JP3154930U - Ceramic parts with built-in electrodes - Google Patents

Abstract

An electrode-embedded ceramic part capable of suppressing variations in etching rate within a wafer surface is provided. A ceramic component with a built-in electrode 10 is built in a ceramic substrate 12 with a disc electrode 14 and a ring electrode 16 spaced apart in the thickness direction so as to be coaxial. The power supply terminal 18 is arranged so as to be in contact with the center of the disk electrode 14. The outer peripheral tablet 20 is arranged at equal intervals on the circumference of a predetermined radius from the center of the disc electrode 14 on the surface of the disc electrode 14 facing the ring electrode 16. The plated layer 24 is formed inside the counterbore 22 that penetrates the ring electrode 16 from the back surface 12 a and reaches the outer peripheral tablet 20, and has a bottom surface in contact with the outer peripheral tablet 20 and a side surface in contact with the ring electrode 16. The plug 26 is made of the same material as the ceramic base 12 and closes the countersink hole 22 in which the plating layer 24 is formed. [Selection] Figure 1

Description

  The present invention relates to a ceramic component with a built-in electrode.

  Conventionally, ceramic parts with a built-in electrode used for ceramic heaters, electrostatic chucks, susceptors (with built-in electrodes for generating plasma), and the like are known. For example, in Patent Document 1, as such a ceramic part with a built-in electrode, as shown in FIG. 7, a disk electrode 214 and a ring electrode 216 are coaxially built apart from each other in the thickness direction on a ceramic base 212. , 216 are electrically connected via a spring 224 made of tungsten or molybdenum (see FIG. 7). By providing the ring electrode 216 in this manner, a region where plasma is generated is widened, so that the plasma generation density at the outer peripheral edge of the wafer W can be increased. In this ceramic part with built-in electrode, a disk electrode 214 is provided on the surface of the first ceramic molded body, a plurality of springs 224 are arranged on the disk electrode 214, and the springs 224 are embedded with ceramic powder, followed by pressure molding. . After that, the ring electrode 216 is disposed so as to be in contact with the end of the spring 224 opposite to the end in contact with the disk electrode 214, and the ring electrode 216 is embedded with ceramic powder and then pressed. Molded into a laminate. Thereafter, this laminated body is fired to obtain a ceramic component with a built-in electrode. In FIG. 7, power supply terminals 218 for applying a voltage are attached to two locations of the ring electrode 216.

JP 2003-163259 A

  However, in the ceramic part with built-in electrode disclosed in Patent Document 1, even if the springs 224 are arranged at equal intervals from the center of the disk electrode 214 on the circumference of a predetermined radius, the springs 224 move when the springs 224 are embedded with ceramic powder. There was something to do. Due to the movement, some springs 224 may not come into contact with the disk electrode 214 or the ring electrode 216, or the springs 224 may not be arranged on the circumference of a predetermined radius from the center of the disk electrode 214 at equal intervals. When the plasma is generated, the etching rate varies on the circumference of the same radius of the wafer placed on the electrode built-in ceramic part, and the chip yield may be deteriorated when cutting the chip from the wafer. .

  The present invention has been made to solve such a problem, and a main object of the present invention is to provide a ceramic component with a built-in electrode that can suppress variations in the etching rate within the wafer surface.

The ceramic part with built-in electrode of the present invention is
A disc electrode and a ring electrode are incorporated in a ceramic base so as to be coaxial with each other in a thickness direction, and a wafer placement surface on which a wafer to be subjected to plasma treatment is placed is provided close to the disc electrode. A ceramic part with a built-in electrode,
A power supply terminal provided so as to be in contact with the center of the disk electrode from the center of the surface of the ceramic substrate opposite to the wafer mounting surface;
Conductive tablets arranged at equal intervals on the circumference of a predetermined radius from the center of the disk electrode on the surface of the disk electrode facing the ring electrode;
A countersink hole reaching the tablet through the ring electrode from the surface opposite to the wafer mounting surface of the ceramic substrate;
A bottomed cylindrical plating layer that is formed inside the counterbore, has a bottom surface in contact with the tablet, and a side surface in contact with the ring electrode;
A plug made of the same material as the ceramic base, plugging the countersink hole in which the plating layer is formed;
It is equipped with.

