CN203631555U

CN203631555U - Backside illuminated image sensor capable of reducing charge residue

Info

Publication number: CN203631555U
Application number: CN201320842163.5U
Authority: CN
Inventors: 郭同辉; 陈杰; 刘志碧; 唐冕; 旷章曲
Original assignee: Beijing Superpix Micro Technology Co Ltd
Current assignee: Beijing Superpix Micro Technology Co Ltd
Priority date: 2013-12-18
Filing date: 2013-12-18
Publication date: 2014-06-04
Anticipated expiration: 2023-12-18

Abstract

The utility model discloses a backside illuminated image sensor capable of reducing charge residue. The image sensor at least comprises a photodiode which is disposed in a semiconductor substrate, a charge transmission transistor which is connected with the photodiode, a floating active zone which is connected with the charge transmission transistor, and a shallow groove isolation zone which is disposed between adjacent pixel photodiodes in a filling manner, wherein grid polycrystalline silicon with preset length in the charge transmission transistor is disposed in the shallow groove isolation zone. By employing the backside illuminated image sensor provided by the utility model, the transfer speed of the charge in the photodiode is improved, and the problem of charge residue is solved.

Description

A kind of residual back side illumination image sensor of electric charge that reduces

Technical field

The utility model relates to technical field of semiconductors, relates in particular to a kind of residual back side illumination image sensor of electric charge that reduces.

Background technology

Imageing sensor has been widely used in digital camera, cell phone, medicine equipment, automobile and other application scenarios.Particularly manufacture CMOS(CMOS (Complementary Metal Oxide Semiconductor)) fast development of image sensor technologies, make people have higher requirement to the output image quality of imageing sensor.

In the prior art, distinguish from structure, cmos image sensor generally has two kinds: front according to formula structure and back-illuminated type structure, back-illuminated type structure is more suitable for small-sized pixel, for example 1.4um pixel.Compare according to formula structure with front, lenticule and colored filter in back-illuminated type structure are arranged at chip back, there is no metal barrier incident ray, and photodiode can receive more light, and then has improved the optical sensitivity of imageing sensor.

As shown in Figure 1, it is a kind of 4T dot structure schematic diagram of back-illuminated cmos image sensors of prior art, comprise photodiode 101, the photodiode 101 ' of neighbor, charge pass transistor 102, floating active area 103, the photodiode 103 ' of neighbor, the shallow trench isolation region 104 in pixel; Also comprise circuit diagram, reset transistor 105, transistor 106 is followed in source, row selecting transistor 107, and row bit line 108.In the time of practical application, photodiode 101 detects light signal and produces photoelectricity electric charge, and by opening charge pass transistor 102, the transmission of photoelectricity electric charge is caused to floating active area 103, and then source follows transistor 106 and detected the variation of 103 electromotive forces before and after electric charge transmission, the variable quantity of this electromotive force is photosignal value.

As shown in Figure 2, be the tangent plane schematic diagram of tangent position shown in Fig. 1, comprising photodiode 201, charge pass transistor 202, shallow trench isolation region 204, colorized optical filtering section 205, lenticule 206, and photodiode 201 ' in neighbor.

The defect that above-mentioned prior art exists is: the degree of depth of back-illuminated photodiode 201 is slightly less than silicon substrate thickness conventionally, and because production technology restriction silicon substrate thickness is conventionally thicker, is greater than 3um; In putting the electric charge at A place (as shown in Figure 2) compared with deep-seated away from the raceway groove of charge pass transistor 202, therefore A place electric charge is difficult for being transferred away, and then produces electric charge residue problem.

Utility model content

The purpose of this utility model is to provide a kind of residual back side illumination image sensor of electric charge that reduces, and improves the transfer velocity of electric charge in photodiode, and then solves electric charge residue problem.

