WO2007029743A1

WO2007029743A1 - Method for formation of film of molecular substance and apparatus for said method

Info

Publication number: WO2007029743A1
Application number: PCT/JP2006/317659
Authority: WO
Inventors: Hideomi Koinuma; Yuji Matsumoto; Kenji Itaka; Seiichirou Yanaginuma
Original assignee: Japan Science And Technology Agency
Priority date: 2005-09-06
Filing date: 2006-09-06
Publication date: 2007-03-15
Also published as: JP4775801B2; JPWO2007029743A1

Abstract

This invention provides a method for formation of a film of a molecular substance, comprising applying light from a light source to a material to be vapor deposited and forming a film of a molecular substance on a substrate while regulating the vapor deposition speed of the vapor deposition material. The film can be formed while maintaining the molecular structure of the molecular substance by applying light with the strength of the continuous wave thereof being selected. In this case, when the light is in a pulse form, in the light irradiation, any one of or a plurality of the pulse wave height value, the pulse width, and the pulse spacing are selected. The apparatus (1) for forming a film of a molecular substance comprises a vacuum tank (3) having a light permeable window (2), a holding fixture (4) for holding a material to be vapor deposited disposed within the vacuum tank (3), a substrate holding fixture (7) for holding a substrate (6) on which the vapor deposition material evaporated from the holding fixture (4) is deposited, and a light source (8) disposed so that light is applied to the vapor deposition material within the vacuum tank (3) through the window (2) of the vacuum tank. The wavelength of the light source (8) has a wavelength energy which can form a film while maintaining the molecular structure of the molecular substance.

Description

Molecular material deposition method and apparatus

Technical field

TECHNICAL FIELD [0001] The present invention relates to a film forming method and apparatus for producing a thin film of a molecular substance, and more particularly to a film forming method and apparatus capable of forming a molecular substance by light irradiation. .

Background art

In recent years, elucidation of the physical properties of organic substances has progressed, and it has become possible to realize conductive characteristics similar to metals, semiconductor characteristics similar to inorganic semiconductors, or light-emitting characteristics that emit light by current. . Compared to inorganic thin films, organic thin films are less likely to break even when bent, and they have excellent flexibility and are easier to make thinner than inorganic thin films. Due to the unique physical properties of organic substances, displays and electronic devices using organic thin films are being put into practical use (see Non-Patent Documents 1 and 2).

[0003] For example, an organic EL (Electro Luminescence) element is composed of an organic thin film as described below. That is, the organic EL element has a configuration in which an organic thin film called an organic light emitting layer having a thickness of less than m is sandwiched by organic thin films called an electron transport layer and a hole transport layer. The organic light-emitting layer is formed of a so-called conjugated molecular layer in which units composed of carbon single bonds and double bonds are periodically linked. The π-electron level of the conjugated molecule is a single bond. It forms an energy band based on the periodicity of units consisting of double bonds! Electrons and holes injected into the organic light-emitting thin film emit light by releasing and recombining photons corresponding to the band gap energy. In addition, in order to increase the luminous efficiency, the thicknesses of the electron transport thin film and the hole transport thin film are set to optimum thicknesses so that the number of electrons and holes supplied to the organic light emitting thin film becomes equal.

[0004] As described above, a device composed of an organic thin film depends on the molecular structure of the molecules that make up the organic thin film. In addition, it is necessary that the molecular structure of the molecules constituting the organic thin film is not damaged. In addition, since organic materials differ greatly in electronic conductivity and hole conductivity compared to inorganic materials, it is essential to manufacture the organic thin film with precise thickness control.

Thus, in order to produce an organic material thin film, it is necessary to solve a specific problem that is not found in inorganic material thin films.

[0005] There is a vapor deposition method as one of conventional methods for producing an organic material thin film. For example, the conventional organic EL element vapor deposition method uses an organic material raw material powder constituting an electron transport layer, an organic material raw material powder constituting an organic light emitting layer, and an organic material raw material powder constituting a hole transport layer, respectively. These are placed on the holder of the material to be deposited, and each holder is sequentially controlled to the sublimation temperature of each raw material to sublimate organic molecules and vapor-deposit on the substrate on which the transparent electrode is formed. .

[0006] As described above with an example of an organic EL element, in order to produce a display or an electronic device using an organic material thin film by vapor deposition, the molecular structure of the deposited organic thin film is destroyed during the production. However, it is essential to be able to precisely control the thickness of the thin film. In order to prevent the molecular structure of the organic thin film from being destroyed and to be able to precisely control the film thickness of the thin film, the temperature at which the entire holder for the deposited material can be deposited without destroying the molecular structure. In other words, it must be precisely controlled to the sublimation temperature of the organic material to be deposited, but if a temperature control device is added to the holder for the deposited material, the surface area, volume and heat capacity of the holder will increase, and the thermal equilibrium state will increase. It takes a long time to reach the desired temperature, and it is extremely difficult to control it to a predetermined temperature in a short time. In addition, since the amount of heat released through the jig that supports the holder is not constant depending on the operating status of the vapor deposition apparatus, the temperature control conditions for the holder set at the beginning of the operation of the apparatus are upset as the temperature of the entire apparatus rises. Arise. For this reason, it is extremely difficult to control to a predetermined temperature for a long time.

For example, as shown in FIG. 14, in the conventional apparatus, the organic material to be deposited is put into Knudsen cells 20 and 21 provided for each organic material to be deposited, and the temperatures of the Knudsen cells 20 and 21 are set to the respective organic materials to be deposited. Vapor deposition is controlled at the sublimation temperature of the material, but as explained above, Knudsen cells 20 and 21 each have a built-in temperature control device, resulting in a thermal equilibrium state with a large surface area, volume and heat capacity. If it takes a long time to control it to a predetermined temperature in a short time, temperature overshoot, that is, overtemperature rise occurs, It is inevitable that the molecular structure of the organic material is damaged. In addition, the molecular orientation of the organic thin film affects the conductivity of the organic thin film, but the molecular orientation also depends on the deposition rate. As described above, the conventional deposition method keeps the deposition rate sufficiently constant. It is difficult to control the orientation sufficiently. Since the temperature control of the Knudsen cell is difficult as described above, it is difficult to control the film thickness, which makes it difficult to keep the deposition rate sufficiently constant. In order to improve the film thickness controllability, in the conventional apparatus, a film thickness sensor 22 is provided in the vicinity of the evaporation substrate, and shutters 20a and 20b are provided to prevent evaporation of the evaporation target substance. The film thickness is controlled by the method of closing the shutters 20a and 20b by detecting the film thickness sensor 20 with the film thickness sensor 20, but waste of depositing valuable organic material on the shutter occurs.

