JP5328017B2 - Method for producing aluminum for sputtering target - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum sheet for a sputtering target which can suppress the generation of splashes during sputtering, and can make the resistance of the metal film to be formed low, and to provide a method for producing the same. <P>SOLUTION: The aluminum sheet for a sputtering target is composed of high purity aluminum of &ge;99.99 mass%, and also, the content of hydrogen per 100 g of aluminum is &le;0.3 cm<SP>3</SP>. The crystal grain diameter in the sputtering face of the aluminum sheet is &le;300 &mu;m, and the occupancy ratio of the ä100} face in the crystal orientations of the sputtering face is 30 to 60%. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention particularly relates to a high-purity aluminum plate for a sputtering target used for a thin film electrode, a thin film wiring or the like of a liquid crystal display or a plasma display, and a method for producing the same.

  Conventionally mainly used for high-melting-point metal such as pure Cr film, pure Ta film, and pure Ti film for liquid crystal display or plasma display, thin film sensor, etc. Pure metal films or their alloy films have been used.

  In recent years, with the increase in size and definition of displays, wiring films and electrode films are required to have low resistance and low stress and to stabilize their characteristics in order to prevent signal delay. For this reason, a high-purity aluminum film having a lower resistance than that of the above metal film has been used.

  The metal film of the substrate forms a plasma discharge between the substrate and a target that is a raw material for forming a thin film, and the target is configured with energy that ionized argon collides with the target. It is formed by a method (sputtering) in which a certain atom is knocked out and deposited on a substrate to form a thin film.

  As the size of the substrate is increased, the target for forming the metal film is also required to be increased in size. Conventionally, a target manufactured in a size of 2 or 3 for the required target size is pasted and used. However, in the divided target, foreign matter is generated from the joint and becomes defective. Is required.

In addition, when a defect such as a crack or a hole exists in the target structure, that is, a space is present, charges are likely to concentrate on the defect during sputtering, and a problem of splash is likely to occur due to abnormal discharge. Splash means that when the surface of the sputtering surface of the target has large irregularities during the sputtering, the projected portion falls on the substrate as aluminum particles having a size of several μm.
As described above, when the target is enlarged as a single unit, it is difficult to prevent defects in the target, so that there is a problem that the problem of splash is likely to occur.

Japanese Patent Laid-Open No. 9-235666 JP 2001-316806 A JP 2002-361400 A

  The present invention has been made in view of such conventional problems, an aluminum plate for a sputtering target that can suppress the occurrence of splash during sputtering and can reduce the resistance of a metal film to be formed, And a method of manufacturing the same.

An aluminum plate for a sputtering target,
The aluminum plate is made of high-purity aluminum of 99.99% by mass or more, and the hydrogen content per 100 g of aluminum is 0.3 cm ³ or less.
There is provided an aluminum plate for a sputtering target, wherein the crystal grain size of the sputtering surface of the aluminum plate is 300 μm or less, and the occupancy of the {100} plane is 30 to 60% of the crystal orientation of the sputtering surface. .

The aluminum plate for a sputtering target has all the above-mentioned conditions for the purity, the crystal grain size of the sputtering surface of the hydrogen content, and the crystal orientation occupancy of the sputtering surface. Therefore, even when the target is enlarged as a single unit, the occurrence of splash during sputtering can be suppressed, and the metal film formed using the aluminum plate can have low resistance.

  The aluminum plate for sputtering target has a purity of 99.99% by mass or more. Therefore, low resistance of the thin film formed using the aluminum plate as a raw material can be realized.

The aluminum plate has a hydrogen content per 100 g of aluminum of 0.3 cm ³ or less. Therefore, it is possible to suppress the generation of porosity (holes) in the aluminum plate, and it is possible to suppress the occurrence of splash when performing sputtering using the aluminum plate.

Moreover, the crystal grain size of the sputtering surface of the said aluminum plate is 300 micrometers or less, and a crystal grain is fine. Moreover, the occupancy ratio of the {100} plane in the crystal orientation of the sputtering surface is 30 to 60%, and the crystal orientation of the sputtering surface is evenly dispersed and randomized.
Note that {100} plane to the extent of ± 10 ° with Euler angles with respect to {100} plane is acceptable. If it is in this range, the effect of the present invention can be sufficiently exhibited.
The {100} plane is a group of equivalent plane groups such as the (100) plane, the (010) plane, and the (001) plane.

