Diagonal deposition and etching processes

Abstract

A method for processing a substrate comprises the steps of: receiving a patterned photoresist formed on the substrate—the patterned photoresist defines initial openings, each of the initial openings including a first side and an opposite second side along a first direction—; preferentially depositing a mask material on a first side within the initial openings using an inclined deposition process performed at a first angle inclined from the first side; and removing a portion of the patterned photoresist using an inclined etching process performed at a second angle inclined from the second side—the remaining portion of the mask material and the patterned photoresist define final openings.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 195,757 filed June 2, 2021 and U.S. Full Application No. 17 / 735,800 filed May 3, 2022, which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a method for processing a substrate in general, and in particular to oblique deposition and etching processes in the embodiments. Background Technology

[0005] Fabricating structures on semiconductor wafers generally involves patterning a photoresist film by lithographic exposure, developing the photoresist film using various chemical developers to create a relief pattern, and then using an etching process to transfer the relief pattern defined by the resist film to one or more underlying layers. The semiconductor industry continues to advance electronic devices, which means that structures and features on wafers are continuously shrinking. Methods for reducing line widths in lithographic processes have historically involved using greater-NA optics, shorter exposure wavelengths, or interface media other than air (e.g., water immersion). As the resolution of conventional lithographic processes reached theoretical limits, manufacturers began to switch to double-patterning (DP) methods to overcome optical limitations.

[0006] In material processing methods (e.g., photolithography), creating patterned layers involves applying a thin layer of a radiation-sensitive material, such as a photoresist, to the upper surface of a substrate. This radiation-sensitive material is transformed into a patterned mask that can be used to etch or transfer a pattern into a base layer on the substrate. Patterning of the radiation-sensitive material generally involves exposure by a radiation source through a reticle (and associated optical instruments) onto the radiation-sensitive material, for example, using a photolithography system. After such exposure, the removal of the irradiated areas (in the case of a positive photoresist) or unirradiated areas (in the case of a negative resist) of the radiation-sensitive material may follow using a developing solvent. This mask layer may comprise a number of sublayers.

[0007] Conventional lithographic techniques for exposing patterns of radiation or light on a substrate have various challenges, such as limiting the size of exposed features and limiting the pitch or space between exposed features.

[0008] According to an embodiment of the present invention, a method for processing a substrate comprises the steps of: receiving a patterned photoresist formed on a substrate—the patterned photoresist defines initial openings, each of the initial openings includes a first side and an opposite second side along a first direction—; preferentially depositing a mask material on a first side within the initial openings using an inclined deposition process performed at a first angle inclined from the first side; and removing a portion of the patterned photoresist using an inclined etching process performed at a second angle inclined from the second side—the remaining portion of the mask material and the patterned photoresist define final openings.

[0009] According to an embodiment of the present invention, a method for processing a substrate comprises the steps of: forming initial recesses in a layer of organic material deposited on the substrate, wherein each initial recess has a rectangular shape having four sides; depositing a mask material in the initial recesses on the first side among the four sides using a first gradient deposition process; depositing a mask material in the initial recesses on the second side among the four sides using a second gradient deposition process, wherein the second side is opposite to the first side; and depositing a mask material in the initial recesses on the third side among the four sides using a third gradient deposition process, wherein the first gradient deposition process, the second gradient deposition process, and the third gradient deposition process are each performed at angles of incident inclined from the first side, the second side, and the third side. The method comprises the step of forming final recesses by removing a portion of the organic material using a gradient etching process—the gradient etching process is controlled to orient the etchants toward the fourth of four sides and is performed at an angle of incidence that is selective with respect to the mask material and inclined from the fourth side, the mask material remaining on the substrate and separating the final recesses.

[0010] According to an embodiment of the present invention, a method for processing a substrate comprises: a step of patterning a photoresist deposited on a substrate using a lithographic process—the patterned photoresist defines initial openings, and the initial openings have a first side and an opposite second side along a first direction—; a step of loading the substrate into a processing chamber; a step of performing a first gradient gas cluster ion beam (GCIB) process in the processing chamber to preferentially deposit a mask material within the initial openings on the first side; and a step of performing a second gradient gas cluster ion beam (GCIB) process in the processing chamber to form final openings by preferentially removing a portion of the photoresist—the portion of the photoresist is between the first side and the second side of the initial openings adjacent to each other in a second direction, and the mask material remains on the substrate and separates the final openings along the second direction. Brief explanation of the drawing

[0011] For a more complete understanding of the present invention and its advantages, the following description, together with the accompanying drawings, is now referred to. FIG. 1 illustrates a plan view of a substrate segment having general trenches or slot-shaped openings. FIGS. 2a through 2e illustrate cross-sectional and plan views of exemplary substrates during a manufacturing process including tip-to-tip critical dimension control at various stages according to various embodiments, FIG. 2a illustrates an incoming substrate including slotted openings defined by a pattern of photoresist, FIG. 2b illustrates a substrate after a slanted deposition step, FIG. 2c illustrates a substrate after a transverse etching step, FIG. 2d illustrates a substrate after a first pattern transfer etching, and FIG. 2e illustrates a substrate after a second pattern transfer etching. FIGS. 3a and 3b illustrate cross-sectional views of exemplary substrates during tip-to-tip critical dimension control according to various embodiments, FIG. 3a illustrates a substrate after a gradient deposition step, and FIG. 3b illustrates a substrate after an etching basque step. FIGS. 4a and 4b illustrate a cross-sectional view and a plan view of an exemplary substrate during a manufacturing process including tip-to-tip critical dimension control at various stages according to alternative embodiments, FIG. 4a illustrates a substrate after inclined deposition steps for three directions, and FIG. 4b illustrates a substrate after a transverse etching step. FIGS. 5a through 5d illustrate cross-sectional and plan views of exemplary substrates during a manufacturing process including tip-to-tip critical dimension control and scum removal at various stages according to different embodiments, FIG. 5a illustrates an incoming substrate including slotted openings defined by a pattern of photoresist and scum of photoresist in one of the slotted openings, FIG. 5b illustrates a substrate after first gradient deposition steps for two directions, FIG. 5c illustrates a substrate after a scum trimming step, and FIG. 5d illustrates a substrate after another gradient deposition step. FIGS. 6a through 6c illustrate exemplary process flow diagrams of a manufacturing process including tip-to-tip critical dimension control, FIG. 6a illustrates an example, FIG. 6b illustrates an alternative example, and FIG. 6c illustrates yet another example. Specific details for implementing the invention

