JP2002319668A - Solid-state imaging device and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately determine black color by reducing the difference in the output signal values between an imaging unit and an optical black part. SOLUTION: A method for manufacturing a solid-stage imaging device comprises steps of preparing a semiconductor substrate 11, in which the imaging unit B1 and the optical black part B2 are formed, forming a plurality of photoelectric converters 22 which are disposed in array, in at least one direction in the substrate 11 and each having a photodetecting surface, forming a charge transfer channel 17 near the converter in the substrate, forming a charge transfer electrode 25a arranged in one direction on the channel 17, forming a metal light-shielding film 30a having openings on the photodetecting surface of the imaging elements and no opening on the photodetecting surface of the optical black part, forming a silicon oxide film, a silicon nitride film or a silicon nitric oxide film 33 thereon by a pressure reducing CVD method or a plasma CVD method, and depositing a reflow film 35a thereon, and forming a flat upper surface through heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid-state imaging device and a method of manufacturing the same, and more particularly, to a solid-state imaging device including an area sensor and a line sensor and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a solid-state imaging device such as a CCD solid-state imaging device, a large number of photoelectric conversion elements are provided in a semiconductor substrate.
A charge transfer channel adjacent to the charge transfer channel is formed, and a plurality of charge transfer electrodes are formed on the charge transfer channel.

Although the photoelectric conversion element has a light receiving surface, a metal light shielding film having an opening only on the light receiving surface is formed on the charge transfer channel and the charge transfer electrode so that light is not irradiated. . In addition, an insulating film (reflow film) that is flattened by reflow is formed on the charge transfer electrode and the metal light-shielding film in order to flatten unevenness due to the charge transfer electrode and the metal light-shielding film. The upper surface of the reflow film becomes flat by the high-temperature heat treatment. On the reflow film whose upper surface is flattened,
By forming the color filter and the micro lens, a clear image with little distortion can be taken.

[0004]

By the way, as the reflow film, for example, BPSG (Boro-PhoshoS) is used.
ilicate Glass) and PSG (Phosho)
Silicate Glass) is used. The reflow film contains impurities such as boron and phosphorus. If impurities diffuse into, for example, the photoelectric conversion element, problems such as a change in the characteristics of the photoelectric conversion element occur.

In addition, in the step of reflowing the reflow film at a high temperature, there has been a problem that the metal light shielding film formed below the reflow film is oxidized. For example, if tungsten (W) is used as the metal light shielding film, 30
Oxidation occurs around 0 ° C. to 400 ° C., and tungsten oxide is formed.

[0006] When the metal light-shielding film is oxidized, for example, the photoelectricity of an image pickup unit (a part which actually contributes to image pickup and an opening of the light-shielding film is formed on the light-receiving surface of the photoelectric conversion element) in the dark is obtained. The output signal value of the conversion element is different from the output signal value of the photoelectric conversion element in the optical black portion (a portion that does not actually contribute to imaging, and the light receiving surface of the photoelectric conversion element is covered by the light-shielding film). Will show the value. Since the output signal value of the optical black section is a black reference value, if a difference occurs in the output signal value between the image pickup section and the optical black section, the black determination will be hindered.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress a decrease in the accuracy of black determination due to oxidation of a metal light-shielding film. Another object of the present invention is to suppress a change in characteristics of a photoelectric conversion element due to diffusion of an impurity when the impurity is included in the reflow film.

[0008]

According to one aspect of the present invention, a step of preparing a semiconductor substrate on which an imaging section for performing imaging and an optical black section for performing black determination are defined; Forming a plurality of photoelectric conversion elements arranged and aligned in at least one direction over the portion and the optical black portion, each having a light receiving surface, and having an opening in each light receiving surface on the imaging section Forming a metal light-shielding film having no opening on each light-receiving surface on the optical black portion; and applying a low-pressure CVD method or plasma C to cover the metal light-shielding film.
Forming a first insulating film including a silicon oxide film, a silicon nitride film, or a silicon oxynitride film by a VD method;
A method of manufacturing a solid-state imaging device includes a step of depositing a reflow film on the first insulating film and a step of reflowing the reflow film by heat treatment to form a second insulating film having a flat upper surface. Provided.

When a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed by a low pressure CVD method or a plasma CVD method so as to cover the metal light shielding film, the oxidation of the metal light shielding film in the reflow step of the reflow film is suppressed. it can.

