JP2004107744A - Photochemical vapor deposition system and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize neighboring field photo CVD (Chemical vapor Deposition) in which the wavelength conditions of light supplied from a light source is relaxed. <P>SOLUTION: In the photochemical vapor deposition system, neighboring field light is applied, so that a gas present in the vicinity of a substrate is composed, and is deposited on the substrate. In this case, light having a wavelength equal to or above that of light equivalent to the dissociation energy of the gas is outputted via an acute part obtained by making optical fiber acute to generate neighboring field light. The gas is dissociated through a multistage transition stage to obtain a decomposed product, and the decomposed product is deposited on the substrate. Thus, the wavelength conditions of the light supplied from the light source can be relaxed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photochemical vapor deposition apparatus and a method used for fabricating a near-field nano-optical device.
[0002]
[Prior art]
In recent years, there has been a need for higher integration and miniaturization of optical elements for increasing the capacity of optical information communication, which has been advanced in recent years, and research has been actively conducted. However, the existing technology based on the wave nature of light has a limit in miniaturization described above due to a diffraction limit. For this reason, a near-field nano-optical device has been proposed which is constituted by a plurality of quantum dots and operates even at dimensions smaller than the diffraction limit (for example, see Non-Patent Document 1).
[0003]
The quantum dots that make up this near-field nano-optical device form a box with a potential that is so fine as to give three-dimensional quantum confinement to excitons. Due to the near-field interaction using this exciton confinement system, the energy levels of the carriers in the quantum dots become discrete, and the density of states becomes sharper as a delta function. It is also possible to manufacture a single-electron memory or the like by utilizing the absorption of light between the sharpened states of the quantum dots.
[0004]
Such a near-field nano-optical device can be accurately manufactured by using near-field optical CVD (Chemical Vapor Deposition) using near-field light (for example, see Non-Patent Document 2).
[0005]
FIG. 7 is a configuration diagram of an optical CVD device 7 using near-field optical CVD. The optical CVD apparatus 7 includes a near-field optical probe 72, a substrate 73, and a stage 74 for mounting the substrate 73 in a chamber 71. And a converter 77 for converting light supplied through the reflecting member 76 into light propagating in the optical CVD probe 72, and further comprising: A gas supply unit 78 for injecting an atmosphere into the inside 71 is provided.
[0006]
The near-field optical probe 72 includes an optical waveguide 81 and a protrusion 82 as shown in FIG. The optical waveguide section 81 is composed of an optical fiber in which a clad 84 is provided around a core 83. The protruding portion 82 is formed by sharpening a core 83 protruding from the clad 84 at one end of the optical waveguide 81. The protruding portion 82 is configured as a conical shape that gradually tapers to the tip. Incidentally, the projecting portion 82 is formed such that the root diameter is shorter than the diameter of the core 83.
[0007]
In such an optical CVD apparatus 7, the substrate 72 is placed on the stage 74 and gas is filled in the chamber 71, and light is transmitted from the light source 75 to the near-field optical probe 72 via the reflection member 76 and the conversion unit 77. By supplying, near-field light can be generated from the protruding portion 82 of the near-field light probe 72. The gas existing near the substrate 73 can be decomposed by the energy of the near-field light, and the decomposition products of the gas can be deposited on the substrate 73.
[0008]
That is, in the conventional near-field optical CVD, as shown in FIG. 9, light (in the band corresponding to the energy difference Ea between the ground level and the excited level) is applied to the gas molecules injected into the chamber 71. Hereinafter, this light is referred to as resonance light.) To excite to an excitation level. Since the excited level exceeds the dissociation energy Eb, gas molecules can be dissociated in the direction indicated by the arrow to be radicalized and deposited on the substrate 73.
[0009]
Since quantum dots can be generated on a nano-scale by using such near-field optical CVD, the above-described near-field nano-optical device can be accurately manufactured.
