A method for chiral-directed block copolymer self-assembly lithography

Abstract

The present invention discloses a method for chiral-directed block copolymer self-assembly lithography, and the method includes: ① grafting a chiral homopolymer layer on the surface of a substrate; ② etching the chiral homopolymer layer into a periodic structure by lithography technology; ③ backfilling and grafting a neutral layer in the gaps of the periodic structure of the chiral homopolymer to form a chiral-directed substrate; ④ spin-coating a chiral block copolymer on the chiral-directed substrate and annealing to obtain a chiral-directed self-assembled structure; wherein the chiral block copolymer includes at least one chiral block, the chiral homopolymer is the same as or a stereoisomer of the chiral block in the chiral block copolymer, and the neutral layer is a polymer with similar two-phase interactions for the chiral block copolymer. This method can significantly improve the guiding force during the directed self-assembly of block copolymers and effectively reduce the defect rate and line edge roughness of the final guiding structure.

Description

Technical Field

[0001] The present invention relates to the field of block copolymer directed self-assembly, and particularly to a method for chiral-directed block copolymer self-assembly lithography. Background Art

[0002] Since its birth in 1946, the computer has evolved from a behemoth weighing more than 30 tons into an easily accessible daily device, and its computing power has increased by hundreds of millions of times. All of this is due to the rapid increase in the transistor density in semiconductor chips. Gordon Moore, one of the founders of Intel, proposed the famous Moore's Law in 1965, that is, the number of transistors that can be accommodated on an integrated circuit will steadily increase at a rate of doubling every 18 months and maintain this momentum in the next few decades.

[0003] With the rapid development of integrated circuits, its technology nodes have shrunk from the micron level and sub-micron level to the nanometer level, which poses increasingly high requirements for lithography technology and its core material, photoresist. In order to obtain smaller processing precision, the wavelength of the lithography light source has experienced a development process from near-ultraviolet G-line (436nm), I-line (365nm) to deep-ultraviolet excimer laser KrF (248nm), ArF (193nm), and then to EUV extreme ultraviolet (13.5nm) and other next-generation photoresists. Although the large-scale application of extreme ultraviolet lithography technology has enabled Moore's Law to continue in the past two years, and the 5nm process technology of TSMC has also been mass-produced, the problems of insufficient power of the extreme ultraviolet light source and low production efficiency still plague the semiconductor manufacturing industry.

[0004] The Directed Self-Assembly (DSA) technology of block copolymers combines the "bottom-up" self-assembly technology of block copolymer thin films and the "top-down" lithography technology. By the chemical or structural inhomogeneity on the substrate surface, the block copolymers are oriented to form an etching template for the fabrication of nanostructures and related semiconductor devices (CN101578232B). Compared with EUV technology, DSA has the advantages of low cost, high resolution, and high yield because it does not require light sources, mask plates, and complex process conditions, and has received extensive attention in the semiconductor industry. Many domestic and foreign semiconductor companies and research institutions, including IBM, Intel, Dow Chemical, JSR, ASML, IMEC, SMIC, Zhejiang University, etc., have carried out corresponding and fruitful research on this technology (CN101611349B, CN104798183B, CN105051863B, CN103187245B, CN101578232A). The International Technology Roadmap for Semiconductors (ITRS) listed the directed self-assembly of block copolymers DSA as one of the next-generation lithography technology solutions in 2013 and pointed out that the main challenges of this technology include improving position accuracy and reducing defect rates. In 2015, ITRS further pointed out that the time node for the industrialization of DSA is around 2018.

