Patent Publication Number: US-9842870-B2

Title: Integrated bio-sensor with nanocavity and fabrication method thereof

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. application Ser. No. 14/987,777 filed Jan. 5, 2016, which is included in its entirety herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a bio-technology inspection field, and more particularly, to a bio-sensor with nanocavity and a fabrication method thereof. 
     2. Description of the Prior Art 
     In recent years, various biological inspection methods have been developed as a result of the progress in biotechnology, in which technologies involving the inspection of deoxyribonucleic acid (DNA) sequence within a specific gene have become especially popular. A gene is typically known as a particular sequence of DNA with deoxyribose and phosphates serving as backbone while having four bases including adenine (A), guanine (G), thymine (T), and cytosine (C). The matching of chemical structures between two single strands of DNA is preferably enhanced by the mutual attraction of hydrogen bonds between adenine and thymine, and between guanine and cytosine to constitute the double helix structure of a DNA. 
     It has been known that DNA sequencing could be achieved by slicing gene sequences waiting to be sequenced into small chunks, connecting the sliced chunks to a converting adaptor, selectively adding micro-beads with polymerase chain reaction (PCR) to multiply gene chucks waiting to be inspected, and finally combining micro-processes, optical inspections, and automated control technologies based on different sequencing principles to quickly decode large quantities of DNA sequence. 
     In addition to DNA sequencing, bio-sensors could also be applied to numerous bio-related inspections, such as bacterial and viral inspections, gene mutations, genetic or hereditary screenings, disease preventions, environmental inspections, pollution controls, and food safety. Moreover, bio-sensors could be applied to fast checks for genetic defects. Based on inspection data obtained, the bio-sensors could be used to provide currently unknown solutions for such as nucleic acid polymorphism differentiation and the relations between diseases and complications. The results thereby may further be used to develop diagnosing and preventing approaches. 
     However, there is still a need in this field to provide an improved bio-sensor capable of not only having advantages such as fast, high accuracy, and high sensitivity, but also having acid and alkali-resistant and anti-corrosive structures. The fabrication method of the improved bio-sensor should also be compatible with CMOS image sensors so that the signal processing circuit chips could be integrated for the purposes of cost reduction, power consumption reduction, and integrity enhancement. 
     SUMMARY OF THE INVENTION 
     To achieve the purposes described above, an integrated bio-sensor with a nanocavity and a fabrication method thereof are provided in the present invention for solving the inadequate parts and the demerits of the prior art. 
     An integrated bio-sensor with a nanocavity is provided in an embodiment of the present invention. The integrated bio-sensor includes a substrate, a light-sensing region, a first dielectric layer, a diffusion barrier layer, a second dielectric layer, a trenched recess structure, a liner layer, a light filter layer, a cap layer, a first passivation layer, a nanocavity construction layer, and a second passivation layer. A plurality of isolation structures is disposed on the substrate, and a plurality of pixel regions is defined by the isolation structures. The light-sensing region is disposed in each of the pixel regions. The first dielectric layer is disposed on the substrate. The diffusion barrier layer is disposed on the first dielectric layer. The second dielectric layer is disposed on the diffusion barrier layer. The trenched recess structure is disposed in the second dielectric layer. The liner layer is disposed conformally on an inner wall of the trenched recess structure. The light filter layer is disposed on the liner layer in the trenched recess structure. The cap layer directly contacts a top surface of the light filter layer, and the light filter layer is capped with the cap layer. The first passivation layer is disposed on the cap layer. The nanocavity construction layer is disposed on the first passivation layer. A nanocavity is disposed in the nanocavity construction layer disposed directly above the light filter layer. The second passivation layer is disposed on a sidewall and a bottom surface of the nanocavity. The light filter layer is configured to block light within a specific wavelength range and filter out noise light, and light within another specific wavelength range may pass through the light filter layer and irradiate the light-sensing region. 
     A fabrication method of an integrated bio-sensor with a nanocavity is provided in an embodiment of the present invention. The fabrication method includes the following steps. A substrate is provided. A plurality of isolation structures is disposed on the substrate, and a plurality of pixel regions is defined by the isolation structures. A light-sensing region is formed in each of the pixel regions. A first dielectric layer is deposited on the substrate. A diffusion barrier layer is deposited on the first dielectric layer. A second dielectric layer is deposited on the diffusion barrier layer. A trenched recess structure is formed in the second dielectric layer. A liner layer is deposited conformally on an inner wall of the trenched recess structure. A light filter layer is formed on the liner layer. The trenched recess structure is filled with the light filter layer. A cap layer is deposited to directly contact a top surface of the light filter layer, and the light filter layer is capped with the cap layer. A first passivation layer is formed on the cap layer. A nanocavity construction layer is deposited on the first passivation layer. A nanocavity is formed in the nanocavity construction layer directly above the light filer layer. A second passivation layer is formed on a sidewall and a bottom surface of the nanocavity. 
