CA2202387A1 - Conformal titanium-based films and method for their preparation - Google Patents

Abstract

Titanium and titanium nitride layers can be produced by chemical vapor deposition (CVD) processes conducted at temperatures below 475 ·C. The layers may serve as diffusion and adhesion barriers for ultra-large scale integration (ULSI) microelectronic applications. The processes use a titanium halide precursor, such as titanium tetraiodide, and hydrogen or hydrogen in combination with nitrogen, argon, or ammonia to either produce pure titanium metal films, titanium films which alloy with the underlying silicon, or titanium nitride films. The deposition of titanium metal from titanium halide and hydrogen or the deposition of titanium nitride from titanium halide with nitrogen and hydrogen is achieved with the assistance of a low energy plasma.
The process allows smooth and reversible transition between deposition of films of either titanium metal or titanium nitride by introduction or elimination of nitrogen or ammonia.

Description

W O 96/12048 pcTrus95ll3243 CONFOR~L~L TIT~NIm~-BASED FI ~ S
n ~:lH~ FOR T~TR P~P~TT~N

Field of the Tnv~nt; ~n The presen~ invention relates to substrates having titanium-based coa~lngs, and to methodology for preparing such coated substrates. More particularly, the present invention is directed to substrates having sub-micron features and conformal Ti and TiN layers and bilayers coated thereon, and to low-temperature and plasma-promoted chemical vapor deposition techniques to provide Ti and TiN coatings.

B~chy. o~ of ~he Tnvont;nn Titanium (Ti) and titanium nitride (TiN) are refractory materials with ionic structure, co~alent bonding and metallic conductivity. These characteristics lead to high specific strengths at elevated temperatures, excellent mechanical, chemical and thermal stabilities, and good resistance ~o corrosion. These properties have made ti~anium and titanium nitride important building blocks in the manufacture of very large scale integrated (VLSI) circuitry, where they function as, for example, adhesion layers and diffusion barriers. VLSI fabricaticn also makes use of Ti-TiN bilayers on silicon substrates, where titanium funct onsas à getter for oxygen at the silicon in~erface. Such a bilayer provides significantly lower and more stable cor.-act resistance than a tilanium nitride single layer, and imp~^~ed adhesion ~nd diffusion barrier properties, compared to a W O96/12048 PCTrUS95/13243 titanium metal single layer, for the subsequent aluminum- or copper-based plug or interconnect layer.
The advent of ultra-large scale integration (ULST) multilevel metallization ~MLM) schemes (see, e.g., M. Rutten et al ., in A~v~nce~l M.eC=Il l; z~tion for UTSI ~;)1 ic~tion~, ed.
V. Rana et al., Mat'l Res. Soc. Pittsburgh, PA, p. 227, 1992), has seen the development of substrates having features, such as holes, vias and trenches, of diameter less than 1 micron, often less than 0. 5 micron and even less than 0.25 micron. These finely patterned substrates tkat are typically used in ULSI circuitry, will be referred to herein as sub-micron substrates. The sub-micron substrates used in ULSI circuitry have 'eatures with aspect ratios, i.e., the ratio of the depth to ~he width of a feature when viewed in cross-section, of about 3:1, sometimes 4:1 and sometimes even 6:1.
Reliable methodo-l-ogy has not heretofore existed for the coating of confGrmal, high-quality Ti and TiN films onto the finely patterned substrates used in ULSI circuitry. And yet there is a critical need for appropriate adhesion layers and diffusion barrie_s which may be met by Ti and TiN '~_ims.
Physical vapor deposition methods, such as sputtering, which were successfully used in manufacturing VLSI devices, are unable to meet the requirements of the new ULSI devices. As 2S ~ea~ure sizes are -educed into the half-micron range and below, sputtering techniques provide undesirably non-conformal coverage. ~or example, sputtering causes thi nn; ~g at vias, hole edges and walls, and keyholes in the vias and trenches. Further, the deposits provided by sput~ering techniques frequently contain trapped sputter gàs and possess a columnar growth structure which seriously inhibits their ~VO 96/12048 PC~US9~n3243 usefulness as ai~fusion barriers. See, e.g., S. Saitoh e~
al ., ibid, p. ~95; M. Jiminez et al ., ~. Vac . Sci . Tech . B9, p. 1492, 1991; and A. Noya e t al ., .Jpn . .J . Appl . Phys ., 3 0, p. L1760, 1991. Efforts to resolve these problems through 5 the developmen- or mod ~ied physical vapor desorption techniques, such as collima~ed reactive sputtering, have been unsucce6sful ~o date because of, ~or example, reduce~
throughput due ~o the use of a collimator, undesirable particulate generation, and increased sensitivity to processing conditions.
Chemical vapor deposition (CVD) is a process whereby a solid ~ilm ls synthesized from the reaction products of gaseous phase precursors. The energy necessary to ac~ivate the precursors and thereby start the chemical reactions which lead to ~ilm ~ormation, may be thermal anajor electrical, and may be reduced by catalytic activity at the sur~ace of the substrate to be coated. It is this reactive process which distinguishes CVD from physical deposition processes, such as sputtering or evaporation. CVD
potentially o~fers many intrinsically attractive features ~or ~abrication o,~ Ti and TiN films as ~e~n~ed by modern microelectronics. For example, CVD can generally provide a high growth rate and conformal coating of substrates having a complex topography o- trenches and vias. In addition, catalysis interaction cf the substrate with CVD source precursors can possibly lead to selective metal growth.
Howeve-, as discussed below, recognized C~D
methodology E-~- ls to provide Ti and TiN coatings with conformal coverage fo- substrates having sub-micron featur-s as typically found in ur~sI circuitry. In addition, standa-d CVD methodology requires processing temperatures in excess 9 CA 02202387 1997-04-lo W O96/12048 PCTrUS95/13243 about 650C, which is higher than can typically be tolerate~
in ULSI fabrication when aluminum serves as the material ~c provide the contacts ~or the circuit. The use o~ aluminum contacts effec~ively requires CVD temperatures of less thar about 500C.
It is known to prepare titanium metal films by use of plasma-assisted CVD (PACVD) of TiCl4 in a mixture of nitrogen and hydrogen; by electron cyclotron resonance (EC~) plasma CVD of TiCli in a nitrogen atmosphere; and by atmospheric pressure CVD (APCVD) using TiC14 and isopropylamine as coreactants. See, e.g., M. Hilton et al ., Thin Solid Films, 139, p. 247, 1986, and T. Akahorl et al., Proc. Int 'l Conf . on Solid State Devices and Materials, Yokohama, Japan, p. 180, 1991. These efforts led to an -appreciable reduction in process temperature, to within the desired range of about 350C-500C. However, film step coverage was only 30~-70% for features of low aspect ratio, and the films exhibited undesirably high resistivities of nearly 200 ~Qcm. In addition, the films suffered from --chlorine contamina~ion to the extent of several a~omic percent.
Early at~empcs at preparing titanium nitride fllms using CVD mostly involved coreacting titanium tetrachloride (TiCl4) and ammonia (NH3) to yield TiN films with resistivities in the range of 50 to 100 ~Qcm. These early attempts provided films having good step coverage and diffusion barrier properties. See, e.g., A. Sherman, J.
Electrochem. Soc., 137, p . 1892 , 1990. In addition, films produced thereby had impurlties, mainly chlorine, at a concentration of less than about one atomic percent. See, W O96112048 PCrAUS95/13243 e.g., J. Hiollman et al. in A~v~nce~ Met~lliz~tion for UT,S-~lic~tions, ed. V. Rana et al., Mat'l Res. Soc. Plt-sburgh, PA, p. 319, 1992. However, the high processin~ temperatures i.nvolved ln producing these films, typically in excess of 650OC, pronibits ~his technology from being used to prepare I~SI devlces, which can tolerate temperatures not greater than about 500C.
There are several reports of the use o~
organometallic precursors to prepare titaniurn and ti~anium nitride films by CVD. For example, there are several recent r.eports on ~etal-organic CVD (MOCVD) of TiN from dialkylamino cleriva~ives o~ titanium o~ the type Ti (NR2) 4, where R ls a methyl or ethyl group. See, e.g., R. Fix et al., MR ~ymp.
~LQ~., 168, p. 357, l990; and K. Ishihara e~ al ., ~pn. u .
Appl. Phys., 29, p. 2103, 1990. Additional MOCVD stuaies Jnvolving the use of single source titanium precursors or .he t:ype TiCl2(NHR2)(NX2R) and TiC14~NR3) 2 have been reported.
',ee, e.g., C. Winter et al . in ~hemic~l Perspectives of M;croelectronic M~teri~ls III. ed. C. Abernathy et al., MRS!_ Pittsburgh, PA lt'92; and K. Ikeda et al., Procee~;ngs of the 1992 Dry Drocess Symposium~ p. 169, 1992 (using cyclopentadienyl titanium compounds, such as bis(cyclopentadlenyl) titanium diazide). The use of diimine analogs o~ ~-diketonates such as Ti(NH)2C2CHR2) 2 in MOCVD has also been reported. See A. Weber, The Drocee~; n~s o ~ the ',chl~m~che- Confere~ce (San Diego, California, 1993).
Ht3wever,-the Ti~ films produced by MOCVD exhibit re-la- ve~y high resistivities of greater than 200 ~Qcm, and a s~ep coverage below 70~ even for f~atures of low aspect ra~io. Tn addition, the films contained hydrogen concentrations of up l_o 50 atomlc percent, and a carbon concentration of several ==

