JP6149725B2 - Semiconductor device and manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.

  2. Description of the Related Art In recent years, semiconductor devices such as thin film transistors that are formed by forming electrodes such as a source, a drain, and a gate and a semiconductor layer over an insulating substrate have attracted attention (for example, Patent Document 1). Such a semiconductor device can be applied to various electronic devices such as an electro-optical device, for example.

JP 2007-123861 A

  In the semiconductor device as described above, further reduction in contact resistance between the source electrode and the semiconductor layer and between the drain electrode and the semiconductor layer is required for further enhancement in performance and functionality.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a semiconductor device that has higher performance and higher functionality than conventional ones. Another object of the present invention is to provide a method for manufacturing such a semiconductor device.

In the present invention, a semiconductor device having a source electrode, a drain electrode, a gate electrode and a semiconductor layer,
Provided is a semiconductor device comprising an amorphous oxide electride thin film containing calcium atoms and aluminum atoms between one or both of the source electrode and the drain electrode and the semiconductor layer. .

  Here, in the semiconductor device according to the present invention, in the electride thin film, the molar ratio (Ca / Al) of aluminum atoms to calcium atoms may be in the range of 0.3 to 5.0.

In the semiconductor device according to the present invention, the electride thin film may have an electron density of 2.0 × 10 ¹⁷ cm ⁻³ or more.

  In the semiconductor device according to the present invention, the thickness of the electride thin film may be 100 nm or less.

  In the semiconductor device according to the present invention, the semiconductor layer may include an oxide semiconductor or an organic semiconductor.

In the semiconductor device according to the present invention, the semiconductor layer may be disposed between the source electrode and the gate electrode, or the semiconductor layer may be disposed on a side farther from the gate electrode than the source electrode. .

Furthermore, in the present invention, a method of manufacturing a semiconductor device having a source electrode, a drain electrode, a gate electrode, and a semiconductor layer,
(1) forming a thin film of an amorphous oxide electride containing calcium atoms and aluminum atoms between one or both of the source electrode and the drain electrode and the semiconductor layer; A method of manufacturing a semiconductor device is provided.

Here, the manufacturing method according to the present invention further includes:
(A) forming a semiconductor layer on the substrate;
(B) forming a source electrode and a drain electrode;
(C) forming a gate electrode;
Have
The step (1) may be performed between the step (a) and the step (b).

The manufacturing method according to the present invention further includes:
(A) forming a source electrode and a drain electrode on a substrate;
(B) forming a semiconductor layer;
(C) forming a gate electrode;
Have
The step (1) may be performed between the step (a) and the step (b).

The manufacturing method according to the present invention further includes:
(A) forming a gate electrode on the substrate;
(B) forming a semiconductor layer;
(C) forming a source electrode and a drain electrode;
Have
The step (1) may be performed between the step (b) and the step (c).

The manufacturing method according to the present invention further includes:
(A) forming a gate electrode on the substrate;
(B) forming a source electrode and a drain electrode;
(C) forming a semiconductor layer;
Have
The step (1) may be performed between the step (b) and the step (c).

  In the production method according to the present invention, the molar ratio (Ca / Al) of aluminum atoms to calcium atoms in the electride thin film may be in the range of 0.3 to 5.0.

In the manufacturing method according to the present invention, the electride thin film may have an electron density of 2.0 × 10 ¹⁷ cm ⁻³ or more.

  In the manufacturing method according to the present invention, the thickness of the electride thin film may be 100 nm or less.

  In the manufacturing method according to the present invention, the semiconductor layer may include an oxide semiconductor or an organic semiconductor.

  In this application, “amorphous oxide electride containing calcium atom and aluminum atom” is also simply referred to as “amorphous oxide electride”, and “amorphous oxidation containing calcium atom and aluminum atom”. The “electride thin film” is also simply referred to as “electride thin film”.

  According to the present invention, it is possible to provide a semiconductor device with higher performance and higher functionality than in the past. The present invention can also provide a method for manufacturing such a semiconductor device.

It is sectional drawing which showed the structure of the conventional semiconductor device roughly. It is the schematic diagram which showed the conceptual structure of the electride of an amorphous oxide. 1 is a cross-sectional view schematically showing a configuration of a semiconductor device according to an embodiment of the present invention. It is sectional drawing which showed typically an example of the semiconductor device by this invention comprised by the top gate structure-bottom contact system. It is sectional drawing which showed typically an example of the semiconductor device by this invention comprised by the bottom gate structure-top contact system. It is sectional drawing which showed typically an example of the semiconductor device by this invention comprised by the bottom gate structure-bottom contact system. It is the figure which showed typically an example of the flow at the time of manufacturing the semiconductor device by one Example of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  First, in order to better understand the features of the present invention, the configuration of a conventional semiconductor device will be briefly described with reference to FIG.

  FIG. 1 shows a schematic cross section of a conventional semiconductor device.

  As shown in FIG. 1, the conventional semiconductor device 1 includes a substrate 10, a semiconductor layer 5, a source electrode 20, a drain electrode 22, and a gate electrode 24.

  The semiconductor layer 5 is disposed on the substrate 10, and the source electrode 20 and the drain electrode 22 are disposed on the semiconductor layer 5. A gate electrode 24 is disposed on the source electrode 20 and the drain electrode 22 with a gate insulating layer 30 interposed therebetween. Usually, as the semiconductor layer 5, a layer made of an oxide semiconductor, a layer made of an organic compound semiconductor, or the like is used.

  Such a semiconductor device 1 can be used for, for example, an electro-optical device such as a liquid crystal panel or electronic paper, a light-emitting display device, and the like.

  Here, in the conventional semiconductor device 1, reduction of contact resistance at the interface between the source electrode 20 and the semiconductor layer 5 and at the interface between the drain electrode 11 and the semiconductor layer 5 is required for higher performance and higher functionality. ing. This is because if the contact resistance at this interface increases, the operating characteristics of the semiconductor device 1 deteriorate.

  In general, when the semiconductor layer 5 is an N-type semiconductor, it is effective to use an ohmic junction when suppressing contact resistance at the interface between the metal source electrode 20 / drain electrode 22 and the semiconductor layer 5. is there. The ohmic junction means a state in which a metal and a semiconductor are bonded so that a space charge layer is not formed on the semiconductor layer side, and in this case, no rectification occurs at the metal / semiconductor interface (that is, electrons are not Flows in both directions).

  However, in order to develop such an ohmic junction at the interface between the metal source electrode 20 / drain electrode 22 and the semiconductor layer 5, the work function of the source electrode 20 / drain electrode 22 is set to the work function of the semiconductor layer 5. It needs to be smaller than the function. However, there are usually not many metal materials having such a work function. In addition, a metal having a low work function is active and highly reactive, and a reaction layer is easily formed with other components. Therefore, it is difficult to directly bond a metal having a low work function and a semiconductor layer. For this reason, such a problem causes a problem that the material of the source electrode 20 / drain electrode 22 is largely limited.

  On the other hand, when the work function of the metal source electrode 20 / drain electrode 22 is larger than that of the semiconductor layer 5, a Schottky barrier is formed at the metal / semiconductor interface. In this case, it can be considered that the space charge layer generated on the semiconductor side is made as thin as possible and the contact resistance is suppressed by the tunnel effect. However, in order to make the space charge layer thin, it is necessary to remarkably increase the carrier density in the semiconductor layer. Therefore, this method may not be a realistic countermeasure.

In contrast, in the present invention, a semiconductor device having a source electrode, a drain electrode, a gate electrode, and a semiconductor layer,
Provided is a semiconductor device comprising an amorphous oxide electride thin film containing calcium atoms and aluminum atoms between one or both of the source electrode and the drain electrode and the semiconductor layer. .

