JPH0832045A - Solid-state image sensor and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Purpose] To achieve both improvement of optical characteristics such as spectral sensitivity and stabilization of interface characteristics leading to reduction of dark current. A light receiving portion 1 and a transfer channel region 14 are formed in a first P-type well region 12 formed on an N-type silicon substrate 11.
Are arranged and formed respectively, and the transfer channel region 14
A transfer electrode 20 is selectively formed on the gate insulating film 19, and the PSG film 22 is formed on the entire surface including the transfer electrode 20.
In the image sensor in which the AL light-shielding film 24 is formed on the PSG film 22 so as to cover the transfer electrode 20, the P-SiN film 23 is formed in the sidewall shape in the peripheral portion of the light receiving portion 1, and at least P-Si having substantially the same optical refractive index as the PSG film 22 in the portion corresponding to the light receiving portion 1.
The O film 25 is formed so as to cover at least the light receiving unit 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device, and more particularly to a solid-state image pickup device for reducing dark current and improving spectral characteristics and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, a charge transfer type solid-state image pickup device (C
CD solid-state image sensor) is a PSG laminated by a CVD method.
(Phosphorus silicate glass) film and plasma nitriding (P-
It is covered with a passivation film of a SiN) film (see, for example, Japanese Patent Laid-Open No. 60-66826).

As shown in FIG. 5, a conventional CCD solid-state image sensor has a PN junction between an N type impurity diffusion region 102 formed by introducing N type impurities into a P type silicon substrate 101 and the silicon substrate. And a light receiving portion 103 formed by a photodiode, and the N-type impurity diffusion region 1
02, a transfer channel region 104 formed by an N-type impurity diffusion region formed by an N-type impurity introduced into a region other than 02, P
And a P-type channel stopper region 105 formed by introducing a P-type impurity.

A transfer electrode 107 of a polycrystalline silicon layer is selectively formed on the transfer channel region 104 with a gate insulating film 106 interposed therebetween. A silicon oxide film 108 is formed on the surface of the transfer electrode 107 by a thermal oxidation process. A PSG film 109 is formed on the entire surface including the transfer electrode 107, and the PSG film 1 is further formed.
A light-shielding Al film 110 (referred to as an Al light-shielding film) is formed on the upper surface of the substrate 09 so as to cover the lower transfer electrode 107.
l Silicon nitride film (hereinafter, simply referred to as P-SiN film) 111 formed by plasma CVD on the entire surface including the light-shielding film 110
Are formed.

Here, the PSG film 109 and P-Si
The N film 111 constitutes a passivation film on the light receiving portion,
The P-type region between the light receiving portion 102 and the transfer channel region 104 constitutes the read gate 112.

Further, the Al light-shielding film 110 is provided in the light receiving portion 1
02, the light is selectively etched away, and the light is exposed through the opening 110 formed by this etching away.
The light is incident on the light receiving unit 102 through a.

It is known that the P-SiN film 111 contains a large amount of hydrogen.
By performing a heat treatment at a temperature of 400 ° C. for about 1 hour after forming the film 111, a large amount of hydrogen ions are easily diffused from the P-SiN film 111 to the silicon substrate 101 side, so that the interface state is sufficiently reduced. , The dark current is reduced to a practical level (this effect is generally called hydrogen annealing effect). As a result, the generation of noise due to dark current is reduced, and a high S / N ratio of the reproduced image pickup signal can be achieved.

[0008]

However, in the conventional CCD solid-state imaging device, the passivation film is composed of the PSG film 109 and the P-SiN film 111. There is an optical defect as shown in.

That is, the light refractive index of the P-SiN film 111 is about 2.0, and the light refractive index of the lower PSG film 109 is 1.5.
Since it is considerably larger than before and after, the fluctuation of the spectral sensitivity characteristic due to the interference effect or the like is large, and the film thickness of each of the films 109 and 111 is limited to obtain the required spectral characteristic, and the degree of freedom in design is increased. Has the inconvenience of being narrowed.

Further, in the peripheral portion of the CCD solid-state image pickup device, the obliquely incident light L is largely refracted at the boundary portion between the P-SiN film 111 and the PSG film 109, whereby the oblique light is emitted. L is the transfer channel area 1
However, there is a problem that it directly enters the image recording medium 04 and causes streak-like noise (generally called smear) in the reproduced image.

As a method of eliminating the above-mentioned optical defects, it is conceivable to form the passivation film by using films having substantially the same refractive index. As one of the proposals, the P-SiN film 111 is replaced. Plasma oxidation (P-Si
The technology of using (O) film is promising. This P
Since the -SiO film has a small optical refractive index of about 1.5, the problems of the spectral sensitivity characteristic and smear can be improved. However, since the P-SiO film does not contain much hydrogen, the hydrogen annealing effect cannot be expected and a new problem arises in that the dark current cannot be reduced.

As described above, conventionally, it has been difficult to combine the hydrogen annealing effect for stabilizing optical characteristics such as spectral sensitivity and interface characteristics.

The present invention has been made in view of the above problems, and an object thereof is to achieve both improvement of optical characteristics such as spectral sensitivity and stabilization of interface characteristics leading to reduction of dark current. It is to provide a solid-state image sensor capable of performing the above.

Another object of the present invention is to easily manufacture a solid-state image pickup device which can achieve both improvement of optical characteristics such as spectral sensitivity and stabilization of interface characteristics leading to reduction of dark current. It is to provide a method of manufacturing a solid-state image sensor capable of performing

[0015]

According to the present invention, the same substrate 11 is used.
The light receiving portions 1 and the transfer channel regions 14 are arranged and formed on the respective surfaces, and the gate insulating film 1 is formed on the transfer channel regions 14.
9, transfer electrodes 20 are selectively formed, an interlayer insulating film 22 is formed on the entire surface including the transfer electrodes 20, and a light shielding film 24 is formed on the interlayer insulating film 22 so as to cover the transfer electrodes 20. In the solid-state imaging device, the hydrogen-containing film 23 is formed in a sidewall shape in the peripheral portion of the light receiving portion 1, and at least the portion corresponding to the light receiving portion 1 has a protective insulating film 25 having substantially the same optical refractive index as the interlayer insulating film 22. At least the light receiving unit 1
Is formed so as to cover.

