Self-aligned multi-patterning method

Abstract

A method of patterning a substrate for microfabrication, the method including forming a first structure on a storage layer, the first structure including a first series of parallel and spaced apart lines, performing a first anti-spacer formation process to form first trenches along sidewalls of the first structure and sidewalls of a first fill material to define a first etch pattern for transfer to the storage layer, forming a second structure on the storage layer, the second series of parallel and spaced apart lines, the second series of lines being offset relative to the first series of lines, and performing a second anti-spacer formation process to form second trenches along sidewalls of the second structure and sidewalls of a second fill material to define a second etch pattern for transfer to the storage layer.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 318,619, filed March 10, 2022, and U.S. Patent Application No. 17 / 989,438, filed November 17, 2022, which are incorporated herein by reference.

[0002] The present invention relates generally to methods for patterning a substrate, and in particular embodiments to a system and method for self-aligned multi-patterning. [Background technology]

[0003] An integrated circuit (IC) is a network of electronic components built as a monolithic structure containing a stack of patterned layers of various materials. The structure is fabricated by processing a semiconductor substrate through a series of patterned levels where at each level the patterned layers are formed using photolithography. Component packing density is roughly doubled every two years to reduce costs. To print smaller features, lithography systems with shorter wavelengths (λ) are being developed. Light sources are changing from mercury lamps with λ of 436 nm, 405 nm, and 365 nm to deep ultraviolet (DUV) excimer lasers with λ of 248 nm and 193 nm. As given by the Rayleigh criterion, the minimum half pitch (HP), limited by the resolution, scales as λ / (4NA), where NA is the numerical aperture. Thus, theoretically, for λ=193 nm, HP≧48 nm, and even for NA=1.33 (using 193 nm immersion (193i)), HP≧36 nm. Nevertheless, 193nm and 193i support nodes from 90nm to 10nm, patterning pitches below the Rayleigh limit using "multiple patterning" techniques where a multiple of the feature density on the reticle is formed in a material layer on the reticle. At the sub-10nm node, multiple patterning will likely be used with 13.5nm extreme ultraviolet (EUV) lithography, so further innovations in multiple patterning are desired. Summary of the Invention

[0004] 1. A method of patterning a substrate, the method comprising: forming a first structure on a storage layer, the first structure including a first row of lines that are parallel to and spaced apart from one another; performing a first anti-spacer formation process to form first trenches along sidewalls of the first structure and a sidewall of a first fill material, the first trenches defining a first etch pattern; transferring the first etch pattern to the storage layer and removing material overlying the storage layer; forming a second structure on the storage layer, the second structure including a second row of lines that are parallel to and spaced apart from one another, the second row of lines being offset in position relative to the first row of lines; performing a second anti-spacer formation process to form second trenches formed along sidewalls of the second structure and a sidewall of a second fill material, the second trenches defining a second etch pattern; and transferring the second etch pattern to the storage layer and removing material overlying the storage layer.

[0005] A method of patterning a substrate, the pattern including an array of parallel final trenches having a first pitch, the method comprising: forming a first hardmask layer over a layer of the substrate to be patterned; forming first stencil trenches over the first hardmask layer, the first stencil trenches having a pitch equal to twice the first pitch, each trench of the first stencil trenches having a first width; forming a pattern of the first hardmask trenches by etching the first hardmask layer using the first stencil trenches as an etch mask; and forming a first block mask over the first hardmask layer, the first stencil trenches being spaced apart from the first stencil trenches. a block mask covering a portion of the first hard mask trenches to form a first etch pattern on the layer to be patterned; transferring the first etch pattern to the layer to be patterned to form a first group of final trenches and removing the first block mask and the first hard mask layer; and transferring a second etch pattern to the layer to be patterned to form a second group of final trenches, wherein the second group of final trenches and the first group of final trenches together form a final trench pattern having a first pitch, and all of the final trenches have the same first width.

[0006] 1. A method for designing a reticle set, the method comprising: providing a final design including a line and space (L / S) pattern having a final pitch; and decomposing the final design into a first reticle design and a second reticle design, the first reticle design and the second reticle design being part of a reticle design in a reticle set for quadruple patterning using an anti-spacer self-aligned litho-etch litho-etch (AS-SALELE) process, the first reticle design configured to pattern a first row of mandrels having a mandrel pitch equal to four times the final pitch, the second reticle design configured to pattern a second row of mandrels having the same mandrel pitch, and a placement of the second row of mandrels is offset relative to the first row of mandrels by a distance equal to the final pitch in a direction parallel to the row of mandrels, and the first reticle design and the second reticle design configured to form an L / S pattern having the final pitch on a substrate. [Brief description of the drawings]

[0007] For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0008] [Figure 1A] 1A-1C are diagrams illustrating an example final design and an exploded view of the final design for an anti-spacer self-aligned litho-etch litho-etch (AS-SALELE) quadruple patterning process, according to some embodiments. [Figure 1B] 1A-1C are diagrams illustrating an example final design and an exploded view of the final design for an anti-spacer self-aligned litho-etch litho-etch (AS-SALELE) quadruple patterning process, according to some embodiments. [Figure 1C]1A-1C are diagrams illustrating an example final design and an exploded view of the final design for an anti-spacer self-aligned litho-etch litho-etch (AS-SALELE) quadruple patterning process, according to some embodiments. [Figure 1D] 1A-1C are diagrams illustrating an example final design and an exploded view of the final design for an anti-spacer self-aligned litho-etch litho-etch (AS-SALELE) quadruple patterning process, according to some embodiments. [Figure 1E] 1A-1C are diagrams illustrating an example final design and an exploded view of the final design for an anti-spacer self-aligned litho-etch litho-etch (AS-SALELE) quadruple patterning process, according to some embodiments. [Figure 1F] 1A-1C are diagrams illustrating an example final design and an exploded view of the final design for an anti-spacer self-aligned litho-etch litho-etch (AS-SALELE) quadruple patterning process, according to some embodiments. [Figure 2A] 1A-1D are cross-sectional views of a semiconductor device at various intermediate stages of processing in a process flow of an in-diffusion anti-spacer formation process. [Figure 2B] 1A-1D are cross-sectional views of a semiconductor device at various intermediate stages of processing in a process flow of an in-diffusion anti-spacer formation process. [Figure 2C] 1A-1D are cross-sectional views of a semiconductor device at various intermediate stages of processing in a process flow of an in-diffusion anti-spacer formation process. [Figure 2D] 1A-1D are cross-sectional views of a semiconductor device at various intermediate stages of processing in a process flow of an in-diffusion anti-spacer formation process. [Figure 2E] 1A-1D are cross-sectional views of a semiconductor device at various intermediate stages of processing in a process flow of an in-diffusion anti-spacer formation process. [Figure 2F] 1A-1D are cross-sectional views of a semiconductor device at various intermediate stages of processing in a process flow of an in-diffusion anti-spacer formation process. [Figure 3A] 1A-1D are cross-sectional views of a semiconductor device at various intermediate stages of processing in a process flow of an out-diffusion anti-spacer formation process. [Figure 3B] 1A-1D are cross-sectional views of a semiconductor device at various intermediate stages of processing in a process flow of an out-diffusion anti-spacer formation process. [Figure 3C] 1A-1D are cross-sectional views of a semiconductor device at various intermediate stages of processing in a process flow of an out-diffusion anti-spacer formation process. [Figure 4A] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 4B] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 4C] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 4D] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 4E] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 4F] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 4G]1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 4H] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 4I] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Diagram 5] 4A-4I depict a flow chart summarizing an embodiment of the process flow shown in FIG. [Figure 6A] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6B] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6C] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6D] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6E] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6F]1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6G] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6H] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6I] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6J] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6K] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6L] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 6M] 1A-1D are cross-sectional and plan views of a semiconductor device at various intermediate stages of processing in a process flow for patterning a substrate using AS-SALELE, according to some embodiments. [Figure 7] 6 is a flow chart summarizing an embodiment of the process flow shown in FIGS. 6A-6M. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] This disclosure describes an embodiment of a method for patterning a substrate by a litho-etch-litho-etch (LELE) multi-patterning technique, in which an etch mask is utilized that includes anti-spacers formed self-aligned to the patterned mandrels. In the anti-spacer formation process, a peripheral region of a layer is chemically modified to significantly increase the solubility of the material in that region in some solvents. The modified material with high solubility is referred to as the anti-spacer material. In an embodiment, the anti-spacer material is formed self-aligned to the mandrels and is selectively removed in a subsequent process step. The spaces vacated by removing the anti-spacer material from the etch mask are the anti-spacers. The anti-spacers include a pattern of trenches, each trench of the pattern of trenches having a width equal to the thickness of the anti-spacer material formed on the side of the respective mandrel and removed therefrom. The multi-patterning technique using self-aligned anti-spacers is referred to in this disclosure as anti-spacer self-aligned LELE (AS-SALELE). In contrast, in the self-aligned LELE (SALELE) multi-patterning technique, spacers are formed self-aligned to the patterned mandrels, and material between the spacers is removed. The gaps created by removing the material between the spacers form an etch mask that includes a pattern of trenches. Each pair of adjacent trenches in the pattern of trenches is separated by one of the spacers. Thus, the line width of each of the lines separating adjacent trenches formed by the SALELE technique is equal to the width of the spacer. In contrast, the trench width of each of the spaces separating adjacent lines formed by the AS-SALELE technique is equal to the thickness of the anti-spacer material.

