GB2422832A - Precursors for chemical vapour deposition comprising metal & ligand with co-ordinating N & O, separated by 2 or 3 carbons, & sterically hindering substituent - Google Patents

Precursors for chemical vapour deposition comprising metal & ligand with co-ordinating N & O, separated by 2 or 3 carbons, & sterically hindering substituent Download PDF

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GB2422832A
GB2422832A GB0502446A GB0502446A GB2422832A GB 2422832 A GB2422832 A GB 2422832A GB 0502446 A GB0502446 A GB 0502446A GB 0502446 A GB0502446 A GB 0502446A GB 2422832 A GB2422832 A GB 2422832A
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nitrogen
oxygen
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Anthony Copeland Jones
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Epichem Ltd
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    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/40Oxides
    • C23C16/405Oxides of refractory metals or yttrium
    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07DHETEROCYCLIC COMPOUNDS
    • C07D263/00Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings
    • C07D263/02Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings
    • C07D263/08Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member
    • C07D263/10Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
    • C07D263/14Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms with radicals substituted by oxygen atoms
    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07FACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00Compounds containing elements of Groups 4 or 14 of the Periodic System
    • C07F7/003Compounds containing elements of Groups 4 or 14 of the Periodic System without C-Metal linkages
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/40Oxides
    • C23C16/401Oxides containing silicon

Abstract

Group 3B, 4B and rare earth metal precursors for chemical vapour deposition comprise the metal and at least one ligand having oxygen and nitrogen available for co-ordination with the metal, the oxygen and nitrogen being separated by 2 or 3 carbon atoms in the ligand and having sterically hindering groups on the nitrogen and/or the oxygen and/or a carbon adjacent to nitrogen and/or oxygen. A preferred ligand is the donor functionalised alkoxy ligand 2-(4,4-dimethyloxazolinyl)- propan-2-olate, [NC(CH3)2CH2OCC(CH3)2O] (abbrev.''dmop'').

Description

Title: Improved precursors for chemical vapour deposition

DESCRIPTION

This invention concerns precursors for chemical vapour deposition. This invention is particularly, but not exclusively concerned with Group 3B, 4B and rare earth (lanthanide) metal precursors for the growth of their oxides and silicates by chemical vapour deposition.

Thin films of Zr02 and Hf02 and the related silicates ZrSiO and HfSiO have important technological applications. In particular, they have high permittivities and are relatively stable in contact with silicon, making them prime candidates to replace Si02 as gate dielectric layers in nextgeneration MOSFET devices in integrated Si circuits. Metalorganic chemical vapour deposition (MOCVD) is an attractive technique for the deposition of these materials, offering the potential for : large area growth, good composition control and film uniformity, and excellent :::. conformal step' coverage at device dimensions less than 2trn, which is particularly SI..

important in microelectronics applications. I..

I

An essential requirement for a successful MOCVD process is the availability of precursors with tile appropriate physical properties for vapour phase transport and a SIll suitable reactivity for deposition. There must be an adequate temperature window between evaporation and decomposition, and for most electronics applications oxide deposition is restricted to temperatures in the region of 500 C, to prevent degradation of the underlying silicon circuitry and metal interconnects.

There are a number of problems associated with existing Zr and Hf CVD precursors. For instance, the halides ZrCI4 and HfCI4 are low volatility solids which need substrate temperatures of 800 C and above for oxide deposition. Metal 13- diketonates, such as {Zr(thd)4] (thd = 2,2,6,6-tetramethylheptane-3, 5cjonate) also require high substrate temperatures (> 600 C) for oxide growth. These are incompatible with the requirements of the electronics industry. Metal alkoxides are more attractive CVD precursors as they allow lower deposition temperatures.

However, the majority of [Zr(OR)4J and [Hf(OR)4] complexes are dimeric or polymeric with limited volatility, due to the pronounced tendency of the Zr(IV) and Hf(IV) to expand their coordination sphere to six, seven or eight. In order to inhibit oligomerisation, sterically demanding ligands such as tert-butoxide have been employed, and [Zr(OBut)4] (D.C. Bradley, Chem. Rev. 1989, 89, 1317) and [Hf(0But)4] (S. Pakswer & P Skoug, in " Thin dielectric oxide films made by oxygen *S..

assisted pyrolysis of alkoxides", The Electrochem. Soc., Los Angeles, CA, USA, 1970, 619 - 636) have been successfully used for the CVD of Zr02 and Hf02.

