JPH1174064A - Wafer heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a large-sized wafer heating device, which is not broken even at the time of being heated rapidly up to a high temperature over 550 deg.C and can be used repeatedly and also has high reliability. SOLUTION: In this wafer heating device, which is composed of a disc-shaped ceramic substrate 2, the upper surface of which is a retaining surface 3 of a wafer W, and a resistance exothermic body 4 buried in its inside, the resistance exothermic body 4 is arranged at the distance of 0.02-0.6 time of the thickness T of the ceramic substrate 2 from a standard face 5, which is an under surface on the opposite side of the retaining surface 3. Also, the existing area (P) of the resistance exothermic body 4 is to form a roughly round shape, and the extreme circumference thereof is located within the distance of 35 mm from the side 6 of the ceramic substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to plasma CVD, low-pressure CVD,
Film deposition equipment such as VD and PVD, plasma etching,
The present invention relates to a wafer heating device used for an etching device such as optical etching.

[0002]

2. Description of the Related Art Conventionally, in a film forming apparatus such as a plasma CVD, a low pressure CVD, an optical CVD, and a PVD used in a manufacturing process of a semiconductor device, and an etching apparatus such as a plasma etching and an optical etching, a deposition gas or the like is used. A chlorine-based or fluorine-based corrosive gas has been used as an etching gas or a cleaning gas.

Further, a stainless steel heater having a built-in resistance heating element is used as a wafer heating device for heating a semiconductor wafer (hereinafter abbreviated as a wafer) to a processing temperature while holding a semiconductor wafer in these gas atmospheres. Was.

[0004] However, the stainless steel heater has a problem that when it is exposed to the above corrosive gas, it is corroded and worn, and particles are generated.

On the other hand, it is also possible to form a wafer heating device using graphite having relatively excellent corrosion resistance to corrosive gas, and to indirectly heat the wafer heating device using an infrared lamp installed outside the chamber. However, there is a problem that the thermal efficiency is lower than that of the direct heating. In addition, in the film forming apparatus, the film is deposited on the wall surface of the chamber, and heat absorption occurs in the film, so that the wafer heating apparatus cannot be heated.

Therefore, as a wafer heating apparatus which solves such a problem, a ceramic heater in which a resistance heating element made of a high melting point metal is embedded in a disk-shaped dense ceramic base has been proposed (see, for example, Japanese Patent Application Laid-Open No. H11-157556). JP-A-4-10
No. 1381).

[0007]

By the way, in recent years, the outer diameter of a wafer has been increased from 8 inches to 12 inches from an original diameter of 6 inches in accordance with an increase in the degree of integration of semiconductor devices. As a result, large wafer heating apparatuses have been required.

[0008] Further, the heating temperature of the wafer has been increasing year by year.
Processing has been performed at a high temperature of 50 ° C. or higher, and a wafer heating apparatus capable of rapidly increasing the temperature has been required in order to increase production efficiency.

However, when a ceramic heater having a size of 8 inches or more is heated to a temperature of 550 ° C. or more, the thermal stress generated in the ceramic heater at the time of raising the temperature is increased, and there is a problem that the ceramic heater is easily broken.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reliable and large-sized wafer heating apparatus which can be repeatedly used without being damaged even if the temperature is rapidly increased to 550 ° C. or higher.

[0011]

The inventor of the present invention has conducted intensive studies on the causes of breakage in a wafer heating apparatus comprising a ceramic heater having a resistance heating element embedded therein. It has been found that the location of the buried resistance heating element is related.

That is, according to the present invention, in a wafer heating apparatus in which the upper surface of a disk-shaped ceramic base is used as a wafer holding surface and a resistance heating element is embedded therein, the lower surface opposite to the holding surface is provided. The resistance heating element is disposed at a distance of 0.02 to 0.6 times the thickness of the ceramic base from the reference plane, and the area where the resistance heating element is present is substantially circular. The outer periphery is located at a distance of not more than 35 mm from the side surface of the ceramic base.

The wafer heating apparatus according to the present invention may have any resistance heating element having any heater pattern. However, in order to uniformly heat a substantially disk-shaped wafer, the resistance heating element may be used. It is desirable that the shape of the region in which is present is substantially circular. In addition, the distance from the outermost periphery of the resistance heating element to the side surface of the ceramic substrate refers to the distance from the outermost resistance heating element in the heater pattern to the side surface of the ceramic substrate.