     According to an embodiment of the present invention, after the step of forming the light filter layer, the fabrication method further includes performing a solidification process for solidifying the light filter layer, and performing a polishing process or an etching back process for removing the light filter layer outside the trenched recess structure. 
     According to an embodiment of the present invention, the first passivation layer and the second passivation layer are formed by physical vapor deposition processes. 
     An integrated bio-sensor with a nanocavity is provided in another embodiment of the present invention. The integrated bio-sensor includes a substrate, a light-sensing region, a first dielectric layer, a diffusion barrier layer, a second dielectric layer, a trenched recess structure, a liner layer, a light filter layer, a cap layer, and a passivation layer. A plurality of isolation structures is disposed on the substrate, and a plurality of pixel regions is defined by the isolation structures. A light-sensing region is disposed in each of the pixel regions. The first dielectric layer is disposed on the substrate. The diffusion barrier layer is disposed on the first dielectric layer. The second dielectric layer is disposed on the diffusion barrier layer. The trenched recess structure is disposed in the second dielectric layer. The liner layer is disposed conformally on an inner wall of the trenched recess structure. The light filter layer is disposed on the liner layer in the trenched recess structure. The light filter layer has a top surface, and the top surface of the light filter layer is lower than a top surface of the first dielectric layer by a predetermined depth for forming a recess part. The cap layer is disposed conformally on the trenched recess structure. The cap layer directly contacts the top surface of the light filter layer; and the light filter layer is capped with the cap layer. The passivation layer is disposed conformally on the cap layer, wherein a surface of the passivation layer is self-aligned with the light filter layer for forming a nanocavity above the recess part. 
     A fabrication method of an integrated bio-sensor with a nanocavity is provided in another embodiment of the present invention. The fabrication method includes the following steps. A substrate is provided. A plurality of isolation structures is disposed on the substrate, and a plurality of pixel regions is defined by the isolation structures. A light-sensing region is formed in each of the pixel regions. A first dielectric layer is deposited on the substrate. A diffusion barrier layer is deposited on the first dielectric layer. A second dielectric layer is deposited on the diffusion barrier layer. A trenched recess structure is formed in the second dielectric layer. A liner layer is deposited conformally on an inner wall of the trenched recess structure. A light filter layer is formed on the liner layer. The trenched recess structure is filled with the light filter layer. A solidification process is performed for solidifying the light filter layer, and a polishing process or an etching back process is performed for removing the light filter layer outside the trenched recess structure. An etching back process is performed to make a top surface of the light filter lower than a top surface of the first dielectric layer by a predetermined depth for forming a recess part. A cap layer is deposited conformally on the recess part. The cap layer directly contacts the top surface of the light filter layer, and the light filter layer is capped with the cap layer. A passivation layer is formed conformally on the cap layer, wherein a surface of the passivation layer is self-aligned with the light filter layer for forming a nanocavity above the recess part. The passivation layer includes metal oxide, such as tantalum oxide. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the embodiments, and are incorporated in and constitute apart of this specification. The drawings illustrate some of the embodiments and, together with the description, serve to explain their principles. In the drawings: 
         FIG. 1  is a schematic drawing illustrating a cross-sectional view of a bio-sensor with a nanocavity according to an embodiment of the present invention. 
         FIGS. 2-6  are schematic drawings illustrating a fabrication method of the bio-sensor with the nanocavity in  FIG. 1 . 
         FIG. 7  is a schematic drawing illustrating a cross-sectional view of a bio-sensor with a self-aligned nanocavity according to another embodiment of the present invention. 
         FIGS. 8-12  are schematic drawings illustrating a fabrication method of the bio-sensor with the self-aligned nanocavity in  FIG. 7 . 
     
    
    
     It is noted that all of the drawings in this specification are schematic drawings. For clearly and conveniently illustration, the size of each part and the scale between the parts in the drawings might be exaggerated or shrunk. Generally, characteristic components and the corresponding modified components will be marked by the same reference symbol, or the corresponding or similar components in different embodiments will be marked by the same reference symbol. 
     DETAILED DESCRIPTION 
     In the following detailed description of the invention, reference is made to the accompanying drawings, which form a part hereof, and in which is shown, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
     The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled. One or more implementations of the present invention will now be described with reference to the attached drawings, wherein like reference numerals are used to refer to like elements throughout, and wherein the illustrated structures are not necessarily drawn to scale. 
     The term substrate is used to refer to and include a base material or a structure for forming components such as semiconductor units thereon. The substrate may be a semiconductor substrate, a semiconductor base material formed on a supporting structure, or a semiconductor substrate with one or more materials, structures, or regions formed thereon. The substrate may be a traditional silicon substrate or a bulk material containing semiconductor material. Apart from the traditional silicon wafer, the term substrate may also include a silicon-on-insulator (SOI) substrate, such as a silicon-on-sapphire (SOS) substrate, a silicon-on-glass (SOG) substrate, and a silicon epitaxial layer on a silicon base material, or other semiconductor or photoelectric materials, such as silicon germanium (SiGe), germanium (Ge), gallium arsenide (GaAs), gallium nitride (GaN), and indium phosphide (InP). 