[0008] Like the Knudsen cell in FIG. 14, the temperature-controlling holder is large, so when manufacturing a device that requires the deposition of a plurality of deposition materials in succession, a large holding The vapor deposition equipment has become extremely large to accommodate multiple tools, and the cost of the equipment is inevitable.

[0009] Also, in the combinatorial film forming technology field, different materials are alternately deposited by several molecular layers (or atomic layers) while moving the mask, and about 10,000 molecular layers (or atomic layers) are deposited. Although a composition gradient film is formed, if the switching speed of the deposition material is not fast, it takes a long time to manufacture.

[0010] Conventionally, a laser ablation method (PLD method) is known as a method for producing a thin film mainly of an inorganic substance. In the laser ablation method, a laser beam with high energy such as visible light or ultraviolet light is irradiated, and the light energy of the laser beam pulse is directly absorbed by the vapor deposition material and evaporated. However, in the case of a laser ablation method, molecular structures are damaged in the case of molecular substances, particularly organic substances, and functions based on the molecular structure of the material to be deposited can be fully expressed. (See Non-Patent Documents 3 and 4).

[0011] Non-patent literature l: http: ZZwww. Nanoelectronics.jp/kaitai/oel/3.htm 20 05/08/05

Non-Patent Document 2: http: ZZ www.nanoelectronics.jp/kaitai/ printableofet / 2.htm 2005/08/05

Non-Patent Document 3: K. ITAKI et al., “Pulsed laser deposition of axis oriented pentacen films” Appl. Phs. A, Vol. 79, pp. 875—877, 2004 Non-Patent Document 4: Jun Yamaguti et al. , "Combinatorial Pulsed Laser Deposition of PentacenFilms for Field Effect Device" Macromol Rapid C ommun., Vol. 25, pp. 334— 338, 2004

Non-Patent Document 5: M. Haemori and 4 others, "Fabrication of Highly Oriented Rubrene Thin Films by the Use of Atomically Finished Substrate and Pentacene Buffer Layer", Jap. J. Appl. Phys., Vol. 44, p. 3740 , 200

Five

Disclosure of the invention

Problems to be solved by the invention

As understood from the above description, in the case of vapor deposition using a Knudsen cell, it takes too much time to control the vapor deposition temperature, and the film deposition rate is not constant. On the other hand, in the case of the laser ablation method, digital control of film formation is possible, but in the case of molecular substances, especially organic substances, the molecular structure is damaged, and the molecular structure of the material to be deposited is damaged. The function based on can not be fully expressed.

[0013] Vapor deposition can be performed without destroying the molecular structure of molecular substances, particularly organic substances. As a result, the physical properties of organic substances can be fully expressed, the deposition rate can be controlled, and the orientation of molecular substances can be controlled. In addition to being able to control the thickness of this thin film sufficiently, low-cost film formation technology and vapor deposition equipment are required, but the method and apparatus have not yet been realized.

[0014] In view of the above problems, the present invention provides a low-cost film-forming method that can be deposited without destroying the molecular structure of a molecular substance, particularly an organic substance, and that can be deposited by controlling the deposition rate. The first object is to provide such a film forming apparatus. Means for solving the problem

[0015] In order to achieve the first object, the present invention is a method of depositing a molecular substance on a substrate by irradiating light to the deposition target material with light source power and controlling the deposition rate of the deposition target substance. Select the intensity of the continuous wave of light to irradiate, or if the light is a pulse, the pulse wave The film formation is performed while maintaining the molecular structure of the molecular substance by selecting and irradiating one or more of the high value, the pulse width, and the pulse interval.

In the above configuration, the light having continuous wave power preferably has a wavelength energy smaller than the binding energy of the molecular substance. The pulsed light source preferably has a wavelength energy smaller than the binding energy of the molecular substance with respect to the peak energy density intensity in the single photon region. The molecular substance may be an organic semiconductor such as pentacene, in which case the light wavelength is in the vicinity of 808 nm to 981 nm.

[0016] According to the conventional method, when a photon equivalent to energy equal to or higher than the band gap energy formed by π electrons is irradiated, the π electrons in the ground state (Highest Occupied Molecular Orbital State) are excited (Lowest Unoccupied Molecular). The electrons excited by (State) become free electrons, causing a phenomenon of free movement. Since organic substances are decomposed into individual molecules during the vapor deposition of organic materials, if this phenomenon occurs during vapor deposition, excited π electrons cannot return to the ground state, and π electrons are The double bond of the organic material that is formed is broken to a single bond, and the conjugated molecular structure of the organic material is destroyed. When the conjugated molecular structure of an organic material is destroyed, the organic device that utilizes the physical properties of π electrons based on the conjugated molecular structure of the organic material loses its function.

On the other hand, according to the method of the present invention, since the molecular substance is formed by irradiating light that can be formed while maintaining the molecular structure of the molecular substance, the above-mentioned phenomenon does not occur. The molecular structure of is not destroyed.

[0017] In addition, the raw material powder of the molecular substance absorbs photons to be irradiated and rises to a temperature corresponding to the number of photons, and the absorbed energy diffuses as thermal energy toward the surrounding low-temperature part, but diffuses. Since the magnitude of the thermal energy is proportional to the temperature difference from the surroundings, the temperature rises until the magnitude of the diffusing thermal energy becomes equal to the photon energy supplied per unit time, and the temperature becomes constant. If the intensity of the continuous wave of light is selected and irradiated, or if the light is a pulse, it is extremely effective to select and irradiate one or more of the pulse peak value, pulse width, and pulse interval. Since the photon energy supplied per unit time can be controlled with a wide range of accuracy and accuracy, the raw material powder of the organic substance can be controlled to a predetermined temperature, and as a result, the deposition rate can be controlled to a desired constant value. Thus, the method of the present invention According to the method, it is possible to carry out deposition without damaging the molecular structure of the molecular substance and precisely controlling the molecular orientation and the film thickness.

