Patent Publication Number: US-8119430-B2

Title: Method of manufacturing semiconductor nanowire sensor device and semiconductor nanowire sensor device manufactured according to the method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2008-0099614, filed on Oct. 10, 2008, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention disclosed herein relates to a method of manufacturing a semiconductor nanowire sensor device and a semiconductor nanowire sensor device manufactured according to the method, and more particularly, to a method of manufacturing a semiconductor nanowire sensor device using an epitaxial growth process and a patterning process, and a semiconductor nanowire sensor device manufactured according to the method. 
     According as a high integration of a semiconductor device progresses, active research is being carried out on nanomaterial to address limitations in scaling down silicon-based semiconductor devices and study new physical phenomena. The nanomaterial includes nanowires, nanobelts, nanoribbons, and nanorods. Specifically, research on the nanowires is being widely carried out. The nanowires can be applied to next-generation electronic devices, bio-sensors, optoelectronic devices, and energy devices. 
     To apply the nanowires to various fields, it is necessary to make the sizes and lengths of the nanowires uniform, and uniformly arrange the nanowires. 
     The nanowires are formed using a bottom-up method such as a vapor-liquid-solid (VLS) growth method. According to the VLS growth method, the diameters and densities of the nanowires are adjusted by controlling metal catalyst nanoparticles. However, in the case of the bottom-up method, it is difficult to make the diameters of the nanoparticles uniform and arrange the nanoparticles at a desired position. 
     To solve these limitations, a technology is suggested in which a nanowire is formed on a silicon-on-insulator (SOI) substrate through top-down type semiconductor micro-machining processes such as a lithography process and an etch process, and then the nanowire is used as a channel to detect biomaterial. However, it is necessary that the nanowire used as the channel has a line width ranging from several nm to tens of nm to detect highly sensitive biomaterial, and a high-cost and low-efficiency nanopatterning technology such as an electron beam lithography technology is required to realize the line width ranging from several nm to tens of nm through the top-down semiconductor micro-machining process. In addition, since a process of manufacturing the SOI substrate used in nano-bio sensors is more complicated and more expensive than a process of manufacturing a typical bulk silicon substrate, it is difficult to secure economic efficiency in the mass production of the nano-bio sensors. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method of manufacturing a semiconductor nanowire sensor device, which is adapted for forming a nanowire on a bulk semiconductor substrate. 
     The present invention also provides a semiconductor nanowire sensor device including a nanowire on a bulk semiconductor substrate. 
     The object of the present invention is not limited to the aforesaid, but other objects not described herein will be clearly understood by those skilled in the art from descriptions below. 
     Embodiments of the present invention provide methods of manufacturing a semiconductor nanowire sensor device, the methods including: preparing a first conductive type single crystal semiconductor substrate; forming a line-shaped first conductive type single crystal pattern from the first conductive type single crystal semiconductor substrate; forming second conductive type epitaxial patterns on both sidewalls of the first conductive type single crystal pattern; and forming source and drain electrodes at both ends of the second conductive type epitaxial patterns. 
     In other embodiments of the present invention, semiconductor nanowire sensor devices include: a first conductive type single crystal semiconductor substrate; a line-shaped first conductive type single crystal semiconductor pattern disposed on the first conductive type single crystal semiconductor substrate; second conductive type epitaxial patterns disposed on both sidewalls of the first conductive type single crystal semiconductor pattern; and source and drain electrodes disposed at both ends of the second conductive type epitaxial patterns. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying figures are included to provide a further understanding of the present invention, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present invention and, together with the description, serve to explain principles of the present invention. In the figures: 
         FIGS. 1 through 7  are schematic views illustrating a method of manufacturing a semiconductor nanowire sensor device according to an embodiment of the present invention; 
         FIG. 8  is a schematic view illustrating a semiconductor nanowire sensor device according to an embodiment of the present invention; 
         FIGS. 9 and 10  are a perspective view and a cross-sectional view illustrating a biomolecule-detecting device including a semiconductor nanowire sensor device according to an embodiment of the present invention; and 
         FIG. 11  is a schematic view illustrating a probe molecule immobilized to a semiconductor nanowire sensor device according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Advantages and features of the present invention, and implementation methods thereof will be clarified through following embodiments described with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Further, the present invention is only defined by scopes of claims. Like reference numerals refer to like elements throughout. 