W O96/12048 PCTnUS95/13243 atomic percent. These impurities are highly detrimen~al to the performance of the resulting films and effectively prohibit their use in ULSI devices.
MOCVD has also been studied for the preparation of titanium films. See, e.g., T. Groshens et al., in Chemic~l Pers~ectives of Microelectronic M~teri~ls III ed. --C. Abernathy et al., MRS, Pittsburgh, PA 1992, for using MOCVD techni~ues with neopentyltitanium (Me3CCH2)4Ti and sila-neopentyltitanium (Me3SiCH2)qTi. Cyclopentadienyl-based compounds have also been explored as precursors to titanium films. See, e.g., N. Awaya et al . , Japanese Patent No.
01/290,771, 1989. However, as in the case of TiN, the resulting Ti films exhibited high resistivity, and carbon and hydrogen content ln excess of 10 atomic percen~, making them undesirable for use in ULSI circuitry fabrication.
It is known that titanium halides will decompose to Ti at temperatures in excess of 1300C. Thi3 reaction, which is known as the Van Arkel process (see, A. Van Arkle e~ ai.
Z. Anorg. Allgem. Chem., 148 , p . 345, 1925) occurs at such -20-- high temperatures that it is not useful for ULSI fabrication.
There thus exists a need for technology to provide Ti and TiN films suitable for ULSI fabrication. Such films must be of ultra-high quality, in terms of purity, with impurity concentrations well below 1 atomic percent. Also, the films should desirably exhibit a non-columnar structure in order to perform appropriately as a barrier layer.
Further, the films should be-conformal to the complex topography of ULSI circuitry, and provide step coverage in excess of 70~. It is desirable that technology be developed which can readily prepare single films containing either T1 or TiN, as well as bilayer films of T1 and TiN, and that such W O 96/12048 PCTrUS95/13243 technology be amenable to process temperatures below about 500C in order to prevent thermally induced device damage during processing.
It is especially desirable that a process be developed which allows for the preparation of the above-mentioned films sequentially and in-si tu, i.e., withou~ the necessity o~ transferring a ~ubstrate coated ~ith a single film (Ti or TiN) to another reaction chambe~ to deposi~ the other film. Thus, according .to current technology, the production o~ a bilayer typically involves the laying down of a first layer in a first reaction chamber, and then transrerring the subs~rate to a second reaction chamber where a second layer is coated onto the first layer. Current technology does not provide a single reaction chamber with lS the versatility to deposit both Ti and TiN films merely by controlling the operating parameters of the chamber. As is known in the art, a process for the i~-situ deposition of sequential bilayers of Ti and TiN is desirable in part because of the high affinity of titanium for oxygen and water. This affinity leads typically to co=ntamination of the Ti film sur~ace during transfer to a second reaction chamber where it is coated with TiN. =-Snmm~y of ~he Tnv~nti~n One aspecl of the invention is a method for ~he chemical vapor deposi.ion of a titanium-based film onto a substrate, which comprises introducing to a deposition chamber the following components: (a) a substrate; (b) vapor of a compound havinc the formula Ti(I4mn)(Brm)(Cln) (hereinafter formula (I)) wherein m is 0-4 and n is 0-2; (c) a first gas selected from the group consisting of ammonia and W O96/12048 PCT~US95/13243 hydrazine; and (d) a second gas selected from the group consisting of hydrogen, nitrogen, argon and xenon. These components are maintained in the deposition chamber at a temperature of about 200C to about 650C, preferably about 350C to about 475C, for a time sufficient ~o deposit a titanium-based film onto the substrate. According to preferred embodiments, the compound of formula (I) is titanium tetraiodide and the molar ratio of nitrogen atoms in component (c) to titanium atoms in component (a) is at least l:1. The method is particularly useful when the substrate is a silicon or silicon dioxide wafer useful in the manufacture ~= of a ULSI device.
According to another aspect of the invention, a method is provided for ~he chemical vapor deposition of a titanium-based film onto a substrate, which comprises introducing to a deposition chamber the following componen-s:
a) a substrate; (b) vapor of a compound having the formula (I) as above, and preferably titanium tetraiodide; and (c) at least one gas selected from the group consisting of hydrogen;
hydrogen and at least one of nitrogen, ~m~onl a, argon and xenon; nitrogen and a~ least one of ammonia, argon and xenon;
ammonia and at least one of argon and xenon. The above components are maintained in said chamber at a temperature of about 200C to about 650C, preferably about 350C to about 475C, in the presence of a plasma having a plasma power density of about 0.1 to about 0.5 W/cm2. The components are maintained under these conditions for a time sufficient to deposit a titanium-based film onto the substrate. Accord c to preferred embodiments, the gas component (c) is hydrogen or hydrogen in combination with nitrogen or hydrogen in combination with at least one of argon and xenon. A

CA 02202387 1997-04-lo W O96/12048 PCTrUS9S113243 prererred substra~e is a silicon or silicon dioxide wafer useful in the manurac~ure of ULSI devices.
According to another aspect of the in~ention, a ~ethod is provided ~or depositing multiple layers or titanium-based film onto a substra~e while the subs~rate rem~nC fixed in a single deposition reactor. The methoa comprises the steps of introducing components, wherein the components are a subs~rate and a source precursor, into a CVD
chamber, where the source precursor is vapor of at least one compound of ~ormula (I) as above, and is preferably vapor ^r titanium tetraiodide. The method comprises seq~Lentially epositing onto the substra~e al~ernating layers of titanium metal ~ilm and ~i~anium nitride film, where either the titanium metal film or the titanium nitride film may be deposited ~irst onto ~he substrate.
According t~ a preferred embodiment, a titanium metal film is deposited onto a substrate to ~rovide a coa~ed subs~rate, and a titanium nitride film is deposited onto the c:oated substrate. The titanium metal film and the titanium nitride film are formed as described above.
Another aspect of the invention provides a substrate ~or integra~ed circuitry having a coating disposed thereon. The substrate has features, such as holes, vias and trenches as typically ound on integrated circuits, with ~llm~n~ions of less than one micron, and preferably less .han about 0.5 microns and more pre~erably less than about 0.2_ microns, and aspect -atios or at least about 3:1, pre~erab y at least about 4:1 and more preferably at least about 6::.
l'he coating is a titanium-based film that is con~ormally deposited onto the substrate with step coverage greater _han ~ . _ about 70~.