[0010] One advantage of using the AS-SALELE technique may be with the placement of anti-spacer material at the location of the trenches in the final design. The final design refers to the pattern that is ultimately etched into the layer to be patterned in the substrate. Consider a final design that includes a line and space (L / S) pattern having a first pitch, where the first pitch is a final pitch P, and each of the trenches (i.e., each of the spaces) has a first width of P / 2, where the first width is a final width. In an exemplary final design of the present disclosure, the final width is P / 2. As described with reference to FIGS. 1A-1F, the final design may be decomposed into two mandrel reticle designs. Two or more reticles are used to form a block mask. Block features are used to terminate the trenches. Each mandrel reticle design is a row of mandrels with a mandrel pitch of 4P. In contrast, as known to those skilled in the art, to pattern the same final design using SALELE, each of the two decomposed reticle designs has features arranged at a pitch of 2P. In other words, compared to the 2x feature density provided by SALELE, AS-SALELE provides 4x feature density with the same number of masks and pitch walking effect. The larger lithography pitch suggests that pitch walking may be reduced due to less process variation in the lithography processing steps. The larger mandrel pitch (4P) in the AS-SALELE resolution results in wider mandrel lines, resulting in higher patterning accuracy and reduced patterning defects, such as stochastic defects in patterning with extreme ultraviolet (EUV) lithography.

[0011] In this disclosure, an exemplary final design and final design decomposition for the AS-SALELE quadruple patterning process will be described with reference to Figures 1A-1F. Next, two exemplary anti-spacer formation processes will be described. In one example, chemically active species diffuse from an adjacent material into the mandrel and react chemically with the mandrel material within a controlled diffusion distance to convert the material therein into the anti-spacer material. This is an in-diffusion process and will be described with reference to Figures 2A-2F. In the other example, chemically active species diffuse out of the mandrel into an adjacent material and react chemically with the adjacent material within a controlled diffusion distance to convert the material therein into the anti-spacer material. This is an out-diffusion process and will be described with reference to Figures 3A-3C. As will be described in more detail below, either an in-diffusion anti-spacer formation process or an out-diffusion anti-spacer formation process can be utilized in the process flow of AS-SALELE quadruple patterning.

[0012] One exemplary embodiment of a process flow for quadruple patterning using AS-SALELE, Flow A, is described with reference to the cross-sectional and plan views of a semiconductor device 400 shown in Figures 4A-4I and summarized in the flowchart shown in Figure 5. Another exemplary embodiment of a process flow for quadruple patterning using AS-SALELE, Flow B, is described with reference to Figures 6A-6M and summarized in the flowchart shown in Figure 7. Both Flows A and B use the decomposition of a reticle shown in Figures 1A-1F and, for illustrative purposes, an in-diffusion anti-spacer formation process to form the final pattern in the patterned layer of a substrate.

[0013] FIG. 1A shows a final design 100 for a pattern of final trenches 102, with the final trenches 102 having sides separated by lines 104 and ends separated by blocks 106. The final trenches 102 are arranged with a final pitch P, and each final trench in the pattern of final trenches 102 has a width equal to half pitch P / 2. In various embodiments, P can be about 10 nm to about 30 nm. Each of the final trenches 102 has the same width. This is a limitation of the AS-SALELE technique, since the final trenches 102 are not written features. That is, each final trench in the pattern of final trenches 102 has a width defined by the width of the anti-spacer, which is defined by the process parameters of the anti-spacer formation process. Typically, such limits may be met when, for example, trenches are subsequently filled with metal to form wiring at the metal level that is used to carry signals over short distances and also to locally supply power drawn from buried power rails (e.g., if the technology platform supports such an option for power distribution over longer distances).

[0014] In the exemplary final design 100, the final trench pattern is a row of columnar final trenches 102, with adjacent columns along the row marked 1 and 1'. The markings are intended to aid in understanding feature placement and dimensions when decomposing the final pattern 100 into a set of reticles.

[0015] The design for the first mandrel reticle R1 and the design for the first block mask BLK1 are described with reference to Figures 1B and 1C, respectively. The features shown in Figures 1B and 1C are overlaid on the background of the final design 100, which is shown in lighter shades in Figures 1B and 1C. The design for the first mandrel reticle R1 and the design for the first block mask BLK1 are for forming a first pattern of trenches that define a first etch pattern for etching the final trenches 102 that are located along the columns marked 1 in the final design 100. Thus, in processing, anti-spacer material is formed along the columns marked 1 to form anti-spacer lines 110 that are located along the sides of each mandrel 120 in the first row of mandrels 120. The anti-spacer lines 110, shown by dashed rectangles in Figure 1B, are not features depicted in the first mandrel reticle R1. The features depicted on the first mandrel reticle R1 are mandrels 120 in a first row of mandrels 120. The first row of mandrels 120 are then printed into a layer formed on a substrate that is utilized to perform the anti-spacer formation process. As described further below, in the process, anti-spacer material is formed self-aligned to the mandrels 120, and after the anti-spacer material is formed, each of the mandrels 120 has a width of 1.5P.

[0016] The final design 100, which is the pattern to be etched into the patterned layer, does not uniquely determine the width of each of the mandrels 120 in the first mandrel reticle R1. Instead, the final design 100 fixes the width of each anti-spacer line 110 to be equal to P / 2 (the width of each of the final trenches 102) and fixes the pitch of the anti-spacer lines 110 along the columns marked 1 to be equal to 2P (the pitch of the final trenches 102 along the columns marked 1). A pitch of 2P and a line width of P / 2 means that the distance between the anti-spacer lines 110 is 1.5P. Thus, as shown in FIG. 1B, the final design 100 requires that the width of one line of the mandrel and anti-spacer composite structure 130 is 2.5P. (The width of the two anti-spacer lines 110, each with a width of P / 2, plus the distance of 1.5P separating the two anti-spacer lines 110 gives a total width of 2.5P.) The space between adjacent lines of the composite mandrel-anti-spacer structure 130 is 1.5P, which is the space between adjacent anti-spacer lines 110. Thus, the row of composite mandrel-anti-spacer structures 130 has a pitch of 4P. Because each composite mandrel-anti-spacer structure 130 has one mandrel, the first mandrel reticle R1 has a first row of mandrels 120 drawn with a pitch of 4P.

[0017] While the pitch 4P does not depend on which antispacer formation process is used, the width of each of the mandrels 120 in the first mandrel reticle R1 depends on the antispacer formation process. In some antispacer formation processes (e.g., the in-diffusion antispacer formation process described below with reference to Figures 2A-2F), the width of the printed mandrels is altered by the antispacer formation process, which converts a portion of the printed mandrels to antispacer material. In such cases, the width of each of the mandrels 120 in the first mandrel reticle R1 must be drawn greater than 1.5P so that after the antispacers are formed, the mandrels are 1.5P wide as defined by the final design 100. If the antispacer formation process does not change the mandrel width (e.g., the out-diffusion antispacer formation process described below with reference to Figures 3A-3C), each mandrel 120 is drawn with a width of 1.5P.

[0018] The exemplary first mandrel reticle R1 shown in FIG. 1B is suitable for use in an in-diffusion anti-spacer formation process in which each anti-spacer line has a width of P / 2. The in-diffusion anti-spacer formation process converts a portion of each mandrel 120 to anti-spacer material. Thus, the mandrels 120 are drawn 2.5P wide in anticipation of the P / 2 wide peripheral region of each printed mandrel being converted to anti-spacer material, as shown by the anti-spacer lines 110 in FIG. 1B.

[0019] The blocks 106 along the columns marked with 1 may be patterned using the design for the first block mask BLK1 shown in Figure 1C. The design for the first block mask BLK1 includes a block feature 140 drawn over the location of the blocks 106 along the columns marked with 1 in the final design 100. As described in more detail below, because the blocks 106 are formed self-aligned to the trenches 102 in the column direction, the extent of the block feature 140 in the column direction may be drawn large enough to provide a sufficient margin for edge placement error (EPE), as long as the block feature 140 does not extend so as to be within the EPE of another final trench 102 along another column marked with 1.

