JP2014027286A - Semiconductor thin film and manufacturing method of the same, and thin film transistor and active-matrix-driven display panel - Google Patents

Semiconductor thin film and manufacturing method of the same, and thin film transistor and active-matrix-driven display panel Download PDF

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JP2014027286A
JP2014027286A JP2013174461A JP2013174461A JP2014027286A JP 2014027286 A JP2014027286 A JP 2014027286A JP 2013174461 A JP2013174461 A JP 2013174461A JP 2013174461 A JP2013174461 A JP 2013174461A JP 2014027286 A JP2014027286 A JP 2014027286A
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indium
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JP5678149B2 (en
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Kiminori Yano
公規 矢野
Kazuyoshi Inoue
一吉 井上
Nobuo Tanaka
信夫 田中
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Idemitsu Kosan Co Ltd
出光興産株式会社
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Abstract

A semiconductor thin film that can be manufactured at a relatively low temperature and can be formed on a flexible resin substrate, is stable to visible light, and has high element characteristics such as transistor characteristics. Provided is a semiconductor thin film which, when used as a driving switching element, does not lower the luminance of a display panel even if it overlaps with a pixel portion.
In a radial distribution function obtained by X-ray scattering measurement, a carrier density is 10 +17 cm −3 or less, a hole mobility is 2 cm 2 / V · sec or more, an energy band gap is 2.4 EV or more. When the maximum value of RDF with an interatomic distance of 0.3 to 0.36 nm is A and the maximum value of RDF with an interatomic distance of 0.36 to 0.42 nm is B, A / B> After forming an amorphous film containing zinc oxide and indium oxide so as to satisfy the relationship of 0.8, the transparent semiconductor thin film 40 is formed by oxidation treatment.
[Selection] Figure 1

Description

  The present invention relates to a semiconductor thin film composed of an amorphous film containing zinc oxide and indium oxide, a manufacturing method thereof, a thin film transistor using such a semiconductor thin film, and an active matrix drive display panel to which such a thin film transistor is applied. About.

Field effect transistors are widely used as unit electronic elements, high frequency signal amplifying elements, liquid crystal driving elements and the like of semiconductor memory integrated circuits, and are the most widely used electronic devices at present.
Among them, with the remarkable development of display devices in recent years, not only liquid crystal display devices (LCD) but also various display devices such as electroluminescence display devices (EL) and field emission displays (FED) are used as display elements. Thin film transistors (TFTs) are frequently used as switching elements that drive a display device by applying a driving voltage.
In addition, silicon semiconductor compounds are most widely used as the material. Generally, silicon single crystals are used for high-frequency amplifying elements and integrated circuit elements that require high-speed operation. Amorphous silicon is used because of the demand for large area.

  However, a crystalline silicon-based thin film needs a high temperature of, for example, 800 ° C. or higher when crystallizing, and is difficult to construct on a glass substrate or an organic substrate. For this reason, there is a problem that it can be formed only on an expensive substrate having high heat resistance such as a silicon wafer or quartz, and a lot of energy and the number of steps are required for manufacturing.

On the other hand, an amorphous silicon semiconductor (amorphous silicon) that can be formed at a relatively low temperature has a lower switching speed than a crystalline one, so that when used as a switching element for driving a display device, a high-speed moving image The display may not be followed.
Furthermore, when visible light is irradiated to the semiconductor active layer, the semiconductor device exhibits electrical conductivity, and there is a problem that characteristics as a switching element are deteriorated, such as leakage current being generated and malfunction. Therefore, a method of providing a light shielding layer that blocks visible light is known. For example, a metal thin film is used as the light shielding layer.
However, providing a light shielding layer made of a metal thin film not only increases the number of processes, but also has a floating potential, so the light shielding layer needs to be at the ground level, and in such a case, parasitic capacitance is generated. is there.
In addition, since the transmittance of visible light is low, if the semiconductor layer protrudes from the electrode part, the transmittance of the display part is lowered, the illumination efficiency by the backlight may be reduced, and the screen may be darkened. It contributed to the cost increase.

Currently, as a switching element for driving a display device, an element using a silicon-based semiconductor film occupies the mainstream, but it has a high switching speed in addition to the stability and workability of the silicon thin film. This is because various performances are good. Such silicon-based thin films are generally manufactured by a chemical vapor deposition (CVD) method.
A conventional thin film transistor (TFT) has a gate electrode, a gate insulating layer, a semiconductor layer such as hydrogenated amorphous silicon (a-Si: H), a source and a drain electrode on a substrate such as glass. There is a stacked inverted staggered structure, which is used as a drive element for flat panel displays such as active matrix liquid crystal displays in the field of large area devices including image sensors. In these applications, even those using amorphous silicon have been required to operate at higher speeds with higher functionality.

