Photomask manufacturing method based on guided self-assembly and photomask manufactured by using method
By combining guided self-assembly technology with traditional lithography technology, the problems of low production throughput and poor graphic quality of high-end masks at advanced nodes have been solved, and high-throughput, high-quality mask preparation has been achieved, bypassing the optical diffraction limit and electron beam proximity effect, and reducing graphic defects and edge roughness.
Patent Information
- Application Number
- CN202410418067.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-08
- Publication Date
- 2025-10-14
AI Technical Summary
Existing electron beam direct writing lithography technology has low production throughput and poor graphic quality when manufacturing advanced node high-end masks, and there are problems with graphic defects and edge roughness.
Combining guided self-assembly technology with traditional photolithography technology, high-quality masks are prepared by forming a specified pattern on a mask substrate, including photolithography, etching, random copolymer filling, block copolymer self-assembly and pattern transfer steps.
High-throughput, high-quality mask preparation is achieved, the optical diffraction limit and electron beam proximity effect are circumvented, graphic defects and edge roughness are reduced, and the preparation cycle is shortened.
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Figure CN120779657A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of semiconductor manufacturing, and in particular to a mask manufacturing method based on directed self-assembly and a mask manufactured using the method. BACKGROUND
[0002] A mask (also known as a mask plate or a photomask) is a patterned mother plate used in photolithography, a common micro-nano processing technology. With the continuous reduction of technology nodes, high-end masks have become one of the most critical components of advanced node photolithography technology. Currently, the manufacturing process of high-end masks suitable for advanced node photolithography technology generally uses electron beam direct writing lithography technology (EBL: E-Beam Lithography) to form a lithography pattern on a mask substrate, and then transfers the lithography pattern to the antireflection layer and the absorption layer of the mask substrate through an etching process. However, this electron beam direct writing lithography technology has the following two problems when manufacturing advanced node high-end masks: first, the production throughput is low, and it takes tens of hours or even several days to manufacture a high-end mask with an advanced node key pattern; second, during the process of using electron beam direct writing lithography, the electron beam will scatter in the photoresist and will also reflect at the bottom of the photoresist, causing proximity effects of the lithography pattern, resulting in pattern defects and poor edge roughness. Therefore, a new photolithography process with high production throughput and high pattern quality is needed to prepare advanced node high-end masks.
[0003] Directed self-assembly technology (DSA: Directed Self-Assembly) is a new resolution enhancement technology, which is listed as one of the candidate solutions for the next generation of advanced semiconductor manufacturing by the International Roadmap for Devices and Systems (IRDS). DSA technology is based on the principle of block copolymer microphase separation, and is mainly completed through process steps such as substrate surface treatment, guide template preparation, and glue coating and annealing. Through the self-assembly of copolymer materials, a nanoscale resolution pattern is formed on the semiconductor substrate. The feature size and edge roughness of the formed pattern are determined by thermodynamic fluctuations, and the final pattern resolution mainly depends on the degree of polymerization of the block copolymer (directly related to the molecular weight). As a patterning technology that directly determines the resolution from the physical thermodynamic Flory-Huggins interaction coefficient and the degree of polymerization of the material, DSA technology can bypass the optical diffraction limit in traditional projection photolithography process and break away from the simple dependence on optical wavelength, and is a very promising technology approach to achieve high-resolution patterning.
[0004] DSA technology can generally be realized by graphic epitaxy or chemical epitaxy, and its combination with conventional photolithography can improve resolution while reducing pattern feature size (Critical Dimension, CD) changes. For example, in graphic epitaxy, the groove defined by photolithography is used as a guide, and the groove has a bottom surface consisting of a material that is neutrally wetted to the polymer block and preferentially wets the sidewall and end of one of the blocks, and is used as a constraint to induce block copolymer self-assembly. In chemical epitaxy, conventional photolithography (using, for example, ultraviolet, deep ultraviolet, electron beam, extreme ultraviolet or ion beam, etc.) can be formed on the surface of the liner material with different chemical affinities (surface wettability) pre-patterns, based on the local change of the surface energy of the liner material to guide the self-assembly of the block material. Summary of the Invention
[0005] Technical problems to be solved by the present invention
[0006] This invention aims to combine DSA technology with traditional photolithography, and to combine DSA's graphoepitaxy with chemical epitaxy, providing a new high-throughput, high-quality approach for producing advanced-node, high-end photomasks. To this end, the invention provides a method for manufacturing photomasks using guided self-assembly technology, enabling the production of high-quality, advanced-node, high-end photomasks at high throughput.
