A kind of CMOS ISFET dual mode image chemical sensor chip for high-throughput gene sequencingTechnical field
The present invention relates to integrated circuit sensor chip, especially for the CMOSISFET of gene sequencingdouble modeimagechemical sensor chip.
Background technology
Traditional ion-sensitive field effect transistor (the ionsensitivefieldeffectivetransistor proposed by Bergveld etc., be called for short ISFET) be the metal oxide semiconductor field effect transistor (MOSFET) (MetalOxideSemiconductorFieldEffectTransistor not having polysilicon gate in essence, be called for short MOSFET)as Fig. 1 (a) shown in, its pH Cleaning Principle be based on ionogen directly on grid oxidation film ion sensitive membrane surface reaction and change the performance (P.Bergveld of transistor, " Developmentofanion-sensitivesolid-statedeviceforneurophy siologicalmeasurements; " IEEETrans.Biomed.Eng., vol.17, no.1, pp.70 – 71, Jan.1970).But, because incompatible with CMOS (ComplementaryMetalOxideSemiconductor, the complementary metal oxide semiconductor) semiconductor fabrication process of standard, traditional ISFET manufacturing cost is expensive.as Fig. 1 (b) shown in, Bausells is by being connected to top-level metallic and oxynitrides passivation layer (J.Bausellsetal. by polysilicon gate, " Ion-sensitivefieldeffecttransistorsfabricatedinacommerci alCMOStechnology; " Sens.ActuatorsBChem., vol.57, pp.56 – 62, Sep.1999), the performance (threshold voltage) of transistor is indirectly changed by the surperficial potential variation produced after the contacted with ions in oxynitrides passivation layer and solution to be measured.In the semiconductor fabrication process of standard, incorporate ISFET first, ISFET cost is reduced, can scale operation.
DNA sequencing has far-reaching influence on Life Science, such as individual genome research, health care, drug development etc.First-generation sequencing technologies in invention in 1975, have employed dideoxy chain termination and fluorescence detection by Sanger, but this optical detection method is not only expensive but also the test duration is long, is not suitable for the detection of the long gene order of the mankind.In order to realize the order-checking of more high-throughput and more low cost, in the past few decades, s-generation DNA sequencing (NGS) instrument based on semiconductor electronic Detection Techniques has had remarkable development, such as be called as the electronics order-checking machine of a human genome machine (PGM) by American I onTorrent company invention (J.M.Rothbergetal., " Anintegratedsemiconductordeviceenablingnon-opticalgenome sequencing, " Nature, vol.475, pp.348 – 352, Jul.2011), owing to adopting cheap semiconductor fabrication techniques, can greatly reduce order-checking cost.Because the base pairing generation pH value of DNA chain in DNA sequencing process changes, the sensor chip based on CMOSISFET of detectable ionic concn has been used in PGM.Its basic sequencing procedure is as follows, first, in order to prepare genome sample, DNA long-chain is cut into single-stranded template, after adhered to cultivate on microballoon, carry out polymerase chain reaction (PolymeraseChainReaction, PCR) increase, then by micro fluidic device microballoon injected and be distributed in the micropore on ISFET sensor array surface.Each micropore is exactly a sequencing reaction pond, comprise a single-stranded DNA templates to be measured and an archaeal dna polymerase, with ISET sensing pixels unit one_to_one corresponding bottom micropore, hole design that is high and aperture makes can only there is a microballoon in each micropore for order-checking.When checking order, the Nucleotide repeating injection four kinds of VITAMIN B4 (A), guanine (G), cytosine(Cyt) (C), thymus pyrimidine (T) different base in ISFET sensor array by permanent order by micro fluidic device matches.Once the base type of current injection and the base pairing of DNA chain to be measured, archaeal dna polymerase this nucleotide polymerization to extend DNA chain on, and discharge the hydrogen ion of a unit, thus the ionic concn of ISFET Pixel surface in current micropore is changed, reduce the pH value of solution, this chemical signal can be detected by ISFET sensing unit and be converted into corresponding electric signal and final digitizing reads.Therefore, the pH change recorded has been converted to the ATCG base sequence of corresponding DNA, completes order-checking.If the pH value change of DNA fragmentation on millions of microballon be accurately positioned can be detected by the ISFET sensor of a large array, namely realize a kind of high-throughout DNA sequencing method by non-optical mode.But facing challenges is the accuracy that will improve order-checking, need to eliminatemistakepH detected result and nonuniformity.
