CN113608285B - Ni column-assisted PMMA (polymethyl methacrylate) microlens array and preparation method thereof - Google Patents

Abstract

The invention discloses a Ni pillar-assisted PMMA microlens array and a preparation method thereof. The method is as follows: 1) electroplating a Ni pillar array on a silicon wafer plated with chrome gold; 2) spin-coating a layer of liquid PMMA on the silicon wafer plated with the Ni pillar array, and then drying; 3) using an overlay technique , align the X-ray mask with the Ni pillars on the silicon wafer, and then expose and develop a sample with a PMMA pillar array, wherein each PMMA pillar in the PMMA pillar array includes a Ni pillar inside; 4) The sample obtained in step 3) is heated in an oven, so that each PMMA column in the PMMA column array is thermally fused into a microlens to obtain a microlens array. The present invention achieves the effect of increasing the contact angle of the microlens by adding the Ni column to the PMMA column, thereby enabling the preparation of a microlens array with a larger contact angle.

Description

A kind of Ni pillar-assisted PMMA microlens array and preparation method thereof

technical field

The invention belongs to the technical field of micro-processing, and relates to a Ni-pillar-assisted PMMA micro-lens array and a preparation method thereof, which can be used to improve the contact angle of the micro-lens array.

Background technique

Microlens arrays are composed of individual lenses arranged in the form of arrays as micro-optical elements, which have a wide range of applications, such as optical communication, integrated imaging, fiber coupling, light field display technology, and so on. The methods of making the microlens array include photolithography hot melt method, hot pressing forming method, micro jet printing method, femtosecond laser direct writing method and so on. Among them, the photolithography hot-melt method is widely used because the process is relatively simple, the requirements for materials and equipment are not high, and the process parameters are stable and easy to control.

LIGA (LIGA is the German word Lithographie, Galvanoformung and Abformung, that is, the abbreviation of lithography, electroforming and injection molding) technology is a MEMS processing technology based on X-ray lithography, mainly including X-ray depth synchrotron radiation lithography, electro Casting and injection moulding replicate three process steps. Due to the very high parallelism, strong radiation intensity and continuous spectrum of X-rays, LIGA technology is very advantageous in the fabrication of three-dimensional structures with large aspect ratios, smooth sidewalls, and parallelism deviations in the sub-micron range. This is not possible with other micromachining techniques. PMMA (organic glass) is a conventional photoresist for LIGA technology X-ray synchrotron radiation, which has the advantages of high transparency, low price, and easy machining.

The traditional manufacturing method of microlens array is to manufacture microlens array by photolithography hot-melt method and LIGA technology. Generally, a columnar microlens array is made first, and then it is heated in a constant temperature chamber. When the heating temperature is higher than the vitrification of PMMA When the temperature is high, the PMMA column will gradually form a spherical shape under the action of surface tension. After maintaining a constant temperature for a period of time, the sample is naturally cooled and taken out to obtain a microlens array. At present, traditional methods cannot further improve the lens contact angle.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the purpose of the present invention is to provide a Ni pillar-assisted PMMA microlens array and a preparation method thereof. The invention combines the LIGA technology with the photoresist hot-melting method, and adds Ni pillars into the PMMA micropillars through the overlay technique, resulting in the contact angle of the obtained microlens being larger than that of the microlens without the Ni pillars. The addition of Ni pillars can increase the contact angle of the microlens, so that a microlens array with a larger contact angle can be prepared.

The present invention achieves the effect of increasing the contact angle of the microlens by adding the Ni column to the PMMA column, thereby enabling the preparation of a microlens array with a larger contact angle.

The technical scheme adopted by the present invention to solve its technical problems is:

1. Spin-coat a layer of AZ4620 photoresist, and after drying, expose and develop it.

2. Electroplating an array of Ni pillars on a chrome-gold-plated silicon wafer, the Ni pillars are 180 μm in diameter and 7 to 10 μm in height.

3. Spin-coat a layer of liquid PMMA on the sample electroplated with Ni column array and dry it.

4. Using the overlay technology, align the X-ray mask with the Ni column of the sample, and obtain the sample with the Ni column located in the middle of the PMMA column through deep synchrotron radiation lithography and development. The PMMA pillars were 245 μm in diameter and 104 μm in height.

