KR101141242B1 - Method and Apparatus for the characterization of interface trap using photo-excited charge-collection spectroscopy, and Recording medium thereof - Google Patents

Abstract

Disclosed are an interface defect analysis method using photoelectric spectroscopy, a recording medium, and an apparatus thereof. According to one or more exemplary embodiments, an interface defect analysis method using photoelectric spectroscopy may include applying a single wavelength optical signal in an order of long wavelength to short wavelength at an interface between a channel semiconductor and a gate insulating layer of a transistor; Measuring a threshold voltage for each wavelength based on the relationship between the gate voltage and the drain current for each wavelength; Calculating a defect charge amount of the interface based on the threshold voltage for each wavelength; And calculating an interface defect concentration per energy level from the defect charge amount. According to the embodiments of the present invention, an analysis result that is extremely sensitive to interface characteristics can be obtained as compared to the conventional analysis method, and the defect concentration for each energy level present in the channel semiconductor / gate insulating film interface can be quantitatively obtained, and all field effect transistors can be obtained. Applicable to the device, it is possible to minimize the deterioration of the analytical specimen during the analysis process by using the optical signal, which is a relatively low energy energy source, does not need to create an abnormal environment, such as vacuum or low temperature environment, even under normal temperature and atmospheric pressure Analysis is possible.

Description

Interfacial defect analysis method using photoelectric spectroscopy, its recording medium and apparatus {Method and Apparatus for the characterization of interface trap using photo-excited charge-collection spectroscopy, and Recording medium

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interface analysis technique of a semiconductor device, and more particularly, to an interface defect analysis method, a recording medium, and a device using photoelectric spectroscopy.

Thin-Film Transisters have been widely used as mandatory switching components in display applications. Organic and oxide semiconductors are expected to contribute to the display field due to their low cost, high transparency, and flexibility. Apart from the type of channel semiconductors, thin film transistor performance is highly dependent on the nature and density of charge traps present at the interface between the channel and the insulating material, and on the thin film channel itself. In particular, light emitting display back panels are sensitive to instability caused by charge traps. Therefore, the characteristics of these defects are important, but there is no suitable methodology for directly analyzing the interface properties, and existing related analysis techniques are not satisfactory.

Photoluminescence (PL) is a technique that allows defects to be observed at deep depths in semiconductors but cannot be used in operating devices with interfaces. Deep-Level Transient Spectroscopy (DLTS) and Gate-Bias Stress techniques can be used in thin film transistor devices using thermal and electrical energy, respectively, to analyze interfacial trap states. . However, DLTS is not suitable for organic devices because of thermal instability, and the gate voltage application technique is a technique that cannot adequately observe the electrical state of a deep-defect defect. Conventional techniques are generally a method of analyzing defect concentrations present in a silicon wafer single crystal or in a silicon (Si) and silicon oxide (SiO ₂ ) interface by applying a stoichiometric / electrical voltage pulse or charge injection. For example, Lang et al. And the techniques described in Goldmann et al. Can estimate the interfacial defect density, but all that is estimated is a shallow depth of information that is only a few hundred meV away from the valence band maximum.

The first technical task of the present invention is to obtain an analysis result that is extremely sensitive to the interface characteristics compared to the conventional analysis method, and photoelectric spectroscopy technique that can quantitatively calculate the defect concentration for each energy level present in the interface of the channel semiconductor / gate insulating film An interface defect analysis method is provided.

A second object of the present invention is to provide a recording medium that can be read by a computer system in which a program for executing the above-described interface defect analysis method using the photoelectric spectroscopy method is recorded in the computer system.

The third technical task of the present invention is to obtain an analysis result that is extremely sensitive to the interface characteristics compared to the conventional analysis method, and photoelectric spectroscopy technique that can quantitatively determine the defect concentration for each energy level present in the interface of the channel semiconductor / gate insulating film It is to provide an interface defect analysis apparatus using the.

According to one or more exemplary embodiments, an interface defect analysis method using photoelectric spectroscopy may include applying a single wavelength optical signal in an order of long wavelength to short wavelength at an interface between a channel semiconductor and a gate insulating layer of a transistor; Measuring a threshold voltage for each wavelength based on the relationship between the gate voltage and the drain current for each wavelength; Calculating a defect charge amount of the interface based on the threshold voltage for each wavelength; And calculating an interface defect concentration per energy level from the defect charge amount.

