CN116149138A

CN116149138A - Preparation method of mixed photoresist and metal electrode

Info

Publication number: CN116149138A
Application number: CN202310176660.4A
Authority: CN
Inventors: 孙铮
Original assignee: Shenzhen Stan Technology Co Ltd
Current assignee: Shenzhen Stan Technology Co Ltd
Priority date: 2023-02-18
Filing date: 2023-02-18
Publication date: 2023-05-23

Abstract

The application provides a preparation method of a mixed photoresist and a metal electrode, and relates to the technical field of luminescence. The raw materials of the mixed photoresist comprise negative photoresist and extinction photoresist, and the volume ratio of the negative photoresist to the extinction photoresist is (2.5-3.5): 1. the preparation method of the metal electrode comprises the following steps: performing first coating on the surface of the set structure by using negative photoresist to obtain a first photoresist layer; continuing to use the mixed photoresist for second coating to obtain a second photoresist layer; exposing the double-layer photoresist layer to obtain a double-layer photoresist layer with a set pattern; providing a metal layer on the second photoresist layer with the set pattern; and stripping the double-layer photoresist layer below the metal layer to obtain the metal electrode.

Description

Preparation method of mixed photoresist and metal electrode

Technical Field

The application relates to the technical field of luminescence, in particular to a preparation method of a mixed photoresist and a metal electrode.

Background

The micro LED display technology is a display technology in which self-luminous micro LEDs are used as light-emitting pixel units, and the light-emitting pixel units are assembled on a driving panel to form a high-density LED array. The display device has the characteristics of high brightness, high luminous efficiency, high contrast ratio, quick response, long service life, high color gamut, self-luminescence, seamless splicing and the like, and has performances far higher than those of the existing LCD and OLED display devices, and is considered as the next generation display technology following the LCD and OLED.

The micro LED has the characteristic of self-luminescence, does not need a backlight source, is easier to debug in color compared with an OLED, and has higher resolution (1500 ppi), faster response speed (ns level), longer service life and higher brightness. However, in the prior art, the electrode size precision of the high resolution micro light emitting device is not high.

Disclosure of Invention

The purpose of the application is to provide a preparation method of a mixed photoresist and a metal electrode. The mixed photoresist capable of reducing the light intensity is provided and used on the surface of the negative photoresist layer in the Lift-off process, so that the photoetching exposure dose when light reaches the negative photoresist layer is reduced, the exposure intensity of the negative photoresist layer is reduced, the photoetching precision of the negative photoresist layer is improved, and the dimensional precision of the metal electrode is further improved.

In order to achieve the above object, the technical scheme of the present application is as follows:

in a first aspect, the present application provides a hybrid photoresist, the raw materials of which include a negative photoresist and a matting photoresist, wherein the volume ratio of the negative photoresist to the matting photoresist in the hybrid photoresist is (2.5-3.5): 1.

preferably, the extinction photoresist comprises black photoresist.

In a second aspect, the present application provides a method for preparing a metal electrode, the method comprising:

performing first coating on the surface of the set structure by using negative photoresist to obtain a first photoresist layer;

performing second coating on the surface of the first photoresist layer by using mixed photoresist to obtain a second photoresist layer; the hybrid photoresist comprises the hybrid photoresist of the first aspect;

exposing the first photoresist layer and the second photoresist layer to obtain the first photoresist layer and the second photoresist layer with set patterns respectively;

providing a metal layer on the second photoresist layer with the set pattern;

and stripping the first photoresist layer and the second photoresist layer below the metal layer to obtain a metal film layer which is a metal electrode.

Preferably, the exposure dose of the exposure is 80mJ/cm ² -100mJ/cm ² 。

Preferably, the first thickness of the sum of the first photoresist layer and the second photoresist layer is 1.5 to 2 times the second thickness of the metal film layer.

Preferably, after the first coating, the method further comprises: performing pre-baking treatment on the negative photoresist;

after the second coating, the method further comprises: and performing pre-baking treatment on the mixed photoresist.