However, these mononuclear precursors contain unsaturated four-coordinate metal centres and the tert-butoxide ligand undergoes a catalytic decomposition reaction in * ** the presence of trace water. This makes them highly air and moisture sensitive and susceptible to pre-reaction in the CVD reactor. Their reactivity also leads to a greatly reduced shelf life, especially in solution-based liquid injection CVD applications.

An object of this invention is to provide Group 4B metal oxide and silicate precursors suitable for use in chemical vapour deposition techniques that have improved stability and volatility.

A further object of the present invention is to provide Group 3B and lanthanide metal precursors suitable for use in chemical vapour deposition techniques that have improved stability and volatility.

Accordingly, a first aspect of the present invention provides a precursor of a Group 3B, 4B or lanthanide metal comprising the metal (M) and at least one ligand (L') having oxygen and nitrogen available for co-ordination with the M, the oxygen and nitrogen being separated by 2 or 3 carbon atoms in the ligand and having sterically hindering groups on the nitrogen and/or on a carbon adjacent the nitrogen and/or oxygen.

Preferably, both the nitrogen and the oxygen or the carbon atom adjacent SIe* thereto are provided with a sterically hindering group, more preferably at least two sterically hindering groups. Preferably, the sterically hindering group is an alkyl groups having I - 4 carbon atoms. The nitrogen andlor oxygen may fo part of a : :.* cyclic ring. The oxygen may be linked to substituted benzene group. * S.. $ S

* , me In particular, it has been surprisingly found that the donor functionalised alkoxy ligand 2-(4,4-dimethyloxazoliny1)propano1ate [NC(CH3)2CH2OCC(CI-13)2QJ (abbrev. "dmop") is effective in inhibiting oligomerisation in Zr and Hf alkoxide complexes, as well as increasing the ambient stability of the complexes. The oxygen and nitrogen atoms can form a five membered ring when coordinated to a Ti, Zr or Hf central atom.

Accordingly, a preferred aspect of the present invention provides a precursor of a Group 4B metal having the following general formula: M(L) [L']4 wherein M is a metal selected from Ti, Zr and Hf L is an alkoxy group having from 1 to 4 carbon atoms; U is a ligand having an oxygen and nitrogen available for co-ordination with the M, the oxygen and nitrogen being separated by 2 or 3 carbon atoms in the ligand and having sterically hindering groups on the nitrogen and/or on a carbon adjacent the nitrogen and/or oxygen; and x is a number from 0 to 3. * S. * . S II. I L's.

S....' The most preferred ligand L is a tertiary-butoxide (OBut) group, although other groups such as iso-propoxide (OPr) can be employed.

S *I5

S

The preferred ligand U is 2-(4,4-dimethyloxazolinyl)-propanol (dmop) S..

* * wherein the precursor has the general formula M(L)[dmop}4 where M and L are as defined above but other donor functionalised alkoxide ligands such as 2- diethylaminomethyl-6-methylphenolate (abbrev. "dammp") niay also carry out the desirable function of inhibiting oligomerisation in Zr, Hf and Ti alkoxides for use in the invention.

Further ligands L' include but are not limited to chelating donor functionalised ligands with the structures shown below: R1 (Me R4 R3 Et, NEt OH

MM

OZOH MeMe ITc

* * Me Me N OH R3 " R8 * a a R2,NR1OH IS.. * S *S** *5 5 * S I * *S

I IS.

S * S R1

* S *s

S

S.. Rfl"? R6 SI..

R

R4 01 " R8 R3>ç_N OH R2 Ri The ligands described in this invention can form five or six-membered chelate rings with the central metal atom M in which the oxygen is bound to the metal by a bond and the nitrogen is coordinated to the metal by a dative bond. The chelate ring stabilises the metal centre from attack by nucleophiles such as 1-120, making the complex less air and moisture sensitive than other Zr or Hf alkoxide complexes, M(OR)4 (wherein R = Me, Et, Pr', But etc...). The bidentate ligands identified above also inhibit the oligornerisation of Zr and Hf alkoxides.

