JP3399250B2 - Method for manufacturing solid-state imaging device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solid-state image pickup device (C
CD: Charge-Coupled Device) manufacturing method.

[0002]

2. Description of the Related Art Conventionally, as a solid-state image pickup device, one having a structure shown in FIGS. 4 and 5, for example, has been known. FIG. 4 is a plan view of an essential part schematically showing the arrangement of the transfer gate electrodes of the solid-state image pickup device. In FIG. 4, reference numeral 1 is a photosensor part formed on the surface layer of a silicon substrate (not shown). Around the photo sensor portions 1, ..., A first transfer gate electrode 2 and a second transfer gate electrode 3 made of polysilicon.
Are formed and arranged on a silicon substrate. Here, a part of the second transfer gate electrode 3 is located directly above the first transfer gate electrode 2, that is, a part of the second transfer gate electrode 3 covers the first transfer gate electrode 2 as shown in FIG. Are arranged. An insulating film functioning as an interlayer film is formed between the first transfer gate electrode 2 and the second transfer gate electrode 3 in a portion covering the first transfer gate electrode 2 as described later.

[0003] Figure 5 is a view taken along line B-B of FIG. 4, FIG. 5
As shown in FIG. 3, in this solid-state imaging device, a charge transfer section 6 is arranged on one side of the photosensor section 1 formed on the surface layer section of the silicon substrate 4 via a reading section 5, and on the other side of the other side. A channel stop 7 is provided in the. Further, another charge transfer unit 6 is arranged beside the channel stop 7, and a reading unit (not shown) and a photosensor unit (not shown) are sequentially arranged beside the charge transfer unit 6. Has been done.

An insulating film 8 made of SiO ₂ is formed on the surface of the silicon substrate 4, and the first transfer gate electrode 2 is formed on the insulating film 8 so as to cover the position directly above the charge transfer portion 6. There is. An insulating film 9 which functions as an interlayer film between the first transfer gate electrode 2 and the second transfer gate electrode 3 is formed on the first transfer gate electrode 2.
Although not shown in FIG. 5, the second transfer gate electrode 3 is formed on the insulating film 9 as shown in FIG. Although not shown, a light shielding film is formed on the insulating film 9 so as to cover the first transfer gate electrode 2 and the second transfer gate electrode 3, and a flattening layer is further formed on the light shielding film.

By the way, in manufacturing the solid-state image pickup device having such a structure, in particular, in order to form the insulating film 8 on the surface of the silicon substrate 4, usually, an oxide film (SiO 2) formed in advance is used.
₂ film) is damaged by dry etching when the first transfer gate electrode 2 is formed. Therefore, in order to remove this damage, the oxide film on the photo sensor part 1 is etched off and the surface of the silicon substrate 4 is exposed. Let Then, by thermally oxidizing the exposed surface again, an insulating film made of SiO ₂ is formed on the photo sensor portion 1.

An insulating film 9 is formed on the first transfer gate electrode 2.
In order to form, the first transfer gate electrode 2 itself made of polysilicon is thermally oxidized, and a thermal oxide film is formed on the surface layer portion of the first transfer gate electrode 2, which is used as the insulating film 9. The insulating film 9 thus obtained is used as an interlayer film between the first transfer electrode 2 and the second transfer electrode 3 as described above.

[0007]

However, the above-mentioned solid-state image pickup device has the following disadvantages in its manufacturing method. In order to reduce the electrode wiring resistance, the first transfer gate electrode 2 and the second transfer gate electrode 3 are W
Although it is often made to have a polycide structure such as polycide, when such a polycide structure is adopted,
As described above, after removing the damage, the thermal oxidation is directly performed again to obtain a thermal oxide film as an insulating film that forms an Si / SiO ₂ interface with the silicon substrate 4. The device characteristics of the solid-state imaging device obtained due to the diffusion deteriorate.

Further, in the photosensor section 1, in order to obtain a Si / SiO ₂ interface which is not damaged as described above, an insulating film serving as an interlayer film is deposited and formed on the first transfer gate electrode 2 by the CVD method, A method may be considered in which a resist pattern is subsequently formed and only the area directly above the photosensor section 1 is etched using this resist pattern. In that case, however, there is a problem of misalignment during the formation of the resist pattern and the CVD film. There is a problem in etching (that is, dry etching has a problem that the silicon substrate 4 and the like remain after the CVD film is etched, and wet etching has a problem in controllability such as a large side etch). Have difficulty.

