CN109801934A - A kind of image sensing cell and preparation method thereof, imaging sensor - Google Patents
A kind of image sensing cell and preparation method thereof, imaging sensor Download PDFInfo
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Abstract
The invention discloses a kind of image sensing cells and preparation method thereof, imaging sensor, wherein, image sensing cell is provided with light trapping structure, incident light reflects by light trapping structure, scatters, is dispersed to all angles after refraction, in addition the reflex of side wall reflecting wall, effective light path of the light in image sensing cell can be extended, so that absorption efficiency of the light in image sensing cell is improved, without increasing thickness of detector；In addition, a kind of production method of image sensing cell, realizes the production of image sensing cell, wherein image sensing cell has the first light trapping structure and the second light trapping structure, and the efficiency of light absorption of image sensing cell can be improved.
Description
Technical field
The present invention relates to photoelectric field, especially a kind of image sensing cell and preparation method thereof, imaging sensor.
Background technique
Imaging sensor is widely used in various electronic equipments, such as digital camera, mobile phone, medical imaging device, peace
Examine equipment, ranging camera etc..As the semiconductor technology of manufacture imaging sensor is constantly progressive, imaging sensor is into one
It walks to low-power consumption, miniaturization, highly integrated direction is developed.Imaging sensor is usually made of photodetector array, image
Sensor unit can be traditional cmos image sensing unit (CIS) or single-photon avalanche diode (SPAD), both
CMOS technology Integrated manufacture can be passed through.In addition, imaging sensor includes imaging sensor and back side illumination image sensing front-illuminated
Device, the cross section structure schematic diagram of imaging sensor front-illuminated since processing circuit is located at silicon as shown in Figure 1, optically, detect
The top of layer, incident light are needed before reaching silicon detecting layer (i.e. photodiode 205) across being covered with plain conductor and medium material
The circuit layer of material, incident light can be absorbed or scatter, and lead to optical detection inefficiency.In addition, quenching due to each imaging unit
It goes out circuit and charging circuit occupies larger area, so that the fill factor of imaging unit is very low.When trial is in the electricity of imaging unit
Road introduces other functions, such as counts, sampling, and whens compression etc., the problem of low fill factor can be more serious；And low fill factor
Result in the detection efficient decline of sensor array.
And the implementation of back side illumination image sensor is as shown in Fig. 2, backside illuminated (back side
Illumination, BSI) imaging sensor is a kind of design that circuit is placed under detecting layer, i.e. photodiode 205
On circuit layer.The specific cross section structure schematic diagram of back side illumination image sensor is as shown in figure 3, the left-half of Fig. 3 is shown
It has anticipated the specific structure of back side illumination image sensor, the right half part of Fig. 3 is the equivalent schematic of back side illumination image sensor,
In, top wafer 48 includes backside illuminated sensing unit array, and external circuits 46 are located among bottom wafer 49, external circuits
46 include that bias offer circuit or signal processing circuit, top wafer 48 and bottom wafer 49 are realized by oxide bond layer 44
Connection, and metal wire 43 precisely aligns and is connected by through-hole 45.It has following excellent relative to imaging sensor front-illuminated
Point: 1. incident lights go directly detecting layer, so that absorption efficiency is improved；2. the deep groove isolation structure 41 between unit can be reduced
The generation of crosstalk；3. so that the fill factor of pixel photosensitive area is improved, and can be supported since circuit is arranged in lower layer
Complicated circuit；4. the pollution that metal material is brought in processing flow is avoided；5. pixel cell area is smaller, so that single
Pixel quantity in plane product is higher, improves imaging resolution；6. since detecting layer and lenticule (are generally located on image sensing
The surface of unit) distance it is closer, therefore the bigger lenticule of numerical aperture can be used in BSI imaging sensor, improves
Collection to large angle incidence light.