[0012] This application relates to a method for processing a substrate, and more specifically, to controlling the distance between adjacent ends of two recesses / openings, referred to as the T2T (tip-to-tip) critical dimension (CD). One challenge in patterning semiconductor substrates is to precisely control the CDs of features fabricated on the substrate. CD control is particularly challenging at sub-resolution dimensions and relatively small dimensions (e.g., less than 100 nm), such as those patterned by extreme ultraviolet radiation lithography (EUVL). Processes requiring precise CD control involve T2T CD control with EUVL single exposure. Further scaling of middle-of-line (MOL) contacts and back-end-of-line (BEOL) interconnects requires reducing the T2T CD. However, as feature sizes decrease, this becomes increasingly difficult. For example, stochastic effects resulting from the random behavior of photons generally cause unpredictable defects and roughness in patterns, which increases T2T CD variation for the wafer. Because photon energies are high in EUV, T2T CD variation after a single EUVL exposure can be too large and lead to catastrophic device failure. Some available techniques, such as self-aligning block techniques, can reduce T2T CD variation, but at the expense of patterning cost and time. Therefore, simpler and more cost-effective T2T CD control processes may be required. Embodiments of the present application disclose methods for T2T CD control based on gradient deposition of etching mask material.Various embodiments may utilize gradient physical vapor deposition (PVD) tools, gas cluster ion beam (GCIB) tools, or similar tools. Techniques may also include directional trimming of photoresist relief patterns.

[0013] The methods described in this disclosure can advantageously reduce T2T CD variation by replacing the relief pattern of the photoresist with deposits formed on the sidewalls of the relief patterns. Oblique deposition enables precise thickness control of the deposits to be formed, thereby reducing the initial CD variation of the relief pattern. Various embodiments of the methods of this invention can advantageously improve various patterning processes, including those based on EUVL single exposure, by reducing dose requirements.

[0014] Hereinafter, an example of the tip-to-tip (T2T) critical dimension (CD) of slotted openings is first introduced in FIG. 1. Next, steps of T2T CD control using slant deposition are described according to various embodiments with reference to FIG. 2a through 2e. Then, a selective etch back step for the formed depositions is described with reference to FIG. 3a through 3b. Examples of slant deposition for more than one direction are described with reference to FIG. 4a through 4b and FIG. 5a through 5d. Exemplary process flow diagrams are illustrated in FIG. 6a through 6c. All drawings of the present disclosure are drawn for illustrative purposes only and are not drawn to a scale including aspect ratios of features.

[0015] FIG. 1 illustrates a plan view of a substrate segment having general trenches or slot-shaped openings.

[0016] In FIG. 1, for example, six slotted openings are illustrated. In this disclosure, the tip-to-tip (T2T) critical dimension (CD) refers to the distance between adjacent ends of two slotted openings as shown in FIG. 1. To prevent catastrophic device failure, it is essential to precisely control the T2T CD using minimal variation between the slotted openings. However, stochastic effects, particularly in EUV lithography, often exacerbate T2T CD variation when the number of photons irradiated per area is small. While this problem of T2T CD variation can be mitigated by increasing the dose of the lithographic exposure (and thus the number of photons per area), it is generally desirable to have a lower radiation dose for many manufacturing techniques in terms of throughput and process efficiency.

[0017] FIGS. 2a through 2e illustrate cross-sectional and top views of an exemplary substrate (200) during a manufacturing process including T2T CD control at various stages according to various embodiments, FIG. 2a illustrates an incoming substrate (200) including slot-shaped openings (250) defined by a pattern of photoresist (240).

[0018] In various embodiments, the substrate (200) may be part of a semiconductor device or may include a semiconductor device and may have undergone a number of processing steps following, for example, a conventional process. Accordingly, the substrate (200) may include layers of semiconductors useful in various microelectronics. For example, a semiconductor structure may include a substrate (100) on which various device regions are formed.

[0019] In one or more embodiments, the substrate (200) may be a silicon wafer or a silicon-on-insulator (SOI) wafer. In certain embodiments, the substrate (200) may include silicon germanium, silicon carbide, gallium arsenide, gallium nitride, and other compound semiconductors. In other embodiments, the substrate (200) includes heterogeneous layers, such as silicon germanium on silicon, gallium nitride on silicon, silicon carbon on silicon, or layers of silicon on a silicon or SOI substrate. In various embodiments, the substrate (200) is patterned or embedded in other components of a semiconductor device.

[0020] As illustrated in FIG. 2a, the substrate (200) may further include a base layer (205). In various embodiments, the base layer (205) may be a layer to be patterned to produce recessed features for middle-of-line (MOL) contacts or back-end-of-line (BEOL) interconnects. In various embodiments, the base layer (205) may be a dielectric layer comprising a silicon-based dielectric material having a low dielectric constant (i.e., low-k value), such as organosilicate glass (SiCOH), dense SiCOH, porous SiCOH, and other porous dielectric materials. The base layer (205) may be deposited using deposition techniques, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD), as well as other plasma processes, such as plasma-enhanced CVD (PECVD) and sputtering. In certain embodiments, wet deposition techniques such as spin-on processes may be used. The feature etched into the base layer (205) may be any suitable feature. For example, while the present disclosure describes "recesses" or "slot-shaped openings" with respect to the drawings of the present disclosure, it will be understood that other suitable features, including lines, holes, trenches, vias, and / or other suitable structures, may be formed on the semiconductor layer using the embodiments of the present disclosure (whether or not they are considered as "recesses").

