JP2005064198A - Semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device and its manufacturing method in which a condensing efficiency on a light receiving region can be enhanced. <P>SOLUTION: This semiconductor device comprises a silicon substrate 1, a light receiving element 3 provided on the silicon substrate 1 for a photoelectric transfer, a passivation 13 provided on the silicon substrate 1 so as to cover the light receiving element 3, and a reflection film 11 for reflecting a light which deviates from above the light receiving element 3 and advances toward the silicon substrate 1 surrounding the light receiving element 3 onto the light receiving element 3 side in the passivation 13. As at least a part of a light which deviates from an intrinsic incident course to the light receiving element 3 and is incident on an interlayer insulating film 9 can be reflected on the light receiving element 3 side by the reflection film 11, the condensing efficiency on the light receiving element 3 can be increased. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a semiconductor device suitable for application to an image sensor or the like provided with a light receiving element that photoelectrically converts an optical signal into an electric signal and a manufacturing method thereof.

Conventionally, a plurality of light receiving elements provided on a semiconductor substrate, a protective film provided on the semiconductor substrate so as to cover the light receiving elements, a microlens provided on a protective film above each light receiving element, etc. Are known (refer to Patent Documents 1 and 2, for example).
The light receiving element is an element that photoelectrically converts an optical signal into an electric signal, and includes a pn junction, an impurity diffusion layer having a pin junction, and the like. The protective film is an insulating film such as a silicon oxide film or a silicon nitride film. With this protective film, the light receiving element is protected from impurities such as outside air, moisture, and Na ⁺ . The microlens is designed so that most of the light incident thereon can be collected in the light receiving element.

  In such an image sensor, light enters the microlens from the outside, and most of the incident light is refracted by a predetermined angle and enters the protective film. The light is incident on the light receiving element through the protective film. In this type of image sensor, a light shielding film is usually provided above a semiconductor substrate around the light receiving element in order to prevent light from entering other than the light receiving element. For example, Patent Document 1 discloses a light shielding film parallel to a semiconductor substrate. Patent Document 2 discloses a stepwise light shielding film with respect to a semiconductor substrate. These light shielding films are made of aluminum (Al).

This is because if light enters the semiconductor substrate other than the light receiving element, unintentional photoelectric conversion may occur due to the incident light, which may be detected as noise in the image sensor. In order to reduce this noise, it has been devised to prevent light from entering other than the light receiving element with a light shielding film.
JP 2002-141488 A JP 2001-53258 A

By the way, according to the conventional image sensor, most of the light incident on the micro lens is refracted by a predetermined angle and enters the protective film, and then enters the light receiving element through the protective film. Yes.
However, a part of the light incident on the microlens is not condensed on the light receiving element due to the relationship between the incident angle of the light and the refractive index of the microlens, and is incident on the light shielding film made of aluminum around the light receiving element. There are many cases. In addition, a part of the light incident on the microlens is scattered in the protective film before entering the light receiving element, and is incident not on the light receiving element but on the light shielding film around the light receiving element. Sometimes.

In this way, when the light incident on the microlens deviates from the original incident course to the light receiving element and enters the light shielding film parallel to the semiconductor substrate or stepped, the light shielding film There is a problem that most of the incident light is reflected to the microlens side and does not collect in the light receiving element.
SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve such problems, and an object of the present invention is to provide a semiconductor device and a method for manufacturing the semiconductor device that can improve the light collection efficiency to the light receiving region.

  In order to solve the above-described problems, a first semiconductor device according to the present invention includes a semiconductor substrate, a light receiving region provided on the semiconductor substrate and performing photoelectric conversion, and the semiconductor substrate so as to cover the light receiving region. An insulating protective film provided on the upper surface, and light that is provided in the protective film and that travels toward the semiconductor substrate around the light receiving region from the upper side of the light receiving region is reflected toward the light receiving region. And a reflecting means.

The second semiconductor device according to the present invention is the above-described first semiconductor device, wherein the reflecting means is made of a metal film, and the protective film has an upper surface side closer to the light receiving region than the protective film. And is inclined in a direction away from the light receiving region.
Here, the term “on the edge of the light receiving region” refers to the upper surface of the edge of the light receiving region or a portion in the protective film that is above the edge of the light receiving region and is away from the upper surface of the edge. The metal film is a film made of, for example, aluminum (Al).

