JPH03147366A - Manufacture of solid-state image pickup device - Google Patents

Abstract

PURPOSE:To prevent the generation of smear by the light entering aslant or the light which has transmitted a light screening film by using the two-layer structure of a titanium nitride film and a light screening film or the three-layer structure of a titanium film, a titanium nitride film, and a light screening film for a light absorbing layer. CONSTITUTION:With the etching of a light absorbing film and a light screening film, if a titanium nitride film 60 and a light screening film 61 of aluminum silicide are dry-etched at the same time, the patterns of the titanium nitride film 60 and the light screening film 61 can be made in self alignment. For a solid image pickup element being formed this way, since the reflectance of the titanium nitride film 60 is low, even if the light 63, which has entered aslant the n-type impurity layer of a photoelectric transfer element part 53, enters the titanium nitride film 60, being reflected by a semiconductor substrate 50, the titanium film 60 absorbs the greater part of the light, so the light entered in the region other than the n-type impurity layer of the photoelectric transfer element part 53 is reduced and the generation of smear is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a solid-state imaging device, and particularly to a method for forming a light-absorbing film.

2. Description of the Related Art In general, a solid-state imaging device samples signal charges from a subject image projected on the light-receiving surface of a photoelectric conversion element in a photosensitive pixel section arranged in a matrix, and transfers the signal charges by a charge transfer section to create an image. It is output as a signal to an external monitor, etc. Signal charges generated in the substrate by photoelectric conversion need to be separated between each pixel. In this case, each pixel must be completely separated optically.

A solid-state image sensor has a photoelectric conversion element part and a charge transfer part formed in a semiconductor substrate, and a separation diffusion layer for electrically separating the photoelectric conversion element part and the charge transfer part. A transfer electrode is formed through the gate oxide film, and then a light shielding film such as aluminum or aluminum silicide is formed on the top surface to block light from entering areas other than the photoelectric conversion element through the oxide film, and finally a protective film is formed. is formed over the entire surface of the semiconductor substrate.

However, in a solid-state imaging device with such a configuration, light that enters the window of the photoelectric conversion element from an oblique direction is reflected on the surface of the semiconductor substrate, passes through the film below the light-shielding film, and is reflected again on the back surface of the light-shielding film. and enters a region other than the photoelectric conversion element section.

When charges generated in a semiconductor substrate by light incident on the semiconductor substrate are transferred directly or by diffusion and output as an image signal, a development called smear occurs on the image.

Smear is a phenomenon that occurs because solid-state imaging devices are not optically separated sufficiently.

In order to reduce smear, it is possible to narrow the aperture of the light receiving window of the photoelectric conversion element where light enters, but this is not an effective measure because the sensitivity of the solid-state imaging device is proportional to the aperture width of the light receiving window. . For this reason, a method has been proposed (Japanese Unexamined Patent Publication No. 64-64355) in which an insulating film having a sufficient thickness and an insulating layer containing phosphorus (P) are formed between the high melting point metal layer and the transfer electrode.

FIG. 4 shows a sectional view of a solid-state imaging device for explaining the above-mentioned conventional invention. A photoelectric conversion element section 2 and a charge transfer section 3, and an isolation diffusion layer 4 for electrically separating the photoelectric conversion element section 2 and charge transfer section 3 are formed on the surface of the semiconductor substrate 1, and a gate oxide film 5 is formed on the semiconductor substrate 1. A transfer electrode film 6 is formed through the transfer electrode film 6, and a thin oxide film is formed on the surface layer of the transfer electrode film 6. Next, after forming a thick oxide film 7 over the entire surface of the semiconductor substrate 1, phosphorus is added and diffused onto the surface of the oxide film 8 to form a phosphorus diffusion layer 9. After this, a high melting point metal layer 10 such as molybdenum silicide (MoSi) is formed.
is formed to cover the charge transfer section 3, and then a light receiving window 11 is formed on the photoelectric conversion element section 2.

Furthermore, an oxide film 12 as an element protection film is formed.
After forming a phosphorus diffusion layer 13 on the surface, a light shielding film pattern 14 of aluminum or aluminum silicide is formed on the upper surface, and finally, a protective insulating film 15 is deposited on the entire surface of the semiconductor substrate 1.

