Strontium precursor, method for preparing same, and method for forming thin film by using same

Abstract

Disclosed herein is a novel strontium precursor containing a beta-diketonate compound. Being superior in thermal stability and volatility, the strontium precursor can form a quality strontium thin film.

Claims

1. A strontium precursor, represented by the following Chemical Formula 5: ##STR00021## wherein, R1, R2, R3, R4, and R5 are independently methyl group (—CH.sub.3); R6 and R7 are independently tertiary-butyl group (—C(CH.sub.3).sub.3); and m and n are independently 1.

2. A method for preparing strontium precursor represented by Chemical Formula 5 of claim 1, using an amino alcohol represented by the following Chemical Formula 6: ##STR00022## wherein, R1, R2, R3, R4, and R5 are independently methyl group (—CH.sub.3); and m and n are independently 1.

3. The method of claim 2, wherein the method comprises: a) reacting a compound represented by the following Chemical Formula 6 with Sr(NR.sub.8R.sub.9).sub.2 to synthesize a compound represented by the following Chemical Formula 7; and b) reacting the compound of Chemical Formula 7 with a compound represented by the following Chemical Formula 8: ##STR00023## wherein, R1, R2, R3, R4, and R5 are independently methyl group (—CH.sub.3); and m and n are independently 1; ##STR00024## wherein, R1, R2, R3, R4, and R5 are independently methyl group (—CH.sub.3); R8 and R9 are independently H, linear or branched alkyl of C1-C10, or trialkylsilyl (—SiR.sub.3); and m and n are independently 1; ##STR00025## wherein, R6 and R7 are independently tertiary-butyl group (—C(CH.sub.3).sub.3).

4. A method for growth of a strontium-containing thin film, using the strontium precursor of claim 1.

5. The method of claim 4, wherein the growth of the strontium-containing thin film is carried out by chemical vapor deposition (CVD) or atomic layer deposition (ALD).

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows TG data of Sr(.sup.3iPrCp)(tmhd).

(2) FIG. 2 shows TG data of Sr(.sup.2t-BuCp)(tmhd).

(3) FIG. 3 depicts a structure of Sr(demamp)(btsa), as determined by X-ray crystallography.

(4) FIG. 4 depicts a structure of Sr(demamp)(tmhd), as determined by X-ray crystallography.

(5) FIG. 5 shows TG data of Sr(demamp)(tmhd).

BEST MODE

(6) In accordance with an aspect thereof, the present invention addresses a strontium precursor represented by the following Chemical Formula 1:

(7) ##STR00009##

(8) wherein, R1, R2, R3, R4 and R5 are independently H, or linear or branched alkyl of C1-C10; and R6 and R7 are independently H, or linear or branched alkyl of C1-C10, or linear or branched fluorinated alkyl of C1-C10.

(9) The strontium precursor represented by Chemical Formula 1 in accordance with the present invention may be expressed as the general formula Sr(Cp′)(bdk). The preparation of this compound may start with the reaction of a cyclopentadiene compound represented by the following Chemical Formula 2 with SrI.sub.2 in an organic solvent, followed by allowing the resulting cyclopentadiene strontium represented by the following Chemical Formula 3 to undergo a substitution reaction with a beta-diketonate represented by the following Chemical Formula 4 in an organic solvent:

(10) ##STR00010##

(11) wherein, R1, R2, R3, R4 and R5 are independently H, or linear or branched alkyl of C1-C10.

(12) ##STR00011##

(13) wherein, R1, R2, R3, R4 and R5 are independently H, or linear or branched alkyl of C1-C10.

(14) ##STR00012##

(15) wherein, R6 and R7 are independently H, or linear or branched alkyl of C1-C10, or linear or branched fluorinated alkyl of C1-C10.

(16) Examples of the solvent useful for the reactions include toluene, tetrahydrofuran, hexane, and diethylether, with preference for toluene.

(17) Reaction procedures of preparing the strontium precursor of the present invention may be as shown in the following Reaction Schemes 1 and 2.

(18) ##STR00013##

(19) wherein, R1, R2, R3, R4, and R5 are independently H, or linear or branched alkyl of C1-C10.

(20) As shown in Reaction Scheme 1, a substitution reaction is carried out at room temperature for 12 hrs to 24 hrs in a solvent such as toluene, tetrahydrofuran, hexane, or diethylether to give Sr′CpI as a yellow solid.

