JPH0785473B2 - Semiconductor wafer heating device - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is applicable to plasma CVD, low pressure CV.
The present invention relates to a semiconductor wafer heating device used in D, plasma etching, photo-etching devices and the like.

[0002]

2. Description of the Related Art In semiconductor manufacturing equipment requiring a super clean state, a corrosive gas such as chlorine gas or fluorine gas is used 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 wafer in contact with these corrosive gases, these gases are used. The exposure to the above-mentioned causes the generation of undesirable particles such as chlorides, oxides and fluorides having a particle size of several μm.

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 object made of a material having good corrosion resistance such as graphite, An indirect heating type wafer heating device has been developed which heats a wafer placed on the upper surface of an object to be heated. However, compared with the direct heating type, this type has a large heat loss, takes a long time to rise in temperature, and the transmission of infrared rays is gradually hindered due to the deposition of the CVD film on the infrared transmitting window. There is a problem that the 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, this heating device was found to be 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 edge of the wafer.
When a film is deposited by the D method, the growth rate of the film is different between the central part and the peripheral part of the wafer, which causes a semiconductor defect.

Furthermore, when silicon nitride is used as a dense ceramic substrate for a ceramic heater, if cleaning is performed with ClF ₃ , NF ₃ or the like at a temperature exceeding 100 ° C., the surface of the silicon nitride substrate is corroded by the cleaning gas. I understand that it will be done. In order to avoid this, after forming the film on the semiconductor wafer, it was necessary to once lower the temperature to 100 ° C. or lower and perform cleaning.

The object of the present invention is to prevent the problems such as contamination of semiconductor wafers and deterioration of thermal efficiency, and to make the heating temperature uniform between the central part and the peripheral part of the semiconductor wafers, thereby improving the yield of semiconductor wafers. It is an object of the present invention to provide a semiconductor wafer heating apparatus capable of improving the temperature.

[0008]

DISCLOSURE OF THE INVENTION A semiconductor wafer heating apparatus according to the present invention is a plate-shaped ceramics heater in which a resistance heating element is embedded in a plate-shaped substrate made of dense ceramics. A wafer mounting plate made of a corrosion-resistant inorganic material fixed so as to abut the heating surface, and a gap is formed between the heating surface of the plate-shaped ceramics heater and the wafer mounting plate, and It is configured to place a semiconductor wafer on the surface, the outer diameter of the semiconductor wafer is less than or equal to the outer diameter of the heat generating surface, the outer diameter of the gap is smaller than the outer diameter of the semiconductor wafer, and the gap of the semiconductor wafer is smaller than that of the semiconductor wafer. It is characterized in that it is located toward the central portion side, and the contact portion between the heating surface and the wafer mounting plate is located towards the side peripheral portion side of the semiconductor wafer. As the "corrosion resistant inorganic material", graphite, aluminum, nickel, quartz glass, silicon carbide, alumina and the like are preferable.

[0009]

FIG. 1 is a sectional view showing a state in which the heating device of this embodiment is attached to the flange portion of a thermal CVD device for semiconductor production. A flange portion 19 is attached to a container of a thermal CVD apparatus for semiconductor production (not shown), and the flange portion 19 constitutes a 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 on the upper side of the flange portion 19.
20 is attached, 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 surface of the flange 19 via a heat insulating ring 16. Case holder 14 and flange 19
There is no direct contact with and there is a slight gap. 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 resistance heating element 4 is embedded in a spiral shape inside a disk-shaped base body 3 made of dense ceramics to form a disk-shaped ceramic heater 5A.
Make up. Bulk terminals 6 are connected to both ends of the resistance heating element 4. The lump terminals 6 are embedded in the ceramic base 3 on the back side of the ceramic base 3 so that the surface thereof is exposed. In the pair of massive terminals 6,
The rod-shaped electrode members 7 are connected to each other, and one end of the electrode member 7 is connected to the lead wire 8.

A thermocouple 10 with a stainless steel sheath is inserted into a hollow sheath 9 made of molybdenum or the like, and a 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. In addition, the pair of electrode members 7 and the hollow sheath 9
An O-ring is used to hermetically seal between the top plate 20 and the top plate 20.

