CN102544031B - The cavity type ultra-deep optical diode of imageing sensor and process thereof - Google Patents
The cavity type ultra-deep optical diode of imageing sensor and process thereof Download PDFInfo
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Abstract
A kind of cavity type ultra-deep optical diode of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor and process thereof.P type substrate ground connection or be connected to negative supply.N-type epitaxy layer is grown in the substrate of P type, and is connected to positive supply.Ultra-deep P type optical diode injection zone is formed in N-type epitaxy layer.Use heat treated to obtain level and smooth and dark doping profile.
Description
Technical field
The present invention relates to a kind of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor, particularly relate to a kind of cavity type ultra-deep optical diode being applied to the cmos image sensor of automobile.
Background technology
CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor is widely used in the camera of mobile phone, network camera, supervision video camera, toy or Medical Devices.Cmos image sensor also can be applicable to severe environment, and such as automobile application, due to the operating environment that it is severe, therefore makes excessive demands for imageing sensor very much.In order to be applied to automobile, some problems of cmos image sensor must be solved.
The first, in order to allow automobile can obtain more details information to judge night, imageing sensor must have higher sensitivity or signal noise ratio (SNR).
Second, because the operating temperature of automobile can higher than general application, the camera of such as mobile phone, therefore lower dark current is needed, in order to maintain high dynamic range, reduce dark signal heterogeneity (darksignalnon-uniformity, DSNU) and reduce dark signal impulsive noise (shotnoise).
3rd, the roadway scene due to night belongs to high dynamic range pattern, and therefore cmos image sensor needs good excessive (blooming) to control in superbright region, waters down to prevent from being subject to the excessive electric charge in superbright region compared with dark areas around it.For some high dynamic range mechanism of tradition, because cumulative (integration) time of its optical diode is different, therefore longer cumulative optical diode can destroy the information of shorter cumulative optical diode.
4th, because automobile tail light and traffic sign have stronger red color light component, therefore ruddiness information is very important for automobile application.Moreover in order to make better judgement, imageing sensor needs to collect the infrared light outside visible spectrum and near infrared light information.
Each pixel of conventional CMOS image sensor represents signal with electronics, and the transistor in pixel is all N-type metal-oxide semiconductor (MOS) (NMOS) transistor.In pixel, the hole that photon produces and electronics are stored in P side and the N side of optical diode respectively.After exposure, NMOS transmission gate only transmits electronics to N-type and to float diffusion (floatingdiffusion, FD) node, then is voltage signal by FD junction capacitance by electronic switch.This voltage signal is then passed to the output of pixel by subsequent conditioning circuit.
In order to improve above-mentioned dark current and excessive problem, thus cavity type optical diode is as shown in Figure 1 disclosed, " the Low-CrosstalkandLow-Dark-CurrentCMOSImage-Sensortechnolo gyUsingaHole-BasedDetector " that can deliver with reference to people such as EricStevens, IEEEInternationalSolid-StateCircuitsConference, 60-61 in 2008.
Cavity type optical diode shown in Fig. 1 comparatively traditional electrical subtype cmos image sensor more can suppress dark current.Wherein, P type substrate 10 can be used as the discharge region in excessive hole, to migrate out substrate (bulk) dark current.In addition, by Si/SiO
2the alloy (dopant) of interface is assembled, and such as, between shallow channel isolation area (STI) 12 and N+ well 14, dark current can significantly reduce, and this differs from electron type cmos image sensor can produce alloy separation in this place.In addition, because the mobility (mobility) in hole is less than electronics, therefore, under identical electric field and CHARGE DISTRIBUTION situation, drift (drift) electric current of cavity type cmos image sensor and dissufion current are much smaller than electron type cmos image sensor.Moreover the P type substrate 10 due to ground connection provides electronegative potential to discharge the excessive hole of cavity type optical diode, thus can provide good excessive control, be urgently applicable to automobile application.
