KR100447888B1 - Ceramic heater - Google Patents

Abstract

It is an object of the present invention to provide a thin and light ceramic heater that is easy to control temperature, and a conductive paste for forming a heating element for use in the heater, and includes metal particles on the surface or inside of a ceramic substrate made of nitride ceramics or carbide ceramics. And a heating element formed by sintering the metal oxides to be mixed together.

In addition, such a conductive paste uses a paste formed by mixing metal particles and metal oxides.

Description

Ceramic Heater {CERAMIC HEATER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to drying ceramic heaters used in the semiconductor industry, and more particularly, to a thin and light ceramic heater that is easy to control temperature and a conductive paste used to form a heating element of the heater.

Typical semiconductor products are manufactured by, for example, applying an etching resist (photosensitive resin) onto a silicon wafer and then etching. In this case, the photosensitive resin applied to the surface of the silicon wafer must be dried after application. In the drying method, the silicon wafer coated with the resin is generally placed on a heater and heated.

Such a heater is typically attached to a heating element on the back surface of a conventional aluminum substrate. However, such a metal heater had the following problem.

That is, since the board | substrate which is a heater main body is made of metal, the thickness must be made thick about 15 mm. This is because, in the thin metal plate, warpage and distortion occur due to thermal expansion due to heating, and the wafer placed on the metal plate is broken or tilted. Therefore, the conventional metal heater has a problem that the weight is large and the volume is large.

The heating of the silicon wafer by the heater is performed by controlling the substrate temperature by adjusting the voltage or current applied to the heating element. However, this method has a problem that since the metal plate is thick, the heater substrate temperature does not quickly follow the change of the voltage or the current, and the temperature control characteristic is bad.

The main object of the present invention is to provide a thin and light heater with easy temperature control.

Another object of the present invention is to provide a conductive paste for a heating element having excellent heat generation characteristics.

1 is a plan view of a ceramic heater of the present invention,

2 is a cross-sectional view showing a usage form of the ceramic heater of the present invention;

3 is an explanatory diagram of a method of manufacturing a ceramic heater of the present invention;

4 is an explanatory diagram showing a state in which a terminal pin is connected to a through hole;

5 is an explanatory diagram showing another example of manufacture of the ceramic heater of the present invention;

6 is an explanatory diagram showing still another example of manufacture of the ceramic heater of the present invention;

Disclosure of the Invention

As a result of studying the above-mentioned problems of the prior art, the inventors have focused on using ceramics having excellent thermal conductivity, in particular, nitride ceramics or carbide ceramics, instead of metals such as aluminum as heater substrates. It has been found that such ceramic substrates do not cause warping or distortion even if they are thin, and are quick and easy in temperature control, and particularly excellent in responsiveness when temperature is controlled by changing the voltage or current applied to the heating element.

In addition, the inventors found that a conductive paste containing metal particles generally has a property of being hard to adhere to nitride ceramics or carbide ceramics. However, the addition of a metal oxide to the conductive paste improves the adhesion through the sintering of the metal particles. Found.

The gist structure of the present invention developed under such knowledge is as follows.

1. A ceramic heater in which a heating element is formed on a surface of a ceramic substrate made of nitride ceramics or carbide ceramics, a surface opposite to the heating element forming surface is a heating surface, and a through hole is formed in the ceramic substrate.

2. A ceramic heater in which a heating element is formed on a surface of a ceramic substrate made of nitride ceramics or carbide ceramics, the surface opposite to the heating element forming surface is a heating surface, and the ceramic substrate has a recess.

3. The heating element is formed on the surface of the ceramic substrate which consists of nitride ceramics or carbide ceramics, The surface on the opposite side to this heating element formation surface is made into the heating surface, and the said heating element is characterized by the ceramic heater which consists of a noble metal.

Best Mode for Carrying Out the Invention

The ceramic heater according to the present invention uses a ceramic substrate made of an insulating nitride ceramic or a carbide ceramic, and forms a heating element on one surface of the ceramic substrate, and heats a semiconductor product such as a silicon wafer on the other surface. It is.

In the ceramic heater of the present invention, the heating elements having a flat cross-sectional shape may be arranged (closed) in the ceramic substrate. In this case, the heating elements are arranged so as to be eccentrically arranged in the substrate thickness direction from the center. In addition, the surface far from the heating element may be used as the heating surface.

The nitride ceramics or carbide ceramics constituting the substrate have a feature that the coefficient of thermal expansion is smaller than that of metal, and even if thin, the ceramics are not bent or distorted by heating. For this reason, a heater board | substrate can be made thin and light.

