KR20120020013A - Method and apparatus for calculating the electrical characteristics of amorphous semiconductor thin-film transistor - Google Patents

Abstract

PURPOSE: An electrical characteristic calculation method of an amorphous semiconductor thin film transistor(TFT) and an apparatus thereof are provided to accurately calculate electrical properties of the amorphous semiconductor TFT including a state density, thereby providing integrated model parameters for utilizing the amorphous semiconductor TFT. CONSTITUTION: C-V(Capacitance-Voltage) characteristics are measured with respect to a plurality of frequencies from a thin film transistor(310). Frequency independent C-V characteristics are calculated using the measured C-V characteristics and a predetermined equivalent model(320). The state density of the thin film transistor is calculated from the calculated frequency independent C-V characteristics(330).

Description

Method and apparatus for calculating the electrical characteristics of amorphous semiconductor thin-film transistor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for calculating the electrical characteristics of an amorphous semiconductor TFT, and in particular, to the process conditions and device structure optimization, device / circuit performance and reliability prediction of amorphous semiconductor TFTs. It is a method of experimentally measuring model parameters including (subgap density of states (DOS)).

Many materials, such as metals and semiconductors, have atoms arranged regularly to form crystals. The grain size varies from microcrystals of about 0.1 μm to large single crystals having a diameter of 0.1 m or more, but amorphous or amorphous refers to a state in which such a long-range periodic atomic array is broken. Solids with three-dimensional periodicity in atomic arrangement are called crystalline. Solids without such periodicity are called amorphous materials. In amorphous materials, the arrangement of atoms at short distances is very similar to that of crystals, but due to the lack of long-range order, physical properties such as melting point are not accurately determined.

A representative material known for a long time as an amorphous material is oxide glass. The glass brought the solidified disordered structure to room temperature without crystallization from the molten state. Amorphous is an enlarged concept here that refers to a solid that does not have a crystal structure. When cooled from the melt, oxides such as SiO ₂ and B ₂ O ₃ are difficult to crystallize into an amorphous state, but metals and semiconductors are easy to crystallize, and amorphous is not obtained by the usual method. A semiconductor using such an amorphous material is an amorphous semiconductor.

In such metals and semiconductors, a method for realizing an amorphous state has been invented and the material obtained therefrom exhibits new physical properties. A representative example of such an amorphous semiconductor is amorphous silicon. Amorphous silicon is a semiconductor, which has a definite band structure and a state within a bandgap, which is a semiconductor, which is inferior in performance to a single crystal. Since control is possible, a pn junction diode or a transistor can be made like a single crystal semiconductor. In addition, it can be used as a thin film transistor or an electrophotographic photosensitive member because it can be deposited in a large area at low temperature, and is used in solar cells because of its large light absorption coefficient. In particular, in recent years, industrial value is increasing in the field of flexible and trasparent display device applications.

Specifically, in the case of the amorphous semiconductor, the lowest point of the conduction band is located in the metal cation ns orbital, so that mobility close to band mobility can be obtained regardless of the crystal directions. The very low point and density of state (DOS) values result in significantly better mobility than single crystalline semiconductors.

In general, in the case of a monocrystalline semiconductor, many studies have been conducted to predict and calculate its electrical characteristics, and models that can be applied to commercial tools for circuit design such as SPICE have been proposed. On the other hand, in the case of amorphous semiconductors, there are difficulties in presenting models that accurately predict the electrical characteristics.

The technical problem to be solved by the present invention is to overcome the limitation of difficult to accurately calculate the electrical characteristics of the amorphous semiconductor TFT, the problem that the conventional techniques could not provide an integrated model parameter that can be used in the simulation for the amorphous semiconductor TFT To solve this problem. Furthermore, the present invention is intended to solve the problem that the accurate simulation of the circuit design and the optimization of the process conditions using the amorphous semiconductor TFT could not be performed because the accurate model parameters are not provided.