However imaging sensor has the disadvantage that
(1) absorptivity of the silicon materials for wavelength in 800-1000nm is lower, and current silicon substrate imaging sensor uses
Be planar structure, photon is vertically into device layer and vertical transmission, and the absorption efficiency of photon and the thickness of device layer are at positive
Pass (specifically follows 1-e-αLLaw, wherein α is absorption efficiency, and L is absorption distance), then light can be improved by increasing thickness
Absorptivity.However blocked up device layer requires the area of imaging sensor also to increase accordingly, and reduces the unit in unit area
Number, and the difficulty of processing of blocked up device layer is big, yield rate is low, is not easy to compatible with CMOS technology, improves cost.
(2) impingement rate of light, but its are improved by increasing anti-reflective film on the planar structure surface of imaging sensor
Antireflective effect can be reduced with the increase of incidence angle, and the absorption efficiency of incident photon is caused to reduce.
(3) it for image sensing cell array, is assembled received by the unit positioned at array edges position by lens
Incident light angle it is larger, may cause the reduction of absorption efficiency.
(4) in the BSI imaging sensor of plane, for certain specific wavelengths, silicon layer can be used as a resonant cavity, make
Its absorption efficiency reaches very high numerical value in specific wavelength.However there are many disadvantages for such method: 1) when the reality of silicon layer adds
When work thickness and design have slight deviations, resonant frequency can shift；2) very sensitive for the wavelength of incident light, for inclined
Light from resonant frequency, absorption efficiency decline to a great extent；3) when the temperature is changed, since the slight change of Refractive Index of Material can also be led
Cause the offset of resonant frequency；4) very sensitive for the variation of incident light angle.
Summary of the invention
The present invention is directed to solve at least some of the technical problems in related technologies.For this purpose, of the invention
One purpose is to provide a kind of image sensing cell and preparation method thereof, improves the efficiency of light absorption of image sensing cell.
For this purpose, improving efficiency of light absorption a second object of the present invention is to provide a kind of imaging sensor.
The technical scheme adopted by the invention is that:
In a first aspect, the present invention provides a kind of image sensing cell, described image sensing unit is set gradually from the bottom to top
There are substrate, circuit layer, silicon oxide layer and silicon detecting layer, the surrounding of the silicon detecting layer is provided with side wall reflecting wall, described image
Light trapping structure is provided in sensing unit.
Further, the upper surface of described image sensing unit is provided with anti-reflection structure.
Further, the anti-reflection structure is the membrane structure being arranged in above the silicon detecting layer, and the membrane structure includes
The different film of at least two refractive index.
Further, the light trapping structure and/or the anti-reflection structure are inverted pyramid structure.
Further, the light trapping structure be arranged in described image sensing unit upper surface and/or the silicon oxide layer
Top and/or the silicon oxide layer lower section.
Further, described image sensing unit further includes lenticule, and the silicon detecting layer is arranged in the lenticule
Top.
Further, described image sensing unit includes SPAD or cmos image sensing unit.
Further, the light trapping structure is nanoscale or micron-sized concaveconvex structure.
Further, the distribution mode of the concaveconvex structure includes cubic solid matter distribution, six side's solid matters distribution or random
Then it is distributed.
Further, the side wall reflecting wall is deep groove isolation structure, and the deep groove isolation structure through-thickness runs through
The silicon detecting layer, the deep groove isolation structure carry out roundtrip to the light come is penetrated.
Further, silica, amorphous silicon, polysilicon or metal are filled in the deep groove isolation structure.
Further, described image sensing unit further includes at least two additional electrodes, and the additional electrodes are for reading
Signal and/or application voltage, the additional electrodes are connect with the silicon detecting layer.
Second aspect, the present invention provide a kind of imaging sensor, including control circuit, reading circuit and multiple figures
As sensing unit, the output end of the control circuit is connect with the input terminal of described image sensing unit, and described image sensing is single
The output end of member is connect with the input terminal of the reading circuit.
The third aspect, the present invention provide a kind of production method of image sensing cell, applied to the image sensing list
Member, comprising the following steps:
Photodiode is made on silicon wafer and obtains the first chip, and the is provided on a surface of the photodiode
One light trapping structure；
By first chip close to the photodiode surface and the second chip close to the surface of external circuits into
Row alignment bonding, second chip are provided with the external circuits；
The silicon wafer of first chip is polished and etched to reduce thickness；
The second light trapping structure is made on the silicon wafer.