  The semiconductor device according to the present invention is characterized in that a thin film of an amorphous oxide electride containing calcium atoms and aluminum atoms is disposed between one or both of the source electrode and the drain electrode and the semiconductor layer. Have

Here, the amorphous oxide electride thin film containing calcium atoms and aluminum atoms has semiconducting electrical characteristics and a relatively low work function. For example, the work function of this thin film is in the range of 2.4 eV to 4.5 eV (eg, 2.8 eV to 3.2 eV). Further, this thin film has a feature of high electron density. The electron density of the thin film is, for example, in the range of 2.0 × 10 ¹⁷ cm ^{−3 to} 2.3 × 10 ²¹ cm ⁻³ .

  In the semiconductor device according to the present invention, the presence of such a thin film can significantly reduce the contact resistance between one or both of the source electrode and the drain electrode and the semiconductor layer. Therefore, the present invention can provide a semiconductor device having higher operating characteristics than conventional ones.

  The present invention is more effective when the semiconductor layer is an N-type semiconductor. This is particularly effective when the work function of the source electrode and the work function of the drain electrode are larger than the work function of the semiconductor layer.

  As described above, in the case of an N-type semiconductor, an ohmic junction can be expressed by lowering the work functions of the source electrode and the drain electrode than the semiconductor layer. However, a metal having a low work function is active and highly reactive, and easily forms a reaction layer with other components, so that it is difficult to develop an ohmic junction. Although the electride thin film according to the present invention has a low work function, it has a high chemical durability and a higher carrier density (electron density). Therefore, an ohmic junction can be developed between the semiconductor layer (N-type semiconductor) and the electride thin film, and a tunnel effect can be developed between the source electrode and the drain electrode (metal). As a result, the contact resistance between one or both of the source electrode and the drain electrode and the semiconductor layer can be significantly reduced, and a high-performance semiconductor device can be provided as compared with the related art.

  The work function of the electride thin film is preferably smaller than the work function of the semiconductor layer. The difference between the work function of the semiconductor layer and the work function of the electride thin film is preferably greater than 0 to 3.0 eV, more preferably 0.1 to 2.5 eV, and even more preferably 0.5 to 2.0 eV. By having such a work function difference, an ohmic junction can be easily developed, and the contact resistance can be significantly reduced.

  The present invention is more effective when the semiconductor layer is an oxide semiconductor, and particularly effective when the semiconductor layer is an N-type oxide semiconductor. For example, a layer made of IGZO (In—Ga—Zn—O) which is an example of an oxide semiconductor is used as the semiconductor layer. The work function of the layer made of IGZO is 4.3 eV to 4.5 eV. When aluminum (Al) is applied as the source and drain electrodes, the work function of the source and drain electrodes made of Al is 4.1 eV. In this case, when one or both of the source electrode and the drain electrode and the semiconductor layer are directly bonded, a reaction layer is generated and the ohmic junction is hardly developed. In contrast, in the present invention, an amorphous oxide electride thin film containing calcium atoms and aluminum atoms is disposed between one or both of the source electrode and the drain electrode and the semiconductor layer. The work function of this electride thin film is in the range of 2.4 eV to 4.5 eV, for example, can be in the range of 2.8 eV to 3.2 eV, which is sufficient compared to the work function of the layer made of IGZO. Can be lowered. Moreover, since this electride thin film is chemically stable, it is difficult to form a reaction layer. In addition, at the interface between the source electrode and drain electrode (metal) and the thin film of electride, the electron resistance of the thin film of electride is high, so that the contact resistance is reduced by the tunnel effect. For this reason, it becomes easy to develop an ohmic junction, and the contact resistance between one or both of the source electrode and the drain electrode and the semiconductor layer can be reduced. As a result, a semiconductor device with higher performance than before can be provided.

The present invention is more effective when the semiconductor layer is an organic semiconductor, and is particularly effective when the semiconductor layer is used as an N-type organic semiconductor. A layer made of an organic semiconductor generally has a carrier density as low as 10 ¹⁰ cm ⁻¹ to less than 10 ¹⁷ cm ⁻¹ and is likely to generate contact resistance with a metal source electrode and drain electrode. In the layer made of organic semiconductor, the carrier type is known to be affected by the relative relationship between the HOMO and LUMO of the layer made of organic semiconductor and the work function of the source electrode and the drain electrode. In the difference in work function between the electrode and the drain electrode, or in the difference between the LUMO of the organic semiconductor layer and the work function between the source electrode and the drain electrode, the P type is used when the former is smaller than the latter, and the N type when the former is larger than the latter. Tend to be. Since the electride thin film has a low work function, electrons can be injected into the layer made of an organic semiconductor. That is, a layer made of an organic semiconductor can be used as an N type.

  For example, a layer made of C60 fullerene, which is an example of an organic semiconductor, is used as the semiconductor layer. The work function of C60 fullerene is 4.6 eV. When gold (Au) is applied as the source and drain electrodes, the work function of the source and drain electrodes made of Au is 5.0 eV. In this case, when the semiconductor layer is directly bonded to both or one of the source electrode and the drain electrode, the work function of the source electrode and the drain electrode is large, so that an ohmic junction is hardly exhibited. In contrast, in the present invention, an amorphous oxide electride thin film containing calcium atoms and aluminum atoms is disposed between one or both of the source electrode and the drain electrode and the semiconductor layer. The work function of this electride thin film is in the range of 2.4 eV to 4.5 eV, for example, in the range of 2.8 eV to 3.2 eV, compared with the work function of the layer made of C60 fullerene. It can be made sufficiently low. Moreover, since this electride thin film is chemically stable, it is difficult to form a reaction layer. In addition, at the interface between the source electrode and drain electrode (metal) and the thin film of electride, the electron resistance of the thin film of electride is high, so that the contact resistance is reduced by the tunnel effect. For this reason, it becomes easy to develop an ohmic junction, and the contact resistance between one or both of the source electrode and the drain electrode and the semiconductor layer can be reduced. As a result, a semiconductor device with higher performance than before can be provided.

  Further, when the difference between the electron affinity and work function in the thin film of electride is ΔF, and the difference between the electron affinity and work function in the semiconductor layer is ΔB, the difference between ΔF and ΔB is preferably close to zero. For example, the absolute value of the difference between ΔF and ΔB is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0. By reducing the absolute value of the difference between ΔF and ΔB as much as possible, when the semiconductor layer and the electride thin film are joined, the energy levels at the bottoms of the respective conduction bands are aligned, so the semiconductor layer and the electride thin film The contact resistance between the two can be reduced. An example in which a layer made of IGZO, which is an example of an oxide semiconductor, is applied as the semiconductor layer will be described. When the electride thin film has an electron affinity of 2.5 eV and a work function of 3.0 eV, ΔF is 0.5 eV. When the layer made of IGZO has an electron affinity of 4.2 eV and a work function of 4.3 eV to 4.5 eV, ΔB is 0.1 eV to 0.3 eV. The difference between ΔF and ΔB is 0.4 or less, and a very low contact resistance can be achieved. By reducing the contact resistance between the semiconductor layer and the thin film of electride, the contact resistance between one or both of the source electrode and the drain electrode and the semiconductor layer can be reduced. As a result, a semiconductor device with higher performance than before can be provided.

  The thin film of electride may have a high ionization potential. The ionization potential of the electride thin film may be 7.0 eV to 9.0 eV, or 7.5 eV to 8.5 eV.

  When the semiconductor layer is an organic semiconductor, the ionization potential of the thin film of electride is preferably larger than the ionization potential of the layer made of the organic semiconductor. The difference in ionization potential between the electride thin film and the organic semiconductor layer may be 1.1 eV to 3.5 eV, 1.3 eV to 3.3 eV, or 1.6 eV to 3.0 eV. It may be.

  Further, it is more preferable that the difference between the ionization potential of the electride thin film and the work function is larger than the difference between the ionization potential and the work function of the layer made of the organic semiconductor. For example, ΔE is the difference (IP−WF) between the ionization potential (IP) and work function (WF) of the electride thin film. A difference between an ionization potential (IP) and a work function (WF) of a layer made of an organic semiconductor is represented by ΔA. The difference (ΔE−ΔA) between the two is preferably 1.3 eV to 5.8 eV, more preferably 2.0 eV to 5.0 eV, and particularly preferably 2.5 eV to 4.5 eV.

