WO2018108628A1

WO2018108628A1 - Process for the generation of thin silicon-containing films

Info

Publication number: WO2018108628A1
Application number: PCT/EP2017/081512
Authority: WO
Inventors: Maraike Ahlf; Kerstin Schierle-Arndt; David Dominique Schweinfurth; Torben ADERMANN; Daniel Loeffler; Sabine Weiguny; Kinga Izabela LESZCZYNSKA; David Scheschkewitz
Original assignee: Basf Se; Universitaet Des Saarlandes
Priority date: 2016-12-13
Filing date: 2017-12-05
Publication date: 2018-06-21

Abstract

The present invention is in the field of processes for the generation of thin inorganic films on substrates. In particular, the present invention relates to a process for producing an inorganic silicon-containing film comprising depositing the compound of general formula (I) onto a solid substrate, wherein R¹, R², R³ and R⁴ are an alkyl group, an alkenyl group, an aryl group, a silyl group, or an amine group, and wherein at least one of R¹ and R² and at least one of R³ and R⁴ is a branched group containing at least five non-hydrogen atoms and wherein not more than one of R¹ and R² and not more than one of R³ and R⁴ is an amine group.

Description

Process for the Generation of Thin Silicon-containing Films Description The present invention is in the field of processes for the generation of thin silicon-containing films on substrates, in particular atomic layer deposition processes.

With the ongoing miniaturization, e.g. in the semiconductor industry, the need for thin inorganic films on substrates increases while the requirements of the quality of such films become stricter. Thin inorganic films serve different purposes such as barrier layers, dielectrics, conducting features, capping, or separation of fine structures. Several methods for the generation of thin inorganic films are known. One of them is the deposition of film forming compounds from the gaseous state on a substrate. Therefore, volatile precursors are required which can be deposited on a substrate and then be transformed into the desired composition in the film.

For silicon-containing thin films typically silicon halogenides, such as S12CI6, are used. However, these compounds are difficult to handle and often leave a significant amount of residual halogens in the film, which is undesirable for some applications.

US 8 802 882 discloses a CVD process employing tetraaminodisilene precursors. However, these precursors are so unstable that they can hardly be handled and do not yield films of suffi- cient quality.

US 8 535 760 discloses a CVD process employing hydrogen or halogen substitued tetrasi- lyldisilene precursors. However, these precursors are also so unstable that they can hardly be handled and do not yield films of sufficient quality.

It was an object of the present invention to provide a process for the generation of thin silicon- containing films with high quality, such as low amounts of impurities and uniform film thickness and composition. Furthermore, it was aimed at a process employing compounds which can be synthesized and handled more easily. The process should also be flexible with regard to parameters such as temperature or pressure in order to be adaptable to various different applications.

These objects were achieved by a process for producing an inorganic silicon-containing film comprising depositing the compound of general formula (I)

onto a solid substrate, wherein R¹, R², R³ and R⁴ are an alkyl group, an alkenyl group, an aryl group, a silyl group, or an amine group, and

wherein at least one of R¹ and R² and at least one of R³ and R⁴ is a branched group containing at least five non-hydrogen atoms and

wherein not more than one of R¹ and R² and not more than one of R³ and R⁴ is an amine group.

The present invention further relates to the use of the compound of general formula (I), wherein R¹, R², R³ and R⁴ are an alkyl group, an alkenyl group, an aryl group, a silyl group, or an amine group, and

wherein not more than one of R¹ and R² and not more than one of R³ and R⁴ is an amine group for a film deposition process.

Preferred embodiments of the present invention can be found in the description and the claims. Combinations of different embodiments fall within the scope of the present invention. In the compound of general formula (I) R¹, R², R³, and R⁴ are an alkyl group, an alkenyl group, an aryl group, a silyl group, or an amine group. It is possible that all R¹, R², R³, and R⁴ are the same or different to each other. Preferably, R¹ and R⁴ are the same and R² and R³ are the same and R¹ and R² are the same or different to each other. At least one of R¹ and R² and at least one of R³ and R⁴ is a branched group containing at least five non-hydrogen atoms. A non-hydrogen atom is any atom except hydrogen, for example carbon, nitrogen, or silicon. In the context of the present invention, a branched group is any group in which the atom which is bound to one of the disilene silicon atoms is bound to at least two further non-hydrogen atoms. The branched group contains at least five non-hydrogen atoms, preferably at least six, more preferably at least seven, in particular at least eight. More preferably, at least three of R¹ , R², R³, and R⁴ are a branched group, in particular all R¹, R², R³, and R⁴ are a branched group. Preferably, at least one of the branched groups is an alkyl substituted aryl group as described below, more preferably at least two of the branched groups are alkyl substituted aryl groups, even more preferably at least three of R¹, R², R³, and R⁴ are alkyl sub- stituted aryl groups, in particular all of R¹ , R², R³, and R⁴ are alkyl substituted aryl groups. Also preferably, at least one of the branched groups is a silyl group as described below, more preferably at least two of the branched groups are silyl groups, even more preferably at least three of R¹, R², R³, and R⁴ are silyl groups, in particular all of R¹, R², R³, and R⁴ are silyl groups. According to the present invention not more than one of R¹ and R² and not more than one of R³ and R⁴ is an amine group. It has been observed that if more than one amine group is attached a silicon atom of the disilene group, the compound of general formula (I) is not stable enough for the process of the present invention. Preferably, R¹ and R⁴ are the same or a different amine group and R² and R³ are an alkyl group, an alkenyl group, an aryl group, or a silyl group.

