CN115369366B

CN115369366B - Back-reinforced monomer target and preparation method thereof

Info

Publication number: CN115369366B
Application number: CN202211299707.8A
Authority: CN
Inventors: 何金江; 刘晓; 万小勇; 罗俊锋; 朱孜毅; 李勇军; 尚再艳; 韩思聪
Original assignee: Youyan Yijin New Material Shandong Co ltd; Grikin Advanced Material Co Ltd
Current assignee: Youyan Yijin New Material Shandong Co ltd; Grikin Advanced Material Co Ltd
Priority date: 2022-10-24
Filing date: 2022-10-24
Publication date: 2023-02-14
Anticipated expiration: 2042-10-24
Also published as: CN115369366A

Abstract

The invention discloses a back-reinforced single target material and a preparation method thereof, wherein the back-reinforced single target material comprises an integrally formed sputtering layer and a reinforcing layer; the grain size of the sputtering layer is less than or equal to 100 mu m; the strengthening layer is positioned on the back of the sputtering layer, the hardness of the strengthening layer is greater than that of the sputtering layer, the thickness of the strengthening layer is 0.5mm-3mm, and the grain size of the strengthening layer is less than or equal to 1 mu m. On one hand, the back-reinforced single target provided by the invention does not need to be additionally provided with a back plate, so that the high cost and the diffusion welding process with a complicated flow are avoided; on the other hand, compared with the overall strong plastic deformation process of the large-size target material, the method provided by the invention only carries out regional strong plastic deformation on the back surface of the target material, and the process is simple and flexible. In addition, the method disclosed by the invention can improve the microstructure of the surface layer of the material, effectively improve the mechanical property of the workpiece and further obviously improve the strength of the target material.

Description

Back-reinforced monomer target and preparation method thereof

Technical Field

The invention belongs to the field of preparation of targets for integrated circuits, and particularly relates to a back-reinforced monomer target and a preparation method thereof.

Background

The high-purity metal sputtering target material is a key material for manufacturing an integrated circuit, and various film functional materials are obtained mainly by a magnetron sputtering technology in the using process. Currently, sputtering targets can be classified according to their chemical composition into: pure metal targets such as aluminum, copper, titanium, tantalum, cobalt, gold, silver, nickel, and the like; alloy target materials, such as aluminum copper, aluminum silicon, copper aluminum, copper manganese, tungsten titanium, nickel platinum, nickel vanadium, silver copper and the like. According to moore's law, the integrated circuit manufacturing process continues to advance, and is continuously updated iteratively, so that higher and higher requirements are put on the performance of various materials, firstly, the purity requirement of the materials is higher and higher, the purity requirement of pure metals is from 99.99% to 99.9999%, even to 99.99999%, the impurity content in the materials is lower and lower, and for alloy targets, the content of main elements is generally controlled within 1 percent by weight. Aluminum and copper are used for manufacturing the most important interconnection line materials in integrated circuit chips, high-purity aluminum and aluminum alloy materials are generally adopted in the process of 90nm and above, high-purity copper materials are adopted in the process of 90-45nm, and high-purity copper-aluminum and copper-manganese alloy materials are mainly adopted in the process of 45-14 nm. High-purity metals such as aluminum, copper and the like and alloy targets thereof are used as key materials for integrated circuits, and the structural performance of the high-purity metals directly influences the service performance of the chip in the sputtering coating process.

