JP2531874B2 - 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 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 Corrosive gases such as chlorine gas and fluorine gas are used as a deposition gas, an etching gas, and a cleaning gas in a semiconductor manufacturing apparatus which requires a super clean state. Therefore, when 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 a state of being brought into 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 on the outside of 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 body 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 of the direct heating system, the temperature rise takes a long time, 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 heat is absorbed in the infrared transmitting window 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 that the soaking property is impaired. 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 becomes larger, it becomes more and more difficult to make it uniform.

As a method of solving this, the present inventor
The technology of controlling the amount of heat generated from the resistance heating element by dividing the disk-shaped ceramics heater into the inner peripheral side and the 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 ceramics heater for heating a semiconductor wafer, which comprises a disc-shaped substrate made of dense ceramics, and a resistance heating element embedded in the disc-shaped substrate. The heat-resistant metal layer and the dense ceramic layer are provided between the resistance heating element and the semiconductor wafer, and the radial dimension of the heat-resistant metal layer is larger than the radial dimension of the board-shaped substrate and the dense ceramic layer. The heat-resistant metal layer is small and is included and embedded in the board-shaped substrate and the dense ceramic layer so as not to be exposed to the outside, and the board-shaped substrate and the dense ceramic layer include and embedded the heat-resistant metal layer. Is formed by integral firing in a state, the board-shaped substrate and the dense ceramics layer are integrated without a bonding interface, and the board-shaped substrate and the dense ceramics layer are made of silicon nitride, Aluminum and consists chosen ceramics from the group consisting of sialon, tungsten material of the refractory metal layer, molybdenum, tantalum,
It is one or more metals selected from the group consisting of niobium, hafnium and rhenium, and the heat-resistant metal layer has a thickness of 100.
The present invention relates to a ceramics heater for heating a semiconductor wafer, which has a thickness of at least μm and at most 800 μm.

[0010]

EXAMPLE FIG. 1 is a sectional view showing a disk-shaped ceramic heater 5B 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 ceramic heater 5B, the resistance heating element 4 is embedded inside the dense ceramic substrate 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.

A heat-resistant metal layer 1B is present on the heating surface 3a side of the disk-shaped substrate 3. On the surface side of this heat resistant metal layer 1B,
A dense ceramics layer 2B is provided. The surface of the dense ceramics layer 2B constitutes the 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 1B must be higher than the heat conductivity of the ceramics forming the dense ceramics layer 2B and the disk-shaped substrate 3. And the dense ceramics layer 2
B and the disk-shaped substrate 3 are integrally sintered, and the heat-resistant metal layer 1B is embedded in the integrally sintered ceramic substrate. The size of the heat-resistant metal layer 1B is slightly smaller than the size of the heat generating surface 3a. Therefore, the edge of the refractory metal layer 1B is also covered with the dense ceramics layer 2B. 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.

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 sheath is inserted into a hollow sheath 9 made of molybdenum, ceramics or the like, and the thin tip of the hollow sheath 9 is joined to the back side of the ceramic base 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. An O-ring hermetically seals between the top plate 20 and the pair of electrode members 7 and the hollow sheath 9.

On the back side of the side peripheral surface of the disk-shaped ceramics heater 5B, the projecting 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 projected in a ring shape from the case body. The supporting portion 11a is formed.
A predetermined space is provided between the disk-shaped ceramics heater 5B 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 5B.
And one side of the interposition pin 21 as a support 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 B. 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 contaminating 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 having 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. Heat is dissipated by 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, which hinders the uniform temperature distribution of the semiconductor wafer 1.

In this respect, in the present 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 1B is bonded to the heat-generating surface 3a side of the disk-shaped substrate 3, the amount of heat in the heat-resistant metal layer 1B moves laterally in FIG. As a result, the temperature gradient is almost eliminated in the heat-resistant metal layer 1B, and the temperature unevenness on the semiconductor wafer heating surface 22 is prevented. Moreover, since the disk-shaped substrate 3 and the dense ceramics layer 2B are integrally sintered, and the refractory metal layer 1B is embedded in the integrally sintered ceramics base material, the refractory metal layer 1B is formed. There is no risk of the metal contaminating the semiconductor wafer.

