METHOD OF FORMING DIELECTRIC FILMS, NEW PRECURSORS AND THEIR USE IN SEMICONDUCTOR MANUFACTURING

• US 20090203222A1
• Filed: 03/16/2007
• Published: 08/13/2009
• Est. Priority Date: 06/02/2006
• Status: Active Grant

• Current Assignee: L'Air Liquide Societe Anonyme Pour L'Etude et L'Exploitation Des Procedes Georges Claude (L'Air Liquide SA)
• Original Assignee: L'Air Liquide Societe Anonyme Pour L'Etude et L'Exploitation Des Procedes Georges Claude (L'Air Liquide SA)
• Inventors: Dussarrat, Christian, Lachaud, Christophe, Blasco, Nicolas, Pinchart, Audrey
• Granted Patent: US 8,668,957 B2
• Time in Patent Office: Days
• US Class Current: 438/778
• CPC Class Codes: C07F 17/00 Metallocenes
• CPC Class Codes: C07F 7/00 Compounds containing elements of Groups 4 or 14 of the Periodic Table
• CPC Class Codes: C07F 7/003 without C-Metal linkages
• CPC Class Codes: C23C 16/18 from metallo-organic compounds
• CPC Class Codes: C23C 16/308 Oxynitrides
• CPC Class Codes: C23C 16/34 Nitrides C23C16/303 takes precedence
• CPC Class Codes: C23C 16/40 Oxides
• CPC Class Codes: C23C 16/403 of aluminium, magnesium or beryllium
• CPC Class Codes: C23C 16/405 of refractory metals or yttrium
• CPC Class Codes: C23C 16/407 of zinc, germanium, cadmium, indium, tin, thallium or bismuth
• CPC Class Codes: C23C 16/45553 characterized by the use of precursors specially adapted for ALD
• CPC Class Codes: H01L 21/02148 the material containing hafnium, e.g. HfSiOx or HfSiON
• CPC Class Codes: H01L 21/02159 the material containing zirconium, e.g. ZrSiOx
• CPC Class Codes: H01L 21/02178 the material containing aluminium, e.g. Al2O3
• CPC Class Codes: H01L 21/02181 the material containing hafnium, e.g. HfO2
• CPC Class Codes: H01L 21/02189 the material containing zirconium, e.g. ZrO2
• CPC Class Codes: H01L 21/02192 the material containing at least one rare earth metal element, e.g. oxides of lanthanides, scandium or yttrium
• CPC Class Codes: H01L 21/02194 the material containing more than one metal element
• CPC Class Codes: H01L 21/02205 the layer being characterised by the precursor material for deposition
• CPC Class Codes: H01L 21/02211 the compound being a silane, e.g. disilane, methylsilane or chlorosilane
• CPC Class Codes: H01L 21/02216 : the compound being a molecule comprising at least one silicon-oxygen bond and the compound having hydrogen or an organic group attached to the silicon or oxygen, e.g. a siloxane
• CPC Class Codes: H01L 21/02271 : deposition by decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition H01L21/02266 takes precedence
• CPC Class Codes: H01L 21/0228 : deposition by cyclic CVD, e.g. ALD, ALE, pulsed CVD
• CPC Class Codes: H01L 21/3141 : Deposition using atomic layer deposition techniques [ALD]
• CPC Class Codes: H01L 21/31641 : Deposition of Zirconium oxides, e.g. ZrO2
• CPC Class Codes: H01L 21/31645 : Deposition of Hafnium oxides, e.g. HfO2

Abstract

Method of deposition on a substrate, of a metal containing dielectric film comprising a compound of the formula (I):

(M¹_1-aM²_a)O_bN_c,  (I)

wherein 0≦a<1, 0<b≦3, 0≦c≦1, M¹ represents a metal selected from (Hf), (Zr) and (Ti); and M² represents a metal atom atoms, which comprises the following steps:

• • A step a) of providing a substrate into a reaction chamber;
  • A step (b) of vaporizing a M¹ metal containing precursor of the formula (II):

(R¹_yOp)_x(R²_tCp)_zM¹R′_4-x-z,  (II)

wherein 0≦x≦3, preferably x=0 or 1, 0≦z≦3, preferably z=1 or 2, 1≦(x+z)≦4, 0≦y≦7, preferably y=2 0≦t≦5, preferably t=1, (R¹_yOp) represents a pentadienyl ligand, which is either unsubstituted or substituted; (R²_tCp) represents a cyclopentadienyl (Cp) ligand, which is either unsubstituted or substituted, to form a first gas phase metal source;

