Patent Application
20100214456
The present invention relates to a small and thin type camera module and a method of manufacturing the camera module.
In recent years, due to the demand for thinning of a camera-equipped mobile phone or the like, the demand for thinning of a camera module has also increased. A camera module mounted on a camera-equipped mobile phone or the like includes a solid-state imaging device (image sensor), an infrared ray cutoff filter, a substrate, passive parts, an imaging lens or the like. In order to miniaturize and thin the camera module, it is important to miniaturize a sensor chip and the passive parts and reduce the height of an optical system.
As to the miniaturization, the miniaturization of the camera module has become possible on the benefit of the development of the mounting technique such as the mounting technique using a substrate having the same size as the sensor chip (CSP: Chip Scale Package) and the miniaturization of the passive parts. On the other hand, the reduction of the height of the optical system is not easy since it is required to build up optical parts such as IR cutoff filter, a diaphragm and an optical lens on the sensor chip.
For example, a configuration shown in
In this manner, since the camera module of the related art requires the lens holder 33, the substrate 31, the solid-state imaging device 34, sealing resin for sealing such the stacked members, or the like, it is not only difficult to assemble the respective parts but also difficult to realize a small and low-height camera module.
Thus, following structures related to thinning the camera module have been proposed.
The first camera module is configured to include a transmissive substrate on one surface of which a wiring portion is formed and a lens is formed at a non-wiring portion, and a solid-state imaging device (image sensor) having an imaging portion. The imaging portion faces the lens portion and the solid-state imaging device is coupled to the wiring portion via a bump (see a patent document 1, for example). Thus, the increase of the thickness due to the wiring portion can be suppressed. Further, since the lens and a lens holder portion are formed within the substrate, the increase of the height of the module due to the increase of the thickness of the substrate can be suppressed. Furthermore, since the number of lens related parts such as the lens holder can be reduced, the manufacturing can be facilitated and the number of the manufacturing processes can be reduced, whereby the manufacturing cost can be suppressed.
The second camera module includes a groove portion penetrating from a rear surface to a front surface, a substrate having a plurality of ball bumps, coupling terminals provided on the substrate so as to be exposed from the groove portion, a solid-state imaging device (semiconductor chip) having an imaging portion, a lens sheet provided on the solid-state imaging device and having an imaging lens portion, and a conductive pattern formed on the substrate and electrically coupling the coupling terminals and the ball bumps (see a patent document 2, for example).
Patent Document 1: JP-A-2003-125294
Patent Document 2: JP-A-2007-12995
However, according to the technique of the patent document 1, since the lens and the wiring portion are formed in the same substrate, it is difficult to suppress the increase of the projection area of the camera module and so it is difficult to miniaturize the camera module. Also, further stacking of the lens is difficult.
According to the technique of the patent document 2, it is difficult to laminate the lens sheet on a semiconductor wafer uniformly and without causing any deformation. In case where any deformation arises, lens aberration appears and the imaging performance is degraded. Further, according to this method, since only one lens face can be prepared, it is difficult to prepare a camera module with a high image-pickup performance. Further, it is difficult to further laminate the lens.
The invention is made in view of the aforesaid circumstances and an object of the invention is to provide a small and low-height camera module and a method of manufacturing the camera module.
In order to achieve the aforesaid object, the first camera module according to the invention includes: a solid-state imaging device; and an imaging lens which is bonded with the solid-state imaging device so as to have a gap therebetween. The imaging lens has a refractive index distribution which is arranged concentrically, wherein the refractive index distribution collect an incident light on an imaging area of the solid-state imaging device.
Thereby, the imaging lens can be formed with an almost same size as the solid-state imaging device (semiconductor chip), and so the camera module can be miniaturized. Further, since the imaging lens is formed so as to have the refractive index distribution, the imaging lens becomes quite thin and the height thereof can be low.
Further, in the second camera module according to the invention, the imaging lens has a combination of a plurality of concentric circular convex structure on a substrate.
Thereby, the imaging lens can be formed with an almost same size as the solid-state imaging device, and so the camera module can be miniaturized. Further, since the refractive index distribution configured by the convex portions of the concentric circular shape is formed on the surface of the substrate to thereby constitute the imaging lens, the imaging lens becomes quite thin and the height thereof can be low.
