JP4848876B2 - Solid-state imaging device cover and solid-state imaging device - Google Patents

Description

  The present invention relates to a solid-state imaging device cover and a solid-state imaging device, and more particularly, to a solid-state imaging device cover that protects a solid-state imaging device housed in a package constituting the solid-state imaging device.

  The above-described solid-state imaging device is used in, for example, a digital still camera, and receives a solid-state imaging device that receives incident light of an object, a package that houses the solid-state imaging device, and a solid-state imaging device that is fixed to the package outside (for example, A solid-state image sensor cover that protects against dust and the like. The solid-state image sensor cover is made of glass as described in Patent Document 1, for example.

  In addition, when receiving incident light by the solid-state imaging device, an anti-reflection (AR) film as described in Patent Document 2, for example, is provided on the solid-state imaging device cover in order to prevent a decrease in light amount due to surface reflection. A film is formed. As the antireflection film, for example, a laminated thin film having a five-layer structure having a mixed oxide layer mainly composed of titanium (Ti) and lanthanum (La) is used. These laminated thin films are formed by using, for example, a vacuum heating vapor deposition method.

Specifically, as shown in FIG. 4, in order from the substrate 111 side, a magnesium fluoride film 112 (MgF ₂ , a refractive index n1 = 1.385, a film thickness d1 = 25.8 nm), an aluminum oxide film 113 (Al ₂ O). ₃ , refractive index n2 = 1.820, film thickness d2 = 98.0 nm), titanium and lanthanum mixed oxide film 114 (refractive index n3 = 2.100, film thickness d3 = 11.4 nm), silicon oxide film 115 ( SiO ₂ , refractive index n4 = 1.480, film thickness d4 = 17.5 nm) and magnesium fluoride film 116 (MgF ₂ , refractive index n5 = 1.385, film thickness d5 = 75.5 nm) are formed. Yes. The total film thickness of these films (antireflection film 101) is 338.2 nm. Further, the reflection characteristics indicating the relationship between the wavelength and the reflectance are as shown in the graph of FIG. The horizontal axis indicates the wavelength (nm), and the vertical axis indicates the reflectance (%).

JP-A-9-69618 JP 2000-227504 A

  However, in recent years, since glass is used for the solid-state image sensor cover, α-rays are generated from heavy metals contained in the glass, and the α-rays adversely affect the solid-state image sensor, resulting in deterioration of characteristics. There was a problem. Further, when the magnesium fluoride films 112 and 116 constituting the antireflection film 101 are formed, since the melting points of the magnesium fluoride films 112 and 116 are low (for example, 1260 ° C.), it is difficult to control the heating, and the vaporization is completely performed. It may evaporate without being attached and may adhere to the substrate 111 or the like in a solid state. As a result, there is a problem that a point defect such that light does not transmit to a portion adhered in a solid state occurs, resulting in a poor appearance. In addition, since the antireflection film 101 has a five-layer structure and the number of film forming steps is relatively large, there is a high possibility that dust or the like is included in the film forming. In addition, since it has a five-layer structure and the total film thickness is relatively thick, the amount of impurities contained in the film material increases, resulting in a problem of poor appearance.

  The present invention solves the problems as described above, and provides a solid-state image sensor cover and a solid-state image pickup device that can suppress the adverse effects on the solid-state image sensor and can suppress the appearance failure. With the goal.

In order to solve the above problems, the solid-state imaging device cover according to the present invention is a solid-state imaging device cover fixed to the package in order to protect the solid-state image pickup element housed in a package, wherein the solid-state imaging device The cover is a Z-cut quartz plate that is cut perpendicular to the optical axis of the quartz crystal .

According to this configuration, since the Z-cut quartz plate is used for the solid-state image sensor cover, α rays generated from heavy metals contained in the glass have an adverse effect on the solid-state image sensor as in the case where glass is used for the solid-state image sensor cover. Can be prevented. Thereby, incident light (optical image) that has passed through the solid-state image sensor cover can be received in a normal state by the solid-state image sensor.
Furthermore, since the solid-state imaging device cover is a Z-cut quartz plate having a refractive index (ns) of 1.53, birefringence due to the ordinary light refractive index and the extraordinary light refractive index does not occur. Can be emitted without being separated.

In the solid-state imaging device cover according to the present invention, a layer mainly composed of a mixed oxide film of titanium (Ti) and lanthanum (La) and a silicon oxide film (SiO ₂ ) are formed on the main surface of the Z-cut quartz plate. An antireflection film having a four-layer structure composed of a main component layer is formed .

