Oblique deposition and etch processes

Abstract

A method of processing a substrate includes receiving a patterned photoresist formed on the substrate, the patterned photoresist defining an initial opening, each of the initial openings including a first side along a first direction and an opposing second side; preferentially depositing a masking material on the first side within the initial opening using an oblique deposition process performed at a first angle oblique to the first side; and removing a portion of the patterned photoresist using an oblique etching process performed at a second angle oblique to the second side, the remaining portion of the masking material and the patterned photoresist defining a final opening.

Description

[Technical Field]

[0001] This application claims the rights of U.S. Provisional Application No. 63 / 195,757, filed June 2, 2021, and U.S. Non-Provisional Application No. 17 / 735,800, filed May 3, 2022, which are incorporated herein by reference.

[0002] The present invention summarizes a method for processing a substrate, and in a particular embodiment, relates to an oblique deposition and etching process. [Previous Technology]

[0003] Fabricating structures on semiconductor wafers typically involves patterning a photoresist film using lithography, developing the photoresist film using various chemical developers to create a relief pattern, and then transferring the relief pattern defined by the photoresist film to one or more underlying layers using an etching process. The semiconductor industry continues to advance electronic devices, meaning that structures and features on wafers continue to shrink. Methods for reducing linewidth in lithography processes have historically involved using larger nano-optical elements, shorter exposure wavelengths, or non-air interface media (e.g., water immersion). As the resolution of conventional lithography processes approaches theoretical limits, manufacturers have begun to turn to double-patterning (DP) methods to overcome optical limitations.

[0004] In a material processing method (e.g., lithography), creating a patterned layer involves applying a thin layer of radiation-sensitive material (e.g., photoresist) to the upper surface of a substrate. This radiation-sensitive material is transformed into a patterned mask, which can be used to etch or transfer a pattern into a lower layer on the substrate. Patterning of the radiation-sensitive material typically involves exposing the material to radiation from a radiation source via a reticle (and associated optics) using, for example, a photolithography system. After such exposure, the irradiated areas of the radiation-sensitive material can then be removed (e.g., in the case of positive photoresist) using a developing solvent, or (e.g., in the case of negative photoresist) the unirradiated areas can be removed. The mask layer may include multiple sublayers.

[0005] Conventional lithography techniques for exposing patterns of radiation or light onto a substrate present numerous challenges that limit the size of the exposed features and the pitch or spacing between them. [Summary of the Invention]

[0006] According to an embodiment of the present invention, a method of processing a substrate includes: receiving a patterned photoresist formed on the substrate, the patterned photoresist defining an initial opening, each of the initial openings including a first side along a first direction and an opposing second side; preferentially depositing a masking material on the first side within the initial opening using an oblique deposition process, the oblique deposition process being performed at a first angle inclined to the first side; and removing a portion of the patterned photoresist using an oblique etching process, the oblique etching process being performed at a second angle inclined to the second side, the remaining portion of the masking material and the patterned photoresist defining a final opening.

[0007] According to an embodiment of the present invention, a method of processing a substrate includes forming initial recesses in an organic material layer deposited on the substrate, each of the initial recesses having a rectangular shape and having four sides; depositing a masking material in the initial recesses on a first side of the four sides using a first oblique deposition process; depositing a masking material in the initial recesses on a second side of the four sides, the second side being opposite to the first side, using a second oblique deposition process; depositing a masking material in the initial recesses on a third side of the four sides using a third oblique deposition process, wherein the first, second, and third oblique deposition processes are performed at multiple incident angles oblique to the first, second, and third sides, respectively; and removing a portion of the organic material by using an oblique etching process to form a final recess, the oblique etching process being controlled to guide an etchant to the fourth side of the four sides, being selective for the masking material, and the oblique etching process being performed at an incident angle oblique to the fourth side, the masking material remaining above the substrate and separating the final recess.

[0008] According to an embodiment of the present invention, a method of processing a substrate includes patterning photoresist deposited on the substrate using a photolithography process, the patterned photoresist defining an initial opening having a first side along a first direction and an opposing second side; loading the substrate into a processing chamber; performing a first oblique gas cluster ion beam (GCIB) process in the processing chamber to preferentially deposit a masking material within the initial opening on the first side; and performing a second oblique gas cluster ion beam (GCIB) process in the processing chamber to form a final opening by preferentially removing a portion of the photoresist located between the first and second sides of the initial opening that are adjacent to each other along a second direction, the masking material remaining on the substrate and spaced apart from the final opening along the second direction.

Implementation Method

[0016] 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 tip-to-tip (CCD) critical dimension. A challenge in semiconductor substrate patterning is precisely controlling the CD of features fabricated on the substrate. CD control is particularly challenging for sub-resolution dimensions and relatively small dimensions (e.g., less than 100 nm), such as those patterned using extreme ultraviolet radiation lithography (EUVL). Processes requiring precise CD control include T2T CD control using a single EUVL exposure. Further scaling of middle-of-line (MOL) contacts and back-end-of-line (BEOL) interconnects necessitates reducing the T2T CD. However, this becomes increasingly challenging as feature sizes become smaller. For example, stochastic effects arising from the random behavior of photons often lead to unpredictable defects and roughness in the pattern, increasing T2T CD variability on the wafer. Because of the high photon energy in EUV, T2T CD variability after a single EUVL exposure can be too large and may result in fatal device defects. Some available techniques, such as self-aligned blocking techniques, can reduce T2T CD variability, but at the cost of patterning costs and time. Therefore, a simpler, more cost-effective T2T CD control process may be needed. Embodiments of this application disclose a T2T CD control method based on oblique deposition of an etch mask material. Numerous embodiments may utilize oblique physical vapor deposition (PVD) tools, gas cluster ion beam (GCIB) tools, or similar tools. Techniques may also include directional trimming of the photoresist relief pattern.