In order to solve the above technical problem, a method of calculating the electrical characteristics of an amorphous semiconductor thin film transistor (TFT) according to the present invention comprises the steps of measuring and receiving the C-V characteristics for a plurality of frequencies from the thin film transistor; Calculating frequency-independent C-V characteristics using the received measured value and a predetermined equivalent model; And calculating a state density of the thin film transistor from the calculated frequency independent C-V characteristic.

In order to solve the above technical problem, the method for calculating the electrical characteristics of the amorphous semiconductor thin film transistor (TFT) according to the present invention by calculating the relationship between the gate voltage and the surface potential from the frequency independent CV characteristics by the gate voltage and energy level It further comprises the step of mapping.

In order to solve the above technical problem, the method for calculating the electrical characteristics of the amorphous semiconductor thin film transistor (TFT) according to the present invention is a gate oxide capacitor (gate oxide capacitor) calculated in the predetermined equivalent model measured frequency independent gate blackout Feeding back the error between the doses.

Further, the following provides a computer readable recording medium having recorded thereon a program for causing a computer to execute the method for calculating the electrical characteristics of the amorphous semiconductor TFT described above.

In order to solve the above technical problem, the apparatus for calculating the electrical characteristics of the amorphous semiconductor thin film transistor according to the present invention includes an input unit for measuring and receiving the C-V characteristics for a plurality of frequencies from the thin film transistor; A storage unit for storing a predetermined equivalent model for the measurement environment; And a processor configured to calculate frequency-independent C-V characteristics using the received measured value and the stored predetermined equivalent model, and calculate a state density of the thin film transistor from the calculated frequency-independent C-V characteristics.

The present invention can provide an integrated model parameter for utilizing an amorphous semiconductor TFT by experimentally accurately calculating the electrical characteristics of the amorphous semiconductor TFT including the state density, and the accurate simulation environment for the circuit design and process conditions optimization. Can be provided.

1 is a diagram illustrating a setup environment for measuring a CV characteristic curve in an amorphous semiconductor thin film transistor.
FIG. 2 is a diagram illustrating a frequency dependency result of a CV characteristic curve measured by applying the measurement setup of FIG. 1 to an amorphous InGaZnO (a-IGZO) TFT as an example of an amorphous oxide semiconductor thin film transistor.
3 is a flowchart illustrating a method of calculating electrical characteristics of an amorphous semiconductor thin film transistor according to an exemplary embodiment of the present invention.
4 is a flowchart illustrating a method of calculating a frequency independent CV characteristic in a process of calculating electrical characteristics of an amorphous semiconductor thin film transistor according to an exemplary embodiment of the present invention.
5A and 5B are diagrams for describing an equivalent model for calculating electrical characteristics of an amorphous semiconductor thin film transistor according to an exemplary embodiment of the present invention.
6 is a graph showing series resistance measured as a function of gate voltage using the equivalent model of FIGS. 5A and 5B.
FIG. 7 is a graph illustrating a frequency independent CV characteristic curve modeled using the equivalent model of FIGS. 5A and 5B.
8 is a graph illustrating the density of states calculated by a method of calculating electrical characteristics of an amorphous semiconductor thin film transistor according to an exemplary embodiment of the present invention.
9A and 9B are graphs showing a comparison result between the TCAD simulation result calculated based on the state density shown in FIG. 8 and the measured IV characteristics.
FIG. 10 is a diagram for describing a method of feeding back an error between a gate oxide capacitor calculated in the equivalent model of FIGS. 5A and 5B and a measured frequency independent gate capacitance.
FIG. 11 is a diagram illustrating an apparatus for calculating electrical characteristics of an amorphous semiconductor thin film transistor according to an exemplary embodiment of the present disclosure.

Prior to describing the embodiments of the present invention, embodiments of the present invention are illustrated and described with reference to an amorphous oxide semiconductor thin-film transistor, but this is only an example for convenience of description. It is to be noted that the present invention can be applied to amorphous semiconductor-based TFTs such as a-Si TFTs, organic TFTs, and metal oxide TFTs. The following embodiments will be described by way of example of an amorphous InGaZnO (a-IGZO) TFT.

