Patent Application
20220025514
In at least one aspect, the present invention relates to methods for forming metal layers by atomic layer deposition at low temperatures.
In the microelectronics industry, smaller device dimensions require the development of new materials. Cobalt has utility as a barrier layer in amorphous CoTix (x=18-83%) alloys. Cobalt and CoTix can replace current W/Ti/TiN contact plugs and other liners in integrated circuits. In this regard, the ALD of cobalt metal is required for deposition in high aspect ratio features. Deposition of cobalt metal is difficult due to the negative electrochemical potential of Co(II), (Co(II)↔Co(0), E°=−0.28 V)
Moreover, ALD growth of cobalt metal is likely to be required for use in future electronics applications such as in magnetic materials, as an intermediate in the deposition of CoSix contacts, for liners and caps of copper features in microelectronics devices, and the replacement of copper in high aspect ratio features
Accordingly, there is a need for an improved process for forming cobalt and similar metal films for microelectronic applications.
In at least one aspect, the present invention provides a method for depositing a metal layer. The method includes a step of contacting a surface of an electrically conductive substrate with a vapor of a metal-containing compound for a first predetermined pulse time to form a modified surface on the electrically conductive substrate. The metal-containing compound is described by formulae 1.1 or 1.2 or oligomers thereof:
wherein:
M is a metal atom;
n is the formal charge of M;
X1 and X2 are each independently O or N—R4;
L is a neutral or anionic ligand;
o is 1, 2, or 3;
p is an integer such that the overall formal charge of the metal-containing compound is 0;
R1, R2, R3, and R4 are each independently H, C1-C5 alkyl, perfluorinated C1-C5 alkyl, partially fluorinated C1-C5 alkyl, or —Si(R5)3; and
R5 is H, halo, C1-C5 alkyl, perfluorinated C1-C5 alkyl, or partially fluorinated C1-C5 alkyl. The modified surface is then contacted with a vapor of a reducing agent having formula 2 for a second predetermined pulse time to form a metal-containing film on the surface of the electrically conductive substrate. The metal-containing film includes the metal atom is in a zero oxidation state in an amount greater than 80 mole percent:
wherein R5 and R6 are each independently H or C1-C5 alkyl and wherein the electrically conductive substrate is at a first predetermined temperature during these two steps.
In another embodiment, a method for depositing a metal layer is provided. The method includes a step of contacting a surface of an electrically conductive substrate with a vapor of a metal-containing compound for a first predetermined pulse time to form a modified surface on the electrically conductive substrate. The metal-containing compound is described by formula 3.3:
wherein:
M is a metal atom selected from the group consisting of Co, Cr, Mn, Fe, Zn, or Ni.
R1, R2, and R3 are each independently H, C1-C5 alkyl, perfluorinated C1-C5 alkyl, partially fluorinated C1-C5 alkyl, or —Si(R4)3. The modified surface is contacted with a vapor of a reducing agent having formula 2 for a second predetermined pulse time to form a metal-containing film on the surface of the electrically conductive substrate:
wherein R5 and R6 are each independently H or C1-C5 alkyl. Characteristically, the metal-containing film includes the metal atom in a zero oxidation state in an amount greater than 80 mole percent, wherein the electrically conductive substrate is at a first predetermined temperature during the two steps set forth above. Moreover, these two steps are successively performed a plurality of times until the metal-containing film is within a predetermined thickness range.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
For a further understanding of the nature, objects, and advantages of the present disclosure, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein:
Reference will now be made in detail to presently preferred compositions, embodiments and methods of the present invention, which constitute the best modes of practicing the invention presently known to the inventors. The Figures are not necessarily to scale. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the invention and/or as a representative basis for teaching one skilled in the art to variously employ the present invention.