W O96/12048 PCTrUS9S/13243 Brief Descri~t~on of the Draw~nqs The foregoing summary, as well as the ~ollowing detailed descrip~-on of preferred embodiments of the invention, will be better understood when read in conjunc~ion with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities~shown. In the drawings:
FIG. l is a diagrammatic representation of a reaction apparatus used to achieve chemical vapor acccrdins to the present inven~ion.
FIG. 2 ls an x-ray diffraction (XRD) pattern of a TiN film produced by the TCVD reaction of TiI~ and NH;. XRD
indicates a clean (111) TiN phase.
FIG. 3 is an x-ray photoelectron spectroscopy (XPS) spectrum o~ a TiN film produced by the TC~ reaction of TiI~
and NH3. XPS results indicate a pure TiN phase with a stoichiomecric Ti to N ratio (1:1) and no light element (e.g., C, O, F, e~c.) contamination.
FIG. 4 is a Rutherford bac~scattering (RBS) spectrum o~ a TiN film produced by the TCVD reaction of TiI
and NH3. RBS results indicate a pure TiN phase with a stoichiometric Ti to N ratio (1:1) and essentially no heavy element (e.g., C-, Mn, etc.) contamination.
FIG. 5 depicts cross sections, magnified by sc~nn; ng electrc-. microscopy, of silicon substrates upon which oxide via patterns, of diameter 0.25 ~m and 4 to 1 aspect ratio, are rormed and upon which conformal TiN

CA 02202387 1997-04-lo coatings have been deposi~ed by TCVD reaction of TiI~ and ~H3. The coating shown in the left-hand micrograph o~ FIG. 5 has a thickness of less than 100 nm, which is a typical fiim t:hickness for ULSI devices. The coating shown in the right-5 hand micrograph of FIG. s has a considerably thicker coatins,and is shown to illustrate that conformal coatings are prepared even at e~traordinarily high thickness.
FIG. 6 is an x-ray diffraction (XRD) pattern of a Ti film produced by the plasma-promoted CVD reaction of TiI
lo and hydrogen in an ~rgon plasma. The XRD spec~ra indicates a clean hexagonal Ti phase.
FIG. 7 is an x-ray pho~oelectron spectroscopy (XPS) spectrum of a Ti film produced by plasma-promo~ed CVD
reaction of TiI4 and hydrogen in an argon plasma. XPS
'-esults indicate a pure Ti phase, as documented by its alloying with Si.
FIG. 8 depicts a cross section, magnified by scanning electron microscopy, of a silicon substrate upon which oxide via patterns, of diameter 0.2 ~m and 6 to 1 i~spect ratio, are formed and upon which a conformal T-i coating has been deposited by plasma-promoted CVD reaction of TiI4 and hydrogen in an argon plasma.

De~;led De~3criDt;~n of 1-h-~ Preferred ~ ho~;m~r~ts Processes utilizing chemlcal vapor deposition (CVD) have been developed which can prepare titanium-based films suitable as, for example, diffusion barriers and adhesion inter-layers in integrated circuit fabrication, and i~
~articular, in ULSI fabrica~ion. The processes of the invention direct carefully selected precursors into a CVD

W O96112048 PCTnUS95/13243 reac~or, under carefully spec;Iied reaction conditions, to achieve high quality titanium-based films of the inven-ion.
As used herein, the term "titanium-based rilm~
refers to a rilm containing titanium. Exemplary titanium-based films include ~ilms of titanium metal, titaniumnitride, titanium silicide and laminates thereof including a bilayer film of titanium metal and titanium nitride. ~he titanium-based films of the invention may be substantially pure, or may contain a mixture of phases of titanium-based materials, e.g., a mixture of titanium metal phases with titanium nitride or titanium silicide phases. In addition, the titanium-based films of the invention~may contain gas molecules, for example, nitrogen.
To prepare titanium-based films according to the invention, thermai chemical vapor deposition ~TCVD) or plasma-promoted chemical vapor deposition (PPCVD), may be employed. As used herein,-~CVD refers to a CVD process wherein all reactants are introduced to the CVD reactor in gaseous form, and the energy necessary for bond cleavage is supplied entirely by thermal energy. As used herein! PPCVD
refers to a CVD process wherein all reactants are intr_duced to the CVD reactor in gaseous form, and the energy necessary for bond cleavage is supplied in part by the high energy electrons formed in a glow discharge or plasma having a plasma power density of below about 0.5 W/cm2. PPCVD takes advantage of the high energy electrons present in glow discharges to assist in the dissociation o~ gaseous molecules, as is the case with plasma-enhanced CVD (PECVD), where PECVD is a well-known techni~ue. However, in ccntrast to PECVD, which uses high plasma power densities, the iow power densities employed in PPCVD do not cause ion-induced W 096/12048 PCTrUS95/13243 subs~rate and film damage, and allow the formation of films with reduced stress ievels. PECVD operated at plasma power density greater than 0.5 W/cm2 is not included within PPCVD
according to the inven~lon.
A deposition reactor suited for T~VD or PPCVD
according to the invention has several basic components: a precursor delivery system (also referred to as bubbler or sublimator) which is used to store and control the delivery of the source precursor; a vacuum chamber and pumping system to maintain an appropriately reduced pressure as necessary; a power supply to create discharge as necessa1y; a temperature control system; and gas or vapor handling capabilities to meter and control the flow of reactants and products that result from the process.
According to one preferred embodiment for the deposition of titanium-based films according to the invention, the deposi-tion~reactor shown in FIG. 1 is employed. The source precursor 10 is placed in the bubbler/sublimator 11 which is heated by a combination of resistance heating tape and an associated power supply ;2 to a desired temperature. The dashed lines in FIG. 1, labeles 12, encompass parts of the CVD reactor which are heated by the resistance heatir.g tape. A mass flow controller 13, which can be isolated from the bubbler by a high vacuum valve 14, controls the flow of carrier gas 15 through feedthrough 16 into the bubbler. While a carrier gas need not be employed, it is preferable to use a carrier gas in orde- to better control and accelerate the rate of flow of the sour_e precursor vapor into the deposition chamber.
~ In a preferred embodiment, the mixture of precursor vapor and carrier gas is transported through feedthrough 17, = ~ ~

