GROUP 2 METAL CONTAINING FILM FORMING COMPOSITIONS AND VAPOR DEPOSITION OF THE FILMS USING THE SAME
20250223696 · 2025-07-10
Assignee
Inventors
Cpc classification
C07F3/00
CHEMISTRY; METALLURGY
C23C16/45534
CHEMISTRY; METALLURGY
C23C16/409
CHEMISTRY; METALLURGY
International classification
C23C16/455
CHEMISTRY; METALLURGY
C07F3/00
CHEMISTRY; METALLURGY
Abstract
A method of forming Group 2 metal containing films on a substrate comprises a) exposing the substrate to a vapor of a Group 2 metal containing film forming composition that contains an alkaline earth metal precursor having the formula:
##STR00001##
wherein M is Be, Mg, Ca, Sr, or Ba; R.sup.1-R.sup.6 each independently are a C.sub.1-C.sub.10 alkyl group, a fluoro group, an alkylsilyl group, a germyl group, an alkylamide or an alkylsilylamide, b) depositing at least part of the alkaline earth metal precursor onto the substrate to form a Group 2 metal-containing film through a vapor deposition process; and c) repeating a) and b) until a desired thickness of the Group 2 metal-containing film is formed.
Claims
1. A method of forming a Group 2 metal containing film on a substrate, the method comprising a) exposing the substrate to a vapor of a Group 2 metal containing film forming composition that contains an alkaline earth metal precursor having the formula: ##STR00010## wherein M is Be, Mg, Ca, Sr, or Ba; R.sup.1-R.sup.6 each independently are a C.sub.1-C.sub.10 alkyl group, a fluoro group, an alkylsilyl group, a germyl group, an alkylamide or an alkylsilylamide; b) depositing at least part of the alkaline earth metal precursor onto the substrate to form the Group 2 metal-containing film through a vapor deposition process; and c) repeating a) and b) until a desired thickness of the Group 2 metal-containing film is formed.
2. The method of claim 1, further comprising exposing the substrate to a co-reactant selected from an oxidizer agent or a nitrogen agent.
3. The method of claim 2, wherein the co-reactant is selected from O.sub.3, O.sub.2, H.sub.2O, H.sub.2O.sub.2, D.sub.2O, ROH wherein RC.sub.1-C.sub.10 linear or branched hydrocarbon, or combination thereof.
4. The method of claim 2, wherein the co-reactant is selected from NH.sub.3, NO, N.sub.2O, hydrazines, amines or combinations thereof.
5. The method of claim 2, wherein the co-reactant is H.sub.2O.
6. The method of claim 1, wherein the alkaline earth metal precursor is liquid.
7. The method of claim 1, wherein the alkaline earth metal precursor is mixed with a solvent.
8. The method of claim 7, wherein the solvent is a substituted or unsubstituted hydrocarbon selected from alkanes, alkenes, alkynes; alcohols selected from alkyl alcohols, amino alcohols; or amines selected from primary-, secondary-, tertiary-amines; tetrahydrofuran; dichloromethane; ethyl acetate; butyl acetate; acetonitrile; dimethylformamide.
9. The method of claim 8, wherein the substituted or unsubstituted hydrocarbons include octane, ethyl benzene, xylene, mesitylene, decalin, decane, dodecane.
10. The method of claim 7, wherein a concentration of the alkaline earth metal precursor in the solvent ranges from approximately 50% w/w and approximately 100.0% w/w.
11. The method of claim 1, wherein the substrate is exposed to the vapor of the Group 2 metal containing film forming composition at a temperature raging from room temperature to approximately 500 C.
12. The method of claim 1, wherein the alkaline earth metal precursor is selected from the group consisting of Bis(tri-sec-butyl cyclopentadienyl)Strontium(II), Sr(sBu.sub.3Cp).sub.2, Bis(tri-sec-butyl cyclopentadienyl)Barium(II), Ba(sBu.sub.3Cp).sub.2, Bis(tri-iso-propyl cyclopentadienyl)Strontium(II), Sr(iPr.sub.3Cp).sub.2, Bis(tri-tert-butyl cyclopentadienyl)Strontium(II), Sr(tBu.sub.3Cp).sub.2, Bis(tri-iso-propyl and cyclopentadienyl)Barium(II), Ba(iPr.sub.3Cp).sub.2,
13. The method of claim 1, wherein the alkaline earth metal precursor is Bis(tri-sec-butyl cyclopentadienyl)Strontium(II), Sr(sBu.sub.3Cp).sub.2.
