JP2015002300A - Bonding structure and semiconductor production apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic member having high bonding strength and ensuring high bonding reliability of a power supply terminal even if it is exposed to heat-cycle.SOLUTION: In a bonding structure consisting of a planar ceramic base material, an electrode and a metallic member buried in the bottom thereof sequentially in contact therewith, a terminal hole reaching the metallic member from the upper surface of the ceramic base material, and a power supply terminal being abutted against the metallic member from above the ceramic base material through the terminal hole, a bonding structure of the edge at an enlarged diameter part formed at the lower end of the power supply terminal and the metallic member is employed, and the bonding strength can be increased by increasing the surface area of a bonding part.

Description

  The present invention relates to a bonding structure and a semiconductor manufacturing apparatus using the bonding structure, and more particularly, a bonding structure for bonding a power supply terminal for supplying power to an embedded electrode embedded in a ceramic substrate, and the bonding structure to an electrostatic chuck or a heater. The present invention relates to a semiconductor manufacturing apparatus to be used.

In recent years, materials having plasma resistance are required for susceptors with heaters, susceptors with plasma electrodes, electrostatic chucks and the like used in semiconductor manufacturing apparatuses for CVD, sputtering, and etching, and in particular, ceramics such as aluminum oxide and aluminum nitride. Is used.

  A bonding electrode used as an electrostatic chuck or heater of the semiconductor manufacturing apparatus has a chuck electrode and a heating element (resistor), and a metal member electrically connected thereto embedded therein. Sintered with ceramics. Further, in order to supply power to the electrodes and the heating element (resistor), a power supply terminal is joined to the metal member.

Conventionally, this joining is often performed by exposing an embedded metal member by drilling or the like and brazing a power supply terminal to the exposed portion.

For example, Patent Document 1 discloses a technique for reducing stress on a ceramic member by eliminating a stress difference due to heat by using a metal having the same thermal expansion coefficient as a power supply terminal and a metal member and brazing. .

However, in the joining method by brazing, there is a possibility that cracks may occur in the ceramics and their joints due to residual stress due to the difference in thermal expansion coefficient between the metal member and the power supply terminal in the process of cooling from the joining temperature to room temperature. . Even if the metal member and the power supply terminal are made of the same material, the thermal expansion coefficient difference cannot be completely eliminated because of the presence of the brazing material at the interface.

As a joining method other than brazing, an invention using beam welding for the purpose of reducing residual stress during joining is known (Patent Document 2). In the above invention, a plate-shaped metal lump and a cylindrical power supply terminal are used. In order to balance the penetration of the metal lump in the depth direction and the penetration depth of the outer periphery of the power supply terminal, the incident angle of the beam is set to a predetermined value. I try to make it a range. Further, the terminal hole to the ceramic is also processed with a taper angle so that the beam does not contact.

However, processing the terminal hole into a tapered shape as in the above-described invention takes time and effort compared to processing the straight, and there is a risk that the ceramic may be further cracked or damaged during processing.

Furthermore, when considering the use as a heater, this member is used under such a condition that it is heated from room temperature to a high temperature of 400 ° C. or higher and then cooled to room temperature again. When the material is used, there is a problem that fatigue due to a difference in thermal expansion is accumulated and the reliability of the joint portion is lacking.

JP 2009-188394 A JP 2012-49185 A

Accordingly, an object of the present invention is to provide a ceramic member that has high bonding strength and high reliability in connection of power supply terminals even when exposed to a thermal cycle.

In order to solve the above problems, the present invention provides:
A plate-like ceramic substrate, and electrodes and metal members embedded while sequentially contacting the bottom,
A terminal hole reaching the metal member from the upper surface of the ceramic substrate;
In a joined structure comprising a power supply terminal that abuts against the metal member through the terminal hole from above the ceramic base material,
By adopting a joint structure in which the edge portion of the enlarged diameter portion formed at the lower end of the power supply terminal and the metal member are joined and increasing the surface area of the joint portion, the joint strength can be increased.

Furthermore, in order to reduce the occurrence of cracks under a thermal cycle, a metal having a similar thermal expansion coefficient is used for the power supply terminal and the metal member, and preferably a bonded structure in which the metal is Mo is used. The power supply terminal may be made of Kovar (FeNiCo alloy).

Further, the power feeding terminal can be easily positioned by fitting the power feeding terminal into a power feeding terminal fitting recess recessed in the metal member.

