Patent Application
20060278166
The present invention relates to a vaporizer suitably used for a film forming apparatus such as a MOCVD film forming apparatus and a vaporizing method, and a CVD thin film forming apparatus and other various types of apparatuses.
A problem arising in the development of DRAM is a decrease in storage capacitance caused by miniaturization. From the viewpoint of software error, capacitance of the same level as that of the old generation is required, so that it is necessary to take some measures. As the measures, although the cell structure up to 1M has been a planar structure, from 4M, a three-dimensional structure called a stack structure or a trench structure has been adopted to increase the capacitor area. Also, for the dielectric film, which has conventionally been a thermally-oxidized film of substrate Si, a film formed by laminating a thermally-oxidized film and a CVD nitrided film on poly Si (this laminated film is generally called an ON film) has been adopted. For 16M DRAM, in order to further increase the area contributing to the capacitance, for the stack type, a three-dimensional type in which the side surface is used, a fin type in which the back surface of plate is used, and the like type have been used.
In such a three-dimensional structure, however, there arises a problem in that the number of processes increases due to the complication of process and the yield decreases due to the increase in height difference. For this reason, it is said that it is difficult to realize DRAM of 256M bits or higher capacitance. Therefore, as one means for further increasing the degree of integration without changing the present structure of DRAM, there has been devised a method in which the dielectric of capacitance is changed over to one having a large dielectric constant. As a dielectric thin film having a large dielectric constant, attention was first paid to a thin film of a large dielectric constant single metal paraelectric oxide such as Ta2O5, Y2O3, and HfO2. The specific dielectric constant of Ta2O5 is 28, that of Y2O3 is 16, that of HfO2 is about 24, which are four to seven times that of SiO2.
However, in application to DRAM of 256M or higher, a three-dimensional capacitor structure is needed. As a material which has a far larger specific dielectric constant than that of these oxides and is expected to be applied to DRAM, three kinds of (BaxSr1-x)TiO3, Pb(ZryTi1-y)O3, and (PbaL1-a) (ZrbTi1-b)O3 have been regarded as very likely. A Bi-based laminar structure having a crystalline structure highly similar to that of a superconductive material has recently received great attention because it has a large dielectric constant and self polarization of ferroelectric characteristic, and hence it is superior as a nonvolatile memory.
Generally, SrBi2TaO9 ferroelectic thin film is formed by the MOCVD (metal organic chemical vapor deposition) method which is practical and promising.
The raw materials for the ferroelectic thin film are, for example, three kinds of organic metal complexes of Sr(DPM)2, Bi(C6H5)3, and Ta(OC3H5)5. Each of these materials is used as a raw material solution by being dissolved in THF (tetrahydrofuran), hexane, or other solvents. Sr(Ta(OEt)6)2 and Bi(OtAm)3 are also used as a raw material solution by being dissolved in hexane or other solvents. DPM is the abbreviation of dipivaloylmethane.
The material properties of these raw materials are given in Table 1.
An apparatus used for the MOCVD method includes a reaction section in which the SrBi2TaO9 thin film raw material undergoes gas phase reaction and surface reaction to form a film and a supply section in which the SrBi2TaO9 thin film raw material and an oxidizing agent are supplied to the reaction section.
The supply section is provided with a vaporizer for vaporizing the thin film raw material.
Conventionally, as a technique concerning the vaporizer, methods shown in
However, in this technique, the metal filter is clogged by vaporization for several hours, which poses a problem in that this metal filter cannot be used for a long period of time. The inventor presumed that the reason for this is that the solution is heated and a substance having a lower vaporization temperature evaporates.
However, in this technique, the minute hole is clogged by vaporization for several hours, which poses a problem in that this minute hole cannot be used for a long period of time.
Also, in the case where the raw material solution is a mixed solution of a plurality of organic metal complexes, for example, a mixed solution of Sr(DPM)2/THF and Bi(C6H5)3/THF and Ta(OC3H5)5/THF, and vaporization is accomplished by the heating of this mixed solution, a solvent having the highest vapor pressure (in this case, THF) vaporizes earliest, which poses a problem in that the raw material cannot be supplied stably because the organic metal complexes deposit on the heated surface. In all methods shown in
Furthermore, in the MOCVD, in order to obtain a film with high homogeneity, it is requested to obtain vaporized gas in which the raw material solution disperses homogeneously. However, the above-described conventional techniques do not necessarily meet the request.
To meet the above-described request, the inventor has separately provided a technique described below.
Specifically, as shown in
(1) a dispersion section having a gas passage formed in the interior, a gas introduction port for introducing a pressurized carrier gas to the gas passage, means for supplying a raw material solution to the gas passage, a gas outlet for sending the carrier gas containing the raw material solution to a vaporization section, means for cooling the gas passage, and a radiation heat preventive blowoff portion cooled so that thermal energy is not applied to the raw material gas in the dispersion section by radiation heat from the vaporization section; and
(2) a vaporization section for heating and vaporizing the carrier gas containing the raw material solution sent from the dispersion section, having a vaporization tube one end of which is connected to a reaction tube of an MOCVD apparatus and the other end of which is connected to the gas outlet, and heating means for heating the vaporization tube; and a radiation heat preventive blowoff portion cooled so that thermal energy is not applied to the raw material gas in the dispersion section by radiation heat from the vaporization section.
This technique provides a vaporizer for MOCVD that is clogged far less than the conventional example so that it can be used for a long period of time, and can supply a raw material stably to the reaction section.
Also, in this technique, an introduction port of oxygen heated beforehand is provided on the downstream side of the vaporization section.
However, in this technique as well, deposition of crystals is found in the gas passage, so that clogging still occurs in some cases.
Also, a large quantity of carbon (30 to 40 at %) is contained in the formed film. In order to remove this carbon, annealing (for example, 800° C., 60 minutes, oxygen atmosphere) must be performed at a high temperature after film formation.
Furthermore, in the case where film formation is accomplished, there occur large variations in percentage composition.
An object of the present invention is to provide a vaporizer which can restrain the occurrence of air bubbles and can be expected to restrain variations in thin film deposit rate caused by the air bubbles, and a vaporizing method.
The present invention provides a vaporizer including:
(1) a dispersion section having
a gas passage formed in the interior,
a gas introduction port for introducing a carrier gas into the gas passage,
means for supplying a raw material solution to the gas passage,
a gas outlet for sending the carrier gas containing the raw material solution to a vaporization section, and
means for cooling the gas passage; and
(2) the vaporization section for heating and vaporizing the carrier gas containing the atomized raw material solution, which is sent from the dispersion section, having
a vaporization tube one end of which is connected to a reaction section of film forming apparatus or other various types of apparatuses and the other end of which is connected to the gas outlet, and
heating means for heating the vaporization tube, characterized in that
the pressure of the reaction section is set lower than the pressure of the vaporization tube.
The film forming apparatus is preferably a normal-pressure CVD apparatus in which the pressure of the reaction section is controlled to 900 to 760 Torr.
The film forming apparatus is preferably a depressurized CVD apparatus in which the pressure of the reaction section is controlled to 20 to 0.1 Torr.
The film forming apparatus is preferably a low-pressure CVD apparatus in which the pressure of the reaction section is controlled to 0.1 to 0.001 Torr.
