JP2002093551A - Ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater superior in temperature uniformity with little dispersion of resistance of a heater resistor. SOLUTION: This is a ceramic heater wherein the heater resistor is formed on a ceramic board, and a groove is formed in the heater resistor, and the groove has a depth not less than 20% of the thickness of the heater resistor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater (hot plate) mainly used for manufacturing and testing semiconductors.

[0002]

2. Description of the Related Art Conventionally, heaters and wafer probers using a metal base material such as stainless steel or an aluminum alloy have been used as semiconductor manufacturing / inspection devices including etching devices and chemical vapor deposition devices. Was.

However, since the heater made of metal has a thick heater plate, there is a problem that the heater is heavy and bulky.
Further, there is a problem in the temperature followability due to these.

Therefore, Japanese Patent Application Laid-Open No. 11-40330 discloses a plate-like body (ceramic substrate) made of a nitride ceramic or a carbide ceramic having a high thermal conductivity and a high strength as a substrate. On the surface of
A ceramic heater provided with a resistance heating element formed by sintering metal particles is disclosed.

As a method of forming a resistance heating element when manufacturing such a ceramic heater, the following method can be mentioned. First, a ceramic substrate having a predetermined shape is manufactured. Thereafter, when a resistance heating element is formed by a coating method, subsequently, a heating element pattern is formed on the surface of the ceramic substrate by using a method such as screen printing. A conductive paste layer was formed, heated and fired to form a resistance heating element.

When a resistance heating element is formed by a physical vapor deposition method such as sputtering or a plating method, a metal layer is formed on a predetermined region of a ceramic substrate by these methods, and then a heating layer is formed. After forming an etching resist so as to cover the body pattern portion, an etching process is performed to form a resistance heating element having a predetermined pattern.

[0007] First, a portion other than the heating element pattern is coated with a resin or the like, and thereafter, the above processing is performed to form a resistance heating element of a predetermined pattern on the surface of the ceramic substrate by a single processing. You can also.

[0008]

However, in the methods such as sputtering and plating, although a precise pattern can be formed, a photolithography method is applied to the surface of the ceramic substrate in order to form a resistive heating element having a predetermined pattern. It is necessary to form an etching resist, a plating resist, and the like by using GaN, so that there is a problem that the cost is high.

On the other hand, in the method using a conductive paste, as described above, although a resistance heating element can be formed at a relatively low cost by using a technique such as screen printing, an attempt is made to form a precise pattern. Then, a short circuit or the like occurs due to a slight mistake at the time of printing, and there is a problem that it is difficult to form a resistive heating element having a precise pattern. Further, there is a problem that the thickness of the printing varies and the resistance value varies.

[0010]

Means for Solving the Problems Accordingly, the present inventors have:
It has been recalled that trimming is performed to adjust the resistance value in order to suppress such variation in the resistance value of the resistance heating element. Further, the present inventors have also studied the trimming shape, and have obtained new knowledge on a suitable trimming shape, and have completed the present invention.

That is, the present invention is a ceramic heater in which a resistance heating element is formed on a ceramic substrate, wherein the resistance heating element has a groove, and the groove has a thickness of 20% or more of the thickness of the resistance heating element. A ceramic heater having a depth.

Since the groove formed by trimming has a depth of 20% or more of the thickness of the resistance heating element, the amount of change in the resistance value due to the trimming is large, and the resistance value can be easily controlled. Further, this groove desirably reaches the surface of the ceramic substrate. This is because the resistance heating element is completely divided by the formed groove, and the trimming length and the amount of change in the resistance value are completely linked, so that the resistance value can be easily controlled.

When the resistance heating element remains at the bottom of the groove formed by the trimming, the resistance value changes depending on the remaining amount. Therefore, the trimming length and the amount of change in the resistance value do not accurately link with each other. The variation in the resistance value increases.
Further, if the resistance heating element remains at the bottom of the groove formed by trimming, the oxidation resistance of the remaining resistance heating element decreases, and the resistance value is liable to change with time. Such a problem does not occur if has reached the bottom of the ceramic substrate.

It is desirable that the groove formed by the trimming is stopped at a depth of about 30% or less of the thickness of the ceramic substrate from the surface of the ceramic substrate. If it exceeds 30%, the strength of the ceramic substrate is reduced, and warpage tends to occur.

In the present invention, it is desirable that the trimming grooves are formed substantially parallel to the direction in which the current of the resistance heating element flows.

As shown in FIG. 5A, if the groove 120 formed by trimming is formed substantially parallel to the direction in which the current flows through the resistance heating element 12, the resistance value locally increases. There is no. The direction in which the current propagates and the direction in which the grooves are formed need not be mathematically parallel to each other.
As shown in FIG. 5B, the groove 130 may be formed so as to draw a curve, and as shown in FIG.
40 may be formed so as to draw a diagonal line with respect to the current propagation direction. In short, it is only necessary that the direction in which the groove is formed is parallel to the direction in which the current propagates, or that the angle between the direction in which the current propagates and the direction in which the groove is formed is an acute angle.

As shown in FIG. 6, when the trimming is performed perpendicularly to the direction in which the current flows through the resistance heating element 22 and the cut 22a is formed, the A of the resistance heating element 22 is formed.
The resistance value of the portion becomes extremely high, and as shown in FIG.
Heating causes the resistance heating element 22 to melt. However, in the present invention, such extreme heat generation does not occur, and damage or the like due to overheating of the resistance heating element does not occur. Furthermore, there is no extreme rise in the resistance value,
%, Preferably 1% or less.

Further, since the variation in the resistance value of the resistance heating element can be reduced in this way, even when the resistance heating element is divided into a plurality of circuits and controlled, the number of divisions can be reduced, and control is facilitated. can do. When the variation in the resistance value is large, it is necessary to finely divide the circuit and control the temperature by changing the input power amount for each circuit (channel). However, in the present invention, since there is almost no variation in the resistance value, the circuit is fine. This eliminates the need for division and facilitates control. Further, it is possible to make the temperature of the heating surface uniform during the transition of the temperature rise.

