Alumina electrostatic chuck as well as preparation method and application thereof

Abstract

The invention relates to an aluminum oxide electrostatic chuck and a preparation method and application thereof, the preparation method comprises the following steps: (1) performing cold isostatic pressing treatment on aluminum oxide ceramic powder containing a sintering aid twice to respectively prepare a first aluminum oxide green body and a second aluminum oxide green body; wherein the thickness of the first aluminum oxide green body is greater than that of the second aluminum oxide green body; (2) coating conductive slurry on the first aluminum oxide green body, and placing the second aluminum oxide green body on the conductive slurry to obtain aluminum oxide green ceramic containing an electrode layer; (3) sequentially carrying out cold isostatic pressing lamination treatment, sheath welding treatment, degassing treatment and hot isostatic pressing treatment on the aluminum oxide raw ceramic containing the electrode layer, and removing a sheath to obtain an aluminum oxide ceramic green body containing the electrode layer; and (4) machining the aluminum oxide ceramic green body containing the electrode layer to obtain the aluminum oxide electrostatic chuck. The problem of co-firing of the alumina ceramic and the electrode material is solved, and the alumina electrostatic chuck with excellent performance is prepared and can be used for fixing silicon wafers in semiconductor processing.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor processing technology, and in particular to an aluminum oxide electrostatic chuck and a preparation method and application thereof. Background Art

[0002] In modern semiconductor manufacturing, the processing of silicon wafers involves multiple steps, such as plasma immersion, ion doping, ion implantation, physical vapor deposition, chemical vapor deposition, etc., all of which require the stable fixation of silicon wafers. Electrostatic chucks can fix silicon wafers through electrostatic adsorption, without causing warping or deformation of the object, and the adsorption force is continuous and stable. At the same time, in semiconductor processing, the silicon wafer needs to be cooled. If the uniform temperature of the silicon wafer surface cannot be guaranteed, the uniformity of the processing cannot be ensured during the processing of the silicon wafer, and the processing accuracy will be greatly affected. Therefore, the main material of the electrostatic chuck also needs good thermal conductivity.

[0003] Alumina ceramic material has good thermal conductivity, dielectric properties and high hardness, and is currently the main material for electrostatic chucks. However, the firing temperature of alumina is high, and the electrode layer material that matches it must have a high melting point. Only tungsten, molybdenum, nickel and manganese can meet the requirements, but these metals have the same characteristic that they are easily oxidized at high temperatures.

[0004] CN117447194A discloses an alumina ceramic target material and its preparation method and application. The preparation method comprises the following steps: (1) alumina powder with a purity of ≥4N and an average particle size of 0.1-1 μm is subjected to cold isostatic pressing in a rubber sheath, and the obtained blank is subjected to milling to obtain an alumina blank; (2) the alumina blank obtained in step (1) is subjected to sheath welding, degassing and hot isostatic pressing in sequence, and the alumina ceramic target material is obtained after removing the sheath. It only discloses the preparation method of the alumina ceramic target material, and does not disclose how to solve the problem of co-firing of alumina ceramics and electrode materials.

[0005] CN107954698A discloses a black alumina with high ceramic performance and a preparation method thereof. The method adjusts the ratio of a sintering aid and a pigment in the alumina ceramic and sinters at 1620°C to obtain black alumina with good toughness and wear resistance. It only discloses a preparation method for alumina ceramic targets, and does not involve how to solve the problem of co-firing alumina ceramics and electrode materials.

[0006] CN107954698A discloses a black alumina with high ceramic performance and a preparation method thereof. By adding a small amount of sintering aid and sintering at a constant temperature of 1280-1320°C in a silicon carbon rod furnace, a low-temperature sintered black alumina ceramic with uniform color is obtained. The black alumina ceramic has the characteristics of low sintering temperature, low dielectric constant, high density, high mechanical strength and high insulation. Similarly, it only discloses the preparation method of alumina ceramic target material, and does not involve how to solve the problem of co-firing alumina ceramic and electrode material.

[0007] In summary, it is necessary to develop a method for preparing an alumina electrostatic chuck to effectively solve the problem of co-firing alumina ceramics and electrode materials, so that the prepared alumina electrostatic chuck can be used to fix silicon wafers in semiconductor processing. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a method for preparing an alumina electrostatic chuck, by placing alumina raw porcelain containing an electrode layer into a sheath, welding it, and then performing a degassing treatment to make the inside of the sheath a vacuum state, and then performing a hot isostatic pressing treatment, thereby solving the problem of co-firing of alumina ceramics and electrode materials, and preparing an alumina electrostatic chuck with excellent performance.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing an alumina electrostatic chuck, the method comprising the following steps:

[0011] (1) performing cold isostatic pressing twice on an alumina ceramic powder containing a sintering aid to prepare a first alumina green embryo and a second alumina green embryo, respectively; wherein the thickness of the first alumina green embryo is greater than the thickness of the second alumina green embryo;

[0012] (2) coating the first alumina green body with a conductive slurry, and placing the second alumina green body on the conductive slurry to obtain an alumina green ceramic containing an electrode layer;

[0013] (3) sequentially subjecting the alumina green ceramic containing the electrode layer to cold isostatic pressing lamination treatment, sheath welding treatment, degassing treatment and hot isostatic pressing treatment, and removing the sheath to obtain an alumina green ceramic containing the electrode layer;

[0014] (4) Mechanically processing the alumina ceramic green body containing the electrode layer to obtain an alumina electrostatic chuck.