  In the ceramic part with built-in electrode of the present invention, the electrical connection between the disk electrode and the ring electrode is made of a conductive tablet arranged on the disk electrode and a bottomed cylindrical shape whose bottom surface is in contact with this tablet and whose side surface is in contact with the ring electrode. And secured by the plating layer. Here, since the tablets are arranged at equal intervals on the circumference of a predetermined radius from the center of the disk electrode, when a voltage is applied to the power supply terminal, the impedance distribution on the concentric circle centering on the power supply terminal Will have rotational symmetry. As a result, the plasma generated with the high-frequency voltage exhibits a uniform concentric distribution, and variations in the etching rate within the wafer surface can be suppressed. In addition, the plug that closes the countersink hole is made of the same material as the ceramic base, so the thermal conductivity of the surrounding parts of the tablet and plated layer in the built-in electrode ceramic parts is not significantly different from that of other parts, and temperature irregularities are prevented from occurring. be able to. Furthermore, since the depth of the countersink hole becomes shallower by the thickness of the tablet than in the case where there is no tablet, the strength of the portion directly above the countersink hole in the ceramic substrate can be maintained. Furthermore, since the electrical connection between the disc electrode and the ring electrode is ensured by a bottomed cylindrical plating layer, this connection is caused by the difference in thermal expansion between the metal and the ceramic compared to the case where the connection is secured by a metal pin. It is possible to prevent the occurrence of peeling and cracks.

  In the electrode-embedded ceramic part of the present invention, the plating layer is preferably a Ni plating layer. Since Ni plating is more resistant to oxidation than Cu plating or the like, electrical connection between the disk electrode and the ring electrode can be secured stably over a long period of time.

In the electrode-embedded ceramic part of the present invention, it is preferable that a carbon thin film is formed on the inner surface of the plating layer. In this way, a high-power high-frequency current can flow. In particular, it is preferable that a Ni plating layer is adopted as the plating layer and a carbon thin film is formed on the inner surface thereof. Although it is possible to adopt a silver thin film in addition to the carbon thin film, silver generates silver ions (Ag ⁺ ) under a high voltage electric field, and the mobility of these silver ions at the insulator interface and surface is very high. Therefore, it is not preferable because long-term use causes migration due to movement of silver ions. On the contrary, the carbon thin film does not cause such a problem, and thus has a long-term reliability. In addition, it is conceivable to use a carbon thin film instead of the plating layer. However, since the carbon paste shrinks greatly when the carbon paste is dried and cured in the carbon thin film formation process, it partially peels from the counterbore or cracks. In particular, since the connection between the side surface and the ring electrode is likely to be unstable, it is not preferable because it is difficult to ensure the electrical connection between the disk electrode and the ring electrode. For this reason, it is preferable to allow a high-power high-frequency current to flow through the carbon thin film while ensuring electrical connection with the plated layer.

  In the electrode-embedded ceramic component of the present invention, when the ceramic substrate is formed of alumina, the disk electrode and the ring electrode are formed of a mixed sintered body of WC and alumina or a mixed sintered body of NbC and alumina. The tablet is formed of a mixed sintered body of at least one powder selected from the group consisting of Pt powder, Nb powder and NbC powder and alumina powder or a mixed sintered body of WC powder and alumina powder. Preferably it is. When the disk electrode and the ring electrode are formed of a mixed sintered body of WC and alumina or a mixed sintered body of NbC and alumina, WC and NbC hardly react with alumina at the time of sintering. Since it does not diffuse into alumina, the resistance of alumina can be kept high. In particular, it is important to keep the resistance of alumina high when used as an electrostatic chuck. Further, by using a mixture with alumina, the thermal expansion coefficient of each electrode approaches that of alumina, and the bonding strength between the ceramic substrate and each electrode is improved.

  In the electrode-embedded ceramic component of the present invention, when the ceramic substrate is formed of aluminum nitride, the disk electrode and the ring electrode are preferably formed of Mo mesh, and the tablet is preferably formed of Mo. The disc electrode and the ring electrode may be formed of a mixed sintered body of WC and aluminum nitride or a mixed sintered body of NbC and aluminum nitride. This is preferable because the rate is low. Moreover, since the tablet is formed with Mo, since the volume resistivity of Mo is low, it is preferable.

  In the present specification, a method for manufacturing an electrode-embedded ceramic part is also disclosed. That is, (a) First, a circular disk electrode in which a tablet is arranged is formed on a disk-shaped ceramic sintered body. At this time, the tablets are arranged at equal intervals on the circumference of a predetermined radius from the center of the disk electrode. (B) Separately, a ring electrode is formed on a disk-shaped ceramic sintered body. (C) Then, both ceramic sintered bodies are laminated via a ceramic powder or a ceramic molded body. At this time, the disk electrode and the ring electrode are stacked so as to be coaxial and face each other to form a stacked body. (D) Next, this laminated body is fired by a hot press method to obtain a ceramic substrate that is built up in the thickness direction so that the disk electrode and the ring electrode are coaxial. (E) Next, a countersink hole that penetrates the ring electrode from the surface on the ring electrode side of the ceramic substrate and reaches the tablet is formed. (F) Next, a bottomed cylindrical plating layer is formed inside the counterbore so that the bottom surface is in contact with the tablet and the side surface is in contact with the ring electrode. (G) The countersink hole in which the plating layer is formed is closed with a plug made of the same material as the ceramic sintered body. Thus, the electrode-embedded ceramic part of the present invention is obtained. According to this manufacturing method, it is possible to prevent the disk electrode from being cut by the tablet when the counterbore hole is drilled. Moreover, compared with the case where a spring is arrange | positioned at a disk electrode like patent document 1, a disk electrode and a ring electrode can be arrange | positioned coaxially reliably.

