SE544829C2 - Method for producing a film of a ternary or quaternary compound by ALD - Google Patents

Method for producing a film of a ternary or quaternary compound by ALD

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Publication number
SE544829C2
SE544829C2 SE2150544A SE2150544A SE544829C2 SE 544829 C2 SE544829 C2 SE 544829C2 SE 2150544 A SE2150544 A SE 2150544A SE 2150544 A SE2150544 A SE 2150544A SE 544829 C2 SE544829 C2 SE 544829C2
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Sweden
Prior art keywords
precursor
metal
metalloid
metalloid precursor
substrate
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Application number
SE2150544A
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Swedish (sv)
Other versions
SE2150544A1 (en
Inventor
Henrik Pedersen
Polla Rouf
Original Assignee
Henrik Pedersen
Polla Rouf
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Publication date
Application filed by Henrik Pedersen, Polla Rouf filed Critical Henrik Pedersen
Priority to SE2150544A priority Critical patent/SE544829C2/en
Priority to PCT/SE2022/050078 priority patent/WO2022231494A1/en
Publication of SE2150544A1 publication Critical patent/SE2150544A1/en
Publication of SE544829C2 publication Critical patent/SE544829C2/en

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    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/455Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
    • C23C16/45523Pulsed gas flow or change of composition over time
    • C23C16/45525Atomic layer deposition [ALD]
    • C23C16/45527Atomic layer deposition [ALD] characterized by the ALD cycle, e.g. different flows or temperatures during half-reactions, unusual pulsing sequence, use of precursor mixtures or auxiliary reactants or activations
    • C23C16/45531Atomic layer deposition [ALD] characterized by the ALD cycle, e.g. different flows or temperatures during half-reactions, unusual pulsing sequence, use of precursor mixtures or auxiliary reactants or activations specially adapted for making ternary or higher compositions
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    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/455Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
    • C23C16/45523Pulsed gas flow or change of composition over time
    • C23C16/45525Atomic layer deposition [ALD]
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    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/301AIII BV compounds, where A is Al, Ga, In or Tl and B is N, P, As, Sb or Bi
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    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/301AIII BV compounds, where A is Al, Ga, In or Tl and B is N, P, As, Sb or Bi
    • C23C16/303Nitrides
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    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/34Nitrides
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    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/448Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for generating reactive gas streams, e.g. by evaporation or sublimation of precursor materials
    • C23C16/4481Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for generating reactive gas streams, e.g. by evaporation or sublimation of precursor materials by evaporation using carrier gas in contact with the source material
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    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/455Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
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    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/455Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
    • C23C16/45523Pulsed gas flow or change of composition over time
    • C23C16/45525Atomic layer deposition [ALD]
    • C23C16/45527Atomic layer deposition [ALD] characterized by the ALD cycle, e.g. different flows or temperatures during half-reactions, unusual pulsing sequence, use of precursor mixtures or auxiliary reactants or activations
    • C23C16/45536Use of plasma, radiation or electromagnetic fields
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    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/46Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for heating the substrate
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/04Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
    • H01L33/06Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier

Abstract

A method for producing a film of a ternary or quaternary compound on a surface of a substrate by atomic layer deposition is provided. The method comprises co-evaporating (S102) a first metal or metalloid precursor and a second metal or metalloid precursor so as to form a mixed precursor vapor. The first metal or metalloid precursor comprises a first metal or metalloid selected from group 13 or group 14 of the periodic table. The second metal or metalloid precursor comprises a second metal or metalloid selected from group 13 or group 14 of the periodic table. The method further comprises subjecting (S103) the surface of the substrate to the mixed precursor vapor in a first precursor pulse, and thereafter subjecting (S105) the surface of the substrate to a third precursor in a second precursor pulse. The third precursor comprises a third element selected from group 15 or 16 of the periodic table.

Description

METHOD FOR PRODUCING A FILM OF A TERNARY OR QUATERNARY COMPOUND BY ALD TECHNICAL FIELD The present disclosure relates in general to a method for producing a film of a ternary or quaternary compound on a surface of substrate by atomic layer deposition.
BACKGROUND Semiconductor materials with various bandgaps are previously known. For example, the binary group 13 nitrides (AlN, GaN and lnN) and ternary group 13 nitrides (AlGaN, AllnN and lnGaN) are semiconductors materials with bandgaps ranging over the whole visible spectral range. By changing the composition of for example the ternary group 13 nitrides materials, different bandgaps can be obtained rendering emission of light with different wavelengths. This is advantageous especially when constructing light emitting diodes (LEDs). The structures required to form LED devices relies on thickness and composition control during deposition of a stack of thin layers, or films, of the materials.
Thin films of semiconductor materials may be deposited with chemical vapor deposition (CVD) which relies on vapor from different precursor molecules to form the film. When performing continuous CVD, the precursor molecules are simultaneously and continuously introduced into the deposition chamber. A sub-class of CVD is atomic layer deposition (ALD) where one atomic layer at a time is deposited by pulsing the precursors into the deposition chamber. More specifically, a first precursor is introduced into the deposition chamber comprising the substrate and adsorbed onto a surface of the substrate. Excess precursor is then removed from the deposition chamber by pumping and purging the deposition chamber with a purging gas. Thereafter, a second metal or metalloid precursor is introduced into deposition chamber and reacted with the adsorbed matter of the first precursor. Again, excess precursor may be removed by pumping and purging. The cycle may thereafter be repeated until a desired thickness is reached. This gives ALD extreme thickness control down to atomic levels, and also makes it possible to conformally deposit thin films even on topographically complex structures.
