JP2000164846A - Solid-state image pickup device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable increase in preventive effect for dark current through hydrogen annealing. SOLUTION: A solid-state image pickup device is provided with a substrate 1 on the surface layer, of which electrical charge transferring parts 2 and channel stop parts 3 are placed alternately, lower-layer transfer electrodes 8 and upper-layer transfer electrodes 10, which are formed on the substrate 1 through a silicon nitride film 5 sandwiched between a lower-layer silicon oxide film and an upper-layer silicon oxide film and openings (a) formed in the silicon nitride film 5 on the channel stop part 3. In this case, the opening (a) is covered with the lower-layer transfer electrodes 8 and the upper-layer transfer electrodes 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid-state image sensor, and more particularly to a CCD solid-state image sensor having a storage region and a gate insulating film using a nitride film, and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 6 is a schematic plan view of a storage area in a solid-state imaging device having a storage area. Also, FIG.
FIG. 7 is a schematic cross-sectional view of a storage region in a solid-state imaging device having a storage region, which is taken along the line AA in FIG. 6. In order to form the solid-state imaging device shown in these figures, first, the charge transfer units 2 (shown only in FIG. 6) and the channel stop units 3 are alternately formed on the surface side of the substrate 1 made of silicon. Next, an ONO (ox) is formed by sequentially stacking a lower silicon oxide film 4 (shown only in FIG. 7), a silicon nitride film 5, and an upper silicon oxide film 6 (shown only in FIG. 7) on the upper portion of the substrate 1.
A gate insulating film 7 having an (ide-nitride-oxide) structure is formed.
Thereafter, a lower transfer electrode 8 made of polysilicon is formed on the gate insulating film 7, and an upper transfer electrode 10 made of polysilicon is formed via an insulating film 9 (shown only in FIG. 7). Lower transfer electrode 8 and upper transfer electrode 1
0 is perpendicular to the charge transfer units 2 and the channel stop units 3 and alternately arranged in parallel.

Thereafter, the upper transfer electrode 10, the lower transfer electrode 8, the upper silicon oxide film 4, and the silicon nitride film 5 above the channel stop portion 3 are removed, and an opening a is formed in the silicon nitride 5, which is an obstacle to hydrogen diffusion. Is provided. Thereafter, although not shown here, a light-shielding film and a planarizing insulating film are formed,
A passivation film (not shown) made of plasma silicon nitride is formed to cover these.

In the solid-state imaging device thus formed, by performing an annealing process, hydrogen in the passivation film is transferred to the substrate 1 and the lower silicon oxide through the opening 1 from which the silicon nitride film 5 has been removed. It is supplied to the interface with the film 4. This makes it possible to suppress the generation of charges other than signals (that is, dark current).

[0005]

However, in the solid-state imaging device having such a structure, the line width between the upper transfer electrode 10 and the lower transfer electrode 8 is locally reduced in the portion where the opening a is formed, and the upper transfer layer is formed. This is a factor that increases the resistance values of the electrode 10 and the lower transfer electrode 8. For this reason, the size and number of the openings a are limited, and the amount of hydrogen supplied to the interface between the substrate 1 and the lower silicon oxide film 4 is also limited.

Accordingly, the present invention provides a solid-state imaging device capable of increasing the area of an opening formed in a nitride film without increasing the resistance value of a transfer electrode, and a method for manufacturing the same. The purpose is to increase the prevention effect.

[0007]

To achieve the above object, a solid-state imaging device according to the present invention comprises: a substrate having charge transfer portions and channel stop portions alternately formed on a surface layer; A transfer electrode formed on the substrate via a nitride film, and a solid-state imaging device including an opening formed in the nitride film on the channel stop portion,
The opening is covered with a transfer electrode.

[0008] In the solid-state imaging device having such a configuration, since the opening formed in the nitride film is covered with the transfer electrode, the line width of the transfer electrode is ensured even in the portion where the opening is formed. Therefore, regardless of the resistance value of the transfer electrode,
The area of the opening is set.

According to a second aspect of the present invention, there is provided a method of manufacturing a solid-state imaging device, comprising: forming a nitride film on a substrate having charge transfer portions and channel stop portions alternately formed on a surface layer; Removing the nitride film on the channel stop portion and forming an opening in the nitride film; forming transfer electrodes vertically in the charge transfer portion and the channel stop portion while covering the opening portion; Is performed.

