CN110911273B - Preparation method of large-area patterned graphene - Google Patents

Abstract

The invention belongs to the technical field of two-dimensional material processing, and in particular relates to a preparation method of large-area patterned graphene and the prepared large-area patterned graphene. The method adopts a three-layer glue process, including spin coating a first layer of a polymer support layer, a second layer of a soluble photoresist sacrificial layer and a third layer of photoresist, as well as development, reactive etching, and glue removal. In the present invention, the three-layer glue process is used to replace the traditional photoresist mask etching method, on the one hand, the problem of photoresist degeneration during the graphene etching process is avoided; It is carried out under the protection of the initial polymer, which avoids the pollution of graphene caused by repeated gluing.

Description

A kind of preparation method of large area patterned graphene

technical field

The invention belongs to the technical field of two-dimensional material processing, and in particular relates to a preparation method of large-area patterned graphene and the prepared large-area patterned graphene.

Background technique

The rapid development of large-scale industrial preparation technology of graphene thin film provides a material guarantee for the basic research and application development of graphene, and the patterning of graphene is the key to its practical application. However, due to the special material properties of graphene, there are still some technical difficulties and challenges in its micro-nano patterning. On the one hand, due to the very thinness of graphene itself, high-performance optoelectronic devices have great influence on its processing accuracy, flatness and spatial resolution. The requirements are very high; on the other hand, the electrical properties of graphene are very sensitive to the surrounding environment, and structural defects and residual glue pollution introduced during processing will affect the performance of the device. Therefore, how to perform high-precision patterning on graphene is the key to improving the performance of graphene-based electronic/optoelectronic devices, which is of great significance.

How to fabricate large-area, high-quality graphene patterns on a large scale is a key scientific and technical problem in the industrialization of many application fields. Using photoresist as a masking layer and realizing the patterning of graphene by exposure and etching is a relatively common method for preparing large-area graphene patterns. However, local carbonization occurs between the photoresist and graphene interface during the etching process, resulting in a large amount of glue residue on the graphene surface during the debonding process. In addition, the entire process from graphene transfer to patterning requires repeated spin-coating and removal of various polymers, which can lead to the generation of a large number of impurities and defects and cause the degradation of graphene film quality. These deficiencies above largely limit the further application and industrialization of graphene. Therefore, it is very important to find a large-area, non-destructive and pollution-free graphene thin film patterning method.

SUMMARY OF THE INVENTION

In view of this, the object of the present invention is to provide a preparation method of large-area patterned graphene and prepared large-area patterned graphene, the preparation method can realize the large-area, ultra-clean preparation of the target graphene pattern, which The graphics precision can reach 1um.

For achieving the above object, the present invention adopts the following scheme:

The preparation method of the large-area patterned graphene adopts a three-layer glue technology, and the three-layer glue technology is as follows:

1) spin-coating the polymer support layer of the first layer on the graphene surface, and transfer it to the surface of the target substrate;

2) spin-coating the second layer of soluble photoresist sacrificial layer, and drying and curing;

3) spin-coating the third layer of photoresist, drying, and carrying out optical exposure to obtain a photoresist pattern with a trapezoidal cross-sectional structure;

4) Utilize reactive ion etching machine to carry out synchronous etching to the polymer support layer and graphene that are not protected by the reticle;

5) The second layer of soluble photoresist, the third layer of photoresist and the polymer support layer are sequentially removed by a degumming solution to obtain patterned graphene.

Further, in step 1), the polymer is an organic substance such as PMMA and PC, the target substrate is a SiO ₂ /Si substrate or a substrate such as ROIC, and the transfer method is wet transfer.

Further, in step 2) the second sacrificial layer is a photoresist that is insoluble in acetone but easily soluble in an alkaline developer, the drying temperature is 80-150 degrees Celsius, and the drying time is 30-60 minutes.

Further, the third layer of photoresist in step 3) is a positive photoresist, such as AZ3100, S1818, S1805, etc., the drying temperature is 100 degrees Celsius, and the drying time is 10-30 minutes. Further, in step 3) the trapezoidal cross section is a gradient step formed by the second sacrificial layer and the third layer of photoresist.