In the case of trimming with a laser, if the trimming is performed perpendicularly to the direction in which the current flows through the resistance heating element, the surface of the ceramic substrate is irradiated with the laser, and the ceramic substrate is discolored and the appearance is poor. Or the strength of the ceramic is reduced.

However, when the grooves are formed substantially parallel to the direction in which the current flows through the resistance heating element as in the present invention, not only the discolored portion is hidden but also excess heat energy is transmitted to the ceramic substrate. Therefore, a decrease in strength can be prevented.

The groove formed by the trimming preferably has a depth of 20% or more of the thickness of the resistance heating element, and more preferably has a depth of 50% or more. This is because, at a depth of less than 20%, there is almost no change in the resistance value. Also,
The width of the resistance heating element is desirably 0.5 mm or more. 0.5
If the diameter is less than mm, the resistance heating element is too thin, and it is difficult to perform trimming substantially parallel to the direction in which the current of the resistance heating element flows.

In the present invention, since the resistance heating element is formed on the ceramic substrate using a metal or a conductor paste containing a metal and an oxide, the resistance heating element is particularly easily trimmed by laser light. This is because the metal is evaporated and removed by the laser, but the ceramic is not removed. Therefore, unlike laser trimming on a semiconductor wafer or a printed wiring board, the laser beam output does not need to be adjusted, and there is no removal residue, and accurate trimming can be realized. Furthermore, since the substrate is a ceramic substrate, the substrate does not warp due to the trimming and the strength is not significantly reduced. Hereinafter, the present invention will be described based on embodiments.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ceramic heater according to the present invention is a ceramic heater having a resistance heating element formed on a ceramic substrate. A groove is formed in the resistance heating element in a direction substantially parallel to the direction in which current flows. The depth of the groove is 20% or more of the thickness of the resistance heating element. In this ceramic heater, it is desirable that the groove formed in the resistance heating element reaches the ceramic substrate, and furthermore, if a groove is also formed in the ceramic substrate, its depth is equal to the thickness of the ceramic substrate. It is desirable to be within 30% of the value.

In the ceramic heater having such a configuration,
Variations in the resistance value can be reduced, and the oxidation resistance of the resistance heating element can be prevented from lowering. Further, the strength of the ceramic substrate is not reduced.

The trimming is formed on the surface (upper surface) of the resistance heating element. This is because if a trimming groove is formed on the side surface of the resistance heating element, a portion where the resistance value locally increases occurs, and the resistance heating element is melted during heat generation. FIGS. 5A to 5C are perspective views schematically showing the resistance heating element 12 when the surface of the resistance heating element is trimmed substantially in parallel along the direction of current flow. Although the grooves 120, 130, and 140 formed by trimming are linear or curved as shown in FIG. 5, a plurality of linear or curved grooves may be formed.

Further, when the resistance heating element is formed in a shape drawing an arc, the resistance value can be largely changed by trimming the inner peripheral side of the circular resistance heating element. This is because the current flows more easily toward the inner circumference.

It is preferable that the groove has a depth of 20% or more of the thickness of the resistance heating element. This is because the resistance value can be changed. If the depth of the groove is less than 20%, the resistance value hardly changes.

Regarding the variation of the resistance value of the resistance heating element, the variation of the resistance value with respect to the average resistance value is preferably 5% or less, more preferably 1%. By reducing the variation in this way, even when the resistance heating element is divided into a plurality of circuits and controlled, the number of divisions can be reduced and control can be facilitated. Further, it is possible to make the temperature of the heating surface uniform during the transition of the temperature rise.

Further, the variation in the resistance value of the resistance heating element is suppressed to 25% or less by making the thickness, width and the like uniform when printing the resistance heating element, and further adjusted to 5% or less by trimming. It is desirable to do. This is because the adjustment by trimming is easier if the variation is reduced at the printing stage of the resistance heating element.

The width of the groove is desirably about 1 to 100 μm. If the width exceeds 100 μm, disconnection or the like is likely to occur, while if the width is less than 1 μm, it is difficult to adjust the resistance value of the resistance heating element. The spot diameter of the laser beam is adjusted to 50 μm to 2 cm.

It is desirable that the trimming be performed by measuring the resistance value of the resistance heating element and based on the measured value. This is because the resistance value can be accurately adjusted. As shown in FIG. 8, the resistance value is measured, for example, by dividing the resistance heating element pattern into l ₁ to l ₆ and measuring the resistance value for each section. Then, a trimming process is performed on a section having a low resistance value.

After completion of the trimming process, the resistance value may be measured again, and if necessary, the trimming may be further performed. That is, the resistance value measurement and the trimming may be performed not only once but also two or more times.

The trimming is desirably performed after printing the resistance heating element paste and firing. This is because the resistance value fluctuates due to firing, and if trimming is performed before firing, peeling may occur due to laser light irradiation. Alternatively, the resistance heating element paste may be first printed in a planar shape (so-called solid shape) and then patterned by trimming. When trying to print in a pattern from the beginning, the thickness varies depending on the printing direction, but when printing in a plane, it is possible to print with a uniform thickness, so this is trimmed and patterned. Thereby, a heating element pattern having a uniform thickness can be obtained.

The trimming can be carried out by irradiating a laser beam, or using a polishing process such as sandblasting or belt sanding. As the laser beam, for example, YAG
A laser, an excimer laser (KrF), a carbon dioxide laser, and the like can be given.

Next, the trimming system of the present invention will be described. FIG. 3 is a block diagram showing an outline of a laser trimming apparatus used for manufacturing the ceramic heater of the present invention. When laser trimming is performed, as shown in FIG. 3, the conductor layer 12m is formed in a concentric circular shape having a predetermined width so as to include the circuit of the resistance heating element to be formed, or the resistance heating element having a predetermined pattern is formed. A disk-shaped ceramic substrate 11 on which a body is formed is fixed on a table 13.

