Patent Publication Number: US-7709286-B2

Title: Image sensor and method for manufacturing the same

Description:
The present application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2007-0112546 (filed on Nov. 6, 2007), which is hereby incorporated by reference in its entirety. 
   BACKGROUND 
   A semiconductor device such as a CIS device can be divided into a photo diode region that receives a light signal and converts the light signal into an electrical signal and a transistor region that processes the electrical signal. A disadvantage of such devices is the generation of a dangling bond at an interface between the photo diode and a substrate, thereby resulting in degradation of the image characteristics. 
   SUMMARY 
   Embodiments relate to an image sensor and a method for manufacturing the same that enhances a leakage source of a substrate surface using a passivation layer at an uppermost surface of a photodiode (PD) without changing the overall thickness of the image sensor. 
   Embodiments relate to an image sensor that may include at least one of the following: a substrate having an active region defined by a device isolating region; a photodiode and a logic unit formed in the active region; a first passivation layer formed on and/or over the photodiode and the logic unit, including a trench on an uppermost surface of the photodiode; and a second passivation layer formed in the trench. 
   Embodiments relate to a method for manufacturing an image sensor that may include at least one of the following steps: defining an active region in a substrate by a device isolating region; and then forming a photodiode and a logic unit in the active region; and then forming a first passivation layer on and/or over the photodiode and the logic unit; and then forming a trench by selectively removing the first protective layer on and/or over the uppermost surface of the photodiode; and then forming a second passivation layer burying the trench. 
   Embodiments relate to an image sensor that may include at least one of the following: a substrate having an active region defined by a device isolating film; a photodiode and a logic unit formed in the active region; a first passivation layer formed on the photodiode and the logic unit, wherein the first passivation layer includes a trench corresponding to an uppermost surface of the photodiode; and a second passivation layer formed in the trench and on the first passivation layer. In accordance with embodiments, the thickness of the second passivation layer in the trench is greater than the thickness of the passivation layer on the first passivation layer. 
   Embodiments relate to a method for manufacturing an image sensor that may include at least one of the following steps: providing a substrate having an active region defined by a pair of isolation layers; and then sequentially forming a photodiode and a logic unit in the active region; and then forming a dummy contact directly on and contacting the isolating layers; and then forming an interlayer insulating layer on the substrate including the photodiode and the isolation layers; and then forming a first passivation layer on the photodiode and the logic unit; and then forming a trench in the first passivation layer corresponding spatially to an uppermost surface of the photodiode; and then forming a second passivation layer directly on and contacting the first passivation layer and in the trench. In accordance with embodiments, the thickness of the second passivation layer in the trench is greater than the thickness of the passivation layer on the first passivation layer. 

   
     DRAWINGS 
     Example  FIGS. 1 to 3  illustrate an image sensor and a method for manufacturing an image sensor, in accordance with embodiments. 
   

   DESCRIPTION 
   Hereinafter, an image sensor and a method for manufacturing the same in accordance with embodiments will be described with reference to the accompanying drawings. In accordance with embodiments, it will be understood that when a layer (or film) is referred to as being “on” another layer or substrate, it can be directly on another layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under another layer, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. 
   Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to affect such feature, structure, or characteristic in connection with other ones of the embodiments. 
   As illustrated in example  FIG. 1 , an image sensor in accordance with embodiments can include substrate  110  having an active region defined by device isolating region  130 ; photodiode  120  and logic unit  150  formed in the active region; first passivation layer  161  formed on and/or over photodiode  120  and the logic unit  150 , including trench T corresponding spatially to an uppermost surface of photodiode  120 ; and second passivation layer  162  formed in trench T and on and/or over first passivation layer. First passivation layer  161  may be formed on and/or over upper metal  155  of the logic unit. Second passivation layer  162  may be formed in trench T and on and/or over first passivation layer  161 . Logic unit  150  may include a transistor, a contact plug and a metal line. The image sensor in accordance with embodiments may thickly form second passivation layer  162  adjacent to photodiode  120  in order to reduce leakage sources from the surface of photodiode  120  by protons (H+) during an annealing process, thereby making it possible to reduce dark current. In essence, the protons (H+) may be implanted to form SiN of second passivation layer  162  so that the leakage sources are reduced, making it possible to reduce generation of dark current. Dummy contact  250  may also be formed on and/or over substrate  110  including device isolating layer  130 . Dummy contact  250  may be formed on and/or over device isolating layer  130  being a boundary of pixels to prevent crosstalk between the pixels, thereby making it possible to collect light in photo diode  120 . 
   As illustrated in example  FIG. 2 , a method for manufacturing an image sensor in accordance with embodiments can include providing substrate  110  having an active region defined by device isolating region  130 . Photodiode  120  and logic unit  150  may then be sequentially formed in the active region. Logic unit  150  may include a transistor, a contact plug and a metal line. Dummy contact  250  may then be formed on and/or over substrate  110  including device isolating layer  130 . Interlayer insulating layer  140  may then be formed on and/or over substrate  110  including photodiode  120  and logic unit  150 . A metal wiring or contact plug  155  may then be formed on and/or over interlayer insulating layer  140  and then first passivation layer  161  is formed thereon and/or thereover. First passivation layer  161  may be an oxide film, but is not limited thereto. Trench T may then be formed by selectively removing a portion of first passivation layer  161  corresponding to the uppermost surface of photodiode  120 . 
   As illustrated in example  FIG. 3 , second protective layer  162  may then be buried in trench T. Second passivation layer  162  may be a nitride film, for example, SiN, but is not limited thereto. The logic unit may include upper metal layer  155  and second passivation layer  162  may be formed on and/or over trench T and first passivation layer  161 . In accordance with embodiments, first passivation layer  161  may be an oxide layer, etc. that is masked using a slightly larger defined mask than photodiode  120 . First passivation layer  161  may then be planarized using a CMP process. A portion of first passivation layer  161  is then removed by a process such as RIE, etc. to form trench T corresponding to the uppermost surface of photodiode  120 . Second passivation layer  162  is then filled in trench T and over first passivation layer  161  by depositing a nitride film such as SiN, etc. In this way, second passivation layer  162  including a large amount of H+ is adjacent to photodiode  120  to perform a role of offsetting a dangling bond on surface of substrate  110  due to H+ in a post-annealing process while also reducing dark current. Also, controlling the thickness of the nitride film, etc. of second protective layer  162  may be used as an anti-reflection film, making it possible to improve sensitivity. A contact may be formed around photodiode  120  in order to improve the sensitivity of photodiode  120 , thereby making it possible to enhance light collection ability. In other words, as requirements for reduced pixel pitch sizes, a light receiving unit may also be reduced, which in turn, reduces the fill factor. Therefore, the maximum collection and focus of light are important issues. 
   Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.