In addition, since such a ceramic substrate has a high thermal conductivity and a thinness, the surface temperature of the ceramic substrate rapidly follows the heating element temperature change. That is, when the temperature of the heating element is changed by changing the voltage and current, the surface temperature of the ceramic substrate is also rapidly harvested and fluctuates.

In addition, the ceramic heater of the present invention has a heating surface on the side opposite to the heating element arranging side or a heating surface far from the flat heating element arranged to be eccentric in the thickness direction from the center of the substrate, so that the heat propagation is applied to the entire substrate. Since it spreads uniformly and rapidly, generation of the temperature distribution limited to the heating element pattern on the heating surface can be suppressed, and the heating temperature distribution can be made uniform.

In this regard, for example, U.S. Patent No. 563483 discloses a technique in which one surface of a quartz substrate is roughened, a heating element is provided with a platinum-palladium paste, and the wafer is placed on the opposite side of the heating element and heated. It is. In addition, US Patent No. 5668524 discloses a ceramic heater with a chuck in which a heater is embedded. In addition, US Patent No. 5566043 discloses heaters each provided with a pyrolytic graphite heating element on the surface of a boron nitride substrate.

However, in the specification of US Pat. No. 5,437,383, a heating element is used by using a quartz substrate and a platinum-palladium paste, and since the oxides are not mixed as in the present invention, the heating element cannot be formed unless it is harmonized.

In addition, the specification of U.S. Patent No. 5668524 does not disclose a specific shape such as an aspect ratio without causing the heating element to be eccentric. For this reason, the temperature uniformity of a heating surface is inferior.

In addition, since US Patent No. 5566043 uses a pyrolytic graphite heating element, heating to 500 ° C. or higher in air causes the heating element to disappear, thereby limiting the use temperature range.

As such, these techniques are completely different from the present invention.

The ceramic substrate may have a thickness of about 0.5 to 5 mm. The reason is that if it is too thin, it is easily broken.

The nitride ceramic which is a material of such a ceramic substrate is preferably a metal nitride ceramic, for example, any one or more selected from aluminum nitride, silicon nitride, boron nitride, titanium nitride and the like. On the other hand, as the carbide ceramics, it is preferable to use any one or more selected from metal carbide ceramics, for example, silicon carbide, corn carbide, titanium carbide, tantalum carbide, tungsten carbide and the like. However, aluminum nitride is suitable among these ceramics. This is because the thermal conductivity of aluminum nitride is the highest at 180 W / m · K.

The heat generators arranged on such ceramic substrates are formed by sintering metal particles or metal oxide particles in the conductive paste. This is because each of the particles can be baked on the surface of the ceramic substrate by heating and firing. The sintering treatment is such that the metal particles or the metal particles and the ceramic are fused together.

Next, since the heat generating element 2 needs to uniformly heat up the whole temperature of the ceramic substrate 1 as shown in FIG. 1, the pattern arrange | positioned concentrically is preferable. Although the thickness of the heat generating body 2 pattern-formed is about 1-50 micrometers, when forming the heat generating body 2 in the surface of the board | substrate 1, 1-10 micrometers is preferable. On the other hand, when forming the heat generating body 2 in the inside of the board | substrate 1, it is preferable to set it as 1-50 micrometers in thickness.

The width of the heating element is preferably about 0.1 to 20 mm. However, when the heating element 2 is formed on the surface of the substrate 1, the heating element 2 is 0.1 to 5 mm. It is preferable to set it as about -20 mm. The reason for limiting these ranges is that, in general, the resistance value can be changed by changing the thickness and width of the heating element 2, but the above range is most effective for temperature control of the heating element. In addition, the resistance value of the heat generating element 2 increases as it becomes thin and thin.

In addition, this heating element 2 can be made larger both in thickness and width when formed in the substrate 1. The reason is that when the heating element 2 is installed inside, the distance between the heating surface and the heating element is shortened and the temperature uniformity of the heating surface of the ceramic substrate 1 is lowered. Therefore, the heating element 2 itself is used to uniformly heat the heating surface. There is a need to widen. On the other hand, when the heating element is provided inside, there is no need to consider the adhesiveness with the nitride ceramics of the substrate, so that a high melting point metal such as tungsten or molybdenum, carbides such as tungsten or molybdenum can be used, and further, the resistance value can be increased. Become. As a result, the thickness of the heating element can be increased for the purpose of preventing disconnection or the like.

The heating element is generally rectangular or oval in cross section, preferably in a flat shape. In particular, when the heating element is provided inside the ceramic substrate 1, it is essential to be flat. The reason is that since the flat shape of the cross section is easy to heat toward the heating surface, the temperature distribution on the heating surface is difficult.

