JP4775801B2 - Molecular material deposition method and apparatus - Google Patents

Description

  The present invention relates to a film forming method and apparatus for forming 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.

  In recent years, the 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 emission characteristics that emit light by current. Compared to inorganic material thin film, organic material thin film has excellent flexibility that it is hard to break even when bent, and has characteristics that it is easier to make thin film than inorganic thin film. Therefore, displays and electronic devices using organic thin films are being put into practical use (see Non-Patent Documents 1 and 2).

  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 μm is sandwiched between 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, and the π-electron level of the conjugated molecule is a single bond and a double bond. An energy band based on the periodicity of units composed of bonds is formed. Electrons and holes injected into the organic light-emitting thin film emit light by emitting photons corresponding to band gap energy and recombining. In addition, in order to increase the light emission 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.

As described above, devices consisting of organic thin films depend on the molecular structure of the molecules that make up the organic thin film. Therefore, in order to make the best use of the physical properties of organic substances, the organic thin film must be configured during production. It is necessary that the molecular structure of the molecules to be damaged is not damaged. In addition, since the organic substance has a significantly different electronic conductivity and hole conductivity than the inorganic substance, it is indispensable to manufacture the organic thin film with a precisely controlled thickness.
Thus, in order to produce an organic substance thin film, it is necessary to solve the peculiar subject which an inorganic substance thin film does not have.

  One conventional method for producing an organic material thin film is a vapor deposition method. For example, a conventional organic EL element vapor deposition method uses an organic material raw material powder that constitutes an electron transport layer, an organic material raw material powder that constitutes an organic light emitting layer, and an organic material raw material powder that constitutes a hole transport layer. It arrange | positions to the holder of a vapor deposition substance, controls each sublimation temperature to the sublimation temperature of each raw material one by one, sublimates an organic molecule, and vapor-deposits and forms on the board | substrate with which the transparent electrode was formed.

As described above with an organic EL element as an example, in order to produce a display or electronic device using an organic material thin film using a vapor deposition method, the molecular structure of the vapor deposited organic thin film is not destroyed during the production, and It is essential that the thickness of the thin film can be precisely controlled.
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 of the entire deposition target holder can be deposited without destroying the molecular structure, that is, Although it is necessary to precisely control the sublimation temperature of the organic material to be deposited, adding a temperature control device to the deposition material holder increases the surface area, volume, and heat capacity of the holder, and increases the time until a thermal equilibrium state is reached. Time is required, and it is extremely difficult to control to a predetermined temperature in a short time. Further, since the amount of heat that escapes through the jig that supports the holder is not constant depending on the operating condition of the vapor deposition apparatus, the temperature control condition of the holder set at the initial stage of operation of the apparatus is distorted as the temperature of the entire apparatus rises. For this reason, it is extremely difficult to control to a predetermined temperature for a long time.

  For example, in the conventional apparatus, as shown in FIG. 14, the organic material to be deposited is put in the Knudsen cells 20 and 21 provided for each organic material to be deposited, and the temperature of the Knudsen cells 20 and 21 is sublimated. Although the vapor deposition is controlled at the temperature, as explained above, the Knudsen cells 20 and 21 each have a built-in temperature control device, so that the surface area, the volume and the heat capacity are large, and it takes a long time to reach a thermal equilibrium state. If time is required and control is performed at a predetermined temperature in a short time, it is inevitable that the temperature overshoots, that is, the overtemperature rises, and the molecular structure of the organic material to be deposited is damaged. In addition, the molecular orientation of the organic thin film affects the electrical conductivity of the organic thin film, but the molecular orientation is also affected by the deposition rate. As described above, the conventional deposition method keeps the deposition rate sufficiently constant. It is difficult to control the orientation. Since temperature control of the Knudsen cell is difficult as described above, it is difficult to keep the deposition rate sufficiently constant, and film thickness control is difficult. In order to improve the film thickness controllability, in the conventional apparatus, the film thickness sensor 22 is provided in the vicinity of the vapor deposition substrate, and the shutters 20a and 20b for preventing evaporation of the vapor deposition material are provided, and the predetermined film thickness is reached. Although the film thickness is controlled by a method in which the film thickness sensor 20 detects this and the shutters 20a and 20b are closed, there is a waste of depositing valuable organic material on the shutter.

  As in the Knudsen cell of FIG. 14, since the temperature control holder is large, when manufacturing a device that needs to continuously deposit a plurality of deposition materials, a plurality of large holders are used. Since the vapor deposition apparatus becomes very large for storage, an increase in apparatus cost is inevitable.

