Patent Application
20090201713
The present invention claims a priority of Korean Patent Application No. 10-2008-0013045, filed on Feb. 13, 2008, which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to semiconductor design technology; and, more particularly, to a One-Time Programmable (OTP) unit cell and a nonvolatile memory device having the same.
2. Description of Related Art
Since One-Time Programmable (OTP) memory devices have nonvolatile characteristics of retaining data, which are stored in memory cells, even in a power-off state, they are becoming widely used as memory devices that can replace memory sticks, Universal Serial Bus (USB) drivers, and hard disks.
Referring to
Hereinafter, a description will be given of a write/read operation of the conventional OTP unit cell.
Write Operation
First, the node B is grounded. Then, a high voltage VPP is applied to the first input terminal A and a logic low level L corresponding to a ground voltage is applied to second and third input terminals C and D. Accordingly, a high electric field is formed between a substrate and a gate of the anti-fuse ANT_FS including a MOS transistor, to break a gate insulating layer formed between the substrate and the gate. Thus, the substrate and the gate of the anti-fuse ANT_FS are electrically shorted.
Read Operation
After completion of the write operation, a power supply voltage VDD is applied to the first input terminal A and a logic high level H corresponding to the power supply voltage VDD is applied to the second and third input terminals C and D. Accordingly, a current path is formed from the first input terminal A, through the anti-fuse ANT_FS and the first and second transistors NM1 and NM2, to the output terminal E. Thus, the power supply voltage VDD applied to the first input terminal A is transferred to the output terminal E so that the power supply voltage VDD is detected.
However, the conventional OTP unit cell illustrated in
As described above, the current path (i.e., data path) formed from the first input terminal A to the output terminal E in the read operation must include the first and second transistors NM1 and NM2 that are connected in series. Accordingly, the final data detected through the output terminal E are outputted in a state of being voltage-dropped by the sum of threshold voltages of the first and second transistors NM1 and NM2 (i.e., VDD—2Vt where ‘Vt’ denotes the threshold voltage of each of the first and second transistors NM1 and NM2). Thus, a sensing margin of the data sensed through the output terminal E degrades by the voltage drop, thus leading to a malfunction. The malfunction causes degradation in the read operation reliability of the OTP unit cell.
An embodiment of the present invention is directed to a unit cell of a nonvolatile memory device and a nonvolatile memory device having the same, which can improve a data sensing margin in a read operation, thereby making it possible to improve the operational reliability.
In accordance with an aspect of the present invention, there is provided a unit cell of a nonvolatile memory device, which includes: an anti-fuse connected between an output terminal and a ground voltage terminal; a first switching unit connected to the output terminal to transfer a write voltage to the output terminal; and a second switching unit connected to the output terminal to transfer a read voltage to the output terminal.
In accordance with another aspect of the present invention, there is provided a unit cell of a nonvolatile memory device, which includes: an anti-fuse connected between a node and a ground voltage terminal; a first switching unit connected to the node to transfer a write voltage to the node; a second switching unit connected between the node and an output terminal; and a third switching unit connected to the output terminal to transfer a read voltage to the output terminal.
In accordance with another aspect of the present invention, there is provided a nonvolatile memory device including: a cell array comprising a plurality of unit cells arranged in a matrix type; a plurality of data lines connected in common to an output terminal of the unit cells; and a plurality of sensor units comprising inverters configured to respectively invert voltages of the data lines.
In accordance with another aspect of the present invention, there is provided a nonvolatile memory device including: a cell array comprising a plurality of the unit cells of claim 1 arranged in a matrix type; a plurality of write driving lines configured to select and control the first switching unit of the unit cell; a plurality of first read driving lines configured to select and control the second switching unit of the unit cell; a plurality of data lines connected to an output terminal of the unit cell; a plurality of third switching units configured to transfer the read voltage to the data line; a second read driving line configured to select and control the third switching units in common; and a plurality of sensor units configured to sense a voltage of the data line.
In accordance with another aspect of the present invention, there is provided a nonvolatile memory device including: a cell array comprising a plurality of the unit cells of claim 2 arranged in a matrix type; a plurality of write driving lines configured to select and control the first switching unit of the unit cell; a plurality of first read driving lines configured to select and control the second switching unit of the unit cell; a plurality of data lines connected to an output terminal of the unit cell; a second read driving line configured to select and control the third switching units of the unit cells in common; and a plurality of sensor units configured to sense a voltage of the data line.
