CN101567337A - CMOS image sensor and preparation method thereof - Google Patents
CMOS image sensor and preparation method thereof Download PDFInfo
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- CN101567337A CN101567337A CNA2009100521900A CN200910052190A CN101567337A CN 101567337 A CN101567337 A CN 101567337A CN A2009100521900 A CNA2009100521900 A CN A2009100521900A CN 200910052190 A CN200910052190 A CN 200910052190A CN 101567337 A CN101567337 A CN 101567337A
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Abstract
The invention discloses a CMOS image sensor and a preparation method thereof, which comprises the following steps of: forming an apparatus isolating layer, a grid and a diffusion zone on a semiconductor underlay provided with an epitaxial layer, using a mask to cover the grid and the diffusion zone and exposing a photodiode area adjacent to the grid, forming a first impurity ion area in the photodiode area through first ion injection, and conducting secondary ion injection in the photodiode area to form a second impurity ion area in the photodiode area near the area of the grid. The method uses the mask shadow effect to form a step potential distribution structure in the photodiode in the manufacturing process of the CMOS image sensor, thereby being capable of improving the transmission speed of electric charges to the floating diffusion zone, reducing image lag, reducing noise and improving the imaging quality of the CMOS image sensor.
Description
Technical field
Designing semiconductor of the present invention is made and the photoelectronic imaging technical field, particularly a kind of cmos image sensor and manufacture method thereof.
Background technology
Imageing sensor is the semiconductor device that picture signal is changed into the signal of telecommunication, and imageing sensor is divided into charge coupled sensor (CCD) and cmos image sensor.
Though CCD good imaging quality, but because manufacturing process complexity, have only the manufacturer of minority to grasp, so cause manufacturing cost high, particularly large-scale CCD, price is very high, and its complicated drive pattern, high energy consumption and multistage photoetching process, make to have a lot of difficulties in its manufacture craft, can not satisfy the demand of product.
The manufacturing technology of CMOS and general computer chip do not have difference, mainly be to utilize silicon and these two kinds of semiconductors that element is made of germanium, make the semiconductor of its band N that coexisting on CMOS (band-) and P (band+) level, image be noted down and be interpreted to these two electric currents that complementary effect produced can by processed chip.
In recent years, because the low energy consumption of cmos image sensor, and few relatively lithographic process steps makes its manufacturing process simple relatively, and cmos image sensor allows control circuit, signal processing circuit and analog to digital converter to be integrated on the chip, make in its product that goes for various sizes and be widely used in various fields, so cmos image sensor receives much attention as the image processor of future generation that overcomes the CCD shortcoming.
Yet cmos image sensor is easily introduced various noises (noise) in circuit, thereby has limited its application in the high-end field to a certain extent.
See also Fig. 1, it is depicted as the circuit diagram of the unit pixel of single pixel 4T type CMOS graphical sensory device in the prior art.
Cmos image sensor has and comprises and be used to read the photodiode 110 of light and the unit pixel of four N type MOS transistor 120～150 in the prior art.
110 one-tenth ends of photodiode shape at the active area at the semiconductor-based end.Four transistors are respectively transfering transistor 120, reset transistor 130, driving transistors 140 and select transistor 150.
Photodiode 110 is used to produce photoelectron; Floating diffusion region 160 is used to store the electronics that is produced by described photodiode 110; Transmission transistor 120 is connected between described photodiode 110 and the described floating diffusion region 160, and the electron transport that is used for being produced by described photodiode 110 is to described floating diffusion region 160; Reset transistor 130 is connected between power supply voltage terminal 170 and the described floating diffusion region 160, is used for being stored in the electron discharge of described floating diffusion region 160 with the described floating diffusion region 160 of resetting; Driving transistors 140 is used to respond from the output signal of described photodiode 110 and serves as the source follower buffer amplifier; Select transistor 150, be connected to described driving transistors 140, be used to carry out addressing operation.
During work, reset transistor 130 and transmission transistor 120 are opened simultaneously, and photodiode 110 is in complete spent condition; Close reset transistor 130 and transmission transistor 120, photodiode 110 absorbing light are to produce electronics thereupon, and a period of time makes it fill electronics.Follow conducting transfering transistor 120, the electronics that photodiode 110 produces moves to floating diffusion region 160, and the electronics that moves to floating diffusion region 160 produces output signals by driving transistors 140.
See also Fig. 2, it is depicted as the circuit diagram of sharing the cmos image sensor of pixel in the prior art.
Its operation principle and above-mentioned single pixel 4T type CMOS graphical sensory device are similar, the different sequential of choosing that only is transmission transistor 220.
