JP7651275B2 - Nickel-platinum alloy sputtering target and preparation method thereof - Google Patents

Description

The present invention relates to a sputtering target suitable for semiconductor processing and a method for preparing the same, and more specifically, to a nickel-platinum alloy sputtering target (Ni-Pt alloy sputtering target) and a method for preparing the same.

Silicides are widely used in semiconductor processing because of their excellent resistance to oxidation at high temperatures and their excellent electrical and thermal conductivity. Specifically, the use of silicides can reduce the contact resistance of the gate, source, and drain of a transistor, thereby improving the drive current, response time, or circuit operating speed of the entire device.

As the development of semiconductor devices moves toward miniaturization, the effect of resistance cannot be ignored, and the research of related silicides has attracted great attention. Generally, titanium silicide and cobalt silicide are used for complementary metal oxide semiconductors (CMOS) with gate lengths of more than 90 nanometers (nm). Nickel silicide is adopted for CMOS with gate lengths of less than 65 nanometers because of its more suitable properties. In particular, when the gate length of CMOS is less than 45 nm, oxide materials with high relative dielectric constants such as hafnium dioxide (HfO ₂ ) are usually selected instead of silicon dioxide as the insulator, and are used in combination with nickel silicide, which has low resistance, low silicon consumption, and low processing temperature, to mitigate the adverse effects of the short channel effect. However, the thermal stability of nickel silicide is insufficient and needs to be improved by adding platinum. Therefore, Ni-Pt alloy sputtering targets are one of the important sources for producing nickel silicide.

In the prior art, there are some studies on Ni-Pt alloy sputtering targets. For example, Patent Document 1 describes that nickel-platinum alloy ingots produced by casting are often too hard and brittle to be further processed into sputtering targets, and this problem can be solved by increasing the purity of the nickel-platinum alloy components to more than 99.99%. However, when the nickel-platinum alloy ingot is further processed, for example by rolling or heat treatment, to produce a sputtering target, excessive deformation of the sputtering target causes cracks on the surface of the produced sputtering target, degrading the quality of the sputtering target. No relevant solution has yet been developed to solve this problem.

Therefore, there is an urgent need to develop related technologies to reduce deformation of the sputtering target, avoid cracks on the sputtering target surface, and provide high-quality Ni-Pt alloy sputtering targets.

China Patent Publication No. 1926254

In view of the above, one object of the present invention is to control the hardness of a Ni-Pt alloy sputtering target within a specific range. This reduces the deformation of the Ni-Pt alloy sputtering target obtained by plastic forming and heat treating a Ni-Pt alloy ingot, and also prevents cracks in the Ni-Pt alloy sputtering target during further processing. In other words, the object of the present invention is to provide a high-quality Ni-Pt alloy sputtering target with good processability.

In order to achieve the above object, the present invention provides a Ni-Pt alloy sputtering target containing nickel (Ni) atoms and platinum (Pt) atoms. The Ni-Pt alloy sputtering target has the following characteristics:
a hardness index, the value of which is represented by H, where H is 100 to 150; an amount of Pt atoms, the amount of which is in the range of 1% to 20% with respect to the total amount of atoms of the Ni-Pt alloy sputtering target, the value of which is represented by X when the amount of Pt atoms is expressed in units of %, an average grain size, the value of which is represented by Y when the average grain size is expressed in units of micrometers (μm); and a grain size variation, the value of which is represented by Z when the grain size variation is expressed in units of %, where H, X, Y, and Z satisfy the following formula (I):
Formula (I): H=10000×(X/Z) ^1/10 /Y

By using the above-mentioned technical means, i.e., by controlling the amount of Pt atoms and the specific relationship of X, Y, and Z to obtain a hardness index of 100-150, the Vickers hardness of the Ni-Pt alloy sputtering target can be maintained within an appropriate range. In this way, the workability and quality of the Ni-Pt alloy sputtering target can be improved by reducing the deformation of the Ni-Pt alloy sputtering target and preventing cracking of the Ni-Pt alloy sputtering target during further processing.

