JP2011222793A - Electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck which is usable over a wide temperature range with reduced warping of a wafer mounting surface during use at a high temperature.SOLUTION: An electrostatic chuck comprises a bipolar electrode for an electrostatic chuck, and an electrode for a heater. When the volume resistivity of a dielectric layer is indicated as ρ1, the volume resistivity between the poles of the bipolar electrode for electrostatic chuck is ρ2, and the volume resistivity between the electrode for the electrostatic chuck and the heater electrode is ρ3, the relationship is ρ1<ρ2<ρ3. It is preferable that the volume resistivity of the dielectric layer gradually decreases from the electrode for the electrostatic chuck towards the wafer mounting surface.

Description

  The present invention includes an etching apparatus, a sputtering apparatus, a plasma CVD apparatus, a low pressure plasma CVD apparatus, a metal CVD apparatus, an insulating film CVD apparatus, a low dielectric constant film (Low-K) CVD apparatus, an MOCVD apparatus, a degas apparatus, an ion implantation apparatus, The present invention relates to a holder used in a semiconductor manufacturing apparatus such as a coater developer, and further to a semiconductor manufacturing apparatus equipped with the holder.

  Conventionally, in a semiconductor manufacturing process, various processes such as a film formation process and an etching process are performed on a semiconductor substrate (wafer) that is an object to be processed. In a semiconductor manufacturing apparatus that performs processing on such a semiconductor substrate, a ceramic holder for holding the semiconductor substrate and heating the semiconductor substrate is used.

As such a conventional ceramic holder, for example, an electrostatic chuck disclosed in Patent Document 1 has an electrode embedded in aluminum nitride, and has a volume characteristic of the dielectric layer between the wafer and the internal electrode. The resistivity is 10 ⁸ to 10 ¹² Ω · cm, and the wafer is attracted by generating a so-called Johnson Rabeck force that increases the attracting force of the wafer at a low temperature.

In general, the volume resistivity of the dielectric layer is 10 ⁹ to 10 ¹¹ Ω · cm. If it is 10 ⁹ Ω · cm or less, a leakage current is generated between the electrodes, and charge polarization on the surface of the dielectric layer is hindered, so that the wafer attracting force is reduced. On the other hand, if it is higher than 10 ¹¹ Ω · cm, the polarization of electric charges hardly occurs in the dielectric layer, and the responsiveness of the dechuck deteriorates.

  That is, the higher the volume resistivity is, the higher the chucking force is, so that no leakage current between the electrodes is generated. On the other hand, the surface of the dielectric layer should have a low volume resistivity so that charge polarization is likely to occur. Since the volume resistivity of aluminum nitride decreases as the temperature increases, it is difficult to suppress the occurrence of leakage current when used at high temperatures.

  However, in the conventional electrostatic chuck, the volume specific resistivity between the electrodes and the volume specific resistivity of the dielectric layer are substantially equal, and thus the usable temperature range is limited to a narrow range.

  With the recent increase in size of semiconductor substrates and miniaturization of wiring patterns, electrostatic chucks that can be used in a wide temperature range have been demanded.

JP 2003-133196 A

  An object of the present invention is to provide an electrostatic chuck that can be used in a wide temperature range.

  The electrostatic chuck of the present invention is an electrostatic chuck having a bipolar electrostatic chuck electrode and a heater electrode, wherein the dielectric layer has a volume resistivity of ρ1 and a gap between the bipolar electrodes of the electrostatic chuck. Ρ1 <ρ2 <ρ3, where ρ2 is a volume specific resistivity and ρ3 is a volume specific resistivity between the electrostatic chuck electrode and the heater electrode.

  The volume resistivity in the dielectric layer is preferably gradually decreased from the electrostatic chuck electrode side toward the wafer mounting surface.