A further aspect of the present invention provides a method of making Group 4B precursors for use in MOCVD techniques comprising reacting the protonated ligand 1] as defined above (such as dmopH) with the corresponding Group 4B metal alkoxide, M(OR)4, or Group 4B metal alkylamide, M(NR2)4, in appropriate molar proportions, where R = alkyl, such as Me, El, Pr', But.

The new alkoxide complexes Zr(OBut)2(dmop)2 and Hf(OBut)2(dmop)2, have : ** been synthesised by the addition of dmopH to Zr(OBu')4 or Hf(OBut)4 in appropriate *S. * *: : * molar proportions. The new alkoxide complexes Zr(dmop)4 and Hf(dmop)4 have been * : ** synthesised by the addition of dmopH to Zr(NMe2)4 or Hf(NMe2)4 in appropriate * * molar proportions. The complexes have high vapour pressures suitable for MOCVD, and are also much less reactive to air and moisture than other M(OR)4 or M(NR2)4 * * * * complexes (wherein M = Zr or Hf, R is an alkyl group) making them easier to handle and use in MOCVD. The reduced air-sensitivity of these new Zr and Hf complexes arises from the replacement of the highly moisture sensitive tert-butoxide groups in [Zr(OBut)4] and [Hf(OBut)4] with the dmop ligand, which is much less susceptible to hydrolysis. The complexes are further stabilised to hydrolysis by an increase in the coordination number of the central Zr or Hf atom.

The ligand L' as defined above can be extended to other metals, which have large atomic radii and are highly positively charged, such as Group 3B (Sc, Y) and the lanthanide elements. To this end, a further aspect of the present invention provides a group 3B metal or lanthanide precursor having the general formula: M'[L']3 Where M' is a group 3B metal or a lanthanide element and U is as defined above.

Group 3B metals include Sc and Y and lanthanide elements include La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The preferred ligand U is drnop in which case the precursors have the following general formula: M'[dniopj3 * * * Where M' is as defined above. * * S * S. S..

Although the preferred ligand for this embodiment of the invention is {dmop], $S ** * ,. other bidentate chelating donor functionalised alkoxide ligands such as those identified above would also be suitable.

The invention also provides a method of making Group 3B and lanthanide metal precursors for use in MOCVD techniques comprising reacting the protonated ligand L' as defined above (such as dmopH or Hdarnmp) with the corresponding Group 3B or lanthanide metal alkylsilylamine, M[N(SiR3)]3 in appropriate molar proportions, where R = alkyl, such as Me or Et.

Precursors according to the invention may be used in depositing single or mixed oxide layers or films by conventional MOCVD, in which the precursor is contained in a metalorganic bubbler, or by liquid injection MOCVD, in which the precursor is dissolved in an appropriate inert organic solvent (eg. an aliphatic hydrocarbon such as toluene, heptane and nonane or an ether such as tetrahydrofuran) and then evaporated into the vapour phase using a heated evaporator.

In liquid injection MOCVD, additives such as polydentate oxygen donor ligands, including tetraglyme, (CH3O(CH2CH2O)4CH3) or related compounds may be .: :* added to the inert solvent to further stabilise the precursor solution (as described in the the Applicant's co-pending PCT Publication No. 2004/083479.). Se. * a *

S

The precursors may also be suitable for use in the deposition of zirconium oxide, hafnium oxide, titanium oxide and Ln203 films by other chemical vapour * *** deposition techniques, such as atomic layer deposition (ALD), in which alternating pulses of the precursor and a suitable oxygen source (such as H20 or ozone) are employed.

Alkoxide ligands which do not contain a hydrogen atom in the second, or J3 position, after the oxygen bonded to the metal are particularly suitable for ALD, as the alkoxide group is not susceptible to decomposition by elimination of a 3- hydrogen:- M-O-CR2-CR2-CR2-- a f3 The dainnip ligand is an example of a preferred ligand for an ALD precursor The precursors can be used for the MOCVD or ALD of Zr02, Hf02, and Ti02, and M'203 (M' = Sc, Y and lanthanide metal), and in combination with other precursors for the MOCVD of complex oxides containing zirconium oxide, hafnium oxide, and lanthanum oxide such as zirconium silicate, hafnium silicate and silicates of the lanthanide elements.

