JP5056029B2 - Wafer holder for semiconductor manufacturing apparatus, manufacturing method thereof and semiconductor manufacturing apparatus equipped with the same - Google Patents

Description

  The present invention relates to a wafer holder used in a semiconductor manufacturing apparatus, a manufacturing method thereof, and a semiconductor manufacturing apparatus equipped with the wafer holder.

  Conventionally, ceramic heaters have been used as wafer holders (susceptors) for semiconductor manufacturing equipment. For example, as described in Japanese Patent Application Laid-Open No. 04-078138, a ceramic heater in which a heating element is embedded has been put into practical use. Further, in recent years, a technique for embedding a high-frequency generating electrode in ceramics, generating plasma, and forming a film on a wafer has been developed.

  For example, Japanese Patent Application Laid-Open No. 06-291049 discloses an aluminum nitride heater in which a high frequency generating electrode is embedded. In this publication, as described in paragraph 0021 of the specification, a high frequency generating electrode is formed by applying a paste of titanium nitride or tungsten to a green sheet of aluminum nitride and laminating the green sheets.

  In addition, a technique for optimizing the heat generation pattern formed on the heater using simulation in order to make the thickness of the film formed on the wafer uniform is also disclosed.

As described above, in the susceptor in which the high-frequency generating electrode is embedded, in order to generate plasma uniformly, it is attempted to solve the problem by making the distance from the wafer to the embedded high-frequency generating electrode constant. However, in actuality, there is also an influence of the impedance of the embedded high-frequency generating electrode itself, so that plasma is uniformly generated on the wafer, and a uniform film thickness that can cope with the recent miniaturization of semiconductor circuits is formed on the entire surface of the wafer. It has not reached.
Japanese Patent Laid-Open No. 04-078138 Japanese Patent Application Laid-Open No. 06-291049

  The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a wafer holder capable of uniformly generating plasma on a wafer and forming a uniform film thickness on the entire surface of the wafer to cope with the recent miniaturization of semiconductor circuits. . It is another object of the present invention to provide a method for manufacturing the wafer holder and a semiconductor manufacturing apparatus on which the wafer holder is mounted.

Wafer holder of the present invention is a wafer holder that embedded high-frequency generating electrode in a ceramic sintered body, wherein the distance from the high-frequency generation electrode to the wafer mounting surface is constant rather than, the The maximum value of the distance is 3 mm or less, the minimum value is 0.2 mm or more, the difference between the maximum value and the minimum value of the distance is 2 mm or less, and the sheet resistance value of the high frequency generating electrode is 50 mΩ / □ or less. The high-frequency generating electrode has a thickness of 3 μm or more and 100 μm or less, and the external connection electrode connected to the high-frequency generating electrode is present at a substantially central portion of the high-frequency electrode . By not making the distance from the wafer mounting surface to the high frequency generating electrode constant, plasma is uniformly generated on the wafer, and a uniform film thickness that can cope with the recent miniaturization of semiconductor circuits is formed on the entire surface of the wafer. Can do. In particular, when the distance is in the above range and the sheet resistance value is 50 mΩ / □ or less, more uniform plasma can be generated.

  If the distance is not constant, the distance from the high-frequency generating electrode to the wafer mounting surface may be increased or decreased from the center to the end of the wafer mounting surface. .

The high-frequency generating electrode may be made of refractory metal such as tungsten, molybdenum, or tantalum, stainless steel, nichrome, or the like. Among these, it is preferable that tungsten is a main component, and it is preferable that the tungsten is formed by thick film printing . By mainly of high-frequency generating electrode tungsten, also to 12 inches or more in size of the wafer, the thermal expansion coefficient difference between the ceramic such as aluminum nitride is small, the production of wafer holder This is preferable because warpage during time, warpage during use, deformation, and the like can be minimized . Sheet over sheet resistance value is more preferably 30 m [Omega] / □, if 10 m [Omega / □, more preferred.

If the thickness of the high-frequency generating electrode is less than 3 μm, the resistance of the high-frequency generating electrode increases, so that the high-frequency generating electrode generates heat and the temperature uniformity of the wafer holder is impaired. On the other hand, when the thickness exceeds 100 μm, the adhesion between the ceramic constituting the wafer holder and the high frequency generating electrode is deteriorated, and a gap is generated between the ceramic and the high frequency generating electrode, and uniform plasma cannot be generated.

  Since the semiconductor manufacturing apparatus on which the wafer holder as described above is mounted can generate plasma uniformly, the yield of the semiconductor to be manufactured can be improved and the performance of the semiconductor can be improved. .

  The wafer holder as described above can be obtained by sandwiching an unfired ceramic molded body in which a high-frequency generating electrode is embedded in a curved jig and applying a pressure of 0.98 kPa or more to sinter. In addition, when the ceramic sintered body on which the high-frequency generating electrode is formed and the ceramic sintered body to be bonded on the high-frequency generating electrode are heat-bonded through the bonding layer, both the ceramic sintered bodies are curved. It can also be obtained by sandwiching both ceramic sintered bodies by sandwiching them in a jig and applying a pressure of 98 kPa or more. Furthermore, the ceramic sintered body in which the high frequency generating electrode is embedded can be sandwiched between curved jigs, heated by applying a pressure of 98 kPa or more, and heated.

  According to the present invention, the distance to the wafer mounting surface of the high frequency generating electrode embedded in the ceramic sintered body is not constant. That is, by controlling the distance of the high-frequency generating electrode to the wafer mounting surface, plasma generation can be made uniform and the thickness of the film formed on the wafer can be made uniform.