Other objects and advantages of the present invention can be understood by the following description, and become apparent with reference to the embodiments of the present invention. Also, it is obvious to those skilled in the art to which the present invention pertains that the objects and advantages of the present invention can be realized by the means as claimed, and combinations thereof.
The advantages, features and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, which is set forth hereinafter. The present invention will now be described with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. However, the invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Like reference numerals in the drawings denote like elements, and thus their description will be omitted for conciseness. A term ‘transistor’ used herein includes any unit that operates as a switching unit according to a control signal input to a gate. Examples of the transistor include a junction field-effect transistor (JFET) and a metal-oxide-semiconductor field-effect transistor (MOSFET).
Referring to
As illustrated
As illustrated
As illustrated in
Hereinafter, a description will be given of an operation of the unit cell of the nonvolatile memory device in accordance with the embodiment 1 of the present invention. Herein, for example, the first switching unit SW1 includes a p-channel transistor and the second switching unit SW2 includes an n-channel transistor. The anti-fuse ANT_FS includes an n-channel transistor.
A description will be made with reference to Table 2 and
Write Operation
First, the ground voltage terminal D is grounded. Then, a high voltage VPP is applied to the first input terminal A and a logic low level L corresponding to a ground voltage is applied to the third and fourth input terminals E and F. Under this condition, only the first switching unit SW1 including a p-channel transistor is turned on. Thus, the first input terminal A and the output terminal C are electrically connected to each other, and the second input terminal B and the output terminal C are electrically disconnected from each other. Accordingly, the high voltage VPP is transferred through the first switching unit SW1 to the anti-fuse ANT_FS to break a gate insulating layer formed between a substrate and a gate of the anti-fuse ANT_FS.
Read Operation
After completion of the write operation, a power supply voltage VDD corresponding to a read voltage is applied to the second input terminal B and a logic high level H corresponding to the power supply voltage VDD is applied to the third and fourth input terminals E and F. Under this condition, only the second switching unit SW2 including an n-channel transistor is turned on.
Thus, the second input terminal B and the output terminal C are electrically connected to each other, and the first input terminal A and the output terminal C are electrically disconnected from each other. Accordingly, a current path is formed from the second input terminal B, through the second switching unit SW2, to the anti-fuse ANT_FS.
In this case, because the gate insulating layer of the anti-fuse ANT_FS is broken, the output terminal C is electrically connected to the ground voltage terminal D through the anti-fuse ANT_FS. Thus, data corresponding to the ground voltage are outputted to the output terminal C, which are sensed by a sensor unit.
Referring to
Also, the unit cell of the nonvolatile memory device in accordance with the embodiment 2 of the present invention further includes a third switching unit SW3 connected in series to the second switching unit SW2. Accordingly, the first switching unit SW1 is connected in parallel to the second and third switching units SW2 and SW3 that are connected in series to each other.
The first switching unit SW1 may include a transistor (i.e., an active device) to transfer a write voltage, to an input terminal of the anti-fuse ANT_FS connected to a node H. Herein, the transistor may be a p-channel transistor or an n-channel transistor. In this case, the transistor has a drain connected to a first input terminal A, a source connected to the node H, and a gate connected to a third input terminal E.
The second switching unit SW2 is connected between an output terminal C and the node H. Like the first switching unit SW1, the second switching unit SW2 may include a transistor (i.e., an active device). Herein, the transistor may be a p-channel transistor or an n-channel transistor. In this case, the transistor has a drain connected to the output terminal C, a source connected to the node H, and a gate connected to a fourth input terminal F.
Like the second switching unit SW2, the third switching unit SW3 may include a transistor (i.e., an active device) to transfer a read voltage to the output terminal C. Herein, the transistor may be a p-channel transistor or an n-channel transistor. In this case, the transistor has a drain connected to a second input terminal B, a source connected to the output terminal C, and a gate connected to a fifth input terminal G.
Meanwhile, the first to third switching units SW1, SW2 and SW3 may have the same channel type or may have different channel types. Preferably, the first and third switching units SW1 and SW3 have a p-channel, and the second switching unit SW2 has an n-channel.
Hereinafter, a description will be given of an operation of the unit cell of the nonvolatile memory device in accordance with the embodiment 2 of the present invention. Herein, for example, the first and third switching units SW1 and SW3 include a p-channel transistor and the second switching unit SW2 includes an n-channel transistor. The anti-fuse ANT_FS includes an n-channel transistor.
