JPH11288926A - Method and device for cleaning of vaporizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sharply reduce the time and the labor spent in cleaning by a method, wherein a special washing solvent inlet port is provided, a cleaning solvent is taken in and out of the port, and a two-stage cleaning is performed using two kinds of solvents. SOLUTION: A solvent inlet port 10 is provided at the downstream of a disc 8 on the side of a cavity 23 o a vaporizer 4. A cleaning solvent is introduced from the inlet 10 into the cavity 23, and the disc 8 and the inside of the cavity 23 are cleaned. Two kinds of solutions are used, and a two-stage cleaning operation is performed. The first solvent is used to dissolve the fixed material, and it is also used as a solution which dissolves the adhered matter of the disc 8 and the cavity 23. However, since the vapor pressure of the first solvent is low, it cannot be removed even when it is evacuated. Therefore, the first solvent is removed by dissolving it using the second solvent having high vapor pressure. Accordingly, the inlet line of the cleaning liquid becomes two. Moreover, the raw material withdrawal operation for cleaning of the vaporizer can be omitted because the solvent inlet line is different from the raw material inlet line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Also, the present invention relates to a vaporizer of a liquid supply device in a CVD apparatus for manufacturing a dielectric film having a high dielectric constant used for a nonvolatile memory. Conventionally, the dielectric film of the DRAM has been SiO ₂ .
It could be easily manufactured by oxidizing the Si substrate and was convenient. However, SiO ₂ has a low dielectric constant. The capacitance of the dielectric film is proportional to the area and the dielectric constant. Since the area can not be increased,
To make finer devices, higher dielectric constant materials are needed.

[0002] SiN is also influential and often used as a dielectric film of a Si wafer. In order to further reduce the occupied area per element, a higher dielectric constant is required.
Therefore, tantalum oxide Ta ₂ O ₅ is being put to practical use as the next dielectric film. Currently 1Gbit DRAM
Development is in progress. At 1 G, the dielectric constant of tantalum oxide is still too low. BST (Ba, Sr, Ti, O) has been proposed as a new material having a higher dielectric constant. BST is a new material, but cannot be made by vacuum deposition. High quality cannot be obtained by sputtering. BST must be formed by a CVD method.

[0005] Researches using a ferroelectric film as a storage material of a nonvolatile memory have been studied. PZ as ferroelectric
T (Pb, Zr, Ti, O), SBT (SrBi ₂ Ta ₂
O ₉ ) is attracting attention. These cannot be formed by sputtering or vacuum evaporation, but only by CVD.

However, these high dielectric Ta ₂ O ₅ ,
BST, PZT, and SBT are all difficult to form by CVD. This is because the material of these thin films is a low vapor pressure organometallic compound, so that it is difficult to stably supply the raw materials to the film formation chamber.

Therefore, these high dielectric constant solid materials are dissolved in an appropriate solvent to be in a liquid state. The solution is sent out by a liquid pump, vaporized by a vaporizer, and led to a CVD film forming chamber.

[0006] A method of forming a liquid by dissolving it in a solvent and converting it into a gas by a vaporizer and supplying it to the film forming chamber in a gaseous state is called a liquid raw material vaporizing film forming method. The solid raw material is also called a precursor. The solid raw materials belonging to PZT, SBT, and BST are listed. PZT includes Pb (DPM) ₂ , Z
r (OtC ₄ H ₉ ) ₄ and Ti (OiC ₃ H ₇ ) ₄ . SBTP includes Sr (DPM) ₂ , Bi (Ot
C ₄ H ₉ ) ₃ and Ta (OC ₂ H ₅ ) ₅ . As BST, Ba (DPM) ₂ , Sr (DPM) ₂ , Ti
(DPM) ₂ etc.

[0007]

2. Description of the Related Art As described above, the organic metal as a raw material of a dielectric film having a high dielectric constant is solid at room temperature. Since solids cannot be transported in a pipe system, they are dissolved in a solvent to form a liquid. The liquid is supplied by a liquid pump by the liquid supply device. Further, immediately before the film forming chamber, the gas is vaporized by the vaporizer and guided to the CVD film forming chamber. FIG. 1 is a schematic diagram of a liquid source vaporization film forming apparatus. The gas cylinder 1 for liquid pressure feeding is a cylinder of an inert gas such as nitrogen or argon. This connects to the liquid source tank 2 and applies pressure to the liquid source in the tank. The liquid source tank 2 is connected to a liquid pump 3. The liquid source is pumped to the vaporizer 4 by the liquid pump 3.
The liquid raw material is heated by the vaporizer 4 and vaporized. This is CVD
It is led to the film formation chamber.

