JP2003163344A - Semiconductor device and its fabricating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a semiconductor device in which an antireflection film can be protected against damage due to etching and a light receiving window having an antireflection film of a uniform thickness can be formed. <P>SOLUTION: The semiconductor device comprises a semiconductor substrate 1 provided with an impurity diffusion layer for light receiving element, a silicon oxide film 18 and a silicon nitride film 19 provided on the impurity diffusion layer, electrodes 10 and 11 bonded to the impurity diffusion layer penetrating these silicon nitride film and silicon oxide film, a silicon oxide film 23 provided in order to insulate these electrodes, and a light receiving window 17 formed on the impurity diffusion layer while having the silicon oxide film 18 and the silicon nitride film 19 and being surrounded by the silicon oxide film 23, and the like. The silicon oxide film 18 and the silicon nitride film 19 are protected by a silicon nitride film 21, and the like, at the time of opening the silicon oxide film 23 selectively to form the light receiving window 17, and then exposed in the light receiving window 17 by removing the silicon nitride film 21, and the like. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light receiving element mixed type in which a light receiving element for photoelectrically converting an optical signal into an electric signal and other elements (for example, a transistor, a capacitance element, a resistance element) are provided on the same semiconductor substrate. The present invention relates to a semiconductor device suitable for application to a semiconductor integrated circuit and the like, and a manufacturing method thereof.

More specifically, after an antireflection film and a protective film are laminated on the surface of a semiconductor substrate on which an impurity diffusion layer for a light receiving element is formed, the impurity diffusion layer is formed on the semiconductor substrate on which the protective film is formed. Electrode part is formed, then an insulating film is formed on the semiconductor substrate on which the electrode part is formed, and the insulating film is selectively opened to expose the protective film to open the opening part. By forming it, the electrode portion and the opening can be formed in a state in which the antireflection film is protected by the protective film, so that the processing damage to the antireflection film due to the etching process can be prevented. It was done.

[0003]

2. Description of the Related Art In recent years, the operating area of a light-receiving element that photoelectrically converts an optical signal into an electric signal is becoming shorter and shorter, and along with this, a semiconductor integrated circuit in which the light-receiving element and other elements are mixedly mounted. In the circuit, how to design a light receiving element with high photoelectric conversion efficiency has been an issue.

In an optical disk device or the like, which is a high-capacity information storage medium which has become mainstream in recent years, the wavelength λ
A design of a light receiving element corresponding to a short wavelength laser of about 400 nm is required.

One of the characteristics of the light receiving element is the light receiving sensitivity characteristic [A / W] which represents the photocurrent [A] with respect to the power [W] of the incident light of the laser. This light receiving sensitivity characteristic becomes lower as the wavelength of the laser light becomes shorter. Further, as the wavelength of the laser light becomes shorter, it becomes technically difficult to improve the output on the output side. For example, as compared with a red laser having a wavelength of λ = 780 [nm], a short-wavelength laser can only be manufactured with a small output.

That is, as the wavelength of the laser light is shortened, both the light receiving sensitivity characteristic and the laser output are lowered, so that the light receiving sensitivity (photocurrent) is inevitably lowered due to both internal and external factors. There is. Therefore, in order to manufacture a light receiving element compatible with a short wavelength laser, the PIN structure of the light receiving element is optimized and an antireflection film for preventing reflection of incident light is being improved.

8 to 11 show a semiconductor device 9 according to a conventional example.
It is process drawing which shows the manufacturing method (No. 1-4) of 0. This semiconductor device 90 includes a light receiving element and a MIS (Metal Insulato).
(r Semiconductor Structure) type capacitive element and the like are mixedly mounted on the light receiving element and the semiconductor integrated circuit.

As shown in FIG. 8A, first, the semiconductor substrate 7
A first silicon oxide film 77 is formed at 6. Then, a first silicon nitride film 78 is formed on the silicon oxide film 77. Next, the silicon nitride film 7 in the capacitive element formation region
8 and the silicon oxide film 77 are removed by dry etching.

Then, as shown in FIG. 8B, a second silicon nitride film 79 is formed on the entire upper surface of the semiconductor substrate 76. The silicon nitride film 79 is an insulating film (dielectric film) of the MIS capacitor element and also an antireflection film of the light receiving element. Thus, the number of steps is reduced by simultaneously forming the antireflection film of the light receiving element and the insulating film of the capacitive element. The antireflection film 87 of the light receiving element is composed of the silicon oxide film 77, the silicon nitride film 78, and the silicon nitride film 79 shown in FIG. 8B. Next, as shown in FIG. 8C, the silicon nitride films 79 and 78 other than the light receiving element forming region and the capacitor element forming region are removed by dry etching.

