WO2014014091A1 - Target assembly - Google Patents

Abstract

Provided is a target assembly in which a plurality of oxide target members are disposed with gaps therebetween on a backing plate via a bonding material. The target assembly includes a support member formed of at least one or more materials selected from the group consisting of Ni, Si, Hf, and Ta, the support member being provided between the oxide target members and the backing plate and bridging the aforementioned gaps.

Description

Target assembly

The present invention relates to a target assembly used when an oxide thin film useful as a semiconductor layer (active layer) of a thin film transistor (TFT) used in a display device such as a liquid crystal display or an organic EL display is formed by sputtering, More specifically, the present invention relates to a target assembly in which a plurality of oxide target members are arranged at intervals on a single backing plate via a bonding material.

An amorphous (amorphous) oxide thin film (hereinafter sometimes referred to as an oxide semiconductor thin film) used for a TFT semiconductor layer has a higher carrier mobility than general-purpose amorphous silicon (a-Si). However, since it has a large optical band gap and can be formed at a low temperature, it is expected to be applied to next-generation displays that require large size, high resolution, and high-speed driving, and resin substrates with low heat resistance.

As an oxide semiconductor film, typically, a film containing indium (In) and zinc (Zn), and a film containing at least one of gallium (Ga) and tin (Sn) can be given. For example, an amorphous oxide semiconductor (In—Ga—Zn—O, hereinafter sometimes referred to as “IGZO”) thin film of In, Ga, Zn, and O is preferable because it has a very high carrier mobility. It is used. Patent Document 1 discloses an oxide semiconductor thin film containing elements such as In, Zn, Sn, and Ga, and Mo, and Examples disclose a material in which Mo is added to IGZO.

In forming an oxide semiconductor thin film, a sputtering method is preferably used in which a sputtering target having the same composition as the film is sputtered. In the sputtering method, an inert gas such as Ar gas is introduced into a vacuum, a high voltage is applied between the substrate and the target member, and the ionized inert gas is caused to collide with the target member and be blown off by the collision. The constituent material of the target member is deposited on the substrate to form a thin film. In-plane uniformity of component composition and film thickness in the film surface direction (in the film surface) is smaller in the thin film formed by sputtering compared to thin films formed by ion plating, vacuum evaporation, and electron beam evaporation. It has an advantage that a thin film having the same composition as the sputtering target can be formed.

A sputtering target used in a sputtering method is generally used in a state of being bonded onto a backing plate (support) made of a metal member using a bonding material, and such a sputtering target is a target bonded body. Also called. For the backing plate, Cu having excellent heat resistance, conductivity and thermal conductivity is widely used, and is used in the form of pure copper or copper alloy. As the bonding material, low melting point solder materials (for example, In-based and Sn-based materials) having good thermal conductivity and conductivity are widely used.

In recent years, the demand for film formation on a large substrate by a sputtering method is increasing, and the size of the sputtering target is also increasing. Since there are some sputtering targets that are difficult to increase in size, as shown in FIGS. 1 and 2, which will be described later, a plurality of small pieces of target members are arranged at intervals on a single backing plate. A target assembly in which a backing plate is bonded with a bonding material is used. Between adjacent target members, adjust so that there is a spacing (gap) of approximately 0.1 to 1.0 mm at room temperature so that adjacent targets will not come into contact with each other due to the deflection of the backing plate and defects will not occur. Arranged. Also, in order to prevent the bonding material from leaking out from the gap, a backing member such as a polymer heat-resistant sheet or a conductive sheet (also called an abutment plate) is usually provided on the back side of the gap (on the bonding side, the side facing the backing plate). May be provided.

For example, in Patent Document 2, warpage of the entire sputtering target due to a difference in thermal expansion coefficient between the target material and the backing plate is suppressed, and further, separation and destruction of the target material and the backing plate due to thermal stress during sputtering are prevented. In order to enable long-term use, a tape-like spacer is arranged between the target material and the backing plate as a backing member. As a material for the tape spacer, copper or a copper alloy is recommended as in the case of the backing plate. When such a tape-shaped spacer is disposed directly below all or part of the split target along the spliced portion and the end portion, the discharge during sputtering becomes uniform and the low melting point solder from the spliced portion. It is described that it is possible to effectively prevent scum from rising on both sides of the sputter.

