Method for preparing wafer-level aluminum-based enediol dry photoresist using molecular layer deposition

Abstract

A method for preparing a wafer-level aluminum-based enediol dry photoresist using molecular layer deposition, using an aluminum source and enediol as precursors, performing molecular layer deposition, and obtaining the aluminum-based enediol dry photoresist after deposition, wherein the specific steps of the molecular layer deposition are as follows: maintaining the aluminum source at room temperature, and heating a source bottle containing enediol to 60-120°C, maintaining the temperature of the reactor at 80-150°C, and using 20sccm of dry nitrogen to purge the reaction, wherein each cyclic reaction consists of two half-cycles: (1) introducing the aluminum source for 50 milliseconds and purging with nitrogen for 16 seconds; and (2) introducing enediol for 150 milliseconds and purging with nitrogen for 25 seconds, with a system pressure of 13 Pa, and the deposition thickness being controlled according to the number of deposition cycles. The thickness of the photoresist of the present invention can be accurately controlled to the angstrom level, and has excellent etching resistance, a selective etching ratio with silicon of more than 80, and good resolution.

Description

Technical Field

[0001] The invention relates to the technical field of photoresist preparation, and in particular to a method for preparing wafer-level aluminum-based-enediol dry photoresist by using molecular layer deposition. Background Art

[0002] As a key technology for manufacturing large-scale integrated circuits (ICs), its development directly determines the future direction of ICs. As IC process nodes continue to shrink, lithography technology continues to advance, now reaching EUV (13.5nm) lithography. Although EUV lithography equipment is now commercially available, the lack of photoresists suitable for EUV lithography significantly hinders the advancement of process nodes below 5nm. Currently, organic photoresists are predominantly used. However, metal-based photoresists are gaining increasing attention. These photoresists primarily consist of metal nanoparticles (such as hafnium oxide, zinc oxide, and zirconium oxide) modified with organic ligands (such as para-hydroxystyrene and methacrylic acid). Compared to traditional organic photoresists, inorganic photoresists offer advantages such as better EUV light absorption, improved etching resistance, improved pattern collapse resistance, and reduced line-edge roughness, attracting extensive research.

[0003] Organic photoresists, composed of light elements such as C, H, and O, absorb EUV light very weakly, resulting in a significant decrease in photosensitivity. Metal-based photoresists have become a promising alternative. However, the advent of high-numerical-aperture (NA) EUV lithography machines requires photoresist thicknesses of less than 20 or even 10 nanometers. The physical spin-coating method currently used for both organic and metal-based photoresists struggles to address this issue. Therefore, a method for producing metal-based photoresists with precisely controlled thickness and high uniformity is urgently needed. Summary of the Invention

[0004] The present invention provides a method for preparing an aluminum-based ethylenediol dry photoresist with precisely controlled film thickness. Using molecular layer deposition (MLD), the aluminum-based ethylenediol dry photoresist can achieve thickness control down to the angstrom (0.1 nanometer) level, exhibiting high uniformity, excellent etch resistance (a selective etching ratio relative to silicon exceeding 80), and good resolution (at least 50 nm).

[0005] The present invention provides a method for preparing an aluminum-based ethylenediol dry photoresist with precisely controlled film thickness. Electron beam, DUV, or EUV lithography is employed, followed by post-baking at 70-90°C for 50-180 seconds, development using a weakly alkaline solution such as ammonia for 5-45 seconds, and transfer of the photoresist pattern to the substrate via ICP etching (using SF6 or C4F8 as the etching gas). The technical solution employed is as follows:

[0006] Aluminum source and enediol are used as precursors to carry out molecular layer deposition, and aluminum-based enediol dry photoresist is obtained after deposition.

[0007] The aluminum source precursor is one of trimethylaluminum, triethylaluminum, aluminum trichloride, diethyl ethoxyaluminum, and dimethyl isopropoxyaluminum.

[0008] The enediol precursor is one of butenediol and its isomers, pentenediol and its isomers, hexenediol and its isomers, heptenediol and its isomers, and octenediol and its isomers.

[0009] The molecular layer deposition is carried out on a silicon or silicon dioxide substrate.

