JP2019075585A - Wafer holder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable wafer holder which is less likely to be damaged due to a difference in thermal expansion. SOLUTION: A substrate 11 made of substantially disk-shaped ceramics having a wafer mounting surface 11a on the upper surface side, an RF electrode 12 embedded inside the substrate 11, for example, and inserted from the lower surface side of the substrate 11. A wafer holder 10 having a metal terminal 13 and a connection terminal 14 for electrically conducting the RF electrode 12 and the metal terminal 13 to each other. The connection terminal 14 is preferably made of the same material as the base 11. It is composed of a conical ceramic member 14a and a metal layer 14b that covers the entire side surface thereof. The upper end of the metal layer 14b is connected to the RF electrode 12, and the lower end of the metal layer 14b is a metal terminal 13. Is connected to the metal member 16 via a metal member 16. [Selection diagram] Fig. 1

Description

  The present invention relates to a ceramic wafer holder mounted on a semiconductor manufacturing apparatus.

  In the process of manufacturing a semiconductor device such as an IC, various processes such as film formation and etching are performed on a semiconductor substrate (wafer) which is an object to be processed. In a semiconductor manufacturing apparatus that performs various types of processing on such a semiconductor substrate, a wafer holder called a susceptor that holds the semiconductor substrate during processing is mounted. Inside the wafer holder, a heater electrode is provided for heating the semiconductor substrate during the above-described processing. In addition, an electrode for electrostatic chuck may be provided on the mounting surface of the wafer holder or the RF electrode for setting the upper part of the semiconductor substrate to a plasma atmosphere at the time of film formation.

  For example, Patent Document 1 discloses a susceptor including a ceramic member in which a conductive member corresponding to a heater electrode for heating or the like is embedded. The ceramic member is provided with a counterbore, and a metal member is disposed inside the counterbore in order to supply power to the conductive member exposed at the bottom of the counterbore. This metal member is joined to the conductive member using an active metal brazing material (hereinafter also referred to as brazing material), and the desired bonding strength can be obtained by controlling the "flowability" of the brazing material to the metal member. It is stated that it can be obtained.

  Further, in Patent Document 2, a screw hole is provided on the lower surface side of a disk-shaped ceramic base having an electric circuit inside to expose the electric circuit, and a metal terminal (an anchor member) is screwed into the screw hole. A ceramic susceptor has been proposed in which one end is connected to an electric circuit and the other end is connected to a conductive member for feeding. The susceptor is said to provide high bonding strength and ensure good electrical connection with the electrical circuit.

  Further, Patent Document 3 discloses a technique for connecting, via a connection terminal, a metal terminal inserted from the lower surface side of a wafer holder to an electrode embedded in a ceramic wafer holder. The connection terminal is formed by metallizing the surface of a ceramic member made of the same material as that of the wafer holder, and the embedded electrode can be electrically conducted to the metal terminal by metallizing the surface. In addition, it is described that it is possible to make the wafer holder thin because there is almost no difference in thermal expansion between the connection terminal and the wafer holder.

Japanese Patent Application Laid-Open No. 10-273371 Japanese Patent Application Publication No. 2003-086663 Patent No. 4858319

  In recent years, with the advancement of the performance of electronic devices, it is required in the semiconductor device manufacturing process to carry out film formation processing at an even higher temperature and to carry out film formation by plasma efficiently by raising the voltage applied to the RF electrode. It is done. Therefore, in the wafer holder as described above, there is a need for a structure that can supply power more reliably to the embedded heater electrode or the RF electrode without causing problems such as breakage due to the thermal expansion difference.

  The present invention has been made in view of such a situation, and in a ceramic wafer holder having a heater circuit, an RF electrode, etc. inside, the power supply to the heater circuit, the RF electrode, etc. is ensured from the outside. In addition, it is an object of the present invention to provide a highly reliable wafer holder which is less likely to be damaged due to a thermal expansion difference in the feeding portion.