An extension portion 5c is formed in a ring shape on the back side of the side peripheral surface of the disk-shaped ceramic heater 5A, while a support portion 11a that also protrudes from the case body in a ring shape is formed on the lower inner periphery of the case 11. Are formed. Place a predetermined interval between the disk-shaped ceramic heater 5A and the case 11,
Do not contact them. Then, as shown in FIGS. 1 and 2, for example, a total of four cylindrical interposition pins 25 are provided in the case 11.
It is interposed between the inner periphery and the side peripheral surface of the ceramics heater 5A, one end of the intervening pin 25 is screwed onto the support portion 11a, fixed by joining, fitting, etc., and the extending portion 5c is provided on the other end. It is placed and the ceramic heater 5A is adiabatically fixed thereby.

The heating surface 5b of the disc-shaped ceraminex heater 5A
As shown in FIG. 3, a concave portion 5a is formed in this. The concave portion 5a is formed substantially imitating the planar shape of the present 6-inch semiconductor wafer, and has an arc-shaped contour 22 and a linear contour 21.

The plane-circular wafer 2A made of corrosion-resistant inorganic material is bonded and fixed to the lower surface of the case 11 and the heating surface of the disk-shaped ceramics heater 5A. A recess 2a is also provided on the wafer mounting surface 2c side of the wafer mounting plate 2A. The shape of the recess 2a is the same as the shape of the recess 5a described above. Also, when viewed in a projection view in the vertical direction A with respect to the heating surface 5b,
The respective members are arranged so that the recess 5a and the recess 2a occupy substantially the same region. The semiconductor wafer 1 is placed on the wafer placement surface 2c. In the example of FIG. 1, the outer diameter of the semiconductor wafer 1 is substantially the same as the outer diameter of the heat generating surface 5b. The atmosphere in the container facing this heating device is usually high vacuum, and thermal CVD
When the gas for supply is supplied into the container, the pressure inside the container increases.

The material of the disk-shaped substrate 3 needs to be a dense body in order to prevent adsorption of the deposition gas, and a material having a water absorption rate of 0.01% or less is preferable. Although it is not subjected to mechanical stress, it is required to have thermal shock resistance that can withstand heating and cooling from room temperature to 1100 ° C. From these points, it is preferable to use a silicon nitride sintered body, sialon, or the like, which is a ceramic having high strength at high temperature.
Furthermore, it is effective to fire the base 3 by hot pressing or the HIP method in order to obtain a dense body.

In the semiconductor manufacturing apparatus, it is necessary to prevent the invasion of alkali metals and alkaline earth metals, and it is preferable not to use alkaline earth metals such as magnesium as a sintering aid for the base body 3. , Alumina and ytterbium are preferred.

As the resistance heating element 4, it is suitable to use tungsten, molybdenum, platinum or the like, which has a high melting point and is excellent in adhesion to silicon nitride. As the resistance heating element, a wire rod, a thin sheet, or the like is used. The material of the interposition pin 25 is preferably ceramics, glass, an inorganic crystal, or a dense non-metal inorganic material,
Silicon oxide glass, quartz and partially stabilized zirconia are more preferable, and silicon oxide glass having a low thermal conductivity is more preferable.

According to the heating device of this embodiment, the following effects can be obtained. Disc-shaped substrate 3 made of dense ceramics
Since the resistance heating element 4 is embedded in the inside of the semiconductor device, there is no possibility of contaminating the inside of the semiconductor device. Further, since the heat generating surface 5b is provided on the disk-shaped substrate 3, the deterioration of the thermal efficiency unlike the case of the indirect heating method does not occur.

When the disk-shaped substrate 3 with the resistance heating element 4 embedded therein is used in vacuum or in a dilute gas, heat radiation, heat transfer from the front surface, the back surface, and the side surface of the disk-shaped substrate 3 or the substrate 3 is supported. The heat is dissipated by the heat conduction to the case 11 for the purpose. 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.

On the other hand, in this embodiment, a gap 23 is provided between the heating surface 5b and the wafer mounting plate 2A by the recess 5a, and a gap is provided between the wafer mounting surface 2c and the semiconductor wafer 1 by the recess 2a. A section 24 is provided. At the contact portion α between the disk-shaped substrate 3 and the wafer mounting plate 2A, the two are in close contact with each other, so that the thermal contact resistance at the interface is extremely small. Similar to this, wafer mounting plate
Even in the contact portion β between the 2A and the semiconductor wafer 1, the two are almost in close contact with each other.

