CN101752392A - Four-transistor CMOS image transducer and manufacturing method thereof - Google Patents
Four-transistor CMOS image transducer and manufacturing method thereof Download PDFInfo
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- CN101752392A CN101752392A CN200810044038A CN200810044038A CN101752392A CN 101752392 A CN101752392 A CN 101752392A CN 200810044038 A CN200810044038 A CN 200810044038A CN 200810044038 A CN200810044038 A CN 200810044038A CN 101752392 A CN101752392 A CN 101752392A
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- image transducer
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Abstract
The invention discloses a four-transistor CMOS image transducer. Part of a floating diffusing capacitance region is provided with a P-N-P node where an N region is thoroughly exhausted, and the built-in potential of the P-N-P node is higher than that of a photodiode. The invention also discloses a method for manufacturing the four-transistor CMOS image transducer. P-well injection is implemented on a P substrate of the floating diffusing capacitance region, N-implantation is implemented on a P substrate of a photodiode region, N implantation is implemented in the P well of the floating diffusing capacitance region, and the concentration of N is higher than that of the N-. P+ implantation is implemented on the surface of the N-implantation region in the photodiode region in order to form the P-N-P node where the N region is thoroughly exhausted, and P+ implantation is implemented on the surface of part of the N implantation region of the floating diffusing capacitance region in order to form the P-N-P node where the N region is thoroughly exhausted. The four-transistor CMOS image transducer improves response to strong light, and increases dynamic range.
Description
Technical field
The present invention relates to semiconductor technology, particularly a kind of cmos image sensor and manufacture method thereof.
Background technology
The cmos image sensor structural profile as shown in Figure 1 for traditional 4T (four-transistors, four transistors).Its structure contains the sensing part of a Pinned PD (clamper photodiode) as light, FD electric capacity (the diffusion capacitance of floating, Floating Diffusion Capacitance) photoelectron is changed into voltage (light signal conversion portion), other has 4 transistors:
1.TG pipe: transfer pipeline, utilize clock control, when it is opened, photoelectron is transferred to FD from PD (photodiode);
2.RS pipe: the pipe of resetting, utilize clock control, FD reset before next signal reads;
3.TSF pipe: source follower, play the effect of amplifying and cushioning input and output;
4.TSEL pipe: row address is selected pipe, when it is opened, and signal output.
Its operation principle is as follows:
Under the initial condition, the RS pipe is opened, then FD electric capacity current potential is reset to operating voltage VDD, when illumination incident, light produces photoelectric current at PD, and PD is charged, PD has just produced a voltage drop Δ Vpd like this, the TG pipe is opened then, because the electrical potential difference between PD and the FD, photoelectric current can flow to FD from PD at the electric charge that PD accumulated, notice since PD when initial condition, its N-just exhausts fully, therefore when electric charge fully after PD flows to FD, the electromotive force on the PD has been got back to original state (initial built-in electrical potential difference) again.After TG turn-offs, T
SELOpen, thereby realize signal output.
From as can be seen above, the 4T transducer has been realized the conversion portion (FD) of probe portion of light (PD) and light signal is separated, the advantage of Here it is 4T transducer.In addition, we are desirable just for big PD electric capacity and little FD electric capacity, because can not only realize big dynamic range like this and obtain high sensitivity.
But little FD electric capacity might limit its dynamic range equally: as shown in Figure 2, the voltage on the FD (diffusion capacitance of floating) is Vfd, the size of the pressure drop Δ Vfd of FD can not surpass the poor of VDD and the initial built-in electrical potential difference of PD, in addition by Q
Fd=C
FdΔ Vfd, therefore, when FD electric capacity is very little, Q
FdAlso limited, be easy under the irradiation of high light and reach capacity, this has just limited its dynamic range, has reduced the performance of transducer.
Dynamic range of sensor (Dynamic Range) as shown in Figure 3.
Summary of the invention
The technical problem to be solved in the present invention is to improve four-transistor CMOS image transducer corresponding to high light, increases the dynamic range of four-transistor CMOS image transducer.
For solving the problems of the technologies described above, the invention provides a kind of four-transistor CMOS image transducer, comprise photodiode region, the diffusion capacitance district of floating, it is characterized in that, part in the diffusion capacitance district of floating is formed with the P-N-P knot that a N district exhausts fully, and the built-in electromotive force of this P-N-P knot is than the built-in electromotive force height of photodiode.
For solving the problems of the technologies described above, the invention also discloses a kind of four-transistor CMOS image transducer manufacture method, its technical process may further comprise the steps:
One. carry out the active area of four-transistor CMOS image transducer CMOS processing procedure and place, grid technology at the P substrate, and on the P substrate, carry out the P trap in the diffusion capacitance zone of floating and inject;
Two. carry out N-at the P of photodiode region substrate and inject, the P trap in the diffusion capacitance district of floating carries out N and injects, and the concentration of described N is greater than described N-concentration;
Three. carry out after the side wall technology, carrying out P+ in the region surface of carrying out the N-injection of photodiode region injects, form the P-N-P knot that a N district exhausts fully, and carry out P+ on a part of surface of carrying out the zone that N injects in the diffusion capacitance district of floating and inject, make this subregion in the diffusion capacitance district of floating form the P-N-P that a N district exhausts fully and tie;
Four. carry out subsequent technique.
