JP6711597B2 - Solid-state imaging device manufacturing method, solid-state imaging device, and imaging system having the same - Google Patents

Description

The present invention relates to a solid-state imaging device manufacturing method, a solid-state imaging device, and an imaging system having the same.

In recent years, active pixel type solid-state image devices represented by CMOS image sensors have been proposed to have a global electronic shutter function.

A solid-state imaging device having a global electronic shutter function has a light receiving unit that performs photoelectric conversion and a charge holding unit that holds charges generated by photoelectric conversion in the light receiving unit. At this time, if light enters the charge holding portion and photoelectric conversion occurs, it becomes a noise signal and image quality may be deteriorated. Therefore, the charge holding portion needs to be covered with a light shielding film to prevent light from entering.

In a solid-state imaging device having a light-shielding structure, since an optically transparent insulating film exists between the substrate and the light-shielding film, the light-shielding performance is improved by preventing light from penetrating from this insulating film.

In Patent Document 1, the light-shielding film is formed after the gate electrode and the sidewall are formed to improve the light-shielding film coverage of the side wall of the gate electrode.

JP, 2014-22421, A

In a solid-state imaging device having a transistor in which a sidewall is formed under a light-shielding film in a pixel portion, when a sidewall is formed after forming a gate electrode, an exposed semiconductor region may be damaged by etching. ..

One aspect of the present invention is
Forming a first semiconductor region of the photoelectric conversion unit and a second semiconductor region of the charge holding unit in the substrate;
On the substrate, a first gate electrode of a first transistor that transfers the charges of the photoelectric conversion unit to the charge holding unit, and a second gate of a second transistor that transfers the charges from the charge holding unit. Forming electrodes,
Forming a first insulating film on the substrate after forming the first gate electrode and the second gate electrode,
Forming a second insulating film on the first insulating film;
By etching the second insulating film so that the first insulating film remains on the first semiconductor region and the second semiconductor region, the side surface of the first gate electrode and the second gate electrode are formed. Forming a first structure body and a second structure body on the side surface of the gate electrode through the first insulating film,
A film is formed after the formation of the first structure and the second structure, and a part of the film is etched, whereby the first gate electrode, the second semiconductor region, and the second Forming a light-shielding film on the gate electrode of
An upper side surface of the first structure has a curved surface shape having a center of curvature on the first gate electrode side,
An upper side surface of the second structure has a curved shape having a center of curvature on the second gate electrode side,
The present invention relates to a method for manufacturing a solid-state imaging device, wherein a distance between the photoelectric conversion unit and an end of the light shielding film that overlaps the photoelectric conversion unit in a plan view is smaller than a distance between an upper surface of the first gate electrode and the substrate.

Further, another aspect of the present invention is
A photoelectric conversion part having a first semiconductor region;
A first transistor that transfers the charge of the photoelectric conversion unit;
A charge holding portion which holds the charges transferred by the first transistor and has a second semiconductor region;
A second transistor that transfers the charge of the charge holding portion;
A first insulating film provided on the first semiconductor region, the first gate electrode of the first transistor, the second semiconductor region, and the second gate electrode of the second transistor;
A first structure which is provided on a side surface of the first gate electrode via the first insulating film and has an upper side surface having a curved surface shape having a center of curvature on the first gate electrode side;
A second structure provided on a side surface of the second gate electrode via the first insulating film, and having a curved surface shape with an upper side surface having a center of curvature on the side of the second gate electrode;
A light-shielding film provided on the first insulating film, the first structure, and the second structure;
Have
In a plan view, the light shielding film overlaps with the first gate electrode, the second semiconductor region, and the second gate electrode,
The present invention relates to a solid-state imaging device, wherein a distance between the photoelectric conversion unit and an end of the light shielding film that overlaps the photoelectric conversion unit in the plan view is smaller than a distance between an upper surface of the first gate electrode and the substrate.

Further, one aspect of the present invention is
A solid-state imaging device,
A signal processing unit that processes the output of the solid-state imaging device;
Have
The solid-state imaging device,
A photoelectric conversion part having a first semiconductor region;
A first transistor that transfers the charge of the photoelectric conversion unit;
A charge holding portion which holds the charges transferred by the first transistor and has a second semiconductor region;
A second transistor that transfers the charge of the charge holding portion;
A first insulating film provided on the first semiconductor region, the first gate electrode of the first transistor, the second semiconductor region, and the second gate electrode of the second transistor;
A first structure which is provided on a side surface of the first gate electrode via the first insulating film and has an upper side surface having a curved surface shape having a center of curvature on the first gate electrode side;
A second structure provided on a side surface of the second gate electrode via the first insulating film, and having a curved surface shape with an upper side surface having a center of curvature on the side of the second gate electrode;
A light-shielding film provided on the first insulating film, the first structure, and the second structure;
Have
In a plan view, the light shielding film overlaps with the first gate electrode, the second semiconductor region, and the second gate electrode,
The present invention relates to an imaging system, wherein a distance between the photoelectric conversion unit and an end portion of the light shielding film that overlaps the photoelectric conversion unit in the plan view is smaller than a distance between an upper surface of the first gate electrode and the substrate.

By providing a structure with a curved surface whose upper portion is convex toward the side opposite to the gate electrode on the side surface of the gate electrode of the transistor existing under the light shielding film, the step of the underlayer of the light shielding film becomes gentle and It is possible to suppress nonuniformity of the film thickness.

In addition, since the insulating film is provided on the semiconductor region when the structure is formed, damage to the semiconductor region due to etching can be reduced.

FIG. 4 is a partial equivalent circuit diagram of the solid-state imaging device according to the first, second, and third embodiments. 3 is a schematic plan view of a part of the solid-state imaging device according to Embodiments 1, 2, and 3. FIG. FIG. 3 is a schematic sectional view of a part of the solid-state imaging device according to the first embodiment. FIG. 3 is a schematic sectional view of a part of the solid-state imaging device according to the first embodiment. FIG. 3 is a schematic sectional view of a part of the solid-state imaging device according to the first embodiment. FIG. 6 is a schematic cross-sectional view of a part of the solid-state imaging device according to the second embodiment. FIG. 6 is a schematic cross-sectional view of a part of the solid-state imaging device according to the second embodiment. FIG. 7 is a schematic cross-sectional view of a part of the solid-state imaging device according to the third embodiment. FIG. 7 is a schematic cross-sectional view of a part of the solid-state imaging device according to the third embodiment. FIG. 16 is a block diagram of an example of an imaging system according to a fourth embodiment.

