JP2004119388A - Heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin and light heater whose temperature is easy to control. <P>SOLUTION: A recessed part for embedding therein a thermocouple is provided in a plate-shaped body made of a metal nitride ceramic or a metal carbide ceramic while a heating element formed by sintering metal particles is provided on a surface thereof. The heating element can contain not only the metal particles but a metal oxide, and its surface can be coated with a nickel layer, or the like. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a drying heater mainly used in the semiconductor industry, and more particularly to a thin and light heater which can be easily controlled in temperature.

Semiconductor products are manufactured by forming a photosensitive resin as an etching resist on a silicon wafer and etching the silicon wafer. The photosensitive resin is applied in a liquid state to the surface of the silicon wafer by a spin coater or the like. However, it must be dried after the application, and the applied silicon wafer is placed on a heater and heated. Conventionally, as such a heater, a heater in which a heating element is wired on the back surface of an aluminum plate is employed.

However, such a metallic heater has the following problems. First, since it is made of metal, the thickness of the heater plate must be as thick as about 15 mm. This is because, in a thin metal plate, warpage and distortion occur due to thermal expansion caused by heating, and the wafer placed on the metal plate is damaged or tilted. For this reason, the weight of the heater becomes large and bulky.

The heating temperature is controlled by changing the voltage and current applied to the heating element.However, the thickness of the metal plate causes the temperature of the heater plate to quickly follow changes in voltage and current. Therefore, there was a problem that it was difficult to control the temperature. An object of the present invention is to provide a thin and light heater that can be easily controlled in temperature.

The inventors have conducted extensive research and have found that when a nitride ceramic or a carbide ceramic having excellent thermal conductivity is used as a heater plate instead of metal, warpage and distortion do not occur even when the heater plate is thin, and the heating element is not heated. The fact that the temperature of the heater plate quickly follows the change of the voltage and the amount of current applied to the heater.

Furthermore, nitride ceramics and carbide ceramics have a property that they are difficult to adhere to a conductive paste containing metal particles, but by adding a metal oxide to the conductive paste, the metal particles are sintered to form a nitride ceramic or carbide ceramic. And the fact that the adhesiveness with the metal is improved.

The configuration of the present invention developed based on the above findings is as follows.
(1) A heating element formed by sintering metal particles is provided on a surface of a plate made of nitride ceramic or carbide ceramic, and a recess is formed in this plate. And heater.

(2) The heater according to (1), wherein the recess is used for embedding a thermocouple.
(3) The heater according to (1), wherein the heating element is formed by sintering metal particles and metal oxide.

In the present invention, the plate-like body (hereinafter, referred to as “heater plate”) needs to be made of a nitride ceramic or a carbide ceramic. Nitride ceramics or carbide ceramics have a lower coefficient of thermal expansion than metals and do not warp or distort when heated, even when thin. Therefore, such a heater plate can be made thin and light. In addition, since the heater plate has a high thermal conductivity and the thickness of the heater plate itself is thin, the surface temperature of the heater plate quickly follows a temperature change of the heating element. In other words, it has excellent characteristics of changing the temperature of the heating element by changing the voltage and the current amount, and can easily control the surface temperature of the heater plate.

The nitride ceramic is preferably a metal nitride ceramic, for example, any one or more selected from aluminum nitride, silicon nitride, boron nitride, and titanium nitride. The carbide ceramic is preferably a metal carbide ceramic, for example, at least one selected from silicon carbide, zirconium carbide, titanium carbide, tantalum carbide, and tungsten carbide. Of these ceramics, aluminum nitride is most preferred. This is because the thermal conductivity is the highest at 180 W / m · K. The heater plate preferably has a thickness of about 0.5 to 5 mm. If it is too thin, it will be easily broken.

In the present invention, it is necessary that the heating element is formed by sintering the metal particles in the conductive paste. This is because it can be baked on the ceramic plate surface by heating and firing. The sintering is sufficient if the metal particles are fused together, or the metal particles and the ceramic are fused. As shown in FIG. 1, the heating element 2 is preferably formed in a concentric pattern because the temperature of the entire heater plate 1 needs to be uniform. The thickness of the pattern of the heating element 2 is desirably 1 to 20 μm, and the width is desirably 0.5 to 5 mm. The resistance value can be changed depending on the thickness and width, but this range is most practical. The resistance value becomes thinner and thinner, and becomes larger.

The conductive paste generally contains a resin, a solvent, a thickener, and the like in addition to the metal particles. As the metal particles, at least one selected from gold, silver, platinum, palladium, lead, tungsten, and nickel is used. This is because these metals are relatively hard to oxidize and have a resistance value sufficient to generate heat. It is desirable that the metal particles have a particle size of 0.1 to 100 μm. If it is too fine, it is easily oxidized, and if it is too large, sintering becomes difficult, and the resistance value becomes large.

