JP4069875B2 - Wafer holding member - Google Patents

Description

  The present invention relates to a wafer holding member such as an electrostatic chuck or a susceptor used for holding and transporting a wafer such as a semiconductor wafer or glass for liquid crystal in a semiconductor or liquid crystal manufacturing apparatus.

  In a semiconductor manufacturing process, a susceptor is used as a holding member for a semiconductor wafer in a CVD apparatus for forming a film on a semiconductor wafer and a dry etching apparatus for performing fine processing on the wafer.

For example, as shown in FIG. 4 , a mounting surface 11a of a wafer 20 is formed on the surface of a ceramic plate-like body 11 to constitute a susceptor. The energizing terminal 13, the heating resistor 14 and the energizing terminals 15 and 15 are embedded.

  If the wafer 20 is placed on the placement surface 11a and a high frequency voltage is applied between the plasma generating electrode 12 and an upper electrode (not shown) provided on the upper portion of the wafer 20, plasma is generated. Can be made. It is also possible to apply a voltage to the heating resistor 14 to heat the wafer 20 to a predetermined temperature.

  Further, although not shown, an electrostatic chuck in which electrostatic electrodes are embedded in the plate-like body 11 and the wafer 20 is electrostatically attracted can be used.

When manufacturing these wafer holding members, the ceramic green sheet is obtained by applying a metal paste such as W or Mo forming the plasma generating electrode 12 or the heating resistor 14 and laminating other ceramic green sheets. Can do. Various ceramics can be used as the ceramic, and a ceramic mainly composed of aluminum nitride having excellent plasma resistance is used (see Patent Document 1).
JP-A-6-151332

  The ceramic forming the plate-like body 11 is extremely high in insulation at room temperature, but tends to have a low resistance value at high temperatures, and when metal components such as W and Mo diffuse into the ceramic during firing. Further, the resistance value was likely to be lowered. Therefore, there has been a problem that leakage current is generated from the voltage applied to the plasma generating electrode 12 and the heating resistor 14 due to a decrease in the resistance value of the ceramic.

  For example, when the leakage current of the high-frequency voltage applied to the plasma generating electrode 12 is transmitted to the heating resistor 14, there is a problem that energization to the heating resistor 14 cannot be controlled or is interrupted. Further, when the leakage current from the heating resistor 14 is transmitted to the lower surface 11b of the plate-like body 11, the leakage current flows to a metal plate or the like that is in contact with the lower surface 11b, making it difficult to control the temperature of the heating resistor 14. There was a problem that.

In particular, ceramics mainly composed of aluminum nitride have a volume resistivity of 1 × 10 ¹⁰ Ω · cm at 300 ° C. and a volume resistivity of 8.7 × 10 ⁸ Ω · cm at 400 ° C. compared to other ceramics. Since the specific resistance is low, the above problem is remarkable.

  In addition, since a large current of about 20 A flows through the plasma generating electrode 12, it is necessary to use a large energizing terminal 13 having a diameter of 10 mm or more in order to reduce the resistance of the energizing terminal 13. Therefore, the stress due to the difference in thermal expansion between the metal energizing terminal 13 and the ceramic plate-like body 11 becomes large, and the ceramic plate-like body 11 side with the temperature change after brazing of the energizing terminal 13 or during use. There was also a problem that cracks were likely to occur.

Therefore, the present invention embeds a heating resistor inside a ceramic plate having a wafer mounting surface, and the ceramic plate is placed between the heating resistor and the surface of the plate. The present invention is characterized in that a wafer holding member is configured by including a leakage current preventing layer made of an insulating layer having a larger volume resistivity than that of the formed ceramic .

The present invention, volume than ceramics constituting the inside heating resistor and the buried and plasma generating electrode, both the ceramic plate body between the ceramic plate-shaped body having a mounting surface of the wafer The present invention is characterized in that a wafer holding member is configured by including a leakage current preventing layer made of an insulating layer having a large specific resistance .

As described above, in the present invention, the insulation having a larger volume resistivity than the ceramic forming the ceramic plate-like body between the heating resistor and the plasma generating electrode or between the heating resistor and the surface of the plate-like body. A leakage current prevention layer composed of layers is provided to prevent the leakage current. Here, the provision of a leakage current prevention layer means provision of a high resistance layer that does not allow leakage current to flow. Specifically, the distance between each of them is increased to a certain value or more. It says often a useful includes an insulating layer of material.

