JP4103582B2 - Optical DNA sensor and DNA reader - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical DNA sensor used for specifying the structure of DNA by utilizing complementary interaction between DNA fragments, and also to a DNA reader using the DNA sensor.
[0002]
[Prior art]
In recent years, genetic information on living organisms has been used in a wide range of fields such as the medical field and the agricultural field. However, elucidation of the DNA structure is indispensable when using genes. DNA has two polynucleotide strands that are kinked and each polynucleotide strand is one-dimensionally composed of four bases (adenine: A, guanine: G, cytosine: C, thymine: T). The bases of one polynucleotide chain are bonded to the bases of the other polynucleotide chain based on the complementarity of adenine and thymine and guanine and cytosine.
[0003]
The elucidation of the structure of DNA is to specify a nucleotide sequence. In order to specify the nucleotide sequence of DNA, a DNA microarray and its reader have been developed. Conventionally, the nucleotide sequence of sample DNA is specified as follows using a DNA microarray and its reader.
[0004]
First, a DNA microarray is prepared in which a plurality of types of probe DNA fragments having known nucleotide sequences are aligned and fixed on a solid support such as a slide glass. Next, the sample DNA is denatured into single-stranded DNA fragments, and a fluorescent substance or the like is bound to the denatured sample DNA fragments.
[0005]
Next, when the sample DNA fragment is added onto the DNA microarray, the sample DNA fragment is immobilized on the DNA microarray by hybridization. That is, the base of the sample DNA fragment is hydrogen-bonded with the base of a complementary DNA fragment among a plurality of types of probe DNA fragments to form a double strand. On the other hand, sample DNA fragments do not bind to probe DNA fragments that do not have complementarity. Since the sample DNA fragment is marked with a fluorescent substance, the probe DNA fragment combined with the sample DNA emits fluorescence. For example, a sample DNA fragment having a nucleotide sequence of TCGGGAA binds only to a probe DNA fragment having a nucleotide sequence of AGCCCTT, and the probe DNA fragment emits fluorescence.
[0006]
Next, the DNA microarray is set in the reader and analyzed by the reader. The reader measures the fluorescence intensity distribution on the DNA microarray.
[0007]
There are roughly two types of reading devices, and there are a planar light method and a confocal laser method (for example, see Patent Document 1).
The planar light type reader irradiates the DNA microarray with excitation light (mainly ultraviolet light), images the DNA microarray onto the CCD image sensor with a lens, and receives the fluorescence emitted from the DNA microarray with the CCD image sensor. The fluorescence intensity distribution in the surface of the DNA microarray is measured by a CCD image sensor.
[0008]
The confocal laser reader uses a collimator lens to focus the excitation light emitted from the laser diode, scans the laser beam two-dimensionally with respect to the DNA microarray, and scans the microscope and photomaru along with the two-dimensional scan of the laser beam. The fluorescence emitted by the laser beam is received by a photomultiplier through a microscope, the fluorescence intensity is measured by the photomultiplier, and the fluorescence intensity distribution in the surface of the DNA microarray is measured by two-dimensional scanning.
[0009]
In any method, the fluorescence intensity distribution on the DNA microarray is output as a two-dimensional image. In the output image, the portion having a high fluorescence intensity indicates that a probe DNA fragment having a nucleotide sequence complementary to the nucleotide sequence of the sample DNA fragment is included. Therefore, the nucleotide sequence of the sample DNA fragment can be determined depending on which part of the two-dimensional image has a high fluorescence intensity.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-23900
[0011]
[Problems to be solved by the invention]
However, the confocal laser type reading device requires a microscope and a mechanism for scanning the laser beam and the microscope with respect to the DNA microarray, and there is a problem that the entire device is large. A planar optical reader requires a lens for imaging a DNA microarray on a CCD image sensor, and is similarly large.
[0012]
In order to suppress the increase in size of the reading apparatus, the present applicant has developed an optical DNA sensor, which is not a known invention in the literature, but has a plurality of types of probe DNA fragments arranged and fixed on the surface of a solid-state imaging device. ing. In order to specify DNA using this optical DNA sensor, a fluorescently labeled sample DNA fragment is hybridized with a complementary probe DNA fragment on a solid-state imaging device, and this optical DNA sensor is set in a reader. When the surface of the solid-state imaging device is irradiated with the excitation light from the light source of the reading device, the probe DNA fragment combined with the sample DNA fragment emits fluorescence, and the reading device displays an image of the fluorescence intensity distribution in which the portion is bright. Read with an imaging device. Since this optical DNA sensor has a probe DNA fragment immobilized on the surface of a solid-state imaging device, a two-dimensional image representing a fluorescence intensity distribution can be captured with a solid-state imaging device without a lens or a microscope. Thus, the reading apparatus can be reduced in size.
[0013]
However, this optical DNA sensor has the following problems. That is, since the solid-state imaging device is sensitive not only to fluorescence but also to excitation light, the portion of the probe DNA fragment that is not bound to the sample DNA fragment also becomes bright, and the contrast of the image obtained by the solid-state imaging device Is low. Therefore, it becomes difficult to specify which part of the image obtained by the solid-state imaging device has a high intensity.
[0014]
Accordingly, an object of the present invention is to be able to acquire an image with high contrast representing a fluorescence intensity distribution.
[0015]
[Means for Solving the Problems]
  In order to solve the above problems, the invention described in claim 1 is, for example, as shown in FIGS.
  In an optical DNA sensor used to identify a sample DNA fragment that emits fluorescence when irradiated with phosphor excitation light,
  A solid-state imaging device (eg, solid-state imaging device 2);
  Surface of the solid-state imaging device~ sideA titanium oxide layer (for example, a titanium oxide layer 34) formed on
  A protective insulating layer interposed between the solid-state imaging device and the titanium oxide layer;
  A conductive layer for discharging charges generated in the titanium oxide layer by irradiation with phosphor excitation light;
  A plurality of kinds of probe DNA fragments (for example, spots 60, 60,...) Having a known base sequence and arranged and fixed on the titanium oxide layer.
[0016]
According to the first aspect of the present invention, the titanium oxide layer formed on the surface of the solid-state imaging device has a property of shielding the phosphor excitation light and transmitting the fluorescence. When multiple types of probe DNA fragments are irradiated with phosphor excitation light, fluorescence is emitted from the probe DNA fragments bound to the sample DNA fragments, but the fluorescence passes through the titanium oxide layer and enters the surface of the solid-state imaging device. To do. On the other hand, the phosphor excitation light is shielded by the titanium oxide layer and does not enter the surface of the solid-state imaging device. Therefore, the brightness difference between the portion of the probe DNA fragment bound to the sample DNA fragment and the portion of the probe DNA fragment not bound to the sample DNA fragment becomes clear, and a high-contrast image is obtained with a solid-state imaging device. can do. Therefore, it is possible to easily specify which part of the image obtained by the solid-state imaging device has high intensity, and to easily specify the base sequence of the sample DNA fragment.
[0021]
  Claim2In the optical DNA sensor according to any one of claims 1 to 3, for example, as shown in FIGS.
  The solid-state imaging device includes a plurality of photoelectric conversion elements (for example, DG-Tr20, 20,...) Arranged so as to correspond to the plurality of types of probe DNA fragments, respectively.
[0022]
  Claim2In the invention described in (2), since the probe DNA fragments are arranged corresponding to the photoelectric conversion elements, the fluorescence intensity is not detected between the probe DNA fragments. Therefore, the image picked up by the solid-state image pickup device is an image having no noise, and does not include the fluorescence intensity data of the portion where the probe DNA fragment is not arranged.
