Binding method of target material and back plate

Abstract

The invention provides a binding method of a target material and a back plate, and belongs to the field of semiconductors, and the method comprises the following steps: preprocessing the target material and the back plate; uniformly coating conductive copper paste on the welding surface of the back plate, and bonding the target material pair on the welding surface; and the target material and the back plate which are bonded are placed in a low-temperature sintering furnace, heating and heat preservation are conducted, then the temperature is reduced to the room temperature at the set cooling rate, and binding is completed. According to the method, the copper material with the high melting point is used as the binding medium of the target material and the back plate, the target material off-target probability caused by high temperature generated by a sputtering machine table in the sputtering process is reduced, and the technical problem that in the prior art, the binding effect of the target material and the back plate is poor is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor, in particular to a binding method of target material and back plate. BACKGROUND

[0002] The target material is the core consumable material in the sputtering plating process of the vapor deposition technology, and the back plate is the supporting carrier in the sputtering plating process with the target material. If the binding degree between the target material and the back plate is poor, the target material will be deformed, cracked and detached from the target in the sputtering process, thereby affecting the performance of the sputtered film, and even causing damage to the sputtering machine.

[0003] Diffusion welding and brazing are commonly used welding processes for welding the target material and the back plate. Diffusion welding refers to that the atoms of the contact surface between the target material and the back plate diffuse to each other under the action of high temperature and high pressure to form a new diffusion layer and thus realize welding. However, diffusion welding requires high temperature and large welding pressure, which is easy to cause abnormal grains of the target material, and the equipment used for diffusion welding is expensive and has high cost.

[0004] Brazing is different from diffusion welding, which is not to connect the target material and the back plate through the action of high temperature and high pressure, but to use liquid filler metal to wet the base material, the filler metal atoms fill the gap of the joint, and the base material is connected by mutual diffusion, which avoids the problems of abnormal grains of the target material and high cost caused by excessive welding pressure in the diffusion welding process. However, since the melting point of the filler metal is low, the risk of target detachment will be increased when the temperature of the sputtering machine is high during use.

[0005] Therefore, it is needed to bind the target material and the back plate by a high-temperature-resistant connecting medium. SUMMARY

[0006] The embodiment of the present application provides a binding method of target material and back plate to solve the problems in the background art.

[0007] According to one aspect of the embodiment of the present application, a binding method of target material and back plate is provided, comprising:

[0008] pretreating the target material and the back plate;

[0009] uniformly coating conductive copper paste on the welding surface of the back plate, and bonding the target material to the welding surface;

[0010] placing the bonded target material and the back plate in a low-temperature sintering furnace, heating and keeping warm, then cooling to room temperature at a set cooling rate, and completing the binding.

[0011] In one possible implementation, before uniformly coating the conductive copper paste onto the backplate welding surface, the method further includes preparing the conductive copper paste. The preparation process of the conductive copper paste includes: cleaning copper powder with dilute hydrochloric acid or acetone and ultrasonically dispersing the copper powder in alcohol; mixing the ultrasonically dispersed copper powder with a glass liquid phase at low temperature and then drying to form a dry gel; mixing at least two of diethylene glycol butyl ether, ethyl cellulose, polyester resin, terpineol, and dibutyl phthalate to obtain an organic carrier; grinding and mixing the dry gel with the organic carrier and rolling it through a three-roll mill to obtain the conductive copper paste.

[0012] In one possible implementation, the glass liquid phase preparation steps include: stirring and mixing tetraethyl orthosilicate, ethanol, and water at room temperature to obtain a tetraethyl orthosilicate pre-hydrolyzed solution; dissolving a metal oxide and boric acid in water or ethanol to obtain an inorganic salt solution; and stirring and mixing the tetraethyl orthosilicate pre-hydrolyzed solution and the inorganic salt solution at room temperature to form a homogeneous glass liquid phase.

[0013] In one possible implementation, the metal oxide includes At least one of them.

[0014] In one possible implementation, the average particle size of the copper powder does not exceed 10 μm, and the purity of the copper powder is between 2N and 4N.

[0015] In one possible implementation, the dry gel is obtained by drying in an oven at a temperature of 80 to 120°C.