[0015] The present invention firstly prepares a first alumina green embryo and a second alumina green embryo by cold isostatic pressing technology; a conductive slurry is coated on the first alumina green embryo, and the second alumina green embryo is placed on the conductive slurry to obtain an alumina green ceramic containing an electrode layer, wherein the first alumina green embryo is used as a base layer of an alumina electrostatic chuck, and the second alumina green embryo is used as an adsorption layer of the alumina electrostatic chuck, and the thickness of the first alumina green embryo is greater than that of the second alumina green embryo, so that the base layer can provide support for the alumina electrostatic chuck, and the prepared alumina electrostatic chuck has sufficient strength and stability to ensure that the alumina electrostatic chuck will not be cracked during use. The alumina green ceramics containing the electrode layer are then subjected to cold isostatic pressing lamination, sheath welding, degassing and hot isostatic pressing in sequence; hot isostatic pressing after degassing can avoid oxidation of the conductive material of the electrode layer during the hot isostatic pressing process. The present invention can solve the problem of co-firing of alumina ceramics and electrode materials by limiting the preparation method of the alumina electrostatic chuck, and prepare an alumina electrostatic chuck with excellent performance.

[0016] As a preferred technical solution of the present invention, the alumina ceramic powder containing a sintering aid includes, by weight percentage, 85-95% alumina, 0.5-2% magnesium oxide, 2-4% silicon dioxide, 0.5-4% iron oxide and 0.5-5% manganese oxide; the weight percentage of the alumina may be 85%, 87%, 89%, 91%, 93% or 95%, the weight percentage of the magnesium oxide may be 0.5%, 0.7%, 1%, 1.5% or 2%, the weight percentage of the silicon dioxide may be 2%, 2.5%, 3%, 3.5% or 4%, the weight percentage of the iron oxide may be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5% or 4%, the weight percentage of the manganese oxide may be 0.5%, 1%, 2%, 3%, 4% or 5%, but is not limited to the listed values, and other values ​​not listed within the above numerical range are equally applicable.

[0017] It should be noted that the present invention uses alumina ceramic powder containing a sintering aid to prepare the alumina electrostatic chuck, rather than high-purity alumina ceramic powder, which increases the difficulty of preparation. The present invention can prepare an alumina electrostatic chuck with excellent performance by limiting its preparation method.

[0018] As a preferred technical solution of the present invention, the cold isostatic pressing treatments performed twice in step (1) are each independently performed in the first package.

[0019] Preferably, the material of the first package includes rubber.

[0020] Preferably, the pressure of the two cold isostatic pressing treatments is independently 150-300 MPa, for example, 150 MPa, 200 MPa, 250 MPa or 300 MPa, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0021] Preferably, the time for the two cold isostatic pressing treatments is independently 2-5 min, for example, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min or 5 min, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0022] As a preferred technical solution of the present invention, the thickness of the first alumina green embryo is 4-9 mm thicker than that of the second alumina green embryo, for example, it can be 4 mm, 5 mm, 6 mm, 7 mm, 8 mm or 9 mm, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0023] Preferably, the thickness of the first alumina green body is 10-12 mm, for example, 10 mm, 10.5 mm, 11 mm, 11.5 mm or 12 mm, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0024] The present invention controls the thickness of the first alumina green embryo to be 10-12 mm, so that the prepared alumina electrostatic chuck has sufficient strength and stability to ensure that the alumina electrostatic chuck will not be deformed or damaged during use. If the thickness of the first alumina green embryo is less than 10 mm, the stability of the overall structure of the electrostatic chuck will be reduced, causing the electrostatic chuck to be deformed or damaged during use, thereby affecting its service life. If the thickness of the first alumina green embryo is greater than 12 mm, the overall weight and inertia of the electrostatic chuck will be increased, thereby reducing the corresponding speed of the electrostatic chuck when clamping and releasing the workpiece, thereby affecting the working efficiency of the electrostatic chuck, and also reducing the heat dissipation performance of the electrostatic chuck, while increasing material costs.

[0025] Preferably, the thickness of the second alumina green body is 3-6 mm, for example, 3 mm, 4 mm, 5 mm or 6 mm, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0026] The present invention controls the thickness of the second alumina green body to be 3-6 mm, and can prepare an alumina electrostatic chuck with high thermal conductivity and excellent adsorption performance. If the thickness of the second alumina green body is less than 3 mm, the adsorption force and adsorption stability of the alumina electrostatic chuck will not meet the process requirements. If the thickness of the second alumina green body is greater than 6 mm, the electrostatic adsorption force generated by the electrode material will be reduced, the workpiece cannot be adsorbed, and the material cost will also increase.