[0023]
  Claim3The invention according to claim 1, for example, as shown in FIGS. 5 to 6, makes the optical DNA sensor according to any one of claims 1 to 4 detachable,
  Driving means (for example, driving circuit 10, top gate driver 11, bottom gate driver 12, drain driver 13 and driving circuit 10) for driving the mounted solid-state imaging device, and a surface facing the plurality of types of probe DNA fragments Light irradiation means (for example, light irradiation means 71) for irradiating phosphor excitation light in a shape
  A DNA reader characterized by the above.
[0024]
  Claim3In the invention described in the above, when the probe DNA fragment is irradiated with the phosphor excitation light by the light irradiation means, fluorescence is emitted from the probe DNA fragment combined with the sample DNA fragment, and when the solid-state imaging device is driven by the driving means, the solid-state imaging device An image representing the fluorescence intensity distribution can be acquired.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.
[0031]
[First embodiment]
FIG. 1 is a perspective view showing an optical DNA sensor to which the present invention is applied, FIG. 2 is a plan view of this optical DNA sensor, and FIG. 3 is a sectional view taken along line II in FIG. It is sectional drawing fractured | ruptured and seeing in the arrow direction.
[0032]
The optical DNA sensor 1 includes a solid-state imaging device 2, a titanium oxide layer 34 formed on the surface of the solid-state imaging device 2, and spots 60, 60,... Arranged and fixed on the titanium oxide layer 34. , And one spot 60 corresponds to each pixel of the solid-state imaging device 2.
[0033]
First, the solid-state imaging device 2 will be described. The solid-state imaging device 2 includes a substantially flat transparent substrate 17 and a plurality of double gate type field effects arranged in a matrix of n rows and m columns (both n and m are integers) on the surface of the transparent substrate 17. Transistors (hereinafter referred to as DG-Tr) 20, 20,.
[0034]
The transparent substrate 17 has transparency (hereinafter simply referred to as translucency) to light having a wavelength range of 350 nm to 1000 nm ranging from ultraviolet to visible light, and has an insulating property, and is a glass substrate such as quartz glass or polycarbonate. It is a plastic substrate such as. The back surface of the transparent substrate 17 forms the back surface of the solid-state imaging device 2. Instead of the transparent substrate 17 having translucency, a substrate having light shielding properties may be used.
[0035]
The DG-Tr20 will be described. FIG. 4A is a plan view showing one DG-Tr 20, and FIG. 4B is a cross-sectional view taken along the II-II break line of FIG. It is.
Each DG-Tr 20 is a photoelectric conversion element serving as a pixel. Each DG-Tr 20 includes a bottom gate electrode 21 formed on the transparent substrate 17, a bottom gate insulating film 22 formed on the bottom gate electrode 21, and a bottom gate insulating film 22 between the bottom gate electrodes 21. A semiconductor film 23 opposite to the bottom gate electrode 21, a channel protective film 24 formed on the central portion of the semiconductor film 23, and an impurity semiconductor film formed on both ends of the semiconductor film 23 so as to be separated from each other 25, 26, a source electrode 27 formed on the impurity semiconductor film 25, a drain electrode 28 formed on the impurity semiconductor film 26, and a top gate insulating film 29 formed on the source electrode 27 and the drain electrode 28. And the top gate insulating film 29 and the channel protective film 24 between the semiconductor film 23 and the top gate It includes an electrode 30, a.
[0036]
On the transparent substrate 17, the bottom gate electrode 21 is formed for each DG-Tr20. In addition, n bottom gate lines 41, 41,... Extending in the horizontal direction are formed on the transparent substrate 17, and the bottom gate electrodes 21 of the DG-Tr 20 in the same row arranged in the horizontal direction are It is formed integrally with the common bottom gate line 41. The bottom gate electrode 21 and the bottom gate line 41 have conductivity and light shielding properties, and are made of, for example, chromium, a chromium alloy, aluminum, an aluminum alloy, or an alloy thereof.
[0037]
On the bottom gate electrode 21 and the bottom gate line 41, a bottom gate insulating film 22 common to all the DG-Trs 20, 20,... Is formed. The bottom gate insulating film 22 has insulating properties and translucency, for example, silicon nitride (SiN) or silicon oxide (SiO 2).₂).
[0038]
On the bottom gate insulating film 22, a semiconductor film 23 is formed for each DG-Tr 20. The semiconductor film 23 has a substantially rectangular shape in plan view, and is a layer formed of amorphous silicon or polysilicon. A channel protective film 24 is formed on the semiconductor film 23. The channel protective film 24 has a function of protecting the interface of the semiconductor film 23 from an etchant used for patterning, has insulating properties and translucency, and is made of, for example, silicon nitride or silicon oxide. The semiconductor film 23 is sensitive to light. When light enters the semiconductor film 23, an amount of electron-hole pairs according to the amount of incident light is centered around the interface between the channel protective film 24 and the semiconductor film 23. It is supposed to occur. In this case, holes are generated as carriers on the semiconductor film 23 side, and electrons are generated on the channel protective film 24 side. Here, the wavelength dependence of the photosensitivity of 50 nm thick amorphous silicon applicable to the semiconductor film 23 is shown in FIG. It has the sensitivity to generate electron-hole pairs in a wide wavelength range from ultraviolet to visible light, and has a sensitivity peak in visible light near 450 nm.
[0039]
An impurity semiconductor film 25 is formed on one end portion of the semiconductor film 23 so as to partially overlap the channel protective film 24, and an impurity semiconductor film 26 is partially channeled on the other end portion of the semiconductor film 23. It is formed so as to overlap the protective film 24. The impurity semiconductor films 25 and 26 are patterned for each DG-Tr 20. The impurity semiconductor films 25 and 26 are made of amorphous silicon containing n-type impurity ions (n⁺Silicon).
[0040]
A source electrode 27 patterned for each DG-Tr 20 is formed on the impurity semiconductor film 25. A drain electrode 28 patterned for each DG-Tr 20 is formed on the impurity semiconductor film 26. In addition, m source lines 42, 42,... And drain lines 43, 43,... Extending in the vertical direction are formed on the bottom gate insulating film 22, and each DG in the same column arranged in the vertical direction. The source electrode 27 of the −Tr 20 is formed integrally with the common source line 42, and the drain electrode 28 of each DG-Tr 20 in the same column arranged in the vertical direction is formed integrally with the common drain line 43. . The source electrode 27, the drain electrode 28, the source line 42, and the drain line 43 have conductivity and light shielding properties, and are made of, for example, chromium, a chromium alloy, aluminum, an aluminum alloy, or an alloy thereof.
[0041]
All of the DG-Trs 20, 20,... Are disposed on the channel protective film 24, the source electrode 27 and the drain electrode 28, and the source lines 42, 42,. ..., a common top gate insulating film 29 is formed. The top gate insulating film 29 has insulating properties and translucency, and is made of, for example, silicon nitride or silicon oxide.
[0042]
A top gate electrode 30 patterned for each DG-Tr 20 is formed on the top gate insulating film 29. Further, n top gate lines 44 extending in the horizontal direction are formed on the top gate insulating film 29, and the top gate electrodes 30 of the DG-Trs 20 in the same row arranged in the horizontal direction are common. It is formed integrally with the top gate line 44. The top gate electrode 30 and the top gate line 44 have conductivity and translucency, for example, indium oxide, zinc oxide, tin oxide, or a mixture containing at least one of them (for example, tin-doped indium oxide ( ITO) and zinc-doped indium oxide). The DG-Tr 20 configured as described above is a photoelectric conversion element using the semiconductor film 23 as a light-receiving unit, and the solid-state imaging device 2 includes a plurality of DG-Trs 20, 20,. It is.
[0043]
On the surface of the solid-state imaging device 2, a protective insulating film 31, a titanium oxide layer 34, a conductive layer 32, and an overcoat layer 33 are laminated in this order. The protective insulating film 31 covers all the DG-Tr 20, 20,... Together, and the top gate electrode 30 and the top gate lines 44, 44,. Formed on top. The protective insulating layer 31 has insulating properties and translucency, and is made of silicon nitride or silicon oxide.
