JPH11162620A - Ceramic heater and its temperature equalizing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equalize the temperature distribution on the heating surface of a ceramic heater within ±1.5% even for a large and high temperature ceramic heater. SOLUTION: This ceramic heater 1 is formed by preparing a ceramic heater 1 composed by burying heater electrodes 4 in a ceramic base substance 2, making the ceramic heater 1 generate heat, then measuring the temperature distribution of the heating surface by a temperature sensing means and thereafter cutting out a surface other than the heating surface, corresponding to a low temperature part based on the temperature distribution of the heating surface, so that a small thickness part A is partially formed on the ceramic base substance 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater in which a heater electrode is buried in a ceramic substrate, and a method for equalizing the temperature of the ceramic heater.
It is suitable as a ceramic heater used for a film forming apparatus such as a VD apparatus or an etching apparatus.

[0002]

2. Description of the Related Art Conventionally, in the manufacturing process of a semiconductor device, C
In a semiconductor manufacturing apparatus such as a film forming apparatus such as a VD apparatus or a PVD apparatus or an etching apparatus, a heater electrode is embedded to hold a semiconductor wafer (hereinafter, referred to as a wafer) and to heat the semiconductor wafer to a predetermined processing temperature. Stainless steel heaters were used.

However, in these semiconductor manufacturing apparatuses, fluorine-based or chlorine-based halogen-based corrosive gases are used as a deposition gas, an etching gas, and a cleaning gas. There has been a problem that the gas is greatly corroded by the gas, and the dust adversely affects the wafer as particles.

In order to solve these problems, a heater electrode is buried inside a ceramic base having both corrosion resistance to corrosive gas and heat resistance.
A ceramic heater whose one main surface serves as a wafer holding surface is used.

The following two methods have been proposed as methods for manufacturing this ceramic heater.

First manufacturing method: A ceramic green sheet on which a conductive paste forming a heater electrode is printed in a predetermined pattern is prepared, another ceramic green sheet is laminated thereon, and a ceramic laminate is produced. (See Japanese Utility Model Application Laid-Open No. 2-56443).

Second manufacturing method: A ceramic powder is filled in a mold, a ceramic body having a concave portion is manufactured by press molding, and a coil-like high melting point metal wire serving as a heater electrode is formed in the concave portion in a predetermined pattern shape. After that, a ceramic powder is further filled and press-molded to produce a molded body in which the heater electrode is embedded, and then hot-pressed (see Japanese Patent Application Laid-Open No. 7-220962).

[0008]

By the way, in recent years, the size of wafers has been increasing, and the diameter of the wafer was initially 6 inches, but has been increasing year by year to 8 inches and further to 12 inches. A large ceramic heater was required.

Further, the processing temperature has been increasing year by year,
℃ to 850 ℃ has been required, and the temperature distribution (difference between the minimum temperature and the maximum temperature with respect to the average temperature) on the holding surface, which is the heating surface of the ceramic heater, is ±. High heat uniformity of 1.5% or less was required.

However, conventional ceramic heaters have not been able to satisfy such characteristics.

That is, in the ceramic heater according to the first manufacturing method, in the step of printing the conductive paste forming the heater electrode, it is difficult to further reduce the printing variation due to accuracy problems in the printing press. However, the temperature distribution on the holding surface could not be increased because of the partial variation of the resistance value.

Further, in the ceramic heater according to the second manufacturing method, when a molded body in which a high-melting-point metal wire is embedded is press-formed, the coil pitch and shape of the high-melting-point metal wire deviate from design values, so that the temperature of the holding surface is reduced. The distribution could not be increased. And the temperature distribution of the holding surface tends to be such that the higher the temperature, the worse the heat uniformity. For example, when the temperature of the ceramic heater, which was within ± 1% at 400 ° C., was increased to 800 ° C., the temperature distribution deteriorated to about ± 3%.

As described above, the larger the size of the ceramic heater becomes, the worse the heat uniformity becomes. Therefore, the conventional manufacturing method has reached the limit of manufacturing a ceramic heater which can meet the demand.

[0014] For this reason, a film having a uniform thickness cannot be formed on a wafer or processed to a predetermined depth, so that the product yield is poor.

