KR101467131B1 - Oxide sintered body and oxide semiconductor thin film - Google Patents

Abstract

An object of the present invention is to provide an oxide sintered body for producing an oxide semiconductor film which does not contain gallium (Ga), which is expensive, and zinc (Zn), which is problematic in film stability. Another object is to provide an oxide semiconductor thin film having the same composition as that of the oxide-sintered body. (In), magnesium (Mg), a metal element X (wherein X represents at least one element selected from Al, Fe, Sn and Ti), oxygen (O) (Mg) / (In + Mg + X) < / = 0.5 and 0.1 < X / [In + Mg + X]? 0.5.

Description

TECHNICAL FIELD [0001] The present invention relates to an oxide-sintered body and an oxide semiconductor thin film,

The present invention relates to an oxide sintered body and an oxide semiconductor thin film useful for manufacturing a thin film transistor in a display device.

The oxide semiconductor is used as an electrode of a solar cell, a touch panel, etc. in addition to an active layer of a thin film transistor in a display device such as a liquid crystal display device, a plasma display device and an organic EL display device. In the past, a transparent In-Ga-Zn-O system (hereinafter referred to as "IGZO system") was known as an oxide semiconductor (see Non-Patent Document 1), and further, (See Patent Documents 1 and 2). However, gallium (Ga), which is an indispensable component of these systems, is a rare element, and because of its high price, and the like, there is a great limitation in industrial use in large quantities.

Examples of transparent oxide semiconductors that do not use Ga include In-Zn-O based materials (see Patent Document 3), In-Zn-Sn-O based materials (see Patent Document 4), and Zn- ).

Japanese Patent Application Laid-Open No. 2008-280216 Japanese Laid-Open Patent Publication No. 2010-118407 Japanese Patent Application Laid-Open No. 2007-142195 Japanese Patent Application Laid-Open No. 2008-243928 Japanese Patent Application Laid-Open No. 2007-142196

 Nature 432, p488-492, October 2004

The oxide semiconductors described in Patent Documents 3 to 5 do not use Ga, which is an indispensable component of the IGZO system, and are advantageous from the viewpoint of manufacturing cost, but there remain problems such as poor environmental stability such as a change in resistivity with time have. Zinc (Zn), which is another indispensable component of the IGZO system, is an element that is easily volatilized. It is caused by a decrease in sintered body density due to volatilization during production of the sintered body, a deviation from the target composition due to volatilization during sputter deposition, And the stability of the film, such as a change over time, has become a factor.

Therefore, an object of the present invention is to provide an oxide sintered body for producing an oxide semiconductor film which is a scarce resource, which is expensive, gallium (Ga), and which does not contain zinc (Zn) which is easily volatilized and has a problem in stability of the film. Another object of the present invention is to provide an oxide semiconductor thin film having the same composition as that of the oxide-sintered body.

The inventor of the present invention has conducted extensive studies in order to solve the above problems. As a result, it has been found that magnesium oxide (Mg) stable as an oxide is used as a substitute for easily susceptible zinc (Zn), gallium (Al) and iron (Fe) which are the same trivalent metal elements as the trivalent metal elements and tin (Sn) and titanium (Ti) which are tetravalent metal elements are used and further the atomic ratio of these elements, , An oxide-sintered body for producing an oxide semiconductor film containing no gallium (Ga) and zinc (Zn) and an oxide semiconductor thin film can be obtained.

The present invention has been completed on the basis of the above findings. In one aspect, the present invention provides a method of manufacturing a semiconductor device, comprising the steps of: depositing indium (In), magnesium (Mg), and a metal element X (wherein X is at least one element selected from Al, Fe, And the atomic ratio of the indium (In), the magnesium (Mg) and the metal element X is 0.2? [In] / [In + Mg + X]? 0.8 and 0.1? [Mg] / [In + Mg + X]? 0.5, and 0.1? [X] / [In + Mg + X]? 0.5.

In another embodiment, the oxide-sintered body related to the present invention has a relative density of 98% or more.

In another embodiment, the oxide sintered body according to the present invention has a bulk resistance of 3 m? Or less.

According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of: depositing indium (In), magnesium (Mg), a metal element X (wherein X represents at least one element selected from Al, Fe, Sn, Ti) (In), magnesium (Mg), and metal element X are in the range of 0.2? [In] / [In + Mg + X]? 0.8, 0.1? [Mg] / [In + Mg + [X] / [In + Mg + X]? 0.5.

