A method of welding a graphite target

Abstract

The application provides a graphite target welding method, which comprises the following steps: (1) hot pressing the welding surface of a graphite target blank to form an infiltration layer; (2) performing infiltration treatment on the welding surface of a back plate and the infiltration layer, and then performing brazing welding on the graphite target blank and the back plate to obtain a graphite target. The welding method provided by the application can avoid the cracking of the graphite target blank during the welding process, and can make the graphite target blank and the back plate have a good welding bonding rate, effectively avoid welding defects, improve the one-time welding qualification rate, reduce the risk of welding separation of the graphite target blank and the back plate, and improve the production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology and relates to a method for welding target materials, and more particularly to a method for welding graphite target materials. Background Technology

[0002] The common welding methods used for semiconductor sputtering targets include isostatic diffusion welding and brazing. For square or elliptical targets used in cryogenic sputtering, brazing is generally used. The wettability of the target and backing plate with the solder is an important factor affecting the brazing bonding rate and strength.

[0003] Graphite target blanks have poor wettability with solder. To improve the welding bond rate, a layer of metal is usually plated on the graphite surface to facilitate solder wetting and improve welding performance. Alternatively, vacuum diffusion welding is used to weld the target blank to the backing plate under high pressure. However, for cryogenic sputtering targets, diffusion welding is more expensive and not suitable for mass production. In addition, due to the high brittleness of graphite, this welding method can easily damage the target blank.

[0004] CN113106401A discloses a graphene copper target and its preparation method. The target assembly includes an outer copper backing plate and a graphene copper target body. A groove is formed inside the outer copper backing plate, and a graphene coating is formed on the outer wall of the graphene copper target body. The outer copper backing plate and the graphene copper backing plate body are welded together. The inner area of ​​the groove is the same as the outer area of ​​the graphene copper target body. The disclosed preparation method improves the welding effect of the graphene copper target by forming a graphene coating on the outer wall of the graphene copper target body. However, its structure is relatively complex, and the preparation method is designed for graphene copper targets and cannot be applied to graphite targets with high brittleness.

[0005] Because it is difficult to achieve wetting between graphite target blanks and solder, a metal layer needs to be plated on the welding surface of the graphite target blank before brazing. Methods for plating this metal layer include, but are not limited to, chemical plating or physical vapor deposition. While these two methods can improve the weldability of the graphite target blank, due to the inherent properties of graphite, chemical plating can introduce acid or alkali solutions into the graphite target blank. If these solutions cannot be completely removed later, there is a risk of weld failure. Physical vapor deposition, on the other hand, is difficult to achieve good coating strength and carries a certain risk of weld failure.

[0006] Therefore, there is a need for a brazing method for graphite targets with low risk of desoldering and high weld bonding rate, specifically for graphite target blanks with poor wettability. Summary of the Invention

[0007] The purpose of this invention is to provide a welding method for graphite targets. This welding method can prevent the graphite target blank from cracking during the welding process, and also ensures a good welding bond between the graphite target blank and the back plate. This effectively avoids welding defects, improves the first-pass yield rate, reduces the risk of desoldering between the graphite target blank and the back plate, and improves production efficiency.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a welding method for graphite targets, characterized in that the welding method includes the following steps:

[0010] (1) The welding surface of the graphite target blank is hot-pressed to form a wetting layer;

[0011] (2) The back plate welding surface and the impregnation layer are impregnated, and then the graphite target blank and the back plate are brazed to obtain the graphite target material.

[0012] The graphite target material of this invention comprises a graphite target blank and a backing plate. This invention uses hot pressing to form the wetting layer, avoiding the problem of contamination of the graphite target blank associated with chemical plating, and also avoiding the target detachment problem caused by low strength of physical vapor deposition coatings. After the graphite target blank undergoes hot pressing to form the wetting layer, it is particularly suitable for brazing with the backing plate, effectively improving the first-pass yield of the welding between the graphite target blank and the backing plate, reducing the risk of target detachment, and increasing production efficiency.

[0013] Preferably, the flatness of the graphite target blank in step (1) is ≤0.05mm, for example, it can be 0.01mm, 0.02mm, 0.03mm, 0.04mm or 0.05mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] The present invention ensures that the flatness of the graphite target blank is ≤0.05mm before hot pressing, which is beneficial to improving the quality of the wetted layer formed by hot pressing and ensuring the welding bonding rate between the graphite target blank and the back plate.

