CN105097850B - Cmos image sensor and its manufacturing method - Google Patents
Cmos image sensor and its manufacturing method Download PDFInfo
- Publication number
- CN105097850B CN105097850B CN201410172641.5A CN201410172641A CN105097850B CN 105097850 B CN105097850 B CN 105097850B CN 201410172641 A CN201410172641 A CN 201410172641A CN 105097850 B CN105097850 B CN 105097850B
- Authority
- CN
- China
- Prior art keywords
- transmission transistor
- grid
- cmos image
- polysilicon gate
- image sensor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Landscapes
- Solid State Image Pick-Up Elements (AREA)
- Transforming Light Signals Into Electric Signals (AREA)
Abstract
This application involves a kind of cmos image sensors to include, photodiode, floating diffusion region, and transmission transistor, the polysilicon gate of the transmission transistor uses non-uniform doping, so that the stepped distribution of potential in the channel region from close to the floating diffusion region to close to the transmission transistor of the photodiode.
Description
Technical field
Present application relates generally to image sensor technologies, in particular to back-illuminated cmos image sensors and its accordingly
Manufacturing method.
Background technique
Compared with the manufacturing process of CCD, the manufacturing process of cmos image sensor and the CMOS technology of standard are compatible, have
Low-power consumption, it is easy of integration, inexpensive the features such as, therefore cmos image sensor is more and more widely used in various electronic equipments
In.The structure of active pixel in cmos image sensor can be divided into variety classes according to the quantity difference of transistor.It is typical
4-T active pixel as shown in Figure 1, including for photosensitive photodiode (photodiode, PD), transmission transistor
(transfer transistor, TX), floating diffusion region (floating diffusion, FD), reset transistor (reset
Transistor, RST), selection transistor (select transistor, SEL).
Traditional cmos image sensor uses front illuminated, but is deposited above photodiode using this mechanism
In various metal layers or oxide layer etc., very big light loss will lead to.Therefore, back-illuminated cmos image sensors, also
It is that the imaging sensor of the mechanism for using the side from the separate circuit layer of substrate to be irradiated is widely used for industry, to increase
The luminous flux of light, and prevent the light crosstalk (crosstalk) of neighboring image sensors pixel unit part.
Summary of the invention
For the transmission transistor in existing cmos image sensor, due in semiconductor substrate and oxide layer
Interface is usually present the defect with negative electricity, therefore, even if still may be used in the case where photodiode is not by illumination
It can there is so-called dark current.Dark current can seriously affect the image quality of imaging sensor.
Hole can be attracted to the defective interface zone of tool by applying negative pressure on the grid of transmission transistor, from
And inhibit dark current.But when transmission transistor is closed, the photo-generated carrier remained in its channel is easy to flow backward to
In photodiode, so-called feedthrough (feedthrough) phenomenon occurs, to influence the quality of generation image.In addition, to
Reaction speed and the picture quality of cmos image sensor are improved it is necessary to improve the efficiency of transmission of transmission transistor.
Therefore, in order to overcome the above problem, this application provides a kind of biographies of polysilicon gate with non-uniform doping
Defeated transistor.Since the polysilicon gate of non-uniform doping can generate different influences to the Potential Distributing in channel region, thus
Make it that stair-stepping distribution be presented.In this way, the transfer efficiency of photo-generated carrier can be improved, again under the action of ladder potential
It can prevent feedthrough phenomenon, to improve picture quality.
Detailed description of the invention
The following detailed description to non-limiting embodiment is read by referring to accompanying drawing, can be more easily to understand
Feature, the objects and advantages of the application.Wherein, the same or similar appended drawing reference represents the same or similar device.
