JP2008171967A - Semiconductor heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor heater capable of carrying out the process of a semiconductor wafer safely until high temperatures even if there is leakage current. <P>SOLUTION: A resistance heat generating element 3 for a ceramics heater 2 is connected to an AC power supply 6 through an insulating transformer 5 and a leakage current breaker 7 is provided between the resistance heat generating element 3 and the insulating transformer 5 so as to be capable of being connected to an earth between the insulating transformer 5 and the leakage current breaker 7 through a magnet switch 8. When the lid 1a of a chamber 1 is closed, the magnet switch 8 is put off and the same is not connected to the earth but when the lid 1a is opened, the magnet switch 8 is put on by the signal of a limit switch 9 and the resistance heat generating element 3 is connected to the earth. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a semiconductor heating device for heating a silicon wafer or the like, and more particularly to a safety device for an electric circuit of a semiconductor heating device including a ceramic heater having a plurality of electric circuits.

  Conventionally, ceramics such as aluminum nitride have been used as heaters for wafer heating in various processes on semiconductor wafers, such as film formation by CVD, curing resist with a coater developer, or inspection of a wafer with a wafer prober. The conventional semiconductor heating device is used.

  Ceramics used as a heater in these semiconductor heating devices are generally insulators at room temperature, but it is known that the electrical insulation properties decrease when the temperature rises due to heating. For this reason, when the temperature rises, the insulation between the electric circuits formed in the ceramic heater is lowered, and a leakage current is likely to be generated in each circuit.

As a means for solving this problem, for example, in Japanese Patent Application Laid-Open No. 08-191049, a heating means such as a ceramic heater and an AC power source are passed through an insulating transformer in order to stop a circuit discharge phenomenon in a semiconductor heating device. There has been proposed a device that is electrically connected.
Japanese Patent Application Laid-Open No. 08-191049

  As proposed in Japanese Patent Application Laid-Open No. 08-191049, electrically connecting a ceramic heater and an AC power source via an insulating transformer is an effective means in terms of preventing leakage current.

  However, when the ceramic heater is energized and heated and the chamber lid is opened and opened to the atmosphere, the heater circuit is not connected to earth (grounded), so even if a leakage occurs in the secondary circuit There is a drawback that it is dangerous because there is no means for detecting it. Although it is conceivable that the secondary circuit is grounded and energized, in this case, it is impossible to prevent leakage between the electric circuits and discharge to the chamber.

  In order to solve such problems in the prior art, the present invention has no leakage current even when the temperature of the ceramic heater rises. Even if there is a leakage current, the leakage will occur when the chamber lid is opened. An object of the present invention is to provide a semiconductor heating apparatus that can detect a current and can safely process a semiconductor wafer up to a high temperature.

  In order to achieve the above object, a semiconductor heating apparatus provided by the present invention is provided with a ceramic heater for heating a wafer in a chamber, and the ceramic heater includes a plurality of electric heaters including at least one resistance heating element via an insulator. In the semiconductor heating device having a circuit, the resistance heating element is connected to an AC power supply via an insulation transformer, and an earth leakage breaker is provided between the resistance heating element and the insulation transformer. When the chamber is closed, it is not connected to the ground, and is connected to the ground when the chamber lid is opened.

  In the semiconductor heating device according to the present invention, the resistance heating element is provided between the insulating transformer and the earth leakage breaker so as to be connectable to the ground via a magnet switch, and a limit switch for sending an ON-OFF signal to the magnet switch is provided in the chamber. It is attached to the lid. As a result, the resistance heating element is not connected to the ground because the magnet switch is turned off by the limit switch signal when the chamber lid is closed, and the limit switch signal when the chamber lid is opened. As a result, the magnet switch is turned on and the resistance heating element is connected to the ground.

  According to the present invention, there is no leakage current even when the temperature of the ceramic heater rises, and the semiconductor wafer can be stably heated. Moreover, even if there is a leakage current, the leakage current can be detected when opening the chamber lid, and the current can be cut off by the leakage breaker, so the semiconductor wafer can be processed safely up to a high temperature. Can do.

