WO2009041774A2

WO2009041774A2 - Electrospray vaporizer

Info

Publication number: WO2009041774A2
Application number: PCT/KR2008/005691
Authority: WO
Inventors: Kang-Ho Ahn; Yong-Taek Kwon; Jeong-Suk Choi; Jin-Hong Ahn
Original assignee: Hyundai Calibration and Certification Technologies Co Ltd
Current assignee: HCT Co Ltd
Priority date: 2007-09-28
Filing date: 2008-09-25
Publication date: 2009-04-02
Anticipated expiration: 2010-03-28
Also published as: WO2009041774A3

Abstract

An electrospray vaporizer is capable of producing fine spray droplets and vapor molecules through electrohydrodynamic spraying of a reagent liquid. The electrospray vaporizer includes a housing with a flow path, a reagent liquid supplying device, a nozzle, a perforated plate, a power supply device and a heating device. The reagent liquid supplying device is designed to supply a reagent liquid containing precursors to the upstream end of the housing. The nozzle is mounted to the upstream end of the housing and connected to the reagent liquid supplying device so that it can spray the reagent liquid into the flow path. The perforated plate is arranged on the downstream side of the nozzle. The power supply device is adapted to apply a high voltage to one of the nozzle and the perforated plate. The heating device is designed to apply thermal energy to the flow path.

Description

Description ELECTROSPRAY VAPORIZER

Technical Field

[1] The present invention relates to an electrospray vaporizer and, more particularly, to an electrospray vaporizer capable of efficiently producing fine spray droplets and vapor molecules through electrohydrodynamic spraying of a reagent liquid. Background Art

[2] Semiconductors, liquid crystal displays, printed circuit boards and the like are manufactured by depositing films of different components on a wafer, a substrate and so forth. For example, quantum dots of a semiconductor element are produced by depositing metal particles or electron pools of nanometer size on a wafer. Nanocrystal metal particles are formed by various kinds of methods such as chemical vapor deposition (CVD), low pressure chemical vapor deposition (LPCVD), differential mobility analysis (DMA) and the like.

[3] The chemical vapor deposition is disclosed in U.S. Patent No. 6,805,907 entitled

"method and apparatus for vapor generation and film deposition". The film deposition apparatus of this patent includes an atomizer, a vaporization chamber and a chemical vapor deposition chamber. A reagent liquid containing metallic materials and a carrier gas are supplied to the atomizer. The atomizer produces an aerosol or spray droplets by spraying the reagent liquid and the carrier gas. The aerosol is supplied to and vaporized in the vaporization chamber. Particles existing in the vapor generated by the vaporization chamber are supplied to the chemical vapor deposition chamber and are deposited on an article.

[4] However, the spray droplets produced by the film deposition apparatus of the above- noted patent have a relatively great size of about 3.5 , which makes it difficult to manage the process quality and becomes a cause of defective products. Furthermore, the concentration of vapor is uneven, which leads to reduction in the particle deposition rate and the film uniformity. An orifice of the atomizer is easily clogged by the particles. The clogged orifice needs to be cleaned periodically, which makes it difficult to perform maintenance and shortens the lifespan of the atomizer.

Disclosure of Invention

Technical Problem

[5] In view of the above-noted and other problems inherent in the prior art, it is an object of the present invention to provide an electrospray vaporizer capable of efficiently producing fine spray droplets and vapor molecules through electrohydrodynamic spraying of a reagent liquid. [6] Another object of the present invention is to provide an electrospray vaporizer that can make uniform the average size of spray droplets and the concentration of vapor.

[7] A further object of the present invention is to provide an electrospray vaporizer that can prevent clogging of an orifice, thereby exhibiting improved maintainability and a prolonged lifespan.

[8] A still further object of the present invention is to provide an electrospray vaporizer capable of measuring the electric current electrostatically induced during the course of electrohydrodynamic spraying of a reagent liquid.

[9] A yet still further object of the present invention is to provide an electrospray vaporizer capable of measuring the mole concentration of spray droplets and vapor molecules.

