JPH11233750A - Method for manufacturing solid-state image pick-up element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reflection prevention effect of a reflection prevention film. SOLUTION: In a manufacturing method, by etching a silicon oxide film 13 at the upper portion of a photo sensor part 11, the film thickness of a silicon oxide film whose film thickness has increased when forming a silicon oxide film 13c by oxidizing a gate electrode 14 is decreased to approximately 10-40 nm. Then, a silicon nitride film 15 is formed on it as thick as approximately 30-80 nm as a reflection prevention film. Further, an interlayer insulation film 17, a metal glare protection film 18, a passivation film 19, and the like are appropriately formed on it, thus manufacturing a solid-state image pick-up element.

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 pickup device, and more particularly, to improving sensitivity by reducing an amount of reflected light by providing an antireflection film above a photosensor portion. The present invention relates to a method for manufacturing a solid-state imaging device.

[0002]

2. Description of the Related Art A conventional CCD (charge-coupled CCD)
A solid-state imaging device using a device (charge-coupled device)
A silicon oxide film is formed above a photosensor portion for performing photoelectric conversion formed in a silicon substrate, and a gate electrode, an interlayer insulating film, a metal light-shielding film, a passivation film, and the like are sequentially formed. However, in such a film configuration, the reflection on the surface of the photosensor portion is large due to the relationship between the refractive index of the silicon oxide film and the photosensor portion, and most of the incident light is lost light. Therefore, in order to suppress the reflection on the sensor unit surface, as shown in FIG.
Attempts have been made to improve the sensitivity by forming an antireflection film 75 thereon (for example, Japanese Patent Application Laid-Open No. Sho 60-17777 discloses a solid-state imaging device having this type of structure).
No. 8). As the antireflection film 75, for example, a silicon nitride film is used, and the sensitivity of the photosensor unit 71 is improved by the interference effect with the silicon oxide film 73a and further by the interference effect including the interlayer insulating film 77 and the like. I have.

As shown in FIG. 8, a gate electrode 84 is provided.
Attempts have also been made to form a silicon nitride film 83b formed between the silicon substrate 80 and the silicon substrate 80 above the photosensor section 81 in order to ensure insulation between the silicon substrate 80 and the silicon substrate 80, thereby forming an antireflection film similar to the above. (For example, Japanese Patent Application Laid-Open No.
No. 1).

[0004]

However, it is difficult to say that the above-mentioned conventional antireflection film can sufficiently suppress the reflection of the signal light incident on the light receiving region.

For example, in the film configuration as shown in FIG. 7, when a silicon oxide film 73c is formed as an insulating film by oxidizing the polycrystalline silicon forming the gate electrode 74, the upper portion of the photosensor portion 71 is formed. There is a problem that the thickness of the silicon oxide film increases, and the reflectance increases with the increase in the thickness. This is because oxygen supplied from the atmosphere for oxidizing the polycrystalline silicon passes through the silicon oxide film 73a and reaches the silicon substrate 70, and the silicon in the substrate is oxidized.
For this reason, for example, the aforementioned Japanese Patent Application Laid-Open No. 60-177778 states that it is difficult to produce a silicon oxide film thinner than 100 nm.

For example, in the film configuration shown in FIG. 8, the silicon oxide film 83a and the silicon nitride film 8
3b is used for insulation between the gate electrode and the silicon substrate and for antireflection, it is not always easy to make the film thickness suitable for the purpose of antireflection. There was a problem that it was not possible to obtain enough.

The present invention has been made in view of the above circumstances, and provides a method of manufacturing a solid-state imaging device having a configuration capable of effectively suppressing reflection of signal light incident on a photosensor section. With the goal.

