KR101344754B1 - Method for extracting subgap density of states of amorphous oxide semiconductor thin-film transistor and apparatus thereof - Google Patents

Method for extracting subgap density of states of amorphous oxide semiconductor thin-film transistor and apparatus thereof Download PDF

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KR101344754B1
KR101344754B1 KR1020130027999A KR20130027999A KR101344754B1 KR 101344754 B1 KR101344754 B1 KR 101344754B1 KR 1020130027999 A KR1020130027999 A KR 1020130027999A KR 20130027999 A KR20130027999 A KR 20130027999A KR 101344754 B1 KR101344754 B1 KR 101344754B1
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capacitance
state density
film transistor
thin film
photoreaction
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배학열
최현준
김대환
김동명
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국민대학교산학협력단
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
    • H01L22/10—Measuring as part of the manufacturing process
    • H01L22/12—Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
    • H01L22/30—Structural arrangements specially adapted for testing or measuring during manufacture or treatment, or specially adapted for reliability measurements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
    • H01L29/76—Unipolar devices, e.g. field effect transistors
    • H01L29/772—Field effect transistors
    • H01L29/78—Field effect transistors with field effect produced by an insulated gate
    • H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
    • H01L29/7869—Thin film transistors, i.e. transistors with a channel being at least partly a thin film having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
    • H01L29/78693—Thin film transistors, i.e. transistors with a channel being at least partly a thin film having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate the semiconducting oxide being amorphous

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Abstract

A method and apparatus for extracting a state density in a bandgap of an amorphous oxide semiconductor thin film transistor are disclosed. In the method for extracting the state density in the bandgap of the amorphous oxide semiconductor thin film transistor according to the exemplary embodiment of the present invention, the method for extracting the state density in the bandgap of the amorphous oxide semiconductor thin film transistor includes a darkroom capacitance according to a gate voltage of the thin film transistor in a dark room. Measuring; Irradiating a light source having a predetermined wavelength to the thin film transistor to measure a photoreaction capacitance of the thin film transistor; Applying a first capacitance model and a second capacitance model to regions below and above a flat-band voltage of the thin film transistor; And a donor state density in a band gap and an acceptor state density in a band gap based on the measured dark room capacitance, the photoreaction capacitance, and the applied first capacitance model and the second capacitance model. By separating and extracting, it is possible to extract the total state density in the bandgap using only experimental measurement data, and to extract the total state density in the bandgap simply and quickly, eliminating repetitive processes and complicated calculations. have.

Description

Method for extracting subgap density of states of amorphous oxide semiconductor thin-film transistor and apparatus

The present invention relates to subgap density-of-states extraction of amorphous oxide semiconductor thin film transistors (TFTs). Specifically, the present invention relates to capacitance and gate voltage ranges measured using a monochromatic photonic. The present invention relates to a method and apparatus for extracting a state density in a bandgap of an amorphous oxide semiconductor thin film transistor capable of extracting an overall state density in a bandgap through a different capacitance model determined accordingly.

The present invention is derived from a study performed as a part of the Basic Research Project-Middle Researcher (Core Research) of the Ministry of Education, Science and Technology and the Ministry of Education, Science and Technology of the Korea Research Foundation. Development and Application of Integrated Thermo-Opto Electronic Characterization Platform for Semiconductor TFT].

Amorphous oxide semiconductor thin film transistors (TFTs) have advantages such as high carrier mobility, uniformity of the thin film over a large area, and reliability in terms of reliability. Amorphous oxide semiconductor TFTs have been actively researched as an alternative to amorphous Si TFTs that are commercialized in display backplanes such as high resolution AM (Active Matrix) -LCD and AM-OLED (Organic Light-Emitting Diode) . Indeed, in the recent 3-4 years, a-IGZO (InGa-ZnO) TFT, which is an amorphous oxide semiconductor TFT, has been applied to various display pixel circuits and 3-D lamination circuits and proved its applicability.

Since the amorphous oxide semiconductor thin film transistor has a large influence on the state density (subgap DOS) existing in the bandgap, extraction of the state density in the bandgap plays a very important role in analyzing the characteristics of the device. In particular, the modeling and characterization of the state density for the device's bandgap (E V <E <E C ) is related to the reliability, stability and robust circuitry, It is very important in evaluating long-term performance.

The conventional method for extracting the total state density in the bandgap of the amorphous oxide semiconductor thin film transistor was performed through a combination of various measurement results and a correlation with the experimental values using a simulator. However, this conventional method has a problem that it is difficult to trust because the error factor is very large, it was performed through an iteration procedure and a complex calculation (complicated calculation).

Therefore, there is a need for a method for extracting the total state density in the bandgap using only experimental measurement data without complicated calculation process.

Korean Registered Patent No. 10-1105273 (registered on January 01, 2012)

The present invention is derived to solve the problems of the prior art, it is possible to experimentally extract the total state density in the bandgap through a different capacitance model determined according to the capacitance and gate voltage range measured using a single light source. It is an object of the present invention to provide a method and apparatus for extracting a state density in a bandgap of an amorphous oxide semiconductor thin film transistor.

Specifically, the present invention measures each capacitance for the presence or absence of a single light source and uses two different capacitance models determined for the two capacitances and the region below the flat-band voltage and the region above the flat voltage. Calculate the photoreaction donor capacitance and photoreaction acceptor capacitance formed by a single light source, and calculate the donor state density in the bandgap and the acceptor state density in the bandgap using the calculated photoreaction donor capacitance and the photoreaction acceptor capacitance. Can be separated and extracted.

