JP2003223971A - Ceramic heater and wafer heating device and fixing device to use the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To aim at maintaining uniform heating even if a high voltage of 200 V or more is applied, and aim at not making the durability deteriorate. <P>SOLUTION: At the main face or the inner part of a plate-formed body composed of ceramics, this is a ceramics heater provided with an exothermic resistor in which the sheet resistance is 100 mΩ/cm<SP>2</SP>or more, and two kinds or more of alloys of metal are contained. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater used for heating a wafer or the like, a wafer heating device using the same, and a fixing device.

[0002]

2. Description of the Related Art For example, in a semiconductor manufacturing apparatus manufacturing process, in a semiconductor thin film forming process, an etching process, a resist film baking process, etc., a wafer is heated to heat a semiconductor wafer (hereinafter referred to as a wafer). The device is being used.

A conventional semiconductor manufacturing apparatus used a batch type in which a plurality of wafers were collectively processed for film formation. However, as the size of the wafers increased from 8 inches to 12 inches, the processing accuracy increased. In order to increase the number, a method called a single-wafer processing, which processes one by one, has been implemented in recent years. However, when the single wafer processing is used, the number of processings per one time is reduced, so that it is necessary to shorten the wafer processing time. Therefore, it has been required for the wafer supporting member to shorten the heating time of the wafer, speed up the adsorption / desorption of the wafer, and improve the heating temperature accuracy.

As an example of the wafer heating device as described above,
For example, Japanese Unexamined Patent Publication (Kokai) No. 11-40330 discloses "a heater characterized in that a plate-shaped body made of nitride ceramics or carbide ceramics is provided with a heating element formed by sintering metal particles." ing. Ceramic heaters used for such semiconductor manufacturing equipment are
The diameter is more than 8 to 12 inches, and it is required to control the temperature distribution on the entire surface to a uniform temperature such as within ± 1 ° C.

When forming a resist film on a semiconductor wafer using such a heater made of ceramics, one of the ceramic heaters 2 made of ceramics such as silicon carbide, aluminum nitride or alumina as shown in FIG. Is a mounting surface 3 on which the wafer W is placed, and the heating resistor 5 is provided on the other main surface with the oxide film 21 and the insulating layer 4 interposed therebetween. A wafer heating device 1 having a structure fixed by an elastic body 8 has been proposed. The ceramic heater 2 is fixed to the support 11 with bolts 17, and the thermocouple 10 is inserted into the ceramic heater 2 to keep the temperature of the ceramic heater 2 at a predetermined temperature. It was a system for adjusting the electric power supplied from 7 to the heating resistor 5. Further, the conduction terminal 7 was fixed to the plate-shaped structure portion 13 via the insulating layer 9.

Then, on the mounting surface 3 of the wafer heating apparatus 1,
After the wafer W coated with the resist solution is placed, the heating resistor 5 is caused to generate heat, whereby the ceramic heater 2
The wafer W on the mounting surface 3 is heated via the above, and the resist solution is dried and baked to form a resist film on the wafer W.

As the heating resistor 5, Au, A
One made of one of g, Pt, Pd, Pb, Ni, etc. was used.

[0008]

Problems to be Solved by the Invention For example, Au, Ag, P
When a simple substance of metal such as d or Pt is used as a heating resistor, the sheet resistance of the heating resistor is reduced to 50 mΩ / □ or less, as disclosed in Japanese Patent Laid-Open No. 2001-6852. When a ceramic heater is manufactured using such a heating resistor, the voltage is adjusted and applied when used in order to adjust the resistance value of the heating resistor for the power supply voltage of 200 to 230V. Otherwise, the line width of the wiring pattern must be reduced to 1 mm or less, for example.

When the line width of the heating resistor is adjusted in this manner, the load applied to the heating resistor when the temperature of the ceramic heater is rapidly raised becomes large, so that the wire breakage easily occurs. Further, when the heating resistor 5 is trimmed with a laser to adjust the resistance value in order to reduce the temperature distribution on the surface of the ceramic heater, the line width is further reduced. Since the amount becomes large, there is a problem that disconnection is likely to occur.

Further, since the line width is narrow, there is a problem that the resistance adjustment width at the time of resistance trimming is also narrowed.

On the other hand, when the line width of the wiring pattern is widened and the output is adjusted on the control side, the temperature of the ceramic heater is greatly overshooted, the ceramic heater is damaged by the rush power, or the surface of the ceramic heater is damaged. There is a problem that the temperature distribution does not become uniform when the temperature distribution inside is controlled uniformly.

When a device for controlling the power supply voltage is installed, for example, when the ceramic heater of the present invention is used in a semiconductor manufacturing device, the cost increases, the space for installing the device is secured, and the weight of the device increases. Therefore, there is a market demand for a ceramic heater that does not require such control.

