JP2003258238A - Solid-state imaging device and its fabricating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower the contact resistance between an interconnect part and a transfer electrode without using aluminum or tungsten. <P>SOLUTION: The solid-state imaging device comprises a semiconductor substrate 12 on which a plurality of photoelectric conversion regions 14 for converting an incident light into a charge signal and a plurality of transfer regions 16 for transferring a charge signal converted in the photoelectric conversion region 14 to the next stage are formed, a plurality of transfer electrodes 20 formed on the semiconductor substrate 12 in correspondence with the plurality of transfer regions 16 and imparting a transfer clock signal to each transfer region 16, and an interconnect part 24 of metal silicide material for applying a supplied transfer clock signal to the plurality of transfer electrodes 20. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device and a manufacturing method thereof, and more particularly to a solid-state image pickup device having a plurality of photoelectric conversion regions for converting light incident from a subject to be imaged into a charge signal and a manufacturing method thereof. .

[0002]

2. Description of the Related Art CCD for converting incident light into a charge signal
Polycrystalline silicon is usually used for the transfer electrode of the solid-state imaging device made of. In this case, since the polycrystalline silicon has a large resistance, a propagation delay occurs and it is difficult to drive at high speed. In particular, in recent years, the solid-state imaging device has been increased in size and the transfer electrode has been lengthened, so that the propagation delay is further increased and it is extremely difficult to perform high-speed driving.

Therefore, a solid-state image pickup device having a shunt wiring structure using a refractory metal such as Al (aluminum) or W (tungsten) is proposed (for example, Japanese Patent Laid-Open No. 6-2.
52376, JP-A-11-274445)
Has been done.

In Japanese Patent Laid-Open No. 6-252376, a shunt wiring made of aluminum for applying a 4-phase transfer clock to each transfer electrode of a plurality of vertical transfer parts,
In a wiring structure having four bus lines arranged at the end of the shunt wiring in a state intersecting with the end and supplying a transfer clock for each phase to the shunt wiring, four bus lines Among them, four shunt wirings are made to intersect with the bus line on the vertical transfer section side every other group within one group, and the point where the shunt wiring intersects the bus line is 1 of the number of vertical transfer columns. A configuration for reducing the number to / 2 is disclosed.

On the other hand, Japanese Patent Application Laid-Open No. 11-274445 discloses a solid-state image pickup device in which a buffer layer including a metal silicide layer is formed between a transfer electrode and a shunt wiring layer made of a metal layer. FIG. 10 is a partial cross-sectional view showing the configuration of this solid-state imaging device. In the figure,
A photoelectric conversion region 44 and a vertical transfer region 46 are formed on the semiconductor substrate 42 by ion implantation or the like. On the upper surface of the insulating film 48 laminated on the semiconductor substrate 42, first and second transfer electrodes 50 made of a polycrystalline silicon layer are formed at positions corresponding to the vertical transfer regions 46. Further, the insulating film 52 is formed over the entire upper surface including the upper surfaces of the transfer electrodes 50, and the metal silicide layer 5 is formed on the upper surface of the insulating film 52 corresponding to the position of the transfer electrodes 50.
4 are formed.

An insulating film 56 is formed on the entire upper surface including the upper surface of the metal silicide layer 54, and a polycrystalline silicon layer 58 is formed on the upper surface of the insulating film 56 corresponding to the position of the metal silicide layer 54. Then, an opening 56a is formed in the insulating film 56 corresponding to the position of the metal silicide layer 54 on the side (left side in the drawing) of the photoelectric conversion region 44 where the charge signal is transferred, and the contact portion 58a of the polycrystalline silicon layer 58 is formed. Are in contact with the upper surface of the metal silicide layer 54. With such a two-layer structure (so-called polycide) of the polycrystalline silicon layer 58 and the metal silicide layer 54,
A buffer layer is formed.

A light shielding film 62 made of aluminum is formed on the upper surface of the insulating film 60 formed over the entire upper surface including the upper surface of the buffer layer. In the light shielding film 62, an opening 62a is formed in a portion corresponding to the central position of the photoelectric conversion region 44. Then, the light shielding film 6
A flattening layer 64 is formed on the upper surfaces of 2 and the opening 62a by spin coating or etch back, and an on-chip microlens 66 is formed on the upper surface of the flattening layer 64. In this on-chip microlens 66, a convex lens portion 66a is formed at a portion corresponding to the position of the opening 62a of the light shielding film 62.

