Device to protect semiconductor device from electrostatic discharge

A device to protect a semiconductor device from electrostatic discharge includes a transferring unit transferring the static electricity inputted to said input/output terminal to the power line, a detecting unit sensing the potential difference between both ends of the transferring unit, located between an input/output terminal and one of the power lines, to output the detection voltage, and a discharging unit driven by said detection voltage and discharging the static electricity led to a specific power line to the other power line, and performs the discharging operation smoothly even with minute electrostatic current and a latter part of the static electricity by using the driving voltage, which is used to drive a conventional detecting unit, as the driving voltage of the ESD protection device, thereby safely protecting an internal circuit of a semiconductor device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Korean patent application number 10-2006-0035015 filed on Apr. 18, 2007, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a device to protect a semiconductor device from electrostatic discharge (ESD), and more particularly, to a device that protects the semiconductor device from ESD and resulting damage from the ESD.

Generally, electrostatic discharge (ESD) is one of the important factors that can adversely influence the reliability of a semiconductor device. Such electrostatic phenomenon can be classified into a human body model (HBM), a machine model (MM) and a charge device model (CDM) according to causes of the occurrence of the static electricity. The HBM is an electrostatic phenomenon resulting from a human body, the MM is an electrostatic phenomenon resulting from contact with a measuring machine and the CDM is a phenomenon in which static electricity accumulated in a device is instantly discharged by grounding with the outside.

If the static electricity is inputted to a semiconductor device, it flows intensively to the weakest portion of the semiconductor device. Because of this, a junction, a contact, a gate oxide film or other components located inside of the semiconductor device are melted, thereby resulting in failure. Therefore, the semiconductor device is necessarily provided with an ESD protection device in every input/output area in order to protect an internal circuit from electrostatic current.

Particularly, the thickness of the gate insulation film of a transistor consisting of an input/output buffer is more reduced with the development of manufacturing technology of semiconductor devices and thus an internal circuit can be more easily damaged. In other words, if the thickness of the gate insulation film of a transistor is reduced, the voltage breaking the gate insulation film is lowered, and thus the gate insulation film of the transistor may be broken by static electricity with the lower voltage in the case of using a conventional ESD protection device. To solve this problem, it is suggested to use a method in which a transistor is used in an ESD protection device.

A conventional device to protect a semiconductor from an ESD, as shown inFIG. 1, includes a transferring unit11, a detecting unit12, a driver13and a discharging unit14.

The transferring unit11transfers static electricity inputted to the semiconductor device through an input/output terminal15to an external voltage (VCC) line17.

The detecting unit12includes a resistance element R1and a capacitor C1serially connected between the external voltage line17and a grounding voltage (VSS) line18, and detects the static electricity inputted to the external voltage line17.

The driver13includes a CMOS type buffer formed by a PMOS transistor P1and a NMOS transistor N1serially connected between the external voltage line17and the grounding voltage line18, and is enabled by the detecting unit12to drive the discharging unit14.

The discharging unit14includes a NMOS transistor N2connected between the external voltage line17and the grounding voltage line18, and is driven by the driver13to interconnect the external voltage line17and the grounding voltage line18.

Referring to operation of the conventional device that protects a semiconductor from an ESD, if static electricity is inputted from the input/output terminal15, then static electricity is transferred to the external voltage line17by the transferring unit11. The detecting unit12detects the voltage drop generated in the node located between the resister R1and the capacitor C1in response to the alternating current in a rising time at the initial stage of generation of the static electricity, and applies it to the driver13. Then, since the PMOS transistor P1of the driver13is turned on and the gate voltage of the NMOS transistor N2of the discharging unit14is raised, thus turning on the NMOS transistor N2, the external voltage line17and the grounding voltage line18are interconnected and thus the static electricity transferred to the external voltage line17is discharged to the grounding voltage line18. As a result, the device protecting the semiconductor device from ESD protects the internal circuit16of the semiconductor device from the static electricity inputted to the input/output terminal15.

In conventional ESD protection devices voltage drop is rapidly generated during the alternating current brought about by the characteristics of the high rising time. In the initial stage of the static electricity, current flows to the capacitor C1of the detecting unit12and passes through the resistance element R1, in which the device is operated prior to the junction breakdown time of the PMOS transistor P1of the driver13.

