrate 400, and subsequent development of the deprotected portion 520a of the filler 120 is repeated until the cumulative depth of deprotection and development of the filler 120 within the recess 110 reaches the corresponding target height 121. For example, FIGS. 5A-5C illustrate the first iteration of this cyclic process, which in this embodiment is sufficient to achieve the target height 121 of the filler 120 within the recess 110. In certain embodiments, additional or fewer iterations may be appropriate to remove sufficient filler 120 to reach the target height 121 of the filler within the recess 110. Further, the predetermined depth of diffusion of the solubility modifier 226 into the filler 120 and subsequent removal of the deprotected portion of the filler 120 may be the same from one iteration to the next (potentially over all iterations) or may vary from one iteration to the next (potentially over all iterations) according to specific needs.

[0086] Subsequent processing can then be performed on the semiconductor substrate 400. For example, process 202 may be integrated into a process for forming semiconductor devices using various deposition and etching processes.

[0087] Process 202 may provide one or more technical advantages, which may be in addition to the advantages described above with reference to Process 102. In certain embodiments, the recess 110 has a high aspect ratio (e.g., the difference between the height 116 and the height 114 is significantly greater than the width 118), which may prevent the wavelength of light (actinic radiation 124) suitable for activating the photoacid generator in the overcoat film 122 from reaching the photoacid generator in the overcoat film 122 for activation. Generally, in a PAG-based process, difficulties may begin to arise in activating the PAG in the overcoat film 122 when the lateral dimension of a feature (e.g., the recess 110) is much shorter than the wavelength of the radiation having an effect. The greater the aspect ratio of the feature (e.g., the recess 110), and thus the greater the depth at which the photons of the actinic radiation 124 interact with the overcoat film 122, the lower the efficiency of photon interaction within the feature at a given dimension smaller than the incident wavelength of the actinic radiation 124. By way of just one example, the width 118 of the gap between the structures 108 may be about 20 nm, and the depth of the recess 110 may be about five times or more that. The thermal acid generator in the overcoat film 222 is activated by heat 127 rather than actinic radiation 124, and in response to sufficient heat, generates a substantially uniform amount of solubility modifier 226 without relying on a specific wavelength of light.

[0088] In Process 202, one or more iterations of the PAG-based process may be performed to establish a relative difference in the target height 121 within the recess 110 based on the position of the recess 110, but one or more subsequent iterations of the TAG-based process may be performed to continue to substantially uniformly embed the filler 120 within the recess 110 until the target height 121 is reached while maintaining the relative difference in the target height 121 established using one or more iterations of the PAG-based process. Further, the TAG-based process is particularly efficient because the solubility modifier 226 diffuses to a predetermined depth within the filler 120 by the thermal process used to activate the thermal acid generator to produce the solubility modifier 226 and without using a separate step (and potentially a separate tool) for exposure to the actinic radiation 124.

[0089] FIG. 6 shows a method, as an example, for processing a semiconductor substrate according to an embodiment. Generally, the method described with reference to FIG. 6 corresponds to process 102 described above with reference to FIGS. 1A-1J and FIGS. 4A-4H.

[0090] In step 600, a substrate 100 / 400 having a microfabrication structure 108 that defines a recess 110 is received. In step 602, a filler 120 is deposited on the substrate 100 / 400 to fill the recess 110 and cover the microfabrication structure 108. The filler 120 may be a resin and is initially resistant to development by a solvent 128. In step 604, an overcoat film 122 is deposited on the substrate 100 / 400. The overcoat film 122 includes a photoactivator generator (e.g., PAG) that reacts to actinic radiation to generate a solubility modifier 126 (e.g., an acid).

[0091] In step 606, the overcoat film 122 is exposed to actinic radiation 124 sufficient for the photoactivator generator within the overcoat film 122 to generate the solubility modifier 126 within the overcoat film 122. The actinic radiation 124 may be a patterned actinic radiation 124 directed towards the substrate 100 / 400 and may be designed to achieve variations at a predetermined depth (and final remaining height) of removal of the filler 120 within the recess 110. In step 608, the solubility modifier 126 is diffused to a predetermined depth within the filler 120 to make the deprotected portion 120a / 420a of the filler 120 soluble in the solvent 128. This may include a plurality of different predetermined depths across the substrate 100 / 400. In one embodiment, the substrate 100 / 400 is baked (or heated) to diffuse the solubility modifier 126 to a predetermined depth within the filler 120. In step 610, the overcoat film 122 and the deprotected portion 120a / 420a of the filler 120 are developed using the solvent 128.