Further, in the third camera module according to the invention; the imaging lens has a combination of a plurality of concentric circular light transmissive film pattern on a substrate.
Thus, the imaging lens can be formed with an almost same size as the solid-state imaging device, and so the camera module can be miniaturized. Further, since the refractive index distribution configured by the pattern of the light transmissive film is formed on the surface of the substrate to thereby constitute the imaging lens, the imaging lens becomes quite thin and the height thereof can be low.
Further, in the fourth camera module according to the invention, the substrate includes a first glass layer and a second glass layer, wherein a melting point of the second glass layer lower than that of the first glass layer.
Thus, the refractive index distribution can be formed easily on the substrate by nano-imprinting technique or the like.
Further, in the fifth camera module according to the invention, the imaging lens is configured by the substrate and thermoset resin pasted on the substrate.
Thus, the refractive index distribution can be formed easily on the substrate by the nano-imprinting technique or the like.
Further, in the sixth camera module according to the invention, the imaging lens is configured by the substrate and UV-curing resin pasted on the substrate.
Thus, the refractive index distribution can be formed easily on the substrate by the nano-imprinting technique etc.
Further, in the seventh camera module according to the invention, the concentric circular convex structure is formed by imprinting on the surface of the imaging lens.
Thus, the refractive index distribution can be formed easily on the substrate by the nano-imprinting technique or the like.
Further, in the eighth camera module according to the invention, the gap has a sealed structure.
Thus, since the gap between the solid-state imaging device and the imaging lens is sealed, dust can be prevented from adhering to the imaging portion of the solid-state imaging device.
Further, in the ninth camera module according to the invention, the gap is filled with inert gas.
Thus, dew is prevented from being formed at the camera module even if the camera module is placed under a low temperature circumstance.
Further, in the tenth camera module according to the invention, the gap is in a vacuum state.
Thus, dew is prevented from being formed at the camera module even if the camera module is placed under a low temperature circumstance.
Further, in the eleventh camera module according to the invention, the imaging lens includes two or more of the substrates, and refractive index distributions formed on the respective substrates differ.
Thus, a plurality of lens surfaces can be formed and so the camera module with a high imaging performance can be manufactured.
Further, in the twelfth camera module according to the invention, the imaging lens includes an infrared ray cutoff filter on a surface of the substrate opposing to the solid-state imaging device.
Thus, since the infrared ray cutoff filter can be formed on the substrate configuring the lens, the height of the camera module can be lowered. Further, since the filter is formed on the flat surface of the substrate, the filter can be formed easily and the characteristics thereof are stable.
Further, in the thirteenth camera module according to the invention, the imaging lens includes an infrared ray cutoff filter which is formed between the substrate and the pattern of the light transmissive film.
Thus, since the infrared ray cutoff filter can be formed on the substrate configuring the lens, the height of the camera module can be lowered. Further; since the filter is formed on the flat surface of the substrate, the filter can be formed easily and the characteristics thereof are stable.
Further, in the fourteenth camera module according to the invention, the imaging lens has a light shielding layer on a surface of the substrate opposing to the solid-state imaging device.
Thus, since the diaphragm of the imaging system can be formed by the light shielding area, the height of the camera module can be lowered.
Further, in the fifteenth camera module according to the invention, through-hole electrodes are formed on the solid-state imaging device.
Thus, since coupling terminals can be formed on the lower surface, for example, of the solid-state imaging device (semiconductor chip), the camera can be miniaturized.
The first method of manufacturing a camera module according to the invention is a method of manufacturing a camera module which includes a solid-state imaging device, and an imaging lens which is bonded with the solid-state imaging device so as to have a gap therebetween, wherein the imaging lens has a refractive index distribution which is arranged concentrically, wherein the refractive index distribution collect an incident light on an imaging area of the solid-state imaging device, the method including the step of: forming the refractive index distribution of the imaging lens after bonding the substrate of the imaging lens and the solid-state imaging device.