The table 13 is provided with a motor and the like (not shown), and the motor and the like are connected to the control unit 17. The motor and the like are driven by a signal from the control unit 17. , The table 13 can be freely moved in the xy directions (or the θ direction in addition thereto).

On the other hand, a galvanometer mirror 15 is provided above the table 13. The galvanometer mirror 15 can be freely rotated by a motor 16, and is also arranged above the table 13. The laser beam 22 emitted from the laser irradiating device 14 strikes the galvanomirror 15 and is reflected to irradiate the ceramic substrate 11.

The motor 16 and the laser irradiation device 1
4 is connected to the control unit 17, and drives the motor 16 and the laser irradiation device 14 by a signal from the control unit 17 to rotate the galvanomirror 15 by a predetermined angle,
The irradiation position can be freely set in the xy directions on the ceramic substrate 11.

As described above, by moving the table 13 on which the ceramic substrate 11 is mounted and / or the galvanomirror 15, an arbitrary position on the ceramic substrate 11 can be irradiated with the laser beam 22.

On the other hand, above the table 13, the camera 2
1 is also installed, and thereby, the ceramic substrate 11
(X, y) can be recognized. The camera 21 is connected to the storage unit 18, whereby the position (x,
y) is recognized, and the position is irradiated with the laser beam 22.

The input unit 20 is connected to the storage unit 18 and has a keyboard or the like (not shown) as a terminal. A predetermined instruction or the like is input through the storage unit 18 or the keyboard. It is supposed to be.

Further, this laser trimming device is provided with a calculation unit 19, and based on data such as the position and thickness of the ceramic substrate 11 recognized by the camera 21,
Calculation for controlling the irradiation position, irradiation speed, laser light intensity, etc. of the laser light 22 is performed, and based on the calculation result, an instruction is issued from the control unit 17 to the motor 16, the laser irradiation device 14, and the like, and the galvanomirror 15 Rotate or
Irradiating the laser beam 22 while moving the table 13,
Trimming is performed substantially in parallel with the unnecessary portion of the conductor layer 12m or the direction in which the current of the resistance heating element pattern flows.

This laser trimming device has a resistance measuring section. The resistance measuring section includes a plurality of tester pins, divides the resistance heating element pattern into a plurality of sections, contacts the tester pins for each section, measures the resistance value of the resistance heating element, and applies laser light to the section. And trimming is performed substantially in parallel along the direction in which the current of the resistance heating element flows.

Next, a method for manufacturing a ceramic heater using such a laser trimming device will be specifically described. Here, the laser trimming step, which is a main part of the present invention, will be described in detail, and other steps will be briefly described. The steps other than the trimming will be described later in more detail.

First, a ceramic substrate is manufactured.
First, a formed body made of a ceramic powder and a resin is prepared. As a method of producing the formed body, a method of producing granules containing a ceramic powder and a resin, then putting the granules in a mold or the like and applying a press pressure, and a method of laminating and pressing green sheets are used. There is a manufacturing method, and a more appropriate method is selected depending on whether or not another conductive layer such as an electrostatic electrode is formed inside. Thereafter, the formed substrate is degreased and fired to produce a ceramic substrate. Thereafter, a through hole for inserting a lifter pin into the ceramic substrate, a bottomed hole for burying a temperature measuring element, and the like are formed.

Next, a conductive paste layer having the shape shown in FIG. 3 is formed on the ceramic substrate 11 in a wide area including a portion serving as a resistance heating element by screen printing or the like, and the conductive paste layer is fired. And

The conductor layer may be formed by using a physical vapor deposition method such as plating or sputtering. In the case of plating,
By forming a plating resist, in the case of sputtering or the like, by performing selective etching,
The conductor layer 12m can be formed in a predetermined region. Further, the conductor layer may be formed as a resistance heating element pattern as described above.

In this manner, the conductor layer 12m is formed in the predetermined area, or the ceramic substrate 11 on which the resistance heating element of the predetermined pattern is formed is fixed at a predetermined position on the table 13. The trimming data, the data of the resistance heating element pattern, both the trimming data and the data of the resistance heating element pattern, etc. are input from the input unit 20 in advance and stored in the storage unit 19. That is, data of a shape to be formed by trimming is stored. The trimming data is data used when trimming the side and surface of the resistance heating element pattern, trimming in the thickness direction, trimming a ladder-like pattern, and the like. It is used when a conductor layer printed in a solid pattern is trimmed to form a resistance heating element pattern. Of course, these can be used in combination.

Further, in addition to these data, desired resistance value data may be input and stored in the storage unit. In the resistance measurement unit, the resistance value is measured, and the difference between the desired resistance values is calculated, and what kind of trimming is performed to correct the desired resistance value is calculated. It generates control data.

Next, the position of the conductor layer 12m and the pattern of the resistance heating element are stored in the storage unit 18 by photographing the fixed ceramic substrate 11 with the camera 21.
An operation is performed in the operation unit 19 based on the data of the position of the conductor layer, the data of the shape to be formed by trimming, and the resistance value data as necessary, and the result is stored in the storage unit 18 as control data. Is done.

Then, a control signal is generated from the control unit 17 based on the calculation result, and a laser beam is irradiated while driving the motor 16 of the galvanomirror 15 and / or the motor of the table 13 so that the conductor layer is formed. 12
An unnecessary part of m or a part where the resistance of the resistance heating element is desired to be increased is trimmed by using the above method.

As shown in FIGS. 3 and 4, the table 13 has a fixing projection 1 in contact with the side surface of the ceramic substrate 11.
3b and a projection 13a for fitting which fits into a through hole into which a lifter pin is inserted. The ceramic substrate 11 is fixed on the table 13a using these projections. Thereafter, the production of the ceramic heater is completed through connection of external terminals, installation of a temperature measuring element, and the like. As shown in FIG. 8, the resistance value is controlled by dividing the resistance heating element pattern into two or more sections (11 to _l ).
₆ ) Then, control the resistance value for each section.

In the present invention, as described above, the resistance value is controlled by forming a groove in a part of the resistance heating element.

