JP2006332068A - Ceramic heater and semiconductor or liquid crystal manufacturing equipment equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater having improved heat uniformity of a workpiece holding surface of a ceramic heater having a surface for holding the workpiece, and a semiconductor or liquid crystal manufacturing apparatus equipped with the ceramic heater.
In a ceramic heater having a surface for holding an object to be processed, a resistance heating element is formed on a surface other than the holding surface or an inner surface, and a lead circuit for supplying power to the resistance heating element is provided with the resistance heater. If it is formed on a surface different from the surface on which the heating element is formed, the temperature uniformity of the ceramic heater can be improved and the temperature distribution on the surface of the object to be processed can be equalized.
[Selection] Figure 1

Description

  The present invention relates to a ceramic heater, and in particular, plasma CVD, low pressure CVD, metal CVD, insulating film CVD, ion implantation, etching, Low-K film formation, where temperature distribution on the surface holding the workpiece is required. The present invention relates to a ceramic heater used in a semiconductor manufacturing apparatus such as a DEGAS apparatus or a liquid crystal manufacturing apparatus, and further to a semiconductor or liquid crystal manufacturing apparatus equipped with the ceramic heater.

  Conventionally, in a semiconductor manufacturing process, various processes such as a film forming process and an etching process are performed on a semiconductor wafer which is an object to be processed. In a processing apparatus for processing such a semiconductor wafer, a ceramic heater for holding the semiconductor wafer and heating the semiconductor wafer is used. In the process of processing the glass substrate for liquid crystal, a ceramic heater for holding and heating the glass for liquid crystal is also used.

  Such a conventional ceramic heater is disclosed in, for example, Japanese Patent Laid-Open No. 4-78138. A ceramic heater disclosed in Japanese Patent Laid-Open No. 4-78138 is a ceramic heater portion in which a resistance heating element is embedded, installed in a container, and provided with a wafer heating surface, and other than the wafer heating surface of the heater portion. And is connected to a resistance heating element and taken out of the container so as not to be substantially exposed to the internal space of the container. Electrode.

  In the present invention, the contamination and the poor thermal efficiency observed in the metal heater which is the previous heater are improved, but the temperature distribution of the semiconductor substrate is not mentioned. However, the temperature distribution on the surface of the semiconductor wafer or the glass for liquid crystal is important because it has a close relationship with the yield when the various processes are performed.

  Therefore, for example, Japanese Patent Application Laid-Open No. 11-317283 discloses a ceramic heater that can make the temperature of the ceramic substrate uniform. In the present invention, a plurality of resistance heating element circuits connected in parallel are formed, the resistance heating elements are divided into several groups for equalization, and the sectional area of the resistance heating elements is measured in advance. In addition, the resistance values are equalized by matching the cross-sectional area of the other group with the cross-sectional area of the group of resistance heating elements having the smallest cross-sectional area, so that the ceramic substrate is heated uniformly.

  In the present invention, the temperature distribution on the semiconductor wafer mounting surface of the ceramic substrate is said to be within ± 1.0%. However, since a part of the resistance heating element is cut in order to match the cross-sectional area, no current flows through the cut resistance heating element and no heat is generated, so that the temperature partially decreases.

In addition, recent semiconductor wafers and liquid crystal substrates have been increased in size. For example, for silicon (Si) wafers, the transition from 8 inches to 12 inches is in progress. In addition, for liquid crystal glass, for example, a very large size of 1000 mm × 1500 mm is being promoted. With the increase in the diameter of the semiconductor wafer and liquid crystal glass, the temperature distribution on the surface of the semiconductor wafer and liquid crystal glass that is the object to be processed is required to be within ± 1.0%. Within 0.5% has been desired.
Japanese Patent Laid-Open No. 04-078138 JP 11-317283 A

  The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a ceramic heater in which the thermal uniformity of the surface of the mounted workpiece is improved and a semiconductor or liquid crystal manufacturing apparatus on which the ceramic heater is mounted.

  The ceramic heater of the present invention has a surface for holding an object to be processed, and a resistance heating element is formed on a surface other than the holding surface or an inner surface, and a lead circuit for supplying power to the resistance heating element is provided. Further, it is formed on a surface different from the surface on which the resistance heating element is formed. The circuit pattern of the resistance heating element is preferably substantially concentric. Furthermore, it is preferable that the lead circuit intersects the resistance heating element circuit three-dimensionally.

