WO2009061581A1

WO2009061581A1 - Method for producing silacyclo materials

Info

Publication number: WO2009061581A1
Application number: PCT/US2008/079458
Authority: WO
Inventors: John Patrick Cannady; William B. Heilig; Binh Thanh Nguyen; Mary Kay Tomalia; Ming-Shin Tzou; Hanh X. Vo
Original assignee: Dow Corning Corporation
Priority date: 2007-11-06
Filing date: 2008-10-10
Publication date: 2009-05-14
Also published as: TW200936599A

Abstract

A method for producing silacycloalkanes by reacting an alkoxysilanc, R1ySi(OR2)4-y with a Grignard reagent, XMgR3MgX where each R1 is independently an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, a hydrogen atom, or CF3 each R2 is independently an alkyl group having 1 to 4 carbon atoms; y has a value of 1 or 2; R3 is selected from an alkylene group having 1 to 10 carbon atoms; and X is a halogen.

Description

METHOD FOR PRODUCING SlLACYCLO MATERIALS

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] None BACKGROUND OF THE INVENTION

[00021 The semiconductor industry is interested in reducing resistive-capacitance (RC) delay, which is an increasingly important issue in future gigascale circuits. One of the most effective ways to achieve the reduction of RC is to move to interlayer dielectric materials with lower dielectric constants. Silicate glass or SiO^ possessing a k value of 4.1 was used for device with 180 nm node technology. Most 65 nm interconnect technologies announced to date employ carbon-doped silicon oxide deposited from

or

(MeHSiO)4 with k value around 2.9-3.0. The International Technology Roadmap for

Semiconductors (ITRSj has a target for effective k values of 2.3-2.6 for 45 nm node and 2.0- 2.4 for 32 nm node. [0003] Dielectric material with k between 2.5 and 3.5 has been obtained when 1.1 -dimethyl- 1-silacyclobutane was used as PECVD precursor. Silacycloalkanes such as 1 , 1 -dimethyl- 1- silacyclobutane, tend Eo retain Si-C- linkage to deposit fragments containing Si-C species to increase carbon doping and thereby decreasing dielectric constant. When the C/Si ratio in the film composition is between 4 and 5, k may decrease from 4.1 for SiO₂ film to the range of 2.4 and 2.5. which is near the range of k for 45 nm node. It is proposed that if the Size of the silacyclic ring is increased from 4 to 5, as it is with 1 ,1-dimethyl-l-silacycloρentane, it may generate silyl fragments containing a larger R group to increase the amount of carbon doping during deposition under plasma enhanced chemical vapor deposition (PECVD) conditions at temperature < 400⁰C. [0004] Methods for producing silacycloalkanes are known in the literature. In the past silacycloalkanes have been typically produced via a Grignard reaction of chlorosilanes or bromosilancs. However, these reactions are carried out under acidic conditions which lead to the formation of undesirable by-products, thereby making the materials not suitable lor electronic applications. BRIEF SUMMARY OF THE INVENTION

This invention pertains to a method for making silacycloalkanes. The method

I 2 3 comprises reacting an alkoxysilane, R _ySi(OR )4_y with a Grignard reagent, XMgR MgX where each R is independently an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, a hydrogen atom, or CFy, each R^" is independently an alkyl group having 1 to 4 carbon atoms; y has a value of 1 or 2; R^' is selected from an alkylene group having 1 to 10 carbon atoms; and X is a halogen. By using an alkoxysilane the reaction can be run under neutral conditions resulting in a silacycloalkane that is suitable for electronic applications. In particular when using an alkoxysilane as a reactant rather than a chlorosilane the chloride level in the silacycloalkane is reduced, the by-product, MgX(OR ), is easier to handle and finally, other by-products (e.g. siloxanes) produced from the reaction of the ether solvent and chlorosilane are eliminated.

DETAILED DESCRPTION OF THE INVENTION

[0006] This invention pertains to a method for the preparation of silacycloalkanes by the reaction of a Grignard reagent with an alkoxysilane. The silacycloalkanes that can be produced using this method include, but are not limited to,

4 where each R is independently an alkyl group having 3 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, a hydrogen atom. CF3, or a OR group. Typically R is methyl, methoxy or ethoxy.