[0014]

Embodiments of the present invention will be described below.

FIG. 1 is a perspective view showing a wafer heating apparatus 1 of the present invention called a susceptor, FIG. 2 is a sectional view taken along line XX of FIG. 1, and FIG. 3 is a schematic view showing a heater pattern of a resistance heating element 4. .

The wafer heating apparatus 1 is composed of a disk-shaped dense ceramic base 2, has an upper surface serving as a holding surface 3 of the wafer W, and has a resistance heating element 4 embedded therein. The thickness T of the ceramic base 2 is usually 5 to 25 m.
m, the lower surface opposite to the holding surface 3 is defined as a reference surface 5, and the resistance heating element 4 is arranged at a distance from the reference surface 5 that is 0.02 to 0.6 times the thickness T of the ceramic base 2. I have.

The heater pattern of the resistance heating element 4 is as follows.
As shown in FIG. 3, the spiral shape from the center to the outer periphery,
The region P where the resistance heating element 4 is present is configured to be substantially circular, so that a substantially disk-shaped wafer can be uniformly heated.

One end of the resistance heating element 4 located at the center of the heater pattern is connected to an external terminal 7 brazed and fixed near the center of the reference surface 5, and the resistance heating element 4 located at the periphery of the heater pattern. 4 is connected to a reference plane 5 via a conductor 8 provided below the resistance heating element 4.
Is connected to the other external terminal 7 brazed and fixed in the vicinity of the center of the substrate. By applying a voltage to both external terminals 7, the resistance heating element 4 is heated, and the wafer W mounted on the holding surface 4 is heated. It is supposed to.

Reference numeral 9 denotes a cylindrical support for installing the wafer heating apparatus 1 in the chamber and for preventing the external terminals 7 from being exposed to corrosive gas in the chamber.

The reason why the embedded position of the resistance heating element 4 is set to a distance of 0.02 to 0.6 times the thickness T of the ceramic base 2 from the reference surface 5 of the ceramic base 2 is that the thickness T of the ceramic base 2 is set. Above 0.6, the resistance heating element 4 is too close to the holding surface 3 of the wafer W.
And the holding surface 3 without the resistance heating element 4
This is because the temperature difference from the upper portion becomes too large, and the temperature variation accompanying the resistance variation of the resistance heating element 4 causes the temperature variation of the holding surface 3 to exceed ± 1%, thereby hindering the soaking. Meanwhile, when the thickness is less than 0.02 times the thickness T of the ceramic base 2, a large thermal stress is applied between the resistance heating element 4 and the holding surface 3 of the ceramic base 2 at the time of rapid temperature rise, as shown in FIG. This is because the ceramic base 2 starting from the reference plane 5 is easily cracked.

In order to achieve rapid temperature rise, it is important that the distance L from the side surface 6 of the ceramic base 2 to the outermost periphery of the resistance heating element 4 be within 35 mm.

When the distance L from the side surface 6 of the ceramic substrate 2 to the outermost periphery of the resistance heating element 4 is larger than 35 mm, a large thermal stress is applied between the side surface 6 of the ceramic substrate 2 and the resistance heating element 4. This is because a crack in the ceramic base 2 starting from the side surface 6 as shown in FIG. Moreover, the outer diameter of the ceramic base 2 is
If it is equal to or slightly smaller than the wafer W, the existence area P of the resistance heating element 4 is too small compared to the wafer W, so that the uniformity at the peripheral portion of the wafer W is reduced, and chips cannot be taken out from the peripheral portion. This is because there is such a disadvantage. However, the distance L from the side surface 6 of the ceramic base 2 to the outermost periphery of the resistance heating element 4 is 0.5 mm.
Making it smaller is difficult in manufacturing.

Therefore, the distance L from the side surface 6 of the ceramic base 2 to the outermost periphery of the resistance heating element 4 is preferably 0.5 to 35 mm.

In the present embodiment, the example in which the heater pattern of the resistance heating element 4 is spiral has been described.
The heater pattern of the present invention is not limited to the spiral pattern, and is not limited to, for example, FIG.
Various heater patterns as shown in (b) can be adopted, as long as the shape of the region P where the resistance heating element 4 exists is substantially circular.

