Abstract:
Disclosed is an electrostatic protection device for a semiconductor device, which protects the semiconductor device from damage due to electrostatic discharge (ESD). The electrostatic protection device includes a delivery unit for inducing the static electricity introduced to the input/output port to an external voltage line, a detection unit for detecting the static electricity induced to the external voltage line and outputting a detected voltage in response to the static electricity induced to the external voltage line, and a driver driven by the detected voltage in order to drive the electrostatic discharge unit in response to the static electricity induced to the external voltage line.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an electrostatic protection device for a semiconductor device, and more particularly to an electrostatic protection device for a semiconductor device, which protects a semiconductor integrated circuit from damage due to electrostatic discharge (ESD).  
         [0003]     2. Description of the Prior Art  
         [0004]     As generally known in the art, electrostatic discharge (ESD) is one of main factors affecting the reliability of a semiconductor chip. This electrostatic discharge causes damage to a semiconductor chip when the semiconductor chip is handled, or installed in a system. Accordingly, an electrostatic protection device is indispensably provided to a data input/output area of a semiconductor device in order to protect the semiconductor device from static electricity. If an electrically charged human body or machine makes contact with a semiconductor device, static electricity charged in the human body or the machine is discharged inside of the semiconductor device through an input/output port of an external pin in the semiconductor device, so that excessive electrostatic current having high energy may inflict fatal damage on an internal circuit of the semiconductor device. Most semiconductor devices include an electrostatic protection device between an input/output port and an internal circuit of the semiconductor device in order to prevent an internal main circuit from being damaged by the static electricity.  
         [0005]     In the meantime, as a technique of manufacturing a semiconductor device becomes developed, the thickness of a gate insulating layer of a transistor included in an input/output buffer is further reduced, so that the internal circuit of the semiconductor device may be more easily damaged due to static electricity. In other words, if the thickness of the gate insulating layer of the transistor is reduced, destructive voltage for the gate insulating layer is lowered. Thus, if a conventional electrostatic protection device is used, the gate insulating layer of the transistor may be destructed even if relatively lower static electricity is applied thereto. In order to solve the problem, a method for employing a transistor for the electrostatic protection device has been suggested.  
         [0006]      FIG. 1  is a circuit diagram illustrating the conventional electrostatic protection device of a semiconductor device.  
         [0007]     The conventional electrostatic protection device includes a delivery module  11 , a control module  12 , a driver  13 , and a discharge module  14 . The delivery module  11  induces static electricity to a line  17  of external voltage (Vcc) instead of an internal circuit in the semiconductor device through an input/output port  15 . Such static electricity induced to the line  17  of the external voltage is delivered to the control module  12 , the driver  13 , and the discharge module  14  connected to the line  17 . The control module  12  includes a resistor R 1  and a capacitor C 1  serially connected between the line  17  of the external voltage (Vcc) and a line  18  of the grounding voltage (Vss). The driver  13  has a CMOS type buffer including a PMOS transistor P 1  and an NMOS transistor N 1  serially connected between the line  17  of the external voltage (Vcc) and the line  18  of the grounding voltage (Vss). The discharge module  14  includes an NMOS transistor N 2  connected between the line  17  of the external voltage VCC and the line  18  of the grounding voltage Vss.  
         [0008]     In the electrostatic protection device for the semiconductor device, the static electricity induced to the line  17  of the external voltage (Vcc) through the delivery module  11  generates a voltage drop by means of the control module  12 , and the PMOS transistor P 1  of the driver  13  is turned on due to the voltage drop. As a result, the NMOS transistor N 2  of the discharge module  14  is turned on, so that the line  17  of the external voltage Vcc is connected to the line  18  of the grounding voltage Vss. Accordingly, static electricity induced to the line  17  of the external voltage Vcc is discharged through the line  18  of the grounding voltage Vss. In other words, static electricity introduced into the input/output port  15  is induced to the line  17  of the external voltage Vcc and then discharged through the line  18  of the grounding voltage Vss. Accordingly, the electrostatic protection device protects the internal circuit  16  of the semiconductor device from static electricity introduced through the input/output port  15 .  
