EP2507298A1

EP2507298A1 - Chloride-containing silicon

Info

Publication number: EP2507298A1
Application number: EP10788298A
Authority: EP
Inventors: Norbert Auner; Christian Bauch; Sven Holl; Rumen Deltschew; Javad MOHSSENI; Gerd Lippold
Original assignee: Spawnt Private SARL
Current assignee: Spawnt Private SARL
Priority date: 2009-12-02
Filing date: 2010-12-02
Publication date: 2012-10-10
Also published as: DE102009056436A1; JP5667203B2; TWI560218B; US20120313037A1; JP2013512839A; WO2011067332A1; TW201132683A; DE102009056436B4

Abstract

The invention relates to a chlorinated polysilane which has the formula SiCl_x wherein x = 0,01 - 0,8 and which can be produced in particular by the thermolysis of a chloropolysilane at a temperature below 600 °C.

Description

Chloride-containing silicon

Chloride-containing silicon is known in various variants. Thus, for example, from WO 2006/125425 Al a procedural ^¬ ren for the preparation of silicon from halosilane, in which in a first step the halosilane is reacted silane to produce a plasma discharge to a halogenated poly which is subsequently in a second step Heating to silicon is decomposed. For the decomposition of the halogenated polysilane, this preference ^¬ is heated to a temperature of 400 ° C - 1,500 ° C. In the embodiments, temperatures of 800 ° C, 700 ° C, 900 ° C and again 800 ° C use. As for the pressure of the employed, so pressure is preferably carried out at ver ^¬ mindertem, is being carried out in the Ausführungsbei play ^¬ under vacuum. With this method, the production of as pure as possible silicon is desired. In particular, the resulting silicon has a low halide content.

A special variant of chloride-containing silicon stel ^¬ len chlorinated polysilanes (PCS). The present invention ^¬ is an object to provide a further variant of such chlorinated polysilanes available.

This object is achieved according to the invention by a chlorinated polysilane having the empirical formula SiCl _x where x = 0.01 to 0.8, which may in particular be amorphous. The chlorinated polysilane of the (empirical) formula SiCl _x with x = 0.01 to 0.8 (which was determined analytically) han ^¬ delt it is a highly cross-linked, chlorinated PolySi ^¬ lan as x <1. Thus, the compound has a spatial silicon skeleton which, in addition to silicon centers with one or more chlorine substituents, must also have silicon centers which have no chlorine substituents but only bonds to further silicon centers or atoms. On the other hand, chlorinated polysilanes of the empirical or analytical formula SiCl _x where 1 <x <2 are compounds which have only a slight crosslinking, since on average each silicon atom has at least one chlorine substituent. These polysilanes can be characterized, for example, by a polycyclic or a flat, two-dimensional structure which additionally has crosslinking sites in comparison with compounds having a chain and / or ring structure and x> 2. Compared with non-amorphous chlorinated polysilane, the amorphous chlorinated polysilane according to the invention usually has an increased reactivity, which should in particular be due to the higher energy state and the less compact structure. This increased reactivity can be utilized, for example, in the use of the amorphous chlorinated polysilanes to remove contaminants from metallurgical silicon.

Preferably, x = 0.5 to 0.7. Such a chlorinated polysilane is particularly suitable in terms of its reactivity for further use. The chloride content is determined here and within the scope of this application by complete digestion of the sample and subsequent titration of the chlorides according to Mohr. The chlorinated polysilane according to the invention has a ^high degree of crosslinking. Therefore, it may in particular be ei ^¬ ne amorphous substance, especially if the herstel ^¬ development is carried out at below 600 ° C and does not exceed a few hours duration. The amorphous consistency was determined by X-ray powder diffractometry. An amorphous state is present when no signals (or no diffraction ^intensities ) are present in the diffractogram. If the preparation is carried out at higher temperatures, for example at 900 ° C., an increasingly crystalline product is obtained, which shows the intensities of silicon in the X-ray powder diffractogram (see FIG. Quite generally, chlorinated polysilane of the present invention usually shows no Sig ^¬ dimensional, which are attributable to crystalline silicon, thus in particular no signals at 2-theta values of 7.84, 8:55, 10:03, 10.76, 28.6, 47.5, 56.3, 69.4, 76.6 and 88.2 (± 0.2). The values refer to a diffraction pattern of a powder recorded by Cu-Κ radiation.