  A third semiconductor device according to the present invention is the above-described second semiconductor device, wherein the protective film is provided on the semiconductor substrate and has an opening on the light receiving region, and the opening. A second protective film provided on the light receiving region and the first protective film so as to be embedded, and the inner wall of the opening is close to the light receiving region on the upper surface side of the first protective film It has a slope inclined in a direction away from the light receiving region along the first protective film as compared with the side, and the metal film is provided on the slope of the inner wall.

According to the first to third semiconductor devices according to the present invention, at least a part of the light that falls off the original incident course to the light receiving region and enters the insulating protective film is used as a metal film or the like. Since it can be reflected to the light receiving area side by the reflecting means comprising, the light collection efficiency to the light receiving area can be increased.
A fourth semiconductor device according to the present invention includes the lens body provided above the light receiving region and on the protective film in the first to third semiconductor devices described above, and the lens body has an external environment. From the above, it has a function of refracting light incident on the lens body toward the light receiving region.

According to the fourth semiconductor device of the present invention, since the light incident on the lens body is refracted toward the light receiving region before entering the protective film, the light collection efficiency to the light receiving region can be further enhanced.
A method of manufacturing a semiconductor device according to the present invention includes a step of forming a light receiving region for performing photoelectric conversion on a semiconductor substrate, and a step of forming an insulating protective film on the semiconductor substrate so as to cover the light receiving region. And forming a reflection means in the protective film for reflecting the light traveling from the upper side of the light receiving region toward the semiconductor substrate around the light receiving region to the light receiving region side. Is.

  According to the method for manufacturing a semiconductor device according to the present invention, at least a part of the light that falls off the original incident course to the light receiving region and enters the insulating protective film is reflected to the light receiving region side. Therefore, it is possible to manufacture an image sensor that can perform the above-described process and contribute to the improvement of the light collection efficiency to the light receiving region.

Hereinafter, a semiconductor device and a manufacturing method thereof according to embodiments of the present invention will be described with reference to the 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.
In FIG. 1, 1 is a silicon substrate, 3 is a light receiving element, 5 is a silicon oxide film, 7 is a silicon nitride film, 9 is an interlayer insulating film, 10 is a light receiving opening (hereinafter referred to as a light receiving opening), 11 Is a reflective film, 13 is a passivation, and 15 is a microlens. The semiconductor device 100 is an image sensor in which a light receiving element 3 that photoelectrically converts an optical signal into an electric signal and a MOS transistor or the like (not shown) are mounted on the same silicon substrate 1.

As shown in FIG. 1, the light receiving element 3 is provided on the surface layer of the silicon substrate 1. The light receiving element 3 is an element that photoelectrically converts an optical signal into an electric signal, and includes, for example, a pn junction, an impurity diffusion layer having a pin junction, and the like.
The silicon oxide film 5 and the silicon nitride film 7 are provided on the silicon substrate 1 in the peripheral region surrounding the light receiving element 3. The silicon nitride film 7 is a film used for preventing over-etching of the light receiving element 3 when the light receiving opening 10 is formed on the light receiving element 3. This point will be described later with reference to FIG.

  Further, an interlayer insulating film 9 is provided on the silicon nitride film 7. As shown in FIG. 1, the side wall of the interlayer insulating film 9 facing the light receiving element 3 extends from the light receiving element 3 along the interlayer insulating film 9 as compared with the side closer to the light receiving element 3 on the upper surface side of the interlayer insulating film 9. The slope is inclined in the direction of leaving. In the semiconductor device 100, a bowl-shaped light receiving opening 10 is defined by the side wall of the interlayer insulating film 9, the side wall of the silicon nitride film 7, and the side wall of the silicon oxide film 5. The interlayer insulating film 9 is made of, for example, a silicon oxide film.

  The reflective film 11 is continuously provided from the interlayer insulating film 9 to the side wall of the interlayer insulating film 9. The reflection film 11 is made of a film that reflects well without substantially absorbing light. For example, the reflection film 11 is made of a metal film such as aluminum. Further, the passivation 13 is provided on the silicon substrate 1 so as to cover the reflective film 11 and the light receiving element 3. With this passivation 13, the light receiving opening 10 is embedded. As shown in FIG. 1, the upper surface of the passivation 13 is flattened by a CMP (chemical mechanical polish) technique or the like.