Thus, the imaging lens can be formed with an almost same size as the solid-state imaging device (semiconductor chip), and so the camera module can be miniaturized. Further, since the imaging lens is formed by the refractive index distribution, the imaging lens becomes quite thin and the height thereof can be low. Further, since the refractive index distribution is formed after bonding the substrate of the imaging lens and the solid-state imaging device (semiconductor chip), the generation of the aberration of the lens can be suppressed even if any deformation arises due to the bonding.
The second method of manufacturing a camera module according to the invention is a method of manufacturing a camera module which includes a solid-state imaging device, and an imaging lens which is bonded with the solid-state imaging device so as to have a gap therebetween, wherein the imaging lens has a refractive index distribution which is arranged concentrically, wherein the refractive index distribution collect an incident light on an imaging area of the solid-state imaging device, the method including the step of: bonding the substrate of the imaging lens and the solid-state imaging device after forming the refractive index distribution on the substrate of the imaging lens.
Thus, the imaging lens can be formed with an almost same size as the solid-state imaging device (semiconductor chip), and so the camera module can be miniaturized. Further, since the refractive index distribution configured by the convex portions of the concentric circular shape is formed on the surface of the substrate to thereby constitute the imaging lens, the imaging lens becomes quite thin and the height thereof can be low.
Further, in the third method of manufacturing the camera module according to the invention, at a time of forming the refractive index distribution of the imaging lens, the method comprising the step of: coating a resin on the substrate; and imprinting the resin.
Thus, the refractive index distribution can be formed easily on the substrate by the nano-imprinting technique etc.
Further, in the fourth method of manufacturing the camera module according to the invention, the substrate includes a first glass layer and a second glass, wherein a melting point of the second glass layer lower than that of the first glass layer, and wherein at a time of forming the refractive index distribution of the imaging lens, the method comprising the step of: heating the substrate to a temperature equal to or higher than the melting point of the second glass layer; and imprinting the second glass layer.
Thus, the refractive index distribution can be formed easily on the substrate by the nano-imprinting technique etc.
According to the camera module of the invention, even if the camera module is miniaturized and the height of the camera module is lowered, the aberration of an imaging optical system can be suppressed and an imaging with a high resolution is possible.
Hereinafter, the embodiments according to the invention will be explained concretely with reference to the drawings. Although the invention is explained by using the following embodiments and attached drawings, these embodiments and drawings are intended to show examples and the invention is not limited thereto.
First, as shown in
The refractive index distribution 3 of the glass material of the SELFOC lens has the characteristics shown in
[Numeral 1]
n(r)=n0·(1−α2·r2/2) (1)
n0=1.6075 (2)
α=0.608 (3)
The phase difference distribution of the glass material of the SELFOC lens has the characteristics shown in
Δφ=−2π·(n−n(r))d/λ
d=850 μm, λ=540 nm
Next, the explanation will be made as to an example of the designing results of the SELFOC lens.
According to these results, it can be understood that the refractive index distribution 3 has the performance as the imaging lens.
Although it is supposed that the thickness of the glass of the aforesaid SELFOC lens is about 850 μm, it is difficult to realize the phase difference of
As an example of the lens using the light transmissive film 10, a lens is designed under the assumption that the radius of the lens is 1,200 μm, the thickness of the light transmissive film 10 is 850 μm and the focal distance of the lens is 1.2 μm. The lens is designed as the aforesaid conversion into the Fresnel-type refractive index distribution.
An example of the relation between the radius of the light transmissive film 10 of the lens and the number of repetition is shown in
In the top view of the refractive index distribution 3 by the light transmissive film 10 shown in
When the period of the light transmissive film 10 (that is, a difference 21 between the radiuses of the outer circumference of the adjacent circular light transmissive film) is almost equal to or smaller than the wavelength of the incident light, the effective refractive index of the light can be calculated by a volume ratio between the light transmissive film 10 and the air. The greatest feature of this structure is that the refractive index can be freely controlled by merely changing the circumferential width 22.
When the period of the light transmissive film 10 is almost equal to or smaller than the wavelength of the incident light, the effective refractive index neff of the light can be represented in the following expression. In this expression, W is the circumferential width 22 of the concentric circle, T0 is a difference (also called a pitch) 21 of the radius of the outer circumferences between the adjacent circular light transmissive films, and nh and n1 are refractive indexes of the light transmissive film 10 (high refractive index material) and the air (low refractive index material), respectively.
n
eff
={Wn
h+(T0−W)n1}/T0 (4)
As shown in
Δn(x)=Δnmax[(Ax2+B×sin Θ)/2π+C] (5)
(A, B, C: Constant)
Further, in the expression (5), parameters can be set in the following manner supposing that the refractive index of the medium on the light incident side is no and the refractive index of the medium on the light outgoing side is n1.