[0008]

In order to achieve the above object, a method of manufacturing a solid-state imaging device according to the present invention comprises the steps of: forming a silicon oxide film on a silicon substrate having a photosensor portion; Forming a gate electrode made of polycrystalline silicon through at least the silicon oxide film; forming a silicon oxide film on the gate electrode by exposing the gate electrode to an oxidizing atmosphere; Forming an anti-reflection film in a light-receiving region through which light incident on the photosensor portion is transmitted, and exposing the gate electrode to an oxidizing atmosphere to form the anti-reflection film. Before the step of performing, the step of reducing the thickness of the silicon oxide film in the light receiving region by etching is performed.

With this manufacturing method, it is possible to improve the antireflection effect by reducing the thickness of the silicon oxide film on the photosensor. Since the antireflection effect is improved as the silicon oxide film is thinner, according to this method, a structure of a solid-state imaging device with improved sensitivity can be realized. Further, even if the etching is performed as described above, the thickness of the silicon oxide film between the gate electrode and the silicon substrate does not decrease, so that the function as an insulating film between the electrode and the substrate is secured.

In the above manufacturing method, it is preferable that the thickness of the silicon oxide film is reduced to 10 nm to 40 nm by etching. According to this preferred example, reflection of incident light can be more effectively suppressed. From the viewpoint of anti-reflection, it is preferable that the thickness of the silicon oxide film above the photosensor portion is thin. However, when the thickness of the silicon oxide film is reduced to less than 10 nm, the silicon substrate is excessively affected by etching or the like performed in a later process, and thus, a defect in image quality such as a so-called white flaw is likely to occur. .

In the above-mentioned manufacturing method, the silicon oxide film in the light receiving region is removed by etching, and the silicon substrate is exposed to an oxidizing atmosphere.
Preferably, a silicon oxide film is formed again on the surface of the silicon substrate in the light receiving region. According to this preferred example, the influence of variations in the thickness of the silicon oxide film is eliminated, and a silicon oxide film having a well-controlled thickness can be obtained. Also in this case, the silicon oxide film to be regenerated has a thickness of 10 nm for the same reason as described above.
~ 40 nm is preferred.

However, according to the method in which the thickness of the insulating film is reduced to a preferable range by direct etching instead of temporarily removing the insulating film, the number of steps is reduced, and
Since there is an advantage that the deterioration of the image quality can be suppressed (this point will be described later), a preferable method may be adopted for adjusting the thickness of the silicon oxide film depending on the case.

Another structure of the method for manufacturing a solid-state image pickup device according to the present invention, which can achieve the above object, includes a step of forming a silicon oxide film on a silicon substrate having a photosensor portion, and a method of preventing reflection on the silicon oxide film. Forming a film, and forming a gate electrode comprising a gate electrode on the silicon substrate via at least the silicon oxide film and the antireflection film, after the step of forming the gate electrode, The method may further include forming an anti-reflection film on the anti-reflection film in a light receiving region through which light incident on the photo sensor unit is transmitted.

By adopting such a manufacturing method, it is possible to improve the antireflection effect by increasing the thickness of the antireflection film on the photosensor. The silicon oxide film and the antireflection film also play a role of appropriately insulating the gate electrode and the silicon substrate. However, even if the above-described manufacturing method is carried out, an appropriate film thickness of these insulating films for insulating the electrode and the substrate can be obtained. Is secured.

In the above manufacturing method, it is preferable that an anti-reflection film is further formed on the anti-reflection film to increase the thickness of the anti-reflection film to 30 nm to 80 nm. According to this preferred example, reflection of incident light can be more effectively suppressed.

Still another configuration of the method for manufacturing a solid-state imaging device according to the present invention, which can achieve the above object, includes a step of forming a silicon oxide film on a silicon substrate having a photosensor section, and a step of forming a silicon oxide film on the silicon oxide film. Forming a nitride film, forming a gate electrode made of polycrystalline silicon on the silicon substrate via at least the silicon oxide film and the silicon nitride film, and exposing the gate electrode to an oxidizing atmosphere; Forming an anti-reflection film on the silicon oxide film and in a light-receiving region through which light incident on the photosensor portion is transmitted, and exposing the gate electrode to an oxidizing atmosphere. Before the step of forming the prevention film, a step of removing the silicon nitride film in the light receiving region by etching is performed.

