A method for controlling the deposition of an oxide layer of a target oxide on a substrate in a TLE system, and a TLE system

Abstract

The present invention relates to a method (80) for controlling the deposition of an oxide layer of a target oxide (82) on a substrate (70) in a thermal laser epitaxy (TLE) system (100), wherein the target oxide (82) has a defined stoichiometric composition and is formed from one or more raw materials that are evaporated and / or sublimated and oxygen derived from a gaseous oxidizer (54), and the TLE system (100) further comprises a reaction chamber (10) and one or more laser light sources (20) for supplying a laser beam (22) into the reaction chamber (10). Furthermore, the present invention relates to a TLE system (100) constructed to carry out the above method.

Description

[Technical Field]

[0001] The present invention relates to a method for controlling the deposition of an oxide layer of a target oxide on a substrate in a thermal laser epitaxy (TLE) system, wherein the target oxide has a defined stoichiometry and is formed from one or more raw materials that are evaporated and / or sublimated, and oxygen derived from a gaseous oxidizing agent, and the TLE system further comprises a reaction chamber and one or more laser light sources for supplying a laser beam into the reaction chamber. Furthermore, the present invention relates to a TLE system constructed to carry out the above method. [Background technology]

[0002] Epitaxial oxide films can currently be manufactured by various methods, including pulsed laser deposition (PLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), sputtering, and molecular beam epitaxy (MBE). While all of these methods can deposit oxide films with relatively good stoichiometric composition, overwhelmingly superior stoichiometric composition can be achieved by growing epitaxial oxide films by MBE in an adsorption-controlled growth mode.

[0003] Adsorption-limited growth is most effective in ultra-high purity environments. Ultra-high purity environments typically refer to ultra-high vacuum or residual gas atmospheres with extremely high gas purity. This means that non-thermal flux generation methods such as sputtering and ablation do not function due to the release of impurities from the chamber walls and raw material holders, or changes to the growth crystal surface caused by charged and / or high-energy raw material atoms and molecules. Therefore, thermal flux generation by evaporation (from molten material) or sublimation (from solid material) is necessary.

[0004] Oxides are difficult to grow in adsorption-controlled growth mode. The main reasons for this are that they require high substrate temperatures due to their high binding energy, and furthermore, the presence of oxygen or an oxidizing agent is necessary to achieve the desired oxidation state. In many cases, the strong oxidation conditions required for stoichiometric growth are incompatible with the Joule heater technology used in MBE. This is because conductors such as metals oxidize and become non-functional at high temperatures and in the presence of oxygen. Therefore, successful examples of oxide growth by MBE in adsorption-controlled growth mode are limited to low substrate temperatures (below approximately 1000°C) and low oxygen or ozone pressure (10°C). -5 It is limited to less than hPa. If the required substrate temperature is high, the oxidation potential also weakens, meaning that even higher oxygen or oxidizing agent pressure is required for high-quality crystal growth, and achieving this condition becomes even more difficult with MBE. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In view of the above, the object of the present invention is to provide an improved method for controlling the deposition of an oxide layer and an improved thermal laser evaporation system that do not have the aforementioned drawbacks of the prior art. In particular, the object of the present invention is to provide an improved method for controlling the deposition of an oxide layer and an improved thermal laser evaporation system that enables the deposition of an oxide layer consisting of one or more elemental components and oxygen, and that can actively control both the stoichiometry of the deposited oxide and the actual deposition of the oxide layer.

[0006] The object of the present invention is achieved by each independent claim. In particular, the object of the present invention is achieved by the method for controlling the deposition of an oxide layer according to independent claim 1 and the TLE system according to independent claim 31. Dependent claims describe preferred embodiments of the present invention. Details and advantages described in the method according to the first aspect of the present invention also apply to the TLE system according to the second aspect of the present invention, and vice versa, where technically meaningful. [Means for solving the problem]

[0007] According to a first aspect of the invention, the object of the present invention is a method for controlling the deposition of an oxide layer of a target oxide on a substrate in a thermal laser epitaxy (TLE) system, wherein the target oxide has a defined stoichiometry and is formed from one or more raw materials that are evaporated and / or sublimated and oxygen derived from a gaseous oxidizer, and the TLE system is further achieved by a method comprising a reaction chamber and one or more laser light sources for supplying a laser beam into the reaction chamber. The method according to the present invention is a) A step of placing the substrate and the first deposition source in the reaction chamber, wherein the first deposition source includes an elemental material as the first raw material, b) The step of filling the reaction chamber with a reaction gas containing one or more oxidants supplied by the gas system of the TLE system, c) A step of irradiating the first raw material with a laser beam from the TLE system at an intensity below the plasma generation threshold of the first raw material to evaporate and / or sublimate the first raw material, thereby providing a flux of the evaporated and / or sublimated first raw material and / or a flux of the first binary oxide formed from the first raw material with the oxidizing agent, wherein the direction of the flux is directed toward the substrate. d) A step of heating the substrate to the deposition temperature with the laser beam of the TLE system, wherein the deposition temperature of the substrate is above the desorption temperature at which the first deposition source and / or the first binary oxide desorb at least partially from the substrate, e) combining the evaporated and / or sublimated one or more raw materials with oxygen derived from the one or more oxidants to form the target oxide, and depositing the target oxide as an oxide layer on the substrate, wherein the formation of the target oxide and the deposition of the oxide layer on the substrate are controlled by controlling the filling of the reaction gas into the reaction chamber in step b), controlling the supply rate of the evaporated and / or sublimated first raw material to the substrate in step c), and / or controlling the deposition temperature in step d); characterized by having.

[0008] The method according to the present invention is intended to be carried out in a thermal laser epitaxy (TLE) system and by using the TLE system. The TLE system is the best option for controlling the deposition of a target oxide having a desired, i.e., defined stoichiometric composition.

[0009] The TLE system includes at least a reaction chamber that provides a reaction space that can be sealed against the ambient environment. One or more deposition sources and a substrate to be coated are arranged in the reaction chamber and held in predetermined positions by positioning means.

[0010] Furthermore, the TLE system includes a gas system that provides a selectable atmosphere in the reaction chamber. The gas system can supply at least a reaction gas into the reaction chamber, and this reaction gas contains one or more gaseous oxidants such as molecular oxygen and ozone. However, the gas system is configured to supply other reaction gases such as molecular nitrogen, and / or evacuate the inside of the reaction chamber to a pressure of a very high vacuum of 10 -12 hPa or less.

[0011] Furthermore, the TLE system includes one or more laser light sources and coupling means provided on and / or corresponding to the reaction chamber to supply a laser beam into the reaction chamber. The laser beam is used for the evaporation and / or sublimation of one or more raw materials, as well as for heating the substrate. This eliminates the need for additional heating of one or more deposition sources and the substrate by electric heating means, as is used in MBE, for example. This avoids the limitations imposed by the heating means on the reaction gas used, such as limitations on the supplied oxidizer and / or its pressure.

[0012] In short, by using a TLE system to carry out the method according to the present invention, a high-purity environment for oxide layer deposition can be provided. Each element of the TLE system, in particular the evaporation and / or sublimation of one or more raw materials, the heating of the substrate, and the gas system supplying the reaction gases, can be individually and actively controlled, thereby ensuring that a target oxide having the desired, i.e., defined stoichiometric composition is deposited.

[0013] In the first step a) of the method according to the present invention, the substrate and the first deposition source are placed in and provided within the reaction chamber. This can be carried out while the reaction chamber is still open to the surrounding environment, but can also be carried out while the reaction chamber is already closed and sealed by a correspondingly available airlock. The reaction chamber is provided with arrangement means for arranging the substrate and one or more deposition sources, respectively. The arrangement means may be provided solely for spatially fixing the substrate and / or one or more deposition sources. Alternatively, these arrangement means may be designed to move the substrate and / or one or more deposition sources, for example, by moving the substrate to the deposition position, moving the substrate from the deposition position, and / or changing the deposition source to be used. In short, after carrying out step a), the first deposition source and the substrate are placed in the reaction chamber.

[0014] In particular, the first deposition source contains elemental material as raw material. In other words, the raw material is pure, meaning that it consists in very high proportions of only single elements on the periodic table, with the exception of oxygen itself. Thus, the elemental material selected to form the non-oxygen component of the target oxide is provided without any precursor molecules. Nevertheless, the surface of the raw material material facing the environment, in particular the surface of the raw material facing the reaction gas containing one or more oxidizing agents after the implementation of step b) of the method according to the present invention, may be oxidized, and as a result, the top layer of the deposition source may be formed of oxides of the elemental material that constitute the bulk of the deposition source.