Therefore, it is considered to be a simpler process that it is effective to leave the deposited CVD film as it is on the photosensor portion 1 without being removed by etching, and it is considered to be effective, but in that case. Is CV
Unlike the thermal oxide film, the D film does not reduce fixed charges, interface states, etc., resulting in deterioration of device characteristics, which is also difficult to implement.

Further, a CCD oxide film formed at a temperature of 800 ° C. to 820 ° C. by a low pressure CVD method which is generally used as an insulating film has a CV with a small amount of fixed charges and interface states.
Although it is said to be a D film, if the film is directly formed on Si in the photosensor portion 1, its characteristics are deteriorated, and therefore its implementation is also difficult. Further, the atmospheric pressure CVD film has a problem of step coverage, and the plasma CVD film has a problem of plasma damage, which is also difficult to adopt.

On the other hand, regarding the formation of the insulating film 9 serving as an interlayer film between the first transfer gate electrode 2 and the second transfer gate electrode 3, as described above, the heat of the first transfer gate electrode 2 made of polysilicon is used. Although it is formed by oxidation, such treatment also has the following disadvantages.

In the solid-state image pickup device, as the size and the number of pixels thereof are increased, the transfer clock is required to have a lower voltage. Under these demands, when the oxide film (interlayer insulating film) is formed by thermally oxidizing polysilicon as described above, as the thinning progresses, a gap between polysilicon electrodes (first transfer gate electrode 2 and The problem that the inter-electrode leakage breakdown voltage is insufficient between the second transfer gate electrode 3) becomes apparent. Further, the thermal oxidation for forming the polysilicon oxide film has a large load even when the heat treatment temperature is lowered. For example, when the polysilicon oxide film is formed by thermal oxidation, the leak voltage of 1 μA is 1.5 MV / c.
If m, an oxide film with a thickness of at least 150 nm is required to secure the maximum V clock amplitude of 22 V, but the gap between the transfer gate electrodes becomes wide, and
The reality is that the transfer amplitude cannot be reduced.

Further, since the transfer gate electrode made of polysilicon has a high resistance, it is not possible to reduce the polysilicon line width between pixels, so that it is not possible to make the gate electrode resistance of a high speed device such as FITCCD. As a countermeasure, it is possible to substitute the WSi electrode (polycide structure) with a polysilicon electrode. In that case,
If the interlayer insulating film is formed by thermal oxidation, the interlayer breakdown voltage deteriorates more than that of the polysilicon electrode, and in addition, the solid-state imaging device obtained due to W diffusion deteriorates in image quality. Further, in the structure using a polycide electrode (particularly, tungsten polysilicide) for the gate electrode, when the interlayer insulating film is formed by directly performing thermal oxidation, it is obtained because the refractory metal such as W diffuses as described above. The element characteristics of the solid-state image sensor to be obtained are deteriorated.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide an insulating film forming an Si / SiO ₂ interface in a photosensor portion or an insulating film serving as an interlayer film between transfer gate electrodes. With respect to the above, it is an object of the present invention to provide a method for manufacturing a solid-state imaging device, which prevents deterioration of device characteristics of the solid-state imaging device obtained due to the formation thereof.

[0015]

[Means for Solving the Problems] Claim 1 in the present invention
In the method for manufacturing a solid-state image sensor described above, a photosensor portion is formed on a surface layer portion of a silicon substrate, an insulating film is formed on a surface of the silicon substrate, and the photosensor portion is provided on the surface side of the silicon substrate through the insulating film. A first transfer gate electrode is formed on the silicon substrate in a bare state, the photosensor portion is exposed to the surface side of the silicon substrate through the insulating film, and a part of the first transfer gate electrode is located directly above the first transfer gate electrode. In forming and arranging the second transfer gate electrode on the silicon substrate in this manner, after the first transfer gate electrode and the second transfer gate electrode are formed, the insulating film located immediately above the photo sensor portion is removed by etching. Then , the silicon oxide film was deposited and formed at a temperature of 700 ° C. to 750 ° C. by the low pressure CVD method, which was a means for solving the above problems.

