KR20100066272A - Method of fabricating fine membrane filter - Google Patents

Abstract

PURPOSE: A method for manufacturing a fine membrane filter having an opening having nanoscopic width by photo lithography process or electron-beam lithography process is provided. CONSTITUTION: A method for manufacturing a fine filter comprises: a step of forming a mold(30) having a first width protrusion(36); a step of forming filter membrane(42) at one side of a substrate; a step of coating a resist film on the filter membrane; a step of forming a resist pattern having a first opening to contact with the filter membrane; a step of forming a second opening by etching the filter membrane using a etching mask; a step of removing the resist film; and a step of exposing the opening of the filter membrane.

Description

Method of fabricating fine membrane filter

The present invention relates to a method for producing a fine filter of nanomolecular size.

The present invention is derived from a study conducted as part of the IT source technology development project of the Ministry of Knowledge Economy and the Ministry of Information and Communication Research and Development. [Task management number: 2006-S-007-03, Task name: Ubiquitous health care module system]

Sample pretreatment is needed to implement early diagnosis and chemical analysis on small chips that are common in the field of bio-microelectromechanical devices (BIO-MEMS). To this end, various filtering techniques such as blood cell filters and macromolecular protein filters are required.

One of the most important components of Lab-on-a-Chip, protein microfilter for pretreatment is mainly implemented by the method of distinguishing particles by pore size with microstructures in between. For example, a classic simple separation method that allows molecules smaller than pores to pass through a membrane containing microstructures but not large molecules, biochemistry to selectively trap only the desired molecules in the microstructures. It may be implemented by an affinity chromatography using a red affinity material. These microfluidic control protein filters include liquid chromatography, protein-based diagnostic chips, DNA-based diagnostic chips, drug delivery systems, and microbiological analysis that require fluid control including accurate and precise protein filtering. It has been applied to a variety of lab-on-a-chip including system) and micro / reactor.

Most of the simple membrane-passing methods have the advantage of no driver and no additional power supply. However, because the pore size is not constant, it is difficult to separate by size precisely in the molecular level filtering, and also there is a limit of poor reproducibility. In addition, it is difficult and generally thick to control the thickness of the filter, which requires a long time for the sample to pass through the filter.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a method of manufacturing a fine membrane filter having an opening having a width of a nano unit smaller than a line width that can be realized by a photolithography process or an electron beam lithography process.

Method for producing a fine filter according to the present invention for achieving the above object, forming a mold having a protrusion of the first width; Forming a filter film on one surface of the substrate; Coating a resist film on the filter film; Forming a first opening in the resist film by stamping the mold such that the protrusion contacts the filter film through the resist film; Forming a second opening to expose the substrate by etching the filter film using the resist film as an etching mask; Removing the resist film; And removing a portion of the substrate on a surface opposite to the one surface to expose the opening of the filter membrane.

After being taken into the mold, the resist layer may be reflowed by viscosity of the resist film so that the first opening may have a lower portion having a second width narrower than the first width. Alternatively, the method may further include reflowing the resist pattern after forming the resist pattern having the first opening.

The forming of the mold may include forming a preliminary resist pattern having a first preliminary opening on a sacrificial substrate; Etching the sacrificial substrate using the preliminary resist pattern as an etching mask to form a mold hole; Removing the preliminary resist pattern; Forming a mold layer including a protrusion inserted into the mold hole on the sacrificial substrate; And removing the sacrificial substrate.

The method may further include forming a seed film on the sacrificial substrate before forming the mold film, wherein the mold film may be formed by an electroplating method.

The mold layer and the seed layer may be formed of at least one or an alloy thereof selected from the group consisting of chromium, nickel, copper, and platinum.

The sacrificial substrate may include at least one of silicon and a silicon compound.

The preliminary resist pattern may be formed through a photolithography process or an electron beam (e-beam) lithography process.

The resist film may be a photoresist film or an electron-beam resist film.