  According to this configuration, an antireflection film having a four-layer structure composed of a mixed oxide film of titanium and lanthanum and a silicon oxide film is formed on the quartz plate. As with the case where it is used, α-rays generated from heavy metals contained in the glass can be prevented from adversely affecting the solid-state imaging device, and the melting point as in the case where magnesium fluoride is used for the antireflection film. It is possible to suppress the appearance defect including point defects due to the low height. Furthermore, by making the antireflection film have a four-layer structure, the film thickness can be made relatively thin and the number of film forming steps can be reduced. Therefore, it is possible to prevent dust and impurities from being included in the antireflection film during film formation, and it is possible to suppress the appearance failure. In addition, the solid-state image sensor can receive incident light close to a normal state that has passed through the solid-state image sensor cover.

In the solid-state imaging device cover according to the present invention, the antireflection film has a four-layer structure in which thin films of a first layer, a second layer, a third layer, and a fourth layer are stacked from the Z-cut quartz plate side. The first layer and the third layer are a mixed oxide film of titanium (Ti) and lanthanum (La), and the second layer and the fourth layer are silicon oxide films (SiO ₂ ). It is characterized by that .

  According to this configuration, since the mixed oxide film of titanium and lanthanum is used for the first layer and the third layer constituting the antireflection film, and the silicon oxide film is used for the second layer and the fourth layer, the antireflection is performed. The appearance defect including point defects due to the low melting point as in the case of using magnesium fluoride for the film can be suppressed. Furthermore, by using a four-layer structure, the film thickness can be made relatively thin and the number of film forming steps can be reduced. Therefore, it is possible to prevent dust and impurities from being included in the antireflection film during film formation, and it is possible to suppress the appearance failure.

  In the solid-state imaging device cover according to the present invention, the refractive index and film thickness of the first layer, the second layer, the third layer, and the fourth layer are set to n1, n2, n3, n4 and d1, d2, d3, respectively. d4 and when the design dominant wavelength is λ0, 0.052λ0 ≦ n1d1 ≦ 0.063λ0, 0.070λ0 ≦ n2d2 ≦ 0.085λ0, 0.432λ0 ≦ n3d3 ≦ 0.528λ0, 0.200λ0 ≦ n4d4 ≦ 0.245λ0 is a characteristic.

  According to this configuration, since the first layer to the fourth layer have the above-described refractive index and film thickness, the reflectance is low (for example, 1.0% or less) in the visible light region (for example, 390 nm to 780 nm). Can be obtained. As a result, it is possible for the solid-state imaging device to receive incident light in which a decrease in the amount of light that has passed through the solid-state imaging device cover (antireflection film and solid-state imaging device) is suppressed.

  In the solid-state imaging device according to the present invention, the solid-state imaging device cover and the package are fixed so that the main surface of the solid-state imaging device cover and the solid-state imaging device housed in the package face each other. Features.

  According to this configuration, since a crystal plate is used for the solid-state image sensor cover, α rays generated from heavy metals contained in the glass adversely affect the solid-state image sensor as in the case where glass is used for the solid-state image sensor cover. Can be prevented. Thereby, incident light (optical image) that has passed through the solid-state image sensor cover can be received in a normal state by the solid-state image sensor.

In the solid-state imaging device, the solid-state imaging device cover includes a layer formed mainly on a mixed oxide film of titanium (Ti) and lanthanum (La) formed on the quartz plate, and a silicon oxide film (SiO _2). And an antireflection film having a four-layer structure composed of a main component.

  According to this configuration, an antireflection film having a four-layer structure composed of a mixed oxide film of titanium and lanthanum and a silicon oxide film is formed on the quartz plate. As with the case where it is used, α-rays generated from heavy metals contained in the glass can be prevented from adversely affecting the solid-state imaging device, and the melting point as in the case where magnesium fluoride is used for the antireflection film. It is possible to suppress the appearance defect including point defects due to the low height. Furthermore, by making the antireflection film have a four-layer structure, the film thickness can be made relatively thin and the number of film forming steps can be reduced. Therefore, it is possible to prevent dust and impurities from being included in the antireflection film during film formation, and it is possible to suppress the appearance failure. In addition, the solid-state image sensor can receive incident light close to a normal state that has passed through the solid-state image sensor cover.

Furthermore, in the above-described solid-state imaging device, the solid-state imaging element cover includes the anti-reflection film, the four layers in which the first layer, the second layer, the third layer, and the fourth layer are stacked from the quartz plate side. The first layer and the third layer are mixed oxide films of titanium (Ti) and lanthanum (La), and the second layer and the fourth layer are silicon oxide films (SiO 2). ₂ ).

