Preparation of group iii and lanthanide element containing precursors and their application to vapor depositions

Abstract

Disclosed are chemicals suitable as vapor phase precursors for forming Y2O3 and SC2O3 and other materials. The chemicals have the common structure: in which R1 and R3 are Hydrogens, R2 are the same and are selected from C1 to C3 alkyl groups, and M is Yttrium or Scandium.

Description

PREPARATION OF GROUP III AND LANTHANIDE ELEMENT CONTAINING PRECURSORS AND THEIR APPLICATION TO VAPOR DEPOSITIONSCross Reference to Related ApplicationsThis application claims priority to US Provisional Patent Application Nos. 63 / 662,198, filed June 20, 2024, and 63 / 727,437, filed December 3, 2024, the entire contents of which are incorporated herein by reference.Technical FieldThe technical field is volatile lanthanide chemicals suitable as vapor deposition precursors.Background ArtIt is well established in the state of the art to use various metalorganic coordination ligands such as cyclopentadienyls and amidines, formamidines, and guanidines. Sengupta, D., A. Gomez-Torres, and S. Fortier. "Guanidinate, Amidinate, and Formamidinate Ligands." Comprehensive Coordination Chemistry 3 (2021 ): 366- 405.Lanthanides (Ln) are no exception to this. Heteroleptically coordinated Ln metals are well documented, including those with cyclopentadienyls and amidines, formamidines, and guanidines. For example, US20090302434A1 describes this genus broadly at

[0055] :• wherein Ln represents the lanthanide group, which includes Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; R1is selected from H or a C1 -C5 alkyl chain; R2is selected from H or a C1 -C5 alkyl chain; R4is selected from H, a C1-C5 alkyl chain, and NR'R", wherein R' and R" are independently selected from a C1 -C5 alkyl chain; m is selected from 1 or 2; and n is selected from 1 or 2.Numerous sub-genus’s and species within this large class of heteroleptically coordinated Ln metals have been synthesized and evaluated for their suitability as vapor phase deposition precursors in semiconductors for LnOs materials and other applications.W02022250400A1 discloses cyclopentadienyl guanidinate Yttrium molecules:In the broadest embodiment, W02022250400A1 includes unsubstituted cyclopentadienyls. However the preferred genus and all identified species include an alkyl group on the cyclopentadienyl (Ri and R2 are C2-C5). And of course the genus is limited to guanidinate containing molecules. Another preferred element is ligand asymmetry, the reason for preference of an alkyl group on the cyclopentadienyl. “The metal precursor compound of the present invention can maintain a liquid state at room temperature due to structural features including an asymmetric cyclopentadiene ligand and a guanidinate ligand, and satisfies sufficient volatility and excellent chemicalthermal stability.”US20220325411A1 discloses cyclopentadienyl amidinate Yttrium molecules:• Chemical Formula I:.[ChemicalFormula I]• wherein, in the above Chemical Formula I, M is selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu,• R1is an n-propyl group (nPr) or iso-propyl group ('Pr), and the Cp is a cyclopentadienyl group.Again, the cyclopentadienyl ligands are substituted with an alkyl group.US20230040334A1 discloses cyclopentadienyl amidinate or formamidinate Yttrium molecules [General Formula (I)]:• wherein, R1is a C1 -C5 linear or branched alkyl group, R2and R3are each a C1 -C8 linear or branched alkyl group, R2having a structure different than that of R3, R4is a hydrogen atom or a C1-C5 linear or branched alkyl group, and n is an integer of 0 to 5.• In an implementation, in General Formula (I), n may be suitably selected according to a purpose of applying a compound represented by General Formula (I). In a manufacturing process of a thin film, which includes a process of vaporizing the compound represented by General Formula (I), the compound having a relatively high vapor pressure and a relatively low melting point may be used. In an effort to help ensure that the compound represented by General Formula (I) exhibits a lower melting point and a higher vapor pressure, R1 may be, e.g., a C1 -C3 alkyl group. In an implementation, R1 may be, e.g., a methyl group or an ethyl group.US20230040334A1 describes both amidinate and formamidinate embodiments and embodiments with substituted or unsubstituted cyclopentadienyl groups (Formulas 1 , 2, 4 and 5, for example). However, the preferred embodiments “to help ensure that the compound represented by General Formula (I) exhibits a lower melting point and a higher vapor pressure” are those with a C1-C3 alkyl group on the cyclopentadienyl groups. This is experimentally demonstrated in Table 1 for the chemicals of Formulae 13-14 (solids) compared to Formulae 16-17 (liquids). Again, ligand asymmetry is used to reduce melting point and enhance volatility: “R2and R3are each a C1 -C8 linear or branched alkyl group, R2having a structure different than that of R3”.Even the very broad US20090302434A1 discloses a clear preference for asymmetric cyclopentadienyls in claim 4 and all the experimental examples for the same stated reasons.

