JP4858319B2 - Wafer holder electrode connection structure - Google Patents

Description

  The present invention relates to a wafer holder used for a semiconductor manufacturing apparatus and its susceptor, and more particularly to electrode connection of a ceramic wafer holder having high reliability.

  Conventionally, in a manufacturing process of a semiconductor device, a film forming process, an etching process, or the like is performed on a semiconductor substrate that is a processing target. In a processing apparatus that performs processing on such a substrate, a susceptor that is a wafer holder for holding a semiconductor substrate during processing is installed.

  As an example of such a conventional susceptor, for example, Japanese Patent Laid-Open No. 10-273371 discloses a susceptor including a ceramic member embedded with a conductive member corresponding to a heater circuit for heating. An opening is formed in the ceramic member, and a metal member for supplying electric power to the conductive member is disposed inside the opening. The conductive member and the metal member are bonded using an active metal brazing material (hereinafter also referred to as a brazing material), and a predetermined bonding strength is obtained by controlling the “flowability” of the brazing material with respect to the metal member. You can do that.

  As another example, Japanese Patent Laid-Open No. 11-012053 discloses a susceptor including a ceramic member in which a conductive member corresponding to a heater circuit or the like is embedded, and an opening is formed in the ceramic member. The thing in which the metal member for supplying electric power to an electroconductive member is arrange | positioned inside the opening part is described. A conductive terminal is disposed on the bottom surface of the opening, and the conductive member and the metal member are electrically connected via the terminal.

  These metal members are fixed in the opening using a brazing material and are also connected to the terminals. In addition, in order to protect molybdenum (Mo) and a metal member containing molybdenum (Mo) from an oxidizing atmosphere such as air, an atmosphere protector is disposed inside the opening so as to surround the metal member. Japanese Patent Application Laid-Open No. 11-012053 describes that a metal member is protected from an oxidizing atmosphere by disposing such an atmosphere protector.

  On the other hand, in Japanese Patent Application Laid-Open No. 2003-086663, a screw hole is provided in a ceramic base material having an electric circuit, and a metal terminal (anchor member) is screwed into the screw hole to be connected to the electric circuit, and power is supplied to the metal terminal. There has been proposed a ceramic susceptor capable of connecting a conductive member to obtain a high bonding strength and ensuring electrical connection with an electric circuit.

JP-A-10-273371 Japanese Patent Laid-Open No. 11-012053 Japanese Patent Application Laid-Open No. 2003-086663

  In the susceptor described in the above Japanese Patent Application Laid-Open No. 10-273371 and Japanese Patent Application Laid-Open No. 11-012053, when a “retention” of brazing material occurs between the metal member and the ceramic member surface inside the opening, Due to the difference in thermal expansion coefficient between the brazing material and the ceramic constituting the ceramic member, cracks occur in the ceramic member after brazing or when a heat cycle test is performed on the susceptor.

  As a result, there is a problem that the reliability of the susceptor is lowered because the joint strength of the joint portion between the metal member and the ceramic member is lowered and the susceptor may be broken from the joint portion. In order to suppress the occurrence of cracks in the brazing portion, it is conceivable to reduce the amount of brazing material used, but in this case, there arises a problem that the bonding strength between the metal member and the ceramic member is lowered. As described above, it is possible to realize a susceptor as a highly reliable wafer holder by suppressing the occurrence of cracks and the like and at the same time realizing sufficient bonding strength at the bonding portion between the metal member and the ceramic member. It was difficult.

  As one of the countermeasures, a screw hole is provided in a ceramic substrate having an electric circuit and a metal terminal is screwed into the screw hole to be connected to the electric circuit as described in the above-mentioned JP-A-2003-086663. There is a ceramic susceptor in which a power supply conductive member is connected to a metal terminal. However, at present, there is a demand for further higher film formation temperature and higher efficiency of film formation by plasma. As a result, the portion on the electrode embedded in the ceramic substrate (upper ceramic substrate) is made thinner. There is a need to do that.

  Thus, when the upper ceramic substrate present on the embedded electrode in the ceramic substrate becomes thin, the heat generated by the heater and the heat generated by the plasma generates stress due to the difference in thermal expansion coefficient between the metal terminal and the ceramic substrate, There is a high possibility that the upper ceramic substrate will be damaged by being pressed by the metal terminal. In addition, when there is a very small gap between the metal terminal and the upper ceramic substrate, the ceramic substrate may be damaged by the entrance of plasma into the gap.

  The present invention has been made to solve such a conventional problem, and at the same time, it is possible to realize a sufficient bonding strength at a joint portion between a metal member and a ceramic member, and at the same time, breakage such as a crack. An object of the present invention is to provide a highly reliable wafer holder.