  The resistance heating element circuit pattern may consist of a plurality of zones, and it is preferable that the heat uniformity of the surface holding the object to be processed is ± 1.0% or less. More preferably, it is ± 0.5% or less. The resistance value of the lead circuit is preferably smaller than the resistance value of the resistance heating element. Furthermore, it is preferable that an electrode connected to the lead circuit for supplying electric power from the outside is formed in the vicinity of the central portion of the ceramic heater.

  The thickness of the ceramic heater is preferably 5 mm or more, and the ceramic main component of the ceramic heater is desirably any of aluminum oxide, silicon nitride, and aluminum nitride.

Further, the main component of the ceramic is preferably aluminum nitride, and the sintering aid to be added is preferably an yttrium compound. Further, the addition amount of the yttrium compound, in terms of yttrium oxide _(Y 2 _{O 3),} 0.01 wt% or more and 1.0 wt% or less.

  Semiconductor or liquid crystal manufacturing equipment equipped with the ceramic heater as described above manufactures semiconductors and liquid crystal display devices with a high yield because the surface temperature of semiconductor wafers and glass for liquid crystals to be processed is more uniform than conventional products. can do.

  According to the present invention, in a ceramic heater having a surface for holding an object to be processed, a resistance heating element is formed on a surface other than the holding surface or an inner surface, and a lead circuit for supplying power to the resistance heating element includes the lead circuit. By forming the resistance heating element circuit pattern on a surface different from the surface on which the resistance heating element is formed, the resistance heating element circuit pattern can be designed without being restricted by the electrode position and the like. A manufacturing apparatus can be provided. If the thickness of the ceramic heater is 3 mm or more, the soaking property can be within ± 1.0%, and if the thickness is 5 mm or more, the soaking property is further improved to within ± 0.5%. be able to.

  In the conventional ceramic heater, for example, as shown in Patent Document 2 and FIG. 5, the electrode 20 for supplying power is arranged near the center of the ceramic heater, and the resistance heating element is formed substantially concentrically. A lead portion 30 for electrically connecting the folded heating portion 10 or the resistance heating element at the outer peripheral portion and the electrode portion 20 is formed on the body circuit pattern. The inventors have found that it is difficult to obtain a uniform heat generation distribution at the folded portion and the lead portion, so that the heat uniformity of the ceramic heater cannot be improved. For this reason, if the resistance heating element circuit is formed in a substantially concentric shape so as not to form the folded portion and the lead portion, the thermal uniformity of the ceramic heater can be improved, and the thermal uniformity of the surface of the workpiece can be improved. Therefore, the present invention has been achieved.

  That is, in order to make the temperature distribution on the surface of the object to be processed within ± 1.0%, and further within ± 0.5%, in a ceramic heater having a surface for holding the object to be processed, a resistance heating element is provided. It has been found that a lead circuit that is formed on a surface other than the holding surface or an inner surface and supplies power to the resistance heating element may be formed on a different surface from the surface on which the resistance heating element is formed. By forming the resistance heating element circuit and the lead circuit on a plurality of separate surfaces in this way, a resistance heating element circuit pattern can be formed regardless of the position of the electrode connected to the lead circuit for supplying power from an external power source. Therefore, the temperature distribution on the surface of the object to be processed can be equalized.

  For example, the resistance heating element circuit and the lead circuit are formed in two layers. The resistance heating element circuit pattern formed in one layer is designed so as to increase the heat uniformity of the workpiece holding surface of the ceramic heater as much as possible. At this time, conventionally, the resistance heating element circuit pattern has to be designed in consideration of the position of the lead circuit and the electrode, and it has been difficult to obtain an optimum circuit pattern for heat uniformity. In the present invention, it is possible to obtain a resistance heating element circuit pattern that is optimal for heat uniformity regardless of the position of the lead circuit or electrode.

  The lead circuit formed in the other layer electrically connects each terminal portion of the resistance heating element circuit pattern and the electrode portion formed near the center of the ceramic heater. In order to electrically connect each terminal portion and the lead circuit, a so-called through-hole method may be used by opening a through hole in the ceramic of each terminal portion.