  Further, in the combinatorial film forming technology field, different materials are alternately deposited by several molecular layers (or atomic layers) while moving the mask to form a composition gradient film of about 10,000 molecular layers (or atomic layers). However, if the switching speed of the vapor deposition material is not fast, the production takes time.

  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 pulse of high energy such as visible light or ultraviolet light is irradiated, and the light energy of the laser beam pulse is directly absorbed by a vapor deposition material and evaporated. However, in the case of a laser ablation method, in the case of a molecular substance, particularly an organic substance, the molecular structure is damaged, and the function based on the molecular structure of the material to be deposited cannot be sufficiently developed (non-patent document). 3 and 4).

http: // www. nanoelectronics. jp / kaitai / oel / 3. htm 2005/08/05 http: // www. nanoelectronics. jp / kaitai / printableofet / 2. htm 2005/08/05 K. ITAKI et al. "Pulsed laser deposition of c * axis oriented pencenten films" Appl. Phs. A, Vol. 79, pp. 875-877, 2004 Jun Yamaguchi et al. "Combinatorial Pulsed Laser Deposition of PentacenFilms for Field Effect Device" Macromol Rapid Commun. , Vol. 25, pp. 334-338, 2004 M.M. Haemori, 4 others, “Fabrication of Highly Oriented Rubrine Thin Films Use of Atomically Finished Substrated and Pentacene Buffer Layer”, Japan. J. et al. Appl. Phys. , Vol. 44, p. 3740, 2005

  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, the film formation can be digitally controlled. However, in the case of a molecular substance, particularly an organic substance, the molecular structure is damaged, and the molecular structure of the material to be deposited is reduced. The function based on it cannot fully be expressed.

  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 and the deposition rate can be controlled. Although film thickness can be sufficiently controlled and low-cost film formation technology and vapor deposition apparatus are required, the method and apparatus have not been realized yet.

  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. A second object is to provide such a film forming apparatus.

In order to achieve the first object, the present invention is a method of depositing a molecular substance on a substrate by irradiating a deposition target material with light from a light source and controlling a deposition rate of the deposition target substance. By selecting the intensity of the continuous wave and irradiating, or when the light is a pulse, select one or more of the pulse peak value, pulse width and pulse interval to irradiate the molecule. The film is formed while maintaining the molecular structure of the active substance.
In the above configuration, the light composed of continuous waves 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 at 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.

  According to the conventional method, when a photon corresponding to energy higher than the band gap energy formed by π electrons is irradiated, π electrons in the ground state (High Occupied Molecular Orbital State) are excited to an excited state (Lowest Unoccupied Molecular State). The excited electrons become free electrons, causing a phenomenon of free movement. During the vapor deposition of organic material, the organic material is decomposed into individual molecules, so if this phenomenon occurs during vapor deposition, the excited π electrons cannot return to the ground state, thus forming π electrons. The double bond of the organic substance is broken to become a single bond, and the conjugated molecular structure of the organic substance is destroyed. When the conjugated molecular structure of the organic material is destroyed, the organic device utilizing 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, the molecular substance is formed by irradiating light that can be formed while maintaining the molecular structure of the molecular substance. The molecular structure of is not destroyed.

  In addition, the raw material powder of the molecular substance absorbs the 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. Since the magnitude is proportional to the temperature difference from the surroundings, the temperature rises and becomes constant until the magnitude of the diffusing thermal energy becomes equal to the photon energy supplied per unit time. If the intensity of the continuous wave of light is selected for irradiation, or if the light is a pulse, it can be extremely selected by selecting one or more of the pulse peak value, pulse width, and pulse interval. Since the photon energy supplied per unit time can be controlled over a wide range and with high accuracy, the raw material powder of the organic substance can be controlled to a predetermined temperature, and as a result, the vapor deposition rate can be controlled to a desired constant value. Therefore, according to the method of the present invention, it is possible to perform deposition while precisely controlling the molecular orientation and film thickness without damaging the molecular structure of the molecular substance.