Preferably, the method further comprises at least one of the following conditions:

a. the first coating and the second coating each independently comprise preparation using a spin-coating process;

b. the spin coating process comprises the following steps: first, carrying out first low-speed spin coating, then carrying out high-speed spin coating, and then carrying out second low-speed spin coating;

c. the spin speeds of the first low-speed spin coating and the second low-speed spin coating are 300rpm-500rpm, and the spin time is 5s-10s;

d. the spin-coating rotating speed of the high-speed spin coating is 1500rpm-2500rpm, and the spin-coating time is 50s-70s;

e. after the first coating, the method further comprises: pre-baking the negative photoresist at 100-120 deg.c for 2-4 min;

f. after the second coating, the method further comprises: performing pre-baking treatment on the mixed photoresist for 3-5 min at the temperature of 100-120 ℃;

g. the thickness of the first photoresist layer is 6-8 mu m, the thickness of the second photoresist layer is 1-2 mu m, and the total thickness of the photoresist layers after the first photoresist layer and the second photoresist layer are overlapped is 3-4 mu m;

h. after the exposure, the method further comprises: baking at 100-120deg.C for 5-10 min, developing in developer, taking out, and post-baking at 100-120deg.C for 3-5 min.

In a third aspect, the present application further provides a method for manufacturing a micro LED chip, including: providing a miniature LED epitaxial wafer, and etching a table surface structure on the miniature LED epitaxial wafer;

preparing a metal electrode on the surface of the mesa structure by using the preparation method of the metal electrode in the second aspect;

and preparing a passivation layer on the surface of the metal electrode, and etching the passivation layer to obtain an electrode contact hole.

Preferably, at least one of the following conditions is also satisfied:

g. the miniature LED epitaxial wafer comprises a substrate, a buffer layer, a third semiconductor layer, a first semiconductor layer, a multiple quantum well structure and a second semiconductor layer from bottom to top in sequence;

h. the etching includes: removing part of the second semiconductor layer and the multiple quantum well structure on the miniature LED epitaxial wafer by adopting an inductive coupling plasma etching method to expose the first semiconductor layer;

i. the preparation method of the passivation layer comprises a plasma enhanced chemical vapor deposition method;

j. the etching includes a process using dry and/or wet etching.

In a fourth aspect, the present application provides a micro LED chip, which is prepared by using the preparation method of the micro LED chip in the third aspect.

In a fifth aspect, the present application further provides a micro light emitting device, including the micro LED chip of the fourth aspect.

The beneficial effects of this application:

according to the mixed photoresist, the negative photoresist and the extinction photoresist in the raw materials have the negative photoresist characteristics of crosslinking and hardening after exposure, so that the mixed photoresist also has the negative photoresist characteristics; meanwhile, the extinction photoresist has extremely strong shading effect, and the whole mixed photoresist can also have a certain effect of reducing illumination intensity by mixing the extinction photoresist in the negative photoresist.

According to the preparation method of the metal electrode, the mixed photoresist is used on the surface of the adhesive layer formed by the negative photoresist in the Lift-off process, so that the photoetching exposure of light reaching the negative photoresist is reduced, the exposure intensity of the negative photoresist is greatly reduced, the photoetching precision of the negative photoresist is improved, the processing precision can be improved under the condition of the same photoetching machine, the dimensional precision of the metal electrode after photoresist stripping is improved, and the photoelectric performance of the miniature LED chip containing the metal electrode is further improved. In addition, the universality of the photoetching machine can be improved, so that the photoetching machine with higher lower limit of exposure can be applied to more processing scenes of semiconductor products, for example, the photoetching machine can be used for preparing products with high-precision metal electrodes.

According to the preparation method of the miniature LED chip, the metal electrode with small size and high precision can be prepared by using the preparation method of the metal electrode, so that the preparation requirements of the miniature LED chip with high resolution and high pixel density are met.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate certain embodiments of the present application and therefore should not be considered as limiting the scope of the present application.

