CN209461463U - A kind of semiconductor structure of back-illuminated detectors - Google Patents

Abstract

The utility model discloses a kind of semiconductor structure of back-illuminated detectors, is applied to safety check imaging and medical imaging field, which is used for a kind of photodetector, which is formed on the substrate.The detector is back-light type photoelectric detector, i.e. signal is incident from substrate back.This utility model discloses a kind of special constructions of substrate cutting, and manufacture the process flow of the structure.The photoresponse of back-light type photoelectric detector can be improved in the structure, and compared with current back-light type photoelectric detector, which can reduce the fragment rate of chip in the fragment rate of silicon wafer during flow and encapsulation process.

Description

A kind of semiconductor structure of back-illuminated detectors

Technical field

The utility model is semiconductor devices, the special but non-exclusive photodetector used in imaging systems.

Background technique

It is usually used in the photodetector of safety check imaging and medical imaging field, core is silicon photoelectric diode chip, core Piece usually couples bonding scintillator material.X-ray signal is converted into visible light signal by scintillator, and optical signal is again by two pole of photoelectricity Pipe is converted into electric signal, and electric signal amplifies through subsequent conditioning circuit, handles.

According to the difference for the position for receiving light, detector can be divided into positive illuminated detector and back-illuminated detectors.Its For middle back-illuminated detectors compared with positive illuminated detector, biggest advantage is to change the structure inside element, i.e., will be photosensitive The element of layer turns direction, light can be entered from back side direct projection, avoiding the light in positive illuminated panel detector structure will receive The influence of structure between other layers such as metal connecting layer and photodiode, improves the efficiency of light receiver.

In x-ray imaging device industry, traditional photodiode be it is front-illuminated, the encapsulation of chip front-illuminated needs to paste Piece, nation's line and line protection, and influence to mount other devices such as scintillator above active area；And back-illuminated detectors chip is usual Only need to plant ball bonding on the pad of substrate.

But back-illuminated detectors are equally faced with some problems, wherein a more serious problem is exactly dark current Problem.Dark current problem refers to that, due to the migration of carrier, photodiode detects electricity in the case where dull thread irradiation Stream, and then increase the noise of the system using photodiode.

In addition, light passes through the hypertelorism of body silicon, optical signal crosstalk is big, and dark current is also big.Therefore usually back side entirety The problem of being easy fragment when being thinned to about 100 microns, but accordingly bringing scribing and encapsulation.

The framework problem of current back-illuminated type is, silicon substrate is thinner than front-illuminated, more fragile, and crosstalk is big.? In the manufacturing process of back side illumination image sensor, need to carry out reduction processing and BDTI (Backside to the backside of wafer Deep Trench Isolation, back side deep trench isolation) processing procedure.After carrying out above-mentioned treatment process, in the silicon of the wafer A large amount of dangling bonds are had on surface, and these dangling bonds will form highdensity defect, defect can play the work in complex centre With can answer trapped electron and hole and be carried out in defect level compound, to generate dark current, and then influence back side illumination image and pass The imaging effect of sensor.

Substrate cutting only finds exist on visible light image sensor CMOS chip at present, but this chip has biography incessantly Sensor, there are also other circuits such as amplifier, and be generally mated lenticule, filter or colored filter etc..And in X-ray Detector field is needed through optical cement direct-coupling scintillator, and specific structure is different from visible light sensor, and in ray There are no precedents in industry.

In addition, usually 16 pixel units share a substrate at present in the application of X-ray industry.Due to visible Light mutual crosstalk between unit channel, and two channels at edge only have side to have crosstalk, therefore edge gateway signal exports It is exported than the signal of intermediate channel small.

In summary, it is desirable to provide it is a kind of it is novel, can solve the above problem, visit for the back-illuminated type of X-ray detection Survey device.

Utility model content

According to the utility model, a kind of substrate including photodetector is provided.The back side of the substrate, it is active with front Area is corresponding a groove.

In the active area of the back side of substrate setting light incidence, and overleaf, light entrance area is carved using dry etching and wet process Erosion carries out cutting.

Preferably, the structure of a substrate is shared using every two pixel unit.

The beneficial effects of the utility model are as follows:

A kind of substrate including photodetector described in the utility model.The back side of the substrate, with front active area phase It is corresponding to have a groove.Groove (specifically, groove isolation construction that the groove and filler are formed) is by BSI image sensing The adjacent pixel of device is completely isolated, to reduce crosstalk.