[0092] In step 612, a determination is made as to whether a predetermined condition is satisfied. Generally, in step 612, a determination is made as to whether the target height 121 of the filling material 120 in the recess 110 is achieved. For example, the predetermined condition may include determining whether a predetermined number of cycles of steps 604 to 610 have been executed, and the predetermined number of cycles is pre-determined to be sufficient to achieve the target height 121 of the filling material 120 in the recess 110. As another example, the predetermined condition may include a real-time analysis of the substrate 100 / 400 to determine whether the target height 121 of the filling material 120 in the recess 110 is achieved.

[0093] If it is determined in step 612 that the predetermined condition is not satisfied, the method returns to step 604 to execute another cycle of steps 604 to 610. If it is determined in step 612 that the predetermined condition is satisfied, the method proceeds to step 614, and the target height 121 of the filling material 120 in the recess 110 is achieved. In step 614, subsequent semiconductor manufacturing processes may be executed.

[0094] FIG. 7 shows a method as an example for processing a semiconductor substrate according to an embodiment. Generally, the method described with reference to FIG. 7 corresponds to the process 202 described above with reference to FIGS. 2A to 2I and FIGS. 5A to 5C.

[0095] Steps 700 to 710 generally correspond to steps 600 to 610 of the method described with respect to FIG. 6. Accordingly, the details of steps 600 to 610 are incorporated by reference and will not be repeated. At step 712, a determination is made as to whether a predetermined condition is satisfied. For example, the predetermined condition may include determining whether a predetermined number of cycles of steps 704 to 710 have been executed. In one embodiment, the predetermined condition is whether a single cycle (e.g., a PAG-based process) of steps 704 to 710 has been executed, although the present disclosure contemplates that a plurality of cycles (e.g., a PAG-based process) of steps 704 to 710 may be executed before proceeding to step 714.

[0096] If it is determined at step 712 that the predetermined condition is not satisfied, the method returns to step 704 to execute another cycle (e.g., a PAG-based process) of steps 704 to 710. If it is determined at step 712 that the predetermined condition is satisfied, the method proceeds to step 714. At step 714, an overcoat film 222 is deposited on the substrate 100 / 400. The overcoat film 222 includes a heat-activated agent generator (e.g., TAG) that reacts to heat to generate a solubility modifier 226 (e.g., an acid). At step 716, the substrate 100 / 400 is sufficiently baked to generate the solubility modifier 226 within the overcoat film 222 and to diffuse the solubility modifier 226 to a predetermined depth within the filler 120, rendering a portion of the filler 120 (e.g., the deprotected portion 220a / 520a) soluble in the solvent 228. At step 718, the overcoat film 122 and the deprotected portion 220a / 520a of the filler 120 are developed using the solvent 228.

[0097] In step 720, a determination is made as to whether a predetermined condition is satisfied. Generally, the determination made in step 720 may relate to whether the target height 121 of the filler 120 within the recess 110 has been achieved and may be similar to the predetermined condition described above in step 612 of FIG. 6. If a determination is made in step 720 that the predetermined condition is not satisfied, the method returns to step 714 to execute another cycle of steps 714-718. If a determination is made in step 720 that the predetermined condition is satisfied, the method proceeds to step 722, where the target height 121 of the filler 120 within the recess 110 has been achieved. In step 722, subsequent semiconductor manufacturing processes may be executed.

[0098] FIG. 8 shows a method as an example for processing a semiconductor substrate according to an embodiment. In step 800, the filler 120 is deposited on the substrate 100 / 400 to fill the recess 110 and cover the microfabrication structure 108 of the substrate 100 / 400. In step 802, local removal of the filler 120 is performed to remove the filler 120 to a respective first depth within the recess 110 using a PAG-based process. In step 804, a determination is made as to whether a predetermined condition is satisfied. For example, the predetermined condition may include determining whether a predetermined number of cycles of step 802 have been executed. In one embodiment, the predetermined condition is whether a single cycle of step 802 has been executed, but the present disclosure contemplates that multiple cycles of step 802 may be executed before proceeding to step 806. If a determination is made in step 804 that the predetermined condition is not satisfied, the method returns to step 802 to execute another cycle of step 802. If a determination is made in step 804 that the predetermined condition is satisfied, the method proceeds to step 806.