  ADVANTAGE OF THE INVENTION According to this invention, the electrostatic chuck which can be used in a wide temperature range compared with the past can be provided. Moreover, the electrostatic chuck which reduced the curvature of the wafer mounting surface at the time of using at high temperature can be provided.

The schematic diagram of the cross-sectional structure of the electrostatic chuck of this invention is shown.

  The electrostatic chuck of the present invention will be described with reference to FIG. FIG. 1 is an example of an embodiment of the present invention. The electrostatic chuck of the present invention has a sectional structure in which a dielectric layer 1, a bipolar electrostatic chuck electrode 3, an insulating layer 4, a heater electrode 5, and a support layer 7 are laminated in order from the wafer mounting surface side. The dielectric layer and the insulating layer, and the insulating layer and the support layer are bonded by adhesive layers 2 and 6, respectively.

  When the volume resistivity of the dielectric layer 1 is ρ1, the volume resistivity of the bipolar electrode 8 between the bipolar electrodes 8 is ρ2, and the volume resistivity of the insulating layer 4 is ρ3, ρ1 <ρ2 <Ρ3.

  Further, in the dielectric layer 1, it is preferable that the volume resistivity decreases sequentially from the adhesive layer 2 side toward the wafer mounting surface side.

  In order to obtain an electrostatic chuck that can be used over a wide temperature range, the inventors have reduced the volume resistivity of the dielectric layer to some extent and the volume resistivity between the bipolar electrodes of the electrostatic chuck electrode is a dielectric. It has been found that by making it higher than the volume resistivity of the layer, leakage current at high temperature can be prevented and electrostatic chucking force can be maintained.

  The main components of the dielectric layer, insulating layer, and support layer of the electrostatic chuck of the present invention are preferably ceramics. As the ceramic, aluminum nitride or silicon carbide having high thermal conductivity is preferable if importance is attached to the uniformity of temperature distribution. If importance is placed on reliability, silicon nitride is preferable because it is strong and resistant to thermal shock. If importance is attached to the cost, aluminum oxide is preferable.

  Among these ceramics, considering the balance between performance and cost, aluminum nitride (AlN) having high thermal conductivity and excellent corrosion resistance is preferable. Below, the manufacturing method of the electrostatic chuck of this invention is explained in full detail in the case of AlN.

The raw material powder of AlN preferably has a specific surface area of 2.0 to 5.0 m ² / g. When the specific surface area is less than 2.0 m ² / g, the sinterability of aluminum nitride is lowered. On the other hand, if it exceeds 5.0 m ² / g, the aggregation of the powder becomes very strong, so that handling becomes difficult. Furthermore, the amount of oxygen contained in the raw material powder is preferably 2 wt% or less. When the amount of oxygen exceeds 2 wt%, the thermal conductivity of the sintered body decreases. The amount of metal impurities other than aluminum contained in the raw material powder is preferably 2000 ppm or less. When the amount of metal impurities exceeds this range, the thermal conductivity of the sintered body decreases. In particular, group IV elements such as Si and iron group elements such as Fe as metal impurities have a high effect of reducing the thermal conductivity of the sintered body, and therefore the content is preferably 500 ppm or less.

  Since AlN is a hardly sinterable material, it is preferable to add a sintering aid to the AlN raw material powder. The sintering aid to be added is preferably a rare earth element compound. The rare earth element compound reacts with the aluminum oxide or aluminum oxynitride existing on the surface of the aluminum nitride powder particles during the sintering to promote the densification of the aluminum nitride and the thermal conductivity of the aluminum nitride sintered body. Therefore, the thermal conductivity of the aluminum nitride sintered body can be improved.