[Non-patent document 1]
M. Ohtsu, K .; Kobayashi, T .; Kawazoe, S.M. Sangu, T .; Yatsui, IEEE J .; Sel. Top. Quant. Electron. , To be published
[Non-patent document 2]
Y. Yamamoto, M .; Kourogi, M .; Ohtsu, V .; Polonski, and G.W. H. Lee, Appl. Phys. Lett. , 76, 2173 (1999)
[0010]
[Problems to be solved by the invention]
However, in the above-described conventional near-field optical CVD, quantum dots cannot be manufactured without always irradiating the resonance light, so that there is a problem that a condition of a wavelength supplied from the light source 71 is greatly restricted. Also, in recent years, it has been necessary to search for optimal manufacturing conditions for the above-described quantum dots by near-field optical CVD using non-resonant light having a longer wavelength than resonant light, and to respond to the demand for mass production of near-field nano-optical devices. Particularly, there is a strong demand for non-resonant light having a wavelength equal to or longer than the wavelength of light corresponding to the dissociation energy Eb.
[0011]
Accordingly, the present invention has been proposed in view of the above-described problems, and an object thereof is to provide a photochemical vapor deposition apparatus and method using non-resonant light having a wavelength equal to or longer than the wavelength of light corresponding to the dissociation energy Eb. To provide.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problem, the present inventor generates near-field light by outputting light having a wavelength equal to or more than the wavelength of light corresponding to the dissociation energy of gas through a sharpened portion obtained by sharpening an optical fiber. Invented a photochemical vapor deposition apparatus and method for irradiating the near-field light to decompose gas existing near the substrate and depositing the gas on the substrate.
[0013]
That is, a photochemical vapor deposition apparatus according to the present invention is a photochemical vapor deposition apparatus that decomposes a gas existing near a substrate by irradiating near-field light and deposits the gas on the substrate. A near-field light probe for generating near-field light by outputting light supplied from the light source through the sharp portion, wherein the wavelength of the light supplied from the light source is gas. Is not less than the wavelength of light corresponding to the dissociation energy of
[0014]
Further, the photochemical vapor deposition method according to the present invention, in the photochemical vapor deposition method of decomposing a gas present near the substrate by irradiating near-field light and depositing the gas on the substrate, The optical fiber is output through a sharpened point to generate near-field light, and the wavelength of the supplied light is equal to or longer than the wavelength of light corresponding to the dissociation energy of gas.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
As an embodiment of the present invention, a photochemical vapor deposition apparatus and a method according to the present invention will be described with reference to an example in which the apparatus and method are applied to a photochemical vapor deposition (CVD) apparatus 1 shown in FIG.
[0016]
The optical CVD apparatus 1 is configured by arranging a near-field optical probe 12, a substrate 13, and a stage 14 for mounting the substrate 13 in a chamber 11, and is configured to transmit light supplied from a light source 15. A reflection member for reflecting the light toward the chamber and a conversion unit for converting light supplied through the reflection member into light propagating in the optical CVD probe; A gas supply unit 18 for injecting, for example, a diethyl zinc (DEZn) atmosphere therein is provided.
[0017]
The chamber 11 is provided to equalize the concentration of the gas to be filled and the like. In order to control the state of adsorption to the substrate 13 in the relationship between gas molecules and the wavelength of light by making the gas concentration in the chamber 11 uniform, the chamber 11 has a gas concentration control device. An adjustment valve (not shown) is provided. The chamber 11 is provided with a pressure valve (not shown) for controlling the internal pressure. In view of an optical CVD process for forming a film under reduced pressure, the pressure in the chamber 11 is, for example, 100 mTorr in a DEZn atmosphere. Is controlled. The chamber 11 is further provided with a window 11a on a surface facing the conversion unit 17, and light can be incident from the conversion unit 17 through the window 11a.
[0018]
The near-field optical probe 12 includes an optical waveguide 21 and a protrusion 22 as shown in FIG. The optical waveguide 21 is composed of an optical fiber in which a clad 24 is provided around a core 23 made of pure quartz. The protruding portion 22 is formed by sharpening a core 23 protruding from the clad 24 at one end of the optical waveguide portion 21. The protruding portion 22 is configured as a conical shape that gradually tapers to the tip. Incidentally, the projecting portion 22 is formed such that the root diameter is shorter than the diameter of the core 23.