  For example, when the semiconductor device of the present invention is a thin film field effect transistor, holes are conducted to the source electrode when the transistor is turned off (when the gate voltage is 0 or a negative voltage is applied as the gate voltage), and the off current (Leakage current) may occur. In particular, when an organic semiconductor is applied as the semiconductor layer, an off-current problem is likely to occur. The occurrence of off-current may cause an increase in power consumption.

  However, as described above, the electride thin film has a high ionization potential, and the ionization potential is sufficiently large for a layer made of an organic semiconductor, and in particular, the difference between the ionization potential and the work function for a layer made of an organic semiconductor. When is sufficiently large, an excellent hole blocking effect can be obtained. This is because the difference (ΔE−ΔA) between the ionization potential of the thin film of electride (ΔE) and the difference between the ionization potential of the organic semiconductor layer and the work function (ΔA) is the energy in hole conduction. It becomes a barrier. By having a sufficiently high energy barrier, hole conduction can be blocked and off current can be suppressed.

(Term definition)
Here, terms relating to "a thin film of an amorphous oxide electride containing calcium atoms and aluminum atoms" included in the semiconductor device according to the present invention will be described.

(Amorphous oxide electride)
In this application, “an electride of an amorphous oxide containing calcium atoms and aluminum atoms”, that is, “an electride of an amorphous oxide” refers to an amorphous composed of calcium atoms, aluminum atoms, and oxygen atoms. It means an amorphous solid substance composed of a solvate having a solvent and electrons as a solute. Electrons in the amorphous oxide act as anions. The electrons may exist as bipolarons.

  FIG. 2 conceptually shows the structure of the amorphous oxide electride.

  As shown in FIG. 2, the amorphous oxide electride 70 has a characteristic partial structure called a bipolaron 74 in an amorphous solvent 72 composed of calcium atoms, aluminum atoms and oxygen atoms. Exist in a distributed state. The bipolarron 74 is configured such that two cages 76 are adjacent to each other, and each cage 76 includes an electron (solute) 78. However, the state of the amorphous oxide is not limited to the above, and two electrons (solutes) 78 may be included in one cage 76. Further, a plurality of these cages may be aggregated, and the aggregated cage can be regarded as a microcrystal. Therefore, a state in which the microcrystal is included in the amorphous is also regarded as amorphous in the present invention.

In the present invention, the amorphous oxide electride is Sr, Mg, Ba, Si, Ge, Ga, in addition to calcium atom, aluminum atom, and oxygen atom within the range in which the cage structure of bipolaron is maintained. One or more atoms selected from the group consisting of In and B may be included. Also, one or more atoms selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, one or more atoms selected from the group consisting of Li, Na, and K, or Ce , Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and one or more atoms selected from the group consisting of Yb may be included.
In the present invention, the amorphous oxide electride may be a compound in which two electrons included in two cages are replaced with other anions. Other anions include, for example, one or more selected from the group consisting of H ⁻ , H ₂ ⁻ , H ²⁻ , O ⁻ , O ₂ ⁻ , OH ⁻ , F ⁻ , Cl ⁻ , and S ²⁻ . Anions may be mentioned.

  In addition, the amorphous oxide electride exhibits semiconducting electrical characteristics and has a low work function. The work function may be 2.4 eV to 4.5 eV, and is preferably 2.8 eV to 3.2 eV. An amorphous oxide electride has a high ionization potential. The ionization potential may be 7.0 eV to 9.0 eV, or 7.5 eV to 8.5 eV.

(Electride thin film)
Bipolaron has almost no light absorption in the visible light range where the photon energy is 1.55 eV to 3.10 eV, and shows light absorption in the vicinity of 4.6 eV. Therefore, the electride thin film according to the present invention is transparent in visible light. Further, by measuring the light absorption characteristics of the thin film sample and measuring the light absorption coefficient in the vicinity of 4.6 eV, whether or not bipolaron is present in the thin film sample, that is, the thin film sample is an amorphous oxide electride. Can be confirmed.

  In the present invention, the molar ratio (Ca / Al) of aluminum atoms to calcium atoms in the electride thin film is preferably in the range of 0.3 to 5.0. When it is 0.3 or more, a high electron density can be maintained. Moreover, it is excellent in the durability of a thin film as it is 5.0 or less. A range of 0.5 to 1.6 is more preferable, and a range of 0.55 to 1.00 is particularly preferable. The composition analysis of the thin film can be performed by XPS method, EPMA method, EDX method or the like. Analysis by the XPS method is possible when the film thickness is 100 nm or less, EPMA method when the film thickness is 50 nm or more, and EDX method when it is 3 μm or more.

In the electride thin film of the present invention, when X-ray diffraction is measured, no peak is observed and only a halo is observed. In the present invention, the electride thin film may contain microcrystals. Whether or not microcrystals are contained in the thin film is determined from, for example, a cross-sectional TEM (transmission electron microscope) photograph of the thin film. The composition in the crystalline state is represented by 12CaO · 7Al ₂ O ₃ , CaO · Al ₂ O ₃ , 3CaO · Al ₂ O _{3 and the} like.

In the present invention, in the electride thin film, the light absorption value at the position of 4.6 eV may be 100 cm ⁻¹ or more, 200 cm ⁻¹ or more, or 1000 cm ⁻¹ or more. is good, may be at 5000 cm ^-1 or more may also be 8000 cm ^-1 or more, it may be 10000 cm ^-1 or higher. In the electride thin film, the absorption value at a position of 4.6 eV can be accurately measured by using a thin film having a thickness of 50 nm or more, preferably a thin film having a thickness of 100 nm or more.

In the present invention, the electride thin film preferably contains electrons in an electron density range of 2.0 × 10 ¹⁷ cm ⁻³ or more and 2.3 × 10 ²¹ cm ⁻³ or less. The electron density is more preferably 1.0 × 10 ¹⁸ cm ⁻³ or more, further preferably 1 × 10 ¹⁹ cm ⁻³ or more, and particularly preferably 1 × 10 ²⁰ cm ⁻³ or more.

  The electron density of the electride thin film can be measured by an iodometric titration method. Incidentally, the density of bipolarons in the electride thin film can be calculated by multiplying the measured electron density by 1/2.

In this iodine titration method, a sample of an electride thin film is immersed in a 5 mol / l iodine aqueous solution and dissolved by adding hydrochloric acid. This is a method for titration detection. In this case, due to dissolution of the sample, iodine in the aqueous iodine solution is ionized by the following reaction:

I ₂ + e ⁻ → 2I ⁻ (1) Formula

When titrating an aqueous iodine solution with sodium thiosulfate,

2Na ₂ S ₂ O ₃ + I ₂ → 2NaI + Na ₂ S ₄ O ₆ (2) Formula

By this reaction, unreacted iodine is changed to sodium iodide. By subtracting the amount of iodine detected by titration from equation (2) from the amount of iodine present in the initial solution, the amount of iodine consumed in the reaction of equation (1) is calculated. Thereby, the electron density in the sample of a thin film of electride can be measured. The iodine titration method can be applied regardless of whether the electride thin film is crystalline or amorphous.

  In the present invention, the thickness of the electride thin film is not limited to this, but may be, for example, 100 nm or less, preferably 10 nm or less, and more preferably 5 nm or less. It may be 0.5 nm or more.

The thin film of electride has conductivity due to hopping conduction of electrons in the cage. The direct current conductivity at room temperature of the electride thin film according to the present invention may be 10 ⁻¹¹ S · cm ⁻¹ to 10 ⁻¹ S · cm ⁻¹ , or 10 ⁻⁷ S · cm ^−1. -10 <^-3> S * cm ^<-1 > may be sufficient.