In the structure of such a solid-state image pickup device, the buffer layer including the metal silicide layer 54 suppresses the fluctuation of the work function in the transfer electrode 50, and the transfer electrode 5
The channel potential shift at 0 can be prevented. Further, the two-layer structure of the polycrystalline silicon layer 58 and the metal silicide layer 54 can reduce the contact resistance between the shunt wiring layers. In addition, the convex lens portion 66a of the on-chip microlens 66 allows the incident light to converge on the opening portion 62a of the light shielding film 62 to improve the sensitivity.

[0009]

However, in the case of the solid-state image pickup device disclosed in Japanese Unexamined Patent Publication No. 6-252376 in the above conventional technique, the shunt wiring is made of aluminum, so that the heat treatment at 600.degree. A buffer layer is required to prevent the shunt wiring from reacting with silicon, the light-shielding film cannot be formed close to the silicon substrate, the sensitivity is lowered, and charges unrelated to the image of the subject are generated. There is a problem that the smear level becomes high by being transferred to the next stage.

On the other hand, in the case of the solid-state image pickup device disclosed in Japanese Patent Laid-Open No. 11-274445, the shunt wiring is made of a refractory metal such as tungsten. A barrier metal such as TiN (titanium nitride) or WN (tungsten nitride) is required in the contact portion because it reacts with crystalline silicon. Therefore, in the case of titanium nitride, it is easy to bond with hydrogen, so that the interface state of the surface of the photoelectric conversion region becomes high, and in the case of tungsten nitride, the contact resistance becomes large, which is not sufficient for further high-speed driving. There was a problem. Further, since the buffer layer having a two-layer structure exists between the shunt wiring and the transfer electrode, the distance between the on-chip microlens and the photoelectric conversion region becomes large, the light collection rate is reduced, and the F-value dependence of the external lens There was a problem that it became stronger.

The present invention has been made in order to solve such a problem, and a solid-state image pickup device capable of reducing the contact resistance between a wiring portion and a transfer electrode without using aluminum or tungsten, and a manufacturing method thereof. The purpose is to provide.

Further, the present invention provides a solid-state image pickup device capable of improving the sensitivity and reducing the smear even if the shunt wiring is formed and then subjected to a heat treatment at 800 ° C. or more, and a manufacturing method thereof. The purpose is to

It is another object of the present invention to provide a solid-state image pickup device capable of improving the light-collecting rate in the photoelectric conversion region and reducing the F-number dependency of the external lens, and a manufacturing method thereof.

[0014]

In order to achieve the above-mentioned object, a solid-state image pickup device of the present invention includes a plurality of photoelectric conversion regions for converting incident light into charge signals and a charge signal converted by the photoelectric conversion regions. A semiconductor substrate on which a plurality of transfer regions to be transferred to the next stage are formed, and a plurality of transfer electrodes formed on the semiconductor substrate corresponding to the plurality of transfer regions and applying a transfer clock signal to each transfer region, And a wiring portion made of a metal silicide material for applying the supplied transfer clock signal to the plurality of transfer electrodes.

Further, in order to achieve the above-mentioned object, the method of manufacturing the solid-state image pickup device of the present invention further comprises a plurality of photoelectric conversion regions for converting incident light into image signals and charge signals converted by the photoelectric conversion regions. A first step of forming a plurality of transfer regions on the semiconductor substrate to be transferred in stages, and a second step of forming a plurality of transfer electrodes for providing a transfer clock signal to each of the plurality of transfer regions on the upper surface of the semiconductor substrate. And a third step of forming a wiring part for applying the supplied transfer clock signal to the plurality of transfer electrodes with a metal silicide material.

In the solid-state image pickup device and the manufacturing method thereof according to the present invention, the wiring portion and the transfer electrode are connected to each other by the shunt wiring using the metal silicide material without using aluminum or tungsten. Further, even if the heat treatment at 800 ° C. or higher is performed after the shunt wiring is formed, the increase in contact resistance due to the reaction between the shunt wiring using the metal silicide material and the transfer electrode is suppressed. Furthermore, by eliminating the buffer layer, the height from the semiconductor substrate is reduced and a concave lens is formed in the reflow layer.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a solid-state image pickup device and a method of manufacturing the same according to the present invention will be described below in detail with reference to the drawings. The solid-state image pickup device in this case is a frame interline CCD, and the charge signals transferred in the vertical direction by the vertical transfer area are transferred by the horizontal transfer area in the horizontal direction, and are transferred to the next stage via the buffer amplifier. Output to.

1 to 7 are partial cross-sectional views in the vertical direction during the manufacture of the solid-state imaging device according to the embodiment.
In FIG. 1, a semiconductor substrate 12 into which p-type impurities are implanted
The photoelectric conversion region 14 and the vertical transfer region 16 which are the sensor section are formed by ion implantation of low-concentration n-type impurities.

