JP6228631B1 - Al alloy sputtering target - Google Patents

Abstract

The present invention provides an Al alloy sputtering target that contributes to an improvement in film formation rate and is excellent in target productivity. Cu is contained more than 6 atomic% and 17 atomic% or less, and the balance is Al and 0.1 to 5.5 atomic% of Nd, La, Y, Sc, Gd, Dy, Lu, Ce, Pr and Tb. An Al alloy sputtering target comprising at least one rare earth element selected from the following and inevitable impurities. Aluminum nitride thin film or aluminum oxide thin film formed by reactive sputtering [selection] None

Description

  The present invention relates to a sputtering target (hereinafter also referred to as a target) used for forming an electrode or an insulating film, and is used in detail for a display device such as a liquid crystal display or an organic EL display or an input device such as a touch panel. The present invention relates to a sputtering target used for electrode formation.

  Al alloys are widely used in the field of display devices such as liquid crystal displays because of their low electrical resistivity and ease of processing, and are used as materials for wiring films, electrode films, or reflective electrode films. Yes.

  For example, an active matrix type liquid crystal display includes a thin film transistor (TFT) as a switching element, and various Al alloy thin films such as a pure Al thin film or an Al—Nd alloy are generally used as the wiring material. .

  For the formation of the Al alloy thin film, a sputtering method using a sputtering target is generally employed.

  The sputtering method has an advantage that a thin film having the same composition as the target can be formed. In particular, an Al alloy thin film formed by sputtering can dissolve an alloy element that does not dissolve in an equilibrium state, and exhibits excellent performance as a thin film. Yes, development of a sputtering target as a raw material is underway.

  In recent years, for the purpose of improving the productivity of an Al alloy thin film, it has been studied to increase the film forming rate as compared with the prior art. For example, methods of Patent Documents 1 and 2 have been proposed. Patent Document 1 discloses a sputtering target which is made of Al or an Al alloy and has a (111) crystal orientation content of 20% or more measured by X-ray diffraction method on the sputtering surface. In the example of Patent Document 1, it is verified that the film-forming rate is improved by setting the crystal orientation to the (111) plane in an Al—Si based alloy in which Si is added to Al.

  Further, Patent Document 2 discloses an Al-based alloy sputtering target characterized by containing Ta. The example of Patent Document 2 shows an Al—Ta alloy in which 1.5 atomic% of Ta is added to Al and the film formation rate is 1.6 times or more the pure Al ratio.

JP-A-6-128737 JP 2012-224742 A

  However, with respect to the method of setting the (111) crystal orientation content in Al or Al alloy described in Patent Document 1 to 20% or more, it is required to further improve the film formation rate from the viewpoint of productivity.

  Moreover, about the Al alloy sputtering target containing Ta of patent document 2, when Ta adds 1 atomic% or more, there exists a concern that a nozzle will be obstruct | occluded at the time of spray forming, and target productivity will fall. For this reason, considering the manufacturability of the target, it is difficult to further improve the film formation rate.

  Accordingly, an object of the present invention is to provide an Al alloy sputtering target that contributes to an improvement in the deposition rate and is excellent in target productivity.

  Conventionally, attention has not been paid to the effect of improving the Cu film formation rate, but the present inventors have proposed that the Al alloy sputtering target to which Cu is added in a high addition amount of more than 6 atomic% and not more than 17 atomic% is Ta. It has been found that it has a high film formation rate as compared with the Al alloy sputtering target contained, and also has excellent manufacturability, and has completed the present invention.

That is, the present invention relates to the following [1] to [ 2 ].
[1] More than 6 atomic% and 17 atomic% or less of Cu , and at least one selected from the group consisting of Nd and Y as a rare earth element is 0.1 to 5.5 atomic% (however, Nd is 2.4) Al alloy sputtering target containing ~ 4.0 atomic%, excluding the range of 2.4-3.0 atomic% for Y) , the balance being Al and inevitable impurities.
[2] More than 6 atomic% and 17 atomic% or less of Cu, and at least one selected from the group consisting of La, Sc, Gd, Dy, Lu, Ce, Pr and Tb as rare earth elements is 0.1 to 5. An Al alloy sputtering target containing 5 atomic% and the balance being Al and inevitable impurities.

