KR20020072659A - Method of fabricating a microlens - Google Patents

Abstract

PURPOSE: A method for fabricating a micro lens is provided, which has a cross section in a shape of a hyperhemisphere. CONSTITUTION: According to the method, a sacrificial layer(20a) is formed on a silicon or glass substrate(10), and an epilayer pattern whose cross section is deformed into a sphere shape by a surface tension according to the heating is formed on the above sacrificial layer. And the sacrificial layer is laterally etched using the epilayer pattern. And the epilayer pattern is reflowed by heating the epilayer pattern. And at least a part of the cross section of the micro lens is in a hyperhemisphere shape.

Description

Manufacturing method of micro lens {Method of fabricating a microlens}

The present invention relates to a method for manufacturing a microlens, and more particularly, to a method for manufacturing a hyperhemisphere microlens using reflow of a material layer pattern.

The lens is the most basic component in implementing a compact optical system. Thus, various methods for making microlenses have been tried to date. In general, the microlenses may be divided into lenses that can be used in the visible and infrared regions according to the available wavelengths, and may be divided into lenses using diffraction and lenses using refraction according to the method of use. Refractive micro lenses can be used in the visible region, including thermal reflow using surface tension, isotropic etching of silicon and plastic molding with isotropic etching of silicon, and glass substrates. It may be prepared by a method such as selective ion exchange in a glass substrate. Among these refractive lenses, the method using reflow is the simplest and most widely used. However, all conventional lenses using reflow are hemispheres. Compared to the hemispherical lens, the hyperhemisphere lens has a larger performance improvement in the application of the optical system. For example, placing a hyperhemisphere lens in the photon absorption region of a CCD camera provides better sensitivity than a hemispherical lens. In addition, the coupling efficiency (coupling efficiency) used to connect the optical line, such as optical fiber and the optical device is further increased than when using a hemispherical lens. Although the superiority of such a hyperhemisphere lens is widely known, it has not been widely used in the absence of manufacturing technology to date.

Accordingly, a technical problem to be achieved by the present invention is to provide a method for manufacturing a microlens having a hyperhemisphere cross section which is known for excellence but has not been used as a member of manufacturing technology.

1A to 1F are cross-sectional views illustrating a method of manufacturing a microlens according to an embodiment of the present invention;

2A and 2B are cross-sectional views illustrating a change in lens shape according to the degree of undercut of a sacrificial layer;

3 is a layout of a mask for fabricating a spherical lens array and a line-shaped lens; And

4 is a cross-sectional view of a cylindrical lens manufactured using a mask having a linear opening of FIG. 3.

Explanation of symbols on the main parts of the drawings

10: substrate

20: sacrificial layer

20a: sacrificial layer pattern

30: photosensitive film

30a: photosensitive film in exposure area

30b: Photosensitive film or photoresist pattern of unexposed areas

30c: microlens formed by reflow

40: mask for photosensitive film pattern formation

50 ultraviolet light for exposure

60a: circular opening of the mask

60b: linear opening of mask

The present invention for achieving the above technical problem is:

Forming a sacrificial layer on the substrate;

Forming a material layer pattern on the sacrificial layer whose cross section is deformed into a spherical shape by surface tension caused by heating;

Lateral etching the sacrificial layer using the material layer pattern;

Heating and reflowing the material layer pattern;

It is characterized in that to provide a method for producing a micro lens having at least a portion of the cross section having a spherical shape.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1A to 1F are cross-sectional views illustrating a method of manufacturing a microlens according to an exemplary embodiment of the present invention.

First, as shown in FIG. 1A, a thin sacrificial layer 20 is formed on a silicon or glass substrate 10. At this time, the sacrificial layer 20 may be a silicon nitride film or a silicon oxide film that can sufficiently withstand the reflow temperature.

Subsequently, as shown in FIG. 1B, a material film, for example, a photosensitive film 30, whose surface is deformed into a spherical shape by surface tension when heated, is formed on the sacrificial layer 20. The photosensitive film 30 may be selectively removed by a phenomenon caused by selective exposure such as ultraviolet rays.

