EP0462158A1

EP0462158A1 - Use of metallo-organic compounds for vapour deposition of thin films

Info

Publication number: EP0462158A1
Application number: EP90904320A
Authority: EP
Inventors: Dietrich Erdmann; Ludwig Pohl; Martin Hostalek
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 1989-03-09
Filing date: 1990-03-03
Publication date: 1991-12-27
Also published as: DE3907579A1; US5209952A; WO1990010726A1; JPH04503974A; KR920701514A

Abstract

On utilise des composés organo-métalliques qui contiennent de l'aluminium, du gallium ou de l'indium en tant que métaux pour déposer des couches minces ou épitaxiales en phase gazeuse.Organometallic compounds which contain aluminum, gallium or indium as metals are used to deposit thin or epitaxial layers in the gas phase.

Description

Use of organometallic compounds for the deposition of thin films from the gas phase

The invention relates to the use of organometallic compounds containing aluminum, gallium or indium as metals for the deposition of thin films or epitaxial layers from the gas phase.

The deposition of such layers from either pure elements of III. Group or from III-V combinations, e.g. Gallium arsenide, indium phosphide or gallium phosphide can be used for the production of electrical, electronic, optical and optoelectronic switching elements, compound semiconductors and lasers. These layers are deposited from the gas phase.

The properties of these films depend on the deposition conditions and the chemical composition of the deposited film.

All known methods such as the metal-organic chemical vapor deposition (MOCVD) method, the photo-metal-organic vapor phase (photo-MOVP) method, in which the substances are exposed to UV radiation, are used for the deposition from the gas phase decomposed, the Laser Chemical Vapor Deposition (Laser CVD) method or the Metal-Organic Magnetron Sputtering (MOMS) method in question. The advantages over other methods are a

REPLACEMENT LEAF Layer growth, precise doping control and easy handling and ease of production due to the normal or low pressure conditions.

In the MOCVD method, organometallic compounds are used which decompose at a temperature below 1100 ° C. upon deposition of the metal. Typical apparatuses which are currently used for MOCVD consist of a "bubbler" with a feed for the organometallic component, a reaction chamber which contains the substrate to be coated, and a source for a carrier gas which acts against the organometallic Component should be inert. The "bubbler" is kept at a constant, relatively low temperature, which is preferably above the melting point of the organometallic compound, but far below the decomposition temperature. The reaction or decomposition chamber preferably has a much higher temperature, which is below 1100 ° C., at which the organometallic compound completely decomposes and the metal is separated. The organometallic compound is brought into the vapor state by the carrier gas and is carried into the decomposition chamber with the carrier gas. The mass flow of the steam can be controlled well, and thus controlled growth of the thin layers is also possible.

So far, mainly metal alkyls such as e.g. Trimethyl gallium, trimethyl aluminum or trimethyl indium are used. However, these compounds are extremely sensitive to air, self-igniting and sometimes even decompose at room temperature. Therefore, complex precautionary measures are necessary for the manufacture, transport, storage and use of these connections. There are also some, somewhat more stable ones

ER ^S ATZBLATT Adducts of the metal alkyls with Lewis bases such as, for example, trimethylamine and triphenylphosphine are known (for example, described in GB 21 23422, EP-A 108 469 or EP-A 176 537), which, however, are only suitable to a limited extent for gas phase separation due to the low vapor pressure. The low vapor pressures are often due to the presence of dimers, trimers or polymers.

It was an object of the present invention to find organometallic compounds which are easy to handle and stable at room temperature and which have a sufficiently high vapor pressure so that they are suitable for the various methods of vapor deposition.

It has now been found that organometallic compounds of aluminum, gallium and indium which contain branched or bulky residues have a suitable vapor pressure and are therefore outstandingly suitable for gas phase deposition.

Similar compounds are known from EP-A 02 95467. However, the compounds described there are mostly dimeric and are therefore not used for the deposition from the gas phase, but rather for the deposition from the liquid phase.