[0015]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly reliable ceramic heater having excellent uniformity even when heated to a high temperature of 550 ° C. or more, and to efficiently manufacture such a ceramic heater. Is to do.

[0016]

In view of the above problems, the present invention is directed to a ceramic heater in which a heater electrode is embedded in a ceramic base, wherein a thin portion is partially provided in the ceramic base. The temperature distribution on the heat-generating surface when heated is set to ± 1.5% or less.

Further, according to the present invention, as a method of equalizing the heat generation surface of a ceramic heater, a ceramic heater having a heater electrode embedded in a ceramic base is prepared in advance, and the ceramic heater is energized by energizing the heater electrode. After the heat is generated, the temperature distribution of the heat generating surface is measured by the temperature detecting means, and the surface other than the heat generating surface corresponding to the low temperature portion is cut off based on the temperature distribution of the heat generating surface to partially cut the ceramic base. A thin portion is formed on the surface of the heat generating surface, or a ceramic piece is joined to a surface other than the heat generating surface corresponding to a portion having a high temperature based on the temperature distribution of the heat generating surface to form a thin portion on the ceramic base. Is soaked.

[0018]

Embodiments of the present invention will be described below.

FIGS. 1A and 1B show an example of a ceramic heater according to the present invention. FIG. 1A is a perspective view seen from the upper side, FIG. 1B is a perspective view seen from the lower side, and FIG. It is XX sectional drawing.

The ceramic heater 1 is a heater for holding a semiconductor wafer and heating it to a predetermined temperature in a semiconductor manufacturing process. One main surface of the disc-shaped ceramic base 2 is used as a wafer holding surface 3. A heater electrode 4 having a film shape as shown in FIG. 2A is embedded in a ceramic base 2. The pattern of the heater electrode 4 embedded in the ceramic base 2 may be any shape as long as the holding surface 3 can be uniformly heated. In addition to the pattern shape shown in FIG. It may have a spiral shape as shown. In this embodiment, the heater electrode 4 has a film-like shape. However, the present invention is not limited to this.
It may be embedded as shown in (a) and (b). A power supply terminal 5 is joined to a bottom surface of the ceramic base 2 opposite to the holding surface 3, and is electrically connected to an end of the heater electrode 4.

As a material constituting such a ceramic substrate 1, a material which is dense and excellent in airtightness, and also excellent in corrosion resistance against corrosive gas and heat resistance at a high temperature of 550 ° C. or more is preferable. , Aluminum nitride,
Ceramics containing silicon nitride, sialon, boron carbide, or the like as a main component can be used. Among them, ceramics containing aluminum nitride or boron carbide as a main component have a thermal conductivity of 60 W / mk or more, and are easy to obtain a uniform temperature.

The material constituting the heater electrode 4 and the power supply terminal 5 is preferably such that the difference in thermal expansion from the ceramic base 2 is as small as possible, for example, a high melting point metal such as tungsten, molybdenum, rhenium, or an alloy thereof. Further, conductive ceramics mainly composed of carbides, nitrides, and silicides of ■ a ■ a and ■ a groups can be used.

By the way, the ceramic heater 1 of the present invention
Is characterized in that the ceramic base 2 has a partially thin portion A.

In FIG. 1, a thin portion A is formed in the ceramic base 2 by partially forming a cutout 6 in the bottom surface of the ceramic base 2 opposite to the holding surface 3.
By forming such a thin portion A, the holding surface 3 of the ceramic heater 1 can be uniformly heated.

That is, when the film-shaped heater electrode 4 is embedded in the ceramic base 2 as in the ceramic heater 1 of FIG. 1, it is manufactured by the first manufacturing method described in the description of the prior art. In the step of printing the conductive paste forming the heater electrode 4, the resistance value of the heater electrode 4 may partially vary due to a problem of accuracy in a printing machine, and the temperature unevenness of the holding surface 3 which is a heating surface may be suppressed. Although not possible, the present invention provides a notch 6 having a depth corresponding to the temperature gradient at a place where the temperature of the ceramic base 2 becomes low due to the variation of the resistance value of the heater electrode 4. Since the thin portion A is formed at the bottom, the heat capacity at that location can be reduced and the temperature can be increased.