But, because N-type dopant overweights P type alloy, make the degree of depth of the P type optical diode 16 of cavity type cmos image sensor be limited to the injection degree of depth of N-type well 18.Such as, the atomic weight of N-type phosphorus be 30.97 or arsenic be 74.92, and the atomic weight of P type boron is 10.81.Therefore, shallow P type optical diode 16 cannot absorb enough electron-hole pairs to contain the absorption region of ruddiness/near infrared light.On the other hand, for the P type optical diode 16 of given depth, the degree of depth of N-type well 18 will be limited to interference (crosstalk) and excessive control.If too dark, then diffusion charge can enter neighborhood pixels, and cannot absorb by P type optical diode 16.
Therefore, need the cmos image sensor proposing a kind of novelty badly, react with the ruddiness/near infrared light improving structure shown in Fig. 1 and maintain its excessive and interference control.
Summary of the invention
In view of above-mentioned, one of object of the embodiment of the present invention is the structure &processes of the cavity type ultra-deep optical diode proposing a kind of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor, and it has the ruddiness/near infrared light reaction of improvement, the interference reduced, excessive and less dark current.
According to the embodiment of the present invention, the cavity type ultra-deep optical diode of cmos image sensor comprises the substrate of P type, N-type epitaxy layer and ultra-deep P type optical diode injection zone.P type substrate ground connection or be connected to negative supply.N-type epitaxy layer is grown in the substrate of P type, and is connected to positive supply.Ultra-deep P type optical diode injection zone is formed in N-type epitaxy layer.Wherein ultra-deep refers to that the thickness of described ultra-deep P type optical diode injection zone is greater than 0.5 micron.
Accompanying drawing explanation
Fig. 1 shows the profile of the cavity type optical diode of conventional CMOS image sensor;
Fig. 2 shows electronics moldeed depth optical diode;
Fig. 3 shows the profile of the cavity type ultra-deep optical diode of the cmos image sensor of the embodiment of the present invention;
Fig. 4 A to Fig. 4 C shows the technique of the cavity type ultra-deep optical diode of the cmos image sensor of the embodiment of the present invention.
Embodiment
React in order to the longer wavelength strengthening ruddiness/near infrared light and reduce diffusion interference, the electron type optical diode that Fig. 2 proposes has deep n-type optical diode 20, and its Absorbable rod electron-hole pair is to contain ruddiness/near-infrared absorption region and to absorb more multi signal.In addition, the diffusion charge of the P type epitaxial loayer 22 be positioned under deep n-type optical diode 20 can be reduced in a large number, therefore, the diffusion charge entering neighborhood pixels can be reduced.In Fig. 1, the interference reduced because of excessive discharge but can cause bad ruddiness/near infrared light reaction.But Fig. 2 does not then have the excessive discharge situation of Fig. 1.
In order to take into account the advantage of Fig. 1 and Fig. 2, Fig. 3 shows the profile of the cavity type ultra-deep optical diode of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor of the embodiment of the present invention.Accompanying drawing only demonstrates main element, and comparatively detailed construction refers to Fig. 4 C.In the present embodiment, " deeply " or " ultra-deep (ultra-deep) " refers to be greater than 0.5 micron, and such as 0.5-2 micron then refers to be greater than 2 microns in a preferred embodiment.Disclosed optical diode is applicable to severe environment, such as automobile application, but not as limit.As described in Figure 1, cavity type optical diode can reach comparatively low-dark current, and therefore the optical diode of the present embodiment can meet the harsh temperature requirement of automobile application.
In the present embodiment, as Fig. 1, P type substrate 30 ground connection or be connected to negative supply.P type substrate 30 is in order to discharge excessive hole, and this is conducive to the high dynamic range scene at night.Under general operation, P type substrate 30 can reduce the interference of ruddiness/near infrared light signal.About " InterlineCCDImageSensorwithanAntibloomingStructure " that the further details of excessive control can be delivered with reference to people such as YasuoIshihara, IEEETransactionsonElectronDevices, Vol.ED-31, No.1, in January, 1984; Or " SuperSmall, Sub2 μm of PixelsForNovelCMOSImageSensors " that the people such as G.Agranov delivers, InternationalImageSensorWorkshop, 7-10 day in June, 2007, Ogunquit, MaineUSA.