[0007] Technical means for solving technical problems
[0008] In order to solve the above technical problems, according to some exemplary embodiments of the present disclosure, a method for manufacturing a mask based on guided self-assembly is provided, wherein a prescribed pattern is formed on a mask substrate by guided self-assembly technology to prepare a mask, comprising: a first photolithography pattern forming step, wherein a photoresist is coated on the mask substrate, and the photoresist is photolithographically processed to form a first photolithography pattern; a second photolithography pattern forming step, wherein the first photolithography pattern is etched to form a second photolithography pattern; a random copolymer filling step, wherein a random copolymer is coated to fill the gaps in the second photolithography pattern, and the random copolymer is subjected to a first annealing treatment so that the upper end surface of the random copolymer is aligned with the second photolithography pattern; The upper end surface of the second photolithographic pattern is roughly flush with but not exceeding; a block copolymer guided self-assembly step, coating a block copolymer having two polymer blocks on the random copolymer and the second photolithographic pattern and performing a second annealing treatment to guide the block copolymer to self-assemble to form a first block pattern and a second block pattern, wherein the second block pattern preferentially self-assembles on the upper end surface of the second photolithographic pattern; a first block pattern removal step, selectively removing the first block pattern; and a pattern transfer step, using the second block pattern as a hard mask layer, transferring the second block pattern to the random copolymer, and further transferring it to the mask substrate.
[0009] In some embodiments, in the step of forming the second photolithographic pattern, the first photolithographic pattern is subjected to plasma etching, and the height and feature size of the second photolithographic pattern after etching are smaller than those of the first photolithographic pattern.
[0010] In some embodiments, a ratio of the height of the second lithographic pattern to a feature size is in a range of 1:1 to 3:1.
[0011] In some embodiments, the random copolymer uses a polyacrylate derivative including polystyrene-r-polymethyl methacrylate (PS-r-PMMA), or a random copolymer compatible with any one of the high-χ value block copolymers including polystyrene-b-polycarbonate (PS-b-PPC), polystyrene-b-polydivinylpyridine (PS-b-P2VP), polystyrene-b-(lactic acid-alt-glycolic acid) (PS-b-PLGA), polystyrene-b-polylactic acid (PS-b-PLA), and polystyrene-b-polymethyl acrylate (PS-b-PMA).
[0012] In some embodiments, the block copolymer uses any one of the high-χ value block copolymers including polystyrene-b-polymethyl methacrylate (PS-b-PMMA), polystyrene-b-polycarbonate (PS-b-PPC), polystyrene-b-polydivinylpyridine (PS-b-P2VP), polystyrene-b-(lactic acid-alt-glycolic acid) (PS-b-PLGA), polystyrene-b-polylactic acid (PS-b-PLA), and polystyrene-b-polymethyl acrylate (PS-b-PMA).
[0013] In some embodiments, in the random copolymer filling step, a rinsing treatment is further performed after the first annealing treatment to remove the random copolymer that has not been cross-linked with the mask base after the first annealing treatment.
[0014] In some embodiments, the upper end surface of the second photolithographic pattern has a preferential affinity for the second polymer block forming the second block pattern.
[0015] In some embodiments, in the step of forming the second photolithographic pattern, the first photolithographic pattern is plasma-etched using a fluorine-based gas, so that the surface of the second photolithographic pattern has a hydrophobic property after the treatment.
[0016] In some embodiments, in the step of removing the first block pattern, an etching rate of the first block pattern is at least twice an etching rate of the second block pattern.
[0017] In some embodiments, in the pattern transfer step, the second block pattern is transferred to an anti-reflection layer and an absorption layer disposed on top of the mask blank.
[0018] In some embodiments, the etching rates of the anti-reflection layer and the absorption layer are both greater than the etching rates of the second block pattern, the second photolithographic pattern, and the random copolymer.
[0019] The present invention also provides a photomask manufactured using any of the above-mentioned photomask manufacturing methods.
[0020] Effects of the Invention
[0021] The photomask manufacturing method based on guided self-assembly provided by the present invention can not only circumvent the optical diffraction limit of deep ultraviolet light, but also avoid the proximity effect of the electron beam, thereby achieving a perfect pattern with high quality, low defects and low edge roughness. Moreover, the photomask pattern preparation cycle is short and the throughput is high, and high-end photomasks with high graphic quality at advanced nodes can be prepared with high production throughput. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the embodiments of the present disclosure, they are used to explain the present disclosure and do not constitute a limitation of the present disclosure. In the accompanying drawings:
[0023] Figure 1 The present invention is a flowchart of a method for manufacturing a photomask based on guided self-assembly technology.