[0015] The backplate of the present invention includes any one of copper backplate, copper alloy backplate, aluminum backplate or aluminum alloy backplate.

[0016] Preferably, the roughness of the welding surface of the graphite target blank in step (1) is ≥6μm, for example, it can be 6μm, 7μm, 8μm, 9μm or 10μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] This invention provides a method for achieving a welding surface roughness ≥ 6 μm on a graphite target blank, including but not limited to sandblasting. The invention does not limit the specific parameters of the sandblasting process, as long as the roughness of the welding surface of the graphite target blank is ≥ 6 μm. This invention, by achieving a welding surface roughness ≥ 6 μm on the graphite target blank, improves the bonding effect between the graphite target blank and the wetting material, and reduces the risk of desoldering after welding the graphite target blank to the backing plate.

[0018] Preferably, the material of the wetting layer in step (1) includes titanium powder.

[0019] Preferably, the titanium powder has a particle size ≤74μm, and more preferably a D50 of 30-40μm.

[0020] The titanium powder with a particle size of ≤74μm mentioned in this invention means that the titanium powder passes through a 200-mesh sieve and the material passing through the sieve is titanium powder that meets the requirement of ≤74μm.

[0021] Preferably, the particle size D50 of the titanium powder is 30-40 μm, for example, it can be 30 μm, 32 μm, 35 μm, 36 μm, 38 μm or 40 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the thickness of the impregnation layer in step (1) is ≤2mm, for example, it can be 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.8mm or 2mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the hot pressing method in step (1) includes:

[0024] (a) The graphite target blank and the impregnation layer material are assembled into a mold, and the welding surface of the graphite target blank is in contact with the impregnation layer material during the assembly process.

[0025] (b) Under vacuum conditions, the material after molding is subjected to a first heating, a first heat preservation, a second heating and a second heat preservation in sequence;

[0026] (c) After the second heat preservation is completed, pressurization and heat preservation and pressure preservation are carried out, and then the furnace is cooled.

[0027] The hot pressing process described in this invention includes a first heating and a first heat preservation. The purpose of the first heat preservation is to ensure that the impregnation layer material and the graphite target blank are fully heated, thereby avoiding the risk of cracking of the graphite target blank during subsequent pressurization and heat preservation and pressure preservation.

[0028] Preferably, the vacuum degree of the vacuum condition described in step (b) is ≤100Pa, for example, it can be 10Pa, 20Pa, 30Pa, 50Pa, 60Pa, 80Pa or 100Pa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] The lower the vacuum level in step (b) of this invention, the better it is for improving the effect of hot pressing to form the wetting layer. However, the lower the vacuum level, the higher the cost of achieving the relevant vacuum level. The welding method provided by this invention only requires a vacuum level ≤100 Pa during hot pressing.

[0030] Preferably, the heating rate of the first heating in step (b) is 4-8℃ / min, for example, it can be 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min or 8℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the endpoint temperature of the first heating in step (b) is 1250-1400℃, for example, it can be 1250℃, 1280℃, 1300℃, 1320℃, 1350℃, 1380℃ or 1400℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the first heat preservation time in step (b) is ≥80 min, for example, it can be 80 min, 95 min, 90 min, 95 min or 100 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] The welding method provided by this invention, during hot pressing, ensures that the wetting layer material and the graphite target blank are fully heated through a first heating and a first holding period. In this invention, the first holding period is ≥80 min, preferably ≥90 min.

[0034] Preferably, the heating rate of the second heating step (b) is 2-5℃ / min, for example, it can be 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the endpoint temperature of the second heating in step (b) is 1450-1600℃, for example, it can be 1450℃, 1480℃, 1500℃, 1540℃, 1550℃, 1580℃ or 1600℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the second heat preservation time in step (b) is ≥1h, for example, it can be 1h, 1.2h, 1.5h, 1.8h or 2h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] The present invention uses a second heat preservation operation to ensure that the temperature of the graphite target blank and the impregnation layer material is uniform after the second heating, thereby preventing the graphite target blank from cracking during the subsequent pressurization process.