The present invention provides a vaporizer including:
(1) a dispersion section having
a gas passage formed in the interior,
a gas introduction port for introducing a carrier gas into the gas passage,
means for supplying a raw material solution to the gas passage,
a gas outlet for sending the carrier gas containing the raw material solution to a vaporization section, and
means for cooling the gas passage; and
(2) the vaporization section for heating and vaporizing the carrier gas containing the raw material solution, which is sent from the dispersion section, having
a vaporization tube one end of which is connected to a reaction section of film forming apparatus or other various types of apparatuses and the other end of which is connected to the gas outlet, and
heating means for heating the vaporization tube, characterized in that
(3) the dispersion section has a dispersion section body having a cylindrical or conical hollow portion and a rod having an outside diameter smaller than the inside diameter of the cylindrical or conical hollow portion,
the rod has one or two or more spiral grooves on the vaporizer side at the outer periphery of the rod, and is inserted in the cylindrical or conical hollow portion, the inside diameter thereof sometimes spreading in a taper shape toward the vaporizer side, and
the pressure of the reaction section is set lower than the pressure of the vaporization tube.
The film forming apparatus is preferably a normal-pressure CVD apparatus in which the pressure of the reaction section is controlled to 900 to 760 Torr.
The film forming apparatus is preferably a depressurized CVD apparatus in which the pressure of the reaction section is controlled to 20 to 0.1 Torr.
The film forming apparatus is preferably a low-pressure CVD apparatus in which the pressure of the reaction section is controlled to 0.1 to 0.001 Torr.
The present invention provides a vaporizer including:
(1) a dispersion section having
a gas passage formed in the interior,
a gas introduction port for introducing a carrier gas into the gas passage,
means for supplying a raw material solution to the gas passage,
a gas outlet for sending the carrier gas containing the raw material solution to a vaporization section, and
means for cooling the gas passage; and
(2) the vaporization section for heating and vaporizing the carrier gas containing the raw material solution, which is sent from the dispersion section, having
a vaporization tube one end of which is connected to a reaction section of film forming apparatus or other various types of apparatuses and the other end of which is connected to the gas outlet, and
heating means for heating the vaporization tube, characterized in that
an oxidizing gas can be added to the carrier gas from the gas introduction port or an oxidizing gas can be introduced from a primary oxygen supply port, and
the pressure of the reaction section is set lower than the pressure of the vaporization tube.
The film forming apparatus is preferably a normal-pressure CVD apparatus in which the pressure of the reaction section is controlled to 900 to 760 Torr.
The film forming apparatus is preferably a depressurized CVD apparatus in which the pressure of the reaction section is controlled to 20 to 0.1 Torr.
The film forming apparatus is preferably a low-pressure CVD apparatus in which the pressure of the reaction section is controlled to 0.1 to 0.001 Torr.
The present invention provides a vaporizer including:
(1) a dispersion section having
a gas passage formed in the interior,
a gas introduction port for introducing a carrier gas into the gas passage,
means for supplying a raw material solution to the gas passage,
a gas outlet for sending the carrier gas containing the raw material solution to a vaporization section, and
means for cooling the gas passage; and
(2) the vaporization section for heating and vaporizing the carrier gas containing the raw material solution, which is sent from the dispersion section, having
a vaporization tube one end of which is connected to a reaction section of film forming apparatus or other various types of apparatuses and the other end of which is connected to the gas outlet, and
heating means for heating the vaporization tube, characterized in that
a radiation preventive portion having a minute hole is provided on the outside of the gas outlet,
the carrier gas and an oxidizing gas can be introduced from the gas introduction port, and
the pressure of the reaction section is set lower than the pressure of the vaporization tube.
The film forming apparatus is preferably a normal-pressure CVD apparatus in which the pressure of the reaction section is controlled to 900 to 760 Torr.
The film forming apparatus is preferably a depressurized CVD apparatus in which the pressure of the reaction section is controlled to 20 to 0.1 Torr.
The film forming apparatus is preferably a low-pressure CVD apparatus in which the pressure of the reaction section is controlled to 0.1 to 0.001 Torr.
The present invention provides a vaporizer including:
a disperser formed with
a plurality of solution passages for supplying a plurality of raw material solutions,
a mixing section for mixing the raw material solutions supplied from the solution passages,
a supply passage one end of which communicates with the mixing section and which has an outlet on the vaporization section side,
a gas passage arranged so that a carrier gas or a mixed gas of the carrier gas and oxygen is blown to the mixed raw material solution coming from the mixing section in the supply passage, and
cooling means for cooling the supply passage; and
a vaporization section for heating and vaporizing the carrier gas containing the raw material solutions, which is sent from the disperser, having
a vaporization tube one end of which is connected to a reaction section of a film forming apparatus or other various types of apparatuses and the other end of which is connected to the outlet of the disperser, and
heating means for heating the vaporization tube, characterized in that
a radiation preventive portion having a minute hole is provided on the outside of the outlet,
a primary oxygen supply port capable of introducing an oxidizing gas is provided just near the dispersion blowoff portion, and
the pressure of the reaction section is set lower than the pressure of the vaporization tube.
The film forming apparatus is preferably a normal-pressure CVD apparatus in which the pressure of the reaction section is controlled to 900 to 760 Torr.
The film forming apparatus is preferably a depressurized CVD apparatus in which the pressure of the reaction section is controlled to 20 to 0.1 Torr.
The film forming apparatus is preferably a low-pressure CVD apparatus in which the pressure of the reaction section is controlled to 0.1 to 0.001 Torr.
The present invention provides a film forming apparatus including the vaporizer as described above.
The present invention provides a vaporizing method in which a raw material solution is introduced into a gas passage, and a carrier gas is sprayed toward the introduced raw material solution, by which the raw material solution is sheared and atomized into raw material mist, and then, the raw material mist is supplied to a vaporization section to be vaporized, characterized in that
control is carried out so that the pressures of the carrier gas and the introduced raw material solution are almost equal in a region in which the carrier gas comes into contact with the introduced raw material solution.
The present invention provides a vaporizing method in which a raw material solution is introduced into a gas passage, and a carrier gas is sprayed toward the introduced raw material solution, by which the raw material solution is sheared and atomized into raw material mist, and then, the raw material mist is supplied to a vaporization section to be vaporized, characterized in that
control is carried out so that the pressure of the carrier gas is lower than the pressure of the introduced raw material solution in a region in which the carrier gas comes into contact with the introduced raw material solution.
Control is preferably carried out so that the pressure of the carrier gas is lower than the pressure of the introduced raw material solution by 760 Torr at a maximum in a region in which the carrier gas comes into contact with the introduced raw material solution.
Control is preferably carried out so that the pressure of the carrier gas is lower than the pressure of the introduced raw material solution by 100 to 10 Torr at a maximum in a region in which the carrier gas comes into contact with the introduced raw material solution.
The present invention provides a vaporizing method in which a raw material solution is introduced into a gas passage, and a carrier gas is sprayed toward the introduced raw material solution, by which the raw material solution is sheared and atomized into raw material mist, and then, the raw material mist is supplied to a vaporization section to be vaporized, characterized in that
control is carried out so that the pressures of the carrier gas and the raw material solution are higher than the vapor pressure of the introduced raw material solution in a region in which the carrier gas comes into contact with the introduced raw material solution.
In a vaporizing method in which a raw material solution is introduced into a gas passage, and a carrier gas is sprayed toward the introduced raw material solution, by which the raw material solution is sheared and atomized into raw material mist, and then, the raw material mist is supplied to a vaporization section to be vaporized,
control is preferably carried out so that the pressures of the carrier gas and the raw material solution are 1.5 times or more higher than the vapor pressure of the introduced raw material solution in a region in which the carrier gas comes into contact with the introduced raw material solution.
Oxygen is preferably contained in the carrier gas in advance.
The present invention provides a film characterized by being formed after vaporization is accomplished by the vaporizing method as described above.
The present invention provides an electronic device including the above-described film.
The present invention provides a CVD thin film forming method characterized in that after a pressurizing gas dissolved in a transfer solution using the pressurizing gas has been removed, the flow rate is controlled, and the vaporizer is connected to a CVD apparatus to form a thin film.