However, the voltage drop generated in the detecting unit12is limited to the alternating current in the rising section of the static electricity and therefore the time in which the detection voltage is detected is short. In other words, since the operational duration of the device is short, it is difficult to protect the internal circuit16from the static electricity. As a result, the internal circuit16may be damaged in sections due to the relatively rapid rise and fall of the static electricity.

To solve the above problem, the present applicant applied a circuit as shown inFIG. 2as Korean Patent Application No. 2004-0114210, and the circuit shown inFIG. 2includes a differently structured detecting unit22that detects electrostatic current transferred to the external voltage line27and drives a driver23by the detection voltage responding to the detected electrostatic current.

The device used to protect the semiconductor device from ESD as shown inFIG. 2is provided with a transferring unit21, the detecting unit22, a driver23and a discharging unit24.

The transferring unit21transfers static electricity inputted through an input/output terminal25to the external voltage line27.

The detecting unit22includes a resistance element R2and a diode D1serially connected between the external voltage line27and the grounding voltage line28, and responds to the electrostatic current flowing on the external voltage line27.

The driver23includes a CMOS type buffer having a PMOS transistor P2and a NMOS transistor N3serially connected between the output terminal of the detecting unit22and the grounding voltage line28, and is turned on by the detecting unit22to drive the discharging unit24. Here, the gate of each of the transistors P2and N3is connected to the external voltage line27and the source of the PMOS transistor P2is connected to the output terminal of the detecting unit22.

The discharging unit24includes a NMOS transistor N4connected between the external voltage line27and the grounding voltage line28, and is driven by the driver23to interconnect the external voltage line27and the grounding voltage line28.

Referring to operation of the further conventional device to protect a semiconductor from an ESD, static electricity inputted from the input/output terminal25is transferred to the external voltage line27by the transferring unit21.

The detecting unit22transfers some of the static electricity inputted to the input/output terminal25through the diode D1to the external voltage line27while sensing the electrostatic current inputted to the external voltage line27, and detects the voltage dropped by the resistance element R2in response to the electrostatic current to apply to the driver23.

Then, since the PMOS transistor P2of the driver23is turned on and the gate voltage of the NMOS transistor N4of the discharging unit24is raised, then the NMOS transistor N4is turned on. Also since the external voltage line27and the grounding voltage line28are interconnected then the static electricity transferred to the external voltage line27is discharged to the grounding voltage line28.

As a result, the device protects the semiconductor device from ESD damage by protecting the internal circuit26of the semiconductor device from the static electricity inputted to the input/output terminal25.

In such a conventional device to protect the semiconductor device from ESD as described above, the detecting unit22continuously detects the detection voltage in a section, when the electrostatic current flowing to the external voltage line27is larger than a predetermined value to drive the driver23so that the discharging time of the device can be extended.

However, as shown inFIG. 3, a voltage Vout, is applied to the gate of the discharging unit24of the conventional device to protect the semiconductor device from ESD damage. Shown inFIG. 2, is the detection voltage V1which is detected in the detecting unit22which is then transferred through the driver23and depends on the detection voltage V1. A forward turn-on of the diode D1must then occur in order to detect the detection voltage V1in the detecting unit22. In other words, the driving voltage of the diode D1must be necessarily greater than the predetermined voltage (approximately 0.7V). In this case, the operation of the device is not sufficient and may damage the internal circuit26of the semiconductor device during a later part of the pulse in which the static electricity becomes small.

SUMMARY OF THE INVENTION

The present invention provides a device to protect a semiconductor device from electrostatic discharge (ESD), which can safely protect an internal circuit from static electricity by performing smoothly a discharging operation with minute current in a latter part of the static electricity.

The device to protect a semiconductor device from electrostatic discharge according to an embodiment of the present invention comprises, when the device is positioned between an external voltage line and a grounding voltage line, in order to protect an internal circuit of the semiconductor device from the static electricity inputted to an input/output terminal, a transferring unit transferring the static electricity inputted to the input/output terminal to one of the power lines; a detecting unit sensing the potential difference between both ends of the transferring unit, connected between the input/output terminal and one of the power lines, to output the detection voltage; and a discharging unit driven by the detection voltage and connecting the specific power line and the other power line to form a discharge path for the static electricity.

The transferring unit includes a first diode having a cathode connected to the external voltage line and an anode connected to the input/output terminal and a second diode having a cathode connected to the input/output terminal and an anode connected to the grounding voltage line.