Then, as shown in FIG. 9A, the silicon oxide film 77 in the region for forming the anode electrode portion of the light receiving element is removed. Then, a polysilicon film 80 is formed on the entire upper surface of the semiconductor substrate 76. This polysilicon film 8
In addition to the anode electrode portion of the light receiving element, 0 is used for a transistor (not shown), an electrode portion of a capacitive element, a resistance element (not shown) itself, and the like.

Next, as shown in FIG. 9B, the polysilicon film 80 is selectively dry-etched (plasma etching, reactive ion etching or the like),
The polysilicon film 80 is formed into an electrode shape. At this time,
The polysilicon film 80 on the antireflection film is removed. This is because the high reflectance of the polysilicon film lowers the light receiving sensitivity of the light receiving element.

After processing the polysilicon film 80 into an electrode shape, a second silicon oxide film 81 is formed as shown in FIG. 9C. This is to maintain insulation between the first polysilicon film and the second polysilicon film when a transistor (not shown) having a double polysilicon structure is formed on the semiconductor substrate 76. Next, the silicon oxide film 81
And 77 are selectively removed to form a light receiving element and an opening for an electrode portion such as a capacitor.

Next, an Al compound 82 is formed on the entire upper surface of the semiconductor substrate 76 shown in FIG. 10A, and the Al compound 82 is formed.
Is selectively etched. As a result, the cathode electrode and the like of the light receiving element are formed.

After forming the Al compound 82, as shown in FIG. 10B, a third silicon oxide film 83 is formed as a wiring interlayer film with the upper wiring. In FIG. 10B, the total thickness of the silicon oxide films 81 and 83 on the antireflection film 87 is about 1 μm.

Next, as shown in FIG. 10C, a third silicon nitride film 84 to be a passivation film is formed. Then, as shown in FIG. 11A, this silicon nitride film 84
Is selectively dry-etched to expose the underlying silicon oxide film 83, and an opening 85 is formed in the light receiving region of the light receiving element.

Next, as shown in FIG. 11B, a resist pattern 86 is formed on the silicon nitride film 84 so as to open the light receiving region of the light receiving element. At this time, the resist pattern 86 is formed on the inner wall of the opening 85 formed in the light receiving region.
Cover with. In FIG. 11B, the width h ′ of the resist pattern 86 extending from the inner wall of the opening 85 toward the center thereof is
It is about several μm. This width h ′ is obtained by wet-etching the silicon oxide films 83 and 81 in a post process and receiving the light receiving window portion 8
8 (see FIG. 11C) is set in accordance with the side etching amount.

Then, using this resist pattern 86 as a mask, the silicon oxide films 83 and 81 of about 1 μm are etched and removed as shown in FIG. 11C. The etching of the silicon oxide films 83 and 81 is performed by wet etching instead of dry etching. This is to avoid etching damage to the underlying antireflection film 87.

Further, by adopting the wet etching, the silicon oxide films 83 and 81 are side-etched by about several μm as shown by the solid arrow in FIG. 11C. However, depending on this side etching amount, the width h ′ of the resist pattern 86 (see FIG. 11B).
By previously setting the value of
4 It is possible to prevent the progress of the side etching down to below.

In this way, the light receiving window portion (light receiving portion) 88 is formed in the light receiving region of the light receiving element. After forming the light receiving window portion 88, the resist pattern 86 is removed to complete the semiconductor device 90 in which the light receiving element and the MIS type capacitance element and the like are mounted together.

[0020]

By the way, according to the method of manufacturing the semiconductor device 90 according to the conventional method, as shown in FIG. 12A, the polysilicon film 80 is formed on the antireflection film 87 in the light receiving element formation region. After that, the polysilicon film 80
Were selectively removed by dry etching.

Therefore, when the polysilicon film 80 is removed, the underlying antireflection film 87 is over-etched, and the thickness of the antireflection film 87 is within the plane of the semiconductor substrate (wafer) or within the lot. There was a risk of becoming uneven.

For example, a low pressure CVD (Chemical Vapor Deposition) apparatus for forming a silicon nitride film 84 or the like has a film-forming variation of about 3% within the wafer surface, whereas a dry etching apparatus has a variation of etching amount on the wafer. There are several 10% in the plane.

As described above, if the film thickness of the antireflection film 87 becomes uneven, the reflectance, the refractive index, the absorptivity, etc. of the light incident on the light receiving window portion 88 will be different, and thus the in-plane or the wafer surface will be different. There is a problem that the light receiving sensitivity of the light receiving element is different among the chips (integrated circuits) in the lot.