[0015] In the next step b) of the method according to the present invention, the atmosphere in the reaction chamber for depositing the oxide layer onto the substrate is appropriately prepared using the gas system of the TLE system. In particular, the reaction chamber is filled with a reaction gas containing one or more oxidizing agents. In the present invention, an oxidizing agent refers to a gaseous substance that can be used as a source of oxygen atoms necessary for the formation of the target oxide. Preferably, the reaction gas consists of one or more oxidizing agents.

[0016] Prior to filling the reaction chamber with the reaction gas described above, it is preferable to evacuate the reaction chamber using the gas system. This ensures, or at least significantly improves, the purity of the reaction atmosphere consisting solely of the reaction gas. After step b), only a reaction gas, preferably consisting of one or more oxidizing agents, with a significantly higher concentration, is present as the atmosphere in the reaction chamber. If an airlock is used in step a) to place the substrate and / or the first deposition source inside the reaction chamber, step b) can be performed before and / or during step a).

[0017] After the reaction chamber is prepared in steps a) and b), the actual evaporation and / or sublimation of the first raw material, i.e., the elemental material, takes place in the next step c). In particular, since the method according to the present invention is carried out by a TLE system, the evaporation and / or sublimation is performed using laser beams supplied from each laser source of the TLE system. The laser beams are coupled to the reaction chamber and irradiated toward the surface of the raw material.

[0018] The intensity of the laser beam is selected to be below the plasma threshold of the first raw material. Thus, evaporation and / or sublimation of the first raw material is achieved solely by heat, without explosive ablation or plasma formation, as can occur in PLD and / or sputtering processes. This yields the evaporated and / or sublimated first raw material. If the surface of the deposition source is oxidized as described above, evaporation and / or sublimation of the oxide of the raw material is also possible. Furthermore, the evaporated and / or sublimated first raw material can react with one or more oxidizing agents in the reaction gas to form a first binary oxide of the first raw material.

[0019] In this invention, a binary oxide refers to an oxide composed of two components, namely an elemental material and oxygen, and the actual stoichiometric composition of such a binary oxide is not fixed. For example, when titanium is used as the metal, the oxides TiO, TiO2, and Ti2O3 are all binary oxides in this invention. The same applies to ternary oxides or polychromatic oxides, that is, oxides containing two or more non-oxygen elemental components.

[0020] In short, step c) provides a flux of the first raw material and / or a flux of the first binary oxide that has been evaporated and / or sublimated. The flux is provided toward the substrate to be coated, for example, by appropriately arranging the first deposition source and the substrate in the reaction chamber in step a) of the method according to the present invention.

[0021] In step d) of the method according to the present invention, a substrate is prepared for the deposition of a target oxide to form a desired oxide layer. For this purpose, the substrate is heated with a laser beam supplied as appropriate from the laser source of the TLE system. Similar to the laser beam used to evaporate and / or sublimate the first raw material, the laser beam for heating the substrate is also coupled to the reaction chamber and irradiated toward the substrate.

[0022] In particular, the substrate is heated so that it reaches a predetermined selected deposition temperature. The deposition temperature is selected to be above the desorption temperature at which the first deposition source and / or the first binary oxide desorbs at least partially from the substrate. Thus, each deposition temperature depends not only on the properties of the substrate itself, but also on the first raw materials used and / or the already formed first binary oxide.

[0023] By setting the deposition temperature above each desorption temperature, the dependence of the deposition rate of the target oxide, and consequently the growth rate of the oxide layer, on the flux density of the evaporated and / or sublimated first raw material is significantly reduced, and preferably eliminated. On the other hand, the elimination of this dependence makes it possible to control the deposition rate by other properties, namely the selection of an appropriate deposition temperature, and especially the amount of oxygen available for the formation of the target oxide. This is based on the finding that, in particular, when the first raw material is in its pure form, i.e., an elemental material or a metastable oxide of this material, it is almost always more volatile than the desired oxide of each material, and that a particular binary oxide of the first raw material also provides a specific desorption temperature that can be considered when selecting the deposition temperature for heating the substrate. In short, by combining these effects, it becomes possible to grow a binary oxide as a target oxide using an adsorption control method.

[0024] Finally, in step e) of the method according to the present invention, a target oxide is formed and deposited onto a substrate in order to form an oxide layer. The target oxide comprises a first raw material and oxygen as constituent elements. The stoichiometric composition of the target oxide is defined and selected. The formation of the target oxide may be carried out directly on the substrate. However, if the target oxide is a first binary oxide that has been formed in advance before deposition on the substrate, this is also considered to be included in the formation of the target oxide in step e) of the present invention. According to the present invention, the formation of the target oxide and the deposition of the oxide layer onto the substrate are controlled, respectively.

[0025] In particular, the formation of the target oxide and / or the deposition of the oxide layer can be controlled by controlling the filling of the reaction chamber with the reaction gas. As described above, the deposition temperature of the substrate can be selected so that the first raw material, in its pure form or in the form of a more unstable oxide, desorbs from the substrate, and, in contrast, the target oxide is adsorbed onto the substrate surface. Therefore, the amount of available oxygen can be controlled by the filling control in step b), and thus the formation rate of the more unstable oxide or the target oxide can be actively adjusted. In other words, by controlling the filling of the reaction chamber with the reaction gas, the growth of the oxide layer by an adsorption control method can be achieved.

[0026] Furthermore, or alternatively, the supply rate of the evaporated and / or sublimated first raw material to the substrate in step c) can also be used to control the formation of the target oxide and / or the deposition of the oxide layer. In particular, the supply rate of the evaporated and / or sublimated first raw material defines the maximum rate at which the target oxide can be formed, i.e., the maximum growth rate of the oxide layer on the substrate. For example, by reducing the supply rate of the evaporated and / or sublimated first raw material by reducing the intensity of the laser beam used for evaporation and / or sublimation, the maximum rate of target oxide formation is also reduced.

[0027] Furthermore, or alternatively, the deposition temperature set for the substrate in step d) also affects the formation of the target oxide and the deposition of the oxide layer onto the substrate. In particular, as mentioned above, different oxides of the first raw material almost always have different desorption temperatures. Therefore, by controlling and appropriately adjusting the deposition temperature, the selection of the target oxide can be actively changed. Also, the desorption rate, i.e., the proportion of the material that collides with the substrate and then desorbs again, almost always depends on the substrate temperature. This property can also be used to control the formation of the target oxide and the deposition of the oxide layer onto the substrate. Finally, and most importantly, deposition is mainly carried out only when the compound to be formed, i.e., the target oxide, has the necessary and appropriate thermodynamic properties that are highly dependent on the substrate temperature. This allows for the active selection of the compound to be deposited, i.e., the target oxide, and thus maximizes the quality of the deposited layer, especially in terms of high purity and low defect density.

[0028] In short, the method according to the present invention enables the deposition of an oxide layer consisting of elemental material components and oxygen with a controlled stoichiometric composition and a similarly controlled growth rate. By implementing the method according to the present invention, the above deposition can be provided using an adsorption-controlled method. This particularly utilizes the fact that deposition is performed only when the compound to be formed, i.e., the target oxide, has necessary and appropriate thermodynamic properties that are highly dependent on the substrate temperature. Therefore, by controlling the substrate temperature in particular, it is possible to produce an oxide layer consisting of the target oxide with extremely high quality, even when a binary oxide is selected as the target oxide. This is because the stoichiometric composition of the target oxide is self-adjusted under adsorption-controlled conditions.

[0029] It is preferable to perform at least steps c), d), and e) of the method according to the present invention simultaneously.

[0030] In a first embodiment, the method according to the present invention is characterized in that, in step d), the deposition temperature is selected such that more than 40%, particularly more than 70%, preferably more than 99.99%, of the inflow flux of the first raw material is desorbed from the substrate, and in step e), the adsorbed portion of the first raw material bonded to oxygen and / or the first binary oxide derived from one or more oxidizing agents forms the target oxide for deposition of the oxide layer. In other words, the first raw material not bonded to a stable stoichiometric target oxide is preferably completely, or at least substantially completely, desorbed from the substrate. Only the target oxide is deposited on the substrate, and if its stoichiometric composition is compatible with the target oxide, the first binary oxide is also deposited on the plate. The formation of the target oxide depends on the availability of oxygen, which is controlled by filling the reaction chamber with reaction gas in step b) of the method according to the present invention, thus more easily providing the advantages of deposition of binary oxides on a substrate by an adsorption control method, in particular, the extremely high structural and stoichiometric quality of the oxide layer deposited by this method.