Japanese Unexamined Patent Publication No. 2009-164393 Japanese Unexamined Patent Publication No. 11-200028

An oxide used as a semiconductor layer of a TFT is required not only to have a high carrier concentration (mobility) but also to have excellent TFT switching characteristics (transistor characteristics, TFT characteristics). Specifically, for example, the on-current (maximum drain current when a positive voltage is applied to the gate electrode and the drain electrode) is high, and the off-current (a negative voltage is applied to the gate electrode and a positive voltage is applied to the drain voltage). And the SS value (Subthreshold Swing, subthreshold swing, and gate voltage necessary to increase the drain current by one digit).

On the other hand, in manufacturing the target assembly, as described above, a gap is provided between a plurality of adjacent oxide target members, so that an ionized inert gas enters through the gap during sputtering. As a result, the Cu backing plate disposed under the target member is also sputtered, Cu is mixed into the formed oxide thin film, and the TFT characteristics are deteriorated. The decrease in TFT characteristics is a major factor in image unevenness when a display is manufactured, and causes a significant deterioration in quality. Therefore, as in Patent Document 2 described above, it is not preferable to use not only the backing plate but also the backing member made of Cu because the Cu contamination phenomenon becomes more prominent.

In addition, regarding the IGZO semiconductor containing Mo described in Patent Document 1 described above, the present inventors formed a Mo-containing IGZO thin film by using a target assembly having a Cu backing plate and a Cu backing member to form a TFT. When the characteristics were examined, it was found that the ON current decreased and the SS value significantly increased compared to IGZO. This result means that Mo cannot effectively suppress the degradation of TFT characteristics due to the contamination phenomenon of Cu in the thin film described above.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent deterioration of TFT characteristics (particularly a decrease in on-current and an increase in SS value) of an oxide semiconductor thin film formed by sputtering. Is to provide a simple target assembly.

The target assembly of the present invention that has solved the above-described problems is a target assembly in which a plurality of adjacent oxide target members are disposed on a backing plate with a gap therebetween with a bonding material interposed therebetween. A backing member made of at least one or more selected from the group consisting of Ni, Si, Hf, and Ta provided across the gap between the oxide target member and the backing plate; It has a gist where it has it.

In a preferred embodiment of the present invention, the oxide target member contains at least In and Zn.

In a preferred embodiment of the present invention, the oxide target member further includes at least one of Ga and Sn.

In a preferred embodiment of the present invention, the backing plate is made of pure Cu or a Cu alloy.

In a preferred embodiment of the present invention, the backing member is one or more selected from the group consisting of Ni, Hf, and Ta.

In a preferred embodiment of the present invention, the bonding material is made of In base material or Sn base material.

In the target assembly of the present invention, by providing a backing member disposed across the gap between the oxide target member and the backing plate, the components of the backing plate are prevented from being mixed (contaminated) into the thin film. can do. Further, since the backing member is made of a material composed of at least one or more of predetermined metal elements (Ni, Si, Hf, and Ta) that do not deteriorate the TFT characteristics of the oxide semiconductor thin film, Even if the predetermined metal element is contaminated, deterioration of TFT characteristics due to contamination can be prevented, and good TFT characteristics can be maintained.

FIG. 1 is a plan view of a target assembly of the present invention. FIG. 2 is an enlarged vertical sectional view taken along line AA in FIG. FIGS. 3A to 3G are graphs showing Id-Vg characteristics of TFTs manufactured using the oxide (IGZO + various additive elements) semiconductor described in Example 1. FIG. FIG. 4 is a diagram showing Id-Vg characteristics of a TFT manufactured using a target assembly in which a Cu or Ni backing member is arranged on the back side (bonding side) of a gap between IGZO target members in Example 2. is there.

In order to effectively prevent a decrease in TFT characteristics (especially a decrease in on-current and an increase in SS value) of an oxide semiconductor thin film formed by sputtering, the present inventors have established an interval between target members (see FIG. 1 and FIG. The backing member used on the back side of (see T in FIG. 2) has been studied repeatedly. As a result, it is effective to use a backing member made of at least one element selected from the group consisting of Ni, Si, Hf, and Ta (hereinafter sometimes represented by an X group element). As a result, the present invention has been completed.