According to the present invention, X, Y, and Z in formula (I) respectively represent the amount of Pt atoms when the amount of Pt atoms is expressed in %, the average particle size when the average particle size is expressed in μm, and the particle size variation when the particle size variation is expressed in %. For example, when the amount of Pt atoms is 1%, the average particle size is 75 μm, the particle size variation is 13%, and X, Y, and Z in formula (I) are 1, 75, and 13, respectively.

According to the present invention, the hardness index is intended to indicate a specific relationship between the amount of Pt atoms, the average grain size, and the grain size variation, and thus the hardness index is not substantially identical to the hardness of a Ni-Pt alloy sputtering target.

Preferably, the grain size variation of the Ni-Pt alloy sputtering target is less than 15%. More preferably, the grain size variation of the Ni-Pt alloy sputtering target is between 7% and less than 15%. More preferably, the grain size variation of the Ni-Pt alloy sputtering target is between 7% and 13%.

Preferably, the average grain size of the Ni-Pt alloy sputtering target is 55 μm to 110 μm. More preferably, the average grain size of the Ni-Pt alloy sputtering target is 60 μm to 100 μm. More preferably, the average grain size of the Ni-Pt alloy sputtering target is 68 μm to 100 μm.

Preferably, the amount of Pt atoms is in the range of 1% to 18% of the total atoms of the Ni-Pt alloy sputtering target. More preferably, the amount of Pt atoms is in the range of 1% to 17% of the total atoms of the Ni-Pt alloy sputtering target.

Preferably, the Vickers hardness of the Ni-Pt alloy sputtering target is 110HV to 150HV. More preferably, the Vickers hardness of the Ni-Pt alloy sputtering target is 120HV to 150HV. Since the Ni-Pt alloy sputtering target has a suitable hardness, it is possible to reduce deformation of the Ni-Pt alloy sputtering target and prevent cracks in the Ni-Pt alloy sputtering target, thereby improving the workability of the Ni-Pt alloy sputtering target. In this specification, the measured Vickers hardness of the Ni-Pt alloy sputtering target refers to the Vickers hardness of the Ni-Pt alloy sputtering target obtained through a plastic forming process.

In order to achieve the above object, the present invention also provides a method for preparing a Ni-Pt alloy sputtering target, comprising the steps of:
Step (a): A step of melting and casting Ni and Pt to obtain a Ni-Pt alloy ingot, the amount of Pt atoms being in the range of 1% to 20% based on the total amount of Ni atoms and Pt atoms.
Step (b): subjecting the Ni-Pt alloy ingot to plastic forming. The maximum temperature during plastic forming is 800°C to 1200°C, and the total reduction rate of the Ni-Pt alloy ingot after plastic forming is 90% to 95%.
Step (c): A step of performing a heat treatment at a temperature of 700° C. to 1000° C. to obtain a Ni—Pt alloy sputtering target.

By adding a specific amount of Pt atoms and controlling the maximum temperature during plastic forming, the total reduction rate of the Ni-Pt alloy ingot after plastic forming, and the heat treatment temperature within the above-mentioned specific ranges, the Ni-Pt alloy sputtering target can obtain a suitable range of hardness and have properties such as good workability, little deformation, and no cracks.

In step (a), the purity of the Pt employed in the preparation method may be greater than 4N5, and the purity of the Ni employed in the preparation method may be greater than 5N. In other words, the purity of the Pt employed in the preparation method may be greater than 99.995%, and the purity of the Ni employed in the preparation method may be greater than 99.999%. Preferably, the purity of the Ni-Pt alloy sputtering target may be greater than 5N (99.999%).

According to the present invention, the melting may be performed by any conventional melting method. For example, but not limited to, the melting may be vacuum induction melting (VIM), electron beam melting (EBM), vacuum arc remelting (VAR), or water-cooled copper crucible melting.