[0031] According to another embodiment, the method according to the present invention, in step a), provides one or more second deposition sources in the reaction chamber, each second deposition source comprising an elemental material as a second raw material, and in step c), irradiates the one or more second raw materials with a laser beam from the TLE system at an intensity below the plasma generation threshold of the one or more second raw materials, thereby evaporating and / or sublimating the one or more second raw materials, and the flux of the evaporated and / or sublimated one or more second raw materials and / or one or more second materials formed by the oxidizing agent from one of the one or more second raw materials. A flux of a binary oxide is provided, the direction of which the flux is directed toward the substrate, and in step e), the first deposition source and / or the first binary oxide combines with one or more second deposition sources and / or the one or more second binary oxides, and optionally further combines with oxygen derived from one or more oxidizing agents, to form the target oxide for deposition of the oxide layer, and in step d), the deposition temperature of the substrate may be above the temperature at which the first deposition source and / or the first binary oxide desorbs if not used to form the target oxide.

[0032] In contrast to the embodiments described above, in step a) of the method according to the present invention, one or more additional second evaporation sources are placed in the reaction chamber. Subsequently, one or more second raw materials (also non-oxygen elemental materials) of the one or more second evaporation sources are evaporated and / or sublimated by a laser beam of a TLE system supplied as appropriate. All the features and advantages described above with respect to the first evaporation source and the first raw materials also apply to each of the one or more second evaporation sources and the one or more second raw materials.

[0033] By providing fluxes of one or more raw materials and / or their respective binary oxides, which are evaporated and / or sublimated, and by providing one or more second raw materials, a ternary oxide can be formed as a target oxide when a single second deposition source is present, and a multi-component oxide can be formed when two or more second deposition sources are present. The target oxide comprises a first raw material, one or more second raw materials, and oxygen as constituent components, and the stoichiometric composition of the target oxide is self-adjusted and selected based on the thermodynamic properties of the target oxide, the substrate temperature, and the flux density of the raw materials and oxidizer.

[0034] In particular, in this embodiment of the method according to the present invention, the heating of the substrate in step d) is controlled such that the resulting deposition temperature of the substrate is high enough for the first raw material and the first binary oxide to desorb, respectively. The deposition of the reaction product onto the substrate is performed only when the first raw material and / or the first binary oxide combine with one or more elements of the second raw material and / or one or more elements of the second binary oxide, depending on their presence on the substrate, to form a target oxide having a selected and defined stoichiometric composition, i.e., when a ternary oxide or polychromatic oxide defined as the target oxide is formed.

[0035] In other words, the deposition of the target oxide is adsorption-controlled. Therefore, by implementing this embodiment of the method according to the present invention, all the advantages described above regarding deposition by adsorption control, in particular, the extremely high structural and stoichiometric quality of the deposited oxide layer, are also brought to oxide layers formed from ternary oxides and polymorphic oxides. Specifically, the first raw material and / or the first binary oxide is the compound to be formed, i.e., the volatile portion of the excess supplied target oxide. Furthermore, one or more second raw materials and / or each second binary oxide forms the rate-limiting non-volatile portion of the compound. Therefore, the flux of one or more second raw materials and / or one or more second binary oxides that are evaporated and / or sublimated determines the formation rate of the target oxide and, consequently, the growth rate of the oxide layer. In short, even with ternary oxides or polymorphic oxides, oxide layers of extremely high quality can be provided by depositing the target oxide.

[0036] Furthermore, the method according to the present invention adjusts the deposition temperature in step d) above so that the amount of the first deposition source and / or the first binary oxide deposited on the substrate is 10 compared to the element of the target oxide. 4 Less than 1 / 1, especially 10 7 Less than 1 / 1, preferably 10 10 This can be improved by selecting a sufficiently high temperature so that it is less than 1 / 1. As described above, an oxide layer of extremely high quality can be produced. Furthermore, the first raw material and the first binary oxide desorb from the substrate at the deposition temperature at which the substrate is provided. However, since deposition is a chemical reaction, there is still a possibility that individual instances of the first raw material and the first binary oxide being deposited on the substrate may still exist. On the other hand, as the substrate temperature increases, the probability of the above-mentioned undesirable deposition of the first raw material and / or the first binary oxide decreases. Therefore, by appropriately selecting the deposition temperature, the defect density, i.e., the ratio of the unit amount of the first raw material and / or the first binary oxide to the unit amount of the target oxide, can be reduced to 10 / 10. 4 Less than 1 / 1, especially 10 7 Less than 1 / 1, preferably 10 10It can be made less than one-tenth.

[0037] Conversely, when the substrate temperature is too high, the same situation occurs. Since the first raw material is taken in with a slight shortage, the unit amount of the first raw material and / or the first binary oxide in the target oxide is 10 4 less than one-tenth, particularly 10 7 less than one-tenth, preferably 10 10 less than one-tenth.

[0038] Furthermore, the above method can also be improved by appropriately controlling the laser beam used to evaporate and / or sublime the one or more second raw materials in step c) above, so as to apply an intermittent, constant, and / or variable flux to the one or more second raw materials and / or the one or more second binary oxides that have been evaporated and / or sublimated. As described above, in the adsorption control method, the one or more second raw materials and, if applicable, the one or more second binary oxides are part of the compounds that limit the formation of the target oxide and thus the growth of the oxide layer. Therefore, by changing the flux of these components, the formation rate of the target oxide and thus the growth rate of the oxide layer can also be actively changed and controlled.

[0039] According to another improved embodiment of the method according to the present invention, the target oxide formed in step e) above has a perovskite structure, a perovskite-related structure, and / or a rudolsdene-popper structure. Perovskites and perovskite-related compounds, in particular the rudolsdene-popper structure, have attracted scientific and industrial attention, especially as strongly correlated electron systems, as candidate materials for odd parity superconductors, and as highly efficient catalysts. For example, perovskite oxides and oxides having rudolsdene-popper layered structures may have interesting properties and / or applications such as colossal magnetoresistance, superconductivity, ferroelectricity, catalytic activity, white light-emitting diodes, scintillators, fuel cells, and solar cells. All of these structures are ternary oxides. Therefore, by using the method according to the present invention, oxide layers can be produced with extremely high quality from target oxides having a perovskite structure, a perovskite-related structure, and / or a rudolsdene-popper structure, thereby improving all of the above-mentioned properties and advantages of these structures.

[0040] Furthermore, the method according to the present invention may be characterized in that, in step d) above, the deposition temperature is selected so that the first raw material, the first binary oxide, one or more second raw materials, and / or one or more second binary oxides move along the surface of the substrate. In other words, the deposition temperature is selected so that all components of the target oxide move to energetically favorable positions on the surface of the substrate, i.e., predetermined ideal positions within the periodic crystal lattice. This can further reduce the lattice defect density of the target oxide and, consequently, the oxide layer.

[0041] Furthermore, the method according to the present invention may include setting the deposition temperature to 250°K or more and 4500°K or less in step d) above. In the method according to the present invention, a variety of elemental materials, particularly elemental metals, and more preferably all metals that can be provided as a solid deposition source, can be used as the first raw material. By setting the deposition temperature to 250°K or more and 4500°K or less, the substrate can be heated to a temperature suitable for all of these available first deposition sources.

[0042] Preferably, the TLE system, particularly each laser light source and the laser beam supplied from said laser light source, is capable of heating the substrate to any temperature within this range, i.e., from a minimum of 250°K to a maximum of 4500°K. This makes it possible to produce an unprecedented variety of oxide layers with extremely high quality using the same TLE system.

[0043] Furthermore, the method according to the present invention may also be characterized in that, in step d) above, the deposition temperature is selected according to the first binary oxide. Compared to the first raw material, the first binary oxide has a different desorption temperature due to its chemical properties which change in the presence of one or more oxygen atoms. Therefore, by selecting the deposition temperature according to the first binary oxide, the selected deposition temperature is, in all cases, high enough to reliably desorb the first deposition source.

[0044] According to an improved embodiment, the method according to the present invention may include selecting the deposition temperature to be at or above the temperatures listed below, depending on the first binary oxide. [Table 1]

[0045] The temperature values ​​listed in the table above are the calculated desorption temperatures of each binary oxide in a vacuum. Note that the actual deposition temperature may differ from the listed temperature if a reaction gas, i.e., one or more oxidizing agents, is present in the reaction chamber. For example, if molecular oxygen at a pressure of 0.001 hPa is present as a reaction gas in the reaction chamber, the appropriate deposition temperature for Al2O3 as the first binary oxide decreases from 1650°K to 1070°K.

[0046] Furthermore, the method according to the present invention may also include using a continuous laser beam or a laser beam with a pulse intensity below a plasma generation threshold in step c), and especially in step d). By using a continuous laser beam, each raw material, and possibly the substrate, can be heated continuously as well. This also applies to pulsed lasers operated for TLE applications so as not to reach a plasma threshold for vaporizing the raw materials. In particular, the pulse width and repetition frequency of each laser beam are preferably selected so that the object to be heated is not significantly cooled during the pulse of the laser beam, i.e., laser heating is performed quasi-continuously. A suitable pulse length can be selected to be 1 μs or more, particularly 1 ms or more, preferably 1 s or more, and a suitable repetition frequency can be selected in the range of 10 kHz to 100 kHz.