In addition, an object of the present invention is to provide a method and apparatus for extracting a state density within a bandgap of an amorphous oxide semiconductor thin film transistor, which can quickly and simply extract the total state density within a bandgap using only experimental measurement data.

In order to achieve the above object, in the bandgap state density extraction method of the amorphous oxide semiconductor thin film transistor according to an embodiment of the present invention, in the bandgap state density extraction method of the amorphous oxide semiconductor thin film transistor, Measuring a dark room capacitance according to a gate voltage of the thin film transistor; Irradiating a light source having a predetermined wavelength to the thin film transistor to measure a photoreaction capacitance of the thin film transistor; Applying a first capacitance model and a second capacitance model to regions below and above a flat-band voltage of the thin film transistor; And a donor state density in a band gap and an acceptor state density in a band gap based on the measured dark room capacitance, the photoreaction capacitance, and the applied first capacitance model and the second capacitance model. Separating and extracting.

In the extracting step, the donor state density in the band gap and the acceptor state density in the band gap may be extracted by further considering physical structure parameters of the thin film transistor.

The first capacitance model may include a depletion capacitance formed by a depletion region and an active capacitance formed by an active region, and further include a photoreaction donor capacitance formed by irradiation of the light source. The photoreaction donor capacitance may be connected in parallel with the depletion capacitance.

The extracting step may include calculating the photoreaction donor capacitance based on the measured dark room capacitance, the photoreaction capacitance, and the applied first capacitance model, and the bandgap based on the calculated photoreaction donor capacitance. The donor state density can be extracted.

The second capacitance model further includes an accumulation capacitance formed by an accumulation region, and further includes a photoreaction acceptor capacitance formed by irradiation of the light source, wherein the photoreaction acceptor capacitance is the accumulation. It can be connected in parallel with the capacitance.

The extracting step may include calculating the photoreaction acceptor capacitance based on the measured darkroom capacitance, the photoreaction capacitance, and the applied second capacitance model, and based on the calculated photoreaction acceptor capacitance. The acceptor state density in the bandgap can be extracted.

In another embodiment, a method for extracting a state density in a bandgap of an amorphous oxide semiconductor thin film transistor may include a method for extracting a state density in a bandgap of an amorphous oxide semiconductor thin film transistor, the dark room corresponding to a gate voltage of the thin film transistor in a dark room. Measuring capacitance; Irradiating a light source having a predetermined wavelength to the thin film transistor to measure a photoreaction capacitance of the thin film transistor; Applying a predetermined capacitance model to a region below the flat-band voltage of the thin film transistor; And extracting a donor state density in a bandgap based on the capacitance of the region below the flat voltage and the capacitance model of the measured dark room capacitance and the photoreaction capacitance.

An apparatus for extracting a state density within a bandgap of an amorphous oxide semiconductor thin film transistor according to an exemplary embodiment of the present invention is an apparatus for extracting a state density within a bandgap of an amorphous oxide semiconductor thin film transistor, the dark room capacitance of the thin film transistor according to the gate voltage of the thin film transistor in a dark room. A measuring unit configured to measure a photoreaction capacitance of the thin film transistor by measuring a light source having a predetermined wavelength to the thin film transistor; An application unit applying a first capacitance model and a second capacitance model to regions below and above the flat-band voltage of the thin film transistor; And a donor state density in a band gap and an acceptor state density in a band gap based on the measured dark room capacitance, the photoreaction capacitance, and the applied first capacitance model and the second capacitance model. It includes an extract to separate and extract.

In another embodiment, an apparatus for extracting a state density within a bandgap of an amorphous oxide semiconductor thin film transistor is a device for extracting a state density within a bandgap of an amorphous oxide semiconductor thin film transistor, the dark room corresponding to a gate voltage of the thin film transistor in a dark room. A measuring unit measuring capacitance and measuring a photoreaction capacitance of the thin film transistor by irradiating a light source having a predetermined wavelength to the thin film transistor; An application unit applying a predetermined capacitance model to a region below a flat-band voltage of the thin film transistor; And an extraction unit configured to extract a donor state density in a band gap based on the capacitance of the region below the flat voltage and the capacitance model among the measured dark room capacitance and the photoreaction capacitance.

According to the present invention, the donor state density and the band in the bandgap are made by using two different capacitance models, which are determined for each of the capacitance and the flat-band voltage under and over the measured region with and without a single light source. By separating and extracting the acceptor state density in the gap, the entire state density in the band gap can be extracted using only experimental measurement data.

In addition, the present invention can simply and quickly extract the total state density in the bandgap using only experimental measurement data without an iteration procedure and complicated calculations, and the total state density in the extracted bandgap. Can improve the reliability.

In particular, the present invention reflects both the material composition of the device, the operating environment, the manufacturing process, the geometrical structure (or physical structure), and the change according to the applied voltage and their dependence, thereby optimizing device performance and reliability through process development. It can be very useful for securing.