The invention thus relates to the use of organometallic compounds of the formula I.

< ^R > 3-n ^M - ^Y n

wherein

REPLACEMENT LEAF M aluminum, gallium or indium,

n 1, 2 or 3,

Y -NR ² R ³ , -PR ² R ³ , -AsR ² R ³ or -SbR ² R ³ ,

and R in each case independently of one another H, an alkyl group with 1-8 C atoms, it being possible for the alkyl group to be partially or completely fluorinated, a cycloalkyl, alkenyl or cycloalkenyl group each with 3-8 C atoms or an aryl group,

R ¹ also l, 2- (CH ₂ ) _p -C ₆ H ₄ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₆ H ₁₀ - (CH ₂ ) _q -Z, l , 2- ^(C H ₂ ⁾ _p - ^C ₆ H ₈ - ^(C H ₂ ⁾ _g -Z, l, 2- (CH ₂ ) _p -C ₆ H ₆ - (CH ₂ ) _g -Z, l, 2 - (CH ₂ ) _p -C ₅ H ₈ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₅ H ₆ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₅ H ₄ - (CH ₂ ) _g -Z or l, 2- (CH ₂ ) _p -C ₄ H ₆ - (CH ₂ ) _g -Z,

p and g each independently 0, 1, 2 or 3,

Δ * _ 4. ^ 4. ^■ _ 4- * 5

Z -NR R, -PR R, -AsR * R or -SbR R

and

R is a branched alkyl or alkenyl group, each with 3-8 C atoms, these

Groups partially or fully fluorinated

REPLACEMENT LEAF can be a cycloalkyl or cyclo alkenyl group each having 3-8 C atoms or an aryl group

mean,

for the deposition of thin films or layers from the gas phase.

The invention furthermore relates to a process for producing thin films and epitaxial layers by vapor deposition from organometallic compounds, in which the compounds of the formula I are used as organometallic substances. It is also an object of the invention that in the process according to the invention for the production of e.g. Compound semiconductors are added during the deposition process to one or more compounds of arsenic, antimony or phosphorus which are gaseous under the reaction conditions used.

The compounds of the formula I are intramolecularly stabilized by electron transfer from the nitrogen, phosphorus, arsenic or antimony atom to the electron-poor III B element. They are therefore stable to air and oxygen, no longer self-igniting and therefore easy to handle.

In the gas phase, however, the compounds according to the invention can easily be decomposed with deposition of the metal. Since the compounds of the formula I contain stable and easily removable leaving groups, a results

REPLACEMENT LEAF less installation of carbon, which has great advantages for the quality of the end products.

The deposited films can be formed from the pure III B element or from combination with elements from the V group on any substrates. Depending on the substrate and the deposition technique, they can be epitaxial in nature.

Those compounds of formula I which are monomeric due to branched or bulky residues and therefore have a higher vapor pressure are very particularly preferred and well suited for MOCVD technology.

In formula I, M means aluminum (Al), gallium (Ga) or indium (In), preferably Ga or In.

Y primarily means -NR 2R3, in the second Li .ni.e preferably -PR2R3 or -AsR2R3.

n is preferably 1.

The radicals R 1, R2, R4 and R5 in the formula I are each preferably a straight-chain or branched alkyl group having 1-8 C atoms, preferably having 1-5 C atoms. The alkyl groups are preferably straight-chain and accordingly preferably mean methyl, ethyl, propyl, butyl, pentyl, further also hexyl, heptyl, octyl, isopropyl, sec-butyl, tert-butyl, 2-methylpentyl, 3-methylpentyl or 2 -Octyl. The alkyl radicals can be partially or completely fluorinated and e.g. Monofluoromethyl,

Difluoromethyl, trifluoromethyl, difluoroethyl, trifluoroethyl,

Pentafluoroethyl or trifluoropropyl mean. Preferably only one of the radicals R 1, R4 or R5 is H.