Fig. 1 (a) show the transmission crystal in the cmos image sensor pixel according to the application one embodiment
Pipe structural schematic diagram；
Fig. 1 (b) show Potential Distributing schematic diagram when transmission transistor shown in Fig. 1 (a) is closed；
Fig. 1 (c) show the Potential Distributing schematic diagram when conducting of transmission transistor shown in Fig. 1 (a)；
Fig. 2 (a) show the transmission crystal in the cmos image sensor pixel according to the application one embodiment
Pipe structural schematic diagram；
Fig. 2 (b) show Potential Distributing schematic diagram when transmission transistor shown in Fig. 2 (a) is closed；
Fig. 2 (c) show the Potential Distributing schematic diagram when conducting of transmission transistor shown in Fig. 2 (a)；
Fig. 3 (a) show the transmission crystal in the cmos image sensor pixel according to the application one embodiment
Pipe structural schematic diagram；
Fig. 3 (b) show Potential Distributing schematic diagram when transmission transistor shown in Fig. 3 (a) is closed；And
Fig. 3 (c) show the Potential Distributing schematic diagram when conducting of transmission transistor shown in Fig. 3 (a).
Specific embodiment
The manufacture and use of embodiments herein are discussed further below.However, it should be understood that this application provides
Many feasible inventive concepts that can implement under various specific backgrounds.The specific embodiment discussed is only to illustrate to manufacture
Concrete mode with the application is used, does not limit the scope of the application.
Fig. 1 (a) show the knot of transmission transistor in the cmos image sensor according to shown in the application one embodiment
Structure schematic diagram.It can be P type substrate according to one embodiment of the application, 102,104 can be n-type doping region, with substrate
102 form photodiode, and photodiode receives the light injected from transmission transistor bottom, and generates photo-generated carrier.
The n-type doping region 104 of photodiode can be used as the source electrode of transmission transistor.Transmission transistor further includes that a N-type is mixed
Drain electrode of the miscellaneous floating diffusion region 108 as the transmission transistor.P type substrate can be semiconductor base, also may include half
Conductor substrate and it is laid with epitaxial layer thereon, the material of semiconductor base can be general semiconductor-based such as silicon, germanium, GaAs
Bottom materials.
Transmission transistor further includes gate oxide 120, and the polysilicon gate 110 on gate oxide 120.According to this
One embodiment of application, polysilicon gate are divided into two parts, and the doping type close to the part 111 of source electrode can be P+, i.e. P
Type heavy doping, the doping close to the part 112 of drain electrode can be N+, i.e. N-type heavy doping.111 and 112 be all polysilicon gate 110
A part, each other without interval or separation.Doping concentration is the needs according to design and determination, for example, both mix
Miscellaneous concentration can be greater than 1019, even up to 1020To 1021The order of magnitude.According to another embodiment, close to the part 111 of source electrode
Doping type can be N-, the doping type of part 112 close to drain electrode can be N+.The part of these polysilicon gates is one
Body, no interval or separation each other.
When closing transmission transistor, the control signal Tx of such as -1V can be applied to polysilicon gate 110.Such as Fig. 1 (b)
Shown, the potential of the channel region under polysilicon gate 110 is lower than the potential level of source electrode 104 and drain electrode 108.According to this Shen
One embodiment please, the potential of the channel region below partial polysilicon grid 111 can be such as -0.45V, and part polycrystalline
The potential of channel region below Si-gate 112 can be slightly above the potential of the channel region below partial polysilicon grid 111.
When opening transmission transistor, the control signal Tx of such as 2.8V can be applied to polysilicon gate 110.Such as Fig. 1 (c)
Shown, Potential Distributing gradually rises from source electrode 104 to drain electrode 108.Particularly, the channel region below partial polysilicon grid 111
Potential can differ such as 1V with the potential of the channel region below partial polysilicon grid 112.Due to this potential gradient
In the presence of the photo-generated carrier such as electronics generated by photodiode, so that it may by the source of slave transmission transistor rapidly and efficiently
Pole is transferred to drain electrode.