Therefore, the wafer mounting plate 2A and the disk-shaped substrate 3
At the contact portion α with, the heat energy generated from the ceramics heater is transported by heat conduction and heat radiation. The same applies to the contact portion β between the wafer installation plate 2A and the semiconductor wafer 1. On the other hand, in the gap 23, thermal energy is simply transferred by thermal radiation. In the gap 24, heat also moves in the same manner.

Since the gaps 23 and 24 are provided on the central side of the disk-shaped substrate 3 and the wafer mounting plate 2A, respectively, the heat supply amount to the side peripheral portion of the semiconductor wafer 1 is relatively large as a whole. Can be increased to This allows
It is possible to offset the heat dissipation from the side peripheral portions of the disk-shaped substrate 3 and the wafer mounting plate 2A, and make the temperature of the semiconductor wafer 1 uniform as a whole.

Further, the disk-shaped substrate 3 is a case 11 made of graphite and a wafer installation plate 2A made of a corrosion-resistant inorganic material.
The disc-shaped substrate 3 is protected by the corrosive etching gas. Therefore, it is possible to effectively prevent corrosion of the dense ceramics forming the disk-shaped substrate 3. Further, it becomes possible to carry out the cleaning at a relatively high temperature of, for example, 150 to 200 ° C.

Next, preferable dimensions of the recesses 2a and 5a will be described. First, the case where the pressure is low will be described. Recess 2
The depth d of a and 5a is preferably equal to or less than the mean free path of gas molecules. Here, the mean free path means an average distance over which a gas molecule can fly without colliding with another gas molecule.

In this case, since the depth d of the recesses 2a and 5a is generally smaller than the mean free path λ of the gas molecules, the gap 23,
At 24, the flow of thermal energy is not proportional to the temperature gradient, but only to the temperature difference between the hot and cold surfaces, independent of the distance d between the hot and cold surfaces. Also, the flow of thermal energy is proportional to the pressure in the gaps 23, 24. The mean free path λ of gas under medium and high vacuum is represented by the following equation. λ = 5 × 10 ^-3 / pp (Torr) Therefore, λ is about 5 cm at 10 ^-3 Torr and about 50 cm at 10 ^-4 Torr.
Becomes Actually, in a metal CVD device etc., 10
^{Since the} semiconductor wafer is heated under a pressure of about ^-4 Torr,
In this case, d should be 50 cm or less.

In a metal CVD apparatus or the like, the pressure for forming a film on a semiconductor wafer is several Torr to several tens To.
rr, which is relatively high, unlike the case where the pressure is low as described above. In such a low vacuum state, in the gaps 23 and 24, the amount of transfer of thermal energy is proportional to the temperature gradient (T ₁ −T ₂ ) / d between the hot surface and the cold surface (T ₁ −T ₂ is , The temperature difference between the hot and cold surfaces), and therefore the depth d of the recesses 2a, 5a.
Depends on. Therefore, it is necessary to determine d according to the required heat treatment temperature. According to the study by the present inventor, from room temperature
In the temperature range of 600 ° C., d was optimally set to 0.1 mm to 2 mm.

Next, the preferable diameter B of the recess 5a will be described with reference to FIGS. First, in this embodiment, in the disk-shaped substrate 3, the amount of heat generated by the resistance heating element 4 embedded in a given area is made substantially constant. Under this condition, due to the principle of heat conduction, as shown in FIG.
The temperature at each position was proportional to the square of the distance from the center O of the heat generating surface 5b. Area of the heat generating surface 5b is so pi] r ² When the radius is r, the area average temperature area pi] r ^2/2
On the circumference of the circle, that is, the distance from the center O is 1 / √2
The temperature T ₀ at the position r. Further, if the temperature of the center O is T ₁ and the temperature on the circumference of the heating surface 5b is T ₂ , then T ₀ is T ₁
And is the median of T ₂ .

