JPH0317271A - Cvd apparatus and film formation using same - Google Patents

Abstract

PURPOSE:To prevent deterioration in raw material and to obtain a good-quality film by providing a mechanism for transferring a liquid raw material by a fixed quantity from a storage chamber to a vaporization chamber, transferring small amounts of raw material necessary for a single film-forming stage each time a film is formed, and carrying out film formation by means of a vaporized gas. CONSTITUTION:This CVD apparatus has a reaction chamber 15, an evacuation system, and a gas-introducing system, and a liquid raw material 4 is used in a gasified state. The above gas-introducing system consists of a liquid raw material storage chamber 3, a liquid raw material vaporization chamber 6, and a mechanism for transferring the liquid by a fixed quantity, and small amounts of liquid raw material necessary for a single film-forming stage are transferred to the above vaporization chamber 6 each time a film is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a CVD apparatus using a liquid as a raw material and a method for coating the same.

(Prior Art) As semiconductor technology advances, LSIs are becoming smaller and more highly integrated. Among these, particularly in IC metallization technology, Affi film is conventionally performed by the Subac method. This /l is indispensable as a wiring material in a semiconductor process using Si. However, recently, as LSIs have become more highly integrated, it has become necessary to coat holes such as contact holes and through holes with a film with good coverage, and to fill and planarize these holes. The currently used sputtering method cannot satisfy the above requirements for submicron-sized holes. Bias sputtering, selective W-CVD, and Al-CVD can be considered as methods to meet this demand.

The bias sputtering method has a problem with the film quality of /l, and furthermore, with the progress of miniaturization of LSI, it seems that there is a limit when processing contacts and through holes of 0.5 μm size.

The selective W-CVD method also poses a problem in terms of speeding up as higher integration progresses and higher speed LSIs are required, as W has a resistivity approximately three times that of Al (approximately 10 μΩ・Cll). seems to occur. In addition, the selection W-CVD can only be used to fill holes, and the wiring in the flat area is performed using the conventional /l, but an increase in resistance at the connection between W and Affi also poses a problem.

On the other hand, although the /l-CVD method currently has the drawback that the film flatness is not very good,
It is expected that this technology will become extremely important in the post-AM era.

Incidentally, various raw material gases are conceivable for AN-CVD, but those suitable for the IC process are required to have the following characteristics. First, the AftC film reaction is carried out at a lower temperature, the amount of impurities that enter the film is small, it is inexpensive, it is stable, the film forming conditions are easy to control, and it is harmless. . At present, a raw material that satisfies all of these requirements has not been found. AI is currently the most widely used technology! ．． These are organic compounds such as trimethylaldinium, triethylaluminum, triisobutylaluminum, dimethylaluminum hydrite, and diisobutylaluminum hydride. Among them, triisobutylaluminum (hereinafter abbreviated as TIBA) is A
It is very superior in that the decomposition temperature of N is as low as about 250°C, and there is little impurity, especially carbon, in the film. However, the drawback is that it is a liquid at room temperature, and its vapor pressure is Q. The vapor pressure is as low as 1 Torr, and when heated above about 50°C, the vapor pressure is 10
-'Torr and even lower diisobutylaluminum hydride.

An example of a conventional CVD apparatus using TIBA is shown in FIG. The TTBA 4 stored in the raw material container 6 is heated by a heater 23 installed around the outer periphery of the container and maintained at about 50°C. Introduce Ar gas from the inactive gas inlet IO and TI
BA is bubbled and gasified, and then introduced into the reaction chamber 15.

In reaction chamber 15, these gases are heated to about 230°C before a film is deposited on substrate 16, which is maintained at about 400°C.
The gas passes through the heated gas distribution plate l7 and is preheated at that time. The effectiveness of this method and device has already been demonstrated by the inventors.

(Tokukan Sho 62-172374 and Patent Application Sho 63-224
(Refer to No. 63) Note that the heating of TIBA at approximately 50"C is due to the low vapor pressure of T.
IBA is effectively supplied to the reaction chamber 15 (at 50°C, TI
BA vapor pressure rises to ~l Torr), basis 16
This is an essential factor to obtain a good film on the top.

(Problems to be Solved by the Invention) However, the apparatus shown in FIG. 4 has the following drawbacks, particularly in the raw material container and its supply section. That is, a large amount of TI
Since BA is stored in the raw material container 6 and the entire container is heated to about 50°C, as a certain film is repeatedly applied over a long period of time, TIBA gradually decomposes into diisobutylaluminum hydride, which has a low vapor pressure. Even if the film conditions are set constant, changes over time are observed in the raw material supply amount and the IK quality of the produced film. As an example, FIG. 5 shows how the quality of the raw film, especially the crystal orientation, changes over time in film formation using TIBA in the above-mentioned apparatus. St as a substrate
The fact that the epitaxial film of Affi (l11) can be controlled when using (111) has already been demonstrated in Japanese Patent Application No. 63-71160 and Japanese Patent Application No. 6318 of the present inventors.
As shown in No. 9177, the orientation changes from (111) to (110) as the film formation is repeated.