14. The method of claim 1, wherein the alkaline earth metal precursor is Bis(tri-sec-butyl cyclopentadienyl)Barium(II), Ba(sBu.sub.3Cp).sub.2.
15. The method of claim 1, wherein the vapor deposition process is a MOCVD process, or an ALD process selected from a thermal ALD, spatial ALD, temporal ALD, or plasma ALD process.
16. The method of claim 1, wherein the vapor deposition process is not a plasma ALD process.
17. The method of claim 1, wherein the Group 2 metal-containing film is a SrO film.
18. The method of claim 1, wherein the Group 2 metal-containing film is a BaO film.
19. A method of depositing a SrO film on a substrate, the method comprising the steps of: a) exposing the substrate to a vapor of Bis(tri-sec-butyl cyclopentadienyl)Strontium(II), Sr(sBu.sub.3Cp).sub.2; b) exposing the substrate to a co-reactant H.sub.2O; c) depositing at least part of the alkaline earth metal precursor onto the substrate to form the SrO film through a vapor deposition process; and d) repeating a)-c) until a desired thickness of the SrO film is formed.
20. A method of depositing a BaO film on a substrate, the method comprising the steps of: a) exposing the substrate to a vapor of Bis(tri-sec-butyl cyclopentadienyl)Barium(II), Ba(sBu.sub.3Cp).sub.2; b) exposing the substrate to a co-reactant H.sub.2O; c) depositing at least part of the alkaline earth metal precursor onto the substrate to form the BaO film through a vapor deposition process; and d) repeating a)-c) until a desired thickness of the BaO film is formed.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0136] For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:
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DESCRIPTION OF PREFERRED EMBODIMENTS
[0147] Disclosed are Group 2 metal containing film forming compositions and using the same to deposit films. More specifically, the disclosed are new class of thermally stable liquid Group 2 organometallic compounds and their use to deposit Group 2 metal-containing films by either ALD or MOCVD processes.
[0148] The Group 2 metal containing film forming compositions may contain steric metallocenes, such as tri-alkyl substituted cyclopentadienyl Ca, Sr or Ba compounds, which are one of the most promising precursors for film deposition in superconductor and semiconductor fabrication due to their high volatilities, thermal stability, stable monomeric structure, and relatively low melting point.
[0149] However, most of the steric metallocenes are solid at room temperature. For example, melting points of some of the exemplary steric metallocenes are listed in Table 1.
TABLE-US-00001 TABLE 1 Compounds Melting points Sr(iPr.sub.3Cp).sub.2 44 C. Sr(tBu.sub.3Cp).sub.2 143 C. Ba(iPr.sub.3Cp).sub.2 92 C.
[0150] In the case of solids, the steric metallocenes usually have strong intermolecular force of attraction, and tightly packed in a regular pattern. Therefore, if molecular structures have asymmetric ligands or long flexible alkyl chains, disorder may be created in the lattice packaging and materials tend to be liquids.
[0151] The disclosed Group 2 metal containing film forming compositions comprise alkaline earth metal precursors. The disclosed alkaline earth metal precursors may be developed by introducing more flexible and linear alkyl chains than iso-propyl or tert-butyl, into cyclopentadienyl-alkaline earth metal compounds to increase the degree of freedom in the molecules.
[0152] The disclosed alkaline earth metal precursors have the following general formula:
##STR00004##
wherein M=Be, Mg, Ca, Sr, or Ba; R.sup.1-R.sup.6 each independently are a C.sub.1-C.sub.10 alkyl group, a fluoro group, an alkylsilyl group, a germyl group, an alkylamide or an alkylsilylamide.