On the other hand, as a material of the ceramic substrate 2 constituting the wafer heating apparatus 1, alumina, silicon nitride, sialon, and aluminum nitride which are excellent in wear resistance and heat resistance can be used. / Mk or more, more preferably 100 W / mk or more, and is also excellent in corrosion resistance and plasma resistance to corrosive gases such as fluorine and chlorine, so that it is suitable as a material of the ceramic base 2. is there.

The resistance heating element 4 embedded in the ceramic substrate 2 may be a wire or a thin sheet film. However, a thin sheet film is preferable in that the temperature rise time can be shortened. preferable. Further, as a material constituting the resistance heating element 4, a high melting point metal such as tungsten, molybdenum, rhenium, platinum, or an alloy thereof, or a carbide or nitride of the 4a, 5a, or 6a group of the periodic table is used. And a material having a small difference in thermal expansion from the ceramic substrate 2 may be appropriately selected and used.

As a method of manufacturing such a wafer heating apparatus 1, when the resistance heating element 4 is in the form of a thin sheet film, first, the ceramic powder forming the ceramic base 2 is first added to the ceramic powder.
A slurry is prepared by adding a binder, a solvent, and the like, and after forming a plurality of green sheets by a tape forming method such as a doctor blade method, several green sheets are laminated in advance, and a resistance heating element 4 is formed on the upper surface thereof. The paste is formed into a spiral heater pattern from the center to the outer periphery as shown in FIG.

Then, after the remaining green sheets are laminated to produce a green sheet laminate, the green sheets are cut into a disk shape. In this laminating step, the buried position of the resistance heating element 4 is located at a distance of 0.02 to 0.6 times the thickness T of the ceramic base 2 from the reference plane 5 in consideration of shrinkage of the green sheet after firing. With the side surface 6 of the ceramic base 2
It is necessary to design so that the distance L from to the outermost periphery of the resistance heating element 4 is 35 mm or less.

Thereafter, the green sheet laminate is fired at a temperature at which the ceramic powder can be sintered to form the ceramic base 2 having the thin sheet film-shaped resistance heating element 4 embedded therein. The upper surface of the ceramic base 2 is polished to form the holding surface 3 of the wafer W, and the lower surface is polished to form the reference surface 5. Near the center of the reference surface 5, the resistance heating element 4 is formed. After drilling two pilot holes, each of which penetrates the resistance heating element 4 by brazing the external terminal 7 to the pilot hole.
And the external terminal 7 may be electrically connected.

When the resistance heating element 4 is a wire,
First, a binder, a solvent, and the like are added to a ceramic powder forming the ceramic substrate 2, kneaded and dried, and then granulated to produce granules. The granules are filled in a disk-shaped mold,
After a groove is formed by the upper punch, a wire forming the resistance heating element 4 is set in this groove in a spiral heater pattern extending from the center to the outer periphery shown in FIG. Then, the granules are filled and hot-pressed to form the ceramic base 2 in which the resistance heating element 4 of the wire is embedded.

Thereafter, the upper surface of the ceramic base 2 is polished to form the holding surface 3 of the wafer W, and the lower surface is polished to form the reference surface 5. After drilling two pilot holes that penetrate the resistance heating element 4, the external terminals 7 may be brazed to the pilot holes to electrically connect the resistance heating element 4 and the external terminals 7.

Although FIG. 1 shows the wafer heating apparatus 1 having only the resistance heating element 4 inside the ceramic base 2, the present invention is not limited to the wafer heating apparatus shown in FIG. Needless to say, a film-shaped electrode 10 for electrostatic adsorption or plasma generation may be buried between the body 4.

Example 1 Here, the wafer heating apparatus 1 of FIG. 1 in which the buried positions of the resistance heating elements 4 were different was prepared, and the temperature variation of the holding surface 3 and the ceramic substrate 2 when the thermal cycle was applied. An experiment was conducted on the crack generation rate of the steel.

In this experiment, the outer diameter was 300 mm and the thickness was T17.
mm disc-shaped ceramic substrate 2 was purified to 99.9 purity.
% Of an aluminum nitride-based sintered body, in which a resistance heating element 4 made of sheet-film-shaped tungsten is embedded. Further, the heater pattern of the resistance heating element 4 was a spiral pattern shown in FIG. 3 in which the existence area P was substantially circular, and the distance L from the side surface 6 of the ceramic base 2 to the outermost periphery of the resistance heating element 4 was 10 mm.