[0017] The method described in this disclosure advantageously reduces T2T CD differences by replacing the photoresist relief pattern with a deposit formed on the sidewalls of the relief pattern. Oblique deposition allows for precise thickness control of the deposit to be formed, thereby reducing the initial CD difference of the relief pattern. Many embodiments of the method described herein advantageously improve various patterning processes, including EUVL single-exposure patterning processes, by reducing dose requirements.

[0018] Below, an example of the end-to-end (T2T) critical dimension (CD) of the slit opening is first introduced in Figure 1. Next, according to various embodiments, the steps for controlling the T2T CD using oblique deposition are described with reference to Figures 2A-2E. Then, an optional etch-back step for the formed deposit is described with reference to Figures 3A-3B. Embodiments for oblique deposition in more than one direction are described with reference to Figures 4A-4B and 5A-5D. Illustrative process flow diagrams are illustrated in Figures 6A-6C. All figures in this disclosure (including aspect ratios of features) are for illustrative purposes only and are not drawn to scale.

[0019] Figure 1 shows a top view of a portion of a substrate with a universal groove or slit opening.

[0020] In Figure 1, for example, six slit openings are shown. In this disclosure, the end-to-end (T2T) critical dimension (CD) refers to the distance between adjacent ends of two slit openings as shown in Figure 1. Precisely controlling the T2T CD between slit openings to have minimal variation is crucial for preventing fatal device defects. However, when the number of photons irradiated per area is low, stochastic effects often exacerbate T2T CD variation, particularly in EUV lithography. This problem of T2T CD variation can be mitigated by increasing the dose of lithography exposure (and thus increasing the number of photons per area), but many manufacturing techniques generally prefer lower doses of radiation for yield and process efficiency.

[0021] Figures 2A-2E show cross-sectional and top views of an exemplary substrate 200 at various stages of a manufacturing process according to various embodiments, the manufacturing process including T2T CD control, wherein Figure 2A shows the substrate 200, which includes a slit opening 250 defined by a pattern of photoresist 240.

[0022] In many embodiments, substrate 200 may be part of or include a semiconductor device, and may be processed in a plurality of steps, for example, after a known process. Therefore, substrate 200 may include a semiconductor layer for various microelectronic devices. For example, a semiconductor structure may include substrate 100 in which various device regions are formed.

[0023] In one or more embodiments, substrate 200 may be a silicon wafer or a silicon-on-insulator (SOI) wafer. In some embodiments, substrate 200 may include silicon germanium, silicon carbide, gallium arsenide, gallium nitride, and other compound semiconductors. In other embodiments, substrate 200 includes a heterolayer, such as silicon germanium on silicon, gallium nitride on silicon, silicon carbon on silicon, and a silicon layer on a silicon or SOI substrate. In many embodiments, substrate 200 is patterned or embedded in other elements of a semiconductor device.

[0024] As shown in FIG. 2A, the substrate 200 may further include a lower layer 205. In many embodiments, the lower layer 205 may be a cover layer to be patterned to create recessed features for middle-of-line (MOL) contacts or back-of-line (BEOL) interconnects. In many embodiments, the lower layer 205 may be a dielectric layer, including a silicon-based dielectric material having a low dielectric constant (i.e., a low k-value), such as organosilicon glass (SiCOH), dense SiCOH, porous SiCOH, and other porous dielectric materials. The lower layer 205 may be deposited using deposition techniques such as vapor deposition, other plasma processes, and sputtering. Vapor deposition includes chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD), and plasma processes include plasma-enhanced CVD (PECVD). In some embodiments, wet deposition techniques, such as spin coating, may be used. Features etched into the lower layer 205 may be any suitable features. For example, although this disclosure primarily describes "recesses" or "slit openings" with respect to the accompanying drawings, it will be appreciated that other suitable features, including (whether or not considered "recesses") lines, holes, grooves, through-holes, and / or other suitable structures, can be formed in the semiconductor layer using embodiments of this disclosure.

[0025] A hard mask 210 may be formed on top of the lower layer 205. In many 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. Suitable deposition techniques may be used to deposit the hard mask 210, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), and other plasma processes such as plasma-enhanced CVD (PECVD), sputtering, and other processes. In many embodiments, the hard mask 210 may have a thickness of about 5 nm to about 50 nm.

[0026] As further shown in FIG. 2A, a three-layer stack can be formed over the hard mask 210. The three-layer stack can be used to generate patterns and transfer the patterns to the hard mask 210, and then to the lower layer 205. In many 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 a carbon material and may be formed by spin coating or, for example, vapor deposition using CVD. The intermediate layer 230 may include a silicon-based material, including but not limited to spin-on glass (SOG), silicon carbide, silicon oxide, silicon carbide, silicon oxynitride, silicon nitride, tin oxide, and a bottom anti-reflective coating (BARC) film. The intermediate layer 230 may also be formed by spin coating or, for example, vapor deposition using CVD.

[0027] A three-layer stack of photoresist 240 can be formed and patterned to define a slit opening 250, which provides an initial pattern to form recessed features in a layer beneath the patterned layer of the photoresist 240. In many embodiments, the photoresist 240 may be an extreme ultraviolet (EUV) photoresist and patterned by an EUV lithography process. In other embodiments, the photoresist 240 may include a 248nm photoresist, a 193nm photoresist, a 157nm photoresist, or an electron beam (EB) sensitive photoresist. The photoresist may be a chemically amplified resist (CAR), a metal oxide resist (MOR), etc. In many embodiments, the photoresist 240 may be deposited on the intermediate layer 230 using a dry or wet process, such as spin coating. The deposited photoresist 240 may then be patterned using a suitable lithography process. In one embodiment, the photoresist 240 has a thickness between 5nm and 100nm. The feature to be patterned using the patterned photoresist 240 may have the desired critical dimension (CD) or width for the overlay to be patterned.