Further, in step 4) the etching gas used is oxygen, and the etching power is 30-100W.

Specifically, the etching time depends on the thickness of the polymer support layer.

Further, the degumming solution in step 5) is a developing solution and acetone.

Specifically, the exposure and development time depends on the thickness and solubility of the two glues.

Further, the substrate needs to be dried before degumming, the drying temperature is 100-170 degrees Celsius, and the time is 10-30 minutes.

Further, before carrying out step 2), the graphene/copper sheet of step 1) needs to be put into the aqueous solution of hydrochloric acid/hydrogen peroxide for 10 hours, and the volume ratio of described HCL, H2O2 and water is 2:1:5.

The beneficial effects of the present invention are:

1) The method replaces the traditional photoresist mask etching method, and the graphene is protected by the polymer support layer throughout the patterning process, avoiding the damage caused to the graphene by the repeated spin coating, degumming and other operations;

2) The second layer of soluble photoresist will not be denatured during the etching process, the existence of this layer isolates the interaction between the photoresist and the underlying material, and avoids the problem that the photoresist cannot be removed due to denaturation;

3) The control of the photoresist cross-section can be realized by controlling the development time, and the photoresist structure of the stepped cross-section can better exert the insulating effect of the second layer of photoresist, so as to realize the clean preparation of the graphene pattern.

Description of drawings

Fig. 1 is a process flow diagram of preparing graphite patterning.

FIG. 2 is a scanning electron microscope picture of a photoresist cross-section at different development times in Example 1. FIG.

FIG. 3 is an optical microscope photo of the graphene patterned array prepared on the surface of Si/SiO2 in Example 1. FIG.

FIG. 4 is a scanning electron microscope picture of the graphene pattern on the surface of the ROIC in Example 2. FIG.

Detailed ways

The examples are given to better illustrate the present invention, but the content of the present invention is not limited to the examples. Therefore, those skilled in the art make non-essential improvements and adjustments to the embodiments according to the above-mentioned contents of the invention, which still belong to the protection scope of the present invention.

Example 1 Preparation of large-area patterned graphene

1. Select 1*1cm graphene grown on the surface of the copper foil and fix it on the carrier sheet, and spin-coat PMMA with a concentration of 6% on the surface as the support layer of graphene;

2. Configure an aqueous solution of hydrochloric acid/hydrogen peroxide, whose volume ratio is HCL:H2O2 _{: H2O} = ₂ :1:5, and put the graphene/copper sheet coated with PMMA into the solution for 10h;

3. After the copper is completely dissolved, the graphene is applied to the SiO2/Si substrate, and the graphene is dried at 120 degrees Celsius;

4. Spin-coat the second layer of LOR-A5 photoresist on the surface of PMMA/graphene, and dry at 100 degrees Celsius for 35 minutes; spin-coat the third layer of photoresist S1805 on the surface, and then dry at 100 degrees Celsius for 10 minutes;

5. Under the occlusion of the target reticle, the substrate is exposed for 5s by an ultraviolet exposure machine, and developed in the developer solution for 50s to obtain a target pattern with a stepped cross-section, and the photoresist cross-section is as shown in Figure 2, wherein a A target pattern with a stepped cross-section is obtained for exposure for 50s, b is a target pattern for a cross-section obtained by exposure for 60s, and c is a target pattern for a cross-section obtained by exposure for 70s. It can be seen that the degree of dissolution of the sacrificial layer can be effectively controlled by controlling the development time. Therefore, an appropriate development time can be selected to form a trapezoidal cross-section of the photoresist and the sacrificial layer (as shown in Figure 2), and finally achieve an effective balance between the degree of protection of graphene and the requirements for patterning accuracy.

6. Use an oxygen plasma etching machine to etch the substrate for 5-10 minutes, and the etching power is 30-100W, and simultaneously remove the exposed PMMA and graphene.

7. Dry the substrate, the drying temperature is 100-150 degrees Celsius, and the time is 10-30 minutes.

8. The second layer of photoresist, the third layer of photoresist and PMMA are removed by developing solution and acetone respectively, to obtain the graphene array with target pattern, and its optical microscope picture is as shown in accompanying drawing 3, wherein a Optical micrograph of the graphene patterned array prepared for the Si/SiO2 surface, b is a further enlarged view of the graphene patterned array.