The back-illuminated detectors of plane formula are typically only capable to be thinned to about 100 microns of thickness at present, if further subtracted It is thin to be easier to fragment, so that decrease in yield, cost be made to further increase.And the groove structure of the utility model can make to have Source region thickness can advanced optimize photoresponse and detection efficient, while not increasing fragment rate less than 100 microns.

In addition, optical cement area used in the interface of chip coupled scintillation body and corresponding coupling is big, therefore couple bonding Intensity it is bigger, increase reliability.

Preferably, using the structure of one substrate of every two units shared, since each channel is equivalent to edge gateway, The signal output in each channel is close, and it is defeated to efficiently solve edge gateway signal in the structure of original each 16 pixels of substrate Relatively low problem out.And substrate becomes smaller, and calculates according to pixel quantity, and the wafer of same diameter can make more multi-detector, Reduce leftover bits, saves cost.

Detailed description of the invention

Fig. 1 shows the basic structure of the photodetector of a known structure.

Fig. 2 to Fig. 5 shows the specific steps of the manufacture photodetector of specific embodiment according to the present utility model.

Specific embodiment

In order to illustrate more clearly of the utility model, the utility model is done into one below with reference to preferred embodiments and drawings The explanation of step.Similar component is indicated in attached drawing with identical appended drawing reference.It will be appreciated by those skilled in the art that below Specifically described content is illustrative and be not restrictive, and should not be limited the protection scope of the present invention.

With reference to the example of the photodetector for safety check imaging system.

It is not drawn to scale although should be pointed out that with reference to Detailed description of the invention the utility model, these figures.

Referring to Fig. 1 to Fig. 4, photoelectricity of the manufacture of embodiment according to the present utility model for safety check imaging system is shown and is visited Survey the selected step of device.The step related to the utility model is understood only is shown, other steps are for those skilled in the art It is well known.

Referring to Fig. 1, the section to form the n-type semiconductor substrate 10 of photodetector components is shown, the area P+ forms the light The active area (active area) 11 of electric diode, active area 11 determines the anode of photodiode, and the area N+ 12 forms light The cathode of electric diode, thin silicon dioxide layer 13 shield as passivation layer, field oxygen layer (field oxide, FOX) 14 Cover the rest part of upper surface of substrate.

In safety check imaging applications field, the processing step for manufacturing Fig. 1 structure is well-known, therefore herein not It describes again.

After structure shown in fig. 1 manufacture, referring to Fig. 2, reduction processing is carried out to silicon chip back side.

Then, photoresist (photo-resist) 15 or other optional protective layers are deposited on silicon chip back side, for subsequent Substrate is protected in technique, as shown in Figure 3.Then photoresist layer is exposed, to form an opening 16, this opening 16 and silicon The positive active area 11 of piece be it is substantially corresponding, as shown in Figure 4.

Then, dry etching is carried out to silicon chip back side, such as Fig. 5 makes to form a groove 17 at opening 16, carry out again later Wet etching is to alleviate dry etching rear projection or pit, to make light is incident to obtain uniformly.

The dangling bonds formed due to etching technics on the surface Si are removed, defect level is reduced, Interface composites are reduced, and reach drop The purpose of low-dark current.

Claims (5)

1. a kind of semiconductor structure of back-illuminated detectors, is applied to safety check imaging and medical imaging field, which is used for one Kind photodetector, the photodetector are formed on the substrate；The photodetector is in the front of substrate；The semiconductor Structure, it is characterized in that: have be engraved in substrate back, corresponding with the active zone position of positive photodetector, area is big In, equal to or less than the slot of positive active region area.

2. semiconductor structure according to claim 1, it is characterized in that: having the slot carved in substrate back.

3. semiconductor structure according to claim 1 or 2, it is characterized in that: belonging to body silicon epitaxial wafer.

4. semiconductor structure according to claim 1, it is characterized in that: being to be carved on to the silicon chip back side after being thinned with dry method Erosion, carries out what wet etching obtained again later, and protrusion or pit after dry etching are eased, and light is incident uniformly.

5. semiconductor structure according to claim 1, it is characterized in that: relatively relatively low with edge gateway response can be reduced Degree, an individual substrate that every Unit two is shared.