In the joining structure described above, when joining the power supply terminal and the metal member, by welding by one welding method selected from electron beam welding, laser welding, arc welding, gas welding, plasma flame welding, Since there is no dissimilar material such as a brazing material on the joint surface, it is possible to further prevent cracks due to the difference in thermal expansion coefficient.

In general, beam welding (electron beam welding, laser welding) has high energy density, so local welding is easy and joining is possible with a small amount of heat input. There is an advantage that is difficult to occur.

  The present invention exhibits an excellent effect that it is possible to create a bonded structure in which cracks due to a difference in thermal expansion coefficient hardly occur under a thermal cycle.

It is sectional drawing when manufacturing the joining structure concerning this invention with a hot press machine. It is a junction structure precursor according to the present invention. It is another sectional drawing when manufacturing the junction structure concerning the present invention with a hot press machine. It is sectional drawing which formed the terminal hole in the ceramic base material. It is another sectional view in which a terminal hole was formed in a ceramic substrate. It is sectional drawing when fitting a power feeding terminal in the recessed part for power feeding terminals. It is sectional drawing which showed the electric power feeding terminal joining method of 1st Embodiment which concerns on this invention. It is an enlarged view of A part of FIG. It is a perspective view of a feed terminal. It is a fragmentary sectional view when butting the end part of an electric power feeding terminal to a metal member without expanding and carrying out electron beam welding. It is a fragmentary sectional view when expanding the diameter of the end portion of the power supply terminal, fitting it to a metal member, and performing electron beam welding. It is sectional drawing which showed the electric power feeding terminal joining method of 2nd Embodiment which concerns on this invention. It is an enlarged view of B part of FIG.

  Hereinafter, an embodiment of a bonded structure according to the present invention will be described with reference to the drawings. In addition, the shape of each figure referred in the following description is a conceptual diagram or a schematic diagram for explaining a suitable shape dimension, and a dimension ratio etc. do not necessarily correspond with an actual dimension ratio. That is, the present invention is not limited to the dimensional ratio in the drawings.

(First embodiment)
As a method for manufacturing a bonded structure according to a preferred embodiment of the present invention, a process of embedding an electrode and a metal member in a ceramic substrate will be described first (first process). Although the manufacturing method of the electrode 2 and the metal member 3 is not specifically limited, Here, it demonstrates by the method of producing the electrode 2 and the metal member 3 separately.

As the material of the ceramic substrate, aluminum nitride, aluminum oxide, yttrium oxide, silicon carbide, silicon nitride, preferably aluminum nitride is used. In addition, you may add an additive suitably for a sinterability or a functional characteristic improvement.

As shown in FIG. 1, first, a ceramic substrate 1a on which an electrode 2 is printed on one side is prepared and placed on a lower mold P2 of a hot press machine with the electrode 2 facing upward. In addition to what is printed on the ceramic substrate, the electrode 2 can be punched metal, metal mesh, metal coil, etc., and considering that the material is integrally fired with ceramic, A refractory metal having a melting point of 1800 ° C. or higher is employed. Specifically, a metal, alloy, carbide or silicide selected from one or more of W, Mo, Nb and the like is employed. When the ceramic substrate is aluminum nitride, W or Mo is preferable because the thermal expansion coefficient is close.

Next, a refractory metal member 3 having a melting point of 1800 ° C. or higher, preferably a plate-like metal member 3 made of Mo as a raw material, is placed on the electrode 2 so as to be in contact with the electrode 2. The width t4 of the metal member 3 can be arbitrarily set. The reason for adopting the high melting point metal for the electrode 2 and the metal member 3 is to first maintain the shape without melting the electrode 2 and the metal member 3 in the pressure sintering step described later. Second, both the refractory metal and the ceramic have a small coefficient of thermal expansion, and the difference in coefficient of thermal expansion is as small as 3.2 × 10 ⁻⁶ or less. This is because cracks are unlikely to occur.

  Here, the mechanism by which cracks are likely to occur in the ceramic substrate 1 due to the difference in thermal expansion coefficient will be described. Since ceramics are unlikely to be plastically deformed like metals, cracks are easily generated and broken without being deformed by thermal stress. That is, when materials having extremely different thermal expansion coefficients are joined, cracks are likely to occur in the ceramic due to the difference in thermal expansion. Therefore, when a refractory metal having a thermal expansion coefficient comparable to that of ceramics is used for the electrode 2 and the metal member 3, the difference in thermal expansion coefficient becomes small and cracks are hardly generated.