It is explanatory drawing of the ceramic component 10 with a built-in electrode, (a) is a top view, (b) is AA sectional drawing. It is an enlarged view of the part in a circle of Drawing 1 (b). It is BB sectional drawing of FIG. It is explanatory drawing of the alumina sintered compact 121 in which the disk electrode 14 was formed, (a) is a top view, (b) is CC sectional drawing. It is explanatory drawing of the alumina sintered compact 122 in which the ring electrode 16 was formed, (a) is a top view, (b) is DD sectional drawing. It is an assembly process figure when assembling the ceramic component 10 with a built-in electrode. It is sectional drawing of the conventional ceramic component with a built-in electrode.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view of a ceramic component 10 with built-in electrodes according to the present invention, wherein (a) is a plan view and (b) is a cross-sectional view taken along line AA. 2 is an enlarged view of a portion in a circle of FIG. 1B, and FIG. 3 is a cross-sectional view taken along the line BB of FIG.

  The ceramic component 10 with a built-in electrode includes a ceramic substrate 12 on which a wafer mounting surface 12a is formed, a disk electrode 14 and a ring electrode 16 built in the ceramic substrate 12, and a surface (back surface) opposite to the wafer mounting surface 12a. ) Each of the power supply terminal 18 formed so as to reach the center of the disk electrode 14 from 12b, a plurality of outer peripheral tablets 20 formed along the outer periphery of the disk electrode 14, and a surface 12b opposite to the wafer mounting surface 12a. A countersink hole 22 that communicates with the outer peripheral tablet 20, a plating layer 24 formed inside the countersink hole 22, and a plug 26 that closes the countersink hole 22 are provided.

  The ceramic substrate 12 can place a wafer W (see FIG. 1B) on which a plasma treatment is performed on a wafer placement surface 12a provided close to the disk electrode 14. Of the ceramic substrate 12, a portion between the wafer mounting surface 12 a and the disk electrode 14 functions as a dielectric layer when the wafer W is attracted. The ceramic substrate 12 is a stepped disk in which a small-diameter portion 12c and a large-diameter portion 12d are continuous, and is formed of a ceramic such as alumina or aluminum nitride.

  The disk electrode 14 is formed in a disk shape and is built in the small diameter portion 12 c of the ceramic substrate 12. Although not shown, the disk electrode 14 is provided with small holes at necessary places. The electrode built-in ceramic part 10 is provided with several through holes that communicate with these small holes and penetrate in the thickness direction. These through holes are used to insert lift pins that move the wafer W up and down. The cooling gas (for example, He gas) for cooling the wafer W is used.

  The ring electrode 16 is formed in a ring shape and is built in the large diameter portion 12 d of the ceramic substrate 12. The ceramic substrate 12, the disk electrode 14 and the ring electrode 16 are formed so as to be coaxial, and the disk electrode 14 and the ring electrode 16 are separated in the thickness direction. The outer diameter of the ring electrode 16 is larger than the diameter of the disk electrode 14, and the inner diameter of the ring electrode 16 (the inner peripheral diameter excluding the protrusions 16 a) is substantially equal to the diameter of the disk electrode 14. The ring electrode 16 has n protrusions 16a (n is an integer of 3 or more) at regular intervals along the inner periphery (see FIG. 5). The protrusion 16a is formed in a semicircular shape, for example.

  The power supply terminal 18 is electrically connected to the center of the disk electrode 14 from the back surface 12 b of the ceramic substrate 12 via the central tablet 19. The power supply terminal 18 has an insertion port 18a for inserting a rod-shaped conductive member (not shown).

