JP3152898B2 - Aluminum nitride ceramic heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride ceramic heater in which a resistance heating element is buried in an aluminum nitride ceramic, for example, an ignition heater for various combustion equipment, various heating equipment and measurement equipment. It is used as a heater for heating equipment, and is particularly used for a film forming apparatus such as plasma CVD, low pressure CVD, optical CVD, and PVD in a semiconductor device manufacturing process, and an etching apparatus such as plasma etching and optical etching. It is suitable as a heater for heating a semiconductor wafer.

[0002]

2. Description of the Related Art Conventionally, tungsten (W) and molybdenum (M) have been used as ceramic heaters in alumina ceramics.
o) is known in which a resistance heating element made of a high-melting metal such as a metal is buried. This ceramic heater has excellent electrical insulation, corrosion resistance, and wear resistance, and is very inexpensive. Widely used.

For example, in a film forming apparatus used in a semiconductor device manufacturing process such as plasma CVD, low pressure CVD, optical CVD, and PVD, and in an etching apparatus such as plasma etching and optical etching, a semiconductor wafer (hereinafter, referred to as a wafer) is used. The above-described ceramic heater has been used as a heater for heating to various processing temperatures while supporting the above-mentioned ceramic heater.

However, in recent years, as the wafer size has increased and the degree of integration has been improved, higher heat uniformity and corrosion resistance have been required, making it difficult to use a ceramic heater made of alumina.

That is, since the thermal conductivity of alumina ceramics is not so high as 15 to 20 W / mk, there is a limit in suppressing the temperature variation on the heating surface of the ceramic heater, and the processing accuracy of the wafer can be improved. Did not. In addition, since the thermal shock resistance of alumina ceramics is not so high, there has been a problem that cracks are generated and broken when rapid heating and cooling are repeated to shorten the processing time.

In order to solve these problems, an aluminum nitride ceramic heater in which a resistance heating element made of a high melting point metal such as tungsten (W) or molybdenum (Mo) is embedded in aluminum nitride ceramics has been proposed. It has been proposed (see JP-A-6-151332).

This aluminum nitride ceramic heater has excellent corrosion resistance to chlorine-based and fluorine-based corrosive gases used as a deposition gas, an etching gas, and a cleaning gas in a film forming apparatus and an etching apparatus. And the thermal conductivity is 50 W / mk or more, and the high thermal conductivity is 180 W / mk or more, so that temperature fluctuation on the heating surface of the ceramic heater can be suppressed. With attention.

As a method for manufacturing such a ceramic heater made of aluminum nitride, a conductive paste containing a refractory metal such as tungsten (W) or molybdenum (Mo) is applied on a green sheet of aluminum nitride to a predetermined heating pattern. And another aluminum nitride green sheet is laminated and integrated so as to cover the heat generation pattern, and then degreased in a nitrogen atmosphere.
Some were manufactured by firing at a temperature of 1900 ° C. to form an aluminum nitride ceramic in which a resistance heating element was buried, and attaching a power supply terminal thereto.

As a method of controlling the temperature of the heat generating surface in this type of ceramic heater, a predetermined constant voltage (for example, 120 V or 200 V) according to the purpose is applied, and the temperature is raised by repeating ON-OFF. A method called PID control for controlling the speed and the heating temperature has been generally adopted.

[0010]

However, in the above-described aluminum nitride ceramic heater, a high melting point metal such as tungsten (W) or molybdenum (Mo) which forms a resistance heating element has a large temperature coefficient of resistance (TCR). Also, since the resistance value increases as the temperature rises, the PID control is performed by performing various treatments on the resistance value of the resistance heating element in the room temperature range (25 ° C.) at the stage of designing the ceramic heater. Must be set much lower than the resistance value determined in the temperature range, as a result,
When the PID control is performed, a very large current (rush current) must be applied in a region until the ceramic heater reaches the processing temperature, particularly at the start of energization. There was danger.

In order to avoid such a problem, it is conceivable to use a power supply device or wiring equipment having a large permissible current. In this case, however, it is necessary to avoid an increase in the size and cost of the power supply device and wiring equipment. I couldn't.

Further, in recent years, as the size of the wafer has been increased, the size of the ceramic heater has been required to be large such that the diameter thereof exceeds 180 mm, and these problems have become more and more important.