     In this specification, when some component is described to be located on or above another component, it is referred to the conditions that the component is directly located right above the other component, the component is directly located adjacent to the other component, the component is directly located under the other component, or the component directly contacts the other component. The conditions that the component is indirectly located right above the other component, the component is indirectly located adjacent to the other component, the component is indirectly located under the other component, or the component does not directly contact the other component are also included in the description mentioned above. On the contrary, when some component is described to be directly located on another component, there is not any other component between this two components. 
     Unless there is a description mentioned specifically in the specification, the materials described in the specification may be formed by any appropriate technology, such as spin coating, slit coating, immersion coating, blanket coating, chemical vapor deposition (CVD), atomic layer deposition (ALD), and physical vapor deposition (PVD), but not limited thereto. Otherwise, the materials may be formed in-situ. One of ordinary skill in the art may select the appropriate technology to deposit or form the materials according to the properties of the specific materials to be formed. 
     Unless there is a description mentioned specifically in the specification, the actions of removing the materials in the specification may be achieved by any appropriate technology, such as etching process or polishing process, but not limited thereto. 
     An integrated bio-sensor is provided in the present invention, and a nanocavity capable of performing biochemical reactions directly is formed on the integrated bio-sensor. The integrated bio-sensor has advantages such as fast, high accuracy, and high sensitivity, and has an acid and alkali resisting and an anti-corrosion structure. The manufacturing process of the bio-sensor may be compatible with the manufacturing process of CMOS image sensor (CIS), the signal processing circuit chip may be integrated, and the purposes of cost reduction, power consumption reduction, and integrity enhancement may be achieved accordingly. 
     Please refer to  FIG. 1 .  FIG. 1  is a schematic drawing illustrating a cross-sectional view of a bio-sensor with a nanocavity according to an embodiment of the present invention. As shown in  FIG. 1 , an integrated bio-sensor  1  includes a substrate  100 , and a plurality of pixel regions  10  arranged in an array configuration is formed in the substrate  100 . For describing conveniently, there are only two pixel regions of the pixel array shown in the figure. According to the embodiment the present invention, the substrate  100  may be a silicon substrate, but not limited thereto. A plurality of isolation structures  112  is disposed on the substrate  100 , and a plurality of the pixel regions  10  is defined by the isolation structures  112 . 
     A gate structure  160  may be formed on the substrate  100  of each pixel region. A light-sensing region  104  and a floating drain region  106  are then formed in the substrate  100  at two sides of the gate structure  160 . The gate structure  160  may include a dielectric layer and a conductive layer. The dielectric layer may be silicon oxide, and the conductive layer may be single-crystal silicon, undoped polycrystalline silicon, doped polycrystalline silicon, amorphous silicon, metal silicide, or the combination of the materials mentioned above. A sidewall spacer may be formed on the sidewall of the gate structure  160 , and the sidewall spacer may be silicon oxide, silicon nitride, or the combination of silicon oxide and silicon nitride. 
     The light-sensing region  104  may be a photodiode including a first conductivity type doped region  142  and a second conductivity type doped region  144 . The first conductivity type is an opposite conductivity type of the second conductivity type. For example, when the substrate is a P type substrate, the first conductivity type doped region  142  may be an N type doped region, the second conductivity type doped region  144  may be a P type doped region, the floating drain region  106  may be an N type doped region, and vice versa. For instance, the first conductivity type doped region  142  may be a lightly doped region, and the second conductivity type doped region  144  and the floating drain region  106  may be heavily doped regions. 
     According to the embodiment of the present invention, multiple dielectric layers, such as a dielectric layer  202 , a dielectric layer  204 , a dielectric layer  206 , and a dielectric layer  208 , may be formed on the substrate  100 . For example, the dielectric layer  202  and the dielectric layer  206  may include silicon dioxide, but not limited thereto. The dielectric layer  204  disposed between the dielectric layer  202  and the dielectric layer  206  may include silicon nitride, but not limited thereto. According to the embodiment of the present invention, the dielectric layer  204  is used as a diffusion barrier layer. The dielectric layer  208  is used as a passivation layer or a protection layer, and the dielectric layer  208  may include silicon nitride, silicon oxynitride, and/or silicon oxide, but not limited thereto. According to the embodiment of the present invention, a metal layer  212  may be formed in the dielectric layer  202 . A metal layer  214 , a metal layer  216 , a metal layer  218 , and a metal connection  217  may be formed in the dielectric layer  206 . It is noted that the metal layer structure in the dielectric layer shown in the figures is only used as an illustration sample. In other embodiments of the present invention, there may be more metal layers formed in the dielectric layers. 