  Since the Al alloy sputtering target of the present invention contains more than 6 atomic% and 17 atomic% or less of Cu, the film forming rate can be improved and the manufacturability is also improved as compared with the Al-Ta alloy.

  Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be arbitrarily modified without departing from the gist of the present invention. “Atom%” and “at%” are synonymous.

  The Al alloy sputtering target of the present invention is an Al alloy sputtering target for forming an Al alloy thin film by sputtering, contains Cu in an amount of more than 6 atomic% and 17 atomic% or less, and the balance is made of Al and inevitable impurities. It is characterized by.

  The Al alloy sputtering target is a sputtering target mainly composed of Al containing pure Al and an alloy element. The Cu content in the Al alloy sputtering target of the present invention is more than 6 atomic%, preferably 7 atomic% or more. By making Cu content more than 6 atomic%, it is excellent in productivity and a high film-forming rate can be obtained.

  Further, the Cu content is 17 atomic% or less, and is preferably 12 atomic% or less in order to further suppress the decrease in the crack limit rolling reduction. By setting the Cu content to 17 atomic% or less, the yield in the SF (spray forming) process and the crack limit reduction rate in the forging process are suppressed, and the target productivity is prevented from abruptly decreasing. be able to.

  The inevitable impurities include, for example, elements inevitably mixed in the manufacturing process, for example, Fe, Si, and the like, and the content of these is preferably 0.03% by mass or less in total. More preferably, the content is 0.01% by mass or less.

  The Al alloy sputtering target of the present invention is excellent in manufacturability by adding a small amount of rare earth element as a second additive element to make an Al-Cu-X alloy (X: rare earth element), and when no rare earth element is added Thus, the film formation rate can be further improved.

  The rare earth element content is preferably 0.1 atomic% or more, more preferably 2 atomic% or more. By setting the content of the rare earth element to 0.1 atomic% or more, the effect of the second additive element described above can be obtained. The rare earth element content is preferably 5.5 atomic percent or less, and more preferably 3.7 atomic percent or less. By setting the rare earth element content to 5.5 atomic% or less, it is possible to suppress a decrease in the yield of the SF process and a decrease in the crack limit rolling reduction, and to prevent the target productivity from deteriorating.

  The rare earth element means an element group in which Sc (scandium) and Y (yttrium) are added to a lanthanoid element (a total of 15 elements from La with atomic number 57 to Lu with atomic number 71 in the periodic table). . Among the rare earth elements, Nd, La, Y, Sc, Gd, Dy, Lu, Ce, Pr, and Tb are preferable and Nd is more preferable from the viewpoint of improving the film forming rate. Of these, one or more can be used in any combination.

  The Al alloy thin film of the present invention is preferably formed by a sputtering method using the above-described sputtering target of the present invention. This is because according to the sputtering method, a thin film having excellent in-plane uniformity of components or film thickness can be easily formed.

  As a method for forming an Al alloy thin film by sputtering, for example, as the above target, Cu is contained more than 6 atomic% and 17 atomic% or less, and the balance is composed of Al and inevitable impurities. The method of forming by the magnetron sputtering method using the Al alloy sputtering target of the same composition as the above, the method of forming by the reactive sputtering method using the target, and the like.

  In view of productivity and film quality control, it is preferable to employ a reactive sputtering method. Examples of the Al alloy thin film formed by the reactive sputtering method include an aluminum nitride thin film and an aluminum oxide thin film.

Specifically, the conditions of the reactive sputtering method may be appropriately controlled according to, for example, the type of the Al alloy to be used, but are preferably controlled as follows.
-Substrate temperature: room temperature to 400 ° C
・ Sputtering power: 100-500W
-Ultimate vacuum: 1 x ^10-5 Torr or less

  The shape of the target includes those processed into an arbitrary shape (for example, a square plate shape, a circular plate shape, a donut plate shape, etc.) according to the shape or structure of the sputtering apparatus.