[0005] However, to date, the DSA technology is still difficult to be applied on a large scale. The reason is that the requirements of low defect rates and low roughness are always difficult to meet. The main reasons for the high defect rates and line edge roughness are the insufficient substrate guiding forces. Generally, there are two guiding methods for DSA, the lithographic epitaxy method and the chemical epitaxy method. They respectively achieve the selective orientation of segments by using the bottom and side walls after manufacturing a groove template on the substrate and achieve the selective wetting orientation of a certain segment after chemically modifying the substrate. The template of the lithographic epitaxy method can be prepared by the mature 193nm lithography technology, but the accuracy of the pre-template will significantly affect the defect rate and the roughness of the structure of the block copolymer guiding, and the structure of the pre-template will be retained in the final pattern, limiting its application. Compared with the lithographic epitaxy, the chemical epitaxy method effectively avoids the limitation of the pre-template grooves and is also beneficial to the improvement of resolution. However, the acting force of chemical wetting is limited, and it is difficult to fully guide the block copolymer during annealing, resulting in high defect rates. Increasing the interaction parameter χ between the two phases can obtain a pattern with higher resolution and stronger guiding force. However, when the χ value is too large, the surface energy difference between the segments is too large, and surface wetting will occur, forming a phase domain structure parallel to the substrate rather than a vertical structure, and the pattern transfer cannot be carried out. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a method for chiral-guided block copolymer self-assembly lithography, which can significantly improve the guiding force during the guided self-assembly of block copolymers and effectively reduce the defect rate and line edge roughness of the final guided structure.

[0007] The technical solution provided by the present invention is as follows:

[0008] A method for chiral-guided block copolymer self-assembly lithography:

[0009] ① Graft a chiral homopolymer layer on the substrate surface;

[0010] ② Etch the chiral homopolymer layer into a periodic structure through lithography technology;

[0011] ③ Backfill and graft a neutral layer in the gaps of the periodic structure of the chiral homopolymer to form a chiral guiding substrate;

[0012] ④ Spin-coat the chiral block copolymer on the chiral guiding substrate and anneal it to obtain a chiral-guided self-assembly structure;

[0013] Among them, the chiral block copolymer includes at least one chiral block, the chiral homopolymer is the same as or a stereoisomer of the chiral block in the chiral block copolymer, and the neutral layer is a polymer with similar two-phase interactions for the chiral block copolymer.

[0014] The chemical structure of the chiral block in the chiral block copolymer is shown in formula (I):

[0015]

[0016] Among them, n represents the degree of polymerization of the structural units in the polymer, which is any integer between 2 and 10,000;

[0017] Among them, A is selected from the 1-22 structures shown below, and B is selected from the 23-32 structures shown below:

[0018]

[0019] Among them, C, D, R1-R4 represent a heteroatom-substituted or unsubstituted aliphatic or aromatic alkane, alkene, alkyne, alcohol, ether, ketone, ester, carbonate or hydrogen atom with 1-20 carbon atoms, and the heteroatom is selected from fluorine, chlorine, bromine, iodine, nitrogen, sulfur or phosphorus atoms;

[0020] Among them, C and R1 cannot have the same structure, and D and R2 cannot have the same structure.

[0021] Preferably, the chiral block in the block copolymer is one or more of poly(propylene carbonate), poly(chloropropylene carbonate), poly(styrene carbonate), poly(cyclohexene carbonate), poly(limonene carbonate), poly(propylene oxide), poly(butylene oxide), poly(cyclohexene oxide), poly(propylene imine), poly(lactide), poly(methyl acrylate), poly(methyl methacrylate), poly(ethyl methacrylate), or poly(tert-butyl methacrylate).

[0022] Another block of the block copolymer is one or more of polystyrene, poly(p-fluorostyrene), poly(p-trimethylsilylstyrene), poly(p-methylstyrene), poly(2-vinylpyridine), poly(4-vinylpyridine), polyethylene, polypropylene, polybutadiene, polyisoprene, polydimethylsiloxane, polyacrylonitrile, polyurethane, polyimide, polyvinyl chloride, or polyvinyl fluoride.

[0023] Preferably, the molecular weight of the chiral block copolymer is between 1000 and 1000000, the molecular weight distribution is between 1.00 and 2.00, and the block ratio of the chiral block to the other block is between 0.1 - 0.9, and the block ratio is the volume ratio.

[0024] Preferably, the molecular weight of the chiral homopolymer is between 1000 and 1000000, and the molecular weight distribution is between 1.00 and 2.00. The chiral homopolymer has groups such as hydroxyl, amino, or epoxy groups that can be fixed on the substrate surface.