[0020] 1D-1F are used to illustrate a design for a second mandrel reticle R2 and a design for a second block mask BLK2 for forming a second pattern of trenches that defines a second etch pattern that is used to etch the final trenches 102 located along the columns marked 1'. The final design 100 is reproduced in FIG. 1D for convenience.

[0021] 1E shows a design for a second mandrel reticle R2 overlaid on the background of the final design 100. Like the first mandrel reticle R1, the second mandrel reticle R2 includes a second row of mandrels 120' that are subsequently printed in a layer formed on a substrate. Also like the first mandrel reticle R1, the second mandrel reticle R2 is suitable for use in an in-diffusion anti-spacer formation process in which each anti-spacer line has a width of P / 2. Thus, as with mandrel 120, each mandrel 120' is drawn 2.5P wide in anticipation of the mandrel material at the location of anti-spacer line 110' being converted to anti-spacer material. As described above, like the first mandrel reticle R1, each composite structure 130' of mandrel and anti-spacer is 2.5P wide and spaced 1.5P from adjacent features, such that the second row of mandrels 120' in the second mandrel reticle R2 has the same pitch, 4P, as the first row of mandrels 120 in the first mandrel reticle R1.

[0022] The anti-spacer lines 110', shown by dashed rectangles in FIG. 1E, are aligned with the columns marked 1', and the anti-spacer lines 110 (from FIG. 1B) are aligned with the columns marked 1. The row of columnar final trenches 102 is arranged with a pitch P (see FIG. 1D). The columns along this row alternate between columns marked 1 and columns marked 1', i.e., a row of columns marked 1' is a row of columns marked 1 displaced along the row by a distance P. Thus, as shown in FIG. 1E, the second row of mandrels 120' is simply the first row of mandrels 120 shifted along the row direction by a distance P.

[0023] 1F, the design for the second block mask BLK2 may be used to pattern blocks 106 along the columns marked with 1'. Similar to the design for the first block mask BLK1, the design for the second block mask BLK2 includes block features 140' drawn over the locations of blocks 106 along the columns marked with 1' in the final design 100.

[0024] As mentioned above, two methods of forming anti-spacers are described in this disclosure. In either method, the anti-spacer material is formed to separate the mandrels and filler lines in an interdigitated pattern of rows of mandrels and filler lines, with the alternating mandrels and filler lines arranged with a pitch of 4P. After the anti-spacer material is formed, regardless of the formation method, a thickness of P / 2 anti-spacer material separates adjacent mandrels and filler lines, with each mandrel and filler line having a width of 1.5P, which is consistent with the pitch of 4P. The pattern including the mandrels, filler lines, and anti-spacer material can be formed using materials that are typically deposited by inexpensive spin-on processes, such as using a spin coater in a lithography track.

[0025] Two methods of forming anti-spacers are described with reference to Figures 2A-2F and 3A-3C, respectively. As shown in Figures 2A-2F and 3A-3C, an interdigitated pattern (as described above) is formed on layer 240 of a substrate that includes an underlayer 250 below layer 240. In the exemplary embodiments described in this disclosure, layer 240 may be a hard mask layer and underlayer 250 may be the layer to be patterned.

[0026] First, the in-diffusion anti-spacer formation process will be described with reference to FIGS. 2A to 2F.

[0027] 2A, a row of mandrels 220 having a pitch 4P is patterned on layer 240, for example, using the first mandrel reticle R1 described above with reference to FIGS. 1A and 1B. The mandrel material may be selected from a variety of materials, for example, flowable materials, photoresists, and inorganic materials. In some embodiments, the mandrel material includes a photoresist, for example, a fast EUV photoresist. The photoresist may be patterned by exposing it to a radiation pattern defined by a reticle design, for example, the first row of mandrels 120 depicted in the first mandrel reticle R1. The radiation pattern is transferred to the exposed photoresist using a suitable developer to form the patterned mandrels 220. As a result of the pattern transfer, each of the patterned mandrels 220 has the same width as each of the mandrels 120 depicted in the first mandrel reticle R1. Thus, the patterned width is 2.5P.

[0028] As mentioned above, the width of each of the patterned mandrels 220 formed on the layer 240 depends on the anti-spacer formation process. In the exemplary embodiment described with reference to Figures 2A-2F, the anti-spacer formation process involves an in-diffusion of chemically active species, which converts a portion of each mandrel 220 in a region near its periphery to the anti-spacer material. By converting the mandrel material to the anti-spacer material, the width of the patterned mandrel 220 shrinks by P and the height shrinks by P / 2. Thus, before conversion in Figure 2A, the width of each of the patterned mandrels 220 is equal to the width of the mandrel and anti-spacer composite structure 130, as described above with reference to Figure 1B, which is 2.5P.

[0029] In FIG. 2B, the pattern of mandrels 220 is covered with a first overcoat 260. The first overcoat 260 includes a chemically active species. For example, the first overcoat 260 can be a photoresist that includes an acid or photoacid that is a chemically active species. The first overcoat 260 can be formed using a spin-on process. In various embodiments, the in-diffusion of the chemically active species and reaction with the mandrels 220 is thermally activated by annealing the substrate at a controlled temperature of about 110° C. to about 220° C. for about 0.5 minutes to about 3 minutes, for example using a baking oven in a lithography track. As shown in FIG. 2C, the annealing temperature and annealing time are selected to cause the chemically active species to diffuse into the mandrels 220 and react with the mandrel material within a certain diffusion distance, converting the mandrel material therein to the anti-spacer material 210. The inwardly pointing arrows in Figure 2C indicate a continuous region of anti-spacer material 210 of thickness P / 2 formed by reaction with mandrel material in peripheral regions along the sides and top of mandrel 220. The printed mandrel 220 (Figures 2A and 2B) of width 2.5P shrinks to 1.5P to form anti-spacer material 210 of thickness P / 2, resulting in a composite mandrel-anti-spacer structure 230 (the combination of mandrel 220 and anti-spacer material 210) of width 2.5P in Figure 2C.

[0030] After the anneal is complete, the first overcoat 260 containing the chemically active species may be selectively removed using the solvent in which the overcoat was cast, as shown in FIG. 2D.

[0031] In FIG. 2E, a first filler material 270 is deposited on the substrate. As shown in FIG. 2E, the first filler material 270 is a flowable material that is intended to flow into the spaces defined by the pattern of the mandrels 220. In some embodiments, the first filler material 270 is a photoresist and can be deposited by an inexpensive spin-on process. Typically, the first filler material 270 overfills the spaces defined by the pattern of the mandrels 220 to cover the surface of the anti-spacer material 210 with a topcoat of the excess first filler material 270. Thus, a controlled recess etch step can be performed to remove the topcoat and expose the anti-spacer material 210 formed on the mandrels 220. The controlled recess etch step can use a solvent that has a slow dissolution rate of the exposed material. In some embodiments, the solvent can be a 0.26 N tetramethylammonium hydroxide (TMAH) developer. Exposing the top surface of the anti-spacer material 210 forms filler lines 280 separated by anti-spacer material 210 in an array of alternating mandrels 220 and filler lines 280 .

[0032] As mentioned above, two exemplary methods of forming antispacers are described in this disclosure. An in-diffusion antispacer formation process is described above with reference to Figures 2A-2F. An out-diffusion antispacer formation process is described below with reference to Figures 3A-3C. In the out-diffusion process, the mandrel provides chemically active species that diffuse into and chemically react with adjacent materials to convert adjacent materials within a controlled diffusion distance into antispacer material. The mandrel material is not chemically converted into antispacer material.

[0033] FIG. 3A shows a cross-sectional view of a semiconductor device in which a row of mandrels 320 having a pitch of 4P, similar to the row of mandrels 220 in FIG. 2A, is patterned on layer 240 using a first mandrel reticle R1, except that in this example, each of the mandrels 120 is depicted to have a width equal to 1.5P instead of 2.5P. The mandrels 220 had to be patterned wider (with a width of 2.5P) in the in-diffusion process because, as explained above, a portion of the mandrel material was converted to anti-spacer material 110 by reaction with chemically active species. In the out-diffusion process, the mandrel width in the row of mandrels 320 remains unchanged at 1.5P. As in the in-diffusion process, in the out-diffusion process, the row of mandrels 320 can be patterned using a suitable lithographic technique (e.g., EUV lithography).

[0034] In the out-diffusion process, the mandrels in the array of mandrels 320 provide the chemically active species. Thus, the mandrel material in Figure 3A may be a photoresist containing an acid or photoacid that is a chemically active species.

