WO2009069846A1

WO2009069846A1 - Method for manufacturing sensing unit made from nano-sized resist-derived carbon

Info

Publication number: WO2009069846A1
Application number: PCT/KR2007/006802
Authority: WO
Inventors: Seung Seob Lee; Jung A Lee; Kwang Cheol Lee; Se Il Park
Original assignee: Korea Research Institute Of Standards And Science; Korea Advanced Institute Of Science And Technology
Priority date: 2007-11-26
Filing date: 2007-12-24
Publication date: 2009-06-04
Also published as: KR100927617B1; KR20090054268A

Abstract

Provided is a method for manufacturing a sensor portion of a biosensor used in detecting biomolecules. The method includes the steps of: applying a photo- sensitive material on a substrate; lithographically etching the photo- sensitive material to form a nano-size sensor portion precursor; and pyrolyzing the sensor portion precursor to form a sensor portion composed of conductive carbon.

Description

METHOD FOR MANUFACTURING SENSING UNIT MADE FROM NANO-SIZED RESIST-DERIVED CARBON

Technical Field

[1] The present invention relates to a method for manufacturing a sensor portion of a biosensor used in detecting biomolecules and, more particularly, to a method for manufacturing a nano-size sensor portion of specified shape composed of pyrolyzed carbon. Background Art

[2] As a method for integrating a micro mechanical device, there is known a semiconductor processing technology using micromachining. The micromachining-based semiconductor processing technology, which is often referred to as "MEMS," has contributed to the development of a two-dimensional silicon processing technology represented by the conventional planar technology to a three-dimensional structure processing technology.

[3] The MEMS (Micro-Electro-Mechanical System) refers to a technology with which a sensor, an actuator and an electro-mechanical device each having an extremely small size in the order of microns are manufactured through a micromachining process derived from a semiconductor manufacturing process, particularly an integrated circuit technology. The micro mechanical device manufactured by the micromachining process has a size and precision degree of several microns or less. Advantages of the micromachining process reside in that it can realize miniaturization, high performance, versatility and integration of a device through an extremely precise micromachining work while enhancing the stability and reliability of the device. In addition, the micromachining technology can realize a unitary integrated system, thereby eliminating the need to perform an additional fabricating operation. This makes it possible to cost- effectively mass-produce micro structures through a series of process steps.

[4] A MEMS used in the field of bio-engineering is referred to as Bio-MEMS. The Bio-

MEMS is a combination term of biotechnology and MEMS and means a micro device capable of analyzing biomolecules in vivo or in vitro. One representative product using the Bio-MEMS is a biosensor. The biosensor refers to an ultra-small sensor which includes a sensor portion for detecting biomolecules and a signal generating portion for generating an electrical or chemical signal corresponding to the biomolecules detected.

[5] The biosensor is divided into a mechanical biosensor and an electrical biosensor. The mechanical biosensor determines the kind and amount of biomolecules by measuring the resonant frequency or displacement of a cantilever having a pressure resistor, a piezoelectric material or a field-effect transistor formed thereon. The resonant frequency or displacement of the cantilever varies when the pressure resistor, the piezoelectric material or the field-effect transistor reacts with biomolecules. In contrast, the electrical biosensor determines the kind and amount of biomolecules by measuring the change in electric resistance of a sensor portion made of a semiconductor nano wire, a carbon nano tube or a conductive polymer. The change in electric resistance occurs when the sensor portion makes a binding reaction with biomolecules.

Disclosure of Invention Technical Problem

[6] The electrical biosensor offers an advantage in that it can accurately determine the biomolecules using a nano-sized sensor portion such as a carbon nano tube or a semiconductor nano wire. However, the chirality of a nano-size material and the change in properties of the nano-size material occurring in a fabricating process make it difficult to freely manufacture a nano-size sensor portion of arbitrary shape. In order to manufacture the nano-size sensor portion using a semiconductor manufacturing process, there is a need to perform additional process steps such as etching, deposition or the like, which makes it costly to produce the sensor portion in a nano size.

[7] Therefore, it is an object of the present invention to provide a novel method for manufacturing a nano-size sensor portion of a biosensor having an arbitrary shape.

[8] Another object of the present invention is to provide a method for cost-effectively manufacturing a sensor portion of a biosensor composed of pyrolyzed carbon.

Technical Solution

[9] In accordance with the present invention, there is provided a method for manufacturing a sensor portion of a biosensor used in detecting biomolecules, including the steps of: applying a photo-sensitive material on a substrate; lithographically etching the photo-sensitive material to form a nano-size sensor portion precursor; and pyrolyzing the sensor portion precursor to form a sensor portion composed of conductive carbon.