[10] An even yet still further object of the present invention is to provide an electrospray vaporizer capable of accurately controlling the mole concentration of spray droplets and vapor molecules. Technical Solution

[11] With these objects in view, the present invention provides an electrospray vaporizer including: a housing having a flow path and an exit opening; a reagent liquid supplying means provided outside the housing for supplying a reagent liquid containing precursors to an upstream end of the housing; a spraying means mounted to the upstream end of the housing and connected to the reagent liquid supplying means for introducing and spraying the reagent liquid into the flow path of the housing; a guide means arranged on a downstream side of the spraying means so that static electricity can be generated between the spraying means and the guide means; a power supply means for applying an increased voltage to one of the spraying means and the guide means to induce static electricity in the reagent liquid sprayed from the spraying means and to produce spray droplets; and a heating means for applying thermal energy to the flow path of the housing to vaporize the spray droplets and to produce vapor molecules. Best Mode for Carrying Out the Invention

[12] Hereinafter, preferred embodiments of an electrospray vaporizer in accordance with the present invention will be described in detail with reference to the accompanying drawings.

[13] Shown in Figs. 1 and 2 is an electrospray vaporizer in accordance with a first embodiment of the present invention. Referring to Fig. 1, the electrospray vaporizer of the first embodiment includes a housing 10 forming a shell of the vaporizer. The housing 10 has a flow path 12 through which fluid is allowed to flow and an exit opening 14 connected to the flow path 12. A plurality of ports 16 connected to the flow path 12 is formed in the upstream portion of the housing 10. An insulation body 18 for closing the flow path 12 is attached to the upstream end of the housing 10. The housing 10 may be formed of a hollow pipe or a duct through which fluid can be conveyed.

[14] The electrospray vaporizer of the first embodiment includes a reagent liquid supplying device 20 installed outside the housing 10. The reagent liquid supplying device 20 serves to supply a reagent liquid L containing a large quantity of precursors Pl to the upstream end of the housing 10. The reagent liquid supplying device 20 includes a reservoir 22 for storing the reagent liquid L, a pump 24 for pumping and delivering the reagent liquid L stored in the reservoir 22 and a liquid flow controller (LFC) 26 for controlling the flow rate of the reagent liquid L fed from the pump 24. The pump 24 may be formed of a syringe pump that can supply a controlled amount of liquid. The precursors Pl are electrohydrodynamically sprayed to produce a large quantity of fine spray droplets S and vapor molecules P2 with a size of several tens nanometer to several micrometer. Examples of the precursors Pl include tetraethoxy- orthosilicate (OCH2(H3)4) and titanium tetraisopropoxide (Ti(OC3H7)4).

[15] Referring to Figs. 1 and 2, a nozzle 30 as a spraying means for introducing the reagent liquid L supplied from the reagent liquid supplying device 20 and spraying the same toward the flow path 12 is attached to the upstream end of the housing 10. The nozzle 30 has a nozzle hole 32 connected to the liquid flow controller 26 through a pipeline 28. The nozzle 30 has a tip 34 protruding into the flow path 12 of the housing 10. While a single nozzle is mounted through the center of the insulation body 18 in Fig. 1, it may be possible to mount two or more nozzles. While the nozzle 30 shown in Fig. 1 is a single-hole nozzle with a single nozzle hole, it may be possible to employ a multi-hole nozzle having a plurality of nozzle holes. While the nozzle 30 shown in Fig. 1 is of a cylindrical shape with a circular cross-section, the nozzle 30 may be constructed to have many other different shapes insofar as it is capable of introducing and spraying the reagent liquid L. For example, the nozzle 30 may be constructed from a slot type nozzle, a tube with an orifice, a capillary tube and so forth.

[16] Referring again to Fig. 1, the electrospray vaporizer of the first embodiment includes a power supply device 40 connected to the nozzle 30 through a conductive wire 42. The power supply device 40 serves to apply a high voltage to the nozzle 30 so that static electricity can be induced in the reagent liquid L ejected from the nozzle 30. A resistor 44 is connected to the conductive wire 42 to control the high voltage applied from the power supply device 40 to the nozzle 30.