  Usually, the high frequency generating electrode embedded in the ceramic sintered body is connected to a grounded part such as a ground point existing outside the ceramic, for example, a container in which a susceptor is installed. At this time, the ground wire connected to the ground point is connected to the high frequency generating electrode embedded in the ceramic. The intensity of the plasma generated on the actual wafer is strongly influenced by the impedance to the ground wire at each point on the wafer. That is, in general, the plasma is strong in a portion where the impedance is small, so that the film thickness is thick. In the portion where the impedance is large, the plasma is relatively weak, and thus the film thickness tends to be thin. However, since the behavior of the plasma changes depending on the type of gas in the chamber, its flow rate, pressure, and wafer temperature, there may be a tendency opposite to the above. However, when the predetermined reaction gas is uniformly supplied onto the wafer by using, for example, a shower head, it is strongly influenced by the impedance and the temperature of the wafer. However, with regard to the temperature of the wafer, development has recently progressed, and soaking characteristics have been improved by using simulation techniques and the like.

  Factors that affect the impedance to the ground wire at each point on the wafer include, when the wafer temperature and wafer thickness are constant, the atmosphere from the wafer to the high-frequency generating electrode, and the dielectric (high-frequency generating electrode). The thickness of the ceramic sintered body between the wafer surface and the wafer mounting surface, that is, the impedance from the wafer surface to be deposited to the high frequency generating electrode and the impedance from the high frequency generating electrode to the ground point. That is, the sum of these factors determines the plasma intensity on the wafer and the thickness of the film formed on the wafer.

  Among the factors affecting the above, regarding the impedance of the high frequency generating electrode, if the resistance value of the unit distance of the high frequency generating electrode embedded in the ceramic is uniform, the impedance to the point connected to the ground wire is It will be proportional. For this reason, when the distance to the high frequency generating electrode embedded in the ceramics at each point on the wafer is constant, the impedance is constant because the distance to the ground wire is different at each point as described above. No. For this reason, it has been found that the intensity of the plasma generated on the wafer is made constant by adjusting the distance from the wafer surface on which the film is formed to the high frequency generating electrode. That is, the present invention is characterized in that the distance from the wafer to the high-frequency generating electrode is not constant. Thus, by controlling (designing) the distance from the wafer surface to the embedded high-frequency generating electrode, the plasma intensity can be made uniform over the entire wafer surface.

  For example, when the wafer mounting surface is a uniform plane and the wafer is parallel to the wafer mounting surface, in order to make the impedance from each point of the wafer to the ground line constant, the wafer mounting surface What is necessary is just to control so that the distance from a mounting surface to the electrode for high frequency generation may become small gradually with respect to the direction which goes to the outer peripheral part of a wafer. That is, uniform plasma intensity can be realized by controlling the difference in impedance from the high frequency generating electrode to the ground point at each point by the thickness of the dielectric from the high frequency generating electrode to the wafer.

  That is, as shown in FIG. 1, in the ceramic sintered body 4 in which the high frequency generating electrode 2 and the heating element 3 are embedded, the distance from the wafer mounting surface 1 to the high frequency generating electrode 2 is from the center to the end. Try to be shorter towards. Conventionally, as shown in FIG. 3, the wafer mounting surface 1, the high frequency generating electrode 2, and the heating element 3 are substantially parallel.

  In recent years, a susceptor in which the mounting surface has a concave shape has been proposed in order to make the temperature of the wafer uniform and to improve the reliability against damage to the susceptor. In such a susceptor, when the wafer is not warped, a space exists between the wafer and the wafer mounting surface of the ceramic susceptor. In this case, the impedance between the wafer and the high frequency generating electrode is the sum of the impedance in the space portion and the impedance in the ceramic portion.

  The impedance in this space portion depends on the kind of gas existing between the wafer and the wafer mounting surface and the pressure thereof, but the dielectric constant is about 1 in general. On the other hand, the dielectric constant of ceramics is about 4 to 12 although it varies depending on the type. Since the impedance is proportional to 1 / ωC (ω: frequency, C: dielectric constant), the smaller the dielectric constant, the greater the influence on the impedance. For this reason, it is necessary to consider the resistance value at the unit distance of the high-frequency generating electrode, but the embedded position of the high-frequency generating electrode is generally closer to the wafer mounting surface as it is closer to the ground point, and conversely far from the ground wire The distance from the wafer mounting surface 1 to the high frequency generating electrode 2 becomes longer from the center to the end as shown in FIG. .

  When there is a space between the wafer and the mounting surface in this way, protrusions such as embosses are formed on the mounting surface and the wafer is supported to minimize the effects of wafer deflection. Can do. There are no particular restrictions on the shape of the emboss, but it may be formed at a pitch that does not allow the wafer to bend, specifically at intervals of 50 mm or less. When the distance exceeds 50 mm, the wafer may be bent between the embosses, which may adversely affect the generation of plasma. A more preferable embossing interval is 30 mm or less. Such an interval is preferable because the influence of the deflection of the wafer can be almost eliminated.

  Further, in order to make the temperature of the wafer uniform and prevent the wafer from being attracted to the mounting surface, embossing may be formed on the wafer mounting surface. In such a case, the embossing interval is the same as described above, and the embedding position of the high frequency generating electrode may be determined in consideration of the impedance at each point on the wafer according to the height of the embossing. For this, the same calculation as in the case where the shape of the wafer mounting surface is a concave shape may be performed.