By adopting such a manufacturing method, when oxidizing polycrystalline silicon, an increase in the thickness of the silicon oxide film on the photosensor due to the presence of the silicon nitride film can be suppressed. The anti-reflection effect can be improved by reducing the thickness of the silicon oxide film, and the manufacture of a solid-state imaging device with improved sensitivity can be realized. Further, since the anti-reflection film is formed by one film forming process, the variation in the thickness of the anti-reflection film is small and the control of the film thickness is easy.

In each of the above manufacturing methods, it is preferable to use a silicon nitride film as the antireflection film.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a process drawing showing an outline of an example of a manufacturing method of the present invention in a sectional direction. First, a photosensor portion (light receiving portion) 11 as an n-type impurity region is formed in a p-type silicon substrate 10 together with a vertical transfer register 12 and the like by an ion implantation method.
On this silicon substrate 10, a silicon oxide film 13a is formed by thermal oxidation. The silicon oxide film 13 at this time
The thickness ta of “a” is about 40 nm to 80 nm. On silicon oxide film 13a, silicon nitride film 13b and polycrystalline silicon film 14 are sequentially formed by CVD. At this time, the thickness of the silicon nitride film 13b is 20
nm to about 60 nm, and the thickness of the polycrystalline silicon film 14 is about 200 nm to 600 nm. Portions of the silicon nitride film 13b and the polycrystalline silicon film 14 are removed by etching, and an opening region is formed so as to include the photosensor portion 11 (FIG. 1A). By such patterning, the polycrystalline silicon film 14 becomes a gate electrode, and the silicon oxide film 13a and the silicon nitride film 13b function as an insulating film between the gate electrode and the silicon substrate.

Next, the polycrystalline silicon film 14 is thermally oxidized to form a silicon oxide film 13c on the polycrystalline silicon film 14. At this time, oxygen in the atmosphere supplied to oxidize the polycrystalline silicon film 14 passes through the silicon oxide film 13a and reaches the silicon substrate 10 as well.
The silicon substrate 10 in the opening region is also oxidized at the same time, and the thickness of the silicon oxide film 13a increases (FIG. 1).
(B)). The increased film thickness tb is typically between 60 nm and 10
It is about 0 nm.

Subsequently, a step of reducing the thickness of the silicon oxide films 13a and 13c by etching is performed (FIG. 1C). Although not particularly limited,
As the etching, for example, wet etching using a hydrofluoric acid (aqueous solution of hydrofluoric acid) -based etchant can be applied. The etching time is such that the thickness tc of the silicon oxide film 13a above the photosensor section 11 is 10 nm.
The thickness is controlled so as to be 40 nm, more preferably 20 nm to 30 nm. In order to easily control the film thickness tc, it is preferable to use a so-called buffered hydrofluoric acid (a mixed solution of hydrofluoric acid and an aqueous solution of ammonium fluoride) as the hydrofluoric acid-based etching solution.

A silicon nitride film 15 is formed by low pressure CVD on the silicon oxide films 13a and 13c whose thickness has been reduced by etching. Thickness t of silicon nitride film 15
d is 20 nm to 120 nm, preferably 30 nm to 8
0 nm, more preferably 50 nm to 70 nm. The silicon nitride film 15 is patterned by forming a resist 16 and etching (FIG. 1D),
As a result, the silicon nitride film 15a remaining above the photosensor section 11 becomes an anti-reflection film (FIG. 1E). Note that dry etching is preferable as the etching of the silicon nitride film.

