An image-sensing device includes a semiconductor substrate including an image-sensing region and a peripheral circuit region surrounding the image-sensing region. The image-sensing device further includes an image-sensing element disposed in the semiconductor substrate in the image-sensing region, and an imaging processing element disposed in the semiconductor substrate in the peripheral circuit region. The image-sensing device further includes a first isolation element disposed in the semiconductor substrate in the peripheral circuit region and adjacent to the image-sensing element in the image-sensing region. The first isolation element includes a metal portion having a coefficient of heat conduction greater than 149 W/m·K, and an imaginary part of a permittivity (Im(ε)) of the metal portion under a light wavelength of 1100 nm is greater than 0.004.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims priority of Taiwan Patent Application No. 105106649, filed on Mar. 4, 2016, the entirety of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to image-sensing devices, and in particular, to an image-sensing device comprising an isolation element disposed between an image-sensing region and a peripheral circuit region to reduce or prevent elements in the image-sensing region from being affected by elements in the peripheral circuit region.

Description of the Related Art

Image-sensing devices are necessary components in many optoelectronic devices, including digital cameras, cellular phones, and toys. Conventional image-sensing devices include both charge coupled device (CCD) image-sensing devices and complementary metal oxide semiconductor (CMOS) image-sensing devices.

Typically, an image-sensing device is a mixed-signal system having both analog circuits and digital circuits on a single device. The analog and digital circuits generate heat energy accumulations, and they may also become an infrared (IR) dipole light source after the long-term operation thereof, thereby becoming a heat source and/or a light source. The heat energy and/or the light energy that is generated may propagate to the sensing elements in the image-sensing region from the analog/digital circuits. Accordingly, the sensing elements in the image-sensing region are interfered with, and image noise such as light spots can be found in the displayed image. Thus the performance of the image-sensing device is adversely affected.

Therefore, a novel technique is needed to minimize or eliminate the aforementioned undesirable effects on the image-display performance of the image-sensing device, these effects having been caused by the heat energy or light energy generated by the analog and digital circuits of the image-sensing device.

BRIEF SUMMARY OF THE INVENTION

An exemplary image-sensing device comprises a semiconductor substrate comprising an image-sensing region and a peripheral circuit region surrounding the image-sensing region. The image-sensing device further comprises an image-sensing element disposed in the semiconductor substrate in the image-sensing region, and an image-processing element disposed in the semiconductor substrate in the peripheral circuit region. The image-sensing device further comprises a first isolation element disposed in the semiconductor substrate in the peripheral circuit region and adjacent to the image-sensing element in the image-sensing region. The first isolation element comprises a metal portion having a coefficient of heat conduction greater than 149 W/m·K, and an imaginary part of a permittivity (Im(ε)) of the metal portion under a light wavelength of 1100 nm is greater than 0.004.

In one embodiment, the image-sensing device further comprises a second isolation element disposed in the semiconductor substrate in the peripheral circuit region, and disposed between the first isolation element and the image-processing element. The second isolation element comprises another metal portion having a coefficient of heat conduction greater than 149 W/m·K, and an imaginary part of a permittivity (Im(ε)) of the other metal portion under a light wavelength of 1100 nm is greater than 0.004.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-2are schematic diagrams shown an image-sensing device100according to an embodiment of the invention, whereinFIG. 1is a schematic top view of the image-sensing device100andFIG. 2is a schematic cross section of the image-sensing device100taken along the line2-2inFIG. 1.

As shown inFIGS. 1-2, the image-sensing device100mainly comprises an image-sensing region150located at a central portion and a peripheral circuit region250disposed around the image-sensing region150. A plurality of image-sensing elements (seeFIG. 2) for image sensing are disposed in the image-sensing region150, and a plurality of image-processing elements (seeFIG. 2) such as analog and/or digital elements for image processing corresponding to the image-sensing elements in the image-sensing region150are disposed in the peripheral circuit region250.

Referring toFIG. 2, the plurality of image-sensing elements in the image-sensing region150can be disposed in an array configuration (not shown). Herein, for purposes of easy description and simplicity of illustration, only one image-sensing element200in the image-sensing region150adjacent to the peripheral circuit region250is illustrated. The image-sensing element200can be, for example, photodiodes or the like.

As shown inFIG. 2, in one embodiment, the image-sensing element200in the image-sensing region150is illustrated as an active-type image-sensing element, which comprises a sensing region60and a source/drain region70formed in the semiconductor substrate50. In addition, the image-sensing element200further comprises a gate structure80formed over the semiconductor substrate50between the sensing region60and the source/drain region70, and a spacer90formed on opposite sidewalls of the gate structure80. Moreover, an isolation element95is disposed in the semiconductor substrate50at a side adjacent to the sensing region60to isolate the image-sensing element200from another image-sensing element200(not shown) adjacent thereto.

In one embodiment, the semiconductor substrate can be a substrate such as a silicon wafer, and the sensing region60can be an image-sensing region having suitable doping properties. The gate structure80comprises a gate dielectric layer80aand a gate electrode layer80bover the gate dielectric layer80awhich are sequentially formed over the semiconductor substrate50. In addition, the isolation element95can be, for example, a shallow trench isolation (STI).

