Method for denting a filler within an opening formed in a patterned substrate

Abstract

A process flow and method for recessing a filler material within an opening formed in a patterned substrate is provided. The opening is formed in a multilayer stack including a target material layer and one or more additional material layers that overlap but are different from the target material layer. After the opening is formed in the multilayer stack, a graft material containing a solubility-shifting agent is selectively deposited within the opening such that the graft material adheres to the target material layer without adhering to the additional material layers overlying the target material layer. A filler material is then deposited within the opening, activating the solubility-shifting agent to change the solubility of portions of the filler material adjacent to and surrounding the graft material. A wet development process is then used to remove the soluble / insoluble portions of the filler material, recessing the filler material within the opening.

Description

Technical Field

[0001] Priority Claim This application claims the priority of U.S. Provisional Patent Application No. 63 / 120,480, filed on December 2, 2020, the entire disclosure of which is expressly incorporated herein by reference in its entirety.

[0002] The present disclosure relates to the processing of substrates. In particular, a new processing flow and method for recessing a film within an opening formed in a substrate are provided. In one embodiment, the processing flow and method disclosed herein may be used for processing semiconductor substrates.

Background Art

[0003] Due to the continuous reduction of geometries in substrate processing, the technical challenges of forming structures on substrates are increasing. To address these challenges, new processing flows and patterning technologies are continuously evolving. In some processing flows, openings (e.g., trenches, contacts, holes, etc.) are formed in a patterned substrate, the openings are filled with a filler, and a plurality of portions of the filler are removed to recess the filler within the openings, thereby forming various structures on the patterned substrate. Controlling the filling of recesses within a patterned substrate or topography is becoming increasingly difficult as geometries shrink and aspect ratios continue to increase. In some advanced processes, nanometer-level accuracy may be required to control the filling of recesses within openings having a narrow and / or high aspect ratio. Unfortunately, current processes (such as timed etching processes) used to control the filling of recesses have throughput, variability, and cost issues.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, it would be desirable to provide an improved process and method for recessing a filler within an opening formed in a patterned substrate.

Means for Solving the Problems

[0005] Provided herein are improved processing flows and methods for recessing a filler within a plurality of openings formed within a patterned substrate. More specifically, the present disclosure provides improved processing flows and methods for recessing a filler within an opening formed within a patterned substrate using selective deposition of a graft material and selective deprotection of the filler.

[0006] Using the processing flows and methods disclosed herein, a filler within a wide variety of openings (e.g., trenches, contacts, holes, etc.) or features (e.g., multi-layer spacers) formed in a patterned substrate such as a semiconductor substrate can be recessed. In the present disclosure, an opening is formed within a multi-layer stack that includes at least one target material layer and one or more additional material layers that cover the target material layer and are different from the target material layer. In some embodiments, the multi-layer stack may include one target material layer and one or more additional material layers that cover the target material layer. In other embodiments, the multi-layer stack may include a plurality of target material layers that are dispersed throughout the multi-layer stack and are separated from each other by additional material layers that are different from the target material layer.

[0007] After an opening is formed within the multi-layer stack, the graft material is selectively deposited within the opening such that the graft material adheres to the target material layer without adhering to the additional material layer that covers the target material layer. The graft material selectively deposited within the opening includes (or is functionalized by) a solubility shift agent that can change the solubility of an adjacent material if activated. Examples of solubility shift agents include, but are not limited to, acid generators such as photoacid generators (PAGs) or thermal acid generators (TAGs). After the graft material is selectively deposited within the opening, a filler is deposited within the opening and the solubility shift agent is activated to change the solubility of the portion of the filler that surrounds and is adjacent to the graft material. If the solubility shift agent is activated and the solubility of the portion of the filler changes, the filler within the opening can be recessed by removing the soluble and / or insoluble portions of the filler from the opening using a wet development process.

[0008] In one embodiment, a method is provided for recessing a filler within an opening formed in a patterned substrate. The method may include receiving a patterned substrate including the opening within a multi-layer stack where the opening is formed within a target material layer and one or more additional material layers covering the target material layer, and where the one or more additional material layers are different from the target material layer. The method further includes selectively depositing a graft material within the opening such that the graft material adheres to the target material layer without adhering to one or more additional material layers covering the target material layer, and where the graft material includes a solubility shifting agent. The method further includes depositing a filler within the opening and diffusing the solubility shifting agent into an interior of a portion of the filler surrounding the graft material, such that the portion of the filler becomes insoluble to a predetermined solvent due to the diffusion of the solubility shifting agent. Further, the method includes recessing the filler within the opening by removing a soluble portion of the filler using the predetermined solvent while leaving a portion of the filler insoluble to the predetermined solvent within the opening.

[0009] In variations of multiple embodiments, the method described above can be adapted such that the predetermined solvent removes the soluble portion of the filler to a certain depth within the opening defined by the solubility shifting agent and physical characteristics of the target material layer. In other variations, the graft material is selectively deposited on opposing sidewalls of the opening at a depth defined by the target material layer, and the solubility shifting agent causes a solubility change reaction within a region radially spreading from the graft material deposited on the opposing sidewalls to the portion of the filler, forming a complete layer of insoluble material at the depth of the target material layer. In yet other variations, the graft material is selectively deposited within the opening by forming a self-assembled monolayer (SAM) on opposing sidewall surfaces of the target material layer, and the filler is an acid-protected resin. In other variations, the predetermined solvent is an organic solvent. In some variations, recessing the filler after removing the soluble portion of the filler using the predetermined solvent further includes removing the portion of the filler insoluble to the predetermined solvent from the opening using an aqueous solvent.

[0010] In some variations of the above embodiments, the SAM is functionalized by a photoacid generator (PAG) or a thermal acid generator (TAG). In some cases, the SAM is functionalized by a photoacid generator (PAG), and diffusing a solubility shifter into the interior of the portion of the filler surrounding the graft material among the fillers includes irradiating the PAG to generate an acid and performing a baking process to diffuse the acid into the interior of the portion of the filler, and the diffusion of the acid converts the acid-protected resin in the portion of the filler into an acid-deprotected resin. In other cases, the SAM is functionalized by a thermal acid generator (TAG), and diffusing a solubility shifter into the interior of the portion of the filler surrounding the graft material among the fillers includes performing a baking process to generate an acid and diffuse the acid into the interior of the portion of the filler, and the diffusion of the acid converts the acid-protected resin in the portion of the filler into an acid-deprotected resin.

