CN102800686B

CN102800686B - Back-illuminated type CMOS

Info

Publication number: CN102800686B
Application number: CN201210310723.2A
Authority: CN
Inventors: 余兴; 肖海波; 费孝爱
Original assignee: Omnivision Technologies Shanghai Co Ltd
Current assignee: Omnivision Technologies Shanghai Co Ltd
Priority date: 2012-08-28
Filing date: 2012-08-28
Publication date: 2016-12-21
Anticipated expiration: 2032-08-28
Also published as: CN102800686A

Abstract

The invention provides a kind of back-illuminated type CMOS, including: device wafers, described device wafers has front and the back side, is formed with photodiode in described device wafers, and described photodiode is near the back side of described device wafers；And positively charged film layer, described positively charged film layer covers the back side of described device wafers.The energy band potential barrier near the device wafers back side is improve by positively charged film layer, improve the difficulty that electronics is fled from from photodiode, thus reduce the probability that electronics is fled from from photodiode, and then improve photon conversion efficiency, improve the image quality of back-illuminated type CMOS.

Description

Back-illuminated type CMOS

Technical field

The present invention relates to image sensor technical field, particularly to a kind of back-illuminated type CMOS.

Background technology

Digital camera is the most widely used electronic product, and includes image sensor in digital camera, its In order to convert light into electric charge.Principle that image sensor can use according to it and divide into charge coupled device (Charge- Coupled Device) image sensor (that is being commonly called as CCD image sensor) and CMOS(Complementary Metal Oxide Semiconductor) image sensor, wherein CMOS is i.e. based on CMOS complementary metal-oxide-semiconductor (CMOS) technology and manufacture.Owing to CMOS is to use traditional cmos circuit technique to make, therefore can be by image Sensor and its required peripheral circuit are integrated.

Illuminate (Front Side Illumination, FSI) technology before traditional CMOS system employing to come Manufacturing the pixel on pel array, its incident illumination need to get to photo-sensing area through the front end (front side) of pixel (photo-sensing area).It is to say, illuminate the structure of CMOS before traditional so that incident illumination needs Photo-sensing area just can be arrived after dielectric layer to be first passed through (dielectric layer), metal level (metal layer), and It is serious that this causes conventional CMOS image sensor need to face between low photon conversion efficiency (quantum efficiency), pixel Cross interference (cross talk) and dark current (dark current) etc. problem.

To this end, propose another kind of CMOS in prior art, it is back lighting (Back Side Illumination, BSI) CMOS, also referred to as back-illuminated type CMOS.It is different from and above illuminates skill Art, back-illuminated type CMOS is built image sensor by the front end of silicon wafer (silicon), and it is by colored filter (color filter) and micromirror (microlens) are positioned over the back (back side) of pixel so that incident illumination is by shadow As the back of sensor enters image sensor.Compared to above illuminating CMOS, this back-illuminated type CMOS image Sensor has less light loss (light loss) and higher photon conversion efficiency.

Wherein, photon conversion efficiency is an important parameter of CMOS, common, and photon conversion efficiency is more Height, then the image quality of CMOS is the highest.Though the photon conversion efficiency of existing back-illuminated type CMOS Relatively above illumination CMOS to be got well, but, in order to obtain higher image quality, it is desirable to improve back-illuminated type CMOS The photon conversion efficiency of image sensor.

Summary of the invention

It is an object of the invention to provide a kind of back-illuminated type CMOS, to improve back-illuminated type CMOS image sensing The photon conversion efficiency of device.

For solving above-mentioned technical problem, the present invention provides a kind of back-illuminated type CMOS, including:

Device wafers, described device wafers has front and the back side, is formed with photodiode, institute in described device wafers State the photodiode back side near described device wafers；And

Positively charged film layer, described positively charged film layer covers the back side of described device wafers.

Optionally, in described back-illuminated type CMOS, the material of described positively charged film layer is oxide.

Optionally, in described back-illuminated type CMOS, the material of described positively charged film layer is borosilicate glass One or more in glass, indium glass and titanizing glass.

Optionally, in described back-illuminated type CMOS, the thickness of described positively charged film layer is 20 angstroms ~ 300 angstroms.

Optionally, in described back-illuminated type CMOS, described positively charged film layer is sunk by chemical gaseous phase Long-pending technique is formed.