In addition, the reflectance, which indicates the degree of surface smoothness of the produced film, also has a wavelength of 50.
For light of 0nII1, it was 90% or more, but it has decreased to 60% or less.

As mentioned above, /l-CVD using TIBA is very superior in terms of the quality of the produced film, but the problem with the TIBA material itself is that it gradually decomposes into diisobutylaluminum hydride and deteriorates when heated. However, with conventional equipment, it has been difficult to produce a high-quality film stably for a long period of time.

(Object of the Invention) The present invention provides a CVD apparatus that can prevent deterioration of liquid raw materials due to heating and form high-quality thin films with good reproducibility over a long period of time, and an e.g. The purpose is to provide a Ft method.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a gas introduction system including a liquid raw material storage chamber, a liquid raw material vaporization chamber, and a quantitative transfer of liquid from the storage chamber to the vaporization chamber. A mechanism is provided to transfer a small amount of raw material required for one film forming process from the storage chamber to the vaporization chamber each time the film is formed. In addition, in order to promote vaporization, a porous metal body is arranged inside the vaporization chamber, and a mechanism for discharging the raw material liquid from the center of the porous metal body and impregnating the porous part, and an inert gas for transportation are installed. A mechanism for ejecting the gas from the center of the porous metal body and a mechanism for heating the entire vaporization chamber to a constant temperature, or an ultrasonic oscillator in the vaporization chamber as a means of promoting vaporization. You can use it to increase its effectiveness.

(Function) According to this precept, the temperature of the raw material storage chamber is kept low, only the minimum amount of raw material necessary for one film formation process is introduced into the vaporization chamber each time, and the vaporized gas is used to form the film. By doing so, the above-mentioned deterioration phenomenon of raw materials will not occur. At this time, if only a small amount of the raw material is used, it may be difficult to vaporize it using the conventional method. This is because the surface area of the raw material has decreased, and in order to promote vaporization, it is necessary to increase the surface area of the liquid raw material. For this purpose, a porous metal body is placed in a vaporization chamber, impregnated with liquid raw material to increase its surface area, and then an inert gas for transportation is passed through the porous metal body to easily remove all of the raw material, even if it is a small amount. It becomes possible to gasify quickly. Alternatively, as a means to promote vaporization, ultrasonic vibrations are applied to the liquid raw material to agitate the raw material molecules and generate droplets.

(Embodiment) FIG. 1 is a diagram showing an outline of an embodiment of a CVD apparatus of the present invention. The high pressure Ar gas in the Ar gas cylinder 1 is reduced to atmospheric pressure by a pressure regulator 2 and connected to the upper part of a liquid raw material (TIBA) storage chamber 3 via a valve. The raw material storage chamber 3 is filled with TIBA 4, which can be transferred to the raw material vaporization chamber 6 via a dip tube 5 inserted until it reaches the bottom of the storage chamber. A valve 7 and a valve 8 are provided between the liquid raw material storage chamber 3 and the raw material vaporization chamber 6, and a pipe from a transportation Ar gas inlet 10 is connected via a hull 9 to an intermediate position between the valves 7 and 8. Dib・
The transfer pipes from the tube 5, valve 7, and valve 8 enter the raw material vaporization chamber 6, and then their tips are connected to the inside of the porous metal body 1. The details of this connection are shown in FIG. The tip of the transfer pipe 13 reaches the center of the porous metal body 11, and a large number of side holes 13 are provided in the transfer pipe 12 at the portion where the two come into contact. The porous metal body l1 is made by bundling fibrous stainless steel m-wires having a diameter of about 0.1M, for example. A metal powder sintered body having open cells may also be used. The entire raw material vaporization chamber 6 is uniformly heated to a constant temperature by a heater 23 installed around the periphery thereof. The outlet of the raw material vaporization chamber is connected to the reaction chamber 15 via a valve l4. The structure of each part inside the reaction chamber is the same as before.