When being again switched off transmission transistor, grid voltage can be reduced to -1V again, due under partial polysilicon grid 112
The potential of the channel region in face can be higher than the potential of the channel region below partial polysilicon grid 111, therefore remain in channel
The electrons in region flow to floating diffusion region 108 and then are reset under the action of potential gradient, without flowing back to photoelectricity two
Interference in pole pipe, so as to avoid the generation of feedthrough phenomenon and its to image.In the present embodiment, not by polysilicon gate 110
The top of the partial region of the photodiode 104 of covering further includes pinning layer 106.According to another embodiment, in two pole of photoelectricity
104 top of n-type doping region of pipe all has pinning layer 106 (situation is not shown).In addition, including 111 and 112 being formed
In the manufacturing process of partial polysilicon gate 110 may be selected first using ion doping injection etch again to be formed polysilicon gate or
First etching forms gate shapes, and doping injection forms polysilicon gate 110 respectively again.
Fig. 2 (a) show transmission transistor in the cmos image sensor according to documented by another embodiment of the application
Structural schematic diagram.Polysilicon gate 210 may include three parts, close to the P+ doped portion 113 of source electrode, close to the N+ of drain electrode
Doped portion 115, and the undoped part 114 among the two, the part of these polysilicon gates be it is integrated, each other it
Between be not spaced or separate.
It can be loaded on polysilicon gate 210 and close the transmission transistor under the control signal of such as -1V, and loaded for example
The voltage of 2.8V opens the transmission transistor.It is not only more in part since the doping situation of 210 different piece of polysilicon gate is different
The gradient that potential can be generated between the channel region below of crystal silicon grid 113 and 115, undoped partial polysilicon grid 114 with
Also the variation that potential can be generated in lower channel region, as shown in Fig. 2 (b)-(c).In the present embodiment, not by polysilicon gate 210
The top of the partial region of the photodiode 104 of covering further includes pinning layer 106.According to another embodiment, in two pole of photoelectricity
104 top of n-type doping region of pipe all has pinning layer 106 (situation is not shown).In addition, including 113,114 being formed
It etches to form polysilicon gate again with may be selected first to inject using ion doping in the manufacturing process of the polysilicon gate 210 of 115 parts
Pole or first etching form gate shapes, and doping injection forms polysilicon gate 210 respectively again.
Transmission transistor in the cmos image sensor according to documented by the another embodiment of the application shown in Fig. 3 (a)
Structural schematic diagram.Polysilicon gate 310 may include three parts, and close to the P+ doped portion 116 of source electrode, the N+ close to drain electrode mixes
Hetero moiety 119, close to the P- doped portion 117 of P+ doped portion 116, i.e. p-type is lightly doped, close to the N- of N+ doped portion 119
Doped portion 118, i.e. N-type are lightly doped, these partial polysilicon grid are integrated, no interval or separation each other.
The switch state of transmission transistor shown in Fig. 3 can be controlled using control signal similar to the above.It is similar
, rising into a ladder from source electrode 104 to drain electrode 108 is produced in the channel region below of polysilicon gate 310 respectively
Potential Distributing, as shown in Fig. 3 (b)-(c).In the present embodiment, the portion for the photodiode 104 not covered by polysilicon gate 310
Subregional top further includes pinning layer 106.According to another embodiment, above the n-type doping region 104 of photodiode all
With pinning layer 106 (situation is not shown).In addition, forming the polysilicon gate including 116,117,118 and 119 parts
It may be selected first to etch to form polysilicon gate or first etch again using ion doping injection in 310 manufacturing process to form grid
Doping injection forms polysilicon gate 310 to shape respectively again.
The transmission transistor which above-mentioned seed type no matter used, in the state of its unlatching, due to more DOPOS doped polycrystalline silicons
The presence of potential gradient in grid lower channel region, the photo-generated carrier such as electronics generated by photodiode, so that it may fast
Speed is efficiently transferred to drain electrode from the source electrode of transmission transistor.And the electricity in the polysilicon gate channel region below of single doping
Gesture is distributed flat, and therefore, the transfer efficiency of photo-generated carrier will be significantly less than transmission transistor described in the application
Transfer efficiency.