As for the aspect ratio (width of the heat generating body / thickness of a heat generating body) of such a heating body 2 cross section, about 10-10000 are preferable, and 50-5000 are preferable. This is because if the adjustment is within this range, the resistance value of the heating element 2 can be increased and the uniformity of the temperature distribution of the heating surface can be ensured.

When the thickness of the heating element 2 pattern arranged on the surface or inside of the ceramic substrate 1 is constant, if the aspect ratio is small, the amount of heat transfer in the direction of the heating surface of the substrate is reduced, and the heating surface is the same as the heating element pattern. It becomes heat distribution. On the contrary, if the aspect ratio is too large, the upper portion of the center of the heating element pattern becomes a high temperature, and as a result, a heat distribution like the heating element pattern is formed on the heating surface. In consideration of such temperature distribution, it is preferable that the aspect ratio (width of the heating element / thickness of the heating element) of the cross section of the heating element 2 is in the range of 10 to 10,000.

This is because cracks and peeling due to thermal shock are less likely to occur by setting the aspect ratio of the heating element 2 to 50 to 5000.

In addition, when the heating element 2 is formed inside the ceramic substrate 1, the aspect ratio can be increased, but when the heating element 2 is installed inside, the distance between the heating surface and the heating element is shortened. Since temperature uniformity falls, it is necessary to make heating element itself into flat shape.

In the present invention, when the heating element 2 is arranged inside the ceramic substrate 1, the heating element 2 can be arranged in an eccentric arrangement of the heating element in the thickness direction, but the degree of eccentricity is 50 on one side (heating surface) of the substrate. It is preferable to set it as the position to% or more and less than 100%. This is because the temperature distribution of the heating surface can be prevented and the warping of the ceramic substrate can be suppressed. Preferably it is 55 to 95%.

When the heat generating element 2 is formed inside the ceramic substrate 1, the heat generating element formation layer may be divided into a plurality of layers. In this case, it is preferable that the patterns of the respective layers are formed so as to complement each other, and in view of the heating side, a complete pattern is formed in any one layer. For example, the structure is arranged in a zigzag pattern on the upper and lower layers so that the whole becomes a complete pattern.

In the case where the heating element 2 is arranged on the surface of the ceramic substrate 1, it is preferable that the heating element 2 is arranged in a state where a part (bottom) of the heating element is embedded in the ceramic substrate. This is because by arranging the heating elements in this manner, it is possible to realize the improvement of the suppression of the resistance of the heating element and the improvement of the adhesion with the ceramic substrate.

Next, a conductive paste used to form the heating element on a ceramic substrate will be described. It is common for this electrically conductive paste to mix resin, a solvent, a thickener, etc. other than the metal particle or electroconductive ceramic to ensure electroconductivity.

As the metal particles, any one or more selected from noble metals (gold, silver, platinum, palladium), lead, tungsten, molybdenum and nickel are used. This is because these metals are relatively hard to oxidize and exhibit sufficient resistance to heat generation. In the conductive ceramic, any one or more selected from tungsten, molybdenum carbide and the like is used.

These metal particles or conductive ceramics preferably have a particle size of 0.1 to 100 mu m. If it is too fine, it is easy to oxidize, while if too large, it is difficult to sinter and the resistance value becomes large.

The metal particles may be spherical, scaly, or a mixture of spherical and scaly. In particular, when the shape is in the shape of scales, it is easy to hold the metal oxide described later between the metal particles, and the adhesion between the heating element and the nitride ceramics and the like is improved.

In addition, epoxy resin, phenol resin, etc. are suitable for resin used for such an electrically conductive paste. Isopropyl alcohol etc. are used as a solvent. As the thickener, cellulose or the like is used.

In addition to the metal particles, the conductive paste may further contain a metal oxide so that the heating element is a mixture sintered body of the metal particles and the metal oxide. That is, when the metal oxide is interposed between the nitride ceramic or carbide ceramic and the metal particles, these adhesion properties can be improved. The reason why the adhesion is improved is not clear, but the metal particle surface and the nitride ceramic or carbide ceramic surface have a slight oxide film but the oxide film shows an affinity for the metal oxide and is easily integrated. Or it is estimated whether carbide ceramics are in close contact with the oxide.

Such metal oxide uses any one or more selected from lead oxide, zinc oxide, silicon oxide, boron oxide, aluminum oxide, yttrium oxide and titanium oxide. This is because these oxides can improve the adhesion between metal particles and nitride ceramics or carbide ceramics without increasing the resistance of the heating element.

The amount of the metal oxide added is preferably less than 0.1 to 10 Wt% based on the metal particles. The reason is that less than 0.1 Wt% does not have an additive effect, while if it is 10 Wt% or more, the resistance of the heating element 2 is too large.