In another embodiment of the method for forming a molecular substance according to the present invention, the material to be deposited is irradiated with light emitted from a light source, and the deposition rate of the substance to be deposited is controlled to form the molecular substance on the substrate. The material to be deposited absorbs light and releases the absorbed light energy as light, and mixes the material that does not react with the molecular material and does not evaporate at the deposition temperature of the molecular material. Select or irradiate, or if the light is a pulsed light, select one of the peak value, pulse width, and pulse interval of the pulse! The film is formed while maintaining the molecular structure of the substance.

In the above configuration, the light having continuous wave power preferably has a wavelength energy smaller than the binding energy of the molecular substance. The pulsed light source preferably has a wavelength energy that is smaller than the binding energy of the molecular substance with respect to the peak energy density in the single photon region. The molecular substance is preferably an organic semiconductor. The substance that does not react with the molecular substance and does not evaporate is, for example, any one of a refractory metal, a carbide, and a nitride.

Preferably, the molecular substance is rubrene or C, does not react with rubrene or C, and

60 60

One material that does not evaporate is Si powder, and the wavelength of the infrared laser is around 808 nm to 981 nm.

According to this method, even if the absorption wavelength of the molecular substance is greatly deviated from the peak wavelength of the light source used, the mixed material force absorbs infrared light and absorbs the absorbed infrared light energy over a wide range. Since it is re-emitted as infrared light having a wavelength, the temperature of the molecular substance can be controlled to the desired temperature, the deposition rate can be kept constant, and thus the molecular structure of the molecular substance can be prevented from being damaged. In addition, the molecular orientation can be controlled, and the film thickness can be precisely controlled for deposition.

The substance to be mixed may be any substance that does not react with the deposition target substance and does not evaporate at the deposition temperature of the molecular substance to be deposited.For example, in the case of an organic substance, Si, refractory metal, SiC It may be a carbide such as NiO or a nitride such as SiN.

3 4

According to this method, it is possible to select the intensity of the continuous wave of light to irradiate, or the infrared light Since the deposition rate can be controlled by selecting one or more of the pulse peak value, pulse width and pulse interval for one pulse, no film thickness sensor or shutter is required, and the deposition material can be controlled. Since no temperature control device for the holding tool is required, a plurality of vapor deposition materials can be arranged in the vacuum layer without increasing the size of the vapor deposition device. Therefore, a thin film having a molecular substance power can be produced at a low cost.

[0019] In order to achieve the second object, the molecular substance film-forming apparatus of the present invention holds a vacuum chamber having a window that transmits light, and a vapor deposition material disposed in the vacuum chamber. And a light source arranged so as to irradiate the vapor deposition material in the vacuum chamber through the window of the vacuum chamber. The wavelength of the light source has a wavelength energy that allows film formation while maintaining the molecular structure of the molecular substance.

In the above configuration, the light source may be a continuous wave light source, and the continuous wave light source has a wavelength energy smaller than the binding energy of the molecular substance. The light source may be a pulsed light source. The Nors light source has a wavelength energy smaller than the binding energy of the molecular substance in the peak energy density intensity of the single photon region. This pulse light source is preferably formed by intermittently supplying a continuous wave light source. A holding tool moving unit that moves the holding tool to the irradiation position of the light source can be further provided.

[0020] According to the molecular substance film-forming apparatus of the present invention, since a light source is used, a molecular substance, for example, a thin film having an organic substance force can be deposited without damaging the molecular structure. For example, when an infrared laser pulse is used, the energy of the irradiated infrared laser is selected by selecting one or more of the peak value, pulse width, and pulse interval of the infrared laser pulse. Because the size of the film can be controlled over a wide range and precisely, the deposition rate can be controlled to the desired value, and as a result, the orientation can be controlled and the film thickness can be controlled precisely. It is.

The invention's effect

[0021] According to the method and apparatus for forming a molecular substance of the present invention, it is possible to form a film by evaporating the deposition target material by irradiating light from a light source. Can be manufactured in a short time. In addition, it is necessary to continuously deposit multiple deposition materials. Even in the case of manufacturing a necessary device, it can be manufactured without increasing the cost of the apparatus.

Brief Description of Drawings

FIG. 1 is a schematic cross-sectional view showing the configuration of a molecular material deposition apparatus using an infrared laser according to the present invention.

FIG. 2 is a diagram showing an absorption spectrum of a pentacene thin film produced by a conventional vapor deposition method using a Knudsen cell.

FIG. 3 is a table showing absorption wavelengths of typical molecular vibrations.

FIG. 4 is a graph showing the relationship between bond dissociation energy in various bonds of a molecular substance and the wavelength of light corresponding to this energy.

FIG. 5 is a diagram showing the relationship between pulse width and pulse peak power density when the light source is a pulse laser.

FIG. 6 is a schematic diagram for explaining a molecular substance vapor deposition step using an infrared laser using the molecular substance vapor deposition apparatus according to the present invention.

FIG. 7 is a diagram showing the crystal structure of the pentacene thin film produced in Example 1.

FIG. 8 is an infrared absorption spectrum of the pentacene thin film produced in Example 1.

FIG. 9 is a view showing a surface SEM (operational electron microscope) image of the pentacene thin film produced in Example 1.

FIG. 10 is a diagram showing infrared absorption spectra of pentacene thin films prepared in Examples 2 and 3 and Comparative Examples 1 and 2.

FIG. 11 is a diagram showing an absorption spectrum in an ultraviolet-visible light region of the pentacene thin film produced in Example 3 and Comparative Example 2.

FIG. 12 is a view showing a measurement result of X-ray diffraction of a rubrene thin film produced in Example 4.

FIG. 13: Diffraction strength of reflection type high-energy electron beam observed during deposition of C thin film prepared in Example 5

60

It is a figure which shows the time dependence of a degree.