In addition to the bipolaron 74, the electride thin film may have an F ⁺ center in which one electron is captured in an oxygen vacancy as a partial structure. The F ⁺ center is configured by a plurality of Ca ²⁺ ions surrounded by one electron and does not have a cage. The F ⁺ center has light absorption in the visible light range of 1.55 eV to 3.10 eV centered on 3.3 eV.

Since the transparency of a thin film increases that the density | concentration of F ⁺ center is less than 5 * 10 < ¹⁸ > cm < ^-3 >, it is preferable. The concentration of the F ⁺ center is more preferably 1 × 10 ¹⁸ cm ⁻³ or less, and further preferably 1 × 10 ¹⁷ cm ⁻³ or less. Note that the concentration of the F ⁺ center can be measured by a signal intensity having a g value of 1.998 in ESR.

  In the electride thin film, the ratio of the light absorption coefficient at a position of 3.3 eV to the light absorption coefficient at a photon energy position of 4.6 eV may be 0.35 or less, more preferably 0.25 or less. 0.15 or less is more preferable.

  Since the electride thin film does not have a crystal grain boundary as compared with the polycrystalline thin film, it is excellent in flatness. The root mean square roughness (RMS) of the surface of the electride thin film according to the present invention may be 0.1 nm to 10 nm, or may be 0.2 nm to 5 nm. It is more preferable that the RMS is 2 nm or less because the characteristics of the device are improved. Further, if the RMS is 10 nm or more, the characteristics of the element may be deteriorated, so that a polishing step or the like needs to be added. The RMS can be measured using, for example, an atomic force microscope.

The composition of the electride thin film may be different from the stoichiometric ratio of 12CaO · 7Al ₂ O ₃ , or may be different from the composition ratio of the target used in the production.

(About a semiconductor device according to an embodiment of the present invention)
Next, a semiconductor device according to an embodiment of the present invention will be described with reference to FIG. FIG. 3 schematically shows a cross section of a semiconductor device (first semiconductor device) 100 according to an embodiment of the present invention.

  As illustrated in FIG. 3, the first semiconductor device 100 includes a substrate 110, a semiconductor layer 105, a source electrode 120, a drain electrode 122, and a gate electrode 124.

  The semiconductor layer 105 is disposed on the substrate 110, and the source electrode 120 and the drain electrode 122 are disposed on the semiconductor layer 105. A gate electrode 124 is disposed on the source electrode 120 and the drain electrode 122 with a gate insulating layer 130 interposed therebetween.

  Here, the first semiconductor device 100 includes an amorphous oxide electride containing calcium atoms and aluminum atoms between the source electrode 120 and the semiconductor layer 105 and / or between the drain electrode 122 and the semiconductor layer 105. The thin film (electride thin film) 150 is arranged.

  For example, in the example of FIG. 3, the first electride thin film 150 a is disposed between the source electrode 120 and the semiconductor layer 105, and the second electride thin film 150 b is disposed between the drain electrode 122 and the semiconductor layer 105. Is arranged.

  As described above, the electride thin films 150a and 150b are characterized by a small work function and a high electron density.

  Therefore, when the first electride thin film 150 a is disposed between the source electrode 120 and the semiconductor layer 105, the contact resistance at the interface between the source electrode 120 and the semiconductor layer 105 can be significantly suppressed. It is done. Similarly, when the second electride thin film 150 b is disposed between the drain electrode 122 and the semiconductor layer 105, the contact resistance at the interface between the drain electrode 122 and the semiconductor layer 105 can be significantly suppressed.

  Therefore, the first semiconductor device 100 can exhibit significantly higher operating characteristics than the conventional one.

(Constituent members of semiconductor device 100)
Next, each member constituting the semiconductor device 100 will be briefly described.

(Substrate 110)
The material of the substrate 110 is not particularly limited. The substrate 110 may be an insulating substrate such as a glass substrate, a ceramic substrate, a plastic substrate, and a resin substrate.

  Or the board | substrate 110 is a semiconductor substrate and a metal substrate, and the insulating layer may be formed in the surface.

(Semiconductor layer 105)
The material of the semiconductor layer 105 is not particularly limited. The semiconductor layer 105 may be made of a general semiconductor material such as an oxide semiconductor and an organic semiconductor.

Examples of the oxide semiconductor include oxides of transition metals such as In, Ti, Nb, Sn, Zn, Gd, Cd, Zr, Y, La, and Ta, SrTiO ₃ , CaTiO ₃ , ZnO · Rh ₂ O _3. , CuGaO ₂ , and oxides such as SrCu ₂ O ₂ .

  For example, the oxide semiconductor may include at least one oxide of In, Sn, Zn, Ga, and Cd. The oxide semiconductor preferably contains at least one oxide of In, Sn, Zn, and Ga, and includes an oxide containing at least one of In, Ga, and Zn (for example, an In—O-based oxide). ) Is more preferable.

  For example, the oxide semiconductor may include at least two of In, Ga, and Zn, for example, all oxides.

  Examples of such an oxide semiconductor include IGZO (In—Ga—Zn—O), ITO (In—Sn—O), ISZO (In—Si—Zn—O), IGO (In—Ga—O), ITZO (In—Sn—Zn—O), IZO (In—Zn—O), IHZO (In—Hf—Zn—O), and the like. A film formed using such an oxide semiconductor may be amorphous, crystalline, or in a state containing amorphous and crystalline.

  On the other hand, examples of organic semiconductors include polycyclic aromatic compounds, conjugated double bond compounds, macrocyclic compounds, metal phthalocyanine complexes, charge transfer complexes, condensed ring tetracarboxylic acid diimides, oligothiophenes, fullerenes, and carbon nanotubes. , Etc. For example, polypyrrole, polythiophene, poly (3-alkylthiophene), polythienylene vinylene, poly (p-phenylene vinylene), polyaniline, polydiacetylene, polyazulene, polypyrene, polycarbazole, polyselenophene, polyfuran, poly (p-phenylene) , Polyindole, polybilidazine, naphthacene, tetracene, pentacene, hexacene, heptacene, pyrene, chrysene, perylene, coronene, terylene, ovalene, quaterylene, triphenodioxazine, triphenodiliadine, hexacene-6,15-quinone, polyvinylcarbazole, polyphenylene Sulfide, polyvinylene sulfide, polyvinyl pyridine, naphthalene tetracarboxylic acid diimide, anthracene tetracarboxylic acid diimide, C6 , C70, C76, C78, C84, and can be used derivatives thereof. Specific examples thereof include pentacene, tetracene, α-sexithiophene (6T), copper phthalocyanine, bis (1,2,5-thiadiazolo) -p-quinobis (1), which are generally P-type semiconductors. , 3-dithiol), rubrene, poly (2,5-thienylenevinylene) (abbreviation: PTV), poly (3-hexylthiophene-2,5-diyl) (abbreviation: P3HT), (poly [(9,9 -Dioctylfluorenyl-2,7-diyl) -co-bithiophene]) (abbreviation: F8T2). In addition, 7,7,8,8, -tetracyanoquinodimethane (abbreviation: TCNQ) perylene-3,4,9,10-tetracarboxylic dianhydride (abbreviation: PTCDA), which is generally an N-type semiconductor, 1,4,5,8-naphthalenetetracarboxylic dianhydride (abbreviation: NTCDA), N, N′-dioctyl-3,4,9,10-perylenetetracarboxylic acid diimide (abbreviation: PTCDI-C8H), copper (II) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-Foxadecafluoro-29H, 31H-phthalocyanine (abbreviation: F16CuPc) 3 ′, 4′-dibutyl-5,5 ″ -bis (dicyanomethylene) -5,5 ″ -dihydro-2,2 ′: 5 ′, 2 ″ -terthiophene) (abbreviation: DCMT), etc. There is. Note that the P-type and N-type characteristics of an organic semiconductor are not unique to the substance, but depend on the relationship with the electrode into which carriers are injected and the strength of the electric field at the time of injection.