[0056] -

[0057] :

[0056] The lanthanide-containing precursors offer unique physical and chemical properties when compared to their corresponding homoleptic compounds, ... Independently fine tuning the substituents on the ligands increases volatility and thermal stability and decreases melting point to yield either liquids or low melting solids (having a melting point below approximately 105° C.).

[0057] In order to synthesize stable lanthanide-containing precursors with properties suited for the vapor deposition process (i.e, a volatile, yet thermally stable, liquid or low melting solid (having a melting point below about 105° C.)), a direct correlation between the properties of the central metal ion (coordination number, ionic radius) and ligands (steric effect, ratio of two heteroleptic ligands) has been observed Preferably R1 is a C1 -C3 alkyl chain; R2 is a C3-C4 alkyl chain, and R4 is H or Me. Preferably the lanthanide-containing precursor has a melting point below about 105° C., preferably below about 80° C., more preferably below about 70° C., and even more preferably below about 40° C. Preferred lanthanide-containing precursors include Ln(R1 Cp)2(NZ-fmd), Ln(R1 Cp)2(NZ-amd), Ln(R1 Cp)(NZ-fmd)2, and Ln(R1 Cp)(NZ-amd)2, wherein Ln is Y, Gd, Dy, Er, or Yb; R1 is Me, Et, or iPr; and Z is iPr or tBu.Following the above direction in the art, a number of candidate vapor precursors have been identified that are a) liquid at 50 degrees C or less, b) sufficiently volatile to vaporize 50% of a starting mass (in TGA analysis) at 240 degrees C or less, ideally also generating a partial vapor pressure of 1 Torr at 200 degrees C or lower, and c) thermally stable at vaporization temperatures, based on residual mass after full vaporization (TGA analysis).A representative listing of reference homoleptic molecules from the art follows:These reference molecules are solids above 50 degrees C, have a 50% TGA vaporization temperature above 240 degrees C, have 1 Torr vapor pressure temperatures above 150 degrees C, or two or more of the foregoing. A representative listing of prior art heteroleptic molecules follows for comparison to the invention:These examples reflect the general view in the art that having asymmetry, via the alkyl groups, lowers melting points and improves volatility, as do C3+ alkyl groups. US7557229 at