[17] The electrospray vaporizer of the first embodiment includes a heating device 50 for applying thermal energy to vaporize the spray droplets S generated when electrohydrodynamically spraying the reagent liquid L. The heating device 50 is constructed from a heater 52 installed in the flow path 12 in a spaced- apart relationship with the nozzle 30. Alternatively, the heater 52 may be installed outside housing 10 so as to heat the outer surface thereof. The heating device 50 is in communication with the exit opening 14 of the housing 10 and may be constructed from a heating chamber to which a heater or a burner is mounted.

[18] The electrospray vaporizer of the first embodiment includes a perforated plate 60 as a guide means electrically grounded and designed to guide the vapor molecules P2 generated when the spray droplets S are vaporized. The perforated plate 60 is spaced apart from the exit opening 14 of the housing 10. The vapor molecules P2 are guided to a well-known process chamber under the guidance of the perforated plate 60. As the spray droplets S and the vapor molecules P2 are guided into the process chamber by means of the perforated plate 60, flat panel display devices such as a thin film transistor-liquid crystal display (TFT-LCD), a plasma display panel (PDP), an electroluminescent element (EL) and the like can be manufactured in the process chamber. The perforated plate 60 may be arranged in the process chamber which is connected to the exit opening 14 of the housing 10 through a pipeline for the manufacture of semiconductor elements, flat panel display devices and so forth.

[19] The electrospray vaporizer of the first embodiment includes a carrier gas supplying device 70 connected to the upstream end of the housing 10 for supplying a carrier gas. The carrier gas supplying device 70 includes a reservoir 72 for storing a carrier gas such as an argon gas, a nitrogen gas, a helium gas or the like, a compressor 74 for compressing and delivering the carrier gas supplied from the reservoir 72 and a mass flow controller (MFC) 76 for controlling the mass flow rate of the carrier gas. The mass flow controller 76 is connected to the upper outer surface of the housing 10 through a pipeline 78. The ports 16 of the housing 10 are positioned above the tip 34 of the nozzle 30. The carrier gas is supplied to the upstream side of the housing 10 by the carrier gas supplying device 70 so that it can transport the spray droplets S and the vapor molecules P2 toward the exit opening 14 along the flow path 12 of the housing 10.

[20] Description will now be made on the operation of the electrospray vaporizer of the first embodiment constructed as above.

[21] Referring to Fig. 1, if the pump 24 of the reagent liquid supplying device 20 comes into operation, the reagent liquid L stored in the reservoir 22 is supplied to the liquid flow controller 26. The reagent liquid L whose flow rate is controlled in the liquid flow controller 26 is fed to the nozzle hole 32 of the nozzle 30 through the pipeline 28. The reagent liquid L is sprayed into the flow path 12 of the housing 10 through the nozzle hole 32 of the nozzle 30.

[22] Referring to Fig. 2, if the power supply device 40 is operated to apply a high voltage to the nozzle 30, electric fields are formed between the nozzle 30 and the perforated plate 60. The electric fields thus generated induce static electricity in the reagent liquid L sprayed from the nozzle 30. The hydrostatic pressure and the surface tension of the reagent liquid L are collapsed by the electrostatic force. The shape of the liquid droplets D formed in the tip 34 of the nozzle 30 varies with the electrostatic force. The liquid droplets D sprayed through the nozzle hole 32 of the nozzle 30 make a cone shape in the tip 34. A cone-jet mode is performed whereby a large quantity of spray droplets S is sprayed at the apex of a cone. The spray droplets S show a very high charging quantity and therefore are self-dispersed into a size of several tens nanometer to several micrometer by the coulomb repulsion, thus minimizing coagulation of the spray droplets S.

[23] Such electrohydrodynamic spraying of the reagent liquid L makes it possible to easily and accurately control the size and dispersion degree of the spray droplets S. The electrohydrodynamic spraying of the reagent liquid L prevents clogging of the orifice, i.e., the nozzle hole 32, which improves operability and maintainability of the electrospray vaporizer and assures a prolonged lifespan thereof. Furthermore, the average size of the spray droplets S and the concentration of the vapor are made uniform, which greatly enhances the process quality.