[0016] In one possible implementation, during the three-roll mill rolling process, the roller spacing is adjusted in descending order until a uniform conductive copper paste is obtained.

[0017] In one possible implementation, conductive copper paste is coated on the backplane solder surface with a thickness of 1 to 4 mm.

[0018] In one possible implementation, the heating temperature for low-temperature sintering is 200 to 300°C, and the holding time is 30 to 60 minutes.

[0019] In one possible implementation, the cooling rate is 3 to 7 °C / min.

[0020] In this invention, the target and backplate are first pretreated. Then, conductive copper paste is uniformly coated on the welding surface of the backplate, and the target is bonded to the welding surface. Finally, the bonded target and backplate are placed in a low-temperature sintering furnace, heated and held at that temperature, and then cooled to room temperature at a set cooling rate to complete the bonding. This achieves bonding of the target and backplate using conductive copper paste as the bonding medium. On the one hand, using conductive copper paste as the bonding medium can avoid the abnormal grains of the target caused by the high temperature and high welding pressure in the diffusion welding process without a bonding medium, and also eliminates the need for expensive equipment used in diffusion welding, thus reducing production costs. On the other hand, since the melting point of copper is 1084.62℃, which is much higher than the melting point of liquid brazing filler metal of 450℃, the target and backplate bonded by conductive copper paste have better resistance to the high temperature generated by the sputtering machine during the sputtering process, and the risk of target detachment is lower. Attached Figure Description

[0021] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding parts, wherein:

[0022] Figure 1 A flowchart illustrating a method for bonding a target material to a backing plate according to an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of a method for bonding a target material to a backing plate according to an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of another method for bonding a target material to a backing plate according to an embodiment of the present invention;

[0025] Figure 4 A schematic diagram illustrating another method for bonding a target material to a backing plate according to an embodiment of the present invention;

[0026] Figure 5 A flowchart illustrating another method for bonding a target material to a backing plate, as provided in an embodiment of the present invention;

[0027] Figure 6 A flowchart illustrating another method for bonding a target material to a backing plate, as provided in an embodiment of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Those skilled in the art should understand that the embodiments described below are only some, not all, of the embodiments disclosed. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] The principles and spirit of the present invention will be explained in detail below with reference to several representative embodiments.

[0030] According to one aspect of the present invention, a method for bonding a target material to a backing plate is provided, such as... Figure 1 As shown, the above-mentioned method for bonding the target material to the backing plate includes:

[0031] S101, pretreatment of the target material and backing plate;

[0032] S102, uniformly coat the conductive copper paste onto the welding surface of the back plate, and bond the target material to the welding surface;

[0033] S103, the bonded target and backing plate are placed in a low-temperature sintering furnace, heated and held at that temperature, and then cooled to room temperature at a set cooling rate to complete the bonding.

[0034] First, perform step S101 above to pre-treat the target and backing plate. It is understood that impurities may exist on the surface of the target and backing plate, such as rust or oxidation on the backing plate surface. To avoid the negative impact of impurities on the bonding process between the target and backing plate, pre-treatment of the target and backing plate is necessary.

[0035] For example, the specific process of pretreating the target and backing plate in step S101 above includes the following steps S101-1 to S101-4.

[0036] S101-1, Sandblasting of the target material and backing plate surfaces.

[0037] For example, the welding surfaces of the backplate and the target material are sandblasted, and the sandblasting pressure is controlled at 6 to 8 during the sandblasting process. The sandblasting distance is controlled at 80 to 130 mm, and the abrasive material can be glass beads with a particle size of 100 to 200 mesh. Through step S101-1, the welding surfaces of the back plate and the target material are sandblasted to roughen the welding surfaces of the back plate and the target material.

[0038] S101-2, Cleaning of the target material and backing plate surfaces.

[0039] It should be noted that during the sandblasting process, the surfaces of the target and backplate are usually contaminated by tooling fixtures and sandblasting equipment, resulting in the adhesion of organic impurities such as cutting oil. These organic impurities need to be removed by cleaning. For example, the target and backplate can be soaked in a sodium hydroxide solution and then ultrasonically cleaned. For example, the target and backplate can be soaked in a 5% sodium hydroxide solution for 15 to 20 minutes and then ultrasonically cleaned at 20 to 30 kHz for 10 to 15 minutes to remove the organic impurities.