[0021] A layer of hard mask (210) may be formed on the base layer (205). In various embodiments, the hard mask (210) may include titanium nitride, titanium, titanium oxide, tantalum, tungsten carbide, other tungsten-based compounds, ruthenium-based compounds, or aluminum-based compounds. The hard mask (210) may be deposited using suitable deposition techniques, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), as well as other plasma processes, such as plasma-enhanced CVD (PECVD), sputtering, and other processes. In various embodiments, the hard mask (210) may have a thickness of about 5 nm to about 50 nm.

[0022] As further illustrated in FIG. 2a, a three-layer stack may be formed on a hard mask (210). The three-layer stack may be used to create a pattern and transfer it to the hard mask (210) and then to a base layer (205). In various embodiments, the three-layer stack may include a bottom layer (220), an intermediate layer (230), and a photoresist (240). The bottom layer (220) may include carbon materials and may be formed via vapor deposition such as a spin-on process or CVD. The intermediate layer (230) may include silicon-based materials, including but not limited to SOG (spin-on glass), silicon carbide, silicon oxide, silicon oxycarbide, silicon oxynitride, silicon nitride, tin oxide, and BARC (bottom anti-reflective coating) films. The intermediate layer (230) may also be formed by vapor deposition such as a spin-on process or CVD.

[0023] The photoresist (240) of the three-layer stack may be formed and patterned to define slot-shaped openings (250) that provide an initial pattern for forming recess features in the layers below the patterned layer of the photoresist (240). In various embodiments, the photoresist (240) may be an extreme ultraviolet (EUV) resist and may be patterned by an EUV lithographic process. In other embodiments, the photoresist (240) may include a 248 nm resist, a 193 nm resist, a 157 nm resist, or an electron beam (EB)-sensitive resist. The photoresist may be a chemically amplified resist (CAR), a metal oxide resist (MOR), etc. In various embodiments, the photoresist (240) may be deposited on an intermediate layer (230) using a dry process or a wet process, for example, a spin coating technique. Afterward, the deposited photoresist (240) can be patterned by a suitable lithographic process. In one embodiment, the photoresist (240) has a thickness between 5 nm and 100 nm. Features to be patterned using the patterned photoresist (240) may have a desired critical dimension (CD) or width for the layers to be patterned.

[0024] In various embodiments, one or more of the slotted openings (250) have a rectangular shape having a length in the horizontal direction (e.g., x direction) and a width in a second direction perpendicular to the horizontal direction (e.g., y direction). Exemplary xy coordinates are illustrated in the plan view of FIG. 2a and are used to refer to the directions below. Similarly, exemplary xz coordinates are illustrated in the cross-sectional view of FIG. 2a. The slotted openings (250) are initially provided by a pattern of photoresist (240), and in certain embodiments, the pattern may have pitches enabled by EUV lithography. In one or more embodiments, the pitch in the y direction (p y) may be between 10 nm and 100 nm. In various embodiments, the length of each slotted opening (250) may be equal to or greater than the width of each slotted opening (250). Although all slotted openings (250) are illustrated in FIG. 2a to have the same dimensions (i.e., length and width), the shape and size of the slotted openings (250) may vary depending on the desired design for the interconnects to be manufactured. FIG. 2a also shows the tip-to-tip (T2T) critical dimension (CD) as the distance between the right end of one of the slotted openings (250) and the left end of the other slotted opening (250) adjacent to the right in the x direction. Thus, slotted openings (250) aligned in the x direction are separated by portions of photoresist (240) having a width of T2T CD. In one or more embodiments, the T2T CD may be between 1 nm and 100 nm. In various embodiments, as illustrated in the plan view of FIG. 2a, slot-shaped openings (250) may be arranged to form first lines (241) of the patterned photoresist in the x-direction, and the first lines (241) of the patterned photoresist are separated by second lines (242) of the photoresist. The cross-sectional view of FIG. 2a illustrates a view corresponding to a cross section at one of the first lines (241) of the patterned photoresist.

[0025] In one embodiment, the length (i.e., x-dimension) of each slotted opening (250) may be about 40 nm, and the 3σ (three standard deviations) of the initial T2T CD may be 5 nm or more. Such levels of variation in the T2T CD may be caused by a low-dose single EUVL exposure process and may be unacceptable for subsequent processes due to large edge placement error (EPE). Various embodiments of the methods of the present disclosure utilize gradient deposition to deposit an etching mask material replacing the patterned photoresist (240) and to redefine the recess patterns, which can advantageously reduce T2T CD variation.

[0026] FIG. 2b illustrates a cross-sectional view and a plan view of a substrate (200) after a slope deposition step.

[0027] In FIG. 2b, according to some embodiments, the etching mask material (260) may be deposited by a gradient deposition step only on one sidewall of each of the slotted openings (250). In the illustrated example, the gradient deposition step is performed from the left side (along the x-axis) indicated by the dashed arrow in FIG. 2b, consequently forming a layer of the etching mask material (260) on the right end of each of the slotted openings (250) (i.e., on the right sidewalls of the patterned photoresist (240)). In other embodiments, as further described in subsequent sections (e.g., FIG. 4a to 4b and FIG. 5a to 5b), the gradient deposition step may include one or more deposition and / or etching back processes from more than one direction to deposit the etching mask material (260) on two or three ends of each of the slotted openings (250).