  According to this configuration, since the mixed oxide film of titanium and lanthanum is used for the first layer and the third layer constituting the antireflection film, and the silicon oxide film is used for the second layer and the fourth layer, the antireflection is performed. The appearance defect including point defects due to the low melting point as in the case of using magnesium fluoride for the film can be suppressed. Furthermore, by using a four-layer structure, the film thickness can be made relatively thin and the number of film forming steps can be reduced. Therefore, it is possible to prevent dust and impurities from being included in the antireflection film during film formation, and it is possible to suppress the appearance failure.

  Still further, in the solid-state imaging device, in the solid-state imaging device cover, the refractive index and film thickness of the first layer, the second layer, the third layer, and the fourth layer are set to n1, n2, n3, n4. And d1, d2, d3, d4, and when the design dominant wavelength is λ0, 0.052λ0 ≦ n1d1 ≦ 0.063λ0, 0.070λ0 ≦ n2d2 ≦ 0.085λ0, 0.432λ0 ≦ n3d3 ≦ 0. 528λ0 and 0.200λ0 ≦ n4d4 ≦ 0.245λ0.

  According to this configuration, since the first layer to the fourth layer have the above-described refractive index and film thickness, the reflectance is low (for example, 1.0% or less) in the visible light region (for example, 390 nm to 780 nm). Can be obtained. As a result, it is possible for the solid-state imaging device to receive incident light in which a decrease in the amount of light that has passed through the solid-state imaging device cover (antireflection film and solid-state imaging device) is suppressed.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view illustrating a configuration of a solid-state imaging device having a solid-state imaging element cover. Hereinafter, the configuration of the solid-state imaging device will be described with reference to FIG.

  As shown in FIG. 1, the solid-state imaging device 11 is used in, for example, a digital still camera, and receives a solid-state imaging device 12 that receives incident light of an object, a package 13 that stores the solid-state imaging device 12, and a package 13. A solid-state image sensor cover 14 that protects the solid-state image sensor 12 from outside (for example, dust).

  The solid-state imaging device 12 is, for example, a CCD (Charge Coupled Device), and is configured by arranging photoelectric elements (pixels) composed of photodiodes whose storage capacities change according to the intensity of incident light in a matrix. ing. When an object is photographed using the solid-state imaging device 12, the storage capacity on the regularly arranged pixels changes, and by spatially sampling this, an electrical signal corresponding to the object is generated, This is converted to form an image. With such a solid-state imaging device 12, incident light incident through the solid-state imaging device cover 14 is converted into an electrical signal.

  The package 13 accommodates the solid-state image sensor 12 as described above, and is formed in a concave shape in which the upper part of the accommodated solid-state image sensor 12 opens.

  The solid-state image sensor cover 14 is fixed via an adhesive material 15 so as to cover a region where the package 13 is opened. The adhesive material 15 seals between the solid-state image sensor cover 14 and the package 13. The solid-state image sensor cover 14 includes a cover 16 and an antireflection film 20.

  FIG. 2 is a schematic cross-sectional view showing the configuration of the solid-state image sensor cover. Hereinafter, the configuration of the solid-state image sensor cover will be described with reference to FIG.

  As shown in FIG. 2, the solid-state image sensor cover 14 includes the cover 16 and the antireflection film 20 as described above.

  The cover 16 is made of, for example, a Z-cut quartz plate, and is fixed to the package 13 (see FIG. 1) so that the main surface 16a faces the solid-state imaging device 12. A Z-cut quartz plate is a quartz plate that is cut perpendicular to the optical axis. The main surface 16a is a surface in contact with the optical axis, and generally refers to a wide surface of the crystal plate (cover 16). The cover 16 has a thickness of, for example, 0.8 mm. In addition, the refractive index (ns) of the cover 16 (Z-cut quartz plate) is 1.53, and birefringence (depending on the ordinary light refractive index and the extraordinary light refractive index) does not occur.

  The antireflection film 20 has a four-layer structure, and thin films of a first layer 21, a second layer 22, a third layer 23, and a fourth layer 24 are laminated in this order from the cover 16 side. The first layer 21 to the fourth layer 24 are formed by, for example, a vacuum heating vapor deposition method. The design dominant wavelength (λ0) is 580 nm.

  The main component of the first layer 21 is a mixed oxide of Ti (titanium) and La (lanthanum). More specifically, the first layer 21 is an oxide of a mixture of Ti and La and has a refractive index (n1) of 2.000 ± 0.200. The film thickness (d1) is 16.7 nm and the optical film thickness (nd1) is 0.058λ0 nm.

