Conductive paste special for electrostatic chuck and preparation method and application of conductive paste

Abstract

The invention relates to a special conductive paste for an electrostatic chuck and a preparation method and application thereof. The conductive paste is prepared from the following components in percentage by mass: 80-85% of tungsten powder, 0.4-0.8% of neodymium oxide, 1-1.5% of aluminum oxide, 1-1.5% of silicon dioxide, 10-16% of an organic carrier and 1.5-2.8% of a dispersing agent. The neodymium oxide particles are introduced into the conductive slurry, so that when the conductive slurry is applied to an electrode layer of an electrostatic chuck, the density of the electrode layer can be remarkably improved, the sheet resistance is reduced, and excellent conductive performance is shown, so that the electrostatic chuck has good electrostatic adsorption capacity; and meanwhile, silicon dioxide and aluminum oxide are cooperated to wet and permeate into the ceramic substrate of the electrostatic chuck and form a mechanical interlocking structure with the ceramic, so that the binding force between the electrode layer and the ceramic substrate is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of electrostatic chucks, and in particular to a conductive slurry specially used for electrostatic chucks, a preparation method thereof, and an application thereof. Background Art

[0002] As a core component of semiconductor manufacturing equipment, the electrostatic chuck fixes the wafer in key processes such as dry etching, which has a significant impact on manufacturing accuracy and efficiency. Among them, the electrode layer, as a core functional component, directly determines the adsorption performance and electrical characteristics of the electrostatic chuck. However, there are two major problems in the existing technology: first, the electrode layer is not dense enough, resulting in a high square resistance, which limits the conductive performance, thereby affecting the electrostatic adsorption capacity and restricting the overall efficiency and reliability of the semiconductor manufacturing equipment; second, the electrode pattern area of ​​the ceramic electrostatic suction cup usually accounts for more than 70%, which is significantly higher than that of conventional high-temperature co-fired ceramic substrates, which places higher requirements on the bonding strength between ceramics and metals. Therefore, how to improve the conductive performance of the electrostatic chuck and enhance the interface bonding strength between the electrode layer and the ceramic substrate has become a key technical bottleneck that needs to be broken through.

[0003] Therefore, the present invention is specially proposed to solve the above technical problems. Summary of the Invention

[0004] The present invention overcomes the deficiencies of the prior art and provides a conductive slurry specifically for an electrostatic chuck, a preparation method, and an application thereof.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a conductive paste specially used for electrostatic chucks, which is prepared by the following mass percentages: 80-85% tungsten powder, 0.4-0.8% neodymium oxide, 1-1.5% aluminum oxide, 1-1.5% silicon dioxide, 10-16% organic carrier, and 1.5-2.8% dispersant.

[0006] Preferably, the average particle size of the tungsten is any one of 0.5 μm, 1.0 μm, and 1.5 μm, and the maximum particle size is less than 3 μm.

[0007] In a preferred embodiment of the present invention, the average particle size of the tungsten is 0.5 μm, and the maximum particle size is less than 3 μm.

[0008] Preferably, the dispersant is any one of soybean lecithin and nonylphenol polyvinyl ether, or a mixture of any two.

[0009] Preferably, the organic vehicle comprises 12-25% by mass of resin and 75-88% by mass of organic solvent.

[0010] Preferably, the resin is any one of acrylic resin and ethyl cellulose or a mixture of any two.

[0011] Preferably, the organic solvent is any one of terpineol and n-butanol, or a mixture of any two.

[0012] The present invention provides a method for preparing a tungsten slurry specifically for an electrostatic chuck, comprising the following steps:

[0013] (1) Using a dry ball mill, weigh tungsten, neodymium oxide, and aluminum oxide powders in proportion for 2 to 3 hours at a speed of 40 to 60 rpm / min to obtain a blended powder A;

[0014] (2) uniformly dispersing the blended powder A and the dispersant in an organic carrier in proportion at a heating temperature of 40 to 90° C. and a stirring speed of 1800 to 2100 r / min, and cooling the mixture to room temperature after the mixing is completed to obtain a conductive paste precursor;

[0015] (3) The conductive paste precursor is rolled in a three-roll mill until the conductive paste fineness is less than 10 μm, and then degassed in a double planetary centrifuge and a mixer for 3 to 8 minutes to obtain a conductive tungsten paste.

[0016] The present invention provides an application of a conductive paste dedicated to an electrostatic chuck. The conductive paste dedicated to an electrostatic chuck is obtained by the aforementioned preparation method and is used to manufacture an electrode layer of an electrostatic chuck.