  In the semiconductor heating device of the present invention, a ceramic heater for heating a wafer installed in a chamber has a plurality of electric circuits including a resistance heating element via an insulator, and at least one of the electric circuits, for example, The high frequency generating electrode and the electrostatic chuck electrode are always connected to the ground. On the other hand, the resistance heating element is connected to an AC power supply via an insulation transformer, and a leakage breaker is provided between the resistance heating element and the insulation transformer. Furthermore, the resistance heating element is not connected to ground when the chamber lid is closed by an electrical switch or mechanical mechanism, and is connected to ground when the chamber lid is opened. Yes.

  Next, the semiconductor heating device of the present invention will be specifically described with reference to FIGS. In the devices shown in these drawings, a ceramic heater 2 installed in a chamber 1 has a circuit of a resistance heating element 3 and a high frequency (RF) generating electrode 4 embedded in the ceramic. Since the high-frequency generating electrode 4 exists as an earth circuit with respect to an upper electrode such as a shower substrate existing above, it is always connected to ground (grounded). The grounding place of the high-frequency generating electrode 4 can be independently connected to the ground, or can be connected to the chamber 1 if the chamber 1 itself is grounded. Further, the resistance heating element 3 is connected to an AC power source 6 through an insulating transformer 5 as in the conventional case.

  In the semiconductor heating device of FIG. 1 according to the present invention, a leakage breaker 7 is provided between the resistance heating element 3 and the insulating transformer 5 and between the insulating transformer 5 and the AC power source 6. Further, the resistance heating element 3 is disposed between the insulating transformer 5 and the earth leakage breaker 7 so as to be connectable to the ground via the magnet switch 8 and is connected to the ground only when the lid 1a of the chamber 1 is opened. As shown, a limit switch 9 for sending an ON-OFF signal to the magnet switch 8 is attached to the lid 1 a of the chamber 1.

  On the other hand, the apparatus shown in FIG. 2 shown for reference includes a leakage breaker 7 between the resistance heating element 3 and the insulation transformer 5 and between the insulation transformer 5 and the AC power source 6 as in FIG. The heating element 3 is always connected to the ground between the insulating transformer 5 and the earth leakage breaker 7. When a voltage is applied to the resistance heating element circuit, the resistance heating element 3 generates heat and the temperature of the ceramic heater 2 rises. As the temperature rises, the insulation resistance between the high-frequency generating electrode 4 and the resistance heating element 3 decreases, and a part of the current leaks out to the high-frequency generating electrode 4 to cause a leakage.

  However, since the ground of the high frequency generating electrode 4 is electrically connected to the ground of the resistance heating element 3, the leaked current is detected by the leakage breaker 7 connected to the resistance heating element circuit, and a predetermined amount of current is detected. When leakage occurs, the earth leakage breaker 7 acts to cut off the energization. For this reason, in the apparatus of FIG. 2, when the ceramic heater 2 becomes high temperature, the amount of leakage current increases, and the leakage breaker 7 that detects this leakage current cuts off the current, so that it becomes difficult to use at high temperature.

  3 is also the same as that of FIG. 1 except that the resistance heating element circuit is not grounded. In this apparatus, since a connection circuit is not formed between the resistance heating element 3 and the high-frequency generating electrode 4, the leakage current is small even at high temperatures, and the apparatus can be used satisfactorily. However, since the heating element circuit is not connected to the ground, even if a current leaks from the high-frequency generating electrode 4, the leakage breaker 7 is not detected, and therefore the leakage breaker 7 does not operate. Dangerous when opened.

  On the other hand, in the apparatus of the present invention described above, as shown in FIG. 1, when the magnet switch 8 is interposed between the resistance heating element 3 and the ground and the lid 1a of the chamber 1 is closed, the magnet switch 8 is in the OFF state. Because it is, it is not connected to the ground. Accordingly, even when the ceramic heater 2 becomes high temperature and the leakage current amount becomes large, the leakage breaker 7 does not detect the leakage current when the lid 1a of the chamber 1 is closed, so that the energization is not interrupted. Can continue.