Then, a voltage is applied to the wafer heating apparatus 1 in which the resistance heating elements 4 are buried at different positions, so that the saturation temperature becomes 85.
Heat was generated so that the temperature became 0 ° C., and the temperature distribution on the holding surface 3 was measured with a product name: Thermoviewer, and the percentage of the difference between the maximum temperature and the minimum temperature with respect to the average temperature was measured.

Next, 30 wafer heating devices 1 each having a different position for burying the resistance heating element 4 were prepared, and the temperature was raised to 850 ° C. at a rate of 50 ° C./min.
After holding for a time, and then performing a thermal cycle test of cooling to 150 ° C. for 500 cycles, the crack generation rate was measured.

The results are as shown in Table 1.

[0038]

[Table 1]

As a result, the position at which the resistance heating element 4 is embedded is from the reference plane 5 of the ceramic base 2 to the thickness T of the ceramic base 2.
At a position smaller than 0.6 times of the above, the temperature variation on the holding surface 3 can be suppressed to 1.0% or less.

However, if the embedded position of the resistance heating element 4 is smaller than 0.02 times the thickness T of the ceramic base 2 from the reference plane 5 of the ceramic base 2, the ceramic base 2
Cracks occurred.

As a result, it can be seen that the buried position of the resistance heating element 4 should be arranged at a distance of 0.02 to 0.6 times the thickness T of the ceramic base 2 from the reference plane 5 of the ceramic base 2.

(Embodiment 2) Next, the embedding position of the resistance heating element 4 is set to a distance of 0.1 times the thickness T of the ceramic base 2 from the reference plane 5 of the ceramic base 2, and the side surface of the ceramic base 2 is set. 30 wafer heating apparatuses 1 each having a different distance L from 6 to the outermost periphery of the resistance heating element 4 were prepared, and the temperature was raised to 850 ° C. at a rate of 50 ° C./min, as in Example 1. The temperature was maintained at this saturation temperature for 2 hours, and then the rate of occurrence of cracks was measured after 500 cycles of a thermal cycle test in which cooling was performed to 150 ° C.

The results are as shown in Table 2.

[0044]

[Table 2]

As a result, when the distance L from the side surface 6 of the ceramic base 2 to the outermost periphery of the resistance heating element 4 was within 35 mm, the ceramic base 2 did not crack.

[0046]

As described above, according to the present invention, in the wafer heating apparatus in which the upper surface of the disc-shaped ceramic base is used as a wafer holding surface and a resistance heating element is embedded therein. The lower surface on the opposite side is used as a reference surface, and the thickness of the ceramic substrate is 0.02 to 0.6
Along with disposing the resistance heating element at twice the distance, the existence area of the resistance heating element is substantially circular, and the outermost periphery is located at a distance within 35 mm from the side surface of the ceramic base. Even if the rapid temperature increase is repeated, the wafer is not damaged by thermal stress, and the uniformity of the holding surface of the wafer W can be improved.

Therefore, by using the wafer heating apparatus of the present invention, the film formation rate and the etching rate can be increased, the production efficiency of the semiconductor device can be improved, and a high-quality semiconductor device can always be provided. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing a wafer heating apparatus of the present invention called a susceptor.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a schematic view showing a heater pattern of a resistance heating element.

FIGS. 4A and 4B are schematic diagrams showing the state of occurrence of cracks in a ceramic substrate.

FIGS. 5A and 5B are schematic diagrams showing another heater pattern of the resistance heating element. FIGS.

FIG. 6 is a longitudinal sectional view showing another wafer heating apparatus of the present invention.

[Explanation of symbols]

1 ... wafer heating device 2 ... ceramic substrate
3 ... holding surface, 4 ... resistance heating element, 5 ... reference surface, 6 ... side surface, 7 ... external terminal, 8 ... conductor, 9 ... cylindrical support, 10 ... membrane electrode, W
..Semiconductor wafers

Claims (1)

[Claims] An upper surface of a disc-shaped ceramic base is used as a wafer holding surface, and a resistance heating element is buried therein. In the wafer heating apparatus, a lower surface opposite to the holding surface is used as a reference surface, The resistance heating element is arranged at a distance of 0.02 to 0.6 times the thickness of the ceramic base from the reference plane, and the area where the resistance heating element is present is substantially circular, and the outermost periphery thereof is the ceramic. 35m from side of base
m, which is within m.