[0025] Preferably, the neutral layer is a random copolymer of the two-phase monomers in the chiral block copolymer.

[0026] The grafting process of the chiral homopolymer layer in step ① includes: spin-coating the chiral homopolymer on the substrate; high-temperature annealing to fix the chiral homopolymer on the substrate surface; ultrasonic treatment with an organic solvent to remove the unfixed chiral homopolymer; wherein, the temperature of the high-temperature annealing is 50 - 300 °C, and the time is 1 - 120 min.

[0027] The periodic structure in step ② is one or more of a grating structure, a square lattice structure, and a hexagonal lattice structure, and the period L s is an integer multiple of the period L0 of the block copolymer domain.

[0028] The lithography technology in step ② includes: ultraviolet lithography, electron beam lithography, ion beam lithography, and nanoimprint technology.

[0029] The formation process of the chiral guiding substrate described in step ③ includes: spin-coating a neutral layer on the periodic chiral homopolymer layer; performing high-temperature annealing to fix the neutral layer polymer in the gaps of the periodic chiral homopolymer on the substrate surface; and performing ultrasonic treatment with an organic solvent to remove the ungrafted neutral layer polymer. Among them, the temperature of the high-temperature annealing is 50-300 °C, and the time is 1-120 min.

[0030] The annealing process described in step ④ is thermal annealing or solvent annealing, with a temperature of 50-300 °C and a time of 1 min-48 h.

[0031] The organic solvents in steps ①, ③, and ④ are one or more of chlorobenzene, dichloromethane, chloroform, carbon tetrachloride, tetrahydrofuran, ether, methyl isobutyl ether, anisole, benzene, toluene, hexane, N,N'-dimethylformamide, dimethyl sulfoxide, methanol, ethanol, isopropanol, acetone, n-butyl ketone, 2-pentanone, cyclopentanone, methyl isobutyl ketone, 4-methyl-2-pentanone, cyclohexanone, ethyl acetate, butyl acetate, and pentyl acetate.

[0032] The method further includes: after obtaining the chiral guiding self-assembled structure, one of the blocks in the chiral block copolymer can be removed by etching, degradation, or hydrolysis to obtain a periodic structure template for pattern transfer.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: the chiral interaction between chiral polymers with the same chirality or enantiomers is utilized to guide the chiral block copolymer, significantly improving the guiding force in the block copolymer guiding self-assembly process, and effectively reducing the defect rate and line edge roughness of the final guiding structure. Description of the Drawings

[0034] Figure 1 Schematic diagram of the chiral guiding block copolymer self-assembly lithography method;

[0035] Figure 2 SEM electron micrograph provided in Example 1 of the present invention;

[0036] Figure 3 SEM electron micrograph provided in Example 1 of the present invention;

[0037] Figure 4 SEM electron micrograph provided in Example 2 of the present invention;

[0038] Figure 5 SEM electron micrograph provided in Example 4 of the present invention;

[0039] Figure 6 SEM electron micrograph provided in Example 5 of the present invention;

[0040] Figure 7 SEM electron micrograph provided for Example 6 of the present invention;

[0041] Figure 8 SEM electron micrograph provided for Example 7 of the present invention;

[0042] Figure 9 SEM electron micrograph provided for Example 8 of the present invention. Detailed implementation manners

[0043] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0044] No special requirements are imposed on the substrates used for block polymer directed self-assembly, and they can be common semiconductor materials such as silicon wafers, germanium metal, gallium nitride, gallium phosphide, gallium arsenide or other semiconductor materials.