The ceramics constituting the ceramics layer 2B and the disk-shaped substrate 3 need to be dense in order to prevent adsorption of the deposition gas, and the water absorption rate is 0.01.
% Or less is preferable. Further, it is preferable to use one having a thermal shock resistance capable of withstanding heating and cooling from room temperature to 1100 ° C., although no mechanical stress is applied. From the viewpoint of thermal shock resistance, silicon nitride ceramics and sialon are preferable. However, when silicon nitride ceramics is adopted, the heat conductivity of this material is low, and therefore the heat-resistant metal layer 1
The action of B becomes more important. It is also preferable to use aluminum nitride ceramics having high thermal conductivity as the material of the disk-shaped substrate 3 and the dense ceramics layer 2B.

As the material of the refractory metal layer 1B, one or more metals selected from the group consisting of tungsten, molybdenum, tantalum, niobium, hafnium and rhenium are used. If gold is used, the gold may diffuse toward the dense ceramic layer 2A during the heat cycle.

The thickness of the dense ceramics layer 2B is 1 m.
It is preferably m or less. This is because if it is too thick, the thermal conductivity in the ceramic layer 2B deteriorates and temperature unevenness occurs again. The heat-resistant metal layer 1B has a thickness of 100-80.
Set to 0 μm. If the thickness is less than 100 μm, the cross-sectional area is small, so that heat is difficult to be transferred in the lateral direction, and the effect of soaking becomes poor. The heat-resistant metal layer 1B has a thickness of 8
If the thickness exceeds 00 μm, the dense ceramics layer and the disk-shaped substrate are integrally sintered in a state where the heat-resistant metal layer 1B is embedded, so that excessive thermal stress is generated when the heating and cooling are repeated. There is a risk that the base material 3 will get caught. By setting this to 800 μm or less, the durability is improved especially when a heat cycle is applied.

A raw material powder for dense ceramics is molded as shown in FIG. 1, and this molded body is integrally fired to obtain the powder shown in FIG.
A disc-shaped ceramic heater as shown in can be prepared.

As the resistance heating element 4, it is suitable to use tungsten, molybdenum 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 preferably ceramics, glass, an inorganic crystalline material, or a dense nonmetallic inorganic material, more preferably silicon oxide glass, crystal, partially stabilized zirconia, or alumina, and silicon oxide having a low thermal conductivity. Quality glass is more preferred.

The ceramic heater of the present invention can also 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. CVD of heat-resistant metal layer 1B
It can also be formed by a sputtering method, a sputtering method, or the like.

[0027]

According to the present invention, since the resistance heating element is embedded inside the board-shaped substrate made of dense ceramics, there is no possibility of contaminating the inside of the device. In addition, since heat is directly generated from the plate-shaped substrate, deterioration of thermal efficiency unlike in the case of the indirect heating method does not occur. Further, since the resistance heating element and the dense ceramics layer are formed of a nitride ceramics base material that is integrally sintered, and the heat-resistant metal layer is embedded therein,
The amount of heat moves within the refractory metal layer. This prevents unevenness of temperature on the wafer heating surface, and there is no possibility that the metal forming the refractory metal layer contaminates the wafer. Furthermore, the resistance heating element and the dense ceramic layer are
When the refractory metal layer is formed of the above-mentioned integrally sintered nitride ceramics and the refractory metal layer is formed of the above-mentioned specific metal, the thickness of the refractory metal layer is set to 100 μm or more so that a sufficient temperature uniformity can be obtained. Property can be ensured, and by setting the thickness to 800 μm or less, it is possible to prevent breakage when repeatedly used.

[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 B.

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

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

[Explanation of symbols]

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

Claims (1)

(57) [Claims] 1. A disk-shaped substrate made of dense ceramics,
A ceramic heater for heating a semiconductor wafer, comprising a resistance heating element embedded inside the board-shaped substrate, wherein a heat-resistant metal layer and a dense ceramic layer are provided between the resistance heating element and the semiconductor wafer. The dimension of the heat-resistant metal layer in the radial direction is smaller than the dimension of the disc-shaped substrate and the dense ceramic layer in the radial direction, and the heat-resistant metal is contained in the disc-shaped substrate and the dense ceramic layer. A layer is included and embedded so as not to be exposed to the outside, and the board-shaped substrate and the dense ceramics layer are formed by integral firing in a state of including the heat-resistant metal layer, and the board-shaped substrate and the dense ceramic layer are formed. The ceramic base layer and the dense ceramics layer are integrated with each other without a bonding interface, and are made of silicon nitride, aluminum nitride and sialon. The refractory metal layer is made of ceramics selected from the group, and the refractory metal layer is made of one or more metals selected from the group consisting of tungsten, molybdenum, tantalum, niobium, hafnium and rhenium, and the refractory metal layer has a thickness of 100 μm. As described above, the ceramic heater for heating a semiconductor wafer has a thickness of 800 μm or less.