  In order to improve the heat uniformity on the surface of the workpiece, it is preferable to form the resistance heating element circuit pattern in a substantially concentric shape. Usually, the outer peripheral side of the ceramic heater is radiated from the outer peripheral portion of the ceramic heater, so the temperature tends to decrease. Therefore, in the resistance heating element circuit, it is necessary to increase the heat generation amount on the outer peripheral side. If the resistance heating element circuit pattern is formed almost concentrically, the resistance value is increased by narrowing the line width of the outer resistance heating element circuit pattern and the pattern interval is reduced in order to increase the heat generation amount on the outer periphery side. This makes it easier to take measures such as increasing the heat generation density.

  Moreover, since the resistance heating element circuit and the lead circuit are formed on different surfaces, they can be crossed in three dimensions. This makes it possible to further form a resistance heating element circuit pattern regardless of the position of the electrode or the like.

  Further, in order to make the temperature distribution on the surface of the object to be processed more uniform, the resistance heating element circuit pattern may be divided into a plurality of zones to obtain an optimum circuit pattern in each zone. This is because it is easy to take measures for each of various factors that hinder the thermal uniformity of the ceramic heater, such as heat radiation from the outer peripheral portion, heat radiation from an electrode formed near the center, a support described later, and the like. As a plurality of zones, there are, for example, two zones of an outer peripheral portion and an inner peripheral portion, four zones each having an outer peripheral portion and an inner peripheral portion as two zones, or divided into left and right, or divided into a plurality of sectors.

  The ceramic heater in which the resistance heating element circuit and the lead circuit are formed as described above is particularly effective when used in a semiconductor manufacturing apparatus or a liquid crystal manufacturing apparatus. In semiconductor manufacturing equipment, since corrosive gas is used in the chamber where the ceramic heater is installed, if the electrode is installed exposed, the electrode is corroded, and electrical conduction to the ceramic heater cannot be secured. The inside is contaminated with the electrode material. Therefore, in order to protect the electrode, a method of joining the shaft to the ceramic heater and storing the electrode in the shaft is used. The number of shafts is preferably small from the viewpoint of manufacturing cost, and a method is generally used in which the electrodes are collected near the center of the ceramic heater and the shaft is joined to the central portion of the ceramic heater at one location. At this time, the method of the present invention is particularly effective for improving the thermal uniformity of the ceramic heater. The thermal uniformity of the surface holding the workpiece of the ceramic heater of the present invention can be ± 1.0% or less. Furthermore, it can be ± 0.5% or less.

  The resistance value per unit area of the lead circuit is preferably smaller than the resistance value per unit area of the resistance heating element circuit. If the resistance value of the lead circuit is higher than the resistance value of the resistance heating element, the heating value of the lead circuit will be larger than the heating value of the resistance heating element, and the temperature of the lead circuit will rise, affecting the thermal uniformity. Since it gives, it is not preferable. In order to reduce the resistance value of the lead circuit, if the material of the circuit is the same as that of the resistance heating element, the cross-sectional area may be made smaller than the cross-sectional area of the resistance heating element. Alternatively, a material having a volume resistivity smaller than that of the material of the resistance heating element circuit may be used for the lead circuit. Further, it is possible to use a technique such as increasing the line width of the lead circuit or increasing the thickness of the circuit.

  Furthermore, the thickness of the ceramic heater of the present invention is preferably 5 mm or more. When the thickness is smaller than this, the heat generated by the resistance heating element cannot be sufficiently diffused into the ceramic, and the temperature distribution on the workpiece holding surface becomes large. This is particularly effective for a ceramic heater for a semiconductor manufacturing apparatus and a ceramic heater for a liquid crystal manufacturing apparatus that require a uniform temperature on the surface of the workpiece.