On top of this, an interlayer insulating film 17, a metal light-shielding film 18, which is patterned so that the upper part of the photosensor portion 11 becomes an opening region 18a, and a passivation film 19 are sequentially formed (FIG. 1F). ). Although not particularly limited, for example, as the interlayer insulating film 17,
The silicon oxide film formed by the low pressure CVD method, the aluminum film formed by the sputtering method as the metal light shielding film 18, the passivation film 19 as the metal film
A silicon nitride film formed by a plasma CVD method can be applied. The thickness of the interlayer insulating film 17 is 80
nm to 400 nm is preferred. Note that the opening area 18a of the metal light-shielding film 18 functions as a light receiving area through which light incident on the photosensor unit 11 passes.

A solid-state imaging device is manufactured by appropriately adding a flattening film forming process and the like to the series of processes described above. During the above process, the thickness of the silicon oxide film is reduced by etching,
The antireflection effect after the formation of the silicon nitride film as the antireflection film is improved.

In the above-mentioned steps, a silicon nitride film (refractive index: 2.0) is exemplified as the antireflection film 15a and the passivation film 19, but the present invention is not limited to this. It can be formed by a process that can be performed, and may be made of a substance having a higher refractive index than the silicon oxide film. For example, the object of the present invention can be achieved by using a silicon oxynitride film (SiON film), a cerium oxide film, a titanium oxide film, a tantalum oxide film, a zirconium oxide film, or a film made of a mixture thereof. . Similarly, as the interlayer insulating film 17, a silicon oxide film (refractive index: 1.45) formed by the CVD method is exemplified, but the interlayer insulating film 17 is not limited to this.

Further, thermal oxidation,
Various CVD methods and the like may be basically performed according to a conventional method. For example, thermal oxidation may be performed at a temperature of about 900 ° C.

(Second Embodiment) FIG. 2 is a process drawing showing the outline of another example of the manufacturing method of the present invention from a sectional direction.
In this manufacturing method, a silicon oxide film 23a, a silicon nitride film 23b and a polycrystalline silicon film 24 that are patterned so that the upper part of the photosensor portion is used as an opening region are sequentially formed on the silicon substrate 20 on which the photosensor portion 21 is formed. The steps up to the step of forming and then thermally oxidizing the polycrystalline silicon film 24 to form the silicon oxide film 23c are the same as the steps described in the first embodiment (FIG. 2).
(A), (b)).

However, the second embodiment differs from the first embodiment in that the subsequent etching of the silicon oxide film is performed only for the silicon oxide film 23a above the photosensor section 21. . That is, in this embodiment, the resist 26a is
Etching is performed after coating and forming on the region excluding the upper part 1, and the silicon oxide film 23 a above the photosensor portion 21 is removed while the silicon oxide film 23 c formed by thermal oxidation of the polycrystalline silicon 24 is protected. (FIG. 2 (c)). Subsequently, the silicon oxide film once removed is formed again by thermal oxidation. The film thickness tc at this time
Is 10 nm to 40 nm, preferably 20 nm to 30 n
m (FIG. 2D).

Subsequent manufacturing steps are basically the same as those shown in FIG. 1, in which a silicon nitride film 25 is formed, and a resist 26b for patterning the nitride film is formed.
Is applied (FIG. 2E), and then the silicon nitride film 2 is formed.
5 is patterned to form an anti-reflection film 25a (FIG. 2).
(F)) Further, an interlayer insulating film 27, a metal light shielding film 28 having an opening region 28a, and a passivation film 29 are sequentially formed (FIG. 2G).

In these series of steps, usable substances, film forming methods, and the like are the same as those in the first embodiment.

According to such an embodiment, similarly to the first embodiment, the thickness of the silicon oxide film under the antireflection film can be set in a preferable range for antireflection. According to this method, since the silicon oxide film is regenerated by thermal oxidation, the variation in the thickness of the silicon oxide film increases because the silicon oxide film is formed through an oxidation process of polycrystalline silicon. tb variation (tb is 100 nm
In this case, it reaches about 10 nm. Since there is no need to be affected by (1), there is an advantage that the adjustment of the thickness of the silicon oxide film is relatively easy.