However, in the configuration of the prior art described above, since molybdenum silicide is used as the high melting point metal layer 10, the reflectance of light is high. Therefore, if a sufficiently thick oxide film 8 and phosphorus diffusion layer 9 are formed between the high melting point metal layer 10 and the transfer electrode layer 6, the light 15 incident on the photoelectric conversion element section 2 from an oblique direction will not reach the surface of the semiconductor substrate 1. After being reflected, it is reflected on the back surface of the high-melting point metal layer 10 and enters a region other than the photoelectric conversion element section 2, causing rust that causes smear. Moreover, part of the light 15 directly incident on the light-shielding film pattern 13 is transmitted and reaches areas other than the photoelectric conversion element portion 3, causing smear.

This is because light that has passed through the light shielding film pattern 13 enters the surface of the high melting point metal layer 10, is diffusely reflected, and then propagates through the oxide film 12 formed on the top layer of the high melting point metal layers 1 and 0. It reaches areas other than the photoelectric conversion element section 3 and causes smear.

As a method to solve such problems, it has been found that an effective method is to form a light-absorbing film on the photoelectric conversion element portion and then form a light-shielding film on the light-absorbing film (Japanese Patent Application Laid-open No. 1-107567). Are known.

FIG. 5 shows a cross-sectional view of an element having a light absorption film on a photoelectric conversion element.

On the surface of the n-type semiconductor substrate 21 on which the p-type well layer 20 is formed, a photoelectric conversion element section 22 and a charge transfer section 23 and a separation diffusion layer 24 for electrically separating the photoelectric conversion element section 22 and the charge transfer section 23 are formed; After forming a gate oxide film 25 and a transfer electrode film 26 thereon, a thin oxide film 27 is formed over the entire surface of the semiconductor substrate 22. Furthermore, after forming a thick oxide film 28 on the entire surface of the semiconductor substrate 20, a light-absorbing film 29 made of a silicon oxide film or magnesium oxide containing 30% by volume of nickel (Ni) particles and a light-shielding film directly on the light-absorbing film 29 are formed. 30
After forming, an oxide film 31 is formed as a protective film.

Problems to be Solved by the Invention However, in the configuration of the prior art described above, the thickness of the light absorption film 29 is 0.1 μm to 1.0 μm, and the thickness is 0.1 μm because the nickel fine particles are included in the oxide film or magnesium oxide.
When using a thin oxide film, roughness occurs on the oxide film surface,
Since a thin oxide film is used, the light absorption rate decreases, resulting in a decrease in reliability.

In addition, when a 1.0 μm film is used to increase the absorption rate, the light shielding film 30 formed on the light absorption film 29 connects to the semiconductor substrate 20 at the contact area with the wiring layer or peripheral circuit in the solid-state image device. Since it is designed to make direct contact, the ratio of the thickness of the lower layer of the light shielding film 30 to the contact window width (aspect ratio) becomes large at the contact portion between the light shielding film 30 and the semiconductor substrate 20. This will cause a disconnection. If a break occurs, not only will it have a negative effect on the electrical characteristics of the element, but the light incident from the break will reach areas other than the photoelectric conversion element 22 near the break, causing smear. Decreases device reliability.

Furthermore, since aluminum or aluminum silicide is used for the light shielding film 30 in the contact portion, there is a drawback that the contact resistance in the contact portion increases.

Further, in the above-mentioned conventional structure, metal is included in the oxide film or magnesium oxide as the light absorption film 29, but magnesium becomes a source of contamination during device formation and reduces the reliability of the device.

In addition, methods for incorporating nickel into an oxide film or magnesium oxide include CVD formation, ion implantation, and spin-on.
- Possible methods include including it in glass, but CVD
Magnesium in the light absorption film 29 becomes a source of contamination.

Furthermore, it is difficult to obtain a gas that can stably generate the nickel contained in the light absorption film.

In the formation method using ion implantation, ions are implanted only into the surface layer of the oxide film, and therefore a thick layer uniformly containing nickel cannot be formed.

When formed by spin cord, the volume of nickel contained is 3
Since the amount is very high (0% by volume), surface roughness occurs, and when the film thickness is increased, cracks occur in the oxide film.

