Precursor compositions for atomic layer deposition and chemical vapor deposition of titanate, lanthanate, and tantalate dielectric films

Information

  • Patent Grant
  • 9534285
  • Patent Number
    9,534,285
  • Date Filed
    Wednesday, June 11, 2014
    9 years ago
  • Date Issued
    Tuesday, January 3, 2017
    7 years ago
Abstract
Barium, strontium, tantalum and lanthanum precursor compositions useful for atomic layer deposition (ALD) and chemical vapor deposition (CVD) of titanate thin films. The precursors have the formula M(Cp)2, wherein M is strontium, barium, tantalum or lanthanum, and Cp is cyclopentadienyl, of the formula
Description
BACKGROUND OF THE INVENTION

Field of the Invention


The present invention relates to precursor compositions having utility for atomic layer deposition and chemical vapor deposition of titanate, lanthanate, and tantalate thin films, e.g., in the manufacture of microelectronic devices, as well as to processes of making and using such precursors, to products formed using such precursor compositions, and to precursor supply systems comprising such precursor compositions in packaged form.


Description of the Related Art


Strontium titanate (SrTiO3), barium titanate (BaTiO3) and barium strontium titanates (BaxSr1-xTiO3 where 0≦×≦1) are high dielectric constant materials that are potentially useful in future generation flash memories as well as other microelectronic products. Lanthanum oxides (La2O3), lanthanum tantalates (LaxTayOz where x, y, and z denote oxides of varying composition), and lanthanum titanates (e.g. LaTiO3) represent another class of high dielectric constant materials potentially useful on future generation microelectronic devices. Uniform coating involving greater than 90% step coverage on high aspect ratio structures is required for such titanate materials to achieve requisite high capacity in flash memory device applications.


Atomic layer deposition (ALD) is currently being explored as a technique for achieving such step coverage, using strontium β-diketonates and titanium β-diketonates as precursors. It is difficult, however, to achieve satisfactory uniform coating of strontium titanate thin films using the β-diketonate precursors that have been developed to date. Similar deficiencies are encountered when chemical vapor deposition (CVD) is used as a deposition technique to form such titanate films.


The art continues to seek new precursors for deposition of thin film titanates, lanthanates and tantalates such as strontium titanate, barium titanate, barium strontium titanate, lanthanum oxide, lanthanum tantalate, and lanthanum titanate.


SUMMARY OF THE INVENTION

The present invention relates to barium, strontium, tantalum and lanthanum precursors having utility for atomic layer deposition of titanate films useful in the manufacture of microelectronic devices such as flash memories. The invention further relates to methods of making and using such precursors, to supply systems for selective dispensing of such precursors, and to microelectronic device products fabricated with the use of such precursors.


In one aspect, the present invention relates to precursors having the formula M(Cp)2, wherein M is strontium or barium, precursors having the formula X3M(Cp)2 wherein M is tantalum and X is H or Si(Ra)3, wherein each Ra can be the same as or different from the other(s), and each is independently selected from among C1-C6 alkyl and C6-C10 aryl; and precursors having the formula M(Cp)3 wherein M is lanthanum, and wherein Cp is cyclopentadienyl, of the formula




embedded image



wherein each of R1-R5 is the same as or different from one another, with each being independently selected from among hydrogen, C1-C12 alkyl, C1-C12 amino, C6-C10 aryl, C1-C12 alkoxy, C3-C6 alkylsilyl, C2-C12 alkenyl (such term being intended to be broadly construed to include substituents containing linear, branched, and/or cyclic moieties containing ethylenic unsaturation, e.g., vinyl, allyl, cyclic-ene species, etc., and substituents containing various types of such moieties therein, e.g., tetramethylpentadienylvinyl), R1R2R3NNR3, wherein R1, R2 and R3 may be the same as or different from one another and each is independently selected from hydrogen and C1-C6 alkyl, and pendant ligands including functional group(s) providing further coordination to the metal center, such as, for example, alkoxyalkyl, aryloxyalkyl, imidoalkyl, and acetylalkyl, wherein suitable groups in these classes include those of the following formulae:




embedded image



wherein: the methylene (—CH2—) moiety could alternatively be another divalent hydrocarbyl moiety; each of R1-R4 is the same as or different from one another, with each being independently selected from among hydrogen and C1-C6 alkyl and C6-C10 aryl; each of R5 and R6 is the same as or different from the other, with each being independently selected from among C1-C6 alkyl; n and m are each selected independently from 0 to 4 with the proviso that m and n cannot be 0 at the same time, and x is selected from 1 to 5;




embedded image



wherein each of R1-R4 is the same as or different from one another, with each being independently selected from among hydrogen, C1-C6 alkyl, and C6-C10 aryl; R5 is selected from among C1-C6 alkyl, and C6-C10 aryl; and n and m are selected independently from 0 to 4, with the proviso that m and n cannot be 0 at the same time;




embedded image



wherein each of R1-R6 is the same as or different from one another, with each being independently selected from among hydrogen, C1-C6 alkyl, and C6-C10 aryl; and n and m are selected independently from 0 to 4, with the proviso that m and n cannot be 0 at the same time;




embedded image



wherein each of R1-R4 is the same as or different from one another, with each being independently selected from among hydrogen, C1-C6 alkyl, and C6-C10 aryl; R5 is selected from among C1-C6 alkyl, and C6-C10 aryl; and n and m are selected independently from 0 to 4, with the proviso that m and n cannot be 0 at the same time.