Example 2 Preparation of large-area patterned graphene

1. The selection of graphene and the dissolution process of copper foil are the same as in Example 1.

2. After the copper is completely dissolved, the graphene is applied to the ROIC substrate with uneven surface, and the graphene is dried at 120 degrees Celsius;

3. Spin-coat the second layer of LOR-A5 photoresist on the surface of PMMA/graphene, and dry at 170 degrees Celsius for 30 minutes; spin-coat the third layer of photoresist S1805 on the surface, and then dry at 100 degrees Celsius for 10 minutes;

4. Under the shielding of the target reticle, the substrate is exposed by an ultraviolet exposure machine for 5s, and developed in a developing solution for 40s to obtain a target pattern with a stepped cross-section.

5. Use an oxygen plasma etching machine to etch the substrate for 5-10 minutes, and the etching power is 30-100W, and simultaneously remove the exposed PMMA and graphene.

6. Dry the etched substrate at 170 degrees Celsius for 10 minutes to achieve tight adhesion between the graphene and the substrate.

7. The second layer of photoresist, the third layer of photoresist and PMMA are respectively removed by developing solution and acetone, that is, the graphene array of the pattern is obtained on the ROIC surface, and its optical microscope picture is as shown in accompanying drawing 4, wherein a is the graphene array patterned on the ROIC surface, b is a further enlarged view of the array based on a, c is a further enlarged view of the array based on b, the substrate and the target reticle can be seen after magnification.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be Modifications or equivalent substitutions without departing from the spirit and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims (7)

1. The preparation method of the large-area patterned graphene is characterized by adopting a three-layer glue process, wherein the three-layer glue process comprises the following steps:

1) spin-coating a first polymer support layer on the surface of graphene, and transferring the polymer support layer to the surface of a target substrate, wherein the polymer is PMMA (polymethyl methacrylate) or PC (polycarbonate), and the target substrate is SiO (silicon oxide) ₂ a/Si substrate or an ROIC substrate, and the transfer method is wet transfer;

2) spin-coating a second soluble photoresist sacrificial layer, and drying and curing;

3) spin-coating the third layer of photoresist, drying, exposing the substrate for 5s through an ultraviolet exposure machine, and developing in a developing solution for 40s or 50s or 60s or 70s to obtain a photoresist pattern with a trapezoidal section structure;

4) synchronously etching the polymer supporting layer and the graphene which are not protected by the mask by using a reactive ion etching machine;

5) removing the second layer of soluble photoresist, the third layer of photoresist and the polymer supporting layer in sequence by using the photoresist solution to obtain patterned graphene;

step 2) the second sacrificial layer is LOR-A5 photoresist which is insoluble in acetone but easily soluble in alkaline developing solution, the drying temperature is 80-150 ℃, and the drying time is 30-60 minutes;

and 3) the third layer of photoresist is positive photoresist, such as AZ3100, S1818, S1805 and the like, the drying temperature is 100 ℃, and the drying time is 10-30 minutes.

2. The method according to claim 1, wherein the trapezoidal section in step 3) is a gradient step formed by the second sacrificial layer and the third photoresist layer.

3. The method according to claim 1, wherein the etching gas used in step 4) is oxygen, and the etching power is 30-100W.

4. The preparation method according to claim 1, wherein the degumming solution of step 5) is a developing solution and acetone.

5. The method as claimed in claim 1, wherein the substrate is dried before the photoresist is removed, wherein the drying temperature is 100 ℃ and 150 ℃ and the drying time is 10-30 minutes.

6. The preparation method of claim 1, wherein the graphene/copper sheet obtained in step 1) is put into an aqueous solution of hydrochloric acid/hydrogen peroxide for 10 hours before step 2), and the HCl and the H are mixed ₂ O ₂ And water in a volume ratio of 2: 1: 5.

7. large area patterned graphene prepared by the preparation method of any one of claims 1 to 6.

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