Under such circumstances, in recent years, a transparent semiconductor thin film made of a metal oxide such as zinc oxide, particularly a transparent made of a zinc oxide crystal, is more stable than a silicon-based semiconductor thin film (amorphous silicon). Semiconductor thin films are attracting attention.
For example, Patent Document 1 and Patent Document 2 describe a method of forming a thin film transistor by crystallizing zinc oxide at a high temperature.

JP 2003-86808 A JP 2004-273614 A

  However, a semiconductor thin film using zinc oxide has a problem that the hole mobility is lowered unless precise crystallization control is performed, so that the field effect mobility is lowered and the switching speed is lowered. In order to increase the crystallinity, it was necessary to form a film on a special substrate having high crystallinity as in the case of the silicon-based thin film, or to perform a treatment at a high temperature of 500 ° C. or higher. Therefore, it is difficult to carry out uniformly over a large area, particularly on a glass substrate, and it has been difficult to put it to practical use in a liquid crystal panel.

  The present invention has been made in view of the above circumstances, is a semiconductor thin film that can be produced at a relatively low temperature and can be formed on a flexible resin substrate, is stable to visible light, and Device characteristics such as transistor characteristics are high, and when used as a switching element for driving a display device, a semiconductor thin film that does not decrease the luminance of the display panel even when overlapped with a pixel portion, and a method for manufacturing such a semiconductor thin film, A thin film transistor using such a semiconductor thin film, having high field effect mobility and high on-off ratio, and lessened the influence of irradiation light such as generation of leakage current, and improved device characteristics, and such thin film transistor An object of the present invention is to provide an active matrix drive display panel to which is applied.

A semiconductor thin film according to the present invention that solves the above problems is a semiconductor thin film made of an amorphous film containing zinc oxide and indium oxide, and has a carrier density of 10 +17 cm −3 or less and a hole mobility of 2 cm 2 / V · sec or more, energy band gap is 2.4 eV or more, and the maximum value of RDF between the atomic distances of 0.3 to 0.36 nm in the radial distribution function (RDF) obtained by X-ray scattering measurement Is A, and the maximum RDF value between the interatomic distances of 0.36 to 0.42 nm is B, the relationship of A / B> 0.8 is satisfied.

By adopting such a configuration, the semiconductor thin film according to the present invention is easy to produce a semiconductor thin film in a wide temperature range, and easily develops uniform physical properties in a large area. Therefore, it is suitable for applications such as a display panel. It becomes.
In the semiconductor thin film according to the present invention, when the carrier density is larger than 10 +17 cm −3 , when an element such as the thin film transistor 1 is formed, a leakage current is generated and the element is normally on. If the -off ratio becomes small, good transistor performance may not be exhibited.
Further, when the hole mobility is smaller than 2 cm 2 / Vs, the field effect mobility of the thin film transistor 1 becomes small, and when used as a switching element for driving the display element, the switching speed is low as in the case of amorphous silicon. May not be able to follow the display of high-speed video.
On the other hand, if the energy band gap is smaller than 2.4 eV, when visible light is irradiated, electrons in the valence band are excited to show conductivity, and a leakage current may easily occur.
Further, the ratio (A / B) is presumed that the indium-oxygen-indium bond form represents the ratio of the ridge sharing and the apex sharing, or the maintenance ratio of the short-range order. If it is 8 or less, the hole mobility and the field effect mobility may be lowered.

  In addition, the semiconductor thin film according to the present invention can form a uniform amorphous film over a large area, and in order to avoid non-uniform film quality, zinc in the amorphous film The atomic ratio of [Zn] to indium [In] is preferably Zn / (Zn + In) = 0.10 to 0.82, and the atomic ratio of zinc Zn to indium In in the amorphous film is Zn More preferably, /(Zn+In)=0.51 to 0.80.

  In addition, the semiconductor thin film according to the present invention preferably has a transmittance of 75% or more at a wavelength of 550 nm. By doing so, even if the semiconductor thin film protrudes from the pixel electrode portion, it is possible to transmit light. It is possible to effectively avoid problems such as a decrease in rate and brightness and a change in color tone.

  The semiconductor thin film according to the present invention is preferably a non-degenerate semiconductor thin film having a work function of 3.5 to 6.5 eV. By setting the work function within the above range, it is possible to effectively avoid deterioration in characteristics of the transistor due to leakage current, energy barrier, or the like. Furthermore, there is a possibility that the carrier concentration cannot be stably controlled at a low concentration if it is a degenerate semiconductor, but such a problem can be effectively avoided by making the semiconductor thin film according to the present invention a non-degenerate semiconductor thin film. it can. Here, the non-degenerate semiconductor thin film refers to a semiconductor thin film in which the carrier concentration varies depending on the temperature, and the temperature dependence of the carrier concentration can be obtained from hole measurement.

