Patent Publication Number: US-2010112342-A1

Title: Substrate for biochip and method of manufacturing the substrate

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Korean Patent Application No. 10-2008-0109466, filed on Nov. 5, 2008, and all the benefits accruing therefrom under 35 U.S.C. §119, the content of which in its entirety is herein incorporated by reference. 
     BACKGROUND 
     1. Field 
     One or more embodiments of the invention relate to a substrate for a biochip, the substrate including nanostructured spots, and a method of manufacturing the substrate. 
     2. Description of the Related Art 
     As genome projects have progressed, nucleotide sequences of genomes have been identified from various organisms. With the information available about the identified nucleotide sequences, gene expression profiles and the function of gene products has been actively studied. 
     Biochips are biometric devices made by combining biological materials such as enzymes, peptides, proteins, antibodies, and deoxyribonucleic acids (DNAs) of living creatures, microorganisms, and cells, organs, and nerves of animals and plants into a microchip similar to a semiconductor chip. The advent of biotechnology, nanotechnology using a semiconductor process, and micro electro mechanical system (“MEMS”) technology has accelerated the development of biochips. 
     Protein chips and DNA chips consisting of microarrays are likely to be commercialized soon. DNA chips are devices for detecting DNAs. DNA chips are made by arranging probe DNAs including several hundred to several ten million DNAs having known sequence and/or function in a small area on a substrate, such as a glass substrate or a semiconductor substrate. When genetic material of a sample is dropped onto such a DNA chip to which probe DNAs are attached, only genes corresponding to the probe DNAs, i.e., only genes having complementary sequences to base sequences of the probe DNAs, are combined with the probe DNAs. Genes that are not combined with the probe DNAs are washed away. Since the sequence and/or function of the base sequences of probe DNAs arranged on the DNA chip are already known, genetic information of the sample may be easily obtained by identifying bases combined with genes in the DNA chip. Accordingly, aspects of a unique genetic expression, single nucleotide polymorphisms and copy number variation in a gene, or mutation in a cell or tissue may be quickly analyzed using the DNA chip. Furthermore, the DNA chip may also be used to analyze genetic expression, or used for pathogenic bacteria infection tests, antibiotic-resistance tests, research on biological reaction to environmental factors, food safety inspections, identification of criminals, development of new drugs, medical inspection of animals and plans, etc. 
     Biochips having probe biomolecules attached to a substrate are formed by synthesizing single stranded DNAs on a desired area of the substrate or by spotting prefabricated single or double stranded DNAs onto a selected area of the substrate. However, it is difficult to control the density of spots of biomolecules attached to the substrate, thereby failing to make a precise analysis. 
     SUMMARY 
     According to one or more embodiments of the invention, a substrate for a biochip, the substrate including: a base, a plurality of spots to which a plurality of biomaterials is attached, wherein each of the plurality of spots includes a plurality of sub spots. 
     In one embodiment, each of the plurality of sub spots may have a shape with a side of about 1 nm to about 1 μm in length. 
     In another embodiment, each of the plurality of sub spots may have a shape with a side of about 1 nm to about 500 nm in length. 
     In another embodiment, a distance between the sub spots may range from about 1 nm to about 1 μm. 
     In another embodiment, each of the plurality of sub spots may have any shape selected from the group consisting of an oval shape, a polygonal shape, a starfish-like shape, a toothed wheel-like shape, and a clover-like shape, 
     According to one or more embodiments, each of the plurality of sub spots may be hydrophilic, and the base may be hydrophobic or the plurality of sub spots and the base may be hydrophilic in which biomolecules are grown only on the lithographically patterned sub spots region. 
     According to one or more embodiments, each of the plurality of sub spots may be formed of any one selected from the group consisting of an oxide, a dielectric material, a polymer, a semiconductor material and any combinations thereof. 
     According to one or more embodiments of the invention, a method of manufacturing a substrate for a biochip, the method including: applying a sub spot forming material to a substrate to form a sub spot material layer; applying a photoresist on the sub spot material layer and performing lithography to form photoresist (PR) patterns; and etching portions of the sub spot material layer which are not covered by the PR patterns to form a plurality of sub spots. 
     In one embodiment, the sub spot forming material may be any one selected from the group consisting of an oxide, a dielectric material, a polymer, and a semiconductor material, and any combinations thereof. 