Although it is fairly easy to make films of binary compounds, it is often much more difficult to make films of ternary or quaternary compounds with sufficiently high quality to make them appropriate for use in semiconductors applications. Considering lnGaN as an example, the phase diagram for lnGaN suggest that only a few atomic percent ln can be incorporated into GaN (or only a few atomic percent Ga can be incorporated into lnN) for the resulting compound to be structurally stable. Higher amount of ln or Ga tend to lead to phase separation to lnN and GaN. Also, when depositing lnGaN with continuous CVD, high temperatures are required (2 800 °C) which is not ideal for lnN-based compounds as the lnN crystal decompose at around 500 °C. This in turn leads to formation of ln metal droplets which in turn affects the quality of the deposited films.
An alternative to continuous CVD for producing films of ternary (or quaternary) compounds is to use ALD. However, as ALD relies on sequentially saturating the surface with metal and reactive species, making ternary materials is difficult by ALD. Attempts have been made by using three steps to make the ternary material by first saturating the surface with the first metal, followed by a pulse comprising a reactive species, and then saturating the surface with the second metal. By way of example, for an lnGaN, first the ln precursor would saturate the surface, then a nitrogen containing precursor (such as NH3), and after that the Ga precursor. This seems to be a controlled way to make ternary materials. However, the composition is only true in the growth direction and not in plane. This is schematically illustrated in Figure 1(a) from which it can be seen that the Ga and ln atoms are ordered in respective parallel layers in the growth direction (illustrated by the arrow). This will result in a material where there is not a true "mixing" of the two metals making this not an ideal approach to obtain ternary materials. Figure 1(b) instead illustrate a desired result wherein there is also an in- plane mixing of the Ga and ln atoms.
EP 2 436 801 A1 discloses a method of depositing a |||-V semiconductor material on a substrate. A group ||| element precursor and a group V element precursor are sequentially introduced to the substrate by alternating spatial positioning of the substrate with respect to a plurality of gas columns. The group ||| element precursor may be generated by thermally decomposing a gas comprising a group ||| element in a gas injector, from which a gas column may be configured to receive the group ||| element precursor. The precursors used for the group ||| element are metal halides. lt is furthermore disclosed fgëjgthat a precursor mixture, including for example GaCl and at least one of lnCl and AlCl, may be formed using such gas injectors. ln such a case, GaClg, may (in the presence of hydrogen) be converted into GaCl and a chlorinated gas in a first branch of a conduit comprising a gas injector, and |nCl3 or AlClg may be converted into lnCl or AlCl in a second branch of the conduit comprising a gas injector. The branches may thereafter converge forming a single gas stream which may be supplied to a gas column. For example, when the precursor mixture comprises GaCl and lnCl, the precursor mixture may allegedly be used in forming lnGaN, lnGaAs or lnGaP on the surface of a substrate. lt is alleged that a concentration of the precursor gases may be tailored for forming a |||-V semiconductor material having a desired composition.
However, ;;š__requires temperatures of the metal halide precursors of about 500 °C to about 1000 °C, and the deposition system should be maintained at temperatures in the range from about 350 °C to about 750 °C. Therefore, due to the high temperatures used, there may be a risk of encountering problems of formation of ln droplets and dividing up to GaN and lnN similar to the problems associated with a continuous CVD process. Furthermore, controlling the concentration of the respective precursors gases may be very difficult in practice. Therefore, it may be difficult to tailor the atomic ratio of the metals in the deposited film.
SUMMARY The object of the present invention is to provide a method for producing a film of a ternary or quaternary compound, which method results in a stable film and allows tailoring of the composition of the ternary or quaternary compound.
The object is achieved by the subject-matter of the appended independent claim(s). ln accordance with the present disclosure, a method for producing a film of a ternary or quaternary compound on a surface of a substrate by atomic layer deposition is provided. The method comprises co-evaporating a first metal or metalloid precursor and a second metal or metalloid precursor so as to form a mixed precursor vapor. The first metal or metalloid precursor comprises a first metal or metalloid selected from group 13 or group 14 of the periodic table. The second metal or metalloid precursor comprises a second metal or metalloid selected from group 13 or group 14 of the periodic table. The method further comprises subjecting the surface of the substrate to the mixed precursor vapor in a first precursor pulse, and thereafter subjecting the surface of the substrate to a third precursor in a second precursor pulse. The third precursor comprises a third element selected from group 15 or 16 of the periodic table.
The present method utilizes atomic layer deposition for producing a film of a ternary or quaternary compound. Thereby, stable films may be made at relatively low temperatures compared to for example a conventional continuous CVD process. This in turn reduces the risk for e.g. phase separation or other defects (such as resulting from liquid metal droplets during deposition) in the film which may sometimes occur in a continuous CVD process. Moreover, the present method also provides all the other advantages of atomic layer deposition, such as conformity, excellent control of growth thickness, and ability to deposit on surfaces with complex topography.
The fact that the present method comprises co-evaporating the first metal or metalloid precursor and the second metal or metalloid precursor provides the possibility for an easy and accurate control of the ratio of the first metal or metalloid to the second metal or metalloid in the mixed precursor vapor, which in turn enables easy and accurate control of the atomic ratio of the first and second metals or metalloids in the film of the compound on the surface of the substrate. Furthermore, the present method leads to a mixing of the first metal or metalloid and the second metal or metalloid not only in the growth direction but also in-plane of the deposited ternary or quaternary compound. ln view of the above-mentioned lower risk for defects and the in-plane mixing of the first metal or metalloid and the second metal or metalloid, the present method also results in a film having improved quality.