The mixing ratio of these metal oxides is 1 to 10 Wt% of lead oxide, 1 to 30 Wt% of silicon oxide, 5 to 50 Wt% of boron oxide, and 20 to 70 Wt% of zinc oxide when the total amount of metal oxide is 100 Wt%. It is preferable to adjust so that the sum may not exceed 100 Wt% in the range of 1-10 Wt% of aluminum oxide, 1-50 Wt% of yttrium oxide, and 1-50 Wt% of titanium oxide. These ranges are particularly effective for improving the adhesion between metal particles and nitride ceramics.

In this way, when the amount of the metal oxide added is adjusted to less than 0.1 to 10 Wt% with respect to the metal particles, the area resistivity of the heating element can be 1 to 45 mPa / □. If the area resistivity is too large, the heat generation amount is too large with respect to the applied voltage, making it difficult to control the case in which the heating elements are arranged on the ceramic substrate surface. In addition, when the amount of metal oxide is 10 Wt% or more, the area resistivity exceeds 50 mPa / ?, and the amount of heat generated is so large that temperature control is difficult and the uniformity of the heater temperature distribution is reduced.

In addition, it has been conventionally considered that it is not suitable as a resistor for a heater unless the area resistivity is not more than 50 mPa / □ (Japanese Patent Application Laid-Open No. 4-300249). It is to ensure uniformity of distribution.

In another embodiment of the present invention, the heating element surface is preferably covered with a metal layer. As described above, since the heating element is a sintered body of metal particles, when it is exposed to air, the heating element is easily oxidized and the resistance value changes. Therefore, oxidation is prevented by covering the surface of the metal particle sintered body with a metal layer. As for the thickness of this metal layer, about 0.1-10 micrometers is preferable. This is because the heating element oxidation is prevented without changing the heating element resistance.

The metal coated on the surface of the metal particle sintered body may be a non-oxidizing metal. For example, any one or more selected from gold, silver, palladium, platinum and nickel may be used. Among them, nickel is suitable. The reason is that a heating element generally requires a terminal for connecting to a power source, and this terminal is attached to the heating element through solder, but so-called nickel has a function of preventing thermal diffusion of the solder. The connecting terminal can use a covar terminal pin.

However, when the heating elements are arranged inside the ceramic substrate, the surface of the heating elements is not oxidized, so coating is unnecessary.

The solder may be a solder alloy such as silver-lead, lead-tin, bismuth-tin, etc., and the thickness of the solder layer is in the range of 0.1 to 50 µm, which is sufficient to secure the connection by soldering.

According to the present invention, the thermocouple 61 may be embedded in the ceramic substrate 1 as shown in FIG. 5D. The thermocouple 61 makes it possible to measure the temperature of the ceramic substrate 1, to adjust the voltage and current based on the data, and to easily and accurately control the heating surface temperature of the ceramic substrate 1.

2 is a partial cross-sectional view showing a state of use of the ceramic heater of the present invention. 3 is a terminal pin, 4 is a metal (Ag-Pb) particle | grain sintered compact, 5 is a metal (Ni) coating layer, and these 4 and 5 comprise the heat generating body 2. As shown in FIG. 6 is a solder layer, through which the terminal pin 3 is attached.

In the ceramic substrate 1, a plurality of through holes 8 are provided, the support holes 7 of the semiconductor wafer are inserted into the through holes 8, and the pins protruding on the ceramic substrate 1 7) The semiconductor wafer 9 is attached to the government through an adjacent or slight gap. In this case, the support pins 7 are raised and lowered when passing the semiconductor wafer 9 to a carrier (not shown) or receiving the semiconductor wafer 9 from the carrier.

Next, the manufacturing method of the ceramic heater concerning this invention is demonstrated.

A. When a heating element is formed on the surface of the ceramic substrate (Fig. 2)

(1) A step of sintering insulating nitride ceramics or insulating carbide ceramic powder to form a plate body (ceramic substrate) made of nitride ceramics or carbide ceramics.

This step is obtained by granulating a nitride ceramic such as aluminum nitride or a carbide ceramic powder such as silicon carbide, or a mixed powder comprising a sintering aid or binder such as yttria as necessary by a method such as spray drying. The granules are formed into plates by pressing the granules in a mold or the like to press them.

If necessary, the product is provided with a through hole 8 for inserting the support pin 7 of the semiconductor wafer and a recess 62 for embedding the thermocouple 61.

Next, the resulting molded body is heated and fired to sinter, thereby producing a ceramic plate-like body. The ceramic substrate for heaters without pores is manufactured by pressurizing at the time of heating. Heat firing should be above the sintering temperature, but suitable for nitride ceramic or carbide ceramic is 1000 ~ 2500 ℃.