[0008] A vaporizer does not merely heat a liquid. Simply heating and evaporating only evaporates the solvent into a gas. High-dielectric-constant raw materials that are originally solid at room temperature are not easily soluble as solutes in their solvents. Simply heating and evaporating only evaporates the solvent and concentrates the solute to solidify and precipitate. That is, the solid raw material (solute) is separated from the solvent. It is the same as distillation.

[0009] Instead, the purpose is to turn the solute into a gas.
So, if the two phases are separated, nothing will happen
No. Therefore, special measures are required for the vaporizer. For example
U.S. Pat. No. 5,361,800 discloses a liquid source vapor deposition method.
A new vaporizer suitable for the above has been proposed. This is 9
Nine thin Inconel discs with holes in the center (disks)
Are overlapped to a thickness of 1.2 mm, and the outer periphery is from the center hole.
It has a disk part that allows the solution to flow toward the part. Disk
The part is ± 1 from normal temperature to 250 ° C by the heating device.
Can be heated with an accuracy of ° C. The raw material liquid is pressed
Pass the narrow gap of the Inconel disc from the disc center
To Pass highly viscous liquid through a small gap of several μm
It is necessary to apply high pressure. Disc center is 17
kg / cm ^TwoAt high pressure, the outer circumference of the disk is about the same as the deposition chamber
Degree of vacuum. Disc also to separate high pressure and vacuum
The gap must be narrow.

[0010] The high pressure causes the solution to pass through the narrow gap of the disk. Since as many as 99 disks are used, the effective contact area is extremely large. It is heated for a short time after passing through the disk and evaporates as a solution. Since the phase transition time is short, it does not separate into two phases. It becomes a gas in the state of a solution (solute + solvent). This is immediately sent to the CVD film forming chamber.

[0011]

The raw material used in the liquid raw material vaporization film forming method is obtained by dissolving an organometallic solid in a solvent as described above. Since organometallic raw materials are solid by nature,
The solute is separated from the solvent by the environmental change in the vaporizer.
The separated solute returns to a solid. Therefore, the separated product of the raw material adheres in the vaporizer. When deposits accumulate, the flow path of the vaporizer is gradually narrowed. Therefore, the vaporization efficiency is reduced, and supply of the vaporized raw material to the film formation chamber is hindered. Therefore, a dielectric film having desired performance may not be obtained. In extreme cases, the vaporizer will clog.

When clogging occurs, the vaporizer must be disassembled to remove deposits from the vaporizer. Since the filter is made up of 99 inconnel thin plates and has a thickness of 1.2 mm, it takes a lot of time to disassemble and clean one by one. Also, it takes time to assemble. The film forming chamber and the peripheral piping are also exposed to the air during that time. Disassembly and cleaning is troublesome, so it is better to avoid clogging.

For this reason, the vaporizer has conventionally been cleaned regularly or as needed. Figure 1 is provided for that purpose.
Solvent tank 18. This is a tank containing only the solvent, and is provided in parallel with the liquid raw material tank 2. This supplies only the solvent to the liquid pump 3 or directly to the vaporizer.

When cleaning the vaporizer, the film forming operation is stopped, and the raw material is completely removed from the raw material introduction system (piping, vaporizer). After the raw material is removed, only the pure solvent flows from the solvent tank 18 into the vaporizer 4. Since there is no special inlet for the vaporizer, the vaporizer is cleaned by introducing a cleaning solvent from the same inlet as the raw material inlet. High pressure is applied because it must pass through a narrow gap in the cleaning disc. This is the same as the case of the raw material liquid. The solvent is pumped from the center to the outer periphery of the disk following the same path as the raw material liquid. The fast flowing solvent will wash the vaporizer disk. Since the deposit is a solid material, it should be dissolved by the solvent. So use the solvent for the cleaning solution. In the vaporizer, the disk is heated and a washing solvent flows. So the solvent becomes a gas. The solvent gas enters the deposition chamber from the vaporizer and is exhausted from here by the vacuum pump. This cleaning method can remove dirt adhering to the vaporizer disk without disassembling the vaporizer.