The microlens 15 is provided above the light receiving element 3 and on the upper surface of the flattened passivation 13. The microlens 15 has a function of refracting light incident on the microlens 15 from the outside toward the light receiving element 3.
According to the semiconductor device 100 of the present invention, the reflective film 11 is inclined in the direction away from the light receiving element 3 along the interlayer insulating film 9 as compared with the side closer to the light receiving element 3 on the upper surface side of the interlayer insulating film 9. Yes. Therefore, as shown in FIG. 2, at least a part of the light 20 that deviates from the original incident course to the light receiving element 3 and enters the interlayer insulating film 9 is reflected by the reflecting film 11 on the light receiving element 3 side. Can be reflected. Thereby, compared with the conventional system, more light can be collected to the light receiving element 3, and condensing efficiency can be improved.

3A to 4C are process diagrams showing a method (No. 1 and No. 2) of manufacturing the semiconductor device 100 according to the embodiment of the present invention. Next, a method for manufacturing the semiconductor device 100 described above will be described.
First, as shown in FIG. 3A, the light receiving element 3 is formed on the silicon substrate 1. The light receiving element 3 is formed using a well-known photolithography technique and ion implantation technique. Next, a silicon oxide film 5 is formed on the silicon substrate 1 on which the light receiving element 3 is formed, and a silicon nitride film 7 is formed on the silicon oxide film 5. The silicon oxide film 5 and the silicon nitride film 7 are formed by using, for example, a well-known CVD (chemical vapor deposition) technique. Then, as shown in FIG. 3B, an interlayer insulating film 9 made of a silicon oxide film is formed on the silicon nitride film 7 using a CVD technique. Before forming the interlayer insulating film 9, a MOS transistor or the like (not shown) is formed on the silicon substrate 1 using a well-known CMOS process.

Next, as shown in FIG. 3B, a resist pattern 17 is formed on the interlayer insulating film 9 so as to open the light receiving element 3 and cover the silicon substrate 1 in other regions. The resist pattern 17 is formed using, for example, a photolithography technique.
Then, using the resist pattern 17 as a mask, isotropic etching is performed on the interlayer insulating film 9 to form an opening 10 ′ above the light receiving element 3 as shown in FIG. Here, the isotropic etching process is, for example, wet etching using a hydrofluoric acid (HF) solution. By wet etching using this hydrofluoric acid solution, the interlayer insulating film (silicon oxide film) 9 exposed from the bottom of the resist pattern 17 is etched not only in the vertical direction but also in the horizontal direction as indicated by arrows. Therefore, as shown in FIG. 3C, the inner wall of the opening 10 ′ is separated from the light receiving element 3 along the interlayer insulating film 9 as compared with the side closer to the light receiving element 3 on the upper surface side of the interlayer insulating film 9. Molded into a slanted surface.

  Further, in the wet etching using this hydrofluoric acid solution, the etching rate of the silicon nitride film 7 is sufficiently smaller than the etching rate of the interlayer insulating film (silicon oxide film) 9. That is, there is sufficient etching selectivity between the interlayer insulating film 9 and the silicon nitride film 7, and the silicon nitride film 7 functions as an etching stopper film. Therefore, even if this interlayer insulating film 9 is somewhat over-etched, etching of the underlying light receiving element 3 can be prevented.

Next, the resist pattern 17 on the interlayer insulating film 9 is removed by ashing. Then, the silicon nitride film 7 exposed from the opening 10 ′ is removed by wet etching with hot phosphoric acid (H ₃ PO ₄ ). In this wet etching using hot phosphoric acid, there is sufficient etching selectivity between the silicon nitride film 7 and the silicon oxide film 5, and the silicon oxide film 5 functions as an etching stopper film. Therefore, even when the silicon nitride film 7 is over-etched, the silicon oxide film 5 remains almost unetched, and exposure from the opening 10 ′ of the light receiving element 3 can be prevented.

  Next, as shown in FIG. 4A, an aluminum film 11 ′ is formed on the interlayer insulating film 9 in which the opening 10 ′ is formed and on the silicon oxide film 5 which is the bottom surface of the opening 10 ′. Form. Then, using a photolithography technique and a dry etching technique, the aluminum film 11 ′ directly formed on the silicon oxide film 5 is removed to form the reflection film 11 (see FIG. 1). Subsequently, using the resist pattern (not shown) covering the reflective film 11 as it is, the silicon oxide film 5 exposed from the opening 10 'is removed using a dilute hydrofluoric acid solution, and FIG. As shown in B), a bowl-shaped light receiving opening 10 is formed.