[0028] Oblique deposition can be realized using a directional physical vapor deposition (PVD) tool or a gas cluster ion beam (GCIB) tool. In various embodiments, the etching mask material (260) can be deposited by oblique deposition at angles of incidence of 10 to 80 degrees with respect to the horizontal surface of the base layers (e.g., base layer (205)). The angle of incidence for oblique deposition can be determined according to the aspect ratio of the features (e.g., the ratio of the height to the width of the slotted openings (250)). Generally, a higher angle of incidence may be selected for features with a higher aspect ratio. In one embodiment, for example, when the slotted openings (250) have an aspect ratio of 1:1 (height:width), the optical angle of incidence may be greater than 45 degrees to enable proper deposition on the sidewall. In other embodiments, the width of the slotted openings (250) may be greater than the height, and an angle of incidence lower than 45 degrees may be selected to minimize deposition on the bottom of the slotted openings (250). The etching mask material (260) may be any suitable material that can be used as an etching mask during subsequent etching steps, such as pattern transfer etching processes. In various embodiments, the etching mask material (260) may include organic materials, oxides, nitrides, carbon, silicon, SiO, SiN, SiON, Sn, Sno, Ti, TiO, TiN, Ta, TaN, Al, Alo, Zr, ZrO, Hf, Hfo, W, or WC. In certain embodiments, the etching mask material (260) may have a thickness of 0.1 nm to 5.0 nm. The use of vapor deposition techniques enables precise thickness control, thereby enabling uniform deposition between slotted openings (250). In one or more embodiments, the 3σ (three standard deviations) of the thickness of the etching mask material (260) may be 3 nm or less, which may be substantially smaller than the variations in T2T CD between the slotted openings (250).

[0029] The gradient deposition process may include a particle beam process. In certain embodiments, one or more GCIB processes may be advantageously used for gradient deposition. For example, a first GCIB may be formed from a first process gas containing a precursor for an etching mask material (260) in a processing chamber, and a substrate (200) may be exposed to the first GCIB at a first angle of incidence between 10 and 80 degrees so that the first GCIB collides on the right sidewalls of the patterned photoresist (240).

[0030] FIG. 2c illustrates a cross-sectional view and a plan view of a substrate (200) after a transverse etching step.

[0031] In FIG. 2c, the transverse etching step removes a portion of the patterned photoresist (240). The transverse etching step may be performed using a gas cluster ion beam (GCIB) process, or anisotropic plasma etching, such as a reactive ion etching (RIE) process. Process conditions may be selected so that the etching of the photoresist (240) is selective with respect to the etching mask material (260). In the illustrated example, the transverse etching step is performed from the right side indicated by the dashed arrow in FIG. 2c (i.e., along the x-axis, but from the side opposite to the oblique deposition). In various embodiments, the transverse etching step may be performed at angles of incidence of 10 to 80 degrees with respect to the horizontal surface of the base layers (e.g., base layer (205)). During the transverse etching step, the removal of the patterned photoresist (240) may occur only from one side of the slotted openings (250) (e.g., from the right side in FIG. 2c). Additionally, vertical etching may also be minimized due to the angle of the transverse etching. As a result, each of the slotted openings (250) may extend toward a side not covered by the etching mask material (260) (e.g., to the left side in FIG. 2c). In various embodiments, the entire portion of the first lines (241) of the patterned photoresist (i.e., the photoresist (240) adjacent to the etching mask material (260) in the x direction) may be removed, and the second lines (242) of the photoresist may remain. Accordingly, the extended slotted openings (250) can be separated in the x direction only by the etching mask materials (260) and in the y direction only by the remaining photoresist (240). In other embodiments, a portion of the photoresist (240) may remain on the etching mask material (260) in the x direction.After the steps of oblique deposition and transverse etching, the initial pattern provided by the photoresist (240) is updated into a final pattern comprising the remainder of the photoresist (240) and the deposited etching mask material (260). The final tip-to-tip (T2T) critical dimension (CD) of the final pattern may have a smaller variation than the variation of the T2T CD of the initial pattern. In various embodiments, the final pattern may be used to further pattern base layers (e.g., intermediate layer (230) and bottom layer (220)) in subsequent processes.

[0032] The oblique etching process may include a particle beam process. In certain embodiments, similar to oblique deposition, one or more GCIB processes may be advantageously used for transverse etching. For example, a second GCIB may be formed from a second process gas containing an etchant in a processing chamber, and the substrate (200) may be exposed to the second GCIB at a second angle of incidence between 10 and 80 degrees so that the second GCIB strikes the left sidewalls of the patterned photoresist (240) to be etched. Using two different GCIB processes in the same processing chamber for oblique deposition and transverse etching may advantageously improve process efficiency. In one or more embodiments, the methods may include the step of switching from the first GCIB process to the second GCIB process by replacing the first process gas with the second process gas and switching from the first angle to the second angle.

[0033] FIG. 2d illustrates a cross-sectional view and a plan view of a substrate (200) after the first pattern transfer etching, and FIG. 2e illustrates a cross-sectional view and a plan view of a substrate (200) after the second pattern transfer etching.

[0034] One or more anisotropic etching processes may be performed to pattern the layers of a three-layer stack (i.e., the intermediate layer (230) and the bottom layer (220)) according to the final pattern provided from the above process including gradient deposition. In FIG. 2d, as illustrated in FIG. 2e, the final pattern of the slotted openings (250) is transferred to the intermediate layer (230) by a first transfer etching and further transferred to the bottom layer (220) by a second transfer etching. In various embodiments, one or more of the pattern transfer etching processes may be timed or stopped at a base (optional) etching stop layer. In certain embodiments, the patterning of the intermediate layer (230) and the bottom layer (220) may be achieved in a single continuous etching process. Once the layers of the three-layer stack are patterned, another pattern transfer may be performed to further transfer the pattern to a hard mask (210). After patterning the hard mask (210), the remaining portions of the photoresist (240), intermediate layer (230), bottom layer (220), and / or etching mask material (260) may be removed. Finally, the patterned hard mask (210) may be used as an etching mask for patterning the base layer (205). In various embodiments, one or more of the anisotropic etching processes may include plasma etching processes, such as reactive ion etching (RIE) processes, or combinations of etching processes. After the second pattern transfer etching, the hard mask (210) may be exposed, and subsequent processes for manufacturing a semiconductor device may be performed. In some embodiments, the patterns may be useful for manufacturing middle-of-line (MOL) contacts or back-end-of-line (BEOL) interconnects. Therefore, subsequent processes may include diffusion barrier layer deposition, metallization, and flattening.In one or more embodiments, the deposition of the diffusion barrier layer may be performed using deposition processes such as sputtering, chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD), as well as other plasma processes such as plasma enhanced CVD (PECVD), metallization may be performed by electroplating following the deposition of a seed layer of metal (e.g., copper) using sputtering or physical vapor deposition (PVD) techniques, and planarization may be performed using a chemical mechanical planarization (CMP) method.