An alkyl group can be linear or branched. Examples for a linear alkyl group are methyl, ethyl, n- propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl. Examples for a branched alkyl group are iso-propyl, iso-butyl, sec-butyl, tert-butyl, 2-methyl-pentyl, 2-ethyl-hexyl, cyclo- propyl, cyclohexyl, indanyl, norbornyl. Preferably, the alkyl group is a Ci to Cs alkyl group, more preferably a Ci to C6 alkyl group, in particular a Ci to C₄ alkyl group, such as methyl, ethyl, iso- propyl or tert-butyl. Alkyl groups can be substituted, for example by halogens such as F, CI, Br, I, in particular F; by hydroxyl groups; by ether groups; or by amines such as dialkylamines.

An alkenyl group contains at least one carbon-carbon double bond. The double bond can include the carbon atom with which the alkenyl group is bound to the rest of the molecule, or it can be placed further away from the place where the alkenyl group is bound to the rest of the molecule, preferably it is placed further away from the place where the alkenyl group is bound to the rest of the molecule. Alkenyl groups can be linear or branched. Examples for linear alkenyl groups in which the double bond includes the carbon atom with which the alkenyl group is bound to the rest of the molecule include 1-ethenyl, 1 -propenyl, 1-n-butenyl, 1 -n-pentenyl, 1 -n- hexenyl, 1 -n-heptenyl, 1 -n-octenyl. Examples for linear alkenyl groups in which the double bond is placed further away from the place where alkenyl group is bound to the rest of the molecule include 1-n-propen-3-yl, 2-buten-1-yl, 1-buten-3-yl, 1-buten-4-yl, 1 -hexen-6-yl. Examples for branched alkenyl groups in which the double bond includes the carbon atom with which alkenyl group is bound to the rest of the molecule include 1 -propen-2-yl, 1-n-buten-2-yl, 2-buten-2-yl, cyclopenten-1-yl, cyclohexen-1-yl. Examples for branched alkenyl groups in which the double bond is placed further away from the place where alkenyl group is bound to the rest of the molecule include 2-methyl-1 -buten-4-yl, cyclopenten-3-yl, cyclohexene-3-yl. Examples for an alkenyl group with more than one double bonds include 1 ,3-butadien-1 -yl, 1 ,3-butadien-2-yl, cyclopen- tadien-5-yl. Preferably, the alkenyl group is a Ci to Cs alkenyl group, more preferably a Ci to C6 alkenyl group, in particular a Ci to C₄ alkenyl group.

Aryl groups include aromatic hydrocarbons such as phenyl, cyclopentadienyl, naphthalyl, an- thrancenyl, phenanthrenyl groups and heteroaromatic groups such as pyrryl, furanyl, thienyl, pyridinyl, quinoyl, benzofuryl, benzothiophenyl, thienothienyl. Several of these groups or combinations of these groups are also possible like biphenyl, thienophenyl or furanylthienyl. Aryl groups can be substituted for example by halogens like fluoride, chloride, bromide, iodide; by pseudohalogens like cyanide, cyanate, thiocyanate; by alcohols; alkyl groups; alkoxy groups; amine groups like dimethylamine or bis(trimethylsilyl)amine; or aryl groups. The aryl group is preferably a Cs to C20 aryl group, more preferably a C6 to C16 aryl group. Alkyl and alkoxy substituted aromatic hydrocarbons are preferred, in particular 2,4, 6-trimethylphenyl, 2-iso- propylphenyl, 2,6-diisopropylphenyl, and 2,4,6-triisopropylphenyl, pentamethylcyclopentadienyl, 2,6-dimethoxyphenyl and 2,4,6-trimethoxyphenyl.

A silyl group is a silicon atom with typically three substituents. Preferably a silyl group has the formula S1E3, wherein E is hydrogen, an alkyl group, an alkoxy group, an alkenyl group, an aryl group, an aryloxy group, or a silyl group. It is possible that all three E are the same or that two E are the same and the remaining E is different or that all three E are different to each other. It is also possible that two E together form a ring including the Si atom. Alkyl and aryl groups are as described above. Examples for silyl groups include S1H3, methylsilyl, trimethylsilyl, triethylsilyl, tri-n-propylsilyl, tri-iso-propylsilyl, tricyclohexylsilyl, dimethyl-tert-butylsilyl, dimethylcyclohexylsi- lyl, methyl-di-iso-propylsilyl, triphenylsilyl, phenylsilyl, dimethylphenylsilyl, pentamethyldisilyl. An amine group is a nitrogen atom with two substituents which is preferably hydrogen, an alkyl group, an aryl group or a silyl group as defined above, more preferably a silyl group, in particular a trialkylsilyl group. It is possible that the two substituents are the same or different to each other. Preferred amine groups bis(trimethylsilyl)amine, tert-butyl-trimethylsilylamine and di(tert- butyl)amine.

It is preferred that the molecular weight of the compound of general formula (I) is up to

1200 g/mol, more preferred up to 1000 g/mol, in particular up to 800 g/mol.

Some preferred examples for compounds of general formula (I) are given in the following table.