[0028] In many embodiments, one or more slit openings 250 have a rectangular shape, having a length in a horizontal direction (e.g., the x-direction) and a width in a second direction (e.g., the y-direction) perpendicular to the horizontal direction. An illustrative xy coordinate system is illustrated in the top view of FIG. 2A and is used for reference to the following directions. Similarly, an illustrative xz coordinate system is illustrated in the cross-sectional view of FIG. 2A. The slit openings 250 are initially provided by a pattern of photoresist 240, and in some embodiments, the pattern may have a spacing achieved by EUV lithography. In one or more embodiments, the spacing py in the y-direction may be between 10 nm and 100 nm. In many embodiments, the length of each slit opening 250 may be equal to or greater than the width of each slit opening 250. Although all slit openings 250 are shown in FIG. 2A as having the same dimensions (i.e., length and width), the shape and size of the slit openings 250 may vary depending on the desired design of the interconnect to be manufactured. Figure 2A further shows the end-to-end (T2T) critical dimension (CD) as the distance between the right end of a slit opening 250 and the left end of another slit opening 250 adjacent to the right side of the first slit opening 250 along the x-direction. Therefore, the x-direction-aligned slit openings 250 are partially separated by photoresist 240 having a width of T2T CD. In one or more embodiments, T2T CD may be between 1 nm and 100 nm. In many embodiments, as shown in the top view of Figure 2A, the slit opening 250 may be configured such that it forms a first arrangement of patterned photoresist 241 along the x-direction, wherein the first arrangement of patterned photoresist 241 is separated by a second arrangement of photoresist 242. The cross-sectional view of Figure 2A shows a cross-sectional view corresponding to one of the first arrangement of patterned photoresist 241.

[0029] In one embodiment, the length (i.e., x-dimension) of each slit opening 250 may be approximately 40 nm, and the initial T2T CD 3σ (three standard deviations) may be 5 nm or greater. Such a level of T2T CD variation 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). Many embodiments of the method disclosed herein utilize oblique deposition to deposit the etch mask material, which replaces the patterned photoresist 240 and redefines the recess pattern, which can advantageously reduce T2T CD variation.

[0030] Figure 2B shows a cross-sectional view and a top view of the substrate 200 after the oblique deposition step.

[0031] In FIG. 2B, according to some embodiments, the etch mask material 260 may be deposited only on one sidewall of each slit opening 250 by an oblique deposition step. In the exemplary example, as indicated by the dashed arrow in FIG. 2B (along the x-axis), the oblique deposition step is performed from the left, thus forming a cladding layer of the etch mask material layer 260 on the right end of each slit opening 250 (i.e., on the right sidewall of the patterned photoresist 240). In other embodiments, as further described herein (e.g., FIG. 4A-4B and 5A-5B), the oblique deposition step may include one or more deposition and / or etch-back processes performed from more than one direction to deposit the etch mask material 260 on two or three ends of each slit opening 250.

[0032] Oblique deposition can be achieved using directional physical vapor deposition (PVD) tools or gas cluster ion beam (GCIB) tools. In many embodiments, the etch mask material 260 can be deposited by oblique deposition at an incident angle of 10 to 80 degrees relative to the horizontal surface of the underlying layer (e.g., underlying layer 205). The incident angle for oblique deposition can be determined based on the aspect ratio of the feature (e.g., the ratio of the height to the width of the slit opening 250). Generally, a higher incident angle can be selected for features with a higher aspect ratio. In one embodiment, for example, where the slit opening 250 has an aspect ratio of 1:1 (height:width), the light incident angle can be 45 degrees or higher to achieve appropriate deposition on the sidewalls. In other embodiments, the width of the slit opening 250 can be greater than its height, and an incident angle lower than 45 degrees can be selected to minimize deposition on the bottom of the slit opening 250. The etching mask material 260 can be any suitable material that can be used as an etching mask during subsequent etching steps (e.g., pattern transfer etching processes). In many 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 some embodiments, the etching mask material 260 may have thicknesses of 0.1 nm and 5.0 nm. The use of vapor deposition technology allows for precise thickness control, thereby achieving uniform deposition between the slit 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 can be significantly smaller than the T2T CD difference between the slit openings 250.

[0033] In some embodiments, one or more GCIB processes may be advantageously used for oblique deposition. For example, in a processing chamber, the first GCIB may be formed by a first process gas comprising a precursor for etching the masking material 260, and the substrate 200 may be exposed to the first GCIB at a first incident angle between 10 and 80 degrees, such that the first GCIB impacts the right sidewall of the patterned photoresist 240.

[0034] Figure 2C shows a cross-sectional view and a top view of the substrate 200 after the transverse directional etching step.