  In order to achieve the above object, an electrode connection structure of a wafer holder provided by the present invention is a connection structure for an electrode embedded in a ceramic wafer holder, and is made of a ceramic connection made of the same material as the wafer holder. A terminal is inserted in close contact with the inside of the wafer holder, and the ceramic connection terminal is subjected to surface metallization to ensure electrical continuity, and the surface metallization is connected to the buried electrode and at the same time a metal terminal It is electrically connected to.

  In the electrode connection structure of the wafer holder of the present invention, more specifically, the wafer holder is bonded to the ceramic substrate covering the buried electrode and the ceramic substrate on which the buried electrode is formed. And an upper ceramic substrate formed.

  In the electrode connection structure of the wafer holder, it is preferable that the ceramic connection terminal and the upper ceramic substrate are in close contact with each other and there is no gap between them. In addition, it is preferable that there is no gap between the ceramic substrate and the ceramic connection terminal. Therefore, the surface of the upper ceramic substrate that contacts the ceramic connection terminal is smaller than the diameter of the ceramic connection terminal. A metal layer that is large and electrically connected to the buried electrode is preferably formed.

  Further, in this electrode connection structure of the wafer holder, the ceramic connection terminal has the same thickness as the ceramic substrate and is inserted into a through hole of the ceramic substrate, and the surface of the ceramic connection terminal The metallization is preferably connected in the same plane as the buried electrode. The ceramic connection terminal is mechanically joined to the ceramic substrate and simultaneously electrically connected. Furthermore, it is preferable that the ceramic connection terminal and the metal terminal are electrically connected by a convex portion of the metal terminal.

  In the electrode connection structure of a wafer holder of the present invention, the ceramic wafer holder and the ceramic connection terminal include a ceramic containing at least one selected from the group consisting of aluminum nitride, silicon nitride, silicon carbide, and aluminum oxide. Preferably it consists of. Moreover, it is preferable that the said metal terminal and the said embedded electrode consist of at least 1 sort (s) chosen from the group which consists of tungsten, molybdenum, copper, and these alloys. Furthermore, the embedded electrode is preferably at least one selected from an RF plasma forming electrode, a heater electrode, and an electrostatic chuck electrode.

  According to the present invention, even if the upper ceramic substrate on the buried electrode is thinned, cracks due to heat generated by heat cycle or plasma are less likely to occur, and at the same time, conductivity with the buried electrode can be ensured, A ceramic wafer holder having high reliability can be provided.

  In the connection structure for the embedded electrode in the ceramic wafer holder according to the present invention, the ceramic connection terminal made of the same material as the wafer holder is inserted in close contact with the interior of the wafer holder, and the ceramic connection terminal is electrically connected to the ceramic connection terminal. Surface metallization is provided to ensure conduction. The surface metallization is connected to the buried electrode and at the same time is electrically connected to the metal terminal, and the metal terminal is further connected to the power supply conductive member.

  As a more specific aspect, the wafer holder may include a ceramic substrate having a buried electrode formed on the surface, and an upper ceramic substrate that covers the buried electrode and is bonded onto the ceramic substrate. The surface-metalized ceramic connection terminal is inserted into the through hole of the ceramic substrate and is electrically connected to the embedded electrode. At the same time, the surface-metalized ceramic connection terminal is connected to a metal terminal provided with a conductive member for power feeding.

  The ceramic connection terminal has the same thickness as the ceramic substrate, and is inserted into the through hole of the ceramic substrate so that the surfaces of the ceramic substrate and the ceramic substrate are flush with each other. Since the ceramic substrate and the ceramic connection terminal are made of the same ceramic material, there will be no step due to thermal expansion even at high temperatures, so the upper ceramic substrate will not be partially stressed and damaged even if the plate thickness is reduced. The possibility of doing is very small. In addition, the ceramic connection terminal and the upper ceramic substrate are in close contact with each other, and the gap between the two is eliminated, thereby preventing plasma from entering.

  The embedded electrode is formed in a state in which a ceramic connection terminal is inserted into a through hole of a ceramic substrate so that the surface is the same surface. Therefore, the surface metallization of the ceramic connection terminal is connected in the same plane as the embedded electrode, and it is difficult for a gap to be generated between the ceramic substrate and the ceramic connection terminal, thereby preventing plasma from entering. Further, in order to eliminate the gap between the ceramic substrate and the ceramic connection terminal and further prevent the entry of plasma, the surface of the upper ceramic substrate that is in contact with the ceramic connection terminal is larger than the diameter of the ceramic connection terminal and embedded. A metal layer electrically connected to the electrode can be formed.