[0011] In another embodiment, a method of recessing a filler within an opening formed in a patterned substrate is provided. The method may include that the opening is formed in a multi-layer stack including a target material layer and one or more additional material layers covering the target material layer, and the one or more additional material layers are different from the target material layer, and receiving the patterned substrate including the opening. The method further includes selectively depositing, within the opening, a graft material including an acid generator to adhere to the target material layer without adhering to one or more additional material layers covering the target material layer. The method also includes depositing, within the opening, a filler that is an acid-protected material. The method further includes activating the acid generator within the graft material to generate an acid and diffusing the acid into the interior of the portion of the filler surrounding the graft material, and the diffusion of the acid converts the portion of the filler into an acid-deprotected material. The method also includes recessing the filler within the opening by removing, using a first solvent, a portion of the acid-protected material covering the portion of the filler including the acid-deprotected material.

[0012] In a modification of the other method, the graft material is selectively deposited on the opposing sidewalls of the opening at a depth defined by the target material layer, and acid diffuses radially from the graft material deposited on the opposing sidewalls into the interior of the portion of the filler material to form a complete layer of the acid deprotection material at the depth of the target material layer. In a plurality of other modifications, the graft material is selectively deposited within the opening by forming a self-assembled monolayer (SAM) on the opposing sidewall surfaces of the target material layer. In yet another plurality of modifications, the head groups of the SAM include thiol, carboxylic acid, phosphinic acid, or silane. In yet another plurality of modifications, the diffusion of the acid is localized in the region including the graft material. In some modifications, the activation of the acid generator includes a baking process, and the diffusion length and profile of the acid diffusion depend on the composition of the acid generator, the composition of the filler material, the baking temperature, the baking time, and / or the molecular weight of the acid. In some modifications, the first solvent is an organic solvent. In some modifications, after removing the portion of the acid-protected material covering the portion of the filler material including the acid deprotection material using the first solvent, denting the filler material further includes removing the portion of the filler material including the acid deprotection material using a second solvent. In some modifications, the second solvent is an aqueous solvent.

[0013] In some embodiments of the above method, the acid generator is a photoacid generator (PAG), and activating the acid generator includes irradiating the PAG to generate acid and performing a baking process to diffuse the acid into the interior of the portion of the filler material. In a plurality of other embodiments, the acid generator is a thermal acid generator (TAG), and activating the acid generator includes generating acid and performing a baking process to diffuse the acid into the interior of the portion of the filler material.

Brief Description of the Drawings

[0014] The present invention and its advantages will be more fully understood by reference to the following description in conjunction with the accompanying drawings, which show the same features with the same reference numerals. However, it should be noted that the accompanying drawings only show exemplary embodiments of the disclosed concept, and therefore, the disclosed concept may include other equally effective multiple embodiments, and should not be considered as limiting the scope of the present invention.

[0015]

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DETAILED DESCRIPTION OF THE INVENTION

[0016] This specification provides an improved processing flow and method for denting the filler within a plurality of openings formed within a patterned substrate. More specifically, the present disclosure provides an improved processing flow and method for denting the filler within an opening formed within a patterned substrate using selective deposition of a graft material and selective deprotection of the filler.

[0017] Using the processing flow and method disclosed herein, the filler within a wide variety of openings (e.g., trenches, contacts, holes, etc.) or features (e.g., multilayer spacers) formed within a patterned substrate such as a semiconductor substrate can be dented. In the present disclosure, the opening is formed within a multilayer stack including at least one target material layer and one or more additional material layers covering the target material layer, the additional material layer being different from the target material layer. In some embodiments, the multilayer stack may include one target material layer and one or more additional material layers covering the target material layer. In other embodiments, the multilayer stack may include a plurality of target material layers scattered throughout the multilayer stack and separated from each other by additional material layers different from the target material layer.

[0018] After an opening is formed in the multi-layer stack, the graft material is selectively deposited within the opening such that it adheres to the target material layer without adhering to an additional material layer that covers the target material layer. The graft material selectively deposited within the opening includes (or is functionalized thereby) a solubility shifting agent that can change the solubility of adjacent materials if activated. Examples of solubility shifting agents include, but are not limited to, acid generators such as photoacid generators (PAGs) or thermal acid generators (TAGs). After the graft material is selectively deposited within the opening, a filler material is deposited within the opening and the solubility shifting agent is activated to change the solubility of the portion of the filler material that surrounds and is adjacent to the graft material. If the solubility shifting agent is activated to change the solubility of the said portion of the filler material, the filler material within the opening is recessed by removing the soluble and / or insoluble portions of the filler material from the opening using a wet development process.

[0019] In one exemplary embodiment, the filler material may be a deprotecting material, and activating the solubility shifting agent can cause the solubility shifting agent to diffuse into the portion of the filler material that surrounds and is adjacent to the graft material. The diffusion of the solubility shifting agent into the said portion of the filler material changes the solubility of the said portion of the filler material. For example, due to the diffusion of the solubility shifting agent, the said portion of the filler material becomes insoluble in a predetermined solvent (such as an organic solvent or a developer, etc.), while the remaining portion of the filler material can be kept soluble in the predetermined solvent. After activating the solubility shifting agent to change the solubility of the said portion of the filler material, the filler material can be recessed within the opening by removing the soluble portion of the filler material from the opening using a predetermined solvent. In some embodiments, by using another solvent (e.g., an aqueous solvent or a developer), the portion of the filler material that is insoluble in the predetermined solvent can be removed from the opening to further recess the filler material within the opening.