The method may comprise mixing a powder of the first metal or metalloid precursor with a powder of the second metal or metalloid precursor. Thereby, a mixed powder comprising the first metal or metalloid precursor and the second metal or metalloid precursor is provided. Evaporation of said mixed powder thereby leads to the co-evaporation of the first metal or metalloid precursor and the second metal or metalloid precursor. Furthermore, mixing a powder of the first metal or metalloid precursor with a powder of the second metal or metalloid precursor further improves the control of the relative amount thereof in the mixed precursor vapor, which in turn facilitates producing a film of a ternary or quaternary compound having a tailored composition.
The first metal or metalloid precursor may comprise a first metal-organic compound. Furthermore, the second metal or metalloid precursor may comprise a second metal-organic compound. Thereby, the co-evaporation of the first metal or metalloid precursor and the second metal or metalloid precursor is further facilitated.
The first metal or metalloid precursor may have a vapor pressure at least overlapping with the vapor pressure of the second metal or metalloid precursor. Thereby, the co-evaporation of the first metal or metalloid precursor and the second metal or metalloid precursor as well as the control of the respective amounts thereof in the mixed precursor vapor may be further facilitated.
The first metal or metalloid precursor may comprise the same ligand as the second metal or metalloid precursor. Thereby, the risk of unwanted interaction between the precursors in the mixed precursor vapor may be reduced, which in turn improves the quality of the film on the surface of the substrate. Furthermore, the co-evaporation of the precursors is facilitated since the volatility and evaporation/sublimation temperature of the different precursors may be similar. This in turn further facilitates the control of the relative amount of the first metal or metalloid precursor and the second metal or metalloid precursor in the mixed precursor vapor, and thus also in the resulting film.
The first metal or metalloid precursor and the second metal or metalloid precursor may each comprise a ligand selected from the group consisting of triazenide, amidinate, guanidinate, and formamidinate. Such precursors are generally solids at room temperature, which facilitates the handling thereof. Moreover, such precursors generally have a relatively low sublimation temperature. Therefore, such precursors _¿_=.gj_§=,__especially suitable for use in the present method.
The method may further comprise controlling the temperature of the substrate to be from 100 °C to 500 °C, preferably from 180 °C to 400 °C, during the first precursor pulse¿»,» »_.» providing enough energy for the precursors of the mixed precursor vapor to react on the surface of the substrate and at the same time ga higher temperature of the substrate than the evaporation/sublimation temperature of the precursors to avoid condensation. Furthermore, when the temperature of the substrate is higher than 500 °C, the risk of possible defects in the film may increase. Moreover, the composition of the ternary or quaternary compound may be controlled by accurately controlling the temperature of the substrate.
The co-evaporation of the first metal or metalloid precursor and the second metal or metalloid precursor may be performed at a temperature of less than 250 °C, preferably less than 200 °C. Thereby, the risk of decomposition of the precursors before reaching the substrate surface is minimized. Furthermore, this enables a lower temperature of the mixed precursor vapor than the temperature of the substrate in the deposition chamber, which in turn reduces the risk for condensation of the precursors on the substrate.
The method may further comprise controlling the relative amount of the first metal or metalloid precursor and the second metal or metalloid precursor before the co-evaporation evaporation of the first metal or metalloid precursor and the second metal or metalloid precursor in dependence of a desired relative amount of the first metal or metalloid and the second metal or metalloid in ternary or quaternary compound. Thereby, the composition of the ternary or quaternary compound may easily be tailored to a desired composition since it affects the composition of the mixed precursor vapor The method may further comprise co-evaporating a dopant precursor with the first metal or metalloid precursor and the second metal or metalloid precursor such that the mixed precursor vapor comprises the dopant. Thereby, the ternary or quaternary compound may be doped with a dopant in a controllable manner.
The method may comprise co-evaporating a fourth metal or metalloid precursor with the first metal or metalloid precursor and the second metal or metalloid precursor such that the mixed precursor vapor further comprises the fourth metal or metalloid precursor. Thereby, a quaternary compound may be achieved by means of the present method.
The ternary or quaternary compound may be a compound selected from the group comprising indium gallium nitride(|nXGa1.XN), indium gallium phosphide(|nXGa1.XP), indium gallium arsenide (InXGaHAs), aluminum gallium nitride(AlXGa1.XN), aluminum gallium phosphide(AlXGa1.XP), aluminum gallium arsenide(AlXGa1.XAs), indium aluminum gallium nitride(|nXAlyGa1.X.yN), indium gallium nitride phosphide (InXGaHNZPH), and silicon germanium nitride(SiXGe1.XN).
The method is particularly suitable for a producing film of a ternary or quaternary compound comprising indium and gallium which have been difficult to produce by previously known methods. Thus, according to one embodiment of the herein described method, the first metal or metalloid precursor comprises indium and the second metal or metalloid precursor comprises gallium. ln such a case, co-evaporating the first metal or metalloid precursor and the second metal or metalloid precursor so as to form a mixed precursor vapor may suitably be performed at a temperature of from 90 °C to 170 °C, and the temperature of the substrate when subjected to the mixed precursor vapor may be from 180 °C to 400 °C. Optionally, the first metal or metalloid precursor and the second metal or metalloid precursor may in such a case be provided, before the co-evaporation, such that the ratio |n:Ga is from 10:90 to 90: BRIEF DESCRIPTION OF DRAWINGS Fig. 1a schematically illustrategg ordering of atoms in a lnGaN produced by ALD in accordance with a previously known method, Fig. 1b schematically illustratef; a desired ordering of atoms in lnGaN, Fig. 2 schematically illustrates a cross sectional view of an apparatus for ALD which may be used in the herein described method, Fig. 3 represents a flowchart schematically illustrating one exemplifying embodiment of the method for producing a film of a ternary or quaternary compound on a surface of substrate by atomic layer deposition according to the present disclosure, Fig. 4 illustrates experimental XRD results of lnGaN films when the temperature of a container comprising the mixture of metal precursors was changed from 110 °C to°C.
