High-conductivity tungsten slurry special for electrostatic chuck and preparation method and application of high-conductivity tungsten slurry

Abstract

The invention discloses special tungsten slurry for a high-conductivity electrostatic chuck as well as a preparation method and application of the special tungsten slurry. The tungsten slurry comprises the following preparation raw materials in percentage by mass: 60-70% of tungsten powder; 10-20% of two kinds of conductive powder; 8-15% of an organic carrier; 0.5-1% of an auxiliary agent; 1.5 to 3 percent of glass powder; and 1-3% of a dispersant. According to the tungsten paste, the double-conductive powder is fused into the nickel powder and the silver powder, the nickel powder fills pores of the tungsten powder layer, a conductive path is increased, meanwhile, the nickel powder serves as a support of the silver powder, the nickel powder and the silver powder can form a good conductive network, and on a basic framework where the nickel powder forms the conductive network, the silver powder can serve as a rapid path in the conductive network; the high-conductivity tungsten powder has the advantages that electron mobility and transmission speed are increased evidently, scattering of electrons in the tungsten powder is reduced, resistance is reduced, high conductivity is achieved, adsorption performance of the electrostatic chuck can be improved effectively when the high-conductivity tungsten powder is applied to an electrode layer of the electrostatic chuck, and accordingly the high-conductivity tungsten powder has good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive materials, in particular to conductive materials of metals or alloys, and specifically to a tungsten slurry specially used for a high-conductive electrostatic chuck, and a preparation method and application thereof. Background Art

[0002] With the rapid development of semiconductor manufacturing technology, the electrostatic chuck (ESC) plays a vital role in the wafer processing process as one of the key equipment. The electrostatic chuck stably adsorbs the wafer by generating electrostatic force to ensure its precise position and stability during the processing; the electrode layer is the core component of the electrostatic chuck, and its conductive properties directly affect the generation and stability of the electrostatic force.

[0003] In the current semiconductor manufacturing field, the electrode layer of the electrostatic chuck is the key part of generating electrostatic force. By applying a DC voltage to generate an electric field, the wafer charge is polarized to achieve adsorption. Tungsten powder is often selected as the material for the electrode layer of the electrostatic chuck due to its high melting point, high hardness and good corrosion resistance. However, in the preparation process of traditional tungsten slurry, due to the limitation of the electrical conductivity of tungsten metal, the conductivity of the electrode layer after formation is not ideal, which makes the electrostatic force generation efficiency of the electrostatic chuck low, thus affecting the accuracy and stability of wafer processing.

[0004] Therefore, it is necessary to improve the deficiencies in the prior art to solve the above problems. Summary of the invention

[0005] The present invention overcomes the shortcomings of the prior art and provides a tungsten slurry specially used for a high-conductivity electrostatic chuck, a preparation method and an application thereof.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a tungsten slurry specially used for a highly conductive electrostatic chuck, wherein the tungsten slurry comprises the following raw materials in the following mass percentages:

[0007]

[0008]

[0009] In a preferred embodiment of the present invention, the conductive powder is one of nickel powder, silver powder, graphene or carbon nanotubes, and the particle size of the conductive powder is 1 to 4 μm, and the tap density is 2 to 6 g / cm 3 The particle size of the tungsten powder is 0.6-1 μm, and the tap density is 3-6 g / cm 3 .

[0010] In a preferred embodiment of the present invention, the tungsten powder and the silver powder are both spherical or flaky, and the nickel powder is spherical.

[0011] In a preferred embodiment of the present invention, the organic carrier comprises 10-25% by weight of resin and 75-90% by weight of organic solvent.

[0012] In a preferred embodiment of the present invention, the resin is an acrylic resin, the molecular weight of the acrylic resin is 500,000-900,000, and the organic solvent comprises 60% by mass of naphtha and 40% by mass of ethanol.

[0013] In a preferred embodiment of the present invention, the auxiliary agent is one of stearic acid, oleic acid or castor oil.

[0014] In a preferred embodiment of the present invention, the particle size of the glass powder is 2-4 μm.

[0015] In a preferred embodiment of the present invention, the dispersant is nonylphenol polyoxyethylene ether.

