JP2004177412A - Temperature measurement element and ceramic base for semiconductor production device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic base which is easy in temperature control as a ceramic heater and superior in temperature uniformity of heating surface, and a temperature measuring element placed on the base. <P>SOLUTION: In a ceramic base constituted by providing a temperature control means on the surface of inside of a ceramic plate and arranging a temperature measuring element inside the substrate, the temperature measuring element is made a thermocouple constituted by connecting two different kinds of metal wires in a sheath whose connection part size is the same as the element diameter of metal wires or larger and less or equal to 0.5 mm. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a ceramic heater and an electrostatic chuck used for drying or sputtering of a semiconductor product mainly used in the semiconductor industry, a ceramic substrate for a semiconductor manufacturing apparatus having a function as a wafer prober, and this ceramic substrate. In particular, the present invention proposes a technique for obtaining a ceramic base material for a semiconductor manufacturing apparatus, which is easy to control the temperature and excellent in ensuring the uniformity of the temperature of the heated surface.

  An electronic circuit of a semiconductor product is formed by applying a photosensitive resin as an etching resist on a silicon wafer and then etching. In this case, since the photosensitive resin applied to the surface of the silicon wafer is applied by a spin coater or the like, it is necessary to dry the photosensitive resin after application. The drying process is performed by placing a silicon wafer coated with a photosensitive resin on a heater and heating it. Conventionally, as such a heater, a heater in which a heating element is wired on the back surface of a substrate made of a metal plate (aluminum plate) is used.

  However, when a heater made of such a metal substrate is used for drying a semiconductor product, there are the following problems. Since the substrate of the heater is made of metal, the thickness of the substrate must be increased to 15 mm or more. This is because, in a thin metal substrate, warpage or distortion occurs due to thermal expansion caused by heating, and the wafer mounted on the substrate is damaged or tilted. Moreover, the conventional heater has a problem that it is heavy and bulky due to its thickness.

  Also, when controlling the heating temperature of the heater by changing the voltage or current applied to the heating element attached to the substrate, if the thickness of the substrate is large, the temperature of the heater substrate quickly changes with the fluctuation of the voltage or current. There is also a problem that the temperature control characteristic of the substrate does not follow and is poor.

  On the other hand, Japanese Patent Publication No. 8-8247 discloses a ceramic heater that controls the temperature of a ceramic plate while measuring the temperature in the vicinity of the heating element by using a nitride ceramic substrate on which a heating element is formed. is suggesting.

  However, when attempting to heat a silicon wafer using such a ceramic heater, there is a problem that a biased temperature distribution is inevitably generated on the heater surface.

  Therefore, an object of the present invention is to provide a ceramic base, a ceramic base provided with a function as a ceramic heater, an electrostatic chuck, and a wafer prober, which is easy to control the temperature and has excellent temperature uniformity on a heating surface, and a temperature measuring element attached to the base. Is to provide.

  While studying the causes of silicon wafer breakage toward realization of the above-mentioned objectives, the main reason why uneven temperature distribution occurs on the ceramic substrate despite performing temperature control is as follows. It was found that the responsiveness of the thermocouple was poor. The inventors continued further research and found that the thermocouple was not responsive enough because the junction of the thermocouple (metal wire junction) was spherical and the heat capacity of this part was large. It has been found that this is because the temperature is not accurately converted to a current value. Therefore, the inventors have focused on a method in which the two metal wire joints are not melted and crimped to form a spherical shape as in the related art, but are joined by spot heating the joint with laser light. By this method, the shape of the joint was slimmed down, and the temperature controllability of the thermocouple was improved. Further, by storing the thermocouple in a sheath, a temperature measuring element having excellent weather resistance and durability, such as prevention of moisture absorption, is realized.

  That is, according to the present invention, in a temperature measuring element including a thermocouple formed by joining two different types of metal wires in a sheath, a size of a joining portion of each of the metal wires is The present invention proposes a temperature measuring element which is the same as or larger than the element wire diameter, but is 0.5 mm or less, which can be mainly used for ceramic substrates.

  Further, a temperature control means is provided on the surface or inside of the ceramic plate, and the ceramic plate is a ceramic substrate for a semiconductor manufacturing apparatus in which a temperature measuring element is arranged, wherein the temperature measuring element is provided in a sheath. Two different types of metal wires are joined together, and the size of the joint is equal to or larger than the wire diameter of each metal wire, but a thermocouple with a size of 0.5 mm or less is inserted through an elastic body. The present invention proposes a ceramic substrate for a semiconductor manufacturing apparatus, which is pressed against a ceramic plate. It is desirable that the ceramic substrate for a semiconductor manufacturing apparatus be provided with a ceramic heater function.

  The ceramic substrate of the present invention preferably has an embodiment in which an electrostatic chuck is provided by embedding an electrostatic electrode inside a ceramic plate. Further, the ceramic substrate of the present invention has a guard electrode and a ground electrode embedded therein, and a chuck top conductor layer formed on the semiconductor wafer mounting surface on the plate surface to provide a wafer prober function. Embodiments are preferred.

  In each of the above configurations of the present invention, the temperature measuring element is fixed to the ceramic plate by pressure contact with an elastic body such as various springs, and is not bonded and fixed. Therefore, thermal deterioration of the adhesive does not occur, and the heater due to the falling off of the temperature measuring element. No heat runaway. In this case, the temperature measuring element may be directly contacted and held on the ceramic substrate, or may be indirectly contacted and held on the ceramic substrate via an insulating material or a heat conductive medium. Even in this case, regardless of whether it is direct or indirect, for example, as shown in FIG. 4A, the temperature measuring element may be pressed against a ceramic substrate with an elastic body such as a spring to be pressed and fixed. . In this case, in particular, since the adhesive is not bonded, the adhesive does not deteriorate due to heat, and the temperature measuring element does not fall off. This guarantees security permanently. The ceramic constituting such a ceramic heater is desirably a nitride ceramic or a carbide ceramic. It is desirable that the heating element of the ceramic heater be divided into at least two or more circuits. The heating element of the ceramic heater desirably has a flat plate-like cross section.

