Crystalline oxide semiconductor thin film, laminate, and sputtering target

Abstract

A crystalline oxide semiconductor thin film according to one embodiment of the present disclosure includes elemental In and elemental B. The ratio of the percentage content [atom%] of In and the percentage content [atom%] of B satisfies formula 1. The average crystal grain size in the surface as observed by an electron microscope is 0.25 µm or more.　(1): B / (In+B)≤0.20

Description

Crystalline oxide semiconductor thin film, laminate, and sputtering target

[0001] The present disclosure relates to a crystalline oxide semiconductor thin film, a laminate, and a sputtering target.

[0002] Thin film transistors (TFTs) are widely used as active elements in organic electroluminescence (EL) displays. Some TFTs use a laminate of oxide semiconductor thin films containing elements such as In (indium), Ga (gallium), and Zn (zinc). ２ O ３ However, an oxide thin film for a TFT having a bixbyite structure is known (Japanese Patent Laid-Open Publication No. 2014-098211).

[0003] JP 2014-098211 A

[0004] Patent Document 1 states that gallium oxide reduces the lattice constant of indium oxide, and that by forming indium oxide into a bixbyite structure, the intermetallic distance is reduced, thereby improving the carrier mobility of the oxide thin film. Generally, semiconductor thin films having an amorphous structure can achieve relatively high carrier mobility, but are prone to high carrier density. Semiconductor thin films having a crystalline structure with relatively large crystal grains can achieve relatively low carrier density, but are difficult to increase carrier mobility. A semiconductor thin film with low carrier density and high carrier mobility is an important factor for the operational stability of a TFT, and achieving both is required.

[0005] In view of the above circumstances, an object of the present disclosure is to provide a crystalline oxide semiconductor thin film that can improve carrier mobility while reducing carrier density.

[0006] A crystalline oxide semiconductor thin film according to one embodiment of the present disclosure contains In and B, the ratio of the In content [atomic %] to the B content [atomic %] satisfies the following formula 1, and the average crystal grain size on the surface observed with an electron microscope is 0.25 μm or more: B / (In+B)≦0.20 (1)

[0007] A crystalline oxide semiconductor thin film according to one embodiment of the present disclosure can improve carrier mobility while reducing carrier density.

[0008] FIG. 1 is an SEM image showing a portion of Test Example 1 in the examples of the present disclosure. FIG. 2 is an SEM image showing a portion of Test Example 2. FIG. 3 is an SEM image showing a portion of Test Example 3. FIG. 4 is an SEM image showing a portion of Test Example 5. FIG. 5 is an SEM image showing a portion of Test Example 6. FIG. 6 is an SEM image showing a portion of Test Example 7. FIG. 7 is an SEM image showing a portion of Test Example 8. FIG. 8 is an SEM image showing a portion of Test Example 9. FIG. 9 is an SEM image showing a portion of Test Example 10. FIG. 10 is an SEM image showing a portion of Test Example 11. FIG. 11 is an SEM image showing a portion of Test Example 12. FIG. 12 is an SEM image showing a portion of Test Example 13. FIG. 13 is an SEM image showing a portion of Test Example 9 that was heat-treated at a temperature different from that of FIG. 8. FIG. 14 is an SEM image showing a portion of Test Example 10 that was heat-treated at a temperature different from that of FIG. 9. FIG. 15 is an SEM image showing a portion of Test Example 11, which was heat-treated at a temperature different from that shown in FIG. 10 . FIG. 16 is an SEM image showing a portion of Test Example 12, which was heat-treated at a temperature different from that shown in FIG. 11 . FIG. 17 is an SEM image showing a portion of Test Example 13, which was heat-treated at a temperature different from that shown in FIG. 12 . FIG. 18 is an SEM image showing a portion of Test Example 18. FIG. 19 is an SEM image showing a portion of Test Example 19. FIG. 20 is an SEM image showing a portion of Test Example 20. FIG. 21 is an IQ map showing a portion of Test Example 18. FIG. 22 is an IQ map showing a portion of Test Example 19. FIG. 23 is an IQ map showing a portion of Test Example 20. FIG. 24 is an SEM image showing a portion of Test Example 25. FIG. 25 is an SEM image showing a portion of Test Example 26. FIG. 26 is an SEM image showing a portion of Test Example 27. FIG. 27 is an SEM image showing a portion of Test Example 28. FIG. 28 is an SEM image showing a portion of Test Example 29. FIG. 29 is an SEM image showing a portion of Test Example 32. FIG. 30 is an SEM image showing a portion of Test Example 33. FIG. 31 is an SEM image showing a portion of Test Example 34. FIG. 32 is an SEM image showing a portion of Test Example 36. FIG. 33 is an SEM image showing a portion of Test Example 37. FIG. 34 is an SEM image showing a portion of Test Example 38. FIG. 35 is an SEM image showing a portion of Test Example 39. FIG. 36 is an SEM image showing a portion of Test Example 40. FIG. 37 is an SEM image showing a portion of Test Example 41.FIG. 38 is an SEM image showing a portion of Test Example 42. FIG. 39 is an SEM image showing a portion of Test Example 43. FIG. 40 is an SEM image showing a portion of Test Example 44. FIG. 41 is an IQ map showing a portion of Test Example 39. FIG. 42 is an IQ map showing a portion of Test Example 40. FIG. 43 is an IQ map showing a portion of Test Example 41. FIG. 44 is an IQ map showing a portion of Test Example 42. FIG. 45 is an IQ map showing a portion of Test Example 43. FIG. 46 is an IQ map showing a portion of Test Example 44. FIG. 47 is a graph showing the particle size distribution of the granulated powder forming the sputtering target material. FIG. 48 is an X-ray diffraction spectrum of the sputtering target material of FIG. 47. FIG. 49 is a reflection electron microscope image of the sputtering target material of FIG. 47.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] In semiconductor thin films, carrier mobility can be improved by suppressing phonon scattering, which is the scattering process of electrons within crystal grains; electron scattering due to impurities such as oxygen vacancies and dopants; and electron scattering at crystal grain boundaries. To achieve this, suppressing defect generation due to solid-phase crystallization is considered effective. Furthermore, increasing crystallinity is required to reduce these defects. In this regard, mixing a specific gas such as hydrogen into the gas (film-forming gas) used during semiconductor thin film deposition could promote solid-phase growth of the semiconductor thin film, i.e., improve the crystallization rate and increase the crystal grain size. However, this may complicate the manufacturing process and increase the manufacturing costs of the semiconductor thin film. Therefore, it is preferable to promote solid-phase growth by adding an element to the semiconductor thin film. While adding Ga (gallium) to the semiconductor thin film is also effective, there is a concern that stable distribution may be difficult due to the rare metal. The inventors of the present invention thoroughly investigated Ga-containing thin films as well as additive elements and the amounts of additive elements that can be supplied relatively stably and promote the solid-phase growth of semiconductor thin films, and completed the present invention.