Except in the examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred. Also, unless expressly stated to the contrary: all R groups (e.g. Ri where i is an integer) include hydrogen, alkyl, lower alkyl, C1-6 alkyl, C6-10 aryl, C6-10 heteroaryl, —NO2, —NH2, —N(R′R″), —N(R′R″R′″)+L−, Cl, F, Br, —CF3, —CCl3, —CN, —SO3H, —PO3H2, —COOH, —CO2R′, —COR′, —CHO, —OH, —OR′, —O−M+, —SO3M+, —PO3−M+, —COO−M+, —CF2H, —CF2R′, —CFH2, and —CFR′R″ where R′, R″ and R′″ are C1-10 alkyl or C6-18 aryl groups; single letters (e.g., “n” or “o”) are 1, 2, 3, 4, or 5; in the compounds disclosed herein a CH bond can be substituted with alkyl, lower alkyl, C1-6 alkyl, C6-10 aryl, C6-10 heteroaryl, —NO2, —NH2, —N(R′R″), —N(R′R″R′″)+L−, Cl, F, Br, —CF3, —CCl3, —CN, —SO3H, —PO3H2, —COOH, —CO2R′, —COR′, —CHO, —OH, —OR′, —O−M+, —SO3−M+, —PO3−M+, —COO−M+, —CF2H, —CF2R′, —CFH2, and —CFR′R″ where R′, R″ and R′″ are C1-10 alkyl or C6-18 aryl groups; percent, “parts of,” and ratio values are by weight; the term “polymer” includes “oligomer,” “copolymer,” “terpolymer,” and the like; molecular weights provided for any polymers refers to weight average molecular weight unless otherwise indicated; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily preclude chemical interactions among the constituents of a mixture once mixed; the first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation; and, unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property.
It must also be noted that, as used in the specification and the appended claims, the singular form “a,” “an,” and “the” comprise plural referents unless the context clearly indicates otherwise. For example, reference to a component in the singular is intended to comprise a plurality of components.
As used herein, the term “about” means that the amount or value in question may be the specific value designated or some other value in its neighborhood. Generally, the term “about” denoting a certain value is intended to denote a range within +/−5% of the value. As one example, the phrase “about 100” denotes a range of 100+/−5, i.e., the range from 95 to 105. Generally, when the term “about” is used, it can be expected that similar results or effects according to the invention can be obtained within a range of +/−5% of the indicated value.
As used herein, the term “and/or” means that either all or only one of the elements of said group may be present. For example, “A and/or B” shall mean “only A, or only B, or both A and B”. In the case of “only A”, the ern also covers the possibility that. B is absent, i.e. “only A, but not B”.
It is also to be understood that this invention is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present invention and is not intended to be limiting in any way.
The term “comprising” is synonymous with “including,” “having,” “containing,” or “characterized by.” These terms are inclusive and open-ended and do not exclude additional, unrecited elements or method steps.
The phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. When this phrase appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.
The phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps, plus those that do not materially affect the basic and novel characteristic(s) of the claimed subject matter.
The phrase “composed of” means “including” or “consisting of” Typically, this phrase is used to denote that an object is formed from a material.
With respect to the terms “comprising,” “consisting of,” and “consisting essentially of,” where one of these three terms is used herein, the presently disclosed and claimed subject matter can include the use of either of the other two terms.
The term “one or more” means “at least one” and the term “at least one” means “one or more.” The terms “one or more” and “at least one” include “plurality” as a subset.
The term “substantially,” “generally,” or “about” may be used herein to describe disclosed or claimed embodiments. The term “substantially” may modify a value or relative characteristic disclosed or claimed in the present disclosure. In such instances, “substantially” may signify that the value or relative characteristic it modifies is within +0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or 10% of the value or relative characteristic.
It should also be appreciated that integer ranges explicitly include all intervening integers. For example, the integer range 1-10 explicitly includes 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Similarly, the range 1 to 100 includes 1, 2, 3, 4 . . . 97, 98, 99, 100. Similarly, when any range is called for, intervening numbers that are increments of the difference between the upper limit and the lower limit divided by 10 can be taken as alternative upper or lower limits. For example, if the range is 1.1. to 2.1 the following numbers 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 can be selected as lower or upper limits.
In the examples set forth herein, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced with plus or minus 50 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples. In a refinement, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced with plus or minus 30 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples. In another refinement, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced with plus or minus 10 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples.
For all compounds expressed as an empirical chemical formula with a plurality of letters and numeric subscripts (e.g., CH2O), values of the subscripts can be plus or minus 50 percent of the values indicated rounded to or truncated to two significant figures. For example, if CH2O is indicated, a compound of formula C(0.8-1.2)H(1.6-20.4)O(0.8-1.2). In a refinement, values of the subscripts can be plus or minus 30 percent of the values indicated rounded to or truncated to two significant figures. In still another refinement, values of the subscripts can be plus or minus 20 percent of the values indicated rounded to or truncated to two significant figures.
