CN107887401A - Back side illumination image sensor and its manufacture method - Google Patents

Abstract

The invention provides a back-illuminated image sensor and a manufacturing method thereof, comprising: a supporting substrate; a wiring layer including a metal wiring layer and a dielectric layer surrounding the metal wiring layer, the metal wiring layer including The connected interconnection metal layer and the lead-out metal layer for electrical lead-out; the metal plug, including the interconnection metal plug connected with the interconnection metal layer, and the lead-out metal plug connected with the lead-out metal layer; back-illuminated An image sensor chip, the circuit on the front side is electrically connected to the interconnection metal layer through the interconnection metal plug; a groove is formed in the back-illuminated image sensor chip and exposes the lead-out metal plug; and A metal pad is formed in the groove and electrically connected with the lead-out metal plug. The invention only needs one photolithography process to realize the electrical lead-out of the back-illuminated image sensor chip, and the invention has a relatively simple process and can greatly reduce the manufacturing cost.

Description

Back-illuminated image sensor and manufacturing method thereof

technical field

The invention belongs to the field of semiconductor manufacturing, in particular to a back-illuminated image sensor and a manufacturing method thereof.

Background technique

In the traditional FSI front-illumination structure, photons need to pass through the insulating layer and metal layer to reach the photodiode. During this period, some photons will be reflected by the insulating layer and metal layer and bounce back into the air, resulting in a decrease in the sensitivity of the image sensor. The biggest optimization of the back-illuminated image sensor is to change the internal structure of the components. The back-illuminated image turns the direction of the components of the photosensitive layer so that the light can enter directly from the back, avoiding the light that is slightly affected by the traditional image sensor structure. The influence of the circuit and transistor between the lens and the photodiode can significantly improve the light efficiency and greatly improve the photosensitive effect under low light conditions. It can be seen that the back-illuminated image sensor will have a qualitative leap in sensitivity compared with the traditional image sensor.

Most of the existing back-illuminated image sensors mainly connect the polysilicon gate and the aluminum pad through the silicon wafer via (TSV), but the contact resistance between the TSV and the polysilicon gate is relatively high. The existing technology of direct contact between the aluminum liner and the metal layer copper has complicated preparation process and high production cost.

The existing new back-illuminated image sensor is shown in FIG. 1 , its main feature is that the aluminum pad 104 is in direct contact with the metal layer copper 101 . The preparation method is to open the first groove of the substrate of the back-illuminated image sensor wafer through the first photolithography-etching process, and deposit a layer of isolation layer in the first groove; Engraving-etching process forms a second groove at the bottom of the first groove, the second groove terminates on the metal layer, and deposits an isolation layer; finally deposits metal aluminum connected to the metal layer copper, An aluminum liner is formed. This kind of process requires two photolithography processes, and its cost is relatively high.

Based on the above, it is necessary to provide a back-illuminated image sensor and a manufacturing method thereof that can effectively reduce process difficulty and manufacturing cost.

Contents of the invention

In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a back-illuminated image sensor and a manufacturing method thereof, which are used to solve the problem of the complex manufacturing process of the aluminum pad of the back-illuminated image sensor in the prior art and the cost of the process. higher question.

In order to achieve the above object and other related objects, the present invention provides a method for manufacturing a back-illuminated image sensor, the manufacturing method comprising: 1) providing a back-illuminated image sensor chip, and forming a back-illuminated image sensor chip on the surface of the back-illuminated image sensor chip Forming a metal plug and a wiring layer, the wiring layer includes an interconnection metal layer for image sensor interconnection and an extraction metal layer for electrical extraction, the metal plug includes an interconnection metal layer connected to the interconnection metal layer plug, and the lead metal plug connected to the lead metal layer, wherein the circuit on the front side of the back-illuminated image sensor chip is electrically connected to the interconnect metal layer through the interconnect metal plug; 2) providing a A supporting substrate, fixing the supporting substrate on the surface of the wiring layer; 3) forming a groove exposing the lead-out metal plug in the back-illuminated image sensor chip; and 4) in the groove A metal liner electrically connected to the lead-out metal plug is formed to realize the electric lead-out of the back-illuminated image sensor.

Preferably, the manufacturing method of the metal plug includes the steps of: a) forming a dielectric layer on the back-illuminated image sensor chip; b) opening the front side of the back-illuminated image sensor chip from the surface of the dielectric layer The first opening hole for circuit extraction and the subsequent second opening hole for the backside extraction of the back-illuminated image sensor chip; and c) filling metal in the first opening hole and the second opening hole to form the The interconnection metal plug and the lead-out metal plug.