A description will be made with reference to Table 3 and
Write Operation
First, a ground voltage terminal D is grounded. Then, a high voltage VPP is applied to the first input terminal A and a logic low level L is applied to the third and fourth input terminals E and F. Also, a logic high level H is applied to the fifth input terminal G. Under this condition, only the first switching is turned on.
Thus, the first input terminal A and the node H are electrically connected to each other, and the second input terminal B and the node H are electrically disconnected from each other. Accordingly, the high voltage VPP is transferred through the first, switching unit SW1 to the anti-fuse ANT_FS to break a gate insulating layer formed between a substrate and a gate of the anti-fuse ANT_FS. That is, the gate and the substrate are electrically shorted.
Read Operation
After completion of the write operation, a power supply voltage VDD corresponding to a read voltage is applied to the second input terminal B and a logic high level H is applied to the third and fourth input terminals E and F. Also, a logic low level L is applied to the fifth input terminal G. Under this condition, the second and third switching units SW2 and SW3 are turned on.
Thus, the second input terminal B and the node H are electrically connected to each other, and the first input terminal A and the node H are electrically disconnected from each other. Accordingly, a current path is formed from the second input terminal B, through the second and third switching units SW2 and SW3, to the anti-fuse ANT_FS. In this case, because the gate insulating layer of the anti-fuse ANT_FS is broken, the output terminal C is electrically connected to the ground voltage terminal D through the second switching unit SW2 and the anti-fuse ANT_FS. Thus, data corresponding to a ground voltage are outputted to the output terminal C, which are sensed by a sensor unit.
Referring to
The sensor unit SA includes an inverter that inverts a voltage outputted through the output terminal C in a read operation. Herein, the inverter includes a CMOS transistor in which a p-channel transistor and an n-channel transistor are connected complementarily. Specifically, a source of the p-channel transistor and a drain of the n-channel transistor are connected to each other. Also, gates of the transistors are connected to each other. Also, a drain of the p-channel transistor is connected to a power supply voltage VDD and a drain of the n-channel transistor is connected to a ground voltage VSS.
Hereinafter, a description will be given of a cell array of a nonvolatile memory device including a unit cell in accordance with the above-described embodiments 1 to 3 of the present invention.
Referring to
Also, the memory cell array of the nonvolatile memory device in accordance with the embodiment 4 of the present invention includes: a plurality of write driving lines WR_CT0 to WR_CTn (n: a natural number) for selecting the first switching unit SW1 of the unit cell UC; and a plurality of read driving lines RD_CT0 to RD_CTm (m: a natural number) for selecting the second switching unit SW2 of the unit cell UC.
The write driving lines WR_CT0 to WR_CTn extend in a row direction to be connected to the first switching unit SW1 of each of the unit cells UC arranged in the row direction, that is, a gate of a p-channel transistor. The read driving lines RD_CT0 to RD_CTm extend perpendicularly to the write driving lines WR_CT0 to WR_CTn in a column direction to be connected to the second switching unit SW2 of each of the unit cells UC arranged in the column direction, that is, a gate of an n-channel transistor.
Also, the memory cell array of the nonvolatile memory device in accordance with the embodiment 4 of the present invention includes data lines DL0 to DLn (n: a natural number) and write voltage supply lines WRL0 to WRLm (m: a natural number). Herein, the data lines DL0 to DLn transfer a read voltage to the respective unit cells UC in a read operation, and transfer data outputted from the respective unit cells UC to the sensor units SA0 to SAn (n: a natural number) in the read operation. The write voltage supply lines WRL0 to WRLm transfer a write voltage to the respective unit cells UC in a write operation.
The data lines DL0 to DLn extend in the row direction to connect an input terminal of each of the sensor units SA0 to SAn and an output terminal of each of the unit cells UC arranged in the row direction. The data line connects the second switching unit SW2 (preferably, a drain of an n-channel transistor) and an input terminal of the sensor units SA0 to SAn.
In a read operation, the data lines DL0 to DLn transfer a read voltage transferred through a third switching unit SW3, that is, a power supply voltage VDD to the second switching unit SW2, and transfer data outputted from the second switching unit SW2 to the corresponding sensor units SA0 to SAn.
The write voltage supply lines WRL0 to WRLm extend in the column direction to be connected to the first switching unit SW1 of each of the unit cells arranged in the column direction, that is, a drain of a p-channel transistor. In a write operation, the write voltage supply lines WRL0 to WRLm transfer a write voltage, that is, a high voltage VPP to the first switching unit SW1 of each of the unit cells UC arranged in the column direction.