1-26 Mes Mes Mes Tmp

1-27 Mes Mes Mes Tmop

1-28 Mes Mes Mes Dmop

1-29 Mes Mes Mes tBu

1-30 Mes Mes Mes TMS

1-31 Tmop Tmop Tmop Tmop

I-32 Dmop Dmop Dmop Dmop

I-33 Tip Tip Tip TMS

I-34 Mes tBu tBu Mes

I-35 tBu Tip Tip tBu

I-36 N(TMS)₂ Cp^* Cp^* N(TMS)₂

I-37 N(TMS)₂ Mes Mes N(TMS)₂

I-38 N(TMS)₂ Dip Dip N(TMS)₂

I-39 N(TMS)₂ Tip Tip N(TMS)₂

I-40 N(TMS)₂ Cp^* N(TMS)₂ Cp^*

1-41 N(TMS)₂ Mes N(TMS)₂ Mes

I-42 N(TMS)₂ Dip N(TMS)₂ Dip

I-43 N(TMS)₂ Tip N(TMS)₂ Tip

I-44 Tip Tip Tip Ph

I-45 Dip Dip Dip Ph

I-46 Mes Mes Mes Ph

I-47 iPr₂MeSi iPr₂MeSi iPr₂MeSi iPr₂MeSi

I-48 iPr₃Si iPr₃Si iPr₃Si iPr₃Si

I-49 tBuMe₂Si tBuMe₂Si tBuMe₂Si tBuMe₂Si

I-50 tBu₂MeSi tBu₂MeSi iPr₂MeSi iPr₂MeSi

1-51 tBuMe₂Si tBuMe₂Si iPr₃Si iPr₃Si

I-52 tBu₂MeSi tBu₂MeSi tBu₂MeSi tBu₂MeSi

I-53 TMS Tip Tip TMS

I-54 tBu Dip Dip tBu

I-55 TMS Dip Dip TMS

I-56 TMS Mes Mes TMS

I-57 Mes t-Bu Mes t-Bu

Me stands for methyl, iPr for iso-propyl, tBu for tert-butyl, TMS for trimethylsilyl, Cp^* for pen- tamethylcyclopentadienyl, Tip for 2,4,6-triisopropylphenyl, Dip for 2,6-diisopropylphenyl, Mes for 2,4,6-trimethylphenyl, Tmp for 2,2,6,6-tetramethylpiperidinyl, Dmop for 2,6-dimethoxyphenyl, Tmop for 2,4,6-trimethoxyphenyl.

The synthesis of compounds of general formula (I) is described for example by West et al. in Science volume 214 (1981 ), page 1343-1344, or by Watanabe et al. in Chemistry Letters, 1987, page 1341-1344, or by Jutzi et al. in Science volume 304 (2004), page 849-851 , or by Meltzer et al. in Organometallics volume 32 (2013), page 6844-6850, or by Bejan et al. in Angewandte Chemie International Edition, volume 46 (2007), page 5783-5786, or by Jeck et al. in Journal of the American Chemical Society, volume 132 (2010), page 17306-17315, or by Scheschkewitz in Angewandte Chemie International Edition, volume 43 (2004) page 2965-2967, or by Iwamoto et al. in Journal of Organometallic Chemistry, volume 686 (2003), page 105-1 1 1 , or by Kira et al. in Angewandte Chemie International Edition, volume 33 (1994), page 1489-1451 , or by Archibald et al. in Organometallics, volume 1 1 (1992), page 3276-3281.

It is possible that two of R¹, R², R³, and R⁴ form a ring together. In a preferred example R¹ and R³ are a silyl group which forms a ring. The compound of general formula (I) hence becomes a compound of general formula (la).

,12 11

/ \ (la)

Si = Si

R¹¹ and R¹² are an alkyl group, an alkenyl group, an aryl group, a silyl group, or an amine group as defined above for R¹, R², R³, and R⁴.

Some preferred examples for compounds of general formula (la) are given in the following table with the abbreviations as for the table relating to the compounds of general formula (I), wherein Ph stands for phenyl.

la-20 Dip Dip Dip N(tBu)₂

la-21 Mes Mes Mes N(tBu)₂

la-22 Tip Tip Tip Tmp

la-23 Dip Dip Dip Tmp

la-24 Mes Mes Mes Tmp

la-25 Tip Tip Tip Tmop

la-26 Dip Dip Dip Tmop

la-27 Mes Mes Mes Tmop

la-28 Tip Tip Tip Dmop

la-29 Dip Dip Dip Dmop

la-30 Mes Mes Mes Dmop

la-31 Tip Tip Tip tBu

la-32 Dip Dip Dip tBu

la-33 Mes Mes Mes tBu

la-34 tBu₂MeSi tBu₂MeSi tBusSi tBusSi

la-35 CH₂tBu CH(TMS)₂ Si(iPr)[CH(TMS)₂] CH(TMS)₂

la-36 CH₂Si(tBu)₂Me tBu₂MeSi tBu₂MeSi tBu₂MeSi

la-37 tBu₂MeSi tBu₂MeSi tBu₂MeSi tBu₂MeSi

The synthesis of compounds of general formula (la) is described for example by Leszczynska et al. in Angewandte Chemie International Edition, volume 51 (2012), page 6785 -6788, by lchinohe et al. in Journal of the American Chemical Society volume 127 (2005), 9978-9979, or by Murata et al. in Journal of the American Chemical Society volume 132 (2010), page 16768- 16770, or by Lee et al. in Journal of the American Chemical Society volume 129 (2007), 2436- 2437, or by lchinohe et al. in Angewandte Chemie International Edition Volume 38 (1999) page 2194-2196.