[0011] (1) A crystalline oxide semiconductor thin film according to one embodiment of the present disclosure contains In and B, the ratio of the In content [atomic %] to the B content [atomic %] satisfies the following formula 1, and the average crystal grain size on the surface observed with an electron microscope is 0.25 μm or more: B / (In+B)≦0.20 (1)

[0012] The crystalline oxide semiconductor thin film (hereinafter also referred to as the first crystalline thin film) contains the elements In (indium) and a predetermined amount of B (boron), and therefore solid-phase growth is promoted by heat treatment during the manufacturing process, and the carrier density can be reduced while the carrier mobility can be improved. Furthermore, by setting the average crystal grain size of the first crystalline thin film to 0.25 μm or more, the carrier density can be further reduced while the carrier mobility can be further improved.

[0013] (2) In the above (1), the first crystalline thin film may further contain Fe (iron). When the first crystalline thin film contains Fe, the crystallinity can be improved.

[0014] (3) In the above (1) or (2), the peak value detected by μPCD may be four or more times the peak value before crystallization by heat treatment. By making the peak value detected by μPCD of the first crystalline thin film crystallized by heat treatment four or more times the value before crystallization, the carrier density can be further reduced and the carrier mobility can be further improved.

[0015] (4) A laminate according to one aspect of the present disclosure is a laminate for forming a thin film transistor, and includes an amorphous oxide semiconductor thin film and any one of the crystalline oxide semiconductor thin films described in (1) to (3) above.

[0016] The stack (hereinafter also referred to as the first stack) is formed by stacking an amorphous oxide semiconductor thin film (hereinafter also referred to as the first amorphous thin film) and the first crystalline thin film, thereby improving the reliability of promoting solid-phase growth.

[0017] (5) In the above (4), the amorphous oxide semiconductor thin film may contain In and B. When the first amorphous thin film contains In and B, the crystallinity of the first crystalline thin film can be further improved.

[0018] (6) A sputtering target material according to one aspect of the present disclosure forms a crystalline oxide semiconductor thin film according to any one of (1) to (3) above.

[0019] The first crystalline thin film can be easily produced by using a sputtering target formed from the sputtering target material.

[0020] (7) A crystalline oxide semiconductor thin film according to an embodiment of the present disclosure contains In, has a crystal grain size of 0.30 μm or more as measured by electron backscatter diffraction, the (111) plane of the crystalline phase is aligned in the Z-axis direction, and has an IQ map with a white / black region ratio of 0.5 or more in the direction normal to the Z-axis.

[0021] The crystalline oxide semiconductor thin film (hereinafter also referred to as the second crystalline thin film) has a relatively large crystal grain size of 0.3 μm or more, and the (111) plane of the crystalline phase is aligned in the Z-axis direction to reduce oxygen vacancies, thereby reducing carrier density and improving carrier mobility. Furthermore, the second crystalline thin film has an IQ (Image Quality) map in the direction normal to the Z-axis with a white / black region ratio of 0.5 or more. The black regions in the IQ map are regions with a relatively large number of defects, i.e., an increase in the proportion of the white regions indicates a decrease in the number of defects. Since the second crystalline thin film has a white / black region ratio of 0.5 or more, the number of defects is small, and carrier mobility can be easily improved. Here, "the (111) planes of the crystal plane are aligned in the Z-axis direction" means that there are many (111) planes in the crystal plane when viewed in the Z-axis direction, and specifically means that the ratio of the area including the (111) planes in the inverse pole figure IPF map of the crystal plane is more than 0.50, or 0.55 or more.

[0022] (8) In the above (7), the crystalline oxide semiconductor thin film may further contain element B. By containing B, it is possible to improve the ease of improving carrier mobility while reducing carrier density.

[0023] (9) In the above (8), the ratio of the In content [atomic %] to the B content [atomic %] may satisfy the following formula 2. By containing B in the second crystalline thin film so as to satisfy the following formula 2, it is possible to efficiently reduce the carrier density while improving the carrier mobility: B / (In+B)≦10 (2)

[0024] (10) A stack according to an embodiment of the present disclosure includes a stack of an amorphous oxide semiconductor thin film containing In and Ga, and a crystalline oxide semiconductor thin film containing In and either Al or Ga.

[0025] The stack (hereinafter also referred to as the third stack) is formed by stacking an amorphous oxide semiconductor thin film containing an In element and a Ga element (hereinafter also referred to as the third amorphous thin film) and a crystalline oxide semiconductor thin film containing an In element and an Al element or a Ga element (hereinafter also referred to as the third crystalline thin film). Therefore, solid-phase growth is promoted in the third crystalline thin film, improving crystallinity, and the carrier mobility can be improved while reducing the carrier density in the third stack.

[0026] (11) In the above (10), the laminate may further include the amorphous oxide semiconductor thin film laminated on the crystalline oxide semiconductor thin film. By further laminating the third amorphous thin film, the crystallinity of both surfaces of the third crystalline thin film can be improved.

[0027] (12) In the above (10) or (11), the ratio of the In content [atomic %] to the Al or Ga content [atomic %] in the crystalline oxide semiconductor thin film may satisfy the following formula 3 or 4. When the Al or Ga content in the third crystalline thin film satisfies the following formula 3 or 4, the reliability of the carrier density reduction effect and carrier mobility improvement effect of the third stack can be improved. Al / (In+Al)≦10 (3) Ga / (In+Ga)≦15 (4)

[0028] (13) In any one of (10) to (12), the crystalline oxide semiconductor thin film may have a crystal grain size of 0.3 μm or more as measured by electron backscatter diffraction, a (111) plane of the crystalline phase aligned in the Z-axis direction, and a white / black area ratio in an IQ map in the direction normal to the Z-axis of 0.5 or more. This can further improve the reliability of the carrier density reduction effect and the carrier mobility improvement effect in the third stack.

[0029] (14) A stack according to an aspect of the present disclosure includes an amorphous oxide semiconductor thin film containing In and Ga and a crystalline oxide semiconductor thin film containing In and B stacked together.

[0030] The stack (hereinafter also referred to as the fourth stack) is formed by stacking an amorphous oxide semiconductor thin film containing In and Ga elements (hereinafter also referred to as the fourth amorphous thin film) and a crystalline oxide semiconductor thin film containing In and B elements (hereinafter also referred to as the fourth crystalline thin film). Therefore, solid-phase growth is promoted in the fourth crystalline thin film, improving crystallinity, and the carrier mobility can be improved while reducing the carrier density in the fourth stack.

[0031] (15) In the above (14), the amorphous oxide semiconductor thin film may be further laminated on the crystalline oxide semiconductor thin film. By further laminating the amorphous oxide semiconductor thin film, the crystallinity of both surfaces of the fourth crystalline thin film can be improved.

[0032] (16) In the above (14) or (15), the amorphous oxide thin film may further contain an element of Zn or B. When the amorphous oxide thin film further contains an element of Zn or B, deterioration of the amorphous oxide thin film can be suppressed.