[0013]

That is, according to the present invention, the sheet resistance is 100 mΩ on the main surface or inside of the ceramic plate.
/ □ or more, and is provided with a heating resistor containing an alloy of two or more kinds of metals.

In the present invention, the heat generating resistor is A
At least 2 of u, Ag, Pd, Pt, Rh, and Ir
15-40% by volume of alloys of 60% to 85% by volume
It is characterized in that it is composed of a binder.

By using such a ceramic heater, even when a high power supply voltage of 200 to 230 V is used, the temperature overshoot of the ceramic heater is reduced, damage due to inrush power is prevented, and the temperature distribution is made uniform. I found that I could do it.

Further, by keeping the ceramic heater in the wafer heating device or the fixing device, it is possible to set the temperature control accuracy in the factory.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 is a cross-sectional view showing an example of a wafer heating apparatus of the present invention, in which one main surface of a ceramic heater 2 made of ceramics is used as a mounting surface 3 on which a wafer W is placed and the other main surface is provided. A heating resistor 5 is formed on the formed SiO ₂ film 21 via an insulating layer 4 made of glass, and a power feeding portion 6 electrically connected to the heating resistor 5 is provided to constitute a wafer heating apparatus. It is a thing.

Further, as the pattern shape of the heating resistor 5, the mounting surface 3 is made uniform, such as a substantially concentric circular shape composed of an arc-shaped electrode portion and a linear electrode portion, or a spiral shape. Any pattern shape that can be heated may be used. It is also possible to divide the heating resistor 5 into a plurality of patterns in order to improve the soaking property.

The heating resistor 5 has a sheet resistance of 100 mΩ.
/ Adjust so that it is more than □. The sheet resistance is 100
If it is less than mΩ / □, in order to reduce the inrush current when a high voltage of 200 V or more is applied, it is necessary to reduce the line width of the heating resistor 5 to 1 mm or less,
When the line width of the heating resistor is adjusted in this manner, the load applied to the heating resistor when the temperature of the ceramic heater is rapidly raised becomes large, and thus the wire breakage easily occurs.

The sheet resistance of the heating resistor 5 is 100 mΩ /
In order to achieve the above, the heating resistor 5 must contain an alloy composed of two or more kinds of metals.
It is preferable that the entire heating resistor 5 has a uniform alloy phase. The metal used for the heating resistor 5 is preferably alloyed in advance, but it is also possible to use a single metal for each and react them in the heat treatment during baking of the heating resistor 5 to form an alloy.

When the heating resistor 5 is trimmed with a laser in order to reduce the temperature distribution on the surface of the ceramic heater, the line width is further reduced, so that the heating amount per unit area of the heating resistor 5 is large. Therefore, disconnection is likely to occur, which is not preferable. In addition, the heating resistor 5 divides one pattern into a plurality of blocks, and adds a pattern for laser processing or resistance adjustment to adjust the resistance value of each block to add a predetermined resistance value. The temperature distribution within the surface of the wafer placed on the placement surface 3 can be adjusted within ± 1% by adjusting The laser processing is used to increase the resistance value of each block of the heating resistor 5, and the pattern addition is used to adjust the resistance value so as to decrease.

Further, in order to increase the resistance value of the heating resistor 5, it is necessary to lengthen the wiring length of the heating resistor 5, so that the time for adjusting the resistance of the heating resistor becomes long, which is not preferable in manufacturing. .

The heating resistor 5 will be described in detail below.

The sheet resistance of the heating resistor 5 is 100 mΩ /
□ To obtain the above value, the heating resistor 5 is made of Au, Ag, P
It is preferable that at least two kinds of alloys of 15 to 40 volume% of the metal components of d, Pt, Rh, and Ir and 60 to 85 volume% of the binder are used.

As a method of alloying the metal material used for the heating resistor 5, Au-Pt, Au-Ag, Pt-R is used.
An alloy such as h or Ag-Pd that is alloyed from the beginning may be used, or powders may be mixed and alloyed during sintering. When alloying during sintering, A
u-Pt, Au-Ag, and Ag-Pd are 900 to 1100.
It suffices to fire in the atmosphere at ℃. Further, in the case of Pt-Rh, it may be fired at 1300 to 1500 ° C.

More preferably, the combination of Au—Pt group metals, where the weight ratio of Au: Pt is 1: 9 to 8: 2, is preferable in order to prevent the resistance value from changing due to the oxidation of the metal material.

By alloying the metals in this way, the resistance value of the heating resistor 5 can be increased to a level several times higher than that when a single metal is used. The sheet resistance can be adjusted to 100 mΩ / □ by adjusting the alloy in the heating resistor 5 to 15 to 40% by volume and adjusting the content of the binder to 60 to 85% by volume.

