JPH065532A - Vertical furnace - Google Patents

Abstract

(57) [Summary] [Purpose] For a vertical furnace with a steep temperature gradient near the furnace opening, the temperature gradient near the furnace opening can be eased when loading and unloading objects such as wafers. (EN) Provided is a vertical furnace which can alleviate heat stress to the furnace and can reduce the decrease in furnace temperature due to an object to be processed, and can realize this advantage without changing the heater length. [Arrangement] A vertical furnace for heat-treating an object to be treated, wherein a preliminary furnace 1 is provided, whereby a temperature gradient of a furnace port for carrying in / out the object to be treated is relaxed, and the preliminary furnace 1 is preferably a core. The shutter 2 for sealing is attached to the lower part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical furnace, and more particularly to a vertical furnace that can be used when heat-treating electronic materials. The vertical furnace of the present invention can be used, for example, as a diffusion furnace that heat-processes a semiconductor wafer to diffuse impurities.

[0002]

2. Description of the Related Art As a heating furnace for heat treatment of electronic materials,
There are vertical furnace and horizontal furnace (Press Journal "Monthly S
semiconductor World "October 1990, 93-97
Page, Watanabe "Vertical and horizontal furnaces"). The vertical furnace has many advantages, and many proposals have been made for this (Japanese Patent Laid-Open Nos. 1-4018, 1-66933, 1-1752).
28 etc.). For example, in a vertical furnace, it is difficult for the heated gas in the furnace to escape to the outside of the furnace, so the oxygen concentration in the furnace is low, and there is little oxidation due to the entrainment of outside air during the loading and unloading of the objects to be processed.
It also has the advantage of being excellent in thermal uniformity of cross section. Also,
The vertical furnace has an advantage that the soaking length occupies a larger proportion than the horizontal furnace. On the other hand, however, on the other hand, the flip side is that the distance from the furnace opening to the soaking area is short and the temperature gradient near the furnace opening becomes steep. Therefore, for example, when a semiconductor wafer is inserted as an object to be processed, the thermal stress applied to the wafer is very large, and the wafer reaches the inside of the furnace in a cooled state, so that the cooling of the furnace temperature by the wafer is also very large. . Therefore, the thermal stress transition (Sl
Occurrence of ip line), oxidation due to delay in furnace temperature recovery, and deterioration of diffusion uniformity are remarkable.

Regarding the thermal stress transition of the Si semiconductor wafer, with respect to the <100> Si substrate wafer having high Slip resistance, an attempt is made to avoid this problem by, for example, adopting a ramping process by slowing the wafer loading / unloading or lowering the temperature. Was being done. However, such slowing down or lowering of temperature is not a preferable means because it is not always easy to set the conditions, and there are problems of throughput, temperature recovery after carrying out / carrying in, and oxide film growth due to oxygen entrainment. Further, with respect to the <111> Si substrate wafer in which Slip is likely to occur, even if the above-mentioned speed reduction and temperature reduction can be performed under proper conditions, the Sl
It is difficult to avoid the occurrence of ip.

Further, as the diameter of the wafer becomes larger, the heat capacity of the wafer also becomes larger, so that the disturbance of the furnace temperature due to the cooling of the wafer will become a problem in the future.

A conventional vertical furnace is shown in FIG. The above problems will be described in more detail below with reference to FIG.

FIG. 2 shows a vertical diffusion furnace for processing Si semiconductor wafers, in which a wafer to be processed and a boat 4 which is a support for mounting the wafer are housed in a core tube 5. Heat treated. A heater 7 for heating the core tube 5 is arranged around the core tube 5, and a soaking tube 6 made of SiC or the like is interposed between the core tube 5 and the heater 7. The lower portion of the furnace core tube 5 is an opening, and the heat insulating cylinder 3 is arranged below the furnace core tube 5. The lower part of the heat retaining cylinder 3 serves as a shutter 2 that opens and closes the lower opening of the core tube 5, which also serves as the base of the heat retaining cylinder 3. The wafer that is the object to be processed and the boat 4 that supports the wafer are transported up and down along the arrow 41 in the figure. This device structure has a structure in which the soaking part is long in the vertical direction. 51 is a core tube flange. Reference numeral 8 is an arrow indicating gas introduction.

The vertical diffusion furnace having the above-mentioned structure is superior in thermal uniformity to the cross section as compared with the horizontal diffusion furnace, and as shown in the drawing, the opening of the core tube is located at the lower side, so that the temperature inside the furnace gas is increased. It has excellent features such as that it is difficult to escape to the outside, and the amount of outside air involved is small. On the other hand, as mentioned above, compared to the horizontal furnace,
Since the distance from the furnace opening to the soaking area is very short, the temperature gradient near the furnace opening becomes steep. Due to this steep temperature gradient, the temperature of the object to be processed abruptly changes when the wafer or the like is taken in and out of the object to be processed, and, for semiconductor wafers, for example, the temperature distribution within the wafer surface becomes very large. As a result, the occurrence of thermal stress transition (Slip Line) becomes more remarkable than in a horizontal furnace, which is an important problem especially for Si semiconductor wafers.