  The rare earth element compound is preferably an yttrium compound that is particularly effective in removing oxygen. The addition amount is preferably 0.01 to 5 wt%. The volume resistivity of the AlN sintered body depends on the amount of the sintering aid added. Moreover, when the addition amount is less than 0.01 wt%, it is difficult to obtain a dense sintered body, and the thermal conductivity of the sintered body decreases. If it exceeds 5 wt%, a sintering aid exists at the grain boundaries of the aluminum nitride sintered body. Therefore, when used in a corrosive atmosphere, the sintering aid present at the grain boundaries is etched. , Cause degranulation and particles. Furthermore, the amount of the sintering aid added is preferably 1 wt% or less. If it is 1 wt% or less, the sintering aid is not present at the triple point of the grain boundary, so that the corrosion resistance is improved.

  As the rare earth element compound, an oxide, nitride, fluoride, stearic acid compound, or the like can be used. Of these, oxides are preferable because they are inexpensive and readily available. In addition, since the stearic acid compound has a high affinity with an organic solvent, when the aluminum nitride raw material powder and the sintering aid are mixed with the organic solvent, the mixing property is particularly preferable.

  Next, a predetermined amount of a solvent, a binder and, if necessary, a dispersant and a glaze are added to and mixed with the aluminum nitride raw material powder and the sintering aid powder. As the mixing method, ball mill mixing, ultrasonic mixing, or the like is possible. A raw material slurry can be obtained by such mixing.

  An aluminum nitride sintered body can be obtained by molding and sintering the obtained slurry. Granules are prepared from the slurry by a technique such as spray drying. The granules are inserted into a predetermined mold and press-molded. At this time, the press pressure is desirably 9.8 MPa or more. When the pressure is less than 9.8 MPa, the strength of the molded body is often not sufficiently obtained, and is easily damaged by handling.

Although the density of a molded object changes with content of a binder, and the addition amount of a sintering auxiliary agent, it is preferable that it is 1.5 g / cm < ³ > or more. If it is less than 1.5 g / cm ³ , the distance between the raw material powder particles becomes relatively large, so that sintering does not proceed easily. Moreover, it is preferable that a molded object density is 2.5 g / cm < ³ > or less. If it exceeds 2.5 g / cm ³ , it will be difficult to sufficiently remove the binder in the molded body by the degreasing process in the next step. For this reason, it becomes difficult to obtain a dense sintered body as described above.

  Next, the molded body is heated in a non-oxidizing atmosphere to perform a degreasing treatment. When the degreasing treatment is performed in an oxidizing atmosphere such as the air, the surface of the AlN powder is oxidized, so that the thermal conductivity of the sintered body is lowered. As the non-oxidizing atmosphere gas, nitrogen or argon is preferable. The heating temperature for the degreasing treatment is preferably 500 ° C. or higher and 1000 ° C. or lower. When the temperature is less than 500 ° C., the binder cannot be sufficiently removed, and therefore excessive carbon remains in the laminated body after the degreasing treatment, which inhibits sintering in the subsequent sintering step. Further, at a temperature exceeding 1000 ° C., the amount of remaining carbon becomes too small, so that the ability of the oxide film present on the surface of the AlN powder to remove oxygen is lowered, and the thermal conductivity of the sintered body is lowered.

  Moreover, it is preferable that the carbon amount which remains in the molded object after a degreasing process is 1.0 wt% or less. If carbon exceeding 1.0 wt% remains, sintering is inhibited, and a dense sintered body cannot be obtained.

  Next, sintering is performed. Sintering is performed at a temperature of 1700 to 2000 ° C. in a non-oxidizing atmosphere such as nitrogen or argon. At this time, it is preferable that the moisture contained in the atmosphere gas such as nitrogen used is −30 ° C. or less in terms of dew point. In the case of containing more moisture than this, AlN reacts with moisture in the atmospheric gas during sintering to form oxynitrides, which may reduce the thermal conductivity. Moreover, it is preferable that the oxygen amount in atmospheric gas is 0.001 vol% or less. If the amount of oxygen is large, the surface of AlN may be oxidized and the thermal conductivity may be reduced.