[0020] In another exemplary embodiment, the filler may be an acid-protected material, and the solubility shifter may be an acid generator that can be activated to generate an acid and diffuse it into the interior of the portion of the filler that surrounds and is adjacent to the graft material. The diffusion of the acid selectively deprotects the portion of the filler that surrounds and is adjacent to the graft material by converting the portion of the filler into an acid-deprotected material. After activating the solubility shifter to deprotect the portion of the filler, the portion of the acid-protected material covering the portion of the filler containing the acid-deprotected material can be removed using a first solvent (e.g., an organic solvent or a developer) to recess the filler within the opening. In some embodiments, the filler within the opening can be further recessed by removing the portion of the filler containing the acid-deprotected material using a second solvent (e.g., an aqueous solvent or a developer).

[0021] Thus, an improved process flow and method for recessing the filler within a plurality of openings formed in a patterned substrate are disclosed herein, where the openings are formed within a multilayer stack including at least one target material layer and one or more additional material layers covering the target material layer, and the additional material layers are different from the target material layer. Unlike conventional processes, the process flow and method disclosed herein (a) selectively deposit a graft material containing (or functionalized by) a solubility shifter on the opposing sidewalls of an opening at a depth defined by the target material layer, (b) activate the solubility shifter to selectively deprotect the portion of the filler that surrounds and is adjacent to the graft material, and (c) form self-aligned recesses within the deprotected filler by progressively removing the protected and deprotected filler from the opening using a wet development process using one or more solvents (e.g., an organic solvent followed by an aqueous solvent). The filler, solubility shifter, and / or solvent may generally be selected such that the deprotected filler has a higher dissolution contrast in the organic and aqueous solvents compared to the protected filler. Thus, in each development step, one layer of the protected or deprotected filler can be removed depending on the composition of the solvent used.

[0022] The amount of recess achieved using the techniques disclosed herein generally may depend on the composition of the multilayer stack (e.g., the number of insulated target material layers included within the multilayer stack), the thickness of the graft material selectively deposited on the sidewall surfaces of the target material layers, and the diffusion length of the solubility shifter. As disclosed herein, after the graft material has been selectively deposited and the filler material has been selectively deprotected, the solvent may be used alternately (e.g., an organic solvent and an aqueous solvent alternately) in a wet development process to progressively remove the protected and deprotected filler materials from the openings. The alternating development process may be repeated any number of times necessary to achieve the desired recess depth within a particular multilayer stack, provided that an insulated target material layer is formed within the stack.

[0023] Figures 1A - 1E illustrate one embodiment of an improved process flow that can be utilized to recess the filler material within a plurality of openings formed in a substrate patterned in accordance with the techniques described herein. As shown in Figure 1A, an opening 114 is formed within a multilayer stack 112 provided in a patterned substrate 100. The multilayer stack 112 may generally be formed over one or more underlying layers such as, but not limited to, a hard mask layer 106, an organic layer 104, and a base substrate layer 102. As will be described in more detail below, the multilayer stack 112 may include at least two different material layers including at least one target material layer and one or more additional material layers covering the target material layer. The opening 114 may be formed within the multilayer stack 112 using a wide range of processes known in the art. In some embodiments, the opening 114 may be a trench, contact, or hole etched or otherwise formed within the multilayer stack 112.

[0024] The base substrate layer 102 may be any substrate where the use of patterned features is desirable. For example, the base substrate layer 102 may be a semiconductor substrate on which one or more semiconductor processing layers are formed thereon. In one embodiment, the base substrate layer 102 may be a substrate that has passed through a plurality of semiconductor processing steps to generate a wide range of structures and layers, all of which are known in the art of substrate processing technology. The hard mask layer 106 and the organic layer 104 shown in FIG. 1A may also be formed from any of a wide range of materials, as is known in the art. Although exemplary underlying layers are described and illustrated, the techniques described herein are not limited to any particular type or number of layers that form the base of the multilayer stack 112. Thus, more, fewer, or other underlying layers may be used.

[0025] In the embodiment shown in FIG. 1A, the multilayer stack 112 includes a target material layer 108 and an additional material layer 110 that covers the target material layer 108. The target material layer 108 and the additional material layer 110 may each be formed from any of a wide range of materials, provided that the target material layer 108 and the additional material layer 110 are formed using different materials. Although two layers are included in the multilayer stack 112 shown in FIG. 1A, the multilayer stack 112 is not limited to any particular number of layers and may include additional layers in other embodiments of the present disclosure. Thus, the "multilayer stack" described herein may include any number of target material layers, which are dispersed throughout the multilayer stack and are separated or insulated from each other by additional material layers that are different from the target material layers. By insulating the target additional layers with additional material layers, the techniques described herein can be applied to vertically scalable designs and / or utilized to achieve any desired recess depth.

[0026] In the embodiment shown in FIG. 1B, the graft material 116 is selectively deposited within the opening 114 so as to adhere to the target material layer 108 without adhering to the additional material layer 110 that covers the target material layer. More specifically, the graft material 116 is selectively deposited on the opposing sidewalls of the opening 114 at a depth (D) defined by the target material layer 108. The graft material 116 can generally be formed from any of a wide range of materials.

[0027] In some embodiments, the graft material 116 may be selectively deposited within the opening 114 by forming a self-assembled monolayer (SAM) on the opposing sidewall surfaces of the target material layer 108. As is known in the art, a SAM is an assembly or chain of molecules (including a head group, a tail group, and a functional end group) that is spontaneously formed on a surface by adsorption. In the present disclosure, the SAM is formed through the organization of the molecular chains of the tail groups following the adsorption of the head groups onto the opposing sidewall surfaces of the target material layer 108. The head groups may include, but are not strictly limited to, for example, thiol, carboxylic acid, phosphinic acid, or silane.

[0028] As is known in the art, the end of the molecular chain, or the functional end group of the SAM, can be functionalized to change one or more properties of the SAM. In the present disclosure, the functional end group is functionalized by a solubility shift agent and then activated to change the solubility of the material adjacent to the graft material 116. In some embodiments of the present disclosure, the functional end group of the SAM may be functionalized with an acid generator such as a photoacid generator (PAG) or a thermal acid generator (TAG). The acid generator, when activated, generates an acid that diffuses into the adjacent material to change the solubility of the adjacent material.