The size of the target increases with increasing wafer size, with the mainstream 300mm wafer fabrication target having a maximum diameter size >520mm and a maximum thickness of the target typically <30mm. Because the high-purity metal such as aluminum, copper, gold, silver and the like and the low-content alloy material have low strength, when the monomer high-purity metal or alloy material large-size thin plate type target material is bombarded by plasma in PVD sputtering, the target material becomes thinner along with the increase of sputtering consumption due to the low strength of the high-purity material, the rigidity is greatly reduced, so that the target material is deformed, sputtering abnormality is caused, and the service life of the target material is shorter. Therefore, high purity metal targets are typically welded to a high strength backing plate to form a target assembly. In addition, the sputtering layer of the early high-purity metal target is a plane, the utilization rate of the target is low, and the service life is short. PVD sputtering machine manufacturers and target material manufacturers continuously improve the structural design of the target material, for example, according to a sputtering profile curve, the sputtering surface of the high-purity metal target material is changed into a non-planar structure, and meanwhile, the connecting interface of the high-purity metal target material and a back plate is also changed into the non-planar structure, so that the service life of the target material can be prolonged to a certain extent. The large-area high-strength welding of the high-purity metal target and the back plate usually adopts a hot isostatic pressing diffusion welding mode, a matched structure of the high-purity metal target and the back plate needs to be precisely processed, vacuum sheathing is carried out, and then hot isostatic pressing is carried out, so that the complexity of the process and the processing cost are undoubtedly and greatly increased. In fact, besides improving the target structure, the service life of the target can be prolonged by improving the control of the target structure performance, the HONEYWELL adopts the ECAP technology of equal channel angular extrusion and strong plastic deformation to prepare the ultrafine crystal target, the crystal grain size reaches the nanometer level, and the strength and the hardness of the material are greatly improved, so that the single target can be adopted, the target component does not need to be welded with a high-strength backboard to form, and the target component can be kept from deformation in long-time sputtering consumption. The ultra-fine grain target material does not need to consider the welding interface between the high-purity metal target material and the back plate, and meanwhile, the strength of the high-purity metal monomer target material is enough to meet the requirement of long-service-life sputtering. However, the strong plastic deformation technology for preparing the large-size ultrafine-grained target material is complex in process and high in requirement on forging equipment, and meanwhile, the ultrafine-grained structure is not required for target material sputtering, and the requirement of sputtering coating can be met by the grain size of the target material being 20-100 microns.

Disclosure of Invention

In view of the problems in the prior art, the development of the monomer target material which has the conventional grain size and can properly improve the mechanical property of the target material to meet the long-time sputtering requirement has important significance in the aspects of simplifying the process of preparing the high-purity metal and alloy sputtering target material of the integrated circuit, improving the efficiency, improving the service performance of the product and the like. Based on this, the invention provides a preparation method of a back-reinforced single target material and the back-reinforced single target material, which specifically comprise the following contents:

a preparation method of a single target material with reinforced back comprises the following steps:

(1) Preparing a target blank: using a high-purity metal or high-purity alloy ingot as a raw material, and preparing a target blank by forging, rolling deformation processing and recrystallization annealing; the purity of the high-purity metal is more than or equal to 99.99 percent, and the content of other impurity elements except the main element in the high-purity alloy is less than 0.01 percent;

(2) Cutting: cutting the target blank obtained in the step (1);

(3) Ultrasonic rolling processing: carrying out continuous ultrasonic rolling strong plastic deformation processing on the back surface of the target blank cut in the step (2) by adopting a hard tool head driven by an ultrasonic generator;

(4) Finish machining: performing finish machining on the front side and the side surface of the target blank subjected to the ultrasonic rolling machining in the step (3) to obtain a single target finished product with a reinforced back surface; the back surface of the target blank obtained by the continuous ultrasonic rolling and strong plastic deformation processing in the step (3) is a strengthening layer, and the front surface of the target blank (namely the back surface of the strengthening layer) is a sputtering layer.

Specifically, compared with the size of a finished single target product with reinforced back surface, the size of the target blank obtained after cutting in the step (2) has machining allowance of 0.1mm-2mm on one side.

Specifically, the working frequency of the ultrasonic generator used in the step (3) is 15-25 kHZ, and the working amplitude of the transducer in the ultrasonic generator is 0.05-0.5 mm.

Specifically, the diameter of the hard tool bit used in the step (3) is 1mm-10mm, the hard tool bit is made of hard alloy or die steel, and the hardness of the hard tool bit is more than or equal to HRC40.

The back-reinforced monomer target material prepared by the preparation method comprises an integrally formed sputtering layer and a reinforcing layer; the grain size of the sputtering layer is less than or equal to 100 mu m, and the grain size of the strengthening layer is less than or equal to 1 mu m; the strengthening layer is positioned on the back of the sputtering layer, the hardness of the strengthening layer is greater than that of the sputtering layer, and the thickness of the strengthening layer is 0.5mm-3mm.

Specifically, the sputtering layer is prepared by forging, rolling deformation processing and recrystallization annealing in the step (1) in the method; the strengthening layer is prepared by the ultrasonic rolling strong plastic deformation processing in the step (3).

Specifically, the high-purity metal or high-purity alloy comprises high-purity aluminum or an alloy thereof, high-purity copper or an alloy thereof, high-purity silver or an alloy thereof, high-purity gold or an alloy thereof, high-purity platinum or an alloy thereof, and high-purity nickel or an alloy thereof.

Specifically, the grain size of the sputtering layer is 20-80 μm.

Specifically, the grain size of the strengthening layer is less than or equal to 500nm.

