JPH07285970A - Cyclic amide of silicon and germanium - Google Patents

Abstract

PURPOSE: To provide a precursor material which is suitable for gas phase vapor deposition of silicon or germanium on any substrate.

CONSTITUTION: A cyclic amide of silicon or germanium represented by the formula: LMHn (wherein M represents silicon or germanium; L represents a satd. amide ligand having the formula: R¹N-CHX-CHY-NR² or an unsatd. amide ligand having the formula: R¹N-CH=CH-NR² (wherein group R¹ and R² each represent a 2-12C open chain or cyclic alkyl group or triallylsilyl group having a 2-12C open chain or cyclic alkyl group; X and Y represent each hydrogen or an alkyl group; and n, as the number of hydrogen atoms H, is 0 or 2) is prepd. in a low-cost and simple manner.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

The present invention relates to the general formula LMHn (where M is silicon or germanium as the central atom, L is a ligand which surrounds the central atom M by two centers in the form of a chelate, The number n of hydrogen atoms H is 0 or 2) and cyclic amides of silicon and germanium. Furthermore, the invention relates to the preparation of such cyclic amides and their use.

[0002]

BACKGROUND OF THE INVENTION The coating of so-called substrates with thin films of semiconductor materials, such as silicon or germanium, is gaining increasing importance for semiconductor technology in various areas. Specifically, the acronym CVD
The deposition of said films by the decomposition of precursors transformed into the gas phase, which became known under the chemical vapor deposition process, occupy a prominent position in the production of solar cells and electronic structural components. Therefore, there is a continuing search for precursors that are characterized by a particularly high degree of flexibility with respect to various deposition conditions. The most important precursor requirements are adequate volatility and controlled decomposition under deposition conditions.

Accordingly, it is an object of the present invention to provide a class of materials from which representatives can be selected which are suitable as precursor molecules for the deposition of silicon or germanium on specific substrates and under specific deposition conditions. Is.

An object of the present invention is the general formula LMHn:
M is silicon or germanium, L is the formula R ¹ N
Unsaturated amide ligands having -CHX-CHY-NR ² or an unsaturated amide ligand having the formula ^{R 1 N-CH = CH-} NR 2,, wherein R ¹ and R ² are,
An open-chain or cyclic alkyl group having 2 to 12 carbon atoms, or a triallylsilyl group containing an open-chain or cyclic alkyl group having 2 to 12 carbon atoms, X and Y being hydrogen or an alkyl group, and The number n of hydrogen atoms is 0
Or 2 was achieved with a cyclic amide of silicon or germanium.

Representatives of the group of substances according to the invention are advantageously synthesized by silicon or germanium tetrachloride. In the case of germanium, an alternative synthetic route is
Proceed with divalent germanium dichloride, which is stabilized by, for example, dioxane and is usually present as an ether adduct. The synthesis of GeCl ₂ / dioxane adducts is described by Georg Bauer (editor) in Handb.
uch der Paranative Anor
ganischen Chemie (Handbook
of Preparative Inorganic
Chemistry), Enke Verlag S
tuttgart 1978, on pages 72
2 and 723. It is described in. The two synthetic routes are shown in general form in equations 1 and 2. MCl ₄ + LH ₂ −− → LMCl ₂ + 2HCl Formula 1 M is silicon or germanium. GeCl ₂ + LH ₂ −− → LGe + 2HCl Formula 2

As can be seen from equation 1, when tetrachloride is used, the still chlorinated diamide is first produced as a separable intermediate which is reduced in further synthetic steps to the target compound ( Equation 3). Reduction LMCl ₂ −−−−− → LMH ₂ Formula 3

Examples of suitable reducing agents are tri-n-butyltin hydride and lithium aluminum hydride.