[0099] In step 806, using a TAG-based process, uniform etching of the remaining portion of the filler 120 is performed to remove the filler 120 having a substantially uniform depth within the recess 110. In step 808, a determination is made as to whether a predetermined condition is satisfied. Generally, the determination made in step 808 relates to whether the target height 121 of the filler 120 within the recess 110 has been achieved, and may be similar to the predetermined conditions described above in step 612 of FIG. 6 and step 720 of FIG. 7, respectively. If it is determined in step 808 that the predetermined condition is not satisfied, the method returns to step 806 to perform another cycle of step 806. If it is determined in step 808 that the predetermined condition is satisfied, the method proceeds to step 810, where the target height 121 of the filler 120 within the recess 110 has been achieved. In step 810, subsequent semiconductor manufacturing processes may be performed.

[0100] Figures 9A - 9C show examples of PAGs and TAGs that can be used in the overcoat film 122 / 222 according to an embodiment. Figure 9A shows an example of an ionic PAG containing triphenylsulfonium triflate and bis(4-tert-butylphenyl)iodonium triflate, which can be used as a photoacid generator for the overcoat film 122. Figure 9A also shows an example of a non-ionic PAG containing N-hydroxynaphthalimide triflate and N-hydroxy-5-norbornene-2,3-dicarboximide perfluoro-1-butanesulfonic acid, which can be used as a photoacid generator for the overcoat film 122. Generally, regardless of being ionic or non-ionic, PAGs can decompose upon exposure to light of a specific wavelength (or wavelength range) to generate strong acids. Figure 9B shows an example of a polymer-bound PAG that can be used as a photoacid generator for the overcoat film 122. Figure 9C shows an example of a TAG that can be used as a thermal acid generator for the overcoat film 222. These TAGs can decompose at high temperatures to generate strong acids. In one embodiment, the TAG can include, by way of example, sulfonic acid esters, onium salts, or halogen-containing compounds.

[0101] Figures 10A-10B illustrate modifications as examples of the solubility of the overcoat film 122 / 222 and / or the filler 120. In particular, Figures 10A-10B illustrate polymer solubility that changes the interaction with strong acids. Figure 10A shows the deprotection chemistry of the tert-butoxycarbonyl group (t-BOC), which can be used in certain photoresists. The material t-BOC can be one of several monomers that make up the polymer of the filler 120 and / or the overcoat film 122 / 222. In this example, the polymer to be protected is hydrophobic (t-butyl group), and the deprotected polymer is a hydroxide and a carboxylic acid. Figure 10B shows vinyl ether de-crosslinking, which can be used in certain developable bottom anti-reflective coatings (dBARCs). In certain embodiments, the interaction with strong acids causes a de-crosslinking reaction, rendering the reacted portion of the film (e.g., the filler 120 and / or the overcoat film 122 / 222) soluble in a given developer (e.g., the solvent 128 / 228).

[0102] It should be understood that the chemistries and systems described above as examples with reference to Figures 9A-9C and Figures 10A-10B are provided as examples only, and that the present disclosure contemplates the use of any suitable chemistries and systems.

[0103] The present disclosure is described in the context of a particular microfabrication process (embedding the filler 120 to a target height 121 within one or more recesses 110 of the substrate 100 / 400), but the present disclosure can be used with any suitable microfabrication process. For example, the present disclosure contemplates controlling the height of any film or other structure / feature of a semiconductor device using the techniques described herein, whether or not such film or other structure / feature is wholly or partially within a recess.

[0104] As a specific example of the use in the embodiments herein, it is the construction of a three-dimensional transistor architecture in which an n-type field effect transistor (NFET) and a p-type FET (PFET) are overlapped and stacked. This may include a vertical stack of lateral gate all-around (GAA) transistors. Epitaxial silicon germanium (SiGe) growth doped with an electron-rich (n-type) species can occur in both the upper and lower layers of uncovered silicon. However, the upper silicon layer can be designed to have electron-deficient (p-type) SiGe. Thus, after the n-type SiGe has grown, the corresponding features leave the upper silicon level that is exposed (uncovered) for subsequent silicon etching and regrowth of p-type SiGe, while at the same time filling to a depth that covers the lower silicon level. The use of the film height control embodiments herein can result in improved control of film height and / or uniformity across the wafer. FIG. 11 shows an example of a stacked transistor architecture that can benefit from precise film height control for selectively growing n-type and p-type SiGe.