It is preferable that the transfer solution using the pressurizing gas be caused to flow in a fluororesin pipe in which transmission speed is controlled, whereby only the pressurizing gas be removed.
It is preferable that when only the pressurizing gas is removed by causing the transfer solution using the pressurizing gas to flow in a fluororesin pipe etc. in which transmission speed is controlled, the removal of the pressuring gas be accelerated by controlling the external environment of the fluororesin pipe etc.
The present invention provides a vaporizing method in which a raw material solution is introduced into a passage and introduced into a depressurized and heated vaporizer, and is sprayed or dripped into the vaporizer, whereby the raw material solution is atomized and vaporized, characterized in that control is carried out so that the pressure of the raw material solution in the tip end portion of the passage is higher than the vapor pressure of the introduced raw material solution.
Control is preferably carried out so that the pressure of the raw material solution is 1.5 times or more the vapor pressure of the introduced raw material solution in the tip end portion of the passage.
The present invention provides a vaporizing method in which a raw material solution and a carrier gas are introduced into a depressurized and heated vaporizer, and are sprayed into the vaporizer, whereby the raw material solution is atomized and vaporized, characterized in that control is carried out so that the pressure of the raw material solution in the tip end portion of the passage is higher than the vapor pressure of the introduced raw material solution.
Control is preferably carried out so that the pressure of the raw material solution is 1.5 times or more the vapor pressure of the raw material solution in the tip end portion of the passage.
Oxygen is preferably contained in the carrier gas in advance.
Control is preferably carried out so that the pressures of the carrier gas and the introduced raw material solution are almost equal in a region in which the carrier gas comes into contact with the introduced raw material solution.
Control is preferably carried out so that the pressure of the carrier gas is lower than the pressure of the introduced raw material solution in a region in which the carrier gas comes into contact with the introduced raw material solution.
Control is preferably carried out so that the pressure of the carrier gas is lower than the pressure of the introduced raw material solution by 760 Torr at a maximum in a region in which the carrier gas comes into contact with the introduced raw material solution.
Control is preferably carried out so that the pressure of the carrier gas is lower than the pressure of the introduced raw material solution by 100 to 10 Torr at a maximum in a region in which the carrier gas comes into contact with the introduced raw material solution.
Control is preferably carried out so that the pressures of the carrier gas and the raw material solution are higher than the vapor pressure of the introduced raw material solution in a region in which the carrier gas comes into contact with the introduced raw material solution.
Control is preferably carried out so that the pressures of the carrier gas and the raw material solution are 1.5 times or more higher than the vapor pressure of the introduced raw material solution in a region in which the carrier gas comes into contact with the introduced raw material solution.
The present invention provides a CVD thin film forming apparatus in which a transfer solution using a pressurizing gas is introduced into the vaporizer via a mass-flow controller, and the vaporizer is connected to the CVD apparatus, whereby a thin film is formed, characterized in that degassing means for removing a pressuring gas is provided on the upstream side of the mass-flow controller.
Also, the present invention is applicable to the following vaporizers and vaporizing methods:
A vaporizer including:
(1) a dispersion section having
a gas passage formed in the interior,
a gas introduction port for introducing a carrier gas into the gas passage,
means for supplying a raw material solution to the gas passage,
a gas outlet for sending the carrier gas containing the raw material solution to a vaporization section, and
means for cooling the gas passage; and
(2) the vaporization section for heating and vaporizing the carrier gas containing the atomized raw material solution, which is sent from the dispersion section, having
a vaporization tube one end of which is connected to a reaction section of film forming apparatus or other various types of apparatuses and the other end of which is connected to the gas outlet, and
heating means for heating the vaporization tube, characterized in that
a radiation preventive portion having a minute hole is provided on the outside of the gas outlet.
A vaporizer including:
(1) a dispersion section having
a gas passage formed in the interior,
a gas introduction port for introducing a carrier gas into the gas passage,
means for supplying a raw material solution to the gas passage, and
a gas outlet for sending the carrier gas containing the raw material solution to a vaporization section, and
(2) the vaporization section for heating and vaporizing the carrier gas containing the raw material solution, which is sent from the dispersion section, having
a vaporization tube one end of which is connected to a reaction section of film forming apparatus or other various types of apparatuses and the other end of which is connected to the gas outlet, and
heating means for heating the vaporization tube, characterized in that
(3) the dispersion section has a dispersion section body having a cylindrical or conical hollow portion and a rod having an outside diameter smaller than the inside diameter of the cylindrical or conical hollow portion,
the rod has one or two or more spiral grooves on the vaporizer side at the outer periphery of the rod, and is inserted in the cylindrical or conical hollow portion, and
(4) a cooled radiation preventive portion is provided which has a minute hole on the gas outlet side on the outside of the gas outlet and the inside diameter of which spreads in a taper shape toward the vaporizer.
A vaporizer including:
(1) a dispersion section having
a gas passage formed in the interior,
a gas introduction port for introducing a carrier gas into the gas passage,
means for supplying a raw material solution to the gas passage,
a gas outlet for sending the carrier gas containing the raw material solution to a vaporization section, and
means for cooling the gas passage; and
(2) the vaporization section for heating and vaporizing the carrier gas containing the atomized raw material solution, which is sent from the dispersion section, having
a vaporization tube one end of which is connected to a reaction section of film forming apparatus or other various types of apparatuses and the other end of which is connected to the gas outlet, and
heating means for heating the vaporization tube, characterized in that
a small quantity of oxidizing gas can be added to the carrier gas such as Ar, N2 or helium from the gas introduction port or an oxidizing gas or the mixed gas thereof can be introduced from a primary oxygen supply port just near a blowoff portion.
A vaporizer including:
(1) a dispersion section having
a gas passage formed in the interior,
a gas introduction port for introducing a carrier gas into the gas passage,
means for supplying a raw material solution to the gas passage,
a gas outlet for sending the carrier gas containing the raw material solution to a vaporization section, and
means for cooling the gas passage; and
(2) the vaporization section for heating and vaporizing the carrier gas containing the raw material solution, which is sent from the dispersion section, characterized in that
a radiation preventive portion having a minute hole is provided on the outside of the gas outlet, and
the carrier gas and an oxidizing gas can be introduced from the gas introduction port.
A vaporizing method in which a raw material solution is introduced into a gas passage, and a carrier gas with a high velocity is sprayed toward the introduced raw material solution, by which the raw material solution is sheared and atomized into raw material gas, and then, the raw material gas is supplied to a vaporization section to be vaporized, characterized in that oxygen is contained in the carrier gas in advance.
A vaporizing method using a vaporizer formed with
a plurality of solution passages for supplying raw material solutions,
a mixing section for mixing the raw material solutions supplied from the solution passages,
a supply passage one end of which communicates with the mixing section and which has an outlet on the vaporization section side,
a gas passage arranged so that a carrier gas or a mixed gas of the carrier gas and oxygen is blown to the mixed raw material solution coming from the mixing section in the supply passage, and
cooling means for cooling the supply passage.