[0044]
On the protective insulating layer 31, a titanium oxide layer 34 is formed on one surface so as to cover all the DG-Trs 20, 20,. Titanium oxide contained in the titanium oxide layer 34 is classified into anatase type and rutile type, and both can be used in the present invention, but rutile type titanium oxide is preferable. Further, the crystal structure of rutile titanium oxide is a tetragonal crystal, and the arrangement of Ti is a body-centered cubic structure.
[0045]
The titanium oxide layer 34 absorbs phosphor excitation light (mainly ultraviolet light, particularly ultraviolet light in a band having a central wavelength of 308 nm) that excites a fluorescent material used in a DNA identification method described later, and the phosphor excitation light. Has a property of transmitting fluorescence (mainly visible light, particularly visible light in a band having a central wavelength of 520 nm) emitted from the fluorescent material excited by the liquid crystal.
The extinction coefficient k (> 0), which is an optical property parameter that characterizes absorption, has the relationship of the following formula (1) with the complex refractive index N.
N = n−ik (1)
In the formula (1), i is an imaginary unit. Here, n determines the phase velocity of the wave of light traveling in a predetermined direction, and the extinction coefficient k has a function of attenuating the amplitude of the wave along with the traveling direction of the wave. When the traveling direction of light is z and the intensity of the light is I, the relationship of the following formula (2) is established between the two.
I (z) = I (0) exp (−αz) (2)
Where α is the absorption coefficient,
α = 2ωk / c (3)
It can be expressed as. c is the speed of light in vacuum, and ω is the angular frequency of light.
The rutile-type crystal titanium oxide layer 34 is tetragonal and has a body-centered cubic structure due to the arrangement of titanium atoms. This crystal is a uniaxial crystal whose optical axis is on the C axis. Strictly speaking, the complex refractive index N differs depending on the angle formed by the electric field vector of the incident light and the C axis, but on average, quenching of ultraviolet rays of about 300 nm is performed. The coefficient k is 2, the extinction coefficient k is 0.06 for visible light of about 440 nm, and k = 0 at 460 nm.
FIG. 5B is a logarithmic graph showing the relationship between the thickness of the titanium oxide layer 34 and the transmittance of phosphor excitation light having a wavelength of 308 nm and fluorescence having a wavelength of 530 nm. As shown in FIG. 5B, as the thickness of the titanium oxide layer 34 increases, the transmittance of the phosphor excitation light decreases, and if the thickness of the titanium oxide layer 34 is 100 nm or more, the phosphor excitation occurs. The light transmittance is 1.0 × 10^-3It becomes as follows. On the other hand, the fluorescence transmittance is not as low as that of the phosphor excitation light, and is 50% or more regardless of the thickness of the titanium oxide layer 34.
[0046]
As shown in FIGS. 3 to 4, a conductive film 32 is formed on the entire surface of the titanium oxide layer 34. The conductive film 32 has conductivity and translucency, and is formed of, for example, indium oxide, zinc oxide, tin oxide, or a mixture containing at least one of these. The titanium oxide layer 34 generates electron-hole pairs by absorbing the phosphor excitation light, and some of them continue to not recombine, but the conductive layer 32 is in contact with the titanium oxide layer 34. Electric charges due to electron-hole pairs are discharged by the conductive layer 32. For this reason, since electrons and holes do not continue to be accumulated in the titanium oxide layer 34 and the protective insulating layer 31 therebelow, there is little effect on the electric field formed by the voltage applied to the top gate electrode 30. .
[0047]
An overcoat layer 33 is formed over the conductive film 32. This overcoat layer 33 has translucency, protects the conductive film 32, and fixes the spots 60, 60,... To the surface of the solid-state imaging device 2.
[0048]
Next, the spot 60 will be described. As shown in FIGS. 1 to 3, a plurality of types of spots 60, 60,... Are spaced apart from each other and arranged on the overcoat layer 33 in a matrix of n rows and m columns. One spot 60 is a cluster in which a large number of single-stranded probe DNA fragments 61 are gathered, and a large number of single-stranded probe DNA fragments 61 included in one spot 60 have the same nucleotide sequence. Further, the nucleotide sequence of the single-stranded probe DNA fragment 61 is different for each spot 60. The nucleotide sequence of any spot 60 has a known base sequence.
[0049]
The spots 60, 60,... Are arranged in correspondence with the DG-Trs 20, 20,. That is, when the solid-state imaging device 2 is viewed in plan as mainly shown in FIGS. 2 and 4, one spot 60 overlaps one DG-Tr 20, and in particular, the semiconductor film 23 of the DG-Tr 20 is one spot. It overlaps with 60.
[0050]
As a method of fixing the spots 60, 60,... To the surface of the solid-state imaging device 2, a solid-state imaging device in which a probe DNA fragment 61 prepared in advance is surface-treated with a polycation (poly-L-lysine, polyethyleneimine, etc.). A method is used in which the liquid is spotted on the surface of 2 using a dispensing device and electrostatically bonded to the surface of the solid-state imaging device 2 using the charge of DNA.
As another fixing method, a method using a silane coupling agent having an amino group, an aldehyde group, an epoxy group or the like is also used. In this case, since an amino group, an aldehyde group, and the like are introduced to the surface of the solid-state imaging device 2 by a covalent bond, they are stably present on the surface of the solid-state imaging device 2 as compared with the case of using a polycation.
As another immobilization method, there is a method in which an oligonucleotide having a reactive group introduced therein is synthesized, the oligonucleotide is spotted on the surface of the surface-treated solid-state imaging device 2 and covalently bonded.
[0051]
Next, a DNA reader using the optical DNA sensor 1 configured as described above will be described with reference to FIGS.
[0052]
As shown in FIGS. 6 and 7, the DNA reading device 70 irradiates the surface of the display device 3, the arithmetic processing device 4 that controls the whole, and the surface of the optical DNA sensor 1 with phosphor excitation light. Light irradiating means 71 for driving, and driving means for driving the optical DNA sensor 1 to acquire an image (comprising a top gate driver 11, a bottom gate driver 12, a drain driver 13 and a driving circuit 10). .
[0053]
The light irradiation means 71 includes a light source 72 that emits light that includes the wavelength range of the phosphor excitation light and does not include much of the fluorescence wavelength range, and guides the light emitted from the light source 72 and emits it in a planar shape from the back surface 73a. A light guide plate 73. The light guide plate 73 has a substantially flat plate shape and is covered with a reflective member except for the side surface 73b and the back surface 73a facing the light source 72. The optical DNA sensor 1 is detachable from the DNA reader 70, and the surface of the solid-state imaging device 2 of the optical DNA sensor 1 mounted on the DNA reader 70 faces the back surface 73 a of the light guide plate 73. It is like that. When the optical DNA sensor 1 faces the back surface 73 a of the light guide plate 73, the light emitted in a planar shape from the back surface 73 a of the light guide plate 73 is uniformly irradiated on the surface of the optical DNA sensor 1.
[0054]
When the optical DNA sensor 1 is mounted on the DNA reader 70, the top gate lines 44, 44,... Of the optical DNA sensor 1 are connected to the terminals of the top gate driver 11, respectively. Similarly, the bottom gate lines 41, 41,... Of the optical DNA sensor 1 are connected to the terminals of the bottom gate driver 12, and the drain lines 43, 43,. 13 terminals are connected to each other. When the optical DNA sensor 1 is mounted on the DNA reader 70, the source lines 42, 42,... Of the optical DNA sensor 1 are connected to a constant voltage source, and are grounded in this example. .
[0055]
The top gate driver 11 is a shift register. In other words, the top gate driver 11 receives the control signal Tcnt from the drive circuit 10 and, in this order, from the top gate line 44 of the first row to the top gate line 44 of the nth row (if the nth row is reached, as necessary. The reset pulse (shown in FIG. 8) is output. The level of the reset pulse is a high level of +5 [V]. On the other hand, the top gate driver 11 applies a low level potential of −20 [V] to each top gate line 44 when no reset pulse is output.