  That is, in the present invention, as shown in the above two examples, the installation position of the high frequency generating electrode is determined up to the wafer mounting surface in consideration of the shape of the wafer mounting surface and the impedance of the high frequency generating electrode itself. Since the distance is not constant, the intensity of plasma on the wafer can be made uniform, and a film having a constant thickness can be formed on the wafer.

  The distance from the wafer placement surface to the high frequency generating electrode is preferably 0.2 mm or more. When the thickness is less than 0.2 mm, the strength of the dielectric existing between the high-frequency generating electrode and the wafer mounting surface becomes small, which is not preferable. That is, it is not preferable because the dielectric may be damaged by a temperature cycle applied to the wafer holder or a temperature impact applied when the wafer is placed on the placement surface. The maximum thickness of the dielectric layer is preferably 3 mm or less. If the distance from the high-frequency generating electrode to the wafer mounting surface exceeds 3 mm, the impedance from the wafer to the high-frequency generating electrode will inevitably increase, and the plasma generation intensity will decrease. Is unfavorable because of lowering. In view of the above, the thickness of the dielectric layer is preferably 0.2 mm to 3 mm. Particularly, if the thickness is 0.3 mm to 2 mm, the dielectric strength can be ensured and a relatively strong plasma can be generated uniformly. Is preferable.

  Further, the distance from the wafer placement surface to the wafer is preferably 1 mm or less. As described above, when a space is formed between the wafer placement surface and the wafer, the influence of the temperature distribution of the wafer holder is reduced, and the thermal uniformity can be improved. However, as described above, since the impedance of the space portion is large, if the distance from the wafer mounting surface to the wafer is increased, the impedance variation at each point on the wafer surface is reduced as a result. Can do. However, as described above, the space between the wafer and the mounting surface has a low dielectric constant and the impedance becomes too large. Therefore, if the wafer is too far from the mounting surface, the intensity of the generated plasma Is not preferable because the throughput is reduced.

  In order not to reduce the intensity of plasma generation, it is more preferable that the height of the embossment be 0.5 mm or less. Even in the absence of embossing, the plasma intensity can be kept high. However, the wafer is attracted to the mounting surface and cannot be separated from the mounting surface. For example, when the wafer is separated from the mounting surface by the lifter pins, the wafer may be damaged. The height is preferably 2 μm or more, and the embossing interval is preferably 50 mm or less as described above. An interval and height below this level are preferable because it is possible to prevent the wafer from being attracted to the mounting surface and to obtain a wafer holder excellent in heat uniformity. Considering heat uniformity, the height of the emboss is preferably 5 μm or more.

  The difference between the maximum value and the minimum value of the distance from the wafer mounting surface to the high frequency generating electrode is preferably 2 mm or less. When the gap difference exceeds 2 mm, the impedance difference may be adjusted by the gap between the wafer placement surface and the wafer, but the space between the wafer and the placement surface is partially increased. For example, in the case of aluminum nitride having a dielectric constant of about 8 to 9, in order to adjust the above difference, it is necessary to form a distance between the wafer mounting surface and the wafer of at least 0.2 mm or more. In this case, a portion where the distance between the wafer mounting surface and the wafer becomes excessively large appears, so that when the wafer is mounted on the mounting surface, temperature distribution is likely to occur in the wafer surface, and the wafer Since it takes time until the in-plane temperature becomes uniform, the throughput decreases, which is not preferable. A preferred distance difference is within 1.5 mm. This level is preferable because variations in the temperature distribution in the wafer are reduced and the decrease in throughput is reduced.

  Moreover, there is no restriction | limiting in particular as a shape of the electrode for high frequency generation, A mesh-like metal, a film-like, foil-like metal, etc. can be selected. For this reason, the impedance is determined by the material of the high-frequency generating electrode to be embedded, its thickness, surface area, and the like. However, even in the case of a mesh with the lowest impedance, there is a limit to the wire diameter of the mesh that can be embedded in ceramics. When embedding by a technique such as hot pressing, the wire diameter of the mesh is 1 mm or less. When the wire diameter exceeds 1 mm, the ceramics and the mesh may be peeled off by the temperature cycle applied to the wafer holder, which is not preferable. If the distance from the wafer placement surface to the wafer in this case is constant, the distance from the wafer placement surface in the vicinity of the ground wire to the high-frequency generating electrode can be determined by considering the distance to the ground wire in terms of the size of the 8-inch wafer. The difference between the distance and the distance from the wafer mounting surface at the high frequency generating electrode end to the high frequency generating electrode must be 0.001 mm.

  In recent years, in order to remove a film attached to the wafer holder, the inside of the chamber including the wafer holder is cleaned using a fluorine-based gas. For this reason, the material of the wafer holder needs to be ceramics. Examples of ceramics that can be used include alumina, silicon carbide, silicon nitride, mullite, boron nitride, and aluminum nitride. Of these, aluminum nitride is most preferable because of its relatively high thermal conductivity, excellent thermal uniformity, and excellent corrosion resistance.