The radius B of the arc-shaped contour 22 of the recess 5a
Is preferably equal to 1 / √2 · r or larger than 1 / √2 · r. The same applies to the dimensions of the recess 2a. The radius B of the arcuate contour of the recesses 5a, 2a is 1 /
√2 · r, the depth d of the recesses 5a, 2a is 2 mm, and
The semiconductor wafer heating device shown in FIG. 4 was produced. A 6-inch wafer 1 is installed as shown in FIG.
Heated at ° C. When the temperature distribution was measured at 30 points with a thermal imager, a temperature distribution of 450 ± 3.1 ° C was obtained.

Incidentally, so-called two-zone heating can be applied when the heat is generated from the heat generating surface 5b. For example, in FIG.
In the above, the heat generation amount per unit area can be made relatively small within the circumference from the center O to the radius B, and the heat generation amount per unit area can be made relatively large outside this circumference. Thereby, even if the heat dissipation amount in the side surface direction of the disk-shaped substrate 3 is large, it is possible to compensate the heat loss due to the heat dissipation amount and prevent deterioration of the heat uniformity.

In order to increase the amount of heat generated per unit area on the heating surface 5b, the number of windings of the resistance heating element is increased, the embedding pitch of the spiral heating element is decreased, and a high resistance material is used. There are methods such as increasing the specific resistance by using it, increasing the specific resistance by reducing the cross-sectional area, and increasing the applied voltage only in that part.

In this case, the total calorific value from the heating surface 5b is
As compared with the case shown in FIG. 4, the average temperature T ₀ also rises. In this case, the temperature of each point on the heat generating surface 5b is integrated, and this integrated value is divided by the area πr ² of the heat generating surface 5b to calculate the average temperature T ₀ of the heat generating surface 5b. And FIG.
The arcuate contour 22 of the recess 5a shown in is located outside the position where the temperature is T ₀ on the heating surface 5b.

5 and 6 are sectional views showing a heating device according to another embodiment of the present invention. However, in FIG.
In FIG. 6, the flange and the like are not shown. Figure 5
In the above, the disc-shaped substrate 3 of the disc-shaped ceramic heater 5B is not provided with the concave portion 5a, and the heating surface 5b is a flat surface. On the other hand, the concave portion 2a is formed on the wafer setting surface 2c side of the wafer setting plate 2B.
Not only is provided, but also a recess 2b is provided on the surface opposite to this. Then, the concave portion 2b forms the gap portion 23A, and the concave portion 2a forms the gap portion 24. The shapes of the gaps 23A, 24 are similar to those of the gaps 23, 24 shown in FIG. Also in this embodiment, the same effect as that of the above embodiment can be obtained.
Moreover, since it is not necessary to process the surface of the disk-shaped substrate 3 made of dense ceramics to form the concave portion, the processing is relatively easy.

In the example shown in FIG. 6, a wafer mounting plate
The recess 2a was not provided in 2C, and the wafer mounting surface 2c was made flat.
Therefore, the temperature of the semiconductor wafer 1 is adjusted by the void 23A.
Done by.

In a ceramic heater having a resistance heating element embedded therein as shown in FIG. 1, a region (hot spot) having a locally higher temperature or a region having a lower temperature locally than the surrounding region may occur. is there. That is, as shown in FIG. 7, when the semiconductor wafer 1 is placed and heated and the temperature of the surface of the semiconductor wafer 1 is measured, a region H having a temperature higher than the surroundings may be generated. In this case, several inorganic plates 26 having substantially the same shape as the region H are inserted to perform thermal insulation. As the inorganic plate 26, it is preferable to use a plate made of tungsten, molybdenum or the like having a thickness of about 0.1 mm.

When a region C having a low temperature locally occurs, a disc-shaped body 27 made of a corrosion-resistant inorganic material such as graphite is fixed in the gap 23, and the disc-shaped body 27 is disc-shaped.
And the wafer setting plate 2A. As a result, the amount of heat transferred to the periphery of the region C is increased, so that the thermal uniformity is improved.

When a region having a lower temperature than the surroundings extends over a wide area, a through hole 28 is formed in the disk-shaped substrate 3, and a pipe 29 is passed through the through hole 28. Then, an inert gas is introduced into the gap 23 through the pipe 29, convection due to heat is promoted in the gap 23, and soaking of the semiconductor wafer 1 is achieved.

