Sample holder

Abstract

To provide a sample holder with excellent heat uniformity. [Solution] The sample holder according to this disclosure comprises a ceramic body and a base plate. The ceramic body has a first surface which is a sample holding surface and a second surface located opposite the first surface. The base plate supports the ceramic body with the second surface and has a coolant channel inside. The base plate comprises a first substrate and a second substrate, and a bonding layer located between the first substrate and the second substrate. The bonding layer is mainly composed of tin.

Description

Technical Field

[0001] The present disclosure relates to a sample holder.

Background Art

[0002] A sample holder used in a semiconductor manufacturing apparatus or the like is known. The sample holder has, for example, a structure in which a ceramic body on which a sample such as a wafer is placed is joined to a conductive base plate that supports the ceramic body.

[0003] In this type of sample holder, a refrigerant flow path is formed inside the base plate, and the sample placed on the ceramic body is cooled by flowing refrigerant through this refrigerant flow path. The refrigerant flow path is formed inside the base plate, for example, by forming a flow path in one of two substrates serving as the base plate and then joining the two substrates with a bonding material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present disclosure provides a sample holder having excellent heat uniformity.

Means for Solving the Problems

[0006] A sample holder according to an aspect of the present disclosure includes a ceramic body and a base plate. The ceramic body has a first surface that is a sample holding surface and a second surface located opposite the first surface. The base plate supports the ceramic body on the second surface and has a refrigerant flow path inside. The base plate includes a first substrate, a second substrate, and a bonding layer located between the first substrate and the second substrate. The main component of the bonding layer is tin. [Effects of the Invention]

[0007] The sample holder of this disclosure offers excellent heat uniformity. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic cross-sectional view showing a sample holder according to the first embodiment. [Figure 2] Figure 2 is a schematic enlarged view of region R shown in Figure 1. [Figure 3] Figure 3 is a schematic cross-sectional view showing another configuration example of region R shown in Figure 1. [Figure 4] Figure 4 is a schematic cross-sectional view showing another example of the configuration of the sample holder according to the first embodiment. [Figure 5] Figure 5 is a schematic cross-sectional view showing a sample holder according to the second embodiment. [Modes for carrying out the invention]

[0009] The embodiments for implementing the sample holder according to this disclosure (hereinafter referred to as "Embodiments") will be described in detail below with reference to the drawings. However, this disclosure is not limited by these embodiments. Furthermore, each embodiment can be combined as appropriate, provided that the processing content is not inconsistent. Also, the same parts are denoted by the same reference numerals in each of the following embodiments, and redundant descriptions are omitted.

[0010] Furthermore, in the embodiments described below, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not require strict adherence to "constant," "orthogonal," "perpendicular," or "parallel" conditions. In other words, each of the above expressions allows for deviations, for example, in manufacturing accuracy or installation accuracy.

[0011] (First Embodiment) First, the configuration of the sample holder 100 according to the first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic cross-sectional view showing the sample holder 100 according to the first embodiment. Figure 2 is a schematic enlarged view of the region R shown in Figure 1.

[0012] As shown in Figure 1, the sample holder 100 comprises a ceramic body 10 and a base plate 20. The dimensions of these components are not limited to the illustrated example and may be similar to those of conventionally known sample holders.

[0013] The ceramic body 10 is made of ceramic. The ceramic body 10 may be formed from a ceramic-containing raw material into a flat plate shape, for example, a disc shape. The ceramic body 10 may mainly contain aluminum oxide (Al2O3), aluminum nitride (AlN), or yttria (Y2O3).

[0014] The ceramic body 10 has, for example, a first surface 10a and a second surface 10b. The first surface 10a is a sample holding surface that supports the workpiece W, such as a semiconductor wafer. The second surface 10b is located on the opposite side from the first surface 10a. The second surface 10b is a surface that is joined to the base plate 20 via a second bonding layer 30, which will be described later. The ceramic body 10 may have a cylindrical protrusion on the first surface 10a.

[0015] The ceramic body 10 may have an internal electrode 11. The internal electrode 11 is connected to an external power source (not shown). The sample holder 100 attracts and holds the object to be processed W on the first surface 10a by electrostatic force generated when a DC voltage is applied from the power source to the internal electrode 11. As the material of the internal electrode 11, metals such as platinum, tungsten, and molybdenum can be used, but the material of the internal electrode 11 is not limited to these. Inside the ceramic body 10, an electrode for a heater (not shown) may be located to adjust the temperature of the sample.