[0056]
The bottom gate driver 12 is a shift register. That is, the read pulse (shown in FIG. 8) is output in the order from the bottom gate line 41 of the first row to the bottom gate line 41 of the nth row (when reaching the nth row, the first row is returned to the first row as necessary). It has become. The level of the read pulse is a high level of +10 [V], and the level when the read pulse is not output is a low level of ± 0 [V].
[0057]
After the top gate driver 11 outputs a reset pulse to the top gate line 44 in the i-th row (i is an integer from 1 to n), the bottom gate driver 12 passes through the carrier accumulation period and then the bottom gate driver 12 enters the i-th bottom gate line. The top gate driver 11 and the bottom gate driver 12 shift the output signal so that a read pulse is output to 41. That is, in each row, the timing at which the read pulse is output is delayed from the timing at which the reset pulse is output. Also, after the reset pulse is input to the top gate line 44 of the i-th row (i is any one of 1 to n), the read pulse is input to the i-th bottom gate line 41. The period until ending is the selection period of the i-th row. The level of the reset pulse is a high level of +5 [V], and the level when the reset pulse is not output is a low level of −20 [V].
[0058]
The drain driver 13 applies precharge pulses (shown in FIG. 8) to all the drain lines 43, 43,... Between the reset pulse output and the read pulse output in the selection period of each row. Is output. The level of the precharge pulse is a high level of +10 [V], and the level when the precharge pulse is not output is a low level of ± 0 [V]. The drain driver 13 amplifies the voltages of the drain lines 43, 43,... After outputting the precharge pulse, and outputs the amplified voltages to the drive circuit 10.
[0059]
The drive circuit 10 is driven by the arithmetic processing unit 4 to output control signals Bcnt, Tcnt, Dcnt to the bottom gate driver 12, the top gate driver 11, and the drain driver 13, respectively, thereby causing the bottom gate driver 12, the top gate, and so on. The driver 11 and the drain driver 13 are configured to output pulses as appropriate. Further, the drive circuit 10 detects the voltage of the drain lines 43, 43,... After a predetermined time has elapsed after the read pulse is output, or the drain circuit 43, 43,. By detecting the time until the voltage reaches a predetermined threshold voltage, an image is acquired and the image is output to the arithmetic processing unit 4. The arithmetic processing device 4 displays an image input from the drive circuit 10 on the display device 3.
[0060]
Since the spots 60, 60,... Are arranged on the surface of the solid-state imaging device 2, it is possible to capture a clear image with the solid-state imaging device 2 without providing the DNA reader 70 with an optical system such as a lens / microscope. it can. Therefore, the DNA reader 70 can be reduced in size.
[0061]
Next, a method for manufacturing the optical DNA sensor 1 will be described.
First, after a conductor layer is formed on the transparent substrate 17 by PVD method or CVD method such as sputtering or vapor deposition, a mask process such as a photolithography method is performed, and a shape processing step that shapes the conductor layer by an etching method or the like is performed. By doing so, the bottom gate electrode 21 and the bottom gate lines 41, 41,... Of each DG-Tr 20 are patterned.
[0062]
Next, a bottom gate insulating film 22 made of silicon nitride or silicon oxide is formed over the transparent substrate 17, and a semiconductor layer to be the semiconductor film 23 is formed over the entire surface of the bottom gate insulating film 22, and the entire surface of the semiconductor layer is formed. An insulating layer made of silicon nitride or silicon oxide to be the channel protective film 24 is formed. Next, the insulating layer is masked and the insulating layer is shaped to pattern the channel protective film 24 for each DG-Tr 20, and thereafter an amorphous silicon layer containing an n-type impurity is formed. Then, by masking the amorphous silicon layer and processing the shape of the amorphous silicon layer, the impurity semiconductor films 25 and 26 are patterned for each DG-Tr 20 and the lower semiconductor film 23 is patterned for each DG-Tr 20.
[0063]
Next, the conductor layer is formed on the entire surface, the conductor layer is masked, and the conductor layer is shaped, thereby patterning the drain electrode 28 and the source electrode 27 for each DG-Tr 20 and the drain line 43. , 43,... And source lines 42, 42,.
[0064]
Next, a top gate insulating film 29 is formed on the entire surface of the bottom gate insulating film 22 on which the drain electrode 28 and the source electrode 27 are formed. Next, a transparent conductor layer such as ITO is formed on the entire surface of the top gate insulating film 29, the transparent conductor layer (ITO layer) is masked, and the shape of the transparent conductor layer is processed. The top gate electrode 30 is patterned for each Tr 20 and the top gate lines 44, 44,... Are integrally formed with the top gate electrode 30.
[0065]
Next, a protective insulating layer 31 is formed on the entire surface of the bottom gate insulating film 22 where the top gate electrode 30 and the top gate line 44 are formed. Next, a titanium oxide layer 34 is formed on the entire surface of the protective insulating layer 31. Next, a conductive film 32 is formed on the entire surface of the titanium oxide layer 34. Next, the conductive film 32 is subjected to chemical treatment, and an overcoat layer 33 made of, for example, polycation (poly-L-lysine, polyethyleneimine, etc.) or a silane coupling agent is formed on the conductive film 32.
[0066]
On the other hand, a plurality of DNA fragments 61 having known nucleotide sequences are generated (the nucleotide sequences of the various DNA fragments 61 are different from each other), and the various DNA fragments 61 are dispersed or dissolved in a solvent to obtain a plurality of types. Prepare a sample solution. The prepared plural kinds of sample solutions are respectively set to a plurality of pipettes of a dispensing device. Further, the solid-state imaging device 2 is set on the mounting table of the dispensing device. In this dispensing apparatus, a plurality of pipettes move in a horizontal plane on the mounting table, and further drop to drop the sample solution.
[0067]
Next, in a state where a positive voltage is applied to the conductive film 32, a plurality of types of sample solutions are spotted from the pipette onto the surface of the solid-state imaging device 2 (on the overcoat layer 33) using a dispensing device. At this time, one type of sample solution is spotted on one DG-Tr 20 so as to overlap in a plan view. The nucleotide chain composed of four types of bases, adenine, guanine, cytosine, and thymine, was negatively charged as a whole because the saccharide bonded to the base is linked to a phosphodiester bond, so that it was applied to the conductive film 32. Since the probe DNA fragment 61 is attracted by the electric field of positive voltage, the probe DNA fragment 61 is easily fixed to the overcoat layer 33.
Thus, the optical DNA sensor 1 is completed.
[0068]
A method for identifying DNA using the optical DNA sensor 1 and the DNA reader 70 will be described.
First, DNA is collected from a specimen, the collected DNA is denatured into a single-stranded DNA fragment, a fluorescent substance is bound to the DNA fragment, and the DNA fragment is labeled with the fluorescent substance. Examples of the fluorescent substance include CyDye Cy2 and Cy3 (manufactured by Amersham). The obtained DNA fragment is contained in the solution. Hereinafter, this DNA fragment is referred to as a sample DNA fragment. As the fluorescent substance, a substance that is excited by the wavelength of the phosphor excitation light emitted from the light irradiation means 71 of the DNA reader 70 is selected. The fluorescent material emits fluorescence when excited by phosphor excitation light, and the wavelength of the fluorescence is a wavelength that generates carriers in the semiconductor film 23 of the optical DNA sensor 1.
[0069]
Next, a solution containing the sample DNA fragment is applied to the surface of the optical DNA sensor 1. The sample DNA fragment binds to probe DNA fragment 61 having complementarity among spots 60, 60,... By hybridization, and does not bind to probe fragments not having complementarity. Of the sample DNA fragments applied to the optical DNA sensor 1, those not hybridized are washed away.