[0007] Silacycloalkanes produced by this method include 1, 1 -dimethyl-l-silacyclopentane, 1 , 1 , -dimethyl- S -silacyclohexane, 1 -ethoxy- 1-niethyl- l -silacyclohexane, and 1-ethoxy-l- methyl- 1 -silacyclopenlane. [0008] The method for producing the silacycloalkane typically comprises producing a Gπgnard reagent by reacting with Mg in a solvent a dihaloalkane having the general formula XRX where X is a halogen and R is an alkylene group having 1 to 10 carbon atoms and thereafter reacting the Grignard reagent wjth an alkoxysilane in the solvent. This process may be carried out stepwise or it may he carried out "in-situ" where the dihaloalkane, Mg, solvent, and alkoxysilane are all added into the reaction mixture thereby producing the Gπgnard reagent in the same reaction as the silacycloalkane.

[0009] The production of the Grignard reagent comprises reacting a dihaloalkane with Mg in a solvent. Dihaloalkanes useful herein are those that have the general formula XRX where X is a halogen and R is an alkylene group having 1 to K) carbon atoms. Dihaloalkanes can be exemplified by, but not limited to, dibromomethane, 1 ,3 dibromopropane, 1 ,4 dibromobutane, 1.5 dibromopentane, 1.6 dibromohexane, and mixtures thereof. The amount of dihaloalkane used is typically from 0.1 to 1 mole per mole of Mg, alternatively 0.25 to 0.5 moles. [0010] The Mg used herein can be any of the known forms of Mg that are currently used for Grignard-type reactions. For example, the Mg can be any of those know in the art that are in the form of powder, flakes, granules, chips, lumps, shavings and the like. [0011] Solvents useful in the production of the Grignard reagent should be those that do not react with the Mg and/or the dihaloalkane. Solvents useful herein include dialkylethers such as dimethyl ether, diethyl ether, ethyl methyl ether, n-butyl methyl ether, n-butyl ethyl ether, di-n-butyl ether, di-isobutyl ether, isobutyl methyl ether, isobutyl ethyl ether and mixtures thereof. Typically the amount of solvent is in the range of 15 to 30 moles per mole of dihaloalkane.

[0012] The Grignard reagent is then reacted with an alkoxysilane in the solvent.

2 Alkoxysilanes useful herein are those that have the general formula, R'_vSi(ϋR 14.x, where each R is independently an alkyl group having 1 to 4 carbon atoms, an alkenyl group having

2 2 to 4 carbon atoms, a hydrogen atom, or CFy, and each R is independently an alkyl group having i to 4 carbon atoms and y has a value of 1 or 2. The alkoxysilanes may be exemplified by, but not limited to dimethyldimethoxysilane, diethyldimethoxysilane, dimethydiethoxysilane, mclhyltπmethoxysilane, methyltπethoxysilanc, ethyltrimethoxysilane, ethyltriethoxysilane and mixtures thereof. To ensure that the entire Grignard reagent is completely consumed during the reaction, the amount of alkoxysilanes is up tolO mo!% more, alternatively up to 5 mol% more than the amount of Grignard reagent. Alternatively to ensure that all of the alkoxysilane is consumed during the reaction the amount of Grignard reagent is up to 10 mol% more, alternatively up to 5 mol% more than the amount of alkoxysilane.

[0013] The solvent used in the reaction between the Grignard reagent and alkoxysilane is typically the same solvent used to produce the Grignard reagent. Typically the amount of solvent is in the range of 15 to 30 moles per mole of alkoxysilane. [0014] The reaction to produce the silacycloalkane can be undertaken in standard type reactors suitable for running Grignard type reactions. The reactor can be a batch, semi-batch, or continuous type of reactor. The reaction should be carried out in a dry, inert atmosphere. Typically the reactor is purged and blanketed with an inert gas such as nitrogen or argon. Typically the reaction is carried out at atmospheric pressure although they can be carried out under pressure. Heat is generated by the exothermic nature of the reaction and therefore typically additional heat is not applied. Typically, the reactor is jacketed and the cxotherm is partially controlled by maintaining the jacket temperature in the range of 10-20⁰C.