  Further, in the semiconductor thin film according to the present invention, it is preferable that nanocrystals are dispersed in an amorphous film. When nanocrystals are dispersed in an amorphous film, the hole mobility is improved and the field effect is improved. This is preferable because mobility may be increased and transistor characteristics may be improved.

  In addition, the semiconductor thin film according to the present invention may contain a third metal element [M] other than indium oxide and zinc oxide and a compound thereof as long as the effects of the present invention are not impaired. The atomic ratio [M / (M + In)] of the third metal element [M] and indium [In] is preferably 0 to 0.5, and the third metal element [M] and indium [In] The atomic ratio [M / (M + In)] is more preferably 0 to 0.3.

In addition, the method for producing a semiconductor thin film according to the present invention provides for the production of a semiconductor thin film as described above under the condition that the partial pressure of water H 2 O in the atmospheric gas is 10 −3 Pa or less. A method for forming an amorphous film containing indium can be employed.

  By adopting such a method, it is possible to effectively avoid the problem that the hole mobility may be lowered.

The method for producing a semiconductor thin film according to the present invention preferably includes a step of oxidizing the amorphous film formed physically at a substrate temperature of 200 ° C. or lower, and the substrate temperature is higher than 200 ° C. Even if the oxidation treatment is performed, there is a possibility that the carrier concentration does not decrease, or that a deformation or dimensional change is caused when a resin substrate is used.
In addition, it is preferable to subject the semiconductor thin film formed in the above range to heat treatment in the presence of oxygen or oxidation treatment such as ozone treatment in order to stabilize the carrier density.
When the heat treatment is performed, it is preferable that the temperature of the film surface during the heat treatment is 100 to 270 ° C. higher than the substrate temperature during the film formation. If this temperature difference is smaller than 100 ° C., there is no heat treatment effect, and if it is higher than 270 ° C., the substrate may be deformed, or the semiconductor thin film interface may be altered to deteriorate the semiconductor characteristics. In order to avoid such problems more effectively, it is more preferable that the temperature of the film surface during heat treatment is 130 to 240 ° C. higher than the substrate temperature during film formation, and it is particularly preferable that the temperature is 160 to 210 ° C. higher.

  In addition, the thin film transistor according to the present invention can be configured to have the semiconductor thin film as described above, and the semiconductor thin film can be configured to be provided on a resin substrate.

  In addition, the active matrix drive display panel according to the present invention can be configured to include the thin film transistor as described above.

  As described above, according to the present invention, an excellent electric field effect that can be formed on a glass substrate or a resin substrate in a wide temperature range, is stable against visible light, hardly causes a malfunction, and has a small leakage current. The semiconductor thin film which comprises a type transistor can be provided. Further, since the semiconductor thin film of the present invention can be formed at a relatively low temperature, it can be formed over a resin substrate to provide a flexible thin film transistor or the like.

Hereinafter, preferred embodiments of the present invention will be described.
FIG. 1 is an explanatory diagram showing an outline of an embodiment of a thin film transistor according to the present invention.

  In the illustrated example, a thin film transistor 1 as a field effect transistor includes a drain electrode 10 and a source electrode 20 which are formed on a substrate 60 so as to be separated from each other, and is in contact with at least a part of each of the drain electrode 10 and the source electrode 20. Thus, the transparent semiconductor thin film 40 is formed, and the gate insulating film 50 and the gate electrode 30 are formed on the transparent semiconductor thin film 40 in this order, and the top gate type thin film transistor 1 is configured.

  In the present embodiment, as the substrate 60, a resin substrate made of polyethylene terephthalate (PET), polycarbonate (PC), or the like can be used in addition to a glass substrate.

Moreover, there is no restriction | limiting in particular in the material which forms each electrode of the gate electrode 30, the source electrode 20, and the drain electrode 10, What is generally used in the range which does not lose the effect of this embodiment is selected arbitrarily. Can do. For example, a transparent electrode such as ITO, IZO, ZnO, or SnO2, a metal electrode such as Al, Ag, Cr, Ni, Mo, Au, Ti, or Ta, or a metal electrode of an alloy including these can be used.
Although not particularly illustrated, each of the gate electrode 30, the source electrode 20, and the drain electrode 10 may have a multilayer structure in which two or more different conductive layers are stacked.

The material for forming the gate insulating film 50 is not particularly limited. What is generally used can be arbitrarily selected as long as the effects of the invention of the present embodiment are not lost. For example, SiO 2, SiNx, Al 2 O 3, Ta 2 O 5, TiO 2, MgO, ZrO 2, CeO 2, K 2 O, Li 2 O, Na 2 O, Rb 2 O, Sc 2 O 3, Y Oxides such as 2 O 3 , Hf 2 O 3 , and CaHfO 3 can be used. Among these, SiO 2, SiNx, Al 2 O 3, Y 2 O 3, Hf 2 O 3, it is preferable to use CaHfO 3, more preferably SiO 2, SiNx, Y 2 O 3, Hf 2 O 3 , CaHfO 3 , particularly preferably SiO 2 , SiNx.
Such a gate insulating film 50 may have a structure in which two or more different insulating films are stacked. The gate insulating film 50 may be crystalline or amorphous, but is preferably amorphous that is easy to manufacture industrially.

