JPH0594865A - Ceramic heater - Google Patents

Abstract

PURPOSE:To provide a ceramic heater the yield of which can be enhance without causing any pollution of wafer and deterioration in thermal efficiency with the wafer heated uniformly. CONSTITUTION:Each resistant heating element 4 is embedded within, for example, a disc shaped substrate 3. Each resistant heating element 4 is embedded in a spiral shape in a plane view, and mass-shaped terminals 6 are connected to both the sides of each resistant heating element 4. A heat resistant metal layer 1A is joined to the heat-generating surface 3a of the disc shaped substrate 3, and a fine natured ceramic layer 2A is then joined on the surface of the heat resistant metal layer 1A. The heat conductivity of a heat resistant metal constituting the heat resistant metal layer 1A is greater than the heat resistant conductivity of the fine natured ceramics constituting the disc shaped substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer heating apparatus used in plasma CVD, low pressure CVD, plasma etching, photo etching apparatus and the like.

[0002]

2. Description of the Related Art A semiconductor manufacturing apparatus requiring a super clean state uses a corrosive gas such as a chlorine gas and a fluorine gas as a deposition gas, an etching gas, and a cleaning gas. Therefore, if a conventional heater in which the surface of the resistance heating element is coated with a metal such as stainless steel or Inconel is used as a heating device for heating the semiconductor wafer in contact with these corrosive gases, these By exposure to gas,
Undesirable particles such as chlorides, oxides and fluorides having a particle size of several μm are generated.

Therefore, an infrared lamp is installed outside the container exposed to the deposition gas and the like, an infrared transmitting window is provided on the outer wall of the container, and infrared rays are radiated to a heated object made of a material having good corrosion resistance such as graphite, An indirect heating type semiconductor wafer heating device for heating a semiconductor wafer placed on the upper surface of an object to be heated has been developed. However, in this system, the heat loss is larger than that in the direct heating system, it takes a long time to raise the temperature, and the transmission of infrared rays is gradually hindered due to the deposition of the CVD film on the infrared transmission window.
There is a problem that the infrared transmitting window absorbs heat and the window is heated.

[0004]

In order to solve the above problems, the present inventors newly embedded a resistance heating element in a disc-shaped dense ceramic, and held this ceramic heater in a graphite case. The heating device was examined. As a result, it was found that this heating device was an extremely excellent device that eliminated the above-mentioned problems. However, when the present inventor further studied, it was found that the following problems still remained.

That is, since the side surface of the ceramic heater is held by a case made of graphite or aluminum having high heat conductivity, heat escapes from this contact portion to the case,
The temperature of the outer peripheral portion of the ceramics heater becomes lower than the temperature of the inner peripheral portion thereof, which causes a problem of impairing the thermal uniformity. Therefore, when the semiconductor wafer is heated, the temperature relatively decreases at the peripheral portion of the wafer. Therefore, for example, when the film is deposited by the thermal CVD method, the growth rate of the film at the central portion and the peripheral portion of the semiconductor wafer is high. Difference occurs, which causes a semiconductor defect.

Particularly in recent years, the size of semiconductor wafers has been increasing, and in order to cope with this, it is necessary to increase the size of ceramic heaters for heating semiconductor wafers. But,
As the diameter of the heated surface of a semiconductor wafer increases, it becomes more and more difficult to equalize it.

As a method of solving this, the present inventor
A technique for controlling the amount of heat generated from the resistance heating element by dividing the disk-shaped ceramic heater into an inner peripheral side and an outer peripheral side and independently controlling the inner peripheral side and the outer peripheral side was studied. But with this method,
The control system becomes complicated, and the cost of the controller that controls the heat generation amount increases. Further, when the ceramic substrate was formed of silicon nitride ceramics and the surface temperature was measured, the temperature still had unevenness. ．

An object of the present invention is to provide a ceramic heater which does not cause problems such as contamination of the wafer and deterioration of thermal efficiency, and which can make the heating temperature of the wafer uniform and improve the yield of the wafer. is there.

[0009]

The present invention relates to a ceramic heater for heating a wafer, which comprises a board-shaped substrate made of dense ceramics and a resistance heating element embedded in the board-shaped substrate. A heat-resistant metal layer and a dense ceramics layer are provided between the resistance heating element and the wafer,
The present invention relates to a ceramic heater in which the surface of the dense ceramic layer constitutes a wafer heating surface.