  According to the ceramic substrate for a semiconductor manufacturing apparatus of the present invention, when this is configured as a ceramic heater, it is possible to accurately measure the temperature of the object to be heated, and to determine the heat generation state of the heating element based on the measurement result of the temperature. The adjustment allows uniform heating of the whole object to be heated such as a silicon wafer. Further, when this is configured as an electrostatic chuck, unevenness in chucking force due to temperature unevenness is eliminated. In particular, when configured as a wafer prober, there is no error in a conduction test due to uneven temperature.

  In the present invention, a heating element or a Peltier element can be used as the temperature control means embedded in the ceramic plate. Further, as a thermocouple formed by joining the free ends of two different types of metal wires, the size of the junction, that is, the diameter of the junction is equal to or larger than the elementary wire diameter of each metal wire. Those having a diameter of 0.5 mm or less are used (see FIG. 3). By adopting such a configuration, the heat capacity concentrated on the joint portion is reduced, the temperature can be accurately and quickly converted to a current value, and the temperature controllability is improved, and when this is applied to a heater, The bias of the temperature distribution on the wafer heating surface can be reduced. Examples of combinations of metal wires of such thermocouples include, for example, K-type, R-type, B-type, S-type, E-type, J-type, as shown in JIS-C-1602 (1980). T-type thermocouples and the like can be mentioned, and among these, K-type thermocouples are preferable as a heating element of the ceramic heater. The K type is a combination of a Ni / Cr alloy wire and a Ni alloy, the R type is a combination of a Pt-13% Rh alloy wire and a Pt wire, and the B type is a Pt-30% Rh alloy wire and a Pt wire. Combination with -65Rh alloy wire, S type is a combination of Pt-10% Rh alloy wire and Pt wire, E type is a combination of Ni / Cr alloy wire and Cu / Ni alloy wire, J type Is a combination of an Fe wire and a Cu / Ni alloy wire, and T-type is a combination of a Cu wire and a Cu / Ni alloy wire.

  It is desirable that the size (cross-sectional diameter) of the metal wire constituting the heating element be about 0.1 to 0.3 mm. The size of the joint (D) is the same as or smaller than the element diameter (d) of the metal wire, and is at most 0.5 mm or less, preferably about 0.2 to 0.3 mm. As described above, the reason for specifically limiting the size is that if the size of the joint (D) is about the same as the wire diameter (d), there is no extra heat capacity and the temperature change can be accurately determined. This is because the temperature can be converted into an electric current, and as a result, an accurate temperature measurement can be performed. Therefore, the heating state of the heating element is adjusted based on the accurate temperature measurement result, so that the object to be heated can be uniformly heated.

As a method of manufacturing such a thermocouple, two kinds of metal wires are brought into contact with each other, and a laser beam is irradiated with a pulse (10 ⁻⁶ to 10 ⁻⁴ seconds) to perform spot heating. As the laser light, a carbon dioxide laser, an excimer laser, an ultraviolet laser, or the like can be used. This is because, when the joint portion of the metal wire is spot-heated by irradiating the laser beam with the pulse, the joint portion does not have the “bulge” as in the related art shown in FIG. In addition, each metal wire of this thermocouple is covered with polyimide or an insulating pipe so as not to contact each other. This thermocouple is stored in a sheath S as shown in FIG. The sheath S is made of a metal such as stainless steel, nickel, or copper having excellent oxidation resistance, or a ceramic such as alumina or silica. The sheath S can be filled with an insulating material 31 (powder may be used) made of ceramic powder such as alumina, silica, magnesia, or a resin such as epoxy resin, polyimide resin, or fluororesin. The insulating material 31 intervenes between the thermocouple 4 and the sheath S to secure insulation, and can also improve heat resistance, mechanical strength, pressure resistance, and the like.

  Next, an example in which the ceramic substrate for a semiconductor manufacturing apparatus according to the present invention is first configured as a ceramic heater will be described. As shown in FIG. 2, the ceramic base material constituting the ceramic heater has a basic shape in which a heating element 2 preferably having a flat cross section is embedded in the surface or inside of a ceramic plate 1. Then, a temperature measuring element is mounted on the surface of the ceramic plate 1 opposite to the heating surface 1a on which the object to be heated is placed. An example of the attachment is a structure as shown in FIG. In this structure, a projection 48 is provided on the outer side of a sheath S containing the temperature measuring element 4, and a coil spring 45 is provided between a bottom plate or a middle bottom plate 41 of a support container (casing) that supports and stores the ceramic plate 1. The temperature measuring element 40 is pressed against the ceramic plate 1 by the elastic force of the coil spring 45 and pressed against the ceramic plate 1. In the present invention, since the temperature measuring element 40 has the thermocouple 4 housed in the sheath S, it has excellent mechanical strength. Absent. Further, a heat transfer medium 42 can be interposed between the ceramic plate 1 and the temperature measuring element 40 having such a structure. A depression is formed in the heat transfer medium 42 to increase the contact area between the temperature measuring element 40 and the ceramic plate 1, thereby improving the responsiveness of the temperature measuring element 40. As the heat transfer medium 42, metal or ceramic can be used. Specifically, as the metal, aluminum, nickel, copper, stainless steel, or the like can be used. In addition, examples of the ceramic include aluminum nitride and silicon carbide. An insulating layer 50 is formed on the surface of the ceramic plate 1 so that insulation between the sheath S and the ceramic plate 1 can be ensured. FIG. 4B shows an example in which a leaf spring 47 is used instead of the coil spring.