The term “alkali metal” means lithium, sodium, potassium, rubidium, caesium, and francium.
The “alkaline earth metal” means chemical elements in group 2 of the periodic table. The alkaline earth metals include beryllium, magnesium, calcium, strontium, barium, and radium.
The term “transition metal” means an element whose atom has a partially filled d sub-shell, or which can give rise to cations with an incomplete d sub-shell. Examples of transition metals includes scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, and gold.
The term “lanthanide” or lanthanoid series of chemical elements” means an element with atomic numbers 57-71. The lanthanides metals include lanthanum, cerium, praseodymium, samarium, europium, gadolinium neodymium, promethium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium.
The term “actinide” or “actinide series of chemical elements” means chemical elements with atomic numbers from 89 to 103. Examples of actinides include actinium, thorium, protactinium, uranium, neptunium, and plutonium.
The term “post-transition metal” means gallium, indium, tin, thallium, lead, bismuth, zinc, cadmium, mercury, aluminum, germanium, antimony, or polonium.
The term “metal” as used herein means an alkali metal, an alkaline earth metal, a transition metal, a lanthanide, an actinide, or a post-transition metal.
Throughout this application, where publications are referenced, the disclosures of these publications in their entireties are hereby incorporated by reference into this application to more fully describe the state of the art to which this invention pertains.
Abbreviations:
“acac” means acetylacetonate.
“ALD” means atomic layer deposition.
“Cy” means cyclohexyl.
“hfac” means hexafluoroacetylacetonate.
“Nacac” means β-ketoiminate.
“TEEDA” means N,N, N′,N′-Tetraethylethylenediamine.
“TMEDA” means tetramethylethylenediamine.
“TMPDA” means tetramethylpropylenediamine
“thd” means 2,2,6,6-tetramethyl-3,5-heptanediketonate.
“Tp” means tris(pyrazolyl)borate.
“tta” means 2-thenoyltrifluoroacetonate.
In an embodiment of the present embodiment, a method for depositing a thin film on a surface of a substrate is provided. With reference to
wherein:
M is a metal atom;
n is the formal charge of M (e.g., 0, 1+, 2+, 3+, 4+, 5+, 6+);
X1 and X2 are each independently O or N—R4;
L is a neutral or anionic ligand;
o is 1, 2, or 3;
p is an integer such that the overall formal charge of the metal-containing compound is 0;
R1, R2, R3, and R4 are each independently H, C1-C5 alkyl, perfluorinated C1-C5 alkyl, partially fluorinated C1-C5 alkyl, or —Si(R5)3; and
R5 is H, halo, C1-C5 alkyl, perfluorinated C1-C5 alkyl, or partially fluorinated C1-C5 alkyl. Note, the wavy lines crossing a straight line indicated the attachment points (e.g., bond-forming) to the metal M. In a refinement, n is 1+, 2+, or 3+; o is 0, 1, 2, or 3; and p is 1, 2, or 3. In another refinement, n is 1+, 2+, or 3+ and p is 1, 2, or 3.
It should be appreciated that a variety of different ligands may be used for L. For example, L can be a two-electron ligand, a multidentate ligand (e.g., a bidentate ligand), charged ligand (e.g., −1 charged), a neutral ligand, and combinations thereof. A specific example for L is Me2NCH2CH2NMe2. Although o gives the number of ligands, each ligand need not be the same for values of o greater than 2. In a refinement, R1, R2, R3, and R4 are each independently H or C1-4 alkyl. Examples of useful alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, sec-butyl, and the like. In another refinement, R1, R2, R3, and R4 are each independently H, methyl, ethyl, propyl, n-butyl, sec-butyl, isobutyl, or t-butyl. In still another refinement, R2 is H and R1, R3, and R4 are each independent methyl, ethyl, propyl, n-butyl, sec-butyl, isobutyl, or t-butyl. In yet another refinement, R1, R3, and R4 are methyl or t-butyl and R2 is hydrogen.
In a refinement of the present embodiment, M is a transition metal atom typically in the 0 to +6 oxidation state. In a further refinement, M is a transition metal atom in the +1 to +3 oxidation state. In still a further refinement, M is a transition metal atom in the +2 oxidation state. Examples of useful metals for M include, but are not limited to, silver, palladium, platinum, rhodium, iridium, cobalt, ruthenium, manganese, nickel, zinc, and copper. In a further refinement, M is Co(II), Cr, Mn, Fe, Zn, or Ni. For example, M can be Co(II), Cr(II), Mn(II), Fe(II), Zn(II), or Ni(II).