Next, as shown in FIG.
A transparent insulating film 18 made of silicon oxide is formed on the upper surface of the insulating film 18, and a transfer electrode 20 is formed on the upper surface of the insulating film 18 corresponding to the position of the transfer region 16. This transfer electrode 20 is
It has a two-layer structure of a first layer and a second layer sandwiching the photoelectric conversion region 14 (on the left and right in the drawing). Further, a transparent insulating film 22 made of silicon oxide is deposited on the entire upper surface including the upper surface of the transfer electrode 20 by vapor phase epitaxy (CVD) or the like.

Next, as shown in FIG. 3, an opening 22a is formed in the insulating film 22 by resist coating and etching using a photomask to expose the central portion 20a of the transfer electrode 20. After that, a metal silicide material is deposited on the entire upper surface by sputtering or the like, and a wiring portion 24 made of a metal silicide material is formed as shown in FIG. 4 by applying a resist and etching using a photomask. Therefore, in the wiring portion 24 on the right side of the drawing, the contact portion 24a protruding downward contacts the exposed portion 20a of the transfer electrode 20 with a low contact resistance through the opening 22a of the insulating film 22. Also in the wiring part 24 on the left side of the drawing, the contact part projecting downward passes through the opening of the insulating film at another position in the vertical direction (not shown) to expose the transfer electrode 20 on the left side of the drawing. To contact.

Next, on the entire upper surface including the upper surface of the wiring portion 24,
A transparent insulating film made of silicon oxide is deposited by CVD or the like. Further, an aluminum layer is deposited on the upper surface of this insulating film by sputtering or the like. Then, as shown in FIG. 5, a light-shielding film 28 made of aluminum is formed on the upper surface of the insulating film 26 by resist coating and etching using a photomask, and the photoelectric conversion region 1 is formed.
An opening 28a is formed in a portion corresponding to 4. next,
As shown in FIG. 6, a transparent reflow layer 30 is formed on the upper surface of the light shielding film 28 and the opening 28a thereof. In forming the reflow layer 30, the concave lens portion 3 is formed at a position corresponding to the opening 28 a of the light shielding film 28 by heating at 800 ° C. or higher.
0a is formed. By this heating, the transfer electrode 20 and the contact portion 24a of the wiring portion 24 are connected by high melting point heating, but in that case as well, the contact resistance is maintained in a low state.

Next, as shown in FIG. 7, a transparent flattening layer 32 is formed on the upper surface of the reflow layer 30 by spin coating, etch back, or CMP technique. Further, the on-chip microlens 34 is formed on the upper surface of the flattening layer 32.
Is formed. In this case, the convex lens portion 34a is formed in the portion of the on-chip microlens 34 corresponding to the opening 28a of the light shielding film 28. As a result, the light incident from the object to be imaged is converged by the convex lens portion 34a of the on-chip microlens 34 and then refracted by the concave lens portion 30a of the reflow layer 30 to generate the photoelectric conversion region 1.
It can be changed to parallel light that irradiates only the central part of 4.

Therefore, the concave lens portion 30 is provided so that the light converged by the convex lens portion 34a does not enter the transfer region 16.
It is possible to prevent smear that occurs when electric charges that are refracted by a and are not related to the image of the subject are transferred to the next stage.

FIG. 8 is a partial plan view of the solid-state image pickup device according to the embodiment. As shown in FIG.
Is connected to the transfer electrode 20 by its contact portion 24a. In the photoelectric conversion region 14, the central portion 14a (predetermined portion) corresponding to the opening 28a of the light shielding film 28 is optically exposed. Therefore, the light converged by the convex lens portion of the on-chip microlens is refracted into parallel light by the concave lens portion of the reflow layer and enters only the central portion 14 a of the photoelectric conversion region 14.

FIG. 9 is a partial plan view of a wider area than the solid-state image pickup device shown in FIG. As shown in the figure, the photoelectric conversion regions 14 which are the sensor units are arranged in a plane matrix in the vertical direction (vertical direction in the drawing) and the horizontal direction (horizontal direction in the drawing). In the figure, wiring portions 24 are four-phase wiring portions 24 (A), 24 (B), 24 in the horizontal direction.
(C) and 24 (D) are a set of shunt wirings extending in the vertical direction. On the other hand, the transfer electrode 20
Is composed of two layers of transfer electrodes 20 (A) and 20 (B), and has a configuration extending in the horizontal direction. Also, four-phase wiring parts 24 (A), 24 (B), 24 (C), 24
Corresponding to the position of (D), a vertical four-phase transfer area 16
(A), 16 (B), 16 (C), 16 (D) extend in the vertical direction.