The chlorinated polysilane according to the invention can also be referred to as chloride-containing silicon.

The chlorinated polysilane according to the invention can also be hydrogen-containing. The hydrogen may in particular be bound to Si. As a rule, the hydrogen content of the polysilane is less than 5 atomic%, in particular less than 2 atomic%, for example less than 1 atomic%. Such amounts of hydrogen may vary in wide ^¬ ren using the polysilane chlorinated lans according to the invention, such as in the synthesis of perchloriertem disilane by chlorination, advantageous in terms of impact on the yield of the reaction.

According to one embodiment, the chlorinated polysilanes according to the invention have an orange-red or a dark red or brown or gray color. An orange-red to brownish color indicate an increased chlorine content and are therefore generally preferred.

According to a further embodiment, the chlorinated polysilane according to the invention has the following solution behavior: When suspending the polysilane in 10 times the amount by weight of an inert solvent, less than 20% of the mass used is soluble; often even when suspended in the 100 times the weight of a (beliebi ^¬ gen) inert solvent is less than 20% of eingesetz- th material are soluble. An inert solvent is understood to mean a solvent which does not react with chlorinated silanes, in particular a non-nucleophilic aprotic solvent. Benzene, toluene, cyclohexane: The above exporting ^¬ conclusions but in particular all of the following solvents apply in particular to the solution behavior to an increasing minimum one.

The highly crosslinked chlorinated polysilane according to the invention is described below with reference to the compounds SiClo, os to

SiClo, o7 and SiClo, 7 explained in more detail. IR spectroscopic

Measurements (ATR technique, diamond single reflection) at Such chloride-containing silicon show, inter alia, a band in the range of 1019 to 1039 wavenumbers, in particular at 1029 cm ^-1 . The strength depends on the Chloridge ^¬ halt and increases with increasing chloride content, as can be seen when comparing the figures 1 and 2. FIG. Further significant bands are found in the range of 840 to 860 and / or in the range of 2300 to 2000 wavenumbers. Bands in the range of 2300 to 2000 wavenumbers occur in particular when the chlorinated polysilane contains hydrogen and can in particular be due to Si-H vibrations. Significant bands means in the context of this application, that the intensity of a band is greater than 10% of the Ban de ^¬ with the highest intensity. NMR studies show the following resulting ^¬ nisse the product obtained from plasma-chemically produced polysilane chlorinated:

(i) ²⁹ Si NMR (solid state): δ ppm; 3.53; -0.37, -4.08, -6.47, -7.82, -18.67, -45.81, -79.91 (sharp); 40 to -21 and -60 to -118 (wide). Sharp, generally means that the half-value width of the relevant signal does not exceed 100 Hz in the context of this publication ^¬ dung. Broad signals ^¬ be indicated generally in the context of this application that the present solid body-NMR half-value widths of about 100 hertz.

(ii) ¹ H-NMR (solid state): The product shows in ¹ H-NMR a broad, weak signal at 3 to 10 ppm, in particular at 5 to 10 ppm, in particular a signal with a maximum in the chemical shift range between 8 and 6 ppm. This is caused by the residual hydrogen content of the product, the signal form being typical for the product is. Further, the signal intensity is expected to ge ^¬ ring, there was also present in the starting material hydrogen in small quantities. The chemical shift of 3 to 10 ppm comprises the expected shift range for the product according to the invention. Therefore, the BEO ^¬ bach preparing ¹ H-NMR spectrum for the product, which was obtained by the inventive method of plasma-chemically produced polysilane chlorinated characteristic. The determination of the H content is carried out by integration of ¹ H-NMR spectra using an internal standard and comparison of the integrals obtained at a known mixing ratio.