Preferably, in step 3), a groove exposing the lead-out metal plug is formed in the back-illuminated image sensor chip by using a photolithography process and a dry etching process.

Preferably, step 4) includes the steps: 4-1) forming an isolation layer on the bottom, sidewall and top of the groove by using a sputtering process or an evaporation process, so as to prevent the metal diffusion of the metal liner and improve the The adhesion strength between the metal liner and the groove; and 4-2) forming the metal liner on the isolation layer by sputtering process or evaporation process.

Further, the material of the isolation layer is selected as titanium/titanium nitride (Ti/TiN) laminate, and the material of the metal liner is selected as aluminum (Al).

Preferably, the material of the interconnection metal layer and the extraction metal layer is copper (Cu), and the material of the interconnection metal plug and the extraction metal plug is tungsten (W).

The present invention also provides a back-illuminated image sensor, comprising: a supporting substrate; a wiring layer formed on the supporting substrate, the wiring layer including a metal wiring layer and a dielectric layer surrounding the metal wiring layer, the The metal wiring layer includes an interconnection metal layer for image sensor interconnection and an extraction metal layer for electrical extraction; a metal plug is formed in the dielectric layer of the wiring layer, and the metal plug includes a connection with the interconnection layer. The interconnection metal plug connected to the metal layer, and the lead-out metal plug connected to the lead-out metal layer; the back-illuminated image sensor chip is fixed on the wiring layer, and the circuit on the front side of the back-illuminated image sensor chip passes through the The interconnection metal plug is electrically connected to the interconnection metal layer; a groove is formed in the back-illuminated image sensor chip and the lead-out metal plug is exposed; and a metal liner is formed in the groove and electrically connected with the lead-out metal plug to realize the electrical lead-out of the back-illuminated image sensor.

Preferably, the metal plug includes: a first opening opened from the surface of the dielectric layer to the interconnection metal layer and a second opening to the lead-out metal layer; forming the interconnection metal plug with metal; and filling the second opening with metal to form the lead-out metal plug.

Preferably, there is an isolation layer between the metal pad and the groove, so as to prevent metal diffusion of the metal pad and improve the adhesion strength between the metal pad and the groove.

Further, the material of the isolation layer is selected as titanium/titanium nitride (Ti/TiN) laminate, and the material of the metal liner is selected as aluminum (Al).

Preferably, the material of the interconnection metal layer and the extraction metal layer is copper (Cu), and the material of the interconnection metal plug and the extraction metal plug is tungsten (W).

As mentioned above, the back-illuminated image sensor and its manufacturing method of the present invention have the following beneficial effects:

In the present invention, a tungsten plug is made on the lead-out metal layer of the wiring layer, and then a lead-out hole is opened from the substrate of the back-illuminated image sensor chip through a photolithography-etching process, and an aluminum liner is made in the lead-out hole. The liner is connected to the lead-out metal layer through the tungsten plug, so that the electrical lead-out of the back-illuminated image sensor chip can be realized. The invention only needs one photolithography process to realize the electrical lead-out of the back-illuminated image sensor chip, and the invention has a relatively simple process and can greatly reduce the manufacturing cost. At the same time, the present invention adopts the connection between the aluminum liner and the tungsten plug, compared with the traditional method of connecting the aluminum liner and the copper layer, it can avoid the increase of the contact resistance caused by the electrochemical reaction at the contact interface between aluminum and copper. defects, thereby effectively reducing the resistance of the wiring structure.

Description of drawings

FIG. 1 is a schematic diagram showing a lead-out structure of an aluminum pad of a back-illuminated image sensor in the prior art.

FIG. 2 is a schematic flow chart showing the steps of the manufacturing method of the back-illuminated image sensor of the present invention.

3 to 8 are schematic structural diagrams of each step of the manufacturing method of the back-illuminated image sensor of the present invention.

Component designation description

201 supporting substrate

202 wiring layer

203 Interconnect metal layers

204 lead out metal layer

205 Interconnect metal plug

206 lead out metal plug

207 back-illuminated image sensor chip

208 grooves

209 isolation layer

210 metal backing

S11～S14 steps

Detailed ways

Embodiments of the present invention are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention.

Please refer to Figure 2 to Figure 8. It should be noted that the diagrams provided in this embodiment are only schematically illustrating the basic idea of the present invention, so that only the components related to the present invention are shown in the diagrams rather than the number, shape and Dimensional drawing, the type, quantity and proportion of each component can be changed arbitrarily during actual implementation, and the component layout type may also be more complicated.