(21) ##STR00014##

(22) wherein, R1, R2, R3, R4, and R5 are independently H, or linear or branched alkyl of C1-C10; and R6 and R7 are independently H, or linear or branched alkyl of C1-C10, or linear or branched fluorinated alkyl of C1-C10.

(23) Next, as illustrated in Reaction Scheme 2, the resulting compound Sr′CpI of Reaction Scheme 1 is allowed to undergo a substitution reaction with compound 3 in a solvent, such as toluene, tetrahydrofuran, hexane, or diethylether, at room temperature for 12 to 24 hrs. After filtration at a reduced pressure, the filtrate is dried in a vacuum to afford the novel strontium precursor as a dark yellow solid. During the procedures of Reaction Schemes 1 and 2, by-products may be produced. They may be removed by sublimation or recrystallization to give the novel strontium precursor of high purity.

(24) In addition, the present invention addresses a strontium precursor represented by the following Chemical Formula 5:

(25) ##STR00015##

(26) wherein, R1, R2 and R3 are independently H, or linear or branched alkyl of C1-C10; R4, R5, R6, and R7 are independently H, or linear or branched alkyl of C1-C10, or linear or branched fluorinated alkyl of C1-C10; and m and n are independently an integer of 1 to 3.

(27) Also, the present invention is concerned with a strontium precursor represented by the following Chemical Formula 7.

(28) ##STR00016##

(29) wherein, R1, R2 and R3 are independently H, or linear or branched alkyl of C1-C10; R4 and R5 are independently H, or linear or branched alkyl of C1-C10, or linear or branched fluorinated alkyl of C1-C10; R8 and R9 are independently H, or linear or branched alkyl of C1-C10, or trialkylsilyl (—SiR.sub.3); and m and n are independently an integer of 1 to 3.

(30) The strontium precursor, represented by Chemical Formula 5, according to the present invention can be prepared by reacting a compound represented by the following Chemical Formula 6 as a starting material with Sr(NR8R9).sub.2 in an organic solvent to synthesize a strontium compound represented by Chemical Formula 7, and then subjecting the strontium compound of Chemical Formula 7 to substitution reaction with a beta-diketonate represented by the following Chemical Formula 8.

(31) ##STR00017##

(32) wherein, R1, R2 and R3 are independently H, or linear or branched alkyl of C1-C10; R4 and R5 are independently H or linear or branched alkyl of C1-C10, or linear or branched fluorinated alkyl of C1-C10; and m and n are independently an integer of 1 to 3.

(33) ##STR00018##

(34) (R6 and R7 are independently H or linear or branched alkyl of C1-C10, or linear or branched fluorinated alkyl of C1-C10.)

(35) Examples of the solvent useful in the reactions include toluene, tetrahydrofuran, hexane, and diethylether, with preference for toluene.

(36) Preparation of a strontium precursor according to the present invention may be as illustrated in the following Reaction Scheme 3.

(37) ##STR00019##

(38) wherein, R1, R2 and R3 are independently H, or linear or branched alkyl of C1-C10; R4 and R5 are independently H, linear or branched alkyl of C1-C10, or linear or branched fluorinated alkyl of C1-C10; and R8 and R9 are independently H, linear or branched alkyl of C1-C10, or trialkylsilyl (—SiR.sub.3); and m and n are independently an integer of 1 to 3.

(39) As shown in Reaction Scheme 3, a substitution reaction is carried out at room temperature for 12 to 24 hrs in a solvent such as tetrahydrofuran, hexane, or diethylether to give an intermediate [Sr(aminoalkoxide)(amide)].sub.2 (1) as a white solid.

(40) Another reaction procedure of preparing a strontium precursor according to the present invention may be as illustrated in the following Reaction Scheme 4.

(41) ##STR00020##

(42) wherein, R1, R2 and R3 are independently H, or linear or branched alkyl of C1-C10; R4, R5, R6, and R7 are independently H, linear or branched alkyl of C1-C10, or linear or branched fluorinated alkyl of C1-C10; and R8 and R9 are independently H, linear or branched alkyl of C1-C10, or trialkylsilyl (—SiR.sub.3); and m and n are independently an integer of 1 to 3.

(43) As illustrated in Reaction Scheme 4, the resulting compound Sr(aminoalkoxide)(amide) (1) of Reaction Scheme 3 is allowed to undergo a substitution reaction with tetramethyl heptane dione in a solvent, such as toluene, tetrahydrofuran, hexane, or diethylether, at room temperature for 12 to 24 hrs. After filtration at a reduced pressure, the filtrate is dried in a vacuum to afford the novel strontium precursor as a white crystalline solid. During the procedures of Reaction Schemes 3 and 4, by-products may be produced. They may be removed by sublimation or recrystallization to give the novel strontium precursor of high purity.