[0010] The specific steps of the molecular layer deposition are:

[0011] The thin films were deposited in an MLD device controlled by LabVIEW. The aluminum source was maintained at room temperature, and the source bottle containing ethylene glycol was heated to 50-120°C. The reactor temperature was maintained at 80-150°C, and 20 sccm of dry nitrogen was used to purge the reaction. Each cycle consisted of two half-cycles: (1) the aluminum source was introduced and nitrogen was purged; (2) the ethylene glycol was introduced and nitrogen was purged. The system pressure was 13-25 Pa, and the deposition thickness was controlled by the number of deposition cycles. For example, when trimethylaluminum and 1,4-butenediol were used as precursors, the growth thickness per cycle was 0.08 nm.

[0012] The technical effect is that the present invention can achieve precise film thickness control, achieving the desired thickness by controlling the number of cycles at 0.08 nanometers per cycle, which is difficult to achieve with traditional spin coating methods. Simultaneously, using a 30keV electron beam for exposure, this photoresist can achieve a resolution of at least 50 nanometers. Due to limitations in exposure equipment, the resolution can be lowered to 20 nanometers with better exposure equipment. Using ICP etching, the selective etching ratio of the photoresist to silicon can reach 150, enabling the production of lines of at least 500 nanometers. Using better etching equipment, at least 50 nanometers can be produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a diagram of the growth principle of photoresist.

[0014] Figure 2 In the figure, a is an AFM side view of the resist surface when the thickness is 30 nm; b is an AFM top view and side view of the resist surface when the thickness is 30 nm; c is an AFM side view of the resist surface when the thickness is 15 nm; d is an AFM top view and side view of the resist surface when the thickness is 15 nm;

[0015] Figure 3 It is the XPS scan of the film before and after exposure.

[0016] Figure 4 In the figure, a is the SEM pattern of 1000 nm, 500 nm, and 300 nm, with L / S=1:1 at 2 keV; b is the SEM pattern of 400 nm, 200 nm, and 80 nm, with L / S=1:2 at 2 keV; c is the SEM pattern of 100 nm, with L / S=1:1 at 30 keV; d is the SEM pattern of 50 nm, with L / S=1:1 at 30 kV; e is the top view of AFM imaging of 100 nm, with L / S=1:3 at 30 kV; f is the top view of AFM imaging of 50 nm, with L / S=1:9 at 30 kV.

[0017] Figure 5 (a) AFM top and oblique views after 0 seconds of ICP etching, showing a trench depth of 17.5 nm; (b) AFM top and oblique views after 12 seconds of ICP etching, showing a trench depth of 315 nm; (c) AFM top and oblique views after 24 seconds of ICP etching, showing a trench depth of 710 nm; (d) AFM top and oblique views after 48 seconds of ICP etching, showing a trench depth of 1503 nm. The line width in a, b, c, and d is 2.5 μm.

[0018] Figure 6 This is an oblique atomic force microscope image of a 500-nanometer line etched by ICP. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to specific examples, but the present invention is not limited to the following examples. The methods described are conventional methods unless otherwise specified. The raw materials described can be obtained from public commercial channels unless otherwise specified. Aluminum-based enediol dry photoresist was prepared using molecular layer deposition. In each complete cycle, the aluminum source ligand combines with the hydroxyl bond on the enediol to form an aluminum-enediol structure, and the final film is obtained through multiple cycle growth. The film thickness can be precisely controlled by the number of cycles. The schematic diagram of the principle of the molecular layer deposition method for growing aluminum-based enediol dry photoresist of the present invention is as follows: Figure 1 shown.

[0020] Example 1: This photoresist was prepared using trimethylaluminum and 1,4-butenediol.

[0021] A 4-inch silicon wafer was placed in an MLD device controlled by LabVIEW for deposition. Trimethylaluminum was kept at room temperature, and the source bottle containing 1,4-butenediol was heated to 80°C. The temperature of the reactor was maintained at 90°C, and 20 sccm of dry nitrogen was used to purge the reaction. Each cycle reaction consisted of two half cycles: (1) 50 milliseconds of aluminum source was introduced, and nitrogen was purged for 16 seconds; (2) 150 milliseconds of 1,4-butenediol was introduced, and nitrogen was purged for 25 seconds. The system pressure was 13 Pa, and the film thickness was 32 nm after 400 cycles of deposition. The schematic diagram is shown in the figure. Figure 1 Surface roughness: When the growth thickness is 30 nm, Rq = 0.2 nm, when the growth thickness is 15 nm, Rq = 0.17 nm, such as Figure 2 .