  The ceramic plate 1 is preferably a nitride ceramic or a carbide ceramic. These ceramics have a coefficient of thermal expansion smaller than that of metal and have a much higher mechanical strength than metal. Therefore, even if the thickness is reduced, the ceramic does not warp or warp. Therefore, the substrate can be made thin and light. Furthermore, since the ceramic plate 1 made of these materials has a high thermal conductivity and a small thickness, the surface temperature of the plate can quickly follow a temperature change of the heating element. That is, when the temperature of the heating element is changed by changing the voltage and the current value, the surface temperature of the ceramic plate can be quickly controlled.

  In the ceramic heater constituted by using the ceramic base material of the present invention, the heating element 2 is formed on one surface of the ceramic plate 1 (see FIG. 2), and the surface on the opposite side is a heated object such as a silicon wafer. Or a heating surface 1a for mounting and heating, or the heating element 2 is buried inside the ceramic plate 1 and its buried position is eccentrically arranged in the thickness direction from the center of the thickness. It is desirable that the surface farther from the heating element 2 be the heating surface 1a.

  By disposing the heating element 2 on the ceramic plate 1 as described above, the heat generated from the heating element 2 is diffused throughout the substrate while propagating to the heating surface 1a, and the object 5 (silicon) is heated. The temperature distribution on the surface for heating a wafer or the like is made uniform, and as a result, the temperature in each part of the object 5 is made uniform.

  For example, FIG. 1 is a bottom view schematically illustrating an example in which the ceramic base material according to the present invention is configured as a ceramic heater. This ceramic heater is provided on a bottom surface of a ceramic plate 1 formed in a disc shape. The heating element 2 is formed in a concentric or spiral pattern in order to heat the heating surface of the ceramic plate 1 so that the temperature distribution over the entire heating surface (the surface opposite to the illustrated bottom surface) is uniform. These heating elements 2 have a configuration in which adjacent double concentric circles are connected as one set so as to form a single line, and terminal pins 6 serving as input / output terminals are connected to both ends thereof. In a portion near the center of the ceramic plate 1, a through hole 8 for inserting a support pin 7 for supporting the object 5 to be heated is formed.

  In the ceramic heater having such a configuration, the thickness of the ceramic plate 1 is preferably 0.5 to 5 mm. If it is thinner than 0.5 mm, it is easily broken, whereas if it is thicker than 5 mm, heat is difficult to propagate, and the heating efficiency becomes poor.

  It is desirable to use a nitride ceramic or a carbide ceramic as the ceramic plate material. Examples of the nitride ceramic include aluminum nitride, silicon nitride, boron nitride, and titanium nitride. These may be used alone or in combination of two or more. Examples of the carbide ceramic include silicon carbide, zirconium carbide, titanium carbide, tantalum carbide, and tungsten carbide. These may be used alone or in combination of two or more. Of these, aluminum nitride is most preferred. This is because the thermal conductivity is the highest at 180 W / m · K, and is excellent in temperature followability.

  In the above ceramic heater, the heating element 2 as one of the temperature control means is preferably divided into at least two or more circuits as shown in FIG. 1, and more preferably divided into two to ten circuits. The reason is that, by dividing the circuit, the amount of heat generated can be changed by controlling the power supplied to each circuit, and the temperature of the heating surface 1a such as a silicon wafer can be accurately controlled. As the wiring pattern of the heating element 2, in addition to the concentric circles shown in FIG. 1, for example, a spiral, an eccentric circle, a bent line, and the like are given.

  In the ceramic heater, when the heating element 2 is formed on the surface of the ceramic plate 1, a conductive paste containing metal particles is applied to the surface of the ceramic plate 1 to form a conductive paste layer having a predetermined pattern. It is preferable to bake this and sinter the metal particles on the surface of the ceramic plate 1. The sintering of the metal particles is sufficient if the metal particles and the metal particles and the ceramic are fused together.

  As shown in FIG. 1, when the heating element 2 is formed on the surface of the ceramic plate 1, the thickness of the heating element 2 is preferably about 1 to 30 μm, and more preferably 1 to 10 μm. On the other hand, when the heating element 2 is formed inside the ceramic plate 1, its thickness is preferably 1 to 50 μm.

  When the heating element 2 is formed on the surface of the ceramic plate 1, the width of the heating element 2 is preferably 0.1 to 20 mm, more preferably 0.1 to 5 mm. On the other hand, when the heating element 2 is buried inside the ceramic plate 1, the width of the heating element 2 is preferably about 5 to 20 μm.

  The resistance of the heating element 2 can be changed by changing its width and thickness, but the above range is the most practical. The resistance value is higher as the thickness is thinner and thinner, and the thickness and width can be increased when the heating element 2 is formed inside the ceramic substrate 1. In particular, when the heating element 2 is buried inside, the distance between the heating surface 1a and the heating element 2 is shortened, and the uniformity of the temperature of the heating surface 1a may be reduced, so that the width of the heating element 2 itself is increased. There is a need. In the case where the heating element 2 is buried inside the ceramic plate 1, there is no need to consider adhesion with nitride ceramics or the like. Therefore, as a material for the heating element, a high melting point metal such as tungsten or molybdenum or the like is used. Tungsten and molybdenum carbide can be used. Further, since the resistance of such a heating element can be increased, the thickness itself may be increased for the purpose of preventing disconnection or the like. It is desirable that the heating element in this case also has the above-described thickness and width.