The purpose of this utility model is achieved through the following technical solutions:

Reduce the residual back side illumination image sensor of electric charge, at least comprise the charge pass transistor that is placed in the photodiode of semiconductor substrate, be connected with described photodiode, and the floating active area that is connected of described charge pass transistor, be filled in neighbor photodiode between shallow trench isolation region; Wherein, in described charge pass transistor, the grid polycrystalline silicon of predetermined length is placed in described shallow trench isolation region.

The technical scheme being provided by above-mentioned the utility model can be found out, in the time shifting the operation of electric charge in photodiode, be conducive to shift the electric charge of photodiode depths by the grid polycrystalline silicon being placed in described shallow trench isolation region, thereby improve the speed of transfer charge, also reduced the residual amount of electric charge in photodiode, and then improved the image quality of back side illumination image sensor simultaneously.

Accompanying drawing explanation

In order to be illustrated more clearly in the technical scheme of the utility model embodiment, below the accompanying drawing of required use during embodiment is described is briefly described, apparently, accompanying drawing in the following describes is only embodiment more of the present utility model, for those of ordinary skill in the art, do not paying under the prerequisite of creative work, can also obtain other accompanying drawings according to these accompanying drawings.

Plane and the circuit diagram of four transistor active pixels of the back-illuminated cmos image sensors of the prior art that Fig. 1 provides for the utility model background technology;

Fig. 2 is photodiode and charge pass transistor and the tangent plane schematic diagram around thereof of the back-illuminated cmos image sensors of prior art;

The back-illuminated cmos image sensors structure tangent plane schematic diagram that Fig. 3 provides for the utility model embodiment mono-;

The schematic diagram of development step when back-illuminated cmos image sensors manufacture method that Fig. 4 provides for the utility model embodiment mono-;

The schematic diagram of the back-illuminated cmos image sensors manufacture method energetic ion etch step that Fig. 5 provides for the utility model embodiment mono-;

The back-illuminated cmos image sensors manufacture method that Fig. 6 provides for the utility model embodiment mono-is removed the schematic diagram of silicon nitride protective layer step;

The schematic diagram of the back-illuminated cmos image sensors manufacture method depositing polysilicon step that Fig. 7 provides for the utility model embodiment mono-;

The back-illuminated cmos image sensors manufacture method that Fig. 8 provides for the utility model embodiment mono-forms the schematic diagram of transistor gate polysilicon step.

Embodiment

Below in conjunction with the accompanying drawing in the utility model embodiment, the technical scheme in the utility model embodiment is clearly and completely described, obviously, described embodiment is only the utility model part embodiment, rather than whole embodiment.Based on embodiment of the present utility model, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to protection range of the present utility model.

Embodiment mono-

The utility model embodiment provides a kind of residual back side illumination image sensor of electric charge that reduces, at least comprise the charge pass transistor that is placed in the photodiode of semiconductor substrate, be connected with described photodiode, and the floating active area that is connected of described charge pass transistor, be filled in neighbor photodiode between shallow trench isolation region, wherein, in described charge pass transistor, the grid polycrystalline silicon of predetermined length is placed in described shallow trench isolation region.

Further, in described shallow trench isolation region, the degree of depth of the grid polycrystalline silicon of predetermined length is less than the degree of depth of described shallow trench isolation region.

In addition, the degree of depth of described shallow trench isolation region is generally 0.4um～0.5um.

For convenience of explanation, be described in detail below in conjunction with accompanying drawing 3.The back-illuminated cmos image sensors structure tangent plane schematic diagram that Fig. 3 provides for the present embodiment, its tangent plane is the tangent plane of tangent position shown in Fig. 1.As shown in Figure 3,301 is photodiode, and for sensitization and generate photoelectricity electric charge, its upper and lower scope approaches respectively silicon substrate surface; 302 is charge pass transistor, for shifting the extremely floating active area of electric charge in photodiode 301; 301 ' is the photodiode of neighbor; 304 be 301 and 301 ' two photodiodes between shallow trench isolation region, packing material is silicon phosphorus glass, the degree of depth is 0.4um～0.5um; 305 is colorized optical filtering section, 306 microlens region; B point characterizes 301 compared with the electric charge of depths, and B point is greater than 2.8um conventionally apart from chip silicon substrate front surface.Wherein, charge pass transistor 302 is arranged at chip front side with shallow trench isolation region 304; Colorized optical filtering section 305 and microlens region 306 are arranged at chip back.