Four-transistor CMOS image transducer of the present invention, because the subregion of FD is formed with the P-N-P knot that a N district exhausts fully, not only do not influence the sensitivity of four-transistor CMOS image transducer to the low light level, and can improve its corresponding to high light, increase the dynamic range of four-transistor CMOS image transducer, thereby promoted the performance of four-transistor CMOS image transducer.
Four-transistor CMOS image transducer manufacture method of the present invention, by adjusting the concentration of N in the FD zone and adding the P trap and the injection of part P+ ion, make this subregion form the P-N-P knot that a N district exhausts fully, and the ion concentration of control P trap and N all P substrate and the N-than the PD district is dense, thereby its built-in electromotive force is higher than Pinned (clamper) photodiode, the existence of this knot does not only influence the sensitivity of transducer to the low light level, and can improve its corresponding to high light, increase the dynamic range of transducer, thereby promoted the performance of transducer.
Description of drawings
Below in conjunction with the drawings and the specific embodiments the present invention is described in further detail.
Fig. 1 is traditional four-transistor CMOS image transducer section of structure;
Fig. 2 is the potential energy diagram of traditional four-transistor CMOS image transducer;
Fig. 3 is traditional four-transistor CMOS image transducer dynamic range schematic diagram;
Fig. 4 is the profile of four-transistor CMOS image transducer of the present invention;
Fig. 5 is the potential energy diagram of four-transistor CMOS image transducer of the present invention;
Fig. 6 is after the four-transistor CMOS image transducer low light level irradiation of the present invention and TG opens later potential energy diagram;
Fig. 7 is the later curve of output of four-transistor CMOS image transducer low light level irradiation of the present invention;
Fig. 8 is after the four-transistor CMOS image transducer strong illumination of the present invention and TG opens later potential energy diagram;
Fig. 9 is the later curve of output of four-transistor CMOS image transducer strong illumination of the present invention;
Figure 10 is four-transistor CMOS image transducer manufacture method of the present invention active area/place, the grid of finishing the traditional cmos processing procedure and carries out P-Well and inject schematic diagram;
Figure 11 is that four-transistor CMOS image transducer manufacture method of the present invention is finished the N-in PD district and the N in FD district injects schematic diagram;
Figure 12 is four-transistor CMOS image transducer manufacture method of the present invention is done PD and FD district after finishing side wall technology a P+ injection schematic diagram;
Figure 13 is that four-transistor CMOS image transducer manufacture method of the present invention is finished follow-up N+ and peripheral P+ high concentration is injected schematic diagram.
Embodiment
Four-transistor CMOS image transducer one execution mode of the present invention as shown in Figure 4, comprise PD zone, FD zone, at FD (Floating Diffusion, the part in the zone diffusion capacitance of floating) (near TG grid one side) is formed with the P-N-P that a N district exhausts fully to be tied, and its built-in electromotive force is than the built-in electromotive force height of clamper photodiode.
The potential energy diagram of four-transistor CMOS image transducer of the present invention as shown in Figure 5.Because the subregion of FD forms P-N-P knot (the Pinned diode that a N district exhausts fully, clamp diode), thereby FD has two different electromotive forces after circuit is reset: the current potential Vrst (equaling VDD substantially) in the non-clamp diode of FD zone after the built-in electromotive force Vpin2 of the clamp diode among the FD and FD reset, and Vpin2 is greater than the Vpin1 (the built-in electromotive force of PD) of PD.
Cause the PD zone to accumulate a part of electric charge as light incident, after TG opens, these electric charges can be transferred to FD from PD, suppose that these light intensities are more weak, as shown in Figure 6, the change that causes the voltage Vfd on the FD (diffusion capacitance of floating) is less than Vrst-Vpin2, then this FD can also have the reaction of comparison sensitivity to weak light intensity, as shown in Figure 7, because Δ Vfd is less than Vrst-Vpin2, therefore the relation of its output and light intensity still is linear under the low light level.
If light intensity is more intense, as shown in Figure 8, the change that causes Vfd is greater than Vrst-Vpin2, and then FD is also played a part to collect electric charge by that part of electric capacity of Pinned (clamper), thereby the slope of curve of output is changed, thereby increase the dynamic range DR of transducer.Be illustrated in figure 9 as the curve of output under the strong illumination, dotted portion is represented the curve of output of traditional four-transistor CMOS image transducer, solid line is partly represented the curve of output of four-transistor CMOS image transducer of the present invention, obviously see from Fig. 9, the subregion of FD forms the P-N-P knot (Pinneddiode that a N district exhausts fully, clamp diode) not only do not influence the sensitivity of four-transistor CMOS image transducer to the low light level, and can improve its corresponding to high light, increase the dynamic range of four-transistor CMOS image transducer, thereby promoted the performance of four-transistor CMOS image transducer.