[0153] Exemplary the alkaline earth metal precursors include Bis(tri-sec-butyl cyclopentadienyl)Strontium(II), Sr(sBu.sub.3Cp).sub.2, Bis(tri-sec-butyl cyclopentadienyl)Barium(II), Ba(sBu.sub.3Cp).sub.2, Bis(tri-iso-propyl cyclopentadienyl)Strontium(II), Sr(iPr.sub.3Cp).sub.2, Bis(tri-tert-butyl cyclopentadienyl)Strontium(II), Sr(tBu.sub.3Cp).sub.2, Bis(tri-iso-propyl cyclopentadienyl)Barium(II), Ba(iPr.sub.3Cp).sub.2, and the like.
[0154] The disclosed Group 2 metal containing film forming composition includes the liquid alkaline earth metal precursor Bis(tri-sec-butyl cyclopentadienyl)Strontium(II), Sr(sBu.sub.3Cp).sub.2.
[0155] The disclosed Group 2 metal containing film forming composition includes the liquid alkaline earth metal precursor Bis(tri-sec-butyl cyclopentadienyl)Barium(II), Ba(sBu.sub.3Cp).sub.2.
[0156] The disclosed Group 2 metal containing film forming composition includes the liquid alkaline earth metal precursor Bis(tri-iso-propyl cyclopentadienyl)Strontium(II), Sr(iPr.sub.3Cp).sub.2.
[0157] The disclosed Group 2 metal containing film forming composition includes the liquid alkaline earth metal precursor Bis(tri-tert-butyl cyclopentadienyl)Strontium(II), Sr(tBu.sub.3Cp).sub.2.
[0158] The disclosed Group 2 metal containing film forming composition includes the liquid alkaline earth metal precursor Bis(tri-iso-propyl cyclopentadienyl)Barium(II), Ba(iPr.sub.3Cp).sub.2.
[0159] The disclosed alkaline earth metal precursors may be liquid at atmosphere pressure and suitable for deposition of metal-containing films, such as SrO or BaO film, by vapor deposition methods, such as, ALD or MOCVD, and have the following advantages: [0160] Normally, the disclosed alkaline earth metal precursors generate less particles compared to solid precursors even in a solution state, such as no particles blowing into a precursor delivery line and therefore, into processing wafers in a chamber. Also, the disclosed alkaline earth metal precursors reduce the frequency of chamber maintenance, leading to a longer life time of using the chamber than using the solid precursors; [0161] The liquid precursor has an advantage to produce very constant delivery of materials, due to the constant surface area inside the canister, compared to the solid precursors which aggregate over the time during heating and show variable surface areas of particles, generating non-constant vapor pressure.
[0162] While the disclosed alkaline earth metal precursor are ideally liquids and vaporized in bubblers or direct liquid injection systems, the use of solid precursors for ALD precursor vaporization is also possible using existing sublimators. Alternatively, the solid precursors may be mixed or dissolved in a solvent to reach a usable melting point and viscosity for usage by Direct Liquid Injection systems. Alternatively, the liquid precursors may also be mixed with a solvent to lower their viscosity.
[0163] The solvent may be substituted or unsubstituted hydrocarbons, such as, alkanes, alkenes, alkynes, etc.; alcohols such as alkyl alcohols, amino alcohols, etc.; or amines, such as primary-, secondary-, tertiary-amines; tetrahydrofuran; dichloromethane; ethyl acetate; butyl acetate; acetonitrile; dimethylformamide. The hydrocarbons may include octane, ethyl benzene, xylene, mesitylene, decalin, decane, dodecane, or the like. A concentration of the alkaline earth metal precursor in the solvent varies, for example, a concentration of the alkaline earth metal precursor in the solvent may range from approximately 50% w/w to approximately 100.0% w/w. Preferably, the solvent contained in the mixture of the liquid precursors and the solvent ranges from 0% to approximately 50%.
[0164] The disclosed metal-containing film-forming compositions may comprise between approximately 50% w/w and approximately 100.0% w/w of the alkaline earth metal precursor.
[0165] To ensure process reliability, the disclosed alkaline earth metal precursor may be purified by continuous or fractional batch distillation or sublimation prior to use to a purity ranging from approximately 95% by weight or w/w to approximately 100% w/w, preferably ranging from approximately 99% w/w to approximately 99.999% w/w, more preferably, ranging from approximately 99% w/w to approximately 100% w/w.