The main component of the second layer 22 is SiO ₂ (silicon oxide film). Specifically, the refractive index (n2) of the second layer 22 is 1.460 ± 0.200, and the film thickness (d2) is 30.8 nm. The optical film thickness (nd2) is 0.078λ0 nm.

  The third layer 23 is a mixed oxide film containing Ti (titanium) and La (lanthanum) as main components. Specifically, the third layer 23 is an oxide of a mixture of Ti and La like the first layer 21 and has a refractive index (n3) of 2.000 ± 0.200. The film thickness (d3) is 139.2 nm and the optical film thickness (nd3) is 0.480λ0 nm.

The main component of the fourth layer 24 is SiO ₂ (silicon oxide film). Specifically, the refractive index (n4) of the fourth layer 24 is 1.460 ± 0.200, and the film thickness (d4) is 88.4 nm. The optical film thickness (nd4) is 0.222λ0 nm. Here, the relationship between the film thickness d and the optical film thickness nd · λ0 at the design principal wavelength λ0 can be expressed as n · d = nd · λ0 using the refractive index n.

  As described above, by using a Z-cut quartz plate for the cover 16, the solid-state imaging device 12 is caused by α rays generated from heavy metals contained in the glass as in the case of using glass for a conventional cover. It can prevent adverse effects.

  Furthermore, the first layer 21 (mixed oxide film of titanium and lanthanum), the second layer 22 (silicon oxide film), the third layer 23 (mixed oxide film of titanium and lanthanum), and the fourth layer 24 (silicon oxide film). By configuring the antireflection film 20 with a four-layer structure, it is possible to prevent appearance defects such as point defects from occurring as in the case of using a magnesium fluoride film as a conventional antireflection film. Furthermore, by forming the antireflection film 20 with a four-layer structure, the total film thickness can be 275.1 nm. Therefore, it can be made thinner than the conventional total film thickness, and the number of film forming steps can be reduced. As a result, it is possible to suppress the amount of dust, impurities, etc. contained in the antireflection film 20 during film formation, and it is possible to suppress the appearance failure.

  FIG. 3 is a graph showing the reflection characteristics (wavelength-reflectance) of the antireflection film. Hereinafter, the reflection characteristics of the antireflection film will be described with reference to FIG.

As shown in FIG. 3, the horizontal axis indicates the wavelength (nm) and the vertical axis indicates the reflectance (%). The solid line A shown in FIG. 3 is the reflection characteristic of the antireflection film 20 of the present embodiment, and the broken line B is the reflection characteristic of the conventional antireflection film. The refractive index and film thickness of the first layer 21, the second layer 22, the third layer 23, and the fourth layer 24 are n1, n2, n3, n4 and d1, d2, d3, d4, and the design dominant wavelength is λ0. If the following expressions (1) to (4) are satisfied, a low reflectance (for example, 1.0% or less) is obtained in almost the entire visible light region (for example, 390 nm to 780 nm). be able to.
(1) 0.052λ0 ≦ n1d1 ≦ 0.063λ0
(2) 0.070λ0 ≦ n2d2 ≦ 0.085λ0
(3) 0.432λ0 ≦ n3d3 ≦ 0.528λ0
(4) 0.200λ0 ≦ n4d4 ≦ 0.245λ0

  As described above, substantially the same reflection characteristics (see the solid line A) can be obtained without degrading the conventional reflection characteristics (see the broken line B). In addition, since the antireflection film 20 having such a configuration and characteristics is formed on the cover 16, it is possible to prevent the quality (light quantity, etc.) of the received incident light from being deteriorated (deteriorated) by the solid-state image sensor cover 14.

  As described above in detail, according to the present embodiment, the following effects can be obtained.

  (1) According to this embodiment, on the cover 16 made of a Z-cut quartz plate, a mixed oxide film layer (first layer 21 and third layer 23) of titanium and lanthanum and a silicon oxide film layer (second) Since the antireflection film 20 having a four-layer structure composed of the layer 22 and the fourth layer 24) is formed, α rays generated from heavy metals contained in the glass are solid as in the case of using glass for the cover. It is possible to prevent adverse effects on the image sensor 12 and suppress appearance defects including point defects due to a low melting point as in the case where magnesium fluoride is used for the antireflection film 20. be able to. Further, by changing the antireflection film 20 from the conventional five-layer structure to the four-layer structure, the total film thickness can be reduced and the number of film forming steps can be reduced. Therefore, it is possible to prevent dust and impurities from being included in the antireflection film 20 during film formation, and it is possible to suppress appearance defects. As a result, the solid-state image sensor cover 14 can suppress the deterioration (deterioration) of the quality of incident light (for example, the amount of light).