[0035] In FIG. 2C, a lateral etch step removes a portion of the patterned photoresist 240. The lateral etch step can be performed using a gas cluster ion beam (GCIB) process or anisotropic plasma etching, such as a reactive ion etching (RIE) process. Process conditions can be selected such that the etching of the photoresist 240 is selective with respect to the etching mask material 260. In the exemplary embodiment, as indicated by the dashed arrow in FIG. 2C, the lateral etch step is performed from the right side (i.e., along the x-axis, but from the opposite side of the oblique deposition). In many embodiments, the lateral etch step can be performed at an incident angle of 10 to 80 degrees relative to the horizontal surface of the underlying layer (e.g., underlying layer 205). During the lateral etch step, the removal of the patterned photoresist 240 can occur only from one side of the slit opening 250 (e.g., from the right side in FIG. 2C). Furthermore, due to the angle of the lateral etch, etching in the vertical direction can also be minimized. Therefore, each slit opening 250 may extend to the side not covered by the etch mask material 260 (e.g., extending to the left side in FIG. 2C). In many embodiments, a whole portion of the patterned photoresist 241 of the first arrangement (i.e., the photoresist 240 adjacent to the etch mask material 260 in the x-direction) may be removed, and the photoresist 242 of the second arrangement may be retained. Thus, the extended slit opening 250 may be separated only by the etch mask material 260 in the x-direction and by the other photoresist 240 in the y-direction. In other embodiments, a portion of the photoresist 240 may remain on the etch mask material 260 in the x-direction. After the oblique deposition and lateral directional etching steps, the initial pattern provided by the photoresist 240 is updated to a final pattern comprising the remaining portion of the photoresist 240 and the deposited etch mask material 260. The difference in the final end-to-end (T2T) critical dimension (CD) of the final pattern may be smaller than the difference in T2T CD of the initial pattern. In many embodiments, the final pattern can be further used in subsequent processes to pattern underlying layers (e.g., intermediate layer 230 and bottom layer 220).

[0036] In some embodiments, similar to oblique deposition, one or more GCIB processes can be advantageously used for lateral directional etching. For example, in a processing chamber, a second GCIB can be formed by a second process gas comprising an etchant, and the substrate 200 can be exposed to the second GCIB at a second incident angle between 10 and 80 degrees, such that the second GCIB impacts the left side wall of the patterned photoresist 240 to be etched. Using two different GCIB processes for oblique deposition and lateral directional etching in the same processing chamber can advantageously improve process efficiency. In one or more embodiments, the method may include 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.

[0037] FIG2D shows a cross-sectional view and a top view of the substrate 200 after the first pattern transfer etching, and FIG2E shows a cross-sectional view and a top view of the substrate 200 after the second pattern transfer etching.

[0038] Based on the final pattern provided by the above-described process (including oblique deposition), one or more anisotropic etching processes can be performed to pattern the overlays of the stacked layers (i.e., the intermediate layer 230 and the bottom layer 220). In FIG. 2D, the final pattern of the slit opening 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, as shown in FIG. 2E. In many embodiments, one or more pattern transfer etching processes can be timed or stopped at the lower etch stop layer (optionally). In some embodiments, the patterning of the intermediate layer 230 and the bottom layer 220 can be achieved in a continuous, single etching process. Once the three-layer stacked overlay is patterned, another pattern transfer can be performed to further transfer the pattern to the hard mask 210. After patterning the hard mask 210, the remainder of the photoresist 240, the intermediate layer 230, the bottom layer 220, and / or the etch mask material 260 can be removed. Finally, the patterned hard mask 210 can be used as an etching mask to pattern the underlying layer 205. In many embodiments, one or more 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 can be exposed, and subsequent processes can be performed to fabricate a semiconductor device. In some embodiments, the pattern can be used to fabricate middle-line (MOL) contacts or back-end-line (BEOL) interconnects. Therefore, subsequent processes may include diffusion barrier layer deposition, metallization, and planarization. In one or more embodiments, diffusion barrier layer deposition can be performed using deposition processes such as sputtering, vapor deposition, and other plasma processes, including chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD). Other plasma processes include plasma-enhanced CVD (PECVD). Metallization can be performed by seed layer deposition of a metal (e.g., copper) followed by electroplating, wherein the seed layer deposition uses sputtering or physical vapor deposition (PVD) techniques and planarization can be performed using a chemical mechanical planarization (CMP) method.

[0039] Figures 3A and 3B show cross-sectional views of an exemplary substrate 200 during end-to-end critical dimension control according to an alternative embodiment. Figure 3A shows a cross-sectional view of the substrate 200 after an oblique deposition step that results in some deposition on the top surface of the patterned photoresist 240. Figure 3B shows a cross-sectional view of the substrate 200 after an optional etch-back step. The substrate 200 may have substantially the same layer structure as in the foregoing embodiments, and therefore details will not be repeated.

[0040] In some embodiments, an optional etch-back process may be performed after oblique deposition (e.g., FIG. 2B) and before lateral etching of the photoresist 240 (e.g., FIG. 2C) to trim a portion of the deposited etch mask material 260. During the oblique deposition step, the deposition of the etch mask material 260 may occur on the top surface of the patterned photoresist 240, as shown in FIG. 3A. Since this top deposit of the etch mask material 260 may hinder subsequent lateral etching of the photoresist 240, it is desirable to remove the top deposit of the etch mask material 260 before lateral etching. This optional etch-back process may be performed using one or more anisotropic etching processes, for example, plasma etching processes such as reactive ion etching (RIE) processes. In one or more embodiments, a gas cluster ion beam (GCIB) process may be used. In many embodiments, depending on the critical dimension (CD) of the target pattern of the intermediate layer 230, this optional etch-back can be skipped because other etch mask materials 260 and photoresist 240 can be used together as an etch mask to pattern the intermediate layer 230. Instead of performing the optional etch-back, the etch conditions during the patterning of the intermediate layer 230 can be adjusted accordingly.

[0041] Figures 4A and 4B show cross-sectional and top views of an exemplary substrate 200 during various stages of a manufacturing process according to an alternative embodiment, including end-to-end critical dimension control. Figure 4A shows a cross-sectional and top view of the substrate 200 after an oblique deposition step performed in three directions. Figure 4B shows a cross-sectional and top view of the substrate 200 after a lateral etch step. The substrate 200 may have substantially the same layer structure as in the foregoing embodiments, and therefore details will not be repeated.