In the case of silicon as the central atom, a two-step synthetic route instead yields the target compound LSiH ₂ .
As shown in equations 4a and 4b, the ligand LH ₂ is first reacted with trichlorosilane. This reaction is preferably assisted by the addition of a stoichiometric amount of base, conveniently triethylamine. In the second step, the resulting separable monochloro derivative is then reduced, preferably with Li [AlH ₄ ]. SiHCl ₃ + LH ₂ −−−− → LSiHCl + 2HCl Formula 4a Reduction LSiHCl −−−−− → LSiH ₂ Formula 4b

An alternative synthetic route to divalent germanium LGe to cyclic amides is by reduction of the dichloride which can be synthesized according to Formula 1. This path is shown in equation 5. Elemental lithium is a particularly suitable reducing agent in this reaction. Reduction LGeCl ₂ −−−−− → LGe Formula 5

The compounds contemplated as the ligand compound LH ₂ leading to the claimed cyclic amides are those derived from ethylenediamine and (formally) 1,2-diaminoethane. The saturated ligand compound has the general formula HR ¹ N—CHX—CHY—NR ² H, the groups X and Y are hydrogen or an alkyl group, and the unsaturated ligand compound has the general formula HR ¹ N—CH═CH—NR. ² H.

The groups R ¹ and R ² of the above formula are open-chain or cyclic alkyl groups having 2 to 12 carbon atoms or trialkylsilyl groups containing open-chain or cyclic alkyl groups having 2 to 12 carbon atoms. Is. Particularly advantageously, these ligand compounds have the groups R ¹ and / or R ² t
It is selected from those having an ert-butyl group.

The ligand compounds can react as neutral compounds LH ₂ (saturated representatives) or salts in which hydrogen atoms are replaced by cations (saturated and unsaturated representatives). When reacted as a neutral compound according to Formula 1, it is conveniently assisted by the addition of at least 2 molar equivalents of base (relative to the particular silicon chloride or germanium chloride compound) and by the addition of triethylamine. Proved. With respect to cyclic derivatives, preferably hydrogen of formula LH ₂ is replaced by a lithium cation (eg according to formula 6). Of course, a salt containing a cation other than lithium can also be used. MCl ₄ + L (Li) ₂ −−−− → LMCl ₂ + 2LiCl Formula 6

To summarize the content of what has been described above, the following general formula is obtained for the claimed target compounds of the invention: 1) tetravalent central atom M (M is Si or Ge): a) saturated ligand L: type (I) b) unsaturated ligand L: type (II) 2) divalent central atom M (M is Ge): a) saturated ligand L: type (III) b) unsaturated ligand L: type (IV)

The precursor used for the synthesis of the saturated ligand compound is preferably 1,2-ethylenediamine or 1,2-dibromomethane, glyoxal or preferably for the synthesis of the unsaturated ligand compound. Substituted 1,3-diazabutadiene is preferably used,
For example, preferably according to formula 7, reduction with lithium gives the salt ligand compound LLi ₂ . Reduction R ¹ N = CH-CH = NR ² --- → (R ¹ N-CH = CH-NR ² ) Li ₂ Formula 7

An essential prerequisite for the use of the compounds according to the invention as precursor molecules in vapor phase deposition processes is a sufficiently high volatility. The cyclic amide is converted into the gas phase at room temperature by an inert gas stream at a temperature of 20 to 50 ° C., preferably at room temperature, or at a temperature of 50 to 200 ° C., preferably 50 to 150 ° C. without decomposition at high temperature. It has been found that this requirement is fully met if it can be done. The variation of the radicals R ¹ , R ² and, if desired, the radicals X and Y ensures that numerous possibilities exist to fulfill this requirement. Preferred compounds are described in the examples which follow.

Methods for the decomposition of precursors present in the gas phase are known. The cyclic amides according to the invention can be decomposed, for example thermally or plasma-chemically (for example in an argon plasma) and can be used for the production of silicon and / or germanium films. . The temperature found for pyrolysis is 20
0 to 1100 ° C, typically 400 to 800 ° C.
A particular advantage is that the decomposition supplies almost completely elemental silicon or germanium and not nitride or carbide compounds. Upon decomposition, the organic groups yield, for example, gaseous isobutylene, isobutane and hydrogen cyanide. Generally, the decomposition temperature of an individual compound is
Above the boiling or sublimation temperature of any starting compound involved in the synthesis. Suitable substrates for film deposition are in particular ceramics, glasses, semiconductors, metals and alloys.