Further, the detecting unit includes a MOSFET transistor and a resister, which are serially connected between the input/output terminal and one of the power lines.

Preferably, the MOSFET has a source connected to the input/output terminal, a gate connected to one of the power lines and a drain connected to the resister.

In addition, the detecting unit further includes a capacitor connected between the resister and one of the power lines.

Furthermore, the device for use in protecting a semiconductor device from ESD damage further comprises an amplifying unit connected in parallel to the detecting unit and the discharging unit and amplifying the detection voltage inputted from the detecting unit to transfer to the discharging unit. The amplifying unit may be provided with an even number of CMOS type inverters.

Another device for use in protecting a semiconductor device from electrostatic discharge damage according to an embodiment of the present invention comprises, when placed between an external voltage line and a grounding voltage line, in order to protect an internal circuit of the semiconductor device from the static electricity inputted to an input/output terminal, a transferring unit transferring the static electricity inputted to the input/output terminal to the grounding voltage line; a detecting unit that senses the potential difference between both ends of the transferring unit, connected between the input/output terminal and the grounding voltage line, to output the detection voltage; and a discharging unit driven by the detection voltage and connecting the external voltage line and the grounding voltage line to form a discharging path for the static electricity.

The transferring unit includes a first diode having a cathode connected to the external voltage line and an anode connected to the input/output terminal and a second diode having a cathode connected to the input/output terminal and an anode connected to the grounding voltage line.

Further, the detecting unit may include a NMOS transistor having a gate connected to the grounding voltage line and a source connected to the input/output terminal and a resister connected between a drain of the NMOS transistor and the grounding voltage line.

In addition, the discharging unit may include a PMOS transistor connected between the external voltage line and the grounding voltage line.

Still yet another embodiment of the device for use in protecting a semiconductor device from electrostatic discharger according to the present invention comprises, when connected between an external voltage line and a grounding voltage line, in order to protect an internal circuit of the semiconductor device from the static electricity inputted to an input/output terminal, comprises a transferring unit transferring the static electricity inputted to the input/output terminal to the external voltage line; a detecting unit sensing the potential difference between both ends of the transferring unit, connected between the input/output terminal and the external voltage line, to output the detection voltage; and a discharging unit driven by the detection voltage and connecting the external voltage line and the grounding voltage line to form a discharging path for the static electricity.

The transferring unit includes a first diode having a cathode connected to the external voltage line and an anode connected to the input/output terminal and a second diode having a cathode connected to the input/output terminal and an anode connected to the grounding voltage line.

In addition, the detecting unit includes a PMOS transistor having a gate connected to the external voltage line and a source connected to the input/output terminal and a resister connected between a drain of the PMOS transistor and the grounding voltage line.

Furthermore, the discharging unit may also include a NMOS transistor connected between the external voltage line and the grounding voltage line.

Still yet another embodiment of the device for use in protecting a semiconductor device from electrostatic discharge damage, according to the present invention comprises, when placed between an external voltage line and a grounding voltage line in order to protect an internal circuit of the semiconductor device from the static electricity inputted to an input/output terminal, comprises: a transferring unit transferring the static electricity inputted to the input/output terminal to the external voltage line; a detecting unit sensing the potential difference between both ends of the transferring unit, connected between the input/output terminal and the external voltage line, to output the detection voltage; an amplifying unit amplifying the detection voltage inputted from the detecting unit to output the amplified detection voltage; and a discharging unit driven by output from the amplifying unit and connecting the external voltage line and the grounding voltage line to form a discharging path for the static electricity.

The transferring unit includes a first diode having a cathode connected to the external voltage line and an anode connected to the input/output terminal and a second diode having a cathode connected to the input/output terminal and an anode connected to the grounding voltage line.

In addition, the detecting unit includes a PMOS transistor having a gate connected to the external voltage line and a source connected to the input/output terminal and a resister connected between a drain of the PMOS transistor and the grounding voltage line.

Preferably, the amplifying unit is provided with an even number of CMOS type inverters.

Furthermore, the discharging unit includes a NMOS transistor connected between the external voltage line and the grounding voltage line.