As used herein, the identification of a carbon number range, e.g., in C1-C6 alkyl or C6-C10 aryl, is intended to include each of the component carbon number moieties within such range. Accordingly, C1-C6 alkyl is intended to include methyl, ethyl, propyl, butyl, pentyl and hexyl, including a straight chain as well as branched groups of such types. It therefore is to be appreciated that identification of a carbon number range, e.g., C1-C6, as broadly applicable to a substituent moiety, enables, in specific embodiments of the invention, the carbon number range to be further restricted, as a sub-group of moieties having a carbon number range within the broader specification of the substituent moiety. By way of example, the carbon number range e.g., C1-C6 alkyl, may be more restrictively specified, in particular embodiments of the invention, to encompass sub-ranges such as C1-C4 alkyl, C2-C6 alkyl, C2-C4 alkyl, C3-C5 alkyl, or any other sub-range within the broad carbon number range.


In another aspect, the invention relates to precursor composition, comprising such precursor in a solvent medium.


A further aspect of the invention relates to a method of forming a barium-, lanthanum- and/or strontium-containing material on a substrate, comprising contacting the substrate with a vapor of a precursor as described above, to deposit barium, lanthanum and/or strontium on the substrate from said vapor.


A still further aspect of the invention relates to an atomic layer deposition process for forming a barium, lanthanum and/or strontium titanate on a substrate, comprising:

  • (a) contacting the substrate with a titanium source under conditions producing a coating of titanium on the substrate;
  • (b) contacting the titanium-coated substrate with an oxidant or water to form a hydroxylated surface;
  • (c) contacting the hydroxylated surface with a barium, lanthanum and/or strontium precursor of the present invention, under conditions producing a coating of barium and/or strontium thereon;
  • (d) contacting the barium, lanthanum and/or strontium-coated substrate with an oxidant or water to form a hydroxylated surface; and
  • (e) repeating steps (a) through (d) for sufficient number of repetitions to produce a barium, lanthanum and/or strontium titanate film of predetermined thickness.


In another aspect, the invention relates to a barium, lanthanum and/or strontium supply package, comprising a vessel enclosing an interior volume holding a barium, lanthanum and/or strontium precursor as described above.


A further aspect of the invention relates to an atomic layer deposition process, comprising pulsing of a vapor of a titanium precursor into a deposition reactor, purging the reactor to remove excess titanium precursor, pulsing water vapor into the reactor, optionally with an oxidant, pulsing a barium, lanthanum and/or strontium source into the reactor, purging the reactor to remove excess barium, lanthanum and/or strontium precursor, and pulsing water vapor into the reactor, optionally with an oxidant.


Additional aspects of the invention relate to forming strontium-, lanthanum- and/or barium-containing films on substrates using the precursors described above, involving the use of chemical vapor deposition or atomic layer deposition, e.g., contacting of a microelectronic device substrate with a vapor of a precursor of the invention.


Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.





BRIEF DESCRIPTION OF THE DRAWINGS


FIG. 1 is a schematic representation of an atomic layer deposition process utilizing a precursor of the present invention.



FIG. 2 is a graph of thermal analysis data including thermogravimetric (TG) analysis and differential scanning calorimetry (DSC) data as a function of temperature, for Ba[(N—Pr)Me4Cp]2 exhibiting a melting endotherm at 85.5° C. and a residue of 10.88%.



FIG. 3 is a graph of thermal analysis data of Sr(Cp*)2 including TG and DSC data as a function of temperature, wherein Cp* is pentamethylcyclopentadienyl.



FIG. 4 is a schematic representation of a material storage and dispensing package containing a barium, strontium or lanthanum precursor according to the present invention, in one embodiment thereof.





DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS THEREOF

The present invention relates to barium, strontium, tantalum and lanthanum precursors having utility for atomic layer deposition of titanate films useful in the manufacture of microelectronic devices such as flash memories. The invention further relates to methods of making and using such precursors, to supply systems for selective dispensing of such precursors, and to microelectronic device products fabricated with the use of such precursors.


In a specific aspect, the present invention relates to precursors having the formula M(Cp)2, wherein M is strontium or barium, precursors having the formula X3M(Cp)2 wherein M is tantalum and X is H or Si(Ra)3, wherein each Ra can be the same as or different from the other(s), and each is independently selected from among C1-C6 alkyl and C6-C10 aryl; and precursors having the formula M(Cp)3 wherein M is lanthanum, and wherein Cp is cyclopentadienyl of the formula




embedded image



wherein each of R1-R5 is the same as or different from one another, with each being independently selected from among hydrogen, C1-C12 alkyl, C1-C12 amino, C6-C10 aryl, C1-C12 alkoxy, C3-C6 alkylsilyl, C2-C12 alkenyl, R1R2R3NNR3, wherein R1, R2 and R3 may be the same as or different from one another and each is independently selected from hydrogen and C1-C6 alkyl, and pendant ligands including functional group(s) providing further coordination to the metal center, such as, for example, aminoalkyl, alkoxyalkyl, aryloxyalkyl, imidoalkyl, and acetylalkyl, wherein suitable groups in these classes may for example include those of the following formulae:




embedded image



wherein each of R1-R4 is the same as or different from one another, with each being independently selected from among hydrogen and C1-C6 alkyl and C6-C10 aryl; each of R5 and R6 is the same as or different from the other, with each being independently selected from among C1-C6 alkyl; n and m are each selected independently from 0 to 4 with the proviso that m and n cannot be 0 at the same time, and x is selected from 1 to 5;




embedded image



wherein each of R1-R4 is the same as or different from one another, with each being independently selected from among hydrogen, C1-C6 alkyl, and C6-C10 aryl; R5 is selected from among C1-C6 alkyl, and C6-C10 aryl; and n and m are selected independently from 0 to 4, with the proviso that m and n cannot be 0 at the same time;




embedded image



wherein each of R1-R6 is the same as or different from one another, with each being independently selected from among hydrogen, C1-C6 alkyl, and C6-C10 aryl; and n and m are selected independently from 0 to 4, with the proviso that m and n cannot be 0 at the same time;




embedded image



wherein each of R1-R4 is the same as or different from one another, with each being independently selected from among hydrogen, C1-C6 alkyl, and C6-C10 aryl; R5 is selected from among C1-C6 alkyl, and C6-C10 aryl; and n and m are selected independently from 0 to 4, with the proviso that m and n cannot be 0 at the same time.


