JP2025065665A - Holding device and manufacturing method thereof - Google Patents

Abstract

To provide a holding device which can exhibit a high cooling performance without causing inconveniences due to the difference of thermal expansion between a metal base part and a ceramic part, and a method for manufacturing the holding device.SOLUTION: A holding device for holding a target object includes: a metal base part in which a coolant passage is formed; and a ceramic part formed in a surface of the metal base part, the target object being held in the ceramic part. The difference of thermal expansion between the metal base part and the ceramic part in a usage temperature range of the ceramic part is 2.0 ppm/°C at a maximum. The ceramic part is directly formed in the metal base part and the metal base part is an additive-manufactured material.SELECTED DRAWING: Figure 1

Description

The present invention relates to a holding device for holding an object and a manufacturing method thereof.

For example, electrostatic chucks have been known as holding devices for holding objects in devices that perform plasma processing such as etching, and have a structure that includes a metal base portion in which a refrigerant flow path is formed and a ceramic portion on top of the metal base portion on which the object is placed.

Known examples of such electrostatic chucks include one that uses aluminum as the metal base portion and a thermally sprayed coating of alumina (Al ₂ O ₃ ) as the ceramic portion (see, for example, Patent Document 1).

As a technique for using an electrostatic chuck to perform plasma processing on an object, for example, Patent Document 2 proposes an electrostatic chuck having a metal base portion in which a refrigerant flow path is formed, a ceramic portion on which the object is placed, and a joint portion formed between the ceramic portion and the base portion and made of a composite material containing an adhesive and an inorganic filler for the purpose of alleviating thermal stress. Patent Document 2 also describes that by constructing the base portion using aluminum, which has a relatively high thermal conductivity and is easy to process, the cooling efficiency of the ceramic portion and the object placed thereon can be improved.

JP 2001-203258 A JP 2023-42825 A

However, with the technology described in Patent Document 1, the ceramic part on which the object is placed rises in temperature due to heat input from the plasma, and the difference in thermal expansion between the ceramic surface and the metallic base metal can cause peeling or deformation, which can reduce the machining accuracy of the object.

On the other hand, in the technology described in Patent Document 2, although the presence of the joint mitigates the thermal expansion difference and allows cooling performance to be maintained, there are cases in which damage to the joint cannot be sufficiently suppressed, and furthermore, it is necessary to control the thermal resistance of the joint and the amount of strain at maximum shear stress, making it difficult to reliably obtain the desired effect.

Therefore, the objective of the present invention is to provide a holding device and a manufacturing method thereof that can provide high cooling performance without causing inconveniences due to differences in thermal expansion between the metal base part and the ceramic part.

The present invention provides the following means (1) to (10).

(1) A holding device for holding an object, comprising:
The device has a metal base portion in which a refrigerant flow path is formed, and a ceramic portion formed on a surface of the metal base portion and for holding an object,
a difference in thermal expansion between the metal base portion and the ceramic portion within a usage temperature range of the ceramic portion is 2.0 ppm/°C or less;
the ceramic portion is formed directly on the metal base portion;
A holding device characterized in that the metal base portion is an additive manufacturing material.

(2) A holding device for holding an object,
The device has a metal base portion in which a refrigerant flow path is formed, and a ceramic portion formed on a surface of the metal base portion and for holding an object,
the ceramic portion is formed directly on the metal base portion;
A holding device characterized in that the metal base portion is an additive manufacturing material made of an Fe-Ni alloy having a thermal expansion difference with the ceramic portion of 2.0 ppm/°C or less within the operating temperature range of the ceramic portion.

(3) The retaining device described in (2) is characterized in that the ceramic part is made of alumina ceramics, the operating temperature range of the ceramic part is -100 to 50°C, and the thermal expansion difference between the Fe-Ni alloy and the alumina ceramics in the range of -100 to 50°C is 1.0 ppm/°C or less.

(4) The holding device according to (3), characterized in that the Fe-Ni alloy contains, by mass%, C: 0.1% or less, Si: 0.30% or less, Mn: 0.8% or less, Ni: 41.0 to 43.0%, with the remainder being Fe and unavoidable impurities.

(5) A retaining device according to any one of (1) to (4), characterized in that the ceramic part is a plasma spray coating.

