CN100433349C - Active pioxel sensor - Google Patents
Active pioxel sensor Download PDFInfo
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- CN100433349C CN100433349C CNB2005100551325A CN200510055132A CN100433349C CN 100433349 C CN100433349 C CN 100433349C CN B2005100551325 A CNB2005100551325 A CN B2005100551325A CN 200510055132 A CN200510055132 A CN 200510055132A CN 100433349 C CN100433349 C CN 100433349C
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- sensing cell
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Abstract
The present invention relates to an active pixel sensor. A grid of a transistor is arranged away from the juncture of an insulating area; as a consequence, a depletion area below the grid can not be in direct contact with the insulating area, which can avoid current leakage caused by the damage of the insulating area. The active pixel sensor comprises the insulating area, a light sensitive diode, a guard ring, a first transistor and a second transistor, wherein the light sensitive diode is arranged in a semiconductor substrate and provided with a first doping area; the guard ring annularly surrounds the first doping area and is provided with a gap and arranged on the juncture of the insulating area on the periphery of the first doping area; the first transistor is provided with a first grid electrically connected with the first doping area; the second transistor and the first transistor share a drain electrode, and the first doping area is electrically connected with a source electrode of the second transistor; the second transistor is provided with a second grid arranged on the semiconductor substrate in the position of the gap, and the second grid is not overlapped to the insulating area.
Description
Technical field
(active pixel sensor APS), particularly relates to a kind of CMOS (Complementary Metal Oxide Semiconductor) (complementary metal-oxide semiconductor, CMOS) CMOS active pixel sensor of element of comprising to the present invention relates to a kind of CMOS active pixel sensor.
Background technology
CMOS active pixel sensor is a kind of general solid-state image sensing element.Because CMOS active pixel sensor comprises high-k metal gate devices, therefore be called the CMOS image sensor again, it utilizes traditional semiconductor technology to make, has the advantage that cost of manufacture is cheap and component size is less, make the CMOS image sensor have and day by day replace carrier coupling device (charge-coupled device, trend CCD).In addition, the CMOS image sensor also has high-quantum efficiency (quantum efficiency) and low noise advantages such as (read-out noise), therefore has been widely used on personal computer camera (PCcamera) and the digital camera electronic products such as (digital camera).
General CMOS active pixel sensor is made of a plurality of active pixel sensing cells, and each active pixel sensing cell comprises a light sensitive diode that is used for the sensing intensity of illumination, and three metal-oxide semiconductor (metal-oxide semiconductor, MOS) transistor is respectively the reset transistor (reset transistor) of being used as replacement element (reset MOS), the column selection transistor (row-select transistor) of being used as the Current draw transistor of Current draw element (current source follower) and being used as column select switch (row selector).Wherein, light sensitive diode mainly comes the processing signals data according to the photoelectric current that its optical sensing area produced, for example optical sensing area is lost electric current (light current) representation signal (signal) in the leakage that produced by light state, optical sensing area is lost electric current (dark current) in the leakage that is not subjected to light state and is produced and is then represented noise (noise), so light sensitive diode can utilize the strong and weak mode of signal noise ratio to come the processing signals data.
Please refer to Fig. 1, Fig. 1 is the schematic diagram of an existing active pixel sensing cell 10.Active pixel sensing cell 10 comprises a light sensitive diode 12, a reset transistor 14, a Current draw transistor 16 and a column selection transistor 18.Wherein, the source of reset transistor 14 is electrically connected on the grid of light sensitive diode 12 and Current draw transistor 16.When active pixel sensing cell 10 running, by opening or close reset transistor 14 voltage of light sensitive diode 12 of can resetting, and, finish sensitization and signal processing by the signal noise ratio that the corresponding time of computing is produced.
Please refer to Fig. 2, Fig. 2 is the component placement top view of active pixel sensing cell 10 shown in Figure 1, wherein, is simplicity of illustration, and display column is not selected transistor 18 in Fig. 2.The both sides of the grid 14a of reset transistor 14 and the grid 16a of Current draw transistor 16 are all N+ doped region (N+dopedregion) 20, as transistorized source electrode or drain electrode, similarly, the light sensitive diode 12 of active pixel sensing cell 10 also is a N+ doped region 20, is arranged at (figure does not show) in a p type wells (P-well) or the P type substrate (P-substrate).Lead 22 is used for being electrically connected grid 16a and light sensitive diode 12, and lead 24 is used for making grid 14a to be electrically connected on reset voltage V
Reset, lead 26 then is used for making doped region 20 to be electrically connected on a circuit operation voltage (circuit operating voltage) V
DdIn addition, active pixel sensing cell 10 is centered on by an insulation layer 28, with each active pixel sensing cell 10 that insulate.