In this case, the hydrogen-containing film 23 is used as the interlayer insulating film 2
It may be formed on the stepped portion formed on the peripheral portion of the light receiving portion 1 on the upper part 2. Further, the light shielding film 24 may be formed so as to cover the transfer electrode 20 and the hydrogen containing film 23.

The interlayer insulating film 22 may be a PSG film, the hydrogen containing film 23 may be a silicon nitride film formed by a plasma CVD method, and the protective insulating film 25 may be a silicon oxide film formed by a plasma CVD method. it can.

Further, according to the present invention, the light receiving section 1 is provided on the same substrate 11.
And a transfer channel region 14 are arranged and formed respectively, and a transfer electrode 20 is selectively formed on the transfer channel region 14 with a gate insulating film 19 interposed therebetween. A step of forming the insulating film 22, a step of forming the hydrogen-containing film 23 in the peripheral portion of the light receiving portion 1 in a sidewall shape, a step of forming the light shielding film 24 so as to cover the transfer electrode 20, and at least the light receiving portion 1
It is characterized by including a step of forming a protective insulating film 25 so as to cover the surface and a step of performing heat treatment on the entire surface.

When the hydrogen containing film 23 is formed in a sidewall shape in the peripheral portion of the light receiving portion 1, after the hydrogen containing film 23 is formed on the entire surface of the interlayer insulating film 22, the hydrogen containing film 23 is anisotropic with respect to the hydrogen containing film 23. This can be achieved by performing an etching process and leaving the hydrogen-containing film 23 in the step portion formed on the PSG film 22 in the peripheral portion of the light receiving portion 1.

In this case, the light shielding film 24 may be formed so as to cover the transfer electrode 20 and the hydrogen containing film 23. Then, the interlayer insulating film 22 may be a PSG film, the hydrogen-containing film 23 may be a silicon nitride film formed by a plasma CVD method, and the protective insulating film 25 may be a silicon oxide film formed by a plasma CVD method.

[0021]

In the solid-state imaging device according to the present invention, since the hydrogen-containing film 23 is formed in the sidewall shape in the peripheral portion of the light receiving portion 1, the passivation film formed on the light receiving portion 1 is formed by interlayer insulation. It is composed of the film 22 and the protective insulating film 25.

The interlayer insulating film 22 and the protective insulating film 25 are
Since the photorefractive indices are substantially the same as each other, the fluctuation of the spectral sensitivity characteristic due to the interference effect or the like is reduced, and as a result, the spectral characteristic varies depending on the film thicknesses of the interlayer insulating film 22 and the protective insulating film 25. It is possible to increase the degree of freedom in design.

Further, in the peripheral portion of the solid-state image pickup device, obliquely incident light is prevented from being greatly refracted at the interface between the interlayer insulating film 22 and the protective insulating film 25 and entering the transfer channel region 14 side. Smear, which is a problem in the image sensor, can be reduced.

In addition, since hydrogen contained in the hydrogen-containing film 23 reaches the interface of the substrate by diffusion, the hydrogen annealing effect can sufficiently reduce the interface level and reduce the dark current.

As described above, according to the solid-state imaging device of the present invention, it is possible to achieve both improvement of optical characteristics such as spectral sensitivity and stabilization of interface characteristics leading to reduction of dark current.

In particular, when the hydrogen-containing film 23 is formed on the interlayer insulating film 22 at the step portion formed in the peripheral portion of the light receiving portion 1, the hydrogen-containing film 23 is formed on the interlayer insulating film 22 at the step portion. Since it is formed in a wheel shape, the interlayer insulating film 22 and the protective insulating film 25, which have substantially the same photorefractive index, are present on the light receiving portion 1, and as described above, the spectral sensitivity and the like. It is possible to achieve both the improvement of the optical characteristics and the stabilization of the interface characteristics, which leads to the reduction of the dark current.

When the light-shielding film 24 is formed so as to cover the transfer electrode 20 and the hydrogen-containing film 23, upward diffusion of hydrogen from the hydrogen-containing film 23 is blocked by the light-shielding film. Therefore, most of the hydrogen diffused from the hydrogen-containing film 23 diffuses toward the interface side of the substrate 11. As a result, the reduction of the interface state due to the hydrogen annealing effect can be efficiently achieved, and the reduction of the dark current can be further improved.

Moreover, the sidewall-like hydrogen-containing film 2
3, the step difference of the transfer electrode 20 becomes gentle, the step coverage of the light shielding film 24 formed on the transfer electrode 20 is improved, and the light shielding film 24 is formed thick even in the portion corresponding to the end portion of the transfer electrode 20. Will be. This makes it possible to sufficiently prevent light from entering the transfer electrode 20 and the transfer channel region 24 by the light shielding film 24.

Then, the interlayer insulating film 22 is a PSG film, the hydrogen-containing film 23 is a silicon nitride film (hereinafter simply referred to as a P-SiN film) formed by a plasma CVD method, and the protective insulating film 25 is a plasma CVD method. When the formed silicon oxide film (hereinafter, simply referred to as P-SiO film) is used, the P-SiN film 2 having a photorefractive index of about 2.0.
3 is formed in a sidewall shape around the light receiving portion 1,
A PSG having a mutual optical refractive index of about 1.5 on the light receiving unit 1.
The film 22 and the P-SiO film 25 are formed in a stacked form.

