JP6081858B2 - heater - Google Patents

Description

  The present invention relates to a heater.

  A heater is known as a component for heating each sample such as a semiconductor wafer in a manufacturing process of a semiconductor integrated circuit or a manufacturing process of a liquid crystal display device. As a heater, the heater board | substrate of patent document 1 is mentioned, for example. The heater substrate described in Patent Document 1 includes a ceramic base and a heating element circuit formed on the back surface of the ceramic base. The heater substrate is used by mounting an object to be heated on the main surface of the ceramic substrate.

JP-A-2005-286106

  However, in the heater substrate described in Patent Document 1, thermal stress may occur between the ceramic base and the heating element circuit under a heat cycle. As a result, cracks are generated from the surface of the heating element circuit that contacts the ceramic substrate, and may reach the surface of the heating element circuit opposite to the surface that contacts the ceramic substrate. As a result, it has been difficult to improve the long-term reliability of the heater substrate.

  The present invention has been made in view of such problems, and an object thereof is to provide a heater having improved long-term reliability.

  A heater according to an aspect of the present invention includes a ceramic body and a heating resistor including metal particles provided on a main surface of the ceramic body. The metal particles on the second surface located on the opposite side of the first surface are longer in the direction parallel to the main surface than the metal particles on the first surface in contact with the ceramic body. .

  According to the heater of one aspect of the present invention, the metal particles on the second surface located on the opposite side of the first surface are more dominant than the metal particles on the first surface in contact with the ceramic body of the heating resistor. Long in the direction parallel to the surface. Thermal stress generated between the first surface having short particles in the direction parallel to the main surface and the ceramic substrate can be reduced. Thereby, generation | occurrence | production of the crack in a heating resistor can be reduced. Further, the second surface having long particles in the direction parallel to the main surface has fewer interfaces in the direction perpendicular to the main surface. Thereby, even if a crack occurs, the progress of the generated crack can be suppressed. As a result, the long-term reliability of the heater can be improved.

It is sectional drawing which shows the heater of one Embodiment of this invention. It is the elements on larger scale which expanded the area | region A of the heater shown in FIG. It is a partial expanded sectional view which shows the modification of the heater of this invention.

  Hereinafter, a heater 10 according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view showing a heater 10 according to an embodiment of the present invention. As shown in FIG. 1, a heater 10 according to an embodiment of the present invention includes a ceramic body 1, a heating resistor 2 provided on the lower surface of the ceramic body 1, and an adsorption electrode 3 provided inside the ceramic body 1. And.

<Configuration of ceramic body 1>
The ceramic body 1 is a plate-like member having a sample holding surface 11 on the upper surface. The ceramic body 1 holds a sample such as a silicon wafer on the sample holding surface 11 on the upper surface. The heater 10 is a member in which the shape of the ceramic body 1 when viewed in plan is a circular shape. The ceramic body 1 is made of a ceramic material such as alumina ceramic, aluminum nitride ceramic, silicon nitride ceramic, or yttria ceramic. A heating resistor 2 is provided on the lower surface of the ceramic body 1. The dimensions of the ceramic body 1 can be set to a diameter of 200 to 500 mm and a thickness of 2 to 15 mm, for example.

  Various methods can be used as a method of holding the sample by the heater 10, but the heater 10 of this embodiment holds the sample by electrostatic force. Therefore, the heater 10 includes the adsorption electrode 3 inside the ceramic body 1.

  The adsorption electrode 3 is composed of two electrodes. One of the two electrodes is connected to the positive electrode of the power source, and the other is connected to the negative electrode. The two electrodes are each formed in a substantially semicircular shape, and are arranged inside the circular ceramic body 1 so that the semicircular strings face each other. The two electrodes are combined, and the entire outer shape of the adsorption electrode 3 is circular. The center of the circular outer shape of the adsorption electrode 3 as a whole is set to be the same as the center of the outer shape of the circular ceramic body 1. The adsorption electrode 3 is made of a metal material such as tungsten or molybdenum.

<Configuration of heating resistor 2>
The heating resistor 2 is a member for heating the sample held on the sample holding surface 11 on the upper surface of the ceramic body 1. The heating resistor 2 is provided on the lower surface of the ceramic body 1. The heating resistor 2 can be heated by applying a voltage to the heating resistor 2 and flowing a current. The heat generated by the heating resistor 2 is transmitted through the inside of the ceramic body 1 and reaches the sample holding surface 11 on the upper surface of the ceramic body 1. Thereby, the sample held on the sample holding surface 11 can be heated. The heating resistor 2 is a linear pattern having a plurality of curved portions, and is formed on almost the entire lower surface of the ceramic body 1. Thereby, it can suppress that dispersion | variation arises in heat distribution in the upper surface of the heater 10. FIG.