According to the present invention, the plastic forming may be performed by any conventional plastic forming method. For example, but not limited to, the plastic forming may be forging, rolling, or other processes of plastic forming. Also, the plastic forming may be, but not limited to, hot plastic forming or cold plastic forming.

In step (c), processing may be performed after the heat treatment to obtain a Ni-Pt alloy sputtering target. For example, the processing may be turning or grinding, but is not limited to these.

Preferably, the maximum temperature during plastic forming may be 850°C to 1150°C. More preferably, the maximum temperature during plastic forming may be 850°C to 1000°C.

Preferably, the total reduction rate of the Ni-Pt alloy ingot after plastic forming may be 90% to 94%. More preferably, the total reduction rate of the Ni-Pt alloy ingot after plastic forming may be 90% to 93%.

Preferably, the heat treatment temperature may be between 800°C and 1000°C. More preferably, the heat treatment temperature may be between 850°C and 1000°C.

In order to clarify the influence of the conditions of the preparation method and the specific relationship between the amount of Pt atoms, the average grain size, and the grain size variation on the hardness and workability of the Ni-Pt alloy sputtering target, the following examples are presented to illustrate the implementation of the present invention. In addition, the different characteristics between the examples and the comparative examples are shown below. Those skilled in the art can easily realize the advantages and effects of the present invention from the following examples. Various modifications and variations are possible for implementing or applying the present invention without departing from the spirit and scope of the present invention.

Examples 1 to 6: Ni-Pt alloy sputtering target According to the difference in the amount of Pt atoms listed in Table 1 below, Ni with a purity of more than 5N and Pt with a purity of more than 4N5 were adopted as the metal components. Then, these metal components were melted to obtain a high-purity Ni-Pt alloy. This high-purity Ni-Pt alloy was cast to obtain a Ni-Pt alloy ingot. Then, this Ni-Pt alloy ingot was processed by plastic forming, and the maximum temperature during plastic forming and the total reduction rate of the Ni-Pt alloy ingot after plastic forming were controlled within a specific range. Next, the Ni-Pt alloy ingot after plastic forming was heat-treated within a specific temperature range and then processed, and the Ni-Pt alloy sputtering targets of Examples 1 to 6 were obtained in suitable sizes.
The maximum temperatures during plastic forming, the total reduction rates of the Ni-Pt alloy ingots after plastic forming, and the heat treatment temperatures in Examples 1 to 6 are listed in Table 1 below.

Comparative Examples 1-5: Ni-Pt Alloy Sputtering Targets The preparation methods of Comparative Examples 1-5 are the same as those of Examples 1-6. According to the difference in the amount of Pt atoms listed in Table 1, Ni and Pt were adopted as the metal components, and then melting, plastic forming, heat treatment, and processing were sequentially performed to obtain the Ni-Pt alloy sputtering targets of Comparative Examples 1-5.
The differences between Examples 1 to 6 and Comparative Examples 1 to 5 are the maximum temperature during plastic forming, the total reduction rate of the Ni-Pt alloy ingot after plastic forming, and the heat treatment temperature, which are also listed in Table 1 below.

Table 1: Amount of Pt atoms in the Ni-Pt alloy sputtering targets of Examples 1 to 6 and Comparative Examples 1 to 5, maximum temperature during plastic forming, total reduction rate of Ni-Pt alloy ingot after plastic forming, and heat treatment temperature

Test Example 1: Evaluation of average grain size and grain size variation As the samples of Test Example 1, Ni-Pt alloy sputtering targets formed by plastic forming and heat treatment of Examples 1 to 6 and Comparative Examples 1 to 5 were adopted. Specifically, each Ni-Pt alloy sputtering target was cut at the center, semi-radius, and edge to obtain a specimen of size 10 mm x 10 mm, and then the specimen was further scraped, polished, and etched to prepare a specimen for observation. The sample was observed using an optical microscope (BX51M, Olympus Corporation) to obtain an optical microscope image of the sample. Then, the optical microscope image was marked with four auxiliary lines using Image J Pro analysis software. Two auxiliary lines were diagonal lines on the optical microscope image. The remaining two auxiliary lines were center lines parallel to the length and width of the optical microscope image, respectively. Specifically, the four auxiliary lines were connected to points opposite to opposite sides of the optical microscope image, respectively.