[0013]

[Means for Solving the Problems] Accordingly, the present inventors have conducted intensive research on a ceramic heater made of aluminum nitride which does not require disconnection of a resistance heating element and does not require a large-sized power supply device and wiring facilities. The problem is eliminated by forming the resistance heating element from one or more metal components of the elements in Groups 4a, 5a and 6a of the periodic table and the metal carbide thereof, and including the metal carbide in a specific range. I figured out what I can do.

That is, the present invention relates to an aluminum nitride ceramic heater in which a resistance heating element is buried in an aluminum nitride ceramic, wherein the resistance heating element is one of Group 4a, 5a and 6a elements of the periodic table. A ratio (I ₂ ) of the sum of the main intensity peaks (I ₁ ) of the metal components and the sum of the main intensity peaks of the metal carbides measured by X-ray diffraction, comprising at least one kind of metal component and the metal carbide thereof.
/ I ₁ ) is set to 0.9 to 6.0.

According to the aluminum nitride-based ceramic heater of the present invention, the resistance heating element embedded in the aluminum nitride-based ceramic is made of at least one metal component of Group 4a, 5a, and 6a elements of the periodic table, especially nitrided. It is composed of tungsten (W) or molybdenum (Mo) whose thermal expansion coefficient is close to that of aluminum ceramics, and metal carbide thereof, and contains a metal carbide having a smaller temperature coefficient of resistance (TCR) than the metal component in a specific range. As a result, the temperature coefficient of resistance (TCR) of the resistance heating element can be reduced.

Therefore, the amount of change in resistance in the region from the room temperature region to the heating to various processing temperatures can be reduced. Large current (rush current)
Therefore, temperature control by PID control can be performed without using a large power supply device or a wiring facility. Further, since the resistance temperature coefficient (TCR) of the resistance heating element is small, it is possible to generate heat stably over a wide temperature range.

In order to obtain such characteristics, the sum of the main intensity peak I ₁ of the metal component measured by X-ray diffraction and the main intensity peak I ₁ of the metal carbide are required.
It is important that the ratio (I ₂ / I ₁ ) to the sum of ₂ is in the range of 0.9 to 6.0.

If the ratio (I ₂ / I ₁ ) is less than 0.9, the effect of lowering the temperature coefficient of resistance (TCR) is small because the amount ratio of metal carbide in the resistance heating element is too small. When the ratio (I ₂ / I ₁ ) is larger than 6.0, the amount ratio of the metal carbide which is fragile compared to the metal or alloy constituting the resistance heating element becomes too large, so that the resistance heating element itself becomes brittle, This is because cracks occur with the repetition of the thermal cycle and the resistance heating element is disconnected.

Therefore, the ratio (I ₂ / I ₁ ) of the sum of the main intensity peak I ₁ of the metal component constituting the resistance heating element to the sum of the main intensity peak I ₂ of the metal carbide thereof is 0.9 to 0.9.
It is preferably in the range of 6.0, and more preferably in the range of 3.0 to 5.0. When the content is within such a range, the temperature coefficient of resistance (TCR) of the resistance heating element in the temperature range from room temperature to 300 ° C. or more is preferable.
Can be reduced to 3 × 10 ⁻³ or less, so that temperature control by PID control can be performed without using a large-sized power supply device or wiring equipment.

The sum of the main intensity peak I ₁ of the metal component is the value of the main intensity peak of the metal when the metal component is only one kind, and when the metal component is an alloy, the alloy is referred to as the alloy. This is a value obtained by adding the main intensity peaks of the constituent metals. Further, the sum of the main intensity peak I ₂ of the metal carbide is the value of the main intensity peak of the metal carbide when the metal carbide is only one kind,
When there are a plurality of metal carbides, this is a value obtained by adding the main intensity peaks of each metal carbide.

On the other hand, the aluminum nitride ceramics constituting the aluminum nitride ceramic heater include high-purity aluminum nitride ceramics having a purity of 99.8% or more, and rare earth elements such as Y ₂ O ₃ and Er as sintering aids. A material containing aluminum nitride in an amount of 50% by weight or more, such as an aluminum nitride ceramic containing an element oxide in a range of 1 to 9% by weight, can be used.
Among them, particularly, high-purity aluminum nitride ceramics have almost no grain boundaries in the sintered body and a small amount of impurities. Therefore, a heater for heating a film forming apparatus or an etching apparatus in a semiconductor device manufacturing process. If it is used as, the aluminum nitride ceramics containing a sintering aid has a thermal conductivity of 70 to 230 W because it is less likely to adversely affect the wafer such as contamination and particles and has excellent corrosion resistance. / Mk and high thermal conductivity, the temperature distribution on the heat generating surface can be made more uniform. It should be noted that which aluminum nitride ceramic is used may be appropriately selected according to the purpose of use.