[0035] In FIG. 3B, a second filler material 370 is deposited over the patterned rows of mandrels 320. The second filler material 370 is a flowable material and is intended to flow into the open spaces defined by the pattern of the rows of mandrels 320. When the second filler material 370 reacts with the chemically active species present in the patterned rows of mandrels 320, it is converted into an anti-spacer material. In some embodiments, the second filler material 370 is a photoresist and may be deposited by a spin-on process. In the exemplary embodiment of FIG. 3B, similar to the first filler material 270, the second filler material 370 overfills the spaces between the mandrels 320, with the excess material forming a topcoat.

[0036] In FIG. 3C, the substrate is annealed to diffuse the chemically active species from the array of mandrels 320 into the second filler material 370. The annealing process can be similar to the annealing in the inward diffusion process described with reference to FIGS. 2B and 2C. In the annealing, the outward diffusing chemically active species react with a portion of the second filler material 370 adjacent to each of the mandrels in the array of mandrels 320. The reaction converts the region within the diffusion distance to the second filler material 370 into the anti-spacer material 310. As described above, the annealing temperature and time are selected and controlled to provide a diffusion distance equal to P / 2. In some embodiments, the topcoat of the second filler material 370 shown in FIG. 3B may be fully converted to the anti-spacer material 310, thereby exposing the anti-spacer material 310 formed over the mandrels 320 to form filler lines 380 separated by the anti-spacer material 310 in an array of alternating mandrels 320 and filler lines 380. In some other embodiments, a residual topcoat may be present, which may be removed by an extended development step where the solvent used to remove the residual topcoat has a minimal dissolution rate and thus slowly and controllably recesses the residual topcoat, thereby exposing the anti-spacer material. Removing the topcoat exposes the anti-spacer material 310 formed over the mandrels 320 to form filler lines 380 separated by the anti-spacer material 310 in an array of alternating mandrels 320 and filler lines 380, as shown in FIG. 3C.

[0037] It should be noted that in an in-diffusion process, the first filler material 270 used to form the filler lines 280 is deposited after the anti-spacer material 210 is formed, whereas in an out-diffusion process, the first filler material 370 used to form the filler lines 380 in the array of alternating mandrels 320 and filler lines 380 separated by the anti-spacer material 310 is deposited before the anti-spacer material 310 is formed.

[0038] Initially, the material that reacts with the chemically active species has low solubility in the solvent before the chemical reaction. The chemistry used in the antispacer formation process is such that the material is transformed into an antispacer material (a material that is highly soluble in the solvent) by reaction with the chemically active species. Thus, after the chemically active species diffuses and reacts to transform the material within the diffusion distance into the antispacer material, the antispacer material can be selectively removed by the solvent. In some embodiments, when the chemically active species is an acid or photoacid that diffuses into and reacts with the photoresist, the solvent that can selectively remove the antispacer material includes tetramethylammonium hydroxide (TMAH).

[0039] The interdigitated rows of mandrels 220 and filler lines 280 separated by anti-spacer material 210 (as shown in FIG. 2F) and the interdigitated rows of mandrels 320 and filler lines 380 separated by anti-spacer material 310 (as shown in FIG. 3C) have the same lateral dimensions. Thus, either anti-spacer formation process can be utilized to form the interdigitated patterns required in the process flow for quadruple patterning using AS-SALELE.

[0040] Flow A will be described with reference to the cross-sectional and plan views of a semiconductor device 400 shown in FIGS. 4A to 4I, and the flow chart shown in FIG.

[0041] As mentioned above, the exemplary embodiment (Flows A and B) of the process flow for implementing the final design 100 (shown in FIG. 1A) using AS-SALELE quadruple patterning uses a reticle set designed for implementation to be consistent with the in-diffusion anti-spacer formation process (shown in FIGS. 2A-2F). Thus, the reticle set selected for Flows A and B has four reticles (shown in FIGS. 1A-1F): a first mandrel reticle R1, a reticle having a design for a first block mask BLK1, a second mandrel reticle R2, and a reticle having a design for a second block mask BLK2. Thus, for Flows A (and Flows B), the initial state of the substrate is the patterned structure shown in cross-section in FIG. 2F formed using the first mandrel reticle R1, referred to herein as the first interdigitated pattern. In flow A, layer 240 (FIG. 2F) is the hardmask layer and underlying layer 250 (FIG. 2F) is the layer to be patterned. For clarity, the references in FIG. 2F, i.e., layer 240 and underlying layer 250, have been changed in FIGS. 4A-4I to hardmask layer 440 and layer to be patterned 450, respectively.

[0042] 4A illustrates cross-sectional and plan views of a semiconductor device 400 after anti-spacer material 210 formed by an in-diffusion anti-spacer formation process (e.g., a first anti-spacer formation process) has been selectively removed from the first interdigitated pattern using a first anti-spacer material removal process. As discussed above, the anti-spacer material 210 may be selectively removed by a solvent such as TMAH.

[0043] Referring to FIG. 4A, a first structure including a first row of parallel and spaced apart lines is formed on a storage layer. The first structure (e.g., mandrels 220) and filler lines 280 (e.g., a first fill material) in FIG. 4A are formed on a storage layer (e.g., hard mask layer 440). The first structure may be formed of photoresist. In some embodiments, hard mask layer 440 may include silicon nitride and patterned layer 450 may include silicon oxide. In some other embodiments, hard mask layer 440 may include silicon carbide, titanium nitride, tantalum nitride, or the like, or a combination thereof, and patterned layer 450 may include a low-k dielectric such as carbon-doped oxide, fluorosilicate glass, porous oxide, or the like.

[0044] The selective removal of the anti-spacer material 210 forms a first pattern 402 of trenches (e.g., first trenches formed along the sidewalls of the first structure and the sidewalls of the first fill material) as shown in FIG. 4A. Each trench of the first pattern 402 of trenches has a width of P / 2, the trenches are aligned with the column marked 1, and the pitch of the first pattern 402 of trenches is 2P. In some embodiments, the trench opening P / 2 may be a critical dimension that limits the packing density, for example, in static random access memory (SRAM) cells embedded in a digital logic IC. By using the thickness of the anti-spacer material to define the width of each trench of the first pattern 402 of trenches, the critical dimension is defined by the diffusion distance. Because the diffusion distance is controlled by the annealing temperature and annealing time instead of lithography, critical dimensions of a few nanometers can be fabricated and controlled trench widths as narrow as 4 nm can be achieved.

[0045] In FIG. 4B, a reticle having a design for the first block mask BLK1 described with reference to FIG. 1C is used to pattern a first block mask 460 over the first pattern of trenches 402. In some embodiments, the first block mask 460 may comprise spin-on glass or titanium nitride and may be formed by selectively etching the mandrels 220, the filler lines 280, and the hard mask 440 using standard etch chemistries for pattern transfer, as known to those skilled in the art. As shown in FIG. 4B, the features of the first block mask 460 cover a portion of the first pattern of trenches 402 shown in FIG. 4A, thereby forming an etch pattern that includes the first pattern of trenches 402 shown in FIG. 4B, which includes the first block mask 460 in addition to the mandrels 220 and the filler lines 280. In this disclosure, the trenches of the first pattern of trenches 402 may be referred to as first stencil trenches because they form an etch pattern (e.g., a first etch pattern) for a subsequently performed pattern transfer etch.

[0046] In Figure 4C, a pattern-transfer etch is performed to transfer the first pattern of trenches 402 (shown in Figure 4A) into the hardmask layer 440 to form a first group of hardmask trenches 404. The pattern-transfer etch may use, for example, an appropriate etch chemistry, e.g., anisotropic reactive ion etching (RIE) with fluorine chemistry, that etches the hardmask 440 and stops on the layer to be patterned 450, as shown in Figure 4C.

[0047] After the first group of hard mask trenches 404 are formed, the mandrels 220, the filler lines 280, and the first block mask 460 are stripped from the substrate. The resulting structure of the semiconductor device 400 is shown in FIG. 4D. As shown in FIG. 4D, the first group of hard mask trenches 404 expose a portion of the layer to be patterned along the columns marked 1'. In this example (Flow A), the pattern of the first group of hard mask trenches 404 is not transferred to the layer to be patterned 450 at this point. Before that, a second group of hard mask trenches is formed to expose another portion of the layer to be patterned 450, which is formed along the columns marked 1'. In Flow A, the layer to be patterned 450 can be etched after exposing the portion along the columns marked 1'.

[0048] The method of forming the second group of hard mask trenches is similar to the method of forming the first group of hard mask trenches 404. After forming the first group of hard mask trenches 404, the in-diffusion anti-spacer formation process flow (described above with reference to FIGS. 2A-2F) can be performed to form a second interdigitated pattern on the hard mask 440 using the second mandrel reticle R2. It should be noted that the in-diffusion anti-spacer formation process is selected for implementation purposes only. It may be replaced with the out-diffusion anti-spacer formation process (described above with reference to FIGS. 3A-3C) using an appropriate material and a reticle forming the same second interdigitated pattern.