When a part of the conductor layer or the like is removed, a portion to be trimmed of the conductor layer or the like is trimmed by irradiating the laser beam, but the underlying ceramic substrate is greatly affected by the laser beam irradiation. It is important not to give.

Therefore, it is necessary to select a laser beam that is well absorbed by metal particles and the like constituting the conductor layer and the like, but is hardly absorbed by the ceramic substrate. As described above, the type of such a laser is, for example, Y
AG laser, carbon dioxide laser, excimer laser, UV
(Ultraviolet) laser and the like. Among these,
A YAG laser and an excimer (KrF) laser are most suitable.

The ceramic substrate 11 is preferably made of a material that hardly absorbs laser light. For example, in the case of an aluminum nitride substrate, a substrate having a carbon content of 5000 ppm or less and a low carbon content is preferable. Further, it is desirable that the surface roughness of the surface is 10 μm or less according to JIS B0601Ra. This is because when the surface roughness is large, the laser light is absorbed.

As the YAG laser, an SAG manufactured by NEC Corporation can be used.
L432H, SL436G, SL432GT, SL41
1B can be adopted. Preferably, the laser is pulsed light. This is because large energy can be applied to the resistance heating element in an extremely short time, and damage to the ceramic substrate can be reduced. The pulse is desirably 1 kHz or less. If the frequency exceeds 1 kHz, the energy of the first pulse of the laser becomes high and the laser is excessively trimmed.

The processing speed is desirably 100 mm / sec or less. If the speed exceeds 100 mm / sec, grooves cannot be formed unless the frequency is increased. As described above, since the upper limit of the frequency is 1 kHz or less, the frequency is desirably 100 mm / sec or less. Further, when forming a groove in the resistance heating element so as to reach the ceramic substrate, the output of the laser is desirably 0.3 W or more.

FIG. 1 is a bottom view schematically showing a ceramic heater 30 having the resistance heating elements 12 (12a to 12d) trimmed by the above method, and FIG.
It is the elements on larger scale sectional view. This ceramic heater 30
Then, the resistance heating elements 12 (12a to 12d) are formed on the bottom surface 11b of the ceramic substrate 11 by a concentric pattern and a bent line pattern in order to heat the wafer heating surface 11a so that the entire temperature becomes uniform. Have been.

In the ceramic heater 30, a through hole 35 for inserting a lifter pin 36 for carrying a silicon wafer 39 or the like is formed near the center.
Further, a bottomed hole 34 for inserting a temperature measuring element is formed. In addition, the resistance heating element 12 includes a metal coating layer 120.
The external terminal 33 is connected to the end of the resistance heating element 12 via a solder layer (not shown) or the like.

In the ceramic heater 30 of the present invention, an object to be heated such as a silicon wafer 39 is placed and heated while being in contact with the heating surface 11 a of the ceramic substrate 11.
Further, a concave portion, a through hole or the like is formed in the ceramic substrate, and a support pin having a spire or hemispherical tip is inserted and fixed in the concave portion or the like with the tip slightly projecting from the surface of the ceramic substrate, and the silicon wafer 39 By supporting the object to be heated, such as, with the support pins, the object may be held at a constant distance from the ceramic substrate. The distance between the heating surface and the wafer is preferably 5 to 5000 μm.

Further, by inserting a lifter pin into the through-hole and raising and lowering the lifter pin 36, an object to be heated such as a silicon wafer 39 or the like is received from the transfer device, or the object to be heated is placed on the ceramic substrate 11. Or heating while supporting the object to be heated.

When a resistance heating element is provided on the surface (bottom surface) of the ceramic substrate as in the ceramic heater of the present invention, it is desirable that the heating surface be on the opposite side of the resistance heating element forming surface. Because the ceramic substrate plays the role of heat diffusion,
This is because the temperature uniformity of the heating surface can be improved.

The ceramic substrate in the ceramic heater of the present invention is preferably a disk, and has a diameter of 1 mm.
Those exceeding 90 mm are desirable. This is because the larger the diameter, the greater the temperature variation on the heating surface.

The thickness of the ceramic substrate of the ceramic heater of the present invention is desirably 25 mm or less. This is because if the thickness of the ceramic substrate exceeds 25 mm, the temperature followability decreases. Also, its thickness is
More preferably, it is more than 1.5 mm and 5 mm or less. When the thickness is more than 5 mm, the heat is difficult to propagate, and the heating efficiency tends to decrease. On the other hand, when the thickness is less than 1.5 mm, the heat propagating in the ceramic substrate is not sufficiently diffused, so that the temperature variation on the heating surface is caused. May occur, and the strength of the ceramic substrate may be reduced to cause breakage.

In the ceramic heater of the present invention, ceramic is used as the material of the substrate. However, the ceramic is not particularly limited, and examples thereof include nitride ceramic, carbide ceramic, and oxide ceramic. Among these, as the material of the ceramic substrate,
Preference is given to nitride ceramics and carbide ceramics. This is because it has excellent heat conduction characteristics.

As the nitride ceramic, for example,
Examples include aluminum nitride, silicon nitride, boron nitride, and titanium nitride. Examples of the carbide ceramic include silicon carbide, titanium carbide, and boron carbide.
Further, examples of the oxide ceramic include alumina, cordierite, mullite, silica, beryllia and the like. These may be used alone or in combination of two or more. Of these, aluminum nitride is most preferred. This is because the thermal conductivity is the highest at 180 W / m · K.

However, the amount of carbon is reduced or the surface of the ceramic substrate is polished to 10 μm according to JIS B0601 Ra so as not to absorb the laser beam.
It is necessary to devise adjustments such as adjustment to m or less. If necessary, a heat-resistant ceramic layer may be provided between the resistance heating element and the ceramic substrate. For example, in the case of a non-oxide ceramic, an oxide ceramic may be formed on the surface.