1 is a perspective view of an embodiment of an amorphous oxide semiconductor TFT.
2 is a flowchart illustrating a method for extracting a state density in a bandgap of an amorphous oxide semiconductor TFT according to an exemplary embodiment of the present invention.
FIG. 3 shows an operation flowchart of an embodiment of step S240 shown in FIG. 2.
4 shows an example graph of measured dark room capacitances and photoreaction capacitances.
5 is a conceptual diagram illustrating an energy band diagram and capacitance characteristics according to a single light source and a gate voltage.
FIG. 6 shows a cross-sectional view of one embodiment of an amorphous oxide semiconductor TFT including capacitance models for regions under and below planar voltage.
7 shows a conceptual diagram of the energy distribution of the overall state density in the band gap based on a single light source in the present invention.
8 shows a donor state density in a band gap, an acceptor state density in a band gap, and an example of modeling the same, extracted by the method according to the present invention.
9 is a flowchart illustrating a method of extracting a state density in a bandgap of an amorphous oxide semiconductor TFT according to another exemplary embodiment of the present invention.
FIG. 10 shows a configuration of an apparatus for extracting a state density in a bandgap of an amorphous oxide semiconductor TFT according to an embodiment of the present invention.
FIG. 11 illustrates a configuration of an apparatus for extracting a state density in a bandgap of an amorphous oxide semiconductor TFT according to another exemplary embodiment of the present invention.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the accompanying drawings.

Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

However, the present invention is not limited to or limited by the embodiments. Like reference symbols in the drawings denote like elements.

Hereinafter, a method and apparatus for extracting state density in a bandgap of an amorphous oxide semiconductor thin film transistor according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 1 to 11.

Amorphous oxide semiconducting TFTs are used as substitute devices due to their high carrier mobility, uniformity of thin films in a large area, and stability from a reliability point of view instead of a-Si TFTs, which are commercially available as switch or driving devices in display backplanes such as AMLCD and AMOLED Be in the spotlight.

In this amorphous oxide semiconductor TFT, extraction of the state density in the bandgap which has a great influence on the electrical characteristics is very important in the analysis of the characteristics of the device. Particularly, in the band gap (E V <E <E C ) Density modeling and characteristics are critical to reliability, stability, and long-term performance of robust circuits and systems due to manufacturing process and layout.

The present invention utilizes experimental capacitance measurement data and different capacitance models predetermined according to a range of gate voltages to easily and quickly extract the overall state density in a bandgap without an iteration procedure and a complicated calculation. The point is that.

Here, the range of the gate voltage is a range of the region below the flat voltage and the excess region, and the capacitance model may use two different models of the first capacitance model for the region below the flat voltage and the second capacitance model for the region above the flat voltage. .

FIG. 1 is a perspective view of an embodiment of an amorphous oxide semiconductor TFT. In the present invention, an amorphous InGaZnO (a-IGZO) TFT is exemplarily described as an amorphous oxide semiconductor TFT.

1, the amorphous oxide semiconductor TFT includes electrodes (gate electrode, source electrode, and drain electrode) 120, 150 and 160 for applying driving power, a gate insulating layer 130, and an amorphous oxide semiconductor active layer layer (140).

Of course, although not shown in FIG. 1, the amorphous oxide semiconductor TFT may include a channel protective layer for protecting a channel or an active region exposed between the drain electrode 150 and the source electrode 160.

The gate electrode 120 is formed on a part of the substrate 110 and overlaps with the drain electrode 150 and the source electrode 160 in part. For example, L OV shown in FIG. 1 indicates an overlap length between the gate electrode 120, the drain electrode 150, and the source electrode 160.

In this case, the gate electrode 120 may be formed to have a predetermined length (L).

The gate insulating layer 130 is a layer for protecting the gate electrode 120 and electrically separating the gate electrode 120, the drain electrode 150, and the source electrode 160. The gate insulating layer 130 has a predetermined dielectric constant ε OX . The material is formed by a predetermined thickness T OX .

At this time, by a gate insulating layer 130 may be formed of a capacitance (C OX), the capacitance formed (C OX) may be obtained by using the physical structure of the gate insulating layer 130. That is, the capacitance C OX formed by the gate insulating layer 130 can be obtained by using the dielectric constant and thickness of the material used for the gate insulating layer 130, and the dielectric constant ε OX of the material and the thickness (T OX ) ratio (ε OX / T OX ).

An amorphous oxide semiconductor (AOS) 140 is formed on the gate insulating layer 130 by a predetermined thickness T IGZO using a material having a predetermined dielectric constant ε IGZO .

At this time, an example of the amorphous oxide semiconductor layer 140, a-IGZO may be an amorphous oxide semiconductor layer 140, the capacitance (C IGZO) can be formed, and the capacitance formed (C IGZO) by the Can be obtained using the physical structure of the amorphous oxide semiconductor layer 140. [ That is, the capacitance C IGZO formed by the amorphous oxide semiconductor layer 140 can be obtained by using the dielectric constant and the thickness of the material used for the amorphous oxide semiconductor layer 140, and the dielectric constant ε IGZO of the material, And the thickness (T IGZO ) (竜IGZO / T IGZO ).

The drain electrode 150 and the source electrode 160 are formed on a portion of the gate insulating layer 130, and the drain electrode 150 and the source electrode 160 are formed to be spaced apart by a predetermined interval.

At this time, the drain electrode 150 and the source electrode 160 may be formed to have a constant width W.