Still referring to
In the next reaction step (step b) of the deposition cycle, the modified surface is contacted with a vapor of a reducing agent having formula 2 for a second predetermined pulse time to form a metal-containing film on the surface of the electrically conductive substrate,
wherein R5 and R6 are each independently H or C1-C5 alkyl. Examples of the reducing agent include, but are not limited to, tBuNHNH2, (CH3)2NNH2, or H2NNH2 (hydrazine). The reducing agent can be provided from reducing agent source 34 which is controlled by control valve 36. In a refinement, the reaction chamber 12 is then purged with an inert gas for a second purge time as set forth above. The second purge time is sufficient to remove the metal-containing compound from the reaction chamber 12 and is typically from 0.5 seconds to 2 minutes. As set forth above, this purging step can be replaced by or supplemented with a pumping step.
During each deposition cycle, the substrate temperature is typically maintained at the first predetermined temperature for steps a) and b). In a refinement, the first predetermined temperature is between 200 to 350° C. In a further refinement, steps a) and b) are performed at a first predetermined pressure of about 0.1 millitorr to 100 Torr.
Characteristically, the metal-containing film includes the metal atom in a zero oxidation state in an amount greater than 80 mole percent. In a refinement, the metal-containing film includes metastable metal nitrides in an amount less than 20 mole percent. In a further refinement, the metal-containing film includes the metal atom in a zero oxidation state in an amount greater than 90 mole percent and metastable metal nitrides in an amount less than 10 mole percent.
In a variation, the method further includes a step of annealing the metal-containing film at a second predetermined temperature for a sufficient time that the metal-containing film includes the metal atom in the zero oxidation state in an amount greater than 98 mole percent. Characteristically, the second predetermined temperature is greater than the first predetermined temperature. In a refinement, the second predetermined temperature is greater than in increasing order of preference, 300° C., 310° C., 325° C., or 330° C. Typically, the second predetermined temperature is less than about 400° C.
In a variation, the metal-containing compound is described by formulae 3.1, 3.2, or 3.3:
Details for R1, R2, R3, and M are the same as above. In a refinement of the compounds having formula 3.1, 3.2, or 3.3, R1, R2, and R3 are each independently H or C1-4 alkyl. Examples of useful alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, sec-butyl, and the like. In another refinement, R1, R2, and R3 are each independently H, methyl, ethyl, propyl, n-butyl, sec-butyl, isobutyl, or t-butyl. In still another refinement, R2 is H and R1 and R3 are each independent methyl, ethyl, propyl, n-butyl, sec-butyl, isobutyl, or t-butyl. In yet another refinement, R1 and R3 are methyl or t-butyl and R2 is hydrogen.
In another variation, the metal-containing compound is described by formulae 4.1, 4.2, 4.3, or 4.4:
Details for R1, R2, R3, R4 and M are the same as above. In a refinement of the compounds having formulae 4.1, 4.2, 4.3, or 4.4, R1, R2, R3, and R4 are each independently H or C1-4 alkyl. Examples of useful alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, sec-butyl, and the like. In another refinement, R1, R2, R3, and R4 are each independently H, methyl, ethyl, propyl, n-butyl, sec-butyl, isobutyl, or t-butyl. In still another refinement, R2 is H and R1, R3, and R4 are each independent methyl, ethyl, propyl, n-butyl, sec-butyl, isobutyl, or t-butyl. In yet another refinement, R1 R3, and R4 are methyl or t-butyl and R2 is hydrogen.
In a variation, the electrically conductive substrate has an electrical resistivity that is less than about, in increasing order of preference 1×10−2 ohm-m, 1×10−3 ohm-m, 1×10−4 ohm-m, 1×10−5 ohm-m, 1×10−6 ohm-m, 1×10−7 ohm-m. Most resistivities are greater than about 1×10−9 ohm-m. In a refinement, the electrically conductive substrate includes one or more surfaces composed of silicon, titanium nitride, tantalum nitride, or a metal. In a further refinement, the electrically conductive substrate includes one or more surfaces composed of copper or ruthenium. Examples of useful electrically conductive substrates include, but are not limited to, silicon (with the native oxide removed), titanium nitride coated substrates, tantalum nitride coated substrate, metal-coated base substrates, metal substrates, and silicon-coated substrates. Advantageously, the metal-containing film grows selectively on surfaces of the one or more electrically conductive films. In a refinement, the electrically conductive substrate includes one or more electrically conductive films disposed over a base substrate.