There is very large non-accuracy in the DNA sequencing based on ISFET.Byfig. 2described, first, because the microballon being attached with DNA profiling is rotated in the microwell array be dispersed randomly on ISFET sensor chip by whizzer, therefore microballon is unknown in the distribution of microwell array, so the pH value response recorded does not associate with the actual distribution physical address of microballon.If there is no microballon in micropore, but detect the interference responded from the pH of adjacent beads, can causefalsepH value report, result inmistakesequencing data.The second, in order to improve sequencing throughput, usually need the ISFET sensor chip of the larger pel array adopting more advanced CMOS technology node to manufacture.But, this also causes there is larger process mismatch in the parameter of transistor, (the B.E.Stineetal. such as such as oxide thickness, channel length and width, " Analysisanddecompositionofspatialvariationinintegratedci rcuitprocessesanddevices; " IEEETrans.Semicond.Manuf., vol.10, no.1, pp.24 – 41, Feb.1997).Therefore, the threshold voltage V between pixeltmismatch, or be fixed pattern noise (Fixedpatternnoise, be called for short FPN) also can increase (K.Yonemoto, andH.Sumi, " ACMOSimagesensorwithasimplefixed-pattern-noise-reduction technologyandaholeaccumulationdiode, " IEEEJ.Solid-StateCircuits, vol.35, no.12, pp.2038 – 2043, Dec.2000).Because ISFET sensor is detection threshold voltage Vtchange, this accuracy that pH value can be made to detect reduces greatly.
In order to solve first difficult problem, usually adopt microscope to observe the horizontal distribution of microballon, but this need heavy optical device and loaded down with trivial details calibration process.In addition, very little owing to being amplified to the field range after micron-sized spatial resolution, microscope needs to scan whole array by physical in-migration, and this process is very slow and may cause more detectionmistake.Notice that traditional opticmicroscope imaging system needs heavy camera lens to amplify as intermediary, this often limits size, weight and cost, causes obstruction to the miniaturization of system.The very promising solution of one adopts contact imaging, contact imaging is a kind of near field induction mode (H.Jietal. without the need to optical lens, " Contactimaging:simulationandexperiment; " IEEETrans.CircuitsSyst.I, Reg.Papers, vol.54, no.8, pp.1698 – 1710, Aug.2007).Therefore, compared with the spatial resolution based on lens imaging, contact imaging system has different geometrical constraints.In traditional optical imaging system, image resolution ratio determined by the number of the pixel in photo detection arrays, this is because camera lens projects on optic sensor array completely.Traditional imaging systems can improve optical resolution by the number increasing pixel.In contact imaging, when the image of object is directly projected on image sensor array, resolving power is mainly determined by the distance of Pixel Dimensions and object and pel array.Therefore, contact imaging is applicable to very much being applied in the biomedicine sensing of miniaturization, such as in DNA sequencing, microballon detects (A.Ozcan, andU.Demirci, " Ultrawide-fieldlens-freemonitoringofcellson-chip, " LabChip, vol.8, no.1, pp.98 – 106, Jan.2008).Therefore, if a kind of ISFET sensor of bimodulus can be utilized, hydrogen ion change in detection microbeads can obtain pH value, also by the position distribution of contact image checking microballon, occur when so ISFET sensor chip uses in the DNA sequencing of current PGMmistakepH test problems just can be resolved.