Have now when being manufactured with the doped region 20 of source pixel sensing cell 10, utilize an ion implantation technology to form N type ion doped region at p type wells or P type substrate top layer.With the p type wells is example, can arsenic (As) as admixture, inject energy and be about 80KeV and carry out ion implantation technology be about 10 so that doped region 20 has one
15Cm
-2Implantation concentration.And because N+ doped region 20 has different admixture kenels with p type wells, therefore engage (junction) zone at the adjacent PN of N+ doped region 20 and p type wells and can produce a depletion region (depletion region), as the zone of light sensitive diode 12 induction light electric currents.Yet, under this existing structure, depletion region can contact with insulation layer 28, as dashed circle sign place among Fig. 2, cause depletion region not being subjected to produce more leakage something lost electric current under the light situation, particularly when insulation layer 28 has flaw, be not subjected to the depletion region of light may be initiated a large amount of something lost electric currents that leak of generation, cause signal noise ratio to reduce, and have influence on the correctness of sensitization.
Be not subjected to the leakage under the light to lose electric current for improving existing structure to reduce photosensitive area, industry works out the structure of another kind of active pixel sensing cell, its photosensitive area periphery at light sensitive diode is provided with a retaining ring (guardring), be not subjected to the leakage under the light to lose electric current and improve signal to reduce, and then improving the sensing degree of the optical sensing area of light sensitive diode noise ratio.
Please refer to Fig. 3, Fig. 3 has the component placement top view of high signal to the active pixel sensing cell of noise ratio for existing one.For ease of explanation, continue to use the component symbol of Fig. 2 among Fig. 3 with Fig. 2 components identical.As shown in Figure 3, the optical sensing area of light sensitive diode 12 is made of the N+ doped region 20 of part, is provided with a retaining ring 30 around it.The formation method of retaining ring 30 is carried out P type ion implantation technology in the periphery of N+ doped region 20, engages P type retaining ring 30 to form one.Yet in order to increase the channel semiconductor width of reset transistor 14, grid 14a must rise to insulation layer 28 to the forward position, makes the active region of being located at grid 14a below also form depletion region, and contacts with insulation layer 28, as dashed circle place among Fig. 3.In the case, can cause depletion region to produce equally and leak the something lost electric current, and be used as noise, and influence the sensitization correctness of active pixel sensing cell 10 by light sensitive diode 12.
From the above, how to design the structure (for example insulation layer) of avoiding depletion region and having heavily stressed and a high defect concentration and contact, to improve the photosensitive effect of active pixel sensing cell, the direction of demanding urgently studying for industry still.
Summary of the invention
Therefore main purpose of the present invention is to provide a kind of CMOS active pixel sensor that can avoid depletion region to contact with insulation layer, to solve the problem of above-mentioned existing CMOS active pixel sensor.
According to the present invention, disclose a kind of active pixel sensing cell, it comprises an insulation layer, a light sensitive diode, a retaining ring, a first transistor and a transistor seconds.Insulation layer is located in the semiconductor substrate, around this active pixel sensing cell setting and isolate this active pixel sensing cell.Wherein, other element of insulation layer and this active pixel sensing cell has insulation layer boundary.Light sensitive diode was arranged in this semiconductor-based end, and had one first doped region, as optical sensing area.First doped region of retaining ring ring-type Sensurround optical diode, and have a breach.In addition, retaining ring is arranged at the insulation layer intersection of the first doped region periphery.The first transistor then has a first grid, is electrically connected on first doped region, and has a shared drain electrode with transistor seconds.The source electrode of transistor seconds is electrically connected on first doped region, and has a second grid, is arranged at at the semiconductor-based end of retaining ring indentation, there, and does not have a common boundary overlapping with insulation layer.
