KR102654589B1 - Method and apparatus for measuring switching charge of ferroelectric element - Google Patents

Abstract

A switching charge measurement device according to an embodiment of the present invention includes a voltage application unit that applies a voltage pulse to the gate of a transistor including a gate oxide, and a well of the transistor and a source of the transistor in response to the voltage pulse. ) and between the well and the drain of the transistor, and a processor that calculates the switching charge based on the measured average direct current and an SMU (source measure unit) that measures the average direct current, and a gate. Oxides may contain ferroelectrics.

Description

Method and device for measuring switching charge of ferroelectric transistor {METHOD AND APPARATUS FOR MEASURING SWITCHING CHARGE OF FERROELECTRIC ELEMENT}

The present invention relates to a method and device for measuring polarization charge of a ferroelectric transistor. More specifically, the present invention relates to a method and device for measuring polarized charge of a ferroelectric transistor using a charge pumping method.

A ferroelectric material based on hafnium oxide (HfO2), unlike the conventional perovskite ferroelectric, has a FinFET, 3D structure, and spontaneous polarization characteristics maintained even at a thickness of 10 nm or less. It has the advantage of being able to apply the existing HKMG CMOS mass production process.

Therefore, research is being conducted to apply it to non-volatile memories such as ferroelectric field effect transistor (FeFET), ferroelectric random access memory (FeRAM), and ferroelectric tunneling junction (FTJ), or low-power devices such as negative capacitance field effect transistor (NCFET). . Typically, since the FeFET device contains a ferroelectric material, the transistor can be maintained in an on or off state when there is no electrical bias due to the permanent spontaneous polarization characteristic of the ferroelectric material.

The electrical characteristics of ferroelectrics are represented by spontaneous polarization, and spontaneous polarization characteristics are generally achieved by inputting a triangular pulse or PUND (positive up negative down) pulse to a ferroelectric transistor and using the current measured in response to the input pulse to determine PV (polarization- voltage) is expressed as a hysteresis curve. Basic information of the ferroelectric transistor, such as switching charge, can be obtained from the displayed PV hysteresis curve.

Conventionally, PV hysteresis curve measurements of ferroelectric transistors have been measured in two-terminal structures, such as MFM (metal-ferroelectric-metal) capacitors or MFS+ (metal-ferroelectric-highly doped Si substrate) capacitors. Meanwhile, in the MFS (metal-ferroelectric-low doped Si substrate) structure using a lightly doped Si plate such as FeFET or NCFET, the applied external voltage is not sufficiently applied to the ferroelectric layer due to Si depletion, causing damage to the ferroelectric layer. This is problematic because SW characteristics cannot be measured.

The problem to be solved by the present invention is to provide a method for easily measuring the switching charge of a ferroelectric transistor, and to provide a measuring device and method for measuring the switching charge of a ferroelectric transistor.

However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems to be solved that are not mentioned can be clearly understood by those skilled in the art to which the present invention pertains from the description below. will be.

A switching charge measurement device according to an embodiment of the present invention includes a voltage applicator that applies a voltage pulse to the gate of a transistor including a gate oxide, and a well of the transistor and a source of the transistor in response to the voltage pulse. A source measurement unit (SMU) that measures at least one of the average direct current between the source and the well and the drain of the transistor, and a processor that calculates the switching charge based on the measured average direct current. and the gate oxide may include a ferroelectric material.

The processor may calculate the switching charge by dividing the measured average direct current by the frequency of the input voltage pulse.

The voltage application unit may apply the voltage pulse having a frequency of 100 Hz or more and 1 GHz or less.

The voltage application unit may apply the voltage pulse of 0.1V or more and 10V or less.

The ferroelectric material may be hafnium oxide (HfO2) or zirconia (ZrO2).

A method of measuring the switching charge of a transistor according to another embodiment of the present invention includes applying a voltage pulse to the gate of the transistor; measuring at least one average direct current between a well of the transistor and a source of the transistor and between a well and a drain of the transistor in response to the voltage pulse; and calculating a switching charge based on the measured average direct current, wherein the gate oxide may include a ferroelectric material.

According to one embodiment of the present invention, the switching charge of a ferroelectric transistor can be easily measured using a method of measuring current in a charge pumping technique, and the switching charge can be measured stably even at a low input voltage. , the characteristics of ferroelectric transistors can be easily understood.