  When the lid 1a of the chamber 1 is opened, an ON signal is issued from the limit switch 9 attached to the lid 1a to the magnet switch 8. Therefore, if a leakage current is generated, the leakage breaker 7 operates, The energization can be cut off. Therefore, in comparison with the above-described devices shown in FIGS. 2 to 3, the ceramic heater 2 can be used at a high temperature, and even if there is a leakage, the power can be cut off when the lid 1a of the chamber 1 is opened. Therefore, it can be said that it is a safer device.

  Further, when the resistance heating element and the electrostatic chuck electrode are provided, the resistance heating element circuit may be connected to the ground when the chamber lid is opened as described above. Furthermore, the present invention can be applied to a case where a plurality of resistance heating elements are provided. For example, for a plurality of resistance heating element circuits, a limit switch is attached to the lid of the chamber, and the signal is connected to each resistance heating element. By being configured to send to the magnet switch, even if a leakage occurs while the lid is opened, the leakage breaker can be operated to cut off the energization.

  Examples of the electric circuit of the semiconductor heating device according to the present invention include the resistance heating element circuit, the high-frequency generating electrode circuit, and the electrostatic chuck electrode circuit described above, but the present invention is also applicable to other circuits. As for ceramic heaters, for example, a metal foil, a metal wire, or a coil can be used as a circuit form such as a resistance heating element, a high-frequency generating electrode, and an electrostatic chuck electrode, and screen printing, vapor deposition, A thin film formed by sputtering or the like can also be used.

  The ceramic constituting the ceramic heater is not particularly limited, but is particularly effective for ceramics whose insulating properties are reduced at high temperatures, that is, having a negative volume resistivity temperature coefficient. Of these, aluminum nitride, in particular, has recently increased in demand due to its excellent corrosion resistance to halogen-based gases used for cleaning chambers, but the volume resistivity of aluminum nitride itself rapidly decreases at high temperatures. It is known.

  Therefore, the ceramic heater made of aluminum nitride (AlN) has a large amount of leakage in a high temperature state, and thus could not be used in the apparatus as shown in FIG. 2, but the present invention provides a safe semiconductor heating apparatus. can do.

Next, a method for producing a ceramic heater made of aluminum nitride will be described. The aluminum nitride powder used as a raw material preferably has a specific surface area of 2.0 to 5.0 m ² / g. When the specific surface area is smaller than 2.0 m ² / g, the sinterability is lowered, and when the specific surface area is larger than 5.0 m ² / g, the aggregation of the powder becomes very strong.

  The amount of oxygen contained in the aluminum nitride powder is preferably 2 wt% or less. If the amount of oxygen exceeds 2 wt%, the thermal conductivity of the sintered body decreases, which is not preferable. The total amount of metal impurities excluding aluminum is preferably 2000 ppm or less. The presence of 2000 ppm or more of metal impurities is not preferable because the thermal conductivity of the sintered body is lowered. Group 4 elements such as Si and iron group elements such as Fe are not particularly preferred as metal impurities because they have a high effect of reducing thermal conductivity, and the content is preferably 500 ppm or less.

  Since aluminum nitride is a difficult-to-sinter material, it is preferable to add a sintering aid. As the sintering aid to be added, a rare earth element compound is preferable. The rare earth element compound reacts with the aluminum oxide or aluminum oxynitride present on the surface of the aluminum nitride particles to promote the densification of the aluminum nitride and to contribute to the decrease in the thermal conductivity of the aluminum nitride. Traps and improves the thermal conductivity. Regarding the rare earth element compound, an yttrium compound having a high trapping capability for removing oxygen from aluminum nitride is particularly preferable.