According to another aspect of the method for forming a molecular substance according to the present invention, when depositing a molecular substance on a substrate by irradiating the target substance with light emitted from a light source and controlling the deposition rate of the target substance. The material to be vapor-deposited absorbs light and releases the absorbed light energy as light, and mixes the material that does not react with the molecular material at the deposition temperature of the molecular material and does not evaporate. Or when the light is pulsed light, select one or more of the pulse peak value, pulse width, and pulse interval to irradiate the molecule of the molecular substance. The film is formed while maintaining the structure.
In the above configuration, the light composed of continuous waves 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 at the peak energy density in the region of single photons. 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 ₆₀ , the substance that does not react with rubrene or C ₆₀ and does not evaporate is Si powder, and the wavelength of the infrared laser is in the vicinity of 808 nm to 981 nm.
According to this method, even if the absorption wavelength of the molecular substance deviates significantly from the peak wavelength of the light source used, the mixed substance absorbs infrared light and absorbs absorbed infrared light energy over a wide range of wavelengths. Therefore, the temperature of the molecular material can be controlled to a desired temperature, the deposition rate can be kept constant, and thus the molecular structure of the molecular material is not damaged, and The film can be deposited by controlling the molecular orientation and precisely controlling the film thickness.
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, etc. Or a nitride such as NiO or Si ₃ N ₄ .
According to this method, the intensity of the continuous wave of light is selected for irradiation, or an infrared laser pulse is selected from one or more of the pulse peak value, pulse width, and pulse interval. Since the deposition rate can be controlled by this, there is no need for a film thickness sensor or shutter, and no need for a temperature control device for the holder that holds the material to be deposited. The deposition material can be disposed in the vacuum layer. Therefore, a thin film made of a molecular substance can be manufactured at a low cost.

In order to achieve the second object, a molecular substance deposition apparatus of the present invention includes a vacuum chamber having a window that transmits light, and a holder that holds a deposition target substance disposed in the vacuum chamber. A substrate holder that holds a substrate on which the evaporation target substance that evaporates from the holder is deposited, and a light source that is disposed so as to irradiate the evaporation target substance 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 pulse light source has a wavelength energy smaller than the binding energy of the molecular substance at the peak energy density intensity in the single photon region. This pulse light source is preferably formed by intermittently supplying a continuous wave light source. A holder moving unit that moves the holder to the irradiation position of the light source can be further provided.

  According to the molecular material film forming apparatus of the present invention, since a light source is used, a thin film made of a molecular material, for example, an organic material can be deposited without damaging the molecular structure. When laser pulses are used, by selecting one or more of the peak value, pulse width and pulse interval of the infrared laser pulse, the energy intensity of the irradiated infrared laser can be varied over a wide range. Moreover, since it can be precisely controlled, the deposition rate can be controlled to a desired value, and as a result, it is possible to manufacture by controlling the orientation and the film thickness.

  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. Further, even in the case of manufacturing a device that needs to continuously deposit a plurality of materials to be deposited, the device can be manufactured without increasing the cost of the apparatus.

It is a general | schematic top view which shows the structure of the vapor deposition apparatus of the molecular material by the infrared-light laser of this invention. It is a figure which shows the absorption spectrum of the pentacene thin film produced by the conventional vapor deposition method using a Knudsen cell. It is a table | surface which shows the absorption wavelength of a typical molecular vibration. It is a graph which shows the relationship between the bond dissociation energy in the various coupling | bonding which a molecular substance has, and the wavelength of the light corresponding to this energy. When a light source is a pulse laser, it is a figure which shows the relationship between a pulse width and the peak power density of a pulse. It is the model for demonstrating the vapor deposition process of the molecular material by the infrared light laser using the vapor deposition apparatus of the molecular material by the infrared light laser of this invention. 2 is a diagram illustrating a crystal structure of a pentacene thin film manufactured in Example 1. FIG. 2 is a diagram showing an infrared absorption spectrum of a pentacene thin film produced according to Example 1. FIG. 2 is a diagram showing a surface SEM (operational electron microscope) image of a pentacene thin film produced according to Example 1. FIG. It is a figure which shows the infrared absorption spectrum of the pentacene thin film produced in Example 2, 3 and Comparative example 1,2. It is a figure which shows the absorption spectrum of the ultraviolet visible light area | region of the pentacene thin film produced in Example 3 and Comparative Example 2. FIG. It is a figure which shows the measurement result of the X-ray diffraction of the rubrene thin film produced in Example 4. A diagram depicting time dependency of the diffraction intensity of the reflection type high energy electron observed during the formation of C ₆₀ films produced in Example 5. It is a figure which shows the conventional vapor deposition apparatus using a Knudsen cell.