  The ceramic substrate and the ceramic connection terminal are fixed by firing, but the shape of the ceramic connection terminal may be tapered in order to further strengthen the fixing force. In this case, the through hole provided in the ceramic substrate has a tapered hole shape in which the diameter on the upper ceramic substrate side is smaller than that on the opposite side so that the ceramic connection terminal does not move and pressurize toward the upper ceramic substrate.

  It is also effective to cut the screw only at the lower part of the ceramic connection terminal. In this case, due to the fixing force by screwing with the ceramic substrate, the stress on the upper ceramic substrate is reduced, and the possibility of breakage is reduced. Furthermore, it is desirable that the upper surface of the ceramic connection terminal has a dish shape so that the metallized surface of the ceramic substrate and the surface metallization of the ceramic connection terminal can be adjusted to be in the same plane.

  A ceramic substrate is bonded to the surface of the ceramic substrate opposite to the upper ceramic substrate. By providing a screw hole in the ceramic base and screwing a metal terminal into the screw hole, the metal terminal can be electrically connected to the ceramic connection terminal in the ceramic substrate.

  In this case, even if the plate thickness of the upper ceramic substrate is reduced, the ceramic connection terminal made of the same material has a thickness of 5 to 15 mm and is connected to the ceramic substrate, so that the metal terminal is screwed into the screw hole of the ceramic substrate. Even if this occurs, the possibility of damage to the upper ceramic substrate is very low. Further, by screwing the metal terminal into the screw hole of the ceramic substrate and mechanically bonding the metal terminal, the bonding strength of the joint between the metal terminal and the ceramic substrate can be sufficiently increased.

  As for the screw hole of the ceramic substrate into which the metal terminal is screwed, it is desirable to leave 1 to 3 mm of a portion where the screw is not cut. In this case, it is desirable that the metal terminal has a convex portion that is slightly longer than the length of the portion of the ceramic substrate that is not threaded. This convex part makes electrical connection between the ceramic connection terminal and the metal terminal, and even if the metal terminal expands, it does not pressurize the upper ceramic substrate excessively, and the damage rate of the upper ceramic substrate is greatly increased. Decrease.

  Furthermore, by attaching a power supply conductive member to the metal terminal, power can be reliably supplied from the power supply conductive member to the embedded electrode. The electrically conductive member for electric power feeding may have a convex part which contacts when connected to the metal terminal. In addition, the metal terminal and the power supply conductive member may be integrated.

  The electrical circuit for the embedded electrode is preferably formed by a metallization method using a screen printing method. Regarding the circuit pattern of the electrodes, an arbitrary pattern can be easily formed, and the degree of freedom in selecting the circuit pattern can be increased. Moreover, it is preferable that a part of the electrode circuit formed on the ceramic substrate wraps around to the side surface of the through hole into which the ceramic connection terminal is inserted. Thereby, it is possible to ensure conduction between the ceramic connection terminal, the buried electrode, and the metal terminal, and it is possible to reduce conduction resistance. Here, the electrode portion provided on the side surface of the through hole can be formed by, for example, a metallization method after applying a tungsten paste to a predetermined region.

  The embedded electrode and the metal layer are preferably at least one selected from the group consisting of tungsten (W), molybdenum (Mo), and alloys thereof. Tungsten, molybdenum, and alloys thereof are all materials having a relatively small difference in thermal expansion coefficient from the ceramics constituting the ceramic substrate and the ceramic substrate. Therefore, if an electrode is formed from these materials, it is possible to suppress the occurrence of defects such as warping of the ceramic substrate due to the presence of this electrode.

  The metal terminal and the conductive material for power supply are selected from the group consisting of tungsten, molybdenum and alloys thereof, nickel, kovar, copper-tungsten alloy, copper-molybdenum alloy, and copper-nickel-iron-tungsten alloy. At least one of them is preferred.

  The wafer holder, that is, the ceramic substrate, the upper ceramic substrate, and the ceramic substrate are preferably at least one selected from the group consisting of aluminum nitride, silicon nitride, silicon carbide, and aluminum oxide. The ceramic connection terminal is made of the same material as the wafer holder.

  The electrode (embedded electrode) embedded in the wafer holder is preferably at least one selected from the group consisting of an RF plasma forming electrode, a heater electrode, and an electrostatic chuck electrode.