  In order to achieve the above object, a wafer holder provided by the present invention comprises a substantially disc-shaped ceramic base provided with a wafer mounting surface on the upper surface side, an electrode embedded inside the base, and A wafer holder having a metal terminal inserted from the lower surface side of a base and a connection terminal electrically connecting the electrodes and the metal terminal to each other, wherein the connection terminal is a ceramic member made of the same material as the base And a metal layer covering the entire side surface, the upper end of the metal layer is connected to the electrode, and the lower end of the metal layer is connected to the metal terminal through a metal member. There is.

  According to the present invention, power can be reliably supplied to an electrode embedded inside a ceramic base without causing damage due to a thermal expansion difference.

It is a typical fragmentary longitudinal cross-sectional view which shows the 1st example of the wafer support body which concerns on this invention. It is a typical fragmentary longitudinal cross-sectional view which shows the 2nd specific example of the wafer support body which concerns on this invention. It is a typical fragmentary longitudinal cross-sectional view showing the 3rd example of a wafer support concerning the present invention. It is a typical fragmentary longitudinal cross-sectional view which shows the 4th example of the wafer support body which concerns on this invention.

  First, embodiments of the present invention will be listed and described. The wafer holder according to the embodiment of the present invention includes a substantially disc-shaped ceramic base provided with a wafer mounting surface on the upper surface side, an electrode embedded inside the base, and insertion from the lower surface side of the base A wafer holder having a metal terminal and a connection terminal electrically connecting the electrode and the metal terminal to each other, wherein the connection terminal is a ceramic member made of the same material as the base, and the entire side surface The upper end of the metal layer is connected to the electrode, and the lower end of the metal layer is connected to the metal terminal through a metal member. This makes it possible to reliably feed power to the electrode embedded inside the ceramic base without causing damage due to the thermal expansion difference.

  The wafer holder of the embodiment of the present invention may have a structure in which the metal terminal is screwed to the base, or a structure in which the metal terminal is screwed to the metal member. In the case of the former structure, the metal terminal can be securely fixed with a simple structure. On the other hand, in the latter case, the contact area between the metal terminal and the metal member is increased, so that it is possible to realize even lower resistance.

  In the wafer holder of the embodiment of the present invention, preferably, the ceramic member of the connection terminal has a frusto-conical shape. This makes it possible to easily bring the connection terminal into close contact with the substrate without any gap when the wafer holder is manufactured. In addition, since the connection terminal can be prevented from moving toward the wafer mounting surface, a portion of the ceramic base which is located above the electrode fed via the connection terminal is the connection. It is possible to prevent the occurrence of troubles such as cracking and warping by being pressed by the terminal.

  In the wafer holder of the embodiment of the present invention, the electrode may be an RF plasma forming electrode, a heater electrode, or an electrostatic chuck electrode. Even if the electrode is any of these, the various effects described above can be obtained.

   Next, a wafer holder 10 according to a first embodiment of the present invention will be described with reference to FIG. The wafer holder 10 according to the first embodiment of the present invention has a substantially disk-shaped base provided on its upper surface with a wafer mounting surface 11a on which a semiconductor wafer (not shown) to be treated is mounted. 11, an RF electrode 12 embedded inside the base 11, a metal terminal 13 inserted from the lower surface side of the base 11, and a connection terminal 14 for electrically conducting the RF electrode 12 and the metal terminal 13 to each other. And.

  Specifically describing each component, the base 11 is a member generally supported horizontally from the bottom by a cylindrical support member, and the material of the base 11 is aluminum nitride, silicon nitride, silicon carbide, or oxide. It is preferable to use a ceramic excellent in rigidity and thermal conductivity such as aluminum, and aluminum nitride is more preferable.

  In the inside of the base 11, an RF electrode 12 is embedded on a surface parallel to the wafer mounting surface 11a for forming a plasma atmosphere above the wafer mounting surface 11a at the time of film formation. In order to feed power to the RF electrode 12 or to ground it, a metal terminal 13 is inserted to the lower surface side of the base 11 in a state in which the lower end portion is protruded. At least the outside of the upper end of the metal terminal 13 is screwed, and the metal terminal 13 is screwed into the screw hole of the base 11 into which the metal terminal 13 is screwed. A conductive wire (not shown) is connected to the lower end portion of the protruding metal terminal 13. A heater electrode 15 for heating a semiconductor wafer mounted on the wafer mounting surface 11 a is embedded in the base 11 at a distance lower than the RF electrode 12. The power supply to the heater electrode 15 may be the same as that of the RF electrode 12 or may be a general terminal structure, so the description thereof will be omitted.