[0017] The beneficial effects of the present invention are:

[0018] (1) After the conductive paste is sintered, the density of the electrode layer is significantly improved and the square resistance is reduced. When used in the electrode layer of the electrostatic chuck, it exhibits excellent conductive properties, thereby enabling the electrostatic chuck to have good electrostatic adsorption capabilities.

[0019] (2) The added neodymium oxide powder can cooperate with alumina and silicon dioxide to wet and penetrate into the interior of the electrostatic chuck ceramic substrate during the high-temperature co-firing process with the ceramic, and form a mechanical interlocking structure with the ceramic, thereby enhancing the bonding force between the electrode layer and the ceramic substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a scanning electron microscope (SEM) image of the conductive paste prepared in Example 3 of the present invention after sintering;

[0021] Figure 2 This is a scanning electron microscope (SEM) image of the conductive paste prepared in Comparative Example 1 of the present invention after sintering. DETAILED DESCRIPTION

[0022] The following is a clear and complete description of 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 those skilled in the art without creative work are within the scope of protection of the present invention.

[0023] The invention discloses a conductive paste specially used for electrostatic chucks. The conductive paste comprises the following raw materials in percentage by mass: 80-85% of tungsten powder, 0.4-0.8% of neodymium oxide, 1-1.5% of aluminum oxide, 1-1.5% of silicon dioxide, 10-16% of an organic carrier, and 1.5-2.8% of a dispersant.

[0024] In some specific embodiments, the average particle size of tungsten may be 0.5 μm, 1.0 μm, or 1.5 μm, and the maximum particle size may be less than 3 μm.

[0025] In some specific embodiments, the particle size of neodymium oxide is 3 to 5 μm.

[0026] In some specific embodiments, the dispersant is any one of soybean lecithin, nonylphenol polyvinyl ether, or a mixture of any two.

[0027] In some specific embodiments, the organic carrier includes 12-25% by mass of resin and 75-88% by mass of organic solvent; the resin is any one of acrylic resin and ethyl cellulose or a mixture of any two; the organic solvent is any one of terpineol and n-butanol or a mixture of any two.

[0028] The present invention provides a method for preparing a tungsten slurry specifically for an electrostatic chuck, comprising the following steps:

[0029] (1) Using a dry ball mill, weigh tungsten, neodymium oxide, and aluminum oxide powders in proportion for 2 to 3 hours at a speed of 40 to 60 rpm / min to obtain a blended powder A;

[0030] (2) uniformly dispersing the blended powder A and the dispersant in an organic carrier in proportion at a heating temperature of 40 to 90° C. and a stirring speed of 1800 to 2100 r / min, and cooling the mixture to room temperature after the mixing is completed to obtain a conductive paste precursor;

[0031] (3) The conductive paste precursor is rolled in a three-roll mill until the conductive paste fineness is less than 10 μm, and then degassed in a double planetary centrifuge and a mixer for 3 to 8 minutes to obtain a conductive tungsten paste.

[0032] The present invention provides an application of a conductive paste dedicated to an electrostatic chuck. The conductive paste dedicated to an electrostatic chuck is obtained by the aforementioned preparation method and is used to manufacture an electrode layer of an electrostatic chuck.

[0033] The following is a detailed description of the overall implementation of the present invention with reference to specific examples.

[0034] The raw material ratios for the preparation of Examples 1 to 6 are different, as shown in Table 1, and the raw materials are measured in percentage by mass.

[0035] Table 1

[0036]

[0037] Example 1

[0038] A method for preparing tungsten slurry for electrostatic chucks comprises the following steps:

[0039] (1) Dry-milling tungsten, neodymium oxide, and aluminum oxide powders weighed in proportion for 2.5 h at a speed of 50 rpm / min to obtain blended powder A;

[0040] (2) uniformly dispersing the blended powder A and the dispersant in an organic carrier in proportion at a heating temperature of 65° C. and a stirring speed of 1950 r / min. After the mixing is completed, the mixture is cooled to room temperature to obtain a conductive paste precursor;

[0041] (3) The conductive paste precursor was rolled in a three-roll mill until the conductive paste fineness was less than 10 μm, and then degassed in a double planetary centrifuge and a mixer for 6 min to obtain a conductive paste.

[0042] Example 2

[0043] This embodiment is basically the same as embodiment 1, except that the raw materials and proportions are different, as shown in Table 1.

[0044] Example 3

[0045] This embodiment is basically the same as embodiment 1, except that the raw materials and proportions are different, as shown in Table 1.

[0046] Example 4

[0047] This embodiment is basically the same as embodiment 1, except that the raw materials and proportions are different, as shown in Table 1.