Specifically, the hardness of the strengthening layer is greater than HV100.

The invention has the beneficial effects that:

(1) According to the preparation method of the back-reinforced single target material disclosed by the invention, after high-purity metal or high-purity alloy material is subjected to deformation processing such as forging and rolling, recrystallization annealing treatment and cutting, an ultrasonic rolling reinforcement process is added, the microstructure of the surface layer of the material can be improved, the mechanical property of a workpiece is effectively improved, and further the strength of the target material is remarkably improved. The principle is as follows: the ultrasonic rolling can greatly increase the dislocation energy and dislocation mobility of the high-purity crystal material, the introduced strong plastic deformation enables the crystal grains on the surface layer of the sample to be refined to a nanometer scale, superfine crystal grains and a strengthening layer are generated, the plastic deformation mechanism is changed, the surface hardness is improved, and meanwhile, the ultrasonic rolling can play a positive role in improving the wear resistance, corrosion resistance and fatigue resistance of the surface of the material.

(2) Compared with a high-purity metal target blank and a high-strength back plate welded target and a preparation method thereof, the back-reinforced single target provided by the invention does not need to be additionally provided with a back plate, so that the high cost and the complicated diffusion welding process are avoided; on the other hand, compared with the overall strong plastic deformation process of the large-size target material, the method provided by the invention only carries out regional strong plastic deformation on the back surface of the target material, the process is simple and flexible, and for the large-size target material, especially the target material for 300mm wafers, the overall strong plastic deformation is very difficult and extremely high in cost; in addition, compared with other surface strengthening technologies, such as shot blasting, impact strengthening, torsion strengthening and the like, the ultrasonic rolling technology can be combined with the existing machining technology, the ultrasonic rolling tool head can be fixed on a machine tool bit clamp for operation, the thickness and the area of a strengthened layer can be accurately controlled, the process is simple, and the cost is low.

Drawings

FIG. 1 is a schematic view of a backside enhanced monolithic target according to the present disclosure;

FIG. 2 is a process flow diagram of a method of preparing a backside-strengthened monolithic target of the present disclosure;

FIG. 3 is an operational diagram of a method for preparing a backside-strengthened monolithic target according to the present disclosure;

FIG. 4 is a schematic view of a monolithic target according to the present disclosure before backside strengthening;

FIG. 5 is a schematic view of the microstructure of the monolithic target of the present invention before ultrasonic rolling;

fig. 6 is a schematic view of the microstructure of the single target material after ultrasonic rolling.

Detailed Description

The invention is described in detail below with reference to the drawings and the detailed description. The embodiments shown below do not limit the inventive content described in the claims. The entire contents of the configurations shown in the following embodiments are not limited to those required as solutions of the inventions described in the claims.

Referring to fig. 1, a single target 1 with reinforced back surface comprises a sputtering layer 11 and a reinforced layer 12 which are integrally formed; the grain size of the sputtering layer 11 is less than or equal to 100 mu m; the strengthening layer 12 is positioned on the back of the sputtering layer 11, and the hardness of the strengthening layer 12 is greater than that of the sputtering layer 11; the thickness of the strengthening layer 12 is 0.5mm-3mm, and the specific thickness can be 0.5mm, 0.8mm, 1.0mm, 2mm, 2.5mm, 2.8mm, or 3mm, etc.; the grain size of the reinforcing layer 12 is not more than 1 μm, and may be 1 μm, 0.8 μm, 0.5 μm, 0.3 μm, 0.2 μm, or the like. The material of the monomer target 1 is high-purity metal or high-purity alloy, and the high-purity metal or high-purity alloy comprises high-purity aluminum or alloy thereof, high-purity copper or alloy thereof, high-purity silver or alloy thereof, high-purity gold or alloy thereof, high-purity platinum or alloy thereof, and high-purity nickel or alloy thereof; the purity of the high-purity metal is more than or equal to 99.99 percent, and the impurity content of the high-purity alloy is less than 0.01 percent. The grain size of the sputtering layer 11 is 20 μm to 80 μm, and specifically, may be 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, or 80 μm. The grain size of the strengthening layer 12 is less than or equal to 500nm, and specifically, less than or equal to 500nm, less than or equal to 400 nm, less than or equal to 300 nm, less than or equal to 200nm, less than or equal to 100nm, less than or equal to 50 nm, and the like. The hardness of the strengthening layer 12 is greater than HV100.

