JPH0722319A - Low pressure cvd device - Google Patents

Abstract

PURPOSE:To avoid the blocking in pipe even if a gas mixed with a high reaction gas is introduced by a method wherein a reaction gas not yet introduced in a reaction chamber is forcedly exhausted through a reaction gas exhaust pipe continuously connected to the reaction gas introducing pipe. CONSTITUTION:An exhaust pipe 17 for introducing a reaction gas flowing through an introducing pipe 16 is continuously connected to the upper end part of the introducing pipe 16. This exhaust pipe 17 arranged from the ceiling part of a reaction chamber 10 extending to the sidewall part on the opposite side sucks in the reaction gas introduced from the lower end part of the introducing pipe 16 to be exhausted out of the system. At this time, a part of said reaction gas is to be introduced in the reaction chamber 10 through gas blowing out holes 18. In such a constitution, any not yet introduced reaction gas left intact as a raw gas is to be forcedly exhausted through the exhaust pipe 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low pressure CVD apparatus for forming a film on a semiconductor wafer by low pressure CVD.

[0002]

2. Description of the Related Art A conventional vertical low pressure CVD apparatus is shown in FIG. 4 (Japanese Patent Laid-Open No. 4-139820). Vertical decompression C
In the VD equipment (hot wall type),
The semiconductor wafers 40 arranged horizontally are stacked in the height direction at regular intervals, and a reaction gas introducing pipe 41 is provided along the stacking direction of the semiconductor wafers 40.
A large number of gas introduction holes 42 are formed in the introduction pipe 41, and the reaction gas is blown out in the horizontal direction through the gas introduction holes 42. Then, the blown out reaction gas passes on the surface of each semiconductor wafer 40 as shown by the arrow in the figure, is sucked from the suction hole 44 of the gas exhaust pipe 43 arranged on the opposite side, and is exhausted to the outside. It is something. In this case, in order to make the thickness of the CVD film uniform, the semiconductor wafer 40 being formed is also rotated in the circumferential direction.

[0003]

[SUMMARY OF THE INVENTION However, in such a vertical type low pressure CVD apparatus, a reactive gas, for example in the case of using SiH ₄ is by heat applied from the surroundings, the SiH ₄ in the inlet pipe 41 It is thermally decomposed, and solid Si is generated inside the introduction pipe. As a result, the introduction pipe 41 and the gas introduction hole 42 are closed, and there is a drawback that the reaction gas cannot be supplied into the reaction chamber.

Further, this drawback becomes particularly remarkable when a highly reactive raw material gas such as a mixed gas of SiH ₄ and N ₂ O is used.

The present invention has been made to solve such a problem, and an object thereof is to provide a low pressure CVD apparatus which prevents clogging of a reaction gas introduction pipe.

Another object of the present invention is to provide a low pressure CVD apparatus capable of preventing the introduction pipe from being blocked even when a highly reactive gas is mixed and introduced.

[0007]

A reduced pressure CV according to the present invention
The device D is a vertical reaction chamber that accommodates a plurality of semiconductor wafers arranged in the height direction, and extends in the height direction along the side wall of the reaction chamber, and is formed in an array on the side wall. The reaction gas introducing pipe for introducing the reaction gas into the reaction chamber through a plurality of gas outlets, and the gas in the reaction chamber extending in the height direction along the side wall portion facing the reaction gas introducing pipe. A reaction chamber exhaust pipe for sucking and exhausting the reaction gas, wherein a reaction gas exhaust pipe for exhausting the reaction gas flowing in the reaction gas introduction pipe to the outside of the system is connected to the reaction gas introduction pipe. Is characterized by.

In addition, a mixed gas introducing pipe for introducing another reaction gas to be mixed with the reaction gas introduced from the gas blowing hole is provided in the reaction chamber in the vicinity of the gas blowing hole. Thus, the reaction gas introduced from the gas blowing hole and the reaction gas introduced from the mixed gas introduction pipe are mixed before reaching the semiconductor wafer.

[0009]

A part of the reaction gas introduced into the reaction gas introducing pipe is introduced into the reaction chamber through each gas outlet.
On the other hand, the reaction gas that has not been introduced into the reaction chamber is forcibly exhausted through the reaction gas exhaust pipe connected to the reaction gas introduction pipe. Therefore, since the reaction gas does not stay in the reaction gas introduction pipe for a long time, solidification due to the thermal decomposition reaction in the introduction pipe is avoided.