  Furthermore, a boron nitride (BN) compact is suitable for the jig used during sintering. Since this BN compact has sufficient heat resistance to the sintering temperature and has a solid lubricating property on its surface, the friction between the jig and the laminate when the laminate shrinks during sintering. Therefore, a sintered body with less distortion can be obtained. The obtained sintered body is processed as necessary.

  Particularly, when the sintered body to be the insulating layer is screen-printed with the conductive paste in the next step, the surface roughness of the sintered body is preferably 5 μm or less in terms of Ra. If the thickness exceeds 5 μm, defects such as pattern bleeding and pinholes are likely to occur when a circuit is formed by screen printing. The surface roughness Ra is more preferably 1 μm or less.

  When polishing the above surface roughness, it is natural to screen print on both sides of the sintered body, but even when screen printing is performed only on one side, the surface opposite to the screen printed side is also polished. It is better to apply. When only the surface to be screen printed is polished, the sintered body is supported by the surface that is not polished during screen printing. At this time, there may be protrusions and foreign matters on the surface that has not been polished, so that the fixing of the sintered body becomes unstable, and the circuit pattern may not be drawn well by screen printing.

  At this time, the parallelism of both processed surfaces is preferably 0.5 mm or less. When the parallelism exceeds 0.5 mm, the thickness of the conductive paste may vary greatly during screen printing. The parallelism is particularly preferably 0.1 mm or less. Furthermore, the flatness of the screen printing surface is preferably 0.5 mm or less. Even in the case of flatness exceeding 0.5 mm, the variation in the thickness of the conductive paste may increase. A flatness of 0.1 mm or less is particularly suitable.

  A conductive paste is applied to the polished sintered body by screen printing to form an electric circuit such as an electrostatic chuck electrode or a heater electrode. The conductive paste can be obtained by mixing a metal powder and, if necessary, an oxide powder, a binder and a solvent. The metal powder is preferably tungsten or molybdenum from the viewpoint of matching the thermal expansion coefficient with ceramics.

In order to increase the adhesion strength with AlN, an oxide powder can also be added. The oxide powder is preferably an oxide of a IIa group element or a IIIa group element, Al ₂ O ₃ , SiO ₂ or the like. In particular, yttrium oxide is preferable because it has very good wettability to AlN. The addition amount of these oxides is preferably 0.1 to 30 wt%. When the content is less than 0.1 wt%, the adhesion strength between the metal layer, which is the formed electric circuit, and AlN is lowered. Moreover, when it exceeds 30 wt%, the electrical resistance value of the metal layer which is an electric circuit will become high.

  The thickness of the conductive paste is preferably 5 μm or more and 100 μm or less after drying. When the thickness is less than 5 μm, the electrical resistance value becomes too high and the adhesion strength also decreases. Moreover, also when exceeding 100 micrometers, adhesive strength falls.

  Moreover, when the electric circuit to be formed is a heater electrode, the interval between the patterns of the electric circuit is preferably 0.1 mm or more. If the interval is less than 0.1 mm, when a current is passed through the heater electrode, a leakage current is generated depending on the applied voltage and temperature, resulting in a short circuit. In particular, when used at a temperature of 500 ° C. or higher, the pattern interval is preferably 1 mm or more, more preferably 3 mm or more.

  In the present invention, a bipolar electrostatic chuck electrode is screen-printed on one side of a sintered body serving as an insulating layer, and a heater electrode is screen-printed on the other side.

  Next, the conductive paste is degreased and fired. Degreasing is performed in a non-oxidizing atmosphere such as nitrogen or argon. The degreasing temperature is preferably 500 ° C. or higher. If the temperature is less than 500 ° C., the binder in the conductive paste is not sufficiently removed and carbon remains in the metal layer, and metal carbide is formed when fired, so that the electric resistance value of the electric circuit becomes high.