In order to avoid the dry etching of the antireflection film (hereinafter, also referred to as antireflection film) 87, the silicon oxide film is formed when the light receiving window portion 88 shown in FIG. 11C is formed. The films 83 and 81 were removed by wet etching. For this reason, as shown in FIG. 12B, the light receiving window portion 88 has taper portions 89A and 89B having a width of about several μm, which makes it difficult to further reduce the chip area.

Therefore, the present invention solves such a problem by making it possible to prevent the processing damage to the antireflection film due to the etching process and to prevent the antireflection film from having a uniform film thickness. It is an object of the present invention to provide a semiconductor device capable of forming a light receiving window portion having a groove and a manufacturing method thereof.

[0026]

In the semiconductor device having a light receiving element, the above-mentioned problems are provided in a semiconductor substrate provided with an impurity diffusion layer for the light receiving element, and provided on the impurity diffusion layer of the semiconductor substrate. An antireflection film, an electrode part that penetrates the antireflection film and is joined to the impurity diffusion layer, an insulating film provided to insulate the electrode part, and a reflection on the impurity diffusion layer. And a light receiving window portion surrounded by an insulating film having an anti-reflection film, and the anti-reflection film is formed when the light receiving window portion is formed by selectively opening the insulating film. This is solved by a semiconductor device, which is protected by a protective film and then exposed in the light receiving window portion by removing the protective film.

According to the semiconductor device of the present invention, it is possible to form the light receiving window portion having the antireflection film having a uniform film thickness. A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device including a light receiving element on a semiconductor substrate, which comprises a step of forming an impurity diffusion layer for the light receiving element on the semiconductor substrate, and a step of forming the impurity diffusion layer. A step of forming an antireflection film on the surface of the formed semiconductor substrate, a step of forming a protective film on the antireflection film, and an impurity diffusion layer on the semiconductor substrate on which the protective film is formed. The step of forming the electrode part reaching the electrode part, the step of forming an insulating film on the semiconductor substrate on which the electrode part is formed, and selectively opening the insulating film to expose the protective film to form the opening part. And a step of removing the protective film exposed from the opening to form the light receiving window.

According to the method of manufacturing a semiconductor device of the present invention, the electrode portion and the opening can be formed in a state in which the antireflection film is protected by the protective film. Prevents processing damage to the film. Therefore, by removing the protective film exposed from the opening, it is possible to form the light receiving window having the antireflection film having a uniform thickness.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION A semiconductor device, a method for manufacturing the same, and a semiconductor manufacturing apparatus according to embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a configuration example of a semiconductor device 100 according to an embodiment of the present invention.

In this embodiment, an antireflection film and a protective film are laminated on the surface of the semiconductor substrate on which the impurity diffusion layer for the light receiving element is formed, and then the semiconductor substrate on which the protective film is formed has impurities. An electrode part is formed to reach the diffusion layer, then an insulating film is formed on the semiconductor substrate on which the electrode part is formed, and the insulating film is selectively opened to expose the protective film and open. Part and the antireflection film is protected by the protection film so that the electrode part and the opening can be formed so that the processing damage to the antireflection film due to the etching process can be prevented. At the same time, the protective film exposed from the opening can be removed to form the light receiving window having the antireflection film having a uniform film thickness.

First, the semiconductor device 100 will be described. As shown in FIG. 1, the semiconductor device 100 is
A light-receiving element (photodiode) 60 that photoelectrically converts a light-receiving signal into an electric signal, a MIS-type capacitance element (hereinafter, also referred to as a capacitance element) 70, and a bipolar element (not shown)
And a resistance element (not shown) and the like are mixedly mounted on the same semiconductor substrate.

First, the semiconductor device 100 includes a semiconductor substrate 1. The semiconductor substrate 1 is a semiconductor wafer made of, for example, P-type silicon. In one region including the light receiving element 60 of the semiconductor substrate 1, a PIN structure as an example of the impurity diffusion layer as shown in FIG. 1, that is, a p ⁺ (p-type impurity) diffusion layer 6 occupying the surface of the light receiving region 6 is formed. And an i (low impurity) layer 7 surrounding the p ⁺ diffusion layer 6,
An n ⁺ (n-type impurity) diffusion layer 8 further surrounding the i layer is provided. An n ⁺ diffusion layer 12 is provided in the other region of the semiconductor substrate 1 including the capacitive element. The n ⁺ diffusion layer 12 functions as a lower electrode of the capacitive element 70.