The fact that the substitutions R ¹ , R ² and, if desired, X and Y can be chosen more or less freely means that the deposition scheme planned for the volatility of the compound under predetermined deposition conditions is It makes it possible to select the most suitable precursor compound for it. Deposition proceeds in high yield due to the ease of removal of ligand and hydrogen. Moreover, although the yields are high, the cyclic amides according to the invention are easy to prepare and can be prepared in any desired batch size.

[0018]

EXAMPLES The preparation of the claimed cyclic amides of silicon and germanium and the use of these cyclic amides for the production of semiconductor films is described in detail below using the preferred compounds as an example. The details given in this description are, of course, not to be understood as limiting the process of the invention.

Example 1) Synthesis of N, N'-bis (tert-butyl) ethylenediamine as a representative of saturated compounds of the ligand compound LH ₂ Volume 4 equipped with reflux condenser and precision glass stirrer
In a 3-liter three-neck flask, 1575 ml t-butylamine (15 mol), 25 ml in 400 ml n-hexane.
9 ml of 1,2-dibromoethane (3 mol) and 40
0 ml of water were reacted with each other with gentle boiling. The use of a small amount of water causes the bromate to crystallize while the solution is still hot, and the use of a large amount of water then requires extraction of the aqueous phase. Carrying out the reaction without water results in a reaction mixture that is difficult to stir and reduces the yield to 50%. Reaction of feedstock in pure form or diluted with n-hexane at room temperature (2 weeks) yields the ligand only in poor yield. In this case, the main product is 1,4-bis (t-butyl) piperazine.

After the reaction has ended, the mixture is allowed to reach room temperature,
A total of 320 g of sodium hydroxide (8 mol) was added in 3 portions to the mixture in the reaction flask with continued stirring. As a result, the mixture was heated until the unconsumed t-butylamine began to boil. The two-layer system obtained was decanted and separated from the bottom sediment consisting of sodium bromide. 100 g of NaOH pellets were added to the upper organic layer and the resulting mixture was distilled off at atmospheric pressure by a 30 cm Vigreux separation column to a boiling temperature of 100 ° C.
The distillation operating facility must have a wash bottle filled with solid sodium hydroxide. Fractional distillation of the residue under reduced pressure with a water pump yielded 450 ml (72%) of N, N'-bis (t-butyl) ethylenediamine as a free-flowing water-clear liquid. Best stored on solid barium oxide or sodium hydroxide under inert gas. A typical example of the compound is a δ of −318.0 ppm in a ¹⁵ N NMR spectrum (C ₆ D ₆ , 25 ° C.).
Value signal, and further ¹ H NMR spectrum (C ₆ D ₆ , 2,
Signals for δ values of 0.83 ppm and 2.38 ppm (both are singlets) at 5 ° C.

