CN108465700B - Tantalum plate rolling method for obtaining sputtering target material with uniform structure and texture - Google Patents

Abstract

The invention discloses a tantalum plate rolling method for obtaining sputtering target materials with uniform tissues and textures, which comprises the following steps: and (3) performing multi-pass asynchronous rolling on the tantalum plate, horizontally rotating the tantalum plate by 90 degrees relative to the feeding direction of the tantalum plate after each pass is finished, and exchanging two rolling surfaces of the tantalum plate, wherein the horizontal rotating direction of the tantalum plate is consistent in the whole rolling process. The tantalum plate is subjected to plastic deformation through asynchronous rolling in combination with the mode that each pass rotates by 90 degrees and the rolling surface is exchanged in each pass, the prepared high-purity tantalum sputtering target is more uniform in tissue and texture distribution, higher and even in Vickers hardness, and uniformly distributed grains are obtained through combination with annealing treatment, so that the tantalum plate can be applied to the field of sputtering films of electronic devices, semiconductors and the like.

Description

Tantalum plate rolling method for obtaining sputtering target material with uniform structure and texture

Technical Field

The invention relates to a plastic deformation method of a target, in particular to an asynchronous rolling method of the target.

Background

Sputtering is one of the main techniques for preparing thin film materials. The solid surface is bombarded with accelerated ions, which exchange momentum with the solid surface atoms, causing the atoms on the solid surface to leave the solid and deposit on the substrate surface, a process known as sputtering. The bombarded solid is the source material for depositing thin films by sputtering, commonly referred to as the target material. Sputtering is a critical process in semiconductor chip fabrication, and the microstructure and texture of the sputtering target plays a crucial role in the quality of the sputtered film.

Tantalum (Ta) is an industrially important metal material, has a series of excellent properties such as high melting point, good processing performance, corrosion resistance, low vapor pressure, small expansion coefficient and the like, and has important application in the fields of electronics, chemical engineering, aerospace and atomic energy industry. The use of tantalum in the manufacture of integrated circuit semiconductor chips has received considerable attention in recent years. With the development of integrated circuits on a very large scale, copper will gradually replace aluminum as a material for metallization wiring on silicon wafers in deep submicron processes, and tantalum can be an ideal barrier layer for preventing copper diffusion because tantalum has high conductivity, high thermal stability and barrier effect against foreign atoms, is inert to copper, and does not form compounds between Cu and Ta. High purity tantalum has become a critical structural material in integrated circuit fabrication. The main manufacturing method of the diffusion barrier layer is Physical Vapor Deposition (PVD), and the sputtering target is a key consumable material used in the process. Thus, tantalum sputtering targets have significant application in modern integrated circuit fabrication. The high-purity tantalum target material is widely used at home at present, and the preparation of the tantalum plate for the target material mainly controls four aspects of purity, grain size, grain uniformity and grain orientation. The higher the purity of the target, the finer the grains (below 100 μm), and the better the sputtering performance of the target. With the increase of the grain size, the film deposition rate is reduced, and the more uniform the grain orientation distribution is, the better within the required grain size range; the better the uniformity of the crystal grains, the more uniform the thickness of the film deposited by the target, and within a proper range of the crystal grain size, the lower the plasma impedance of the target when in use, the high film deposition rate and the good film uniformity.

In earlier studies, the applicant refined grains and optimized the structure by a heat treatment method, and proposed chinese patent 201610042110.3. In further research on tantalum plate target blanks, the applicant wants to further improve the uniformity of the texture and texture of the tantalum plate; chinese patents 200680011590.1 and 201110393399.0 disclose that tantalum plates are treated by pulse rolling, and in the rolling process, the tantalum plates are rotated by a certain angle in each pass to optimize the grain and tissue distribution, but the pulse rolling operation process is tedious, the time period is long, and the pulse rolling operation process is not favorable for performing plastic deformation on the tantalum plates quickly, simply and conveniently, and the cost is high; asynchronous rolling (asymmetric rolling) is a process which is beneficial to rolling deformation by changing the deformation conditions in a deformation zone by utilizing the linear velocity difference of an upper roller and a lower roller, and has the advantages of reducing the rolling pressure, producing thinner products with higher precision and the like. In an attempt to replace the pulse rolling with asynchronous rolling, the applicant found that results similar to those obtained by the pulse rolling could not be obtained and that the uniformity of texture and texture was not good. Therefore, the asynchronous rolling treatment of tantalum plates needs to be improved in process.

Disclosure of Invention

In order to solve the problems existing in the asynchronous rolling treatment of the tantalum plate, the invention provides a tantalum plate rolling method for obtaining a sputtering target material with uniform structure and texture.