Due under the closed state that is reentered after transmission transistor is opened, non-uniform doping polysilicon gate ditch below
Potential Distributing in road region is still in a degree of ladder distribution, therefore remains in the electrons of channel region in potential ladder
Floating diffusion region 108 is flowed under the action of degree, without flowing back in photodiode, thus avoid feedthrough phenomenon generation and
Its interference to image.Pass through the reset to floating diffusion region, so that it may eliminate the influence of these residual carriers.
According to one embodiment of the application, the polysilicon gate 110,210 or 310 of the transmission transistor shown in Fig. 1-3
On can also have one layer of metal silicide layer, control signal can be applied directly on metal silicide layer.
It can be controlled in the embodiment of the present application using the control signal for being traditionally used for control cmos image sensor
Cmos image sensor.Closing voltage-the 1V and cut-in voltage 2.8V for the transmission transistor spoken of above are only an example.
According to different components size, technique setting can be adjusted the level of the control voltage.In addition, according to the one of the application
A embodiment, for transmission transistor shown in Fig. 1-3, control signal can load more in the part of P+ and/or N+ doping
On crystal silicon grid.
In addition, the transmission transistor in cmos image sensor disclosed in the present application can also include being located at substrate 102
The P-doped zone (not shown) on surface, also known as pinning layer, it is dark caused by the defect for inhibiting silicon and silica surface
Electric current.
In addition, at least part part in the polysilicon gate of the transmission transistor covers channel region, at least in addition
Part covers at least part of photodiode.
The transmission transistor is also possible to buried channel transistor, that is to say, that its channel region is apart from semiconductor substrate surface
With a certain distance.
Manufacture the process flow and traditional technique of the transmission transistor in cmos image sensor disclosed in the present application
Process the difference is that, to generate the polysilicon gate with non-uniform doping.According to one embodiment, etching can be first passed through
Technique forms the polysilicon gate of required size, then carries out doping heterogeneous to the grid again.Alternatively, according to another reality
Example is applied, non-uniform doping first can be carried out to the polysilicon layer on transmission transistor gate oxide layers, then again to the polysilicon
Layer performs etching the grid to form required size.
Those skilled in the art are easy for learning, can change material and method within the scope of application, such as
Do not need in the case where making the creative labor, so that it may by n-type doping and p-type doping mutually exchange, corresponding carrier by
It is hole that electronics, which is exchanged, and constructs the transmission transistor complementary with the embodiment of the present application.It should also be understood that in addition to
In illustrating except the specific context of embodiment, the utility model provides many applicable inventive concepts.Correspondingly, appended
Claim is intended to include the range at them by such process, machine, manufacture, substance synthesis, device, method or step
It is interior.
Claims (13)
1. a kind of back-illuminated cmos image sensors, which is characterized in that the cmos image sensor includes:
Photodiode, by forming the second conductivity type regions in the first conductive type semiconductor substrate, to form light
Electric diode, wherein second conductivity type regions are as photo-generated carrier collecting region；
Floating diffusion region is formed in the first conductive type semiconductor substrate, has the doping of the second conduction type；And
Transmission transistor, the source electrode of the transmission transistor be the photodiode second conductivity type regions,
Drain electrode is the floating diffusion region；The transmission transistor further includes polysilicon gate, the polysilicon gate covering transmission
The transmission channel region of transistor, and at least partly cover the photodiode；The polysilicon gate is mixed using non-homogeneous
It is miscellaneous, the distribution so that potential in the channel region of the transmission transistor is stepped,
Wherein the transmission transistor further includes gate oxide, and the channel region of the transmission transistor connects with the gate oxide
The drain electrode is extended to from the source electrode in the case where touching, and
Wherein the polysilicon gate of non-uniform doping includes at least two grid subregions, wherein close to two pole of photoelectricity
The first grid subregion of pipe has the first conduction type heavy doping, and the first grid subregion at least partly covers the light
Electric diode, the second grid subregion close to the floating diffusion region have the second conduction type heavy doping, the second gate
Pole subregion at least partly covers the channel of the transmission transistor.