[0033] (17) A sputtering target material according to one embodiment of the present disclosure includes elements In and B, and is formed from an oxide sintered body in which the ratio of the In content [atomic %] to the B content [atomic %] satisfies the above formula 2.

[0034] By using this sputtering target material, a thin film with high carrier mobility can be easily obtained.

[0035] (18) A sputtering target material according to one embodiment of the present disclosure is formed from an oxide sintered body containing an In element and an Al element or a Ga element, and in which the ratio of the In content [atomic %] to the Al or Ga content [atomic %] satisfies the above formula 3 or 4.

[0036] By using this sputtering target material, a thin film with high carrier mobility can be easily obtained.

[0037] (19) A sputtering target material according to one aspect of the present disclosure is formed from an oxide sintered body containing In, B, and Ga, and having a B content [atomic %] that satisfies the following formula 5: 0.1≦B≦40 (5)

[0038] By using the sputtering target, an amorphous oxide semiconductor thin film for forming a stack having high carrier mobility can be easily obtained.

[0039] The average crystal grain size refers to a calculation of the average crystal grain size by drawing lines 2.5 μm long in three or more locations on an image obtained using an electron microscope and electron backscatter diffraction (EBSD). Among the particles (crystals) on these lines, the number of crystals with a misorientation of 2° or more that is thought to affect carrier mobility was counted, and the average crystal grain size of these crystals was calculated. Specifically, crystals were detected from an orientation mapping (a map derived from the orientation of each pixel) derived using the EBSD method, and the drawings of these crystals were extracted and counted. While some conventional methods have targeted crystals with a misorientation of approximately 10° or more, the present disclosure targets crystals with a misorientation of 2° or more, which tend to result in a small average crystal grain size, by tightening the conditions. "Crystalline" means that crystal grains are visible when observed with an SEM at 10,000 magnifications, and "amorphous" means that no crystal grains are visible when observed with an SEM at 10,000 magnifications.

[0040] [Details of the embodiment of the present disclosure] Hereinafter, the embodiment of the present disclosure will be described in detail with reference to the drawings as appropriate. Note that with respect to the numerical values ​​described in this specification, it is possible to adopt only one of the upper limit value and the lower limit value described, or to arbitrarily combine the upper limit value and the lower limit value. In this specification, all numerical ranges from the upper limit value to the lower limit value that can be combined are described as suitable ranges.

[0041] First Embodiment The crystalline oxide semiconductor thin film contains In and B, the ratio of the In content [atomic %] to the B content [atomic %] satisfies the following formula 1, and the average crystal grain size on the surface observed with an electron microscope is 0.25 μm or more: B / (In+B)≦0.20 (1)

[0042] The first crystalline thin film is preferably entirely crystalline, and at least partly (or partially) crystalline. That is, the oxide forming the first crystalline thin film is entirely or partially crystalline. The crystallinity of the first crystalline thin film can improve carrier mobility while reducing carrier density.

[0043] The first crystalline thin film may further contain element Fe, which can promote solid-phase growth by heat treatment at a relatively low temperature.

[0044] (In) In is an element that improves the crystallization rate and contributes to improving the carrier mobility. The larger the In content, the more the carrier mobility of the first crystalline thin film improves, and the more the conductivity improves. In is contained in the first crystalline thin film. ２ O ３ The upper limit of the In content relative to the total metal elements contained in the first crystalline thin film is less than 100 atomic %. The lower limit of the content is not particularly limited and may be, for example, 75 atomic % or 80 atomic %. By setting the In content within the above range, sufficient carrier mobility can be obtained.

[0045] (B) B is an element that increases the crystal grain size during solid phase growth and contributes to reducing the carrier density. ２ O ３ and B(OH) ３ (boric acid: oxoacid of boron) ２ O ３ is a material that is difficult to crystallize, ２ O ３ It is believed that the crystallization temperature of B(OH) is shifted to the higher temperature side, resulting in an increase in the crystal grain size. ３ It is believed that B has the effect of passivating the above defects. ２ O ３ By entering the gaps between the first and second crystalline thin films, B also contributes to improving carrier mobility. The B content in the first crystalline thin film satisfies the above formula 1. The lower limit of the B content in the first crystalline thin film is more than 0 atomic %.

[0046] (Fe) Fe is considered to be an element that contributes to improving crystallinity. The upper limit of the content of Fe relative to the total of the metal elements contained in the first crystalline thin film is preferably 2 atomic %, more preferably 1 atomic %. When the first crystalline thin film contains Fe in the above range, FeO and B ２ O ３ This facilitates the formation of a complex, which acts as a nucleus for crystals, thereby effectively contributing to crystallization.

[0047] In the first crystalline thin film, elements other than those mentioned above are O (oxygen) and inevitable impurities. The inevitable impurities may be contained due to raw materials, materials, manufacturing equipment, etc. Examples of such inevitable impurities include Pb (lead), Si (silicon), Ni (nickel), Ti (titanium), Mg (magnesium), Cr (chromium), and Zr (zinc). The content of the inevitable impurities in the first crystalline thin film is preferably 0.02 atomic % or less for each element, and more preferably 0.01 atomic % or less. The content rates of In, B, and Fe in the first crystalline thin film can also be considered as the proportions of all elements excluding O.

[0048] The lower limit of the film thickness of the first crystalline thin film is not particularly limited and may be 30 nm, 35 nm, or 40 nm. The upper limit of the film thickness is not particularly limited and may be 150 nm, 125 nm, or 100 nm. By setting the film thickness within the above range, productivity of the first crystalline thin film can be improved.

[0049] The average crystal grain size at the surface of the first crystalline thin film observed with an electron microscope is 0.25 μm or more. The lower limit of the average crystal grain size may be 0.35 μm or 0.45 μm. The upper limit of the average crystal grain size is not particularly limited and may be 1.00 μm. By setting the average crystal grain size within the above range at a film thickness within the above range, grain boundary defects can be effectively suppressed and carrier mobility can be improved.

[0050] The peak value of the first crystalline thin film detected by the μPCD method is preferably at least four times the peak value before crystallization. That is, the peak value of the first crystalline thin film crystallized by film formation and heat treatment is preferably at least four times the peak value before film formation and heat treatment (before crystallization). The lower limit of the ratio of the peak value after crystallization to the peak value before crystallization may be 5 or 6. The upper limit of the ratio is not particularly limited and may be, for example, 10. The peak value is obtained from an attenuation waveform obtained by measuring the first crystalline thin film by the μPCD method and graphing the values. When the ratio of the peak value after crystallization to the value before crystallization is within the above range, a sufficient effect of reducing carrier density and a sufficient effect of improving carrier mobility can be obtained.

[0051] [Laminate] The first crystalline thin film can be a laminate (first laminate) for forming a thin film transistor by being laminated on an amorphous oxide semiconductor thin film (first amorphous thin film). The first laminate is a laminate for forming a thin film transistor, and includes a first amorphous thin film and the first crystalline thin film laminated on the first amorphous thin film.