  The cross section of the heating element 2 in the width direction may be rectangular or elliptical in diameter, but is desirably a flat so-called plate shape. This is because a flat cross section is more likely to uniformly transmit heat toward the heating surface, and therefore, it is difficult to form a non-uniform temperature distribution on the heating surface. The degree of the flatness is desirably about 10 to 5000 in terms of a cross-sectional aspect ratio (width of heating element / thickness of heating element). Adjusting to this range can increase the resistance value of the heating element 2 and ensure uniformity of the temperature of the heating surface 1a.

  That is, when the thickness of the heating element 2 is assumed to be constant, if the aspect ratio is smaller than the above range, the amount of heat propagation in the direction of the heating surface of the ceramic plate 1 becomes small, and the pattern approximates the pattern of the heating element 2. If a uniform temperature distribution is generated on the heating surface, and if the aspect ratio is too large, the temperature just above the center of the heating element 2 becomes high, and the temperature distribution approximate to the pattern of the heating element 2 is eventually obtained. Will occur. Therefore, in consideration of the temperature distribution, the aspect ratio of the cross section is preferably set to about 10 to 5000 as described above.

  When the heating element 2 is formed on the surface of the ceramic plate 1, the sectional aspect ratio is 10 to 200. When the heating element 2 is formed inside the ceramic plate 1, the sectional aspect ratio is 200 to 5000. Is more preferable. In this regard, when the heating element 2 is formed inside the ceramic plate 1, the cross-sectional aspect ratio can be increased. This means that, when the heating element 2 is provided inside, the distance between the heating surface 1a and the heating element 2 is shortened, and the temperature uniformity of the heating surface is reduced by that much, so that the heating element 2 itself is made flatter. This is necessary.

  By the way, this heating element 2 can be embedded eccentrically in the thickness direction inside the ceramic plate 1, but its position is on the opposite side (bottom surface) to the heating surface 1 a of the ceramic plate 1. It is desirable that the position be more than 50% and up to 99% of the distance from the heating surface 1a to the bottom surface at a position close to If the embedding position is 50% or less, the temperature is too close to the heating surface, causing an uneven temperature distribution. Conversely, if the eccentric amount exceeds 99%, the ceramic plate 1 itself warps. This may cause damage to the silicon wafer to be processed during heating.

  When the heating element 2 is embedded in the ceramic plate 1, the heating element forming layer may be provided in a plurality of layers. In this case, the patterns of the respective layers are in a mutually complementary relationship, that is, in a state where the heating element 2 of any layer is always patterned in any region when viewed from above the heating surface 1a. It is desirable to do. As such a structure, for example, a structure in which the arrangement is staggered with respect to each other can be given.

  The conductor paste for forming a heating element is not particularly limited, but preferably contains not only metal particles or conductive ceramic for ensuring conductivity, but also a resin, a solvent, a thickener, and the like.

Next, a method for manufacturing the ceramic heater will be described.
(1) A step of mixing a ceramic powder such as a nitride ceramic and a carbide ceramic with a binder and a solvent to obtain a green sheet (form): In the process of this step, the ceramic powder may be aluminum nitride, silicon carbide, or the like. Element and the like, and a sintering aid such as yttria may be added as necessary. The binder is preferably at least one selected from an acrylic binder, ethyl cellulose, butyl cellosolve, and polyvinylal. Further, as the solvent, at least one selected from α-terpione and glycol is desirable. The conductive paste obtained by mixing them is formed into a sheet by a doctor blade method to produce a green sheet. A through hole 8 for inserting the support pin 7 for the silicon wafer 5 can be opened in the green sheet as needed. These through holes 8 can be formed by applying a punching method or the like. The thickness of the green sheet is preferably about 0.1 to 5 mm.

(2) A step of printing a conductive paste serving as a heating element on the green sheet: in the processing of this step, a conductive paste made of metal particles or conductive ceramic is applied to a heating element forming portion on the green sheet; Print. These conductive pastes include conductive metal particles and conductive ceramic particles. Examples of such metal particles include noble metals (gold, silver, platinum, palladium), lead, tungsten, and molybdenum. , Nickel and the like are preferable. These may be used alone or in combination of two or more. This is because these metals are relatively hard to oxidize and have a resistance value sufficient to generate heat. Further, as the conductive ceramic particles, carbide of tungsten or molybdenum is most suitable. This is because it is difficult to be oxidized and the thermal conductivity is not easily reduced. These may be used alone or as a mixture.

  As such a conductive paste, metal particles or conductive ceramic particles: 85 to 97 parts by weight, at least one or more binders selected from acrylic, ethyl cellulose, butyl cellosolve, and polyvinylal: 1.5 to 10 parts by weight, α-terpione And at least one solvent selected from glycols and glycols: tungsten paste or molybdenum paste prepared by mixing and adjusting 1.5 to 10 parts by weight.

  The metal particles or the conductive ceramic particles contained in the conductive paste preferably have a particle size of 0.1 to 100 μm. If it is smaller than 0.1 μm, it is easily oxidized. On the other hand, if it is larger than 100 μm, sintering becomes difficult and the resistance value increases. The shape of the metal particles may be spherical or scaly. When these metal particles are used, they may be a mixture of the above-mentioned spherical material and the above-mentioned scaly material. When the metal particles are scaly, or a mixture of spherical and scaly, it is easy to hold the metal oxide between the metal particles, and the adhesion between the heating element and the nitride ceramic is improved. This is advantageous because it is possible to increase the resistance and increase the resistance value.