Example 2) Synthesis of [N, N'-bis (tert-butyl) ethylenediamide] -germanium chloride as an intermediate according to formula 1 First 43.0 g (0.20 mol) of germanium tetrachloride, then 40 0.5 g (2 molar equivalents) of dry triethylamine was added to a solution of 34.5 g (0.2 mol) of the diamine described in Example 1 in 300 ml of n-hexane and the mixture was then refluxed for 30 hours. Then G3Sc
Filter through hlenk-type filtration tubes, 50m each
It was washed twice with 1 n-hexane. The filtrate was evaporated in vacuo to give 62.0 g of solid crude product which was then sublimed at 50 ° C. and 1 mm Hg to give 54.6 g (86%) of pure product in the form of matt silk crystal platelets. In the air,
The compound remained unchanged for a long period of time. Elemental analysis results: Calculated value: C38.27 H7.07 Cl22.59
N8.93 Found: C38.56 H7.07 Cl22.39.
N9.21 Molecular weight: 314 (EI MS) Characteristic display: ¹ H NMR (270.17 MHz, C ₆ D ₆ , 25
C.): δ = 1.21 ppm [s, C (C H ₃ ) ₃ ],
2.75 [s, C H ₂ ]. ¹³ C-NMR (67.94 MHz, C ₆ D ₆ , 25
° C): δ = 29.3 ppm [q, ¹ J (C, H) = 12
5.7 Hz, C ( C H ₃ ) ₃ ], 43.6 [t, ¹ J
(C, H) = 139.4 Hz, C H ₂ ], 54.0
[S, C (CH _{3) 3].} ¹⁵ N NMR (40.51 MHz, C ₆ D ₆ , 25
C): δ = -302.5 ppm [s, no ¹ J ( ⁷³ G
e, ¹⁵ N) coupling].

Example 3) Synthesis of [N, N'-bis (tert-butyl) ethylenediamide] -silicon dioxide as an intermediate according to formula 1 First 43.4 g (0.255 mol) of silicon tetrachloride, then 56 3.9 g of triethylamine, 300 ml of n
44. of the diamine described in Example 1 in hexane
Added to 0 g (0.255 mol) solution. The solution was refluxed for 30 hours. After cooling to room temperature, the mixture is mixed with G3Sc.
Filter through a hlenk type filter tube, wash the residue twice with 50 ml each of n-hexane and evaporate the filtrate in vacuo to give 47.1 g of brown crystals, then at 50 ° C.
Sublimation at 1 mmHg gave a pure product in the form of matte silk, colorless crystalline platelets. Yield = 40.1 g (58
%). Characteristic display: ¹ H NMR (399.8 MHz, C ₆ D ₆ , 25
℃): δ = 1.20ppm _{[s, C (C H 3)} 3 ],
2.71 [s, C H _3]. ¹³ C NMR (100.54 MHz, C ₆ D ₆ , 25
° C): δ = 29.0 ppm [q, ¹ J (C, H) = 12
5.5 Hz, C (C H ₃ ) ₃ ], 41.7 [t, ¹ J
(C, H) = 140.0 Hz, C H ₂ ], 51.8
[S, C (CH _{3) 3].} ¹⁵ N NMR (40.51 MHz, C ₆ D ₆ , 25
° C): δ = -350.1 ppm [s, ¹ J ( ¹⁹ Si, ¹⁵
N) = 37.8 Hz]. ²⁹ Si NMR (35.67 MHz, C ₆ D ₆ , 25
° C): δ = -34.7 ppm [s].

Example 4) [N, N'-bis (t) as the target product of type (I) according to formulas 4a and 4b.
Synthesis of ert-butyl) ethylenediamide] -silane a) The reaction described in Example 3) was repeated, except that trichlorosilane was used instead of silicon tetrachloride as the starting material. b) The crude product evaporated from step a) was used for further processing to give LSiH ₂ . At the end of this, 3.9
6 g (20.9 mmol) of Li [AlH ₄ ] (as a 20% solution in diethyl ether), with ice cooling, 9.75 of LSiHCl in 30 ml of tetrahydrofuran.
g solution. The solution was stirred at room temperature for 3 hours then evaporated in vacuo. The solvent removed by condensation is a small amount of S
It contained iH ₄ and needed to be safely guarded during evaporation. The residue was extracted with 30 ml n-pentane. 65
At ℃ evaporation of the solvent at the pressure of the oil bath temperature and 1mmHg and the residual colorless oil distillation to give the product LSiH ₂ as a colorless oil. Yield: 8.52 g (87%). Characteristic display: ¹ H NMR (399.8 MHz, C ₆ D ₆ , 25
C.): δ = 1.15 ppm [s, C (C H ₃ ) ₃ ],
2.86 [s, C H ₂ ], 5.13 [s, Si H ]. ¹³ C NMR (100.5 MHz, C ₆ D ₆ , 25
° C): δ = 29.0 ppm [q, ¹ J (C, H) = 12
5.1 Hz, C ( C H ₃ ) ₃ ], 44.1 [t, ¹ J
(C, H) = 136.6 Hz, C H ₂ ], 50.7
[S, C (CH _{3) 3].} ²⁹ Si NMR (35.67 MHz, C ₆ D ₆ , 25
C.): δ = −37.6 ppm [t, ¹ J (Si, H) −
216.5 Hz].