However, when manufacturing a solid-state imaging device according to this embodiment, care must be taken so that the so-called gate bird's beak does not affect the performance of the solid-state imaging device. That is, when the silicon substrate is oxidized at the same time as the silicon oxide film is regenerated by thermal oxidation, the silicon oxide film expands, and as shown in FIG. Membrane 6
3a pushes the end of the polycrystalline silicon film 64 serving as the gate electrode upward (as if by a bird's beak), and also presses the silicon substrate 60 at the corresponding position. Such deformation or compression of the gate electrode or the silicon substrate is not preferable because it causes dark current (a cause of so-called white flaws and a factor of deteriorating image quality) resulting from signal defects. Therefore, from such a viewpoint, it is preferable that the thickness of the silicon oxide film is reduced according to the first embodiment, and even when the silicon oxide film is regenerated according to the second embodiment, the gate bird's beak can reduce the image quality. It is preferable to adjust the conditions of thermal oxidation and the like so as not to affect the influence.

(Third Embodiment) FIG. 3 is a process drawing showing the outline of still another example of the manufacturing method of the present invention by each cross section. First, in the p-type silicon substrate 30, the photosensor section 31, which is an n-type impurity region, is provided with a vertical transfer register 3.
2 and the like are formed by ion implantation, and a silicon oxide film 33a is formed on the substrate 30 by thermal oxidation. The thickness te of the silicon oxide film 33a is 20 nm
４０40 nm. On silicon oxide film 33a, silicon nitride film 33b and polycrystalline silicon film 34 are formed by a CVD method. At this time, the thickness tf of the silicon nitride film 33b is about 20 nm to 40 nm, and the thickness of the polycrystalline silicon film 34 is 200 nm to 60 nm.
It is about 0 nm. Part of the polycrystalline silicon film 34
An opening region is formed so as to include the photosensor portion 31 by being removed by etching (FIG. 3A). By the patterning by this etching, the polycrystalline silicon film 34 functions as a gate electrode and the silicon oxide film 33a
The silicon nitride film 33b functions as an insulating film between the gate electrode and the silicon substrate.

Next, the polycrystalline silicon 34 is thermally oxidized,
A silicon oxide film 33c is formed on polycrystalline silicon. Further, a silicon nitride film 35 is formed on the silicon oxide film 33c by low pressure CVD (FIG. 3B).
By forming the silicon nitride film, the photo sensor unit 3 is formed.
1 also increases the thickness of the silicon nitride film (tg). This film thickness tg is 20 nm to 120 nm, preferably 30 n
m to 80 nm, more preferably 50 nm to 70 nm.

Subsequently, a resist 36 is formed on the silicon nitride film 35 above the photosensor section 31 (FIG. 3).
(C)), etching is performed (preferably dry etching), and the thickness of the silicon nitride film in a portion not protected by the resist is reduced (FIG. 3D). In this embodiment, the etching is performed by adjusting the time so that only the thickness of the additionally formed silicon nitride film 35 is removed. In this manner, a silicon nitride film having a thickness greater than that of the other portions is formed only in the region covered with the resist 36 above the photosensor portion 31.

Thereafter, in the same steps as described in the first embodiment, the interlayer insulating film 37, the metal light shielding film 38 having the opening region 38a, and the passivation film 39
Are formed in order (FIG. 3E), and further, a step of forming a flattening film and the like are appropriately added to manufacture a solid-state imaging device.

According to the above process, the silicon nitride film used as the anti-reflection film has the thickness tf originally formed.
The thickness tg is more effective than antireflection, so that a solid-state imaging device with improved sensitivity can be manufactured.

In the above process, the silicon nitride film is used for both the antireflection film, but the invention is not limited to this.
It may be a film as exemplified above, or may have a stacked structure of two or more layers by using a combination of different kinds of films.

In these series of steps, usable substances, film forming methods, and the like are the same as those in the first embodiment.