The oxide semiconductor thin film according to the present invention is, in another embodiment, amorphous.

A ^3-oxide semiconductor thin film according to the present invention In a further embodiment, the carrier concentration is 10 ¹⁶ ~ 10 ¹⁸ ㎝.

In another embodiment of the oxide semiconductor thin film according to the present invention, the mobility is 1 cm 2 / Vs or more.

According to another aspect of the present invention, there is provided a thin film transistor including the oxide semiconductor thin film as an active layer.

According to another aspect of the present invention, there is provided an active matrix driving display panel including the thin film transistor.

According to the present invention, it is possible to provide an oxide sintered body for producing an oxide semiconductor film which is a rare resource, which is expensive gallium (Ga), and which is easily volatilized and contains no zinc (Zn) According to the present invention, an oxide semiconductor thin film having the same composition as that of the oxide-sintered body can be provided.

(Composition of oxide-sintered body)

The oxide-sintered body according to the present invention comprises indium (In), magnesium (Mg), a metal element X (wherein X represents at least one element selected from Al, Fe, Sn and Ti) ) As constituent elements. However, in the process of purifying a generally available raw material, it is preferable that the elements which are inevitably contained or the impurity elements which are inevitably incorporated in the oxide sintered body production process are inevitably contained at a concentration inevitably, for example, about 10 ppm Are included in the sintered body related to the present invention.

The ratio [In] / [In + Mg + X] of the number of atoms of indium to the total number of atoms of indium, magnesium and metal element X is 0.2 to 0.8. If [In] / [In + Mg + X] is less than 0.2, the relative density at the time of target production becomes small, the bulk resistance becomes high, and anomalous discharge during sputtering tends to occur. If [In] / [In + Mg + X] exceeds 0.8, the carrier concentration of the film obtained by sputtering the target of the composition becomes excessively high, and the on / off ratio of the channel layer of the transistor becomes small. [In] / [In + Mg + X] is more preferably in the range of 0.25 to 0.6, and more preferably in the range of 0.3 to 0.5. Here, [In] represents the number of atoms of indium, [Mg] represents the number of atoms of magnesium, and [X] represents the number of atoms of metal element X, respectively.

The ratio [Mg] / ([In] + [Mg] + [X]) of the number of atoms of magnesium to the total number of atoms of indium, magnesium and metal element X is 0.1 to 0.5. If [Mg] / ([In] + [Mg] + [X]) is less than 0.1, the carrier concentration of the film becomes excessively large and an abnormal discharge during sputtering tends to occur easily. If [Mg] / ([In] + [Mg] + [X]) exceeds 0.5, the relative density at the time of target production becomes small. [Mg] / ([In] + [Mg] + [X]) is more preferably in the range of 0.15 to 0.4, and more preferably in the range of 0.2 to 0.35.

The ratio [X] / ([In] + [Mg] + [X]) of the total number of atoms of the metal element X to the total number of atoms of the indium, magnesium and the metal element X is 0.1 to 0.5. If [X] / ([In] + [Mg] + [X]) is less than 0.1, the carrier concentration of the film obtained by sputtering the target of the composition becomes excessively high and the on / off ratio of the channel layer of the transistor becomes small. Conversely, when [X] / ([In] + [Mg] + [X]) exceeds 0.5, the relative density at the time of target production becomes small and the bulk resistance becomes high and an abnormal discharge during sputtering tends to occur . [X] / ([In] + [Mg] + [X]) is more preferably in the range of 0.15 to 0.4, and more preferably in the range of 0.2 to 0.35.

(Relative density of oxide-sintered body)

The relative density of the oxide-sintered body has a correlation with the occurrence of a line on the surface at the time of sputtering. When the oxide-sintered body is low-density, when a sputtering process is performed by processing the oxide-sintered body as a target, a high-resistance portion called nodule on the projection, which is a low-grade oxide of indium, is generated on the surface of the sputtering film, It is likely to become a starting point of an abnormal discharge. In the present invention, the relative density of the oxide-sintered body can be made 98% or more by appropriately adjusting the composition range and the manufacturing conditions, and if the density is so high, there is little adverse effect caused by the nodules at the time of sputtering. The relative density is preferably 99% or more, and more preferably 99.5% or more.