The foregoing precursors can be usefully employed with a suitable titanium precursor to form titanate films of barium, strontium, tantalum and/or lanthanum, e.g. by ALD, CVD or other suitable deposition process.


In one embodiment, wherein the precursor is Ba(Cp)2, the precursor is used in a form that is not coordinated with any Lewis bases or other complexation agents, that is, without complexation with adduct-forming groups such as tetrahydrofuran, dienes, trienes, glymes, diglymes, triglymes, tetraglymes, etc.


Additionally, or alternatively, the R groups on the cyclopentadienyl rings of such Ba(Cp)2 precursor may in specific embodiments be constituted to exclude the following substituent combinations as being identically present on each of the two cyclopentadienyl rings: (i) wherein R1-R5 are all methyl, (ii) wherein three of such R1-R5 substituents are isopropyl and the remaining two of such substituents are H, (iii) wherein three of such R1-R5 substituents are t-butyl and the remaining two of such substituents are H, (iv) wherein four of such R1-R5 substituents are methyl and the remaining substituent is (Me)2NCH2CH2—, and (v) wherein four of such R1-R5 substituents are methyl and the remaining substituent is EtOCH2CH2— where Et is ethyl.


Correspondingly, the Sr(Cp)2 precursor may be selected in specific embodiments wherein at least one of the following criteria are met: (a) the precursor is not coordinated with tetrahydrofuran, and (b) R1-R5 are selected to exclude the following substituent combinations as being identically present on each of the two cyclopentadienyl rings: (i) wherein R1-R5 are all methyl, and (ii) wherein three of such R1-R5 substituents are isopropyl and the remaining two of such substituents are H.


In another embodiment, the invention contemplates Sr(Cp)2 compounds that are uncoordinated with any complexation agents.


In yet another embodiment, the precursor compounds of the invention may be stabilized with Lewis base ligands, subject to the exceptions stated in the preceding paragraphs. Lewis bases suitable for such purpose include, without limitation, alkenes, dienes, cycloalkenes, cyclooctatetraenes, alkynes, substituted alkynes (symmetrical or asymmetrical), amines, diamines, triamines, tetraamines, polyamines, ethers, diglymes, triglymes, tetraglymes, tetramethyl sulfides, dialkylsulfides, ethylenediamine, vinyltrimethylsilane, allyltrimethylsilane, and pentamethyl diethylenetriamine.


In one embodiment, the cyclopentadienyl ligand includes a ligand formed according to the following reaction (wherein the second reactant and final ligand are represented with kappa (κ) donor notation):




embedded image


The precursors of the invention may be supplied in any suitable form for volatilization to produce the precursor vapor for deposition contacting with the substrate, e.g., in a liquid form that is vaporized or as a solid that is dissolved or suspended in a solvent medium for flash vaporization, as a sublimable solid, or as a solid having sufficient vapor pressure to render it suitable for vapor delivery to the deposition chamber, or in any other suitable form.


When solvents are employed for delivery of the precursors of the invention, any suitable solvent media can be employed in which the precursor can be dissolved or dispersed for delivery. By way of example, the solvent medium may be a single-component solvent or a multicomponent solvent mixture, including solvent species such as C3-C12 alkanes, C2-C12 ethers, C6-C12 aromatics, C7-C16 arylalkanes, C10-C25 arylcycloalkanes, and further alkyl-substituted forms of aromatic, arylalkane and arylcycloalkane species, wherein the further alkyl substituents in the case of multiple alkyl substituents may be the same as or different from one another and wherein each is independently selected from C1-C8 alkyl. Particularly preferred solvents include alkanes, alkyl-substituted benzene compounds, benzocyclohexane (tetralin), alkyl-substituted benzocyclohexane and ethers, with tetrahydrofuran, xylene, 1,4-tertbutyltoluene, 1,3-diisopropylbenzene, tetralin, dimethyltetralin, octane and decane being particularly preferred solvent species.


In instances where liquid delivery is employed in deposition processes of the invention to form deposited metal films, it may be preferable to utilize high boiling point solvents in order to avoid metal precursor deposits in the delivery system, such as in flow circuitry, and in vaporizers that are utilized to volatilize the metal precursor to form a corresponding precursor vapor, where the system is otherwise susceptible to solids deposition and clogging. For example, in delivery systems utilizing low boiling solvents for delivery of the precursor, e.g., a strontium precursor for liquid delivery atomic layer deposition, residual precursor of solution in the vaporizer and delivery lines will evaporate leaving behind solid precursor. Eventually such precursor builds up and clogs the delivery system.


Accordingly, in various embodiments of the invention, it may be desirable to utilize high boiling aromatic solvents, e.g., aromatic solvents having a boiling point at 1 atmosphere pressure in a range of from about 140° C. to about 250° C. For example, in liquid delivery strontium precursor applications for atomic layer deposition processes, suitable solvents may include xylene, 1,4-tertbutyltoluene, 1,3-diisopropylbenzene, tetralin, dimethyltetralin and other alkyl-substituted aromatic solvents.


In general, the precursor compositions of the invention may alternatively comprise, consist, or consist essentially of any of the components and functional moieties discloses herein, in specific embodiments of the invention.


The titanium precursors useful with the barium, strontium, tantalum and/or lanthanum precursors of the invention include those of the formula X2TiCp2, where Cp is the same as described above, and each X is independently selected from among chlorine, bromine, iodine, C1-C4 alkyl and C1-C4 alkoxy, dialkylamido (such as those of the formula R1R2N—, where R1 and R2 are independently selected from C1-C4 alkyls,) and cyclic alkylamido (such as those of the formula (CH2)yN—, where y is an integer selected from among 2, 3, 4, 5 and 6).