[0048] Example 5

[0049] This embodiment is basically the same as embodiment 1, except that the raw materials and proportions are different, as shown in Table 1.

[0050] Example 6

[0051] This embodiment is basically the same as embodiment 1, except that the raw materials and proportions are different, as shown in Table 1.

[0052] Example 7

[0053] This embodiment is basically the same as embodiment 1, except that the raw materials and proportions are different, as shown in Table 1.

[0054] Comparative Example 1

[0055] This comparative example is basically the same as Example 3, except that no neodymium oxide is added.

[0056] Comparative Example 2

[0057] This comparative example is basically the same as Example 2, except that no neodymium oxide is added.

[0058] Comparative Example 3

[0059] This comparative example is basically the same as Example 4, except that no neodymium oxide is added.

[0060] Comparative Example 4

[0061] This comparative example is basically the same as Example 3, except that no aluminum oxide and neodymium oxide are added.

[0062] Comparative Example 5

[0063] This comparative example is basically the same as Example 3, except that silicon dioxide and neodymium oxide are not added.

[0064] Comparative Example 6

[0065] This comparative example is basically the same as Example 3, except that no alumina and silica are added.

[0066] Comparative Example 7

[0067] This embodiment is basically the same as the embodiment 3, except that the raw materials and the proportions are different: tungsten powder accounts for 82.4% and neodymium oxide accounts for 0.2%.

[0068] Comparative Example 8

[0069] This embodiment is basically the same as the embodiment 3, except that the raw materials and the proportions are different, namely, tungsten powder accounts for 81.1% and neodymium oxide accounts for 1.5%.

[0070] Comparative Example 9

[0071] This comparative example is basically the same as Example 3, except that no aluminum oxide, neodymium oxide, or silicon dioxide is added.

[0072] Test Case

[0073] Sinterability: Figure 1 This is a scanning electron microscope (SEM) image of the conductive paste prepared in Example 3 of the present invention printed on an alumina green tape with a thickness of 1 mm and sintered;

[0074] Figure 2 This is a scanning electron microscope (SEM) image of the conductive paste prepared in Comparative Example 1 of the present invention printed on an alumina green tape with a thickness of 1 mm and sintered;

[0075] Depend on Figure 1 and Figure 2 By comparison, it can be seen that the sintered body formed by the conductive paste with the addition of neodymium oxide has excellent sintering properties.

[0076] Bonding strength test after co-firing: The conductive pastes prepared in Examples 1 to 7 and Comparative Examples 1 to 9 were printed on a 1 mm thick alumina green tape. The printed pattern was a 20 mm * 20 mm square. After drying, the conductive pastes were co-fired at 1550 ° C, nickel-plated, and brazed to produce tensile test pieces. The hanging weight method was used to test the welding area of ​​1 mm. 2 The maximum tensile force that a lead wire bent 90° can withstand within 10s. The results are shown in Table 2

[0077] Square resistance test: The conductive pastes prepared in Examples 1-7 and Comparative Examples 1 to 9 were printed on alumina green porcelain tape through a 420-mesh screen. The printing thickness was 15 μm and the porcelain tape size was 100 mm * 100 mm. After printing, the pastes were dried at 120°C for 30 minutes to solidify. The co-firing temperature was 1600°C and the pastes were kept warm for 2 hours. The pastes were cooled with the furnace. The surface square resistance of the tungsten metallization layer was measured using an SDY-5 dual-electric four-probe tester. The results are shown in Table 2.

[0078] Table 2

[0079] Test Case Binding force (N) Square resistance (mΩ / □) Example 1 24 14.3 Example 2 23 14.6 Example 3 24 14.6 Example 4 24 11.3 Example 5 22 11.7 Example 6 23 11.9 Example 7 23 12.3 Comparative Example 1 20 18.5 Comparative Example 2 19 18.8 Comparative Example 3 19 17.9 Comparative Example 4 16 18.3 Comparative Example 5 15 17.9 Comparative Example 6 13 14.4 Comparative Example 7 20 18.2 Comparative Example 8 22 18.6 Comparative Example 9 9 19.4