DETAILED DESCRIPTION The invention will be described in more detail below with reference to exemplifying embodiments and the accompanying drawings. The invention is however not limited to the exemplifying embodiments discussed and/or shown in the drawings, but may be varied within the scope of the appended claims. Furthermore, the drawings shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate the invention or features thereof. ln the present disclosure, the term "co-evaporating" is considered to mean bringing a plurality of substances in a liquid or solid state into a gas state. The prefix "co-" is here used for the purpose of clarifying that said bringing into àgas state is performed simultaneously for the plurality of substances. "Co-evaporation" thus encompasses both co-evaporation and co-sublimation in the present disclosure, unless explicitly disclosed otherwise.
The present disclosure provides a method for producing a film of a ternary or quaternary compound on a surface of substrate by atomic layer deposition. More specifically, the present disclosure provides a method for producing a film of a ternary or quaternary compound comprising at least a first metal or metalloid selected from group 13 or group 14 of the periodic table, a second metal or metalloid selected from group 13 or group 14 of the periodic table, and a third element selected from group 15 or 16 of the periodic table. The film of the ternary or quaternary compound may be doped with one or more dopants, if desired, as will explained further below.
The present method is an atomic layer deposition (ALD) method. ALD is a low temperature time- resolved form of chemical vapor deposition (CVD) in which the different precursors are pulsed into the deposition chamber sequentially. This process allows for the deposition of the resulting film to be governed by surface chemical reactions. By repeating the cycle of pulses, films with a highly controlled thickness may be deposited. Furthermore, the films have excellent large-area uniformity and conformity.
The present method for producing a film of a ternary or quaternary compound on a surface of a substrate comprises a step of co-evaporating at least a first metal or metalloid precursor and a second metal or metalloid precursor so as to form a mixed precursor vapor. The first metal or metalloid precursor comprises a first metal or metalloid selected from group 13 or group 14 of the periodic table. The second metal or metalloid precursor comprises a second metal or metalloid (other than the first metal or metalloid) selected from group 13 or 14 of the period table. ln the following, the first metal or metalloid precursor is simply referred as the ”first precursor" and the second metal or metalloid precursor is simply referred as the ”second precursor".
The method further comprises a step of subjecting a surface of a substrate to the mixed precursor vapor in a first precursor pulse, thereby adsorbing atoms of the first metal or metalloid and atoms of the second metal or metalloid on the surface of the substrate. Thereafter, the method comprises subjecting the surface of the substrate to a third precursor in a second precursor pulse. The third precursor comprises a reactive third element selected from group 15 or group 16 of the periodic table. Thereby, the third element reacts with the atoms of the first metal or metalloid and the second metal or metalloid present on the surface of the substrate, whereby a layer of the compound is formed on the surface of the substrate. The third element may be a metalloid or a non-metal.
The first and second precursor pulses may be separated by a first purge pulse wherein any excess of the mixed precursor vapor is removed. Similarly, a second purge pulse may be performed after the second precursor pulse in order to remove any excess of the third precursor. The first precursor pulse, the first purge pulse, the second precursor pulse and the second purge pulse mayjointly be referred to as a growth cycle. Said growth cycle may be repeated until a desired thickness of the film is achieved.
When using the present method for producing a film of a ternary compound, the first precursor and the second precursor are co-evaporated. ln such a case, the mixed precursor vapor may essentially consist of the first precursor and the second precursor, optionally with the presence of one or more dopants if desired. However, if producing a film of a quaternary compound, the method may comprise co-evaporating the first precursor, the second precursor and a fourth precursor so as to form the mixed precursor vapor. ln such a case, the mixed precursor vapor may essentially consist of the first precursor, the second precursor and the fourth precursor, optionally with the presence of one or more dopants. The fourth precursor may be metal or metalloid precursor comprising a third metal or metalloid selected from group 13 or group 14 of the period table. Alternatively, the fourth element of the quaternary compound may be introduced together with the third precursor in the second precursor pulse. ln the latter case, the fourth precursor, introduced with the third precursor during the second precursor pulse, comprises an element selected from selected from group 15 orof the periodic table (other than the third element).
By means of the present method, it is for example possible to achieve in-plane mixing of the first metal or metalloid and the second metal or metalloid (compare with Figure lb). This is in contrast to the previously proposed method comprising first saturating the surface of the substrate with a first metal, followed by reaction with nitrogen and thereafter saturating the surface with a second metal, which to a layered structure of the metal atoms (compare with Figure la). Moreover, the present method enables an easy and accurate control of the ratio of the first metal or metalloid and the second metal or metalloid in the deposited film. Therefore, the present method provides the possibility for tailoring the composition of the ternary or quaternary compound to a desired composition suitable for an intended use. By way of example, it is possible to tailor the composition of a ternary or quaternary compound to achieve a desired bandgap.
The present method may for example be used to produce doped or un-doped films of compounds selected from the group comprising indium gallium nitride (InXGa 1.XN),indium gallium phosphide (|nXGa1.XP),indium gallium arsenide(|nXGa1.XAs), aluminum gallium nitride(AlXGa1.XN), aluminum gallium phosphide(AlXGa1.XP), aluminum gallium arsenide(AlXGa1.XAs), indium aluminum gallium nitride(|nXAlyGa1.X.yN), indium gallium nitride phosphide (InXGaHNZPH), and silicon germanium nitride (sixGel-XN).