In the present embodiment, the transparent semiconductor thin film 40 is made of an amorphous material containing zinc oxide and indium oxide, has a carrier density determined by hole measurement of 10 +17 cm −3 or less, a hole mobility of 2 cm 2 / Vs or more, The energy band gap between the conduction band and the valence band is formed to be 2.4 eV or more.
Such an amorphous film containing zinc oxide and indium oxide is easy to produce in a wide temperature range, and it becomes easy to express uniform physical properties in a large area by using an amorphous film. In particular, it is preferable for use in an active matrix drive display panel.
In addition, it can confirm that it is an amorphous film | membrane by a clear peak not appearing by X-ray diffraction.

Here, when the carrier density is higher than 10 +17 cm −3 , when an element such as the thin film transistor 1 is configured, a leakage current is generated, and the device is normally on, or the on-off ratio is small. As a result, good transistor performance may not be exhibited. In order to avoid such problems more effectively, the carrier density is preferably 10 +16 cm -3 or less, more preferably 10 +15 cm -3 or less, and 10 +14 cm -3 or less. Is particularly preferred.

Further, when the hole mobility is smaller than 2 cm 2 / Vs, the field effect mobility of the thin film transistor 1 becomes small, and when used as a switching element for driving the display element, the switching speed is low as in the case of amorphous silicon. May not be able to follow the display of high-speed video. In order to avoid such a defect more effectively, the hole mobility is preferably 5 cm 2 / Vs or more, more preferably 8 cm 2 / Vs or more, further preferably 11 cm 2 / Vs or more, and 14 cm. 2 / Vs or more is particularly preferable.

Thus, by forming the transparent semiconductor thin film 40 with a carrier density of 10 +17 cm −3 or less and a hole mobility of 2 cm 2 / Vs or more, the on-off ratio is high as well as the field-effect mobility. It is possible to obtain a new and excellent field effect transistor capable of increasing the area in place of the conventional field effect transistor using amorphous silicon, which shows mari-off and has a clear pinch-off.

  On the other hand, if the energy band gap is smaller than 2.4 eV, when visible light is irradiated, electrons in the valence band are excited to show conductivity, and a leakage current may easily occur. In order to avoid such problems more effectively, the energy band gap is preferably 2.6 eV or more, more preferably 2.8 eV or more, still more preferably 3.0 ev or more, and particularly preferably 3.2 eV or more. .

The specific resistance of the transparent semiconductor thin film 40 is usually 10 −1 to 10 +8 Ωcm, preferably 10 −1 to 10 +8 Ωcm, and more preferably 10 0 to 10 +6 Ωcm. It is more preferably +1 to 10 +4 Ωcm, and particularly preferably 10 +2 to 10 +3 Ωcm.

Furthermore, by containing indium oxide in the transparent semiconductor thin film 40, high hole mobility is realized, oxygen partial pressure in the atmospheric gas during film formation, water H 2 O or hydrogen H 2 in the atmospheric gas. The hole mobility can be controlled by controlling the content of.

It is effective to contain zinc oxide together with indium oxide. During crystallization, carrier traps are generated by substituting with positive trivalent indium sites, and the carrier density is lowered without significantly reducing hole mobility. It is estimated that
By adding zinc, which is a positive divalent element, to indium, which is a positive trivalent element, the carrier concentration is reduced, and as described later, the hole mobility is reduced by performing an oxidation treatment after film formation. It is also possible to control the carrier concentration without causing it.

The atomic ratio [Zn / (Zn + In)] of indium [In] and zinc [Zn] contained in the semiconductor thin film 50 can be set to 0.10 to 0.82.
If the atomic ratio [Zn / (Zn + In)] is less than 0.10 and the zinc content is low, crystallization is facilitated, and a uniform amorphous film over a large area can be obtained unless appropriate manufacturing conditions are selected. There is a risk of not being able to.
On the other hand, if the atomic ratio [Zn / (Zn + In)] is larger than 0.82 and the zinc content is excessive, chemical resistance is reduced, or crystals of zinc oxide are generated and the film quality becomes uneven. There is a risk of
In the present embodiment, in order to more effectively avoid the above problems, the atomic ratio [Zn / (Zn + In)] is preferably 0.51 to 0.80, more preferably 0.55. It is -0.80 and 0.6-0.75 is especially preferable.

