JPS60245215A - Vertical furnace - Google Patents

Abstract

PURPOSE:To prevent economically shorter life even if the diameter of a furnace core tube is made greater and to reduce the deterioration of a wafer by heating the end zone contiguous to the bottom of a center zone with a lower heater which is different from an upper heater which heats the end zone contiguous to the top of the center zone. CONSTITUTION:If the length of a lower heater 4 is made longer than hitherto, the effect of heat dissipation of the lower end of a furnace core tube 1 against the lower part of a center zone (a) is reduced and the heating rate of the lower heater 4 can be reduced from hitherto and simultaneously, the maximum temperature at an end zone (b) can be lowered. By making the heating rate of an upper heater 5 equal to the heating rate of the lower heater 4, the length of the upper heater can be reduced and if the length of the lower heater is made longer, the length of the center zone (a) is not made shorter but can rather be made longer. Thus, even if the diameter of the furnace core tube 1 is made greater, the economically shorter life of a vertical furnace can be prevented and the deterioration of a wafer can be reduced comparing to hitherto even if the temperature of heat treatment is higher.

Description

DETAILED DESCRIPTION OF THE INVENTION (al) Field of Industrial Application The present invention relates to a vertical furnace, and in particular to a vertical furnace used for heat treatment of wafers for manufacturing semiconductor chips, which are the main components of semiconductor devices. Regarding.

The heat treatment of the wafer includes, for example, formation of a thermal oxide film, formation of a film by chemical vapor deposition (CV, D), diffusion of impurities, and the like.

In any of these cases, the vertical furnace used for mass production is required to be able to uniformly process a large number of wafers as objects to be processed at once. It is desired that the temperature of the center zone in the heated state is uniform. This demand remains unchanged even when wafers become larger as production volume increases.

(b) Conventional technology Figure 2 is a side sectional view schematically showing a typical configuration of a conventional vertical furnace. For example, a furnace core tube l made of quartz glass,
A cap 2 made of fallen quartz glass that covers the opening of the furnace core tube 1, heaters 3.4 and 5 disposed around the furnace core tube 1 to heat the furnace core tube 1, and a heat insulating material such as quartz glass wool. It consists of a heat insulating layer 6 that covers the outside of the empty reheaters 3 to 5 and the exposed portion of the furnace core tube 1 to suppress heat radiation from the furnace core tube 1 and the heaters 3 to 5. Note that 1a and 1b are provided in the furnace core tube 1 and are a gas inlet and a gas outlet, respectively, when passing gas into the furnace core tube 1.

The heater 3 is located in the center zone a region of the furnace core tube 1 where the wafer A is inserted and heat-treated, and heats the center zone a. The heater (upper heater) 5 is located in the zone b region and heats the end zone b, and the heater (upper heater) 5 is located in the end zone C region continuous above the center zone a and heats the end zone C. Note that B is a support rod for supporting and inserting the wafer A.

The lengths of heaters 4 and 5 (in the vertical direction) are approximately the same, about a little less than half the length of heater 3, and these heaters 3 to 5 are made of the same heating wire, such as a Kanthal wire. , are arranged around the furnace core tube 1 with substantially the same density, such as being wound at equal intervals, for example.

When heat-treating wafer A in a vertical furnace with this configuration, it is desirable to make the temperature in the center zone a uniform, and to achieve this, the temperature in the vertical direction in the furnace core tube l − The distribution is as shown in FIG.

That is, when heating is performed only by the heater 3, the temperature at the top and bottom of the center zone a becomes lower than the temperature at the center due to heat dissipation in the vertical direction.
and 5 are provided, but even if the heaters 4 and 5 are heated to the same heating degree (heating amount per length) as the heater 3, the heat dissipation from the upper and lower ends of the furnace core tube 1 cancels out the heat dissipation. is not done enough. Of course, if the heaters 4 and 5 are long enough, the effect of the end of the furnace core tube l will be eliminated, but the relative length of the center zone a will be too short to be practical.