[10] Preferably, the sensor portion has a center region and opposite end regions. The width of the center region is smaller than that of the opposite end regions. Alternatively, the sensor portion may have a width that grows smaller from the opposite end regions toward the center region.

Advantageous Effects

[11] With the present invention, it is possible to cost-effectively and easily manufacture a nano-size sensor portion having an arbitrary shape by forming a sensor portion precursor through a photolithography process and then pyrolyzing the sensor portion precursor to form a sensor portion composed of conductive carbon. Brief Description of Drawings [12] Fig. 1 is a perspective view showing a biosensor manufactured in accordance with one embodiment of the present invention.

[13] Fig. 2 illustrates a process for forming a sensor portion precursor using a lithography method.

[14] Fig. 3 illustrates a process for forming a sensor portion by pyrolyzing the sensor portion precursor of specified pattern.

[15] Fig. 4 shows one example of the sensor portion manufactured in accordance with the present invention.

[16] Fig. 5 shows another example of the sensor portion manufactured in accordance with the present invention.

[17] Fig. 6 shows a further example of the sensor portion manufactured in accordance with the present invention.

[18] Fig. 7 shows a still further example of the sensor portion manufactured in accordance with the present invention. Best Mode for Carrying out the Invention

[19] Hereinafter, a method for manufacturing a sensor portion of a biosensor in accordance with the present invention will be described in detail with reference to Figs. 1 through 7.

[20] Fig. 1 is a perspective view showing a biosensor manufactured in accordance with one embodiment of the present invention. Referring to Fig. 1, an underlying insulation layer 2 is formed on the upper surface of a substrate 1. On the upper surface of the underlying insulation layer 2, there are formed electrodes 3 and alignment marks 4. A silicon, quartz or ceramic substrate may be used as the substrate 1. A silicon oxide or silicon nitride film may be used as the underlying insulation layer 2. A sensor portion 8 composed of pyrolyzed carbon is formed on the upper surface of the underlying insulation layer 2.

[21] A covering insulation layer 10 is formed on the upper surface of the underlying insulation layer 2 on which the sensor portion 8 is formed. The task of forming the covering insulation layer 10 on the underlying insulation layer 2 is performed by applying PMMA (polymethyl methacrylate), SOG (spin-on-glass), polyimide or the like on the upper surface of the underlying insulation layer 2 in a liquid or gas phase.

[22] An exposure window 11 through which to expose the sensor portion 8 to biomolecules is formed in the covering insulation layer 10 to lie just above the sensor portion 8. If a test solution is allowed to flow over the covering insulation layer 10 of the biosensor, a part of the test solution enters the exposure window 11 and makes contact with the sensor portion 8. Thus the biomolecules contained in the test solution adhere to the sensor portion 8. In this case, the electric resistance of the sensor portion 8 varies with the kind and amount of the biomolecules adhering to the sensor portion 8. The electric resistance of the sensor portion 8 can be measured by supplying an electric current to the sensor portion 8 through the electrodes 3. Based on the electric resistance thus measured, it is possible to detect the kind and amount of the biomolecules adhering to the sensor portion 8.

[23] Fig. 2 illustrates a process for lithographically forming a sensor portion precursor.

Referring to Fig. 2, a photo-sensitive layer 5 composed of a polymer is applied on the upper surface of the underlying insulation layer 2 on which the electrodes 3 and the alignment marks 4 have been formed. A polymer mask 6 having a sensor portion pattern pierced therethrough is attached to the upper surface of the photo-sensitive layer 5. The alignment marks 4 are used in aligning the sensor portion pattern of the polymer mask 6 at a specified position on the underlying insulation layer 2.

[24] The photo-sensitive layer 5 is lithographed using the polymer mask 6 having the sensor portion pattern pierced therethrough. First, electron beams B are irradiated on the photo-sensitive layer 5 from above the polymer mask 6, at which time only the electron beams passed through the sensor portion pattern reach the photo-sensitive layer 5. The photo-sensitive layer 5 is preferably made of a high molecular polymer. After the electron beams B are irradiated on the photo-sensitive layer 5 through the sensor portion pattern, the polymer mask 6 is separated from the photo-sensitive layer 5 and is then developed with a developer solution. As the photo-sensitive layer 5 is developed with the developer solution, the portion of the photo-sensitive layer 5 irradiated with the electron beams is left intact, but the portion of the photo-sensitive layer 5 not irradiated with the electron beams is completely dissolved away in the developer solution. Thus only a portion of the photo- sensitive layer 5 corresponding to the sensor portion pattern of the polymer mask 6, i.e., a sensor portion precursor, is left on the upper surface of the underlying insulation layer 2.