As described above, the present invention, the ceramic plate between the inside of the heating resistor is embedded, the heat-generating resistor and the plate-shaped surface of the ceramic plate-shaped body having a mounting surface of the wafer Since the wafer holding member is configured with a leakage current prevention layer made of an insulating layer having a larger volume specific resistance than the ceramics forming the rod-like body, the voltage applied to the heating resistor leaks to the outside through the surface of the plate-like body It is possible to prevent adverse effects on the control of the heating resistor.

Further, according to the present invention, the heating resistor and the plasma generating electrode are embedded in the ceramic plate-like body having the wafer mounting surface, and the ceramic plate-like body is formed between the two. By configuring the wafer holding member with a leakage current prevention layer made of an insulating layer having a large volume resistivity, the leakage current due to the voltage applied to the plasma generating electrode is prevented from being transmitted to the heating resistor. Can be prevented from adversely affecting the control.

  Hereinafter, embodiments of a wafer holding member of the present invention will be described with reference to the drawings by taking a susceptor as an example.

  In the holding member shown in FIG. 1, the surface of a disk-like plate-shaped body 11 made of ceramics is used as a wafer mounting surface 11a, and a plasma generating electrode 12 and its energizing terminal 13 and a heating resistor 14 and its energizing are contained therein. Terminals 15 and 15 are embedded.

  Now, when a wafer 20 such as a semiconductor wafer is placed on the placement surface 11a, a high frequency voltage is applied between the plasma generating electrode 12 and an upper electrode (not shown) disposed on the upper side of the wafer 20. Plasma can be generated. Further, the wafer 20 can be heated to a predetermined temperature by applying a voltage to the heating resistor 14 to generate heat.

Then, the wafer holding member of the present invention, the leakage current preventing layer made of large insulating layer having a volume resistivity than ceramics forming the ceramic plate-shaped body 11 between the heating resistor 14 and the plasma generation electrode 12 It is characterized by having. Here, the leakage current preventing layer is that of the high resistance layer so as to prevent leakage current between the plasma generating electrode 12 and the heat generating resistor 14, in particular plate-like between the two persons It means that an insulating layer 16 having a resistance value larger than that of the ceramic forming the body 11 is interposed.

First, when the distance d ₁ (cm) between the plasma generating electrode 12 and the heating resistor 14 is increased, the power Q (W) applied to the plasma generating electrode 12 and the operating temperature of the ceramics forming the plate-like body 11 are used. It may be set so that d ₁ ≧ 3 × 10 ⁶ × Q / ρ is satisfied with respect to the volume specific resistance ρ (Ω · cm). If the distance d ₁ is increased in this way, the insulating layer 16 need not be provided.

  Further, when the insulating layer 16 having a large resistance value is interposed, a ceramic having a larger resistance value than the ceramic forming the plate-like body 11 may be interposed. For example, the plate-like body 11 itself is formed of an aluminum nitride ceramic, and an insulating layer 16 made of a silicon nitride ceramic having a resistance value higher than that of aluminum nitride is interposed between the plasma generating electrode 12 and the heating resistor 14. It ’s fine.

  As described above, by providing the leakage current prevention layer between the plasma generating electrode 12 and the heating resistor 14, the leakage current of the high frequency voltage applied to the plasma generating electrode 12 is prevented from being transmitted to the heating resistor 14. be able to.

Further, in the present invention, a leakage current preventing layer made of an insulating layer having a larger volume resistivity than the ceramic forming the ceramic plate 11 is provided between the heating resistor 14 and the lower surface 11b of the plate 11. It is characterized by. And the leakage current preventing layer is that of the high resistance layer so as to prevent leakage current between the heating resistors 14 and the lower surface 11b, ceramics specifically constituting the plate-like body 11 between the two persons Insulating layer 16 having a larger resistance value is interposed.

First, when the distance d ₂ between the heating resistor 14 and the lower surface 11b is increased, the distance d ₂ may be set to 0.1 mm or more, preferably 0.5 mm or more, and more preferably 1 mm or more.

When an insulating layer having a higher resistance value is interposed, a ceramic having a higher resistance value than that of the ceramic forming the plate-like body 11 may be provided . Formed in advance example if the plate-like body 11 of aluminum nitride ceramics, it Sonaere greater insulating layer 16 having a volume resistivity such as alumina ceramics or silicon nitride ceramics on its lower surface 11b side. The insulating layer 16 may be bonded in advance to or prepared by laminating simultaneously baking or or another body in the green sheet stage.