[0047] In all cases, the laser beam is continuously, or at least substantially continuously, irradiated onto each raw material, and possibly onto the substrate. Therefore, each laser beam does not operate in a pulsed manner, i.e., in a manner with high laser energy and / or laser pulse lengths in nanoseconds. In this way, a particularly constant, controllable, or adjustable energy transfer from the laser beam to each raw material, and possibly the substrate, can be achieved. In this way, a constant and / or controllable and adjustable temperature, and consequently the evaporation rate and / or sublimation rate, can be obtained for each raw material. Furthermore, if necessary, a constant and / or controllable and adjustable temperature can also be obtained for the substrate.

[0048] According to a further embodiment of the method according to the present invention, in step b) above, the pressure and / or composition of the reaction gas is changed by appropriately controlling the gas system of the TLE system, thereby actively changing the stoichiometric composition of the target oxide to be formed without changing the constituent components. By changing the properties of the reaction gas, such as its pressure and / or the relative or absolute composition of the oxidizing agent, the amount of oxygen atoms available for target oxide formation can be actively changed. Therefore, it is possible to actively select, or at least assist in, which of several possible stoichiometric compositions of the target oxide to form. For example, when Sr is used as the first raw material and Ru as the second raw material, the pressure on the substrate surface is 10 -4 10 hPa or higher -3 When molecular oxygen (O2) is used as the reaction gas in the range below hPa, Sr2RuO4 is more likely to be formed as the target oxide. On the other hand, when the pressure is 5 × 10 with the same reaction gas... -3 hPa or higher: 2 x 10 -2 In the range below hPa, target oxides having SrRuO3 as their stoichiometric composition are likely to form.

[0049] Alternatively, or further, the method according to the present invention may include, in step c), appropriately controlling the laser beam of the TLE system used in step c), thereby changing the provided flux of the evaporated and / or sublimated first raw material and / or first binary oxide, and actively changing the stoichiometric composition of the formed target oxide without changing the constituent components. As described above, in most cases, the first raw material and / or first binary oxide are present in excess on the substrate. However, by controlling the amount of the first raw material and / or first binary oxide present, the formed target oxide can also be influenced.

[0050] Alternatively, the method according to the present invention can be further improved by appropriately controlling the laser beam of the TLE system in step d) above, thereby changing the deposition temperature of the substrate and actively altering the stoichiometric composition of the formed target oxide without changing the constituent components. As described above, the temperature of the substrate determines which elements or compounds are desorbed from the substrate surface. Therefore, by appropriately selecting the deposition temperature, the selection of the target oxide to be deposited on the substrate can be performed automatically.

[0051] Regarding the changes in reaction gases, in the examples of Sr and Ru described above, setting the desorption temperature in the range of 730°K to 1030°K is effective in selecting Sr2RuO4 as the target oxide. On the other hand, setting the deposition temperature in the range of 330°K to 730°K makes it easier to form a target oxide having SrRuO3 as its stoichiometric composition.

[0052] According to another improved embodiment, the method according to the present invention may include the following: the change in reaction gas, the change in the provided flux of the evaporated and / or sublimated first raw material and / or first binary oxide, and / or the change in deposition temperature, which may occur before, during, and / or after the iteration of step c). In step c), the first raw material, and if present, one or more second raw materials, are evaporated and / or sublimated. Thus, by performing the respective changes before and / or after the iteration of step c), it is possible to select different target oxides in the iteration of the next step c). This makes it possible to achieve a steep transition of oxide layers from one target oxide to another. On the other hand, by performing the respective changes during the execution of step c), it is possible to achieve a smoother transition from one target oxide to the next target oxide.

[0053] Regarding the abrupt transitions in the oxide layers described above, the method according to the present invention has another advantage. Since the supply of each raw material is based on the evaporation and / or sublimation of that raw material, continuous heating of the raw material is necessary to continuously supply each evaporated and / or sublimated raw material. Without this heating, the raw material would cool immediately by radiative cooling, and evaporation and / or sublimation would stop. Therefore, for example, by providing shutters on the beamlines of each laser beam, a predetermined deposition interval can be defined by starting and stopping each laser beam. This makes it possible to control the thickness of the deposited oxide layer and further enable abrupt transitions between different oxide layers.

[0054] Furthermore, the above method can be improved by including two or more continuous sublayers formed of target oxides having the same constituent components but different stoichiometric compositions, preferably different perovskite structures, perovskite-related structures, and / or rudolsden-popper structures. This can be achieved, in particular, by the above-mentioned changes in reaction gas, changes in the flux of the first raw material, changes in the flux of the first binary oxide, and / or changes in the deposition temperature. This makes it possible to provide oxide layers with diverse properties. For example, the above-mentioned examples of target oxides composed of Sr, Ru, and O actually have a rudolsden-popper structure. Furthermore, in addition to the examples of Sr2RuO4 and SrRuO3 already mentioned, Sr2RuO4, Sr3Ru2O7, and Sr4Ru3O 10 These are also possible target oxides for different sublayers of the oxide layer.

[0055] According to another embodiment of the method according to the present invention, the first raw material and / or one or more second raw materials are elemental metals. Metals are an extremely diverse group of elements, and metal oxides exhibit an extremely diverse range of properties, such as electrical conductivity, thermal conductivity, or physical properties such as hardness and toughness. Thus, by carrying out the method according to the present invention, it is possible to provide binary oxides, ternary oxides, and even multi-component oxides based on metals as non-oxygen components as target oxides for the oxide layer produced.

[0056] Furthermore, the method according to the present invention may also be characterized in that the first raw material and / or one or more second raw materials are selected from the group of materials consisting of Li, Na, K, Ca, Sr, Y, Ag, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pb, Bi, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Zr, Mo, Ru, Rh, Pd, In, Sn, Sb, Be, B, Mg, Si, Cu, Zn, Ge, Se, Cd, Te, Cs, Re, Pt, Au, Hg, Tl, Th, U, Np, Pu, Am, Tc, Os, Rb, and As. This makes it possible to provide a variety of binary oxides, ternary oxides, and even multi-component oxides as possible target oxides for the oxide layer produced by carrying out the method according to the present invention.

[0057] The method according to the present invention may include performing step b) continuously while steps c), d), and / or e) are being performed. In step b), the reaction chamber is filled with a reaction gas, which comprises, preferably, one or more oxidizing agents. By performing step b) continuously while steps c), d), and / or e) are being performed, the reaction chamber is simultaneously filled with the reaction gas during the evaporation and / or sublimation of the first raw material and, if applicable, one or more second raw materials, during the heating of the substrate, and / or during the formation of the target oxide and deposition of the oxide layer. This ensures that the atmosphere in the reaction chamber is maintained at high purity throughout the deposition process, preferably in steps c), d), and e) during the implementation of the method according to the present invention.

[0058] Furthermore, the method according to the present invention may be characterized in that, in step b), the filling of the reaction chamber includes supplying a flow of the reaction gas directed toward the substrate in a specified direction. The target oxide is deposited on the substrate, thereby forming an oxide layer on the substrate. By supplying a flow of the reaction gas in a specified direction, and consequently a flow of one or more oxidizers in a specified direction, the oxygen flux density necessary for forming the target oxide on the substrate can be reliably increased. In particular, oxygen deficiency can be avoided in adsorption-controlled deposition processes.

[0059] Simultaneously, the flow of the reaction gas in the specified direction reduces the background pressure of the reaction gas in the unspecified direction. This reduces the scattering of raw materials along the path from the source to the substrate, and with reduced scattering, the reaction gas flux density on the substrate surface can be relatively increased, enabling a higher growth rate or stronger oxidation of the target oxide than when the background gas is uniformly distributed.

[0060] Furthermore, the method according to the present invention can be improved by having the reaction gas consist of a single oxidizing agent. In other words, after step b), the entire reaction chamber is filled with only this single oxidizing agent. This ensures the purity of the reaction atmosphere in the reaction chamber and contributes to further improving the extremely high quality of the oxide film provided.

[0061] According to another embodiment of the method according to the present invention, the one or more oxidizing agents are molecular oxygen (O2), ozone (O3), plasma-activated oxygen (O2) * ), ionized oxygen (O - The oxidizing agent is selected from the group consisting of ), atomic oxygen (O), and combinations thereof. This list is not limited, and other oxidizing agents that provide the oxygen necessary for target oxide formation can also be used. In particular, the oxidizing agents listed above consist of oxygen atoms. This helps to avoid contamination with other elements by the oxidizing agent.