[0038] Preferably, the pressurization rate in step (c) is 0.1-0.4 MPa / min, for example, it can be 0.1 MPa / min, 0.2 MPa / min, 0.3 MPa / min or 0.4 MPa / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the final pressure of pressurization in step (c) is 20-40 MPa, for example, it can be 20 MPa, 25 MPa, 30 MPa, 35 MPa or 40 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the heat preservation and pressure preservation time in step (c) is 1-3 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] As a preferred technical solution, step (c) of the present invention further includes a step of introducing inert gas to adjust the relative pressure to -0.06MPa to -0.08MPa between heat preservation, pressure holding and furnace cooling. Taking hot pressing operation in a vacuum sintering furnace as an example, this operation can reduce pressure fluctuations caused by direct pressure release and furnace shutdown.

[0042] Taking hot pressing in a vacuum sintering furnace as an example, the furnace cooling described in this invention includes cooling the furnace to a temperature ≤200℃, then removing the mold and graphite target blank, and drying them to room temperature.

[0043] Preferably, the temperature of the immersion treatment in step (2) is 180-220°C, for example, it can be 180°C, 190°C, 200°C, 210°C or 220°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the impregnation treatment method in step (2) includes ultrasonic impregnation.

[0045] The ultrasonic impregnation described in this invention involves impregnating the surface with a steel brush under ultrasonic conditions. The endpoint of ultrasonic impregnation is to make the surface color of the impregnated material match the color of the solder.

[0046] Preferably, a pressure block is provided during the brazing process.

[0047] Preferably, the mass-to-area ratio of the pressure block to the welding area is 1:(1200-1800), and the unit of the mass-to-area ratio is kg:mm.2 .

[0048] In this field, the welding area between the graphite target and the backing plate is ≥30000 mm². 2 For example, it could be 30000mm 2 32000mm 2 35000mm 2 36000mm 2 40000mm 2 Or 49000mm 2 However, this does not limit the listed values; other unlisted values ​​within the range are also applicable.

[0049] The brazing temperature described in this invention is the same as the wetting temperature, which is 180-220℃. For example, it can be 180℃, 190℃, 200℃, 210℃ or 220℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] After the brazing process is completed and the temperature is reduced to room temperature, the graphite target blank and the back plate are welded together to obtain the graphite target blank.

[0051] The room temperature described in this invention is 15-30℃, for example, it can be 15℃, 18℃, 20℃, 24℃, 25℃, 28℃ or 30℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] This invention uses hot pressing to form the wetting layer, avoiding the problem of contamination of the graphite target blank associated with chemical plating, and also avoiding the target desoldering problem caused by low strength of physical vapor deposition coating. After the graphite target blank is hot-pressed to form the wetting layer, it is particularly suitable for brazing with a backing plate, effectively improving the first-pass yield of welding between the graphite target blank and the backing plate, reducing the risk of target desoldering, and improving production efficiency. Detailed Implementation

[0054] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0055] In this specific embodiment of the invention, the graphite target blank is a circular graphite target blank, and the back plate is a copper back plate; the welding surface area between the graphite target blank and the copper back plate is 49000 mm². 2 The above limitations are merely for clearly illustrating the technical solution of the present invention and are not intended to further limit the present invention.

[0056] Example 1

[0057] This embodiment provides a welding method for graphite targets, the welding method comprising the following steps:

[0058] (1) A wetted layer with a thickness of 1.5 mm is formed by hot pressing the welding surface of the graphite target blank; the flatness of the graphite target blank is 0.05 mm, and the roughness of the welding surface of the graphite target blank is 6 μm.

[0059] The material of the wetting layer is titanium powder with a particle size ≤ 74 μm, and the particle size D50 of the titanium powder is 35 μm;

[0060] (2) The back plate welding surface and the impregnation layer are subjected to ultrasonic impregnation treatment at 200°C, and then the graphite target blank and the back plate are brazed. After the brazing is completed, the temperature is reduced to 25°C to obtain the graphite target material. The solder used for the brazing is indium solder.

[0061] The hot pressing in step (1) is carried out in a vacuum sintering furnace and includes the following steps:

[0062] (a) The graphite target blank and the impregnation layer material are assembled into a mold, and the welding surface of the graphite target blank is in contact with the impregnation layer material during the assembly process.

[0063] (b) Under a vacuum of 100 Pa, the material after molding is subjected to a first heating, a first holding, a second heating and a second holding in sequence;

[0064] The heating rate of the first heating is 6℃ / min, and the final temperature is 1300℃; the holding time of the first heat preservation is 90min.