The semiconductor substrate 1 is provided with an antireflection film (hereinafter also referred to as an antireflection film) so as to cover the above-mentioned p ⁺ diffusion layer 6. This antireflection film is
It has a laminated structure composed of a first silicon oxide film 18 and a first silicon nitride film 19 provided on the first silicon oxide film 18. This antireflection film suppresses the reflection of light incident on the light receiving window portion (light receiving portion) of the light receiving element,
It has a function of allowing the light to reach the p ⁺ diffusion layer 6.

In FIG. 1, the thickness of the silicon oxide film 18 is, for example, about 50 nm, and the silicon nitride film 19 is used.
Has a thickness of, for example, about 30 nm. In addition, the type of film forming the antireflection film, the film thickness of each film, and the like can be arbitrarily set according to the wavelength of light entering the light receiving window portion, the amount of light, and the like.

Next, the silicon nitride film 19 excluding the light receiving window portion
A second silicon oxide film 20 as an example of a base film is formed on the upper surface.
Is provided. The film thickness of the silicon oxide film 20 is
For example, it is about 100 nm. Further, a second silicon nitride film 21 which is an example of a protective film is provided on the silicon oxide film 20. This silicon nitride film 2
The film thickness of 1 is, for example, about 50 nm. Regarding the silicon oxide film 20 and the silicon nitride film 21,
I will explain later.

Then, on the silicon nitride film 21,
A third silicon oxide film 22 is provided. The silicon oxide film 22 is a film having a function of insulating between first polysilicon and second polysilicon of a transistor (not shown) having a double polysilicon structure.
Therefore, when a transistor or the like having a double polysilicon structure is not mounted on the semiconductor substrate 1, the silicon oxide film 22 can be omitted.

On the p ⁺ diffusion layer 6 of the semiconductor substrate 1,
On the n ⁺ diffusion layer 8, the above-described antireflection film, the silicon oxide film 20, the silicon nitride film 21, and the contact hole penetrating the silicon oxide film 22 are provided.

In the contact hole on the p ⁺ diffusion layer 6, for example, an electrode portion 11 for the cathode is provided. The electrode portion 11 is made of an Al compound film. Further, in the contact hole on the n ⁺ diffusion layer 8, for example, an electrode portion 10 for an anode is provided. The electrode portion 10 has a laminated structure including, for example, a polysilicon film and an Al compound film.

In FIG. 1, a negative voltage (-) is applied to the electrode portion 11.
Is applied to deplete the i layer 7 and an optical signal is made incident on the light receiving window portion in this state, the incident optical signal is photoelectrically converted into an electric signal (hole and electron) in the depletion layer. Then, the generated electrons flow to the electrode portion 10, and the holes flow to the electrode portion 11.

On the other hand, a contact hole penetrating the antireflection film, the silicon oxide film 20, the silicon nitride film 21, and the silicon oxide film 22 is also provided on the n ⁺ diffusion layer 12 of the semiconductor substrate 1. An electrode portion 27 connected to the lower electrode (n ⁺ diffusion layer) is provided in the contact hole. The electrode portion 27 is made of an Al compound film.

The antireflection film on the n ⁺ diffusion layer 12 is provided with an opening having a predetermined area, and the insulating silicon nitride film 21 is provided in the opening. In the capacitive element 70, the silicon nitride film 21 serves as a dielectric film.
Further, an electrode portion 29 serving as an upper electrode is provided on the silicon nitride film 21 as the dielectric film. The electrode portion 29 has a laminated structure including, for example, a polysilicon film and an Al compound film.

In FIG. 1, an electrode portion 29 serving as an upper electrode
Positive voltage (+) is applied to ⁺Connection with diffusion layer 12
By applying a negative voltage (-) to the electrode section 27
Therefore, the electric charge according to the applied voltage can be stored in the capacitor 70.
It

A fourth silicon oxide film 23, which is an example of an insulating film, is formed above the semiconductor substrate 1 except the light receiving window so as to cover these electrode portions 27 and 29 and the like.
Is provided. With this silicon oxide film 23,
The electrodes and the wiring patterns described above are sufficiently insulated. The film thickness of the silicon oxide film 23 is, for example, 900
It is about nm.

The silicon oxide film 23 has a third
Of the silicon nitride film 24. The silicon nitride film 24 is a so-called passivation film, and is for protecting the semiconductor device 100 from moisture, stress due to a package (not shown), and the like. The film thickness of the silicon nitride film 24 is, for example, about 1 μm. In the semiconductor device 100 shown in FIG. 1, the silicon oxide films 18, 20, 22, 23 and the silicon nitride film 1 described above are used.
The light receiving window portion 1 is formed on the p ⁺ diffusion layer 6 surrounded by 9, 21, and 24.
7 is provided.