It should be appreciated that pulse times, purge times, and pump times also depend on the properties of the chemical precursors and the geometric shape of the substrates. Thin film growth on flat substrates uses short pulse and purge times and/or pump times, but pulse and purge times and/or pump times here too in ALD growth on 3-dimensional substrates can be very long. Therefore, in one refinement, pulse times and purge times and/or pump times are each independently from about 0.0001 to 200 seconds. In another refinement, pulse and purge times and/or pump times are each independently from about 0.1 to about 10 seconds.
In another variation, steps a) and b) are repeated a plurality of times. For example the deposition cycle can be repeated 1 to 5000 times. The desired metal film thickness depends on the number of deposition cycles. For example, for a cobalt metal film 1000 cycles typically results in a thickness of about 500 angstroms. Therefore, in a refinement, the deposition cycle is repeated a plurality of times to form a predetermined thickness of the metal film. In a further refinement, the deposition cycle is repeated a plurality of times to form a metal film having a thickness from about 5 nanometers to about 200 nanometers. In still another refinement, the deposition cycle is repeated a plurality of times to form a metal film having a thickness from about 5 nanometers to about 300 nanometers. In yet another refinement, the deposition cycle is repeated a plurality of times to form a metal film having a thickness from about 5 nanometers to about 100 nanometers.
During film formation by the method of the present embodiment, the substrate temperature will be at a temperature suitable to the properties of the chemical precursor(s) and film to be formed. In a refinement of the method, the substrate is set to a temperature from about 0 to 1000° C. In another refinement of the method, the substrate has a temperature from about 150 to 450° C. In another refinement of the method, the substrate has a temperature from about 150 to 400° C. In still another refinement of the method, the substrate has a temperature from about 200 to 350° C. In another refinement of the method, the substrate has a temperature from about 200 to 300° C.
Similarly, the pressure during film formation is set at a value suitable to the properties of the chemical precursors and film to be formed. In one refinement, the pressure is from about 1×10−6 Torr to about 760 Torr. In another refinement, the pressure is from about 0.1 millitorr to about 100 Torr. In another refinement, the pressure is from about 0.1 millitorr to about 100 Torr. In still another refinement, the pressure is from about 1 to about 10 millitorr. In yet another refinement, the pressure is from about 1 to 20 millitorr.
The following examples illustrate the various embodiments of the present invention. Those skilled in the art will recognize many variations that are within the spirit of the present invention and scope of the claims.
Grazing incidence X-ray diffraction data was collected for a film grown on copper for 2000 cycles.
X-ray photoelectron spectroscopy depth profile data was collected for films grown at various temperatures and with a post-deposition anneal. Four films were grown using 2000 cycles and submitted for analysis: 22 nm thick film grown at 265° C.; 18 nm thick film grown at 275° C.; 38 nm thick film grown at 285° C.; and 30 nm thick film grown at 285° C.+post-deposition anneal at 400° C. All films were grown on ruthenium substrates. For this analysis, films were sputtered using a 3.0 keV argon ion beam to obtain depth profiles.
Atomic force microscopy data was also collected on samples using the deposition conditions set forth for
In conclusion, cobalt metal has been deposited using Co(thd)2 and 1,1-dimethyl hydrazine. GI-XRD analysis of a film grown on copper was consistent with cobalt metal or cobalt-copper alloy, XPS data indicated low levels of carbon, nitrogen, and oxygen in films deposited at various temperatures and treatment of a film with a post-deposition anneal resulted in a high-quality film with no carbon or nitrogen impurities. AFM data reveals that deposition temperature had little effect on surface roughness. There is a nonlinear relationship between film thickness and number of cycles while there is a linear increase in cobalt concentration, indicating the density of the film increases with an increasing number of cycles. Resistivity measurements are similar to the resistivity of the bare ruthenium substrates until the film thickness approaches 50 nm where it drops notably.