  The transparent semiconductor thin film 40 preferably has a transmittance of 75% or more at a wavelength of 550 nm. If the transmittance at a wavelength of 550 nm is smaller than 75%, the transmittance may be reduced when the semiconductor thin film protrudes from the pixel electrode portion, and the luminance may be lowered or the color tone may be changed. In order to avoid such problems more effectively, the transmittance at a wavelength of 550 nm is preferably 80% or more, and particularly preferably 85% or more.

  The transparent semiconductor thin film 40 preferably has a work function of 3.5 to 6.5 eV. If the work function is less than 3.5 eV, the transistor characteristics may be deteriorated, for example, the injection of a valence at the interface with the gate insulating film and the occurrence of a leakage current. On the other hand, when the voltage is larger than 6.5 eV, an energy barrier or the like is generated at the interface with the gate insulating film, and the transistor characteristics may be deteriorated, for example, the pinch-off characteristic is deteriorated. In order to avoid such a defect more effectively, the work function is preferably 3.8 to 6.2 eV, more preferably 4.0 to 6.0 eV, still more preferably 4.3 to 5.7 eV, 4.5 to 5.5 eV is particularly preferable.

The transparent semiconductor thin film 40 is preferably a non-degenerate semiconductor thin film. If it is a degenerate semiconductor, the carrier concentration may not be stably controlled at a low concentration.
Here, the non-degenerate semiconductor thin film is a semiconductor thin film in which the carrier concentration changes depending on the temperature, whereas the degenerate semiconductor thin film shows a constant value in which the carrier concentration does not depend on the temperature. A semiconductor thin film. The temperature dependence of the carrier concentration can be obtained from Hall measurement.

The transparent semiconductor thin film 40 preferably has nanocrystals dispersed in an amorphous film. It is preferable that nanocrystals are dispersed in the amorphous film because hole mobility is improved, field effect mobility is increased, and transistor characteristics may be improved.
The presence of nanocrystals can be confirmed by observing with TEM.

Here, the transparent semiconductor thin film 40 may contain a third metal element other than indium oxide and zinc oxide or a compound thereof as long as the effects of the present embodiment are not impaired.
However, in this case, the atomic ratio [M / (M + In)] of indium [In] and the third metal element [M] is set to 0 to 0.5. If the atomic ratio [M / (M + In)] exceeds 0.5, the hole mobility may be reduced. This is presumed to be because the number of bonds between main elements decreases and percolation conduction becomes difficult.
In order to avoid such a defect more effectively, the atomic ratio [M / (M + In)] is preferably 0 to 0.3.

The transparent semiconductor thin film 40 has a maximum RDF value between A and 0.36 nm in the radial distribution function (RDF) determined by X-ray scattering measurement, and the interatomic distance is 0. When the maximum value of RDF between .36 and 0.42 nm is B, the relationship of A / B> 0.8 is satisfied.
This ratio (A / B) is presumed that the indium-oxygen-indium bond form represents the ratio of the ridge share and the apex share, or the short-range order maintenance ratio, and this ratio (A / B) If B) is 0.8 or less, the hole mobility and the field effect mobility may be lowered.
In order to avoid such a problem more effectively, the ratio (A / B) preferably satisfies A / B> 0.9, more preferably A / B> 1.0. A / B> 1.1 is most preferable, and a large ratio (A / B) is presumed that the short-range indium-indium short-range order is maintained. For this reason, an electron movement route is secured, and improvement in hole mobility and field effect mobility is expected.

  In the present embodiment, as a film forming method for forming the transparent semiconductor thin film 40, a physical film forming method can be used in addition to a chemical film forming method such as a spray method, a dip method, and a CVD method. From the viewpoint of easy control of carrier density and improvement of film quality, a physical film forming method is preferred.

Examples of the physical film forming method include a sputtering method, a vacuum deposition method, an ion plating method, a pulse laser deposition method, and the like. Industrially, a sputtering method with high mass productivity is preferable.
Examples of the sputtering method include a DC sputtering method, an RF sputtering method, an AC sputtering method, an ECR sputtering method, and a counter target sputtering method. Among these, the DC sputtering method and the AC sputtering method are preferable because they are industrially high in mass productivity and can easily lower the carrier concentration than the RF sputtering method. Moreover, in order to suppress the deterioration of the interface due to the film formation, to suppress the leakage current, and to improve the characteristics of the transparent semiconductor thin film 40 such as the on-off ratio, the ECR sputtering method in which the film quality can be easily controlled, The facing target sputtering method is preferable.

When the sputtering method is used, a sintered target containing indium oxide and zinc oxide may be used, or co-sputtering may be performed using a sintered target containing indium oxide and a sintered target containing zinc oxide. Alternatively, reactive sputtering may be performed while introducing a gas such as oxygen using a metal target made of indium or zinc, or an alloy target.
In view of reproducibility and uniformity over a large area, it is preferable to use a sintered target containing indium oxide and a positive divalent oxide.