  Here, Table 1 shows the difference in thermal expansion coefficient between the thermal expansion coefficients of Mo, W, Kovar (FeNiCo-based alloy), Ti, Ni, and aluminum nitride. The thermal expansion coefficient is calculated by measuring the elongation from room temperature to a set temperature (700 ° C.). The set temperature is a temperature at which aluminum nitride has a limit to the corrosion resistance to fluorine-based gas used in the semiconductor manufacturing process, and the use of aluminum nitride at 700 ° C. or lower is suitable. The difference in thermal expansion coefficient (Δα) indicates how much the absolute value is relative to the thermal expansion coefficient of aluminum nitride. As the difference in thermal expansion coefficient is smaller, cracks are less likely to occur.

Furthermore, the ceramic powder 1b is put in the hot press processing machine on the upper surface. When there is an additive, it may be mixed in advance, and it is preferable to use granulated powder by spray drying because the fluidity is improved.

The ceramic substrate 1a, the ceramic powder 1b, the electrode 2 and the metal member 3 are preliminarily pressed by the upper mold P1 and the lower mold P2 of the hot press processing machine, and hot-press fired at 1800 ° C. and 100 kg / cm 2. As shown in FIG. 2, the electrode 2 and the metal member 3 are embedded in the ceramic base material 1 to form an integrated bonded structure precursor 1 c.

In the first step, the ceramic substrate 1 can be formed only from the ceramic powder 1b. That is, as shown in FIG. 3, the ceramic powder 1b is first placed on the press machine P2, and then the electrode 2 is placed. Then, a high melting point metal having a melting point of 1800 ° C. or higher, preferably a metal member 3 made of Mo as a raw material, is placed on the electrode 2 so as to be in contact with the electrode, and the ceramic powder ( The mixed powder) may be placed in a hot press machine and hot pressed at 1800 ° C. and 100 kg / cm 2.

  Furthermore, as described above, the manufacturing method of the electrode 2 and the metal member 3 is not particularly limited, and after the electrode 2 and the metal member 3 are integrally formed from the beginning, they are embedded in the ceramic powder 1b and hot pressed. Firing is also possible. Moreover, after forming the electrode 2 and the metal member 3 separately, they may be integrated by welding, caulking, etc., and embedded in the ceramic powder, followed by hot press firing.

  Next, as shown in FIG. 4, the ceramic substrate 1 is cut with a diamond tool in a direction perpendicular to the bottom surface until the metal member 3 is exposed to form the terminal holes 4 (second step). The joint structure precursor 1c is cut in the range of the width t1 (3 to 10 mm) until the metal member 3 is exposed, and the terminal hole 4 is formed.

  Here, the width t1 of the terminal hole 4 may be smaller, larger, or even equal to the width t4 of the metal member. By making the width t1 of the terminal hole 4 smaller than the width t4 of the metal member 3, even if a large stress is applied to the metal member 3, since the terminal hole 4 is small, the metal member 3 is sandwiched between the ceramic substrate 1 and the terminal. It will not fall out of the hole 4. On the other hand, as shown in FIG. 5, by making the width t1 of the terminal hole 4 larger or equal to the width t4 of the metal member 3, a crack due to the difference in thermal expansion coefficient generated between the metal member 3 and the ceramic substrate 1 occurs. It becomes difficult.

Then, as shown in FIG. 6, a power supply terminal fitting recess 4a into which a power supply terminal 5 described later is fitted is cut to have a width t2 (3 to 10 mm) smaller than the width t1 of the terminal hole 4 (third step). . By forming the power supply terminal fitting recess 4a, the power supply terminal 5 described later can be positioned, and the power supply terminal fitting recess 4a is cut at t2 having a width smaller than t1, and the power supply having a width smaller than t2 is supplied. By fitting the terminal 5, a sufficient gap t3 (1 to 3 mm) can be formed between the metal member 3 and the power supply terminal 5 without cutting the ceramic substrate 1 into a taper. The ceramic substrate 1 and the power supply terminal 5 can be easily welded.

  Next, as shown in FIGS. 7 and 8, the feeding terminal 5 is fitted into the feeding terminal fitting recess 4a and selected from electron beam welding, laser welding, arc welding, gas welding, and plasma flame welding 1 The metal member 3 and the edge portion 6a of the power supply terminal 5 are welded by one welding method or joining by brazing (fourth step). In the following description, the case of welding by electron beam welding will be described.