Explanation of symbols

1: Molecular material deposition system (evaporation system)
2: Light transmission window 3: Vacuum chamber 4: Deposited material holders 4a, 4b, 4c: Deposited material holder 5: Vapor of deposited material 6: Substrate 7: Substrate holder 8: Light source (laser device)
9: Holder mounting table 10: Rod 11: Irradiation light (continuous wave or pulsed light)

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 light transmitting window 2, a holder 4 for holding a vapor deposition material disposed in the vacuum chamber 3, and evaporation from the holder 4. A substrate holder 7 that holds a substrate 6 on which a deposition target material 5 to be deposited is held, and a light source 8 that can irradiate light disposed outside the vacuum chamber 3 are provided. The light source 8 includes a lamp, a laser device, and the like. The light source 8 is disposed 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 deposition material holders 4 may be arranged according to the number of deposition materials. The holder 4 that holds the deposition material is movably held at the irradiation position of the irradiation light 11. For example, as shown in the figure, a plurality of holders 4 are provided on the circumference of the holder mounting base 9. The desired holder 4 is moved to the irradiation position of the irradiation light 11 by rotating the rod 10 mounted and coupled to the holder mounting base 9. The substrate holder 7 may be a 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.
In the case where 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 a conjugated molecular organic material can be determined from the absorption spectrum of the organic material. For example, FIG. 2 shows an absorption spectrum of a pentacene thin film prepared by a conventional vapor deposition method using a Knudsen cell. As is clear from the figure, since the absorption is low at about 700 nm or more, the pentacene band is shown. 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, the 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. The infrared laser device may be an infrared laser device that outputs a temporally coherent infrared laser continuous wave, and controls the intensity of the infrared laser continuous wave or the infrared laser continuous wave. The pulse width and the pulse interval may be controlled by interrupting the wave with an optical chopper and controlling the rotation frequency of the optical chopper.

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 typical absorption wavelengths of molecular vibrations. FIG. 3 shows the absorption wavelength due to the stretching motion, which is a typical molecular vibration. The molecular vibration includes, in addition, an angular vibration, a rotational vibration, and a combined vibration of these vibrations. Including the absorption due to, the infrared absorption wavelength range reaches from 0.7 μm to 20 μm.

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 represents wavelength (nm) and the vertical axis represents bond dissociation energy (kJ / mol).
As is apparent from the figure, C≡C bond (828 kJ / mol (8.58 eV)), C═C bond (607 kJ / mol (6.29 eV)), O—H bond (463 kJ / mol (4.8 eV)) It can be seen that the bond dissociation energy (also called bond energy) decreases in the order of C—H bond (413 kJ / mol (4.28 eV)) and C—C bond (348 kJ / mol (3.61 eV)). For example, when the molecular substance has a C—C bond, the bond dissociation energy is 3.61 eV, and the wavelength of light corresponding to this energy is about 344 nm. When the molecular substance has only C—C bonds, a light source having a photon energy of 3.61 eV or less, which is a bond dissociation energy, is used to form a film while maintaining the molecular structure of the molecular substance. May be used. In other words, the light source 8 may have a wavelength of about 344 nm or more. When the molecular substance is the above bond or a combination of these bonds, the light source 8 corresponding to the wavelength having the lowest bond dissociation energy may be used.

Accordingly, the light of the light source 8 used in the apparatus of the present invention can maintain the molecular structure of the molecular substance in consideration of 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. The wavelength may be used. For example, the emission wavelength can be in the range of 0.7 μm to 20 μm. The light source 8 can be selected from gas lasers such as a CO ₂ laser, a CO laser, an HF laser, and a YAG laser according to the type of vapor deposition material. Further, GaAs, GaAlAs, PbSnSe, PbSSe, and InAsSb semiconductor lasers made of a semiconductor may be used. A free electron laser may be used. The light source 8 may be a lamp including a filter that transmits only a wavelength that can maintain the molecular structure of the molecular substance.

  In the case where the light source 8 is a pulse, for example, a laser device such as an infrared light that outputs a continuous wave and an optical chopper that interrupts the output light are combined to interrupt the continuous light, and an infrared laser. Form a pulse. 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 a short light pulse with a short wavelength tends to be generated. In the case of a substance, the ground state electrons may be excited to an excited state and the molecular structure may be damaged, or the atoms of the atoms constituting the deposited material may be excited to cause damage to the molecular structure. Since the laser pulse 8 formed intermittently is a temporally coherent wave, multi-photon excitation does not occur and the molecular structure is not damaged.