  Examples of the resin contained in the conductor paste include an epoxy resin and a phenol resin. Examples of the solvent include isopropyl alcohol. Examples of the thickener include cellulose and the like. As described above, it is desirable to add a metal oxide to metal particles and sinter this to a conductor paste to be a heating element to be a heating element. By sintering the metal oxide together with the metal particles in this way, the adhesion between the metal particles and the nitride ceramic or carbide ceramic as the ceramic plate 1 is improved. It is not clear why mixing the metal oxide with the metal particles in the conductive paste improves the adhesion with the nitride ceramic or the carbide ceramic. The surface of is slightly oxidized to form an oxide film, and this oxide film sinters and integrates through the metal oxide, and the metal particles and the nitride ceramic or carbide ceramic adhere to each other. It is thought that there is not.

As the metal oxide, for example, at least one selected from the group consisting of lead oxide, zinc oxide, silica, boron oxide (B ₂ O ₃ ), alumina, yttria, and titania is preferable. This is because these oxides can improve the adhesion between the metal particles and the nitride ceramic or the carbide ceramic without increasing the resistance value of the heating element 2.

The ratio of the lead oxide, zinc oxide, silica, boron oxide (B ₂ O ₃ ), alumina, yttria, and titania is such that when the total amount of the metal oxide is 100 parts by weight, the lead oxide is 1 to 10 by weight. , Silica is 1 to 30, boron oxide is 5 to 50, zinc oxide is 20 to 70, alumina is 1 to 10, yttria is 1 to 50, titania is 1 to 50, and the total exceeds 100 parts by weight. It is desirable that it be adjusted within a range that does not exist. By adjusting the amounts of these oxides in these ranges, the adhesion to the nitride ceramic can be particularly improved. The amount of the metal oxide added to the metal particles is preferably 0.1% by weight or more and less than 10% by weight.

  The area resistivity when the heating element 2 is formed using the conductor paste having such a configuration is preferably 1 to 45 mΩ / □. If the sheet resistivity exceeds 45 mΩ / □, the amount of heat generated becomes too large with respect to the applied voltage, and it is difficult to control the amount of heat generated by a ceramic heater having a heating element provided on the surface of a ceramic plate. If the addition amount of the metal oxide is 10% by weight or more, the sheet resistivity exceeds 50 mΩ / □, the calorific value becomes too large, the temperature control becomes difficult, and the uniformity of the temperature distribution decreases. .

  When the heating element 2 is formed on the surface of the ceramic plate 1, it is desirable that a metal coating layer (see FIG. 2) 9 be formed on the surface of the heating element 2. This is to prevent the internal metal sintered body (heating element 2) from being oxidized to change the resistance value. The thickness of the metal coating layer 9 is preferably 0.1 to 10 μm. The metal used for forming the metal coating layer 9 is not particularly limited as long as it is a non-oxidizing metal, and specific examples include gold, silver, palladium, platinum, and nickel. These may be used alone or in combination of two or more. Of these, nickel is preferred.

(3) At least each of a green sheet printed with the conductive paste for the heating element 2 obtained in the step (2) and a green sheet not printed with the paste obtained in the same step as the step (1) Step of laminating one or more sheets: In this step, when laminating two or more types of green sheets, one or more layers are laminated on the upper side (meaning the heating surface side) of the green sheet with the conductive paste for the heating element of (2). It is important that the number of the green sheets to be formed is smaller than the number of the green sheets laminated on the lower side (1) so that the embedded position of the heating element 2 is eccentric in the thickness direction. Specifically, 20 to 50 sheets are stacked on the upper side, and 5 to 20 sheets are stacked on the lower side.

(4) A step of heating and pressing the green sheet laminate to sinter the green sheet and the conductive paste to form a ceramic plate and a heating element: the heating element 2 needs terminals for connecting to a power supply. This terminal is attached to the heating element 2 via solder. Nickel is preferable because it prevents solder from diffusing. Examples of the connection terminal include a terminal pin 6 made of Kovar. When the heating element 2 is formed inside the ceramic plate 1, the surface of the heating element 2 is not oxidized, so that the above-described coating 9 is unnecessary. When the heating element 2 is formed inside the ceramic plate 1, a part of the heating element 2 may be exposed on the surface, and through holes 23 and 24 for connecting the heating element 2 are provided in the terminal portion. The external terminal connection pins 6 may be connected to and fixed to the through holes 23 and 24. When the external terminal connection pins 6 are connected, an alloy of silver-lead, lead-tin, bismuth-tin, or the like can be used as the solder. Note that the thickness of the solder layer is preferably 0.1 to 50 μm. This is because the range is sufficient to secure connection by soldering.

In this step, the heating is carried out at a temperature of 1000 to 2000 ° C. and a pressure of 100 to 200 kg / cm ² in an inert gas atmosphere. As the inert gas, argon, nitrogen and the like can be used.

(5) Finally, openings for inserting external terminal connection pins 6 are formed in the through holes (connection pads) 23 and 24. Then, after solder paste is printed as a brazing material in the opening, the external terminal connection pins 6 are inserted, heated, and reflowed. The heating temperature is preferably from 200 to 500C. Furthermore, the temperature measuring element 40 can be embedded as needed.

  Next, a method of using the above ceramic heater will be described with reference to FIG. First, when power is supplied to the ceramic heater by operating the control unit 15, the temperature of the ceramic substrate 1 itself starts to rise, but the surface temperature of the outer peripheral portion becomes slightly low. The data measured by the temperature measuring element 40 is first stored in the storage unit 16. Next, the temperature data is sent to a calculating unit 17, which calculates a temperature difference ΔT at each measurement point, and further calculates data ΔW necessary for uniformizing the temperature of the heating surface 1a. Calculate. For example, if there is a temperature difference ΔT between the heating element 2a and the heating element 2b, and the heating element 2a is lower, power data ΔW that makes ΔT zero is calculated and transmitted to the control unit 15, Is applied to the heating element 2a to raise the temperature.