[0040] S101-3, Remove oxide layer.

[0041] It should be noted that, since the backplate and target are made of metal, they are prone to forming an oxide layer when exposed to air for a long time, such as on the surface of a copper backplate. For the backplate and target material, soak them in 5% to 10% dilute hydrochloric acid for 5 to 8 minutes to allow the dilute hydrochloric acid to react with the metal oxide to form a soluble salt, thereby removing the oxide layer formed by the metal oxide.

[0042] S101-4, cleaned with deionized water.

[0043] Understandably, after cleaning the target and backplate through steps S101-3, the surfaces of the target and backplate will be covered with the reaction products (soluble salts) of dilute hydrochloric acid and oxide layer. Therefore, the target and backplate need to be rinsed with deionized water. For example, the target and backplate should be rinsed three times with deionized water, each rinse lasting at least 5 minutes, to ensure that there are no residual electrolytes on the surface of the target and backplate, thereby preventing residual salts from precipitating and damaging the copper paste structure during subsequent sintering.

[0044] The pretreatment of the target and backplate is achieved through the above steps S101-1 to S101-4, and then the above step S102 is performed to uniformly coat the conductive copper paste on the welding surface of the backplate and bond the target to the welding surface.

[0045] As one possible implementation, the aforementioned conductive copper paste is coated on the backplate soldering surface with a thickness of 1 to 4 mm, without any specific limitation.

[0046] For example, a metal mold can be used to bond the target material to the welding surface. Figure 2 As shown, within the open metal mold 21, a back plate 22 is first placed in the lower part of the mold 21. Further, conductive copper paste 24 is coated onto the welding surface 23 of the back plate 22, which is used to mate with the target material 25. Then, the target material 25 is placed on the welding surface 23 coated with conductive copper paste 24, thereby achieving bonding between the back plate 22 and the target material 25 through the conductive copper paste 24. Optionally, the metal mold 21 can be made of stainless steel; no specific limitation is made here.

[0047] In one possible implementation, a concave backplate with solder grooves can be used to achieve step S102 above. For example, see... Figures 3 to 4 First, such as Figure 3 As shown, the backplate 31 is concave in shape and contains a solder groove 32. The solder groove 32 includes a sidewall 32a and a bottom wall 32b. The backplate 31 also has an upper edge surface 33. Conductive copper paste 41 is coated in the bottom wall 32b of the backplate 31, and then a target material 42 with the same bottom dimensions as the bottom wall 32b is placed inside. Figure 3 The backplate 31 and the target 42 are bonded together in the solder bath 32 using conductive copper paste. It should be noted that, in this embodiment, the height of the target 42 is not less than the height of the sidewall 32a.

[0048] In another possible implementation, see Figure 3 Conductive copper paste is applied to both the sidewalls 32a and 32b of the backplate 31. Then, a target with the same bottom dimensions as the bottom wall 32b is placed in the solder bath 32 to bond the backplate 31 and the target together using the conductive copper paste. It should be noted that in this embodiment, the height of the target is not less than the height of the sidewall 32a.

[0049] By implementing the relevant embodiments of step S102 above, the target material and the backing plate are initially bonded with conductive copper paste, providing the necessary structural connection foundation for the subsequent bonding process of the target material and the backing plate in step S103, thereby successfully achieving stable bonding between the target material and the backing plate.

[0050] Optionally, before performing step S103 above, the bonded target and backing plate can be left to stand for 5 to 10 minutes to allow the organic carrier in the conductive copper paste to evaporate slightly, thereby increasing the initial adhesion between the conductive copper paste and the substrate and preventing the target from shifting when transferred to the sintering furnace.

[0051] It is understandable that, through the above step S103, the bonded target material and backing plate are placed in a low-temperature sintering furnace, heated and kept at a certain temperature, and then cooled to room temperature at a set cooling rate to complete the bonding of the target material and backing plate.

[0052] Optionally, the heating temperature for low-temperature sintering in step S103 is 200 to 300°C, and the holding time is 30 to 60 minutes.