  The outer peripheral tablet 20 is a small cylindrical body having conductivity, and n pieces are arranged on the surface of the disk electrode 14 facing the ring electrode 16 at equal intervals from the center of the disk electrode 14 on the circumference of a predetermined radius. . Here, the predetermined radius is set to coincide with the radius of the circle connecting the centers of the protrusions 16a of the ring electrode 16, that is, to coincide with the PCD (pitch / circle / diameter) of the protrusions 16a. The outer peripheral tablet 20 is opposed to the protrusion 16a formed on the ring electrode 16 (see FIGS. 2 and 3). For this reason, the number of outer peripheral tablets 20 matches the number of protrusions 16 a of the ring electrode 16. Here, n is preferably 8 or more. In this way, the high-frequency voltage applied to the power supply terminal 18 is likely to spread radially and uniformly, and the impedance distribution on the concentric circle centered on the power supply terminal 18 has rotational symmetry, so that the concentric circular distribution is uniform. This is because plasma is easy to stand. In the case where the protrusion 16a is not formed on the ring electrode 16, by making the inner diameter of the ring electrode 16 smaller than the diameter of the disk electrode 14, there is a region where the disk electrode 14 and the ring electrode 16 overlap in plan view. In this way, the predetermined radius may be set so that the outer peripheral tablet 20 is arranged in the region. However, if the area where the disk electrode 14 and the ring electrode 16 overlap increases, the plasma may become unstable in that area. Therefore, the ring electrode 16 is provided with a protrusion 16a as in this embodiment, and only the protrusion 16a is present. It is preferable to overlap the disk electrode 14.

  The counter bore 22 is provided so as to penetrate the protrusion 16 a of the ring electrode 16 from the back surface 12 b of the ceramic substrate 12 and reach the outer peripheral tablet 20.

  The plated layer 24 is formed inside the counterbored hole 22 so as to have a bottomed cylindrical shape (cup shape), the bottom surface is in contact with the outer peripheral tablet 20, and the side surface is in contact with the protrusion 16a of the ring electrode 16 (FIG. 2). And FIG. 3). The plating layer 24 is preferably a Ni plating layer. This is because the Ni plating layer is excellent in oxidation resistance and can secure electrical connection between the disk electrode 14 and the ring electrode 16 stably over a long period of time. The plating layer 24 preferably has a carbon thin film formed on the inner surface. This is because, when a carbon thin film is formed on the inner surface, a high-power high-frequency current can flow.

  The plug 26 is a cylindrical body formed of the same material as that of the ceramic base 12 and closes the countersink hole 22 in which the plating layer 24 is formed. The plug 26 has a tip portion in close contact with the inner peripheral surface of the bottomed cylindrical plating layer 24, and a base end portion in close contact with the inner peripheral surface of the counterbore hole 22. The plug 26 is fixed in the counterbore 22 with an adhesive. Note that there is a gap between the outer peripheral surface of the distal end portion of the plug 26 and the inner peripheral surface of the plating layer 24, or between the outer peripheral surface of the proximal end portion of the plug 26 and the inner peripheral surface of the counterbore hole 22. May be filled with an adhesive.

  Here, when the ceramic substrate 12 is formed of alumina, the disk electrode 14 and the ring electrode 16 are formed of a mixed sintered body of WC and alumina or a mixed sintered body of NbC and alumina, and the outer peripheral tablet 20 is It is preferably formed of a mixed sintered body of at least one powder selected from the group consisting of Pt powder, Nb powder and NbC powder and an alumina powder or a mixed sintered body of WC powder and alumina powder. When the disk electrode 14 and the ring electrode 16 are formed of a mixed sintered body of WC and alumina or a mixed sintered body of NbC and alumina, WC and NbC hardly react with alumina at the time of sintering. , 16 does not diffuse into the surrounding alumina, so that the resistance of alumina can be kept high. In particular, it is important to keep the resistance of alumina high when used as an electrostatic chuck. Further, by using a mixture with alumina, the thermal expansion coefficient of each of the electrodes 14 and 16 approaches that of alumina, and the bonding strength between the ceramic substrate 12 and each of the electrodes 14 and 16 is improved.

  On the other hand, when the ceramic substrate 12 is made of aluminum nitride, the disk electrode 14 and the ring electrode 16 are preferably made of Mo mesh, and the outer peripheral tablet 20 is also preferably made of Mo. The disc electrode and the ring electrode may be formed of a mixed sintered body of WC and aluminum nitride or a mixed sintered body of NbC and aluminum nitride. This is preferable because the rate is low. Moreover, since the tablet is formed with Mo, since the volume resistivity of Mo is low, it is preferable.