As a resin used for the conductive paste, an epoxy resin, a phenol resin, or the like is preferable. In addition, isopropyl alcohol or the like is used as the solvent. Examples of the thickener include cellulose and the like.

Preferably, the conductive paste contains a metal oxide in addition to the metal particles, and the heating element is formed by sintering the metal particles and the metal oxide. The reason for this is to make the nitride ceramic or carbide ceramic adhere to the metal particles. The reason why the metal oxide improves the adhesion between the nitride ceramic or the carbide ceramic and the metal particles is not clear, but a slight oxide film is formed on the surface of the metal particles and the surface of the nitride ceramic or the carbide ceramic. It is presumed that the oxide films are sintered and integrated via the metal oxide, and the metal particles and the nitride ceramic or the carbide ceramic adhere to each other.

The metal oxide is preferably at least one selected from the group consisting of lead oxide, zinc oxide, silica, boron oxide (B ₂ O ₃ ), alumina, yttria, and titania. 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.

In the present invention, it is preferable that the surface of the heating element is covered with a metal layer. The reason for this is that the heating element is a sintered body of metal particles, and when exposed, is easily oxidized and the resistance value changes. Therefore, the surface of the heating element is covered with a metal layer to prevent oxidation. The thickness of the metal layer is desirably 0.1 to 10 μm. This is because the oxidation of the heating element can be prevented without changing the resistance value of the heating element.

The metal used for coating may be a non-oxidizing metal. Specifically, at least one selected from gold, silver, palladium, platinum, and nickel is preferable. Of these, nickel is preferred. The heating element requires a terminal for connection to a power supply, and this terminal is attached to the heating element via solder. Nickel prevents thermal diffusion of the solder. As the connection terminal, a terminal pin made of Kovar can be used.

Further, as the solder, an alloy such as silver-lead, lead-tin, bismuth-tin or the like can be used. Note that the thickness of the solder layer is desirably 0.1 to 50 μm. This is because the range is sufficient to secure the connection by soldering. In the present invention, a recess is provided in the heater plate to embed a thermocouple. This is because the temperature of the heater plate can be controlled by measuring the temperature of the heater plate with a thermocouple and changing the voltage and current based on the data.

Further, as shown in FIG. 2, a plurality of through holes 8 are provided in the heater plate 1 and support pins are inserted into the through holes 8 so that the support pins 7 on the side opposite to the side on which the heating element 2 is provided. A semiconductor wafer 9 can be mounted thereon. Further, the semiconductor wafer 9 can be received by moving the support pins 7 up and down.

Next, a method for manufacturing the heater will be described.
(1) Step of sintering powder of nitride ceramic or carbide ceramic to form a plate (heater plate) made of nitride ceramic or carbide ceramic: nitride ceramic such as aluminum nitride or silicon carbide described above Powder of carbide ceramic, sintering aid such as yttria, binder if necessary, granulate by spray drying etc., press this granule into a mold etc., press and form into plate shape Manufacture features.

The formed body is provided with a recess for embedding a thermocouple and a through hole for inserting a support pin of a semiconductor wafer. Next, the formed body is fired and sintered to produce a ceramic plate. During heating and firing, a heater plate without pores can be manufactured by applying pressure. The heating and sintering may be performed at a sintering temperature or higher, but is performed at 1000 to 2500 ° C. for a nitride ceramic or a carbide ceramic.

(2) A step of printing a conductive paste made of metal particles on a ceramic plate (heater plate) in step (1): The conductive paste is generally a high-viscosity fluid composed of metal particles, a resin, and a solvent. is there. This conductive paste is printed on a portion where a heating element is to be provided by screen printing or the like. Since the heating element needs to have a uniform temperature over the entire heating plate, it is desirable to print the heating element in a concentric pattern as shown in FIG.

(3) Heating and sintering the conductive paste to provide a heating element on the surface of a ceramic plate (heater plate): heating and sintering the conductive paste to remove the resin and the solvent and remove the metal Sinter the particles. The heating and firing temperature is 500 to 1000C. If a metal oxide is added to the conductive paste, the metal particles, the ceramic plate and the metal oxide are sintered and integrated, so that the adhesion between the heating element and the ceramic plate is reduced. Is improved.

(4) Further, it is desirable to cover the surface of the heating element with a metal layer. The coating can be performed by electrolytic plating, electroless plating, or sputtering, but in consideration of mass productivity, electroless plating is optimal.
(5) Attach the terminal for connection with the power supply to the end of the pattern of the heating element by soldering.