[0053] It should be noted that the aforementioned conductive copper paste contains organic carriers (such as diethylene glycol butyl ether and terpineol). To ensure complete volatilization, a sintering temperature of at least 200°C is required. Furthermore, to avoid damaging the target material (as the grain size of the copper target increases from 10 μm to over 50 μm at temperatures above 350°C, leading to increased brittleness), the sintering temperature should not be too high. Temperatures below 300°C can completely inhibit grain growth. Additionally, to ensure a sufficient and complete reaction, the holding time is preferably 30 to 60 minutes.

[0054] For example, in one possible implementation, the bonded target and backing plate are heated at 250°C in a low-temperature sintering furnace for 45 minutes. In another possible implementation, the bonded target and backing plate are heated at 280°C in a low-temperature sintering furnace for 30 minutes.

[0055] Optionally, the cooling rate in step S103 above is 3 to 7 °C / min.

[0056] It should be noted that, due to the difference in the coefficient of thermal expansion between the target material and the backing plate, if the temperature is rapidly reduced from the insulation temperature to room temperature (e.g., at a cooling rate of 20°C / min), the target material and the backing plate will generate huge internal stress due to the difference in the coefficient of thermal expansion. At this time, the target material shrinks slowly while the backing plate shrinks quickly, and the shrinkage force of the backing plate will tear the target material. Therefore, a lower cooling rate is required to allow the internal stress to be released gradually. Thus, the cooling rate in step S103 can be selected as 3 to 7°C / min.

[0057] For example, in one possible implementation, after the target and backing plate are heated to 200°C and held in a low-temperature sintering furnace, they can be cooled to room temperature at a cooling rate of 3°C / min; in another possible implementation, after the target and backing plate are heated to 300°C and held in a low-temperature sintering furnace, they can be cooled to room temperature at a cooling rate of 7°C / min; in yet another possible implementation, after the target and backing plate are heated to 300°C and held in a low-temperature sintering furnace, they can also be cooled to room temperature at a cooling rate of 3°C / min.

[0058] For example, the operation of cooling to room temperature at a set cooling rate in step S103 can be carried out in a nitrogen protective atmosphere to avoid oxidation of copper by contact with air during the cooling process. No specific limitation is made here.

[0059] Through the above steps S101 to S103, the target and backplate are first pretreated. Then, conductive copper paste is uniformly coated on the welding surface of the backplate, and the target is bonded to the welding surface. Finally, the bonded target and backplate are placed in a low-temperature sintering furnace, heated and held at a set cooling rate to room temperature to complete the bonding. This achieves the bonding of the target and backplate using conductive copper paste as the bonding medium. On the one hand, using conductive copper paste as the bonding medium can avoid the abnormal grains of the target caused by the high temperature and high welding pressure in the diffusion welding process without a bonding medium, and also eliminates the need to use the expensive equipment used in diffusion welding, thus reducing production costs. On the other hand, since the melting point of copper is 1084.62℃, which is much higher than the melting point of liquid brazing filler metal of 450℃, the target and backplate bonded by conductive copper paste have better resistance to the high temperature generated by the sputtering machine during the sputtering process and have a lower risk of target detachment.

[0060] Optionally, as an optional implementation, before uniformly coating the conductive copper paste onto the backplate welding surface in step S102, the bonding method between the target material and the backplate further includes preparing the conductive copper paste, such as... Figure 5 As shown, the preparation process of the above-mentioned conductive copper paste includes:

[0061] S201, use dilute hydrochloric acid or acetone to clean the copper powder, and then ultrasonically disperse the copper powder in alcohol;

[0062] S202 involves mixing ultrasonically dispersed copper powder with a glass liquid phase at low temperature, followed by drying to form a dry gel.

[0063] S203, at least two of diethylene glycol butyl ether, ethyl cellulose, polyester resin, terpineol, and dibutyl phthalate are mixed to obtain an organic carrier;

[0064] S204 involves grinding and mixing a dry gel with an organic carrier, and then rolling it through a three-roll mill to obtain a conductive copper paste.

