JPWO2011132418A1 - Deposition method - Google Patents

Abstract

Sputtering a target made of a metal oxide in a gas atmosphere containing a rare gas atom and a water molecule, wherein the content of the water molecule is 0.1 to 10% in a partial pressure ratio with respect to the rare gas atom, A film forming method for forming a thin film on a substrate.

Description

  The present invention relates to a film forming method.

  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 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), drive voltages are applied to display elements. Thin film transistors (TFTs) are frequently used as switching elements that are applied to drive display devices.

Conventionally, an amorphous silicon-based semiconductor thin film has been used in a liquid crystal driving transistor of a large liquid crystal display device. However, with the recent demands for further enlargement and higher definition, amorphous silicon is lacking in mobility, so that image writing is not in time. Further, with respect to organic electroluminescence (organic EL) displays, a technology for increasing the size is in progress, and a material having a large area, a uniform area, and high mobility is required more than ever for the backplane.
Therefore, a transparent semiconductor thin film made of a metal oxide, particularly an oxide made of indium oxide, zinc oxide, or gallium oxide, which can be enlarged as an amorphous silicon-based semiconductor thin film and has the second highest mobility after crystalline silicon. Semiconductor thin films are attracting attention.

  Conventionally, an oxide semiconductor film used for a TFT active layer is generally formed in an atmosphere into which oxygen gas is introduced in order to control the electrical characteristics of the film. However, there is a problem that the carrier concentration in the film changes greatly due to a slight fluctuation of the oxygen partial pressure, and the semiconductor characteristics fluctuate.

As a means for solving this problem, it is known to increase the power density at the time of sputter film formation to moderate the oxygen partial pressure dependence of the carrier concentration in the film (Patent Document 1).
However, when the power density is increased, the film formation rate is increased and the oxygen supply rate is relatively decreased, so that the carrier concentration in the film is approximately 10 ¹⁸ cm ⁻³ or more. There was a problem that good characteristics could not be obtained.

In order to solve the above problem, the carrier concentration needs to be 10 ¹⁸ cm ⁻³ or less, and for this purpose, the oxygen partial pressure must be increased. When the oxygen partial pressure is increased, there is another problem that the film forming speed is lowered and the productivity is deteriorated. Therefore, it has been difficult to manufacture a favorable thin film transistor using an oxide semiconductor in a state where the power density at the time of sputtering film formation is increased and the film formation speed is increased.

Patent Document 2 uses a top gate type semiconductor film having an atomic ratio of In: Ga: Zn = 0.98: 1.02: 4 formed by introducing a partial pressure of water vapor and a channel layer having a thickness of 45 nm. A thin film transistor is disclosed. Patent Document 3 discloses an amorphous oxide semiconductor containing at least one of In and Zn, and hydrogen.
However, these are all technologies applied to a target of 4 inches or less, and there is room for improvement in high-speed film formation assuming actual production.

Non-Patent Document 3 forms a semiconductor film with an atomic ratio of In: Ga: Zn = 1.3: 1.3: 1.0 at a water vapor partial pressure of 10 ⁻² Pa or more, and the channel layer has a thickness of 30 nm. A thin film transistor having a bottom gate configuration and a bottom contact configuration is disclosed.
However, a thin film transistor formed by introducing a partial pressure of water vapor has an electric field mobility of about 3 cm ² / Vs, which is lower than that when oxygen is introduced, and is not suitable for use in a large-area and high-definition display device. It is enough.

  In addition to the above-mentioned problems, the size of the base when manufacturing flat displays such as liquid crystal displays is increasing year by year due to the increase in display size and intense cost reduction competition. Recently, liquid crystals using a glass base of 3 m square or more are used. Panel manufacturing is needed. However, when the substrate size increases, it becomes difficult to uniformly form the film thickness and film quality of the channel layer (semiconductor layer), and another problem is that the variation in characteristics due to the nonuniformity of the film thickness and film quality increases. was there.

For example, when the channel layer thickness is increased, the uniformity of the film thickness and the film quality is improved. However, in the oxide semiconductor typified by IGZO, the mobility decreases, and the threshold voltage is negative. (Non-patent Document 1). In particular, when manufacturing a channel etch type transistor with a low manufacturing cost, the channel layer (semiconductor layer) is exposed to an etching solution, so that the problem of non-uniformity when the base is enlarged is significant (non- Patent Document 2).
Therefore, until now, in a thin film transistor using an oxide semiconductor, a channel layer is usually formed with a thin film thickness of 50 nm or less (Non-Patent Document 3), and a thick film of the channel layer is thick (for example, 50 nm or more, further Thin film transistors having good characteristics such as mobility and threshold voltage have been demanded.

  Patent Documents 4 and 5 disclose production examples of large area ITO using an AC sputtering apparatus. However, in the case of an oxide semiconductor, control of oxygen vacancies is more important, and it has been unclear how the carrier concentration of the semiconductor affects the power and frequency.

International Publication No. 2009/084537 Pamphlet Japanese Patent Laid-Open No. 2007-73697 JP 2010-80936 A JP 2005-290550 A JP 2007-031816 A

Kyoung-Seok et al. , SID 08 DIGEST, p633 Je-hun Lee et al. , SID 08 DIGEST, p625 Takafumi Aoi et al. , Thin Solid Films 518 (2010)

An object of the present invention is to provide a method for forming an oxide semiconductor film that suppresses the carrier concentration in the film to 10 ¹⁸ cm ⁻³ or less without decreasing the film formation speed even in a state where the power density during sputtering film formation is high. Is to provide.
Another object of the present invention is to provide a thin film transistor having good transistor characteristics such as mobility even when the channel layer (semiconductor layer) is thick.

As a result of intensive studies, the present inventors have successfully introduced water vapor instead of introducing oxygen at the time of sputtering film formation, so that the film formation rate does not decrease even when the power density at the time of sputtering film formation is high. It has been found that the carrier concentration inside can be 10 ¹⁸ cm ⁻³ or less.
Further, the present inventors have found a method for manufacturing a semiconductor film that is stable without extending the manufacturing time by using the film forming method.