Also, the memory cell array, the nonvolatile memory device in accordance with the embodiment 4 of the present invention includes a plurality of the sensor units SA0 to SAn that are provided respectively to the corresponding data lines DL0 to DLn to sense data outputted through the corresponding data lines DL0 to DLn. The sensor units SA0 to SAn may include an inverter or a differential amplifier (see
Also, the memory cell array the nonvolatile memory device in accordance with the embodiment 4 of the present invention includes the third switching unit SW3 that transfer a read voltage, that is, the power supply voltage VDD to the corresponding data lines DL0 to DLn in response to a read operation signal RD_EN in a read operation. Herein, the third switching unit SW3 may include an n-channel transistor or a p-channel transistor. Preferably, the third switching unit SW3 includes a p-channel transistor that is superior in driving capability to an n-channel transistor.
Hereinafter, a description will be given of a write/read operation of the nonvolatile memory device in accordance with the embodiment 4 of the present invention. Herein, for example, a description will be given of a write/read operation of the unit cell UC connected to both the write driving line WR_CT0 and the read driving line RD_CT0.
A description will be made with reference to Table 4.
Write Operation
First, one end of the anti-fuse ANT_FS is grounded. Then, a write voltage, that is, a high voltage VPP is applied to the write voltage supply lines WRL0 to WRLm. Also, a logic low level L is applied to the write driving line WR_CT0 and a logic high level H is applied to the other write driving lines WR_CT1 to WR_CTn. Also, a logic level L is applied to the read driving lines RD_CT0 to RD_CTm.
Also, a read operation signal RD_EN is applied in a logic high state. Under this condition, only the first switching unit SW1 is turned on, so that the write voltage supply line WRL0 and the anti-fuse ANT_FS are electrically connected to each other. Accordingly, the high voltage VPP applied through the write voltage supply line WRL0 is transferred through the first switching unit SW1 to the anti-fuse ANT_FS. Thus, a gate insulating layer formed between a substrate and a gate of the anti-fuse ANT_FS is broken by a high electric field.
Read Operation
After completion of the write operation, a logic high level H is applied to the write driving line WR_CT0. Also, a logic high level H is applied to the read driving line RD_CT0 and a logic low level L is applied to the other read driving lines RD_CT1 to RD_CTm. Also, the read operation signal RD_EN is applied in a logic low state.
Under this condition, the second and third switching units SW2 and SW3 are turned on, so that a read voltage, that is, a power supply voltage VDD is transferred through the third switching unit SW3 to the corresponding data line DL0. Accordingly, a current path is formed from the data line DL0, through the second switching unit SW2, to the anti-fuse ANT_FS.
In this case, because a gate insulating layer of the anti-fuse ANT_FS is broken, the data line DL0 is electrically connected to a ground voltage terminal through the second switching unit SW2 and the anti-fuse ANT_FS. Thus, the sensor unit SA0 senses data corresponding to the ground voltage from the data line DL0.
Referring to
The other components, except the sensor units SA0 to SAn, are identical to those of the embodiment 4, and thus their detailed description will be omitted for conciseness.
Referring to
The other components, except the unit cell UC, are identical to those of the embodiment 4, and thus their detailed description will be omitted for conciseness.
Referring to
Accordingly, unlike the embodiment 6, the embodiment 7 does not need a plurality of data lines DL0 to DLn that connect output terminals of a plurality of unit cells UC, which are arranged in a row direction, in common to the sensor unit SA0 to SAn. Thus, the embodiment 7 can minimize a data loss, that is, a data loss by a resistance value of the data line, which may be generated in the memory cell array structure in accordance with the embodiment 6 and the embodiment 5 including the data line, thereby making it possible to improve the data sensing margin.
The other components, except the unit cell UC, are identical to those of the embodiment 4, and thus their detailed description will be omitted for conciseness.
Referring to
Also, the memory cell array of the nonvolatile memory device in accordance with the embodiment 8 of the present invention includes a plurality of second switching units SW2 that are disposed respectively to corresponding rows to transfer a write voltage, that is, a high voltage VPP to the first switching unit SW1. Herein, the second switching unit SW2 may include an n-channel transistor or a p-channel transistor, and transfers the high voltage VPP to the first switching unit SW1 in response to a write operation signal WR_EN0 to WR_ENn.
Also, the memory cell array of the nonvolatile memory device in accordance with the embodiment 8 of the present invention includes a plurality of read driving lines RD_CT0 to RD_CTm (m: a natural number) for selecting the first switching unit SW1 of the unit cell UC. The read driving lines RD_CT0 to RD_CTm extend in a column direction to be electrically connected to the first switching unit SW1 of each of the unit cells UC arranged in the column direction, that is, a gate of a p-channel transistor.