[0035] FIGS. 3a and 3b illustrate cross-sectional views of an exemplary substrate (200) during tip-to-tip critical dimension control according to alternative embodiments. FIG. 3a illustrates a cross-sectional view of the substrate (200) after a slope deposition step that causes some deposition on the top surfaces of the patterned photoresist (240). FIG. 3b illustrates a cross-sectional view of the substrate (200) after an optional etching back step. The substrate (200) may have substantially the same layer structure as the previous embodiments described above, and thus details will not be repeated.

[0036] In certain embodiments, after gradient deposition (e.g., FIG. 2b) and before transverse etching of the photoresist (240) (e.g., FIG. 2c), an optional etching back may be performed to trim a portion of the deposited etching mask material (260). Deposition of the etching mask material (260) during the gradient deposition step may occur on the top surfaces of the patterned photoresist (240) as illustrated in FIG. 3a. Since such top deposits of the etching mask material (260) may interfere with the subsequent transverse etching of the photoresist (240), it may be desirable to remove the top deposits of the etching mask material (260) before transverse etching. This optional etching back may be performed using one or more anisotropic etching processes, such as plasma etching processes like reactive ion etching (RIE) processes. In one or more embodiments, gas cluster ion beam (GCIB) processes may be used. In various embodiments, depending on the critical dimension (CD) of the target pattern for the intermediate layer (230), this optional etching back may be omitted because the remaining etching mask material (260) and the photoresist (240) can both collectively function as an etching mask for patterning the intermediate layer (230). Instead of performing the optional etching back, the etching conditions during patterning the intermediate layer (230) may be adjusted accordingly.

[0037] FIGS. 4a and 4b illustrate a cross-sectional view and a plan view of an exemplary substrate (200) during a manufacturing process including tip-to-tip critical dimension control at various stages according to alternative embodiments. FIG. 4a illustrates a cross-sectional view and a plan view of the substrate (200) after inclined deposition steps performed in three directions. FIG. 4b illustrates a cross-sectional view and a plan view of the substrate (200) after a transverse etching step. The substrate (200) may have substantially the same layer structure as the previous embodiments described above, and thus details will not be repeated.

[0038] Previous embodiments describe a gradient deposition (e.g., FIG. 2b) to form a deposition of etching mask material (260) on only one end of the slotted openings (250), but in other embodiments, the etching mask material (260) may be deposited on two or three ends of the slotted openings (250). To make this possible, one or more gradient deposition steps may be performed. In the example illustrated in FIG. 4a, three ends of the slotted openings (250) are coated with etching mask material (260), and these are the top and bottom ends (i.e., two sidewalls of the photoresist (240) along the x-direction) and the right end (i.e., one sidewall of the photoresist (240) along the y-direction). The etching mask material (260) deposited on the upper and lower ends can advantageously improve the directionality of the subsequent transverse etching step to etch a portion of the photoresist (240) by preventing the slotted openings (250) from widening in the y-direction (Fig. 4b). After the transverse etching step, subsequent processes may follow the steps described in previous embodiments (e.g., Figs. 2d to 2e). In various embodiments, various processing sequences of multiple oblique deposition and subsequent etching steps may be applied.

[0039] FIGS. 5a through 5d illustrate cross-sectional and plan views of an exemplary substrate (200) during a manufacturing process including tip-to-tip (T2T) critical dimension (CD) control and scum removal at various stages according to alternative embodiments. FIG. 5a illustrates a cross-sectional and plan view of an incoming substrate (200). The substrate (200) may have substantially the same layer structure as the previous embodiments described above, and thus details will not be repeated.

[0040] In FIG. 5a, the substrate (200) may further contain scum (540) of photoresist, which is unwanted residue remaining within one of the slot-shaped openings (250) after the previous step. The scum (540) of photoresist may be formed, for example, due to incomplete development of the photoresist. Methods of gradient deposition and etching may be used to clean up the scum (540) of photoresist during the process for T2T CD control. It should be noted that scum of material other than photoresist (240) may also be removed based on the method.

[0041] FIG. 5b illustrates a cross-sectional view and a plan view of a substrate (200) after inclined deposition steps for two directions.

[0042] In FIG. 5b, a first oblique deposition of the etching mask material (260) can be performed on the top and bottom ends of the slotted openings (250). Unlike previous embodiments, in this stage, neither the left nor the right end of the slotted openings (250) is covered with the etching mask material (260), which may be beneficial for minimizing the deposition of the etching mask material (260) on the scum (540) of the photoresist. Because the length of the slotted openings (250) may be greater than the width (i.e., the dimension is larger in the x direction), the shadowing effect during oblique deposition may be greater in the y direction than in the x direction. Accordingly, slope deposition for the two ends in the x direction can be performed first at this stage, whereas another slope deposition step for the third end of the slotted openings (250) can be performed later, for example, after the scum trimming step (Fig. 5c) (e.g., Fig. 5d).

[0043] FIG. 5c illustrates a cross-sectional view and a plan view of a substrate (200) after a scum trimming step.

[0044] The scum trimming step may be performed using one or more etching processes, such as plasma etching processes like reactive ion etching (RIE) processes. In various embodiments, during the scum trimming step, a portion of the patterned photoresist (240) may also be removed in addition to the scum of the photoresist (540), and as a result, the slotted openings (250) are extended in the x-direction. This extension in the x-direction corresponds to a reduction in the tip-to-tip (T2T) critical dimension (CD). Thus, the scum trimming step may need to be precisely timed to avoid punching through the walls due to excessive removal of the photoresist. Meanwhile, the etching mask material (260) deposited on the top and bottom ends of the slotted openings (250) may be a protective layer to prevent the slotted openings (250) from widening in the y-direction.