W O96112048 PCTnUS95/13243 - 14 -high vacuum isola~io., valves 18 and 19, and delivery line 20 into the depositior. reactor 21. All transport and delivery lines and high vacuum isolation valves 17, 18, 19, and 20 are maintained at the same temperature as the bubbler/sublimator ll, again using a c^mb1nation resistance heating tape and associated power supply 22. The dashed lines in FIG. 1 labeled 22 encompass parts of the CVD reactor heated by resistance heating tape, where the heating tape heats the apparatus to prevent precursor recondensation.
The reac~or 21 is a cold-wall stainless steel CVD
reactor of size sur~icient to hold an 8" wafer. It is e~uipped with a diode-type parallel plate-~ype plasma configuration made o_ two electrodes 23 and 24. The upper plate 23 serves as the active electrode and is driven by a plasma generator 25. This upper plate is constructed in a "mesh" type pattern to allow unrestricted reactant flow to a substrate 26, where 26 which sits on the lower, g~ounded plasma electrode 2~. The substrate 26 is heated to a process temperature by an 8" boron nitride (BN)-encapsulated grapX~lte heater 27. The showe~ head 28 and associated pumping lines 29 as shown in Fig. 1 are employed to ensure proper reactant mixing and uni~ormity in reactant delivery and ~low over the = substrate.
E~acuation of the deposition reactor is possible through use of a pumping stack 30. The pumping stack 30 consists of two pumping packages, where the first is cryogenic pump-based, and the second is roots blower pump-based. The pumping~s''tack may be isolated from the reactor by the high vacuum gate valve 31. The cryogenic pump-based package is used to ensure high vacuum base pressure in the reactor, while t~e roots blower-based package is employed ~or ~0 96/12048 PCTrUS95/13243 appropriate handl ng of ~he high gas throughput during actual C~D runs.
A high vacuum load lock system 32 is used for t:ransport and loaaing o~ substrate into and out of the r.eactor. Finaily, a side line 33 is employed to feed additional gaseous reactants, i.e., auxiliary gas, into the reactor. The side line gas flow is controlled by the mass f.low controller 34 and associated isolation valve 35.
The source precursor lo according to the inven~ion ls at least one titanium containing compound of the formula ~I) Ti(I4-m-n)(Brm)(cln) (I) _ wherein m is an integer within the range 0-4 and n is an integer within the range 0-2. Preferably, the compound of iormula (I) has n = 0, i.e., there are no chlorine ligands.
More preferably, the source precursor 10 is titanium t:etraiodide, i.e., TiI4.
After being charged to the bubbler/sublimator ll, t:he source precursor is taken to a temperature which is high enough to ensure the precursor's sublimation or vaporization, but not too high to cause premature decomposition.
]?referably, the source precursor is heated to a temperature of about 90C to about 160C.
The ca-rier gas can be any gaseous subs~ance which - ls not reac~ive with compounds of formula (I). Exemplary carrier gases are hydrogen, helium, nitrogen, neon, shlorine, bromine, argon, krypton and xenon. While halogenated gases can function as the carrier gas, non-halogenated gases are W O96/12048 PCT~US9SI13243 preferred because they cannot contribute any halogen contaminatlon to the tltanium-based film. The preferred carrier gases are hydrogen, nitrogen and argon. Of course, the carrier gas may also be a mixture of pure gases.
Hydrogen is a particularly preferred carrier gas for both TCVD and PPCVD according to the invention.
The flow rate of the carrier gas through the source precursor is controlled by the mass flow controller 13. The flow rate of the carrier gas is about 10 sccm to abou~ 100 sccm, and preferably about 20 scc~ to about 60 sccm. A flow rate of about 20 sccm to about 60 sccm is preferred for both TCVD and PPCVD according to the invention.
Under action of the carrier gas, the flow rate o~
the vapor of the source precursor is about 0.001 sccm to about 1,000 sccm. Preferably, the flow rate of source precursor vapor into the CVD chamber is about 0.1 sccm to about 200 sccm.
The auxiliary gas is at least one o~ hydrogen, helium, nitrogen, ammonia, hydrazine, neon, chlorine, = ~0 bromine, argon, krypton and xenon. As with the carrier gas, the preIerred auxiliary gases are non-halogenated. The flow - of the auxiliary gas, which may be a pure gas or a mix~ure of gases, is pre~erably about 10 sccm to about 10,000 sccm, and is more preferably about 100 sccm to about 1,000 sccm.
Although for convenience the gas(es) entering mass flow controller 13 is denoted herein as the carrier gas, and the gas(es) entering the mas-s flow controller 34 is denoted herein as the auxiliary gas, this terminolosy should not be misconstrued. In fact, in addition to carrying the vapor of the source precursor into the reaction chamber, the carrier gas may and typically does undergo reaction in the chamber W O96112~48 PCTnUS9SlI3243 - 17 -during the deposition process. The auxiliary gas may be inert or include iner~ components, in which case some or all of the auxiliary gas serves merely to dilute the reactive atmosphere lnside the deposition chamber. ~ikewise, the carrier gas may be inert or contain inert components. The auxiliary gas may also undergo reaction in the CVD chamber.
According to a preferred embodiment of PPCVD, hydrogen is the carrier gas and there is no auxiliary gas.
According ~o another preferred embodiment ~or PPCVD, hydrogen is introduced into the deposition chamber simultaneously with an inert gas such as neon, argon, krypton or xenon.
Preferably, hydrogen is introduced as the carrier gas and at leas~ one o~ argon and xenon is the auxiliary gas. However, the inert gas may be introduced in admixture with hydrogen, lS where the mixture serves-as the carrier gas. It is also possible for the inert gas to serve as the carrier gas, and have hydrogen introduced as the auxiliary gas. In each of the above instances, a titanium metal film is produced.
PPCVD according to the invention can also be used

2 Q ~ to prepare titanium nitride (TiN) films. To prepare a TiN
film by PPCVD, a nitrogen-containing gas must be introduced ~ - into the reactor chamber. Nitrogen ~N2), aMmonia and hydrazine are exemplary nitrogen-containing gases according to the invention. When nitrogen (N2) is the nitrogen-con~aining gas, it may be introduced as either a carrier or auxiliary gas, and hydrogen or an inert gas such as argon or xenon may be introduced simu-l-taneously therewith as elther a - carrier or auxiliary gas. Preferably, at least one of nitrogen, hydrogen and an inert gas ls a carrier gas.
When ammonia or hydrazine is the nitrogen-containing gas cluring PPCVD of a TiN film, then it will ~e W O96/12048 PCTrUS95/13243 introduced into the àeposition chamber as an auxiliary gas, and hydrogen and/or an inert gas such as argon or xenon may be the carrier gas. Hydrogen and/or an inert gas may also be co-introduced as the auxiliary gas, i.e., hydrogen and/or an inert gas may be in admixture with the ammonia or hydrazine gas. Nitrogen in combination with at least one of ammonia and hydrazine may be the sole gases present in the deposition chamber during the preparation of TiN, in which case nitrogen will be the carrier gas. According to a preferred embodimen~
to prepare TiN film by PPCVD, hydrogen and nitrogen are introduced into the reactant chamber simultaneously with the source precursor.
Titanium nl~_ide films may also be prepared usins TCVD according to the invention. To prepare a TiN film by TCVD, ammonia and/or hydrazine is introduced to the deposition chamber as an auxiliary gas, and at least one of hydrogen, nitrogen or an inert gas such as argon or xenon serves as a carrier gas. According to a pre~erred embodiment, hydrogen is a carrier gas while ammonia is an auxiliary gas.
Regardless of whether TCVD or PPCVD is used to prepare the TiN film, and regardless of the exact identities of the nitrogen-containing gas and the carrier and auxiliary gases, it is important to maintain a~ least one mole of nitrogen atoms in the reac~ion chamber for each mole of titanium in the reaction chamber. If insufficient nitrogen rs present in the aeposition chamber, then titanium metal may be deposited rather than titanium nitride, thereby allowing ~he forma~ion of a mixed-phase fi;m, i.e., a film having phases of ti~anium and phases of titanium nitride. While a mixed-phase film may be desired for some applications, and ~NO 96/12048 PC~US95/13243 me~hodology to prepare such titanium-based films and substrates having .~ese ~ilms coated thereon is within .he scope of this invention, in instances where a pure TiN ri lm is desired, i.e., a film having a Ti:N molar ratio or about l:l, then an adequate supply of nitrogen atoms must be supplied to the depcsition chamber. Excess nitrogen may enhance ~ilm stability, and the diffusion barrier proper~ies of a film made with excess nitrogen may demonstrate enhanced dif~usion barrier properties.
According to the preferred PPCVD method, the plasma is generated through use o~ radiofre~uency (RF) glow discharges, having frequencies in the MHz range, although plasmas with rrequencies ranging from kHz to GHz could ke employed. See, generally, Hess, D. W. and Graves D. a., "Plasma-Assis~ed Chemical Vapor Deposition", Chapter 7 in ~hem;c~l V~por Depos~rion Pr~c;ples ~n~ ~ppl;c~tlons, Hitchman M. L. and Jensen, K. F. eds., Academic Press ~1993).
A pre~erred ~requency is about 1 to about 100 MHz, with about 14 MHz being particularly preferred.
Prior to beginning a sequence of deposition runs, and periodically be~ween depositions conducted during a sequence o~ run, the deposition reactor is baked under a nitrogen atmosphere -o below 0.3 torr and then pumped down to below 10 torr ~or an hour at 150 C. This process assures cleanliness of the reactor, and is conducted ~or both TCV~
and PPCVD runs.
The substrate 26 is placed into the CVD reactor and then prererably exposed to a cleaning regime. Pre-depcs-_ion substrate cleaning is pre~erably accomplished by exposing ~he substrate in si tu tc a hydrogen plasma having a plasma power W O96/12048 PCTrUS95/13243 density of abou~ 0.1 to about 1.0 W/cm~. Substrate cleaning as descrlbed is performed for both TCVD and PPCVD.
Prior to introducing the source precursor in~o the CVD deposition chamber, the chamber atmosphere is evacuated, and the and reactor is heated to a process temperature.
Preferably, the pressure in the chamber is about 0.001 torr to about 760 torr during the deposition process. More pre~erably, the atmosphere in the chamber during the deposition has a pressure of about 0.1 torr to about 10 torr.
The process temperature during deposition ls less than about 650C. Preferably, the process temperature is about 250C to about 500C, and more preferably about 350C to about 475C.
A plasma may be presen~ during the deposition process in order to promote reaction of the source precursor with other gas(es) present in the reactant chamber. The plasma has a plasma power density of about 0.1 to abou~ 0.5 W/cm2, and preferably has a density of about 0.15 W/cm- to about 0.3 W/cm2. As described above, when a titanium nitride film is desirably deposited by PPCVD onto a substrate, or onto a coated substrate, the gases nitrogen and hydrogen are preferably present with the source precursor vapor, in the presence of a plasma. When a titanium metal film is desirably deposited onto the subs~rate, or onto a co-ated substrate, by PPCVD, hydrogen gas, optionally with at leas~
one of argon and xenon are present with the source precursor, in the presence of a plasma.
The deposi~ion rate of the films of the invention is observed tP be about 25 to about 2000 angstroms per minute (A/min). A typical deposilion rate is about 400 A/min to about 500 A/min. The films of the invention have a thickness of about 50 angstroms to about 2 microns, and have a preferred thickness of about 500 A to about 1500 A. The deposition time is therefore seen to be quite rapid, on the order of seconds or mlnutes.
The appearance and composition of the titanium-based films prepared according to the inventive methods, as well as their structural and electrical properties, will be described next It should be noted that the ormation or titanium silicide films (TiSi), occurs only when the substrate is silicon or polysilicon and the tltanium being deposited is particularly pure titanium metal. In such cases, the substrate-titanium interface can react to form a layer of TiSi. It has been observed that a silicon substra~e can catalyze the reaction(s) leading to the deposition of t tanium metal.
Titanium and titanium silicide films were prepared in the deposition reactor shown in FIG. 1, according to the PPCVD method of the invention. The source precursor was titanium tetraiodide and it was sublimed at a temperature within the range of 120C to 160C. Films were prepared during reactions wherein the working pressure inside the deposition reactor was from 200 to 400 mtorr, the carrier gas was hydrogen wi~h a flow rate of from 10 to 60 sccm, the auxiliary gas was argon with a flow rate of 400 to 600 sccm and the substrate temperature was from 300C to 450C. The films were deposited cnto a silicon wafer.
The titanium and titanium silicide films thus produced were metallic, continuous, and silver colored. X-- ray diffraction (XRD) analysis of a Ti film grown at 450C is shown in FIG. 6 for a 1000 A-thick film on Si. The XRD
analysis shows that the film has a hexagonal Ti phase. X-ray photoelectron spec~roscopy (XPS) was performed using a W O96tl2048 PCTrUS95/13243 Perkin-Elmer Physical Elec~ronics Model 10-360 spherical capacitor analyzer. The gold f7/2 line at 83.8 eV was taken as reference line and the analyzer calibrated accordingly. All spectra were obtained using a pass energy of 5 eV at a resolution of 0.8 eV. A primary x-ray beam (Mg K~, 127 eV) of 15 keV and 300 W was employed. The analysis chamber pressure was in the lo~l torr range, and the results were standardized using a sputtered Ti sample. The XPS survey spectra (FIG. 7) indicated that, within the detection limits of XPS, the Ti films produced below 400C contained less than 20 atomic percent oxygen, while Ti films produced above 400C
were free of oxygen and exhibited significan~ interac~ions with the Si substrate, which requires pure Ti to occur. No carbon or any other light element cont~m;n~nts were observed in the films, regardless of substrate temperature. As used herein, light elements refer to elements having atomic number between 3 and 13, inclusive. The presence of iodine was detected at levels o~ about 0.4 to 1.5 atomic percen~. Four-point probe resistivity measurements found that film resistivities as low as 90 ~Qcm could be obtained.
The na~ure of the titanium and titanium silicide films vis-à-vis a silicon substrate was next ~x~mined. The adherence of the titanium films to either silicon or silicon dioxide was observed to be good. Cross-section SEM analysis was carried out on a Zeiss DSM940 microscope, employing a 20 keV primary electron beam and a beam current of 4 ~A. An SEM
micrograph (FIG. 8) o~ a 1000 A-thick Ti film showed conformal step coverage of 0.20 ~m vias with aspect ratlo of 6.
Titanium nitride films were prepared in the deposition reactor shown in FIG. 1, according to the TCVD