Referring to fig. 2-6, a method for preparing a backside-strengthened monolithic target includes the following steps:

(1) Using a high-purity metal or high-purity alloy ingot as a raw material, and preparing a target blank by performing deformation processing such as forging, rolling and the like and recrystallization annealing; the purity of the high-purity metal is more than or equal to 99.99 percent, and the impurity content of the high-purity alloy is less than 0.01 percent;

(2) Cutting the target blank obtained in the step (1); compared with the size of a finished single target product with reinforced back surface, the size of the cut target blank has machining allowance of 0.1-2 mm on one side;

(3) Carrying out ultrasonic rolling strong plastic deformation processing on the back surface of the target blank cut in the step (2); the specific operation is as follows: carrying out continuous rolling processing on the back surface of the target blank cut in the step (2) by adopting a hard tool head 3 driven by an ultrasonic generator 2, wherein the frequency of the ultrasonic generator 2 is 15-25 kHZ, and specifically can be 15-18 kHZ, 20-23 kHZ, 25-kHZ and the like; the amplitude of the transducer 21 in the ultrasonic generator 2 is 0.05mm-0.5mm, specifically 0.05mm, 0.08mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.45mm, 5mm, etc.; the diameter of the hard tool head 3 is 1mm-10mm, specifically 1mm, 2mm, 3mm, 5mm, 7mm, 8mm, 9mm, or 10mm, the hard tool head 3 is made of hard alloy or die steel, and the hardness is more than or equal to HRC40;

(4) Performing finish machining on the front side and the side surface of the target blank subjected to the ultrasonic rolling machining in the step (3) to obtain a finished product of the single target material 1 with the reinforced back surface;

and (3) carrying out continuous ultrasonic rolling and strong plastic deformation processing to obtain a target blank, wherein the back surface of the target blank is a strengthening layer, and the front surface of the target blank (namely the back surface of the strengthening layer) is a sputtering layer.

The method for preparing the back-reinforced monomer target material comprises the steps of firstly selecting high-purity metal or high-purity alloy cast ingots as raw materials, wherein the high-purity metal or high-purity alloy is selected from high-purity aluminum and alloy thereof, high-purity copper and alloy thereof, high-purity silver and alloy thereof, high-purity gold and alloy thereof, high-purity platinum and alloy thereof, high-purity nickel and alloy thereof and the like, the purity of the high-purity metal is usually more than or equal to 99.99%, and the purity of the high-purity alloy except main elements is more than or equal to 99.99%. The grains of the ingot are typically coarse, typically on the order of hundreds of microns or even millimeters. The method comprises the steps of crushing coarse grains by deformation means such as forging and rolling, refining the grains and stabilizing the structure by recrystallization annealing heat treatment, processing an ingot into a plate blank to meet the size requirement of a subsequent target, and describing related deformation and heat treatment processes in more detail in a plurality of documents describing the target preparation technology without more limitation. After deformation processing by a forging hammer or an oil press, a rolling mill and the like and a proper recrystallization annealing process, a microstructure with the grain size of less than or equal to 100 mu m can be obtained, the optimized size is between 20 mu m and 80 mu m, and the requirement of sputtering coating is met. If ultra-fine grains are to be obtained, for example, the grain size is less than or equal to 1 mu m or smaller, a special strong plastic deformation process such as equal channel angular Extrusion (ECAP) is required, the requirements on extrusion equipment and an extrusion die are far higher than those of common deformation processing, the strength of the ultra-fine grain target material is superior to that of a common fine grain target material, and therefore the ultra-fine grain target material can bear longer sputtering use, but the sputtering performance of the target material is not completely superior to that of the conventional target material with the grain size less than or equal to 100 mu m, the equipment investment for preparing the whole ultra-fine grain target material is large, the processing efficiency is low, and the method is uneconomical.