Particularly, if laser trimming is performed to increase the resistance value more than twice, the line width of the heating resistor 5 is halved and the durability of the heating resistor 5 is reduced. Set the sheet resistance of the heating resistor 5 to 10
It is very important to adjust to 0 mΩ / □ or more.

When the sheet resistance of the heating resistor 5 becomes large, the ratio of the conductor portion in the pattern of the heating resistor 5 becomes too small and the rate of change in resistance becomes large.
It is preferably Ω / □ or less.

The average particle size of the metal component is 0.5-5.
It is preferable to use one having a diameter of 0 μm and an average particle diameter of the binder added to the metal component of 2 to 15 μm. At this time, the average particle size of the binder is preferably twice or more the average particle size of the metal component. By adjusting the particle diameter of the raw material in this way, as shown in FIG. 4A, the metal component 31 of the heating resistor 5 is formed into a film so that the binder 32 surrounds the metal component 31, and the resistance of the heating resistor 5 is reduced. The value can be increased, and at the same time, it becomes easy to form a continuous structure, which improves durability.

On the other hand, in the case of the heating resistor 5 in which, for example, Ag as the metal component 31 and the binder 32 are mixed outside the range of the above grain size, as shown in FIG. Is segregated on the surface of the heating resistor 5 and the resistance value becomes low. Therefore, the resistance value of the heating resistor 5 is set to be low irrespective of the addition of the binder 32, and the resistance value has to be adjusted by the width and the thickness of the heating resistor 5, resulting in durability. It is not preferable because it deteriorates the property.

It is preferable to use glass as the binding material 32 of the heating resistor 5. This glass may be either crystallized glass or amorphous glass,
It is preferable to use a glass whose melting point temperature is 100 ° C. or more higher than the working temperature of the ceramic heater. By doing so, it is possible to reduce the resistance change of the heating resistor 5 and improve the durability.

The temperature coefficient of resistance of the heating resistor 5 is 20.
If it is set to 00 ppm / ° C. or less, even if the resistance value distribution of the heating resistor 5 is deviated, the heat generation variation can be absorbed by the heat conduction of the ceramic heater 2, so that the entire temperature can be rapidly raised with a good temperature distribution. become able to.

Although an example of a binary system is shown here as the alloy, a heating resistor 5 made of a ternary or quaternary metal alloy may be used, and the temperature coefficient of resistance in that case will be described. Is also the same.

Further, the heating resistor 5 contains glass for enhancing the adhesion to the insulating layer 4, and the softening point of this glass is lower than the transition point of the glass contained in the insulating layer 4 for heating. It is preferable for improving the processing accuracy of. Glass is considered to be a viscous fluid with high viscosity at temperatures above the transition point. Therefore, when the heating resistor 5 is formed on the insulating layer 4, the softening point of the glass contained in the heating resistor 5 is made lower than the transition point of the glass contained in the insulating layer 4, and the heating resistor 5 is baked. At times, the insulating layer 4 serving as the base material is not affected. It is preferable to use such glass as the above-mentioned binding material 32.

The reason why the heating resistor 5 is formed on the surface of the ceramic heater 2 is to finely adjust the resistance distribution of the heating resistor 5 after the heating resistor 5 is formed.
As a method for adjustment, there is a method of scraping off a part of the heat generating resistor 5, but this method always causes a defect in the heat generating resistor 5. Therefore, in the present invention, by using a method of applying a resistor pattern over the heating resistor 5, it is possible to prevent defects from being generated in the heating resistor 5 and improve durability.

Here, a method of adjusting the resistance value of the heating resistor 5 will be described with reference to FIG. If the heating resistor 5 has a resistance adjusting portion 5a higher than the target resistance value, a new resistor pattern 5'is overlaid on the resistance adjusting portion 5a to adjust the resistance value distribution to the target value level. can do.

It is an object of the present invention to control the resistance value distribution by reducing the resistance value of the resistor pattern 5'by overcoating it. In the resistance value distribution control by laser trimming, the heating resistor 5 pattern is processed so as to have a high resistance value at a low resistance value, whereas the present invention controls the resistance value distribution by the reverse operation. Will be done.

Regarding the place where the resistor pattern 5'is formed, the heating resistor 5 is divided into a large number of subdivided blocks, and the target resistance value of each block is set. The resistance is adjusted so that only the part that is out of alignment with the target value is met.

Further, by adjusting the specific resistance of the resistance correcting resistor pattern 5'to be higher than the specific resistance of the heating resistor 5, the width of the resistance value control by pattern formation can be made smaller, so the heating resistor 5 The resistance value of can be precisely adjusted. It is preferable to adjust the specific resistance to be 10% or higher.
When the resistance value is adjusted by overcoating, if the resistance adjustment width is small, it is necessary to reduce the coating width of the resistor pattern 5'or to reduce the coating thickness. The accuracy of this coating is one of the factors that determine the variation in resistance correction.

