wafer table

Abstract

This invention provides a wafer mounting stage capable of non-destructively inspecting a first electrode embedded in a ceramic substrate and a first junction of a first power supply terminal supplying power to the first electrode. An electrostatic chuck heater includes a ceramic substrate, a heater electrode, a heater power supply terminal, a junction, and an electrostatic electrode. The heater electrode is embedded in the ceramic substrate. The heater power supply terminal is inserted from a surface of the ceramic substrate opposite to the wafer mounting surface toward the heater electrode. The junction connects the heater electrode to the heater power supply terminal. The electrostatic electrode is disposed between the wafer mounting surface and the heater electrode. A straight portion (P) inside the ceramic substrate, extending from the heater electrode opposite to the junction to the wafer mounting surface, is made of the same material as the ceramic substrate.

Description

Technical Field

[0001] This invention relates to a wafer mounting stage. Background Technology

[0002] As a component for semiconductor manufacturing apparatus, a wafer mounting stage is known. For example, the wafer mounting stage described in Patent Document 1 includes: a ceramic substrate having a wafer mounting surface; a heater electrode embedded in the ceramic substrate; and an electrostatic electrode embedded in the ceramic substrate between the wafer mounting surface and the heater electrode in a manner that covers the heater electrode. A heater power supply terminal for supplying power to the heater electrode is inserted from the side of the ceramic substrate opposite to the wafer mounting surface toward the heater electrode and is electrically connected to the heater electrode.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-86919 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In such wafer mount stages, voids sometimes form at the junction of the heater electrode and the heater power supply terminal. In this case, the resistance at the junction increases, resulting in higher temperatures at and around the junction when power is supplied to the heater electrode via the heater power supply terminal, thus reducing the wafer's heat homogenization. Therefore, it is desirable to inspect the junction from the wafer mounting surface side using an ultrasonic flaw detector without damaging the wafer mount stage. However, the junction of the heater electrode and the heater power supply terminal is covered by an electrostatic electrode. Therefore, the ultrasonic waves emitted from the ultrasonic flaw detector are blocked by the electrostatic electrode, resulting in the inability to detect the junction. This problem is not limited to the junction of the heater electrode and the heater power supply terminal; it can also occur at the junction of electrodes embedded in a ceramic substrate and the power supply terminal connected to those electrodes.

[0008] The present invention was made to solve such a problem, and its main objective is to enable the inspection of the first junction between the first electrode embedded in the ceramic substrate in the wafer stage and the first power supply terminal supplying power to the first electrode in a non-destructive manner.

[0009] Solution for solving the problem

[0010] The wafer mounting stage of the present invention comprises:

[0011] A ceramic substrate having a wafer mounting surface;

[0012] The first electrode is embedded in the aforementioned ceramic substrate;

[0013] The first power supply terminal is inserted from the side of the ceramic substrate opposite to the wafer mounting surface toward the first electrode;

[0014] A first junction portion connects the first electrode to the first power supply terminal; and

[0015] The second electrode is disposed between the wafer mounting surface and the first electrode in the ceramic substrate.

[0016] The linear portion inside the ceramic substrate, extending from the position opposite to the first junction in the first electrode to the wafer mounting surface, is made of the material of the ceramic substrate.

[0017] In this wafer mounting stage, the linear portion inside the ceramic substrate, extending from the position opposite to the first bonding portion in the first electrode to the wafer mounting surface, is made of the same material as the ceramic substrate. That is, there is no metal or similar material present in this linear portion. Therefore, when performing non-destructive inspection of the first bonding portion from the wafer mounting surface side using an ultrasonic flaw detector, the ultrasonic waves incident from the wafer mounting surface onto the linear portion will reach the position opposite to the first bonding portion in the first electrode without being blocked by metal or similar material, and then the reflected ultrasonic waves will return to the wafer mounting surface side without being blocked. Therefore, non-destructive inspection of the first bonding portion is possible.

[0018] In the wafer mounting stage of the present invention, the second electrode may have a through hole at the position where the first bonding portion is projected vertically onto the second electrode, and the interior of the through hole is filled with the material of the ceramic substrate to form part of the straight portion. In this way, even if a second electrode covering the first electrode is provided between the wafer mounting surface in the ceramic substrate and the first electrode, non-destructive inspection of the first bonding portion can be performed.