The ternary or quaternary compound may be a semiconductor. For example, the ternary or quaternary compound may be a so called |||-V semiconductor material.
As previously mentioned, the present method comprises co-evaporating a first precursor, a second precursor and optionally a fourth precursor so as to form a mixed precursor vapor. For the purpose of enabling said co-evaporation, the method may comprise an initial step of mixing a powder of the first precursor with a powder of the second precursor, and optionally a powder of the fourth precursor. ln other words, the first precursor, the second precursor and, if present, the fourth precursor may be in solid form when they are mixed. Thereby, a powder mixture of the precursors is provided. Evaporation of the powder mixture leads to co-evaporation of the first precursor, the second precursor and, if present, the fourth precursor. Mixing of the powders of the different precursors enables an easy control of the respective amounts, for example by simply weighing the amounts of the respective powders, which in turn enables an accurate control of the respective amounts of the first metal or metalloid, the second metal or metalloid and, where applicable the fourth metal or metalloid element. Thereby, when evaporating the powder mixture, the resulting mixed precursor vapor may have a desired composition. The composition of the mixed precursor vapor remain when introduced in a deposition chamber of the ALD apparatus in the first precursor pulse. Thus, the co-evaporation ensures accurate control of the composition of the mixed precursor vapor to which the substrate is subjected to. lt should here be noted that the present method is not limited to mixing of the precursors before evaporation, although this is preferred. The first precursor, the second precursor and the optional fourth precursor (if it is to be introduced during the first precursor pulse) may be provided in an unmixed form as long as they may be co-evaporated. Co-evaporation provides the advantage, compared to for example a case of mixing precursor vapors, of enabling a considerable better control of the composition of the mixed precursor vapor since it does not rely on controlling gas flows etc. for obtaining a desired gas composition.
The first precursor, the second precursor and, if present, the fourth precursor (if it is to be introduced during the first precursor pulse) may suitably be selected such that they are in solid form ;_room temperature, thereby facilitating the handling thereof as well as the step of mixing the powders of the respective precursors. This may be achieved by the respective precursors each comprising an appropriately selected ligand.
According to one embodiment of the present disclosure, the first precursor may comprise a first metal-organic compound. Similarly, the second metal precursor may comprise a second metal- organic compound. The fourth precursor, where applicable, may also comprise a metal-organic compound. Metal-organic compounds are a class of materials that, in addition to metal, contain organic ligands. ln contrast to organometallic compounds, which also comprise organic ligands, metal-organic compounds lack direct metal-carbon bonds. The ligand of the metal-organiccompound may be selected to achieve a desired volatility and evaporation/sublimation temperature. When the first precursor and the second precursors are metal-organic compounds, lower temperatures may be used for the formation of the mixed metal precursor vapor compared to if, for example, metal halides would be used. Examples of suitable ligands include, but are not limited to, triazenide, amidinate, guanidinate, or formamidinate. These exemplified ligands are previously known in metal precursors used for producing films of binary compounds by atomic layer deposition. lt should be noted that the precursors may alternatively comprise organometallic compounds, if desired.
For the purpose of avoiding unwanted reactions or other problems in the co-evaporation step, the first precursor may suitably comprise the same ligand as the second precursor. Thereby, essentially no interaction between the first precursor and the second precursor will occur in the mixed precursor vapor. Naturally, in case a fourth precursor is to be co-evaporated with the first precursor and the second precursor, said fourth precursor may suitably comprise the same ligand as the first precursor and the second precursor.
For the purpose of illustration, one example of a suitable precursor in case the first metal is indium is a |n(|||) triazenide precursor. This precursor is previously known from O'Brien at al., "ln Situ Activation of an Indium(III) Triazenide Precursor for Epitaxial Growth of lndium Nitride by Atomic Layer Deposition", Chem. Mater. 2020, 32, 4481-4489. Another example of a suitable precursor, in this case comprising Ga, is a Ga(|||) triazenide precursor. This precursor is described in Rouf et al., "Hexacoordinated Gallium(III) Triazenide Precursor for Epitaxial Gallium Nitride by Atomic Layer Deposition", Chi. Mater., 2021, https://pubs.acs.org/doi/abs/10.1021/acs.chemmater.1c00244. Both the |n(|||) triazenide precursor and the Ga(|||) triazenide precursor are solids at room temperature. Other examples of suitable precursors include germanium(||) amidinate and tin(||) triazenide. lt should however be noted that the above-mentioned precursors are merely examples of possible precursors, and the present disclosure is not limited thereto.
The method may further comprise controlling the temperature of the substrate, at least during the first precursor pulse. More specifically, the method may comprise controlling the temperature of the substrate, at least during the first precursor pulse, to be higher than the temperature of ígšfgggvmixed precursor vapor to which the substrate is subjected. Thereby, the risk of condensation of the precursors on the substrate is minimized. The temperature of the su bstrate may for example be controlled to be from 100-500 °C (including the end vales of the range), preferably 180-400 °C (including the end values). The appropriate temperature of the substrate is dependent on thetemperature at which the precursors are co-evaporated. Therefore, lower sublimation temperatures of the first precursor, the second precursor and the optional fourth precursor allows lower su bstrate tempefatUfeS.