Recently, amorphous semiconductor TFTs have been used as core devices for forming a display backplane, such as a large-area high-resolution active matrix liquid crystal display (AMLCD) and active matrix organic light-emitting diode display (AMOLED). In the case of the amorphous semiconductor TFT, it is important to measure the state density function inside the band gap, and as a parameter representing the state density function, there is a subgap DOS density. The subgap state density is defined as carrier density, field-effect mobility (μ _FE ), threshold voltage (V _T ), and sub-threshold swing (inside the thin film) under specific voltage and current driving conditions. All electrical parameters such as subthreshold swing (SS), turn-on voltage (V _on ), I _ON , I _ON / I _OFF , and capacitance are determined. It is also a very important parameter that determines stress time dependence, photo-sensitivity due to backlight, temperature dependence, etc. under current / voltage stress, which are very important for TFT mass production. Therefore, in designing and mass-producing TFT-based circuits and systems, the density of states of amorphous semiconductor thin films can be determined according to various process and layout conditions such as elemental composition, deposition conditions and thickness of thin films, type and thickness of gate insulating film, TFT device structure, and the like. Measuring quickly and easily is very important.

Amorphous semiconductor thin films have inherent subgap state densities depending on the composition of the element, process conditions and device structure. In the embodiments of the present invention to obtain a C-V characteristic curve at a plurality of frequencies through the measurement of the LCR meter and to propose a method for experimentally calculating the state density using the same. Hereinafter, various embodiments of the present invention will be described in detail with reference to the drawings.

1 is a diagram illustrating a setup environment for measuring a C-V characteristic curve in an amorphous semiconductor thin film transistor. Figure 1 shows a two-terminal C-V measurement setup of a-IGZO TFT. For example, the Agilent 4284A may be used as the measurement LCR meter, and various measurement means corresponding thereto may be utilized.

FIG. 2 is a diagram illustrating a frequency-dependence result of a C-V characteristic curve measured by applying the measurement setup of FIG. 1 to an amorphous InGaZnO (a-IGZO) TFT as an example of an amorphous oxide semiconductor thin film transistor.

As can be seen in Figure 2, the CV characteristic curve measured at a frequency in the range of 100 Hz ~ 1 MHz shows a sensitive change with frequency. The carrier trapping-detrapping (capture-emission) process through sub-gap states of a-IGZO varies with frequency, and source / drain depends on small signals. / drain: The speed of the charge current supplied from the S / D) electrode is also frequency-dependent. For this reason, it is difficult to obtain reliable quantitative information (for example, the gate voltage-surface potential (V _GS -f _S )) from the CV characteristic curve of the TFT. That is, it is difficult to measure the static characteristics, and the difference between the actual signal and the quasi-static signal is large and complicated, so that there are many difficulties in device modeling.

This frequency-dependent C-V characteristic curve is a phenomenon that occurs in TFTs made of almost all amorphous semiconductor thin films used for a-IGZO as well as large-area uniformity and mass production. Therefore, not only when the physical parameters such as the density of states are to be extracted from the C-V characteristic curve, but also the question of which frequency the C-V characteristic should be measured at is difficult to trust the measured characterization results.

3 is a flowchart illustrating a method of calculating electrical characteristics of an amorphous semiconductor thin film transistor according to an exemplary embodiment of the present invention, which is proposed to solve the above problems, and includes the following steps.

In operation 310, C-V characteristics of a plurality of frequencies are measured and input from the amorphous thin film transistor. The measurement of the C-V characteristics for a plurality of frequencies may be performed according to the method of FIG. 1 described above, and as illustrated, the C-V characteristics may be measured and input through a measuring means such as an LCR meter. This input process is performed by inputting to the apparatus for calculating the electrical characteristics of the amorphous semiconductor thin film transistor in which the present embodiment is implemented as electronic data.