The present invention is to extract the overall state density in the bandgap of the amorphous oxide semiconductor TFT having such a geometric or physical structure, the capacitance and flatness measured using a capacitance measured in the dark room and a monochromatic photonic The donor state density in the bandgap and the acceptor state density in the bandgap are separately extracted using a capacitance model modeled for each of the under and over regions of the voltage.

A method of extracting the state density in the band gap of the amorphous oxide semiconductor TFT according to the present invention will be described with reference to FIGS. 2 to 8.

2 is a flowchart illustrating a method for extracting a state density in a bandgap of an amorphous oxide semiconductor TFT according to an exemplary embodiment of the present invention.

2, the method according to the present invention measures the capacitance according to the gate voltage in the dark room (hereinafter referred to as "dark room capacitance") for the amorphous oxide semiconductor TFT, and irradiates the TFT with a single predetermined light source The capacitance according to (hereinafter referred to as "photoreaction capacitance") is measured (S210, S220).

Steps S210 and S220 may be reversed depending on the situation.

Here, the capacitance can be measured using a measurement means, for example, an Agilent 4156C semiconductor parameter analyzer or an HP4284 LCR meter, and various corresponding measurement means can be utilized.

The single light source irradiated with the amorphous oxide semiconductor TFT in step S220 may be a single light source having energy in a range smaller than the energy band gap of the TFT, for example, an energy of 2.6 [eV], as shown in the example illustrated in FIG. 4. The dark capacitance and the photoreaction capacitance can be measured using the presence or absence of a green light source with an energy of 2.6 [eV].

The amorphous oxide semiconductor TFT is a single light source, for example, as shown in FIGS. 5A and 5B, when a green single light source having a wavelength of 532 [nm] and an energy E ph of 2.6 [eV] is irradiated. Due to photonic excitation, localized trapped electrons are generated from localized traps within a specific energy range (E C -E ph <E <E F ), and due to the generated electrons the capacitance according to the gate voltage The characteristics will be different.

4 and 5, in an amorphous oxide semiconductor TFT to which a depletion bias (V ON <V GS <V FB ) is applied in a region below the flat voltage V FB , a single light source is used. When irradiated, the photoreaction charge (Q ph , do ) due to free electrons from the donor-like state excited from the trap of the donor state density (g D (E)) in the bandgap is dominant and flat. In an amorphous oxide semiconductor TFT in an accumulation mode in which the gate voltage V FB <V GS <V T is applied between the voltage V FB and the threshold voltage V T , a single light source is irradiated to suppress the band gap. It can be seen that the photoreaction charges Q ph and ac are dominant due to the free electrons from acceptor-like states excited from the trap of the acceptor state density g A (E).

When the darkroom capacitance and the photoreaction capacitance are measured by the steps S210 and S220, different capacitance models are applied to the region below the flat voltage V FB and the region above the flat voltage (S230).

For example, the first capacitance model shown in FIG. 6A is applied to the region below the flat voltage, and the second capacitance model shown in FIG. 6B is applied to the region above the flat voltage.

As shown in FIG. 6A, the first capacitance model when a depletion bias (V GS << V FB ) of less than the flat voltage is applied is a depletion capacitance (C dep ), amorphous formed by a depletion region. oxide active capacitance formed by the semiconductor layers of the active region (C IGZO) and the optical response donor capacitance (C ph, D) generated from the local traps of the donor density of states of the total density of states within the bandgap by the irradiation of a single light source, and And a capacitance C OX formed by the gate insulating layer, and the depletion capacitance C dep and the photoreaction donor capacitance C ph and D are connected in parallel.

On the other hand, as shown in FIG. 6B, the second capacitance model when the gate bias (V GS > V FB ) for the accumulation mode is applied when the flat voltage is exceeded is the accumulation capacitance formed by the accumulation region (accumulation region). C acc ) and the photoreaction acceptor capacitance C ph , A generated from a local trap of the acceptor state density among the total state densities in the bandgap by irradiation of a single light source, and the capacitance C formed by the gate insulating layer. OX ), and the accumulation capacitance C acc and the photoreaction acceptor capacitance C ph, A are connected in parallel.

As such, when the first capacitance model in the region below the flat voltage and the second capacitance model in the region above the flat voltage are applied, based on the dark room capacitance and the photoreaction capacitance measured in steps S210 and S220, and the two capacitance models applied in step S230. The donor state density in the band gap and the acceptor state density in the band gap are separated and extracted (S240).

In this case, step S240 may separate and extract the donor state density in the band gap and the acceptor state density in the band gap by further considering the geometric or physical structural parameters of the amorphous oxide semiconductor TFT.

A process of separating and extracting the donor state density in the band gap and the acceptor state density in the band gap in step S240 will now be described with reference to FIG. 3.

FIG. 3 shows an operation flowchart of an embodiment of step S240 shown in FIG. 2.

Referring to FIG. 3, in operation S240 of separating and extracting the donor state density and the acceptor state density in a bandgap, the photoreaction donor capacitance is calculated based on the measured dark room capacitance, the photoreaction capacitance, and the first capacitance model. The donor state densities in the band gap are extracted based on the calculated photoreaction donor capacitance (S310 and S320).

Hereinafter, a process of calculating the photoreaction donor capacitance and extracting the donor state density in the bandgap using the calculated photoreaction donor capacitance will be described with reference to Equation.

The dark capacitance (C D, m ) and the photoreaction capacitance (C P, m ) measured according to the gate voltage (V GS ) in the region below the flat voltage are represented by Equation 1 and Equation 2 below. Can be.