[0065] The second heating rate is 4℃ / min, and the final temperature is 1500℃; the second holding time is 1h.

[0066] (c) After the second heat preservation is completed, pressurize to 30MPa at a rate of 0.2MPa / min, then keep it at the same temperature and pressure for 2 hours, then introduce helium to adjust the relative pressure to -0.07MPa, and then cool it to 200℃ with the furnace. Take out the mold and graphite target blank and dry it to 25℃.

[0067] Example 2

[0068] This embodiment provides a welding method for graphite targets, the welding method comprising the following steps:

[0069] (1) A wetted layer with a thickness of 1.5 mm is formed by hot pressing the welding surface of the graphite target blank; the flatness of the graphite target blank is 0.05 mm, and the roughness of the welding surface of the graphite target blank is 6 μm.

[0070] The material of the wetting layer is titanium powder with a particle size ≤ 74 μm and a particle size D50 of 30 μm;

[0071] (2) The back plate welding surface and the impregnation layer are subjected to ultrasonic impregnation treatment at 180°C, and then the graphite target blank and the back plate are brazed. After the brazing is completed, the temperature is reduced to 20°C to obtain the graphite target material. The solder used for the brazing is indium solder.

[0072] The hot pressing in step (1) is carried out in a vacuum sintering furnace and includes the following steps:

[0073] (a) The graphite target blank and the impregnation layer material are assembled into a mold, and the welding surface of the graphite target blank is in contact with the impregnation layer material during the assembly process.

[0074] (b) Under a vacuum of 100 Pa, the material after molding is subjected to a first heating, a first holding, a second heating and a second holding in sequence;

[0075] The heating rate of the first heating is 4℃ / min, and the final temperature is 1250℃; the holding time of the first heat preservation is 90min.

[0076] The second heating rate is 2℃ / min, and the final temperature is 1450℃; the second holding time is 1h.

[0077] (c) After the second heat preservation is completed, pressurize to 20MPa at a rate of 0.1MPa / min, then keep it at the heat and pressure for 3 hours, then introduce helium to adjust the relative pressure to -0.07MPa, and then cool it to 200℃ with the furnace. Take out the mold and graphite target blank and dry it to 20℃.

[0078] Example 3

[0079] This embodiment provides a welding method for graphite targets, the welding method comprising the following steps:

[0080] (1) A wetted layer with a thickness of 1.5 mm is formed by hot pressing the welding surface of the graphite target blank; the flatness of the graphite target blank is 0.05 mm, and the roughness of the welding surface of the graphite target blank is 6 μm.

[0081] The material of the wetting layer is titanium powder with a particle size ≤ 74 μm and a particle size D50 of 40 μm;

[0082] (2) The back plate welding surface and the impregnation layer are subjected to ultrasonic impregnation treatment at 220°C, and then the graphite target blank and the back plate are brazed. After the brazing is completed, the temperature is reduced to 20°C to obtain the graphite target material. The solder used for the brazing is indium solder.

[0083] The hot pressing in step (1) is carried out in a vacuum sintering furnace and includes the following steps:

[0084] (a) The graphite target blank and the impregnation layer material are assembled into a mold, and the welding surface of the graphite target blank is in contact with the impregnation layer material during the assembly process.

[0085] (b) Under a vacuum of 100 Pa, the material after molding is subjected to a first heating, a first holding, a second heating and a second holding in sequence;

[0086] The heating rate of the first heating is 8℃ / min, and the final temperature is 1400℃; the holding time of the first heat preservation is 90min.

[0087] The second heating rate is 5℃ / min, and the final temperature is 1600℃; the second holding time is 1h.

[0088] (c) After the second heat preservation is completed, pressurize to 40MPa at a rate of 0.4MPa / min, then keep it at the heat and pressure for 1 hour, then introduce helium to adjust the relative pressure to -0.07MPa, and then cool it to 200℃ with the furnace. Take out the mold and graphite target blank and dry it to 20℃.

[0089] Example 4

[0090] This embodiment provides a welding method for graphite targets. Except that the roughness of the welding surface of the graphite target blank is 8μm, the rest is the same as in Embodiment 1.

[0091] Example 5

[0092] This embodiment provides a welding method for graphite targets. Except that the roughness of the welding surface of the graphite target blank is 4μm, the rest is the same as in Embodiment 1.