According to this method of manufacturing a solid-state image pickup device, after the first transfer gate electrode and the second transfer gate electrode are formed, the insulating film located immediately above the photosensor portion is removed by etching, and then, for example, by a low pressure CVD method. If the silicon oxide film is deposited and formed at less than 800 ° C., the obtained silicon oxide film becomes a CVD oxide film at a relatively low temperature, and becomes an insulating film with less fixed charges and interface states.

In the method of manufacturing a solid-state image pickup device according to a third aspect of the present invention, a photosensor portion is formed on a surface layer portion of a silicon substrate, an insulating film is formed on a surface of the silicon substrate, and the photo film is formed through the insulating film. A first transfer gate electrode is formed on the silicon substrate with the sensor portion facing the front surface of the silicon substrate, the photosensor portion is exposed to the front surface of the silicon substrate through the insulating film, and the first transfer is performed. When forming and arranging the second transfer gate electrode on the silicon substrate so that a part of the gate electrode is directly above the gate electrode,
After forming the first transfer gate electrode and prior to forming the second transfer gate electrode, the insulating film located at least in a region where the second transfer gate electrode is to be formed and not located immediately below the first transfer gate electrode is formed. The silicon oxide film is removed by etching and then deposited at a temperature of 700 ° C. to 750 ° C. by a low pressure CVD method so as to cover the first transfer gate electrode, and the silicon oxide film is used to form the first transfer gate electrode and the second transfer gate electrode. The formation of the interlayer film between the transfer gate electrode and the gate insulating film of the second transfer gate electrode was taken as a means for solving the above problems.

According to this method of manufacturing a solid-state image pickup device, after the first transfer gate electrode is formed and before the second transfer gate electrode is formed, the first transfer gate electrode is located in the region where the second transfer gate electrode is to be formed and the first transfer gate electrode is formed. The insulating film that is not located directly below the gate electrode is removed by etching, and then a silicon oxide film is deposited at a temperature of, for example, less than 800 ° C. by a low pressure CVD method so as to cover the first transfer gate electrode, and the silicon oxide film is used to form a first oxide film. Since the interlayer film between the first transfer gate electrode and the second transfer gate electrode is formed and the gate insulating film of the second transfer gate electrode is formed, the obtained silicon oxide film becomes a CVD oxide film at a relatively low temperature. As a result, the interlayer film has a high breakdown voltage, and the gate insulating film has a small amount of fixed charges and interface states.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The manufacture of the solid-state image sensor of the present invention will be described below.
The manufacturing method will be described in detail. First, the manufacturing method according to claim 1.
An example embodiment of the method will be described. In this example, shown in Figure 5
In the same way as the conventional method for obtaining the
Impurities are injected into the plate 4 by ion implantation, etc.
This is diffused, and the photo sensor unit 1, the reading unit 5, the electric charge
The transfer unit 6 and the channel stop 7 are formed respectively. Continued
The silicon substrate 4 surface by the thermal oxidation method or the CVD method.
SiO₂An insulating film 8 made of is formed. Where is this
A part of the edge film 8 is a gate of a first transfer gate electrode described later.
That functions as a gate insulating film (MOS gate insulating film)
Is. The insulating film 8 is made of SiO 2.₂From
ONO (SiO ₂-SiN-Si
O₂) It may be a structure.

Next, a polysilicon film is formed by the CVD method, and the polysilicon film is formed by a known resist technique,
Patterning is performed by a photolithography technique and a dry etching technique to form a first transfer gate electrode 2 as shown in FIG. 1 is a diagram showing a main part of a cross section taken along the line AA in the conventional plan view of the main part shown in FIG. Next, an insulating film such as SiO ₂ is formed in a state of covering the first transfer gate electrode 2 by the CVD method or the like, and this is used as the interlayer film 10. Then, a polysilicon film is formed in the same manner as the first transfer gate electrode 2 and is further patterned to form the second transfer gate electrode 3. When the gate electrode structure has three or more layers,
Following the formation of the second transfer gate electrode 3, the formation of the interlayer film and the formation of the transfer gate electrode may be repeated.