First, the background to the present invention will be described. The target assembly on which the present invention is based uses a Cu backing plate, and uses an oxide containing at least In and Zn, and further containing at least one of Ga and Sn as an oxide target member. Is. Preferably, a low melting point solder material of In or Sn is used as the bonding material. Further, in providing the backing member that is the subject of the present invention, studies were made focusing on elements that do not degrade the TFT characteristics when added to the oxides that are the subject of the present invention. With such an element, even when the element enters from the gap of the target member during sputtering, a thin film containing the element in the oxide (useful for improving TFT characteristics) is formed at the substrate position corresponding to the gap. This is because it was considered that the TFT characteristics of the oxide semiconductor thin film after the film formation did not deteriorate. As a result, at least one or two or more elements selected from the group consisting of Ni, Si, Hf, and Ta (hereinafter may be represented by group X elements) in the form of pure metal or alloy elements. It has been found that it can be used as a backing member.

Hereinafter, the target assembly of the present invention will be described in detail with reference to FIG. 1 and FIG. FIG. 1 is a plan view of a target assembly of the present invention, and FIG. 2 is an enlarged vertical sectional view taken along line AA of FIG. However, the target assembly of FIGS. 1 and 2 is an example of a preferred embodiment of the present invention, and the target assembly of the present invention is not intended to be limited to this. For example, in the following drawings, a rectangular sputtering target is shown, but the present invention is not limited to this, and for example, a disk-shaped one may be used.

A target assembly 1 shown in FIGS. 1 and 2 includes a sputtering target 2 in which four oxide target members 4a to 4d are arranged side by side in front, back, left, and right, and a backing plate 3 that fixes (supports) the target. The plurality of oxide target members 4a to 4d and the low melting point solder bonding materials 11a to 11c for bonding the backing plate 3 to each other. A backing member 5 is provided on the back side of the interval T between the adjacent oxide target members 4a to 4d (on the low melting point solder bonding material 11a side) so as to close the interval T. Spacers 12 (Cu wires) are arranged between the oxide target members 4a to 4d and the backing plate 3 so as to form a uniform distance.

Although not shown in FIGS. 1 and 2, a cooling mechanism is provided on the back side of the backing plate 3 (on the side opposite to the side on which the oxide target members 4a to 4d are disposed). The oxide target members 4a to 4d are configured to be indirectly cooled through the gap.

The oxide target members 4a to 4d are oxides targeted in the present invention (oxides containing at least In and Zn, and further containing Ga and / or Sn; hereinafter, [In—Zn (Ga / Sn) oxide). In some cases.). Specifically, In—Zn—O (IZO), In—Ga—Zn—O (IGZO), In—Zn—Sn—O (IZTO), and In—Ga—Zn—Sn—O (IGZSO) can be given. It is done. The ratio of each element is appropriately determined according to the composition of the oxide thin film formed on the substrate (not shown in FIGS. 1 and 2).

1 and 2, the oxide target members 4a to 4d are made of a rectangular plate material, but are not limited to this, and may have a commonly used shape (for example, a disk shape). Further, the thickness and size of the oxide target members 4a to 4d are not particularly limited, and those normally used in the field of the target assembly can be selected.

A space T is provided between the oxide target members 4a to 4d. The width of the interval T is preferably set appropriately according to the oxide target member to be used, the sizes of the low melting point solder bonding materials 11a to 11c, the size of the backing plate 3, and the like. The thickness is preferably 2 mm to 1.0 mm. Below, the said space | interval T may be called a "gap part."

The backing plate 3 is made of pure Cu or Cu alloy having excellent heat resistance, conductivity, and thermal conductivity. Any Cu backing plate can be used as long as it is normally used in the field of sputtering targets. Examples of the Cu alloy include a Cu—Cr alloy. The backing plate 3 has a predetermined plane area and a predetermined thickness so that the oxide target members 4a to 4d can be placed thereon.

As the low-melting-point solder bonding materials 11a to 11c, typically, an In-based material or an Sn-based material can be given. The type is not particularly limited, and any type can be used as long as it is usually used in the field of sputtering targets. Examples of the In base material include an In—Ag alloy. Examples of the Sn-based material include a Sn—Zn alloy. An In-based material is preferable. In FIG. 2, the same or different low melting point solder bonding materials can be used for 11a to 11c, but it is preferable to use the same material in consideration of work efficiency and the like.

The spacers 12 are arranged so that a uniform gap is formed between the oxide target members 4a to 4d and the backing plate 3 so that the bonding material can flow in. The spacer is not particularly limited as long as it has excellent conductivity and thermal conductivity, and any spacer can be used as long as it is usually used in the field of sputtering targets. Examples of the spacer 12 include a Cu wire. 1 and 2 show a spacer formed in a ring shape, but the present invention is not limited to this shape.