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 (W / cm ² ). The peak power density is also called the peak value of the energy density, and is the maximum value of the power density in one pulse. In order to form a film while maintaining the molecular structure of the molecular substance, the photon intensity of the pulse laser, that is, the peak power density is equal to or less than the dotted line (about 5 × 10 ⁵ W / cm ² ) shown in the figure, which is a single photon region. The peak power density is sufficient. The figure also shows the relationship between the pulse width and peak power density used in the conventional PLD. 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 method of forming a molecular substance of the present invention using the molecular substance deposition apparatus of the present invention. Hereinafter, the case where three types of organic thin films are stacked 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 types of raw material powders a, b, and c of the organic thin film, the relationship between the deposition rate and the peak 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, the substrate 6 is mounted on the substrate holder 7, and the vacuum chamber 3 is evacuated. 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 light laser pulse 11, and the deposition rate of the raw material powder a and the infrared light laser pulse 11 determined in advance. Using the relationship between the crest value, the pulse width, and the pulse interval, select one or more of the crest value, the pulse width, and the pulse interval at which the desired deposition rate is realized, and according to the desired film thickness. Irradiation with an infrared laser pulse 11 is performed for a 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 light laser pulse 11, and the vapor deposition rate of the raw material powder b and the infrared light laser pulse obtained in advance. Using the relationship between 11 crest values, pulse widths and pulse intervals, one or more of crest values, pulse widths and pulse intervals at which a desired deposition rate is realized is selected, and depending on the desired film thickness Irradiation with the infrared laser pulse 11 is performed for a predetermined time.
(5) Further, 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 light laser pulse 11, and the vapor deposition rate of the raw material powder c and the infrared light laser pulse 11 determined in advance. Using the relationship between the crest value, the pulse width, and the pulse interval, select one or more of the crest value, the pulse width, and the pulse interval at which the desired deposition rate is realized, and according to the desired film thickness. Irradiation with an infrared laser pulse 11 is performed for a time.
(6) After the deposition is completed, the substrate 6 is taken out and completed.

  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.

  The light source 8 may be a light source composed of a continuous wave. In this case, if the light source comprising a continuous wave has a wavelength energy smaller than the binding energy of the molecular substance and the intensity of the continuous wave is selected and irradiated, the molecular structure of the molecular substance The film can be formed while holding.

  In the pulse light source 8, one or more of the peak value, pulse width, and pulse interval of the light pulse is selected and irradiated. In this case, if the pulse light source 8 has a wavelength energy smaller than the binding energy of the molecular substance in the peak energy density intensity of the single photon region, the molecular structure of the molecular substance is maintained. A film can be formed.

The molecular substance film forming method of the present invention operates as follows. In other words, when visible light or ultraviolet light is irradiated to a molecular substance connected by the bonding of a plurality of atoms, electrons of atoms constituting the molecular substance are excited, and this excitation generally damages the molecular structure of the molecular substance. give. On the other hand, the shared electrons of a molecular substance act like a spring that connects the atoms that make up the molecule. When a photon with an energy equivalent to the natural vibration energy of this spring is irradiated, the molecular substance absorbs the photon energy. Cause molecular vibrations. Since the natural vibration energy of molecular vibration is sufficiently small and generally in the infrared light region, the electrons constituting the atoms of the molecular substance are not excited, and therefore the molecular structure of the molecular substance is not destroyed.
Further, since the molecular vibration is a harmonic vibration, the photon to be irradiated is absorbed and excited by molecular vibration energy corresponding to the number of photons. The excited molecular vibrational energy diffuses as thermal energy toward the surrounding low-temperature part, but the magnitude of the thermal energy that diffuses is proportional to the temperature difference from the surroundings. The temperature rises until it becomes equal to the photon energy supplied to and the temperature becomes constant at this temperature. Accordingly, the intensity of the continuous wave light source to be irradiated is selected and irradiated, or one or more of the crest value, pulse width, and pulse interval of the light pulse is selected and irradiated to supply the unit time. Since the photon energy 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.

  According to the apparatus and method of the present invention, for example, only the raw material powder is irradiated with an infrared light laser pulse or a continuous wave infrared light laser, and the temperature of the raw material powder is directly heated to a predetermined temperature with these lasers. Therefore, it solves the problem of damage to the molecular structure of the organic material to be deposited due to the time required to reach the thermal equilibrium state or the overshoot of the temperature that occurs when trying to control to a predetermined temperature in a short time, which was a problem in the prior art. To do.

  According to the apparatus and method of the present invention, one or more of the crest value, pulse width and pulse interval of an optical pulse 8 such as an infrared laser pulse are selected, or a continuous wave light source 8 such as infrared light is selected. If the intensity of the continuous wave of the laser is selected and irradiated, a desired constant deposition rate can be realized. Therefore, the problem of the prior art that the orientation cannot be sufficiently controlled because it is difficult to keep the deposition rate sufficiently constant is solved.