[0016] The base plate 20 is a disc-shaped member that supports the ceramic body 10. The base plate 20 is joined to the second surface 10b of the ceramic body 10 via the second joining layer 30. The second joining layer 30 is a layer provided between the ceramic body 10 and the base plate 20 and joins the two. The second joining layer 30 may be, for example, a cured adhesive made of an insulating material. As such an adhesive, for example, a silicone-based adhesive can be used. Further, inside the base plate 20, a refrigerant flow path 23 for flowing refrigerant is formed. By supplying refrigerant from the outside to the refrigerant flow path 23, the base plate 20 is cooled. The arrangement of such a refrigerant flow path 23 will be described later.

[0017] The base plate 20 includes a first base 21, a second base 22, and a first joining layer 24. The first base 21 and the second base 22 are made of, for example, a metal matrix composite (MMC) such as AlSiC or SiSiC. AlSiC is close to the thermal expansion coefficient of ceramics and has excellent thermal conductivity.

[0018] The first base 21 has a third surface 21a and a fourth surface 21b. The third surface 21a is the surface joined to the ceramic body 10 via the second joining layer 30. The fourth surface 21b is located on the opposite side of the third surface 21a. The fourth surface 21b is the surface joined to the second base 22 via the first joining layer 24. The first base 21 may have a cylindrical convex portion on the third surface 21a.

[0019] The second base 22 has a fifth surface 22a. The fifth surface 22a is the surface joined to the fourth surface 21b of the first base 21 via the first joining layer 24. The refrigerant flow path 23 may be formed, for example, as shown in FIG. 1, by providing a groove portion on the fifth surface 22a of the second base 22 and formed by this groove portion and the fourth surface 21b of the first base 21. The groove portion serving as the refrigerant flow path 23 may be located on the fifth surface 22a of the second base 22 while drawing a predetermined pattern such as a meander shape or a spiral shape in a plan view.

[0020] The first bonding layer 24 is located between the first substrate 21 and the second substrate 22.

[0021] Here, the base plate as described above was conventionally manufactured by heating while pressing with a bonding sheet made of aluminum sandwiched between two AlSiC base materials. That is, in the conventional base plate, a first bonding layer mainly composed of aluminum was used.

[0022] However, when the first bonding layer mainly contains aluminum, the aluminum in the first bonding layer gradually oxidizes over a long period of use, and the thermal conductivity decreases, which may reduce the heat uniformity of the sample holder.

[0023] In the sample holder 100 according to the first embodiment of the present disclosure, the main component of the first bonding layer 24 is tin (Sn). Here, the main component means a component contained in an amount exceeding 50% by wt among the components constituting the first bonding layer 24. The first bonding layer 24 may contain tin in an amount of 70% or more by wt. Further, the first bonding layer 24 may contain tin in an amount of 90% or more by wt.

[0024] Tin is excellent in thermal conductivity even when oxidized as compared with aluminum. Therefore, since the main component of the first bonding layer 24 is tin, the first bonding layer 24 has excellent heat uniformity. Also, since tin is softer than aluminum, the stress applied to the first bonding layer 24 is relaxed, and the first bonding layer 24 is less likely to deteriorate. Therefore, the sample holder 100 has excellent heat uniformity over a long period.

[0025] The first bonding layer 24 may contain aluminum. By containing aluminum, which has a lower electrical resistance than tin, the electrical conductivity and thermal conductivity of the first bonding layer 24 are improved, and the sample holder 100 has excellent heat uniformity. When the first bonding layer 24 contains aluminum, aluminum may be in an amount of 0.05 wt% or more and 10 wt% or less, or 0.1 wt% or more and 2 wt% or less among the components constituting the first bonding layer 24.

[0026] The first bonding layer 24 may contain silver. The inclusion of silver, which has lower electrical resistance than tin, improves the electrical and thermal conductivity of the first bonding layer 24, resulting in superior uniform heating of the sample holder 100. When the first bonding layer 24 contains silver, the amount of silver in the components constituting the first bonding layer 24 may be 0.05 wt% to 30 wt%, or 0.1 wt% to 2 wt%.