[0045] Example 1:

[0046] Self-assembly of AB-type polystyrene-(S) polypropylene carbonate (PS-b-(S)PPC) block copolymer under the chiral guidance of (R)PPC, as Figure 1 shown:

[0047] Dissolve 5 mg of (R)PPC homopolymer in 1.0 g of chlorobenzene. Among them, the molecular weight of (R)PPC is 6.7 kDa, the molecular weight distribution is 1.03, and the e.e. value > 99%. Spin-coat the completely dissolved (R)PPC chlorobenzene solution onto the hydrophilically modified silicon wafer (obtain a silicon dioxide layer with a thickness of about 1.5 nm through oxygen plasma etching or piranha solution oxidation) at a speed of 4000 rpm, anneal at 180 °C for 2 h, and ultrasonically wash with chlorobenzene for 5 minutes, 5 times in total, to remove the ungrafted (R)PPC homopolymer, and obtain a (R)PPC polymer brush with a thickness of 5 nm. Spin-coat PMMA-950 photoresist on the (R)PPC polymer brush, and use electron beam lithography and etching processes to obtain a (R)PPC grating structure with a period of 78 nm and a line width of 29 nm. Backfill the structure with a random copolymer neutral layer with a molar ratio of hydroxyl-terminated PPC to PS of 4:1, with a molecular weight of 6.1 kDa, anneal at 180 °C for 2 h, and ultrasonically wash with chlorobenzene for 5 minutes, 5 times in total, to remove the ungrafted neutral layer, and obtain a chiral guiding substrate of PS-b-(S)PPC.

[0048] Dissolve 5 mg of PS-b-(S)PPC block copolymer in 0.5 g of chlorobenzene, where the number-average molecular weight of the PS block is 12.4 kDa, the number-average molecular weight of the (S)PPC block is 14.7 kDa, the e.e. value > 99%, the molecular weight distribution is 1.04, and the volume ratio of the two blocks is 0.50. Spin-coat the completely dissolved PS-b-(S)PPC chlorobenzene solution onto the chiral guiding substrate at a speed of 4000 rpm to obtain a block copolymer thin film with a thickness of about 19 nm. Heat-anneal at 120 °C for 2 hours under vacuum conditions to obtain a phase domain arrangement perpendicular to the silicon wafer surface, and a large-area defect-free guiding self-assembled grating structure as Figure 2 shown in the scanning electron microscope photograph, with a half-pitch of 9.7 nm. After removing the PS phase using the continuous infiltration synthesis (SIS) method and oxygen plasma etching method, a hard template of the grating structure for pattern transfer is obtained, and the scanning electron microscope photograph is as Figure 3 shown, with a half-pitch of 9.7 nm.

[0049] Example 2:

[0050] Under the same preparation method, equipment, and operating conditions as in Example 1, only change the molecular weight of the block copolymer from 12.4k / 14.7k (PS / PPC) to 8.9k / 10.8k (PS / PPC), the volume ratio of the two blocks is 0.50, and the period and line width of the chiral guiding substrate are changed from 78 / 29 nm to 56 / 21 nm. As can be seen from the scanning electron microscope photograph shown in Figure 4 , a large-area defect-free vertically phase-domain-guided self-assembled grating structure is obtained, with a half-pitch of 7.1 nm.

[0051] Example 3:

[0052] Under the same preparation method, equipment, and operating conditions as in Example 1, only change the molecular weight of the block copolymer from 12.4k / 14.7k (PS / PPC) to 12.4k / 27.2k (PS / PPC), the volume ratio of the two blocks is 0.35, the film thickness is changed from 19 nm to 28 nm, and the chiral guiding substrate is changed from a grating structure with a period and line width of 78 / 29 nm to a hexagonal lattice structure with a period of 56 nm and a dot diameter of 14 nm. A large-area defect-free vertically phase-domain-guided self-assembled hexagonal lattice structure is obtained, with a half-pitch of 13.8 nm.