Even yet another embodiment of the device for use in protecting a semiconductor device from damage brought about by electrostatic discharge, according to the present invention comprises, when placed between an external voltage line and a grounding voltage line, in order to protect an internal circuit of the semiconductor device from the static electricity inputted to an input/output terminal, comprises: a transferring unit transferring the static electricity inputted to the input/output terminal to the external voltage line; a first detecting unit detecting the voltage drop in response to alternating current in an initial rising section of the static electricity, which is transferred to the external voltage line as the first detection voltage; a second detecting unit sensing the potential difference between both ends of the transferring unit, connected between the input/output terminal and the external voltage line, to output a second detection voltage; and a discharging unit driven by the first and second detection voltages and connecting the external voltage line and the grounding voltage line to form a discharging path for the static electricity.

The transferring unit includes a first diode having a cathode connected to the external voltage line and an anode connected to the input/output terminal and a second diode having a cathode connected to the input/output terminal and an anode connected to the grounding voltage line.

The first detecting unit includes a capacitor and a resister, which are serially connected between the external voltage line and the grounding voltage line.

In addition, the second detecting unit includes a PMOS transistor having a gate connected to the external voltage line and a drain connected to the first detecting unit.

Preferably, the first and second detecting unit provide the first and second detection voltage, respectively, to the discharging unit as a common input.

Preferably, the first and second detecting unit provide the first and second detection voltage respectively to the discharging unit using a shared resister.

Furthermore, the discharging unit includes a NMOS transistor connected between the external voltage line and the grounding voltage line.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Practical and presently preferred embodiments of the present invention are illustrative as shown in the following Examples and Comparative Examples.

FIG. 4is a circuit diagram illustrating a device for use in protecting a semiconductor device from ESD damage according to a first embodiment of the present invention.

The device to protect a semiconductor device from ESD according to a first embodiment of the present invention is provided with a transferring unit41, a detecting unit42and a discharging unit43.

The transferring unit41includes diodes D2and D3, which are serially connected between an external voltage line47and a grounding voltage line48. A cathode of the diode D2is connected to the external voltage line47and an anode of the diode D3is connected to the grounding voltage line48. The transferring unit41transfers static electricity to the external voltage line47so that the static electricity inputted from the input/output terminal45is not transferred to an internal circuit.

The detecting unit42includes a PMOS transistor P3and a resistance element R3, which are serially connected between the input/output terminal45and the grounding voltage line48. Here, the gate of the PMOS transistor23is connected to the external voltage line47, the source to the input/output terminal45and the drain to the resistance element R3.

The discharging unit43includes a NMOS transistor N5connected between the external voltage line47and the grounding voltage line48. The drain of the NMOS transistor N5is connected to the external voltage line47, the source to the grounding voltage line48and the gate to an output terminal of the detecting unit42.

Referring to the operation of the device to protect a semiconductor from an ESD according to the first embodiment of the present invention, the transferring unit41leads the static electricity to the power lines47and48so that the static electricity inputted through the input/output terminal45is not transferred to the internal circuit46.

When transferring the static electricity inputted from the input/output terminal45through the diode D2of the transferring unit41to the external voltage line47, the voltage drop can be generated by a parasitic resister (not shown) of the diode D2. As the result, the voltage drop is generated between the external voltage line47and the input/output terminal45.

The detecting unit42is turned on as the voltage dropped across by the parasitic resister of the diode D2and is applied to the gate of the PMOS transistor P3, and applies a detection voltage Vout2dropped by the resistance element R3to the gate of the discharging unit43.

If the detection voltage applied to the gate of the NMOS transistor N5is raised, thus turning on the discharging unit43, the discharging unit43interconnects the external voltage line47and the grounding voltage line48to discharge the static electricity led to the external voltage line47to the grounding voltage line48. As a result, the device for use in protecting a semiconductor device from ESD protects the internal circuit46of the semiconductor device from the static electricity inputted to the input/output terminal45.

As such, in the device for use in protecting a semiconductor device from ESD damage, according to the first embodiment of the present invention, the discharging operation can be sufficiently performed even in a latter part of a pulse in which an electrostatic current becomes small by using the voltage, which has been lost as a driving voltage of the diode D1in the conventional detecting unit22, as the driving voltage of the ESD protection device.

FIG. 5is a graph illustrating the voltage that is applied to the gate of the discharging unit43of the device to protect a semiconductor device from ESD of the present invention shown inFIG. 4.