Because both MCp2 and X2TiCp2 are highly sensitive to hydroxyl-terminated surfaces, such precursors react readily to form respective self-limiting monolayers on substrate surfaces such as semiconductor wafers having free hydroxyl functionality thereon. MO and TiO2 can be deposited sequentially from these precursors, and post-annealed to achieve various dielectrics, e.g., strontium titanate (STO) dielectrics, lanthanum titanate (LTO) dielectrics, barium titanate (BTO) dielectrics and barium strontium titanate (BSTO) dielectrics.


The cyclopentadienyl precursors of the invention are particularly useful in atomic deposition layer processes, such as the illustrative process schematically represented in FIG. 1.


As shown in FIG. 1, a silicon substrate 10 is shown as having a noble metal electrode 12 thereon (Step 1). This structure then is subjected to contact with titanium precursor of the formula TiR2X2 under suitable deposition conditions to form a structure (Step 2) in which the noble metal electrode 10 is functionalized on its upper surface with titanium moieties. The thus-functionalized structure then is submitted to contact with an oxidant [O] such as oxygen, ozone, etc., or water. A wide variety of oxidants can be used for such purpose. The surface then reacts with the oxidant to form a hydroxylated surface (Step 3).


The hydroxylated surface of the device structure next is contacted with the strontium reagent, Sr(Cp)2, to yield the strontiated (strontium-functionalized) surface (Step 4). The strontiated surface then is contacted with oxidant or water to form the hydroxylated surface (Step 5), and the hydroxylated surface thereafter is processed by contact with the titanium precursor, with repetition of the above-described steps (Steps 2-5) any suitable number of times to build up a layer 14 of strontium titanate, SrTiO3 (Step 6).


In this repetitive manner, a dielectric film of strontium titanate is built up over the electrode layer in the device structure, with the deposition process being conducted through multiple steps of titanium functionalization, hydroxylation, strontiation and hydroxylation, to build up the strontium titanate film to a desired thickness.


Analogous processes can be carried out utilizing alternating layers of Ba, Sr, and Ti, Ba and Sr mixtures and Ti, La and Ta, and La and Ti.


In one embodiment of such process, the oxidant is selected from among oxygen, ozone and oxygen plasma. The use of such oxidant may eliminate the need for a final annealing step, such as rapid thermal annealing.


In general, the thickness of the titanate layer in the practice of the present invention can be of any suitable value. In a specific embodiment of the invention, the thickness of the titanate layer can be in a range of from 5 nm to 500 nm or more.


The titanium precursors usefully employed in the broad practice of the invention can be of any suitable type, and include, without limitation, the aforementioned Cp2TiX2, as well as titanium alkoxides, Ti(OR)4, such as Ti(OPr-i)4 and Ti(OBu-t)4, and titanium beta-diketonate alkoxides, Ti(β-diketonate)2(OR)2, such as Ti(thd)2(OPr-i)2 and Ti(thd)2(OBu-t)2.


One preferred reagent for forming a titanate film is Ba[(n-Pr)Me4Cp]2. FIG. 2 is a graph of thermal analysis data including thermogravimetric (TG) analysis and differential scanning calorimetry (DSC) data, as a function of temperature, for Ba[(n-Pr)Me4Cp]2, exhibiting a melting endotherm at 85.5° C. and a residue of 10.88%.


Another preferred strontium precursor in the practice of the present invention is bis(pentamethylcyclopentadienyl) strontium. FIG. 3 is a graph of thermal analysis data including TG and DSC data as a function of temperature, for Sr(Cp*)2, wherein Cp* is pentamethylcyclopentadienyl.


The strontium, lanthanum, tantalum and barium precursors of the invention may be provided in any suitable packaged form, as appropriate to storage of the precursor and its subsequent delivery in use. In one embodiment, the precursor package comprises a vessel defining a closed interior volume holding the precursor, with the vessel having a valve head assembly connected thereto. The valve head assembly may include a manual or automatic valve controller, to modulate the position of a valve element in the value head assembly, between a fully opened and a fully closed position, as required for storage and dispensing use of the package.


In general, the precursor may be provided in a form appropriate for delivery and use, e.g., in a form for liquid delivery or alternatively for solid precursor delivery of vapor.



FIG. 4 is a schematic representation of a material storage and dispensing package 100 containing a barium, strontium, tantalum or lanthanum precursor, according to one embodiment of the present invention.


The material storage and dispensing package 100 includes a vessel 102 that may for example be of generally cylindrical shape as illustrated, defining an interior volume 104 therein. In this specific embodiment, the barium or strontium precursor is a solid at ambient temperature conditions, and such precursor may be supported on surfaces of the trays 106 disposed in the interior volume 104 of the vessel, with the trays having flow passage conduits 108 associated therewith, for flow of vapor upwardly in the vessel to the valve head assembly, for dispensing in use of the vessel.


The solid precursor can be coated on interior surfaces in the interior volume of the vessel, e.g., on the surfaces of the trays 106 and conduits 108. Such coating may be effected by introduction of the precursor into the vessel in a vapor form from which the solid precursor is condensed in a film on the surfaces in the vessel. Alternatively, the precursor solid may be dissolved or suspended in a solvent medium and deposited on surfaces in the interior volume of the vessel by solvent evaporation. For such purpose, the vessel may contain substrate articles or elements that provide additional surface area in the vessel for support of the precursor film thereon.


As a still further alternative, the solid precursor may be provided in granular or finely divided form, which is poured into the vessel to be retained on the top supporting surfaces of the respective trays 106 therein.