[0105] The SAB process is a method of patterning dense features at advanced process nodes. The steps in the SAB process flow can benefit from partial recesses of certain films such as spin-on carbon films as shown in FIGS. 12A-12B. If this film is etched up or down relative to the surrounding spacers by even a small margin, the final pattern in the process flow may not be correctly transferred and defects may occur. The techniques herein can provide a very flat surface potentially across the entire wafer, thereby improving the control and reproducibility of the SAB process.

[0106] To facilitate the understanding of the various embodiments, various techniques have been described as a plurality of individual operations. The order of the description should not be construed as suggesting that these operations are necessarily order-dependent. The described operations can be executed in a different order than the described embodiments. Various additional operations can be performed and / or the described operations can be omitted in additional embodiments.

[0107] Although the present disclosure has been described with reference to exemplary embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present disclosure, will be apparent to those skilled in the art upon reference to the description. Accordingly, the appended claims are intended to embrace any such modifications or embodiments.

Claims

1. 1. A method for processing a semiconductor substrate, the method comprising: Receiving a substrate having a microfabricated structure defining a recess; depositing a resin film on the substrate, the resin film filling the recess and covering the microfabricated structure, the resin film being initially resistant to development by a first solvent; depositing a first overcoat film on the substrate, the first overcoat film including a first drug generating component that generates a first solubility modifier in response to actinic radiation; exposing the first overcoat film to first actinic radiation sufficient to generate the first solubility modifier in the first overcoat film; diffusing the first solubility modifier to a first predetermined depth within the resin film, a first portion of the resin film becoming soluble in the first solvent; developing the first overcoat film and the first portion of the resin film using the first solvent; depositing a second overcoat film on the substrate, the second overcoat film including the first drug generating component that generates the first solubility modifier in response to actinic radiation; exposing the second overcoat film to second actinic radiation sufficient to generate the first solubility modifier in the second overcoat film; diffusing the first solubility modifier to a second predetermined depth within the resin film, where a second portion of the resin film becomes soluble in the first solvent; developing the second overcoat film and the second portion of the resin film with the first solvent, wherein the resin film fills a first combined depth in each of the recesses; The method comprising:

2. The method of claim 1 , wherein diffusing the first solubility modifier to the first predetermined depth within the resin film comprises heating the substrate.

3. diffusing the first solubility modifier to a second predetermined depth within the resin film, a second portion of the resin film becoming soluble in the first solvent; diffusing the first solubility modifier to a first depth within a first recess of the recess; diffusing the first solubility modifier to a second depth within a second recess of the recess, the first depth being greater than the second depth; developing the second portion of the resin film using the first solvent, The resin film is embedded such that a first bonded depth in the first recess is deeper than the first bonded depth in the second recess; 2. The method of claim 1, comprising:

4. The method of claim 1 , wherein the first drug generating component comprises a photoacid generator.

5. The method of claim 1 , wherein the sufficient first actinic radiation and the sufficient second actinic radiation have substantially equal characteristics.

6. moreover, depositing a third overcoat film on the substrate, the third overcoat film including a second agent generating component that generates a second solubility modifier in response to heating the substrate; heating the substrate sufficiently to generate the second solubility modifier in the third overcoat film and to diffuse the second solubility modifier to a third predetermined depth within the resin film, wherein a third portion of the resin film becomes soluble in the first solvent; developing the third portion of the resin film with the first solvent, wherein the resin film is embedded to a second combined depth in each of the recesses; 2. The method of claim 1, comprising:

7. The step of developing the first overcoat film and the first portion of the resin film using the first solvent includes removing the first overcoat film and the first portion of the resin film; 2. The method of claim 1, wherein developing the second overcoat film and the second portion of the resin film with the first solvent removes the second overcoat film and the second portion of the resin film.