The compound of general formula (I) used in the process according to the present invention is preferably used at high purity to achieve best results. High purity means that the substance employed contains at least 90 wt.-% compound of general formula (I), preferably at least 95 wt.-% compound of general formula (I), more preferably at least 98 wt.-% compound of general formula (I), in particular at least 99 wt.-% compound of general formula (I). The purity can be determined by elemental analysis according to DIN 51721 (Prufung fester Brennstoffe - Bestimmung des Gehaltes an Kohlenstoff und Wasserstoff - Verfahren nach Radmacher-Hoverath, August 2001 ).

The compound of general formula (I) can be deposited from the gaseous or aerosol state. It can be brought into the gaseous or aerosol state by heating it to elevated temperatures. In any case a temperature below the decomposition temperature of the compound of general formula (I) has to be chosen. Preferably, the heating temperature ranges from slightly above room temperature to 400 °C, more preferably from 30 °C to 300 °C, even more preferably from 40 °C to 250 °C, in particular from 50 °C to 200 °C. Another way of bringing the compound of general formula (I) into the gaseous or aerosol state is direct liquid injection (DLI) as described for example in US 2009 / 0 226 612 A1 . In this method the compound of general formula (I) is typically dissolved in a solvent and sprayed in a carrier gas or vacuum. Depending on the vapor pressure of the compound of general formula (I), the temperature and the pressure the compound of general formula (I) is either brought into the gaseous state or into the aerosol state. Various solvents can be used provided that the compound of general formula (I) shows sufficient solubility in that solvent such as at least 1 g/l, preferably at least 10 g/l, more preferably at least 100 g/l. Examples for these solvents are coordinating solvents such as tetrahydrofuran, dioxane, diethoxyethane, pyridine or non-coordinating solvents such as hexane, heptane, benzene, toluene, or xylene. Solvent mixtures are also suitable. The aerosol comprising the compound of general formula (I) should contain very fine liquid droplets or solid particles. Preferably, the liquid droplets or solid particles have a weight average diameter of not more than 500 nm, more preferably not more than 100 nm. The weight average diameter of liquid droplets or solid particles can be determined by dynamic light scattering as described in ISO 22412:2008. It is also possible that a part of the compound of general formula (I) is in the gaseous state and the rest is in the aerosol state, for example due to a limited vapor pressure of the compound of general formula (I) leading to partial evaporation of the compound of general formula (I) in the aerosol state. Alternatively, the metal-containing compound can be brought into the gaseous state by direct liquid evaporation (DLE) as described for example by J. Yang et al. (Journal of Materials Chemistry C, volume 3 (2015) page 12098-12106). In this method, the metal-containing compound or the reducing agent is mixed with a solvent, for example a hydrocarbon such as tetradecane, and heated below the boiling point of the solvent. By evaporation of the solvent, the metal-con- taining compound or the reducing agent is brought into the gaseous state. This method has the advantage that no particulate contaminants are formed on the surface.

It is preferred to bring the compound of general formula (I) into the gaseous or aerosol state at decreased pressure. In this way, the process can usually be performed at lower heating temper- atures leading to decreased decomposition of the compound of general formula (I).

It is also possible to use increased pressure to push the compound of general formula (I) in the gaseous or aerosol state towards the solid substrate. Often, an inert gas, such as nitrogen or argon, is used as carrier gas for this purpose. Preferably, the pressure is 10 bar to 10^"7 mbar, more preferably 1 bar to 10^-3 mbar, in particular 10 to 0.1 mbar, such as 1 mbar.

It is also possible that the compound of general formula (I) is deposited or brought in contact with the solid substrate from solution. Deposition from solution is advantageous for compounds which are not stable enough for evaporation. However, the solution needs to have a high purity to avoid undesirable contaminations on the surface. Deposition from solution usually requires a solvent which does not react with the compound of general formula (I). Examples for solvents are ethers like diethyl ether, methyl-tert-butylether, tetrahydrofurane, 1 ,4-dioxane; ketones like acetone, methylethylketone, cyclopentanone; esters like ethyl acetate; lactones like 4-butyrolac- tone; organic carbonates like diethylcarbonate, ethylene carbonate, vinylenecarbonate; aromatic hydrocarbons like benzene, toluene, xylene, mesitylene, ethylbenzene, styrene; aliphatic hydrocarbons like n-pentane, n-hexane, n-octane, cyclohexane, iso-undecane, decaline, hexa- decane. Ethers are preferred, in particular diethylether, methyl-tert-butyl-ether, tetrahydrofurane, and 1 ,4-dioxane. The concentration of the compound of general formula (I) depend among others on the reactivity and the desired reaction time. Typically, the concentration is 0.1 mmol/l to 10 mol/l, preferably 1 mmol/l to 1 mol/l, in particular 10 to 100 mmol/l. The reaction temperature for solution deposition is typically lower than for deposition from the gaseous or aerosol phase, typically 20 to 150 °C, preferably 50 to 120 °C, in particular 60 to 100 °C.

The deposition takes place if the substrate comes in contact with the compound of general formula (I). Generally, the deposition process can be conducted in two different ways: either the substrate is heated above or below the decomposition temperature of the compound of general formula (I). If the substrate is heated above the decomposition temperature of the compound of general formula (I), the compound of general formula (I) continuously decomposes on the surface of the solid substrate as long as more compound of general formula (I) in the gaseous or aerosol state reaches the surface of the solid substrate. This process is typically called chemical vapor deposition (CVD). Usually, an inorganic layer of homogeneous composition, e.g. the metal oxide or nitride, is formed on the solid substrate as the organic material is desorbed from the metal M. Typically the solid substrate is heated to a temperature in the range of 300 to 1000 °C, preferably in the range of 350 to 600 °C.