In addition, still referring toFIG. 2, the peripheral circuit region250comprises a plurality of image-processing elements for processing sensed data from the plurality of image-sensing elements (e.g. the image-sensing elements200) in the image-sensing region150. Herein, for the purpose of easy description and to simplify the illustrations, only one image-processing element300in the peripheral circuit region250is illustrated.

As shown inFIG. 2, the image-processing element300in the peripheral circuit region250comprises a pair of source/drain regions180formed in the semiconductor substrate50. In addition, the image-processing element300further comprises a gate structure190formed over the semiconductor substrate50between the pair of source/drain regions180, and a spacer170formed on opposite sidewalls of the gate structure190. In one embodiment, the image-processing element300can be an analog element and/or an digital element applied in a related circuit for image-processing. Herein, the gate structure190comprises a gate dielectric layer190aand a gate electrode layer190bover the gate dielectric layer190awhich are sequentially formed over the semiconductor substrate50.

In addition, an isolation element350is disposed in the semiconductor substrate50at a place that is adjacent to the image-sensing element200in the image-sensing region150to isolate the image-sensing element200from the adjacent image-processing element300in the peripheral circuit region250. Herein, compared with the isolation element95in the image-sensing region150, the isolation element350has a deeper depth D in the semiconductor substrate50, and the isolation element350is a distance P away from the image-processing element300in the peripheral circuit region250. In addition, the isolation element350is a distance P′ away from the image-processing element300in the peripheral circuit region250, and the image-processing element300in the peripheral circuit region250is a distance X away from the image-sensing element200in the image-sensing region150. Moreover, the semiconductor substrate50has a thickness Y.

In an embodiment, the isolation element350shown inFIG. 2has a width W greater than at least 0.5 μm. Herein, the isolation element350comprises a metal portion350aand an insulating liner layer350bformed between the metal portion350aand the semiconductor substrate50. The metal portion350amay have a coefficient of heat conduction greater than 149 W/m·K, and the imaginary part of the permittivity (Im(ε)) of the metal portion350aunder a light wavelength of 1100 nm is greater than 0.004. In one embodiment, the metal portion350aof the isolation element350may comprise aluminum, tungsten, copper, titanium or the like, and the insulating liner layer350bof the isolation element350may comprise silicon oxide, silicon oxynitride, silicon nitride, or the like. The insulating liner layer350bof the isolation element350may have a thickness of at least 50 Å. The insulating liner layer350bof the isolation element350may isolate the metal portion350aof the isolation element350from the semiconductor substrate50, such that the metal portion350ais prevented from contacting the semiconductor substrate50, thereby preventing increases of dark currents.

In one embodiment, fabrications of the metal portion350aand the insulating liner layer350bof the isolation element350can be formed by semiconductor fabrications such as photolithography, etching, and film deposition and processing (not shown). The isolation element350can be formed before, during, or after fabrication of the image-sensing element200and the image-processing element300based on designs of the image-sensing device100.

Referring toFIG. 1, a schematic top view of the image-sensing device100shown inFIG. 2is illustrated, andFIG. 2shows a schematic cross section taken along line2-2inFIG. 1. As shown inFIG. 1, the isolation element350comprising the metal portion350aand the insulating liner layer350bis illustrated with a continuous configuration entirely surrounding the image-sensing region150.

As shown inFIGS. 1-2, in one embodiment, the thickness Y of the semiconductor substrate50, the distance P from the isolation element350to the image-sensing element200in the image-sensing region150, the distance P′ from the isolation element350to the image-processing element300in the periphery circuit region250, and the distance X from the image-processing element300in the periphery circuit region250to the image-sensing element200in the image-sensing region150may satisfy the following equation (1):

While heat-energy generated and/or an infrared (IR) dipole light source is formed due to the long-term operation of the image-processing element300in the peripheral circuit region250, the generated heat-energy and/or light energy may propagate from the peripheral circuit region250toward the image-sensing region150through the semiconductor substrate50. However, compared to the semiconductor material (e.g. silicon) of the semiconductor substrate50, since the metal materials used for the metal portion350aof the isolation element350have better heat dissipation properties and light-absorption properties, the heat-energy that is generated can be dissipated by the isolation element350itself. Radiation such as infrared light emitted from the image-processing element300can also be blocked by the light-absorption properties of the metal materials. In addition, due to the width of the isolation element350being greater than at least 0.5 μm and the conditions of the distance P from the isolation element350to the image-sensing element200in the image-sensing region150, the distance P′ from the isolation element350to the image-processing element300in the periphery circuit region250, and the distance X from the image-processing element300in the periphery circuit region250to the image-sensing element200in the image-sensing region150in the above equation (1), the possibility of light energy infrared light that propagated from the image processing region250to the image-sensing region150can be prevented. Therefore, the thermal energy that propagates from the peripheral circuit region250toward the image-sensing region150can be reduced or prevented, and the light energy that propagates from the peripheral circuit region250toward the image-sensing region150can be shielded, thereby reducing or preventing thermal energy and/or light energy produced by the circuit elements such as the image-processing element300in the peripheral circuit region250from affecting the image-sensing element such as image-sensing element200in the image-sensing region150, and ensuring image performance of the image-sensing device100. Therefore, no undesired image noise such light spot will be presented in the image-sensing region150.