Next, a resist pattern is formed by using a known resist technique or photolithography technique, and the insulating film 8 and the interlayer film 10 located right above the photosensor portion 1 are dry-etched by using this resist pattern. Then, the surface of the silicon substrate 1 immediately above the photosensor portion 1 is exposed. By removing the insulating film 8 and the interlayer film 10 by etching in this way, the damages that the films 8 and 10 suffer when the transfer gate electrodes 2 and 3 are formed can be simultaneously removed from the silicon substrate 4.

Thereafter, a silicon oxide film is deposited and formed at a temperature of less than 800 ° C. by a low pressure CVD method, and the photosensor is covered with the first transfer gate electrode 2 and the second transfer gate electrode 3 as shown in FIG. A new insulating film 11 is formed immediately above the portion 1. Here, the deposition of the silicon oxide film (insulating film 11) is performed at a temperature lower than 800 ° C.
If the temperature exceeds 800 ° C., the interface level of the Si / SiO ₂ interface formed between the obtained film and the silicon substrate 4 increases, and the solid-state imaging device obtained thereby deteriorates in characteristics. Is. This is due to the formation of a trapped oxide film when the wafer (silicon substrate 4) is loaded into the reaction tube and the formation of a nitric oxide film during purging in the furnace with N ₂ O before film formation, for example. ing.

On the other hand, if the insulating film 11 is formed at a temperature lower than 700 ° C., the film forming rate becomes 1/10 or less as compared with the case where the film forming temperature is generally 800 ° C.
The film forming process takes too much time, which is not preferable in the process. 2 is a view showing a cross section taken along the line BB in the plan view of the main part shown in FIG. 4 of the related art. After the insulating film 11 is formed in this way, the insulating film 1 is further formed.
A light-shielding film (not shown), a flattening film (not shown), peripheral wiring (not shown), an overpassivation film (not shown), etc. are sequentially formed on the substrate 1 to obtain a solid-state image sensor. .

In the method of manufacturing such a solid-state image pickup device, after forming the first transfer gate electrode 2 and the second transfer gate electrode 3, a silicon oxide film is deposited and formed by the low pressure CVD method, and then the insulating film is formed. Since the insulating film 11 is formed, the insulating film 11 is not damaged during the formation of the first transfer gate electrode 2 and the second transfer gate electrode 3, and therefore the dark current caused by this damage is prevented. can do. In addition, by low pressure CVD method, 70
A silicon oxide film is deposited and formed at a relatively low temperature of 0 ° C. to 750 ° C., and the HTO film formed by this CVD method is used as the photo sensor unit 1.
Since it is a new insulating film 11 that forms the Si / SiO ₂ interface immediately above the insulating film 11,
Since the HTO film is formed at a lower temperature than the HTO film formed at 00 ° C to 820 ° C, it is possible to reduce the amount of trapped oxidation and the amount of nitrification oxidation due to N ₂ O, and reduce fixed charges and interface states. Therefore, it is possible to prevent the generation of dark current.

Although the first transfer gate electrode 2 and the second transfer gate electrode 3 are both made of polysilicon in the above embodiment, one of the first transfer gate electrode 2 and the second transfer gate electrode 3 is used. Alternatively, both may have a polycide structure such as W polycide. In that case, since thermal oxidation for forming an insulating film is not performed as in the conventional case,
Diffusion of refractory metal such as W due to this thermal oxidation treatment can be eliminated, whereby the resistance of the transfer gate electrode can be reduced and a high-sensitivity, low-smear solid-state imaging device can be obtained. Further, in the above-described embodiment, the insulating film 11 is formed at a temperature lower than a general film forming temperature. However, the insulating film 11 at this low temperature is merely Si / SiO ₂ with the surface of the silicon substrate 4. A thickness capable of forming an interface, that is, a thickness of about several nm to 10 nm may be sufficient. After securing this thickness, the film forming temperature is increased to about 800 ° C. to shorten the film forming processing time. You may plan.

Further, the insulating film 1 at a low temperature as described above
After the formation of No. 1, a thermal oxide film made of SiO ₂ is formed on the insulating film 11 by a thermal oxidation method in order to secure the film thickness required as the insulating film, and the thermal oxide film is formed in conformity with the insulating film 11 at the low temperature. An insulating film having a desired thickness may be formed. In that case, even if one or both of the first transfer gate electrode 2 and the second transfer gate electrode 3 has a polycide structure such as W polycide as described above, these transfer gate electrodes are once formed by a film (insulating film 11) at a low temperature. Since it is covered, this film functions as a cover that blocks the diffusion of the refractory metal from the polycide electrode, thereby avoiding the inconvenience that white spots are generated due to the diffusion of the refractory metal.