The beneficial effects of the present invention are:
Image sensing cell of the invention is provided with light trapping structure, and incident light is reflected by light trapping structure, scattered, after refraction
All angles are dispersed to, in addition the reflex of side wall reflecting wall, can extend effective light of the light in image sensing cell
Journey, without increasing thickness of detector, overcomes and deposits in the prior art to improve absorption efficiency of the light in image sensing cell
In the low technical problem of the efficiency of light absorption of image sensing cell；In addition, a kind of production method of image sensing cell, is realized
The production of image sensing cell, wherein image sensing cell has the first light trapping structure and the second light trapping structure, can be improved
The efficiency of light absorption of image sensing cell.
In addition, image sensing cell of the invention is additionally provided with anti-reflection structure for improving the transmitance of light, light is reduced
The refractive index of line improves the quantity that light enters image sensing cell, further increases its efficiency of light absorption.
Detailed description of the invention
Fig. 1 is the cross section structure schematic diagram of imaging sensor front-illuminated；
Fig. 2 is the cross section structure schematic diagram of back side illumination image sensor；
Fig. 3 is the specific cross section structure schematic diagram of back side illumination image sensor；
Fig. 4 is a kind of the first embodiment cross section structure schematic diagram of image sensing cell in the present invention；
Fig. 5 is the operation principle schematic diagram of the image sensing cell of Fig. 4；
Fig. 6 is the photon detection efficiency schematic diagram whether there is or not light trapping structure；
Fig. 7 is a kind of second of embodiment cross section structure schematic diagram of image sensing cell in the present invention；
Fig. 8 is a kind of the third embodiment cross section structure schematic diagram of image sensing cell in the present invention；
Fig. 9 is an a kind of specific embodiment photon detection efficiency schematic diagram of image sensing cell in the present invention；
Figure 10 is an a kind of specific embodiment cross section structure schematic diagram of image sensing cell in the present invention；
Figure 11 a, Figure 11 b, Figure 11 c are one of a kind of shape of the light trapping structure of image sensing cell and arrangement in the present invention
Specific embodiment schematic diagram；
Figure 12 is an a kind of specific embodiment cross section structure schematic diagram of the anti-reflection structure of image sensing cell in the present invention；
Figure 13 is transmitance schematic diagram of the anti-reflection structure to the light of vertical incidence of Figure 12；
Figure 14 is transmitance schematic diagram of the anti-reflection structure to the light of different incidence angles of Figure 12；
Figure 15 is the photon detection efficiency schematic diagram of the anti-reflection structure of Figure 12；
Figure 16 is a kind of 4th kind of embodiment cross section structure schematic diagram of image sensing cell in the present invention；
Figure 17 is a kind of 5th kind of embodiment cross section structure schematic diagram of image sensing cell in the present invention；
Figure 18 is an a kind of specific embodiment schematic diagram of imaging sensor in the present invention；
Figure 19 is an a kind of specific embodiment flow diagram of the production method of image sensing cell in the present invention；
Wherein, 201- filter plate；202- plain conductor；203- light receiving layer；204- substrate；205- photodiode；
206- deep groove isolation structure；41- deep groove isolation structure；42- oxide skin(coating)；43- metal wire；44- oxide bond layer；45- is logical
Hole；46- external circuits；47- dielectric protective layer；48- top wafer；49- bottom wafer；410- photodiode；1- falls
Pyramid structure；2- oxide skin(coating)；3- filled cavity；4- external circuits；5- dielectric protective layer；6- silicon detecting layer；7- diffraction
Grating light trapping structure；8- silicon oxide layer；9- carrier silicon substrate；The first chip of 10-；11- metal wire；12- anti-reflective film；121-
A kind of membrane material；Second of membrane material of 122-；13- shallow ditch groove structure；14- lenticule；15- through-hole；16- image sensing cell battle array
Column；17- photodiode；18- reading circuit；19- control circuit；The first additional electrodes of 20-；The second additional electrodes of 21-.