Because the retaining ring of active pixel sensing cell of the present invention is provided with along the insulation layer intersection of insulation layer and other element of active pixel sensing cell (for example doped region), and second grid is in close proximity to retaining ring and be provided with, therefore second grid can not be arranged at the insulation layer intersection, the semiconductor-based end that can guarantee the second grid below, is when forming depletion region, can not produce leakage because of contacting and lose electric current and reduce signal noise ratio, can improve the sensing correctness of active pixel sensing cell with insulation layer.
Description of drawings
Fig. 1 is the schematic diagram of an existing active pixel sensing cell.
Fig. 2 is the top view of the component placement of active pixel sensing cell shown in Figure 1.
Fig. 3 has the component placement top view of high signal to the active pixel sensing cell of noise ratio for existing one.
Fig. 4 is the schematic diagram of the present invention's one active pixel sensing cell
Fig. 5 is the top view of the component placement of active pixel sensing cell shown in Figure 4.
Fig. 6 is the sectional arrangement drawing of dashed circle shown in Figure 5 place along AA ' tangent line.
The simple symbol explanation
10 active pixel sensing cells, 12 light sensitive diodes
14 reset transistor 14a, 16a grid
16 Current draw transistors, 18 column selection transistors
20 doped regions, 22,24,26 leads
28 insulation layers, 30 retaining rings
50 active pixel sensing cells, 51 silicon base
52 light sensitive diodes, 54 reset transistors
54a, 56a grid 54b channel semiconductor
56 Current draw transistors, 58 column selection transistors
59 lightly mixed drain areas, 60 doped regions
62,64,66 leads, 68 insulation layers
70 retaining ring 70a retaining rings, first end
70b retaining ring second end 71 retaining ring breach
72 grid oxic horizons, 74 depletion regions
Embodiment
Please refer to Fig. 4 and Fig. 5, Fig. 4 is the schematic diagram of the present invention's one active pixel sensing cell 50, and Fig. 5 is the component placement top view of active pixel sensing cell 50 shown in Figure 4.Active pixel sensing cell 50 comprises a light sensitive diode 52 and three CMOS transistors, is reset transistor 54, Current draw transistor 56 and column selection transistor 58 (be simplicity of illustration, be not shown in Fig. 5).Wherein, light sensitive diode 52 is arranged in the semiconductor substrate, and in a preferred embodiment of the invention, the semiconductor-based end is a silicon base.The one source pole of reset transistor 54 (or drain electrode) is electrically connected on light sensitive diode 52, and its another drain electrode (or source electrode) is then shared with Current draw transistor 56, becomes one and shares drain electrode, is electrically connected on a current practice voltage V by lead 66
DdThe grid 54a of reset transistor 54 and the grid 56a of Current draw transistor 56 are made of the doped polysilicon layer or other electric conducting material that are arranged on the silicon base, and lead 64 is used for making grid 54a to be electrically connected on reset voltage V
Reset, 62 in lead is electrically connected on grid 56a and light sensitive diode 52.In addition, the source electrode of reset transistor 54, Current draw transistor 56 and drain electrode, and the optical sensing area of light sensitive diode 52 is all and is located at p type wells or the suprabasil N+ doped region 60 of P type, in the present embodiment, N+ doped region 60 is arranged in the p type wells of silicon base, forms by ion implantation.
Each active pixel sensing cell 50 is insulated district's 68 isolation of surrounding, wherein, insulation layer 68 can be field oxide (field oxide layer, FOX) or shallow-channel insulation (shallow trench isolation, STI), and with silicon base has an insulation intersection 73.Moreover, in order to improve signal noise ratio, be provided with a retaining ring 70 around the light sensitive diode 52 in addition, in the present embodiment, retaining ring 70 forms P type doped region that an ion engage in silicon base with the insulation intersection 73 of insulation layer 68 by P type ion implantation, improves generating noise with direct the contact with insulation layer 68 of depletion region of avoiding light sensitive diode 52.