[0166] The disclosed alkaline earth metal precursor may contain any of the following impurities: undesired congeneric species; solvents; chlorinated metal compounds; or other reaction products. In one alternative, the total quantity of these impurities is below 5.0% w/w, preferably, below 0.1% w/w.
[0167] Solvents, such as hexane, pentane, dimethyl ether, or anisole, may be used in the precursor's synthesis. The concentration of the solvent in the disclosed Metal-containing precursors may range from approximately 0% w/w to approximately 5% w/w, preferably from approximately 0% w/w to approximately 0.1% w/w. Separation of the solvents from the precursor may be difficult if both have similar boiling points. Cooling the mixture may produce solid precursor in liquid solvent, which may be separated by filtration. Vacuum distillation may also be used, provided the precursor product is not heated above approximately its decomposition point.
[0168] In one alternative, the disclosed alkaline earth metal precursors contain less than 5% v/v, preferably less than 1% v/v, more preferably less than 0.1% v/v, and even more preferably less than 0.01% v/v of any of its undesired congeneric species, reactants, or other reaction products. This alternative may provide better process repeatability. This alternative may be produced by distillation of the disclosed alkaline earth metal precursors.
[0169] In another alternative, the disclosed alkaline earth metal precursors may contain between 5% v/v and 50% v/v of one or more of congeneric metal-containing precursors, reactants, or other reaction products, particularly when the mixture provides improved process parameters or isolation of the target compound is too difficult or expensive. For example, a mixture of two alkaline earth metal precursors may produce a stable, liquid mixture suitable for vapor deposition.
[0170] In another alternative, the disclosed alkaline earth metal precursors may contain between approximately 0 ppbw and approximately 500 ppbw metal impurities.
[0171] The concentration of trace metals and metalloids in the disclosed alkaline earth metal precursors may each range from approximately 0 ppb to approximately 100 ppb, and more preferably from approximately 0 ppb to approximately 10 ppb.
[0172] In addition to the disclosed alkaline earth metal precursors, a reactant or a co-reactant may also be introduced into the reaction chamber. The co-reactant may be an oxygen-containing gas or a nitrogen-containing gas for metal oxide film deposition. The co-reactants include, but are not limited to, oxidizers such as, O.sub.3, O.sub.2, H.sub.2O, H.sub.2O.sub.2, D.sub.2O, ROH (RC.sub.1-C.sub.10 linear or branched hydrocarbon), etc.
[0173] The ALD sequence may include sequential pulses of several compounds. For instance, the surface may be exposed to O.sub.2/O.sub.3 followed by H.sub.2O in order to increase the density of hydroxyl groups on the surface.
[0174] Alternatively, the co-reactant may be a nitrogen-containing gas for Nitrogen-containing film deposition. The nitrogen-containing gas includes, but is not limited to, NH.sub.3, NO, N.sub.2O, hydrazines, primary amines such as methylamine, ethylamine, tertbutylamine; secondary amines such as dimethylamine, diethylamine, di-isopropylamine, ethylmethylamine, pyrrolidine; tertiary amines such as trimethylamine, triethylamine, trisilylamine, N.sub.2, N.sub.2/H.sub.2 mixture thereof, preferably NH.sub.3. The co-reactant may be selected from NH.sub.3, NO, N.sub.2O, hydrazines, amines or combinations thereof.
[0175] Also disclosed are methods or processes for forming Group 2 metal-containing film on a substrate through vapor deposition process. In one embodiment, the method for forming a Group 2 metal-containing film on a substrate comprises the steps of a) providing the substrate in a reaction chamber, b) exposing the substrate to a vapor including a disclosed Group 2 metal containing film forming composition that contains a disclosed alkaline earth metal precursor, c) depositing at least part of the disclosed alkaline earth metal precursor onto the substrate to form a Group 2 metal-containing film through a vapor deposition process, and-repeating b) and c) until a desired thickness of the Group 2 metal-containing film is formed.