         [0009]     As described above, the conventional electrostatic protection device for a semiconductor device operates earlier than a time point of a junction breakdown. However, the conventional electrostatic protection device has a fast operation speed because a voltage drop of the control module  12  swiftly occurs. However, since the voltage drop is generated only during a rising interval of the static electricity, the operation duration of the electrostatic protection device is short. In other words, since the voltage drop of the control module  12  occurs only during a rising interval of static electricity, the driver  13  operates only during the rising interval so as to discharge static electricity. As a result, since the internal circuit of the semiconductor device is not protected from static electricity during intervals except for the rising interval of the static electricity (e.g., a peak interval of a static electricity and a falling interval of a static electricity), the internal circuit may be damaged during the intervals.  
         [0010]     In order to solve this problem, as shown in  FIG. 2 , U.S. Pat. No. 5,946,177 suggests that a electrostatic protection device for a semiconductor device additionally includes a delay module  29  in order to reduce the attenuation time of voltage applied to the discharge module  24  by the driver  23 .  
         [0011]     In other words, an electrostatic protection device for a semiconductor device shown in  FIG. 2  includes a delivery module  21 , a control module  22 , a driver  23 , a discharge module  24 , and a delay module  29 . Static electricity introduced through an input/output port  25  is induced to the line  27  of an external voltage Vcc through the delivery module  21 , and then the control module  22  performs voltage drop for the static electricity so as to operate the driver  23 . Accordingly, the discharge module  24  delivers static electricity induced to the line  27  of the external voltage Vcc to a line  28  of a grounding voltage Vss, thereby discharging the static electricity. At this time, the delay module  29  delays an attenuation time of voltage applied in order to operate the discharge module  24  through the operation of a resistor element R 3  and a capacitor C 3 . Accordingly, the electrostatic protection device shown in  FIG. 2  may further increase an operation duration time as compared with the electrostatic protection device shown in  FIG. 1 . However, a constant value of an RC approximating to a time, in which a static electricity signal is continuously maintained, is required in order to delay voltage attenuation due to the resistor R 3  and the capacitor C 3  of the delay module  29 . In other words, since the driver  23  does not operate after a rising duration, voltage used for operating the discharge module  24  is attenuated according to a time as charges filled in the capacitor C 3  are slowly discharged through the resistor R 3 . Voltage according to a time is expressed as an equation,  
         v   ⁡     (   t   )       =          v        ⁢       ⅇ     -     t   RC         .           
 
         [0012]     Herein, the t, the R, the C, and |ν| denote time, resistance of a resistor, capacitance of a capacitor, and the peak value of the voltage ν(t).  
         [0013]     Accordingly, voltage required for operating the driver  23  due to voltage drop through the control module  22  is determined by a constant value of RC obtained based on the resistor R 2  and the capacitor C 2 , and voltage required for operating the discharge module  24  by the driver  23  is determined by a constant value of RC obtained based on the resistor R 3  and the capacitor C 3  of the delay module. The control module  22  must have an RC value smaller than or equal to 10 ns in order to allow the electrostatic protection device to swiftly respond to static electricity and operate, and the delay module  29  must have an RC value larger than or equal to 100 ns, which is the time interval of the electrostatic discharge pulse width.  
         [0014]     In other words, the resistor R 3  and the capacitor C 3  of the delay module  29  must have values larger than or equal to 10 times values of the resistor R 2  and the capacitor C 2  of the control module  22 . As a result, the size of the semiconductor device may increase.  
       SUMMARY OF THE INVENTION  
       [0015]     Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a electrostatic protection device for a semiconductor device, which can stably protect a semiconductor device from electrostatic discharge by discharging the static electricity in the duration of static electricity without increasing the size of the semiconductor device.  
         [0016]     In order to accomplish the object, there is provided an electrostatic protection device for a semiconductor device for protecting an internal circuit of the semiconductor device by discharging static electricity introduced into an input/output port through an electrostatic discharge unit, the electrostatic protection device including a delivery unit for inducing the static electricity introduced to the input/output port to an voltage line, a detection unit for detecting the static electricity induced to the voltage line and outputting a detected voltage in response to the static electricity induced to the voltage line, and a driver driven by the detected voltage in order to drive the electrostatic discharge unit in response to the static electricity induced to the voltage line.  