Further, during spin coding, the metal contained in the spin-on-glass gathers around the substrate, causing variations in the concentration of metal inside the substrate, causing absorption rates to vary depending on location.

In this way, it is difficult to stably form an oxide film containing 30% by volume of nickel, and the process of forming the light absorption film 29 is complicated, which reduces the reliability of the device.

An object of the present invention is to solve the above-mentioned problems, and to prevent light that is obliquely incident on the photoelectric conversion element section or light that is incident after passing through the light-shielding film from entering areas other than the photoelectric conversion element section. At the same time, the process of forming the light-absorbing film is simple, and a stable film with good reproducibility can be formed uniformly, and even with a thin film thickness, it has sufficient light absorption rate, and there is no breakage at the contact area.
The present invention also provides a method for manufacturing a solid-state imaging device that can reduce contact resistance with a semiconductor substrate.

Means for Solving the Problems In order to solve the problem described in item 1-, the present invention provides a photoelectric conversion element portion and a charge transfer portion on the surface of a semiconductor substrate, and a diffusion layer for separating the photoelectric conversion element portion and the charge transfer portion. forming a separation layer,
A gate insulating film and a transfer electrode film are formed on the semiconductor substrate, a predetermined position of the transfer electrode film is etched away, an insulating film is formed thereon, and a predetermined region of the insulating film is etched away to remove the semiconductor substrate. After the exposure, a titanium nitride film and a light shielding film are formed, and predetermined areas of the two-layer film of the titanium nitride film and the light shielding film are etched at once.

In addition, a photoelectric conversion element section, a charge transfer section, a diffusion separation layer, a gate insulating film, and a transfer electrode film are formed on the surface of the semiconductor substrate (7. Predetermined positions of the transfer electrode film are etched and removed, an insulating film is formed, and an insulating film is removed. After etching a predetermined region of the film to expose the substrate, a titanium film, a titanium nitride film, and a light shielding film are formed, and a predetermined region of the three-layer film of the titanium film, titanium nitride dual film, and light shielding film is etched. Etching at once.

In addition, a photoelectric conversion element section, a charge transfer section, a diffusion separation layer, a gate insulating film, and a transfer electrode film are formed on the surface of the semiconductor substrate, a predetermined position of the transfer electrode film is etched away, an insulating film is formed, and an insulating film is formed. After exposing the substrate by etching a predetermined area, a titanium film, a titanium nitride film, and a light shielding film are successively formed on the base without exposing it to the outside air. A predetermined area of the layer is etched at once.

Function The present invention uses a two-layer structure of a titanium nitride film and a light-shielding film for the light absorption layer, or a three-layer structure of a titanium film, a WE-treated titanium film, and a light-shielding film, thereby absorbing light that is incident from an angle or light that has passed through the light-shielding film. In addition to preventing the occurrence of smearing, the light-absorbing film and light-shielding film can be formed in the same sputtering device, making the process of forming the light-absorbing film simple and allowing a stable film to be formed with good reproducibility.Even a thin film can have sufficient light absorption. Furthermore, since the aspect ratio of the contact portion can be made small, no breakage occurs in the light absorbing film or the light shielding film. Contact resistance can also be reduced.

Embodiment FIG. 1 shows a process cross-sectional view of a method for manufacturing a solid-state imaging device, which is a first embodiment of the present invention.

The present invention will be explained in detail with reference to FIG.

As the semiconductor substrate 50, n-type (100) resistivity 20Ω・c
A silicon wafer of rn-30Ω·cm is used.

First, a thermal oxide film of about 0.02 μm is formed on the semiconductor substrate 50 as a mask for ion implantation, and then boron ions are implanted at an acceleration voltage of 100 KeV and an implantation amount of 3.4×lQ crr+-2, and then annealed. The p-type well layer 52 is formed by activating boron. Next, a resist pattern is formed on the thermal oxide film 51 in which a region of the charge conversion element section 53 is opened, and using this resist pattern as a mask, for example, an acceleration voltage of 160 KeV and an implantation amount of 2.9 x 1012 are applied.
>-2, phosphorus ions are implanted to form the photoelectric conversion element portion 53. Similarly, using a resist pattern with a window opened in the region of the charge transfer section 54 as a mask, for example,
Phosphorus ions are implanted at 0 KeV and at an implantation dose of 3.4×10 12 cm −2 to form the charge transfer portion 54 .