[0010]

EXAMPLE FIG. 1 is a sectional view showing a disk-shaped ceramics heater 5A according to an example of the present invention, and FIG. 2 shows a state in which the heater of this example is attached to a flange portion 19 of a thermal CVD apparatus for semiconductor manufacturing. Schematic sectional view, FIG. 3 is III-II of FIG.
FIG.

In the disk-shaped ceramics heater 5A, the resistance heating element 4 is embedded inside the dense ceramics base 3. The resistance heating element 4 is formed by winding a wire having a diameter of about 0.4 mm in a coil shape. The resistance heating element 4 is embedded in the disk-shaped substrate 3 in a spiral shape when seen in a plan view. Bulk terminals 6 are connected to both ends of the resistance heating element 4, and the surfaces of the bulk terminals 6 are exposed on the surface of the disk-shaped substrate 3. An annular protrusion 3b is formed on the side peripheral surface of the disk-shaped substrate 3.

The heat-resistant metal layer 1A is bonded to the heat-generating surface 3a of the disk-shaped substrate 3, and the heat-resistant metal layer 1A is joined to the surface of the heat-resistant metal layer 1A.
The dense ceramics layer 2A is joined. The surface of the dense ceramics layer 2A constitutes a semiconductor wafer heating surface 22. The semiconductor wafer is placed directly on the heating surface 22 or via another susceptor. The heat conductivity of the refractory metal layer 1A must be higher than the heat conductivity of the ceramics forming the dense ceramic layer 2A and the disk-shaped substrate 3.

A flange portion 19 is attached to a container of a semiconductor manufacturing thermal CVD apparatus (not shown).
Constitutes the ceiling surface of the container. An O-ring 17 hermetically seals between the flange portion 19 and a container (not shown). A removable top plate 20 is attached to the upper side of the flange portion 19, and the top plate 20 covers the circular through hole 19a of the flange portion 19. The water cooling jacket 18 is attached to the flange portion 19.

A ring-shaped case holder 14 made of graphite is fixed to the lower side surface of the flange portion 19 via a heat insulating ring 16. The case holder 14 and the flange portion 19 are not in direct contact with each other, and a slight gap is provided. A substantially ring-shaped case 11 made of graphite is fixed to the lower surface of the case holder 14 via a heat insulating ring 13. The case 11 and the case holder 14 are not in direct contact with each other, and a slight gap is provided.

A thermocouple 10 with a stainless steel sheath is inserted into a hollow sheath 9 made of molybdenum, ceramics or the like, and a thin tip of the hollow sheath 9 is joined to the back side of the ceramic substrate 3. The pair of electrode members 7 and the hollow sheath 9 are in a state of penetrating the top plate 20 and projecting their ends outside the container. Further, the pair of electrode members 7 and the hollow sheath 9 and the top plate 20 are hermetically sealed with an O-ring.

On the back side of the side peripheral surface of the disk-shaped ceramics heater 5A, the protruding portion 3b is formed in a ring shape as described above, while on the other hand, in the lower inner circumference of the case 11, it is also protruded from the case body in a ring shape. The supporting portion 11a is formed.
A predetermined space is provided between the disk-shaped ceramics heater 5A and the case 11 so that they are not in contact with each other. Then, as shown in FIGS. 2 and 3, for example, a total of four cylindrical interposition pins 21 are provided on the inner circumference of the case 11 and the ceramic heater 5A.
And the end of the intervening pin 21 is supported by the supporting part.
11a is fixed by screwing, joining, fitting, etc., and the protrusion 3b is placed on the other end, whereby the ceramic heater 5
Insulate and fix A. A rod-shaped electrode member 7 is connected to each of the pair of massive terminals 6, and one end of the electrode member 7 is connected to the lead wire 8.

According to this embodiment, since the resistance heating element 4 is embedded inside the disk-shaped substrate 3 made of dense ceramics, there is no possibility of polluting the inside of the semiconductor device. Also,
Since heat is directly generated from the disk-shaped substrate 3, there is no deterioration in thermal efficiency as in the case of the indirect heating method.