Therefore, the fluctuation of the spectral sensitivity characteristic due to the interference effect is reduced, and as a result, the PSG film 22 and the P-Si are reduced.
The spectral characteristics do not vary depending on the film thickness of the O film 25, and the degree of freedom in design can be increased. Further, in the peripheral portion of the solid-state image sensor, the obliquely incident light is reflected by the PSG film 22 and P. There is no longer a large amount of refraction at the interface with the -SiO film 25 to enter the transfer channel region 14 side, and smear which is a problem in a solid-state image sensor can be reduced. Moreover, since hydrogen contained in the P-SiN film 23 reaches the interface of the substrate by diffusion, the hydrogen annealing effect can sufficiently reduce the interface state and reduce the dark current.

Next, in the method of manufacturing the solid-state image pickup device according to the present invention, first, the interlayer insulating film 22 is formed on the entire surface including the transfer electrode 20, and then the hydrogen-containing film 23 is formed around the light receiving portion 1.
The interlayer insulating film 22 is formed on the light receiving portion 1 so as to cover the light receiving portion 1 at the stage of forming the sidewall shape. However, the hydrogen-containing film 23 is formed only in the peripheral portion of the light receiving portion 1. Will be formed in a sidewall shape. From this state, the protective insulating film 2 covers at least the light receiving portion 1.
After the step 5 is formed, a passivation film composed of a laminated film of the interlayer insulating film 22 and the protective insulating film 25 is formed on the light receiving portion 1.

Then, in the subsequent heat treatment step, hydrogen diffuses from the hydrogen-containing film 23 formed in the sidewall shape to the interface side of the substrate 11. Due to the hydrogen diffusion from the hydrogen-containing film 23, the interface state of the substrate 11 is sufficiently reduced, and the dark current can be reduced.

Further, since the interlayer insulating film 22 and the protective insulating film 25 forming the passivation film have almost the same photorefractive index, the fluctuation of the spectral sensitivity characteristic due to the interference effect is reduced, and as a result, the interlayer insulating film The spectral characteristics do not vary depending on the thicknesses of the insulating film 22 and the protective insulating film 25, and the degree of freedom in design can be expanded.

Further, in the peripheral portion of the solid-state image pickup device, obliquely incident light is prevented from being greatly refracted at the interface between the interlayer insulating film 22 and the protective insulating film 25 and entering the transfer channel region 14 side. Smear, which is a problem in the image pickup device, can be reduced.

As described above, in the method for manufacturing the solid-state image pickup device according to the present invention, it is possible to achieve both improvement of optical characteristics such as spectral sensitivity and stabilization of interface characteristics leading to reduction of dark current. Can be easily manufactured.

In particular, the hydrogen-containing film 23 is provided around the light receiving portion 1.
In the case of forming the sidewalls, the hydrogen-containing film 23 is formed on the entire surface of the interlayer insulating film 22, and the hydrogen-containing film 23 is anisotropically etched to form the light receiving portion 1 on the interlayer insulating film 22. By leaving the hydrogen-containing film 23 in the stepped portion formed in the peripheral portion of, the hydrogen-containing film 23 can be easily formed in the sidewall shape in the peripheral portion of the light receiving portion 1.

When the light-shielding film 24 is formed so as to cover the transfer electrode 20 and the hydrogen-containing film 23, of the hydrogen diffusion from the hydrogen-containing film 23 generated in the heat treatment step, the upward hydrogen diffusion is shielded. Since it is blocked by the film 24, most of the hydrogen diffused from the hydrogen-containing film 23 will diffuse toward the interface side of the substrate 11. As a result, the reduction of the interface state due to the hydrogen annealing effect can be efficiently achieved, and the reduction of the dark current can be further improved.

Then, the interlayer insulating film 22 is a PSG film,
The hydrogen-containing film 23 is a silicon nitride film (hereinafter, simply referred to as P-SiN film) formed by a plasma CVD method, and the protective insulating film 25 is a silicon oxide film (hereinafter, simply referred to as P-SiN film) formed by a plasma CVD method. -It is described as a SiO film)
In such a case, first, the PSG film 23 is formed on the entire surface including the transfer electrode 20, and then P- is formed on the peripheral portion of the light receiving portion 1.
At the stage where the SiN film 23 is formed in the side wall shape, the PSG film 22 is formed on the light receiving portion 1 so as to cover the light receiving portion 1, but the P-SiN film 23 is formed on the light receiving portion 1. The sidewalls are formed only in the peripheral portion. From this state, at the stage where the P-SiO film 25 is formed so as to cover at least the light receiving portion 1, a passivation film composed of a laminated film of the PSG film 22 and the P-SiO film 25 is formed on the light receiving portion 1. It becomes a shape.

Then, in the subsequent heat treatment step, hydrogen diffuses from the sidewall-shaped P-SiN film 23 to the interface side of the substrate 11, and the P-SiN film 2 is formed.
By diffusing hydrogen from 3, the interface state of the substrate 11 is sufficiently reduced, and the dark current can be reduced.

PS which constitutes the passivation film
Since the G film 22 and the P-SiO film 25 have substantially the same optical refractive index of about 1.5, the spectral sensitivity characteristic fluctuations due to interference effects and the like are reduced, and as a result, the PSG film 2
2 and the P-SiO film 25 do not change the spectral characteristics due to the respective film thicknesses, and the degree of freedom in design can be expanded.

Further, in the peripheral portion of the solid-state image pickup device, the obliquely incident light is not largely refracted at the interface between the PSG film 22 and the P-SiO film 25 and enters the transfer channel region 14 side. Smear, which is a problem in the image pickup device, can be reduced.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment (hereinafter referred to as an image sensor according to the embodiment) in which a solid-state image pickup device according to the present invention is applied to, for example, a CCD image sensor of a frame interline transfer (FIT) system is shown in FIGS. This will be described with reference to FIG.