The paste for forming the resistor pattern 5'can be applied by a printing method, or the resistor pattern 5'having a preset resistance adjustment width can be applied by transfer. Further, it is preferable that the paste forming the resistor pattern 5 ′ is baked at a temperature lower by 10 ° C. or more than the baking temperature of the heating resistor 5. By performing the baking of the resistor pattern 5 ′ as described above, it is possible to suppress the initial resistance value of the heating resistor 5 from changing due to the baking temperature of the paste forming the resistor paste 5 ′.

The structure of the wafer heating apparatus 1 according to one embodiment of the present invention will be described in detail with reference to FIG. An insulating layer 4 is formed on the surface of a substrate forming the ceramics heater 2, and a heating resistor 5 containing an alloy of at least two kinds of Au, Pd, Ag and Pt group metals is further formed on the insulating layer 4.
Is formed, and a power feeding portion 6 is formed on the heating resistor 5 to form the ceramic heater 2. The ceramic heater 2 is bonded to the support 11, and the conduction terminal 7 is pressed and connected to the power feeding portion 6 to form a wafer heating device. Further, the wafer W is held by the support pins 22 while being separated from the mounting surface 3. This prevents the problem that the wafer W hits the ceramic heater 2 one-sided and the temperature distribution deteriorates.

The insulating layer 4 is made up of the ceramic heater 2
It is appropriately formed in order to secure the electrical insulation with the substrate forming the substrate and to improve the adhesive strength of the heating resistor 5 to the substrate. The insulating layer 4 has a thickness of 10 to 600 μm. If the thickness is less than 10 μm, electrical insulation between the substrate forming the ceramic heater 2 and the heating resistor 5 will be insufficient. On the other hand, if the thickness exceeds 600 μm, the glass has a low thermal conductivity, so that the heating resistor 5
The heat transfer from the wafer to the wafer W mounting surface 3 is delayed, which is not preferable.

The flatness of the surface of the insulating layer 4 made of glass is preferably 300 μm or less. If the flatness exceeds 300 μm, the variation in thickness when the heating resistor 5 is formed on the surface of the insulating layer 4 increases, and the resistance value variation of the heating resistor 5 increases, which is not preferable.

The flatness of the insulating layer 4 made of glass is set to 300.
In order to make the thickness of the ceramic heater 2 or less, the flatness of the side of the ceramic heater 2 on which the insulating layer 4 is applied is set to 300 μm or less, and at the same time, the coefficient of thermal expansion of glass is 0 with respect to the coefficient of thermal expansion of the ceramics constituting the ceramic heater 2. ~ 0.9 x 10
It is preferable to make it small in the range of ^-6 deg ^-1 . This is because the stress due to contraction when the glass is sintered is not sufficiently relaxed by the heat treatment during baking, and a warp that makes the insulating layer 4 side concave is likely to remain. As described above, reducing the warpage of the ceramic heater 2 by making the thermal expansion coefficient of the glass smaller than that of the ceramics forming the ceramic heater 2 is effective for improving the flatness.

The flatness of the insulating layer 4 is 300 μm.
If it is larger, the heating resistor 5 whose thickness is controlled is formed in advance on the transfer sheet, and the heating resistor 5 is formed on the insulating layer 4 by transfer to make the thickness of the heating resistor 5 uniform. It is possible to uniformly heat the substrate forming the ceramic heater 2.

Further, the insulating layer 4 made of glass is formed by forming a film having a constant thickness by printing or transferring and heat-treating the film at a temperature equal to or higher than the working point of the glass. The coefficient of thermal expansion of glass is preferably set to be slightly smaller than the coefficient of thermal expansion of the ceramic base material of the ceramic heater 2. This is because when the glass is sintered and melted, the stress due to the shrinkage is not sufficiently relaxed and the stress due to the shrinkage remains in the form of warp, and this is absorbed. As a result, the stress remaining in the glass becomes a compressive stress, and cracks are less likely to occur due to thermal stress.

Further, the flatness of the substrate forming the ceramic heater 2 after being fixed to the support 11 is 80 μm or less,
More preferably, it is preferably 40 μm or less. The flatness of the substrate forming the ceramic heater 2 is 80μ.
The reason why it is less than m is that the wafer W and the ceramic heater 2
This is because the temperature within the plane of the wafer W can be precisely controlled when the temperature of the wafer W is rapidly raised by controlling the distance between the substrate and the substrate.