[0049] The second interdigitated pattern (formed using the second mandrel reticle R2) is the same as the first interdigitated pattern (formed using the first mandrel reticle R1), except that the anti-spacer lines in the second interdigitated pattern are aligned along columns marked 1' instead of along columns marked 1. In other words, the second interdigitated pattern is obtained by shifting the first interdigitated pattern along the columns by a distance P. The second mandrel reticle R2 is also designed to be used in the same inward diffusion anti-spacer formation process as the first mandrel reticle R1 to form a second interdigitated pattern, i.e., the width of the mandrels 120 of the first mandrel reticle R1 (FIG. 1B) and the width of the mandrels 120' of the second mandrel reticle R2 (FIG. 1E) are 2.5P, and similarly, the pitch of the first row of mandrels (of the first mandrel reticle R1) and the pitch of the second row of mandrels (of the second mandrel reticle R2) are 4P.

[0050] The materials and processes for forming the second interdigitated pattern can be similar to those described above for forming the first interdigitated pattern.

[0051] After forming the second interdigitated pattern, the anti-spacer material formed by the in-diffusion anti-spacer formation process (e.g., the second anti-spacer formation process) is removed from the second interdigitated pattern (i.e., the second anti-spacer material removal process). Figure 4E shows the structure of the semiconductor device 400 after the anti-spacer material has been selectively removed by a solvent such as TMAH.

[0052] Referring to FIG. 4E, a second structure including a second row of lines parallel to each other and spaced apart from each other is formed on the storage layer. Removal of the anti-spacer material results in a row of mandrels 220′ (e.g., second structure) and filler lines 280′ (e.g., second fill material) that are alternately arranged and separated by a second pattern of trenches 406 formed on the hard mask layer 440 (e.g., storage layer). The second pattern of trenches (e.g., second trenches formed along the sidewalls of the first structure and the sidewalls of the first fill material) 406 in FIG. 4E may be the same as the first pattern of trenches 402 (FIG. 4A), but is offset by a distance P in a direction parallel to the row with respect to the first pattern of trenches 402. Because they are offset by P along the columns, the first group of hard mask trenches 404 of FIGS. 4C and 4D are now covered by mandrels 220' and filler lines 280' that are 1.5P wide, as shown in FIG. 4E.

[0053] In FIG. 4F, the design for the second block mask BLK2 described with reference to FIG. 1F is used to pattern a second block mask 460′ over the second pattern of trenches 406. As shown in FIG. 4F, the features of the first block mask 460′ cover a portion of the second pattern of trenches 406 as seen in FIG. 4E, thereby forming an etch pattern that includes the second pattern of trenches 406 shown in FIG. 4F, in which the definition of the second pattern of trenches 406 includes the second block mask 460′, in addition to the mandrels 220′ and filler lines 280′. In this disclosure, the trenches of the second pattern of trenches 406 may be referred to as second stencil trenches because they form an etch pattern (e.g., a second etch pattern) for a subsequently performed pattern transfer etch.

[0054] The materials and processes used to form the second block mask 460 ′ may be similar to the materials used to form the first block mask 460 .

[0055] In Figure 4G, a pattern transfer etch is performed to transfer the second pattern of trenches 406 (shown in Figure 4E) into the hardmask layer 440 to form a second group of hardmask trenches 408. The etch process can be similar to that used to form the first group of hardmask trenches 404.

[0056] In FIG. 4H, material above hardmask layer 440, including mandrels 220′, filler lines 280′, and second block mask 460′, has been removed after forming second group of hardmask trenches 408. Second group of hardmask trenches 408 and first group of hardmask trenches 404 together form hardmask trench pattern 410 having final pitch P, as shown in FIG. 4H. As can be seen from a comparison of the plan view of semiconductor device 400 to final design 100 in FIG. 4I, hardmask trench pattern 410 matches final design 100. Thus, hardmask trench pattern 410 can be used as an etch mask to pattern patterned layer 450 with a pattern that replicates final design 100.

[0057] FIG. 4I shows the semiconductor device 400 after the patterned layer 450 has been etched using the hard mask trench pattern 410 (shown in FIG. 4H) as an etch mask and the hard mask 440 has been removed. The hard mask trench pattern 410 is transferred by etching to the patterned layer 450 to form the final trench pattern 420. The final trench pattern 420 includes a row of columnar trenches with a final pitch P, with each trench in the final trench pattern 420 having a width of P / 2. As can be seen by comparing the plan view of the semiconductor device 400 in FIG. 4I with the final design 100, the final design 100 is replicated by the final trench pattern 420 in the patterned layer 450. Two cross-sectional views are shown in FIG. 4I. The first cross-sectional view marked A is in a plane where no features of the block mask 460′ were present during processing, and the second cross-sectional view marked B shows two blocked trenches in the final trench pattern 420.

[0058] A summary of process flow A for quadruple patterning using AS-SALELE described above with reference to FIGS. 4A-4I is summarized in the flow chart shown in FIG.

[0059] A final design is provided for patterning in a patterned layer, as shown in box 510. The final design includes final trenches having a width of half the final pitch (P / 2) and arranged in an L / S pattern at the final pitch P.

[0060] In box 520, the final design is decomposed into a first reticle design and a second reticle design, each design including rows of mandrels with a pitch of 2P, where the rows are identical except for a shift of P along the row.

[0061] Flow A provides a first mandrel reticle having a first reticle design and a second mandrel reticle having a second reticle design, along with a substrate having a layer to be patterned and a hard mask layer formed over the layer to be patterned, as shown in box 530.

[0062] A first pattern of trenches is formed using a first mandrel reticle and a first block mask in boxes 540 and 542. In Flow A, the first block mask is formed and included in the first pattern of trenches prior to transferring the first pattern of trenches to the hard mask layer.

[0063] Note that, as described in more detail below, Flow B differs from Flow A in that the first pattern of trenches is transferred into a hard mask layer prior to forming the first block mask.

[0064] In box 550, the first pattern of trenches is transferred to the hardmask layer to form a first group of hardmask trenches. As described above, the first pattern of trenches are spaces formed by selectively etching away anti-spacer material from rows of alternating mandrel and filler lines separated by the anti-spacer material. As shown in box 550, after forming the first group of hardmask trenches, material overlying the hardmask layer is removed.

[0065] The operations in boxes 540, 542, and 550 used to form the first group of hardmask trenches are repeated in the operations in boxes 560, 562, and 570, but this time using a second mandrel reticle and a second block mask to form a second group of hardmask trenches such that the second group of hardmask trenches are formed in columns that are offset by P along the row direction relative to the columns in which the first group of hardmask trenches are formed.

[0066] It should be noted that in Flow A, the first and second groups of hardmask trenches are formed in the same hardmask layer, whereas Flow B, as described in more detail below, forms a pattern of first hardmask trenches in a first hardmask layer and a pattern of second hardmask trenches in a second hardmask layer.

[0067] The first group of hardmask trenches and the second group of hardmask trenches together form a pattern of hardmask trenches that is transferred to the layer to be patterned, as shown in box 580. As noted in box 580, the pattern transfer etch forms a final trench pattern that replicates the final design, with the trenches having a width of P / 2 and a pitch P.

[0068] Another exemplary embodiment of a process flow for quadruple patterning using AS-SALELE, Flow B, is described with reference to Figures 6A-6M and summarized in the flow chart shown in Figure 7. Those skilled in the art will appreciate that process flows other than Flow A and Flow B may be constructed using the inventive aspects of the embodiment of quadruple patterning using AS-SALELE described in this disclosure.

[0069] Flow B replicates the final design 100 (shown in FIG. 1A ) in the patterned layer 450 of the semiconductor device 400 using the same set of reticles used in Flow A to replicate the final design 100 in the patterned layer 450, i.e., the first mandrel reticle R1, the reticle having a design for the first block mask BLK1, the second mandrel reticle R2, and the reticle having a design for the second block mask BLK2 (described above with reference to FIGS. 1A-1F ). As described above, the first mandrel reticle R1 and the second mandrel reticle R2 are designed to be compatible with the in-diffusion anti-spacer formation process (shown in FIGS. 2A-2F ). The in-diffusion anti-spacer formation process is selected for implementation purposes only. Thus, a first interdigitated pattern (as shown in FIG. 2F) is formed in Flow B using the reticle design for the first mandrel reticle R1 and the first block mask BLK1.