In other words, the aluminum plate has a random crystal orientation on the sputtering surface and is fine. Therefore, generation of large irregularities on the sputtering surface can be prevented, and the surface can be made uniform. Thereby, generation | occurrence | production of a splash can be suppressed during sputtering and the thin film of a uniform film thickness can be formed.
The occupancy refers to the area ratio of crystal grains having each crystal orientation, and is measured by EBSP.

Thus, it is possible to suppress the splash generation during sputtering, a metal film formed can provide an aluminum plate for a sputtering target which can be a low resistance.

The present invention has a rolling step of obtaining a plate having the final thickness by rolling from an ingot made of high-purity aluminum of 99.99% by mass or more,
In the rolling step, the total rolling reduction from the ingot is 50% or more, and the rolling temperature of all passes is in the range of 100 ° C to 300 ° C.
At least for the final pass, the rolling temperature is in the range of 200 ° C. or more and 300 ° C. or less, and the rolling satisfies the relational expression of rolling reduction (%) ≧ {30000 / (rolling temperature (° C.) + 273)} − 25. It is in the manufacturing method of the aluminum plate for sputtering targets characterized by rolling at a rate ( Claim 1 ).

  The manufacturing method of the aluminum plate for sputtering targets of this invention can suppress generation | occurrence | production of the splash in sputtering by performing a rolling process on the said specific conditions with respect to the said ingot, The metal film to form is formed. An aluminum plate for a sputtering target that can have a low resistance can be produced.

The said ingot consists of high-purity aluminum 99.99 mass% or more.
Thereby, the aluminum plate for sputtering targets obtained is made of high-purity aluminum of 99.99% by mass or more, and as described above, the low resistance of the thin film formed using the aluminum plate obtained by the production method of the present invention as a raw material. Can be realized.

In the rolling step, the total rolling reduction from the ingot (= (ingot plate thickness−plate thickness after rolling) / ingot plate thickness × 100) is 50% or more, and the rolling temperature of all passes is 100 ° C. or more. It is performed in the range of 300 ° C. or lower.
Thereby, the coarsening of the crystal grain diameter of the aluminum plate for sputtering targets obtained can be suppressed.

  In the rolling step, at least for the final pass, the rolling temperature is in the range of 200 ° C. or higher and 300 ° C. or lower, and the rolling reduction (%) ≧ {30000 / (rolling temperature (° C.) + 273)} − 25. Rolling is performed at a reduction rate that satisfies the following relational expression. By setting the temperature to 200 ° C. or higher, high pressure can be realized, the crystal orientation of recrystallized grains can be randomized, and the occupancy ratio of the {100} plane that is most likely to be accumulated can be 30 to 60%. . And it can refine | miniaturize a crystal grain by setting it to 300 degrees C or less and rolling under high pressure. Therefore, the crystal grain size of the sputtering surface of the aluminum plate can be 300 μm or less.

  The rolling process is basically performed in a plurality of passes, but can be performed in one pass. In the case of one pass, the final one-pass condition is applied.

Moreover, in order to set the hydrogen content per 100 g to 0.3 cm ³ or less, it is preferable to perform a degassing treatment of blowing an inert gas into the molten metal as necessary.

That is, the sputtering target aluminum plate obtained by the production method of the present invention is made of high-purity aluminum of 99.99 mass% or more, and the hydrogen content per 100 g of aluminum is 0.3 cm ³ or less, and the sputtering surface. And the occupancy of the {100} plane in the crystal orientation of the sputtering surface is 30 to 60%, and the excellent properties described in the first invention can be obtained.
Thus, according to the present invention, it is possible to provide a method for manufacturing an aluminum plate for a sputtering target that can suppress the occurrence of splash during sputtering and can reduce the resistance of a metal film to be formed.

As described above, the sputtering target aluminum plate is made of 99.99 mass% or more of high-purity aluminum.
When the purity of the aluminum plate is less than 99.99% by mass, the resistance value of the formed metal film becomes high, and it becomes difficult to obtain the desired quality.

The hydrogen content per 100 g of aluminum in the aluminum plate is 0.3 cm ³ or less.
When the amount of hydrogen contained per 100 g of aluminum exceeds 0.3 cm ³ , porosity is likely to be generated on the aluminum plate, and there is a problem that the portion of the porosity becomes uneven at the stage of sputtering and splash is likely to occur.