Specific embodiment
It should be noted that in the absence of conflict, the features in the embodiments and the embodiments of the present application can phase
Mutually combination.
Embodiment 1
A kind of image sensing cell, image sensing cell be disposed with from the bottom to top substrate, circuit layer, silicon oxide layer and
Silicon detecting layer, the surrounding of silicon detecting layer are provided with side wall reflecting wall, are provided with light trapping structure in image sensing cell.Further
Ground, the upper surface of image sensing cell are additionally provided with anti-reflection structure.
Due to being provided with light trapping structure, quilt after incident light is reflected by light trapping structure, scattered, reflecting in image sensing cell
All angles are distributed to, in addition the reflex of side wall reflecting wall, can extend effective light path of the light in image sensing cell,
Its absorption efficiency near infrared light can be significantly improved, overcomes and deposits in the prior art under conditions of not increasing silicon layer thickness
In the low technical problem of the efficiency of light absorption of image sensing cell；The increase for being not need to rely on silicon layer thickness can improve
Efficiency of light absorption, therefore not will lead to the increase of shaky time will not increase the difficulty of processing of detector silicon wafer, cost and bad
Product rate.Further, image sensing cell includes SPAD or cmos image sensing unit, the thought of solution of the invention
It can be applied to both image sensing cells.It further, is a kind of image sensing cell in the present invention with reference to Fig. 4, Fig. 4
The first embodiment cross section structure schematic diagram, wherein the image sensing cell of Fig. 4 is back side illumination image sensing unit, and substrate is
The top of image sensing cell is arranged in carrier silicon substrate 9, silicon detecting layer 6, can inherit back side illumination image sensor in this way
Advantage, and further increase its efficiency of light absorption.
Embodiment 2
Further improvement based on embodiment 1 obtains embodiment 2, and the upper surface of image sensing cell is arranged in light trapping structure
And/or silicon oxide layer top and/or silicon oxide layer lower section, image sensing cell be separately provided upper surface light trapping structure,
The light trapping structure below light trapping structure or silicon oxide layer above silicon oxide layer can improve its efficiency of light absorption, can also be with
It is used in combination.Further, light trapping structure is nanoscale or micron-sized concaveconvex structure, for example, light trapping structure can be down gold
(as shown in Figure 10, shallow ditch groove structure 13 is arranged in image sensing cell for word tower structure 1 (referring to Fig. 4) or shallow ditch groove structure 13
Upper surface) or surface be honeycomb surface, sinusoidal grating textured surfaces, the orderly surface of dimple shape, periodical pyramid
The structure on body structure surface or two-dimensional grating surface etc..The material of light trapping structure can be a variety of insulating dielectric materials, in this implementation
It is made in example of silica.With reference to Figure 11 a, Figure 11 b and Figure 11 c, the shape of light trapping structure can be rectangular (in such as Figure 11 a
Small square), round (circle in such as Figure 11 b) or polygon (the small octagon in such as Figure 11 c)；The arrangement of light trapping structure
Mode can be uniformly arrangement or non-homogeneous arrangement (i.e. random distribution), and uniformly arrangement can be divided into cubic solid matter distribution (such as
The square profile of Figure 11 a) or six side's solid matters distribution (the hexagon distribution of such as Figure 11 b and Figure 11 c signal), it can be column battle array
Arrange (nano-pillar array) (poroid array (nano-hole array) such as Figure 11 a complementary with Figure 11 b) or mutually
(such as Figure 11 c).
It is the operation principle schematic diagram of the image sensing cell of Fig. 4 with reference to Fig. 4 and Fig. 5, Fig. 5；Side wall reflecting wall is deep trouth
Isolation structure, deep groove isolation structure through-thickness through-silicon detecting layer 6, deep groove isolation structure carry out back and forth to the light come is penetrated
Reflection, deep groove isolation structure include side wall insulating layer and the filled cavity 3 that is formed by side wall insulating layer, and the side wall insulating layer is oxygen
Compound layer 2 fills silica, amorphous silicon, polysilicon or metal in filled cavity 3, is preferably filled with the preferable metal of conductivity.