The ceramic material of the ceramic heater of the present invention is not particularly limited as long as it has high thermal conductivity and corrosion resistance, but it is preferable that any of aluminum oxide (alumina), silicon nitride, and aluminum nitride is a main component. . Since alumina (Al ₂ O ₃ ) is relatively inexpensive, a ceramic heater can be manufactured at low cost. Since silicon nitride (Si ₃ N ₄ ) has high material strength, it has excellent thermal shock resistance and is suitable for use in locations subject to temperature cycles and thermal shock. In addition, aluminum nitride (AlN) has a high thermal conductivity, so that the temperature distribution in the ceramic is likely to be uniform, and is therefore particularly suitable when soaking is required. Aluminum nitride is particularly suitable for use in this field because it has excellent corrosion resistance against corrosive gases used in semiconductor manufacturing processes.

  Below, an example of the manufacturing method of the ceramic heater 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%. If it 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. There are two types of methods, a cofire method and a post metallization method.

  First, the post metallization method will be described. 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. When screen-printing 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 by screen printing to the polished sintered body to form an electric circuit. The conductive paste can be obtained by mixing metal powder, oxide powder as necessary, binder and solvent. The metal powder is preferably tungsten (W), molybdenum (Mo) or tantalum (Ta) 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 a Group IIa element or Group IIIa element oxide, 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.

  Moreover, Ag metal, such as Ag-Pd and Ag-Pt, can also be used as the metal powder. In this case, the resistance value can be controlled by the content of palladium (Pd) or platinum (Pt). In addition, the same oxide powder as in the case of tungsten or the like can be added. When the amount of the oxide added is increased, the resistance value is increased, and when the amount of addition is decreased, the resistance value is decreased. The amount of oxide added is preferably 1 wt% or more and 30 wt% or less as described above.

  These powders are mixed, a binder and a solvent are added to prepare a paste, and a predetermined circuit pattern is formed by screen printing. At this time, the thickness of the conductive paste is preferably 5 μm or more and 100 μm or less as a thickness 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.

  In addition, when the circuit pattern to be formed is a resistance heating element circuit, the pattern interval is preferably 0.1 mm or more. If the interval is less than 0.1 mm, when a current is passed through the resistance heating element, 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.

  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 baked, so that the electrical resistance value of the metal layer becomes high.

  Firing is preferably performed at a temperature of 1500 ° C. or higher in the case of W, Mo, or Ta 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 fired metal layer 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 metal layer. The adhesion strength of the is reduced.

  In the case of an Ag-based metal, the firing temperature is preferably 700 ° C to 1000 ° C. The firing atmosphere can be performed in air or nitrogen. In this case, the degreasing process can be omitted.

  Next, in order to ensure the insulation of the formed metal layer, an insulating coat can be formed on the metal layer. The material of the insulating coat is preferably the same material as the ceramic on which the metal layer is formed. If the materials of the ceramic and the insulating coat are significantly different, problems such as warping after sintering occur due to the difference in thermal expansion coefficient. For example, in the case of AlN, a predetermined amount of Group IIa element or Group IIIa element oxide or carbonate is added to the AlN powder as a sintering aid, mixed, and a binder or solvent is added thereto, and the paste is used as a paste. It can apply | coat on the said metal layer by screen printing.

  At this time, the amount of the sintering aid to be added is preferably 0.01 wt% or more. If it is less than 0.01 wt%, the insulating coating will not be densified, and it will be difficult to ensure the insulating properties of the metal layer. Moreover, it is preferable that the amount of sintering aid does not exceed 20 wt%. If it exceeds 20 wt%, an excessive sintering aid penetrates into the metal layer, and the electrical resistance value of the metal layer may change. 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.

  Next, a ceramic substrate can be further laminated as required. Lamination is preferably performed via a bonding agent. The bonding agent is obtained by adding a IIa group element compound or a group IIIa element compound and a binder or a solvent to aluminum oxide powder or 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.

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 ceramic substrates to be stacked are superposed, a predetermined load is applied, and the ceramic substrates are bonded together by heating in a non-oxidizing atmosphere. The load is preferably 4.9 kPa (0.05 kg / cm ² ) or more. When the load is less than 4.9 kPa, sufficient bonding strength cannot be obtained, or the above-mentioned bonding defect is likely to occur.

  The heating temperature for bonding is not particularly limited as long as the ceramic substrates 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.

