Nanocrystal photoresist-free photolithographic method based on organophosphorus ligand

Abstract

A nanocrystal photoresist-free photolithographic method based on an organophosphine ligand.By means of introducing an organic molecule containing a phosphorus group to serve as a photosensitive ligand to convert a nanocrystal into a photosensitive coating, direct patterning is realized. The solution solves the problem of effectively reducing the performance loss of the nanocrystal during the process of completing patterning, and has the following advantages: 1) high regiospecificity / stereospecificity; 2) a photosensitive interval being adjustable, and being suitable for photolithography using DUV, i-line and h-line light sources; 3) having high reaction sensitivity and requiring an extremely low exposure dose; and 4) being insensitive to the environment, being operable in an air atmosphere, involving mild reaction conditions and being easily operated. The process is expected to be applied to the commercialization of nanocrystals in the field of electroluminescent and photoluminescent quantum dot displays.

Description

A nanocrystal resist-free lithography method based on organophosphorus ligands Technical Field

[0001] The invention belongs to the technical field of nano material patterning methods, and in particular relates to a nano crystal non-resin photolithography method based on organic phosphorus ligands. Background Art

[0002] Colloidal nanocrystals are emerging materials for building next-generation electronic, optoelectronic, and photonic devices. Patterning technology is a prerequisite for their practical application in system-level integrated platforms, such as full-color high-resolution displays and multiplexed image sensors. Several digitally controlled patterning techniques, including photolithography, transfer printing, inkjet printing, screen printing, and laser writing, have been extensively studied to optimize the resolution, throughput, fidelity, and cost of each pattern element. Optical lithography remains an attractive option due to its high resolution, high throughput, and wide availability.

[0003] Currently, the primary method for optical patterning of nanocrystals is direct photolithography. This strategy involves introducing a photoacid generator or photosensitive molecule into the colloidal nanocrystal system, transforming the nanocrystal solution into a photosensitive solution. At specific wavelengths, the photosensitive substance decomposes or polymerizes, causing changes in the surface environment of the nanocrystals. This affects their stability in certain solvents, allowing the corresponding solvent to be eluted to remove the unexposed areas, thus achieving patterning.

[0004] However, existing optical patterning technologies for nanocrystals still have shortcomings. First, current non-resin lithography technology still requires the introduction of photosensitive additives to transform nanocrystals into photosensitive coatings. However, these molecules, apart from photosensitivity, do not improve the performance of the nanocrystals themselves, but have some negative effects on the performance of the device. For example, photosensitive organic ligands decompose under light, thereby changing the composition of the nanocrystal surface, resulting in changes in the wavelength and half-peak width of its emission spectrum; and the protons generated by the photoacid generator under light will damage the surface of the nanocrystal, affecting the optical properties of the nanocrystal, and further causing damage to subsequent devices. More importantly, under strong light, water and oxygen in the air are extremely destructive to the surface of the nanocrystal. Therefore, existing non-resin lithography needs to be completed in a low-water / oxygen system, which is not suitable for use in actual production processes.

[0005] Summary of the Invention

[0006] The present invention solves the above-mentioned technical problems existing in the prior art, and successfully realizes direct photolithographic patterning of nanocrystals by introducing organic molecules containing phosphorus groups as photosensitive ligands. The present invention designs a class of multifunctional organic phosphorus ligands. This type of ligand has three functions: 1) acting as a photosensitive molecule to transform the nanocrystals into photosensitive coatings, assisting the nanocrystals in achieving direct patterning; 2) acting as a Z-type ligand to passivate surface defects of the nanocrystals, thereby improving the fluorescence quantum efficiency (PLQY) of the nanocrystals and simultaneously improving the stability of the nanocrystals in the corresponding solvents; 3) acting as a sacrificial agent to capture water / oxygen present in the system, thereby reducing the damage of water / oxygen to the surface of the nanocrystals during the photolithography process. Therefore, this invention has the following advantages: 1) high regional / stereospecificity; 2) adjustable photosensitive range, suitable for DUV, i-line and h-line light source lithography; 3) high reaction sensitivity, requiring extremely low exposure dose; 4) insensitive to the environment, can be operated in an air atmosphere, with mild reaction conditions and easy operation.