In the present embodiment, the light trapping structure of 8 top of silicon oxide layer is diffraction grating light trapping structure 7, specifically, diffraction grating light trapping structure
7 be shallow ditch groove structure.In the present embodiment, image sensing cell light trapping structure (the i.e. inverted pyramid structure containing upper surface simultaneously
1), wherein light trapping structure (the i.e. diffraction grating light trapping structure 7) composition of 8 top of light trapping structure and silicon oxide layer of upper surface is multiple
Close light trapping structure.In fact, the inverted pyramid structure 1 that image sensing cell upper surface is arranged in can be between air and silicon layer
Formed a gentle gradual change variations in refractive index, substantially reduce originally interface as refractive index be mutated and caused by high reflection
Rate improves the transmitance of incident light so that more light enters image sensing cell, serves anti-reflection, and such characteristic is width
Band, not for a certain specific wavelength.Meanwhile incident light pass through upper surface inverted pyramid structure 1 when, by reflection,
Scattering, modes, the incident light such as refraction can be dispersed to all angles, increase effective light path of the light in silicon detecting layer, rise and fall into
Light action, to improve absorption efficiency of the light in image sensing cell.It is real in the following table surface construction of image sensing cell again
Matter is light trapping structure, that is, diffraction grating light trapping structure 7 of diffraction grating, can be by the optical diffraction of vertical incidence to certain angle, then is tied
The reflex for closing deep groove isolation structure, makes light roundtrip in a layer of silicon, further increases efficiency of light absorption.Specifically, originally
In embodiment, partially vertically into the incident light of image sensing cell after acting on diffraction grating light trapping structure 7, generation is spread out
The component that light has horizontal direction is penetrated, the roundtrip in the silicon substrate of image sensing cell increases effective light path, improves and absorbs
Rate, theoretically by this kind of mode, the absorptivity of light in a layer of silicon can approach its theoretical boundary Yablonovitch
limit.Compound light trapping structure, which is arranged, in image sensing cell can effectively improve efficiency of light absorption.With reference to Fig. 6, Fig. 6 be whether there is or not
The photon detection efficiency schematic diagram of light trapping structure；By emulation, the image sensing cell whether there is or not light trapping structure can be calculated
Absorption efficiency, as seen from Figure 6, the image sensing cell without make compound light trapping structure common for one,
850nm to 960nm wave band absorption efficiency in 5% to 20% range, for the absorption at the 905nm wavelength focused in application
Rate is about 15%, in contrast, for there is the image sensing cell of light trapping structure (such as Fig. 4), for 850 to 960nm light
Absorption efficiency be integrally significantly enhanced, at 905nm, absorption efficiency has been greatly improved 38%, compared to without fall into
The efficiency of light absorption of the image sensing cell of photo structure significantly improves.
It is a kind of second of embodiment cross section structure schematic diagram of image sensing cell in the present invention with reference to Fig. 7, Fig. 7；It falls into
Photo structure (the diffraction grating light trapping structure 7 in such as Fig. 7) can also process the lower section in silicon oxide layer 8, equally can be in principle
Play the role of sunken light to enhance absorption efficiency.In Fig. 7, the upper surface of image sensing cell is also provided with inverted pyramid structure
1, upper and lower light trapping structure combines so that falling into light effect more preferably.Further, image sensing cell further includes at least two additional
Electrode, for reading signal and/or applying voltage, additional electrodes are connect additional electrodes with silicon detecting layer.With reference to Fig. 4 and Fig. 7, originally
In embodiment, image sensing cell include the first additional electrodes 20 and the second additional electrodes 21, one end of the first additional electrodes 20,
One end of second additional electrodes 21 is electrically connected with silicon detecting layer 6, the other end of the first additional electrodes 20, the second additional electrodes 21
The other end connect with external circuits 4.