[Equation 1]

Figure 112013022676629-pat00001

&Quot; (2) &quot;

Figure 112013022676629-pat00002

Here, C OV means overlap capacitance formed by overlap between the gate electrode, the source electrode, and the drain electrode, and the overlap capacitance C OV may be expressed as Equation 3 below.

&Quot; (3) &quot;

Figure 112013022676629-pat00003

Here, C IGZO refers to the capacitance formed by the amorphous oxide semiconductor layer of the amorphous oxide semiconductor TFT, C OX refers to the capacitance formed by the gate insulating layer, W means the width of the source electrode or drain electrode , L OV means an overlapping length between the gate electrode, the source electrode, and the drain electrode.

At this time, the capacitance C OX is the ratio of the dielectric constant of the material used for the gate insulating layer (ε OX) and thickness (T OX) (ε OX / T OX ) and the capacitance C IGZO In addition, the ratio of the dielectric constant of the material used for the amorphous oxide semiconductor layer (IGZO ε) and thickness (T IGZO) (ε IGZO / T IGZO ). Equations 1 and 2 may be represented by Equation 4 and Equation 5 below, and the photoreaction donor capacitance C ph, D calculated using Equations 4 and 5 is It can be expressed as Equation 6 below.

&Quot; (4) &quot;

Figure 112013022676629-pat00004

&Quot; (5) &quot;

Figure 112013022676629-pat00005

&Quot; (6) &quot;

Figure 112013022676629-pat00006

The donor state density (g D (E)) in the bandgap for a specific energy level can be extracted using the photoreaction donor capacitance calculated in Equation 6 below. Can be extracted through.

[Equation 7]

Figure 112013022676629-pat00007

Here, ΔC ph , D means that the photoreaction donor capacitance calculated in the region below the flat voltage is differentiated according to the gate voltage, L means the length of the gate electrode as shown in FIG. 1, and T IGZO is amorphous. The thickness of the oxide semiconductor layer, and V GS1 and V GS2 refer to the gate voltage between the turn-on voltage (V on ) and the flat voltage (V FB ). Of course, depending on the situation V GS1 and V GS2 may be a voltage below the turn-on voltage (V on ).

[Equation 8]

Figure 112013022676629-pat00008

As can be seen from Equation 8, the donor state density (g D (E)) in the bandgap can be extracted through the derivative of the photoreaction donor capacitance, and the photoreaction donor capacitance is measured darkroom capacitance and photoresponse capacitance and Since it can be calculated using the physical structure parameters of the amorphous oxide semiconductor TFT, it can be seen that the donor state density in the bandgap in the present invention can be extracted through the experimentally measured value as a result. That is, the donor state density in the bandgap is extracted using the capacitance of the region below the flat voltage and the physical structure parameters of the measured capacitance.

Since the donor state density in the bandgap extracted by Equation 8 is the state density for the energy level, the gate voltage must be converted to the surface potential (energy level), and the gate voltage in the region below the flat voltage Surface potential (

Figure 112013022676629-pat00009
) Can be converted by Equation 9 below.

&Quot; (9) &quot;

Figure 112013022676629-pat00010

Through this process it is possible to extract the donor state density (g D (E)) in the bandgap according to the present invention.

Once the donor state density in the bandgap is extracted, the photoreceptor capacitance is calculated on the basis of the measured dark capacitance, the photoreaction capacitance and the second capacitance model, and the acceptor state in the bandgap is based on the calculated photoreaction acceptor capacitance. Extract the density (S330, S340).

Hereinafter, a process of calculating the photoreaction acceptor capacitance and extracting the acceptor state density in the bandgap using the calculated photoreaction acceptor capacitance will be described with reference to Equation.

The darkroom capacitance (C D, m ) and the photoreaction capacitance (C P, m ) measured according to the gate voltage (V GS ) in the region beyond the flat voltage are represented by Equations 10 and 11 below. Can be.

&Quot; (10) &quot;

Figure 112013022676629-pat00011

&Quot; (11) &quot;

Figure 112013022676629-pat00012

The photoreactive receptor acceptance capacitance C ph, A can be calculated using Equation (10) and Equation (11), and the calculated photoreactive receptor acceptance capacitance (C ph, A ) can be expressed by Equation (12) .

&Quot; (12) &quot;

Figure 112013022676629-pat00013

The acceptor state density (g A (E)) in the bandgap for a particular energy level can be extracted using the photoreaction acceptor capacitance calculated in Eq. (12) and (14). Can be extracted via>.

&Quot; (13) &quot;

Figure 112013022676629-pat00014

Here, ΔC ph , A means that the photoreaction acceptor capacitance calculated in the region above the flat voltage is differentiated according to the gate voltage, and V GS3 and V GS4 are between the flat voltage V FB and the threshold voltage V T. Means the gate voltage. Of course, depending on the situation, V GS3 and V GS4 may be a gate voltage greater than or equal to the threshold voltage V T.

&Quot; (14) &quot;

Figure 112013022676629-pat00015

As can be seen from Equation 14, the acceptor state density (g A (E)) in the bandgap can also be extracted through the derivative of the photoreaction acceptor capacitance and exceeds the flat voltage between the measured dark room capacitance and the photoresponse capacitance. It can be extracted using the capacitance of the region and the physical structure parameters. Therefore, the acceptor state density in the band gap in the present invention can also be extracted through experimentally measured values.