Example 5) The type (II
Synthesis of 2,5-bis (tert-butyl) -2,5-diaza-1-germacyclopentane as the target product of I) 2 molar equivalents of granular lithium (0.570 g) in THF
12.9 g of the product synthesized in Example 2) in 50 ml
(41.2 mmol) was added to the solution. Lithium completely dissolves with stirring at room temperature in 5 to 6 hours, and is initially transparent, begins to turn reddish brown, and becomes cloudy toward the end of the reaction. The solvent was removed in vacuo to give 100 ml of n
-Heptane was added to the residue. This resulted in the formation of a solid bottom sediment, which was finely ground with a spoon and after thorough stirring for a short time, the mixture was filtered through a G3 Schlenk type filter tube. Evaporation of the filtrate left 11.0 g of a pale yellow oil, which slowly crystallized at room temperature into a pure gel. If necessary, the product can be purified by sublimation and then 10.0 g (81%) of pure product, colorless, entangled needle-like crystals can be obtained. Elemental analysis result: Calculated value: C49.86 H8.37 Ge30.14
N11.63 Found: C49.45 H9.13 Ge29.89.
N11.53 Molecular weight: 242 (CI MS) Characteristic display: ¹ H NMR (270 MHz, C ₆ D ₆ , 25 ° C.): δ
= 1.28Ppm _{[s, C (C H 3)} 3 ], 3.27
[S, C H ₂ ]. ¹³ C-NMR (270 MHz, C ₆ D ₆ , 25 ° C.): δ
= 32.1 ppm [q, ¹ J (C, H) = 125.1H
z, C ( C H ₃ ) ₃ ], 49.7 [t, ¹ J (C, H)]
= 135.2 Hz, ² J (C, H) = 3.6 Hz, C H
₂ ], 54.3 [s, C (CH ₃ ) ₃ ]. ¹⁴ N NMR (270 MHz, C ₆ D ₆ , 25 ° C.): δ
= -207.3 ppm [s, Δυ = 820 Hz). ¹⁵ N NMR (40.51 MHz, C ₆ D ₆ , 25
C.): δ = −206.9 ppm.