When a layer is described herein as "on" another layer or substrate, that layer may be directly on top of the other layer or substrate, with another layer interposed therebetween. May be. When an element is described as being "directly above" another element, that element is provided above and in contact with the other element.

In the present specification, the same reference numerals indicate the same or similar members or members having the same or similar functions.

(Embodiment 1)
Embodiments for carrying out the present invention will be described below with reference to the drawings.

FIG. 1A is an equivalent circuit diagram of a part of the solid-state imaging device according to the present embodiment, and FIG. 1B is a schematic plan view of a part of the solid-state imaging device according to the present embodiment. Here, as a part of the pixel portion 501, pixels 401 each having a charge holding portion are arranged in three rows and three columns.

The pixel portion 501 includes a light shielding film 303, a photoelectric conversion portion 402 that is a light receiving portion, a charge holding portion 403, a floating diffusion portion 404 (hereinafter, FD portion), a power supply portion 405, and a pixel output portion 406. Further, as shown in FIG. 1A, the pixel unit 501 includes a first transfer transistor 4 that transfers the charges of the photoelectric conversion unit 402, a second transfer transistor 5 that transfers the charges from the charge holding unit 403, and an FD unit. It has a resetting transistor 9 for resetting the electric charges of. Further, the pixel portion 501 has an amplification transistor 10, a selection transistor 7, and an overflow drain (hereinafter, OFD) transistor 6 which serves as a charge discharging portion.

2A is a schematic cross-sectional view of a part of the solid-state imaging device shown in FIG. 1B, and shows a cross section of a portion of the pixel portion indicated by AB in FIG. 1B and a cross-sectional portion of an arbitrary transistor in the peripheral circuit portion 502. Is. The substrate 100 is a semiconductor substrate and has wells 101 and 102 and an element isolation portion 103.

The first transfer transistor 4 has a gate electrode 600, the second transfer transistor 5 has a gate electrode 601, and the reset transistor 9 has a gate electrode 602. The amplification transistor 10 has a gate electrode 603, the selection transistor 8 has a gate electrode 604, and the OFD transistor 6 has a gate electrode 415. These plan views are shown in FIG. 1B. In the well 101 of the pixel portion 501, an N-type semiconductor region 420 that forms the photoelectric conversion unit 402, an N-type semiconductor region 421 that forms the charge holding unit 403, and an N-type semiconductor region 422 that forms the FD unit 404. Are formed. Further, P-type semiconductor regions 430 and 431 functioning as a surface protection layer are formed on the N-type semiconductor regions 420 and 421. In addition to the well 101 of the pixel portion 501, N-type semiconductor regions 423 and 424 functioning as the source/drain of the pixel portion transistor and an N-type semiconductor region 425 forming the pixel output portion 406 are arranged. ..

In the well 102 of the peripheral circuit portion 502, semiconductor regions 426, 427, and 428 that function as the source/drain of the transistors in the peripheral circuit portion are formed. A silicide layer 432 is formed on the source/drain and the gate electrode of the transistor in the peripheral circuit portion in order to reduce the resistance of the contact portion of the contact plug. As the silicide layer 432, a silicide film of cobalt silicide, titanium silicide, nickel silicide, or the like can be used.

In plan view, the gate electrode 600 of the first transfer transistor is formed so as to be adjacent to the photoelectric conversion unit 402, and the gate electrode 601 of the second transfer transistor is formed so as to be adjacent to the charge holding unit 403. Further, the gate electrode 602 of the reset transistor, the gate electrode 603 of the amplification transistor, and the gate electrode 604 of the selection transistor are arranged on the well 101. Gate electrodes 605 and 606 of the transistors in the peripheral circuit section are arranged on the well 102.

Here, when an insulating layer is formed on the gate electrodes 600 and 601, and a light-shielding film is formed thereon, the film thickness of the light-shielding film locally decreases at the end portions of the gate electrodes 600 and 601 and the light-shielding performance is reduced. May decrease. When the light shielding performance is deteriorated, for example, photoelectric conversion occurs due to the light with which the charge holding portion is irradiated, and a noise signal may be generated.

Therefore, in order to suppress the reduction in the thickness of the light-shielding film, a structure in which at least the upper side surface is a curved surface and the center of curvature of the curved surface is on the gate electrode 600 side is provided on the side surface of the gate electrode 600. Similarly, a structure in which at least an upper side surface is a curved surface and a center of curvature of the curved surface is on the gate electrode 601 side is provided on a side surface of the gate electrode 601. Accordingly, the surface of the light-shielding film which faces the light-shielding film to be covered (here, the upper surface of the gate electrodes 600 and 601 and the surface which connects the side surfaces of the structures 813 and 814) is gently undulated, and thus the light-shielding film is formed. It is possible to suppress the film thickness reduction.

Such a structure is formed by forming a film on the gate electrode and dry-etching the film, for example, similarly to the sidewall spacer provided on the side surface of the gate electrode of the transistor in the peripheral circuit portion 502. be able to.

On the other hand, if the film is etched to form the structure, the semiconductor region of the photoelectric conversion portion 402 or the semiconductor region of the charge holding portion 403 may be damaged. Therefore, in order to reduce damage due to etching, an insulating film is formed over the semiconductor region of the photoelectric conversion portion 402 or the semiconductor region of the charge holding portion 403 after the gate electrodes 600 and 601 are formed and before the structure is formed. Accordingly, at the time of etching for forming the structure, the semiconductor region of the photoelectric conversion unit 402 and the semiconductor region of the charge holding unit 403 are covered with the insulating film, so that damage to these semiconductor regions can be suppressed. ..