In each of the above examples, the outer diameter of the semiconductor wafer 1 is set to be substantially the same as the outer diameter of the heat generating surface 5b.
The outer diameter of the semiconductor wafer 1 may be smaller. The present invention can also be applied to a semiconductor wafer heating device in a plasma etching device, a photo etching device, or the like.

[0038]

According to the present invention, since the resistance heating element is embedded inside the board-shaped substrate made of dense ceramics, there is no risk of contamination of the semiconductor device. Further, since the heat generating surface is provided on the board-shaped substrate, the deterioration of thermal efficiency as in the case of the indirect heating method does not occur.

Further, since the wafer mounting plate made of the corrosion resistant inorganic material is brought into contact with the heat generating surface of the plate-shaped ceramic heater, corrosive gas such as etching gas does not directly contact the heat generating surface. Therefore, the corrosion of the heating surface can be effectively prevented.

Further, a gap is formed between the heating surface of the plate-shaped ceramics heater and the wafer mounting plate, and heat is transferred in this gap by heat radiation and heat transfer by gas molecules. Therefore, the heat transfer amount in the gap portion is smaller than the heat transfer amount in the contact portion. And
The outer diameter of the semiconductor wafer is less than or equal to the outer diameter of the heat generation surface, the outer diameter of the gap is smaller than the outer diameter of the semiconductor wafer, and the gap is located on the center side of the semiconductor wafer. The contact portion with the plate is located on the side of the peripheral portion of the semiconductor wafer. As a result, it is possible to offset the heat dissipation from the side peripheral portion of the plate-shaped substrate or the wafer mounting plate, and to make the temperature of the semiconductor wafer uniform as a whole between the central portion side and the side peripheral portion side.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a semiconductor wafer heating apparatus according to an embodiment of the present invention is attached to a flange.

FIG. 2 is a sectional view taken along the line II-II of FIG.

FIG. 3 is a plan view of the disk-shaped ceramics heater as viewed from the heating surface side.

FIG. 4 is a graph showing an example of the relationship between the temperature of the heat generating surface and the distance from the center of the heat generating surface.

FIG. 5 is a sectional view showing a semiconductor wafer heating apparatus according to another embodiment of the present invention.

FIG. 6 is a sectional view showing a semiconductor wafer heating apparatus according to still another embodiment of the present invention.

FIG. 7 is a cross-sectional view of essential parts showing a semiconductor wafer heating apparatus according to still another embodiment of the present invention.

[Explanation of symbols]

 1 Semiconductor wafer 2A, 2B, 2C Wafer mounting plate 2a, 2b Recess 2c Wafer mounting surface 3 Disc-shaped substrate 4 Resistance heating element 5A, 5B Disc-shaped ceramic heater 5a Recess 5b Heating surface 23, 23A, 24 Gap

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/285 C 8826-4M 21/3065

Claims (2)

[Claims] 1. A disk-shaped ceramics heater having a resistance heating element embedded in a disk-shaped substrate made of dense ceramics, and a corrosion-resistant inorganic material fixed so as to be in contact with a heating surface of the disk-shaped ceramics heater. A wafer mounting plate, a gap is formed between the heating surface of the plate-shaped ceramics heater and the wafer mounting plate, and a semiconductor wafer is mounted on the surface of the wafer mounting plate. The outer diameter of the semiconductor wafer is less than or equal to the outer diameter of the heat generating surface, the outer diameter of the gap portion is smaller than the outer diameter of the semiconductor wafer, and the gap portion is located on the central portion side of the semiconductor wafer. The semiconductor wafer heating apparatus is characterized in that the contact portion between the heat generating surface and the wafer mounting plate is located on the side of the side peripheral portion of the semiconductor wafer. 2. A gap is formed between the wafer mounting plate and the back surface of the semiconductor wafer, and the outer diameter of the gap is smaller than the outer diameter of the semiconductor wafer, and the gap is the semiconductor. 2. The semiconductor wafer according to claim 1, wherein the semiconductor wafer is located on a central portion side of the wafer, and a contact surface between the wafer mounting plate and the semiconductor wafer is located on a side peripheral portion side of the semiconductor wafer. Heating device.