[0019] Here, the first joint is preferably circular with a diameter d, and the through hole is preferably circular with a diameter of d / 2 or more and 2d or less. If the diameter of the through hole is d / 2 or more, the ultrasonic wave can reliably return to the wafer mounting surface after reaching the position opposite to the first joint in the first electrode from the wafer mounting surface side. Furthermore, if the diameter of the through hole is 2d or less, the function of the second electrode can be well maintained.

[0020] In the wafer mounting stage of the present invention, the second electrode may be arranged to avoid the straight portion. In this way, even if the second electrode is provided between the wafer mounting surface and the first electrode in the ceramic substrate, non-destructive inspection of the first joint can be performed.

[0021] In the wafer stage of the present invention, the first electrode can be a heater electrode or an RF electrode. When the first electrode is a heater electrode, the second electrode can be an electrostatic electrode, an RF electrode, or a heater electrode different from the first electrode. Furthermore, when the first electrode is an RF electrode, the second electrode can be an electrostatic electrode, a heater electrode, or an RF electrode different from the first electrode. For example, when the second electrode is a unipolar electrostatic electrode or an RF electrode, it is preferable to provide a through-hole at the position where the first junction portion is projected vertically onto the second electrode, and to fill the through-hole with the material of the ceramic substrate. When the second electrode is a bipolar electrostatic electrode or a heater electrode, it is preferable to arrange the second electrode in a manner that avoids straight sections.

[0022] In the wafer stage of the present invention, the first electrode can be a heater electrode formed of a resistive heating element. More preferably, the resistive heating element is a two-dimensional shape (e.g., a flat and elongated strip shape) with a thickness of 1 μm or more and 100 μm or less. This improves the accuracy of non-destructive inspection of the first junction between the first electrode (resistive heating element) and the first power supply terminal from the wafer mounting surface side. Attached Figure Description

[0023] Figure 1 This is a three-dimensional view of the electrostatic chuck heater 10.

[0024] Figure 2 yes Figure 1 AA sectional view.

[0025] Figure 3 This is a cross-sectional view of the electrostatic chuck heater 10 after it has been horizontally cut along the heater electrode 14, viewed from above.

[0026] Figure 4 This is a cross-sectional view of the cut surface after the electrostatic chuck heater 10 has been horizontally cut along the electrostatic electrode 18, viewed from above.

[0027] Figure 5 This is a cross-sectional view showing the comb-shaped electrodes 118, 118.

[0028] Symbol Explanation

[0029] 10: Electrostatic chuck heater; 12: Ceramic substrate; 12a: Wafer mounting surface; 12b: Surface opposite to the wafer mounting surface; 14: Heater electrode; 15: Resistance heating element; 15a: End; 16: Heater power supply terminal; 17: Joint; 18: Electrostatic electrode; 18a: Through hole; 19: Rod terminal; 118: Comb electrode; P: Straight section; U: Ultrasonic wave; W: Wafer. Detailed Implementation

[0030] Embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a perspective view of the electrostatic chuck heater 10 according to this embodiment. Figure 2 yes Figure 1 AA section view, Figure 3 This is a cross-sectional view taken from above, showing the cut surface of the electrostatic chuck heater 10 after it has been horizontally cut along the heater electrode 14. Figure 4 This is a cross-sectional view, viewed from above, of the cut surface after the electrostatic chuck heater 10 has been horizontally cut along the electrostatic electrode 18. Figure 2 The diagram also shows a magnified view of the area within the circle containing the single-dotted line. In the following description, the terms "up / down," "left / right," and "front / back" are sometimes used, but these are merely to indicate relative positional relationships. It should be noted that in this specification, the "~" signifying a numerical range is used to indicate that the values ​​preceding and following it are the lower and upper limits.

[0031] The electrostatic chuck heater 10 is a wafer mounting stage, and heater electrodes 14 and electrostatic electrodes 18 are embedded inside the ceramic substrate 12.

[0032] The ceramic substrate 12 is a circular plate made of ceramic (e.g., alumina or aluminum nitride). A wafer mounting surface 12a is provided on the surface of the ceramic substrate 12 for mounting the wafer W.