The distance between the substrate forming the ceramic heater 2 and the wafer W is preferably narrower in the central portion than in the outer peripheral portion. In order to keep the temperature distribution of the ceramic heater 2 constant, the heat generation distribution of the heat generation resistor 5 is such that the outer peripheral portion where heat easily escapes has a larger amount of heat generation than the central portion. Therefore, when the temperature is rapidly raised, the temperature of the central portion of the wafer W tends to be delayed. In order to reduce this tendency, it is preferable that the distance between the substrate forming the ceramic heater 2 and the wafer W is narrower in the central portion than in the outer peripheral portion because the responsiveness to the temperature change of the ceramic heater 2 becomes faster. .

As the ceramics forming the ceramic heater 2, silicon carbide, boron carbide, boron nitride,
It is possible to use one containing at least one of silicon nitride and aluminum nitride as a main component.

As the silicon carbide-based sintered body, for the main component silicon carbide, for the sintered body containing boron (B) and carbon (C) as a sintering aid, or for the main component silicon carbide, A sintered body containing alumina (Al ₂ O ₃ ) and yttria (Y ₂ O ₃ ) as a sintering aid and fired at 1900 to 2200 ° C. can be used, and silicon carbide is mainly α-type. thing,
Alternatively, any of those mainly composed of β type may be used.

Further, as the boron carbide sintered body, carbon is mixed as a sintering aid in an amount of 3 to 10% by weight with respect to boron carbide as a main component and sintered by hot press firing at 2000 to 2200 ° C. You can get the body.

As the boron nitride sintered body, 30 to 45 wt% as a sintering aid is added to the main component boron nitride.
A sintered body can be obtained by mixing 5 to 10% by weight of the rare earth element oxide with aluminum nitride and hot-baking the mixture at 1900 to 2100 ° C. As a method for obtaining a sintered body of boron nitride, there is another method in which borosilicate glass is mixed and sintered, but in this case, the thermal conductivity is significantly lowered, which is not preferable.

As the silicon nitride sintered material, 3 to 12% by weight of a rare earth element oxide and 0.5 to 3% by weight of Al ₂ O ₃ as a sintering aid are added to silicon nitride as a main component. Further, SiO ₂ is mixed so that the amount of SiO ₂ contained in the sintered body is 1.5 to 5% by weight, and the sintered body can be obtained by hot press firing at 1650 to 1750 ° C. The amount of SiO ₂ shown here is the sum of SiO ₂ produced from the impurity oxygen contained in the silicon nitride raw material, SiO ₂ as an impurity contained in other additives, and SiO ₂ intentionally added. .

Further, the aluminum nitride-based sintered body includes aluminum nitride as a main component, rare earth element oxides such as Y ₂ O ₃ and Yb ₂ O ₃ as sintering aids, and CaO and the like as necessary. After adding an alkaline earth metal oxide and mixing it well, and processing it into a flat plate, it is 1900 to 210 in nitrogen gas.
Obtained by firing at 0 ° C.

Further, the ceramic heater 2 is made elastic by inserting a bolt 17 around the outer periphery of the ceramic heater 2 and the support 11 and screwing a nut 19 from the ceramic heater 2 side with an elastic body 8 and a washer 18 interposed. It is fixed to. As a result, even if the support 11 is deformed when the temperature of the ceramic heater 2 is changed or a wafer is placed on the mounting surface 3 and the temperature of the ceramic heater 2 is changed, the elastic body 8 absorbs the deformation. As a result, the warp of the ceramic heater 2 can be prevented, and the temperature distribution on the surface of the wafer W during the heating of the wafer W can be prevented.

The thermocouple 10 for adjusting the temperature of the ceramic heater 2 is installed near the wafer mounting surface 3 at the center of the ceramic heater 2, and the temperature of the ceramic heater 2 is adjusted based on the temperature of the thermocouple 10. adjust. Heating resistor 5
Is divided into a plurality of blocks, and in the case of individually controlling the temperature, a thermocouple 10 for temperature measurement is installed in each block of the heating resistors 5. As the thermocouple 10, it is preferable to use a sheath-type thermocouple 10 having an outer diameter of 1.0 mm or less from the viewpoint of its responsiveness and workability of holding. Further, the plate-shaped structure portion 1 of the support portion 7 is provided in the middle of the thermocouple 10 so that no force is applied to the tip portion embedded in the ceramic heater 2.
It is held at 3. At the tip of the thermocouple 10, a hole is formed in the substrate that forms the ceramic heater 2, and it is necessary to press and fix it to the inner wall surface of the cylindrical metal body installed therein with a spring material for reliable temperature measurement. Preferred for improving.

When the heating resistor 5 is divided into a plurality of blocks, it is preferable to install a temperature control thermocouple 10 at the center of each block and control the temperature independently.