The vessel 102 has a neck portion 109 to which is joined the valve head assembly 110. The valve head assembly is equipped with a hand wheel 112 in the embodiment shown. The valve head assembly 110 includes a dispensing port 114, which may be configured for coupling to a fitting or connection element to join flow circuitry to the vessel. Such flow circuitry is schematically represented by arrow A in FIG. 4, and the flow circuitry may be coupled to a downstream ALD or chemical vapor deposition chamber (not shown in FIG. 4).


In use, the vessel 102 is heated, such input of heat being schematically shown by the reference arrow Q, so that solid precursor in the vessel is at least partially volatilized to provide precursor vapor. The precursor vapor is discharged from the vessel through the valve passages in the valve head assembly 110 when the hand wheel 112 is translated to an open valve position, whereupon vapor deriving from the precursor is dispensed into the flow circuitry schematically indicated by arrow A.


In lieu of solid delivery of the precursor, the precursor may be provided in a solvent medium, forming a solution or suspension. Such precursor-containing solvent composition then may be delivered by liquid delivery and flash vaporized to produce a precursor vapor. The precursor vapor is contacted with a substrate under deposition conditions, to deposit the metal, e.g., strontium, barium, tantalum and/or lanthanum, on the substrate as a film thereon.


In one embodiment, the precursor is dissolved in an ionic liquid medium, from which precursor vapor is withdrawn from the ionic liquid solution under dispensing conditions.


As a still further alternative, the precursor may be stored in an adsorbed state on a suitable solid-phase physical adsorbent storage medium in the interior volume of the vessel. In use, the precursor vapor is dispensed from the vessel under dispensing conditions involving desorption of the adsorbed precursor from the solid-phase physical adsorbent storage medium.


Supply vessels for precursor delivery may be of widely varying type, and may employ vessels such as those commercially available from ATMI, Inc. (Danbury, Conn.) under the trademarks SDS, SAGE, VAC, VACSorb, and ProE-Vap, as may be appropriate in a given storage and dispensing application for a particular precursor of the invention.


The precursors of the invention thus may be employed to form precursor vapor for contacting with a substrate to deposit a thin film of barium, strontium, tantalum or lanthanum thereon, in connection with concurrent or sequential deposition of titanium from a suitable titanium source reagent, to produce titanate films as barium titanate, lanthanum titanate, tantalum titanate, strontium titanate, and barium strontium titanate.


In a preferred aspect, the invention utilizes the barium, strontium, tantalum and/or lanthanum precursors to conduct atomic layer deposition in connection with the use of a suitable titanium source reagent, yielding ALD films of superior high dielectric character that are uniformly coated on the substrate with high step coverage even on high aspect ratio structures.


Accordingly, the barium, strontium, tantalum and lanthanum precursors of the present invention enable a wide variety of microelectronic devices, e.g., semiconductor products, flat panel displays, etc., to be fabricated with high dielectric constant titanate films of superior quality.


The features and advantages of the invention are more fully shown by the following non-limiting example.


EXAMPLE 1

In the synthesis of bis(pentamethylcyclopentadienyl)strontium ((Cp*)2Sr), potassium pentamethylcyclopentadiene (KCp*, 5.11 grams, 29.29 mmol) was added to a stirred suspension of strontium diiodide (SrI2, 5.00 grams, 14.64 mmol) in 300 ml of diethyl ether. The mixture was stirred for 48 hours, filtered, and concentrated in vacuo giving 4.10 grams of the bis(pentamethylcyclopentadienyl)strontium diethyl ether adduct ((Cp*)2Sr(OEt2)). The coordinated diethyl ether was removed by a toluene reflux process. In a typical, but non-limiting example, 3.00 grams of (Cp*)2Sr(OEt2) were dissolved in 150 ml of toluene. The toluene solution was heated to 110° C. and the toluene/diethyl ether removed slowly in vacuo giving an off yellow solid. This process was repeated three more times to give the ether free (Cp*)2Sr. High purity (Cp*)2Sr can be obtained by sublimation at 120-130° C.


An atomic layer deposition process is carried out as generally schematically shown in FIG. 1, in which the process involves pulsing of a titanium source into the deposition reactor, purging the reactor to remove excess titanium precursor, then pulsing water vapor into the reactor, with or without oxidant (such as O2, O3 or N2O,) followed by pulsing the strontium source into the reactor and then purging, followed by introduction of water vapor with or without oxidant. This process is repeated until a desired film thickness of the strontium titanate layer is reached. Deposition temperature is advantageously in a range of from 250° C. to 500° C. Pulse rates can be on the order from 10 milliseconds to 30 seconds or more. After deposition, the film may require rapid thermal annealing (RTA) to obtain a crystalline SrTiO3 film, by RTA treatment at temperature in a range of from 500° C. to 900° C., for an annealing period of from a few seconds to 30 minutes or more. An oxygen plasma may be used in the reactant step, in addition to or in lieu of the forgoing annealing treatment.


Corresponding synthesis can be carried out to form other cyclopentadienyl compounds of the invention, e.g., tantalum compounds.


While the invention has been disclosed herein with respect to particular illustrative embodiments, aspects and features, it will be recognized that the invention is not thus limited, but rather extends to and encompasses other variations, modifications and alternative embodiments, as will readily suggest themselves to those of ordinary skill in the art based on the disclosure herein. Accordingly, the claims set out hereinafter are intended to be construed to encompass all such variations, modifications and alternative embodiments, as being within the spirit and scope of such claims.