W O 96/12048 PCTAUS9~n3243 method of the invention. The source precursor was ei~her titanium tetraiodide or titanium tetrabromide, and ~ne sublimation temperatures were from 120C to 160C and from ..
90C to 140C respectively. Films were prepared during reactions wherein the working pressure inside the depositlon reactor was from 200 to 3 50 mtorr, the carrier gas was hydrogen with a flow rate of ~rom 20 to 60 sccm, the auxiliary gas was ammonia with a flow rate of 400 to 600 sccm and the substrate temperature was from 300C to 450C. The films were deposited onto a silicon wa~er.
The titanium nitride films were typically metallic, continuous and gold colored. X-ray di~rac~ion (XRD) analysis of a TiN film grown at 350C from TiI4 is shown in FIG. 2 for a lOoO A-thick ~_im on Si. The film showed a polycrystalline TiN phase with major diffraction peaks appearing at 2~ = 36.66(111), 42.59(200), 61.81(220), and 74.07(311). Esséntially-t~he same spectra was observed when TiBr4 was the source precursor. X-ray photoelectron spectroscopy (XPS) measurements were performed using a Perkin-Elmer Physical Electronics Model 10-360 spher~ical capacitor analyzer. The gold f,/2 line at 83.8 eV was taken as reference line and .he analyzer calibrated accordingly.
All spectra were obtained using a pass energy of 5 eV at a resolution of 0.8 eV. A primary x-ray beam (Mg Ka, 127 ev) of 15 keV and 300 W was employed. The analysis chamber pressure was in the 10-l torr range, and the results were st~n~rdized using a sputtered TiN sample. Ali samples were sputter-cleaned before data acquisition. The XPS survey spectra (FIG. 3) indicated that, within the detection limits of XPS, a TiN
film prepared from TiI4 as the source precursor was free of W O96/12048 PCTrUS95/13243 oxygen, carbon, and similar light element cont~min~nts. Tn general, iodine concen~rations, ranging from 0.4-1.5 atomic percent, were detected in the films. Rutherford backscattering (RBS) spectra were taken using a 2 MeV HE-beam, and calibrated with a bulk sample of silicon. The ~BSresults, shown in FIG. 4 for a 1000 A-thick TiN film on silicon, confirmed the XPS findings that the PPCVD process yields TiN films with ex~remely low iodine concentratlons.
In general, the TiN films contained greater than 99 atomic percent TiN, and this was observed when either Ti~4 or TiBr~
was the source precursor.
Four-point probe resistivity measurements determined that film resistivities as low as 44 ~Qcm where obtained when the source precursor was titanium tetraicaiae.
However, when the source precursor was titanium tetrabr-mlde, film resistivities as low as 120 ~Qcm were obtained.
The nature o~ the titanium nitride film~vis-à-vis a silicon substrate was next examined. Cross-section SEM
analysis were carried out on a Zeiss DSM940 microscope, employing a 20 keV primary electron beam and-beam current of 4 ~A. The SEM micrograph (FIG. 5) of a 700 A-thick TiN film prepared ~rom titanium tetraiodide as the source precurs~r, showed conformal step coverage of 0.25 ~m vias with aspect ratio of ~. The adherence of the titanium nitride to eir.er silicon or silicon dioxide was found to be good. Essentially the same results were obtained when titanium tetrabromide was the source precursor.
.
The fllms prepared according to the inventive methods are seen to have very high purity, and thus are well suited for use in, ,or example, microelectronic applica~ions where purity d~m~n~ are quite stringent. The films of the ~096112~48 PCTrUS95/13243 invention have carbcn and hydrogen impurity levels of iess than about 15 a.omic percent, preferably less than about 10 atomic percent and more preferably less than about 1 atomic percent. The f lms of the invention have minimal or no halogen contamination, where the halogens are iodine, bromine or chlorine. Th~s, films according to the inventicn will have halogen concamination o~ less than about 15 atomic percent, preferably less than about 5 atomic percent, and more preferably less than about 1 atomic percent.
Due in oart to their high purity, the titanium-based films of the invention are seen to have desirahly low resistivities. ~he inventive films have a resistivity of about 40 to about 5,000 microOhm-centimeters (~Qcm), preferably about 0 to about 1,000 ~Qcm, and more preferably about 40 to about 150 ~Qcm.
The ti~anium-based films of the invention may advantageously be tailored to columnar or non-columnar structure. The titanium-based films of the invention also have excellent adhesive properties when formulated into ULSI
circuitry.
The inventive titanium nitride film, whether prepared by PPCVD or TCVD according to the invention, --typically has a titanium to nitrogen ratio of about 0.9-1.1:0.9-1.1, anà more preferably have a titanium to nitrogen ratio of about ;:i.
While our invention allows the separate and independent production of citanium-based films, and particularly films~comprising mainly titanium metal or - titanium nitride, in a preferred embodiment, the inventive method provides _or in si~u sequential CVD ln which the deposition mode of a single precursor is smoothly and W O96112048 PCT~US95/13243 reversibly switched be~ween Ti and TiN by changing auxiliary gases that can also act as carriers.
Thus, according to the inventive method, the reactor according to FIG. 1 is charged to contain vapor from a compound of formula (I), and preferably titanium tetraiodide vapor, in the presence of argon, hydrogen, and a plasma having a plasma power density of about 0.1 W/cm2 to about O.S W/cm2. As described previously, these reaction conditions result in the formation of a titanium film on a substrate. Then the plasma is turned off and the auxiliary gas is changed from argon to ammonia. Under these revised reaction conditions, a film of titanium nitride is deposited on top of the previously laid down titanium film, to provide a bilayer film of ~he invention.
It should be understood that the process could be reversed, i.e., the titanium nitride film could be laid down first on the substrate, followed by deposition of titanium metal film. Preferably, the titanium film is laid down so as to contact with the substrate, which is preferably a silicon substrate. It should also be understood that more than two compositionally diverse layers may be deposited on a substrate, without the need to remove the substrate from the reaction chamber.
It should also be understood that in prepa~ing bilayer films, any method for preparing a titanium me~al film according to the invention could ~e followed or preceded by any method for preparing a titanium nitride film according to the invention. For example, PPCVD with hydrogen carrier gas could be used to deposit a titaniLm metal film, followed by PPCVD with hydrogen and nitrogen as carrier and/or auxiliary W ~96J1204~ PC'rAUS9~13243 .
gases, ~o deposit a titanium nitride film and thereby produce a bilayer.
The i~ situ deposition of a titanium-based bilayer as described is very convenient for the preparation ot ULSI
devices. The inven~ive method allows the forma~ion or a bilayer without the necessi~y of transferring the par~ially coated substrate between reaction chambers. That the bilayer can be made in a single reaction chamber greatly minimizes the risk or contamination of the film, which may occur during transfer of the partially coated substrate between reaction chambers. Contamination is a particular problem ~or the titanium-based films of the inven~ion, because these films are often very reac~ive and even slight amounts of contamination can destroy ~heir usefulness in ULSI devices.
The titanium-based films of the invention may be deposited on~o a wide range of substrates, in order to prepare ma~erials useful in refractive, mechanical, microelectronic and decorative applications, to name a few.
There is really no limitation on the identity of the 2~0 _= substrate, however preferably the substrate is stable to the conditions used to deposit the film or coating onto the ~~- substrate. That is, the substrate should be stable to temperatures of about 200C to about 650C, preferably to about 350C to about 500C, and ~o pressures of about 0.1 torr to about lO tor-, preferably about 0.5 torr to about 5 torr.
The substrate of the invention may be metallic, that is, t may be comprised mainly of a metal. Exemplary metals include, without limitation, aluminum, berylllum, cadmium, cerium, chromium, cobalt, copper, gallium, gold, iron, lead, manganese, molybdenum, nickel, palladium, ~ CA 02202387 1997-04-10 platinum, rhenium, rhodium, silver, stainless steel, s~eel, strontium, tin, ~itanium, .ungsten, zinc, zirconium, and alloys tnereof.
In mlcroelectronic applications, a preferred 5 substrate is intended to become an integrated circuit, and has a complex topography formed o~ holes, trenches, vias, etc., to provide the necessary connections between materials of various electrical conduc~ivities that form a semiconductor device. The substrate is preferably formed of, for example, silicon, silicon dioxide, silicon nitride, or doped versions and mixtures thereof.
The subs~ra~es of ~he invention are preferably intended for ultra-large scale integrated (UhSI) circui~ry, and are patterned with holes, trenches and other featu_es with diame~ers of less than 1.0 micron, often less than 0.50 microns, and even 0.25 microns or less. Substrates having such small features are known herein as sub-micron substrates. Sub-micron substrates which may be coated according to the invention also typically have features wi~h high aspect ratios, from about 3:1 to about 6:1, where the ratio of a fea~ure's depth ~o its diameter, as viewed in cross-sec~ion, is termed ~he aspect ratio or the fea~u-e. As used herein, sub-micron substrate have feature diame~ers of less than about one micron and the aspect ratio of the features is larger than about 3:1. Features having an aspect ratio of about 4:1 to abou~ 6:1 are found on typical substrates for U~S~ circultry.
According ~o the chemical vapor deposition processes of the invention, conformal coatings may be placed on sub-micron substrates. Conformal coatings of Ti or Ti/Si may be placed on sub-mic-on substra~es having feature ~VO96/12048 PCTrUS9S/13243 - 29 -diameters as sma; as about 0.25 micron with aspect ra~ os as large as about 6:-. Conformal coatings of TiN or TiN/Ti bilayer may be placed on sub-mlcron substrates having _-a~ure diameters as smal' as about C.25 micron with aspect ra.ios as large as abou~ a:l.
As used herein, the term conformal coating rerers to a coating ~hat evenly covers a substrate having a com~lex topography. The evenness of the coating can be measured by, for example, examining the thickness o~ the coating along the lo walls and bottom or a hole in the substrate, and determining the variation in the thickness of that coating. Accoraing to the invention, su~-micron substrates are conformally coa~ea, when the coating nas a thickness, measured at any poin.
normal to the sur ace of a wall or floor of a hole in .he sur~ace or the suDstrate, which is within ~5~ o~ tne thickness a~ any cther point in the hole. According .o a preferred embodiment, the variation in coating thickness is with 10~, i.e., at no point is the thickness of the coating either 10~ greate_ or 10~ smaller than the average thickness of the coating. The preferred coatings are titanium metal and titanium nitride, and the preferred substrate comprises at least one or s-licon or silicon oxide.
As usea herein, the term step co~erage refers to the ratio of the coating thickness at the bottom of a feature such as a trench ^r via, to the thickness of the coati-g on the top surface cr the substrate adjacent to the featu_e, where the ratio s multiplied by 100 to provide a perc~n.
value. The processes of the invention pro~ide conformally coated sub-micron substrates having step coverage of g-ea~er than about 25~ for features of high-aspect ratios, where high aspect ratios are considered to be greater than about 3:1.

