JP2022109210A - Substrate fixing device - Google Patents

Abstract

To provide a substrate fixing device capable of improving the uniformity of the temperature of an attraction surface of an electrostatic attraction member.SOLUTION: A substrate fixing device 1 includes a base plate 10, an electrostatic attraction member 50 that attracts and holds a substrate, and a first adhesive layer 20 for adhering the electrostatic attraction member to the base plate, and within the temperature range of -110°C to 250°C, the storage modulus of the first adhesive layer is 25 MPa or less. Also, the thickness of the first adhesive layer is 0.4 mm or less. Also, the thermal conductivity of the first adhesive layer is 0.5 W/(m K) or more.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a substrate securing device.

Generally, in a substrate fixing device used for fixing a substrate such as a wafer, an electrostatic adsorption member is adhered to a base plate using an adhesive layer.

WO2016/035878 JP 2014-207374 A WO2009/107701 JP 2011-091297 A Japanese Patent Application Laid-Open No. 2020-023088 JP 2015-061913 A JP 2019-220503 A JP 2007-299837 A

In the conventional substrate fixing device, it may not be possible to obtain sufficient heat uniformity on the attracting surface of the electrostatic attracting member. In other words, the temperature of the attraction surface of the electrostatic attraction member may vary.

An object of the present disclosure is to provide a substrate fixing device capable of improving the uniformity of the temperature of the attraction surface of the electrostatic attraction member.

According to one aspect of the present disclosure, the apparatus includes a base plate, an electrostatic attraction member that attracts and holds a substrate, and a first adhesive layer that adheres the electrostatic attraction member to the base plate, and is -110°C to 250°C. The substrate fixing device is provided, wherein the storage modulus of the first adhesive layer is 25 MPa or less within the temperature range of .

According to the present disclosure, it is possible to improve the temperature uniformity of the attraction surface of the electrostatic attraction member.

1 is a cross-sectional view showing a substrate fixing device according to a first embodiment; FIG. It is a figure which shows the relationship between the temperature and storage elastic modulus in the example of an adhesion layer. FIG. 4 is a diagram showing the relationship between temperature and storage modulus in an example of an adhesive layer and an example of an auxiliary adhesive layer. FIG. 5 is a diagram showing the relationship between temperature and storage elastic modulus in another example of an adhesive layer; It is a figure which shows the result of a reliability test. It is a sectional view showing a substrate fixing device concerning a 2nd embodiment. It is a sectional view showing a substrate fixing device concerning a 3rd embodiment.

The inventors of the present application conducted extensive studies to find out the cause of temperature variations on the attracting surface of the electrostatic attracting member in the conventional substrate fixing device. As a result, when the substrate fixing device is exposed to a low temperature of about -60°C, a large difference occurs between the amount of thermal deformation of the electrostatic attraction member and the amount of thermal deformation of the base plate, and a large stress acts on the adhesive layer. , it became clear that cohesive failure may occur in the adhesive layer. The occurrence of cohesive failure lowers the in-plane uniformity of the thermal resistance of the adhesive layer, resulting in variations in the temperature of the attraction surface of the electrostatic attraction member.

The present disclosure has been made based on such knowledge, and even when the substrate fixing device is exposed to low temperatures, the cohesive failure of the adhesive layer is suppressed, and the temperature uniformity of the adsorption surface of the electrostatic adsorption member is improved. improve.

Embodiments of the present disclosure will be specifically described below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration may be denoted by the same reference numerals, thereby omitting redundant description.

(First embodiment)
First, the first embodiment will be described. FIG. 1 is a cross-sectional view showing the substrate fixing device according to the first embodiment.

As shown in FIG. 1, the substrate fixing device 1 according to the first embodiment has a base plate 10, an adhesive layer 20, an auxiliary adhesive layer 21, and an electrostatic adsorption member 50 as main components. there is

The base plate 10 is a member for mounting the electrostatic attraction member 50 thereon. The thickness of the base plate 10 can be, for example, approximately 20 mm to 50 mm. The base plate 10 is made of aluminum, for example, and can be used as an electrode or the like for controlling plasma. By supplying a predetermined high-frequency power to the base plate 10, the energy for colliding ions or the like in the generated plasma state with the substrate such as a wafer adsorbed on the electrostatic adsorption member 50 is controlled, thereby effecting the etching process. can be done systematically.