[0027] Preferably, the thickness of the conductive paste is 0.01-0.2 mm, for example, 0.01 mm, 0.05 mm, 0.1 mm, 0.15 mm or 0.2 mm, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0028] As a preferred technical solution of the present invention, the second alumina green embryo is placed after the conductive paste is dried.

[0029] Preferably, the conductive material in the conductive paste includes any one of tungsten, molybdenum, nickel or manganese, or a combination of at least two of them, wherein typical but non-limiting combinations include: a combination of tungsten and molybdenum, a combination of tungsten and nickel, a combination of tungsten and manganese, a combination of molybdenum and nickel, a combination of molybdenum and manganese, a combination of nickel and manganese, a combination of tungsten, molybdenum and nickel, a combination of tungsten, molybdenum and manganese, a combination of tungsten, nickel and manganese, a combination of molybdenum, nickel and manganese, and a combination of tungsten, molybdenum, nickel and manganese.

[0030] Preferably, the pressure of the cold isostatic pressing lamination treatment in step (3) is 50-200 MPa, for example, 50 MPa, 100 MPa, 150 MPa or 200 MPa, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0031] Preferably, the time for the cold isostatic pressing lamination treatment in step (3) is 5-15 minutes, for example, 5 minutes, 7 minutes, 10 minutes, 13 minutes or 15 minutes, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0032] As a preferred technical solution of the present invention, the material of the sheath used in the sheath welding process includes stainless steel.

[0033] Preferably, the temperature of the degassing treatment is 400-500°C, for example, it can be 400°C, 420°C, 440°C, 450°C, 470°C, 490°C or 500°C, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0034] The present invention limits the temperature of the degassing treatment to 400-500°C, which can enhance the structural stability of the alumina material. If the temperature of the degassing treatment is lower than 400°C, the degassing time will increase, which will lead to reduced production efficiency. If the temperature of the degassing treatment is higher than 500°C, the excessively high temperature may destroy the crystal structure of the alumina ceramic, thereby affecting the adsorption capacity of the electrostatic chuck. At the same time, excessively high temperature will also cause residual stress in the alumina ceramic material. These stresses will cause the material to crack, deform and other problems during subsequent processing or use, thereby affecting the reliability and service life of the electrostatic chuck.

[0035] Preferably, the degassing treatment time is 6-9 hours, for example, it can be 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours or 9 hours, but it is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0036] Preferably, the degassing treatment makes the vacuum degree in the package reach 1.0×10 -3 -1.0×10 -2 Pa, for example, can be 1.0×10 -3 Pa, 3.0×10 -3 Pa, 5.0×10 -3 Pa, 7.0×10 -3 Pa, 9.0×10 -3 Pa or 1.0×10 -2 Pa, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0037] As a preferred technical solution of the present invention, the temperature of the hot isostatic pressing treatment is 1000-1250°C, for example, it can be 1000°C, 1050°C, 1100°C, 1150°C, 1200°C or 1250°C, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0038] The present invention limits the temperature of hot isostatic pressing treatment to 1000-1250°C, which can significantly improve the density and surface flatness of the material, optimize the microstructure, so as to enhance the adsorption capacity of the electrostatic chuck and improve the mechanical properties and stability of the material. If the temperature of hot isostatic pressing treatment is lower than 1000°C, the microstructure of the alumina ceramic material may not be fully optimized, resulting in uneven grain size, shape and distribution, and further leading to insufficient material density, decreased adsorption capacity, and impaired mechanical properties and stability. If the temperature of hot isostatic pressing treatment is higher than 1250°C, it will cause abnormal growth of grains in the alumina ceramic material, thereby reducing the adsorption capacity and stability of the electrostatic chuck. At the same time, excessively high temperature will also cause greater thermal stress inside the alumina ceramic material, so that the electrostatic chuck is at risk of cracking during subsequent use, thereby reducing the service life of the electrostatic chuck.

[0039] Preferably, the pressure of the hot isostatic pressing treatment is 100-120 MPa, for example, 100 MPa, 105 MPa, 110 MPa, 115 MPa or 120 MPa, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0040] The present invention limits the pressure of hot isostatic pressing treatment to 100-120MPa, which can effectively compress and fill the gaps between the alumina ceramic powder particles, significantly improve the density of the material, and at the same time enhance the internal bonding force of the alumina ceramic powder, so that it has higher strength and toughness, and improves its stability. If the pressure of hot isostatic pressing treatment is less than 100MPa, the gaps between the alumina ceramic powder particles cannot be effectively compressed and filled, and its grains cannot be effectively refined, which will reduce the adsorption force of the electrostatic chuck. If the pressure of hot isostatic pressing treatment is greater than 120MPa, the pressure is too high, and the grains of the alumina ceramic material may be excessively squeezed, resulting in abnormal grain shape and distribution. This abnormal grain structure will affect the surface area and surface energy of the material, thereby reducing the adsorption force of the electrostatic chuck. At the same time, excessive pressure may also destroy the pore structure inside the alumina material, making it uneven or too dense, thereby reducing its adsorption capacity and heat dissipation capacity.