The relative density of the oxide-sintered body can be obtained by dividing the density calculated from the weight and the external dimension after the oxide-sintered body has been processed into the predetermined shape by the theoretical density of the oxide-sintered body.

(Bulk resistance of oxide-sintered body)

The bulk resistance of the oxide-sintered body is related to the occurrence of an abnormal discharge easily at the time of sputtering, and when the bulk resistance is high, an abnormal discharge easily occurs at the time of sputtering. In the present invention, the bulk resistance can be made to be 3 m? Cm or less by appropriately setting the appropriate range of the composition and the manufacturing conditions, and there is little adverse effect on the generation of the abnormal discharge at the time of sputtering. The bulk resistance is preferably 2.7 m? Cm or less, and more preferably 2.5 m? Cm or less.

In addition, the bulk resistance can be measured using a resistivity meter by the 4-probe method.

(Manufacturing method of oxide-sintered body)

The oxide-sintered bodies of various compositions according to the present invention can be obtained, for example, by mixing the raw material powders such as indium oxide and magnesium oxide as raw materials, the particle diameter of the raw powder, the grinding time, the sintering temperature, the sintering time, Can be obtained by adjusting the conditions.

The raw material powder preferably has an average particle diameter of 1 to 2 占 퐉. If the average particle diameter exceeds 2 占 퐉, the density of the sintered body is not improved well, so that the raw material powder alone or mixed powder may be subjected to wet milling or the like to reduce the average particle diameter to about 1 占 퐉. It is also effective to preliminarily sinter for the purpose of improving the sinterability before wet mixing and grinding. On the other hand, a raw material less than 1 탆 is difficult to obtain, and if it is too small, agglomeration between the particles tends to occur and handling becomes difficult. Here, the average particle diameter of the raw material powder refers to a value measured by a laser diffraction measurement method. It is preferable that the raw material mixture powder after the pulverization is granulated by a spray dryer or the like to increase fluidity and moldability before molding. The molding can be carried out by a conventional method such as press molding or cold isostatic pressing.

Thereafter, the molded product is sintered to obtain a sintered body. The sintering is preferably performed at 1400 to 1600 ° C for 2 to 20 hours. As a result, the relative density can be set to 98% or more. When the sintering temperature is less than 1400 DEG C, the density is not improved sufficiently. If the sintering temperature exceeds 1600 DEG C, the composition of the sintered body changes due to the volatilization of the constituent elements or the like, or the density decreases due to the generation of pores due to volatilization . An atmosphere can be used as the atmospheric gas at the time of sintering, and a high-density sintered body can be obtained by the effect of suppressing volatilization from the sintered body. However, depending on the composition of the sintered body, a sintered body having a sufficiently high density can be obtained even if the atmosphere gas is oxygen.

(Sputter Deposition)

The oxide-sintered body obtained as described above can be used as a target for sputtering by performing processing such as grinding or polishing, and an oxide film having the same composition as that of the target can be formed by forming the target. At the time of processing, it is preferable to grind the surface by a method such as planar grinding to set the surface roughness Ra to 5 m or less. By reducing the surface roughness, it is possible to reduce the starting point of nodule generation which causes anomalous discharge.

The target for sputtering can be obtained by sticking to a backing plate made of copper or the like, placing it in a sputtering apparatus, and sputtering under appropriate conditions such as appropriate degree of vacuum, atmospheric gas, sputtering power, etc. to obtain a film having almost the same composition as the target.

In the case of the sputtering method, it is preferable to set the degree of vacuum in the chamber before the film formation to 2 x 10 < ^-4 > Pa or less. If the pressure is excessively high, there is a possibility that the mobility of the obtained film is lowered due to the influence of the impurities in the residual atmosphere gas.

A mixed gas of argon and oxygen may be used as the sputter gas. As a method for adjusting the oxygen concentration in the mixed gas, for example, a gas bombardment of 100% argon and a gas bombardment of 2% oxygen in argon are used to increase the supply flow rate from each gas cylinder to the chamber, As shown in FIG. Here, the oxygen concentration in the mixed gas means an oxygen partial pressure / (oxygen partial pressure + argon partial pressure), which is equivalent to the flow rate of oxygen divided by the sum of the flow rates of oxygen and argon. The oxygen concentration may be appropriately changed depending on the desired carrier concentration, and may be typically 1 to 3%, and more typically 1 to 2%.