  Firing is preferably performed at a temperature of 1500 ° C. or higher in a non-oxidizing atmosphere such as nitrogen or argon. When the temperature is less than 1500 ° C., the particle growth of the metal powder in the conductive paste does not proceed, so that the electric resistance value of the electric circuit after firing becomes too high. The firing temperature should not exceed the sintering temperature of the ceramic. When the conductive paste is fired at a temperature exceeding the sintering temperature of the ceramic, the sintering aid contained in the ceramic begins to evaporate, and further, the grain growth of the metal powder in the conductive paste is promoted, and the ceramic and the electric circuit. The adhesion strength of the is reduced.

  Moreover, it is also possible to use a mixture or alloy of silver, palladium, platinum or the like as the conductive paste. Since these metals increase the volume resistivity of the conductor by adding palladium or platinum to the silver content, the addition amount may be adjusted according to the circuit pattern. Moreover, since these additives have an effect of preventing migration between circuit patterns, it is preferable to add 0.1 parts by weight or more with respect to 100 parts by weight of silver.

  Moreover, it is also possible to use a mixture and alloy of Ni and Cr as the conductive paste. In particular, by adding about 20% by weight of Cr to Ni, it is possible to form a heating element having high electrical resistance and excellent heat resistance and corrosion resistance. In order to reduce the cost, Fe may be added up to 25% by weight, or in order to increase workability, 1% by weight of Mn may be added.

  A metal oxide is preferably added to these metal powders in order to ensure adhesion with AlN. For example, aluminum oxide, silicon oxide, copper oxide, boron oxide, zinc oxide, lead oxide, rare earth oxide, transition metal element oxide, alkaline earth metal oxide, or the like can be added. The addition amount is preferably 0.1 wt% or more and 50 wt% or less. If the content is less than this, the adhesion with aluminum nitride is lowered, which is not preferable. Further, if the content is higher than this, sintering of metal components such as silver is inhibited, which is not preferable.

  These metal powders and inorganic powders are mixed, an organic solvent or a binder is further added to form a paste, and a circuit can be formed by screen printing as described above. In this case, the formed circuit pattern is baked in a temperature range of 700 ° C. to 1000 ° C. in an inert gas atmosphere such as nitrogen or in the air.

  Further, in this case, in order to ensure insulation between circuits, crystallized glass, glaze glass, organic resin, or the like is applied, and the insulating layer can be formed by baking or curing. As the glass type, borosilicate glass, lead oxide, zinc oxide, aluminum oxide, silicon oxide, and the like can be used. An organic solvent and a binder are added to these powders to form a paste, which is applied by screen printing. Although there is no restriction | limiting in particular in the thickness to apply | coat, It is preferable that it is 5 micrometers or more. This is because if it is less than 5 μm, it is difficult to ensure insulation. The firing temperature is preferably lower than the temperature at which the circuit is formed. Baking at a higher temperature than the circuit baking is not preferable because the resistance value of the circuit pattern changes greatly.

  Next, an AlN sintered body on which an electric circuit is formed, a dielectric layer and a support layer are laminated. For the dielectric layer and the support layer, an AlN sintered body is produced in the same manner as described above by changing the addition amount of the sintering aid according to the target volume resistivity.

  Lamination is performed via an adhesive layer. The adhesive layer is formed by applying a bonding agent to the AlN sintered body, degreasing, and firing. The bonding agent is a paste obtained by adding a group IIIa element compound, a binder or a solvent to aluminum nitride powder, and applying the paste to the bonding surface by a method such as screen printing. Although there is no restriction | limiting in particular in the thickness of the bonding agent to apply | coat, it is preferable that it is 5 micrometers or more. When the thickness is less than 5 μm, bonding defects such as pinholes and bonding unevenness easily occur in the bonding layer.

In the present invention, the bonding agent is obtained by adding Y ₂ O ₃ to aluminum nitride powder or by adding Yb ₂ O ₃ , Nd ₂ O ₃ , CaCO ₃ , SiO ₂ , Al ₂ O ₃ to the aluminum nitride powder. Particularly preferred.