     According to the embodiment of the present invention, a trenched recess structure  200  is formed in the dielectric layer  206  and the dielectric layer  208  above the light-sensing region  104  corresponding to each pixel region  10 . According to the embodiment of the present invention, a bottom part of the trenched recess structure  200  is a top surface of the dielectric layer  204 . In other words, a depth of the trenched recess structure  200  is substantially equal to a total thickness of the dielectric layer  206  and the dielectric layer  208 . According to the embodiment of the present invention, a liner layer  220 , such as silicon nitride layer, is formed conformally on the bottom part and an inner wall of the trenched recess structure  200 , but not limited thereto. According to the embodiment of the present invention, the liner layer  220  may be further formed on a top surface of the dielectric layer  208  for forming a continuous liner layer. 
     According to the embodiment of the present invention, the trenched recess structure  200  may be filled with at least one light filter layer  310 . According to the embodiment of the present invention, the light filter layer  310  is capable of blocking light within a specific wavelength range (such as a green light laser) and filtering out noise light, and light within another specific wavelength range (such as a fluorescence generated by a specific biochemical reaction) may pass through the light filter layer  310  and irradiate the pixel region  10  below. Corresponding electrical current signals may be generated by the photoelectric reaction in the pixel region  10  and then be received by the light-sensing region  104 . 
     According to the embodiment of the present invention, the light filter layer  310  may include high concentration metal ions, such as sodium ions (Na + ). In the present invention, in order to prevent the metal ions from diffusing outward to the dielectric layer and inducing corrosion or deterioration of the metal layer, the surroundings and the bottom part of the light filter layer  310  are covered by the liner layer  220  for preventing the adjacent dielectric layer from directly contacting the light filter layer  310 . Additionally, the dielectric layer  204  may be used as a diffusion barrier layer configured to keep the light filter layer  310  from diffusing downward to the surface of the substrate  100  and affecting the characteristics and performance of the devices. 
     According to the embodiment of the present invention, a cap layer  320  is stacked on the light filter layer  310  and the liner layer  220 , and the cap layer  320  may be a silicon nitride layer for example, but not limited thereto. According to the embodiment of the present invention, the cap layer  320  directly contacts the top surface of the light filter layer  310 , and the light filter layer  310  is capped with the cap layer  320 . According to the embodiment of the present invention, the cap layer  320 , the liner layer  220  and the dielectric layer  204  may be used to completely block the metal ions in the light filter layer  310  from diffusing outward. 
     According to the embodiment of the present invention, a first passivation layer  330  is formed on the cap layer  320 . The first passivation layer  330  may be metal oxide, such as tantalum oxide (TaO), but not limited thereto. According to the embodiment of the present invention, the first passivation layer  330  has to be transparent, acid resistant, and alkali-resistant. The first passivation layer  330  has high etching selectivity in comparison with a nanocavity construction layer  340 , such as a silicon nitride layer. According to the embodiment of the present invention, the first passivation layer may be used as an etching stop layer. According to the embodiment of the present invention, the first passivation layer  330  may be formed by a physical vapor deposition (PVD) process, but not limited thereto. 
     According to the embodiment of the present invention, a nanocavity construction layer  340 , such as a silicon nitride layer, is formed on the first passivation layer  330 , but not limited thereto. A nanocavity  300  is formed in the nanocavity construction layer  340  directly above the light filer layer  310 . A depth of the nanocavity  300  is substantially equal to a thickness of the nanocavity construction layer  340 . The sidewall of the nanocavity  300  is a bevel sidewall, and an included angle θ between the sidewall and a horizontal level may range between 60 degrees and 80 degrees, but not limited thereto. 
     According to the embodiment of the present invention, a second passivation layer  350  is conformally formed on the nanocavity construction layer  340 , the sidewall of the nanocavity  300 , and a bottom surface of the nanocavity  300 . The second passivation layer  350  may be metal oxide, such as tantalum oxide (TaO), but not limited thereto. According to the embodiment of the present invention, the second passivation layer  350  has to be transparent, acid resistant, and alkali-resistant so as to prevent from the corrosion of biochemical reactions. According to the embodiment of the present invention, the second passivation layer  350  may be formed by a physical vapor deposition (PVD) process, but not limited thereto. The nanocavity  300  mentioned above has the bevel sidewall, and the step coverage of depositing the second passivation layer  350  may be better accordingly. 
     According to the embodiment of the present invention, for example, a reference sample may be disposed in the nanocavity, and a target sample may then be injected in each nanocavity  300 . After a radiation by a specific laser light source, biochemical reactions are caused by the reference sample and the target sample for generating a fluorescence having a wavelength in a specific range. The specific wavelength fluorescence mentioned above may pass through the light filter layer  310  and irradiate the light-sensing region  104  for being sensed. The laser beam of the laser light source mentioned above will be filtered out by the light filter layer  310 . 