[0176] The method further comprises the step of exposing the substrate to a co-reactant following the step b), wherein the co-reactant is selected from O.sub.3, O.sub.2, H.sub.2O, H.sub.2O.sub.2, D.sub.2O, ROH (RC.sub.1-C.sub.10 (linear or branched)) hydrocarbon, NH.sub.3, NO, N.sub.2O, hydrazines, amines or combinations thereof. For example, one or a combination of the above co-reactants may be used for deposition of silicon oxynitride films, either by co-flowing the co-reactant, or sequentially.
[0177] In an alternative embodiment, the method for forming a Group 2 metal-containing film on a substrate comprises the steps of a) providing a substrate in a reaction chamber, b) exposing the substrate to a vapor of a disclosed Group 2 metal containing film forming composition that contains a disclosed alkaline earth metal precursor such as, Bis(tri-sec-butyl cyclopentadienyl)Strontium(II), Sr(sBu.sub.3Cp).sub.2, Bis(tri-sec-butyl cyclopentadienyl)Barium(II), Ba(sBu.sub.3Cp).sub.2, Bis(tri-iso-propyl cyclopentadienyl)Strontium(II), Sr(iPr.sub.3Cp).sub.2, Bis(tri-tert-butyl cyclopentadienyl)Strontium(II), Sr(tBu.sub.3Cp).sub.2, Bis(tri-iso-propyl cyclopentadienyl)Barium(II), Ba(iPr.sub.3Cp).sub.2, and c) depositing the Group 2 metal-containing film on the substrate in a vapor deposition process. The method further comprises the step of exposing the substrate to a co-reactant following the step b), wherein the co-reactant is selected from O.sub.3, O.sub.2, H.sub.2O, H.sub.2O.sub.2, D.sub.2O, ROH (RC.sub.1-C.sub.10 (linear or branched)) hydrocarbon, NH.sub.3, NO, N.sub.2O, hydrazines, amines or combinations thereof. The method further comprises the steps of repeating the exposing to the vapor of the Group 2 metal containing film forming composition and the exposing to the co-reactant until a desired thickness of the Group 2 metal-containing film is formed, and purging excess vapor of the Group 2 metal containing film forming composition and excess co-reactant using an inert gas, respectively, to separate each exposure, wherein the inert gas is N.sub.2, Ar, Kr or Xe.
[0178] The disclosed processes using the disclosed alkaline earth metal precursors include ALD processes for deposition of Group 2 metal containing films. Suitable ALD methods include thermal ALD, spatial ALD, and temporal ALD. Suitable ALD methods may also include plasma ALD methods. Preferably the suitable ALD methods do not use a plasma, as it is extremely difficult to grow conformal films in high aspect ratio with this type of ALD. It is understood that the suitable ALD may operate in a non-perfect self-limited growth regime, allowing some parasitic CVD to happen. Such parasitic CVD may not be a problem as long as the deposited film meets conformity requirements.
[0179] The disclosed processes using the disclosed alkaline earth metal precursors also include MOCVD process for deposition of Group 2 metal containing films.
[0180] The reaction chamber may be any enclosure or chamber of a device in which deposition methods take place, such as, without limitation, a parallel-plate type reaction chamber, a hot-wall type reaction chamber, a single-wafer reaction chamber, a multi-wafer reaction chamber, or other such types of deposition systems. All of these exemplary reaction chambers are capable of serving as an ALD reaction chamber.