[0052] The first amorphous thin film preferably contains the element In and the element B. The first amorphous thin film may further contain the element Ga and the element Zn.

[0053] The ratio of the content [atomic %] of at least one of Ga and Zn to the content [atomic %] of In in the first amorphous thin film is preferably 0.5 to 1.5. The ratio of the content [atomic %] of B to the content [atomic %] of In in the first amorphous thin film is preferably 0.5 to 2.

[0054] By forming the first crystalline thin film on the first amorphous thin film, the average crystal grain size tends to become smaller, but the crystallinity can be improved. This is because the In of the first crystalline thin film is increased by laminating the first crystalline thin film on the first amorphous thin film. ２ O ３ This is thought to be because the number of crystal nuclei formed at the interface between the first amorphous thin film and the second amorphous thin film changes, causing differences in the growth of crystal grains and resulting in changes in crystal grain size. Specifically, the presence of many crystal nuclei at the interface makes it easier for crystal grains to collide with each other, which is thought to reduce the average crystal grain size but suppress orientation irregularities.

[0055] [Sputtering target material] The first crystalline thin film is preferably formed using a sputtering target. That is, the first crystalline thin film is preferably formed by a sputtering method using a sputtering target. After film formation, a heat treatment is performed to improve the film quality.

[0056] The sputtering target for producing the first crystalline thin film contains the elements In and B, and is formed from a sputtering target material whose contents satisfy the above formula 1. The sputtering target material may further contain Fe. Elements other than those mentioned above in the sputtering target material are unavoidable impurities. The sputtering target material is formed as an oxide sintered body.

[0057] The method for forming the first crystalline thin film using the sputtering target is not particularly limited, and may be a known method. For example, the first crystalline thin film may be obtained by forming the film using a mixed gas of argon and oxygen as a film forming gas, with an oxygen partial pressure of 24 / 1 sccm (4%), at room temperature (normal temperature), and then heat-treating the film in an air atmosphere at 250°C or higher and 400°C or lower for 0.5 hours or higher and 2 hours or lower.

[0058] Second Embodiment A crystalline oxide semiconductor thin film (second crystalline thin film) according to another embodiment of the present disclosure contains In, has crystal grains with a grain size of 0.30 μm or more as measured by electron backscatter diffraction, has the (111) plane of the crystalline phase aligned in the Z-axis direction, and has a white region / black region ratio of 0.5 or more in an IQ map in the direction normal to the Z-axis.

[0059] The second crystalline thin film may further contain the element B. Since B bonds relatively strongly with O, it is possible to suppress the loss of O. Furthermore, since B has high hygroscopicity, it is possible to reduce the difference between the air atmosphere and the water vapor treatment in the heat treatment in the manufacturing process of the second crystalline thin film.

[0060] The amount of B added should be such that the ratio of the In content [atomic %] to the B content [atomic %] satisfies the following formula 2. By adding B so as to satisfy the following formula 2, solid-phase growth can be efficiently promoted: B / In+B≦10 (2)

[0061] The lower limit of the film thickness of the thin film is not particularly limited and may be 5 nm or 10 nm. The upper limit of the film thickness is not particularly limited and may be 120 nm, 100 nm, 80 nm, or 60 nm. By setting the film thickness within the above range, an increase in the crystal grain size can be promoted.

[0062] When the film thickness is 25 nm or less, or 20 nm, the upper limit of the formula 2 is preferably set to 5.

[0063] [Sputtering Target Material] The second crystalline thin film is preferably formed using a sputtering target, that is, the second crystalline thin film is preferably formed by a sputtering method using a sputtering target.

[0064] The sputtering target material forming the sputtering target contains In and B as elements, and the contents thereof satisfy the above formula 2. The sputtering target material is formed as an oxide sintered body.

[0065] The upper limit of the formula 2 may be set to 5 depending on the heat treatment temperature after film formation using the sputtering target (for example, 350° C. or higher).

[0066] Third Embodiment A stack (the third stack) according to another embodiment of the present disclosure includes a stack of an amorphous oxide semiconductor thin film containing In and Ga, and a crystalline oxide semiconductor thin film containing In and either Al or Ga.

[0067] (Ga) The element Ga (gallium) improves the oxygen barrier function of the above-mentioned thin films (amorphous oxide semiconductor thin film and crystalline oxide semiconductor thin film), thereby suppressing deterioration.

[0068] (Al) Al (aluminum) is H ２ and H ２ This can prevent O from penetrating into the third crystalline thin film, thereby improving the light stress resistance of the third crystalline thin film.

[0069] The third laminate may further include the third amorphous thin film laminated on the third crystalline thin film. That is, the third laminate may be a three-layer laminate in which the third amorphous thin film is laminated on both surfaces of the third crystalline thin film. By laminating the third amorphous thin film on both surfaces of the third crystalline thin film, the crystallinity of both surfaces can be improved, and carrier mobility can be easily improved.

[0070] By laminating the third crystalline thin film on the third amorphous thin film, the crystal size tends to decrease, but the orientation in the (111) plane improves, thereby improving carrier mobility.

[0071] It is preferable that the ratio of the In content [atomic %] to the Al or Ga content [atomic %] in the third crystalline thin film satisfies the following formula 3 or 4. If the Al or Ga content is increased so as not to satisfy formula 3 or 4, a heat treatment at a high temperature will be required in the manufacturing process of the third crystalline thin film, which may reduce productivity. Al / (In+Al)≦10 (3) Ga / (In+Ga)≦15 (4)

[0072] The third crystalline thin film preferably has crystal grains having a grain size of 0.3 μm or more as measured by electron backscatter diffraction, the (111) plane of the crystalline phase being aligned in the Z-axis direction, and the white area / black area ratio in an IQ map in the direction normal to the Z-axis being 0.5 or more.

[0073] [Sputtering Target Material] The third crystalline thin film may be formed by using a sputtering target, that is, by sputtering using a sputtering target.

[0074] The sputtering target material forming the sputtering target contains an In element and an Al element or a Ga element, and the ratio of the In content [atomic %] to the Al or Ga content [atomic %] satisfies the above formula 3 or 4. The sputtering target material is formed as an oxide sintered body.

[0075] Fourth Embodiment A stack (fourth stack) according to another embodiment of the present disclosure includes a stack of an amorphous oxide semiconductor thin film (fourth amorphous thin film) containing In and Ga, and a crystalline oxide semiconductor thin film (fourth crystalline thin film) containing In and B.

[0076] The fourth amorphous thin film may be further laminated on the fourth crystalline thin film. The fourth amorphous oxide thin film may further contain Zn or B.

[0077] (Zn) Zn is H ２ and H ２ The penetration of O into the fourth amorphous thin film is suppressed.

[0078] [Sputtering Target Material] The fourth amorphous thin film may be formed using a sputtering target, that is, the fourth amorphous thin film may be formed by a sputtering method using a sputtering target.