     Please refer to  FIGS. 2-6 .  FIGS. 2-6  are schematic drawings illustrating a fabrication method of the bio-sensor with the nanocavity in  FIG. 1 . As shown in  FIG. 2 , a substrate  100  is provided first. A plurality of pixel regions  10  arranged in an array configuration is formed in the substrate  100 . For describing conveniently, there are only two pixel regions of the pixel array shown in the figures. According to the embodiment the present invention, the substrate  100  may be a silicon substrate, but not limited thereto. A plurality of isolation structures  112  is disposed on the substrate  100 , and a plurality of the pixel regions  10  is defined by the isolation structures  112 . 
     A gate structure  160  may be formed on the substrate  100  of each pixel region. A light-sensing region  104  and a floating drain region  106  are then formed in the substrate  100  at two sides of the gate structure  160 . The gate structure  160  may include a dielectric layer and a conductive layer. The dielectric layer may be silicon oxide, and the conductive layer may be single-crystal silicon, undoped polycrystalline silicon, doped polycrystalline silicon, amorphous silicon, metal silicide, or the combination of the materials mentioned above. A sidewall spacer may be formed on the sidewall of the gate structure  160 , and the sidewall spacer may be silicon oxide, silicon nitride, or the combination of silicon oxide and silicon nitride. 
     The light-sensing region  104  may be a photodiode including a first conductivity type doped region  142  and a second conductivity type doped region  144 . The first conductivity type is an opposite conductivity type of the second conductivity type. For example, when the substrate is a P type substrate, the first conductivity type doped region  142  may be an N type doped region, the second conductivity type doped region  144  may be a P type doped region, the floating drain region  106  may be an N type doped region, and vice versa. For instance, the first conductivity type doped region  142  may be a lightly doped region, and the second conductivity type doped region  144  and the floating drain region  106  may be heavily doped regions. 
     As shown in  FIG. 3 , multiple dielectric layers including a dielectric layer  202 , a dielectric layer  204 , a dielectric layer  206 , and a dielectric layer  208 , a metal layer  212 , a metal layer  214 , a metal layer  216 , and a metal layer  218  are deposited on the substrate  100 . For example, the dielectric layer  202  and the dielectric layer  206  may include silicon dioxide, but not limited thereto. The dielectric layer  202  and the dielectric layer  206  may be composed of multiple dielectric layers. The dielectric layer  204  formed between the dielectric layer  202  and the dielectric layer  206  may include silicon nitride, but not limited thereto. According to the embodiment of the present invention, the dielectric layer  204  is used as a diffusion barrier layer. The dielectric layer  208  is used as a passivation layer or a protection layer, and the dielectric layer  208  may include silicon nitride, silicon oxynitride, and/or silicon oxide, but not limited thereto. According to the embodiment of the present invention, the metal layer  212  may be formed in the dielectric layer  202 . The metal layer  214 , the metal layer  216 , the metal layer  218 , and the metal connection  217  may be formed in the dielectric layer  206 . It is noted that the metal layer structure in the dielectric layer shown in the figures is only used as an illustration sample. In other embodiments of the present invention, there may be more metal layers formed in the dielectric layers. 
     As shown in  FIG. 4 , a photolithographic process and an etching process are then performed to form a trenched recess structure  200  in the dielectric layer  206  and the dielectric layer  208  above the light-sensing region  104  corresponding to each pixel region  10 . In the above-mentioned etching process for forming the trenched recess structure  200 , the dielectric layer  204  may be used as an etching stop layer. According to the embodiment of the present invention, a bottom part of the trenched recess structure  200  is a top surface of the dielectric layer  204 . In other words, a depth of the trenched recess structure  200  is substantially equal to a total thickness of the dielectric layer  206  and the dielectric layer  208 . A liner layer  220 , such as silicon nitride layer, is then deposited conformally on the bottom part and an inner wall of the trenched recess structure  200 , but not limited thereto. According to the embodiment of the present invention, the liner layer  220  may be further formed on a top surface of the dielectric layer  208  for forming a continuous liner layer. 
     As shown in  FIG. 5 , the trenched recess structure  200  may then be filled with at least one light filter layer  310 . According to the embodiment of the present invention, after the step of forming the light filter layer  310 , a solidification process may then be performed for solidifying the light filter layer  310 . According to the embodiment of the present invention, a polishing process or an etching back process may then be performed for removing the light filter layer  310  outside the trenched recess structure  200 . According to the embodiment of the present invention, the light filter layer  310  is capable of blocking light within a specific wavelength range and filtering out noise light, and light within another specific wavelength range may pass through the light filter layer  310  and irradiate the pixel region  10  below. 