According to the present invention, the following film forming method and the like are provided.
1. Sputtering a target made of a metal oxide in a gas atmosphere containing a rare gas atom and a water molecule, wherein the content of the water molecule is 0.1 to 10% in a partial pressure ratio with respect to the rare gas atom, A film forming method for forming a thin film on a substrate.
2. 2. The film forming method according to 1, wherein the gas pressure is 0.1 to 5.0 Pa.
3. 3. The film forming method according to 1 or 2, wherein the sputtering is direct current sputtering.
4). 3. The film forming method according to 1 or 2, wherein the sputtering is alternating current sputtering.
5. 4. The film forming method according to 3, wherein the direct current power density is 1 to 5 W / cm ² .
6). The substrate is sequentially transferred to a position facing three or more targets arranged in parallel in the vacuum chamber at a predetermined interval,
A method of forming a thin film on the surface of the substrate by alternately applying a negative potential and a positive potential to each target from an AC power source to generate plasma on the target,
The film formation method according to 4, wherein the film formation is performed while switching a target to which a potential is applied between two or more targets branched and connected to at least one of the outputs from the AC power source. .
7). The film-forming method of 4 or 6 whose alternating current power density is 5-20 W / cm < ² >.
8). The film-forming method in any one of 4, 6, and 7 whose frequency of the said AC power supply is 10 kHz-1 MHz.
9. The film-forming method in any one of 1-8 whose film-forming speed | rate of the orthogonal | vertical direction is 1-100 nm / min with respect to the film-forming surface of a board | substrate.
10. The film forming method according to any one of 1 to 9, wherein a distance between the target and the substrate is 1 to 15 cm in a direction perpendicular to a film forming surface of the substrate.
11. The film-forming method in any one of 1-10 whose magnetic field intensity of the said atmosphere is 300-1000 gauss.
12 The metal oxide contains at least one element selected from the group consisting of gallium element (Ga), zinc element (Zn) and tin element (Sn), and indium element (In),
The film-forming method in any one of 1-11 with which content of the indium element in a target satisfy | fills the following atomic ratio.
0.2 ≦ [In] / all metal atoms ≦ 0.8
(In the formula, [In] is the number of atoms of indium element in the target.
The total metal atom is the number of atoms of all metal atoms included in the target. )
13. The metal oxide contains indium element (In), gallium element (Ga) and zinc element (Zn);
The film forming method according to any one of 1 to 11, wherein the contents of indium element, gallium element and zinc element in the target satisfy the following atomic ratio.
0 <[In] / [Ga] <0.5
0.2 <[In] / ([In] + [Ga] + [Zn]) <0.9
(In the formula, [In] is the number of atoms of indium element in the target, [Ga] is the number of atoms of gallium element in the target, and [Zn] is the number of atoms of zinc element in the target.)
14 The metal oxide contains indium element (In), tin element (Sn), and zinc element (Zn),
The film-forming method in any one of 1-11 with which content of the indium element in a target, a tin element, and a zinc element satisfy | fills the following atomic ratio.
0.2 <[In] / ([In] + [Sn] + [Zn]) <0.9
0 <[Sn] / ([In] + [Sn] + [Zn]) <0.5
(In the formula, [In] is the number of atoms of indium element in the target, [Sn] is the number of atoms of tin element in the target, and [Zn] is the number of atoms of zinc element in the target.)
15. A method for producing an oxide semiconductor thin film, comprising annealing a thin film obtained by the film forming method according to any one of 15.1 to 14 at 150 to 400 ° C. for 5 to 120 minutes.
16. 16. The method for producing an oxide semiconductor thin film according to 15, wherein the annealing treatment is performed in an atmosphere containing at least oxygen.
A field effect thin film transistor element comprising an oxide semiconductor thin film obtained by the method for producing a thin film according to 17.15 or 16.
18. 18. The field effect thin film transistor element according to 17, wherein the oxide semiconductor thin film is a channel layer.
19. The field effect thin film transistor element according to 17 or 18, which has a mobility of 10 cm ² / Vs or more and a threshold voltage of −5 to 5 V.

According to the present invention, there is provided a method for forming an oxide semiconductor film, which does not decrease the film formation speed even when the power density at the time of sputtering film formation is high and suppresses the carrier concentration in the film to 10 ¹⁸ cm ⁻³ or less. Can be provided.
Further, according to the present invention, a thin film transistor having favorable transistor characteristics such as mobility can be provided even when the channel layer (semiconductor layer) is thick.

It is a figure which shows the principal part of an example of a sputtering device. It is a schematic sectional drawing which shows one Embodiment of the thin-film transistor provided with the oxide semiconductor of this invention. It is a schematic sectional drawing which concerns on other embodiment of the thin-film transistor provided with the oxide semiconductor of this invention. It is a figure which shows the relationship between oxygen concentration or hydrogen concentration, and the carrier concentration of the thin film obtained.

The film forming method of the present invention comprises a metal oxide in a gas atmosphere containing a rare gas atom and a water molecule, and the content of the water molecule is 0.1 to 10% in a partial pressure ratio with respect to the rare gas atom. A target is sputtered to form a thin film on the substrate.
The partial pressure ratio of water molecules to rare gas atoms is represented by [H ₂ O] / ([H ₂ O] + [rare gas atoms]), where [H ₂ O] is the water molecule in the gas atmosphere. It is a partial pressure, and [rare gas atom] is a partial pressure of a rare gas atom in a gas atmosphere.

  When the film forming method of the present invention is used, by introducing a small amount of water molecules, OH groups are taken into the film, and oxygen vacancies are generated more efficiently than when oxygen is introduced (film formation of carriers). Occurrence) can be avoided. Further, since the amount of water molecules introduced is small, for example, a semiconductor film can be formed without reducing the sputtering rate.

The gas atmosphere during sputtering contains rare gas atoms and water molecules, and the content of water molecules is 0.1 to 10%, preferably 0.5 to 7%, in terms of partial pressure ratio with respect to the rare gas atoms. More preferably, it is 1.0 to 5%, and particularly preferably 1.0 to 3.0%.
The partial pressure of water during sputtering is preferably 5 × 10 ^{−3 to} 5 × 10 ⁻¹ Pa. When the pressure is less than 5 × 10 −3 Pa, the amount of OH groups taken into the film decreases, so that the degree of oxidation of the thin film becomes insufficient and the carrier concentration tends to increase. If it exceeds 5 × 10 ⁻¹ Pa, a large amount of OH groups are taken into the film, so that oxidation is promoted and the carrier concentration and mobility are lowered. Therefore, the field effect mobility may be lower than a desired value when the TFT element is used.
The optimum moisture pressure varies depending on various sputtering conditions such as the power density of discharge and the TS distance. For example, when the discharge power density is 2.5 W / cm ² , the moisture pressure is preferably 3 × 10 ⁻³ Pa to 1.5 × 10 ⁻² Pa, and the discharge power density is 5.0 W / cm ^2. In this case, the moisture pressure is preferably 1 × 10 ⁻² Pa to ¹ × 10 ⁻¹ Pa, and when the discharge power density is 7.4 W / cm ² , the moisture pressure is preferably 2.0 × 10 8. ⁻² Pa to 3.5 × 10 ⁻² Pa. By setting the moisture pressure within these ranges, the carrier concentration of the obtained thin film can be in the latter half of the 10 ¹⁷ cm ⁻³ unit, and a high field effect mobility of 10 cm ² / Vs or more can be obtained when a TFT element is obtained. it can.

When the content of water molecules is less than 0.1% in terms of partial pressure ratio with respect to rare gas atoms, OH groups are not sufficiently taken into the film, so that the effect of suppressing the generation of oxygen vacancies cannot be obtained, and the carrier in the film There is a possibility that the concentration cannot be reduced sufficiently. On the other hand, when the content of water molecules is more than 10% in the partial pressure ratio with respect to the rare gas atoms, the OH groups are excessively taken into the film and are excessively oxidized, so that the carrier concentration and mobility are lowered. There is a possibility that the mobility of the obtained TFT element is lowered.
The rare gas atom is not particularly limited, but is preferably an argon atom. In addition to rare gas atoms and water, oxygen and nitrogen may be included within a range that does not affect the TFT element.