As shown in FIG. 3, the holding structure of the thermocouple 10 has a concave portion 21 formed on the main surface of the ceramic heater 2 on which the heating resistor 5 is formed. In order to improve the reliability of temperature measurement by the thermocouple 10, the thermocouple 10 is installed through the metal foil 23 having a thermal conductivity of 65 W / mK or more, and the ceramic heater 2 having a thermal conductivity of 2 from above.
The metal chip 22 which is 40 to 170% of that of the substrate forming the substrate, the pressing jig 24 having a thermal conductivity of 50 W / m · K or less, and the support rod 25 may be pressed and fixed by the elastic body 26. preferable. Further, the diameter of the recess 21 is preferably 3 to 5 mmφ.

The support 11 is composed of a plate-shaped structure 13 and a side wall portion, and a conductive terminal 7 for supplying electric power to the heating resistor 5 is installed on the plate-shaped structure 13 via an insulating material 9. Thus, an air injection port and a thermocouple holding portion (not shown) are formed. The conductive terminal 7 has a structure in which it is pressed against the feeding portion 6 by the elastic body 8. The plate-shaped structure 13 is composed of a plurality of layers.

Further, by making the connection between the power supply portion 6 formed on the ceramic heater 2 and the conduction terminal 7 contact by pressing, the difference in expansion due to the temperature difference between the ceramic heater 2 and the support 11 is brought into contact. Since it can be relaxed by slippage of the portion, it is possible to provide a wafer heating device having good durability against a thermal cycle during use. As the elastic body 8 which is the pressing means, a coiled spring as shown in FIG. 1 or a leaf spring may be used for pressing.

As a pressing force of the elastic body 8, a load of 0.3 N or more may be applied to the conductive terminal 7. The reason why the pressing force of the elastic body 8 is 0.3 N or more is that the conductive terminal 7 has to move in response to the dimensional change due to the expansion and contraction of the substrate 11 and the support body 11 forming the ceramic heater 2. In order to prevent the conducting terminal 7 from being separated from the feeding portion 6 due to friction with the sliding portion of the conducting terminal 7, the conducting terminal 7 is pressed from the lower surface of the ceramic heater 2 to the feeding portion 6 due to the above constitution. Is.

Further, it is preferable that the diameter of the contact surface side of the conduction terminal 7 with the feeding portion 6 is 1.5 to 4 mm. Further, as the insulating material 9 for holding the conductive terminals 7, a PEEK (polyethoxyethoxyketone resin) material in which glass fibers are dispersed can be used at a temperature of 200 ° C. or lower depending on the use temperature. In addition, when used at a temperature higher than that, it is possible to use a ceramic insulating material 9 made of alumina, mullite, or the like.

At this time, it is preferable that at least the contact portion of the conduction terminal 7 with the power supply portion 6 is formed of a metal made of at least one of Ni, Cr, Ag, Au, stainless steel and platinum group metals. . Specifically, the conduction terminal 7 itself is formed of the above metal, or the conduction terminal 7
A coating layer made of the metal can be provided on the surface of the.

Alternatively, by inserting a metal foil made of the above metal between the conductive terminal 7 and the power feeding portion 6, contact failure due to oxidation of the surface of the conductive terminal 7 is prevented and the durability of the ceramic heater 2 is improved. Is possible.

Further, by preventing the contacts from making point contact by roughening the surface by subjecting the surface of the conductive terminal 7 to blaching or sandblasting, the reliability of contact can be further improved. The wafer heating apparatus 1 adjusts the temperature within the surface of the substrate forming the ceramic heater 2 to be uniform, but the ceramic heater 2 and the support member 9 are structurally structured during heating, wafer replacement, and the like.
The temperature relationship is not constant. Because of this temperature difference, the power supply section 6 and the conductive terminal 7 often come into contact with each other in a twisted positional relationship. Therefore, if these contacts are processed flat, one-sided contact is likely to occur and contact failure occurs.

In order to heat the wafer W by the wafer heating device 1, the mounting surface 3 is moved by a transfer arm (not shown).
After the wafer W carried to the upper part of the wafer W is supported by lift pins (not shown), the lift pins 8 are lowered to mount the wafer W on the mounting surface 3.

Next, the power supply section 6 is energized to generate heat in the heating resistor 5, and the wafer W on the mounting surface 3 is heated via the substrate forming the insulating layer 4 and the ceramic heater 2. When the substrate forming the ceramic heater 2 is formed of a silicon carbide sintered body, the deformation is small even when heat is applied and the plate thickness can be made thin. Therefore, the temperature rising time until heating to a predetermined processing temperature and the predetermined processing temperature are performed. The cooling time from the cooling to near room temperature can be shortened, the productivity can be improved, and the thermal conductivity of 80 W / m · K or more can be achieved. The Joule heat can be quickly transmitted, and the temperature variation of the mounting surface 3 can be made extremely small.