FIGS. 7(a) and 7(b) are sectional views showing modifications of a gas passage of a vaporizer for MOCVD in accordance with example 4;
FIGS. 16(a) and 16(b) are sectional views of a conventional vaporizer for MOCVD;
In this example, the vaporizer includes:
a dispersion section 8 having a gas passage 2 formed in a dispersion section body 1 forming a dispersion section,
a gas introduction port 4 for introducing a pressurized carrier gas 3 to the gas passage 2,
means (raw material supply hole) 6 for supplying a raw material solution 5 to the carrier gas passing through the gas passage 2 and for making the raw material solution 5 in a mist form,
a gas outlet 7 for sending the carrier gas (raw material gas) containing the mist-form raw material solution 5 to a vaporization section 22, and
means (cooling water) 18 for cooling the carrier gas flowing in the gas passage 2; and
the vaporization section 22 for heating and vaporizing the carrier gas in which the raw material solution is dispersed, which is sent from the dispersion section 8, having
a vaporization tube 20 one end of which is connected to a reaction tube of an MOCVD apparatus and the other end of which is connected to the gas outlet 7 of the dispersion section 8, and
heating means (heater) 21 for heating the vaporization tube 20, and
a radiation preventive portion 102 having a minute hole 101 is provided on the outside of the gas outlet 7.
Next, this example is explained in more detail.
In the example shown in
The cross sectional area of the gas passage is preferably 0.10 to 0.5 mm2. If it is less than 0.10 mm2, the fabrication is difficult to do. If it exceeds 0.5 mm2, it is necessary to use a high-pressure carrier gas with a high flow rate to speed up the carrier gas.
If the carrier gas with a high flow rate is used, a high-capacity large vacuum pump is needed to keep a reaction chamber in a depressurized state (for example, 1.0 Torr). Since it is difficult to use a vacuum pump having an evacuation capacity exceeding 10,000 liters/min (at 1.0 Torr), in order to achieve industrially practical application, a proper flow rate, i.e., a gas passage area of 0.10 to 0.5 mm2 is preferable.
At one end of this gas passage 2, the gas introduction port 4 is provided. The gas introduction port 4 is connected with a carrier gas (for example, N2, Ar, He) source (not shown).
At the side of a substantially central portion of the dispersion section body 1, the raw material supply hole 6 is provided so as to communicate with the gas passage 2, so that the raw material solution 5 is introduced into the gas passage 2, and thus the raw material solution 5 can be dispersed in the carrier gas passing through the gas passage 2 to form the raw material gas.
At one end of the gas passage 2, the gas outlet 7 communicating with the vaporization tube 20 of the vaporization section 22 is provided.
In the dispersion section body 1, a space 11 for causing the cooling water 18 to flow is formed. By causing the cooling water 8 to flow in this space, the carrier gas flowing in the gas passage 2 is cooled. Alternatively, in place of this space, a Peltier element etc. may be provided to cool the carrier gas. Since the interior of the gas passage 2 of the dispersion section 8 is thermally affected by the heater 21 of the vaporization section 22, a solvent and an organic metal complex of the raw material solution do not vaporize at the same time in the gas passage 2, and only the solvent vaporizes. Therefore, by cooling the carrier gas in which the raw material solution is dispersed, flowing in the gas passage 2, vaporization of only the solvent is prevented. In particular, the cooling on the downstream side of the raw material supply hole 6 is important, and therefore at least a portion on the downstream side of the raw material supply hole 6 is cooled. The cooling temperature is a temperature equal to or lower than the boiling point of solvent. For example, in the case of THF, the cooling temperature is 67° C. or lower. In particular, the temperature at the gas outlet 7 is important.
In this example, the radiation preventive portion 102 having the minute hole 101 is further provided on the outside of the gas outlet 7.Reference numerals 103 and 104 denote sealing members such as O-rings. This radiation preventive portion 102 can be formed of Teflon (registered trade name), stainless steel, ceramics, or the like. Also, the radiation preventive portion 102 is preferably formed of a material having high thermal conductivity.
According to the knowledge of the inventor, in the conventional technique, the heat in the vaporization section overheats the gas in the gas passage 2 via the gas outlet 7 as radiation heat. Therefore, even if the gas is cooled by the cooling water 18, a low melting point component in the gas deposits near the gas outlet 7.
The radiation preventive portion is a member for preventing the radiation heat from propagating to the gas. Therefore, the cross-sectional area of the minute hole 101 is preferably smaller than the cross-sectional area of the gas passage 2. It is preferably equal to or less than ½, more preferably equal to or less than ⅓ of the cross-sectional area of the gas passage 2. Also, the minute hole is preferably miniaturized. In particular, it is preferably miniaturized to a size such that the flow velocity of emitting gas is subsonic.
Also, the length of the minute hole is preferably equal to or more than five times, more preferably equal to or more than ten times the minute hole size.
Also, by cooling the dispersion section, blockage due to carbide in the gas passage (especially the gas outlet) is prevented even if the vaporizer is used for a long period of time.
On the downstream side of the dispersion section body 1, the dispersion section body 1 is connected to the vaporization tube 20. The connection between the dispersion section body 1 and the vaporization tube 20 is made by a joint 24, and this portion serves as a connecting portion 23.
As the vaporization tube 20, stainless steel, for example, SUS316L is preferably used. The dimensions of the vaporization tube 20 may be determined appropriately so that its length is enough to heat the vaporized gas. For example, when a SrBi2Ta2O9 raw material solution of 0.04 ccm is vaporized, the vaporization tube 20 having an outside diameter of ¾ inches and a length of several hundred millimeters can be used.
The downstream side end of the vaporization tube 20 is connected to a reaction tube of an MOCVD apparatus. In this example, an oxygen supply port 25 is provided on the vaporization tube 20 as oxygen supply means so that oxygen heated to a predetermined temperature can be fed to the carrier gas.
First, the supply of raw material solution to the vaporizer is described.
As shown in
Also, the reserve tanks 32a, 32b, 32c and 32dare connected with a carrier gas bomb 33.
The details of the reserve tank are shown in
The reserve tank is filled with the raw material solution. The carrier gas (for example, inert gas Ar, He, Ne) of, for example, 1.0 to 3.0 kgf/cm2 is sent into each of the reserve tank (content volume: 300 cc, made of SUS). Since the interior of the reserve tank is pressurized by the carrier gas, the raw material solution is pushed up in the tube on the side contacting with the solution, and is sent under pressure to the liquid mass-flow controller (manufactured by STEC, full-scale flow rate: 0.2 cc/min), where the flow rate is controlled. The raw material solution is conveyed to the raw material supply hole 6 through a raw material supply inlet 29 of the vaporizer.
The raw material solution, whose flow rate has been controlled to a fixed value by the mass-flow controller, is conveyed to a reaction section by the carrier gas. At the same time, oxygen (oxidizing agent), whose flow rate has been controlled to a fixed value by a mass-flow controller (manufactured by STEC, full-scale flow rate: 2 L/min), is also conveyed to the reaction section.
Since in the raw material solution, a liquid-form or solid-form organic metal complex is dissolved in THF and other solvents at ordinary temperature, if it is left as it is, the organic metal complex is deposited by the evaporation of THF solvent, and it finally becomes in a solid form. Therefore, it is assumed that the tube in contact with the raw liquid may be blocked by the deposited organic metal complex. In order to restrain the blockage of tube, a cleaning line is provided considering that the interior of the tube and vaporizer should be cleaned with THF and other solvents after the film forming work has been finished. In the cleaning operation, a portion fitting to each work including raw material container replacement work in a section from the container outlet side to the vaporizer is washed off with the solvent.
The valves 31b, 31c and 31dwere opened, and the carrier gas was sent under pressure into the reserve tanks 32b, 32c and 32d. The raw material solution is sent under pressure to the mass-flow controller (manufactured by STEC, full-scale flow rate: 0.2 cc/min), where the flow rate is controlled. The raw material solution is conveyed to the raw material supply hole 6 of the vaporizer.
On the other hand, the carrier gas was introduced through the gas introduction port of the vaporizer. The maximum pressure on the supply port side is preferably equal to or lower than 3 kgf/cm2. At this time, the maximum flow rate of gas capable of passing through is about 1200 cc/min, and the flow velocity in the gas passage 2 reaches one hundred and several tens meters per second.