[0029] In the embodiment shown in FIG. 1C, after the graft material 116 is selectively deposited on the sidewall surface of the target material layer 108, the opening 114 is filled with a material (i.e., the filler 118). A wide range of techniques and processes may be used to fill the opening 114 with the filler 118. In some embodiments, the filler 118 may be deposited within the opening 114 using chemical vapor deposition (CVD), plasma enhanced CVD (PECVD), physical vapor deposition (PVD), atomic layer deposition (ALD), spin coating, spray coating, and / or other deposition processes. Other processes known in the art may also be used to fill the opening 114 with the filler 118. In addition to filling the opening 114, in some embodiments of the present disclosure, the filler 118 can be deposited or separately formed on the top of the patterned substrate 100. The specific materials utilized in the various layers shown in FIGS. 1A-1C can vary depending on the specific process flow and application that utilizes the techniques described herein. In some embodiments, the target material layer 108 may include an oxide or a nitride. In some embodiments, the additional material layer 110 may include silicon, an oxide (e.g., silicon oxide, titanium oxide, or hafnium oxide), or a nitride (e.g., silicon nitride or titanium nitride). In some embodiments, the graft material 116 may include a thiol, a carboxylic acid, or a silane. In some embodiments, the filler 118 may include an ester, an acetal, or a vinyl ether. However, other wide-ranging materials may also be used in the practice of the techniques described herein.

[0030] In the present disclosure, the filler 118 can be realized by a wide range of deprotecting materials. As is known in the art, a "deprotecting material" is a material in which a protecting group is added to the molecular structure of the material to prevent a chemical reaction from occurring later. In some cases, the deprotecting material, i.e., the "protected material," can be deprotected by removing the protecting group from the molecular structure. Once the protecting group is removed, the "protected material" is converted into a "deprotected material" that does not inhibit subsequent reactions.

[0031] In some embodiments, the filler 118 can be realized using an acid-deprotectable resin (also referred to as an acid-protected resin) that can be deprotected by an acid. However, it can be understood that the filler 118 is not strictly limited to an acid-deprotectable resin and can be realized with other deprotectable materials.

[0032] In the embodiment shown in FIG. 1D, the solubility shifter in the graft material 116 is activated, and the solubility shifter diffuses into the interior of the portion 120 of the filler 118 that surrounds and is adjacent to the graft material 116. Due to the activation and diffusion of the solubility shifter, a solubility change reaction occurs within the portion 120 of the filler 118. In some embodiments, due to the activation and diffusion of the solubility shifter, the portion 120 can become insoluble in a predetermined solvent.

[0033] In some embodiments, the solubility shifter in the graft material 116 may include an acid generator such as a photoacid generator (PAG) or a thermal acid generator (TAG). When the graft material 116 contains (or is functionalized by) PAG, the solubility shifter may be activated by irradiating the PAG to generate an acid and performing a baking process to diffuse the acid into the interior of the portion 120 of the filler 118. When the graft material 116 contains (or is functionalized by) TAG, the solubility shifter may be activated by performing a baking process to generate an acid and diffusing the acid into the interior of the portion 120 of the filler 118. In either case, the diffusion of the acid changes the solubility of the portion 120 of the filler 118 that surrounds and is adjacent to the graft material 116 by converting the acid-protected resin in the portion 120 into an acid-deprotected resin. In other words, the diffusion of the acid deprotects the portion 120 of the filler 118 that surrounds and is adjacent to the graft material 116.

[0034] As shown in FIG. 1D, due to the activation and diffusion of the solubility shift agent, a solubility change reaction occurs that is localized at the depth (D) of the target material layer 108. More specifically, due to the activation and diffusion of the solubility shift agent, a solubility change reaction occurs within a region (shown by a dashed line in FIG. 1D) that extends radially inward from the graft material 116 deposited on the opposing sidewall surfaces of the target material layer 108 into the portion 120 of the filler 118. The diffusion length of the acid (e.g., the radial distance that the acid diffuses into the filler 118) is preferably selected to be the same as or greater than the radius of the opening 114 such that a complete layer of insoluble material (e.g., an acid deprotection resin) is formed at the depth of the target material layer 108.

[0035] The thickness of the insoluble material layer formed through the diffusion of the acid into the portion 120 generally depends on the diffusion length of the acid and the thickness of the graft material 116. In some embodiments, the diffusion length and profile of the acid may depend on the composition of the acid generator contained within the graft material 116, the molecular weight of the acid generated, the composition of the filler 118, the bake temperature, and / or the bake time. In some embodiments, one or more of these properties or parameters can be adjusted or controlled to change the diffusion length and / or profile of the acid diffusion.

[0036] After activating the solubility shift agent to selectively deprotect the portion 120 of the filler 118 that surrounds and is adjacent to the graft material 116, the filler 118 within the opening 114 is recessed using a wet development process. In some embodiments, through the wet development process, as shown in FIG. 1E, the filler 118 can be recessed within the opening 114 by removing the protected portion 122 of the filler 118 that covers the deprotected portion 120 using a first solvent (e.g., an organic solvent). In some embodiments, the wet development process may be terminated if the protected portion 122 of the filler 118 has been removed.

[0037] In other embodiments, the wet development process can recess the fill material 118 within the opening 114 by progressively removing the protected and deprotected portions of the fill material 118 from the opening 114 using multiple solvents alternately. For example, the wet development process can (a) remove the protected portion 122 of the fill material 118 that covers the deprotected portion 120 of the fill material 118 (as shown in FIG. 1E), and then (b) alternately remove the deprotected portion 120 of the fill material 118 using a second solvent (not shown). In some embodiments, the first solvent can be an organic solvent and the second solvent can be an aqueous solvent. However, it can be seen that the solvents used for removing the protected and deprotected portions of the fill material 118 are not strictly limited to organic and aqueous solvents. As is known in the art, other solvents can be used to remove the protected / deprotected portions of the fill material. In some embodiments, the first solvent can be n-butyl acetate or 2-heptanone, and the second solvent can be tetramethylammonium hydroxide.