Cobalt diketonates,1 amine adducts,2 ketoiminates,3 and pyrazolyl borates4 were synthesized and purified according to general literature procedures using standard air-free Schlenk line and glovebox techniques. Co(thd)2 (thd=2,2,6,6-tetramethylheptanedionate) required additional processing to obtain material of high enough purity for deposition. Crude Co(thd)2 was dissolved in diethyl ether, washed with brine, dried with MgSO4, precipitated from degassed diethyl ether at −30° C., filtered, and sublimed at 120° C./0.5 Torr. Cobalt diketiminates were synthesized by modified literature procedures using CoCl2 in place of MnCl2 and purified by sublimation at 134° C./0.5 Torr. Melting point measurements were taken using a Thermo Scientific Mel-temp 3.0 and are uncorrected. Thermogravimetric analysis experiments were conducted on a TA Instruments SPT 2960 with a heating rate of 5° C./min.
Atomic layer deposition experiments were performed on a Picosun R200 ALD reactor operating at 6-10 Torr from 200-300° C. on Ru (35 or 45 nm), Cu (30 nm), Pt (100 nm), SiO2, high resistivity Si, and in situ ALD TiN2 substrates. Cobalt precursors were delivered using a Picosolid booster. Nitrogen-based co-reactants were used as received from Sigma-Aldrich and delivered using a vapor draw bubbler. A flow restricting VCR gasket (100 μm) installed in the bubbler line was used to limit co-reactant consumption. Ultrahigh purity N2 (99.999%, Airgas) was used as the carrier and purge gas. Cobalt metal was deposited using Co(thd)2 and 1,1-dimethyl hydrazine (DMH) from 265-300° C. using the following pulse sequence: Co(thd)2 (3.0 s), N2 purge (10 s), DMH (0.2 s), N2 purge (10 s). Co(thd)2 was delivered to the reaction chamber at 130° C. and DMH was delivered at ambient temperature (˜22° C.). Except for a film submitted for XPS analysis, Co films were not subjected to any post-deposition treatment. Annealing for XPS experiments was completed immediately following deposition by heating the reaction chamber to 400° C. for ˜3 h.
Film thicknesses were measured by cross-sectional scanning electron microscopy experiments using a JEOL-6510LV scanning electron microscope. Sheet resistance was measured at room temperature using a Jandel RM3000+ four-point probe. X-ray fluorescence measurements were completed using a Shimadzu EDX-7000. Atomic force microscopy (AFM) measurements were conducted using a VEECO Dimension 3100 atomic force microscope operated in tapping mode. NanoScope (version 5.31R1) was used to collect the data. Gwyddion (version 2.44) was used to calculate the root mean square (RMS) roughness values and generate images of the surfaces (512-pixel resolution).
X-ray photoelectron spectroscopy (XPS) measurements used an Al Kα (1486.6 eV) X-ray source (pass energy=23.5 eV, step size=0.200 eV) at a chamber base pressure of 10−10 Torr. Spectra were recorded using a 16-channel detector with a hemispherical analyzer using a PHI 5000 VersaProbe II XPS instrument. An XPS software package (MultiPak, version 9.4.0.7) was used to collect the data focusing on the Co 2p, O Is, N Is, C Is, Ru 3p, and Ru 3d core levels. Sputtering was performed over a 2×2 mm2 area using 3 keV argon ions supplied by an argon sputter gun positioned at a 45° angle with respect to the substrate normal. Measurements were made over a 0.2×0.2 mm2 area. All spectra are uncorrected. Peak fitting was performed with CasaXPS (version 2.3.17PR1.1) using absolute sensitivity factors (ASF) for Co 2p (3.590), O is (0.711), N is (0.477), C is (0.296), and Ru 3d (4.273).3 Spectra of ALD-grown films were fit using the models and constraints derived from fitting the spectra of cobalt and ruthenium metal standards. Cobalt 2p ionizations were modeled using a doublet with a Lorentzian (LA) lineshape for the metallic contribution (area ratio=1:2, Δ=15.1 eV), a Gaussian Lorentzian (GL) lineshape for the Auger feature, and a pair of doublets with GL lineshapes for the oxide contribution (area ratio=1:2). Ruthenium 3d ionizations were modeled using a doublet with a Lorentzian damped tail (LF) lineshape (area ratio=2:3, Δ=4.2 eV). Carbon, nitrogen, and oxygen ionizations were modeled using three GL lineshapes each. A Shirley background was used for all spectra.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.