Further, the shape of the aluminum nitride ceramic heater is not particularly limited, and may be various shapes such as a plate, a bar, or the like having a plane shape of a circle, an ellipse, or a polygon.

As a method of manufacturing such an aluminum nitride ceramic heater of the present invention, first, the above-mentioned sintering aid is added to aluminum nitride powder, if necessary, and a binder and a solvent are added and mixed. Then, a slurry is formed, and an aluminum nitride green sheet is formed by a tape forming method such as a doctor blade method.

Then, on the aluminum nitride-based green sheet, a conductor paste forming a resistance heating element is laid in a predetermined heating pattern by a screen printing method or the like. Conductive paste obtained by mixing a powder of any one of metals of Group 4a, 5a and 6a or an alloy thereof with a carbon powder and a binder and a solvent, or a binder and a solvent on a carbide of a Group 4a, 5a and 6a element of the periodic table Is used. As described above, by mixing the carbon powder with the constituent metal of the resistance heating element or using the carbide of the constituent metal, the metal carbide can be present in the resistance heating element after sintering.

Next, an aluminum nitride green sheet separately prepared so as to cover the laid heat generation pattern is laminated and thermocompression bonded to be integrated.

Then, the obtained green sheet laminate is degreased in a nitrogen atmosphere and then degreased in an oxidizing atmosphere, so that a conductor paste obtained by mixing carbon powder with metal powder has a reaction as shown in Chemical formula 1. In a conductive paste using a metal carbide, a reaction such as Chemical Formula 2 or Chemical Formula 3 is performed to adjust the amount ratio of the metal carbide in the resistance heating element. At this time, the degreasing temperature is 320 to 365. Good range of ° C.

[0027]

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[0028]

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[0029]

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This is because when the degreasing temperature is higher than 365 ° C., the ratio (I ₂ / I ₁ ) of the peak intensity by X-ray diffraction of the resistance heating element after firing becomes less than 0.9, and the resistance temperature of the resistance heating element is reduced. This is because the effect of lowering the coefficient (TCR) is small. Conversely, if the degreasing temperature is lower than 320 ° C., the ratio (I ₂ / I ₁ ) of the peak intensity by X-ray diffraction of the resistance heating element after firing is 6.0. Aluminum nitride-based ceramics after sintering due to the fact that the resistance heating element becomes brittle due to an excessively large amount ratio of fragile metal carbide compared to the metal or alloy constituting the resistance heating element, and the sinterability deteriorates This is because large voids are generated therein, and mechanical strength, corrosion resistance, heat resistance, heat conduction characteristics, and the like are greatly reduced.

The resistance heating element is buried by firing the green sheet laminate degreased in an oxidizing atmosphere at a temperature of 1800 to 2100 ° C. in a non-oxidizing atmosphere such as nitrogen or an inert gas. A densely sintered aluminum nitride ceramic is manufactured, and this ceramic is subjected to cutting and drilling to expose a part of the resistance heating element to serve as an electrode extraction portion, and to be provided on the surface of the ceramic including the electrode extraction portion. The aluminum nitride ceramic heater of the present invention can be obtained by brazing and fixing the power supply terminal.

[0032]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view showing an example of an aluminum nitride ceramic heater 1 of the present invention as a heater for heating called a susceptor used in a semiconductor device manufacturing process. , Tungsten (W), molybdenum (Mo), etc., composed of at least one metal component of the Group 4a, 5a, and 6a elements of the Periodic Table and a metal carbide thereof. The ratio (I ₂₎ of the sum of the main intensity peak I _{1 and} the sum of the main intensity peak I ₂ of the metal carbide
/ I ₁ ) is buried in the resistance heating element 4 in the range of 0.9 to 6.0, and the upper surface of the aluminum nitride ceramics 2 is used as the heating surface 3 for supporting and heating the semiconductor wafer W. A power supply terminal 5 electrically connected to the resistance heating element 4 is joined to the lower surface of the aluminum nitride ceramics 2. The power supply terminal 5 is energized to cause the resistance heating element 4 to generate heat, thereby heating the semiconductor wafer W supported on the heating surface 3. The resistance heating element 4 is made of aluminum nitride ceramics having high thermal conductivity. 2, the heat generated by the resistance heating element 4 is immediately transmitted to the heating surface 3 and the semiconductor wafer W on the heating surface 3 can be uniformly heated.