However, this is a time-consuming method. It is necessary to perform a complicated work of completely removing the raw material from the raw material introduction line prior to the cleaning. Otherwise, the solvent does not enter the liquid pump 3 or the vaporizer 4 from the solvent tank 18. Next, the solvent is introduced from the raw material introduction line to the vaporizer and washed. After that, it is necessary to drain the cleaning liquid. Conventionally, a system that reaches a film forming chamber is used in combination to extract a liquid after dissolving the deposits. Then, vacuum is drawn by a vacuum pump of the film forming apparatus. Since the film forming chamber is connected to the vaporizer, both the film forming chamber and the vaporizer are evacuated. However, the volume of the film formation chamber is large, and the volume of a pipe connected to the film formation chamber is large. Furthermore, since the vapor pressure of the solvent itself was low, it took a long time to deaerate the vaporizer and piping. Therefore, it took time to remove and dry the solvent after washing. If it takes time to clean the vaporizer, the time available for film formation decreases.

It is a first object of the present invention to provide a vaporizer cleaning method capable of eliminating the trouble of extracting raw materials. It is a second object of the present invention to provide a cleaning method that can reduce the time required for removing a solvent when a solvent is put as a cleaning liquid in a vaporizer.

[0017]

According to the vaporizer cleaning method of the present invention, a vaporizer is provided with an inlet for newly introducing a cleaning solvent, and a first solvent capable of dissolving the raw material solid is introduced through the inlet to vaporize the vaporizer. After washing the vessel and extracting the first solvent,
In this method, a first solvent is dissolved, a second solvent having a high vapor pressure is introduced into a vaporizer, and the first solvent is dissolved and removed. In other words, a special inlet for the washing solvent is created, the washing solvent is taken in and out from this, and two kinds of solvents are used. The first solvent dissolves the deposits, and the second solvent dissolves and removes the first solvent. Like that. It is a novel two-step washing method that skillfully combines solvents with different properties.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A vaporizer cleaning apparatus according to the present invention for realizing such a cleaning method has the following mechanism. (1) The vaporizer is newly provided with an inlet for taking in and out the washing solvent. (2) The solvent introduction port is provided downstream of the raw material evaporation disk (disk) in the vaporizer. (3) The deposits in the vaporizer are dissolved and removed by the solvent introduced from the solvent inlet. (4) A liquid introduction line and a liquid discharge line introduce and discharge a solvent from a solvent inlet provided in a vaporizer. (5) Connect the liquid discharge line to a dedicated discharge pump. (6) A solvent (first solvent X) for dissolving the raw material flows into the first system of the two systems of the liquid introduction line, and is first introduced into the vaporizer to wash the vaporizer. A solvent having a high vapor pressure capable of dissolving the first solvent (second solvent Y) flows into the second system, and is introduced into a vaporizer to wash out the first solvent.

[0019]

FIG. 2 is a sectional view showing the internal structure of a vaporizer for carrying out the vaporizer cleaning method of the present invention.
The vaporizer 4 has a liquid material introduction port 5 on an end face in the longitudinal direction. The opposite end face has a vaporized raw material outlet 9. Further on the side there is a carrier gas inlet 7. From here, an inert gas such as argon or nitrogen is introduced. A carrier gas valve 32 is provided between a gas cylinder (not shown) and the carrier gas inlet 7. A wide cavity 23 is formed inside the vaporizer 4. The gas passes through the gas passage 24
To the cavity 23.

A raw material flow path 22 is provided following the liquid raw material inlet 5, and a raw material valve 6 is provided in the middle of the flow path 22. Cavity 23
Is provided at the tip of the raw material flow path 22 with a liquid evaporation disk 8 formed by stacking thin Inconel plates.
As described above, for example, 99 plates are stacked to have a thickness of 1.2 mm. There is a hole in the center, through which the raw material passes, so that the raw material liquid radiates radially from the center. The liquid raw material obtained by dissolving the solid raw material in the solvent enters the vaporizer through the inlet 5, passes through the valve 6, passes through the narrow gap of the heated liquid evaporation disk (disk), and is instantaneously vaporized. The vaporized material spreads in the cavity 23. Since there are argon, nitrogen and the like as carrier gas there, they are mixed with the carrier gas.

FIG. 4A shows the state of the vaporizer during such a film forming operation. Since the film formation chamber connected to the vaporizer is evacuated by a vacuum pump (not shown), the mixed gas is blown into the film formation chamber. A source valve 33 is provided between the vaporized source outlet 9 and the film forming chamber. A heated substrate (such as a Si substrate) is provided in the film forming chamber, and products (BST, SBT, etc.) that have undergone a gas phase reaction are deposited thereon as a thin film. The configuration described above is similar to a conventional vaporizer.