[0045] FIG. 5d illustrates a cross-sectional view and a plan view of the substrate (200) after another slope deposition step.

[0046] After the scum trimming step, another inclined deposition step may be performed to deposit an etching mask material (260) on the third end of the slotted openings (250) (e.g., the right end of the slotted openings (250)). Subsequently, similar to previous embodiments, a transverse etching step (e.g., FIG. 2c), pattern transfer etching steps (e.g., FIG. 2d to FIG. 2e), and other processes may follow.

[0047] FIGS. 6a through 6c illustrate exemplary process flow diagrams of a manufacturing process including tip-to-tip critical dimension control, FIG. 6a illustrates an example, FIG. 6b illustrates an alternative example, and FIG. 6c illustrates yet another example. The process flow may lead to the figures discussed above ( FIGS. 2a through 2e, FIGS. 4a through 4b, and FIGS. 5a through 5d), and thus will not be described again.

[0048] In FIG. 6a, the process flow (60) begins with a step of patterning a photoresist deposited on a substrate using a lithographic process to define initial openings (Block 610, FIG. 2a). In certain embodiments, prior to patterning the photoresist, the process flow (60) may include a step of forming a base layer on the substrate (Block 602), followed by a step of depositing a photoresist on the base layer (Block 604). After patterning the photoresist, a mask material may be deposited within the initial openings on the side using a gradient deposition process (Block 620, FIG. 2b). In one embodiment, prior to the gradient deposition process (Block 620), T2T CD variation for the initial openings on the substrate may be optionally measured (Block 614), and a process recipe for gradient deposition, a gradient etching process, or both may be determined accordingly. In certain embodiments, after gradient deposition, if the mask material covers a portion of the top surfaces of the photoresist, an optional etching back may be performed to trim the mask material (Block 625, FIG. 3a). Then, the process may proceed to a step of forming final openings by removing a portion of the photoresist using a gradient etching process (Block 630, FIG. 2c). Subsequently, the final openings may be extended vertically into the base layer by etching the base layer using the mask material as an etching mask (Block 635, FIG. 2d to 2e).

[0049] In FIG. 6b, the process flow (62) begins with the step of forming initial recesses in a layer of organic material deposited on a substrate (Block 612, FIG. 2a). Next, a series of gradient depositions may be performed for three directions (Fig. 4a) as follows: a first gradient deposition process for depositing mask material within initial recesses on a first side (Block 621); a second gradient deposition process for depositing mask material within initial recesses on a second side (Block 622); and a third gradient deposition process for depositing mask material within initial recesses on a third side (Block 624). In certain embodiments, between the second gradient deposition process and the third gradient deposition process, optional etching may be performed, for example, to remove residues containing organic material within the initial recesses (Block 623, FIG. 5c). After a series of slope depositions, final recesses can be formed by removing a portion of the organic material (Block 632, FIG. 4b and FIG. 5d).

[0050] In FIG. 6c, the process flow (64) begins with a step of patterning the photoresist deposited on the substrate using a lithographic process to define initial slot-shaped openings (Block 610, FIG. 2a). Next, the substrate can be loaded into a processing chamber (Block 615). Inside the processing chamber, a first oblique gas cluster ion beam (GCIB) process can be performed to deposit mask material within the initial slot-shaped openings on the sides (Block 626, FIG. 2b). Then, a second oblique GCIB process can be performed in the processing chamber to form final slot-shaped openings by removing a portion of the photoresist (Block 636, FIG. 2c).

[0051] Exemplary embodiments of the present invention are summarized herein. Other embodiments may also be understood from the claims set forth herein as well as from the entire specification.

[0052] Example 1. A method for processing a substrate comprises the steps of: receiving a patterned photoresist formed on the substrate—the patterned photoresist defines initial openings, each of the initial openings including a first side and an opposite second side along a first direction—; preferentially depositing a mask material on the first side within the initial openings using a slanted deposition process performed at a first angle inclined from the first side; and removing a portion of the patterned photoresist using a slanted etching process performed at a second angle inclined from the second side—the remaining portion of the mask material and the patterned photoresist define final openings.

[0053] Example 2. In the method of Example 1, the step of receiving a patterned photoresist formed on a substrate includes forming a base layer on the substrate; depositing a photoresist on the base layer; and patterning the photoresist using a lithographic process.

[0054] Example 3. In the method of either Example 1 or Example 2, the lithographic process includes a single exposure of EUV (extreme UV).

[0055] Example 4. In the method of one of Examples 1 to 3, the tip-to-tip critical dimensions (T2T CD) of the final apertures are smaller than the optical resolution of a single EUV exposure.

[0056] Example 5. In the method of one of Examples 1 to 4, the method further includes the step of vertically extending final openings into the base layer by etching the base layer using a mask material as an etching mask.

[0057] Example 6. In the method of one of Examples 1 to 5, the method further includes the step of performing an anisotropic etching process to remove a portion of the mask material that is not on the first side before removing a portion of the patterned photoresist.

[0058] Example 7. In the method of one of Examples 1 to 6, the gradient deposition process or gradient etching process includes a gas cluster ion beam (GCIB) process.

[0059] Example 8. In the method of one of Examples 1 through 7, the tip-to-tip critical dimensions (T2T CD) of all initial openings of the substrate have a first standard deviation, and the T2T CDs of all final openings of the substrate have a second standard deviation, and the first standard deviation is greater than the second standard deviation.

[0060] Example 9. In the method of one of Examples 1 to 8, the tip-to-tip critical dimensions (T2T CD) of the final openings are between 0.1 nm and 5 nm, and the 3σ value of the T2T CDs of the final slotted openings is less than 3 nm.

[0061] Example 10. In the method of one of Examples 1 to 9, the photoresist comprises an organic photoresist, and the mask material comprises a dielectric material.