5. The sample is heated in an oven to obtain a microlens array.

The present invention has the following innovations:

1. The use of Ni pillars can change the morphology of the lenses in the microlens array.

2. The Ni pillar increases the lens contact angle of the microlens array.

The advantages of the present invention are as follows:

1. Compared with the method of surface modification in which the contact angle of the lens is changed, the present invention has simple operation and strong controllability.

2. The addition of Ni pillars can prepare photoresist pillars with a larger aspect ratio, further exerting the advantages of LIGA technology.

Description of drawings

Figure 1 is a flow chart of the present invention.

Figure 2 is a graph of experimental results;

(a) PMMA column with Ni column in the thermal melting result map,

(b) Thermal fusion result of Ni-free column in PMMA column.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings. The examples are only used to explain the present invention, but not to limit the scope of the present invention.

The preparation method flow chart of the present invention is shown in Figure 1, and its steps include:

1. Spin-coat a layer of 10μm photoresist on a 2-inch chrome-gold-plated silicon wafer. After UV exposure and development, a mold for electroplating Ni pillars was obtained; the samples were electroplated in the Ni electroplating pool, the electroplating current was set to 0.03A, the electroplating time was 45 minutes, and the AZ4620 photoresist was removed with a degumming solution, and the AZ4620 photoresist was cleaned and dried. Afterwards, a sample with an array of Ni pillars can be obtained. Among them, the Ni columnarity is 7 to 10 μm, and the diameter is 180 μm.

2. Put the electroplated samples into the glue removal solution to remove the glue, and then you can get the Ni column (no big requirement, the interval will not cause adhesion phenomenon, and the quantity is not required), the height is 7 to 10μm, the diameter is 180μm.

3. Spin-coat a layer of liquid PMMA on the sample with the electroplated Ni column, put it on a 95°C hot plate, and heat it for 2 hours to dry the liquid PMMA.

4. Pass the sample through the overlay technique to make the Ni pillar and the X-ray mask (the pattern on the mask is the template for the subsequent obtaining of the sample with the Ni pillar located in the middle of the PMMA pillar, and the X-ray mask pattern area, that is, the circular array is not Light-transmitting, PMMA is a positive glue, and the opaque part is not revealed by the developer) after the pattern is aligned, and then exposed with X-rays.

5. After the exposed sample is developed and dried, a PMMA column array with a height of 104 microns and a diameter of 240 microns is obtained, which is then placed in an oven to heat and fuse into microlenses. A microlens array in which the contact angle of the microlens is increased by Ni pillars can be obtained.

6. Comparing the experimental samples, as shown in Figure 2, the production process of the samples without Ni columns is similar to that with Ni columns, and the steps of preparing Ni columns can be removed. The PMMA pillars without Ni pillars are 109 μm in height and 235 μm in diameter.

Although specific embodiments of the present invention have been disclosed for illustrative purposes, the purpose is to assist in understanding the contents of the present invention and implementing them accordingly, and those skilled in the art will appreciate that: without departing from the spirit and scope of the present invention and the appended claims Within, various substitutions, changes and modifications are possible. Therefore, the present invention should not be limited to the contents disclosed in the preferred embodiments, and the scope of protection of the present invention shall be subject to the scope defined by the claims.

Claims (5)

1. A preparation method of a Ni pillar-assisted PMMA micro lens array comprises the following steps:

1) electroplating a Ni pillar array on a silicon wafer plated with chrome gold;

2) spin-coating a layer of liquid PMMA on the silicon wafer electroplated with the Ni column array, and then drying;

3) aligning an X-ray mask plate with the Ni columns on the silicon wafer by using an alignment technology, and then carrying out exposure and development to obtain a sample with a PMMA column array, wherein each PMMA column in the PMMA column array comprises a Ni column;

4) putting the sample obtained in the step 3) into an oven for heating, and carrying out hot melting on each PMMA column in the PMMA column array to obtain the microlens array.

2. The method of claim 1, wherein the Ni pillars have a diameter of 180 μm and a height of 7 to 10 μm.

3. The method of claim 2, wherein the PMMA columns have a diameter of 245 μm and a height of 104 μm.

4. A method as claimed in claim 1, 2 or 3, wherein in step 2), the sample spin-coated with a layer of liquid PMMA is placed on a hot plate at 95 ℃ and heated for 2 hours to dry the liquid PMMA.

5. The method of claim 1, 2 or 3, wherein in step 4), the sample is placed in an oven for heating, the hot-melt temperature is 240 ℃ and the hot-melt time is 30 minutes.

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