[0181] The reaction chamber contains one or more substrates onto which the films will be deposited. A substrate is generally defined as the material on which a process is conducted. The substrates are cleaned to remove native oxides and dried before deposition. The substrates may be any suitable substrate used in semiconductor, photovoltaic, flat panel, or LCD-TFT device manufacturing. Examples of suitable substrates include wafers, such as metal (e.g., W, Ge, etc.), silicon, SiGe, silica, or glass. The substrate may also have one or more surface areas of differing materials already deposited upon it from a previous manufacturing step. For example, the wafers may include dielectric surfaces and conductive or electrode surfaces exposed simultaneously, such as, metal surfaces, metal oxide surfaces, silicon surfaces, silicon layers (crystalline, amorphous, porous, etc.), silicon oxide layers/surfaces, silicon nitride layers/surfaces, silicon oxy nitride layers/surfaces, carbon doped silicon oxide (SiCOH) layers/surfaces, or combinations thereof. Additionally, the wafers may include copper, cobalt, ruthenium, tungsten and/or other metal layers (e.g., platinum, palladium, nickel, ruthenium, or gold). The wafers may include barrier layers or electrodes, such as tantalum, tantalum nitride, etc. The wafers may be planar or patterned. The substrate may include layers of oxides which have the oxide surface exposed and are used as dielectric materials in 3D NAND, MIM, DRAM, or FeRam technologies (for example, ZrO.sub.2 based materials, HfO.sub.2 based materials, TiO.sub.2 based materials, rare earth oxide based materials, ternary oxide based materials, etc.) or from nitride-based films (for example, TaN, TiN, NbN) that are used as electrodes. The disclosed processes may deposit the metal-containing layer directly on the wafer or directly on one or more than one (when patterned layers form the substrate) of the layers on top of the wafer. 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 be a trench or a line. Throughout the specification and claims, the wafer and any associated layers/surfaces thereon are referred to as substrates. The actual substrate utilized may also depend upon the specific precursor embodiment utilized.
[0182] The disclosed processes using the disclosed alkaline earth metal precursors may be performed for substrates having a temperature range from room temperature to approximately 500 C.
[0183] The temperature of the reaction chamber may be controlled by either controlling the temperature of the substrate holder or controlling the temperature of the reaction chamber wall. Devices used to heat the substrate are known in the art. The reaction chamber wall is heated to a sufficient temperature to obtain the desired film at a sufficient growth rate and with desired physical state and composition. A non-limiting exemplary temperature range to which the reaction chamber wall may be heated includes from room temperature to approximately 500 C.
[0184] The substrate exposure time in the reaction chamber in the disclosed processes using the disclosed precursors may range from 1 millisecond to 5 minutes, preferably from 1 millisecond to 60 seconds. The co-reactant exposure time in the reaction chamber in the disclosed processes may range from 1 millisecond to 1 minute, preferably from 100 milliseconds to 30 seconds.
[0185] The pressure within the reaction chamber are held at conditions suitable for the precursor to react with the surface of the substrate. For instance, the pressure in the chamber may be held between approximately 0.1 mTorr and approximately 1000 Torr, preferably between approximately 1 mTorr and approximately 400 Torr, more preferably between approximately 0.1 Torr and approximately 100 Torr, even more preferably between approximately 0.5 Torr and approximately 10 Torr.
[0186] The disclosed process or sequence typically includes steps to remove excess precursor and excess co-reactant from the deposition surface by providing a purge step, either by purging a reaction chamber with an inert gas, or passing the substrate in a sector under high vacuum and/or a carrier gas curtain. The inert gas is N.sub.2, Ne, Ar, Kr, or Xe, preferably, N.sub.2 or Ar.
[0187] The disclosed alkaline earth metal precursors and the co-reactants may be introduced into the reaction chamber sequentially (ALD). The reaction chamber may be purged with an inert gas between the introduction of the precursor and the introduction of the co-reactant and after the introduction of the co-reactant. Alternatively, the substrate can be moved from one area for precursor exposure to another area for co-reactant exposure (spatial ALD).
[0188] Depending on the particular process parameters, deposition may take place for a varying length of time. Generally, deposition may be allowed to continue as long as desired or necessary to produce a film with the necessary thickness. Typical film thicknesses may vary from an atomic monolayer to several hundreds of microns, depending on the specific deposition process, preferably between 0.1 and 100 nm, more preferably between 0.1 and 50 nm. The deposition process may also be performed as many times as necessary to obtain the desired film.
[0189] In one non-limiting exemplary ALD process, the vapor phase of the disclosed alkaline earth metal precursor is introduced into the reaction chamber, where the alkaline earth metal precursor physisorbs or chemisorbs on a substrate. Excess composition may then be removed from the reaction chamber by purging and/or evacuating the reaction chamber. A desired gas (for example, oxidizer H.sub.2O or O.sub.3) is introduced into the reaction chamber where it reacts with the physisorbs or chemisorbed precursor in a self-limiting manner. Any excess oxidizer gas is removed from the reaction chamber by purging and/or evacuating the reaction chamber.
