JP2662993B2 - Liquid raw material vaporizer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for vaporizing a liquid source used in a low pressure chemical vapor deposition (hereinafter, referred to as a low pressure CVD).

(Prior Art) There is a bubbler method as a general method for vaporizing a liquid raw material used in a CVD method.

In this method, a liquid material is placed in an airtight container (bubbler),
In this method, a transport gas (carrier gas) is blown into the liquid, and the raw material vapor generated by bubbling is introduced into a reaction chamber of a CVD apparatus together with the carrier gas.

However, this method has a drawback that the raw material is dewed or fog-ized in the transport tube due to a decrease in gas temperature due to adiabatic expansion.

In addition, as another method of vaporizing a liquid material, a liquid is atomized in a mist form from a nozzle into a gas-tight evaporating tank heated to a temperature sufficient to vaporize the liquid material, or atomization using ultrasonic waves. There is a method using an evaporating tank which is introduced and vaporized, and is introduced into a reaction chamber of a CVD apparatus together with a carrier gas.

This method has the advantage that the evaporation efficiency is good because the raw material liquid is atomized.However, when this method is performed under reduced pressure, particularly when the method is performed at a reduced pressure close to 10 KPa or lower, droplets are not easily generated. Due to the liquefaction or solidification resulting from the adiabatic expansion and the reduced residence time due to the increased gas flow rate, it is difficult to completely remove the droplets in the evaporation tank.

If the raw material droplets are introduced into the reaction chamber without being vaporized, defects such as loss of uniformity of the formed film and generation of dust such as oxides of raw material components occur.

Furthermore, when vaporizing directly from a raw material container such as a bubbler, the absolute value of the pressure difference between the bubbler, the reaction chamber of the CVD device, and the inside of the bubbler is small. There is a disadvantage that the liquid raw material is contaminated by reaction products, oxide dust, droplets and the like generated in the reaction chamber.

(Problems to be Solved) The present invention is directed to a method of vaporizing a raw material liquid used in a low pressure CVD method by vaporizing only a controlled minimum volume flow without atomizing the raw material liquid into a reaction chamber of a low pressure chemical vapor deposition apparatus. It is intended to provide a vaporizer for introducing only gas without introducing gas.

(Means for Solving the Problems) The present invention is to vaporize a liquid raw material without being atomized and to quickly reach an equilibrium between an injection liquid amount and a vaporized liquid amount per unit time by increasing evaporation efficiency. With the goal.

FIG. 1 shows an embodiment of the present invention. The present invention will be described in detail with reference to FIG.

A liquid raw material injection pipe 3 is provided in the vaporization tank 1, and the tip of the liquid raw material injection pipe 3 is an inlet 4 for hair details. A gutter 6 is provided on the inner wall of the vaporization tank 1 in a spiral shape with a gentle inclination. The injection port 4 in the hair detail at the tip of the liquid material injection pipe can inject the material liquid onto the gutter 6 without causing liquid leakage.

The injected liquid material slowly flows down the gutter 6 to wet the wall surface of the vaporization tank 1 and does not cause liquid accumulation.

A heating element such as a heater is installed outside the vaporization tank 1, and heats the wall of the vaporization tank at a constant temperature.

The raw material liquid is gently heated and vaporized on the inner wall of the vaporization tank before reaching the bottom of the vaporization tank, and is adjusted so that the raw material liquid does not accumulate as a liquid at the bottom of the vaporization tank.

In the vaporizer according to the present invention, since the vaporization process is performed, the raw material liquid does not cause bumping due to heating, and accordingly does not generate droplets. In addition, the raw material liquid does not fall to the bottom of the vaporization tank to generate fine droplets.

In the present invention, since the entire wall of the vaporization tank can be used for vaporizing the liquid, the wet area of the liquid raw material is increased, and a sufficient heat transfer area for gentle evaporation can be obtained. The stay time can be effectively lengthened.

The vaporized source gas flows out of the gas outflow pipe 2 together with the carrier gas introduced from the carrier gas introduction pipe 5 installed at the bottom of the vaporization tank, and is introduced into the reaction chamber of the CVD apparatus.