[0041] Preferably, the hot isostatic pressing treatment time is 3-6 hours, for example, it can be 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but is not limited to the listed values, and other values ​​not listed in the above numerical range are also applicable.

[0042] As a preferred technical solution of the present invention, the preparation method further comprises: removing the sheath in step (3) by mechanical processing.

[0043] Preferably, the mechanical processing in step (3) includes any one of milling, turning or grinding, or a combination of at least two of them, wherein typical but non-limiting combinations include: a combination of milling and turning, a combination of milling and grinding, a combination of turning and grinding, and a combination of milling, turning and grinding.

[0044] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0045] (1) subjecting alumina ceramic powder containing a sintering aid to cold isostatic pressing twice in a first package at a pressure of 150-300 MPa and a time of 2-5 min, respectively, to prepare a first alumina green embryo and a second alumina green embryo, wherein the thickness of the first alumina green embryo is 4-9 mm thicker than that of the second alumina green embryo;

[0046] (2) coating the first alumina green body with a thickness of 0.01-0.2 mm with a conductive paste, and placing the second alumina green body after the conductive paste is dried to obtain an alumina green porcelain containing an electrode layer;

[0047] (3) The alumina green ceramic containing the electrode layer is subjected to a cold isostatic pressing lamination treatment at a pressure of 50-200 MPa for 5-15 min, and a sheath welding treatment at a temperature of 400-500° C. for 6-9 h and a vacuum degree of 1.0×10 -3 -1.0×10 -2 Pa degassing treatment and hot isostatic pressing treatment at a temperature of 1000-1250° C., a pressure of 100-120 MPa, and a time of 3-6 hours, and then removing the sheath by mechanical processing to obtain an alumina ceramic green body containing an electrode layer;

[0048] (4) Mechanically processing the alumina ceramic green body containing the electrode layer to obtain an alumina electrostatic chuck.

[0049] In a second aspect, the present invention provides an alumina electrostatic chuck prepared according to the preparation method described in the first aspect.

[0050] The aluminum oxide electrostatic chuck prepared by the invention has good adsorption capacity and heat dissipation capacity.

[0051] In a third aspect, the present invention provides an aluminum oxide electrostatic chuck obtained according to the preparation method described in the first aspect, which is used to fix silicon wafers during semiconductor processing.

[0052] The aluminum oxide electrostatic chuck prepared by the present invention has good adsorption and heat dissipation capabilities, and therefore can be used to fix silicon wafers during semiconductor processing.

[0053] Compared with the prior art, the present invention has at least the following beneficial effects:

[0054] The present invention solves the problem of co-firing of alumina ceramics and electrode materials by limiting the preparation method of the alumina electrostatic chuck, and prepares an alumina electrostatic chuck with good adsorption and heat dissipation capabilities, whose thermal conductivity can reach above 32W / m·K. At the same time, the temperature difference of its second alumina green layer can be controlled within 0.14°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a structural diagram of the alumina electrostatic chuck prepared in Example 1.

[0056] Among them, 1 is the first alumina green layer; 2 is the electrode layer; 3 is the second alumina green layer. DETAILED DESCRIPTION

[0057] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0058] Example 1

[0059] This embodiment provides a method for preparing an aluminum oxide electrostatic chuck, the method comprising the following steps:

[0060] (1) In terms of weight percentage, the alumina ceramic powder containing a sintering aid comprises 90% alumina, 1% magnesium oxide, 3% silicon dioxide, 3% iron oxide and 3% manganese oxide; the alumina ceramic powder containing a sintering aid is subjected to a cold isostatic pressing treatment at a pressure of 200 MPa for a time of 4 minutes in a rubber sheath to prepare a first alumina green embryo, and at the same time, the alumina ceramic powder containing a sintering aid is subjected to a cold isostatic pressing treatment at a pressure of 180 MPa for a time of 3 minutes in a rubber sheath to prepare a second alumina green embryo; wherein the thickness of the first alumina green embryo is 10 mm, the thickness of the second alumina green embryo is 3 mm, and the thickness of the first alumina green embryo is 7 mm thicker than the thickness of the second alumina green embryo;

[0061] (2) coating the first alumina green body with a thickness of 0.05 mm and a conductive paste composed of bisphenol A epoxy resin (E-03), polyethylene glycol (PEG-1000) and tungsten, wherein the mass ratio of bisphenol A epoxy resin (E-03), polyethylene glycol (PEG-1000) and tungsten is 20:5:75, and placing the second alumina green body after drying the conductive paste to obtain alumina green porcelain containing an electrode layer;

[0062] (3) The alumina green porcelain containing the electrode layer is subjected to a cold isostatic pressing lamination treatment at a pressure of 100 MPa for 10 min, and then the alumina green porcelain containing the electrode layer is placed in a stainless steel sheath, and the sheath is welded and then degassed, wherein the degassed temperature is 450° C. for 8 h, and the vacuum degree in the stainless steel sheath is 5.0×10 -3 Pa, hot isostatic pressing the degassed sheath at an operating temperature of 1100° C., a pressure of 110 MPa, and a time of 4 h, and then removing the sheath by milling to obtain an alumina ceramic green body containing an electrode layer;

[0063] (4) Mechanically processing the alumina ceramic green body containing the electrode layer to obtain an alumina electrostatic chuck, the structure of the alumina electrostatic chuck is as follows: Figure 1 As shown, it includes a first alumina green layer, an electrode layer and a second alumina green layer arranged in sequence.