  In addition, as the material for the high frequency generating electrode embedded in the wafer holder, ceramics is preferably used for the wafer holder, so that the thermal expansion is close to that of the ceramics. For example, refractory metals such as tungsten, molybdenum, and tantalum, stainless steel, nichrome, and the like can be raised. As described above, when aluminum nitride having excellent corrosion resistance and soaking is used as a wafer holder, molybdenum or tantalum having a relatively small difference in thermal expansion coefficient is particularly preferable. Moreover, since these materials have a very high melting point, they can be sintered simultaneously with aluminum nitride. These materials can also be processed into meshes and foils. These can be embedded in a molded body and sintered to form a wafer holder.

  Further, the high frequency generating electrode can be formed by a method such as screen printing. In screen printing, a relatively uniform film can be formed in a plane. When a metal mesh is used as the high frequency generating electrode, the distance from the wafer placement surface to the high frequency generation electrode is not present when the metal wire constituting the metal mesh is present directly below the wafer placement surface. In some cases, the distance to the high-frequency generating electrode is slightly different, which may cause plasma non-uniformity. Moreover, in the metal mesh, even if it is the wafer mounting surface at the same distance to the ground wire, since the metal wire is knitted, the portion connected to the ground wire in a straight line and the two straight lines are connected. The impedance differs from the portion. This phenomenon is particularly noticeable when the mesh is coarse, and is particularly noticeable at 5 mesh or less. Moreover, if the high frequency generating electrode is formed of a metal foil, the above-described problems can be solved.

  In other words, the high frequency generating electrode is present directly below any location on the wafer mounting surface, and can be connected by a straight line to any location up to the ground wire. However, when a metal foil is inserted into ceramics, for example, the metal foil is placed in a molded body, and the ceramic is sintered by a technique such as hot pressing. However, sufficient adhesion strength is provided between the metal foil and the ceramics. It may not be obtained. In view of the above, as the high-frequency generating electrode, a film applied by a technique such as screen printing that hardly causes the above-described problems is preferable.

  The sheet resistance value of the high frequency generating electrode formed in the ceramic is preferably 50 mΩ / □ or less. This is because the area of the high-frequency generating electrode has increased with the recent increase in wafer size (12 inches). At this time, the distance to the ground wire inevitably increases, and the absolute value of the impedance increases. For this reason, the intensity of the plasma generated on the wafer is weakened, the time for forming a film with a predetermined film thickness is increased, and this may cause a reduction in throughput, which is not preferable. A suitable sheet resistance value of 10 mΩ / □ or less is particularly preferable because a sufficiently low impedance can be obtained.

  The film thickness of the high frequency generating electrode is preferably 3 μm or more. With the recent increase in size of wafers, the power applied to the high frequency generating electrode increases, and in some cases, a current exceeding several amperes (A) flows through the high frequency generating electrode. The generating electrode itself generates heat, which may impair the thermal uniformity of the wafer. In the worst case, the RF circuit itself may be burned out, which is not preferable. Preferably it is 5 micrometers or more, Furthermore, it is 10 micrometers or more. A thickness of 10 μm or more is preferable because a calorific value is relatively small even when a current of about 20 A flows. However, when the film thickness exceeds 100 μm, the adhesion of the high frequency generating electrode to the ceramic begins to deteriorate, and in some cases, a gap may be formed between the ceramic and the electrode, and the predetermined impedance value increases. May end up. The most preferable film thickness is about 10 μm to 50 μm.

  Moreover, the installation position of the ground wire is not particularly limited, but is preferably substantially at the center of the wafer holder. The presence of the ground wire near the center makes the impedance distribution of the high frequency generating electrode itself concentric. For this reason, since it becomes easy to control to the impedance value below a predetermined value in comparatively any part, it is preferable. In addition, it is preferable to install in the vicinity of the center portion because the flow of high frequency applied to the ground wire from each direction becomes constant and the variation in high frequency depending on the direction of the ground wire is reduced.

  The ground wire connected to the center part preferably has a large surface area. In particular, when a high frequency of 1 MHz or more is applied to the high frequency generating electrode, the ratio of the high frequency flowing on the outer surface of the metal becomes high. For this reason, when the ground wire is cut along a cross section through which a high frequency flows, the length of the outer peripheral portion is preferably 3.14 mm or more. For example, when the diameter of the ground wire is 1 mm, the length of the outer surface of the cut surface is 3.14 mm. Therefore, in particular, when a high frequency of 10 MHz or more is applied to a 12-inch wafer holder, it is necessary to have an outer peripheral length of 6.28 mm or more. In order to have this length, for example, a ground wire having a diameter of 2 mm can be used, or two ground wires having a diameter of 1 mm can be used. When the outer peripheral length is not satisfied as described above, the ground wire itself generates heat, so that the heat uniformity on the wafer holder may be reduced, and in the worst case, the ground wire may be melted.

Also, since the ground wire transmits high frequency, plasma may be generated in the ground wire itself. In such a case, metal atoms constituting the ground wire itself may be turned into plasma , and therefore it is preferable to use a covering material such as an insulating pipe in order to avoid this. In addition, it is preferable to coat a metal such as nickel which is difficult to contaminate the wafer even if plasma is generated. Examples of the coating method include thermal spraying and plating.

  There are three methods for manufacturing the wafer holder described above. First, a ceramic green sheet is prepared. For example, the thickness is set to 0.5 mm. Here, a high frequency generating electrode is applied and formed by screen printing. Laminate and laminate unprinted sheets there. At this time, it is also possible to stack sheets on which the heating element circuit pattern is printed. This is degreased and sintered, but the jig to be used at that time is formed into the shape of the high frequency generating electrode, the molded body is set on it, and the opposite of the jig set on the lower side of the molded body A wafer holder having a predetermined RF shape can be formed by setting a jig having the following shape, degreasing, and sintering. At this time, a predetermined shape can be formed by applying a predetermined pressure to the compact during sintering.