As shown in FIGS. 2 to 8 , this embodiment provides a method for manufacturing a back-illuminated image sensor, and the method includes:

As shown in FIGS. 2 to 3 to 4, step 1) S11 is first performed to provide a back-illuminated image sensor chip 207, and a metal plug and a wiring layer are formed on the surface of the back-illuminated image sensor chip 207. The wiring The layers include an interconnection metal layer 203 for image sensor interconnection and an extraction metal layer 204 for electrical extraction, the metal plug includes an interconnection metal plug 205 connected to the interconnection metal layer, and an The lead-out metal plug 206 connected to the metal layer, wherein the circuit on the front side of the back-illuminated image sensor chip 207 is electrically connected to the interconnection metal layer 203 through the interconnection metal plug 206 .

Specifically, the manufacturing method of the metal plug includes the steps of:

Step a), forming a dielectric layer on the back-illuminated image sensor chip 207;

Step b), opening the first opening for the circuit lead out of the front side of the back-illuminated image sensor chip and the second opening hole for the subsequent lead-out of the back side of the back-illuminated image sensor chip from the surface of the medium layer ;

Step c) filling the first opening and the second opening with metal to form the interconnection metal plug 205 and the lead-out metal plug 206 .

As an example, the interconnection metal plug 205 and the lead-out metal plug 206 are made of tungsten (W).

As an example, the material of the interconnection metal layer 203 and the extraction metal layer 204 is copper (Cu), and the material of the dielectric layer is silicon dioxide. The wiring layer includes a metal layer and a dielectric layer. The interconnection metal layer 203 and the extraction metal layer 204 can be a multi-layer structure, and the interconnection metal layer 203 and the extraction metal layer 204 of each layer are passed through The dielectric layers are spaced apart, and interconnections are formed through metal connection holes in the spaced apart dielectric layers.

Specifically, the manufacturing method of the wiring layer includes:

Step 1, forming a first metal layer on the metal plug, and patterning the metal layer according to interconnection requirements;

In the second step, forming a first dielectric layer on the first metal layer, forming a through hole in the first dielectric layer, filling the through hole with metal to form a metal connection hole;

Step 3, forming a second metal layer on the surface of the first dielectric layer, and patterning the metal layer according to interconnection requirements;

In the fourth step, repeat the above steps from the first step to the third step to obtain a wiring layer that meets interconnection requirements.

As an example, after the wiring layer 202 is formed on the back-illuminated image sensor chip 207 , the area of the back-illuminated image sensor chip 207 corresponding to the lead-out metal plug 206 is a non-functional substrate area.

As shown in FIG. 2 and FIG. 5 , step 2) S12 is then performed to provide a supporting substrate 201 and fix the supporting substrate 201 on the wiring layer.

As an example, the supporting substrate 201 is selected as a silicon wafer. Of course, the supporting substrate 201 can also be selected as a substrate such as glass, ceramics, polymer, etc., so as to effectively reduce costs.

As an example, the supporting substrate 201 may be fixed on the wiring layer by bonding or adhesive bonding.

As shown in FIG. 2 and FIG. 6 , proceed to step 3) S13, forming a groove 208 exposing the lead-out metal plug 206 in the back-illuminated image sensor chip 207;

As an example, the groove 208 exposing the lead-out metal plug 206 is formed in the back-illuminated image sensor chip 207 by using a photolithography process and a dry etching process.

As an example, the cross-sectional shape of the groove 208 is an inverted trapezoid, so as to facilitate subsequent fabrication of the metal liner 210 . Since the groove of the present invention is a single inverted trapezoidal structure, compared with the traditional "double trapezoidal structure" etched on both sides, it can effectively reduce the difficulty of metal filling and improve the quality of metal filling to improve Mechanical stability of the metal backing.

As shown in Fig. 2 and Fig. 7-8, step 4) S14 is finally carried out to form a metal pad 210 electrically connected to the lead-out metal plug 206 in the groove 208, so as to realize the back-illuminated image The electrical lead of the sensor.

As an example, step 4) includes the steps of:

Step 4-1), using a sputtering process or an evaporation process to form an isolation layer 209 on the bottom, side walls and top of the groove 208, so as to prevent the metal diffusion of the metal pad 210 and improve the metal pad 210. 210 adhesion strength to said groove 208; and

Step 4-2), forming a metal pad 210 on the isolation layer 209 by sputtering or evaporation.

As an example, the material of the isolation layer 209 is selected as a titanium/titanium nitride (Ti/TiN) laminate, and the material of the metal liner 210 is selected as aluminum (Al). Of course, the material of the isolation layer 209 can also be changed according to requirements, and is not limited to the examples mentioned here.