(44) In these reactions, the reactants are used at stoichiometric ratios.

(45) The novel strontium precursor represented by Chemical Formula 1 or 5 takes the form of a white solid at room temperature, and is thermally stable and highly volatile.

(46) As a precursor for use in thin films, the novel strontium precursor of the present invention can be applied to chemical vapor deposition or atomic layer deposition both of which are widely used for the preparation of STO or BST.

(47) A better understanding of the present invention may be obtained through the following examples that are set forth to illustrate, but are not to be construed as limiting the present invention.

Mode for Invention

Synthesis of Strontium Precursor

Example 1: Preparation of Sr(3iPrCp)(tmhd)

(48) In a 200 mL Schlenk flask, a solution of strontium iodide (0.4 g, 1.2 mmol, 1 eq) in THF (100 mL) was mixed with 2,3,5-triisopropyl cyclopentadiene potassium (0.27 g, 1.2 mmol, 1 eq) in THF (50 mL) while stirring for 24 hrs. After removing potassium iodide by filtration, the filtrate was reacted with 2,2,6,6-tetramethyl heptanedione sodium (0.25 g, 1.2 mmol) in THF (50 mL) while stirring for an additional 24 hrs. Distillation in a vacuum was carried out to dryness to afford the compound as a yellow solid: Yield 52%.

(49) The compound Sr(.sup.3iPrCp)(tmhd) was analyzed for .sup.1H-NMR (THF-d8), .sup.1H-NMR (C.sub.6D.sub.6), and FT-IR, as follows.

(50) NMR data: (.sup.1H, THF-d8) δ 1.07 (s, 18H), 1.03-1.1 (several singlets, 18H), 2.8 (m, 3H), 5.4 (s, 1H), 6.02 (s, 1H).

(51) NMR data: (.sup.1H, C.sub.6D.sub.6) δ 1.05-1.4 (several singlets, 18H), 1.24 (s, 18H), 2.8 (m, 3H), 5.9 (s, 1H), 6.2 (s, 1H). (.sup.13C, C.sub.6D.sub.6) δ 22.9, 23.2, 26.3, 27.0, 28.9, 29.0, 30.2, 39.1, 41.6, 91.5, 124.02, 141.6, 143.9, 152.3, 201.6.

(52) FT-IR (cm.sup.−1): 2960 (s), 2868 (m), 1580 (s), 1537 (w), 1500 (s), 1410 (s), 1357 (m), 1130 (w), 866 (w), 814 (w), 472 (w).

Example 2: Preparation of Sr(2t-ButCp)(tmhd)

(53) In a 200 mL Schlenk flask, a solution of strontium (0.4 g, 1.2 mmol, 1 eq) in THF (100 mL) was mixed with a solution of 1,3-di-t-butyl cyclopentadiene potassium (0.26 g, 1.2 mmol, 1 eq) in THF (50 mL) while stirring for 24 hrs. After removing potassium iodide by filtration, the filtrate was reacted with 2,2,6,6-tetramethyl heptanedione sodium (0.25 g, 1.2 mmol) in THF (50 mL) while stirring for an additional 24 hrs. Vaporization was carried out in a vacuum to dryness to afford the compound as a yellow solid: Yield 56%.

(54) The compound Sr(.sup.2t-ButCp)(tmhd) was analyzed for .sup.1H-NMR (C.sub.6D.sub.6), and FT-IR, as follows.

(55) NMR data: (.sup.1H, C.sub.6D.sub.6) δ 1.13-1.32 (several singlets, 18H), 1.23 (s, 18H), 5.9 (s, 1H), 6.4 (singlets, 2H).

(56) FT-IR (cm.sup.−1): 2960 (s), 2867 (m), 1598 (s), 1580 (s), 1500 (s), 1420 (s), 1360 (s), 1130 (w), 866 (w), 793 (w), 476 (w).

Example 3: Preparation of Sr(demamp)(btsa) (1)

(57) In a Schlenk flask, a solution of 1-((2-(dimethylamino)ethyl)(methyl)amino)-2-methylpropan-2-ol (demampH) (0.17 g, 1 mmol) in 15 mL of toluene was dropwise added to a solution of Sr(btsa).sub.2.2DME (0.59 g, 1 mmol, 1 eq) in 15 mL of toluene. After stirring at room temperature for 15 hrs, the resulting reaction mixture was filtered, and the toluene was removed by distillation to dryness to afford the compound as a white solid (0.4 g, yield 95%). During quenching, X-ray crystals grew in the concentrated toluene.