Claims
  • 1. A method of depositing a thin film on a substrate, said method comprising contacting the substrate with a vapor of a precursor composition, wherein the precursor composition includes a compound of the formula M(Cp)2 wherein M(Cp)2 is bis(tetramethyl-n-propylcyclopentadienyl)strontium, and wherein the compound is not coordinated with letrahydrofuran, to form a thin film comprising strontium on the substrate; andcontacting the thin film comprising strontium with an oxidant selected from the group consisting of oxygen, ozone and water.
  • 2. The method according to claim 1, comprising chemical vapor deposition or atomic layer deposition.
  • 3. The method according to claim 2, comprising chemical vapor deposition.
  • 4. The method according to claim 2, comprising atomic layer deposition.
  • 5. The method according to claim 1, further comprising concurrent or sequential deposition of titanium from a titanium source reagent to produce a titanate film.
  • 6. The method according to claim 5, wherein the titanate film is strontium titanate.
  • 7. The method according to claim 5, comprising concurrent deposition.
  • 8. The method according to claim 5, comprising sequential deposition.
  • 9. The method according to claim 1, further comprising a solvent medium.
  • 10. The method according to claim 9, wherein the solvent medium comprises a solvent species selected from the group consisting of C3-C12 alkanes, C2-C12 ethers, C6-C12 aromatics, C7-C16 arylalkanes, C10-C25 arylcycloalkanes, and further alkyl-substituted forms of aromatic, arylalkane and arylcycloalkane species, wherein the further alkyl substituents in the case of multiple alkyl substituents may be the same as or different from one another and wherein each is independently selected from C1-C8 alkyl.
  • 11. The method according to claim 9, wherein the solvent medium is tetrahydrofuran, xylene, 1,4-tertbutyltoluene, 1,3-diisopropylbenzene, tetrahydronaphthalene, dihydrodimethylnaphthalene, octane or decane.
  • 12. The method according to claim 5, wherein the oxidant is oxygen or ozone.
  • 13. The method according to claim 12, wherein the titanate film produced is not annealed.
CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 13/370,072, filed Feb. 9, 2012, which is a continuation of U.S. patent application Ser. No. 12/619,165, filed Nov. 16, 2009, now U.S. Pat. No. 8,206,784, which is continuation of U.S. patent application Ser. No. 12/282,511, now U.S. Pat. No. 7,638,074, filed on Sep. 10, 2008, which is a United States national phase, filed under the provisions of 35 USC §371, of International Application No. PCT/US07/63825 filed Mar. 12, 2007, which in turn claims the benefit and priority of U.S. Provisional Patent Application No. 60/781,291 filed Mar. 10, 2006; U.S. Provisional Patent Application No. 60/791,299 filed Apr. 12, 2006; U.S. Provisional Patent Application No. 60/844,867 filed Sep. 15, 2006; and U.S. Provisional Patent Application No. 60/884,728 filed Jan. 12, 2007. The disclosures of such U.S. applications, national phase application, international application and U.S. provisional applications are hereby incorporated herein by reference in their respective entireties, for all purposes.