Can see that from above-mentioned operation principle cmos image sensor adopts switching mode, and use the output of a plurality of MOS transistor probe unit pixels.Limitation during cmos image sensor work needs the regular hour with regard to being the transmission of electric charge from the photodiode to the floating diffusion region.When if preceding pulsatile once reads, the electronics that photodiode exposure back produces can not be transferred in the floating diffusion region fully rapidly, like this when pulse is read next time, before once do not have electrons transmitted just can be added to this transmission on, thereby produce the incomplete phenomenon of charge transfer, cause occurring the problem of image lag (Image Lag).
Summary of the invention
The present invention is intended to solve in the prior art, because the electronics that the exposure of the photodiode in cmos image sensor back is produced can not be transferred in the floating diffusion region fully rapidly, causes occurring the problem of image lag.
In view of this, the invention provides a kind of manufacture method of cmos image sensor, may further comprise the steps:
Have in growth on the Semiconductor substrate of epitaxial loayer and form device isolation layer, grid and diffusion region;
Utilize mask to cover described grid and described diffusion region, expose photodiode region adjacent to described grid;
By the first time ion be infused in the described photodiode region and form first impurity ion region;
Carry out the ion injection second time at described photodiode region, the zone near described grid in described photodiode region forms second impurity ion region.
Further, the described ion injection second time is vertically to tilt to carry out the ion injection near described grid.
Further, the angle of described inclination is 30 ° to 45 °.
Further, energy, the dosage that the described second time, ion injected all is lower than the described ion injection first time.
Further, described second impurity ion region is more shallow than described first impurity ion region.
Further, described separator is a fleet plough groove isolation structure.
The present invention also provides a kind of cmos image sensor, comprising: photodiode, have step-like Potential Distributing structure, and be used to produce photoelectron; Floating diffusion region is used to store the electronics that is produced by described photodiode; Transmission transistor is connected between described photodiode and the described floating diffusion region, and the electron transport that is used for being produced by described photodiode is to described floating diffusion region; Reset transistor is connected between power supply voltage terminal and the described floating diffusion region, is used for being stored in the electron discharge of described floating diffusion region with the described floating diffusion region of resetting; Driving transistors is used for response and serves as the source follower buffer amplifier from described photodiode output signals; Select transistor, be connected to described driving transistors, be used to carry out addressing operation.
Further, described step-like Potential Distributing structure first and second impurity ion region in described photodiode, superposeing.
Further, described second impurity ion region is more shallow than described first impurity ion region.
In sum, the manufacture method of cmos image sensor provided by the invention, in making cmos image sensor, utilize the mask shadow effect in photodiode, to form step-like Potential Distributing structure, and then can improve the transmission speed of electric charge to floating diffusion region, reduce image lag (Image Lag), reduced the appearance of noise, improved the quality of cmos image sensor imaging effect.
Description of drawings
Figure 1A is depicted as the unit pixel schematic layout pattern of single pixel 4T type cmos image sensor in the prior art;
Figure 1B is depicted as the unit pixel equivalent circuit theory figure of single pixel 4T type cmos image sensor in the prior art;
Figure 2 shows that the circuit diagram of sharing the cmos image sensor of pixel in the prior art;
The cross-sectional view that the method that provides according to one embodiment of the invention is made cmos image sensor is provided Fig. 3 A to Fig. 3 D.
Figure 4 shows that the circuit diagram of the cmos image sensor that another embodiment of the present invention provides;
The potential profile of the method manufacturing cmos image sensor that provides according to one embodiment of the invention is provided.
Embodiment
For purpose of the present invention, feature are become apparent, provide preferred embodiment also in conjunction with the accompanying drawings, the invention will be further described.
Please, be depicted as the cross-sectional view that the method that provides according to the embodiment of the invention is made cmos image sensor in conjunction with referring to Fig. 3 A to Fig. 3 E.
It is example that the embodiment of the invention has the Semiconductor substrate of P type epitaxial loayer with growth.
See also Fig. 3 A, by epitaxial process, form lightly doped P type epitaxial loayer 302 in Semiconductor substrate 301, wherein, Semiconductor substrate 301 is formed by highly doped P type silicon.This moment, epitaxial loayer 302 had big and dark depletion region in photodiode region, was used to collect the capacity of the low-voltage photodiode of electric charge with raising, and improved light sensitivity.In the Semiconductor substrate 301 that includes epitaxial loayer 302, form shallow ditch groove structure (STI) layer 303, be used for the isolation of device.
Then, on the whole surface of the epitaxial loayer 302 that includes STI layer 303, form gate insulator 304 and conductive layer (as, doped polycrystalline silicon layer) successively, carry out selective removal, thereby form grid 305, the formation of CVD method be handled or be utilized to gate insulator 304 can with thermal oxide.
See also Fig. 3 B, 306 cover on the surface of the Semiconductor substrate that comprises grid 305 with photoresist, and photoresist 306 exposed and development treatment, make it cover photodiode region, and expose source electrode and drain region, make with photoresist 306 as mask, inject source electrode and the drain region that n type foreign ion is injected into exposure, form lightly doped n type expansion area 307 by ion.