[0080] It can be seen from the table that the square resistances of Examples 1 to 7 and Comparative Examples 1 to 9 are 14.3 mΩ / □, 14.6 mΩ / □, 14.6 mΩ / □, 11.3 mΩ / □, 11.7 mΩ / □, 11.9 mΩ / □, 12.3 mΩ / □, 18.5 mΩ / □, 18.8 mΩ / □, 17.9 mΩ / □, 18.3 mΩ / □, 17.9 mΩ / □, 14.4 mΩ / □, 18.2 mΩ / □, 18.6 mΩ / □, and 19.4 mΩ / □, respectively. The sheet resistance of the electrode layer formed by the sintered conductive paste is directly related to its sintering densification degree. The denser the electrode layer, the lower its surface sheet resistance and the better its conductive performance. By comparing the sheet resistance values ​​of Examples 1 to 7 with those of Comparative Examples 1 to 5 and Comparative Examples 7 to 9, it can be seen that the sheet resistance values ​​of the former are significantly lower, which indicates that by adding a specific amount of neodymium oxide to the conductive paste, the density of the electrode layer can be significantly improved. It is speculated that the reason may be that Nd 3+During the sintering process, the migration of other ions is inhibited, thereby reducing the grain boundary migration rate, inhibiting grain growth, and promoting the formation of a densified structure. Although the electrode layers of Comparative Examples 4 to 6 have a square resistance of 14.4 mΩ / □, their bonding force is only 14 N. Therefore, the electrode layer prepared with the conductive paste of Comparative Example 6 cannot be used in an electrostatic chuck.

[0081] It can be seen from the table that the bonding forces of Examples 1 to 7 and Comparative Examples 1 to 9 are 24N, 23N, 24N, 24N, 22N, 23N, 23N, 20N, 19N, 19N, 16N, 15N, 13N, 20N, 22N, and 9N, respectively. It can be seen that the bonding forces of Examples 1 to 7 are higher than those of Comparative Examples 1 to 7 and Comparative Example 9. By comparing the bonding forces of Example 3 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 4 and Comparative Example 3, it can be seen that adding an appropriate amount of neodymium oxide to the conductive paste can further increase the bonding force between the electrode layer and the ceramic substrate. It is speculated that the reason may be that neodymium oxide has wettability. During the sintering process of alumina ceramics, Nd 3+ After entering the alumina lattice, the significant difference in radius between the two causes deformation and defects in the alumina lattice, prompting lattice activation. This reduces the sintering activation energy at the interface between the ceramic substrate and the electrode layer, facilitating the formation of a densified structure at the interface and thus strengthening the bonding strength between the electrode layer and the ceramic substrate. Although the bonding strength of Comparative Example 8 is 22, its sheet resistance is 18.6 mΩ / □. Therefore, the electrode layer prepared using the conductive paste in Comparative Example 8 cannot be used in electrostatic chucks.

[0082] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A conductive paste for electrostatic chucks, characterized by: The conductive paste includes the following weight percentages: 80-85% tungsten powder, 0.4-0.8% neodymium oxide, 1-1.5% aluminum oxide, 1-1.5% silicon dioxide, 10-16% organic vehicle, and 1.5-2.8% dispersant.

2. The conductive paste for electrostatic chuck according to claim 1, characterized in that: The average particle size of the tungsten is any one of 0.5 μm, 1.0 μm, and 1.5 μm, and the maximum particle size is less than 3 μm.

3. The conductive paste for electrostatic chuck according to claim 1, characterized in that: The average particle size of the tungsten is 0.5 μm.

4. The conductive paste for electrostatic chuck according to claim 1, characterized in that: The dispersant is any one of soybean lecithin and nonylphenol polyvinyl ether, or a mixture of any two of them.

5. The conductive paste for electrostatic chuck according to claim 1, characterized in that: The organic carrier comprises 12-25% by mass of resin and 75-88% by mass of organic solvent.

6. The conductive paste for electrostatic chuck according to claim 5, characterized in that: The resin is any one of acrylic resin and ethyl cellulose or a mixture of any two.

7. The conductive paste for electrostatic chuck according to claim 2, characterized in that: The organic solvent is any one of terpineol and n-butanol, or a mixture of any two.

8. A method for preparing a conductive paste for electrostatic chucks according to claims 1 to 7, characterized in that: The following steps are involved: Use dry ball milling to ball mill tungsten, neodymium oxide, and aluminum oxide powders weighed in proportion for 2 to 3 hours at a speed of 40 to 60 rpm / min to obtain blended powder A; The blended powder A and the dispersant are uniformly dispersed in an organic carrier in proportion at a heating temperature of 40-90° C. and a stirring speed of 1800-2100 r / min. After the mixing is completed, the mixture is cooled to room temperature to obtain a conductive paste precursor; The conductive paste precursor is rolled in a three-roll mill until the conductive paste fineness is less than 10 μm, and then degassed in a double planetary centrifuge and a mixer for 3 to 8 minutes to obtain a conductive tungsten paste.

9. Application of a conductive paste for electrostatic chucks, characterized by: The electrostatic chuck-specific conductive paste is obtained by the preparation method as described in claim 8 and is used to make the electrode layer of the electrostatic chuck.

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