[0059] , “Alkyl groups with more than one stereoisomer, such as secbutyl, also lead to lower melting points.” Ibid. The effects of these design strategies are reflected in the above table of data from US20230040334A1 .The state of the art is still in need of Lanthanide chemicals (termed in the art “precursors”) that are liquid, highly volatile, thermally stable and capable of use in vapor phase depositions for Lanthanide containing films and other coatings at a commercially viable deposition rate and with low amounts of contaminating atoms (e.g. Y2O3 with less than 1 % Carbon).Summary of InventionAs defined in US20090302434A1 , the state of the art includes a chemical structure cloud or genus defined broadly by:. Ln(R1Cp)m(R2— N— C(R4)=N— R2)n,• wherein Ln represents the lanthanide group, which includes Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; R1is selected from H or a C1 -C5 alkyl chain; R2is selected from H or a C1 -C5 alkyl chain; R4is selected from H, a C1-C5 alkyl chain, and NR'R", wherein R' and R" are independently selected from a C1 -C5 alkyl chain; m is selected from 1 or 2; and n is selected from 1 or 2.However, the state of the art generally directs one to species within this cloud that have one or more of the above identified structural features, namely:• Structural asymmetry on the Cyclopentadienyls (Cp’s) by nonsymmetrical alkyl substitutions, generally a single alkyl group.• Asymmetric alkyl groups in the bridged nitrogens, these preferably being three of more carbon alkyl groups, and with isomeric alkyls such as secbutyl preferred for one of these (e.g. iso-propyl and sec-butyl groups).• An alkyl group on the bridging carbon (i.e. an amidinate) or an alkylated guanidinate.All of these features are present in the general structural cloud along with species lacking one or more of these features. Based on the foregoing, extensively empirically validated, molecular design rules, a skilled artisan would not expectmolecules lacking all of these features to be viable candidates for vapor phase deposition precursors.Applying the above design rules requires more complex synthesis schemes, especially using asymmetric alkyl groups in the bridged nitrogens. Nonetheless, the art has viewed this feature as one of the primary means of rendering these chemical liquid and volatile. It was therefore surprising to discover that certain species lacking any of the above features are viable, and even superior, vapor phase deposition precursors, compared to the many demonstrated species in the state of the art.In one embodiment, the novel molecules can be used for Chemical Vapor Deposition and more precisely high temperature epitaxy of thin film of alloys such as Scandium Aluminum Nitride (ScAIN) and Yttrium Aluminum Nitride (YAIN). ScAIN CVD processes have been reported using conventional unscalable precursors such as ScCp3, Sc(MeCp)3, and suffer from low growth rate limited by the amount of Sc precursor delivered to the CVD chamber, which is directly resulting from the Sc precursor vapor pressure. ScAIN or YAIN can be deposited by reacting the novel molecules disclosed herein with vapors of other molecules such as trimethylaluminum (TMA) and ammonia (NH3) at temperatures ranging from 400°C to 700°C, preferably 500°C to 600°C. The resulting films are expected to be crystalline and with low carbon contamination.Disclosure of InventionA subgenus defined by:• R1is Hydrogen (i.e. the Cp is unsubstituted)• R2is the same (i.e. symmetrical) and selected from a Ci to C3 alkyl group, preferably C2 or C3.• R3is Hydrogen (i.e. a formamidinate).The most preferred members of this small subgenus are Cp2Sc[EtNC(H)NEt] ;Cp2Y[EtNC(H)NEt] ; and Cp2Sc[ / PrNC(H)N / Pr] :As demonstrated below, these molecules have a surprisingly optimal combination of properties compared to the closest members in the larger chemical cloud with the preferred structural feature(s). Figure 1 is a table of benchmarking values for the above chemicals. Some near chemical analogs in the genus are shown for comparison. The initial criteria is a melting point below 50 degrees C. Volatility may be assessed by two art standard criteria:• The temperature required to produce a 1 torr partial vapor pressure of the chemical.• The temperature at which half of a mass of chemical evaporates in a thermogravimetric analysis.Thermal stability may also be assessed by two art standard criteria:• The weight percent of nonvolatile residual mass of chemical after complete evaporation in a thermogravimetric analysis.• Decomposition temperature measured by Differential Scanning Calorimetry (DSC).The data in Figure 1 demonstrate the high degree of variability and unpredictability of the various properties. Consistent structure function correlations are not strong in this subgenus of the larger cloud of chemicals. In particular, melting point and volatility are not consistently correlated as one might expect. For the precursors with melting points in the more preferred range below 35 degrees C, the most volatile chemicals are Cp2Y[EtNC(H)NEt], ScCp2(iPr-fmd), and ScCp2(Et-fmd), which do not have with any of the art recognized features for increased volatility. In regard to Cp2Y[EtNC(H)NEt], this exceptional volatility is despite the closest comparison molecules having a lower melting point. Cp2Y[EtNC(H)NEt] is especially unique in its combination of low melting point and surprisingly high volatility.While melting point and volatility are important, these are screening criteria. A chemical still has to function efficiently in vapor phase deposition to yield films ofacceptable quality for a target application. Ideally, precursor chemicals can operate in an atomic layer deposition (ALD).Figure 2 shows the results from ALD with water for Cp2Y[EtNC(H)NEt] compared to (EtCp)2Y[iPrNC(CH3)NiPr] and