[0007] The technical solutions of the present invention are as follows:

[0008] An organophosphorus ligand-based nanocrystal can be used for photolithographic patterning, wherein the organophosphorus ligand-based nanocrystal comprises an organophosphorus ligand and a nanocrystal;

[0009] The organophosphorus ligand is:

[0010] where R 1 、R 2 and R 3 It can be an alkyl chain of various lengths or a group containing any functional group such as a hydrocarbon group, an ester group, a benzene ring, and a heterocyclic ring;

[0011] Preferably, the R 1 、R 2 and R 3 are the same, such as:

[0012] The R 1 、R 2 、R 3 Any two are the same, such as:

[0013] The R 1 、R 2 and R 3 Different, such as:

[0014] In addition to the above monophosphine organic molecules, suitable organophosphorus ligands also include polyphosphine-terminated organic molecules composed of tertiary phosphine end groups, such as

[0015] Preferably, the nanocrystals further include an original ligand, and the original ligand is any one or a combination of oleic acid, oleylamine, octadecylamine, trioctylphosphine, octadecylphosphonic acid, didodecyldimethylammonium bromide, 3-(N,N-dimethylmyristylammonio)propanesulfonate, natural lecithin, and thiol.

[0016] Preferably, the nanocrystals are II-VI group nanocrystals, III-V group nanocrystals, IV-VI group nanocrystals, core-shell structure quantum dot nanocrystals, perovskite nanocrystals, metal nanocrystals or metal oxide nanocrystals.

[0017] Preferably, the nanocrystals are selected from semiconductors CdSe, CdS, CdTe, PbS, PbSe, HgTe, HgSe, HgS, CdZnSeS / ZnS and InP / ZnSe / ZnS quantum dots, CdSe / ZnS core-shell nanosheets, Cd x Zn 1-x Se, Cd x Zn 1-x S, Hg x Cd 1-x S, Hg x Cd 1-x Se, Hg x Cd 1-x Te, Hg x Zn 1-x Te, where 0 < x < 1, InP, InAs, InN, InSb, InAs 1-x Sb x , GaAs, GaN, GaP, GaSb, AlN, AlP, AlAs, where 0 < x < 1, CdSe / ZnS, CdSe / CdS, CdTe / CdSe, PbS / CdS, ZnSe / CdS, ZnSe / CdSe, CuInS2 / CuInS2, CuInS2 / ZnS, HgSe / CdS, HgSe / CdSe, HgSe / CdSe / CdS, Cd 1-x Zn x S / ZnS, where 0 < x < 1, etc.), oxides (CeO2, TiO2, ZnO, and ZrO2, etc.), magnetic materials (Fe3O4 and Mn3O4, etc.), upconversion (NaYF4:Yb,Er@CaF2), perovskites (CsPbX3, CH3NH3PbX3, FAPbX3, where X = Cl, Br or I, and FA is formamidinium), metal nanoparticles (Co, Ag, Ni, and Au, etc.).

[0018] The nanocrystals based on the organophosphorus ligands can be used to prepare nanocrystal coatings, wherein the nanocrystals based on the organophosphorus ligands and a non-polar solvent include toluene, cyclohexane or octane.

[0019] Preferably, in the nanocrystalline coating based on organophosphorus ligand, the mass fraction of the organophosphorus ligand is 5-40%.

[0020] Preferably, the concentration of the nanocrystals in the nanocrystal coating based on the organophosphorus ligand is 5-50 mg / mL.

[0021] A method for preparing a nanocrystalline coating based on an organophosphorus ligand comprises the following steps:

[0022] Step 1, dispersing the nanocrystals containing the original ligand in a non-polar solution to prepare nanocrystal ink;

[0023] Step 2: adding the organophosphorus ligand to the nanocrystal ink and dissolving the organophosphorus ligand to prepare a nanocrystal coating based on the organophosphorus ligand.