It is desirable that the resistance heating element formed on the surface or inside of the ceramic substrate is divided into at least two or more circuits. This is because, by dividing the circuit, the amount of heat generated can be changed by controlling the power supplied to each circuit (channel), and the temperature of the heating surface of the silicon wafer can be adjusted. The number of circuits is 15
It is desirable that the number of circuits be less than. It is easy to control. In the present invention, the variation in the resistance value can be reduced, so that the number of circuits can be reduced to less than 15.

As the pattern of the resistance heating element, for example,
Concentric circles, spirals, eccentric circles, bending lines, etc.
From the point that the temperature of the entire ceramic substrate can be made uniform, a concentric one as shown in FIG.
A combination of a concentric shape and a bent shape is preferable. When the resistance heating element is formed using the above laser, it is advantageous that the wirings have a narrow and crowded pattern.

As a method for forming the resistance heating element on the surface of the ceramic substrate, the above-described method is used. That is,
A conductor paste is applied to a predetermined area of the ceramic substrate, and then a trimming process is performed by a laser after forming a conductor paste layer, or a trimming process is performed by a laser after the conductor paste is baked, and a predetermined pattern of resistance is obtained. Form a heating element. By firing, metal particles can be sintered on the surface of the ceramic substrate via a glass frit or the like. The sintering of the metal is sufficient if the metal particles and the metal particles and the ceramic are fused. The trimming is optimal after firing. This is because the resistance value fluctuates due to firing, and the resistance value can be controlled more accurately after firing. Note that a conductor layer may be formed in a predetermined region by using a plating method, a sputtering method, or the like, and may be subjected to laser trimming.

When the resistance heating element is formed on the surface of the ceramic substrate, the thickness of the resistance heating element is preferably 1 to 30 μm, more preferably 1 to 15 μm. The width of the resistance heating element is preferably 0.5 to 20 mm, and 0.5 to 5 m.
m is more preferred. Although the resistance value of the resistance heating element can be varied depending on its width or thickness, the above range is most practical. This resistance value (volume resistivity) can be adjusted by using laser light as described above.

The resistance heating element may be rectangular, semi-cylindrical or elliptical in cross section, but is preferably flat. This is because the flat surface is more likely to dissipate heat toward the heating surface, so that the temperature distribution on the heating surface is less likely to occur. The aspect ratio of the cross section (the width of the resistance heating element / the thickness of the resistance heating element) is desirably 10 to 5000. By adjusting to this range, the resistance value of the resistance heating element can be increased, and the uniformity of the temperature of the heating surface can be ensured.

When the thickness of the resistance heating element is constant, if the aspect ratio is smaller than the above range, the amount of heat transmission in the direction of the heating surface of the ceramic substrate becomes small, and the heat distribution approximates the pattern of the resistance heating element. If the aspect ratio is too large, on the other hand, if the aspect ratio is too large, the temperature immediately above the center of the resistance heating element becomes high, and eventually, a heat distribution similar to the pattern of the resistance heating element occurs on the heating surface. Would. Therefore, considering the temperature distribution, the aspect ratio of the cross section is 1
It is preferably from 0 to 5000.

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

As the metal particles, for example, noble metals (gold, silver, platinum, palladium), lead, tungsten, molybdenum, nickel and the like are preferable. These may be used alone or in combination of two or more. This is because these metals are relatively hard to oxidize and have a resistance value sufficient to generate heat. Examples of the conductive ceramic include carbides of tungsten and molybdenum. These may be used alone or in combination of two or more.

The particle size of these metal particles or conductive ceramic particles is preferably from 0.1 to 100 μm. 0.1μ
If the particle size is too small, it is easily oxidized.
If it exceeds μm, sintering becomes difficult and not only the resistance value becomes large, but also printing becomes difficult.

Although the shape of the metal particles is spherical,
It may be scaly. When these metal particles are used, they may be a mixture of the above-mentioned spheres and the above-mentioned flakes. When the metal particles are flakes or a mixture of spheres and flakes, the metal oxide between the metal particles is easily retained, and the adhesion between the resistance heating element and the nitride ceramic or the like is improved. And it is advantageous because the resistance value can be increased.

As the resin used for the conductor paste,
For example, an epoxy resin, a phenol resin, and the like can be given. Examples of the solvent include isopropyl alcohol, butyl carbitol, diethylene ether monoether, and the like. Examples of the thickener include cellulose and the like.

It is preferable that the conductor paste is obtained by adding a metal oxide (glass frit) to metal particles and sintering the resistance heating element, the metal particles and the metal oxide. In this way, by sintering the metal oxide together with the metal particles, the ceramic substrate, such as a nitride ceramic, and the metal particles can be more closely adhered.

It is not clear why the mixing with the metal oxide improves the adhesion to the nitride ceramic or the like, but the surface of the metal particles or the surface of the nitride ceramic is slightly oxidized to form an oxide film. It is considered that these oxide films are sintered and integrated via the metal oxide, and the metal particles and the nitride ceramics or the like adhere to each other. Further, when the ceramic constituting the ceramic substrate is an oxide ceramic, the surface is naturally made of an oxide, so that a conductor layer having excellent adhesion is formed.

As the metal oxide, for example,
Lead, zinc oxide, silica, boron oxide (B _Two O_Three ), Al
Selected from the group consisting of Mina, Yttria and Titania
At least one is preferred.

This is because these oxides can improve the adhesion between the metal particles and the nitride ceramic without increasing the resistance value of the resistance heating element 12.

The ratio of the above-mentioned lead oxide, zinc oxide, silica, boron oxide (B ₂ O ₃ ), alumina, yttria, and titania is such that, when the total amount of the metal oxide is 100 parts by weight, the lead oxide is in a weight ratio. 1-10, silica 1-30, boron oxide 5-50, zinc oxide 20-70, alumina 1
-10, yttria 1-50, titania 1-50, and the total is preferably adjusted within a range not exceeding 100 parts by weight. By adjusting the amounts of these oxides within these ranges, the adhesion to nitride ceramics and the like can be particularly improved.