In such a manufacturing method, since the transfer electrodes are arranged and formed so as to cover the openings after the openings are formed in the nitride film, the nitride film under the transfer electrodes can be formed without removing the transfer electrodes. An opening is formed in the opening. Therefore, the line width of the transfer electrode is ensured regardless of the formation of the opening.

Further, according to a third aspect of the present invention, there is provided a method for manufacturing a solid-state imaging device, comprising: forming a nitride film on a substrate having charge transfer portions and channel stop portions alternately arranged on a surface layer; Arranging lower transfer electrodes vertically on the charge transfer unit and the channel stop unit on the nitride film, removing the nitride film on the channel stop unit using the lower transfer electrode as a mask, A step of forming openings in the nitride film and a step of arranging upper transfer electrodes between the lower transfer electrodes via an insulating film while covering the openings.

In such a manufacturing method, the opening is formed in the nitride film using the lower transfer electrode as a mask, and then the upper transfer electrode is formed so as to cover the opening. Therefore, the lower transfer electrode and the upper transfer electrode are formed. An opening is formed in the nitride film without removing the oxide film. Therefore, the line width of the lower transfer electrode and the upper transfer electrode is ensured regardless of the formation of the opening.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a solid-state imaging device to which the present invention is applied and a method of manufacturing the same will be described below with reference to the drawings. Here, an embodiment in which the present invention is applied to a frame solid-state transfer (hereinafter, referred to as FIT) type CCD solid-state imaging device and a method of manufacturing the same will be described.

FIG. 5 is an overall plan view of an FIT type solid-state imaging device. As shown in the figure, the FIT type solid-state imaging device is provided with an imaging region 23, a storage region 25, and a peripheral region 27 surrounding these regions on the same substrate 21. On the surface layer of the substrate 1 in the imaging region 23, a light receiving unit 29 composed of a photo sensor for performing photoelectric conversion is provided.
Are arranged on a matrix, and each light receiving section 29
A vertical charge transfer unit 31 is provided beside the column. The vertical charge transfer section 31 extends on the surface layer of the substrate 1 in the accumulation region 25. The horizontal charge transfer section 33 is provided on the surface layer of the substrate 1 in the peripheral region 27.
And an output unit 35 and the like connected thereto. In the following embodiments, the solid-state imaging device and a method for manufacturing the same will be described, focusing on the configuration of the storage region 25 and the procedure for forming the storage region 25 in the solid-state imaging device having such a configuration.

(First Embodiment) FIG. 1 is a plan view of a main part of a storage region for explaining a solid-state image sensor according to a first embodiment and a method of manufacturing the same. 2 (1) to 2 (4)
FIG. 5 is a sectional process view of a main part of the storage region, showing the manufacturing method according to the first embodiment, which is taken along the line AA in FIG. 1. Hereinafter, using each of FIGS. 1 and 2 (1) to 2 (4),
An embodiment to which the manufacturing method of claim 2 is applied will be described, and then the configuration of the solid-state imaging device of claim 1 obtained by this method will be described. Note that components similar to those of the conventional solid-state imaging device described with reference to FIGS. 6 and 7 are denoted by the same reference numerals and described.

First, as shown in FIG. 1 and FIG.
Charge transfer sections 2 and channel stop sections 3 are alternately formed on a surface layer of a substrate 1 made of silicon. This charge transfer unit 2 is composed of the vertical charge transfer unit (3) described with reference to FIG.
1), and the channel stop unit 3 is provided between the charge transfer units 2 to separate the charge transfer units 2.

Thereafter, a lower silicon oxide film 4 (shown only in FIG. 2) is formed on the substrate 1 by a thermal oxidation method, and then a silicon nitride film 5 is formed on the lower silicon oxide film 4. (A film corresponding to the nitride film described in Item 2).

Thereafter, the silicon nitride film 5 is patterned, the silicon nitride film 5 on the channel stop portion 3 is removed, and an opening a is formed in the silicon nitride film 5. At this time, a resist pattern (not shown) is formed on the silicon nitride film 5 by a lithography method, and the silicon nitride film 5 is patterned by etching using the resist pattern as a mask to obtain an opening a.

Next, as shown in FIG. 1 and FIG.
An upper silicon oxide film 6 (shown only in FIG. 2) is formed on the lower silicon oxide film 4 so as to cover the patterned silicon nitride film 5. Thus, a gate insulating film 7 having a three-layer ONO structure including the lower silicon oxide film 4, the silicon nitride film 5, and the upper silicon oxide film 6 is formed on the charge transfer unit 2.