In the present invention, a pure metal or an alloy element of the X group element used as the backing member can be used as the spacer 12. That is, the backing member used in the present invention is also useful as a spacer. For example, when used with being fixed with the low-melting-point solder bonding material 11, the target material and the backing plate are peeled or broken due to thermal stress during sputtering. Can be used for a long period of time.

The backing member 5 that characterizes the present invention is made of a pure metal of Ni, Ta, Si, or Hf (X group element), or an alloy component composed of two or more of the above X group elements. The X group element is not only excellent in conductivity and thermal conductivity, but also when added to the oxide [In—Zn (Ga / Sn) oxide] targeted in the present invention, the mobility of the TFT, The characteristics of the on-current and SS value are not deteriorated, and the same or better characteristics are exhibited (see Table 2 of Example 1 described later). The X group elements (Ni, Ta, Hf) excluding Si have a higher specific gravity than In or Sn, which is a typical component of the low-melting-point solder bonding materials 11a to 11c (the table of Example 1 described later). Therefore, it is preferably used in consideration of work efficiency at the time of manufacturing the target assembly. Of the X group elements, Ni and Si are preferable from the viewpoint of on-current and the like, and more preferably Ni.

In FIG. 2, the backing member may be composed of a single material (for example, pure Ni), or may be configured as a laminated body (for example, pure Ni and Ni alloy).

Specifically, as shown in FIG. 2, the backing member 5 and the backing plate 3 are joined by a low melting point solder bonding material 11b, and the backing member 5 and the oxide target members 4a and 4b are joined by a low melting point solder bonding material. Joined at 11a. Since the low melting point solder bonding material 11a is scraped and does not exist in the portion Q immediately below the interval T, here, the backing member 5 is directly connected to the oxide target members 4a and 4b without passing through the low melting point solder bonding material 11a. It is joined.

However, in the present invention, it suffices that at least the backing member is disposed on the back side of the interval T, and the presence form of the backing member is not limited to the mode of FIG. In addition, as shown in FIG. 2, it is preferable that the low melting point solder bonding material 11a does not exist in the portion Q immediately below the interval T. However, if there is a low melting point solder bonding material in the Q portion, heat is generated during sputtering. In addition, the bonding material melts and abnormal discharge occurs, and particles and splash are generated. In particular, when the bonding material rises through a gap, such a phenomenon becomes remarkable. Therefore, in order to avoid the phenomenon, it is preferable that the bonding material does not exist as much as possible in the portion Q immediately below.

The size (width and thickness) of the backing member 5 is appropriately set according to the size of the oxide target members 4a to 4d and the low melting point solder bonding materials 11a to 11c to be used, the size of the backing plate 3, and the like. The thickness is preferably about 0.2 to 1.0 mm. When the thickness of the backing member 5 is thinner than 0.2 mm, the effect of suppressing the warpage of the entire sputtering target due to the difference in thermal shrinkage between the target material and the backing plate is not sufficiently exhibited. On the other hand, if the thickness of the backing member 5 exceeds 1.0 mm, the low melting point solder bonding materials 11a to 11c may flow out of the gap portion before solidifying. A more preferable thickness of the backing member 5 is about 0.25 to 0.50 mm.

The width of the backing member 5 is preferably about 5 to 30 mm. If the width of the backing member 5 is smaller than 5 mm, alignment becomes difficult when the backing member is disposed immediately below the oxide target members 4a to 4d along the interval. On the other hand, if the width of the backing member 5 exceeds 30 mm, it may be difficult to sufficiently obtain the warp suppressing effect of the entire sputtering target. A more preferable width of the backing member 5 is about 10 to 25 mm.

The target assembly of the present invention has been described in detail above.

The method for manufacturing the target assembly according to the present invention described above is not particularly limited. For example, the method described in Patent Document 2 described above can be referred to. An example of a preferred manufacturing method embodiment is shown below. First, a bonding material such as a low melting point metal material is filled on the backing plate and heated to a melting point or higher than the melting point of the low melting point metal material. Next, the backing member is arranged side by side at a predetermined location. If necessary, arrange a spacer. As a result, the backing member having a larger specific gravity than the low melting point metal material settles in the low melting point metal material. When the specific gravity of the backing member is smaller than that of the low melting point metal material, the backing member is allowed to settle down. Next, the plurality of oxide target members are arranged side by side at intervals, and then cooled. By cooling, the low melting point metal material is re-solidified, and a target assembly in which the oxide target member and the backing plate are joined via the low melting point metal layer is obtained.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be implemented with modifications within a range that can meet the purpose described above and below. They are all included in the technical scope of the present invention.