A specific example of the structure of the image pickup apparatus having the above characteristics will be described with reference to FIG. 2A. In the pixel portion 501, an insulating film 701 is formed so as to cover the gate electrodes 600 to 604. Structures 813, 814, 815, 816, and 817 are provided on the side surfaces of the gate electrodes 600, 601, 602, 603, and 604 with the insulating film 701 interposed therebetween.

In each of the structures 813, 814, 815, 816, and 817, at least the upper side surface is a curved surface, and the curvature center of the curved surface is on the corresponding gate electrode side. For example, each of the structures 813, 814, 815, 816, and 817 has a curved shape in which an upper portion is convex outward (a side opposite to a corresponding gate electrode).

Therefore, since the structures 813 to 817 are provided on the side surfaces of the gate electrodes 600 to 604, the step between the gate electrode and the substrate can be made gentle, and a local film of the light-shielding film formed thereover can be formed. It is possible to suppress a decrease in thickness.

Here, the insulating film 701 is provided between the gate electrode and the structure, but even in that case, the step is made gentle by providing the structure, so that the effect of reducing the local decrease in the thickness of the light-shielding film can be obtained. Obtainable.

The insulating film 701 on the photoelectric conversion portion 402 also functions as an antireflection film. Therefore, it is preferable that the material and the thickness of the insulating film 701 take into consideration the refractive index of the substrate 100, the insulating film formed over the insulating film 701, or the like. Here, the insulating film 701 can be formed using a nitride film or a stacked layer of an oxide film and a nitride film. For example, a film containing silicon nitride as a main component or a film containing silicon oxide as a main component and silicon nitride is used. The film can be formed by stacking films having as a main component.

The structures 813 to 817 can be formed by forming an oxide film, for example, a film containing silicon oxide as a main component over the substrate as the insulating film 702 so as to cover the gate electrodes 600 to 604 and etching.

In the peripheral circuit portion 502, structures 801 and 802 are provided on the side surfaces of the gate electrodes 605 and 606, respectively, in which at least the upper side surface is a curved surface and the center of curvature of the curved surface is on the corresponding gate electrode side. Since the structures 801 and 802 are formed of the insulating film 701, the structures 801 and 802 and the insulating film 701 have the same main component.

Further, in the peripheral circuit portion 502, an insulating film 703 is formed over the substrate so as to cover the gate electrodes 605 and 606 and the structures 801 and 802. The insulating film 703 is formed of a nitride film, or a stack of an oxide film and a nitride film, for example, a film containing silicon nitride as a main component or a stack of a layer containing silicon oxide as a main component and a layer containing silicon nitride as a main component. be able to.

The insulating film 703 functions as a diffusion prevention layer that prevents a metal element forming a silicide such as cobalt, titanium, or nickel from diffusing from the silicide layer 432. Therefore, by using a silicon nitride film having a higher density than the silicon oxide film or a stacked-layer structure including a silicon nitride film, metal diffusion can be further reduced.

Further, the insulating film 301 is provided over the insulating film 701 and the structures 813 to 817 of the pixel portion 501 and the insulating film 703 of the peripheral circuit portion 502. By providing the insulating film 301, the step difference can be further reduced. The insulating film 301 can be formed using an oxide film, for example, a film containing silicon oxide as its main component. Note that here, although an example in which the insulating film 301 is provided is shown, since the steps between the gate electrode and the substrate are alleviated by the structures 813 and 814, the solid-state imaging device is provided with the insulating film 301. It may be configured not to be provided.

A light-blocking film 303 is formed over the insulating film 301 so as to cover the gate electrode 600 of the first transfer transistor, the semiconductor region of the charge holding portion 403, and the gate electrode 601 of the second transfer transistor. The light-blocking film 303 can be formed by forming a film of a material having a high light-blocking property, for example, a tungsten film, and etching unnecessary portions such as a portion formed on the photoelectric conversion portion 402 and a contact formation portion.

That is, at least a part of the portion formed on the photoelectric conversion unit 402 is etched so that the light shielding film 303 does not hinder the incidence of light. Further, in order to suppress photoelectric conversion in the charge holding portion 403, the light-shielding film 303 has at least the gate electrode 600 and the semiconductor of the charge holding portion 403 in a plan view (viewed from the thickness direction of the gate insulating film 104). The region and the region overlapping with the gate electrode 601 are provided.

In order to suppress unnecessary light from entering the charge holding unit 403, it is preferable that the distance from the semiconductor region of the charge holding unit 403 to the light shielding film 303 is small. Therefore, in the case where the insulating film 301 is provided between the light-shielding film 303 and the gate electrodes 600 and 601, and the structures 813 and 814, the insulating film 301 has a flat upper surface by embedding these. It is made smaller than the flattening film. Specifically, the thickness of the insulating film 301 is preferably smaller than the thickness of the gate electrodes 600 and 601.

Therefore, the light shielding film 303 is provided so as to cover at least a part of the side surfaces of the gate electrodes 600 and 601. That is, the light shielding film 303 extends from above the gate electrodes 600 and 601 to the side surface beyond the end portions of the gate electrodes 600 and 601. From the viewpoint of light-shielding performance, the end portion of the light-shielding film 303 is preferably located closer to the substrate than the upper end portion of the gate electrode in the direction parallel to the side surface of the gate electrode 600 or 601 (height direction).

For example, when the solid-state imaging device has the insulating film 301, the light shielding film 303 covers at least a part of the side surfaces of the gate electrodes 600 and 601 with the insulating film 301 interposed therebetween. That is, the light shielding film 303 extends from above the gate electrodes 600 and 601 to the side surface beyond the end portions of the gate electrodes 600 and 601 through the insulating film 301. From the viewpoint of light-shielding performance, the edge of the light-shielding film 303 is preferably located closer to the substrate than the upper edge of the gate electrode in the direction parallel to the side surface of the gate electrode 600 or 601.

That is, the distance between the edge of the light shielding film 303 (eg, the edge of the light shielding film 303 on the photoelectric conversion portion 402) and the substrate is smaller than the distance between the upper surface of the gate electrode 600 and the substrate. Form 303. From the viewpoint of light-shielding property, the distance between the end of the light-shielding film 303 (for example, the end of the light-shielding film 303 on the photoelectric conversion unit 402) and the substrate is half or less than the distance between the upper surface of the gate electrode 600 and the substrate. Is more preferable. Here, the distance between the two members refers to the shortest distance between the two members.