Also, the memory cell array of the nonvolatile memory device in accordance with the embodiment 8 of the present invention includes data lines DL0 to DLn (n: a natural number). In a read operation, the data lines DL0 to DLn transfer a read voltage to an output terminal N of each unit cell UC (i.e., a connection between the first and second switching units), and transfer data outputted from the respective unit cells UC to sensor units SA0 to SAn (n: a natural number) in the read operation.
The data lines DL0 to DLn extend in the row direction to connect an input terminal of each of the sensor units SA0 to SAn and an output terminal of each of the unit cells UC arranged in the row direction. The data line connects the first switching unit SW1 (specifically, a drain of a p-channel transistor) and an input terminal of the sensor units SA0 to SAn. In a read operation, the data lines DL0 to DLn transfer a read voltage transferred through a third switching unit SW3, that is, a power supply voltage VDD to the first switching unit SW1, and transfer data outputted from the first switching unit SW1 to the corresponding sensor units SA0 to SAn.
Also, the memory cell array the nonvolatile memory device in accordance with the embodiment 8 of the present invention includes a plurality of the sensor units SA0 to SAn that are provided respectively to the corresponding data lines DL0 to DLn to sense data outputted through the corresponding data lines DL0 to DLn. The sensor units SA0 to SAn include an inverter that has an input terminal connected to an end of the data lines DL0 to DLn.
Also, the memory cell array the nonvolatile memory device in accordance with the embodiment 8 of the present invention includes the third switching unit SW3 that transfer a read voltage, that is, the power supply voltage VDD to the corresponding data lines DL0 to DLn in response to a read operation signal RD_EN. Herein, the third switching unit SW3 may include an n-channel transistor or a p-channel transistor. Preferably, the third switching unit SW3 includes a p-channel transistor that is superior in driving capability to an n-channel transistor.
Hereinafter, a description will be given of a write/read operation of the nonvolatile memory device in accordance with the embodiment 8 of the present invention. Herein, for example, a description will be given of a write/read operation of the unit cell UC selected by the read driving line RD_CT0 and the write operation signal WR_EN0.
A description will be made with reference to Table 5.
Write Operation
First, one end of the anti-fuse ANT_FS is grounded. Then, the write operation signal WR_EN0 is applied in a logic low state and the other write operation signals WR_EN1 to WR_ENn are applied in a logic high state. Also, a logic low level L is applied to the read driving line RD_CT0 and a logic high level H is applied to the other read driving lines RD_CT1 to RD_CTm. Also, the read operation signal RD_EN is applied in a logic high state. Accordingly, the write voltage, that is, the high voltage VPP is transferred through the first and second switching units SW1 and SW2 to the anti-fuse ANT_FS. Thus, a gate insulating layer formed between a substrate and a gate of the anti-fuse ANT_FS is broken by a high electric field.
Read Operation
After completion of the write operation, the write operation signal WR_EN0 is applied in a logic high state. Also, a logic low level L is applied to the read driving line RD_CT0 and a logic high level H is applied to the other read driving lines RD_CT1 to RD_CTm. Also, the read operation signal RD_EN is applied in a logic low state.
Under this condition, the first and third switching units SW1 and SW3 are turned on, so that a read voltage, that is, a power supply voltage VDD is transferred through the third switching unit SW3 to the corresponding data line DL0. Accordingly, a current path is formed from the data line DL0, through the first switching unit SW1, to the anti-fuse ANT_FS. In this case, because a gate insulating layer of the anti-fuse ANT_FS is broken, the data line DL0 is electrically connected to a ground voltage terminal through the first switching unit SW1 and the anti-fuse ANT_FS. Thus, the sensor unit SA0 senses data corresponding to the ground voltage from the data line DL0.
The following effects can be achieved by the present invention including the above-described configuration.
First, in accordance with the present invention, the first and second switching units connected to the anti-fuse are connected in parallel to each other to transfer the write voltage and the read voltage to the anti-fuse through different paths. Thus, the present invention minimizes a read voltage loss in the read operation and improves a sensing margin of data sensed by the output terminal of the unit cell, thereby making it possible to improve the operational reliability.
Second, in accordance with the present invention, the sensor unit sensing data outputted from the unit cell is implemented using an inverter. Thus, the present invention simplifies the circuit structure, thereby making it possible to reduce the occupation area and the power consumption.
While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-0013045 | Feb 2008 | KR | national |