[0070] Similar to Flow A, after forming the first interdigitated pattern, the anti-spacer material 210 is selectively removed to form the same structure for the semiconductor device 400, as shown in FIG. 6A (replicated from FIG. 4A). The structure shown in FIG. 4A is identical to the structure shown in FIG. 6A, so the same reference numbers are used for the mandrels 220, the filler lines 280, and the columns of the layer to be patterned 450. However, the hard mask layer 440 in FIG. 4A is changed to a first hard mask layer 640 in FIG. 6A. The change from 440 to 640 is because, unlike Flow A, in Flow B, the first hard mask layer 640 is removed in a subsequent step and a second hard mask layer is formed on the layer to be patterned 450. Also, the first pattern of trenches 402 in FIG. 4A is referred to as the first pattern of trenches 602 in FIG. 6A. The change from 402 to 602 is because in Flow A, the first block mask 460 is included in defining the etch pattern of the first pattern of trenches 402 that is then transferred to the hard mask layer 440, whereas in Flow B, the first pattern of trenches 602 that is transferred to the first hard mask layer 640 to form the first hard mask trench pattern 604 does not include the first block mask 460.

[0071] In Figure 6B, a pattern transfer etch is performed before transferring the unaltered first pattern of trenches 602 to the first hard mask layer 640. The etch process removes exposed portions of the first hard mask layer 640 to form the first hard mask trench pattern 604. The structure of semiconductor device 400 after the pattern transfer etch is completed shown in Figure 6B shows that the first hard mask trench pattern 604 has trenches that are unblocked and expose portions of the layer 450 that is patterned along the columns marked with 1.

[0072] In Figure 6C, the rows of mandrels 220 and filler lines 280 (seen in Figure 6B) are removed, and a first block mask 460 is formed using a reticle having a design for the first block mask BLK1. The first block mask 460 covers a portion of the first hard mask trenches 604. As shown in Figure 6C, the pattern of first hard mask trenches 604, partially covered by the first block mask 460, forms a first etch pattern on the layer to be patterned 450.

[0073] 6D shows the structure of semiconductor device 400 after the first etch pattern has been transferred to patterned layer 450 to form the final first group of trenches 606. Each pattern-transfer etch is a selective etch that is blocked in areas covered by first block mask 460 or first hard mask layer 640 while removing exposed portions of patterned layer 450.

[0074] After forming the first group of final trenches 606, the first block mask 460 and the first hard mask layer 640 are sequentially removed from the substrate as shown in Figures 6E and 6F. Figure 6E illustrates the structure of the semiconductor device 400 after the first block mask 460 is removed, and Figure 6F illustrates the structure of the semiconductor device 400 after the first hard mask layer 640 is removed.

[0075] As described above and as can be seen from FIGS. 6B-6E, the patterned first hard mask layer 640 covers the patterned layer 450 in the areas between adjacent columns marked with a 1. This covered area is therefore protected from removal by the pattern transfer etch performed via the first etch pattern (described above with reference to FIGS. 6C-6D). The first hard mask trench pattern 604, when formed, exposes the patterned layer 450 unblocked along the entire length of each of the columns marked with a 1 (see FIG. 6B). However, the first block mask 460, when formed over the first hard mask trench pattern 604, fills a portion of the first hard mask trench pattern 604 (see FIG. 6C). This filling protects the portion of the patterned layer 450 adjacently located below from removal (see FIG. 6D). Thus, as can be seen from the plan view of Figure 6E, the trenches of the first group of final trenches 606 running along the columns marked 1 are blocked by unremoved portions of the patterned layer 450, which are protected from the etchant by the first block mask 460 that fills respective portions of the trenches of the first hard mask trench pattern 604. Because the first block mask 460 has been removed in Figure 6E, the cross-sectional view of the semiconductor device 400 in Figure 6E shows the portions of the first hard mask trench pattern 604 that are now unfilled.

[0076] In FIG. 6F, the first block mask 460 is removed, followed by the first hard mask layer 640. The top view of the semiconductor device 400 in FIG. 6F shows that the pattern of the first group of final trenches 606 replicates the portion of the final design 100 along the columns marked 1 in the layer to be patterned 450. As shown in FIG. 6F, each trench in the first group of final trenches 606 has a final width of P / 2, and the pattern including the first group of final trenches 606 has a pitch of 2P. The portion of the final design 100 along the columns marked 1' has not yet been replicated in the layer to be patterned 450 because the area between adjacent columns marked 1 includes the column marked 1'.

[0077] Figure 6G shows a second hardmask layer 650 formed over the layer to be patterned 450. Similar processes and materials to those used to form the hardmask layer 440 described with reference to Figure 4A (which is similar to the first hardmask layer 640) can be used to form the second hardmask layer 650 that fills the first group of final trenches 606 along the columns marked 1.

[0078] After forming the second hard mask layer 650, the second group of final trenches 612 may be formed along the columns marked 1' by repeating the steps described above with reference to Figures 6A-6F, but by replacing the first mandrel reticle R1 with the second mandrel reticle R2 and by replacing the reticle having the design for the first block mask BLK1 with a reticle having the design for the second block mask BLK2. Using these reticles, the pattern of the second group of final trenches 612 replicates the portion of the final design 100 along the columns marked 1' in the patterned layer 450. Figures 6H-6M show plan and cross-sectional views of the semiconductor device 400 at various intermediate stages of forming the second group of final trenches 612. The structure of the semiconductor device 400 after the process of forming the second group of final trenches 612 is completed and the second hard mask layer 650 is removed is shown in Figure 6M.

[0079] 6H shows a second pattern of trenches 608 (similar to the first pattern of trenches 602 of FIG. 6A) formed by removing anti-spacer material from a second interdigitated pattern formed on the second hard mask layer 650 using a second mandrel reticle R2. As explained above, the second interdigitated pattern is offset from the first interdigitated pattern by a distance P in a direction perpendicular to the mandrels of the row of mandrels 220′, thereby locating the trenches of the second pattern of trenches 608 along the columns marked 1′.

[0080] In FIG. 6I (similar to FIG. 6B ), a second hardmask trench pattern 610 is etched into the second hardmask layer 650 along the columns marked 1′ through the second pattern of trenches 608.

[0081] In Figure 6J (similar to Figure 6C), the row of mandrels 220' and filler lines 280' (similar to Figure 6I) are removed and a second block mask 460' is formed using a reticle having a design for second block mask BLK2. Second block mask 460' covers a portion of second hard mask trench 610 to form a second etch pattern on patterned layer 450.

[0082] In FIG. 6K, a second group of final trenches 612 are formed in patterned layer 450 by performing a pattern transfer etch via a second etch pattern.

[0083] After forming the second group of final trenches 612, similar to the processing performed after forming the first group of final trenches 606 (see FIGS. 6E and 6F), the second block mask 460′ and the second hard mask layer 650 are sequentially removed from the substrate, as shown in FIGS. 6L and 6M, respectively. Note that the first group of final trenches 606 and the second group of final trenches 612 formed using Flow B together form the same pattern of final trenches 420 (shown in FIG. 4I) formed using Flow A. Thus, the final design 100 can be replicated in layer 450 patterned using either Flow A or Flow B.

[0084] The structure of semiconductor device 400 after removing second hard mask layer 650 is shown in Figure 6M. The final trench pattern 420 (the combination of the first group of final trenches 606 and the second group of final trenches 612) includes an array of columnar trenches having a final pitch P, with each trench in final trench pattern 420 having a width of P / 2. As expected, the two cross-sectional views of the semiconductor device 400 structure in Figure 6M are the same as the respective two cross-sectional views of the semiconductor device 400 structure in Figure 4I.

[0085] A summary of process flow B for quadruple patterning using AS-SALELE described above with reference to FIGS. 6A-6M is summarized in the flow chart shown in FIG.

[0086] As shown in box 710, a first hard mask layer is formed over the layer of the substrate to be patterned.

[0087] In box 712, a first pattern of mandrels is formed on the first hard mask layer. The mandrels are arranged in a row with a pitch of 4P, where P is the final pitch and P / 2 is the final width of the final trench pattern.

[0088] At box 714, a first interdigitated pattern of alternating rows of mandrels and filler lines separated by anti-spacer material is formed from the first pattern of mandrels. The anti-spacer material is formed in self-alignment to the mandrels using an anti-spacer forming process.

[0089] As shown in box 716, anti-spacer material is selectively removed from a first interdigitated pattern of alternating rows of mandrels and filler lines. Gaps created by the removal form a first pattern of trenches. The first pattern of trenches has a pitch 2P, and each trench in the first pattern of trenches has a width P.

[0090] In box 718, the first pattern of trenches is used as an etch mask for a pattern transfer etch that etches the first hardmask layer to form a pattern of first hardmask trenches. After forming the pattern of first hardmask trenches, material overlying the first hardmask layer (i.e., the mandrel and filler lines) is removed.

[0091] In box 720, a first block mask is formed over the first hard mask layer. The first block mask covers a portion of the first hard mask trenches to form a first etch pattern over the layer to be patterned.