The pressure of the gas atmosphere (sputtering pressure) is not particularly limited as long as the plasma can be stably discharged, but is preferably 0.1 to 5.0 Pa.
The sputtering pressure refers to the total pressure in the system at the start of sputtering after introducing argon, water, oxygen or the like.

The film formation rate of sputtering is usually 1 to 250 nm, preferably 1 to 100 nm / min, more preferably 10 to 80 nm / min, and particularly preferably 30 to 50 nm in the direction perpendicular to the film formation surface of the substrate. 60 nm / min.
When the film formation rate is less than 1 nm / min, the film formation rate is low, and thus productivity may be deteriorated. On the other hand, when the film formation rate exceeds 250 nm / min, the film formation rate becomes too high, resulting in poor controllability of the film thickness, and OH groups are not uniformly incorporated into the film, resulting in impaired in-plane uniformity of characteristics. There is a risk of being. Further, if the film formation rate is too high, OH groups are not sufficiently taken into the film, so that it is necessary to introduce an excessive amount of water molecules during sputtering film formation.

The distance between the target and the substrate is preferably 1 to 15 cm, more preferably 5 to 15 cm, and further preferably 4 to 8 cm in the direction perpendicular to the film formation surface of the substrate.
When this distance is less than 1 cm, the kinetic energy of the target constituent element particles reaching the substrate increases, and there is a possibility that good film characteristics cannot be obtained, and in-plane distribution of film thickness and electrical characteristics occurs. There is a risk that. On the other hand, if the distance between the target and the substrate exceeds 15 cm, the kinetic energy of the target constituent element particles reaching the substrate becomes too small to obtain a dense film, and good film characteristics can be obtained. It may not be possible.

It is desirable to perform sputtering in an atmosphere having a magnetic field strength of 300 to 1000 gauss.
When the magnetic field strength is less than 300 gauss, the plasma density becomes low, so there is a possibility that sputtering cannot be performed in the case of a high resistance sputtering target. On the other hand, if it exceeds 1000 gauss, the controllability of the film thickness and electrical characteristics in the film may be deteriorated.

The method of sputtering is not particularly limited, and any of DC sputtering with low plasma activity and high-frequency sputtering with a frequency of 10 MHz or less may be used. The sputtering may be pulse sputtering.
Here, DC sputtering refers to a sputtering method (DC sputtering) performed by applying a DC power supply, and high-frequency sputtering (RF sputtering) refers to sputtering performed by applying an AC power supply (AC sputtering). Pulse sputtering refers to sputtering performed by applying a pulse voltage.

Since RF sputtering has a higher plasma density and lower discharge voltage than DC sputtering, lattice disturbance and the like can be reduced, and carrier mobility can be increased. In general, RF sputtering tends to provide a film with good in-plane uniformity.
Therefore, a film obtained by RF sputtering is expected to have high field effect mobility when used as a TFT element. However, since RF sputtering is generally slower than DC sputtering, DC sputtering is industrially adopted.

The power density applied to the target at the time of DC sputtering film formation is preferably 1 to 10 W / cm ² , and more preferably ² to 5 W / cm ² . Most preferably, it is 2.5-5 W / cm < ² >.
If the power density is less than 1 W / cm ² , the film formation rate may be slowed, resulting in poor productivity, and the discharge may not be stable. On the other hand, when the sputtering power density is more than 10 W / cm ² , the film formation rate becomes too fast, and the film thickness controllability and the uniformity of characteristics may be deteriorated.

Examples of suitable alternating current sputtering include the following methods.
The substrate is sequentially transported to a position facing three or more targets arranged in parallel at a predetermined interval in the vacuum chamber, and negative and positive potentials are alternately applied to each target from an AC power source, Plasma is generated on the target to form a film on the substrate surface.
At this time, film formation is performed while switching a target to which a potential is applied between two or more targets branched and connected to at least one of the outputs from the AC power supply. That is, at least one of the outputs from the AC power supply is branched and connected to two or more targets, and film formation is performed while applying different potentials to adjacent targets.

  As an apparatus that can be used for this sputtering, for example, an AC (alternating current) sputtering apparatus for large area production described in Patent Document 3 can be cited. By using this apparatus, it is possible to form a film at a higher speed, and to set the film carrier concentration to a predetermined value with good reproducibility.

Specifically, the AC sputtering apparatus includes a vacuum chamber, a substrate holder disposed inside the vacuum chamber, and a sputtering source disposed at a position facing the substrate holder. A main part of the sputtering source is shown in FIG.
The sputter source has a plurality of sputter units, each of which has plate-like targets 100a to 100f, and when the surface to be sputtered of each target 100a to 100f is a sputter surface, each target has a sputter surface on the same plane. It is arranged to be located.
Each of the targets 100a to 100f is formed in an elongated rectangular parallelepiped having a longitudinal direction, each target has the same shape, and the edge portions (side surfaces) in the longitudinal direction of the sputtering surface are arranged in parallel at a predetermined interval. Therefore, the side surfaces of the adjacent targets 100a to 100f are parallel.

AC power supplies 300a to 300c are arranged outside the vacuum chamber, and two corresponding electrodes are connected to each of these AC power supplies. Of the two terminals of each of the AC power supplies 300a to 300c, one terminal is connected to one of the two adjacent electrodes, and the other terminal is connected to the other electrode.
Two terminals of each of the AC power supplies 300a to 300c output voltages of positive and negative different polarities, and the targets 100a to 100f are attached in close contact with the electrodes. AC voltages having different polarities are applied to 100f from the AC power supplies 300a to 300c. Therefore, when one of the targets 100a to 100f adjacent to each other is placed at a positive potential, the other is placed at a negative potential.

  Magnetic field forming means 200a to 200f are arranged on the surface of the electrode opposite to the targets 100a to 100f. Each of the magnetic field forming means 200a to 200f has an elongated ring-shaped magnet whose outer periphery is substantially equal to the outer periphery of the targets 100a to 100f, and a rod-shaped magnet shorter than the length of the ring-shaped magnet.

  Each ring-shaped magnet is arranged in parallel with the longitudinal direction of the targets 100a to 100f at a position directly behind the corresponding one of the targets 100a to 100f. As described above, since the targets 100a to 100f are arranged in parallel at a predetermined interval, the ring-shaped magnets are also arranged at the same interval as the targets 100a to 100f.

When using said apparatus, 3-20 W / cm < ² > is preferable for a power density. When it is less than 3 W / cm ² , the film formation rate is slow, which is not economical for production. If it exceeds 20 W / cm ² , the target may be damaged. Power density is more preferably 5~20W / cm ^2, more preferably from 4~10W / cm ^2.