         [0017]     The driver includes a CMOS type buffer connected between an output port of the detection unit and a grounding port, and an input port of the CMOS type buffer is connected to the voltage line.  
         [0018]     The detection unit includes a resistor and a diode serially connected to the voltage line and the input/output port.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0020]      FIG. 1  is a circuit diagram for explaining an electrostatic protection device of a semiconductor device in the conventional technique;  
         [0021]      FIG. 2  is a circuit diagram for explaining another electrostatic protection device of a semiconductor device in the conventional technique;  
         [0022]      FIG. 3  is a circuit diagram for explaining a electrostatic protection device for a semiconductor device according to a preferred embodiment of the present invention; and  
         [0023]      FIG. 4  is a circuit diagram for explaining a electrostatic protection device for a semiconductor device according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the following description and drawings, the same reference numerals are used to designate the same or similar components, and so repetition of the description on the same or similar components will be omitted.  
         [0025]      FIG. 3  is a circuit diagram for explaining an electrostatic protection device for a semiconductor device according to the present invention.  
         [0026]     The electrostatic protection device for a semiconductor device according to the present invention includes a delivery module  31 , a detection module  32 , a driver  33 , and a discharge module  34 . The delivery module  31  includes diodes D 1  and D 2  serially connected between a line  37  of an external voltage Vcc and a line  38  of a grounding voltage Vss. Cathodes of the diodes D 1  and D 2  are connected to the side of the line  37  of the external voltage Vcc, and anodes of the diodes D 1  and D 2  are connected to the side of the line  38  of the grounding voltage Vss. The delivery module  31  induces static electricity to the line  37  of the external voltage Vcc such that static electricity introduced through an input/output port  35  is not delivered to an internal circuit  36 .  
         [0027]     The detection module  32  includes a resistor R 4  and a diode D 3  serially connected between the line  37  of the external voltage Vcc and an input port  35  of the internal circuit  36 . The detection module  32  detects static electricity induced to the line  37  of the external voltage Vcc and applies detected voltage to the driver  33  in response to the static electricity. The detected voltage is obtained by performing voltage drop through a resistor R 4  with respect to the static electricity induced to the line  37  of the external voltage Vcc. In other words, the detected voltage is voltage of a common connection port of the resistor R 4  and the diode D 3 , and the driver  33  operates based on the detected voltage.  
         [0028]     The driver  33  includes a PMOS transistor P 2  and an NMOS transistor N 3  serially connected between an output port of the detection module  32  and the line  38  of the grounding voltage Vss. In other words, the driver  33  includes a CMOS type buffer unit formed by the PMOS transistor P 2  and the NMOS transistor N 3 . The detected voltage inputted from the detection module  32  is applied to a source port of the PMOS transistor (P 2 ), and the driver  33  is driven by the detected voltage. The detected voltage inputted from the detection module  32  becomes a supply voltage of the CMOS type buffer unit. When the CMOS type buffer operates based on the detected voltage, the static electricity induced to the line  37  of the external voltage Vcc is applied to the input ports of the CMOS type buffer, that is, gate ports of the PMOS transistor P 2  and the NMOS transistor N 3 . Accordingly, the driver  33  operates the discharge module  34 .  
         [0029]     The discharge module  34  includes an NMOS transistor N 4  connected between the line  37  of the external voltage Vcc and the line  38  of the grounding voltage Vss. A drain port of the NMOS transistor N 4  is connected to the line  37  of the external voltage Vcc, and the source port of the NMOS transistor N 4  is connected to the line  38  of the grounding voltage Vss. If the discharge module  34  is enabled by the driver  33 , the NMOS transistor N 4  is turned on. Accordingly, static electricity induced to the line  37  of the external voltage Vcc is delivered to the line  38  of the grounding voltage Vss through the NMOS transistor N 4 . In other words, the static electricity introduced to the input/output port  35  is induced to the line  37  of the external voltage Vcc and then discharged through the line  38  of the grounding voltage Vss. Accordingly, the electrostatic protection device protects the internal circuit  36  of the semiconductor device from static electricity introduced to the input/output port  35 .  