EXAMPLES
[0190] The following non-limiting examples are provided to further illustrate embodiments of the invention. However, the examples are not intended to be all inclusive and are not intended to limit the scope of the inventions described herein.
Example 1 Synthesis of Bis(tri-sec-butyl cyclopentadienyl)Strontium(II), Sr(sBu.SUB.3.Cp).SUB.2
##STR00005##
[0191] To a solution of SrI.sub.2 (1.88 g, 5.51 mmol) in 30 mL of THE at 30 C., was added dropwise a solution of K(sBu.sub.3Cp) (3.3 g, 12.11 mmol). The reaction mixture was warmed slowly to room temperature with stirring overnight. After filtration, the solvent was removed under reduced pressure to obtain a brown liquid. The material was then purified by distillation up to 130 C.@25 mTorr to give 1.2 g (40.0%) of yellow oil. The material was characterized by NMR .sup.1H (, ppm, C.sub.6D.sub.6): 5.62 (m, 4H), 2.57 (m, 6H), 1.52 (m, 12H), 1.34, 1.18 (m, 18H), 0.96, 0.88 (m, 18H).
[0192] The purified product left a 3.8% residual mass and showed no melting point during open-cup TGA/DTA analysis measured at a temperature rising rate of 10 C./min in an inert atmosphere that flows nitrogen at 200 mL/min. These results are shown in
Example 2 Synthesis of Bis(tri-sec-butyl cyclopentadienyl)Barium(II), Ba(sBu.SUB.3.Cp).SUB.2
##STR00006##
[0193] To a solution of BaI.sub.2 (2 g, 5.1 mmol) in 30 mL of THE at 30 C., was added dropwise a solution of K(sBu.sub.3Cp) (3.2 g, 11.76 mmol). The reaction mixture was warmed slowly to room temperature with stirring overnight. After filtration, the solvent was removed under reduced pressure to obtain a brown liquid. The material was then purified by distillation up to 130 C.@25 mTorr to give 1.0 g (32.5%) of yellow oil. The materials was characterized by NMR .sup.1H (, ppm, C.sub.6D.sub.6): 5.5 (m, 4H), 2.63 (m, 6H), 1.66, 1.54 (m, 12H), 1.27, 1.20 (m, 18H), 0.99 (m, 18H).
[0194] The purified product left a 2.7% residual mass and showed no melting point during open-cup TGA/DTA analysis measured at a temperature rising rate of 10 C./min in an inert atmosphere that flows nitrogen at 200 mL/min. These results are shown in
Comparative Example 1 Bis(tri-iso-propyl cyclopentadienyl)Strontium(II), Sr(iPr.SUB.3.Cp).SUB.2
##STR00007##
[0195] Melting point has been shown at 44 C. during open-cup DTA analysis measured at a temperature rising rate of 10 C./min in an inert atmosphere that flows nitrogen at 200 mL/min. These result is shown in
Comparative Example 2 Bis(tri-tert-butyl cyclopentadienyl)Strontium(II), Sr(tBu.SUB.3.Cp).SUB.2
##STR00008##
[0196] Melting point has been shown at 143 C. during open-cup DTA analysis measured at a temperature rising rate of 10 C./min in an inert atmosphere that flows nitrogen at 200 mL/min. These result is shown in
Comparative Example 3 Bis(tri-iso-propyl cyclopentadienyl)Barium(II), Ba(iPr.SUB.3.Cp).SUB.2
##STR00009##
[0197] Melting point has been shown at 92 C. during open-cup DTA analysis measured at a temperature rising rate of 10 C./min in an inert atmosphere that flows nitrogen at 200 mL/min. These result is shown in
[0198] The pyrolysis test showed that the precursor was stable up to 450 C. and decomposed above 500 C. It demonstrated the new Sr precursor is thermally stable so that it can allow a high temperature process with ozone to deposit SrO films.
[0199] It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above and/or the attached drawings.
[0200] While embodiments of this invention have been shown and described, modifications thereof may be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and not limiting. Many variations and modifications of the composition and method are possible and within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims which follow, the scope of which shall include all equivalents of the subject matter of the claims.