Next, an embodiment of the manufacturing method according to claim 3 will be described. Also in this example, similarly to the conventional method for obtaining the structure shown in FIG. 5, first, impurities are injected into the silicon substrate 4 by ion implantation or the like and further diffused, and the photosensor unit 1, the reading unit 5, the charge Transfer unit 6,
Each channel stop 7 is formed. Subsequently, the insulating film 8 made of SiO ₂ is formed on the surface of the silicon substrate 4 by the thermal oxidation method or the CVD method. A part of the insulating film 8 functions as a gate insulating film (MOS gate insulating film) of the first transfer gate electrode, which will be described later, as in the above example. Also in this embodiment, the gate insulating film 8, instead of the structure consisting of SiO ₂ ONO (SiO ₂ -
SiN-SiO ₂₎ may have a structure.

Next, a polysilicon film is formed by the CVD method, and the polysilicon film is formed by a known resist technique,
The patterning is performed by the photolithography technique and the dry etching technique to form the first transfer gate electrode 2 as shown in FIG. 3 is a view showing a main part of a cross section taken along the line AA in the conventional plan view of the main part shown in FIG. Then, the resist mask used for patterning the first transfer gate electrode 2 is used as it is, or a resist mask formed in the same manner is used, and the insulating film 8 immediately below the first transfer gate electrode 2 is formed. The portions other than those in are removed by etching. When the insulating film 8 is removed in this manner, not only the portion directly above the photosensor portion 1 but also the portion not directly below the first transfer gate electrode 2 and located in the area where the second transfer gate electrode 3 is to be formed are formed. The surface of the silicon substrate 4 is exposed at these positions.

Here, especially the insulating film 8 is formed of SiO 2.₂With one layer of membrane
When formed, this SiO₂Wet etching the film
When removing by wet etching,
Prevents side etching below the first transfer gate electrode 2.
There is a need to. Further, the insulating film 8 has an ONO structure.
In some cases, SiO₂/ SiN / SiO₂From top to bottom
May be removed, and the first transfer gate may be removed.
Continue to the SiN film when dry etching the gate electrode 2.
The remaining SiO. ₂You can remove the film
Yes.

Next, the low pressure CVD method is applied at 700 ° C. to 750 ° C.
A silicon oxide film is deposited and formed at a temperature of .degree. C., and an insulating film 12 is formed in a state of covering the first transfer gate electrode 2 as shown in FIG. This insulating film 12 is not located directly above the photosensor portion 1 and directly below the first transfer gate electrode 2,
Since the insulating film 8 is removed at the position in the region where the transfer gate electrode 3 is to be formed, the insulating film 8 is also formed on the surface of the silicon substrate 4 at these positions, and particularly the second transfer gate electrode 3 is to be formed. The insulating film 12 formed in the region functions as a gate insulating film of the second transfer gate electrode 3. Also, covering the first transfer gate electrode 2,
In addition, the insulating film 12 formed in the region where the second transfer gate electrode 3 is to be formed functions as an interlayer film between the first transfer gate electrode 2 and the second transfer gate electrode 3 described later.

Here, the deposition of the silicon oxide film (insulating film 12) is performed at a temperature of less than 800 ° C., as in the previous example, between the film obtained when the temperature exceeds 800 ° C. and the silicon substrate 4. This is because the interface state of the formed Si / SiO ₂ interface increases and the dark current increases accordingly. On the other hand, if the insulating film 12 is formed below 700 ° C.,
The film forming process takes too much time, which is not preferable in the process.

Although the insulating film 12 was formed at a temperature lower than a general film forming temperature, the insulating film 11 at this low temperature is just the silicon substrate 4 as in the previous example.
A thickness capable of forming a Si / SiO ₂ interface with the surface, that is, a thickness of several nm to 10 nm,
After such a thickness is secured, the film forming temperature may be raised to about 800 ° C. to shorten the film forming processing time. In addition, regarding the portion functioning as the gate insulating film of the second transfer gate electrode 3, particularly when it is desired to adopt the ONO structure,
The films may be sequentially formed in a film structure of CVD oxide film + thermal oxidation / SiN / CVD oxide film.