FIG. 1 is a flow chart of a process for preparing a metal electrode;

fig. 2 is a schematic diagram of an initial structure of a micro LED epitaxial wafer;

FIG. 3 is a schematic diagram of a mesa structure after etching of a micro LED epitaxial wafer;

FIG. 4 is a schematic diagram of the structure after a metal electrode is disposed on the mesa structure;

FIG. 5 is a schematic diagram of a structure in which a passivation layer is disposed on the surface of a metal electrode;

FIG. 6 is a schematic diagram of the structure after etching the passivation layer;

FIG. 7 is a mirror image of the dual layer photoresist of example 1 after exposure development;

FIG. 8 is a mirror image pattern after vapor deposition stripping in example 1;

FIG. 9 is a mirror image of the negative photoresist layer of comparative example 1 after exposure development;

fig. 10 is a mirror pattern of the negative photoresist layer of comparative example 1 after vapor deposition stripping.

Detailed Description

The term as used herein:

"prepared from … …" is synonymous with "comprising". The terms "comprising," "including," "having," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

The conjunction "consisting of … …" excludes any unspecified element, step or component. If used in a claim, such phrase will cause the claim to be closed, such that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of … …" appears in a clause of the claim body, rather than immediately following the subject, it is limited to only the elements described in that clause; other elements are not excluded from the stated claims as a whole.

When an equivalent, concentration, or other value or parameter is expressed as a range, preferred range, or a range bounded by a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when ranges of "1 to 5" are disclosed, the described ranges should be construed to include ranges of "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. When a numerical range is described herein, unless otherwise indicated, the range is intended to include its endpoints and all integers and fractions within the range.

In these examples, the parts and percentages are by mass unless otherwise indicated.

"parts by mass" means a basic unit of measurement showing the mass ratio of a plurality of components, and 1 part may be any unit mass, for example, 1g may be expressed, 2.689g may be expressed, and the like. If we say that the mass part of the a component is a part and the mass part of the B component is B part, the ratio a of the mass of the a component to the mass of the B component is represented as: b. alternatively, the mass of the A component is aK, and the mass of the B component is bK (K is an arbitrary number and represents a multiple factor). It is not misunderstood that the sum of the parts by mass of all the components is not limited to 100 parts, unlike the parts by mass.

"and/or" is used to indicate that one or both of the illustrated cases may occur, e.g., a and/or B include (a and B) and (a or B).

The inventors of the present application have found that it is necessary to fabricate a metal electrode of high thickness and small size, specifically, a metal electrode of 1-2 μm in thickness and 1-2 μm in diameter, on a bonding metal layer when fabricating a micro light emitting device of high resolution and high pixel density. Therefore, the negative photoresist with high precision, high thickness and easy stripping is manufactured by using a Lift-off process, and when the stripping process is used for stripping the used negative photoresist, the negative photoresist is required to meet the requirement of high thickness after exposure, and high-precision curing size can be realized under the condition of high thickness, so that the metal electrode remained after stripping the photoresist on the substrate can accurately present the pattern required by the electrode. The negative photoresist with high viscosity value can meet the requirement of high thickness, but after exposure by using a photoetching machine, the negative photoresist with high viscosity value cannot form a pattern with high precision and meeting the size of a metal electrode, so that the metal electrode manufactured later cannot reach the preset size, and further the performance of the miniature luminescent device is affected.

In the actual specific operation process, the applicant found that after the negative photoresist is coated, and the photoresist is subjected to photolithography by using a common photolithography machine and developed by using a developing solution, a part of photoresist is remained in a place which is not directly subjected to illumination radiation, so that after the photoresist is removed in a Lift-off process, the pattern of the remained metal layer is deviated from the expected pattern, and particularly for small-size metal electrodes with the diameter of only 1-2 mu m, if excessive photoresist is remained on the metal layer pattern, the excessive deviation between the size of the finally prepared metal electrode and the expected required size is inevitably caused.

Further research shows that after the negative photoresist is subjected to photoetching, part of photoresist is remained at the place which is not irradiated by the illumination, and the photoresist residue can be greatly reduced because overexposure light occurs and the exposure quantity of a photoetching machine is reduced. However, for a general lithographic machine, even if adjusted to the lowest exposure of the apparatus itself (80 mJ/m ² ) The photoresist still remains, and the pattern of the metal electrode layer still cannot meet the design requirements, except for replacing the lithography machine with lower exposure, but this also means that higher production cost is required.