  The frequency of AC sputtering is preferably in the range of 10 kHz to 1 MHz. If it is less than 10 kHz, there is a risk of noise problems. If the frequency exceeds 1 MHz, plasma spreads too much, so that sputtering is performed at a position other than the desired target position, and uniformity may be impaired. A more preferable frequency of AC sputtering is 20 kHz to 500 kHz.

  Moreover, when using said apparatus, the film-forming speed | rate becomes like this. Preferably it is 70-250 nm / min, More preferably, it is 100-200 nm / min.

  The target used for the film-forming method of this invention will not be specifically limited if it is a target which consists of metal oxides, Preferably they are the following 1st-3rd targets.

A first target that can be suitably used in the film formation method of the present invention is a target made of a metal oxide, and the metal oxide includes a gallium element (Ga), a zinc element (Zn), and a tin element ( Sn) contains at least one element selected from the group and indium element (In), and the content of indium element in the target satisfies the following atomic ratio.
0.2 ≦ [In] / all metal atoms ≦ 0.8
(In the formula, [In] is the number of atoms of indium element in the target.
The total metal atom is the number of atoms of all metal atoms included in the target. )

The atomic ratio is preferably 0.25 ≦ [In] / all metal atoms ≦ 0.75, and more preferably 0.3 ≦ [In] / all metal atoms ≦ 0.7.
When [In] / total metal atoms (atomic ratio) is less than 0.2, the carrier concentration may be lower than that of the semiconductor region. On the other hand, when [In] / total metal atoms (atomic ratio) is more than 0.8, the sputtered thin film is likely to be crystallized, and in-plane electrical characteristics may be non-uniform when formed in a large area. There is.

The second target that can be suitably used in the film forming method of the present invention is a target made of a metal oxide, and the metal oxide contains indium element (In), gallium element (Ga), and zinc element ( Zn) and the contents of indium element, gallium element and zinc element in the target satisfy the following atomic ratio.
0 <[In] / [Ga] <0.5
0.2 <[In] / ([In] + [Ga] + [Zn]) <0.9
(In the formula, [In] is the number of atoms of indium element in the target, [Ga] is the number of atoms of gallium element in the target, and [Zn] is the number of atoms of zinc element in the target.)

The metal oxide of the second target preferably satisfies the following atomic ratio.
0 <[In] / [Ga] <0.45
0.3 <[In] / ([In] + [Ga] + [Zn]) <0.9
More preferably, the metal oxide of the second target satisfies the following atomic ratio.
0 <[In] / [Ga] <0.35
0.4 <[In] / ([In] + [Ga] + [Zn]) <0.9

The effect of sputtering by introducing water molecules in any composition region of the metal oxide of the second target can be obtained, but when [In] / [Ga] is 0.5 or more, oxygen molecules Even when a film is formed by introducing a film, the oxidation effect is large, so that the carrier concentration is too low, and when the obtained thin film is used for a TFT element, a field effect mobility of only about 2 cm ² / Vs can be obtained. . When [In] / ([In] + [Ga] + [Zn]) is 0.2 or less, the resistance of the target becomes high, and there is a possibility that DC sputtering or AC sputtering cannot be performed. In addition, when [In] / ([In] + [Ga] + [Zn]) is 0.9 or more, the obtained thin film is easily crystallized. May be non-uniform.

In the second target, by reducing the proportion of gallium element and increasing the proportion of indium element, carrier concentration and carrier mobility can be increased, and high field effect mobility can be obtained.
When the composition ratio of the second target is, for example, 0 <[In] / [Ga] <0.45 and 0.3 <[In] / ([In] + [Ga] + [Zn]) <0.9 The field effect mobility can be 5-10 cm ² / Vs, and 0 <[In] / [Ga] <0.35 and 0.4 <[In] / ([In] + [Ga] + [Zn ]) <0.9 is desirable because the field effect mobility can be 10 cm ² / Vs or more.

A third target that can be suitably used in the film formation method of the present invention is a target made of a metal oxide, and the metal oxide contains indium element (In), tin element (Sn), and zinc element ( Zn) and the contents of indium element, tin element and zinc element in the target satisfy the following atomic ratio.
0.2 <[In] / ([In] + [Sn] + [Zn]) <0.9
0 <[Sn] / ([In] + [Sn] + [Zn]) <0.5
(In the formula, [In] is the number of atoms of indium element in the target, [Sn] is the number of atoms of tin element in the target, and [Zn] is the number of atoms of zinc element in the target.)

The metal oxide of the third target preferably satisfies the following atomic ratio.
0.2 <[In] / ([In] + [Sn] + [Zn]) <0.9
0 <[Sn] / ([In] + [Sn] + [Zn]) <0.35
More preferably, the metal oxide of the third target satisfies the following atomic ratio.
0.3 <[In] / ([In] + [Sn] + [Zn]) <0.9
0 <[Sn] / ([In] + [Sn] + [Zn]) <0.2

In the third target metal oxide, when [In] / ([In] + [Ga] + [Zn]) is 0.2 or less, the resistance of the target becomes high resistance. There is a possibility that AC sputtering cannot be performed. In addition, when [In] / ([In] + [Ga] + [Zn]) is 0.9 or more, the obtained thin film is easily crystallized. May be non-uniform. Furthermore, since tin element becomes a carrier scattering source, when [Sn] / ([In] + [Sn] + [Zn]) is 0.5 or more, the carrier mobility becomes low, and the resulting thin film May be 5 cm ² / Vs or less.

In the third target, by reducing the ratio of tin element and increasing the ratio of indium element, the carrier concentration and carrier mobility can be controlled, and high field effect mobility can be obtained.
The composition ratio of the third target is, for example, 0.2 <[In] / ([In] + [Sn] + [Zn]) <0.9 and 0 <[Sn] / ([In] + [Sn] + [Zn]) <0.35, the field effect mobility can be 5-10 cm ² / Vs, and 0.3 <[In] / ([In] + [Sn] + [Zn]) < When 0.9 and 0 <[Sn] / ([In] + [Sn] + [Zn]) <0.2, the field-effect mobility can be 10 cm ² / Vs or more.

In Non-Patent Document 3, in order to control the carrier concentration, the target contains a Ga element, and the atomic number ratio of the Ga element target to all metal elements is 0.33.
However, when the Ga element content exceeds 0.33 in terms of the atomic ratio with respect to the total metal elements of the target, Ga serves as a scattering source, and the mobility of the TFT element in which the thin film obtained is a semiconductor layer decreases. There was a risk of it. On the other hand, when the content of Ga element is less than 0.33 in terms of the atomic ratio with respect to the total metal elements of the target, the amount of Ga serving as a scattering source becomes small, and there is an advantage that high mobility can be expected. There is a problem that it becomes difficult to control the ^thickness to 10 ¹⁸ cm ⁻³ or less.

  In the film forming method of the present invention, when the film is formed using the second target having a Ga element content of less than 0.5 in terms of the number ratio of atoms relative to the indium element, or the third target not containing the Ga element. Also, a suitable TFT element can be obtained. In particular, when the third target is used, chemical resistance can be improved, so that the source / drain electrodes can be formed by wet etching without forming an etching stopper layer, and more preferably. An operating TFT element can be manufactured, and the manufacturing cost can be reduced.