, CA 02202387 1997-04-10 W O96/12048 PCT~US9S/13243 FIG. 5 shows micrograph of two TiN films which were deposited onto sub-micron substrates using TCVD according to the invention. The micrograph on the left-hand side of FIG.
5 shows that a TiN film according to the invention is conformal to a via with a diameter of 0.25 micron and a 4:1 aspect ratio. The micrograph on the right-hand side of FIG.
5 shows a very thick coating of TiN deposited onto a silicon substrate having the same ~eature dimensions as depicted in the micrograph on the right-hand side of FIG. 5, and it can be seen that even after an extended deposition time, TCVD
according to the invention provides a conformal coating with high step coverage. The films were prepared from titanium tetraiodide as the source precursor, and ~mmo~la as the aux1,lary gas.
FIG. 8 shows a micrograph of a Ti film which was deposited onto a sub-micron substrate having a via diameter of 0.2 microns and a 6:1 a-spect ratio. The deposition was accomplished by PPCVD according to the invention, with titanium tetraiodide as the source precursor and hydrogen as the carrier gas and an argon plasma. The coating is seen to be conformal.
we have discovered that selec~ed perhalogenated titanium compounds, in combination with argon, can be converted by means of mixed hydrogen-argon plasma in a CVD
system, into high quality titanium films. Similarly, under thermal conditions, titanium nitride can be produced rrom reacting the same tetrahalotitanium compounds with ammonia, in the presence of a carrier gas. Exemplary reac-ions according to the invention can be summarized by the lollowing equations, wherein TiI4 is an exemplary ~etrahalotitanium compound.