Alternatively, the substrate is below the decomposition temperature of the metal-containing compound. Typically, the solid substrate is at a temperature equal to or slightly above the temperature of the place where the metal-containing compound is brought into the gaseous state, often at room temperature or only slightly above. Preferably, the temperature of the substrate is 5 °C to 40 °C higher than the place where the metal-containing compound is brought into the gaseous state, for example 20 °C. Preferably, the temperature of the substrate is from room temperature to 600 °C, more preferably from 100 to 450 °C, such as 150 to 350 °C, for example 220 °C or 280 °C.

The deposition of compound of general formula (I) onto the solid substrate is either a physisorp- tion or a chemisorption process. Preferably, the compound of general formula (I) is chemisorbed on the solid substrate. One can determine if the compound of general formula (I) chemisorbs to the solid substrate by exposing a quartz microbalance with a quartz crystal having the surface of the substrate in question to the compound of general formula (I) in the gaseous or aerosol state. The mass increase is recorded by the eigenfrequency of the quartz crystal. Upon evacuation of the chamber in which the quartz crystal is placed the mass should not decrease to the initial mass, but about a monolayer of the residual compound of general formula (I) remains if chemisorption has taken place. In most cases where chemisorption of the compound of general formula (I) to the solid substrate occurs, the X-ray photoelectron spectroscopy (XPS) signal (ISO 13424 EN - Surface chemical analysis - X-ray photoelectron spectroscopy - Reporting of results of thin-film analysis; October 2013) of M changes due to the bond formation to the substrate. If the temperature of the substrate in the process according to the present invention is kept below the decomposition temperature of the compound of general formula (I), typically a monolayer is deposited on the solid substrate. Once a molecule of general formula (I) is deposited on the solid substrate further deposition on top of it usually becomes less likely. Thus, the deposition of the compound of general formula (I) on the solid substrate preferably represents a self- limiting process step. The typical layer thickness of a self-limiting deposition processes step is from 0.005 to 1 nm, preferably from 0.01 to 0.5 nm, more preferably from 0.02 to 0.4 nm, in particular from 0.05 to 0.2 nm. The layer thickness is typically measured by ellipsometry as described in PAS 1022 DE (Referenzverfahren zur Bestimmung von optischen und dielektrischen Ma- terialeigenschaften sowie der Schichtdicke diinner Schichten mittels Ellipsometrie; February 2004).

Often it is desired to build up thicker layers than those just described. In order to achieve this in the process according to the present invention it is preferable to decompose the deposited compound of general formula (I) by removal of organic parts after which further compound of gen- eral formula (I) is deposited. This sequence is preferably performed at least twice, more preferably at least 10 times, in particular at least 50 times. Normally, the sequence is performed not more than 1000 times. Removing all organic parts in the context of the present invention means that not more than 10 wt.-% of the carbon present in the deposited compound of general formula (I) remains in the deposited layer on the solid substrate, more preferably not more than 5 wt.-%, in particular not more than 1 wt.-%. The decomposition can be effected in various ways. The temperature of the solid substrate can be increased above the decomposition temperature.

Furthermore, it is possible to expose the deposited compound of general formula (I) to a plasma like an oxygen plasma, hydrogen plasma, ammonia plasma, or nitrogen plasma; to oxidants like oxygen, oxygen radicals, ozone, nitrous oxide (N2O), nitric oxide (NO), nitrogendioxde (NO2) or hydrogenperoxide; to ammonia or ammonia derivatives for example tert-butylamine, iso-propyl- amine, dimethylamine, methylethylamine, or diethylamine; to hydrazine or hydrazine derivatives like Ν,Ν-dimethylhydrazine; to solvents like water, alkanes, or tetrachlorocarbon; or to boron compound like borane. The choice depends on the chemical structure of the desired layer. For silicon oxide, it is preferable to use oxidants, plasma or water, in particular oxygen, water, oxygen plasma or ozone. For silicon nitride, ammonia, hydrazine, hydrazine derivatives, nitrogen plasma or ammonia plasma are preferred. For silicon boride boron compounds are preferred. For silicon carbide, alkanes or tetrachlorocarbon are preferred. For silicon carbide nitride, mixtures including alkanes, tetrachlorocarbon, ammonia and/or hydrazine are preferred. A deposition process comprising a self-limiting process step and a subsequent self-limiting reaction is often referred to as atomic layer deposition (ALD). Equivalent expressions are molecular layer deposition (MLD) or atomic layer epitaxy (ALE). Hence, the process according to the present invention is preferably an ALD process. The ALD process is described in detail by George (Chemical Reviews 1 10 (2010), 1 1 1 -131 ).

In the process according to the present invention a compound of general formula (I) is deposited on a solid substrate. The solid substrate can be any solid material. These include for example metals, semimetals, oxides, nitrides, and polymers. It is also possible that the substrate is a mixture of different materials. Examples for metals are tantalum, tungsten, cobalt, nickel, platinum, ruthenium, palladium, manganese, aluminum, steel, zinc, and copper. Examples for semimetals are silicon, germanium, and gallium arsenide. Examples for oxides are silicon dioxide, titanium dioxide, zirconium oxide, and zinc oxide. Examples for nitrides are silicon nitride, aluminum nitride, titanium nitride, tantalum nitride and gallium nitride. Examples for polymers are pol- yethylene terephthalate (PET), polyethylene naphthalene-dicarboxylic acid (PEN), and polyam- ides.