N-type epitaxy layer 31 is formed in P type substrate 30, and is connected to positive supply AVDD.Dark P type optical diode 32 injection region is formed in N-type epitaxy layer 31.Because the present embodiment uses N-type epitaxy layer 31 but not as the N-type well of Fig. 1, the injection degree of depth that therefore can not be subject to heavier N-type dopant limits.Because P type alloy is comparatively light, therefore, compared to traditional electrical subtype optical diode, dark P type optical diode 32 injection region of the present embodiment can be comparatively dark, thus can improve signal noise when ruddiness/near infrared light reaction.
Isolated area, such as shallow channel isolation area (STI) 33 is formed in N-type epitaxy layer 31.N+ structure cell (cell) separator 34 is formed on the side in shallow channel isolation area 33 and bottom.Compared to the P type separator 24 of Fig. 2, because N-type dopant is heavier, the thermal diffusion of the N-type separator 34 of the present embodiment can reduce greatly.Therefore, Miniaturizable separator, and stay more spaces to optical diode 32.By this, signal absorption and interference problem can be improved.
Transmission gate 35 is formed in N-type epitaxy layer 31, and is positioned at dark P type optical diode 32 injection region and P type and floats and spread (P+FD) 36 between injection region.
Fig. 4 A to Fig. 4 C shows the technique of the cavity type ultra-deep optical diode of the cmos image sensor of the embodiment of the present invention.The element identical with Fig. 3 indicates with similar elements symbol.Each step can use conventional semiconductor processing techniques, and its details is omitted.
In Fig. 4 A, P type substrate (or being called for short substrate) 30 is provided, then grows N-type epitaxy layer (or referred to as epitaxial loayer) 31 thereon.In the present embodiment, the thickness of epitaxial loayer 31 is 6 microns or is greater than 6 microns, but not as limit.
Then, still consult Fig. 4 A, perform repeatedly dark P type optical diode and inject, to form dark P type optical diode (or referred to as optical diode) 32 injection region.This injection is executed in the region that shielding (not being shown in graphic) defines.Injecting each time to use different-energy to reach required profile.In addition, after each injection, heat treatment can be used to make its contour smoothing.Its profile also can determine according to the heat treatment of subsequent process steps.Then, shallow channel isolation area 33 is formed in epitaxial loayer 31.
In Fig. 4 B, structure cell separator (or structure cell N-type well) 34 is injected in the side in shallow channel isolation area 33 and bottom, and injects dark separator (or deep N-well) 37 for 34 times in structure cell separator.In addition, inject N-type raceway groove 38 injection zone in epitaxial loayer 31 upper epidermis region, it is positioned at above dark optical diode 32 injection region.Above-mentioned structure cell separator 34, dark separator 37 and raceway groove 38 injection zone can perform according to suitable order.Then, transmission gate 35 is formed on epitaxial loayer 31.
In Fig. 4 C, inject the tip (pinning) 39 injection zone in epitaxial loayer 31 upper epidermis region.In the present embodiment, the N-type tip 39 injection zone is positioned at raceway groove 38 injection zone.Implanting p-type surface light diode 40 injection zone between raceway groove 38 injection zone and dark optical diode 32 injection region, as main cavity type optical diode.In the present embodiment, the tip 39 injection zone and raceway groove 38 injection zone are mainly in order to suppress dark current and optimization transmission gate 35.The tip 39 injection zone and surface light diode 40 injection zone can perform according to suitable order.Then, inject P+ to float diffusion 36 injection zone.
The foregoing is only the preferred embodiments of the present invention, and be not used to limit interest field of the present invention; Under all other does not depart from the spirit that invention discloses, the equivalence that completes changes or modifies, and all should be included in following right.
Claims (16)
1. a cavity type ultra-deep optical diode for CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor, comprises:
The substrate of P type, ground connection or be connected to negative supply;
N-type epitaxy layer, be grown in the substrate of described P type, described N-type epitaxy layer is connected to positive supply; And
Ultra-deep P type optical diode injection zone, is formed in described N-type epitaxy layer,
Wherein ultra-deep refers to that the thickness of described ultra-deep P type optical diode injection zone is greater than 0.5 micron.
2. the cavity type ultra-deep optical diode of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor as claimed in claim 1, the thickness of wherein said ultra-deep P type optical diode injection zone is 0.5-2 micron.