the commercial precursor (EtCp)sY. As shown, Cp2Y[EtNC(H)NEt] works well in ALD with a wide ALD “window” or temperature range in which ALD occurs (200 - 450 degrees C). The lower end of the ALD window is significantly below the comparison molecules due in part to the unexpected higher volatility of Cp2Y[EtNC(H)NEt], ScCp2(iPr-fmd) similarly had an ALD window extending down to 200 degrees C due to its extremely high volatility.Ideal ALD produces highly uniform films. As shown in Figure 3, Cp2Y[EtNC(H)NEt] produces superior uniformity, with ideal ALD behavior in the 200 degree C to 350 degree C range for substrate temperature. This is substantially superior to the two precursors used for comparison. ScCp2(iPr-fmd) ALD films had similar uniformity from 225 degrees C to 475 degrees C .XPS etching analysis was performed on an ALD film deposited using water coreactant and Cp2Y[EtNC(H)NEt] at 350 degrees C. The film contained undetectable (less than 0.5% atomic) levels of Carbon, Silicon and Nitrogen. The Yttrium and Oxygen contents were 40% and 60%, respectively, corresponding to Y2O3. ScCp2(iPr- fmd) for ALD at 325 degrees C with ozone as a co-reactant produced an SC2O3 film with 40% / 60% atomic composition and undetectable (less than 0.5% atomic) levels of Carbon, Silicon and Nitrogen.Consistent with an ALD film, the Y2O3 films formed with water co-reactant had a highly uniform film thickness of 98% step coverage on a blank test silicon wafer with a trench (35.7 nm to 35.0 nm thickness range in the trench assessed by SEM images of sectioned wafers). Similarly, the SC2O3 films were uniform 26.9 nm thick (i.e. 100% step coverage).The ALD results demonstrate superior performance and results for Cp2Y[EtNC(H)NEt] in forming Y2O3 and ScCp2(iPr-fmd) in forming SC2O3.Brief Description of DrawingsFigure 1 shows a table of relevant properties for the demonstrated chemicals herein and several comparison chemicals;Figure 2 shows results from a ALD depositions using Cp2Y[EtNC(H)NEt] and water at several temperatures;Figure 3 shows the degree of nonuniformity of the films deposited.Mode(s) for Carrying Out the InventionSynthesisSynthesis of the chemicals described herein may be performed according to any of the methods described in the state of the art, including those of the background section references and further including US8012536B2.MP, TGA and VPThemogravimetric analyses (TGA) was performed on a METTLER TOLEDO® Thermal Analysis System TGA / DSC 3+ instrument with the amount of sample approximately 20 mg to approximately 40 mg under a constant N2 inert gas flow of 100 mL / min and employing a heating rate of 10 °C / min. TGA instrument is in glove box with <0.5 ppm of oxygen and moisture.Vapor pressure (VP) measurements were performed on a METTLER TOLEDO® Thermal Analysis System TGA / DSC 3+ with the amount of sample approximately 25 mg to approximately 45 mg under a constant N2 inert gas flow of 200 mL / min using the stepped isothermal TGA method in a range selected between 100- 260 °C in 10 °C steps. The steps were held for 10 minutes at the respective temperatures to allow the evaporation rate to reach an equilibrium. The standard, analytically pure anthracene was run by the same VP methods as the investigated sample, right after the measurement of sample. VP of standard at each point from DIPPR [https: / / dippr.aiche.org / ] used for calibration of VP measurement.Melting point (MP) measurements were performed on a METTLER TOLEDO® Thermal Analysis System DSC 3+ instrument with the amount of sample approximately 5 mg to approximately 15 mg employing a heating rate of 10 °C / min.ALDThe thin films were prepared in a shower head type ALD reactor. The precursor was placed in a vessel and gas delivery lines were heated 20 oC higher than vessel temperature. A carrier gas was supplied to the reactor and precursor lines through mass flow controllers. High purity argon was used both as a carrier gas to transfer the precursor and as a purge gas to remove byproducts and excess gases from the reactor. Typically, the reactor was operated at 0.5 - 2 torr achieved by argon gas flowwith a throttle valve.XPSFilm composition and impurities were analyzed by X-ray photoelectronUniformityFilm thickness was measured by an ellipsometer. Thickness was measured at 25 points on a 6-inch wafer, excluding the 7 mm edge. Non-uniformity was calculated by Min-Max method which is (MAX - MIN) / (2*AVERAGE)*100%.Industrial ApplicabilityThe present invention is at least industrially applicable to forming coatings and films for semiconductors.While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.Notation and NomenclatureThe following detailed description and claims utilize a number of abbreviations, symbols, and terms, which are generally well known in the art, and include:• The singular forms "a", "an" and "the" include plural referents, unless the context clearly dictates otherwise.• "Comprising" in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms "consisting essentially of" and “consisting of” unless otherwise indicated herein.• “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.• Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.• Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range.• As used herein, “about” or “around” or “approximately” in the text or in a claim means±10% of the value stated.• As used herein, “room temperature” in the text or in a claim means from approximately 20° C. to approximately 25° C.• The term “ambient temperature” refers to an environment temperature approximately 20° C. to approximately 25° C.