The solid substrate can have any shape. These include sheet plates, films, fibers, particles of various sizes, and substrates with trenches or other indentations. The solid substrate can be of any size. If the solid substrate has a particle shape, the size of particles can range from below 100 nm to several centimeters, preferably from 1 μηη to 1 mm. In order to avoid particles or fibers to stick to each other while the compound of general formula (I) is deposited onto them, it is preferably to keep them in motion. This can, for example, be achieved by stirring, by rotating drums, or by fluidized bed techniques.

A particular advantage of the process according to the present invention is that the compound of general formula (I) is very versatile, so the process parameters can be varied in a broad range. Therefore, the process according to the present invention includes both a CVD process as well as an ALD process.

Depending on the number of sequences of the process according to the present invention performed as ALD process, films of various thicknesses are generated. Preferably, the sequence of depositing the compound of general formula (I) onto a solid substrate and decomposing the deposited compound of general formula (I) is performed at least twice. This sequence can be re- peated many times, for example 10 to 500, such as 50 or 100 times. Usually, this sequence is not repeated more often than 1000 times. Ideally, the thickness of the film is proportional to the number of sequences performed. However, in practice some deviations from proportionality are observed for the first 30 to 50 sequences. It is assumed that irregularities of the surface structure of the solid substrate cause this non-proportionality.

One sequence of the process according to the present invention can take from milliseconds to several minutes, preferably from 0.1 second to 1 minute, in particular from 1 to 10 seconds. The longer the solid substrate at a temperature below the decomposition temperature of the compound of general formula (I) is exposed to the compound of general formula (I) the more regular films formed with less defects. The process according to the present invention yields a silicon-containing film. The film can be only one monolayer of deposited compound of formula (I), several consecutively deposited and decomposed layers of the compound of general formula (I), or several different layers wherein at least one layer in the film was generated by using the compound of general formula (I). The film can contain defects like holes. These defects, however, generally constitute less than half of the surface area covered by the film. The film is preferably an inorganic film. In order to generate an inorganic film, all organic parts have to be removed from the film as described above. The film can contain silicon oxide, silicon nitride, silicon boride, silicon carbide, or mixtures such as silicon carbide nitride, preferable the film contains silicon oxide and silicon nitride. The film can have a thickness of 0.1 nm to 1 μηη or above depending on the film formation process as described above. Preferably, the film has a thickness of 0.5 to 50 nm. The film preferably has a very uniform film thickness which means that the film thickness at different places on the substrate varies very little, usually less than 10 %, preferably less than 5 %. Furthermore, the film is preferably a conformal film on the surface of the substrate. Suitable methods to determine the film thickness and uniformity are XPS or ellipsometry.

The film obtained by the process according to the present invention can be used in an electronic element or in the fabrication of an electronic element. Electronic elements can have structural features of various sizes, for example from 10 nm to 100 μηη, such as 100 nm or 1 μηη. The process for forming the films for the electronic elements is particularly well suited for very fine struc- tures. Therefore, electronic elements with sizes below 1 μηη are preferred. Examples for electronic elements are field-effect transistors (FET), solar cells, light emitting diodes, sensors, or capacitors. In optical devices such as light emitting diodes or light sensors the film according to the present invention serves to increase the reflective index of the layer which reflects light. An example for a sensor is an oxygen sensor, in which the film can serve as oxygen conductor, for example if a metal oxide film is prepared. In field-effect transistors out of metal oxide semiconductor (MOS-FET) the film can act as dielectric layer or as diffusion barrier.

It has surprisingly been found out that the process according to the present invention yields silicon-containing films with decreased etch-rates, i.e. films which are more stable in etch pro- cesses in comparison to silicon-containing films. This effect is particularly pronounced if etching is performed with hydrogen fluoride (HF) or ammonium fluoride (NH₄F). Such increased etching stability is of advantage in the chip production in which complex layer architectures are made by depositing films and selectively removing parts of them, for example by employing photo resists and shadow masks.

Brief Description of the Figures Figure 1 shows the thermogravimetric analysis of compound 1-1 .

Figure 2 shows the thermogravimetric analysis of compound I-7.

Figure 3 shows the thermogravimetric analysis of compound la-1

Figure 4 shows the thermogravimetric analysis of compound la-2

Figure 5 shows the thermogravimetric analysis of compound la-5

Examples

Example 1 (Synthesis of compound 1-1 1 )

+ 4.5 Li/C₁₀H₈

dme DiP Dip

2 Dip₂SiCI₂ *■ Si=Si

- 4 LiCI Dip Dip

A solution of Dip2SiCl2 (1 .60 g, 3.80 mmol) in DME (-15 mL) was added dropwise to a precooled (bath temp. -78 °C) solution of Li naphthalenide (8.36 mmol) in DME (-70 mL). The reaction mix- ture was stirred slowly (-4 h) warming up to room temperature and stirred additional 0.5 h at room temperature. The solvent was removed in vacuo. The remaining yellow/orange solid was kept in vacuum at 60 °C for 4 h to remove naphthalene. The residue was extracted with hexane (-150 mL) and filtered. Yellow filtrate was concentrated to -15 mL and stored overnight at -30 °C. The product was isolated as yellow crystals (0.68 g, 0.97 mmol), yield 51 %. H NMR (300.13 MHz, 300 K, benzene-ofe): δ = 7.17 (t,

7.6 Hz, 4H, Ar-C para), 7.05 (d, br, 4.52 (sept, ³J_H- H=

.7 Hz, 12H, iPr- CHz), 1 .32 (d,

6.7 Hz, 12H, iPr-C ), 0.58 (d, 6.7 Hz, 12H, iPr-C ), 0.56 (d, ³J_H- H= 6.7 Hz, 12H, iPr-C ).

3C{¹ H} NMR (75.46 MHz, 300 K, benzene-ok): § = 155.04, 154.77, 136.24 (each s, Ar- C), 130.42, 124.64, 123.41 (each s, Ar- CH), 38.70, 36.49 (each s, iPr-C ^, 25.16, 24.36, 23.76, 22.88 (each s, iPr-OH₃).