The amount of the metal oxide added to the metal particles is preferably 0.1% by weight or more and less than 10% by weight. The area resistivity when the resistance heating element 12 is formed using the conductor paste having such a configuration is 1 mΩ / □ to 50 mΩ / □.
mΩ / □ is preferred.

When the area resistivity exceeds 50 mΩ / □, the heat generation becomes too large with respect to the applied voltage, and the ceramic substrate 11 having the resistance heating element 12 on the surface of the ceramic substrate controls the heat generation. Because it is hard to do. If the addition amount of the metal oxide is 10% by weight or more, the sheet resistivity exceeds 50 mΩ / □, the calorific value becomes too large, the temperature control becomes difficult, and the uniformity of the temperature distribution decreases. . Further, if necessary, the sheet resistivity is set to 50 mΩ.
/ □ to 10Ω / □. When the sheet resistivity is increased, the width of the pattern can be increased, so that there is no problem of disconnection.

When the resistance heating element is formed on the surface of the ceramic substrate, it is desirable that a metal coating layer is formed on the surface of the resistance heating element. This is to prevent the internal metal sintered body from being oxidized to change the resistance value.
The thickness of the metal coating layer to be formed is preferably 0.1 to 10 μm.

The metal used for forming the metal coating layer is not particularly limited as long as it is a non-oxidizing metal, and specific examples thereof include gold, silver, palladium, platinum and nickel. . These may be used alone or in combination of two or more. Of these, nickel is preferred. Further, as the coating layer, an inorganic insulating layer such as glass or a heat-resistant resin can be used.

The resistance heating element requires a terminal for connection to a power supply, and this terminal is attached to the resistance heating element via solder. Nickel prevents thermal diffusion of solder. Examples of the connection terminal include those made of Kovar.

Next, a method of manufacturing a ceramic heater according to the present invention including laser processing will be described in more detail with reference to FIG. 10 regarding steps other than the laser processing step. Since the laser processing step has been described in detail above, it will be briefly described here. FIGS. 10A to 10D are cross-sectional views schematically showing a part of the method for manufacturing a ceramic heater of the present invention including laser processing.

(1) Manufacturing process of ceramic substrate Powder of ceramic such as aluminum nitride is added
Yttria (Y_Two O _Three ), Sintering aids, binders, etc.
After preparing a slurry by mixing
Granulate by a method such as laser drying, and granulate the granules
Into a plate, etc. by pressing into
Make a body (green).

Next, as necessary, a portion serving as a through hole 35 into which a lifter pin 36 for transporting an object to be heated such as a silicon wafer 39 is inserted, or a temperature measuring element such as a thermocouple is provided. A portion having a bottomed hole for embedding is formed.

Next, the formed body is heated, fired and sintered to produce a ceramic plate. Thereafter, the ceramic substrate 11 is manufactured by processing into a predetermined shape (see FIG. 10A), but may be formed into a shape that can be used as it is after firing. Further, for example, by performing heating and baking while applying pressure from above and below, it becomes possible to manufacture a ceramic substrate 11 having no pores. Heating and firing may be performed at a temperature equal to or higher than the sintering temperature.

Normally, after firing, a through hole 35 and a bottomed hole (not shown) for inserting a temperature measuring element are provided. The through holes 35 and the like can be formed by performing a drilling process such as sand blasting using SiC particles or the like after surface polishing.

(2) Step of Printing Conductive Paste on Ceramic Substrate The conductive paste is generally a high-viscosity fluid composed of metal particles, resin and solvent. This conductor paste is printed on the region where the resistance heating element is to be provided by screen printing or the like to form a conductor paste layer 12m (FIG. 10B). The pattern of the resistance heating element is
Since it is necessary to make the temperature of the entire ceramic substrate uniform, it is desirable to form a pattern having a concentric shape and a bent shape as shown in FIG. 3, but the conductive paste layer is formed so as to include these patterns. A wide concentric or circular pattern is used.

(3) Firing of Conductive Paste The conductive paste layer printed on the bottom surface of the ceramic substrate 11 is heated and fired to remove the resin and the solvent, and sinter the metal particles.
After forming a conductor layer having a predetermined width (see FIG. 1), by performing the above-described laser trimming process,
A resistive heating element 12 having a predetermined pattern is formed (FIG. 10).
(C)). The temperature of heating and firing is 500-1000 ° C
Is preferred. Alternatively, a pattern such as a concentric circle, a spiral, a bent pattern, or the like may be formed first, and a part of the pattern may be trimmed to adjust its resistance value, thereby forming the resistance heating element 12.

(4) Formation of Metal Coating Layer It is desirable to provide a metal coating layer 1200 on the surface of the resistance heating element 12 as shown in FIG. Metal coating layer 12
00 can be formed by electrolytic plating, electroless plating, sputtering, or the like, but considering mass productivity,
Electroless plating is optimal. FIG. 10 does not show the metal coating layer 1200. Also, instead of metal,
It may be covered with a cover such as glass or resin.

(5) Attachment of Terminals, etc. Terminals (external terminals 33) for connection to a power supply are attached to the ends of the pattern of the resistance heating element 12 via solder (see FIG. 10D). Also, a thermocouple is inserted into the bottomed hole 34 and sealed with a heat-resistant resin such as polyimide or the like, and the production of the ceramic heater is completed.

The ceramic heater of the present invention can be used as an electrostatic chuck by providing an electrostatic electrode inside the ceramic substrate, and a chaptop conductor layer is provided on the surface, and a guard electrode or the like is provided inside. By providing a ground electrode, it can be used as a wafer prober.

The present invention will be described in more detail with reference to the following examples.

(Example 1) (1) Aluminum nitride powder (average particle size: 0.6 μm) 1
A composition comprising 00 parts by weight, 4 parts by weight of yttria (average particle size: 0.4 μm), 12 parts by weight of an acrylic binder and alcohol was spray-dried to prepare a granular powder.

(2) Next, this granular powder was put into a mold and molded into a flat plate to obtain a green body (green).