  Hereinafter, an electrode connection structure of a wafer holder according to the present invention will be described in more detail with reference to the drawings. 1 and 2 are partially enlarged views of a ceramic wafer holder according to the present invention. The ceramic connection terminal 5b shown in FIG. 2 is an example in which a male screw is cut at the bottom of the ceramic connection terminal 5a in FIG. 1, and a female screw is cut into a part of the through hole of the ceramic substrate 3 and screwed together. By doing so, both can be mechanically fixed.

  In any of the wafer holders, ceramic connection terminals 5a and 5b, which are made of the same material as the ceramic substrate 3 and are subjected to surface metallization on the entire surface, are inserted into the through holes of the ceramic substrate 3. An electric circuit of the buried electrode 2 is formed on the same surface of the connection terminals 5a and 5b. An embedded electrode 2 is formed between the upper ceramic substrate 1 and the ceramic substrate 3 by bonding the upper ceramic substrate 1 so as to cover the electric circuit.

  The upper ceramic substrate 1, the ceramic substrate 3, and the ceramic base 4 are joined simultaneously after the electric circuit of the embedded electrode 2 is formed. Then, the ceramic base 4 is threaded and the metal terminals 6a and 6b are screwed to be connected to the surface metallization of the ceramic connection terminals 5a and 5b. The power supply conductive member 7 is connected to the metal terminals 6a and 6b with sufficient bonding strength so that power can be supplied from the metal terminals 6a and 6b to the embedded electrode 2 through the ceramic connection terminals 5a and 5b.

  Since the ceramic substrate 3 and the ceramic connection terminals 5a and 5b are made of the same material, the generation of stress due to a difference in thermal expansion can be suppressed, and the embedded electrode 2 and the upper ceramic substrate 1 on the ceramic connection terminals 5a and 5b can be suppressed. The possibility of breakage due to stress can be made extremely low. In FIG. 1, the convex portion of the metal terminal 6a is connected to the ceramic connecting terminal 5a, whereas in FIG. 2, the metallic terminal 6b is not provided with a convex portion. Good conduction can be obtained.

  On the other hand, the connection structure shown in FIG. 3 is an example in which the surface-metalized ceramic connection terminal is not used, and the metal terminal 6 c is screwed into the ceramic substrate 3 and the ceramic base 4 and directly connected to the embedded electrode 2. In this case, when the upper ceramic substrate 1 on the embedded electrode 2 becomes thin, stress due to a difference in thermal expansion coefficient between the metal terminal 6c and the ceramic substrate 3 is generated, and the embedded electrode 2 and the upper ceramic substrate 1 may be damaged. Get higher.

  In order to confirm the effect of the present invention, samples of the ceramic wafer holder according to the present invention were prepared, and the continuity as an electric circuit and durability by a heat cycle test were investigated for each sample. Hereinafter, the preparation of the sample, the test method, and the results will be described.

  Aluminum nitride (AlN) was used as a material for the ceramic substrate and the ceramic connection terminal. The ceramic connection terminals were coated with a tungsten paste over the entire surface and then fired and subjected to surface metallization so that the entire surface could be electrically connected. Two types of ceramic connection terminals were prepared: 5a shown in FIG. 1 and 5b shown in FIG. 2 (partially formed with external threads). Further, the ceramic connection terminal 5a was tapered (average diameter 4 mm), and the ceramic connection terminal 5b was dish-shaped on the upper surface.

  These surface metallized ceramic connection terminals are inserted into tapered through holes provided on the same thickness ceramic substrate or through holes that are partially threaded, and the surface of the ceramic substrate and the ceramic connection terminals are the same. It was prepared to be a surface. After that, an embedded electrode electric circuit was formed on the upper surface of the ceramic substrate including the ceramic connection terminals by screen printing of tungsten paste, and then fired to obtain an embedded electrode. At this point, it was confirmed that the ceramic connection terminals and the electrical circuit for the buried electrode were all conductive.

  Thereafter, an upper ceramic substrate (AlN: thickness 5 mm) is laminated on the ceramic substrate (AlN: thickness 9 mm) so as to cover the electric circuit, and a ceramic substrate (AlN: thickness 9 mm) is laminated on the opposite side. Baked and joined. The ceramic substrate was machined to form screw holes for screwing metal terminals. At that time, in addition to the two types of ceramic connection terminals 5a and 5b, three different types of screw holes were formed for each sample, such as for the case without ceramic connection terminals. Further, cutting was performed by changing the thickness of the upper ceramic substrate so that the depth of the embedded electrode was 0.5 to 3.0 mm.

  In the obtained wafer holder, 20 types of two types of connection terminals made of ceramics 5a and 5b and a type using only metal terminals 6c were prepared as connection terminal types. Moreover, the buried electrode was used as a heater circuit for temperature control. The wafer holder produced in this way is designated as sample A.