If the aluminum nitride adding _Y 2 _{O 3,} the addition amount of Y 2 _{O 3} is preferably in the range of 0.1 to 10 wt%. If it is less than 0.1% by weight, bonding defects are likely to occur in the adhesive layer. On the other hand, if it exceeds 10% by weight, the electric resistance of the metal layer becomes high.

In the case of adding Yb ₂ O ₃ , Nd ₂ O ₃ , CaCO ₃ , SiO ₂ , Al ₂ O ₃ , it is preferable that the total addition amount thereof is 2% by weight or more. If it is less than 2% by weight, bonding defects are likely to occur in the adhesive layer.

  The ceramic substrate coated with the bonding agent is degreased at a temperature of 500 ° C. or higher in a non-oxidizing atmosphere. Thereafter, the AlN sintered bodies to be laminated are overlapped, a predetermined load is applied, and the AlN sintered bodies are joined together by heating in a non-oxidizing atmosphere. The load is preferably 0.1 MPa or more. When the load is less than 0.1 MPa, sufficient bonding strength cannot be obtained, or the above-mentioned bonding defect tends to occur.

  The heating temperature for bonding is not particularly limited as long as the AlN sintered bodies are sufficiently adhered to each other through the bonding layer, but is preferably 1500 ° C. or higher. If it is less than 1500 degreeC, sufficient joint strength is hard to be obtained and it will be easy to produce a joint defect. Nitrogen or argon is preferably used for the non-oxidizing atmosphere during the degreasing and bonding.

  The dielectric layer and the insulating layer, and the insulating layer and the support layer can be laminated separately, but depending on the binder, they can be laminated at the same time. As described above, the electrostatic chuck of the present invention can be obtained.

  Next, a power supply electrode is attached to the electrostatic chuck. Attachment can be performed by a known method. For example, a counterbore process is performed from the opposite side of the workpiece mounting surface of the electrostatic chuck to the electrical circuit, and the electrical circuit is metalized or directly active metal brazing without metallization, and the extraction electrode 10 such as molybdenum or tungsten is used. Can be connected. Thereafter, the electrode can be plated as necessary to improve oxidation resistance.

  Further, a semiconductor wafer can be processed by incorporating the electrostatic chuck of the present invention into a semiconductor device. The holding body for a semiconductor manufacturing apparatus of the present invention can produce a semiconductor or a liquid crystal having excellent quality with few troubles of breakage of the ceramic holding portion and the support.

Mix 96 parts by weight of aluminum nitride powder and 4 parts by weight of Y ₂ O ₃ powder, mix 10 parts by weight and 5 parts by weight of polyvinyl butyral as binder and dibutyl phthalate as solvent, and granulate by spray drying. Created granules. The granules were formed by a uniaxial press so as to have a diameter of 350 mm and a thickness of 8 mm after sintering and processing. The aluminum nitride powder used had an average particle size of 0.6 μm and a specific surface area of 3.4 m ² / g.

  This molded body was degreased at 900 ° C. in a nitrogen atmosphere, and sintered in a nitrogen atmosphere at 1900 ° C. for 5 hours. The obtained sintered body had a thermal conductivity of 180 W / mK. After sintering, the upper and lower surfaces were polished so that Ra was 1 μm or less.

A W paste was prepared using 100 parts by weight of W powder having an average particle size of 2.0 μm, 1 part by weight of Y ₂ O ₃ , 5 parts by weight of ethyl cellulose as a binder, and butyl carbitol as a solvent. A lightning machine and three rolls were used for mixing. This W paste was screen printed to print a heater electrode pattern on one surface of the 350 mm diameter AlN sintered body. Further, an electrostatic chuck electrode was printed on the other surface of the AlN sintered body. This was degreased at 900 ° C. in a nitrogen atmosphere and baked by heating at 1850 ° C. for 1 hour in a nitrogen atmosphere.