When the plurality of contact portions 24a of the wiring portion 24 (A) are connected to, for example, the odd-numbered transfer electrodes 20 (A), the plurality of contact portions 24c of the wiring portion 24 (C) are It is connected to the even-numbered transfer electrodes 20 (A). Further, the plurality of contact portions 24b of the wiring portion 24 (B) are connected to the odd-numbered transfer electrodes 20 (B),
The plurality of contact portions 24d of the wiring portion 24 (D) are connected to the even-numbered transfer electrodes 20 (B).

A four-phase transfer clock signal is supplied to the wiring portion 24 composed of such a four-phase shunt wiring, and is branched and applied to the connected transfer electrodes. By applying the transfer clock signal, the charge signal of each photoelectric conversion region 14 is vertically transferred by the vertical transfer region 16, transferred by the horizontal transfer region (not shown), and output to the next stage.

As described above, according to the solid-state image pickup device of the above-described embodiment, the wiring portion 24 and the transfer electrode 20 are formed by the wiring portion 24 of the shunt wiring structure using the metal silicide material without using aluminum or tungsten.
The contact resistance with can be reduced to a low value. Further, even if the heat treatment at 800 ° C. or higher is performed after forming the shunt wiring, by suppressing the increase in contact resistance due to the reaction between the wiring portion 24 of the shunt wiring structure using the metal silicide material and the transfer electrode 20. In addition, the buffer layer and the buffer layer are not required, so that it is possible to improve the sensitivity and reduce the smear. Further, by eliminating the buffer layer, the height from the semiconductor substrate 12 to the on-chip microlens 34 is reduced, and by forming the concave lens 30a in the reflow layer 30, the convex lens 34a of the on-chip microlens 34 converges. By converting the emitted light into parallel light, it is possible to improve the light condensing rate on the photoelectric conversion region 14 and reduce the F value dependency of the external lens.

In the above embodiment, the wiring portion 24 is composed of four-phase shunt wiring.
(N is an integer) The wiring portion may be configured by phase shunt wiring, and the n-phase transfer clock signal may be applied to the transfer electrodes. In this case, the contact resistance can be made lower.

Further, although the present invention has been described in the above embodiment by taking the CCD solid-state image pickup device of the frame / inline type as an example, the present invention is also applied to the CCD solid-state image pickup device of the inline type. can do.

[0031]

According to the present invention, the contact resistance between the wiring portion and the transfer electrode can be lowered to a low value by the shunt wiring using the metal silicide material without using aluminum or tungsten. In addition, even if heat treatment is performed at 800 ° C. or higher after forming the shunt wiring, the buffer layer or the buffer layer is suppressed by suppressing an increase in contact resistance due to the reaction between the shunt wiring using the metal silicide material and the transfer electrode. Is unnecessary, and it becomes possible to improve sensitivity and reduce smear. Further, by eliminating the buffer layer, the height from the semiconductor substrate can be reduced, and by forming the concave lens in the reflow layer, the light collection rate to the photoelectric conversion region can be improved and the F-value dependency of the external lens can be improved. Can be reduced.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a solid-state imaging device according to an embodiment of the present invention during manufacturing.

FIG. 2 is a partial cross-sectional view of the solid-state imaging device in the process of manufacturing following the manufacturing process of FIG.

FIG. 3 is a partial cross-sectional view of the solid-state imaging device in the process of manufacturing, which is subsequent to FIG.

FIG. 4 is a partial cross-sectional view of the solid-state imaging device during the manufacturing process following the manufacturing process of FIG. 3;

5 is a partial cross-sectional view of the solid-state imaging device in the process of manufacturing, which is subsequent to FIG. 4.

FIG. 6 is a partial cross-sectional view of the solid-state imaging device in the process of manufacturing, following the manufacturing process of FIG. 5;

7 is a partial cross-sectional view of the solid-state imaging device in the process of manufacturing, which is subsequent to FIG.

FIG. 8 is a partial plan view of the solid-state imaging device according to the embodiment of the present invention.

9 is a partial plan view of a wider area than the solid-state imaging device shown in FIG.

FIG. 10 is a partial cross-sectional view of a conventional solid-state imaging device.

[Explanation of symbols]

12 ... Semiconductor substrate, 14 ... Photoelectric conversion region, 16 ...
Transfer area, 20 ... Transfer electrode, 22 ... Insulating film, 22a
...... Insulating film opening, 24 ...... Wiring part, 24a ...... Contact part, 28 ...... Light shielding film, 28a ...... Light shielding film opening, 30 ...... Reflow layer, 30a ...... Reflow layer concave lens part, 34 ... On-chip microlens, 34a ...
… Convex lens part of on-chip micro lens.