[0024] A nanocrystal non-resist photolithography method based on an organophosphorus ligand comprises the following steps:

[0025] The nanocrystal coating based on the organic phosphorus ligand is spin-coated on a substrate to form a film, covered with a mask plate, and then developed after being exposed to light.

[0026] Preferably, the method of forming the thin film is spin coating.

[0027] Preferably, the substrate is a silicon wafer, a quartz wafer or an ITO glass.

[0028] Preferably, the method of developing after exposure to light is specifically: exposing to ultraviolet light and then washing with toluene or n-octane, and the unexposed parts are washed away to obtain a pattern.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] 1) High regio / stereospecificity;

[0031] 2) The photosensitivity range is adjustable, suitable for DUV (254nm), i-line (365nm) and h-line (405nm) light source lithography;

[0032] 3) It has high reaction sensitivity and requires extremely low exposure dose;

[0033] 4) It is not sensitive to the environment and can be operated in an air atmosphere. The reaction conditions are mild and easy to operate.

[0034] 5) During the experimental nanocrystal patterning process, the functional molecular ligand can also act as a protective agent to prevent the nanocrystals from being damaged during the patterning process.

[0035] In summary, the present invention solves the problem of effectively reducing the performance loss of nanocrystals during the patterning process. This process is expected to be applied in the commercialization of nanocrystals in the fields of electroluminescent and photoluminescent quantum dot displays. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic diagram of the protection mechanism of organophosphine ligands;

[0037] Figure 2 shows the protective effect of triethylphosphine on nanocrystals: Figure a compares the UV absorption and fluorescence spectra of nanocrystals before and after the addition of organic molecules; Figure b compares the UV absorption spectra of nanocrystals before and after UV irradiation in air atmosphere before and after the addition of organic molecules;

[0038] Figure 3 is a schematic diagram of the patterning mechanism and process;

[0039] FIG4 is a patterned photograph of CdSe nanocrystals;

[0040] FIG5 is a patterned photograph of CdSeS / ZnS nanocrystals;

[0041] FIG6 is a patterned photograph of CsPbBr3 nanocrystals;

[0042] FIG7 is a photograph of patterned CdSe nanocrystals. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0044] Case Study 1: Protective Effect of Triethylphosphine Ligand on CdSe Nanocrystals

[0045] The following operations were all performed in an air atmosphere, and the protective mechanism is shown in Figure 1. Taking CdSe nanocrystals as an example, their surface ligand is oleic acid, and n-octane is used as the solvent, with a concentration of 5-50 mg / mL. The solution was then divided into two, with one serving as a control group. The changes in the UV absorption spectrum of the solution before and after 254 nm UV irradiation for half an hour were compared. Then, 5-40% triethylphosphine organic molecules were added to the other solution, which still maintained a stable colloidal solution state. The changes in the UV absorption spectrum of the solution before and after 254 nm UV irradiation were compared. The changes in the experimental group and the control group were also compared, with the results shown in Figure 2.

[0046] Case Study 2: Patterning of CdSe Nanocrystals with Trimethylphosphine Ligands

[0047] The following operations are all carried out in an air atmosphere, and the process and reaction mechanism are shown in Figure 3. Taking CdSe nanocrystals as an example, the original ligand on its surface is oleic acid. Using n-octane as the solvent, its concentration is prepared to 5-50 mg / mL, and 25-100 μL of its colloidal solution is taken. Then, trimethylphosphine organic molecules with a mass fraction of 5-40% are added thereto. At this time, a stable colloidal solution state can still be maintained. Take 5-30 μL or more of the mixed solution, apply it on a clean silicon wafer, and then spin coat it into a film. First, spread the gel at 500 r / min for 2-10 seconds, and then spin coat at 3000 r / min for 20-50 seconds. At this time, a uniform nanocrystal film can be obtained on the surface of the silicon wafer. Cover the silicon wafer coated with the nanocrystal film with a mask and expose it to 20-300 mJ / cm2 of ultraviolet light with a wavelength of 254 nm. 2 After cleaning with n-octane, the unexposed areas are washed away to obtain a pattern, as shown in FIG4 .