[0033] The heater electrode 14 is formed from a strip-shaped (flat and elongated strip-shaped) resistive heating element 15 formed on a surface parallel to the wafer mounting surface 12a. "Parallel" includes not only perfectly parallel surfaces but also substantially parallel surfaces (e.g., within tolerance ranges). The strip-shaped resistive heating element 15 is not particularly limited; for example, it can be set to a width of 0.1–10 mm, a thickness of 1–100 μm, and a line spacing of 0.1–5 mm. The heater electrode 14 extends from one of a pair of ends 15a, 15a of the resistive heating element 15 in a single, non-crossing manner across the entire ceramic substrate 12. Such a heater electrode 14 can be formed, for example, by printing a conductive paste. A cylindrical heater power supply terminal 16 is joined to the end 15a of the resistive heating element 15 via a joint 17. That is, the joint 17 joins the heater electrode 14 to the heater power supply terminal 16. The diameter of the heater power supply terminal 16 is not particularly limited, but is preferably 1–10 mm, more preferably 3–7 mm. The diameter of the joint 17 is approximately the same as the diameter of the heater power supply terminal 16. The heater power supply terminal 16 is inserted into a terminal hole extending from the surface 12b of the ceramic substrate 12 opposite to the wafer mounting surface 12a to the lower surface of the end 15a of the resistive heating element 15. The joint 17 is, for example, a circular member formed of metal solder, with the same diameter as the heater power supply terminal 16. A pair of heater power supply terminals 16, 16 are connected to a heater power supply (not shown). Examples of materials for the resistive heating element 15 include tungsten carbide, metallic tungsten, molybdenum carbide, and metallic molybdenum. Preferably, a material with a coefficient of thermal expansion close to that of the ceramic used in the ceramic substrate 12 is selected, and the ceramic used in the ceramic substrate 12 may also be added. Examples of materials for the heater power supply terminal 16 include metallic tungsten, metallic molybdenum, metallic nickel, and nickel alloys.

[0034] The electrostatic electrode 18 is a circular conductive film parallel to the wafer mounting surface 12a. The electrostatic electrode 18 is an electrode disposed between the wafer mounting surface 12a and the heater electrode 14. A cylindrical rod-shaped terminal 19 is electrically connected to the electrostatic electrode 18 via solder. The rod-shaped terminal 19 is inserted into a terminal hole extending from the surface 12b of the ceramic substrate 12 opposite to the wafer mounting surface 12a to the lower surface of the electrostatic electrode 18. The rod-shaped terminal 19 is configured to maintain an insulating distance from the heater electrode 14 in a manner that prevents short circuits. A DC power supply (not shown) is connected to the rod-shaped terminal 19. The portion of the ceramic substrate 12 between the electrostatic electrode 18 and the wafer mounting surface 12a functions as a dielectric layer. Examples of materials for the electrostatic electrode 18 include tungsten carbide, metallic tungsten, molybdenum carbide, and metallic molybdenum. Preferably, a material with a coefficient of thermal expansion close to that of the ceramic used in the ceramic substrate 12 is selected, and the ceramic used in the ceramic substrate 12 may also be added. Materials used for the rod-shaped terminal 19 include, for example, tungsten, molybdenum, nickel, and nickel alloys.

[0035] The electrostatic electrode 18 has a through hole 18a at a position where the junction 17 is projected vertically upwards onto the electrostatic electrode 18. The interior of the through hole 18a is filled with the same material as the ceramic substrate 12. As a result, a straight portion P (refer to) is formed inside the ceramic substrate 12, extending from the position in the heater electrode 14 opposite to the junction 17 (the upper surface of the end 15a of the resistive heating element 15) to the wafer mounting surface 12a. Figure 2 (A partial enlarged view) is made of the material of the ceramic substrate 12. The interior of the through hole 18a forms part of the straight portion P. The through hole 18a is preferably a circular hole, and its diameter D is more than d / 2 and less than 2d (d is the diameter of the joint 17). Alternatively, the diameter of the through hole 18a can also be a value obtained by adding 0 to 5 mm to the diameter of the heater power supply terminal 16 (in mm).

[0036] Next, an example of using the electrostatic chuck heater 10 will be described. A wafer W is placed on the wafer mounting surface 12a of the electrostatic chuck heater 10. A voltage from a DC power supply (not shown) is applied between the electrostatic electrode 18 and the wafer W, thereby using electrostatic force to attract the wafer W to the wafer mounting surface 12a. In this state, plasma CVD film deposition or plasma etching is performed on the wafer W. Furthermore, the temperature of the wafer W is kept constant by applying a voltage from a heater power supply (not shown) to the two ends 15a, 15a of the resistive heating element 15.