[0079] The sputtering target material forming the sputtering target contains an In element, a B element, and a Ga element, and is formed from an oxide sintered body in which the B content [atomic %] satisfies the following formula 5: 0.1≦B≦40 (5)

[0080] The sputtering target material preferably has substantially equal contents of In, B, and Ga (In:B:Ga=1:1:1).

[0081] [Other Embodiments] The above-described embodiments do not limit the configuration of the present invention. Therefore, the above-described embodiments may include omissions, substitutions, or additions of components based on the description in this specification and common general technical knowledge, and all of these should be construed as falling within the scope of the present invention.

[0082] The present invention will be described in detail below based on examples, but the present invention should not be construed as being limited by the descriptions in these examples.

[0083] First Example An oxide semiconductor thin film containing In, an oxide semiconductor thin film containing In and Ga, and an oxide semiconductor thin film containing In and B were formed on a substrate made of glass. ２ The gas pressure was 1 m / Torr with a flow rate of 24 / 1 sccm, an oxygen partial pressure of 4 vol% or 60 vol%, and a stage temperature of 100 m / Torr. The stage temperature was room temperature, and films were deposited to a thickness of 40 nm or 100 nm by sputtering at DC 250 W. After deposition, the carrier mobility and carrier density were measured (Hall measurement) for films that were heat-treated in an air atmosphere and those that were not heat-treated, and compared. The results are shown in Table 1. In Table 1, "-" indicates that the measurement was not performed, and "O.R." indicates that the measurement was below the measurement limit (over range).

[0084]

[0085] Comparing the carrier mobilities in Table 1, at a film thickness of 100 nm and a heat treatment temperature of 350° C., Test Examples 3 and 4, which contain B, are relatively high, while Test Examples 1 and 2, which do not contain B, are relatively low. At a film thickness of 40 nm and a heat treatment temperature of 350° C., Test Example 10, which contains B, is the highest, while Test Examples 5 to 9, which do not contain B, are relatively low.

[0086] Comparing the carrier density in Table 1, the carrier density of the samples that were heat-treated at 350°C compared to the samples that were not heat-treated was reduced in Test Example 1, Test Examples 3 to 7, and Test Examples 10 to 12, and increased in Test Example 9. Test Example 10, which contains B, was further reduced by the heat treatment at 400°C. Test Example 11, which contains B and Fe, had a lower carrier density than Test Example 10, which contains only B.

[0087] [SEM Observation] The surface of each thin film was observed using a backscattered electron image under an electron microscope. Figure 1 shows surface images of Test Example 1, Test Example 2, and Test Example 3, all of which were heat-treated at 350°C. Test Example 1, which did not contain B, had an average crystal grain size of 0.025 µm, while Test Example 3, which contained B, had an average crystal grain size of 0.63 µm.

[0088] 4 to 12 show surface images of thin films heat-treated at 350° C. Fig. 4 is an image of Test Example 5, Fig. 5 is an image of Test Example 6, Fig. 6 is an image of Test Example 7, Fig. 7 is an image of Test Example 8, Fig. 8 is an image of Test Example 9, Fig. 9 is an image of Test Example 10, Fig. 10 is an image of Test Example 11, Fig. 11 is an image of Test Example 12, and Fig. 12 is an image of Test Example 13.

[0089] Among the test examples not containing B, crystal grains were observed in test examples 5 to 8. The average crystal grain size was 0.037 μm in test example 5 and 0.16 μm in test example 7. The average crystal grain size in test example 6 was 0.23 μm, but as described below, crystallization began at temperatures lower than 350°C. In test example 8, the average crystal grain size was 0.03 μm, but there was no change from before heat treatment (crystallization had occurred before heat treatment). In test example 9, crystal grains were not observed, but crystal grains were observed after heat treatment at 400°C. In test example 9, which was heat treated at 400°C, the average crystal grain size was relatively large at 0.56 μm, but crystalline and amorphous phases were mixed (fine crystal grains were mixed among relatively large crystal grains). Figure 13 shows test example 9, which was heat treated at 400°C.

[0090] In the test examples containing B, in test example 10, no crystal grains were observed after heat treatment at 350°C, but crystal grains of 0.91 μm were observed after heat treatment at 400°C. In test example 11, which contained B and Fe, the average crystal grain size was 0.36 μm after heat treatment at 350°C and 0.44 μm after heat treatment at 400°C. In test example 12, the average crystal grain size was 0.53 μm after heat treatment at 350°C and 0.71 μm after heat treatment at 400°C. In test example 13, no crystal grains were observed after heat treatment at 350°C, but crystal grains with an average crystal grain size of 0.71 μm were observed after heat treatment at 400°C. Figures 14, 15, 16, and 17 show test examples 10, 11, 12, and 13, respectively, which were heat treated at 400°C.

[0091] [μPCD Measurement] In Test Examples 5 to 11, the average crystal grain size was measured and the peak value of the μPCD measurement was extracted after heat treatment at 350°C, or after heat treatment at 400°C in the case of amorphous films heat treated at 350°C. The results, the estimated crystallization temperature, and the state (shape) of the crystals on the thin film surface are shown in Table 2. In Table 2, "facet" under "crystal state" means that relatively fine (small) granular crystals were observed to be spread out on the thin film surface, and "dendrite" means that relatively coarse (large) dendritic crystals were observed on the thin film surface. In Table 2, "-" means that no measurement was performed.

[0092]

[0093] In Test Example 5, many crystal nuclei were generated at low temperatures, and crystallization was promoted at temperatures below 250°C. However, it is believed that the crystal grain size was reduced due to frequent collisions between adjacent crystals. However, the crystal grains obtained after heat treatment at 250°C had high crystallinity and a large peak value (just over 2000 mV).

[0094] In Test Example 6, which contained a small amount of Ga, the crystallization behavior was similar to that of Test Example 5, but the crystallization temperature increased to about 250°C, and the average crystal grain size expanded. In Test Example 7, which contained a larger amount of Ga, the crystallization temperature increased to about 350°C, and the average crystal grain size increased slightly, and the crystal state became streamlined like fireworks. On the other hand, the peak value of Test Example 7 was lower than that of Test Example 6. In Test Example 8, which contained the same amount of Ga as Test Example 7 and had an oxygen partial pressure of 60% by volume, no change in crystal grain size was observed due to heat treatment. In Test Example 9, which contained a larger amount of Ga than Test Example 7, the crystallization temperature was further increased, and streamlined crystals became dominant. However, the crystallization temperature became too high, and amorphous regions were observed in some areas even after heat treatment at 400°C.

[0095] It is believed that the high oxygen content in the deposition gas in Test Example 8 resulted in the formation of many crystal nuclei, resulting in microcrystallization at a low temperature. This is also suggested by the small crystal grains in the SEM image at 350°C (see FIG. 7) and the high peak value in the non-thermal treatment.