• • A step c) of introducing the first gas phase metal source in the reaction chamber, in order to provoke their contact with said substrate, to generate the deposition of a metal containing dielectric film comprising a compound of the formula (I) as hereinbefore defined, on said substrate. Compound the formula (II₁):

(R²_tCp)M¹[N(R³⁹)(R⁴⁰)]₃  (II₁)

corresponding to the formula (II) as hereinabove defined in Claim 1, wherein x=0, z=1 and R′ represents the group N(R³⁹)(R⁴⁰).

Claims

1-18. -18. (canceled)

19. A method of deposition on a substrate, of at least one metal containing dielectric film comprising a compound of the formula (I):

(M¹_1-aM²_a)O_bN_c, 

 

(1)

wherein;

0≦

a<

1,

0<

b≦

3, preferably 1.5≦

c b≦

2.5;

0≦

c≦

1,

M¹ represents a metal selected from hafnium (Hf), zirconium (Zr) and titanium (Ti); and

M² represents a metal atom selected from magnesium (Mg), calcium (Ca), zinc (Zn), bore (B), aluminum (A), indium (In), silicon (Si), germanium (Ge), tin (Sn), hafnium (Hf), zirconium (Zr), titanium (Ti), vanadium (V), niobium (Nb), tantalum (Ta); and

the Lanthanides atoms, more particularly scandium (Sc), yttrium (Y) and lanthanum (La) and rare-earth metal atoms,

which comprises the following steps;

a step a) of providing a substrate into a reaction chamber;

a step b) of vaporizing at least one M¹ metal containing precursor of the formula (II);

(R¹_yOp)_x(R²_tCp)_zM¹R′

_4-x-z 

 

(II)

wherein;

M¹ is as hereinabove defined;

0≦

x≦

3, preferably x=0 or 1;

z=1

0≦

y≦

7, preferably y=2

0≦

t≦

5, preferably t=1;

(R¹_yOp) represents a pentadienyl (Op) ligand, which is either unsubstituted or substituted by one or more R¹ groups, y representing the number of substituting R¹ groups on said pentadienyl ligand;

(R²_tCp) represents a cyclopentadienyl (Cp) ligand, which is either unsubstituted or substituted by one or more R² groups, t representing the number of substituting R² groups on said cyclopentadienyl ligand;

R¹ and R² are identical or different and are independently selected from the group consisting of the chloro group, the linear or branched, alkyl groups having from one to four carbon atoms, the N-alkyl amino groups, wherein the alkyl group is linear or branched and has from one to four carbon atoms, the N,N-dialkyl amino groups, wherein each alkyl group, identical or different from the other, is linear or branched and has from one to four carbon atoms, the linear or branched alkoxy groups, having from one to four carbon atoms, the alkylsilylamides groups, the amidinates groups and the carbonyl group;

R′

represents a ligand independently selected from the N-alkyl amino groups, wherein the alkyl group is linear or branched and has from one to four carbon atoms, the N,N-dialkyl amino groups, wherein each alkyl group, identical or different from the other, is linear or branched and has from one to four carbon atoms, the linear or branched alkoxy groups, having from one to four carbon atoms, the alkylsilyl amino groups wherein the alkyl group is linear or branched and has from one to four carbon atoms, the dialkylsilyl amino groups wherein each alkyl group, identical or different from the other, is linear or branched and has from one to four carbon atoms, the trialkylsilyl amino groups wherein each alkyl group, identical or different from the other, is linear or branched and has from one to four carbon atoms, the amidinates groups and the carbonyl, being understood that, if said formula (II) comprises more than one R′

groups, each R¹ may be identical or different one from another,

to form a first gas phase metal source;

optionally a step b′

) of vaporizing at least one M² metal containing precursor, M² being as hereinabove defined;

to form an optional second gas phase metal source;

a step c) of introducing said first gas phase metal source and said optional second gas phase metal source, in the reaction chamber, in order to provoke their contact with said substrate, to generate the deposition of a metal containing dielectric film comprising a compound of the formula (I) as hereinbefore defined, on said substrate.