Embodiment 3
Further improvement based on embodiment 1 obtains embodiment 3, is a kind of image sensing in the present invention with reference to Fig. 8, Fig. 8
The third embodiment cross section structure schematic diagram of unit；Light trapping structure and/or anti-reflection structure are inverted pyramid structure 1, golden word
Tower structure 1 is provided simultaneously with sunken light and anti-reflection effect, and specifically, the upper surface of image sensing cell is arranged in inverted pyramid structure 1
(being located at the top of silicon detecting layer 6), inverted pyramid structure 1 are to fill silica after etching in silicon substrate and obtain.This implementation
In example, dielectric protective layer 5 is provided with for protecting image sensing cell in the top of inverted pyramid structure 1.Specifically, if
The folding of a gentle gradual change can be formed between air and silicon layer by setting the inverted pyramid structure 1 in image sensing cell upper surface
Penetrate rate variation, substantially reduce originally in interface as refractive index mutation and caused by high reflectance so that more light enters
To image sensing cell, the transmitance of incident light is improved, serves anti-reflection, such characteristic is broadband, not for a certain spy
Standing wave is long.Meanwhile incident light, when passing through the inverted pyramid structure 1 of upper surface, by reflection, scattering, the modes such as refraction are incident
Light can be dispersed to all angles, increase effective light path of the light in silicon detecting layer 6, light trapping effect be played, to improve light
Absorption efficiency in image sensing cell.It emulates and obtains the photon detection efficiency schematic diagram of Fig. 9, photon detection efficiency (pde,
Photon detection efficiency) according to simulation result as it can be seen that setting upper surface inverted pyramid structure 1 make figure
As sensing unit have excellent efficiency of light absorption, efficiency of light absorption is generally 0.25 or more.
Embodiment 4
Further improvement based on embodiment 1 obtains embodiment 4, and the upper surface of image sensing cell is provided with anti-reflection knot
Structure, specifically, anti-reflection structure are the membrane structure being arranged in above silicon detecting layer, and membrane structure includes that at least two refractive index are different
Film.In fact, anti-reflection structure is by plating the material that multilayer has different refractivity in the upper surface of BSI image sensing cell
Obtained from excellent antireflective effect anti-reflective film (anti-reflection coating), anti-reflective film is to certain wave
Transmitance of the Duan Shixian close to 100%, it is fully reflective to the incident light except selected wave band.It is this hair with reference to Figure 12, Figure 12
An a kind of bright middle specific embodiment cross section structure schematic diagram of the anti-reflection structure of image sensing cell；Anti-reflective film 12 includes two kinds
The different membrane material of refractive index (the first membrane material 121 and second of membrane material 122) makes anti-reflection structure, the first membrane material
121 be silica, and second of membrane material 122 is silicon nitride.The light penetration and photon detection efficiency of anti-reflective film 12 are such as
Shown in Figure 13, Figure 14 and Figure 15, it can be seen that the anti-reflection structure of Figure 12 has very strong selectivity to the wavelength of incident light, such as schemes
Shown in 13, in 890nm to 910nm, transmitance is close in 1, for the incident light except this range, transmitance close to
0, environmental background light bring noise can be effectively reduced in this characteristic.Response of the anti-reflective film for different wave length and incidence angle
Characteristic is different, and simulation result is as shown in figure 14, and for the incident light of wavelength near 905nm, when incidence angle is greater than 20 degree, this is anti-
The transmitance of reflectance coating is from the horizontal rapid drawdown close to 100% to 10% or less, it is seen that it has very the incident angle of incident light
Big selectivity.In image sensing cell, there is horizontal direction component for what is generated by bottom light trapping structure diffraction
Light, when being incident on upper surface from below, since incident angle is larger (> 45 °), it will be reflected back toward in silicon layer, to mention
High-selenium corn efficiency.The image sensing cell of Figure 12 also uses the anti-reflection structure of upper surface and light trapping structure (the i.e. diffraction of lower surface
Grating light trapping structure 7) in conjunction with mode more effectively improve the efficiency of light absorption of image sensing cell.It is arranged in image sensing
The anti-reflection structure of unit upper surface can also be combined with the light trapping structure (such as inverted pyramid structure) of image sensing cell upper surface
To realize the efficiency of light absorption for improving image sensing cell.