Fig. 3 is a schematic diagram illustrating the operation of preparing the single target 1 by the method of the present invention for strengthening the back surface, wherein the direction indicated by the arrow is the moving direction. After the preparation of the target blank is finished, the blank is subjected to rough machining in the modes of driving, milling and the like, the size of the blank is close to that of a finished product, and machining allowance of 0.1mm-2mm is reserved on each machined surface on average. At this time, the back of the target blank is subjected to ultrasonic rolling processing by adopting the hard tool head 3 driven by the ultrasonic generator 2, the hard tool head 3 is externally connected with the ultrasonic generator, the ultrasonic vibration frequency is 15k-25kHZ, the amplitude of the transducer 21 is amplified by the amplitude modulator and the hard tool head 3 and is 0.05mm-0.5mm, the diameter of the hard tool head 3 driven by the ultrasonic generator 2 is 1mm-10mm, and the hard tool head 3 is made of materials such as hard alloy, die steel and the like, and the hardness is more than HRC40. The hardness of high-purity metal and alloy with grain size of tens of microns is below HV100, and the hardness of common high-purity materials, such as high-purity aluminum, is between HV25 and HV30, the hardness of high-purity AlCu0.5 alloy is between HV30 and HV35, the hardness of high-purity copper is between HV35 and HV45, and the hardness of high-purity CuMn0.69 alloy is between HV40 and HV 50. The hard tool head 3 driven by the ultrasonic generator 2 is arranged on a lathe and is used for rolling the back surface of the monomer target 1 to generate a reinforcing layer with the thickness of more than 0.5mm, and the thickness of the maximum reinforcing layer can exceed 3mm. Fig. 4 is a schematic view of an untreated target blank having fine and uniform grain sizes within several tens of microns, and fig. 1 is a schematic view of an ultrasonic rolling process having a uniform fine grain strengthened layer 12 formed on the back side. Fig. 5-6 are schematic diagrams showing the grain refinement and change under the ultrasonic rolling action, the fault energy and dislocation mobility of a high-purity crystal material are greatly increased under the high-frequency ultrasonic vibration rolling action of the recrystallized crystal, the introduced strong plastic deformation enables the surface layer grains of the sample to be refined to a nanometer scale, an ultra-fine grain strengthening layer is generated, the plastic deformation mechanism is changed, the surface layer hardness is improved, the surface layer hardness reaches over HV100, meanwhile, the strengthening layer also has obvious compressive stress, the surface roughness is also obviously reduced, and the wear resistance and fatigue resistance of the back plate are greatly improved. And finally, performing finish machining on the front side, the side face and the like of the monomer target 1 to obtain the size of a finished product according to a finished product drawing.

Example 1

The preparation of the long-life high-purity AlCu0.5 target material for manufacturing the 200mm wafer comprises the following steps:

firstly, a 5N5 high-purity aluminum-copper alloy ingot formed by semi-continuous casting is selected, the diameter of the ingot is phi 180mm, and the grain size is 300-500 mu m. The ingot is subjected to deformation processing such as die forging, rolling and the like by an oil press, the integral deformation is about 90%, the size of the target blank is phi 380 multiplied by 25mm, recrystallization annealing is carried out at 320 ℃, and the average size of crystal grains is refined to about 70 mu m.

The target blank is roughly machined on a lathe, the maximum excircle is machined to phi 377mm, the target thickness is machined to 23mm, then the machining is carried out on the lathe provided with an ultrasonic rolling tool, the frequency of an ultrasonic generator is 25kHZ, the amplitude of an ultrasonic transducer is 0.05mm, the diameter of a die steel tool head driven by the ultrasonic generator is 3mm, and the hardness is HRC42. After rolling the back of the target by ultrasonic waves, a strengthening layer with the size of about 1mm is generated, the size of crystal grains in the hardening layer is very small and is about 100nm, the surface hardness reaches HV110, and finally, the front and the side of the target are finely processed to the size of a finished product, the maximum excircle of the target is phi 375mm, and the thickness is 21mm.

The sputtering service life of the target material without the ultrasonic rolling treatment is usually 700kwh, while the sputtering service life of the target material of the embodiment reaches 850kwh, and after the sputtering use, the residual target is not obviously deformed.

Example 2

Preparing a long-life high-purity Cu target for manufacturing a 300mm wafer:

firstly, a vacuum casting formed 6N high-purity copper ingot is selected, the diameter of the ingot is 200mm, and the grain size reaches 1-5mm. The ingot is subjected to deformation processing such as die forging, rolling and the like by an oil press, the overall deformation is about 90%, the size of the target blank is phi 532 x 29mm, recrystallization annealing is carried out at 300 ℃, and the average size of crystal grains is refined to about 50 mu m.

The target blank is roughly machined on a lathe, the maximum excircle is machined to be phi 524mm, the target thickness is machined to be 26.8mm, then machining is carried out on the lathe provided with an ultrasonic rolling tool, the frequency of an ultrasonic generator is 25kHz, the amplitude of an ultrasonic transducer is 0.3mm, the diameter of a die steel tool head driven by the ultrasonic generator is 3mm, and the hardness is HRC42. After the back of the target is subjected to rolling treatment by ultrasonic waves, a strengthening layer with the thickness of about 2mm is generated, the size of crystal grains in the hardening layer is very small, about 200nm, the surface hardness reaches HV120, and finally, the front and the side of the target are subjected to finish machining to the size of a finished product, wherein the maximum excircle of the target is phi 521mm, and the thickness is 25.4mm.