[0024] Figure 2 Schematic diagram of the structure of the mask base in this embodiment.
[0025] 3(a) and 3(b) are schematic diagrams of a first photolithography pattern forming step in this embodiment.
[0026] Figure 4 FIG. 1 is a schematic diagram of a second photolithography pattern forming step in this embodiment.
[0027] Figure 5 It is a schematic diagram of the random copolymer filling step in this embodiment.
[0028] FIG6(a) and FIG6(b) are schematic diagrams of the block copolymer-guided self-assembly steps in this embodiment.
[0029] Figure 7 Schematic diagram of the first block pattern removal step in this embodiment.
[0030] 8( a ) and 8 ( b ) are schematic diagrams of the pattern transfer step in this embodiment.
[0031] FIG9(a) and FIG9(b) are schematic diagrams of a mask pattern prepared by the conventional electron beam lithography technology and a mask pattern obtained by the mask manufacturing method of the present invention, respectively. DETAILED DESCRIPTION
[0032] The specific embodiments of the present disclosure will be described below. It should be noted that in the specific description of these embodiments, in order to provide a concise description, this specification cannot provide a detailed description of all the features of the actual embodiments. It should be understood that in the actual implementation of any embodiment, just as in the process of any engineering project or design project, in order to achieve the specific goals of the developer and to meet system-related or business-related restrictions, various specific decisions are often made, and this will also change from one embodiment to another. In addition, it is also understandable that although the efforts made in this development process may be complex and lengthy, for ordinary technicians in the field related to the content disclosed by this disclosure, some design, manufacturing or production changes based on the technical content disclosed by this disclosure are just conventional technical means and should not be understood as the content of this disclosure being insufficient.
[0033] Unless otherwise defined, the technical or scientific terms used in the claims and description should have the usual meaning understood by people with ordinary skills in the technical field to which the present disclosure belongs. The words "first", "second" and similar words used in the patent application description and claims of this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "one" or "a" do not indicate a quantitative limitation, but rather indicate the existence of at least one. Words such as "include" or "comprising" mean that the elements or objects appearing before "include" or "comprising" cover the elements or objects listed after "include" or "comprising" and their equivalents, and do not exclude other elements or objects. Words such as "connect", "couple" or "connected" are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections.
[0034] In the present disclosure, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined with each other to form new technical solutions. In the present disclosure, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form new technical solutions.
[0035] In the description of the embodiments of the present disclosure, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.
[0036] The following describes in detail a method for manufacturing a photomask based on guided self-assembly technology according to an embodiment of the present disclosure and a photomask manufactured using the method with reference to the accompanying drawings.
[0037] <Mask Manufacturing Process>
[0038] Figure 1 4 is a flow chart of a photomask manufacturing method based on guided self-assembly technology according to an embodiment of the present invention.
[0039] <Photomask Blank Preparation Step>
[0040] First, in step S10 , a mask blank suitable for a high-end mask at an advanced node is prepared. Figure 2 The schematic structural diagram of the photomask base of this embodiment is shown in FIG. Figure 2 As shown, the structure of the mask blank includes, from top to bottom, an anti-reflection layer 200 , an absorption layer 300 , a covering layer 400 , a multi-layer film structure 500 , a low thermal expansion coefficient material layer 600 and a back conductive layer 700 .
[0041] The anti-reflection layer 200 is primarily used to reduce light reflection during the photolithography process and can be made of materials such as silicon dioxide (SiO2), silicon nitride (SiN), tantalum oxide (Ta2O5), tantalum boron oxide (TaBO), indium tin oxide (ITO), and chromium oxide (Cr2O3). In subsequent processes, when the mask substrate of this embodiment is subjected to DUV (deep ultraviolet) photolithography, the anti-reflection layer 200 is used to reduce the residual reflection of deep ultraviolet light from the absorption layer 300 described later, change the phase of any deep ultraviolet radiation reflected from the absorption layer 300, and reduce the intensity of the reflected deep ultraviolet radiation through destructive interference. The manufacturing method of the anti-reflection layer 200 includes, but is not limited to: physical vapor deposition (PVD) processes, such as evaporation, radio frequency or direct current sputtering; chemical vapor deposition (CVD) processes, such as atmospheric pressure, low pressure, plasma enhanced, and high density plasma chemical vapor deposition; atomic layer deposition (ALD) processes; ion beam deposition processes; liquid phase non-vacuum methods, such as sol-gel methods and organometallic decomposition methods.
