JP2005311015A - Solid-state imaging device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the influence of multiplex interference and reflection to a light-receiving portion, while avoiding the problem in shape controllability and the problem of increase in the capacity, when a Cu wiring and a Cu diffusion preventing film are provided in multilayered wiring. <P>SOLUTION: An antireflection film 113 is provided on a silicon substrate 111 in which a photodiode 112 is formed. On the film, a multilayered wiring layer is constituted by stacking interlayer films 115, 122, 132, and 142, Cu wiring films 116, 123, and 133, and Cu diffusion preventing films 121, 131, and 141. On the multilayered wiring layer, a protection film 161, a color filter 162, and a microlens 163 are formed. By removing the Cu diffusion preventing films at a region above the light-receiving region of the photodiode, a region arranged on the light-receiving region of the multilayered wiring layer is allowed to be formed with only a silicon oxide film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid-state imaging device such as a CCD image sensor or a CMOS image sensor and a manufacturing method thereof, and more particularly to a solid-state imaging device effective when a copper wiring is used as a wiring and a manufacturing method thereof.

In recent years, in this type of solid-state imaging device, the number of pixels and the size of pixels have been reduced, and the wiring used has been changed from Al wiring to Cu wiring (see, for example, Patent Document 1). ).
FIG. 14 is a cross-sectional view showing an example of a laminated structure around a light receiving portion in a conventional solid-state imaging device.
A plurality of photodiodes 312 that perform photoelectric conversion are formed in an upper layer of the silicon substrate 311, for example, in a two-dimensional array, and an SiN film 313 and a poly interlayer film 314 are disposed on the upper surface of the silicon substrate 311, on which A Cu first wiring 316 and a first wiring interlayer film 315 are arranged.
A first diffusion prevention film 321, a second wiring interlayer film 322, and a Cu second wiring 323 are disposed thereon, and further, a second diffusion prevention film 331, a third wiring interlayer film 332, and a Cu wiring are disposed thereon. A third wiring 333 is arranged to constitute a multilayer wiring layer. Further thereon, a third diffusion preventing film 341 and an interlayer film 342 are disposed, and an SiN protective film 361, a color filter 362, and a microlens 363 are disposed thereon.
Note that SiO ₂ is used for the interlayer films 315, 322, 332, and 342, and SiC films are used for the diffusion prevention films 321, 331, and 341.

As shown in FIG. 14, when Cu wiring is applied, since the diffusion coefficient of Cu in the oxide film is large, it is necessary to form a layer for preventing diffusion of Cu.
In general, a barrier metal composed of Ta or TaN is formed on the bottom and side surfaces of the wiring, and a SiN film or a SiC film is formed on the upper layer of the wiring.
Accordingly, as shown in FIG. 14, when a multilayer Cu wiring is applied to a solid-state imaging device, a normal interlayer film and a SiN film or SiC film as a Cu diffusion prevention film are configured in a multilayer in the light receiving portion. Become.
Japanese Patent Laid-Open No. 11-121725

However, in the conventional solid-state imaging device, a layer having a different refractive index is laminated on the light receiving portion (photodiode) of the silicon substrate, which means that reflection at the interface of each interlayer film (for example, the arrow shown in FIG. 14). Line 371) and multiple interference (for example, arrow 372 shown in FIG. 14) may cause a decrease in the amount of incident light to the light receiving unit and noise generation.
Forming an interlayer film with the same material as the Cu diffusion barrier film is advantageous from the viewpoint of multiple interference. For example, the shape controllability in a dual damascene process or the dielectric constant of the interlayer film The problem of an increase in wiring capacity due to an increase in rate occurs.

  Therefore, the present invention can reduce the influence of reflection and multiple interference on the light receiving portion without matching the materials of the respective films even when a diffusion prevention film or the like is provided in the multilayer wiring, for example, improving the light amount and reducing the noise. It is an object of the present invention to provide a solid-state imaging device that can be realized and a manufacturing method thereof.