1 is a block diagram illustrating a switching charge measurement device according to an embodiment of the present invention.
Figure 2 shows the structure of a FeFET device containing a ferroelectric material.
Figure 3 shows input voltage pulses of a transistor according to one embodiment of the invention.
Figure 4 is a graph showing the number of charges as an output current value according to an input peak voltage according to an embodiment of the present invention.
Figure 5 is a block diagram for explaining a switching charge measurement device from a hardware perspective, according to an embodiment of the present invention.
Figure 6 is a flowchart of a switching charge measurement method according to another embodiment of the present invention.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The present embodiments are merely provided to ensure that the disclosure of the present invention is complete and to be understood by those skilled in the art. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims.

In describing embodiments of the present invention, if a detailed description of a known function or configuration is judged to unnecessarily obscure the gist of the present invention, the detailed description will be omitted. The terms described below are terms defined in consideration of functions in the embodiments of the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, the definition should be made based on the contents throughout this specification.

1 is a block diagram illustrating a switching charge measurement device according to an embodiment of the present invention.

The switching charge measurement device 100 may include a voltage pulse application unit 110, a current measurement unit 120, and a switching charge calculation unit 130.

In order to measure the switching charge of a transistor containing a ferroelectric material, the switch charge measurement device 100 applies a voltage pulse to the transistor, measures the average direct current in response, and calculates the switching charge. .

While the existing switching charge measurement method applies a triangle pulse or PUND pulse to a transistor containing a ferroelectric material, measures the alternating current in response, and then uses this to calculate the switching charge by integrating the PV history curve, the switch The charge measurement device 100 may calculate the switching charge by measuring the average direct current output in response to the input voltage pulse and dividing the output average direct current by the frequency of the voltage pulse.

Figure 2 shows the structure of a ferroelectric field-effect transistor (FeFET) transistor containing a ferroelectric material.

Referring to FIG. 2, the FeFET device 200 may include a gate electrode (electronode), a gate oxide containing ferroelectric and dielectric materials, a source electrode, a drain electrode, and a well. You can.

Since the FeFET device 200 contains a ferroelectric material (FE), the transistor can be maintained in an on or off state when there is no electrical bias due to the permanent spontaneous polarization characteristics of the ferroelectric material (FE), and this FeFET device The characteristic that exhibits the spontaneous polarization characteristic of (200) is the switching charge. It can be said that the larger the size of the switching charge, the better the spontaneous polarization characteristics of the ferroelectric are shown, and the smaller the size of the switching charge, the less clearly the spontaneous polarization characteristics of the ferroelectric are shown.

The ferroelectric material (FE) included in the gate oxide according to an embodiment of the present invention may be hafnium oxide (HfO2) or zirconia (ZrO2).

Figure 3 shows an input voltage pulse of a transistor according to an embodiment of the present invention, and Figure 3(a) shows an input voltage pulse applied in a charge pumping method according to an embodiment of the present invention. 3(b) represents an input voltage pulse according to another embodiment of the present invention.

Referring further to FIGS. 1 and 3, the voltage pulse application unit 110 may input a periodic pulse to the gate 210 of the FeFET device 200, and the current measurement unit 120 may input a periodic pulse to the gate 210 of the FeFET device 200. To measure the current between the well 230 and the source or between the well 230 and the drain, a 3-terminal is used between the point 220 connecting the source and the drain and the well 230. Thus, the average direct current can be measured.

The charge pumping method is a method of measuring the interface trap density of a MOSFET by inputting periodic voltage pulses to the gate of the MOSFET and measuring the recombination output direct current of holes and electrons. The voltage pulse applicator 110 is An input voltage pulse such as (a) in FIG. 3 may be applied. Here, Vbase, the lowest voltage of the applied input voltage pulse, can be applied to fall below Vflatband, the voltage at which the current in the MOSFET is completely cut off, and the highest voltage of the input voltage pulse is the voltage at which current flows in the channel containing the ferroelectric material. It can be applied above the Vthreshold voltage. In other words, the charge pumping method can measure the amount of traps trapped as the MOSFET repeats ON-OFF.

According to one embodiment, the voltage pulse applicator 110 may apply the voltage pulse used in the charge pumping method as shown in (a) of FIG. 3 to the gate 210 of the FeFET device 200.