[0064] Example 2

[0065] This embodiment provides a method for preparing an aluminum oxide electrostatic chuck, the method comprising the following steps:

[0066] (1) In terms of weight percentage, the alumina ceramic powder containing a sintering aid comprises 85% of alumina, 2% of magnesium oxide, 4% of silicon dioxide, 4% of iron oxide and 5% of manganese oxide; the alumina ceramic powder containing a sintering aid is subjected to a cold isostatic pressing treatment at a pressure of 150 MPa for a time of 5 min in a rubber sheath to prepare a first alumina green embryo; and at the same time, the alumina ceramic powder containing a sintering aid is subjected to a cold isostatic pressing treatment at a pressure of 150 MPa for a time of 4 min in a rubber sheath to prepare a second alumina green embryo; wherein the thickness of the first alumina green embryo is 11 mm, the thickness of the second alumina green embryo is 4 mm, and the thickness of the first alumina green embryo is 7 mm thicker than the thickness of the second alumina green embryo;

[0067] (2) coating the first alumina green body with a thickness of 0.01 mm and a conductive paste composed of hydrogenated bisphenol A epoxy resin (EP-4080E), hydroxyethyl cellulose (BR-F1259) and molybdenum, wherein the mass ratio of hydrogenated bisphenol A epoxy resin (EP-4080E), hydroxyethyl cellulose (BR-F1259) and molybdenum is 16:4:80, and placing the second alumina green body after drying the conductive paste to obtain alumina green porcelain containing an electrode layer;

[0068] (3) The alumina green porcelain containing the electrode layer is subjected to a cold isostatic pressing lamination treatment at a pressure of 200 MPa for 5 min, and then the alumina green porcelain containing the electrode layer is placed in a stainless steel sheath, and the sheath is welded and then degassed, wherein the degassed temperature is 500° C. for 6 h, and the vacuum degree in the stainless steel sheath is 1.0×10 -3 Pa, hot isostatic pressing the degassed sheath at an operating temperature of 1000° C., a pressure of 120 MPa, and a time of 6 h, and then removing the sheath by lathing to obtain an alumina ceramic green body containing an electrode layer;

[0069] (4) Mechanically processing the alumina ceramic green body containing the electrode layer to obtain an alumina electrostatic chuck.

[0070] Example 3

[0071] This embodiment provides a method for preparing an aluminum oxide electrostatic chuck, the method comprising the following steps:

[0072] (1) In terms of weight percentage, the alumina ceramic powder containing a sintering aid comprises 95% alumina, 0.5% magnesium oxide, 2% silicon dioxide, 0.5% iron oxide and 2% manganese oxide; the alumina ceramic powder containing a sintering aid is subjected to cold isostatic pressing treatment at a pressure of 300 MPa for a time of 2 min in a rubber sheath to prepare a first alumina green embryo; and at the same time, the alumina ceramic powder containing a sintering aid is subjected to cold isostatic pressing treatment at a pressure of 300 MPa for a time of 2 min in a rubber sheath to prepare a second alumina green embryo; wherein the thickness of the first alumina green embryo is 12 mm, the thickness of the second alumina green embryo is 6 mm, and the thickness of the first alumina green embryo is 6 mm thicker than the thickness of the second alumina green embryo;

[0073] (2) coating the first alumina green body with a thickness of 0.2 mm and a conductive paste composed of bisphenol S epoxy resin (300S), polyvinyl butyral (B60H) and nickel, wherein the mass ratio of bisphenol S epoxy resin (300S), polyvinyl butyral (B60H) and nickel is 10:5:85, and placing the second alumina green body after drying the conductive paste to obtain alumina green porcelain containing an electrode layer;

[0074] (3) The alumina green porcelain containing the electrode layer is subjected to a cold isostatic pressing lamination treatment at a pressure of 50 MPa for 15 min, and then the alumina green porcelain containing the electrode layer is placed in a stainless steel sheath, and the sheath is welded and then degassed, wherein the degassed temperature is 400° C. for 9 h, and the vacuum degree in the stainless steel sheath is 1.0×10 -2Pa, hot isostatic pressing the degassed sheath at an operating temperature of 1250° C., a pressure of 100 MPa, and a time of 3 h, and then removing the sheath by grinding to obtain an alumina ceramic green body containing an electrode layer;

[0075] (4) Mechanically processing the alumina ceramic green body containing the electrode layer to obtain an alumina electrostatic chuck.