²⁹Si{¹ H} NMR(59.62 MHz, 300 K, benzene-ofe): δ = 52.38.

M. p. > 265 °C (dec).

Elemental analysis: calculated for C48H₆8Si₂: C, 82.22%; H , 9.77%. Found: C, 82.31 ; H, 9.71 .

Example 2 (Synthesis of compound la-2) Step 1 :

Trichloro(2,6-diisopropylphenyl)silane DipSiC , dichlorobis(2,6-diisopropylphenyl)silane

Dip2SiCl2, 1 ,2,2-tris(2,6-diisopropylphenyl)disilenyllithium were prepared based on the procedures given by Abersfelder in PhD Thesis, Imperial College London 2012, page 278-279. A precooled solution of DipSiC (0.430 g, 1 .46 mmol) in thf (-10 mL) was added to a precooled (— 100 °C) and stirred solution of Dip-disilenide (1 .06 g, 1 .46 mmol) in thf (-12 mL) placed in a 10OmL-Schlenk flask. The reaction mixture was stirred slowly warming up to RT (-1 h) and overnight at RT to afford an orange/brownish solution. All volatiles were removed in vacuo and the residue was washed with hexane (-10 mL). Extraction with hexane (-60 mL), filtration and sol- vent evaporation in vacuum afforded 0.25 g of the target compound (0.31 mmol) as a yellow solid. Further extraction with toluene (-60 mL), filtration and solvent evaporation in vacuum gave 0.78 g (0.81 mmol) of Dip-silyl disilene; combined yield: 88.2% (1 .03 g, 1 .29 mmol). H NMR (300.13 MHz, 300 K, benzene-ofe): δ =7.25-7.18 (m, 2H, Dip, Ar-C ^,7.13-7.06 (m, 4H, Ar-CH), 7.02-6.95 (m, 4H, Dip, Ar-CH), 6.92 (d,

7.8 Hz, 2H, Dip, Ar-C _meta) , 4.31 (sept,

6.7 Hz, 2H, Dip, \Pr-CH), 1 .45-0.5 (m, br, 48H, iPr-CH₃).

¹³C{¹ H} NMR (75.46 MHz, 300 K, benzene-ofe): δ = 155.78, 155.04, 153.79, 137.14, 136.21 , 133.06, 132.35 (each s, Ar- C), 132.00, 131 .14, 130.86, 130.53, 128.18, 124.51 , 124.40, 124.1 1 (each s, Ar-CH), 39.17, 38.31 , 37.72 (each s, iPr- OH), 34.03 (s, br, iPr-OH), 24.92 (br, iPr-OH₃), 24.1 1 (s, iPr- OHs).

²⁹Si{ H} NMR (59.62 MHz, 300 K, benzene-ofe): δ = 97.02, 55.45 (SiDip₂, Dip5ASi(Dip)CI₂), 10.97 (DipSi-5/(Dip)Cl2). M. p. 203-205 °C (dec). Step 2:

A yellow suspension of Dip-dichlorosilyl disilene (1 .75 g, 2.19 mmol) in Et₂0 (-30 mL) was added to a stirred suspension of Mg powder (0.100 g, 4.1 1 mmol) in Et₂0 (-5 mL). The reaction mixture was intensely stirred at room temperature and a conversion was monitored by ¹ H NMR. After 7 h conversion was completed. The solvent was removed in vacuum and the residue was extracted with pentane (-50 mL), filtrated through Celite, concentrated to -5 mL and left to crystallize at -30 °C. la-2-pentane was isolated as orange crystals with a yield 44.4% (0.780 g, 0.973 mmol).

Compound la-2 co-crystallized with pentane.

H NMR (300.13 MHz, 300 K, benzene-ofe): δ = 7.24 (d,

7.6 Hz, 2H, Dip₂Si, Ar-C _meta) , 7.19 (d,

8.5 Hz, 2H, Dip₂Si, Ar-C _meta) , 7.15 (br, 2H, DipSi,

7.4 Hz, 4H, DipSi, Ar-C _meta) , 6.97 (very br, 2H, Dip₂Si, Ar-CH_para), 4.91 (br, 2H, Dip₂Si, \Pr-CH), 3.91 (sept,

3.62 (br, 2H, Dip₂Si, iPr-C i), 1 .70-1 .05 (br, 48H, iPr-CHs, overlapping with pentane -CH₂), 0.86 (t, 7.2 Hz, pentane CM), 0.70-0.50 (br, 6H, iPr-C ).