[0015] Once the reaction is complete the silacycloalkane can be recovered by filtering to

2 remove the MgX(OR ) salt and removing the solvent. Methods for removing the solvent typically comprise distillation. Once the salt and solvent is removed the silacycloalkane can be purified by known techniques such as distillation.

[0016] The method of the instant invention is particularly suited for producing 1,1 -dimethyl- 1-silacyclopentane by the coupling reaction of 1 ,4-dimagnesiobromobutane and dimethyldimethoxysilane in diethyl ether as shown by the following:

In particular the 1 , 1 -dimethyl- l-silacyclopentane can be produced by the in-situ reaction of 1 ,4-dibromobutane, Mg, with (CH3)2Si(OCH3)2 in diethyl ether. This reaction may be summarized as follows:

+ 2 MgBrOMe

For above reaction, the amount of magnesium is 1 to 6 moles, dibromobutane is 0.5 to 2.5 moles and dibromoethane is 0.01 Io 0.5 mole for each mole of dimethyldimethoxysilanc.

EXAMPLES

[0018] The following examples are included to demonstrate preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventor to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the an should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.

[0019] In these Examples, several sources of magnesium (Mg) were used such as Aldrich 50 mesh Mg powder (99+%). and Timminco chips. Molecular sieves were added to the dimethyl dimethoxysilane and dibromobutane prior to their use to remove any trace of water.

E-iajnr^jilejLLθO

[0020] These examples were carried out using the general process described below. Amounts of reactants process condition variables are given in Table I . Yields vs. reaction time are given in Table 2. To determine the yield, the reaction was sampled and monitored by GC.

[0021] Mg and of diethyl ether (EtpO) were loaded into the reactor at room temperature. 1,2-

Dibromoethane was then injected through sampling line to activate the Mg. Within IO minutes, an exotherm was observed as well with vigorous Et₂O reflux and ethylene (CH₂-CH₂) evolution. The temperature rose from 2O⁰C to 35⁰C. The Mg activation resulted in the formation of a hazy solution.

[0022] A premixcd solution of 1,4-dibromobutane, Me2Si(OMe)2 and ether was prepared and added drop wise to the already activated Mg in Et^O, Ten minutes after addition, a cloudy reaction mixture was observed which indicated the formation of MgBr(OMe) salt. The reaction mixture reached a maximum exothermic temperature of 35.5⁰C. It took approximate 3.5 hours to complete the addition. At the end of the addition a milky, flowable reaction mixture was observed. The reaction mixture was allowed to stir overnight ( 18 hours) for reaction completion. [0023] The crude reaction mixture was filtered through a 10-micron membrane filter to remove MgBr(OMe) salt and excess Mg. The resulting material was distilled to remove the ether. The distilled solution contained a large amount of white precipitate after most of the ether was removed, most likely due to MgBr(OMe) salt remaining in solution after filtration. [0024] After removing salt, water and ether, the crude was stripped .under vacuum to remove high boilers. The stripped intermediate solution was loaded into a 1-liter flask of a 36"' long spinning band distillation column for final purification at ambient pressure. The spinning band column is composed of a spinning still made of tantalum wire cloth or Teflon.

Table \ Process Conditions

T= Timminco Mg chips A- Aldπch Mg powdei R- Rcade Mg chips

Table 2: Yield v. Time

The results show clearly that the use of Timminco magnesium gives a much faster reaction than that of the Aldrich magnesium powder or Readc magnesium chips. The one exception was run 30 which had very poor mixing, causing much of the magnesium to lie at the bottom of the reactor. This reaction is highly dependant on mass transfer, thus the mixing rate is very important to good conversion. A mixing study was run using the Timminco magnesium. The reaction conditions were held constant at 60% excess of Mg. 1 :20 mole ration of dibromobutane to ether, and

1.0:0.95 mole ration of dibromobutane to Me2Si(OMe)2. As can be seen from the results, for instance in the Examples 12 to 17, there is a dependence on the agitation rate and product yield. Mixing speeds of 500 rpm and above seem to give a higher conversion to product in shorter time.

