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  Image sensor and method for forming the sameUSPTO Application #: 20060057760Title: Image sensor and method for forming the same Abstract: A reliable image sensor and a method for forming the same are provided. The image sensor includes a photo-detective device. At least one transistor is electrically connected to the photo-detective device for outputting charges stored in the photo-detective device. A transistor directly connected to the photo-detective device includes a gate electrode pattern and an ion-implantation interrupting pattern arranged on the gate electrode pattern. Since the ion-implantation interrupting pattern is located on an upper portion of the gate electrode pattern of the transistor in the vicinity of the photo-detective device, a threshold voltage of the gate electrode pattern of the transistor in the vicinity of the photo-detective device is adjusted to a desired value. (end of abstract)
Agent: Mills & Onello LLP - Boston, MA, US Inventors: Duk-Min Yi, Sung-Keun Won, Jun-Yeoul You USPTO Applicaton #: 20060057760 - Class: 438057000 (USPTO) Related Patent Categories: Semiconductor Device Manufacturing: Process, Making Device Or Circuit Responsive To Nonelectrical Signal, Responsive To Electromagnetic Radiation The Patent Description & Claims data below is from USPTO Patent Application 20060057760. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This U.S. non-provisional patent application claims priority under 35 U.S.C. .sctn. 119 of Korean Patent Application 2004-74264 filed on Sep. 16, 2004, the entire contents of which are hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] The present invention relates to an image sensor and a method for forming the same, more particularly to a complementary metal-oxide semiconductor (CMOS) image sensor and a method for forming the same. [0003] Recently, digital technologies, such as the digital camera, have been rapidly advanced. Main elements for determining image quality of the digital camera are an optical lens and an image sensor. The image sensor converts light input through the optical lens into an electric signal having an excellent image quality. [0004] The image sensor includes a pixel array composed of a plurality of pixels that are two-dimensionally arranged in a matrix form. Each pixel includes photo-detective, transfer, and readout devices. According to the types of the transfer and readout devices, the image sensor is classified as a charge coupled device (hereinafter referred to as CCD) or a CMOS image sensor (hereinafter referred to as CIS). The CCD uses MOS capacitors for transfer and readout operations. Respective MOS capacitors are arranged adjacent to each other, a charge carrier due to an electric potential difference is stored in one capacitor and is transferred to an adjacent capacitor. In contrast to this, a CIS is provided with MOS (metal-oxide semiconductor) transistors of the same number as the pixels and employs a switching mode to detect outputs in an orderly manner by using the MOS transistors. [0005] The CCD image sensor has lower noise and higher image quality than the CIS. The CIS, compared to the CCD image sensor, has a simple operational scheme and is capable of implementing various scanning types. A single processing circuit for the CIS can be integrated into a single chip so that it is possible to miniaturize products. Also, use of compatible CMOS technique provides advantages of reducing manufacturing costs, owing to low and single power, random access with image data. Accordingly, the CIS can be used in any device that displays images, e.g., digital cameras, surveillance cameras, smart phones, PDAs, notebook computers, bar code reader, HDTV resolution cameras, toys and so forth. Currently, uses and applications of the CMOS image sensor have become progressively broader. [0006] Unlike the CCD image sensor, the CIS is proper to integrate unit pixels, peripheral analog elements, and MOS elements on a single chip thereof by applying a CMOS fabricating process thereto. As the integration degrees of MOS transistors increase, each gate electrode of MOS transistors formed at the peripheral circuit region becomes lower in height. For example, when the heights of the gate electrodes in the MOS transistor are too high, it is impossible to implant halo ions because an aspect ratio of a space defined between the gate electrodes becomes larger. Accordingly, it is preferred that gate electrode of MOS transistors of the pixel array region be shallowly formed like those of the MOS transistors of the peripheral circuit region in the CIS. [0007] FIG. 1 is a cross-sectional view showing a pixel of a pixel array region that illustrates an impurity ion implantation for a photo diode in a manufacturing process of a CIS, relevant to the problem arising from the CIS when the gate electrode of a MOS transistor is low in height. In FIG. 1, reference numeral 11 represents a P-type substrate, reference numeral 13 represents a gate insulation layer, and reference numerals 15a and 15b represent gate electrodes. Reference numeral 17 notes an ion implantation mask, reference numeral 19 notes an N-type impurity ion implantation for forming a photo diode, and reference numeral 21 denotes an N-type impurity diffusion region of the photo diode. [0008] Referring to FIG. 1, the N-type impurity diffusion region of the photo diode is formed at a gate electrode 15a in the vicinity thereof by a self-alignment method, as indicated by a dotted line. However, since the gate electrodes 15a and 15b are shallow, they have a high energy, for example, about 500 keV. As an injected impurity ion passes through the gate electrode 15a, an N-type impurity diffusion region 21 is formed at a lower portion of the gate electrode 15a. As a result, it is difficult to adjust a threshold voltage of a MOS transistor having the gate electrode 15a. This does not allow a reliable image sensor to be implemented. SUMMARY OF THE INVENTION [0009] The present invention is directed to a reliable image sensor and a method of forming the same. [0010] According to a first aspect, the invention is directed to an image sensor comprising a photo-detective device and at least one transistor