[0042] The absorption layer 300 is used to absorb incident light during the photolithography process. For example, in the case of DUV lithography, it absorbs light irradiated onto the photomask substrate by a 193nm ArF light source. The absorption layer 300 can have a single-layer structure or a multi-layer structure. Its materials can be composed of tantalum nitride (TaN), tantalum boron nitride (TaBN), molybdenum (Mo), palladium (Pd), zirconium (Zr), nickel (Ni), nickel oxide (NiO), nickel silicide (NiSi), titanium (Ti), titanium nitride (TiO2), chromium (Cr), chromium oxide (Cr2O3), aluminum oxide (Al2O3), aluminum-copper alloy (Al-Cu), etc. The preparation method of the absorption layer 300 includes but is not limited to: physical vapor deposition (PVD) process, such as evaporation, radio frequency or direct current sputtering; chemical vapor deposition (CVD) process, such as atmospheric pressure, low pressure, plasma enhanced, high density plasma chemical vapor deposition; atomic layer deposition (ALD) process; ion beam deposition (IBD) process; liquid phase non-vacuum method, such as sol-gel method, organometallic decomposition method, etc.
[0043] The cover layer 400 can protect the multilayer film structure 500 below it from being contaminated during the patterning process. The cover layer 400 can be made of any material selected from the group consisting of silicon (Si), ruthenium (Ru), and ruthenium oxide (RuO2). The preparation method of the cover layer 400 includes, but is not limited to: ion beam deposition (IBD) process; physical vapor deposition (PVD) process, such as evaporation, radio frequency or DC sputtering; chemical vapor deposition (CVD) process, such as atmospheric pressure, low pressure, plasma enhanced, and high-density plasma chemical vapor deposition; atomic layer deposition (ALD) process; liquid phase non-vacuum method, such as sol-gel method, organometallic decomposition method, etc.
[0044] The multilayer film structure 500 acts as a reflective film and is composed of a periodic structure in which molybdenum (Mo) layers and silicon (or beryllium) layers are alternately stacked. In some embodiments, the thickness of each molybdenum (Mo) layer in the multilayer film structure 500 is 2 to 7 nm, and the thickness of each silicon (Si) layer is 2 to 7 nm. The thicknesses of the two layers can be the same or different. In some embodiments, the total number of layers of molybdenum layers and silicon (or beryllium) layers alternately stacked can be approximately 20 to 60 layers. The preparation method of the multilayer film structure 500 includes but is not limited to: physical vapor deposition (PVD) process, such as evaporation, radio frequency (RF) or direct current (DC) sputtering; chemical vapor deposition (CVD) process, such as atmospheric pressure, low pressure, plasma-enhanced or high-density plasma chemical vapor deposition; atomic layer deposition (ALD) process; ion beam deposition; liquid phase non-vacuum method, such as sol-gel method, organometallic decomposition method, etc.
[0045] The low thermal expansion coefficient material layer 600 is used to maintain shape stability during the photolithography process and can be made of a low thermal expansion coefficient glass material such as titanium oxide-doped silicon dioxide (SiO2), or other low thermal expansion coefficient materials such as quartz (SiO2), silicon (Si), silicon carbide (SiC), etc. In some embodiments, the low thermal expansion coefficient material layer 600 has low defects (such as a high-purity single crystal substrate) and low surface roughness.
[0046] The back conductive layer 700 can be made of ceramic, and its material can be selected from any one of tantalum boride (TaB), tantalum boron nitride (TaBN), tantalum boron oxide (TaBO), tantalum oxide (TaO), tantalum nitride (TaN), chromium nitride (CrN), chromium oxide (CrO), etc. As long as it can meet the electrostatic suction cup force of the mask, the material of the back conductive layer 700 is not particularly limited.
[0047] <First Photolithography Pattern Formation Step>
[0048] The photomask manufacturing method of the embodiment of the present invention is to Figure 2 The mask substrate with the structure shown is subjected to DSA (Directed Self Assembly) enhanced lithography to form a prescribed pattern, thereby preparing a high-end mask suitable for advanced nodes. Figure 1 In step S20, Figure 2 The photomask substrate is subjected to photolithography to form a first photolithographic pattern. Figures 3(a) and 3(b) are detailed schematic diagrams of the first photolithographic pattern forming step S20.
[0049] As shown in FIG3(a), a layer of photoresist 100 is spin-coated on the reflective layer 200 of the mask substrate, and is exposed and developed using photolithography technology to form a first photolithography pattern 110 as shown in FIG3(b). The photolithography technology in step S20 can adopt deep ultraviolet (DUV) lithography, such as 193nm immersion lithography. At this time, the photoresist 100 can use, for example, 193nm positive photoresist. Regarding the specific photolithography and development technology in the first photolithography pattern forming step S20, existing well-known technologies can be used, and they will not be repeated here. In addition, FIG3(b) also shows the width (feature size) d1 and height h1 of the first photolithography pattern 110.