The image sensor according to this embodiment is shown in FIG.
As shown in FIG. 5, a large number of light receiving portions 1 that perform photoelectric conversion into electric charges according to the amount of incident light are arranged in a matrix, and further, among the large number of light receiving portions 1, with respect to the light receiving portions 1 arranged in the column direction. There is no common light receiving portion 1 formed in the image portion 3 and the image portion 3 arranged in the row direction and having a plurality of common vertical transfer registers 2. The image unit 3 has a plurality of vertical transfer registers 2 and a storage unit 5 in which only a large number of vertical transfer registers 4 are continuously formed.

Further, two horizontal transfer registers, which are adjacent to the storage section 5 and are common to a large number of vertical transfer registers 4, are arranged in parallel. Where 2
Of the horizontal transfer registers of the book, the horizontal transfer register located on the storage unit 5 side is the first horizontal transfer register H1,
The other horizontal transfer register is referred to as a second horizontal transfer register H2.

Between the storage section 5 and the first horizontal transfer register H1, the signal charges transferred to the final stage of the vertical transfer register 4 in the storage section 5 are transferred to the first horizontal transfer register H1. Two vertical-horizontal transfer registers VH1 and VH2 are formed in common for a plurality of vertical transfer registers 4 and in parallel with each other. These two vertical-horizontal transfer registers VH1 and VH
Vertical-horizontal transfer pulses φVH1 and φVH2 are supplied to H2, respectively, and the signal charges from the vertical transfer register 4 are supplied to the first horizontal transfer register H1 by the supply of these transfer pulses φVH1 and φVH2.
Will be transferred to.

Further, the first and second horizontal transfer registers H
1 and H2, the signal charges transferred to the first horizontal transfer register H1 are selectively supplied to the second horizontal transfer register H2.
The horizontal-horizontal transfer registers HH that are transferred to the side are arranged in the horizontal direction along the horizontal transfer registers H1 and H2. In this horizontal-horizontal transfer register HH,
The horizontal-horizontal transfer pulse φHHG is supplied, and the first transfer pulse φHHG is supplied.
Signal charges in the horizontal transfer register H1 of the second
Will be transferred to the horizontal transfer register H2.

The final stages of the first and second horizontal transfer registers H1 and H2 have first and second stages, respectively.
Output units 6a and 6b are connected. These first and second output units 6a and 6b are connected to each horizontal transfer register H.
1 and H2 for converting the signal charge transferred from the final stage into an electric signal (for example, a voltage signal), for example, a charge-electric signal conversion unit 7 including a floating diffusion or a floating gate, and this charge-
The electric signal from the electric charge-electrical signal conversion unit 7 and the reset gate RG that sweeps out the signal charge after the electric signal conversion is performed in the electric signal conversion unit 7 to the drain region D according to the input of the reset pulse Pr It has an amplifier 8 for amplification. The power supply voltage Vdd is applied to the drain region D.

On the vertical transfer register 2 in the image section 3 and the vertical transfer register 4 in the storage section 5, although not shown, four vertical transfer electrodes made of, for example, two layers of polycrystalline silicon are insulating films. Is formed through. That is, four vertical transfer electrodes are set as one set, and a large number of the sets are sequentially arranged in the vertical direction. The four vertical transfer electrodes φ in the image section 3 are supplied to the four vertical transfer electrodes φ having different phases.
IM1 to φIM4 are supplied respectively, and the storage unit 5
The four vertical transfer electrodes φST1 to φST4 having different phases from each other are supplied to the four vertical transfer electrodes in FIG.

By supplying the vertical transfer pulses φIM1 to φIM4 in the image section 3 and the four vertical transfer pulses φST1 to φST4 in the storage section 5,
The potential distributions under the vertical transfer electrodes in the image part 3 and the storage part 5 are sequentially changed, and as a result,
The signal charges are respectively transferred to the vertical transfer register 2 in the image part 3 and the vertical transfer register 4 in the storage part 5.
Will be transferred in the vertical direction (on the side of the first horizontal register H1).

Particularly, in the image section 3, the light receiving section 1
In the vertical blanking period, the signal charges accumulated in the vertical transfer register 2 are first read into the vertical transfer register 2, and then in the vertical blanking period, the signal charges transferred to the vertical transfer register 2 are quickly stored in the storage unit 5. To the vertical transfer register 4.

The storage section 5 transfers the signal charges transferred to the vertical transfer register 4 in the vertical blanking period to the first horizontal transfer register H1 side by row in the subsequent horizontal blanking period. As a result, the signal charges in the final stage of the vertical transfer register 4 are first transferred to the first horizontal transfer register H1 via the two vertical-horizontal transfer registers VH1 and VH2. The charges are transferred to the second horizontal transfer register H2 via the horizontal-horizontal transfer register HH.

Then, in the next horizontal scanning period, the first
And by applying two-phase horizontal transfer pulses φH1 and φH2 of two different phases to the horizontal transfer electrodes formed of, for example, two layers of polycrystalline silicon formed on the second horizontal transfer registers H1 and H2, signal charges are sequentially applied. Transferred to the corresponding charge-electric signal converter 7 on the side of the output units 6a and 6b,
It is converted into an electric signal in each electric charge-electrical signal converter 7, and is taken out as the image pickup signals S1 and S2 from the corresponding output terminal 9 via the amplifier 8, respectively.