  Next, the usage example of the electrode built-in ceramic component 10 of this embodiment is demonstrated. A wafer W is mounted on the wafer mounting surface 12a of the electrode-containing ceramic component 10, and an electrostatic force is generated by applying a DC high voltage to the disk electrode 14 and the ring electrode 16 through the power supply terminal 18, Thereby, the wafer W is attracted to the wafer mounting surface 12a. In this state, plasma CVD film formation or plasma etching is performed on the wafer W. Specifically, a high-frequency voltage is applied to the disk electrode 14 and the ring electrode 16 via a power supply terminal 18 in a vacuum chamber (not shown), and the opposing horizontal electrode and the electrode built-in ceramic component 10 installed in the upper part of the vacuum chamber are applied. Plasma is generated between parallel plate electrodes composed of the embedded electrodes 14 and 16, and the wafer W is subjected to CVD film formation or etching using the plasma. A focus ring (also referred to as a protection ring) (not shown) is placed on the outer peripheral step portion of the electrode-embedded ceramic component 10. The focus ring is made of quartz, alumina, metal silicon or the like, and is designed so that the surface thereof is the same height as the wafer mounting surface 12a. By placing such a focus ring on the outer peripheral stepped portion, the stepped surface is protected in order to prevent plasma from directly contacting the stepped surface of the ceramic substrate 12. In addition, the focus ring deteriorates due to plasma with use, but in that case, it is replaced with a new one. The focus ring may be placed on the outer circumferential step portion, but may not be placed depending on circumstances.

  According to the electrode-embedded ceramic component 10 of the present embodiment described in detail above, the outer peripheral tablet 20 is arranged at equal intervals on the circumference of a predetermined radius from the center of the disk electrode 14, so that a voltage is applied to the power supply terminal 18. When applied, the impedance distribution on a concentric circle centered on the power supply terminal 18 has rotational symmetry. As a result, the plasma generated with the high-frequency voltage exhibits a uniform concentric distribution, and variations in the etching rate within the wafer surface can be suppressed. Moreover, since the plug 26 that closes the counterbored hole 22 is made of the same material as the ceramic substrate 12, the thermal conductivity of the periphery of the outer peripheral tablet 20 and the plated layer 24 in the ceramic component 10 with built-in electrode is not significantly different from that of other portions, and the temperature Generation of unevenness can be suppressed. Furthermore, since the depth of the countersink hole 22 is reduced by the thickness of the outer peripheral tablet 20 as compared with the case without the outer peripheral tablet 20, the strength of the portion directly above the countersink hole 22 in the ceramic base 12 can be maintained. it can. Furthermore, since the electrical connection between the disk electrode 14 and the ring electrode 16 is ensured by the bottomed cylindrical plating layer 24, the thermal expansion between the metal and the ceramic is greater than when securing this connection with a metal pin. It is possible to prevent peeling and cracks due to the difference.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

[Example 1]
Example 1 will be described with reference to FIGS. 4A and 4B are explanatory views of the alumina sintered body 121 on which the disk electrode 14 is formed, in which FIG. 4A is a plan view and FIG. 4B is a cross-sectional view taken along the line CC. 5A and 5B are explanatory views of the alumina sintered body 122 in which the ring electrode 16 is formed, in which FIG. 5A is a plan view and FIG. 5B is a DD cross-sectional view. FIG. 6 is an assembly process diagram for assembling the electrode built-in ceramic component 10.

  First, alumina powder with a purity of 99.5% was fired to a density of 99.5% or higher and ground to obtain a disc-shaped alumina sintered body 121 having an outer diameter of 350 mm and a thickness of 4 mm. Next, on the alumina sintered body 121, a disk conductive layer to be the disk electrode 14 is formed by screen printing using a paste obtained by mixing terpineol with a mixed powder of WC powder 83 wt% and alumina powder 17 wt%. did. The disk conductive layer was a circle with a diameter of 297 mm, and a small hole was formed at a required location. In the small hole portion, a pin for raising and lowering the wafer and a through hole for introducing gas are provided later. Next, this disk conductive layer was dried and heated at 600 ° C. for 2 hours in 1 atmosphere of nitrogen to decompose and disappear terpineol to form a disk electrode 14. Next, an outer peripheral tablet 20 made of a mixed sintered body of WC 50 wt% having a diameter of 3 mm and a thickness of 1 mm and 50 wt% of alumina is arranged at eight positions on the circumference of the PCD 292 mm of the disc electrode 14 at equal intervals. And glued with glue. A central tablet 19 made of the same mixed sintered body was placed at the center of the disk electrode 14 and adhered with glue. Thus, the alumina sintered body 121 (refer FIG. 4) which formed the center tablet 19 and the outer periphery tablet 20 on the disk electrode 14 was obtained. The alumina sintered body 121 of FIG. 4 was placed in a mold, and alumina powder with a purity of 99% or more was filled on the surface on which the disc electrode 14 was formed, and the thickness was 3 mm, and uniaxial pressure molding was performed. Thus, the 1st intermediate body 101 (refer FIG. 6) which laminated | stacked the alumina molded object 130 on the alumina sintered compact 121 was obtained.