[0050] <Second Photolithography Pattern Formation Step>
[0051] Then, in Figure 1 In step S30, the first photoresist pattern 110 is patterned by plasma etching technology to form a second photoresist pattern 120. Figure 4FIG3 is a schematic diagram of the second photolithographic pattern forming step S30. The plasma etching gas used in step S30 includes oxygen (O2), carbon dioxide (CO2), nitrogen (N2), argon (Ar), fluorine-based gases (including carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), hexafluoroethane (C2F6), and nitrogen trifluoride (NF3)). Using a fluorine-based gas for etching makes the surface of the second photolithographic pattern 120 hydrophobic, which is preferred, as will be described in detail below.
[0052] In addition, Figure 4 Also shown is the width (feature dimension) d2 and height h2 of the second photolithographic pattern 120. After plasma etching, the feature dimension d2 and height h2 of the second photolithographic pattern 120 are both smaller than the feature dimension d1 and height h1 of the first photolithographic pattern 120. That is, the first photolithographic pattern 110 is modified into the second photolithographic pattern 120 by plasma etching. In some embodiments, the ratio of the height h2 to the feature dimension d2 of the second photolithographic pattern 120 is preferably 1:1 to 3:1.
[0053] <Random Copolymer Filling Step>
[0054] Then, in Figure 1 In step S40, a random copolymer 130 is coated on the second photolithographic pattern 120 to fill each columnar pattern (such as Figure 4 and performing a first annealing treatment to provide a template guide for the subsequent block copolymer guided self-assembly.
[0055] Figure 5 is a schematic diagram of the random copolymer filling step S40. In this embodiment, the random copolymer 130 can be, for example, a polyacrylate derivative including polystyrene-r-polymethyl methacrylate (PS-r-PMMA), or a random copolymer compatible with other high-χ block copolymers such as polystyrene-b-polycarbonate (PS-b-PPC), polystyrene-b-polydivinylpyridine (PS-b-P2VP), polystyrene-b-(lactic acid-alt-glycolic acid) (PS-b-PLGA), polystyrene-b-polylactic acid (PS-b-PLA), and polystyrene-b-polymethyl acrylate (PS-b-PMA).
[0056] After coating the random copolymer 130, an annealing treatment is performed at a temperature of 180°C to 270°C in an atmosphere of air, nitrogen or an inert gas for 3 to 100 minutes, so that the gaps between the columnar patterns of the second photolithographic pattern 120 are filled with the annealed random copolymer 130, that is, the upper end surface of the annealed random copolymer 130 is approximately flush with but does not exceed the upper end surface of the second photolithographic pattern 120 in the height direction.
[0057] After the random copolymer filling step S40, as Figure 5 As shown, the surface formed by the roughly flush upper end surface, that is, the upper end surface of the random copolymer 130 and the upper end surface in the height direction of the second photolithography pattern 120, can have different chemical affinities (surface wettability) for different polymer blocks in the block copolymer described later. Therefore, based on the local change in energy of the surface, the self-assembly of the block material can be guided, that is, a template guide is provided for the self-assembly of the block copolymer.
[0058] In some embodiments, the upper surface of the annealed random copolymer 130 may be slightly lower than the upper surface of the second photolithographic pattern 120. In this case, as long as the height difference between the two upper surfaces is sufficiently smaller than the thickness of the subsequently coated block copolymer, the surface formed by the two upper surfaces can also provide a template guide for the self-assembly of the block copolymer through chemical interaction.
[0059] In addition, after the above-mentioned annealing treatment, the random copolymer 130 and the anti-reflection layer 200 in the mask base are completely cross-linked or partially cross-linked. If the two are partially cross-linked, a rinsing process can be further performed after annealing. For example, a rinsing solution such as photoresist thinner OK73 can be used to rinse the surface of the annealed random copolymer 130 to remove the uncross-linked random copolymer. After rinsing, the surface can be cleaned with deionized water and dried. Here, the rinsing time can be 10 to 120 seconds, and the drying temperature after rinsing can be 100°C to 150°C. If the two are fully cross-linked, the rinsing process can be omitted after annealing.
[0060] <Block Copolymer-Directed Self-Assembly Step>
[0061] Back to Figure 1 In step S50, a block copolymer 140 is coated on the annealed random copolymer 130 (strictly speaking, above the annealed random copolymer 130 and the second photolithography pattern 120) and annealed, so that the block copolymer 140 undergoes microphase separation to form a guided self-assembled micro-nano pattern of different blocks.