Claims (17)

[Claims] 1. A semiconductor substrate having a plurality of photoelectric conversion regions for converting incident light into charge signals and a plurality of transfer regions for transferring the charge signals converted by the photoelectric conversion regions to the next stage, A plurality of transfer electrodes formed on the semiconductor substrate corresponding to the transfer regions and applying a transfer clock signal to each transfer region, and a metal silicide material for applying the supplied transfer clock signals to the plurality of transfer electrodes. A solid-state imaging device, comprising: 2. The solid-state imaging device according to claim 1, wherein the wiring portion has a shunt wiring structure for dividing and applying an n-phase transfer clock signal to each transfer electrode. 3. The wiring part has a contact part connected to each transfer electrode through an opening formed in an insulating film deposited on the upper surface of each transfer electrode. 1. The solid-state imaging device according to 1. 4. A light-shielding film which is deposited on the upper surface of the wiring portion and on the upper surface other than the wiring portion, and which has an opening at a position corresponding to a predetermined portion of the photoelectric conversion region, An on-chip microlens having a convex lens portion formed above the opening of the light-shielding film; and the on-chip microlens formed by being deposited between the light-shielding film and the upper surface of the opening and the on-chip microlens. The solid-state imaging device according to claim 1, further comprising: a reflow film having a concave lens portion on a portion of an upper surface of the opening for converging the converged light on a predetermined portion of the photoelectric conversion region. . 5. The concave lens portion of the reflow film refracts light converged by the on-chip microlens and converts it into parallel light that irradiates only a predetermined portion of the photoelectric conversion region. The solid-state imaging device described. 6. The solid-state imaging device according to claim 4, wherein the concave lens portion of the reflow film refracts light converged by the on-chip microlens so that the light does not enter a transfer region. 7. The solid-state image pickup device according to claim 1, wherein the CCD is a frame in-line transfer type CCD. 8. The solid-state image pickup device according to claim 1, wherein the CCD is an in-line transfer type CCD. 9. A first step of forming, on a semiconductor substrate, a plurality of photoelectric conversion regions for converting incident light into image signals and a plurality of transfer regions for transferring a charge signal converted by the photoelectric conversion regions to a next stage. A second step of forming, on the upper surface of the semiconductor substrate, a plurality of transfer electrodes that apply a transfer clock signal to each of the plurality of transfer regions; and applying the supplied transfer clock signal to the plurality of transfer electrodes. A wiring part to be formed of a metal silicide material
And a method of manufacturing a solid-state imaging device, comprising: 10. The solid-state imaging device according to claim 9, wherein in the third step, a wiring portion having a shunt wiring structure for dividing and applying an n-phase transfer clock signal to each transfer electrode is formed. Device manufacturing method. 11. The third step comprises forming an opening at a predetermined position of an insulating film formed on the upper surface of each transfer electrode, and forming a contact portion that comes into contact with each transfer electrode through the opening. The method for manufacturing a solid-state imaging device according to claim 9, wherein the wiring portion having the wiring portion is formed. 12. A fourth step of forming an insulating film on an upper surface of the wiring portion and an upper surface other than the wiring portion, and at a position corresponding to a predetermined portion of the photoelectric conversion region on the upper surface of the deposited insulating film. A fifth step of forming a light-shielding film having an opening, and condensing light converged by a convex lens portion of an on-chip microlens formed above the opening of the light-shielding film on a predetermined portion of the photoelectric conversion region. 10. The method for manufacturing a solid-state imaging device according to claim 9, further comprising: a sixth step of forming a reflow film having a concave lens portion on the upper surface of the opening. 13. The sixth step is characterized in that, when heat treatment at 800 ° C. or higher is performed to form the concave lens portion, the transfer electrode and the contact portion of the wiring portion are connected by high melting point heating. The method for manufacturing a solid-state imaging device according to claim 12. 14. The reflow film having a concave lens portion for refracting the light converged by the on-chip microlens and converting it into parallel light that irradiates only a predetermined portion of the photoelectric conversion region, in the sixth step. The solid-state imaging device manufacturing method according to claim 12, wherein the solid-state imaging device is formed. 15. The reflow film having a concave lens portion for refracting the light converged by the on-chip microlens so as not to enter the transfer region, in the sixth step. 13. The method for manufacturing a solid-state imaging device according to item 12. 16. The method for manufacturing a solid-state image pickup device according to claim 9, wherein a CCD of a frame / inline transfer system is manufactured. 17. The method for manufacturing a solid-state image pickup device according to claim 9, wherein a CCD of an in-line transfer system is manufactured.