(3) Next, the green compact was hot-pressed at 1800 ° C. and a pressure of 20 MPa to obtain an aluminum nitride plate having a thickness of about 3 mm. Next, a disk having a diameter of 210 mm was cut out from the plate to obtain a ceramic plate (ceramic substrate 11). The ceramic substrate was drilled to form a through hole 35 for inserting a lifter pin 36 of a silicon wafer and a bottomed hole 34 (diameter: 1.1 mm, depth: 2 mm) for embedding a thermocouple.

(4) The ceramic substrate 11 obtained in the above (3)
Then, a conductor paste layer was formed by screen printing. The printing pattern was a pattern as shown in FIG.
As the conductor paste, Ag 48% by weight, Pt21
Wt%, SiO ₂ 1.0 wt%, B ₂ O ₃ 1.2 wt%, ZnO4.1 wt%, PbO3.4 wt%, ethyl acetate 3.4 wt%, butyl carbitol 17.9 wt%
The composition having the following composition was used. This conductor paste
It is an Ag-Pt paste, and the silver particles have an average particle size of 4.
It was 5 μm and scaly. Further, the Pt particles were spherical with an average particle diameter of 0.5 μm.

(5) Further, after the conductor paste layer of the heating element pattern is formed, the ceramic substrate 11 is heated and fired at 850 ° C. to sinter Ag and Pt in the conductor paste and to bake the ceramic paste on the ceramic substrate 11. Was.

As shown in FIG. 1, the pattern of the resistance heating element is seven channels 12a to 12g. Perimeter 4
Table 1 shows the variation of the resistance values in the channels before and after the trimming of the two channels (resistance heating elements 12a to 12d). Note that the channel is a circuit that performs one control by applying the same voltage when performing control. In the present embodiment, each channel has a resistance heating element (12a to 12a) formed as a continuous body.
12g).

Each channel (resistance heating elements 12a-12)
In the resistance variation in d), the inside of the channel is further divided into 20, the resistance is measured at both ends in the divided range, the average is taken as the average divided resistance value (the average value in Table 1), and Was calculated from the difference between the highest resistance value and the lowest resistance value and the average divided resistance value. Also, the resistance value in each channel (resistance heating elements 12a to 12d)
It is the sum of all resistance values measured by dividing.

(6) Next, as a trimming device, a YAG laser having a wavelength of 1060 nm (S14 manufactured by NEC Corporation)
3AL output 5W, pulse frequency 0.1-40kHz
z) was used. This device includes an XY stage, a galvanometer mirror, a CCD camera, and a Nd: YAG laser, and has a built-in controller for controlling the stage and the galvanometer mirror. The controller is connected to a computer (FC-9821 manufactured by NEC Corporation). Have been. The computer has a CPU that doubles as an arithmetic unit and a storage unit. In addition, it has a hard disk serving as a storage unit and an input unit, and a 3.5-inch FD drive.

The heating element pattern data is input from the FD drive to the computer, and the position of the conductor layer is read (reading is performed with reference to a specific portion of the conductor layer or a marker formed on the ceramic substrate). Calculate the appropriate control data, irradiate the heating element pattern almost in parallel along the direction of current flow, remove the conductor layer in that part, and remove 30%, 60%, 90% of the thickness of the resistance heating element, ceramic Until reaching the substrate, grooves each having a width of 50 μm were formed until a 2 μm groove was formed in the ceramic substrate.
The measurement was performed using a laser displacement meter manufactured by Keyence Corporation.

FIGS. 9 (a) to 9 (d) show 30%, 60%, and 90% of the thickness of the resistance heating element and grooves reaching the ceramic substrate, respectively.
The middle section is a graph showing the cross-sectional shape (height and position),
The lower part is a cross-sectional view when cut in the direction of the arrow in the external view of the upper part. However, the photos and graphs above
In order to clearly show the grooves, the grooves are formed perpendicular to the direction in which the current of the resistance heating element flows, and are actually different from the grooves formed in the above embodiment.

The resistance heating element has a thickness of 10 μm and a width of 2.4.
mm. The laser has a frequency of 1 kHz, 0.4
W output, byte size is 10 μm, machining speed is 1
0 mm / sec. Table 2 shows the resistance values of the outer four channels (resistance heating elements 12a to 12d) after trimming and the variations in each channel. The resistance variation in the channel is divided into 20 parts in the channel.
The resistance was measured at both ends within the divided range, the average was taken as the average divided resistance value, and the variation was calculated from the difference between the highest resistance value and the lowest resistance value in the channel and the average divided resistance value. The resistance value in the channel is the sum of all resistance values measured separately.

(8) Ni plating is applied to a portion to which the external terminal 33 for securing the connection with the power supply is to be attached, and then silver-lead solder paste (manufactured by Tanaka Kikinzoku Co., Ltd.) by screen printing.
Was printed to form a solder layer. Next, the external terminal 33 made of Kovar was placed on the solder layer, and heated and reflowed at 420 ° C., and the external terminal 33 was attached to the surface of the resistance heating element 12.

(9) A thermocouple for temperature control was sealed with polyimide to obtain a ceramic heater 30.

Example 2 A ceramic heater was manufactured in the same manner as in Example 1 except that the ceramic substrate was manufactured as described below, and the variation in the resistance value of the resistance heating element was measured. (1) Spray-drying a composition comprising 100 parts by weight of SiC powder (average particle size: 1.1 μm), ₄ parts by weight of B ₄ C, 12 parts by weight of an acrylic binder and alcohol,
A granular powder was produced.

(2) Next, the granular powder was put into a mold and molded into a flat plate to obtain a formed product (green).

(3) Next, the formed body was hot-pressed at 1890 ° C. and a pressure of 20 MPa to obtain a SiC plate having a thickness of about 3 mm. Further, the surface was polished with a # 800 diamond grindstone and polished with a diamond paste to Ra = 0.08 μm. Further, a glass paste (G-5177 manufactured by Shoei Chemical Industry Co., Ltd.) was applied to the surface, and the temperature was raised to 600 ° C. to form a SiO ₂ layer having a thickness of 3 μm. Next, a disk having a diameter of 210 mm was cut out from the plate, and a ceramic plate (ceramic substrate 1) was cut out.
1). Drill this ceramic substrate,
Through hole 3 for inserting lifter pin 36 of silicon wafer
5. A bottomed hole 34 for embedding a thermocouple (diameter: 1.1
mm, depth: 2 mm).