[0062] Figs. 6(a) and 6(b) are schematic diagrams of the block copolymer-directed self-assembly step S50. As shown in Fig. 6(a), a block copolymer 140 is first coated on the top surface of each of the random copolymer 130 and the second lithographic pattern 120. The block copolymer 140 can use any of diblock copolymers, such as polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA), polystyrene-b-poly(carbonate) (PS-b-PPC), polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP), polystyrene-b-(lactic acid-alt-glycolic acid) (PS-b-PLGA), polystyrene-b-poly(lactic acid) (PS-b-PLA), polystyrene-b-poly(methyl acrylate) (PS-b-PMA), or other high χ value block copolymers.
[0063] In addition to the above-mentioned diblock copolymers, copolymers having multiple polymer blocks, such as triblock copolymers, can also be used as needed. In the present embodiment, taking the case of a diblock copolymer as an example, the two polymer blocks that make up the diblock copolymer are referred to as a first block and a second block, respectively. For example, in the case of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA), the poly(methyl methacrylate) (PMMA) is referred to as the first block, and the polystyrene (PS) is referred to as the second block.
[0064] Next, the block copolymer 140 in Fig. 6(a) is subjected to an annealing process at a temperature of 180°C to 270°C for an annealing time of 3 to 300 minutes in an atmosphere of air, nitrogen, or an inert gas, so that the block copolymer 140 as a diblock copolymer undergoes microphase separation, thereby forming a first block pattern 141 and a second block pattern 142 of the block copolymer-directed self-assembly, as shown in Fig. 6(b). The first block pattern 141 is formed of the first block in the block copolymer 140, and the second block pattern 142 is formed of the second block in the block copolymer 140. For example, in the case where the block copolymer 140 uses polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA), the first block pattern 141 is formed of the poly(methyl methacrylate) (PMMA) as the first block, and the second block pattern 142 is formed of the polystyrene (PS) as the second block. The first block pattern 141 and the second block pattern 142 have different etching rates. In some embodiments, the etching rate of the first block pattern 141 is at least about 2 times the etching rate of the second block pattern 142.
[0065] As shown in FIG6(b), the surfaces formed by the upper end surfaces of the second photolithographic pattern 120 and the random copolymer 130 formed in steps S30 and S40 provide a template guide for the self-assembly of the block copolymer 140. Because the upper end surface of the random copolymer 130 and the upper end surface of the second photolithographic pattern 120 have different surface wetting properties (chemical affinities) for the various blocks of the block copolymer 140, in FIG6(b), the upper end surface of the second photolithographic pattern 120 has a preferential affinity for the second block (PS) of the block copolymer 140. Therefore, the second block pattern 142 formed by the second block (PS) preferentially self-assembles on the upper end surface of the second photolithographic pattern 120. In other words, the second block pattern 142, which has a relatively slow etching rate, preferentially self-assembles on the upper end surface of the second photolithographic pattern 120. Thus, a periodic structure in which the first block patterns 141 and the second block patterns 142 are alternately arranged is formed as shown in FIG. 6( b ), and the second block pattern 142 is overlapped directly above each columnar pattern of the second photolithographic pattern 120 .
[0066] The chemical affinity of the upper end surfaces of each of the second photoresist pattern 120 and the random copolymer 130 for the polymer blocks of the block copolymer 140 can be adjusted by modifying the surface properties of each upper end surface before applying the block copolymer 140. In addition, in some embodiments, when the first photoresist pattern 110 is etched using a fluorine-based gas in step S30, the surface of the treated second photoresist pattern 120 has a hydrophobic property, thereby further improving the chemical affinity of the upper end surface of the second photoresist pattern 120 for the block copolymer 140.
[0067] <First Block Pattern Removal Step>
[0068] Figure 7 yes Figure 1 Schematic diagram of the first block pattern removal step S60. In step S60, as Figure 7 As shown, since the etching rate of the first block pattern 141 is greater than the etching rate of the second block pattern 142, the first block pattern 141 is selectively removed by etching technology, and the second block pattern 142 is retained. The etching gas used here can be carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2), argon (Ar), etc.