An interface defect analysis apparatus using photoelectric spectroscopy according to an embodiment of the present invention includes a light applying unit for applying a single wavelength optical signal in an order of short wavelength to an interface between a channel semiconductor and a gate insulating film of a transistor; And converting the transistor into an on-state by applying a voltage to a gate of the transistor, measuring a threshold voltage for each wavelength based on the relationship between the gate voltage and the drain current for each wavelength, and for each wavelength. And a defect analyzing unit that calculates the amount of defect charges at the interface based on a voltage and calculates an interface defect concentration per energy level from the amount of defect charges.

According to the embodiments of the present invention, an analysis result that is extremely sensitive to interface characteristics can be obtained as compared to the conventional analysis method, and the defect concentration for each energy level present in the channel semiconductor / gate insulating film interface can be quantitatively obtained, and all field effect transistors can be obtained. Applicable to the device, it is possible to minimize the deterioration of the analytical specimen during the analysis process by using the optical signal, which is a relatively low energy energy source, does not need to create an abnormal environment, such as vacuum or low temperature environment, even under normal temperature and atmospheric pressure Analysis is possible.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention illustrated below may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

In one embodiment of the present invention, the photoelectric characteristics of the transistor device according to the application of the continuous single wavelength optical signal are analyzed to determine the defect concentration according to the energy level in the band gap. To this end, the interface defect charge amount is obtained by changing the threshold voltage characteristic sensitive to the interface characteristic, and the interface defect concentration is measured by analyzing the interface defect charge amount.

1 illustrates an interface defect analysis apparatus using photoelectric spectroscopy according to an embodiment of the present invention.

The interfacial defect analysis apparatus of FIG. 1 is comprised by the light application part 1, 2, 4, and the defect analysis part 3. As shown in FIG. The transistor to be analyzed is composed of a substrate 5, a gate 6, a gate insulating film 7, a channel semiconductor 8, a source electrode 9, a drain electrode 10, and the like.

The light applying units 1, 2, and 4 apply a single wavelength optical signal in the order of long wavelength to short wavelength at the interface between the channel semiconductor 8 and the gate insulating film 7 of the transistor.

More specifically, the multi-wavelength light source 1 generates an optical signal having two or more different wavelengths, that is, an optical signal of multiple wavelengths. The single wavelength filter 2 outputs an optical signal having a single wavelength by filtering a multi-wavelength optical signal, and the output optical signal is output in order of long wavelength to short wavelength. The optical fiber 4 irradiates the interface with the light filtered by the single wavelength filter 2.

The defect analysis unit 3 applies a voltage to the gate 6 of the transistor to turn the transistor into an on-state. The defect analysis unit 3 measures threshold wavelengths for each wavelength based on the relationship between the gate voltage and the drain current for each wavelength of the optical signal applied by the light applying units 1, 2, and 4. The defect analysis unit 3 calculates the amount of defect charge at the interface based on the threshold voltage for each wavelength, and calculates the interface defect concentration per energy level from the calculated amount of charge.

2 is a flowchart illustrating an interface defect analysis method using photoelectric spectroscopy according to an embodiment of the present invention.

First, as shown in FIG. 1, a measurement apparatus capable of simultaneously measuring drain current variation characteristics according to a gate voltage through an analysis of voltage and current characteristics under an optical signal is applied. Thereafter, a single wavelength optical signal is applied to the interface between the channel semiconductor 8 and the gate insulating film 7 of the transistor in the order of long wavelength to short wavelength (S210). This process (S210) is a process of continuously applying a single wavelength optical signal to the top of the device such as an inorganic oxide thin film transistor or an organic thin film transistor using a multi-wavelength light source 1, a single wavelength filter (2), an optical fiber (4). Can be.

Next, the threshold voltage for each wavelength is measured based on the relationship between the gate voltage and the drain current for each wavelength (S220). This process (S220) is a process of starting a measurement from the on-state of the transistor in order to excite all the defect levels in the interface of the channel semiconductor 8 / gate insulating film 7 in the transistor. More specifically, this process (S220) includes the step of measuring the threshold voltage change from the characteristic curve of the drain current according to the gate voltage under each wavelength when the optical signal is sequentially applied to the interface in the order of long wavelength to short wavelength.

Thereafter, the amount of charge induced at the interface, that is, the amount of defect charge, is calculated based on the threshold voltage for each wavelength (S230). The threshold voltage V _th of the thin film transistor changes with wavelength as shown in Equation 1 below.

Where Q _eff ( ε ) is the effective defect charge at the interface, ε is the energy of the single wavelength optical signal, φ _ms is the work function level difference between the gate electrode 6 and the channel semiconductor 8, and ψ _{s, max} is the semiconductor surface The surface energy level of, Q _G is the amount of charges excited by the energy level change of the gate insulating film 7 in response to the gate voltage application, and C _ox represents the capacitance of the gate insulating film 7. If both sides of Equation 1 are differentiated by ε , Equation 2 for the threshold voltage change for each wavelength can be obtained.