Example 1
In this example, a TFT including an oxide semiconductor thin film containing an X group element (Ni, Si, Hf, Ta) selected as a constituent component of a backing member in the present invention has mobility and good TFT characteristics. I investigated.

In this example, a TFT was manufactured as follows. First, a Ti thin film of 100 nm and a gate insulating film SiO ₂ (200 nm) were sequentially formed as a gate electrode on a glass substrate (Corning Eagle 2000, diameter 100 mm × thickness 0.7 mm). The gate electrode was formed using a pure Ti sputtering target by DC sputtering at a film forming temperature: room temperature, a film forming power: 300 W, a carrier gas: Ar, and a gas pressure: 2 mTorr. The gate insulating film was formed by plasma CVD using a carrier gas: a mixed gas of SiH ₄ and N ₂ O, a deposition power of 100 W, and a deposition temperature of 300 ° C.

Next, oxide thin films having various compositions described in Table 1 were formed using a sputtering target (described later). Sputtering uses a “CS-200” apparatus manufactured by ULVAC, Inc., and is formed by DC sputtering using a film forming temperature: room temperature, film forming power: 200 W, gas pressure: 1 mTorr, oxygen partial pressure: 100 × O ₂ / ( An IGZO thin film with a film thickness of 50 nm was formed under the conditions of Ar + O ₂ ) = 10% and target target size: 101.6 mm [In: Ga: Zn: O = 1: 1: 1: 4 (atomic ratio)] .

As the oxide thin film, in addition to IGZO-X containing X element in IGZO, for comparison, IGZO and IGZO containing an element (Cu, Cr, Mo) other than X group element were also formed.

Among these, in forming an IGZO film, a sputtering target having an In: Ga: Zn ratio (atomic ratio) of 1: 1: 1 is used to form an oxide semiconductor thin film containing other elements in the IGZO. In this case, a film was formed using a Co-Sputter method in which two sputtering targets having different compositions were discharged simultaneously. Specifically, as a sputtering target, a sputtering target having In: Ga: Zn = 1: 1: 1, and a target in which a pure metal chip of an X group element, Cu, Cr, or Mo is mounted on the sputtering target. One was used.

Each content of the metal element in the oxide thin film thus obtained was analyzed by an XPS (X-ray Photoelectron Spectroscopy) method. Specifically, after sputtering the range from the outermost surface to a depth of about 5 nm with Ar ions, analysis was performed under the following conditions.
X-ray source: Al K _α
X-ray output: 350W
Photoelectron extraction angle: 20 °

After forming the oxide semiconductor thin film as described above, patterning was performed by photolithography and wet etching. “ITO-07N” manufactured by Kanto Chemical Co., Ltd. was used as the wet etchant solution.

After patterning the oxide semiconductor thin film, a pre-annealing process was performed to improve the film quality. The pre-annealing was performed at 350 ° C. for 1 hour in a 100% oxygen atmosphere and atmospheric pressure.

Next, pure Ti was used to form source / drain electrodes by a lift-off method. Specifically, after patterning using a photoresist, a Ti thin film was formed by DC sputtering (film thickness was 100 nm). The method for forming the Ti thin film for the source / drain electrodes is the same as that for the gate electrode described above. Subsequently, unnecessary photoresist was removed by applying an ultrasonic cleaner in acetone, and the channel length of the TFT was 10 μm and the channel width was 200 μm.

After forming the source / drain electrodes in this manner, a protective film for protecting the oxide semiconductor was formed. As the protective film, a laminated film of SiO ₂ (film thickness 200 nm) and SiN (film thickness 200 nm) was used. The formation of the SiO ₂ and SiN was performed using “PD-220NL” manufactured by Samco and using the plasma CVD method. In this embodiment, after performing plasma treatment with N ₂ O gas, SiO ₂ and SiN films were sequentially formed. A mixed gas of N ₂ O and SiH ₄ was used for forming the SiO ₂ film, and a mixed gas of SiH ₄ , N ₂ , and NH ₃ was used for forming the SiN film. In both cases, the film formation power was 100 W, and the film formation temperature was 150 ° C.