  As described above, a ceramic laminated sintered body serving as a ceramic heater can be obtained. Note that the electrical circuit does not use conductive paste, for example, a resistance heating element circuit, a molybdenum wire (coil), an electrostatic adsorption electrode, an RF electrode, etc., a molybdenum or tungsten mesh (network-like). Body) can also be used.

In this case, the molybdenum coil and mesh are incorporated in the AlN raw material powder, and can be produced by a hot press method. The hot press temperature and atmosphere may be the same as the AlN sintering temperature and atmosphere, but the hot press pressure is preferably 980 kPa (10 kg / cm ² ) or more. If it is less than 980 kPa, a gap may be formed between the molybdenum coil or mesh and AlN, and the performance of the ceramic heater may not be achieved.

  Next, the cofire method will be described. The raw material slurry described above is formed into a sheet by a doctor blade method. Although there is no restriction | limiting in particular regarding sheet shaping | molding, As for the thickness of a sheet | seat, 3 mm or less is preferable after drying. If the thickness of the sheet exceeds 3 mm, the amount of drying shrinkage of the slurry increases, so that the probability of cracking in the sheet increases.

  A metal layer to be an electric circuit having a predetermined shape is formed on the above-described sheet by applying a conductive paste by a technique such as screen printing. The same conductive paste as that described in the post metallization method can be used. However, in the cofire method, there is no problem even if the oxide powder is not added to the conductive paste.

  Next, the sheet on which the circuit is formed and the sheet on which the circuit is not formed are stacked. In the laminating method, each sheet is set at a predetermined position and overlapped. At this time, a solvent is applied between the sheets as necessary. In the state of being overlaid, heat as necessary. When heating, it is preferable that heating temperature is 150 degrees C or less. When heated to a temperature exceeding this, the laminated sheets are greatly deformed. Then, the stacked sheets are integrated by applying pressure. The applied pressure is preferably in the range of 1 to 100 MPa. If the pressure is less than 1 MPa, the sheets may not be sufficiently integrated and may peel during the subsequent steps. Further, when a pressure exceeding 100 MPa is applied, the deformation amount of the sheet becomes too large.

  This laminated body is degreased and sintered in the same manner as the above-described post metallization method. The degreasing treatment and sintering temperature, the amount of carbon, etc. are the same as in the post metallization method. When printing the conductive paste on a sheet as described above, a ceramic heater having a plurality of electric circuits can be easily created by printing a heater circuit, an electrostatic chucking electrode, etc. on a plurality of sheets and laminating them. It is also possible to do. In this way, a ceramic laminated sintered body that becomes a ceramic heater can be obtained.

  The obtained ceramic laminated sintered body is processed as necessary. Usually, in the sintered state, the accuracy required for a semiconductor manufacturing apparatus is often not reached. As for the processing accuracy, for example, the flatness of the wafer holding surface is preferably 0.5 mm or less, more preferably 0.1 mm or less. If the flatness exceeds 0.5 mm, a gap is likely to be generated between the wafer and the ceramic heater, and the heat of the ceramic heater is not transmitted uniformly to the wafer, and the temperature of the wafer is likely to be uneven.

  Further, the surface roughness of the wafer holding surface is preferably 5 μm or less in terms of Ra. If the Ra exceeds 5 μm, AlN degranulation may increase due to friction between the ceramic heater and the wafer. At this time, the shed particles become particles, which adversely affects processing such as film formation and etching on the wafer. Further, the surface roughness is preferably 1 μm or less in terms of Ra.

As described above, the ceramic heater body can be manufactured. Further, a shaft is attached to the ceramic heater. The material of the shaft is not particularly limited as long as it has a thermal expansion coefficient that is not significantly different from that of the ceramic of the ceramic heater, but the difference in thermal expansion coefficient from the ceramic heater is 5 × 10 ⁻⁶ / K or less. Preferably there is.

If the difference in thermal expansion coefficient exceeds 5 × 10 ⁻⁶ / K, it can be used repeatedly even if cracks occur near the joint between the ceramic heater and the shaft during mounting, or cracks do not occur during bonding. In the meantime, a thermal cycle is applied to the joint, and cracks and cracks may occur. For example, when the ceramic heater is AlN, the shaft material is most preferably AlN, but silicon nitride, silicon carbide, mullite, or the like can be used.