However, the isolation element of the invention is not limited to the isolation element350shown inFIGS. 1-2.FIGS. 3-4are schematic diagrams showing an image-sensing device100′ according to another embodiment of the invention, whereinFIG. 3is a schematic top view, andFIG. 4is a schematic cross section of an image-sensing device100′ taken along the line4-4inFIG. 3.

Herein, the image-sensing device100′ shown inFIGS. 3-4is modified from the image-sensing device100shown inFIGS. 1-2. The same reference numbers shown inFIGS. 1-2andFIGS. 3-4represent the same elements, and only differences between the image-sensing devices100and100′ are discussed below.

Referring toFIGS. 3-4, similar to those shown inFIGS. 1-2, another isolation element350can additionally be disposed between the isolation element350in the peripheral circuit region250and the image-processing element300to further reduce or prevent thermal energy propagating from the peripheral circuit region250toward the image-sensing region150, and to shield the light energy that propagates from the peripheral circuit region250toward the image-sensing region150, thereby reducing or preventing thermal energy and/or light energy produced by the circuit elements such as the image-processing element300in the peripheral circuit region250from affecting the image-sensing element such as image-sensing element200in the image-sensing region150, and ensuring image performance of the image-sensing device100′. Therefore, no undesired image noise such as light spot will be presented in the image-sensing region150. As shown inFIG. 3, these two isolation elements350are illustrated as continuous isolation elements both entirely surrounding the image-sensing region150.

In one embodiment, similar to those disclosed inFIGS. 1-2, each of the isolation elements350may have a depth D, and each of the isolation elements350may have a width W of about 0.5 μm. The additional isolation element350is a distance P′ away from the adjacent image-processing element300in the periphery circuit region250, and the thickness Y of the semiconductor substrate50, a distance P from the left isolation element350to the image-sensing element200in the image-sensing region150, a distance P′ from the right isolation element350to the image-processing element300in the periphery circuit region250, and a distance X from the image-processing element300in the periphery circuit region250to the image-sensing element200in the image-sensing region150may satisfy the following equation (2):

FIGS. 5-6are schematic diagrams showing an image-sensing device100″ according to yet another embodiment of the invention, whereinFIG. 5is a schematic top view, andFIG. 6is a schematic cross section of an image-sensing device100″ taken along line6-6inFIG. 5.

Herein, the image-sensing device100″ shown inFIGS. 5-6is modified from the image-sensing device100shown inFIGS. 1-2. The same reference numbers shown inFIGS. 1-2andFIGS. 5-6represent the same elements, and only differences between the image-sensing devices100and100″ are discussed below.

Referring toFIGS. 5-6, the continuous isolation element350entirely surrounding the image-sensing region150shown inFIGS. 1-2are now modified as non-continuous isolation element350′. Therefore, the isolation element350′ used inFIGS. 5-6are made of a plurality of discontinuous segments, and the adjacent segments of the isolation elements350are isolated from each other by the semiconductor substrate50. Preferably, the non-continuous segments forming the isolation element350′ surround the four corners of the image-sensing region150.

As shown inFIGS. 5-6, similar to the isolation element350, the isolation element350′ may comprise a metal portion350a′ and an insulating liner layer350b′ formed between the metal portion350a′ and the semiconductor substrate50. Herein, materials and fabrications of the metal portion350a′ and the insulating liner layer350b′ are similar to materials and fabrications of the metal portion350aand the insulating liner layer350bthat were mentioned previously, so that the segments forming the isolation element350′ can still reduce or prevent thermal energy from propagating from the peripheral circuit region250toward the image-sensing region150, and to shield the light energy that propagates from the peripheral circuit region250toward the image-sensing region150, thereby reducing or preventing thermal energy and/or light energy produced by the circuit elements such as the image-processing element300in the peripheral circuit region250from affecting the image-sensing element such as image-sensing element200in the image-sensing region150. Therefore, no undesired image noise such as light spot will be presented in the image-sensing region150, and image performance of the image-sensing device100″ can be ensured.

In addition, in other embodiments (not shown), configurations of the isolation elements350and350′ shown inFIGS. 1-6can be properly adjusted and arranged according to designs of the circuit elements in the peripheral circuit region250. Suitable combinations of the isolation elements350and350′ can be applied to reduce or prevent thermal energy from propagating from the peripheral circuit region250toward the image-sensing region150, and to shield the light energy that may propagate from the peripheral circuit region250toward the image-sensing region150, thereby reducing or preventing thermal energy and/or light energy produced by the circuit elements such as the image-processing element300in the peripheral circuit region250from affecting the image-sensing element such as image-sensing element200in the image-sensing region150. Therefore, no undesired image noise such as light spots will be presented in the image-sensing region150, and image performance of the image-sensing device can be ensured. The isolation elements350and350′ shown inFIGS. 1-6are not used to limit the scope of the invention.