  The heating resistor 2 includes a conductor component and a glass component. As a conductor component, metal particles, such as silver palladium, platinum, aluminum, or gold | metal | money, are contained, for example. In order to suppress the foaming of the glass component, it is preferable to select a metal that can be sintered in the atmosphere as the metal material. The glass component includes oxides of materials such as silicon, aluminum, bismuth, calcium, boron and zinc.

  The following method can be used for temperature control of the heater 10. Specifically, the temperature of the heating resistor 2 can be measured by bringing a thermocouple into contact with the ceramic body 1 and measuring the thermoelectromotive force of the thermocouple. The temperature of the heating resistor 2 can also be measured by bringing a resistance temperature detector into contact with the ceramic body 1 and measuring the resistance of the resistance temperature detector. The temperature of the heater 10 can be controlled to be constant by adjusting the voltage applied to the heating resistor 2 based on the temperature of the heating resistor 2 measured as described above.

As described above, the heating resistor 2 includes a glass component as a raw material. Since the heating resistor 2 contains a glass component, the temperature required for sintering is low. Moreover, the heat generating resistor 2 has improved adhesion to the ceramic body 1 by having a glass component.

  Here, as shown in FIG. 2, the heating resistor 2 is located on the opposite side of the first surface 21 from the metal particles on the first surface 21 in contact with the ceramic body 1 when viewed in cross section. The metal particles on the surface 22 are longer in the direction parallel to the main surface. In the first surface 21 having short particles in a direction parallel to the main surface, thermal stress generated between the first surface 21 and the ceramic substrate can be reduced. Thereby, generation | occurrence | production of the crack in the heating resistor 2 can be reduced. Further, the second surface 22 having long particles in a direction parallel to the main surface has fewer interfaces in the direction perpendicular to the main surface. Thereby, even if a crack occurs on the first surface 21, it is possible to suppress the generated crack from progressing to the second surface 22. As a result, the long-term reliability of the heater 10 can be improved.

  If the heating resistor 2 is made of an alloy of silver and palladium, the length of the metal particles in the direction parallel to the main surface of the first surface 21 is about 3 μm, and the main surface of the second surface 22 is The length of the metal particles in the parallel direction can be set to about 5 μm.

  As a method of lengthening the particles on the second surface 22 in the direction parallel to the main surface, the following method can be used. Specifically, a paste containing metal particles having different particle diameters is applied a plurality of times. By reducing the metal particle size contained in the paste on the first surface 21 and increasing the metal particle size contained in the paste on the second surface 22, the particles on the second surface 22 are aligned in a direction parallel to the main surface. Can be long.

  Furthermore, the heating resistor 2 preferably has a porosity on the second surface 22 smaller than a porosity on the first surface 21. Thereby, even if a crack occurs in the first surface 21, the progress of the crack can be suppressed in the vicinity of the second surface 22. Thereby, the long-term reliability of the heater 10 can be improved.

  As a method for making the porosity on the second surface 22 smaller than the porosity on the first surface 21, the following method can be used. Specifically, the glass component may be properly used so that the melting point of the glass component used for the paste on the first surface 21 is higher than the melting point of the glass component used for the paste on the second surface 22. During the firing of the heating resistor 2, the temperature is higher than the melting point of the glass component used for the paste on the second surface 22 and lower than the melting point of the glass component used for the paste on the first surface 21 for a certain time. A heating step may be provided. Thereby, since the glass component is melted only in the paste on the second surface 22, the porosity on the second surface 22 can be reduced. Moreover, the following method can be used for confirmation of the porosity. Specifically, the total area of voids per unit area on the first surface 21 may be compared with the total area of voids per unit area on the second surface 22 by SEM observation.

  Furthermore, as shown in FIG. 3, the heating resistor 2 preferably has a shape in which the shape of the metal particles on the second surface 22 extends in a direction parallel to the main surface. Thereby, even if a crack occurs from the second surface 22, the crack progresses at an acute angle with respect to the second surface 22, so that the crack can be made difficult to progress. Thereby, the long-term reliability of the heater 10 can be improved.

In order to make the shape of the metal particles on the second surface 22 expand in a direction parallel to the main surface, the following method can be used. Specifically, after the heating resistor 2 is formed, the surface (second surface 22) of the heating resistor 2 may be polished with a lapping machine or the like. Thereby, the metal particles on the second surface 22 are deformed in a direction parallel to the main surface. As a result, the metal particles on the second surface 22 can be shaped to expand in a direction parallel to the main surface.