(Source electrode 120, drain electrode 122)
The material of the source electrode 120 and the drain electrode 122 is not particularly limited as long as it has conductivity. The source electrode 120 and the drain electrode 122 may be made of metal, for example.
The source electrode 120 and the drain electrode 122 may be an alloy containing at least one element selected from Al, Ag, Au, Cr, Cu, Ta, Ti, Mo, and W, for example. The source electrode 120 and the drain electrode 122 are made of, for example, ITO, antimony oxide (Sb ₂ O ₃ ), zirconium oxide (ZrO ₂ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), or IZO (Indium Zinc). Oxide), AZO (ZnO—Al ₂ O ₃ : zinc oxide doped with aluminum), GZO (ZnO—Ga ₂ O ₃ : zinc oxide doped with gallium), Nb-doped TiO ₂ , Ta-doped TiO ₂ , And IWZO (In ₂ O ₃ —WO ₃ —ZnO: indium oxide doped with tungsten trioxide and zinc oxide). Further, the source electrode 120 and the drain electrode 122 may be transparent electrodes using a metal that is thin enough to transmit visible light.

  When the semiconductor layer 105 is composed of an organic semiconductor, the source electrode 120 and the drain electrode 122 are formed of metals such as platinum, gold, aluminum, chromium, nickel, cobalt, copper, titanium, magnesium, calcium, barium, and sodium, and the like. You may comprise with the alloy containing.

  The semiconductor layer 105 may have a work function of 3.5 to 7.0 eV, and is preferably 4.0 to 5.0 eV.

The semiconductor layer 105 may have a carrier density of less than 10 ¹¹ to 10 ¹⁷ cm ⁻³ , and preferably 10 ¹⁴ to 10 ¹⁶ cm ⁻³ .

(Gate electrode 124)
The material of the gate electrode 124 is not particularly limited as long as it has conductivity.

The gate electrode 124 is, for example, an element selected from Al, Ag, Au, Cr, Cu, Ta, Ti, Mo, and W, or a metal or alloy containing these elements as a component, or an alloy that combines the above-described elements. Etc. The gate electrode 124 is made of, for example, ITO, antimony oxide (Sb ₂ O ₃ ), zirconium oxide (ZrO ₂ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), IZO (Indium Zinc Oxide), or AZO. (ZnO—Al ₂ O ₃ : zinc oxide doped with aluminum), GZO (ZnO—Ga ₂ O ₃ : zinc oxide doped with gallium), Nb-doped TiO ₂ , Ta-doped TiO ₂ , and IWZO ( In ₂ O ₃ —WO ₃ —ZnO: indium oxide doped with tungsten trioxide and zinc oxide) may be used. Alternatively, the gate electrode 124 may be a transparent electrode using a metal thin enough to transmit visible light.

  The gate insulating layer 130 may be made of an inorganic insulating material such as silicon oxide, silicon nitride, silicon oxide containing nitrogen and silicon nitride containing oxygen, or an organic insulating material such as acrylic or polyimide.

  Alternatively, the gate insulating layer 130 has a skeleton structure formed of a bond of silicon and oxygen, and has an organic group (for example, an alkyl group or an aryl group) containing at least hydrogen as a substituent and a fluoro group, a so-called siloxane-based material. It may be constituted by.

  The gate insulating layer 130 may be a single layer or may be composed of two or more layers.

(About the structure of semiconductor devices)
The first semiconductor device 100 shown in FIG. 3 has a so-called top gate structure-top contact method. However, the arrangement structure of each member constituting the semiconductor device is not limited to this.

  Here, for example, (i) top gate structure-top contact system, (ii) top gate structure-bottom contact system, (iii) bottom gate structure-top contact system, and (Iii) There exists a bottom gate structure-bottom contact method and the like.

  Hereinafter, these arrangement structures will be briefly described.

  FIG. 3 described above shows an example of the semiconductor device 100 configured by the top gate structure-top contact method.

  As shown in FIG. 3, in the semiconductor device 100, the gate electrode 124 is disposed on the semiconductor layer 105 (top gate structure), and the source electrode 120 and the drain electrode 122 are also disposed on the semiconductor layer 105. (Top contact method). Note that in the semiconductor device 100, the semiconductor layer 105 may be a channel etch type or a channel protection type.

  Next, FIG. 4 shows an example of a semiconductor device configured by a top gate structure-bottom contact method.

  As shown in FIG. 4, the semiconductor device 400 includes a semiconductor layer 405 formed on a substrate 410, a source electrode 420 and a drain electrode 422, a gate insulating layer 430, and a gate electrode 424.

  In this example, the gate electrode 424 is disposed on the semiconductor layer 405 (top gate structure). On the other hand, the source electrode 420 and the drain electrode 422 are disposed below the semiconductor layer 405 (bottom contact method).

  In the example of the semiconductor device 400 shown in FIG. 4, the first electride thin film 450 a is disposed between the source electrode 420 and the semiconductor layer 405, and the first electride thin film 450 a is disposed between the drain electrode 422 and the semiconductor layer 405. An electride thin film 450b is disposed. However, one of the first electride thin film 450a and the second electride thin film 450b may be omitted.

  Next, FIG. 5 shows an example of a semiconductor element configured by a bottom gate structure-top contact method.

  As shown in FIG. 5, the semiconductor device 500 includes a semiconductor layer 505, a source electrode 520 and a drain electrode 522, a gate insulating layer 530, and a gate electrode 524 over a substrate 510.

  In this example, the gate electrode 524 is disposed below the semiconductor layer 505 (bottom gate structure). On the other hand, the source electrode 520 and the drain electrode 522 are disposed above the semiconductor layer 505 (top contact method). Note that in the semiconductor device 500, the semiconductor layer 505 may be a channel etch type or a channel protection type.

  In the example of the semiconductor device 500 shown in FIG. 5, the first electride thin film 550 a is disposed between the source electrode 520 and the semiconductor layer 505, and the first electrode thin film 550 a is disposed between the drain electrode 522 and the semiconductor layer 505. 2 electride thin film 550b is disposed. However, one of the first electride thin film 550a and the second electride thin film 550b may be omitted.

  Next, FIG. 6 shows an example of a semiconductor element configured by a bottom gate structure-bottom contact method.

  As illustrated in FIG. 6, the semiconductor device 600 includes a semiconductor layer 605, a source electrode 620 and a drain electrode 622, a gate insulating layer 630, and a gate electrode 624 over a substrate 610.

  In this example, the gate electrode 624 is disposed below the semiconductor layer 605 (bottom gate structure). On the other hand, the source electrode 620 and the drain electrode 622 are also disposed below the semiconductor layer 605 (bottom contact method).

  In the example of the semiconductor device 600 illustrated in FIG. 6, a first electride thin film 650 a is disposed between the source electrode 620 and the semiconductor layer 605, and the second electrode 622 and the semiconductor layer 605 are disposed between the second electrode 622 and the semiconductor layer 605. An electride thin film 650b is disposed. However, one of the first electride thin film 650a and the second electride thin film 650b may be omitted.

  Thus, various aspects exist in the structure of a semiconductor device. The semiconductor device in the present invention may be configured in any of these modes. In any of these configurations, the semiconductor device according to the present invention has an effect that the contact resistance can be significantly suppressed at the interface between the source electrode and the semiconductor layer and / or the interface between the drain electrode and the semiconductor layer. It will be clear.

  In the present invention, the type of the semiconductor device is not particularly limited. The semiconductor device may be a field effect transistor such as a thin film transistor as shown in FIGS.

  In the case of using an organic semiconductor as the semiconductor layer, a bottom contact structure is preferable. The deterioration of the organic semiconductor due to the manufacturing process can be further prevented.

(About the manufacturing method of the semiconductor device by this invention)
Next, an example of a manufacturing method of the first semiconductor device 100 shown in FIG. 3 will be described with reference to FIG.