  Further, the thermal conductivity of the shaft is preferably lower than the thermal conductivity of the ceramic of the ceramic heater. When the thermal conductivity of the shaft is higher than the thermal conductivity of ceramics, the heat generated by the ceramic heater can easily escape from the shaft, and the temperature of the workpiece holding surface directly above the part where the shaft is joined decreases. Soaking is reduced.

The attachment is performed via a bonding layer. The component of the bonding layer is preferably composed of AlN, Al ₂ O _{3 and a} rare earth oxide. These components are preferable because they have good wettability with ceramics such as ceramic heaters and shaft materials such as AlN, so that the bonding strength is relatively high and the airtightness of the bonding surface is easily obtained.

  The flatness of the joint surfaces of the shaft and ceramic heater to be joined is preferably 0.5 mm or less. Beyond this, a gap is likely to occur on the joint surface, making it difficult to obtain a joint with sufficient airtightness. The flatness is more preferably 0.1 mm or less. The flatness of the joining surface of the ceramic heater is more preferably 0.02 mm or less. Further, the surface roughness of each joint surface is preferably 5 μm or less in terms of Ra. In the case of surface roughness exceeding this, a gap is easily generated on the joint surface. The surface roughness is more preferably 1 μm or less in terms of Ra.

  Next, an electrode is attached to the ceramic heater. Attachment can be performed by a known method. For example, it is only necessary to apply counterbore processing from the opposite side of the wafer holding surface of the ceramic heater to the electric circuit, and to apply metallization to the electric circuit or directly connect an electrode such as molybdenum or tungsten using an active metal brazing without metallization. . Thereafter, the electrode can be plated as necessary to improve oxidation resistance. In this way, a ceramic heater can be manufactured.

  Also, the semiconductor heater can be processed by incorporating the ceramic heater of the present invention into a semiconductor manufacturing apparatus. In the ceramic heater of the present invention, since the temperature of the wafer holding surface is uniform, the temperature distribution on the wafer surface is also more uniform than before, so that stable characteristics can be obtained with respect to the formed film, heat treatment, and the like. .

  Moreover, the glass for liquid crystals can be processed by incorporating the ceramic heater of the present invention into a liquid crystal production apparatus. Since the temperature of the wafer holding surface is uniform in the ceramic heater of the present invention, the temperature distribution on the glass surface for liquid crystal is also more uniform than before. Can do.

99 parts by weight of aluminum nitride powder and 1 part by weight of Y ₂ O ₃ powder are mixed, and polyvinyl butyral is used as a binder and dibutyl phthalate is used as a solvent. A green sheet having a thickness of 430 mm and a thickness of 1.0 mm was formed. 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. Further, 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 , 1 part by weight of Al ₂ O ₃ , ethyl cellulose as a binder of 5 parts by weight, and butyl as a solvent W paste was prepared using carbitol. A pot mill and three rolls were used for mixing.

  A resistance heating element circuit pattern shown in FIG. 1 was formed on the green sheet by screen printing of the W paste. That is, the resistance heating element circuit patterns 2 and 3 having substantially concentric circles were formed in an inner peripheral area within a radius of 70% from the center and an outer peripheral area, respectively. The resistance heating elements 2 and 3 had a line width of 5 mm at the center of 2 and gradually narrowed toward the outer periphery, and 3 mm at the third outer periphery. The intervals were all 3 mm, and the thickness after drying was 30 μm. Through holes 6 were formed at the start point and the end point 5 of each resistance heating element circuit pattern so as to be electrically connected to the lead circuit. Note that the reason why the line width of the resistance heating element circuit is gradually reduced from the central part to the outer peripheral part in this way is that the amount of heat radiation at the outer peripheral part of the ceramic heater is large. This is because the line width of the circuit is narrowed to increase the resistance value and increase the amount of heat generation.

  Moreover, the lead circuit 4 shown in FIG. 2 was formed on another green sheet. The line width of the lead circuit 4 was 10 mm, and the thickness after drying was 40 μm. As shown in FIG. 3, the start point and the end point 5 of the resistance heating element circuit pattern are electrically connected to the electrode 7 through the through hole 6 and the lead circuit 4. The electrode 7 was formed near the center of the ceramic heater.