(2) A step of forming a metal particle layer (4) by printing a conductive paste containing metal particles on the surface of a ceramic plate (heater plate, that is, a ceramic substrate) obtained in the step (1).

This process prints the electrically conductive paste which has the high fluidity | liquidity which consists of metal particle, resin, and a solvent in predetermined position by methods, such as screen printing. The reason why the conductive paste is applied by printing to form the metal particle layer 4 is to accurately form a concentric pattern as shown in FIG. 1 in order to form the heating element 2 for heating the entire ceramic substrate to a uniform temperature. It is because it is preferable.

In addition, it is preferable that the cross-sectional shape of the heat generating element is a flat cross-sectional shape based on the quadrangle.

(3) A step of forming the heating element 2 on the surface of the ceramic substrate 1 by heating and sintering the metal particle layer formed by printing on the ceramic substrate.

The metal particle layer formed by printing the conductive paste is heated and fired to remove the resin and the solvent, and at the same time, the metal particles are sintered (heating firing temperature is 500 to 1000 ° C). In this regard, for example, when a metal oxide is added to the conductive paste, the metal particles, the plate-shaped body made of ceramic, and the metal oxide are sintered and integrated, so that the adhesion between the heating element and the plate-shaped body made of ceramic is improved.

(4) Moreover, the metal coating layer 5 may be formed on the surface of the said metal particle layer 4 as needed. This treatment can be carried out by electroplating, electroless plating or sputtering, but considering mass production, electroless plating is optimal.

(5) The terminal pins 3 for connection with the power supply are attached to the end of the pattern of the heating element 2 thus obtained by soldering.

B. Installing a heating element inside the ceramic substrate (Fig. 3)

(1) The green sheet 31 is obtained by mixing ceramic powders such as nitride ceramics and carbide ceramics with a binder and a solvent.

As the ceramic powder, aluminum nitride, silicon carbide, or the like may be used, and if necessary, a sintering aid such as yttrium oxide (yttria) may be added. In addition, the binder is preferably at least one selected from an acrylic binder, ethyl cellulose, butyl cellosolve, and polyvinylral. As the solvent, it is preferable to use any one or more selected from α-terpineol and glycol.

The paste obtained by mixing them is molded into a sheet by the doctor blader method to manufacture the green sheet 31. The obtained green sheet can be provided with recesses 62 for embedding the through holes 8 for inserting the support pins 7 of the silicon wafer and the thermocouple 61 as necessary. The through holes 8 and the recesses 62 are formed by punching or the like.

The thickness of the green sheet is preferably about 0.1 to 5 mm.

(2) Next, a metal particle layer to be a heating element is printed on the green sheet.

The metal particle layer 4 which becomes a heat generating body is formed by printing the electrically conductive paste using metal paste or electroconductive ceramic.

These pastes contain metal particles or conductive ceramic particles. Tungsten or molybdenum is preferable for such metal particles, and tungsten or molybdenum carbide is most suitable for the conductive ceramic particles. It is because it is difficult to oxidize and there is little thermal conductivity fall.

The average particle diameter of the tungsten particles or molybdenum particles is preferably 0.1 to 5 mu m. If too large or too small, conductive paste printing becomes difficult. Such conductive paste is composed of 85 to 97 parts by weight of metal particles or conductive ceramic particles, 1.5 to 10 parts by weight of at least one binder selected from acryl, ethyl cellulose, butyl cellosolve, and polyvinylral, α-terpineol, and glycol. Tungsten paste or molybdenum paste prepared by mixing 1.5 to 10 parts by weight of at least one selected solvent is optimal.

(3) Next, the green sheet 31 which printed the heat generating body 2 of (2), and one or more other green sheet 31 obtained by the method similar to (1) process are laminated | stacked.

In the illustrated example, 37 sheets are laminated and bonded on the upper surface of the metal particle layer 4 (the heating surface side) and 17 sheets on the opposite side thereof. That is, in the case of lamination, the number of the green sheets of (1) laminated on the upper side (heating surface side) of the heating element printed green sheet of (2) is larger than the number of green sheets laminated on the lower side, and the position of forming the heating elements 2 in the thickness direction. To be eccentric. Preferably, the number of green sheets of the same thickness is laminated so that the ratio between the upper side and the lower side is 1/1 to 1/99. Specifically, 20 to 50 sheets are stacked on the upper side and 5 to 20 sheets are stacked on the lower side.

(4) Heat and press to sinter the green sheet and the conductive paste. Heating temperature is 1000-2000 degreeC, and pressurization is 100-200 kg / cm <^2> in inert gas atmosphere. Argon, nitrogen, etc. can be used as an inert gas.