When using the sputtering method, the partial pressure of water H 2 O contained in the atmospheric gas is set to 10 −3 Pa or less. When the partial pressure of water H 2 O is larger than 10 −3 Pa, the hole mobility may be lowered. It is presumed that this is because hydrogen bonds to indium or oxygen having a bixbite structure to share the apex of the edge sharing portion of the oxygen-indium bond. In order to avoid such a problem more effectively, the partial pressure of H 2 O is preferably 8 × 10 −4 Pa or less, more preferably 6 × 10 −4 Pa or less, and further preferably 4 × 10 − 4 Pa or less, and 2 × 10 −4 Pa or less is particularly preferable.

Further, the hydrogen H 2 partial pressure in the atmospheric gas is usually preferably 10 −2 Pa or less, 5 × 10 −3 Pa or less, more preferably 10 −3 Pa or less, further preferably 5 × 10 −4 Pa or less, 2 × 10 −4 Pa or less is particularly preferable. When H 2 is present in the atmospheric gas, not only the carrier concentration increases, but also the hole mobility may decrease.

In addition, the oxygen O 2 partial pressure in the atmospheric gas is usually 40 × 10 −3 Pa or less. If the oxygen partial pressure in the atmospheric gas is higher than 40 × 10 −3 Pa, the hole mobility may be lowered, or the hole mobility and the carrier concentration may be unstable. This is presumably because if the amount of oxygen in the atmospheric gas during film formation is too large, oxygen taken in between the crystal lattices increases, causing scattering, or easily leaving the film and destabilizing.
To avoid such an inconvenience more effectively, the oxygen partial pressure in the atmospheric gas is preferably 15 × 10 -3 Pa or less, and more preferably not more than 7 × 10 -3 Pa, 1 × 10 - It is particularly preferably 3 Pa or less.

The ultimate vacuum is usually 10 −5 Pa or less. Ultimate vacuum, and greater than 10 -5 Pa, the partial pressure of water H 2 O is increased, the partial pressure of water H 2 O there may not be a 10 -3 Pa or less. In order to avoid such a problem more effectively, the ultimate pressure is preferably 5 × 10 −6 Pa or less, and particularly preferably 10 −6 Pa or less.

  When a large area is formed by sputtering, it is preferable to take a method such as rotating the folder to which the substrate is fixed or moving a magnet to widen the erosion range in order to have uniformity in film quality.

In such a film forming process, a physical film is usually formed at a substrate temperature of 200 ° C. or less, and after the film forming process is finished, an oxidation treatment is performed on a thin film containing indium oxide and zinc oxide. The carrier concentration in the transparent semiconductor thin film 40 can be controlled.
Here, if the substrate temperature is higher than 200 ° C. at the time of film formation, the carrier concentration may not be lowered even if the oxidation treatment is performed, or deformation or dimensional change may occur when a resin substrate is used. In order to avoid such problems more effectively, the substrate temperature is preferably 180 ° C. or lower, more preferably 150 ° C. or lower, still more preferably 120 ° C. or lower, and particularly preferably 90 ° C. or lower.

In this embodiment, after completing such a film forming process, the carrier concentration in the transparent semiconductor thin film 40 can be controlled by performing an oxidation process on the thin film containing indium oxide and zinc oxide. it can.
Although there is a method of controlling the carrier concentration by controlling the concentration of a gas component such as oxygen at the time of film formation, such a method may reduce the hole mobility. This is presumed that the gas component introduced for carrier control is taken into the film and becomes a scattering factor.

As the oxidation treatment, heat treatment is usually performed in the presence of oxygen under conditions of 80 to 650 ° C. and 0.5 to 12000 minutes.
If the temperature of the heat treatment is lower than 80 ° C., the treatment effect may not be exhibited or it may take too much time, and if it is higher than 650 ° C., the substrate may be deformed. In order to avoid such a defect more effectively, the treatment temperature is preferably 120 to 500 ° C, more preferably 150 to 450 ° C, still more preferably 180 to 350 ° C, and particularly preferably 200 to 300 ° C.
Also, if the heat treatment time is shorter than 0.5 minutes, there is a risk that the time for heating to the inside will be insufficient and the treatment may be insufficient. If it is longer than 12000 minutes, the treatment apparatus becomes large and cannot be used industrially. There is a risk of damage or deformation of the substrate. In order to avoid such problems more effectively, the treatment time is preferably 1 to 600 minutes, more preferably 5 to 360 minutes, still more preferably 15 to 240 minutes, and particularly preferably 30 to 120 minutes.

  In addition, as the oxidation treatment, heat treatment can be performed by a lamp annealing device (LA), a rapid thermal annealing device (RTA) or a laser annealing device in the presence of oxygen. It can also be applied.