The metal oxide of the first target is preferably an oxide consisting essentially of or only of indium element and zinc element. Similarly, the metal oxide of the second target is preferably indium element and gallium element. In addition, the third target metal oxide is preferably an oxide that is substantially or only composed of an indium element, a tin element, and a zinc element.
The first to third targets are, for example, Mg, Ca, Sr, Ba, Ti, Zr, Hf, Al, Ge, Cu, Co, Fe, Ni, Mo, and rare earth elements as long as the effects of the present invention are not impaired. One or more elements selected from lanthanoid elements can be included.

By annealing the thin film obtained by the film formation method of the present invention, the OH group taken into the thin film enters oxygen defects as O, so that the carrier concentration can be lowered. The annealing treatment condition is preferably an annealing treatment at 150 to 400 ° C. for 5 to 120 minutes.
When the annealing temperature is less than 150 ° C., the OH groups incorporated in the film do not sufficiently form oxygen bonds, so it is difficult to obtain the effect of reducing the carrier concentration. When the annealing temperature exceeds 400 ° C., crystallization proceeds. There is a risk that. The same applies to the processing time.

  The annealing treatment is not particularly limited as long as it is in the temperature range of 150 ° C. to 400 ° C., but is preferably performed in an atmosphere containing at least oxygen. By performing in an atmosphere containing oxygen, it is possible to suppress variation in characteristics when the annealed thin film is used as a TFT.

An oxide semiconductor obtained by annealing a thin film obtained by the film formation method of the present invention (hereinafter sometimes simply referred to as the oxide semiconductor of the present invention) can be suitably used as a semiconductor thin film of a thin film transistor.
The field-effect transistor including an oxide semiconductor of the present invention is a transistor with high field-effect mobility and on-off ratio, normally-off, and clear pinch-off. In addition, since the field-effect transistor including an oxide semiconductor of the present invention can form an oxide semiconductor at a low temperature, the field-effect transistor can be formed over a substrate having a limit of heat resistance such as alkali-free glass.

  The oxide semiconductor of the present invention is usually used in an n-type region, but it can be used in combination with various P-type semiconductors such as P-type Si-based semiconductors, P-type oxide semiconductors, P-type organic semiconductors, and the like. It can be used for various semiconductor devices. The TFT can also be applied to various integrated circuits such as logic circuits, memory circuits, and differential amplifier circuits. In addition to field effect transistors, it can be applied to electrostatic induction transistors, Schottky barrier transistors, Schottky diodes, and resistance elements.

  As the structure of the transistor, known structures such as a bottom gate, a top gate, a bottom contact, and a top contact can be used without limitation. In particular, the bottom gate configuration is advantageous because high performance can be obtained as compared with amorphous silicon or ZnO TFTs. The bottom gate configuration is preferable because it is easy to reduce the number of masks at the time of manufacturing, and it is easy to reduce the manufacturing cost for uses such as a large display.

  For large-area displays, a channel-etched bottom gate thin film transistor is particularly preferable. A channel-etched bottom gate thin film transistor has a small number of photomasks at the time of a photolithography process, and can produce a display panel at a low cost. Among these, a thin film transistor having a channel etch type bottom gate structure and a top contact structure is particularly preferable because it has excellent characteristics such as mobility and is easily industrialized.

The field effect transistor including an oxide semiconductor of the present invention can be suitably operated even when the film thickness of a semiconductor film, which has conventionally been difficult to obtain good characteristics, is 50 nm or more, further 60 nm or more, 70 nm or more. . In addition, the field-effect transistor including the oxide semiconductor of the present invention has preferable mobility, on / off ratio, and S value.
Note that the upper limit of the thickness of the semiconductor film is, for example, 100 nm.

  The S value of the field effect transistor including an oxide semiconductor of the present invention is preferably 1 V / decade or less, more preferably 0.7 V / decade or less, and particularly preferably 0.5 V / decade or less. If the S value exceeds 1 V / decade, the transistor may not exhibit good switching characteristics such as an increase in driving voltage.

  The threshold voltage of the field effect transistor containing the oxide semiconductor of the present invention is usually −5.0 to 5.0 V, preferably −1.0 to 2.0 V, more preferably −1.0 to 1.0 V. More preferably, it is 0-1.0V. If it is greater than 5 V, the drive voltage may increase and the power consumption may increase, and if it is less than −5 V, the power consumption may increase.

The channel length of the field effect transistor including the oxide semiconductor of the present invention is not particularly limited as long as it is in a range usually used, but is usually 10 to 70 μm, preferably 20 to 50 μm.
The channel width of the field effect transistor including the oxide semiconductor of the present invention is usually 10 to 100 μm, preferably 20 to 70 μm.

In order to increase the definition of the display, it is necessary to make the TFT minute. In that case, in order to obtain a desired on-current, the semiconductor film used for the TFT channel layer needs high mobility.
Since the field effect transistor including the oxide semiconductor of the present invention has high mobility, it can be expected to be suitably used in a 1 to 10 μm region, and further in a 2 to 8 μm region. In addition, regarding the channel width, the field effect transistor including the oxide semiconductor of the present invention can be expected to be suitably used in a region of 1 to 10 μm, and further in a region of 2 to 8 μm.

FIG. 2 is a schematic cross-sectional view showing an embodiment of a thin film transistor including the oxide semiconductor of the present invention.
The thin film transistor 1 which is a field effect transistor is a bottom gate type, and a gate electrode 30 is formed on a glass substrate 60 and a gate insulating film 50 is formed thereon. An oxide semiconductor film 40 is formed on the gate insulating film 50, and the drain electrode 10 and the source electrode 20 are further formed on the oxide semiconductor film 40.

There are no particular limitations on the material for forming the drain electrode 10, the source electrode 20, and the gate electrode 30, and any commonly used material can be selected.
For example, a transparent electrode such as ITO, IZO, ZnO, or SnO ₂ , a metal electrode such as Al, Ag, Cu, Cr, Ni, Mo, Au, Ti, or Ta, or a metal electrode made of an alloy containing these may be used. it can.

  Each of the drain electrode 10, the source electrode 20, and the gate electrode 30 may have a multilayer structure in which two or more different conductive layers are stacked. For example, in FIG. The first conductive layer 31, 21, 11 and the second conductive layer 32, 22, 12 are respectively configured. In particular, since the source / drain electrode has a strong demand for low-resistance wiring, a good conductor such as Al or Cu may be sandwiched with a metal having excellent adhesion such as Ti or Mo.

The material for forming the gate insulating film 50 is not particularly limited, and a commonly used material can be arbitrarily selected.
Examples of the material of the gate insulating film 50 include 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, and Rb _2. Compounds such as O, Sc ₂ O ₃ , Y ₂ O ₃ , HfO ₃ , CaHfO ₃ , PbTi ₃ , BaTa ₂ O ₆ , SrTiO ₃ , and AlN can be used. Among these, it is preferably _{SiO 2, SiNx, Al 2 O} 3, Y 2 O 3, HfO 3, CaHfO 3, more preferably _{SiO 2, SiNx, Y 2 O} 3, HfO 3, CaHfO 3 .
Note that the number of oxygen in the oxide does not necessarily match the stoichiometric ratio (for example, it may be SiO ₂ or SiO x).

