Method for the preparation of hydridosilane oligomers

Abstract

A method prepares hydridosilane oligomers, where the obtainable hydridosilane oligomers are useful. A method can also be used for preparing coating compositions and for preparing a silicon-containing layer.

Claims

1: A method for preparing hydridosilane oligomers, comprising: reacting a hydridosilane composition (I) comprising at least one linear hydridosilane Si.sub.nH.sub.2n+2 with n≥2 in the presence of a branched hydridosilane compound (II), wherein the branched hydridosilane compound (II) comprises at least one quaternary silicon atom Si(SiR.sub.3).sub.4, wherein R is chosen from the group consisting of H; Si.sub.nH.sub.2n+1 with n≥1; Si.sub.mH.sub.2m with m≥2; and Si.sub.jH.sub.2j−1 with j≥3.

2: The method according to claim 1, wherein the branched hydridosilane compound (II) is present in a range of 0.05 to 50 wt.-%, based on a total weight of the hydridosilane composition (I) and the branched hydridosilane compound (II).

3: The method according to claim 1, wherein the branched hydridosilane compound (II) is selected from the group consisting of neopentasilane, neopentasilane oligomer, 2,2-disilyltetrasilane, 2,2-disilylpentasilane, 3,3-disilylpentasilane, 2,2,3-trisilyltetrasilane, 1,1-disilylcyclopentasilane, 2,2,3,3-tetrasilyltetrasilane, 2,2,3-trisilylpentasilane, 2,2,4-trisilylpentasilane, 2,2-disilylhexasilane, 3,3-disilylhexasilane, 1,1-disilylcyclohexasilane, 1,1,2-trisilylcyclopentasilane, 1,1,3-trisilylcyclopentasilane, 2,2-disilylheptasilane, 3,3-disilylheptasilane, 4,4-disilylheptasilane, 2,2,3-trisilylheptasilane, 2,2,4-trisilylheptasilane, 2,3,3-trisilylheptasilane, 3,3,4-trisilylheptasilane, 3,3,5-trisilylheptasilane, 3-disilaneyl-3-silylhexasilane, 2,2,3,3-tetrasilylpentasilane, 2,2,3,4-tetrasilylpentasilane, 2,2,4,4-tetrasilylpentasilane, 2,3,3,4-tetrasilylpentasilane, 3-disilaneyl-2,2-disilylpentasilane, 3,3-bis(disilaneyl)pentasilane, 1,1,2-trisilylcyclohexasilane, 1,1,3-trisilylcylohexasilane, 1,1,4-trisilylcyclohexasilane, 1,1,2,2-tetrasilylcyclohexasilane, 1,1,3,3-tetrasilylcyclohexasilane, 1,1,4,4-tetrasilylcyclohexasilane, 1,1,2,3-tetrasilylcyclohexasilane, 1,1,2,4-tetrasilylcyclohexasilane, 1,1,3,4-tetrasilylcyclohexasilane, and a mixture thereof.

4: The method according to claim 1, wherein the hydridosilane composition (I) is reacted in the presence of the branched hydridosilane compound (II), in absence of a catalyst and/or wherein the reaction is solvent free.

5: The method according to claim 1, wherein the hydridosilane composition (I) comprises at least one linear hydridosilane Si.sub.nH.sub.2n+2, wherein n is 2 to 9.

6: The method according to claim 1, wherein the hydridosilane composition (I) is reacted in the presence of the branched hydridosilane compound (II), at a temperature in the range of 50° C. to 300° C. and by irradiating with electromagnetic radiation.

7: The method according to claim 1, wherein the hydridosilane composition (I) comprises hydridosilane mixtures having a mass average molecular weight of M.sub.w in the range of 200 to 5,000 g/mol, measured by gel permeation chromatography, and/or wherein the branched hydridosilane compound (II) is a neopentasilane oligomer which has a mass average molecular weight of M.sub.w in the range of 500 to 5,000 g/mol, measured by gel permeation chromatography.

8: The method according to claim 1, wherein the branched hydridosilane compound (II) consists of 80 to 98 wt.-% of neopentasilane and 2 to 20 wt.-% of a neopentasilane oligomer, based on a total weight of the branched hydridosilane compound (II).