[0016] The present invention provides a method for preparing a tungsten slurry specially used for a high-conductivity electrostatic chuck, comprising the following steps:

[0017] S1. Weigh the resin and the organic solvent in proportion, stir in a reaction kettle at a temperature of 60 to 90° C. and a speed of 800 to 1000 r / min for 1 to 3 hours to obtain an organic carrier;

[0018] S2, placing tungsten powder and two conductive powders in a high-energy ball mill, adding anhydrous ethanol and ball milling for 2 to 4 hours, filtering, and drying at a temperature of 50 to 60° C. for 1 to 2 hours to obtain a blended conductive metal powder;

[0019] S3, adding the blended conductive metal powder, organic carrier, dispersant, additive and glass powder into a high-speed disperser, stirring at a speed of 1800-2100 r / min for 5-10 min to obtain a tungsten slurry precursor;

[0020] S4. Roll the tungsten slurry precursor in a three-roll mill until the tungsten slurry fineness is less than 10 μm, and degas in a double planetary centrifugal mixer for 3 to 8 minutes to obtain a highly conductive tungsten slurry.

[0021] The present invention provides an application of a high-conductivity tungsten slurry, wherein the high-conductivity tungsten slurry is obtained by the preparation method as described above and is used to make an electrode layer of an electrostatic chuck.

[0022] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0023] (1) The present invention provides a tungsten slurry specially used for a high-conductivity electrostatic chuck, and a preparation method and application thereof. The present invention fuses dual-conductive powders into a tungsten slurry of nickel powder and silver powder, and optimizes process materials. Since nickel powder has good conductivity, it fills the pores of the tungsten powder layer, increases the conductive path, and serves as a support for the silver powder, so that the nickel powder and the silver powder can form a good conductive network. The synergistic effect formed by the silver powder and the nickel powder is that on the basic framework of the conductive network formed by the nickel powder, the silver powder can serve as a fast path in the conductive network, significantly improving the mobility and transmission speed of electrons, and reducing the scattering of electrons in the tungsten powder, reducing resistance, and thus achieving the effect of high conductivity. When the nickel powder is used in the electrode layer of the electrostatic chuck, it can effectively improve the electrostatic force generation efficiency of the electrostatic chuck, further improving the adsorption performance, and thus has a good application prospect.

[0024] (2) In the present invention, by adjusting the appropriate mass ratio of nickel powder to silver powder, the distribution of nickel powder and silver powder in the tungsten slurry can reach a better balance point, thereby avoiding excessive aggregation of silver powder or insufficient nickel powder. Good contact can be formed between the nickel powder and silver powder particles, forming a stable conductive connection, providing a good migration path, allowing electrons to bypass obstacles, further optimizing the construction of the conductive network, improving electron mobility, enhancing the synergistic effect and reducing the porosity, thereby achieving the best conductivity of the tungsten slurry, which not only improves the conductive performance of the tungsten slurry, but also improves its overall performance in applications such as electrostatic chucks.

[0025] (3) In the present invention, the flat shape of the flaky silver powder can be used as a positioning overlap surface in the tungsten slurry, and the spherical nickel powder is filled between and around the flaky silver powder in a point-connected manner, thereby increasing the contact points between the conductive particles. The combination of the flaky silver powder and the spherical nickel powder effectively prevents the flaky silver powder from slipping in a one-dimensional direction, thereby avoiding the reduction of contact performance and the interruption of the conductive path, and at the same time helps to improve the density between the powders, thereby further improving the conductive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 The present invention is a flow chart of a method for preparing a tungsten slurry specially used for a high-conductivity electrostatic chuck according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0030] It should be noted that the raw materials, equipment and reagents used in the present invention can be purchased from the market or obtained through the preparation methods of existing technologies.

[0031] A tungsten slurry specially used for a highly conductive electrostatic chuck, the tungsten slurry comprising the following raw materials in percentage by mass:

[0032]

[0033]

[0034] In some specific embodiments, the conductive powder is one of nickel powder, silver powder, graphene or carbon nanotubes, and the particle size of the conductive powder is 1 to 4 μm, and the tap density is 2 to 6 g / cm 3 ; The particle size of tungsten powder is 0.6-1μm, and the tap density is 3-6g / cm 3 .

[0035] In some specific embodiments, the tungsten powder and the silver powder are both in a spherical shape or a flake shape, and the nickel powder is in a spherical shape.