  Regarding the power calculation algorithm, the simplest method is to calculate the power required to raise the temperature from the specific heat of the ceramic plate 1 and the weight of the heating area, and a correction coefficient due to the heating element pattern may be added to this. . Alternatively, a temperature rise test may be performed on a specific heating element pattern in advance, and a function of the temperature measurement position, the input power, and the temperature may be obtained in advance, and the input power may be calculated from the function. Then, the applied voltage and the time corresponding to the power calculated by the calculation unit 17 are transmitted to the control unit 15, and the control unit 15 supplies power to each heating element 2 based on the values.

  FIG. 2 is a diagram showing a preferred embodiment of the present invention. In the ceramic heater shown in this figure, heating elements 2a and 2b are formed on the bottom surface 1b of the ceramic plate 1, and a metal coating layer 9 is formed around the heating elements 2a and 2b. An external terminal connection pin 6 is connected and fixed to these heating elements 2 a and 2 b via a metal coating layer 9, and a socket 18 is attached to the pin 6. The socket 18 is connected to the control unit 15 having a power supply.

  Next, as another embodiment of the ceramic substrate of the present invention, in order to electrostatically adsorb an object such as a silicon wafer on the chuck surface of the ceramic plate 1, an electrostatic electrode is provided inside the ceramic plate 1. Is embedded to provide an electrostatic chuck function. That is, as shown in FIG. 6, the positive and negative electrostatic electrodes 11 are embedded in the ceramic plate 1 together with the heating element 2 or independently. The electrostatic electrode 11 is composed of a comb-shaped electrode composed of a positive electrode and a negative electrode. By applying a voltage to the electrode, an electrostatic field is generated to attract the silicon wafer 5 set on the ceramic plate 1. Used to support.

  As still another embodiment of the present invention, there is a ceramic substrate provided with a wafer prober function in the ceramic plate 1 together with the heating element 2 and the electrostatic electrode 11 or independently. As shown in FIGS. 7A and 7B, the ceramic substrate provided with the wafer prober function has a guard electrode 12 and a ground electrode 13 embedded inside the ceramic plate 1 and a surface of the ceramic plate 1. And a chuck top conductor layer 14 formed thereon. A silicon wafer 5 is placed on the chuck top conductor layer 14, a probe card with tester pins is pressed while heating, and a continuity test can be performed by applying a voltage to the chuck top conductor layer 14. It has become. In this wafer prober, the same voltage as that of the chuck top conductor layer 14 is applied to the guard electrode 12 to cancel the capacitance. The ground electrode 13 is provided for removing noise from the heating element 2.

  The operation of this type of ceramic heater is the same as that of the ceramic heater shown in FIG. 2. The temperatures of the heating elements 2 a and 2 b are measured at regular time intervals and stored in the storage unit 16. A voltage value or the like to be controlled is calculated, and based on the calculation, a predetermined voltage is applied from the control unit 15 to the heating elements 2a and 2b, so that the temperature of the entire heating surface 1a of the ceramic heater can be made uniform. It has become.

Hereinafter, the present invention will be described in more detail based on examples.
Test material 1-1
(Manufacture of temperature measuring element) A metal wire having a cross-sectional diameter of 0.2 mm made of a Pt-13% Rh alloy and a metal wire having a cross-sectional diameter of 0.2 mm made of Pt were joined and irradiated with a pulsed carbon dioxide laser for ^10-4 seconds. Both were joined. A thermocouple 4 was formed by inserting a polyimide resin pipe 20 having an inner diameter of 0.3 mm and a thickness of 0.02 mm into a metal wire for insulation. As shown in FIG. 3, the thermocouple 4 is joined to the joint of the two types of metal wires 4a and 4b without forming a spherical melt 4c. As shown in FIG. 3B, the thermocouple 4 is housed in a sheath S together with an insulating material 31 of magnesia powder, and is fixed by fitting a sleeve 50 made of a fluorine resin for waterproofing at one end. Have been.

Test material 1-2 (manufacture of temperature measuring element)
A Ni / Cr wire and a Ni alloy wire each having a cross-sectional diameter of 0.2 mm were spot-welded by irradiating a pulse excimer laser for ^10-6 seconds. A thermocouple 4 was formed by inserting an alumina pipe 20 having an inner diameter of 0.3 mm and a thickness of 0.02 mm into a metal wire for insulation. In the thermocouple 4, a spherical melt 4c of about 0.2 mm is formed and joined to a joint between the metal wires 4a and 4b. Thereafter, as shown in FIG. 3 (b), the thermocouple is housed in a sheath S together with a magnesia powder material 31 and a sleeve 50 made of waterproof fluororesin is fitted into one end. Fixed.

Example 1
Manufacture of ceramic heater made of aluminum nitride (see Fig. 1)
(1) 100 parts by weight of aluminum nitride powder (average particle size: 1.1 μm), 4 parts by weight of yttria (average particle size: 0.4 μm), 12 parts by weight of acrylic binder and alcohol are spray-dried to obtain granules. A powder was prepared.
(2) Next, this granular powder was placed in a mold and molded into a flat plate to obtain a formed product (green). The green sheet is drilled to form a through hole 8 for inserting a support pin of a silicon wafer and a bottomed hole 3 for embedding a thermocouple (diameter: 1.1 mm, depth: 2 mm). Was formed.
(3) The processed green sheet was hot-pressed at 1800 ° C. and a pressure of 200 kg / cm ² to obtain an aluminum nitride plate having a thickness of 3 mm. Next, a disk having a diameter of 12 inches (300 mm) was cut out from the plate to obtain a ceramic plate (ceramic plate 1).