  At this time, the pressure is applied at a temperature lower than the sintering temperature. However, if the pressure is applied at a temperature lower than 500 ° C., the molded body may be damaged, which is not preferable. The pressure applied at the time of sintering may be 0.98 kPa or more. A pressure lower than this is not preferable because it may not be deformed into a predetermined shape during sintering. Moreover, it is preferable to continue applying the pressure to a temperature lower by 200 ° C. or more than the sintering temperature. If the pressure is released at a temperature higher than this, it may not change into a predetermined shape, which is not preferable.

  By adopting such a manufacturing method, the embedding position of the high frequency generating electrode in the ceramic can be suppressed to a variation of 0.5 mm or less with respect to the design value. This is because the ceramic is deformed at a high temperature as described above, so that it can be easily deformed along the shape of the jig. Further, it is particularly preferable to apply a pressure of 4.9 kPa or more because the embedded position can be formed in a shape of 0.1 mm or less with respect to a predetermined design value.

  The jig used for degreasing is preferably a porous jig, and examples thereof include carbon, graphite, and BN compacts. Regarding sintering, a jig having lubricity such as a BN molded body is preferable when performing normal pressure sintering, and a carbon or graphite jig is preferable when using a hot press or the like.

  It can also be produced by sandwiching a metal foil or mesh between laminated sheets and laminating and hot pressing. A wafer holder can be formed by processing the surface of the wafer holder thus completed.

  As another method, a flat jig is used for the molded body and the degreased body, and first, a sintered body in which the high-frequency generating electrode and the wafer mounting surface are parallel is manufactured. Thereafter, there is also a technique of hot pressing using a jig designed to have a high-frequency generating electrode shape designed as described above. In this case, the temperature at which pressure starts to be applied to the sintered body during hot pressing needs to be 200 ° C. or lower than the temperature at which the sintered body was sintered. This temperature is preferable because the ceramic itself is relatively softened and the ceramic sintered body is not damaged by the load by hot pressing. If pressure is applied suddenly at a low temperature exceeding 200 ° C., the sintered body may be damaged, which is not preferable. The applied pressure is preferably 98 kPa or more. A low pressure of less than 98 kPa is not preferable because the sintered body may not be deformed into a predetermined shape. By adopting such a manufacturing method, the embedding position of the high frequency generating electrode in the ceramic can be suppressed to a variation of 0.5 mm or less with respect to the design value. This is also because the ceramic sintered pair is deformed at a high temperature as described above and can be easily deformed along the shape of the jig. Further, it is particularly preferable to apply a pressure of 490 kPa or more because the embedded position can be formed in a shape of 0.1 mm or less with respect to a predetermined design value.

  There is also a technique in which a compact is prepared in advance using a technique such as press molding, and a metal foil or a metal mesh is sandwiched between the compacts and hot pressing is performed. Even at this time, the shape of the molded body may be deformed according to the RF shape designed in advance and hot pressed. Since the pressure applied at this time sandwiches a metal mesh or foil, a pressure of 98 kPa or more is necessary. A pressure of less than 98 kPa is not preferable because a mesh, a metal foil, or the like may not sufficiently adhere to the ceramic. By adopting such a manufacturing method, the embedding position of the high frequency generating electrode in the ceramic can be suppressed to a variation of 0.5 mm or less with respect to the design value. This is because the ceramic is deformed at a high temperature as described above, so that it can be easily deformed along the shape of the jig. Further, it is particularly preferable to apply a pressure of 490 kPa or more because the embedded position can be formed in a shape of 0.1 mm or less with respect to a predetermined design value.

  In addition, a plurality of sintered bodies are formed in advance by a technique such as press molding or sheet molding, a high frequency generating electrode is formed on the surface of the sintered body by screen printing, and another sintered body is formed as a sintered body. A material having at least one component contained in the material and having a softening temperature lower than that of the sintered body is applied as a bonding agent to the surface of the sintered body and bonded. At this time, if hot pressing is performed by hot pressing using a jig formed in the shape of a high frequency generating electrode in the same manner as described above, a high frequency generating electrode having a predetermined shape can be obtained. The applied pressure is preferably 98 kPa or more. When the pressure is less than 98 kPa, the sintered body may not be deformed into a predetermined shape, which is not preferable. By adopting such a manufacturing method, the embedding position of the high frequency generating electrode in the ceramic can be suppressed to a variation of 0.5 mm or less with respect to the design value. This is because the ceramic is deformed at a high temperature as described above, so that it can be easily deformed along the shape of the jig. Further, it is particularly preferable to apply a pressure of 490 kPa or more because the embedded position can be formed in a shape of 0.1 mm or less with respect to a predetermined design value.

  Of the above methods, when hot pressing is performed, it is necessary to continue to apply pressure to at least the softening temperature of the sintered body. Specifically, it is necessary to continue to apply pressure to a temperature that is at least 200 ° C. lower than the sintering temperature when the sintered body is formed. If the pressure is released in the middle, it may be deformed from a predetermined shape, which is not preferable.

  In the wafer holder manufactured as described above, the high-frequency generating electrode has a predetermined shape, and according to the shape, surface processing of the wafer mounting surface is performed, and a wafer pocket, embossing, etc. Thus, the wafer holder can be completed.