     In the following description, the technical terms are used only for explain a specific exemplary embodiment while not limiting the present invention. The terms of a singular form may include plural forms unless referred to the contrary. The meaning of “include,” “comprise,” “including,” and/or “comprising,” specifies a property, a region, a fixed number, a step, a process, an element and/or a component but does not exclude other properties, regions, fixed numbers, steps, processes, elements and/or components. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. 
     Additionally, the embodiment in the detailed description will be described with cross-sectional views and/or plan views as ideal exemplary views of the present invention. In the figures, the dimensions of layers and regions are exaggerated for clarity of illustration. Accordingly, shapes of the exemplary views may be modified according to manufacturing techniques and/or allowable errors. Therefore, the embodiments of the present invention are not limited to the specific shape illustrated in the exemplary views, but may include other shapes that may be created according to manufacturing processes. Areas exemplified in the drawings have general properties, and are used to illustrate a specific shape of a semiconductor package region. Thus, this should not be construed as limited to the scope of the present invention. 
     Hereinafter, it will be described about exemplary embodiments of the present invention in conjunction with the accompanying drawings. 
       FIGS. 1 through 7  are schematic views illustrating a method of manufacturing a semiconductor nanowire sensor device according to an embodiment of the present invention. 
     Referring to  FIG. 1 , a first conductive type single crystal semiconductor substrate  100 , to be provided with nanowires, is prepared. A bulk silicon substrate, a bulk germanium substrate, or a bulk silicon-germanium substrate may be used for the single crystal semiconductor substrate  100 . 
     A line-shaped mask pattern  110  is formed on the first conductive type single crystal semiconductor substrate  100 . The mask pattern  110  may have a line width ranging from about 1 μm to about 100 μm. The mask pattern  110  has an etch selectivity with respect to the single crystal semiconductor substrate  100 . For example, the mask pattern  110  may be formed of photoresist, silicon nitride, or silicon oxide. 
     Referring to  FIG. 2 , the first conductive type single crystal semiconductor substrate  100  is etched using the line-shaped mask pattern  110  as an etch mask. The single crystal semiconductor substrate  100  may be recessed with a depth ‘d’ ranging from about 1 nm to about 100 nm from its surface. The etching of the semiconductor substrate  100  is adjusted by controlling process conditions such as the type of an etch gas, the flow rate ratio of an etch gas, and an etch time. 
     After that, referring to  FIG. 3 , the mask pattern  110  may be removed to provide a line-shaped first conductive type single crystal pattern  102  protruding from the surface of the single crystal semiconductor substrate  100 . That is, the first conductive type single crystal pattern  102  may have a height ranging from about 1 nm to about 100 nm, and a line width ranging from about 1 μm to about 100 μm. 
     Referring to  FIG. 4 , a second conductive type epitaxial layer  120  is formed on the entire surfaces of the first conductive type single crystal semiconductor substrate  100  and the first conductive type single crystal pattern  102 . 
     Particularly, an epitaxial growth process is performed on the entire surfaces of the first conductive type single crystal semiconductor substrate  100  and the first conductive type single crystal pattern  102 . Since the epitaxial growth process is performed on the entire surfaces without a mask, the epitaxial layer  120  conforms with the entire surfaces of the first conductive type single crystal semiconductor substrate  100  and the first conductive type single crystal pattern  102 . Since the epitaxial layer  120  is grown using the single crystal semiconductor substrate  100  and the single crystal pattern  102  as a seed layer, the epitaxial layer  120  may have a single crystal structure. The epitaxial layer  120  may be grown to a thickness ‘t’ ranging from about 1 nm to about 100 nm. The line width of the nanowire may depend on the thickness of the epitaxial layer  120 . 
     While growing the epitaxial layer  120 , the epitaxial layer  120  may be doped in-situ with a dopant such as boron, phosphorous, arsenic, indium, or antimony, or an ion implantation process may be performed. Accordingly, the epitaxial layer  120  may have the second conductive type that is opposite to the first conductive type. That is, when the first conductive type is a p-type conductive type, the epitaxial layer  120  may be doped with an n-type dopant to have the second conductive type. 