FIG. 14 is a view showing a conventional vapor deposition apparatus using a Knudsen cell.

Explanation of symbols

[0023] 1: Molecular material deposition system (vapor deposition system) 2: Light transmission window

3: Vacuum chamber

4: Deposition material holder

4a, 4b, 4c: Deposition material holder

5: Vapor of vapor deposition material

6: Board

7: Board holder

8: Light source (laser device)

9: Holder mounting table

10: Rod,

11: Irradiation light (continuous wave or pulsed light)

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

First, the apparatus of the present invention will be described.

FIG. 1 is a schematic diagram showing a configuration of a molecular substance film forming apparatus according to the present invention. The molecular substance film-forming apparatus 1 of the present invention includes a vacuum chamber 3 having a window 2 that transmits light, a holder 4 that holds a deposition target substance disposed in the vacuum chamber 3, and an evaporation from the holder 4. At least a substrate holder 7 for holding a substrate 6 for depositing a deposition target material 5 to be deposited and a light source 8 capable of irradiating light disposed outside the vacuum chamber 3 are provided. The light source 8 also has power such as a lamp and a laser device. The light source 8 is arranged such that the irradiation light 11 generated by the light source 8 irradiates the deposition material disposed on the deposition material holder 4 through the window 2 of the vacuum chamber. A plurality of the deposition target material holders 4 may be arranged according to the number of the deposition target materials. The holder 4 for holding the vapor deposition material is held so as to be movable to the irradiation position of the irradiation light 11. For example, as shown in the figure, a plurality of holders 4 are arranged on the circumference of the holder mounting base 9. 4 is mounted, and the desired holder 4 is moved to the irradiation position of the irradiation light 11 by rotating the rod 10 coupled to the holder mounting base 9. The substrate holder 7 may be the substrate holder 7 provided with a substrate temperature control unit that can control the temperature of the substrate 6.

Next, the light source 8 will be described. First, the case where the molecular substance is a conjugated molecular organic substance will be described as an example. When the molecular substance is a conjugated molecular organic substance, a light source 8 that outputs photons corresponding to energy less than the band gap energy of the conjugated molecular organic substance is used. The band gap energy of organic materials of conjugated molecular system can be obtained from the absorption spectrum of organic materials. For example, Fig. 2 shows the absorption spectrum of a pentacene thin film prepared by a conventional vapor deposition method using a Knudsen cell. As is clear from the figure, the absorption spectrum is low at about 700 nm or more. It can be seen that the absorption edge wavelength corresponding to the gap energy is about 700 nm. Therefore, in the case of pentacene, for example, a light source 8 having a wavelength longer than 700 nm may be used. As such a light source 8, for example, an infrared laser such as a semiconductor laser may be used. This infrared laser device can control the intensity of the infrared laser continuous wave as long as it is an infrared laser device that outputs a time-coherent infrared laser continuous wave. The pulse width and the pulse interval may be controlled by intermittently switching the wave with the optical chisba and controlling the rotation frequency of the optical chitna.

Next, the light source 8 when the molecular substance is other than a conjugated molecular organic substance will be described.

FIG. 3 is a diagram showing the absorption wavelength of a typical molecular vibration. Fig. 3 shows the absorption wavelength due to stretching motion, which is a typical molecular vibration, but there are other types of molecular vibration, including angular vibration, rotational vibration, and combinations of these vibrations. Including the absorption due to vibration, the infrared absorption wavelength range reaches from 0.7 m to 20 m.

[0027] FIG. 4 is a diagram showing the relationship between bond dissociation energy in various bonds of a molecular substance and the wavelength of light corresponding to this energy. In the figure, the horizontal axis indicates the wavelength (nm) and the vertical axis indicates the bond dissociation energy (kj / mol).

As shown in the figure, C≡C bond (828kjZ mole (8.58eV)), C = C bond (607kjZ mole (6.29eV)), OH bond (463kjZ mole (4.8eV)), CH bond (413kjZ) It can be seen that the bond dissociation energy (also called the bond energy) decreases in the order of mol (4.28 eV)) and CC bond (348 kjZ mol (3.6 leV)). For example, molecular substances

In the case of having a CC bond, the bond dissociation energy is 3.61 eV. The wavelength of light corresponding to one is about 344 nm. When a molecular substance has only C—C bonds, a light source having a photon energy of 61 eV or less is the bond dissociation energy in order to form a film while maintaining the molecular structure of the molecular substance. Should be used. That is, the wavelength may be the light source 8 having a wavelength of about 344 nm or more. When the molecular substance is the above bond or a combination of these bonds, use the light source 8 corresponding to the wavelength with the lowest bond dissociation energy.

[0028] Therefore, the light of the light source 8 used in the apparatus of the present invention is not limited to the molecular substance considering the band gap energy of the molecular substance, the molecular vibration, the bond binding energy in the binding of the molecular substance, and the like. What is necessary is just to set it as the wavelength which can hold | maintain molecular structure. For example, the emission wavelength can be in the range of 0.7 IX m to 20 m. For light source 8, select the internal force of gas laser such as CO laser, CO laser, HF laser and YAG laser according to the type of material to be deposited

2

can do. Further, GaAs, GaAlAs, PbSnSe, PbSSe and In AsSb semiconductor lasers made of semiconductors may be used. A free electron laser may be used. The light source 8 may be a lamp having a filter for transmitting only a wavelength capable of maintaining the molecular structure of the molecular substance.

[0029] When the light source 8 is a pulse, for example, a combination of a laser device such as an infrared light that outputs a continuous wave and an optical chiba that interrupts the output light, and the continuous light is intermittently red. An external light laser pulse is formed. Since the infrared laser pulse formed by the Q switch is a frequency coherent wave, multi-photon excitation occurs depending on the type of material to be deposited, and it tends to be a short light pulse with a short wavelength. In this case, the ground state electrons may be excited to an excited state to damage the molecular structure, or the atoms of the atoms constituting the deposition material may be excited to cause damage to the molecular structure. Since the laser pulse 8 formed intermittently is a temporally coherent wave, it does not cause damage to the molecular structure without the occurrence of multiphoton excitation.