  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, such as an infrared laser. By selecting and irradiating the intensity of the continuous wave, it is possible to achieve a desired constant deposition rate, and in order to realize a predetermined film thickness, it is only necessary to control the irradiation time of the infrared laser pulse. This eliminates the need for film thickness sensors and shutters required by the technology, and eliminates unnecessary consumption of valuable organic materials.

  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, pulse width and pulse interval of the infrared laser pulse, or the continuous wave light source 8 such as red Since it can be controlled only by selecting and irradiating the intensity of the continuous wave of the external laser, the surface area, volume, and heat capacity, which are necessary in the prior art, have a built-in heating device that maintains a predetermined temperature for each raw material. It does not require a large holding tool, it only needs to have a small shape that can hold the raw material powder, and since it is small, it can store more holding tools in the vacuum layer and continuously deposit multiple deposition materials. Even in the case of manufacturing a device that needs to be manufactured, the device can be manufactured without increasing the cost of the apparatus.

  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, the molecular structure of the molecular material is changed as described above. Since pulsed light or continuous light that can be held is used, vapor deposition can be performed without damaging the molecular structure of the material to be deposited.

Next, another embodiment according to the present invention will be described.
Depending on the type of the material to be deposited, the absorption wavelength of the infrared light of the material to be deposited is greatly deviated from the center wavelength of the infrared laser used, and therefore, sufficient heating may not be possible. In such a case, it is also possible to use an infrared laser device having a peak in the absorption wavelength, or to match the peak wavelength to the absorption wavelength by using a tunable laser, but the cost of the device is high. There is a problem that said. In such a case, a method capable of vapor deposition without changing the infrared laser device will be described.
That is, 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 the raw material 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.

Such a material to be deposited may be organic or inorganic as long as it is a molecular substance that does not absorb or weakly absorb infrared light and cannot be heated to the evaporation temperature by an irradiation light source. Examples of the organic substance include rubrene and fullerene (C ₆₀ ). Further, anthracene bandgap (bandgap) is relatively large material, tetracene, and the like C _70.

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 Si ₃ N ₄ can be used. For example, in the case of an organic substance composed of a conjugated molecule, a metal such as Al, Si, or SiC can be used.

  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 the infrared laser and absorbs the absorbed infrared light. Since the energy is released as infrared light including the absorption wavelength of the deposition material, the deposition material can be indirectly heated and evaporated.

Next, the present invention will be described in more detail with reference to examples.
Example 1 is a case where the molecular substance is an organic substance composed of a conjugated molecule, and an infrared laser pulse corresponding to energy less than the band gap energy formed by π electrons of the organic substance in the raw material powder of the organic substance. This is an embodiment of a method of performing vapor deposition by controlling the vapor deposition rate of a material to be vapor-deposited by selecting and irradiating any one or a plurality of pulse peak values, pulse widths and pulse intervals.
Using the film forming apparatus of the present invention, a pentacene thin film was prepared using the pentacene raw material powder by the method of the present invention. In Example 1, the continuous wave of an infrared semiconductor laser having a wavelength of 0.808 μm (808 nm) is used for the infrared laser pulse from the absorption short wavelength of pentacene shown in FIG. 2 using the apparatus shown in FIG. Was used intermittently. The pulse width was 1 sec, the repetition frequency was 0.5 Hz, and the irradiation energy density was about 10 W / cm ² . As the substrate, a sapphire substrate was used, and the substrate temperature was 100 ° C. The thickness of the formed pentacene thin film was 50 nm. The vapor deposition rate at this time was 4.4 nm / min.

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. The power per unit area of the infrared semiconductor laser was 12 W / cm ² . The thickness of the formed pentacene thin film was 100 nm. The vapor deposition rate at this time was 4.4 nm / min. The infrared semiconductor laser of the above laser has a wavelength fluctuation of about ± 5 nm due to fluctuations in the output level, etc., but this degree of wavelength fluctuation did not affect the film forming speed or the like.

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. The power per unit area of the infrared semiconductor laser was 8 W / cm ² . The thickness of the formed pentacene thin film was 100 nm. The vapor deposition rate at this time was 4.4 nm / min.