Next, another embodiment of the present invention will be described.

The ceramic heater 2 of the present invention can be suitably used for a toner fixing device in an image forming apparatus such as a copying machine.

A commonly used ceramic heater for a fixing device is a rectangular plate-shaped ceramic plate made of alumina or the like on which a heating resistor made of a metal such as Ag or Pd is formed. However, since alumina has a low thermal conductivity, it has been difficult to accurately soak the entire surface of the ceramic plate.

On the other hand, as shown in FIG. 5, sheet resistance including alloy is provided on the surface of a rectangular plate-shaped substrate made of high thermal conductive ceramics such as silicon carbide or aluminum nitride via an insulating layer 4 made of glass. When the ceramic heater 2 of the present invention in which the heating resistor 5 having a resistance of 100 mΩ / □ or more is formed, the temperature distribution of ± 1% or less can be achieved by adjusting the resistance value distribution of the heating resistor 5 by trimming.

Therefore, if the paper on which the toner has been fixed is brought into contact with the upper surface of the ceramic heater 2 and the paper is allowed to pass through the surface, the uneven temperature distribution on the surface can prevent uneven printing.

[0075]

Example 1 A silicon carbide raw material was mixed with 3% by weight of B ₄ C and 2% by weight of carbon by using an appropriate amount of a binder and a solvent, granulated, and then molded at a molding pressure of 100 MPa in a non-oxidizing atmosphere. 1900-
By firing at 2100 ° C., a disc-shaped silicon carbide-based sintered body having a thermal conductivity of 80 W / m · K and an outer diameter of 230 mm was obtained. Then, after both surfaces are ground, heat treatment is performed at 1200 ° C. for 1 hour to form a film 21 made of SiO ₂ .
A glass paste of 200 μm was printed on one surface and baked at 1000 ° C. to form the insulating layer 4. The coefficient of thermal expansion of glass is 3.4 × 1.
The one used was 0 ^-6 deg ^-1 .

On the surface of a disk-shaped silicon carbide sintered body on which an insulating layer made of glass is formed, a total of 5 blocks, each of which is divided into 4 parts so that the center part and the outer periphery are 90 degrees, are shown in Table 1. Ag, Au-Pt, Au- having the composition shown in
A sheet resistance of 40, 80, 100, 250, 3 was obtained by applying a paste composed of Pd and Au-Ag powder and glass having a working point of 750 ° C. and baking it at 750 ° C.
00, 500 mΩ / □ heating resistor 5 was formed.

The support 11 is made of SUS304 having a thickness of 2.5 mm and having an opening formed on 30% of the main surface.
One plate-like structure 13 is prepared, five thermocouples 10 for temperature adjustment and ten conducting terminals 7 are formed at a predetermined position on one of the plate-like structures 13, and a side wall portion and a screw made of SUS304 are also formed. The support 11 was prepared by fixing by tightening. The thermocouple 10 was installed in the center of each heating resistor block with the structure shown in FIG.

After that, the ceramic heater 2 was superposed on the support 11, and the outer periphery of the ceramic heater 2 was fastened with screws via the elastic body 8 to obtain the wafer heating apparatus 1 shown in FIG.

A wafer W having a thermocouple 10a for temperature measurement fixed thereon was placed on the mounting surface 3 of the wafer heating apparatus 1, and the temperature distribution in the wafer W surface was measured by the thermocouple 10a. The thermocouple 10a for measurement has a radius of the wafer W of 1 /
It was installed at 6 points at the radius of 2 and 7 points in the center.

The wafer heating device 1 thus prepared
After maintaining at 0 ° C and adjusting the temperature distribution within the wafer W within ± 0.5 ° C, the temperature is lowered to 50 ° C and the wafer W
The in-plane temperature distribution was within ± 0.4 ° C., and the maximum value of the overshoot of the in-plane temperature of the wafer W when the temperature was raised to 200 ° C. was evaluated. Prepare 5 samples each,
The overshoot of each 5 cycles was measured and the maximum value was taken as the overshoot temperature.

Further, this ceramic heater is set to 100 ° C.
Temperature rise from below to 500 ° C in 5 minutes and 100 minutes in 10 minutes
The cycle of cooling to ℃ or less was repeated 3000 times, and the rate of change in resistance value of the heating resistor at that time was measured.

As an evaluation criterion, samples with an overshoot temperature of 10 ° C. or higher and a resistance change rate of more than 2% in the durability test were rated as NG.

Further, regarding whether or not two or more kinds of metals are alloyed, the distribution of each metal component in the heating resistor 5 is measured by using a wavelength dispersive X-ray microanalyzer (EPMA: WDS). Confirmed by

The results are shown in Table 1.