(Fourth Embodiment) FIG. 4 is a process drawing showing the outline of still another example of the manufacturing method of the present invention by each cross section. Also in this step, a silicon oxide film 43a, a silicon nitride film 43b, and a polycrystalline silicon film 44 patterned so that the upper part of the photosensor part 41 is an open area are formed on the silicon substrate 40 on which the photosensor part 41 is formed. The polycrystalline silicon film 44 is thermally oxidized to form a silicon oxide film 43c, and a silicon nitride film 45 is further formed to increase the thickness of the silicon nitride film above the photosensor portion 41. Part 41
The steps up to the step of applying the resist 46 only upward are the same as the steps described in the third embodiment (FIGS. 4A to 4D).

However, the present embodiment is different from the third embodiment in that the subsequent etching of the silicon nitride film is performed until the silicon nitride film other than the portion protected by the resist 46 is removed ( FIG.
(E)).

Thereafter, in the same steps as described in the first embodiment, an interlayer insulating film 47, a metal light shielding film 48 having an opening region 48a, and a passivation film 49 are formed in this order (FIG. 4F). .

According to such a process, as in the third embodiment, it is possible to manufacture a solid-state imaging device in which the thickness of the silicon nitride film is partially optimized as an antireflection film.

In these series of steps, usable substances, film forming methods, and the like are the same as those in the first embodiment.

In the third and fourth embodiments, a silicon nitride film serving as an antireflection film is formed on a silicon substrate, and a gate electrode is formed thereon. Due to the silicon nitride film, the silicon substrate is not oxidized, and gate bird's beak does not occur. For this reason, it is possible to reliably prevent the occurrence of white flaws that degrade image quality.

Further, since it is not necessary to adjust the oxide film thickness by etching the oxide film as in the first embodiment, the silicon oxide film on the photodiode has the same thickness within the same wafer or between wafers. Can be suppressed, and an element having stable optical characteristics can be supplied. Furthermore, since a wet etching process is not required, the manufacturing process can be simplified.

(Fifth Embodiment) FIG. 5 is a process drawing showing the outline of still another example of the manufacturing method of the present invention by each cross section. In this step, a silicon oxide film 53a, a silicon nitride film 53b, and a polycrystalline silicon film 54 patterned so as to open above the photosensor unit 51 are formed on the silicon substrate 50 on which the photosensor unit 51 is formed. Up to the step of forming the silicon oxide film 53c by thermally oxidizing the polycrystalline silicon film 54,
This is the same as the process described in the third embodiment (FIG. 5).
(A) to FIG. 5 (b)).

However, in the present embodiment,
A step of removing the silicon nitride film 53b on the photo sensor unit 51 by etching is performed (FIG. 5).
(C)). This etching is preferably dry etching.

Next, a silicon nitride film 55 is newly formed by a low pressure CVD method (FIG. 5D). The silicon nitride film 55 has a thickness of 20 to 120 nm, preferably 30 to 120 nm.
-80 nm, more preferably 50-70 nm.
The silicon nitride film 55 is patterned by forming a resist 56 and etching (FIG. 5E). As a result, the silicon nitride film 55a remaining above the photosensor unit 51 becomes an antireflection film (FIG. 5F). )). Note that the etching of the silicon nitride film 55 is preferably dry etching.

Thereafter, in the same steps as described in the first embodiment, the interlayer insulating film 57, the metal light shielding film 58 having the opening region 58a, and the passivation film 59
Are formed in order (FIG. 5E), and a process of forming a flattening film and the like are added as appropriate to manufacture a solid-state imaging device.

In the above process, the silicon nitride film is used as the antireflection film. However, the present invention is not limited to this, and the films exemplified above can be used. In a series of steps, usable substances, film forming methods, and the like are the same as those in the first embodiment.