The technical scheme is as follows:

a rolling method of a tantalum plate for obtaining sputtering target materials with uniform structures and textures is characterized by comprising the following steps: and (3) performing multi-pass asynchronous rolling on the tantalum plate, horizontally rotating the tantalum plate by 90 degrees relative to the feeding direction of the tantalum plate after each pass is finished, and exchanging two rolling surfaces of the tantalum plate, wherein the horizontal rotating direction of the tantalum plate is consistent in the whole rolling process.

Preferably, the rotation speed ratio of the two rollers in asynchronous rolling is k, and k is more than 1 and less than or equal to 1.2.

Further preferably, the rotation speed ratio of the two rollers in asynchronous rolling is k, and k is more than or equal to 1.1 and less than or equal to 1.2.

Preferably, the tantalum plate is rolled asynchronously in 12 passes for a total rolling reduction of 80%.

Preferably, before each pass, the tantalum plate is kept at 900 ℃ for 20min and then subjected to rolling of the corresponding pass.

Preferably, the tantalum plate is subjected to homogenization annealing treatment and then asynchronous rolling.

Further preferably, the tantalum plate homogenizing annealing treatment process comprises the following steps: and (3) heating the constant temperature furnace to 1200 ℃, putting the target material into the constant temperature furnace for heat preservation, keeping the tantalum plate in a vacuum or atmosphere protection state during heat preservation for 60min, and then taking out the constant temperature furnace for cold water quenching treatment.

The tantalum plate is a high-purity tantalum plate, and the purity is more than 99.5%.

Drawings

FIG. 1 is a schematic diagram of the operation of asynchronous rolling;

FIG. 2 is a schematic view of the rotation and rolling surface turning of a tantalum plate during asynchronous rolling;

FIG. 3 is an orientation view of a tantalum plate after simultaneous rolling;

FIG. 4 is an orientation of a tantalum plate after asynchronous rolling at a speed ratio of 1.1;

FIG. 5 is an orientation of a tantalum plate after asynchronous rolling at a speed ratio of 1.2;

FIG. 6 is a texture content chart of a tantalum plate after synchronous rolling;

FIG. 7 is a graph of texture content of tantalum plates after asynchronous rolling at a speed ratio of 1.1;

FIG. 8 is a graph of the texture content of tantalum plates after asynchronous rolling at a speed ratio of 1.2;

FIG. 9 is a graph of Vickers hardness distribution of tantalum plates after rolling.

Detailed Description

The present invention will be further explained below with reference to the following examples and the accompanying drawings.

As shown in fig. 1 and 2, a tantalum plate rolling method for obtaining a sputtering target material with a uniform structure and texture is performed according to the following steps:

firstly, selecting a high-purity tantalum plate with the purity of more than 99%, and carrying out homogenization annealing treatment on the tantalum plate before rolling, wherein the method specifically comprises the following steps: heating the constant temperature furnace to 900 ℃, then putting in a tantalum plate, continuing to heat the constant temperature furnace to 1200 ℃, starting timing, keeping the temperature for 60min, then taking out the tantalum plate, keeping the temperature in a vacuum or atmosphere protection state, and then taking out and carrying out cold water quenching treatment;

the atmosphere protection is gas which does not react with tantalum at the temperature of less than 1300 ℃, such as argon, argon-hydrogen mixed gas and the like.

Putting the tantalum plate into a constant temperature furnace at 900 ℃ and keeping the temperature for 20min, taking out the tantalum plate and then feeding the tantalum plate into a space between two rollers, controlling the rotation speed ratio k of the two rollers to be more than 1 and less than or equal to 1.2, preferably more than or equal to 1.1 and less than or equal to 1.2, and carrying out asynchronous rolling on the tantalum plate;

step three, repeating the step two, horizontally rotating the tantalum plate by 90 degrees relative to the feeding direction of the tantalum plate in the same direction before the tantalum plate is fed into the roller, and simultaneously exchanging two rolling surfaces of the tantalum plate; the tantalum plate is rolled in 12 passes in total, and the total rolling quantity is controlled to be 80%.

The present invention will be further explained below with reference to test examples and drawings.

Three groups of samples including a test group, a control group and a blank group are set, each group of samples comprises 5 high-purity tantalum plates, and all the tantalum plates are subjected to the same heat treatment process according to the method so as to carry out homogenization annealing treatment on the tantalum plates.

(1) And the rolling method of the test group comprises the following steps:

putting the tantalum plate into a constant temperature furnace at 900 ℃ and keeping the temperature for 20min, taking out the tantalum plate and then feeding the tantalum plate into a space between two rollers to perform asynchronous rolling on the tantalum plate, wherein the rotation speed ratio of the two rollers during the asynchronous rolling is k, and k is more than 1 and less than or equal to 1.2;

repeating the operations, and before the tantalum plate is fed into the roller each time, rotating the tantalum plate clockwise by 90 degrees relative to the previous rolling level along the feeding direction of the tantalum plate, and simultaneously exchanging the two rolling surfaces of the tantalum plate;

the tantalum plate is rolled in 12 passes in total, and the total rolling amount is 80%.