In operation 320, the frequency-independent C-V characteristic is calculated using the measured value and the predetermined equivalent model input in operation 310. The predetermined equivalent model refers to a model used to correspond to a capacitance function that can be derived from an experimental C-V characteristic measurement environment as described above with reference to FIG. 1 and a modeled capacitance function. That is, it is intended to deform from the capacitance function for the measurement environment of the C-V characteristic to the modeled capacitance function by using the equivalent relationship between the capacitance function for the measurement environment of the C-V characteristic and the modeled capacitance function.

The purpose of using this equivalent model is to overcome the limitation that the experimental C-V characteristic measurement environment is frequency dependent. As discussed above, in order to ensure the reliability of the measured characteristic analysis results, a reliable characterization result can be obtained by modeling a function that is not frequency dependent and replacing the capacitance function with the measurement environment. Embodiments of the present invention attempt to obtain frequency-independent C-V characteristics by using the equivalent model to exclude already obtained measurement values or predetermined constants.

In step 330, the state density of the thin film transistor is calculated from the frequency-independent C-V characteristic calculated in step 320. If the frequency-independent CV characteristic was calculated in the previous step 320, the frequency-dependent resistance values are erased in the process, and localized charge trapped in the subgap state is generated. The density of states can be obtained from the capacitance due to charge). That is, the present embodiment can extract the state density experimentally and obtain the frequency-independent C-V characteristics by using the equivalent model described above.

4 is a flowchart illustrating a method of calculating frequency-independent C-V characteristics in a process of calculating electrical characteristics of an amorphous semiconductor thin film transistor according to an exemplary embodiment of the present invention. Steps 410 and 430 of FIG. 4 correspond to steps 310 and 330 of FIG. 3, respectively, and will be described below by focusing on steps 421 and 422.

In operation 421, a capacitance function of the C-V characteristic measured at the plurality of frequencies is calculated using a predetermined equivalent model. In the embodiments of the present invention, the CV characteristic is measured for at least three frequencies for convenience of calculation, and the selection of the target frequency is performed by a person skilled in the art to which the present invention pertains according to an implementation environment or an embodiment. It may be appropriately selected.

In operation 422, a frequency-independent gate capacitance model is calculated by combining each of the capacitance functions calculated in operation 421. If the C-V characteristic is measured for three frequencies in step 421, the input measurement value will also include three sets. Thus, the capacitive function reflecting each input value will also be three sets, and combining these functions can eliminate frequency dependent function components. The result is a frequency-independent gate capacitance model.

5A and 5B are diagrams for describing an equivalent model for calculating electrical characteristics of an amorphous semiconductor thin film transistor according to an exemplary embodiment of the present invention.

Referring to FIG. 5A, the basic idea of the equivalent model 500 will be described as follows.

First, in operation 510, a first capacitance function including a frequency-dependent capacitance is modeled based on the measurement environment of the C-V characteristic. In operation 520, a second capacitance function including a frequency-independent resistor and a capacitor is modeled from the first capacitance function modeled in operation 510. Then, the impedance of the second capacitance function described above corresponds to the impedance of the first capacitance function previously modeled. That is, the first capacitance function and the second capacitance function form an equivalent relationship.

In operation 530, a third capacitance function including a capacitance and a resistance due to trapped charge is modeled from the second capacitance function. In operation 540, a fourth frequency-independent function is modeled from the modeled third capacitance function.

Details of the development process of the equivalent model will be described below with reference to FIG. 5B.

5B equivalently shows a capacitance model for extracting the state density of the a-IGZO TFT presented as an example of an amorphous semiconductor TFT. Here, the definition of each parameter and variable is as follows. C _M and R _M refer to capacitance and resistance measured under the measurement environment of FIG. 1, respectively (Measured capacitance and resistance from a parallel mode of the LCR meter). C _OX stands for gate insulator capacitance, C _CH and R _CH stands for channel capacitance and resistance, respectively, and R _S stands for series resistance. resistance including S / D spreading and contact resistance). C _LOC stands for Capacitance due to localized trapped charge, C _FREE stands for Capacitance due to free charge, and R _L stands for resistance related to frequency dependence. (Resistance related frequency dependences of capture-emission events).