[0038] In some embodiments, the fill material 118, solubility shifter (e.g., acid generator), and / or solvent can be selected to ensure that the deprotected portion 120 of the fill material 118 within the selected solvent has a high dissolution contrast compared to the protected portion 122 of the fill material 118. Thus, in each development step, one layer of protected or deprotected fill material can be removed depending on the composition of the solvent used.

[0039] In some embodiments, the amount of recesses realized by using the techniques shown in FIGS. 1A - 1E may depend on the composition of the multilayer stack 112 (e.g., the number of insulating target material layers 108 provided within the multilayer stack 112), the thickness of the graft material 116 selectively deposited on the sidewall surfaces of the target material layer 108, and the diffusion length of the solubility shift agent. As shown in FIGS. 1B - 1D and described herein, on the premise that after the graft material 116 is selectively deposited and the filler 118 is selectively deprotected, an insulated target material layer 108 is formed within the stack, a wet development process using solvents alternately (e.g., an organic solvent and an aqueous solvent alternately) may be repeated the number of times necessary to achieve the desired recess depth within a particular multilayer stack.

[0040] It can be seen that the techniques disclosed herein may be used during the processing of a wide range of substrates. The substrate may be any substrate for which patterning of the substrate is desirable. For example, in one embodiment, the substrate may be a semiconductor substrate having one or more semiconductor processing layers (which may all together constitute the substrate) formed thereon. Thus, in one embodiment, the substrate may be a semiconductor substrate that has passed through a plurality of semiconductor processing steps that form a wide range of structures and layers that are all known in the substrate processing art and may be considered part of the substrate. For example, in one embodiment, the substrate may be a semiconductor wafer having one or more semiconductor processing layers formed thereon. The concepts disclosed herein may be used at any stage of the substrate processing flow, e.g., any of the numerous photolithography steps used in the formation of a finished substrate.

[0041] It can be seen that the technology disclosed in this specification may be used when manufacturing extensive semiconductor structures and / or elements on / within a substrate. For example, FIGS. 2A - 2M show an example of a process flow using the technology described in this specification to recess a filler within an opening formed in a multilayer stack used for forming a complementary field - effect transistor (CFET). Another example of a process flow used for forming a recess in a self - aligned block (SAB) process is shown in FIGS. 3A - 3B. It can be seen that the disclosed technology is not limited to the examples of process flows illustrated and described in this specification and may be used when forming other semiconductor structures and / or elements.

[0042] FIGS. 2A - 2M show an example of a process flow for selective epitaxial silicon growth in a monolithic complementary FET (CFET) design. With a monolithic CFET design, n - type and p - type transistors can be vertically stacked. The manufacture of vertically stacked complementary transistors requires that many selective processes, depending on each transistor type, be performed without interfering with the manufacture of other transistor types. One major process is the growth of doped epitaxial silicon for each corresponding transistor type and, if necessary, blocking silicon channels that are inhibitory factors during such growth. As shown in FIGS. 2A - 2M and described in more detail below, the technology disclosed in this specification can be used to define n / p separation in a monolithic CFET design and provide a self - aligned and scalable process that enables selective epitaxial silicon growth in each complementary doped channel.

[0043] Figures 2A - 2M illustrate an example of a processing flow for recessing a filler within an opening formed in a multilayer stack 212 provided in one or more underlying layers 202 of a patterned substrate 200 using the techniques disclosed herein. In the embodiment shown in Figures 2A - 2M, the multilayer stack 212 includes an upper silicon channel 204 and a lower silicon channel 206 that are doped to form n - type and p - type channel regions in a monolithic CFET design. In the embodiment shown in Figure 2A, the silicon channels are separated or insulated by a silicon germanium (SiGe) layer 208. In some embodiments, a nitride layer 210 may be formed on the uppermost SiGe layer 208.

[0044] After inner spacers 207 are formed on each of the SiGe layers 208, a grafting material 216 (self - aligned monolayer, i.e., SAM, etc.) is selectively deposited within an opening 214 formed in the multilayer stack 212. More specifically, as shown in Figure 2B, the grafting material 216 is selectively deposited on the exposed sidewall surfaces of the upper silicon channel 204 and the lower silicon channel 206. As described above, the grafting material 216 can include or be functionalized with a solubility - shifting agent (such as an acid - generating agent) that can be activated to change the solubility of the layer adjacent to the grafting material 216.

[0045] After the grafting material 216 is selectively deposited, the opening 214 is filled with a de - protective material 218 as shown in Figure 2C. In some embodiments, the de - protective material 218 may be an acid - de - protectable resin (or acid - protected resin) that can be de - protected by an acid.

[0046] After the opening 214 is filled with the deprotective material 218, a solubility shifting agent (e.g., an acid generator) is activated within the graft material 216 to generate an acid that localizes in the graft material 216. The patterned substrate 200 is then fired as shown in FIG. 2D to diffuse the acid outwardly into the interior of the deprotective material 218. Due to the activation and diffusion of the solubility shifting agent, a solubility change reaction occurs within a radial distance from the sidewall surfaces of the upper silicon channel 204 and the lower silicon channel 206, so that a complete layer of the deprotective material 220 (e.g., a deprotective resin layer) is formed in the vicinity of the upper and lower silicon channels. The thickness of the deprotective resin layer is defined by the thickness of the silicon channel and the diffusion length of the acid. The separation between the n-type channel and the p-type channel is designed such that a layer of the deprotective material 218 (acid-protected resin) remains between the n-type channel region and the p-type channel region.

[0047] In FIG. 2E, the patterned substrate 200 is developed with an organic solvent to remove the deprotective material 218 (acid-protected resin) from the uppermost portion of the patterned substrate 200. This development step exposes the uppermost layer of the deprotective material 220 formed adjacent to the upper silicon channel 204 and recesses the deprotective material 218 within the opening 214 to a depth defined by the uppermost layer of the deprotective material 220.