[0027] Additionally the rates of reaction based on magnesium amount and ratio of dibromobutane to Me₂Si(OMe)₂ were studied. As can be seen, the reaction is much slower using 40% excess IVIg, for instance in Example 3 for the generation of Grignard reagent, however there is not as much difference between the use of 80% and 120% excess, for instance in Examples 8, 9 and 11. The % conversion at time (t) =18 hours of the 120% excess run, has only slightly higher conversion than that of the 80% excess runs (83.5% vs. 80% respectively). Also shown is the effect of changing the ratio of starting materials, dibromobutane and MCoSi(OMe^. With the exception of run 7, there appears to be slightly better conversion if the ratio is 1.0:0.95 dibromobutane to Me2Si(OMe)2-

Example 31

[0028] 3J I g Mg and of 6000 ml of diethyl ether (E?2θ) were loaded into the reactor at room temperature. 22ml of 1 ,2-Dibromoethane was then added to activate the Mg. Within 10 minutes, an exotherm was observed as well with vigorous Et₂O reflux and ethylene

(CH₂=CH₂) evolution. The temperature rose from 20⁰C to 30⁰C. The Mg activation resulted in the formation of a hazy solution.

[0029] A premixcd solution of 920 g of 1 ,4-dibromopentanc, 457 g of Mc2Si(OMe)2 and

2353 ml ether was prepared and added drop wise to the already activated Mg in Et2θ. Thirty minutes after addition, a cloudy reaction mixture was observed which indicated the formation of MgBr(OMe) .salt. The reaction mixture reached a maximum exothermic temperature of 35.⁰C. At the end of the addition a milky, flowable reaction mixture was observed. Stirring was stopped to observe the phases in the system: the solid phase was readily precipitated. [003Of The crude reaction mixture was filtered through a 10-micron membrane filter to remove MgBr(OMe) salt and excess Mg. The resulting material was distilled to remove the ether. The distilled solution contained a large amount of white precipitate after most of the ether was removed, most likely due to MgBr(OMe) salt remaining in solution after filtration. After removing salt and ether, the solution was stripped under vacuum to remove high boilers. The stripped crude was loaded into a i -liter flask of a 36" long spinning band distillation column for final purification at ambient pressure. The spinning band column is composed of a spinning still made of tantalum wire cloth or Teflon. The distilled 1 , 1 - dimethyl-1-silacyclohexane had a purity of >99,92% and a total metal content of <500 ppb.

Example 32

[0031] 4 g Mg and of lOOg of diethyl ether (Et'iO) were loaded into the reactor at room temperature. A few drops of 1 ,2-Dibromoethane was then added to activate the Mg. Within 10 minutes the Mg was activated and a hazy reaction mixture was observed,

[0032] A prcmixed solution of 10 g of MeSj(OEt)-J, 10 g 1,5 dibromopentane and 30 g ether was prepared and added to the already activated Mg in Et2θ. A cloudy reaction mixture was observed which indicated the formation of MgBr(OEt). The mixture was re fluxed at 34°C for 3 hours. At the end of the addition a milky, flowable reaction mixture was observed and the reaction was allowed to stir overnight. GC analysis of the liquid phase a t=18 hours determined that the reaction to be; 24.6 area% methylethoxysilacyclohexane with 48 area% unrcacted MeSi(OEt)3 and 25.8 area% unreactcd dibromopentane.

Example 33 [0033] 254 g Mg and of 3000 ml of diethyl ether (Et2θ) were loaded into the reactor at room temperature. 15 ml of 1 ,2-Dibromoethane was then added to activate the Mg. Within 10 minutes the temperature rose from 19.4°C Io 29.7°C, and EI2O refluxed from the condenser, the Mg was activated and a hazy reaction mixture was observed. I] A premixed solution of 668 g Of MeSi(OFu)^, 750 g 1,5 dibromopeniane and 1767 ml ether was prepared and added to the already activated Mg in Et2θ over a 3 hour period. The reaction mixture reached an exothermic temperature of 33.5°C and the reaction was allowed to run overnight.

$5] GC analysis of the liquid phase a t=l 8 hours determined that the reaction to be: 79.9 area% methylethoxysilacyclohexane with 13.3 area% unreacfed MeSi(OEt)3 and 2.8 area% unreacied dibromopentane.