Since the acceptor state density in the bandgap extracted by Equation 14 is the state density for the energy level, the gate voltage should be converted into the surface potential (energy level), and the surface potential for the gate voltage in the region beyond the flat voltage

Figure 112013022676629-pat00016
) Can be converted by Equation 15 below.

&Quot; (15) &quot;

Figure 112013022676629-pat00017

Through this process it is possible to extract the acceptor state density (g A (E)) in the band gap according to the present invention.

Although the steps S310 to S340 are sequentially performed in FIG. 3, the present invention is not limited thereto, and the donor state density in the band gap and the acceptor state density in the band gap may be extracted in parallel. That is, the processes of steps S310 and S320 and the processes of steps S330 and S340 may be performed in parallel.

As shown in FIG. 7, the donor state density in the band gap and the acceptor state density in the band gap extracted through the processes of FIGS. 2 and 3 may be represented in a tail state (g TD ) in exponential form. E), g TA (E)) and a deep state (g DD (E), g DA (E)) may be modeled to be superposition. In addition, as shown in FIG. 7, in the present invention, in order to extract the donor state density in the band gap adjacent to the balance band maximum value E V , a high energy λ

Figure 112013022676629-pat00018
532 nm, E ph
Figure 112013022676629-pat00019
By using an incident ray with 2.6 eV), we extract the total state density in the bandgap in the 2.6 [eV] energy range from the conduction band (E c ) to the balance band (E V ). can do.

At this time, the donor state density in the bandgap and the acceptor state density in the bandgap extracted by the method of the present invention overlap the tail state and the dip state in an exponential form as shown in Equation 16 and Equation 17 below. Can be modeled.

&Quot; (16) &quot;

Figure 112013022676629-pat00020

&Quot; (17) &quot;

Figure 112013022676629-pat00021

Here, N DD denotes a donor state density at a deep state, k denotes a Boltzmann constant at a predetermined value, and N TD denotes a donor state density at a tail state KT DD denotes the characteristic energy of the deep state with respect to the donor state density, kT TD denotes the characteristic energy of the tail state with respect to the donor state density, and N DA denotes the deep state N TA denotes the acceptor state density at the tail state, kT DA denotes the state of the deep state at the acceptor state density, Energy, and kT TA is the characteristic energy of the tail state with respect to the acceptor state density.

For example, as shown in FIG. 8A, the donor state density in the bandgap extracted by the present invention may be represented by a model modeled by Equation 16, as shown in FIG. 8B. In addition, the acceptor state density in the bandgap extracted by the present invention may also be represented by a model modeled by Equation 17.

As such, the method according to the present invention uses donor states in a bandgap using two different capacitance models predetermined for each of the capacitances measured by the presence or absence of a single light source and for areas below the flat-band voltage and above the excess area. By separating and extracting the density and the acceptor state density in the bandgap, the entire state density in the bandgap can be extracted using only experimental measurement data.

In addition, the present invention provides a structure and material because it is possible to simply and quickly extract the total state density in the bandgap using only experimental measurement data without an iteration procedure and complicated calculations. ), It can be used as a powerful tool to obtain robustness of the overall state density in the bandgap, which is process dependent.

Furthermore, the present invention reflects both the material composition of the device, the operating environment, the manufacturing process, the geometry (or physical structure), and the dependence on the applied voltage and their dependence, It can be used very usefully.

FIG. 9 is a flowchart illustrating a method for extracting a state density in a bandgap of an amorphous oxide semiconductor TFT according to another embodiment of the present invention. Of course, the acceptor state density among the total state densities in the band gap can be used not only for the method of the present invention but also for any method capable of extracting the acceptor state density. That is, the method in FIG. 9 extracts donor state density in the bandgap using only experimental data, and the acceptor state density in the bandgap can be extracted using various conventional methods.

Referring to FIG. 9, the method according to the present invention measures the dark capacitance of the amorphous oxide semiconductor TFT according to the gate voltage in the dark room, and irradiates a single predetermined light source to the TFT to measure the photoreaction capacitance according to the gate voltage ( S910, S920).

In this case, the execution order of steps S910 and S920 may be reversed.

Here, the capacitance can be measured using a measurement means, for example, an Agilent 4156C semiconductor parameter analyzer or an HP4284 LCR meter, and various corresponding measurement means can be utilized.

The single light source irradiated with the amorphous oxide semiconductor TFT in step S920 may be a single light source having energy in a range smaller than the energy band gap of the TFT as described above.

When the darkroom capacitance and the photoresponse capacitance are measured by steps S910 and S920, a predetermined capacitance model is applied to a region below the flat voltage V FB (S930).

In this case, the applied capacitance model is a capacitance model shown in FIG. 6A as described above, and is formed by an active region which is a depletion capacitance C dep formed by a depletion region and an amorphous oxide semiconductor layer. Photoreaction donor capacitances C ph and D generated from a local trap of donor state density in the bandgap by irradiation of the active capacitance C IGZO and a single light source, and capacitances C OX formed by the gate insulating layer It may include. Depletion capacitance C dep and photoreaction donor capacitance C ph, D are connected in parallel.

When the capacitance model is applied, the light response donor capacitance is calculated based on the measured capacitance, that is, the capacitance in the region below the flat voltage among the dark capacitance and the photo response capacitance, and the capacitance model applied in step S930, and based on the calculated photo response donor capacitance. The donor state density in the band gap is extracted (S940 and S950).