Moreover, the AlN sintered compact used as the support layer of diameter 350mm and thickness 9mm was produced using the granule similar to the above. Furthermore, 99.5 parts by weight of aluminum nitride powder and 0.5 parts by weight of Y ₂ O ₃ powder were mixed, and an AlN sintered body that was a dielectric layer having a diameter of 350 mm and a thickness of 3 mm was produced in the same manner as described above.

A surface which is printed an electrostatic chuck electrode in the bipolar, the _Yb 2 _{O 3} 1% by weight AlN powder, _Nd 2 _{O 3} 1% by weight, the CaCO ₃ 0.25 wt%, a SiO ₂ 0.25 A kneading agent in which ethylene cellulose binder was added and kneaded was applied to a bonding agent to which 0.4% by weight of Al ₂ O ₃ was added. On the surface on which the heater electrode was printed, a mixture obtained by adding and kneading an ethylene cellulose binder to a bonding agent in which 4% by weight of Y ₂ O ₃ was added to AlN powder was applied.

  The AlN sintered body to which the bonding agent was applied was degreased at 900 ° C. in a nitrogen atmosphere. The surface on which the electrostatic chuck electrode is formed and the dielectric layer are combined, and the surface on which the heater electrode is formed and the support layer are combined, and a load of 0.1 MPa is applied to prevent deviation, It heated at 1700 degreeC for 1 hour, and joined.

  Counterbore processing was performed from the bottom surface side of the support layer to the heater electrode and the electrostatic chuck electrode to partially expose the heater electrode and the electrostatic chuck electrode. An electrode made of W is directly joined to the exposed heater electrode and electrostatic chuck electrode at 850 ° C. using an active metal brazing, a lead wire electrically connected outside the system is joined, and a dielectric layer is further formed. An electrostatic chuck having a dielectric layer thickness of 0.5 mm was prepared by polishing.

The chucking force of the produced electrostatic chuck was measured at room temperature (25 ° C.), 100 ° C., 200 ° C., 300 ° C., and 400 ° C. The chucking force is measured by energizing the heater electrode and raising the temperature to each set temperature, and then applying ± 500 V to the electrostatic chuck electrode to adsorb the Si wafer. × a case in which peeling in cm ²⁾ or less of the force, was evaluated as ○ the case you did not peel off even 7.84kPa (80g / cm ^2).

  Further, after measuring the chucking force, the electrostatic chuck is broken, and a sample is cut out from the dielectric layer, between the bipolar electrodes of the electrostatic chuck electrode (between electrodes, part 8 in FIG. 1), and the insulating layer at 300 ° C. The volume resistivity of was measured. For the measurement of the volume resistivity, the resistance value was measured with a 500 V mega tester and converted into the volume resistivity.

For comparison, Comparative Example 1 was prepared in the same manner as described above in which the Y ₂ O ₃ of the dielectric layer was 4% by weight, and the bonding agent for the dielectric layer and the insulating layer was the same as the bonding agent for the insulating layer and the support layer. In addition, Y ₂ O ₃ of the dielectric layer, the insulating layer, and the support layer is 0.5% by weight, and 0.5% by weight of Y ₂ O is added to the AlN powder for bonding the dielectric layer and the insulating layer and the insulating layer and the support layer. Comparative Example 2 as a bonding agent to which ₃ was added was also prepared and evaluated in the same manner as described above. These results are shown in Tables 1 and 2.

  As can be seen from Table 1, the electrostatic chuck of the present invention maintains the chucking force in the range from room temperature (25 ° C.) to 400 ° C., but in Comparative Example 1 it is 300 ° C. or higher, and in Comparative Example 2 it is 200 ° C. The chucking force can only be maintained under the following conditions.