A water channel 15 is provided inside the base plate 10 . The water channel 15 has a cooling water introduction portion 15a at one end and a cooling water discharge portion 15b at the other end. The water channel 15 is connected to a cooling water control device (not shown) provided outside the substrate fixing device 1 . A cooling water control device (not shown) introduces the cooling water from the cooling water introduction portion 15a into the water passage 15 and discharges the cooling water from the cooling water discharge portion 15b. By cooling the base plate 10 by circulating cooling water through the water channel 15, the substrate attracted on the electrostatic attraction member 50 can be cooled. In addition to the water channel 15 , the base plate 10 may be provided with a gas channel or the like for introducing an inert gas for cooling the substrate adsorbed on the electrostatic adsorption member 50 .

The electrostatic chucking member 50 has a heating portion 30 and an electrostatic chuck 40, and chucks and holds a substrate such as a wafer as an chucking target. A primer 62 is applied to the surface of the electrostatic adsorption member 50 on the side of the base plate 10 . Primer 62 may include titanium, for example. Primer 62 is an example of a second primer.

The heat generating portion 30 has an insulating layer 31 and a heat generating element 32 embedded in the insulating layer 31 . The periphery of the heating element 32 is covered with an insulating layer 31 and protected from the outside. As the heating element 32, for example, a sintered body of tungsten or molybdenum can be used. A rolled alloy may be used as the heating element 32 . Note that the heating element 32 does not necessarily need to be built in the central portion of the insulating layer 31 in the thickness direction. It may be unevenly distributed on the 40 side.

As the insulating layer 31, for example, an epoxy resin, a bismaleimide triazine resin, or the like having high thermal conductivity and high heat resistance can be used. It is preferable that the thermal conductivity of the insulating layer 31 is 3 W/(m·K) or more. By including a filler such as alumina or aluminum nitride in the insulating layer 31, the thermal conductivity of the insulating layer 31 can be improved. Also, the glass transition temperature (Tg) of the insulating layer 31 is preferably 250° C. or higher. The thickness of the insulating layer 31 is preferably about 100 μm to 150 μm, and the thickness variation of the insulating layer 31 is preferably ±10% or less.

In order to improve the adhesion between the heating element 32 and the insulating layer 31 at high temperatures, it is preferable that at least one surface (one or both of the upper and lower surfaces) of the heating element 32 is roughened. Of course, both the upper and lower surfaces of the heating element 32 may be roughened. In this case, different roughening methods may be used for the upper and lower surfaces of the heating element 32 . The roughening method is not particularly limited, but examples include a method by etching, a method using a coupling agent-based surface modification technique, and a method using dot processing with a UV-YAG laser with a wavelength of 355 nm or less.

The electrostatic chuck 40 attracts and holds a substrate such as a wafer, which is an attraction target. The diameter of the substrate, which is the object to be attracted by the electrostatic chuck 40, can be, for example, about 8 inches, 12 inches, or 18 inches.

The electrostatic chuck 40 is provided on the heating portion 30 . The electrostatic chuck 40 has a base 41 and an electrostatic electrode 42 . Electrostatic chuck 40 is, for example, a Johnsen-Rahbek type electrostatic chuck. However, the electrostatic chuck 40 may be a Coulomb force type electrostatic chuck.

The substrate 41 is a dielectric, and ceramics such as aluminum oxide (Al ₂ O ₃ ) and aluminum nitride (AlN) can be used as the substrate 41 . The thickness of the substrate 41 can be, for example, about 1 mm to 10 mm, and the dielectric constant of the substrate 41 can be, for example, about 9 to 10 at a frequency of 1 kHz. The electrostatic chuck 40 and the insulating layer 31 of the heating portion 30 are directly bonded. The heat-resistant temperature of the substrate fixing device 1 can be improved by directly bonding the heat-generating part 30 and the electrostatic chuck 40 without an adhesive. The heat-resistant temperature of the substrate fixing device that joins the heat-generating part 30 and the electrostatic chuck 40 with an adhesive is about 150.degree.

The electrostatic electrode 42 is a thin film electrode and embedded in the base 41 . The electrostatic electrode 42 is connected to a power source provided outside the substrate fixing device 1 , and when a predetermined voltage is applied, an electrostatic attraction force is generated between the electrostatic electrode 42 and a substrate such as a wafer. A substrate can be adsorbed and held thereon. The attraction holding force becomes stronger as the voltage applied to the electrostatic electrode 42 becomes higher. The electrostatic electrode 42 may be monopolar or bipolar. As the electrostatic electrode 42, for example, a sintered body of tungsten or molybdenum can be used.