Since the resistance heating element 4 contains a metal carbide constituting the resistance heating element 4 at the ratio of the main intensity peak (I ₂ / I ₁ ), the resistance temperature of the resistance heating element 4 The coefficient (TCR) can be reduced to 3 × 10 ⁻³ or less. Therefore, the resistance value of the resistance heating element 4 in the room temperature range at the design stage of the ceramic heater 1 does not need to be so small, and the temperature of the heating surface 3 is controlled by PID control without using a large power supply device or wiring equipment. Control can be performed.

In addition, since the aluminum nitride ceramics have excellent heat resistance, corrosion resistance, and plasma resistance, they are significantly corroded and worn even when the semiconductor wafer W is attached to or detached from the semiconductor wafer or exposed to plasma in a corrosive gas atmosphere. Therefore, the semiconductor wafer W can be used for a long time without adversely affecting the semiconductor wafer W.

In the present embodiment, the heater for use in the manufacturing process of the semiconductor device has been described as an example.
It goes without saying that it can also be used as a heater for ignition of combustion equipment or a heater for heating equipment or measuring equipment.

(Experimental Example) Here, aluminum nitride ceramic heaters having different amounts of metal carbide in the resistance heating element (ratio of the main intensity peak of the metal component and the metal carbide by X-ray diffraction) were manufactured as a trial. An experiment was conducted to examine the relationship between the above-described metal carbide content ratio and the temperature coefficient of resistance (TCR) of the resistance heating element.

In this experiment, the width r25m as shown in FIG.
m, a length s50 mm, and a thickness t5 mm of a ceramic heater 11 made of a plate-like body.
9.85% high-purity aluminum nitride ceramics 1
2 and tungsten as a metal component of a resistance heating element embedded inside.

The ceramic heater 11 is prepared by adding an acrylic binder, a solvent and a plasticizer to aluminum nitride powder and mixing them for about 12 to 30 hours with a rotary mill to produce a slurry. Thus, a plurality of aluminum nitride green sheets were manufactured.

On the other hand, a conductor paste is prepared by adding a cellulosic binder, a solvent, a dispersant and a plasticizer to the tungsten carbide powder, and this conductor paste is applied to one of the above aluminum nitride green sheets as shown in FIG. After laying by a screen printing method so as to form a heat generating pattern, the remaining aluminum nitride green sheets were laminated so as to cover the heat generating pattern and integrated by thermocompression bonding. Then, the green sheet laminate is degreased in a nitrogen atmosphere, then degreased by changing the temperature in an oxidizing atmosphere, and then baked at a temperature of about 2000 ° C., thereby forming a nitrided body in which the resistance heating element 14 is embedded. After the aluminum ceramics 12 is formed and a concave portion communicating with the resistance heating element 14 is formed in the aluminum ceramic 12, a power supply terminal 15 made of an iron-cobalt-nickel alloy (trade name: Kovar) is fixed to the concave portion by brazing. Thus, the aluminum nitride ceramic heater 11 shown in FIG. 2 was manufactured.

The resistance of the aluminum nitride ceramic heater 11 in the room temperature range (25 ° C.) was measured, and the resistance at 600 ° C. was determined from the voltage and current when the heating surface 13 was heated to 600 ° C. Find the value,
The temperature coefficient of resistance was measured according to Equation 1.

The composition of the metal carbide in the resistance heating element and the amount ratio of the metal carbide were measured by X-ray diffraction.
The peak with the value closest to 0 or 100 was taken.

[0043]

(Equation 1)

The respective results are as shown in Table 1 and FIG.

[0045]

[Table 1]

As a result, as shown in Table 1, the resistance heating element 1
4 is made of tungsten and tungsten carbide, and the ratio of the amount of metal carbide is about 0.9 from FIG.
It can be seen that the temperature coefficient of resistance (TCR) of No. 4 is greatly reduced. In particular, it is understood that the temperature coefficient of resistance (TCR) of the resistance heating element 14 can be made extremely small by setting the amount ratio of the metal carbide to 3 or more.