As previously mentioned, the present method enables tailoring the composition of the ternary or quaternary compound as desired as well as ensures that the respective elements of the compound are mixed both in the growth direction (i.e. perpendicular to the surface of the substrate) and in- plane. The resulting composition of the film of the ternary or quaternary compound depends on a plurality of parameters that may be easily controlled. Firstly, the resulting composition naturally depends on the precursors used as well as the optional presence of one or more dopants. Secondly, the resulting composition depends on the relative amount of the precursors when co-evaporated. Thirdly, the resulting composition may depend on the temperature at which the precursors are co- evaporated. This is in turn to some extent affected by the precursors used. For example, if one of the precursors has a lower sublimation temperature than another of the precursors, the mixed precursor vapor will likely comprise a higher amount of the precursor having a lower sublimation temperature, at least if assuming that the precursors are present in essentially the same amount. Lastly, the temperature of the substrate when subjected to the mixed precursor vapor in the first precursor pulse may affect the relative amount of the first metal or metalloid, the second metal or metalloid and, if applicable, the third metal or metalloid (resulting from the fourth precursor). This is due to reactivity enhancement of the different precursors upon changing the temperature. Upon increasing the temperature, the precursor or precursors with higher reactivity will lead to higher amount of the metals or metalloids that the precursors contain or vice versa. Thus, tailoring the resulting composition may be performed by altering the above-mentioned parameters so as to arrive at the desired composition of the film of the ternary or quaternary compound. This may for example be made by conventional experimental tests for the purpose of selecting the appropriate parameters depending on the desired composition of the film of the ternary or quaternary compound.
The substrate on which the film is deposited may be any previously known substrate onto which a compound may be deposited by means of atomic layer deposition. Examples of suitable substrates include, but are not limited to, a Si substrate, a SiC substrate, a sapphire (AlzOg) substrate, or a GaN substrate. A substrate having the same crystal structure as the crystal structure of the ternary or quaternary compound may be used. Thereby, the possibility for an epitaxial growth of the film is facilitated. For example, 4H-SiC (0001), 6H-SiC (0001) or sapphire (0001) are examples of suitable substrates in the case of producing an lnGaN film.The present method may further be utilized for producing structures comprising a plurality of films on the surface of the substrate, wherein at least a first film comprises the ternary or quaternary compound. Such structures may further comprise a second film comprising a different compound than the first film. The second film may for example comprise a binary compound, or a ternary or quaternary compound having a different composition than the ternary or quaternary compound of the first film. This type of structures may for example be achieved by changing the precursors in different growth cycles during the deposition of the structure. ln other words, such a structure may, if desired, be produced in a single deposition chamber of an ALD apparatus without removing the substrate therefrom between deposition of the different films.
Figure 2 schematically illustrates a cross sectional view of an apparatus 1 for atomic layer deposition (ALD) wherein the present method may be performed. The present disclosure is however not limited to the apparatus shown in Figure 2. ln fact, the present method may be performed in any previously known apparatus for atomic layer deposition as long as the apparatus allows for co-evaporation of a first metal or metalloid precursor and a second metal or metalloid precursor so as to form a mixed precursor vapor.
The apparatus 1 comprises a deposition chamber 2. A vacuum pump 3 is connected to the deposition chamber 2. The vacuum pump 3 is configured to control the atmosphere inside the deposition chamber 2. Furthermore, a substrate holder 4 is arranged inside the deposition chamber 2. The substrate holder 4 is configured to hold a substrate 5, onto which a film should be deposited. The substrate holder 4 may comprise a heating element (not shown) for the purpose of controlling the temperature of the substrate holder 4 and thereby also the temperature of the substrate.
The apparatus 1 further comprises a plasma source 6 configured to generate a plasma 6a inside the deposition chamber 2 during at least a portion of a film deposition process. Moreover, the apparatus 1 comprises an evaporation or sublimation chamber 7 connected to the deposition chamber 2 via a first conduit 8. The first conduit 8 may typically comprise a first valve 9 configured to control the introduction of vapor from the evaporation or sublimation chamber 7 to the deposition chamber 2. More specifically, the first valve 9 may be configured to control the flow and the duration of a precursor pulse during which gas comprising one or more precursors are introduced into the deposition chamber The evaporation or sublimation chamber 7 is configured to comprise a container 11 configured to hold one or more precursors 10 to be evaporated/sublimated. The evaporation or sublimationchamber 7 further comprises a heating element (not shown) configured to control the temperature inside the evaporation or sublimation chamber 7 and/or the temperature of the container 11. Such a heating element may for example be arranged so as to be in contact with the container 11, or alternatively be comprised in the container For the purpose of facilitating transport of vapor from the evaporation or sublimation chamber 7 to the deposition chamber 2, the apparatus may further comprise a second conduit 12 configured to introduce a transport gas/carrier gas into the evaporation or sublimation chamber. The second conduit 12 may comprise a second valve 13 configured to control the flow of such a transport gas/carrier gas into the evaporation chamber Although not shown in Figure 2, the apparatus 1 may comprise further conduits connected to the deposition chamber 2 for the purpose of enabling introduction of other gaseous species, if desired.
Figure 3 represents a flowchart schematically illustrating one exemplifying embodiment of the method for producing a film of a ternary or quaternary compound on a surface of substrate by atomic layer deposition according to the present disclosure.