  The 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, polycrystalline, or amorphous, but is preferably polycrystalline or amorphous that is easy to manufacture industrially.

The oxide semiconductor film 40 is an oxide semiconductor obtained by the film formation method of the present invention.
In the oxide semiconductor film 40, the carrier density obtained by hole measurement is usually less than 10 ¹⁸ cm ⁻³ , preferably less than 5 × 10 ¹⁷ cm ⁻³ , more preferably less than 1 × 10 ¹⁷ cm ^−3. It is. When the carrier density is 10 ¹⁸ cm ⁻³ or more, the leakage current may increase.
Note that the lower limit of the carrier density is preferably, for example, 10 ¹⁵ cm ⁻³ or more, although it depends on the use of the element including the oxide semiconductor film 40.

As for the specific resistance of the oxide semiconductor film 40, the value obtained by the four-terminal method is usually 10 ⁻¹ to 10 ⁸ Ωcm, preferably 10 ¹ to 10 ⁷ Ωcm, and more preferably 10 ² to 10 ⁶ Ωcm. It is.
When the specific resistance is less than 10 ⁻¹ Ωcm, electricity may flow easily and may not function as a semiconductor thin film. On the other hand, when the specific resistance exceeds 10 ⁸ Ωcm, there is a possibility that the semiconductor does not function unless a strong electric field is applied.

The thickness of the oxide semiconductor film 40 is appropriately selected in accordance with the specific resistance of the oxide semiconductor 40 itself, and is preferably thick from the viewpoint of uniformity. From the viewpoint of (time), a thinner film thickness is preferable.
The thickness of the oxide semiconductor film 40 is usually 20 to 500 nm, preferably 50 to 150 nm, more preferably 60 to 140 nm, particularly preferably 70 to 130 nm, and particularly preferably 70 to 110 nm.
When the thickness of the oxide semiconductor is less than 20 nm, the characteristics of the manufactured TFT may be non-uniform due to non-uniformity of the thickness when the oxide semiconductor is formed over a large area. On the other hand, when the film thickness exceeds 500 nm, the film formation time becomes long and there is a possibility that it cannot be adopted industrially.

The field effect mobility of the thin film transistor 1 is usually 1 cm ² / Vs or more, preferably 5 cm ² / Vs or more, more preferably 10 cm ² / Vs or more, further preferably 18 cm ² / Vs or more, particularly preferably 30 cm ² / Vs. Above, most preferably 50 cm ² / Vs or more.
When the field effect mobility is less than 1 cm ² / Vs, the switching speed may be slow. The upper limit of the field effect mobility is, for example, 500 cm ² / Vs.

The on-off ratio of the thin film transistor 1 is usually 10 ³ or more, preferably 10 ⁴ or more, more preferably 10 ⁵ or more, still more preferably 10 ⁶ or more, and particularly preferably 10 ⁷ or more.
The thin film transistor 1 is preferably normally off with a positive threshold voltage (Vth) from the viewpoint of low power consumption. If the threshold voltage (Vth) is negative and normally on, power consumption may increase.

The manufacturing method of the field effect transistor containing the oxide semiconductor of this invention can be manufactured, for example with the following method.
First, a metal film is formed on an insulating substrate to form a gate electrode. As the metal film, Mo, Al, Cr and alloys containing these as main components are preferably used. A laminated film of these metal films may be used.
A gate insulating film is formed on the gate electrode and the insulating substrate by plasma CVD. Next, a semiconductor layer to be a channel is formed by a sputtering method. Next, a semiconductor layer in a region to be a TFT is formed in an island shape through a photolithography process and an etching process. Subsequently, a second metal film for forming a source electrode and a drain electrode is formed. For the second metal film, a material such as Al, Cr, Mo, or an alloy containing these can be used in the same manner as the gate electrode. It is also possible to configure with a laminated film.
A transistor is obtained by obtaining a pattern of a source electrode and a drain electrode having desired shapes from the formed second metal film by a photolithography process and an etching process.

Examples 1-30
A 2-inch target having the target composition shown in Tables 1 to 3 is mounted on a magnetron sputtering apparatus, a silicon wafer with a thermal oxide film having a thickness of 100 nm is used as the substrate A1, and a slide glass (# 1737 manufactured by Corning) as the substrate B1. Each was fitted.
After conveying the substrate into the chamber and setting it to a predetermined ultimate pressure, Ar gas and H ₂ O gas having a partial pressure ratio shown in Tables 1 to 3 were introduced, and the film thickness was 50 nm under the sputtering conditions shown in Tables 1 to 3. Were formed on the substrate A1 and the substrate B1, respectively.
The obtained thin film was annealed in an oven under the annealing conditions shown in Tables 1 to 3 to obtain an oxide semiconductor laminated on the substrate A1 and the substrate B1.

The substrate B1 including the oxide semiconductor after the heat treatment was cut into 1 cm ² and Au electrodes were attached to the four corners. An Au electrode and a copper wire were bonded with a silver paste to form a Hall effect measuring element B1, and the carrier concentration was evaluated. The results are shown in Tables 1-3.
The carrier concentration was measured by performing Hall effect measurement using a ReiTest 8300 type (manufactured by Toyo Technica Co., Ltd.) at room temperature.

The substrate A1 including the oxide semiconductor after the heat treatment is mounted again on the 2-inch cathode magnetron sputtering apparatus, an Au target is mounted on the cathode, and a dedicated metal mask is used, and W / L = 1000/200 μm. An Au electrode was formed so that the TFT element A1 was manufactured.
The obtained TFT element A1 was set to Keithley 4200SCS, and the transfer characteristics were evaluated under the conditions of drain voltage Vds = 10V and gate voltage Vgs = -20 to 20V. The results are shown in Tables 1-3.

Comparative Examples 1-12 and Reference Examples 1-2
Using a target having the target composition shown in Tables 4 and 5, Ar gas and H ₂ O gas (Comparative Examples 5 to 6 and Reference Examples 1 and 2) or Ar gas and O ₂ having a partial pressure ratio shown in Tables 4 and 5 A gas (Comparative Examples 1-4, 7-12) was introduced, and an oxide film was formed in the same manner as in Examples 1-30 except that an amorphous film was formed and annealed under the conditions shown in Tables 4 and 5. A semiconductor was manufactured, and a Hall effect measurement element B1 was manufactured and the carrier concentration was evaluated in the same manner as in Examples 1 to 30, and a TFT element A1 was manufactured and the transfer characteristics were evaluated. The results are shown in Tables 4 and 5.

  Based on the results of Examples and Comparative Examples, FIG. 4 shows the relationship between the oxygen concentration or the hydrogen concentration and the carrier concentration of the obtained thin film.