In addition, the four models illustrated in FIG. 5B are capacitive models sequentially derived by an equivalent relationship, each of which is as follows. The first model shows a capacitance model for an LCR meter (2-element capacitance model for parallel mode of LCR meter). The second model is a capacitance model proposed to form an equivalent relationship with the first model, and includes four components as shown (4-element capacitance model by de-embedding C _OX and R _S ). The third model is a physically-based gate capacitance model of a-IGZO TFTs, which introduces C _LOC , C _FREE and R _L as new components. The fourth model is a finally calculated frequency independent gate capacitance model.

If the acceptor-like DOS g (E) of the amorphous semiconductor thin film is expressed by Equation 1 below, the series of models of FIG. 5B are represented by the state density parameters N _TA , kT _TA , N _DA ,. a capacitance model used to experimentally extract kT _DA, etc.).

The first model includes two components (C and _M R _M), shows the raw data (raw data) C _M to be measured in the LCR meter.

The second model is proposed to form an equivalent relationship with the first model. The second model is modified to model the frequency-independent capacitance C _M with a frequency-independent resistor and capacitor. Here, since C _ox and R _S represent gate insulator capacitance and S / D series resistance, respectively, Z _CH determined by C _CH and R _CH has an intrinsic channel impedance. The 2-element capacitance model impedance Z ₂ and the impedance of 4-element capacitance model impedance Z ₄ are represented by Equations 2 and 3, respectively. .

Therefore, using the above-described equivalent relationship (Z ₂ = Z _{4 )} , R _CH and C _CH are functions of C _ox , R _S , C _M , and R _M as shown in Equations 4, 5, and 6 below. It can be described as

Where C and _M and R _M is a measure, C _ox is can be calculated from the thickness T _ox of the gate oxide film, R _S can be extracted only if it is possible to calculate the R _CH and C _CH.

FIG. 6 is a graph showing series resistance measured as a function of gate voltage using the equivalent model of FIGS. 5A and 5B, with gate voltage V _G and source / drain series resistance R measured; The relationship with _S is shown.

An inset inserted in FIG. 6 shows a process of measuring R _S at a specific V _G. Gained, which is saturated (saturation) at a high frequency (high frequency) | | magnitude of the Z _M measured by the LCR meter | Z _M Z _M | Obtain R _S from the value. More specifically, impedance Z _M being measured (i.e., the first model and second model means the assumption that the equivalence relations.) Home is the same as Z _4, accept the, and of Z ₄ magnitude | Z ₄ | is also converge so as R _S at a high frequency as in the second model of 5b, the size of the measured Z _M | Z _M | When the saturation at a constant value at high frequency, this can be referred to shortly R _S. The graph inserted in FIG. 6 shows a result of measuring R _S when V _GS = 3 V. When the measuring method of this embodiment is performed on various V _GS values using an LCR meter, the graph is shown in V _GS as shown in FIG. 6. Dependent R _S can be measured.

Accordingly, Z _CH , C _CH , and R _CH may be obtained by using Equations 4 to 6 and Equation 7 below.

When all the parameters of the second element (4-element capacitance model) are determined, it is converted into a third model which is a physics-based gate capacitance model of a-IGZO TFT. In the third model, C _LOC and R _L are presented to model resistance related frequency dependences of capture-emission events and capacitance due to localized trapped charge, respectively. Here, Z _CH may be expressed as Equation 7, and Z _IGZO may be expressed as Equation 8.

Therefore, if the equivalent relationship (Z _CH = Z _IGZO ) of the second model and the third model is the same, R _L is expressed as a function of C _FREE , C _LOC , C _CH , R _CH and ω as shown in Equation 9 below. Can be.

Here, if C _CH and R _CH have already been obtained previously, and R _L is independent of the frequency ω, R _L , C _FREE , and C _LOC using the following Equation 10 for at least three different frequencies ω Can be obtained.

Equation 10 means that R _Ls calculated for three different frequencies ω ₁ , ω _2, and ω ₃ are independent of the frequency, so that the simultaneous equations are solved in correspondence with each other. As described above, these different frequencies may be appropriately selected by those skilled in the art.