[0085]

[Table 1]

As shown in Table 1, the sheet resistance is 100.
No. which is less than mΩ / □. For Nos. 1 to 3, the overshoot temperature increased when the resistance value was set lower.

On the other hand, the sheet resistance is 100 mΩ.
/ No. Nos. 2 to 11 showed good results in terms of overshoot temperature and durability. Also, EPMA
By confirming the distribution of the metal components by analysis, it was confirmed that the metal components of the heating resistor 5 were alloyed.

However, it has been found that when the resistance value is set higher, the line width of the heating resistor 5 becomes narrower, so that the current density increases and the resistance change rate increases. In addition, the sheet resistance of sheet No. exceeds 500 mΩ / □. 11 is a heating resistor 5
Since the ratio of the conductor part in the pattern becomes too small,
The resistance change rate was large, which was not preferable.

Example 2 Here, Au, Ag, Pd, Pt, and
A metal material composed of at least two kinds of Rh and Ir is used, and the weight ratio of these metals is 1: 2 with respect to Au.
Variable from 0 to 9: 1, and further the metal material and the binder 32
The ratio of the above-mentioned metal is 10 to 50% by volume.
On the other hand, the heating resistor is manufactured by adjusting the amount of the binder 32 to be 90 to 50% by volume.
The resistance change was confirmed after 5,000 cycles of energizing, heating up from 100 ° C. or less to 500 ° C. in 5 minutes, and further cooling to 100 ° C. in 10 minutes.

The average particle size of the metal material is 1.0 to
The average particle diameter is 5.
3 μm zinc borate-based glass was used. The evaluation criteria of the durability test were the same as in Example 1.

The results are shown in Table 2.

[0092]

[Table 2]

As shown in Table 2, No. Sheet resistance values of 2 to 14 can be set to 100 mΩ / □ or more, and in particular, Au—Pt is used and the weight ratio thereof is 1: 9 to 8 :.
The resistance within the range of 2 was able to reduce the resistance change. It has been found that it is preferable to use the heating resistor 5 within the above range as the heating resistor 5 used in the oxidizing atmosphere.

[0094]

As described above, according to the present invention, a heating resistor having a sheet resistance of 100 mΩ or more and containing an alloy of two or more kinds of metals is provided on the main surface or inside of a ceramic plate. By using such a ceramic heater, it is possible to reduce the temperature overshoot at the time of rapid temperature rise and obtain a ceramic heater having good durability.

[Brief description of drawings]

FIG. 1 is a sectional view showing a wafer heating apparatus using a ceramic heater of the present invention.

FIG. 2 is a partially enlarged sectional view of a heating resistor of the wafer heating apparatus of the present invention.

FIG. 3 is a partial enlarged cross-sectional view of a wafer heating apparatus using the ceramic heater of the present invention.

4A and 4B are cross-sectional views showing the structure of a heating resistor of the ceramic heater of the present invention.

5A and 5B are views showing a fixing device using the ceramic heater of the present invention.

[Explanation of symbols]

1: Wafer heating device 2: Ceramic heater 3: Mounting surface 4: Insulation layer 5: Heating resistor 5 ': conductor pattern 5a: resistance adjusting unit 6: Power supply unit 7: Conductive terminal 8: Elastic body 10: Thermocouple 11: Support 31: Metal component 32: Binder W: Semiconductor wafer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 3/12 H05B 3/16 3/16 3/18 3/18 3/20 328 3/20 328 393 393 3/74 3/74 H01L 21/30 567 F term (reference) 2H033 AA03 AA23 AA24 BA25 BA26 3K034 AA02 AA10 AA34 AA37 BB06 BB14 BC04 BC12 BC17 JA01 3K092 PP09 QA05 QB02 RF02 RF045V15 RF22 RF11 RF19 RF19 RF11 RF19 RF19 RF11 RF11 RF19 RF19 RF11 RF19 RF11 RF19 RF19 RF11 RF19 RF11 RF19 RF11 RF19 RF11 RF19 RF11 RF19 RF22 KA04

Claims (5)

[Claims] 1. A ceramic heater characterized in that a heating resistor having a sheet resistance of 100 mΩ / □ or more and an alloy of two or more kinds of metals is provided on or in the main surface of a ceramic plate. 2. The heating resistor is Au, Ag, Pd, P
Alloy of at least two kinds of t, Rh, and Ir 15
The ceramic heater according to claim 1, wherein the ceramic heater comprises -40% by volume and 60-85% by volume of a binder. 3. The alloy in the heating resistor contains an Au—Pt alloy as a main component, and the weight ratio of Au: Pt is 1: 9 to 8: 2.
The ceramic heater according to claim 2, wherein 4. A wafer heating apparatus comprising the ceramic heater according to claim 1 and a wafer mounting surface. 5. A fixing device using the ceramic heater according to claim 1.