9: The method according to claim 1, wherein at least one dopant selected from the group consisting of BH.sub.xR.sub.3−x, wherein x=0-3 and R=C.sub.1-C.sub.10-alkyl radical, unsaturated cyclic, optionally ether- or amino-complexed C.sub.2-C.sub.10-alkyl radical; Si.sub.5H.sub.9BR.sub.2, wherein R=H, Ph, or C.sub.1-C.sub.10-alkyl radical; Si.sub.4H.sub.9BR.sub.2, wherein R=H, Ph, or C.sub.1-C.sub.10-alkyl radical; red phosphorous; white phosphorous (P.sub.4); PH.sub.xR.sub.3−x, wherein x=0-3 and R=Ph, SiMe.sub.3, or C.sub.1-C.sub.10-alkyl radical; P.sub.7(SiR.sub.3).sub.3, wherein R=H, Ph, or C.sub.1-C.sub.10-alkyl radical; Si.sub.5H.sub.9PR.sub.2, wherein R=H, Ph, or C.sub.1C.sub.10-alkyl radical; and Si.sub.4H.sub.9PR.sub.2, wherein R=H, Ph, or C.sub.1-C.sub.10-alkyl radical; is added before, during, or after the reaction.

10: A hydridosilane oligomer obtainable by the method according to claim 1.

11: The hydridosilane oligomer according to claim 10, wherein the hydridosilane oligomer has a mass average molecular weight of M.sub.w in the range of 500 to 5,000 g/mol, measured by gel permeation chromatography.

12: A method for preparing a coating composition, the method comprising: (i) preparing a hydridosilane oligomer according to the method according to claim 1; and (ii) diluting the hydridosilane oligomer with an organic solvent.

13: The method according to claim 12, wherein the coating composition comprises 0.1 to 99 wt.-% of the organic solvent, based on a total weight of the hydridosilane oligomer and the organic solvent.

14: A method for preparing a silicon-containing layer, the method comprising: (a) preparing a hydridosilane oligomer according to the method according to claim 1; (b) optionally, diluting the hydridosilane oligomer with an organic solvent; (c) applying a hydridosilane oligomer formulation, obtained from (a) and optionally (b), on a substrate; and (d) converting the hydridosilane oligomer formulation into amorphous silicon.

15: The method according to claim 14, wherein (c) is carried out by printing, spraying, aerosol assisted chemical vapor deposition, direct liquid injection chemical vapor deposition, spin-coating, dip-coating, meniscus coating, slit coating, slot-die coating, or curtain coating; and/or wherein (d) is carried out thermally and/or by using electromagnetic radiation and/or by electron ion bombardment.

16: A method, comprising: producing an optoelectronic or electronic component, wherein the optoelectronic or electronic component comprises a hydridosilane oligomer obtained by the method according to claim 1.

17: The method according to claim 3, wherein the branched hydridosilane compound (II) is selected from the group consisting of neopentasilane, neopentasilane oligomer, and a mixture thereof.

18: The method according to claim 8, wherein the branched hydridosilane compound (II) consists of 90 to 92 wt.-% of the neopentasilane and 8 to 10 wt.-% of the neopentasilane oligomer, based on the total weight of the branched hydridosilane compound (II).

19: The method according to claim 12, wherein the organic solvent is selected from the group consisting of toluene and cyclooctane.

20: The method according to claim 14, wherein the organic solvent is selected from the group consisting of toluene and cyclooctane.

Description

FIGURES

[0056] FIG. 1 shows an optical photograph demonstrating the layer quality of coatings prepared with the formulation of comparative example CE-1. On the right side of each glass substrate is a ruler with a mm scale.

[0057] FIG. 2 shows an optical photograph demonstrating the layer quality of coatings prepared with the formulation of comparative example CE-2. On the right side of each sample is a ruler with a mm scale.

[0058] FIG. 3 shows an optical photograph demonstrating the layer quality of coatings prepared with the formulation of comparative example CE-3. On the right side of each sample is a ruler with a mm scale.

[0059] FIG. 4 shows an optical photograph demonstrating the layer quality of coatings prepared with the formulation of inventive example E-1. On the right side of each sample is a ruler with a mm scale.

[0060] FIG. 5 shows an optical photograph demonstrating the layer quality of coatings prepared with the formulation of inventive example E-2. On the right side of each sample is a ruler with a mm scale.