By the way, in the semiconductor device 100, as shown in FIG.
7B and silicon nitride film 21 and n ⁺Between the diffusion layers 12
Is the first silicon oxide film 18 as indicated by the solid arrow.
And a first silicon nitride film 19 and a second silicon oxide film.
A membrane 20 is provided. That is, the conventional semiconductor device
Compared with the device 90, it has a thickness of about 100 nm between them.
A silicon oxide film 20 is added. Therefore, dielectric
The silicon nitride film 21 and n other than the portion used as the body film⁺Expansion
Since the separation distance between the diffusion layers 12 can be increased, the capacitive element 70
The parasitic capacitance of can be reliably reduced.

Next, a method of manufacturing the semiconductor device according to the present invention will be described. 2 to 6 are process diagrams showing a method of manufacturing the semiconductor device 100 (Nos. 1 to 5). here,
It is assumed that the semiconductor device 100 described above is manufactured.

First, as shown in FIG. 2A, the above-mentioned p⁺
Diffusion layer 6, i layer 7, n⁺Diffusion layer 8, n ⁺Diffusion layer 12 etc.
A pure substance diffusion layer is formed on the semiconductor substrate 1. Formation of these
Is produced by well-known manufacturing techniques such as ion implantation and thermal diffusion.
To do.

Next, on the semiconductor substrate 1, a first silicon oxide film 18 and a first silicon nitride film 19, which are an example of an antireflection film, are sequentially formed. The silicon oxide film 18 is formed, for example, by thermally oxidizing the semiconductor substrate 1. The formation of the silicon nitride film 19 is performed by LP (Low Pr
essure) CVD or the like. After forming the antireflection film, a second silicon oxide film 20 as an example of a base film is formed on the film. The method of forming the silicon oxide film 20 is, for example, the CVD method.

Next, a resist pattern (not shown) for opening a region (hereinafter, also referred to as a capacitive element forming region) where the MIS type capacitive element 70 (see FIG. 1) is formed is formed on the silicon oxide film 20. Form. The resist pattern is formed by, for example, photolithography.

Then, using this resist pattern as a mask, the silicon oxide film 20, the silicon nitride film 19, and the
The silicon oxide film 18 and the silicon oxide film 18 are sequentially etched and removed.
This etching process is performed by, for example, dry etching using an F-based gas such as CF ₄ . After the etching process described above is completed, the resist pattern is removed by ashing which is a well-known manufacturing technique.

Then, as shown in FIG. 2B, a second silicon nitride film 21, which is an example of a protective film, is formed on the entire upper surface of the semiconductor substrate 1 so as to be in contact with the n ⁺ diffusion layer 12 in the capacitive element formation region. To form. This silicon nitride film 21 is
It functions as a dielectric film of a capacitive element.

Next, a region for forming a light receiving element (hereinafter,
A resist pattern (not shown) covering the p ⁺ diffusion layer 6 of the light receiving element forming region) and the capacitor element forming region is formed on the silicon nitride film 21. Then, using this resist pattern as a mask, the second silicon nitride film is dry-etched. As a result, as shown in FIG. 2C, the silicon nitride film 21 is removed except on the n ⁺ diffusion layer 6 and the capacitive element formation region.

After removing this resist pattern by ashing, as shown in FIG. 3A, a resist pattern 35 having an opening in a region where the electrode portion 11 (see FIG. 1) is formed is formed. Then, using the resist pattern 35 as a mask, the silicon oxide film 20, the silicon nitride film 19, and
The silicon oxide film 18 is sequentially removed by etching, and n ⁺
The diffusion layer 8 is exposed. This etching process is performed by dry etching.

Next, the resist pattern 35 is removed by ashing. Then, as shown in FIG. 3B, a polysilicon film 32 is formed on the entire upper surface of the semiconductor substrate 1. The polysilicon film 32 is used not only for the electrode portion of the light receiving element 60 and the electrode portion of the capacitive element 70 described above, but also for the electrode portion of the transistor (not shown) and the main body of the resistance element (not shown). To do. This polysilicon film 3
The formation of 2 is performed, for example, by LPCVD.

After forming the polysilicon film 32, the POC is formed.
The polysilicon film 32 is doped with phosphorus using l ₃ gas or the like. As a result, the polysilicon film 32 can have conductivity.

Next, the electrode portion 10 of the light receiving element (see FIG. 1)
A resist pattern (not shown) is formed on the polysilicon film 32 so as to cover the region for forming the capacitor and the region for forming the capacitive element.