For second difficult problem, irradiate at process layer Useful UV line and remove the trapped charge accumulated on ISFET grid, but the external calibration source (M.J.Milgrew that this extra demand need converge for a long time, andD.R.S.Cumming, " MatchingthetransconductancecharacteristicsofCMOSISFETarr aysbyremovingtrappedcharge; " IEEETrans.ElectronDevices, vol.55, no.4, pp.1074 – 1079, Apr.2008).The technology of some other circuit layer is also suggested.P.Georgiou, andC.Toumazou, " CMOS-basedprogrammablegateISFET, " Electron.Lett., vol.44, no.22, pp.1289 – 1290, Oct, 2008 ISFET reporting a grid (PG) able to programme, by applying to floating gate capacitance coupling the working point that bias voltage sets ISFET, also offset the impact of trapped charge and charge shift, but this also requires other auxiliary circuit simultaneously.C.Z.D.Gohetal., " ACMOS-basedISFETchemicalimagerwithauto-calibrationcapabi lity; " IEEESensorsJ., vol.11, no.12, pp.3253 – 3260, Dec.2011 discloses to eliminate based on PG-ISFET back-end digital Automatic Calibration Technique and does not mate.The main restriction of aforesaid method is not suitable for the large Array Design towards high-throughout DNA sequencing.P.A.Hammondetal., " Designofasingle-chippHsensorusingaconventional0.6-μm of CMOSprocess; " IEEESensorsJ., vol.4, no.6, pp.706 – 712, Dec.2004 proposes the differential readout method based on reference electrode, the method does differential readout to reference field effect transistor (REFET) and ISFET, thus reduces noise.But because REFET and ISFET is not identity unit, noise may due to uncorrelated mutually and cannot cancel out each other.
Based on above Problems existing, we propose this invention, a kind of CMOSISFET of split hair caccuracy high-throughput gene sequencingdouble modeimagechemical sensor chip.
Summary of the invention
The object of the invention is to provide a kind of CMOSISFETdouble modeimagechemical sensor chip, this chip can carry out optical image acquisition and chemical pH value detects, and avoids the interference of adjacent beads pH value response in the order-checking of monotype ISFET chemical sensor array chip; Additionally provide a kind of parallel correlated-double-sampling (CDS) sensing circuit of high speed row being adapted to image and the double mode sensing of chemistry simultaneously, reduce threshold voltage V between pixel with thistdo not mate; Large Array sensor and signal read circuits are integrated on same chip, the signal of induction are rapidly converted into numerary signal and export; For gene sequencing, there is pinpoint accuracy and high-throughout advantage.
The present invention relates to a kind of CMOSISFET for high-throughput gene sequencingdouble modeimagechemical sensor chip, include the circuit such as double mode pel array, row decode/driver, row decode/driver, row parallel gain adjustable amplifier, row parallel single-slope analog to digital converter, static RAM, sense amplifier, Low Voltage Differential Signal reading module, static register, phaselocked loop, ramp generator and digital control current source.
Double mode pel array be expert at decode/driver effect under, the signal of sensor array is read out line by line row parallel gain adjustable amplifier and row parallel single-slope analog to digital converter; The signal of row parallel single-slope analog to digital converter, through the control of row decode/driver, divides into groups to read into static RAM and sense amplifier, reads module by data pio chip eventually through high velocity, low pressure differential signal.
Static register controls the working order of the change in gain of row parallel gain adjustable amplifier, row decode/driver and row decode/driver; Phaselocked loop provides stable counting clock signal to row parallel single-slope analog to digital converter; Ramp generator provides periodic ramp voltage signal to row parallel single-slope analog to digital converter; Digital control current source provides bias current to row parallel gain adjustable amplifier and row parallel single-slope analog to digital converter.
Each sensing pixels in described double mode pel array includes the pixel structure of the ISFET ion field effect transistor of image sensor pixel framework and standard CMOS process manufacture.
Photorectifier PD plus earth in image sensor pixel framework, negative pole is connected with the source electrode of transfer tube M6; Transfer tube M6 grid meets transmission of control signals TX, and transfer tube M6 drains and connects suspension spreading area FD; Suspension spreading area FD is connected with the source electrode of reset transistor M1, and the drain electrode of reset transistor M1 meets the voltage of supply VAAPIX of pel array, and the grid of reset transistor M1 controls by pixel reset signal RST; Suspension spreading area FD connects with the grid of source follower transistor M2, and the drain electrode of source follower transistor M2 meets the voltage of supply VAAPIX of pel array, and the source electrode of source follower transistor M2 selects the drain electrode of triode M3 to be connected with row; Row selects the grid of triode M3 to meet row selection signal ROW, and row selects the source electrode of triode M3 to meet pixel output node PIXOUT; Pixel output node PIXOUT is connected with cascade current source capsule M4, M5, the grid of cascade current source triode M4, M5 meets control signal VLN_CASC, VLN, in cascade current source, the source electrode of two triodes M4, M5 is connected with drain electrode, the source ground of a triode M5 in cascade current source.