  By such a method, as shown in FIG. 4B, the side wall of the interlayer insulating film 9 facing the light receiving element 3 is separated from the side of the interlayer insulating film 9 where the upper surface side of the interlayer insulating film 9 is closer to the light receiving element 3. And a saddle-shaped light receiving opening 10 can be formed above the light receiving element 3. Then, the reflective film 11 can be formed on the side wall forming the slope of the interlayer insulating film 9, that is, on the inner wall of the light receiving opening 10.

  Next, as shown in FIG. 4C, a silicon oxide film 13 ′ is formed on the light receiving element 3 exposed from the light receiving opening 10 and the reflective film 11 so as to bury the light receiving opening 10. Form. Then, the upper surface of the silicon oxide film 13 ′ is planarized using a CMP technique to form a passivation 13 (see FIG. 1). Thereafter, the microlens 15 is attached on the passivation 13 above the light receiving element 3 to complete the semiconductor device 100 as shown in FIG.

As described above, according to the method for manufacturing the semiconductor device 100 according to the present invention, at least a part of the light that deviates from the original incident course to the light receiving element 3 and enters the interlayer insulating film 9 is received. An image sensor that can be reflected toward the third side can be manufactured, which can contribute to an improvement in light collection efficiency to the light receiving element.
In this embodiment, the silicon substrate corresponds to the substrate of the present invention, and the light receiving element 3 corresponds to the light receiving region of the present invention. Further, a film having a laminated structure including the interlayer insulating film 9, the silicon nitride film 7 and the silicon oxide film 5 corresponds to the first protective film of the present invention, and the light receiving opening 10 is an opening of the first protective film of the present invention. Corresponds to the department. Further, the reflective film 11 corresponds to the reflecting means (metal film) of the present invention, and the passivation 13 corresponds to the second protective film of the present invention. The microlens 15 corresponds to the lens body of the present invention, and the semiconductor device 100 corresponds to the semiconductor device of the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration example of a semiconductor device 100 according to the embodiment. The conceptual diagram which shows the example of reflection of the light 20 which deviated from the original incident course. Process drawing which shows the manufacturing method (the 1) of the semiconductor device 100. FIG. Process drawing which shows the manufacturing method (the 2) of the semiconductor device 100. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Silicon substrate, 3 Light receiving element, 5 Silicon oxide film, 7 Silicon nitride film, 9 Interlayer insulation film, 10 Light-receiving opening part, 11 Reflective film, 13 Passivation, 15 Microlens, 17 Resist pattern, 20 (From original incident course Off) light, 100 semiconductor device

Claims (5)

A semiconductor substrate;
A light receiving region provided on the semiconductor substrate and performing photoelectric conversion;
An insulating protective film provided on the semiconductor substrate so as to cover the light receiving region;
Reflecting means provided in the protective film and configured to reflect light that travels toward the semiconductor substrate around the light receiving region from the upper side of the light receiving region toward the light receiving region. Semiconductor device.   The reflective means is made of a metal film, and the upper surface side of the protective film is inclined in a direction away from the light receiving region along the protective film as compared with a side closer to the light receiving region. A semiconductor device according to 1. The protective film is
A first protective film provided on the semiconductor substrate and having an opening on the light receiving region;
A second protective film provided on the light receiving region and the first protective film so as to embed the opening,
The inner wall of the opening has an inclined surface that is inclined in a direction away from the light receiving region along the first protective film as compared with a side closer to the light receiving region on an upper surface side of the first protective film,
The semiconductor device according to claim 2, wherein the metal film is provided on the slope of the inner wall. A lens body provided on the protective film above the light receiving region;
The lens body is
4. The semiconductor device according to claim 1, wherein the semiconductor device has a function of refracting light incident on the lens body from the outside toward the light receiving region. 5. Forming a light receiving region for performing photoelectric conversion on a semiconductor substrate;
Forming an insulating protective film on the semiconductor substrate so as to cover the light receiving region;
Forming a reflection means in the protective film for reflecting light traveling from the upper side of the light receiving region toward the semiconductor substrate around the light receiving region to the light receiving region side. Device manufacturing method.

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