     Referring to  FIG. 5 , second conductive type epitaxial patterns  122  are formed on both sidewalls of the line-shaped first conductive type single crystal pattern  102  protruding from the first conductive type single crystal semiconductor substrate  100 . The second conductive type epitaxial patterns  122  may be formed by performing a blanket anisotropic etch process on the second conductive type epitaxial layer  120 . The second conductive type epitaxial patterns  122  may have a line width ranging from about 1 nm to about 100 nm. That is, as the nanowires of the nanowire sensor device, the line-shaped second conductive type epitaxial patterns  122  may be formed, having a line width ranging from several nm to several tens of nm. The second conductive type epitaxial patterns  122  may be used as channel regions in the nanowire sensor device according to the current embodiment of the present invention. 
     Since the second conductive type epitaxial patterns  122  are formed by performing the blanket anisotropic etch process on the epitaxial layer  120 , the second conductive type epitaxial patterns  122  may be formed in pair on the both sidewalls of the first conductive type single crystal pattern  102 . In other words, the nanowires according to the current embodiment of the present invention may be provided in pair with the first conductive type single crystal pattern  102  there-between, and have the second conductive type that is opposite to the first conductive type. 
     As such, since the first conductive type single crystal pattern  102  is opposite in conductive type to the second conductive type epitaxial patterns  122 , when a reverse bias is applied between the second conductive type epitaxial pattern  122  and both the first conductive type single crystal semiconductor substrate  100  and the first conductive type single crystal pattern  102 , the second conductive type epitaxial pattern  122  may be electrically isolated through a junction isolation from both the first conductive type single crystal semiconductor substrate  100  and the first conductive type single crystal pattern  102 . 
     Referring to  FIG. 6 , second conductive type impurity regions  124  for forming electrodes are formed at both ends of the second conductive type epitaxial patterns  122 , that is, at both ends of the nanowires. 
     Particularly, a mask pattern (not shown) is formed, which exposes the both ends of the second conductive type epitaxial patterns  122 . The mask pattern may expose both ends of the first conductive type single crystal pattern  102 . That is, the mask pattern may cross and cover the centers of the second conductive type epitaxial patterns  122  and the first conductive type single crystal pattern  102 . 
     The both ends of the second conductive type epitaxial patterns  122  are doped with impurities through the mask pattern covering the centers of the second conductive type epitaxial patterns  122  and the first conductive type single crystal pattern  102 . The second conductive type impurity regions  124  may be formed by ion-implanting second conductive type impurities through an ion implantation process. After the second conductive type impurity regions  124  are formed, a heat treating process is performed to remove defects due to the ion implantation process and activate the ion-implanted impurities. 
     That is, the second conductive type impurity regions  124  may be formed at the both ends of the second conductive type epitaxial patterns  122  and the first conductive type single crystal pattern  102 . Accordingly, the second conductive type impurity regions  124  may be connected in common to the second conductive type epitaxial patterns  122 . 
     Referring to  FIG. 7 , ohmic electrodes  132  are formed on the second conductive type impurity regions  124 , respectively. An ohmic electrode  134  may be formed on the first conductive type single crystal semiconductor substrate  100 . Although not shown, the ohmic electrode  134  may be formed on the first conductive type single crystal pattern  102 . 
     The ohmic electrodes  132  and  134  may be formed of a material exhibiting an ohmic contact characteristic with the second conductive type impurity regions  124  and the single crystal semiconductor substrate  100 . For example, the ohmic electrodes  132  and  134  may be formed from a doped poly-silicon layer, a metal layer, a conductive metal oxide layer, or a metal silicide layer. 
     A voltage difference is applied to the ohmic electrodes  132  on the second conductive type impurity regions  124  at the ends of the second conductive type epitaxial patterns  122  such that a current flows through the second conductive type epitaxial patterns  122 . A voltage is applied to the ohmic electrode  134  on the first conductive type single crystal semiconductor substrate  100  and/or the first conductive type single crystal pattern  102  such that a reverse bias is applied between the second conductive type epitaxial pattern  122  and both the first conductive type single crystal semiconductor substrate  100  and the first conductive type single crystal pattern  102 . 