According to another aspect of the present invention, there is provided a step of preparing a semiconductor substrate on which an imaging section for performing imaging and an optical black section for performing black determination are defined, and wherein the imaging section and the optical black are defined. Forming a plurality of photoelectric conversion elements arranged and aligned in at least one direction, and having a light receiving surface on each of the light receiving surfaces on the imaging unit; Forming a metal light-shielding film having no opening on each light-receiving surface on the portion, and a silicon oxide film, a silicon nitride film, or a silicon oxynitride film covering the metal light-shielding film by a low pressure CVD method or a plasma CVD method. Forming a first insulating film including: a step of forming a self-planarizing film on the first insulating film; and heat-treating the self-planarizing film to form a second insulating film. Method for manufacturing a solid-state imaging device includes a film formation process is provided.

When a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed by a low pressure CVD method or a plasma CVD method so as to cover the metal light shielding film, the oxidation of the metal light shielding film in the step of heat-treating the self-planarizing film is suppressed. can do.

According to another aspect of the present invention, at least one of a semiconductor substrate on which an imaging section for performing imaging and an optical black section for determining black color are defined, and the imaging section and the optical black section are defined. A plurality of photoelectric conversion elements arranged in the direction, each having a light receiving surface,
Each of the light receiving surfaces in the imaging unit has an opening,
A metal light-shielding film having no opening in each of the light-receiving surfaces in the optical black portion; and a metal light-shielding film covering the metal light-shielding film and being formed in contact with the metal light-shielding film. A first insulating film covering the
A first insulating film formed using a silicon oxide film, a silicon nitride film, or a silicon oxynitride film, and a second insulating film formed over the first insulating film, the upper surface of which is formed by reflow or self-planarization. And a second insulating film having a flat surface.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In this specification, a reflow membrane and
Is higher than the melting temperature of the film
The upper surface is flattened by heat treatment at the high temperature above
Possible film or the film is flattened by heat treatment etc.
Film. In this case, for example, SiO _TwoInside, phosphorus or boron
Mixing elements as impurities lowers the melting point of the film.
You.

In this specification, the term "self-planarizing film" refers to a film formed under the condition that the upper surface of the film is flattened during the film formation. In this case, the subsequent heat treatment
The main purpose is to improve the reliability of the film, for example, to make it denser. Also in this case, for example, phosphorus or boron can be mixed as an impurity in SiO ₂ .

Hereinafter, the manufacturing technique of the solid-state imaging device according to the first embodiment of the present invention will be described with reference to FIGS.
The description up to (H) and FIGS. 6 and 7 will be described. FIG. 1A is a plan view of the solid-state imaging device, and FIG.
FIG. 2 is a partially enlarged view of FIG. FIGS. 2A to 5H are cross-sectional views illustrating the steps of manufacturing the solid-state imaging device. FIG. 6 shows an OB (Optica) in the case where the solid-state imaging device manufacturing technique according to the first embodiment of the present invention is used.
1 Black) and the OB step when a normal atmospheric pressure CVD method is used. FIG. 7 is a diagram illustrating the manufacturing technique of the solid-state imaging device according to the first embodiment of the present invention. FIG. 4 is a diagram comparing the OB output when the OB output is present with the OB output when a general normal pressure CVD method is used.

FIG. 1A is a schematic plan view of a CCD solid-state imaging device. The solid-state imaging device A includes a semiconductor substrate 11
A large number of photoelectric conversion elements (photodiodes) 18, a vertical charge transfer channel 17, a horizontal charge transfer channel 14,
A drive unit for applying a voltage to a charge transfer electrode for transferring charges in a charge transfer channel;
6 is included.

The vertical charge transfer channels 17 are provided adjacent to the photoelectric conversion elements 18 arranged in the column direction, and are provided one for each photoelectric conversion element row. Vertical charge transfer channel 1
Read gate 1 for reading out the charges stored in the photoelectric conversion element 18 between the photoelectric conversion element 18 and the photoelectric conversion element 18
9 are provided. The driving unit 12 generates a driving signal for transferring charges in the vertical charge transfer channel 17. The horizontal charge transfer channel 14 transfers the charge transferred from the vertical charge transfer channel 17 toward the output amplifier 16. The output amplifier 16 amplifies a signal of the charge transferred in the horizontal charge transfer channel and outputs the amplified signal to the outside.

In the solid-state imaging device A, an imaging section B1 that actually contributes to imaging and an optical black section B2 that does not contribute to imaging are formed. Optical black section B2
May actually be arranged in a plurality of rows up and down or in a plurality of columns left and right. The photoelectric conversion element formed in the optical black portion B2 has a light-shielding film formed on the light receiving surface of the photoelectric conversion element 18 as described later, and does not actually accumulate charges by photoelectric conversion.