Also in this embodiment, the thickness of the resistance heating element is set at 30.
%, 60%, 90%, until it reaches the ceramic substrate
Grooves each having a width of 50 μm were formed until a groove having a depth of 2 μm was formed on the ceramic substrate.

Comparative Example 1 A ceramic heater was manufactured in the same manner as in Example 1 except that the depth of the groove was set to 15% of the thickness of the resistance heating element, and the variation of the resistance value of the resistance heating element was measured. did.

Table 1 shows the variation in the resistance values of the ceramic heaters according to Examples 1 and 2 and the ceramic heater according to Comparative Example 1 before and after trimming. The ceramic heater obtained through the above steps was evaluated by the following indices.

(1) Warpage of Substrate The flatness was measured at 17 places on the ceramic substrate using a flatness measuring device (manufactured by Nexiv). (2) Oxidation Resistance of Heating Element Heated to 350 ° C. and left for 2 weeks, and the rate of change in resistance was measured. In addition, the rate of change of the resistance value was calculated by the following equation (1). Rate of change of resistance value (%) = [(resistance value after heating−resistance value before heating) / resistance value before heating] × 100 (1)

(3) Decrease in strength of substrate A test piece was cut out in accordance with JIS R 1601, and the strength was lowered.
The lower rate was measured. The strength of the specimen is
Test machine (Type 4507 load cell 500 kgf)
Crosshead speed in air with temperature between 25 and 1000 ° C
0.5 mm / min, span distance L = 30 mm, specimen thickness
Length = 3.06 mm, width of test piece = 4.03 mm
Then, using the following calculation formula (1), the three-point bending strength σ (kg
f / mm ^Two ) Was calculated. Table 2 shows that 2
This is the bending strength at 5 ° C.

[0121]

(Equation 1)

[0122]

[Table 1]

[0123]

[Table 2]

As is clear from Table 1, when the depth of the formed groove is less than 20% of the thickness of the resistance heating element (Comparative Example 1), it is found that the variation in the resistance value cannot be suppressed. Also, as is clear from the results shown in Table 2,
In the case of the first and second embodiments, since the groove is formed at a depth of 20% or more of the thickness of the resistance heating element, the variation of the resistance value can be surely suppressed. Also, there is almost no warpage or reduction in strength of the substrate. Note that if the heating element remains at the bottom of the groove, it is presumed that a slight change in resistance is caused. Therefore, the groove reaching the ceramic substrate is optimal.

[0125]

As described above, according to the ceramic heater of the present invention, since the resistance value of the resistance heating element hardly varies, a ceramic heater excellent in temperature uniformity of the heating surface can be obtained. Further, the substrate is not damaged, and the oxidation resistance of the heating element is not reduced.

[Brief description of the drawings]

FIG. 1 is a bottom view schematically showing an example of a ceramic heater according to the present invention.

FIG. 2 is a partially enlarged sectional view of the ceramic substrate shown in FIG.

FIG. 3 is a block diagram showing an outline of a laser trimming apparatus used when manufacturing the ceramic heater of the present invention.

FIG. 4 is a perspective view schematically showing a table constituting the laser trimming device shown in FIG. 3;

FIG. 5 is a perspective view schematically showing a resistance heating element in which a groove formed by trimming is formed substantially in parallel along a direction in which a current flows.

FIG. 6 is a perspective view schematically showing a resistance heating element in which a groove formed by trimming is formed perpendicularly to a direction in which a current flows.

FIG. 7 is a photograph showing a molten resistance heating element.

FIG. 8 is a perspective view showing how a resistance heating element is divided into a plurality of regions in order to measure a resistance value.

9 (a) to 9 (d) each show a groove reaching 30%, 60% and 90% of the thickness of the resistance heating element and the ceramic substrate, and the upper part is a photograph showing the appearance, and the middle part is a photograph showing the outer appearance. It is a graph showing the shape (height and position) of the cross section.
It is sectional drawing in the case of cutting | disconnecting in the direction of arrow in the external view of an upper stage.

FIGS. 10A to 10D are cross-sectional views illustrating respective steps when manufacturing the resistance heating element of the present invention.

[Explanation of symbols]

 Reference Signs List 11 ceramic substrate 11a heating surface 11b bottom surface 12 (12a to 12g) resistance heating element 12m conductor layer 13 table 13a fitting projection 13b fixing projection 14 laser irradiation device 15 galvanometer mirror 16 motor 17 control unit 18 storage unit 19 arithmetic unit Reference Signs List 20 input unit 21 camera 22 laser beam 30 ceramic heater 33 external terminal 34 bottomed hole 35 through hole 36 lifter pin 39 silicon wafer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 3/16 H05B 3/20 393 3/20 393 H01L 21/30 567 F-term (Reference) 3K034 AA02 AA08 AA10 AA21 AA22 AA34 AA37 BB06 BB14 BC01 BC15 BC29 CA02 CA15 CA26 DA04 DA08 HA01 HA10 JA02 3K092 PP20 QA05 QB02 QB18 QB44 QB45 QB47 QB74 QB76 QC02 QC18 QC32 QC42 QC52 RF03 RF11 RF25 VO18 V01 VO05 VO05 KA04

Claims (3)

[Claims] 1. A ceramic heater having a resistance heating element formed on a ceramic substrate, wherein the resistance heating element has a groove formed therein, and the groove has a depth of 20% or more of the thickness of the resistance heating element. Ceramic heater characterized by having. 2. The ceramic heater according to claim 1, wherein a groove is formed along a direction in which a current of the resistance heating element flows. 3. The ceramic heater according to claim 1, wherein the variation of the resistance value with respect to the average resistance value of the resistance heating element is 5% or less.