2. cmos image sensor according to claim 1, which is characterized in that the transmission transistor further includes being located at institute
State between the second conductivity type regions of photodiode and the semiconductor substrate surface with first conduction type every
From area.
3. cmos image sensor according to claim 1, which is characterized in that the polysilicon gate is along close to described floating
It successively includes: the second grid subregion, that diffusion region, which is set, by the transmission transistor channel to the photodiode
Four grid subregions are lightly doped with the second conduction type, there is third grid subregion the first conduction type to be lightly doped, is described
First grid subregion.
4. cmos image sensor according to claim 1, which is characterized in that the polysilicon gate is along close to described floating
Setting diffusion region to the close photodiode successively includes: the second grid subregion, undoped third grid
Region, the first grid subregion.
5. cmos image sensor according to claim 1, which is characterized in that also covered in the polysilicon gate pole surface
It is stamped metal silicide layer.
6. cmos image sensor according to claim 1, which is characterized in that first conduction type is p-type, institute
Stating the second conduction type is N-type.
7. a kind of forming method of back-illuminated cmos image sensors characterized by comprising
The second conduction type doped region is formed in the first conduction type dope semiconductor substrates, to form two pole of photoelectricity
Pipe, wherein the second conduction type doped region is as photo-generated carrier collecting region；
The floating diffusion region being located in the first conductive type semiconductor substrate is formed, the floating diffusion region has second to lead
Electric type doping；
Transmission transistor is formed, the source electrode of the transmission transistor is second conductivity regions of the photodiode
Domain drains as the floating diffusion region；The transmission transistor further includes polysilicon gate, and the polysilicon gate covers institute
The channel region of transmission transistor is stated, and at least partly covers the photodiode, wherein the transmission transistor further includes grid
Oxide layer, the channel region of the transmission transistor extend in the case where contacting with the gate oxide from the source electrode described
Drain electrode；
The polysilicon gate is formed using non-uniform doping, so that along close to the floating diffusion region to the close photoelectricity two
Potential is stepped distribution in the transmission transistor channel region of pole pipe；
Form several metal interconnection layers for being located at the upper surface of substrate；And
Wherein the polysilicon gate of non-uniform doping includes at least two grid subregions, wherein close to two pole of photoelectricity
The first grid subregion of pipe has the first conduction type heavy doping, and the first grid subregion at least partly covers the light
Electric diode, the second grid subregion close to the floating diffusion region have the second conduction type heavy doping, the second gate
Pole subregion at least partly covers the channel of the transmission transistor.
8. the forming method of cmos image sensor according to claim 7, which is characterized in that it is brilliant to be initially formed the transmission
Body pipe rest part re-forms the floating diffusion region in the first conductive type semiconductor substrate.
9. the forming method of cmos image sensor according to claim 7, which is characterized in that form the transmission crystal
Before the step of pipe, further includes: the photodiode second conductivity type regions to the semiconductor substrate surface
Between formed have the first conduction type isolated area.
10. the forming method of cmos image sensor according to claim 7, which is characterized in that the polysilicon gate
It is sequentially formed with along close to the floating diffusion region to close to the photodiode: the second grid subregion, the 4th grid
Pole subregion is lightly doped with the second conduction type, there is third grid subregion the first conduction type to be lightly doped, described first
Grid subregion.
11. the forming method of cmos image sensor according to claim 7, which is characterized in that the polysilicon gate
Along close to the floating diffusion region to being sequentially formed with close to the photodiode: the second grid subregion, without mixing
Miscellaneous third grid subregion, the first grid subregion.
12. the forming method of cmos image sensor according to claim 7, which is characterized in that it is brilliant to form the transmission
After the step of body pipe, further includes: form the metal silicide layer covered on the polysilicon gate pole surface.