Therefore, the temperature distribution of the holding surface 3 when the ceramic heater 1 generates heat is adjusted to the required ± 1.5
% Or less.

By the way, as a method of equalizing the temperature of the ceramic heater 1, the disk-shaped ceramic heater 1 in which the notch 6 is not formed is heated in advance, and the temperature distribution of the holding surface 3 is adjusted by a thermocouple, a thermoviewer, or the like. After the measurement by the temperature detecting means, the bottom surface of the ceramic substrate 2 at a high temperature is masked with a resin or a gum tape based on the temperature distribution, and the ceramic substrate 2 at a low temperature is measured.
After the notch 6 is formed by performing a trimming process on the bottom surface of the substrate, masking may be removed. As the means for forming the notch 6, blasting, machining, and laser processing can be used, and among these, blasting and machining are particularly preferable because of good processing accuracy and finished state.

According to the soaking method, it is possible to easily obtain a temperature distribution of ± 1.5% or less, which cannot be achieved in the manufacturing process of the ceramic heater 1.

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

FIGS. 3A and 3B show another example of the ceramic heater of the present invention. FIG. 3A is a perspective view seen from the upper surface side, and FIG.
FIG. 3 is a perspective view as viewed from the lower surface side, and FIG. 3C is a sectional view taken along line YY in FIG.

The ceramic heater 11 is configured such that one main surface of a disk-shaped ceramic base 12 is attached to a wafer holding surface 13.
A heater electrode 14 in which a coil-like high melting point metal wire is spirally arranged as shown in FIG. 2B is embedded in a ceramic base 12. A power supply terminal 15 is joined to a bottom surface of the ceramic base 12 opposite to the holding surface 13, and is electrically connected to an end of the heater electrode 14.

In the ceramic heater 11, the ceramic piece 16 is partially joined to the bottom surface of the ceramic base 12 to provide a partial thin portion A 'on the ceramic base 2 to equalize the temperature of the holding surface 13. It is like that.

That is, when the heater electrode 14 made of a coil-like high melting point metal wire is embedded in the ceramic base 12 like the ceramic heater 11 of FIG. 3, it is manufactured by the second manufacturing method described in the description of the prior art. However,
According to this manufacturing method, the coil pitch and the shape of the refractory metal wire deviate from the design values during press molding for embedding the refractory metal wire, and as a result, it is impossible to suppress the temperature unevenness of the holding surface 13. In this method, a ceramic piece 16 having a thickness corresponding to the temperature gradient is joined to a high-temperature portion of the ceramic base 12 to increase the heat capacity of the portion and lower the temperature.

Therefore, the temperature distribution of the holding surface 3 when the ceramic heater 1 is heated is set to ± 1.5% as required.
It can be:

By the way, as a method of equalizing the temperature of the ceramic heater 11, the disk-shaped ceramic heater 11 to which the ceramic pieces 16 are not bonded in advance is heated, and the temperature distribution of the holding surface 13 is adjusted by a thermocouple, a thermoviewer, or the like. After the measurement by the temperature detecting means, the ceramic piece 16 having a thickness corresponding to the temperature gradient may be joined to a location having a high temperature based on the temperature distribution. This ceramic piece 1
As the joining means 6, a concave portion is provided on the bottom surface of the ceramic base 12 for joining the ceramic piece 16, a threaded metal member is inserted and fixed in the concave portion, and the ceramic piece 16 is bolted or the ceramic piece 16 is fixed. After a ceramic paste of the same composition is applied to the bottom surface of the ceramic base 12 to be joined, the ceramic pieces 16 may be bonded together and integrally fired to join.

(Example) A specific example of the ceramic heater 1 shown in FIG. 1 will be described below.

First, a ceramic heater 1 in which a film-like heater electrode 4 made of tungsten shown in FIG. 2A is embedded in a ceramic base 2 mainly composed of aluminum nitride is manufactured.