Then, using this resist pattern as a mask, the polysilicon film 32 is dry-etched. As a result, as shown in FIG. 3C, the electrode portion 11 of the light receiving element is formed.
(See FIG. 1) A lower layer portion and an electrode portion 29 (see FIG. 1) lower layer portion of the capacitive element can be formed. In addition, the shape of this resist pattern, the gate electrode of the transistor or the like described above,
The shape of the resistive element body and the like and the formation region are also made to correspond. As a result, the electrode portion of the transistor, the resistance element body, and the like can be formed from the polysilicon film 32. For this dry etching, an etching gas such as CF ₄ or CF ₄ —O ₂ is used.

In the light receiving element, the high reflectance of the polysilicon film causes a decrease in light receiving sensitivity, and therefore the polysilicon film 32 above the p ⁺ diffusion layer 6 must be removed. At this time, the silicon nitride film 1 forming the antireflection film
A silicon oxide film 20 and a silicon nitride film 21 are formed on the substrate 9.
Is provided.

Therefore, even if the polysilicon film 32 is over-etched, the antireflection film can be protected by the silicon nitride film 21, so that etching damage to the antireflection film can be prevented. As a result, it is possible to prevent the film thickness of the antireflection film from being reduced, so that it is possible to prevent the film thickness of the antireflection film from varying within the surface of the semiconductor substrate (wafer) or within the lot. therefore,
Compared with the conventional method, the quality of the antireflection film can be surely improved.

Next, as shown in FIG. 4A, the semiconductor substrate 1
A third silicon oxide film 22 having a thickness of about 100 nm is formed on the entire surface above. Then, this silicon oxide film 22
Then, the silicon nitride film 21, the silicon oxide film 20, the silicon nitride film 19, and the silicon oxide film 18 are selectively etched in order to form a contact hole reaching the p ⁺ diffusion layer 6 formed in the semiconductor substrate 1. To do. Further, a via hole reaching the polysilicon film 32 is formed in parallel with the formation of this contact hole.

Then, the Al compound film 1 is formed on the entire upper surface of the semiconductor substrate 1 in which the contact hole and the via hole are formed.
4 is deposited and the Al compound film 14 is patterned. Thereby, the electrode portions 10 and 11 shown in FIG. 4B, the electrode portion 29 (see FIG. 1) of the MIS type capacitance element 70, and the like can be formed.

Next, a fourth silicon oxide film 2 as an example of an insulating film is formed on the entire upper surface of the semiconductor substrate 1 on which the electrodes are formed.
3 is formed. This silicon oxide film 23 is
It is a wiring interlayer insulating film for insulating between wiring patterns. The deposition of the silicon oxide film 23 is performed by, for example, O ₃ -T
Performed by EOS.

Further, a third silicon nitride film 24 is formed on this silicon oxide film. This silicon nitride film is
It has a function of protecting the semiconductor device 100 from moisture, package stress, and the like. The silicon nitride film 24 is formed by, for example, P (Plasma) -CVD.

Next, as shown in FIG. 4C, the p ⁺ diffusion layer 6 is formed.
A resist pattern 37 that selectively opens above is formed on the silicon nitride film 24. Then, using the resist pattern 37 as a mask, the silicon nitride film 24 is dry-etched. As a result, an opening for receiving light can be formed in the silicon nitride film 24. Further, by providing an opening (not shown) of the resist pattern 37 on each electrode portion, a pad portion for exchanging charges with external terminals can be defined on the electrode.

Next, the resist pattern 37 is removed by ashing. Then, as shown in FIG. 5A, the inner wall of the opening provided in the silicon nitride film 24 is covered, and p
⁺ A resist pattern 39 that selectively opens above the diffusion layer 6 is formed on the silicon nitride film 24.

Then, as shown in FIG. 5B, the silicon oxide film 23 is formed using the resist pattern 39 as a mask.
And the silicon oxide film 22 are removed by dry etching to form a light receiving opening.

For this dry etching, an etching condition is selected in which the etching rate for the silicon oxide film is higher than the etching rate for the silicon nitride film.
This etching condition is, for example, reactive ion etching using CF ₄ —H ₂ or the like, which has a high etching selection ratio between the silicon oxide film and the silicon nitride film. As a result, the silicon oxide film on the silicon nitride film 21 can be removed with high selectivity.

Next, as shown in FIG. 5C, the silicon nitride film 21 exposed from the silicon oxide films 23 and 22 is removed by dry etching. For this dry etching, etching conditions in which the etching rate for the silicon nitride film is higher than the etching rate for the silicon oxide film, for example, plasma etching using CF ₄ —O ₂ or the like is selected. As a result, the silicon nitride film 21 on the silicon oxide film 20 can be removed with high selectivity.