20. The method of claim 19, wherein the vaporization step b) and the vaporization step b′

) are combined in one vaporization step b″

) of both sources.

21. The method of claim 19, wherein the M² metal containing precursor, is selected from the group consisting of:

silicon derivatives or their germanium homologues, such as;

disiloxane, trisilylamine, disilane, trisilane, alkoxysilane of the formula;

(III₁)

SiH_x(OR³)_4-x, 

 

(III₁)

wherein;

0≦

x≦

3 and R³ represents a linear or branched hydrocarbon group having 1 to 6 carbon atoms;

silanol derivative of the formula (III₂);

Si(OH)_x(OR⁴)_4-x 

 

(III₂)

wherein;

1≦

x≦

3 and R⁴ represents a linear or branched alkyl group, having 1 to 6 carbon atoms, preferably Si(OH)(OR⁴)₃ and more preferably Si(OH)(OtBu)₃;

aminosilane derivative of the formula (III₃);

SiH_x(NR⁵R⁶)_4-x 

 

(III₃)

wherein;

0≦

x≦

3 and R⁵ and R⁶ are identical or different and independently represents an hydrogen atom or a linear or branched alkyl having 1 to 6 carbon atoms, preferably SiH(NMe₂)₃ (TriDMAS);

SiH₂(NHtBu)₂ (BTBAS);

SiH₂(NEt₂)₂ (BDEAS)) and mixtures thereof;

aluminum derivatives, such as trimethylaluminum [Al(CH₃)₃], dimethyl aluminum hydride [AlH(CH₃)₂], alkoxyalane of the formula (IV₁);

AlR⁸_x(OR⁷)_3-x 

 

(IV₁)

wherein;

0≦

x≦

3 and R⁷ represents a linear or branched alkyl having 1 to 6 carbon atom, and R⁸, identical to or different from R⁷, represents an hydrogen atom, or preferably AlR⁹R¹⁰(OR⁷), with R⁹ and R¹⁰ identical or different, which independently represent an linear or branched alkyl having 1 to 6 carbon atoms, most preferably AlMe₂(OiPr);

amidoalane of the formula (IV₂);

AlR¹¹_x(NR¹²R¹³)_3-x 

 

(IV₂)

wherein;

0≦

x≦

3 and R¹² and R¹³ identical or different, represent an hydrogen atom or a linear or branched alkyl having 1 to 6 carbon atoms, and R¹¹, identical to or different from R⁷ and, represents an hydrogen atom or a linear or branched alkyl having 1 to 6 carbon atoms;

tantalum derivatives, such as;

Ta(OMe)₅, Ta(OEt)₅, Ta(NMe₂)₅, Ta(NEt₂)₅, Ta(NEt₂)₅, a tantalum derivative of the formula (V₁);

Ta(OR¹⁴)₄[O—

C(R¹⁵)(R¹⁶)—

CH₂—

OR¹⁷]

wherein R¹⁴, R¹⁵, R¹⁶ and R¹⁷, identical or different, independently represent an hydrogen atom or a linear or branched alkyl having 1 to 6 carbon atoms, preferably Ta(OEt)₄(OCMe₂CH₂—

OMe) (TAT-DMAE), a tantalum derivative of the formula (V₂);

Ta(OR¹⁸)₄[O—

C(R¹⁹)(R²⁰)—

CH₂—

N(R²¹)(R²²)] 

 

(V₂)

wherein R¹⁸, R¹⁹, R²⁰, R²¹ and R²², identical or different, independently represent an hydrogen atom or a linear or branched alkyl having 1 to 6 carbon atoms, a tatalum derivative of the formula (V₃);

Ta(═

NR²⁴)(NR²⁵R²⁶)₃ 

 

(V₃)

wherein R²⁴, R²⁵ and R²⁶, identical or different, independently represent an hydrogen atom or a linear or branched alkyl having 1 to 6 carbon atoms;

Niobium derivatives, such as Nb(OMe)₅, Nb(OEt)₅, Nb(NMe₂)₅, Nb(NEt₂)₄, Nb(NEt₂)₅, a niobium derivative of the formula (VI₁);

Nb(OR²⁷)₄(O—

C(R²⁸)(R²⁹)—

CH₂—

OR³⁰) 

 