Claims

That which 1 claimed is:

1 , A method for producing a silacycloalkane comprising reading an alkoxysiiane,

1 2 3 1 R ySifOR )4__y with a Grignard reagent, XMgR MgX where each R is independently an alky! group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, a hydrogen atom, or CF3; each R is independently an alkyl group having 1 to 4 carbon atoms; y has a value of 1 or 2; R^" is selected from an alkylene group having 1 to 10 carbon atoms; and X is a halogen,

2. The method as claimed in claim 1 where in the sϋacycloalkane is selected from

4 where each R is independently an alky! group having I to 4 carbon atoms, an alkenyl group

2 having 2 to 4 carbon atoms, a hydrogen atom, CF3, or a OR^" group.

3. The method as claimed in claim 1 wherein the alkoxysiiane is selected from dimethyldimeihoxysilane, diethyldimethoxysilane, dimeihydiethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane or mixtures thereof.

4. The method as claimed in claim 1 wherein the reaction is carried out in a solvent,

5. The method as claimed in claim 4 wherein the solvent is sleeted from dimethyl ether, diethyl ether, elhylmethyl ether, n-butylmethyl ether, n-bulylethyl ether, di-n-bulyl ether, di- isobutyl ether, isobutylmethyl ether, isobutylethyl ether or mixtures thereof.

6. The method as claimed in claim I wherein there is up to 10 mol% more of the Grignard reagent as compared io the amount of alkoxysilane,

7. The method as claimed in claim 1 wherein there is up to 5 mol% more of the Grignard reagent as compared to the amount of alkoxysilane.

8. The method as claimed in claim i wherein there is up tolO mol% more of the alkoxysilane as compared to the amount of Grignard reagent.

9. The method as claimed in claim 1 wherein there is up to 5 mol% more of the alkoxysilane as compared to the amount of Grignard reagent.

10. The method as claimed in claim S wherein the amount of solvent is 15 to 30 moles per mole of alkoxysilane.

1 1. The method as claimed in claim 1 wherein the Grignard reagent is selected from

BrMgCH₂CH₂CH₂MgBr₁ BrMgCH₂CH₂CH₂CH₂MgBr₁ BrMgCH₂CH₂CH₂CH₂Cf-I₂MgBr and mixtures thereof.

12. A method for producing a silacycloalkane comprising producing a Grignard reagent by reacting with Mg in a solvent a dihaloalkane having ihe general formula XRX where

X is a halogen and R is an alkylene group having 1 to 10 carbon atoms i 2 and thereafter reacting the Grignard reagent with an alkoxysilane, R ySi(OR )4_y where each R is independently an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, a hydrogen atom, or CFy each R^"' is independently an alkyl group having 1 to 4 carbon atoms; and y has a value of 1 or 2.

13. The method as claimed in claim 1 1 wherein the method is carried out in-situ.

14, The method as claimed in claim 1 i where in the silacycloalkane is selected from

.4 . where each R ^' is independently an alky! group having i to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, a hydrogen atom, CF3, or a OR group.

15. The method as claimed in claim 1 ! wherein the alkoxysiiane is selected from dimethyldimcthoxysilanc, diethyldimethoxysilane, dimethydiethoxysilane, methyltiϊmethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane or mixtures thereof,

16. The method as claimed in claim 1 1 wherein the reactions are carried out in a solvent.

17, The method as claimed in claim 15 wherein the solvent is selected from dimethyl ether, diethyl ether, ethyl methyl ether, n-butyl methyl ether, n-butyl ethyl ether, di-n-butyl ether, di-isobutyl ether, isobutyl methyl ether, isobutyl ethyl ether or mixtures thereof,

18, The method as claimed in claim 1 1 wherein there is up to 10 mol% more of the Grignard reagent as compared to the amount of alkoxysiiane.

19. The method as claimed in claim 1 1 wherein there is up to 5 mol% more of the Grignard reagent as compared to the amount of alkoxysiiane,

20. The method as claimed in claim 1 1 wherein there is up to 10 mol% more of the alkoxysiiane as compared to the amount of Grignard reagent.

21. The method as claimed in claim 1 ! wherein there is up to 5 mol% more of the alkoxysiiane as compared to the amounl of Grignard reagent. The method as claimed in claim 1 i wherein there is 0.1 to 1 mole of dihalosilane per mole of Mg.