     In another embodiment, the lithography may use any one selected from the group consisting of i-line, KrF, ArF, F2, extreme ultraviolet (EUV) light, X-ray, and electron beam. 
     In another embodiment, the lithography may use a mask having a plurality of serifs. 
     In another embodiment, the lithography may be any one selected from the group consisting of maskless lithography, nanoimprint lithography, spacer lithography, and immersion lithography. 
     In another embodiment, the etching of the portions of the sub spot material layer may include etching the portions of the sub spot material layer using dry etching or wet etching; and if an interlayer between PR and the sub spot material should be introduced, the interlayer material patterned and etched using PR can provide a secondary layer of mask, so called hard mask, in order to make a finer structure for the sub spot material than PR patterning. 
     Accordingly, the uniformity and the density of biomolecules attached to the biochip may be improved, and thus the reliability of data derived from detection may be improved. Furthermore, the substrate for the biochip may be mass-produced using a semiconductor process, and thus economic efficiency may be improved. 
     One or more embodiments of the invention are not limited to the embodiments described above, and may also include other embodiments. These and other embodiments and features of the invention will become more fully apparent from the following description or may be learned by practice of the illustrated embodiments, as will be apparent to those of ordinary skill in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a schematic diagram illustrating a top plan view of an exemplary embodiment of a substrate for a biochip according to the invention; 
         FIG. 2  is a schematic diagram illustrating a top plan view illustrating sub spots of the substrate of  FIG. 1 ; 
         FIG. 3  is a diagram illustrating a side view of an exemplary embodiment of sub spots of the substrate of  FIG. 1 ; 
         FIG. 4  illustrates exemplary shapes of sub spots of the substrate of  FIG. 1 ; 
         FIGS. 5A through 5F  are schematic diagrams illustrating cross-sectional views of an exemplary embodiment of a method of manufacturing a substrate for a biochip, according to the invention; 
         FIG. 6A  is a schematic diagram illustrating a cross-sectional view of an exemplary embodiment of sub spots formed by dry etching; 
         FIG. 6B  is a schematic diagram illustrating across-sectional view illustrating of an exemplary embodiment of sub spots formed by wet etching; 
         FIG. 7  is a schematic diagram illustrating a mask having serifs. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. The sizes of elements and layers in the drawings are exaggerated for clarity. In this regard, the illustrated embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain features of the description. 
     It will be understood that when an element or layer is referred to as being “on” or “connected to” another element or layer, the element or layer can be directly on or connected to another element or layer or intervening elements or layers. In contrast, when an element is referred to as being “directly on” or “directly connected to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the invention. 
     Spatially relative terms, such as “under” and the like, may be used herein for ease of description to describe the relationship of one element or feature to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “under” relative to other elements or features would then be oriented “above” relative to the other elements or features. Thus, the exemplary term “under” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Embodiments of the invention are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     All methods described herein can be performed in a suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”), is intended merely to better illustrate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention as used herein. 
     Hereinafter, the invention will be described in detail with reference to the accompanying drawings. 
     In one embodiment, a substrate for a biochip comprising a base, a plurality of spots, wherein each of the plurality of spots includes a plurality of sub spots, the sub spots have a plurality of biomaterials attached thereto. 
       FIG. 1  is a schematic diagram illustrating a top plan view of an embodiment of a substrate  10  for a biochip according to the invention. 
     Referring to  FIG. 1 , the substrate  10  includes a base  11  and a plurality of spots  12  formed on the base  11 . Biomolecules having the same base sequences, for example, probe DNAs, are attached to the plurality of spots  12 . The base sequences for probe DNAs attached to the plurality of spots  12  may be the same or different for individual spots. 
     In one embodiment, the base  11  of the substrate  10  may be a flexible substrate or a rigid substrate. For example, the base  11  may be formed of silicon, glass or plastic. Generally, the base  11  is formed of a hydrophobic material such that biomolecules are not attached to the base  11 . 
     In one embodiment, each of the plurality of spots  12  includes an array of sub spots  13 .  FIG. 2  is a top plan view illustrating sub spots  13  of the plurality of spots  12  of the substrate  10  of  FIG. 1 . Biomolecules having the same base sequences, for example, probe DNAs, are attached to the array of sub spots  13 . The base sequences for probe DNAs attached to the sub spots  13  may be the same or different for individual sub spots. 