[0062] Furthermore, in step b) above, the method according to the present invention adds 10 to the reaction gas. -9 From hPa to 10 5 A range of hPa, preferably 10 -5 From hPa to 10 5 The method can be characterized by applying a pressure selected within the range of hPa. In the method according to the present invention, a variety of elemental materials, in particular all metals available as solid raw materials, can be used as the first raw material, and optionally as one of one or more second raw materials. This results in an extremely wide variety of selectable target oxides, each target oxide having a reaction gas pressure and / or reaction gas pressure range that is most suitable for depositing that particular target oxide as an oxide layer. -9 From hPa to 10 5 A range of hPa, preferably 10 -5 From hPa to 10 5 By applying a pressure selected within the hPa range, the most appropriate pressure and / or pressure range for the reaction gas can be selected for almost all target oxides.

[0063] TLE systems, especially gas systems in TLE systems, can handle any pressure within this range, i.e., a minimum of 10 -9 hPa, preferably 10 -5 From hPa up to 10 5 It is preferable to be able to supply the reaction gas up to hPa. This makes it possible to produce oxide layers with extremely high quality and unprecedented diversity using the same TLE system, resulting in deposited target oxides.

[0064] In another embodiment, the method according to the present invention may include, prior to step c), a step of preparing the surface of the substrate for which the oxide layer is to be deposited. The surface condition of the substrate affects the deposition of the oxide layer. For example, in the case of a crystalline substrate, defects in the crystal lattice of the substrate, steps due to misalignment of the cut plane relative to the crystal plane of the substrate, and / or surface impurities may persist as defects in the deposited layer. By introducing a step of preparing the surface of the substrate, the surface condition of the substrate can be improved for the deposition of the target oxide as a subsequent oxide layer. This helps to provide an oxide layer of extremely high quality that can be achieved during the implementation of the method according to the present invention.

[0065] The method according to the present invention can be further improved by including a step of preparing the surface which involves tempering the surface by heating the substrate with the laser beam of the TLE system, preferably the laser beam used in step d). Heating the substrate allows for the removal of impurity atoms and the repair of defects in the bulk, and in particular, allows atoms forming the substrate surface to move to find energetically favorable positions on the substrate surface, i.e., ideal positions on the substrate surface, especially in the case of crystalline substrates, positions within the periodic crystal lattice of the substrate. In other words, heating the substrate induces an annealing effect, particularly on the substrate surface. This makes it possible to provide a substrate surface more suitable for the deposition of a target oxide as a subsequent oxide layer.

[0066] Furthermore, or alternatively, the method according to the present invention may include a step of preparing the surface, which involves coating the surface with one or more buffer layers. These one or more buffer layers can help smooth out any unevenness on the substrate surface. Moreover, particularly in the case of crystalline substrates, the target oxide deposited as an oxide layer may have a different lattice structure and / or lattice constant than the substrate. Therefore, at least the first atomic layer of the target oxide on the substrate needs to compensate for these differences. However, the buffer layer can be appropriately selected to have similar, if not identical, crystalline properties compared to the target oxide in the oxide layer. Thus, by adding such appropriately selected buffer layers between the substrate and the oxide layer, differences in each crystal lattice within the buffer layer can be compensated, giving the oxide layer an ideal crystalline structure from the first atomic layer of the target oxide.

[0067] According to a first improved embodiment, the method according to the present invention can be improved by comprising the buffer layer comprising, preferably, the first raw material and / or an oxide of the first raw material, particularly the first binary oxide.

[0068] According to an additional or alternative second improved embodiment, the method according to the present invention can be improved by comprising, preferably comprising, one of the one or more second raw materials and / or an oxide of one of the one or more second raw materials, in particular one of the one or more second binary oxides.

[0069] Furthermore, according to an additional or alternative third improved embodiment, the method according to the present invention can be improved by the buffer layer comprising, preferably comprising, the material of the substrate.

[0070] In the first two alternative embodiments, the buffer layer is formed by evaporation and / or sublimation of raw materials already present in the reaction chamber for the deposition of the target oxide as a subsequent oxide layer. In both of these improved alternative embodiments, the need to provide an additional deposition source containing additional raw materials is eliminated. Depending on the lattice structure of the target oxide, the optimal composition of the buffer layer can be selected based on components already present in the TLE system, i.e., the first raw material or an oxide of the first raw material, or, where applicable, one or more oxides of one or more second raw materials. In the third alternative embodiment, it may be necessary to provide each deposition source that provides the above-mentioned constituent components of the substrate material, preferably as elemental materials. Providing a buffer layer containing, preferably consisting of, the substrate material offers the advantage of being able to deposit the buffer layer with high quality. This allows for the smoothing of surface defects on the substrate itself. Furthermore, if suitable for the deposition of the target oxide forming the subsequent oxide layer, a buffer layer containing two or more sublayers of these materials can also be implemented.

[0071] Furthermore, the method according to the present invention may be characterized in that, prior to step c), a step of preparing for evaporation and / or sublimation is performed, wherein the first raw material and / or the one or more second raw materials are heated by a laser beam, preferably the laser beam used in step c), to clean the first raw material and / or the one or more second raw materials, and no material is deposited on the substrate. In step c) of the method according to the present invention, the first raw material and, optionally, one or more second raw materials are also evaporated and / or sublimated by their respective laser beams. In other words, the laser beam is irradiated onto the surface of each deposition source, and each raw material is evaporated and / or sublimated. However, particularly at the start of the evaporation and / or sublimation process, the surface of each deposition source may be contaminated with impurities. By preheating each raw material, the impurities can be removed by evaporation and / or sublimation. To avoid the evaporated and / or sublimated impurities being deposited on the substrate, the substrate may be shielded and / or moved aside. Also, in this preparation step, the substrate may be removed from the reaction chamber, preferably via an airlock. In short, the above preparation step makes it possible to achieve evaporation and / or sublimation of each raw material with high purity from the start of step c) of the method according to the present invention.

[0072] According to a second aspect of the present invention, the object of the present invention is achieved by a TLE system constructed to carry out the method according to the first aspect of the present invention. The TLE system according to the second aspect of the present invention is - The above reaction chamber, - One or more laser light sources that heat the substrate and supply a laser beam for evaporating and / or sublimating one or more of the raw materials, - A coupling means for coupling one or more laser beams to the reaction chamber, - Arrangement means for arranging the substrate and the one or more deposition sources that supply the one or more raw materials in the reaction chamber, - The gas system for supplying the reaction gas into the reaction chamber and It is equipped with.

[0073] A TLE system according to the second aspect of the present invention is constructed to carry out the method according to the first aspect of the present invention. Therefore, all the features and advantages described in detail with respect to the method according to the first aspect of the present invention may also be provided by the TLE system according to the second aspect of the present invention.

[0074] As already mentioned, it is preferable that the TLE system, particularly each laser light source and the laser beam supplied by the laser light source, be able to heat the substrate to any temperature within this range, i.e., from a minimum of 250°K to a maximum of 4500°K. This makes it possible to produce an unprecedented variety of oxide layers with extremely high quality using the same TLE system.

[0075] Furthermore, or alternatively, as already mentioned, TLE systems, and especially the gas systems of TLE systems, can operate at any pressure within this range, namely a minimum of 10 -9 hPa, preferably 10 -5 From hPa up to 10 5 It is preferable to be able to supply the reaction gas up to hPa. This makes it possible to produce oxide layers with extremely high quality and unprecedented diversity using the same TLE system, resulting in deposited target oxides.

[0076] A single laser light source may be used to evaporate and / or sublimate each raw material, with a separate laser beam supplied to each raw material. Alternatively, separate laser light sources may be implemented, each providing a laser beam selected for each raw material.

[0077] The reaction chamber may be provided with an airlock to allow access to the reaction chamber without disturbing and / or contaminating the existing atmosphere within the reaction chamber. The airlock can be used, for example, to install and / or remove the substrate and / or one or more deposition sources.

[0078] The present invention will be described in detail below based on embodiments with reference to the drawings. In particular, the drawings are as shown below. [Brief explanation of the drawing]

[0079] [Figure 1] This is a phase diagram of SrTiO3. [Figure 2] This is a schematic diagram of the TLE system according to the present invention. [Figure 3] This is a schematic diagram of the method according to the present invention. [Figure 4] This is a phase diagram of the Sr-Ru-O rudolsden=popper material. [Figure 5] This figure shows the relationship between the growth rate of Al2O3 and the deposition temperature. [Figure 6] This figure shows the relationship between the growth rate of Al2O3 and the reaction gas pressure. [Modes for carrying out the invention]

[0080] Figure 1 shows the calculated phase diagram of a possible target oxide 82, i.e., SrTiO3, known in the prior art. In this figure, the pressure, and therefore the flux, of SrO as the first binary oxide 34 of the first raw material 32 (not explicitly shown) is shown for the possible deposition temperature 72 of the substrate 70. Ideally, the target oxide 82 should be deposited on the substrate 70 as an oxide layer 80 (see Figure 2).