[0096] In Test Example 10 containing B, the crystal grains were in a dendritic and faceted state as in Test Example 7, and the average crystal grain size increased due to the high crystallization temperature. On the other hand, the amorphous regions observed in Test Example 7 were not observed in Test Example 10. In the thin film 11 containing B and Fe, crystallinity similar to that of Test Example 10 could be obtained by heat treatment at a relatively low temperature.

[0097] [Laminate] A laminate was formed on a glass substrate, and Hall measurement was performed to compare the laminates. The laminate was formed by forming an amorphous oxide semiconductor thin film (first amorphous thin film) with a thickness of 10 nm on a glass substrate, and then laminating a crystalline oxide semiconductor thin film (thin film) on this first amorphous thin film. The ratio of the contents of the elements contained in the first amorphous thin film shown in Table 3 was 1:1:1 in all cases. The thin film and the first amorphous thin film were formed under the film formation conditions of Ar / O ２ The gas pressure was 1 m / Torr, with a flow rate of 24 / 1 sccm, an oxygen partial pressure of 4 volume %, and a stage temperature of 250 W DC, and the first amorphous thin film was deposited to a thickness of 10 nm and the second amorphous thin film was deposited to a thickness of 40 nm by sputtering. The heat treatment after deposition was carried out for 1 hour in an air atmosphere at 350°C or 400°C. The elements contained in the thin film, the elements contained in the first amorphous thin film, the heat treatment temperature, the results of the Hall measurement, and the results of the crystallinity of the thin film for each test example are shown in Table 3.

[0098]

[0099] Crystallization was not confirmed in either of the thin films of Test Example 14 or Test Example 15. By increasing the heat treatment temperature, the carrier density decreased in Test Example 14, but increased in Test Example 15. On the other hand, by increasing the heat treatment temperature, the carrier mobility improved in both Test Examples 14 and 15. In Test Examples 16 and 17, in which the first amorphous thin film contained B, crystallization was confirmed, the carrier density was relatively low, and the carrier mobility was also favorable. This is thought to be because the inclusion of In and B in the first amorphous thin film modulated the interface between the thin film and the first amorphous thin film, thereby controlling interfacial defects that serve as nuclei for crystallization.

[0100] Second Example An oxide semiconductor thin film containing In and an oxide semiconductor thin film containing In and 1 atomic % of B were formed on a substrate made of glass. ２The conditions were: 1.5 / 1 sccm, 2.5 / 1 sccm, and 1 m / Torr gas pressure. The stage temperature was room temperature, and films were formed to thicknesses of 15 nm, 23 nm, or 40 nm by sputtering at DC 250 W. After film formation, the films were heat-treated at 350°C in an air atmosphere or a water vapor atmosphere. The carrier mobility and carrier density of each thin film formed were measured (Hall measurement) and compared. The carrier mobility was 14 cm ２ The results are shown in Table 4. In Table 4, "-" indicates that the measurement was not performed.

[0101]

[0102] In Test Example 18, where the film thickness is 15 nm, the carrier mobility is 14 cm ２ / Vs was not achieved. In Test Examples 22 and 23, where the film thickness was increased to 23 nm and 40 nm, the carrier mobility further decreased. On the other hand, Test Example 19 shows that the carrier mobility was sufficiently improved when the film was heated in a water vapor atmosphere during deposition. Furthermore, Test Examples 20, 21, and 24, where 1 atomic % B was added, showed sufficient carrier mobility improvement even with a film thickness of 15 nm. The crystal grain size in Table 4 was calculated using the Number method. Larger grain sizes tend to result in higher carrier mobility. When IPF maps were created for the crystal planes, it was found that for samples with high carrier mobility, the (111) plane tended to be more dominant in the IPF(Z) map than in the IPF(X) and IPF(Y) maps. SEM images of the oxide semiconductor thin films of Test Examples 18 to 20 are shown in Figures 18 to 20. IQ maps of the oxide semiconductor thin films of Test Examples 18 to 20 are shown in Figures 21 to 23.

[0103] An oxide semiconductor thin film containing In and an oxide semiconductor thin film containing In and B were formed on a glass substrate. The B content was varied in the range of 1 to 10 atomic %. The film formation conditions were Ar / O ２ The conditions were: 1) SiO2 / 1 sccm, 2) SiO2 / 1 sccm, and 3) SiO2 / 1 Torr. The stage temperature was room temperature, and the films were deposited to a thickness of 15 nm or 40 nm by sputtering at DC 250 W. After deposition, the films were heat-treated in an air atmosphere at 350°C. The results of the crystal layer of each thin film are shown in Table 5.

[0104]

[0105] 24 to 28 are SEM images of Test Examples 25 to 29. It can be seen that the grain size increases as the amount of B added increases.

[0106] Example 3 An oxide semiconductor thin film containing In and 8.5 atomic % Al, an oxide semiconductor thin film containing In and 10.0 atomic % Ga, and a laminate formed by laminating these thin films on an underlayer containing In, Ga, and Zn in a ratio of 1:1:1 were formed and compared. Each of the thin films and the laminate was formed on a substrate made of glass. The film formation conditions for each of the thin films and the underlayer were a film formation gas of Ar / O ２ The flow rate was 24 / 1 sccm, and the gas pressure was 1 m / Torr. The stage temperature was room temperature, and the film was formed to a thickness of 15 nm or 40 nm by sputtering at DC 250 W. After film formation, the film was heat-treated at 350°C in an air atmosphere. The carrier mobility and carrier density of the formed thin film and the laminate were measured (Hall measurement) and compared. The carrier mobility was 14 cm ２ The results are shown in Table 6. In Table 6, "-" indicates that the measurement was not performed.

[0107]

[0108] In a thin film containing In and Al and having a thickness of 15 nm (Test Example 30), the carrier mobility was 14 cm ２ / Vs or more, but by forming a laminate (Test Example 31), the carrier mobility was increased to 14 cm ２ However, when the film thickness was increased to 100 nm (Test Example 35), the carrier mobility decreased. Even when a thin film containing In and Ga was used as a laminate, the carrier mobility was 14 cm ２ / Vs or more (Test Examples 37 and 38). In Test Example 36, the grain size and the orientation of the (111) plane could not be confirmed because the grains were so small.

[0109] SEM images of Test Examples 32, 33, and 34 are shown in Figures 29, 30, and 31, and SEM images of Test Examples 36, 37, and 38 are shown in Figures 32, 33, and 34. For thin films containing In and Al and having a thickness of 40 nm (Test Examples 32 and 33), the grain size in the single layer was larger than the grain size in the laminate (Figures 29 and 30). This tendency was also observed for thin films containing In and Ga and having a thickness of 40 nm (Test Examples 37 and 38) (Figures 33 and 34). For the single layer thin films containing In and Al (Test Examples 32 and 34), the grain size decreased as the film thickness increased (Figures 29 and 31).