• The term “substrate” refers to a material or materials on which a process is conducted. The substrate may refer to a wafer having a material or materials on which a process is conducted. The substrates may be any suitable wafer used in semiconductor, photovoltaic, flat panel, or LCD-TFT device manufacturing. The substrate may also have one or more layers of differing materials already deposited upon it from a previous manufacturing step. For example, the wafers may include silicon layers (e.g., crystalline, amorphous, porous, etc.), silicon containing layers (e.g., SiO2, SiN, SiON, SiCOH, etc.), metal containing layers (e.g., copper, cobalt, ruthenium, tungsten, platinum,palladium, nickel, ruthenium, gold, etc.) or combinations thereof. Furthermore, the substrate may be planar or patterned. The substrate may be an organic patterned photoresist film. The substrate may include layers of oxides which are used as dielectric materials in MEMS, 3D NAND, MIM, DRAM, or FeRam device applications (for example, ZrO2 based materials, HfO2 based materials, Ti02 based materials, rare earth oxide based materials, ternary oxide based materials, etc.) or nitride-based films (for example, TaN, TiN, NbN) that are used as electrodes. One of ordinary skill in the art will recognize that the terms “film” or “layer” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may be a trench or a line. Throughout the specification and claims, the wafer and any associated layers thereon are referred to as substrates.• Note that herein, the terms “film” and “layer” may be used interchangeably. It is understood that a film may correspond to, or related to a layer, and that the layer may refer to the film. Furthermore, one of ordinary skill in the art will recognize that the terms “film” or “layer” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may range from as large as the entire wafer to as small as a trench or a line.• The standard abbreviations of the elements from the periodic table of elements are used herein. It should be understood that elements may be referred to by these abbreviation (e.g., Si refers to silicon, N refers to nitrogen, 0 refers to oxygen, C refers to carbon, H refers to hydrogen, F refers to fluorine, etc.).• The unique CAS registry numbers (i.e., “CAS”) assigned by the Chemical Abstract Service are provided to identify the specific molecules disclosed.• As used herein, the term “hydrocarbon” refers to a saturated or unsaturated function group containing exclusively carbon and hydrogen atoms. As used herein, the term “alkyl group” refers to saturated functional groups containing exclusively carbon and hydrogen atoms, An alkyl group is one type of hydrocarbon. Further, the term “alkyl group” refers to linear, branched, or cyclic alkyl groups. Examples of linear alkyl groups include without limitation, methyl groups, ethyl groups, propyl groups, butyl groups, etc. Examples of branched alkyls groups include without limitation, t-butyl.Examples of cyclic alkyl groups include without limitation, cyclopropyl groups, cyclopentyl groups, cyclohexyl groups, etc.• As used herein, the abbreviation “Me” refers to a methyl group; the abbreviation “Et” refers to an ethyl group; the abbreviation “Pr” refers to any propyl group (i e., n-propyl or isopropyl); the abbreviation “iPr” refers to an isopropyl group; the abbreviation “Bu” refers to any butyl group (n-butyl, isobutyl, tert-butyl, sec-butyl): the abbreviation “tBu” refers to a tert-butyl group; the abbreviation “sBu” refers to a sec-butyl group; the abbreviation “iBu” refers to an iso-butyl group; the abbreviation “Ph” refers to a phenyl group; the abbreviation “Am” refers to any amyl group (iso-amyl, sec-amyl, tertamyl); the abbreviation “Cy” refers to a cyclic hydrocarbon group (cyclobutyl, cyclopentyl, cyclohexyl, etc.); the abbreviation “amd” refers to ZNC(CH3)=NZ, wherein Z is a defined alkyl group such as iPr or tBu; the abbreviation “fmd” refers to ZNC(H)=NZ, wherein Z is a defined alkyl group such as iPr or tBu;.• Please note that the silicon-containing films, such as Si, SiN, SiO, SiOC, SiON, SiCON, are listed throughout the specification and claims without reference to their proper stoichiometry. The silicon-containing films may also include dopants, such as B, P, As, Ga and / or Ge. The fact that the film contains some residual hydrogen is also omitted from the film composition description. For instance, a SiOC film may contain residual H.• Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range. Any and all ranges recited herein are inclusive of their endpoints (i.e. , x=1 to 4 or x ranges from 1 to 4 includes x=1 , x=4, and x=any number in between), irrespective of whether the term “inclusively” is used.• Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the sameembodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.”• As used herein, the term “independently” when used in the context of describing R groups should be understood to denote that the subject R group is not only independently selected relative to other R groups bearing the same or different subscripts or superscripts, but is also independently selected relative to any additional species of that same R group. For example in the formula MR1 x (NR2R3)(4-x), where x is 2 or 3, the two or three R1 groups may, but need not be identical to each other or to R2 or to R3. Further, it should be understood that unless specifically stated otherwise, values of R groups are independent of each other when used in different formulas.• As used in this application, the word “exemplary” is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word exemplary is intended to present concepts in a concrete fashion.• Additionally, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or”. That is, unless specified otherwise, or clear from context, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then “X employs A or B” is satisfied under any of the foregoing instances. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form.