  Next, a disc-shaped alumina sintered body 122 having an outer diameter of 350 mm and a thickness of 4 mm was separately prepared, and a ring conductive layer to be the ring electrode 16 was formed thereon by using the same printing paste as that of the disc conductive layer. The ring conductive layer was a flat plate ring having an inner diameter of 296 mm and an outer diameter of 334 mm, and had a total of eight protrusions protruding radially inward at every 45 ° of the inner circumference. This ring conductive layer was subjected to the same heat treatment as that of the disk conductive layer to form a ring electrode 16 to obtain a second intermediate 102 (see FIG. 5). The protrusion 16a of the ring electrode 16 has a substantially semicircular shape with a circle diameter of 8 mm, and the PCD connecting the center point of the semicircle of the protrusion 16a is 292 mm, which corresponds to the arrangement position of the outer peripheral tablet 20 of the first intermediate body 101. I tried to do it.

Next, the ring electrode 16 of the second intermediate body 102 is in contact with the alumina molded body 130 of the first intermediate body 101, and the position of the outer peripheral tablet 20 installed on the disk electrode 14 and the protrusion 16 a of the ring electrode 16 are arranged. The layers were stacked so that the positions of the two coincided (see FIG. 6A). Specifically, the first intermediate body 101 is marked in advance on the outer peripheral surface so that the position of the outer peripheral tablet 20 is known, and the second intermediate body 102 is known so that the position of the protrusion 16a of the ring electrode 16 is known. The outer peripheral surface was marked in advance and laminated so that the respective marks coincided. Then, the laminated intermediates 101 and 102 are placed in a graphite die of a hot press furnace and heated for 2 hours by a hot press method at a nitrogen temperature of 1550 ° C. and a uniaxial pressure of 200 kg / cm ² in 1.02 atm. Baked. In this way, an alumina ceramic substrate 12 in which the disk electrode 14 and the ring electrode 16 were embedded was obtained (see FIG. 6B).

  The ceramic substrate 12 was ground so that the diameter of the wafer mounting surface 12a was 299 mm, the height of the outer peripheral step portion was 2 mm, the outer diameter of the outer step portion was 338 mm, and the total thickness was 5.5 mm (see FIG. 6 (c)). At this time, the disk electrode 14 was positioned at a depth of 0.4 mm from the wafer mounting surface 12a, and the ring electrode 16 was positioned at a depth of 0.4 mm from the step surface. Incidentally, the diameter of the wafer mounting surface 12a is smaller than the diameter of 300 mm of the wafer W to be mounted thereon.

  Next, countersink holes 21 having a diameter of 5 mm were formed in the thickness direction from the center of the back surface 12 b of the ceramic substrate 12 until reaching the central tablet 19 of the disk electrode 14. In addition, a countersink hole 22 having a diameter of 2 mm and a depth of 4.2 mm from the back surface 12 b passes through the protrusion 16 a of the embedded ring electrode 16 at a position corresponding to eight PCD 292 mm positions of the protrusion 16 a of the ring electrode 16, The outer peripheral tablet 20 installed on the disk electrode 14 was drilled so that the bottom of the countersink hole 22 could reach (see FIG. 6D). The positions where the counterbores 21 and 22 were drilled were previously confirmed by X-ray transmission photography.

  Next, Ni plating with a thickness of 4 μm was applied from the surface of the outer peripheral tablet 20 (that is, the bottom surface of the counterbore 22) to a height of 2 mm. First, as a pretreatment, the back surface 12b of the ceramic substrate 12 was turned up, a tin chloride solution was injected into the countersink hole 22 from the back surface 12b to a position of 2.2 mm, held for 2 to 3 minutes, and then discharged. Next, the same amount of Pt solution was added and discharged after 2-3 minutes. Further, the entire ceramic substrate 12 is heated to 70 ° C., an electroless Ni plating solution is injected into the countersink hole 22 at 70 ° C. and held for 10 minutes, then the plating solution is discharged, and the inside of the countersink hole is washed with water and dried. The bottomed cylindrical plating layer 24 was formed in the counterbore 22 (see FIG. 6E). The plated layer 24 had a bottom surface in contact with the outer peripheral tablet 20 and a side surface in contact with the protrusion 16 a of the ring electrode 16. Here, the tin chloride solution is a Sensitizer (trade name) manufactured by Okuno Pharmaceutical Co., Ltd., the Pt solution is an activator (trade name) manufactured by the same company, and the Ni plating solution is a top chemialloy (trade name) manufactured by the same company. Was used.

  Next, an external connection power supply terminal 18 made of Ti was joined to the counterbore hole 21 opened in the center of the ceramic substrate 12 by In solder bonding. The temperature of In solder bonding was 200 ° C. Finally, a cylindrical alumina plug 26 having a diameter of 1.8 mm and a length of 4.1 mm is inserted into the countersink hole 22 with silicone adhesive applied to the surface, and the adhesive is cured to countersink. The hole 22 was sealed airtight. The electrode built-in ceramic component 10 was completed as described above (see FIG. 6F).