         [0030]     Such an electrostatic protection device for a semiconductor device according to the present invention induces static electricity introduced to the input/output port  35  to the line  37  of the external voltage Vcc through the delivery module  31 . In addition, the electrostatic protection device always detects static electricity induced to the line  37  of the external voltage Vcc through the detection module  32 . In addition, the detection module  32  applies a detected voltage to the driver  33  in response to the static electricity, thereby operating the driver  33 . Thus, the driver  33  operates in response to static electricity, so that static electricity induced to the line  37  of the external voltage Vcc is delivered to the line  38  of the grounding voltage Vss through the discharge module  34  and discharged. In other words, when static electricity is introduced to the input/output port  35 , the electrostatic protection device for the semiconductor device according to the present invention always operates in response to static electricity. In addition, the electrostatic protection device operates during all intervals of the static electricity. Accordingly, the electrostatic protection device for the semiconductor device according to the present invention operates during all intervals including a rising interval of static electricity introduced to the input/output port  35 , thereby protecting the internal circuit  36  of the semiconductor device from static electricity.  
         [0031]      FIG. 4  is a circuit diagram for explaining an electrostatic protection device for a semiconductor device according to another embodiment of the present invention. Hereinafter, only components different from the components shown in  FIG. 3  will be described.  
         [0032]     The electrostatic protection device for a semiconductor device according to the present embodiment includes a detection module  42  having a resistor R 5  and a diode type transistor T 1  differently from the prior embodiment including the detection module  32  having the resistor R 4  and the diode D 3 . In other words, the detection module  42  of the electrostatic protection device for the semiconductor device according to an embodiment of the present invention includes a resistor element R 5  and a diode type transistor T 1  connected serially between a line  47  of an external voltage Vcc and an input/output port  45  of the internal circuit  46 . A source port of the diode type transistor T 1  is commonly connected to the resistor R 5 , a gate port of the transistor T 1  is connected to the line  47  of the external voltage Vcc, and a drain port of the transistor T 1  is connected to an input port of the internal circuit  46 . The detection module  42  detects static electricity induced to the line  47  of the external voltage Vcc and applies the detected static electricity to the driver  43  as a detected voltage by performing voltage drop with respect to the detected static electricity. In other words, the detection module  42  delivers voltage of the common connection port of the diode type transistor T 1  and the resistor R 5  to the driver  43  as the detected voltage in response to static electricity.  
         [0033]     Such an electrostatic protection device for a semiconductor device according to the present embodiment induces static electricity introduced to the input/output port  45  to the line  47  of the external voltage Vcc through the delivery module  41  and always detects the static electricity induced to the line  47  of the external voltage Vcc through the detection module  42 . In addition, the detection module  42  applies a detected voltage to the driver  43  in response to static electricity, thereby operating the driver  43 . Thus, the driver  43  operates in response to the static electricity, so that static electricity induced to the line  47  of the external voltage Vcc is delivered to the line  48  of the grounding voltage Vss through the discharge module  44  and discharged. In other words, when static electricity is introduced to the input/output port  45 , the electrostatic protection device for a semiconductor device according to the present invention always responds to static electricity and operates during all intervals of the static electricity. Accordingly, the electrostatic protection device for a semiconductor device according to the present invention operates during all intervals including a rising interval of the static electricity introduced to the input/output port  45 , thereby protecting the internal circuit  46  from static electricity.  
         [0034]     The electrostatic protection device according to the present embodiment may be realized to have the same effects as that according to a prior embodiment.  
         [0035]     As described above, according to the present invention, static electricity introduced to an input/output port is detected through a detection module, so that the static electricity can be discharged during all intervals for the introduction of the static electricity. Accordingly, it is possible to stably protect an internal circuit of a semiconductor device from static electricity introduced to an input/output port and to prevent any increase in the size of the semiconductor device.  
         [0036]     Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.