It should be noted that retaining ring 70 ring-types around light sensitive diode 52, and have a breach 71, be respectively the first end 70a and the second end 70b of retaining ring 70 in the both sides of breach 71, be in close proximity to grid 54a respectively and be provided with, that is grid 54a just is arranged in the breach 71 of ring-type retaining ring 70.Therefore, the width W of the channel semiconductor of reset transistor 54 is decided by breach 71 sizes of retaining ring 70, the i.e. spacing of the first end 70a and the second end 70b.As shown in Figure 6, Fig. 6 is the sectional arrangement drawing of dashed circle shown in Figure 5 place along AA ' tangent line.Grid 54a is arranged on the grid oxic horizon 72, and the silicon base 51 of its both sides then is the first end 70a and the second end 70b of retaining ring 70.When grid 54a opens, can thereunder produce corresponding channel semiconductor 54b.Because retaining ring 70 is arranged between insulation layer 68 and the grid 54a, therefore the formed depletion region 74 of active region below grid 54a can directly not contact with insulation layer 68, can effectively avoid active region to produce leakage and lose electric current and reduce signal to noise ratio.
In addition, the length of the channel semiconductor 54b of reset transistor 54 is determined L due to the distance of source electrode and drain electrode, that is the N+ doped region 60 of light sensitive diode 52 and the spacing of sharing the N+ doped region 60 that drains.In a preferred embodiment of the invention, wherein, reset transistor 54 also has a lightly mixed drain area (lightly doped drain with the shared drain electrode of Current draw transistor 56, LDD) 59, therefore, the length L of the channel semiconductor 54b of reset transistor 54 is decided by the spacing of the photosensitive area of LDD 59 and light sensitive diode 52.
In another embodiment of the present invention, light sensitive diode also can be arranged in a N type well or the substrate of N type, and this moment, optical sensing area and each transistorized source electrode of light sensitive diode then were P type doped region with drain electrode, and retaining ring is for engaging N type retaining ring.
Compared to prior art, the grid of reset transistor of the present invention is arranged at the breach of retaining ring and is in close proximity to retaining ring and is provided with, and is not overlapping with retaining ring; In addition, retaining ring is arranged at the intersection of insulation layer and silicon base, under this design, the grid of reset transistor can directly not contact with insulation layer, therefore channel semiconductor that forms under grid and depletion region are engaged the retaining ring isolation fully, just be difficult for producing to leak losing electric current, can guarantee that institute's light sensitive diode can obtain more correct signal noise ratio, and then improve the sensitization correctness of CMOS active pixel sensor.
The above only is the preferred embodiments of the present invention, and all equalizations of doing according to claim of the present invention change and modify, and all should belong to covering scope of the present invention.
Claims (25)
1. active pixel sensing cell, it comprises:
One insulation layer is located in the semiconductor substrate, and the edge that is positioned at this active pixel sensing cell is to isolate this active pixel sensing cell, and wherein this insulation layer has insulation layer boundary with this semiconductor-based end;
One light sensitive diode was arranged in this semiconductor-based end, and wherein this light sensitive diode has one first doped region;
One retaining ring, ring-type surround this first doped region and have a breach, and this retaining ring is arranged at this insulation layer intersection of this first doped region periphery;
One the first transistor, it has a first grid, is electrically connected on this first doped region; And
One transistor seconds, the drain electrode of this transistor seconds is shared by this first transistor, become one and share drain electrode, and this first doped region is electrically connected on the source electrode of this transistor seconds, this transistor seconds has a second grid and is arranged on this semiconductor-based end of this indentation, there, and this second grid does not have a common boundary overlapping with this insulation layer.
2. active pixel sensing cell as claimed in claim 1, wherein when opening this transistor seconds, this semiconductor-based end of this second grid below, can produce the semiconductor passage.
3. active pixel sensing cell as claimed in claim 2, wherein the shape of this channel semiconductor is subject to the size of this breach.
4. active pixel sensing cell as claimed in claim 3, wherein this retaining ring has one first end and one second end, and the spacing of this first end and this second end is this breach.
5. active pixel sensing cell as claimed in claim 4, wherein the width of this channel semiconductor is decided by the spacing of this first end and this second end.
6. active pixel sensing cell as claimed in claim 2, wherein the length of this channel semiconductor is decided by this first doped region and the spacing that should share drain electrode.
7. active pixel sensing cell as claimed in claim 2 wherein should share drain electrode and also comprise a lightly mixed drain area, and the length of this channel semiconductor is decided by the spacing of this first doped region and this lightly mixed drain area.
8. active pixel sensing cell as claimed in claim 1, wherein this retaining ring is a joint retaining ring.