  Further, as another upper ceramic substrate made of AlN, a circular pattern having a diameter of 8 mm was formed by screen printing of tungsten paste at a location where a ceramic connecting terminal was connected, and was fired to form a metal layer. A wafer holder for sample B was prepared in the same manner as above except that this upper ceramic substrate was laminated with the above ceramic substrate and ceramic substrate, sintered and joined.

  Each wafer holder (samples A and B) was heated from 250 ° C. to 550 ° C. at a heating rate of 10 ° C./min in a vacuum, held for 30 minutes, and then cooled to 250 ° C. at 5 ° C./min. Each heat cycle was performed 50 times. After this heat cycle test, the number of non-conducting locations where conduction was not achieved in the 20 connecting portions and the number of locations where breakage such as cracks occurred in the upper ceramic substrate in the 20 connecting portions were confirmed. The results obtained for the wafer holder of sample A are shown in Table 1 below.

  As can be seen from the results in Table 1 above, for the wafer holder using the ceramic connection terminal made of the same material as the ceramic substrate, even if the thickness of the upper ceramic substrate is reduced to 0.5 mm, It was confirmed that breakage such as cracks did not occur and conduction was sufficient. However, in the case of only the metal terminal 6c (without the ceramic connection terminal), the number of non-conductions and the number of breaks increased as the thickness of the upper ceramic substrate was reduced to 1.5 mm or less. Further, it was confirmed that the same tendency as described above was obtained for the wafer holder of sample B.

  Furthermore, each connection terminal part was cut and the cross section was confirmed. In the wafer holder using the ceramic connection terminal, both the sample A and the sample B are between the connection terminal and the embedded electrode and the upper ceramic substrate. It was confirmed that no gap was generated.

It is a general | schematic expanded sectional view which shows the connection terminal part of the ceramic wafer holders by this invention. It is a general | schematic expanded sectional view which shows another connection terminal part of the ceramic wafer holder by this invention. It is a general | schematic expanded sectional view which shows the connection terminal part using only the metal terminal by a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper ceramic substrate 2 Embedded electrode 3 Ceramic substrate 4 Ceramic base | substrate 5a, 5b Ceramic connection terminal 6a, 6b, 6c Metal terminal 7 Conductive member for electric power feeding

Claims (10)

  A connection structure for an electrode embedded in a ceramic wafer holder, wherein a ceramic connection terminal made of the same material as the wafer holder is inserted in close contact with the inside of the wafer holder, An electrode connection structure for a wafer holder, wherein surface metallization for ensuring electrical continuity is applied, and the surface metallization is electrically connected to a metal terminal at the same time as being connected to the buried electrode.   The said wafer holding body contains the ceramic substrate which formed the said embedded electrode on the surface, and the upper ceramic substrate joined on the said ceramic substrate so that this embedded electrode was covered, The Claim 1 characterized by the above-mentioned. The electrode connection structure of the wafer holder.   The electrode connection structure for a wafer holder according to claim 2, wherein the ceramic connection terminal and the upper ceramic substrate are in close contact with each other, and there is no gap between them.   A metal layer larger than the diameter of the ceramic connection terminal and electrically connected to the embedded electrode is formed on a surface of the upper ceramic substrate that contacts the ceramic connection terminal. 4. An electrode connection structure for a wafer holder according to claim 2 or 3.   The ceramic connection terminal has the same thickness as the ceramic substrate and is inserted into a through hole of the ceramic substrate, and the surface metallization of the ceramic connection terminal is connected in the same plane as the embedded electrode. The electrode connection structure of a wafer holder according to any one of claims 2 to 4, wherein   The ceramic connection terminal is mechanically joined to the ceramic substrate and at the same time electrically connected to an embedded electrode formed on the ceramic substrate. The electrode connection structure of a wafer holder according to any one of the above.   The electrode connection structure for a wafer holder according to claim 1, wherein the ceramic connection terminal and the metal terminal are electrically connected by a convex portion of the metal terminal.   The ceramic wafer holder and the ceramic connection terminal are made of ceramics including at least one selected from the group consisting of aluminum nitride, silicon nitride, silicon carbide, and aluminum oxide. An electrode connection structure for a wafer holder according to any one of the above.   9. The wafer holding according to claim 4, wherein the embedded electrode, the metal terminal, and the metal layer are made of at least one selected from the group consisting of tungsten, molybdenum, and alloys thereof. Body electrode connection structure.   10. The wafer holder electrode according to claim 1, wherein the embedded electrode is at least one selected from an RF plasma forming electrode, a heater electrode, and an electrostatic chuck electrode. Connection structure.

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