* The invention will now be further described by means of the following * S. S * ** examples and with reference to the accompanying drawings, in which: * Figure 1 shows the structure of an uncoordinated protonated drnopH ligand; * Figure 2 shows an envisaged structure for Zr(OBut)2(drnop)2; Figure 3 shows an envisaged structure of Hf(OBut)2(dmop)2 frI St Figure 4 shows an envisaged structure of Hf(dmop)4; Figure 5 shows X-ray diffraction data for Zr02 film grown by liquid injection MOCVD using Zr(OBut)2(dmop)2; Figure 6 shows X-ray diffraction data for Hf02 film grown by liquid injection MOCVD using Hf(OBut)2; Figure 7 is a scanning electron micrograph of a Hf02 film deposited by liquid injection MOCVD at 550 C using Hf(OBut)2 (dmop)2; Figure 8 shows high frequency C-V data for {Al/Zr02/n-Si] capacitor structure grown by liquid injection MOCVD using Zr(OBut)2 (dmop)2; Figure 9 shows high frequency C-V data for [Al/Hf02/n- Si] capacitor structure grown by liquid injection MOCVD using Hf(OBu')2 (dmop)2; Figure 10 shows X-ray diffraction spectrum of Hf02 deposited by liquid injection MOCVD using Hf(dmop)4 as a function of deposition temperature; Figure 11 shows the structure of an uncoordinated protonated dammpH ligand; Figure 12 shows H NMR for damrnpH in deuterated benzene solvent; arid Figure 13 shows H NMR spectrum of La(dammp)3 in deuterated benzene solvent. * S. * S * S.. *

Example 1 SSSe *5 * * S S S.

* . It has surprisingly been found that the donor functionalised alkoxy ligand 2- * : * :.* (4,4-dimethyloxazolinyl)-propanolate, [NC(CH3)2CH2OCC(CH3)20] (abbrev. S..

* , "dmop") is effective in inhibiting oligomerisation in Zr and Hf alkoxide complexes, as well as increasing the ambient stability of the complexes. Ill

The structure of the uncoordinated prolonated dmopH ligand is shown schematically in Figure 1, and it can be seen that the oxygen and nitrogen atoms can form a five membered ring when coordinated to a Ti, Zr or Hf central atom.

Preparation of dmopH 2-(4,4-dimethy1oxazolinyl)propano1 dmopH was synthesized by literature methods (L.N. Pridgen and G. Miller, J. Heterocyclic. Chem., 1983, vol. 20, 1223): 2- hydroxyjsobutyric acid (26.Og, 0.25 moles) and 2-amino-2-methyl-1- propanol (22.5g, O.25moles) were heated together in xylene (100 cm3) until lOmI of aqueous solution had been collected in a dean-stark trap (- S 16 hours). At the end of this time the reaction flask was cooled and the solvent removed by fractional distillation. The residue was slowly distilled using Kugelrohr apparatus. The product was fine white crystals. Mp 3 8-40 C.

: *. H NMR (400MHz, CDCL3): ô 1.28 (s, 61-I, NC(CH3)2CH2), 1.44 (s, 6H, S. . * . OC(CH3)2C), 4.03 (s, 2H, C(CH3)2CO). 3C{'H} NMR (400MHz, CDCI3): 28.10 S.., (OC(CH3)2), 28.59 (NC(CH3)2C), 67.37 (NC(CH3)2), 69.07 (OC(CH3)2C), 80.96 (OCH2C(CH3)2), 171.10 (N=CO). * S * SS*

Example 2.

Preparation of Zr(OBut)2(dmop)2 dmopH (2g, 0.013 moles) was dissolved in 50rn1 of anhydrous hexane. The solution was gently heated to insure all of the dmopH ligand dissolved. [Zr(OBut)4] (2.49g, 0.0065 moles) was then added. The solution was stirred for 8 hours in an ice- bath. All volatiles were removed in vacuo, and the crude product recrystallised from hexane. Compound I, Yield 1.79g (50.8% wrt [Zr(OBut)4] ).

H NMR (400MHz, CoD6): 3 1.43 (bs, 1211, NC(CH3)2CH2), 1.66 (s, 18H, C(C113)3), 1.71 (bs, 12H, OC(CI-13)2C), 3.79 (s, 411, C(CH3)2CH20).

An envisaged structure for Zr(OBut)2(dmop)2 is shown in Figure 2 of the drawings.

Example 3

.: :* Preparation of Hf(OBut)2(dmop)2 *S.. * S..

dmopH (1.8g, 0.0116 moles) was dissolved in 5Ornl of anhydrous hexane.