Under optical mode:
Photorectifier PD collects photon and converts electronics in proportion, and electronics displacement under DC Electric Field forms photoelectric current; The inherent junction capacitance of photorectifier PD stores the electric charge produced, and after certain time shutter, the intensity of incident light is converted into corresponding charge value; Controlled by the transmission of control signals TX of transfer tube M6 grid, electric charge is transferred to the suspension spreading area FD be connected that to drain with transfer tube M6 and changes into voltage signal; The corresponding voltage signal of optical imagery reads pixel output node PIXOUT by follower triode M2 under being expert at and selecting the control of the grid row selection signal ROW of triode M3; Pixel output node PIXOUT is that multirow pixel shares output node, and row selects triode M3 to export for isolating different pixels; That selects the source electrode of triode M3 to be connected is cascade current source M4, M5 with row, grid suspension control signal VLN_CASC, VLN control of cascade current source triode M4, M5; Current source provides bias current to the pixel of these row, and this current source is that all row pixels of these row share; Therefore, represent that microballon shadow image is detected by contact imaging.
Under chemistry model:
Source follower transistor M2 grid is connected to top-level metallic and the silicon nitride passivation of standard semi-conductor processes, as the ion-sensitive film of ISFET ion field effect transistor by metal; Transmission of control signals TX as optical image signal is in off-state; Change due to hydrogen ion concentration can cause the threshold voltage V of source follower transistor M2tproportional change, magnitude of voltage corresponding is like this associated with pH value, is read by the source electrode of source follower transistor M2; Consider threshold voltage V in ISFETtchange, i.e. source follower SF triode M2, will in source follower output node PIXOUT place's appearance one counteracting, i.e. VpIXOUT=α (VfD– Vt), wherein α is the gain of source follower, VfDand VpIXOUTthe input and output voltage of source follower.
Compared with prior art, beneficial effect of the present invention is:
(1) present invention achieves the double mode CMOSISFET image chemical sensor of a large array.First, in standard C IS technique, incorporated the dual mode transducer pixel of ISFET and cmos image sensor pixel by one, the sensing that optics sensing also can carry out pH value can be carried out.Because microballon and the surface of sensor directly contact, the image of microballon distribution can not need lens just can detect based on contact image-forming principle.Therefore, an accurate pH-image correlation distribution can be generatedfigure, the micropore deleting sky with this occurs because of interferencemistakepH value.
(2) present invention also offers a high speed for image and pH value two patterns and arrange parallel correlated-double-sampling sensing circuit, reduce V between pixel with thistdo not mate, i.e. fixed pattern noise, fixed pattern noise reduces to 0.3% from 4%.
(3) present invention also offers the fast signal reading circuit that is applicable to large Array sensor, sensor and reading circuit are integrated on same chip, induced signal is directly changed into numerary signal and export, improve speed of response.
(4) dual mode transducer of the present invention adds the accuracy of the DNA sequencing based on ISFET, reduces costs, and improve accuracy, realize high-throughput, can reach the susceptibility of 26.2mV/pH, reading speed can reach 1200 frames (fps) per second.
Accompanying drawing explanation
fig. 1for traditional ion-sensitive field effect transistor section manufactured with standard CMOS processfigure.
fig. 2for existing for the ISFET sensor of DNA sequencing.
fig. 3for the circuit theory of double mode (Dual-mode) of the present invention pixel structurefigure.
fig. 4for high speed reading circuit embodiment of the present inventionfigure.
fig. 5for high speed read pixel sequential of the present inventionfigure.
fig. 6for the framework of chip of the present inventionfigure.
fig. 7for the section of bimodulus pixel of the present inventionfigure.
fig. 8for the dual mode image that the present invention records.
Embodiment
Below in conjunction withaccompanying drawingthe present invention is described in detail further.
fig. 3for the circuit theory of double mode (Dual-mode) of the present invention pixel structurefigure.Each bimodulus pixel structure contains a 4T-CIS image pixel framework to detect the shadow image of the microballon of contact imaging formation.Meanwhile, source follower SF can measure each microballon as ISFET ion field effect transistor the pH value that produces changes due to base reaction in sequencing procedure.