[0070]
Next, when the optical DNA sensor 1 is set in the DNA reader 70, the top gate lines 44, 44,... Are connected to the terminals of the top gate driver 11, respectively, and the bottom gate lines 41, 41,. The drain lines 43, 43,... Are connected to the terminals of the drain driver 13, respectively.
[0071]
Next, the light source 72 is turned on, and the phosphor excitation light is irradiated from the light guide plate 73 onto the surface of the optical DNA sensor 1 in a planar manner, whereby reading by the DNA reader 70 is started. Thus, the probe DNA fragment 61 of the spots 60, 60,... And the sample DNA fragment pair bound to the probe DNA fragment 61 emits fluorescence from the phosphor attached to the sample DNA fragment and does not bind to the sample DNA fragment. The probe DNA fragment 61 does not emit fluorescence. Fluorescence emitted from the spot 60 including the probe DNA fragment 61 bonded to the sample DNA fragment is emitted from the overcoat layer 33, the conductive layer 32, the titanium oxide layer 34, the protective insulating layer 31, the top gate electrode 30, the interlayer insulating film 20, and the channel. The light passes through the protective film 24 and enters the semiconductor film 23 of the DG-Tr 20 corresponding to the fluorescent spot 60. Here, a part of the phosphor excitation light is incident on the titanium oxide layer 34 without being converted into fluorescence, but is absorbed by the titanium oxide layer 34 and hardly reaches the semiconductor film 23. On the other hand, no fluorescence is incident on the semiconductor film 23 of the DG-Tr 20 corresponding to the spot 60 composed of the probe DNA fragment 61 not bonded to the sample DNA fragment. For this reason, the phosphor excitation light is incident on the titanium oxide layer 34, but is hardly absorbed by the titanium oxide layer 34 and therefore hardly reaches the semiconductor film 23. Therefore, it does not reach the semiconductor film 23 of any DG-Tr20. That is, when the phosphor excitation light emitted from the light source 72 is directly incident on the semiconductor film 23, the semiconductor film 23 is not excited, and an electron-hole pair with sufficient drain current is generated in the semiconductor film 23. It will never be done. Therefore, the semiconductor film 23 of DG-Tr20 corresponding to the spot 60 composed of the probe DNA fragment 61 not bonded to the sample DNA fragment is not exposed, and corresponds to the spot 60 including the probe DNA fragment 61 bonded to the sample DNA fragment. The semiconductor film 23 of DG-Tr20 is exposed to light.
[0072]
Then, the DNA reading device 70 drives the optical DNA sensor 1 so that the optical DNA sensor 1 detects the intensity of fluorescence or the amount of fluorescence with each DG-Tr 20, and the fluorescence on the optical DNA sensor 1. Is acquired as two-dimensional image data.
[0073]
The image acquisition operation of the DNA reader 70 is as follows.
That is, the drive circuit 10 outputs the control signal Tcnt to the top gate driver 11, and the top gate driver 11 is sequentially reset from the top gate line 44 in the first row to the top gate line 44 in the nth row as shown in FIG. Output a pulse. The drive circuit 10 outputs a control signal Bcnt to the bottom gate driver 12, and the bottom gate driver 12 sequentially outputs read pulses from the bottom gate line 41 in the first row to the bottom gate line 41 in the nth row. Further, the drive circuit 10 outputs a control signal Dcnt to the drain driver 13, and the drain driver 13 precharges between the reset period in which the reset pulse is output in each row and the period in which the read pulse is output in each row. Pulses are output to all drain lines 43, 43,.
[0074]
The operation of each DG-Tr 20 in the i-th row will be described in detail. As shown in FIG. 8, when the top gate driver 11 outputs a reset pulse to the i-th top gate line 44, the i-th top gate line 44 goes to a high level. While the i-th top gate line 44 is at a high level (this period is referred to as a reset period), in each DG-Tr 20 in the i-th row, accumulation is performed in the vicinity of the interface between the semiconductor film 23 and the channel protective film 24. The generated carriers (here, holes) are repelled and discharged by the voltage of the top gate electrode 30.
[0075]
Next, the top gate driver 11 ends outputting the reset pulse to the i-th top gate line 44. The fluorescence from the phosphor attached to the sample DNA fragment bonded to the probe DNA fragment 61 of the closest spot 60 is incident on the semiconductor film 23 of the DG-Tr 20, and the top gate line 44 in the i-th row. Until the read pulse is output to the i-th bottom gate line 41 (this period is referred to as a carrier accumulation period). Electron-hole pairs are generated in the semiconductor film 23, and the holes are accumulated near the interface between the semiconductor film 23 and the channel protective film 24 by the electric field of the top gate electrode 30.
[0076]
Next, during the carrier accumulation period, the drain driver 13 outputs a precharge pulse to all the drain lines 43, 43,. While the precharge pulse is output (referred to as a precharge period), in each DG-Tr20 in the i-th row, the potential applied to the top gate electrode 30 is −20 [V], and the bottom gate Since the potential applied to the electrode 21 is ± 0 [V], the potential between the gate and the source is low only with the charge of the holes accumulated near the interface between the semiconductor film 23 and the channel protective film 24. A channel is not formed in the film 23, and no current flows between the drain electrode 28 and the source electrode 27. Since no current flows between the drain electrode 28 and the source electrode 27 in the precharge period, the precharge pulse output to the drain lines 43, 43,... Charge is charged.
[0077]
Next, the drain driver 13 finishes outputting the precharge pulse, and the bottom gate driver 12 outputs a read pulse to the i-th bottom gate line 41. While the bottom gate driver 12 outputs a read pulse to the i-th bottom gate line 41 (this period is referred to as a read period), the bottom gate electrode 21 of each DG-Tr 20 in the i-th row is +10 [ Since the potential V] is applied, each DG-Tr 20 in the i-th row is turned on.
[0078]
In the read period, the carriers accumulated in the carrier accumulation period work so as to relax the voltage between the top gate electrode 30 and the bottom gate electrode 21, and thus the voltage between the bottom gate electrode 21 and the top gate electrode 30. As a result, a channel is formed in the semiconductor film 23, and a current flows from the drain electrode 28 to the source electrode 27. Therefore, in the read period, the voltages of the drain lines 43, 43,... Tend to gradually decrease with time due to the drain-source current.
[0079]
Here, as the amount of fluorescent light incident on the semiconductor film 23 increases in the carrier accumulation period, the number of accumulated carriers also increases, and as the number of accumulated carriers increases, it flows from the drain electrode 28 to the source electrode 27 in the lead period. The current level also increases. Therefore, the voltage change tendency of the drain lines 43, 43,... During the lead period is deeply related to the amount of fluorescence incident on the semiconductor film 23 during the carrier accumulation period. Then, the drive circuit 10 passes through the drain driver 13 between the read period of the i-th row and the next (i + 1) -th precharge period, and after a predetermined time has elapsed since the start of the read period. The voltage of the drain lines 43, 43,... Is detected. Thereby, it converts into the intensity | strength of fluorescence. The drive circuit 10 detects the time until the predetermined threshold voltage is reached via the drain driver 13 between the read period of the i-th row and the precharge period of the next (i + 1) -th row. Also good. Even in this case, it is converted into fluorescence intensity. Further, in FIG. 8, the rising timing of the reset pulse of the (i + 1) -th row of the top gate driver 11 is after the read pulse of the i-th row of the bottom gate driver 12 falls. The rising timing of the reset pulse of the (i + 1) -th row of the gate driver 11 is from immediately after the falling edge of the reset pulse of the i-th row of the top gate driver 11 to the falling edge of the read pulse of the i-th row of the bottom gate driver 12. It may be. However, the output of the precharge pulse output to the drain lines 43, 43,... For the DG-Tr 20 in the (i + 1) th row is after the falling edge of the read pulse in the i-th row of the bottom gate driver 12. Is set to
[0080]
The series of image reading operations described above is set as one cycle, and the same processing procedure is repeated for each DG-Tr 20 in all rows, whereby the fluorescence intensity distribution on the optical DNA sensor 1 is acquired as an image. Then, an image representing the fluorescence intensity distribution is output from the drive circuit 10 to the arithmetic processing unit 4. The arithmetic processing device 4 causes the display device 3 to display an image representing the fluorescence intensity distribution. The nucleotide sequence of the sample DNA fragment is specified according to which part of the displayed image has a high light intensity.