  Further, since the aluminum nitride ceramics forming the plate-like body 11 diffuses the metal component of the heating resistor 14 at the time of firing and the resistance value is lowered, the aluminum nitride ceramics which do not cause such metal diffusion are separately provided. It can also be produced and bonded as the insulating layer 16.

  As the ceramic forming the insulating layer 16, silicon nitride ceramics with high thermal conductivity having a thermal conductivity of 50 W / m · K or more at room temperature and 30 W / m · K or more at 500 ° C. are suitable.

  Thus, by providing the leakage current prevention layer between the heating resistor 14 and the lower surface 11b, the leakage current of the voltage applied to the heating resistor 14 is prevented from being transmitted to the metal plate supporting the holding member through the lower surface 11b. can do.

  In FIG. 2, the plate-like body 11 is not provided with a plasma generating electrode, and the heating resistor 14 is provided on the lower surface 11b side. Therefore, the leakage current preventing layer is provided on the lower surface 11b side. What is necessary is just to provide a leakage current prevention layer between 14 and the surface of the plate-like body 11 nearest to this.

Further, as the ceramics forming the plate-like body 11, ceramics mainly composed of one or more of Al ₂ O ₃ , AlN, ZrO ₂ , SiC, Si ₃ N _{4 and the} like are used. Among these, from the viewpoint of plasma resistance, alumina ceramics containing 99% by weight or more of Al ₂ O ₃ as a main component and containing sintering aids such as SiO ₂ , MgO, CaO, etc., and AlN as a main component, a periodic table. Aluminum nitride ceramics containing Group 2a element oxides or Group 3a element oxides in the range of 0.5 to 20% by weight, or high purity aluminum nitride ceramics mainly containing 99% by weight or more of AlN Either is preferred.

  Further, the plasma generating electrode 12 and the heating resistor 14 are made of a refractory metal such as W or Mo. For example, the refractory metal paste is applied on the ceramic green sheet, By laminating ceramic green sheets and firing them integrally, the wafer holding member of the present invention can be manufactured.

  The energization terminals 13 and 15 are columnar bodies made of metal, and are inserted into insertion holes formed on the lower surface 11b side of the plate-like body 11 so as to be electrically connected to the plasma generating electrode 12 and the heating resistor 14, and the brazing material. Etc. are joined together.

  Among these, the energizing terminal 13 to the plasma generating electrode 12 particularly flows a large current of about 20 A at a high frequency of, for example, 13.56 MHz, and this current mainly flows on the surface of the energizing terminal 13. For this reason, the stress relaxation portion is formed so as to increase the surface area as much as possible in order to reduce the resistance at the energizing terminal 13 and to prevent adverse effects due to the difference in thermal expansion from the ceramic plate 11.

Specifically, or form a through hole 13a in the electricity supply terminal 13 as shown in FIG. 2 (a), or a slit 13b on one end side of the energizing terminal 13 as shown in FIG. 2 (b) It is. Therefore, temperature change occurring when using the holding member, even when stress due to the difference in thermal expansion between the ceramic made plate-like body 11, through holes 13a and slits 13b of the metallic conductive terminal 13 is stress to act as a relieving part, it is possible to prevent the cracks occurring in the ceramic-made plate-like body 11.

Further, since the surface area through which the high-frequency current flows can be increased by providing these through holes 13a and slits 13b, the resistance value can be reduced even if the current-carrying terminal 13 itself is downsized. For example, in the case of a solid cylindrical body of the energization terminal 13, but in order to flow a current of 20A at 13.56MHz is required to be more than the diameter 10 mm, when the electricity supply terminal 13 shown in FIG. 2 (a) The outer diameter may be about 6 mm and the inner diameter may be about 4 mm, and the size can be reduced.

  In addition, it is suitable if the stress relaxation part is similarly formed also about the electricity supply terminal 15 to the heating resistor 14. In addition, screw holes can be formed in the energization terminals 13 and 15 so that power supply terminals can be connected.