[0081] The upper line, indicated as desorption temperature 36, indicates the boundary temperature at which the first binary oxide 34 desorbs from the surface of the substrate 70 below and to the right of this line, depending on the pressure of the first binary oxide 34. The second unsigned line indicates the boundary temperature at which the substrate 70 and / or the target oxide 82 on the substrate 70, and consequently the oxide layer 80, lose sufficient stability for effective growth and undergo phase separation into the more stable TiO2 and gaseous SrO below and to the right of this line. In the region between these lines, labeled as the “growth window”, the first binary oxide 34 (SrO) desorbs, preferably completely, and the flux density or local pressure of the second binary oxide 44 (TiO) limits and thus determines the growth rate of the target oxide 82 (SrTiO3), thus enabling adsorption-controlled growth of the target oxide 82 (SrTiO3).

[0082] However, Figure 1 also shows the range achievable with conventional MBE and PLD processes. In the conventional deposition processes known above, the achievable temperature range of the substrate 70 is (550°C-900°C, up to 1200°C in special cases) and the SrO pressure range is (10 -7 from 10 -5 Since the intersection of the hPa values ​​does not exist within the growth window for a technically useful growth rate (0.01 to 1 unit layer / second), it can be clearly confirmed that deposition of SrTiO3 as the target oxide 82 in a growth mode with limited adsorption is impossible.

[0083] However, thermal laser epitaxy is a deposition process that essentially does not include the limitations on the possible deposition temperature 72 of the substrate 70 present in MBE, and at the same time can provide flux of almost any raw material with significantly higher purity than PLD. In fact, the purity of the raw materials of the flux provided is at least equivalent to, and in most cases better than, that achievable with the MBE process.

[0084] Therefore, according to the present invention, a method for controlling the deposition of the oxide layer 80 of the target oxide 82 on the substrate 70 is carried out using a properly constructed TLE system 100 as shown in Figure 2, as shown in Figure 3. The TLE system 100 and the method according to the present invention will be described together below.

[0085] As previously stated, the method according to the present invention is carried out in a well-constructed TLE system 100. The main part of the TLE system 100 is a reaction chamber 10 in which an oxide layer 80 is deposited on a substrate 70. Other parts of the TLE system 100 are one or more (three illustrated as an example) laser light sources 20 for supplying a laser beam 22, and a gas system 50 fluidly connected inside the reaction chamber 10.

[0086] The laser beams 22 are used for both the evaporation and / or sublimation of the raw materials 32 and 42, and for heating the substrate 70. Appropriate coupling means 12 are provided to guide the laser beams 22 to their respective irradiation targets within the reaction chamber 10. The laser beams 22 are preferably continuous light or have a pulse intensity at least below the plasma generation threshold. In the latter case, the pulse length can be selected to preferably be 1 μs or more, particularly 1 ms or more, and preferably 1 s or more.

[0087] The gas system 50 can at least fill the reaction chamber 10 with reaction gas 52, which is, for example, molecular oxygen (O2), ozone (O3), plasma-activated oxygen (O2) * ), ionized oxygen (O - The reaction gas 52 comprises, preferably, one or more oxidizing agents 54, such as ), atomic oxygen (O), and combinations thereof. The reaction gas 52 may be supplied as a flow toward the substrate 70 in a specified direction. The reaction gas 52 preferably consists of a single oxidizing agent 54. One or more oxidizing agents 54 are sources of oxygen atoms necessary for the formation of the target oxide 82, as will be described later. The gas system 50 delivers the reaction gas 52 at various pressures, preferably 10 -5 From hPa to 105 The gas can be supplied at a pressure selected within the range of hPa. In most embodiments, the gas system 50 can not only supply the reaction gas 52 but also exhaust the reaction chamber 10.

[0088] Furthermore, a substrate 70 to be coated with an oxide layer 80 is placed inside the reaction chamber 10 and held in place by the placement means 60. The oxide layer 80 is formed by depositing a target oxide 82 having a defined stoichiometry and formed from one or more raw materials 32, 42 that have been evaporated and / or sublimated, and oxygen derived from a gaseous oxidizing agent 54. As will be described later, one of the laser beams 22 is used to heat the substrate 70 to a deposition temperature 72 appropriately selected for the intended deposition of the oxide layer 80.

[0089] One or more components of the target oxide 82 other than oxygen are supplied by evaporating and / or sublimating one or more raw materials 32, 42. In the illustrated embodiment of the TLE system 100, a first deposition source 30 containing an elemental material, preferably an elemental metal, as the first raw material 32, and a second deposition source 40 containing an elemental material, preferably an elemental metal, as the second raw material 42, are appropriately constructed and held in place within the reaction chamber 10, in particular, by provided arranging means 60. Each raw material 32, 42 is evaporated and / or sublimated by the corresponding laser beam 22. Because the raw materials 32, 42 are supplied as elemental materials, the evaporated and / or sublimated raw materials 32, 42 can be made extremely pure. The first binary oxide 34 and the second binary oxide 44 can be formed only by reaction of the reaction gas 52 with one or more oxidizing agents 54.

[0090] The raw materials 32 and 42 that can be used in the TLE system 100 and the method according to the present invention are diverse. In particular, all elemental materials, especially Li, Na, K, Ca, Sr, Y, Ag, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pb, Bi, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Zr, Mo, Ru, Rh, Pd, In, Sn, Sb, Be, B, Mg, Si, Cu, Zn, Ge, Se, Cd, Te, Cs, Re, Pt, Au, Hg, Tl, Th, U, Np, Pu, Am, Tc, Os, Rb, and As can be used as raw materials 32 and 42.

[0091] The method according to the present invention will now be described in detail. Note that step a)A has already been completed in the TLE system 100 shown in Figure 2. Furthermore, note that steps b)B, c)C, d)D, and e)E can be performed simultaneously.

[0092] In the first step a)A, the substrate 70 and all the deposition sources 30 and 40 to be used are placed inside the reaction chamber 10. Then, the reaction chamber 10 is closed and sealed to the surrounding environment and preferably evacuated by the gas system 50.

[0093] This makes it possible to fill the reaction chamber 10 with the reaction gas 50 in the next step b)B. It should be noted that it is preferable that the filling in step b)B can be carried out continuously throughout all subsequent steps c)C, d)D, and e)E of the method according to the present invention.

[0094] To ensure the purity of the reaction gas 52 is maintained, the filling of the reaction gas 52, preferably from one side of the TLE system 100, and more preferably through a nozzle facing forward of the substrate 70, and the exhaust of the reaction gas 52 from the other side of the TLE system 100 may be performed simultaneously by different parts of the gas system 50 (not shown).

[0095] Furthermore, as preparation for the subsequent deposition of the oxide layer 80 onto the substrate 70, the surface of the substrate 70 may be prepared, for example, by heating the substrate and performing an annealing treatment. Alternatively, as shown in Figure 2, a buffer layer 74 consisting of elements already present in the reaction chamber 10, such as the first raw material 32, the first binary oxide 34, the second raw material 42, and / or the second binary oxide 44, may be deposited onto the surface of the substrate 70.

[0096] Further preparation steps may include preheating the raw materials 32, 42 for cleaning purposes, thereby avoiding the deposition of already evaporated and / or sublimated materials onto the substrate.

[0097] In the next step c)C of the method according to the present invention, the actual evaporation and / or sublimation of the raw materials 32, 42 is performed. For this purpose, the intensity of each laser beam 22 is selected to be below the plasma threshold of each raw material 32, 42. This makes it possible to achieve strictly thermal evaporation and / or sublimation. The flux of the evaporated and / or sublimated raw materials 32, 42, or the binary oxides 34, 44 formed thereon, is directed toward the substrate 70 for subsequent coating of the substrate 70.

[0098] In the next step d)D, the substrate 70 is heated by a laser beam 22 supplied as appropriate. In this important step, the substrate 70 is heated to an deposition temperature 72 that is at least the desorption temperature 36 (see Figure 5) of the first raw material 32 or the first binary oxide 34. Depending on each first raw material 32, and especially each first binary oxide 34, the deposition temperature 72 can preferably be selected in the range of 250°K to 4500°K.