       FIG. 8  is a schematic view illustrating a semiconductor nanowire sensor device according to an embodiment of the present invention. 
     Referring to  FIG. 8 , in the semiconductor nanowire sensor device according to the current embodiment of the present invention, source and drain electrodes  132   a  may be formed at the both ends of one of the second conductive type epitaxial patterns  122 , and source and drain electrodes  132   b  may be formed at the both ends of the other of the second conductive type epitaxial patterns  122 . 
     That is, after the second conductive type epitaxial patterns  122 , having a line width ranging from several nm to tens of nm, are formed as illustrated in  FIG. 5 , second conductive type impurity regions  124   a  are formed at the both ends of one of the second conductive type epitaxial patterns  122 , and second conductive type impurity regions  124   b  are formed at the both ends of the other of the second conductive type epitaxial patterns  122 . The second conductive type impurity regions  124   a  and  124   b  may be formed partially in the first conductive type single crystal semiconductor substrate  100  and the first conductive type single crystal pattern  102 . Ohmic electrodes  132   a  may be formed on the second conductive type impurity regions  124   a , and ohmic electrodes  132   b  may be formed on the second conductive type impurity regions  124   b.    
     The semiconductor nanowire sensor devices according to the embodiments of the present invention may be used as a bio-sensor detecting biomolecules, which will now be described with reference to  FIGS. 9 through 11 . The biomolecules, which are organic molecules exhibiting specific strains, have the same meaning as target molecules or analytes in the present disclosure. 
       FIGS. 9 and 10  are a perspective view and a cross-sectional view illustrating a biomolecule-detecting device including a semiconductor nanowire sensor device according to an embodiment of the present invention.  FIG. 11  is a schematic view illustrating one of probe molecules  151  immobilized to the semiconductor nanowire sensor device according to an embodiment of the present invention. 
     Referring to  FIGS. 9 and 10 , in the semiconductor nanowire sensor device, a fluid channel  200  for supplying solutions may be disposed on the second conductive type epitaxial pattern  122  equivalent to a channel region. Particularly, the fluid channel  200  may be disposed on the first conductive type single crystal pattern  102  protruding from the first conductive type single crystal semiconductor substrate  100  and disposed on the second conductive type epitaxial pattern  122 . 
     When appropriate voltages are applied to the ohmic electrodes  132  and  134 , the probe molecules  151 , binding with target molecules that will be detected, are immobilized to the channel region, that is, to a surface of the second conductive type epitaxial pattern  122  disposed between the second conductive type impurity regions  124 . 
     Particularly, a voltage difference V 1  is applied to the ohmic electrodes  132  equivalent to source and drain electrodes, so that a current I flows through the second conductive type epitaxial pattern  122 . A voltage V 2  is applied to the ohmic electrode  134  disposed on the first conductive type single crystal semiconductor substrate  100  such that a reverse bias is supplied to the first conductive type single crystal semiconductor substrate  100  and the second conductive type epitaxial pattern  122 . 
     The probe molecules  151  may be immobilized directly to the surface of the second conductive type epitaxial pattern  122 , or immobilized to the surfaces using organic molecules as media. A method of immobilizing the probe molecules  151  will now be described in detail with reference to  FIG. 11 . 
     According to biomolecules (i.e. target molecules  153 ) to be detected, the probe molecules  151  may be proteins, cells, viruses, or nucleic acids. The proteins may be any biomolecules such as antigens, antibodies, matrix proteins, enzymes, and coenzymes. The nucleic acids may be DNA, RNA, PNA, LNA or a combination thereof. 
     The probe molecules  151  may be immobilized to a surface of the protruding first conductive type single crystal pattern  102  as well as to the surface of the second conductive type epitaxial pattern  122 . However, the reverse bias, supplied to the second conductive type epitaxial pattern  122  and the first conductive type single crystal pattern  102 , prevents the probe molecules  151  immobilized to the surface of the first conductive type single crystal pattern  102  from affecting the channel region (i.e., the second conductive type epitaxial pattern  122 ). 