[24] Referring again to Figs. 1 and 2, if the heater 52 is operated to apply thermal energy to the flow path 12 of the housing 10, the spray droplets S are vaporized. A large quantity of vapor molecules P2 is generated upon vaporization of the spray droplets S containing the precursors Pl. If the compressor 74 of the carrier gas supplying device 70 comes into operation, the carrier gas stored in the reservoir 72 is supplied to the mass flow controller 76. The carrier gas whose mass flow rate is controlled by the mass flow controller 76 is supplied to the flow path 12 of the housing 10 through the pipeline 78 and the ports 16. The carrier gas passes through the ports 16 and flows from the upstream side of the tip 34 of the nozzle 30 toward the exit opening 14, thereby forming a gas stream. The spray droplets S and the vapor molecules P2 are moved toward the exit opening 14 together with the gas stream. The vapor molecules P2 discharged from the exit opening 14 are guided to the perforated plate 60 and then supplied to the process chamber.

[25] Fig. 3 shows another example of the spraying means employed in the electrospray vaporizer of the first embodiment. Referring to Fig. 3, the spraying means of this example has four nozzles 130a to 130d integrally connected to a hollow connecting pipe 136. Referring collectively to Figs. 1 and 3, the connecting pipe 136 is connected to the reagent liquid supplying device 20 through the pipeline 28. The power supply device 40 is adapted to apply a high voltage to the connecting pipe 136. The perforated plate 60 is spaced apart from the tips 134 of the nozzles 130a to 130d and is electrically grounded. While three nozzles 130a to 130d are illustrated in Fig. 3, the number of the nozzles may be greater or lesser.

[26] If the power supply device 40 is operated to apply a high voltage to the connecting pipe 136, electric fields are formed between the tips 134 of the nozzles 130a to 130d and the perforated plate 60. A large quantity of spray droplets S is generated by elec- trohydrodynamically spraying the reagent liquid L through the nozzle holes 132 of the nozzles 130a to 130d. The spray droplets S are vaporized by the thermal energy of the heater 52, thereby producing vapor molecules P2. The vapor molecules P2 are guided to the perforated plate 60 and then supplied to the process chamber. Since the reagent liquid L are electrohydrodynamically sprayed from the tips 134 of the nozzles 130a to 130d in this manner, the spray droplets S and the vapor molecules P2 are produced in a greater quantity than when using a single nozzle.

[27] Fig. 4 shows a further example of the spraying means employed in the electrospray vaporizer of the first embodiment. Referring to Fig. 4, the spraying means of this example is constructed from a porous spraying member 230 having a multiplicity of fine pores 232. While the porous spraying member 230 shown in Fig. 4 is of a cylindrical shape, this is to merely illustrate the invention. The porous spraying member 230 may have many different shapes such as a conical shape, a polygonal shape, a disk shape and the like.

[28] Referring collectively to Figs. 1 and 4, if the reagent liquid supplying device 20 is operated to supply the reagent liquid L to the porous spraying member 230, the reagent liquid L is sprayed through the pores 232 of the porous spraying member 230. As a high voltage is applied to the porous spraying member 230 by the power supply device 40, electric fields are formed between the porous spraying member 230 and the perforated plate 60. A large quantity of spray droplets S is generated by electrohydrodynamically spraying the reagent liquid L through the pores 232 of the porous spraying member 230. The spray droplets S are vaporized by the thermal energy of the heater 52, thereby producing vapor molecules P2. The vapor molecules P2 are guided to the perforated plate 60 and then supplied to the process chamber. Since the reagent liquid L are electrohydrodynamically sprayed from the pores 232 of the porous spraying member 230 in this manner, the spray droplets S and the vapor molecules P2 are produced in a greater quantity and with increased efficiency.

[29] Shown in Figs. 5 through 7 is an electrospray vaporizer in accordance with a second embodiment of the present invention. Referring to Fig. 5, the electrospray vaporizer of the second embodiment includes a housing 10, a reagent liquid supplying device 20, a nozzle 30, a heating device 50, a carrier gas supplying device 70, a power supply device 340, a perforated plate 360, an electrometer 380 and a mole concentration monitor 390. The housing 10, the reagent liquid supplying device 20, the nozzle 30, the heating device 50 and the carrier gas supplying device 70 are the same in the electrospray vaporizers of the first and second embodiments and therefore are designated by like reference numerals, with no detailed description made in that regard. In the electrospray vaporizer of the second embodiment, the nozzle 30 may be constructed from either the nozzles 130a to 130d or the porous spraying member 230, both of which have been set forth above.