Further, in the same way, a p
An impurity layer 55 is formed. After etching, the resist pattern is removed, and the thermal oxide film is further removed by wet etching (FIG. 1(a)).

Next, a gate oxide film 56 is formed on the entire surface of the semiconductor substrate 50.
．． After forming a thermal oxide film with a thickness of 1 μm, a polysilicon film with a thickness of about 0.3 μm is formed as a transfer electrode 57 using CVD. Thereafter, a resist pattern is formed in a region that will become the transfer electrode 57, and polysilicon is etched using the resist pattern as a mask to form a polysilicon electrode pattern. Thereafter, the resist pattern is removed, and the surface of the polysilicon is thermally oxidized to a thickness of about 0.15 μm to 0.3 μm to form an oxide film 58.

Next, on the entire surface of the semiconductor substrate 50, a film with a thickness of 0.2 μm −〇, 5
A CVD insulating film 59 having a thickness of μm is formed. Here about 0.3
It was carried out in μm (Fig. 1(b)).

Next, the peripheral circuit section of the solid-state imaging device (
After forming a resist pattern with windows in contact with the semiconductor substrate 50 in areas (3) and the like, the CVD insulating film 59 and the underlying oxide film 58 are etched away using reactive ion etching, and the surface of the substrate 50 is etched away. Reveal.

After this, the resist pattern is removed.

Next, titanium target material was added to the mixed gas of nitrogen (N2) and argon (Ar) (N2/Ar=70/30).
, a titanium nitride film 60 with a film thickness of 0.1 μm is sputtered at a gas pressure of 10 rr+Torr on a semiconductor substrate 50.
Form on the entire surface.

Here, an example is shown in which the titanium nitride B film 60 is used with a thickness of 0.1 .mu.m, but a thickness of 0.03 .mu.m-=0.27 zm may be used.

Next, a light-shielding film 61 of aluminum silicide (approximately 1% silicon in aluminum) is applied to the titanium nitride@60 using a sputtering method to a thickness of 0.5 μm to 1.0 μm.
(FIG. 1(C)).

After that, a photoresist is applied on the light shielding film 61.

A resist pattern is formed in an area to prevent extra light from entering by exposure and development.

Next, both the titanium nitride film 60 and the aluminum silicide light shielding film 61 are etched simultaneously using reactive ion etching to form a light shielding film pattern 61a.

Finally, a plasma silicon oxide film or a plasma oxynitride film is deposited to a thickness of 0.4 μm over the entire surface of the semiconductor substrate 50 as a surface protection film 62 by plasma CVD (
Figure 1(d)).

As described in -1- above, in the titanium nitride film 60 used in the present invention, as the film thickness becomes thinner, the light absorption rate on the surface of the titanium nitride film 60 increases, suppressing the occurrence of smear, and further improving the semiconductor substrate 50. Since the applied stress can also be reduced, reliability of device characteristics increases.

Furthermore, the titanium nitride film 60 at the contact portion with the surface of the semiconductor substrate 50 becomes difficult to peel off, but it can be used without any problems compared to the conventionally used aluminum silicide, although the contact resistance may increase. .

Conversely, as the film thickness increases, the reflectance increases, the film is more likely to peel off, and the stress applied to the semiconductor substrate 50 also increases. On the other hand, contact resistance becomes smaller.

As described above, the thickness of the titanium nitride film 60 influences the device characteristics, and the thickness of the titanium nitride film 60 is 0.05%.
If the thickness is less than 0.03 μm, film formation by sputtering will not be uniformly performed, which will reduce the reliability of the device. If the thickness is 0.2 μm or more, peeling of the film becomes noticeable and the yield of device formation decreases.

For these reasons, it is optimal to use a film thickness of 0.1 μm.

Further, in the present invention, the titanium nitride film 60 and the light shielding film 61 of aluminum silicide can be continuously formed in the chamber of the same sputtering apparatus.

That is, the titanium nitride film 60 is formed by sputtering a titanium target with a mixed gas of argon and nitrogen, then the semiconductor substrate 50 is moved under the aluminum silicide target in the same chamber, and the light shielding film 61 of aluminum silicide is formed with argon gas. Form by sputtering.

In the embodiment, aluminum silicide with a film thickness of 0.8 μm is used, and this film thickness is selected so as to satisfy both the reliability of the wiring and the reliability as a light shielding film.

In etching the light absorbing film and the light shielding film, an RF power of approximately 250 W is used to dry-etch the titanium nitride film 60 and the aluminum silicide light shielding film 61 at the same time.
, gas pressure 2Q Q mTorr, gas type and gas flow rate are trichloroboron (BCl2) 20 sccrn and chlorine (
C1'z) 70sec and triku oo meta 7 (CDC
l2) When etching is performed using a parallel plate type plasma etching apparatus using a mixed gas of 10 sec and nitrogen (N2) 50 sec, the edge of the titanium nitride film 60 and the edge of the upper aluminum silicide light shielding film 61 are almost aligned. The pattern of the titanium nitride film 60 and the light shielding film 61 can be formed by self-alignment.

In the solid-state image sensor formed as described above, the titanium nitride film 60 has a lower reflectance (higher absorption) than a conventional high-melting point metal layer, such as molybdenum silicide, so the photoelectric conversion element portion 53 is Even if light 63 incident obliquely on the type impurity layer is reflected by the semiconductor substrate 50 and incident on the titanium nitride film 60, most of the light is absorbed by the titanium nitride film 60 (reflectance is 20% compared to aluminum). molybdenum silicide is about 90% that of aluminum), the light incident on regions other than the n-type impurity layer of the photoelectric conversion element portion 53 is reduced, and the occurrence of smear is suppressed.

In addition, since the titanium nitride film 60 is formed in contact with the light shielding film 61, the light 64 that is directly incident on the light shielding film 61 made of aluminum silicide and transmitted is absorbed by the titanium nitride double film 60 and is used as a photoelectric conversion element. Since the impurity does not enter into regions other than the n-type impurity layer of the portion 53, the occurrence of smear can be suppressed.

Furthermore, in the conventional technology, a light shielding film is formed after forming an insulating film on a high-melting point metal layer, so light entering the solid-state imaging device is reflected by each thin film layer that it passes through before reaching the transfer electrode. A thick layer is formed that allows light to propagate within the layer. In contrast, in the solid-state imaging device of the present invention, since the thickness from the transfer electrode 57 to the light shielding film 61 is formed thin, the occurrence of smear due to incident light can be reduced.

In addition, when contacting the light shielding film 61 in the peripheral circuit section, in the conventional technology, the total thickness of the lower layer of the light shielding film is approximately 2.0 μm.
However, in the present invention, the film thickness is only about 1.0 μm, which is half the thickness, so the aspect ratio is halved, and the light shielding film 61 formed in the contact area is less likely to break, improving the reliability of the device. Improves sex. Therefore, it is possible to prevent light incident from the cut-off portion from entering the transfer electrode and causing smear.

FIG. 2 shows a process cross-sectional view of a method for manufacturing a solid-state imaging device according to a second embodiment of the present invention.

The present invention will be explained in detail according to FIG.

N-type (100) resistivity 20Ω-a as semiconductor substrate 50
After forming a thermal oxide film of approximately 0.02 μm as a mask for ion implantation on the semiconductor substrate 50 using silicon unihara of m-30 Ω'Cm, the p-type well layer 52, photoelectric conversion element portion 53, and charge transfer are formed by ion implantation. 54 and a p impurity layer 55 for element isolation are formed. Thereafter, the resist pattern is removed, and the thermal oxide film is further removed by wet etching (FIG. 2(a)).

Next, a gate oxide film 56 is formed on the entire surface of the semiconductor substrate 50.
．． After forming a thermal oxide film with a thickness of 1 μm, a polysilicon film with a thickness of approximately 0.3 μm is formed as a transfer electrode 57 using VD. After this, a resist pattern is formed, and polysilicon is deposited using the resist pattern as a mask. A polysilicon electrode pattern 57a is formed by etching, and the resist pattern is removed.

After this, the surface of polysilicon is 0.15 μm to 0.3 μm.
An oxide film 58 is formed by thermal oxidation to a certain extent.

Furthermore, a CVD insulating film 5 with a film thickness of 0.2 μm to 0.5 μm
9 (Fig. 2(b)).

Next, the peripheral circuit section of the solid-state imaging device (
After forming a resist pattern in which a window is opened at a portion that contacts the semiconductor substrate 50 in region I), etc., the CVD insulating film 59 and the underlying oxide film 58 are etched away using reactive ion etching, and the surface of the semiconductor substrate 50 is etched. Reveal. After this, the resist pattern is removed.

The above configuration is the same as that of the first embodiment.

Next, the titanium target was exposed to argon (Ar) gas.
A titanium film 80 is deposited to a thickness of 0.01 μrn=0.1 μI by sputtering at a gas pressure of 10 mTorr.

At the point where the titanium film 80 has been deposited to a thickness of about 0.02 μm, nitrogen gas is started to be introduced into the sputtering chamber.
) The mixed gas ratio of argon (Ar) is N2/A,
r = 70 / 30, gas pressure I Q mTor
A titanium nitride film 81 having a thickness of approximately 0.03 μm to 0.2 μm is formed by sputtering a titanium target at r.

Furthermore, after stopping the nitrogen gas in the same chamber, the semiconductor substrate 50 is moved under the aluminum silicide target, and sputtered continuously with argon gas to form aluminum silicide (containing about 1% silicon in aluminum) on the titanium nitride film 81. The light shielding film 82 of 0.
Formed to a thickness of 5 μm-1,0 μm (Figure 2 (C)
).

After that, a photoresist is applied on the light shielding film 82, exposed to light,
A resist pattern is formed in the area where it is to be developed to prevent excess light from entering.

Next, all layers of the titanium film 80, titanium nitride film 81, and aluminum silicide light shielding film 82 are simultaneously etched using reactive ion etching to form a light shielding film pattern 82a.

Finally, a plasma silicon oxide film or a plasma oxynitride film is deposited to a thickness of approximately 0.4 μm as a surface protective film 83 on the entire surface of the semiconductor substrate 50 by plasma CVD (
Figure 2(d)).

As described above, in the present invention, the titanium film 80, the titanium nitride film 81, and the light shielding film 82 made of aluminum silicide can be formed continuously without taking them out to the outside. As described in the first embodiment, the thickness of the titanium nitride film 81 used can be reduced. For example, the reflectance of light on the titanium nitride film 81 is reduced, the occurrence of smear is suppressed, and the stress applied to the semiconductor substrate 50 can also be reduced, thereby increasing the reliability of device characteristics.

Further, although the titanium nitride film 81 in the portion in contact with the surface of the substrate 50 becomes difficult to peel off, the contact resistance increases.

Conversely, as the thickness of the film used increases, the reflectance increases, the film is more likely to peel off, and the stress applied to the semiconductor substrate 50 also increases. On the other hand, the contact resistance becomes small.

However, when the titanium film 80 is thin, it is difficult to peel off, the stress applied to the semiconductor substrate 50 is reduced, and the leakage current at the contact portion can be reduced, but the contact resistance increases.

The light absorption rate of the titanium film 80 is about 50% that of aluminum, but the absorption rate is higher than that of a high melting point metal such as molybdenum silicide.

On the other hand, if the film is thick, the film is likely to peel off, and the stress applied to the semiconductor substrate 50 increases, but the contact resistance decreases.

By appropriately combining these two films, it is possible to form a light absorption film that does not peel off, applies little stress to the semiconductor substrate 50, and has low contact resistance.

FIG. 3 shows the relationship between contact resistance values when the film thickness 81 of the titanium nitride film 80 is kept constant at 0.1 μm and the film thickness of the titanium film 80 is varied in the second embodiment.

When the titanium film thickness is '0', it indicates that the titanium nitride film 81 is in direct contact with the silicon substrate 50.

From this, the contact resistance of the titanium film 60 is 0.
．． It saturates at 0.02 μm or more, and its value is 8.
The process time is approximately 100 minutes in case of No. 1.

From this result, it is possible to completely solve the drawback of increased contact resistance that occurs when using a thin titanium nitride film 81 by using a light absorption film with a two-layer structure of titanium film 80 and titanium nitride film 81. Can be done.

In addition, the two-layer structure of the titanium nitride film 81 and the titanium film 80 suppresses the reflectance of light, resulting in less smearing, no peeling of the film, less stress on the substrate, and a solid-state imaging device with low contact resistance. can be formed.

In the present invention, the titanium film 80 and the titanium nitride film 81
To simultaneously dry-etch the light-shielding film 82 made of aluminum silicide, the RF power is about 250 W, the gas pressure is 200 mTorr, and the gas types and gas flow rates are trichloroboron (BC4!a) at 20 scem and chlorine (C12).
70sec and trichlormeth” (CHCl, +
) and nitrogen (N2) at 50 sec in a parallel plate plasma etching apparatus, the edge of the titanium film 80 and the titanium nitride film 8 are etched.
1 and the upper layer of aluminum silicide light shielding film 8
The titanium film 80 and the titanium nitride film 8 are etched so that the two ends almost match each other and are self-aligned.
1 and a pattern of the light shielding film 82 can be formed.

Conventionally, variations in the deposited film thickness within the wafer and in-plane variations in etching differed between the light-shielding film and the absorbing film, reducing the reliability of devices and even lowering the yield.However, the present invention improves reliability. High-quality solid-state imaging devices can now be produced in large quantities.

The solid-state image sensor formed in the second embodiment has the same effect as that described in the first embodiment, i.e., light incident obliquely on the n-type impurity layer of the photoelectric conversion element portion 53. It is possible to reduce the amount of light that is reflected and enters areas other than the photoelectric conversion element portion 53, and the amount of light that is transmitted through the light shielding film and attempts to enter the transfer electrodes is also reduced, making it possible to prevent the occurrence of smear.

Furthermore, as shown in the first embodiment, it is possible to prevent disconnection during contact formation in the peripheral circuit section. However, although the thickness of the titanium film 80 is thicker than in the first embodiment, the thickness is at most about 0.02 μm, which is negligible.

Finally, when we measured the smear of the conventional solid-state imaging device and the solid-state imaging device manufactured in this example, we found that the amount of smear generated was 0.1% in the conventional device and 0.01% in this example. It has become possible to reduce smear by more than an order of magnitude.

Here, the amount of smear generation was determined from the following formula.

From the above, the film thickness of the titanium film 80 is 0.02
When the thickness is about μm, the contact resistance is low and the film is less likely to peel off.

In this embodiment, the p-type well layer is formed on an n-type semiconductor substrate, but the same thing can be done using an n-type semiconductor substrate.

In this example, a titanium film was used as the high melting point metal film, and a titanium nitride film was used as the high melting point metal compound film, but a high melting point metal film such as a tungsten film, a molybdenum film, a chromium film, etc. Good too,
Further, the same effect as in the above embodiment can be obtained even if a high melting point metal compound such as a titanium tungsten film or a molybdenum nitride film is used instead of the titanium nitride or ium film.

Effects of the Invention An object of the present invention is to solve the above-mentioned problems, and to prevent light that enters the photoelectric conversion element from an oblique direction or light that passes through a light-shielding film from entering an area other than the photoelectric conversion element. At the same time, the formation process of the light-absorbing film is simple, and a stable film with good reproducibility can be formed, and even a thin film has sufficient light-absorbing performance.Furthermore, the aspect ratio of the contact part can be made small, which prevents breakage. do not have. Furthermore, the contact resistance with the substrate at the contact portion can be reduced. That is, according to the present invention, a highly reliable solid-state imaging device can be formed in a stable process with a high yield.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the manufacturing process of a solid-state imaging device for explaining the first embodiment of the present invention, and FIG. 2 is a sectional view of the manufacturing process of the solid-state imaging device for explaining the second embodiment of the invention. FIG. 3 is a diagram showing the relationship between contact resistance and titanium film thickness, FIG. 4 is a diagram for explaining the conventional technique, and FIG. 5 is a diagram for explaining the conventional technique. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Photoelectric conversion element section, 3... Charge transfer section, 4... Separation diffusion layer, 5...・Gate oxide film, 6...
Transfer electrode film, 7... Oxide film, 9... Phosphorus diffusion layer, 10... High melting point metal layer, 11...
... window, 12 ... oxide film, 13 ... phosphorus diffusion layer, 14 ... light shielding film pattern, 15 ...
...Protective insulating film, 20...P-type well layer, 21
... Semiconductor substrate, 22 ... Photoelectric conversion element section, 23 ... Charge transfer section, 24 ...
Separation diffusion layer, 25... Gate oxide film, 26...
...Transfer electrode film, 27... Oxide film, 28.
... Oxide film, 29 ... Light absorption film, 30.
... Light shielding film, 31 ... Oxide film, 50 ...
... Semiconductor substrate, 52 ... P-type well layer,
53...Photoelectric conversion element section, 54...Charge transfer section, 55...Impurity layer, 56...
・Gate oxide film, 57... Transfer electrode film, 58.
...Oxide film, 59...CVD insulation pattern, 6
0...Titanium nitride film, 61...
Light shielding film, 62...Surface protection film, 63...
・Light incident from an angle, 64... Light transmitted,
80... Titanium film, 81... Old titanium nitride film, 82... Light shielding film, 83...
...Surface protective film.

Claims (4)

[Claims] (1) A step of forming a photoelectric conversion element section and a charge transfer section on the surface of the semiconductor substrate, a step of forming a diffusion separation layer that separates the photoelectric conversion element section and the charge transfer section, and a step of forming a gate insulation layer on the semiconductor substrate. a step of forming a film and a transfer electrode film, a step of etching away a predetermined position of the transfer electrode film, a step of forming an insulating film on the semiconductor substrate, and a step of etching away a predetermined region of the insulating film. a step of exposing the semiconductor substrate, a step of forming a high melting point metal compound film on the semiconductor substrate, a step of forming a light shielding film on the high melting point metal compound film, and a step of forming the high melting point metal compound film and the light shielding film. A method of manufacturing a solid-state imaging device, comprising the step of etching a predetermined region of the two-layer film to form an opening at the bottom through which the surface of the insulating film is exposed. (2) A step of forming a photoelectric conversion element section and a charge transfer section on the surface of the semiconductor substrate, a step of forming a diffusion separation layer that separates the photoelectric conversion element section and the charge transfer section, and a step of forming gate insulation on the semiconductor substrate. a step of forming a film and a transfer electrode film, a step of etching away a predetermined position of the transfer electrode film, a step of forming an insulating film on the semiconductor substrate, and a step of etching away a predetermined region of the insulating film. a step of exposing the semiconductor substrate, a step of forming a refractory metal film on the semiconductor substrate, a step of forming a refractory metal compound film on the refractory metal film, and a step of forming a refractory metal compound film on the refractory metal compound film. the step of forming a light shielding film; and the step of etching a predetermined region of the three-layer film of the high melting point metal film, the high melting point metal compound film, and the light shielding film to form an opening on the bottom surface through which the surface of the insulating film is exposed. A method of manufacturing a solid-state imaging device, characterized in that: (3) A step of forming a photoelectric conversion element section and a charge transfer section on the surface of the semiconductor substrate, a step of forming a diffusion separation layer that separates the photoelectric conversion element section and the charge transfer section, and a step of forming gate insulation on the semiconductor substrate. a step of forming a film and a transfer electrode film, a step of etching away a predetermined position of the transfer electrode film, a step of forming an insulating film on the semiconductor substrate, and a step of etching away a predetermined region of the insulating film. a step of exposing the semiconductor substrate by exposing the semiconductor substrate, and continuously forming a high melting point metal film on the semiconductor substrate, a high melting point metal compound film on the high melting point metal film, and a light shielding film on the high melting point metal compound film without exposing to the outside air. and a step of etching a predetermined region of the three-layer film of the high melting point metal film, the high melting point metal compound film, and the light shielding film to form an opening on the bottom surface through which the insulating film surface is exposed. A method for manufacturing a solid-state imaging device, characterized by: (4) A method for manufacturing a solid-state imaging device according to claims 1 and 2, characterized in that a titanium film is used as the high melting point metal film, and a titanium nitride film is used as the high melting point metal compound film. .