[0048] Case Study 3: Patterning of CdSeS / ZnS Nanocrystals with Methyldiphenylphosphine Oxide Ligands

[0049] The following operations are all carried out in an air atmosphere, and the process and reaction mechanism are shown in Figure 3. Taking CdSeS / ZnS nanocrystals as an example, the original ligand on its surface is oleic acid. Using toluene as the solvent, its concentration is prepared to 5-50 mg / mL, and 25-100 μL of its colloidal solution is taken. Then, 5-40% of methyldiphenylphosphine oxide organic molecules are added thereto. At this time, a stable colloidal solution state can still be maintained. Take 5-30 μL of the mixed solution, apply it on a clean silicon wafer, and then spin coat it into a film. First, spread the gel at 500 r / min for 2-10 seconds, and then spin coat at 3000 r / min for 20-50 seconds. At this time, a uniform nanocrystal film can be obtained on the surface of the silicon wafer. Cover the silicon wafer coated with the nanocrystal film with a mask and expose it to 20-300 mJ / cm under ultraviolet light with a wavelength of 365 nm. 2 The unexposed areas were then washed away with toluene to obtain a pattern, as shown in FIG5 .

[0050] Case Study 4: Patterning of Perovskite Nanocrystals with Ethylmethylphenylphosphine Ligands

[0051] The following operations are all carried out in an air atmosphere, and the process and reaction mechanism are shown in Figure 3. Taking CsPbBr3 nanocrystals as an example, the original ligands on their surface are oleic acid and oleylamine. Using toluene as the solvent, the concentration is prepared to 5-50 mg / mL. Take 25-100 μL of its colloidal solution, and then add 5-40% of ethylmethylphenylphosphine organic molecules to it. At this time, it can still maintain a stable colloidal solution state. Take 5-30 μL of the mixed solution, apply it on a clean silicon wafer, and then spin coat it into a film. First, spread the glue at 500 r / min for 2-10 seconds, and then spin coat at 3000 r / min for 20-50 seconds. At this time, a uniform nanocrystal film can be obtained on the surface of the silicon wafer. Cover the silicon wafer coated with the nanocrystal film with a mask and expose it to 50-500 mJ / cm under ultraviolet light with a wavelength of 405 nm. 2 The unexposed areas were then washed away with toluene to obtain a pattern, as shown in FIG6 .

[0052] Example 5:

[0053] Similar to Example 4, the present invention uses triethyl phosphine, triphenyl phosphine oxide, dimethylphenyl phosphine, methyldiphenyl phosphine oxide, 2,4,6-trimethylbenzoyl ethyl phosphate, and 1,4-bis(diphenylphosphino)butane instead of ethylmethylphenylphosphine as the organophosphorus ligand, and the technical effect shown in Figure 6 can be achieved.

[0054] Example 6: Patterning of CdSe Nanocrystals Containing Trioctylphosphine Ligands

[0055] The following operations are all carried out in an air atmosphere, and the process and reaction mechanism are shown in Figure 3. Taking CdSe nanocrystals as an example, the original ligands on their surface are oleic acid and trioctylphosphine. Toluene is used as the solvent to prepare a concentration of 5-50 mg / mL. 25-100 μL of the colloidal solution is taken and applied on a clean silicon wafer, and then spin-coated to form a film. First, the gel is spread at 500 r / min for 2-10 seconds, and then spin-coated at 3000 r / min for 20-50 seconds. At this time, a uniform nanocrystal film can be obtained on the surface of the silicon wafer. The silicon wafer coated with the nanocrystal film is covered with a mask and exposed to 50-500 mJ / cm2 of ultraviolet light with a wavelength of 405 nm. 2 The unexposed areas were then washed away with toluene to obtain a pattern, as shown in FIG7 .

