JP5558066B2 - target - Google Patents

Description

  The present invention relates to a target used in PVD methods such as sputtering and ion plating, and more particularly to a technique for suppressing the occurrence of arcing in a target during the formation of a thin film.

  In recent years, thin films of metals and ceramics have been used in various fields such as electronics fields such as LSI (Large Scale Integration), FPD (Flat Panel Display), and solar cells, and fields such as corrosion resistance, wear-resistant materials and decoration.

  For thin film formation, a physical vapor deposition method (hereinafter referred to as PVD method) such as vacuum vapor deposition, sputtering or ion plating, or a chemical vapor deposition method (CVD method) for forming a film by gas reaction is known. In the field of electronics used as an electrode material, since a dense film formation on the order of nm is desired, a sputtering method is often used.

  In such a thin film, there is a problem that impurities are mixed during the film formation. For example, when a foreign material having a diameter of several μm is mixed when trying to form a multilayer wiring with a thickness of several hundreds of nanometers, it causes conduction through the insulating barrier layer, or when the foreign material is an oxide, it causes a wiring conduction failure. It causes troubles such as.

  Impurities generated during film formation by the PVD method are droplets in the ion plating, splash in the sputtering, and particles that are dust due to a peeled film as seen in the PVD method in general. In order to reduce these, in the PVD method, not only the improvement of the apparatus but also the improvement of the target has been studied.

  As a mechanism of droplets and splash, due to voids, impurities, and protrusions in the target, charge concentration occurs in the vicinity of the interface with the voids and impurities and at the protrusions. ) And droplets and splashes are known to jump out. In order to suppress the occurrence of such droplets and splashes, measures such as increasing the density of the target, increasing the purity, and reducing the surface roughness are generally used. Furthermore, in the sputtering method, many studies have been made to suppress the occurrence of arcing by controlling the grain size and crystal plane orientation of the crystal grains constituting the target.

  Patent Document 1 describes that the grain size of crystal grains is made uniform to suppress the occurrence of arcing.

  Patent Document 2 describes that the generation of arcing is suppressed by making the crystal structure fine and uniform. Patent Document 2 describes that it is possible to suppress the occurrence of arcing by further aligning the crystal orientation.

  Patent Document 3 describes that, by conversely making the crystal orientation random, it is possible to suppress the occurrence of arcing.

  According to Patent Document 4, by using the spray forming method, the crystal directions are aligned, and the crystals with the closest density are increased to reduce the crystals with low atomic density, thereby enabling high deposition rate and low arcing sputtering. It is described that it becomes.

  However, none of the above-mentioned patent documents can sufficiently suppress the arcing of the target.

JP 2000-234167 A JP-T-2002-518593 JP 2009-197332 A JP 2008-127623 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a sputtering target in which the occurrence of arcing during film formation is suppressed.

  In order to solve the above problems, the present inventors have created the following means.

(1) Of two crystals adjacent to each other at the grain boundary on the sputtering surface of the sputtering target, the crystal orientation in the normal direction of the sputtering surface of one crystal is <h ₀ k ₀ l ₀ >, and the other crystal When the crystal orientation in the normal direction of the sputtering surface is <h ₁ k ₁ l ₁ >, at least 80% or more of the crystal grain boundaries in the region where erosion of the sputtering target can occur is <h ₀ A sputtering target characterized by satisfying a relationship in which an angle formed by k ₀ l ₀ > and <h ₁ k ₁ l ₁ > is 30 degrees or less.

(2) Of the two crystals adjacent to each other at the crystal grain boundary on the sputtering surface of the sputtering target, the crystal orientation in the normal direction of the sputtering surface of one crystal is <h ₀ k ₀ l ₀ >, and the other crystal When the crystal orientation in the normal direction of the sputter surface is <h ₁ k ₁ l ₁ >, 80% or more of the crystal grain boundaries of the sputter surface are <h ₀ k ₀ l ₀ > and <h ₁ A sputtering target characterized by satisfying a relationship in which an angle formed by k ₁ l ₁ > is 30 degrees or less.

  According to the present invention, it is possible to provide a sputtering target in which the occurrence of arcing during film formation is suppressed.

It is the figure of the cross section of a sputter target, and is the figure which showed the definition of the crystal orientation of a crystal grain, and the crystal orientation difference (psi) between adjacent crystal grains. It is a schematic diagram of the cross section after performing sputtering of the sputtering target shown in FIG.

  As a result of studying a method for suppressing the occurrence of arcing, the present inventor has found that the difference in the crystal orientation in the normal direction between the adjacent crystal grains at the crystal grain boundary on the sputtering surface of the sputtering target is smaller than a predetermined value. By doing so, it was found that a target capable of suppressing the occurrence of arcing and performing uniform film formation can be obtained.

  This is because the difference in the crystal orientation in the normal direction of the sputtered surface between adjacent crystal grains via the crystal grain boundary is controlled so as to satisfy a predetermined condition. This is considered to be because the step can be reduced.