  In the inside of the base 11, a connection terminal 14 is further embedded, which is formed of a truncated conical ceramic member 14a made of the same material as the base 11 and a metal layer 14b covering the entire side surface. The connection terminal 14 is embedded with its central axis directed in the thickness direction of the base 11, and the tapered end face end face abuts on the lower side of the RF electrode 12 and the lower end face opposite thereto. The end face is in contact with the upper end face of the metal terminal 13 via the disc-shaped metal member 16.

  As described above, when the ceramic member 14a is formed of the same material as the base 11, a thermal expansion difference hardly occurs over a wide temperature range, so that thermal stress is hardly generated between the connection terminal 14 and the periphery thereof. Even if the substrate 11 has a thin plate thickness, breakage such as cracks is less likely to occur. The shape of the ceramic member 14a may be a cylindrical shape, a prismatic shape, a columnar shape with a reduced or enlarged diameter at the middle portion, a truncated pyramid shape, etc., but a more reliable connection terminal structure can be easily manufactured. The truncated cone shape described above is most preferred.

  The materials of the metal layer 14b and the metal member 16 described above and the materials of the RF electrode 12 and the heater electrode 15 described above are preferably tungsten (W), molybdenum (Mo), or an alloy of these, except for unavoidable impurities. All of these metals have a relatively small difference in thermal expansion coefficient from that of the ceramic forming the substrate 11, and can suppress the occurrence of defects such as warping or cracking of the wafer holder. Further, the material of the metal terminal 13 is selected from the group consisting of tungsten, molybdenum, and alloys thereof, nickel, kovar, copper-tungsten alloy, copper-molybdenum alloy, copper-nickel-iron-tungsten alloy except for unavoidable impurities. At least one of the above is preferred.

  The disk-shaped metal member 16 in contact with the lower end side end face of the connection terminal 14 has an outer diameter larger than the outer diameter of the lower end side end face of the connection terminal 14. Thus, the annular upper end of the metal layer 14b of the connection terminal 14 abuts the RF electrode 12 over the entire circumference, and the annular lower end also abuts the metal member 16 over the entire circumference. it can. Therefore, the upper end portion of the metal terminal 13 and the RF electrode 12 can be electrically conducted more reliably than the conventional feeding terminal, and troubles such as local generation of Joule heat are less likely to occur at the time of feeding. The shape of the metal member 16 is not limited to the disk shape as long as the annular lower end portion of the metal layer 14b can abut on the entire circumference, and is a polygonal plate-like member, an annular member or the like. It may be.

  The above-described wafer holder can be manufactured, for example, by the following method. That is, first, three ceramic substrates made of the same material and having the same outer diameter are prepared, and through holes are provided at the positions where the connection terminals 14 described above are embedded in one of the substrates. The through hole has a tapered structure in which the inner diameter gradually decreases toward the wafer mounting surface 11a. Then, a truncated conical ceramic member having a tapered structure fitted to the through hole and made of the same material as the ceramic substrate is prepared, and the side surface is a metal layer having substantially the same thickness over the entire periphery. cover.

  As a method of covering the side surface of the ceramic member with a metal layer, for example, a tungsten layer having a thickness of about 10 to 50 μm may be coated by a metallizing method of applying and baking tungsten paste. A sleeve-like member made of tungsten and having a thickness of about 50 μm to 2 mm may be separately prepared and attached to the side surface of the ceramic member. By inserting the ceramic member covered with the metal layer into the through hole of the substrate and bringing the ceramic member into close contact with the substrate more reliably, almost no gap exists in the peripheral portion of the ceramic member covered with the metal layer. It can prevent entry.