A rubrene 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, rubrene powder and Si powder were used as raw materials, and a sapphire substrate was used. Filmed. The power per unit area of the infrared semiconductor laser was 8 W / cm ² . Since the rubrene thin film has poor orientation to the substrate, first, as a buffer layer for promoting two-dimensional growth of rubrene, one molecular layer of pentacene was formed on the substrate, and then the rubrene thin film was formed. The thickness of the rubrene thin film was 20 nm. The deposition rate at this time was 3.0 nm / min.

A C ₆₀ 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, and fullerene (C ₆₀ ) powder and Si powder were used as raw materials. did. The power per unit area of the infrared semiconductor laser was 8 W / cm ² . The thickness of the deposited C ₆₀ thin film was 100 nm. The vapor deposition rate at this time was 3.92 nm / min. Note that a mica substrate was used as a substrate when examining the diffraction intensity of a reflection type high-speed electron beam described later.

Next, a comparative example for the embodiment will be described.
(Comparative Example 1)
A pentacene thin film having the same thickness as that of Example 1 was formed using a PLD method using an ultraviolet pulse laser as a heating source. 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 0.04 J / cm ² .

(Comparative Example 2)
A pentacene thin film having the same thickness as that of Example 1 was formed using a PLD method using an infrared pulse laser as a heating source. 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 .

(Comparative Example 3)
The rubrene 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 not evaporated.

The measurement results of the crystal structure and infrared absorption wavelength of the produced pentacene and rubrene thin films of Example 1 and Comparative Example will be described.
7A and 7B are diagrams showing the crystal structure of the pentacene thin film produced in Example 1. FIG. 7A shows the θ / 2θ diffraction X-ray measurement result, and FIG. 7B shows 2θ in the diffraction peak (001). The result of measuring the crystal grain size by fixing the sample and rotating the angle θ of the sample to measure the half width of the diffraction peak is shown. For comparison, results of a pentacene thin film manufactured by a conventional MBE method using a Knudsen cell are also shown.
From FIG. 7 (a), the crystal structure agrees very well with the result of the pentacene thin film prepared by the MBE method, and from FIG. 7 (b), the peak half-value width is extremely different from the result 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 ⁻¹ ), and the vertical axis indicates the absorption rate (arbitrary scale). For comparison, an infrared absorption spectrum of pentacene powder as a raw material is also shown. As the measuring apparatus, FTIR (Fourier transform infrared spectrophotometer) was used.
From FIG. 8, it can be seen that the infrared absorption spectrum of the pentacene thin film produced in Example 1 agrees very well with the infrared absorption spectrum of the pentacene powder. Note that the difference in strength is due to the difference in the amount of pentacene deposited in the FTIR measurement between the powder and the thin film.
Therefore, also from this result, according to Example 1, a pentacene thin film can be produced without damaging the molecular structure of pentacene.

  FIG. 9 is a diagram showing a surface SEM (scanning electron microscope) image of the pentacene thin film produced in Example 1, and for comparison, an image of the pentacene thin film produced by the conventional MBE method using a Knudsen cell is also shown. is doing. From FIG. 9, it can be seen that it has in-plane crystallinity equivalent to that of a pentacene thin film produced by a conventional MBE method using a Knudsen cell.

From the results of FIGS. 7 to 9 shown above, it can be seen that the method of the present invention can produce a pentacene thin film with no damage to the molecular structure. This effect is mainly due to the use of an infrared laser pulse corresponding to an energy less than the band gap energy formed by the π electrons of pentacene in the method of the present invention, but when a visible light laser pulse is used. Compared to the irradiation peak power density (peak value) of 10 MW / cm ² or more (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 10 W / One of the factors is that it is extremely low, about cm ² .

FIG. 10 is a diagram showing infrared absorption spectra of the pentacene thin films prepared in Examples 2 and 3 and Comparative Examples 1 and 2. In the figure, the horizontal axis indicates the wave number (cm ⁻¹ ), and the vertical axis indicates the transmittance (arbitrary scale). For comparison, the infrared absorption spectrum of pentacene powder is also shown. As the measuring apparatus, FTIR was used.
From FIG. 10, it can be seen that the infrared absorption spectrum of the pentacene thin film produced 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, since the infrared absorption spectrum of the pentacene thin film prepared by irradiating the ultraviolet pulsed laser beam by the conventional PLD method of Comparative Example 1 has a larger irradiation peak energy density than that of Examples 1 and 2, it is almost molecular. No structure was observed, indicating that the molecular structure was destroyed. The infrared absorption spectrum of the pentacene thin film prepared by irradiating infrared light pulsed laser light by the conventional PLD method of Comparative Example 2 is observed in Examples 1 and 2 because the molecular structure is observed but the irradiation peak energy density is large. It was found that the transmittance was remarkably reduced as compared with, and a part of the molecular structure was destroyed.