Therefore, in order to make the temperature of the center zone a uniform, the degree of heating of the heaters 4 and 5 needs to be greater than that of the heater 3. From this, the temperature distribution becomes as shown in FIG.

Here, the maximum temperature in end zone b is higher than in end zone C because the insulation on the opening side of furnace core tube 1 is lower than on the opposite side. In addition, as a characteristic of the vertical furnace, the heat inside the furnace core tube 1 moves upward within the furnace core tube 1, so the degree of heating of the heater 4 needs to be greater than that of the other heaters 3 and 5. There is. If the wafer A becomes larger, that is, the diameter of the furnace core tube l becomes larger,
Since the maximum temperature in the end zone b becomes higher and the amount of heat transferred increases, the heating degree of the heater 4 needs to be extremely high.

From the above, in the vertical furnace of this configuration, especially when the diameter of the furnace core tube 1 is large for large wafers, the heater 3
If configurations 5 to 5 are formed to match the heating degree of heater 3 or 5, heater 4 will be overloaded and the life of the vertical furnace will be shortened. For example, the vertical furnace has the problem of being expensive, and furthermore, when the wafer A passes through the end zone b when the wafer A is taken in and out of the center zone a, the heat treatment temperature is high. , there is also the problem that wafer A deteriorates.

Note that some vertical furnaces have the opening of the furnace core tube facing upward, but the effect of the heat transfer within the furnace core tube is more Since the influence on the lower heater is greater, even if the situation with the lower heater is alleviated somewhat, it will not make much of a difference.

(C1 Problem to be Solved by the Invention The problem to be solved by the present invention is that when the diameter of the furnace core tube becomes large for large wafers, the lifespan of the vertical furnace with the conventional heater configuration is shortened. It can be short or expensive, and it can degrade the wafer if the heat treatment temperature is high.

(dl Means for solving the problem) The above problem is that the lower heater that heats the end zone below the center zone is different from the upper heater that heats the end zone above the center zone. It can be resolved by taking measures.

In the practice of the present invention, the length of the lower heater is made longer than the product length of the upper heater, and the allowable heating capacity per length of the lower heater is made greater than the capacity of the upper heater.

(e) Effect In the vertical furnace shown in Figure 2, if the length of the lower heater (heater 4) is made longer than before, the effect of heat radiation from the lower end of the furnace core tube 1 on the lower part of the center zone a will be reduced. So,
It becomes possible to make the heating degree of the lower heater smaller than before, and at the same time, it becomes possible to lower the maximum temperature in the end zone b. Furthermore, by matching the heating degree of the upper heater (heater 5) to this heating degree, the length of the upper heater becomes shorter, and even if the lower heater becomes longer, the length of the center zone a will not become shorter. , rather it becomes possible to make it longer. In this way, even if the diameter of the furnace core tube 1 becomes larger, it is possible to economically suppress the shortening of the life of the vertical furnace, and even when the heat treatment temperature is high, the deterioration of wafers can be reduced to the same level as before. It becomes possible to reduce the amount by comparison.

On the other hand, increasing the heating capacity of the lower heater is as follows:
This method takes measures to prevent overloading only on the lower heater, which becomes overloaded when the diameter of the furnace core pipe becomes larger and dominates the life of the vertical furnace. It is possible to suppress shortening of life. However, since the temperature distribution shown in FIG. 3 is the same as the conventional one, it is suitable for heat treatment at a lower temperature than the previous one.

Note that the above-mentioned situation is also the same in a vertical furnace in which the opening of the furnace core tube is upward.

(f) Example Embodiments according to the present invention will be described below with reference to the drawings.

The same reference numerals refer to the same objects throughout the design.