[0056] It should be noted that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Equivalent replacements or substitutions made on the basis of the above embodiments all fall within the scope of protection of the present invention.

Claims

1. An application of nanocrystals based on organic phosphorus ligands in optical patterning, characterized in that: The nanocrystal based on organic phosphorus ligand comprises organic phosphorus ligand and nanocrystal; The organophosphorus ligand is: Where R 1 , R 2 and R 3 It may be an alkyl chain or a group containing any functional group such as a hydrocarbon group, an ester group, a benzene ring, and a heterocyclic ring.

2. The use according to claim 1, characterized in that The organic phosphorus ligand is any one of triethylphosphine, triphenylphosphine oxide, dimethylphenylphosphine, methyldiphenylphosphine oxide, ethylmethylphenylphosphine, 2,4,6-trimethylbenzoylethyl phosphate, 1,4-bis(diphenylphosphino)butane, and trioctylphosphine, or a combination of several thereof.

3. The use according to claim 1, characterized in that The nanocrystals based on organic phosphorus ligands also include original ligands, which are any one or a combination of oleic acid, oleylamine, octadecylamine, trioctylphosphine, octadecylphosphonic acid, didodecyldimethylammonium bromide, 3-(N,N-dimethylmyristylammonium)propanesulfonate, natural lecithin, and thiols.

4. The use according to claim 1, characterized in that The nanocrystals are any one or a combination of several of CdSe, CdS, CdTe, PbS, PbSe, HgTe, HgSe, HgS, CdZnSeS / ZnS, InP / ZnSe / ZnS, CdSe / ZnS, Cd x Zn 1-x Se, Cd x Zn 1-x S, Hg x Cd 1-x S, Hg x Cd 1-x Se, Hg x Cd 1-x Te, Hg x Zn 1-x Te, InP, InAs, InN, InSb, InAs 1-x Sb x 、GaAs, GaN, GaP, GaSb, AlN, AlP, AlAs, CdSe / ZnS, CdSe / CdS, CdTe / CdSe, PbS / CdS, ZnSe / CdS, ZnSe / CdSe, CuInS2 / CuInS2, CuInS2 / ZnS, HgSe / CdS, HgSe / CdSe, HgSe / CdSe / CdS, Cd 1-x Zn x S / ZnS, CeO2, TiO2, ZnO, ZrO2, Fe3O4, Mn3O 、 , NaYF4:Yb,Er@CaF2, CsPbX3, CH3NH3PbX3, FAPbX3, Co, Ag, Ni, Au, where 0 < x < 1, X = Cl, Br or I, and FA is formamidinium.

5. A nanocrystalline coating based on an organic phosphorus ligand, characterized in that: It comprises the nanocrystal based on the organic phosphorus ligand as claimed in claim 1 and a non-polar solvent.

6. The nanocrystal coating according to claim 5, characterized in that: The non-polar solvent is toluene, cyclohexane or octane.

7. The nanocrystal coating according to claim 5, characterized in that: The mass fraction of the organic phosphorus ligand is 5-40%.

8. The nanocrystal coating according to claim 5, characterized in that: The concentration of the nanocrystals is 5-50 mg / mL.

9. The method for preparing the nanocrystalline coating according to any one of claims 5 to 8, characterized in that: The following steps are involved: Step 1, dispersing nanocrystals containing original ligands in a non-polar solution to prepare nanocrystal ink; Step 2, adding the organophosphorus ligand to the nanocrystal ink, and dissolving the organic phosphorus ligand to form a nanocrystal coating based on the organic phosphorus ligand.

10. A non-resist photolithography method based on the nanocrystal coating according to any one of claims 5 to 8, comprising the following steps: The nanocrystal coating based on the organic phosphorus ligand is spin-coated on a substrate to form a film, covered with a mask plate, and then developed after being exposed to light.

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