Subsequently, the frequency-independent gate capacitance model may be obtained by removing the frequency-independent resistance components R _S and R _L from the third model (Physics-based gate capacitance model).

FIG. 7 is modeled from a frequency-independent gate capacitance model using the equivalent model of FIG. 5A and FIG. 5B (meaning that the third and fourth models are in an equivalent relationship). It is a graph showing a frequency-independent CV curve.

The process of calculating the frequency independent CV characteristic is performed by calculating an capacitance function for the CV characteristic measured at a plurality of frequencies using an equivalent model, and combining the calculated capacitance functions to generate a frequency independent gate capacitance model. By calculating.

FIG. 7 shows that the CV characteristic curves calculated by _three frequency combinations ω ₁ , ω ₂ , and ω ₃ for each of various frequency bands form the same curve regardless of each frequency.

As a result, it can be understood that the frequency-dependent CV characteristic curve of FIG. 2, which was initially measured, is derived from frequency-dependent dispersion by various R and C components of the third model of FIG. 5B. In this case, if R _L and R _S that cause frequency-dependence are removed, the frequency-independent gate capacitance determined by C _ox , C _LOC , and C _FREE as shown in the fourth model of FIG. independent gate capacitance).

At this time, since the obtained C _LOC is a capacitance due to localized charge trapped in a subgap state, it contains information on the state density g (E). Therefore, C _LOC 'and g (V _GS ) can be calculated from C _LOC according to V _{GS as shown} in Equations 11 and 12 below. Here, T _AOS means the thickness of the amorphous semiconductor thin film.

According to the embodiments of the present invention described above, by experimentally accurately calculating the electrical characteristics of the amorphous semiconductor TFT including the state density, it is possible to provide an integrated model parameter for utilizing the amorphous semiconductor TFT, circuit design and process conditions In addition to optimizing, we can provide an accurate simulation environment for this.

Now look at the relationship between V _GS and energy level E. The following equation 13 holds between the gate voltage V _GS and the surface potential f _S.

Since the change according to V _GS of Q _LOC and Q _FREE corresponds to the measured frequency-independent gate capacitance C _G , the above equation 13 is differentiated with respect to V _GS . You can get 14.

Here, C _G is Integrating again from V _FB for the equation (14) above is obtained through the frequency-independent CV curve measured by the present embodiment performs a result, as shown in figure 7 the V _GS to V _GS following equation As shown in Fig. 15, the surface potential f _S can be obtained.

That is, the V _GS -f _S relation, that is, the V _GS -E relation, can be extracted from the frequency independent CV characteristic curve. As described above, the exemplary embodiment of the present invention may further include mapping the gate voltage and the energy level by calculating the relationship between the gate voltage and the surface potential from the frequency-independent CV characteristics finally extracted.

FIG. 8 is a graph showing the density of states calculated by a method for calculating electrical characteristics of an amorphous semiconductor thin film transistor according to an embodiment of the present invention, and finally for a-IGZO TFT illustrated as an example of an amorphous semiconductor TFT. The extracted state density g (E) is shown.

It can be seen from FIG. 8 that almost identical state densities are obtained regardless of three different frequency combinations (ω ₁ , ω ₂ , ω ₃ ). The table shown as a graph represents a parameter set of the finally extracted state density, and the model of the graph represents a state density model drawn using the parameters of the illustrated table and Equation 1 described above. In addition, the shape of the energy distribution has the form of an exponential function having two different slopes as shown in Equation 1 below.

9A and 9B are graphs showing the results of a comparison between the TCAD simulation results calculated based on the final extracted state density shown in FIG. 8 and the measured IV characteristics (I _DS -V _GS and I _DS -V _DS ). to be. This graph is proposed to verify the validity of the extracted state density. The model state density (model DOS) of FIG. 8 is applied to the TCAD as a C-interpreter to simulate IV characteristics.