The sectional view shown in FIG.
It is sectional drawing which follows the Ia-IIa 'line. The manufacturing process of the solid-state imaging device will be described with reference to FIGS. 1B and 2A to 5H. A p-type semiconductor layer 21 is formed on an n-type silicon semiconductor substrate 11. N-type impurity diffusion region 17 and n-type impurity diffusion region 22 are formed in p-type semiconductor layer 21. The photoelectric conversion element 18 having a pn junction is formed by the n-type impurity diffusion region 22 and the p-type semiconductor layer 21. The n-type impurity diffusion region 17 is a vertical charge transfer channel 17 for transferring charges accumulated in the photoelectric conversion element 18. N-type impurity diffusion region 22
Is a light receiving surface, and a region including the upper surface of the n-type impurity diffusion region 17 is a non-light receiving surface. Vertical charge transfer channel 1
A read gate section 19 is provided between 7 and the n-type impurity diffusion region 22. Vertical charge transfer channel 17
A channel stop layer 28 is formed by a high-concentration p-type impurity diffusion region in a region other than the region including the photoelectric conversion element 18 and the read gate unit 19.

On the vertical charge transfer channel 17, a first charge transfer electrode 25a is formed of a first polycrystalline silicon (1 poly) layer via a first insulating film 20 formed of, for example, silicon oxide. .

As shown in FIG. 2B, the surface of the first charge transfer electrode 25a is oxidized to form a silicon oxide film 26. By performing heat treatment in an oxygen atmosphere,
A silicon oxide film 26 is formed on the surface of the charge transfer electrode 25a formed of polycrystalline silicon, and the surface is subjected to insulation treatment.

A second charge transfer electrode 25b (FIG. 1B) is formed of a second layer of polycrystalline silicon (2 poly) on a region partially overlapping the first charge transfer electrode 25a.
First charge transfer electrode 25a and second charge transfer electrode 25b
Are alternately formed in the vertical direction along the vertical charge transfer channels 17, and together with the vertical charge transfer channels 17, form a vertical charge transfer path. The vertical charge transfer path transfers charges accumulated in the photoelectric conversion elements 18 in the vertical direction (column direction).

As shown in FIG. 3C, the charge transfer electrode 2
An insulating film 29 made of, for example, silicon oxide is formed on the silicon substrate 1 so as to cover 5a (25b). If the surface of the second charge transfer electrode 25b is insulated, the insulating film 29 need not be formed. Whether or not to form the insulating film 29 is optional. On the insulating film 29, a high melting point metal film, for example, a tungsten (W) film 30 is deposited by, for example, a CVD method. As the refractory metal film, a molybdenum film or the like can be used in addition to the tungsten film. In addition, a nitride film of a high melting point metal such as WN may be used, or a barrier metal such as TiN may be formed between the insulating film 29 and the high melting point metal film 30. A film in which these films are stacked with the above-mentioned high melting point metal film is also included in the category of the high melting point metal film.

The tungsten film 30 is subjected to reactive ion etching (Rea) using, for example, CF ₄ gas as a reactive gas.
It is processed by an active ion etching (RIE) method.

As shown in FIG. 3D, an opening 30b for opening the light receiving surface of the photoelectric conversion element 18 formed in the imaging section B1 (FIG. 1A) is formed in the tungsten film 30. The tungsten film 30 serves as the imaging unit B1 (FIG. 1A).
The upper portion covers the vertical charge transfer channel 17 and the charge transfer electrodes 25a (25b), and also covers the entire region on the optical black portion B2 (FIG. 1A) (an opening is not formed on the light receiving surface). Conductive light shielding film 30
Functions as a.

As shown in FIG. 4E, the conductive light shielding film 3
A first insulating film 33 is formed on the insulating film 29 so as to cover Oa. The first insulating film 33 is a silicon oxide film grown by plasma CVD (hereinafter referred to as PCVD) using TEOS / O ₂ .

[0027]

[Table 1] Table 1 shows the growth conditions for the PCVD method and the normal pressure CVD method. The growth conditions of the PCVD method and the ordinary atmospheric pressure CVD method will be compared with reference to Table 1. First, in the pCVD method, TEOS (Tetra Ethy
l OrthoSilicate or Tetra Et
Hoxy Silicate: Si (OC ₂ H ₅ ) ₄ ) and O ₂ are used.

On the other hand, in the normal pressure CVD method, a mixed gas of SiH ₄ / N ₂ , O ₂ gas and N ₂ gas is used as a reaction gas. In the pCVD method, the gas pressure is 2.67 × 10 ²
Pa, while the gas pressure is 1.01 in the normal pressure CVD method.
It is as high as × 10 ⁵ Pa (atmospheric pressure).