In this regard, the application proposes to use a special photoresist to reduce the sensitivity of the negative photoresist to light, and when the special photoresist is covered on the surface of the negative photoresist, the special photoresist can block and absorb a part of light, so that the light intensity reaching the lower negative photoresist layer finally is reduced, and the negative photoresist layer can be hardened under the normal exposure dose, so that no light is emitted, and the size of the metal layer prepared by the Lift-off process is ensured.

In a first aspect, the specific photoresist proposed in the present application is a hybrid photoresist, the raw materials of which include a negative photoresist and a matting photoresist, and the volume ratio of the negative photoresist and the matting photoresist in the hybrid photoresist is (2.5-3.5): 1, for example, may be 2.5: 1. 2.8: 1. 3: 1. 3.2: 1. 3.5:1 or (2.5-3.5): 1.

In a preferred embodiment, the matting photoresist comprises a black photoresist.

It should be noted that, the negative photoresist and the black photoresist may be any type of colloid commercially available.

The preparation method of the mixed photoresist specifically comprises the following steps: mixing the two photoresists according to the formula proportion, and then carrying out vacuum defoaming treatment by using a vacuum defoaming machine to ensure that no bubbles exist in the mixed photoresists.

In a second aspect, the present application provides a method for preparing a metal electrode, as shown in fig. 1, including:

s1, carrying out first coating on the surface of a set structure by using negative photoresist to obtain a first photoresist layer;

s2, performing second coating on the surface of the first photoresist layer by using the mixed photoresist to obtain a second photoresist layer; the hybrid photoresist comprises the hybrid photoresist of the first aspect;

s3, exposing the first photoresist layer and the second photoresist layer to obtain the first photoresist layer and the second photoresist layer with set patterns;

s4, arranging a metal layer on the second photoresist layer with the set pattern;

s5, stripping the first photoresist layer and the second photoresist layer below the metal layer, wherein the obtained metal film layer is a metal electrode.

The configuration mentioned in S1 mainly refers to a base structure in which a metal electrode is to be formed on the surface. For the micro light-emitting device, the substrate is actually referred to as a micro LED epitaxial wafer with a mesa structure, and the micro LED chip and the micro light-emitting device can be prepared by preparing a metal electrode on the micro LED epitaxial wafer.

In a preferred embodiment, the exposure dose required for the exposure in S3 is 80mJ/cm ² -100mJ/cm ² . The exposure dose is mainly (2.5-3.5): the preferred exposure amount required for the mixed photoresist at the volume ratio of 1 can be adjusted by increasing the proportion of the extinction photoresist in the mixed photoresist if the exposure dose is increased, whereas if the exposure dose is lowered, the proportion of the extinction photoresist in the mixed photoresist is decreased.

In a preferred embodiment, the first thickness of the sum of the first photoresist layer and the second photoresist layer is 1.5 to 2 times, for example, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, or 2 times the second thickness of the metal film layer.

It can be appreciated that when the Lift-off process is used to prepare the metal film, if the thickness of the photoresist layer to be stripped is close to that of the metal film, the metal film on the surface of the photoresist layer, which also needs to be stripped, is easily adhered to the metal film which does not need to be stripped, so that the accuracy of the metal film obtained after stripping is lower.

In a preferred embodiment, after the first coating in S1, the method further comprises: and performing pre-baking treatment on the first photoresist layer made of the negative photoresist. It is further preferred that the pre-baking treatment is performed at 100℃to 120℃for 2min to 4min, and more preferred that the baking is performed on a hot plate at 110℃for 2 min.

In a preferred embodiment, after the second coating in S2, the method further comprises: and performing pre-baking treatment on the second photoresist layer made of the mixed photoresist. It is further preferred that the pre-baking treatment is performed at 100℃to 120℃for 3min to 5min, and more preferred that the baking is performed on a hot plate at 110℃for 3 min.

It should be noted that the pre-baking treatment mainly includes removing most of the solvent in the photoresist by baking, so as to primarily cure the photoresist layer.

In a preferred embodiment, the first coating in S1 and the second coating in S2 each comprise a preparation using a spin-coating process.