According to the fifth embodiment, as in the third and fourth embodiments, a silicon nitride film is formed on a silicon substrate, and a gate electrode is formed thereon. Even after the subsequent oxidation step, the silicon substrate is not oxidized, and the thickness of the silicon oxide film above the light receiving region does not increase. Therefore, since it is not necessary to adjust the oxide film thickness by etching the oxide film as in the first embodiment, it is possible to suppress the variation in the film thickness of the silicon oxide film on the photodiode and to improve the optical characteristics. A stable element can be supplied. In addition, since the gate bird's beak does not occur, it is possible to reliably prevent the occurrence of white flaws that degrade the image quality. In the fifth embodiment, after the step of oxidizing the gate electrode, the silicon nitride over the light receiving region is removed. The film is once removed, and then a new silicon nitride film is formed as an antireflection film. Therefore, as in the third and fourth embodiments, the anti-reflection film is formed twice (the anti-reflection film forming step performed before the polycrystalline silicon is formed and the anti-reflection film is formed after the thermal oxidation of the polycrystalline silicon) The thickness of the anti-reflection film is less scattered than in the case where the anti-reflection film is formed by the thickness increasing step of the anti-reflection film, and the film thickness can be easily adjusted.

[0054]

As described in detail above, according to the present invention, a step of forming a silicon oxide film on a silicon substrate having a photosensor portion and a step of forming a silicon oxide film on the silicon substrate via at least the silicon oxide film Forming a gate electrode made of polycrystalline silicon; forming a silicon oxide film on the gate electrode by exposing the gate electrode to an oxidizing atmosphere; Forming an anti-reflection film in a light-receiving region through which the incident light passes, after the step of exposing the gate electrode to an oxidizing atmosphere and before the step of forming the anti-reflection film, By performing the process of reducing the thickness of the silicon oxide film inside by etching, it is possible to effectively suppress the reflection of signal light incident on the photosensor section. It is possible to manufacture a solid-state imaging device having the configuration.

A step of forming a silicon oxide film on a silicon substrate having a photosensor portion, a step of forming an antireflection film on the silicon oxide film, and forming at least the silicon oxide film on the silicon substrate. Forming a gate electrode made of polycrystalline silicon via an anti-reflection film, and after the step of forming the gate electrode, the anti-reflection in a light receiving region through which light incident on the photosensor portion is transmitted. By further performing the step of forming an anti-reflection film on the film, a solid-state imaging device having a configuration capable of effectively suppressing the reflection of signal light incident on the photosensor portion can be manufactured.

Further, a step of forming a silicon oxide film on a silicon substrate having a photosensor portion, a step of forming a silicon nitride film on the silicon oxide film, and forming at least the silicon oxide film and the silicon oxide film on the silicon substrate Forming a gate electrode made of polycrystalline silicon through a silicon nitride film, exposing the gate electrode to an oxidizing atmosphere, receiving light incident on the silicon oxide film and incident on the photosensor portion. Forming an anti-reflection film in the region, etching the silicon nitride film in the light receiving region after the step of exposing the gate electrode to an oxidizing atmosphere and before the step of forming the anti-reflection film. Has a configuration that can effectively suppress the reflection of signal light incident on the photosensor section by performing the removing step. It is possible to manufacture a solid-state imaging device.

[Brief description of the drawings]

FIG. 1 is a process chart sequentially showing steps of an example of a manufacturing method of the present invention in a sectional view.

FIG. 2 is a process diagram sequentially showing steps of another example of the manufacturing method of the present invention in cross-sectional views.

FIG. 3 is a process chart sequentially showing the steps of another example of the manufacturing method of the present invention in cross-sectional views.

FIG. 4 is a process chart sequentially showing the steps of another example of the manufacturing method of the present invention in a sectional view.

FIG. 5 is a process drawing sequentially showing the steps of another example of the manufacturing method of the present invention in a sectional view.

FIG. 6 is an enlarged view of a part of a cross-sectional view corresponding to FIG. 2D for explaining a gate bird's beak.