3C{ H} NMR (75.46 MHz, 300 K, benzene-ok): § = 155.51 (s, Ar- C), 152.78 (s, br, Ar-C), 142.35, 133.56 (each s, Ar- C), 131 .28, 129.38 (each, s, Ar- CH), 124.37 (s, br, Ar- CH), 123.09 (s, Ar-CH), 37.05 (s, iPr- CH), 35.60, 34.48 (each s, br, iPr-CH), 34.27 (C5H12), 26.23 (s, br, iPr- CH₃), 24.66 (s, iPr-OHs), 23.67 (s, br, iPr-CH₃), 22.50, 14.10 (C5H12).

2⁹Si{¹ H} NMR (59.62 MHz, 300 K, benzene-ofe): δ = 43.21 (s, 5/Dip), -23.62 (£ ip₂).

Melting point. 210-212 °C (dec).

Elemental analysis: calculated for C48H₆8Si3*C5Hi₂: C, 79.43%; H, 10.06%. Found: C, 78.53, H, 9.33.

The thermogravimetric analysis curve of la-2 is depicted in Figure 4.

Example 3 (Synthesis of compound la-5)

+ Cp^*SiNTMS₂ Dip Dip

Si=Si ' .

„. / \ ., . SI=SI

Dip Li dme₂ . . , / „_^

z - L Cp^* Dip NTMS₂

Hexane (-25 mL) was added to a mixture of Dip-disilenide (1 .49 g, 2.05 mmol) and

Cp*SiNTMS₂ (0.780 g, 2.41 mmol) placed in 50-mL Schlenk flask equipped with a stirrer. The reaction mixture was stirred 6 days at room temperature to give an orange solution and a white solid. The post-reaction mixture was filtered and the solid residue was extracted with an additional portion of hexane (-10 mL). Combined hexane filtrates were concentrated to -5 mL and left to crystallize at RT to give yellow/orange crystals which were washed with cold hexane (-1 mL) and kept in vacuum 0.5 h. Yield 54.5% (0.82 g, 1 .13 mmol). H NMR (300.13 MHz, 300 K, benzene-ofe): δ = 7.22 (br, Dip₂Si, 4H, Ar-C _meta) , 7.12 (br, t, ³J_H- H= 7.6 Hz, 1 H , DipSi, Ar-CH_pam), 6.99 (d,

7.6 Hz, 2H, DipSi, Ar-C _meta) , 6.97 (very br, 2H, Dip₂Si, Ar-CA para) , 5.47 (br, 1 H, Dip₂Si,

6.7 Hz, 2H, DipSi, iPr-C^, 3.42 (br, 1 H, Dip₂Si, iPr-C^, 1 .8-1 .0 (very br, 30H , iPr-C ), 0.7-0.4 (br, 6H, iPr-C ), 0.25 (s, 18H, TMS-C ).

3C{¹ H} NMR (75.46 MHz, 300 K, benzene-ofe): δ = 156.12 (s, Ar- C), 151 .24 (s, br, Ar-C), 134.00 (s, Ar-C), 131 .04 (s, Ar- CH), 129.24 (s, br, Ar- CH), 128.17 (s, overlapping with C₆D₆, Ar- CH), 124.41 (s, br, Ar-CH), 123.04 (s, Ar-CH), 37.22 (s, iPr-C^, 35.42, 33.08 (s, br, iPr-C^, 26.52 (s, br, iPr- CHa), 24.81 (s, iPr-CH₃), 23.76 (s, br, iPr-CH₃), 4.06 (TMS- CH3).

2⁹Si{¹ H} NMR (59.62 MHz, 300 K, benzene-ofe): δ = 26.89, 6.02 (TMS-5/), 4.57, -15.10.

Melting point: 238-240 °C (minor dec).

Elemental analysis: calculated for C₄₂H₆9NSi₅: C, 69.25%; H , 9.55%; N, 1 .92%. Found: C, 68.82; H, 9.67; N, 1 .71 .

The thermogravimetric analysis curve of la-5 is depicted in Figure 5.

Claims

A process for producing an inorganic silicon-containing film comprising depositing the compound of general formula (I)

1

R R

\ /

Si = Si (I)

R ' V

onto a solid substrate, wherein R¹ , R², R³ and R⁴ are an alkyl group, an alkenyl group, an aryl group, a silyl group, or an amine group, and

The process according to claim 1 , wherein at least two of R¹, R², R³ and R⁴ are an alkyl substituted aryl group.

The process according to claim 1 or 2, wherein R¹ and R⁴ are an amine group.

The process according to claim 1 or 2, wherein the compound of general formula (I) is a compound of general formula (la)

R¹¹ and R¹² are an alkyl group, an alkenyl group, an aryl group, a silyl group, or an amine group.

5. The process according to any of the claims 1 to 4, wherein the compound of general formula (I) is deposited from the gaseous or aerosol phase onto the solid substrate.

6. The process according to any of the claims 1 to 5, wherein the compound of general formula (I) is deposited from solution onto the solid substrate.

7. The process according to any of the claims 1 to 6, wherein the deposited compound of general formula (I) is decomposed by removing all organic parts.

8. The process according to claim 7, wherein decomposition is effected by exposure to ammonia, hydrazine, a hydrazine derivative, ammonia plasma, or nitrogen plasma.

9. The process according to claim 7, wherein decomposition is effected by exposure to oxy- gen, water, ozone or an oxygen plasma.

10. The process according any of the claims 1 to 9, wherein a sequence of depositing the compound of general formula (I) onto a solid substrate and decomposing the deposited compound of general formula (I) is performed at least twice.

1 1. Use of the compound of general formula (I), wherein R¹ , R², R³ and R⁴ are an alkyl group, an alkenyl group, an aryl group, a silyl group, or an amine group, and