Therefore, the amount ratio of the metal carbide is 0.9 or more,
It is understood that preferably 3 or more is good.

Next, an experiment was conducted to examine the durability by a heat cycle test in which the aluminum nitride ceramic heater 11 was heated from a room temperature range (25 ° C.) to a temperature of 600 ° C., kept in this state for 1 hour, and then cooled naturally. went.

The results are as shown in Table 2.

[0050]

[Table 2]

As a result, if the amount ratio of the metal carbide in the resistance heating element 14 is 6.0 or less, the resistance heating element 14 does not break even in the 400 thermal cycle tests, and it is possible to satisfactorily generate heat. Met.

From these results, in order to obtain a ceramic heater 11 in which the temperature of the resistance heating element 14 can be adjusted by PID control without disconnection of the resistance heating element 14 even when a heat cycle is applied, the resistance heating element 14 was measured by X-ray diffraction. it can be seen that the main intensity peak metal component when (I ₁₎ and the ratio of the metal carbide main intensity peak _{(I 2) (I 2 /} I 1) may, if the range of 0.9 to 6.0.

In this experimental example, an example is shown in which tungsten (W) is used as the metal component constituting the resistance heating element 14, but a metal such as molybdenum (Mo), titanium (Ti), rhenium (Re), or the like is used. Simple substance or tungsten (W)-
Similar results were obtained with alloys such as molybdenum (Mo) if the ratio of the main intensity peak of the metal component to the metal carbide by X-ray diffraction was in the range of 0.9 to 6.0.

[0054]

As described above, according to the present invention, in a ceramic heater in which a resistance heating element is buried in an aluminum nitride ceramic, the resistance heating element is a group 4a, 5a, 6a of the periodic table. A ratio of the sum of the main intensity peak (I ₁ ) of the metal component and the sum of the main intensity peaks of the metal carbide, which is composed of at least one metal component of the elements and the metal carbide thereof, and is measured by X-ray diffraction. (I ₂ /
By setting I ₁ ) to 0.9 to 6.0, the temperature coefficient of resistance (TCR) of the resistance heating element can be reduced to 3 × 10 ⁻³ or less. Without providing, it is possible to control the temperature of the heat generating surface by PID control, and to suppress the temperature unevenness of the heat generating surface,
Heat can be generated uniformly. Moreover, Periodic Table 4
Since the metal carbides of the elements a, 5a, and 6a are contained in the above-mentioned ratio, the plastic deformation of the resistance heating element is not hindered. Long-term use is possible without disconnection. In addition, since the aluminum nitride ceramics constituting the ceramic heater is excellent in corrosion resistance and plasma resistance, even if it is used as a heater for a film forming device or an etching device in a semiconductor device manufacturing process, for example, a semiconductor wafer Therefore, high quality products can be manufactured efficiently with little adverse effects such as particles and contamination.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example in which an aluminum nitride ceramic heater of the present invention is used for a heater called a susceptor used in a semiconductor device manufacturing process.

FIG. 2 is a perspective view showing an aluminum nitride ceramic heater used in an experiment.

FIG. 3 is a diagram showing a heat generation pattern of a resistance heating element embedded in the aluminum nitride ceramic heater of FIG.

FIG. 4 is a graph showing a relationship between an amount ratio of a metal carbide in a resistance heating element and a temperature coefficient of resistance of the resistance heating element.

[Explanation of symbols]

 1, 11: Aluminum nitride ceramic heater 2, 12: Aluminum nitride ceramic 3, 13: Heating surface 4, 14: Resistance heating element 5, 15: Power supply terminal W: Semiconductor wafer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI H05B 3/20 377 H05B 3/20 377 393 393 (58) Fields surveyed (Int. Cl. ⁷ , DB name) H05B 3/18 H01L 21/324 H01L 21/68 H05B 3/12 H05B 3/14 H05B 3/20 377 H05B 3/20 393

Claims (1)

(57) [Claims] 1. A ceramic heater in which a resistance heating element is embedded in an aluminum nitride ceramic, wherein the resistance heating element includes at least one metal component of Group 4a, 5a, and 6a elements of the periodic table and a metal component thereof. Consisting of metal carbide, X
The ratio (I ₂ / I ₁ ) of the sum of the main intensity peaks (I ₁ ) of the metal component and the sum of the main intensity peaks of the metal carbide measured by line diffraction is 0.9 to 6.0. An aluminum nitride ceramic heater characterized by the above.