When the insulating film is grown by the PCVD method, one kind of first gas selected from the group consisting of TEOS, SiH ₄ and SiF ₄ , NH ₃ , O ₂ and N ₂
A mixed gas of at least one gas selected from the group consisting of O and N ₂ can be used. pC
The film forming temperature by VD is generally 300 ° C. to 4 ° C.
Conditions within the range of 00 ° C. are preferred. The preferable range of the gas pressure varies depending on the structure of the reactor chamber of the pCVD apparatus or the like, but generally, the conditions within the range of 60 Pa to 400 Pa are preferable.

When a silicon oxide film is formed by the PCVD method, a film having a conformal shape along the surface irregularities is formed. On the other hand, when the normal pressure CVD method is used, the vicinity of the end of the projection becomes slightly overhanged.

Before forming the first insulating film 33,
A pre-cleaning treatment or a surface modification treatment may be performed. As an example of the surface modification treatment, plasma treatment using N ₂ gas may be performed. By performing these treatments, the hydrophilicity or the hydrophobicity of the surface can be changed, and the characteristics of the first insulating film formed thereon can be adjusted.

Next, the first insulating film 33 is covered with a BPSG film (second insulating film) 35 by a normal pressure CVD method using B ₂ H ₆ , PH ₃ and a Si source as a reaction gas. To form At this point, the BPSG film 35 has a shape substantially along the irregularities on the substrate surface. 700 ° C
To 1000 ° C, preferably 800 ° C to 900 ° C
The heat treatment is performed in an atmosphere such as oxygen or nitrogen at a temperature between ℃. The BPSG film 35 reflows, and as shown in FIG. 4F, a reflow film (BPSG) having a flat upper surface.
A film 35a is formed. The shape of the reflow film changes depending on conditions such as the impurity concentration, the heat treatment temperature, the heat treatment time, and the atmosphere of the heat treatment. PSG as reflow film
The same applies when a film is used.

As shown in FIG. 5G, a passivation film 40 made of a silicon nitride film is formed on the BPSG reflow film 35a by a pCVD method. Further, an on-chip color filter film 41 and an on-chip micro lens 43 are formed on the passivation film 40 on a region corresponding to each photoelectric conversion element 18. FIG.
The structure shown in (G) is a cross-sectional view of the solid-state imaging device in the imaging unit B1 (FIG. 1A).

As shown in FIG. 5H, in the optical black portion B2 (FIG. 1A), the light shielding film 30a
Is formed to cover the entire surface of the optical black portion B2.

Through the above steps, a solid-state imaging device having an imaging section and an optical black section is formed.

The first insulating film 33 has two functions. The first function is that during the heat treatment step of reflowing the BPSG film 35, the conductive light-shielding film 30 formed by W is formed.
It is a function of suppressing the oxidation of a. The second function is BPS
During the heat treatment process for reflowing the G film 35, BP
It functions as a diffusion prevention film for preventing impurities such as B and P existing in the SG film 35 from diffusing into, for example, the impurity diffusion region 22 constituting the photoelectric conversion element.

FIG. 6 shows the OB in the case of forming the first insulating film formed on the metal light shielding film by the normal pressure CVD method and the case of forming the first insulating film by the pCVD method in the manufacturing process of the solid-state imaging device. It is the graph which plotted the step.
Note that the OB step on the vertical axis in the figure indicates a case where the solid-state imaging device is shielded from light and all photoelectric conversion elements (sensors) are placed in a black state, that is, a case where light incident on the photoelectric conversion element unit is shielded (when dark) 5 shows a difference in output signal between the photoelectric conversion element in the optical black unit and the photoelectric conversion element in the imaging unit in FIG.

The larger the absolute value of the OB step, the larger the difference between the output signals of the photoelectric conversion elements between the image pickup unit and the optical black unit in the dark. When performing the black color determination, it is preferable that the OB step is as small as possible.

The process conditions were the same except for the step of forming the first insulating film.

As shown in FIG. 6, first pCVD method is used.
It can be seen that the absolute value of the OB step is significantly smaller when the insulating film is formed than when the first insulating film is formed by the normal pressure CVD method. Further, it can be seen that the variation of the OB step is reduced.

As shown in FIG. 7, the OB output (output value of the photoelectric conversion element in the optical black portion) itself is also pCV
By forming the first insulating film by the method D, the normal pressure C
The size can be significantly reduced as compared with the case of forming by the VD method. Ideally, the OB output is zero, but pCVD
It can be seen that, when the first insulating film is formed by using the method, an OB output value that is substantially ideal can be obtained.

As described above, according to the solid-state imaging device manufacturing technique according to the first embodiment, it is possible to prevent impurities in the reflow film from diffusing toward the substrate and also prevent oxidation of the light-shielding film. it can. Therefore, the output difference of the photoelectric conversion element between the imaging unit and the optical black unit in the dark can be reduced. In addition, it is possible to reduce the absolute value of the output signal of the photoelectric conversion element in the optical black section at the time of darkness. Therefore, it is possible to accurately determine the black color.