     Referring to  FIG. 2 , each of the plurality of spots  12  of the substrate  10  includes an array of sub spots  13 . In one embodiment, each of the sub spots  13  may have a rectangular shape with a side of about 1 nm to about 1 μm in length, and the number of the sub spots  13  is not limited. For example, if each of the plurality of sub spots  13  has a rectangular shape, two sides L 1  and L 2  of each of the plurality of sub spots  13  may be equal to each other (L 1 =L 2 ), or either one of the two sides L 1  and L 2  may be greater than the other (L 1 &gt;L 2 , L 1 &lt;L 2 ). Both the size of each of the plurality of sub spots  13  and the distance L 3  between the sub spots  13  may range from about 1 nm to about 1 μm. 
     According to one or more embodiments, the sub spots  13  may be formed of an oxide, a dielectric material, a polymer or a semiconductor material. Generally, the sub spots  13  may be formed of a hydrophilic material such that biomolecules may attach to the sub spots  13 . As noted above, the base  11  is hydrophobic such that biomolecules are not attached to the base  11 , and the sub spots  13  are hydrophilic such that biomolecules are attached to the sub spots  13 . In contrast, if the base  11  is hydrophilic and the sub spots  13  are hydrophobic, biomolecules may be distributed between the sub spots  13  on the base  11 . In another embodiment, the entire substrate  10 , both the plurality of sub spots  13  and the base  11  may be hydrophilic in which biomolecules are grown only on the lithographically patterned sub spots region. 
       FIG. 3  is a diagram illustrating a side view of an embodiment of sub spots  13  of the substrate  10  of  FIG. 1 . Referring to  FIG. 3 , the plurality of sub spots  13  are formed on the base  11 . Biomolecules  14  are to be attached to the plurality of sub spots  13  when the biochip is formed. 
     Although each of the plurality of sub spots  13  has a rectangular shape in  FIG. 2 , the invention is not limited thereto, and each of the plurality of sub spots  13  may have an oval shape, a polygonal shape, a starfish-like shape, a toothed wheel-like shape, a clover-like shape, or the like as shown in  FIG. 4 . The shape of each of the plurality of sub spots  13  may vary depending on the shape of a mask or an etching method used when forming the plurality of sub spots  13 , which will be explained later in detail. 
     As described above, the substrate  10  includes the plurality of spots  12  including the plurality of sub spots  13  each of which has a size of about 1 nm to about 1 μm. Accordingly, since the area of each of the sub spots  13  to which biomolecules are attached is much smaller than the surface area of each of the plurality of spots  12 , an electrostatic force is increased, thereby leading to active binding between biomolecules and the sub spots  13 . That is, unlike a substrate for a biochip which includes one flat spot, since each of the plurality of spots  12  includes the plurality of sub spots  13 , conjugation, binding, and linking of biomolecules may be improved. 
     Since the typical substrate includes one flat spot, a biomolecule density difference between positions on the spot is high. However, since the substrate  10  of  FIG. 1  may significantly increase a binding force between the plurality of sub spots  13  and biomolecules, a uniform biomolecule density may be achieved. Accordingly, when probe biomolecules and target biomolecules are hybridized and then the target biomolecules are analyzed using either an electrical detection or a fluorescence imaging, data variation according to the position of an image on the spots may be reduced. 
     In one embodiment, each of the plurality of sub spots  13  has a feature size smaller than a fluorescent wavelength A, for example, each having a diameter of about 1 nm to about 500 nm that is smaller than the fluorescence wavelength. If each of the plurality of sub spots  13  has a feature size smaller than a fluorescent wavelength A, for example, 500 nm, and has a diameter of about 1 nm to about 500 nm that is smaller than the fluorescence wavelength, a scanner reads an average of data of neighboring sub spots, not individual data of one sub spot in an optical detection process. Accordingly, non-uniformity among neighboring sub spots in one spot may be reduced. Accordingly, the size and the shape of each of the plurality of sub spots  13  may be properly adjusted considering various fluorescent wavelengths. 
     In one embodiment, a method of manufacturing a substrate for a biochip, the method comprising applying a sub spot forming material to a substrate to form a sub spot material layer; applying a photoresist on the sub spot material layer and performing lithography to form photoresist (PR) patterns; and etching portions of the sub spot material layer which are not covered by the PR patterns to form a plurality of sub spots. 