[0069] <Graphic Transfer Steps>
[0070] Figure 8(a) and Figure 8(b) are Figure 1Schematic diagram of the pattern transfer step S70 in step S70. In step S70, the second block pattern 142 is used as a hard mask layer, and the second block pattern 142 is transferred to the random copolymer 130 by plasma etching technology to obtain a random copolymer pattern 131, as shown in Figure 8 (a). As a result, a periodic structure consisting of the second photolithographic pattern 120 and the random copolymer pattern 131 alternately arranged is formed above the anti-reflection layer 200. Then, by further etching, the second block pattern 142 is further transferred to the anti-reflection layer 200 and the absorption layer 300 of the mask base, forming the anti-reflection layer pattern 201 and the absorption layer pattern 301 in sequence, as shown in Figure 8 (b). That is, the pattern transfer step S70 is a step of transferring the pattern of the second block pattern 142 to the mask base.
[0071] The etching gas used in step S70 includes chlorine (Cl2), fluorine-based gas (including carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), hexafluoroethane (C2F6), nitrogen trifluoride (NF3)), etc.
[0072] In step S70 , the second block pattern 142 is used as a hard mask layer. Therefore, the etching rates of the anti-reflection layer 200 and the absorption layer 300 are greater than the etching rates of the second block pattern 142 , the second photoresist pattern 120 and the random copolymer pattern 131 .
[0073] In addition, the etching rates of the anti-reflection layer 200 and the absorption layer 300 are much higher than the etching rate of the cover layer 400 , thereby preventing over-etching from damaging the cover layer 400 and the multi-layer film structure 500 thereunder.
[0074] Finally, in Figure 1 In step S80, the surface of the etched mask is cleaned using a wet process, thereby obtaining the advanced node high-end mask of the present invention.
[0075] FIG9(a) and FIG9(b) are schematic diagrams of a mask pattern prepared by the conventional electron beam lithography technology and a mask pattern obtained by the mask manufacturing method of the present invention, respectively.
[0076] As shown in Figure 9(a), in the process of preparing advanced node high-end masks with traditional electron beams, the electron beam will be scattered in the photoresist and reflected at the bottom of the photoresist, resulting in a proximity effect of the photolithography pattern, causing pattern defects and poor edge roughness. For example, there are pits or burrs on the edges of the linear pattern in the figure.
[0077] As shown in Figure 9(b), the mask manufacturing method based on guided self-assembly of the present invention produces a higher quality mask pattern. It not only circumvents the optical diffraction limit of deep ultraviolet light but also avoids the proximity effect of the electron beam, achieving a perfect pattern with high quality, low defects, and low edge roughness.
[0078] Therefore, a comparison of Figures 9(a) and 9(b) demonstrates that the present invention's mask manufacturing method is capable of achieving high-end masks suitable for advanced nodes with higher resolution and smaller CD variations. Furthermore, the present invention utilizes guided self-assembly lithography enhancement technology to produce high-end masks suitable for advanced nodes. This allows for a short mask pattern preparation cycle and high throughput, with the preparation cycle for one mask being controlled within four hours. This enables the production of high-quality, advanced-node, high-end masks with high throughput.
[0079] According to this embodiment of the method for manufacturing advanced-node, high-end photomasks based on guided self-assembly technology, a first photolithographic pattern formed by photolithography is subjected to a plasma etching process, for example, to obtain a second photolithographic pattern. A random copolymer is then filled into the gaps between adjacent columnar structures in the second photolithographic pattern. Annealing results in the roughly flush upper surfaces of the second photolithographic pattern and the upper surfaces of the random copolymer providing a template guide for the block copolymer, enabling self-assembly. By selectively removing blocks of the copolymer, a hard mask layer is formed, achieving pattern transfer to the photomask backing. The resulting photomask backing exhibits low edge roughness, enabling higher resolution and smaller CD variation for high-end photomasks suitable for advanced nodes.
[0080] Therefore, the present invention not only combines DSA technology with traditional photolithography technology, bypassing the optical diffraction limit in traditional projection photolithography process and getting rid of the simple dependence on optical wavelength, but also can achieve high-resolution pattern preparation even when using deep ultraviolet (DUV) light source. Moreover, the present invention also combines the graphic epitaxy method of DSA technology with the chemical epitaxy method, filling the gap of the second photolithography pattern formed by the photoresist with a random copolymer, and the surface formed by the upper end face thus obtained provides a template guide for the self-assembly of the block copolymer, thereby being able to prepare advanced node high-end masks with high graphic quality with high production throughput.
[0081] It should be understood that the above description is illustrative and not restrictive. For example, the above embodiments (and / or aspects thereof) can be used in combination with each other. In addition, without departing from the scope of the present disclosure, many modifications can be made to adapt specific conditions or materials to the teachings of the various embodiments of the present disclosure. Although the sizes and types of materials described herein are used to define the parameters of the various embodiments of the present disclosure, the various embodiments are not meant to be restrictive, but rather exemplary embodiments. Upon reading the above description, many other embodiments will be apparent to those skilled in the art. Therefore, the scope of the various embodiments of the present disclosure should be determined with reference to the appended claims, and the full range of equivalents to which these claims are intended to protect.