FIG. 7 schematically shows an example of a flow for manufacturing the first semiconductor device. As shown in FIG.
Forming a semiconductor layer on the substrate (step S110);
Forming a thin film of an amorphous oxide electride containing calcium atoms and aluminum atoms (step S120);
Forming a source electrode and a drain electrode (step S130);
Forming a gate electrode (step S140);
Have

  Hereinafter, each step will be described. In the following description, for the sake of clarity, the reference numerals shown in FIG. 3 are used for the respective members.

(Step S110)
First, the semiconductor layer 105 is formed over the substrate 110.

  The method for forming the semiconductor layer 105 is not particularly limited, and the semiconductor layer 105 may be formed on the substrate 110 by a conventionally performed method.

  In the case where the semiconductor layer 105 is an oxide semiconductor, the semiconductor layer 105 is formed over the substrate 110 by a general sputtering method or the like. In the case where the semiconductor layer 105 is an organic semiconductor, the semiconductor layer 105 is formed over the substrate 110 by an evaporation method, a spin coating method, a droplet discharge method, or the like.

  The formed semiconductor layer 105 is patterned into a desired pattern. For example, the semiconductor layer 105 can be patterned into a desired pattern by performing photolithography or the like. In the case of an organic semiconductor, the pattern of the semiconductor layer 105 can be directly formed by a droplet discharge method or the like.

(Step S120)
Next, an electride thin film is formed on the semiconductor layer 105. This thin film of electride later becomes the thin film 150a of the first electride and / or the thin film 150b of the second electride.

As an example, as a method of forming a thin film of electride,
A step of preparing a target of crystalline C12A7 electride having an electron density of 2.0 × 10 ¹⁷ cm ^{−3 to} 2.3 × 10 ²¹ cm ⁻³ (S121);
A step of forming a film on the semiconductor layer by a vapor deposition method in an atmosphere having an oxygen partial pressure of less than 0.1 Pa using the target (S122);
A film forming method having the above will be described.

(Step S121)
First, a deposition target used in the subsequent step S120 is prepared.

  The target is composed of crystalline C12A7 electride.

(Crystalline C12A7)
In the present application, “crystalline C12A7” means a crystal of 12CaO · 7Al ₂ O ₃ and an isomorphous compound having a crystal structure equivalent to this. The mineral name of this compound is “mayenite”.

The crystalline C12A7 in the present invention is a compound in which some or all of Ca atoms and / or Al atoms in the C12A7 crystal skeleton are substituted with other atoms within a range in which the cage structure formed by the skeleton of the crystal lattice is maintained. In addition, the same type compound may be used in which some or all of the free oxygen ions in the cage are replaced with other anions. Incidentally, C12A7 _is sometimes denoted as Ca _{12 Al} 14 _{O 33} or _Ca 24 _Al 28 _{O 66.}

Examples of the isomorphous compound include, but are not limited to, the following compounds (1) to (5).
(1) An isomorphous compound in which some or all of the Ca atoms in the crystal are substituted with one or more metal atoms selected from the group consisting of Sr, Mg, and Ba. For example, a compound in which some or all of Ca atoms are substituted with Sr is strontium aluminate Sr ₁₂ Al ₁₄ O ₃₃ , and calcium strontium aluminum is used as a mixed crystal in which the mixing ratio of Ca and Sr is arbitrarily changed. Nate Ca _12-x Sr _X Al ₁₄ O ₃₃ (x is an integer of 1 to 11; in the case of an average value, a number of more than 0 and less than 12).
(2) An isomorphous compound in which some or all of the Al atoms in the crystal are substituted with one or more atoms selected from the group consisting of Si, Ge, Ga, In, and B. For _example, like _{Ca 12 Al 10 Si 4 O 35} .
(3) A part of metal atoms and / or nonmetal atoms (excluding oxygen atoms) in the 12CaO.7Al ₂ O ₃ crystal (including the compounds of (1) and (2) above) is Ti, One or more atoms selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, and Cu, one or more alkali metal atoms selected from the group consisting of Li, Na, and K, or Ce, Pr , Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. The same type compound substituted with one or more rare earth atoms selected from the group consisting of Yb.
(4) A compound in which some or all of the free oxygen ions included in the cage are replaced with other anions. Other anions include, for example, one or more selected from the group consisting of H ⁻ , H ₂ ⁻ , H ²⁻ , O ⁻ , O ₂ ⁻ , OH ⁻ , F ⁻ , Cl ⁻ , and S ²⁻ . There are anions and nitrogen (N) anions.
(5) A compound in which part of oxygen in the cage skeleton is substituted with nitrogen (N) or the like.

(Crystalline C12A7 electride)
In the present application, the “crystalline C12A7 electride” means that in the above-mentioned “crystalline C12A7”, free oxygen ions included in the cage (in the case of having other anions included in the cage, the anions) ) Means a compound in which part or all of them are substituted with electrons.

In the crystalline C12A7 electride, the electrons included in the cage are loosely bound in the cage and can move freely in the crystal. For this reason, crystalline C12A7 electride shows electroconductivity. In particular, crystalline C12A7 in which all free oxygen ions are replaced with electrons may be expressed as [Ca ₂₄ Al ₂₈ O ₆₄ ] ⁴⁺ (4e ⁻ ).

  “Crystalline C12A7 electride” includes Ca atoms, Al atoms, and O atoms, the molar ratio of Ca: Al is in the range of 13:13 to 11:15, and the molar ratio of Ca: Al is 12.5. It is preferably in the range of 13.5 to 11.5: 14.5, and more preferably in the range of 12.2: 13.8 to 11.8: 14.2.

  The method for producing the target made of crystalline C12A7 electride is not particularly limited. The target may be manufactured using, for example, a conventional method for manufacturing a bulk crystalline C12A7 electride. For example, by heating the sintered body of crystalline C12A7 to about 1150 ° C. to 1460 ° C., preferably about 1200 ° C. to 1400 ° C. in the presence of a reducing agent such as Ti, Al, Ca or C, A target made of crystalline C12A7 electride may be manufactured. A green compact formed by compressing a crystalline C12A7 electride powder may be used as a target. By heating the sintered body of crystalline C12A7 at 1230 ° C. to 1415 ° C. in the presence of carbon and metal aluminum while keeping the sintered body and metal aluminum not in contact with each other, a large area can be efficiently obtained A target made of crystalline C12A7 electride can be produced.

Here, the electron density of the target, that is, crystalline C12A7 electride is in the range of 2.0 × 10 ¹⁷ cm ^{−3 to} 2.3 × 10 ²¹ cm ⁻³ . The electron density of the crystalline C12A7 electride is preferably 1 × 10 ¹⁸ cm ⁻³ or more, preferably 1 × 10 ¹⁹ cm ⁻³ or more, more preferably 1 × 10 ²⁰ cm ⁻³ or more, 5 × 10 ²⁰ cm ⁻³ or more is more preferable, and 1 × 10 ²¹ cm ⁻³ or more is particularly preferable. The higher the electron density of the crystalline C12A7 electride constituting the target, the easier it is to obtain an electride thin film having a lower work function. In particular, in order to obtain an electride thin film having a work function of 3.0 eV or less, the electron density of the crystalline C12A7 electride is more preferably 1.4 × 10 ²¹ cm ⁻³ or more, and 1.7 × 10 ^21. cm ⁻³ or more is more preferable, and 2 × 10 ²¹ cm ⁻³ or more is particularly preferable. In particular, when all free oxygen ions (or other anions when they have other anions) are replaced with electrons, the electron density of the crystalline C12A7 electride is 2.3 × 10 ²¹ cm ⁻³ . When the electron density of crystalline C12A7 electride is less than 2.0 × 10 ¹⁷ cm ⁻³ , the electron density of the electride thin film obtained by film formation is reduced.