Finally, after solder paste is printed on the terminal pin 3 attachment portion, the terminal pin 3 is placed, heated, and reflowed to fix it. The heating temperature for reflow of the solder paste is suitably 200 to 500 ° C. In addition, thermocouples can be embedded as needed.

Example

Example 1 A heater made of an aluminum nitride ceramic substrate

(1) The mixed composition which consists of 100 weight part of aluminum nitride powders (average particle diameter 1.1 micrometers), 4 weight parts yttria (average particle diameter 0.4 micrometers), 12 weight part of acrylic binders, and alcohol was used as the granular powder by the spray dryer method.

(2) The granular powder was put in a mold and molded into a flat plate to obtain a product shaped body. Through-holes 8 for inserting the semiconductor wafer support pins were drilled to form the formed bodies, and recesses (not shown) for embedding the thermocouple were provided.

(3) The resulting molded product was hot pressed at 1800 ° C. and a pressure of 200 kg / cm ² to obtain an aluminum nitride plate-like body having a thickness of 3 mm. This was cut out into a circular shape having a diameter of 210 mm to obtain a ceramic plate-like body (ceramic substrate; 1).

(4) A conductive paste was printed on the ceramic substrate 1 obtained in the above (3) by screen printing. The printing pattern was a pattern of concentric circles as shown in FIG. As the conductive paste, Solvest PS603D manufactured by Tokuriki Chemical Research Institute, which was used for through hole formation of the printed wiring board, was used. This conductive paste is a silver / lead paste, which is a metal oxide (a weight ratio of 5/55/10/25/10) composed of a mixture of lead oxide, zinc oxide, silica, boron oxide and alumina, 7.5 Wt with respect to the amount of silver. It is to contain%. In addition, silver was used in the form of scales with an average particle diameter of 4.5 m.

(5) The ceramic substrate 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 be baked on the ceramic substrate 1. The pattern by the silver-lead sintered compact 4 was 5 micrometers in thickness, 2.4 mm in width, and area resistivity was 7.7 mPa / square.

(6) The ceramic substrate of (5) in an electroless nickel plating bath consisting 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. (1) was immersed, and the 1-micrometer-thick nickel metal layer 5 was deposited on the surface of the sintered compact 4 of silver-lead, and the heat generating body 2 was formed.

(7) A silver-lead solder paste was printed in screen printing 1 on a portion to which a terminal for securing a connection with a power source was attached to form a solder layer (manufactured by Tanaka Precious Metals; 6). Subsequently, a covar terminal pin 3 was placed on the solder layer 6 and heated and reflowed at 420 ° C., and the terminal pin 3 was attached to the surface of the heating element 2.

(8) A thermocouple (not shown) for temperature control was embedded to obtain a heater 100 (FIGS. 1 and 2).

(Example 2) Silicon carbide ceramic substrate heater

A SiO ₂ layer having a thickness of 1 μm on the surface by basically following the same process as in Example 1 but using silicon carbide powder having an average particle diameter of 1.0 μm, sintering temperature of 1900 ° C., and sintering at 1500 ° C. for 2 hours. Formed.

(Example 3)

The heaters of Examples 1 and 2 were measured for the temperature followability of the heating surface of the ceramic substrate and the pull strength of the heating element 2 with respect to the change in voltage and current. That is, when a voltage was applied to each heater, the temperature change was observed in the heater of Example 1 at 0.5 seconds, and the temperature change was observed in the heater of Example 2 at 2 seconds. On the other hand, about the full strength of the heat generating body 2, the heater of Example 1 was 3.1 kg / mm <^2> , and the heater of Example 2 was 3 kg / mm <^2> .

(Example 4) A heater having a heating element formed therein (FIGS. 3 and 5)

(1) 100 parts by weight of aluminum nitride powder (manufactured by Tokuyama, average particle diameter: 1.1 μm), 4 parts by weight of yttria (average particle size: 0.4 μm), 11.5 parts by weight of an acrylic binder, 0.5 parts by weight of a dispersant, and 1-butanol and ethanol A mixed composition obtained by mixing 53% by weight of alcohol was formed with a doctor bladder to obtain a green sheet (31) having a thickness of 0.47 mm.

(2) After drying the green sheet 31 at 80 ° C. for 5 hours, punching through holes for inserting semiconductor wafer support pins of 1.8 mm, 3.0 mm, and 5.0 mm in diameter and through-holes for connecting the heating element and the terminal pins by punching. (38) was installed.

(3) 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, and 3.5 parts by weight of an α-terpineol solvent and 0.3 parts by weight of a dispersant were mixed to obtain an electrically conductive paste A.