ER ^SA TZBLATT 1 2 4 5

If R, R, R and / or R represent a cycloalkyl or cycloalkenyl group with 3-8 C atoms, they preferably mean cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cyclohexadienyl, cycloheptyl, cycloheptenyl, Cycloheptadienyl, cyclooctyl,

Cyclooctenyl, Cyclooctadienyl, Cyclooctatrienyl or

Cyclooctatetraenyl.

R 1, R2, R4 and / or R5 are preferably also alkenyl groups with 3-8 C atoms, preferably with 3-5 C atoms. Accordingly, they preferably mean propenyl, butenyl,

Pentenyl also hexenyl, heptenyl or octenyl.

Compounds of the formula I are furthermore preferred in which

R 1, R2, R4 and / or R5 mean aryl groups. Aryl group preferably means a phenyl group. This phenyl group can also be substituted. Since these substituents have no significant influence on the intended use, all substituents are permitted which have no disruptive influence on the decomposition reaction.

The radical R can occur several times and can then have different or the same meaning.

R ¹ in formula I may also be 1,2- (CH ₂₎ - (C ₆ H ₄ - (CH ₂₎ -Z, l, 2- (CH ₂₎ _p -C ₆ H ₁₀ - (CH ₂₎ _g - Z, l, 2- (CH ₂ ) _p -C ₆ H ₈ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₆ H ₆ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₅ H ₈ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₅ H ₆ - (CH ₂ ) _g -Z, 1,2- (CH _{2 p} -C ₅ H ₄ - (CH ₂ ) _g -Z or 1,2- ₄ (CH ₅ _.) PC ₄ 4: H _fi θ- (C ₄ H ₉ ^) qZ, where Z is preferably -NR R or -AsR R and p and q each preferably denote 0, 1 or 2.

REPLACEMENT LEAF Accordingly, the following groups (I) - (9) are particularly preferred for R ¹ :

(1) (2) (3)

(4) (5) (6)

(7) (8) (9)

R in formula I preferably represents a branched alkyl group with 3-8 C atoms, preferably with 3-5 C atoms, which can also be partially or completely fluorinated. Accordingly, R 3 is preferably isopropyl, sec.

Butyl, tert-butyl, 1-methylbutyl, 2-methylbutyl, 1,2-dirnethylpropyl, and also 2-methylpentyl, 3-methylpentyl, 2-octyl or 2-hexyl.

REPLACEMENT LEAF ₃ If R is a cycloalkyl or cycloalkenyl group, preference is given to those groups which are also for R,

2 4 5 R, R and R are given as preferred.

Thus, the compounds of the formula I always contain at least one bulky ligand, in the form of a branched one

Group or a cyclic radical. Compounds in which R '2 and R3 are branched alkyl groups are preferred.

The following compounds are, for example, preferred representatives of the compounds of the formula I:

Ethyl i-propyl

Ga-N ethyl ^ i-propyl

Methyl i-propyl Ga-N

Methyl i-propyl

Ga-As methyl i-propyl

Methyl i-propyl In-P

Methyl i-propyl

Propyl tert. Butyl Al-N Propyl ^ tert. Butyl

Butyl

^E R ^S ATZBLATT Propyl _^ i-propyl

Al-P

Methyl '"phenyl

Butyl 2-octyl

In-N butyl propyl

<_} -CH, i-propyl

^• \

In-P methyl i-propyl

Propyl cyclohexyl

Ethyl tert. Butyl Ga-As

Ethyl ^ tert. Butyl

The compounds of the formula I are outstandingly suitable for the MOCVD epitaxy or MOCVD method, since they decompose at higher temperatures with the release of the corresponding metal. They are also suitable for other methods of gas phase deposition such as PhotoMOVP, Laser CVD or MOMS.