  The electron density of the crystalline C12A7 electride can be measured by a light absorption measurement method. Since the crystalline C12A7 electride has a specific light absorption around 2.8 eV, the electron density can be determined by measuring the absorption coefficient. In particular, when the sample is a sintered body, it is convenient to use the diffuse reflection method after pulverizing the sintered body into a powder.

  The obtained target is used as a raw material source when an amorphous oxide electride thin film is formed in the next step.

  Note that the surface of the target may be polished by mechanical means or the like before use. Generally, a bulk body of crystalline C12A7 electride obtained by a conventional method may have a very thin film (foreign material) on the surface. When a film forming process is performed using a target having such a film formed on the surface as it is, the composition of the obtained thin film may deviate from a desired composition ratio. However, such a problem can be significantly suppressed by carrying out the polishing treatment of the target surface.

(Step S122)
Next, film formation is performed on the semiconductor layer by a vapor deposition method using the target manufactured in the above-described step S121.

  In the present application, “vapor deposition” refers to vapor deposition of a target material including a physical vapor deposition (PVD) method, a PLD method, a sputtering method, and a vacuum deposition method, and then depositing this material on a substrate. This is a general term for film formation methods.

  Among the “vapor deposition methods”, the sputtering method is particularly preferable. In the sputtering method, a thin film can be formed relatively uniformly in a large area. The sputtering method includes a DC (direct current) sputtering method, a high frequency sputtering method, a helicon wave sputtering method, an ion beam sputtering method, a magnetron sputtering method, and the like.

  Hereinafter, step S122 will be described by taking as an example the case where film formation is performed by a sputtering method.

  The temperature of the substrate on which the thin film of electride is formed is not particularly limited, and any temperature in the range from room temperature to, for example, 700 ° C. may be adopted. It should be noted that the substrate need not necessarily be “positively” heated when depositing the electride thin film. However, there may be a case where the temperature of the deposition target substrate rises “incidentally” due to the radiant heat of the vapor deposition source. For example, the temperature of the deposition target substrate may be 500 ° C. or lower, or 200 ° C. or lower.

  When the film formation substrate is not “positively” heated, it is possible to use a material whose heat resistance is lowered on the high temperature side exceeding 700 ° C., such as glass or plastic, for example.

The oxygen partial pressure during film formation (oxygen partial pressure in the chamber) is preferably less than 0.1 Pa. The oxygen partial pressure is preferably 0.01 Pa or less, more preferably 1 × 10 ⁻³ Pa or less, further preferably 1 × 10 ⁻⁴ Pa or less, and 1 × 10 ⁻⁵ Pa or less. It is particularly preferred that When the oxygen partial pressure is 0.1 Pa or more, oxygen is taken into the deposited thin film, which may reduce the electron density.

  On the other hand, the hydrogen partial pressure during film formation is preferably less than 0.004 Pa. When the pressure is 0.004 Pa or more, hydrogen or OH component is taken into the formed thin film, which may reduce the electron density of the amorphous oxide electride thin film.

The sputtering gas used is not particularly limited. The sputtering gas may be an inert gas or a rare gas. The inert gas, eg, N ₂ gas. In addition, examples of the rare gas include He (helium), Ne (neon), Ar (argon), Kr (krypton), and Xe (xenon). These may be used alone or in combination with other gases. Alternatively, the sputtering gas may be a reducing gas such as NO (nitrogen monoxide).

The pressure of the sputtering gas (pressure in the chamber) is not particularly limited, and can be freely selected so that a desired thin film can be obtained. In particular, the pressure P (Pa) of the sputtering gas (pressure in the chamber) is such that when the distance between the substrate and the target is t (m) and the diameter of the gas molecule is d (m),

8.9 × 10 ⁻²² / (td ² ) <P <4.5 × 10 ⁻²⁰ / (td ² ) (3) Formula

It may be selected to satisfy. In this case, the mean free path of the sputtered particles becomes substantially equal to the distance between the target and the deposition target substrate, and the sputtered particles are suppressed from reacting with the remaining oxygen. In this case, as a sputtering method apparatus, it is possible to use an inexpensive and simple vacuum apparatus having a relatively high back pressure.

  The method for forming an amorphous oxide electride thin film has been briefly described above by taking the sputtering method as an example. However, the method of forming the amorphous oxide electride thin film is not limited to this, and the above-described two steps (steps S121 and S122) may be appropriately changed or various steps may be added. It is clear that it is also good.

  For example, in the above-described step S122, a pre-sputtering process (a dry etching process of the target) may be performed on the target before starting the formation of the amorphous oxide electride by the sputtering method. .

  By performing the pre-sputtering process, the surface of the target is cleaned, and it becomes easy to form a thin film having a desired composition in the subsequent film formation process (main film formation).

  For example, when the target is used for a long time, oxygen is taken into the surface of the target, and the electron density of the crystalline C12A7 electride constituting the target may decrease. When such a target is used, there is a possibility that the electron density is lowered even in the formed thin film. Further, when the target is used for a long time, the composition of the target may deviate from the initial composition due to the difference in sputtering rate of each component constituting the target (ie, crystalline C12A7 electride). When such a target is used, the composition may deviate from a desired value even in the formed thin film. However, such a problem is suppressed by performing the pre-sputtering process.

Note that the gas used in the pre-sputtering process may be the same as or different from the sputtering gas used in the main film formation. In particular, the gas used for the pre-sputtering process is preferably He (helium), Ne (neon), N ₂ (nitrogen), Ar (argon), and / or NO (nitrogen monoxide).

  In this manner, an electride thin film is formed on the patterned semiconductor layer 105.

  Thereafter, the first and / or second electride thin films 150a and 150b can be formed by patterning the electride thin film into a desired pattern by photolithography or the like.

  In the case where the semiconductor layer 105 is an oxide semiconductor, a thin film of the semiconductor layer 105 and the electride can be continuously formed by a sputtering method without exposing the deposition target substrate to the air. In the top gate structure-top contact system or the bottom gate structure-top contact system, it is preferable to continuously form the semiconductor layer 105 and the thin film of electride.

  The electride thin film is preferably heat-treated after patterning. The heat treatment temperature is preferably 300 ° C. or higher, more preferably 500 ° C. or higher. The temperature is lower than the temperature at which the coating film and the deposition target substrate can withstand, and is preferably 700 ° C. or lower. The holding time at the predetermined temperature may be 1 minute to 2 hours, or 10 minutes to 1 hour. The timing of the heat treatment may be after patterning the electride thin film, after forming the source electrode and the drain electrode on the electride thin film (for example, the example of FIG. 3), or the electride thin film. It may be after the semiconductor layer is formed thereon (for example, the example of FIG. 4). By heat treatment, recovery can be achieved when the thin film of electride is damaged during patterning.

(Step S130)
Next, the source electrode 120 and the drain electrode 122 are formed on the first and / or second electride thin films 150a and 150b.

  Various methods conventionally used can be used to form the source electrode 120 and the drain electrode 122.

  After the conductive layer for forming the source electrode 120 and the drain electrode 122 is formed, the source electrode 120 and the drain electrode 122 can be formed by performing a photolithography process or the like on the film.

  Here, the source electrode 120 is disposed on the first electride thin film 150a and / or the drain electrode 122 is disposed on the second electride thin film 150b.

  Thereby, the contact resistance at the interface between the source electrode 120 and the semiconductor layer 105 and / or the interface between the drain electrode 122 and the semiconductor layer 105 is reduced.

  In the cross-sectional view of FIG. 3, an example in which the semiconductor layer 105 and the source electrode 102 and / or the drain electrode 122 do not have a direct contact portion is schematically shown. However, in the present invention, as long as the contact resistance can be reduced by the presence of the electride thin film, the semiconductor layer may have a portion in direct contact with the source electrode and / or the drain electrode. . For example, a thin film of a semiconductor layer and an electride is continuously formed and patterned in a lump by a photolithography process. The side surface of the pattern of the semiconductor layer is likely not to be covered with the electride thin film. Next, a source electrode and a drain electrode are formed on the electride thin film. At this time, the side surface of the pattern of the semiconductor layer may be in contact with the source electrode and the drain electrode.

