Patent Application
20100309353
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2009-135254, filed Jun. 4, 2009; the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a solid-state imaging device serving as a camera module using, for example, a CMOS image sensor, and a semiconductor device.
A camera module having a CMOS image sensor and a lens unit includes analog circuits and digital circuits which are combined to process an image sensing signal. An analog circuit is easily influenced by noise. Hence, to attain a high-quality camera module, anti-noise measures are necessary.
Conventional anti-noise measures ensure grounding from the lower surface side of a substrate by adding external terminals for grounding or using a semiconductor substrate formed from a heavily doped p-type substrate and an n-type epitaxial layer. In addition, a technique has been developed, in which a ground sheet is provided on the entire lower surface of an image sensor, and a grid-shaped ground land having the same outer shape as that of the ground sheet of the image sensor is also provided on the upper surface of a substrate. The image sensor and substrate are bonded by an adhesive, thereby suppressing noise.
However, to meet recent requirements of reducing the sizes of electronic devices, CMOS image sensors are becoming more compact and sophisticated with lower voltages, and this is making the anti-noise measures more important than ever. For example, there is a strong demand to reduce the size of a camera module mounted in a cellular phone. There has recently been developed a camera module called a chip-scale camera module (CSCM) which has almost the same size as that of a chip. Such a CSCM structure also requires to sufficiently suppress EMC.
In general, according to one embodiment, a solid-state imaging device includes a substrate, a lens, a lens holder, and a metal shield. The substrate includes a pixel region having a first well and has a second well at a periphery thereof, the second well being independent of the first well. The lens is provided above the pixel region in the substrate. The lens holder holds the lens. The metal shield is provided on the substrate and the lens holder and electrically connected to the second well of the substrate.
An embodiment will now be described with reference to the accompanying drawing. The same reference numbers denote the same parts throughout the drawing.
As shown in
The image sensor chip 10 has, on its upper surface (first surface), a pixel region (not shown) and a circuit region including analog circuits and digital circuits. More specifically, for example, the pixel region is arranged at the central portion of the surface of the image sensor chip 10, and the circuit region is arranged around the pixel region. The image sensor chip 10 also has, on its lower surface (second surface parallel to the first surface), a plurality of solder balls 100.
The glass plate 20 is bonded to the upper surface of the image sensor chip 10 by, for example, an adhesive 80 provided in the periphery. The glass plate 20 protects the pixel region of the image sensor chip 10. A region without the adhesive 80 is provided between the glass plate 20 and the image sensor chip 10. This aims at preventing the condensing effect of a microlens (not shown) provided in the pixel region of the image sensor chip 10 from being destroyed because the microlens and the adhesive 80 have almost the same refractive index.
The lens unit 60 is bonded to the glass plate 20 by an adhesive 81. The lens unit 60 includes, for example, an infrared ray (IR) cut filter 30, a plurality of lenses 40, and a lens holder 50 for holding them, and has desired optical characteristics. More specifically, for example, the IR cut filter 30 and the plurality of lenses 40 are provided above the pixel region of the image sensor chip 10, and the lens holder 50 is provided around them.
The metal shield 70 is attached around the image sensor chip 10, glass plate 20, and lens holder 50. The metal shield 70 is bonded to the lens holder 50 by an adhesive 82. This allows the shielding from light that would otherwise strike the side surfaces of the image sensor chip 10. The metal shield 70 is also bonded to the side surfaces of the image sensor chip 10 by a conductive adhesive material 90. The metal shield 70 is thus electrically connected to the image sensor chip 10. The metal shield 70 is, for example, a metal can with an opening portion in the bottom portion. As shown in
As shown in
In the silicon substrate 14, the n-type epitaxial layer 12 is formed on the upper surface of p-type substrate 11. The n-type epitaxial layer 12 is formed by, for example, VPE or CVD. A p-well (first p-well) (not shown) is formed in the n-type epitaxial layer 12. An n-well with an adjusted impurity concentration is formed in the p-well or n-type epitaxial layer 12, thereby forming a circuit. Especially, the p-well of an analog circuit portion is formed by implanting ions at high energy, and electrically connected to the p-type substrate 11. A p-well is also formed in the pixel region and used as a pixel isolating region. The p-well 13 (second p-well) is formed by implanting ions at high energy into the periphery of the p-type substrate 11 and the n-type epitaxial layer 12 (dicing region). The p-well 13 (second p-well) is independent of the first well.