US Referenced Citations (128)
Number Name Date Kind
4915988 Erbil Apr 1990 A
4927670 Erbil May 1990 A
4948623 Beach et al. Aug 1990 A
4960916 Pazik Oct 1990 A
4962214 Villacorta et al. Oct 1990 A
5204057 Ishigami et al. Apr 1993 A
5204314 Kirlin et al. Apr 1993 A
5225561 Kirlin et al. Jul 1993 A
5280012 Kirlin et al. Jan 1994 A
5453494 Kirlin et al. Sep 1995 A
5536323 Kirlin et al. Jul 1996 A
5555154 Uchikawa et al. Sep 1996 A
5711816 Kirlin et al. Jan 1998 A
5721043 Summerfelt et al. Feb 1998 A
5770921 Aoki et al. Jun 1998 A
5820664 Gardiner et al. Oct 1998 A
5837417 Rahman et al. Nov 1998 A
5840897 Kirlin et al. Nov 1998 A
5919522 Baum et al. Jul 1999 A
6002036 Kadokura Dec 1999 A
6024847 Rosenberg et al. Feb 2000 A
6025222 Kimura et al. Feb 2000 A
6087500 Fukuda et al. Jul 2000 A
6110529 Gardiner et al. Aug 2000 A
6110531 Paz de Araujo et al. Aug 2000 A
6111122 Paw et al. Aug 2000 A
6177558 Brennan et al. Jan 2001 B1
6218518 Baum et al. Apr 2001 B1
6277436 Stauf et al. Aug 2001 B1
6287965 Kang et al. Sep 2001 B1
6340386 Hendrix et al. Jan 2002 B1
6342445 Marsh Jan 2002 B1
6440495 Wade et al. Aug 2002 B1
6479100 Jin et al. Nov 2002 B2
6506666 Marsh Jan 2003 B2
6511706 Hendrix et al. Jan 2003 B1
6562678 Uchiyama et al. May 2003 B1
6599447 Stauf et al. Jul 2003 B2
6646122 Nuhlen et al. Nov 2003 B1
6660331 Hendrix et al. Dec 2003 B2
6673646 Droopad Jan 2004 B2
6680251 Won et al. Jan 2004 B2
6743739 Shimamoto et al. Jun 2004 B2
6787186 Hintermaier Sep 2004 B1
6849122 Fair Feb 2005 B1
6984591 Buchanan et al. Jan 2006 B1
6989457 Kamepalli et al. Jan 2006 B2
7108747 Leskela et al. Sep 2006 B1
7211509 Gopinath et al. May 2007 B1
7250367 Vaartstra et al. Jul 2007 B2
7285308 Hendrix et al. Oct 2007 B2
7300038 Gregg et al. Nov 2007 B2
7635441 Kadokura et al. Dec 2009 B2
7638074 Xu et al. Dec 2009 B2
7790629 Holme et al. Sep 2010 B2
8034407 Hendrix et al. Oct 2011 B2
8092721 Gatineau et al. Jan 2012 B2
8206784 Xu et al. Jun 2012 B2
8455049 Cameron et al. Jun 2013 B2
20020004266 Hashimoto et al. Jan 2002 A1
20020067917 Takamatsu et al. Jun 2002 A1
20020090815 Koike et al. Jul 2002 A1
20020146513 Jin et al. Oct 2002 A1
20030012876 Min et al. Jan 2003 A1
20030020122 Joo et al. Jan 2003 A1
20030032238 Kim et al. Feb 2003 A1
20030038594 Seo et al. Feb 2003 A1
20030072882 Niinisto et al. Apr 2003 A1
20030129306 Wade et al. Jul 2003 A1
20030165615 Aaltonen et al. Sep 2003 A1
20030205823 Leu et al. Nov 2003 A1
20040038808 Hampden-Smith et al. Feb 2004 A1
20040043149 Gordon et al. Mar 2004 A1
20040166671 Lee et al. Aug 2004 A1
20040197946 Vaartstra et al. Oct 2004 A1
20040211998 Araujo et al. Oct 2004 A1
20040214354 Marsh et al. Oct 2004 A1
20040238861 Hwang et al. Dec 2004 A1
20050009325 Chung et al. Jan 2005 A1
20050153073 Zheng et al. Jul 2005 A1
20050186341 Hendrix et al. Aug 2005 A1
20050208699 Furkay et al. Sep 2005 A1
20050217575 Gealy et al. Oct 2005 A1
20050277780 Gordon et al. Dec 2005 A1
20060006449 Jeong et al. Jan 2006 A1
20060027451 Park et al. Feb 2006 A1
20060035462 Millward Feb 2006 A1
20060049447 Lee et al. Mar 2006 A1
20060115595 Shenai-Khatkhate et al. Jun 2006 A1
20060118968 Johnston et al. Jun 2006 A1
20060128150 Gandikota et al. Jun 2006 A1
20060138393 Seo et al. Jun 2006 A1
20060172067 Ovshinsky et al. Aug 2006 A1
20060172083 Lee et al. Aug 2006 A1
20060180811 Lee et al. Aug 2006 A1
20060275545 Yoshinaka et al. Dec 2006 A1
20060288928 Eom et al. Dec 2006 A1
20070004226 Tweet et al. Jan 2007 A1
20070049021 Basceri Mar 2007 A1
20070053139 Zhang et al. Mar 2007 A1
20070054487 Ma et al. Mar 2007 A1
20070116888 Faguet May 2007 A1
20070154637 Shenai-Khatkhate et al. Jul 2007 A1
20070190362 Weidman Aug 2007 A1
20080194088 Srinivasan et al. Aug 2008 A1
20080242111 Holme et al. Oct 2008 A1
20080254218 Lei et al. Oct 2008 A1
20080254232 Gordon et al. Oct 2008 A1
20080317972 Hendriks et al. Dec 2008 A1
20090001618 Kadokura et al. Jan 2009 A1
20090002917 Kil et al. Jan 2009 A1
20090004383 Kadokura et al. Jan 2009 A1
20090058953 Arakawa et al. Mar 2009 A1
20090074965 Xu et al. Mar 2009 A1
20090087561 Chen et al. Apr 2009 A1
20090215225 Stender et al. Aug 2009 A1
20090275164 Chen et al. Nov 2009 A1
20090321733 Gatineau et al. Dec 2009 A1
20100015800 Hara et al. Jan 2010 A1
20100062150 Xu et al. Mar 2010 A1
20100095865 Xu et al. Apr 2010 A1
20100291299 Cameron et al. Nov 2010 A1
20110195188 Hendrix et al. Aug 2011 A1
20110215679 Naono Sep 2011 A1
20110292134 Sasaki et al. Dec 2011 A1
20120064719 Lubguban, Jr. et al. Mar 2012 A1
20120141675 Xu et al. Jun 2012 A1
20130251918 Cameron et al. Sep 2013 A1
Foreign Referenced Citations (22)
Number Date Country
0904568 Apr 2001 EP
1645656 Apr 2006 EP
1798307 Jun 2007 EP
2000561 Dec 2008 EP
2-225317 Sep 1990 JP
7-70747 Mar 1995 JP
7-249616 Sep 1995 JP
10-125237 May 1998 JP
10-273779 Oct 1998 JP
2004-527651 Sep 2004 JP
2006-37123 Feb 2006 JP
10-0443350 Jul 2004 KR
10-2008-0079514 Sep 2008 KR
768457 Oct 1980 SU
0015865 Mar 2000 WO
0166834 Sep 2001 WO
2004046417 Jun 2004 WO
2006012052 Feb 2006 WO
2007064376 Jun 2007 WO
2008088563 Jul 2008 WO
2008117582 Oct 2008 WO
2009020888 Feb 2009 WO
Non-Patent Literature Citations (26)
Entry