[0110] Comparing Test Example 34 and Test Example 35, in which the oxide semiconductor thin film had a thickness of 100 nm, the carrier mobility of the stack (Test Example 35) was lower. This is thought to be because increasing the film thickness reduced the crystal grain size, and the stack further reduced the crystal grain size. When Test Example 32 and Test Example 33 were evaluated by EBSD, it was confirmed that the orientation of the (111) plane was more aligned in the Z-axis direction in the oxide semiconductor thin film of Test Example 33 (stacked body). For this reason, the thickness of the oxide semiconductor thin film in the stacked body should be 100 nm or less, preferably 80 nm or less, and more preferably 60 nm or less.

[0111] Fourth Example An oxide semiconductor thin film containing In, an oxide semiconductor thin film containing In and B, an oxide semiconductor thin film containing In and 8.5 atomic % Al, and stacked bodies formed by stacking these thin films on an underlayer were formed and compared. Three types of underlayer films were prepared: one containing In, Ga, and Zn in a ratio of 1:1:1, one containing In, Ga, and B in a ratio of 1:1:1, and one containing In, B, and Zn in a ratio of 1:1:1. Each thin film and stacked body was formed on a glass substrate. The film formation conditions for the above thin films and the underlayer thin films were a film formation gas of Ar / O ２The flow rate was 24 / 1 sccm, and the gas pressure was 1 m / Torr. The stage temperature was room temperature, and the film was formed to a thickness of 15 nm or 40 nm by sputtering at DC 250 W. After film formation, the film was heat-treated at 350°C in an air atmosphere. The carrier mobility and carrier density of the formed thin film and the laminate were measured (Hall measurement) and compared. The carrier mobility was 14 cm ２ The results are shown in Table 7. In Table 7, "-" indicates that the measurement was not performed.

[0112]

[0113] In a thin film containing In and Al and having a thickness of 100 nm, the crystallinity is faceted in a single layer (Test Example 34), but the carrier mobility is 14 cm ２ By laminating the layer on a 40 nm thick underlayer containing In, Ga, and Zn (Test Example 36), the crystal grains became small (below the measurement limit), and the mobility decreased.

[0114] In a thin film containing In and having a thickness of 15 nm, the carrier mobility was improved by laminating the thin film on an underlayer containing In, Ga, and Zn (Test Example 39) compared to a single layer (Test Example 18). On the other hand, the carrier mobility was not improved when the thin film was laminating on an underlayer containing In, Ga, and B (Test Example 40).

[0115] In a thin film containing In and 1 atomic % B and having a thickness of 15 nm, the carrier mobility was improved by laminating the thin film on an underlayer containing In, Ga, and Zn, and on an underlayer containing In, Ga, and B (Test Examples 41 and 42) compared to a single layer (Test Example 21). On the other hand, the carrier mobility was not improved when the thin film was laminating the thin film on an underlayer containing In, B, and Zn (Test Example 43).

[0116] SEM images of the laminate surfaces of Test Examples 39 to 44 are shown in Figures 35 to 40, and IQ maps are shown in Figures 41 to 46. Although SEM images are not available for the thin films containing In and Al, the grain size of the crystals was smaller when laminated on an underlayer compared to a single layer. The crystallinity of the thin film containing In was dendritic when it was a single layer (Test Example 18), but became faceted when laminated on an underlayer containing In, Ga, and Zn (Test Example 39) (Figure 35). On the other hand, when laminated on an underlayer containing In, Ga, and B (Test Example 40), it became dendritic (Figure 36).

[0117] The crystallinity of the thin film containing In and B was dendritic when it was a single layer (Test Example 21). When the B content was 1 atomic %, it also remained dendritic when laminated on an underlayer containing In, Ga, and Zn (Test Example 41) ( FIG. 37 ). When the B content was 2 atomic %, it became an intermediate shape between dendrites and facets when laminated on an underlayer containing In, Ga, and Zn (Test Example 45). Even when the B content was 1 atomic %, it became facets when laminated on an underlayer containing In, Ga, and B (Test Example 42). On the other hand, it remained dendritic when laminated on an underlayer containing In, B, and Zn (Test Example 43).

[0118] When evaluated by EBSD, the thin film containing In and Al had a single layer with a thickness of 100 nm, and the (111) plane was oriented in the Z-axis direction. However, the ratio of white regions to black regions, as seen in the IQ map (not shown), was low, and the crystallinity was poor. In contrast, when the thin film was made into a laminate, the crystal grain size became small and reached the measurement limit of EBSD. Therefore, in Test Example 36, the grain size, the orientation of the (111) plane, and the ratio of white regions to black regions could not be measured.

[0119] In the case of a thin film containing In, by laminating it on an underlayer film of In, Ga, and Zn (Test Example 39), the (111) plane was oriented in the Z-axis direction, and the IQ maps showed that the crystallinity was improved (FIGS. 35 and 41). When it was laminated on an underlayer film containing In, Ga, and B (Test Example 40), the crystallinity was improved, although the orientation was random, not limited to the (111) plane (FIGS. 36 and 42).

[0120] When a thin film containing In and 1 atomic % B was laminated on an underlayer of In, Ga, and Zn (Test Example 41), the crystal orientation was not limited to the (111) plane but was randomly oriented, and the crystallinity was poor (Figures 37 and 43). However, when a thin film containing In and 2 atomic % B was laminated on an underlayer of In, Ga, and B (Test Example 45), the crystallinity improved, with a shape intermediate between dendrites and facets. When laminated on an underlayer of In, Ga, and B (Test Example 42 and Test Example 44), the (111) plane was oriented in the Z-axis direction, and the IQ map also showed improved crystallinity (Figures 38, 44, 40, and 46). When laminated on an underlayer of In, B, and Zn (Test Example 43), the crystal orientation was not limited to the (111) plane but was randomly oriented, and the crystallinity was poor (Figures 39 and 45).

[0121] The TFT (Thin Film Transistor) characteristics were evaluated for Test Examples 39 to 42 and Test Example 44. The results are shown in Table 8.

[0122]

[0123] When a thin film containing In was laminated on an underlayer containing In, Ga, and Zn, or an underlayer containing In, Ga, and B (Test Examples 39 and 40), the carrier mobility was 20 cm ２ When a thin film containing In and B was laminated on an underlayer thin film containing In, Ga, and Zn (Test Example 41), the carrier mobility was 30 cm ２ / Vs, but the S value, which indicates the steepness of the rise of the drain current, became relatively large. When a thin film containing In and B was laminated on an underlayer thin film containing In, Ga, and B (Test Examples 42 and 44), the carrier mobility was further improved and the S value could be made relatively low.

[0124] Fifth Example A sputtering target for forming an amorphous oxide semiconductor thin film containing In and B elements was prepared.

[0125] First, In ２ O ３ (indium oxide) and B ２ O ３The raw material powder was weighed so that the atomic percentage ratio of In:B was 99:1 (excluding O) at the target value, and the weighed raw material powder, water, and an organic dispersant were added to a nylon pod using zirconia balls as media, and mixed in a ball mill for 3 hours to obtain a slurry.