(4) A conductive paste was printed on the ceramic plate 1 obtained in (3) by screen printing. The printing pattern was a concentric pattern as shown in FIG. As this conductive paste, Solvest PS603D manufactured by Tokuri Kagaku Kenkyusho, which is used for forming through holes in a printed wiring board, was used. This conductive paste is a silver-lead paste, and based on 100 parts by weight of silver, lead oxide (5% by weight), zinc oxide (55% by weight), silica (10% by weight), boron oxide (25% by weight) ) And 7.5 parts by weight of a metal oxide consisting of alumina (5% by weight). The silver particles had an average particle size of 4.5 μm and were scaly.

(5) Next, the ceramic plate 1 on which the conductive paste was printed was heated and fired at 780 ° C. to sinter silver and lead in the paste and baked on the plate 1 to form a heating element 2. . The silver-lead heating element 2 had a thickness of 5 μm, a width of 2.4 mm, and a sheet resistivity of 7.7 mΩ / □.
(6) An electroless nickel plating bath composed of an aqueous solution having a concentration of 80 g / l of nickel sulfate, 24 g / l of sodium hypophosphite, 12 g / l of sodium acetate, 8 g / l of boric acid, and 6 g / l of ammonium chloride as described in (5) above. Was immersed to deposit a metal coating layer 9 (nickel layer) having a thickness of 1 μm on the surface of the silver-lead heating element 2.
(7) A silver-lead solder paste (manufactured by Tanaka Kikinzoku) was printed by screen printing on a portion to which an external terminal for securing connection to a power supply was attached, to form a solder layer. Then, a Kovar external terminal connection pin 6 was placed on the solder layer, and heated and tapped at 420 ° C., and the pin 6 was attached to the surface of the heating element 2.

(8) The temperature measuring element 40 of the test material 1-1 for temperature control was pressed against the ceramic substrate by a spring via an aluminum plate 42 as shown in FIG. 4 to obtain a heater.

Example 2
Electrostatic chuck (with ceramic heater) Basically the same as in Example 1, except that a positive electrode comprising a semicircular portion on the outer periphery of the green sheet and a number of linear portions extending in parallel and equidistantly from that portion, An electrostatic electrode 11 having a negative electrode arranged in a comb-tooth shape is printed, and this green sheet is laminated with the green sheet on which the heating element 2 is printed, and hot-pressed at 1890 ° C. and a pressure of 150 kg / cm ² for 3 hours to have a thickness of 3 mm. Was obtained. This was cut into a 300 mm disk shape, and an electrostatic chuck with a heater having a heating element having a thickness of 6 μm and a width of 10 mm and a comb-shaped electrostatic electrode 11 was formed therein.

Example 3 Wafer prober (with ceramic heater)
(1) 100 parts by weight of aluminum nitride powder (manufactured by Tokuyama, average particle size 1.1 μm), 4 parts by weight of yttria (yttrium oxide, average particle size 0.4 μm), 11.5 parts by weight of acrylic binder, 0.1 dispersant. A composition in which 5 parts by weight and 53% by weight of alcohol composed of 1-butanol and ethanol were mixed was formed with a doctor blade to obtain a 0.47 mm thick green sheet.
(2) After the green sheet was dried at 80 ° C. for 5 hours, a hole for a through hole for connecting the heating element 2 and the external terminal connection pin 6 by punching was provided.
(3) A conductive paste A was prepared by mixing 100 parts by weight of tungsten carbide particles having an average particle diameter of 1 μm, 3.0 parts by weight of an acrylic binder, 3.5 parts by weight of an α-terpione solvent, and 0.3 parts by weight of a dispersant. A conductive paste B was prepared by mixing 100 parts by weight of tungsten particles having an average particle diameter of 3 μm, 1.9 parts by weight of an acrylic binder, 3.7 parts by weight of α-terpione solvent, and 0.2 parts by weight of a dispersant. The printed material for the guard electrode 12 and the printed material for the ground electrode 13 were printed in a grid pattern on the green sheet by screen printing on the conductive paste A to form an electrode pattern. Further, as shown in FIG. 1, a heating element 2 having a concentric pattern was printed on the back surface of the green sheet. In addition, the conductive paste B was filled in through-holes for connecting to the terminal pins 6. Then, 50 printed green sheets and unprinted green sheets were laminated and integrated at 130 ° C. under a pressure of 80 kg / cm ² .

(4) The laminate was degreased in nitrogen gas at 600 ° C. for 5 hours, and hot-pressed at 1890 ° C. under a pressure of 150 kg / cm ² for 3 hours to obtain a 3 mm-thick aluminum nitride plate. This was cut into a circular shape having a diameter of 230 mm to obtain a ceramic plate. The size of the through hole was 0.2 mm in diameter and 0.2 mm in depth. The thickness of the guard electrode 12 and the ground electrode 13 is 6 μm, the formation position of the guard electrode 2 is 0.7 mm from the wafer mounting surface, the formation position of the ground electrode 13 is 1.4 mm, and the position of the heating element 2 is 2.8 mm.