As the starting material obtained polysilane chlorinated empirical formula SiCl _x with x = 0.2-0.8 can, in particular by thermolysis of Chlorpolysilan, for example (SiCl ₂₎ _x, which has been prepared by a method plasmache ^¬ premix or thermally, may be used. Chloropolysilane produced in a plasma-mixed manner, for example (SiCl ₂ ) _x, may in particular be a halogenated polysilane as pure compound or as a mixture of compounds each having at least one direct bond Si-Si, where the substituents consist of halogen or of halogen and hydrogen and wherein in the composition the atomic ratio substituent: silicon is at least 1: 1, where a. The H content of the polysilane is less than 2 atomic%,

b. the polysilane almost no branched chains and

Containing rings, the content of branching the short-chain fraction, in particular the added-up fraction of perhalogenated derivatives of neohexasilane, neopentasilane, isotetrasilane, isopentasilane and isohexasilane, is less than 1%, based on the total product mixture,

c. it has a Raman molecular vibration spectrum of I100 / I132 greater than 1, where I100 is the Raman intensity at 100 cm ^-1 and I132 is the Raman intensity at 132 cm ^-1 ,

d. it has its significant product signals in the chemical shift range of +15 ppm to -7 ppm in ²⁹ Si NMR spectra when the substituents are chlorine. The content of branching sites is determined by integration of the ²⁹ Si NMR signals for the tertiary and quaternary Si atoms. The short-chain content is the proportion of halogenated polysilanes referred to all silanes with up to six silicon atoms. According to an alternative embodiment, the proportion of chlorinated short-chain silanes can be determined particularly quickly if the following procedure is followed. First, the range of from +23 ppm to -13 ppm is integrated in the ²⁹ Si NMR (in particular the signals to find the primary and secondary Siliziumato- are me) and subsequently the signals for tertiae ^¬ ren and quaternary Si atoms in the range of - 18 ppm to -33 ppm and from -73 ppm to -93 ppm of the perchlorinated derivatives of the following compounds: neohexasilane, neopentasilane, isotetrasilane, isopentasilane and isohexasilane. Subsequently, the ratio of the respective Integratio ^¬ NEN Ikurzketti _g: / determined Iprimär secondary. This is regarding the added integration for each of the perchlorinated derivatives of neohexasilane, neopentasilane, isotetrasilane, isopentasilane and isohexasilane less than 1: 100. Moreover, the synthesis and characterization of these long-chain halogenated polysilanes in the patent application WO 2009/143823 A2 will be described, which is incorporated in Be ^¬ train to the characterization and synthesis of full content ^¬ Lich by reference.

Furthermore perhalogenated polysilanes can be used ^¬ the ones as they are described in WO 2006/125425 Al described, is also referred to in terms of the characterization and synthesis incorporated by reference, it being understood that the plasma used therein a higher Power density has, resulting in a changed product ^¬ spectrum.

Thermally produced chloropolysilane, for example (SiCl 2) _x , may in particular be a chlorinated polysilane as pure compound or as a mixture of compounds each having at least one direct bond Si-Si, where the substituents consist of chlorine or of chlorine and hydrogen and wherein in the composition the atomic ratio substituent: silicon is at least 1: 1, where a. the polysilane of rings and chains with a high

Proportion of branching points, which is> 1 relative to the total product mixture,

b. it has a Raman molecular vibrational spectrum of I ₁₀₀ / I 132 is less than 1, wherein I _{100 is} the intensity of Raman- at 100 cm ^" and I132 denote the Raman intensity at 132 cm ^-1 ,

c. in ²⁹ Si NMR spectra, it shows its significant product signals in the chemical shift range from + 23 ppm to -13 ppm, from -18 ppm to -33 ppm, and from

-73 ppm to -93 ppm.

The synthesis and characterization of these branched halogenated polysilanes is described in the patent application WO

2009/143824 A2, which is hereby incorporated by reference for characterization and synthesis.