FIG. 5 is a diagram showing the relationship between the pulse width and the peak power density of the pulse when the light source 8 is a pulse laser. In the figure, the horizontal axis indicates the pulse width (s), and the vertical axis indicates the peak power density (WZcm ² ). The peak power density is also called the peak value of the energy density, and is the maximum power density in one pulse. Molecular substances In order to form a film while maintaining the child structure, the photon intensity of the pulse laser, that is, the peak power density, is a peak below the dotted line (about 5 × 10 ⁵ W / cm ² ) shown in the figure, which is a single photon region. The power density may be used. The figure also shows the relationship between the pulse width and peak power density used in conventional PLDs! The photon intensity in the pulse used in this conventional PLD is not a single photon region but a multiphoton region.

Next, the process of vapor-depositing the molecular substance using the light of the present invention using the vapor deposition apparatus for forming the molecular substance by the light of the present invention will be described.

FIG. 6 is a schematic diagram for explaining a film formation method of the molecular substance of the present invention using the molecular substance vapor deposition apparatus of the present invention. Hereinafter, a case where three types of organic thin films are laminated as in the case of manufacturing an organic EL element using an infrared laser pulse as the light source 8 will be described.

(1) First, for each of the three kinds of raw material powders a, b, and c of the organic thin film, the relationship between the deposition rate and the crest value, pulse width, and pulse interval of the infrared laser pulse 11 is determined.

(2) Next, the raw material powders a, b, and c of the three kinds of organic thin films are loaded into the vapor deposition material holders 4a, 4b, and 4c, respectively, and the substrate 6 is attached to the substrate holder 7 and the vacuum chamber Vacuum 3 After reaching a predetermined degree of vacuum, the substrate holder 7 is heated to hold the substrate 6 at a predetermined temperature.

(3) The holder 4a loaded with the raw material powder a of the organic thin film to be deposited first is moved to the irradiation position of the infrared laser pulse 11, and the deposition rate of the raw material powder a and the infrared laser pulse 11 determined in advance. Using the relationship between the crest value, pulse width, and pulse interval, select one or more of the crest value, pulse width, and pulse interval at which the desired deposition rate is achieved, and achieve the desired film thickness. Irradiation with an infrared laser pulse 11 is performed for a corresponding time.

(4) Next, the holder 4b loaded with the raw material powder b of the organic thin film to be deposited is moved to the irradiation position of the infrared laser pulse 11, and the deposition rate of the raw material powder b and the infrared laser pulse determined in advance are moved. Using the relationship between 11 crest values, pulse width, and pulse interval, select one or more of crest values, pulse width, and pulse interval that achieve the desired deposition rate, and Irradiate the infrared laser pulse 11 for a time according to the desired film thickness.

(5) Also, the holder 4c loaded with the raw material powder c of the organic thin film to be deposited is moved to the irradiation position of the infrared laser pulse 11, and the deposition rate of the raw material powder c and the infrared laser pulse 11 determined in advance. Using the relationship between the crest value, pulse width, and pulse interval, select one or more of the crest value, pulse width, and pulse interval at which the desired deposition rate is achieved, and achieve the desired film thickness. Irradiation with an infrared laser pulse 11 is performed for a corresponding time.

(6) After deposition is completed, the substrate 6 is taken out and completed.

[0032] When the molecular substance is an organic molecule, a π-conjugated organic molecule or an organic molecule having a benzene ring can be used. Specifically, examples of the organic molecule include pentacene, fullerene, acene organic molecule, thiophene organic molecule, and derivatives thereof.

[0033] The light source 8 may be a continuous wave light source. In this case, the light source comprising a continuous wave has a wavelength energy that is smaller than the binding energy of the molecular substance. It is possible to form a film while maintaining the molecular structure.

[0034] In the pulse light source 8, one or more of the peak value, pulse width, and pulse interval of the optical pulse is selected and irradiated. In this case, the pulsed light source 8 has a peak energy density intensity in the single photon region, which is smaller than the binding energy of the molecular substance and has a wavelength energy. The film can be formed while maintaining the molecular structure.

[0035] The film formation method for a molecular substance of the present invention operates as follows. In other words, when a molecular substance connected by the bonding of multiple atoms is irradiated with visible light or ultraviolet light, the electrons of the atoms constituting the molecular substance are excited, and this excitation generally involves the molecular structure of the molecular substance. To damage. On the other hand, the shared electrons of a molecular substance act like a panel that connects the atoms that make up the molecule, and when a photon with an energy equivalent to the natural vibration energy of this panel is irradiated, the molecular substance absorbs the photon energy. Cause molecular vibrations. Since the natural vibrational energy of molecular vibrations is sufficiently small and is generally in the infrared region, the electrons that make up the atoms of the molecular substance are not excited. The child structure is not destroyed.

In addition, since molecular vibration is harmonic vibration, it absorbs photons to be irradiated and is excited by molecular vibration energy corresponding to the number of photons. The excited molecular vibrational energy is a force that diffuses as thermal energy toward the surrounding low-temperature part.The magnitude of the diffused thermal energy is proportional to the temperature difference from the surroundings. The temperature rises until it becomes equal to the photon energy supplied per unit time, and the temperature becomes constant at this temperature. Therefore, the unit time can be determined by selecting and irradiating one or more of the intensity of the continuous wave light source to irradiate, the irradiating force, the crest value of the light pulse, the pulse width and the pulse interval. Since the photon energy supplied to the substrate can be controlled, the deposition material can be controlled to a predetermined temperature, and as a result, the deposition rate can be controlled to a predetermined desired constant value. Therefore, according to the method of the present invention, deposition can be performed without damaging the molecular structure of the molecular substance, controlling the molecular orientation, and controlling the film thickness precisely.

[0036] According to the apparatus and method of the present invention, for example, only the raw material powder is irradiated with an infrared laser pulse or a continuous wave infrared laser, and the temperature of the raw material powder is directly determined with these lasers. Since it is heated to a temperature, the molecular structure of the organic material to be deposited due to the time required to reach a thermal equilibrium state, which is a problem in the prior art, or the overshoot of the temperature that is generated when trying to control to a predetermined temperature in a short time The problem of damage is solved.