The solution was placed in an ice-bath and stirred. [Hf(OBut)4] (2.73 g, 0.0058 moles) was added and the reaction was left stirring in the icebath for 8 his. All volatiles were removed in vacuo and the crude product, compound 2 [Hf(OBut)2(dmop)2} was purified by recrystallisation from hexane. Yield 1. 58g (41.3% wrt Hf(OBut)4).

II NMR (400MHz, d8-tol): ô 1.26 (bs, 12H, NC(CH3)2CH2), 1.52 (s, 18H, C(C113)3), 1.54 (bs, 12H, OC(CH3)2C), 3.70 (s, 4H, C(CH3)2CjO).

An envisaged structure for Hf(OBut)2(dmOp)2 is shown in Figure 3 of the drawings.

Example 4

Preparation of Hf(dmop)4 50m1 of 0.758M solution of dmopH (0.03 75 moles) in anhydrous hexane was added slowly to a solution of Hf(NMe2)4 in anhydrous hexane kept at 0 C. Once the addition was complete the reaction mixture was stirred for 6 hrs at room temp. All volatiles were removed in vacuo. The product Hf(dmop)4 was a white crystalline solid. Yield S.07g (67.02% wrt. {Hf(NMe2)4]). Anal. Calcd. for HQC8H14NO2]4 : * 803.299: C, 47.85, Found: 47.53; H, 7.03, Found: 7.04; N, 6.97, Found: 6.97. S.. * * S..

S

111 NMR (400MHz, do-benz): ô 1.37 (s, 3H, NC(CH3)2CH2); 1.90 (s, 3H, OC(CH3)2C); 3.87 (s, 1H, C(CH3)2C1-120). S * * S *

An envisaged structure for Hf(dmop)4 is shown in Figure 4 of the accompanying drawings.

Example 5

Zirconium oxide and hafnium oxide deposition from Zr(OBu')2(dmop)2, Hf(OBut)2(drnop)2 and Hf(dmop)4 All three complexes were found to be excellent precursors for the deposition of Zr02 and Hf02 thin films by MOCVD. The Zr02 and Hf02 films were deposited by liquid injection MOCVD using the general conditions shown in Table 1 below.

Table 1 Growth conditions used for the growth of Zr02 or Hf02 thin films by liquid injection MOCVD using Zr(OBut)2(dmop)2, Hf(OBut)2(dmop)4 or Hf(dmop)4 Reactor pressure j mbar Precursor solution concentration 0. 1M in toluene Precursor solution injection rate 4 cm3 hr Evaporator temperature 160 C Argon carrier gas flow rate 400 cm3 min1 : *.. Oxygen flow rate 100 cm3 min' * S.. * *S..

a...,' Substrates Si(100) Substrate temperature 350-550 C Oxide growth rate 0.01 -0.40 m hr * S __________________________________________ * S * S. S... a *555

The identity of the films grown using the Zr(OBu1)2(dmop)2 and Hf(OBut) 2(dmop)2 precursors was confirmed as Zr02 or Hf02 by X-ray diffraction (see Figures 5 and 6 respectively). The X-ray diffraction patterns of the Hf02 thin films show that the films are amorphous at deposition temperatures of 400 C and below. At substrate temperatures above 450 C, the films adopt a monoclinic (LI- F1f02) phase (JCPDS 6-03 18). The a-Hf02 (200) reflection is observed at a 20 value of 35.3 but as the deposition temperature is increased to 550 C the (002) intensity decreases and the (020) reflection at 34.83 becomes predominant and can be attributed to a temperature driven texturing effect. The X-ray diffraction patterns from Zr02 films deposited in the temperature range 400 C to 550 C show a different behaviour to the Hf02 growth habit. The Zr02 thin films exhibit a tetragonal phase at 400 C and this phase becomes prominent at about 500 C. It then changes to the more stable monoclinic phase at 550 C.

The composition of the films deposited using Zr(OBut)2(dmop)2 and Hf(OBut) 2(dmop)4 was determined by Auger electron spectrosdcopy and the results are given in Table 2.