  A green sheet on which a resistance heating element circuit and a lead circuit were printed was laminated with another green sheet on which the RF electrode circuit 8 was printed and a green sheet on which nothing was printed, thereby producing a laminate. Lamination was performed by stacking sheets on a mold, and thermocompression bonding at a pressure of 10 MPa for 2 minutes while heating to 70 ° C. with a press. Then, degreasing was performed at 850 ° C. in a nitrogen atmosphere, and sintering was performed at 1850 ° C. for 3 hours in a nitrogen atmosphere to produce a ceramic heater body. At this time, the dew point of the used nitrogen is −60 ° C.

After sintering, the workpiece holding surface was polished so that Ra was 1 μm or less, and the shaft joint surface was Ra 1 μm or less. The outer diameter was also finished. The processed ceramic heater body 1 has an outer diameter of 330 mm and a thickness of 8 mm.

In the vicinity of the center of the surface opposite to the workpiece holding surface, the lead circuit and the RF electrode circuit were counterbored to partially expose the lead circuit and the RF electrode circuit. Next, an AlN shaft having an outer diameter of 60 mm, an inner diameter of 50 mm, and a length of 200 mm was bonded using an Al ₂ O ₃ —Y ₂ O ₃ —AlN-based bonding agent. Furthermore, Mo electrodes were directly joined to the exposed lead circuit and RF electrode circuit using an active metal braze. The ceramic heater body was heated by energizing this electrode, and the thermal uniformity was measured.

  The soaking property was measured by measuring the temperature distribution on the workpiece holding surface with a thermoviewer. The supplied power was adjusted so that the temperature at the center of the workpiece holding surface was 700 ° C. As a result, the temperature of the workpiece holding surface was within the range of 697 ° C. to 703 ° C. as shown in FIG. 3, and the temperature distribution was very uniform at ± 0.43%.

  A ceramic heater body having a thickness changed as shown in Table 1 was produced in the same manner as in Example 1, and the thermal uniformity was evaluated in the same manner as in Example 1. The results are shown in Table 1.

  As can be seen from Table 1, by setting the thickness of the ceramic heater body to 3 mm or more, the temperature distribution on the workpiece holding surface can be within ± 1.0%. Furthermore, by setting the thickness of the ceramic heater body to 5 mm or more, the temperature distribution on the workpiece holding surface can be within ± 0.5%. In addition, No. 3 is the same as Example 1.

  A ceramic heater similar to that of Example 1 was produced. However, the line width and thickness of the lead circuit were the dimensions shown in Table 2, and the thickness of the ceramic heater body was 15 mm. Note that the line width and thickness of the resistance heating element are the same as those in the first embodiment. The thermal uniformity of each ceramic heater was measured in the same manner as in Example 1. The results are shown in Table 2.

As can be seen from Table 2, the cross sectional area of the resistance heating element is larger than the cross sectional area of 0.15 mm ² . 10-No. The thermal uniformity of No. 12 was ± 0.5% or less. The thermal uniformity of 13 is ± 0.5% or more, and heat generation in the lead circuit portion cannot be ignored, so that the thermal uniformity decreases. In addition, No. No. 10 in Example 2 1 is the same.

  The same ceramic heater as in Example 1 was produced using silicon nitride and alumina as materials. The thermal uniformity of the ceramic heater was measured in the same manner as in Example 1. As a result, the ceramic heater made of silicon nitride was ± 0.82%, and the ceramic heater made of alumina was ± 0.94%. It can be seen that the higher the thermal conductivity of the ceramic, the better the soaking.

  Each ceramic heater of Examples 1 to 4 was incorporated in a semiconductor manufacturing apparatus, and a W film was formed on a Si wafer having a diameter of 12 inches. As a result, regardless of which ceramic heater was used, the W film thickness variation was 10% or less and the film thickness variation was small, and a good W film could be formed.

  Each ceramic heater of Examples 1 to 4 was incorporated in a liquid crystal manufacturing apparatus, and a tantalum electrode was formed on a glass for liquid crystal of 1000 mm × 1500 mm. As a result, even when any ceramic heater was used, a tantalum electrode could be uniformly formed on the entire glass substrate.