[0065] The following provides a detailed explanation of steps S201 to S204:

[0066] Regarding step S201, it should be noted that copper powder is easily oxidized during storage and preparation, forming an oxide layer on its surface. The oxide layer is an insulating material; if it remains, it will block the conductive pathways between copper powder particles, significantly reducing the conductivity of the conductive copper paste. Dilute hydrochloric acid can remove the oxide layer through acid washing, and through chemical reactions (such as…) The oxide layer is dissolved into soluble copper chloride and discharged with the cleaning solution; the concentration of dilute hydrochloric acid can be controlled at 5% to 10% to avoid excessive corrosion of the copper powder itself due to excessive concentration, which would lead to damage to the particle morphology.

[0067] Furthermore, copper powder preparation may leave behind organic impurities such as cutting oil and release agents, or adsorb organic dust from the air. These impurities can hinder the bonding of copper powder with the subsequent glass liquid phase and organic carrier, leading to uneven mixing. Acetone, on the other hand, is an organic solvent for degreasing, and its high volatility and boiling point of 56°C make it easy to remove through subsequent drying, leaving no new organic impurities.

[0068] Understandably, if the copper powder is mainly composed of oxidized impurities, dilute hydrochloric acid is used for cleaning; if the copper powder is mainly composed of organic impurities, acetone is used for cleaning. Then, the copper powder cleaned with dilute hydrochloric acid or acetone is ultrasonically dispersed in alcohol.

[0069] It should be noted that copper powder tends to agglomerate due to van der Waals forces between particles; that is, small particles clump together into large clumps. If copper powder is directly introduced into subsequent mixing steps, these agglomerates are difficult to break up, leading to uneven particle size distribution in the copper paste and consequently, defects. Therefore, it is necessary to use ultrasound to generate high-frequency vibrations in alcohol to break up the copper powder agglomerates. Alcohol's high volatility allows for rapid removal, preventing residue in the copper powder.

[0070] Optionally, the ultrasound time can be selected from 10 to 30 minutes to avoid the agglomerates not being broken up due to the short time, and the ultrasound power can be selected from 500 to 1000W, without specific limitation.

[0071] Optionally, the average particle size of the copper powder is no more than 10 μm, and the purity of the copper powder is 2N to 4N grade, without specific limitation.

[0072] Then, step S202 is performed, in which the ultrasonically dispersed copper powder is mixed with the glass liquid phase at low temperature and then dried to form a dry gel. That is, conductive copper powder and a glass liquid phase with binding function are mixed to form a stable solid dry gel.

[0073] It should be noted that mixing glass liquid phase with copper powder can reduce the amount of copper powder used in conductive copper paste, and the glass liquid phase can isolate the copper powder from air, thus playing an anti-oxidation role.

[0074] Furthermore, after the copper powder and the glass liquid phase are mixed at low temperature, they are dried to form a dry gel. It should be noted that the dry gel formed by mixing and drying the copper powder and the glass liquid phase has a porous and loose structure. Therefore, the above-mentioned dry gel allows the organic carrier in S203 to penetrate into the interior more easily, achieving a thorough mixing of the dry gel and the organic carrier.

[0075] In one possible implementation, the dry gel is obtained by drying in an oven at a temperature of 80 to 120°C.

[0076] For example, the copper powder and glass liquid phase mixture can be dried in a vacuum environment to avoid oxidation of the copper powder caused by oxygen in the air; the drying time can be 2 to 4 hours, and no specific limit is made here.

[0077] Furthermore, for step S203, at least two of diethylene glycol butyl ether, ethyl cellulose, polyester resin, terpineol, and dibutyl phthalate are mixed to obtain an organic carrier. It should be noted that step S203 can be parallel to or sequential with steps S201 and S202. That is, step S203 can be performed after, before, or simultaneously with steps S201 and S202, as long as the preparation of the dry gel and the organic carrier is completed before step S204. No specific limitation is made here.

[0078] It should be noted that the above-mentioned organic carrier not only provides a liquid environment, but also provides adhesion, increasing the adhesion effect of conductive copper paste to the backplate and the target material. However, a single organic component cannot achieve the above-mentioned functions of the organic carrier. It is necessary to mix at least two of the five organic components: diethylene glycol butyl ether, ethyl cellulose, polyester resin, terpineol, and dibutyl phthalate. The following is a specific analysis of the functions of the above five organic components.