  The present embodiment will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a cross section of a sputter target, showing the definition of the crystal orientation of adjacent crystal grains and the crystal orientation difference ψ between adjacent crystal grains. As shown in FIG. 1, in the present embodiment, the orientation (crystal orientation) of each crystal grain with respect to the normal direction of the sputtering surface of the target surface is expressed as <h _i k _i l _i > Define. If the orientation of any one crystal grain as a reference is <h ₀ k ₀ l ₀ > and the orientation of an adjacent crystal grain via a grain boundary is <h ₁ k ₁ l ₁ >, these The difference in crystal orientation ψ can be expressed by the following formula (1).

  The crystal orientation described above can be obtained by analyzing the target by EBSP (Electron Back Scattering Pattern). In EBSP, an electron beam is incident on a tilted target surface, and the Kikuchi line diffraction pattern obtained from the reflected electrons generated at this time is analyzed to obtain a crystal orientation at the electron beam incident position.

  In addition, since many materials used as metal or alloy targets have a cubic crystal system, the crystal orientation of an arbitrary crystal grain can be expressed as <h k l>.

In the target of the present embodiment, the crystal orientation difference in the normal direction of the sputtered surface between adjacent crystal grains at the crystal grain boundary on the sputtered surface is preferably 30 degrees or less. For example, in FIG. 1, when the difference in crystal orientation between <h ₀ k ₀ l ₀ > and <h ₁ k ₁ l ₁ > is 30 degrees or less, as shown in FIG. This is because arcing is less likely to occur because the level difference between the generated crystal grains is reduced.

  For example, when the orientations of adjacent crystals are <111> and <211>, the crystal orientation difference is 19.5 degrees, but in this case, there is almost no step even when sputtering is performed, and arcing does not occur. There wasn't.

On the other hand, if the crystal orientation difference exceeds 30 degrees, arcing is likely to occur. Specifically, for example, in FIG. 1, when the crystal orientation difference between <h ₀ k ₀ l ₀ > and <h ₂ k ₂ l ₂ > is larger than 30 degrees, when sputtering is performed, as shown in FIG. Steps between crystal grains become large, and arcing tends to occur at the step portions. For the above reasons, the crystal orientation difference is desirably 30 degrees or less.

  On the other hand, when the crystal orientation difference in the normal direction of the sputtered surface between all adjacent crystal grains on the sputtered surface is set to 30 degrees or less, it is necessary to perform very complicated control in the manufacturing process, and the cost increases. End up. When 80% or more of the crystal grain boundaries have a crystal orientation difference of 30 degrees or less, since it can be manufactured by a general target manufacturing method, an effect that costs can be suppressed is also obtained.

  In the target of the present embodiment, the crystal orientation difference in the normal direction of the sputtered surface between all adjacent crystal grains on the sputtered surface does not need to be 30 degrees or less, and at least erosion occurs on the sputtered surface during sputtering. The crystal orientation difference of 30% or more of the crystal grain boundaries existing in the region (hereinafter also referred to as “erosion target region”) may be 30 degrees or less. This is because arcing can be sufficiently suppressed when 80% or more of the crystal grain boundaries existing in the erosion target region have a crystal orientation difference of 30 degrees or less. On the other hand, if the area satisfying the above condition is less than 80%, the number of times arcing occurs increases, which is not preferable.

  Here, the erosion target region is a portion that contributes to sputtering of the target when sputtering is performed, and is a region where atoms are blown off from the target in the process of film formation.

  In many cases, a large block is manufactured and a target having a predetermined size is cut out therefrom. It is produced so that properties such as crystal orientation are uniform both in the plate surface direction and in the plate thickness direction so that it can be cut out from anywhere. Therefore, if the target satisfies the condition that 80% or more of the crystal grain boundaries existing on the entire sputtering surface have a crystal orientation difference of 30 degrees or less, even if the erosion target region varies depending on the film forming apparatus, arcing must be suppressed. The effect of doing can be obtained.

  Here, the target manufacturing method of the present embodiment includes a step of manufacturing a block manufactured by a melting method or a powder metallurgy method including HIP, a step of plastically deforming the heated block by rolling, and a step of heat treatment. Further, a production method comprising a step of imparting plastic deformation by rolling or the like and a step of further heat treatment is preferable. In the process of performing heat treatment after rolling once, since there are many large crystal orientation differences between adjacent crystal grains, by repeating the process of performing heat treatment after rolling at least twice, A large crystal orientation difference between adjacent crystal grains can be reduced.

  The rolling rate is 50 to 90% and the rolling temperature depends on the material. For example, Mo is preferably 700 to 850 ° C, Cr is 1150 to 1250 ° C, and the heat treatment temperature is preferably 1100 to 1200 ° C.

  It should be noted that the embodiments of the present invention described above are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. Is. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

  Hereinafter, the present invention will be specifically described by way of examples.

  In the examples, Mo and Cr targets are given as examples, but the present invention is not limited to Mo and Cr, and can be applied to all metal or alloy targets whose crystal orientation can be measured. .

