Microcrystalline silicon film detector preparation method and application thereof
Technical field
The present invention relates to microcrystalline silicon film detector preparation method and application thereof, specifically be meant microcrystalline silicon film is applied to the thin film detector in the X ray flat panel detector, utilize the higher carrier mobility of microcrystalline silicon film, improve aperture opening ratio and image taking speed.
Background technology
The X ray flat panel detector is applied to the X ray digital imaging system, and effect is to convert X ray into digital picture, and wherein the amorphous silicon flat panel detector is used widely owing to manufacturing process is ripe.The amorphous silicon flat panel detector is made up of scintillator, thin film detector, control circuit, and wherein thin film detector comprises thin-film transistor and photodiode.Amorphous silicon flat panel detector operation principle is; Scintillator converts X ray into visible light; Photodiode converts visible light into the signal of telecommunication, and thin-film transistor is connected and exports the signal of telecommunication of photodiode, the break-make of control circuit control TFT with photodiode.Thin-film transistor and photodiode are fabricated on the same glass substrate, and each photodiode constitutes a pixel with a thin-film transistor that is connected.Having only photodiode is effective sensitization area, so will reduce the thin-film transistor area occupied in order to improve image quality and dynamic range.But thin-film transistor will have enough mutual conductances to guarantee image taking speed, so under the prerequisite of given thin-film transistor carrier mobility, the area of thin-film transistor can't reduce arbitrarily as signaling switch.Except picture quality and dynamic range this index, flat panel detector is also toward more large scale development.When size increases,, must in each pixel, increase driving transistors (active pixel) for reducing noise jamming; To amplify photodiode output signals; And under existing amorphous silicon technology, increase the driving diode and can further reduce photodiode area, reduce the detector aperture opening ratio.
For solving the low excessively problem of amorphous silicon membrane carrier mobility, show that at LCD/OLED the situation of TFT has appearred making with low-temperature polysilicon film instead of amorphous silicon film in the field.The manufacture method of low-temperature polysilicon film is that deposition of amorphous silicon films on substrate carries out PRK to amorphous silicon membrane then and scalds fire in order to remove hairs to form polysilicon membrane.Because the polysilicon membrane carrier mobility is much larger than the amorphous silicon membrane carrier mobility; So the TFT area can significantly reduce; The area of each pixel can reduce thereupon, so the display screen that this mode is made can reach high resolution, and because drive circuit also is produced on the glass substrate with the form of thin-film transistor; Reduced discrete device, made display screen lighter.Low temperature polycrystalline silicon also has the application in detector field, like the patent CN102403329 of Shanghai Yi Rui photoelectron Science and Technology Ltd..But because PRK is scalded this height of pyrogene in order to remove hairs, low-temperature polysilicon film is mainly used in the small-medium size panel at present.
Microcrystalline silicon film has the carrier mobility between amorphous silicon membrane and polysilicon membrane; Manufacturing process is similar with amorphous silicon membrane and use identical manufacturing equipment; Therefore might under the prerequisite that does not increase cost, make thin film detector, to improve image taking speed and picture quality with the microcrystal silicon instead of amorphous silicon.
Summary of the invention
The shortcoming of prior art the object of the present invention is to provide a kind of preparation method and application thereof of microcrystalline silicon film detector in view of the above, to improve the image taking speed and the picture quality of X ray flat panel detector.