[30] The perforated plate 360 is designed to induce static electricity in the reagent liquid L sprayed from the nozzle 30, thereby producing spray droplets S and guiding the flow of the spray droplets S. The perforated plate 360 is electrically conductive and is arranged on the downstream side of the nozzle 30 within the flow path 12 of the housing 10. The spray droplets S pass through the holes 362 of the perforated plate 360 and then flows toward the exit opening 14 of the housing 10. The perforated plate 360 serves as a guide means and may be constructed from a conductive mesh member. The heating device 50 is installed in the flow path 12 of the housing 10. The heater 52 is arranged on the downstream side of the perforated plate 360 and is designed to apply thermal energy to the flow path 12 of the housing 10, thereby vaporizing the spray droplets S generated when electrohydrodynamically spraying the reagent liquid L.

[31] The power supply device 340 is adapted to apply a high voltage to the perforated plate 360 so that static electricity can be generated between the nozzle 30 and the perforated plate 360. The power supply device 340 is connected to the perforated plate 360 through a conductive wire 342. A resistor 344 is connected to the conductive wire 342 to control the high voltage applied from the power supply device 340 to the perforated plate 360. The electrometer 380 is connected to the nozzle 30 through a conductive wire 382 and is designed to measure the electric current electrostatically induced in the nozzle 30. A resistor 384 is connected to the conductive wire 382 to control the electric current.

[32] The mole concentration monitor 390 is connected to the housing 10 near the exit opening 14 and is adapted to measure the mole concentration of the spray droplets S and the vapor molecules P2. The mole concentration monitor 390 has a sampling tube 392 connected to the outer surface of the housing 10 near the exit opening 14. The mole concentration monitor 390 may be constructed from a condensation particle counter or a condensation nucleus counter.

[33] Referring to Fig. 7, the electrospray vaporizer of the second embodiment includes a controller 400 connected to the liquid flow controller 26 of the reagent liquid supplying device 20, the mass flow controller 76 of the carrier gas supplying device 70, the electrometer 380 and the mole concentration monitor 390. The electric current flowing through the nozzle 30 measured by the electrometer 380 and the mole concentration of the spray droplets S and the vapor molecules P2 measured by the mole concentration monitor 390 are inputted to the controller 400. By processing the data inputted from the electrometer 380 and the mole concentration monitor 390, the controller 400 controls the liquid flow controller 26 of the reagent liquid supplying device 20 and the mass flow controller 76 of the carrier gas supplying device 70. The controller 400 may be constructed from a computer.

[34] Referring to Figs. 5 and 6, if the power supply device 340 is operated to apply a high voltage to the perforated plate 360, electric fields are generated between the nozzle 30 and the perforated plate 360. Under the influence of the electric fields thus generated, the reagent liquid L is electrohydrodynamically sprayed through the nozzle 30.

[35] The spray droplets S are positively or negatively charged by the static electricity. The spray droplets S whose polarity is opposite from that of the perforated plate 360 flow from the nozzle 30 toward the perforated plate 360 along the flow path 12. Then, the spray droplets S pass through the holes 362 of the perforated plate 360 and flow toward the downstream side of the housing 10. If static electricity is generated between the nozzle 30 and the perforated plate 360, an electric current is induced in the nozzle 30. The electrometer 380 measures the electric current induced in the nozzle 30 and inputs the measured value to the controller 400.

[36] If the heater 52 is operated to apply thermal energy to the flow path 12 of the housing

10, the spray droplets S are vaporized. A large quantity of vapor molecules P2 is generated upon vaporization of the spray droplets S containing the precursors Pl. The carrier gas whose mass flow rate is controlled by the mass flow controller 76 is supplied to the flow path 12 of the housing 10 through the pipeline 78 and the ports 16. The carrier gas passes through the ports 16 and flows from the upstream side of the tip 34 of the nozzle 30 toward the exit opening 14, thereby forming a gas stream. The spray droplets S and the vapor molecules P2 are moved toward the exit opening 14 together with the gas stream. The vapor molecules P2 discharged from the exit opening 14 are supplied to the process chamber.