[0048] In FIG. 2F, the patterned substrate 200 is developed with an aqueous medium to remove the uppermost layer (deprotective resin layer) of the deprotective material 220 from the opening 214. This development step exposes the upper silicon channel 204 and the deprotective material 218 (acid-protected resin) disposed between the upper silicon channel 204 and the lower silicon channel 206.

[0049] In FIG. 2G, a second organic development is performed to remove the layer of the deprotective material 218 (acid-protected resin) disposed between the upper silicon channel 204 and the lower silicon channel 206. By this development step, the next layer of the deprotective material 220 formed adjacent to the lower silicon channel 206 is exposed, and the deprotective material 218 within the opening 214 is recessed to a desired recess depth defined by the next layer of the deprotective material 220. By using the processing steps shown in FIGS. 2B-2G, the deprotective material 218 within the opening 214 can be recessed to a desired recess depth to expose the upper silicon channel 204 while protecting the lower silicon channel 206 from subsequent processing using the techniques disclosed herein.

[0050] In FIG. 2H, a liner 222 is conformally deposited covering the uppermost portion of the patterned substrate 200, the sidewalls of the opening 214, and the uppermost portion of the remaining deprotective material 220. In FIG. 2I, anisotropic etching is performed to remove the liner 222 from the upper portion of the patterned substrate 200 and to remove the remaining deprotective material 220, leaving the sidewall surfaces of the opening 214 covered by the liner 222 at a desired recess depth. After the patterned substrate 200 has received a silicon cleaning step, an epitaxial feature 224 is selectively formed on the lower silicon channel 206 as shown in FIG. 2J. After the epitaxial feature is formed on the lower silicon channel 206, the liner 222 is removed in FIG. 2K, and a encapsulation layer 226 selectively grows on the epitaxial feature 224 formed on the lower silicon channel in FIG. 2L. After the encapsulation layer 226 has grown, additional epitaxial processing is performed to enable selective growth of the epitaxial feature 224 on the upper silicon channel 204 without interference from or contamination of the underlying layer (as shown in FIG. 2M).

[0051] Self-aligned block (SAB) is an advanced multi-color processing flow designed to pattern sub-resolution cuts into high-resolution features for state-of-the-art integrated circuits. In a major step of the processing flow, it is often required to partially recess a filler (e.g., spin-on glass, etc.) within an opening formed between spacers provided on a patterned substrate. This recessing step typically requires nanometer-level accuracy. If the recess formed between the spacers is too shallow or too deep, the entire process may fail. To avoid this problem, the various techniques disclosed herein can be implemented by converting a spacer pattern into a multi-layer stack having a target material layer and at least one additional layer covering the target material layer, and the thickness of the target material layer is adjusted to a desired recess depth.

[0052] Figures 3A - 3B show an example of a processing flow that may be used to form recesses in self-aligned block (SAB) processing. More specifically, FIG. 3A shows an example of a patterned substrate 300 after a filler 318 has been deposited on the patterned substrate 300 to fill an opening formed between a plurality of multi-layer spacers 310 provided on the patterned substrate 300 and formed according to SAB processing. FIG. 3B shows the patterned substrate 300 shown in FIG. 3A after the filler 318 has been recessed within the multi-layer spacers 310 according to the techniques described herein.

[0053] The multilayer spacer 310 shown in FIG. 3A may generally be formed on one or more underlying layers. In some embodiments, for example, the multilayer spacer 310 may generally be formed on one or more underlying layers such as, but not limited to, the hard mask layer 308, the interlevel dielectric layer 306, the low-k dielectric layer 304, and the base substrate layer 302. The base substrate layer 302 may be any substrate where the use of patterned features is desirable. The hard mask layer 308, the interlevel dielectric layer 306, and the low-k dielectric layer 304 shown in FIG. 3A may be formed from any of a wide range of materials known in the art. Although exemplary underlying layers are described and illustrated, the techniques described herein are not limited to any particular type or number of layers beneath the multilayer spacer 310. Thus, more, fewer, or other underlying layers may be used.

[0054] To utilize the techniques disclosed herein, the multilayer spacer 310 shown in FIGS. 3A - 3B may be formed to include at least two different material layers including at least one target material layer 312 and one or more additional material layers 314 covering the target material layer. In some embodiments, the multilayer spacer 310 may be formed using self-aligned multiple patterning (SAMP) processes such as, for example, self-aligned double patterning (SADP) process, self-aligned quadruple patterning (SAQP) process, self-aligned octuple patterning (SAOP) process. SAMP processes are known in the art.

[0055] In one example of the SAMP process, the multi-layer spacer 310 can be formed on the patterned substrate 300 by forming the target material layer 312 on the hard mask layer 308, forming a plurality of mandrels (not shown) on the target material layer 312, and forming one or more additional material layers 314 on the exposed surfaces of the mandrels and the target material layer 312. Once the additional material layer 314 is formed, an etching process can be used to remove a portion of the additional material layer 314 from the upper surface of the mandrel and the exposed surface of the target material layer 312, leaving an additional material layer spacer on the sidewalls of the mandrel. After performing a mandrel extraction step to remove the mandrel from the patterned substrate 300, the multi-layer spacer 310 shown in FIGS. 3A - 3B can be formed by etching the target material layer 312 using another etching process.

[0056] After the multi-layer spacer 310 is formed, as shown in FIG. 3B, a spin-on carbon (SOC) layer 316 may be formed on the patterned substrate 300. Next, a filler 318 may be deposited (or separately formed) on the top of the patterned substrate 300 and within the openings 320 formed in the SOC layer 316. In one example embodiment, the filler 318 may be spin-on glass (SOG).

[0057] After the openings 320 are filled with the filler 318, the filler 318 can be recessed within the multi-layer spacer 310 using the techniques shown in FIGS. 1B - 1E and described above. By using the techniques disclosed herein, the filler 318 can be recessed within the multi-layer spacer 310 with high precision to a desired recess depth defined by the target material layer 312 contained within the multi-layer spacer 310 (as shown in FIG. 3B).