The electrode pad 16 connected to, for example, the circuit region is formed on the upper surface of the silicon substrate 14. The insulating film 17 is formed on the lower surface of the silicon substrate 14. The interconnection 18 is formed on the insulating film 17. The interconnection 18 and the electrode pad 16 are connected by the through-via 15 formed in the silicon substrate 14. The through-via 15 is insulated from the substrate 11 by the insulating film 17. The solder balls 100 are formed on the interconnection 18. The solder resist 19 is formed on the interconnection 18 and the insulating film 17 except the solder balls 100. The solder balls 100 are connected to interconnections formed on the mount substrate 200.
On the other hand, the bottom portion of the metal shield 70 bonded to the side surfaces of the image sensor chip 10 by the conductive adhesive 90 is electrically connected to the ground interconnection (GND) of the mount substrate 200 via the solder balls 100. That is, the p-well 13 of the image sensor chip 10 is electrically connected to the metal shield 70 by the conductive adhesive 90, and the metal shield 70 is connected to the ground interconnection (GND) via the solder balls 100. This allows enhancement of the grounding of the analog circuit portion.
Note that in the camera module of this embodiment, a conductive material capable electrically connecting the image sensor chip 10 to the metal shield 70 may be used in place of the conductive adhesive 90.
As shown in
As shown in
According to the embodiment, the conductive adhesive 90 is applied to the side surfaces of the image sensor chip 10 so that the image sensor chip 10 is bonded to the metal shield 70 by the conductive adhesive 90. The p-well 13 formed at the periphery of the image sensor chip 10 is thus electrically connected to the metal shield 70. When the metal shield 70 is connected to the ground interconnection (GND) of the mount substrate 200, the p-well 13 of the image sensor chip 10 can be grounded from the mount substrate 200 via the metal shield 70. It is therefore possible to suppress the influence of noise and obtain a reliable camera module.
In addition, since the side surfaces of the image sensor chip 10 need only be bonded to the metal shield 70 by the conductive adhesive 90, size reduction of the camera module can be maintained, and assembly is easy.
It should be noted that the camera module explained herein is only exemplary and the embodiment should not be limited to the camera module. The embodiment is also applicable to a semiconductor device comprising: a substrate which includes an analog circuit having a first p-well and has a second p-well at a periphery thereof, the second p-well being independent of the first p-well; and an external electrode which is provided on the substrate and electrically connected to the second p-well of the substrate. This application of the embodiment to the semiconductor allows enhancement of the grounding of the analog circuit portion in the semiconductor device.
Modifications of the camera module according to the embodiment will be described next. In each modification, a description of the same parts as in
As shown in
According to the first modification, the same effects as in the embodiment can be obtained. In addition, according to the first modification, since the conductive adhesive 90 is unnecessary, the manufacturing process can further be facilitated.
As shown in
According to the second modification as well, the same effects as in the embodiment can be obtained. In addition, according to the second modification, not only the side surfaces but also the lower portion of the p-well 13 is electrically connected to the metal shield 70. This increases the ground area of the p-well 13 so as to ensure grounding of the image sensor chip 10. Note that each of the side surfaces and lower portion of the p-well 13 may be bonded to the metal shield 70 by the conductive adhesive 90.
As shown in
According to the third modification as well, the same effects as in the embodiment can be obtained. In addition, according to the third modification, the metal shield 70 is formed only on the side surfaces of the image sensor chip 10, and has no bottom portion. That is, the metal shield 70 has no angled portions between the side surfaces and the bottom portion. It is difficult to form right-angled portions in the process, resulting in round portions. For this reason, when the metal shield 70 is attached to the lens unit 60, and the angled portions on the lower surface of the image sensor chip 10 abut against the round portions of the metal shield 70, a gap is formed between the metal shield 70 and the side surfaces of the image sensor chip 10. This may make pressing insufficient. In the third modification, however, since no angled portions exist, sufficient pressing can be obtained. Note that the image sensor chip 10 may be bonded to the metal shield 70 by the conductive adhesive 90.
In the embodiment and the first to third modifications, a metal can is used as the metal shield 70. However, the embodiment is not limited to this. Instead of using a metal can, for example, a metal may be deposited on the side surfaces of the image sensor chip 10, and directly connected to the p-well 13.
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 methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems 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 |
|---|---|---|---|
| 2009-135254 | Jun 2009 | JP | national |
