Patent Application
20110220970
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-52450, filed on Mar. 10, 2010, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a solid state imaging device.
A solid state imaging device such as a CCD (Charge Coupled Device) or a CMOS sensor (Complementary Metal Oxide Semiconductor Sensor) is provided with a solid state imaging element. The solid state imaging device is widely used for a cellular phone, a camera, a video camera or a personal computer. With miniaturization and high functionalization of these electronic equipments, miniaturization and high performance have been required with respect to the solid state imaging device.
In a solid state imaging device, in order to promote miniaturization, a penetration electrode may be provided in a semiconductor substrate in which a solid state imaging element is formed. The penetration electrode connects a principal surface of the semiconductor substrate, in which the solid state imaging element is formed, with a back-surface on its opposite side, electrically. An interconnection is led out from the principal surface to the back-surface.
A first electrode is formed on the semiconductor substrate on the back-surface side, and a second electrode is formed on a mount substrate. A solder ball connects the first electrode with the second electrode directly. A silicon substrate may be used as the semiconductor substrate.
The thickness of the semiconductor substrate is thinly formed to be about 100 μm in many cases, in consideration of the throughput at the time of forming the penetration electrode. As the semiconductor substrate becomes thinner, the quantity of infrared light incident into the solid state imaging element from the back-surface increases more so that the problem of causing photographing in the element occurs.
JP 2009-99591A discloses a solid state imaging device provided with a light intercepting layer on a back-side surface of a semiconductor substrate in which a solid state imaging element is formed. In the light intercepting layer, particles of a material such as carbon or pigment are distributed.
The light intercepting layer of the solid state imaging device presents an effect of intercepting visible light as well as an effect of intercepting incident infrared light from the back-side surface. Therefore, as the light intercepting layer is thickened more so as to enhance the effect of intercepting infrared light, the effect of intercepting visible light increases more. As a result, the alignment between the semiconductor substrate and a transfer mask using visible light can not be ensured so that the manufacturing yield may be reduced.
According to one embodiment, a solid state imaging device having a semiconductor substrate is provided. The semiconductor substrate has first and second principal surfaces opposite to each other. The semiconductor substrate has a penetration hole extending from the first principal surface to the second principal surface. An imaging element portion is formed on the first principal surface side. A first insulating film is formed on the first principal surface side.
An interconnection electrode is formed in the first insulating film and connected to the imaging element portion. A second insulating film is provided to cover the surface of the penetration hole and the second principal surface except at least a portion facing the interconnection electrode. The second insulating film contains particles and is configured to intercept an infrared ray and to transmit a visible light. A conductor film contacts the interconnection electrode and is formed on the second insulating film. The conductor film is led out on a side of the second principal surface.
According to another embodiment, a solid state imaging device having a semiconductor substrate is provided. The semiconductor substrate has first and second principal surfaces opposite to each other. The semiconductor substrate has a penetration hole extending from the first principal surface to the second principal surface. An imaging element portion is formed on the first principal surface side. A first insulating film is formed on the first principal surface side.
An interconnection electrode is formed in the first insulating film and connected to the imaging element portion. A second insulating film is provided to cover a surface of the penetration hole and the second principal surface except at least a portion facing the interconnection electrode. A conductor film is formed to cover the second insulating film and to contact the interconnection electrode and to be led out on a side of the second principal surface. A third insulating film covers the conductor film. The third insulating film is configured to intercept an infrared ray and to transmit a visible light.
Hereinafter further embodiments will be described with reference to the drawings. In the drawings, the same numerals denote the same or similar portions respectively.
In the following, a surface of a semiconductor substrate existing on a side where an imaging element is formed is mentioned as “a principal surface”, simply, or “a first principal surface”, and a surface of the semiconductor substrate existing on the opposite side is mentioned as “a back surface” or “a second principal surface”.
A solid state imaging device according to a first embodiment will be described with reference to
As shown in
The optical lens 51 is fixed to a lens holder 53 which is made of a light intercepting material. Adhesion materials 41, 45 and 49 fix the solid state imaging device 5, the glass substrate 43, the light filter 47 and the lens holder 53 respectively in this order. A light intercepting plate 57 is fixed to a side surface of the lens holder 53 via an adhesion material 55.
The light intercepting plate 57 covers side surfaces of the solid state imaging device 5, the glass substrate 43 and the light filter 47. The light intercepting plate 57 intercepts unnecessary light which enters into the solid state imaging device 5 from the side surfaces. Infrared light unnecessary for imaging proceeds to enter from a side of an object to be photographed. The light filter 47 has an effect of intercepting the infrared light unnecessary for imaging. The solid imaging device 5 has plural solder balls 31 disposed in array as external terminals. The solder balls 31 are formed on the back surface, i.e., on a surface on a lower side of the semiconductor substrate 11.