[Example 2]
A ceramic part 10 with a built-in electrode was produced in the same manner as in Example 1 except that a carbon thin film was formed on the inner surface of the plated layer 24 of the counter bore 22. Specifically, Ni plating is applied to the counterbore 22 to form a plating layer 24, and then a conductive carbon paste is applied to the inner surface of the plating layer 24 and dried by heating to 120 ° C. It was 1 to 0.2 mm. The plug 26 inserted into the countersink hole 22 was made by grinding the diameter of the 2.5 mm long portion near the bottom of the countersink hole 22 to 1.5 mm to make it thinner.

[Example 3]
An aluminum nitride powder having a purity of 99.5% was filled in a mold and press-molded to obtain an aluminum nitride molded body having an outer diameter of 350 mm and a thickness of 5 mm. Next, a disc electrode 14 having a diameter of 297 mm was cut out from a mesh sheet made of Mo (a material made by braiding metal fine wires into a wire mesh shape). As in the first embodiment, the outer peripheral tablet 20 is glued to the disc electrode 14 at eight equal intervals on the circumference of the PCD of 292 mm, and the central tablet 19 is glued to the central position (to which the external connection terminal is connected). Glued. Each tablet 19 and 20 was made of Mo having a diameter of 3 mm and a thickness of 1 mm.

  On the aluminum nitride molded body, the disc electrode 14 was placed so that the center thereof overlapped with the center of the molded body and the tablets 19 and 20 were on the upper side. After further filling with aluminum nitride powder, press molding was performed.

  On the other hand, as the ring electrode 16, a flat plate ring having an inner diameter of 296 mm and an outer diameter of 334 mm was cut from the Mo mesh sheet so as to have a total of eight protrusions 16a projecting radially inwardly at every 45 °. The protrusion 16a is a semicircle with a circle diameter of 8 mm, and the PCD connecting the center points of the semicircles of the protrusion 16a is 292 mm.

Then, the ring electrode 16 is placed on the compact obtained by press molding, and the aluminum nitride powder is placed on the compact on which the ring electrode 16 is placed, and uniaxially pressed in the mold. Thus, a molded body in which the disk electrode 14 and the ring electrode 16 were embedded was produced. The formed body was hot-press fired under the conditions of nitrogen at 1.02 atm, temperature of 1750 ° C., and pressure of 200 kg / cm ² to obtain an aluminum nitride sintered body.

  This aluminum nitride sintered body was ground so as to have the same dimensions as in Example 1. However, the disk electrode 14 was positioned at a depth of 1.0 mm from the wafer mounting surface, and the ring electrode 16 was positioned at a depth of 1.0 mm from the step surface. Next, in order to connect the disk electrode 14 and the ring electrode 16 in the same manner as in Example 1, countersink holes 21 and 22 and a plating layer 24 were formed, and the countersink hole 22 was closed with a plug 26. However, the counterbore hole 22 had a depth of 3.6 mm. The plug 26 inserted into the counterbore hole 22 was an aluminum nitride rod. Further, the power supply terminal 18 is made of Ni. The electrode built-in ceramic component 10 was produced by the same method as in Example 1 except for the above.

[Example 4]
An electrode built-in ceramic component 10 was produced in the same manner as in Example 3 except that a carbon thin film was formed on the inner surface of the plated layer 24 of the counterbore 22. Since the specific method for forming the carbon thin film is the same as that in Example 2, the description thereof is omitted here.

[Comparative Example 1]
The electrode built-in ceramic part of FIG. 7 was made of aluminum nitride. The production method is the same as in Example 3, but a spring produced by folding a strip-shaped Mo mesh in place of the Mo tablet was used. When filling the aluminum nitride powder thereafter, care was taken that the tip of the spring appeared on the surface of the powder when leveling the filled powder. The external dimensions of the produced electrode-embedded ceramic part are the same as in Example 3. However, the power supply terminal was not formed at the center of the ceramic part with a built-in electrode, but was formed by drilling countersink holes at two locations of the ring electrode.

[Evaluation]
Each of the produced electrode-containing ceramic parts was joined to an Al cooling board having a diameter of 338 mm using a silicone joining sheet and placed in a semiconductor process chamber for evaluation. And the wafer for temperature measurement was installed in the wafer mounting surface. The temperature measuring wafer can measure the temperature of 28 points in the surface and transmit data to an external receiver wirelessly. Next, the inside of the chamber was decompressed and replaced with Ar, and the atmosphere was set to 70 Pa.