Moreover, the crystal grain diameter of the sputtering surface of the said aluminum plate is 300 micrometers or less.
The crystal grain size is a surface parallel to the sputtering surface, which is measured by a polarizing optical microscope texture and measured by a cutting method according to ASTM E112.
When the crystal grain size of the sputtering surface exceeds 300 μm, there is a problem that a sharp crystal grain boundary is generated at the stage of sputtering, thereby increasing the unevenness and easily causing splash.

Moreover, the occupancy rate of the {100} plane in the crystal orientation of the sputtering plane is 30 to 60%.
When the occupancy ratio of the {100} plane exceeds 60%, there is a problem that a portion of the {100} plane having a high occupancy ratio is intensively sputtered to increase unevenness, and splash is likely to occur. On the other hand, when the occupancy ratio of the {100} plane is less than 30%, other azimuths are preferentially developed, and therefore, portions with high occupancy ratios are intensively sputtered and unevenness is large. Therefore, there is a problem that splash is likely to occur during sputtering.
The occupation ratio of the {100} plane is more preferably 45 to 60%.
Moreover, since the thickness of the said aluminum plate for sputtering targets influences total sputtering time, the thicker one is preferable. Usually, it is 10 mm or more.

The manufacturing method of the aluminum plate for sputtering targets of this invention has the rolling process which obtains the board which has final board thickness by rolling from the ingot which consists of 99.99 mass% or more high-purity aluminum, as mentioned above.
When the purity of the ingot is less than 99.99% by mass, the resistance value of the thin film formed using the obtained aluminum plate is increased, and the necessity of using aluminum as a target is eliminated.

And the said rolling process is performed in the range whose total rolling reduction from the said ingot is 50% or more, and the rolling temperature of all the passes is 100 degreeC or more and 300 degrees C or less.
When the total reduction ratio rolled from the ingot to the final plate thickness is less than 50%, there is a problem that the crystal grain of the aluminum plate becomes coarse and the crystal grain size of the sputtering surface exceeds 300 μm.

  Further, when rolling is performed at a rolling temperature of less than 100 ° C., there is a problem that deformation resistance increases and rolling becomes difficult. On the other hand, when rolling is performed at a rolling temperature exceeding 300 ° C., there is a problem that the crystal grains become coarse and the crystal grain size of the sputtering surface exceeds 300 μm.

And at least for the last pass, the rolling temperature is in the range of 200 ° C. or higher and 300 ° C. or lower, and the reduction ratio (%) ≧ {30000 / (rolling temperature (° C.) + 273)} − 25. Rolling is performed at a reduction rate that satisfies the requirement.
When the final pass is performed at a rolling temperature of less than 200 ° C., there is a problem that it is difficult to realize high pressure because the reduction ratio becomes too high. In addition, since the processed structure is largely introduced, if the final annealing described later is not performed, the occupancy ratio of the {100} plane becomes too small and other orientations are easily developed with priority. There is a problem that the splash is likely to occur. In addition, when the final annealing described later is performed, the crystal grains are likely to be coarse, and the occupancy of the {100} plane is also likely to be increased, so that splash is likely to occur during sputtering. is there. On the other hand, when the final pass is performed at a rolling temperature exceeding 300 ° C., there is a problem that the crystal grains are likely to be coarsened and the crystal grain size of the sputtering surface exceeds 300 μm.

  Further, when the rolling reduction of the final pass of rolling is rolling reduction (%) <{30000 / (rolling temperature (° C.) + 273)} − 25, there arises a problem that crystal grains become coarse. For example, when the rolling temperature is 200 ° C., a reduction ratio of 38.4% or more is required, and when the rolling temperature is 300 ° C., a reduction ratio of 27.4% or more is required.

Moreover, it is preferable that the said manufacturing method performs an annealing process at the temperature of 250 degreeC or more and 350 degrees C or less after the said rolling ( Claim 2 ).
In this case, residual strain of the aluminum plate that is likely to cause splash can be removed.
The effect cannot be obtained when annealing is performed at less than 250 ° C. On the other hand, when the annealing treatment is performed at a temperature exceeding 350 ° C., there is a problem that the crystal grains are secondary recrystallized during the annealing treatment and become coarser to 300 μm or more.

Example 1
In this example, an aluminum plate for sputtering target according to an example of the present invention and a method for manufacturing the same will be described.
In this example, an aluminum plate for sputtering target (sample E1 to sample E8) as an example and an aluminum plate for sputtering target (sample C1 to sample C10) as a comparative example were produced.