For realizing above-mentioned purpose and other relevant purposes, the present invention provides a kind of preparation method of microcrystalline silicon film detector, and the preparation method may further comprise the steps at least:
(1) glass substrate (10) is provided, on this glass substrate, deposits the first metal layer, this first metal layer of etching is to form TFT grid (11);
(2) deposition first insulating barrier (12);
(3) continue deposition intrinsic micro crystal silicon thin film (131) and n doped microcrystalline silicon thin film (132) successively, the said two-layer microcrystalline silicon film of etching is to form the TFT active area then;
(4) continue deposition second metal level, n doped microcrystalline silicon layer (132) to the intrinsic micro crystal silicon thin film (131) of this second metal level of etching and this second metal level below is gone up to form TFT source electrode (142) and TFT drain electrode (141);
(5) continue deposition second insulating barrier, this second insulating barrier of etching is to form second insulating barrier (15) that covers TFT then;
(6) continue to go up deposition n doped amorphous silicon film (164), intrinsic amorphous silicon film (163), p doped amorphous silicon film (162) and transparency conducting layer ito thin film (161) in TFT drain electrode (141) successively; The above-mentioned four-level membrane of etching is to form photodiode then;
(7) continue deposition the 3rd insulating barrier (17) to cover second insulating barrier (15) and above-mentioned photodiode;
(8) the 3rd insulating barrier (17) of the said photodiode of etching top forms the perforate that is positioned at transparency conducting layer ito thin film (161) top; Deposit the 3rd metal level then, etching the 3rd metal level is to form the electrode (18) that transparency conducting layer ito thin film (161) is drawn.
Preferably, said first, second with the 3rd insulating barrier be the SiNx film.
Preferably, said first, second with the 3rd metal level be the alloy (Mo/Al/Mo) of molybdenum/aluminium/molybdenum.
The present invention also provides a kind of microcrystalline silicon film panel detector structure, and this structure is arranged with matrix form by the active pixel that thin-film transistor and photodiode constitute; Said active pixel is made up of a thin-film transistor TFT and a photodiode; Said thin-film transistor TFT comprises the active area that is made up of intrinsic micro crystal silicon thin film (131) and n doped microcrystalline silicon thin film (132), be positioned at second insulating barrier (15), TFT drain electrode (141), the TFT source electrode (142) on this active area and be arranged at the grid (11) of said active area below; This grid (11) is connected in the control circuit that is used for control TFT TFT break-make; This source electrode (142) is connected in data acquisition unit; The signal of telecommunication that is used for output photodiode when the TFT conducting; Said photodiode comprises that the TFT as n utmost point electrode drains (141), is positioned at successively n doped amorphous silicon layer (164), intrinsic amorphous silicon layer (163) p doped amorphous silicon layer (162) on this n utmost point electrode and the transparent conductive film (161) that is used as p utmost point electrode; TFT drain electrode (141) is shared with photodiode n utmost point electrode; When the TFT conducting, accumulate in the charge transfer of photodiode n utmost point electrode and arrive TFT source electrode (142), be transferred to data acquisition unit again; The 3rd insulating barrier (17) covers said thin-film transistor TFT and photodiode; The 3rd metal level 18 is drawn photodiode p utmost point electrode through the 3rd insulating barrier (17), and is connected in the photodiode biasing circuit.
The present invention also provides a kind of active pixel is applied to the circuit structure of microcrystalline silicon film detector, and this circuit structure comprises photodiode (07) and first, second and the 3rd thin-film transistor TFT; The p utmost point of said photodiode is provided with bias voltage VSS; The n utmost point of this photodiode is connected in the source electrode of the first film transistor T FT (04); This first film transistor drain is connected in positive source VDD; When the transistorized grid RST of the first film high level, the first film transistor T FT (04) conducting accumulates in the electric charge of said photodiode (07) the n utmost point and is cleared;
The second thin-film transistor TFT (05) is used as the voltage that source follower is used for amplifying the photodiode n utmost point, and its drain electrode is connected in positive source VDD;
The drain electrode of the 3rd thin-film transistor TFT (06) is connected in the source electrode of the second thin-film transistor TFT (05); The source electrode of the 3rd thin-film transistor TFT (06) is connected in data wire; When the grid G ate high level of the 3rd thin-film transistor TFT (06); Signal after said second thin-film transistor TFT (05) and the 3rd thin-film transistor TFT (06) conducting simultaneously, said photodiode (07) n pole tension are amplified through the second thin-film transistor TFT (05) is exported from the 3rd thin-film transistor TFT (06) source electrode;
Said first, second comprises the active area that is made up of intrinsic micro crystal silicon thin film and n doped microcrystalline silicon thin film, the grid that is positioned at second insulating barrier, TFT drain electrode, the TFT source electrode on this active area and is arranged at said active area below with the 3rd thin-film transistor TFT.