Since the structures 813 and 814 are provided below the light-shielding film 303 on the side surfaces of the gate electrodes 600 and 601 with the insulating film 701 interposed therebetween, the thickness of the light-shielding film 303 is locally reduced or The deterioration of the light-shielding property due to is suppressed.

A structure in which an interlayer insulating film 901 and conductive layers 902 to 904 are formed over the light-blocking film 303 is shown in FIG. In FIG. 2B, an interlayer insulating film 901 is provided over the light-blocking film 303 of the pixel portion 501 and the insulating film 301 of the peripheral circuit portion 502. A conductive layer 902 that electrically connects the semiconductor region 423 and the power supply circuit may be provided in the opening provided in the interlayer insulating film 901 and on the interlayer insulating film 901. Similarly, a conductor 903 that electrically connects the semiconductor region 425 and the signal output line may be formed in the opening provided in the interlayer insulating film 901 and on the insulating film 901.

Further, in the pixel portion 501, the wiring 904 may be formed over the interlayer insulating film 901. Similarly, in the peripheral circuit portion 502, the conductive layer in the opening provided in the interlayer insulating film 901 may be electrically connected to the semiconductor region 432 and the wiring.

Note that in this embodiment mode, the structures 801, 802, and 813 to 817 are not provided above the gate electrodes 605, 606, and 600 to 604, respectively. The structure according to the present embodiment is not limited to this structure, and may be any structure that can suppress a local decrease in the thickness of the light shielding film. Therefore, for example, even if the structures 801, 802, and 813 to 817 extend to above the gate electrodes 605, 606, and 600 to 604, near the end of the gate electrode, the center of curvature corresponds to the gate electrode side. Any shape having a curved surface shape may be used.

Next, a method of manufacturing the solid-state imaging device of this embodiment as shown in FIG. 2A will be described with reference to FIG.

Embodiments for carrying out the present invention will be described below with reference to the drawings.

The element isolation portion 103 is formed on the substrate (semiconductor substrate) 100 by the STI method (Shallow Trench Isolation method) or the LOCOS method (Local Oxidation of Silicon method). Next, wells 101 and 102 are formed in the substrate by the ion implantation method. Further, the N-type semiconductor region 420 and the P-type semiconductor region 430 of the photoelectric conversion unit 402 and the N-type semiconductor region 421 and the P-type semiconductor region 431 of the charge holding unit 403 are formed in the pixel unit 501 by the ion implantation method.

After that, the gate insulating film 104 is formed, polysilicon is deposited thereon, and the gate electrodes 600, 601, 602, 603, 604, 605, and 606 are formed by using photolithography and etching techniques. After that, impurities are introduced into the substrate by ion implantation to form N-type semiconductor regions 422, 423, 424, and 425 (FIG. 3A).

Here, although the charge holding portion 403 is ion-implanted before the gate electrode is formed, the photoelectric conversion portion 402 and the semiconductor region 420 of the charge holding portion 403 are self-aligned by performing the ion implantation after forming the gate electrode. .421, 430, and 431 may be formed. For example, by performing ion implantation using the gate electrodes 600 and 601 of the first and second transfer transistors as masks, the semiconductor regions 420.421, 430, and 431 of the photoelectric conversion unit 402 and the charge holding unit 403 are self-aligned. Can be formed.

After that, an insulating film 701 is formed over the substrate 100 so as to cover the gate electrodes 600 to 606 by a CVD method or the like. A resist is applied to the pixel portion 501, and the insulating film 701 is etched only in the peripheral circuit portion 502 to form structures 801 and 802 which function as sidewall spacers.

The insulating film 701 can be used as an antireflection film in the pixel portion by being formed of, for example, a silicon nitride film or a stacked layer of a silicon oxide film and a silicon nitride film. In this embodiment mode, the insulating film 701 which forms the structures 801 and 802 of the peripheral circuit portion 502 is left as an insulating film which functions as a protective film and an antireflection film in the semiconductor region in the pixel portion. Therefore, when the structures 801 and 802 of the peripheral circuit portion 502 are formed, the insulating film forming the structures 801 and 802 is also etched in the pixel portion 501, and a protective film or an antireflection film of the pixel portion is separately formed. In comparison, the number of steps and cost can be reduced.

Next, as shown in FIG. 3B, in the peripheral circuit portion 502, the structures 801 and 802 are used as sidewall spacers to perform ion implantation to self-align the source/drain of the transistors in the peripheral circuit portion. Form. Next, the insulating film 702 is formed over the pixel portion 501 and the peripheral circuit portion 502. The insulating film 702 can be formed using silicon oxide, for example. After forming the insulating film 702, a resist is applied to the pixel portion, and a part of the insulating film 702 is removed by dry etching only in the peripheral circuit portion.

Next, a cobalt metal film is formed and annealed to form a silicide layer 432 on the exposed peripheral circuit portion. At this time, the insulating film 702 in the pixel portion functions as a protective film.

Immediately after forming the silicide layer 432, the insulating film 703 is formed. The insulating film 703 is for preventing diffusion of the silicide layer, a resist is applied to the peripheral circuit portion, and the insulating film 703 formed in the pixel portion is removed by etching. The insulating film 703 can be formed, for example, of a silicon nitride film or a stacked layer of a silicon oxide film and a silicon nitride film. At this time, the insulating film 702 is also etched to form structures 813 to 817 in the pixel portion 501 (FIG. 3C).

When the structures 813 to 817 are formed, the insulating film 702 is etched by dry etching while adjusting the time so that the insulating film 701 remains over the semiconductor regions 420, 421, 430, and 430. Note that the step of forming the structures 823 to 817 from the insulating film 702 may be performed at the same time as the etching of the insulating film 703, or may be performed separately by changing the etchant.