[0037] Next, the inspection of the joint 17 of the electrostatic chuck heater 10 using an ultrasonic flaw detector will be described. The probe of the ultrasonic flaw detector is positioned directly above the joint 17 on the wafer mounting surface 12a, and the ultrasonic wave U transmitted from the probe to the joint 17 (refer to…) is measured. Figure 2 (A magnified view of a portion of the image) The time it takes for the reflected ultrasound to return to the probe and the intensity of the returned ultrasound are used to evaluate whether a cavity has been formed at the joint 17.

[0038] Here, the correspondence between the constituent elements of this embodiment and the constituent elements of the present invention is clarified. In this embodiment, the electrostatic chuck heater 10 corresponds to the wafer mounting stage of the present invention, the heater electrode 14 corresponds to the first electrode, the heater power supply terminal 16 corresponds to the first power supply terminal, the joint portion 17 corresponds to the first joint portion, the electrostatic electrode 18 corresponds to the second electrode, and the straight portion P corresponds to the straight portion.

[0039] In the electrostatic chuck heater 10 of this embodiment described above, the linear portion P inside the ceramic substrate 12, extending from the position opposite to the junction 17 in the heater electrode 14 to the wafer mounting surface 12a, is made of the same material as the ceramic substrate 12. That is, there is no metal or the like in the linear portion P. Therefore, when performing non-destructive inspection of the junction 17 from the wafer mounting surface 12a side using an ultrasonic flaw detector, the ultrasonic waves incident from the wafer mounting surface 12a onto the linear portion P will reach the end 15a of the resistive heating element 15, which is connected to the heater power supply terminal 16, without being blocked by metal or the like. Afterward, the reflected ultrasonic waves will return unobstructed to the wafer mounting surface 12a side. Therefore, non-destructive inspection of the junction 17 between the heater electrode 14 and the heater power supply terminal 16 can be performed.

[0040] Furthermore, the electrostatic electrode 18 has a through hole 18a at the position where the junction 17 of the heater electrode 14 and the heater power supply terminal 16 is projected vertically onto the electrostatic electrode 18. The interior of the through hole 18a is filled with the material of the ceramic substrate 12 to form part of the straight portion P. Therefore, even if the heater electrode 14 is covered by the electrostatic electrode 18, non-destructive inspection of the junction 17 can be performed.

[0041] Furthermore, the joint 17 is preferably circular with a diameter d, the through hole 18a is preferably circular, and its diameter D is preferably d / 2 or more and 2d or less, more preferably d or more and 2d or less. If the diameter D of the through hole 18a is d / 2 or more, the ultrasonic wave can be reliably reflected back to the wafer mounting surface 12a after reaching the end 15a of the resistive heating element 15 from the wafer mounting surface 12a side. In addition, if the diameter D of the through hole 18a is 2d or less, the function of the electrostatic electrode 18 can be well maintained.

[0042] Furthermore, the thickness of the resistive heating element 15 is more preferably 1 μm or more and 100 μm or less. This improves the accuracy of non-destructive inspection of the joint 17 from the wafer mounting surface 12a side.

[0043] It should be noted that the present invention is not limited to any of the above embodiments. It goes without saying that as long as it falls within the technical scope of the present invention, it can be implemented in various ways.

[0044] In the above embodiments, a unipolar electrostatic chuck with one electrostatic electrode 18 is illustrated, but it is also possible to use a unipolar electrostatic chuck with one electrostatic electrode 18. Figure 5 As shown, a bipolar electrostatic chuck with a pair of comb-shaped electrodes 118, 118 is used. In this case, by applying a predetermined voltage to the pair of comb-shaped electrodes 118, 118, the wafer W can be attracted to the wafer mounting surface 12a. Figure 5In this embodiment, no through-holes are provided in the comb-shaped electrodes 118, 118, but the straight portion P is disposed in the gap between the comb-shaped electrodes 118, 118. In other words, the pair of comb-shaped electrodes 118, 118, which serve as the second electrodes, are arranged to avoid the straight portion P. Thus, the straight portion P is made of the material of the ceramic substrate 12. In this way, the probe of the ultrasonic flaw detection device can be placed directly above the straight portion P in the wafer mounting surface 12a to evaluate whether a void has been generated in the joint 17. It should be noted that, instead of placing the straight portion P directly above the gap between the comb-shaped electrodes 118, 118, the straight portion P can be placed directly above the surface of the comb-shaped electrodes 118, 118, and a through-hole of the same type as the through-hole 18a in the above embodiment can be provided at that location, and the interior of the through-hole can be filled with the same material as the ceramic substrate 12.