3. the cavity type ultra-deep optical diode of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor as claimed in claim 1, the thickness of wherein said ultra-deep P type optical diode injection zone is greater than 2 microns.
4. the cavity type ultra-deep optical diode of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor as claimed in claim 1, also comprises:
Isolated area, is formed in described N-type epitaxy layer.
5. the cavity type ultra-deep optical diode of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor as claimed in claim 4, wherein said isolated area is shallow channel isolation area.
6. the cavity type ultra-deep optical diode of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor as claimed in claim 4, also comprises:
N-type structure cell separator, is formed at side and the bottom of described isolated area.
7. a process for the cavity type ultra-deep optical diode of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor, comprises:
The substrate of P type is provided;
Growth N-type epitaxy layer is in the substrate of described P type; And
Form ultra-deep P type optical diode injection zone in described N-type epitaxy layer,
Wherein ultra-deep refers to that the thickness of described ultra-deep P type optical diode injection zone is greater than 0.5 micron.
8. the process of the cavity type ultra-deep optical diode of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor as claimed in claim 7, the formation of wherein said ultra-deep P type optical diode injection zone comprises use different-energy and repeatedly injects to perform.
9. the process of the cavity type ultra-deep optical diode of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor as claimed in claim 8, also comprises:
Heat treatment is imposed after described injection each time or by subsequent process steps.
10. the process of the cavity type ultra-deep optical diode of CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensor as claimed in claim 7, also comprises:
Form isolated area in described N-type epitaxy layer.
The process of the cavity type ultra-deep optical diode of 11. CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensors as claimed in claim 10, also comprises:
Form N-type structure cell separator in the side of described isolated area and bottom; And
Inject the dark separator of N-type under described structure cell separator.
The process of the cavity type ultra-deep optical diode of 12. CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensors as claimed in claim 7, also comprises:
Inject Channeling implantation region in the upper epidermis region of described N-type epitaxy layer, wherein said Channeling implantation region is positioned at above described ultra-deep P type optical diode injection zone.
The process of the cavity type ultra-deep optical diode of 13. CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensors as claimed in claim 12, also comprises:
Inject N-type tip injection zone in the upper epidermis region of described N-type epitaxy layer; And
Implanting p-type surface light diode injection zone is in described N-type epitaxy layer, as the charge storage of a main cavity type optical diode, wherein said surface light diode injection zone is between described Channeling implantation region and described ultra-deep P type optical diode injection zone.
The process of the cavity type ultra-deep optical diode of 14. CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensors as claimed in claim 7, also comprises:
Form transmission gate in described N-type epitaxy layer; And
Form P type and float diffusion injection zone in described N-type epitaxy layer, wherein said transmission gate floats at described ultra-deep P type optical diode injection zone and described P type and spreads between injection zone.
The process of the cavity type ultra-deep optical diode of 15. CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensors as claimed in claim 7, the thickness of wherein said ultra-deep P type optical diode injection zone is 0.5-2 micron.
The process of the cavity type ultra-deep optical diode of 16. CMOS (Complementary Metal Oxide Semiconductor) (CMOS) imageing sensors as claimed in claim 7, the thickness of wherein said ultra-deep P type optical diode injection zone is greater than 2 microns.
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| CN101473441A (en) * | 2006-06-20 | 2009-07-01 | 伊斯曼柯达公司 | PMOS pixel structure with low cross talk |
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| US6514785B1 (en) * | 2000-06-09 | 2003-02-04 | Taiwan Semiconductor Manufacturing Company | CMOS image sensor n-type pin-diode structure |
| US7910961B2 (en) * | 2008-10-08 | 2011-03-22 | Omnivision Technologies, Inc. | Image sensor with low crosstalk and high red sensitivity |
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| CN101473441A (en) * | 2006-06-20 | 2009-07-01 | 伊斯曼柯达公司 | PMOS pixel structure with low cross talk |
| CN101159282A (en) * | 2006-10-04 | 2008-04-09 | 株式会社东芝 | Amplifying type solid cameraing element |
| CN101202246A (en) * | 2006-12-15 | 2008-06-18 | 中芯国际集成电路制造(上海)有限公司 | Forming method of pixel unit of CMOS image sensor |
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