Conventionally, the Slip caused by the in-plane temperature distribution of the wafer has become a problem because the vertical furnace has been rapidly spread mainly in the process field using the <100> Si semiconductor substrate having high Slip resistance. It didn't happen,
Since the <111> Si semiconductor substrate used in the bipolar process has a weak Slip resistance, it has become difficult to cope with the increase in the diameter of the wafer only by lowering the temperature and speed of the wafer loading / unloading which have been conventionally performed as a countermeasure against the Slip. And it is said that Slip resistance is high <10
As described above, it is not desirable to reduce the speed and the temperature of the 0> Si substrate wafer. Furthermore, because the distance from the furnace opening to the soaking zone is extremely short, when the article to be treated is loaded, it reaches the inside of the oven (soaking zone) without sufficient heating of the article to be treated. However, this caused the temperature inside the furnace to drop, and it was ± 1 immediately after the end of loading.
There has been a problem that a temperature gradient of several hundreds of degrees Celsius is generated in the soaking region controlled to about degrees Celsius. Since it takes a considerable time to recover from the temperature disturbance, the thermal history between the objects to be processed (between the wafers to be heated) becomes non-uniform, and the uniformity such as oxidation and diffusion is deteriorated. In addition, since the temperature distribution in the surface of the object to be processed (wafer) exists even immediately after the completion of unloading / importing of the object to be processed (wafer), the Slip also occurs due to the subsequent temperature rise (Ramping). .

[0009]

It is an object of the present invention to reduce the temperature gradient in the vicinity of the furnace port when a workpiece such as a wafer is taken in and out, in a vertical furnace in which the temperature gradient near the furnace port is steep. With the object of providing a vertical furnace that can reduce the thermal stress on the body and reduce the decrease in furnace temperature due to the object to be treated,
Further, it is an object of the present invention to provide a vertical furnace that can realize such advantages without changing the heater length, and further to provide a vertical furnace that can reduce the problem of oxygen entrainment. To do.

[0010]

The invention according to claim 1 of the present invention is a vertical furnace for heat-treating an object to be processed, characterized in that a preliminary furnace is provided. This achieves the above object.

The invention according to claim 2 of the present invention is a vertical furnace for heat-treating an object to be processed, wherein a preliminary furnace for relaxing the temperature gradient of the furnace port for carrying in and out the object to be processed is provided. This is a characteristic vertical furnace, which achieves the above object.

According to a third aspect of the present invention, there is provided a vertical furnace for heat-treating an object to be processed, wherein a preliminary furnace for relaxing a temperature gradient of a furnace port for carrying in / out the object is a shutter for core closing. It is a vertical furnace characterized by being attached to the bottom from
This achieves the above object.

The invention according to claim 4 of the present invention is the vertical furnace according to any one of claims 1 to 3, wherein the preliminary furnace is a preliminary furnace for preheating and / or cooling an object to be processed, This achieves the above object.

The invention according to claim 5 of the present invention is a vertical diffusion furnace for processing a semiconductor device according to any one of claims 1 to 4, which achieves the above object. is there.

[0015]

According to each invention of the present application, since the preliminary furnace is provided in the vertical furnace including the invention of claim 1, the temperature gradient of the furnace port can be relaxed by this preliminary furnace, or It is possible to prevent a rapid temperature change of the processing body.

That is, according to the second aspect of the invention, the object to be processed is carried out.
Since the preliminary furnace for relaxing the temperature gradient of the furnace port to be carried in is provided, it is possible to prevent the adverse effect on the object to be processed such as the occurrence of the slip line due to the steep temperature gradient.

According to the third aspect of the invention, since the auxiliary furnace is attached to the lower part from the core sealing shutter, it is not necessary to change the heater length.

According to the fourth aspect of the present invention, since the object to be processed is preheated or cooled by the preliminary furnace, it is possible to prevent the temperature gradient from being disturbed due to the temperature difference from the core and the rapid temperature change of the object to be processed.

The invention of claim 5 can be effectively used as a diffusion furnace for processing semiconductor wafers.

[0020]

Embodiments of the present invention will now be described with reference to the drawings. However, as a matter of course, the present invention is not limited to the examples described below.

Example 1 This example is an embodiment of each invention of the present application.
In particular, it is embodied as a vertical diffusion furnace for processing Si semiconductor wafers. The vertical furnace of this example is shown in FIG.

The vertical furnace of this embodiment is, as shown in FIG.
It is a vertical furnace for heating an object to be processed (here, a Si semiconductor wafer), and has a preliminary furnace 1.

In particular, this embodiment is provided with a preliminary furnace 1 for alleviating the temperature gradient at the furnace port for carrying in / out the object to be processed.

In particular, in this embodiment, the preliminary furnace 1 is attached to the lower part from the shutter 2 for sealing the core.

In the present embodiment, the preliminary furnace 1 preheats and / or cools the object to be treated.

The present embodiment is embodied as a vertical diffusion furnace for semiconductor processing.