Then, the total amount of particles on the four auxiliary lines was counted by a simple random sampling method. The length of each auxiliary line was divided by the amount of particles on the corresponding auxiliary line to obtain the partial average particle size. Then, all the partial average particle sizes on each auxiliary line were calculated to obtain the average particle size and the standard deviation . The standard deviation was divided by the average particle size and multiplied by 100% to calculate the normalized uniformity of the particle size. The larger the value of the normalized uniformity of the particle size, the larger the variation in particle size, suggesting that the distribution was not uniform.
The average particle size and particle size variation of each of Examples 1 to 6 and Comparative Examples 1 to 5 are listed in Table 2 below.

Test Example 2: Evaluation of Hardness As the samples of Test Example 2, Ni-Pt alloy sputtering targets formed by plastic forming and heat treatment of Examples 1 to 6 and Comparative Examples 1 to 5 were adopted. Specifically, each Ni-Pt alloy sputtering target was cut at the center, semi-radius, and edge to obtain a specimen of 10 mm x 10 mm in size, and the specimen was further scraped and polished to prepare a measurement specimen. The Vickers hardness of the polished surface of each sample was measured using a Vickers microhardness tester (HMV-2, Shimadzu Corporation), and the sample Vickers hardness measured at three different points on one Ni-Pt alloy sputtering target was averaged to represent the Vickers hardness of the sputtering target.
The Vickers hardness of each of the Ni-Pt alloy sputtering targets of Examples 1 to 6 and Comparative Examples 1 to 5 is listed in Table 2 below.

Test Example 3: Evaluation of deformation of sputtering target and cracks on sputtering target The Ni-Pt alloy sputtering targets formed by plastic forming and heat treatment in Examples 1 to 6 and Comparative Examples 1 to 5 were used as samples in Test Example 3. Specifically, each Ni-Pt alloy sputtering target was placed on a horizontal plane, and a right-angle ruler was used to measure the warpage of the Ni-Pt alloy sputtering target surface with respect to the horizontal plane.
The measurement results, which represent the deformation of the sputtering target, are listed in Table 2 below.

Next, the Ni-Pt alloy sputtering targets formed by the plastic working and heat treatment of Examples 1 to 6 and Comparative Examples 1 to 5 were further processed to a uniform size (φ450×4 mm) under the same conditions. Thereafter, the surface of each processed Ni-Pt alloy sputtering target was visually observed to confirm the presence of cracks.
The results for cracks on the sputtering targets are also listed in Table 2 below.

In addition, by using the results of the deformation and cracks of the sputtering target shown in Test Example 3 in combination, it becomes possible to further evaluate the workability of the Ni-Pt alloy sputtering target. Specifically, a state in which the deformation of the sputtering target exceeds 0.3 mm and obvious cracks are visually observed on the surface of the sputtering target after processing is marked with △. A state in which the deformation of the sputtering target is about 0.3 mm and no cracks are visually observed on the surface of the sputtering target after processing is marked with ○. A state in which the deformation of the sputtering target is less than 0.2 mm and no cracks are visually observed on the surface of the sputtering target after processing is marked with ◎.
The workability results of the Ni-Pt alloy sputtering targets are listed in Table 2 below.