  Further, the addition amount of the sintering aid is preferably 0.01 to 5.0 wt% in terms of oxide. If the sintering aid to be added is less than 0.01 wt%, it is not only difficult to obtain a sufficiently dense sintered body, but also the thermal conductivity is lowered, which is not preferable. If the amount of the sintering aid exceeds 5.0 wt%, the sintering aid exists at the grain boundary of the sintered body. Therefore, when the sintered body is used in a corrosive atmosphere, it exists at this grain boundary. This is not preferable because the sintering aid part to be etched is etched and causes degranulation and particles. In particular, when the amount of the sintering aid is 1.0 wt% or less, the sintering aid does not exist at the triple point of the grain boundary, and the corrosion resistance is further improved.

  In addition, as the form of the rare earth element compound as the sintering aid, oxides, nitrides, fluorides, stearic acid compounds, and the like can be used. Of these, oxides have the advantage of being particularly inexpensive and easy to obtain. Moreover, since the stearic acid compound has high affinity with the organic solvent, the mixing property is particularly high when the raw material powder and the sintering aid are mixed with the organic solvent.

  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 powder and the raw material powder for the sintering aid. As a mixing method, ball mill mixing or ultrasonic mixing is possible. A slurry is prepared by mixing them. The obtained slurry is formed into a sheet by a doctor blade method. Although there is no restriction | limiting in particular in sheet | seat shaping | molding, As thickness of a sheet | seat, it is preferable that the thickness after drying is 3.0 mm or less. If the thickness of the sheet exceeds 3.0 mm, the amount of drying shrinkage of the slurry increases, which increases the possibility of cracking in the sheet, which is not preferable.

  Next, with the cofiring method, a circuit pattern having a predetermined shape, that is, a circuit such as a resistance heating element, a lead circuit for electrical connection to the sheet, and the like are formed on the completed sheet by a method such as screen printing. . At this time, the resistance value of the lead circuit can be made lower than that of the heating element by increasing the film thickness compared to the heating element circuit or increasing the circuit width. As the conductive paste used for screen printing, the same paste as the post metallization method described later can be used. However, the amount of oxide contained in the paste is preferably 30 wt% or less. In the case of the cofiring method, since the metal layer is sintered at the same time as the sheet, the metal layer is relatively easily sintered, and a circuit can be formed without adding an oxide.

  A sheet on which the circuit is formed and a sheet on which no circuit is formed are stacked. As a lamination method, the sheets are set at predetermined positions and overlapped. In this state, if necessary, a solvent is applied between the sheets and heated. Since the heating temperature depends on the flexibility of the finished sheet, it may be unnecessary, but it is preferably about 150 ° C. or lower. If a temperature higher than this is applied to the sheet, the sheet is greatly deformed, which is not preferable.

  Then, pressure is applied to the stacked sheets to integrate them. As a pressure to apply, the range of 1-100 Mpa is preferable. A pressure of less than 1 MPa is not preferable because the sheets do not sufficiently adhere to each other and so-called delamination occurs in the subsequent steps such as degreasing and sintering. On the other hand, if the pressure exceeds 100 MPa, the amount of deformation of the sheet becomes too large, which is not preferable. Degreasing of the finished laminated molded body can be performed under the same conditions as degreasing of an aluminum nitride press body by a post metallization method described later.

  The laminated molded body after degreasing is sintered at a temperature of about 1700 to 2000 ° C. in a non-oxidizing atmosphere. As the non-oxidizing atmosphere gas to be used, nitrogen, argon, or the like is preferable, and nitrogen is particularly preferable because it is relatively inexpensive. Moreover, as a moisture content contained in the nitrogen used at this time, it is preferable that a dew point is -30 degrees C or less. This is because when it contains more moisture, oxynitride may be formed by the reaction between aluminum nitride and moisture contained in the atmosphere during sintering, which may cause a decrease in thermal conductivity. The amount of oxygen contained in the nitrogen used is preferably 0.001% or less for the same reason as described above.

  Furthermore, a jig made of boron nitride (BN) is suitable as a jig for placing the laminated molded body during the sintering. This boron nitride jig not only has heat resistance against the above sintering temperature, but also has solid lubricity on the surface, so when the laminated molded body shrinks due to sintering, the jig and laminated molded body This is particularly preferable because the friction can be reduced and a sintered body with less deformation can be obtained.