[0126] Next, the slurry was granulated using a spray dryer, and the composition of the resulting granulated powder was investigated by ICP atomic emission spectroscopy. It was confirmed that the In:B ratio was 99.2 [atm%]:0.8 [atm%], which was close to the target value. Figure 47 shows the particle size distribution of the granulated powder. This particle size was measured using an electromagnetic vibration sieve. The granulated powder had a maximum particle size distribution of 38 to 63 μm, with most particles being 75 μm or less.

[0127] Next, the granulated powder was degreased in air at 200°C for 12 hours to obtain a defatted granulated powder. This defatted granulated powder was sintered by hot pressing to obtain a sputtering target material containing InB oxide. Sintering is not limited to hot pressing, and atmospheric sintering or hot isostatic pressing (HIP) may also be used. The sintering by hot pressing was performed at a sintering temperature of 950°C, a sintering pressure of 40 MPa, and a sintering time of 8 hours in a nitrogen atmosphere. Since there is a positive correlation between the sintering pressure and the relative density of the resulting sintered body (sputtering target material), it is possible to increase the relative density of the sintered body by sintering at a pressure higher than the above sintering pressure.

[0128] The composition of the obtained sputtering target material (excluding O) was investigated by ICP atomic emission spectroscopy, and it was found that In:B = 99.2 [atm%]:0.8 [atm%], confirming that there was no change in the composition ratio due to sintering under high temperature and high pressure. To investigate the crystallinity of the above sputtering target material, observation was carried out using X-ray diffraction (manufactured by Rigaku Corporation: Cu target, Kβ filter) and a scanning electron microscope. The X-ray diffraction spectrum is shown in Figure 48, and a reflection electron microscope image is shown in Figure 49.

[0129] Looking at the X-ray diffraction spectrum (FIG. 48), the main diffraction peak is In ２ O３ In addition, a trace amount of InBO ３ The diffraction peak of InBO was observed. ３ It can be seen that crystals are also formed. ２ O ３ ,InBO ３ The ratio of In to Fe was 98.9:0.7:0.4. The trace amount of In detected in the sputtering target material is thought to be due to reduction from the graphite mold in the hot press.

[0130] Looking at the electron microscope image (Figure 49), three different contrasts were observed. Based on the semi-quantitative results of the crystalline phase shown in Figure 48, the A region, which accounts for the majority, is In. ２ O ３ The region B, which has a darker contrast than the region A, is InBO ３ The white C regions scattered in the A region are thought to be In. Except for the trace amount of In generated by the reduction of the graphite mold during sintering at 950°C, the oxides of In and B are In. ２ O ３ and InBO ３ It is thought to be composed of the following crystalline phases.

[0131] This sputtering target material was machined and bonded to produce a sputtering target. The machining was carried out in the order of roughening, peripheral machining, and finishing to produce a target (φ101.5 mm x t5.2 mm) for a 4-inch diameter sputtering target. After washing and drying the target, a target inspection was carried out to measure the dimensions, weight, etc. The relative density of the target calculated from the dimensions and weight was 80.5%. The resistivity of the target measured with a four-point probe was 1.6 x 10, which is sufficient for use in a DC discharge sputtering device. －２ The resistance was Ωcm.

[0132] As a final step, the target was bonded to a water-cooled backing plate. The target was then bonded to a Cu backing plate using indium to complete an InB oxide sputtering target, which was then inspected after the bonding process. The post-bonding misalignment was 0.19 mm, and the warpage was -0.04 mm (convex warpage on the back plate side). The adhesion rate measured using a UT measuring device was 100%.

[0133] As described above, the crystalline oxide semiconductor thin film according to one embodiment of the present disclosure has high operational stability and can be used in thin film transistors suitable for organic EL displays and the like.

Claims

1. A crystalline oxide semiconductor thin film containing In and B, wherein the ratio of the In content [atomic %] to the B content [atomic %] satisfies the following formula 1, and the average crystal grain size on the surface observed with an electron microscope is 0.25 μm or more: B / (In+B)≦0.20 (1) 2. The crystalline oxide semiconductor thin film according to claim 1, further containing Fe.

3. A crystalline oxide semiconductor thin film according to claim 1 or 2, wherein the peak value detected by μPCD is at least four times the peak value before crystallization by heat treatment.

4. A laminate for forming a thin film transistor, comprising: an amorphous oxide semiconductor thin film; and the crystalline oxide semiconductor thin film according to claim 1 laminated together.

5. The laminate according to claim 4, wherein the amorphous oxide semiconductor thin film contains In and B elements.

6. A sputtering target material for forming the crystalline oxide semiconductor thin film according to claim 1 or 2.

7. A crystalline oxide semiconductor thin film containing In, having an average crystal grain size of 0.30 μm or more as measured by electron backscatter diffraction, the (111) plane of the crystalline phase being aligned in the Z-axis direction, and having an IQ map with a white area / black area ratio of 0.5 or more in the direction normal to the Z-axis.

8. The crystalline oxide semiconductor thin film according to claim 7, further containing B element.

9. The crystalline oxide semiconductor thin film according to claim 8, wherein the ratio of the In content [atomic %] to the B content [atomic %] satisfies the following formula 2: B / (In+B)≦10 (2) 10. A stacked body in which an amorphous oxide semiconductor thin film containing In and Ga elements and a crystalline oxide semiconductor thin film containing In and Al or Ga elements are stacked.

11. The laminate according to claim 10, wherein the amorphous oxide semiconductor thin film is further laminated on the crystalline oxide semiconductor thin film.

12. The laminate according to claim 10 or 11, wherein the ratio of the content [atomic %] of In to the content [atomic %] of Al or Ga in the crystalline oxide semiconductor thin film satisfies the following formula 3 or 4: Al / (In+Al)≦10 (3) Ga / (In+Ga)≦15 (4).

13. The laminate according to claim 10 or 11, wherein the crystalline oxide semiconductor thin film has a crystal grain size of 0.30 μm or more as measured by electron backscatter diffraction, the (111) plane of the crystalline phase is aligned in the Z-axis direction, and the white area / black area ratio in an IQ map in the direction normal to the Z-axis is 0.5 or more.

14. A stacked body in which an amorphous oxide semiconductor thin film containing In and Ga elements and a crystalline oxide semiconductor thin film containing In and B elements are stacked.

15. The laminate according to claim 14, wherein the amorphous oxide semiconductor thin film is further laminated on the crystalline oxide semiconductor thin film.

16. The laminate according to claim 14 or 15, wherein the amorphous oxide thin film further contains Zn or B.

17. A sputtering target material formed from an oxide sintered body containing the element In and the element B, wherein the ratio of the In content [atomic %] to the B content [atomic %] satisfies the above formula 2.

18. A sputtering target material formed from an oxide sintered body containing an In element and an Al element or a Ga element, wherein the ratio of the In content [atomic %] to the Al or Ga content [atomic %] satisfies formula 3 or formula 4.

19. A sputtering target material formed from an oxide sintered body containing elements In, B, and Ga, wherein the content of B [atomic %] satisfies the following formula 5: 0.1≦B≦40 (5)

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