Four-transistor CMOS image transducer manufacture method one execution mode of the present invention such as Figure 10～shown in Figure 13, its technical process is as follows:
1. carry out AA (active area/place), Gate (grid) technology of traditional four-transistor CMOS image transducer CMOS processing procedure at the P substrate, and on the P substrate, carry out the P trap in the FD zone and inject;
2. carry out N-at the P in PD district substrate and inject, carry out N at the P in FD district trap and inject, the concentration of described N is greater than described N-concentration;
3. carry out after Spacer (side wall) technology, carrying out the P+ high concentration ion in the region surface of carrying out the N-injection in PD district injects, and carry out P+ high concentration ion (for example Boron/BF2) on a part of surface of carrying out the zone that N injects in FD district and inject, make this subregion form the P-N-P knot (Pinned diode, clamp diode) that a N district exhausts fully;
4. finishing follow-up N+ and peripheral P+ high concentration ion injects;
5. subsequent technique is with traditional four-transistor CMOS image transducer technology unanimity.
Four-transistor CMOS image transducer manufacture method of the present invention, by adjusting the concentration of N in the FD zone and adding Pwell (P trap) and the injection of part P+ ion, make this subregion form the P-N-P knot that a N district exhausts fully, and the ion concentration of control Pwell and N all P-sub and the N-than the PD district is dense, thereby its built-in electromotive force is than the height of Pinned photodiode, the existence of this knot does not only influence the sensitivity of transducer to the low light level, and can improve its corresponding to high light, increase the dynamic range of transducer, thereby promoted the performance of transducer.
Claims (3)
1. four-transistor CMOS image transducer, comprise photodiode region, the diffusion capacitance district of floating, it is characterized in that the part in the diffusion capacitance district of floating is formed with the P-N-P knot that a N district exhausts fully, and the built-in electromotive force of this P-N-P knot is than the built-in electromotive force height of photodiode.
2. four-transistor CMOS image transducer according to claim 1 is characterized in that, is formed with the P-N-P knot that a N district exhausts fully in the side of diffusion capacitance district near the transfer pipeline grid of floating.
3. a four-transistor CMOS image transducer manufacture method is characterized in that, its technical process may further comprise the steps:
One. carry out the active area of four-transistor CMOS image transducer CMOS processing procedure and place, grid technology at the P substrate, and on the P substrate, carry out the P trap in the diffusion capacitance zone of floating and inject;
Two. carry out N-at the P of photodiode region substrate and inject, the P trap in the diffusion capacitance district of floating carries out N and injects, and the concentration of described N is greater than described N-concentration;
Three. carry out after the side wall technology, carrying out P+ in the region surface of carrying out the N-injection of photodiode region injects, form the P-N-P knot that a N district exhausts fully, and carry out P+ on a part of surface of carrying out the zone that N injects in the diffusion capacitance district of floating and inject, make this subregion in the diffusion capacitance district of floating form the P-N-P that a N district exhausts fully and tie.
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| CN200810044038A CN101752392A (en) | 2008-12-02 | 2008-12-02 | Four-transistor CMOS image transducer and manufacturing method thereof |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102752560A (en) * | 2012-06-21 | 2012-10-24 | 吉林大学 | Ultra-wide dynamic range image sensor based on pixel charge compensation technology |
| CN104377211A (en) * | 2013-08-15 | 2015-02-25 | 全视科技有限公司 | Image sensor pixel cell with switched deep trench isolation structure |
| CN105280660A (en) * | 2014-07-24 | 2016-01-27 | 佳能株式会社 | Imaging device |
| CN111276502A (en) * | 2020-02-19 | 2020-06-12 | 宁波飞芯电子科技有限公司 | Photoelectric conversion unit and image sensor |
-
2008
- 2008-12-02 CN CN200810044038A patent/CN101752392A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102752560A (en) * | 2012-06-21 | 2012-10-24 | 吉林大学 | Ultra-wide dynamic range image sensor based on pixel charge compensation technology |
| CN104377211A (en) * | 2013-08-15 | 2015-02-25 | 全视科技有限公司 | Image sensor pixel cell with switched deep trench isolation structure |
| CN104377211B (en) * | 2013-08-15 | 2017-05-31 | 豪威科技股份有限公司 | Image sensor pixel cells with suitching type deep trench isolation structure |
| CN105280660A (en) * | 2014-07-24 | 2016-01-27 | 佳能株式会社 | Imaging device |
| CN111276502A (en) * | 2020-02-19 | 2020-06-12 | 宁波飞芯电子科技有限公司 | Photoelectric conversion unit and image sensor |
| CN111276502B (en) * | 2020-02-19 | 2023-04-25 | 宁波飞芯电子科技有限公司 | Photoelectric conversion unit and image sensor |
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Open date: 20100623 |