Under optical mode, photorectifier PD first collects incident photon and then they is converted to certain proportion electronics, and the drift of electronics forms photoelectric current again.Inherent junction capacitance due to photorectifier PD can store the electric charge produced, and after certain time shutter, the intensity of the incident light of the electric charge maintenance of some amount is converted into a magnitude of voltage.The plus earth of photorectifier PD, negative pole is connected with the source electrode of transfer tube M6.Controlled by the control signal TX of transfer tube M6 grid, electric charge can be transferred to the suspension spreading area FD be connected that to drain with transfer tube M6 and produce voltage signal.Suspension spreading area FD is connected with the source electrode of reset transistor M1, and the drain electrode of reset transistor M1 meets pixel power voltage VAAPIX.Therefore, represent that the voltage signal of microballon shadow image is detected by contact imaging.Then, the corresponding voltage signal of optical imagery is buffered by connecting with the grid of source follower transistor M2.The drain electrode of source follower transistor M2 meets the voltage of supply VAAPIX of pel array, and source electrode selects the drain electrode of triode M3 to be connected with row.Row selects the grid of triode M3 to control by row selection signal ROW.Optical voltage signal reads pixel output node PIXOUT by source electrode under being expert at and selecting the control of the grid row selection signal ROW of triode M3.Owing to there being large number of rows pixel to share same output node PIXOUT, row selects triode M3 to be used to isolate different pixel output, only has when this row is selected can read when reading.That select the source electrode of triode M3 to be connected is cascade current source M4, M5 with row, they provide bias current to the pixel of these row, the grid of cascade current source triode M4 and M5 is by VLN_CASC and VLN signal control, and the source electrode of M4 is connected with the drain electrode of M5, the source ground of M5.In order to better currents match, this current source is that all row share.
Under chemistry model, source follower transistor M2 grid is connected to top-level metallic and silicon nitride passivation always, as the ion-sensitive film of ISFET.Change due to hydrogen ion concentration can cause the threshold voltage V of source follower transistor M2tproportional change, magnitude of voltage corresponding is like this associated with pH value, is read by the source electrode of source follower transistor M2.Consider threshold voltage V in ISFETtchange, i.e. source follower SF triode M2, will in source follower output node PIXOUT place's appearance one counteracting, i.e. VpIXOUT=α (VfD– Vt), wherein α is the gain of source follower, VfDand VpIXOUTthe input and output voltage of source follower.What show in the figure 7 is the cross section of pixel domain, does not use any one photorectifier, contains hinged diode (p+-n+-p) reduce due to dark current produce surface imperfection noise.Pinned photodiode (p+-n+-p) depletion layer almost extend to the interface of silicon and silicon-dioxide, make interface be full of this interface of p-type layer perfection isolation of aperture, what allow loss become is very low.
fig. 4for high speed reading circuit embodiment of the present inventionfigure.
The pixel output PIXOUT of double mode pel array and column amplifier input capacitance CcOLIbottom crown be connected, column amplifier input capacitance CcOLItop crown, column amplifier feedback capacity CcOLFbottom crown, column amplifier feedback switch RSTcOLone end be connected with the input terminus of column amplifier, column amplifier feedback capacity CcOLFtop crown, column amplifier feedback switch RSTcOLthe other end, comparer input capacitance CcOMbottom crown be connected with the output terminal of column amplifier, the bias current of column amplifier is provided by digital control current source module; Comparer input capacitance CcOMtop crown, the drain electrode of comparer reset transistor be connected with an input terminus of comparer, another input terminus of comparer and the output terminal V of ramp generatorrAMPconnect, the reference voltage of comparer connects common mode voltage VcM, the output of comparer is connected with the source electrode of the input terminus of ripple counter, comparer reset transistor, and the grid of comparer reset transistor is by comparer reset clock RSTcOMcontrol; The control that ripple counter is subject to positive and negative counting clock UD, count resets clock RSTB, counting keeps the counting clock PLL of clock KEEP, phaselocked loop input, forward and the negative sense that can carry out seamless connection count, and realize the two sampling of digital correlation and read; The output of ripple counter is connected to the input of latch, the output of latch is connected with the input of static RAM, static RAM is subject to reading clock RD and the control writing clock WR, the output terminal of static RAM is connected with sense amplifier, data after final digitizing read the high speed readout of module through Low Voltage Differential Signal, realize the high-throughout double mode detection of high speed.