Example 31
A field effect transistor having a bottom gate structure and a top contact structure was fabricated.
An ITZO sputtering target having an atomic ratio of In: Sn: Zn = 36: 15: 49 is mounted on a DC magnetron sputtering film forming apparatus to perform sputtering, and a semiconductor layer (film thickness) is formed on a silicon substrate with a thermal oxide film (100 nm). 80 nm) was formed.
Sputtering conditions were ultimate pressure 2 × 10 ⁻⁴ Pa, sputtering pressure 0.65 Pa, partial pressure ratio [H ₂ O] / ([H ₂ O] + [Ar]) = 3%, partial pressure ratio [O ₂ ] / ( [O ₂ ] + [Ar]) = 0%, power density 5.0 W / cm ² , T-S distance 5 cm, deposition rate 95 nm / min. It was.

The obtained semiconductor layer was subjected to photolithography to form a semiconductor region (so-called island), and heat-treated at 300 ° C. for 1 hour in the atmosphere. After forming the photoresist film, a laminated metal film of Ti / Au / Ti was formed by DC sputtering, and patterning was performed by lift-off to form a source electrode and a drain electrode, respectively. Thereafter, heat treatment was performed at 300 ° C. for 1 hour in the atmosphere.
Next, SiOx and SiNx were formed in this order by plasma CVD to form a first protective layer and a second protective layer, respectively. Contact holes were formed and connected to external wiring. Thereafter, heat treatment was performed in the atmosphere at 300 ° C. for 1 hour to produce a field effect transistor having W = 20 μm and L = 20 μm and having a bottom gate configuration and a top contact configuration using a Si substrate as a gate electrode.

The obtained field effect transistor was evaluated for its characteristics.
As a result, the field effect mobility was 21 cm ² / Vs, the on / off ratio was 10 ⁸ or more, the threshold voltage was 0.3 V, and the S value was 0.2 V / decade.
The evaluation was performed using a semiconductor parameter analyzer (Keutley 4200) in an atmosphere of dry nitrogen at atmospheric pressure, room temperature, and in a light-shielded environment.

Comparative Example 13
The partial pressure ratio [H ₂ O] / ([H ₂ O] + [Ar]) = 0% and the partial pressure ratio [O ₂ ] / ([O ₂ ]) for the water vapor partial pressure and the oxygen partial pressure at the time of forming the semiconductor layer, respectively. A field effect transistor was manufactured and evaluated in the same manner as in Example 31 except that + [Ar]) = 10%.
As a result, the obtained field effect transistor was normally on with a threshold voltage of −20 V or less. In the oxygen partial pressure control, it was confirmed that it was difficult to produce a thin film transistor having a channel layer of 80 nm.

Example 32
By using Mo for the source electrode and the drain electrode, and wet etching the Mo electrode on the channel layer using a phosphoric acid-based wet etching solution, a field-effect transistor having a channel-etched bottom gate configuration and a top-contact configuration is obtained. A field effect transistor was prepared and evaluated in the same manner as in Example 31 except that it was manufactured.
As a result, the obtained field effect transistor has a field effect mobility of 19 cm ² / Vs, an on / off ratio of 10 ⁸ or more, a threshold voltage of 0.3 V, and an S value of 0.2 V / decade. Met.

Example 33
RF sputtering was performed on a glass substrate at room temperature to deposit 200 nm of molybdenum metal, followed by patterning by dry etching to produce a gate electrode. The gate electrode was forward tapered after etching. On the substrate on which the gate electrode was laminated, SiNx and SiO ₂ were formed in this order by a plasma enhanced chemical vapor deposition apparatus (PECVD), and the laminated film was used as a gate insulating film.
The same sputtering target as in Example 31 was mounted on a DC magnetron sputtering film forming apparatus and sputtered under the same conditions as in Example 31 to form a semiconductor layer (film thickness of 80 nm) on the gate insulating film. Then, it heat-processed at 300 degreeC for 1 hour.

  A SiOx film was formed by PECVD to form a SiOx thin film. Subsequently, a resist film was formed and patterned. The thin film was patterned by dry etching (RIE) to form a first protective layer (etch stopper). After applying and forming a lift-off photoresist resist film, a Ti / Au / Ti metal laminate film was formed by DC sputtering, and lift-off and patterning were performed to form a source electrode and a drain electrode, respectively. Furthermore, SiNx was formed by PECVD (PECVD SiNx: H) to form a second protective layer. Contact holes were formed and connected to external wiring. Thereafter, heat treatment was performed in the atmosphere at 300 ° C. for 1 hour to manufacture an etch stopper type field effect transistor having a bottom gate structure of W = 20 μm and L = 20 μm.

The obtained field effect transistor was evaluated in the same manner as in Example 31.
As a result, the field effect mobility was 18 cm ² / Vs, the on / off ratio was 10 ⁸ or more, the threshold voltage was 0.3 V, and the S value was 0.2 V / decade.

Example 34
Sputtering was performed using the film forming apparatus of FIG. 1 under the conditions shown in Table 6 without heating a glass substrate having a width of 1100 mm, a length of 1250 mm, and a thickness of 0.7 mm.

  Here, In: Sn: Zn (atomic ratio) = 36: 15: 49, six targets 100a to 100f having a width of 200 mm, a length of 1700 mm, and a thickness of 10 mm are used, and the targets 100a to 100f are formed on the substrate. Parallel to the width direction, the distance between the targets was 2 mm. The width of the magnetic field forming means 200a to 200f was set to 200 nm, which is the same as that of the targets 100a to 100f.

Ar and H ₂ O, which are sputtering gases, were introduced from the gas supply system into the system at a flow rate ratio of 99: 1. The film forming atmosphere at this time was 0.5 Pa. The power of the AC power source was 3 W / cm ² (= 10.2 kW / 3400 cm ² ), and the frequency was 10 kHz.
The film was formed under the above conditions for 8 seconds, and the thickness of the obtained ITZO was measured to be 15 nm. The film formation rate was as high as 112.5 nm / min, which was suitable for mass production.
Moreover, it put into the glass substrate electric furnace with ITZO obtained in this way, and after heat-treating on the conditions of 400 degreeC for 15 minutes in air, it cut out to the size of 1 cm < ² > and measured the hole by the 4-probe method. As a result, the carrier concentration was 2.5 × 10 ¹⁶ cm ⁻³ , and it was confirmed that the semiconductor was sufficiently semiconductorized.

Examples 35-39
A semiconductor thin film was obtained in the same manner as in Example 34 except that the target composition and sputtering conditions were changed as shown in Table 6. Further, after heat treatment in the same manner as in Example 34, hole measurement was performed, and it was confirmed that all semiconductors were formed.

Comparative Example 14
A semiconductor thin film was obtained in the same manner as in Example 34 except that the sputtering conditions were changed as shown in Table 6. ITZO was formed by introducing argon and oxygen without using water as the introduced gas. As a result of the hole measurement, the carrier concentration was 2.5 × 10 ¹⁷ cm ⁻³ and the semiconductor was made, but the film formation rate was as slow as 36 nm / min. This film formation rate is considered to leave a problem in mass production.