Optionally, in described back-illuminated type CMOS, also include metal shielding layer, described metal shielding layer Cover described positively charged film layer.

Optionally, in described back-illuminated type CMOS, the material of described metal shielding layer is aluminum or tungsten.

In the back-illuminated type CMOS that the present invention provides, improve near device brilliant by positively charged film layer The energy band potential barrier at the circle back side, improves the difficulty that electronics is fled from from photodiode, thus reduces electronics from photoelectricity two pole The probability fled from pipe, and then improve photon conversion efficiency, improve the image quality of back-illuminated type CMOS.

Accompanying drawing explanation

Fig. 1 is the generalized section of existing back-illuminated type CMOS；

Fig. 2 is the generalized section of the back-illuminated type CMOS of the embodiment of the present invention；

Fig. 3 is back-illuminated type CMOS and the photoelectricity in existing back-illuminated type CMOS of the present embodiment The energy band potential well comparison diagram of diode.

Detailed description of the invention

The back-illuminated type CMOS provided the present invention below in conjunction with the drawings and specific embodiments is made the most in detail Describe in detail bright.According to following explanation and claims, advantages and features of the invention will be apparent from.It should be noted that, accompanying drawing is equal Use the form simplified very much, only in order to facilitate, to aid in illustrating lucidly the purpose of the embodiment of the present invention.

As described in the background art, back-illuminated type CMOS technology is above illuminating the skill of CMOS Growing up in art, it is by changing the position that light is irradiated in CMOS, for above illuminating CMOS image The problem that photon conversion efficiency in sensor is low has carried out certain improvement.As it is shown in figure 1, it is existing back-illuminated type CMOS The generalized section of image sensor.This existing back-illuminated type CMOS 1 includes:

Device wafers 11, described device wafers 11 has front 111 and the back side 112, is formed in described device wafers 11 Photodiode 12, described photodiode 12 is near the back side 112 of described device wafers 11；And

High-K dielectric layer (i.e. dielectric layer of high dielectric constant) 13, described high-K dielectric layer 13 covers the back of the body of described device wafers 11 Face 112.

Though this existing back-illuminated type CMOS 1 is compared to the photon conversion above illuminating CMOS Efficiency increases, and so based on the continuous pursuit to the CMOS quality of image, it is desirable to improve further back-illuminated The photon conversion efficiency of formula CMOS, but this point always produces little effect.

For this problem, inventor has carried out continuous further investigation, finally finds:

In existing back-illuminated type CMOS 1, in light 14 incides photodiode 12, and at photoelectricity Diode 12 creates a large amount of electronics 15, during realizing CMOS photon conversion, will have a certain amount of Electronics 15 flees from the constraint of photodiode 12, and fleeing from just because of these electronics 15, cause CMOS The low problem of photon conversion efficiency.

After being found that the problem of this obstruction CMOS photon conversion efficiency, inventor grinds further Study carefully, base this, it is proposed that improve back-illuminated type CMOS photon conversion efficiency solution.

Concrete, refer to Fig. 2, it is the generalized section of back-illuminated type CMOS of the embodiment of the present invention. As in figure 2 it is shown, described back-illuminated type CMOS 2 includes:

Device wafers 21, described device wafers 21 has front 211 and the back side 212, is formed in described device wafers 21 Photodiode 22, described photodiode 22 is near the back side 212 of described device wafers 21；And

Positively charged film layer 23, described positively charged film layer 23 covers the back side 212 of described device wafers 21.

In the present embodiment, the material of described positively charged film layer 23 is oxide, concrete, can be Pyrex, One or more in indium glass and titanizing glass.Preferably, the thickness of described positively charged film layer 23 is 20 angstroms ~ 300 Angstrom, such as, the thickness of described positively charged film layer 23 can be 40 angstroms, 60 angstroms, 80 angstroms, 100 angstroms, 120 angstroms, 150 angstroms, 170 angstroms, 200 angstroms, 230 angstroms, 250 angstroms or 270 angstroms.