[0036] In some specific embodiments, the organic carrier includes 10-25% by weight of resin and 75-90% by weight of organic solvent; the resin is acrylic resin, the molecular weight of the acrylic resin is 500,000-900,000, and the organic solvent includes 60% by weight of naphtha and 40% by weight of ethanol.

[0037] In some embodiments, the adjuvant is one of stearic acid, oleic acid or castor oil.

[0038] In some specific embodiments, the particle size of the glass powder is 2-4 μm.

[0039] In some embodiments, the dispersant is nonylphenol ethoxylate.

[0040] like Figure 1As shown, the present invention provides a method for preparing a tungsten slurry specially used for a high-conductivity electrostatic chuck, comprising the following steps:

[0041] S1. Weigh the resin and the organic solvent in proportion, stir in a reaction kettle at a temperature of 60 to 90° C. and a speed of 800 to 1000 r / min for 1 to 3 hours to obtain an organic carrier;

[0042] S2, placing tungsten powder and two conductive powders in a high-energy ball mill, adding anhydrous ethanol and ball milling for 2 to 4 hours, filtering, and drying at a temperature of 50 to 60° C. for 1 to 2 hours to obtain a blended conductive metal powder;

[0043] S3, adding the blended conductive metal powder, organic carrier, dispersant, additive and glass powder into a high-speed disperser, stirring at a speed of 1800-2100 r / min for 5-10 min to obtain a tungsten slurry precursor;

[0044] S4. Roll the tungsten slurry precursor in a three-roll mill until the tungsten slurry fineness is less than 10 μm, and degas in a double planetary centrifugal mixer for 3 to 8 minutes to obtain a highly conductive tungsten slurry.

[0045] The present invention provides an application of a high-conductivity tungsten slurry, which is obtained by the preparation method as described above and is used to make an electrode layer of an electrostatic chuck.

[0046] The following is a detailed description of the overall implementation of the present invention in conjunction with specific examples.

[0047] The raw material ratios of Examples 1-6 are different, as shown in Table 1, and the raw materials are measured in mass percentage.

[0048] Table 1:

[0049]

[0050] Example 1

[0051] A method for preparing a tungsten slurry specially used for a high-conductivity electrostatic chuck comprises the following steps:

[0052] S1. Weigh acrylic resin and acetone in proportion, stir in a reaction kettle at 80° C. and 850 r / min for 2 h to obtain an organic carrier;

[0053] S2. Place tungsten powder, nickel powder and silver powder in a high-energy ball mill, add tungsten powder, nickel powder and silver powder, and half of the total mass of the mixed powder in anhydrous ethanol and ball mill for 3 hours, filter, and dry at 60° C. for 1.5 hours to obtain a blended conductive metal powder;

[0054] S3, adding the blended conductive metal powder, organic carrier, nonylphenol polyoxyethylene ether, oleic acid and glass powder into a high-speed disperser, stirring at a speed of 2000 r / min for 5 minutes to obtain a tungsten slurry precursor;

[0055] S4. Roll the tungsten slurry precursor in a three-roll mill until the tungsten slurry fineness is less than 10 μm, and degas in a double planetary centrifugal mixer for 5 minutes to obtain a highly conductive tungsten slurry.

[0056] The tungsten powder is in flake form with a particle size of 1 μm and a tap density of 5.2 g / cm 3 ; Nickel powder is spherical, with a particle size of 3.7 μm and a tap density of 4.3 g / cm 3 ; Silver powder is flake-shaped, with a particle size of 2.5 μm and a tap density of 4.8 g / cm 3 ; The particle size of the glass powder is 3.1 μm; the molecular weight of the acrylic resin is 760,000.

[0057] Example 2

[0058] This embodiment is basically the same as embodiment 1, except that the raw materials and proportions are different, as shown in Table 1.

[0059] Example 3

[0060] This embodiment is basically the same as embodiment 1, except that the raw materials and proportions are different, as shown in Table 1.

[0061] Example 4

[0062] This embodiment is basically the same as embodiment 1, except that the raw materials and proportions are different, as shown in Table 1.

[0063] Example 5

[0064] This embodiment is basically the same as embodiment 1, except that the raw materials and proportions are different, as shown in Table 1.

[0065] Example 6

[0066] This embodiment is basically the same as embodiment 1, except that the raw materials and proportions are different, as shown in Table 1.