Here, looking at the cross section around the light receiving portion 1 of this image sensor, as shown in FIG. 2, for example, the first P-type well region 12 formed on the N-type silicon substrate 11 is formed.
N-type impurity diffusion region 13 for forming the light receiving portion 1 on the surface of, the N-type transfer channel region 14 and the P-type channel stopper region 15 forming the vertical transfer register 2.
And a P-type positive charge accumulation region 16 is formed on the surface of the N-type impurity diffusion region 13, and a second P-type well region is formed immediately below the N-type transfer channel region 14 for the purpose of reducing smear. 17 are formed respectively. The P-type region 18 between the N-type impurity diffusion region 13 and the transfer channel region 14 constitutes a read gate portion.

In this image sensor, as shown in the figure, a first P-type well region 12 is formed on the surface of an N-type silicon substrate 11, and the light receiving portion is provided in the first P-type well region 12. By forming the N-type impurity diffusion region 13 which constitutes No. 1, it has a so-called electronic shutter function. That is, by setting the substrate potential supplied to the silicon substrate 11 to a high level in synchronization with the shutter pulse, the potential barrier in the first P-type well region 12 is lowered, and the charges accumulated in the light receiving unit 1 (in this case, , Electrons) are swept away in the vertical direction beyond the potential barrier, that is, toward the silicon substrate 11 side. As a result, the period from the final application time of the shutter pulse to the time of reading out the electric charge becomes a substantial exposure period,
It is possible to prevent inconveniences such as afterimages.

In this image sensor, the N-type impurity diffusion region 13 and the first P-type well region 1 are used.
A light receiving portion 1 (photoelectric conversion portion) is configured by a photodiode having a PN junction with 2, and a large number of the light receiving portions 1 are arranged in a matrix to form an imaging region. In the case of the color imaging method, one pixel is formed in four light receiving units 1 adjacent to each other, for example, depending on the color arrangement of color filters (three primary color filters or complementary color filters) formed corresponding to the light receiving unit 1. It is designed to be configured.

In this embodiment, the first polycrystalline silicon layer and the transfer channel region 14, the channel stopper region 15 and the read gate portion 18 are formed with the gate insulating film 19 made of, for example, SiO ₂ interposed therebetween. Four transfer electrodes are formed by the second layer of polycrystalline silicon layer,
The transfer channel region 14, the gate insulating film 19 and the transfer electrodes constitute the vertical transfer register 2. Note that, in the sectional view of FIG. 3, only the transfer electrode (to which the vertical transfer pulse φ is applied) 20 made of, for example, the first-layer polycrystalline silicon layer is shown as the transfer electrode.

In this embodiment, as shown in FIG. 2, a silicon oxide film (SiO ₂ film) 21 by thermal oxidation is formed on the surface of the transfer electrode 20, and PSG which is an interlayer insulating film is further formed on the entire surface. The film 22 is formed. At this time, the PSG film 22 is formed along the shape of the transfer electrode 20, and a step is formed in a portion corresponding to the end surface of the transfer electrode 20. Further, in this embodiment, a silicon nitride film (hereinafter simply referred to as a P-SiN film) 23 formed by a plasma CVD method on the step portion of the PSG film 22.
Are formed in a sidewall shape, and the P-SiN film 2 is formed.
3 is formed on the PSG film 22 at a portion corresponding to the peripheral edge of the light receiving portion 1.

Further, the transfer electrode 20 on the PSG film 22.
A light-shielding Al film (hereinafter referred to as an Al light-shielding film) 24 is formed in a portion corresponding to the above so as to cover the lower transfer electrode 20 and the sidewall-shaped P-SiN film 23, and light incident from the outside is formed. Are configured so as not to enter the transfer electrode 20 side.

A silicon oxide film (hereinafter referred to as P-SiO) formed by a plasma CVD method is formed on the entire surface including the Al light-shielding film 24.
A film) 25 is formed. Here, the PSG film 2
2 and the P-SiO film 25 form a passivation film on the light receiving portion 1. Further, the Al light-shielding film 24 is selectively etched and removed on the light receiving portion 1, and light is made to enter the light receiving portion 1 through the opening 24a formed by this etching removal.

In the sectional view of FIG. 3, for the sake of simplicity, the protective film, the flattening film, the color filter, the micro condenser lens and the like on the Al light shielding film 24 are omitted.

Next, a method of manufacturing the image sensor according to the above embodiment will be described with reference to the manufacturing process diagrams of FIGS. The same reference numerals are given to those corresponding to FIG.

First, as shown in FIG. 3A, a normal C
Using the CD process, necessary impurities such as N-type impurities (phosphorus (P) and boron (B)) are introduced by, for example, ion implantation or film diffusion, and activated by heat treatment to perform N-type silicon substrate 11 Upper first P-type well region 1
2, the N-type transfer channel region 14, the P-type channel
The stopper region 15 and the second P-type well region 17 are formed. After that, for example, SiO is formed on the transfer channel region 14.
A transfer electrode 20 made of a polycrystalline silicon layer is formed via a gate insulating film 19 made of ₂ or the like. After that, thermal oxidation is performed to form a thin thermal oxide film (SiO ₂ film) on the surface of the transfer electrode 20.
21 is formed. The gate insulating film 19 may be formed by thermal oxidation of the silicon substrate 11,
The deposition may be performed by the CVD method.

Thereafter, the transfer electrode 20 is used as a mask for the first
N-type impurities, such as phosphorus (P), are ion-implanted into the surface of the P-type well region 12 of, and further activated to generate the first P
An N-type impurity diffusion region 13 is formed on the surface of the well region 12. At this time, the light receiving portion (photodiode) 1 is formed by the PN junction between the N-type impurity diffusion region 13 and the first P-type well region 12. After the light receiving portion 1 is formed, P-type impurities, for example, boron (B) are ion-implanted again using the transfer electrode 20 as a mask, and further activated to form a P-type positive impurity on the surface of the N-type impurity diffusion region 13. The hole accumulation region 16 is formed. In the above ion implantation of impurities, the gate insulating film 19 formed on the surface of the silicon substrate 11 functions as a buffer layer for absorbing irradiation damage caused by ion implantation.

