Abstract:
In order to reduce crosstalk caused between control signal wires in a semiconductor apparatus without increasing the size of the semiconductor apparatus, a noise guard circuit is provided at the opposite end of the control signal wire to the driver circuit. The noise guard circuit controls in such a way as to increase the impedance between the relevant control signal wire and a fixed potential when the logic of the relevant control signal wire is positive logic for driving the element, and as to decrease the impedance between the relevant control signal wire and a fixed potential when the logic of the relevant control signal wire is negative logic for driving the element.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2005-028446, filed on Feb. 4, 2005, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION  
     1. Field of the Invention 
     The present invention relates to a technology for reducing crosstalk noise between signal wires in a semiconductor apparatus, such as a solid-state image sensing device and the like. 
     2. Description of the Prior Art 
     Some semiconductor apparatus, such as a solid-state image sensing device, a liquid crystal displaying device, semiconductor memory and the like, comprises a plurality of driver circuits, a plurality of types of control signal wires connected to the driver circuits, for transmitting control signals and a group of elements which are connected to the plurality of types of control signal wires and driven by the driver circuits. 
     Such a semiconductor apparatus always has the problem of crosstalk between signal wires and a mis-operation due to it. This problem is described below using a solid-state image sensing device as an example. 
     As described in the following Patent reference 1 and Patent reference 2, a solid-state image sensing device, such as a complementary metal-oxide semiconductor (CMOS) image sensor or the like, has an array of pixels which are composed of a photo diode and a plurality of transistors, a shift register for specifying a pixel to read and a driver circuit for controlling the transistors of each pixel and the like which are disposed around the pixels, and control signal wires are wired in the array. 
     With the development of a semiconductor integrated circuit technology, the size of the pixel of the solid-state image sensing device has decreased and an array size has increased beyond a mega-pixel (that is, one side of the array has got long. Then, crosstalk easily occurs between control signals in the pixel. 
     When the control signal of the first control wire in the pixel changes, crosstalk noise occurs in the second control signal wire installed adjacently to the first control wire, and the second control signal sometimes changes unintentionally. 
     For example, if the first and second control signals are a charge transfer control signal and a pixel reset signal, respectively, the pixel reset signal resets a stored signal unintentionally and an output image degrades. Since the degree of this phenomenon varies depending on a distance from a driver in the pixel array, the output image obtains a shading characteristic. 
     Prior technical literatures related to the present invention are introduced below. 
     As described above, each of Patent Reference 1 and Patent Reference 2 discloses a solid-state image sensing device. Patent Reference 1 relates to a technology for expanding the dynamic range of a sensor in a solid-state image sensing device to a high-illuminance side or the like. Although as to noise in an image sensor, it discloses reset noise caused when initializing signal charge, it does not disclose crosstalk between control signals in a pixel. 
     Patent Reference 2 discloses that the number of wires is reduced in a solid-state image sensor. The solid-state image sensor described in Patent Reference 2 is provided with a shift register for selecting a pixel located in the vertical direction, on each side of a pixel array. However, even Patent Reference 2 fails to disclose crosstalk between control signals in the pixel. 
     Patent Reference 3 relates to a liquid crystal display and discloses that a compensation voltage application circuit is provided on the opposite side of a signal driver across a liquid crystal display device in order to solve a problem that display variation (crosstalk) occurs on a screen. In Patent Reference 3 too, pixels are disposed in array and signal wires are wired, but it fails to disclose crosstalk problem between signal wires. 
     As described above, conventionally, as measures for reducing crosstalk between signal wires, a sufficient distance is secured between signal wires in a design stage. Or, countermesure at each element in a semiconductor apparatus is considered for preventing mis-operation due to crosstalk. However, such measures lead to increase a chip area and to increase the size of the semiconductor apparatus, which is not favorable. 
     It is not preferable to adopt such crosstalk reduction measures that increase the number of wires in the semiconductor apparatus, or interfere with the logic for driving each element in the semiconductor apparatus and restrict the driving logic. 