(VI₁)

wherein R²⁷, R²⁸, R²⁹ and R³⁰, identical or different, independently represent an hydrogen atom or a linear or branched alkyl having 1 to 6 carbon atoms, preferably Nb(OEt)₄(OCMe₂CH₂—

OMe) (NBT-DMAE), a niobium derivative of the formula (VI₂);

Nb(OR³¹)₄[O—

C(R³²)(R³³)—

CH₂—

N(R³⁴)(R³⁵)] 

 

(VI₂)

wherein R³¹, R³², R³³, R³⁴ and R³⁵, identical or different, independently represent an hydrogen atom or a linear or branched alkyl having 1 to 6 carbon atoms, a niobium derivative of the formula (VI₃);

Nb(═

NR³⁶)(NR³⁷R³⁸)₃ 

 

(VI₃)

wherein R³⁶, R³⁷ and R³⁸, identical or different independently represent an hydrogen atom or a linear or branched alkyl having 1 to 6 carbon atoms;

lanthanide derivatives, such as scandium derivatives, yttrium derivatives, cerium derivatives, praesidium derivatives, gadolinium derivatives or Nd derivatives, a derivative with at least one β

-diketonate ligand or at least a cyclopentadienyl ligand optionally substituted with one or several linear or branched alkyl groups having 1 to 6 carbon atoms;

divalent metal derivatives, such as strontium (Sr), barium (Ba), magnesium (Mg), calcium (Ca) or zinc (Zn) derivatives, with at least one β

-diketonate ligand or at least a cyclopentadienyl ligand optionally substituted with one or several linear or branched alkyl groups having 1 to 6 carbon atoms;

other metal derivatives such as tungsten (W), molybdenum (Mo), hafnium (Hf) or zirconium (Zr) derivatives, for example the alkoxy derivatives, the amino derivatives or adducts containing these species, being understood that said derivatives are not compounds of the formula (II) as hereinbefore defined.

22. The method of claim 19, which further comprises:

A step d), wherein the at least one M¹ metal containing precursor of the formula (II), and if necessary, the at least one M² metal containing precursor, is mixed to at least one reactant specie prior to step c).

23. The method of claim 19, which further comprises:

a step d′

) wherein the at least one M¹ metal containing precursor of the formula (II) and if necessary, the at least one M² metal containing precursor, is mixed to at least one reactant specie in the reaction chamber.

24. The method of claim 19, wherein the step b) consists of a step b₁) of mixing at least one first metal containing precursor of the formula (II) together with at least a second of the following precursors:

M¹(NMe₂)₄, M¹(NEt₂)₄, M¹(NMeEt)₄, M¹(mmp)₄, M¹(OtBu)₄, M¹(OtBu)₂(mmp)₂ and mixtures thereof and a step (b₂) of vaporizing said mixture.

25. The method of claim 19, wherein the M¹ metal containing precursor is of the formula (II₁):

(R²_tCP)M¹[N(R³⁹)(R⁴⁰)]₃ 

 

(II₁)

corresponding to the formula (II), wherein x=0, z=1 and R′

represents the group N(R³⁹)(R⁴⁰), wherein R³⁹ and R⁴⁰, identical or different, independently represent an hydrogen atom, a linear or branched alkyl group having from one to four carbon atoms, an alkylsilyl group, wherein the alkyl group is linear or branched and has from one to four carbon atoms, a dialkylsilyl group, wherein each alkyl group, identical or different from the other, is linear or branched and has from one to four carbon atoms or a trialkylsilyl group wherein each alkyl group, identical or different from the other, is linear or branched and has from one to four carbon atoms.

26. The method of claim 19 of deposition of a metal containing dielectric film comprising a compound of the formula (I₁):

M¹O₂ 

 

(I₁)

corresponding to the formula (I), wherein a=0, b=2 and c=0, wherein the metal containing precursor of the formula (II) is selected from the group consisting of;

Zr(MeCp)(NMe₂)₃, Zr(EtCp)(NMe₂)₃, ZrCp(NMe₂)₃, Zr(MeCp)(NEtMe)₃, Zr(EtCp)(NEtMe)₃, ZrCp(NEtMe)₃, Zr(MeCp)(NEt₂)₃, Zr(EtCp)(NEt₂)₃, ZrCp(NEt₂)₃, Zr(iPr₂Cp)(NMe₂)₃, Zr(tBu₂Cp)(NMe₂)₃, Hf(MeCp)(NMe₂)₃, Hf(EtCp)(NMe₂)₃, HfCp(NMe₂)₃, Hf(MeCp)(NEtMe)₃, Hf(EtCp)(NEtMe)₃, HfCp(NEtMe)₃, Hf(MeCp)(NEt₂)₃, Hf(EtCp)(NEt₂)₃, HfCp(NEt₂)₃, Hf(iPr₂Cp)(NMe₂)₃, Hf(tBu₂Cp)(NMe₂)₃, and mixtures thereof.