Specifically, a slurry was prepared by adding a binder and a solvent to AlN powder having a purity of 99%, and a plurality of ceramic green sheets having a thickness of about 0.4 mm were formed by a doctor blade method. A WC paste mixed with AlN powder is printed on the surface of one of the ceramic green sheets in a pattern shape shown in FIG. 2B by a screen printer, and the remaining ceramic green sheets are sequentially laminated and adhered. After being cut into a disk shape and subjected to a binder removal treatment in a nitrogen atmosphere at a temperature of several hundred degrees, it is further baked at a high temperature of 2000 ° C. in a nitrogen atmosphere to thereby bury the film-shaped heater electrode 4 made of tungsten. Substrate 2 was obtained.

Then, the ceramic substrate 2 is subjected to grinding and polishing to form a holding surface 3 on one main surface,
After two recesses communicating with the ends of the heater electrodes 4 were formed in the other bottom surface, the power supply terminals 5 were brazed to the recesses to manufacture the ceramic heater 1.

Next, a power supply was connected to the power supply terminal 5 of the ceramic heater 1 and an AC voltage of 60 Hz and 150 V was applied to heat the ceramic heater 1 to 800 ° C.
The temperature distribution on the holding surface 3 was measured with a thermoviewer. As a result, the temperature distribution of the holding surface 3 as the heat generating surface was ± 3%.

Next, based on the temperature distribution measured by the thermoviewer, the bottom surface of the ceramic base 2 corresponding to a high temperature portion is masked with a resin, and a cutout 6 corresponding to a temperature gradient is formed by blasting. After the trimming process, the resin was removed to obtain the ceramic heater 1 shown in FIG.

Then, when an AC voltage of 60 Hz and 150 V is applied again to the ceramic heater 1 to heat the ceramic heater 1 to 800 ° C., the temperature distribution of the holding surface 3 which is the heating surface is set to ± 1.0%. As a result, the required value of ± 1.5% or less was sufficiently satisfied.

[0043]

As described above, according to the ceramic heater of the present invention, a ceramic heater in which a heater electrode is embedded in a ceramic base is prepared, and the ceramic heater is caused to generate heat so that the temperature distribution on the heat generating surface is controlled. After the measurement by the detecting means, based on the temperature distribution of the heat-generating surface, the surface other than the heat-generating surface corresponding to the low-temperature portion is cut off to partially form a thin portion on the ceramic base, or the temperature of the heat-generating surface is measured. Since the ceramic piece was joined to the surface other than the heat generating surface corresponding to the high temperature portion based on the distribution to form a thin portion on the ceramic base,
Even with a large-sized and high-temperature ceramic heater, the temperature distribution on the heating surface can be easily soaked to ± 1.5% or less.

Therefore, if the ceramic heater of the present invention is used in a film forming apparatus, a uniform film can be formed, and if it is used in an etching apparatus, it can be processed to a predetermined depth. Can be greatly increased.

[Brief description of the drawings]

1A and 1B are views showing an example of a ceramic heater according to the present invention, wherein FIG. 1A is a perspective view as viewed from above, FIG. 1B is a perspective view as viewed from below, and FIG. It is an X-ray sectional view.

FIGS. 2A and 2B are diagrams respectively showing the pattern shapes of heater electrodes.

3A and 3B are views showing another example of the ceramic heater of the present invention, wherein FIG. 3A is a perspective view seen from the upper side, FIG. 3B is a perspective view seen from the lower side, and FIG. It is YY line sectional drawing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ceramic heater 2 ... Ceramic base 3 ... Holding surface 4 ... Heater electrode 5 ... Power supply terminal 6 ... Notch part A ... Thin part

Claims (2)

[Claims] 1. A ceramic heater having a heater electrode embedded in a ceramic substrate, wherein a temperature distribution on a heating surface is reduced to ± 1.5% or less by forming a thin portion partially on the ceramic substrate. Ceramic heater characterized by doing. 2. A ceramic heater in which a heater electrode is embedded in a ceramic substrate is prepared, and the heater electrode is energized to generate heat, so that the temperature distribution on the heating surface is measured by a temperature detecting means. The surface other than the heat-generating surface corresponding to the low-temperature portion is cut off based on the temperature distribution of the heat-generating surface to form a thin portion partially on the ceramic substrate, or the temperature is calculated based on the temperature distribution of the heat-generating surface. The ceramic heater is characterized by forming a thin part in the ceramic base by joining a ceramic piece to the surface other than the heat generating surface corresponding to the high part, and making the heat generating surface uniform. Method.