The adhesive layer 20 adheres the heat generating portion 30 to the base plate 10 . Adhesive layer 20 is in direct contact with primer 62 . As the adhesive layer 20, for example, a silicone-based adhesive can be used. The adhesive layer 20 may contain a filler such as alumina or aluminum nitride. Within the temperature range R1 of −110° C. to 250° C., the storage modulus of the adhesive layer 20 is 25 MPa or less, and preferably within the temperature range R2 of −100° C. to 140° C. 21 MPa or less. FIG. 2 is a diagram showing the relationship between temperature and storage elastic modulus in an example of the adhesive layer 20. As shown in FIG. The relationship shown in FIG. 2 can be obtained by dynamic mechanical analysis (DMA). FIG. 2 shows properties of a first example 20A and a second example 20B of the adhesive layer 20. As shown in FIG. In both the first example 20A and the second example 20B, the storage modulus decreases as the temperature rises, is 25 MPa or less at −110° C., and is 25 MPa within the temperature range R1. Moreover, in both the first example 20A and the second example 20B, the storage elastic modulus is 21 MPa or less within the temperature range R2 of -100°C to 140°C. In particular, in the first example 20A, it is 11 MPa or less at −100° C. and 11 MPa within the temperature range R2. The adhesive layer 20 is an example of a first adhesive layer.

The thickness of the adhesive layer 20 is preferably 0.4 mm or less. This is because if the thickness of the adhesive layer 20 exceeds 0.4 mm, the thermal resistance between the electrostatic chuck 40 and the base plate 10 may become excessive. The thickness of the adhesive layer 20 is more preferably 0.3 mm or less, and even more preferably 0.2 mm or less. In addition, from the viewpoint of securing adhesive strength, the thickness of the adhesive layer 20 is preferably 0.1 mm or more.

Within the temperature ranges R1 and R2, the thermal conductivity of the adhesive layer 20 is preferably 0.5 W/(m·K) or more, more preferably 0.9 W/(m·K) or more. This is because if the thermal conductivity of the adhesive layer 20 is less than 0.5 W/(m·K), the thermal resistance between the electrostatic chuck 40 and the base plate 10 may become excessive. Within the temperature ranges R1 and R2, the thermal conductivity of the adhesive layer 20 is more preferably 1.0 W/(m·K) or greater, and even more preferably 1.1 W/(m·K) or greater.

The auxiliary adhesive layer 21 is thinner than the adhesive layer 20 . The thickness of the auxiliary adhesive layer 21 is, for example, 0.12 mm or less. The thermal conductivity of the auxiliary adhesive layer 21 is preferably higher than that of the adhesive layer 20 within the temperature ranges R1 and R2. For example, within the temperature ranges R1 and R2, the thermal conductivity of the auxiliary adhesive layer 21 is greater than or equal to 2.0 W/(m·K). The auxiliary adhesive layer 21 is an example of a second adhesive layer.

In the substrate fixing device 1 according to the first embodiment, the storage elastic modulus of the adhesive layer 20 is as low as 25 MPa or less within the temperature range R1 of -110°C to 250°C. Therefore, even if there is a large difference between the amount of thermal deformation of the electrostatic attraction member 50 and the amount of thermal deformation of the base plate 10, the adhesive layer 20 is easily deformed within the temperature range R1. stress acting on is suppressed. Therefore, cohesive failure of the adhesive layer 20 can be suppressed, and excellent heat uniformity can be obtained on the attraction surface of the electrostatic attraction member 50 . That is, the temperature uniformity of the attraction surface of the electrostatic attraction member 50 can be improved.

The storage modulus of the auxiliary adhesive layer 21 is preferably higher than that of the adhesive layer 20 within the temperature range S of -100°C to 0°C. This is because the stress acting on the adhesive layer 20 can be easily relaxed. FIG. 3 is a diagram showing the relationship between temperature and storage elastic modulus in an example of the adhesive layer 20 (first example 20A, second example 20B) and an example of the auxiliary adhesive layer 21. As shown in FIG. The relationship shown in FIG. 3 can be obtained by DMA. In the example shown in FIG. 3, the storage modulus of the auxiliary adhesive layer 21 is higher than that of the adhesive layer 20 within the temperature ranges R1 and R2. That is, the storage elastic modulus of the auxiliary adhesive layer 21 is higher than that of the adhesive layer 20 within the temperature range S of -100°C to 0°C.

The auxiliary adhesive layer 21 and the primer 62 may not be provided.

In addition, when manufacturing the substrate fixing device 1 according to the first embodiment, an adhesive having a viscosity of 2 Pa·s to 40 Pa·s, for example, can be used as a raw material of the adhesive layer 20 . The adhesive may be provided by coating, or a semi-cured (B-stage) insulating resin film may be used.