electrically connected to the photo-detective device for outputting charges stored in the photo-detective device. The transistor connected to the photo-detective device includes a gate electrode pattern and an ion-implantation interrupting pattern arranged on the gate electrode pattern. [0011] In one embodiment, the ion-implantation interrupting pattern covers a part of the gate electrode pattern, and one side of the ion-implantation interrupting pattern in the vicinity of the photo-detective device is vertically aligned with one side of the gate electrode pattern in the vicinity of the photo-detective device. [0012] In one embodiment, the ion-implantation interrupting pattern includes a dielectric layer pattern and a conductive layer pattern that are sequentially stacked. The sensor can further comprise a metal interconnection electrically connected to a gate electrode pattern region that is exposed to an outer side of the ion implantation interrupting pattern. The photo-detective device is a photo diode comprising: a first impurity diffusion region formed at a semiconductor substrate of a first conductivity type, the first impurity diffusion region being of a second conductivity type; and an impurity diffusion region of the first conductivity type formed in the first impurity diffusion region of the second conductivity type. The transistor directly connected to the photo-detective device includes a second impurity diffusion region of the second conductivity type formed on the semiconductor substrate at another outer side of the gate electrode pattern opposite to the photo-detective device. [0013] In one embodiment, the photo-detective device is a photo diode comprising: a first impurity diffusion region formed at a semiconductor substrate of a first conductivity type, the first impurity diffusion region being of a second conductive type; and an impurity diffusion region of the first conductivity type formed in the first impurity diffusion region of the second conductivity type. The at least one transistor includes a transfer transistor, a reset transistor, a sensing transistor, and an access transistor that are serially connected to the photo-detective device. Third impurity diffusion regions of the second conductivity type are disposed in the semiconductor substrate between gate electrode patterns of the respective transistors. A gate electrode pattern of the sensing transistor is electrically connected to a third impurity diffusion region of the second conductivity type between the transfer and reset transistors. [0014] In one embodiment, the gate electrode pattern and the conductive layer pattern are made of the same material, the dielectric layer pattern has a structure in which oxide layer-nitride layer-oxide layer are sequentially stacked. [0015] In one embodiment, the sensor further comprises a capacitor formed of the gate electrode pattern, the dielectric layer pattern, and the conductive layer pattern which are sequentially stacked over the semiconductor substrate. [0016] In one embodiment, the ion-implantation interrupting pattern is smaller than the gate electrode pattern and partially exposes the gate electrode pattern at a portion that is not adjacent to the photo-detective device. [0017] According to another aspect, the invention is directed to an image sensor comprising a photo diode and a transistor directly connected to the photo diode. The photo diode has a first impurity diffusion region formed on a semiconductor substrate of a first conductivity type, the first impurity diffusion region being of a second conductivity type, and an impurity diffusion region of the first conductivity type in the first impurity diffusion region of the second conductivity type. The transistor includes a stacked gate pattern in the vicinity of the first impurity diffusion region of the second conductivity type, and a second impurity diffusion region of the second conductivity type formed on the semiconductor substrate at an outer side of the gate electrode pattern opposite to the first impurity diffusion region of the second conductivity type. The stacked gate pattern includes a gate electrode pattern, a dielectric layer pattern, and a conductive layer pattern that are sequentially formed on the semiconductor substrate, interposing a gate insulation layer therebetween. [0018] In one embodiment, the dielectric and conductive layer patterns cover a part of the gate electrode pattern, and one side of the conductive layer pattern in the vicinity of the photo diode is vertically aligned with one side of the gate electrode pattern in the vicinity of the photo diode. In one embodiment, the sensor further comprises a metal interconnection electrically connected to a gate electrode pattern region that is exposed to an outer side of the conductive layer pattern through a contact plug. [0019] In one embodiment, the sensor further comprises a capacitor formed of the gate electrode pattern, the dielectric layer pattern, and the conductive layer pattern which are sequentially stacked on the semiconductor substrate. [0020] According to another aspect, the invention is directed to a transfer transistor for transferring a charge stored in a photo-detective device. The transfer transistor comprises: a gate electrode pattern to which a bias voltage is applied; and a dielectric layer pattern and a conductive layer pattern stacked on the gate electrode pattern. The dielectric layer pattern and the conductive layer pattern are smaller than the gate electrode pattern, and one side of the conductive layer pattern and one side of the gate electrode pattern in the vicinity of the photo diode are vertically aligned with each other. [0021] In one embodiment, the transfer transistor further comprises a metal interconnection electrically connected to a gate electrode pattern region that is exposed to an outer side of the conductive layer pattern through a contact plug, for applying a bias to the transfer transistor. Continue reading... Full patent description for Image sensor and method for forming the same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Image sensor and method for forming the same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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