The chlorinated polysilane according to the invention can be prepared by thermolytic decomposition of chlorinated polysilane, in particular in a temperature range from 350 ° C. to 1200 ° C. In order to obtain an amorphous chlorinated polysilane, the temperature will regularly be lower than 600 ° C; For example, it can be between 400 and 500 ° C. However, amorphous chlorinated Polysi ^¬ lan can be obtained even at higher temperatures, if the reaction time is chosen correspondingly short.

The thermolytic decomposition can be carried out at any pressure. However, a reduced pressure relative to normal pressure, for example a pressure <300 hPa, can be advantageous, since then short-chain chlorosilanes which are formed during the thermolysis are automatically distilled off. However, the pressure is usually more than 100 hPa in order not to over-distill the distillate. For reactions at low temperatures and higher chlorine contents But even lower pressures can make sense. If work is carried out at atmospheric pressure, however, distilling off or removal of the short-chain chlorosilanes by extraction by means of S1CI ₄ can also take place at a later time.

Embodiment 1

In a continuous thermolysis, the temperature in a suitable reaction vessel was set at 450 ° C, and the reaction vessel was evacuated to 250 hPa. A Polychlorsilangemisch having an average molecular formula of Si _n Cl _2n (0n = l 8) was added dropwise in the form of an 80% Lö ^¬ sung in SiCl ₄ before the thermolysis at a local temperature of 120 ° C. The polychlorosilane mixture was passed through the hot zone of the apparatus (450 ° C) by means of a feeder. The residence time in the hot zone is here in particular between 30 minutes and one hour. In this case, the poly ^¬ chlorosilane polysilane (chloride containing silicon) of the empirical formula SiClo, 7 of orange to red color, and short-chain chlorosilanes transformed to a tough, highly crosslinked chlorinated to tured. The SiClo, 7 was collected in a collection container. The diluent S1CI ₄ and through the Ther ^¬ molyse resulting short chain chlorosilanes (S1CI _4, S1 ₂ CI _6, S1 ₃ CI ₈₎ are derived as a vapor and condensed.

Yields based on the starting material: 20% by mass SiClo, 7, and 80 mass% short chain chlorosilanes (diluent ^¬ amount not included). Embodiment 2

A 50-60% solution of a Polychlorsilangemisches having an average molecular formula of Si _n Cl _2n (0n = l 8) in S1CI ₄ is placed in a quartz glass container and at a pressure of 300 to 500 mbar within 2 to 3 hours

Heated to 300 ° C. Thereafter, the pressure is gradually reduced to last ^¬ Lich 10 ^_1 to 10 ^{~ 2} mbar and heated to 900 ° C in the course of 3 h. Finally, the temperature is left at 900 ° C for 1 h. The vapors emerging during the thermal decomposition of the polychlorosilane mixture are condensed out in a cold trap cooled with liquid nitrogen. The polychlorosilane mixture was transformed into a solid, highly crosslinked chlorinated polysilane (chloride-containing silicon) of the empirical formula SiClo, os to SiClo, o7 of gray color and short-chain chlorosilanes. Upon completion of the reaction, the container was allowed to cool and the solid product was removed under inert gas.

Yields relative to the starting material: 10-15 mass% SiClo, o5 to SiClo, o7 and 85-90 mass% short-chain chlorosilane (amount of diluent not included).

The following Figures 1 and 2 show IR spectra of a chloride-containing silicon of composition SiClo, os to SiCl ₀ , o7 (Figure 1) and SiCl ₀ , 7 (Figure 2). The IR spectra were recorded as solids using a Bruker Optics IFS48 spectrometer equipped with an ATR (Golden Gate, Diamond Window, Single Reflection) measuring unit, Figures 3 and 4 show ²⁹ Si solid-state NMR spectroscopy. Spectra of a chloride-containing silicon with the empirical formula SiClo, 7, wherein FIG. 4 shows a detail from FIG. FIG. 5 shows the H solid-state NMR spectrum for the chloride-containing silicon having the empirical formula SiClo, 7. The solid-state NMR spectra were recorded with a Bruker DSX-400 NMR spectrometer, the measurement conditions were on the one hand ²⁹ Si HPDec, 79.5 MHz, rotational frequency: 7000 Hz, externally referenced to TMS = 0 ppm, on the other hand for ^X H with the pulse program zg4pm.98 at 400 MHz, rotation frequency: 31115 Hz with 2.5 mm MAS head, referenced to TMS = 0 ppm, where the measurements were made at room temperature with the undiluted samples, unless it was for integration added an internal standard. FIG. 6 shows a Raman spectrum for the silicon containing silicon with the empirical formula SiClo, os- FIG. 7 shows an X-ray powder diffractogram (Cu-K _a ) of a chlorinated polysilane obtained at high temperature, in which signals for crystalline fractions can be recognized which are due to silicon.