  The target of the present invention is produced by a method in which a sintered plate of Mo and Cr is rolled and then subjected to heat treatment. It was found that the crystal orientation difference between adjacent crystal grains greatly depends on the subsequent heat treatment conditions rather than the rolling conditions. Here, a sputter target and a crystal orientation measurement sample are cut out from a plate produced by changing the heat treatment conditions of the rolled plate, the former is subjected to a sputtering experiment to measure arcing, and the latter is used to determine the crystal orientation difference between adjacent crystal grains. It was measured. In the sputtering experiment, a magnetron sputtering apparatus SPF-430HS made by Canon Anelva was used, DC 600 W was applied to a 4-inch target having a thickness of 5 mm, and arcing was measured using FS-1000 made by Harada Sangyo. Here, the number of occurrences of arcing when a 1 μm film was formed was measured 10 times.

  The crystal orientation is obtained by EBSP analysis of a sample cut out to a predetermined size from the block manufactured by the above-described manufacturing method, which is the original material from which the target is cut out.

The difference in crystal orientation between adjacent crystal grains was measured using an EBSP analyzer manufactured by TSL Solution attached to FE-SEM. Specifically, first, EBSP data is image-analyzed, the grain boundary position of the crystal grain is recognized from the SEM data, and the orientation of the adjacent crystal grain is analyzed from the reverse pole figure data, The values <h ₀ k ₀ l ₀ > and <h ₁ k ₁ l ₁ > were obtained. From this value, the crystal orientation difference ψ is calculated using Equation (1). This analysis is performed for each grain boundary existing on an arbitrary line set along the EBSP scan direction, and when the analysis of one line is completed, the length of the average grain size of the separately obtained crystal is measured. Each crystal orientation difference in the measurement target region was obtained by repeatedly performing the same analysis by setting the next line at a position shifted in the vertical direction with respect to the measured line. The measurement target region of the crystal orientation difference by this analysis method was set in the range of about 10 to 20 times the grain size of the crystal grains, and the grain boundaries being measured were over 100. For each crystal orientation difference obtained in this way, the ratio of the crystal orientation difference of 25 degrees or less and the ratio of 30 degrees or less were calculated.

  Note that with such an analysis method that performs processing exceeding 100 points, there is almost no statistical difference compared to the case where all crystal grain boundaries existing in the measurement target region are analyzed.

  In addition, when actually measuring the crystal orientation difference, measurement is performed on a sample of a part of the target as a representative of the entire target. However, since the target usually has a small difference in properties such as crystal orientation over the entire sputtering surface. By measuring a part, data on an effective crystal orientation difference that can be estimated with respect to the entire sputtering surface can be obtained.

  Hereinafter, for each of the examples manufactured by the above-described manufacturing method and the comparative example, the number of times of arcing when sputtering is actually performed, and the measurement of the ratio of the grain boundaries where the crystal orientation difference in the target is 30 degrees or less The results will be described. In Table 1, the rolling conditions and the heat treatment conditions after rolling, the ratio of crystal grain boundaries where the crystal orientation difference between adjacent crystal grains is 25 degrees or less and 30 degrees or less, and the number of arcing measurements during sputtering were measured 10 times. Data and average number of 10 times are shown. The heat treatment after rolling was performed for 2 hours after the first rolling and after the second rolling.

  In Comparative Examples 1 and 3 as rolled, the proportion of crystal grains of 30 degrees or less was low, and arcing during sputtering was observed twice or more in all 10 film formations.

  In the case where the heat treatment after rolling was performed at 1100 ° C. to 1200 ° C. for 2 hours, the ratio of the crystal orientation difference between adjacent crystal grains was 30 ° or less exceeded 80%, and arcing was hardly observed, and a good film Was formed.

  In particular, in the case where the heat treatment after rolling was performed at 1125 ° C. to 1175 ° C. for 2 hours, the ratio of the crystal orientation difference between adjacent crystal grains of 25 degrees or less exceeded 80%, and once during 10 film formations. No arcing was observed, and a more suitable film could be formed. That is, a more preferable range is when the ratio of the crystal orientation difference between adjacent crystal grains is 25 degrees or less exceeds 80%.

  In the case where the heat treatment after rolling was performed at 1250 ° C. for 2 hours, the crystal orientation difference with the adjacent crystal grains became large, and the ratio of 30 degrees or less fell below 80%. The number of arcing during sputtering was also observed 3 times or more during all 10 film formations, and many sputtered portions with a foreign substance of several μm were observed on the surface of each sputtered film, which was not a good film.

Claims (3)

A sputtering target of molybdenum or chromium, and of two crystals adjacent to each other at a crystal grain boundary on the sputtering surface of the sputtering target, the crystal orientation in the normal direction of the sputtering surface of one crystal is <h ₀ k ₀ l _When the crystal orientation in the normal direction of the sputter surface of the other crystal is <h ₁ k ₁ l ₁ >, 80% or more and less than 100% of the crystal grain boundary of the sputter surface A sputtering target characterized by satisfying a relationship in which an angle formed by ₀ k ₀ l ₀ > and <h ₁ k ₁ l ₁ > is 30 degrees or less.   The method for producing a sputtering target according to claim 1, wherein the sintered metal plate is subjected to a rolling treatment and a heat treatment after the rolling treatment at least twice.   The manufacturing method according to claim 2, wherein the heat treatment is performed at 1100 to 1200 ° C.