Comparative Example 15
In Comparative Example 14, the output power was increased to 20 W / cm ² and high speed film formation was performed. As a result, the deposition rate increased to 90 nm / min. However, the carrier concentration was 7.5 × 10 ¹⁸ cm ⁻³ and it was not made into a semiconductor.

Comparative Example 16
A semiconductor thin film was obtained in the same manner as in Comparative Example 14 except that the sputtering conditions were changed as shown in Table 6. The carrier concentration was 5.5 × 10 ¹⁹ cm ⁻³ and it was not made semiconductor.

Examples 40-46
A 2-inch target having the target composition shown in Table 7 was mounted on the magnetron sputtering apparatus, a silicon wafer with a thermal oxide film having a thickness of 100 nm was used as the substrate A1, and a slide glass (# 1737 manufactured by Corning) was used as the substrate B1. Installed.
After transporting the substrate into the chamber and setting it to a predetermined ultimate pressure, Ar gas and H ₂ O gas having a partial pressure ratio shown in Table 7 were introduced, and an amorphous film having a film thickness of 50 nm under the sputtering conditions shown in Table 7 A film was formed on each of the substrate A1 and the substrate B1.
The obtained thin film was annealed in an oven under the annealing conditions shown in Table 7 to obtain an oxide semiconductor laminated on the substrate A1 and the substrate B1.

The substrate B1 including the oxide semiconductor after the heat treatment was cut into 1 cm ² and Au electrodes were attached to the four corners. An Au electrode and a copper wire were bonded with a silver paste to form a Hall effect measuring element B1, and the carrier concentration was evaluated. The results are shown in Table 7.
The carrier concentration was measured by performing Hall effect measurement using a ReiTest 8300 type (manufactured by Toyo Technica Co., Ltd.) at room temperature.

The substrate A1 including the oxide semiconductor after the heat treatment is mounted again on the 2-inch cathode magnetron sputtering apparatus, an Au target is mounted on the cathode, and a dedicated metal mask is used, and W / L = 1000/200 μm. An Au electrode was formed so that the TFT element A1 was manufactured.
The obtained TFT element A1 was set to Keithley 4200SCS, and the transfer characteristics were evaluated under the conditions of drain voltage Vds = 10V and gate voltage Vgs = -20 to 20V. The results are shown in Table 7.

Examples 47-51
Using a target having the target composition shown in Table 8, Ar gas and H ₂ O gas having a partial pressure ratio shown in Table 8 were introduced, and an amorphous film was formed and annealed under the conditions shown in Table 8. Others manufacture oxide semiconductor like Example 40-46, manufacture Hall effect measuring element B1 like Example 40-46, evaluate carrier concentration, and manufacture TFT element A1 The transfer characteristics were evaluated. The results are shown in Table 8.

  The oxide semiconductor obtained by the oxide semiconductor manufacturing method of the present invention can be widely used as a semiconductor thin film of a field effect transistor such as a thin film transistor.

Although several embodiments and / or examples of the present invention have been described in detail above, those skilled in the art will appreciate that these exemplary embodiments and / or embodiments are substantially without departing from the novel teachings and advantages of the present invention. It is easy to make many changes to the embodiment. Accordingly, many of these modifications are within the scope of the present invention.
The entire contents of the documents described in this specification are incorporated herein by reference.

Claims (19)

  Sputtering a target made of a metal oxide in a gas atmosphere containing a rare gas atom and a water molecule, wherein the content of the water molecule is 0.1 to 10% in a partial pressure ratio with respect to the rare gas atom, A film forming method for forming a thin film on a substrate.   The film forming method according to claim 1, wherein the pressure of the gas is 0.1 to 5.0 Pa.   The film forming method according to claim 1, wherein the sputtering is direct current sputtering.   The film forming method according to claim 1, wherein the sputtering is alternating current sputtering. The film forming method according to claim 3, wherein the direct current power density is 1 to 5 W / cm ² . The substrate is sequentially transferred to a position facing three or more targets arranged in parallel in the vacuum chamber at a predetermined interval,
A method of forming a thin film on the surface of the substrate by alternately applying a negative potential and a positive potential to each target from an AC power source to generate plasma on the target,
5. The film formation according to claim 4, wherein the film formation is performed while switching a target to which a potential is applied between two or more targets branched and connected to at least one of the outputs from the AC power source. Membrane method. The film forming method according to claim 4, wherein the AC power density is 5 to 20 W / cm ² .   The film forming method according to claim 4, wherein the frequency of the AC power source is 10 kHz to 1 MHz.   The film forming method according to claim 1, wherein a film forming speed in a direction perpendicular to the film forming surface of the substrate is 1 to 100 nm / min.   The film forming method according to claim 1, wherein a distance between the target and the substrate is 1 to 15 cm in a direction perpendicular to a film forming surface of the substrate.   The film forming method according to claim 1, wherein the magnetic field strength of the atmosphere is 300 to 1000 gauss. The metal oxide contains at least one element selected from the group consisting of gallium element (Ga), zinc element (Zn) and tin element (Sn), and indium element (In),
The film forming method according to claim 1, wherein the content of indium element in the target satisfies the following atomic ratio.
0.2 ≦ [In] / all metal atoms ≦ 0.8
(In the formula, [In] is the number of atoms of indium element in the target.
The total metal atom is the number of atoms of all metal atoms included in the target. ) The metal oxide contains indium element (In), gallium element (Ga) and zinc element (Zn);
The film-forming method in any one of Claims 1-11 with which content of the indium element in a target, a gallium element, and a zinc element satisfy | fills the following atomic ratio.
0 <[In] / [Ga] <0.5
0.2 <[In] / ([In] + [Ga] + [Zn]) <0.9
(In the formula, [In] is the number of atoms of indium element in the target, [Ga] is the number of atoms of gallium element in the target, and [Zn] is the number of atoms of zinc element in the target.) The metal oxide contains indium element (In), tin element (Sn), and zinc element (Zn),
The film forming method according to claim 1, wherein the contents of indium element, tin element and zinc element in the target satisfy the following atomic ratio.
0.2 <[In] / ([In] + [Sn] + [Zn]) <0.9
0 <[Sn] / ([In] + [Sn] + [Zn]) <0.5
(In the formula, [In] is the number of atoms of indium element in the target, [Sn] is the number of atoms of tin element in the target, and [Zn] is the number of atoms of zinc element in the target.)   The manufacturing method of the oxide semiconductor thin film which anneals the thin film obtained by the film-forming method in any one of Claims 1-14 at 150-400 degreeC for 5-120 minutes.   The method for manufacturing an oxide semiconductor thin film according to claim 15, wherein the annealing treatment is performed in an atmosphere containing at least oxygen.   A field effect thin film transistor element comprising an oxide semiconductor thin film obtained by the method for producing a thin film according to claim 15.   The field effect thin film transistor element according to claim 17, wherein the oxide semiconductor thin film is a channel layer. The field effect thin film transistor element according to claim 17 or 18, which has a mobility of 10 cm ² / Vs or more and a threshold voltage of -5 to 5 V.