  The upper end and the lower end of the metal layer are annularly exposed on the front and back surfaces of the ceramic substrate, respectively. A patterned layer of tungsten paste, for example, is applied by screen printing to form RF electrodes and heater electrodes on the front and back surfaces of the ceramic substrate. After coating, the patterning layer is dried, degreased in a nitrogen atmosphere at about 800 ° C., and the remaining two substrates are superposed on the front and back surfaces, respectively, and hot pressed in a nitrogen atmosphere at about 1800 ° C. As a result, a disk-shaped combined body in which three ceramic substrates are integrated is obtained.

  Next, a counterbore hole having an inner diameter that fits the metal terminal from the lower surface side of the disc-like combination toward the ceramic member is formed, and the lower end of the ceramic member is exposed together with the metal layer covering the side surface Let Then, a metal member is joined to the exposed metal layer and the lower end portion of the ceramic member by brazing or metallizing with tungsten preferably. Further, while screwing in the metal terminal whose tip is screwed into the counterbore hole, the tip end face is brought into contact with the lower end face of the metal member. Thus, the wafer holder is completed.

  Next, a wafer holder according to a second embodiment of the present invention will be described. As shown in FIG. 2, in the wafer holder 20 according to the second embodiment of the present invention, the metal terminal 23 and the substrate 21 are not screwed together, and instead, the metal terminal 23 and the metal member 26 are formed. It is characterized in that it is screwed to each other, and basically has the same structure as the wafer holder 10 of the first embodiment of the present invention described above.

  Specifically, a substantially disk-shaped base 21 made of, for example, aluminum nitride, having a wafer mounting surface 21 a on the upper surface side, an RF electrode 22 embedded inside the base 21, and a lower surface side of the base 21. It has a metal terminal 23 inserted, a connection terminal 24 for electrically connecting the RF electrode 22 and the metal terminal 23 to each other, and a heater electrode 25 embedded below the RF electrode 22 with a space therebetween. ing. The connection terminal 24 is composed of a frusto-conical ceramic member 24 a made of the same material as the base 21 and a metal layer 24 b covering the entire side surface, and its tapered tip end face is under the RF electrode 22. The lower end side end face on the opposite side is in electrical contact with the upper end face of the metal terminal 23 through the disc-shaped metal member 26 while being in contact with the side.

  In order to screw the metal terminal 23 and the metal member 26 together, as shown in FIG. 2, a male screw portion protruding downward is provided on the lower surface of the metal member 26, and a female screw to be screwed thereto is formed. In addition to providing an externally threaded male screw projecting upward at the tip of the metal member, the female screw may be provided on the lower surface side of the metal member. . In either case, the contact area between the metal terminal and the metal member is increased, so that lower resistance can be realized.

  Next, a wafer holder according to a third embodiment of the present invention will be described. As shown in FIG. 3A, in the wafer holder 30 of the third embodiment of the present invention, the inner diameter of the screw hole is made by providing a step in the screw hole of the substrate 31 into which the metal terminal 33 is inserted. The cylindrical sealing member 37 is covered with the large diameter portion so as to surround the metal terminal 33. The space between the annular tip end of the sealing member 37 and the step of the screw hole is sealed with a glass 38. As a result, it is possible to prevent the atmosphere or the atmosphere gas from invading the screwed portion between the metal terminal 33 and the substrate 31 and thereby preventing adverse effects such as corrosion.

  The wafer holder of the third embodiment of the present invention is basically the same as the wafer holder 10 of the first embodiment of the present invention except for the cylindrical sealing member 37 and the glass 38 described above. It has a structure. Specifically, a substantially disk-shaped base 31 made of, for example, aluminum nitride, having a wafer mounting surface 31 a on the upper surface side, an RF electrode 32 embedded inside the base 31, and a lower surface side of the base 31 It has a metal terminal 33 inserted, a connection terminal 34 electrically connecting the RF electrode 32 and the metal terminal 33 to each other, and a heater electrode 35 embedded below the RF electrode 32 so as to be separated therefrom. ing. The connection terminal 34 is composed of a frusto-conical ceramic member 34 a made of the same material as that of the base body 31 and a metal layer 34 b covering the entire side surface thereof. The lower end side end face on the opposite side is electrically connected to the upper end face of the metal terminal 33 through the disc-like metal member 36 while being in contact with the side.