Referring to the simulation results of FIGS. 9A and 9B, it can be seen that the TCAD calculation result calculated based on the extracted state density reproduces the measurement results of the transfer curve and the output curve well. Accordingly, it can be seen that the embodiments of the present invention are appropriate and appropriate for the state density measurement method of the amorphous semiconductor TFT.

In addition, embodiments of the present invention can solve the mapping problem between V _GS and E very easily by extracting the V _GS −f _S relationship from a frequency independent CV state curve. In addition, it is possible to verify to what frequency band the modeled state density is valid.

FIG. 10 is a view for explaining a method of feeding back an error between a gate oxide capacitor calculated in the equivalent model of FIGS. 5A and 5B and a measured frequency independent gate capacitance, and in particular, a 4-element capacitance model. And a feedback process for checking the self-consistency of the C _ox values between the third model (physics-based gate capacitance model).

As described above, the C _G value saturated under the high V _GS condition in the frequency independent CV state curve of FIG. 7 corresponds to C _ox according to the equivalent model. In particular, since this part corresponds to a strong accumulation region, the effects of C _LOC and C _FREE on C _G can be ignored. Therefore, the C _G value saturated under the high V _GS condition in the frequency independent CV characteristic curve of FIG. 7 should agree well with the C _ox value calculated from T _ox and e _ox . In the proposed embodiment, C _ox that is already calculated from the second element (4-element capacitance model) of FIG. 5B is used. Therefore, a verification operation is necessary to confirm whether the used C _ox matches the saturated C _G of FIG. 7.

To this end, the embodiment of the present invention can be extended by further feeding back an error between the gate oxide capacitor calculated in the equivalent model and the measured frequency independent gate capacitance. According to this extended embodiment, when the calculated C _ox does not coincide with the saturated C _G value in the frequency independent CV characteristic curve and a slight error occurs, the second element (4-element capacitance model) is applied. This problem can be solved by feeding back using _COx .

FIG. 11 is a diagram illustrating an apparatus 1100 for calculating electrical characteristics of an amorphous semiconductor thin film transistor according to an exemplary embodiment of the present invention, and proposes an apparatus for performing the exemplary embodiment of FIG. 3.

The input unit 1110 receives and measures C-V characteristics of a plurality of frequencies from the thin film transistor. The input unit 1110 corresponds to step 310 of FIG. 3 and may receive a measurement value from a measuring device such as the LCR meter of FIG. 1. The input unit 1110 may be implemented as an input unit of a data processing apparatus capable of receiving data in an electronic form, and in a narrow sense, includes hardware for general data input, and in a broad sense, the data of the data through a wired or wireless network. It may also comprise a receiving means.

The storage unit 1120 stores an equivalent model for the measurement environment. The storage unit 1120 is a physical space for storing the equivalent model described above, and a detailed description of the equivalent model will be omitted. Such a storage unit may be implemented as data storage means of a conventional computing device, and thus may include a hard disk (HDD), a memory, various optical / magnetic disks, and the like.

The processor 1130 calculates a frequency independent CV characteristic by using the measured value input through the input unit 1110 and an equivalent model stored in the storage unit 1120, and calculates a state density of the thin film transistor from the calculated frequency independent CV characteristic. Calculate The processor 1130 corresponds to steps 320 and 330 of FIG. 3, and thus a detailed description thereof will be omitted. Since the processor 1130 needs to perform various operations based on the measured values stored in the electronic form and the equivalent model stored therein, the processor 1130 may include a processor capable of performing such a calculation process and a memory required therefor. have. In addition, the processor 1130 includes not only the hardware listed above but also a software code necessary for the process of performing the processor 1130.

In addition, a person skilled in the art of the present invention calculates the capacitance function for the CV characteristics measured by the processor 1130 at a plurality of frequencies using the equivalent model through the above embodiments, and the calculated power failure It can be seen that by combining each of the capacitance functions, a frequency independent gate capacitance model can be calculated.