Next, an insulating film 301 is formed by using a CVD method or the like, and is used as an adhesion layer at the time of forming the light shielding film. The insulating film 301 can be formed using, for example, silicon oxide. A film having a light-shielding property, for example, a film made of at least one of tungsten, tungsten silicide, and aluminum is formed thereon by a PVD method or the like. When it is desired to further improve the adhesiveness, a metal film such as titanium or titanium nitride may be formed on the insulating film.

Next, a portion of the film having a light-shielding property, which is formed above the photoelectric conversion portion 402, a contact formation portion, or the like, is etched to form a light-shielding film 303 (FIG. 3D). The etching is performed so that a portion of the film which covers the gate electrode 600 of the first transfer layer transistor, the charge holding portion 403, and the gate electrode 601 of the second transfer transistor is left.

In the solid-state imaging device manufacturing method, by providing the structures 813 and 814 on the side surfaces of the gate electrodes 600 and 601, respectively, the coverage with the light-shielding film 303 formed thereon is improved.

In addition, the insulating film 701 is formed after the gate electrodes 600 and 601 are formed and before the structures 813 and 814 are formed, the gate electrodes 600 and 601, the semiconductor regions 420 and 430 of the photoelectric conversion portion 402, and the semiconductor region 421 of the charge holding portion 403. And 431 are formed. Accordingly, damage that occurs in the semiconductor region of the photoelectric conversion portion 402 and the semiconductor region of the charge holding portion 403 during etching of the insulating film 702 for forming the structures 813 and 814 can be reduced.

Furthermore, since the flatness of the portion where the light-shielding film 303 is provided is improved, the light-shielding film residue can be further suppressed even when the light-shielding film 303 is removed by etching, and the occurrence of leak defects can be suppressed.

(Embodiment 2)
FIG. 4 is a schematic cross-sectional view of a part of the solid-state imaging device according to another embodiment than the first embodiment. Here, description of the same parts as those of the first embodiment will be omitted, and mainly different parts will be described below.

In the pixel portion 501, structures 813 to 817 are formed on the side surfaces of the gate electrodes 600 to 604 of Embodiment 1 (FIG. 2B) via the insulating film 701, respectively, and on the side surfaces of the structures 813 to 817, Further, structures 823 to 827 are provided, respectively. In each of the structures 823 to 827, at least an upper side surface is a curved surface, and a curvature center of the curved surface is on a corresponding gate electrode side. The structures 823 to 827 include, for example, silicon oxide as a main component.

In the solid-state imaging device of this embodiment, the structure 821 is provided on the side surface of the gate electrode 605 of Embodiment 1 (FIG. 2B) with the structure 801 and the insulating film 703 interposed therebetween, and the structure of the gate electrode 606 is reduced. The structure body 822 is provided on the side surface with the structure body 802 and the insulating film 703 provided therebetween. The upper portions of the structures 821 and 822 have curved side surfaces each having a center of curvature on the corresponding gate electrode side. The structures 801 and 802 include, for example, silicon oxide as a main component.

An insulating film 301 is formed over the substrate so as to cover the insulating film 701, the structures 823 to 827, and the structures 821 and 822.

A light-shielding film 303 is formed over the insulating film 301 so as to cover the gate electrode 600 of the first transfer transistor, the semiconductor region of the charge holding portion 403, and the gate electrode 601 of the second transfer transistor.

As described above, by further providing the structure having a curved surface shape having the center of curvature on the side of the corresponding gate electrode at least on the upper side surface, in the region where the light-shielding film 303 is formed, the step difference between the structure and the substrate is further reduced. It can be mild. Therefore, it is possible to further suppress the local reduction of the film thickness of the light shielding film 303, and it is possible to further suppress the deterioration of the light shielding performance due to the reduction of the film thickness of the light shielding film.

A method of manufacturing the solid-state imaging device according to the embodiment shown in FIG. 4 will be described with reference to FIG.

5A to 5C are the same as those in the first embodiment (FIGS. 3A to 3C).

Next, an insulating film 704 is formed, and the insulating film 704 is etched back in both the pixel portion 501 and the peripheral circuit portion 502, and further, the structures 813 to 817 and the structures 801 and 802 are further provided with structures 823 to 827, respectively. Structures 821 and 822 are formed (FIG. 5D). The structures 823 to 827 and the structures 821 and 822 can be formed using a material and a method similar to those of the structures 801, 802 and the structures 813 to 817.

Next, an insulating film 301 is formed by using a CVD method or the like, and is used as an adhesion layer at the time of forming the light shielding film. A film having a light-shielding property, for example, a film made of at least one of tungsten, tungsten silicide, and aluminum is formed thereon by a PVD method or the like. If it is desired to further improve the adhesion, a metal film of titanium, titanium nitride or the like may be formed on the insulating film.

For the light-shielding film 303, the light-shielding film 303 is formed by etching away the film formed above the photoelectric conversion portion 402, the contact formation portion, and the like (FIG. 5E). The etching is performed so that a portion of the film having a light-blocking property, which covers the gate electrode 600 of the first transfer layer transistor, the charge holding portion 403, and the gate electrode 601 of the second transfer transistor, remains.

By thus forming a plurality of structures on the side surface of the gate electrode, the coverage with the light shielding film 303 formed thereon is further improved.

In addition, the insulating film 701 is formed after the gate electrodes 600 and 601 are formed and before the structures 813 and 814 are formed, the gate electrodes 600 and 601, the semiconductor regions 420 and 430 of the photoelectric conversion portion 402, and the semiconductor region 421 of the charge holding portion 403. And 431 are formed. Accordingly, damage that occurs in the semiconductor region of the photoelectric conversion portion 402 and the semiconductor region of the charge holding portion 403 during etching of the insulating film 702 for forming the structures 813 and 814 can be reduced.

Furthermore, since the flatness of the portion where the light-shielding film 303 is provided is improved, the light-shielding film residue can be further suppressed even when the light-shielding film 303 is removed by etching, and the occurrence of leak defects can be suppressed.

(Embodiment 3)
FIG. 6 is a schematic cross-sectional view of a part of a solid-state imaging device according to an embodiment different from the first and second embodiments. Here, description of the same parts as those of the first or second embodiment is omitted, and mainly different parts will be described below.