Further, since the mixed gas introducing pipe is arranged in the vicinity of the gas blowing hole in the reaction chamber, the introduced reaction gases are mixed before reaching the semiconductor wafer. Therefore, the reaction due to the gas mixing does not occur in the introduction pipe, and the blockage due to the mixed reaction does not occur.

[0011]

EXAMPLE A low pressure CVD apparatus according to this example will be described below.
It will be described with reference to the accompanying drawings. As shown in FIG. 1, the low pressure CVD apparatus includes a reaction chamber 10 having a cylindrical shape (see FIGS. 2 and 3), and a large number of semiconductor wafers 12 horizontally supported by a support boat 11 are provided inside the reaction chamber 10. Is housed. Further, each support boat 11 has its lower end fixed to a support substrate 13, and this support substrate 13 is connected to a drive motor 14 via a rotary shaft 15. Therefore, the rotation of the drive motor 14 causes the support boat 11 to rotate.
Rotates, which causes the semiconductor wafer 12 to rotate in its circumferential direction.

On the side wall of the reaction chamber 10, the reaction chamber 10
From the lower part to the upper part, a substantially semi-cylindrical tubular body is provided so as to project, and an introducing pipe 16 for introducing a reaction gas (here, SiH ₄ ) is formed. A plurality of gas blowing holes 18 are arranged and formed in the side wall portion where the introducing pipe 16 is arranged, and a part of the reaction gas pressure-fed in the introducing pipe 16 passes through the gas blowing holes 18. It is blown out horizontally into the reaction chamber 10 via.

An exhaust pipe 17 for guiding the reaction gas flowing in the introduction pipe 16 is connected to the upper end of the introduction pipe 16. The exhaust pipe 17 is arranged from the upper portion of the reaction chamber 10 to the side wall on the opposite side (see FIGS. 2 and 3), and sucks the reaction gas introduced from the lower end of the introduction pipe 16, Exhaust to the outside of the system. Therefore, a part of the reaction gas introduced from the lower end portion of the introduction pipe 16 is the gas outlet 1
The reaction gas introduced into the reaction chamber 10 via 8 is forcibly discharged as raw gas via the exhaust pipe 17 without being introduced. Therefore, the introduction pipe 16 or the exhaust pipe 17
The reaction gas does not stay inside, and the ratio of solid Si deposited by the thermal decomposition reaction of SiH ₄ in these pipes is sufficiently reduced.

Further, as shown by a dotted line in FIG. 2, inside the reaction chamber 10, an introduction pipe for introducing another reaction gas (here, N ₂ 0) to be mixed is provided on both sides in the vicinity of the gas blowing hole 18. 20 are provided. This introducing pipe 20 is provided with a large number of gas blowing holes 21 at predetermined intervals, and each of these gas blowing holes 21 is formed toward the gas blowing hole 18 side of the introducing pipe 16 located at the center. As a result, the SiH ₄ introduced into the reaction chamber 10 through the gas blowing holes 18 of each introducing pipe 16 is mixed with N ₂ 0 introduced through the gas blowing holes 21 of the introducing pipe 20 immediately after this introduction. As a result, the mixed gas reaches the semiconductor wafer 12.

Since SiH ₄ and N ₂ 0 used as the reaction gas have extremely high reactivity with each other, they are separately introduced until just before being introduced into the semiconductor wafer 12 as described above. It avoids the situation where the reaction progresses.

On the other hand, an exhaust pipe 30 is arranged on the side wall portion of the reaction chamber 10 facing the installation portion of the introduction pipe 16. A plurality of gas exhaust holes 31 are arranged and formed on the side wall portion where the exhaust pipe 30 is arranged, and the gas inside the reaction chamber 10 is
The gas is exhausted from the gas exhaust hole 31 and exhausted to the outside via the exhaust pipe 30.

Although not shown in FIGS. 2 and 3, the reaction chamber 1
A resistance wire heating body 4 for heating the reaction chamber 10 is provided on the outer peripheral portion of 0.
0 is set.