A=−(kon1)/2f (6)
B=−kon
1 (7)
ko=2π/λ (8)
Thus, the lens can be optimized at every target focal distance and at each wavelength. In the aforesaid expression (5), the item defined as the quadratic function of the distance x from the center of the pixel represents a light converging component.
The greatest feature of such the camera module 100 is that the phase distribution can be freely determined by merely changing the circumferential width 22 of the light transmissive film 10 and so the lens function according to the camera module 100 can be realized.
Next, the explanation will be made as to an example of the manufacturing method of the camera module 100.
Succeedingly, as shown in
Succeedingly, as shown in
According to the manufacturing processes of
Further, since the semiconductor process is employed, it is easy to fill inert gas into the gap or place the gap in a vacuum state.
Succeedingly, as shown in
According to the manufacturing processes of
When the refractive index distribution 3 is formed after bonding the transparent substrate 2 on the solid-state imaging device 1 (image sensor), the influence of strain caused at the time of bonding the substrate can be avoided.
When the substrate is the hard transparent substrate 2, the substrate may be bounded on the semiconductor wafer after forming the refractive index distribution 3 by the semiconductor processing or the like.
Succeedingly, as shown in
Thereafter, the ball bumps 4 are formed by gold on the rear surface (the surface on the opposite side of the surface where the spacer ribs 7 are formed on the semiconductor wafer). The ball bumps 4 may be formed before cutting the semiconductor wafer.
When the transparent substrate 2 is formed by glass of two or more layers having different melting points, the refractive index distribution can be formed easily on the substrate by the nano-imprinting technique or the like.
As described above, in the camera module 100 according to the invention, since the imaging lens is realized in a manner that the refractive index distribution 3 is formed by the light transmissive film with the film thickness of about 1 μm, the height can be made low. Further, since the module is formed by bonding the semiconductor wafers, the assembling process can be simplified and performed with a high accuracy, whereby the camera module with a low cost and a high performance can be realized. Furthermore, since the module can be formed with a size almost same as the solid-state imaging device (image sensor) 1, the module can be miniaturized.
Furthermore, when inorganic material or high heat resistance material is employed as the material, the camera module 100 capable of employing the reflow soldering can be realized.
Furthermore, since the gap between the solid-state imaging device and the substrate is sealed by the spacer, dust can be prevented from adhering to the image pickup portion.
Furthermore, when the gap is filled with the inactive gas or placed in a vacuum state, dew is prevented from being formed at the module even if the camera module 100 is placed under a low temperature circumstance.
Further, in
In this embodiment, the explanation will be made as to a camera module added with another function.
As shown in
According to such the camera module 100B, since the imaging lens is realized in a manner that the refractive index distribution 3 is formed by the light transmissive film 10 with the film thickness of about 1 μm, the height can be made low even when a plurality of the transparent substrates 2 each forming the refractive index distribution 3 are formed. Further, since the module is formed by bonding the semiconductor wafers, the assembling process can be simplified and performed with a high accuracy, whereby the camera module with a low cost and a high performance can be realized. Furthermore, since the module can be formed with a size almost same as the solid-state imaging device (image sensor) 1, the module can be miniaturized:
Further, when inorganic material or high heat resistance material is employed as the material, the camera module capable of employing the reflow soldering can be realized.
Although the invention is explained in detail with reference to the particular embodiment, it will be apparent for those skilled in the art that various changes and modifications may be possible without departing from the spirit and range of the invention.
The present application is based on Japanese Patent Application No. 2007-262395 filed on Oct. 5, 2007, the content of which is incorporated herein by reference.
The invention is useful for a small-sized and low-height camera module etc. and can be used for a device having an image pickup function such as a camera-equipped mobile phone.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-262395 | Oct 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/002773 | 10/2/2008 | WO | 00 | 11/10/2009 |