(58) The compound Sr(demamp)(btsa)(1) was analyzed for .sup.1H-NMR and FT-IR, as follows.

(59) .sup.1H NMR (C.sub.6D.sub.6, 300 MHz): δ 0.38 (s, 18H), 1.23 (s, 3H), 1.46 (s, 3H), 1.54 (m, 1H), 1.68 (m, 1H), 2.00 (m, 1H), 2.07 (s, br, 6H), 2.11 (d, 1H), 2.15 (s, 3H), 2.33 (d, 1H), 2.65 (m, 1H).

(60) FTIR: (cm.sup.−1) 2945 (s), 2837 (w), 1484 (w), 1244 (w), 1059 (s), 961 (w), 883 (w), 817 (m), 659 (w).

(61) Anal. Calcd for C.sub.30H.sub.78N.sub.6O.sub.2Si.sub.4Sr.sub.2: C, 42.76; H, 9.33; N, 9.97.

(62) Found: C, 41.92; H, 9.15; N, 9.54.

Example 4: Preparation of Sr(demamp)(tmhd)(2)

(63) In a Schlenk flask, a solution of tetramethylheptanedione (tmhd) (0.19 g, 1 mmol) in 5 mL of toluene was dropwise added to a solution of Sr(demamp)(btsa)(1) (0.84 g, 1 mmol) in 5 mL of toluene at room temperature, and then stirred for 12 hrs. After completion of the reaction, toluene was distilled, and the residue was dissolved in hexane, and filtered to give the compound as a white solid (0.41 g, Yield 93%). During quenching, X-ray crystals grew in the concentrated solution.

(64) The resulting compound Sr(demamp)(tmhd)(2) was analyzed for .sup.1H-NMR and FT-IR as follows.

(65) .sup.1H NMR (C.sub.6D.sub.6, 300 MHz): δ 1.21 (s, br), 1.34 (s, 18H), 1.41 (s, br), 2.08 (s), 2.14 (s), 2.44 (s, br), 5.87 (s, 1H).

(66) FTIR: (cm.sup.−1) 2950 (s), 2863 (m), 1589 (s), 1534 (w), 1504 (m), 1450 (s), 1423 (s), 1355 (m), 1225 (w), 1198 (w), 1185 (w), 864 (w), 470 (w).

(67) Anal. Calcd for C.sub.40H.sub.80N.sub.4O.sub.6Sr.sub.2: C, 54.08; H, 9.08; N, 6.31.

(68) Found: C, 53.71; H, 9.35; N, 6.01.

(69) Analysis of Strontium Precursors

(70) Sr(.sup.3iPrCp)(tmhd) of Example 1 and Sr(.sup.2t-ButCp)(tmhd) of Example 2 were measured for thermal stability, volatility, and degradation temperature by a thermogravimetric analysis (TGA) method. In the TGA method, the products were heated at a rate of 10° C./min to 900° C. while argon gas was introduced at a pressure of 1.5 bar/min. TGA graphs of the strontium precursor compounds synthesized in Examples 1 and 2 are given in FIGS. 1 and 2, respectively. As shown in FIG. 1, the strontium precursor compound obtained in Example 1 started to degrade at around 124° C., with a total of mass loss by 64% or higher at 500° C. As can be seen in FIG. 2, the strontium precursor compound obtained in Example 2 started to undergo mass loss at around 123° C. with a total of mass loss of 89% or higher at 315° C.

(71) Structural examination was made on the strontium precursor compounds synthesized in Examples 3 and 4, using Bruker SMART APEX II X-ray Diffractometer, and their X-ray structures are depicted in FIGS. 3 and 4, respectively. As can be seen, concrete structures of Sr(demamp)(btsa)(1) and Sr(demamp)(tmhd)(2) could be obtained.

(72) Also, a Thermo Gravimetric Analysis (TGA) method was used to examine the thermal stability, volatility, and degradation temperature of Sr(demamp)(tmhd)(2). In the TGA method, the product was heated at a rate of 10° C./min to 900° C. while argon gas was introduced at a pressure of 1.5 bar/min. FIG. 5 is a TGA graph of the strontium precursor compound synthesized in Example 4. As can be seen in FIG. 9, the strontium precursor compound obtained in Example 4 was observed to start degradation at 273° C., with a total of mass loss of 83% at 398° C.