[0061] FIG. 6 demonstrates the layer thickness in nm vs. the inverse spin speed in 1/rpm. The formulation based on comparative example CE-4 is represented by crosses and a solid line. The formulation based on the inventive example E-1 is represented by dots and a dotted line.

EXAMPLES

General Considerations

[0062] All experimental work is conducted in glove boxes manufactured by M Braun Inertgas-Systeme GmbH or via standard Schlenk technique (D. F. Shriver, M. A. Drezdzon, The manipulation of air sensitive compounds, 1986, Wiley VCH, New York, USA) under an inert atmosphere of dry nitrogen (N.sub.2; O.sub.2-level: <10 ppm; H.sub.2O level: <10 ppm). Moreover, all experiments are carried out with dry and oxygen-free solvents. Dry, oxygen-free solvents (cyclooctane, toluene) are prepared via a solvent purification system of type MB-SPS-800-Auto manufactured by M Braun Inertgas-Systeme GmbH.

Test methods

Gel Permeation Chromatography (GPC)

[0063] GPC measurements are performed with an Agilent LC 1100 series system equipped with a PSS SDV linear S column. Cyclooctane is used as eluent and polybutadiene as reference.

GC/MS Measurement

[0064] Mass spectra are measured on a HP 5971/A/5890-II GC/MS coupling (HP 1 capillary column, length 25 m, diameter 0.2 mm, 0.33 μm poly(dimethylsiloxane)).

Spin Coating

[0065] Spin coating is performed on a G3P-8 spin coater manufactured by SCS Specialty Coating Systems, Inc.

Preparation of Wet Films

[0066] The respective formulation is applied with a 1 mL syringe through a syringe filter (polytetrafluorethylene (PTFE)) with a 1 μm pore width onto a respective substrate. Wet films are generated by spin coating at 25° C. at certain revolutions per minute (rpm) for a certain time.

Ellipsometry Measurement

[0067] Ellipsometry measurements are performed with a SENpro ellipsometer manufactured by SENTECH Gesellschaft für Sensortechnik mbH with fixed incidence angles between 40 and 90° (5° steps).

Density Measurement

[0068] Density measurements are performed with a DMA 500 manufactured by Anton Paar GmbH.

Surface Tension Measurements

[0069] Surface tension measurements are performed with a Pocket Dyne bubble pressure tensiometer manufactured by Krüss GmbH.

Kinematic Viscosity Measurement

[0070] Kinematic viscosity measurements are performed manually by means of micro-Ostwald viscometers of type 516 manufactured by SI Analytics GmbH.

Characterization of Hydridosilane Composition

[0071] The hydridosilane composition 1 used in the following examples is provided from a commercial SiH.sub.4-based fluidized bed reactor (FBR) process for polysilicon production.

[0072] The hydridosilane composition 1 is a liquid, colorless oil. A density of 0.95 g/mL, a dynamic viscosity of 8.3 mPas and a surface tension of 29.3 mN/m are determined by the methods as described above. The hydridosilane composition 1 has a mass average molecular weight of M.sub.w=1058 g/mol, a number average molecular weight of Mn=568 g/mol and a polydispersity of D=1.86 determined by GPC measurement as described above.

[0073] The hydridosilane composition 1 is composed of silane (1.2%), disilane (4.0%), trisilane (5.2%), tetrasilane isomers (4.0%), n-pentasilane (2.7%), iso-pentasilane (4.9%), hexasilane isomers (15.9%), heptasilane isomers (10.2%), octasilane isomers (9.3%), nonasilane isomers (13.5%) and higher silanes (Si.sub.nH.sub.2n+2 with n>9; 29.2%) determined by GC/MS as described above.

Comparative Example 1 (CE-1)

[0074] The hydridosilane composition 1 is diluted in a ratio of 1:2 with a toluene mixture containing 10% of cyclooctane. The formulation is prepared at ambient temperature (20° C.) and applied with a syringe through a syringe filter (PTFE) with a 1 μm pore width onto a pre-cleaned EagleXG glass substrate (Corning Inc.). Pre-cleaning is carried out by putting the substrates into acetone, isopropanol and subsequently deionized water in an ultrasonic bath for 10 minutes each. Before coating, substrates are dried completely in a nitrogen flow. Wet films are generated by spin coating at 25° C. at 4500, 9000 and 9999 rpm for 10 sec. Conversion of the wet films is conducted by thermal treatment on a hot plate at 500° C. for 60 sec.