As mentioned above, the present invention only needs one photolithography-etching process to expose the prefabricated lead-out metal plug 206, and then directly fabricate the metal liner 210 to realize the electrical performance of the back-illuminated image sensor. To draw out, compared with the traditional method of exposing the copper wiring layer 202 through two photolithography-etching processes, the process of the present invention is relatively simple, and the manufacturing cost can be greatly reduced. At the same time, the present invention adopts the connection between the aluminum liner and the tungsten plug, compared with the traditional method of connecting the aluminum liner and the copper layer, it can avoid the increase of the contact resistance caused by the electrochemical reaction at the contact interface between aluminum and copper. defects, thereby effectively reducing the resistance of the wiring structure.

As shown in FIG. 8 , this embodiment also provides a back-illuminated image sensor, including: a supporting substrate 201; a wiring layer 202 formed on the supporting substrate 201, and the wiring layer 202 includes a metal wiring layer 202 And a dielectric layer surrounding the metal wiring layer 202, the metal wiring layer 202 includes an interconnection metal layer 203 for image sensor interconnection and an extraction metal layer 204 for electrical extraction; a metal plug is formed on the wiring In the dielectric layer of layer 202, the metal plugs include interconnection metal plugs 205 connected to the interconnection metal layer 203, and lead-out metal plugs 206 connected to the lead-out metal layer 204; back-illuminated image sensor chip 207 , fixed on the wiring layer 202, the circuit on the front side of the back-illuminated image sensor chip 207 is electrically connected to the interconnection metal layer 203 through the interconnection metal plug 205; the groove 208 is formed in the In the back-illuminated image sensor chip 207, the lead-out metal plug 206 is exposed; and a metal liner 210 is formed in the groove 208 and electrically connected with the lead-out metal plug 206 to realize the back-illuminated image sensor chip 207. The electrical leads of the image sensor.

As an example, the cross-sectional shape of the groove 208 is an inverted trapezoid, so as to facilitate subsequent fabrication of the metal liner 210 . Since the groove of the present invention is a single inverted trapezoidal structure, compared with the traditional "double trapezoidal structure" etched on both sides, it can effectively reduce the difficulty of metal filling and improve the quality of metal filling to improve Mechanical stability of the metal backing.

As an example, the metal plug includes: a first opening opening from the surface of the dielectric layer to the interconnection metal layer 203 and a second opening opening to the lead-out metal layer 204; The interconnection metal plug 205 is formed by filling the hole with metal; and the lead-out metal plug 206 is formed by filling the second hole with metal.

As an example, there is an isolation layer 209 between the metal liner 210 and the groove 208 to prevent the metal diffusion of the metal liner 210 and improve the adhesion between the metal liner 210 and the groove 208. With strength.

As an example, the material of the isolation layer 209 is selected as a titanium/titanium nitride (Ti/TiN) laminate, and the material of the metal liner 210 is selected as aluminum (Al).

As an example, the material of the interconnection metal layer 203 and the lead-out metal layer 204 is copper (Cu), and the material of the interconnection metal plug 205 and the lead-out metal plug 206 is tungsten (W).

The invention adopts the connection between the aluminum liner and the tungsten plug, compared with the traditional method of connecting the aluminum liner and the copper layer, it can avoid the defect that the contact resistance of the aluminum and copper contact interface increases due to the electrochemical reaction, Therefore, the resistance of the wiring structure is effectively reduced.

As mentioned above, the back-illuminated image sensor and its manufacturing method of the present invention have the following beneficial effects:

In the present invention, a tungsten plug is made on the lead-out metal layer 204 of the wiring layer 202, and then a lead-out hole is opened from the substrate of the back-illuminated image sensor chip 207 through a photolithography-etching process, and an aluminum liner is made in the lead-out hole The aluminum liner is connected to the lead-out metal layer 204 through a tungsten plug, so that the electrical lead-out of the back-illuminated image sensor chip 207 can be realized. The present invention only needs one photolithography process to realize the electrical lead-out of the back-illuminated image sensor chip 207, the process of the present invention is relatively simple, and the manufacturing cost can be greatly reduced. At the same time, the present invention adopts the connection between the aluminum liner and the tungsten plug, compared with the traditional method of connecting the aluminum liner and the copper layer, it can avoid the increase of the contact resistance caused by the electrochemical reaction at the contact interface between aluminum and copper. defects, thereby effectively reducing the resistance of the wiring structure.

Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial application value.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed in the present invention should still be covered by the claims of the present invention.

Claims (11)

1. a kind of manufacture method of back side illumination image sensor, it is characterised in that the manufacture method includes：

1) provide a back side illumination image sensor chip, in the back side illumination image sensor chip surface formed metal closures and Wiring layer, the wiring layer include the extraction metal for being used for the interconnecting metal layer of imaging sensor interconnection and being drawn for electricity Layer, the metal closures include the interconnection metal closures being connected with the interconnecting metal layer, and be connected with the extraction metal level Draw metal closures, wherein, the circuit of the back side illumination image sensor chip front side by the interconnection metal closures with it is described mutually Even metal level is electrically connected with；

2) support substrate is provided, the support substrate is fixed on the wiring layer surface；

3) groove for exposing the extraction metal closures is formed in the back side illumination image sensor chip；And

4) metal gasket electrically connected with the extraction metal closures is formed in the groove, to realize that the back side illumination image passes The electrical extraction of sensor.

2. the manufacture method of back side illumination image sensor according to claim 1, it is characterised in that：The system of the metal closures Making method includes step：

A) in forming dielectric layer on the back side illumination image sensor chip；

B) open the circuit extraction for the back side illumination image sensor chip front side from the dielectric layer surface first opens Hole and the second perforate for being subsequently used for the back side illumination image sensor chip back extraction；And

C) metal is filled in first perforate and the second perforate, to form the interconnection metal closures and the extraction metal Plug.

3. the manufacture method of back side illumination image sensor according to claim 1, it is characterised in that：In step 3), use Photoetching process and dry etch process are formed in the back side illumination image sensor chip exposes the recessed of the extraction metal closures Groove.

4. the manufacture method of back side illumination image sensor according to claim 1, it is characterised in that：Step 4) includes step Suddenly：

Separation layer 4-1) is formed in the bottom of the groove, side wall and top using sputtering technology or evaporation process, to prevent The metal for stating metal gasket spreads and improves the adhesion strength of the metal gasket and the groove；And

4-2) using sputtering technology or evaporation process in forming metal gasket on the separation layer.

5. the manufacture method of back side illumination image sensor according to claim 4, it is characterised in that：The material of the separation layer For material from being titanium/titanium nitride (Ti/TiN) lamination, the material selection of the metal gasket is aluminium (Al).

6. the manufacture method of back side illumination image sensor according to claim 1, it is characterised in that：The interconnecting metal layer And the material selection for drawing metal level is copper (Cu), the material selection of the interconnection metal closures and the extraction metal closures is Tungsten (W).

A kind of 7. back side illumination image sensor, it is characterised in that including：

Support substrate；

Wiring layer, it is formed in the support substrate, the wiring layer includes metal wiring layer and surrounds the metal line The dielectric layer of layer, the metal wiring layer include being used for the interconnecting metal layer of imaging sensor interconnection and drawn for what electricity was drawn Go out metal level；

Metal closures, it is formed in the dielectric layer of the wiring layer, the metal closures are mutual including being connected with the interconnecting metal layer Even metal closures, and the extraction metal closures being connected with the extraction metal level；

Back side illumination image sensor chip, it is fixed on the wiring layer, the electricity of the back side illumination image sensor chip front side Road is electrically connected with by the interconnection metal closures with the interconnecting metal layer；

Groove, being formed in the back side illumination image sensor chip and exposing has the extraction metal closures；And

Metal gasket, it is formed in the groove and is electrically connected with the extraction metal closures, to realize that the back side illumination image passes The electrical extraction of sensor.

8. back side illumination image sensor according to claim 7, it is characterised in that：The metal closures include：

From dielectric layer surface opening until the first perforate and until the extraction metal level of the interconnecting metal layer The second perforate；

In the interconnection metal closures that first perforate filling metal is formed；And

Metal is filled in second perforate and forms the extraction metal closures.

9. back side illumination image sensor according to claim 7, it is characterised in that：The metal gasket and the groove it Between also there is separation layer, to prevent the metal of the metal gasket from spreading and improve the adhesion of the metal gasket and the groove Intensity.

10. back side illumination image sensor according to claim 9, it is characterised in that：The material selection of the separation layer is Titanium/titanium nitride (Ti/TiN) lamination, the material selection of the metal gasket is aluminium (Al).

11. back side illumination image sensor according to claim 7, it is characterised in that：The interconnecting metal layer and described draw The material selection for going out metal level is copper (Cu), and the interconnection metal closures and the material selection for drawing metal closures are tungsten (W).