8. 1. A method for processing a semiconductor substrate, the method comprising: Receiving a substrate having a microfabricated structure defining a recess; depositing a resin film on the substrate, the resin film filling the recess and covering the microfabricated structure, the resin film being initially resistant to development by a first solvent; depositing a first overcoat film on the substrate, the first overcoat film including a first drug generating component that generates a first solubility modifier in response to actinic radiation; exposing the first overcoat film to actinic radiation sufficient to generate the first solubility modifier within the first overcoat film; diffusing the first solubility modifier to a first predetermined depth within the resin film, a first portion of the resin film becoming soluble in the first solvent; developing the first portion of the resin film using the first solvent; depositing a second overcoat film on the substrate, the second overcoat film including a second drug generating component that generates a second solubility modifier in response to heating the substrate; baking the substrate sufficiently to generate the second solubility modifier in the second overcoat film and to cause the second solubility modifier to diffuse to a second predetermined depth within the resin film, wherein a second portion of the resin film is soluble in the first solvent; developing the second portion of the resin film with the first solvent, wherein the resin film fills a combined depth of each of the recesses; The method comprising:

9. 9. The method of claim 8, further comprising the step of periodically removing additional portions of the resin film until the resin film has a respective predetermined thickness in the recesses.

10. The method of claim 8, wherein a depth of at least one of the recesses prior to deposition of the resin film on the substrate is at least five times a width of at least one of the recesses.

11. the first drug generating component comprises a photoacid generator; The method of claim 8 , wherein the second drug generating component comprises a thermal acid generator.

12. The step of developing the first overcoat film and the first portion of the resin film using the first solvent includes removing the first overcoat film and the first portion of the resin film; 9. The method of claim 8, wherein developing the second overcoat film and the second portion of the resin film with the first solvent removes the second overcoat film and the second portion of the resin film.

13. 1. A method for processing a semiconductor substrate, the method comprising: depositing a resin film on a substrate, the substrate having a micro-fabricated structure defining a recess, the resin film filling the recess and covering the micro-fabricated structure; performing localized removal of the resin film using a photoacid generator (PAG) based process, the resin film being removed to a first depth in each of the recesses, at least two of the first depths being different depths; repeatedly performing uniform removal of the remaining portion of the resin film using a thermal acid generator (TAG) based process until a predetermined condition is met, where a substantially uniform depth of the resin film within the recess is removed; The method comprising:

14. The PAG-based process comprises: depositing a first overcoat film on the substrate, the first overcoat film comprising a PAG; exposing the first overcoat film to a first pattern of radiation, the PAG generating a first acid in the first overcoat film in accordance with the first pattern of radiation; heating the substrate sufficiently to diffuse the first acid into the resin film to a first depth of each of the recesses, such that a first portion of the resin film becomes soluble in a first solvent, the first portion extending to the first depth of each of the recesses; developing the first overcoat film and the first portion of the resin film with the first solvent, wherein the resin film is removed to a first depth of each of the recesses; 14. The method of claim 13, comprising:

15. The TAG-based process includes: depositing a second overcoat film on the substrate, the second overcoat film comprising TAG; heating the substrate sufficiently to generate a second acid in the second overcoat film by the TAG, the second acid diffusing to a second depth into a remaining portion of the resin film such that the second portion of the resin film is soluble in a second solvent; developing the second overcoat film and the second portion of the resin film with a second solvent, the resin film filling the recess defined by the microfabricated structure to a predetermined depth; 15. The method of claim 14, comprising:

16. The method of claim 15 , wherein the first solvent and the second solvent are the same type of solvent.

17. 14. The method of claim 13, wherein performing a localized removal of the resin film using the PAG-based process, where the resin film is removed to a first depth in each of the recesses, comprises repeating the PAG-based process at least two times.

18. The method of claim 13 , wherein satisfying the predetermined condition comprises repeating the TAG-based process a predetermined number of times.

19. 14. The method of claim 13, wherein repeatedly performing the uniform removal of the remaining portion of the resin film using the TAG-based process until the predetermined condition is met comprises performing the TAG-based process once.

20. 14. The method of claim 13, wherein the step of satisfying the predetermined condition includes removing the resin film to a predetermined depth of each of the recesses and leaving a respective height of the resin film in the recesses corresponding to each predetermined height.

21. 14. The method of claim 13, wherein a concentration of TAG in the overcoat film during a first performance of the TAG-based process is different from a concentration during a subsequent performance of the TAG-based process.

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