[37] The spray droplets S and the vapor molecules P2 flowing toward the exit opening 14 of the housing 10 are partially supplied to the mole concentration monitor 390 through the sampling tube 392. The mole concentration of the spray droplets S and the vapor molecules P2 supplied through the sampling tube 392 is measured by the mole concentration monitor 390 and then inputted to the controller 400. The controller 400 controls the liquid flow controller 26 and the mass flow controller 76 by processing the electric current of the nozzle 30 inputted from the electrometer 380 and the mole concentration of the spray droplets S and the vapor molecules P2 inputted from the mole concentration monitor 390. The correlation between the electric current and the mole concentration can be calculated using the electric current and the mole concentration measured as above. The correlation between the electric current and the mole concentration can be controlled by the flow rates of the reagent liquid L and the carrier gas. This makes it possible to accurately control the mole concentration of the spray droplets S and the vapor molecules P2.

[38] Shown in Fig. 8 is an electrospray vaporizer in accordance with a third embodiment of the present invention. Referring to Fig. 8, the electrospray vaporizer of the third embodiment includes a housing 10, a reagent liquid supplying device 20, a nozzle 30, a heating device 50, a carrier gas supplying device 70, a perforated plate 360, a power supply device 440 and an electrometer 480. The housing 10, the reagent liquid supplying device 20, the nozzle 30, the heating device 50, the carrier gas supplying device 70 and the perforated plate 360 are essentially the same in the electrospray vaporizers of the second and third embodiments and therefore are designated by like reference numerals, with no detailed description made in that regard.

[39] In the electrospray vaporizer of the third embodiment, the power supply device 440 is connected to the nozzle 30 through a conductive wire 442. A resistor 444 is connected to the conductive wire 442 to control the high voltage supplied from the power supply device 440 to the nozzle 30. The electrometer 480 is connected to the perforated plate 360 through a conductive wire 482 and is adapted to measure the electric current electrostatically induced in the perforated plate 360. A resistor 484 is connected to the conductive wire 482 to control the electric current.

[40] If the power supply device 440 is operated to apply a high voltage to the nozzle 30, electric fields are formed between the nozzle 30 and the perforated plate 360. Under the influence of the electric fields thus formed, the reagent liquid L is electrohydrody- namically sprayed through the nozzle 30. As in the electrospray vaporizer of the second embodiment, the electrometer 480 measures the electric current induced in the perforated plate 360 and inputs the measured value to a controller (not shown). The controller controls the liquid flow controller 26 and the mass flow controller 76 by processing the electric current of the perforated plate 360 inputted from the electrometer 480 and the mole concentration of the spray droplets S and the vapor molecules P2 inputted from the mole concentration monitor 390.

[41] Fig. 9 shows another example of the spraying means employed in the electrospray vaporizer of the third embodiment. Referring to Fig. 9, the spraying means of this example has a plurality of nozzles 130a to 130d integrally connected to a hollow connecting pipe 136. The connecting pipe 136 is connected to the power supply device 440 that serves to apply a high voltage. If the power supply device 440 is operated to apply a high voltage to the connecting pipe 136, electric fields are formed between the tips 134 of the nozzles 130a to 130d and the perforated plate 360. A large quantity of spray droplets S containing precursors Pl is generated by electrohydrodynamically spraying the reagent liquid L through the nozzle holes 132 of the nozzles 130a to 130d. The spray droplets S are guided to pass through the holes 362 of the perforated plate 360. The electrometer 480 measures the electric current electrostatically induced in the perforated plate 360.

[42] Fig. 10 shows a further example of the spraying means employed in the electrospray vaporizer of the third embodiment. Referring to Fig. 10, the spraying means of this example is constructed from a porous spraying member 230 having a multiplicity of fine pores 232. If the reagent liquid supplying device 20 is operated to supply the reagent liquid L to the porous spraying member 230, the reagent liquid L is electrohy- drodynamically sprayed through the pores 232 of the porous spraying member 230. This produces a large quantity of spray droplets S containing precursors Pl.