[0076] Example 4

[0077] This embodiment provides a method for preparing an alumina electrostatic chuck, which is different from Embodiment 1 only in that, except that the thickness of the second alumina green body is 8 mm, that is, the thickness of the second alumina green body is too large, and the thickness of the first alumina green body is 2 mm thicker than the thickness of the second alumina green body, the rest is the same as Embodiment 1.

[0078] Example 5

[0079] This embodiment provides a method for preparing an alumina electrostatic chuck, which is different from Embodiment 1 only in that, except that the thickness of the first alumina green body is 15 mm, that is, the thickness of the first alumina green body is too large, and the thickness of the first alumina green body is 12 mm thicker than the thickness of the second alumina green body, the rest is the same as Embodiment 1.

[0080] Example 6

[0081] This embodiment provides a method for preparing an alumina electrostatic chuck, which is the same as that of embodiment 1 except that the temperature of the degassing treatment in step (3) is 300°C.

[0082] Example 7

[0083] This embodiment provides a method for preparing an alumina electrostatic chuck, which is the same as that of embodiment 1 except that the temperature of the degassing treatment in step (3) is 600°C.

[0084] Example 8

[0085] This embodiment provides a method for preparing an alumina electrostatic chuck, which is the same as that of Embodiment 1 except that the temperature of the hot isostatic pressing treatment in step (3) is 900°C.

[0086] Example 9

[0087] This embodiment provides a method for preparing an alumina electrostatic chuck, which is different from the embodiment 1 only in that the temperature of the hot isostatic pressing treatment in step (3) is 1300° C., and the rest is the same as the embodiment 1. Since the hot isostatic pressing treatment temperature is too high, the prepared alumina electrostatic chuck cracks.

[0088] Example 10

[0089] This embodiment provides a method for preparing an alumina electrostatic chuck, which is the same as that of Embodiment 1 except that the pressure of the hot isostatic pressing treatment in step (3) is 90 MPa.

[0090] Embodiment 11

[0091] This embodiment provides a method for preparing an alumina electrostatic chuck, which is different from the embodiment 1 only in that, except that the pressure of the hot isostatic pressing treatment in step (3) is 130 MPa, the rest is the same as the embodiment 1. Since the hot isostatic pressing pressure is too high, the prepared alumina electrostatic chuck cracks.

[0092] Comparative Example 1

[0093] This comparative example provides a method for preparing an alumina electrostatic chuck, which is the same as Example 1 except that the thickness of the first alumina green embryo is equal to the thickness of the second alumina green embryo.

[0094] Comparative Example 2

[0095] This comparative example provides a method for preparing an alumina electrostatic chuck, which is the same as Example 1 except that the alumina ceramic powder containing a sintering aid is replaced with an alumina ceramic powder with a purity ≥ 4N.

[0096] The thermal conductivity of the prepared alumina electrostatic chuck was tested using a laser thermal conductivity meter. At the same time, for the prepared alumina electrostatic chuck, the average temperature of the second alumina green layer was controlled to be 60°C. An infrared thermal imager was used to detect the temperature distribution in the second alumina green layer, and the highest and lowest temperatures were recorded. The temperature difference was the difference between the highest and lowest temperatures. The test results are shown in Table 1.

[0097] Table 1

[0098]

[0099]

[0100] The test results show that:

[0101] (1) It can be seen from Examples 1 to 3 that the present invention uses cold isostatic pressing, degassing and hot isostatic pressing technology to prepare an alumina electrostatic chuck with good adsorption and heat dissipation capabilities, and its thermal conductivity can reach above 32 W / m·K. At the same time, the temperature difference of its second alumina green layer can be controlled within 0.14°C.

[0102] (2) It can be seen from Examples 1 to 4-5 that in Example 1, the thickness of the second alumina green embryo is 3 mm, the thickness of the first alumina green embryo is 7 mm thicker than the thickness of the second alumina green embryo, the thermal conductivity of the alumina electrostatic chuck prepared in Example 1 is 33 W, and the temperature difference is 0.12°C, while in Example 4, the thickness of the second alumina green embryo is 8 mm, the thickness of the first alumina green embryo is 2 mm thicker than the thickness of the second alumina green embryo, that is, the thickness of the second alumina green embryo is too large, and the thermal conductivity of the alumina electrostatic chuck prepared in Example 4 is 29 W, and the temperature difference is 1.20°C; in Example 5, the thickness of the first alumina green embryo is 15 mm, the thickness of the first alumina green embryo is 2 mm thicker than the thickness of the second alumina green embryo. The thickness of the second alumina green body is 12 mm, that is, the thickness of the first alumina green body is too large. The thermal conductivity of the alumina electrostatic chuck prepared in Example 5 is 28 W, and the temperature difference is 1.15°C. This shows that the present invention controls the thickness of the first alumina green body to 10-12 mm, so that the prepared alumina electrostatic chuck has sufficient strength and stability to ensure that the alumina electrostatic chuck will not be deformed or damaged during use. At the same time, by controlling the thickness of the second alumina green body to 3-6 mm, an alumina electrostatic chuck with high thermal conductivity and excellent adsorption performance can be prepared. However, when the total thickness of the disc body increases, it will be unfavorable for heat loss and temperature uniformity control.