The substrate may include at least one of silicon and a silicon compound.

The filter film may include a silicon nitride film.

The method may further comprise hydrophilic treatment of the surface of the filter membrane.

The width of the first preliminary opening may be formed to a minimum size that can be realized by a photolithography process or an electron beam (e-beam) lithography process, and the width of the second opening may be smaller than the width of the first preliminary opening. have.

The height of the protrusion is preferably larger than the thickness of the resist film.

In the method of manufacturing a fine filter according to an embodiment of the present invention, a sacrificial substrate is etched using a preliminary resist pattern having a preliminary resist opening having a minimum width that can be implemented by a photolithography process or an electron beam lithography process as an etching mask, and the sacrificial substrate is etched. A mold film is formed on it. Therefore, the protrusion of the mold composed of the mold layer has a minimum width that can be realized by a photolithography process or an electron beam lithography process. When a resist film that can be reflowed is coated on a filter film, and the mold is stamped on the resist film, the shape of the protrusion is transferred to the resist film, and an opening is formed in the resist film to expose the filter film. However, the resist film is reflowed so that the lower width of the opening exposing the filter film is smaller than the width of the preliminary opening. Accordingly, when the filter film is etched using the resist film having such openings as an etching mask, openings having a width smaller than the minimum line width that can be realized by the photolithography process or the electron beam lithography process may be formed in the filter film. In addition, since the preliminary resist pattern is formed through a lithography process, there is reproducibility and uniformity of the pattern size.

In addition, when one mold is made, a plurality of fine filters can be manufactured by repeatedly using the mold. Therefore, the expensive photolithography process or the electron beam lithography process is performed only once when forming the mold, which is very economical. In addition, by producing a fine filter by stamping the mold can increase the work speed and efficiency.

Objects, other objects, features and advantages of the present invention will be readily understood through the following preferred embodiments associated with the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

In the present specification, when it is mentioned that a film is on another film or substrate, it means that it may be formed directly on another film or substrate or a third film may be interposed therebetween. In addition, in the drawings, the thicknesses of films and regions are exaggerated for effective explanation of technical contents. In addition, in various embodiments of the present specification, terms such as first, second, and third are used to describe various regions, films, and the like, but these regions and films should not be limited by these terms. . These terms are only used to distinguish any given region or film from other regions or films. Thus, the film quality referred to as the first film quality in one embodiment may be referred to as the second film quality in other embodiments. Each embodiment described and exemplified herein also includes its complementary embodiment.

1 to 14 are process cross-sectional views sequentially illustrating a method of manufacturing a fine filter according to an embodiment of the present invention. 1 to 7 illustrate a process of forming a mold.

Referring to FIG. 1, a preliminary mask layer 12 is formed on the sacrificial substrate 10. The sacrificial substrate 10 may include silicon or a silicon compound. The preliminary mask layer 12 may be, for example, a silicon nitride layer. A preliminary resist film 14 is formed on the preliminary mask film 12. The preliminary resist layer 14 may be formed of a photoresist or an electron-beam or e-beam resist. After coating the preliminary resist layer 14, a soft baking process may be further performed. In addition, the exposure process may be performed using the photomask 20.

Referring to FIG. 2, the preliminary resist layer 14 having undergone the exposure process is developed to form a preliminary resist pattern 14a having a first preliminary opening 16 exposing the mask layer 12. When the preliminary resist layer 14 is a positive photoresist pattern, a portion exposed in the exposure process may be developed. When the preliminary resist layer 14 is a negative photoresist pattern, an unexposed portion may be developed in the exposure process. When the preliminary resist film 14 is an electron beam resist film, a portion hit by the electron beam may be cured or melted in a developer. The first preliminary opening 16 may be formed to have a minimum width that can be realized in a photolithography process or an electron beam lithography process.