[0037] According to the apparatus and method of the present invention, a force for selecting one or more of the peak value, pulse width, and pulse interval of an optical pulse 8, eg, an infrared laser pulse, a continuous wave light source 8, eg, If the intensity of the continuous wave of the infrared laser is selected and irradiated, a desired constant deposition rate can be realized. Therefore, it is difficult to keep the deposition rate sufficiently constant, so that the orientation cannot be controlled sufficiently.

[0038] According to the apparatus and method of the present invention, for example, one or more of the peak value, pulse width, and pulse interval of the infrared laser pulse 8 are selected, or the continuous wave light source 8, for example, red By selecting and irradiating the intensity of the continuous wave of the external light laser, a desired constant deposition rate can be realized, and in order to achieve a predetermined film thickness, it is only necessary to control the irradiation time of the infrared laser pulse. Therefore, the film thickness sensor and shutter required by the conventional technology In addition, valuable organic materials are not wasted.

[0039] According to the apparatus and method of the present invention, the temperature of the raw material powder is selected from one or more of the peak value of the infrared laser pulse, the pulse width and the pulse interval, or the continuous wave light source 8 For example, since it can be controlled only by selecting and irradiating the intensity of the continuous wave of the infrared laser, the surface area that incorporates a heating device that maintains a predetermined temperature for each raw material, which is necessary in the prior art. In addition, it is sufficient to have a small shape that can hold the raw material powder without the need for a large volume and heat capacity holder. Even devices that require continuous deposition of materials can be manufactured without increasing equipment costs.

[0040] Since the conventional laser ablation method uses visible light or ultraviolet light, the molecular structure of the material to be deposited is damaged. According to the apparatus and method of the present invention, as described above, Since pulsed light and continuous light that can maintain the molecular structure of the active substance are used, it is possible to deposit without damaging the molecular structure of the deposited material.

Next, another embodiment according to the present invention will be described.

Depending on the type of material to be deposited, the infrared absorption wavelength of the material to be deposited is significantly deviated from the center wavelength of the infrared laser to be used, so that sufficient heating may not be possible. In such a case, using an infrared laser device having a peak in the absorption wavelength, or using a tunable laser to match the peak wavelength to the absorption wavelength is a solution. There is a problem I said. In such a case, a method capable of vapor deposition without changing the infrared laser apparatus will be described.

In other words, it is a substance that efficiently absorbs infrared light, re-emits the absorbed infrared light energy as infrared light in a wide wavelength range, does not react with the material to be deposited at the deposition temperature of the raw material powder, and In this method, a powder of a substance that does not evaporate at the deposition temperature of the powder is mixed with the raw material powder, and this mixed powder is used as the raw material powder.

[0042] Such a vapor deposition substance may be organic or inorganic as long as it is a molecular substance and does not absorb infrared light to be used or cannot be heated to the evaporation temperature by a weak irradiation light source. Examples of the organic substance include rubrene and fullerene (C 3). In addition,

60

Anthracene, tetracene, and c, which are materials with a relatively large forbidden band (band gap) And so on.

[0043] As a material to be mixed with the material to be deposited, a carbide such as Si, a refractory metal, SiC, or a nitride such as NiO or SiN can be used. For example, organic matter consisting of conjugated molecules

3 4

In the case of quality, examples include metals such as A1, Si, and SiC.

[0044] According to this method, even if the absorption wavelength of the material to be deposited is significantly deviated from the center wavelength of the infrared laser used, this material efficiently absorbs and absorbs the infrared laser. Since the infrared light energy is emitted as infrared light including the absorption wavelength of the deposited material, the deposited material can be heated and evaporated indirectly.

Example 1

Next, the present invention will be described in further detail with reference to examples.

Example 1 shows a case where the molecular substance is an organic substance such as a conjugated molecular molecule. In the raw material powder of the organic substance, red corresponding to the energy less than the band gap energy formed by π electrons of the organic substance. In the embodiment of the method for vapor deposition, the external light laser pulse is irradiated by selecting one or more of the pulse peak value, pulse width, and pulse interval to control the vapor deposition rate of the material to be deposited. is there.

Using the film forming apparatus of the present invention, a pentacene thin film was produced using the pentacene raw material powder by the method of the present invention. In Example 1, using the apparatus shown in FIG. 1, from the absorption short wavelength of pentacene shown in FIG. 2, the infrared laser pulse is continuously transmitted from an infrared semiconductor laser having a wavelength of 0.808 (808 nm). The wave was used intermittently. The pulse width was lsec, the repetition frequency was 0.5 Hz, and the irradiation energy density was about lOWZcm ² . A sapphire substrate was used as the substrate, and the substrate temperature was 100 ° C. The thickness of the deposited pentacene thin film was 50 nm. The deposition rate at this time was 4.4 nmZ.

Example 2

A pentacene thin film was formed in the same manner as in Example 1 except that a continuous wave infrared semiconductor laser having a wavelength of 981 nm and an output of 2.5 W was used. Power per unit area of the infrared semiconductor laser was 12WZcm ^2. The thickness of the deposited pentacene thin film was lOOnm. The deposition rate at this time was 4.4 nmZ. The above-mentioned infrared semiconductor lasers have the ability to change the wavelength by ± 5 nm due to fluctuations in the output level. It did not affect the degree.

Example 3

A pentacene thin film was formed in the same manner as in Example 1 except that a continuous wave infrared semiconductor laser having a wavelength of 808 nm and an output of 2.5 W was used. Power per unit area of the infrared semiconductor laser was 8WZcm ^2. The thickness of the deposited pentacene thin film was lOOnm. The deposition rate at this time was 4.4 nmZ.

Example 4

[0048] As in Example 1, except that a continuous wave infrared semiconductor laser with a wavelength of 981 nm and an output of 2.5 W was used, rubrene powder and Si powder were used as raw materials, and a sapphire substrate was used. A rubrene thin film was formed. The power per unit area of the infrared semiconductor laser was 8WZcm2. Since the rubrene thin film has poor orientation to the substrate, first, a single molecular layer of pentacene was formed on the substrate as a buffer layer to promote the two-dimensional growth of rubrene, and then the rubrene thin film was formed. The thickness of the rubrene film was 20 nm. The deposition rate at this time was 3. OnmZ.