  Furthermore, the heating resistor 2 has a shape in which the shape of the metal particles on the second surface 22 has a longitudinal direction and a short direction in a direction parallel to the main surface, and a plurality of metals on the second surface 22. It is preferable that the particles are arranged so that their longitudinal directions are aligned. Thereby, since the direction in which current flows easily is aligned, adjacent metal particles generate the same amount of heat, so that it is possible to suppress unevenness in the temperature distribution. Thereby, the thermal uniformity in the sample holding surface 11 of the heater 10 can be improved.

  In order to make the shape of the metal particles on the second surface 22 a shape having a longitudinal direction and a short direction in a direction parallel to the main surface, and to arrange the longitudinal directions to be aligned, the following method is used. be able to. Specifically, after the heating resistor 2 is formed, the surface (second surface 22) of the heating resistor 2 may be polished with a lapping machine or the like. Thereby, the metal particles on the second surface 22 can be arranged to have a shape having a longitudinal direction and a short direction in a direction parallel to the main surface, and the longitudinal directions are aligned.

  Returning to FIG. 1, a part of the plasma etching apparatus 100 using the heater 10 described above will be described. The plasma etching apparatus 100 includes a vacuum chamber (not shown), a base plate 4 having a high-frequency application electrode (not shown) disposed in the vacuum chamber, and a heater 10 mounted on the base plate 4. Yes.

  The base plate 4 is a plate-like member having therein a cooling medium flow path (not shown) and a flow path for flowing a heat transfer gas such as helium or argon on the upper surface of the heater 10. As the base plate 4, for example, a metal material such as aluminum or titanium, a ceramic material such as silicon carbide, or a composite material of silicon carbide and aluminum can be used.

  The heating resistor 2 of the heater 10 is covered with an insulating layer 5. As the insulating layer 5, an adhesive material or a ceramic material containing a ceramic filler is used. The insulating layer 5 is bonded to the upper surface of the base plate 4 with a resin layer 6.

  As the resin layer 6, an adhesive resin can be used. Specifically, a silicone resin, an epoxy resin, an acrylic resin, or the like can be used. The resin layer 6 may contain a filler. By containing the filler, the thermal conductivity of the resin layer 6 can be improved. Any filler may be used as long as it has higher thermal conductivity than a resin material such as a ceramic material or a metal material. Specifically, when the filler is made of a metal, for example, a filler made of aluminum can be used. When the filler is made of a ceramic material, alumina, silicon carbide, aluminum nitride, or silicon nitride can be used.

  The plasma etching apparatus 100 includes a base plate 4 and a high-frequency application electrode (not shown) facing the inside of the chamber. A plasma is generated by applying a high frequency such as 13.56 MHz to the opposing high frequency application electrodes.

<Method for Manufacturing Heater 10>
Below, an example of the manufacturing method of the heater 10 shown in FIG. 1 and FIG. 3 is demonstrated. In addition, although the case where an alumina ceramic is used for the ceramic body 1 will be described as an example, the same technique can be used for other ceramic materials such as aluminum nitride ceramics.

First, a predetermined amount of alumina powder having a particle diameter of 0.1 to 2 μm as a main raw material and a small amount of sintering aid are weighed, and 24 to 72 together with ion-exchanged water or an organic solvent and high purity alumina balls in a ball mill. Perform wet milling mixing for hours.

  A predetermined amount of an organic binder such as polyvinyl alcohol, polyvinyl butyral or acrylic resin and a plasticizer and an antifoaming agent as auxiliary organic materials are added to the raw slurry thus pulverized and mixed, and further mixed for 24 to 48 hours. The mixed organic-inorganic mixed slurry is formed into a ceramic green sheet having a thickness of 20 μm to 20 mm by a doctor blade method, a calender roll method, a press forming method or an extrusion forming method.

  Then, a paste-like electrode material such as platinum or tungsten for forming the adsorption electrode 3 is printed and formed on the ceramic green sheet forming the ceramic body 1 by a known screen printing method or the like.

  Here, the ceramic green sheet on which the paste-like electrode material is not printed and the electrode-formed green sheet on which the paste-like electrode material is printed are overlapped so that the adsorption electrode 3 is formed at a predetermined position in the ceramic body 1. Laminate. Lamination is performed at a predetermined temperature while applying a pressure equal to or higher than the yield stress value of the ceramic green sheet. As the pressure application method, a known technique such as a uniaxial pressing method or an isotropic pressing method may be applied. The obtained laminated body is fired at a predetermined temperature and in a predetermined atmosphere, whereby the ceramic body 1 in which the adsorption electrode 3 is embedded is manufactured.

  Next, the ceramic body 1 is processed into a predetermined shape and thickness using a machining center, a rotary processing machine, or a cylindrical grinder. Furthermore, after processing the sample holding surface 11 to a specified surface roughness, grooves are formed by a blast processing machine or the like.