In order to achieve the above-described object, a solid-state imaging device according to the present invention includes a semiconductor substrate on which a light receiving portion that performs photoelectric conversion is formed, and a plurality of wiring films and interlayers that are stacked on the surface of the semiconductor substrate facing the light receiving portion. A multilayer wiring layer including an insulating film; and an upper layer stacked on the multilayer wiring layer. The multilayer wiring layer has a region disposed on a light receiving region of the light receiving unit. It is characterized by being formed of a film having a single refractive index different from the refractive index of at least one film included in the multilayer wiring layer.
The manufacturing method of the present invention also includes a multilayer wiring including a semiconductor substrate having a light receiving portion for performing photoelectric conversion, and a plurality of wiring films and an interlayer insulating film laminated on the surface of the semiconductor substrate facing the light receiving portion. A solid-state imaging device having a layer and an upper layer stacked on an upper layer of the multilayer wiring layer,
In the step of forming the multilayer wiring layer, the region disposed on the light receiving region of the light receiving unit is a film having a single refractive index different from the refractive index of at least one film included in the multilayer wiring layer. It is characterized by forming.

According to the solid-state imaging device and the method of manufacturing the same of the present invention, in the multilayer wiring layer stacked on the semiconductor substrate, the region disposed on the light receiving region of the light receiving unit is formed by a film having a single refractive index. Therefore, it is possible to reduce the influence of reflection on the light receiving unit and multiple interference, and it is possible to improve the light amount and reduce the noise.
In addition, since the film having a single refractive index has a refractive index different from that of, for example, the diffusion prevention film included in the multilayer wiring layer, it is not necessary to match the interlayer film with the diffusion prevention film. For example, it is possible to easily perform processing without causing problems of shape controllability in a damascene process and an increase in wiring capacity due to an increase in relative dielectric constant of an interlayer film.
As a result, even when a diffusion prevention film or the like is provided in the multilayer wiring, for example, the effects of reflection on the light receiving unit and multiple interference can be reduced without matching the materials of each film, improving the light quantity and reducing noise. There is an effect that it is possible to provide a highly sensitive solid-state imaging device that can be realized.

In the embodiment of the present invention, an antireflection film is provided on a silicon substrate on which a photodiode (light receiving portion) is formed, and an interlayer film made of a silicon oxide film, a wiring film made of Cu, and a Cu diffusion prevention film made of SiC are laminated thereon. The multilayer wiring layer is formed, and upper layers such as a protective film, a color filter, and a microlens are formed thereon.
Then, by removing the Cu diffusion preventing film in the upper region of the light receiving region of the photodiode, the region disposed on the light receiving region of the multilayer wiring layer has a single refractive index different from that of the Cu diffusion preventing film. It is formed by a silicon oxide film.
As this manufacturing method, each time a Cu diffusion prevention film is formed, a method is used in which a region corresponding to the light receiving region of the Cu diffusion prevention film is opened and the next film is laminated, or a multilayer is formed. After forming the wiring layer, it is possible to use a method in which an opening recess that penetrates the multilayer wiring layer is formed in a region corresponding to the light receiving region, and a new insulating film is embedded in the opening recess.

FIG. 1 is a cross-sectional view showing a laminated structure around a light receiving portion in a solid-state imaging device according to Embodiment 1 of the present invention. It should be noted that in the description of the present embodiment and the respective drawings, detailed configurations such as element regions and element isolation regions formed on the silicon substrate are omitted for the sake of simplicity.
A plurality of photodiodes (light receiving portions) 112 that perform photoelectric conversion are formed in an upper layer of a silicon substrate (semiconductor substrate) 111, for example, in a two-dimensional array, and an SiN film 113 and a poly interlayer film are formed on the upper surface of the silicon substrate 111. 114 is arranged, and a first wiring 116 and a first wiring interlayer film 115 are arranged thereon.
A first diffusion prevention film 121, a second wiring interlayer film 122, and a second wiring 123 are disposed thereon, and further, a second diffusion prevention film 131, a third wiring interlayer film 132, and a third wiring 133 are disposed thereon. The third diffusion prevention film 141 and the interlayer film 142 are arranged thereon to form a three-layer wiring layer (generally referred to as a multilayer wiring layer).
Further, an SiN protective film 161, a color filter 162, and a microlens 163 are disposed as upper layers thereon.
In this example, all the wirings 116, 123, 133 are Cu wirings, and the film thickness is 200 nm in all layers. The interlayer films 115, 122, 132, 142 are all made of SiO ₂ , and the film thickness is 150 nm for the first wiring interlayer film 115, about 450 nm for the second and third wiring interlayer films 122, 132, and the upper interlayer film. 142 is about 150 nm. Each of the diffusion prevention films 121, 131, and 141 is a SiC film, and the film thickness is all 50 nm. Further, the poly interlayer film 114 is 450 nm, and the film thickness of the SiN film 113 is 50 nm.