[0053] Example 4:

[0054] Self-assembly of AB-type polystyrene-(R) poly(propylene carbonate) (PS-b-(R)PPC) block copolymer under the chiral guidance of (S)PPC:

[0055] Under the same preparation method, equipment, and operating conditions as in Example 1, only the optical activity of the block copolymer was changed from the S type to the R type, the molecular weight was changed from 12.4k / 14.7k (PS / PPC) to 12.4k / 14.4k (PS / PPC), the volume ratio of the two blocks was 0.51, and the chiral homopolymer in the chiral guiding substrate was changed from R-type PPC to S-type PPC. From Figure 5 As can be seen from the scanning electron microscope photographs shown in

[0056] Example 5:

[0057] Self-assembly of ABA-type polystyrene-(S)-poly(propylene carbonate) ((S)PPC-b-PS-b-(S)PPC) block copolymer under the chiral guidance of (R)PPC:

[0058] Under the same preparation method, equipment, and operating conditions as in Example 1, only the block copolymer was changed from an AB-type diblock copolymer to an ABA-type triblock copolymer, the molecular weight was changed from 12.4k / 14.7k (PS / PPC) to 12.6k / 15.0k (PS / PPC), and the volume ratio of the two blocks was 0.50. From Figure 6 As can be seen from the scanning electron microscope photographs shown in

[0059] Example 6:

[0060] Self-assembly of AB-type polystyrene-(S)-poly(cyclohexylene carbonate) (PS-b-(S)PCHC) block copolymer under the chiral guidance of (R)PCHC:

[0061] Under the same preparation method, equipment, and operating conditions as in Example 1, only the (S)PPC block in the block copolymer was changed to the (S)PCHC block, the molecular weight was changed from 12.4k / 14.7k (PS / PPC) to 12.4k / 13.8k (PS / PCHC), and the volume ratio of the two blocks was 0.51. From Figure 7 As can be seen from the scanning electron microscope photographs shown in

[0062] Example 7:

[0063] Self-assembly of AB-type poly(4-vinylpyridine)-(S)-poly(propylene carbonate) (P4VP-b-(S)PPC) block copolymer under the chiral guidance of (R)PPC:

[0064] Under the same preparation method, equipment and operating conditions as in Example 1, only the PS block in the block copolymer was changed to a P4VP block, the molecular weight was changed from 12.4k / 14.7k (PS / PPC) to 13.5k / 14.5k (P4VP / PPC), and the volume ratio of the two blocks was 0.51. From Figure 8 As can be seen from the scanning electron microscope photograph shown, a vertically phase-domain oriented self-assembled grating structure without large-area defects was obtained, and its half pitch was 9.2 nm.

[0065] Example 8:

[0066] Self-assembly of AB-type polystyrene-(D)-polylactide (PS-b-(D)PLA) block copolymer under the chiral guidance of (L)PLA:

[0067] Under the same preparation method, equipment and operating conditions as in Example 1, only the (S)PPC block in the block copolymer was changed to a (D)PLA block, the molecular weight was changed from 12.4k / 14.7k (PS / PPC) to 12.4k / 16.7k (PS / PLA), the volume ratio of the two blocks was 0.49, and the chiral homopolymer in the chiral guiding substrate was changed from (R)PPC to (L)PLA. As can be seen from Figure 9 the scanning electron microscope photograph shown, a vertically phase-domain oriented self-assembled grating structure without large-area defects was obtained, and its half pitch was 10.2 nm.

[0068] Example 9:

[0069] Self-assembly of AB-type polystyrene-(S)-poly(PS-b-(S)PMMA) block copolymer under the chiral guidance of (R)PMMA:

[0070] Under the same preparation method, equipment and operating conditions as in Example 1, only the (S)PPC block in the block copolymer was changed to a (S)PMMA block, the molecular weight was changed from 12.4k / 14.4k (PS / PPC) to 12.4k / 17.0k (PS / PLA), the volume ratio of the two blocks was 0.49, and the chiral homopolymer in the chiral guiding substrate was changed from (R)PPC to (R)PMMA. A vertically phase-domain oriented self-assembled grating structure without large-area defects was obtained, and its half pitch was 9.9 nm.

Claims

1. A method for chiral-directed block copolymer self-assembly lithography, characterized in that The method includes: ① grafting a chiral homopolymer layer on the surface of the substrate; ② etching the chiral homopolymer layer into a periodic structure by photolithography technology; ③ backfilling the gaps of the periodic structure of the chiral homopolymer with a grafted neutral layer to form a chiral guiding substrate; ④ spin-coating a chiral block copolymer on the chiral guiding substrate and annealing to obtain a chiral guiding self-assembled structure; wherein the chiral block copolymer includes at least one chiral block, and the chiral homopolymer is the same as or a stereoisomer of the chiral block in the chiral block copolymer, the neutral layer is a random copolymer of two-phase monomers in the chiral block copolymer.