  The obtained sintered body is processed as necessary. This is because the required accuracy for the dimensions is very high because the sintered body is used for semiconductor manufacturing equipment. As processing accuracy, for example, the flatness of the wafer mounting surface is preferably 0.5 mm or less, and more preferably 0.1 mm or less. When the flatness of the wafer mounting surface exceeds 0.5 mm, a gap is likely to occur between the wafer to be mounted and the mounting surface of the ceramic heater, and temperature unevenness occurs when the heat generated by the ceramic heater is transferred to the wafer. Since it becomes easy to do, it is not preferable.

  Moreover, as for the surface roughness in a wafer mounting surface, it is preferable that Ra is 5 micrometers or less. When the surface roughness is higher than this, ceramic degranulation may increase due to friction between the ceramic and the wafer. In this case, the dropped particles become particles, which is not preferable because it adversely affects processing such as film formation and etching on the wafer. It is more preferable that the surface roughness of the wafer mounting surface is 1.0 μm or less in terms of Ra.

Next, the post metallization method will be described. A slurry is prepared in the same manner as the above-mentioned cofire method, and granules are prepared from the obtained slurry by a technique such as a spray dryer. This granule is inserted into a mold having a predetermined shape, and press molding is performed. The pressing pressure at this time is preferably 0.1 t / cm ² or more. If this pressure is not reached, the strength of the molded body is often not sufficient, and it tends to be damaged by handling or the like, which is not preferable.

Further, the density of the molded body is preferably 1.5 g / cm ³ or more, although it varies depending on the binder content and the amount of auxiliary agent added. When the density of the molded body is lower than this, the distance between particles becomes relatively large, and sintering is difficult to proceed. However, the compact density is preferably 2.5 g / cm ³ or less. When the green body density exceeds 2.5 g / cm ³ , it becomes difficult to sufficiently remove the binder component in the green body during the degreasing process. For this reason, excess carbon and a carbon compound remain in the molded body during sintering, and this inhibits the sintering of aluminum nitride, so that the density of the obtained sintered body is not sufficient.

  The obtained molded body is degreased in a non-oxidizing atmosphere. When the molded body is degreased in an oxidizing atmosphere such as air, the surface of the aluminum nitride powder is oxidized, which causes a decrease in the thermal conductivity of the sintered body. As processing temperature, the range of 500-1000 degreeC is preferable. When degreasing is performed at a temperature lower than 500 ° C., the binder component is not sufficiently removed, and excessive carbon remaining is not preferable because it inhibits sintering. The amount of carbon present in the molded body after degreasing is preferably 1.0 wt% or less. If the residual carbon amount exceeds 1.0 wt%, the carbon and carbon compound in the molded body hinder the sintering of aluminum nitride, which is not preferable.

  The molded body after degreasing is sintered at a temperature of about 1700 to 2000 ° C. in a non-oxidizing atmosphere. As the atmospheric gas to be used, nitrogen, argon, or the like is preferable, and nitrogen is particularly preferable because it is relatively inexpensive. As a moisture content contained in the nitrogen used at this time, it is preferable that a dew point is -30 degrees C or less. This is because when it contains more moisture, oxynitride is formed by the reaction between aluminum nitride and moisture contained in the atmosphere during sintering, which may cause a decrease in thermal conductivity.

  Similarly, the amount of oxygen contained in the nitrogen to be used is preferably 0.001% or less for the same reason as described above. Further, as a jig used for sintering, a boron nitride jig is suitable. This boron nitride jig not only has heat resistance to the above-mentioned sintering temperature, but also has solid lubricity on the surface, so that the friction with the jig is reduced when the compact shrinks due to sintering. This is particularly preferable because a sintered body with less deformation can be obtained.