Next, contact holes for probing for transistor characteristic evaluation were formed in the protective film by photolithography and dry etching. Next, an ITO film (film thickness: 80 nm) was formed using a DC sputtering method with a carrier gas: a mixed gas of argon and oxygen gas, a film formation power: 200 W, and a gas pressure: 5 mTorr, to manufacture a TFT.

For each TFT thus obtained, transistor characteristics (drain current-gate voltage characteristics, Id-Vg characteristics), on-current, SS value, and field-effect mobility (hereinafter referred to as “mobility”) are as follows. ) _FE was determined.

(1) Measurement of transistor characteristics For transistor characteristics (Id-Vg characteristics), a semiconductor parameter analyzer “4156C” manufactured by Agilent Technology was used. Detailed measurement conditions are as follows.
Source voltage: 0V
Drain voltage: 10V
Gate voltage: -30V to 30V (measurement interval: 1V)

(2) On-current and SS value The on-current is a drain current with a gate voltage of 30 V and is a current value when the transistor is in an on state, and is the minimum value of the gate voltage required to increase the drain current by one digit. Was the SS value.

(3) Mobility μ _FE
The field effect mobility μ _FE was derived from the TFT characteristics in a linear region where V _g > V _d −V _th . In the linear region, V _g and V _d are the gate voltage and drain voltage, V _th is the voltage when the drain current exceeds 1 nA, I _d is the drain current, L and W are the channel length and channel width of the TFT element, respectively. C _i is the capacitance of the gate insulating film, and μ _FE is the field effect mobility. μ _FE is derived from the following equation. In this example, the field effect mobility μ _FE was derived from the slope of the drain current-gate voltage characteristic (Id-Vg characteristic) in the vicinity of the gate voltage satisfying the linear region.

In this example, each mobility obtained in this way was converted into a percentage (ratio to IGZO) when the mobility of IGZO was 100%, and evaluated based on the following criteria.
◎: Ratio to IGZO is 90% or more ○: Ratio to IGZO is 70% or more and less than 90% △: Ratio to IGZO is 50% or more and less than 70% ×: Ratio to IGZO is less than 50%

These results are shown in Tables 1 and 2 and FIGS. 3 (a) to (g).

First, refer to Table 1. Table 1 shows the results of mobility when each element is added to IGZO. Table 1 shows the results of Al, Ge, Sn, and Ti for reference in addition to the X group elements (Ni, Si, Hf, Ta), the conventional example (Mo), and the comparative examples (Cu, Cr). Show. The addition amount of each element [addition amount with respect to IGZO (atomic%)] is 2 atomic%.

Furthermore, Table 1 also shows the specific gravity values of each element. This value is taken from the JIS handbook.

From Table 1, it can be seen that when the X group element (Ni, Si, Hf, Ta) selected as the material of the backing member used in the present invention is added to IGZO, all have good mobility. In addition to Si, Ni, Hf, and Ta have a higher specific gravity than In and Sn, which are typical low melting point solder bonding materials, and thus are very useful in terms of workability of the target assembly.

On the other hand, when Cu or Cr was added to IGZO, good mobility could not be obtained. In addition, Al and Ge did not have such a high mobility as the X group element was added in the oxide composition of this example. In addition, since these elements have a lower specific gravity than In and Sn, the workability of the target assembly is inferior.

Next, refer to Table 2. Table 2 shows the results of on-state current and SS value when using oxide semiconductor thin films in which the addition amount of the X group element (Ni, Si, Hf, Ta) is variously changed with respect to IGZO. . In Table 2, the addition amount of the group X element is the addition amount (atomic%) with respect to IGZO.

Table 2 shows that when an X group element is added to IGZO, an on-current and an SS value equal to or higher than those obtained when a conventional IGZO not containing an X group element is used, and good TFT characteristics are obtained. Was confirmed.

On the other hand, when Cu or Cr was added to IGZO, the on-current decreased. Note that the SS value was not measured because the static characteristics of the transistor were not obtained and switching was not performed (described as “−” in Table 2).

Also, when Mo was added to IGZO, both the on-current and SS value were degraded as compared to conventional IGZO.

Next, refer to FIGS. 3 (a) to 3 (g). 3 (a) to 3 (g) include, among the experimental examples shown in Table 2, an X group element (addition amount 2 atomic%) or Cu, Cr, and Mo (all addition amounts 0.5 atomic%). The result of Id-Vg characteristic is shown. FIGS. 3A to 3G show the results of two measurements.