Thereafter, as shown in FIGS. 1 and 2 (3), a lower transfer electrode 8 is formed on the upper silicon oxide film 6 so as to be perpendicular to the charge transfer section 2 and the channel stop section 3. Then, the opening a
Cover a part of. The lower transfer electrode 8 is made of, for example, polysilicon into which impurities are introduced, and is formed by forming a polysilicon film, forming a resist pattern by lithography, and etching the polysilicon film using the resist pattern as a mask. .

Next, as shown in FIGS. 1 and 2 (4),
The upper transfer electrodes 10 are arranged and formed between the lower transfer electrodes 8 via an insulating film 9 (omitted in FIG. 1) so that the edges overlap the lower transfer electrodes 8. The lower transfer electrode 8 and the upper transfer electrode 10 cover the upper part of the opening a. The upper transfer electrode 10 is formed in the same manner as the lower transfer electrode 8. The lower transfer electrode 8 and the upper transfer electrode 10
Corresponds to the transfer electrode according to the first and second aspects.

After the above, a light-shielding film made of aluminum and a flattening film made of PSG (phosphorus silicate glass) which are not shown here are formed, and a plasma silicon nitride film (by a plasma CVD method) is formed so as to cover these. (A formed silicon nitride film).

The solid-state imaging device obtained as described above is
The opening a formed in the silicon nitride film 5 corresponds to the lower transfer electrode 8.
In addition, since it is covered with the upper transfer electrode 10, the line width of the lower transfer electrode 8 and the upper transfer electrode 10 is ensured even in the portion where the opening a is formed. For this reason, the lower transfer electrode 8
And without increasing the resistance value of the upper transfer electrode 10.
It is possible to set the area of the opening a wider. Therefore, the hydrogen supplied from the passivation film is
Through the opening a formed in the silicon nitride film 5, the substrate 1
, And the effect of preventing dark current by hydrogen annealing can be enhanced. Further, even when the solid-state imaging device is miniaturized or highly integrated, the area of the opening a can be secured. Further, since an increase in the resistance value can be suppressed, it is possible to prevent a reduction in the amount of charge handled and a decrease in transfer efficiency due to a propagation delay.

(Second Embodiment) FIG. 3 is a plan view of a main part of a storage region for explaining a solid-state imaging device and a method of manufacturing the same according to a second embodiment. 4 (1) and 4 (2).
FIG. 7 is a sectional process view of a main part of a storage region showing a manufacturing method according to the second embodiment, and is a sectional view taken along the line AA in FIG. 3. In the following, using FIGS. 3 and 4 (1) to 4 (2),
An embodiment to which the manufacturing method of claim 3 is applied will be described, and then the configuration of the solid-state imaging device of claim 1 obtained by this method will be described. Note that components similar to those of the conventional solid-state imaging device described with reference to FIGS. 6 and 7 are denoted by the same reference numerals and described.

First, as shown in FIGS. 3 and 4 (1),
Charge transfer portions 2 (shown only in FIG. 3) and channel stop portions 3 are alternately formed on a surface layer of a substrate 1 made of silicon. The charge transfer unit 2 is the vertical charge transfer unit (31) described with reference to FIG.
Are provided between the charge transfer units 2 to separate these charge transfer units 2.

Thereafter, a lower silicon oxide film 4 (shown only in FIG. 4) is formed on the substrate 1 by a thermal oxidation method, and then a silicon nitride film 5 (ie, claim 1 and claim 2) is formed on the lower silicon oxide film 4. 4) is formed, and an upper silicon oxide film 6 (FIG. 4) is formed.
Only shown). Thereby, the charge transfer unit 2
A gate insulating film 7 having a three-layer ONO structure including a lower silicon oxide film 4, a silicon nitride film 5, and an upper silicon oxide film 6 is formed thereon.

Thereafter, the lower transfer electrodes 8 are formed on the upper silicon oxide film 6 so as to be perpendicular to the charge transfer section 2 and the channel stop section 3. This lower transfer electrode 8
It is formed similarly to the lower transfer electrode of the first embodiment.

Next, a resist pattern (not shown) having a shape covering the charge transfer portion 2 is formed by lithography. Then, the upper silicon oxide film 6 and the silicon nitride film 5 are patterned by etching using the resist pattern and the lower transfer electrode 8 as a mask. Thereby, the opening a is formed in the silicon nitride film 5 by removing the silicon nitride film 5 on the channel stop portion 3.