Further preferably, in spin coating using the negative electrode photoresist, first low-speed spin coating may be performed, followed by high-speed spin coating, and then second low-speed spin coating may be performed. When the surface of the first photoresist layer is spin-coated with the mixed photoresist, the first low-speed spin-coating may be performed first, then the high-speed spin-coating may be performed, and then the second low-speed spin-coating may be performed.

Further preferably, the spin speeds of the first low-speed spin coating and the second low-speed spin coating are 300rpm to 500rpm, for example, 300rpm, 400rpm, 500rpm, or any value between 300rpm and 500rpm, and the time of the low-speed spin coating is 5s to 10s, for example, 5s, 6s, 7s, 8s, 9s, 10s, or any value between 5s to 10 s. The spin speeds and times of the first low-speed spin coating and the second low-speed spin coating may be the same or different. More preferably, the parameters of both the first low-speed spin coating and the second low-speed spin coating are maintained at 500rpm for 5 seconds.

It should be noted that, the first low-speed spin coating is performed first, and the purpose of the first low-speed spin coating is to cover the photoresist on the surface of the entire substrate structure, that is, on the surface of the entire micro LED epitaxial wafer with the mesa structure.

Further preferably, the spin speed of the high-speed spin coating is 1500rpm to 2500rpm, which may be, for example, 1500rpm, 1800rpm, 1900rpm, 2000rpm, 2200rpm, 2500rpm or any value between 1500rpm and 2500rpm, and the spin time is 50s to 70s, which may be, for example, 50s, 55s, 60s, 65s, 70s or any value between 50s to 70 s. More preferably, the parameters of the high speed spin coating are maintained at 2000rpm for 60s.

In a preferred embodiment, the thickness of the first photoresist layer obtained in S1 is 6 μm to 8 μm, and the thickness of the second photoresist layer obtained in S2 is 1 μm to 2 μm, and the total thickness of the photoresist layers after the first photoresist layer and the second photoresist layer are stacked is 3 μm to 4 μm because the two photoresists are mutually dissolved during spin coating.

In a preferred embodiment, after exposure in S3, the method further comprises: baking at 100-120deg.C for 5-10 min, developing in developer, taking out, and post-baking at 100-120deg.C for 3-5 min. More preferably, baking is performed for 10min on a hot plate at 110 ℃, then the mixture is put into a developing solution for 2min for development, and after the mixture is taken out, the mixture is put on the hot plate at 110 ℃ for 3min for post-baking.

It will be appreciated that the baking for 5min to 10min is mainly performed to sufficiently perform the crosslinking reaction in the photoresist after exposure, and particularly to ensure that the crosslinking reaction in the underlying first photoresist layer sufficiently proceeds. And then post-baking treatment is carried out to further remove the solvent of the photoresist layer. The choice of the developer is mainly made according to the kind of the photoresist itself.

Further, after the photoresist is placed into a developing solution for development, microscopic examination is carried out on the developed sample, so that the interior of the pattern is ensured to be developed cleanly, and no massive photoresist remains. After post-baking treatment, dry plasma photoresist stripping is performed, for example, a sample can be placed into a machine of Asher or descum for photoresist stripping, so that no photoresist residue exists in the pattern.

Before the metal layer is provided in S4, the total thickness of the first photoresist layer and the second photoresist layer needs to be tested by using a step gauge, and when the total thickness is 1.5-2 times the thickness of the planned metal coating layer, a coating process of the metal layer is performed, for example, an electron beam evaporation coating process may be used.

In a preferred embodiment, the stripping in S5 specifically includes: and (3) immersing the sample provided with the metal layer in photoresist removing solution or acetone, then stripping the first photoresist layer and the second photoresist layer by ultrasonic treatment, removing the metal layer on the surface of the second photoresist layer, taking out the sample, cleaning and drying by using deionized water, and performing microscopic examination by using a microscope.

In a third aspect, the present application further provides a method for manufacturing a micro LED chip, including:

(1) Providing a miniature LED epitaxial wafer, and etching a table surface structure on the miniature LED epitaxial wafer;

(2) Preparing a metal electrode on the surface of the mesa structure by using the preparation method of the metal electrode in the second aspect;

(3) And preparing a passivation layer on the surface of the metal electrode, and etching the passivation layer to obtain an electrode contact hole.