In the solid-state imaging device of this embodiment, as shown in the figure, each diffusion prevention film 121, 131, 141 is formed with each diffusion prevention film in a state where the conventional example shown in FIG. 14 covers the entire multilayer wiring layer. Unlike the case, an opening corresponding to the light receiving region of the photodiode 112 is provided. Note that the openings of the diffusion prevention films 121, 131, and 141 are located on the inner side of the wirings 116, 123, and 133.
For this reason, the diffusion preventing films 121, 131, 141 made of SiC are not arranged on the light receiving region of the photodiode 112, but the interlayer films 115, 122 made of the SiN film 113, the poly interlayer film 114, the SiO ₂ film, 132, 142, a SiN protective film 161, a color filter 162, and a microlens 163 are arranged.
Therefore, in this solid-state imaging device, compared to the solid-state imaging device shown in FIG. 14, it is possible to suppress the variation in the refractive index of each layer in the upper layer region of the light receiving unit, and to reduce the influence of reflection on the light receiving unit and multiple interference, It becomes possible to improve the amount of light and reduce the noise.

Next, a method for manufacturing the solid-state imaging device of this embodiment will be described.
2-7 is sectional drawing explaining the manufacturing method of a present Example.
First, in FIG. 2, a SiN film 113, a poly interlayer film 114, a first wiring 116, and a first wiring interlayer film 115 are formed on a silicon substrate 111 on which a photodiode 112 is formed, and a first diffusion prevention film is formed thereon. At the stage where the entire surface 121 is formed, a resist 151 serving as a mask for forming an opening corresponding to the light receiving region is formed in the first diffusion prevention film 121 using a lithography technique.
Then, in FIG. 3, the Cu diffusion prevention film 121 is processed by the RIE technique, and the resist 151 is peeled off by the ashing technique and the post-processing technique, thereby forming an opening corresponding to the light receiving region in the first diffusion prevention film 121. . Next, in FIG. 4, the second wiring interlayer film 122 is laminated by, for example, the CVD method. At this time, a step may occur in the second wiring interlayer film 122 due to the effect of the step generated by removing the Cu diffusion prevention film 121 on the light receiving region. Therefore, in this example, after the upper surface of the second wiring interlayer film 122 is planarized by CMP in FIG. 5, the second wiring 123 is embedded in the upper surface of the second wiring interlayer film 122 in FIG. In this example, planarization is performed by the CMP method, but this is not always necessary. In addition, when the second wiring interlayer film is formed of a coating material, there is a high possibility that no step is generated, and thus such a process is unnecessary.
Thereafter, in FIG. 7, after the second Cu diffusion prevention film 131 is formed on the entire surface, the same steps as described in FIGS. 2 to 6 are repeated to form Cu diffusion prevention films 131 and 141 having openings, respectively. After that, the upper protective film 161, the color filter 162, and the microlens 163 are formed in the same process as the conventional one, and finally the solid-state imaging device shown in FIG. 1 is created.

  In this embodiment, an example in which a manufacturing method by a general via first method is applied will be described, and a manufacturing method by a dual damascene method will not be described, but these can be appropriately applied. The SiN film 113 functions as an antireflection layer from the silicon substrate 111. However, the SiN film 113 is deleted, and the interlayer insulating film on the lower layer side of the uppermost SiN film is made a single refracting layer on the light receiving region. It is also possible to have a structure having a rate. Further, in this type of solid-state imaging device, a color filter and a microlens are not necessarily required, and can be similarly applied to a structure in which these are not provided.

FIG. 8 is a cross-sectional view showing a laminated structure around the light receiving portion in the solid-state imaging device according to Embodiment 2 of the present invention. It should be noted that in the description of the present embodiment and the respective drawings, detailed configurations such as element regions and element isolation regions formed on the silicon substrate are omitted for the sake of simplicity.
A plurality of photodiodes (light receiving portions) 212 that perform photoelectric conversion are formed in a two-dimensional array, for example, on the upper layer of the silicon substrate 211, and the SiN film 213 and the poly interlayer film 214 are disposed on the upper surface of the silicon substrate 211. The first wiring 216 and the first wiring interlayer film 215 are disposed thereon.
A first diffusion prevention film 221, a second wiring interlayer film 222, and a second wiring 223 are disposed thereon, and further, a second diffusion prevention film 231, a third wiring interlayer film 232, and a third wiring 233 are disposed thereon. Are arranged to constitute a multilayer (three layers) wiring layer. Further thereon, a third diffusion prevention film 241 and an interlayer film 242 are disposed, and an SiN protective film 261, a color filter 262, and a micro lens 263 are disposed thereon. Note that the material and thickness of each film are the same as those in the first embodiment.
In the solid-state imaging device of the present embodiment, an opening recess 252 corresponding to the light receiving region of the photodiode 212 is formed from the lowermost first diffusion prevention film 221 to the upper interlayer film 242, and this opening recess 252. An insulating film 253 is embedded in the inside. That is, in this embodiment, by providing such an optical waveguide, variation in the refractive index of the upper layer of the photodiode 212 can be suppressed, the influence of reflection on the light receiving unit and multiple interference can be reduced, and the amount of light can be improved. Noise can be reduced.