Next, as shown in FIG. 6A, when the silicon oxide films 23 and 22 and the silicon nitride film 21 are dry-etched, the resist pattern used as a mask is removed by ashing. Next, as shown in FIG. 6B, the silicon oxide films 23 and 22 and the silicon nitride film 2 are formed.
Resist pattern 41 that covers the inner wall of the opening 43 provided in the No. 1 and selectively opens above the p ⁺ diffusion layer 6
Are formed above the semiconductor substrate 1. At this time, the opening 4
The width h of the resist pattern 41 extending from the inner wall of 3 toward the center thereof is, for example, about several hundred nm. This width h
Is set according to the side etching amount when the silicon oxide film 20 is wet-etched to form the light receiving window portion 17 (see FIG. 6C) in a later step.

Then, as shown in FIG. 6C, the silicon oxide film 20 is removed by wet etching using the resist pattern 41 as a mask to form the light receiving window portion 17. The chemical solution used for this wet etching is, for example, a hydrofluoric acid aqueous solution.

Since the silicon oxide film 20 is removed by wet etching, the underlying silicon nitride film 19 can be prevented from being damaged by etching which may damage the crystal structure. Further, since the etching rate of the hydrofluoric acid aqueous solution with respect to the silicon oxide film 20 is higher than the etching rate with respect to the silicon nitride film 19, the silicon nitride film 19 is not thinned.

Further, as shown in FIG. 7A, since the thickness of the silicon oxide film to be wet-etched is smaller than that in the conventional method, the side etching amount can be reduced according to the difference in the thickness. For example, the width of the taper portions 45A and 45B of the light receiving window portion 17 shown in FIG. 7A is about several hundred μm. Therefore, the chip area can be further reduced.

As described above, according to the method of manufacturing a semiconductor device of the present invention, when the light receiving element 60 is formed on the semiconductor substrate 1, the p ⁺ diffusion layer 6, the i layer 7, and the n ⁺ diffusion layer 8 are formed. After the silicon oxide film 18 and the silicon nitride film 19, the silicon oxide film 20, and the silicon nitride film 21 are laminated on the semiconductor substrate 1 on which the silicon nitride film 21 is formed, the n ⁺ diffusion layer is formed on the semiconductor substrate 1 on which the silicon nitride film 21 is formed. 8 and the electrode portions 10 and 11 reaching the p ⁺ diffusion layer 6 respectively, and then the electrode portion 1
The silicon oxide film 2 is formed on the semiconductor substrate 1 on which 0 and 11 are formed.
2 and 23 are formed, and the silicon oxide films 23 and 22 are selectively opened to expose the silicon nitride film 21 to form the opening 43.

Therefore, since the electrode portions 10 and 11 and the opening portion 43 can be formed in a state in which the silicon nitride film 19 is protected by the silicon oxide film 20 and the silicon nitride film 21, the silicon nitride film 19 can be formed by dry etching or the like. The processing damage of can be prevented.

Further, the silicon nitride film 21 exposed from the opening 43 is removed by dry etching, and then the silicon oxide film 20 is removed by wet etching, so that the light receiving portion having the silicon nitride film 19 having a uniform thickness is obtained. The window portion 17 can be formed.

Therefore, the reflectance, the refractive index, the absorptivity, etc. of the light incident on the light receiving window 17 can be made substantially uniform between the chips in the surface of the semiconductor substrate (wafer) or in the lot. The light receiving sensitivity of 60 can be stabilized.

[0077]

According to the semiconductor device of the present invention, a light receiving window portion surrounded by an insulating film having a reflection preventing film on an impurity diffusion layer for a light receiving element is provided. The protective film is protected by the protective film when the insulating film is selectively opened to form the light receiving window, and then the protective film is removed to expose the inside of the light receiving window. It consists of

With this structure, it is possible to form the light receiving window portion having the antireflection film having a uniform film thickness. Therefore, it is possible to provide a semiconductor device having a light receiving element with stabilized light receiving characteristics.

Further, according to the method for manufacturing a semiconductor device of the present invention, when the light receiving element is formed on the semiconductor substrate, an antireflection film is formed on the surface of the semiconductor substrate on which the impurity diffusion layer for the light receiving element is formed, After laminating the protective film, an electrode portion reaching the impurity diffusion layer is formed on the semiconductor substrate on which the protective film is formed, and then an insulating film is formed on the semiconductor substrate on which the electrode portion is formed. The insulating film is selectively opened to expose the protective film to form an opening.