[0103] (3) It can be seen from Examples 1 to 6-7 that the temperature of the degassing treatment in step (3) of Example 1 is 450°C, the thermal conductivity of the alumina electrostatic chuck prepared in Example 1 is 33W, and the temperature difference is 0.12°C, while the temperature of the degassing treatment in step (3) of Example 6 is 300°C, the thermal conductivity of the alumina electrostatic chuck prepared therefrom is 25W, and the temperature difference is 2.50°C, and the temperature of the degassing treatment in step (3) of Example 7 is 600°C, the thermal conductivity of the alumina electrostatic chuck prepared therefrom is 26W, and the temperature difference is 2.80°C. This shows that the present invention can enhance the structural stability of the alumina material by controlling the degassing temperature to 400-500°C. If the degassing temperature is too low, the density requirement after sintering cannot be met, and the thermal conductivity decreases. If the degassing temperature is too high, the conductive slurry may be oxidized. That is, if the degassing temperature is too low or too high, the adsorption capacity and heat dissipation capacity of the alumina electrostatic chuck will be affected.

[0104] (4) It can be seen from Examples 1 to 8 that the temperature of the hot isostatic pressing treatment in step (3) of Example 1 is 1250°C, the thermal conductivity of the alumina electrostatic chuck prepared in Example 1 is 33W, and the temperature difference is 0.12°C, while the temperature of the hot isostatic pressing treatment in step (3) of Example 8 is 900°C, and the thermal conductivity of the alumina electrostatic chuck prepared therefrom is 25W, and the temperature difference is 2.48°C. This shows that the present invention limits the temperature of the hot isostatic pressing treatment to 1000-1250°C, which can significantly improve the density and surface smoothness of the material, optimize the microstructure, enhance the adsorption capacity of the electrostatic chuck, and improve the mechanical properties and stability of the material. If the temperature of the hot isostatic pressing treatment is lower than 1000°C, the material density will be insufficient, the adsorption capacity will be reduced, and the mechanical properties and stability will be impaired, which will ultimately affect the adsorption capacity and heat dissipation capacity of the alumina electrostatic chuck.

[0105] (5) It can be seen from Examples 1 to 10 that the pressure of the hot isostatic pressing treatment in step (3) of Example 1 is 110 MPa, and the thermal conductivity of the alumina electrostatic chuck prepared in Example 1 is 33 W, and the temperature difference is 0.12°C. The pressure of the hot isostatic pressing treatment in step (3) of Example 10 is 90 MPa, and the thermal conductivity of the alumina electrostatic chuck prepared therefrom is 24 W, and the temperature difference is 2.65°C. This shows that the present invention limits the pressure of the hot isostatic pressing treatment to 100-120 MPa, which can effectively compress and fill the gaps between the alumina ceramic powder particles, significantly improve the density of the material, and at the same time enhance the internal bonding force of the alumina ceramic powder, so that it has higher strength and toughness, and improves its stability. If the pressure of the hot isostatic pressing treatment is less than 100 MPa, the gaps between the alumina ceramic powder particles cannot be effectively compressed and filled, and the grains cannot be effectively refined, which ultimately affects the adsorption capacity and heat dissipation capacity of the alumina electrostatic chuck.

[0106] (6) It can be seen from Example 1 and Comparative Example 1 that the thickness of the first alumina green embryo in Comparative Example 1 is equal to the thickness of the second alumina green embryo, and the thermal conductivity of the alumina electrostatic chuck prepared therefrom is 22W, and the temperature difference is 3.20°C, which shows that the thickness of the first alumina green embryo is greater than the thickness of the second alumina green embryo, wherein the first alumina green embryo as a base layer can provide support for the alumina electrostatic chuck, so that the prepared alumina electrostatic chuck has sufficient strength and stability to ensure that the alumina electrostatic chuck will not be deformed or damaged during use. At the same time, during use, the second alumina green embryo acts as an adsorption layer to contact the surface of the workpiece to be fixed. The slightly smaller thickness of the second alumina green embryo can make the adsorption layer have a certain conductivity and uniformity, so as to enhance its electrostatic adsorption effect, so that the prepared alumina electrostatic chuck has good adsorption capacity and heat dissipation capacity.

[0107] (7) It can be seen from Example 1 and Comparative Example 2 that in Comparative Example 2, alumina ceramic powder with a purity of ≥4N is processed, and the thickness of the first alumina green embryo is made equal to the thickness of the second alumina green embryo. The thermal conductivity of the alumina electrostatic chuck prepared therefrom is 25W, and the temperature difference is 2.80°C. This shows that even if high-purity alumina ceramic powder is used as the raw material to reduce the difficulty of preparation, it is still necessary to make the thickness of the first alumina green embryo greater than the thickness of the second alumina green embryo in order to prepare an alumina electrostatic chuck with good adsorption and heat dissipation capabilities.