As shown in
The insulating film 23 covers an inner surface of a penetration hole 21 and the second principal surface. The penetration hole 21 extends from the first principal surface to the second principal surface of the semiconductor substrate 11. The insulating film 23 contains particles 65 shown in
The imaging element portion 13 includes CMOS sensors, for example. The imaging element portion 13 is formed in the surface region of the semiconductor substrate 11 by a well-known manufacturing process. The imaging element portion 13 is connected to the interconnection electrode 16. On the interlayer insulating film 15, micro lenses 19 are formed. The micro lenses 19 introduce incidence light for imaging to the imaging element portion 13 efficiently.
The penetration hole 21 of the semiconductor substrate 11 has a taper shape. The opening diameter of the taper shape is large on the lower side and small on the upper side. The penetration hole 21 penetrates the semiconductor substrate 11 in an up and down direction, and reaches the interlayer insulating film 15. An upper end of the insulating film 23 is projected to an inside of the penetration hole 21 in an opening diameter direction in order to form a projection portion. By the projection portion, the insulating film 23 contacts the interlayer insulating film 15 more certainly. When the thickness of the insulating film 23 is large enough, the projection portion is not always formed.
As shown in
The particles 65 have a spherical or oval-spherical shape, and have an average particle diameter of about 20 nm. The insulating films 67 are a silicon oxide film, for example. The insulating films 67 coat the particles 65 so as to avoid direct contact of the particles with each other. The particles 65 have large and small particle diameters so far as they are shown in the sectional view of
Return to
A portion of the conductor film 25 is patterned on the side of the second principal surface of the semiconductor substrate 11 to form an interconnection electrode. The interconnection electrode is connected to the conductor film 25 and is led out to the lower surface of the semiconductor substrate 11. The conductor film 25 may be composed of a seed layer of titanium (Ti) or copper (Cu) and a metal film of copper, for example, which is coated on the seed layer by plating.
The insulating film 23 and the conductor film 25 are covered by a solder resist film 27. Openings are opened at portions of the solder resist film 27 on the second principal surface film 27. In the openings, the solder balls 31 to be connected to the conductor film 25 are provided respectively. The solder balls 31 are also connected with electrodes (not illustrated) of a mount substrate 59, when the solid state imaging device 5 is used as electronic equipment.
A method of manufacturing the solid state imaging device 5 will be described with reference to the sectional views shown in
As shown in
The semiconductor substrate 11 is wafer-shaped. A back-side surface (an upper-side surface in
On the back-side surface of the semiconductor substrate 11, a resist film (not illustrated) is formed via an oxide film, for example. The resist film is patterned by a selective exposure and a selective etching so as to correspond to an opening of a penetration hole 21 to be formed.
The penetration hole 21 is formed in the flat semiconductor substrate 11 to extend from the back-side surface. The penetration hole 21 is formed using the patterned resist film as a mask, by a RIE (Reactive Ion Etching) method. For the selective exposure of the patterned resist film, an apparatus such as a double-sided aligner or a double-sided stepper is employed. In the apparatus, an infrared light is radiated from the back surface side via the substrate 11 to the principal surface side.
Using the infrared light, alignment of a glass mask (not shown) is performed to an alignment mark (not shown) which is provided on the principal surface side (a lower side in
Desirably, the penetration hole 21 is formed in such a tapered shape as the hole 21 becomes narrower gradually as the penetration hole 21 extends in a direction of the interlayer insulating film 15. The hole 21 becomes narrower gradually as the penetration hole 21 extends from the opening formed on the back surface side of the semiconductor substrate 11. The resist film is removed after forming the penetration hole 21, and a residual substance produced by the RIE is removed if necessary.
As shown in
The solvent volatilizes by calcination finally, and an insulating film 23 with the particles 65 distributed in the resin 69 is obtained. The quantity of the particles 65 to be distributed and the film thickness of the insulating film 23 to be applied are arranged according to the transmission rate of an infrared ray to be intercepted.
As shown in
In stead of the above method where the holes are formed using the patterned resist film as a mask, the following method may be employed. In the method, a photosensitive resin is used as the resin 69 constituting the insulating film 23. The insulating film 23 is patterned, and a hole is opened in the interlayer insulating film 15 by using the patterned insulating film as a mask.
The insulating film 23 is substantially transparent to a visible light (400-800 nm) as shown by the curve “a”. This enables alignment of a glass mask accurately by detecting a mark reflective for the visible light and provided on the semiconductor substrate 11, for example. The alignment is performed using the visible light which is transmitted through the substrate 11. The glass mask has a pattern to be transferred, and is arranged closely to the surface of the resist film formed on the semiconductor substrate 11. As a result, positional error of the glass mask in plane (XY) and rotation directions can be corrected accurately. Since the alignment using visible light can be performed by a well-known alignment method, increase of the number of manufacturing steps is suppressed.
Then, as shown in
Then, the above resist film is removed. A portion of the seed layer which does not contact the penetration electrode and the interconnection is further removed by a wet processing, for example. By removing the portion of the seed layer, a portion of the insulating film 23 is exposed.