  Hereinafter, the present invention will be described in more detail with reference to specific examples.

[Example 1]
(1) Production and evaluation of sputtering target Production of target As raw materials, indium oxide having an average particle diameter of 3.4 μm and zinc oxide having an average particle diameter of 0.6 μm have an atomic ratio [In / (In + Zn)] of 0.28 and an atomic ratio [Zn / (In + Zn)] was mixed to 0.72, and this was supplied to a wet ball mill, and mixed and ground for 72 hours to obtain a raw material fine powder.
After granulating the obtained raw material fine powder, it is press-molded to a size of 10 cm in diameter and 5 mm in thickness, placed in a firing furnace, and fired under conditions of 1,400 ° C. and 48 hours under pressurized oxygen gas. Thus, a sintered body (target) was obtained. At this time, the rate of temperature increase was 3 ° C./min.
2. Evaluation of target The density and bulk resistance value of the obtained target were measured. As a result, the theoretical relative density was 99%, and the bulk resistance value measured by the four probe method was 0.8 mΩ.

(2) Film formation of transparent semiconductor thin film The sputtering target obtained in the above (1) is mounted on a DC magnetron sputtering film forming apparatus, which is one of DC sputtering methods, and is transparent on a glass substrate (Corning 1737). A conductive film was formed.
As sputtering conditions here, substrate temperature: 25 ° C., ultimate pressure: 1 × 10 −3 Pa, atmospheric gas: Ar 100%, sputtering pressure (total pressure); 4 × 10 −1 Pa, input power 100 W, film formation The time was 20 minutes.
As a result, a transparent conductive glass in which a transparent conductive oxide having a film thickness of about 100 nm was formed on the glass substrate was obtained.
When the obtained film composition was analyzed by the ICP method, the atomic ratio [In / (In + Zn)] was 0.28, and the atomic ratio [Zn / (In + Zn)] was 0.72.

(3) Oxidation treatment of transparent semiconductor thin film The transparent semiconductor thin film obtained in (2) above was heated in the atmosphere (in the presence of oxygen) at 150 ° C. for 100 hours (thermal treatment in the atmosphere) to carry out the oxidation treatment.

(4) Evaluation of physical properties of transparent semiconductor thin film The carrier concentration and hole mobility of the transparent semiconductor thin film obtained in the above (3) were measured with a hole measuring device. The carrier concentration was 8 × 10 15 cm −3 and the hole mobility was 16 cm 2 / Vs. The specific resistance value measured by the four probe method was 48 Ωcm.
It was confirmed by X-ray diffraction that the film was an amorphous film.

The Hall measuring device and the measurement conditions were as follows.
[Hall measuring device]
Toyo Technica: Resi Test8310
[Measurement condition]
Room temperature (25 ° C), 0.5 [T], AC magnetic field Hall measurement

  Furthermore, regarding the transparency of this transparent conductive oxide, the light transmittance for light having a wavelength of 550 nm was 85% by a spectrophotometer, and the transparency was also excellent. The energy band gap was sufficiently large as 3.3 eV.

[Examples 2-7, Comparative Examples 1-4]
Production evaluation was performed in the same manner as in Example 1 except that the composition ratio of the raw materials, the film formation conditions, and the oxidation treatment conditions were adjusted as shown in Table 1.

  Moreover, about the semiconductor thin film of an Example and a comparative example, the thin film transistor was manufactured as follows and the evaluation was performed.

[Top gate type transparent thin film transistor]
On the PET substrate, except for the film formation time, a 30 nm transparent semiconductor thin film prepared under the same conditions as in Examples 1 to 7 and Comparative Examples 1 to 4 was used, and the channel length L = A top-gate thin film transistor having a thickness of 10 μm and a channel W = 150 μm was formed.
At this time, yttrium oxide having a high dielectric constant was used as a gate insulating film with a thickness of 170 nm. In addition, IZO having a thickness of 150 nm was used as each of the gate electrode, the source electrode, and the drain electrode.

The obtained thin film transistor was evaluated according to the following criteria. The results are shown in Table 1 together with the on-off ratio.
[Evaluation criteria]
Good: Hysteresis of IV characteristics is small even after repeating the operation 10 times or more.
Slightly good: When the operation is repeated 10 times or more, large hysteresis occurs in the IV characteristic.
Defect: Large hysteresis occurs in the IV characteristics when the operation is repeated less than 10 times.

  Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. Nor.

  For example, in the above-described embodiment, an example of a thin film transistor has been described. However, the semiconductor thin film according to the present invention can be applied to various field effect transistors.

  The semiconductor thin film in the present invention can be widely used as a semiconductor thin film used for a field effect transistor such as a thin film transistor.

It is explanatory drawing which shows the outline of embodiment of the thin-film transistor which concerns on this invention.