A DC adsorption voltage V (V) was applied to the power supply terminal while a 20 ° C. refrigerant was passed through the cooling board to adsorb the wafer. After that, a high frequency voltage was applied to the power supply terminal, and plasma was generated between the parallel plate electrodes composed of the opposed plate electrode installed in the upper part of the chamber and the embedded electrode (disk electrode and ring electrode) of the ceramic component with built-in electrode. . A high frequency voltage was applied for 2 minutes, and the temperature distribution of the temperature measuring wafer immediately after the application was stopped was measured. The difference ΔT between the maximum value and the minimum value of the entire temperature distribution, and the difference ΔTxxx between the maximum value and the minimum value on concentric circles with different diameters (xxx is the diameter (unit: mm) of the circle at the measurement point) Table 1 shows. The temperature distribution is measured here because there is a strong correlation between the temperature distribution and the etching rate, and if there is a distribution in the heat input from the plasma, the temperature distribution is obtained. This is because it can be seen how uniform plasma is generated.

Since Examples 1 and 2 function as a Coulomb type electrostatic chuck, it is necessary to increase the applied adsorption voltage V. On the other hand, since Examples 3 and 4 and Comparative Example 1 function as a Johnson-Rahbek type electrostatic chuck, the applied adsorption voltage may be relatively small. As is apparent from Table 1, in Examples 1 to 4, the temperature distribution ΔT is small and uniform plasma can be generated regardless of whether the electrostatic chuck is a Coulomb type or a Johnson-Rahbek type. . In particular, ΔT on the concentric circles is small and it can be seen that there is no bias in the plasma. On the other hand, in Comparative Example 1, the temperature distribution is poor and the plasma is not generated so as to have rotational symmetry. This is presumably because the power feeding terminal is not at the center, and there are variations in the position of the spring connecting the disk electrode and the ring electrode and poor conduction.

  Next, the high frequency power to be applied was increased, and the temperature distribution measurement was performed in the same manner. Even when the high frequency power is high, the temperature distributions of Examples 2 and 4 in which the carbon paste is applied on the Ni plating are hardly deteriorated. This is because the resistance at the connection between the disk electrode and the ring electrode is sufficiently low, so that the high frequency power is sufficiently transmitted to the ring electrode, and the plasma on the ring electrode is stably generated, and the plasma is close to the plasma on the disk electrode. This is thought to be due to the density.

DESCRIPTION OF SYMBOLS 10 Electrode built-in ceramic component, 12 Ceramic base | substrate, 12a Wafer mounting surface, 12b Back surface, 12c Small diameter part, 12d Large diameter part, 14 Disk electrode, 16 Ring electrode, 16a Protrusion, 18 Feeding terminal, 18a Plug, 19 Center Tablet, 20 outer peripheral tablet, 21 countersink hole, 22 countersink hole, 24 plated layer, 26 plug, 101 first intermediate, 102 second intermediate, 121 alumina sintered body, 122 alumina sintered body, 130 alumina molding Body, 212 ceramic substrate, 214 disk electrode, 216 ring electrode, 224 spring.

Claims (5)

A disc electrode and a ring electrode are incorporated in a ceramic base so as to be coaxial with each other in a thickness direction, and a wafer placement surface on which a wafer to be subjected to plasma treatment is placed is provided close to the disc electrode. A ceramic part with a built-in electrode,
A power supply terminal provided so as to be in contact with the center of the disk electrode from the center of the surface of the ceramic substrate opposite to the wafer mounting surface;
Conductive tablets arranged at equal intervals on the circumference of a predetermined radius from the center of the disk electrode on the surface of the disk electrode facing the ring electrode;
A countersink hole reaching the tablet through the ring electrode from the surface opposite to the wafer mounting surface of the ceramic substrate;
A bottomed cylindrical plating layer that is formed inside the counterbore, has a bottom surface in contact with the tablet, and a side surface in contact with the ring electrode;
A plug made of the same material as the ceramic base, plugging the countersink hole in which the plating layer is formed;
Ceramic parts with built-in electrodes. The plating layer is a Ni plating layer.
The ceramic part with a built-in electrode according to claim 1. The plating layer has a carbon thin film formed on the inner surface.
The ceramic part with a built-in electrode according to claim 1 or 2. The ceramic substrate is formed of alumina;
The disk electrode and the ring electrode are formed of a mixed sintered body of WC and alumina or a mixed sintered body of NbC and alumina,
The tablet is formed of a mixed sintered body of at least one powder selected from the group consisting of Pt powder, Nb powder and NbC powder and alumina powder or a mixed sintered body of WC powder and alumina powder.
The ceramic part with a built-in electrode according to any one of claims 1 to 3. The ceramic substrate is formed of aluminum nitride;
The disk electrode and the ring electrode are formed of Mo mesh,
The tablet is made of Mo,
The ceramic part with a built-in electrode according to any one of claims 1 to 3.

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