As shown in
As shown in
As shown in
In the camera module 1, a light which enters through the optical lens 51 from an object to be photographed is received by an imaging element portion 13 of
The effect of intercepting an infrared light which proceeds to enter from the back surface of the semiconductor substrate 11 will be explained. The infrared light is intercepted in the solid state imaging device 5. The solid state imaging device 5 is incorporated in the camera module 1 and has the insulating film 23 which intercepts infrared ray.
As shown in
The sunlight is a light which has a distribution in an ultraviolet area, a visible area and an infrared area. The semiconductor substrate 11 of silicon has a band gap wavelength of 1.11 μm, and has a characteristic easy to transmit an infrared ray adjacent to the visible area. The infrared light goes through the semiconductor substrate 11 of an about 100 μm thickness, reaches the imaging element portion 13, and becomes an obstructive light, i.e., a noise light to a light for imaging which enters from a direction of the object to be photographed.
Further, as shown by the curve “b” in
On the other hand, the insulating film 23 for intercepting infrared ray contains the particles of the oxide such as the SnO2—Sb2O3 series oxide or In2O3—SnO2 series oxide coated with the insulating films 67, as shown in
The insulating film 23 has a characteristic opposite to that of the semiconductor substrate 11 of the about 100 μm thickness. The transmission rate of incidence light of the semiconductor substrate 11 becomes larger gradually, when the wavelength of the light exceeds approximately 800 nm.
In
Since the insulating film 23 transmits a visible light, alignment of the semiconductor substrate 11 can be performed easily by the visible light in a subsequent manufacturing process of the solid state imaging device 5. Therefore, the positional accuracy of a pattern of the conductor film 25 can be ensured. As a result, the solid state imaging device 5 can be made without dropping manufacturing yield due to inaccurate alignment. Further, manufacturing of the solid state imaging device 5 is difficult to be influenced by an infrared light for alignment use which enters from the back-surface side of the semiconductor substrate 11. Accordingly, the device 5 presents a high performance.
A solid state imaging device according to a modification of the first embodiment will be explained with reference to
As shown in
The solid imaging device 6 is manufactured by steps similar to those of the first embodiment until formation of the solder resist film 27 shown in
The black-color insulating film 71 may be a film made by causing polyimide to contain at least one of carbon particles, inorganic pigment particles or organic pigment particles. The transmission characteristic of the black insulating film 71 for a visible light depends on its thickness.
Further, openings are formed in the solder resist film 27 and in the black-color insulating film 71, by a photolithography method. A solder ball 31 is arranged in the openings, as shown in
As shown by the curve “c” in
In the solid state imaging device 6, the black-color insulating film 71 is thinly formed on the undersurface side of the solder resist film 27. The solid state imaging device 6 may have the same effects as the solid state imaging device 5 of the first embodiment. In addition, the solid state imaging device 6 has an effect of intercepting the light 61 incidence to the back surface side more by adding the black-color insulating film 71.
A solid state imaging device according to a second embodiment will be explained with reference to
As shown in
The solid imaging device 7 is manufactured by steps similar to those of the manufacturing method of the solid state imaging device of the first embodiment until formation of a penetration hole 21 shown in
Then, the following manufacturing steps are employed. The manufacturing steps are similar to the step of
Since the solid state imaging device 7 has the laminated structure of the insulating film 75, insulation of the insulating particles 65 is more effective. Especially, the insulation between the semiconductor substrate 11 and the conductor film 25 is enhanced.
Further, a black-color insulating film may be thinly formed on an outside of the solder resist film 27 of the solid state imaging device 7, like the modification of the first embodiment.
A solid state imaging device according to a third embodiment will be explained with reference to
As shown in
The solid imaging device 8 is manufactured by steps similar to those of the manufacturing method of the solid state imaging device according to the first embodiment until formation of a penetration hole 21 shown in
Further, an insulating film 83 for intercepting infrared ray is formed on the undersurface side of the solder resist film 27 by an applying method. Then, by a photolithography method, openings are formed in the solder resist film 27 and in the insulating film 83 formed on the undersurface side of the film 27. A solder ball 31 is arranged in the openings. Subsequently, the following manufacturing steps are employed. The manufacturing steps are similar to the manufacturing method of the solid state imaging device according to the first embodiment. As a result, the solid state imaging device 8 is completed. Since the insulating film 83 is capable of transmit visible light as the insulating film 23 shown in
Since, in the solid state imaging device 8, the insulating film 83 for intercepting infrared ray covers the whole surface of the solder resist film 27, the device 8 can present effects similar to those of the solid state imaging device 5 of the first embodiment.
A black-color insulating film may be thinly formed further on the undersurface side of the insulating film 83 that is the lowest layer of the solid state imaging device 8.
While certain-embodiments have been described, these embodiments have been presented by way of example only and are not intended to limit the scope of the inventions. Indeed, the novel devices described herein may be embodied in a variety of other forms; furthermore, various omissions and substitutions and changes in the form of the devices described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-052450 | Mar 2010 | JP | national |