[0042] Although the oblique deposition described in the previous embodiments forms an etch mask material 260 deposit only at one end of the slit opening 250 (e.g., FIG. 2B), in other embodiments, the etch mask material 260 may be deposited at two or three ends of the slit opening 250. For this purpose, one or more oblique deposition steps may be performed. In the example shown in FIG. 4A, the etch mask material 260 is coated at the three ends of the slit opening 250, namely the top and bottom ends (i.e., the two sidewalls of the photoresist 240 along the x-direction) and the right end (i.e., the sidewall of the photoresist 240 along the y-direction). By preventing the slit opening 250 from widening in the y-direction (FIG. 4B), the etch mask material 260 deposited at the top and bottom ends can advantageously improve the directionality of the subsequent lateral etching step used to etch the portion of the photoresist 240. After the lateral etching step, subsequent processes may follow the steps described in the previous embodiments (e.g., FIG. 2D-2E). In many embodiments, various processing sequences of oblique deposition and subsequent etching steps can be applied.

[0043] Figures 5A-5D show cross-sectional and top views of an exemplary substrate 200 at various stages of a manufacturing process according to other embodiments, including end-to-end (T2T) critical dimension (CD) control and residue removal. Figure 5A shows a cross-sectional and top view of the incoming substrate 200. The substrate 200 may have substantially the same layer structure as in the foregoing embodiments, and therefore details will not be repeated.

[0044] In FIG. 5A, the substrate 200 may further include residue of photoresist 540, which is an undesirable residue remaining in one of the slit openings 250 after the previous step. For example, the residue of photoresist 540 may be formed due to incomplete development of the photoresist. During the process for T2T CD control, the residue of photoresist 540 can be removed using oblique deposition and etching methods. It should be noted that material residues other than photoresist 240 can also be removed using this method.

[0045] Figure 5B shows a cross-sectional view and a top view of the substrate 200 after the oblique deposition steps in two directions.

[0046] In FIG. 5B, the first oblique deposition of the etch mask material 260 can be performed on the top and bottom ends of the slit opening 250. Unlike the previous embodiment, at this stage, neither the left nor right end of the slit opening 250 is covered with the etch mask material 260, which may help to minimize the deposition of the etch mask material 260 on the photoresist 540 residue. Since the length of the slit opening 250 can be greater than its width (i.e., a larger dimension in the x direction), the shading effect during oblique deposition can be greater in the y direction than in the x direction. Therefore, at this stage, oblique deposition can be performed first on both ends in the x direction, and then, for example, after the residue trimming step (FIG. 5C), another oblique deposition step can be performed on the third end of the slit opening 250 (e.g., FIG. 5D).

[0047] Figure 5C shows a cross-sectional view and a top view of the substrate 200 after the residue trimming step.

[0048] One or more etching processes can be used to perform the residue trimming step, for example, a plasma etching process such as reactive ion etching (RIE). In many embodiments, during the residue trimming step, in addition to the residue of photoresist 540, a portion of the patterned photoresist 240 may be removed, causing the slit opening 250 to extend in the x-direction. This extension in the x-direction corresponds to a reduction in the end-to-end (T2T) critical dimension (CD). Therefore, the residue trimming step may require precise timing to avoid wall penetration due to excessive removal of photoresist. On the other hand, the etch masking material 260 deposited at the top and bottom of the slit opening 250 may serve as a protective layer to prevent the slit opening 250 from widening in the y-direction.

[0049] Figure 5D shows a cross-sectional view and a top view of the substrate 200 after another oblique deposition step.

[0050] After the residue trimming step, another oblique deposition step may be performed to deposit the etch mask material 260 on the third end of the slit opening 250 (e.g., the right end of the slit opening 250). Subsequently, similar to the previous embodiments, a lateral etching step (e.g., FIG. 2C), a pattern transfer etching step (e.g., FIG. 2D-2E), and other processes may be performed.

[0051] Figures 6A-6C show exemplary process flow diagrams of a manufacturing process that includes end-to-end critical dimension control, wherein Figure 6A shows one embodiment, Figure 6B shows an alternative embodiment, and Figure 6C shows yet another embodiment. The process flow can follow the figures discussed above (Figures 2A-2E, 4A-4B, and 5A-5D), and therefore will not be described again.

[0052] In FIG. 6A, process flow 60 begins by patterning photoresist deposited on a substrate using a lithography process to define an initial opening (block 610, FIG. 2A). In some embodiments, prior to patterning the photoresist, process flow 60 may include forming a lower layer on the substrate (block 602) and then depositing photoresist on the lower layer (block 604). After patterning the photoresist, a masking material may be deposited within the initial opening on one side using an angled deposition process (block 620, FIG. 2B). In one embodiment, optionally prior to the angled deposition process (block 620), the T2T CD difference may be measured for the initial opening on the substrate (block 614), and the process formulation for angled deposition, angled etching, or both may be determined accordingly. In some embodiments, after angled deposition, if the masking material covers a portion of the top surface of the photoresist, an optional etch-back process may be performed to trim the masking material (block 625, FIG. 3A). Then, by removing a portion of the photoresist using an oblique etching process, the process can continue to form the final opening (block 630, FIG. 2C). Subsequently, by using a masking material as an etching mask to etch the underlying layer, the final opening can extend vertically into the underlying layer (block 635, FIG. 2D~2E).

[0053] In FIG. 6B, process flow 62 begins by forming an initial recess in an organic material layer deposited over the substrate (block 612, FIG. 2A). Next, a series of oblique depositions are performed in three directions (FIG. 4A) as follows: a first oblique deposition process to deposit a masking material within the initial recess on the first side (block 621); a second oblique deposition process to deposit the masking material within the initial recess on the second side (block 622); and a third oblique deposition process to deposit the masking material within the initial recess on the third side (block 624). In some embodiments, an optional etching process may be performed between the second and third oblique deposition processes to remove residues, such as organic material within the initial recess (block 623, FIG. 5C). After this series of oblique depositions, a final recess (block 632, FIG. 4B and 5D) is formed by removing a portion of the organic material.