Additionally, according to another embodiment, the voltage pulse applicator 110 may apply a voltage pulse such as (b) in FIG. 3 to the gate 210 of the FeFET device 200. The voltage pulse in (b) of FIG. 3 is in the form of an input voltage pulse for drawing a conventional PV history curve, and is adjusted to conditions including the size and period of the input voltage pulse in accordance with the conditions of the charge pumping method used in the present invention. It was done.

To measure the switching charge of the FeFET device 200, the input voltage pulse applied by the voltage pulse applicator 110 to the gate 210 may be a triangular or square pulse, and the input voltage pulse is 0.1 second or more and 10 seconds. Approval may be granted during the following period:

Additionally, the frequency of the input voltage pulse applied by the voltage pulse applicator 110 to the gate 210 may be 100 Hz or more and 1 GHz or less, and the height or size of the input voltage pulse may be 0.1 V or more and 10 V or less.

When a voltage pulse is applied to the gate 210 of the FeFET device 200 by the voltage pulse application unit 110, the current measurement unit 120 can measure the average output current output in response to the voltage pulse. To this end, the current measurement unit 120 may be a source measurement unit (SMU) rather than a waveform generator/fast measurement unit (WGFMU) or an oscilloscope that measures alternating current.

AC measurement equipment including WGFMU or oscilloscope, which were conventionally used to measure switching charges, can measure alternating current at every point and draw a PV history curve accordingly, and integrate the PV curve as shown in Equation 1 below. While it was possible to measure switching charges containing ferroelectric materials, the SMU according to an embodiment of the present invention can measure switching charges by measuring the average direct current value.

In Equation 1, Q may represent the switching charge amount, and i may correspond to the current at each point in the PV history curve.

Unlike the conventional method, the switching charge calculation unit 130 measures the average direct current measured by the current measurement unit 120 and converts it into the frequency of the input voltage and Ampere, a unit of current, as shown in Equation 2 below. The switching charge of the FeFET device 200 can be calculated by dividing by the product.

In Equation 2, I may be the average direct current value measured by the current measurement unit 120, f may be the frequency of the input voltage, and A may be Ampere, a unit of current. may be the switching charge of the FeFET device 200 calculated by the switching charge calculation unit 130.

Because the switching charge calculation unit 130 measures the average direct current measured by the current measurement unit 120, unlike the conventional measurement method in which noise is greatly affected when a small amount of current is measured, even when a small amount of current is measured The influence of noise can be reduced, allowing more accurate switching charge measurement. In addition, the switching charge calculation unit 130 performs only division to measure the switching frequency, unlike integration calculations in conventional measurement methods, so the switching charge can be measured more simply and easily.

Figure 4 is a graph in which the same input voltage pulse is applied to compare the conventional method and the charge pumping method according to an embodiment of the present invention, showing the number of charges per unit area according to the maximum value (Vpeak) of the applied input voltage pulse. (y-axis).

Referring further to FIG. 4, in order to compare the conventional method and the charge pumping method, the voltage pulse applicator 110 may apply the voltage of (b) in FIG. 3 to the gate 210 of the FeFET device 200, For various comparisons, the ferroelectric material (FE) of the FeFET device 200 may be hafnium oxide (HfO2) or zirconia (ZrO2).

Comparing the conventional method and the method according to the embodiment of the present invention, it can be seen that the charge pumping method used by the switching charge measurement device 100 measures more points at the maximum value of all input voltage pulses, and the ferroelectric material (FE) ), you can see that more points are measured accurately, regardless of whether it is a hafnium oxide or zirconia material.

In particular, when the maximum value of the input voltage pulse is 2V or less, the point of the number of charges per unit area calculated by measuring the current with a conventional WGFMU has many unclear values because noise is generated in the output current, but in the embodiment of the present invention, In this case, since the output current corresponding to the maximum value of the low input voltage pulse is measured as the average direct current, a clear number of charges per unit area can be obtained, and the switching charge can be easily and accurately calculated using this.

Figure 5 is a block diagram for explaining a switching charge measurement device from a hardware perspective, according to an embodiment of the present invention.

1 and 5, the switching charge measurement device 100 includes a storage device 151 that stores at least one command, a processor 152 that executes at least one command of the storage device, and a transmission and reception device 153. ), a voltage pulse application device 154, and an SMU 155.