13. the forming method of cmos image sensor according to claim 7, which is characterized in that described first is conductive
Type is p-type, and the second conduction type is N-type.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410172641.5A CN105097850B (en) | 2014-04-25 | 2014-04-25 | Cmos image sensor and its manufacturing method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410172641.5A CN105097850B (en) | 2014-04-25 | 2014-04-25 | Cmos image sensor and its manufacturing method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN105097850A CN105097850A (en) | 2015-11-25 |
| CN105097850B true CN105097850B (en) | 2019-03-29 |
Family
ID=54577915
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201410172641.5A Active CN105097850B (en) | 2014-04-25 | 2014-04-25 | Cmos image sensor and its manufacturing method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN105097850B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113382184B (en) * | 2021-06-09 | 2023-12-01 | 上海矽印科技有限公司 | Method for automatically adjusting high dynamic range pixel by gain |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7288788B2 (en) * | 2004-12-03 | 2007-10-30 | International Business Machines Corporation | Predoped transfer gate for an image sensor |
| KR100997326B1 (en) * | 2007-12-27 | 2010-11-29 | 주식회사 동부하이텍 | Image Sensor and Methof for Manufacturing Thereof |
| US8299505B2 (en) * | 2011-02-17 | 2012-10-30 | International Business Machines Corporation | Pixel sensor cell with a dual work function gate electode |
| US9698185B2 (en) * | 2011-10-13 | 2017-07-04 | Omnivision Technologies, Inc. | Partial buried channel transfer device for image sensors |
| JP6127128B2 (en) * | 2012-03-20 | 2017-05-10 | ヘプタゴン・マイクロ・オプティクス・ピーティーイー・エルティーディーＨｅｐｔａｇｏｎ Ｍｉｃｒｏ Ｏｐｔｉｃｓ Ｐｔｅ．Ｌｔｄ． | Demodulated pixel with pn structure gate |
| CN203826392U (en) * | 2014-04-25 | 2014-09-10 | 格科微电子（上海）有限公司 | Back-illuminated CMOS image sensor |
-
2014
- 2014-04-25 CN CN201410172641.5A patent/CN105097850B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN105097850A (en) | 2015-11-25 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR101301900B1 (en) | Co-implant for backside illumination sensor | |
| CN104377216B (en) | Image sensor and fabricating method of image sensor | |
| TWI740958B (en) | Photogate for front-side-illuminated infrared image sensor and method of manufacturing the same | |
| CN103035715A (en) | Transistors, methods of manufacturing thereof, and image sensor circuits with reduced rts noise | |
| CN103811510B (en) | Pixel cell of imageing sensor and forming method thereof | |
| CN105161462A (en) | Method for improving carrier transmission efficiency of backside illumination image sensor | |
| CN101221966A (en) | CMOS image sensor and method for manufacturing the same | |
| CN102272930A (en) | Solid state imaging device | |
| US20210111201A1 (en) | Image Sensor Structure and Method of Forming the Same | |
| CN103413816B (en) | Dot structure of cmos image sensor and forming method thereof | |
| CN109065557A (en) | Back-illuminated cmos image sensors and forming method thereof | |
| CN102347337A (en) | CMOS (complementary metal-oxide semiconductor) image sensor with irradiation on back surface | |
| CN203826392U (en) | Back-illuminated CMOS image sensor | |
| CN109560098A (en) | Imaging sensor and forming method thereof | |
| CN105518861B (en) | Gate controlled charge modulation device for cmos sensor | |
| CN105097850B (en) | Cmos image sensor and its manufacturing method | |
| CN100428487C (en) | Photodiode of cmos image sensor and method for manufacturing the same | |
| CN102593139A (en) | CMOS (Complementary Metal-Oxide-Semiconductor Transistor) image sensor | |
| CN102479793B (en) | Complementary metal-oxide-semiconductor (CMOS) image sensor and manufacture method thereof | |
| CN110176467A (en) | Cmos image sensor and its manufacturing method | |
| CN101304035B (en) | Image sensor and method for forming the same | |
| CN101304036B (en) | Image sensor and method for forming the same | |
| CN104269419B (en) | Image sensor and forming method thereof | |
| CN104332481B (en) | Imaging sensor and forming method thereof | |
| WO2009020318A2 (en) | Unit pixel suppressing dead zone and afterimage |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |