JP2003282853A - Solid state imaging device, method for manufacturing the same, and method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid state imaging device capable of restricting an occurrence of a non-etched part of a shading film in a step part formed by wirings, and a method for manufacturing the solid state imaging device in which a reduction in an underlying film existing in a lower layer of the shading film can be intended to suppress, and a side plane of the shading film after etching can be formed in a forward tapered shape. <P>SOLUTION: A silicon oxide film, an etching restricting film 14 and a shading film 15 are formed in succession on a semiconductor substrate 10 having a photodiode. Next, the shading film 15 on the photodiode is removed by reactive ion etching containing sulfur hexafluoride and chlorine but not containing oxygen. Next, an etching restricting film on the photodiode is removed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device, a method for manufacturing a semiconductor device, and a method for manufacturing a solid-state imaging device, and more particularly to a structure of a lower layer of a light-shielding film in a solid-state imaging device and patterning of the light-shielding film.

[0002]

2. Description of the Related Art Generally, a film of a refractory metal used as a conductive material, especially a tungsten film is used by being laminated with a polysilicon film, and this laminated film is called a so-called polymetal film. Moreover, since the tungsten film has a good light-shielding property, it is used as a light-shielding film for a solid-state imaging device.

FIG. 5 is a plan view showing the structure of a conventional solid-state image pickup device. As shown in FIG. 5, the solid-state imaging device includes a photodiode 51 and a photodiode 51 on a silicon substrate 50.
The vertical transfer unit 52 and the horizontal transfer unit 53 are provided and the photodiodes 51 are arranged in a matrix.

In the example of FIG. 5, the photodiodes 51 and the vertical transfer units 52 arranged in the rightmost column are
Optical black part 55 for generating a reference signal in the dark
Are configured. The other photodiodes 51 and the vertical transfer unit 52 form a light receiving unit 54. The arrows in FIG. 5 indicate the flow of charges.

Further, as shown in FIG. 5, the light receiving portion 54 and the optical black portion 55 are covered with a light shielding film 60. The light shielding film is provided in the hatched area. In the portion of the light shielding film that covers the light receiving portion 54,
An opening 51a for guiding incident light to the photodiode is provided.

Such a light-shielding film can be obtained by forming a tungsten film in the entire area of the solid-state image pickup device and then forming the tungsten film into a desired shape by etching or the like. As a method of etching a refractory metal film such as a tungsten film, a dry etching method represented by RIE (Reactive Ion Etching) is generally used. However, in the solid-state imaging device, the transfer electrode is often formed of a polysilicon film, and the light-shielding film is also formed on the polysilicon film via a silicon oxide film or the like, which is different from the polymetal film. That is the point. And for etching the tungsten film,
The following two etching methods were used.

One of the etching methods is a method in which the etching temperature is room temperature or 0 ° C. or lower and etching is performed using SF ₆ type gas. According to this etching method, the chemical reaction rate of the etching species is reduced and
Since lateral migration can be suppressed, an anisotropic shape can be obtained.

Another etching method is a method of keeping the etching temperature higher than room temperature and etching using Cl ₂ / O ₂ gas. According to this etching method, the vapor pressure of tungsten oxychloride, which is an etching product, can be increased to promote the separation, and thus the etching can be rapidly advanced.

[0009]

However, the above-mentioned two etching methods are suitable for forming a remaining pattern having a large aperture ratio, such as a case of forming a pattern of a polymetal film on a gate oxide film. This is an etching method. Therefore, when forming a blank pattern having a small aperture ratio, such as a light-shielding film of a solid-state image pickup device having a base step, there are the following problems.

In the former method, there is a problem in the patterning of the tungsten film (light-shielding film) that the selectivity between the tungsten film and the underlying silicon oxide film, which is the underlying film, cannot be secured. For this reason,
Due to the decrease of the base film on the photodiode, BPSG
Shortening the diffusion distance between B and P from the film may cause white scratches.

FIG. 6 is a cross-sectional view showing a step of etching a light-shielding film formed in a horizontal transfer portion of a conventional solid-state image pickup device, and shows a cross section taken along a cutting line BB in FIG. In addition, FIGS. 6A to 6C show a series of steps.

As shown in FIG. 6A, the horizontal transfer section is
On the silicon substrate 50 on which the silicon oxide film 56 is formed, a transfer electrode 58 made of a polysilicon film or the like is formed, a base film (silicon oxide film) 57 is provided, and then the transfer electrode 5 is formed.
8, a transfer electrode 59 is formed so as to partially overlap 8 and a base film 57 is further provided thereon. Due to such a configuration, a step portion is formed in the horizontal transfer portion. The light shielding film 60 is formed on the base film 57.

Next, as shown in FIG. 6B, the light shielding film 6
0 is etched by the former method described above,
The state shown in FIG. 6C is obtained. Here, as can be seen from FIG. 6C, since the selection ratio between the light-shielding film 60 and the base film 57 cannot be ensured by the former method, considering the thickness of the base film 57, the light-shielding film in the step portion is considered. There is a possibility that a portion 60a of the above will remain without being etched, and this will act as a wiring to cause a leak. Therefore, it is desirable that the light shielding film does not remain even if it is a part.

Further, the part 60a of the light shielding film remaining in the step portion can be removed by further performing overetching, but in this case, the transfer electrode 58 is exposed due to the film reduction of the base film 57, The charge leaks.

Further, in the former method, if the etching temperature is too low, the difference between the etching rates of the polysilicon film and the tungsten film causes the NMOS and the PMOS.
There is also a problem that the difference in line width between and increases.

In the latter method, the selection ratio between the tungsten film and the underlying film can be ensured, and there is no problem as in the former method. However, there is a problem that side etching occurs in the light-shielding film and the dimensional accuracy of the light-shielding film deteriorates, causing smear due to oblique light. This problem will be described with reference to FIG.

FIG. 7 is a cross-sectional view showing a step of etching a light-shielding film formed on a photodiode of a conventional solid-state image pickup device, and shows a cross section taken along a cutting line AA in FIG. 7A to 7C show a series of steps.

As shown in FIG. 7A, in the light receiving section, a transfer electrode 61 forming a vertical transfer section is formed on a silicon substrate 50 on which a silicon oxide film 56 is formed, and a base film 57 is formed.
Is provided. Then, a light shielding film 60 is provided so as to cover the base film 57.

Next, as shown in FIG. 7B, the opening 51
When a resist pattern 62 having a hole corresponding to a is formed on the light shielding film 60 and etching is performed by the latter method described above, the state shown in FIG. 7C is obtained. Further, when the resist pattern 62 is removed, the state shown in FIG.
As can be seen from FIG. 7 (d), in the latter method above,
The side surface of the light-shielding film 60 located on the photodiode 51 is formed in an inverse tapered shape, which causes smear due to oblique light.

Further, in the latter method described above, the etching gas contains oxygen. Therefore, the oxygen gas may cause a dimensional shift due to side etching, and the side surface of the tungsten film may be formed in an inverse tapered shape.

Further, the latter method described above has a problem that the etching temperature has to be set to a high temperature close to 100 ° C. because it is necessary to give a sufficient vapor pressure to the etching product.

An object of the present invention is to solve the above problems and to suppress the generation of etching residue of the light shielding film in the step portion formed by the wiring, and the film reduction of the underlying film under the light shielding film. It is an object of the present invention to provide a method for manufacturing a semiconductor device or a solid-state imaging device, which is capable of suppressing the above, and which can form the side surface of the light shielding film after etching into a forward tapered shape.

[0023]

In order to achieve the above object, a solid-state image pickup device according to the present invention is a solid-state image pickup device having a light receiving region having a photodiode on a semiconductor substrate and an optical black region. An etching suppressing film containing a titanium-based compound is provided on a substrate, and a light shielding film is formed on the etching suppressing film, and the etching suppressing film has an opening on the photodiode and on the optical black region. It is characterized by

As described above, in the solid-state imaging device according to the present invention, the opening is provided on the optical black region in the etching inhibiting film of the titanium-based compound, so that hydrogen is supplied to the semiconductor substrate through the optical black region. Therefore, generation of dark current can be suppressed.

Next, in order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention comprises a step of sequentially forming an etching suppressing film and a tungsten film on a semiconductor substrate, and sulfur hexafluoride and chlorine. And a step of removing a part of the tungsten film by reactive ion etching using an etching gas containing oxygen and containing no oxygen.

As described above, in the method of manufacturing a semiconductor device according to the present invention, since the etching suppressing film is provided in the lower layer of the tungsten film, the selection ratio of the conventional tungsten film and the underlying silicon oxide film is secured. The problem of not being able to be solved can be solved.

Further, since the etching gas does not contain oxygen, the etching does not proceed isotropically and the dimensional shift can be suppressed. In particular, when the semiconductor device is a solid-state imaging device, it is difficult to form the opening side wall of the light-shielding film in an inverse tapered shape, so that smear can be suppressed.

In the method for manufacturing a semiconductor device according to the present invention, in the reactive ion etching, the temperature of the semiconductor substrate and the internal temperature of the chamber of the etching device are 25 ° C. or less, particularly -20 ° C. to 0 °. It is a preferred embodiment that the temperature is set to 0 ° C. In this case, the shape of the tungsten film after etching can be improved.

In the method of manufacturing a semiconductor device according to the present invention, it is a preferable aspect that a film formed of a material containing a titanium compound or a polysilicon film is used as the etching suppressing film. In this case, the selection ratio between the tungsten film and the etching suppressing film at the time of etching can be secured, and the film can be made favorable.

In order to achieve the above object, a method of manufacturing a solid-state image pickup device according to the present invention comprises a step of sequentially forming an insulating film, an etching suppressing film and a light shielding film on a semiconductor substrate having a photodiode, A step of removing the light-shielding film on the photodiode by reactive ion etching using an etching gas containing sulfur hexafluoride and chlorine, and a step of removing the etching suppressing film on the photodiode; At least.

As described above, in the method of manufacturing the solid-state image pickup device according to the present invention, unlike the conventional method, the etching suppressing film is formed, so that the insulating film serving as the base film is thinned and the photodiode is damaged. Can be suppressed.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A solid-state image pickup device according to an embodiment of the present invention, a method of manufacturing the same, and a method of manufacturing a semiconductor device will be described below with reference to FIGS.

First, a solid-state image pickup device according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram schematically showing a solid-state imaging device according to an embodiment of the present invention. 2A is a diagram showing a cross section of a light receiving portion of the solid-state imaging device shown in FIG. 1, FIG. 2B is a diagram showing a cross section of an optical black portion of the solid-state imaging device shown in FIG. 1, and FIG. ) Is a view showing a cross section of the horizontal transfer section shown in FIG. 1, and is a cross section taken along line XX, YY in FIG. 1,
The ZZ cross section is shown.

As shown in FIG. 1, the solid-state image pickup device according to the present embodiment is similar to the solid-state image pickup device shown in FIG.
The photodiodes 1, the vertical transfer portions 2, and the horizontal transfer portions 3 are provided on the silicon substrate 10, and the photodiodes 1 are arranged in a matrix.

Also in this embodiment, the photodiodes 1 and the vertical transfer sections 2 arranged in the rightmost column constitute an optical black section 5 for generating a reference signal in the dark. The other photodiode 1 and the vertical transfer unit 2 photoelectrically convert incident light, and the resulting charges are transferred to the horizontal transfer unit 3.
The light receiving unit 4 is configured to transfer the light. The arrows in FIG. 1 indicate the flow of charges.

Further, similar to the solid-state image pickup device shown in FIG. 5, the solid-state image pickup device according to the present embodiment is also provided with a light shielding film (not shown in FIG. 1). The region where the light shielding film is provided is the same as the region shown in FIG. However, in the present embodiment, unlike the solid-state imaging device shown in FIG. 5, the etching suppressing film 14 is provided below the light shielding film. The etching film 14 is a film having an etching rate lower than that of the light-shielding film under the same etching condition, and suppresses etching of the base film when the light-shielding film is patterned by etching as described later, Functions as a stopper.

The "identical etching conditions" referred to here are gas species used, gas mixture ratio, flow rate, pressure, RF power, electrode temperature, number of wafers, surface area of film to be etched, aspect ratio of shape. Etc. are the same.

In FIG. 1, the hatched area indicates the area where the etching suppressing film 14 is provided.
In the present embodiment, the etching suppressing film 14 is provided so as to cover only the light receiving portion 4.

The cross-sectional structure of the etching suppressing film 14 will be described. As shown in FIG. 2A, the etching suppressing film 14 includes the base film 13 and the light shielding film 15 in the light receiving portion.
It is formed so as to be sandwiched between and. From this, it can be seen that the etching suppressing film 14 functions as an etching stopper when the light shielding film 15 is etched. In addition, the opening 1 a of the light shielding film 15 is also formed in the etching suppressing film 14.
An opening 14a similar to the above is provided.

As shown in FIG. 2B, the light shielding film 15 is formed directly on the base film 13 in the optical black portion. Further, as shown in FIG. 2C, the light shielding film 15 and the etching suppressing film 14 are not provided in the horizontal transfer portion. In FIG. 2, 11
Is a silicon oxide film formed on the semiconductor substrate 10,
Is a transfer electrode forming a vertical transfer portion, and 16 and 17 are transfer electrodes forming a horizontal transfer portion.

As described above, in the solid-state image pickup device according to the present embodiment, since the etching suppressing film 14 under the light shielding film 15 functions as an etching stopper for the base film 13, when the light shielding film 15 is patterned, It is possible to prevent the underlying film 13 on the bottoms of the openings 1a and 14a from being greatly reduced. Therefore, in the solid-state imaging device according to the present embodiment, it can be said that the occurrence of white scratches is suppressed as compared with the conventional solid-state imaging device shown in FIG.

In the present embodiment, the light shielding film 15 is made of a tungsten film. The patterning of the light-shielding film 15 is performed by using sulfur hexafluoride (SF ₆ ) as described later.
The etching is performed by using a mixed gas containing gas and chlorine gas but not oxygen gas. Therefore, as a material for forming the etching suppressing film 14 in the present embodiment, a material having an etching rate lower than that of tungsten, for example, a titanium-based compound such as titanium nitride, polysilicon, or the like can be used.

Of these, in the present embodiment, the light shielding film 15
The titanium-based compound is used as a material for forming the etching suppressing film 14 because the selection ratio of the etching suppressing film to the etching suppressing film can be 10 or more.

However, when a titanium compound is used as a material for forming the etching suppressing film 14, the etching suppressing film 14 covers only the light receiving portion 4, that is, the optical black as shown in FIGS. 1 and 2. It is preferable to form the portion 5 and the horizontal transfer portion 3 so as not to be covered. This is because the dark current increases due to the hydrogen-trapping action of the titanium-based compound.

On the other hand, when using a material having a small hydrogen-acquiring action, for example, polysilicon, the etching suppressing film 14 may be provided so as to cover the optical black portion 5 and the horizontal transfer portion 3.

Further, the etching suppression film 14 is preferably kept substantially constant without being largely changed in in-plane uniformity due to film formation, and is preferably as thin as possible, so that the etching suppression film 14 is preferable. Is preferably 40 nm or less, and particularly preferably in the range of 5 nm to 10 nm.

Next, a method of manufacturing the solid-state image pickup device according to the embodiment of the present invention and a method of manufacturing the semiconductor device will be described with reference to FIGS. Fig.3 (a)-
4D and 4E to 4H are views showing the manufacturing process of the solid-state imaging device shown in FIG. 1 in cross sections of the light receiving portion, the optical black portion, and the horizontal transfer portion, and FIGS. Figure 4
(H) shows a continuous series of steps. Note that FIG.
4 and FIG. 4, the cross section on the left side of the drawing is the cross section (X
-X cross section), the center cross section in the figure is the cross section of the optical black portion (YY cross section), and the cross section on the right side of the figure is the cross section of the horizontal transfer section (ZZ cross section).

First, as shown in FIG. 3A, a silicon oxide film 11 and a vertical transfer portion are formed on the semiconductor substrate 10 in which the photodiode 1 is formed in the regions to be the light receiving portion and the optical black portion. The transfer electrode 12, the transfer electrode 16 and the transfer electrode 17 forming the horizontal transfer portion are formed. Next, a base film (silicon oxide film) 13, which is an insulating film, is formed in all regions of the light receiving portion, the optical black portion, and the horizontal transfer portion. Then, like the base film 13,
Etching suppression film 1 made of titanium compound in all regions
4 is formed.

Next, as shown in FIG. 3B, in order to remove the etching suppressing film 14 in the optical black portion, a resist pattern 18 is formed by a lithography method so as to cover the light receiving portion and the horizontal transfer portion. ,
Selective etching is performed. Etching is performed using a mixed gas of Ar and Cl ₂ as an etching gas at room temperature or lower, for example, 0 ° C. to −30 ° C., preferably −20 ° C.

Next, as shown in FIG. 3C, the resist pattern 18 is removed. Since the base film 13 is formed of a silicon oxide film, it can be said that the selection ratio of the silicon oxide film to the titanium-based compound is high under the above etching conditions. Therefore, in the optical black portion, it can be said that the film loss of the base film 13 is small, while the etching suppression film 14 is completely removed. The end point of etching may be determined by using an end point monitor, but it may be determined by the etching time calculated in advance from the film thickness and the etching rate.

Next, as shown in FIG. 3 (d),
The light-shielding film 15 is formed of tungsten in all regions of the optical black portion and the horizontal transfer portion. The light shielding film 15 is formed by a vapor deposition method. this is,
Since the tungsten film formed by the CVD method has extremely weak adhesion to the silicon oxide film, the tungsten film is directly formed on the silicon oxide film which is the base film 13 in the optical black portion as in the present embodiment. This is because the tungsten film may peel off in the embodiment.

However, in the present embodiment, the base film 1
It is also possible to form a tungsten film on the silicon oxide film of No. 3 by sputtering and further form a tungsten film on it by the CVD method so that two layers of tungsten film having different formation methods can be used as the light shielding film 15. .

In the case of such a two-layer structure, since the tungsten film formed by sputtering adheres to the silicon oxide film, the problem that the tungsten film is peeled off at the optical black portion can be solved. Further, since the step coverage of the light shielding film 15 can be improved, the light transmission to the optical black portion can be improved. Furthermore, since the thickness of the light shielding film 15 can be reduced, the sensitivity of the photodiode 1 can be improved. When the light-shielding film 15 has a two-layer structure as described above, the thickness of the tungsten film formed by sputtering is preferably 50 nm or less.

Next, as shown in FIG. 4E, the light shielding film 1
An opening 1a for applying a resist on the surface 5 and guiding the incident light
Patterning is performed by known lithography so that the area to be formed and the horizontal transfer portion are exposed. Reference numeral 19 is a resist pattern. Then, the light shielding film 15 is etched. The etching is performed by reactive etching using a reactive ion etching apparatus until the etching suppressing film 14 is exposed. FIG. 4F shows a state after etching.

As described above, in the present embodiment, unlike the conventional case, the etching suppressing film 14 is formed before the formation of the light shielding film 15 to be etched, and the etching suppressing film 1 is formed.
Etching is performed on the light-shielding film 15 formed on the surface 4. For this reason, as described above, it is possible to prevent the film thickness of the base film 13 from being reduced, and it is possible to suppress the occurrence of white defects in the light receiving portion and the occurrence of charge leakage in the horizontal transfer portion.

In this embodiment, the light shielding film 15 is etched by a narrow gap parallel plate type reactive ion etching (RIE) device. This reactive ion etching apparatus is provided with a gas supply mechanism for supplying an etching gas and two electrodes (upper electrode and lower electrode) facing each other inside the chamber. The upper electrode is connected to the RF power supply via a matching box,
The lower electrode is grounded. In the present embodiment, the processing pressure of the reactive ion etching apparatus is 0.4 Pa, Mag
The power is set to 400 W and the RF bias power is set to 50 W, but it is not limited to this.

In the present embodiment, as the etching gas for etching the light-shielding film 15, a mixed gas of SF ₆ gas and Cl ₂ gas, which does not contain O ₂ gas, is used. When the gas containing no O ₂ gas is used as described above, the side surface (hereinafter referred to as “etching side surface”) of the portion of the light-shielding film 15 left unetched due to the dimension shift due to side etching has an inverse tapered shape (FIG. This is to suppress the formation of the film (see 7). Also, it is possible to prevent WOx from being generated by the reaction between the O ₂ gas in the etching gas and the tungsten film,
This is to miniaturize the semiconductor device and prolong the maintenance cycle.

The use of the mixed gas of SF ₆ gas and Cl ₂ gas prevents the dimensional shift due to the etching by Cl radicals and causes the etching side surface of the light shielding film 15 to have an inverse taper shape during overetching. This is to suppress it. That is, by forming tungsten hexafluoride (WF ₆ ) on the etching side surface of tungsten by using F radicals, the etching toward the etching side surface is suppressed. Further, it is because the strong anisotropy of the F radical allows the etching to proceed in the direction normal to the semiconductor substrate 10 and suppresses the dimensional shift. If etching is performed only with F radicals,
Although a reaction product is likely to be generated and inhibits etching, this reaction product can be etched by Cl radicals. Further, such an effect becomes remarkable when the flow rate of Cl ₂ gas is made larger than the flow rate of SF ₆ gas.

In this embodiment, SF ₆ gas and Cl _{2 are used.}
The flow rate ratio with the gas may be set in the range of 2: 7 to 4: 6, and is preferably set to 3: 7. Specifically, SF ₆
Gas flow rate 20ml / min-40ml / min, C
The flow rate of l ₂ gas is 60 ml / min to 80 ml / min
The flow rate of SF ₆ gas is 30 ml / min, and the flow rate of Cl ₂ gas is 70 ml / min.
Set to min.

Further, in the present embodiment, the light shielding film 1
The etching temperature when etching 5 is, specifically,
The substrate temperature of the semiconductor substrate 10 and the temperature in the chamber are
It is set to room temperature (25 ° C) or lower. The etching temperature is set to room temperature (25 ° C.) or lower as described above, since the etching side surface of the light-shielding film 15 is likely to be formed in an inverted taper shape (see FIG. 7) when set to a temperature higher than room temperature. Is.

This point will be described. If the etching temperature is higher than room temperature, the F radicals have a larger energy and are more likely to react with other atoms to easily generate reaction products, so that the etching side surface of the light shielding film 15 has an inverse tapered shape. It is also thought that this is suppressed. However, since the energy of all radicals also increases, the kinetic energy of radicals increases, and the isotropicity of etching also increases. As a result, even if a reaction product is formed, the radicals violently collide with the reaction product and immediately exfoliate it, so that the etching proceeds toward the etching side surface.

For example, when the opening 1a of the light-shielding film 15 is formed, if the etching temperature is set to 50 ° C. to 60 ° C. and etching is performed, a size shift of 0.1 μm occurs with respect to the resist opening size of 1 μm. However, the etching side surface of the opening 1a of the light shielding film 15 has an inverse taper shape. In this case, it is difficult to allow it in consideration of the miniaturization of the design rule, and it causes smear and a decrease in sensitivity in the solid-state imaging device.

On the other hand, if the etching temperature is lower than room temperature, it becomes difficult to form reaction products. However, since the movement of radicals is also suppressed, as the etching proceeds, the kinetic energy of the radicals decreases until reaching the etching side surface. Therefore, as a result, the reaction product adheres to the etching side surface, and this reaction product becomes an obstacle to the etching toward the etching side surface, and the etching toward the etching side surface is suppressed. For example, when the etching temperature is −20 ° C. to 0 ° C., the etching side surface of the light shielding film 15 has a forward tapered shape.

For example, when the etching temperature is set to -50 ° C., the effect of making the etching side surface of the light-shielding film 15 into a forward tapered shape becomes small, and it becomes difficult to obtain the effect by lowering the etching temperature. Therefore, in this embodiment, the etching temperature is preferably −30.
C. to 0.degree. C., particularly preferably -20.degree. C. to 0.degree.

As described above, in the present embodiment, the etching temperature is set to room temperature or lower, and a mixed gas of SF ₆ gas and Cl ₂ gas containing no O ₂ gas is used as the etching gas. Then, the light shielding film 15 is patterned. Therefore, anisotropic etching can be promoted, so that the etching side surface of the light-shielding film 15 can be suppressed from having an inverse tapered shape, and a forward tapered etching side surface with almost no dimensional shift can be obtained.

The detection of the end point in the etching of the light shielding film 15 can be carried out by monitoring the light emission of, for example, 501 nm and detecting the point at which the light emission intensity sharply increases. Further, if the emission intensity is second-ordered, the detection sensitivity in the end point detection can be improved, and the end point can be detected with high accuracy. However, if the device structure is not flat, for example,
When the base of the light-shielding film 15 has irregularities and the base shape differs from part to part, the end point detection is preferably performed by level determination. As a result, the influence of the difference in device structure can be minimized, and the end point detection in the etching of the light shielding film 15 can be stably performed.

Further, in the present embodiment, the light shielding film 1
The etching of No. 5 is performed in two steps of main etching and over etching. Specifically, the main etching is performed under the above-described conditions, the end point is detected, and then the RF power of the reactive ion etching apparatus is gradually reduced to perform overetching. Specifically, over-etching is performed by reducing the RF power from 50 W for main etching to about 20 W. The overetching time can be set by appropriately adjusting the time of the main etching. Also, overetching may be performed in stages.

In the present embodiment, since the etching suppressing film 14 exists under the light shielding film 15, unlike the conventional case,
Even if overetching is performed, it is possible to prevent the base film 13 from being thinned. In addition, due to the over-etching, the light-shielding film 1 left on the stepped portion in the horizontal transfer portion in particular.
It is possible to completely remove a part of 5 and the residue.

Performing such dry etching with reduced RF power increases the selection ratio of the light shielding film 15 to the base film (silicon oxide film) 13,
This has an effect of reducing the film loss of the base film 13. Therefore, in the portion where the etching suppression film is not provided, such as the optical black portion 5, damage to the base film 13 can be suppressed, and the occurrence of white scratches can be reduced. Further, by adjusting the overetching time, the base film 13
It is also possible to make the film thickness uniform.

Next, as shown in FIG. 4F, the etching suppressing film 14 is etched. In the present embodiment, this etching is performed by etching the light shielding film 15 (see FIG.
The reactive ion etching apparatus used in (e)) is used. That is, the etching of the light shielding film 15 and the etching of the etching suppressing film 14 are performed as a continuous process in the same chamber. Also in this process
The processing pressure of the reactive ion etching device is 0.4 Pa,
Mag power is 400W, RF bias power is 50W
Is set to. FIG. 4G shows the state after etching.

In the present embodiment, the etching gas for etching the etching suppressing film 14 is
A mixed gas of Ar gas and Cl ₂ gas is used.
The flow rate ratio of Ar gas to Cl ₂ gas may be set in the range of 2: 7 to 4: 6, and is preferably set to 3: 7. Specifically, the flow rate of Ar gas is 20 ml / min to 40 m.
1 / min, the flow rate of Cl ₂ gas is 60 ml / min to 8
It may be set in the range of 0 ml / min, and preferably,
The flow rate of Ar gas is set to 30 ml / min, and the flow rate of Cl ₂ gas is set to 70 ml / min.

Further, in the present embodiment, the etching temperature when etching the etching suppressing film 14, specifically, the substrate temperature of the semiconductor substrate 10 and the temperature inside the chamber are the same as those in the case of etching the light shielding film 15. Similarly, the temperature is set to room temperature (25 ° C.) or lower. This is because the etching side surface of the etching suppression film 14 has a forward tapered shape, and the selection ratio of the etching suppression film 14 to the base film 13 is dramatically improved.

However, in the etching of the etching suppressing film 14, if the etching temperature is too low, the etching rate is lowered and, as a result, the reaction products attached are increased. Therefore, also in this step, the etching temperature is preferably 0 ° C. to −30 ° C., particularly preferably −20.
It is better to set it to ℃.

Unlike the case of the light-shielding film 15, the end point of the etching of the etching suppressing film 14 can be detected by calculating the etching time in advance from the film thickness and the etching rate. This is because the etching suppressing film 14 has high selectivity with respect to the base film 13. For example, the thickness of the etching suppression film 14 is 10 nm to 30 n.
In the case of m, the etching time is 30 sec. Therefore, the etching suppressing film 14 can be removed by performing the etching only during this time.

The etching suppressing film 1 in this step
Since the etching of No. 4 is highly isotropic and has a high selection ratio between titanium nitride (TiN), which is a titanium compound, and the underlying silicon oxide film, etching residue is not generated in the step portion of the horizontal transfer portion. The etching suppression film 14 can be removed. Further, since the etching is highly isotropic, it is necessary to increase the anisotropy by lowering the etching temperature. Thereby, the shapes of the etching side surfaces of the etching suppressing film 14 sandwiched between the light shielding film 15 and the underlying oxide film 13 can be made uniform.

Next, etching is performed at room temperature with the resist pattern 19 provided. In the present embodiment, such etching is performed because SF ₆ gas is used as the etching gas for the light shielding film 15 and the etching temperature is set to room temperature or lower as described above. This is because the tungsten-based protective film is formed on the side surface, and the reaction product generated by etching adheres to the etched portion and its periphery. Further, it is difficult to remove such a residue by the above-mentioned overetching.

Specifically, immediately after the light-shielding film 15 and the etching suppressing film 14 are etched, the semiconductor substrate 10 is immediately placed in a chamber of another etching apparatus kept at room temperature.
And is etched under high pressure using a mixed gas of O ₂ gas and CHF ₃ gas. In this embodiment, the temperature of the semiconductor substrate 10 and the temperature in the chamber are 2
The temperature is set to 5 ° C and the flow rate of O ₂ gas is 800 ml /
The flow rate of min and CHF ₃ gas is set to 40 ml / min. The processing pressure of the etching apparatus is 100.
Pa and the processing time are set to 30 sec.

The light shielding film 15 and the etching suppressing film 1
The etching of No. 4 is performed at a low temperature as described above.
Therefore, when the semiconductor substrate 10 is transferred to the outside of the chamber immediately after the etching of the light-shielding film 15 and the etching suppression film 14, and another process is performed in the atmosphere, dew condensation occurs on the semiconductor substrate 10 by reacting with moisture in the outside air. Resulting in. Such dew condensation becomes a major obstacle in the semiconductor manufacturing process.

Therefore, it can be said that once the temperature is returned to room temperature and etching is performed as in this embodiment, dew condensation on the semiconductor substrate 10 can be prevented. Further, the etching at room temperature has an effect called ashing such that the resist pattern 19 on the light shielding film 15 is peeled off.

Next, as shown in FIG. 4H, the semiconductor substrate 10 that has been etched at room temperature is wet-etched to completely remove the resist pattern 19 and the reaction product generated by the etching. To remove. As the etching liquid, DHF (250 parts of water and fluorine):
A liquid obtained by mixing at a ratio of 1) or an NH ₄ OH liquid can be used. The etching time may be set to 3 min in the former case and 2 min in the latter case. From the viewpoint of alleviating damage to the silicon oxide film such as the base film 13, NH ₄ O is used as an etching solution.
It can be said that it is preferable to use the H liquid.

As described above, the solid-state imaging device shown in FIG. 1 can be obtained by the series of steps shown in FIGS. 3 (a) to 4 (h). Note that, although the case where the solid-state imaging device is manufactured is described as an example in this embodiment, the present invention is not limited to the solid-state imaging device as long as the semiconductor device requires patterning of the tungsten film. Can be applied without.

[0082]

As described above, according to the solid-state image pickup device and the method of manufacturing the same according to the present invention, charge leakage occurs due to the light-shielding film remaining when the light-shielding film covering the insulating film on the wiring is etched. Can be suppressed.
Further, according to the method for manufacturing a solid-state imaging device and the method for manufacturing a semiconductor device according to the present invention, it is possible to suppress the occurrence of side etching in the patterning of a light-shielding film, particularly a light-shielding film formed of a tungsten film, and to improve the etching side surface. It can be tapered. Therefore, by using the solid-state imaging device manufacturing method according to the present invention, it is possible to obtain a solid-state imaging device in which the occurrence of smear is suppressed.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing a solid-state imaging device according to an embodiment of the present invention.

2A is a diagram showing a cross section of a light receiving part of the solid-state imaging device shown in FIG. 1, and FIG. 2B is a diagram showing a cross section of an optical black part of the solid-state imaging device shown in FIG. Figure 2
(C) is a diagram showing a cross section of the horizontal transfer unit shown in FIG. 1.
1 shows an XX section, a YY section, and a ZZ section in FIG. 1, respectively.

3 (a) to 3 (d) are views showing a manufacturing process of the solid-state imaging device shown in FIG. 1 in cross sections of a light receiving portion, an optical black portion, and a horizontal transfer portion.

4 (e) to 4 (h) are views showing a manufacturing process of the solid-state imaging device shown in FIG. 1 in cross sections of a light receiving portion, an optical black portion, and a horizontal transfer portion.

FIG. 5 is a plan view showing a configuration of a conventional solid-state imaging device.

6 is a cross-sectional view showing a step of etching a light-shielding film formed in a horizontal transfer portion of a conventional solid-state imaging device, FIG.
The cross section in the cutting line BB in the inside is shown.

FIG. 7 is a cross-sectional view showing a step of etching a light-shielding film formed on a photodiode of a conventional solid-state imaging device, showing a cross section taken along a cutting line AA in FIG.

[Explanation of symbols]

1 Photodiode 1a Opening of light shielding film 2 Vertical transfer section 3 Horizontal transfer section 4 Light receiving part 5 Optical black section 10 Semiconductor substrate 11 Silicon oxide film 12, 16, 17 Transfer electrodes 13 Base film 14 Etching suppression film 14a Opening of etching suppression film 15 Light-shielding film

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4M118 AA05 AB01 BA13 CA02 FA06                       GB03 GB08 GB09 GB11 GB19                       GB20                 5F004 AA05 AA12 BA04 DA04 DA18                       DB08 DB12 EB01

Claims (5)

[Claims] 1. A solid-state imaging device comprising a semiconductor substrate having a light receiving region having a photodiode and an optical black region, the etching suppressing film containing a titanium compound on the substrate, and the etching suppressing film formed on the etching suppressing film. The solid-state imaging device according to claim 1, wherein the etching suppression film has an opening on the photodiode and on the optical black region. 2. The tungsten is formed by a step of sequentially forming an etching suppressing film and a tungsten film on a semiconductor substrate, and by reactive ion etching using an etching gas containing sulfur hexafluoride and chlorine and containing no oxygen. And a step of removing a part of the film. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the reactive ion etching is performed by setting the temperature of the semiconductor substrate and the internal temperature of the chamber of the etching apparatus at 25 ° C. or lower. 4. The method of manufacturing a semiconductor device according to claim 2, wherein the etching suppressing film is a film or a polysilicon film formed of a material containing a titanium compound. 5. A step of sequentially forming an insulating film, an etching suppressing film, and a light-shielding film on a semiconductor substrate having a photodiode, the light-shielding film on the photodiode containing sulfur hexafluoride and chlorine and containing oxygen. A method of manufacturing a solid-state imaging device, comprising: at least a step of removing by reactive ion etching using an etching gas not containing; and a step of removing the etching suppression film on the photodiode.