The method may comprise a step S101 of mixing a first metal or metalloid precursor, a second metal or metalloid precursor and optionally a fourth metal or metalloid precursor. ln step S101, the first, second and fourth precursors may be present in solid form, such as in powder form. ln case the film should comprise one or more dopants, one or more powders comprising the one or more dopants may be mixed with the precursors in step S The method comprises a step S102 of co-evaporating the first metal or metalloid precursor, the second metal or metalloid precursor and, where applicable, the fourth metal or metalloid precursor. Thereby, a mixed precursor vapor is obtained. The step of co-evaporation may be performed in an evaporation or sublimation chamber, such as the evaporation or sublimation chamber 7 of the apparatus 1 shown in Figure The method further comprises a step S103 of subjecting a surface of a substrate to the mixed precursor vapor. This is performed by introducing the mixed precursor vapor into a deposition chamber, wherein the substrate is arranged, during a first precursor pulse. The deposition chamber may for example be the deposition chamber 2 of the apparatus 1 shown in Figure 2. Subjecting the substrate to the mixed precursor vapor leads to atoms of the first metal or metalloid, atoms of the second metal or metalloid, and where applicable, atoms of the third metal being adsorbed on the surface of the substrate.
After step S103, the method may comprise a step S104 of purging the deposition chamber. Thereby, the excess of the mixed precursor vapor may be removed from the deposition chamber.
Thereafter, the method comprises a step S105 of subjecting the substrate to a third precursor. This is performed by introducing the third precursor into the deposition chamber during a second precursor pulse. The third precursor comprises an element selected from group 15 or group 16 of the periodic table. Thereby, said element selected from group 15 or 16 reacts with the atoms adsorbed on the surface of the substrate during the first precursor pulse, thereby forming the ternary or quaternary compound.
After step S105, the method may comprise a step S106 of purging the deposition chamber. Thereby, excess of the third precursor may be removed from the deposition chamber.
Thereafter, the method may be reverted back to step S103 for a subsequent growth cycle comprising the steps S103 and S105, until a desired thickness of the film has been obtained.
As previously mentioned, the herein described method may be used for producing films of various ternary or quaternary compounds on surfaces of substrates. The method is especially advantageous for producing films of ternary or quaternary compounds which may be difficult to produce by other methods with sufficient quality. One particular example thereof es :gternary or quaternary compounds comprising two or three metals selected from group Thus, according to one aspect of the present disclosure, a method for producing a film of a ternary or quaternary compound, comprising at least two metals from group 13 of the periodic table, on a surface of a substrate is provided. The method according to said aspect comprises: co-evaporating a first metal precursor and a second metal precursor so as to form a mixed precursor vapor, wherein the first metal precursor comprises a first metal selected from group 13 of the periodic table, and the second metal precursor comprises a second metal selected from group 13 of the periodic table; subjecting the surface of the substrate to the mixed precursor vapor in a first precursor pulse; andthereafter subjecting the surface of the substrate to a third precursor in a second precursor pulse, wherein the third precursor comprises a third element selected from group 15 or 16 of the periodic table. Preferably, the third element is selected from group 15, such as nitrogen, phosphorus or arsenic.
Experimental results Films of lnGaN were deposited in a Picosun R-200 ALD system equipped with a Litmas Remote lnductively Coupled Plasma Source. The system used a base pressure of 400 Pa with continuous NZ (99.999%, further purified with a getter filter to remove moisture) flow through the deposition chamber. Si (100) substrates were used, and were cut into 1.5><1.5 cm pieces and Si (100) were used without further cleaning. The su bstrates were loaded into the deposition chamber onto a heated substrate holder and the system was heated to 450 °C for 120 minutes before each run with a continuous NZ flow (300 sccm) to minimize the oxygen content in the chamber. ln the experiments, |n(|||) triazenide was used as an ln precursor and Ga(|||) triazenide was used as a Ga precursor. Approximately 800 mg in total of the ln precursor and the Ga precursor was added to a container (here a glass vial in a stainless-steel bubbler without a dip-tube for incoming carrier gas). Mixing of the ln precursor and the Ga precursor was performed by simply stirring manually with a spoon. When investigating different precursors ratios simply different amount of the ln precursor and Ga precursor, respectively, was weighted to obtain the desired precursor mixture in the container. The temperature of the container was varied for some experiments otherwise it was set at 130 °C with a NZ flow of 100 sccm to aid transporting the precursor vapor into the deposition chamber. A 10 second precursor pulse was used for the mixed precursor vapor. Thereafter, a 10 second NZ purge was used said precursor pulse. The NH3 (AGA/Linde, 99.999 %) plasma used as the nitrogen source was an Ar (99.999 %, further purified with a getter filter to remove moisture)/NH3 (100/75 sccm) mixture, ignited using a plasma power of 2800 W. A plasma pulse of 12 seconds followed by a 10 second purge was used with the above parameters unless otherwise stated. The growth cycle was repeated 1000 times. ln the first screening, different temperatures of the container containing both the Ga and ln precursors (molecules) were investigated. The deposition temperature, i.e. the temperature of the substrate, was set to 350°C and the ln and Ga precursors were mixed in a 1:1 ratio, same amount (at.-%) of ln as Ga. The composition of the resulting film was analyzed by XPS (X-ray photoelectron spectroscopy) and the results are shown in Table 1 below.Table 1. XPS data of the film when varying the container temperature (sublimation temperature) Container temp. ln (at.%) Ga (at.%) (°C) 90 72110 67120 65130 80140 87150 55170 65The crystallinity of the films was further analyzed by XRD (X-ray diffraction) and it was found that the films are crystalline reviled by the (002) plane. When changing the container temperature from 100 °C to 150 °C, a shift in the (002) peak appear towards higher Ztheta values indicating higher Ga content in the film, see Figure 4. This is in line with the XPS data shown in Table 1 were the Ga ratio increases when varying the temperature from 110°C to 150°C. The films are x-ray amorphous (no peak in the XRD) when having the container at 90°C.