[0027] The first bonding layer 24 may contain titanium. The inclusion of titanium improves the adhesion strength with the first substrate 21 or the second substrate 22, making it difficult for the first substrate 21 and the second substrate 22 to peel off from the first bonding layer 24. When the first bonding layer 24 contains titanium, the titanium content may be between 0.05 wt% and 10 wt%, or between 0.1 wt% and 2 wt%. Alternatively, the first bonding layer 24 may contain zirconium or niobium instead of titanium. The elements and their content in the first bonding layer 24 can be confirmed, for example, by performing analysis using EPMA (Electron Probe Microanalyzer) or EDS (Energy Dispersive X-ray Spectroscopy) on a cross-section as shown in Figure 2. The presence or absence of components can also be confirmed by color mapping.

[0028] As described above, the second substrate 22 may have grooves on the fifth surface 22a that constitute the refrigerant flow path 23. As shown in Figure 1, the grooves may be covered by a cover portion 25. With this configuration, the first bonding layer 24 does not come into contact with the refrigerant flowing through the refrigerant flow path 23, thus preventing erosion of the first bonding layer 24 by the refrigerant. The cover portion 25 may be made of titanium, for example.

[0029] The first bonding layer 24 may be located between the lid portion 25 and the first base body 21.

[0030] Next, with reference to Figure 3, other configuration examples of the base plate 20 according to the first embodiment will be described. Figure 3 is a schematic cross-sectional view showing other configuration examples of region R shown in Figure 1.

[0031] As shown in Figure 3, the base plate 20 may have intermediate layers 26 and 27. Intermediate layer 26 is located between the first substrate 21 and the first bonding layer 24. Intermediate layer 27 is located between the second substrate 22 and the first bonding layer 24. Intermediate layers 26 and 27 are made of, for example, SnSiC.

[0032] Because the base plate 20 has intermediate layers 26 and 27, stress concentration in the first bonding layer 24 is reduced, and the sample holder 100 has excellent stress relaxation properties. Therefore, the sample holder 100 is less prone to deterioration.

[0033] In this example, the base plate 20 has intermediate layers 26 and 27 both between the first substrate 21 and the first bonding layer 24, and between the second substrate 22 and the first bonding layer 24, but it is not limited to this. For example, the base plate 20 may have only the intermediate layer 26 located between the first substrate 21 and the first bonding layer 24, or it may have only the intermediate layer 27 located between the second substrate 22 and the first bonding layer 24.

[0034] Furthermore, in the example shown in Figure 3, the first bonding layer 24 may also contain aluminum or silver. By including aluminum or silver, which have lower electrical resistance than tin, the electrical conductivity and thermal conductivity of the first bonding layer 24 are improved, and the sample holder 100 has excellent heat uniformity.

[0035] Furthermore, the first bonding layer 24 may contain titanium. In this case, the intermediate layers 26 and 27 may also contain titanium. As a result, the sample holder 100 has excellent bonding strength between the first substrate 21 and the first bonding layer 24, or between the second substrate 22 and the first bonding layer 24.

[0036] The elements contained in the intermediate layers 26 and 27 can be identified, for example, by performing elemental analysis using EPMA, EDS, etc., with a cross-section as shown in Figure 3 as the observation surface.

[0037] The manufacturing method of the base plate 20 shown in Figure 3, which is part of the first embodiment, will be described below.

[0038] Two substrates made of AlSiC or SiSiC are prepared. Next, grooves that will serve as refrigerant channels are formed on the surface of one of the substrates. Then, a titanium lid is placed over these grooves.

[0039] Next, a thin film containing titanium (first thin film) is formed on the surface of each of the two substrates. The thickness of this first thin film is, for example, between 80 nm and 600 nm. Then, a thin film containing at least one of aluminum and silver (second thin film) is formed on top of the first thin film. The thickness of this second thin film is, for example, between 50 and 1000 nm.

[0040] Next, a bonding sheet mainly composed of tin is placed on the surface of one of the two substrates on which the second thin film is formed. Then, the other substrate is placed on top of this bonding sheet so that the surface on which the second thin film is formed overlaps the bonding sheet. After that, the two substrates are heated under pressure for a predetermined time. At this time, the predetermined time is 1 hour or more and 10 hours or less, the pressure is 1 kPa or more and 100 kPa or less, and the temperature is 200°C or more and 400°C or less. As a result, the bonding sheet becomes a bonding layer that joins the two substrates, and the base plate 20 is manufactured. Alternatively, molten metal mainly composed of tin may be dropped onto the surface of one of the two substrates on which the second thin film is formed, and the other substrate may be placed on top so that the surface on which the second thin film is formed overlaps the molten metal.