2. The method of chiral-directed block copolymer self-assembly lithography according to claim 1, wherein The chemical structure of the chiral block in the chiral block copolymer is shown in formula (I): wherein n represents the degree of polymerization of the structural units in the polymer, which is any integer between 2 and 10,000; wherein A is selected from the 1-22 structures shown below, and B is selected from the 23-32 structures shown below: wherein C, D, R1-R4 represent a heteroatom-substituted or unsubstituted aliphatic or aromatic alkane, alkene, alkyne, alcohol, ether, ketone, ester, carbonate or hydrogen atom with 1-20 carbon atoms, and the heteroatom is selected from fluorine, chlorine, bromine, iodine, nitrogen, sulfur or phosphorus atoms; wherein C and R1 cannot be of the same structure, and D and R2 cannot be of the same structure.

3. The method for chiral-directed block copolymer self-assembly lithography according to claim 2, wherein The other block in the chiral block copolymer is selected from one or more of polystyrene, poly(p-fluorostyrene), poly(p-trimethylsilylstyrene), poly(p-methylstyrene), poly(2-vinylpyridine), poly(4-vinylpyridine), polyethylene, polypropylene, polybutadiene, polyisoprene, polydimethylsiloxane, polyacrylonitrile, polyurethane, polyimide, polyvinyl chloride or polyvinyl fluoride.

4. The method for chiral-directed block copolymer self-assembly lithography according to claim 1, characterized in that, The molecular weight of the chiral block copolymer is between 1,000 and 1,000,000, the molecular weight distribution is between 1.00 and 2.00, and the block ratio of the chiral block to the other block is between 0.1 and 0.9, and the block ratio is the volume ratio; the molecular weight of the chiral homopolymer is between 1,000 and 1,000,000, and the molecular weight distribution is between 1.00 and 2.

00.

5. The method for chiral-directed block copolymer self-assembly lithography according to claim 1, characterized in that, The chiral homopolymer has a hydroxyl group, an amino group or an epoxy group.

6. The method for chiral-directed block copolymer self-assembly lithography according to claim 1, characterized in that The grafting process of the chiral homopolymer layer in step ① includes: spin-coating the chiral homopolymer on the substrate; performing high-temperature annealing to fix the chiral homopolymer on the surface of the substrate; performing ultrasonic treatment with an organic solvent to remove the unfixed chiral homopolymer; wherein the temperature of the high-temperature annealing is 50-300°C and the time is 1-120 min.

7. The method for chiral-directed block copolymer self-assembly lithography according to claim 1, characterized in that The periodic structure described in step ② is one or more of a grating structure, a square lattice structure, and a hexagonal lattice structure, and the period L of the periodic structure s is an integer multiple of the period L0 of the block copolymer domain structure.

8. The method for chiral-directed block copolymer self-assembly lithography according to claim 1, wherein The formation process of the chiral guiding substrate in step ③ includes: spin-coating the neutral layer on the periodic chiral homopolymer layer; performing high-temperature annealing to fix the neutral layer polymer on the surface of the substrate and in the gaps of the periodic chiral homopolymer; performing ultrasonic treatment with an organic solvent to remove the ungrafted neutral layer polymer; wherein the temperature of the high-temperature annealing is 50-300°C and the time is 1-120 min.

9. The method for chiral-directed block copolymer self-assembly lithography according to claim 1, wherein The annealing process in step ④ is thermal annealing or solvent annealing, and its temperature is 50-300°C and the time is 1 min-48 h.

10. The method for chiral-directed block copolymer self-assembly lithography according to claim 1, characterized in that, The method includes: after obtaining a chiral-directed self-assembled structure, removing one of the blocks in the chiral block copolymer by etching, pyrolysis or hydrolysis to obtain a periodic structure template that can be used for pattern transfer.

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