The aluminum plate for sputtering target (samples E1 to E8) of this example is made of high-purity aluminum of 99.99% by mass or more, and the hydrogen content per 100 g of aluminum is 0.3 cm ³ or less. Moreover, the crystal grain size of the sputtering surface of the said aluminum plate is 300 micrometers or less, and the occupation rate of the {100} plane is 30 to 60% among the crystal orientations of the said sputtering surface.
This will be described in detail below.

In producing the sputtering target aluminum plates (samples E1 to E8 and samples C1 to C10), first, an ingot made of high-purity aluminum of 99.99 mass% or more was prepared.
In the rolling process, a plate having the final thickness was obtained from the ingot by rolling.
Table 1 shows the total rolling reduction ratio from the ingot and the rolling temperature ranges of all passes in the rolling process. In addition, about the sample E6, the sample E8, the sample C6, the sample C8, and the sample C10, the rolling process performed only 1 pass.

  Table 1 also shows the rolling temperature, rolling reduction (A1), {30000 / (rolling temperature (° C.) + 273)} − 25 value (B1), and final one pass of the second pass from the final. , Rolling temperature, rolling reduction (A2), {30000 / (rolling temperature (° C.) + 273)} − 25 (B2). The magnitudes of A1 and B1 and the magnitudes of A2 and B2 are also shown in Table 1.

  As shown in Table 1, samples E1 to E8 as examples are obtained by rolling a plate having a final plate thickness from an ingot made of high-purity aluminum of 99.99% by mass or more in a rolling process. In the rolling step, the total rolling reduction from the ingot is 50% or more, and the rolling temperature of all passes is in the range of 100 ° C. or more and 300 ° C. or less. In addition, at least for the final pass, a relational expression of a rolling temperature in the range of 200 ° C. to 300 ° C. and a reduction ratio (%) ≧ {30000 / (rolling temperature (° C.) + 273)} − 25 Rolling is performed at a reduction rate that satisfies the requirement.

  Next, for the obtained Samples E1 to E8 and Samples C1 to C10, the amount of hydrogen contained, the crystal grain size of the sputtering surface, and the crystal orientation were observed. The results are shown in Table 2. When the measurement of the hydrogen content, the measurement of the crystal grain size of the sputtering surface, and the crystal orientation were all within the scope of the present invention, the evaluation was evaluated as “Good”, and when they were out of the scope, the evaluation was “Poor”.

<Hydrogen content>
As for the hydrogen content, hydrogen gas mass analysis was performed by a temperature programmed desorption method using a mass filter, and the hydrogen content per 100 g of aluminum was measured.

<Crystal grain size of sputtering surface>
The crystal grain size of the sputtering surface is measured by a cutting method in accordance with ASTM E 112, after observing the surface parallel to the sputtering surface with emery paper, further observing a polarizing optical microscope structure for a sample prepared by electrolytic polishing and electrolytic etching. did.
As an example of the observation results, photographs of the sputtering surfaces of sample E2 and sample C2 observed with an optical microscope at 50 times magnification are shown in FIGS.

<Crystal orientation>
The crystal orientation is observed by using an EBSP device attached to the SEM after polishing the surface parallel to the actual sputtering surface with emery paper and then mirror-finishing it by electrolytic polishing and setting it on a scanning electron microscope (SEM). Observation was carried out at a magnification of 50 times.
And the occupancy of {100} plane was measured among the crystal orientations of the sputtering surface.

  Moreover, sputtering was performed using the aluminum plates for the sputtering target (samples E1 to E8 and samples C1 to C10).

As shown in Table 2, Samples E1 to E8 as examples have a hydrogen content per 100 g of aluminum of 0.3 cm ³ or less, a crystal grain size on the sputtering surface of the aluminum plate of 300 μm or less, and sputtering. Of the crystal orientation of the plane, the occupation ratio of the {100} plane is 30 to 60%.