According to various embodiments of the present invention, frequency-independent CV characteristics and various electrical characteristics may be calculated by applying an equivalent model to most amorphous semiconductor TFTs having a state density at which carriers may be trapped inside the band gap. Can be. In particular, ZnO compound-based amorphous oxide semiconductors such as a-IGZO have lower state density values than a-Si: H TFTs, so that free electrons in the conduction band of charge formed in the channel are reduced. The specific gravity of charge by (free electron) is higher than that of a-Si: H TFT or organic TFT. This leads to the advantage of higher mobility, but at the same time integrated field linking bulk state density and channel charge, μ _FE , IV since field effect mobility μ _FE is determined as a function sensitive to V _GS . You need a model. The above embodiments can meet this demand through a model and calculation methodology suitable for such an amorphous oxide semiconductor TFT.

Furthermore, when the process of the present embodiments and the equations presented are inputted into a commercial circuit design tool such as SPICE by a macro-model or a verilog-A method, a circuit design using an amorphous semiconductor TFT is generated. It becomes possible. In addition, it is possible to clearly analyze the causes of V _T , SS , μ _CH , IV, etc. according to various process conditions and contribute to future TFT process, structure, and circuit optimization.

Meanwhile, the present invention can be embodied as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored.

Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like, which may also be implemented in the form of carrier waves (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. In addition, functional programs, codes, and code segments for implementing the present invention can be easily deduced by programmers skilled in the art to which the present invention belongs.

The present invention has been described above with reference to various embodiments thereof. Those skilled in the art will understand that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1100: Device for calculating electrical characteristics of an amorphous semiconductor thin film transistor
1110: input unit
1120: storage unit
1130: processing unit

Claims (11)

In the method for calculating the electrical characteristics of the amorphous semiconductor thin film transistor (TFT),
Measuring and receiving CV characteristics of a plurality of frequencies from the thin film transistor;
Calculating a frequency independent CV characteristic using the received measured value and a predetermined equivalent model; And
Calculating a state density of the thin film transistor from the calculated frequency independent CV characteristic. The method of claim 1,
The predetermined equivalent model is
Model a first capacitance function comprising a frequency dependent capacitance based on the measurement environment,
After modeling a second capacitance function comprising a frequency independent resistor and a capacitor from the first capacitance function,
And matching the impedance of the second capacitance function to the impedance of the first capacitance function. The method of claim 2,
The predetermined equivalent model is
Modeling a third capacitance function comprising a capacitance and a resistance due to trapped charge from the second capacitance function. The method of claim 1,
Computing the frequency independent CV characteristic,
Calculating a capacitance function for the CV characteristic measured at the plurality of frequencies using the predetermined equivalent model; And
Calculating a frequency independent gate capacitance model by combining each of the calculated capacitance functions. The method of claim 1,
Mapping the gate voltage and energy level by calculating a relationship between gate voltage and surface potential from the frequency independent CV characteristic. The method of claim 1,
Feedbacking an error between the gate oxide capacitor calculated in the predetermined equivalent model and the measured frequency independent gate capacitance. A non-transitory computer-readable recording medium having recorded thereon a program for executing the method of claim 1. In the device for calculating the electrical characteristics of the amorphous semiconductor thin film transistor,
An input unit configured to receive and input CV characteristics of a plurality of frequencies from the thin film transistor;
A storage unit for storing a predetermined equivalent model for the measurement environment; And
And a processor configured to calculate a frequency independent CV characteristic by using the received measured value and the stored predetermined equivalent model, and calculate a state density of the thin film transistor from the calculated frequency independent CV characteristic. The method of claim 8,
The predetermined equivalent model is
Model a first capacitance function comprising a frequency dependent capacitance based on the measurement environment,
After modeling a second capacitance function comprising a frequency independent resistor and a capacitor from the first capacitance function,
And the impedance of the second capacitance function to correspond to the impedance of the first capacitance function. The method of claim 9,
The predetermined equivalent model is
And model a third capacitance function that includes a capacitance and a resistance due to trap charge from the second capacitance function. The method of claim 8,
Wherein,
Calculating a capacitance function for the CV characteristic measured at the plurality of frequencies using the predetermined equivalent model,
And calculate a frequency independent gate capacitance model by combining each of the calculated capacitance functions.

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