According to an experiment by the inventor, when the oxide film or the oxynitride film is formed when the film is grown under reduced pressure by the pCVD method, it is known that the tungsten light shielding film has not caused an oxidation reaction.

In normal pressure CVD, an interval of several minutes is required from the time when the substrate is set in the apparatus and the temperature of the substrate is started to be increased, to the time when the actual film formation is started. Since the substrate temperature is about 300 ° C. to 500 ° C., the substrate heated to 300 ° C. to 500 ° C. is exposed to the atmosphere for several minutes. Therefore, the tungsten film is easily oxidized from the surface.

On the other hand, when the pCVD method is used, the substrate is under reduced pressure, and the actual growth can be started several seconds after the substrate is heated. Therefore, it is possible to suppress the oxidation of the tungsten film.

When an oxide film or an oxynitride film is formed by pCVD, since the tungsten film is not oxidized after the formation, whether the oxidation of the tungsten film in the heat treatment at a high temperature during reflow is suppressed, or pCV
It is not clear at present whether the oxidation during reflow is suppressed by the difference in the quality of the grown oxide film or oxynitride film between the D method and the normal pressure CVD method.

However, the oxide film and the oxynitride film formed by the pCVD and the low-pressure CVD method are denser than the normal pressure CVD, and the elasticity can be improved even in the heat treatment at the reflow temperature by optimizing the film forming conditions. Deformation occurs.

On the other hand, in the atmospheric pressure CVD, plastic deformation occurs even in the heat treatment at the reflow temperature. That is, the Si—O bond is broken in the reflow step, and O is easily supplied to tungsten. Therefore, WO
It is thought that ₃ is likely to be formed.

In the first embodiment, the case where the BPSG film is used as the reflow film has been described as an example. However, similar results can be obtained when the PSG film is used as the reflow film. Incidentally, as impurities in the reflow film,
It is also possible to use germanium or arsenic in addition to phosphorus or boron.

Next, the manufacturing technique of the solid-state imaging device according to the first modification of the first embodiment of the present invention will be described.

In the manufacturing technique of the solid-state imaging device according to the first modification, the second insulating film 35 shown in FIGS. 4E and 4F is self-planarized instead of a reflow film such as BPSG. Use a membrane. Other steps are the same as in the first embodiment.

When a silicon oxide film is grown using a combination of TEOS, O _2, and O ₃ as a source gas, a self-flattening (a phenomenon that the upper surface is automatically flattened during film formation) occurs. At the time when the film formation is stopped (even without performing the heat treatment step for reflow), the upper surface of the film can be flattened. When O ₃ is combined with the reaction gas, the self-planarizing action is further promoted. When these reaction gas systems are used, O ₂ and O ₃ are decomposed into oxygen radicals during film formation. By the action of this oxygen radical, TEOS is polymerized to form an oligomer (multimer). The oligomer is adsorbed on the surface of the substrate to form a pseudo liquid layer. The pseudo liquid layer has fluidity and flattens during film formation. The heat treatment performed thereafter is not for reflow but rather for improving the reliability of the film. Also in this case, a step of adding phosphorus or boron and reflowing may be performed. Also in this case, the coverage (coverability) of the step (unevenness) immediately after the film formation is remarkably improved as compared with the case where SiH ₄ and O ₂ are used. Even when reflow is performed under the same heat treatment conditions, the subsequent flatness is better than when the above-described SiH ₄ and O ₂ are used. Incidentally, when O ₃ is combined with the reaction gas, the self-planarizing action is further promoted, but the oxidation of the tungsten film becomes remarkable. Therefore,
The need for an antioxidant film on the metal light-shielding film is further increased.

Next, a description will be given of a technique for manufacturing a solid-state imaging device according to a second modification of the first embodiment of the present invention.

In the second modification, a first insulating film is grown by a low pressure CVD method. Other steps are the same as those in the solid-state imaging device manufacturing technique according to the first embodiment or the first modification thereof. When the first insulating film is grown by using the low pressure CVD method, TEOS, SiH ₄ and SiH ₂ Cl
₂ , a first gas selected from the group consisting of Si ₂ H ₆ , SiCl ₄ and SiHCl ₃ , NH ₃ and O ₂
It is preferable to use a mixed gas of at least one gas selected from the group consisting of N ₂ O and N ₂ .

A multilayer film (laminated structure) may be used as the first insulating film. Of course, the technique of applying the multilayer film as the first insulating film can also be applied to the technique according to the first embodiment of the present invention or the first modification thereof.

The first embodiment and its first embodiment
The second modification has been described by taking a CCD area sensor as an example, but it is of course applicable to a CCD line sensor.