As described above, in the present invention, the liquid raw material component is small, and therefore, the carrier gas having a large evaporation ability starts to contact from the end of the wetting surface of the inner wall of the vaporization tank to bring about effective vaporization, and the wetted area is reduced. It has the effect of becoming constant.

The shape of the gutter may be a multi-staged one instead of a spiral shape.

Further, instead of the gutter, a cutout or a lathe-like groove may be provided on the wall of the vaporization tank.

The material of the vaporization tank, gutter and the like is determined by the physical properties of the raw material liquid to be used. In the case of a corrosive liquid such as tetraethoxysilane, stainless steel is preferable.

As the carrier gas, an inert gas, nitrogen or the like is used,
It is preferable to preheat to a certain temperature before entering the vaporization tank.

Further, a method in which the carrier gas is introduced into the nozzle of the carrier gas introduction pipe 5 in the form of a nozzle so that the carrier gas is ejected and swirled in the vaporization tank also has a large source gas transport effect.

FIG. 2 shows that a liquid material inlet and a gas outlet are provided as a double pipe in the upper part of the vaporization tank, and the flow of the carrier gas and the flow of the liquid raw material introduced from the carrier gas inlet provided in the lower part of the vaporization tank are shown. This is an example in the case of countercurrent.

FIG. 2 is a partial sectional view of only the upper portion of the vaporization tank, and the lower portion is the same as that of FIG.

In the drawing, the liquid raw material injected from the liquid raw material injection pipe 8 reaches the hair detail (narrow surface) 9 at the tip of the inner pipe while wetting the wall of the gap between the double pipe, the outer pipe and the inner pipe. The liquid is adjusted so as to wet the inner wall of the vaporization tank and drop on the wall without dropping to the bottom of the vaporization tank as droplets on the narrow gap surface).

On the other hand, the source gas and the carrier gas vaporized by the vaporization method similar to the vaporization method described with reference to FIG. 1 flow out from the gas outflow pipe 7 and are introduced into the reaction chamber of the CVD apparatus.

As described above, in the present invention, the liquid material injection port and the gas outlet are formed in a double tube at the upper part of the vaporization tank, and the portion where the liquid material starts to wet the inner wall of the vaporization tank is defined as hair detail (narrow surface). The structure is also very effective.

(Effect of the Invention) According to the present invention, a raw material liquid used in a low pressure CVD method can be gently vaporized without being atomized,
Since droplets of the raw material are not introduced into the reaction chamber, the uniformity of the formed film is extremely excellent, and there is a feature that dust such as an oxide of the raw material component is not generated.

Further, according to the present invention, since the entire inner wall of the vaporization tank can be used for vaporizing the liquid raw material, there is a feature that the evaporation efficiency can be increased.

Further, according to the present invention, since the volume of liquid staying in the vaporization tank is small and the liquid raw material container and the vaporization tank can be isolated, the reaction product generated in the reaction chamber, the oxide dust, the liquid, etc. There is a feature that the raw material is not contaminated.

[Brief description of the drawings]

FIG. 1 is a sectional view of one embodiment of a vaporizer according to the present invention. In the figure, 1 is a vaporization tank, 2 is a gas outflow pipe, 3 is a liquid material injection pipe, 4 is a capillary inlet of the liquid material injection pipe, 5 is a carrier gas introduction pipe, and 6 is a spiral gutter. FIG. 2 is a partial sectional view of one embodiment of the upper part of the vaporization tank. In the figure, 1 is a vaporization tank, 7 is a gas outflow pipe, 8 is a liquid raw material injection pipe, and 9-1 and 9-2 are hair details (narrow surface) of liquid raw material injection.

Claims (1)

(57) [Claims] In a closed container provided with a liquid material inlet, a carrier gas inlet and a gas outlet, the liquid material flows down the inner wall of the container. Liquid material vaporization characterized by providing a gutter or a groove, and providing a narrow gap surface at an injection portion for causing a liquid material entering through an injection port to leak at an equal level on the gutter or the groove. apparatus.