  The cylindrical sealing member and the sealing with glass may be applied to the power supply terminal structure of the wafer holder 130 of the second specific example as described above as shown in FIG. Further, as shown in the wafer holder 230 of FIG. 3C, a flange portion 233a is formed at the position of the step portion of the screw hole of the substrate 231 in the metal terminal 233, and the lower surface side of the flange portion 233a and the screw hole The distal end surface of the cylindrical sealing member 37 may be opposed to the step surface, and the opposite portion may be filled with the glass 38. In this case, since the sealing surface by the glass 38 is perpendicular to the pressing direction of the cylindrical sealing member 37, it is possible to seal more reliably.

  Thus, when forming a flange part in a metal terminal and sealing, it is especially preferable to apply to the electric power feeding terminal structure of the above-mentioned 2nd example. The reason is that, as can be seen by comparing the wafer holder 330 of FIG. 3 (d) applied to the second example with the wafer holder 230 of FIG. 3 (c) described above, Since the separation distance L2 between the tip of the metal terminal 333 fixed to the substrate and its flange portion 333a can be shorter than the separation distance L1 in the case of the wafer holder 230, between the substrate and metal terminal of different materials This is because the influence of the thermal expansion difference can be reduced.

  Next, a wafer holder according to a fourth embodiment of the present invention will be described. As shown in FIG. 4 (a), the wafer holder 40 according to the fourth embodiment of the present invention includes the sealing member 47 on the top of a cylindrical sealing member 47 externally fitted to the metal terminal 43. An annular member 49 of substantially the same diameter is provided. The glass 48 is filled between the sealing member 47 and the annular member 49, and the glass is not filled between the annular member 49 and the step portion of the screw hole.

  The wafer holder of the fourth embodiment of the present invention is basically the wafer holder of the first embodiment of the present invention described above except for the cylindrical sealing member 47, the annular member 49 and the glass 48 described above. It has the same structure as that of No. 10. Specifically, a substantially disc-shaped base 41 made of, for example, aluminum nitride, having a wafer mounting surface 41 a on the upper surface side, an RF electrode 42 embedded in the base 41, and a lower surface side of the base 41 It has a metal terminal 43 inserted, a connection terminal 44 electrically connecting the RF electrode 42 and the metal terminal 43 to each other, and a heater electrode 45 embedded below the RF electrode 42 with a space therebetween. ing. The connection terminal 44 is composed of a frusto-conical ceramic member 44 a made of the same material as that of the base 41, and a metal layer 44 b covering the entire side surface thereof. The lower end side end face on the opposite side is in electrical contact with the upper end face of the metal terminal 43 via the disc-shaped metal member 46 while being in contact with the side.

  When glass is filled in a corner A such as a stepped portion of a screw hole of a ceramic substrate, stress may concentrate on the glass at the corner and a crack may occur, but as described above, the sealing member Since it is not necessary to fill the corner A with the glass by filling the glass between the and the annular member, it is possible to seal more reliably. In this case, it is more preferable to form the corner A of the stepped portion of the screw hole with a smooth curved surface. The wafer holders 140, 240 and 340 of FIGS. 4 (b) to 4 (d) correspond to the wafer holders 130, 230 and 330 of FIGS. 3 (b) to 3 (d) of the third example described above. In addition to the effects of the third embodiment of the present invention, the effects of the two-divided sealing members are obtained.

  Although the wafer holder of the present invention has been described by taking a plurality of specific examples, the present invention is not limited to these specific examples, and can be practiced in various aspects within the scope of the present invention. is there. For example, in the wafer holder of the above-described specific example, the electrodes (embedded electrodes) embedded in the inside are the RF electrode for plasma formation and the heater electrode, but instead of any of these electrodes or these electrodes In addition to at least one of the above, an electrostatic chucking electrode may be embedded, and the above-described power supply terminal structure may be applied to at least one of these electrodes.

