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New Trimethyl Boron Synthesis Method

IP.com Disclosure Number: IPCOM000198321D
Publication Date: 2010-Aug-04

Publishing Venue

The IP.com Prior Art Database

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NEW TRIMETHYL BORON SYNTHESIS METHOD

Disclosed herein are non-limiting embodiments of methods, apparatus, and compounds which may be used in the manufacture of semiconductor, photovoltaic, LCD-TFT, or flat panel type devices.

Background

Boron is an important element used principally as dopant in semiconductor and photovoltaic industry.  It is usually used to dope silicon, germanium, or silicon carbide.  The boron element has one less valence electron than the host atom therefore it donates a hole and thus we obtain a p-type conductivity.

Traditional method of introducing boron into the semiconductor is based on atomic diffusion occurring at high temperatures.  Common processes use boron oxide B2O3 and/or the liquid BBr3 but also more and more gas sources such as B2H6, BF3 and more and more BMe3, TMB.

TMB knows an increasing use in photovoltaic applications.  It is mainly used blended with hydrogen, H2, allowing a better process control.

Product purity is something critical in electronics and semiconductor industry.  Nowadays, TMB is produced at a high cost and typical purity obtain is around 99.5%, pretty far from the 5N (“five nines”) industry standard for product/material purity.

It is therefore critical to be able to produce with cost effective method trimethyl boron having ultra high purity.

 


Prior Art

Trimethyl boron (TMB) synthesis method has been reported as early as 1921.  The following chart summarizes what is already done.  We can see a variety of synthesis method giving different yields.  In a second part, we can see a clear detail of the reaction that was done or described.

People

Year

Method

Yield

Stock et al.

1921

ZnMe2 + BCl3

NA

British Thomson-Houston Co.

1949

BCl3 + MeCl (1:2 ratio) over Zn mesh

NA

Perrine et al.

1958

AlMe3 condensed in B2O3

low

Iyoda et al.

1959

Me3Al2Cl3 was added to B(OBu)3, B2O3, and Na2B4O7 separately

68.8-93.6%

Witz et al.

1959

MeCl + magnesium boride

8.90%

Joly et al.

1959

MeZnBr in HCONMe2 --> BF3 bubbling

NA

Muetterties

1960

MeCl+xxxx

97%

Anderson

et al.

1960

MeAl sesquichloride with B2O3

32%

Murib et al.

1960

TMA+ boron oxide in autoclave

NA

Stone et al.

1960

BCl3 + PbR4

90%

Ashby et al.

1962

(ROBO)3+organoaluminum

NA

Ross et al.

1962

H3NBMe3+HCl

55%

Katal'nikov et al.

1965

BF3 treated with Bu2O --> treated with MeMgI

99%

Casanova et al.

1969

AlMe3+(MeO)3B in diglyme at -18C

50-55%

Koeaster et al.

1973

Me3Al2Cl3+(BuO)3B in xylene at 80C

95%

Rees et al.

1990

(MeAl3 in Bu2O)+(BBr3 in hexane)

98-99%

We can see that there are mainly 2 reactants:  Boron halides (BX3) and metal boride with alkyl halides.

-     The first method uses organometallics with this reaction:

3MeX + 3Mg + BX3 à Me3B + 3MgX2 (reaction done in diethyl ether, THF heated at ~325-350C).  Zinc can be added to the reaction instead of magnesium.  X is Chlorine or iodine.

This is a cost effective method; however, it requires high temperature and a recycling of the solvent.  Moreover, it is difficult to separate the solv...