     Patent reference 1: Japanese Published Patent Application No. 2004-159274 
     Patent reference 2: Japanese Published Patent Application No. 2003-134399 
     Patent reference 3: Japanese Published Patent Application No. H08-129158 
     SUMMARY OF THE INVENTION  
     It is an object of the present invention to reduce the influence of crosstalk noise caused between control signal wires inside a semiconductor apparatus without increasing the size of the semiconductor apparatus especially in a semiconductor apparatus comprising a plurality of driver circuits, a plurality of control signal wires connected to each of the plurality of driver circuits, for transmitting control signals from each of the driver circuits and a plurality of elements which are connected to the plurality of the control signal wires, and are supplied and driven with control signals by the driver circuits. 
     A noise guard circuit for a control signal wire to reduce the influence of crosstalk noise is provided at the opposite end of the control signal wire to the driver circuit. The noise guard circuit controls in such a way as to increase the impedance between the relevant control signal wire and a fixed potential when the logic of the relevant control signal wire is positive logic for driving the element, and as to decrease the impedance between the relevant control signal wire and a fixed potential when the logic of the relevant control signal wire is negative logic for driving the element. 
     Thus, a mis-operation due to crosstalk can be prevented and also the increase of a chip area can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  shows the basic configuration of the present invention. 
         FIG. 2  shows the circuit configuration of the first preferred embodiment of the present invention. 
         FIG. 3  is the operational timing chart of the control signal wires in the first preferred embodiment of the present invention. 
         FIG. 4  shows the circuit configuration of the second preferred embodiment of the present invention. 
         FIG. 5A  is the first operational timing chart of control signal wires in the second preferred embodiment of the present invention. 
         FIG. 5B  is the second operational timing chart of control signal wires in the second preferred embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     The present invention is described below using a solid-state image sensing device as an example of the semiconductor apparatus, and both a reset signal wire for resetting a stored pixel and a transfer gate signal wire for controlling the transfer of charge stored in a pixel as examples of the control signal wires. 
       FIG. 1  shows the basic configuration of the present invention. A V shift register  11  for selecting a pixel located in the vertical direction and the driver  12  of a control signal wire are disposed on one side of a pixel array  10  and a noise guard  13  is disposed on the other side. As the control signal wires, a transfer gate (TG) signal wire  14 , a reset (RST) signal wire  15  and a selection (SEL) signal wire  16  are described. Only the reset signal wire  15  is connected to the noise guard  13 . 
     The reset signal wire  15  is divided into an arrow line from the driver side and an arrow line from the noise guard side. This indicates that in the present invention, sufficient reset signals are supplied on the noise guard side that is far away from the driver side which is the other side. 
     The preferred embodiments of the present invention are described below with reference to  FIGS. 2 through 5 . 
     The First Preferred Embodiment 
       FIG. 2  shows the circuit configuration of the first preferred embodiment displaying one pixel of the solid-state image sensing device of the present invention and a noise guard provided on a line to which the pixel belongs.  FIG. 3  is the operational timing chart of the control signal wires at the time of pixel reading in the first preferred embodiment. 
     The noise guard  23  shown in  FIG. 2  comprises an inverter  231  for inverting the logic of the reset signal wire  15 , and an N-channel MOS transistor  232  to the gate of which the output of the inverter  231  is connected, the drain of which is connected to the reset signal wire  15  and the source of which is connected to the ground. 
     As shown in  FIG. 3 , at the time of pixel reading, firstly the selection signal SEL rises up, and a read transistor  26  is becomes ON. Then, when the reset signal becomes High, a reset transistor  25  becomes ON and residual charge is eliminated. At a predetermined time after the reset signal returns to Low, the transfer signal becomes High and a charge transfer transistor  24  becomes ON. Thus, signal charge stored in a photo diode  27  is extracted, is amplified by an amplification transistor  28  and is outputted to an output signal line  29  via the read transistor  26 . A line with a reference numeral  21  is a power feeding line. 
     The noise guard  23  adopts the logic of a reset signal, and its impedance is low when there is no reset signal since the transistor  231  is ON. Therefore, even when the transfer gate signal rises up, crosstalk noise can be reduced. 