  Furthermore, a ground wire having a predetermined shape can be connected to the high frequency generating electrode of the completed wafer holder, and a heater electrode can be connected as necessary to complete the wafer holder.

  As described above, the wafer holder of the present invention always generates stable plasma on the wafer because the distance to the wafer mounting surface of the high frequency generating electrode is not constant as in the prior art. Is possible. That is, the semiconductor manufacturing apparatus equipped with the wafer holder of the present invention makes the plasma generated on the wafer uniform, and the plasma CVD apparatus can form a more uniform film on the wafer than ever.

0.5 part by weight of yttrium oxide (Y ₂ O ₃ ) is added to 99.5 parts by weight of aluminum nitride (AlN) powder, an acrylic binder and an organic solvent are added, and they are mixed for 24 hours in a ball mill to obtain an AlN slurry. Was made. Granules were produced from this slurry by spray drying, press molded, degreased in a nitrogen atmosphere at 700 ° C., and sintered in a nitrogen atmosphere at 1900 ° C. The sintered body has a diameter of 330 mm, and the thickness is 1 sheet of 2 mm and 2 sheets of 10 mm.

A heating element was formed on one side of a sintered body having a thickness of 10 mm by screen printing with W paste. The W paste used was prepared by adding 0.5 wt% of Y ₂ O ₃ to W powder having an average particle size of 2.0 μm, and further adding a binder and a solvent. A pot mill and three rolls were used for mixing. Next, a high-frequency generating electrode having a diameter of 320 mm was formed on the opposite surface by screen printing in the same manner as the heating element. After printing on both sides, degreasing was performed in a nitrogen atmosphere, and the heating element and the high frequency generating electrode were fired in a nitrogen atmosphere at 1850 ° C. The thickness of the high frequency generating electrode after firing was 20 μm.

Next, an aluminum nitride paste was applied to both sides by screen printing. The aluminum nitride paste used at this time was 99.5% aluminum nitride plus 0.5% yttrium oxide. After degreasing this was fired at 1850 ° C. in a nitrogen atmosphere, AlN (20 _wt%) as a bonding paste on both surfaces of the substrate _{- Al 2 O 3 (50wt%} ) - Y 2 O 3 a paste (30 wt%) A 2 mm thick AlN sintered body was attached to the surface on the high frequency generating electrode forming side, and a 10 mm thick AlN sintered body was attached to the heating element side, and heat treatment was performed at 1800 ° C. with a hot press to form a wafer holder. . At this time, by changing the curvature of the contact surface with the AlN sintered body such as BN jig, carbon jig, graphite jig, etc. used for hot pressing, the embedding position of the electrode for generating high frequency can be various. changed. At the time of bonding, no pressure was applied up to 1750 ° C., pressure was applied from 1750 ° C., and finally a pressure of 2.2 MPa (20 t) was applied, and the pressure was applied and cooled to room temperature. The finished holding body can be subjected to processing such as polishing, and embossing or the like can be formed as necessary.

  Table 1 shows the shape of the finished wafer holder. In Table 1, the coordinate position when the coordinate of the center part of the wafer mounting surface is 0 is described. As for the coordinate position, the thickness of the dielectric layer was measured using an eddy current meter. In any of the wafer holders, the sheet resistance value of the high frequency generating electrode was 5 mΩ / □.

  As the external connection electrode connected to the high frequency generating electrode, a W rod having a diameter of 5 mm was used at the center of the wafer holder. This W rod was connected by performing counterboring from the opposite side of the wafer holding surface of the wafer holder, bringing the W electrode into contact with the high-frequency generating electrode, and silver brazing. The surface is formed with nickel plating of 3 μm.

  Embosses having a diameter of 5 mm were formed on the wafer mounting surface at a pitch of 1 inch. The embossing height was 20 μm. When the surface formed by the lower end of the emboss is curved, the shortest emboss height is set to 20 μm.

  These wafer holders were subjected to counterboring from the wafer mounting surface to the end of the heating element circuit pattern, and a W electrode for power feeding was brazed. The W electrode connected to the high frequency generating electrode was connected to a chamber portion (earth) where the wafer holder was set.

Then, a maximum voltage of 200 V was applied to the heating element of the wafer holder, and the wafer holder was heated to 500 ° C. Then, a 12-inch Si wafer was mounted on the wafer holder, a high frequency of 13.56 MHz was applied, plasma was generated, silane gas and nitrogen gas were passed, and Si ₃ N ₄ was formed. The film thickness was formed so that the center value was 2 μm, and after the film formation was completed, the thickness variation of the film deposited on the wafer was measured. The results are shown in Table 1.

＊：比較例

*: Comparative example

  In sample 1, the wafer mounting surface (wafer) and the high-frequency generating electrode are parallel, and the film thickness variation at this time is a very large value of 11%. On the other hand, when the end of the high frequency generating electrode is made to be close to the wafer mounting surface (sample 2), the thermal uniformity of the wafer is not changed, but the end impedance is lower than that of sample 1. Therefore, it can be seen that the variation in film thickness is small. In Sample 3, the heat uniformity of the wafer was improved by making the distance from the wafer at the end of the wafer mounting surface uniform. However, since the distance from the wafer to the high-frequency generating electrode was relatively large, It can be seen that the film time is longer. Further, although the sample 4 shows a decrease in the thermal uniformity, it can be seen that the film thickness variation in film formation is smaller than that in the comparative example.