Table 2. Atomic composition of the Zr-oxide and Hf-oxide films grown using :.: : Zr(OBut)2(drnop)2 and Hf(OBut)2(dmop)2 determined by Auger electron spectroscopy * * * Se* ______________________________________ ________ Deposition Argon I1ow Oxygen flow Composition Jat.-%J * :*. Precursor temperature rate (cni3 rate (cm3 0/NI ( C) mind) min') Zr Hf 0 C 450 400 100 22 74.6 3.4 3.39 1 550 400 100 28.4 67.4 4.2 2.37 **..

450 500 0 24 70.7 5.3 2.95 450 400 100 32 66.1 1.9 2.07 2 550 400 100 35.9 56.1 8 1.56 450 500 0 31.8 63 5.2 1.98 Scaiming electron microscopy (SEM) shows that the thin films deposited using Zr(OBut)2(drnop)2 and Hf(OBut)2(dnlop)2 at 5OOC or lower are featureless on the micron scale. However, a columnar growth structure is evident in the Zr02 and Hf02 films deposited at 550 C, and a typical Scanning electron micrograph of Hf02 is shown in Figure 7.

High-frequency capacitance-voltage (C-V) measurements were carried out on {Al/M02/n-Si] capacitor structures to measure the dielectric properties of the Zr02 and Hf02 films grown using Zr(OBut)2(drnop)2 and Hf(OBut) 2(dmop)2 (see Figs. 8 and 9 respectively). Accumulation, depletion and inversion regions are clearly seen in both cases, typical of good quality dielectric films. The Zr02 film (Fig. 8) showed a relatively small hysteresis between the voltage sweeps in the forward and reverse directions of approx. O.05V, with a flat band voltage shift of O.2V. The hysteresis of O.IV in the Hf02 film (Fig. 9) was slightly larger than in the Zr02 film, and there is * :* also a larger shift in the flatband voltage (- lv), indicative of more trapped charge at * S..

the M02/Si interface. The hysteresis was clockwise for both films, indicative of electron trapping in electronic states at the Si/MO2 interface and/or in the bulk of the dielectric oxide film. The permittivity values (c) of the Zr02 and Hf02 films, as * : *. calculated from thickness measurements using Ellipsometry and capacitance measurements in accumulation (at f=lOOkHz), were 21.3 and 18. 6, respectively. The reduction fi-orn the expected value for each film of K 25 can be mainly attributed to the presence of a low permittivity mixed layer of metal (Zr or Hf) oxide and native Si02 (K = 3.9) on the nonetched Si substrates.

The identity of the films grown using the Hf(dmop)4 precursor was confirmed as Hf02 by X-ray diffraction (see Figure 10). The data shows that the films are amorphous at deposition temperatures of 400 C and below. At substrate temperatures above 450 C, the films adopt a mixture of cubic- Hf02 and monoclinic (a-Hf02) phase. The cubic- Hf02 (111) reflection is observed at a 20 value of 30.87 but as the deposition temperature is increased to 600 C the (111) a-Hf02 intensity appear and the (111) cubic- Hf02 reflection at 30.87 disappear.

The composition of the films deposited using Hf(dmop)4 was determined by Auger electron spectroscopy and the results are given in Table 3.

Table 3. Atomic composition of the Hf-oxide films grown using Hf(dmop)4 determined by Auger electron spectroscopy Deposition Argon Oxygen Thin film composition Film :.: . temperature flow rate flow rate (at.-%) 0/Hf **** no. ( C) (cm3 min') (cm3 min') Hf 0 N I C 1 400 400 100 30.3 59.9 1.9 7.9 1.98 2 450 400 100 33 60.5 1.4 5.1 1.83 * S * * * ___________ ___________ S 3 500 400 100 37.6 58.9 0 3.5 1.57 *S..

S

-________ _______________

4 500 500 0 31.8 66.1 0 2.l 2.08 500 250 250 32.3 54.2 1.8 11.6 1.68 6 650 400 100 32.7 63.7 0.4 3.2 1.95

Example 6.

Other donor functionalised alkoxide ligands such as 2-diethylaminomethyl6- methyl-phenolate (abbrev. "dammp") may also carry out the desirable function of inhibiting oligornerisation in Zr, Hf and Ti alkoxides for use in the invention.

The structure of the uncoordinated protonated ligand dammpH is shown in Figure 11 of the accompanying drawings.