Then, a polysilicon film is formed on the insulating film 12 in the same manner as the first transfer gate electrode 2, and the second transfer gate electrode 3 is formed by patterning the polysilicon film. When the gate electrode structure has three or more layers, the formation of the insulating film 12 and the formation of the transfer gate electrode may be repeated. After the second transfer gate electrode 3 is formed in this manner, a light-shielding film (not shown), a planarizing layer (not shown), and the like are formed on the insulating film 12 and the second transfer gate electrode 3 in the same manner as in the conventional case. Peripheral wiring (not shown), overpassivation film (not shown), etc. are sequentially formed to obtain a solid-state image sensor.

In the method of manufacturing such a solid-state image pickup device, after the first transfer gate electrode 2 is formed and before the second transfer gate electrode 3 is formed, the insulating film not directly under the first transfer gate electrode 2 is formed. 8 is removed by etching, then low pressure CVD
The silicon oxide film by the method of forming the first transfer gate electrode 2
Since the insulating film 12 is formed by depositing so as to cover the first transfer gate electrode 2 and the second transfer gate electrode 3, the second insulating film 12 can form an interlayer film between the first transfer gate electrode 2 and the second transfer gate electrode 3. The gate insulating film of the transfer gate electrode 3 can be formed. Therefore, since the insulating film 12 is formed of a film at a relatively low temperature, the interlayer film to be formed can have a small heat load and a high breakdown voltage, and the gate insulating film has a small amount of fixed charges and interface states. Can be one. Further, since the insulating film 12 is formed from the film due to the low temperature even at the position directly above the photo sensor portion 1 and thereby the Si / SiO ₂ interface is formed with the silicon substrate 4, the fixed charge and the interface state are not generated. It is possible to reduce the amount, and thus it is possible to prevent the generation of dark current.

Although the first transfer gate electrode 2 and the second transfer gate electrode 3 are both made of polysilicon in the above embodiment, one of the first transfer gate electrode 2 and the second transfer gate electrode 3 is used. Alternatively, both may have a polycide structure such as W polycide. In that case, since thermal oxidation for forming an interlayer film or an insulating film is not performed as in the conventional case, a high melting point such as W associated with such thermal oxidation treatment is used. It is possible to eliminate the diffusion of the metal, which makes it possible to reduce the resistance of the transfer gate electrode and obtain a solid-state image sensor with high sensitivity and low smear.

Further, in the above-described embodiment, the insulating film 8 located directly above the photosensor portion 1 is also removed by etching when the insulating film 8 is etched, and then the CVD film (oxidation) at a low temperature is also formed directly above the photosensor portion 1. Although a silicon film) is formed, a thermal oxide film or the like is formed immediately above the photosensor portion 1 by a method similar to the conventional one, and an interlayer film between the first transfer gate electrode 2 and the second transfer gate electrode 3 is formed. Alternatively, only the gate insulating film of the second transfer gate electrode 3 may be formed of the CVD film (silicon oxide film).

[0037]

As described above, in the method of manufacturing a solid-state image pickup device according to the first aspect of the present invention, after the first transfer gate electrode and the second transfer gate electrode are formed, the low pressure CVD method is applied to 700 ° C. to 750 ° C. Since a silicon oxide film is deposited and formed at a temperature of ℃, and an insulating film is formed from this,
This insulating film is not damaged during the formation of the first transfer gate electrode and the second transfer gate electrode, and therefore it is possible to prevent the generation of dark current due to this damage. Further, since the silicon oxide film is deposited and formed at a relatively low temperature by the low pressure CVD method, and the film by the CVD method is used as a new insulating film for forming the Si / SiO ₂ interface at the position directly above the photo sensor portion, the insulating film is formed. Since it is composed of an HTO film at a relatively low temperature, it is possible to reduce fixed charges and interface states, thereby preventing the generation of dark current.