(5) After polishing the plate-like body obtained in (4) with a diamond grindstone, a mask is placed, and a groove 19 for wafer suction (width 0.5 mm, depth 0 .5 mm) (FIG. 7 (b)).
(6) A film composed of three layers of titanium, molybdenum and nickel was formed on the surface where the groove 19 was formed by sputtering. As a device for sputtering, SV-4540 manufactured by Japan Vacuum Engineering Co., Ltd. was used. The conditions were as follows: the pressure was 0.6 Pa, the temperature was 100 ° C., the power was 200 W, and the time was 30 seconds to 1 minute. The thickness of the obtained three-layer film was 0.5 μm for titanium, 4 μm for molybdenum, and 1.5 μm for nickel from the image of the X-ray fluorescence spectrometer.

(7) The ceramic substrate 1 obtained in (6) is immersed in an electroless nickel plating bath composed of an aqueous solution having a concentration of nickel sulfate 30 g / l, boric acid 30 g / l, ammonium chloride 30 g / l, and Rochelle salt 60 g / l. Then, nickel having a thickness of 7 μm and a boron content of 1% by weight or less was deposited and laminated on the surface of the film on the groove 19 side, and annealed at 120 ° C. for 3 hours. Further, an electroless gold plating solution comprising 2 g / l of potassium gold cyanide, 75 g / l of ammonium chloride, 50 g / l of sodium citrate, and 10 g / l of sodium hypophosphite on the surface at 93 ° C. The chuck top conductor layer 14 was formed by immersing for 1 minute and forming a gold plating layer having a thickness of 1 m on the nickel plating layer 15.

(8) The air suction hole 22 that escapes from the groove 19 to the back surface is drilled, and holes for exposing the through holes 23 and 24 are provided. Using a gold braze made of a Ni-Au alloy (Au81.5, Ni18.4, impurity 0.1), the holes were heated and reflowed at 970 ° C. to connect the Kovar terminal pins 6 to the holes. As shown in FIG. 4A, the temperature measuring element 40 of 1-1 was pressed by a coil spring 45 to form a wafer prober.

Comparative Example 1
A thermocouple similar to the test material 1-1, but heat-fused was prepared. The thickness of the joint was 0.8 mm.
Comparative Example 2
The thermocouple of the test material 1-1 was not fixed to the sheath but was fixed with an inorganic adhesive (Alon ceramic manufactured by Toa Gosei).

The difference between the maximum temperature and the minimum temperature of the disc-shaped ceramic plate having a diameter of 300 mm when the temperature was raised to 200 ° C. was examined for Examples 1 to 6 and Comparative Examples using a thermoviewer. Table 1 shows the results. The temperature was raised to 400 ° C., and after 1000 hours, the presence or absence of the drop of the thermocouple was examined. Further, after cooling to 4 ° C. to cause dew condensation, the temperature was raised again to 200 ° C., and the difference between the maximum temperature and the minimum temperature was examined for Examples 1 to 3 and Comparative Examples 1 and 2 using a thermoviewer.

  In the present invention, since the thermocouple is protected by the sheath, the thermocouple can be pressed and pressed against the ceramic plate, and it is not necessary to fix the temperature measuring element with an adhesive as in the related art. Therefore, the temperature measuring element does not fall off due to thermal deterioration. Further, since the thermocouple is housed in the sheath, the water resistance does not decrease.

It is a bottom view which shows typically the example comprised as a ceramic heater. (a) is a block diagram schematically showing an example when the present invention is configured as a ceramic heater. (A) is a schematic diagram of a thermocouple used in the present invention. (B) The temperature measuring element of the present invention. (A) (b) The mounting structure of the temperature measuring element of the present invention. It is a schematic diagram of the thermocouple of a prior art. It is a schematic diagram of the ceramic base material provided with an electrostatic chuck function. It is a schematic diagram of the ceramic base material provided with a wafer prober function.

Explanation of reference numerals

Reference Signs List 1 ceramic substrate 1a heating surface 1b bottom surface 2 heating element 3 bottomed hole 4 thermocouple 5 silicon wafer 6 terminal pin 7 support pin 8 through hole 9 metal coating layers 10, 23, 24 through hole 11 electrostatic electrode 12 guard electrode 13 ground Electrode 14 Chuck top electrode 15 Control unit 16 Storage unit 17 Operation unit 19 Groove 22 Air suction hole

Claims (7)

In a temperature measuring element configured to house a thermocouple formed by joining two different types of metal wires in a sheath, whether the size of the joining portion of each of the metal wires is the same as the wire diameter of each of the metal wires A temperature measuring element characterized by having a size of 0.5 mm or less, though larger. The temperature measuring element according to claim 1, wherein the sheath is made of metal or ceramic. The temperature measuring element according to claim 1, wherein the sheath is filled with an insulating material. A ceramic substrate for a semiconductor manufacturing apparatus, wherein a temperature control means is provided on the surface or inside of a ceramic plate, and a temperature measuring element is disposed on the ceramic plate, wherein the temperature measuring element is different in a sheath. Two types of metal wires are joined together and the size of the joint is equal to or larger than the wire diameter of each metal wire, but a thermocouple with a size of 0.5 mm or less is connected via an elastic body. A ceramic substrate for a semiconductor manufacturing apparatus, which is pressed against a ceramic plate. The ceramic substrate for a semiconductor manufacturing device according to claim 4, wherein the ceramic substrate for a semiconductor manufacturing device is provided with a ceramic heater function. 6. The ceramic substrate for a semiconductor manufacturing apparatus according to claim 4, wherein an electrostatic chuck function is provided by embedding an electrostatic electrode inside the ceramic plate. 5. A wafer prober function, wherein a guard electrode and a ground electrode are buried inside the ceramic plate, and a chuck top conductor layer is formed on a surface of the ceramic plate on which the semiconductor wafer is mounted. 7. The ceramic substrate for a semiconductor manufacturing apparatus according to any one of items 1 to 6.

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