Claims

claims

Amorphous chlorinated polysilane with the formula SiCl _x where x = 0.01 to 0.8.

Polysilane according to claim 1, characterized in that x is 0.5 to 0.7.

Polysilane according to claim 1 or 2, characterized in that in the ²⁹ Si-NMR spectrum of a broad signal in the chemical shift range of 0 to 10 ppm, the greater has a half value width of 100 Hz, and another broad peak in the chemical Verschiebungsbe ^¬ rich of -60 to -100 ppm, which has a half-value width greater than 100 Hz.

Polysilane according to one of the preceding claims, characterized in that it comprises in ²⁹ Si-NMR spectra of sharp signals in the chemical shift range of 10 ppm to -20 ppm, which signals in particular ^¬ sondere present in the following chemical shift regions: at least one signal between: - 18 and -20 ppm and / or at least four signals between 8 and -10 ppm and / or at least one signal between -75 to -85 ppm, in particular between -78 to -81 ppm.

Polysilane according to the preceding claim, characterized in that it min ^¬ least comprising in ²⁹ Si-NMR spectra respectively a sharp signal in the following chemical shift regions: between 7 to 2 ppm, between 1 and -1 ppm, between -3 and - 5 ppm, between -5.5 and -7.5 ppm, between -7.5 to -9 ppm and Zvi ^¬ rule -18 and -20 ppm.

Polysilane according to one of the preceding claims, characterized in that it additionally contains hydrogen, the hydrogen being in particular bound to Si.

Polysilane the preceding claim, characterized in that the hydrogen content of the polysilane is less than 5 atomic%, in particular less than 2 atomic%, for example less than 1 atomic%.

Polysilane according to one of the preceding claims, characterized in that it has in ¹ H-NMR spectra a broad signal in the chemical shift range between 10 to 5 ppm, which has a half-width greater than 100 Hz, in particular a signal with a maximum in the chemical shift range between 8 and 6 ppm.

Polysilane according to one of the preceding claims, characterized in that it has at least one band in the IR spectrum in the range of 840 to 860 and / or in the range of 1019 to 1039 and / or in the range of 2300 to 2000 wavenumbers.

Polysilane according to the preceding claim, characterized in that it has a band in the range from 840 to 860, a band in the range of 1019 in the IR spectrum to 1039 and a band in the range of 2300 to 2000 wavenumbers.

11. polysilane according to any one of the preceding claims, characterized in that in the Raman spectrum in each case at least one band in the range of 280 to 330 and / or 510 to 530 and / or in the range of 910 to 1000 and / or a band in the range from 2300 to 2000 wavenumbers.

Polysilane according to one of the preceding claims, characterized in that it has an orange-red or dark red or brown or gray color.

Polysilane according to one of the preceding claims, characterized in that when suspended in the polysiloxane in the 10-fold amount by weight of an inert solvent less than 20% of the mass used is soluble.

Polysilane according to one of the preceding claims, characterized in that it is obtainable by thermolytic decomposition of chlorinated polysilane.

Polysilane according to one of the preceding claims, characterized in that it is obtained from thermally prepared chlorinated polysilane.

Polysilane according to one of the preceding claims, characterized in that it is obtained from plasmaschemisch forth posited chlorinated polysilane. Process for the preparation of a polysilane according to one of the preceding claims, comprising the following steps:

A) provision of a chloropolysilane, which is produced in particular thermally or plasma-chemically,

B) Thermolysis of the provided material at a temperature below 600 ° C.