When the raw material solution is introduced through the raw material supply hole 6 to the carrier gas flowing in the gas passage 2 of the vaporizer, the raw material solution is sheared by the high-velocity flow of carrier gas and changed to ultrafine particles. As a result, the raw material solution is dispersed in the carrier gas in an untrafine particle state. The carrier gas in which the raw material solution is dispersed in an untrafine particle state (raw material gas) is atomized as being in a high-velocity state by the vaporization section 22 and is released. The angle formed between the gas passage and the raw material supply hole is optimized. In the case where the angle between the carrier flow path and the raw material solution introduction port is an acute angle (30 degrees), the solution is drawn by the gas. If the angle is equal to or larger than 90 degrees, the solution is pushed by the gas. The optimum angle is determined from the viscosity and flow rate of solution. When the viscosity or the flow rate is high, the solution is caused to flow smoothly by making the angle more acute. In the case where hexane is used as the solvent to form an SBT film, an angle of about 84 degrees is preferable because both viscosity and flow rate are low.
Three kinds of raw material solutions, whose flow rate has been controlled to a fixed value, flow into the gas passage 2 through the raw material supply hole 6 via the raw material supply inlet 29, and after moving in the gas passage together with the carrier gas, which forms a high-velocity gas flow, they are released to the vaporization section 22. In the dispersion section 8 as well, the raw material solution is heated by the heat from the vaporization section 22, and the evaporation of THF and other solvents is accelerated. Therefore, a section from the raw material supply inlet 29 to the raw material supply hole 6 and a section of the gas passage 2 are cooled by water or other cooling media.
The vaporization of the raw material solution, which is dispersed in the carrier gas in a fine particle form, released from the dispersion section 8 is accelerated during the conveyance in the vaporization tube 20 heated to a predetermined temperature by the heater 21. By the feeding of oxygen heated to a predetermined temperature from the oxygen supply port 25 provided just before the raw material solution reaches the reaction tube of MOCVD, a mixed gas is formed, and flows into the reaction tube. In this example, evaluation was carried out by analyzing the reaction mode of vaporized gas in place of film formation.
A vacuum pump (not shown) was connected from an exhaust outlet 42 to remove water and other impurities in the reaction tube 44 by means of an evacuating operation for about 20 minutes, and a valve 40 on the downstream side of the exhaust outlet 42 was closed.
Cooling water was caused to flow in the vaporizer at a flow rate of about 400 cc/min. On the other hand, a carrier gas of 3 kgf/cm2 was caused to flow at a flow rate of 495 cc/min. After the reaction tube 44 was sufficiently filled with the carrier gas, the valve 40 was opened. The temperature at the gas outlet 7 was lower than 67° C.
The interior of the vaporization tube 20 was heated to 200° C., a section from the reaction tube 44 to a gas pack 46 and the gas pack were heated to 100° C., and the interior of the reaction tube 44 was heated to 300° C. to 600° C.
The interior of the reserve tank was pressurized by the carrier gas, and a predetermined liquid was caused to flow by the mass-flow controller.
Sr(DPM)2, Bi(C6H5)3, Ta(OC2H5)5, and THF were caused to flow at flow rates of 0.04 cc/min, 0.08 cc/min, 0.08 cc/min, and 0.2 cc/min, respectively.
After 20 minutes, a valve just in front of the gas pack 46 was opened to recover a reaction product in the gas pack 46. The reaction product was analyzed with a gas chromatograph, and it was examined whether the detected product coincides with the product in the reaction formula studied based on the reaction theory. As a result, in this example, the detected product coincided well with the product in the reaction formula studied based on the reaction theory.
Also, the amount of carbides adhering to the external surface on the gas outlet 7 side of the dispersion section body 1 was measured. As the result, the amount of adhering carbides was very small, and was further smaller than in the case where the apparatus shown in
In the case of a raw material solution in which a metal to be used as a film raw material is mixed with or dissolved in a solvent, the raw material solution is generally such that the metal is a complex and in a liquid/liquid state (perfect solvent solution). However, as the result of a careful examination of raw material solution conducted by the inventor, there was gained a knowledge that the metal complex is not necessarily in a scattered molecular state, and the metal complex itself is present as fine particles with a size of 1 to 100 nm in the solvent in some cases or is partially present as a solid/liquid state. It is considered that the clogging at the time of vaporization is liable to occur especially when the raw material solution is in such a state. When the evaporator in accordance with the present invention is used, clogging does not occur even when the raw material solution is in such a state.
Also, in a solution in which the raw material solution is present, the fine particles are liable to settle at the bottom by means of the gravity thereof. Therefore, to prevent clogging, it is preferable that convection be caused in the solution by heating the bottom portion (to a temperature equal to or lower than the evaporating temperature of solvent) to homogeneously disperse the fine particles. Also, it is preferable that not only the bottom portion be heated but also the side face of the container upper surface be cooled. Needless to say, the heating is performed at a temperature equal to or lower than the evaporating temperature of solvent.
It is preferable that a heater set or control the quantity of heat for heating the evaporation tube upper region so as to be larger than the quantity of heat for heating the downstream region. Specifically, since water-cooled gas blows off from the dispersion section, it is preferable that there be provided a heater that sets or controls the quantity of heat for heating so as to be large in the evaporation tube upper region and be small in the downstream region.
In this example, a cooling water passage 106 was formed at the outer periphery of the radiation preventive portion 102, and cooling means 50 was provided at the outer periphery of the connecting portion 23 to cool the radiation preventive portion 102.
Also, a concave portion 107 was provided around the outlet of the minute hole 101.
Other points are the same as in example 1.
In this example, the detected product coincided better with the product in the reaction formula studied based on the reaction theory than in the case of example 1.
Also, the amount of carbides adhering to the external surface on the gas outlet 7 side of the dispersion section body 1 was measured, with the result that the amount of adhering carbides was about ⅓ of the case of example 1.
In this example, the radiation preventive portion 102 has a taper 51. This taper 51 eliminates a dead zone in this portion, so that the retention of raw material can be prevented.
Other points are the same as in example 2.
In this example, the detected product coincided better with the product in the reaction formula studied based on the reaction theory than in the case of example 2.
Also, the amount of carbides adhering to the external surface on the gas outlet side 7 of the dispersion section body 1 was measured, with the result that the amount of adhering carbides was nearly zero.
In
The grooves may be formed in plural numbers in parallel with the axis in the lengthwise direction of the rod 10, or they may be formed in a spiral form in the surface of the rod 10. In the case of the spiral form, a raw material gas having high homogeneity can be obtained.
The examples shown in FIGS. 7(a) and 7(b) are examples in which the surface of the rod 10 is machined. However, it is a matter of course that a rod having a circular cross section is used, and concave portions are formed in the surface of hole to provide gas passages. It is preferable that the rod be arranged in accordance with H7×h6−JS7 specified in JIS.
Example 5 is explained with reference to
The vaporizer for MOCVD of this example includes:
a dispersion section 8 having
a gas passage formed inside,
a gas introduction port 4 for introducing a pressurized carrier gas 3 into the gas passage,
means for supplying raw material solutions 5a and 5b to the gas passage, and a gas outlet 7 for sending the carrier gas containing the raw material solutions 5a and 5b to a vaporization section 22; and
the vaporization section 22 for heating and vaporizing the carrier gas in which the raw material solutions are contained, which is sent from the dispersion section 8, having
a vaporization tube 20 one end of which is connected to a reaction tube of an MOCVD apparatus and the other end of which is connected to the gas outlet 7 of the dispersion section 8, and
heating means for heating the vaporization tube 20, and
the dispersion section 8 has a dispersion body 1 having a cylindrical hollow portion and a rod 10 having an outside diameter smaller than the inside diameter of the cylindrical hollow portion;
one or two or more spiral grooves 60 are formed on the vaporizer side at the outer periphery of the rod 10;
the rod 10 is inserted in the cylindrical hollow portion; and
a radiation preventive portion 101 is provided which has a minute hole 101 on the outside of the gas outlet 7 and the inside diameter of which spreads in a taper shape toward the vaporizer 22.