[0099] This causes the first raw material 32 or the first binary oxide 34 to desorb from the substrate 70. The deposition temperature 72 can preferably be selected so that more than 40%, particularly more than 70%, and preferably more than 99.9%, of the inflow flux of the first raw material 32 and, if present, the first binary oxide 34 desorbs from the substrate 70. This ensures that the deposition of the target oxide 82 depends only on the additional components required to form the target oxide 82. This is the amount of oxygen available on the substrate if the target oxide 82 is a binary oxide (see Figure 6), and if the target oxide 82 is a ternary or polyoxide, it is one or more additional second raw materials 42 or each of the second binary oxides 44 of the second raw materials 42.

[0100] In short, the heating of the substrate 70 in step d) enables controlled adsorption deposition of the target oxide 82, and consequently the oxide layer 80, in step e) of the method according to the present invention. In other words, the amount of compounds required in addition to the first raw material 32 and / or the first binary oxide 34, i.e., mainly the amount of one or more second raw materials 42 and / or one or more second binary oxides 44, and optionally the amount of available oxygen supplied by one or more oxidizing agents 54, also independently determines and thus controls the formation rate of the target oxide 82, and consequently the growth rate of the oxide layer 80. For the above control, one or more second raw materials 42 and / or each of the one or more second binary oxides 44 can be supplied in intermittent, constant, and / or variable flux, thereby changing the growth rate of the oxide layer 80.

[0101] In particular, the desorption of the first raw material 32 and / or the first binary oxide 34, if present, from the substrate can provide extremely high quality for the formation of the target oxide 82 and the deposition of the oxide layer 80 onto the substrate 70. This is due to the physical effect that the deposition of the target oxide 82 is carried out only when the compound to be formed, i.e., the target oxide 82, has the necessary and appropriate thermodynamic properties that are highly dependent on the substrate temperature, i.e., the deposition temperature 72. This allows for the active selection of the compound to be deposited, i.e., the target oxide 82, and as a result, the quality of the deposited oxide layer 80, especially in terms of high purity and low defect density, can be maximized. On the other hand, the defect density of the deposited elements of the first raw material 32 and / or the first binary oxide 34 can be reduced to 10 4 Less than 1 / 1, especially 10 7 Less than 1 / 1, preferably 10 10 It can be reduced to less than 1 / 2.

[0102] Figure 4 illustrates another advantage of the method according to the present invention. By appropriately controlling the variables of the deposition process, the actual target oxide 82 can be accurately selected. As shown in the figure, target oxide 82 with the same constituent components but different stoichiometric compositions can be provided. In particular, this selection can be achieved in an extremely short time of less than 5 seconds. This makes it possible to provide an oxide layer 80 containing multiple sublayers having the same constituent components but different structures.

[0103] Figure 4 shows the thermodynamic phase diagrams of different Sr-Ru-O rudolsden-popper materials. Such rudolsden-popper materials, and oxides having a perovskite structure or perovskite-related structure, can be deposited with extremely high quality by carrying out the method according to the present invention.

[0104] This phase diagram shows how the optimal deposition temperature 72 for selecting each structure as the target oxide 82 depends on the oxygen pressure supplied by the reaction gas 52. It is clear that by appropriately controlling the above pressure and the heating of the substrate 70, the target oxide 82 used for deposition of the oxide layer 80 can be accurately selected.

[0105] Experimentally, deposition temperatures of 1000°C to 1300°C, and 10 -4 from 10 -2 It was found that the pressure of oxygen as the oxidizing agent 54 at hPa (≒Torr) results in the deposition of a high-quality epitaxial crystalline film of Sr2RuO4 as the target oxide 82 for the oxide layer 80.

[0106] Similarly, deposition temperatures from 600°C to 1000°C, and 5 × 10 -3 From 2 x 10 -2 It was found that the pressure of oxygen as the oxidizing agent 54 at hPa (≒ Torr) resulted in the deposition of a high-quality epitaxial crystalline film of SrRuO3 as the target oxide 82 for the oxide layer 80.

[0107] In either case, Ru(5 × 10) is used as the first raw material 32. 12 and 3 × 10 14 atoms / s * cm 2 ) and Sr(1 × 10) as the second raw material 42 13 and 1 × 10 15 atoms / s * cm 2 The supply flux was identical.

[0108] Figures 5 and 6 demonstrate the principle of implementing this method using a binary oxide, namely Al2O3, as the target oxide 82. Figures 5 and 6 will be explained below in conjunction. In short, the ability of TLE to grow epitaxially adsorbed binary materials was demonstrated by the adsorption-controlled growth of the illustrated c-plane sapphire (Al2O3). It should be noted that Al2O3 is predicted to have the highest level of deposition temperature 72 when grown under adsorption control (1650°K in a vacuum environment). Furthermore, Al2O3 has high scientific and industrial significance due to its high band gap (9 eV), high dielectric constant (9), high thermal conductivity (46 W / Km), and high thermal stability. For example, Al2O3 is used in numerous optical applications as a high dielectric constant gate oxide and is a subject of research in the field of high-power electronics.

[0109] This high thermal stability correlates with the aforementioned high deposition temperature 72 required to induce volatility. Figure 5 shows the growth rate against substrate temperature when the elemental flux is kept constant. The growth rate drops sharply at 900°C, which is the desorption temperature 36 of Al2O3 when the pressure of the reaction gas 52 (see Figure 2) is 0.001 hPa. At this temperature of 900°C, the species that are actually desorbed are the suboxide of Al2O3 and the first raw material 32 (see Figure 2), which is pure Al.

[0110] The growth rate in the selectable adsorption control region, which can be achieved by heating the substrate 70 to a temperature significantly exceeding the desorption temperature 36 shown in Figure 5, is determined by the supply flux of the reaction gas 52 or oxidizing agent 54, thereby enabling oxidation to the less volatile Al2O3. This is shown in Figure 6. Figure 6 shows the growth rate as a function of pressure of the reaction gas 52 (O2 in this example) when the flux of the first raw material 32 (pure Al) is kept constant and the substrate 70 is heated to an deposition temperature 72 of 1600°C.

[0111] As is clear from the figure, the growth rate increases with increasing supply of the oxidizing agent 54 (molecular oxygen in this example), but the mean free path limits the growth rate in the high-pressure range. On the other hand, this demonstrates the ability to grow Al2O3 using an adsorption control method. The growth of binary materials using an adsorption control method had not been demonstrated until now. Furthermore, it is shown that the formation rate of the target oxide 82, and consequently the growth rate of the oxide layer 80, can be controlled by actively controlling the filling of the reaction chamber 10 with reaction gas 52. [Explanation of Symbols]

[0112] 10…Reaction Chamber 12...Coupling means 20… Laser light source 22… Laser beam 30...first vapor deposition source 32…First ingredient 34…First binary oxide 36…Desorption temperature 40...Second deposition source 42…Second raw material 44…Second binary oxide 50…Gas system 52…Reaction gas 54… Oxidizing agent 60…Arrangement means 70... Circuit board 72...Vaporization temperature 74... Buffer layer 80…Oxide layer 82…Target Oxide 100...TLE system A…Step a) B...Step b) C…Step c) D...Step d) E...Step e)

Claims

1. A method for controlling the deposition of an oxide layer (80) of a target oxide (82) on a substrate (70) in a thermal laser epitaxy (TLE) system (100), wherein the target oxide (82) has a defined stoichiometric composition and is formed from one or more raw materials that are evaporated and / or sublimated and oxygen derived from a gaseous oxidizer (54), and the TLE system (100) further comprises a reaction chamber (10) and one or more laser light sources (20) for supplying a laser beam (22) into the reaction chamber (10), a) A step of placing the substrate (70) and the first deposition source (30) in the reaction chamber (10), wherein the first deposition source (30) includes an elemental material as the first raw material (32), b) A step of filling the reaction chamber (10) with a reaction gas (52) containing one or more oxidizing agents (54) supplied by the gas system (50) of the TLE system (100), c) Irradiating the first raw material (32) with a laser beam (22) of the TLE system (100) at an intensity below the plasma generation threshold of the first raw material (32) to evaporate and / or sublimate the first raw material (32), thereby providing a flux of the evaporated and / or sublimated first raw material (32) and / or a flux of the first binary oxide (34) formed from the first raw material (32) by the oxidizing agent (54), wherein the direction of the flux is directed toward the substrate (70), d) A step of heating the substrate (70) to a deposition temperature (72) with the laser beam (22) of the TLE system (100), wherein the deposition temperature (72) of the substrate (70) is at or above the desorption temperature (36) at which the first deposition source (30) and / or the first binary oxide (34) desorb at least partially from the substrate (70), e) A step of forming the target oxide (82) by combining one or more evaporated and / or sublimated raw materials with oxygen derived from one or more oxidizing agents (54), and depositing the target oxide (82) as an oxide layer (80) onto the substrate (70), wherein the formation of the target oxide (82) and the deposition of the oxide layer (80) onto the substrate (70) are controlled by controlling the filling of the reaction chamber (10) with the reaction gas (52) in step b), controlling the supply rate of the evaporated and / or sublimated first raw materials (32) to the substrate (70) in step c), and / or controlling the deposition temperature (72) in step d). A method characterized by having the following:

2. The method according to claim 1, A method characterized in that, in step d), the deposition temperature (72) is selected such that more than 40%, particularly more than 70%, preferably more than 99.9%, of the inflow flux of the first raw material (32) is desorbed from the substrate (70), and in step e), the adsorbed portion of the first raw material (32) bonded with oxygen derived from one or more oxidizing agents (54) and / or the first binary oxide (34) forms the target oxide (82) for deposition of the oxide layer (80).