[0093] Example 6

[0094] This embodiment provides a welding method for graphite targets, which is the same as that in Embodiment 1 except that the first heat preservation time is 60 minutes.

[0095] Example 7

[0096] This embodiment provides a welding method for graphite targets, which is the same as that in Embodiment 1 except that the first heat preservation is not performed.

[0097] Example 8

[0098] This embodiment provides a welding method for graphite targets, which is the same as that in Embodiment 1 except that the second heat preservation time is 50 minutes.

[0099] Example 9

[0100] This embodiment provides a welding method for graphite targets, which is the same as that in Embodiment 1 except that a second heat preservation is not performed.

[0101] Example 10

[0102] This embodiment provides a welding method for graphite targets. Except for the pressurization rate of 0.5 MPa / min in step (c), the rest is the same as in embodiment 1.

[0103] Due to excessively rapid pressurization, cracks appeared in the graphite target blank during the hot pressing process.

[0104] Comparative Example 1

[0105] This comparative example provides a welding method for graphite targets. Except that the welding method forms a wetting layer on the welding surface of the graphite target according to the method of CN113290293A, the rest is the same as in Example 1.

[0106] The first-pass yield of the welding methods provided in Examples 1-10 and Comparative Example 1, and the welding bonding rate of the graphite targets obtained in Examples 1-10 and Comparative Example 1 are shown in Table 1.

[0107] Table 1

[0108]

[0109]

[0110] The “-” in Table 1 indicates that cracks appeared in the graphite target blank during the welding process, making effective welding impossible.

[0111] In summary, this invention uses hot pressing to form the wetting layer, avoiding the problem of contaminating the graphite target blank associated with chemical plating, and also avoiding the target desoldering problem caused by low strength of physical vapor deposition coatings. After the graphite target blank undergoes hot pressing to form the wetting layer, it is particularly suitable for brazing with a backing plate, effectively improving the first-pass yield of the welding between the graphite target blank and the backing plate, reducing the risk of target desoldering, and increasing production efficiency.

[0112] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method of welding a graphite target material, characterized by, The welding method comprises the following steps: (1) hot pressing the welding surface of the graphite target blank to form an infiltration layer; (2) performing infiltration treatment on the welding surface of the back plate and the infiltration layer, and then performing brazing welding between the graphite target blank and the back plate to obtain a graphite target material; The thickness of the infiltration layer in step (1) is ≤2 mm; The hot pressing method in step (1) comprises: (a) assembling the graphite target blank and the infiltration layer material into a mold, and the welding surface of the graphite target blank is in contact with the infiltration layer material during the assembly; (b) sequentially performing first temperature rising, first holding, second temperature rising and second holding on the assembled material under vacuum condition; (c) after the second holding is completed, performing pressure increasing and holding, and then performing furnace cooling; In step (b), the vacuum degree of the vacuum condition is ≤100 Pa; In step (b), the first temperature rising has a temperature rising rate of 4-8 ℃ / min, and the terminal temperature is 1250-1400 ℃; In step (b), the first holding has a time of ≥80 min; In step (b), the second temperature rising has a temperature rising rate of 2-5 ℃ / min, and the terminal temperature is 1450-1600 ℃; In step (b), the second holding has a time of ≥1 h; In step (c), the pressure increasing has a pressure increasing rate of 0.1-0.4 MPa / min, the terminal pressure is 20-40 MPa, and the holding time is 1-3 h.

2. The welding method according to claim 1, characterized in that, In step (1), the flatness of the graphite target blank is ≤0.05 mm.

3. The welding method of claim 1, wherein, In step (1), the roughness of the welding surface of the graphite target blank is ≥6 μm.

4. The welding method of claim 1, wherein, In step (1), the material of the infiltration layer comprises titanium powder.

5. The welding method of claim 4, wherein, The particle size of the titanium powder is ≤74 μm.

6. The welding method of claim 5, wherein, The D50 of the titanium powder is 30-40 μm.

7. The welding method of claim 1, wherein, In step (2), the temperature of the infiltration treatment is 180-220 ℃.

8. The welding method of claim 1, wherein, In step (2), the method of the infiltration treatment comprises ultrasonic infiltration.

9. The welding method of claim 1, wherein, A pressure block is arranged during the brazing welding.

10. The welding method of claim 9, wherein, The mass of the briquette to the mass area ratio of the welding area is 1:(1200-1800), the unit of the mass area ratio is kg:mm 2 .

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