(6) A method for manufacturing a holding device for holding an object, comprising:
forming a metal base part having a coolant flow path formed therein by additive manufacturing;
forming a ceramic portion for holding an object directly on a surface of the metal base portion;
having
A method for manufacturing a holding device, characterized in that the difference in thermal expansion between said metal base portion and said ceramic portion within the operating temperature range of said ceramic portion is 2.0 ppm/°C or less.

(7) A method for manufacturing a holding device for holding an object, comprising:
forming a metal base part having a coolant flow path formed therein by additive manufacturing;
forming a ceramic portion for holding an object directly on a surface of the metal base portion;
having
The method for manufacturing a retaining device is characterized in that the metal base portion is made of an Fe--Ni alloy having a thermal expansion difference with the ceramic portion of 2.0 ppm/° C. or less within the operating temperature range of the ceramic portion.

(8) The method for manufacturing a holding device described in (7) is characterized in that the ceramic part is made of alumina ceramics, the operating temperature range of the ceramic part is -100 to 50°C, and the thermal expansion difference between the Fe-Ni alloy and the alumina ceramics in the range of -100 to 50°C is 1.0 ppm/°C or less.

(9) The method for manufacturing a retaining device described in (8) is characterized in that the Fe-Ni alloy contains, by mass%, C: 0.1% or less, Si: 0.30% or less, Mn: 0.8% or less, Ni: 41.0 to 43.0%, with the remainder being Fe and unavoidable impurities.

(10) A method for manufacturing a retaining device according to any one of (6) to (9), characterized in that the ceramic part is a sprayed coating formed by plasma spraying.

The present invention provides a holding device and a method for manufacturing the holding device that can provide high cooling performance without causing inconveniences due to differences in thermal expansion between the metal base part and the ceramic part.

1 is a cross-sectional view showing a holding device according to an embodiment of the present invention. FIG. 1 is a diagram showing the thermal expansion coefficients of an Fe—Ni-based additive manufacturing alloy (material of the present invention) and alumina in the range from 20° C. to each temperature. FIG. 1 is a diagram for explaining a cooling performance test in an example.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
1 is a cross-sectional view showing a holding device according to an embodiment of the present invention. The holding device 10 is configured as an electrostatic chuck and holds an object S in a plasma processing device such as a plasma etching device. The object S may be a substrate such as a semiconductor wafer.

The holding device 10 has a metal base portion 1 in which a refrigerant flow path is formed, and a ceramic portion 2 formed on the surface of the metal base portion 1 and for holding an object. When the holding device is an electrostatic chuck, when performing plasma processing in a plasma processing device, a DC voltage is applied to an electrode provided in the ceramic portion 2, and the object is electrostatically attracted and held by Coulomb force or the like.

The metal base part 1 has a refrigerant flow path 3 formed therein, and a refrigerant at a predetermined temperature flows through the refrigerant flow path 3. The refrigerant flow path 3 is formed within the metal base part 1. As shown in the figure, the metal base part 1 may have a structure having a flow path forming part 1a in which the refrigerant flow path 3 is formed, and a heat transfer adjustment part 1b below that, for example, having a hollow structure. The ceramic part 2 is formed directly on the metal base part 1, and is formed, for example, as a thermal spray coating. The thermal spray coating may be a plasma thermal spray coating.

When the holding device 10 is used in a device that performs plasma processing such as plasma etching, in order to suppress the temperature rise of the object S due to heat input from the plasma and maintain processing precision, a refrigerant with a temperature of -100°C or lower, for example, about -110°C, is passed through the refrigerant flow passage 3, and the operating temperature range of the ceramic part heated by the plasma is set to -100 to 50°C. For example, a fluorine-based refrigerant can be used as the refrigerant.

The metal base part 1 and the ceramic part 2 are designed so that the difference in thermal expansion between them in a temperature range including the operating temperature is 2.0 ppm/°C or less. This makes it possible to reduce the difference in thermal expansion between them compared to the conventional case in which aluminum is used as the metal base member 1, and makes it possible to reduce thermal stress even when the ceramic part 2 is formed directly on the metal base part 1. Any method can be used to directly form the ceramic part 2 on the metal base part 1, but it is preferable to form the ceramic part 2 as a sprayed coating such as a plasma sprayed coating. By forming the ceramic part 2 directly on the metal base part 1 in this way, these joints are unnecessary and the joints will not be damaged by plasma.