Also, the total rolling reduction from the ingot is 50% or more, the rolling temperature of all passes is in the range of 100 ° C. or more and 300 ° C. or less, and the final one pass is the rolling temperature in the range of 200 ° C. or more and 300 ° C. or less. And rolling at a rolling rate satisfying the relational expression of rolling reduction (%) ≧ {30000 / (rolling temperature (° C.) + 273)} − 25, the final two passes are 200 ° C. or more and 300 ° C. or less. Regardless of whether the rolling temperature is within the range and rolling is performed at a rolling reduction rate satisfying the relational expression of rolling reduction (%) ≧ {30000 / (rolling temperature (° C.) + 273)} − 25, for a desired sputtering target It can be seen that an aluminum plate is obtained.
Sample E3 to sample E5 and sample E7 were further annealed at a temperature of 250 ° C. or higher and 350 ° C. or lower after the rolling step, and the residual strain of the aluminum plate could be removed.

  And the said sample E1-sample E8 could suppress generation | occurrence | production of the splash during sputtering, and was able to form the low resistance metal film.

  Thus, according to this example, it is possible to provide an aluminum plate for a sputtering target that can suppress the occurrence of splash during sputtering and can reduce the resistance of a metal film to be formed, and a method for manufacturing the same. I understand that I can do it.

In addition, Sample C1 and Sample C2 as comparative examples were obtained because the final one pass was performed at a reduction ratio of% reduction (%) <{30000 / (rolling temperature (° C.) + 273)} − 25. Further, the crystal grain size of the sputtering surface of the aluminum plate for sputtering target was increased, and the occupation ratio of the {100} plane exceeded the upper limit of the present invention. Splash was generated during sputtering.
Moreover, since the hydrogen content per 100g of aluminum exceeded the upper limit of this invention, the sample C3 as a comparative example generate | occur | produced the porosity in the aluminum plate and the splash generate | occur | produced during sputtering.

Sample C4 as a comparative example has a final one-pass temperature lower than the lower limit of the present invention, and a reduction ratio (%) <{30000 / (rolling temperature (° C.) + 273)} − 25. Since the final annealing was performed, the crystal grains became coarse and the occupancy of the {100} plane exceeded the upper limit of the present invention. Splash was generated during sputtering.
Moreover, since the rolling temperature of all the passes and the temperature of the last 1 pass exceeded the upper limit of this invention, the sample C5 as a comparative example became coarse. Splash was generated during sputtering.

Further, in Sample C6 as a comparative example, the total reduction amount was below the lower limit of the present invention, so the crystal grains became coarse and the {100} plane occupancy exceeded the upper limit of the present invention. Splash was generated during sputtering.
In addition, the sample C7 as a comparative example was measured at a rolling reduction ratio of the final one pass at a rolling reduction ratio (%) <{30000 / (rolling temperature (° C.) + 273)} − 25. It was coarse and the {100} plane occupancy exceeded the upper limit of the present invention. Splash was generated during sputtering.

Further, in the sample C8 as a comparative example, the final one-pass temperature is lower than the lower limit of the present invention and the final annealing is performed, so that the crystal grains are coarse and the {100} plane occupancy is that of the present invention. The upper limit was exceeded. Splash was generated during sputtering.
Further, Sample C9 as a comparative example had a pass in which the rolling temperature exceeded the upper limit of the present invention, so that the crystal grains became coarse and the occupancy of the {100} plane exceeded the upper limit of the present invention. Splash was generated during sputtering.

  Further, in the sample C10 as a comparative example, the final one-pass temperature is lower than the lower limit of the present invention, and since the final annealing is not performed, the occupancy of the {100} plane is lower than the lower limit of the present invention. Azimuth was preferentially developed. Splash was generated during sputtering.

The drawing substitute photograph which shows the metal structure of the sample E2 in Example 1. FIG. The drawing substitute photograph which shows the metal structure of the sample C2 in Example 1. FIG.

Explanation of symbols

  1 Aluminum plate for sputtering target

Claims (2)

  Having a rolling step of obtaining a plate having a final plate thickness by rolling from an ingot made of high-purity aluminum of 99.99% by mass or more,
  In the rolling step, the total rolling reduction from the ingot is 50% or more, and the rolling temperature of all passes is in the range of 100 ° C to 300 ° C.
  At least for the final pass, the rolling temperature is in the range of 200 ° C. or more and 300 ° C. or less, and the rolling satisfies the relational expression of rolling reduction (%) ≧ {30000 / (rolling temperature (° C.) + 273)} − 25. The manufacturing method of the aluminum plate for sputtering targets characterized by rolling at a rate.   2. The method for producing an aluminum plate for a sputtering target according to claim 1, wherein after the rolling, an annealing treatment is further performed at a temperature of 250 ° C. or higher and 350 ° C. or lower.