In a preferred embodiment, the micro LED epitaxial wafer 100 includes, from bottom to top, a substrate 110, a buffer layer 120, a third semiconductor layer 130, a first semiconductor layer 140, a multiple quantum well structure 150, and a second semiconductor layer 160, as shown in fig. 2. The epitaxial wafer may be prepared in advance, or may be deposited layer by layer on a substrate. It should be understood that this embodiment is only an exemplary micro LED epitaxial wafer structure that may include other layers or other structures, and is not particularly limited herein.

The resulting mesa 200 after etching on the micro LED epitaxial wafer is shown in fig. 3. The mesa 200 includes a plurality of bumps 210, which may be used to form an array, thereby forming a chip array.

In a preferred embodiment, the etching comprises: and removing part of the second semiconductor layer and the multiple quantum well structure on the miniature LED epitaxial wafer by adopting an inductive coupling plasma etching method to expose the first semiconductor layer.

Specifically, photoresist is spin-coated on the surface of the miniature LED epitaxial wafer, a mesa pattern is photoetched, and then an Inductively Coupled Plasma (ICP) method is adopted, and Cl is used ₂ And Ar, etching is performed from the second semiconductor layer 160 until the first semiconductor layer 140 is exposed, and finally the photoresist is removed to form the mesa structure 200 shown in fig. 3. Thereafter, a metal electrode 170 is formed on the surface of the mesa structure 200 using the method for forming a metal electrode described in the second aspect above, as shown in fig. 4.

In a preferred embodiment, as shown in fig. 5, the method for preparing the passivation layer 180 on the surface of the metal electrode 170 includes: plasma enhanced chemical vapor deposition. The passivation layer 180 may be made of silicon dioxide, silicon nitride, aluminum oxide, or the like.

In a preferred embodiment, the passivation layer 180 is etched, specifically including: using dry and/or wet etching processes. If the process requirement is not high, the electrode contact hole 190 can be obtained by dry etching or wet etching, if the process requirement is high, the electrode contact hole 190 is obtained by dry etching and then wet etching, as shown in fig. 6.

In a fourth aspect, the present application further provides a micro LED chip, which is prepared by using the preparation method of the micro LED chip in the third aspect.

In a fifth aspect, the present application provides a micro light emitting device, including the micro LED chip described in the fourth aspect.

Embodiments of the present application will be described in detail below with reference to specific examples, but it will be understood by those skilled in the art that the following examples are only for illustration of the present application and should not be construed as limiting the scope of the present application.

Example 1

The embodiment provides a hybrid photoresist, and the preparation method comprises the following steps:

the volume ratio of the negative photoresist to the black photoresist is 3:1, and then placing the mixture in a vacuum deaeration machine for vacuum deaeration treatment to obtain the mixed photoresist.

The embodiment provides a metal electrode, and a preparation method of the metal electrode may include:

(1) And spin-coating the wafer sample with the negative photoresist to obtain a negative photoresist layer, wherein the spin-coating parameters can be 500rpm/5s-2000rpm/60s-500rpm/5s, and then performing pre-baking on a hot plate at 110 ℃ for 2min to remove most of the solvent in the first photoresist layer, so that the first photoresist layer is primarily cured.

(2) Spin coating is performed on the first photoresist layer in the step (1) by using the mixed photoresist provided in the embodiment to obtain a mixed photoresist layer, spin coating parameters can be 500rpm/5s-2000rpm/60s-500rpm/5s, then pre-baking is performed on a hot plate at 110 ℃ for 3min, and most of the solvent of the second photoresist layer is removed to be primarily solidified.

(3) The sample obtained in the step (2) is put into a photoetching machine for exposure, and the exposure dose is 80mJ/cm ² . And after the exposure is finished, the sample is placed on a hot plate at 110 ℃ for 10min to bake, so that the crosslinking reaction in the double-layer photoresist is fully carried out, and then the sample is placed in a developing solution for development for about 2 min.

(4) Microscopic examination is carried out after development, so that the interior of the graph is ensured to be developed cleanly without massive photoresist residues; and then placing the sample on a hot plate at 110 ℃ for 3min for post-baking, and further removing the solvent in the photoresist.