See also Fig. 3 C, after removing photoresist 306 fully, photoresist 308 is coated on the whole surface of Semiconductor substrate 101, then photoresist 308 is carried out patterning, expose photodiode region by exposure and development.Photoresist 308 behind the use image conversion is injected into epitaxial loayer 302 by the ion injection first time with n type dopant ion, thereby forms first impurity ion region 309 in photodiode region as mask, forms photodiode.
See also Fig. 3 D, utilize the photoresist 308 behind the image conversion to continue as mask, by the second time ion inject n type dopant ion be injected into epitaxial loayer 302, the zone near described grid in described photodiode region forms second impurity ion region 310.
Ion injection for the second time is vertically to tilt to carry out ion injection, 30 ° to 45 ° of the angles of its inclination near grid 305.
Energy, the dosage of ion injection for the second time all is lower than the described ion injection first time, and second impurity ion region, 310 to the first impurity ion regions 309 of Xing Chenging are shallow like this, thereby form step-like Potential Distributing structure at photodiode region.
Please in conjunction with referring to Fig. 5, the method that it is depicted as one embodiment of the invention provides is made the potential profile of cmos image sensor.
The photodiode region electromotive force of grid 305 sides of close transfering transistor is higher, because the relation of photodiode internal electrical potential difference makes the electronics that produces mainly accumulate in second impurity ion region 310 of photodiode, when opening transmission transistor, photodiode region is lower than suitable amount of grid 305 electromotive forces, this structure effectively reduces the channel resistance near grid 305, improved the speed that electric charge can flow to diffusion region 307 greatly.
Utilize cmos image sensor that the manufacture method of the cmos image sensor that the embodiment of the invention provides produces on the one hand the electric charge that produces of photodiode because the relation of photodiode internal electrical potential difference makes the electronics that produces mainly accumulate in second impurity ion region of photodiode, after transmission transistor is opened, electric charge can flow to floating diffusion region rapidly, thereby improved the speed of charge transfer greatly, effectively reduced the problem of image lag.
On the other hand,, make electronics move to corresponding the reducing of channel resistance of transfering transistor Tx because ion injects second impurity ion region 310 that forms for the second time, after transmission transistor is opened, the easier inflow floating diffusion region of the electronics in the photodiode; Simultaneously also promoted reset transistor speed, thereby further improved the speed of electric transmission, the corresponding frame frequency (Frame Rate) that improves the image transmission has improved the quality of imaging.
See also Fig. 4, it is depicted as the circuit diagram of the cmos image sensor that another embodiment of the present invention provides.
This cmos image sensor comprises: photodiode 400, have step-like Potential Distributing structure, and be used to produce photoelectron; Described step-like Potential Distributing structure first and second impurity ion region 411,412 in described photodiode, superposeing; Second impurity ion region 412 is than described first impurity ion region shallow 411.
Floating diffusion region 460 is used to store the electronics that is produced by described photodiode 400;
Transmission transistor 420 is connected between described photodiode and the described floating diffusion region, and the electron transport that is used for being produced by described photodiode is to described floating diffusion region;
Reset transistor 430 is connected between power supply voltage terminal 470 and the described floating diffusion region 460, is used for being stored in the electron discharge of described floating diffusion region 460 with the described floating diffusion region 460 of resetting;
Driving transistors 440 is used to respond from the output signal of described photodiode 400 and serves as the source follower buffer amplifier;
Select transistor 450, be connected to described driving transistors 440, be used to carry out addressing operation.
In sum, the manufacture method of the cmos image sensor that the embodiment of the invention provides, in making cmos image sensor, utilize the mask shadow effect in photodiode, to form step-like Potential Distributing structure, and then can improve the transmission speed of electric charge to floating diffusion region, reduce image lag (ImageLag), reduced the appearance of noise, improved the image quality of cmos image sensor.
Though the present invention discloses as above with preferred embodiment; right its is not in order to limit the present invention; have in the technical field under any and know the knowledgeable usually; without departing from the spirit and scope of the present invention; when can doing a little change and retouching, so protection scope of the present invention is as the criterion when looking claims person of defining.
Claims (9)
1. the manufacture method of a cmos image sensor is characterized in that, may further comprise the steps:
Have in growth on the Semiconductor substrate of epitaxial loayer and form device isolation layer, grid and diffusion region;
Utilize mask to cover described grid and described diffusion region, expose photodiode region adjacent to described grid;
By the first time ion be infused in the described photodiode region and form first impurity ion region;
Carry out the ion injection second time at described photodiode region, the zone near described grid in described photodiode region forms second impurity ion region.