When the raw material solution 5 is supplied to the gas passage through which the high-velocity carrier gas 3 flows, the raw material solution is sheared and atomized. Specifically, the raw material solution, which is a liquid, is sheared by a high-velocity flow of carrier gas, and made particles. The raw material solution having been made particles is dispersed in the carrier gas in a particulate state. This point is the same as in example 1.
In order to accomplish the shearing and atomization in the optimum manner, the following conditions are favorable.
The raw material solution 5 is supplied preferably at 0.005 to 2 cc/min, more preferably at 0.005 to 0.02 cc/min, and still more preferably at 0.1 to 0.3 cc/min. When a plurality of raw material solutions (including solvent) are supplied at the same time, the total quantity thereof should preferably be as described above.
Also, the carrier gas is supplied preferably at a rate of 10 to 200 m/sec, more preferably at a rate of 100 to 200 m/sec.
There is a mutual relation between the flow rate of raw material solution and the flow rate of carrier gas. It is a matter of course to select a cross-sectional area and a shape of flow path that realizes the optimum shearing and atomization and can obtain ultrafine particle mist.
In this example, the spiral groove 60 is formed at the outer periphery of the rod 10, and a gap space is present between the dispersion section body 1 and the rod 10. Therefore, the carrier gas containing the atomized raw material solution goes straight in this gap space as a straight flow, and also forms a swirl flow along the spiral groove 60.
The inventor found that the atomized raw material solution is dispersed uniformly in the carrier gas in the state in which the straight flow and the swirl flow coexist. The reason why uniform dispersion can be obtained if the straight flow and the swirl flow coexist is not necessarily clear. However, the following reason is possible. The existence of swirl flow produces a centrifugal force in the flow, and a secondary flow is produced. This secondary flow accelerates the mixture of the raw material with the carrier gas. That is, it is considered that the secondary derived flow is produced in the direction perpendicular to the flow by the centrifugal effect of swirl flow, and thereby the atomized raw material solution is dispersed uniformly in the carrier gas.
Next, this example is explained in more detail.
In this example, the configuration is such that as one example, four kinds of raw material solutions 5a, 5b , 5c and 5d (5a, 5b and 5c are organic metal raw materials and 5d is a solvent raw material such as THF) are supplied to the gas passage.
In order to mix the carrier gas containing the raw material solutions having been atomized and made in an ultrafine particle shape (referred to as a “raw material gas”), in this example, a portion in which the spiral groove is absent is provided on a downstream side of a portion corresponding to a raw material supply hole 6 of the rod 10. This portion serves as a premixing portion 65. In the premixing portion 65, the raw material gas of three kinds of organic metals is mixed to some extent, and further a perfectly mixed raw material gas is formed in the region of the downstream spiral structure. In order to obtain a uniformly mixed raw material gas, the length of the mixing portion 65 is preferably 5 to 20 mm, more preferably 8 to 15 mm. If the length thereof is out of the above range, only on kind of mixed raw material gas with a high concentration of the raw material gases of three kinds of organic metals is sometimes sent to the vaporization section 22.
In this example, an end portion 66 on the upstream side of the rod 10 is provided with a parallel portion 67 and a taper portion 58. In the cylindrical hollow portion of the dispersion section body 1 as well, a parallel portion having an inside diameter equal to the outside diameter of the parallel portion 67 of the rod 10, which corresponds to the parallel portion 67, and a taper portion with the same taper as the taper of the rod 10, which corresponds to the taper portion 58, are provided. Therefore, when the rod 10 is inserted from the left-hand side in the figure, the rod 10 is held in the hollow portion of the dispersion section body 1.
In this example, unlike the case of example 1, since the rod 10 is held with the taper being provided, even if a carrier gas having a pressure higher than 3 kgf/cm2 is used, the rod 10 can be prevented from moving. Specifically, if the holding technique shown in
As shown in
For the holding of the rod 10 and the formation of gas passage, the construction shown in
The number of the spiral grooves 60 may be one as shown in
The size and shape of the spiral groove 60 is not subject to any special restriction. The size and shape shown in
In this example, as shown in
Also, in this example, an expansion section 69 is independently provided in front of the inlet of the dispersion section 22, and the lengthwise radiation preventive portion 102 is arranged in this expansion section 69.
The minute hole 101 is formed on the gas outlet 7 side of the radiation preventive portion, and the inside diameter of the minute hole 101 spreads in a taper shape toward the vaporizer side.
The expansion section 69 also serves to prevent the retention of raw material gas, which has been described in example 3. Needless to say, there is no need for independently provide the expansion section 69. The integrated construction as shown in
The expansion angle θ of the expansion section 69 is preferably 5 to 10 degrees. When the expansion angle θ is within this range, the raw material gas can be supplied to the dispersion section without destroying the swirl flow. Also, when the expansion angle θ is within this range, the fluid resistance due to expansion becomes a minimum and also the presence of dead zone becomes a minimum, so that the presence of eddy current due to the presence of dead zone can be made a minimum. The expansion angle θ is more preferably 6 to 7 degrees. In the case of the example shown in
The apparatus shown in
Quantity of Introduced Raw Material Solutions:
As a vaporizing apparatus, the apparatus shown in
The raw material solutions were supplied from the raw material supply hole 6, and the carrier gas was supplied by changing the velocity thereof variously. From the raw material supply hole, Sr(DPM) 2 was supplied to the groove 67a, Bi(C6H5)3 was supplied to the groove 67b, Ta(OC2H5)5 was supplied to the groove 67c, and THF and other solvents were supplied to the groove 67d.
Heating was not performed in the vaporization section, and the raw material gas was sampled at the gas outlet 7 to measure the particle diameter of raw material solution in the sampled raw material gas.
The measurement result is shown in
In example 7, a rod formed with a spiral groove was used.
Other points are the same as in example 6.
In example 6, in an extended portion of the groove, the concentration of raw material solution supplied to the groove was high. Specifically, in an extended portion of the groove 67a, the concentration of Sr(DPM)2 was high, in an extended portion of the groove 67b, the concentration of Bi(C6H5)3 was high, and in an extended portion of the groove 67b, the concentration of Ta(OC2H5)5 was high.
However, in this example, for the mixed raw material gas obtained at the end of spiral groove, each organic metal raw material was uniform in any portions.
Example 8 is shown in
Conventionally, oxygen has been introduced only on the downstream side of the vaporization section 22 as shown in
The inventor found that the cause for this relates to the introduction position of oxygen. Specifically, it was found that if as shown in
It is optional to mix oxygen with the carrier gas in advance and to introduce this mixed gas through the gas introduction port 4.
By using the vaporizer shown in
Concretely, the conditions of vaporizer and reaction chamber were controlled as described below, and an SBT film was formed on a substrate obtained by forming platinum of 200 nm on an oxidized silicon substrate.
Concrete Conditions:
Reaction oxygen temperature 216° C. (temperature is controlled by a heater provided separately before reaction oxygen is introduced from a dispersion blowoff portion lower portion)
Results:
SBT film thickness about 300 nm (deposition speed about 150 nm/min)
The difference between the composition in the formed film and the composition in the raw material solution was very small, and the deposition speed was about five times the conventional speed. It is found that the effect of introducing small amount of oxygen through the gas introduction port 4 together with the carrier gas is extremely great. The carbon content is as low as 3.5 at %.