[0062] Example 11. In the method of one of Examples 1 to 10, the initial openings further comprise a third side and an opposite fourth side along a second direction perpendicular to the first direction, and the method further comprises the step of depositing mask material within the initial openings on the third side or the fourth side using a different inclined deposition process, wherein the different inclined deposition process is performed at a third angle inclined from the third side or a fourth angle inclined from the fourth side.

[0063] Example 12. A method for processing a substrate comprises the steps of: forming initial recesses in a layer of organic material deposited on the substrate—each initial recess having a rectangular shape with four sides—; depositing a mask material within the initial recesses on the first side of the four sides using a first gradient deposition process; depositing a mask material within the initial recesses on the second side of the four sides using a second gradient deposition process—the second side being opposite to the first side—; and depositing a mask material within the initial recesses on the third side of the four sides using a third gradient deposition process—the first gradient deposition process, the second gradient deposition process, and the third gradient deposition process are each performed at angles of incidence inclined from the first side, the second side, and the third side, respectively—; The method comprises the step of forming final recesses by removing a portion of the organic material using a gradient etching process—the gradient etching process is controlled to orient the etchants toward the fourth of four sides and is performed at an angle of incidence that is selective with respect to the mask material and inclined from the fourth side, the mask material remaining on the substrate and separating the final recesses.

[0064] Example 13. In the method of Example 12, the initial recesses contain a residue of organic material at the bottom of the initial recesses, and the method further includes the step of removing the residue using an etching process after depositing mask material in the initial recesses on the first and second sides and before depositing mask material in the initial recesses on the third side.

[0065] Example 14. In the method of one of Example 12 or Example 13, the etching process includes a selective plasma etching process for the mask material, and the mask material provides protection of the first and second sides during the etching process.

[0066] Example 15. In the method of one of Examples 12 to 14, the first slope deposition process, the second slope deposition process, and the third slope deposition process are performed sequentially in a processing chamber, and the method further includes the step of changing the direction of deposition of the mask material to switch from the first slope deposition process to the second slope deposition process and to switch from the second slope deposition process to the third slope deposition process.

[0067] Example 16. A method for processing a substrate comprises the steps of: patterning a photoresist deposited on a substrate using a lithographic process—the patterned photoresist defines initial openings, and the initial openings have a first side along a first direction and a second side opposite to it—; loading the substrate into a processing chamber; performing a first oblique gas cluster ion beam (GCIB) process within the processing chamber to preferentially deposit a mask material within the initial openings on the first side; and performing a second oblique gas cluster ion beam (GCIB) process within the processing chamber to form final openings by preferentially removing a portion of the photoresist—the portion of the photoresist is between the first side and the second side of the initial openings adjacent to each other in the second direction, and the mask material remains on the substrate and separates the final openings along the second direction.

[0068] Example 17. The method of Example 16 further comprises the steps of: forming a base layer on a substrate before patterning the photoresist; depositing the photoresist on the base layer; and, after removing a portion of the photoresist, etching the base layer using a mask material as an etching mask to vertically extend final openings into the base layer.

[0069] Example 18. In the method of one of Example 16 or Example 17, the first inclined GCIB process comprises forming a first GCIB from a first process gas containing a precursor for a mask material in a processing chamber; and exposing a substrate to the first GCIB at a first angle so that the first GCIB collides on a first side, and the second inclined GCIB process comprises forming a second GCIB from a second process gas in a processing chamber; and exposing a substrate to the second GCIB at a second angle so that the second GCIB collides on a second side.

[0070] Example 19. In the method of one of Examples 16 to 18, the method further includes the step of switching from a first GCIB process to a second GCIB process by replacing the first process gas with a second process gas and switching from a first angle to a second angle.

[0071] Example 20. In the method of one of Examples 16 to 19, the tip-to-tip critical dimensions (T2T CD) of the initial openings have a first standard deviation, and the T2T CDs of the final openings have a second standard deviation, and the first standard deviation is greater than the second standard deviation.

[0072] Although the present invention has been described with reference to exemplary embodiments, this description is not intended to be interpreted in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present invention, will be apparent to those skilled in the art upon reference to this description. Accordingly, the appended claims are intended to include any such modifications or embodiments.