Example 5

[0049] A C thin film was formed in the same manner as in Example 1 except that a continuous wave infrared semiconductor laser with a wavelength of 981 nm and an output of 2.5 W was used, and fullerene (C) powder and Si powder were used as raw materials. Film formation

60 60

It was. Power per unit area of the infrared semiconductor laser was 8WZcm ^2. Thin film C

60 The film thickness was lOOnm. The deposition rate at this time was 3.92 nmZ. When examining the diffraction intensity of the reflection type high-speed electron beam described later, a mica substrate was used as the substrate.

[0050] Next, a comparative example for the embodiment will be described.

(Comparative Example 1)

Using a PLD method using an ultraviolet pulse laser as a heating source, a pentacene thin film having the same thickness as in Example 1 was formed. The wavelength of the pulse laser was 266 nm, the pulse width was 5 ns, the repetition frequency was 10 Hz, and the irradiation energy per unit area was 0.0 j / cm ² .

[0051] (Comparative Example 2)

Using PLD method with infrared pulse laser as heating source V ヽ, pentacene with the same film thickness as Example 1 A thin film was formed. The wavelength of this pulse laser was 1064 nm, the pulse width was 6 ns, the repetition frequency was 10 Hz, and the irradiation energy per unit area was 0.08 j / cm ² .

[0052] (Comparative Example 3)

The raw material powder was heated in the same manner as in Example 3 using only the Si powder without mixing the Si powder. In this case, it was found that the rubrene thin film was not formed on the substrate and the rubrene powder was evaporated.

[0053] The measurement results of the crystal structures and infrared absorption wavelengths of the pentacene and rubrene thin films of Example 1 and Comparative Example that were produced will be described.

FIG. 7 is a diagram showing the crystal structure of the pentacene thin film prepared in Example 1, where (a) shows the Θ / 2 Θ diffraction X-ray measurement results, and (b) shows the diffraction peak (001) 2 The result of measuring the half-width of the diffraction peak by rotating the angle Θ of the sample while fixing Θ and measuring the size of the crystal grain is shown. For comparison, the results for the pentacene thin film produced by the conventional MBE method using Knudsen cells are also shown.

From Fig. 7 (a), the crystal structure agrees very well with the results of the pentacene thin film prepared by the MBE method, and from Fig. 7 (b), the peak half-value width is very similar to the results of the pentacene thin film prepared by the conventional method. You can see that they match well. Therefore, by using the method and thin film production apparatus of the present invention, a pentacene thin film can be produced without damaging the molecular structure of pentacene.

FIG. 8 is a diagram showing an infrared absorption spectrum of the pentacene thin film of Example 1 produced by the method and apparatus of the present invention. In the figure, the horizontal axis indicates the wave number (cm 2) and the vertical axis indicates the absorptance (arbitrary scale). For comparison, the infrared absorption spectrum of the pentacene powder used as a raw material is also shown. The measurement device used was an FTIR (Fourier transform infrared spectrophotometer).

From FIG. 8, it can be seen that the infrared absorption spectrum of the pentacene thin film prepared in Example 1 agrees very well with the infrared absorption spectrum of the pentacene powder. The difference in strength is due to the difference in the amount of pentacene deposited in the FTIR measurement between the powder and thin film.

Therefore, also from this result, according to Example 1, it is possible to produce a pentacene thin film without damaging the molecular structure of pentacene. [0055] FIG. 9 is a diagram showing a surface SEM (scanning electron microscope) image of the pentacene thin film produced in Example 1. For comparison, the pentacene produced by the conventional MBE method using a Knudsen cell. A thin film image is also shown. Figure 9 shows that the in-plane crystallinity is equivalent to that of a pentacene thin film fabricated by the conventional MBE method using Knudsen cells.

From the results of FIGS. 7 to 9 shown above, it can be seen that a pentacene thin film with no damage to the molecular structure can be produced by the method of the present invention. This effect is mainly due to the fact that the method of the present invention uses an infrared laser pulse corresponding to an energy less than the band gap energy formed by the π electrons of pentacene. Compared with the irradiation peak power density (peak value) of lOMWZc m ² or higher in (see Fig. 5 and Non-Patent Document 3), the irradiation peak power density of the infrared laser pulse by the method of the present invention is about lOWZcm ² One of the factors is that it is extremely low.

FIG. 10 is a diagram showing an infrared absorption spectrum of the pentacene thin film produced in Examples 2 and 3 and Comparative Examples 1 and 2. In the figure, the horizontal axis indicates wave number (cm 2), and the vertical axis indicates transmittance (arbitrary scale). For comparison, the infrared absorption spectrum of pentacene powder is also shown. FTIR was used.

FIG. 10 shows that the infrared absorption spectrum of the pentacene thin film prepared by irradiating with continuous laser light in Examples 1 and 2 agrees very well with the infrared absorption spectrum of the pentacene powder.

On the other hand, the infrared absorption spectrum of the pentacene thin film prepared by irradiating with ultraviolet light pulsed laser light by the conventional PLD method of Comparative Example 1 has a higher irradiation peak energy density than that of Examples 1 and 2, and thus is almost molecular. The structure was not observed, and the molecular structure was destroyed. Although the molecular structure is observed in the infrared absorption spectrum of the pentacene thin film produced by irradiating infrared light pulsed laser light by the conventional PLD method of Comparative Example 2, the irradiation peak energy density is large, so that Example 1 and Compared with 2, the transmittance was remarkably lowered, and it was found that a part of the molecular structure was destroyed.