The material constituting the metal base part 1 is not particularly limited as long as it has a thermal expansion difference of 2.0 ppm/°C or less with respect to the ceramic part 2 in the operating temperature range of the ceramic part, but for example, an Fe-Ni alloy can be preferably used. An Fe-Ni alloy exhibits low expansion close to 0 at a Ni content of 36% Ni, and thermal expansion increases with increasing or decreasing Ni content. Therefore, by adjusting the Ni content, it is possible to adjust the thermal expansion difference between the metal base part 1 and the ceramic part 2 in the operating temperature range of the ceramic part to 2.0 ppm/°C or less.

The metal base 1 is an additive manufacturing material. Additive manufacturing is a technology in which alloy powder is supplied, and the alloy powder is melted using a laser beam, electron beam, or plasma as a heat source, and then layered in three dimensions to create a shape. By appropriately selecting the parameters of the laser beam, electron beam, or plasma, the cooling rate during solidification can be made extremely fast, at 5000°C/sec or more, which is not achievable with general casting. In this way, Fe-Ni-based additive manufacturing alloys to which additive manufacturing technology is applied have a finer structure, and the microsegregation of Ni seen in general cast products and forged products is reduced. As a result, they tend to have a lower thermal expansion coefficient than general cast products and forged products, and have high properties such as toughness and strength.

The ceramic portion 2 is not particularly limited as long as it has the resistance required for the usage state, such as heat resistance and plasma resistance, but typical examples include alumina (Al ₂ O ₃ ) and aluminum nitride (AlN).

When the holding device 10 is used in a device that performs plasma processing such as plasma etching, as described above, a refrigerant flows through the refrigerant flow path 3 and the operating temperature range of the ceramic part is -100 to 50°C. In this case, the average thermal expansion coefficient of alumina is 4.1 ppm/°C from -100 to 20°C and 5.4 ppm/°C from 20 to 50°C.

In this range of -100 to 50°C, the composition of the Fe-Ni-based additive manufacturing alloy can be adjusted to reduce the thermal expansion difference with alumina to 1.0 ppm/°C or less. As such an Fe-Ni-based additive manufacturing alloy, an alloy with a Ni content in the range of 41.0 to 43.0 mass% can be used. Specifically, an alloy containing, in mass%, C: 0.1% or less, Si: 0.3% or less, Mn: 0.8% or less, Ni: 41.0 to 43.0%, with the balance being Fe and unavoidable impurities can be used. C is an element that increases thermal expansion, so 0.1% or less is preferable. In addition, Si and Mn are elements effective for deoxidization, but if they are too high, they increase thermal expansion, so it is preferable to set Si: 0.3% or less and Mn: 0.8% or less. The Fe-Ni-based additive manufacturing alloy with this composition has a thermal expansion coefficient in the range of 4.5 to 4.9 ppm/°C in the range of -100 to 50°C, and the thermal expansion difference between it and alumina, which has a coefficient of 4.2 to 5.4 ppm/°C, is well within the range of 1.0 ppm/°C or less.

As an example, Figure 2 shows the thermal expansion coefficients of an Fe-Ni additive manufacturing alloy with 0.001% C, 0.01% Si, 0.03% Mn, 41.88% Ni, and the balance being Fe + unavoidable impurities, and alumina in the range from 20°C to each temperature. For comparison, Figure 2 also shows the thermal expansion coefficient of 42Ni alloy (forged alloy), which has long been known as an alloy with a thermal expansion coefficient similar to that of alumina ceramics. As shown in Figure 2, the Fe-Ni-based additive manufacturing alloy of the above composition has a thermal expansion coefficient very close to that of alumina at -100 to 50°C, and the thermal expansion difference with alumina is 1.0 ppm/°C or less within this temperature range. However, the thermal expansion difference with alumina of the 42Ni alloy (forged alloy) is greater than that of the Fe-Ni-based additive manufacturing alloy of the above composition at 10°C or less, and the difference exceeds 1.0 ppm/°C at -50°C or less.

Another major advantage of using the metal base 1 as an additive manufacturing material is that the design freedom of the refrigerant flow path 3 is dramatically increased compared to cutting, making it possible to adjust the cooling performance.