[0075] Photographs of the respective silicon-containing layer are shown in FIG. 1. Dark grey areas represent coated substrate surface by amorphous silicon. Light grey/white areas result from dewetted substrate surface. It is evident that a conformal and continuous layer is not obtained.

Comparative Example 2 (CE-2)

[0076] The hydridosilane composition 1 is applied neat with a syringe through a syringe filter (PTFE) with a 1 μm pore width onto a pre-cleaned EagleXG glass substrate (Corning Inc.). Pre-cleaning is carried out by putting the substrates into acetone, isopropanol and subsequently deionized water in an ultrasonic bath for 10 minutes each. Before coating, substrates are dried completely in a nitrogen flow. Wet films are generated by spin coating at 25° C. at 2000, 4500 and 9999 rpm for 10 sec. Conversion of the wet films is conducted by thermal treatment on a hot plate at 500° C. for 60 sec.

[0077] Photographs of the respective silicon-containing layer are shown in FIG. 2. Dark grey areas represent coated substrate surface by amorphous silicon. Light grey/white areas result from dewetted substrate surface. All films show almost complete dewetting. It is evident that a conformal and continuous layer is not obtained.

Comparative Example 3 (CE-3)

[0078] The hydridosilane composition 1 is put into a glass apparatus equipped with a reflux condenser. The hydridosilane composition 1 is oligomerized by heating to 100° C. for two hours while stirring and illuminating with a cold light lamp, which is connected to the reactor via fiber optics purchased from Micro-Epsilon Eltrotec GmbH. During the oligomerization reaction, the gas volume above the liquid reactant is purged with inert gas. The oligomerization reaction is monitored by means of GPC and the mass average molecular weight of the final hydridosilane oligomer 1 is M.sub.w=1761 g/mol.

[0079] The hydridosilane oligomer 1 is diluted in a ratio of 1:2 with a toluene mixture containing 10% of cyclooctane. The formulation is prepared at ambient temperature (20° C.) and applied with a syringe through a syringe filter (PTFE) with a 1 μm pore width onto a pre-cleaned EagleXG glass substrate (Corning Inc.). Pre-cleaning is carried out by putting the substrates into acetone, isopropanol and subsequently deionized water in an ultrasonic bath for 10 minutes each. Before coating, substrates are dried completely in a nitrogen flow. Three wet films are generated by spin coating at 25° C. at 9999 rpm for 10 sec each. Conversion of the wet films is conducted by thermal treatment on a hot plate at 500° C. for 60 sec.

[0080] Photographs of the respective silicon-containing layer are shown in FIG. 3. Dark grey areas represent coated substrate surface by amorphous silicon. Light grey/white areas result from dewetted substrate surface. All films show significant dewetting. It is evident that a conformal and continuous layer is not obtained.

Example 1 (E-1)

[0081] A high molecular weight neopentasilane oligomer (4 wt.-%) having a mass average molecular weight of M.sub.w=2531 g/mol is added to the hydridosilane composition 1 (96 wt.-%). The resulting reaction mixture is put into a glass apparatus equipped with a reflux condenser. The reaction mixture is oligomerized by heating to 100° C. for two hours while stirring and illuminating with a cold light lamp, which is connected to the reactor via fiber optics purchased from Micro-Epsilon Eltrotec GmbH. During the oligomerization reaction, the gas volume above the liquid reactant is purged with inert gas. The oligomerization reaction is monitored by means of GPC and the mass average molecular weight of the final hydridosilane oligomer 2 is M.sub.w=1742 g/mol.

[0082] The hydridosilane oligomer 2 is diluted in a ratio of 1:2 with a toluene mixture containing 10% of cyclooctane. The formulation is prepared at ambient temperature (20° C.) and applied with a syringe through a syringe filter (PTFE) with a 1 μm pore width onto a pre-cleaned EagleXG glass substrate (Corning Inc.). Pre-cleaning is carried out by putting the substrates into acetone, isopropanol and subsequently deionized water in an ultrasonic bath for 10 minutes each. Before coating, substrates are dried completely in a nitrogen flow. Three wet films are generated by spin coating at 25° C. at 9999 rpm for 10 sec each. Conversion of the wet films is conducted by thermal treatment on a hot plate at 500° C. for 60 sec.