  Examples of the method for producing the target include a method obtained by producing an ingot made of an Al-based alloy by a melt casting method, a powder sintering method, a spray forming method, and a preform (final dense body) made of an Al-based alloy. And a method obtained by densifying the preform by a densifying means after the intermediate) is obtained.

  The present invention also includes a display device and an input device provided with the Al alloy thin film. Examples of the display device include a display device in which the Al alloy film is used for a source-drain electrode and a signal line of a thin film transistor, and the drain electrode is directly connected to a transparent conductive film. Moreover, as an aspect of an input device, the input device provided with the input means in the display apparatus like a touch panel etc. is mentioned, for example.

  The present invention will be described more specifically with reference to the following examples and comparative examples. However, the present invention is not limited to these examples, and is implemented with modifications within a range that can be adapted to the gist thereof. All of which are within the scope of the present invention.

(1) Production of sputtering target After 110 kg was melted by spray forming to obtain an Al alloy preform, the weight of the preform was measured with a weigh scale, and the yield at the time of spray forming (SF yield) was calculated. The obtained preform was enclosed in a capsule, degassed, and densified with a HIP apparatus. And after heating at 450 degreeC, the rolling reduction was computed using the following formula at the forge process.
Reduction ratio: (L ₀ -L ₁ ) / L ₀ × 100 (%)
Initial sample length: L ₀ , sample length after reduction: L ₁
Moreover, the crack of the sample was visually confirmed at the time of rolling, and the rolling reduction just before the cracking was confirmed was made into the cracking critical rolling reduction.

The SF yield was evaluated according to the following criteria.
SF yield = preform weight / melting raw material (110 kg) x 100 (%)
○: 40% or more Δ: more than 30% to less than 40% ×: 30% or less

The crack limit rolling reduction was evaluated according to the following criteria.
○: 50% or more Δ: more than 30% to less than 50% ×: 30% or less

(2) Film formation Using an alkali-free glass plate (plate thickness 0.7 mm, diameter 4 inches) as a transparent substrate, an Al alloy shown in Table 1 was formed on the surface by DC magnetron sputtering. In film formation, the atmosphere in the chamber is once adjusted to an ultimate vacuum of 3 × 10 ⁻⁶ Torr before film formation, and then a disk-type sputtering target having a diameter of 4 inches having the same composition as that of the metal film. Sputtering was performed under the following conditions.

(Sputtering conditions)
Ar gas pressure: 2 mTorr
Ar gas flow rate: 19 sccm
・ Sputtering power: 500W
-Substrate temperature: Room temperature-Film formation temperature: Room temperature-Film formation time: 10 minutes

(3) Calculation of film-forming rate The film thickness of the produced thin film was measured with a stylus step meter (Alpha Step 250 manufactured by NTS). The film thickness was measured at three points in the radial direction from the center of the thin film, and the average value was defined as the film thickness (Å). The film thickness thus obtained was divided by the sputtering time (s) to calculate the average film formation rate (Å / s).

  In Example 1 described later, the deposition rate ratio was determined by dividing the Al alloy average deposition rate by the pure Al average deposition rate. Although not shown in Table 1, the film formation rate ratio (film formation rate: pure Al ratio) of Al-1 atomic% Ta was 1.5 times. Therefore, the case where the film formation rate ratio exceeds 1.50, which is the film formation rate ratio of Al-1 atomic% Ta, was set as a range in which the effect of improving the film formation rate by alloying was recognized. In Example 2, the film formation rate ratio was determined by dividing the average film formation rate of the Al-7 atomic% Cu-rare earth alloy by the Al alloy containing 7 atomic% of Cu.