Comparative Example 1
A ceramic heater was produced in the same manner as in Example 1. However, the resistance heating element circuit pattern is as shown in FIG. 5, the lead circuit 30 is formed on the same surface as the resistance heating element circuit, and the Mo electrode for power feeding is directly joined to the resistance heating element circuit. The result of measuring the thermal uniformity of this ceramic heater in the same manner as in Example 1 is shown in FIG. As can be seen from FIG. 6, the temperature in the vicinity of the lead circuit decreased and the temperature on the opposite side increased, and the overall temperature uniformity was about ± 3%.

Comparative Example 2
Comparative Example 1 A ceramic heater was incorporated in a semiconductor manufacturing apparatus, and a W film was formed on a Si wafer having a diameter of 12 inches. As a result, the variation in the film thickness of W was 15% or more, and the variation in the film thickness was so large that a good W film could not be formed.

  According to the present invention, in a ceramic heater having a surface for holding an object to be processed, a resistance heating element is formed on a surface other than the holding surface or an inner surface, and a lead circuit for supplying power to the resistance heating element includes the lead circuit. By forming the resistance heating element circuit pattern on a surface different from the surface on which the resistance heating element is formed, the resistance heating element circuit pattern can be designed without being restricted by the electrode position and the like. A manufacturing apparatus can be provided. If the thickness of the ceramic heater is 3 mm or more, the soaking property can be within ± 1.0%, and if the thickness is 5 mm or more, the soaking property is further improved to within ± 0.5%. be able to.

An example of the resistance heating element circuit pattern of the ceramic heater of this invention is shown. An example of the lead circuit connected to the resistance heating element circuit of FIG. 1 is shown. The schematic sectional schematic diagram (partially omitted) of the ceramic heater of the present invention is shown. The temperature distribution of the wafer holding surface of Example 1 is shown. An example of the resistance heating element circuit pattern of the conventional ceramic heater is shown. The temperature distribution of the wafer holding surface of the comparative example 1 is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic heater 2 Inner peripheral side resistance heating element circuit pattern 3 Outer periphery side resistance heating element circuit pattern 4, 30 Lead circuit 5 Start point and end point of resistance heating element 6 Through hole 7, 20 Electrode 8 RF electrode circuit 10 Folding part

Claims (13)

  In a ceramic heater having a surface for holding an object to be processed, a resistance heating element is formed on a surface other than the holding surface or an inner surface, and a lead circuit for supplying power to the resistance heating element is formed by the resistance heating element. A ceramic heater, characterized in that the ceramic heater is formed on a surface different from the formed surface.   The ceramic heater according to claim 1, wherein the circuit pattern of the resistance heating element is substantially concentric.   The ceramic heater according to claim 1 or 2, wherein the lead circuit intersects the resistance heating element circuit in three dimensions.   The ceramic heater according to any one of claims 1 to 3, wherein the resistance heating element circuit pattern includes a plurality of zones.   The ceramic heater according to any one of claims 1 to 4, wherein the temperature uniformity of the surface holding the workpiece is ± 1.0% or less.   6. The ceramic heater according to claim 1, wherein a resistance value of the lead circuit is smaller than a resistance value of the resistance heating element.   The ceramic heater according to any one of claims 1 to 6, wherein an electrode connected to the lead circuit for supplying electric power from the outside is formed in the vicinity of a central portion of the ceramic heater.   The ceramic heater according to any one of claims 1 to 7, wherein the thickness of the ceramic heater is 5 mm or more.   9. The ceramic heater according to claim 1, wherein the ceramic main component of the ceramic heater is any one of aluminum oxide, silicon nitride, and aluminum nitride.   The ceramic heater according to claim 9, wherein a main component of the ceramic is aluminum nitride.   11. The ceramic heater according to claim 10, wherein the main component of the ceramic is aluminum nitride, and the sintering aid to be added is an yttrium compound. 12. The ceramic heater according to claim 11, wherein the amount of the yttrium compound added is 0.01 wt% or more and 5.0 wt% or less in terms of yttrium oxide (Y ₂ O ₃ ). 13. A semiconductor or liquid crystal manufacturing apparatus, wherein the ceramic heater according to claim 1 is mounted.

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