[0058] Figures 4-5 illustrate an exemplary method of using the techniques described herein. It will be recognized that the multiple embodiments shown in Figures 4-5 are merely exemplary, and additional methods may utilize the techniques described herein. Further, since the steps described above are not intended to be exclusive, additional processing steps may be added to the methods shown in Figures 4-5. Further, the order of the steps is not limited to the order shown, as different orders may occur and / or various steps may be combined or performed simultaneously.

[0059] Figure 4 shows an embodiment of a method 400 of recessing a filler within a plurality of openings formed within a patterned substrate. The method 400 shown in Figure 4 may generally begin with receiving (in step 410) a patterned substrate that includes openings. In method 400, the openings formed within the patterned substrate are formed within a multi-layer stack that includes a target material layer and one or more additional material layers that cover the target material layer, and the additional material layers are different from the target material layer. Figures 1-3 provide examples of various openings that may be formed within a multi-layer stack. However, it will be recognized that the method 400 shown in Figure 4 is not strictly limited to the examples illustrated and described herein.

[0060] In step 420, method 400 selectively deposits a grafting material within the openings such that the grafting material adheres to the target material layer without adhering to one or more additional material layers that cover the target material layer. In the embodiment shown in Figure 4, the grafting material includes a solubility shifting agent.

[0061] After selectively depositing (in step 420) the grafting material, method 400 deposits (in step 430) a filler within the openings before diffusing (in step 440) the solubility shifting agent into the portion of the filler that surrounds the grafting material. In the embodiment shown in Figure 4, the diffusion of the solubility shifting agent renders the portion of the filler insoluble in a predetermined solvent. In step 450, method 400 recesses the filler within the openings by removing the soluble portion of the filler using the predetermined solvent while leaving the portion of the filler that is insoluble in the predetermined solvent within the openings.

[0062] Figure 5 shows another embodiment of a method 500 for recessing a filler within a plurality of openings formed in a patterned substrate. Similar to method 400 shown in FIG. 4, method 500 shown in FIG. 5 may generally begin by receiving (at step 510) a patterned substrate that includes openings. As described above, the openings may be formed within a multi-layer stack that includes a target material layer and one or more additional material layers that cover the target material layer, and the additional material layers are different from the target material layer.

[0063] At step 520, method 500 selectively deposits a grafting material within the openings such that the grafting material adheres to the target material layer without adhering to one or more additional material layers that cover the target material layer. In the embodiment shown in FIG. 5, the grafting material includes an acid generator.

[0064] After selectively depositing (at step 520) the grafting material, method 500 deposits (at step 530) a filler within the openings, and the filler is an acid-protected material. At step 540, method 500 operates an acid generator within the grafting material to generate and diffuse acid into the interior of the portion of the filler that surrounds the grafting material. Due to the diffusion of the acid, the portion of the filler is converted into an acid-deprotected material. At step 550, method 500 recesses the filler within the openings by removing, using a first solvent, a portion of the acid-protected material that covers the portion of the filler that includes the acid-deprotected material.

[0065] Note that one or more of the material layers illustrated and described herein can be formed using various deposition processes. For example, one or more depositions can be performed using chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), physical vapor deposition (PVD), atomic layer deposition (ALD), and / or other deposition processes. Further note that one or more of the material layers illustrated and described herein can be etched using various etching processes. For example, one or more etching processes can be performed using a plasma etching process, a discharge etching process, and / or other desired etching processes.

[0066] Various operating parameters can also be adjusted to control the various deposition and / or etching processes described herein. Examples of operating parameters include, but are not limited to, chamber temperature, chamber pressure, power (such as source / bias power), gas flow rate, gas type or chemical composition of the gas, and / or other operating variables of the process step. Modifications can also be implemented while still utilizing the techniques described herein.

[0067] Throughout this specification, the expression "one embodiment" or "an embodiment" means that the specific features, structures, materials, or characteristics described in connection with the embodiment are included in at least one embodiment of the present invention, but it is noted that this does not imply that they are present in all embodiments. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the present invention. Furthermore, the specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. Various additional layers and / or structures may be included in other embodiments, and / or the described features may be omitted.

[0068] As used herein, the term "substrate" means and includes a substrate or structure on which materials are formed. It will be understood that the substrate may include a single layer or multiple layers having within it a single material, multiple layers of different materials, regions of different materials or different structures, etc. These materials may include semiconductors, insulators, conductors, or combinations thereof. For example, the substrate may be a semiconductor substrate, a base semiconductor layer on a support structure, a metal electrode, or a semiconductor substrate on which one or more layers, structures or regions are formed. The substrate may be a conventional silicon substrate or other bulk substrate including a layer of semiconductive material. As used herein, the term "bulk substrate" includes not only silicon wafers, but also silicon-on-insulator (SOI) substrates such as silicon-on-sapphire ("SOS") substrates and silicon-on-glass ("SOG") substrates, epitaxial layers of silicon on a base semiconductor foundation, and other semiconductors or optoelectronic materials such as silicon germanium, germanium, gallium arsenide, gallium nitride, indium phosphide, etc. The substrate may or may not be doped.

[0069] Systems and methods for processing substrates are described in various embodiments. The substrate may include any material portion or structure of an element, particularly a semiconductor or other electronic element, and may be, for example, a base substrate structure such as a thin film, or a semiconductor substrate or layer on or covering the base substrate structure. Thus, the substrate is not intended to be limited to any particular base structure, patterned or unpatterned underlying or overlying layer, and is intended to include such layers or base structures and any combination of multiple layers and / or base structures.

[0070] Those skilled in the relevant art will understand that various embodiments can be implemented without one or more specific details, or using other alternative and / or additional methods, materials, or elements. In other instances, well-known structures, materials, or details of operations are not illustrated or described so as not to obscure aspects of various embodiments of the present invention. Similarly, for purposes of explanation, specific numbers, materials, and configurations are disclosed so that the present invention can be fully understood. Nevertheless, the present invention can be implemented without specific details. Further, it should be understood that the various embodiments shown in the figures are exemplary representations and are not necessarily drawn to scale.