In the present embodiment, the energy near device wafers 21 back side 212 can be improved by above-mentioned positively charged film layer 23 Band potential barrier；Due to can band potential barrier improve, when light 24 is from the back side of device wafers 21 near device wafers 21 back side 212 212 when inciding photodiode 22, and electronics 25 dyschezia formed in photodiode 22 is to escape from photodiode 22 From, the most just can reduce the probability that electronics 25 is fled from from photodiode 22, and then improve back-illuminated type CMOS image sensing The photon conversion efficiency of device, and improve the image quality of back-illuminated type CMOS.

Refer to Fig. 3, it is back-illuminated type CMOS and the existing back-illuminated type CMOS image biography of the present embodiment In sensor, photodiode can band potential well comparison diagram.As it is shown on figure 3, the degree of depth in wherein abscissa represents photodiode, Unit is micron, and the degree of depth near the device wafers back side is the biggest；Vertical coordinate represents potential energy, and unit is volt；Light is from device wafers Back surface incident in photodiode, shown in Fig. 3, be on the right side of coordinate system incident.

As can be seen from Fig. 3, away from the part photodiode at the device wafers back side, the back-illuminated type CMOS of the present embodiment Image sensor with in existing back-illuminated type CMOS photodiode can carry essentially identical, and potential energy is the most non- Chang great, therefore, the electronics in this part photodiode is difficult to flee from the constraint of photodiode；And carrying on the back near device wafers In the part photodiode in face, the gesture of the part photodiode of the back-illuminated type CMOS that the present embodiment is provided Can (in Fig. 3 by dashed box in L1 indicate) apparently higher than the part photoelectricity of back-illuminated type CMOS of prior art In the potential energy diagram 3 of diode by dashed box in L2 indicate).

The back-illuminated type CMOS provided due to the present embodiment greatly improves near the device wafers back side Energy band potential barrier, when light is from the back surface incident of device wafers to photodiode, compared to the back-illuminated type CMOS of prior art Image sensor, the electronics dyschezia formed in the photodiode of the back-illuminated type CMOS of the present embodiment is with from light Electric diode is fled from, the most just can reduce the probability that electronics is fled from from photodiode, and then improve back-illuminated type CMOS The photon conversion efficiency of image sensor, and improve the image quality of back-illuminated type CMOS.

Further, described positively charged film layer 23 can be formed by chemical vapor deposition method.Concrete, can be by described Device wafers 21 is inserted in chemical vapor deposition chamber, it is preferred that the temperature of described chemical vapor deposition chamber is 300 DEG C ~ 800 DEG C, (according to selected material difference, being passed through different reacting gas accordingly, this is existing skill to then pass to reacting gas Art, this is repeated no more by the application), form described positively charged film layer 23 by chemical vapor deposition method.

In the present embodiment, described back-illuminated type CMOS 2 also includes metal shielding layer (not shown in Fig. 2), Described metal shielding layer covers described positively charged film layer 23, it is preferred that the material of described metal shielding layer is aluminum or tungsten.Logical Cross described metal shielding layer it can be avoided that the problem of back-illuminated type CMOS color cross talk, improve described back-illuminated further The quality of formula CMOS.

Foregoing description is only the description to present pre-ferred embodiments, not any restriction to the scope of the invention, this Any change that the those of ordinary skill in bright field does according to the disclosure above content, modification, belong to the protection of claims Scope.

Claims

1. a back-illuminated type CMOS, it is characterised in that including:

Device wafers, described device wafers has front and the back side, is formed with photodiode, described light in described device wafers Electric diode is near the back side of described device wafers；And

2. back-illuminated type CMOS as claimed in claim 1, it is characterised in that the material of described positively charged film layer For oxide.

3. back-illuminated type CMOS as claimed in claim 2, it is characterised in that the material of described positively charged film layer For one or more in Pyrex, indium glass and titanizing glass.

4. the back-illuminated type CMOS as described in any one in claims 1 to 3, it is characterised in that described band is just The thickness of electric charge film layer is 20 angstroms ~ 300 angstroms.

5. the back-illuminated type CMOS as described in any one in claims 1 to 3, it is characterised in that described band is just Electric charge film layer is formed by chemical vapor deposition method.

6. the back-illuminated type CMOS as described in any one in claims 1 to 3, it is characterised in that also include gold Belonging to shielding layer, described metal shielding layer covers described positively charged film layer.

7. back-illuminated type CMOS as claimed in claim 6, it is characterised in that the material of described metal shielding layer is Aluminum or tungsten.