[0022] The photoresist is exposed using an electron beam, then dried at 80°C for 90 seconds, and then developed with 5 wt% ammonia for 15 seconds to obtain exposed lines. 2keV can produce 1000 nm to 80 (line / space = 1:2) nanometer lines, and 30keV can produce 50 (line / space = 1:1) nanometer lines. Figure 4 .

[0023] The specific etching recipe for ICP etching is: temperature 20°C, chamber pressure 15mTorr, excitation power 400W, bias power 20W, SF6: 15sccm, C4F8: 60sccm. We can etch silicon to a depth of 1500nm using 18nm photoresist, with a selective etching ratio of 83 to silicon (etching line size 2.5μm). Figure 5 . Etching 500 nm lines such as Figure 6 .

[0024] Example 2: A 4-inch silicon wafer was placed in an MLD device controlled by LabVIEW for deposition. Trimethylaluminum was maintained at room temperature, and the source bottle containing 1,5-pentenediol was heated to 85°C. The reactor temperature was maintained at 90°C, and 20 sccm of dry nitrogen was used to purge the reaction. Each cycle consisted of two half-cycles: (1) 50 milliseconds of aluminum source introduction and 15 seconds of nitrogen purge; (2) 150 milliseconds of pentanediol introduction and 30 seconds of nitrogen purge. The system pressure was 13 Pa. Exposure and etching tests were the same as in Example 1.

[0025] Example 3: A 4-inch silicon wafer was placed in an MLD device controlled by LabVIEW for deposition. Triethylaluminum was maintained at room temperature, and the source bottle containing 1,4-butenediol was heated to 85°C. The reactor temperature was maintained at 100°C, and 20 sccm of dry nitrogen was used to purge the reaction. Each cycle consisted of two half-cycles: (1) 50 milliseconds of aluminum source introduction and 15 seconds of nitrogen purge; (2) 150 milliseconds of 1,4-butenediol introduction and 25 seconds of nitrogen purge. The system pressure was 13 Pa. Exposure and etching tests were the same as in Example 1.

[0026] Example 4: A 4-inch silicon wafer was placed in an MLD device controlled by LabVIEW for deposition. Triethylaluminum was maintained at room temperature, and the source bottle containing 1,2-butenediol was heated to 50°C. The reactor temperature was maintained at 80°C, and 20 sccm of dry nitrogen was used to purge the reaction. Each cycle consisted of two half-cycles: (1) 50 milliseconds of aluminum source introduction followed by a 20-second nitrogen purge; (2) 150 milliseconds of 1,2-butenediol introduction followed by a 20-second nitrogen purge. The system pressure was 13 Pa. Exposure and etching tests were the same as in Example 1.

Claims

1. A method for preparing a wafer-level aluminum-based ethylene glycol dry photoresist using molecular layer deposition, characterized by: Using aluminum source and enediol as precursors, molecular layer deposition is performed to obtain aluminum-enediol dry photoresist. The specific steps of molecular layer deposition are as follows: The aluminum source was kept at room temperature, and the source bottle containing enediol was heated to 60-120°C. The temperature of the reactor was kept at 80-150°C, and 20 sccm of dry nitrogen was used to purge the reaction. Each cycle reaction consisted of two half cycles: (1) the aluminum source was introduced for 50 milliseconds, and nitrogen was purged for 16 seconds; (2) the enediol was introduced for 150 milliseconds, and nitrogen was purged for 25 seconds. The system pressure was 13 Pa, and the deposition thickness was controlled according to the number of deposition cycles. The enediol precursor is one of butenediol and its isomers, pentenediol and its isomers, hexenediol and its isomers, heptenediol and its isomers, and octenediol and its isomers; The aluminum source precursor is one of trimethylaluminum, triethylaluminum, aluminum trichloride, diethyl ethoxyaluminum, and dimethyl isopropoxyaluminum.

2. The method for preparing wafer-level aluminum-based ethylene glycol dry photoresist using molecular layer deposition according to claim 1, wherein: The molecular layer deposition is carried out on a silicon or silicon dioxide substrate.

3. The method for preparing wafer-level aluminum-based ethylene glycol dry photoresist using molecular layer deposition according to claim 1, wherein: The deposition thickness was 32 nm after 400 cycles, or 0.08 nm / cycle.

4. The method for preparing wafer-level aluminum-based ethylene glycol dry photoresist using molecular layer deposition according to claim 1, wherein: In each complete cycle, the aluminum source ligand combines with the hydroxyl bond on the enediol to form an aluminum-enediol structure, and the final film is grown through multiple cycles.

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