In this embodiment mode, the structures 831 and 842 provided on the sidewalls of the gate electrodes 605 and 606 arranged in the peripheral circuit portion 502 in Embodiment Mode 1 (FIG. 2B) are not limited to the insulating film 701 and the insulating film 701. It is formed of 701 and an insulating film 702. The upper portions of the structures 831 and 832 have curved side surfaces each having a center of curvature on the corresponding gate electrode side.

The structures 831 and 832 of this embodiment include structures 841 and 842 which are provided on the side surfaces of the gate electrode and contain silicon nitride as a main component, and structures 841 and 842 which are provided on the side surfaces and contain silicon oxide as a main component, for example. And structures 851 and 852 that In the case where the insulating film 701 is a stack of silicon oxide and silicon nitride, the structures 831 and 832 are composed of two structures 841 and 842 including two layers of silicon oxide and silicon nitride, and silicon oxide from the side surface of the gate electrode. Will have structures 841 and 842.

Further, structures 823 to 827 are further provided on side surfaces of the structures 813 to 817 of the pixel portion 501, respectively. Each of the structures 823 to 827 has a structure in which at least an upper side surface has a curved shape having a center of curvature on the corresponding gate electrode side.

In the peripheral circuit portion 502, an insulating film 703 is provided over the substrate so as to cover the structures 831 and 832, and structures 821 and 822 are provided on side surfaces of the structures 831 and 832 with the insulating film 703 interposed therebetween. Has been.

Next, a method for manufacturing the solid-state imaging device of the present embodiment as shown in FIG. 6 will be described with reference to FIG.

Embodiments for carrying out the present invention will be described below with reference to the drawings.

The element isolation portion 103 is formed on the substrate 100 which is a semiconductor substrate by the STI method or the LOCOS method. Next, the wells 101 and 102 are formed by the ion implantation method. Next, the N-type semiconductor region 420 of the photoelectric conversion unit 402, the P-type semiconductor region 430, the N-type semiconductor region 421 of the charge holding unit 403, and the P-type semiconductor region 431 are formed in the pixel unit 501 by an ion implantation method.

After that, the gate insulating film 104 is formed, polysilicon is deposited thereon, and the gate electrodes 600, 601, 602, 603, 604, 605, and 606 are formed by using photolithography and etching techniques. After that, N-type semiconductor regions 422, 423, 424, and 425 are formed by ion implantation (FIG. 7A).

Here, the photoelectric conversion portion 402 and the charge holding portion 403 are ion-implanted before forming the gate electrode. However, after forming the gate electrode, the photoelectric conversion unit 402 and the charge holding unit 403 are ion-implanted, and the photoelectric conversion unit 402 and the charge are self-aligned using the gate electrodes 600 and 601 of the first and second transfer transistors. It is also possible to form the holding portion 403.

After that, as illustrated in FIG. 7B, an insulating film 701 and an insulating film 702 are formed over the gate electrode by a CVD method or the like. A resist is applied to the pixel portion 501, and the insulating films 701 and only a part of the insulating film 702 in the peripheral circuit portion are removed by dry etching, whereby structures 831 and 832 are formed. The structure body 831 includes a structure body 841 formed of the insulating film 701 and a structure body 851 formed of the insulating film 702. In addition, the structure body 832 includes a structure body 841 formed of the insulating film 701 and a structure body 852 formed of the insulating film 702.

Ion implantation is performed in the peripheral circuit portion 502 using the gate electrodes 605 and 606, the first structure body 831, and the second structure body 832 as masks, so that source/drain of transistors in the peripheral circuit portion are formed in a self-aligned manner. To do. The insulating film 701 functions as an antireflection film of the pixel portion 501 by forming a silicon nitride film or a stacked layer of a silicon oxide film and a silicon nitride film.

In this embodiment mode, the insulating film 701 which forms the structures 841 and 842 of the peripheral circuit portion 502 is left as an insulating film which functions as a protective film and an antireflection film in the semiconductor region in the pixel portion. Therefore, when the structures 841 and 842 of the peripheral circuit portion 502 are formed, the insulating film forming the structures 841 and 842 is also etched in the pixel portion 501, and a protective film or an antireflection film for the pixel portion is separately formed. In comparison, the number of steps and cost can be reduced.

Next, as in the first and second embodiments, a cobalt metal film is formed and annealed to form the silicide layer 432 on the exposed peripheral circuit portion 502. At this time, the insulating film 702 functions as a protective film when the silicide layer 432 is formed in the peripheral circuit portion 502.

Immediately after forming the silicide layer 432, the insulating film 703 is formed. This insulating film is for preventing diffusion of the silicide layer, and a resist is applied on the insulating film 703 in the peripheral circuit portion 502 and is removed by etching in the pixel portion 501. At this time, the insulating film 702 is also etched at the same time to form structures 813 to 817 in the pixel portion 501 (FIG. 7C).

Next, an insulating film 704 is formed, and the insulating film 704 is etched back for both the pixel portion 501 and the peripheral circuit portion 502, so that structures 823 to 817, 831, and 832 have side surfaces 823 to 827. 821 and 822 are formed (FIG. 7D).

Next, as shown in FIG. 7E, an insulating film 301 is formed by using a CVD method or the like to serve as an adhesion layer at the time of forming the light shielding film, and the light shielding film 303 is formed thereon.

The light-shielding film is formed as follows. A film having a light-shielding property, for example, a film formed of at least one of tungsten, tungsten silicide, and aluminum is formed over the insulating film 301 by a PVD method or the like. If it is desired to further improve the adhesion, a metal film of titanium, titanium nitride or the like may be formed on the insulating film. The light shielding film 303 is formed by etching the portion of the film above the photoelectric conversion portion 402, the contact formation portion, and the like (FIG. 7E). The etching is performed so that a portion of the film which covers the gate electrode 600 of the first transfer layer transistor, the charge holding portion 403, and the gate electrode 601 of the second transfer transistor is left.