Next, as illustrated in FIG. 1C, by irradiating the photosensitive film with ultraviolet light 50 selectively using the mask 40 having a desired shape, the exposed area 30a and the unexposed area 30b are formed.

In the case where the used photoresist film is a positive type, the development of the photoresist film in the exposed region is removed, and as shown in FIG. 1D, the photoresist pattern 30b is formed in the unexposed photoresist region.

Subsequently, an isotropic etching process is applied to the sacrificial layer using a wet etchant, but a predetermined undercut is generated in the sacrificial layer under the photoresist pattern 30b by adjusting the etching time. Do it. Therefore, as shown in FIG. 1E, the sacrificial layer pattern 20a having a smaller area than the photosensitive film pattern 30b is formed. As will be described later, the spherical shape of the microlenses is determined by the degree of such undercut.

Then, when the heat treatment is performed, a spherical micro lens 30c is formed by the surface tension of the photosensitive film. At this time, the heat treatment temperature depends on the type of photoresist film to be used as a lens and can be generally set within 180 ~ 300 ℃.

2A and 2B are cross-sectional views illustrating a change in lens shape according to an undercut degree of a sacrificial layer. Referring to FIG. 2A, it can be seen that the degree of undercut is so severe that the smaller the sacrificial layer pattern 20a is, the closer the shape of the microlens 30c is to the spherical shape. Referring to FIG. 2B, it can be seen that the degree of undercut is insignificant, so that as the sacrificial layer pattern 20a increases, the shape of the microlens 30c becomes closer to the hemisphere shape. Lateral etching of the sacrificial layer to be smaller than the diameter of the sphere gives a hyperhemisphere. As such, by adjusting the degree of undercut of the sacrificial layer, the shape of the microlens may be adjusted.

3 is a layout of a mask for fabricating a spherical lens array and a cylindrical lens. In the case of using the positive photoresist film, referring to FIG. 3, it can be seen that the circular openings 60a are arranged for the spherical lens array, and the linear openings 60b are required for the mask for the cylindrical lens. Therefore, the shape of various lenses can be implemented according to the shape of the mask. As such, the openings of the mask may have any shape, such as triangles or squares, as well as circles.

4 is a cross-sectional view of a cylindrical lens manufactured using a mask having a linear opening of FIG. 3. The method of manufacturing such a cylindrical lens can be applied to the production of optical fibers.

According to the spherical microlenses of the present invention as described above, a larger performance improvement can be brought about in the application of the optical system than the conventional hemispherical microlenses.

As described above, the present invention has been described by the above-described embodiments and the accompanying drawings, but is not limited thereto, and various substitutions and changes may be made without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

Claims (8)

Forming a sacrificial layer on the substrate; Forming a material layer pattern on the sacrificial layer whose cross section is deformed into a spherical shape by surface tension caused by heating; Laterally etching the sacrificial layer using the material layer pattern to generate an undercut; Heating and reflowing the material layer pattern; The manufacturing method of the microlens provided with at least one part of a cross section spherical shape. The method of manufacturing a microlens according to claim 1, wherein the shape of the microlens is controlled by the degree of undercut of the sacrificial layer. The method of manufacturing a microlens according to claim 1, wherein the material layer is a photosensitive film that can be developed by exposure. The method of manufacturing a microlens according to claim 1, wherein the sacrificial layer is a silicon oxide film or a silicon nitride film that can sufficiently withstand the reflow temperature. The method of manufacturing a microlens according to claim 1, wherein the substrate is a silicon substrate or a glass substrate. The method of claim 1, wherein the material layer pattern is linear and the microlens is cylindrical. The method of claim 1, wherein the reflowing of the material layer pattern by heating the material layer pattern is performed at a temperature within 180 ° C. to 300 ° C., depending on a material used as a micro lens. The method according to any one of claims 1 to 7, wherein a plurality of the material layer patterns are formed on the sacrificial layer in a two-dimensional array, and at least a part of each cross section has a two-dimensional array having a spherical shape. Manufacturing method of a micro lens.