[0079] Diethylene glycol butyl ether and terpineol are used as solvents to provide a liquid environment, ethyl cellulose and polyester resin are used as binders to enhance adhesion, and dibutyl phthalate is used as a plasticizer to prevent the conductive copper paste from drying and cracking after coating.

[0080] Understandably, organic carriers require at least one solvent and at least one binder. For example, an organic carrier can be obtained by mixing diethylene glycol butyl ether as a solvent and ethyl cellulose as a thickener. Alternatively, an organic carrier can also be obtained by mixing diethylene glycol butyl ether as a solvent and polyester resin as a thickener. Yet another example is the use of terpineol as a solvent and polyester resin as a thickener.

[0081] To prevent cracking of the conductive copper paste film after drying, dibutyl phthalate can be selectively added. For example, the organic carrier can be obtained by mixing diethylene glycol butyl ether, ethyl cellulose, and dibutyl phthalate. Alternatively, the organic carrier can be obtained by mixing terpineol, ethyl cellulose, and dibutyl phthalate. Furthermore, the organic carrier can be obtained by mixing diethylene glycol butyl ether, polyester resin, and dibutyl phthalate.

[0082] It should be noted that the ratio of solvent, binder, and plasticizer dibutyl phthalate determines the viscosity, crack resistance, and evaporation rate of the organic carrier. During preparation, it is necessary to avoid excessively high or low viscosity of the organic carrier. If the viscosity is too low, the adhesion between the target and the backing plate will decrease, making it prone to detachment during subsequent sintering. If the viscosity is too high, particles may appear in the conductive copper paste. Optionally, the ratio of solvent to binder can range from 3:1 to 2:3. If a plasticizer is added, the ratio of solvent, binder, and plasticizer should range from 3:1 to 2:3, and the ratio of binder to plasticizer should range from 4:1 to 2:1. For example, the ratio of the three can be set to 3:2:1; no specific limitation is made here.

[0083] After obtaining the organic carrier through step S203 and the dry gel through steps S201 to S202, step S204 is performed to grind and mix the dry gel with the organic carrier and roll it through a three-roll mill to obtain conductive copper paste.

[0084] Understandably, the purpose of step S204 is to thoroughly mix the solid particles of the dry gel with the organic carrier, while refining the particles and eliminating air bubbles to obtain a stable conductive copper paste. Specifically, for grinding and mixing, this process initially mixes the dry gel with the organic carrier, allowing the organic carrier to penetrate into the porous structure of the dry gel.

[0085] For example, a ball mill is used with zirconia balls as the milling media to avoid introducing metal impurities. The speed is 200 to 300 rpm and the grinding time is 30 to 60 minutes until the mixture of dry gel and organic carrier is a uniform paste without obvious solid lumps.

[0086] Furthermore, a three-roll mill is used for rolling. The high-speed rotation of the rollers generates strong shearing and extrusion forces, which completely disperses the small agglomerates of copper powder and glass powder remaining after grinding. At the same time, it can also squeeze out the tiny air bubbles introduced during grinding, thus avoiding defects such as pinholes and bubbles in the conductive copper paste film after coating.

[0087] In one possible implementation, during the three-roll mill rolling process, the roller spacing is adjusted in descending order until a uniform conductive copper paste is obtained.

[0088] For example, the initial roll gap is set to 50 μm to break up agglomerates, and then gradually reduced to 10 μm to achieve fine dispersion. For example, with 50 μm as the initial roll gap, it can be reduced by 10 μm each time it is rolled, and the roll gap is reduced to 10 μm after four rolling passes.

[0089] Through the above steps S201 to S204, on the one hand, copper powder is cleaned with dilute hydrochloric acid or acetone and ultrasonically dispersed in alcohol. Then, the ultrasonically dispersed copper powder is mixed with a glass liquid phase at low temperature and subsequently dried to form a dry gel. On the other hand, at least two of diethylene glycol butyl ether, ethyl cellulose, polyester resin, terpineol, and dibutyl phthalate are mixed to obtain an organic carrier. Further, the dry gel and the organic carrier are ground and mixed, and rolled by a three-roll mill to obtain the above-mentioned conductive copper paste.