Next, a solid-state imaging device according to a second embodiment of the present invention and a method of manufacturing the same will be described with reference to FIG.

FIG. 8 is a cross-sectional view showing an example of a MOS type solid-state image pickup device, and is a cross-sectional view of an image pickup section contributing to image pickup. The MOS-type solid-state imaging device 200b includes the photoelectric conversion element 1
20, various transistors and wirings attached to the photoelectric conversion element 120, a scanning unit such as a row readout scanning unit, an output unit such as an analog signal output unit, and a control unit are formed on the semiconductor substrate 101 on which they have been formed. For example, a metal shielding film 112 made of tungsten is formed.

The semiconductor substrate 101 includes, for example, an n-type semiconductor substrate 101a and a p-type well 101b formed on one surface side of the n-type semiconductor substrate 101a.

The individual photoelectric conversion elements 120 are, for example, p
An n-type impurity region 120a formed at a predetermined position of the mold well 101b and a p-type impurity region formed on the n-type impurity region 120a are formed. And a photoelectric conversion element (photodiode) 120 having a mold impurity region 120b. Although the photoelectric conversion element 120 has a buried diode structure, the buried diode structure is applicable to the CCD solid-state imaging device according to the first embodiment.

For example, the channel stop region 102 surrounding each photoelectric conversion element 120 in plan view is the p-type well 1
01b. An insulating film 103 is formed on the surface of the semiconductor substrate 101. In other places of the semiconductor substrate 101, a gate electrode is formed on the insulating film 103, and n-type source / drain regions are formed on both sides of the gate electrode to form a transistor.

FIG. 8 shows an output signal line 1 among various wirings.
30 and the electrical insulating film 130a formed on the surface thereof are shown. The metal shielding film 112 is
Has an opening 112a on the light receiving surface of each one. The opening 112a opens the light receiving surface of the photoelectric conversion element 120. In the optical black portion that does not contribute to imaging, the metal light shielding film 11 is also formed on the light receiving surface of the photoelectric conversion element 120.
2 are formed.

As in the case of the first embodiment, the first insulating film 115 formed by the pCVD method
2 is formed. The first insulating film 115 is a silicon oxide film or a silicon oxynitride film.

A reflowed BPSG film or PSG film (second insulating film) 116 containing phosphorus or boron as an impurity
Is formed on the first insulating film 115. BPSG film 1
Reference numeral 16 denotes a reflow film reflowed by the heat treatment.
A color filter 117 is formed on the reflow film 116. The micro lens 119 is formed on the color filter 117 or on the flattening film 118 formed thereon. These microlenses 119 are provided one by one above the individual photoelectric conversion elements 120.

In the above MOS type solid state imaging device,
The first insulating film 115 prevents impurities such as boron or phosphorus contained in the reflow film (second insulating film) 116 from diffusing toward the substrate due to heat treatment at the time of reflow.
It has a function of preventing oxidation of the metal light shielding film.

According to the manufacturing technique of the solid-state imaging device according to the second embodiment, it is possible to prevent impurities in the reflow film from diffusing toward the substrate and also prevent oxidation of the metal light shielding film. . Therefore, the output difference of the photoelectric conversion element between the imaging unit and the optical black unit in the dark can be reduced. In addition, it is possible to reduce the absolute value of the output signal of the photoelectric conversion element in the optical black section at the time of darkness. Therefore, it is possible to accurately determine the black color.

As in the case of the first modification of the first embodiment, the second insulating film 116 may be formed by a self-flattening process. Further, similarly to the second modification, the first insulating film may be formed by a low pressure CVD method. The first insulating film may be formed using a multilayer film such as an ONO film.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to these embodiments. It will be apparent to those skilled in the art that various other modifications, improvements, and combinations are possible.

[0069]

According to the present invention, oxidation of the metal light-shielding film can be prevented in the manufacturing process of the solid-state imaging device, particularly in the heat treatment process. By preventing the metal light-shielding film from being oxidized, the output difference of the photoelectric conversion element between the imaging unit and the optical black unit in the dark can be reduced. In addition, it is possible to reduce the absolute value of the output signal of the photoelectric conversion element in the optical black section at the time of darkness. Therefore, it is possible to accurately determine the black color.

Further, when impurities are contained in the reflow film, diffusion of the impurities to the substrate side can be prevented, and deterioration of characteristics of the photoelectric conversion element can be prevented.

[Brief description of the drawings]

FIG. 1 is a plan view of a solid-state imaging device according to a first embodiment of the present invention, and FIG. 1A is a plan view illustrating an entire configuration. FIG. 1B is a plan view showing a part of FIG. 1A and shows a configuration including a charge transfer electrode.