After the solder paste is printed on the mounting portion, the terminal is placed, and heated to reflow. The heating temperature is preferably from 200 to 500C. Then, a thermocouple is embedded in the concave portion provided in the formed body. Hereinafter, description will be given along an example.

As described above, the heater according to the present invention can be thin and light, and is practical. In addition, since a nitride ceramic or a carbide ceramic is used as the plate-like body and is thin, it has excellent temperature followability to changes in voltage and current amount, and a recess is provided to embed a thermocouple. There is an effect that the temperature can be easily controlled.

Hereinafter, Examples 1 and 2 and Comparative Examples embodying the present invention will be described.
(Example 1)
Aluminum nitride ceramic plate (1) A composition comprising 100 parts by weight of aluminum nitride powder (average particle size: 1.1 μm), 4 parts by weight of yttria (yttrium oxide, average particle size: 0.4 μm), 12 parts by weight of acrylic binder, and alcohol Was granulated by a spray drier method.
(2) The granular powder was placed in a mold and molded into a flat plate to obtain a formed product. Drilling was performed on the formed body to provide a through hole 8 for inserting a semiconductor wafer support pin, and a concave portion (not shown) for embedding a thermocouple.
(3) The green compact was hot-pressed at 1800 ° C. and a pressure of 230 kg / mm ² 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 (heater plate) 1.

(4) A conductive paste was printed on the heater plate 1 obtained in (3) by screen printing. The printing pattern was a concentric pattern as shown in FIG. As the conductive paste, Solvest PS603 manufactured by Tokuri Chemical Laboratory was used. This conductive paste is a silver / lead paste and contains a metal oxide.
(5) The heater plate on which the conductive paste was printed was heated and fired at 780 ° C. to sinter silver and lead in the conductive paste and to bake the heater plate 1. The pattern of the silver-lead sintered body 4 had a thickness of 5 μm and a width of 2.4 mm.

(6) An electroless nickel plating bath composed of an aqueous solution having a concentration of 80 g / l nickel sulfate, 24 g / l sodium hypophosphite, 12 g / l sodium acetate, 8 g / l boric acid, and 6 g / l ammonium chloride, ) Was immersed to deposit a nickel layer 5 having a thickness of 1 μm on the surface of the silver-lead sintered body 4 to obtain a heating element 2.

(7) A silver-lead solder paste was printed by screen printing 1 on a portion where a terminal for securing connection to a power supply was to be attached, to form a solder layer (made of Tanaka precious metal) 6. Next, the terminal pins 3 made of Kovar were placed on the solder layer 6, and heated and reflowed at 420 ° C. to attach the terminal pins 3 to the surface of the heating element 2.
(8) A thermocouple (not shown) for temperature control was embedded in the concave portion to obtain a heater 100.

(Example 2)
Silicon Carbide Ceramic Plate Basically the same as in Example 1, except that silicon carbide powder having an average particle size of 1.0 μm was used and the sintering temperature was 1900 ° C.

With respect to the heaters of Examples 1 and 2, the followability of temperature to changes in voltage and current and the pull strength of the heating element were measured. When a voltage was applied to the heater, the heater of Example 1 exhibited a temperature change in 0.5 seconds, and the heater of Example 2 exhibited a temperature change in 2 seconds. Regarding the pull strength of the heating element 2, the heater of Example 1 was 3.1 kg / mm ² , and the heater of Example 2 was 3 kg / mm ² .

(Comparative example)
Using a nichrome wire sandwiched between silicon rubbers as an aluminum plate heating element, an aluminum plate having a thickness of 15 mm and a contact plate were sandwiched between the heating elements, and fixed with bolts to obtain a heater. When a voltage was applied to the heater of the comparative example, it took 24 seconds until a temperature change was observed.

It is a schematic diagram of the heater of the present invention. It is sectional drawing showing the use condition of the heater of this invention.

Explanation of reference numerals

1. Ceramic plate (heater plate)
2 Heating element 3 Terminal pin 4 Metal (silver-lead) particle sintered body 5 Metal (nickel) coating layer 6 Solder layer 7 Semiconductor wafer support pin 8 Through hole 9 Semiconductor product 100 Heater

Claims (5)

 A heater characterized in that a heating element formed by sintering metal particles is provided on a surface of a plate made of a nitride ceramic or a carbide ceramic, and a recess is formed in the plate. .  The heater according to claim 1, wherein the recess is used to embed a thermocouple. The heater according to claim 1, wherein the heating element is formed by sintering a metal particle and a metal oxide.  The heater according to claim 3, wherein the metal oxide is at least one selected from the group consisting of lead oxide, zinc oxide, silica, boron oxide, alumina, yttria, and titania. The heater according to any one of claims 1 to 4, wherein the heater is used as a semiconductor wafer heater.

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