[0090] In the aforementioned conductive copper paste, the glassy liquid phase melts during low-temperature sintering, filling microscopic voids through capillary action. Upon cooling, it forms a robust glass network that "bonds" the copper powder together, potentially reacting chemically with the backing surface to form strong chemical bonds. This prevents cracking and deformation of the target material during high-speed rotation, vibration, or thermal expansion and contraction. Furthermore, because copper has a higher melting point than liquid brazing filler metal, it exhibits stronger high-temperature resistance during sputtering compared to targets and backing materials bonded by brazing, reducing the likelihood of target detachment due to high temperatures. After sintering, the copper powder particles in the conductive copper paste come into contact with each other, forming a continuous copper powder network. Ultimately, electrons can be efficiently transported through this tightly connected network, ensuring uniform current distribution across the entire target surface during magnetron sputtering. This generates stable plasma, guaranteeing the stability of the sputtering process and the quality of the coating.

[0091] As an optional implementation, before step S202 where the ultrasonically dispersed copper powder is mixed with the glass liquid phase at low temperature, the bonding method between the target material and the backing plate further includes preparing the glass liquid phase, such as... Figure 6 As shown, the preparation steps of the above-mentioned glass liquid phase include:

[0092] S301, Tetraethyl orthosilicate, ethanol and water are stirred and mixed at room temperature to prepare a pre-hydrolyzed tetraethyl orthosilicate solution;

[0093] S302 dissolves metal oxides and boric acid in water or ethanol to prepare an inorganic salt solution;

[0094] S303 involves mixing a pre-hydrolyzed tetraethyl orthosilicate solution with an inorganic salt solution at room temperature to form a homogeneous glass liquid phase.

[0095] The following provides a detailed explanation of steps S301 to S303:

[0096] For step S301, this step involves preparing a pre-hydrolyzed solution of tetraethyl orthosilicate to provide an active solution capable of reacting with inorganic salt solutions. However, the pre-hydrolyzed solution of tetraethyl orthosilicate is inert and cannot react with inorganic salt solutions. Therefore, the tetraethyl orthosilicate needs to be hydrolyzed. The hydrolysis chemical formula is: The reaction produces The active molecules in the group can react with inorganic salt solutions. In addition, if the tetraethyl orthosilicate is left to the later stage without pre-hydrolysis, it will decompose during sintering, which will generate a large amount of C2H5OH gas, causing the sintered conductive copper paste to bulge and crack.

[0097] In step S302 above, the metal oxide is dissolved in water or ethanol to prepare an inorganic salt solution. Optionally, the metal oxide includes... , , , , At least one of them. For example, will To prepare an inorganic salt solution, boric acid is dissolved in water or ethanol; for example, boric acid is dissolved in water or ethanol. , It can be dissolved in water or ethanol with boric acid to prepare an inorganic salt solution, without specific limitations.

[0098] It should be noted that the purpose of step S302 is to introduce a metal oxide that can lower the softening point of the glass liquid phase, thereby achieving low-temperature softening of the glass liquid phase to match the lower sintering temperature of the conductive copper paste. However, the aforementioned metal oxide is poorly soluble in water, and boric acid can react with the metal oxide to form a soluble complex (such as...). It can be evenly dispersed at room temperature to avoid localized enrichment in the later stage.

[0099] For step S303 above, the tetraethyl orthosilicate prehydrolyzed solution and the inorganic salt solution are stirred and mixed at room temperature to form a uniform glass liquid phase. For example, the volume ratio between the tetraethyl orthosilicate prehydrolyzed solution and the inorganic salt solution is in the range of 1:1 to 1:2, the stirring speed is 150 to 250 rpm, and the reaction is carried out at room temperature for 60 to 90 minutes. Room temperature can avoid the reaction being too fast and causing gelation. Stirring ensures that the reaction is uniform and all active components are fully combined.