Further, in manufacturing the substrate fixing device 1 according to the first embodiment, an adhesive having a viscosity of 40 Pa·s to 70 Pa·s, for example, can be used as a raw material for the auxiliary adhesive layer 21 . The adhesive may be provided by coating, or a semi-cured (B-stage) insulating resin film may be used. Grinding may be performed after application and curing of the adhesive.

The substrate fixing device 1 according to the first embodiment can be manufactured, for example, as follows. First, the auxiliary adhesive layer 21 is formed on the base plate 10 . Surface grinding of the auxiliary adhesive layer 21 may be performed after the auxiliary adhesive layer 21 is formed. Also, the primer 62 is applied to the lower surface of the electrostatic adsorption member 50 and air-dried. Then, the upper surface of the auxiliary adhesive layer 21 and the lower surface of the electrostatic adsorption member 50 coated with the primer 62 are adhered to each other by the adhesive layer 20 . At this time, a spacer may be used to adjust the distance between the base plate 10 and the electrostatic attraction member 50 .

Materials for the adhesive layer 20 and the auxiliary adhesive layer 21 are not limited. Examples of materials for the adhesive layer 20 and the auxiliary adhesive layer 21 include silicone resin, epoxy resin, acrylic resin, and polyimide resin. These composite materials may be used for adhesive layer 20 and auxiliary adhesive layer 21 . Also, the adhesive layer 20 and the auxiliary adhesive layer 21 may contain a filler. Examples of fillers include silica, alumina, and aluminum nitride.

Next, the reliability test results of the substrate fixing device (device No. 1) manufactured according to the first embodiment will be described while comparing with the reliability test results of the reference example (device No. 2). do.

Device no. 1 has a first example 20A of adhesive layer 20 and an auxiliary adhesive layer 21 with the properties shown in FIG. The thickness of the adhesive layer 20 was set to 0.2 mm, and the thickness of the auxiliary adhesive layer 21 was set to 0.1 mm.

Device no. 2 has an adhesive layer 22 having the properties shown in FIG. 1 is the same as the configuration of FIG. The thickness of the adhesive layer 22 was set to 0.2 mm. FIG. 4 is a diagram showing the relationship between temperature and storage elastic modulus in another example of the adhesive layer (adhesive layer 22). The relationship shown in FIG. 4 can be obtained by DMA.

The adhesive layers 20 and 22 contain a filler, and the filler content of the adhesive layer 20 (mass of filler per unit mass of the adhesive layer) is lower than the filler content of the adhesive layer 22 .

In the reliability test, the heat load was repeated with a temperature drop to -45°C and a temperature rise to 150°C (test A), and the heat load was repeated with a temperature drop to -45°C and a temperature rise to 170°C (test A). Test B) was performed. Then, the variation in temperature on the adsorption surface was measured after a predetermined number of days had passed since the start of the test. The number of heat load repetitions per day in Test A was 16, and the number of heat load repetitions per day in Test B was 11 times. These results are shown in FIG. FIG. 5 is a diagram showing the results of the reliability test. The horizontal axis in FIG. 5 indicates the number of days elapsed, and the vertical axis indicates the variation in temperature on the attracting surface.

As shown in FIG. 5, in both test A and test B, apparatus No. The variation in the temperature of the attracting surface of apparatus No. 1 is It is much smaller than the temperature variation of the adsorption surface of No. 2. This indicates that the cohesive failure of the adhesive layer 20 is less likely to occur than the cohesive failure of the adhesive layer 22, and that the thermal resistance uniformity of the adhesive layer 20 is good over a long period of time.

The surface of the base plate 10 may be insulated by thermal spraying of alumina or the like. The insulation treatment can more reliably suppress discharge between the base plate 10 and the electrostatic electrode 42 .

The heating element 32 may be incorporated in the base 41 without the insulating layer 31 provided. Moreover, the heat generating part 30 may not be provided. In these cases, adhesive layer 20 adheres substrate 41 to base plate 10 .

(Second embodiment)
Next, a second embodiment will be described. The second embodiment differs from the first embodiment mainly in the configuration of the electrostatic attraction member. FIG. 6 is a cross-sectional view showing a substrate fixing device according to the second embodiment.

As shown in FIG. 6, in the substrate fixing device 2 according to the second embodiment, the electrostatic adsorption member 50 does not include the heating portion 30, and the electrostatic chuck 40 incorporates the heating element 32. As shown in FIG. Other configurations are the same as those of the first embodiment.