In the present invention, in addition to the conventional structure, the cavity 2
A solvent inlet 10 is provided on the side of 3 and downstream of the disk 8. This is one feature of the vaporizer of the present invention.
From here, a cleaning solvent is introduced into the cavity to clean the disk and the inside of the cavity. Moreover, two types of solvents are used, and two-stage washing is performed. The first solvent has a property of dissolving the raw material solid. This dissolves the deposit on the disk or cavity to form a solution. However, since the first solvent has a low vapor pressure, it does not easily come off even when vacuum is applied. Therefore, the first solvent is dissolved and extracted using a second solvent having a high vapor pressure to dissolve the first solvent. This two-step cleaning is the most prominent feature of the present invention.

A line for supplying and discharging the solvent for this purpose will be described with reference to FIG. Since two types of solutions are used for two-stage cleaning, the number of cleaning liquid introduction lines is also two. In contrast, there is one discharge line. Of course there are 2 discharge lines
It may be separated into books. The first liquid introduction line 11 is for introducing the first solvent into the vaporizer 4. The first valve 13 and the first inlet pipe 26 pass through the pipes 28 and 29, pass through the supply / discharge valve 17, and enter the cavity 23 of the vaporizer 4 from the solvent inlet 10. Second liquid introduction line 12
Leads the second solvent to the vaporizer.

The vaporizer cleaning can be performed in the following procedure. This is performed while the film forming operation in the film forming chamber is stopped. The gas valve 32, the raw material valve 6 in the vaporizer, the valve 33 at the vaporized raw material outlet, the solvent discharge valve 30, and the second valve 14 are closed. The cavity 23 of the vaporizer 4 is in a state of being evacuated.

The first valve 13 of the first liquid introduction line 11 is opened, and the supply / discharge valve 17 is further opened. The first solvent enters the cavity 23 of the vaporizer from the side. This is (2) in FIG.
This is the state shown in FIG. The first solvent is filling the cavity. The stain dissolves in the first solvent. The first valve 13 and the supply / discharge valve 17 are closed. T ₁ is left appropriate time in that state. The first solvent is a solvent that dissolves the solid raw material. It may be the same as or different from the solvent used as the solvent for the film forming raw material. Dirt attached to the disk or inner wall of the vaporizer with the first solvent X (eg, solid material separated and solidified)
Dissolve. The cleaning solvent enters the gap from the outer periphery of the disk of the liquid evaporation disk 8. After a while, the solvent discharge valve 30 is opened and the first solvent containing dirt is extracted from the vaporizer 4. Apply further vacuum. FIG. 4C shows the state of the vaporizer after the first solvent is discharged.

Next, the valve 30 is closed, the first valve 13 is opened again, and the first solvent X is introduced into the vaporizer 4. Similarly, after a certain waiting time T ₁ , the first solvent X is removed from the vaporizer.
And vacuum is applied. Thus, the first number of times
Solvent X is put into a vaporizer to repeatedly wash away dirt. When the dirt is removed, the first solvent may be completely removed. However, since the first solvent has a low vapor pressure, it cannot be easily removed only by pulling with a vacuum pump. As shown in FIG.
Solvent droplets remain. That is why the second solvent is used.

The valves 32, 33, 30, and 13 are closed, and the second valve 14 of the second liquid introduction line 12 is opened. The second solvent Y passes through the valve 14, the pipes 27, 28, 29, and the valve 17, and passes through the solvent inlet 10 through the cavity 2 inside the vaporizer 4.
Enter 3. The dirt has already been removed, but the first solvent remains and the inner wall and the disk are wet. The second solvent is a solvent having a high vapor pressure and dissolving the first solvent. (4) in FIG.
Shows a vaporizer in such a state. The second solvent Y suitable for the first solvent X differs depending on the first solvent X.

When the first solvent X is n-butyl acetate, the second solvent X
The solvent Y is ethanol, isopropyl alcohol, methanol, tetrahydrofuran, normal hexane, or the like. By closing the valve 14 and 17, appropriate time T ₂ waits. The valve 30 is opened to discharge the second solvent Y. Use a vacuum pump to draw a vacuum. This is the state shown in FIG. The dissolution and removal of the first solvent by the second solvent may be performed only once, or may be performed a plurality of times. Since the second solvent has a higher vapor pressure, it can be easily removed from the vaporizer by a vacuum pump. Since the two-step washing is performed using two kinds of solvents as described above, the first solvent can be completely removed. Arrangement and combination of piping and valves of the solvent introduction / discharge unit 16 are arbitrary. The valve 17 can be omitted.