Next, the joining structure of the energization terminal 13 will be described. As shown in FIG. 3 (a), the lower surface 11b side of the plate-like body 11, is formed a counterbore 11c around the insertion hole 11d of the conductive terminal 13. The energizing terminal 13 is inserted into the insertion hole 11d, and the brazing material 17 is interposed between the energizing terminal 13 and the insertion hole 11d and the counterbore 11c, and is joined by brazing. Incidentally, as shown in FIG. 3 (b), a counterbore 11c as tapered, may be interposed brazing material 17 in the counterbore 11c.

  Here, the brazing material 17 of the spot facing 11c is a smooth arc-shaped meniscus whose thickness decreases toward the periphery. Therefore, the stress produced by the difference in thermal expansion between the ceramic plate 11 and the metal energizing terminal 13 can be gradually relaxed. In order to achieve such a stress relaxation action, it is preferable to reduce the angle α of the peripheral portion of the brazing material 17 forming the meniscus to 60 ° or less.

  Further, the energization terminal 15 on the heating resistor 14 side can also have a joint structure similar to the above.

  In the example shown in FIGS. 1 to 4, the susceptor type wafer holding member has been described, but an electrostatic electrode may be embedded in the plate-like body 11 to form an electrostatic chuck type wafer holding member. .

  Further, the wafer holding member of the present invention can be suitably used when holding a semiconductor wafer in a process using high-frequency plasma such as plasma CVD, low pressure CVD, PVD, plasma etching, etc. in a semiconductor manufacturing process. In addition, it can be used for various purposes such as holding glass for liquid crystal in the manufacturing process of liquid crystal.

As an embodiment of the present invention, a wafer holding member shown in FIG. 1 will be described .

A slurry was prepared by adding a solvent and a binder to high-purity aluminum nitride powder, and a plurality of green sheets were formed by a tape forming method such as a doctor blade method. Of these, a tungsten paste to which aluminum nitride powder is added is printed on one green sheet by screen printing to form the plasma generating electrode 12 and the heating resistor 14, and another green sheet is laminated so as to cover it. Then, a laminated body was formed by thermocompression bonding at 50 ° C. and a pressure of about 30 kg / cm ² . This is cut into a disk shape, vacuum degreased, subsequently reduced and fired at a temperature of about 2000 ° C., and subjected to grinding to provide the plasma generating electrode 12 and the heating resistor 14 inside. A wafer holding member made of a plate-like body 11 was obtained.

Here, samples having different distances d ₁ between the plasma generating electrode 12 and the heating resistor 14 were prepared, and when 2 kW of power was applied to the plasma generating electrode 12 at different temperatures, the plasma generating electrode Whether the control of the heating resistor 14 side becomes impossible due to the leakage current from 12 is examined.

The results are as shown in Table 1. From this result, it was found that the volume resistivity of the aluminum nitride ceramic forming the plate-like body 11 decreases as the temperature rises, so that the heating resistor 14 cannot be controlled unless the distance d ₁ is increased. . In order to enable control of the heating resistor 14, the volume specific resistance ρ (Ω · cm) at the operating temperature of the electric power Q (W) applied to the plasma generating electrode 12 and the ceramics forming the plate 11. ) On the other hand, it was found that d ₁ ≧ 3 × 10 ⁶ × Q / ρ.

It is sectional drawing which shows the wafer holding member of this invention. (A) (b) is a perspective view which shows the electricity supply terminal used for the wafer holding member of this invention. (A) (b) is a fragmentary sectional view which shows the joining structure of the energization terminal in the wafer holding member of this invention. It is sectional drawing which shows the conventional wafer holding member.

Explanation of symbols

11: plate-like body 11a: mounting surface 11b: lower surface 11c: spot facing 11d: insertion hole 12: electrode 13 for plasma generation: energizing terminal 13a: through-hole 13b: slit 14: heating resistor 15: energizing terminal 16: insulation Layer 17: brazing material 20: wafer

Claims (2)

A heating resistor is embedded inside a ceramic plate having a wafer mounting surface, and is more volume specific than the ceramic that forms the ceramic plate between the heating resistor and the surface of the plate. A wafer holding member comprising a leakage current prevention layer made of an insulating layer having high resistance . Buried and internal to the heating resistor and the plasma generating electrode of the ceramic plate-shaped body having a mounting surface of the wafer, a large insulation volume resistivity than ceramics forming the ceramic plate body therebetween features and to roux E Ha holding member further comprising a leakage current preventing layer made of the layer.

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