Each of the components 151, 152, 153, 154, and 155 included in the switching charge measurement device 100 are connected by a data bus 156 and can communicate with each other.

The storage device 151 may include memory or at least one of a volatile storage medium and a non-volatile storage medium. For example, the storage device 151 may include at least one of read only memory (ROM) and random access memory (RAM).

The storage device 151 may further include at least one instruction to be executed by the processor 152, which will be described later.

The processor 152 is a central processing unit (CPU), a graphics processing unit (GPU), a micro controller unit (MCU), or a dedicated processor on which methods according to embodiments of the present invention are performed. It can mean.

Referring further to FIG. 1, the processor 152, as described above, can perform the function of the switching charge operation unit 130 by at least one program command stored in the storage device 1510 and is in the form of one module. It can be stored in memory and executed by the processor.

The transmitting and receiving device 153 is connected wirelessly or wired to an external device and can transmit measured or calculated result values or receive information necessary to calculate switching charges.

The voltage pulse application device 154 performs the function of the voltage pulse application unit 110 and can apply a voltage pulse to a transistor containing a ferroelectric material. In this specification, the voltage pulse application device 154 is expressed as existing within the switching charge measurement device 100, but it may also exist as a separate device and is not limited thereto. Additionally, the voltage pulse application device 154 may include any type of signal generator capable of applying voltage to the transistor.

The SMU 155 performs the function of the current measurement unit 120 and may refer to an electronic device capable of sourcing and measurement at the same time. Additionally, the SMU may transmit the measured result to the processor 152 or an external device using the data bus 156 or the transmission/reception device 153.

In the above, a switching charge measurement device according to an embodiment of the present invention has been described. Hereinafter, a switching charge measurement method executed by processor operation in a switching charge measurement device according to another embodiment of the present invention will be described.

Figure 6 is a flowchart of a switching charge measurement method according to another embodiment of the present invention.

1, 2, and 6, the voltage pulse application unit 110 in the switching charge measurement device 100 can apply an input voltage pulse to the gate 210 of a transistor containing a ferroelectric material (FE). There is (S100).

The input voltage pulse applied by the voltage pulse applicator 110 may be a triangular or square pulse, and the input voltage pulse may be applied for 0.1 second or more and 10 seconds or less.

Additionally, the frequency of the input voltage pulse applied by the voltage pulse applicator 110 may be 100 Hz or more and 1 GHz or less, and the height or size of the input voltage pulse may be 0.1 V or more and 10 V or less.

Additionally, the ferroelectric material included in the gate oxide of a transistor containing a ferroelectric material (FE) may be hafnium oxide (HfO2) or zirconia (ZrO2).

Subsequently, the current measurement unit 120 may measure the average direct current between the well and the source/drain of the transistor including the ferroelectric material (FE) as an output current corresponding to the input voltage pulse (S200).

Using the average direct current measured by the current measurement unit 120, the switching charge calculation unit 130 may calculate the switching charge of the transistor including the ferroelectric material (FE) (S300).

Therefore, according to an embodiment of the present invention, a user can measure the switching charge of a transistor containing an accurately calculated ferroelectric material (FE), compared to the existing method of measuring the switching charge, and use this to determine the characteristics of the device. It can be easily and accurately identified.

Combinations of each block of the block diagram and each step of the flow diagram attached to the present invention may be performed by computer program instructions. Since these computer program instructions can be mounted on the encoding processor of a general-purpose computer, special-purpose computer, or other programmable data processing equipment, the instructions performed through the encoding processor of the computer or other programmable data processing equipment are included in each block or block of the block diagram. Each step of the flowchart creates a means to perform the functions described. These computer program instructions may also be stored in computer-usable or computer-readable memory that can be directed to a computer or other programmable data processing equipment to implement a function in a particular way, so that the computer-usable or computer-readable memory The instructions stored in can also produce manufactured items containing instruction means that perform the functions described in each block of the block diagram or each step of the flow diagram. Computer program instructions can also be mounted on a computer or other programmable data processing equipment, so that a series of operational steps are performed on the computer or other programmable data processing equipment to create a process that is executed by the computer, thereby generating a process that is executed by the computer or other programmable data processing equipment. Instructions that perform processing equipment may also provide steps for executing functions described in each block of the block diagram and each step of the flow diagram.