9. active pixel sensing cell as claimed in claim 1, wherein should share drain electrode is one second doped region.
10. active pixel sensing cell as claimed in claim 9, wherein this first with this second doped region be the N+ doped region, and this retaining ring is one to engage P type doped region.
11. active pixel sensing cell as claimed in claim 9, wherein this first with this second doped region be P type doped region, and this retaining ring is one to engage N type doped region.
12. active pixel sensing cell as claimed in claim 1, wherein this first transistor is as a Current draw element, and this transistor seconds is as a replacement element.
13. active pixel sensing cell as claimed in claim 1, wherein this active pixel sensing cell also comprises one the 3rd transistor, as a column selection element.
14. active pixel sensing cell as claimed in claim 1, wherein this insulation layer is a shallow-channel insulation or a field oxide.
15. a transistor is located in the semiconductor substrate, this semiconductor-based end, comprise an insulation layer around this transistor setting, and this transistor comprises:
One first ion doped region and one second ion doped region were located in this semiconductor-based end; And
One grid was located on this semiconductor-based end, and when this gate turn-on, the semiconductor-based end of this under this grid can produce the semiconductor passage, and this channel semiconductor does not contact with this insulation layer,
Wherein this transistor application is in an active pixel sensing cell.
16. transistor as claimed in claim 15 wherein is provided with a P/N bonding land, to isolate this channel semiconductor and this insulation layer between this channel semiconductor and this insulation layer.
17. transistor as claimed in claim 16, wherein this first with this second doped region be the N+ doped region, and this P/N bonding land is one to engage P type doped region.
18. transistor as claimed in claim 16, wherein this first with this second doped region be P type doped region, and this P/N bonding land is one to engage N type doped region.
19. transistor as claimed in claim 16, wherein the both sides of this grid are located in this P/N bonding land, have one first end and one second end, and the width of this channel semiconductor are decided by the spacing of this first end and this second end.
20. transistor as claimed in claim 16, wherein this P/N bonding land ring-type is surrounded this first doped region or this second doped region.
21. transistor as claimed in claim 15, wherein this first doped region is used for being used as a light sensitive diode of this active pixel sensing cell.
22. transistor as claimed in claim 15, wherein this transistor is used for being used as a reset transistor of this active pixel sensing cell.
23. transistor as claimed in claim 22, wherein this active pixel sensing cell also comprises a Current draw transistor, and this second doped region is transistorized shared drain electrode of this reset transistor and this Current draw or source electrode.
24. transistor as claimed in claim 15, wherein the length of this channel semiconductor be decided by this first with the spacing of this second doped region.
25. transistor as claimed in claim 15, wherein this insulation layer is a shallow-channel insulation or a field oxide.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100551325A CN100433349C (en) | 2005-03-17 | 2005-03-17 | Active pioxel sensor |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100551325A CN100433349C (en) | 2005-03-17 | 2005-03-17 | Active pioxel sensor |
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| CN1835244A CN1835244A (en) | 2006-09-20 |
| CN100433349C true CN100433349C (en) | 2008-11-12 |
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| CNB2005100551325A Active CN100433349C (en) | 2005-03-17 | 2005-03-17 | Active pioxel sensor |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20020022295A1 (en) * | 1999-11-29 | 2002-02-21 | Jui-Hsiang Pan | Method of forming a photo sensor in a photo diode |
| US20020109187A1 (en) * | 2001-02-13 | 2002-08-15 | Mitsubishi Denki Kabushiki Kaisha | Semiconductor device and method of manufacturing the same |
| US6858912B2 (en) * | 2000-08-16 | 2005-02-22 | Qinetiq Limited | Photodetector circuit |
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2005
- 2005-03-17 CN CNB2005100551325A patent/CN100433349C/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20020022295A1 (en) * | 1999-11-29 | 2002-02-21 | Jui-Hsiang Pan | Method of forming a photo sensor in a photo diode |
| US6858912B2 (en) * | 2000-08-16 | 2005-02-22 | Qinetiq Limited | Photodetector circuit |
| US20020109187A1 (en) * | 2001-02-13 | 2002-08-15 | Mitsubishi Denki Kabushiki Kaisha | Semiconductor device and method of manufacturing the same |
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| Publication number | Publication date |
|---|---|
| CN1835244A (en) | 2006-09-20 |
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