[0092] In box 722, the first etch pattern is transferred to the layer to be patterned to form a first group of final trenches. After forming the first group of final trenches, the first block mask is removed. After removing the first block mask, the first hard mask layer is removed.

[0093] As shown in box 730, a second etch pattern is formed on the layer to be patterned by repeating the processes in boxes 710, 712, 714, 716, 718, and 720, except that the reticle used in forming the first pattern of mandrels and the reticle used in forming the first block mask are changed to form a second pattern of mandrels and a second block mask. The second pattern of mandrels is shifted a distance P from the first pattern of mandrels in a direction perpendicular to the mandrels.

[0094] In box 732, the second etch pattern is transferred to the layer to be patterned to form a second group of final trenches. After forming the second group of final trenches, the second block mask is removed. After removing the second block mask, the second hard mask layer is removed. The second group of final trenches and the first group of final trenches together form a final trench pattern. The final trench pattern has a final pitch P, and each of the final trenches has a final width P / 2.

[0095] In this disclosure, two exemplary embodiments of quadruple patterning using AS-SALELE have been described. In both embodiments (Flow A and Flow B), the final design 100 includes a pattern of parallel trenches of width P / 2 arranged at pitch P, which is replicated in patterned layer 450 by forming a final trench pattern 420 also having final pitch P and final width P / 2.

[0096] An interdigitated pattern, each comprising a row of mandrels and filler lines separated by anti-spacer material, can be formed on a substrate using commonly available materials and inexpensive spin-on processes and ovens available at lithography tracks.

[0097] The critical dimension (CD), trench width P / 2, is defined by the thickness of the anti-spacer material formed self-aligned to the mandrel. Thus, in quadruple patterning using AS-SALELE, the CD control is determined by the thickness control of the anti-spacer formation process. This offers the advantage of tighter control than is possible with photolithographically defined CD. In various embodiments, the thickness of the anti-spacer material can be controlled to a 3-sigma variation of about 1 nm to about 2 nm.

[0098] Each of the mandrel patterns used in the exemplary embodiment of quadruple patterning with AS-SALELE is a row of mandrels arranged with a pitch of 4P. The patterns are printed using a reticle with line and space feature sizes of 1.5P and 2.5P. At sub-10 nm technology nodes, the final pitch P can be scaled down to the extent that EUV lithography is used to form the mandrel patterns. As known to those skilled in the art, in EUV lithography, patterning capabilities are often limited by stochastic effects. The large resist feature sizes of 1.5P and 2.5P used in the embodiment of quadruple patterning with AS-SALELE provide the advantage of reducing stochastic effects in EUV lithography.

[0099] Another advantage of quadruple patterning with mandrel self-aligned anti-spacers as opposed to mandrel self-aligned spacer patterning is that the number of trench columns in the final design is constrained to a multiple of two for anti-spacer quadruple patterning, instead of a multiple of four for spacer quadruple patterning.

[0100] Example 1. A method of patterning a substrate, the method including: forming a first structure on a storage layer, the first structure including a first series of lines parallel to and spaced apart from one another; performing a first anti-spacer formation process to form first trenches along sidewalls of the first structure and a sidewall of a first fill material, the first trenches defining a first etch pattern; transferring the first etch pattern to the storage layer and removing material overlying the storage layer; forming a second structure on the storage layer, the second structure including a second series of lines parallel to and spaced apart from one another, the second series of lines being offset in position relative to the first series of lines; performing a second anti-spacer formation process to form second trenches formed along sidewalls of the second structure and a sidewall of a second fill material, the second trenches defining a second etch pattern; transferring the second etch pattern to the storage layer and removing material overlying the storage layer.

[0101] Example 2. The method of Example 1, further comprising forming a first block mask over the first trench prior to transferring the first etch pattern to the storage layer, the first block mask covering a portion of the first trench, and the first etch pattern comprising the first block mask.

[0102] Example 3. The method of example 1 or 2, further comprising forming a second block mask over the second trench prior to transferring the second etch pattern to the storage layer, the second block mask covering a portion of the second trench, and the second etch pattern comprising the second block mask.

[0103] Example 4. The method of any one of Examples 1-3, further comprising patterning a patterned layer disposed below the storage layer based on the first etch pattern in the storage layer and the second etch pattern in the storage layer.

[0104] Example 5. The method of any one of Examples 1-4, wherein performing a first anti-spacer formation process includes covering the first structure with a first overcoat, annealing the substrate to form a layer of anti-spacer material along sides of the first structure, where the layer of anti-spacer material is formed from the first structure and the first overcoat, and after forming the anti-spacer material, selectively removing the first overcoat to form a plurality of trenches, and filling the plurality of trenches with a filler material.

[0105] Example 6. The method of any one of Examples 1-5, wherein the first anti-spacer formation process comprises an in-diffusion process, and a peripheral region of the first structure is converted to form a layer of anti-spacer material.

[0106] Example 7. The method of any one of Examples 1-6, wherein filling the plurality of trenches includes overfilling the plurality of trenches with a filler material and exposing an outer surface of the anti-spacer material using a controlled recess etch step.

[0107] Example 8. The method of any one of Examples 1-7, wherein performing a first anti-spacer formation process includes covering the first structure with a filler material and annealing the substrate to form a layer of anti-spacer material along sides of the first structure, wherein the layer of anti-spacer material is formed from the first structure and the filler material.

[0108] Example 9. The method of any one of Examples 1-8, wherein the first anti-spacer formation process includes an out-diffusion process, and a portion of the filler material is converted to form a layer of anti-spacer material.

[0109] Example 10. The method of any one of Examples 1-9, wherein performing the first anti-spacer formation process further comprises exposing an outer surface of the layer of anti-spacer material using a controlled recess etch process.

[0110] Example 11. The method of any one of Examples 1-10, wherein the first anti-spacer material removal process includes exposing the substrate to a solvent to selectively remove the anti-spacer material formed in self-alignment with the first structure.

[0111] Example 12. The method of any one of Examples 1 to 11, wherein the solvent comprises tetramethylammonium hydroxide (TMAH).

[0112] Example 13. A method of patterning a substrate, the pattern including an array of parallel final trenches having a first pitch, the method comprising: forming a first hardmask layer over a layer of the substrate to be patterned; forming first stencil trenches over the first hardmask layer, the first stencil trenches having a pitch equal to twice the first pitch, each trench of the first stencil trenches having a first width; forming a pattern of first hardmask trenches by etching the first hardmask layer using the first stencil trenches as an etch mask; and forming a first block mask over the first hardmask layer; 1. A method comprising: a first block mask covering a portion of a first hard mask trench to form a first etch pattern on the layer to be patterned; transferring the first etch pattern to the layer to be patterned to form a first group of final trenches and removing the first block mask and the first hard mask layer; and transferring a second etch pattern to the layer to be patterned to form a second group of final trenches, wherein the second group of final trenches and the first group of final trenches together form a final trench pattern having a first pitch, and all of the final trenches have the same first width.

[0113] Example 14. The method of example 13, wherein the first width is equal to half the first pitch.

[0114] Example 15. The method of Example 13 or 14, wherein forming the first stencil trench includes forming a first pattern of mandrels on the first hard mask layer, the first pattern of mandrels being a row of mandrels having four times the first pitch; forming from the first pattern of mandrels a first interdigitated pattern of alternating rows of mandrels and filler lines separated by anti-spacer material, the filler lines and the anti-spacer material being formed self-aligned to the mandrels, each mandrel and each filler line of the first interdigitated pattern having a combined width equal to three times the first width; and selectively removing the anti-spacer material from the first interdigitated pattern to form the first stencil trench.

[0115] Example 16. The method of any one of Examples 13-15, wherein selectively removing the anti-spacer material includes exposing the substrate to a solvent to remove the anti-spacer material from the first interdigitated pattern to form a first stencil trench.

[0116] Example 17. The method of any one of Examples 13-16, wherein the solvent comprises tetramethylammonium hydroxide (TMAH).

[0117] Example 18. Prior to transferring the second etch pattern to the patterned layer, the method includes forming a second hard mask layer over the patterned layer and a first group of final trenches in the substrate; and forming second stencil trenches over the first hard mask layer having a pitch equal to twice the first pitch, each trench of the second stencil trenches having a first width, the second stencil trenches being formed self-aligned to mandrels of a second pattern of mandrels, the second pattern of mandrels being formed to have a pitch equal to twice the first pitch. 18. The method of any one of Examples 13-17, further comprising: offsetting the first pattern of mandrels by a distance equal to the first pattern of mandrels; etching the second hardmask layer using the second stencil trenches as an etch mask to form a second pattern of hardmask trenches; and forming a second block mask on the second hardmask layer, the second block mask covering a portion of the second hardmask trenches to form a second etch pattern on the layer to be patterned.