Preparation of Gd(dammp)3 2-dicthylarninomethyl)6rnethylpheno1 was prepared by the method described by Grillot et a!, J. Am. Chem. Soc. 1945, 67, 1968, and the crude product was distilled under vacuum (80-85 C, 0.03 torr) to give pure product. The H NMR spectrum of dammpH is shown in Fig. 12. **a. S... * . S

* .. Example 7

S * S.

S

* : :.* Preparation of Gd(damrnp)3 *S.* * S...

Gd[N(SiMe3)2]3 (3.190g, 0.0050 moles) was dissolved in the minimum amount of dry toluene (ca. 20 cm3) and cooled in an ice bath. Three equivalents of 2- (di eth lyami nomethyl)-6-methylphenol, Hdammp, (3. 064g, 0.0158 moles) was dissolved in dry pentane (ca. 20 cm3) and added to the cooled, stirred Gd[N(SiMe3)2]3 solution. The reaction mixture was stirred for at least 3 hours while maintained in the ice bath. Solvents were removed in vacuo to leave an oily residue. This was washed with pentane (3x 10 cm3) to remove unreacted ligand. A colourless crystalline material remained which was dried in vacuo with a yield of 40 %. Crystals suitable for XRD were prepared by layering pentane above a concentrated toluene solution and cooling in a refrigerator.

Example 8.

Preparation of La(dammp)3.

La[N(SiMe3)2]3 (2.546g, 0.0041 moles) was dissolved in dry pentane (ca. 30 cm3) and cooled in an ice bath. Three equivalents of 2(diethlyaminomethyl)-6- methylphenol, Hdammp, (2.494g, 0.0129 moles) was dissolved in dry pentane (ca. 30 cm3) and added to the cooled, stirred La[N(SiMe3)2}3 solution. Volatiles were * 1 removed in vacuo to leave an oily residue. On standing overnight amorphous product I...

was precipitated. The residue was washed with pentane (3 x 10 cm3) and the ** remaining material dried in vacuo. Yield -32 %. * I * S * a.

*, For NMR product was dissolved in toluene and transferred to a NMR tube, solvent was removed in vacuo and product redissolved in C6D.

The NMR spectrum of La(dammp)3 is shown in Fig. 13.

Claims (26)