[0067] Performance test: The tungsten paste obtained in the above embodiments 1-6 was printed on alumina raw porcelain tape through a 420 mesh screen, with a printing thickness of 15 μm and a porcelain tape size of 100 mm*100 mm. After printing, it was dried at 120°C for 30 minutes for curing. After sintering at 1550°C, the resistivity was tested using a Fluke17B+ multimeter. The performance test results are shown in Table 2.

[0068] Table 2:

[0069] Performance Testing <![CDATA[Resistivity (10 -7 Ω / m)]]> Square resistance (mΩ / □) <![CDATA[Conductivity (10 6 S / m)]]> Example 1 1.56 23.4 6.42 Example 2 1.94 29.1 5.14 Example 3 1.90 28.5 5.27 Example 4 2.06 30.9 4.85 Example 5 2.13 32.0 4.69 Example 6 1.92 28.8 5.21

[0070] It can be seen from Table 2 that:

[0071] The conductivity (10 6 S / m) comparison shows that the dual conductive powder fused in the present invention is a tungsten paste of nickel powder and silver powder, and its conductivity is 6.42 10 6 S / m, the conductivity of other dual conductive powders is between 4.69 and 5.27 10 6 S / m. The present invention optimizes the process materials. Since nickel powder has good electrical conductivity, it fills the pores of the tungsten powder layer, increases the conductive path, and serves as a support for the silver powder, so that the nickel powder and the silver powder can form a good conductive network. The synergistic effect formed by the silver powder and the nickel powder, on the basic framework of the nickel powder forming the conductive network, the silver powder can serve as a fast path in the conductive network, significantly improving the mobility and transmission speed of electrons, and reducing the scattering of electrons in the tungsten powder, reducing resistance, and thus achieving the effect of high conductivity. When it is used in the electrode layer in the electrostatic chuck, it can effectively improve the electrostatic force generation efficiency of the electrostatic chuck, further improve the adsorption performance, and thus has a good application prospect.

[0072] In order to further make the purpose and effect of the present invention simple and easy to understand, the present invention is further described in conjunction with specific comparative examples.

[0073] Comparative Example 1

[0074] This comparative example is basically the same as Example 1, except that the ratio of raw materials is different, nickel powder is 8.5wt%, silver powder is 1.5wt%, and tungsten slurry with a mass ratio of nickel powder to silver powder of 5.7:1 is obtained.

[0075] Comparative Example 2

[0076] This comparative example is basically the same as Example 1, except that the ratio of raw materials is different, nickel powder is 8wt%, silver powder is 2wt%, and tungsten slurry with a mass ratio of nickel powder to silver powder of 4:1 is obtained.

[0077] Comparative Example 3

[0078] This comparative example is basically the same as Example 1, except that the ratio of raw materials is different, nickel powder is 7.5wt%, silver powder is 2.5wt%, and tungsten slurry with a mass ratio of nickel powder to silver powder of 3:1 is obtained.

[0079] Comparative Example 4

[0080] This comparative example is basically the same as Example 1, except that the ratio of raw materials is different, nickel powder is 2.5wt%, silver powder is 7.5wt%, and tungsten slurry with a mass ratio of nickel powder to silver powder of 1:3 is obtained.

[0081] Comparative Example 5

[0082] This comparative example is basically the same as Example 1, except that the silver powder is spherical.

[0083] The tungsten slurries prepared in Comparative Examples 1-5 were tested using the same performance testing method as the tungsten slurries obtained in Examples 1-6. The performance test results are shown in Table 3.

[0084] Table 3:

[0085]

[0086]

[0087] It can be seen from Table 3 that:

[0088] The conductivity (10 6 S / m) comparison shows that the conductivity of the tungsten slurries prepared in Comparative Examples 1-3 with nickel-silver ratios of 5.7:1, 4:1 and 3:1 is 6.03 10 6 S / m, 5.86 10 6 S / m and 5.4710 6 S / m. When the nickel-silver ratio is 9:1, the distribution of nickel powder and silver powder in the tungsten slurry can reach a better balance point, avoiding excessive aggregation of silver powder or insufficient nickel powder, and then the nickel powder and silver powder particles can form good contact, forming a stable conductive connection, providing a good migration path, allowing electrons to bypass obstacles, further optimizing the construction of the conductive network, improving electron mobility, enhancing the synergistic effect and reducing porosity, so that the conductivity of the tungsten slurry is optimal, which not only improves the conductive performance of the tungsten slurry, but also improves its overall performance in applications such as electrostatic chucks; by comparing Example 1 with Comparative Example 4, it can be seen that when the content of silver powder is too high, it is easy to cause the silver powder particles to be too dense, increase the contact points, and affect the effectiveness of forming a conductive channel with more contact points, resulting in excessive silver powder particles may block each other, forming a silver island effect, so that the synergistic effect between nickel powder and silver powder is weakened, thereby reducing the overall conductivity. At the same time, during sintering, excessive diffusion of silver powder also has a certain impact on the bonding.