[0019]
The protruding portion 22 of the near-field optical probe 11 is manufactured by performing selective chemical etching on the optical waveguide portion 21. This selective chemical etching selectively sharpens the core 23 by immersing the fiber in a buffered hydrofluoric acid solution consisting of, for example, NH ₄ F, HF, H ₂ O for about 1 hour and removing the end of the cladding 24. In the present invention, the dissolution rate is controlled by the composition of the etchant and the material constituting the optical fiber, for example, by using the method proposed in JP-A-10-82791, so that the tip of the core 23 has, for example, a tip radius of curvature. It may be sharpened to 10 nm. Finally, the sharpened core 23 is finished by coating a metal layer of, for example, Au on the side surface excluding the tip.
[0020]
The substrate 13 is made of a conductive material such as, for example, NaCl, KCl, or CaF ₂ to deposit semiconductor quantum dots. The stage 14 is provided with a mounting portion (not shown) for mounting the substrate 13 and a heating mechanism (not shown) for heating the substrate 13. You can control.
[0021]
The light source 15 includes, for example, a gas laser light source, a semiconductor laser light source, or a solid-state laser light source, and emits light having a predetermined wavelength to the reflection member 16. Details of the wavelength of the light emitted from the light source 15 will be described later. The reflecting member 16 is configured by, for example, a beam splitter or the like, and reflects light emitted from the light source 15 by 90 ° and emits the light to the conversion unit 17.
[0022]
In such an optical CVD apparatus 1, the substrate 12 is placed on the stage 14, and the gas is supplied from the gas supply unit 18 into the chamber 11. Then, by supplying light from the light source 15 to the near-field light probe 12 via the reflection member 16 and the conversion unit 17, near-field light can be generated from the protruding portion 22 of the near-field light probe 12. The gas existing near the substrate 13 can be decomposed by the energy of the near-field light, and the decomposition product of the gas can be deposited on the substrate 13. By the way, when DEZn is used as a gas atmosphere, a decomposition product Zn obtained by decomposing DEZn by irradiating near-field light with the optical CVD apparatus 1 can be deposited on the substrate 12.
[0023]
Next, light emitted from the light source 15 of the optical CVD apparatus 1 to which the present invention is applied will be described.
[0024]
FIG. 3 shows the relationship between the potential energy and the interatomic distance in the gas filled in the chamber. In normal optical CVD, gas molecules injected into the chamber 71 are irradiated with light in a band corresponding to the energy difference Ea between the ground level and the excited level (hereinafter, this light is referred to as resonance light). By doing so, it is excited to an excited level. Since this excited level exceeds the dissociation energy Eb, gas molecules can be dissociated in the direction indicated by the arrow to be radicalized and deposited on the substrate 13. The optical CVD apparatus 1 to which the present invention is applied has a non-resonant light irradiation mode for irradiating gas molecules with non-resonant light having a longer wavelength than the resonance light, in addition to the resonance light irradiation mode for irradiating the resonance light.
[0025]
In the non-resonant light irradiation mode, an S1 mode in which non-resonant light having a wavelength equal to or less than the wavelength of light corresponding to the dissociation energy Eb of the gas molecule is irradiated, and a non-resonant light having a wavelength equal to or more than the light corresponding to the dissociation energy Eb of the gas molecule are used. S2 mode for irradiation.
[0026]
Gas molecules in such a non-resonant light irradiation mode can be dissociated through excitation (multi-step transition process) by light absorption a plurality of times. For example, in the S2 mode as shown in FIG. 4, gas molecules receive non-resonant light having a wavelength equal to or greater than the wavelength of Eb and are once excited to a molecular orbital level. , And can be excited to an excited level or a molecular dissociated orbital level by excitation by the third light absorption.
[0027]
Thus, the reason that gas molecule vibration can be excited is that the irradiation of near-field light on gas molecules breaks the Born-Oppenheimer approximation and causes direct excitation of the molecule to the vibration level. Because it is.
[0028]
FIG. 5 shows the relationship between the light intensity and the distance between the gas molecules and the probe tip. Normal propagating light has a uniform light intensity. For this reason, even if normal propagating light is applied to gas molecules, it cannot be symmetrically stretched and vibrated along the internuclear axis, and the intermolecular distance cannot be changed. No direct excitation can occur. On the other hand, in the near-field light, the distance between the gas molecule and the tip of the probe is short, and the spatial displacement of the light is severe. For this reason, when near-field light is applied to gas molecules, the gas molecules can be symmetrically stretched and vibrated along the internuclear axis, and the intermolecular distance can be changed. Can be caused.