Referring toFIG. 5, the voltage Vout2applied to the gate of the discharging unit43is influenced by the detection voltage V2detected in the detecting unit42. However, since it is not necessary for the driving voltage (approximately 0.7V [0.7→0.7V]) for turning on the diode D1as shown inFIG. 2, the detection voltage V2of the present invention is larger by approximately 0.7V than the conventional detection voltage V1inFIG. 3. Therefore, the voltage Vout2applied to the gate of the discharging unit43is higher than the voltage Vout1applied to the gate of the conventional discharging unit24inFIG. 2. Thus, the discharging operation can be sufficiently performed even in a latter part of a pulse in which an electrostatic current becomes small and is thereby capable of protecting the internal circuit46of the semiconductor device.

FIGS. 6 to 8are circuit diagrams illustrating devices for use in protecting a semiconductor device from ESD damage, according to the second, third and Fourth embodiments of the present invention.

Only those portions different from the elements ofFIG. 4will be described hereinafter.

The device to protect a semiconductor device from ESD according to the second embodiment of the present invention shown inFIG. 6is adapted to protect an internal circuit66from negative (−) static electricity inputted to the input/output terminal65in a case in which the elements in the internal circuit66connected to the external voltage line67are very weak.

InFIG. 6a PMOS transistor P4is provided as a discharging unit63unlike the first embodiment in which a NMOS transistor N5is provided as the discharging unit43, as shown inFIG. 4. Further, the detecting unit62includes a resistance element R4and a NMOS transistor N6, which are serially connected between the external voltage line67and a grounding voltage line68. Here, the gate of the NMOS transistor N6is connected to the grounding voltage line68, the drain to the input/output terminal and the source to the resistance element R4.

Referring to the operation of the device to protect a semiconductor from an ESD according to the second embodiment of the present invention, if negative (−) static electricity is inputted to the input/output terminal65, the voltage of the grounding voltage line68is inputted to the input/output terminal65through the diode D5of the transferring unit61. At this time, the voltage drop is generated across the parasitic resister (not shown) of the diode D5. Thus, the NMOS transistor N6of the detecting unit62is turned on to apply voltage applied to the common connection terminal of the resistance element R4and the NMOS transistor N6to the gate of the discharging unit63.

If the detection voltage applied to the gate of the PMOS transistor P5is lowered, thus turning on the discharging unit63, the discharging unit63interconnects the external voltage line67and the grounding voltage line68to flow and discharge the current from the external voltage line67to the grounding voltage line68. As a result, the device for use in protecting a semiconductor device from ESD damage, protects the internal circuit66of the semiconductor device from the static electricity inputted to the input/output terminal65.

The device for use in protecting a semiconductor device from ESD according to the third embodiment of the present invention shown inFIG. 7is further provided with an amplifying unit74between the detecting unit72and the discharging unit73to enhance the driving ability of the discharging unit73.

The amplifying unit74includes two CMOS type inverters having a PMOS transistor and a NMOS transistor, which are serially connected between the external voltage line77and the grounding voltage line78.

Discharging operation can be performed more stably as the detection voltage detected in the detecting unit72is sufficiently amplified by the amplifying unit74and then applied to the discharging unit73. Thus, the device to protect a semiconductor device from ESD protects the internal circuit76of the semiconductor device from the static electricity inputted to the input/output terminal75.

The device for use in protecting a semiconductor device from ESD damage according to the fourth embodiment of the present invention shown inFIG. 8includes as a detecting unit82a PMOS transistor P8and resistance element R6, which are serially connected between an input/output terminal85and a grounding voltage line88, and a capacitor C2connected between the output end of the PMOS transistor P8and the external voltage line87.

Thus, the detecting unit82senses the potential difference between both ends of the transferring unit81across all of a section. In which static electricity is generated to apply the detected voltage to the gate of the discharging unit83, and detects the voltage dropped across the resistance element R6through the capacitor C2when alternating current flows rapidly in the initial stage of the static electricity to apply it to the discharging unit83, thereby driving the discharging unit83to more rapidly protect an internal circuit86of a semiconductor device.

As described above, the present invention performs the discharging operation smoothly even with minute electrostatic current and uses a latter part of the static electricity by using the driving voltage, which is used to drive a conventional detecting unit, as the driving voltage of the ESD protection device, thereby more safely protecting an internal circuit of a semiconductor device.