Claims

CLAIMS:1 . A chemical defined by the formula:wherein R1and R3are Hydrogens,R2are the same and are selected from Ci to C3 alkyl groups, and M is Yttrium or Scandium.

2. The chemical of claim 1 , wherein is R2selected from an ethyl group or an isopropyl group.

3. The chemical of claim 2, wherein is R2is an ethyl group.

4. The chemical of claim 2, wherein is R2is an isopropyl group.

5. The chemical of claims 1 , 2, 3 or 4, wherein M is Yttrium.

6. The chemical of claims 1 , 2, 3 or 4, wherein M is Scandium.

7. A composition comprising the chemical of any one of claims 1 -6, wherein said composition is liquid at 50 degrees C or less, preferably 35 degrees C or less, most preferably 25 degrees C or less.

8. A vapor phase composition comprising the chemical of any one of claims 1 -7.

9. The vapor phase composition of claim 8, further comprising an additional gas or chemical vapor.

10. The vapor phase composition of claim 9, wherein the additional gas is a carrier gas, preferably selected from nitrogen, hydrogen, helium, or argon.

11. A method of depositing a material on a surface, the method comprising the steps of: a) first, exposing the surface to a vapor of the chemical of any one of claims 1-7, or the vapor phase composition of claim 8, and b) second, exposing the surface to a co-reactant, to thereby form a deposit of Yttrium or Scandium containing material on the surface.

12. The method of claim 11 , wherein the co-reactant is an oxidant, preferably selected from water and ozone.

13. The method of claims 11 or 12, wherein the method comprises an atomic layer deposition.

14. The method of any one of claims 11-13, wherein the temperature of the surface is maintained at from 200 degrees C to 475 degrees C, optionally within the subrange of 200 degrees C to less than 225 degrees C.

15. The method of claim 11 , wherein the co-reactant comprises an Aluminum source and a Nitrogen source.

16. The method of claim 15, wherein the Aluminum source is trimethylaluminum (TMA) and the nitrogen source is ammonia (NH3).

17. The method of claims 15 or 16, wherein a temperature of steps a) and / or b) ranges from 400 degrees C to 700 degrees C, preferable from 500 degrees C to 600 degrees C.

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