As stated, the objective of the invention is to release a kind of microcrystalline silicon film detector, its advantage is:
1, microcrystalline silicon film detector aperture opening ratio is higher, speed is faster.
2, the microcrystalline silicon film manufacture craft is similar with the amorphous silicon membrane manufacture craft, is fit to large size panel.
3, the equipment of preparation microcrystalline silicon film with prepare the identical of amorphous silicon membrane, realized the zero cost of technology alteration.
4, can under the prerequisite that does not reduce aperture opening ratio, in pixel, increase driving transistors, improve picture quality and adapt to the needs of detector toward the large scale development.
Description of drawings
Fig. 1 is the dot structure profile of microcrystalline silicon film detector of the present invention.
Fig. 2 is the dot structure profile of the microcrystalline silicon film detector processing procedure first step of the present invention.
Fig. 3 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 2.
Fig. 4 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 3.
Fig. 5 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 4.
Fig. 6 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 5.
Fig. 7 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 6.
Fig. 8 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 7.
Fig. 9 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 8.
Figure 10 is microcrystalline silicon film detector circuit figure of the present invention.
Figure 11 is the circuit diagram of microcrystalline silicon film detector using active pixel of the present invention.
Figure 12 is the pixel domain of microcrystalline silicon film detector using active pixel of the present invention.
Figure 13 is the sequential chart of microcrystalline silicon film detector using active pixel of the present invention.
The element numbers explanation
Embodiment
Below through specific instantiation execution mode of the present invention is described, those skilled in the art can understand other advantages of the present invention and effect easily by the content that this specification disclosed.The present invention can also implement or use through other different embodiment, and each item details in this specification also can be based on different viewpoints and application, carries out various modifications or change under the spirit of the present invention not deviating from.
See also shown in Figure 1.Need to prove; The diagram that is provided in the present embodiment is only explained basic conception of the present invention in a schematic way; Satisfy only show in graphic with the present invention in relevant assembly but not component count, shape and plotted when implementing according to reality; Kenel, quantity and the ratio of each assembly can be a kind of random change during its actual enforcement, and its assembly layout kenel also maybe be more complicated.
Combine accompanying drawing to specifically describe technical scheme of the present invention at present.
Shown in Figure 1 is microcrystalline silicon film detector pixel section of structure.Each pixel is made up of a thin-film transistor (TFT) and a photodiode.The active area that TFT is made up of intrinsic micro crystal silicon thin film (131) and n doped microcrystalline silicon thin film (132), the grid (11) that is incorporated into insulating barrier (15), drain electrode (141), the source electrode (142) on the active area and is arranged at said active area below constitute.Grid (11) is connected in control circuit (the Gate unit among Figure 10), control TFT break-make.Source electrode (142) is connected in data acquisition unit (the Data unit among Figure 10), the signal of telecommunication of output photodiode when the TFT conducting.Photodiode comprises p doped amorphous silicon layer (162), intrinsic amorphous silicon layer (163), n doped amorphous silicon layer (164), n utmost point electrode (141) and p utmost point electrode (161).TFT drain electrode (141) is connected in photodiode n utmost point electrode (141).When the TFT conducting, accumulate in the charge transfer of photodiode n utmost point electrode (141) and arrive TFT source electrode (142), be transferred to data acquisition unit again.Insulating barrier (17) covers TFT and photodiode.Metal level 18 is drawn photodiode p utmost point electrode (161) through insulating barrier (17), and is connected in photodiode biasing circuit (Vcom among Figure 10).
During exposure, TFT turn-offs, after X ray changes visible light into through scintillator (demonstration in the drawings), by the photodiode collection and convert electric charge into and be accumulated in p utmost point electrode (161) and n utmost point electrode (141).Behind the end exposure, the electric charge that is accumulated in n utmost point electrode (141) is transferred to TFT source electrode (142) under the control of grid (11), and the electric charge of source electrode (142) is transferred to data acquisition unit again.
Because the active area that microcrystalline silicon film (131,132) constitutes has higher carrier mobility than amorphous silicon, causes charge transfer faster, so image taking speed is faster, the TFT area occupied can reduce to increase aperture opening ratio simultaneously.