[0054] In Figure 6C, process flow 64 begins by patterning photoresist deposited on the substrate using a lithography process to define an initial slit opening (block 610, Figure 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 masking material within the initial slit opening on one side (block 626, Figure 2B). Then, a second oblique GCIB process can be performed in the processing chamber to form the final slit opening by removing a portion of the photoresist (block 636, Figure 2C).

[0055] This document summarizes exemplary embodiments of the invention. Other embodiments may also be understood from the entire specification and the scope of the patent applications filed herein.

[0056] Example 1. A method of processing a substrate includes: receiving a patterned photoresist formed on a substrate, the patterned photoresist defining an initial opening, each of the initial opening including a first side along a first direction and an opposing second side; preferentially depositing a masking material on the first side within the initial opening using an oblique deposition process, the oblique deposition process being performed at a first angle oblique to the first side; and removing a portion of the patterned photoresist using an oblique etching process, the oblique etching process being performed at a second angle oblique to the second side, the masking material and a remaining portion of the patterned photoresist defining a final opening.

[0057] Example 2. The method of processing a substrate as in Example 1, wherein receiving the patterned photoresist formed on the substrate includes: forming a lower layer on the substrate; depositing a photoresist on the lower layer; and patterning the photoresist using a photolithography process.

[0058] Example 3. A method for processing a substrate as in Example 1 or 2, wherein the lithography process includes extreme ultraviolet (EUV) single exposure.

[0059] Example 4. A method of processing a substrate as in one of Examples 1 to 3, wherein the end-to-end critical dimension (T2T CD) of the final opening is less than the optical resolution of a single EUV exposure.

[0060] Example 5. The method of processing a substrate as in any of Examples 1 to 4 further includes: etching the underlying layer by using the masking material as an etching mask, thereby extending the final opening vertically into the underlying layer.

[0061] Example 6. The method of processing a substrate as in any of Examples 1 to 5 further includes: performing an anisotropic etching process to remove a portion of the masking material that is not on the first side before removing the portion of the patterned photoresist.

[0062] Example 7. A method for processing a substrate as described in any of Examples 1 to 6, wherein the oblique deposition process or the oblique etching process includes a gas cluster ion beam (GCIB) process.

[0063] Example 8. A method of processing a substrate as in any of Examples 1 to 7, wherein the end-to-end critical dimension (T2T CD) of all the initial openings of the substrate has a first standard deviation, wherein the T2T CD of all the final openings of the substrate has a second standard deviation, and wherein the first standard deviation is greater than the second standard deviation.

[0064] Example 9. A method of processing a substrate as in one of Examples 1 to 8, wherein the end-to-end critical dimension (T2T CD) of the final opening is between 0.1 nm and 5 nm, and wherein the 3σ value of the T2T CD of the final slit opening is less than 3 nm.

[0065] Example 10. A method of processing a substrate as in any of Examples 1 to 9, wherein the photoresist includes an organic photoresist and the masking material includes a dielectric material.

[0066] Example 11. A method for processing a substrate as described in any of Examples 1 to 10, wherein the initial opening further includes a third side along a second direction and an opposing fourth side, the second direction being perpendicular to the first direction, the method for processing the substrate further includes: depositing the masking material in the initial opening on the third side or the fourth side using another oblique deposition process, the other oblique deposition process being performed at a third angle inclined to the third side or at a fourth angle inclined to the fourth side.

[0067] Example 12. A method of processing a substrate includes: forming initial recesses in an organic material layer deposited on a substrate, each of the initial recesses having a rectangular shape and having four sides; depositing a masking material in the initial recess on a first side of the four sides using a first oblique deposition process; depositing the masking material in the initial recess on a second side of the four sides using a second oblique deposition process, the second side being opposite to the first side; and depositing the masking material in the initial recess on a third side of the four sides using a third oblique deposition process, wherein the first, second, and third oblique deposition processes are used to deposit the masking material in the initial recess on a third side of the four sides. The second and third oblique deposition processes are performed at multiple incident angles oblique to the first, second, and third sides, respectively; and a portion of the organic material is removed by using an oblique etching process to form the final recess, the oblique etching process being controlled to guide the etchant to a fourth side of the four sides, the oblique etching process being selective relative to the masking material, and the oblique etching process being performed at an incident angle oblique to the fourth side, the masking material remaining above the substrate and separating the final recess.

[0068] Example 13. A method of processing a substrate as in Example 12, wherein the initial recess includes a residue of the organic material at a bottom of the initial recess, and the method of processing the substrate further includes: after depositing the masking material in the initial recess on the first side and the second side, and before depositing the masking material in the initial recess on the third side, removing the residue using an etching process.

[0069] Example 14. A method of processing a substrate as in Example 12 or 13, wherein the etching process includes a plasma etching process selectively applied to a masking material, wherein the masking material provides protection for the first side and the second side during the etching process.

[0070] Example 15. A method for processing a substrate as described in any of Examples 12 to 14, wherein the first oblique deposition process, the second oblique deposition process, and the third oblique deposition process are performed continuously in a processing chamber, and the method for processing a substrate further includes: changing the direction of deposition of the masking material to switch from the first oblique deposition process to the second oblique deposition process, and switching from the second oblique deposition process to the third oblique deposition process.

[0071] Example 16. A method of processing a substrate includes: patterning a photoresist deposited on a substrate using a photolithography process, the patterned photoresist defining an initial opening having a first side along a first direction and an opposing second side; loading the substrate into a processing chamber; performing a first oblique gas cluster ion beam (GCIB) process in the processing chamber to preferentially deposit a masking material within the initial opening on the first side; and performing a second oblique gas cluster ion beam (GCIB) process in the processing chamber to form a final opening by preferentially removing a portion of the photoresist located between the first side and the second side of the initial opening that are adjacent to each other along a second direction, the masking material remaining on the substrate and spaced apart from the final opening along the second direction.