Conventionally used aluminum metal base materials can be machined, so the refrigerant flow paths are formed by machining. Although only relatively simple refrigerant flow paths can be formed by machining, aluminum is a material with high thermal conductivity, so good cooling performance can be obtained even with relatively simple refrigerant flow paths. On the other hand, if a material with a lower thermal conductivity than aluminum is used, even if the refrigerant flow paths can be formed by machining, it is difficult to ensure cooling performance equivalent to that of aluminum. In particular, Fe-Ni alloys have a lower thermal conductivity than aluminum, and are difficult to process, so it is difficult to form refrigerant flow paths by machining. In contrast, when the metal base part 1 is made of an additive manufacturing material, the design of the refrigerant flow path 3 is highly flexible because the structure can be manufactured as designed. Therefore, a refrigerant flow path 3 with higher cooling properties can be formed, and even if the metal base part is made of a material with low thermal conductivity, cooling performance close to that of the conventional aluminum metal base part can be obtained. In particular, when an Fe-Ni additive manufacturing alloy is used as the metal base material 1, the difference in thermal expansion coefficient between the ceramic part and the metal part can be set to a desired small value, and the refrigerant flow path can be optimized by additive manufacturing to exhibit the desired cooling performance.

Although the embodiments of the present invention have been described above, these should be considered as merely examples and not restrictive. The above embodiments may be omitted, substituted, or modified in various ways without departing from the spirit of the present invention.

For example, in the above embodiment, an Fe-Ni-based additive manufacturing alloy is exemplified as the metal base part, but this is not limited as long as the thermal expansion difference between the metal base part and the ceramic part in the operating temperature range of the ceramic part is 2.0 ppm/°C or less. Also, alumina is exemplified as the ceramic part, but the ceramic part is not limited to alumina. Furthermore, although -100 to 50°C is exemplified as the operating temperature range of the ceramic part, this is not limited thereto, and these materials may be selected so that the thermal expansion difference between the metal base part and the ceramic part is 2.0 ppm/°C or less in the selected operating temperature range.

Examples of the present invention will now be described.
First, aluminum, which is a comparative material, and the material of the present invention (Fe-Ni-based additive manufacturing alloy containing 0.001% C, 0.01% Si, 0.03% Mn, 41.88% Ni, and the remainder being Fe + unavoidable impurities) were used as the base material (φ40 mm × 10 mm), and a 300 μm thick alumina spray coating was formed thereon by plasma spraying to produce sample A (base material is aluminum) and sample B (base material is the material of the present invention). The average thermal expansion coefficients at -100 to 20 ° C are about 4.5 ppm / ° C for the material of the present invention, about 21 ppm / ° C for aluminum, and about 4.1 ppm for the alumina spray coating.

Samples A and B were subjected to a five-cycle heat treatment cycle test between -196°C and 500°C. Sample A, which used aluminum as a comparison material, showed peeling of the alumina spray coating after the fourth cycle, but sample B, which used the material of the present invention, showed no peeling of the alumina spray coating even after five cycles.

Next, a cooling performance test was performed. Here, three cooling performance test samples (samples C, D, and E) shown in Figures 3(a) to (c) were created. All samples have a structure in which a 3 mm thick alumina plate is provided on a φ400 mm base material having a refrigerant flow path. As shown in Figure 3(a), sample C is made of aluminum, which is a comparative material, as the base material, and the refrigerant flow path is formed 10 mm from the surface. As shown in Figure 3(b), sample D is made of the present invention material (Fe-Ni-based additive manufacturing alloy of C: 0.001%, Si: 0.01%, Mn: 0.03%, Ni: 41.88%, balance: Fe + unavoidable impurities) as the base material, and the refrigerant flow path is formed 10 mm from the surface like sample C. As shown in Figure 3(c), sample E is made of the present invention material similar to sample D as the base material, and the cooling flow path is formed 1 mm from the surface.

A silicon wafer (φ300 mm) was placed on the surface of the ceramic part of these samples, and a cooling performance test was performed by passing a -110°C refrigerant through the refrigerant flow path at a flow rate of 0.5 L/s and measuring the wafer temperature. The heat transfer to the wafer was 5 kW.

As a result, the wafer temperature for sample C was -94.8°C, while for sample D it was -74.0°C. This is thought to be because, despite the use of an Fe-Ni alloy as the base material, which has a lower thermal conductivity than aluminum, sample D had the same refrigerant flow path as sample C, resulting in insufficient cooling (heat dissipation). Meanwhile, for sample E, the wafer temperature was -94.1°C, close to that of sample C. This is thought to be because the cooling flow path was positioned closer to the wafer, improving the cooling performance (heat dissipation) of the wafer.