The compounds of the formulas I are prepared by methods known per se, as described in the literature (e.g. G. Bahr, P. Burba, methods of organic

Chemistry, Volume XII1 / 4, Georg Thieme Verlag, Stuttgart (1970)) are described, under reaction conditions that are known and suitable for the reactions mentioned. Use can also be made of variants which are known per se and are not mentioned here in detail.

ER ^SA TZBLATT For example, compounds of the formula I can be prepared by reacting metal alkyl chlorides with an alkali metal organanyl of the corresponding Lewis base or a Grignard compound in an inert solvent.

The reactions are preferably carried out in inert solvents. Suitable solvents are all those who do not interfere with the reaction and do not intervene in the reaction. The reaction temperatures essentially correspond to those resulting from the

Literature for the preparation of similar compound are known.

In the process according to the invention for producing thin films or epitaxial layers on any substrates, the stabilized metalloorganic compounds of the formula I are used as starting compounds in the gas-phase deposition processes of organometallic compounds known per se. The reaction conditions can be selected analogously to the values known from the literature and familiar to the person skilled in the art.

To produce compound semiconductors, electronic and optoelectronic components, one or more compounds of arsenic, antimony or phosphorus, for example AsH ,, As (CH ₃ ) ₃ , can be used in the process according to the invention during the deposition process in the decomposition chamber in the process according to the invention. PH ₃ or SbH _{3 can} also be added. Another variant of the method according to the invention consists in that dopants are added during the deposition process in addition to the organometallic compounds of the formula I according to the invention. Volatile organometallic compounds are used as dopants

E _R SET _B LATT Compounds of iron, magnesium, zinc or chromium are used. Zn (CH ₃ ) ₂ , Mg (CH ₃ ) ₂ or Fe (C ₅ H ₅ ) ₂ are, for example, preferred compounds.

It is also possible to add the compounds of the formula I as dopants during the deposition process of other organometallic compounds.

The layers produced by the method according to the invention can be used for the production of electronic, electrical, optical and optoelectronic switching elements, compound semiconductors or lasers.

Since only about 1-10% of the free metal alkyls used can be deposited as an epitaxial layer on the substrate in the epitaxy systems currently in use for theirmodynamic reasons, the destruction of the excess metal alkyls, which, owing to their extreme sensitivity, does not reset on the other hand, because of their high stability, the compounds of the formula I according to the invention open up new possibilities for the risk-free destruction or for the recovery of the valuable III B compounds.

The following examples are intended to explain the invention in more detail. Temperatures are always in degrees Celsius. Mp. Means melting point and Kp. Boiling point.

REPLACEMENT LEAF example 1

10.6 g (0.064 mol) of diethylgallium chloride (Et ₂ GaCl) are added to a mixture of 6.9 g (0.064 mol) of lithium diisopropylamide (iPr ₂ N-Li) and 80 ml of hexane within one hour. The hexane is distilled off and the product Et ₂ Ga-N Pr_ is fractionally distilled in vacuo. Kp = 42 ° C / 0.6 mbar

H-NMR spectrum (δ values in ppm); 250 MHz:

Ethyl groups: 0.82 (g, 4H) 1.66 (tr, 6H) iPr ₂ N group: 1.05 (d, 12H); 3.05 (m, 2H).

Example 2

To a mixture of 17.5 g (0.16 mol) of lithium diisopropylamide (iPr_N-Li) and 150 ml of hexane is added 28.8 g (0.16 mol) of dirnethylindium chloride within one hour. The hexane is distilled off and the product Me ₂ In-NiPr ₂ is fractionally distilled in vacuo.