(2) And the rolling method of the comparison group comprises the following steps:

putting the tantalum plate into a constant temperature furnace at 900 ℃ and keeping the temperature for 20min, taking out the tantalum plate and then sending the tantalum plate into a space between two rollers to roll the tantalum plate asynchronously;

repeating the operations, and before the tantalum plate is fed into the roller each time, rotating the tantalum plate clockwise by 90 degrees relative to the previous rolling level along the feeding direction of the tantalum plate, wherein the directions of two rolling surfaces of the tantalum plate are always kept consistent;

the tantalum plate is rolled in 12 passes in total, and the total rolling amount is 80%.

(3) The blank group rolling method comprises the following steps:

putting the tantalum plate into a constant temperature furnace at 900 ℃ and keeping the temperature for 20min, taking out the tantalum plate and then sending the tantalum plate into a space between two rollers to roll the tantalum plate asynchronously; the above operations are repeated for 12 times, the postures of the tantalum plates are kept consistent during each rolling, and the total rolling quantity is 80%.

And (3) respectively carrying out orientation imaging on the tantalum plates treated in the test group, the control group and the blank group, wherein the orientation imaging can be seen from the orientation imaging:

after 80% of deformation of the tantalum plate obtained by the test group treatment, the texture gradient in the thickness direction is weakened, the texture components are uniformly distributed, the orientation distribution is {101}, {111} and {100} oriented crystal grains are alternately distributed, and the structure distribution from the surface layer to the central layer is uniform;

secondly, after the tantalum plate obtained by the treatment of the control group is subjected to 80% deformation, the texture gradient along the thickness direction is obvious, the texture components are unevenly distributed, a strong {111} texture is formed at the position close to the central layer, and the texture distribution from the surface layer to the central layer is uneven;

thirdly, after 80% of deformation of the tantalum plate obtained by blank group treatment, the texture gradient along the thickness direction is very obvious, the texture components are very unevenly distributed, the position close to the central layer has a very strong {111} texture, and the texture distribution from the surface layer to the central layer is very uneven;

(4) in order to distinguish the asynchronous rolling effect from the synchronous rolling effect and the asynchronous rolling effect under different rotation speed ratios, a verification group is further arranged corresponding to the test group, a first test group and a second test group are arranged in the test group, the processing method of the tantalum plate by the verification group is consistent with that of the test group, and the process differences of the verification group, the first test group and the second test group are only that the synchronous rolling rotation speed ratio k of the verification group is 1, the asynchronous rolling rotation speed ratio k of the first test group is 1.1, and the asynchronous rolling rotation speed ratio k of the second test group is 1.2;

the orientation profiles corresponding to the validation set, the first trial set and the second trial set are shown in fig. 3, 4 and 5, respectively;

texture content graphs of the near-surface layer (S ≈ 0.96), the near-1/4 layer (S ≈ 0.52), and the central layer (S ═ 0) corresponding to the validation group, the first test group, and the second test group are respectively shown in fig. 6, 7, and 8;

the vickers hardness profiles of the near-surface layer (S ≈ 0.96), the near-1/4 layer (S ≈ 0.55), and the core layer (S ═ 0) corresponding to the verification group, the test group one, and the test group two are shown in fig. 9.

Firstly, the analysis of fig. 3, 4 and 5 is carried out:

in the original image of the orientation distribution map, different textures are displayed in three colors of red, blue and green, a blue region (corresponding to a region with the darkest color in a gray scale map) represents a {111} texture, a green region (corresponding to a region with the lightest color in the gray scale map) represents a {101} texture, and a red region (corresponding to a region with the darkest and lightest color in the gray scale map) represents a {001} texture.

As can be seen from fig. 3: when the deformation reaches 80%, the texture gradient along the thickness direction is large, the texture deformation is uneven, and the part close to the central layer has a strong {111} texture;

as can be seen from fig. 4: after 80% of deformation, the texture gradient along the thickness direction is weakened, and the texture component distribution homogenization is improved to some extent for the asynchronously rolled sample with the rotation speed ratio of 1.1;

as can be seen from fig. 5: in the asynchronously rolled sample with the rotation speed ratio of 1.2, after 80% of deformation amount, the orientation distribution of the deformed crystal grains in the thickness direction is {111} and {100} oriented crystal grains are alternately distributed, and the structure distribution from the surface layer to the central layer is relatively uniform.