[0071] Further variations and alternative embodiments of the systems and methods described herein will be apparent to those skilled in the art from the description herein. Accordingly, it will be recognized that the systems and methods described are not limited to these exemplary configurations. It should be understood that the forms of the systems and methods illustrated and described herein are to be regarded as exemplary embodiments. Various changes can be made to the implementation. Thus, although the present invention is described herein with reference to specific embodiments, various changes and modifications can be made without departing from the scope of the present invention. Accordingly, the present specification and drawings are exemplary rather than limiting in a restrictive sense, and such changes are intended to be included within the scope of the present invention. Further, any advantages, effects, or problem-solving solutions described herein with respect to specific embodiments are not intended to be construed as essential, required, or inherent features or elements of any or all of the claims.

Claims

1. A method of indenting a filler within an opening formed in a patterned substrate, comprising: receiving the patterned substrate including the opening, wherein the opening is formed within a multilayer stack including a target material layer and one or more additional material layers covering the target material layer, and the one or more additional material layers are different from the target material layer; selectively depositing the grafting material within the opening such that the grafting material adheres to the target material layer without adhering to the one or more additional material layers covering the target material layer, wherein the grafting material includes a solubility shift agent; depositing the filler within the opening; diffusing the solubility shift agent into an interior of a portion of the filler surrounding the grafting material, wherein due to the diffusion of the solubility shift agent, the portion of the filler becomes insoluble in a predetermined solvent; indent the filler within the opening using the predetermined solvent to remove a soluble portion of the filler while leaving the portion of the filler insoluble in the predetermined solvent within the opening.

2. The method of claim 1, wherein the predetermined solvent removes the soluble portion of the filler to a certain depth within the opening defined by the solubility shift agent and physical characteristics of the target material layer.

3. The method of claim 1, wherein the grafting material is selectively deposited on opposing sidewalls of the opening at a depth defined by the target material layer, and the solubility shift agent causes a solubility change reaction within a region radially spreading from the grafting material deposited on the opposing sidewalls to the portion of the filler to form a complete layer of insoluble material at the depth of the target material layer.

4. The method of claim 1, wherein the grafting material is selectively deposited within the opening by forming a self-assembled monolayer (SAM) on opposing sidewall surfaces of the target material layer, and the filler is an acid-protected resin.

5. The method of claim 4, wherein the SAM is functionalized by a photoacid generator (PAG) or a thermal acid generator (TAG).

6. The SAM is functionalized by a photoacid generator (PAG), and diffusing the solubility shift agent into the interior of the portion of the filler surrounding the grafting material includes: irradiating the PAG to generate an acid; Performing a baking process to diffuse the acid into the interior of the portion of the filler, wherein diffusing the acid includes diffusing the acid to convert the acid-protected resin in the portion of the filler into an acid-deprotected resin, the method according to claim 4. **Claim 7** the SAM is functionalized by a thermal acid generator (TAG), and diffusing the solubility shifter into the interior of the portion of the filler surrounding the graft material Performing a baking process to generate an acid and diffuse the acid into the interior of the portion of the filler, wherein diffusing the acid includes diffusing the acid to convert the acid-protected resin in the portion of the filler into an acid-deprotected resin, the method according to claim 4. **Claim 8** The method according to claim 1, wherein the predetermined solvent is an organic solvent. **Claim 9** After removing the soluble portion of the filler using the predetermined solvent, further denting the filler The method according to claim 1, including removing, from the opening, a portion of the filler that is insoluble in the predetermined solvent using an aqueous solvent. **Claim 10** A method of denting a filler within an opening formed in a patterned substrate, the method comprising: Receiving the patterned substrate including the opening, the opening being formed in a multi-layer stack including a target material layer and one or more additional material layers covering the target material layer, the one or more additional material layers being different from the target material layer; Selectively depositing the graft material within the opening such that the graft material adheres to the target material layer without adhering to one or more additional material layers covering the target material layer, the graft material including an acid generator; Depositing the filler within the opening, the filler being an acid-protected material; Activating the acid generator within the graft material to generate an acid and diffuse the acid into the interior of the portion of the filler surrounding the graft material, the portion of the filler being converted into an acid-deprotected material by the diffusion of the acid; Denting the filler within the opening using a first solvent to remove a portion of the acid-protected material covering the portion of the filler including the acid-deprotected material. **Claim 11** The method according to claim 10, wherein the graft material is selectively deposited on the opposing sidewalls of the opening at a depth defined by the target material layer, and the acid diffuses radially from the graft material deposited on the opposing sidewalls into the interior of the portion of the filler material to form a complete layer of the acid deprotection material at the depth of the target material layer.

12. The method according to claim 10, wherein the graft material is selectively deposited within the opening by forming a self-assembled monolayer (SAM) on the surface of the opposing sidewalls of the target material layer.

13. The method according to claim 12, wherein the head group of the SAM comprises thiol, carboxylic acid, phosphinic acid or silane.

14. The acid generator is a photoacid generator (PAG), and activating the acid generator comprises: irradiating the PAG to generate the acid; and performing a baking process to diffuse the acid into the interior of the portion of the filler material. The method according to claim 10.

15. The acid generator is a thermal acid generator (TAG), and activating the acid generator comprises generating the acid and performing a baking process to diffuse the acid into the interior of the portion of the filler material. The method according to claim 10.

16. The method according to claim 10, wherein diffusing the acid is localized in the region including the graft material.

17. The activation of the acid generator includes a baking process, and the diffusion length and profile of the acid diffusion depend on the composition of the acid generator, the composition of the filler material, the baking temperature, the baking time, and / or the molecular weight of the acid. The method according to claim 10.

18. The method according to claim 10, wherein the first solvent is an organic solvent.

19. After removing the portion of the acid-protected material covering the portion of the filler material containing the acid deprotection material using the first solvent, further denting the filler material includes removing the portion of the filler material containing the acid deprotection material using a second solvent. The method according to claim 10.

20. The method according to claim 19, wherein the second solvent is an aqueous solvent.

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