(4) Comprehensive judgment The comprehensive judgment was evaluated according to the following criteria.
◯: The film formation rate ratio is 1.50 or more, and at least one of the SF yield and the crack limit rolling reduction is ◯.
(Triangle | delta): The film-forming rate ratio is 1.50 or more, and neither SF yield nor crack limit rolling reduction is (circle).
X: The film formation rate ratio is 1.50 or more, but at least one of SF yield and crack limit rolling reduction is x, or the film formation rate ratio is 1.50 or less.

<Example 1>
An Al film having the composition shown in Table 1 was formed, and the film formation rate and manufacturability were evaluated. The results are shown in Table 1. In Table 1, Examples 1 to 4 are examples, and Examples 5 to 8 are comparative examples.

  As shown in Table 1, in pure Al of Examples 1 to 7, Al-1 atomic% Cu to Al-17 atomic% Cu, an improvement in the film formation rate was confirmed as the amount of Cu added increased. With 17 atomic% Cu, the pure Al ratio was improved to 2.12 times.

  In Examples 1-4, Al-6.1 atomic% Cu to Al-17 atomic% Cu were confirmed to have a higher film forming speed than Al-1 atomic% Ta (1.50 times), but the film forming rate was improved. . On the other hand, the film formation rate ratios of pure Al, Al-1 atomic% Cu and Al-5 atomic% Cu shown in Examples 5 to 8 are less than or equal to Al-1 atomic% Ta, and the film formation rate does not improve. It was. From this result, it was found that the film formation rate was improved by setting the Cu content in the Al alloy sputtering target to be more than 6 atomic%.

  Moreover, as shown in Example 4, when the Cu content exceeds 12 atomic%, the crack limit rolling reduction decreases, so by setting the Cu content to 12 atomic% or less, the crack critical rolling reduction is decreased. It was found that can be suppressed. It is considered that as a factor that the crack limit rolling reduction decreased with the increase in the Cu content, the metal hardness in the target increased with the increase in the added elements, so that the target hardness increased and as a result cracking occurred.

  Further, as shown in Example 8, it was found that, in the range where the amount of Cu added is larger than that of Al-17 atomic% Cu, cracks frequently occur in the processing step during target production, resulting in poor productivity. From this result, it was found that the productivity of the target can be improved by setting the Cu content to 17 atomic% or less.

<Example 2>
By adding a rare earth element, which has been confirmed to improve the film formation rate in a small amount, to the Al—Cu alloy extracted in Example 1, an Al—Cu—X alloy (X: rare earth element) can be further added. The effect of improving the deposition rate was confirmed. Table 2 shows the results of evaluating the film formation rate and manufacturability. In Table 2, Examples 9 to 24 are Examples, and Examples 25 and 26 are Comparative Examples.

  As shown in Table 2, in the Al-7 atom% Cu-rare earth alloys of Examples 9 to 24, the film formation rate ratio with respect to the Al-7 atom% Cu alloy is 1.01 to 1.78. Improvement effect was confirmed. On the other hand, in Example 25, since the addition amount of the rare earth element was too small, 0.05 atomic%, the film forming rate improving effect by the second additive element was not confirmed. In addition, in Example 26, the amount of rare earth element added was too large at 6 atomic%, so that the critical crack reduction did not reach the standard.

  From this result, it was found that the film formation rate of the Al alloy sputtering target can be improved by adding 0.1 to 5.5 atomic% of a rare earth element as the second additive element.

Claims (2)

More than 6 atomic% and 17 atomic% or less of Cu , and at least one selected from the group consisting of Nd and Y as a rare earth element is 0.1 to 5.5 atomic% (however, Nd is 2.4 to 4. An Al alloy sputtering target containing 0 atomic%, excluding the range of 2.4 to 3.0 atomic% for Y), and the balance consisting of Al and inevitable impurities. 0.1 to 5.5 atomic percent of Cu at least 6 atomic percent and 17 atomic percent or less, and at least one selected from the group consisting of La, Sc, Gd, Dy, Lu, Ce, Pr and Tb as rare earth elements An Al alloy sputtering target that contains Al and inevitable impurities.