Next, a method for manufacturing the solid-state imaging device of this embodiment will be described.
9-12 is sectional drawing explaining the manufacturing method of a present Example.
First, in FIG. 9, an opening recess 252 penetrating the multilayer wiring layer is formed on the silicon substrate 111 on which the photodiode 112 is formed by the same manufacturing method as before until the uppermost interlayer film 242 is formed. A resist 251 serving as a mask for formation is patterned using a lithography technique.
Next, in FIG. 10, using this resist as a mask, the multilayer film on the light receiving region is processed so as to be removed up to the first Cu diffusion prevention film 221 by the RIE technique, and is processed by the ashing technique and the post-processing technique. In this embodiment, the first Cu diffusion prevention film 221 is processed, but it may be further processed up to the lower layer and exposed to the silicon substrate 211.
Next, in FIG. 11, an insulating film 253 is embedded in the opening recess 252 by, for example, HDP-CVD. At this time, the insulating film 253 is desired to be a film transparent to visible light, and is preferably a film having the same refractive index as that of the first wiring interlayer film 215 and the poly interlayer film 214. In this example, a SiO ₂ film was used. When the opening recess 252 is formed up to the silicon substrate 211 or the SiN film 213, the buried insulating film 253 is not necessarily limited to a material having the same refractive index as that of the first wiring interlayer film 215 and the poly interlayer film 214. .
Next, as shown in FIG. 12, the insulating film 253 formed on the interlayer film 242 is removed by CMP and planarized.
Thereafter, a process of forming a protective film 261 of SiN, a color filter 262, and a microlens 263 is performed to complete the solid-state imaging device shown in FIG.

Also in this embodiment, the microlens is not necessarily required, and the SiN film 213 that functions as an antireflection layer from the silicon substrate 211 exists on the light receiving portion, but this SiN film 213 is deleted, On the light receiving portion, the interlayer insulating film below the uppermost SiN protective film 261 may have a structure having a single refractive index.
Further, in this embodiment, the transparent insulating film is formed in the optical waveguide by the HDP-CVD method, but may be applied by a coating method. Further, if planarization can be realized at the same time by the coating method, the above-described planarization process by the CMP method can be eliminated.

FIG. 13 is a cross-sectional view showing a laminated structure around a light receiving portion in a solid-state imaging device according to Embodiment 3 of the present invention. Note that the third embodiment is a modification of the second embodiment, and in FIG. 13, the same components as those in the solid-state imaging device shown in FIG.
In Example 2 described above, the opening recess 252 is formed on the light receiving region of the photodiode, and the insulating film 253 is buried by the HDP-CVD method and planarized by CMP. A material having a refractive index higher than that of the insulating film 253, for example, a SiN film 254 is formed on the buried insulating film 253, and etch back or CMP is performed so that the SiN film 254 remains only above the light receiving region. As shown in FIG. 13, a concave lens made of the SiN film 254 was formed so that the light was efficiently condensed on the waveguide of the insulating film 253. The rest of the configuration is the same as that of the second embodiment, and a description thereof will be omitted.