27. The method of claim 19 of deposition of a metal containing dielectric film comprising a compound of the formula (I₂):

M¹O_bN_c, 

 

(I₂)

corresponding to the formula (I), wherein a=0, 1.5≦

b≦

2.5 and 0<

c≦

0.5, wherein the metal containing precursor of the formula (II) is selected from the group consisting of;

Zr(MeCp)(NMe₂)₃, Zr(EtCp)(NMe₂)₃, ZrCp(NMe₂)₃, Zr(MeCp)(NEtMe)₃, Zr(EtCp)(NEtMe)₃, ZrCp(NEtMe)₃, Zr(MeCp)(NEt₂)₃, Zr(EtCp)(NEt₂)₃, ZrCp(NEt₂)₃, Zr(iPr₂Cp)(NMe₂)₃, Zr(tBu₂Cp)(NMe₂)₃, Hf(MeCp)(NMe₂)₃, Hf(EtCp)(NMe₂)₃, HfCp(NMe₂)₃, Hf(MeCp)(NEtMe)₃, Hf(EtCp)(NEtMe)₃, HfCp(NEtMe)₃, Hf(MeCp)(NEt₂)₃, Hf(EtCp)(NEt₂)₃, HfCp(NEt₂)₃, Hf(iPr₂Cp)(NMe₂)₃, Hf(tBu₂Cp)(NMe₂)₃ and mixture thereof.

28. The method of claim 19 of deposition of a metal containing dielectric film comprising a compound of the formula (I₃):

(M¹_1-aM²_a)O_b 

 

(I₃)

corresponding to the formula (I), wherein 0≦

a<

1 and c=0, wherein the metal containing precursor of the formula (II) is selected from the group consisting of;

Zr(MeCp)(NMe₂)₃, Zr(EtCp)(NMe₂)₃, ZrCp(NMe₂)₃, Zr(MeCp)(NEtMe)₃, Zr(EtCp)(NEtMe)₃, ZrCp(NEtMe)₃, Zr(MeCp)(NEt₂)₃, Zr(EtCp)(NEt₂)₃, ZrCp(NEt₂)₃, Zr(iPr₂Cp)(NMe₂)₃, Zr(tBu₂Cp)(NMe₂)₃, Hf(MeCp)(NMe₂)₃, Hf(EtCp)(NMe₂)₃, HfCp(NMe₂)₃, Hf(MeCp)(NEtMe)₃, Hf(EtCp)(NEtMe)₃, HfCp(NEtMe)₃, Hf(MeCp)(NEt₂)₃, Hf(EtCp)(NEt₂)₃, HfCp(NEt₂)₃, Hf(iPr₂Cp)(NMe₂)₃, Hf(tBu₂Cp)(NMe₂)₃ and the M² metal containing precursor is preferably selected from the silicon derivatives or their germanium homologues, the tantalum derivatives, lanthanide derivatives, and the magnesium derivatives as hereabove defined.

29. The method of claim 19 of deposition of a metal containing dielectric film comprising a compound of the formula (I₄):

(M¹_1-aM²_a)O_bN_c 

 

(I₄)