The sputtering service life of the target material without ultrasonic rolling treatment is generally 2100kwh, while the sputtering service life of the target material of the embodiment reaches 2600kwh, and after the target material is used in a sputtering mode, the residual target is not obviously deformed.

Compared with the traditional target preparation process, the invention provides a preparation method of the long-life monomer target on the basis of the existing target preparation technology, the long-life target has a strengthening layer with a certain thickness on the back surface, ultrasonic rolling processing is carried out on the back surface of the target before finish machining of a product, and strong plastic deformation is introduced by high-frequency ultrasonic rolling, so that ultrafine grains and the strengthening layer are generated on the back surface of the target, and the strength and the deformation resistance of the target are effectively improved. The target sputtering layer has the conventional grain size, can improve the mechanical property of the monomer target on the back of the target, can meet the long-time sputtering requirement, and has important significance in the aspects of simplifying the process of preparing the high-purity metal and alloy sputtering target of an integrated circuit, improving the efficiency, improving the service performance of a product and the like.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The preparation method of the back-reinforced single target is characterized by comprising the following steps of:

(1) Preparing a target blank: using high-purity metal or high-purity alloy cast ingots as raw materials, and preparing a target blank by forging, rolling deformation processing and recrystallization annealing; the purity of the high-purity metal is more than or equal to 99.99 percent, and the content of other impurity elements except the main element in the high-purity alloy is less than 0.01 percent; the high-purity metal or high-purity alloy comprises high-purity aluminum or an alloy thereof, high-purity copper or an alloy thereof, high-purity silver or an alloy thereof, high-purity gold or an alloy thereof, high-purity platinum or an alloy thereof, and high-purity nickel or an alloy thereof;

(2) Cutting: cutting the target blank obtained in the step (1);

(3) Ultrasonic rolling processing: carrying out continuous ultrasonic rolling strong plastic deformation processing on the back surface of the target blank cut in the step (2) by adopting a hard tool head driven by an ultrasonic generator; the working frequency of the ultrasonic generator is 20-25 kHZ, and the working amplitude of a transducer in the ultrasonic generator is 0.05-0.5 mm; the diameter of the hard tool head is 1mm-10mm, the hard tool head is made of hard alloy or die steel, the hardness of the hard tool head is more than or equal to HRC40, and the grain size of a strengthened layer subjected to ultrasonic rolling treatment is less than or equal to 1 mu m;

(4) And (3) finish machining: and (4) performing finish machining on the front side and the side surface of the target blank subjected to the ultrasonic rolling machining in the step (3) to obtain a finished product of the monomer target with the reinforced back surface, wherein the hardness of the reinforced layer of the monomer target is greater than HV100, and the thickness of the reinforced layer of the monomer target is 1-3 mm.

2. The method for preparing a back-reinforced monolithic target according to claim 1, wherein the size of the target blank obtained after cutting in step (2) has a single edge with a machining allowance of 0.1mm-2mm compared with the size of the finished back-reinforced monolithic target.

3. A backside-strengthened monolithic target prepared by the preparation method according to any one of claims 1 to 2, comprising an integrally formed sputtering layer and a strengthening layer; the grain size of the sputtering layer is less than or equal to 100 mu m, and the grain size of the strengthening layer is less than or equal to 1 mu m; the strengthening layer is positioned on the back of the sputtering layer, the hardness of the strengthening layer is greater than that of the sputtering layer, and the thickness of the strengthening layer is 1mm-3mm; the hardness of the strengthening layer is greater than HV100.

4. The backside-strengthened monolithic target of claim 3, wherein the sputtered layer is prepared by forging, roll-deforming and recrystallization annealing in step (1); the strengthening layer is prepared by the ultrasonic rolling strong plastic deformation processing in the step (3).

5. The backside-strengthened monolithic target of claim 3, wherein the high-purity metal or high-purity alloy comprises high-purity aluminum or an alloy thereof, high-purity copper or an alloy thereof, high-purity silver or an alloy thereof, high-purity gold or an alloy thereof, high-purity platinum or an alloy thereof, and high-purity nickel or an alloy thereof.

6. The backside-strengthened monolithic target according to claim 3, wherein the grain size of the sputtered layer is 20 μm to 80 μm.

7. The backside-strengthened monolithic target of claim 3, wherein the grain size of the strengthening layer is 500nm or less.