When the disk-shaped substrate 3 with the resistance heating element 4 embedded therein is used in a vacuum or in a dilute gas, heat radiation, heat transfer from the front surface, back surface, and side surfaces of the disk-shaped substrate 3 or the substrate 3 is performed. The heat is dissipated by the heat conduction to the case 11 for supporting the. Of these, the dissipation of heat from the side surface causes the temperature to decrease from the center of the disk-shaped substrate 3 toward the side surface, and hinders uniform heat distribution of the semiconductor wafer 1.

In this respect, in this embodiment, the disk-shaped substrate 3 is supported by the interposition pins 21 without directly contacting the side peripheral surface of the disk-shaped substrate 3 and the case 11. Therefore, the heat escaping from the side peripheral surface of the disk-shaped substrate 3 by heat conduction can be reduced.

Since the heat-resistant metal layer 1A is bonded to the heating surface 3a of the disk-shaped substrate 3, the heat-resistant metal layer 1A is formed.
Inside, the amount of heat moves laterally in FIG. As a result, the temperature gradient is almost eliminated in the refractory metal layer 1A,
Temperature unevenness on the semiconductor wafer heating surface 22 is prevented. Moreover, since the refractory metal layer 1A is covered with the dense ceramics layer 2A, there is no possibility that the metal constituting the refractory metal layer 1A will contaminate the semiconductor wafer.

The materials of the ceramics layer 2A and the disk-shaped substrate 3 need to be dense in order to prevent the adsorption of the deposition gas, and a material having a water absorption rate of 0.01% or less is preferable. In addition, no mechanical stress is applied, but at room temperature 1100
Those having a thermal shock resistance capable of withstanding heating up to and cooling down are preferable. From the viewpoint of thermal shock resistance, silicon nitride ceramics and sialon are preferable. However, when silicon nitride ceramics is used, the action of the refractory metal layer 1A becomes more important because the thermal conductivity of this material is low.

As the material of the heat-resistant metal layer 1A, copper, silver,
Examples include platinum, tungsten, molybdenum, nickel, tantalum, niobium, hafnium, rhenium, gold and the like. However, if gold is used, gold may diffuse toward the dense ceramics layer 2A during the heat cycle. Disk-shaped substrate 3, dense ceramics layer 2
When aluminum nitride ceramics having a high thermal conductivity is used as the material of A, the heat-resistant metal plate 1A must be formed of copper, silver, nickel or the like having a higher thermal conductivity than this.

The thickness of the dense ceramic layer 2A is 1 mm.
The following is preferable. This is because if it is too thick, the thermal conductivity in the ceramic layer 2A deteriorates and temperature unevenness occurs again. The thickness of the heat-resistant metal layer 1A is 100-800
It is preferably μm. If this is too thin, the cross-sectional area is too small to transmit heat in the lateral direction, and the effect of soaking becomes poor. If the heat-resistant metal layer 1A is too thick, excessive heat stress may be applied to the disk-shaped substrate 3 when heating and cooling are repeated.

Dense ceramics layer 2A and heat-resistant metal layer 1
There are several methods for joining the heat-resistant metal layer 1A and the disk-shaped substrate 3 to each other. That is, the high melting point metal powder may be interposed between the respective members for diffusion bonding, or for brazing with silver brazing, gold brazing or the like. Further, the raw material powder for the dense ceramics is molded as shown in FIG. 1, and this molded body is integrally fired, so that the disc-shaped ceramic heater 5A as shown in FIG. 1 can be produced.

As the resistance heating element 4, it is suitable to use tungsten, molybdenum, platinum or the like. As the resistance heating element, a wire rod, a thin sheet, or the like is used. The material of the interposition pin 21 is ceramics,
Or glass, an inorganic crystal body, a dense non-metal inorganic material is preferable, silicon oxide glass, quartz, partially stabilized zirconia,
Alumina is more preferable, and silicon oxide glass having a low thermal conductivity is more preferable.

FIG. 4 is a sectional view showing a disk-shaped ceramic heater 5B according to another embodiment of the present invention. The same functional members as those shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

On the heating surface 3a of the disk-shaped ceramic substrate 3,
The circular refractory metal layer 1B is joined. At this time, the size of the refractory metal layer 1B is made slightly smaller than the size of the heat generating surface 3a. Then, the dense ceramics layer 2 is formed on the surface of the refractory metal layer 1B.
B is provided. At this time, the edge of the refractory metal layer 1B is also covered with the dense ceramics layer 2B, and the end surface of the ceramics layer 2B is brought into contact with the edge of the disk-shaped substrate 3 to bond them. As a result, the refractory metal layer 1B is embedded in the dense ceramics and is not exposed at all in the semiconductor manufacturing container.