Referring to FIG. 3, the preliminary mask layer 12 is anisotropically etched using the preliminary resist pattern 14a including the first preliminary opening 16 as an etching mask. As a result, the preliminary mask pattern 12a including the second preliminary opening 16a having the first width W1 exposing the sacrificial substrate 10 is formed. By the anisotropic etching process, the first width W1 may be formed to be substantially the same as or smaller than the width of the first preliminary opening 16.

Referring to FIG. 4, the preliminary resist pattern 14a is removed by an ashing process or the like. In this case, the cleaning process may be performed to remove etching by-products due to the reaction between the preliminary resist pattern 14a and the etching gas.

4 and 5, the sacrificial substrate 10 is anisotropically etched using the preliminary mask pattern 12a as an etching mask. As a result, a hole 16b having a first depth D1 and a second width W2 is formed in the sacrificial substrate 10. The first depth D1 is preferably larger than the thickness of the resist film 44 of FIG. 8 to be described later. By the anisotropic etching process, the second width W2 is about equal to or smaller than the first width W1. The preliminary mask pattern 12a is removed by a wet etching process or the like. If the mask pattern 12a is formed of a silicon nitride film, it may be removed using phosphoric acid.

Referring to FIG. 6, a mold 30 having a surface profile of the sacrificial substrate 10 is formed on the sacrificial substrate 10. For this purpose, the seed film 32 is conformally deposited on the sacrificial substrate 10. The seed layer 32 may be formed by, for example, atomic layer deposition. The mold layer 34 is formed on the seed layer 32 by electroplating. The seed layer 32 and the mold layer 34 may include at least one material selected from the group consisting of nickel, platinum, cobalt, and copper, or an alloy thereof. The mold layer 34 is formed by filling the hole 16b to form the protrusion 36. The protrusion 36, the mold layer 34, and the seed layer 32 constitute the mold 30.

Referring to FIG. 7, the sacrificial substrate 10 is selectively removed. As a result, the mold 30 may be formed. The protrusion 36 is formed to have a first height H1 and a third width W3. The first height H1 has a size substantially the same as the first depth D1, and the third width W3 has a size substantially the same as the second width W2.

In the present embodiment, the mold 30 is composed of a seed film formed by atomic thin film deposition and a mold film formed by electroplating. However, the mold 30 is formed using only chemical vapor deposition (CVD) or physical vapor deposition (PVD) without a seed film. It may be composed of a mold film.

Referring to FIG. 8, a filter film 42 is formed on the substrate 40. The substrate 40 may include silicon or a silicon compound. The filter layer 42 may be a silicon nitride layer. The resist film 44 is coated on the filter film 42. The resist film 44 may be a photoresist film or an electron beam resist film. The resist film 44 preferably has a high viscosity. At this time, it is preferable that the soft baking process is not performed on the resist film 44.

8 and 9, the mold 30 is positioned on the resist film 44, and the mold 30 is photographed so that the protrusion 36 contacts the filter film 42. As a result, the shape of the protrusion 36 is transferred to the resist film 44.

Referring to FIG. 10, by separating the mold 30 from the resist film 44, a first opening 45 is formed in the resist film 44 to expose the filter film 44. At this time, since the resist film 44 has not been baked, the liquid film maintains a high viscosity liquid state and reflows to the region where the protrusion 36 has been present. Thus, the first opening 45 may be formed to have an upper portion of the fourth width W4 and a lower portion of the fifth width W5 that is narrower than the fourth width W4. The fourth width W4 may have substantially the same size as the third width W4. The resist film 44 having the first opening 45 may be referred to as a resist pattern 44a.

Alternatively, the resist film 44 may be soft baked before being taken into the mold 30, and after being taken into the mold 30, a reflow process may be performed to form the first opening 45.

Referring to FIG. 11, the filter layer 42 is etched using the resist pattern 44a as an etching mask. As a result, a second opening 46 having a sixth width W6 may be formed in the filter membrane 42. The sixth width W6 may be formed to be substantially the same as or smaller than the fifth width W5.