Next, for samples C, D, and E, the same refrigerant was used, but the refrigerant flow rate was increased to 0.8 L/s, and the wafer temperature was similarly measured. As a result, the wafer temperature was -97.1°C for sample C, -76.3°C for sample D, and -96.4°C for sample E. In other words, it was confirmed that when an Fe-Ni alloy is used as the base material, increasing the flow rate (equivalent to increasing the cross-sectional area of the refrigerant flow path, for example) also improves the cooling performance (heat dissipation) of the wafer.

These results confirmed that by forming the base material using additive manufacturing with a material that has a low thermal expansion coefficient similar to that of the ceramic part, such as an Fe-Ni alloy, and adjusting the position and cross-sectional area of the coolant flow path, it is possible to obtain wafer cooling performance (heat dissipation) similar to that when aluminum is used as the base material.

REFERENCE SIGNS LIST 1: Metal base portion 1a: Flow passage forming portion 1b: Heat transfer adjustment portion 2: Ceramic portion 3: Coolant flow passage 10: Holding device

Claims (10)

A holding device for holding an object,
The device has a metal base portion in which a refrigerant flow path is formed, and a ceramic portion formed on a surface of the metal base portion and for holding an object,
a difference in thermal expansion between the metal base portion and the ceramic portion within a usage temperature range of the ceramic portion is 2.0 ppm/°C or less;
the ceramic portion is formed directly on the metal base portion;
A holding device characterized in that the metal base portion is an additive manufacturing material.
A holding device for holding an object,
The device has a metal base portion in which a refrigerant flow path is formed, and a ceramic portion formed on a surface of the metal base portion and for holding an object,
a difference in thermal expansion between the metal base portion and the ceramic portion within a temperature range including the operating temperature is 2.0 ppm/°C or less;
the ceramic portion is formed directly on the metal base portion;
A holding device characterized in that the metal base portion is an additive manufacturing material. A holding device for holding an object,
The device has a metal base portion in which a refrigerant flow path is formed, and a ceramic portion formed on a surface of the metal base portion and for holding an object,
the ceramic portion is formed directly on the metal base portion;
A holding device characterized in that the metal base portion is an additive manufacturing material made of an Fe-Ni alloy having a thermal expansion difference with the ceramic portion of 2.0 ppm/°C or less within the operating temperature range of the ceramic portion. The retaining device according to claim 2, characterized in that the ceramic part is made of alumina ceramics, the operating temperature range of the ceramic part is -100 to 50°C, and the thermal expansion difference between the Fe-Ni alloy and the alumina ceramics in the range of -100 to 50°C is 1.0 ppm/°C or less. The holding device according to claim 3, characterized in that the Fe-Ni alloy contains, by mass%, C: 0.1% or less, Si: 0.30% or less, Mn: 0.8% or less, Ni: 41.0 to 43.0%, with the remainder being Fe and unavoidable impurities. The holding device according to any one of claims 1 to 4, characterized in that the ceramic part is a plasma spray coating. A method for manufacturing a holding device for holding an object, comprising the steps of:
forming a metal base part having a coolant flow path formed therein by additive manufacturing;
forming a ceramic portion for holding an object directly on a surface of the metal base portion;
having
A method for manufacturing a holding device, characterized in that the difference in thermal expansion between said metal base portion and said ceramic portion within the operating temperature range of said ceramic portion is 2.0 ppm/°C or less. A method for manufacturing a holding device for holding an object, comprising the steps of:
forming a metal base part having a coolant flow path formed therein by additive manufacturing;
forming a ceramic portion for holding an object directly on a surface of the metal base portion;
having
The method for manufacturing a retaining device is characterized in that the metal base portion is made of an Fe--Ni alloy having a thermal expansion difference with the ceramic portion of 2.0 ppm/° C. or less within the operating temperature range of the ceramic portion. The method for manufacturing a retaining device according to claim 7, characterized in that the ceramic part is made of alumina ceramics, the operating temperature range of the ceramic part is -100 to 50°C, and the Fe-Ni alloy has a thermal expansion difference with the alumina ceramics in the range of -100 to 50°C of 1.0 ppm/°C or less. The method for manufacturing a retaining device according to claim 8, characterized in that the Fe-Ni alloy contains, by mass%, C: 0.1% or less, Si: 0.30% or less, Mn: 0.8% or less, Ni: 41.0 to 43.0%, with the remainder being Fe and unavoidable impurities. The method for manufacturing a retaining device according to any one of claims 6 to 9, characterized in that the ceramic part is a sprayed coating formed by plasma spraying.

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