To explain the procedure for forming a film using this apparatus, the mass valve 7 and the valve 9 are closed, the valve 8 and the valve 14 are opened, and the reaction chamber 15, the raw material vaporization chamber 6, and the transfer pipe 12 are evacuated. At this time, the raw material vaporization chamber 6 is sufficiently heated by the heater 23 to reduce residual gas as much as possible. After evacuation, the raw material vaporization chamber is maintained at approximately 70°C. Thereafter, the valve 8 and the valve I4 are closed, the substrate 16 is placed, and the inside of the reaction chamber is evacuated to a high vacuum. Substrate holder 18 and gas distribution plate 17
When the temperature reaches a predetermined value, by opening the valve 7, the T
The IBA is pushed out through valve 7 to valves 7, 8,
It flows into the pipe surrounded by 9. In this example,
The volume of the area surrounded by valves 7 and 8 was set to approximately 1 cc. Next, when the valve 7 is closed and the valve 8 is opened, a certain amount of TIBA in the area surrounded by the valves 7, 8, and 9 passes through the transfer pipe 12 and is impregnated into the porous metal body 11 in the vaporization chamber 6. A large number of side holes 13 provided in the transfer pipe 12
This inclusion is made relatively uniform because of the After that, Ar gas whose flow rate is controlled is introduced from the inlet 10,
When the valves 9 and 14 are opened, the TIBA impregnated into the porous metal body 11 is relatively easily vaporized due to its increased surface area, and is carried by Ar gas for transportation and guided into the reaction chamber. One film step's worth of Af is deposited on the base $H16.

This is repeated below.

FIG. 3 is a schematic diagram of another embodiment of the present invention. Since the structure other than the vaporization chamber is the same as that in FIG. 1, illustration thereof is omitted. In this embodiment, a magnetostrictive vibrator 30 for ultrasonic oscillation is directly bonded to the bottom of the raw material vaporization chamber 6.

The TII3A, which was quantitatively transferred in the same manner as in the previous embodiment, accumulates on the vibrating part of the magnetostrictive vibrator at the bottom of the raw material vaporization chamber 6, which is preset at 50°C. After opening the valve 14, applying power of several tens of watts at 24 KHz from the power source 3l accelerates the vaporization of TIBA.

A membrane is carried out as in the previous example with the introduction of transport Ar gas. In this embodiment, stainless steel is used for the entire raw material vaporization chamber, but the thickness of the bottom plate is made as thin as about IM in order to reduce the attenuation of ultrasonic waves. It is known that if the applied power is too large, re-condensation will occur at the outlet of the vaporization chamber, which is undesirable.

In both of the above two examples, a small amount of TIB
Practical vaporization efficiency was obtained with A, and a high-quality thin film could be produced stably over a long period of time with good reproducibility.

Furthermore, although TIBA is used as a raw material in the above examples, it should be noted that TIBA is a material that does not deteriorate due to heating.
It is clear that the present invention can be effectively used in the general field of CVD using organic compounds (2) and liquids as raw materials. The present invention is particularly useful when the vapor pressure of the raw material is low.

(Effects of the Invention) According to the present invention, even if raw materials that tend to deteriorate due to heating of liquid raw materials are used, there is no deterioration in the film quality of raw films, and high-quality films can be produced stably over a long period of time with good reproducibility. Being able to produce this has high industrial value.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention. FIG. 2 is a partially enlarged sectional view of FIG. 1. FIG. 3 is a schematic diagram of another embodiment of the invention. FIG. 4 is a schematic diagram of an example of a conventional CVD apparatus using TIBA. FIG. 5 shows the change in crystal conformity of an Al film produced by a conventional apparatus and method depending on the number of films. 3... Liquid raw material storage chamber, 6... Raw material vaporization chamber, 15.
...Reaction chamber, l1... Porous metal body, 30... Magnetostrictive oscillator.

Claims (5)

[Claims] (1) In a CVD apparatus that uses a liquid raw material and is equipped with a reaction chamber, a vacuum evacuation system, and a gas introduction system, the gas introduction system supplies the liquid from a liquid raw material storage chamber, a liquid raw material vaporization chamber, and the liquid raw material storage chamber. A CVD apparatus characterized by being equipped with a mechanism for quantitatively transferring a liquid to a raw material vaporization chamber. (2) In the CVD apparatus according to claim 1, a porous metal body is provided in the liquid raw material vaporization chamber, and a fixed amount of raw material transferred from the raw material storage chamber is transferred to the center of the porous metal body. a mechanism for discharging liquid raw material to impregnate it into the porous metal body; a mechanism for spouting an inert gas for transporting the vaporized raw material gas from the center of the porous metal body; and a mechanism for heating the entire liquid raw material vaporization chamber to a constant temperature. A CVD apparatus characterized by being provided with a mechanism. (3) A CVD apparatus according to claim 2, wherein the porous metal body is a bundle of thin metal wires. (4) A CVD apparatus according to claim 1, wherein the liquid raw material vaporization chamber is provided with an ultrasonic oscillator for promoting vaporization of the liquid raw material. (5) In a CVD apparatus that gasifies and uses a liquid raw material, the minimum amount of liquid raw material required for one film forming process is transferred to the liquid raw material vaporization chamber each time the film is formed and used for CVD. A film forming method characterized by the following.