In Example 1, since Y ₂ O ₃ of the dielectric layer was lowered to 0.5 wt%, Y ₂ O ₃ diffused from the insulating layer of 4 wt% and high Y ₂ O _{3 to} the bonding layer in the bonding step. Thus, it is considered that Y ₂ O _{3 in} the bonding layer between the dielectric layer and the insulating layer increased and the volume resistivity between the electrodes increased. Since the volume resistivity of the dielectric layer is low and the volume resistivity between the electrodes is high, the leakage current is small up to a high temperature and it can function as an electrostatic chuck in a wide temperature range.

On the other hand, in Comparative Example 1, since all the layers were 4% by weight Y ₂ O ₃ , the volume resistivity between the electrodes was high and the leakage current could be reduced, but the volume resistivity of the dielectric layer was also low. Since it is high, it did not function as an electrostatic chuck at low temperatures.

Further, in Comparative Example 2, since 0.5 wt% Y ₂ O ₃ in all layers, the volume resistivity between the electrodes is low, and the leakage current increases at high temperatures, so that it functions as an electrostatic chuck at high temperatures. I did not.

The bonding agent between the dielectric layer and the insulating layer was made by adding 0.5% by weight of Y ₂ O ₃ to AlN powder, and the bonding temperature between the dielectric layer and the insulating layer and between the insulating layer and the support layer was 1800. An electrostatic chuck similar to that of Example 1 was prepared except that the temperature was changed to ° C.

The electrostatic chuck was evaluated in the same manner as in Example 1. As a result, it functioned as an electrostatic chuck in a temperature range from room temperature (25 ° C.) to 400 ° C. The volume resistivity of the dielectric layer is 5.8 × 10 ⁸ Ωcm, the volume resistivity between the electrodes is 1.1 × 10 ¹⁰ Ωcm, and the volume resistivity of the insulating layer is 1.9 × 10 ¹⁰ Ωcm. It was.

The amount of warpage in Example 1 was 10.1 μm higher at the center, whereas the amount of warpage on the wafer mounting surface in Example 2 was 6.8 μm higher at the center. This is because the bonding temperature in Example 1 is lower than that in Example 2 and thus Y ₂ O ₃ did not diffuse, whereas in Example 2, the bonding temperature was high, so Y ₂ O _3. It is considered that the amount of warpage is reduced because the amount of Y ₂ O ₃ in the dielectric layer increases and approaches the composition of the insulating layer and the support layer.

Samples were cut out from the dielectric layers (wafer mounting surface side, intermediate portion, adhesive layer side), adhesive layer, and insulating layer of the electrostatic chucks of Example 1, Comparative Examples 1, 2 and Example 2, and the amount of Y ₂ O ₃ Were analyzed by EPMA. The results are shown in Table 3.

In Example 2, the amount of Y ₂ O ₃ in the dielectric layer is from the adhesive layer side toward the wafer mounting surface. Since it decreases gradually, it turns out that volume resistivity is decreasing sequentially.

  ADVANTAGE OF THE INVENTION According to this invention, the electrostatic chuck which can be used in a wide temperature range compared with the past can be provided. Moreover, the electrostatic chuck which reduced the curvature of the wafer mounting surface at the time of using at high temperature can be provided.

DESCRIPTION OF SYMBOLS 1 Dielectric layer 2 Adhesive layer 3 Electrode for bipolar electrostatic chucks 4 Insulating layer 5 Heater electrode 6 Adhesive layer 7 Support layer 8 Between electrodes of bipolar electrostatic chuck 10 Extraction electrode

Claims (2)

  An electrostatic chuck comprising a bipolar electrostatic chuck electrode and a heater electrode, wherein the dielectric layer has a volume resistivity of ρ1, a volume resistivity of the electrostatic chuck electrode between the bipolar electrodes is ρ2, static An electrostatic chuck characterized in that ρ1 <ρ2 <ρ3, where ρ3 is a volume resistivity between the electrode for the electric chuck and the heater electrode.   2. The electrostatic chuck according to claim 1, wherein the volume resistivity in the dielectric layer is gradually decreased from the electrostatic chuck electrode side toward the wafer mounting surface. 3.

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