  Next, after the bottom surface of the ceramic body 1 is roughened by sandblasting, a paste in which a metal component such as silver palladium and a glass component composed of oxides of materials such as silicon, bismuth, calcium, aluminum and boron are added Is applied and baked at a temperature of about 800 ° C. to form the heating resistor 2. Furthermore, by polishing the heating resistor 2 with a lapping machine or the like, the metal particles on the second surface 22 are deformed in a direction parallel to the main surface. As a result, the metal particles on the second surface 22 can be shaped to expand in a direction parallel to the main surface.

  The heater 10 can be manufactured as described above.

  In the present embodiment, a heater 10 using alumina ceramics for the ceramic body 1 will be described.

  First, a predetermined amount of alumina powder having a particle size of 0.1 to 2 μm as a main raw material and a small amount of sintering aid are weighed, and ion-exchanged water, an organic solvent or an organic dispersant and a high purity alumina ball in a ball mill. In addition, 48 hours of wet pulverization and mixing were performed. Predetermined amounts of an organic binder such as polyvinyl alcohol, polyvinyl butyral, and an acrylic resin, and a plasticizer and an antifoaming agent as auxiliary organic materials were added to the raw material slurry thus pulverized and mixed, and further mixed for 3 hours. The mixed organic-inorganic mixed slurry was formed into a 100 μm ceramic green sheet by a doctor blade method.

A tungsten paste electrode material for forming the adsorption electrode 3 was formed on the ceramic green sheet forming the ceramic body 1 by screen printing. Here, the ceramic green sheet on which the paste-like electrode material is not printed and the electrode-formed green sheet on which the paste-like electrode material is printed are laminated so that the adsorption electrode 3 is formed at a predetermined position in the ceramic body 1. Then, the laminate was molded by pressing with a uniaxial press. Next, the obtained laminate was fired at a temperature of 1570 ° C. in a reducing atmosphere of hydrogen gas. The ceramic body 1 is formed into a predetermined shape using a machining center, a rotary processing machine, or a cylindrical grinder so that the thickness from the adsorption electrode 3 to the sample holding surface 11 is 0.3 mm, and the total thickness of the ceramic body 1 is 2 mm. It was processed into.

  Thereafter, a paste containing silver palladium as a metal component and silicon, boron and bismuth oxides as a glass component was applied. The metal particle size contained in the paste was set to about 3 μm. Then, the paste of the same component which set the metal particle size to about 4 micrometers was further apply | coated. Then, it baked at 780-850 degreeC. The heating resistor 2 was formed by this firing. The dimensions of the heating resistor 2 were set to a width of 1.5 mm and a thickness of 0.5 mm.

  Further, as a comparative example, a heater was manufactured in which a heating resistor was fired after a paste having a metal particle size set to about 3 μm was applied only once.

  Next, a durability test was performed on the manufactured heater 10. With the lower surface of the sample holder cooled to 20 ° C., a voltage of 250 V was applied to the heating resistor 2. Specifically, the voltage is applied until the temperature of the heater 10 reaches 130 ° C., the voltage application is stopped when the temperature reaches 130 ° C., the cooling is performed until the heater 10 reaches 50 ° C., and again. A cycle test was performed in which a voltage of 250 V was applied to bring the heater 10 to 130 ° C.

  As a result, in the heater of the comparative example, the resistance value of the heating resistor increased after 500 cycles, but in the example of the present invention, the resistance value of the heating resistor 2 did not change even after 500 cycles. It was.

  At this time, the particle size of the metal particles on the first surface 21 of the heating resistor 2 of the heater 10 of the example was about 3 μm, and the particle size of the metal particles on the second surface 22 was about 3 μm.

Ceramic body: 1
Heating resistor: 2
First side: 21
Second side: 22
Adsorption electrode: 3
Base plate: 4
Insulating layer: 5
Resin layer: 6
Heater: 10
Sample holding surface: 11
Plasma etching equipment: 100

Claims (4)

  A ceramic body; and a heating resistor including metal particles provided on a main surface of the ceramic body, the heating resistor being in a first surface in contact with the ceramic body when viewed in cross section. The heater according to claim 1, wherein the metal particles on the second surface located on the opposite side of the first surface are longer in the direction parallel to the main surface than the metal particles.   2. The heater according to claim 1, wherein the heating resistor has a porosity on the second surface smaller than a porosity on the first surface. 2. The heating resistor has a shape in which the shape of the metal particles on the second surface is expanded in a direction parallel to the main surface rather than a direction perpendicular to the main surface. The heater according to claim 2.   The heating resistor has a shape in which the shape of the metal particles on the second surface has a longitudinal direction and a short direction in a direction parallel to the main surface, and a plurality of the second particles on the second surface. The heater according to claim 3, wherein the metal particles are arranged so that their longitudinal directions are aligned.

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