[0072] Example 17. The method of processing a substrate as in Example 16 further includes: forming a lower layer on the substrate before patterning the photoresist; depositing the photoresist on the lower layer; and after removing the portion of the photoresist, etching the lower layer by using the masking material as an etching mask, thereby extending the final opening vertically into the lower layer.

[0073] Example 18. A method for processing a substrate as in Example 16 or 17, wherein the first GCIB process includes: forming a first GCIB in the processing chamber by a first process gas, the first process gas including a precursor for the masking material; and exposing the substrate to the first GCIB at a first angle such that the first GCIB impacts the first side; and wherein the second GCIB process includes: forming a second GCIB in the processing chamber by a second process gas; and exposing the substrate to the second GCIB at a second angle such that the second GCIB impacts the second side.

[0074] Example 19. The method of processing a substrate as described in any of Examples 16 to 18 further includes: 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.

[0075] Example 20. A method of processing a substrate as in one of Examples 16 to 19, wherein the end-to-end critical dimension (T2T CD) of the initial opening has a first standard deviation, wherein the end-to-end critical dimension (T2T CD) of the final opening has a second standard deviation, and wherein the first standard deviation is greater than the second standard deviation.

[0076] Although the present invention has been described with reference to illustrative embodiments, this description is not intended to be limiting. Those skilled in the art will recognize numerous modifications and combinations of the illustrative embodiments and other embodiments of the invention by referring to the description. Therefore, the appended claims cover any such modifications or embodiments. [Simplified Explanation of the Diagram]

[0009] To gain a more complete understanding of the present invention and its advantages, the following description is provided in conjunction with the accompanying drawings, wherein:

[0010] Figure 1 shows a top view of a portion of a substrate with a general groove or slit opening.

[0011] Figures 2A-2E show cross-sectional and top views of exemplary substrates at various stages of a manufacturing process according to various embodiments, the manufacturing process including end-to-end critical dimension control, wherein Figure 2A shows an incoming substrate including a slit opening defined by a photoresist pattern, Figure 2B shows a substrate after an oblique deposition step, Figure 2C shows a substrate after a lateral etch step, Figure 2D shows a substrate after a first pattern transfer etching, and Figure 2E shows a substrate after a second pattern transfer etching.

[0012] Figures 3A and 3B show cross-sectional views of an exemplary substrate according to various embodiments, the substrate being in the process of end-to-end critical dimension control, wherein Figure 3A shows the substrate after the oblique deposition step, and Figure 3B shows the substrate after the etch-back step.

[0013] Figures 4A and 4B show a cross-sectional and top view of an exemplary substrate at various stages of a manufacturing process according to an alternative embodiment, the manufacturing process including end-to-end critical dimension control, wherein Figure 4A shows the substrate after a three-direction oblique deposition step, and Figure 4B shows the substrate after a lateral directional etching step.

[0014] Figures 5A-5D show cross-sectional and top views of exemplary substrates at various stages of a manufacturing process according to other embodiments, including end-to-end critical dimension control and scum removal. Figure 5A shows an incoming substrate including a slit opening defined by a photoresist pattern and photoresist residue in one of the slit openings. Figure 5B shows a substrate after a first oblique deposition step in two directions. Figure 5C shows a substrate after a scum trimming step. Figure 5D shows a substrate after another oblique deposition step.

[0015] Figures 6A-6C show exemplary process flow diagrams of a manufacturing process that includes end-to-end critical dimension control, wherein Figure 6A shows one embodiment, Figure 6B shows an alternative embodiment, and Figure 6C shows yet another embodiment.

Claims

1. A method for processing a substrate, comprising: A patterned photoresist formed on the substrate is received, the patterned photoresist defining an initial opening, each of the initial openings including a first side along a first direction and an opposing second side; a masking material is preferentially deposited on the first side within the initial opening using an oblique deposition process performed at a first angle to the first side; and a portion of the patterned photoresist is removed using an oblique etching process performed at a second angle to the opposing second side, the masking material and a remaining portion of the patterned photoresist defining a further opening.

2. The method of processing a substrate as claimed in claim 1, wherein receiving the patterned photoresist formed on the substrate comprises: A square layer is formed on the substrate; A photoresist is deposited on the underlying layer; and the photoresist is patterned using a photolithography process.

3. The method of processing a substrate as claimed in claim 2, wherein the lithography process includes extreme ultraviolet (EUV) single exposure.

4. The method of processing a substrate as claimed in claim 3, wherein the end-to-end critical dimension (T2T CD) of the further opening is less than the optical resolution of the extreme ultraviolet single exposure.

5. The method for processing a substrate as claimed in claim 2, wherein the further opening is a final opening, the method for processing the substrate further includes: The underlying layer is etched by using the masking material as an etching mask, thereby extending the final opening vertically into the underlying layer.

6. The method for processing a substrate as described in claim 1 further includes: Before removing that portion of the patterned photoresist, an anisotropic etching process is performed to remove a portion of the masking material that is not on the first side.

7. The method of processing a substrate as claimed in claim 6, wherein the initial opening includes a residue of the photoresist at a bottom of the initial opening, and the method of processing the substrate further includes: After the masking material is deposited within the initial opening, and before removing the portion of the patterned photoresist, the residue is removed using an etching process.

8. The method of processing a substrate as claimed in claim 1, wherein the oblique deposition process or the oblique etching process includes a particle beam process.