As shown in FIG. 9, the power supply terminal 5 has an enlarged diameter portion 6 having a lower end whose diameter is larger than that of the other end portion. By expanding the diameter of the lower end of the power supply terminal 5, the distance between the terminal hole 4 and the power supply terminal 5 can be increased to t3 (1 to 3 mm), and it is not necessary to consider the welding angle or the like as in the prior art. The power supply terminal 5 can be welded by easily applying an electron beam to the edge portion 6a of the enlarged diameter portion 6 and the metal member 3 from directly above (in the direction of arrow Z). The end on the side not joined to the metal member 3 is coupled to the external power supply conductor by screwing, welding, or the like. The external power supply conductor may be joined after the metal member 3 and the power supply terminal 5 are welded, or may be joined in advance before joining them.

  Next, the power supply terminal 5 is fitted into the power supply terminal fitting recess 4 a, and the power supply terminal 5 is erected in the terminal hole 4 for positioning. Thus, by providing the enlarged diameter portion in the power supply terminal 5, the enlarged diameter portion 6 itself becomes a base of the power supply terminal 5, and the power supply terminal 5 can be stably stood vertically in the terminal hole 4 and welded. Easy to weld. The illustrated power supply terminal 5 has a cylindrical shape as an example, but is not limited to a cylindrical shape, and may be a polygonal prism shape such as a quadrangular prism or a triangular prism.

Here, how much the welding area differs between the conventional electron beam welding and the electron beam welding according to the present invention will be compared in the drawings. As shown in FIG. 10, in the conventional electron beam welding, the electron beam is only applied in an oblique direction (arrow X <b> 1 direction) toward the contact portion between the power supply terminal 5 and the metal member 3. There are only two surfaces, the side surface and the upper surface of the metal member 3.

On the other hand, as shown in FIG. 11, in the electron beam welding according to the present invention, the electron beam is vertically (in the direction of the arrow X2) in the vicinity of the edge portion 6a of the feeding terminal 5 and the corner portion 4b of the feeding terminal fitting recess 4a. Therefore, there are four welding surfaces Y2 (the upper surface of the metal member 3, the side surface of the power supply terminal fitting recess 4a, the upper surface of the enlarged diameter portion 6, and the side surface of the edge portion 6a). Therefore, naturally the amount of metal melting is larger than that of conventional electron beam welding, so that the bonding strength can be increased. Moreover, since it is easy to aim when it is perpendicular | vertical compared with the case from the diagonal direction, generation | occurrence | production of poor welding can be prevented and it can weld with sufficient reproducibility.

  Furthermore, if the metal member 3 and the power supply terminal 5 are made of a metal having the same thermal expansion coefficient, metal fatigue caused by the difference in thermal expansion coefficient does not easily occur even under a thermal cycle, and cracks in the welded portion hardly occur. Preferably, when Mo is used for the metal member 3 and the power supply terminal 5, the thermal expansion coefficients of ceramic and Mo are approximately the same, and the difference in thermal expansion coefficient between the metal member 3 or the power supply terminal 5 and the ceramic substrate 1. Since it is difficult to generate cracks in the ceramic substrate 1, the bonding strength of the power supply terminal 5 can be further increased.

As another welding method, the metal member 3 and the power supply terminal 5 may be brazed to prevent the occurrence of cracks in the bonded structure due to the difference in thermal expansion coefficient. When the metal member 3 and the power supply terminal 5 are brazed by using the power supply terminal 5 having an enlarged diameter at the end, it is possible to apply brazing to the diameter-enlarged portion of the power supply terminal 5, so that the power supply is not expanded. The bonding strength can be increased as compared with the case where a terminal is used, and this is effective in preventing the occurrence of cracks.

(Second Embodiment)
Next, the manufacturing method of the junction structure which is another embodiment of the present invention is explained. In 2nd Embodiment, the 3rd process of forming the recessed part 4a for electric power feeding terminal fitting of above-described 1st Embodiment is not required. That is, the power supply terminal 5 is inserted near the center of the terminal hole 4, placed on the metal member 3, and welded from the upper surface of the edge portion 6 a of the power supply terminal 5 as shown in FIG. 12.

  Thus, even if it welds from the upper surface of the edge part 6a, since the thickness t5 of the enlarged diameter part 6 is thinly formed with 0.3-0.5 mm, it is fully metal member 3 irrespective of the welding method. The power supply terminal 5 can be welded as shown in FIG. Also in this case, since the amount of metal melting is larger than that of the conventional welding method, the power supply terminal 5 can be welded to the metal member 3 with high strength.