FIG. 1 is a side cross-sectional view schematically showing the configuration of one embodiment of a vertical furnace according to the present invention, FIG. 4 is a side cross-sectional view schematically showing the configuration of another embodiment, and FIG. 2 is a diagram showing a comparison of the temperature distributions of those and the vertical furnace shown in FIG. 2.

The vertical furnace shown in FIG. 1 is a modified version of the conventional vertical furnace having the configuration shown in FIG.
Only the length has been changed, and the heating wires and their arrangement density have been replaced with heaters 3a to 3c, which are the same as before, and the rest is the same as before. In addition, with this remodeling, each region of the center zone a and end zones b and C is different from the conventional arrangement, following the arrangement of the heaters 3a to 3C.

The length of each heater before and after remodeling and the ratio of the heating degree of each heater when making the temperature of the center zone a uniform are shown in the table below.

Before modification After modification Heater length 3.3a Approx. 100cm Approx. 105cm 4.4a Approx. 4
0cm Approx. 50c+a 5.5a Approx. 40cm Approx. 25cm Heater heating degree ratio 3.3a 1.0 1.0 4.4a Approx. 1.4 Approx. 1.2 5.5a Approx. 1.1 Approx. 1.2 Heating like this The longitudinal temperature distribution in the furnace core tube 1 in this case is as shown in Figure 5, and the line ■ represents the case before modification.
Line ■ indicates the case after modification.

Before the modification, as mentioned earlier, end zone b
The maximum temperature of end zone B was higher than the maximum temperature of end zone C, but after the modification, the maximum temperature of end zone B is lower than before, and the maximum temperature of end zone C is higher than before, and the two are almost the same temperature. It has become.

The vertical furnace shown in FIG. 4 is a conventional vertical furnace with the configuration shown in FIG. 2, in which only the heater 4 is replaced with a heater 4b. The thickness of the lines is approximately 1.1 times larger, and the density of their arrangement is approximately 1.2 times larger.

By doing so, it is possible to prevent the heating capacity of the heater 4a from becoming approximately 1.3 times that of the heater 4, resulting in an overload, and it is possible to suppress shortening of the life of the vertical furnace.

In this vertical furnace, the center zone a and end zones b and c are the same as the conventional ones, and the vertical temperature distribution inside the furnace core tube 1 when heated is also as shown in Fig. 5. The line 3 shown in the figure is similar to the line 2 in the conventional case.

(gl Effects of the Invention As explained above, by taking the measures of the present invention, even if the diameter of the furnace core tube becomes large for large wafers in a vertical furnace, it is possible to economically shorten the lifespan. Furthermore, even when the heat treatment temperature is high, it is possible to reduce the deterioration of the wafer compared to the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view schematically showing the configuration of an embodiment of a vertical furnace according to the present invention; FIG. 2 is a side sectional view schematically showing a typical configuration of a conventional vertical furnace; 3 is a diagram showing the temperature distribution, FIG. 4 is a side sectional view schematically showing the configuration of another embodiment, and FIG. 5 is a vertical view of the structure shown in FIGS. 1, 2, and 4. FIG. 2 is a diagram showing a comparison of the temperature distribution of a type furnace. In the drawings, 1 is a furnace core tube, la is a gas inlet, 1b is a gas outlet, 2 is a cage, 3.4.5.3a, 4a, 5a, 4b are heaters 6 are heat insulating layers, A is a wafer, B are the support rods and , respectively.

Claims (3)

[Claims] (1) A furnace core tube is arranged in the vertical direction, and a lower heater that heats an end zone extending below the center zone in which the object to be processed is arranged in the furnace core tube is installed in the end zone extending above the center zone. A vertical furnace that is different from the top heater. (2) The vertical length of the lower heater is equal to the upper Q −
The vertical furnace according to claim 1, wherein the length is longer than the length of the vertical furnace. (3) The vertical furnace according to claim (1), wherein the heating capacity per length in the vertical direction of the lower heater is greater than the capacity of the upper heater.