[0029]
FIG. 6 shows the relationship between the light intensity in each non-resonant light irradiation mode (S1, S2 mode) and the deposition rate. In FIG. 6, the squares are the measurement data in the S1 mode, and the circles are the measurement data in the S2 mode, and the measurement results are fitted by solid lines. Incidentally, in DEZn that resonates at a wavelength of 290 nm or less, the wavelength of light used in the S1 mode is 488 nm, and the wavelength of light used in the S2 mode is 684 nm. The light intensity of the near-field light to be irradiated is changed between 120 μW and 10 mW.
[0030]
As shown in FIG. 6, even in the non-resonant light irradiation mode, the amount of the decomposition products deposited on the substrate 13 tends to depend on the light intensity. It can be seen that irradiation with field light allows a decomposition product to be formed on the substrate 13. Decomposition products can also be formed in the S2 mode in which non-resonant light having a wavelength equal to or more than the wavelength of light corresponding to the dissociation energy Eb of gas molecules is applied.
[0031]
That is, the optical CVD apparatus 1 to which the present invention is applied outputs non-resonant light having a wavelength equal to or more than the light energy corresponding to the dissociation energy of the gas through the sharpened portion formed by sharpening the optical fiber, and outputs the non-resonant light. By generating the field light, the decomposition products obtained by dissociation through the multi-step transition process can be deposited on the substrate, and the wavelength condition of the light supplied from the light source 15 can be relaxed.
[0032]
In addition, the optical CVD apparatus 1 using the near-field light can use the near-field optical probe 12 whose tip is sharpened to a scale of about 10 nm. Can be manufactured with high accuracy regardless of the wavelength of the light source.
[0033]
【The invention's effect】
As described above in detail, the photochemical vapor deposition apparatus and method according to the present invention provide a non-resonant light having a wavelength equal to or longer than the wavelength of light corresponding to the dissociation energy of a gas, by using a sharpened optical fiber. Output through the section to generate near-field light, the decomposition products obtained by dissociation through a multi-step transition process can be deposited on the substrate, and the wavelength conditions of the light supplied from the light source are relaxed. It is possible to do.
[0034]
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a photo-CVD apparatus to which the present invention is applied.
FIG. 2 is a diagram for explaining details of a near-field optical probe.
FIG. 3 is a diagram for explaining a resonance light irradiation mode and a non-resonance light irradiation mode.
FIG. 4 is a diagram for explaining a multi-stage transition process.
FIG. 5 is a diagram showing a relationship between a light intensity and a distance between a gas molecule and a probe tip.
FIG. 6 is a diagram showing the relationship between the light intensity in each non-resonant light irradiation mode (S1, S2 mode) and the deposition rate.
FIG. 7 is a diagram showing a typical configuration of an optical CVD apparatus.
FIG. 8 is a diagram showing a typical configuration of a near-field optical probe.
FIG. 9 is a diagram showing a relationship between potential energy and distance between gas atoms.
[Explanation of symbols]
Reference Signs List 1 optical CVD apparatus, 11 chamber, 12 near-field optical probe, 13 substrate, 14 stage, 15 light source, 16 reflecting member, 17 conversion unit, 18 gas supply unit

Claims (2)

In a photochemical vapor deposition apparatus that decomposes a gas present near the substrate by irradiating near-field light and deposits the gas on the substrate,
A light source,
A near-field light probe which is provided with a sharpened portion obtained by sharpening an optical fiber and outputs the light supplied from the light source through the sharpened portion to generate the near-field light,
The wavelength of light supplied from the light source is equal to or longer than the wavelength of light corresponding to the dissociation energy of the gas. In a photochemical vapor deposition method of decomposing a gas present near the substrate by irradiating near-field light and depositing the gas on the substrate,
The near-field light is generated by outputting the supplied light through a sharpened portion where the optical fiber is sharpened,
The wavelength of the supplied light is equal to or longer than the wavelength of light corresponding to the dissociation energy of the gas.

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