On the other hand, when the measurement of the threshold voltage and the defect charge amount for the optical signal of the applied wavelengths is completed (S240), the interface defect concentration per energy level is calculated from the defect charge amount (S250). On the other hand, if there is an optical signal of the wavelength not yet applied, the above process is repeated from the step of applying the optical signal after changing the wavelength of the optical signal to be applied (S210). The defect charge amount may be defined as in Equation 3 according to the n-type or p-type characteristics of the channel.

for n-channel

for n-channel

for p-channel

for p-channel

Where q is the unit charge, CBM is the conduction band minimum, VBM is the valence band maximum, D (E) is the interface defect concentration per energy level, and E is the energy level. .

Differentiate Equation 3 according to the continuous short wavelength energy, and then apply Equation 2 to obtain the interfacial charge concentration D _it according to the energy level, which is defined as Equation 4 according to the n-type or p-type characteristics of the channel. Can be.

for n-channel

for n-channel

for p-channel

for p-channel

In one embodiment of the present invention, the defect analysis unit 3 may calculate the interface defect concentration according to the energy level using Equation 4.

3A and 3B are diagrams illustrating band diagrams between n-channel and p-channel semiconductors, a gate insulating layer, and a gate electrode for explaining a principle of defect concentration measurement according to an exemplary embodiment of the present invention.

In FIG. 3A, 11a is the gate electrode, 15a is the work function energy level of the gate electrode, 16a is the conduction band energy level of the channel semiconductor, 17a is the conduction band energy level of the channel semiconductor of the channel semiconductor, and 19a is the work function of the n-channel semiconductor. Energy level. When the single wavelength optical signal 18a is applied to the interface between the gate insulating film 12a and the n-channel semiconductor 13a, the electrons 21a are excited by the single wavelength optical signal 18a.

In FIG. 3B, 11b is the gate electrode, 15b is the work function energy level of the gate electrode, 16b is the conduction band energy level of the channel semiconductor, 17b is the conduction band energy level of the channel semiconductor of the channel semiconductor, and 20b is the work function of the p-channel semiconductor. Energy level. When the single wavelength optical signal 18b is applied to the interface between the gate insulating film 12b and the p-channel semiconductor 14b, the hole electrons 22b are excited by the single wavelength optical signal 18b.

When the interfacial impurity charges as much as the energy of the single-wavelength optical signal incident on the interface between the gate insulating film 7 and the channel semiconductor 8 are excited in the conduction band or the electrical appliance diagram, the threshold voltage changes as much as the amount thereof. .

4A and 4B illustrate examples of a gate voltage-drain current characteristic curve for each wavelength when applying the interface defect analysis method using photoelectric spectroscopy according to an embodiment of the present invention.

More specifically, FIG. 4A shows a change in wavelength-specific electrical characteristics curves and threshold voltages V _th for a zinc oxide (ZnO) thin film transistor, and FIG. 4B shows a change in wavelength-specific electrical characteristics curves for a pentacene thin film transistor. And a change in the threshold voltage V _th .

5A and 5B show the results of applying an interface defect analysis method using photoelectric spectroscopy according to an embodiment of the present invention, and are examples of concentration distribution curves for each defect energy level of a channel semiconductor / gate insulating layer interface.

5A is a concentration distribution curve for each defect energy level of a channel semiconductor / gate insulating film interface obtained through the measurement of the present invention of a zinc oxide thin film transistor.

5B illustrates a graph for each thin film transistor. The graph 23 indicated by black dots is a curve of defect energy concentration distribution at the channel semiconductor / gate insulating film interface of the pentacene thin film transistor processed on the silicon oxide film (SiO ₂ ) gate insulating film. The graph 24 indicated by the white dots is a defect energy concentration distribution curve of the channel semiconductor / gate insulating film interface of the pentacene thin film transistor processed on the polymer gate insulating film.

The invention can be implemented via software. Preferably, a method for performing an interface defect analysis method using photoelectric spectroscopy according to embodiments of the present invention may be provided by recording a program for executing in a computer on a computer-readable recording medium. When implemented in software, the constituent means of the present invention are code segments that perform the necessary work. The program or code segments may be stored on a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network.

Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system. Examples of the computer readable recording medium include ROM, RAM, CD-ROM, DVD 占 ROM, DVD-RAM, magnetic tape, floppy disk, hard disk, optical data storage, and the like. The computer readable recording medium can also be distributed over network coupled computer devices so that the computer readable code is stored and executed in a distributed fashion.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and variations may be made therefrom. And, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Embodiments of the present invention are required for all field effect transistor applications requiring interface characterization, and may be applied to a semiconductor industry requiring transistor processes such as display-related devices.

1 illustrates an interface defect analysis apparatus using photoelectric spectroscopy according to an embodiment of the present invention.

2 is a flowchart illustrating an interface defect analysis method using photoelectric spectroscopy according to an embodiment of the present invention.

3A and 3B are band diagram schematic diagrams of n- and p-channel semiconductors, gate insulating films, and gate electrodes.

4A and 4B illustrate examples of a gate voltage-drain current characteristic curve for each wavelength when applying the interface defect analysis method using photoelectric spectroscopy according to an embodiment of the present invention.

5A and 5B are graphs illustrating the results of applying an interface defect analysis method using photoelectric spectroscopy according to an embodiment of the present invention.

Claims (11)

Applying a single wavelength optical signal in an order of long wavelength to short wavelength at an interface between the channel semiconductor of the transistor and the gate insulating film; By switching the transistor to an on-state and exciting the defect level in the interface, the threshold voltage for each wavelength based on the relationship between the gate voltage and the drain current for each wavelength of the optical signal of the sequentially applied wavelengths Measuring; Calculating a defect charge amount induced at the interface based on the threshold voltage for each wavelength; And Computing the interface defect concentration per energy level from the defect charge amount, Interface defect analysis method using photoelectric spectroscopy. The method of claim 1, The step of applying the optical signal And filtering the multi-wavelength optical signal generated by the multi-wavelength light source in the order of long wavelength to short wavelength with a single wavelength filter. The method of claim 2, The step of applying the optical signal And irradiating the interface of the light filtered by the single wavelength filter to the interface with an optical fiber. The method of claim 1, The step of calculating the interface defect concentration per energy level Q _eff ( ε ) is the defect charge at the interface, q is the unit charge, CBM is the conduction band minimum, ε is the energy of the single-wavelength optical signal, and VBM is the valence band maximum. When E is an energy level, the interface defect concentration D (E) per energy level is

Comprising a step of calculating using a relational formula, characterized in that the interface defect analysis method using photoelectric spectroscopy. The method of claim 1, The step of calculating the interface defect concentration per energy level Q _eff ( ε ) is the amount of defect charge at the interface, q is the unit charge amount, ε is the energy of the single wavelength optical signal, VBM is the valence band maximum, and E is the energy level. Interfacial defect concentration D (E)

Comprising a step of calculating using a relational formula, characterized in that the interface defect analysis method using photoelectric spectroscopy. A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 1 to 5 on a computer system. A light applying unit for applying a single wavelength optical signal in an order of short wavelength to an interface between the channel semiconductor and the gate insulating film of the transistor; And By applying a voltage to the gate of the transistor to switch the transistor to an on-state and to excite a defect level in the interface, the gate voltage and the drain current for each wavelength for the optical signal of the sequentially applied wavelengths A defect analysis unit for measuring a threshold voltage for each wavelength based on the relationship between the signals, calculating a defect charge amount induced at the interface based on the threshold voltage for each wavelength, and calculating an interface defect concentration per energy level from the defect charge amount. Interface defect analysis device using the photoelectric spectroscopy. The method of claim 7, wherein The light applying unit A multi-wavelength light source for generating a multi-wavelength optical signal; And And a single wavelength filter for filtering the optical signals in the order of the long wavelength to the short wavelength from the multi-wavelength optical signal. The method of claim 8, The light applying unit And an optical fiber for irradiating the interface with the light filtered out by the single wavelength filter. The method of claim 8, The defect analysis unit When CBM is the conduction band minimum of the conduction band, V _th is the threshold voltage, ε is the energy of the single wavelength optical signal, C _ox is the capacitance of the insulating film, and q is the unit charge. Interfacial charge concentration according to energy level

An apparatus for analyzing interface defects using photoelectric spectroscopy, characterized by obtaining. The method of claim 8, The defect analysis unit VBM the capacitance of the maximum energy (Valence Band Maximum), V _th of the valence band has a threshold voltage, ε is the energy, C _ox of the single wavelength optical signal insulation, when q a unit charge amount, the derivative of the successive short wavelength energy Interfacial charge concentration according to energy level

An apparatus for analyzing interface defects using photoelectric spectroscopy, characterized by obtaining.

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