~VO96/12048 PCTAUS95/13243 PPCVD: TiI4 ~ ~2 Ti + XI (major byprodl~ct) PPCVD: TiI4 + N2 + ~2 -----------~ TiN + HI (major bvoroduct) TCVD: TiI4 . N~3 + H2 --------- ~ TiN + NHlI (major bvprodu~t) s In contrast to prior art chemical vapor deposition methods, our invention provides films of higher puri~v, due to the near or complete absence of carbon and chlorine contamination. In contrast to sputtering techniques, our inven~ion provides coatings on substrates suitable for ULSI
fabrication.
While not wishing to be bound by theory, we offer the ollowing explana~ion for the e~ficacy o~ our processes.
In our method, we have selected inorganic titanium ccmDouncs in which the dissociation energy o~ primary bonds is relatively low, and thus we believe recombination can be interrupted by nitrogen radicals formed by interaction o~
diatomic nitrogen with a hydrogen plasma flow or by hydrogen radicals. The ~ollowing Table 1, which shows properties o.
selected titanium halides, indicates that the bond energies of Ti-I and Ti-Br are much lower than that of Ti-Cl, as indicated by their lower heat of ~ormaticn.

. .

CA 02202387 l997-04-lO
W O96/12048 PCTrUS95/13243 Table 1 ~Hformation m-p- b-p- Molecular Fo ~ ~ 298 C C C Weight% Ti kcal/mole TiF4 solid -394 284 sublimes 123.89 38.6 TiCl4 liquid -192 -24 136189.71 25.2 TiBr4 solid -148 38 233 367. 54 13.0 TiI4 solid - 92 155 377 555.508.6 We believe that, under the conditions of plasma-promoted chemical vapor deposition, titanium tetraiodide dissociates in a first step to titanium triiodide and other lower coordinate species, and tha~ the reassociation of titanium with iodine is interrupted by the presence of plasma nitrogen, leading to the formation of titanium nitride. This is in significant contrast ~o the reaction of titanium chloride with ammonia in which higher coordinate species must be involved in both transport and decomposition. See, e.g., R.T. Cowdell and G.P.A. Fowles, J.C.S. p. 2522, (1960).
In the case of tl_anium metal deposition, we believe that the deposition involves the formation of a titanium hydride intermediate from the titanium tetraiodide, and that the intermediate dissociates to form titanium by ; eliminating either hydrogen or hydrogen iodide.
The following examples are set forth as a means of illustrating the present ~nvention and are not to be construed as a limitation thereon.

~WO96/12048 PCTAUS95113243 ~MPT.~ 1 Pre~r~tion of ~i~ ~ lms ~v T~VD using TiI4/H~/NH3 Thermally promoted che~ical vapor deposition (T~VD) was carried out with the reactor shown in FIG. 1, using TlI 5 as the titanium source precursor. The tetraiodotitanium (TiI4) precursor 10 was placed in the bubbler/sublimator 1', and 11 was heated by a combination of heating tape ~nd an associated power supply 17, to 140C during the CVD process.
A mass flow controller 13, which can be isolated ~rom the bubbler by a hiyh vacuum valve 14, controlled a flow of 20 sccm hydrogen carrier gas lS through feedthrough 16 into the bubbler. The mixture of precursor vapor and hydrogen carrier gas was then transpor~ed ~hrough feedthrough 17, high vacuum isolation valves 18 and 1~, and delivery line 20 into tke CVD
reactor 21. All transport and delivery lines and high vacuum isolation valves 17, 18, 19 and 20 were maintained at 120C, uslng a combination hea~ing tape and associated power supply 22, to prevent precursor recondensation.
The reactor 21 was a cold-wall, stainless-steel CVD
reactor of size sufficient to hold an 8" wafer. It was equipped with a diode-type parallel plate-type plasma configuration made of two electrodes 23 and 24. The upper plate 23 served as the active electrode and was driven by the radio frequency (13.56 MHz) power supply 25. It was cons~ructed in a "meshn type pattern to allow unrestricted reactant flow to the substrate 26.
The substra~e (wafer) 26 was placed on the lower, - grounded plasma electrode 24, and was heated to 425C by an 8" boron nitride (3~)-encapsulated graphite heater 27. A
hydrogen plasma was used for in-situ pre-deposition substrate cl~nins at a plasma pcwer density of 0.25 W/cm2, wnile no W O96tl2048 PCTrUS95/13243 plasma was employeà during actual deposition. The shower head 28 and associated pumping lines 29 as shown in Fig. 1 were employed co ensure proper reactant mixing and uni ormisy in reactan~ delivery and flow over the 8' wafer.
The pumping stack 30 consisted of two pumping packages: the ~irst, -ryogenlc pump-based, and the second, -~
roots blower pump-based The pumping stack was isolated from the reactor by the high vacuum gate valve 31. The cryogenic pump-based package was used to ensure high vacuum base pressure in the reactor while the roots blower-based package was employed ~or appropriate handling o~ the high gas throughput during ac~al C~D runs. A high vacuum load lock system 32 was used for transport and loading of 8" wafers into the reactor. Finaily, a side line 33 was employed to feed the ammonia (NH3) gas into the reactor. The NH3 flow was ~25 liters~minu~e and was controlled by the mass flow con~roller 34 and associated isolation valve 35. Processing pressure was 0.2 torr.
The resulting TiN film was metallic, continuous and = ~0=. gold-colored, and had properties typical of TiN films according to the inven~ion, as previously described.
. ~
MPT.~! 2 Prep~r~tion of T~N fi'm~ hy TCVD using TiRr~ /NH2 The process as described in Example 1 was essentially repeated, but the source precursor was changed to titanium tetrabromi~e (TiBr4~~instead of TiI4. The runs were performed under processing condi~ions similar to those lis~ed above for TiI4, excep~ the temperature of the bubbler/sublimator 11 was heated in this case to 100C during the CVD process. All transport and delivery lines and high CA 02202387 l997-04-lO
W O96/12048 PCTrUS95/13243 vacuum isolation valves 17, 18, 19 and 20 were maintained a~
temperature cf 90C, using a co~bination heating tape and associated power supply 22, to prevent precursor recondensation.
The ~iN films produced by TCVD of TiBr4 were again metallic, conti-.uous, and gold colored. Analyses by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Rutherford backscattering (RBS), four-point probe, and cross-sectional SEM (CS-SEM), indicated that their structural, chemical, and electrical properties are equivalent to those produced by TCV3 of TiI4 as in Example 1, except for film resistivity, which was 1~0 ~Qcm in this case.