     Subsequently, a cap layer  320  is deposited on the light filter layer  310  and the liner layer  220 , and the cap layer  320  may be a silicon nitride layer for example, but not limited thereto. According to the embodiment of the present invention, the cap layer  320  directly contacts the top surface of the light filter layer  310 , and the light filter layer  310  is capped with the cap layer  320 . According to the embodiment of the present invention, the cap layer  320 , the liner layer  220  and the dielectric layer  204  may be used to completely block the metal ions in the light filter layer  310  from diffusing outward. A first passivation layer  330  is deposited on the cap layer  320  by a physical vapor deposition (PVD) process. The first passivation layer  330  may be metal oxide, such as tantalum oxide (TaO), but not limited thereto. A nanocavity construction layer  340 , such as a silicon nitride layer, is then deposited on the first passivation layer  330 , but not limited thereto. 
     As shown in  FIG. 6 , a photolithographic process and an etching process are then performed for forming a nanocavity  300  in the nanocavity construction layer  340  directly above each of the light filer layers  310 . A depth of the nanocavity  300  is substantially equal to a thickness of the nanocavity construction layer  340 . The sidewall of the nanocavity  300  is a bevel sidewall, and an included angle θ between the sidewall and a horizontal level may range between 60 degrees and 80 degrees, but not limited thereto. Finally, a second passivation layer  350  is deposited conformally on the nanocavity construction layer  340 , the sidewall of the nanocavity  300 , and a bottom surface of the nanocavity  300  by a physical vapor deposition (PVD) process. The second passivation layer  350  may be metal oxide, such as tantalum oxide (TaO), but not limited thereto. The integrated bio-sensor with the nanocavity in the present invention may then be formed by the fabrication method described above. 
     Please refer to  FIG. 7 .  FIG. 7  is a schematic drawing illustrating a cross-sectional view of a bio-sensor with a self-aligned nanocavity according to another embodiment of the present invention. As shown in  FIG. 7 , an integrated bio-sensor  1   a  also includes a substrate  100 , and a plurality of pixel regions  10  arranged in an array configuration is formed in the substrate  100 . For describing conveniently, there are only two pixel regions of the pixel array shown in the figure. According to the embodiment the present invention, the substrate  100  may be a silicon substrate, but not limited thereto. A plurality of isolation structures  112  is disposed on the substrate  100 , and a plurality of the pixel regions  10  is defined by the isolation structures  112 . 
     A gate structure  160  may be formed on the substrate  100  of each pixel region. A light-sensing region  104  and a floating drain region  106  are then formed in the substrate  100  at two sides of the gate structure  160 . The gate structure  160  may include a dielectric layer and a conductive layer. The dielectric layer may be silicon oxide, and the conductive layer may be single-crystal silicon, undoped polycrystalline silicon, doped polycrystalline silicon, amorphous silicon, metal silicide, or the combination of the materials mentioned above. A sidewall spacer may be formed on the sidewall of the gate structure  160 , and the sidewall spacer may be silicon oxide, silicon nitride, or the combination of silicon oxide and silicon nitride. 
     The light-sensing region  104  may be a photodiode including a first conductivity type doped region  142  and a second conductivity type doped region  144 . The first conductivity type is an opposite conductivity type of the second conductivity type. For example, when the substrate is a P type substrate, the first conductivity type doped region  142  may be an N type doped region, the second conductivity type doped region  144  may be a P type doped region, the floating drain region  106  may be an N type doped region, and vice versa. For instance, the first conductivity type doped region  142  may be a lightly doped region, and the second conductivity type doped region  144  and the floating drain region  106  may be heavily doped regions. 
     According to the embodiment of the present invention, multiple dielectric layers, such as a dielectric layer  202 , a dielectric layer  204 , a dielectric layer  206 , and a dielectric layer  208 , may be formed on the substrate  100 . For example, the dielectric layer  202  and the dielectric layer  206  may include silicon dioxide, but not limited thereto. The dielectric layer  204  disposed between the dielectric layer  202  and the dielectric layer  206  may include silicon nitride, but not limited thereto. According to the embodiment of the present invention, the dielectric layer  204  is used as a diffusion barrier layer. The dielectric layer  208  is used as a passivation layer or a protection layer, and the dielectric layer  208  may include silicon nitride, silicon oxynitride, and/or silicon oxide, but not limited thereto. According to the embodiment of the present invention, a metal layer  212  may be formed in the dielectric layer  202 . A metal layer  214 , a metal layer  216 , a metal layer  218 , and a metal connection  217  may be formed in the dielectric layer  206 . It is noted that the metal layer structure in the dielectric layer shown in the figures is only used as an illustration sample. 