[0100] Through steps S301 to S303, on the one hand, tetraethyl orthosilicate, ethanol, and water are stirred and mixed at room temperature to prepare a pre-hydrolyzed tetraethyl orthosilicate solution; on the other hand, metal oxide and boric acid are dissolved in water or ethanol to prepare an inorganic salt solution. The pre-hydrolyzed tetraethyl orthosilicate solution and the inorganic salt solution are then stirred and mixed at room temperature to form a homogeneous glass liquid phase. The resulting glass liquid phase can melt at a relatively low temperature and form a dense, uniform inorganic bonding layer between the copper powders and between the target and the backing plate, thereby achieving high-strength bonding between the target and the backing plate.

[0101] The above embodiments of the present invention achieve the bonding of the target material and the backplate using conductive copper paste as a bonding medium. On the one hand, using conductive copper paste as a bonding medium can avoid the abnormal grains of the target material caused by the high temperature and large welding pressure in the diffusion soldering process without a bonding medium, and also eliminates the need to use the expensive equipment used in diffusion soldering, thus reducing production costs. On the other hand, since the melting point of copper is 1084.62℃, which is much higher than the melting point of liquid brazing filler metal of 450℃, the target material and backplate bonded by conductive copper paste have better resistance to the high temperature generated by the sputtering machine during the sputtering process, and the risk of target detachment is lower.

[0102] The above-described preferred embodiments of the present invention are provided as examples, but it will be apparent to those skilled in the art that such embodiments are provided merely by way of example. Many modifications, alterations, and alternatives will occur to those skilled in the art without departing from the spirit and intent of the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in the practice of the invention. The appended claims are intended to define the scope of protection of the invention and therefore cover the modular compositions, equivalents, or alternatives within the scope of these claims.

Claims

1. A method for bonding a target material to a backing plate, characterized in that, include: Pre-treatment of the target material and backing plate; The conductive copper paste is uniformly coated onto the welding surface of the back plate, and the target material is bonded to the welding surface. The bonded target and the backing plate are placed in a low-temperature sintering furnace, heated and held at that temperature, and then cooled to room temperature at a set cooling rate to complete the bonding.

2. The method according to claim 1, characterized in that, Before uniformly coating the conductive copper paste onto the backplate soldering surface, the method further includes preparing the conductive copper paste, the preparation process of which includes: The copper powder was cleaned with dilute hydrochloric acid or acetone and then ultrasonically dispersed in alcohol. The ultrasonically dispersed copper powder was mixed with a glass liquid phase at low temperature and then dried to form a dry gel. At least two of diethylene glycol butyl ether, ethyl cellulose, polyester resin, terpineol, and dibutyl phthalate are mixed to obtain an organic carrier; The dry gel is ground and mixed with the organic carrier, and then rolled by a three-roll mill to obtain the conductive copper paste.

3. The method according to claim 2, characterized in that, Before mixing the ultrasonically dispersed copper powder with the glass liquid phase at low temperature, the method further includes preparing the glass liquid phase, the preparation steps of which include: Tetraethyl orthosilicate, ethanol and water were stirred and mixed at room temperature to prepare a pre-hydrolyzed tetraethyl orthosilicate solution; Inorganic salt solutions are prepared by dissolving metal oxides and boric acid in water or ethanol. The tetraethyl orthosilicate prehydrolyzed solution and the inorganic salt solution were stirred and mixed at room temperature to form a homogeneous glass liquid phase.

4. The method according to claim 3, characterized in that, The metal oxide includes At least one of them.

5. The method according to claim 2, characterized in that, The average particle size of the copper powder does not exceed 10 μm, and the purity of the copper powder is 2N to 4N grade.

6. The method according to claim 2, characterized in that, The dry gel is obtained by drying in an oven at a temperature of 80 to 120°C.

7. The method according to claim 2, characterized in that, During the three-roll mill rolling process, the roller spacing is adjusted in descending order until a uniform conductive copper paste is obtained.

8. The method according to claim 1, characterized in that... The conductive copper paste is coated on the backplate welding surface with a thickness of 1 to 4 mm.

9. The method according to claim 1, characterized in that, The heating temperature for the low-temperature sintering is 200 to 300°C, and the holding time is 30 to 60 minutes.

10. The method according to claim 1, characterized in that, The cooling rate is 3 to 7 °C / min.

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