Claims

Claim 1 A method for processing a substrate, comprising the steps of: receiving a patterned photoresist formed on the substrate, wherein the patterned photoresist defines initial openings, and each of the initial openings includes a first side and an opposite second side along a first direction; preferentially depositing a mask material on the first side within the initial openings using an oblique deposition process performed at a first angle inclined from the first side; and removing a portion of the patterned photoresist using an oblique etching process performed at a second angle inclined from the opposite second side, wherein the remaining portion of the mask material and the patterned photoresist define additional openings. Claim 2 A method for processing a substrate according to claim 1, wherein the step of receiving the patterned photoresist formed on the substrate comprises: forming an underlying layer on the substrate; depositing a photoresist on the underlying layer; and patterning the photoresist using a lithographic process. Claim 3 A method for processing a substrate according to paragraph 2, wherein the lithographic process comprises a single EUV (extreme UV) exposure. Claim 4 A method for processing a substrate according to paragraph 3, wherein the tip-to-tip critical dimensions (T2T CD) of the additional openings are smaller than the optical resolution of the EUV single exposure. Claim 5 A method for processing a substrate according to claim 2, wherein the additional openings are final openings, and the method further comprises the step of extending the final openings vertically into the base layer by etching the base layer using the mask material as an etching mask. Claim 6 A method for processing a substrate according to claim 1, further comprising the step of performing an anisotropic etching process to remove a portion of the mask material not on the first side before removing a portion of the patterned photoresist. Claim 7 A method for processing a substrate according to claim 6, wherein the initial openings comprise a residue of the photoresist at the bottom of the initial openings, and the method further comprises the step of removing the residue using an etching process after depositing the mask material within the initial openings and before removing a portion of the patterned photoresist. Claim 8 A method for processing a substrate according to claim 1, wherein the gradient deposition process or the gradient etching process comprises a particle beam process. Claim 9 A method for processing a substrate according to claim 1, wherein the tip-to-tip critical dimensions (T2T CD) of all initial openings of the substrate have a first standard deviation, and the T2T CDs of all additional openings of the substrate have a second standard deviation, and the first standard deviation is greater than the second standard deviation. Claim 10 A method for processing a substrate according to claim 1, wherein the tip-to-tip critical dimensions (T2T CD) of the additional openings are between 0.1 nm and 5 nm, and the 3σ value of the T2T CDs of the additional openings is less than 3 nm. Claim 11 A method for processing a substrate according to claim 1, wherein the patterned photoresist comprises an organic photoresist and the mask material comprises a dielectric material. Claim 12 A method for processing a substrate according to claim 1, wherein the initial openings further comprise a third side and an opposite fourth side along a second direction perpendicular to the first direction, and the method further comprises the step of depositing the mask material within the initial openings on the third side or the opposite fourth side using a different inclined deposition process, wherein the different inclined deposition process is performed at a third angle inclined from the third side or a fourth angle inclined from the opposite fourth side. Claim 13 A method for processing a substrate according to claim 12, wherein the initial openings do not have a residue of the patterned photoresist at the bottom of the initial openings. Claim 14 A method for processing a substrate, comprising the steps of: forming initial recesses in a layer of organic material deposited on the substrate, wherein each of the initial recesses has a rectangular shape having four sides; depositing a mask material within the initial recesses on the first side among the four sides using a first gradient deposition process; depositing the mask material within the initial recesses on the second side among the four sides using a second gradient deposition process, wherein the second side is opposite to the first side; and depositing the mask material within the initial recesses on the third side among the four sides using a third gradient deposition process, wherein the first gradient deposition process, the second gradient deposition process, and the third gradient deposition process are each performed at angles of incident inclined from the first side, the second side, and the third side. A method for processing a substrate, comprising the step of forming final recesses by removing a portion of the organic material using a gradient etching process—wherein the gradient etching process is controlled to orient the etchants toward a fourth side of the four sides and is performed selectively with respect to the mask material and at an angle of incidence inclined from the fourth side, wherein the mask material remains on the substrate and separates the final recesses. Claim 15 A method for processing a substrate according to claim 14, wherein the initial recesses comprise a residue of the organic material at the bottom of the initial recesses, and the method further comprises the step of removing the residue using an etching process after depositing the mask material in the initial recesses on the first side and the second side and before depositing the mask material in the initial recesses on the third side. Claim 16 A method for processing a substrate according to claim 15, wherein the etching process comprises a selective plasma etching process for the mask material, and the mask material protects the first side and the second side during the etching process. Claim 17 A method for processing a substrate according to claim 14, wherein the first slope deposition process, the second slope deposition process, and the third slope deposition process are performed sequentially in a processing chamber, and the method further comprises the step of changing the direction of deposition of the mask material to switch from the first slope deposition process to the second slope deposition process and to switch from the second slope deposition process to the third slope deposition process. Claim 18 A method for processing a substrate, comprising: a step of patterning a photoresist deposited on the substrate using a lithographic process, wherein the patterned photoresist defines initial openings, said initial openings have a first side and an opposite second side along a first direction; a step of loading the substrate into a processing chamber; a step of performing a first gradient particle beam process within the processing chamber to preferentially deposit a mask material within the initial openings on the first side; and a step of performing a second gradient particle beam process within the processing chamber to form additional openings by preferentially removing a portion of the photoresist, said portion of the photoresist is between the first side and the opposite second side of the initial openings adjacent to each other in a second direction, and said mask material remains on the substrate and separates the additional openings along the second direction. Claim 19 A method for processing a substrate according to claim 18, wherein the additional openings are final openings, and the method further comprises the steps of: forming a base layer on the substrate before patterning the photoresist; depositing the photoresist on the base layer; and extending the final openings vertically into the base layer by etching the base layer using the mask material as an etching mask after removing a portion of the photoresist. Claim 20 A method for processing a substrate according to claim 18, wherein the first inclined particle beam process comprises forming a first particle beam from a first process gas containing a precursor for the mask material in the processing chamber; and exposing the substrate to the first particle beam at a first angle such that the first particle beam strikes the first side, and the second inclined particle beam process comprises forming a second particle beam from a second process gas in the processing chamber; and exposing the substrate to the second particle beam at a second angle such that the second particle beam strikes the opposite second side. Claim 21 A method for processing a substrate according to claim 20, further comprising the step of switching from the first inclined particle beam process to the second inclined particle beam process by replacing the first process gas with the second process gas and switching from the first angle to the second angle. Claim 22 A method for processing a substrate according to claim 18, wherein the tip-to-tip critical dimensions (T2T CD) of the initial openings have a first standard deviation, the T2T CDs of the additional openings have a second standard deviation, and the first standard deviation is greater than the second standard deviation. Claim 23 A method for processing a substrate according to claim 18, wherein the initial openings further comprise a third side and an opposite fourth side along a second direction, the second direction being perpendicular to the first direction, and the method further comprises the step of performing a third inclined particle beam process to preferentially deposit the mask material in the initial openings on the third side within the processing chamber after performing the first inclined particle beam process and before performing the second inclined particle beam process; and the step of performing a fourth inclined particle beam process to preferentially deposit the mask material in the initial openings on the opposite fourth side within the processing chamber after performing the third inclined particle beam process and before performing the second inclined particle beam process. Claim 24 A method for processing a substrate according to claim 23, wherein the initial openings comprise a residue of the photoresist at the bottom of the initial openings, and the method further comprises the step of removing the residue using an etching process after depositing the mask material within the initial openings. Claim 25 A method for processing a substrate according to claim 18, further comprising the step of performing an anisotropic etching process to remove a portion of the mask material not on the first side before performing the second inclined particle beam process.

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