Claims
1. A method for manufacturing a photomask based on guided self-assembly, wherein a predetermined pattern is formed on a photomask substrate by guided self-assembly technology to prepare a photomask, characterized in that: include: a first photolithography pattern forming step of coating a photoresist on the mask substrate and performing photolithography on the photoresist to form a first photolithography pattern; a second photolithographic pattern forming step of etching the first photolithographic pattern to form a second photolithographic pattern; a random copolymer filling step of coating a random copolymer to fill the gaps in the second photolithographic pattern, and performing a first annealing treatment on the random copolymer so that the upper end surface of the random copolymer is substantially flush with the upper end surface of the second photolithographic pattern and does not exceed the upper end surface of the second photolithographic pattern; a block copolymer guided self-assembly step, coating a block copolymer having two polymer blocks on the random copolymer and the second photolithographic pattern and performing a second annealing treatment to guide the block copolymer to self-assemble to form a first block pattern and a second block pattern, wherein the second block pattern preferentially self-assembles on the upper end surface of the second photolithographic pattern; a first block pattern removing step of selectively removing the first block pattern; as well as The pattern transfer step uses the second block pattern as a hard mask layer to transfer the second block pattern to the random copolymer and further transfer it to the mask base.
2. The method for manufacturing a photomask according to claim 1, wherein: In the second photolithographic pattern forming step, the first photolithographic pattern is subjected to plasma etching, and the height and feature size of the second photolithographic pattern after etching are smaller than those of the first photolithographic pattern.
3. The method for manufacturing a photomask according to claim 2, wherein: The ratio of the height of the second photolithographic pattern to the feature size is in the range of 1:1 to 3:
1.
4. The method for manufacturing a photomask according to any one of claims 1 to 3, wherein: The random copolymer uses a polyacrylate derivative including polystyrene-r-polymethyl methacrylate (PS-r-PMMA), or a random copolymer compatible with any one of the high-χ value block copolymers including polystyrene-b-polycarbonate (PS-b-PPC), polystyrene-b-polydivinylpyridine (PS-b-P2VP), polystyrene-b-(lactic acid-alt-glycolic acid) (PS-b-PLGA), polystyrene-b-polylactic acid (PS-b-PLA), and polystyrene-b-polymethyl acrylate (PS-b-PMA).
5. The photomask manufacturing method according to any one of claims 1 to 3, wherein: The block copolymer uses any one of high-χ value block copolymers including polystyrene-b-polymethyl methacrylate (PS-b-PMMA), polystyrene-b-polycarbonate (PS-b-PPC), polystyrene-b-polydivinylpyridine (PS-b-P2VP), polystyrene-b-(lactic acid-alt-glycolic acid) (PS-b-PLGA), polystyrene-b-polylactic acid (PS-b-PLA), and polystyrene-b-polymethyl acrylate (PS-b-PMA).
6. The method for manufacturing a photomask according to any one of claims 1 to 3, wherein: In the random copolymer filling step, a rinsing process is further performed after the first annealing process to remove the random copolymer that has not been cross-linked with the mask base after the first annealing process.
7. The photomask manufacturing method according to any one of claims 1 to 3, wherein: The upper end face of the second photolithographic pattern has a higher affinity for the second polymer block forming the second block pattern than for the first polymer block forming the first block pattern.
8. The photomask manufacturing method according to any one of claims 1 to 3, wherein: In the second photolithography pattern forming step, the first photolithography pattern is plasma-etched using a fluorine-based gas, so that the surface of the second photolithography pattern after the processing has a hydrophobic property.
9. The method for manufacturing a photomask according to any one of claims 1 to 3, wherein: In the first block pattern removing step, an etching rate of the first block pattern is at least twice an etching rate of the second block pattern.
10. The photomask manufacturing method according to any one of claims 1 to 3, wherein: In the pattern transfer step, the second block pattern is transferred to the anti-reflection layer and the absorption layer disposed on top of the mask blank.
11. The method for manufacturing a photomask according to claim 10, wherein: The etching rates of the anti-reflection layer and the absorption layer are both greater than the etching rates of the second block pattern, the second photolithography pattern and the random copolymer.
12. A photomask, characterized in that: The photomask is manufactured using the photomask manufacturing method according to any one of claims 1 to 11.