Secondly, analyzing the images in the figures 6, 7 and 8:

as shown in fig. 6, as a sample for verifying that the synchronous rolling was performed at a rotation speed ratio of 1.0, when the deformation amount reached 80%, the texture contents of θ fibers ({100} orientation) in the near-surface layer, near-1/4 layer, and near-center layer were not high, the texture contents of γ fibers in the near-surface layer and near-1/4 layer were not high, and the texture contents of γ fibers ({111} orientation) in the center layer were very high; the integral content of theta fiber texture is not high, and the distribution of gamma fiber texture is unbalanced.

As shown in fig. 7, after 80% of deformation, the content of the θ fiber texture near the surface layer is reduced, the content of the θ fiber texture near the 1/4 layer and the center layer is increased, the content of the γ fiber texture near the surface layer and the 1/4 layer is increased, and the content of the γ fiber texture in the center layer is reduced in the asynchronously rolled sample with the rotation speed ratio of 1.1; the integral content of the theta fiber texture is increased, and the condition of unbalanced distribution of the gamma fiber texture is improved.

As shown in fig. 8, in the asynchronous rolled sample with the rotation speed ratio of 1.2, after 80% of deformation, the content of the theta fiber texture of the near-surface layer, the near-1/4 layer and the central layer is increased and is distributed more uniformly; the content of the gamma fiber texture of the near surface layer and the near 1/4 layer is increased, the content of the gamma fiber texture of the central layer is reduced, the distribution of the gamma fiber texture is more uniform, and the texture state of the alternating distribution of the gamma texture and the theta texture is formed in the whole thickness layer.

Analysis is performed on fig. 9:

to verify that the samples subjected to synchronous rolling at a rotation speed ratio of 1.0 have a high vickers hardness of the center layer and low vickers hardnesses of the near-surface layer and the near-1/4 layer and have a large difference from the center layer when the deformation reaches 80%;

after 80% of deformation, the Vickers hardness of the near-surface layer and the near-1/4 layer of the asynchronously rolled sample with the rotating speed ratio of 1.1 is improved, but the Vickers hardness of the central layer is reduced;

in the asynchronous rolled sample with the rotation speed ratio of 1.2, after 80% of deformation, the vickers hardness of the center layer was equivalent to the center vickers hardness at the rotation speed ratio of 1.0, and the vickers hardnesses of the near-surface layer and the near-1/4 layer were increased to a level equivalent to the vickers hardness of the center layer.

(5) Conclusion

The beneficial effects of the invention can be obtained by the above experiments: the tantalum plate is subjected to plastic deformation through asynchronous rolling in combination with the mode that each pass rotates by 90 degrees and the rolling surface is exchanged in each pass, the prepared high-purity tantalum sputtering target is more uniform in tissue and texture distribution, higher and even in Vickers hardness, and uniformly distributed grains are obtained through combination with annealing treatment, so that the tantalum plate can be applied to the field of sputtering films of electronic devices, semiconductors and the like. In the process, the tantalum sputtering target with more uniform tissue and texture distribution cannot be prepared after asynchronous rolling is lacked, each pass is rotated by 90 degrees, and any element of a rolling surface is exchanged in each pass.

Finally, it should be noted that the above-mentioned description is only a preferred embodiment of the present invention, and those skilled in the art can make various similar representations without departing from the spirit and scope of the present invention.

Claims (1)

1. A rolling method of a tantalum plate for obtaining sputtering target materials with uniform structures and textures is characterized by comprising the following steps: the tantalum plate target material is subjected to multi-pass asynchronous rolling, after each pass is finished, the tantalum plate target blank is horizontally rotated by 90 degrees relative to the feeding direction, two rolling surfaces of the tantalum plate target blank are exchanged, and the horizontal rotating directions of the tantalum plate target blank are consistent in the whole rolling process;

the rotation speed ratio of the two rollers during asynchronous rolling is k, and k is more than or equal to 1.1 and less than or equal to 1.2;

the asynchronous rolling of the tantalum plate is carried out for 12 passes in total, and the total rolling amount is 80%;

before each pass, the tantalum plate is kept at 900 ℃ for 20min, and then rolling is carried out for corresponding passes;

firstly carrying out homogenization annealing treatment on the tantalum plate, and then carrying out asynchronous rolling;

the tantalum plate homogenizing annealing treatment process comprises the following steps: heating the constant temperature furnace to 1200 ℃, putting the tantalum plate into the constant temperature furnace for heat preservation, keeping the tantalum plate in a vacuum or atmosphere protection state during heat preservation for 60min, and then taking out the tantalum plate for cold water quenching treatment;

the tantalum plate is a high-purity tantalum plate, and the purity is more than 99.5%.

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