No assignee for this patent application has been made.
Reporters obtained the following quote from the background information supplied by the inventors: "The present invention relates to an image sensor, and more particularly, to an image sensor formed through a back side process.
"As the development of electronic products such as digital cameras and scanners progresses, the demand for image sensors increases accordingly. In general, commonly used image sensors are nowadays divided into two main categories: the charge coupled device (CCD) sensors and the CMOS image sensors (CIS). Primarily, CMOS image sensors have certain advantages of low operating voltage, low power consumption, and property of random access. Furthermore, CMOS image sensors can currently be integrated in semiconductor fabrication processes. Based on those benefits, the application of CMOS image sensors has increased significantly.
"The CMOS image sensor separates incident light into a combination of light beams of different wavelengths. For example, the CMOS image sensor can consider incident light as a combination of red, blue, and green light. The light of different wavelengths is received by respective optically sensitive elements such as photodiodes and is subsequently transformed into digital signals of different intensities. Thus, it can be seen that a monochromatic color filter array (CFA) must be set above every optical sensor element for separating the incident light.
"In conventional process, a CMOS image sensor has a binding pad formed on the surface to connect other components, the manufacturing method of the bonding pad includes: forming an opening to expose the metal trace, filling a conductive material in the opening to form the bonding pad, and after the bonding pad is formed, forming a color filter array and a micro lens. As shown in FIG. 1, which is a schematic drawing illustrating a conventional image sensor. A CMOS image sensor 10 has a dielectric layer 12 and a metal trace 14 on its surface, an opening 16 is formed to expose the metal trace 14, and a conductive layer 18 is then filled in the opening 16 to form a bonding pad and to connect other components. Besides, an insulating layer 21 may be selectively formed on the sidewall of the opening 16 to provide shielding effect and prevent the current flowing through the bonding pad from influencing other components.
"Afterwards, a color filter array 36 is formed on the dielectric layer 12 through a spin coating process; a planarizing layer 38 is then formed on the color filter array 36, and a plurality of micro-lenses 40 corresponding to the color filter array 36 are formed on the planarizing layer 38. However, there is an issue in conventional processes: as mentioned above, the color filter array 36 is formed on the dielectric layer 12 through spin coating after the opening 16 is completed. It is worth noting that the existence of the opening 16 has the color filter layer stored up in the opening 16, which is then spun out from the opening 16 during the spin coating step, thereby affecting the uniformity of a thickness of the color filter layer, and causing striation. Striation is disadvantageous to the pixel performances since it affects, for example, the saturation of the CMOS image sensor 10."
In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventor's summary information for this patent application: "The present invention therefore provides methods for fabricating an image sensor with improved performances and that prevent it from being affected by the striation caused during the formation of the color filters.
"The present invention provides an image sensor including a substrate with a front side and a back side, wherein the substrate has a sensor array region and a peripheral region defined thereon, a plurality of image sensor devices disposed in the sensor array region, a first metal layer disposed on the front side within the peripheral region, a bonding pad disposed on the back side within the peripheral region; and at least one connecting element penetrating the substrate and substantially contacting the first metal layer and the bonding pad, wherein parts of the substrate are between the first metal layer and the bonding pad.
"The present invention provides a method for fabricating an image sensor. The method comprises steps of providing a substrate with a front side and a back side, wherein the substrate has a sensor array region and a peripheral region defined thereon, forming a first metal layer disposed on the front side within the peripheral region, forming an opening penetrating the substrate from the back side, forming a conductive layer on the back side and in the opening, wherein a connecting element is formed by the conductive layer in the opening, forming a bonding pad through patterning the conductive layer, forming a plurality of color filters on the back side within the sensor array region, forming a planarizing layer disposed on the color filter; and forming a plurality of micro lenses disposed on the planarizing layer.
"According to the image sensor provided in the present invention, the bonding pad is formed on the back side of the substrate, and at least a part of the substrate is between the bonding pad and the first metal layer, so that the color filter layer would not be stored up in the opening/recess during the spin coating process. Thus the effect of striation to the pixel performance of the image sensor is prevented as the striation itself is prevented.
"These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
"FIG. 1 is a schematic drawing illustrating parts of a conventional image sensor.
"FIGS. 2.about.6 are schematic, cross-sectional view diagrams showing a method for fabricating an image sensor according to the first preferred embodiment of the present invention.
"FIG. 7 is a bottom view diagram of the cross section line I-I' in FIG. 6 accordance with the first preferred embodiment.
"FIG. 8.about.10 are bottom view diagrams of the cross section line I-I' in FIG. 6 according to three different embodiments."
For more information, see this patent application: Kao, Ching-Hung. Image Sensor and Fabricating Method Thereof. Filed
Keywords for this news article include: Patents.
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