       FIGS. 5A through 5G  are schematic diagrams illustrating cross-sectional views illustrating an exemplary embodiment of method of manufacturing a substrate for a biochip, according to an embodiment of the present invention. 
     Referring to  FIG. 5A , a base  21  is prepared. The base  21  may be a formed with flexible substrate or a rigid substrate. For example, the base  21  may be formed of silicon, glass or plastic. 
     Referring to  FIG. 5B , a sub spot material layer  22  is formed on the base  21 . The sub spot material layer  22  may be formed of a dielectric material, a polymer or a semiconductor material. Either the base  21  or the sub spot material layer  22  may be hydrophilic and the other may be hydrophobic by controlling materials of the base  21  and the sub spot material layer  22 . Accordingly, biomolecules may be attached to or between sub spots. In another embodiment, both the sub spot material layer  22  and the base  21  may be hydrophilic in which biomolecules are grown only on the lithographically patterned sub spots region. 
     Referring to  FIG. 5C , a photoresist layer  23  is applied to the sub spot material layer  22 . Referring to  FIG. 5D , the photoresist layer  23  is patterned by photolithography to form photoresist (PR) patterns  23   a . The photoresist  23  may be patterned by photolithography using a mask, maskless lithography, nanoimprint lithography, spacer lithography, or immersion lithography, which generally uses i-line, KrF, ArF, F2, extreme ultraviolet (EUV), X-ray, or electron beam. If an interlayer between PR and the sub spot material should be introduced, the interlayer material patterned and etched using PR can provide a secondary layer of mask, so called hard mask, in order to make a finer structure for the sub spot material than PR patterning. 
     Referring to  FIGS. 5E and 5F , portions of the sub spot material layer  22  which are not covered by the PR patterns  23   a  are etched to form a plurality of sub spots  22   a . The size and the shape of each of the plurality of sub spots  22   a  may vary depending on an etching method. For example, dry etching, e.g., reactive ion etching (RIE), having directivity may be performed. Further, as exemplified in  FIG. 3 , the method may further comprise attaching biomolecules  14  to the plurality of sub spots  13  (not shown in  FIG. 5 ). 
       FIG. 6A  is a cross-sectional view illustrating sub spots  22   a  formed by dry etching. Referring to  FIG. 6A , if etching is vertically performed, top surfaces of the sub spots  22   a  on which the PR patterns  23   a  are formed are not affected by an etching time.  FIG. 6B  is a cross-sectional view illustrating sub spots  22   a  formed by we etching. However, referring to  FIG. 6B , if wet etching is isotropically performed, top surfaces of the sub spots  22   a  are not protected by the PR patterns  23   a  and are etched as an etching time increases. That is, as shown in  FIG. 6B , in the case of wet etching, as the etching time increases, the size of each of the sub spots  22   a  is reduced, the surface area of each of the sub spots  22   a  is reduced, and finally a flat surface of each of the sub spots  22   a  is etched away and thus removed. That is, the size and the shape of each of the sub spots  22   a  vary depending on an etching method and an etching time as well as lithography. 
       FIG. 7  is a schematic view illustrating a mask  70  having a plurality of serifs  72 . In order to form sub spots having various shapes as shown in  FIG. 4 , the mask  70  including a mask pattern  71  and the plurality of serifs  72  as shown in  FIG. 7 , which are added to the mask pattern  71  for the purpose of optical proximity correction, as one pattern may be used. Accordingly, the size and the shape of each of the sub spots and spacing between the sub spots may be controlled using the mask  70 . The size and the shape of each of the sub spots and the spacing between the sub spots determined using the mask  70  may affect binding stability between a substrate for a biochip and biomolecules in a subsequent process and a signal to noise ratio (SNR) in a detection process. 
     As described above, each of the sub spots of the substrate for the biochip according to the one or more embodiments of the present invention has a shape with a side of about 1 nm to about 1 μm in length. The size of each of the sub spots may be adjusted considering the fluorescent wavelength of fluorescence that is present in sample genes to be attached to the biochip and is emitted when being excited. 
     While one or more embodiments of the present invention have been particularly shown and described it will be understood by those of ordinary skill in the art that various modifications in form and detail may be made therein without departing from the spirit and scope of the teachings of the present invention as defined by the following claims. The exemplary embodiments should be considered in a descriptive sense only and not for purposes of limitation. Therefore, all such modifications are intended to be included within the scope of the claims.