Table 2: Pt atom amount (Pt), hardness index (H), grain size variation (Var. grain size), average grain size (Ave. grain size), Vickers hardness, deformation of sputtering target (deformation), cracks on sputtering target (cracks), and workability of Ni-Pt alloy sputtering targets of Examples 1-6 and Comparative Examples 1-5

Discussion of Experimental Results According to Tables 1 and 2, by controlling the maximum temperature during plastic forming, the total reduction rate of the Ni-Pt alloy ingot after plastic forming, and the heat treatment temperature within specific ranges, each Ni-Pt alloy sputtering target of Examples 1 to 6 had a specific amount of Pt atoms, average grain size, and grain size variation, and therefore had a specific hardness index. Therefore, the Vickers hardness of all the Ni-Pt alloy sputtering targets of Examples 1 to 6 was within a suitable range. Therefore, the Ni-Pt alloy sputtering targets of Examples 1 to 6 were less deformed and did not crack even after further processing. Therefore, the processability was improved, and the quality of the sputtering target could be maintained at a high level.
In contrast, for the Ni-Pt alloy sputtering targets of Comparative Examples 1 to 5, unless at least one of the technical features of the maximum temperature during plastic forming, the total reduction rate of the Ni-Pt alloy ingot after plastic forming, and the heat treatment temperature is controlled within a specific range, there is no specific relationship between the amount of Pt atoms, the average grain size, and the grain size variation. Therefore, the hardness index of the Ni-Pt alloy sputtering targets of Comparative Examples 1 to 5 was not in a suitable range. Therefore, in Comparative Examples 1 to 4, the sputtering targets were largely deformed, and cracks were easily generated in the sputtering targets after processing, thereby reducing the workability of the sputtering targets. For Comparative Example 5, although the sputtering target was only slightly deformed, the hardness was high, and subsequent processing failed.

In addition, referring to the results of Example 2, Comparative Example 1, Example 4, and Comparative Example 3, the amount of Pt atoms in Example 2 and Comparative Example 1 was 3% and the amount of Pt atoms in Example 4 and Comparative Example 3 was 7%, but the heat treatment temperatures in Comparative Example 1 and Comparative Example 3 were 550°C and 11000°C, respectively, which were not within the range of 700°C to 1000°C. Specifically, the heat treatment temperature of 550°C was not higher than the recrystallization temperature of the Ni-Pt alloy, and the heat treatment temperature of 1100°C caused overgrowth of particles. That is, the average grain size and grain size variation of the Ni-Pt alloy sputtering targets of Comparative Examples 1 and 3 were too large to bring the hardness index into the range of 100 to 150, and as a result, the Vickers hardness of the Ni-Pt alloy sputtering targets of Comparative Examples 1 and 3 was too low. Therefore, in Comparative Examples 1 and 3, the deformation of the sputtering target could not be reduced, and cracks were visually observed on the sputtering target after processing, indicating insufficient processability.

Furthermore, referring to the results of Example 3 and Comparative Example 2, the amount of Pt atoms in Example 3 and Comparative Example 2 was the same, but the total reduction rate of the Ni-Pt alloy ingot after plastic forming in Comparative Example 2 was less than 90%, and sufficient kinetic energy for grain refinement was lacking. Therefore, the average grain size and grain size variation of the Ni-Pt alloy sputtering target in Comparative Example 2 were too large to bring the hardness index within the range of 100 to 150, lowering the Vickers hardness of the Ni-Pt alloy sputtering target in Comparative Example 2. Therefore, in Comparative Example 2, although no cracks were visually observed on the sputtering target after processing, the deformation of the sputtering target was still large, thus affecting the processability.

Furthermore, referring to the results of Example 5 and Comparative Example 4, the amount of Pt atoms in Example 5 and Comparative Example 4 was 10%, but the maximum temperature during plastic forming in Comparative Example 4 was obviously too low, resulting in an insufficient total reduction rate of the Ni-Pt alloy ingot after plastic forming, and thus no significant grain refinement was obtained. Therefore, the average grain size and grain size variation of the Ni-Pt alloy sputtering target of Comparative Example 4 were too large to bring the hardness index within the range of 100 to 150. That is, the Vickers hardness of the Ni-Pt alloy sputtering target of Comparative Example 4 was only 97 HV. Therefore, in Comparative Example 4, the sputtering target was deformed a lot, and cracks were visually observed on the sputtering target after processing, further affecting the processability.