[0081]
As described above, in the present embodiment, the phosphor excitation light is absorbed and shielded by the titanium oxide layer 34 and is hardly incident on the semiconductor layer 23, but the fluorescence is incident on the semiconductor layer 23 without being shielded. Therefore, only the semiconductor film 23 of DG-Tr 20 corresponding to the spot 60 bonded to the sample DNA fragment is exposed. Accordingly, there is a difference between the light intensity detected by the DG-Tr20 corresponding to the spot 60 bound to the sample DNA fragment and the light intensity detected by the DG-Tr20 corresponding to the spot 60 not bound to the sample DNA fragment. growing. Therefore, the contrast of the image representing the fluorescence intensity distribution is improved, and the nucleotide sequence of the sample DNA fragment can be easily identified.
[0082]
In the above description, the titanium oxide layer 34 is stacked on the protective insulating layer 31. However, the titanium oxide layer 34 may be stacked between the top gate insulating film 29 and the top gate electrode 30. It may be laminated between the protective insulating layer 31 or may be laminated between the conductive layer 32 and the overcoat layer 33. That is, the titanium oxide layer may be laminated between any layers as long as it is on the surface of the solid-state imaging device 2 and between the semiconductor film 23 and the spot 60.
[0083]
Moreover, although the solid-state imaging device 2 using DG-Tr20,20, ... as a photoelectric conversion element was demonstrated to the example, you may use the solid-state imaging device using a photodiode as a photoelectric conversion element. Solid-state imaging devices using photodiodes include CCD image sensors and CMOS image sensors.
[0084]
In a CCD image sensor, photodiodes are arranged in a matrix on a substrate, and around each photodiode, a vertical CCD and a horizontal CCD for transferring an electrical signal photoelectrically converted by the photodiode. Is formed. Similarly to the solid-state imaging device 2, a protective insulating film is formed on one surface so as to cover a plurality of photodiodes, and a conductive film is formed on the protective insulating film over the entire surface. A plurality of types of spots are arranged on the conductive film through the overcoat film, but one spot overlaps one photodiode in plan view.
[0085]
In a CMOS image sensor, photodiodes are arranged in a matrix on a substrate, and a pixel circuit for amplifying an electrical signal photoelectrically converted by the photodiodes is provided around each photodiode. Yes. Similarly to the solid-state imaging device 2, a protective insulating film is formed on one surface so as to cover a plurality of photodiodes, and a conductive film is formed on the protective insulating film over the entire surface. A plurality of types of spots are arranged on the conductive film through the overcoat film, but one spot overlaps one photodiode in plan view.
[0086]
Whether it is a CCD image sensor or a CMOS image sensor, if a titanium oxide layer is laminated between the spot and the photodiode and the photodiode is covered with the titanium oxide layer, ultraviolet rays do not enter the photodiode. .
[0087]
Further, instead of the titanium oxide layer 34, a layer that shields phosphor excitation light and transmits fluorescence may be provided.
[0088]
[Second Embodiment]
Next, a second embodiment of the present invention will be described.
The difference from the optical DNA sensor 1 of the first embodiment resides in the conductive layer 32 or the top gate electrode 30 of the optical DNA sensor 1. In the second embodiment, the titanium oxide layer 34 may not be provided or may be provided in the optical DNA sensor of the second embodiment. The other components of the optical DNA sensor of the second embodiment are the same as the components of the optical DNA sensor 1 of the first embodiment, and the second embodiment has the same configuration with reference to FIGS. Different points will be described in detail by attaching the same reference numerals to the elements.
[0089]
That is, in the first embodiment, the titanium oxide layer 34 has the property of absorbing and shielding the phosphor excitation light and transmitting the fluorescence, but in the second embodiment, the conductive layer 32 and the top gate electrode 30 are used. At least one of them has the property of absorbing and shielding the phosphor excitation light and transmitting the fluorescence.
[0090]
More specifically, the conductive layer 32 and the top gate electrode 30 are formed of ITO as in the first embodiment. By controlling the film formation speed, the oxygen concentration in the atmosphere during film formation, and the like. , Carrier density 1.0 × 10²⁰[1 / cm^Three] It is as follows. That is, the carrier density of ITO is 1.0 × 10²⁰[1 / cm^ThreeBy adjusting the following, the threshold value that separates the wavelength of light absorbed by ITO and the wavelength of light that is not absorbed is shifted (Burstein-Moss shift) to absorb the phosphor excitation light and not the fluorescence. To do. This is because the band gap is changed by carriers generated by oxygen defects in ITO or doped tin occupying the bottom of the conduction band.
[0091]
FIG. 9 shows the relationship between the carrier density in ITO and the absorption wavelength edge. FIG. 9 shows that light having a shorter wavelength than the absorption wavelength end is absorbed by ITO, and it can be seen that the absorption wavelength end shifts to a longer wavelength as the carrier density of ITO decreases. In addition, the carrier density of ITO is 1.0 × 10²⁰[1 / cm^Three], The absorption wavelength end is low, and the phosphor excitation light is transmitted without being absorbed. However, the carrier density of ITO is 1.0 × 10²⁰[1 / cm^Three], The absorption wavelength end becomes 308 nm, ITO absorbs phosphor excitation light of 308 nm or less, and the carrier density is 1.0 × 10 6.¹⁹[1 / cm^Three], The absorption wavelength end is 325 nm. Absorbs phosphor excitation light of 325 nm or less and transmits fluorescence.
[0092]
As described above, the light absorption edge of at least one of the ITO of the conductive layer 32 and the top gate electrode 30 is shifted toward a larger energy as the carrier density is increased. Can absorb light. FIG. 5C shows the ITO carrier density of the conductive layer 32 or the top gate electrode 30 of the optical DNA sensor 1 in the structure of the first embodiment.¹⁹[1 / cm^ThreeAnd the optical constant N of ITO (308 nm) = 2.2−0.34i (where i is an imaginary unit), the thickness of the titanium oxide layer 34, the phosphor excitation light of 308 nm wavelength, and the wavelength of 530 nm The relationship with the transmittance | permeability of the fluorescence of is shown with a logarithmic graph. The carrier density of both the conductive layer 32 and the top gate electrode 30 is 1.0 × 10¹⁹[1 / cm^Three], The phosphor excitation light with a wavelength of 308 nm is further shielded by the conductive layer 32 or the top gate electrode 30. FIG.
[0093]
The manufacturing method of the optical DNA sensor of the second embodiment is almost the same as the manufacturing method of the optical DNA sensor 1 of the first embodiment. However, when the ITO layer and the conductive layer 32 of the top gate electrode 30 are formed. The carrier density is 1.0 × 10²⁰[1 / cm^ThreeThe film formation rate and the oxygen concentration in the atmosphere are adjusted so as to be as follows. When the film formation rate is constant, the oxygen partial pressure in the ITO film formation reactor is increased to increase the oxygen concentration, thereby reducing oxygen defects in the ITO and reducing the carrier density. In addition, when the oxygen partial pressure in the ITO film formation reactor, that is, the oxygen concentration in the reactor atmosphere is constant, oxygen defects in the ITO decrease and the carrier density decreases as the film formation rate decreases. It is desirable to slow down the ITO film formation rate in a state where the oxygen partial pressure is high.