The same effects as those of the first embodiment can be obtained by the second embodiment.

(Third embodiment)
Next, a third embodiment will be described. The third embodiment differs from the first embodiment mainly in the configuration of the portion between the base plate 10 and the electrostatic attraction member 50. FIG. FIG. 7 is a cross-sectional view showing a substrate fixing device according to the third embodiment.

As shown in FIG. 7, in the substrate fixing device 3 according to the third embodiment, a primer 61 is applied to the surface of the base plate 10 on the electrostatic adsorption member 50 side. Primer 61 may contain titanium, for example. The substrate fixing device 3 does not include the auxiliary adhesive layer 21 , and the adhesive layer 20 is in direct contact with the primer 61 . Other configurations are the same as those of the first embodiment. Primer 61 is an example of a first primer.

Effects similar to those of the first embodiment can also be obtained by the third embodiment. Moreover, since the auxiliary adhesive layer 21 is not provided, the thermal resistance between the electrostatic attraction member 50 and the base plate 10 can be further reduced.

The substrate fixing device 3 according to the third embodiment can be manufactured, for example, as follows. First, the primer 61 is applied to the upper surface of the base plate 10 and dried. A primer 62 is applied to the lower surface of the electrostatic attraction member 50 and dried. The primers 61 and 62 may be dried by heating. Then, the adhesive layer 20 bonds the upper surface of the base plate 10 coated with the primer 61 and the lower surface of the electrostatic adsorption member 50 coated with the primer 62 to each other. At this time, a spacer may be used to adjust the distance between the base plate 10 and the electrostatic attraction member 50 .

In the second embodiment, as in the third embodiment, the primer 61 is applied to the surface of the base plate 10 on the side of the electrostatic attraction member 50, the auxiliary adhesive layer 21 is not provided, and the adhesive layer 20 is in direct contact with the primer 61. You may have

The distance between the base plate 10 and the electrostatic adsorption member 50 is preferably 0.025 mm to 1.025 mm or less, more preferably 0.050 mm to 1.000 mm or less. This is for compatibility between good adhesion and heat dissipation.

Although the preferred embodiments and the like have been described in detail above, the present invention is not limited to the above-described embodiments and the like, and various modifications can be made to the above-described embodiments and the like without departing from the scope of the claims. Modifications and substitutions can be made.

Reference Signs List 1, 2, 3 Substrate fixing device 10 Base plate 20 Adhesive layer 21 Auxiliary adhesive layer 30 Heat generating part 40 Electrostatic chuck 50 Electrostatic adsorption member 61, 62 Primer

Claims (11)

a base plate;
an electrostatic attraction member that attracts and holds the substrate;
a first adhesive layer that adheres the electrostatic adsorption member to the base plate;
has
The substrate fixing device, wherein the storage elastic modulus of the first adhesive layer is 25 MPa or less within a temperature range of -110°C to 250°C. The substrate fixing device according to claim 1, wherein the storage elastic modulus of the first adhesive layer is 21 MPa or less within a temperature range of -100°C to 140°C. 3. The substrate fixing device according to claim 1, wherein the thickness of said first adhesive layer is 0.4 mm or less. 3. The substrate fixing device according to claim 1, wherein the thickness of said first adhesive layer is 0.2 mm or less. 5. The substrate fixing device according to claim 1, wherein the thermal conductivity of the first adhesive layer is 0.5 W/(mK) or more within the temperature range. . a first primer provided on the surface of the base plate on the side of the electrostatic adsorption member;
The substrate fixing device according to any one of claims 1 to 5, wherein the first adhesive layer is in direct contact with the first primer. a second adhesive layer provided between the base plate and the first adhesive layer and thinner than the first adhesive layer;
6. The substrate fixing device according to claim 1, wherein the thermal conductivity of the second adhesive layer is higher than the thermal conductivity of the first adhesive layer within the temperature range. . 8. The substrate fixing device according to claim 7, wherein the storage elastic modulus of the second adhesive layer is higher than the storage elastic modulus of the first adhesive layer within a temperature range of -100.degree. C. to 0.degree. 9. The substrate fixing device according to claim 7, wherein the second adhesive layer has a thickness of 0.12 mm or less. a second primer provided on the base plate side surface of the electrostatic adsorption member;
10. The substrate fixing device according to claim 1, wherein said first adhesive layer is in direct contact with said second primer. 11. The substrate fixing device according to claim 1, wherein the distance between said base plate and said electrostatic adsorption member is 0.025 mm to 1.025 mm or less.

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