~!lr2~MPT.~;! 3 Prep~r~tlon or Ti film hy P~CVD llsing T;T,~ /H2/Ar The CVD reactor shown in FIG. 1 was employed for the deposition of Ti by PPCVD. The tetraiodotitanium (TiI4) precursor 10 was placed in the bubbler/sublimator 11 which was heated by a comblnation heating tape and associated power supply 12 to 140C during actual processing. A mass flow controller 13, which can be isolated from the bubbler by a high vacuum valve 14, controlled a flow of 28 sccm hydrogen carrier gas 15 through feedthrough 16 into the bubbler. The mixture of precursor vapor and hydrogen carrier gas was then transported through feedthrough 17, high vacuum isolation valves 18 and 19, and delivery line 20 into the CVD reactor 21. All transport and delivery lines and high vacuum isolation valves 17, 18, 19, and 20 were maintained at temperatures in the range 120 to 160C using a combina~on heating tape and associa~ed power supply 22, to prevent precursor recondensation. The reactor 21 was equipped with a . CA 02202387 1997-04-10 W O96112048 PCTrUS95/13243 diode-type parallel plate-type plasma configuration maae of two electrodes 23 and 24. The upper plate 23 served as the active electrode and was driven by the radio frequency (13.56 MHz) power supply 25.
In this case, plasma-promoted CVD (PPCVD) was employed for the growth of Ti thin films. Accordingly, a hydrogen plasma was used for ~n situ pre-deposition substrate cleaning at a plasma power density o about 0.25 w/cm-, while an argon plasma was employed during actual deposition at a plasma power density of about 0.25 W/cm2. The side line 33 was employed to feed the argon (Ar) gas into the reac~or.
~~- The argon flow of 500 liters/minute was controlled by ~he mass flow controller 34 and associated isolation valve 35.
The substrate (wafer) 26 was placed on the lower, grounded plasma electrode 24, and was heated to 450C by an 8n boron nitride (BN)-encapsulated graphite heater 27.
The titanium metal film thus produced was metallic, continuous silver-colored and had physical and electrical properties identical to those previously described for typical titanium metal films made according to the in~ention.

l;!lrl~MPT.~! 4 In-situ Sequential Preparation of Ti/TiN bilayers by PE~CVD tlsing TiI,l/H~./Ar foIlowe~ hy TCVD us;n~ TiI~/H2/NH3 The CVD reactor shown in FIG. 1 was employed for the in-situ sequential deposition of a Ti/TiN bilayer from TiI4. The Ti layer was first grown by the PPCVD described in Example 3. Then the plasma was turned off and the auxiliary gas changed from argon to ammonia to form a TiN layer essentially as described in Example l. A TiN layer was thus W O96/12048 PCTAUS9Sfl3243 - 37 _ grown on top of ~he Ti layer to form a laminate bilayer. The Ti and TiN films were analyzed as described earlier and found to exhibit typical properties.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof.
It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope o~ the present invention as defined by the appended claims.

~ .~

. _

Claims (26)

- 38 -

1. A method for the chemical vapor deposition of a titanium-based film onto a substrate, comprising introducing to a deposition chamber the following components:
(a) a substrate;
(b) vapor of a compound having the formula (I) Ti(I4-m-n) (Brm) (Cln) (I) wherein m is 0-4 and n is 0-2;
(c) a first gas selected from the group consisting of ammonia and hydrazine; and (d) a second gas selected from the group consisting of hydrogen, nitrogen, argon and xenon; and maintaining said chamber containing said components at a temperature of about 200°C to about 650°C for a time sufficient to deposit a titanium-based film onto the substrate.

2. A method according to claim 1 wherein the chamber is maintained at about 350°C to about 475°C.

3. A method according to claim 1 wherein the compound of formula (I) is titanium tetraiodide.

4. A method according to claim 1 wherein the molar ratio of nitrogen atoms in component (c) to titanium atoms in component (a) is at least 1:1.

5. A method according to claim 1 wherein the substrate is a silicon or silicon dioxide water useful in the manufacture of a ULSI device.

6. A method for the chemical vapor deposition of a titanium-based film onto a substrate, comprising introducing to a deposition chamber the following components:
(a) a substrate;
(b) vapor of a compound having the formula (I) Ti(I4-m-n) (Brm) (Cln) (I) wherein m is 0-4 and n is 0-2; and (c) at least one gas selected from the group consisting of hydrogen; hydrogen and at least one of nitrogen, ammonia, argon and xenon; nitrogen and at least one of ammonia, argon and xenon; ammonia and at least one of argon and xenon; and maintaining said chamber containing said components a. a temperature of about 200°C to about 650°C, where said chamber contains a plasma having a plasma power density of about 0.1 to about 0.5 w/cm2, or a time sufficient to deposit a titanium-based film onto the substrate.

7. A method according to claim 6 wherein the temperature is about 350°C to about 475°C.

8. A method according to claim 6 wherein the compound of formula (I) is titanium tetraiodide.

9. A method according to claim 6 wherein the gas component (c) is hydrogen.

10. A method according to claim 6 wherein the gas component (c) is hydrogen and nitrogen.

11. A method according to claim 6 wherein the gas component (c) is hydrogen and at least one of argon and xenon.

12. A method according to claim 6 wherein the substrate is a silicon or silicon dioxide wafer useful in the manufacture of ULSI devices.

13. A method for depositing multiple layers of titanium-based film onto a substrate while the substrate remains fixed in a single deposition reactor, comprising the steps of introducing the components of a substrate and source precursor into a CVD chamber, where the source precursor is vapor of at least one compound of formula (I) Ti(I4-m-n) (Brm) (Cln) (I) wherein m is 0-4 and n is 0-2; and sequentially depositing onto the substrate alternating layers of titanium metal film and titanium nitride film, where either the titanium metal film or the titanium nitride film may be deposited first onto the substrate.

14. The method according to claim 13 wherein a titanium metal film is deposited onto a substrate to provide a coated substrate, and a titanium nitride film is deposited onto the coated substrate.

15. The method according to claim 13 wherein hydrogen gas is present in the deposition reactor with said vapor and said substrate, and said chamber containing said hydrogen gas, vapor and substrate is maintained at a temperature of about 200°C to about 650°C, where said chamber contains a plasma having a plasma power density of about 0.1 to about 0.5 w/cm2, for a time sufficient to deposit a titanium metal film onto the substrate.

16. The method according to claim 15 wherein an inert gas selected from the group consisting of argon and xenon is additionally present in the chamber during deposition of the titanium metal film.

17. The method according to claim 13 wherein a gas selected from the group consisting of (a) hydrogen and at least one of nitrogen, ammonia or hydrazine;
(b) nitrogen and at least one of ammonia, argon or xenon; and (c) ammonia and at least one of argon and xenon; is present in said-deposition chamber with said substrate and said vapor; and said chamber containing said gas, vapor and substrate is maintained at a temperature of about 200°C to about 650°C, where said chamber contains a plasma having a plasma power density of about 0.1 to about 0.5 W/cm2, for a time sufficient to deposit a titanium nitride film onto the substrate.

18. The method according to claim 17 wherein the chamber is maintained at about 350°C to about 475°C.

19. The method according to claim 17 wherein the gas is hydrogen and nitrogen.

20. The method according to claim 13 wherein the deposition chamber additionally contains a first gas selected from the group consisting of ammonia and hydrazine; and a second gas selected from the group consisting of hydrogen, nitrogen, argon and xenon; and said deposition chamber containing said substrate, said vapor, said first gas and said second gas is maintained at a temperature of about 200°C
to about 650°C, for a time sufficient to deposit a titanium nitride film onto the substrate.

21. The method according to claim 20 wherein the first as is ammonia and the second gas is hydrogen.

22. A substrate for integrated circuitry having a coating disposed thereon, wherein the substrate has features with dimensions of less than one micron and aspect ratios of at least about 3:1, and the coating is a titanium-based film according to claim 1 being conformally deposited on the substrate with step coverage greater than about 70%.

23. A substrate for integrated circuitry having a coating disposed thereon according to claim 22, wherein the substrate has features with dimensions of less than about 0.25 micron and with an aspect ratio of at least about 4:1.

24. A substrate for integrated circuitry having a coating disposed thereon, wherein the substrate has features with dimensions of less than one micron and aspect ratios of at least about 3:1, and the coating is a titanium-based film according to claim 6 being conformally deposited on the substrate with step coverage greater than about 70%.

25. A substrate for integrated circuitry having a coating disposed thereon according to claim 24, wherein the substrate has features with dimensions of less than about 0.25 micron and aspect ratios of at least about 6:1.

26. A substrate for integrated circuitry having a coating disposed thereon, wherein the substrate has features with dimensions of less than one micron and aspect ratios of at least 3:1, and the coating is a titanium-based film according to claim 13 being conformally deposited on the substrate with step coverage greater than about 30%.