Referring to FIG. 12, the resist pattern 44a is removed by an ashing process or the like.

Referring to FIG. 13, a support mask pattern 50 is formed at the edge of the rear surface of the substrate 40. The support mask pattern 50 may be, for example, a silicon nitride layer.

Referring to FIG. 14, a third opening 48 exposing the lower surface of the filter layer 42 by selectively etching the rear surface of the substrate 40 using the support mask pattern 50 as an etching mask. To form. Thereby, the fine filter 50 can be completed. The surface of the fine filter 50 may be hydrophilic. The third opening 48 may be used as a sample liquid inlet when the microfilter 50 is used.

15 is a photograph of a fine filter manufactured by a method according to an embodiment of the present invention.

Referring to FIG. 15, it can be seen that holes having sizes of 20 to 30 nm much smaller than 50 nm, which is a line width limit of the electron beam lithography process, are formed.

16 shows an example of use of a fine filter manufactured by the method according to an embodiment of the present invention.

Referring to FIG. 16, the micro filter 50 manufactured in the embodiment of the present invention is mounted on the channel portion 504 of the microfluidic device. When the sample liquid 502 such as blood is dropped into the microfilter 50, the blood protein such as white blood cells or red blood cells and the macromolecule protein 503 such as albumin may be added to the microfilter 50. Only small molecules 505 of small size, such as serum, cannot pass through the microfilter 50 and enter the channel portion 504. This enables early separation of large numbers of macromolecular molecules, which are the main component of nonspecific binding, before the sample is injected into the microfluidic device, thereby greatly improving the diagnostic reliability and precision of the microfluidic device. have.

1 to 14 are process cross-sectional views sequentially illustrating a method of manufacturing a fine filter according to an embodiment of the present invention.

15 is a photograph of a fine filter manufactured by a method according to an embodiment of the present invention.

16 shows an example of use of a fine filter manufactured by the method according to an embodiment of the present invention.

Claims (10)

Forming a mold having a protrusion of a first width; Forming a filter film on one surface of the substrate; Coating a resist film on the filter film; Forming a resist pattern having a first opening by dipping into the mold such that the protrusion contacts the filter film through the resist film; Forming a second opening to expose the substrate by etching the filter film using the resist pattern as an etching mask; Removing the resist film; And And removing a portion of the substrate on a surface opposite to the one surface to expose the opening of the filter membrane. The method of claim 1, And after taking with the mold, reflowed by viscosity of the resist film so that the first opening is formed to have a lower portion of the second width narrower than the first width. The method of claim 1, And after the forming of the resist pattern having the first opening, reflowing the resist pattern. The method of claim 1, Forming the mold, Forming a preliminary resist pattern having a first preliminary opening on the sacrificial substrate; Etching the sacrificial substrate using the preliminary resist pattern as an etching mask to form a mold hole; Removing the preliminary resist pattern; Forming a mold layer including a protrusion inserted into the mold hole on the sacrificial substrate; And And removing the sacrificial substrate. The method of claim 4, wherein Before forming the mold layer, further comprising forming a seed layer on the sacrificial substrate, The mold film is a method of manufacturing a fine filter, characterized in that formed by electroplating or electroless plating method. The method of claim 5, And the mold film and the seed film are formed of at least one or an alloy thereof selected from the group consisting of chromium, nickel, copper and platinum. The method of claim 1, And the resist film is a photoresist film or an electron-beam resist film. The method of claim 1, The substrate is a method of manufacturing a fine filter, characterized in that it comprises at least one of silicon and silicon compounds. The method of claim 4, wherein The width of the first preliminary opening is formed to a minimum size that can be implemented by a photolithography process or an electron beam (e-beam) lithography process, and the width of the second opening is formed to be narrower than the width of the first preliminary opening. The manufacturing method of the fine filter characterized by the above-mentioned. The method of claim 1, The height of the protrusion is greater than the thickness of the resist film manufacturing method of the fine filter.

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