[25] Fig. 3 illustrates a process for forming a sensor portion by pyrolyzing the sensor portion precursor. Referring to Fig. 3, a sensor portion precursor 7 composed of a high molecular polymer is formed on the underlying insulation layer 2 after the photosensitive layer 5 is developed. Heat H is applied on the sensor portion precursor 7 to pyrolyze the same. The sensor portion precursor 7 thus pyrolyzed is converted to a sensor portion composed of conductive carbon. In other words, if the sensor portion precursor 7 is heated to an elevated temperature, nitrogen, oxygen and the like constituting the sensor portion precursor 7 are removed and only a carbon component is left as it is. The carbon component has an amorphous structure. The electric conductivity and residual stress of the pyrolyzed sensor portion precursor 7 varies depending on the heating temperature and time of the sensor portion precursor 7, the chemical components of the polymer constituting the sensor portion precursor 7 and the kind of additives added to the sensor portion precursor 7. Preferably, the sensor portion precursor 7 is pyrolyzed by heating the same to a temperature of from 500⁰C to 700⁰C for 0.5 to 2 hours in an oven. This produces a sensor portion 8 made from the pyrolyzed photo-sensitive sensor portion precursor.

[26] Figs. 4 and 5 show examples of the sensor portion 8 manufactured in accordance with the present invention. In the sensor portion 8 shown in Fig. 4, the width of the center region is smaller than that of the opposite end regions. In the sensor portion 8 shown in Fig. 5, the width thereof grows smaller from the opposite end regions toward the center region. This makes it possible to detect biomolecules with increased sensitivity and within a shortened period of time. The reason is that the biomolecules tend to adhere to the center region in a greater quantity than to the opposite end regions.

[27] Fig. 6 shows another example of the sensor portion 8 manufactured in accordance with the present invention. In the example shown in Fig. 6, the sensor portion 8 includes a plurality of parallel bars differing in length and width from one another. By changing the length and width of the bars constituting the sensor portion 8, it is possible to control the sensitivity of the sensor portion depending on the kinds of the biomolecules to be detected. Furthermore, it becomes possible to detect both the biomolecules with a lower concentration and the biomolecules with a higher concentration.

[28] Fig. 7 shows a further example of the sensor portion 8 manufactured in accordance with the present invention. In the example shown in Fig. 7, the sensor portion 8 includes a plurality of parallel bars each having a gap of predetermined size. When the biomolecules to be detected are coupled with the gap of each of the bars, the kinds of the biomolecules can be determined by measuring the change in electric resistance of the sensor portion 8. Industrial Applicability

[29] The present invention provides a novel method for manufacturing a nano-size sensor portion of a biosensor having an arbitrary shape and composed of pyrolyzed carbon.

[30] With the present invention, it is possible to cost-effectively and easily manufacture a nano-size sensor portion having an arbitrary shape by forming a sensor portion precursor through a photolithography process and then pyrolyzing the sensor portion precursor to form a sensor portion composed of conductive carbon.

[31] The embodiments set forth hereinabove have been presented for illustrative purpose only and, therefore, the present invention is not limited to these embodiments. It will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention defined in the claims.

Claims

[1] A method for manufacturing a sensor portion of a biosensor used in detecting biomolecules, comprising the steps of: applying a photo- sensitive material on a substrate; lithographically etching the photo-sensitive material to form a nano-size sensor portion precursor; and pyrolyzing the sensor portion precursor to form a sensor portion composed of conductive carbon. [2] The method as recited in claim 1, wherein the sensor portion precursor is pyrolyzed at a temperature of from 500⁰C to 700⁰C for 0.5 to 2 hours. [3] The method as recited in claim 1, wherein the sensor portion has a center region and opposite end regions, the center region having a width smaller than that of the opposite end regions. [4] The method as recited in claim 1, wherein the sensor portion has a center region and opposite end regions, the sensor portion having a width that grows smaller from the opposite end regions toward the center region. [5] The method as recited in claim 1, wherein the sensor portion includes a plurality of parallel bars differing in length and width from one another. [6] The method as recited in claim 1, wherein the sensor portion has a gap with which the biomolecules to be detected are coupled.