Thereafter, as shown in FIGS. 3 and 4 (2), an insulating film 9 (shown only in FIG. 4) is placed between the lower transfer electrodes 8 so that the edges thereof overlap with the lower transfer electrodes 8. The upper-layer transfer electrodes 10 are formed in an array. Then, the upper part of the opening a is covered with the upper transfer electrode 10. The upper transfer electrode 10 is formed in the same manner as the lower transfer electrode 8.

After the above, a light-shielding film made of aluminum and a flattening film made of PSG (phosphorus silicate glass), not shown here, are formed, and a plasma silicon nitride film (by plasma CVD) is formed in a state of covering these. (A formed silicon nitride film).

The solid-state imaging device obtained as described above is
The opening a formed in the silicon nitride film 5 corresponds to the upper transfer electrode 1
Since it is covered with 0, the line width of the lower-layer transfer electrode 8 and the upper-layer transfer electrode 10 is ensured even in the portion where the opening a is formed. For this reason, similarly to the solid-state imaging device obtained in the first embodiment, the area of the opening a can be set larger without increasing the resistance values of the lower transfer electrode 8 and the upper transfer electrode 10. Become. Therefore, hydrogen is sufficiently supplied from the passivation film to the surface of the substrate 1 through the opening a, and the effect of preventing dark current due to hydrogen annealing can be enhanced. Further, even if the solid-state imaging device is downsized, the area of the opening a can be secured. Further, since an increase in the resistance value can be suppressed, it is possible to prevent a reduction in the amount of charge handled and a decrease in transfer efficiency due to a propagation delay.

[0032]

As described above, according to the first aspect of the present invention,
According to the solid-state imaging device described above, by adopting a configuration in which the opening formed in the nitride film is covered with the transfer electrode, the line width of the transfer electrode can be secured even in the portion where the opening is formed. The area of the opening can be increased without increasing the resistance value of the electrode. Therefore, the amount of hydrogen supplied from the passivation film to the surface of the substrate via the opening can be increased, and the effect of preventing dark current due to hydrogen annealing can be enhanced.

According to the method for manufacturing a solid-state imaging device according to the second and third aspects of the present invention, the transfer electrodes are arranged and formed so as to cover the openings after forming the openings in the nitride film. By employing the method, an opening can be formed in the nitride film without removing the transfer electrode. Therefore, it is possible to obtain a solid-state imaging device in which the area of the opening is increased without increasing the resistance value of the transfer electrode.

[Brief description of the drawings]

FIG. 1 is a plan view of a main part of a storage region for describing a solid-state imaging device and a method of manufacturing the same according to a first embodiment.

FIG. 2 is a sectional process view of a main part of a storage region, illustrating a method of manufacturing the solid-state imaging device according to the first embodiment.

FIG. 3 is a plan view of a main part of a storage region for describing a solid-state imaging device and a method of manufacturing the same according to a second embodiment.

FIG. 4 is a sectional process view of a main part of a storage region showing a method for manufacturing a solid-state imaging device according to a second embodiment.

FIG. 5 is an overall plan view of a solid-state imaging device to which the present invention is applied.

FIG. 6 is a plan view of a main part of a storage region for explaining a conventional solid-state imaging device and a method of manufacturing the same.

FIG. 7 is a cross-sectional view of a main part of a storage region for describing a conventional solid-state imaging device and a method of manufacturing the same.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Charge transfer part, 3 ... Channel stop part,
5 silicon nitride film (nitride film), 8 lower transfer electrode (transfer electrode), 9 insulating film, 10 upper transfer electrode (transfer electrode), a opening

Claims (3)

[Claims] 1. A substrate in which charge transfer portions and channel stop portions are alternately formed on a surface layer, a transfer electrode formed on the substrate via a nitride film, and the nitride on the channel stop portion. A solid-state imaging device comprising: an opening formed in a film; wherein the opening is covered with the transfer electrode. 2. A step of forming a nitride film on a substrate in which charge transfer portions and channel stop portions are alternately formed on a surface layer; and removing the nitride film on the channel stop portion to form a nitride film. Forming an opening in the film, and performing a step of arranging transfer electrodes vertically with respect to the charge transfer section and the channel stop section while covering the opening, Production method. 3. A step of forming a nitride film on a substrate in which charge transfer portions and channel stop portions are alternately formed on a surface layer; and forming a charge transfer portion and a channel stop portion on the nitride film. Arranging lower transfer electrodes vertically with respect to the electrode, removing the nitride film on the channel stop portion using the lower transfer electrodes as a mask, and forming openings in the nitride film; Arranging upper transfer electrodes between the lower transfer electrodes via an insulating film while covering the lower transfer electrodes.