In this case, in step S950, the relationship between the surface potential with respect to the gate voltage and the energy level may be mapped as needed, and the donor state density in the band gap may be extracted as the energy level using the relationship between the mapped gate voltage and the surface potential. Can be. Further, step S950 may extract the donor state density in the band gap by additionally considering the physical structural parameters of the amorphous oxide semiconductor TFT.

Since the process of calculating the photoreaction donor capacitance and the process of extracting the donor state density in the bandgap using the same have been described above in detail, the description thereof will be omitted.

FIG. 10 shows a configuration of an apparatus for extracting a state density in a bandgap of an amorphous oxide semiconductor TFT according to an embodiment of the present invention.

Referring to FIG. 10, the apparatus 1000 according to the present invention includes a measuring unit 1010, an applying unit 1020, a mapping unit 1030, and an extracting unit 1040.

The measuring unit 1010 measures the dark room capacitance according to the gate voltage of the amorphous oxide semiconductor TFT in the dark room, and measures the photoreaction capacitance of the TFT by irradiating the TFT with a single light source having a predetermined wavelength.

In this case, the measuring unit 1010 can measure the dark room capacitance and the photoreaction capacitance by using a measurement means such as an Agilent 4156C semiconductor parameter analyzer or an HP4284 LCR meter.

The application unit 1020 applies different predetermined capacitance models for the region below the planar voltage and the region above the amorphous oxide semiconductor TFT.

At this time, the application unit 1020 applies the first capacitance model as shown in FIG. 6A to the region below the flat voltage, and applies the second capacitance model as shown in FIG. 6B to the region above the flat voltage. Can be.

The first capacitance model applied by the application unit 1020 includes a single depletion capacitance C dep formed by a depletion region, and an active capacitance C IGZO formed by an active region that is an amorphous oxide semiconductor layer. A photoreaction donor capacitance C ph , D generated from a local trap of donor state density among the total state densities in the bandgap by irradiation of a light source, and a capacitance C OX formed by the gate insulating layer, and depletion The capacitance C dep and the photoreaction donor capacitance C ph, D are connected in parallel.

On the other hand, the second capacitance model applied by the application unit 1020 has an acceptor state density of the total state densities in the bandgap by irradiation of a single light source and an accumulation capacitance C acc formed by an accumulation region. A photoreaction acceptor capacitance (C ph , A ) generated from a local trap of the capacitor, and a capacitance (C OX ) formed by the gate insulating layer, and include an accumulation capacitance (C acc ) and a photoreaction acceptor capacitance (C ph , A ) are connected in parallel.

The mapping unit 1030 uses the darkroom capacitance measured by the measuring unit 1010 to map the surface potentials of the gate voltage in the region below the flat voltage and the gate voltage in the region above the flat voltage.

That is, the mapping unit 1030 maps the surface potential with respect to the gate voltage using the above Equation 9 for the region under the flat voltage, and uses the above equation 15 with respect to the gate voltage over the flat voltage region. Map surface potentials.

At this time, the mapping unit 1030 may further convert the gate voltage into the surface potential for the energy level in consideration of the physical structure parameters of the TFT.

The extractor 1040 calculates the donor state density in the band gap and the acceptor state density in the band gap based on the darkroom capacitance measured by the measuring unit 1010, the photoreaction capacitance, and the capacitance model applied by the application unit 1020. Extract it separately.

At this time, the extraction unit 1040 may extract the donor state density in the band gap and the acceptor state density in the band gap by further considering the physical structural parameters of the amorphous oxide semiconductor TFT.

The extractor 1040 extracts the donor state density in the bandgap, based on the first capacitance model, which is a capacitance model in the region under the flat voltage and a capacitance model in the region under the flat voltage, among the measured dark capacitance and the photoreaction capacitance. The donor capacitance is calculated and the donor state density in the bandgap is extracted based on the calculated photoreaction donor capacitance.

Of course, the extractor 1040 may extract the donor state density in the band gap according to the energy level by using the surface potential according to the gate voltage of the region below the flat voltage mapped by the mapping unit 1030.

In addition, the extractor 1040 extracts the acceptor state density in the bandgap, and includes the capacitance of the flat voltage excess region and the second capacitance model, which is the capacitance model of the flat voltage excess region, among the measured dark room capacitance and the photoreaction capacitance. Based on the calculated photoreaction acceptor capacitance, the photoresist acceptor capacitance is extracted based on the calculated photoreaction acceptor capacitance.

Similarly, the extractor 1040 may extract the acceptor state density in the band gap according to the energy level by using the surface potential according to the gate voltage of the planar voltage excess region mapped by the mapping unit 1030.

FIG. 11 illustrates a configuration of an apparatus for extracting a state density in a bandgap of an amorphous oxide semiconductor TFT according to another exemplary embodiment of the present invention.

Referring to FIG. 11, the apparatus 1100 according to the present invention includes a measuring unit 1110, an applying unit 1120, a mapping unit 1130, and an extracting unit 1140.

The measuring unit 1110 measures the dark room capacitance according to the gate voltage of the amorphous oxide semiconductor TFT in the dark room, and irradiates the TFT with a single light source having a predetermined wavelength to measure the photoreaction capacitance of the TFT.