(5) The Asher machine can be used for carrying out oxygen plasma dry photoresist stripping on the sample, and the sample is placed into the machine, so that no photoresist residue in the graph can be ensured. In practice, the treatment conditions may be 100w, 5min.

(6) And (3) measuring the film thickness of the double-layer photoresist layer on the surface of the sample in the step (5) by using a step instrument, and evaporating the sample after confirming that the film thickness is 1.5-2 times of the thickness of the planned metal coating film to obtain the metal layer.

(7) And (3) immersing the sample coated in the step (6) in a photoresist removing solution, then removing the double-layer photoresist layer outside the pattern and the metal on the surface of the double-layer photoresist layer by ultrasonic, and finally washing the double-layer photoresist layer with deionized water and performing microscopic examination on the pattern.

Example 2

the volume ratio of the negative photoresist to the black photoresist is 2.5:1, and then placing the mixture in a vacuum deaeration machine for vacuum deaeration treatment to obtain the mixed photoresist.

This example provides a metal electrode, which is prepared by the same method as example 1, except that: the hybrid photoresist of the present embodiment is used in step (2); the exposure dose in the step (3) is 90mJ/cm ² 。

Comparative example 1

This comparative example provides a metal electrode prepared in the same manner as in example 1, except that: and (2) without the step (2), after the negative photoresist layer is obtained in the step (1), placing a sample of the single-layer negative photoresist layer into a photoetching machine for exposure, development and other processes.

Comparative example 2

This comparative example provides a hybrid photoresist, as in example 1.

This comparative example provides a metal electrode prepared in the same manner as in example 1, except that: the step (1) is not performed, but the mixed photoresist is directly spin-coated on the surface of a 4-inch wafer sample to obtain a single-layer mixed photoresist layer, and then the single-layer mixed photoresist layer sample is placed into a photoetching machine for exposure, development and other processes.

The results of microscopic examination of the metal electrodes prepared in example 1 and comparative example 1 are shown in fig. 7 to 10.

FIG. 7 is a photograph of a photo-resist pattern of example 1 after exposure development of a bilayer resist (negative resist layer + hybrid resist layer), wherein the stripe pattern is stripe holes left after the photo-resist development, and the total of ten stripe holes have widths of 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.8 μm, 0.5 μm in order from large to small. FIG. 8 is a microscopic image of example 1 after step (7). FIG. 9 is a photograph of a single negative photoresist layer of comparative example 1 after exposure development, using the same photomask and the same lithography conditions as in example 1. Fig. 10 is a mirror image of comparative example 1 after stripping the single layer negative photoresist layer.

Comparing fig. 7 and fig. 9, it can be seen that the pattern size obtained after the photolithography in example 1 is larger than that obtained in comparative example 1, and particularly, the pattern width at the longest stripe in the middle of the stripe patterns in both the two figures can be compared, and it is obvious that the width at the longest stripe in fig. 7 is larger than that in fig. 9; and the pattern boundaries in fig. 7 are also more clear than those in fig. 9. This shows that the use of the technical solution of embodiment 1 reduces the exposure intensity of the negative photoresist and reduces the residual photoresist area in the unexposed area.

Comparing fig. 8 and fig. 10, it can be clearly seen that the metal layer obtained after evaporation and stripping in fig. 10 is more severely stripped than that of fig. 8, especially the strip metal with the width of less than 1 μm is stripped, which indicates that under the same exposure condition, example 1 can effectively reduce the exposure intensity of the negative photoresist, ensure the metal size obtained after evaporation and stripping, and also prove that the negative photoresist has residual photoresist at the bottom of the metal pattern due to overlarge exposure dose, and further the metal obtained after evaporation and stripping is easy to be stripped.

In comparative example 2, because the solvents required in the negative photoresist and the black photoresist are different, after the mixed photoresist is subjected to suspension coating, the mixed photoresist formed by mixing the negative photoresist and the black photoresist is mutually dissolved, so that the whole adhesive layer is thinned, and a metal layer with a thicker thickness cannot be obtained. Therefore, the thickness of the metal layer after the metal plating and peeling of comparative example 2 was not satisfactory.