  The obtained sintered body is processed as necessary. That is, when a circuit is formed by screen printing in the subsequent process, the surface roughness is preferably Ra of 5.0 μm or less. This is because when the surface roughness is higher than this, pattern blurring or printing defects such as pinholes are likely to occur when a circuit is formed by screen printing. The surface roughness Ra is more preferably 1.0 μm or less. Moreover, when processing a sintered compact, it is preferable to process not only a printing surface but both main surfaces (front surface and back surface).

  When printing is performed on one main surface and only the printing surface is polished, the unpolished surface supports the workpiece. For this reason, when the work is likely to be unstable due to the presence of protrusions or foreign matters existing on the unpolished surface, it is preferable to polish both surfaces to the surface roughness or less. At this time, the parallelism of both processed surfaces is preferably 0.5 mm or less. When the degree of parallelism exceeds 0.5 mm, it is not preferable because the variation in film thickness may increase during screen printing. The parallelism is particularly preferably 0.1 mm or less. Further, the flatness of the printed surface is preferably 0.5 mm or less. This is because when the flatness is larger than this, the film thickness tends to vary during screen printing. The flatness is particularly preferably 0.1 mm or less.

  Circuits such as resistance heating elements and high-frequency generating electrodes are formed by screen printing on the sintered substrate that has been processed. As the metal powder to be used, tungsten, molybdenum, tantalum or the like is preferable from the viewpoint of matching the thermal expansion coefficient with ceramics. In addition, an oxide can be added to these metal powders in order to ensure adhesion strength with the aluminum nitride sintered body.

The oxide to be added is not particularly limited as long as it is wetted by both aluminum nitride and the refractory metal. Specifically, oxides of Group 2A elements, Group 3A elements, Al ₂ O ₃ , SiO _{2 and the} like are preferably used. Of these oxides, yttrium oxide is particularly preferable because it has very good wettability with respect to aluminum nitride. The addition amount of these oxides is preferably 0.1 to 30 wt%. If the addition amount of the oxide is less than 0.1 wt%, the effect of improving the adhesion strength between the metal layer and the ceramic is small, and if it exceeds 30 wt%, the resistance value of the metal layer increases, which is not preferable.

  Further, depending on the use temperature and use environment of the heater, a metal such as Ag—Pd or Ag—Pt can be used as the resistance heating element. In order to increase the resistance value of the circuit, it is also possible to increase the content of palladium or platinum. In this case, the glass component to be added is not particularly limited as long as it is a glass component that can be fired at 600 to 1000 ° C. according to the firing temperature. The added amount of the glass component may be increased when the resistance value is increased, and may be decreased when the resistance value is decreased, but approximately 1 to 30 wt% is preferable.

  Next, these powders are sufficiently mixed, and a binder and a solvent are added to prepare a paste. A circuit pattern is formed by screen printing this paste. The dry film thickness of the paste at this time is preferably in the range of 5 to 100 μm. A film thickness of less than 5 μm is not preferable because the resistance value becomes too high and the adhesion strength becomes low. Moreover, even if a film thickness exceeds 100 micrometers, since the fall of contact | adhesion intensity | strength is caused, it is unpreferable. The pattern spacing of the resistance heating element is preferably 0.1 mm or more. An interval smaller than this is not preferable because a leakage current is generated depending on the applied voltage and temperature when a current is passed through the resistance heating element. In particular, when used at a temperature exceeding 500 ° C., the pattern interval is preferably 1 mm or more, and more preferably 3 mm or more.

  Next, the formed circuit pattern is degreased in a non-oxidizing atmosphere. As processing temperature, 500 degreeC or more is preferable. A temperature lower than this is not preferable because carbon remains in the formed metal layer and may form a refractory metal and carbide when fired.

  The circuit pattern after degreasing is fired in a non-oxidizing atmosphere. The firing temperature is preferably 1500 ° C. or higher. Below this temperature, grain growth of the refractory metal powder does not proceed and the resistance becomes very high, which is not preferable. The firing temperature should not exceed the firing temperature of ceramics. When the metal layer is fired at a temperature exceeding the firing 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 metal layer is promoted, This is not preferable because the adhesion strength of the resin is lowered.