By forming the structures 813 and 814 and the structures 823 and 824 on the side surfaces of the gate electrodes 600 and 601, the coverage with the light-blocking film 303 formed thereon is improved. By providing the structures 823 and 824 in addition to the structures 813 and 814, a surface of the light-shielding film which faces the light-shielding film to be covered (here, upper surfaces of the gate electrodes 600 and 601, and side surfaces of the structures 823 and 824) is provided. The undulations on the surface that connects the two are more gentle. Therefore, it is possible to further suppress the reduction in the thickness of the light shielding film, and the coverage with the light shielding film 303 is further improved.

That is, by forming a plurality of structures on the side surface of the gate electrode in this way, the coverage of the light-shielding film formed thereon is further improved.

In addition, the insulating film 701 is formed after the gate electrodes 600 and 601 are formed and before the structures 813 and 814 are formed, the gate electrodes 600 and 601, the semiconductor regions 420 and 430 of the photoelectric conversion portion 402, and the semiconductor regions of the charge holding portion 403. It is formed so as to cover 421 and 431. Accordingly, damage that occurs in the semiconductor region of the photoelectric conversion portion 402 and the semiconductor region of the charge holding portion 403 during etching of the insulating film 702 when the structures 813 and 814 are formed can be reduced.

Furthermore, since the flatness of the portion where the light-shielding film is provided is improved, the light-shielding film residue can be suppressed even when the light-shielding film is removed by etching, and the occurrence of leak defects can be suppressed.

(Fourth Embodiment)
An imaging system according to the fourth embodiment of the present invention will be described. Imaging systems include digital still cameras, video cameras, digital camcorders, copying machines, facsimiles, mobile phones, in-vehicle cameras, observation satellites, and the like. FIG. 8 shows a block diagram of a digital still camera as an example of the imaging system according to the fourth embodiment.

8, the imaging system includes a barrier 1001 for protecting the lens, a lens 1002 for forming an optical image of a subject on the solid-state imaging device 1004, a diaphragm 1003 for changing the amount of light passing through the lens 1002, and a mechanical shutter 1005. Equipped with. The imaging system further includes the solid-state imaging device 1004 described in any of the above-described first to third embodiments, and the solid-state imaging device 1004 converts the optical image formed by the lens 1002 as image data. Here, it is assumed that an AD conversion unit is formed on the semiconductor substrate of the solid-state imaging device 1004.

The imaging system further includes a signal processing unit 1007, a timing generation unit 1008, an overall control/arithmetic unit 1009, a memory unit 1010, a recording medium control I/F unit 1011, a recording medium 1012, and an external I/F unit 1013. The signal processing unit 1007 compresses various corrections and data on the imaging data output from the solid-state imaging device 1004. The timing generator 1008 outputs various timing signals to the solid-state imaging device 1004 and the signal processor 1007.

The overall control/arithmetic unit 1009 controls the entire digital still camera, and the memory unit 1010 functions as a frame memory for temporarily storing image data. The recording medium control I/F unit 1011 performs recording or reading on a recording medium. The recording medium 1012 is composed of a detachable semiconductor memory or the like, and records or reads imaging data. The external I/F unit 1013 is an interface for communicating with an external computer or the like.

Here, the timing signal or the like may be input from the outside of the imaging system, and the imaging system includes at least the solid-state imaging device 1004 and a signal processing unit 1007 that processes the imaging signal output from the solid-state imaging device 1004. do it.

(Other embodiments)
The embodiments described above are merely specific examples for carrying out the present invention, and the technical scope of the present invention is not limitedly interpreted by these. That is, the present invention can be implemented in various forms without departing from the technical idea thereof.

For example, the present invention can be used in a solid-state imaging device having a structure in which not only a step due to a gate electrode of a transistor but also a step due to a member located under a light-shielding film in a light-shielding portion may occur. Further, in the above-described embodiments, the solid-state imaging device having signal charges as electrons has been described as an example, but the present invention can be similarly applied to a solid-state imaging device having signal charges as holes. In this case, the conductivity type of the semiconductor region described above is opposite between P type and N type.

The planar layout of the pixel circuit of the solid-state imaging device shown in FIG. 1B is an example, and the planar layout of the pixel circuit of the solid-state imaging device to which the present invention is applicable is not limited to this. Absent.

402 photoelectric conversion unit 403 charge holding unit 420, 421 N-type semiconductor region 430, 431 P-type semiconductor region 600, 601, 602, 603, 604, 605, 606 gate electrode 701 insulating film 813, 814 structure 303 light-shielding film

Claims (16)