Because the temperature of the reaction oxygen (200 cc/min) was precisely controlled (to 216° C.) by the separately provided heater before the reaction oxygen was introduced from the dispersion blowoff portion lower portion 25, from the fact that contamination of the lower part of evaporation tube was eliminated, it was verified that the effect of restraining the re-condensation/sublimation(solidification) of vaporized organic metal compound is great.
After the SBT thin film has been formed, crystallization treatment was performed at 750° C. for 30 minutes in an oxygen atmosphere, and measurement and evaluation were carried out by forming an upper electrode. As a result, high crystallization characteristics and polarization characteristics were exhibited. These results are shown in
If an oxidizing gas such as oxygen is merely introduced through the gas introduction port 4 or a primary oxygen supply port just near a blowoff port, it is preferable that, as shown in
The content of carbon in the formed film can be decreased to 5 to 20% of the conventional example.
An example of an SBT thin film deposition process is explained with reference to
A valve 2 is opened, and a valve 1 is closed, by which a reaction chamber is evacuated to a high vacuum. After several minutes, a wafer is transferred from a load lock chamber to a reaction chamber.
At this time, in a vaporizer,
At this time, the pressure gage is controlled to 4 Torr by the automatic pressure regulating valve.
When the temperature becomes stable several minutes after the wafer has been transferred, the valve 1 is opened, and the valve 2 is closed, by which the following gas is caused to flow into the reaction chamber to start deposition.
The reaction pressure chamber pressure is controlled to 1 Torr (by a not described automatic pressure regulating valve).
After predetermined time (20 minutes, in this example) has elapsed, the valve 2 is opened, and the valve 1 is closed, by which the deposition is finished.
The reaction chamber is evacuated to a high vacuum to remove the reaction gas completely, and after one minute, the wafer is taken out to the load lock chamber.
Capacitor Structure
Conventionally, since the reaction oxygen (for example, 200 sccm) has been put in the vaporization tube in a room temperature state, the organic metal gas has been cooled, and adhered and deposited in the vaporization tube.
When the temperature of the reaction oxygen supplied from the lower portion of evacuation section is controlled, conventionally, a heater has been wound around a stainless steel tube (outside dimension: ¼ to 1/16 inch, length: 10 to 100 cm) to control the temperature of external wall of the stainless steel tube (to 219° C., for example).
It has been considered that the temperature of external wall of the stainless steel tube (219° C., for example) is equal to the temperature of oxygen (flow rate: 200 sccm) flowing inside.
However, the measurement of oxygen temperature with a minute thermocouple revealed that the temperature rise is only about 35° C. in this example.
Therefore, the temperature of oxygen after being heated was measured directly with a minute thermocouple, and the heater temperature was controlled, by which the oxygen temperature was controlled accurately.
Since it was not easy to raise the temperature of gas such as oxygen flowing in the tube, the heat exchange efficiency was improved by putting a filler in the heating tube, and the temperature of heated oxygen gas was measured, by which the heater temperature was controlled properly.
Means for such control is a heat exchanger shown in
Example 10 is shown in
In the above-described examples, gas is blown to each of the raw material solutions to atomize the single raw material solution, and subsequently, the atomized raw material solutions are mixed with each other. This example provides an apparatus in which a plurality of raw material solutions are mixed, and the mixed raw material solutions are atomized.
The evaporator of this example includes:
a disperser 150 formed with a plurality of solution passages 130a and 130b for supplying raw material solutions 5a and 5b , a mixing section 109 for mixing the raw material solutions 5a and 5b supplied through the solution passages 130a and 130b, a supply passage 110 one end of which communicates with the mixing section 109 and which has an outlet 017 on the vaporization section 22 side, a gas passage 120 arranged so that a carrier gas or a mixed gas of the carrier gas and oxygen is blown to the mixed raw material solution coming from the mixing section 109 in the supply passage 110, and cooling means for cooling the interior of the supply passage 110; and
a vaporization section 22 for heating and vaporizing the gas containing the raw material solutions, which is sent from the disperser 150, having a vaporization tube one end of which is connected to a reaction tube of an MOCVD apparatus and the other end of which is connected to the outlet 107 of the disperser 150, and heating means 2 for heating the vaporization tube, and a radiation heat preventive material 102 having a minute hole 101 is arranged on the outside of the outlet 107.
This example is effective for the raw material solutions the reaction of which does not proceed even if being mixed. Since the raw material solutions are atomized after being once mixed, the composition is exact as compared with the case where the raw material solutions are mixed after being atomized. Also, means (not shown) for analyzing the composition of mixed raw material solution in the mixing section 109 is provided, and the supply amounts of the raw material solutions 5a and 5b are controlled based on the analysis result, by which more exact composition can be obtained.
Also, in this example, a rod (reference numeral 10 in
Although the number of minute holes is one in the above-described examples, it is a matter of course that number of minute holes may be plural. Also, the diameter of the minute hole is preferably equal to or smaller than 2 mm. When a plurality of minute holes are provided, the diameter can be made far smaller.
Also, in the above-described examples, in the case where the carrier flow path and the raw material solution introduction port make an acute angle (30 degrees), the solution is drawn by the gas. If the angle is equal to or larger than 90 degrees, the solution is pushed by the gas. Therefore, the angle is preferably 30 to 90°. Concretely, the optimum angle is determined from the viscosity and flow rate of solution. When the viscosity is high or the flow rate is high, the solution is caused to flow smoothly by making the angle more acute. Therefore, in implementation, the optimum angle corresponding to the viscosity and flow rate has only to be determined in advance by an experiment etc.
Also, in the above-described examples, it is optional to provide a mechanism for controlling the distance of space between a shower head and a susceptor to an arbitrary distance.
Furthermore, it is preferable that a liquid mass-flow controller for controlling the flow rate of raw material solution be provided, and degassing means for gas removal be provided on the upstream side of the liquid mass-flow controller. If degassing is not accomplished and the raw material solution is introduced to the mass-flow controller, variations in the formed films occur on the same wafer or between wafers. By introducing the raw material solution to the mass-flow controller after the removal of helium etc., the above-described variations in film thickness are decreased remarkably.
By providing means for controlling the temperature of raw material solution, helium transfer container, liquid mass-flow controller, and pipes in front of and behind the mass-flow controller to a fixed temperature, the variations in film thickness can further be prevented. Also, the change of properties of a chemically unstable raw material solution can be prevented. When the SBT thin film is formed, control is precisely carried out in the range of 5 to 20° C. The range of 12° C. ±1° C. is especially preferable.
Also, in a substrate surface treatment apparatus in which a predetermined gas is blown to the substrate surface of a silicon substrate etc. to carry out surface treatment on the substrate surface as shown in
Also, the substrate surface treatment apparatus preferably has a heat conversion plate 304 thermally connected to the heating medium circulation path in a predetermined plane in the heating medium circulation path and in a plane formed in the flow path of the heating medium in the parallel direction so that the portion in the plane of the heat conversion plate 304 can be heated to a substantially uniform temperature by the heating medium.
Further, in the plane of the heat conversion plate 304, a plurality of vent holes for causing the predetermined gas to pass through in the vertical direction of the plane are preferably formed so that the predetermined gas passing through the vent hole can be heated to a substantially uniform temperature in the plane.
Thereupon, the configuration is such that the flow path direction from the upstream ring to the downstream ring between the adjacent heat transfer paths of the heating medium circulation path is alternated. Therefore, the difference in temperature in a region adjacent to the heat transfer path is configured so as to be high/low/high/low. . . . By this configuration, the heat conversion plate can be heated or cooled uniformly. Further, a heat conversion plate thermally connected to the heating medium circulation path is provided in a plane formed in the flow path of heating medium in the parallel direction. Therefore, a portion in the plane of this heat conversion plate can be heated to a substantially uniform temperature by the heating medium.