Habermeier, H., “Thin films of perovskite-type complex oxides”, “Materials Today”, Oct. 2007, pp. 34-43, vol. 10, No. 10.
Ju, Y., et al., “Growth of Thin-Film Layered Perovskite Cathodes by Pulsed Laser Deposition and their Electrochemical Studies in IT-SOFCs”, “Journal of the Electrochemical Society”, Apr. 18, 2014, pp. F698-F702, vol. 161, No. 6.
Marozau, I., et al., “RF-plasma assisted pulsed laser deposition of nitrogen-doped SrTiO3 thin films”, “Appl Phys A”, Jun. 13, 2008, pp. 721-727, vol. 93.
Anderson, Q., et al., “Synthesis and Characterization of the First Pentaphenylcyclopentadienyl Copper(I) Complex, (Ph5Cp)Cu(PPh3)”, “Organometallics”, 1998, pp. 4917-4920, vol. 17.
Artaud-Gillet, M., et al., “Evaluation of copper organometallic sources for CuGaSe2 photovoltaic applications”, “Journal of Crystal Growth”, 2003, pp. 163-168, vol. 248.
Burns, C., et al., “Organometallic Coordination Complexes of the BIS (Pentamethylcyclopentadienyl)-Alkaline Earth Compounds, (ME5C5)2MLN, Where M is Mg, Ca, Sr, or Ba and ME5C5BECL”, “Journal of Organometallic Chemistry”, 1987, pp. 31-37, vol. 325.
Christen, H., et al., “Semiconducting epitaxial films of metastable SrRu0.5Sn0.5O3 grown by pulsed laser deposition”, “Applied Physics Letters”, 1997, pp. 2147-2149 (Title and Abstract), vol. 70, No. 16.
Hatanpaa, T., et al., “Synthesis and characterisation of cyclopentadienyl complexes of barium: precursors for atomic layer deposition of BaTiO3”, “Dalton Trans.”, Mar. 22, 2004, pp. 1181-1188, vol. 8.
Holme, T., et al., “Atomic Layer Deposition and Chemical Vapor Deposition Precursor Selection Method Application to Strontium and Barium Precursors”, “J. Phys. Chem.”, Jul. 27, 2007, pp. 8147-8151, vol. 111, No. 33.
Kirlin, P., et al., “Thin Films of Barium Fluoride Scintillator Deposited by Chemical Vapor Deposition”, “Nuclear Instruments and Methods in Physics Research”, 1990, pp. 261-264, vol. A289.
Kirlin, P., et al., “Growth of High Tc YBaCuO Thin Films by Metalorganic Chemical Vapor Deposition”, “SPIE”, 1989, pp. 115-127, vol. 1187.
Kosola, A., et al., “Effect of annealing in processing of strontium titanate thin films by ALD”, “Applied Surface Science”, 2003, pp. 102-112, vol. 211.
Kvyatkovskii, O., “On the Nature of Ferroelectricity in Sr1-xAxTiO3 and KTa1-xNbxO3 Solid Solutions”, “Physics of the Solid State”, 2002, pp. 1135-1144, vol. 44, No. 6.
Leskela, M., et al., “Atomic layer deposition chemistry: recent developments and future challenges”, “Angew. Chem. Int. Ed.”, Nov. 24, 2003, pp. 5548-5554, vol. 42, No. 45.
Lu, H., et al., “Evolution of itinerant ferromagnetism in SrxPb1-xRuO3 (0 less than or equal to x less than or equal to 1): Interplay between Jahn-Teller distortion and A-site disorder”, “Applied Physics Letters”, Mar. 22, 2011, pp. 1-3, vol. 98, No. 122503.
Macomber, D., et al., “(n5-Cyclopentadienyl)- and (n5-Pentamethylcyclopentadienyl)copper Compounds Containing Phosphine, Carbonyl, and n2-Acetylenic Ligands”, “J. Am. Chem. Soc.”, 1983, pp. 5325-5329, vol. 105.
McCormick, M., et al., “Solution Synthesis of Calcium, Strontium, and Barium Metallocenes”, “Polyhedran”, 1988, pp. 725-730, vol. 7, No. 9.
Niinistoe, J., et al., “Atomic Layer Deposition of High-k Oxides of the Group 4 Metals for Memory Applications”, “Advanced Engineering Materials”, Mar. 9, 2009, pp. 223-234, vol. 11, No. 4.
Papadatos, F., et al., “Characterization of Ruthenium and Ruthenium Oxide Thin Films deposited by Chemical Vapor Deposition for CMOS Gate Electrode Applications”, “Mat. Res. Soc. Symp. Proc.”, 2003, pp. N3.3.1-N3.3.6, vol. 745.
Ren, H., et al., “Synthesis and structures of cyclopentadienyl N-heterocyclic carbene copper(I) complexes”, “Journal of Organometallic Chemistry”, Jun. 21, 2006, pp. 4109-4113, vol. 691.
Selg, P., et al., “Solution Infrared Spectroscopic Studies on Equilibrium Reactions of Co With the Decamethylmetallocenes CP2MII, Where M=Mg, Ca, Sr, Ba, Sm, Eu, Yb”, “Organometallics”, Jun. 22, 2002, pp. 3100-3107, vol. 21, No. 15.
Singh, R., et al., “In-Situ Processing of Epitaxial Y—Ba—Cu—O High Tc Superconducting Films on (100) SrTiO3 and (100) Ys—ZrO2 Substrates at 500-650 Degrees Celsius”, “Applied Physics Letters”, May 29, 1989, pp. 2271-2273, vol. 54, No. 22.
Vehkamaki, M., et al., “Growth of SrTiO3 and BaTiO3 Thin Films by Atomic Layer Deposition”, “Electrochemical Solid-State Letters”, Aug. 5, 1999, pp. 504-506, vol. 2, No. 10.
Vehkamaki, M., et al., “Atomic Layer Deposition of SrTiO3 Thin Films from a Novel Strontium Precursor-Strontium-bis(tri-isopropylcyclopentadienyl)”, “Chemical Vapor Deposition”, Mar. 2001, pp. 75-80, vol. 7, No. 2.
Wu, L., et al., “Humidity Sensitivity of Sr(Sn, Ti)03 Ceramics”, “Journal of Electronic Materials”, 1990, pp. 197-200, vol. 19, No. 2.
Hanusa, T., “Ligand Influences on Structure and Reactivity in Organoalkaline-Earth Chemistry”, Chem. Rev., May 1993, pp. 1023-1036, vol. 93.
Related Publications (1)
Number Date Country
20140295071 A1 Oct 2014 US
Provisional Applications (4)
Number Date Country
60781291 Mar 2006 US
60791299 Apr 2006 US
60844867 Sep 2006 US
60884728 Jan 2007 US
Continuations (3)
Number Date Country
Parent 13370072 Feb 2012 US
Child 14301861 US
Parent 12619165 Nov 2009 US
Child 13370072 US
Parent 12282511 US
Child 12619165 US