[0094]
The optical DNA sensor of the second embodiment can also be used in the DNA reader 70 in the same manner as the optical DNA sensor 1 of the first embodiment, and the DNA identification method is the same as in the first embodiment.
[0095]
As described above, in the second embodiment, the phosphor excitation light is absorbed and shielded by the conductive layer 32 or the top gate electrode 30, but the fluorescence is incident on the semiconductor layer 23 without being shielded. Therefore, only the semiconductor film 23 of DG-Tr 20 corresponding to the spot 60 bonded to the sample DNA fragment is exposed. Therefore, the contrast of the image representing the fluorescence intensity distribution is improved, and the nucleotide sequence of the sample DNA fragment can be easily identified.
[0096]
Even in an optical DNA sensor using a CCD image sensor or a CMOS image sensor, the carrier density is 1.0 × 10.²⁰[1 / cm^ThreeThe following ITO layer may be laminated on the surface of the image sensor, and the ITO layer may be disposed between the spot and the photodiode.
[0097]
[Third embodiment]
Next, a third embodiment of the present invention will be described.
FIG. 10A is a plan view showing one pixel of the optical DNA sensor in the third embodiment, and FIG. 10B is an arrow broken along the line III-III in FIG. It is sectional drawing seen from the direction.
[0098]
In the optical DNA sensor 1 of the first embodiment, the titanium oxide layer 34 is laminated between the layers from the semiconductor film 23 to the spot 60, whereas in the optical DNA sensor of the third embodiment, A dielectric multilayer film 35 is laminated between the layers from the semiconductor film 23 to the spot 60.
[0099]
The dielectric multilayer film 35 is composed of a dielectric H layer having a high refractive index and a dielectric L layer having a lower refractive index than the dielectric H layer alternately with an optical film thickness that is ¼ of the center wavelength of the phosphor excitation light. It has a multilayered structure. The center wavelength of the phosphor excitation light is λ, and the refractive index of the dielectric H layer is n₁Then, the film thickness of the dielectric H layer is λ / 4n.₁And the refractive index of the dielectric L layer is n₂Then, the film thickness of the dielectric L layer is λ / 4n.₂It is. For example, high refractive index titanium oxide (TiO₂: Refractive index 2.2) as dielectric H layer, low refractive index silicon oxide (SiO₂: Refractive index 1.47) are alternately laminated as dielectric L layers, the dielectric multilayer film 35 is completed. Reflection due to the difference in refractive index occurs at the interface of each layer of the dielectric multilayer film 35, and the phosphor excitation light in the band including the center wavelength interferes with each other so that the phosphor excitation light is reflected with an extremely high reflectance. Become. On the other hand, the fluorescence passes through the dielectric multilayer film 35 without being reflected by the dielectric multilayer film 35.
The dielectric multilayer film 35 is not limited to two types of dielectric layers that are alternately stacked with an optical film thickness that is 1/4 of the center wavelength of the phosphor excitation light, but three or more types having different refractive indexes. The dielectric layer may be periodically laminated with an optical film thickness of ¼ of the center wavelength of the phosphor excitation light.
[0100]
In FIG. 10, the dielectric multilayer film 35 is laminated between the top gate electrode 35 and the protective insulating layer 32. However, the dielectric multilayer film 35 may be laminated between the protective insulating layer 31 and the conductive layer 32. It may be laminated between the layer 32 and the overcoat layer 33.
[0101]
The optical DNA sensor of the third embodiment can also be used in the DNA reader 70 in the same manner as the optical DNA sensor 1 of the first embodiment, and the DNA identification method is the same as in the first embodiment.
[0102]
As described above, in the third embodiment, the phosphor excitation light is reflected by the dielectric multilayer film 35, but the fluorescence is incident on the semiconductor layer 23 without being reflected. Therefore, only the semiconductor film 23 of DG-Tr 20 corresponding to the spot 60 bonded to the sample DNA fragment is exposed. Therefore, the contrast of the image representing the fluorescence intensity distribution is improved, and the nucleotide sequence of the sample DNA fragment can be easily identified.
[0103]
In an optical DNA sensor using a CCD image sensor or a CMOS image sensor, a dielectric multilayer film is laminated on the surface of the image sensor, and the dielectric multilayer film is disposed between the spot and the photodiode. good.
[0104]
[Fourth embodiment]
Next, a fourth embodiment of the present invention will be described.
In the first embodiment, the light irradiation means 71 of the DNA reader 70 irradiates the surface of the mounted optical DNA sensor 1 with the phosphor excitation light in a planar shape, whereas in the fourth embodiment, The light illuminating means of the DNA reader irradiates the surface of the optical DNA sensor 1 mounted in a planar manner with evanescent light from the near field as phosphor excitation light.
[0105]
FIG. 11 is a side view showing the DNA reader of the fourth embodiment. The light irradiation means of the DNA reader includes a light source (not shown) that emits ultraviolet light, and a waveguide body 171 that propagates the ultraviolet light emitted from the light source. Ultraviolet light emitted from the light source propagates through the waveguide body 171, enters the total reflection surface 171 a of the waveguide body 171 at an angle greater than the critical angle, and is totally reflected. As a result, evanescent light is emitted from the total reflection surface 171a toward the outside of the waveguide body 171.
[0106]
Also in the fourth embodiment, the optical DNA sensor 1 is detachable from the DNA reader, and the surface of the optical DNA sensor 1 attached to the DNA reader is the total reflection surface 171a of the waveguide body 171. The spots 60, 60,... Are close to the back surface 171 a of the waveguide body 171.
[0107]
Further, the DNA reading device of the fourth embodiment is similar to the DNA reading device 70 of the first embodiment in that the display device 3, the arithmetic processing device 4, the top gate driver 11, the bottom gate driver 12, and the drain driver. 13 and the drive circuit 10.
[0108]
The DNA identification method using the DNA reader of the fourth embodiment is complementary to the spots 60, 60,... Of the optical DNA sensor 1 in the same manner as in the first embodiment. After hybridization, the optical DNA sensor 1 is set in the DNA reader. Then, the spots 60, 60,... Are close to the total reflection surface 171 a of the waveguide body 171, and the light source is turned on, whereby evanescent light is converted from the total reflection surface 171 a to the spots 60, 60,. Irradiated. Of the spots 60, 60,..., Those that bind to the sample DNA fragment emit fluorescence, and those that do not bind to the sample DNA fragment do not emit fluorescence. Then, the DNA reader acquires the fluorescence intensity distribution on the optical DNA sensor 1 as a two-dimensional image by driving the optical DNA sensor 1 with the drivers 11, 12, 13 and the drive circuit 10. An image representing the fluorescence intensity distribution is displayed on the display device 3 by the arithmetic processing device 4. The nucleotide sequence of the sample DNA fragment is specified according to which part of the displayed image has a high light intensity.
[0109]
As described above, in the fourth embodiment, since the evanescent light hardly propagates through the medium, the evanescent light does not reach the semiconductor film 23 of the DG-Tr 20, 20,. Therefore, only the semiconductor film 23 of DG-Tr 20 corresponding to the spot 60 bonded to the sample DNA fragment is exposed, the contrast of the image representing the fluorescence intensity distribution is improved, and the nucleotide sequence of the sample DNA fragment can be easily specified. .
[0110]
The optical DNA sensors of the second embodiment and the third embodiment can also be used for the DNA reader of the fourth embodiment. In any case, it is not necessary to form the titanium oxide layer 34 on the optical DNA sensor, and the carrier density of the conductive layer 32 is 1.0 × 10 6.²⁰[1 / cm^ThreeThe following is not necessary, and the dielectric multilayer film 35 may not be laminated.