After that, a PSG film 22 as an interlayer insulating film is deposited on the entire surface to a thickness of about 200 to 400 nm, for example, by the CVD method. After that, the silicon nitride film 23 is formed on the entire surface by the plasma CVD method. This plasma CVD
The silicon nitride film formed by the method, that is, the P-SiN film 23 contains a large amount of hydrogen.

Next, as shown in FIG. 3B, the P-
Vertical processing by anisotropic etching is applied to the entire surface of the SiN film 23. For example, RIE (reactive ion etching) is performed in the vertical mode. This etching is stopped when the P-SiN film 23 disappears in a flat portion of the PSG film 22, such as a portion corresponding to the transfer electrode 20 and a portion corresponding to the light receiving portion 1. At this time, the P-SiN film 23 remains on the side wall of the step portion of the PSG film 22. That is, the P-SiN film 23 is formed in the sidewall shape in the step portion of the PSG film 22. PS
By leaving the iN film 23 in the step portion of the PSG film 22, the step difference of the PSG film 22 due to the transfer electrode 20 becomes gentle.

Next, as shown in FIG.
After forming the light-shielding film 24, for example, R in the vertical mode is used.
The Al light shielding film 24 is patterned by IE (reactive ion etching) to form the light receiving portion opening 24a. The opening width D1 of the light receiving portion opening 24a is smaller than the width D2 defined by the P-SiN film 23 remaining in the step portion of the PSG film 22. Therefore, the transfer electrode 20 and the P-SiN film 23 are present under the Al light-shielding film 24. In other words, the Al light-shielding film 24 is formed so as to cover the transfer electrode 20 and the P-SiN film 23. become.

Then, as shown in FIG. 4B, a silicon oxide film 25 for surface protection is formed on the entire surface including the Al light-shielding film 24.
To have a thickness of about 300 to 500 nm by a plasma CVD method. The silicon oxide film (that is, the P-SiO film 25) and the lower PSG film 22 formed by the plasma CVD method form a passivation film on the light receiving portion 1. The optical refractive index of this P-SiO film 25 is
It is almost the same as the optical refractive index of the G film 22 and is about 1.5.

After the element is formed in this way, 400 ° C.
Heat treatment is performed for about 1 hour before and after. At this time, the sidewall-shaped P- formed on the stepped portion of the PSG film 22.
A large amount of hydrogen contained in the SiN film 23 diffuses to the silicon substrate 11 side. By this hydrogen diffusion, the interface of the silicon substrate 11 is hydrogenated and, for example, the silicon crystal 1
The dangling bond generated in the minute defect in No. 1 is terminated by hydrogen, and the generation of dark current that becomes noise of the image sensor is suppressed.

As described above, in the image sensor according to the above-mentioned embodiment, P-SiN having a light refractive index of about 2.0.
Since the film 23 is formed in a sidewall shape in the peripheral portion of the light receiving portion 1, particularly in the step portion of the PSG film 22, the PSG film 2 having a mutual optical refractive index of about 1.5 is formed on the light receiving portion 1.
2 and the P-SiO film 25 are formed in a stacked form,
The laminated film constitutes the passivation film on the light receiving portion 1.

Therefore, the fluctuation of the spectral sensitivity characteristic due to the interference effect is reduced, and as a result, the PSG film 22 and P-Si
The spectral characteristics do not vary depending on the film thickness of the O film 25, and the degree of freedom in design can be expanded.

In the peripheral part of the image sensor,
The obliquely incident light is not largely refracted at the interface between the PSG film 22 and the P-SiO film 25 and enters the vertical transfer register 2 side, and smear which is a problem in the image sensor can be reduced.

In addition, since hydrogen contained in the P-SiN film 23 reaches the interface of the silicon substrate 11 by diffusion, the hydrogen annealing effect can sufficiently reduce the interface level.
Dark current can be reduced.

As described above, according to the image sensor of this embodiment, it is possible to improve the optical characteristics such as spectral sensitivity and stabilize the interface characteristics leading to the reduction of dark current.

The Al light shielding film 24 is formed on the transfer electrode 20.
Since it is formed so as to cover the P-SiN film 23 and the P-SiN film 23, upward diffusion of hydrogen from the P-SiN film 23 is blocked by the Al light-shielding film 24.
Most of the hydrogen diffused from the P-SiN film 23 will diffuse toward the interface side of the silicon substrate 11. As a result, the reduction of the interface state due to the hydrogen annealing effect can be efficiently achieved, and the reduction of the dark current can be further improved.

Further, the P-SiN film is provided in the peripheral portion of the light receiving portion 1,
Particularly, since the PSG film 22 is formed to have a sidewall shape at the step portion, the step of the transfer electrode becomes gentle,
Thereby, the step coverage of the Al light shielding film 24 formed on the transfer electrode 20 is improved, and the Al light shielding film 24 is formed.
Will be formed thick even in the portion corresponding to the end of the transfer electrode 20. As a result, the invasion of light into the transfer electrode 20 and the transfer channel region 24 by the Al light shielding film 24 can be sufficiently exhibited.

Further, according to the method of manufacturing the image sensor in this embodiment shown in FIGS. 3 and 4, the PSG film 22 is formed when the P-SiN film 23 is formed in the sidewall shape in the peripheral portion of the light receiving portion 1. After the P-SiN film 23 is formed thereon, the P-SiN film 23 is anisotropically etched (vertical mode RIE) to be formed on the PSG film 22 in the peripheral portion of the light receiving portion 1. P- on the step
Since the SiN film 23 is left, the P-SiN film 23 can be easily formed in a sidewall shape in the peripheral portion of the light receiving portion 1, and optical characteristics such as spectral sensitivity can be improved and dark current can be reduced. It is possible to easily manufacture the image sensor according to the present embodiment that can achieve the stabilization of the connected interface characteristics together.