  In addition, when an Ag-based circuit pattern is formed, the firing temperature can be about 700 to 1000 ° C., and the atmosphere can be fired with air or nitrogen. For this reason, in the case of an Ag-based circuit pattern, it is usually unnecessary to degrease the circuit pattern.

  Next, in order to ensure insulation between the formed circuit patterns, an insulating coat can be formed on the circuit patterns. The material used is preferably the same material as the ceramic on which the metal layer is formed. This is because, if the composition of the ceramic and the insulating coating film are significantly different, the coefficient of thermal expansion is naturally different, which causes problems such as warping after firing.

  For example, when the insulating coat is aluminum nitride, a predetermined amount of 2A group or 3A group oxide or carbonate is added to aluminum nitride as a sintering aid and mixed, and then a binder or solvent is added to form a paste. It can be applied on the metal layer by screen printing. The amount of sintering aid added at this time is preferably 0.01 wt% or more. If it is less than this, the ceramics will not be densified, and the effect for securing insulation between circuit patterns will be reduced. On the other hand, if the amount of the sintering aid to be added exceeds 20 wt%, excessive sintering aid may penetrate into the metal layer and change the resistance value of the resistance heating element, which is not preferable. Note that when an Ag-based circuit is used, the thickness of the insulating coating is preferably 5 μm or more. If the thickness is less than this, it is difficult to obtain the desired insulation.

  Next, it is also possible to bond a ceramic substrate to the ceramic substrate on which a circuit pattern such as a resistance heating element is formed as described above and an insulating layer is formed as necessary. As a joining method, a binder or a solvent is added to aluminum oxide or aluminum nitride to a 2A group element compound or a 3A group element compound, and a paste is applied to the joining surface by a technique such as screen printing. Although there is no restriction | limiting in particular regarding the thickness of the joining layer at this time, It is preferable that it is 5 micrometers or more. If the thickness is less than this, since the bonding layer is thin, bonding defects are likely to occur.

Next, the applied bonding layer is degreased at a temperature of 500 ° C. or higher in a non-oxidizing atmosphere. Thereafter, the substrates to be bonded are superposed, a predetermined load is applied, and the substrates are heated in a non-oxidizing atmosphere to bond the substrates. Although there is no restriction | limiting in particular as a load amount at this time, It is preferable that it is 0.05 kg / cm < ² > or more. A load below this is not preferable because sufficient bonding strength cannot be obtained, or bonding defects such as pinholes and bonding unevenness are likely to occur. The bonding temperature is not particularly limited as long as the bonding layer bonded to the substrate can be sufficiently adhered, but is preferably 1500 ° C. or higher. A temperature lower than this is not preferable because sufficient bonding strength is difficult to obtain and bonding defects are likely to occur. The bonding atmosphere is preferably carried out in a non-oxidizing atmosphere such as nitrogen or argon in order to prevent the ceramics from being oxidized.

It is also possible to use a molybdenum coil as the resistance heating element circuit and a molybdenum or tungsten mesh as the high frequency generating electrode circuit. As a manufacturing method in this case, the above-described metal coil or mesh is incorporated in the raw material powder, and a ceramic heater molded body can be formed by a hot press method. Regarding the sintering temperature and atmosphere in this case, the conditions may conform to the sintering temperature of the aluminum nitride, but it is necessary to apply a pressure of 10 kg / cm ² or more. A pressure lower than this is not preferable because a gap is generated between the metal part and the ceramic. For processing the finished sintered body, a method similar to the cofiring method may be applied.

An aluminum nitride (AlN) green sheet to which 0.5 wt% of Y ₂ O ₃ was added as a sintering aid was produced. Further, 0.5 Wt% of Y ₂ O ₃ and Al ₂ O ₃ were added to the W powder, respectively, and an organic binder and solvent were further added to prepare a W paste. Using this W paste, a resistance heating element pattern was formed on an aluminum nitride green sheet by screen printing. This heating element had a maximum line width of 5 mm and a dry film thickness of 30 μm.