Fig. 2 is the dot structure profile of the microcrystalline silicon film detector processing procedure first step of the present invention.Go up depositing metal layers at glass substrate (10), this metal level of etching is to form TFT grid (11).The material of this metal level may be selected to be the alloy (Mo/Al/Mo) of molybdenum/aluminium/molybdenum.
Fig. 3 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 2.Depositing insulating layer on the basis of Fig. 2 (12) (for example can select the SiNx film).
Fig. 4 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 3.Deposition intrinsic micro crystal silicon thin film on the basis of Fig. 3 (131) and n doped microcrystalline silicon thin film (132), the said two-layer microcrystalline silicon film of etching is to form the TFT active area then.
Fig. 5 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 4.Depositing metal layers on the basis of Fig. 4, (material of this metal level may be selected to be the alloy (Mo/Al/Mo) of molybdenum/aluminium/molybdenum.) the n doped microcrystalline silicon layer (132) of this metal level of etching and metal level below to be to form TFT source electrode (142) and drain (141).
Fig. 6 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 5.Deposition SiNx film on the basis of Fig. 5, this film of etching is to form the insulating barrier (15) that covers TFT then.
Fig. 7 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 6.On the basis of Fig. 6, deposit n doped microcrystalline silicon thin film (164), intrinsic micro crystal silicon thin film (163), p doped microcrystalline silicon thin film (162), transparency conducting layer ITO (161) successively, the said four-level membrane of etching is to form photodiode then.
Fig. 8 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 7.Deposition another insulating barrier SiNx film (17) on the basis of Fig. 7.
Fig. 9 is microcrystalline silicon film detector processing procedure of the present invention next step pixel profile after Fig. 8.Etching SiNx film (17) forms the perforate be positioned at ITO electrode (161) top on the basis of Fig. 8, depositing metal layers then, and the material of this metal level may be selected to be the alloy (Mo/Al/Mo) of molybdenum/aluminium/molybdenum.This metal level of etching is to form the electrode (18) that ITO electrode (161) is drawn.
Figure 10 is microcrystalline silicon film detector circuit figure of the present invention.Pixel (03) by thin-film transistor (01) and photodiode (02) constitute is arranged with matrix form.In each pixel, the thin-film transistor drain electrode is connected in the corresponding photodiode n utmost point.The film crystal tube grid of each row pixel links to each other, by Gate unit controls thin-film transistor break-make.The thin-film transistor source electrode of each row pixel links to each other, and is exported by Data unit controls thin-film transistor source signal.All photodiode p utmost points are connected in same bias voltage Vcom.
Figure 11 is the circuit diagram of microcrystalline silicon film detector using active pixel of the present invention.Active pixel is made up of photodiode (07), thin-film transistor (04,05,06).The active area of thin-film transistor (04,05,06) is made up of microcrystalline silicon film.
Figure 12 is the pixel domain of microcrystalline silicon film detector using active pixel of the present invention.(RST VDD) constitutes each pixel for Data, Gate by photodiode (07), thin-film transistor (04,05,06) and connecting line.
Figure 13 is the sequential chart of microcrystalline silicon film detector using active pixel of the present invention.RST is connected in TFT (04) grid among the figure, and Gate is connected in TFT (06) grid.
Figure 11, Figure 12 and Figure 13 provide the structural representation that active pixel is applied to the microcrystalline silicon film detector.Because the microcrystalline silicon film carrier mobility is greater than amorphous silicon membrane, the area of single TFT can reduce, and just can under the prerequisite that does not reduce aperture opening ratio, in pixel, increase driving transistors.VSS is the bias voltage of the photodiode p utmost point, and the photodiode n utmost point is connected in TFT (04) source electrode.TFT (04) is used for emptying photodiode (07), and drain electrode is connected in positive source VDD, and when grid (RST among the figure) high level, TFT (04) conducting accumulates in the electric charge of photodiode (07) the n utmost point and is cleared.TFT (05) is a source follower, and drain electrode is connected in positive source VDD, and TFT (05) is used for amplifying the voltage of the photodiode n utmost point.TFT (06) drain electrode is connected in TFT (05) source electrode; TFT (06) source electrode is connected in data wire (Data among the figure); When grid (Gate among the figure) high level; Signal after TFT (05) and TFT (06) conducting simultaneously, photodiode (07) n pole tension are amplified through TFT (05) is exported from TFT (06) source electrode.Before each exposure, RST is the output high level pulse earlier, empties the electric charge of photodiode (07), then exposure; After exposure was accomplished, Gate exported high level pulse, reads photodiode (07) signal.The time t that the Gate high level pulse continues depends on the parameter setting of subsequent integration circuit.