In the above-mentioned embodiment, the example applied to the FIT type image sensor is shown. However, the present invention can also be applied to the interline transfer (IT) type image sensor. In this case, the storage unit shown in FIG. 1 may be omitted.

[0078]

According to the solid-state imaging device of the present invention, the light receiving portions and the transfer channel regions are arranged and formed on the same substrate, and the transfer electrodes are selectively formed on the transfer channel regions via the gate insulating film. In the solid-state imaging device, which is formed, an interlayer insulating film is formed on the entire surface including the transfer electrode, and a light shielding film is formed on the interlayer insulating film so as to cover the transfer electrode. Since the film is formed in a sidewall shape and a protective insulating film having a photorefractive index substantially the same as that of the interlayer insulating film is formed at least in a portion corresponding to the light receiving portion so as to cover at least the light receiving portion, It is possible to achieve both improvement of optical characteristics such as sensitivity and stabilization of interface characteristics leading to reduction of dark current.

Further, according to the present invention, in the above structure, the hydrogen-containing film is formed in the step portion formed on the interlayer insulating film in the peripheral portion of the light receiving portion.
On the light receiving part, there is an interlayer insulating film and a protective insulating film having almost the same photorefractive index, which leads to improvement of optical characteristics such as spectral sensitivity and reduction of dark current as described above. Stabilization of interfacial properties can be achieved together.

Further, according to the present invention, in the above structure, the light-shielding film is formed so as to cover the transfer electrode and the hydrogen-containing film, so that the interface state can be efficiently reduced by the hydrogen annealing effect. Therefore, it is possible to further improve the reduction of dark current, improve the step coverage of the light-shielding film formed on the transfer electrode, and prevent light from entering the transfer electrode and the transfer channel region by the light-shielding film. It can be fully demonstrated.

According to the present invention, in the above structure, the interlayer insulating film is a PSG film, and the hydrogen-containing film is a plasma CV.
Since the silicon nitride film formed by the D method and the above-mentioned protective insulating film are the silicon oxide films formed by the plasma CVD method, the P-SiN film having a photorefractive index of about 2.0 is provided around the light receiving portion. And a PSG film and a P-SiO film having a photorefractive index of about 1.5 are laminated on the light receiving portion.
This reduces fluctuations in the spectral sensitivity characteristics due to interference effects and the like. As a result, the spectral characteristics do not vary depending on the film thickness of the PSG film and the P-SiO film,
The degree of freedom in design can be expanded, and in the peripheral portion of the solid-state image sensor, the obliquely incident light can be absorbed by the PSG film and the P
Smear, which is a problem in a solid-state image pickup device, can be reduced since it is prevented from being greatly refracted at the interface with the —SiO film and entering the transfer channel region side. Moreover, since hydrogen contained in the P-SiN film diffuses and reaches the interface of the substrate, the hydrogen annealing effect can sufficiently reduce the interface level and reduce the dark current.

Further, according to the method of manufacturing the solid-state image pickup device of the present invention, the light receiving portion and the transfer channel region are arranged and formed on the same substrate, and the transfer electrode is selected on the transfer channel region via the gate insulating film. In a method of manufacturing a solid-state image sensor formed in a specific manner, a step of forming an interlayer insulating film on the entire surface including the transfer electrode, a step of forming a hydrogen-containing film in a peripheral portion of the light receiving portion in a sidewall shape, and the transfer Since it has a step of forming a light-shielding film so as to cover the electrodes, a step of forming a protective insulating film so as to cover at least the light receiving portion, and a step of subjecting the entire surface to heat treatment, in the heat treatment step, Hydrogen diffuses from the sidewall-containing hydrogen-containing film to the interface side of the substrate, and the interface level of the substrate is sufficiently reduced by the hydrogen diffusion from the hydrogen-containing film. So that it is possible to reduce the dark current.

Further, since the interlayer insulating film and the protective insulating film forming the passivation film have almost the same optical refractive index, the fluctuation of the spectral sensitivity characteristic due to the interference effect or the like is reduced, and as a result, the interlayer insulating film is reduced. Since the spectral characteristics do not change due to the respective film thicknesses of the protective insulating film, the degree of freedom in design can be expanded.

Further, in the peripheral portion of the solid-state image sensor, obliquely incident light is not largely refracted at the interface between the interlayer insulating film and the protective insulating film and enters the transfer channel region side. It is possible to reduce the problematic smear.

As described above, in the method of manufacturing the solid-state image pickup device according to the present invention, it is possible to achieve both improvement of optical characteristics such as spectral sensitivity and stabilization of interface characteristics leading to reduction of dark current. Can be easily manufactured.

Further, according to the present invention, in the step of forming a hydrogen containing film in a sidewall shape in the peripheral portion of the light receiving portion,
After forming the hydrogen-containing film on the interlayer insulating film, the hydrogen-containing film is subjected to anisotropic etching treatment to form the PS film.
Since the hydrogen containing film is left on the stepped portion formed on the G film in the peripheral portion of the light receiving portion, the hydrogen containing film can be easily formed in a sidewall shape in the peripheral portion of the light receiving portion.

Further, according to the present invention, in the above manufacturing method, the light shielding film is formed so as to cover the transfer electrode and the hydrogen containing film. Therefore, among hydrogen diffusion from the hydrogen containing film in the heat treatment step, Since the upward diffusion of hydrogen is blocked by the light-shielding film, most of the hydrogen diffused from this hydrogen-containing film will diffuse toward the interface side of the substrate. As a result, the reduction of the interface state due to the hydrogen annealing effect can be efficiently achieved, and the reduction of the dark current can be further improved.