corresponding to the formula (I), wherein 0≦

a<

1 and 0<

c≦

0.5, wherein the metal containing precursor of the formula (It) is selected from the group consisting of HfCp₂Cl₂, Hf(MeCp)₂Me₂, HfCp(MeCp)Cl₂, Hf(MeCp)₂Cl₂, HfCp(MeCp)Me₂, Hf(EtCp)(MeCp)Me₂, Hf(EtCp)₂Me₂, Hf(MeCp)₂(CO)₂, ZrCp₂Cl₂, Zr(MeCp)₂Me₂, ZrCp(MeCp)Cl₂, Zr(MeCp)₂Cl₂, ZrCp(MeCp)Me₂, Zr(EtCp)(MeCp)Me₂, Zr(EtCp)₂Me₂, Zr(MeCp)₂(CO)₂, Zr(MeCp)(NMe₂)₃, Zr(EtCp)(NMe₂)₃, ZrCp(NMe₂)₃, Zr(MeCp)(NEtMe)₃, Zr(EtCp)(NEtMe)₃, ZrCp(NEtMe)₃, Zr(MeCp)(NEt₂)₃, Zr(EtCp)(NEt₂)₃, ZrCp(NEt₂)₃, Zr(iPr₂Cp)(NMe₂)₃, Zr(tBu₂Cp)(NMe₂)₃, Hf(MeCp)(NMe₂)₃, Hf(EtCp)(NMe₂)₃, HfCp(NMe₂)₃, Hf(MeCp)(NEtMe)₃, Hf(EtCp)(NEtMe)₃₁ HfCp(NEtMe)₃, Hf(MeCp)(NEt₂)₃, Hf(EtCp)(NEt₂)₃, HfCp(NEt₂)₃, Hf(iPr₂Cp)(NMe₂)₃, Hf(tBu₂Cp)(NMe₂)₃, the M² metal containing precursor is preferably selected from the silicon derivatives or their germanium homologues, the tantalum derivatives, lanthanide derivatives, and the magnesium derivatives as hereabove defined, and at least one oxygen containing precursor and at least one nitrogen containing precursor is introduced into the reactor.

30. Compound of the formula (II₁):

(R²_tCp)M¹[N(R³⁹)(R⁴⁰)]₃ 

 

(II₁)

corresponding to the formula (II) as hereinabove defined in claim 19, wherein x=0, z=1 and R′

represents the group N(R³⁹)(R⁴⁰), wherein R³⁹ and R⁴⁰, identical or different, independently represent an hydrogen atom, a linear or branched alkyl group having from one to four carbon atoms, an alkylsilyl group, wherein the alkyl group is linear or branched and has from one to four carbon atoms, a dialkylsilyl group, wherein each alkyl group, identical or different from the other, is linear or branched and has from one to four carbon atoms or a trialkylsilyl group wherein each alkyl group, identical or different from the other, is linear or branched and has from one to four carbon atoms.

31. Compound of the formula (II₁) as defined in claim 30, wherein R², R³⁹ and R⁴⁰, identical or different, independently represent a radical selected from the methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl groups.

32. The following compounds the formula (II₁) as defined in claim 31:

Zr(MeCp)(NMe₂)₃, Zr(EtCp)(NMe₂)₃, ZrCp(NMe₂)₃, Zr(MeCp)(NEtMe)₃, Zr(EtCp)(NEtMe)₃, ZrCp(NEtMe)₃, Zr(MeCp)(NEt₂)₃, Zr(EtCp)(NEt₂)₃, ZrCp(NEt₂)₃, Zr(iPr₂Cp)(NMe₂)₃, Zr(tBu₂Cp)(NMe₂)₃, Hf(MeCp)(NMe₂)₃, Hf(EtCp)(NMe₂)₃, HfCp(NMe₂)₃, Hf(MeCp)(NEtMe)₃, Hf(EtCp)(NEtMe)₃, HfCp(NEtMe)₃, Hf(MeCp)(NEt₂)₃, Hf(EtCp)(NEt₂)₃, HfCp(NEt₂)₃, Hf(iPr₂Cp)(NMe₂)₃, Hf(tBu₂Cp)(NMe₂)₃.

33. The following compounds the formula (II₁) as defined in claim 32:

Zr(EtCp)(NMe₂)₃, Zr(MeCp)(NMe₂)₃, ZrCp(NMe₂)₃, Hf(EtCp)(NMe₂)₃, Hf(MeCp)(NMe₂)₃ and HfCp(NMe₂)₃.

34. Process for the preparation of a compound of the formula (II₁), as defined in claim 31, comprising:

a step 1, consisting of the preparation of the compound of the formula (VII₁);

(R²_tCp)M¹Cl₃ 

 

(VII₁)

wherein M¹, R² and t are as hereinabove defined for the formula (II), by the reaction of M¹Cl₄ with (R²_tCp)Na;

a step 2, consisting of the reaction of the compound of the formula (VII₁) prepared in step 1, with NH(R³⁹)(R⁴⁰), to produce the compound of the formula (II₁).

35. (canceled)