Technical scheme of the present invention is divided into two parts.First is the preparation method of microcrystalline silicon film detector, and with the active area of microcrystal silicon formation thin-film transistor, photodiode is made up of amorphous silicon membrane, and the drain electrode of thin-film transistor connects the n utmost point electrode of photodiode.Second portion is structure and the method that active pixel is applied to the microcrystalline silicon film detector.
Microcrystalline silicon film panel detector structure involved in the present invention is as shown in Figure 1, and its corresponding preparation flow such as Fig. 2 are to shown in Figure 9.The microcrystalline silicon film detector circuit is shown in figure 10.Figure 11 to Figure 12 passes the electrical block diagram that is contained in the microcrystalline silicon film detector with active pixel.
Microcrystalline silicon film detector involved in the present invention is made up of control element TFT, photodiode.Shown in Figure 2 is glass substrate (10) and TFT grid (11), on glass substrate, deposits the layer of metal layer, is etched into the grid (11) of TFT then.Deposit layer of sin x film (12) at substrate (10) and grid (11) top among Fig. 3.Go up priority at SiNx film (12) among Fig. 4 and deposit one deck intrinsic micro crystal silicon thin film (131) and one deck n doped microcrystalline silicon thin film (132), then said two-layer microcrystalline silicon film is etched into the TFT active area.Among Fig. 5 on the basis of Fig. 4 depositing metal layers, this metal level of etching and n doped microcrystalline silicon thin film (132) then, this metal level are etched to TFT drain electrode (141) and source electrode (142), drain electrode (141) while is as photodiode n utmost point electrode.On the basis of Fig. 5, deposit the SiNx film among Fig. 6, this SiNx film of etching is to form TFT surface insulation layer (15) then.Go up the making photodiode at photodiode n utmost point electrode (141) among Fig. 7; Step is for deposit n doped amorphous silicon film (164), intrinsic amorphous silicon film (163), p doped amorphous silicon film (162), p utmost point electrode successively; Wherein p utmost point electrode is transparent conductive film ITO (161), then the said four-level membrane of etching.On the basis of Fig. 7, deposit SiNx film (17) among Fig. 8, the said SiNx film of etching forms the perforate that is positioned at photodiode p utmost point electrode top then.Among Fig. 9 on the basis of Fig. 8 depositing metal layers, the said metal level of etching then forms electrode (18) so that photodiode p utmost point electrode is drawn at SiNx film (17) tapping.Above-mentioned metal level all can may be selected to be the alloy (Mo/Al/Mo) of molybdenum/aluminium/molybdenum.
In sum, the present invention adopts the microcrystalline silicon film detector, under the prerequisite that does not increase the manufacturing process complexity, has improved the speed and the resolution of X-ray detector, has saved manufacturing cost; The method that the present invention also provides active pixel to be applied to the microcrystalline silicon film detector is to improve picture quality and to adapt to the needs of detector toward the large scale development.So the present invention has effectively overcome various shortcoming of the prior art and the tool high industrial utilization.
The foregoing description is illustrative principle of the present invention and effect thereof only, but not is used to limit the present invention.Any be familiar with this technological personage all can be under spirit of the present invention and category, the foregoing description is modified or is changed.Therefore, have common knowledge the knowledgeable in the affiliated such as technical field, must contain by claim of the present invention not breaking away from all equivalence modifications of being accomplished under disclosed spirit and the technological thought or changing.