9. The method of processing a substrate as claimed in claim 1, wherein the end-to-end critical dimension (T2T CD) of all the initial openings of the substrate has a first standard deviation, wherein the T2T CD of all the further openings of the substrate has a second standard deviation, and wherein the first standard deviation is greater than the second standard deviation.

10. The method of processing a substrate as claimed in claim 1, wherein the end-to-end critical dimension (T2T CD) of the further opening is between 0.1 nm and 5 nm, and wherein the 3σ value of the T2T CD of the further opening is less than 3 nm.

11. The method of processing a substrate as claimed in claim 1, wherein the patterned photoresist includes an organic photoresist and the masking material includes a dielectric material.

12. The method of processing a substrate as claimed in claim 1, wherein the initial opening further includes a third side along a second direction and an opposing fourth side, the second direction being perpendicular to the first direction, the method of processing the substrate further comprising: Using another oblique deposition process, the masking material is deposited within the initial opening on the third side or the opposite fourth side, the other oblique deposition process being performed at a third angle inclined to the third side or at a fourth angle inclined to the opposite fourth side.

13. The method of processing a substrate as claimed in claim 12, wherein the initial opening is free of any residue of the patterned photoresist at a bottom of the initial opening.

14. A method for processing a substrate, comprising: An initial recess is formed in an organic material layer deposited on the substrate, each of the initial recesses having a rectangular shape and having four sides; a masking material is deposited in the initial recess on a first side of the four sides using a first oblique deposition process; the masking material is deposited in the initial recess on a second side of the four sides using a second oblique deposition process, the second side being opposite to the first side. The masking material is deposited in the initial recess on a third side of the four sides using a third oblique deposition process, wherein the first oblique deposition process, the second oblique deposition process, and the third oblique deposition process are performed at multiple incident angles oblique to the first side, the second side, and the third side, respectively; and a portion of the organic material is removed by using an oblique etching process to form the final recess, the oblique etching process being controlled to guide the etchant to a fourth side of the four sides, the oblique etching process being selective relative to the masking material, and the oblique etching process being performed at an incident angle oblique to the fourth side, the masking material remaining above the substrate and separating the final recess.

15. The method of processing a substrate as claimed in claim 14, wherein the initial recess includes a residue of the organic material at a bottom of the initial recess, and the method of processing the substrate further includes: After the masking material is deposited in the initial recesses on the first and second sides, and before the masking material is deposited in the initial recesses on the third side, the residue is removed using an etching process.

16. The method of processing a substrate as claimed in claim 15, wherein the etching process includes a plasma etching process selectively applied to the masking material, wherein the masking material provides protection for the first side and the second side during the etching process.

17. The method of processing a substrate as claimed in claim 14, wherein the first oblique deposition process, the second oblique deposition process, and the third oblique deposition process are performed continuously in a processing chamber, and the method of processing a substrate further includes: The direction of the deposition of the masking material is changed to switch from the first oblique deposition process to the second oblique deposition process, and from the second oblique deposition process to the third oblique deposition process.

18. A method for processing a substrate, comprising: A photoresist is patterned and deposited on a substrate using a photolithography process. The patterned photoresist defines an initial opening having a first side along a first direction and an opposing second side. The substrate is loaded into a processing chamber. In the processing chamber, a first oblique particle beam process is performed to preferentially deposit a masking material within the initial opening on the first side. In the processing chamber, a second oblique particle beam process is performed to form a further opening by preferentially removing a portion of the photoresist located between the first side and the opposing second side of the initial opening, which are adjacent to each other along a second direction. The masking material remains on the substrate and separates the further opening along the second direction.

19. The method of processing a substrate as claimed in claim 18, wherein the further opening is a final opening, the method of processing the substrate further comprising: Before patterning the photoresist, a surface layer is formed on the substrate; The photoresist is deposited on the underlying layer; And after removing that portion of the photoresist, the underlying layer is etched by using the masking material as an etching mask, thereby extending the final opening vertically into the underlying layer.

20. The method of processing a substrate as claimed in claim 18, wherein the first oblique particle beam process includes: In the processing chamber, a first particle beam is formed by a first process gas, the first process gas including a precursor for the shielding material; The substrate is exposed to the first particle beam at a first angle, such that the first particle beam impacts the first side, and the second oblique particle beam process includes: forming a second particle beam from a second process gas in the processing chamber. And expose the substrate to the second particle beam at a second angle, such that the second particle beam strikes the opposite second side.

21. The method for processing a substrate as described in claim 20 further includes: By replacing the first process gas with the second process gas and switching from the first angle to the second angle, the process can be switched from the first oblique particle beam process to the second oblique particle beam process.

22. The method of processing a substrate as claimed in claim 18, wherein the end-to-end critical dimension (T2T CD) of the initial opening has a first standard deviation, wherein the T2T CD of the further opening has a second standard deviation, and wherein the first standard deviation is greater than the second standard deviation.

23. The method of processing a substrate as claimed in claim 18, wherein the initial opening further includes a third side along a second direction and an opposing fourth side, the second direction being perpendicular to the first direction, the method of processing the substrate further comprising: After performing the first oblique particle beam process and before performing the second oblique particle beam process, a third oblique particle beam process is performed in the processing chamber to preferentially deposit the masking material within the initial opening on the third side; and after performing the third oblique particle beam process and before performing the second oblique particle beam process, a fourth oblique particle beam process is performed in the processing chamber to preferentially deposit the masking material within the initial opening on the opposite fourth side.

24. The method of processing a substrate as claimed in claim 23, wherein the initial opening includes a residue of the photoresist at a bottom of the initial opening, and the method of processing the substrate further includes: After depositing the masking material within the initial opening, the residue is removed using an etching process.

25. The method for processing a substrate as described in claim 18 further includes: Before performing the second oblique particle beam process, an anisotropic etching process is performed to remove a portion of the masking material that is not on the first side.

Images