Regarding Measures Against Air Bubbles Occurring in a CVD Solution:
When the CVD solution is pressurized to 3 to 4 kg/cm2 by using gas (argon, helium, etc.), and the flow rate thereof is controlled by using a liquid mass-flow controller, the pressurizing gas dissolves in the solvent (for example, hexane).
Just after the solution has passed through an MFC, the pressure of solution is decreased to 1 to 0 kg/cm2 by pressure loss. Therefore, most of dissolved pressurizing gas comes out as air bubbles.
The occurring air bubbles cause fluctuations in the flow rate of solution, so that it is necessary to restrain the occurrence of air bubbles.
The solubility of gas (argon, helium, etc.) in the solvent is as described below according to Chemical Handbook (edited by The Chemical Society of Japan, revised 4th edition, published by Maruzen).
The argon solubility of 25.2e-4 mol means that 65 cc of argon dissolves in 1 mol (130 cc) of hexane. Since the quantity of dissolution is proportional to the gas pressure, gas of two to three times the above-described quantity dissolves. The solubility of helium is about 10% of that of argon.
Next, a method for removing (degassing) the dissolved gas is carried out.
The pressurizing gas dissolves, and is observed as air bubbles when the solution is depressurized. This system is shown in
It is found that when helium is used as the pressurizing gas, degassing can be accomplished to a level at which problems scarcely arise by causing the gas to pass through a PFA tube of 15 to 60 cm. However, when the pressure becomes equal to or lower than 400 Torr, air bubbles of several percent are observed, so that the solution pressure cannot be decreased to a value equal to or lower than 400 Torr.
When argon is used as the pressurizing gas, 50% or more of the interior of pipe is occupied by the occurring air bubbles.
It was found that argon can scarcely be removed even if a PFA tube having high gas permeability is used. As shown in Table 2, the vapor pressure of hexane is about 120 Torr at 20° C. Therefore, it is apparent that it is necessary to keep the pressure of hexane solution equal to or higher than 120 Torr to restrain the occurrence of air bubbles.
The properties of solvents are given in Table 3.
(1): Air bubble evaluation result
(2): Pressurizing gas
(3): Container pressure (kgf/cm2)
(4): LMFC (coM)
(5): Length of PFA tube (cm)
(6): Air bubble occurrence and air bubble percentage (%)
(7): Presure at line outlet (Torr)
(8): Container pressure is indicated by gage pressure. LFMC is an abbreviation of liquid mass-flow controller, showing values at 25° C. and 1 atm.
(9): Pressure at line outlet (Torr) is indicated by absolute pressure.
(10): Outside and inside diameters of each tube are as follows:
PFA 1/8″ tube: O.D. 3.2 mm, I.D. 1.32 mm
PFA 1/16′ tube: O.D. 1.6 mm, I.D. 0.8 mm
Polyimide tube: O.D. 2.6 mm, I.D. 2.25 mm
(11): Explanation of symbols in air bubble occurrence and air bubble percentage:
◯: indicates that air bubble occurrence could not seen
Δ: indicates that air bubble occurrence was seen slightly
X: indicates that air bubble occurrence was seen in large quantities
(12): Air bubble percentage was obtained by measuring length of air bubbles formed from LMFC to observation position for a fixed time and length of liquid and by dividing the length of air bubbles by the total length.
(1).Name of solvent
(2).Molecular formula
(3).Molecular weight
(4).Heat of vaporization (KJ/Kg)
(5).Specific gravity
(6).Boiling point (CC)
(7).Vapor pressure (Torr/20° C.)
(8).Ignition point
(9).Gas volume (cc/ml)
(10).Butyl acetate
(11).THE
(12).Ethanol
(13).Di-isopropyl ether
(14).Hexane
(15).Dibutyl ether
(16).Toluene
(17).Isopropyl alcohol
(18).Octane
(19).Decane
(20).Dociecane
(21).Dimethoxyethane
(22).Diethoxyethane
(23).Tetraglime
(24).Isopropyl acetate
(25).Cyclohexane
(26).Dipivaloylmethane
(27).Result
(28).Candidate
Regarding Restraint of Air Bubbles in Depressurized Vaporizer:
The configuration is such that Sr/Ta raw material and Bi raw material are mixed with each other in front of an evaporation head, and a source flows in one flow path of the two flow paths in the head, and only a carrier gas flows in the other flow path.
Hexane with a flow rate of 0.09 ccm was caused to flow, and the carrier pressure and air bubble occurrence were evaluated.
The results are given in Table 4. As shown in Table 4, the carrier pressure was stable, and air bubbles did not occur.
Note:
Carrier pressure in Table is indicated value of Bourdon tube pressure gage.
Regarding Restraint of Air Bubbles in Depressurized Vaporizer:
An example of an SBT thin film deposition process is explained with reference to
A valve 2 is opened, and a valve 1 is closed, by which a reaction chamber is evacuated to a high vacuum. After several minutes, a wafer is transferred from a load lock chamber to a reaction chamber.
At this time, in a vaporizer,
At this time, the pressure gage is controlled to 4 Torr by the automatic pressure regulating valve.
When the temperature becomes stable several minutes after the wafer has been transferred, the valve 1 is opened, and the valve 2 is closed, by which the following gas is caused to flow into the reaction chamber to start deposition.
The reaction pressure chamber pressure is controlled to 1 Torr (by a not described automatic pressure regulating valve).
Although air bubbles were not observed before the formation of film, air bubbles began to appear after three hours from the start of film formation. Also, the pressure of carrier gas at the start time was 600 Torr, but only the pressure of carrier gas in a line through which a source is supplied varied in the range of 720 to 780 Torr. Also, air bubbles occurred at any time in both Sr/Ta and Bi systems. The air bubbles exhibit behavior of repeated advance, retreat, and stagnation (
Regarding Restraint of Air Bubbles in Depressurized Vaporizer:
An example of an SBT thin film deposition process is explained with reference to
In this example, the pressure of CVD solution was increased from the conventional 3 atm. to 4 atm. (gage pressure).
A valve 2 is opened, and a valve 1 is closed, by which a reaction chamber is evacuated to a high vacuum. After several minutes, a wafer is transferred from a load lock chamber to a reaction chamber.
At this time, in a vaporizer,
At this time, the pressure gage is controlled to 4 Torr by the automatic pressure regulating valve.
When the temperature becomes stable several minutes after the wafer has been transferred, the valve 1 is opened, and the valve 2 is closed, by which the following gas is caused to flow into the reaction chamber to start deposition.
The reaction pressure chamber pressure is controlled to 1 Torr (by a not described automatic pressure regulating valve).
Before the start of film formation, air bubble were not observed. Even after 10 hours has elapsed from the start of film formation, air bubbles did not appear.
In example 13, it was considered that the carrier gas was caused to flow backward in a solution line by fluctuations in the pressure of carrier gas caused by the occurring air bubbles. Therefore, the pressure of solution was increased, and hence the flow rate thereof was increased, by which this problem could be solved.
According to the present invention, there is provided a vaporizer used for a film forming apparatus such as a MOCVD film forming apparatus, which can be used for a long period of time without being clogged, and can supply raw materials stably to a reaction section.
In this vaporizer, the occurrence of air bubbles can be restrained, and also variations in thin film deposition speed caused by the air bubbles can be expected to be restrained.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-75263 | Mar 2002 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP03/03271 | 3/18/2003 | WO | 10/24/2005 |