Embodiment 5
It is a kind of 4th kind of embodiment cross section structure schematic diagram of image sensing cell in the present invention with reference to Figure 16, Figure 16,
Image sensing cell further includes lenticule 14, and the top of silicon detecting layer 6 is arranged in lenticule 14.In the present embodiment, detected in silicon
It is additionally provided with dielectric protective layer 5 on layer 6, lenticule 14 is added on dielectric protective layer 5；In addition, in the present embodiment, it is micro-
Lens 14 further increase the efficiency of light absorption of image sensing cell herein in connection with the diffraction grating light trapping structure 7 of lower surface.?
The upper surface of image sensing cell improves the collection efficiency to larger angle incident light by covering lenticule, is equivalent to and mentions
High fill factor.It is that a kind of 5th kind of embodiment cross section structure of image sensing cell shows in the present invention with reference to Figure 17, Figure 17
It is intended to；At the same time with the image sensing list of upper and lower light trapping structure (i.e. inverted pyramid structure 1 and diffraction grating light trapping structure 7)
Lenticule 14 is covered in member, can be further improved it for the collection efficiency of large angle incidence light.
To sum up, BSI image sensing cell of the invention, due to being provided with the sunken light of anti-reflection structure, lenticule, upper and lower surface
Structure, for inevitably the deviation of processing thickness, temperature, wavelength and incidence angle has very high tolerance in practice, more
Working environment and actual use situation suitable for the system (such as optical imaging system) based on image sensing cell.
Embodiment 6
It is an a kind of specific embodiment schematic diagram of imaging sensor in the present invention with reference to Figure 18, Figure 18；A kind of image biography
Sensor, including control circuit 19, reading circuit 18 and array (the i.e. image sensing being made of multiple image sensing cells
Cell array 16), image sensing cell array 16 include array distribution image sensing cell (in Figure 18, image sensing list
Member photodiode 17 indicates), it with reference to Fig. 4, is separated between described image sensing unit by deep groove isolation structure, institute
The output end for stating control circuit 19 is connect with the input terminal of described image sensing unit, the output end of described image sensing unit with
The input terminal of the reading circuit 18 connects.Specifically, silica, polysilicon, metal can be filled in deep groove isolation structure
Or other insulating materials are to realize isolation.Wherein, it is realized and is isolated by deep groove isolation structure between image sensing cell, guaranteed
It is not in crosstalk between image sensing cell.Imaging sensor comprising image sensing cell, due to image sensing list
Member, efficiency of light absorption is improved and between image sensing cell the case where being not in signal cross-talk.
Embodiment 7
A kind of production method of image sensing cell, applied to the image sensing cell, in the present embodiment, with reference to figure
4, with the figure for the compound light trapping structure that the diffraction grating light trapping structure of inverted pyramid structure and lower surface with upper surface is constituted
It is one of a kind of production method of image sensing cell in the present invention with reference to Figure 19, Figure 19 as being illustrated for sensing unit
Specific embodiment flow diagram；The following steps are included:
Firstly, producing photodiode on the silicon wafer of epitaxial growth to obtain with the conventional process of image sensing cell
First chip 10, is provided with the first light trapping structure on a surface of photodiode, in the present embodiment, in photodiode
Upper surface (i.e. the top of silicon oxide layer) makes the first light trapping structure, and the first light trapping structure is diffraction grating light trapping structure 7.
Then, at low temperature by the first chip 10 close to the surface of photodiode and the second chip close to external circuits 4
Alignment bonding is carried out, the second chip is provided with external circuits 4, and external circuits 4 include that bias provides circuit or signal processing electricity
Road can be used mechanical or optical mode and be aligned, is bonded by polymer adhesive or oxide.After bonding
Chip turn-over is located above the silicon wafer of the first chip 10, as shown in third picture in Figure 19.
The silicon wafer of the first chip 10 is polished and etched to reduce its thickness again；Specifically, pass through mechanical grinding
Its thickness is decreased to by mode by silicon wafer wear down of original 1mm thickness or so to 50um or so, then by way of chemical etching
5um。
Produce the second light trapping structure on the silicon wafer of the first chip 10 again, in the present embodiment, the second light trapping structure is to fall
Pyramid structure 1.