Example 6) 2,5-bis (tert) as the target product of type (IV) according to formula 2 and formula 7
-Butyl) -2,5-diaza-1-germa-3-cyclopentene 0.830 g of granular lithium (2 molar equivalents) 10.0 g (59.4 mmol) of 1,4- in 300 ml of tetrahydrofuran Bis (tert-butyl) -1,4-
Diaza-1,3-butadiene [G. Schmid: A.
Golloch, H .; M. Gus, P.G. Sartori
(Ed.), Anorganisch-chemisc.
he Prepare (Inorganic Ch
electronic Syntheses), P.P. 113-1
14, de Gruyter, Berlin, New
(Synthesized by York 1985)] until the lithium is completely dissolved (about 60 minutes, red color)
The mixture was stirred at room temperature. Ultrasound can also be used to help initiate the reaction, if after 1 hour the reaction has not yet started (red). The solution thus obtained of the reduced diazadiene was added to GeCl ₂ (1,
4-dioxane) was added drop-wise to a solution of 13.8 g without further cooling. This process was allowed to proceed for about 30 minutes resulting in a brown coloration and heated to 30-40 ° C. After stirring at room temperature for 3 hours, the solvent was removed in vacuo and the residue was replaced with 100 ml
Stir with n-heptane, and mix the mixture with G3Schle.
Filtered through nk type filter tube. The filtrate was evaporated in vacuo to give 12.0 g of a yellow, microcrystalline solid that was sublimed to give the pure product, matte silk, colorless needles. Elemental analysis result: Calculated value: C49.86 H8.37 N11.63 Measured value: C50.33 H8.41 N11.69 Molecular weight: 241 (CI MS) Characteristic display: ¹ H NMR (270 MHz, C ₆ D ₆ , 25 ℃): δ
= 1.43Ppm [s, C (C H) _3], 7.05Pp
m [s, C H = C H ]. ¹³ C-NMR (270 MHz, C ₆ D ₆ , 25 ° C.): δ
= 33.2 ppm (q, ¹ J (C, H) = 125.1H
z, C ( C H ₃ ) ₃ ], 55.7 [s, C (C
H ₃ ) ₃ ], 121.4 ppm [dd, ¹ J (C, H)
= 173.0Hz, ² J (C, H) = 11.0Hz, H
C = C H]. ¹⁴ N NMR (270 MHz, C ₆ D ₆ , 25 ° C.): δ
= -136.3 ppm [s, Δυ = 400 Hz]. CI MS (70 eV, pos.ions): m / z
(Rel.int.%) = 242 (60), 194 (4
7), 169 (47), 169 (100).

Example 7) Type (IV) at atmospheric pressure
Thermal Deposition of Germanium from Cyclogermylene of 2.0 g of 2,5-diaza-1-germa-3-cyclopentene synthesized according to Example 6), horizontally aligned quartz with a diameter of 2 cm and a length of 50 cm. Pyrolysis was carried out in an argon carrier gas in a glass tube (15 cm tubular furnace). Several quartz glass microscope slides (length 2 cm, width 1 cm) were placed in the heating zone of the glass tube. When the tube temperature rises to 700-750 ° C, 97
A black, thin skin covering, characterized by elemental analysis as germanium with a purity of>%, was deposited within 1 hour on the inner wall and on the glass slide of the microscope. HCN
The waste gas condensed in the cooling trap containing the is isobutylene and isobutane (MS and GC / IR / MS
Was detected).

Example 8) Thermal Deposition of Germanium from Cyclogermylene of Type (IV) in Vacuum 500 mg of the product synthesized in Example 6) was added to 10 ^-4 m 2.
It was enclosed in a quartz glass ampoule under a vacuum of mHg. The ampoule, protected by a steel case, is placed in a tubular furnace at 80
Heated at 0 ° C. for 2 hours. The ampoule was then opened carefully (cooling with liquid air). The black skin with metallic luster (mirror surface) on the inner wall was germanium with a purity of 98%. Hereinafter, preferred examples of the present invention will be described. 1. A cyclic amide according to claim 1, which can be converted into the gas phase at atmospheric pressure or at a temperature of 50 to 200 ° C in a high vacuum without decomposition by an inert gas stream at a temperature of 20 to 50 ° C. 2. A cyclic amide according to claim 1 or claim ^{1, wherein the} groups R ¹ and R ² are tert-butyl groups.

Claims (2)

[Claims] 1. The general formula LMHn: wherein M is silicon or germanium, L is a saturated amide ligand having the formula R ¹ N—CHX—CHY—NR ² , or the formula R ¹ N—CH═CH—NR. An unsaturated amide ligand having ² wherein the groups R ¹ and R ² contain an open chain or cyclic alkyl group of 2 to 12 carbon atoms, or an open chain or cyclic alkyl group of 2 to 12 carbon atoms. A cyclic amide of silicon or germanium having a triallylsilyl group, X and Y are hydrogen or an alkyl group, and the number n of hydrogen atoms H is 0 or 2. 2. Use of the cyclic amide according to claim 1 for the deposition of elemental silicon or germanium.