The total pressure of the sputter gas is about 0.3 to 0.8 Pa. If the total pressure is lower than this, the plasma discharge becomes difficult to occur, and even if it occurs, the plasma becomes unstable. If the total pressure is higher than the above range, the film forming speed is slowed, and the productivity is adversely affected.

When the target size is 6 inches, the sputtering power is about 200 to 1200 W. If the sputtering power is too small, the deposition rate is low and the productivity is low. On the contrary, if the sputtering power is too large, problems such as cracking of the target occur. 200 to 1200 W is preferably 1.1 W / cm 2 to 6.6 W / cm 2 and 3.2 to 4.5 W / cm 2 in terms of the sputter power density. Here, the sputter power density is obtained by dividing the sputtering power by the area of the sputtering target, and is different from that of the sputtering target in that the sputtering target actually receives different powers depending on the sputtering target size even under the same sputtering power, It is an index to express power uniformly.

As a method of obtaining a film from the oxide sintered body, a vacuum deposition method, an ion plating method, a PLD (Pulsed Laser Deposition) method, or the like can be used, but an industrially applicable method is a method of satisfying requirements such as large area, high speed film formation, DC magnetron sputtering method.

There is no need to heat the substrate at the time of sputtering. This is because even if the substrate is not heated, a relatively high mobility can be obtained, and it is not necessary to apply time or energy for raising the temperature. When the substrate is sputtered without heating, the resulting film becomes amorphous. However, by heating the substrate, it is expected that the same effect as annealing after the room temperature film formation can be obtained.

(Carrier concentration of oxide film)

The carrier concentration of the oxide film is related to various characteristics of the transistor when the film is used for the channel layer of the transistor. When the carrier concentration is too high, a minute leakage current is generated even when the transistor is turned off, and the on-off ratio is lowered. On the other hand, if the carrier concentration is too low, the current flowing through the transistor becomes small. In the present invention, by the appropriate range of composition, the oxide film carrier concentration 10 ¹⁶ ~ 10 ¹⁸ ㎝ ^- can be a ^3, Within this range, the characteristics can be produced in good transistor.

(Mobility of oxide film)

The mobility is one of the most important characteristics among the characteristics of the transistor, and it is preferable that the mobility of the amorphous silicon which is the content material of the oxide semiconductor used as the channel layer of the transistor is 1 cm 2 / Vs or more. Basically, the higher the mobility, the better. The oxide film according to the present invention can have a mobility of 1 cm 2 / Vs or more, preferably 3 m 2 / Vs or more, more preferably 5 cm 2 / Vs or more . As a result, it is superior to amorphous silicon and has higher industrial applicability.

The oxide semiconductor thin film related to the present invention can be used, for example, as an active layer of a thin film transistor. In addition, the thin film transistor obtained by using the above-described manufacturing method can be used as an active element and used for an active matrix driving display panel.

Example

Examples of the present invention will be described below with reference to comparative examples. However, these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention. Therefore, the present invention includes all modes or modifications other than the embodiments within the scope of the technical idea of the present invention.

In the following Examples and Comparative Examples, physical properties of the sintered body and the film were measured by the following methods.

(A) Composition of sintered body and membrane

And was determined by ICP (High Frequency Inductively Coupled Plasma) analysis using SPS3000 manufactured by SII Nanotechnology.

(B) Relative density of sintered body

The weight and the external dimensions, and the theoretical density from the constituent elements.

(C) Bulk resistance of the sintered body

4 device manufactured by NPS (NPS) by the 4-probe method (JIS K 7194).

(D) Thickness

(Manufactured by Veeco, type Dektak 8 STYLUS PROFILER).

(E) Carrier concentration and mobility of the film

A glass substrate having a film thickness of about 10 mm was cut out, and an indium electrode was attached to each of the four corners of the glass substrate. The indium electrode was set on a hole measuring apparatus (Model Resitest 8200, manufactured by Toyotec Corporation).

(F) Crystals or amorphous structures of membranes

Crystallinity was determined using a RINT-1100 X-ray diffractometer manufactured by Rigaku Corporation. From this X-ray diffraction, it was judged to be amorphous in that no significant peak above the background level was observed.