FIGS. 2A and 2B are cross-sectional views for explaining a method of manufacturing the solid-state imaging device according to the first embodiment of the present invention, and are IIa-IIa of FIG. 1A. FIG. 3 is a cross-sectional view along the line.

FIGS. 3C and 3D are cross-sectional views illustrating a method for manufacturing the solid-state imaging device according to the first embodiment of the present invention, and are IIa-IIa in FIG. 1A. FIG. 3 is a cross-sectional view along the line.

FIGS. 4E and 4F are cross-sectional views for explaining a method of manufacturing the solid-state imaging device according to the first embodiment of the present invention, and are IIa-IIa in FIG. 1A. FIG. 3 is a cross-sectional view along the line.

FIG. 5G is a cross-sectional view for explaining the method for manufacturing the solid-state imaging device according to the first embodiment of the present invention, and is along IIa-IIa 'line in FIG. 1A. It is sectional drawing. FIG. 5H is a cross-sectional view for explaining the method for manufacturing the solid-state imaging device according to the first embodiment of the present invention, and is a cross-sectional view along the line Vh-Vh ′ in FIG. .

FIG. 6 is a graph in which measured values of OB steps of the solid-state imaging device manufactured by the method for manufacturing a solid-state imaging device according to the first embodiment of the present invention are plotted. At the same time, normal pressure CV
FIG. 3 is a diagram also showing an OB step in a solid-state imaging device when an insulating film is grown by a D method.

FIG. 7 is a graph in which measured values of the OB output of the solid-state imaging device manufactured by the method for manufacturing the solid-state imaging device according to the first embodiment of the present invention are plotted. At the same time, normal pressure CV
FIG. 9 is a diagram also showing OB outputs of the solid-state imaging device when an insulating film is grown by the D method.

FIG. 8 is a sectional view of a solid-state imaging device according to a second embodiment of the present invention, and is a sectional view of a MOS solid-state imaging device.

[Explanation of symbols]

 Reference Signs List A solid-state imaging device B1 imaging unit B2 optical black unit 11 semiconductor substrate 12 vertical driving unit 14 horizontal charge transfer channel 16 output amplifier 17 vertical charge transfer channel 18 photoelectric conversion element 19 readout gate 20 gate insulating film 22 impurity diffusion regions 25a, 25b Transfer electrode (polycrystalline silicon layer) 26 Surface oxide film 28 Channel stop layer 29 Insulating film 30 Tungsten film 30a Conductive light-shielding film 30b Opening 33 First insulating film 35, 35a BPSG film (reflow film) 40 Second insulating Film 41 On-chip color filter 43 On-chip micro lens

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H04N 5/335 H01L 31/10 A (72) Inventor Toru Hachiya 1-6-6 Matsuzakadaira, Yamato-cho, Kurokawa-gun, Miyagi Prefecture Address FUJIFILM Micro Devices Co., Ltd. F term (reference) 4M118 AA05 AA06 AB01 BA13 CA03 CA32 DA03 EA20 FA06 FA26 GB03 GB11 GD04 GD07 5C024 CX32 CY47 GZ36 5F049 MA02 NB05 RA02 RA08 SZ12 SZ13 TA12 TA03 5F058 BA05 BA05 BA09 BF07 BF23 BF25 BF29 BF30 BF32 BF33 BH08 BJ10

Claims (16)