  In order to confirm the effect of the present invention, the wafer holder of the first example of the present invention as shown in FIG. 1 was manufactured and operated. Specifically, first, three aluminum nitride (AlN) disks having an outer diameter of 330 mm and a thickness of 9 mm, 5 mm, and 9 mm, respectively, were prepared. Among these three sheets, a tapered through hole having an average inner diameter of 4 mm was provided in one ceramic plate having a thickness of 9 mm, and an aluminum nitride truncated cone having the same taper angle as this taper angle was prepared. After applying a tungsten paste to the side of this truncated cone, it was fired to provide a metal layer with a thickness of 0.03 mm.

  The truncated cone whose side surface is metallized is fitted and fixed in the through hole of the above-mentioned ceramic plate. Patterned layers of tungsten paste for RF electrode and heater electrode were respectively applied by screen printing on the front and back surfaces of the ceramic plate, and then fired to form electrodes. The above-described 5 mm ceramic plate was superimposed on the RF electrode side of the ceramic plate having electrodes formed on the front and back surfaces, and the 9 mm ceramic plate was superimposed on the heater electrode side on the opposite side. In this state, the three ceramic plates were integrated by hot pressing.

  Next, a counterbore hole was machined from the lower surface side of the integrated substrate toward the truncated cone, and the lower end of the truncated cone was exposed together with the metal layer on the side surface. Then, using tungsten paste, a tungsten disc having an outer diameter of 5.0 mm and a thickness of 1 mm was bonded to the exposed metal layer and the lower end portion of the truncated cone. Then, while the tungsten metal terminal having the tip portion screwed into it was screwed into the counterbore, the tip surface was brought into contact with the lower end surface of the tungsten disk. In addition, after making a screw hole from the lower surface side and exposing the heater electrode, it was made to connect by screwing the metal terminal made from tungsten into this screw hole.

  A cylindrical support was attached to the lower surface of the wafer holder manufactured as described above, and was installed in a vacuum chamber of a semiconductor manufacturing apparatus. Further, a conductive wire was connected to the inside of the cylindrical support portion to a metal terminal protruding from the lower surface of the wafer holder. Then, after feeding the conductive wire for the heater electrode in a vacuum atmosphere to raise the temperature of the wafer holder to 550 ° C., the conductive wire for the RF electrode is maintained at 550 ° C. by an alternating voltage of 1600 W and 13.56 MHz. ON (60 seconds) / OFF (30 seconds) were repeated 10,000 times. As a result, it was possible to operate satisfactorily without problems such as overheating and cracking.

10, 20, 30, 40 Wafer holders 11, 21, 31, 41 Substrates 11a, 21a, 31a, 41a Wafer mounting surfaces 12, 22, 32, 42 RF electrodes 13, 23, 33, 43 Metal terminals 14, 24 , 34, 44 connection terminals 14a, 24a, 34a, 44a ceramic members 14b, 24b, 34b, 44b metal layers 15, 25, 35, 45 heater electrodes 16, 26, 36, 46 metal members 37, 47 sealing members 38, Reference Signs List 48 glass 49 annular member 130, 230, 330 wafer holder 140, 240, 340 wafer holder 233, 333 metal terminal 233a, 333a flange portion A corner portion

Claims (4)

A substantially disk-shaped ceramic base having a wafer mounting surface on the upper surface side, an electrode embedded inside the base, a metal terminal inserted from the lower surface side of the base, and the electrode and the metal terminal And a connection terminal electrically connecting the two with each other,
The connection terminal comprises a ceramic member of the same material as the base and a metal layer covering the entire side surface, the upper end of the metal layer is connected to the electrode, and the lower end of the metal layer Is a wafer holder connected to the metal terminal through a metal member.   The wafer holder according to claim 1, wherein the metal terminal is screwed to the base or the metal member.   The wafer holder according to claim 1, wherein the ceramic member has a frusto-conical shape.   The wafer holder according to any one of claims 1 to 3, wherein the electrode is an RF plasma formation electrode, a heater electrode, or an electrostatic chuck electrode.

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