1. A precursor of a Group 3B, 4B or lanthanide metal comprising the metal (M) and at least one ligand (L') having oxygen and nitrogen available for co-ordination with the M, the oxygen and nitrogen being separated by 2 or 3 carbon atoms in the ligand and having sterically hindering groups on the nitrogen andlor on a carbon adjacent the nitrogen and/or oxygen.
2. A precursor as claimed in claim 1 wherein both the nitrogen and the oxygen or the carbon atom adjacent thereto are provided with a sterically hindering group.
3. A precursor as claimed in claim 2 wherein both the nitrogen and the oxygen or the carbon atom adjacent thereto are provided with at least two sterically hindering groups.
4. A precursor as claimed in claim 1, 2 or 3 wherein the sterically hindering group is an alkyl group having I to 4 carbon atoms.
5. A precursor as claimed in any one of claims I to 4 wherein the nitrogen and/or oxygen form part of a cyclic ring.
6. A precursor as claimed in any one of claims 1 to 5 wherein the oxygen is * * linked to a substituted benzene group. *. *
7. A precursor as claimed in claim 1 wherein the ligand L' is 2-(4,4- * ** * : dimelhyloxazolinyl)-propanolate, [NC(CH3)2CH2OCC(CH3)20] (abbrev. "drnop").
8. A precursor as claimed in claim 1 wherein the ligand L' is 2-
I
diethylaminornethyl-6-methyl-phenolate (abbrev. "dammp").
9. A precursor as claimed in claim 1 wherein L' is selected from the group consisting of: R1 R6<"OH (9''Me
R
R4 R3 EtNEtOH 7 MM
RN
R2R1 Mee R I:T:I:R fj R>SçN OH R8)çN OH MeMe R2 R1
I * I ç *.. * IS.. * S 1 R1 S. * I 4 * I.
I S.. R4R3 * . * I I - *4 I.-.
I II..
10. A precursor of a Group 4B metal having the general formula: M(L)[L']4 wherein M is a metal selected from Ti, Zr and Hf L is an alkoxy group having from 1 to 4 carbon atoms; U is a ligand having an oxygcn and nitrogen available for co-ordination with the M, the oxygen and nitrogen being separated by 2 or 3 carbon atoms in the ligand and having sterically hindering groups on the nitrogen and/or on a carbon adjacent the nitrogen andlor oxygen; and x is a number from 0 to 3.
Ii. A precursor as claimed in claim 10 wherein L is a tertiary-butoxide (OBut) group or a iso-propoxide (OPr') group.
12. A precursor as claimed in claim 10 or claim 11 wherein U is 2-(4,4dirnethyloxazolinyl)-propanol (dmop).
* ,
13. A precursor as claimed in claim 10 or claim 11 wherein U is 2- Si, * a diethylaminomethyl-6-methyl-phenolate (abbrev. "dammp"). * as.
14. A method making Group 4B precursors for use in MOCVD techniques * SI * a.
comprising reacting the protonated ligand U as defined in any one of claims ito 9 * * with the corresponding Group 4B metal alkoxide (M(OR)4) or Group 4B metal * * a.
* * alkylamide (M(NR2)4), in appropriate molar proportions, where R is an alkyl group having 1 to 4 carbon atoms.
15. A method as claimed in claim 14 for the preparation of Zr(OBut)2(dmop) 2 wherein dmopH is added to Zr(OBut)4
16. A method as claimed in claim 14 for the preparation of Hf(OBut)2(dmop) 2 wherein dmopH is added to Hf(OBut)4
17. A method as claimed in claim 14 for the preparation of Zr(dmop)4 wherein dmopH is added to Zr(NMe2)4
18. A method as claimed in claim 14 for the preparation of Hf(dmop)4 wherein dmopH is added to Hf(NMe2)4
19. A Group 3B metal or lanthanide precursor having the general formula: M'[L']3 where M' is a group 3B metal or a lanthanide element and L' is as defined by any one of claims ito 9.
20. A precursor as claimed in claim 19 wherein L' is dmop.
21. A method of making Group 3B and lanthanide metal precursors for use in MOCVD techniques comprising reacting the protonated ligand L' as defined in any one of claims I to 9 with the corresponding Group 3B or lanthanide metal alkylsilylamine, M[N(SiR3)2]3 in appropriate molar proportions, where R = alkyl *S..
having 1 to4carbon atoms.
S
. .:
22. A method of depositing single or mixed oxide layers or films by MOCVD *: using a precursor of a Group 3B, 4B or lanthanide metal comprising the metal (M) and at least one ligand (U) having oxygen and nitrogen available for co-ordination a... S *
with the M, the oxygen and nitrogen being separated by 2 or 3 carbon atoms in the ligand and having sterically hindering groups on the nitrogen andlor on a carbon adjacent the nitrogen and/or oxygen, in which the precursor is contained in a metalorganic bubbler.
23. A method of depositing single or mixed oxide layers or films by MOCVD using a precursor of a Group 3B, 4B or lanthanide metal comprising the metal (M) and at least one ligand (U) having oxygen and nitrogen available for co-ordination with the M, the oxygen and nitrogen being separated by 2 or 3 carbon atoms in the ligand and having sterically hindering groups on the nitrogen andlor on a carbon adjacent the nitrogen and/or oxygen, in which the precursor is dissolved in an appropriate inert organic solvent and then evaporated into the vapour phase using a heated evaporator.
24. A method of depositing single or mixed oxide films by atomic layer deposition (ALD) using a precursor of a Group 3B, 4B or lanthanide metal comprising the metal (M) and at least one ligand (U) having oxygen and nitrogen available for co- ordination with the M, the oxygen and nitrogen being separated by 2 or 3 carbon atoms in the ligand and having sterically hindering groups on the nitrogen andlor on a carbon adjacent the nitrogen and/or oxygen, in which alternating pulses of the * S. :. * precursor and a suitable oxygen source are provided. S... S *
25. A method as claimed in claim 24 wherein the precursor has an alkoxide ligand * : , U which does not contain a hydrogen in the second or 13 position, after the oxygen *5.
bonded to the metal. * . * S *
*
26. A method as claimed in claim 25 wherein the ligand is dammp. S * *SS*
GB0502446A 2005-02-07 2005-02-07 Precursors for chemical vapour deposition comprising metal & ligand with co-ordinating N & O, separated by 2 or 3 carbons, & sterically hindering substituent Withdrawn GB2422832A (en)

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