The grid polycrystalline silicon extension of charge pass transistor 302 shown in Fig. 3 causes in shallow trench isolation region, has shortened the distance of B district electric charge and charge pass transistor 302 grids.In the time that unlatching charge pass transistor 302 shifts the operation of photodiode 301 interior electric charges, B district electric charge is easy to be adsorbed in charge pass transistor 302 raceway grooves, shift thereby shortened the interior electric charge of photodiode 301 time that causes floating active area, improved the operating rate of imageing sensor; And charge pass transistor structure of the present utility model has reduced even to eliminate the residue problem of 301 interior electric charges, further promote the picture quality of imageing sensor.

On the other hand, the imageing sensor described in the utility model embodiment, can adopt the step shown in accompanying drawing 4-accompanying drawing 8 to manufacture, concrete:

1) as shown in Figure 4, apply certain thickness silicon nitride protective layer in chip front side, and with shallow trench isolation region lap, opening is being set.This step belongs to the development part in back side illumination image sensor manufacture method.Wherein, 401 is silicon nitride protective layer, and the thickness of silicon nitride is generally 150nm～200nm; 304 is shallow trench isolation region, and its degree of depth is 0.4um～0.5um, and its filler is megohmite insulant silicon phosphorus glass.

2) as shown in Figure 5, utilize energetic ion etching technique etching shallow trench isolation region, energetic ion generally adopts inert element, for example helium; The degree of depth that shallow trench isolation region is etched approaches but is less than the degree of depth of shallow trench isolation region filler silicon phosphorus glass.

3) as shown in Figure 6, remove silicon nitride protective layer.Removing after silicon nitride, produce one deck grid oxide layer at exposed silicon face, the manufacture craft of this grid oxide layer is identical with traditional logic technique, does not repeat at this.

4) as shown in Figure 7, to the groove depositing polysilicon etching.Wherein 701 is transistor gate and line polysilicon used thereof, and the thickness of this polysilicon is identical with traditional handicraft.This polysilicon needs chemical mechanical milling tech operation before formation, and object is that polysilicon is polished, even thickness; And polysilicon has filled up the part that shallow trench isolation region 304 is etched.

5) as shown in Figure 8, form transistor gate polysilicon 302, this transistor gate polysilicon is charge transfer transistor.Form in this step transistor gate polysilicon process identical with traditional handicraft operation.

The above; it is only preferably embodiment of the utility model; but protection range of the present utility model is not limited to this; any be familiar with those skilled in the art the utility model disclose technical scope in; the variation that can expect easily or replacement, within all should being encompassed in protection range of the present utility model.Therefore, protection range of the present utility model should be as the criterion with the protection range of claims.

Claims

1. one kind is reduced the residual back side illumination image sensor of electric charge, at least comprise the charge pass transistor that is placed in the photodiode of semiconductor substrate, be connected with described photodiode, and the floating active area that is connected of described charge pass transistor, be filled in neighbor photodiode between shallow trench isolation region, it is characterized in that, in described charge pass transistor, the grid polycrystalline silicon of predetermined length is placed in described shallow trench isolation region.

2. imageing sensor according to claim 1, is characterized in that, in described shallow trench isolation region, the degree of depth of the grid polycrystalline silicon of predetermined length is less than the degree of depth of described shallow trench isolation region.

3. imageing sensor according to claim 1 and 2, is characterized in that, the degree of depth of described shallow trench isolation region is 0.4um～0.5um.