FIG. 11 is a graph showing an absorption spectrum in the ultraviolet-visible light region of the pentacene thin film produced in Example 3 and Comparative Example 2. In the figure, the horizontal axis indicates the wavelength (nm), and the vertical axis indicates the absorption rate (arbitrary scale). From FIG. 11, in the absorption spectrum in the ultraviolet-visible light region of the pentacene thin film prepared by irradiating with continuous laser light having a wavelength of 808 nm in Example 3, a peak due to the band edge is observed in the vicinity of 700 nm. Absorption structures were also observed at other wavelengths, but the optical absorption structure was not observed in the pentacene thin film fabricated in Comparative Example 2! In Comparative Example 2, the absorption spectrum is not observed in the ultraviolet-visible light region! Because the peak power of the pulsed light is very large, the multiphoton process occurs and the molecular structure of pentacene is destroyed. It is estimated that

[0059] FIG. 12 is a diagram showing a measurement result of X-ray diffraction of the rubrene thin film produced in Example 4. In the figure, the horizontal axis indicates the angle (°), that is, an angle corresponding to twice the incident angle Θ of the X-ray to the atomic plane, and the vertical axis indicates the diffracted X-ray intensity (cps).

From Fig. 12, it can be seen that the crystal structure of the rubrene produced is in good agreement with the crystal structure of the pentacene thin film produced by the MBE method (see Non-Patent Document 5). Therefore, according to the method and apparatus of the present invention, a rubrene thin film can be produced without damaging the molecular structure of rubrene.

FIG. 13 shows the reflection high-speed electron beam observed during the deposition of the C thin film prepared in Example 5.

60

It is a figure which shows the time dependence of folding strength. In the figure, the horizontal axis indicates time (seconds), and the vertical axis indicates electron beam intensity (arbitrary scale).

From Fig. 13, the intensity of the diffracted electron beam of C force during fabrication

60

The diffraction pattern of the electron beam shown in the inset is also clear, c

It was found that 60 molecular structures were formed without damage.

[0061] In the above description, an example of an organic substance as a molecular substance has been described. However, the vapor deposition method and apparatus of the present invention can be applied as long as it is a substance bonded by a covalent bond. It is clear that it is also effective for the production of molecular substances consisting of, for example, KBr thin films. Industrial applicability

[0062] As understood from the above description, according to the present invention, a thin film of a molecular material that does not damage the molecular structure of the molecular material can be produced, and the deposition rate is controlled to a predetermined constant rate. Therefore, the orientation of the thin film of the molecular substance can be controlled and the film thickness can be accurately controlled. Therefore, device growth using organic thin films is expected for future growth. It is extremely useful if it is used in the manufacture of devices using superlattices that have a molecular material force, in which the fabrication of semiconductor devices and the control of film thickness are extremely important.

Claims

The scope of the claims

[1] A method of forming a molecular substance on a substrate by irradiating light from a light source to the substance to be vapor-deposited and controlling a vapor deposition rate of the substance to be vapor-deposited,

Force to select and irradiate the intensity of the continuous wave of light, or if the light is a pulse

A film formed while maintaining the molecular structure of the molecular substance by selecting and irradiating any one or more of the crest value, pulse width, and pulse interval of the Norse. Film forming method.

[2] The method for forming a molecular substance according to [1], wherein the light composed of the continuous wave has a wavelength energy smaller than a binding energy of the molecular substance.

[3] The pulsed light source has a peak energy density intensity in a single photon region.

2. The method for forming a molecular substance according to claim 1, wherein the molecular substance has a wavelength energy smaller than the binding energy of the molecular substance.

[4] The method of forming a molecular substance according to claim 1, wherein the molecular substance is an organic semiconductor.

[5] The method for forming a molecular substance according to claim 4, wherein the organic semiconductor is pentacene, and the wavelength of the light is in the vicinity of 808 nm to 981 nm.

[6] A method of irradiating a material to be deposited with light emitted from a light source and controlling the deposition rate of the material to be deposited to form the molecular material on a substrate.

The material to be deposited is mixed with a raw material composed of a material that absorbs light and emits absorbed light energy as light and does not react with the molecular material at the deposition temperature of the molecular material and does not evaporate. And

The irradiation power by selecting the intensity of the continuous wave of the light, or if the light is pulsed light, select one or more of the pulse peak value, pulse width, and pulse interval for irradiation. Thus, the method for forming a molecular substance is characterized in that the film is formed while maintaining the molecular structure of the molecular substance.

7. The method for forming a molecular substance according to claim 6, wherein the light comprising the continuous wave has a wavelength energy smaller than the binding energy of the molecular substance.

[8] The pulsed light source has a peak energy density in a single photon region. 7. The method for forming a molecular substance according to claim 6, wherein the molecular substance has a wavelength energy smaller than the binding energy of the molecular substance.

[9] The method for forming a molecular substance according to claim 6, wherein the molecular substance is an organic semiconductor.

10. The method for forming a molecular substance according to claim 6, wherein the substance that does not react with the molecular substance and does not evaporate is any one of a refractory metal, a carbide, and a nitride.

[11] The molecular substance is rubrene or C, does not react with the rubrene or C, and is vaporized.

60 60

7. The method for forming a molecular substance according to claim 6, wherein the substance that does not emit is Si powder, and the light is infrared laser light having a wavelength in the vicinity of 808 nm to 98 lnm.

[12] A vacuum chamber having a window that transmits light, a holder that is disposed in the vacuum chamber, and holds a substrate on which the evaporated material evaporated from the holder is deposited. A substrate holder,

A light source arranged so as to irradiate the deposition material in the vacuum chamber through the window of the vacuum chamber,

The molecular light source film forming apparatus, wherein the light source has a wavelength energy that allows film formation while maintaining the molecular structure of the molecular material.

13. The molecular property according to claim 12, wherein the light source is a continuous wave light source, and the continuous wave light source has a wavelength energy smaller than a binding energy of the molecular substance. Material deposition equipment.

[14] The light source is a pulse light source, and the pulse light source has a wavelength energy that is smaller than the binding energy of the molecular substance with respect to the peak energy density in a single photon region! 13. The molecular substance deposition apparatus according to claim 12, wherein

15. The molecular substance deposition apparatus according to claim 14, wherein the pulsed light source is formed by intermittently supplying a continuous wave light source.

16. The molecular substance deposition apparatus according to claim 12, further comprising a holder moving unit that moves the holder to an irradiation position of the light source.