  A wafer holder similar to that of Example 1 was produced. However, hot press sintering was performed using a flat jig having no curved surface. The completed wafer holder was further hot-pressed using a BN jig having a curved surface in contact with the AlN sintered body, and the burying position of the high-frequency generating electrode was changed.

  Table 2 shows the shape of the completed wafer holder. In Table 2, the coordinates of the central portion of the wafer mounting surface are expressed as coordinate positions where 0 is assumed. In any of the wafer holders, the sheet resistance value of the high frequency generating electrode was 4 mΩ / □.

The wafer mounting surface was embossed in the same manner as in Example 1, and Si ₃ N ₄ was formed and evaluated in the same manner as in Example 1. The results are shown in Table 2.

＊比較例

* Comparison example

  In Example 2, since the bonded wafer holder was further hot-pressed, the sheet resistance value of the high-frequency generating electrode was reduced, so that the film formation time was longer than in Example 1. There was no significant difference in variation.

  A slurry was prepared in the same manner as in Example 1. Thereafter, a green sheet having a thickness of 0.5 mm was prepared by a doctor blade method. A high frequency generating electrode was printed on the completed green sheet by screen printing in the same manner as in Example 1. A heater circuit pattern was formed on a separate sheet by screen printing. A sheet not printed separately from the printed sheet was laminated at 130 ° C. and degreased in the same manner as in Example 1. The completed degreased body was set on a BN jig. The BN jig used at this time is curved assuming the shape of the high frequency generating electrode. And after heating to 1800 degreeC, the pressure of 98 kPa was applied to the BN jig, it heated up to 1900 degreeC, and the aluminum nitride was sintered. At this time, the pressure was continuously applied until it was cooled to room temperature. This was processed by the same method as in Example 1 and evaluated. The results are shown in Table 3. The film thickness of the high-frequency generating electrode of the completed wafer holder was 20 μm, and the sheet resistance value was 5 mΩ / □.

＊比較例

* Comparison example

  As can be seen from the above results, it can be seen that the same results as in Example 1 are obtained.

  Granules having the same composition as in Example 1 were prepared. And the press body was produced by press molding, the counterbore process was given to the molded body, the molybdenum coil was installed as a heater, the granule was further replenished on it, and the heater was embed | buried by pressing. Further, a molybdenum mesh having a wire diameter of 300 μm and 20 mesh was installed, and the granules were replenished and pressed to produce a molded product of a wafer holder. Thereafter, sintering was performed in the same manner as in Example 3, and the surface was processed into a predetermined shape to obtain a wafer holder. This was evaluated by the same method as in Example 1. The results are shown in Table 4.

  It can be seen that when a molybdenum coil is used as the heating element, the thermal uniformity is slightly worse than in Example 1, and the film thickness variation is slightly larger.

  A wafer holder having the same high frequency generating electrode shape as that of Sample 2 of Example 1 was produced. However, the same evaluation as in Example 1 was performed by changing the distance between the wafer mounting surface and the high frequency generating electrode. The results are shown in Table 5.

  From the results in Table 5, when the minimum value of the distance from the high-frequency generating electrode to the wafer mounting surface is less than 0.2 mm (sample 18), the dielectric strength decreases, so that the film is formed five times. Cracks occurred on the wafer mounting surface. It can also be seen that if the distance from the high-frequency generating electrode to the wafer mounting surface exceeds 3 mm (sample 23), the film formation time becomes longer and the throughput decreases. It can also be seen that when the difference between the maximum value and the minimum value of the distance between the wafer mounting surfaces of the high-frequency generating electrode exceeds 2.0 mm (sample 27), the film thickness variation increases.

  A wafer holder having the same high-frequency generating electrode shape as Sample 3 of Example 1 was produced. However, the same evaluation as in Example 1 was performed by changing the distance between the wafer mounting surface and the high frequency generating electrode. The results are shown in Table 6.

  From the above results, it can be seen that when the difference between the maximum value and the minimum value of the distance between the wafer mounting surfaces of the high-frequency generating electrode exceeds 2.0 mm (sample 31), the film thickness variation increases.

  A wafer holder was produced in the same manner as in Example 1. However, although the electrode for high frequency generation was produced by screen printing, the sheet resistance value was adjusted by the film thickness at this time and the additive added to the paste, and the same test as in Example 1 was performed. The results are shown in Table 7. The high frequency generating electrode of Sample 32 was made of the same paste as Sample 2, and the film thickness was 10 μm. Similarly, the sample 33 had a thickness of 5 μm, the sample 34 had a thickness of 3 μm, and the sample 35 had a thickness of 2 μm. Among these, the sample 35 could not be evaluated because peeling was observed on a part of the W film when the printed film was baked. The film thickness is adjusted by reducing the screen mesh used during printing.

  Sample 36 was prepared by adding the same amount of aluminum nitride powder to the above W paste composition. The film thickness at this time was 20 μm. Sample 37 was made of the same paste as sample 36, the film thickness was 10 μm, sample 37 was 5 μm thick, sample 38 was 3 μm thick, and sample 39 was 2 μm thick. Among these, regarding the sample 39, since the W film was peeled like the sample 35, the film formation evaluation could not be performed. Furthermore, the sample 40 used the W paste similar to the sample 2, and the film thickness was 50 micrometers. Sample 41 had a thickness of 100 μm, and sample 42 had a thickness of 150 μm. Regarding sample 41, although a part of the W film was peeled off, it could be in close contact with the upper substrate by hot pressing as in Example 1. However, since the sample 42 was peeled off at a part of the W film and could not be bonded even if the substrate was hot-pressed in the same manner as in Example 1, a wafer holder could not be formed. There wasn't.