3 (a) to 3 (g), all of the IGZO added with the group X element exhibit good switching characteristics, but when Cu, Cr, or Mo is added, the transistor switches in any case. There wasn't.

From these experimental results, the X group element is extremely useful as an element for improving the mobility and TFT characteristics of IGZO, and the X group element excluding Si is extremely useful for improving the working efficiency of the target assembly. It was confirmed that it was useful. These experimental results show that when the oxide thin film is manufactured by the sputtering method using the target assembly, even if the X group element enters from the target gap, the oxide is placed on the oxide at the substrate position corresponding to the gap. This indicates that since a thin film containing an X group element (an oxide thin film useful for improving TFT characteristics) is formed, the TFT characteristics of the oxide semiconductor thin film after film formation do not deteriorate. The usefulness of a backing member composed of two or more types is indirectly verified.

In addition, although the result when using IGZO as an oxide is shown in the present Example, it is thought that the same result is obtained also about all the oxides made into object by this invention.

Example 2
In this example, in order to compare and examine the usefulness as a backing member, a target assembly was manufactured using pure Ni (example of the present invention) or pure Cu (comparative example), and TFT characteristics were evaluated.

First, the target assembly was manufactured by the manufacturing method of the preferred embodiment described above. In this example, a pure Cu backing plate (φ132 mm, thickness 8.5 mm) was used as the backing plate, an In-based alloy was used as the bonding material, and a Cu wire was used as the spacer. The width of the interval T between the oxide target members was 0.3 mm.

Next, a TFT was produced in the same manner as in Example 1 except that the target assembly was used, and the on-current and SS value were evaluated. The thickness after sputtering (residual thickness) was 6 mm or 1 mm.

For reference, each characteristic was evaluated in the same manner as described above using a target assembly without a gap. Under actual operation, as described above, a target assembly having a gap between target members is manufactured. In this embodiment, a target without a gap is used for convenience in order to obtain a reference example that eliminates the influence of the gap. An assembly was used.

These results are shown in Table 3, Table 4 and FIG. FIG. 4 is a graph showing Id-Vg characteristics under the conditions described in Table 3 and Table 4.

From these results, when the Ni backing member was used, good on-current and SS values comparable to those when the target assembly without a gap was used were obtained. These results were seen regardless of the thickness after sputtering.

On the other hand, when a Cu backing member was used, the on-current and SS value characteristics were degraded. In particular, as shown in Table 4, when the thickness after sputtering became 1 mm, the above-mentioned characteristics were more markedly reduced, the on-current was significantly reduced, and the SS value was significantly increased.

Although this application has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on July 20, 2012 (Japanese Patent Application No. 2012-162125), the contents of which are incorporated herein by reference.

In the target assembly of the present invention, by providing a backing member disposed across the gap between the oxide target member and the backing plate, the components of the backing plate are prevented from being mixed (contaminated) into the thin film. can do. Further, since the backing member is made of a material composed of at least one or more of predetermined metal elements (Ni, Si, Hf, and Ta) that do not deteriorate the TFT characteristics of the oxide semiconductor thin film, Even if the predetermined metal element is contaminated, deterioration of TFT characteristics due to contamination can be prevented, and good TFT characteristics can be maintained.

DESCRIPTION OF SYMBOLS 1 Target assembly 2 Sputtering target 3 Backing plates 4a-4d Oxide target member 5 Backing member 11a, 11b, 11c Low melting-point solder bonding material 12 Spacer T Space | interval Q The part immediately under space | interval T

Claims (6)

A target assembly in which a plurality of oxide target members are arranged at intervals on a backing plate via a bonding material,
Between the oxide target member and the backing plate, having a backing member made of one or more selected from the group consisting of Ni, Si, Hf, and Ta provided across the gap A target assembly. 2. The target assembly according to claim 1, wherein the oxide target member contains at least In and Zn. The target assembly according to claim 2, wherein the oxide target member further includes at least one of Ga and Sn. The target assembly according to claim 1, wherein the backing plate is made of pure Cu or a Cu alloy. The target assembly according to claim 1, wherein the backing member is made of one or more selected from the group consisting of Ni, Hf, and Ta. The target assembly according to claim 1, wherein the bonding material is made of an In-based material or an Sn-based material.

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