     When the reset signal rises up, the transistor  231  becomes OFF and the same effect as obtained when a reset signal is also supplied from the opposite side of the driver  12  can be obtained. 
     The Second Preferred Embodiment 
       FIG. 4  shows the circuit configuration of the second preferred embodiment of the present invention. The same reference numerals are attached to the same parts as in the first preferred embodiment. A pixel part is the same as in  FIG. 2 , and the configuration of a noise guard  33  is different from that shown in  FIG. 2 . Each of  FIGS. 5A and 5B  is the operational timing chart of each control signal wire at the time of pixel reading in the second preferred embodiment. 
     In the noise guard  33  in the second preferred embodiment, the logic of a reset signal wire is supplied to the gate of a transistor  332  via an NOR circuit  331 . The signal of a disenable terminal is supplied to the other input of the NOR circuit  331 . 
     Namely, the noise guard  33  in the second preferred embodiment is obtained by replacing the inverter  231  of the noise guard  23  in the first preferred embodiment with the NOR circuit  331  and a control signal can be inputted from the outside. 
     As to the selection (SEL) signal, reset signal and transfer gate signal, the operational timing of each control signal wire at the time of pixel reading shown in  FIGS. 5A and 5B  is the same as in the first preferred embodiment shown in  FIG. 3 , and the second preferred embodiment differs from the first preferred embodiment in that a reset hold (RSTHLD) signal to be supplied to the disenable terminal is added. 
     The reset hold signal shown in  FIG. 5A  is used when a reset signal wire is guarded for a long time. The reset hold signal rises up immediately before the reset signal rises up, and falls down immediately after the reset signal falls down. Therefore, the impedance between the reset signal wire and the ground becomes high during a reset period, and otherwise it becomes low. Therefore, a reset operation can be secured, and also the influences of crosstalk from the transfer gate signal wire and other noise can be avoided. 
     The reset hold signal shown in  FIG. 5B  is used when the reset signal wire is guarded for a short time. The reset hold signal falls down from High to Low before the transfer gate signal rises up and after the reset signal falls down, and returns to High after the transfer gate signal falls down. Therefore, the impedance between the reset signal wire and the ground can be kept low before the transfer gate signal rises up. Therefore, crosstalk by the transfer gate signal can be prevented. 
     The use of the disenable terminal shown in  FIG. 4  is not limited to the reset hold signal shown in  FIGS. 5A and 5B  and the disenable terminal can also be used for a variety of signal inputs according to its application. For example, the disenable terminal can also be used to always keep the transistor  332  OFF. 
     So far how to reduce crosstalk between the reset signal wire and transfer gate wire of a solid-state image sensing device is described in detail using an example. However, it is obvious for a person having an ordinary skill in the art that the target of the present invention is not limited to the crosstalk between the reset signal wire and transfer gate wire of a solid-state image sensing device. 
     The noise guard of the present invention is provided at the opposite end to the driver side of a control signal wire, which is a noise guard target, and in case of the minimum configuration, it can be realized by one transistor and one inverter. Therefore, it does not increase a chip area much. Furthermore, since the noise guard of the present invention basically operates on the logic of its control signal wire, it requires no special control signal for it. Therefore, there is no need to increase the number of wires, and the logic is compatible with other control logic since it does not interfere with the other control logic. 
     As the one transistor for reducing the impedance of a control signal wire, one with a large size can be adopted in order to further reduce the impedance. 
     If the present invention is applied in order to reduce the crosstalk between the reset signal wire and transfer gate wire of a solid-state image sensing device, the following effects can further obtained.
     (1) Since unintentional reset can be prevented, the pixel position dependency of an output image (shading) can be reduced.   (2) Since a noise guard is provided outside a pixel, the filfactor of a pixel is never reduced.   (3) Since the filfactor of a pixel and the number of wires are not changed, sensitivity does not degrade.   (4) The present invention is compatible with a device requiring the logic of pixel scanning, such as blooming countermeasures or the like.   

     The present invention is not limited to the above-mentioned preferred embodiments, and a variety of its variations and modifications can be possible as long as the subject matter of the present invention is not deviated.