  (2) According to the present embodiment, since the first layer 21 to the fourth layer 24 constituting the antireflection film 20 have the refractive index and the film thickness as described above, without reducing the conventional reflection characteristics, A low reflectance (for example, 1.0% or less) can be obtained in the visible light region (for example, 390 nm to 780 nm).

  In addition, this embodiment is not limited above, It can also implement with the following forms.

  (Modification 1) As described above, instead of forming the antireflection (AR) film 20 on the cover 16 made of a Z-cut quartz plate, for example, an infrared (IR) absorption film, ultraviolet ( A UV) absorbing film and an ultraviolet / infrared (UVIR) absorbing film may be formed. According to this, it is possible to obtain the effects using the respective films, and it is possible to prevent the photodiodes caused by α rays from being adversely affected as in the case of using the glass for the cover, similar to the effects described above. .

  (Modification 2) As described above, the solid-state imaging device 12 is not limited to a CCD, and may be, for example, a CMOS (Complementary Metal Oxide Semiconductor), a CPD (Charge Priming Device), or the like.

  (Modification 3) As described above, the cover 16 is not limited to using a Z-cut quartz plate. For example, the normal of the main surface of the quartz plate is 0 ° to the Z axis that is the optical axis of the quartz crystal. You may make it use the quartz plate cut by the angle which becomes the range of 90 degrees. If the cover 16 that is cut at 45 ° (the angle between the normal of the main surface of the crystal plate and the Z axis) is used instead of 0 ° (Z cut), the cut angle of the crystal plate is separated at two points. Can be used as a type of low-pass filter.

1 is a schematic cross-sectional view illustrating a configuration of a solid-state imaging device according to an embodiment of the present invention. The schematic cross section which shows the structure of a solid-state image sensor cover. The graph which shows the reflective characteristic of an antireflection film. The schematic cross section which shows the structure of the conventional antireflection film. The graph which shows the reflective characteristic of the conventional antireflection film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Solid-state imaging device, 12 ... Solid-state image sensor which comprises solid-state imaging device, 13 ... Package which comprises solid-state imaging device, 14 ... Solid-state imaging device cover which comprises solid-state imaging device, 15 ... Adhesion which comprises solid-state imaging device Material: 16 ... Cover constituting the solid-state image sensor cover, 16a ... Main surface, 20 ... Antireflection film constituting the solid-state image sensor cover, 21 ... First layer constituting the anti-reflection film, 22 ... Constructing the anti-reflection film The second layer 23, the third layer constituting the antireflection film 24, the fourth layer constituting the antireflection film 24.

Claims (5)

A solid-state image sensor cover fixed to the package to protect the solid-state image sensor housed in the package,
The solid-state image sensor cover is a Z-cut crystal plate cut perpendicularly to the optical axis of the crystal . The main surface of the Z-cut quartz plate is composed of a layer mainly composed of a mixed oxide film of titanium (Ti) and lanthanum (La) and a layer mainly composed of a silicon oxide film (SiO ₂ ). The solid-state image sensor cover according to claim 1, further comprising an antireflection film having a four-layer structure .   The antireflection film has a four-layer structure in which thin films of a first layer, a second layer, a third layer, and a fourth layer are stacked from the Z-cut quartz plate side,
  The first layer and the third layer are a mixed oxide film of titanium (Ti) and lanthanum (La),
  The second layer and the fourth layer are formed of a silicon oxide film (SiO ₂ The solid-state imaging device cover according to claim 2, wherein The solid-state image sensor cover according to claim 3,
The refractive index and film thickness of the first layer, the second layer, the third layer, and the fourth layer are n1, n2, n3, n4 and d1, d2, d3, d4, and the design dominant wavelength is λ0. And when
0.052λ0 ≦ n1d1 ≦ 0.063λ0,
0.070λ0 ≦ n2d2 ≦ 0.085λ0,
0.432λ0 ≦ n3d3 ≦ 0.528λ0,
0.200λ0 ≦ n4d4 ≦ 0.245λ0,
The solid-state image sensor cover characterized by having a relationship of The main surface of the solid-state image sensor cover according to any one of claims 1 to 4,
The solid-state imaging device, wherein the solid-state imaging device cover and the package are fixed so that the solid-state imaging device housed in the package faces each other.

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