Next, using the ceramic heater 5A as shown in FIGS. 1 and 2, the power supply cable 8 is energized,
The resistance heating element 4 was heated to a target temperature of 450 ° C. Then, the temperature distribution of 30 points on the semiconductor wafer heating surface 22 was measured by the thermal imager. In addition, in FIG. 1 and FIG. 2, the disc-shaped ceramic heater of the type without the heat-resistant metal layer 1A and the dense ceramic layer 2A is also
The same measurement as this was performed.

First, when silicon nitride ceramics is used as the material of the disk-shaped substrate 3, the temperature distribution on the heating surface 3a is 450 ±.
It reached 10 ° C. On the other hand, in FIG. 1, when the refractory metal layer 1A is formed of silver and the dense ceramic layer 2A is formed of silicon nitride ceramics, the semiconductor wafer heating surface 22
Temperature distribution of 450 ± 1 ℃. However, both the heat-resistant metal layer 1A and the dense ceramic layer 2A have a thickness of about 50.
It was set to 0 μm.

In the above experiment, the disk-shaped substrate 3
When aluminum nitride ceramics was used as the material, the temperature distribution on the heating surface 3a was 450 ± 3 ° C. When the heat-resistant metal layer 1A is further formed of silver and the dense ceramic layer 2A is formed of aluminum nitride ceramics, the temperature distribution of the semiconductor wafer heating surface 22 is 450 ± 0.5.
℃ was reached.

The ceramic heater of the present invention can be applied to heating Fe wafers, Al wafers and the like. Further, the disc-shaped substrate includes not only the disc-shaped substrate 3 described above but also a disc-shaped substrate, a hexagonal disc, or the like. The heat-resistant metal layers 1A and 1B are replaced by C
It can also be formed by a VD method, a sputtering method, or the like.

[0032]

According to the present invention, since the resistance heating element is embedded in the board-shaped substrate made of dense ceramics, there is no possibility of polluting the inside of the device. In addition, since heat is directly generated from the board-shaped substrate, deterioration of thermal efficiency as in the case of the indirect heating method does not occur.

Further, since the refractory metal layer is provided between the resistance heating element and the dense ceramic layer, the amount of heat moves within the refractory metal layer. This prevents temperature unevenness on the wafer heating surface. Moreover, since the surface of the dense ceramics layer constitutes the wafer heating surface, there is no risk of the metal constituting the refractory metal layer contaminating the wafer.

[Brief description of drawings]

FIG. 1 is a ceramic heater 5 according to an embodiment of the present invention.
It is sectional drawing which shows A.

FIG. 2 is a schematic cross-sectional view showing a state in which the ceramic heater 5A of FIG. 1 is attached to a flange portion 19 of a semiconductor manufacturing thermal CVD apparatus.

3 is a sectional view taken along the line III-III of FIG. 2 (the electrode member 7 and the like are omitted in the drawing).

FIG. 4 is a sectional view showing a ceramic heater 5B according to another embodiment of the present invention.

[Explanation of symbols]

 1A, 1B Heat-resistant metal layer 2A, 2B Dense ceramic layer 3 Disc-shaped substrate 4 Resistance heating element 5A, 5B Disc-shaped ceramic heater 22 Semiconductor wafer heating surface

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location H01L 21/324 H 8617-4M H05B 3/14 B 8715-3K

Claims (2)

[Claims] 1. A ceramic heater for heating a wafer, comprising: a board-shaped base made of dense ceramics; and a resistance heating element embedded inside the board-shaped base,
A ceramic heater in which a heat resistant metal layer and a dense ceramic layer are provided between the resistance heating element and the wafer, and the surface of the dense ceramic layer constitutes a wafer heating surface. 2. The refractory metal layer is formed of a refractory metal selected from the group consisting of copper, silver, tungsten, molybdenum, tantalum, hafnium, rhenium, niobium, platinum and nickel. Ceramic heater.