  In Samples 34 to 38, since the sheet resistance value of the high-frequency generating electrode is high, the thermal uniformity is slightly deteriorated, so that the film thickness variation is also large. It can be seen that when the sheet resistance value exceeds 30 mΩ / □, the time required to form a film with a predetermined film thickness becomes long, causing a decrease in throughput. Further, when the sheet resistance value exceeded 50 mΩ / □ (samples 35 and 39), peeling occurred in a part of the W film.

  A wafer holder was formed in the same manner as in Example 1. At this time, the case where the connection position of the external connection electrode with respect to the electrode for high frequency generation was set at the center and the case where the connection position was set away from the center position were compared. The position of the external connection electrode at this time is indicated by the distance from the center of the wafer holder. The external connection terminals are plated with nickel of 5 μm.

  From the above, it can be seen that the external connection electrode is preferably installed in the vicinity of the substantially central portion of the wafer holder.

  A wafer holder was formed in the same manner as in Example 1. At this time, the pressure for joining the substrates was changed, and the degree of deviation of the joining state and the embedded position of the high frequency generating electrode from the design value was measured. The results are shown in Table 9. The amount of displacement of the burying position is measured at a total of nine locations including the central portion of the wafer holder, four locations on the circumference of 70 mm in diameter, and four locations on the circumference of 140 mm in diameter, and the average value is shown.

  Sample 52 had an unbonded portion at the end of the substrate, and a wafer holder could not be produced. In addition, the samples 48 to 51 were all in a good bonding state, processed into the same shape as the sample 2, and subjected to a film formation test. All the results were the same as the sample 2.

  A wafer holder was formed in the same manner as in Example 3. At this time, the pressure for joining the substrates was changed, and the degree of deviation of the joining state and the embedded position of the high frequency generating electrode from the design value was measured. The results are shown in Table 10. The amount of deviation was measured in the same manner as in Example 9.

In Samples 53 to 57, the high frequency generating electrode could be deformed into a predetermined shape. However, since Sample 58 has a small amount of deformation and is hardly deformed, it is impossible to form a wafer holder having a shape as designed. could not.

A wafer holder was formed in the same manner as in Example 2. At this time, the pressure for joining the substrates was changed, and the degree of deviation of the joining state and the embedded position of the high frequency generating electrode from the design value was measured. The results are shown in Table 11. The amount of deviation was measured in the same manner as in Example 9.

  In Samples 59 to 61, the high frequency generating electrode could be deformed into a predetermined shape, but in Sample 62, the amount of deformation was small, and a wafer holder having a shape as designed could not be formed.

  A wafer holder similar to that of Example 1 was produced. At this time, the film formation test was performed in the same manner as in Example 1 by changing the diameter of the connection terminal connected to the high frequency generating electrode. The results are shown in Table 12.

  In the sample 66 using the connection terminal having a diameter of 1 mm, the connection terminal was melted during film formation.

  According to the present invention, the distance to the wafer mounting surface of the high frequency generating electrode embedded in the ceramic sintered body is not constant. That is, by controlling the distance of the high-frequency generating electrode to the wafer mounting surface, plasma generation can be made uniform and the thickness of the film formed on the wafer can be made uniform.

An example of the cross-sectional structure of the wafer holder of this invention is shown. The other example of the cross-section of the wafer holder of this invention is shown. An example of the cross-sectional structure of the conventional wafer holder is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wafer holding surface 2 Electrode for high frequency generation 3 Heating element 4 Ceramics

Claims (7)

A wafer holder which in the ceramic sintered body has embedded a high frequency generating electrode, the distance from the high-frequency generation electrode to the wafer mounting surface rather than a constant, the maximum value of the distance is less than 3mm The minimum value is 0.2 mm or more, the difference between the maximum value and the minimum value of the distance is 2 mm or less, the sheet resistance value of the high-frequency generating electrode is 50 mΩ / □ or less, and the high-frequency generating electrode The wafer holder has a thickness of 3 μm or more and 100 μm or less, and the external connection electrode connected to the high-frequency generating electrode is present at substantially the center of the high-frequency electrode . Before Ki距 away is, a wafer holder according to claim 1, characterized in that the longer toward the end from a central portion of the wafer mounting surface. Before Ki距 away is, a wafer holder according to claim 1, characterized in that shorter toward the end from a central portion of the wafer mounting surface. A semiconductor manufacturing apparatus on which the wafer holder according to any one of claims 1 to 3 is mounted. The ceramic molded body unfired buried high frequency generating electrode, sandwiched curved jig, according to any one of claims 1 to 3, characterized in that added sintering pressure than 0.98kPa Manufacturing method of the wafer holder. A jig in which both ceramic sintered bodies are curved when a ceramic sintered body formed on a high frequency generating electrode and a ceramic sintered body bonded on the high frequency generating electrode are heat-bonded via a bonding layer. The method for manufacturing a wafer holder according to any one of claims 1 to 3 , wherein the ceramic sintered body is bonded to each other by applying a pressure of 98 kPa or more. The ceramics sintered body was embedded high-frequency generating electrode, sandwiched curved jig, applying a pressure of more than 98 kPa, wafer holder as claimed in any one of claims 1 to 3, characterized in that heating Manufacturing method.

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