In this case, the measurement unit 1110 may measure the dark room capacitance and the photoreaction capacitance by using a measuring means such as an Agilent 4156C semiconductor parameter analyzer or an HP4284 LCR meter.

The application unit 1120 applies a predetermined capacitance model to the region below the flat voltage of the amorphous oxide semiconductor TFT.

In this case, the application unit 1120 may apply a capacitance model as shown in FIG. 6A to a region below the flat voltage, and the applied capacitance model is a depletion capacitance C dep formed by a depletion region. ), an amorphous oxide semiconductor layer is the active capacitance formed by the active region (C IGZO) and the optical response donor capacitance generated from the local traps of the donor density of states of the total density of states within the bandgap by the irradiation of the single light source (C ph, D ) and a capacitance C OX formed by the gate insulating layer, and the depletion capacitance C dep and the photoreaction donor capacitance C ph and D may be connected in parallel.

The mapping unit 1130 maps the surface potential with respect to the gate voltage of the region under the flat voltage using the dark room capacitance measured by the measuring unit 1110.

That is, the mapping unit 1130 maps the surface potential with respect to the gate voltage by using Equation 9 described above for the region under the flat voltage.

In this case, the mapping unit 1130 may convert the gate voltage into the surface potential with respect to the energy level by further considering the physical structure parameters of the TFT.

The extractor 1140 extracts the donor state density in the band gap based on the darkroom capacitance measured by the measuring unit 1110, the photoreaction capacitance, and the capacitance model applied by the application unit 1120.

At this time, the extraction unit 1140 may extract the donor state density in the band gap by further considering physical structure parameters of the amorphous oxide semiconductor TFT.

In extracting the donor state density in the bandgap, the extractor 1140 calculates the photoreaction donor capacitance based on the measured darkroom capacitance and the capacitance of the region below the flat voltage and the capacitance model of the region below the flat voltage. The donor state density in the bandgap is extracted based on the calculated photoreaction donor capacitance.

Of course, the extractor 1140 may extract the donor state density in the band gap according to the energy level by using the surface potential according to the gate voltage of the region below the flat voltage mapped by the mapping unit 1130.

Further, the extractor 1140 may extract the acceptor state density in the band gap, and the acceptor state density in the band gap may be extracted using various existing state density extraction methods.

The state density extraction method in the bandgap of the amorphous oxide semiconductor thin film transistor according to the exemplary embodiment of the present invention may be implemented in the form of program instructions that may be executed by various computer means and may be recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

As described above, the present invention has been described by specific embodiments such as specific components and the like. For those skilled in the art, various modifications and variations are possible from these descriptions.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (6)

A method for extracting a state density in a bandgap of an amorphous oxide semiconductor thin film transistor,
Measuring a dark room capacitance according to a gate voltage of the thin film transistor in a dark room;
Irradiating a light source having a predetermined wavelength to the thin film transistor to measure a photoreaction capacitance of the thin film transistor;
Applying a predetermined capacitance model to a region below the flat-band voltage of the thin film transistor; And
Extracting a donor state density in a bandgap based on the capacitance of the region below the flat voltage and the capacitance model among the measured dark room capacitance and the photoreaction capacitance;
State density extraction method in the band gap of the amorphous oxide semiconductor thin film transistor comprising a. The method of claim 1,
The capacitance model is
A method for extracting state density within a bandgap of an amorphous oxide semiconductor thin film transistor comprising a depletion capacitance formed by a depletion region and an active capacitance formed by an active region. 3. The method of claim 2,
The capacitance model is
Further comprising a photoreaction donor capacitance formed by the irradiation of the light source,
The photoreaction donor capacitance is
Connected in parallel with the depletion capacitance,
The extracting step
And extracting the donor state density in the band gap based on the capacitance in the region below the flat voltage, the photoreaction donor capacitance, and the capacitance model. The method of claim 1,
Applying a second predetermined capacitance model to the planar voltage excess region of the thin film transistor; And
Extracting the acceptor state density in a bandgap based on the measured capacitance of the excess voltage region and the second capacitance model among the measured dark room capacitance and the photoreaction capacitance;
Further comprising:
The second capacitance model is
A method for extracting state density in a bandgap of an amorphous oxide semiconductor thin film transistor comprising an accumulation capacitance [C acc ] formed by an accumulation region. In the band gap state density extraction apparatus of an amorphous oxide semiconductor thin film transistor,
A measuring unit measuring a dark room capacitance according to a gate voltage of the thin film transistor in a dark room, and measuring a photoreaction capacitance of the thin film transistor by irradiating a light source having a predetermined wavelength to the thin film transistor;
An application unit applying a predetermined capacitance model to a region below a flat-band voltage of the thin film transistor; And
An extraction unit for extracting a donor state density in a band gap based on the capacitance of the region below the flat voltage and the capacitance model among the measured dark room capacitance and the photoreaction capacitance;
State density extraction apparatus in a band gap of the amorphous oxide semiconductor thin film transistor comprising a. The method of claim 5,
The capacitance model is
A depletion capacitance formed by a depletion region and an active capacitance formed by an active region, and further comprising a photoreaction donor capacitance formed by irradiation of the light source connected in parallel with the depletion capacitance,
The extracting unit
And extracting donor state density in the bandgap based on the capacitance in the region below the flat voltage, the photoreaction donor capacitance, and the capacitance model.
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