Under optical mode, the signal of pel array exposes parallel read-out line by line, and chip captures contact microspheres image; In the pixel reading stage that row selection signal ROW is high, first pixel is made to export reset level by the pixel reset signal RST of one section of high level; This level is through the amplification input comparator of column amplifier, and comparer is by comparer reset clock RSTcOMcontrol first remove imbalance; The digitizing of pixel reset signal can by calculating as ramp signal level VrAMPtime equal with pixel reset signal level, the number of the counting clock PLL that phaselocked loop inputs realizes, and this hour counter is the counting that declines; Afterwards, counter change counting direction can be made to carry out the digitizing of signal level by the control of positive and negative counting clock UD; By arranging the transmission of control signals TX of a section high, pixel output signal level can be made; Now, counter has been configured to the counting that rises, and therefore by the automatic impact deducting reset level from pixel signal level, obtains actual picture element signal and exports; After completing the conversion of row parallel A/D, digitized pixel data entered latch, static RAM, sense amplifier, read eventually through Low Voltage Differential Signal module at a high speed.
Under chemistry model, owing to not relating to the reading of LED P D signal, optical delivery control signal TX disconnects always; Before interpolation reaction soln, closed pixel reset signal RST, by the control same with under optical mode, can read pixel reset signal digitizing now, first by these data in sheet external memory; After loading bead solution, by changing the counting direction of counter, by the automatic impact deducting reset level from pixel signal level, obtaining actual picture element signal and exporting, keeping the counting that rises ever since; After completing the conversion of row parallel A/D, digitized pixel data entered latch, static RAM, sense amplifier, read eventually through Low Voltage Differential Signal module at a high speed, the reset level data that the result obtained deducts sheet external memory can obtain actual chemical signal data.
The pixel output node PIXOUT connecting column parallel gain adjustable amplifier of described double mode pel array, row parallel single-slope analog to digital converter, static RAM, sense amplifier, the high-speed low-noise correlated-double-sampling signal-obtaining under optical image acquisition and chemical ion measurement of concetration two kinds of patterns can be realized, and eventually pass through Low Voltage Differential Signal module high speed readout, realize high speed high throughput testing.
fig. 5for high speed read pixel sequential of the present inventionfigure,fig. 5 (a) for optical mode reads sequential at a high speedfigure,fig. 5 (b) for chemistry model reads sequential at a high speedfigure.
Under optical mode, chip captures contact microspheres image, captures the correlated-double-sampling clock control signal of contact microspheres imageas Fig. 5in (a) part shown in.At the pixel column fetch phase that row selection signal ROW is high, first pixel is made to export reset level by the pixel reset signal RST of one section of high level; This level is through the amplification input comparator of column amplifier, and comparer is by comparer reset clock RSTcOMcontrol first remove imbalance; The digitizing of pixel reset signal can by calculating as ramp signal level VrAMPtime equal with pixel reset signal level, the number of the counting clock PLL that phaselocked loop inputs realizes, and this hour counter is the counting that declines; Afterwards, counter change counting direction can be made to carry out the digitizing of signal level by the control of positive and negative counting clock UD; By arranging the transmission of control signals TX of a section high, pixel output signal level can be made; Now, counter has been configured to the counting that rises, and therefore by the automatic impact deducting reset level from pixel signal level, obtains actual picture element signal and exports; After completing the conversion of row parallel A/D, digitized pixel data entered latch, static RAM, sense amplifier, read eventually through Low Voltage Differential Signal module at a high speed.
Under chemistry model, owing to not relating to the reading of LED P D signal, optical delivery control signal TX disconnects always;as Fig. 5 (b) shown in, before interpolation reaction soln, closed pixel reset signal RST, by the control same with under optical mode, can read pixel reset signal digitizing now, first by these data in sheet external memory; After loading bead solution, by changing the counting direction of counter, by the automatic impact deducting reset level from pixel signal level, obtaining actual picture element signal and exporting, keeping the counting that rises ever since; After completing the conversion of row parallel A/D, digitized pixel data entered latch, static RAM, sense amplifier, read eventually through Low Voltage Differential Signal module at a high speed, the reset level data that the result obtained deducts sheet external memory can obtain actual chemical signal data.