[43] The embodiments set forth hereinabove have been presented for illustrative purposes only and, therefore, the present invention is not limited to these embodiments. It will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention defined in the claims. Industrial Applicability

[44] With the present electrospray vaporizer described above, it is possible to efficiently produce fine spray droplets and vapor molecules by electrohydrodynamically spraying a reagent liquid. The average size of the spray droplets and the mole concentration of vapor are made uniform, which makes it possible to greatly improve the process quality. The electrohydrodynamic spraying of the reagent liquid prevents clogging of an orifice, which in turn improves operability and maintainability of the electrospray vaporizer and assures a prolonged lifespan thereof. In addition, it is possible to accurately control the electrospray vaporizer by measuring the electric current electrostatically induced during the course of electrohydrodynamic spraying of the reagent liquid and by measuring the mole concentration of the spray droplets and the vapor molecules.

Claims

[1] An electrospray vaporizer comprising: a housing having a flow path and an exit opening; a reagent liquid supplying means provided outside the housing for supplying a reagent liquid containing precursors to an upstream end of the housing; a spraying means mounted to the upstream end of the housing and connected to the reagent liquid supplying means for introducing and spraying the reagent liquid into the flow path of the housing; a guide means arranged on a downstream side of the spraying means so that static electricity can be generated between the spraying means and the guide means; a power supply means for applying an high voltage to one of the spraying means and the guide means to induce static electricity in the reagent liquid sprayed from the spraying means and to produce spray droplets; and a heating means for applying thermal energy to the flow path of the housing to vaporize the spray droplets and to produce vapor molecules.

[2] The electrospray vaporizer as recited in claim 1, wherein the power supply means is connected to the spraying means, the guide means being spaced apart from the exit opening of the housing and being electrically grounded to guide the vapor molecules, the heating means including a heater arranged within the flow path in a spaced- apart relationship with the spraying means.

[3] The electrospray vaporizer as recited in claim 2, wherein the spraying means includes at least one nozzle having a nozzle hole through which the reagent liquid is sprayed into the flow path and a tip protruding into the flow path.

[4] The electrospray vaporizer as recited in claim 2, wherein the spraying means includes a porous spraying member having a multiplicity of pores through which the reagent liquid is sprayed into the flow path.

[5] The electrospray vaporizer as recited in claim 1, further comprising an electrometer connected to one of the spraying means and the guide means for measuring an electrostatically induced electric current.

[6] The electrospray vaporizer as recited in claim 5, wherein the reagent liquid supplying means includes a liquid flow controller for controlling the flow rate of the reagent liquid, and further comprising a carrier gas supplying means for supplying a carrier gas into the flow path of the housing to transport the spray droplets and the vapor molecules toward the exit opening, the carrier gas supplying means including a mass flow controller connected to the flow path of the housing for controlling the mass flow rate of the carrier gas.

[7] The electrospray vaporizer as recited in claim 6, further comprising a mole concentration monitor connected to the housing for measuring the mole concentration of the spray droplets and the vapor molecules and a controller connected to the liquid flow controller, the mass flow controller, the electrometer and the mole concentration monitor for controlling the liquid flow controller and the mass flow controller depending on the electric current measured by the electrometer and the mole concentration measured by the mole concentration monitor.

[8] The electrospray vaporizer as recited in claim 5, wherein the power supply means is connected to the guide means, the guide means including a perforated plate installed within the flow path in a spaced-apart relationship with the spraying means, the heating means including a heater arranged within the flow path in a spaced-apart relationship with the perforated plate.

[9] The electrospray vaporizer as recited in claim 8, wherein the spraying means includes at least one nozzle having a nozzle hole through which the reagent liquid is sprayed into the flow path and a tip protruding into the flow path.

[10] The electrospray vaporizer as recited in claim 8, wherein the spraying means includes a porous spraying member having a multiplicity of pores through which the reagent liquid is sprayed into the flow path.