Forming a first semiconductor region of the photoelectric conversion unit and a second semiconductor region of the charge holding unit in the substrate;
On the substrate, a first gate electrode of a first transistor that transfers the charges of the photoelectric conversion unit to the charge holding unit, and a second gate of a second transistor that transfers the charges from the charge holding unit. Forming electrodes,
Forming a first insulating film on the substrate after forming the first gate electrode and the second gate electrode,
By etching the first insulating film in the peripheral circuit portion, a third structure is formed on a side surface of the third gate electrode of the third transistor in the peripheral circuit portion,
In the peripheral circuit part, impurities are introduced into the substrate using the third gate electrode and the third structure as a mask,
Forming a second insulating film on the first insulating film after introducing the impurities;
By etching the second insulating film so that the first insulating film remains on the first semiconductor region and the second semiconductor region, the side surface of the first gate electrode and the second gate electrode are formed. Forming a first structure body and a second structure body on the side surface of the gate electrode through the first insulating film,
A film is formed after the formation of the first structure and the second structure, and a part of the film is etched, whereby the first gate electrode, the second semiconductor region, and the second Forming a light-shielding film on the gate electrode of
An upper side surface of the first structure has a curved surface shape having a center of curvature on the first gate electrode side,
An upper side surface of the second structure has a curved shape having a center of curvature on the second gate electrode side,
A side surface of an upper portion of the third structure has a curved shape having a center of curvature on the third gate electrode side,
A method for manufacturing a solid-state imaging device, wherein a distance between the photoelectric conversion unit and an end of the light shielding film which overlaps the photoelectric conversion unit in a plan view is smaller than a distance between an upper surface of the first gate electrode and the substrate. Forming a first semiconductor region of the photoelectric conversion unit and a second semiconductor region of the charge holding unit in the substrate;
On the substrate, a first gate electrode of a first transistor that transfers the charges of the photoelectric conversion unit to the charge holding unit, and a second gate of a second transistor that transfers the charges from the charge holding unit. Forming electrodes,
Forming a first insulating film on the substrate after forming the first gate electrode and the second gate electrode,
By etching the first insulating film in the peripheral circuit portion, a third structure is formed on a side surface of the third gate electrode of the third transistor in the peripheral circuit portion,
Forming a second insulating film on the first insulating film;
By etching the second insulating film so that the first insulating film remains on the first semiconductor region and the second semiconductor region, the side surface of the first gate electrode and the second gate electrode are formed. Forming a first structure body and a second structure body on the side surface of the gate electrode through the first insulating film,
After forming the first structure and the second structure, a fifth insulating film is formed on the substrate, and the fifth insulating film is etched to form the first structure, Forming a fourth structure, a fifth structure, and a sixth structure on the side surfaces of the second structure and the third structure, respectively,
A film is formed after formation of the fourth structure, the fifth structure, and the sixth structure, and a part of the film is etched to form the first gate electrode and the second structure. A light-shielding film is formed on the semiconductor region and the second gate electrode,
An upper side surface of the first structure has a curved surface shape having a center of curvature on the first gate electrode side,
An upper side surface of the second structure has a curved shape having a center of curvature on the second gate electrode side,
A side surface of an upper portion of the third structure has a curved shape having a center of curvature on the third gate electrode side,
A distance between the photoelectric conversion unit and an end of the light-shielding film that overlaps the photoelectric conversion unit in a plan view is smaller than a distance between an upper surface of the first gate electrode and the substrate,
The fourth structure body, the fifth structure body, and the sixth structure body are each a method for manufacturing a solid-state imaging device in which upper side surfaces are curved surfaces having a curvature center on the corresponding gate electrode side. After forming the first structure and the second structure and before forming the film, a third structure that covers the photoelectric conversion unit, the first transistor, the charge holding unit, and the second transistor. Forming an insulating film of
The method for manufacturing a solid-state imaging device according to claim 1, wherein the film is formed directly on the third insulating film. After forming the second insulating film, forming a silicide layer in the peripheral circuit portion before forming the first structure and the second structure, and immediately after forming the silicide layer, a silicide layer is formed. The method for manufacturing a solid-state imaging device according to claim 1, wherein an insulating film is formed. After forming the first structure and the second structure and before forming the film, a fifth insulating film is formed on the substrate, and the fifth insulating film is etched. Forming a fourth structure, a fifth structure, and a sixth structure on the side surfaces of the first structure, the second structure, and the third structure, respectively,
In each of the fourth structure, the fifth structure, and the sixth structure, the upper side surface is a curved surface having a center of curvature on the corresponding gate electrode side,
The method for manufacturing a solid-state imaging device according to claim 1, wherein in the peripheral circuit section, the sixth structure is formed on a side surface of the third structure via a fourth insulating film. The method for manufacturing a solid-state imaging device according to claim 1, wherein the etching of the second insulating film for forming the first to third structures is dry etching. A floating diffusion portion to which the electric charge is transferred from the electric charge holding portion by the second transistor,
7. The solid-state imaging device according to claim 1, wherein the first structure body and the second structure body are formed so that the first insulating film remains on the floating diffusion portion. Device manufacturing method. A photoelectric conversion part having a first semiconductor region in the substrate;
A first transistor that transfers the charge of the photoelectric conversion unit;
A charge holding unit that holds the charge transferred by the first transistor and has a second semiconductor region in the substrate;
A second transistor that transfers the charge of the charge holding portion;
A third transistor having a third gate electrode provided in the peripheral circuit portion;
A first insulating film provided on the first semiconductor region, the first gate electrode of the first transistor, the second semiconductor region, and the second gate electrode of the second transistor;
A first structure which is provided on a side surface of the first gate electrode via the first insulating film and has an upper side surface having a curved surface shape having a center of curvature on the first gate electrode side;
A second structure provided on a side surface of the second gate electrode via the first insulating film, and having a curved surface shape with an upper side surface having a center of curvature on the side of the second gate electrode;
A third structure provided on a side surface of the third gate electrode and having a curved surface shape in which an upper side surface has a center of curvature on the third gate electrode side;
A second insulating film provided on the third structure and covering the third transistor, and a second insulating film provided on a side surface of the third structure with the second insulating film interposed therebetween. 4 and a light shielding film provided on the first insulating film, the first structure, and the second structure,
The first structure body, the second structure body, the third structure body, and the fourth structure body are insulating films,
In a plan view, the light shielding film overlaps with the first gate electrode, the second semiconductor region, and the second gate electrode,
A solid-state imaging device in which a distance between the photoelectric conversion unit and an end of the light shielding film that overlaps the photoelectric conversion unit in the plan view is smaller than a distance between an upper surface of the first gate electrode and the substrate. The distance between the substrate and an end of the light-shielding film that overlaps the photoelectric conversion unit in the plan view is half or less than a distance between the upper surface of the first gate electrode and the substrate. Solid-state imaging device. The solid-state imaging device according to claim 8, wherein the first structure body, the second structure body, and the first insulating film have different main components. 11. The first structure body and the second structure body contain silicon oxide as a main component, and the first insulating film contains silicon nitride as a main component. Solid-state imaging device. The solid-state imaging device according to claim 8, wherein the third structure body, the fourth structure body, and the second insulating film have different main components. 13. The third structure body and the fourth structure body contain silicon oxide as a main component, and the second insulating film contains silicon nitride as a main component. The solid-state imaging device described. It is provided on the first semiconductor region and has the first structure body, the second semiconductor region, and a third insulating film provided between the second structure body and the light shielding film. The solid-state imaging device according to any one of claims 8 to 13. The solid-state imaging device according to any one of claims 8 to 14, wherein an end portion of the light-shielding film is on the photoelectric conversion unit via the first insulating film. A floating diffusion portion to which the electric charge is transferred from the electric charge holding portion by the second transistor,
The solid-state imaging device according to claim 8, wherein the first insulating film is provided on the floating diffusion portion.

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