2. the manufacture method of cmos image sensor according to claim 1 is characterized in that, the described ion injection second time is vertically to tilt to carry out the ion injection near described grid.
3. the manufacture method of cmos image sensor according to claim 2 is characterized in that, 30 ° to 45 ° of the angles of described inclination.
4. the manufacture method of cmos image sensor according to claim 1 is characterized in that, energy, the dosage that the described second time, ion injected all is lower than the described ion injection first time.
5. the manufacture method of cmos image sensor according to claim 1 is characterized in that, described second impurity ion region is more shallow than described first impurity ion region.
6. the manufacture method of cmos image sensor according to claim 1 is characterized in that, described separator is a fleet plough groove isolation structure.
7. a cmos image sensor is characterized in that, comprising:
Photodiode has step-like Potential Distributing structure, is used to produce photoelectron;
Floating diffusion region is used to store the electronics that is produced by described photodiode;
Transmission transistor is connected between described photodiode and the described floating diffusion region, and the electron transport that is used for being produced by described photodiode is to described floating diffusion region;
Reset transistor is connected between power supply voltage terminal and the described floating diffusion region, is used for being stored in the electron discharge of described floating diffusion region with the described floating diffusion region of resetting;
Driving transistors is used for response and serves as the source follower buffer amplifier from described photodiode output signals;
Select transistor, be connected to described driving transistors, be used to carry out addressing operation.
8. cmos image sensor according to claim 7 is characterized in that, described step-like Potential Distributing structure first and second impurity ion region for superposeing in described photodiode.
9. cmos image sensor according to claim 7 is characterized in that, described second impurity ion region is more shallow than described first impurity ion region.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102222681A (en) * | 2011-07-05 | 2011-10-19 | 上海宏力半导体制造有限公司 | Complementary metal oxide semiconductor (CMOS) image sensor and manufacturing method thereof |
| CN102222680A (en) * | 2011-07-05 | 2011-10-19 | 上海宏力半导体制造有限公司 | Method for manufacturing CMOS (complementary metal-oxide-semiconductor transistor) image sensor |
| CN102709303A (en) * | 2012-06-21 | 2012-10-03 | 上海华力微电子有限公司 | Cmos image sensor and manufacturing method thereof |
| CN102738190A (en) * | 2012-07-03 | 2012-10-17 | 上海华力微电子有限公司 | Cmos image sensor and manufacturing method thereof |
| CN102222681B (en) * | 2011-07-05 | 2016-12-14 | 上海华虹宏力半导体制造有限公司 | Cmos image sensor and manufacture method |
| CN107665898A (en) * | 2016-07-28 | 2018-02-06 | 中芯国际集成电路制造(上海)有限公司 | A kind of cmos image sensor and preparation method thereof and electronic installation |
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| CN1992209A (en) * | 2005-12-28 | 2007-07-04 | 东部电子股份有限公司 | Method for manufacturing cmos image sensor |
| CN101211940A (en) * | 2006-12-29 | 2008-07-02 | 东部高科股份有限公司 | CMOS image sensor and method of manufacturing thereof |
| CN101238583A (en) * | 2005-08-13 | 2008-08-06 | （株）赛丽康 | Image sensor pixel and fabrication method thereof |
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Patent Citations (4)
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| US6232626B1 (en) * | 1999-02-01 | 2001-05-15 | Micron Technology, Inc. | Trench photosensor for a CMOS imager |
| CN101238583A (en) * | 2005-08-13 | 2008-08-06 | （株）赛丽康 | Image sensor pixel and fabrication method thereof |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102222681A (en) * | 2011-07-05 | 2011-10-19 | 上海宏力半导体制造有限公司 | Complementary metal oxide semiconductor (CMOS) image sensor and manufacturing method thereof |
| CN102222680A (en) * | 2011-07-05 | 2011-10-19 | 上海宏力半导体制造有限公司 | Method for manufacturing CMOS (complementary metal-oxide-semiconductor transistor) image sensor |
| CN102222681B (en) * | 2011-07-05 | 2016-12-14 | 上海华虹宏力半导体制造有限公司 | Cmos image sensor and manufacture method |
| CN102709303A (en) * | 2012-06-21 | 2012-10-03 | 上海华力微电子有限公司 | Cmos image sensor and manufacturing method thereof |
| CN102738190A (en) * | 2012-07-03 | 2012-10-17 | 上海华力微电子有限公司 | Cmos image sensor and manufacturing method thereof |
| CN102738190B (en) * | 2012-07-03 | 2015-04-22 | 上海华力微电子有限公司 | Cmos image sensor and manufacturing method thereof |
| CN107665898A (en) * | 2016-07-28 | 2018-02-06 | 中芯国际集成电路制造(上海)有限公司 | A kind of cmos image sensor and preparation method thereof and electronic installation |
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Application publication date: 20091028 |