With this structure, the electrode portion and the opening can be formed in a state in which the antireflection film is protected by the protection film, so that the processing damage to the antireflection film due to the etching process can be prevented.

Therefore, by removing the protective film exposed from the opening, it is possible to form the light receiving window having the antireflection film having a uniform film thickness. Moreover, since the film thickness of the antireflection film can be made uniform, a light receiving element having stable light receiving characteristics can be formed on the semiconductor substrate with high reliability and good reproducibility.

The present invention is extremely suitable for application to a light receiving element-mixed type semiconductor integrated circuit in which a light receiving element for photoelectrically converting an optical signal into an electric signal and a capacitive element and the like are provided on the same semiconductor substrate.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a semiconductor device 100 according to an embodiment of the present invention.

2A to 2C are process diagrams showing a manufacturing method (1) of the semiconductor device 100. FIG.

3A to 3C are process diagrams showing a manufacturing method (No. 2) of the semiconductor device 100.

4A to 4C are process diagrams showing a manufacturing method (3) of the semiconductor device 100.

5A to 5C are process diagrams showing a manufacturing method (4) of the semiconductor device 100.

6A to 6C are process diagrams showing a manufacturing method (5) of the semiconductor device 100.

7A and 7B are cross-sectional views showing configuration examples of a light receiving element 60 and a capacitive element 70.

8A to 8C are process drawings showing a manufacturing method (1) of a semiconductor device 90 according to a conventional example.

9A to 9C are manufacturing methods of a semiconductor device 90 (No. 2).
FIG.

10A to 10C are process diagrams showing a manufacturing method (3) of the semiconductor device 90.

11A to 11C are process diagrams showing a manufacturing method (4) of the semiconductor device 90.

12A and 12B are cross-sectional views showing a problem of the semiconductor device 90.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 17 ... Light receiving window part, 18, 2
0, 22, 23 ... Silicon oxide film, 19, 21, 2
4 ... Silicon nitride film, 32 ... Polysilicon film,
60 ... Light receiving element, 70 ... Capacitance element, 100 ...
・ Semiconductor device

Claims (5)

[Claims] 1. A semiconductor device having a light-receiving element, a semiconductor substrate having an impurity diffusion layer for the light-receiving element, an antireflection film provided on the impurity diffusion layer of the semiconductor substrate, and the reflection. An electrode portion that penetrates the prevention film and is joined to the impurity diffusion layer; an insulating film provided to insulate the electrode portion; and an antireflection film on the impurity diffusion layer. And a light receiving window portion surrounded by the insulating film, and the antireflection film is a protective film when the insulating film is selectively opened to form the light receiving window portion. A semiconductor device, which is protected by a film, and is then exposed in the light receiving window portion by removing the protective film. 2. A method of manufacturing a semiconductor device including a light receiving element on a semiconductor substrate, comprising: forming an impurity diffusion layer for the light receiving element on the semiconductor substrate; and forming a surface of the semiconductor substrate on which the impurity diffusion layer is formed. Forming an antireflection film, forming a protective film on the antireflection film, and forming an electrode portion reaching the impurity diffusion layer on the semiconductor substrate on which the protective film is formed. And a step of forming an insulating film on the semiconductor substrate having the electrode portion formed thereon, and a step of selectively opening the insulating film to expose the protective film to form an opening. And a step of removing the protective film exposed from the opening to form a light receiving window portion, the method for manufacturing a semiconductor device. 3. The insulating film is selectively opened to expose the protective film under an etching condition in which an etching rate for the insulating film is higher than an etching rate for the protective film, The method of manufacturing a semiconductor device according to claim 2, wherein an opening is formed. 4. An antireflection film is formed on the surface of the semiconductor substrate on which the impurity diffusion layer is formed, a base film is formed on the antireflection film, and the protection film is formed on the base film. And forming an electrode portion reaching the impurity diffusion layer on the semiconductor substrate on which the protective film is formed, forming an insulating film on the semiconductor substrate on which the electrode portion is formed, and forming the insulating film. The opening is formed by selectively opening the protective film to expose the protective film, and then exposing from the opening under an etching condition in which an etching rate for the protective film is higher than an etching rate for the base film. The light receiving window is formed by removing the protective film to expose the base film, and further performing wet etching on the exposed base film to remove the base film. The semiconductor described in 2. Method of manufacturing location. 5. The protective film is used as a dielectric film of the capacitive element when manufacturing a semiconductor device in which the light receiving element and the capacitive element are mixedly mounted on the semiconductor substrate. 2. The method for manufacturing a semiconductor device according to 2.