(G) Average particle size of powder

The average particle diameter of the powder was measured by SALD-3100 manufactured by Shimadzu Corporation.

≪ Example 1 >

(In: Mg: Sn) of 0.4: 0.3: 0.3 (average particle diameter: 1.0 占 퐉), magnesium oxide (average particle diameter: 1.0 占 퐉) And wet-mixed and pulverized. The average particle diameter of the mixed powder after the pulverization was 0.8 탆. This mixed powder was assembled with a spray dryer, filled in a mold, press-molded, and then sintered in an air atmosphere at a high temperature of 1450 DEG C for 10 hours. The obtained sintered body was processed into a disk having a diameter of 6 inches and a thickness of 6 mm to form a sputtering target. The relative density of the target was calculated from the measurement results of the weight and the external dimensions and the theoretical density, and as a result, it was found to be 99.8%. The bulk resistance of the sintered body measured by the 4-probe method was 2.1 m? Cm.

The sputtering target prepared above was attached to a copper backing plate using indium as a brazing material, and the sputtering target was placed in a DC magnetron sputtering apparatus (SPL-500 sputtering apparatus manufactured by ANELVA). The glass substrate using the Corning 1737, and the sputtering conditions, the substrate temperature: 25 ℃, ultimate pressure: 1.2 × 10 ^-4 ㎩, atmosphere gas: Ar 99%, 1% oxygen, the sputtering pressure (total pressure): 0.5 ㎩, And an input power of 500 W, thereby producing a thin film having a film thickness of about 100 nm. During the film formation of the oxide semiconductor thin film, no abnormal discharge was observed.

Hole measurement of the obtained film was carried out to determine the carrier concentration and mobility. As a result of the measurement by X-ray diffraction, the film was amorphous.

≪ Examples 2 to 15 >

The oxide-sintered body and the oxide semiconductor thin film were obtained in the same manner as in Example 1, except that the composition ratios of the raw material components were set to the respective values shown in Table 1. Each of the relative density, bulk resistance, carrier concentration, and mobility were as shown in Table 1. The compositions of the sintered body and the film were the same as those of the raw material powder. No abnormal discharge was observed at the time of forming the oxide semiconductor thin film.

≪ Comparative Examples 1 to 12 >

The oxide-sintered body and the oxide semiconductor thin film were obtained in the same manner as in Example 1, except that the composition ratios of the raw material components were set to the respective values shown in Table 1. Each of the relative density, bulk resistance, carrier concentration, and mobility were as shown in Table 1. The compositions of the sintered body and the film were the same as those of the raw material powder.

Examples 1-15 In, the carrier concentration of 10 ¹⁶ ~ 10 ¹⁸ ㎝ ^- in the range of ^3, also, the mobility was 1 ㎠ / Vs or more.

On the other hand, in Comparative Examples 1, 4, 6, 8, 10, and 12, the carrier concentration was less than 10 ¹⁶ cm ^-3 and the mobility was less than 1 cm 2 / Vs.

Further, Comparative Examples 2, 3, 5, 7, 9, 11, the carrier concentration is 10 ¹⁸ ㎝ ^{- 3} was exceeded.

Claims (9)

(Mg), a metal element X (wherein X represents at least one element selected from Al, Fe, and Sn), and oxygen (O)
Mg, X, and Y satisfy the following relationship: 0.2? [In] / [In + Mg + X]? 0.8, 0.1? [Mg] / [In + Mg + X]? 0.5, and 0.1? X] / [In + Mg + X]? 0.5, and the relative density is 98% or more. delete The method according to claim 1,
And the bulk resistance is 3 m? Or less. (Mg), a metal element X (wherein X represents at least one element selected from Al, Fe, and Sn), and oxygen (O)
(In), [Mg], [Mg], [Mg], [Mg], and the atomic ratio of the metal element X is in the range of 0.2 [In] / [In + Mg + ] satisfies ≤0.5, and the carrier concentration is 10 ¹⁶ ~ 10 ¹⁸ ㎝ ^-3 of the oxide semiconductor thin film. 5. The method of claim 4,
Amorphous, oxide semiconductor thin film. delete The method according to claim 4 or 5,
Wherein the mobility is at least 1 cm 2 / Vs. A thin film transistor comprising the oxide semiconductor thin film according to claim 4 or 5 as an active layer. An active matrix driving display panel comprising the thin film transistor according to claim 8.