Further, 100 parts by weight of tungsten particles having an average particle diameter of 3 µm, 1.9 parts by weight of the acrylic binder, and 3.7 parts by weight of the α-terpione solvent and 0.2 parts by weight of the dispersant were mixed to obtain a conductive paste B.

The conductive paste A was depicted and printed on the green sheet 31 by screen printing. The printing pattern was concentric circles as shown in FIG. In addition, the conductive paste B was filled in the through hole through hole 38 for connecting with the terminal pin.

Further, 37 sheets of the green sheet 31 on which the conductive paste A was not printed were stacked on the upper side (heating surface) and 17 on the lower side, and were integrated at 130 ° C. and 80 kg / cm ² to form a laminate (FIG. 3).

(4) The laminate was degreased at 600 ° C. for 5 hours in nitrogen gas, hot pressed at 1890 ° C. and 150 kg / cm ² for 3 hours to obtain an aluminum nitride plate-like body having a thickness of 3 mm. This was cut into a circular shape having a diameter of 230 mm to obtain a ceramic substrate 51 having a heating element having a thickness of 6 μm and a width of 10 mm (Fig. 5A).

(5) After polishing the ceramic substrate 51 obtained in (4) with a diamond grindstone, the mask was placed and a thermocouple receiving hole 62 was formed by blasting with glass beads (FIG. 5D).

(6) Moreover, a part of the surface of the through-hole hole 58 is scraped off, and the recessed part 48 as shown in FIG. 4 is formed, and this lead part is supplied with the gold solder which becomes Ni-Au alloy, and is then 700 degreeC. It heated by reflow, and the terminal pin 60 made from a kovar was connected (FIG. 5C).

In addition, it is preferable to make the connection of the terminal pin 60 into the structure which the terminal pin 60 is supported by three points using the said recessed part 48 for ensuring connection reliability.

(7) A plurality of thermocouples 61 for temperature control were embedded in the holes 62 to obtain ceramic heaters (FIG. 5D).

(Comparative Example 1) Aluminum Plate Heater

Using a nichrome wire sandwiched with silicone rubber as the heat generating element, an aluminum plate and a pad having a thickness of 15 mm were sandwiched with a heat generating element, and fixed with bolts to form a heater. When voltage was applied to this heater, 24 seconds were required before the temperature change was seen.

Comparative Example 2 Alumina Heater

Basically, it is the same as Example 1, but the composition which consists of 100 weight part of alumina powder (average particle diameter 1.0 micrometer), 12 weight part of acrylic binders, and alcohol is made into granular form by the spray dryer method, it is put in the metal mold | die, it shape | molded in flat form The resulting product was hot pressed at 1200 ° C. under a pressure of 200 kg / cm ² to obtain an alumina substrate having a thickness of 3 mm.

In the conductive paste, 100 parts by weight of tungsten particles having an average particle diameter of 3 µm, 1.9 parts by weight of an acrylic binder, and 3.7 parts by weight of an α-terpineol solvent were mixed and 0.2 parts by weight of a dispersant to prepare a conductive paste, which was printed. Tungsten was sintered by heating and firing the ceramic substrate printed with the conductive paste at 1000 캜.

(Example 5)

Basically, it was the same as Example 4, but the square (an aspect ratio 1) of 20 micrometers in thickness x 20 micrometers in width was used for the heat generating body not having a flat shape.

(Example 6)

Basically, it was the same as Example 4, but the printing element was changed and the heating element was not flat, but the cross section used the thing of thickness of 5 micrometers x width 72mm (aspect ratio 12000).

(Example 7)

Basically, as in Example 4, 24 sheets were stacked on the lower side of the green sheet printed with the conductive paste and 25 sheets were placed on the upper side, where the heating element was placed in the center of the ceramic substrate.

(Example 8)

Basically, it was the same as Example 1, but it adjusted to have the following composition instead of Solvest PS603D.

Silver powder sphere shape, average particle size: 5.0㎛ 100 parts by weight

7.5 parts by weight of metal oxides (lead oxide, zinc oxide, silica, boron oxide, alumina, each weight ratio is 5/55/10/25/5)

The area resistivity was 4 mPa / sq.

(Example 9)

(1) A composition comprising 100 parts by weight of aluminum nitride powder (average particle size: 1.1 μm), 4 parts by weight of yttria (referred to yttrium acid, average particle diameter: 0.4 μm), 12 parts by weight of an acrylic binder, and an alcohol by spray spraying It was made.

(2) The granular powder was put into a mold and formed into a flat plate to obtain a green sheet. The green sheet was drilled to provide a through hole for inserting a semiconductor wafer support pin and a bottom hole for embedding a thermocouple.