     According to the embodiment of the present invention, a trenched recess structure  200  is formed in the dielectric layer  206  and the dielectric layer  208  above the light-sensing region  104  corresponding to each pixel region  10 . According to the embodiment of the present invention, a bottom part of the trenched recess structure  200  is a top surface of the dielectric layer  204 . In other words, a depth of the trenched recess structure  200  is substantially equal to a total thickness of the dielectric layer  206  and the dielectric layer  208 . According to the embodiment of the present invention, a liner layer  220 , such as silicon nitride layer, is formed conformally on the bottom part and an inner wall of the trenched recess structure  200 , but not limited thereto. According to the embodiment of the present invention, the liner layer  220  may be further formed on a top surface of the dielectric layer  208  for forming a continuous liner layer. 
     According to the embodiment of the present invention, the trenched recess structure  200  may be filled with at least one light filter layer  310 . According to the embodiment of the present invention, the light filter layer  310  is capable of blocking light within a specific wavelength range (such as a green light laser) and filtering out noise light, and light within another specific wavelength range (such as a fluorescence generated by a specific biochemical reaction) may pass through the light filter layer  310  and irradiate the pixel region  10  below. Corresponding electrical current signals may be generated by the photoelectric reaction in the pixel region  10  and then be received by the light-sensing region  104 . 
     According to the embodiment of the present invention, the light filter layer  310  may include high concentration metal ions, such as sodium ions. In order to prevent the metal ions from diffusing outward to the dielectric layer and inducing corrosion or deterioration of the metal layer, the surroundings and the bottom part of the light filter layer  310  are covered by the liner layer  220  for preventing the adjacent dielectric layer from directly contacting the light filter layer  310 . Additionally, the dielectric layer  204  may be used as a diffusion barrier layer configured to keep the light filter layer  310  from diffusing downward to the surface of the substrate  100  and affecting the characteristics and performance of the devices. 
     According to the embodiment of the present invention, the light filter layer  310  has a top surface  310   a , and the top surface  310   a  is lower than the top surface of the dielectric layer  208  by a predetermined depth for still forming a recess part at a top end of the trenched recess structure  200  after the step of forming the light filter layer  310 . According to the embodiment of the present invention, a cap layer  420  is formed conformally on the light filter layer  310  and the liner layer  220 , and the cap layer  420  may be a silicon nitride layer for example, but not limited thereto. According to the embodiment of the present invention, the cap layer  420  directly contacts the top surface of the light filter layer  310 , and the light filter layer  310  is capped with the cap layer  420 . 
     According to the embodiment of the present invention, a passivation layer  430  is formed conformally on the cap layer  420 . The passivation layer  430  may be metal oxide, such as tantalum oxide, but not limited thereto. According to the embodiment of the present invention, the passivation layer  430  has to be transparent, acid resistant, and alkali-resistant. According to the embodiment of the present invention, the passivation layer  430  may be formed by a physical vapor deposition process, but not limited thereto. The cap layer  420  and the passivation layer  430  are self-aligned with the light filter layer  310  for forming a nanocavity  400  because the top surface  310   a  of the light filter layer  310  is lower than the top surface of the dielectric layer  208  by a predetermined depth for forming the recess part. 
     Additionally, according to the embodiment of the present invention, the metal layer  214 , the metal layer  216 , the metal layer  218 , the metal connection  217 , and a metal connection  219  may encompass the surroundings of the nanocavity  400  for reflecting the specific wavelength fluorescence generated by the biochemical reactions to the light-sensing region  104  and avoiding the interference of the light generated by the adjacent nanocavity  400 . 
     Please refer to  FIGS. 8-12 .  FIGS. 8-12  are schematic drawings illustrating a fabrication method of the bio-sensor with the self-aligned nanocavity in  FIG. 7 . As shown in  FIG. 8 , a substrate  100  is also provided first. A plurality of pixel regions  10  arranged in an array configuration is formed in the substrate  100 . For describing conveniently, there are only two pixel regions of the pixel array shown in the figures. According to the embodiment the present invention, the substrate  100  may be a silicon substrate, but not limited thereto. A plurality of isolation structures  112  is disposed on the substrate  100 , and a plurality of the pixel regions  10  is defined by the isolation structures  112 . 
     A gate structure  160  may be formed on the substrate  100  of each pixel region. A light-sensing region  104  and a floating drain region  106  are then formed in the substrate  100  at two sides of the gate structure  160 . The gate structure  160  may include a dielectric layer and a conductive layer. The dielectric layer may be silicon oxide, and the conductive layer may be single-crystal silicon, undoped polycrystalline silicon, doped polycrystalline silicon, amorphous silicon, metal silicide, or the combination of the materials mentioned above. A sidewall spacer may be formed on the sidewall of the gate structure  160 , and the sidewall spacer may be silicon oxide, silicon nitride, or the combination of silicon oxide and silicon nitride. 