It is sectional drawing which shows the laminated structure around the light-receiving part in the solid-state image sensor by Example 1 of this invention. It is sectional drawing which shows the manufacturing method of the solid-state image sensor shown in FIG. It is sectional drawing which shows the manufacturing method of the solid-state image sensor shown in FIG. It is sectional drawing which shows the manufacturing method of the solid-state image sensor shown in FIG. It is sectional drawing which shows the manufacturing method of the solid-state image sensor shown in FIG. It is sectional drawing which shows the manufacturing method of the solid-state image sensor shown in FIG. It is sectional drawing which shows the manufacturing method of the solid-state image sensor shown in FIG. It is sectional drawing which shows the laminated structure around the light-receiving part in the solid-state image sensor by Example 2 of this invention. It is sectional drawing which shows the manufacturing method of the solid-state image sensor shown in FIG. It is sectional drawing which shows the manufacturing method of the solid-state image sensor shown in FIG. It is sectional drawing which shows the manufacturing method of the solid-state image sensor shown in FIG. It is sectional drawing which shows the manufacturing method of the solid-state image sensor shown in FIG. It is sectional drawing which shows the laminated structure around the light-receiving part in the solid-state image sensor by Example 2 of this invention. It is sectional drawing which shows the laminated structure around the light-receiving part in the conventional solid-state image sensor.

Explanation of symbols

  111... Silicon substrate, 112... Photodiode (light receiving portion), 113... SiN film, 114... Poly interlayer film, 115, 122, 132. 131, 141... Diffusion prevention film, 142... Interlayer film, 161... SiN protective film, 162... Color filter, 163.

Claims (15)

A multi-layer wiring layer including a semiconductor substrate on which a light-receiving portion for performing photoelectric conversion is formed; a plurality of wiring films and an interlayer insulating film stacked on a surface of the semiconductor substrate facing the light-receiving portion; and the multi-layer wiring layer An upper layer laminated on the upper layer,
The multilayer wiring layer is formed of a film having a single refractive index different from a refractive index of at least one film included in the multilayer wiring layer in a region disposed on the light receiving region of the light receiving unit. Yes,
A solid-state imaging device.   The solid-state imaging device according to claim 1, wherein at least one film included in the multilayer wiring layer is removed in a region corresponding to a light receiving region of the light receiving unit.   2. The solid-state imaging device according to claim 1, wherein the at least one film included in the multilayer wiring layer includes a diffusion preventing film for preventing diffusion of the wiring film.   The solid-state imaging device according to claim 1, wherein the upper layer includes a color filter and a microlens.   The solid-state imaging device according to claim 1, wherein a protective film having a refractive index different from the film having the single refractive index is disposed between the multilayer wiring layer and the upper layer.   6. The solid-state imaging device according to claim 5, wherein the film having a single refractive index is made of a silicon oxide film, and the protective film is made of a silicon nitride film.   An antireflection film having a refractive index different from that of the film having a single refractive index and preventing reflection from the semiconductor substrate is disposed between the semiconductor substrate and the multilayer wiring layer. The solid-state imaging device according to claim 1.   8. The solid-state imaging device according to claim 7, wherein the film having a single refractive index is made of a silicon oxide film, and the antireflection film is made of a silicon nitride film.   4. The solid-state imaging device according to claim 3, wherein the wiring film is made of a Cu film, and the diffusion prevention film is made of a SiC film. A multi-layer wiring layer including a semiconductor substrate on which a light-receiving portion for performing photoelectric conversion is formed; a plurality of wiring films and an interlayer insulating film stacked on a surface of the semiconductor substrate facing the light-receiving portion; and the multi-layer wiring layer A method of manufacturing a solid-state imaging device having an upper layer stacked on an upper layer of
In the step of forming the multilayer wiring layer, the region disposed on the light receiving region of the light receiving unit is a film having a single refractive index different from the refractive index of at least one film included in the multilayer wiring layer. Form,
A method for manufacturing a solid-state imaging device.   In forming the multilayer wiring layer, when forming at least one film included in the multilayer wiring layer, the multilayer wiring layer is formed in a pattern having an opening in a region corresponding to a light receiving region of the light receiving unit. The manufacturing method of the solid-state image sensor of Claim 10.   In the formation step of the multilayer wiring layer, after the multilayer wiring layer is laminated and formed, an opening recess that penetrates the multilayer wiring layer is formed in a region corresponding to the light receiving region of the light receiving unit, and the inside of the opening recess The method for manufacturing a solid-state imaging device according to claim 10, wherein a film having a single refractive index is embedded in the film.   11. The method for manufacturing a solid-state imaging device according to claim 10, wherein the at least one film included in the multilayer wiring layer includes a diffusion preventing film for preventing diffusion of the wiring film.   11. The method of manufacturing a solid-state imaging device according to claim 10, wherein the film having a single refractive index is made of a silicon oxide film.   14. The method of manufacturing a solid-state imaging device according to claim 13, wherein the wiring film is made of a Cu film, and the diffusion prevention film is made of a SiC film.

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