Comparing the pattern sizes, pattern boundaries and the like of the metal electrodes prepared in the above examples and comparative examples shows that by covering the mixed photoresist on the surface of the negative photoresist layer, the photoetching exposure of light reaching the negative photoresist is greatly reduced, the exposure intensity of the negative photoresist is reduced, thus improving the photoetching precision of the negative photoresist, improving the processing precision, improving the dimensional precision of the metal electrode after photoresist stripping and further improving the photoelectric performance of the micro LED chip containing the metal electrode under the condition of the same photoetching machine. In addition, the universality of the photoetching machine can be improved, so that the photoetching machine with relatively low exposure lower limit can be applied to processing scenes of more semiconductor products, for example, the photoetching machine can be used for preparing products with high-precision metal electrodes. In addition, the metal electrode in the embodiment of the application can also be prepared on the mesa structure of the micro LED epitaxial wafer, and the micro LED chip is prepared by using the preparation method of the micro LED chip, and the metal electrode on the micro LED chip is small in size and high in precision, so that the area utilization rate of the epitaxial wafer is greatly increased, and the micro LED chip is beneficial to manufacturing a display array with high PPI and high resolution.

The application also provides a miniature light-emitting device, which comprises the miniature LED chip. The micro light emitting device can be applied to electronic equipment to realize augmented Reality (XR) technology such as augmented Reality (Augmented Reality, AR), virtual Reality (VR), mixed Reality (MR) and the like. For example, the micro light emitting device may be a projection part of an electronic apparatus, such as a projector, head Up Display (HUD), or the like; for another example, the micro light emitting device may also be a display portion of an electronic apparatus, for example, the electronic apparatus may include: any device with a display screen, such as a smart phone, a smart watch, a notebook computer, a tablet computer, a vehicle recorder, a navigator, a head-mounted device, and the like; also for example, the micro light emitting device may also be an illumination portion of an electronic device, which may include: vehicles, street lamps, etc. any device having a lighting assembly.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Furthermore, those skilled in the art will appreciate that while some embodiments herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the present application and form different embodiments. For example, in the claims below, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is only for enhancement of understanding of the general background of the application and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Claims

1. The mixed photoresist is characterized by comprising a negative photoresist and a extinction photoresist, wherein the volume ratio of the negative photoresist to the extinction photoresist in the mixed photoresist is (2.5-3.5): 1.

2. the hybrid photoresist of claim 1 wherein the matt photoresist comprises a black photoresist.

3. A method of making a metal electrode, the method comprising:

performing second coating on the surface of the first photoresist layer by using mixed photoresist to obtain a second photoresist layer; the hybrid photoresist comprising the hybrid photoresist of claim 1 or 2;

exposing the first photoresist layer and the second photoresist layer to obtain the first photoresist layer and the second photoresist layer with set patterns;

providing a metal layer on the second photoresist layer with the set pattern;

4. The method according to claim 3, wherein the exposure dose of the exposure is 80mJ/cm ² -100mJ/cm ² 。

5. The method of claim 3 or 4, wherein the first thickness of the first photoresist layer and the second photoresist layer after being stacked is 1.5-2 times the second thickness of the metal film layer.

6. The method of manufacturing according to claim 3, wherein after the first coating, further comprising: performing pre-baking treatment on the negative photoresist;

7. A method of preparing as claimed in claim 3, wherein the method comprises at least one of the following conditions:

e. after the first coating, the method further comprises: pre-baking the negative photoresist for 2-4 min at the temperature of 100-120 ℃;

8. The preparation method of the miniature LED chip is characterized by comprising the following steps of: providing a miniature LED epitaxial wafer, and etching a table surface structure on the miniature LED epitaxial wafer;

preparing a metal electrode on the surface of the mesa structure by using the preparation method of the metal electrode in any one of claims 3-7;

9. The method of manufacturing a micro LED chip as set forth in claim 8, wherein at least one of the following conditions is also satisfied:

j. the etching includes a process using dry and/or wet etching.

10. A micro LED chip, characterized in that it is manufactured by using the manufacturing method of the micro LED chip according to claim 8 or 9.