- "Ή-N R spectrum (δ values in ppm); 250 MHz:

Methyl groups: 0.2 (s, 6H) iPr ₂ N group: 1.0 (d, 12H); 2.85 (.2H)

REPLACEMENT LEAF

Claims

1. Use of organometallic compounds of the formula I

< ^Rl > 3-n ^M - ^Y n ^τ

wherein

M aluminum, gallium or indium,

n 1, 2 or 3,

9 3 2 3 2 3 _? ^■ _

Y -NR ^ R, -PR R, -AsR ^ R ° or -SbR R,

1 2 4 R, R, R * and R are each independently H, one

Alkyl group with 1-8 C atoms, where the alkyl group can be partially or completely fluorinated, a cycloalkyl, alkenyl or cycloalkenyl group each with 3-8 C atoms or an aryl group,

REPLACEMENT LEAF R ¹ and 1,2- (CH ₂₎ -C ₆ H ₄ - (CH ₂₎ -Z, l, 2- (CH ₂₎ _p -C ₆ H ₁₀ - (CH ₂₎ _g -Z _(l, 2 - (CH ^) _p -C ₆ H ₈ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₆ H ₆ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₅ H ₈ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₅ H ₆ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₅ H ₄ - (CH ₂ ) _g -Z or l, 2- (CH ₂ ) _p -C ₄ H ₆ - (CH ₂ ) _g -Z,

p and g each independently 0, 1, 2 or 3,

Z -NR ⁴ R ⁵ , -PR ⁴ R ⁵ , -AsR ⁴ R ⁵ or -SbR ⁴ R ⁵

and

R 3 is a branched alkyl or alkenyl group each having 3-8 C atoms, where these groups can be partially or completely fluorinated, a cycloalkyl or cyclo¬ alkenyl group each having 3-8 C atoms or an aryl group

mean,

for the deposition of thin films or layers from the gas phase.

2. Use of the organometallic compounds according to claim 1 for the deposition of epitaxial layers.

3. Process for the production of thin films on substrates by vapor deposition from organometallic

Compounds, characterized in that as

REPLACEMENT LEAF organometallic compounds the compounds of formula I.

(R ¹ ) ₃ _ _n MY _n I

wherein

M aluminum, gallium or indium,

n 1, 2 or 3,

Y -NR ² R ³ , -PR ² R ³ , -AsR ² R ³ or -SbR ² R ³ ,

and R each independently of one another H, an alkyl group with 1-8 C atoms, the

Alkyl group can be partially or fully fluorinated, a cycloalkyl,

Alkenyl or cycloalkenyl group each with 3-8 C atoms or an aryl group,

R also l, 2- (CH ₂ ) _p -C ₆ H ₄ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₆ H ₁₀ - (CH ₂ ) _g -Z, l, 2- ^(C H ₂ ⁾ _p - ^C ₆ H ₈ - ^(C H ₂ ⁾ _g -Z, l, 2- (CH ₂ ) _p -C ₆ H ₆ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₅ H _g - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₅ H ₆ - (CH ₂ ) _g -Z, l, 2- (CH ₂ ) _p -C ₅ H ₄ - (CH ₂ ) _g -Z or l, 2- (CH ₂ ) _p -C ₄ H ₆ - (CH ₂ ) _g -Z,

p and g each independently 0, 1, 2 or 3,

ERSA _T ZBLATT -NR ⁴ R ⁵ , -PR ⁴ R ⁵ , -AsR ⁴ R ⁵ or -SbR ⁴ R ⁵

and

3 R is a branched alkyl or alkenyl group each having 3-8 C atoms, where these groups may be partially or completely fluorinated, a cycloalkyl or cycloalkenyl group each having 3-8 C atoms or an aryl group

mean,

be used.

4. The method according to claim 3, characterized in that for the production of compound semiconductors, electrical, electronic, optical and opto¬ electronic components during the deposition process one or more gaseous compounds of arsenic, antimony or phosphorus are additionally supplied under the reaction conditions used.

5. The method according to claim 3, characterized in that in addition to the organometallic compounds of formula I dopants are added during the Abscheidungs¬ process.

6. The method according to claim 3, characterized in that the compounds of formula I are added during the deposition process of other organometallic compounds.

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