The vertical furnace of this embodiment is used for processing objects (wafers).
Alleviates the steep temperature gradient near the furnace opening when moving in and out,
It has a furnace opening structure capable of suppressing the occurrence of slip lines or suppressing a decrease in the temperature inside the furnace due to the wafer.

The vertical furnace of the present embodiment is a vertical diffusion furnace for processing Si semiconductor wafers, in which a wafer to be processed and a boat 4 which is a support for mounting the wafer are placed in a furnace core tube 5. It is stored and heat treated. A heater 7 for heating the core tube 5 is arranged around the core tube 5, and a soaking tube 6 made of SiC or the like is interposed between the core tube 5 and the heater 7. The lower portion of the furnace core tube 5 is an opening, and the heat insulating cylinder 3 is arranged below the furnace core tube 5. The lower part of the heat retaining cylinder 3 serves as a shutter 2 that opens and closes the lower opening of the core tube 5, which also serves as the base of the heat retaining cylinder 3. In this embodiment,
The auxiliary furnace 1 is attached from below the shutter 2.

The Si semiconductor wafer, which is the object to be processed, and the boat 4 supporting the same are vertically moved at the arrow 41 in the figure, and the soaking portion has a structure that is long in the vertical direction. Reference numeral 51 is a core tube flange, and the shutter 2 is provided below the flange 51. Reference numeral 8 is an arrow indicating gas introduction.

In the vertical furnace of this embodiment, a core tube 5 and a preliminary furnace 1 for temperature gradient relaxation are integrated, and a shutter for sealing the core tube 5 (in this example, a quartz shutter plate is used). The auxiliary furnace 1 made of a heat-resistant material such as quartz or SiC is provided below the flange portion 51 of the furnace core tube 5 in which the heat insulating cylinder base) is located.

In this preliminary furnace 1, when the shutter 2 (here, the quartz shutter plate) is open, the furnace main body side (core tube 5)
Side) or heated by the rising gas in the furnace, the temperature gradient near the furnace opening is moderated. Further, when the shutter 2 is closed, the structure is substantially the same as that of the conventional structure, and the excellent characteristics of the vertical furnace can be obtained.

Since the preliminary furnace 1 is unnecessary in the cap closed state, it can be constructed so that it can be moved so that it is installed only when the wafer to be processed is loaded and unloaded.
With this configuration, the same effect can be obtained.

Due to the presence of the preliminary furnace 1, the region where the oxygen concentration is high due to the entrainment of the outside air during wafer loading and unloading moves to the region of the preliminary furnace where the temperature is low, so that the amount of oxidation due to the entrainment of outside air during the wafer loading and unloading is suppressed. Is also fulfilled at the same time.

According to this embodiment, since the temperature gradient near the furnace opening becomes gentle when the object to be processed (wafer) is taken in and out,
The thermal stress is weakened, and the thermal stress transition caused by the occurrence of the temperature distribution of the object to be processed (temperature distribution in the wafer surface) can be suppressed.

Further, when the object to be processed (wafer) is inserted,
Since the object to be processed (wafer) reaches the inside of the furnace while being gradually heated, cooling by the object to be processed (wafer) is reduced.

Further, since the region of high oxygen concentration due to the entrainment of outside air when the object to be processed (wafer) is taken in and moved to the region of the preliminary furnace where the temperature is low, oxidation due to entrainment of outside air when taking in and out the object to be processed (wafer) is carried out. Can be suppressed.

[0037]

According to the present invention, in a vertical furnace having a steep temperature gradient in the vicinity of the furnace opening, the temperature gradient in the vicinity of the furnace opening at the time of loading and unloading an object to be processed such as a wafer can be relaxed. It is possible to provide a vertical furnace that can reduce the thermal stress on the object to be processed, and can reduce the decrease in furnace temperature due to the object to be processed, and realize such advantages without changing the heater length. It is possible to provide a vertical furnace that can be used, and further to provide a vertical furnace that can reduce the problem of oxygen entrainment.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a vertical furnace of Example 1.

FIG. 2 is a configuration diagram showing a conventional vertical furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Preliminary furnace 2 Shutter 3 Thermal insulation tube 4 Object to be treated and its support (wafer and boat) 5 Core tube 6 Soaking tube 7 Heater

Claims (5)

[Claims] 1. A vertical furnace for heating an object to be processed, wherein a vertical furnace is provided. 2. A vertical furnace for heating an object to be processed,
A vertical furnace equipped with a preliminary furnace that relaxes the temperature gradient at the furnace port that carries in and out the object to be processed. 3. A vertical furnace for heating an object to be processed,
A vertical furnace characterized in that a preliminary furnace for relaxing the temperature gradient of the furnace port for carrying in and out the object to be processed is attached to the lower part from the shutter for core closing. 4. The vertical furnace according to claim 1, wherein the preliminary furnace is a preliminary furnace for preheating and / or cooling an object to be processed. 5. The vertical furnace according to claim 1, which is a vertical diffusion furnace for processing semiconductor devices.