[0041] It goes without saying that if the two substrates are joined without forming the first and second thin films, the resulting base plate 20 will have a first bonding layer 24 between the first substrate 21 and the second substrate 22, the main component of which is tin. Also, although Figure 1 shows an example in which the base plate 20 has a lid portion 25, the base plate 20 is not limited to this and does not have to have a lid portion 25. Figure 4 is a schematic cross-sectional view showing another example of the configuration of the sample holder 100 according to the first embodiment.

[0042] As shown in Figure 4, the base plate 20 may have a configuration without a lid. In this case, the first bonding layer 24 may be located in a region of the fifth surface 22a other than the groove that constitutes the refrigerant flow path 23.

[0043] (Second Embodiment) Figure 5 is a schematic cross-sectional view showing a sample holder 100 according to the second embodiment. As shown in Figure 5, the refrigerant flow path 28 may be located on the first base 21 of the base plate 20.

[0044] The first substrate 21 has grooves on its fourth surface 21b that constitute a refrigerant flow path 28. Similar to the first embodiment, the grooves may be covered with a titanium cover 29. With this configuration, the first bonding layer 24 does not come into contact with the refrigerant flowing through the refrigerant flow path 23, thus preventing erosion of the first bonding layer 24 by the refrigerant.

[0045] The first bonding layer 24 may be located between the lid portion 29 and the second substrate 22. Also, as shown in Figure 5, the sample holder 100 according to this embodiment may have no internal electrodes 11.

[0046] As described above, the first bonding layer 24 of the sample holder 100 according to this embodiment has tin as its main component. As a result, the first bonding layer 24 has excellent heat uniformity. In addition, because tin is soft, the stress on the first bonding layer 24 is relieved, and the first bonding layer 24 is less likely to deteriorate. Therefore, the sample holder 100 maintains excellent heat uniformity over a long period of time.

[0047] Furthermore, this technology can also be configured as follows. (1) A ceramic body having a first surface which is a sample holding surface and a second surface located opposite the first surface, A base plate supporting the ceramic body on the second surface and having a refrigerant flow path inside Equipped with, The aforementioned base plate is First substrate and second substrate, A bonding layer located between the first substrate and the second substrate Equipped with, The aforementioned bonding layer is a sample holder whose main component is tin. (2) The sample holder according to (1), further comprising an intermediate layer between the first substrate and the bonding layer, and between the second substrate and the bonding layer, at least one of these intermediate layers. (3) The bonding layer contains aluminum, as described in (1) or (2). (4) The bonding layer contains silver, as described in (1) or (2). (5) The bonding layer contains titanium, as described in (1) or (2). (6) The first or second substrate has grooves on its opposing surface that constitute the refrigerant flow path, The sample holder according to any one of (1) to (5), wherein the groove portion is covered with a titanium lid portion. (7) The sample holder according to (6), wherein the bonding layer is located between the lid and the first substrate or the second substrate. [Explanation of Symbols]

[0048] 10 Ceramic body 10a 1st page 10b 2nd side 11 Internal electrode 20 base plates 21 First Substrate 22 Second Substrate 23,28 Refrigerant flow path 24 1st bonding layer 25,29 Lid 26,27 Middle class 30 Second bonding layer 100 Sample holders W - Workpiece

Claims

1. A ceramic body having a first surface which is a sample holding surface and a second surface located opposite the first surface, A base plate supporting the ceramic body on the second surface and having a refrigerant flow path inside Equipped with, The aforementioned base plate is First substrate and second substrate, A bonding layer located between the first substrate and the second substrate Equipped with, The aforementioned bonding layer is a sample holder whose main component is tin.

2. The sample holder according to claim 1, further comprising an intermediate layer between the first substrate and the bonding layer, and between the second substrate and the bonding layer, at least one of these.

3. The sample holder according to claim 1, wherein the bonding layer contains aluminum.

4. The sample holder according to claim 1, wherein the bonding layer contains silver.

5. The sample holder according to claim 1, wherein the bonding layer contains titanium.

6. The first or second substrate has grooves on its opposing surface that constitute the refrigerant flow path, The sample holder according to claim 1, wherein the groove is covered with a titanium lid.

7. The sample holder according to claim 6, wherein the bonding layer is located between the lid and the first substrate or the second substrate.

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