fig. 6for CMOSISFET of the present inventiondouble modeimagechemical sensor chipframeworkfigure.The module that it comprises comprises double mode CMOSISFET array of sensing pixels, and under decode/driver of being expert at effect, the signal of sensor array is read out line by line row parallel gain adjustable amplifier and row parallel single-slope analog to digital converter; The signal of row parallel single-slope analog to digital converter module, through the control of row decode/driver, divides into groups to read into static RAM and sense amplifier, reads module by data pio chip eventually through high velocity, low pressure differential signal.
fig. 7for of the present invention be the section of bimodulus pixelfigure., when carrying out DNA sequencing detection, in micropore, a microballoon can only be there is at most in a corresponding micropore of double mode CMOSISFET sensing pixels.Whether the existence of microballoon is detected by sensing pixels optical mode.Microsphere surface has the DNA fragmentation of strand, the ATCG base that can flow into order is reacted, when the base in solution and the base pairing on DNA fragmentation, meeting release hydrogen ions, pH value in corresponding change micropore, is read by the perception of surface nitrogen SiClx passivation layer is also final by the CMOSISFET sensor pixel of below.
fig. 8for the dual mode image that the present invention records, the designed double mode sensor of CMOS of Experimental results show well to record the pH value distribution of high correlationfigurewith microballon optical profile image.
Although the present invention is suitable for different amendments and alternative form, exist by means of embodimentin accompanying drawingshow its details, and be described in detail.But, should be appreciated that invention is not limited to described specific embodiments by the present invention.On the contrary, the invention is intended to cover all modifications scheme, equivalent and the replacement scheme that fall in the scope of the invention.
By Chinataiwanthe CIS technique flow of IC manufacture limited-liability company (TSMC) 0.18um manufactures two CMOSISFET image chemical sensor chips of one piece of 64*64 array, also can adopt more advanced CMOS or CIS manufacture technics.The section of the bimodulus pixel of designfigurebe illustrated infig. 7in.Notice that the guard ring of N-type and P type is placed on around pel array, make the influence of noise from peripheral circuit minimum.Image sensor is directly combined (or directly contacting) with very little spacing with destination sample point, can to white light be cast through microballon formed shade detect and Direct Acquisition samplefigurepicture.By this method, actual in the microballon that the pH value of this locality and contact imaging obtain by each pixel in bimodulus is associated.ThusmistakepH value Report a Problem and be resolved.
In addition, in order to make in the array of the ISFET sensor of large array the unmatched nonuniformity of threshold voltage between pixel reduce to minimum, need configuration CDS sensing circuit further.The framework of sensorfigurexiefig. 6in, bimodulus CMOSISFET sensor contains the CIS-ISFET pel array of a 64*64.All pixels are read line by line.Row decoder and line driver process every a line sequentially, the parallel output of column decoder gated sweep 64 row pixel sequentially.CDS is implemented by row parallel A/D converter module.Static register can arrange the operating mode of sensor.Digital control current source provides the bias current that chip needs.The digital timing circuit outside chip is realized by FPGA, can the operating mode of Controlling System and all compositions of Circuit tuning.
After flow manufactures, chip encapsulates with the contact pin grid array (PGA) of 100 of 33.5mm*33.5mm pins.Because experimentation needs to carry out under aqueous environment, suitable hermetically sealed of sensor chip is very necessary for protection circuit.Therefore, we encapsulate whole chip with epoxy resin, only allow for the pixel array region detected unlimited.In addition, bonding wire and pad also cover with epoxy resin.In order to keep the aqueous samples at sensor chip top, the 3D meeting PGA encapsulation with prints plastic containers and is placed in Chip Packaging, and with the gap on epoxy resin filling four limit.Plastic containers are also designed to the reference electrode of fixing silver or silver chloride.By the socket of 100 pins, packaged chip is installed on a specially designed printed circuit board (PCB) (PCB).Then be connected to by PCB on Xilinx company Virtex-6XC6VLX240TFPGA development board, the exploitation version of this design provides power supply and digital sequential controller signal to sensor chip.Based under the graphic user interface of MATLAB, we can the chemical property of detection chip.Through experiment test, the good pH value distribution of designed CMOS double mode transducer flexfigurewith the dependency of microballon optical profile image, and reach the susceptibility of 26.2mV/pH, fixed pattern noise reduces to 0.3% from 4%, and the speed of sensing circuit can reach 1200 frames (fps) per second.