     The light-sensing region  104  may be a photodiode including a first conductivity type doped region  142  and a second conductivity type doped region  144 . The first conductivity type is an opposite conductivity type of the second conductivity type. For example, when the substrate is a P type substrate, the first conductivity type doped region  142  may be an N type doped region, the second conductivity type doped region  144  may be a P type doped region, the floating drain region  106  may be an N type doped region, and vice versa. For instance, the first conductivity type doped region  142  may be a lightly doped region, and the second conductivity type doped region  144  and the floating drain region  106  may be heavily doped regions. 
     As shown in  FIG. 9 , multiple dielectric layers including a dielectric layer  202 , a dielectric layer  204 , a dielectric layer  206 , and a dielectric layer  208 , a metal layer  212 , a metal layer  214 , a metal layer  216 , a metal layer  218 , a metal connection  217 , and a metal connection  219  are deposited on the substrate  100 . For example, the dielectric layer  202  and the dielectric layer  206  may include silicon dioxide, but not limited thereto. The dielectric layer  202  and the dielectric layer  206  may be composed of multiple dielectric layers. The dielectric layer  204  formed between the dielectric layer  202  and the dielectric layer  206  may include silicon nitride, but not limited thereto. According to the embodiment of the present invention, the dielectric layer  204  is used as a diffusion barrier layer. The dielectric layer  208  is used as a passivation layer or a protection layer, and the dielectric layer  208  may include silicon nitride, silicon oxynitride, and/or silicon oxide, but not limited thereto. According to the embodiment of the present invention, the metal layer  212  may be formed in the dielectric layer  202 . The metal layer  214 , the metal layer  216 , the metal layer  218 , the metal connection  217 , and the metal connection  219  may be formed in the dielectric layer  206  and the dielectric layer  208 . 
     As shown in  FIG. 10 , a photolithographic process and an etching process are then performed to form a trenched recess structure  200  in the dielectric layer  206  and the dielectric layer  208  above the light-sensing region  104  corresponding to each pixel region  10 . In the above-mentioned etching process for forming the trenched recess structure  200 , the dielectric layer  204  may be used as an etching stop layer. According to the embodiment of the present invention, a bottom part of the trenched recess structure  200  is a top surface of the dielectric layer  204 . In other words, a depth of the trenched recess structure  200  is substantially equal to a total thickness of the dielectric layer  206  and the dielectric layer  208 . A liner layer  220 , such as silicon nitride layer, is then deposited conformally on the bottom part and an inner wall of the trenched recess structure  200 , but not limited thereto. According to the embodiment of the present invention, the liner layer  220  may be further formed on a top surface of the dielectric layer  208  for forming a continuous liner layer. 
     As shown in  FIG. 11 , the trenched recess structure  200  may then be filled with at least one light filter layer  310 . According to the embodiment of the present invention, after the step of forming the light filter layer  310 , a solidification process may then be performed for solidifying the light filter layer  310 . According to the embodiment of the present invention, a polishing process may then be performed for removing the light filter layer  310  outside the trenched recess structure  200 . An etching back process is then performed to make the top surface  310   a  lower than the top surface of the dielectric layer  208  by a predetermined depth for forming a recess part at a top end of the trenched recess structure  200 . According to the embodiment of the present invention, the light filter layer  310  is capable of blocking light within a specific wavelength range and filtering out noise light, and light within another specific wavelength range may pass through the light filter layer  310  and irradiate the pixel region  10  below. 
     As shown in  FIG. 12 , subsequently, a cap layer  420  is formed conformally on the light filter layer  310  and the liner layer  220 , and the cap layer  420  may be a silicon nitride layer for example, but not limited thereto. According to the embodiment of the present invention, the cap layer  420  directly contacts the top surface of the light filter layer  310 , and the light filter layer  310  is capped with the cap layer  420 . A passivation layer  430  is then formed conformally on the cap layer  420 . The passivation layer  430  may be metal oxide, such as tantalum oxide, but not limited thereto. According to the embodiment of the present invention, the passivation layer  430  has to be transparent, acid resistant, and alkali-resistant. According to the embodiment of the present invention, the passivation layer  430  may be formed by a physical vapor deposition process, but not limited thereto. The cap layer  420  and the passivation layer  430  are self-aligned with the light filter layer  310  for forming a nanocavity  400  because of the recess part. 
     In the present invention, the integrated bio-sensor with the nanocavity is fabricated by the processes compatible with the manufacturing process of CMOS image sensor. The light filter layer  310  and the aligned nanocavity  300 / 400  may be directly formed above the light-sensing region  104  corresponding to each pixel region  10 . The integrated bio-sensor in the present invention has the structure for acid and alkali resisting and anti-corrosion, and the metal ions in the light filter layer  310  may be kept from diffusing outward. The volume of each nanocavity  300 / 400  may be controlled precisely. Accordingly, the improved bio-sensor in the present invention has advantages such as fast, high accuracy, and high sensitivity, and the industrial utilization of the bio-sensor in the present invention is actually very high. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.