1 Thin film transistor 40 Transparent semiconductor thin film

Claims (13)

  1. A semiconductor thin film made of an amorphous film containing zinc oxide and indium oxide,
    The carrier density is 10 +17 cm −3 or less, the hole mobility is 2 cm 2 / V · sec or more, and the energy band gap is 2.4 eV or more,
    In the radial distribution function (RDF) obtained by X-ray scattering measurement, the maximum value of RDF between the atomic distances of 0.3 to 0.36 nm is A, and the interatomic distance is between 0.36 to 0.42 nm. A semiconductor thin film characterized by satisfying the relationship of A / B> 0.8, where B is the maximum value of RDF.
  2.   2. The semiconductor thin film according to claim 1, wherein an atomic ratio of zinc [Zn] and indium [In] in the amorphous film is Zn / (Zn + In) = 0.10 to 0.82.
  3.   2. The semiconductor thin film according to claim 1, wherein an atomic ratio of zinc Zn and indium In in the amorphous film is Zn / (Zn + In) = 0.51 to 0.80.
  4.   The semiconductor thin film according to any one of claims 1 to 3, wherein a transmittance at a wavelength of 550 nm is 75% or more.
  5.   5. The semiconductor thin film according to claim 1, wherein the semiconductor thin film has a work function of 3.5 to 6.5 eV.
  6.   The semiconductor thin film according to claim 1, wherein nanocrystals are dispersed in the amorphous film.
  7.   A third metal element [M] is contained, and an atomic ratio [M / (M + In)] of the third metal element [M] and indium [In] is 0 to 0.5. The semiconductor thin film of any one of Claims 1-6.
  8.   A third metal element [M] is contained, and an atomic ratio [M / (M + In)] of the third metal element [M] and indium [In] is 0 to 0.3. The transparent oxide semiconductor thin film of any one of Claims 1-6.
  9. In manufacturing the semiconductor thin film according to any one of claims 1 to 8,
    A method for producing a semiconductor thin film, comprising forming an amorphous film containing zinc oxide and indium oxide under a condition that a partial pressure of water H 2 O in an atmospheric gas is 10 −3 Pa or less.
  10.   9. The method of manufacturing a semiconductor thin film according to claim 8, comprising a step of oxidizing the amorphous film physically formed at a substrate temperature of 200 [deg.] C. or less.
  11.   A thin film transistor comprising the semiconductor thin film according to claim 1.
  12.   The thin film transistor according to claim 11, wherein the semiconductor thin film is provided on a resin substrate.
  13.   An active matrix drive display panel comprising the thin film transistor according to claim 11.
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JP2000228516A (en) * 1999-02-08 2000-08-15 Hiroshi Kawazoe Semiconductor laminated thin film, electronic device and diode
WO2004038757A2 (en) * 2002-05-21 2004-05-06 The State Of Oregon Acting By And Through The State Board Of Higher Education On Behalf Of Oregon State University Transistor structures and methods for making the same
JP2004235180A (en) * 2003-01-28 2004-08-19 Sanyo Electric Co Ltd Semiconductor device and its manufacturing method
WO2005088726A1 (en) * 2004-03-12 2005-09-22 Japan Science And Technology Agency Amorphous oxide and thin film transistor
WO2005093850A1 (en) * 2004-03-12 2005-10-06 Hewlett-Packard Development Company, L.P. Semiconductor device having channel comprising multicomponent metal oxide
JP5376750B2 (en) * 2005-11-18 2013-12-25 出光興産株式会社 Semiconductor thin film, manufacturing method thereof, thin film transistor, active matrix drive display panel

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000228516A (en) * 1999-02-08 2000-08-15 Hiroshi Kawazoe Semiconductor laminated thin film, electronic device and diode
WO2004038757A2 (en) * 2002-05-21 2004-05-06 The State Of Oregon Acting By And Through The State Board Of Higher Education On Behalf Of Oregon State University Transistor structures and methods for making the same
JP2006502597A (en) * 2002-05-21 2006-01-19 ザ・ステート・オブ・オレゴン・アクティング・バイ・アンド・スルー・ザ・ステート・ボード・オブ・ハイヤー・エデュケーション・オン・ビハーフ・オブ・オレゴン・ステート・ユニバーシティ Transistor structure and manufacturing method thereof
JP2004235180A (en) * 2003-01-28 2004-08-19 Sanyo Electric Co Ltd Semiconductor device and its manufacturing method
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WO2005093850A1 (en) * 2004-03-12 2005-10-06 Hewlett-Packard Development Company, L.P. Semiconductor device having channel comprising multicomponent metal oxide
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JP5376750B2 (en) * 2005-11-18 2013-12-25 出光興産株式会社 Semiconductor thin film, manufacturing method thereof, thin film transistor, active matrix drive display panel

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