According to a third aspect of the present invention, in the method for manufacturing a solid-state image sensor, after forming the first transfer gate electrode and before forming the second transfer gate electrode, the insulating film not directly under the first transfer gate electrode is removed by etching. , Then by low pressure CVD method 7
The silicon oxide film at a temperature of 00 ° C. to 750 ° C.
Since the insulating film is formed by depositing so as to cover the transfer gate electrode, the insulating film can form an interlayer film between the first transfer gate electrode and the second transfer gate electrode. A gate insulating film of the second transfer gate electrode can be formed. Therefore, since the insulating film is composed of the HTOCVD film at a relatively low temperature, the interlayer film to be formed can have a small heat load and a high withstand voltage, and the gate insulating film has a small amount of fixed charges and interface states. It is possible to improve the image quality of the solid-state imaging device obtained as a single product. Further, by thus forming the interlayer film between the first transfer gate electrode and the second transfer gate electrode at a low temperature, it is possible to achieve a high breakdown voltage, thereby the miniaturization of the solid-state imaging device, a low voltage Can be enabled. For example, by forming a HOT of 5 MV / cm with a thickness of 50 nm, the gap between transfer gate electrodes can be reduced to 1/3 as compared with the conventional 150 nm polysilicon thermal oxide film, and a 25 V interlayer breakdown voltage higher than the conventional one can be secured. .

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part for explaining an example of an embodiment of the present invention.

FIG. 2 is a cross-sectional view of main parts for explaining the exemplary embodiment shown in FIG.

FIG. 3 is a main-portion cross-sectional view for explaining another embodiment of the present invention.

FIG. 4 is a plan view of a main part of a solid-state image sensor according to the present invention.

5 is a sectional view taken along line B-B of FIG.

[Explanation of symbols]

1 Photosensor Part 2 First Transfer Gate Electrode 3
Second transfer gate electrode 4 Silicon substrate 8 Insulating film 11 Insulating film
12 Insulating film

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 27/148

Claims (5)

(57) [Claims] 1. A photosensor portion is formed on a surface layer portion of a silicon substrate, an insulating film is formed on a surface of the silicon substrate, and the photosensor portion is exposed to the silicon substrate surface side through the insulating film. A first transfer gate electrode is formed on a silicon substrate, the photosensor portion is exposed to the surface side of the silicon substrate through the insulating film, and a part of the photosensor portion is located directly above the first transfer gate electrode. A method for manufacturing a solid-state imaging device by forming and arranging a second transfer gate electrode on a substrate, the method comprising: forming an insulating film directly above the photo sensor unit after forming the first transfer gate electrode and the second transfer gate electrode. Is removed by etching, and then 700 ° C.
A method for manufacturing a solid-state imaging device, comprising depositing and forming a silicon oxide film at a temperature of 750 ° C. 2. The method for manufacturing a solid-state image pickup device according to claim 1, wherein a thermal oxidation process is performed after the silicon oxide film is deposited and formed by the low pressure CVD method. 3. A photosensor portion is formed on a surface layer portion of a silicon substrate, an insulating film is formed on a surface of the silicon substrate, and the photosensor portion is exposed to the surface side of the silicon substrate through the insulating film. A first transfer gate electrode is formed on a silicon substrate, the photosensor portion is exposed to the surface side of the silicon substrate through the insulating film, and a part of the photosensor portion is located directly above the first transfer gate electrode. A method of manufacturing a solid-state imaging device by forming and arranging a second transfer gate electrode on a substrate, comprising: forming at least the second transfer gate electrode after forming the first transfer gate electrode and before forming the second transfer gate electrode. located in forming region, and said insulating film not located directly under the first transfer gate electrode is removed by etching, the temperature of 700 ° C. to 750 ° C. subsequent pressure CVD A silicon oxide film, with the interlayer film between the the first deposited on the state of covering the transfer gate electrode to the silicon oxide film first transfer gate electrode and the second transfer gate electrode, the second transfer A method for manufacturing a solid-state imaging device, which comprises forming a gate insulating film of a gate electrode. 4. The method for manufacturing a solid-state image pickup device according to claim 3, wherein a thermal oxidation treatment is performed after the silicon oxide film is deposited and formed by the low pressure CVD method. 5. An insulating film located immediately above the photosensor portion when etching away the insulating film located in the region where the second transfer gate electrode is to be formed and not located directly below the first transfer gate electrode. Is also removed by etching, and when a silicon oxide film is deposited and formed by the low pressure CVD method,
The method for manufacturing a solid-state image pickup device according to claim 3, wherein an insulating film directly above the photosensor portion is also formed by the silicon oxide film.