[Claims] A step of preparing a semiconductor substrate on which an imaging unit for performing imaging and an optical black unit for performing black determination are defined; and
Forming a plurality of photoelectric conversion elements arranged in at least one direction, each having a light receiving surface, and having an opening in each light receiving surface on the imaging unit and receiving light on the optical black unit Forming a metal light-shielding film having no opening in the surface, and a low pressure CVD method or a plasma CVD method covering the metal light-shielding film.
Forming a first insulating film including a silicon oxide film, a silicon nitride film, or a silicon oxynitride film by a method, depositing a reflow film on the first insulating film, and reflowing the reflow film by heat treatment Forming a second insulating film having a flat upper surface. 2. The method according to claim 1, wherein the reflow film is a silicon oxide film containing at least one of boron and phosphorus. 3. The method according to claim 1, wherein the step of forming the metal light-shielding film includes a step of forming a high-melting-point metal film. 4. The method according to claim 1, wherein the step of forming the first insulating film comprises a TEO.
One kind of first gas selected from the group consisting of S, SiH ₄ and SiF _4, and at least one first gas selected from the group consisting of NH ₃ , O ₂ , N ₂ O and N ₂ 4. The method for manufacturing a solid-state imaging device according to claim 1, further comprising a step of forming an insulating film by a plasma CVD method using a mixed gas of different types of gases. 5. The method according to claim 1, wherein the step of forming the first insulating film comprises a TEO.
S, SiH ₄ , SiH ₂ Cl ₂ , Si ₂ H ₆ , SiCl ₄ and S
one type of first gas selected from the group consisting of iHCl ₃ and at least one type of gas selected from the group consisting of NH ₃ , O ₂ , N ₂ O and N ₂ 4. The method for manufacturing a solid-state imaging device according to claim 1, wherein the step of forming an insulating film by a reduced pressure CVD method using a mixed gas. 6. A step of forming, on the second insulating film, a color filter film to which a predetermined color is assigned to each of the photoelectric conversion elements; Forming a microlens on the photoelectric conversion element according to any one of claims 1 to 5. The method for manufacturing a solid-state imaging device according to any one of claims 1 to 5, further comprising: 7. A step of preparing a semiconductor substrate on which an imaging section for performing imaging and an optical black section for performing black determination are defined; and
Forming a plurality of photoelectric conversion elements arranged in at least one direction, each having a light receiving surface, and having an opening in each light receiving surface on the imaging unit and receiving light on the optical black unit Forming a metal light-shielding film having no opening in the surface, and a low pressure CVD method or a plasma CVD method covering the metal light-shielding film.
Forming a first insulating film including a silicon oxide film, a silicon nitride film, or a silicon oxynitride film by a method; forming a self-planarizing film on the first insulating film; Forming a second insulating film by heat-treating the substrate. 8. The method of forming a self-planarizing film according to claim
Using a mixed gas of EOS, oxygen and ozone as a reaction gas, C
The method for manufacturing a solid-state imaging device according to claim 7, further comprising a step of forming an insulating film by a VD method. 9. The method according to claim 7, wherein the step of forming the metal light-shielding film includes the step of forming a high-melting-point metal film. 10. The step of forming the first insulating film includes forming a first insulating film
One kind of first gas selected from the group consisting of OS, SiH _4, and SiF _4, and at least one first gas selected from the group consisting of NH ₃ , O ₂ , N ₂ O, and N ₂ 10. The method according to claim 7, wherein the step of forming an insulating film by a plasma CVD method using a mixed gas with a different kind of gas.
13. The method for manufacturing a solid-state imaging device according to item 10. 11. The step of forming the first insulating film includes forming a first insulating film
One kind of first gas selected from the group consisting of OS, SiH ₄ , SiH ₂ Cl ₂ , Si ₂ H ₆ , SiCl ₄ and SiHCl ₃ , NH ₃ , O ₂ , N ₂ O and N the solid-state imaging according to any one of claims 7 is a step of forming an insulating film by low pressure CVD to 9 using at least one of a gas mixture of gas selected from a group consisting of ₂ Metropolitan Device manufacturing method. 12. A step of forming, on the second insulating film, a color filter film in which a predetermined color is assigned to each of the photoelectric conversion elements; and forming each of the color filter films on the color filter film. Forming a microlens on the photoelectric conversion element according to any one of claims 7 to 11. The method for manufacturing a solid-state imaging device according to claim 7, further comprising: 13. A semiconductor substrate on which an imaging section for performing imaging and an optical black section for performing black color determination are defined, and the imaging section and the optical black section.
A plurality of photoelectric conversion elements arranged in at least one direction, each having a light receiving surface, and having an opening in each of the light receiving surfaces in the imaging unit,
A metal light-shielding film having no opening in each of the light-receiving surfaces in the optical black portion, and formed in contact with the metal light-shielding film so as to cover the metal light-shielding film;
A first insulating film conformally covering the metal light-shielding film, wherein the first insulating film is formed of a silicon oxide film, a silicon nitride film, or a silicon oxynitride film; A second insulating film to be formed,
And a second insulating film including at least one of boron and phosphorus and having an upper surface planarized by reflow or self-planarization. 14. The solid-state imaging device according to claim 13, wherein the metal light shielding film is a metal light shielding film including a high melting point metal film. 15. A color filter film formed on the second insulating film and assigned a predetermined color to each of the photoelectric conversion elements; and the color filter film formed on the color filter film and 2. A micro lens provided on each conversion element.
15. The solid-state imaging device according to 3 or 14. 16. A method for preparing a semiconductor substrate, comprising: a step of preparing a semiconductor substrate;
Forming a plurality of photoelectric conversion elements arranged in at least one direction and each having a light receiving surface; forming a metal light shielding film having an opening in each light receiving surface on the imaging unit; Low pressure CVD method or plasma CVD covering the light shielding film
Forming a first insulating film including a silicon oxide film, a silicon nitride film, or a silicon oxynitride film by a method; depositing a reflow film or a self-planarizing film on the first insulating film; Heat-treating the film or the self-planarizing film to form a second insulating film having a flat upper surface.