The light irradiation means for irradiating the evanescent light includes a light source that emits ultraviolet light as parallel light, and a waveguide plate that has a plate shape and propagates the parallel light emitted from the light source so as to be parallel to the surface. And may be provided. In this case, when the optical DNA sensor 1 is mounted on a DNA reader, the spots 60, 60,... When the parallel light propagates through the waveguide plate, evanescent light is emitted from the surface of the waveguide plate to the outside and is incident on the spots 60, 60,.
[0111]
[Fifth embodiment]
Next, a fifth embodiment of the present invention will be described.
In the first embodiment and the third embodiment, layers (a titanium oxide layer 34 and a dielectric multilayer film 35) for shielding phosphor excitation light are formed between the layers from the semiconductor film 23 to the spot 60. However, as shown in FIG. 12, the optical DNA sensor of the fifth embodiment is not formed with a layer for shielding the phosphor excitation light, and the conductive layer 32 is formed directly on the protective insulating layer 31. It is a membrane. Further, the conductive layer 32 is 1.0 × 10 10 unlike the second embodiment.²⁰[1 / cm^Three] So that the phosphor excitation light is not shielded. Other components of the optical DNA sensor of the fifth embodiment are the same as those of the optical DNA sensor 1 of the first embodiment.
[0112]
In the first embodiment, the light irradiation means 71 of the DNA reader 70 irradiates phosphor excitation light toward the surface of the solid-state imaging device 2, whereas in the fifth embodiment, the DNA reader The light irradiation means 271 irradiates the back surface of the mounted solid-state imaging device 2 with phosphor excitation light in a planar shape.
[0113]
The light irradiation means 271 of this DNA reader includes a light source 272 that emits phosphor excitation light, and a light guide plate 273 that guides the phosphor excitation light emitted from the light source 272 and emits it in a planar shape from the surface 273a. Prepare. The light guide plate 273 has a substantially flat plate shape and is covered with a reflecting member except for the side surface 272b and the surface 273a facing the light source 272.
[0114]
Also in the fifth embodiment, the optical DNA sensor 1 is detachable from the DNA reader, and when the optical DNA sensor 1 attached to the DNA reader is attached, the back surface of the solid-state imaging device 2 is It faces the surface 273a of the light guide plate 273. When the back surface of the solid-state imaging device 2 faces the front surface 273a of the light guide plate 273, the phosphor excitation light emitted in a planar shape from the front surface 273a of the light guide plate 273 is evenly irradiated to the back surface of the solid-state imaging device 2. ing.
[0115]
In this case, since the bottom gate electrode 21 of the DG-Tr 20, 20,... Has a light shielding property, the phosphor excitation light does not directly enter the semiconductor film 23. On the other hand, the phosphor excitation light is transmitted between the DG-Trs 20, 20,... And enters the spots 60, 60,. And the spot 60 couple | bonded with the sample DNA fragment emits fluorescence by fluorescent substance excitation light, and fluorescence injects into the semiconductor film 23 of DG-Tr20 corresponding to the spot 60. FIG.
[0116]
As described above, in the fifth embodiment, the phosphor excitation light is shielded by the bottom gate electrode 21 of the DG-Tr 20, 20,..., But the fluorescence emitted from the spot 60 is incident on the semiconductor layer 23 without being reflected. To do. Therefore, only the semiconductor film 23 of DG-Tr 20 corresponding to the spot 60 bonded to the sample DNA fragment is exposed. Therefore, the contrast of the image representing the fluorescence intensity distribution is improved, and the nucleotide sequence of the sample DNA fragment can be easily identified.
[0117]
The present invention is not limited to the above-described embodiments, and various improvements and design changes may be made without departing from the spirit of the present invention.
For example, in the optical DNA sensor of each embodiment, one DG-Tr20 corresponds to one spot 60, but one spot 60 corresponds to two or more adjacent DG-Tr20. It may be fixed to the surface of the imaging device 2. However, every spot 60 in the surface has the same number of corresponding DG-Tr20, and the number of DG-Tr20 included in one set is A (A is 2 or more), and the number of sets is set. If B, the number of spots 60 is B, and the number represented by (A × B) is the number of DG-Tr 20 included in the solid-state imaging device 2.
[0118]
【The invention's effect】
According to the invention described in claims 1 to 8, the difference in brightness between the portion of the probe DNA fragment bound to the sample DNA fragment and the portion of the probe DNA fragment not bound to the sample DNA fragment becomes clear. A high-contrast image can be acquired with a solid-state imaging device. Therefore, it is possible to easily specify which part of the image obtained by the solid-state imaging device has high intensity, and to easily specify the base sequence of the sample DNA fragment.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an optical DNA sensor to which the present invention is applied.
FIG. 2 is a plan view showing the optical DNA sensor.
3 is a cross-sectional view taken along the line II cut in FIG.
FIG. 4 (a) is a plan view showing one pixel of a solid-state imaging device provided in the optical DNA sensor, and FIG. 4 (b) is a cross-sectional view taken along line II-II. FIG.
5A is a diagram showing the wavelength dependence of the photosensitivity of amorphous silicon, and FIG. 5B is a graph showing the thickness of a titanium oxide layer formed on the surface of the solid-state imaging device and the phosphor. It is the logarithm graph which showed the relationship with the transmittance | permeability of excitation light and fluorescence, (c) is the film thickness of the titanium oxide layer when further controlling the carrier density of ITO, and the transmittance | permeability of fluorescent substance excitation light and fluorescence It is the logarithmic graph which showed the relationship.
FIG. 6 is a diagram showing a circuit configuration of a DNA reader using the optical DNA sensor.
FIG. 7 is a view showing an embodiment in which the optical DNA sensor is set in the DNA reader.
FIG. 8 is a timing chart showing the transition of the level of an electric signal output by the driver of the solid-state imaging device.
FIG. 9 is a plan view showing the relationship between the carrier density of tin-doped indium oxide and the light absorption wavelength end.
10A is a plan view showing one pixel of a solid-state imaging device provided in an optical DNA sensor different from the optical DNA sensor in FIG. 1, and FIG. It is sectional drawing fractured | ruptured and shown by the -II breaking line.
11 is a view showing an embodiment in which an optical DNA sensor is set in a DNA reader different from the DNA reader of FIG.
12 is a view showing an embodiment in which an optical DNA sensor is set in a DNA reading device different from the DNA reading devices in FIGS. 7 and 11. FIG.
[Explanation of symbols]
1 Optical DNA sensor
2 Solid-state imaging device
10 Drive circuit (drive means)
11 Top gate driver (drive means)
12 Bottom gate driver (drive means)
13 Drain driver (driving means)
20 Double-gate field effect transistor (photoelectric conversion element)
21 Bottom gate electrode
23 Semiconductor film
30 Top gate electrode
31 Protective insulating film (protective layer)
32 conductive film (tin-doped indium oxide layer)
34 Titanium oxide layer
35 Dielectric multilayer
60 spots (probe DNA fragments)
70 DNA reader
71 Light irradiation means
171 Light irradiation means
271 Light irradiation means

Claims (3)

In an optical DNA sensor used to identify a sample DNA fragment that emits fluorescence when irradiated with phosphor excitation light,
A solid-state imaging device;
A titanium oxide layer formed on the surface side of the solid-state imaging device;
A protective insulating layer interposed between the solid-state imaging device and the titanium oxide layer;
A conductive layer for discharging charges generated in the titanium oxide layer by irradiation with phosphor excitation light;
An optical DNA sensor comprising: a plurality of types of probe DNA fragments having a known base sequence and arranged and fixed on the titanium oxide layer. The optical DNA sensor according to claim 1 , wherein the solid-state imaging device has a plurality of photoelectric conversion elements arranged so as to correspond to the plurality of types of probe DNA fragments, respectively. While making the optical DNA sensor according to claim 1 or 2 detachable,
A DNA reader comprising: drive means for driving the mounted solid-state imaging device; and light irradiation means for irradiating phosphor excitation light in a plane toward the plurality of types of probe DNA fragments.

Images