  Next, a high frequency generating electrode was formed on another aluminum nitride green sheet by the same method. The film thickness at this time was 40 μm. In addition to these, an aluminum nitride green sheet on which nothing was printed was prepared, and these were laminated and laminated at 70 ° C. and a pressure of 10 MPa. Then, the ceramic heater was produced by degreasing at 850 degreeC in nitrogen atmosphere, and also sintering at 1850 degreeC in nitrogen atmosphere. The dew point of nitrogen used at this time was −60 ° C.

  The finished ceramic heater was polished, and drilling was performed to ensure electrical continuity between the resistance heating element and the high frequency generating electrode. Next, a counterbore process having a diameter of 301 mm and a depth of 0.6 mm was performed on the portion corresponding to the wafer mounting surface. And the shape of the heater outer peripheral part was adjusted and it was set as 330 mm in diameter. Finally, a Mo heater was attached to each electrode portion of the resistance heating element and the high frequency generating electrode with an active metal brazing to complete a ceramic heater.

  The obtained ceramic heater was installed in the chamber, and the apparatus provided with each electric circuit shown to FIGS. 1-3 was produced, and it heated up to 750 degreeC, respectively. As a result, in the configuration of the electric circuit in FIG. 2, when the temperature reaches about 300 ° C., the amount of leakage exceeds 30 mA, and the leakage breaker 7 cuts off the energization to the resistance heating element 3, so that the temperature can be raised to a higher temperature. could not. On the other hand, in the configuration of the electric circuit of FIGS. 1 and 3, it was possible to raise the temperature to 750 ° C.

  Furthermore, when the chamber lid is opened, in the configuration of the electric circuit of FIG. 1 according to the present invention, if the leakage current exceeds 30 mA, the leakage breaker 7 is activated and the resistance heating element 3 is cut off. Although it was possible, the earth leakage breaker 7 did not operate in the configuration of FIG. From this result, it can be seen that the circuit structure of FIG. 1 that can detect the amount of electric leakage in the electric circuit is a safer circuit. In the resistance heating element circuit of FIGS. 1 and 3, the leakage current when the circuit is not installed is less than 2 mA. When the heater is heated to a high temperature, it is necessary not to install the resistance heating element circuit. I understand that.

It is a circuit diagram of the ceramic heater in one specific example of the semiconductor heating device of the present invention. It is a circuit diagram of the ceramic heater in the semiconductor heating apparatus of a reference example. It is a circuit diagram of the ceramic heater in the semiconductor heating apparatus of another reference example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamber 1a Lid 2 Ceramic heater 3 Resistance heating element 4 Electrode for high frequency generation 5 Insulation transformer 6 AC power supply 7 Earth leakage breaker 8 Magnet switch 9 Limit switch

Claims (5)

  A ceramic heater for heating a wafer is installed in the chamber, and the ceramic heater has a plurality of electric circuits including at least one resistance heating element via an insulator, and the resistance heating element passes through an insulation transformer. Is connected to an AC power source, and has an earth leakage breaker between the resistance heating element and the insulation transformer. The resistance heating element is not connected to the ground when the chamber lid is closed, and the chamber lid is opened. A semiconductor heating device, wherein the semiconductor heating device is connected to ground when it is applied.   The resistance heating element is provided between the insulating transformer and the earth leakage breaker via a magnet switch so that it can be connected to the ground. A limit switch for sending an ON-OFF signal to the magnet switch is attached to the lid of the chamber. 2. The semiconductor heating device according to claim 1, wherein when the is opened, the magnet switch is turned on by a signal from a limit switch and the resistance heating element is connected to the ground.   The semiconductor heating device according to claim 1, wherein at least one of the plurality of electric circuits is a high frequency generating electrode.   The semiconductor heating device according to claim 1, wherein at least one of the plurality of electric circuits is an electrostatic chuck electrode.   The semiconductor heating apparatus according to claim 1, wherein the ceramic heater is made of aluminum nitride.

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