<Film Forming Example> Here, a film forming example will be specifically described. As described above, SiH ₄ as a reaction gas is
e was introduced from the introduction pipe 16 as a carrier gas. Further, N ₂ 0 to be mixed with this SiH ₄ was introduced through the introduction pipe 20. Each gas to be introduced is SiH ₄ 200
(Cc / min), He is 800 (cc / min), N
₂₀ was introduced at a rate of 4000 (cc / min). Under this condition, of the gases transported through the introduction pipe 16,
It was set so that 20% was introduced into the reaction chamber 10 through the gas outlet 18 and the remaining 80% was exhausted out of the system through the exhaust pipe 17. That is, SiH ₄ is added to 40 (cc /
min) and He (160 (cc / min)) were respectively introduced into the reaction chamber 10, where N ₂ of 4000 (cc / min) was introduced.
min) and formed SiO ₂ . At this time, the temperature of the reaction chamber 10 is set to 800 ° C., and the internal pressure is set to 7
The pressure was set to 0 Pa, and the exhaust pressure from the exhaust pipe 17 was set to 700 Pa, which was about 10 times the pressure inside the reaction chamber 10.
At this time, no backflow of gas from the reaction chamber 10 to the introduction pipe 16 side occurred.

As a result of film formation under these conditions, the semiconductor wafer 1
The in-plane variation of the film thickness of 2 is about 5%,
It was confirmed that it was halved compared to about%.

As described above, in the present embodiment, the example in which the exhaust pipe 17 is formed along the outer peripheral portion of the reaction chamber 10 has been shown, but the present invention is not limited to this structure, and the introduction pipe 16 is not limited thereto.
It suffices if the reaction gas flowing in the chamber can be exhausted to the outside of the system. Further, it is also possible to circulate the reaction gas exhausted from the exhaust pipe 17 so as to be reintroduced as the reaction gas.

Further, as reaction gases, SiH ₄ and N _{2 are used.}
Although 0 and 0 were used, there is no particular limitation on the type of gas.

[0022]

As described above, in the low pressure CVD apparatus according to the present invention, a part of the reaction gas introduced into the reaction gas introduction pipe is introduced into the reaction chamber through the gas blowing hole,
The reaction gas that has not been introduced is forcibly exhausted through the reaction gas exhaust pipe. Therefore, it is possible to avoid a situation in which the highly reactive reaction gas stays in the reaction gas introducing pipe and solidifies in the pipe, prevents the reaction gas introducing pipe from being blocked, and enables long-term use.

Further, since the mixed gas introducing pipe is arranged in the vicinity of the gas blowing hole in the reaction chamber, the introduced reaction gases are mixed immediately before reaching the semiconductor wafer and outside the introducing pipe. Therefore, even when a highly reactive gas is mixed and introduced, it is possible to prevent the introduction pipe from being blocked.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a low pressure CVD apparatus according to the present embodiment, and is a sectional view taken along the line AA ′ in FIG.

FIG. 2 is a schematic perspective view showing a reaction chamber of the low pressure CVD apparatus shown in FIG.

3 is a cross-sectional view of the reaction chamber shown in FIG.

FIG. 4 is a partial cross-sectional view showing a main part of a conventional low pressure CVD apparatus.

[Explanation of reference numerals] 10 ... Reaction chamber, 16 ... Introducing pipe (reaction gas introducing pipe), 17
… Exhaust pipe (reaction gas exhaust pipe), 18… Gas blowout hole, 2
0 ... Introduction pipe (mixed gas introduction pipe), 30 ... Exhaust pipe (reaction chamber exhaust pipe).

Claims (2)

[Claims] 1. A vertical reaction chamber for accommodating a plurality of semiconductor wafers arranged in a height direction, extending in the height direction along a side wall of the reaction chamber, and formed in an array on the side wall. A reaction gas introducing pipe for introducing a reaction gas into the reaction chamber through a plurality of gas outlets, and extending in the height direction along a side wall portion facing the reaction gas introducing pipe, A reaction chamber exhaust pipe for sucking and exhausting the reaction gas, and a reaction gas exhaust pipe connected to the reaction gas introduction pipe for exhausting the reaction gas flowing in the reaction gas introduction pipe to the outside of the system. A characteristic low-pressure CVD apparatus. 2. A mixed gas introducing pipe for introducing another reaction gas to be mixed with the reaction gas introduced from the gas blowing hole is provided in the reaction chamber in the vicinity of the gas blowing hole. 2. The low pressure CVD apparatus according to claim 1, wherein the reaction gas introduced from the gas blowing hole and the reaction gas introduced from the mixed gas introducing pipe are mixed before reaching the semiconductor wafer.