[0045] In the above embodiments, a DC voltage is applied to the electrostatic electrode 18 to attract the wafer W to the wafer mounting surface 12a. However, the electrostatic electrode 18 can also be used as an RF electrode (high-frequency electrode) for generating plasma. Alternatively, the electrostatic electrode 18 can be used as an RF electrode instead of being used for the electrostatic attraction of the wafer W.

[0046] In the above embodiment, a heater electrode 14 is provided on the ceramic substrate 12, but other heater electrodes may also be provided on a different layer than the heater electrode 14 (e.g., between the electrostatic electrode 18 and the heater electrode 14). In this case, it is sufficient to make the straight portion P pass through the lines of the resistive heating element forming the other heater electrode.

[0047] In the electrostatic chuck heater 10 of the above-described embodiment, a cooling plate may also be mounted on the lower surface of the ceramic substrate 12. The cooling plate is preferably a circular metal plate (e.g., made of aluminum or aluminum alloy) with a built-in refrigerant passage for refrigerant (e.g., water). A through hole is provided on the cooling plate to allow the heater power supply terminal 16 and the rod-shaped terminal 19 to pass through. In this case, the heater power supply terminal 16 and the rod-shaped terminal 19 are electrically insulated from the cooling plate.

[0048] In the electrostatic chuck heater 10 of the above embodiment, ejector pin holes and vent holes penetrating the ceramic substrate 12 in the vertical direction may also be provided. Ejector pin holes are holes through which ejector pins are inserted, lifting the wafer W placed on the wafer mounting surface 12a, or placing the lifted wafer W back onto the wafer mounting surface 12a. Vent holes are holes for supplying gas (e.g., He gas) toward the back side of the wafer mounting surface 12a. Alternatively, multiple circular protrusions may be provided on the wafer mounting surface 12a, supporting the wafer W on the upper surface of the circular protrusions. In this case, an annular protrusion of the same height as the circular protrusions may be provided along the outer edge of the wafer mounting surface 12a as a sealing strip.

[0049] In the above embodiments, a heater electrode 14 is used as the first electrode of the present invention, and an electrostatic electrode 18 is used as the second electrode, but the invention is not particularly limited to this. For example, an RF electrode may be used as the first electrode, and an electrostatic electrode, a heater electrode, or an RF electrode may be used as the second electrode. When both the first and second electrodes are RF electrodes, the RF electrodes are formed in two layers (multiple layers), and the two RF electrodes can be connected by through-hole conductors in the vertical direction to make them have the same potential. Alternatively, the RF electrode serving as the first electrode may be formed in a ring shape, and the RF electrode serving as the second electrode may be formed in a circular plate shape.

Claims

1. A wafer mounting stage, comprising: A ceramic substrate having a wafer mounting surface; The first electrode is embedded in the ceramic substrate; A first power supply terminal is inserted from the side of the ceramic substrate opposite to the wafer mounting surface toward the first electrode; A first junction portion connects the first electrode to the first power supply terminal; as well as The second electrode is disposed between the wafer mounting surface in the ceramic substrate and the first electrode. The linear portion inside the ceramic substrate, extending from the position of the first electrode opposite to the first bonding portion to the wafer mounting surface, is made of the same material as the ceramic substrate. The second electrode has a through hole at the position where the first junction is projected vertically onto the second electrode, and the interior of the through hole is filled with the material of the ceramic substrate to form part of the straight portion.

2. The wafer mounting stage according to claim 1, wherein the first joint is a circle with a diameter d, and the through hole is a circular hole with a diameter of d / 2 or more and 2d or less.

3. The wafer mounting stage according to claim 1 or 2, wherein the first electrode is a heater electrode or an RF electrode. When the first electrode is a heater electrode, the second electrode is an electrostatic electrode, an RF electrode, or a heater electrode different from the first electrode. When the first electrode is an RF electrode, the second electrode is an electrostatic electrode, a heater electrode, or an RF electrode different from the first electrode.

4. The wafer stage according to claim 1 or 2, wherein the first electrode is a heater electrode formed by a resistive heating element, the resistive heating element being two-dimensional in shape and having a thickness of 1 μm or more and 100 μm or less.

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