[0083] Photographs of the respective silicon-containing layer are shown in FIG. 4. Dark grey areas represent coated substrate surface by amorphous silicon. Light grey/white areas result from dewetted substrate surface. All films show reduced dewetting. A conformal and continuous amorphous silicon film is obtained on more than 50% of the substrate surface.

Example 2 (E-2)

[0084] A high molecular weight neopentasilane oligomer (4 wt.-%) having a mass average molecular weight of M.sub.w=2531 g/mol is added to a mixture of neopentasilane (46 wt.-%) and the hydridosilane composition 1 (50 wt.-%). The resulting reaction mixture is put into a glass apparatus equipped with a reflux condenser. The reaction mixture is oligomerized by heating to 100° C. for two hours while stirring and illuminating with a cold light lamp, which is connected to the reactor via fiber optics purchased from Micro-Epsilon Eltrotec GmbH. During the oligomerization reaction, the gas volume above the liquid reactant is purged with inert gas. The oligomerization reaction is monitored by means of GPC and the mass average molecular weight of the final hydridosilane oligomer 3 is M.sub.w=1732 g/mol.

[0085] The hydridosilane oligomer 3 is diluted in a ratio of 1:2 with a toluene mixture containing 10% of cyclooctane. The formulation is prepared at ambient temperature (20° C.) and applied with a syringe through a syringe filter (PTFE) with a 1 μm pore width onto a pre-cleaned EagleXG glass substrate (Corning Inc.). Pre-cleaning is carried out by putting the substrates into acetone, isopropanol and subsequently deionized water in an ultrasonic bath for 10 minutes each. Before coating, substrates are dried completely in a nitrogen flow. Wet films are generated by spin coating at 25° C. at 2000, 4500 and 9999 rpm for 10 sec. Conversion of the wet films is conducted by thermal treatment on a hot plate at 500° C. for 60 sec.

[0086] Photographs of the respective silicon-containing layer are shown in FIG. 5. Dark grey areas represent coated substrate surface by amorphous silicon. Light grey/white areas result from dewetted substrate surface. For all films, the dewetting is reduced further compared to E-1. A conformal and continuous amorphous silicon film is obtained on more than 80% of the substrate surface.

Comparative Example 4 (CE-4)

[0087] Neopentasilane is put into a glass apparatus equipped with a reflux condenser. The neopentasilane is oligomerized by heating to 140° C. for two hours while stirring and illuminating with a cold light lamp, which is connected to the reactor via fiber optics purchased from Micro-Epsilon Eltrotec GmbH. During the oligomerization reaction, the gas volume above the liquid reactant is purged with inert gas. The oligomerization reaction is monitored by means of GPC and the mass average molecular weight of the final hydridosilane oligomer 4 is M.sub.w=1751 g/mol.

[0088] The hydridosilane oligomer 4 is diluted in a ratio of 1:2 with a toluene mixture containing 10% of cyclooctane. The formulation is prepared at ambient temperature (20° C.) and applied with a syringe through a syringe filter (PTFE) with a 1 μm pore width onto a pre-cleaned EagleXG glass substrate (Corning Inc.). Pre-cleaning is carried out by putting the substrates into acetone, isopropanol and subsequently deionized water in an ultrasonic bath for 10 minutes each. Before coating, substrates are dried completely in a nitrogen flow.

[0089] Wet films are generated by spin coating at 25° C. at 1750, 2000, 4500, 8000 and 9999 rpm for 10 sec. Conversion of the wet films is conducted by thermal treatment on a hot plate at 500° C. for 60 sec.

Determination of Layer Thickness

[0090] The layer thicknesses of the silicon-containing layers of E-2 and CE-4 are determined by means of spectral ellipsometry as described above and are shown in FIG. 6. It is evident, that formulations based on the hydridosilane oligomer 3 give significant higher layer thicknesses of the corresponding amorphous silicon layers than the formulations based on hydridosilane oligomer 4 featuring the same solid contents and solvent mixtures.