[0118] Example 19. The method of any one of Examples 13-18, wherein forming the second stencil trenches includes forming a second pattern of mandrels on the second hard mask layer, the second pattern of mandrels being offset relative to the first pattern of mandrels by a distance equal to the first pitch, and forming a second interdigitated pattern from the second pattern of mandrels using an anti-spacer formation process.

[0119] Example 20. A method of designing a reticle set, the method including: providing a final design including a line-and-space (L / S) pattern having a final pitch; and decomposing the final design into a first reticle design and a second reticle design, the first reticle design and the second reticle design being part of a reticle design in a reticle set for quadruple patterning using an anti-spacer self-aligned litho-etch litho-etch (AS-SALELE) process; and a reticle design configured to pattern a first row of mandrels with a mandrel pitch equal to four times the final pitch, a second reticle design configured to pattern a second row of mandrels with the same mandrel pitch, the placement of the second row of mandrels being offset relative to the first row of mandrels in a direction parallel to the row of mandrels by a distance equal to the final pitch, and the first reticle design and the second reticle design configured to form an L / S pattern on the substrate with the final pitch.

[0120] Example 21. The method of example 20, wherein the spaces of the L / S pattern have a width equal to half the final pitch.

[0121] Example 22. The method of example 20 or 21, further comprising decomposing the final design into designs for a first block reticle and a second block reticle, the first block reticle and the second block reticle being part of a reticle set, the first block reticle being configured to form a first block mask, and the second block reticle being configured to form a second block mask.

[0122] Example 23. The method of any one of Examples 20-22, wherein a first block mask includes a plurality of first blocks and is configured to block a first hard mask trench configured to be formed on a side of one of the first rows of mandrels, and a second block mask includes a plurality of second blocks and is configured to block a second hard mask trench configured to be formed on a side of one of the second rows of mandrels.

[0123] Example 24. The method of any one of Examples 20-23, wherein one of the first blocks is spaced from an adjacent one of the second blocks by a space greater than half the final pitch.

[0124] Example 25. The method of any one of Examples 20-24, wherein one of the first blocks is spaced from an adjacent one of the first blocks by a space greater than half the final pitch.

[0125] While the present invention has been described with reference to exemplary embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present invention, will become apparent to those skilled in the art upon reading the above description. It is therefore intended that the appended claims cover any such modifications or embodiments.

Claims

1. 1. A method of patterning a substrate, the method comprising: forming a first structure over the storage layer, the first structure including a first array of parallel and spaced apart lines; performing a first anti-spacer formation process to form a first trench along a sidewall of the first structure and a sidewall of a first fill material, the first trench defining a first etch pattern; transferring the first etch pattern into the storage layer and removing material overlying the storage layer; forming a second structure over the storage layer, the second structure including a second series of parallel and spaced apart lines, the second series of lines being offset relative to the first series of lines; performing a second anti-spacer formation process to form a second trench formed along a sidewall of the second structure and a sidewall of a second fill material, the second trench defining a second etch pattern; transferring the second etch pattern into the storage layer and removing material overlying the storage layer; A method comprising:

2. 10. The method of claim 1 , further comprising forming a first block mask over the first trench prior to transferring the first etch pattern to the storage layer, the first block mask covering a portion of the first trench, and the first etch pattern comprising the first block mask.

3. 3. The method of claim 2, further comprising forming a second block mask over the second trench prior to transferring the second etch pattern to the storage layer, the second block mask covering a portion of the second trench, and the second etch pattern comprising the second block mask.

4. performing the first anti-spacer formation process; covering the first structure with a first overcoat; annealing the substrate to form a layer of anti-spacer material along sides of the first structure, the layer of anti-spacer material being formed from the first structure and the first overcoat; selectively removing the first overcoat after forming the anti-spacer material to form a plurality of trenches; filling the plurality of trenches with a filler material; The method of claim 1 , comprising:

5. 5. The method of claim 4, wherein the first anti-spacer formation process comprises an in-diffusion process, in which a peripheral region of the first structure is converted to form the layer of the anti-spacer material.

6. filling the plurality of trenches, overfilling the plurality of trenches with a filler material; exposing an outer surface of said anti-spacer material using a controlled recess etch process. The method of claim 4 , comprising:

7. performing the first anti-spacer formation process; covering the first structure with a filler material; annealing the substrate to form a layer of anti-spacer material along sides of the first structure, the layer of anti-spacer material being formed from the first structure and the filler material; The method of claim 1 , comprising:

8. 8. The method of claim 7, wherein the first anti-spacer formation process comprises an out-diffusion process, in which a portion of the filler material is converted to form the layer of the anti-spacer material.

9. performing the first anti-spacer formation process; exposing an outer surface of said layer of said anti-spacer material using a controlled recess etch process. The method of claim 7 further comprising:

10. 2. The method of claim 1, wherein a first anti-spacer material removal process comprises exposing the substrate to a solvent to selectively remove anti-spacer material formed in self-alignment with the first structures.

11. 1. A method of patterning a substrate, the pattern comprising an array of parallel final trenches having a first pitch, the method comprising: forming a first hard mask layer over a layer of a substrate to be patterned; forming first stencil trenches on the first hard mask layer having a pitch equal to twice the first pitch, each trench of the first stencil trenches having a first width; forming a pattern of first hardmask trenches by etching the first hardmask layer using the first stencil trenches as an etch mask; forming a first block mask over the first hard mask layer, the first block mask covering a portion of the first hard mask trenches to form a first etch pattern on the patterned layer; transferring the first etch pattern into the patterned layer to form a first group of final trenches and removing the first block mask and the first hard mask layer; transferring a second etch pattern into the patterned layer to form a second group of final trenches, the second group of final trenches and the first group of final trenches together forming a final trench pattern having the first pitch, all of the final trenches having the same first width; A method comprising:

12. The method of claim 11 , wherein the first width is equal to half the first pitch.

13. forming the first stencil trench; forming a first pattern of mandrels over the first hard mask layer, the first pattern of mandrels being an array of mandrels having four times the first pitch; forming a first interdigitated pattern of alternating rows of mandrels and filler lines from the first pattern of mandrels and separated by anti-spacer material, the filler lines and the anti-spacer material being formed self-aligned to the mandrels, each mandrel and each filler line of the first interdigitated pattern having a combined width equal to three times the first width; selectively removing the anti-spacer material from the first interdigitated pattern to form the first stencil trench; The method of claim 11 , comprising:

14. Prior to transferring the second etch pattern to the patterned layer, the method further comprises: forming a second hard mask layer over the patterned layer of substrate and the first group of final trenches; forming second stencil trenches on the first hard mask layer having a pitch equal to twice the first pitch, each of the second stencil trenches having the first width, the second stencil trenches being formed self-aligned to mandrels of a second pattern of mandrels, the second pattern of mandrels being offset with respect to the first pattern of mandrels by a distance equal to the first pitch; forming a pattern of second hard mask trenches by etching the second hard mask layer using the second stencil trenches as an etch mask; forming a second block mask over the second hard mask layer, the second block mask covering a portion of the second hard mask trenches to form a second etch pattern on the patterned layer; The method of claim 13 further comprising:

15. 1. A method for designing a reticle set, the method comprising: providing a final design including a line and space (L / S) pattern having a final pitch; decomposing the final design into a first reticle design and a second reticle design, the first reticle design and the second reticle design being part of a reticle design in the reticle set for quadruple patterning using an anti-spacer self-aligned litho-etch litho-etch (AS-SALELE) process, the first reticle design configured to pattern a first row of mandrels having a mandrel pitch equal to four times the final pitch, the second reticle design configured to pattern a second row of mandrels having the same mandrel pitch, the placement of the second row of mandrels being offset relative to the first row of mandrels by a distance equal to the final pitch in a direction parallel to the row of mandrels, and the first reticle design and the second reticle design configured to form an L / S pattern having the final pitch on a substrate; A method comprising:

16. The method of claim 15 , wherein the spaces of the L / S pattern have a width equal to half the final pitch.

17. decomposing the final design into designs for a first block reticle and a second block reticle, the first block reticle and the second block reticle being part of the reticle set, the first block reticle being configured to form a first block mask, and the second block reticle being configured to form a second block mask; The method of claim 15 further comprising:

18. 18. The method of claim 17, wherein the first block mask comprises a plurality of first blocks and is configured to block a first hard mask trench configured to be formed on a side of one of the first rows of mandrels, and the second block mask comprises a plurality of second blocks and is configured to block a second hard mask trench configured to be formed on a side of one of the second rows of mandrels.

19. 20. The method of claim 18, wherein one of the first blocks is spaced from an adjacent one of the second blocks by a space greater than half of the final pitch.

20. 20. The method of claim 18, wherein one of the first blocks is spaced from an adjacent one of the first blocks by a space greater than half of the final pitch.

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