3. The method according to claim 1, In step a), one or more second deposition sources (40) are provided in the reaction chamber (10), and each second deposition source (40) contains an elemental material as a second raw material (42). Step c) involves irradiating the one or more second raw materials (42) with the laser beam (22) of the TLE system (100) at an intensity below the plasma generation threshold of the one or more second raw materials (42), thereby evaporating and / or sublimating the one or more second raw materials (42), and forming one or more fluxes of the evaporated and / or sublimated second raw materials (42) and / or one or more of the oxidizing agent (54) from one of the one or more second raw materials (42). A flux of a second binary oxide (44) is provided, the direction of which the flux is directed toward the substrate (70), and in step e), the first deposition source (30) and / or the first binary oxide (34) combine with one or more second deposition sources (40) and / or the one or more second binary oxides (44), and optionally further combine with oxygen derived from one or more oxidizing agents (54) to form the target oxide (82) for deposition of the oxide layer (80). The method is characterized in that, in step d), the deposition temperature (72) of the substrate (70) is at or above the temperature at which the first deposition source (30) and / or the first binary oxide (34) desorb when not used for forming the target oxide (82).

4. The method according to claim 3, The deposition temperature (72) in step d) is set such that the amount of the first deposition source (30) and / or the first binary oxide (34) deposited on the substrate (70) is 10 times the amount of the elements of the target oxide (82). 4 Less than 1 / 1, especially 10 7 Less than 1 / 1, preferably 10 10 A method characterized by selecting a value that is sufficiently high so that it is less than 1 / 2.

5. The method according to claim 3 or 4, A method characterized in that, in step c), the laser beam (22) used to evaporate and / or sublimate the one or more second raw materials (42) is appropriately controlled to impart intermittent, constant, and / or variable flux to the one or more second raw materials (42) and / or the one or more second binary oxides (44) that have been evaporated and / or sublimated.

6. A method according to any one of claims 3 to 5, The method is characterized in that the target oxide (82) formed in step e) has a perovskite structure, a perovskite-related structure, and / or a rudrusden-popper structure.

7. A method according to any one of claims 1 to 6, The method is characterized in that, in step d), the deposition temperature (72) is selected so that the first raw material (32), the first binary oxide (34), the one or more second raw materials (42), and / or the one or more second binary oxides (44) move along the surface of the substrate (70).

8. A method according to any one of claims 1 to 7, A method characterized in that, in step d), the deposition temperature (72) is set to 250°K or more and 4500°K or less.

9. A method according to any one of claims 1 to 8, The method is characterized in that, in step d), the deposition temperature (72) is selected according to the first binary oxide (34).

10. The method according to claim 9, A method characterized in that the deposition temperature (72) is selected to be at or above the temperatures listed below, depending on the first binary oxide (34). Table 2

11. A method according to any one of claims 1 to 10, The method is characterized in that, in step c), and especially in step d), a continuous laser beam (22) or a laser beam (22) having an intensity below a plasma generation threshold is used.

12. A method according to any one of claims 1 to 11, A method characterized in that, in step b), the pressure and / or composition of the reaction gas (52) is changed by appropriately controlling the gas system (50) of the TLE system (100), thereby actively changing the stoichiometric composition of the target oxide (82) that is formed without changing the constituent components.

13. A method according to any one of claims 1 to 12, A method characterized in that, in step c), by appropriately controlling the laser beam (22) of the TLE system (100) used in step c), the supplied flux of the evaporated and / or sublimated first raw material (32) and / or first binary oxide (34) is changed, thereby actively changing the stoichiometric composition of the formed target oxide (82) without changing the constituent components.

14. A method according to any one of claims 1 to 13, A method characterized in that, in step d), the deposition temperature (72) of the substrate (70) is changed by appropriately controlling the laser beam (22) of the TLE system (100), thereby actively changing the stoichiometric composition of the formed target oxide (82) without changing the constituent components.

15. A method according to any one of claims 12 to 14, A method characterized in that the changes in the reaction gas (52), the changes in the supplied flux of the evaporated and / or sublimated first raw material (32) and / or first binary oxide (34), and / or the changes in the deposition temperature (72) are performed before, during, and / or after the repetition of step c).

16. A method according to any one of claims 12 to 15, The method is characterized in that the oxide layer (80) deposited in step e) comprises two or more continuous sublayers formed of target oxides (82) having the same constituent components but different stoichiometric compositions, preferably different perovskite structures, perovskite-related structures, and / or rudolsden-popper structures.

17. A method according to any one of claims 1 to 16, A method characterized in that the first raw material (32) and / or the one or more second raw materials (42) are elemental metals.

18. A method according to any one of claims 1 to 17, A method characterized in that the first raw material (32) and / or the one or more second raw materials (42) are selected from the group of materials consisting of Li, Na, K, Ca, Sr, Y, Ag, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pb, Bi, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Zr, Mo, Ru, Rh, Pd, In, Sn, Sb, Be, B, Mg, Si, Cu, Zn, Ge, Se, Cd, Te, Cs, Re, Pt, Au, Hg, Tl, Th, U, Np, Pu, Am, Tc, Os, Rb, and As.

19. A method according to any one of claims 1 to 18, A method characterized by performing step b) continuously while performing step c), step d), and / or step e).

20. A method according to any one of claims 1 to 19, The method is characterized in that, in step b), the filling of the reaction chamber (10) includes supplying a flow of the reaction gas (52) directed toward the substrate (70) in a specified direction.

21. A method according to any one of claims 1 to 20, A method characterized in that the reaction gas (52) consists of a single oxidizing agent (54).

22. A method according to any one of claims 1 to 21, The one or more oxidizing agents (54) are molecular oxygen (O 2 ), ozone (O 3 ), plasma activated oxygen (O 2 * ), ionized oxygen (O - A method characterized by selecting from the group consisting of ), atomic oxygen (O), and combinations thereof.

23. A method according to any one of claims 1 to 22, In step b), a pressure selected in the range of 10 -9 hPa to 10 5 hPa, preferably in the range of 10 -5 hPa to 10 5 hPa is applied to the reaction gas (52).

24. A method according to any one of claims 1 to 23, A method characterized by performing a step of preparing the surface of the substrate (70) for which the oxide layer (80) is to be deposited before step c).

25. The method according to claim 24, A method characterized in that the step of preparing the surface includes tempering the surface by heating the substrate (70) with the laser beam (22) of the TLE system (100), preferably the laser beam (22) used in step d).

26. The method according to claim 24 or 25, A method characterized in that the step of preparing the surface includes coating the surface with one or more buffer layers (74).

27. The method according to claim 26, A method characterized in that the buffer layer (74) contains, preferably comprises, the first raw material (32) and / or an oxide of the first raw material (32), particularly the first binary oxide (34).

28. The method according to claim 26 or 27, A method characterized in that the buffer layer (74) comprises, preferably, one of the one or more second raw materials (42) and / or an oxide of one of the one or more second raw materials (42), particularly one of the one or more second binary oxides (44).

29. A method according to any one of claims 26 to 28, A method characterized in that the buffer layer (74) contains, preferably consists of, the material of the substrate (70).

30. A method according to any one of claims 1 to 29, A method characterized in that, prior to step c) above, a step of preparing for evaporation and / or sublimation is performed, the first raw material (32) and / or the one or more second raw materials (42) are heated by a laser beam (22), preferably the laser beam (22) used in step c) above, in order to wash the first raw material (32) and / or the one or more second raw materials (42), and no material is deposited on the substrate (70).

31. A TLE system (100) constructed for carrying out a method according to any one of claims 1 to 30, - The reaction chamber (10) and, - One or more laser light sources (20) that heat the substrate (70) and supply a laser beam (22) for evaporating and / or sublimating one or more raw materials (32, 42), - A coupling means (12) for coupling one or more laser beams (22) to the reaction chamber (10), - Arrangement means (60) for arranging the substrate (70) and one or more deposition sources (30, 40) that supply the one or more raw materials (32, 42) inside the reaction chamber (10), - The gas system (50) for supplying the reaction gas (52) into the reaction chamber (10) and A TLE system (100) equipped with the following.

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