Additionally, each block or each step may represent a module, segment, or portion of code that includes one or more executable instructions for executing specified logical function(s). Additionally, it should be noted that in some alternative embodiments it is possible for the functions mentioned in blocks or steps to occur out of order. For example, two blocks or steps shown in succession may in fact be performed substantially simultaneously, or the blocks or steps may sometimes be performed in reverse order depending on the corresponding function.

The above description is merely an illustrative explanation of the technical idea of the present invention, and those skilled in the art will be able to make various modifications and variations without departing from the essential quality of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but rather to explain it, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention shall be interpreted in accordance with the claims below, and all technical ideas within the scope equivalent thereto shall be construed as being included in the scope of rights of the present invention.

100: switching charge measurement device
110: Voltage pulse applicator
120: Current measuring unit
130: Switching charge operation unit
151: storage device
152: processor
153: Transmitting and receiving device
154: Voltage pulse application device
155: Source Measurement Unit (SMU)
156: data bus
200: FeFET

Claims (12)

a voltage application unit that applies a voltage pulse to the gate of a transistor including a gate oxide;
In response to the voltage pulse, a source measure (SMU) measures the average direct current between at least one of the well of the transistor and the source of the transistor and between the well and the drain of the transistor. unit); and
It includes a processor that calculates switching charge based on the measured average direct current,
The gate oxide includes a ferroelectric material,
The SMU measures the average direct current using a 3-terminal between the point connecting the source and the drain and the well,
Switching charge measurement device According to claim 1,
The processor,
Calculating the measured average direct current divided by the frequency of the input voltage pulse as the switching charge.
Switching charge measurement device. According to claim 2,
The voltage application unit,
Applying the voltage pulse having a frequency of 100 Hz or more and 1 GHz or less,
Switching charge measurement device. According to claim 1,
The voltage application unit,
Applying the voltage pulse of 0.1V or more and 10V or less,
Switching charge measurement device. According to claim 1,
The ferroelectric material is,
A material containing hafnium oxide (HfO2) or zirconia (ZrO2),
Switching charge measurement device. In a method of measuring the switching charge of a transistor including a gate oxide,
applying a voltage pulse to the gate of the transistor;
measuring at least one average direct current between a well of the transistor and a source of the transistor and between a well and a drain of the transistor in response to the voltage pulse; and
Comprising a step of calculating switching charge based on the measured average direct current,
The gate oxide includes a ferroelectric material,
The step of measuring the average direct current is measuring the average direct current using a 3-terminal between the point connecting the source and the drain and the well.
Switching charge measurement method. According to claim 6,
The step of calculating the switching charge is,
Calculating the measured average direct current divided by the frequency of the input voltage pulse as the switching charge.
Switching charge measurement method. According to claim 7,
The step of applying the voltage pulse is,
Applying the voltage pulse with a frequency of 100 Hz or more and 1 GHz or less
Switching charge measurement method. According to claim 6,
The step of applying the voltage pulse is,
Applying the voltage pulse of 0.1V or more and 10V or less,
Switching charge measurement method. According to claim 6,
The ferroelectric material is,
A material containing hafnium oxide (HfO2) or zirconia (ZrO2),
Switching charge measurement method. A computer program stored on a computer-readable recording medium,
The computer program is,
Includes instructions for causing the processor to perform a method of measuring the switching charge of a transistor including a gate oxide,
applying a voltage pulse to the gate of the transistor;
measuring at least one average direct current between a well of the transistor and a source of the transistor and between a well and a drain of the transistor in response to the voltage pulse; and
Comprising a step of calculating switching charge based on the measured average direct current,
The gate oxide includes a ferroelectric material,
The step of measuring the average direct current is measuring the average direct current using a 3-terminal between the point connecting the source and the drain and the well.
computer program. A computer-readable recording medium storing a computer program,
The computer program is,
Includes instructions for causing the processor to perform a method of measuring the switching charge of a transistor including a gate oxide,
applying a voltage pulse to the gate of the transistor;
measuring at least one average direct current between a well of the transistor and a source of the transistor and between a well and a drain of the transistor in response to the voltage pulse; and
Comprising a step of calculating switching charge based on the measured average direct current,
The gate oxide includes a ferroelectric material,
The step of measuring the average direct current is measuring the average direct current using a 3-terminal between the point connecting the source and the drain and the well.
A computer-readable recording medium.

Images