Then different deposition temperatures, i.e. temperature of the substrate, were investigated, and the composition of the resulting films was analyzed by XPS. The result is shown in Table 2. The ratio between the ln and Ga precursor was still 1:1 in the container and the container temperature was set to 130°C for these set of experiments. The results show that when lowering the deposition temperature, more Ga is found in the film and a nearly 1:1 ratio of ln and Ga may be achieved. The films deposited at 250°C and 200°C were found to be x-ray amorphous, the other films were found to be crystalline.Table 2. Composition analysed by XPS of the film when varying the deposition temperature.
Deposition Temp. (°C) ln (at.%) Ga (at.%) 400 90380 98350 80250 59200 52Furthermore, the deposition temperature was set to 350°C and the container temperature to 130°C while different ratios of the ln and Ga precursor were mixed in the container to analyze the effect on the film composition. The result is presented in Table 3. When the premixed precursor in the container has a higher ratio ln compared to Ga, the resulting film have more or less the same composition as the premixed ratio. However, the Ga content in the film does not exceed 48 at% even when the premixed precursor ratio contains majority of Ga precursor. All the different ratios showed crystalline film analyzed by XRD.
Table 3. Different ratio of the precursors premixed before the deposition and the resulting film composition.
Container ratio ln (at.%) Ga (at.%) Ga:|n :90 9930:70 7250:50 8070:30 7190:10 52Moreover, the experimental test of a film produced from 50:50 ratio of Ga:|n using a container temperature of 130 °C and a deposition temperature 350 °C was repeated but for a different substrate, namely 4H-SiC (0001). The sample was investigated by selective area diffraction (SAED) in a transmission electron microscope. An epitaxial relationship between the lnGaN film and the SiC substrate was found.

Claims (1)

1. A method for producing a film of a ternary or quaternary compound on a surface of a substrate by atomic layer deposition, the method comprising: co-evaporating (S102) a first metal or metalloid precursor and a second metal or metalloid precursor so as to form a mixed precursor vapor, wherein the first metal or metalloid precursor comprises a first metal or metalloid selected from group 13 or group 14 of the periodic table, and the second metal or metalloid precursor comprises a second metal or metalloid selected from group 13 or group 14 of the periodic table; subjecting (S103) the surface of the substrate to the mixed precursor vapor in a first precursor pulse; and thereafter subjecting (S105) the surface of the substrate to a third precursor in a second precursor pulse, wherein the third precursor comprises a third element selected from group 15 or 16 of the periodic table. The method according to claim 1, comprising mixing (S101) a powder of the first metal or metalloid precursor with a powder of the second metal or metalloid precursor. The method according to any one of claims 1 or 2, wherein the first metal or metalloid precursor comprises a first metal-organic compound, and the second metal or metalloid precursor comprises a second metal-organic compound. The method according to any one of the preceding claims, wherein the first metal or metalloid precursor has a vapor pressure at least overlapping with the vapor pressure of the second metal or metalloid precursor. The method according to any one of the preceding claims, wherein the first metal or metalloid precursor comprises the same ligand as the second metal or metalloid precursor. The method according to any one of the preceding claims, wherein the first metal or metalloid precursor and the second metal or metalloid precursor each comprise a ligand selected from the group consisting of triazenide, amidinate, guanidinate, and formamidinate. The method according to any one of the preceding claims, further comprising controlling the temperature of the substrate to be from 100 °C to 500 °C, preferably from 180 °C to 400 °C, during the first precursor pulse. The method according to any one of the preceding claims, wherein co-evaporation of the first metal or metalloid precursor and the second metal or metalloid precursor is performed at a temperature of less than 250 °C, preferably less than 200 °C. The method according to any one of the preceding claims, further comprising controlling the relative amount of the first metal or metalloid precursor and the second metal or metalloid precursor before the co-evaporation evaporation of the first metal or metalloid precursor and the second metal or metalloid precursor in dependence of a desired relative amount of the first metal or metalloid and the second metal or metalloid in ternary or quaternary compound. The method according to any one of the preceding claims, further comprising co-evaporating a dopant precursor with the first metal or metalloid precursor and the second metal or metalloid precursor such that the mixed precursor vapor comprises the dopant. The method according to any one of the preceding claims, further comprising co-evaporating a fourth metal or metalloid precursor with the first metal or metalloid precursor and the second metal or metalloid precursor such that the mixed precursor vapor further comprises the fourth metal or metalloid precursor. The method according to any one of the preceding claims, wherein the ternary or quaternary compound is a compound selected from the group comprising indium gallium nitride(|nXGa1. XN), indium gallium phosphide(|nXGa1.XP), indium gallium arsenide(|nXGa1.XAs), aluminum gallium nitride(AlXGa1.XN), aluminum gallium phosphide(AlXGa1.XP), aluminum gallium arsenide(AlXGa1.XAs), indium aluminum gallium nitride(|nXAlyGa1.X.yN), indium gallium nitride phosphide (InXGaHNZPH), and silicon germanium nitride(SiXGe1.XN). The method according to any one of the preceding claims, wherein the first metal or metalloid precursor comprises indium, the second metal or metalloid precursor comprises gallium, co-evaporating the first metal or metalloid precursor and the second metal or metalloid precursor so as to form a mixed precursor vapor is performed at a temperature of from 90 °C to 170 °C, and the temperature of the substrate during the first precursor pulse is from 180 °C to°C.14. The method according to claim 13, wherein the first metal or metalloid precursor and the second metal or metalloid precursor are provided before the co-evaporation such that the ratio |n:Ga is from 10:90 to 90:10.
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