(3) The green sheet was hot pressed at 1800 ° C and a pressure of 200 kg / cm ² to obtain an aluminum nitride substrate having a thickness of 3 mm. This was cut into a circular shape having a diameter of 210 mm to obtain a ceramic substrate 1.

In addition, after forming a metal mask on the ceramic substrate 1, sandblasting treatment was performed using an alumina powder having a diameter of 1 mu m, and a groove having a width of 2.4 mm and a depth of 6 mu m was formed at the heating element formation position.

(4) A conductive paste was printed on the groove of the ceramic substrate 1 obtained in (3) by screen printing to form a metal particle layer to be a heating element. The metal particle layer pattern was made into the concentric pattern as shown in FIG. As the conductive paste, Solvest PS603D manufactured by Tokuriki Chemical Research Institute, which was used for through hole formation of the printed wiring board, was used. This conductive paste is a silver / lead paste, containing 7.5% by weight of a metal oxide (each weight ratio is 5/55/10/25/5) of lead oxide, zinc oxide, silica, boron oxide, and alumina, relative to the amount of silver. It is. In addition, the shape of silver used the thing of the scale piece in 4.5 micrometers of average particle diameters.

(5) The ceramic substrate on which the metal particle layer was formed was heated and fired at 780 ° C to sinter silver and lead in the metal particle layer (conductive paste) and to bake on the ceramic substrate 1. The pattern by the sintered compact 4 of silver-lead was 5 micrometers in thickness, 2.4 mm in width, and area resistivity was 7.7 mPa / square.

(6) The ceramic substrate of (5) is placed in an electroless nickel plating bath consisting 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. It calcined and the nickel layer 5 of thickness 1micrometer was deposited on the surface of the sintered compact 4 of silver-lead, and it was set as the heating element.

(7) A silver-lead solder paste was printed by screen printing 1 on a portion to which terminal pins for securing a connection with a power source were attached, thereby forming a solder layer (manufactured by Tanika Precious Metals; 6). Subsequently, the Kovar terminal pins were placed on the solder layer 6, reflowed at 420 ° C., and the terminal pins were attached to the heating element surface (see FIG. 6).

In this embodiment, as shown in Fig. 6A, the heating element is embedded in the ceramic substrate, but is exposed from the surface. 6B may be partially embedded in the ceramic substrate and partially exposed.

In this example, response time, temperature difference, and pull strength were measured in the same manner as in Examples 1 and 8. The results are shown in Table 1.

(Comparative Example 3)

Basically, it was the same as Example 1, but lead oxide and zinc oxide were added to Solvest PS603D, and the amount of metal oxides was adjusted to 10 Wt%. The area resistivity of the obtained heating element was 50 mPa / square.

Moreover, the time (response time) until the temperature change after voltage application was confirmed about 8 in Example 1 (except Example 3) and 3 in Comparative Example 1 was measured. Moreover, the difference between the maximum temperature and minimum temperature of the heating surface at the time of making surface temperature into 600 degreeC was measured. In addition, in Examples 1 and 8, the full strength (unit: kg / 2mm square) was measured in 2 mm x 2 mm area | region.

The results are shown in Table 1 together.

Response time (seconds) Temperature difference (℃) Full Strength (kg / 2mm □) Example 1 0.5 8 12.4 Example 2 2.0 9 Example 4 1.0 8 Example 5 1.6 15 Example 6 0.8 18 Example 7 0.7 18 Example 8 0.7 18 6.0 Example 9 0.8 9 24.0 Comparative Example 1 24 15 Comparative Example 2 40 22 Comparative Example 3 0.8 15

As described above, the ceramic heater of the present invention is thin and light and practical, and is used for heating and drying the product, especially in the semiconductor industry.

In addition, since the ceramic heater according to the present invention uses nitride ceramics or carbide ceramics as a ceramic substrate and is light in weight, it is excellent in temperature followability of the heating surface against changes in voltage and current amount, and temperature control is easy. Moreover, since it is excellent also in the uniformity of the temperature distribution of a heating surface, efficient drying of a semiconductor product is attained.

Claims (3)

A heating element is formed on the surface of the ceramic substrate made of nitride ceramics or carbide ceramics, and a surface opposite to the heating element forming surface is a heating surface, and a through hole for inserting a support pin of a semiconductor wafer is formed in the ceramic substrate. Ceramic heater characterized in that. A heating element is formed on a surface of a ceramic substrate made of nitride ceramics or carbide ceramics, and a surface opposite to the heating element forming surface is a heating surface, and the ceramic substrate has a recess for thermocouple embedding. heater. delete