According to the present invention, in the above manufacturing method, the interlayer insulating film is a PSG film and the hydrogen containing film is a plasma CV.
Silicon nitride film (P-SiN) formed by the D method
Since the protective insulating film is a silicon oxide film (P-SiO film) formed by a plasma CVD method, the passivation formed of a laminated film of a PSG film and a P-SiO film is formed on the light receiving portion. The film is formed.

Then, in the subsequent heat treatment step, hydrogen diffuses from the P-SiN film formed in the sidewall shape to the interface side of the substrate. Due to the hydrogen diffusion from the P-SiN film, the interface state of the substrate is sufficiently reduced, and the dark current can be reduced.

Further, PS constituting the passivation film
Since the G film and the P-SiO film have approximately the same optical refractive index of about 1.5, the fluctuations in the spectral sensitivity characteristics due to interference effects and the like are reduced, and as a result, the PSG film and the P-SiO film are reduced.
The spectral characteristics do not vary depending on the film thickness of each film, and the degree of freedom in design can be expanded.

Further, in the peripheral portion of the solid-state image sensor, obliquely incident light is not largely refracted at the interface between the PSG film and the P-SiO film and enters the transfer channel region side. It is possible to reduce the problematic smear.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment (hereinafter, referred to as an image sensor according to the embodiment) in which a solid-state imaging device according to the present invention is applied to, for example, a frame / interline transfer (FIT) type CCD image sensor. .

FIG. 2 is a cross-sectional view showing a light receiving portion of the image sensor according to the present embodiment and its periphery.

FIG. 3 is a manufacturing process diagram showing a method of manufacturing the image sensor according to the present embodiment, wherein FIG. 3A shows a stage in which a P-SiN film is formed on the entire surface of the PSG film on the transfer electrode. b)
Shows the stage where the vertical mode RIE process was applied to the P-SiN film.

FIG. 4 is a manufacturing process drawing showing the manufacturing method of the image sensor according to the present embodiment. FIG. 4A is a transfer electrode and P-SiN.
The stage where an Al light-shielding film is formed so as to cover the film is shown, and FIG. 7B shows the stage where a P-SiO film is formed on the entire surface including the Al light-shielding film and further heat-treated.

FIG. 5 is a cross-sectional view showing a light receiving portion of an image sensor according to a conventional example and its periphery.

[Explanation of symbols]

1 Light-Receiving Section 2 Vertical Register 3 Image Section 5 Storage Section 11 N-type Silicon Substrate 12 First P-type Well Region 13 N-type Impurity Diffusion Region 14 N-type Transfer Channel Region 15 P-type Channel stopper region 16 P type hole accumulation region 17 second P-type well region 18 readout gate unit 19 a gate insulating film 20 transfer electrodes 21 thermal oxide film (SiO ₂₎ 22 PSG film 23 P-SiN film 24 Al light-shielding film 25 P-SiO film

Claims (8)

[Claims] 1. A light receiving portion and a transfer channel region are arranged and formed on the same substrate, and a transfer electrode is selectively formed on the transfer channel region via a gate insulating film, and an interlayer is formed on the entire surface including the transfer electrode. In a solid-state imaging device in which an insulating film is formed and a light-shielding film is formed on the interlayer insulating film so as to cover the transfer electrode, a hydrogen-containing film is formed in a sidewall shape in the peripheral portion of the light receiving portion, and at least the above A solid-state image sensor, comprising: a protective insulating film having a photorefractive index substantially equal to that of the interlayer insulating film is formed in a portion corresponding to the light receiving portion so as to cover at least the light receiving portion. 2. The solid-state imaging device according to claim 1, wherein the hydrogen-containing film is formed on a stepped portion formed on the interlayer insulating film in a peripheral portion of the light receiving portion. 3. The solid-state imaging device according to claim 1, wherein the light shielding film is formed so as to cover the transfer electrode and the hydrogen-containing film. 4. The interlayer insulating film is a PSG film, the hydrogen-containing film is a silicon nitride film formed by a plasma CVD method, and the protective insulating film is a silicon oxide film formed by a plasma CVD method. The solid-state image sensor according to claim 1, 2 or 3, wherein 5. A method of manufacturing a solid-state imaging device, wherein light-receiving portions and transfer channel regions are arranged and formed on the same substrate, and transfer electrodes are selectively formed on the transfer channel regions via a gate insulating film. A step of forming an interlayer insulating film on the entire surface including the transfer electrode, a step of forming a hydrogen-containing film in the peripheral portion of the light receiving portion in a sidewall shape, and a step of forming a light shielding film so as to cover the transfer electrode, A method of manufacturing a solid-state imaging device, comprising: a step of forming a protective insulating film having a photorefractive index substantially the same as that of the interlayer insulating film so as to cover at least the light receiving portion; and a step of subjecting the entire surface to heat treatment. 6. The step of forming a hydrogen-containing film in the shape of a sidewall in the peripheral portion of the light receiving portion includes a step of forming a hydrogen-containing film on the entire surface of the interlayer insulating film, and an anisotropic method with respect to the hydrogen-containing film. 6. A method for manufacturing a solid-state image pickup device according to claim 5, further comprising a step of subjecting the hydrogen-containing film to a step portion formed on the PSG film in a peripheral portion of the light receiving portion on the PSG film. . 7. The method for manufacturing a solid-state imaging device according to claim 5, wherein the light-shielding film is formed so as to cover the transfer electrode and the hydrogen-containing film. 8. The interlayer insulating film is a PSG film, the hydrogen-containing film is a silicon nitride film formed by a plasma CVD method, and the protective insulating film is a silicon oxide film formed by a plasma CVD method. The method for producing a solid-state image sensor according to claim 5, 6 or 7, which is a film.