Furthermore, with reference to Comparative Example 5, only the total reduction rate of the Ni-Pt alloy ingot after plastic forming in Comparative Example 5 exceeded 95%, which was not within the range claimed by the present invention. However, the hardness index of Comparative Example 5 was still not within the range of 110-150. Therefore, the Vickers hardness of the Ni-Pt alloy sputtering target of Comparative Example 5 was a maximum of 184 HV, and therefore the Ni-Pt alloy sputtering target of Comparative Example 5 was not very suitable for further processing.

In summary, according to the results of Test Examples 1 to 3, the present invention provides a technical means for controlling the amount of Pt atoms, the maximum temperature during plastic forming, the total reduction rate of the Ni-Pt alloy ingot after plastic forming, and the heat treatment temperature during preparation of the Ni-Pt alloy sputtering target, thereby making the amount of Pt atoms, the average particle size, and the particle size variation of the Ni-Pt alloy sputtering target within a specific range, and obtaining a Ni-Pt alloy sputtering target with suitable hardness. In other words, the Ni-Pt alloy sputtering target of the present invention can reduce the deformation of the sputtering target and prevent cracks on the sputtering target, specifically, it is possible to promote workability and maintain the quality of the Ni-Pt alloy sputtering target.

Although many of the features and advantages of the present invention have been described above, together with details of the structure and features of the invention, the disclosure is merely illustrative. Changes may be made within the principles of the invention, particularly in matters relating to shape, size, and arrangement of parts, to the full extent indicated by the broad general meaning of the terms expressed in the appended claims.

Claims (7)

A nickel-platinum alloy sputtering target comprising nickel atoms and platinum atoms,
a hardness index, the value of which is expressed as H, where H is 100 to 150;
the amount of platinum atoms is in the range of 1% to 20% relative to the total amount of atoms of the nickel-platinum alloy sputtering target, and the value is represented by X when the unit of the amount of platinum atoms is expressed in %,
an average particle size, the value of which is represented by Y when the average particle size is expressed in micrometers;
a particle size variation, the value of which is represented by Z when the unit of particle size variation is expressed in percentage, and the particle size variation is calculated by dividing the standard deviation by the average particle size and multiplying the result by 100%;
wherein H, X, Y, and Z are represented by the following formula (I):
Formula (I): H=10000×(X/Z) ^1/10 /Y
The present invention is characterized in that
Nickel-platinum alloy sputtering target. The nickel-platinum alloy sputtering target of claim 1, characterized in that the grain size variation is less than 15%. The nickel-platinum alloy sputtering target according to claim 1 or 2, characterized in that the average grain size is 55 micrometers to 110 micrometers. The nickel-platinum alloy sputtering target according to any one of claims 1 to 3, characterized in that the Vickers hardness is 110 HV to 150 HV. A method for preparing a nickel-platinum alloy sputtering target, comprising the steps of:
Step (a): Melting and casting nickel and platinum to obtain a nickel-platinum alloy ingot, the amount of platinum atoms being in the range of 1% to 20% based on the total amount of nickel atoms and platinum atoms;
Step (b): subjecting the nickel-platinum alloy ingot to plastic forming, the maximum temperature during the plastic forming is 800°C to 1200°C, and the total reduction rate of the nickel-platinum alloy ingot after the plastic forming is 90% to 95%; and
Step (c): A step of performing a heat treatment at a temperature of 850 ° C. to 1000° C. to obtain a nickel-platinum alloy sputtering target.
Preparation method. The preparation method according to claim 5, characterized in that the maximum temperature during plastic forming is 850°C to 1150°C. The preparation method according to claim 5 or 6, characterized in that the total reduction rate of the nickel-platinum alloy ingot after plastic forming is 90% to 94%.