     After the probe molecules  151  are immobilized to the second conductive type epitaxial patterns  122 , a solution  150  containing the target molecules  153  is provided to the surface of the second conductive type epitaxial pattern  122 . The solution  150  may further contain nonspecific molecules  155  that do not bind with the probe molecules  151 . 
     The target molecules  153  (or analytes), coming from a living body, are biomolecules exhibiting a specific strain. For example, the target molecules  153  may be proteins, nucleic acids, organic molecules, inorganic molecules, oxides, or metal oxides. The proteins may be any biomolecules such as antigens, antibodies, matrix proteins, enzymes, and coenzymes. The nucleic acids may be DNA, RNA, PNA, LNA or a combination thereof. 
     When the solution  150  containing the target molecules  153  is supplied to the second conductive type epitaxial patterns  122 , the target molecules  153  bind with the probe molecules  151  on the surfaces of the second conductive type epitaxial patterns  122 . 
     The binding of the probe molecules  151  with the target molecules  153  on the surfaces of the second conductive type epitaxial patterns  122  may be any binding, known to those skilled in the art, including nucleic acid hybridization, antigen-antibody reaction, and enzyme link reaction. 
     After the target molecules  153  bind with the probe molecules  151 , the target molecules  153  provide new positive charge or new negative charge to the surface of the second conductive type epitaxial pattern  122 . Accordingly, the amount of the current I flowing through the second conductive type epitaxial pattern  122  may depend on the amount of net charge (positive charge or negative charge) of the target molecules  153 . 
     Thus, the amount of the current I flowing through the second conductive type epitaxial pattern  122  are measured according to the target molecules  153  binding the probe molecules  151 , so as to detect the presence and the amount of the target molecules  153 . 
     Referring to  FIG. 11 , the method of immobilizing the probe molecule  151  to the surface of the second conductive type epitaxial pattern  122  will now be described in detail. A method of immobilizing a monoclonal antibody of prostate specific antigen (anti-PSA) will be exemplified. The monoclonal anti-PSA is a probe molecule adapted for detecting PSA that is a target molecule. 
     To immobilize the probe molecule  151 , a surface-treating process may be performed on the surface of the second conductive type epitaxial pattern  122  equivalent to the channel region between the ohmic electrodes  132  that are source and drain electrodes. For example, a carboxyl group (—COOH), a thiol group (—SH), a hydroxyl group (—OH), a silane group, an amine group, or an epoxy group may be induced on the surface of the second conductive type epitaxial pattern  122  after the surface-treating process. 
     For example, an O 2  plasma ashing process is performed on the surface of the second conductive type epitaxial pattern  122  to form the hydroxyl group (—OH). 
     An ethanol solution, in which an 1% aminopropyltriethoxy silane (APTES) is dispersed, is supplied to the surface of the second conductive type epitaxial pattern  122  provided with the hydroxyl group (—OH), then an agitating process is performed for a predetermined time, and then washing and drying processes are performed. 
     Then, a 25 weight percent (wt %) glutaraldehyde solution is supplied to the surface of the second conductive type epitaxial pattern  122  to form an aldehyde group (—CHO). 
     After that, a solution containing the probe molecules  151  (e.g., anti-PSA) is supplied to the surface of the second conductive type epitaxial pattern  122  to bind the anti-PSA with the aldehyde group (—CHO). Accordingly, the probe molecule  151  may be immobilized on the surface of the second conductive type epitaxial pattern  122 . 
     According to the present invention, the method of manufacturing a semiconductor nanowire sensor device and the semiconductor nanowire sensor device manufactured according to the method are adapted for forming nanowires having a line width ranging from several nm to tens of nm, on the bulk semiconductor substrate through the lithography process and the epitaxial growth process. 
     In addition, the nanowire equivalent to the channel region is electrically isolated from the semiconductor substrate through the PN junction, thereby realizing the semiconductor nanowire sensor device on the bulk semiconductor substrate. 
     Therefore, the reproducibility and reliability of the semiconductor nanowire sensor device are secured, and mass production is achieved at low costs. 
     The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true spirit and scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.