(Third embodiment)
In the first and second embodiments, the problem of the present invention has been solved by expanding the diameter of the lower end of the power supply terminal 5. However, the power supply terminal 5 and the metal member 3 have the same melting point of 1800 ° C. or higher. If welding is performed using metal, preferably Mo, the problem can be solved by simply welding the outer periphery of the end of the power supply terminal 5 without increasing the diameter of the lower end of the power supply terminal 5. The welding in this case means any one welding method selected from electron beam welding, laser welding, arc welding, gas welding, and plasma flame welding.

Thus, the high melting point metal having a thermal expansion coefficient comparable to that of the bonded structure, that is, the high melting point metal having a difference in thermal expansion coefficient of 3.2 × 10 ⁻⁶ or less to the power supply terminal 5 and the metal member 3. Thus, preferably by using Mo, it is possible to prevent cracks in the joined structure caused by a difference in thermal expansion coefficient between the ceramic substrate 1 and the power supply terminal 5 or the metal member 3 when the joined structure is formed or used.

In addition, when the power supply terminal 5 and the metal member 3 are welded and joined with the same kind of high melting point metal, since the dissimilar material is not included in the joint interface between the power supply terminal 5 and the metal member 3, the power supply terminal 5 and the metal member are also subjected to heat cycle. There is no difference in thermal expansion coefficient from 3, and the occurrence of cracks at the joint portion can be prevented. However, since the diameter of the lower end of the power supply terminal 5 is not enlarged, the bonding strength is smaller than that in the first and second embodiments.

  INDUSTRIAL APPLICABILITY The present invention can be widely used for bonding structures used for electrostatic chucks, heaters, etc. for semiconductor manufacturing apparatuses.

1: Ceramic base material, 1a: Ceramic substrate, 1b: Ceramic powder, 2: Electrode, 3: Metal member, 4: Terminal hole, 4a: Recess for fitting power supply terminal, 4b: Corner part, 5: Power supply terminal, 6: Expanded diameter part, 6a: edge part.

Claims (12)

The plate-shaped ceramic substrate (1) and the electrode (2) and metal member (3) stacked or embedded while sequentially contacting the bottom thereof, and the terminal hole (4) reaching the metal member from the upper surface of the ceramic substrate ) And a feeding terminal (5) that abuts against the metal member (3) through the terminal hole (4) from above the ceramic base material,
The joining structure characterized by joining the edge part of the enlarged diameter part formed in the lower end of the said electric power feeding terminal, and the said metal member. 2. The bonding according to claim 1, wherein each of the ceramic base material, the power supply terminal, and the ceramic base material and the metal member has a difference in thermal expansion ΔΔ of 3.2 (10 ⁻⁶ / K) or less. Structure. The bonded structure according to claim 2, wherein the metal member is a refractory metal having a melting point of 1800 ° C. or higher. The joint structure according to any one of claims 1 to 3, wherein the power supply terminal is fitted in a power supply terminal fitting recess provided in the metal member. The joint structure according to claim 1, wherein the power supply terminal and the metal member are joined by welding. The joining structure according to claim 5, wherein the welding is joining by one welding method selected from electron beam welding, laser welding, arc welding, gas welding, and plasma flame welding. The joining structure according to claim 5, wherein the welding is joining by brazing.   The joining structure according to claim 1, wherein the ceramic substrate is selected from aluminum nitride, aluminum oxide, yttrium oxide, silicon carbide, and silicon nitride. The plate-shaped ceramic substrate (1) and the electrode (2) and metal member (3) stacked or embedded while sequentially contacting the bottom thereof, and the terminal hole (4) reaching the metal member from the upper surface of the ceramic substrate And a feeding terminal (5) welded to the metal member (3) through the terminal hole (4) from above the ceramic base material,
The junction structure, wherein the ceramic base material and the power supply terminal, and the ceramic base material and the metal member each have a difference in thermal expansion ΔΔ of 3.2 (10 ⁻⁶ / K) or less.   The bonded structure according to claim 9, wherein the ceramic substrate is selected from aluminum nitride, aluminum oxide, yttrium oxide, silicon carbide, and silicon nitride. 10. The joint structure according to claim 9, wherein the power supply terminal is made of Mo, W, an alloy mainly containing these, or Kovar. The semiconductor manufacturing apparatus comprised from the joining structure of any one of Claims 1-10 by an electrostatic chuck.

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