[0029]

[Table 1]

It is a skill of the present invention that the first solvent is used to wash the inside of the vaporizer and the disk, and then the second solvent is used to wash away the first solvent. As the first solvent, butyl acetate can be used as described above. It is necessary to select an appropriate one depending on the solid raw material (solute). The second solvent does not depend on the solute, and the condition is that the first solvent can be dissolved and the vapor pressure is high. When the first solvent is n-butyl acetate, the second solvent is ethanol, isopropyl alcohol (boiling point 82.7 ° C.), methanol (boiling point 64.56 ° C.), tetrahydrofuran (boiling point 66.0 ° C.), normal Hexane (boiling point 69.0
° C).

[0031]

(1) Since the solvent introduction line is a separate system from the raw material introduction line, it is not necessary to extract the raw material from the raw material line for cleaning the vaporizer. By omitting the raw material extraction work, the cleaning time and labor can be greatly reduced. (2) By unifying the liquid introduction line and the liquid discharge line for the vaporizer, it is not necessary to largely change the structure of the vaporizer. When the valve 17 is provided, the internal volume of the vaporizer does not change significantly. (3) Of the two liquid introduction lines, the first uses the same solvent as that used for dissolving or dissolving the raw material, and the second uses the first solvent for the second system. By using a second solvent having a high vapor pressure, for example, ethanol, solubilizing the solvent used in the system, and finally reducing the time required for completely removing the solvent by evacuation of the vaporizer. Can do things. (4) When the liquid supply device is used intermittently, it can be cleaned with a solvent when not in use.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a liquid source supply device that vaporizes a liquid source obtained by dissolving a solid source in a solvent and introduces the liquid source into a film formation chamber.

FIG. 2 is a cross-sectional view of a vaporizer for vaporizing a liquid material obtained by dissolving a solid material in a solvent.

FIG. 3 is a system diagram of a piping valve and the like of a vaporizer provided with a solvent introduction / discharge unit for performing the vaporizer cleaning method of the present invention.

FIG. 4 is a schematic sectional view showing various states of the vaporizer. FIG.
(1) is a state at the time of the film forming operation. 4 (2) is a state when the first solvent is introduced, FIG. 4 (3) is a state where the first solvent is discharged and evacuated, and FIG. 4 (4) is a state when the second solvent is introduced.
(5) shows a state at the time of discharging the second solvent.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas cylinder for liquid pressure feed 2 Liquid source tank 3 Liquid pump 4 Vaporizer 5 Liquid source inlet 6 Source valve 7 Carrier gas inlet 8 Liquid evaporation disk 9 Vaporized source outlet 10 Solvent inlet 11 First liquid inlet line 12 2 liquid introduction line 13 1st valve 14 2nd valve 16 Solvent introduction and discharge part 17 Supply and discharge valve

Claims (2)

[Claims] 1. A vaporizer having a liquid raw material inlet, a vaporized raw material outlet, a cavity, and a liquid evaporating disk, and for applying pressure and heat to evaporate a liquid raw material obtained by dissolving a raw material that is solid at room temperature in a solvent, by applying pressure and heat. A method for cleaning, in which a solvent inlet is provided in addition to a liquid material inlet and a vaporized material outlet, and a first solvent X capable of dissolving the raw material solid is introduced into the vaporizer through the solvent inlet to clean the inside. And then repeating the operation of discharging one or more times, and introducing or discharging the second solvent Y capable of dissolving the first solvent and having a higher vapor pressure than the first solvent into the vaporizer once or more times. A method for cleaning a vaporizer, characterized by being repeated. 2. A vaporizer having a liquid material inlet, a vaporized material outlet, a cavity, and a liquid evaporating disk, and for applying pressure and heat to vaporize a liquid material obtained by dissolving a raw material that is solid at room temperature in a solvent. A device for cleaning, a solvent inlet provided in the vaporizer separately from the liquid material inlet and the vaporized material outlet,
A first liquid introduction line leading to the solvent inlet and introducing the first solvent X into the vaporizer; a second liquid introduction line leading to the solvent inlet and introducing the second solvent Y into the vaporizer; A vaporizer cleaning device, comprising a solvent discharge line connected to a mouth for discharging a solvent.