(Step S140)
Next, a gate insulating film 130 is formed so as to cover the source electrode 120 and the drain electrode 122.

The gate insulating film 130 may be formed by a coating method such as a dipping method, a spin coating method, a droplet discharge method, a casting method, a spinner method, a printing method, a CVD method, a sputtering method, or the like.

  Thereafter, the gate electrode 124 is formed on the gate insulating film 130. Various methods conventionally used can be used to form the gate electrode 124. For example, the gate electrode 124 may be formed by a sputtering method, an evaporation method, or the like. The gate electrode 124 can be formed by performing a photolithography process or the like on the film after forming the conductive layer for forming the gate electrode 124.

  Through the above steps, the first semiconductor device 100 can be manufactured.

  In the above description, an example of a method for manufacturing a semiconductor device according to the present invention has been described using the first semiconductor device 100 shown in FIG. 3 as an example.

  However, it will be apparent to those skilled in the art that the semiconductor device 400, the semiconductor device 500, and the semiconductor device 600 can be manufactured by a similar method. That is, by changing the order of the steps shown in FIG. 7, the semiconductor device having each configuration can be manufactured.

  Moreover, a transparent semiconductor device can be manufactured by making all the substrates, electrodes, and semiconductor layers used in the semiconductor device of the present invention transparent materials.

The semiconductor device of the present invention can be used for a light emitting display device. The organic electroluminescence element included in the light emitting display device may have any of the following configurations.
(1) A substrate, an anode, and a cathode are provided in this order, and the substrate side is a light extraction surface. An electride thin film exists between the anode and the cathode, or constitutes a cathode.
(2) A substrate, an anode, and a cathode are provided in this order, and the cathode side is a light extraction surface, and a thin film of electride exists between the anode and the cathode, or constitutes the cathode.
(3) A substrate, a cathode, and an anode are provided in this order, and the substrate side is a light extraction surface, and an electride thin film exists between the anode and the cathode or constitutes the cathode.
(4) A substrate, a cathode, and an anode are provided in this order, and the anode side is a light extraction surface, and an electride thin film exists between the anode and the cathode or constitutes the cathode.

  The “electride thin film” included in the organic electroluminescence element may be “an amorphous oxide electride thin film including calcium atoms and aluminum atoms” included in the semiconductor device of the present invention.

In addition, the organic electroluminescence element may have a configuration in which a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer are sequentially provided between the anode and the cathode. However, the hole injection layer, the hole transport layer, the electron transport layer, and / or the electron injection layer may be omitted. The thin film of electride can constitute, for example, an electron injection layer. When an electride thin film is used for the electron injection layer, an electron transport layer made of a metal oxide may be disposed between the light emitting layer and the electron injection layer (electride thin film). The electron transport layer may be in the form of amorphous, crystalline, or a mixed phase of amorphous and crystalline. For example, the electron transport layer may be composed of ZnO—SiO ₂ , In ₂ O ₃ —SiO ₂ , SnO ₂ —SiO ₂ , ZnO, In—Ga—Zn—O, In—Zn—O, or SnO _2. good.

  The present invention can be applied to, for example, a semiconductor device used in various electronic devices such as an electro-optical device. For example, it can be used for electronic devices such as displays such as televisions, electrical appliances such as washing machines and refrigerators, and information processing devices such as mobile phones and computers. The semiconductor device of the present invention can also be used for electronic devices included in automobiles and various industrial equipment.

DESCRIPTION OF SYMBOLS 1 Conventional semiconductor device 5 Semiconductor layer 10 Substrate 20 Source electrode 22 Drain electrode 24 Gate electrode 30 Gate insulating layer 70 Electride of amorphous oxide 72 Solvent (amorphous)
74 Bipolaron 76 Cage 78 Electron (solute)
DESCRIPTION OF SYMBOLS 100 1st semiconductor device 105 Semiconductor layer 110 Substrate 120 Source electrode 122 Drain electrode 124 Gate electrode 130 Gate insulating layer 150a, 150b Electrode thin film 400, 500, 600 Semiconductor device 405, 505, 605 Semiconductor layer 410, 510, 610 Substrate 420, 520, 620 Source electrode 422, 522, 622 Drain electrode 424, 524, 624 Gate electrode 430, 530, 630 Gate insulating layer 450a, 450b, 550a, 550b, 650a, 650b Thin film of electride

Claims (15)

A semiconductor device having a source electrode, a drain electrode, a gate electrode and a semiconductor layer,
A semiconductor device comprising an amorphous oxide thin film containing calcium atoms and aluminum atoms between one or both of the source electrode and the drain electrode and the semiconductor layer.   2. The semiconductor device according to claim 1, wherein in the electride thin film, a molar ratio (Ca / Al) of aluminum atoms to calcium atoms is in a range of 0.3 to 5.0. The semiconductor device according to claim 1, wherein the thin film of electride has an electron density of 2.0 × 10 ¹⁷ cm ⁻³ or more.   4. The semiconductor device according to claim 1, wherein a thickness of the electride thin film is 100 nm or less. 5.   The semiconductor device according to claim 1, wherein the semiconductor layer includes an oxide semiconductor or an organic semiconductor. 6. The semiconductor device according to claim 1, wherein the semiconductor layer is disposed between the source electrode and the gate electrode, or the semiconductor layer is disposed on a side farther from the gate electrode than the source electrode. A semiconductor device according to 1. A method of manufacturing a semiconductor device having a source electrode, a drain electrode, a gate electrode and a semiconductor layer,
Forming a thin film of an amorphous oxide electride containing calcium atoms and aluminum atoms between one or both of the source electrode and the drain electrode and the semiconductor layer. Manufacturing method. further,
(A) forming a semiconductor layer on the substrate;
(B) forming a source electrode and a drain electrode;
(C) forming a gate electrode;
Have
Between the step (a) and the step (b), an amorphous oxide containing calcium atoms and aluminum atoms is interposed between one or both of the source electrode and the drain electrode and the semiconductor layer. The manufacturing method of Claim 7 which implements the step which forms the thin film of an electride. further,
(A) forming a source electrode and a drain electrode on a substrate;
(B) forming a semiconductor layer;
(C) forming a gate electrode;
Have
Between the step (a) and the step (b), an amorphous oxide containing calcium atoms and aluminum atoms is interposed between one or both of the source electrode and the drain electrode and the semiconductor layer. The manufacturing method of Claim 7 which implements the step which forms the thin film of an electride. further,
(A) forming a gate electrode on the substrate;
(B) forming a semiconductor layer;
(C) forming a source electrode and a drain electrode;
Have
Between the step (b) and the step (c), an amorphous oxide containing calcium atoms and aluminum atoms is interposed between one or both of the source electrode and the drain electrode and the semiconductor layer. The manufacturing method of Claim 7 which implements the step which forms the thin film of an electride. further,
(A) forming a gate electrode on the substrate;
(B) forming a source electrode and a drain electrode;
(C) forming a semiconductor layer;
Have
Between the step (b) and the step (c), an amorphous oxide containing calcium atoms and aluminum atoms is interposed between one or both of the source electrode and the drain electrode and the semiconductor layer. The manufacturing method of Claim 7 which implements the step which forms the thin film of an electride.   The manufacturing method according to claim 7, wherein in the electride thin film, a molar ratio (Ca / Al) of an aluminum atom to a calcium atom is in a range of 0.3 to 5.0. 13. The method according to claim 7, wherein the electride thin film has an electron density of 2.0 × 10 ¹⁷ cm ⁻³ or more.   The manufacturing method according to any one of claims 7 to 13, wherein a thickness of the electride thin film is 100 nm or less.   The manufacturing method according to claim 7, wherein the semiconductor layer includes an oxide semiconductor or an organic semiconductor.

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