FIG. 7 is a cross-sectional view illustrating an example of a conventional solid-state imaging device.

FIG. 8 is a cross-sectional view illustrating another example of a conventional solid-state imaging device.

[Explanation of symbols]

10, 20, 30, 40, 50, 60, 70, 80
Silicon substrate 11, 21, 31, 41, 51, 61, 71, 81
Photo sensor 13a, 23a, 33a, 43a, 53a, 63a, 73a, 83a
Silicon oxide film 13b, 23b, 33b, 43b, 53b, 63b, 73b, 83b
Silicon nitride film 13c, 23c, 33c, 43c, 53c, 63c, 73c, 83c
Silicon oxide film 14, 24, 34, 44, 54, 64, 74, 84
Polycrystalline silicon film 15, 25, 35, 45, 55, 65, 85
Silicon nitride film 16, 26a, 26b, 36, 46, 56
Resist 17, 27, 37, 47, 57, 67, 77
Interlayer insulating film 18, 28, 38, 48, 58, 68, 78
Metal light shielding film 19, 29, 39, 49, 59, 69, 79
Passivation film 69
Gate birds beak

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shoji Tanaka 1-1, Komachi, Takatsuki-shi, Osaka Matsushita Electronics Corporation

Claims (7)

[Claims] A step of forming a silicon oxide film on a silicon substrate having a photosensor portion; a step of forming a gate electrode made of polycrystalline silicon on the silicon substrate via at least the silicon oxide film; Forming a silicon oxide film on the gate electrode by exposing the gate electrode to an oxidizing atmosphere; and forming an anti-reflection film in a light receiving region on the silicon oxide film, through which light incident on the photosensor unit is transmitted. After the step of exposing the gate electrode to an oxidizing atmosphere and before the step of forming the antireflection film, a step of reducing the thickness of the silicon oxide film in the light receiving region by etching. A method for manufacturing a solid-state imaging device, which is implemented. 2. A silicon oxide film is again formed on the surface of the silicon substrate in the light receiving region by removing the silicon oxide film in the light receiving region by etching and exposing the silicon substrate to an oxidizing atmosphere. A method for manufacturing the solid-state imaging device according to claim 1. 3. The method according to claim 1, wherein the thickness of the silicon oxide film in the light receiving region is 10 nm to 40 nm before the antireflection film is formed.
The method for manufacturing a solid-state imaging device according to claim 1, wherein m is adjusted to m. 4. A step of forming a silicon oxide film on a silicon substrate having a photosensor portion, a step of forming an antireflection film on the silicon oxide film, and forming at least the silicon oxide film on the silicon substrate. Forming a gate electrode made of polycrystalline silicon via an anti-reflection film, and after the step of forming the gate electrode, the anti-reflection in a light receiving region through which light incident on the photosensor portion is transmitted. A method for manufacturing a solid-state imaging device, further comprising a step of forming an antireflection film on the film. 5. An anti-reflection film is further formed on the anti-reflection film so that the thickness of the anti-reflection film is 30 nm.
5. The method for manufacturing a solid-state imaging device according to claim 4, wherein the thickness is increased to about 80 nm. 6. A step of forming a silicon oxide film on a silicon substrate having a photosensor portion, a step of forming a silicon nitride film on the silicon oxide film, and forming the silicon oxide film and the silicon on the silicon substrate. Forming a gate electrode made of polycrystalline silicon through a nitride film, and exposing the gate electrode to an oxidizing atmosphere;
Forming an anti-reflection film on the silicon oxide film and in a light-receiving region through which light incident on the photosensor portion is transmitted, and exposing the gate electrode to an oxidizing atmosphere. A method for manufacturing a solid-state imaging device, comprising, before the step of forming a prevention film, a step of removing the silicon nitride film in the light receiving region by etching. 7. The method according to claim 1, wherein a silicon nitride film is used as the antireflection film.