[0108] In summary, the present invention solves the co-firing problem of alumina ceramics and electrode materials by placing alumina raw porcelain containing an electrode layer into a sheath, welding it, and then performing a degassing treatment to make the inside of the sheath a vacuum state, and then performing a hot isostatic pressing treatment, thereby preparing an alumina electrostatic chuck with good adsorption and heat dissipation capabilities, which can be used to fix silicon wafers in the semiconductor processing process.

[0109] The applicant declares that the above is only a specific implementation mode 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 thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing an alumina electrostatic chuck, characterized in that: The preparation method comprises the following steps: (1) performing cold isostatic pressing twice on an alumina ceramic powder containing a sintering aid to prepare a first alumina green embryo and a second alumina green embryo, respectively; wherein the thickness of the first alumina green embryo is greater than the thickness of the second alumina green embryo; (2) coating the first alumina green body with a conductive slurry, and placing the second alumina green body on the conductive slurry to obtain an alumina green ceramic containing an electrode layer; (3) sequentially subjecting the alumina green ceramic containing the electrode layer to cold isostatic pressing lamination treatment, sheath welding treatment, degassing treatment and hot isostatic pressing treatment, and removing the sheath to obtain an alumina green ceramic containing the electrode layer; (4) Mechanically processing the alumina ceramic green body containing the electrode layer to obtain an alumina electrostatic chuck.

2. The preparation method according to claim 1, characterized in that: According to weight percentage, the alumina ceramic powder containing sintering aids includes 85-95% of aluminum oxide, 0.5-2% of magnesium oxide, 2-4% of silicon dioxide, 0.5-4% of iron oxide and 0.5-5% of manganese oxide.

3. The preparation method according to claim 1 or 2, characterized in that: The cold isostatic pressing treatments performed twice in step (1) are each independently performed in the first package; Preferably, the material of the first package includes rubber; Preferably, the pressure of the cold isostatic pressing treatments performed twice is independently 150-300 MPa; Preferably, the duration of the two cold isostatic pressing treatments is independently 2-5 minutes.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The thickness of the first alumina green embryo is 4-9 mm thicker than that of the second alumina green embryo; Preferably, the thickness of the first alumina green body is 10-12 mm; Preferably, the thickness of the second alumina green embryo is 3-6 mm; Preferably, the thickness of the conductive paste is 0.01-0.2 mm.

5. The preparation method according to any one of claims 1 to 4, characterized in that: After the conductive slurry is dried, placing the second alumina green embryo; Preferably, the conductive material in the conductive paste includes any one of tungsten, molybdenum, nickel or manganese, or a combination of at least two thereof; Preferably, the pressure of the cold isostatic pressing lamination treatment in step (3) is 50-200 MPa; Preferably, the cold isostatic pressing lamination treatment time in step (3) is 5-15 minutes.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The material of the sheath used in the sheath welding process includes stainless steel; Preferably, the temperature of the degassing treatment is 400-500°C; Preferably, the degassing treatment time is 6-9h; Preferably, the degassing treatment makes the vacuum degree in the package reach 1.0×10 -3 -1.0×10 -2 Pa.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The temperature of the hot isostatic pressing treatment is 1000-1250°C; Preferably, the pressure of the hot isostatic pressing treatment is 100-120 MPa; Preferably, the hot isostatic pressing treatment time is 3-6 hours.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) subjecting alumina ceramic powder containing a sintering aid to cold isostatic pressing twice in a first package at a pressure of 150-300 MPa and a time of 2-5 min, respectively, to prepare a first alumina green embryo and a second alumina green embryo, wherein the thickness of the first alumina green embryo is 4-9 mm thicker than that of the second alumina green embryo; (2) coating the first alumina green body with a thickness of 0.01-0.2 mm with a conductive paste, and placing the second alumina green body after the conductive paste is dried to obtain an alumina green porcelain containing an electrode layer; (3) The alumina green ceramic containing the electrode layer is subjected to a cold isostatic pressing lamination treatment at a pressure of 50-200 MPa for 5-15 min, and a sheath welding treatment at a temperature of 400-500° C. for 6-9 h and a vacuum degree of 1.0×10 -3 -1.0×10 -2 Pa degassing treatment and hot isostatic pressing treatment at a temperature of 1000-1250° C., a pressure of 100-120 MPa, and a time of 3-6 hours, and then removing the sheath by mechanical processing to obtain an alumina ceramic green body containing an electrode layer; (4) Mechanically processing the alumina ceramic green body containing the electrode layer to obtain an alumina electrostatic chuck.

9. An alumina electrostatic chuck, characterized in that: The alumina electrostatic chuck is prepared according to the preparation method according to any one of claims 1-8.

10. An application of the alumina electrostatic chuck according to claim 9, characterized in that: The alumina electrostatic chuck is used to fix silicon wafers in semiconductor processing.

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