FIG. 11 is a diagram showing absorption spectra in the ultraviolet-visible light region of the pentacene thin films 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 of the pentacene thin film produced by irradiating 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. The absorption structure was also observed at the wavelength of 1, but the optical absorption structure was not observed in the pentacene thin film prepared in Comparative Example 2. The reason why the absorption spectrum is not observed in the ultraviolet-visible light region in Comparative Example 2 is that the peak power of the pulsed light is so large that a multiphoton process occurs and the molecular structure of pentacene is destroyed. Presumed.

FIG. 12 is a diagram showing the X-ray diffraction measurement results of the rubrene thin film produced in Example 4. In the figure, the horizontal axis represents an angle (°), that is, an angle corresponding to twice the incident angle θ of the X-rays on the atomic plane, and the vertical axis represents the diffracted X-ray intensity (cps).
From FIG. 12, it can be seen that the crystal structure of the manufactured rubrene agrees very well with the crystal structure of the pentacene thin film manufactured 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 is a diagram showing the time dependence of the diffraction intensity of the reflective high-speed electron beam observed during the formation of the C ₆₀ thin film produced in Example 5. In the figure, the horizontal axis represents time (seconds), and the vertical axis represents electron beam intensity (arbitrary scale).
From FIG. 13, the intensity of the diffracted electron beam from C ₆₀ during fabrication is first vibrated, and the electron diffraction pattern shown in the inset is also clear, and the molecular structure of C ₆₀ is damaged. It was found that the film was formed.

  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, and therefore, a molecular substance made of an inorganic element. For example, it is clear that it is also effective for manufacturing a KBr thin film.

  As understood from the above description, according to the present invention, a thin film of a molecular material can be produced without damaging the molecular structure of the molecular material, and the deposition rate can be controlled to a predetermined constant rate. In addition, the orientation of the thin film of molecular substance can be controlled, and the film thickness can be accurately controlled. Therefore, it is extremely useful if it is used for the manufacture of devices using organic thin films that are expected to grow in the future, and for the manufacture of devices using superlattices made of molecular substances, where film thickness control is extremely important. is there.

Claims (5)

A method of irradiating a deposition target material with light from a light source and controlling a deposition rate of the deposition target material to form a molecular substance on a substrate,
The molecular substance is pentacene, the wavelength of the light is set from 808 nm to 981 nm,
By the Ruco be irradiated by selecting the intensity of the continuous wave of the light, characterized in that film while retaining the molecular structure of the pentacene film forming method of the molecular substance. A method of irradiating a deposition target material with light from a light source and controlling a deposition rate of the deposition target material to form a molecular substance on a substrate,
The molecular substance is pentacene, the wavelength of the light is set from 808 nm to 981 nm,
A molecular substance characterized by forming a film while maintaining the molecular structure of pentacene by selecting and irradiating one or more of the peak value, pulse width and pulse interval of the light pulse. The film forming method. A method of irradiating a deposition target material with light emitted from a light source and controlling a deposition rate of the deposition target material to form a molecular substance on a substrate,
The molecular substance is rubrene or C ₆₀ And
Absorbs light and releases the absorbed light energy as light, and the rubrene or C ₆₀ The rubrene or C at the deposition temperature of ₆₀ A raw material composed of a substance that does not react with the substance and does not evaporate is mixed with the deposition target substance,
The wavelength of the light is set from 808 nm to 981 nm,
By selecting and irradiating the intensity of the continuous wave of the light, the rubrene or C ₆₀ A method for forming a molecular substance, wherein the film is formed while maintaining the molecular structure. A method of irradiating a deposition target material with light emitted from a light source and controlling a deposition rate of the deposition target material to form a molecular substance on a substrate,
The molecular substance is rubrene or C ₆₀ And
Absorbs light and releases the absorbed light energy as light, and the rubrene or C ₆₀ The rubrene or C at the deposition temperature of ₆₀ A raw material composed of a substance that does not react with the substance and does not evaporate is mixed with the deposition target substance,
The wavelength of the light is set from 808 nm to 981 nm,
By selecting and irradiating one or more of the peak value, pulse width and pulse interval of the light pulse, the rubrene or C ₆₀ A method for forming a molecular substance, wherein the film is formed while maintaining the molecular structure. Rubrene or C ₆₀ 5. The method for forming a molecular substance according to claim 3, wherein the substance that does not react with the substance and does not evaporate is Si.

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