Finally, plating dielectric protective layer 5 on inverted pyramid structure 1.
A kind of production method of image sensing cell, realizes the production of image sensing cell, and production method is simple, is not required to
Increase silicon layer thickness, therefore not will increase difficulty of processing, wherein there is image sensing cell the first light trapping structure and second to fall into
The efficiency of light absorption of image sensing cell can be improved in photo structure.
It is worth noting that the production method of the image sensing cell with other light trapping structures can refer to the present embodiment description
Production method, such as lenticule can then protect in dielectric after image sensing cell plates dielectric protective layer
Lenticule is added on sheath.
It is to be illustrated to preferable implementation of the invention, but the invention is not limited to the implementation above
Example, those skilled in the art can also make various equivalent variations on the premise of without prejudice to spirit of the invention or replace
It changes, these equivalent deformations or replacement are all included in the scope defined by the claims of the present application.
Claims (14)
1. a kind of image sensing cell, which is characterized in that described image sensing unit is disposed with substrate, circuit from the bottom to top
Layer, silicon oxide layer and silicon detecting layer, the surrounding of the silicon detecting layer are provided with side wall reflecting wall, set in described image sensing unit
It is equipped with light trapping structure.
2. image sensing cell according to claim 1, which is characterized in that the upper surface of described image sensing unit is arranged
There is anti-reflection structure.
3. image sensing cell according to claim 2, which is characterized in that the anti-reflection structure is that setting is visited in the silicon
The membrane structure above layer is surveyed, the membrane structure includes the different film of at least two refractive index.
4. image sensing cell according to claim 2, which is characterized in that the light trapping structure and/or the anti-reflection knot
Structure is inverted pyramid structure.
5. image sensing cell according to claim 1, which is characterized in that the light trapping structure setting is passed in described image
Feel the upper surface of unit and/or the top of the silicon oxide layer and/or the lower section of the silicon oxide layer.
6. image sensing cell according to any one of claims 1 to 5, which is characterized in that described image sensing unit is also
Including lenticule, the top of the silicon detecting layer is arranged in the lenticule.
7. image sensing cell according to any one of claims 1 to 5, which is characterized in that described image sensing unit packet
Include SPAD or cmos image sensing unit.
8. image sensing cell according to any one of claims 1 to 5, which is characterized in that the light trapping structure is nanometer
Grade or micron-sized concaveconvex structure.
9. image sensing cell according to claim 8, which is characterized in that the distribution mode of the concaveconvex structure includes four
Square solid matter distribution, the distribution of six side's solid matters or random distribution.
10. image sensing cell according to any one of claims 1 to 5, which is characterized in that the side wall reflecting wall is deep
Recess isolating structure, the deep groove isolation structure through-thickness run through the silicon detecting layer, and the deep groove isolation structure is next to penetrating
Light carry out roundtrip.
11. image sensing cell according to claim 10, which is characterized in that filled in the deep groove isolation structure aerobic
SiClx, amorphous silicon, polysilicon or metal.
12. image sensing cell according to any one of claims 1 to 5, which is characterized in that described image sensing unit is also
Including at least two additional electrodes, the additional electrodes for read signal and/or apply voltage, the additional electrodes with it is described
The connection of silicon detecting layer.
13. a kind of imaging sensor, which is characterized in that any including control circuit, reading circuit and multiple claims 1 to 12
Image sensing cell described in, the output end of the control circuit is connect with the input terminal of described image sensing unit, described
The output end of image sensing cell is connect with the input terminal of the reading circuit.
14. a kind of production method of image sensing cell, which is characterized in that it is described in any item to be applied to claim 1 to 12
Image sensing cell, comprising the following steps:
Photodiode is made on silicon wafer and obtains the first chip, and first is provided on a surface of the photodiode and is fallen into
Photo structure；
First chip is carried out pair close to the surface of the photodiode and the second chip close to the surface of external circuits
Quasi- bonding, second chip are provided with the external circuits；
The silicon wafer of first chip is polished and etched to reduce thickness；
The second light trapping structure is made on the silicon wafer.
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