[0089] By comparing Example 1 with Comparative Example 5, it can be seen that although a suitable nickel-silver ratio can achieve better conductive properties, when the silver powder and the nickel powder are both spherical, the contact between the silver powder and the nickel powder is point contact, and the tunneling resistance and the concentrated resistance are both large, which causes the resistivity to decrease. In addition, due to its flat shape, the flaky silver powder can be used as a positioning overlap surface in the tungsten slurry, and the spherical nickel powder is filled between and around the flaky silver powder in a point-connected manner, increasing the contact points between the conductive particles. The combination of the flaky silver powder and the spherical nickel powder effectively prevents the flaky silver powder from slipping in a one-dimensional direction, thereby avoiding the reduction of contact performance and the interruption of the conductive path, and also helps to improve the density between the powders, thereby further improving the conductive properties.

[0090] The above is based on the ideal embodiment of the present invention. Through the above description, it is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0091] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A tungsten slurry specially used for a highly conductive electrostatic chuck, characterized in that: The tungsten slurry includes the following raw materials in percentage by weight:

2. The tungsten slurry for a highly conductive electrostatic chuck according to claim 1, characterized in that: The conductive powder is one of nickel powder, silver powder, graphene or carbon nanotubes, and the particle size of the conductive powder is 1 to 4 μm, and the tap density is 2 to 6 g / cm 3 The particle size of the tungsten powder is 0.6-1 μm, and the tap density is 3-6 g / cm 3 .

3. The tungsten slurry for a highly conductive electrostatic chuck according to claim 2, characterized in that: The tungsten powder and the silver powder are both in a spherical or flaky shape, and the nickel powder is in a spherical shape.

4. The tungsten slurry for a highly conductive electrostatic chuck according to claim 1, characterized in that: The organic carrier comprises 10-25% by mass of resin and 75-90% by mass of organic solvent.

5. The tungsten slurry for a highly conductive electrostatic chuck according to claim 4, characterized in that: The resin is acrylic resin, the molecular weight of the acrylic resin is 500000-900000, and the organic solvent comprises 60% by mass of naphtha and 40% by mass of ethanol.

6. The tungsten slurry for a highly conductive electrostatic chuck according to claim 1, characterized in that: The auxiliary agent is one of stearic acid, oleic acid or castor oil.

7. The tungsten slurry for a highly conductive electrostatic chuck according to claim 1, characterized in that: The particle size of the glass powder is 2-4 μm.

8. The tungsten slurry for a highly conductive electrostatic chuck according to claim 1, characterized in that: The dispersant is nonylphenol polyoxyethylene ether.

9. A method for preparing a tungsten slurry for a highly conductive electrostatic chuck according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Weigh the resin and the organic solvent in proportion, stir in a reaction kettle at a temperature of 60 to 90° C. and a speed of 800 to 1000 r / min for 1 to 3 hours to obtain an organic carrier; S2, placing tungsten powder and two conductive powders in a high-energy ball mill, adding anhydrous ethanol and ball milling for 2 to 4 hours, filtering, and drying at a temperature of 50 to 60° C. for 1 to 2 hours to obtain a blended conductive metal powder; S3, adding the blended conductive metal powder, organic carrier, dispersant, additive and glass powder into a high-speed disperser, stirring at a speed of 1800-2100 r / min for 5-10 min to obtain a tungsten slurry precursor; S4. Roll the tungsten slurry precursor in a three-roll mill until the tungsten slurry fineness is less than 10 μm, and degas in a double planetary centrifugal mixer for 3 to 8 minutes to obtain a highly conductive tungsten slurry.

10. An application of a highly conductive tungsten slurry, characterized in that: The highly conductive tungsten slurry is obtained by the preparation method as described in claim 9 and is used to make an electrode layer of an electrostatic chuck.

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