RU2447078C1 - Method of purifying liquids, volatile alkylsiloxanes and alkylsilazanes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to fine purification of alkylsiloxanes and alkylsilazanes which are used in making light-sensitive resistors and in microelectronics. Disclosed is a purification method comprising three basic steps: fractionation, filtration in liquid and vapour phases on porous polymer filters with pore size 0.1-0.2 mcm and evaporation, followed by condensation in bubble-free conditions at evaporation rate of 0.01-0.2 cm³/h·cm².

EFFECT: disclosed method enables to obtain highly pure alkylsiloxanes and alkylsilazanes with basic substance content of about 99,99 wt % and content of heterogeneous trace elements less than 10 particles per cm³.

1 cl, 6 ex

Description

The present invention relates to the chemistry of organosilicon compounds and directly relates to methods for purifying liquid, volatile alkylsiloxanes and and alkylsilazanes, used, for example, as adhesion promoters of photoresistors, as well as starting materials in the production of microelectronic components.

Liquid volatile alkylsilazanes and alkylsiloxanes include chemicals such as 1,1,1,3,3,3-hexamethyldisilazane, 1,1,3,3-tetra-methyldisilazane, 1,1,1,3,3,3-hexamethyldisiloxane 1,1,3,3-tetramethyl-disiloxane, 1,1,3,3,5,5-hexamethyltrisilazane, 1,1,3,3,5,5-hexamethyl-cyclotrisilazane. It is known that this group of chemical compounds is widely used in high-tech fields of technology, for example, in semiconductor nanotechnology, microelectronics, photolithography, and in the manufacture of dielectrics (EP 1708975, C04B 35/565, 2006; WO 2005/121382, H01L 21/02, 2004; EP 1120826, H01L 21/02, 2001; WO 2006/104352, H01L 21/4763, 2006). One of the requirements for the initial products for these areas of technology is their high degree of purity. The synthesized alkylsilazanes or alkylsiloxanes are known to contain various homogeneous and heterogeneous impurities of organic or inorganic origin. Therefore, before using these compounds in these high-tech areas of technology, an additional purification step is necessary. For example, in the synthesis of 1,1,1,3,3,3-hexamethyldisilazane from ammonia and trimethylchlorosilane, a final product is obtained containing impurities of ammonium chloride that can be removed by various methods: distillation (US 4644076, 260-448.1981), by centrifugation or filtration under pressure (GB 2014171, C3S 56, 1979). However, the purity of hexamethyldisilazane obtained by methods protected by these patents is at a loss of 80-90%. Also known are methods in which the purification of the organosilicon of various organic impurities is described. For example, for the purification of 1,1,1,3,3,3-hexamethyldisiloxane from low-boiling organic impurities, a sequential multi-stage treatment is used, including distillation, treatment with acid resins and treatment with activated carbon (EP 0277825, C07F 7/20, 1988), and for the purification of organosilicon compounds from the group of organosiloxanes from organic halides, for example methyl chloride, biphenyl chloride, chlorobenzene, a purification method is used that includes treating organosilicon compounds with organolithium compounds (JP 63316788, C07F 7/02, 1988). To clean the organosilicon compounds under consideration from organic compounds, the azeotropic distillation method is also used. For example, if this method is used to purify 1,1,1,3,3,3-hexamethyl-disiloxane, chemical solvents such as acetone or acetonitrile are used as an azeotropic component (JP 61087686, B01D 3/36, 1986; JP 57158794, C07F 7/00, 1982). However, the above methods do not provide high purity organosilicon compounds.

The closest to the new method in terms of its technical essence and the results obtained is the well-known method for producing highly pure organosilicon compounds for microelectronics, including the stage of deep purification of these compounds (Efremov A.A., Ryabenko E.A., Nechaeva G.Yu. and others. Physicochemical fundamentals of obtaining highly pure organosilicon compounds for microelectronics. High-purity substances, No. 6. 1993). The purification of organosilicon compounds in this method is carried out by two known methods: rectification and subsequent microfiltration. The purification process in the cited article is illustrated by the example of purification of 1,1,1,3,3.3-hexamethyldisilazane and 1,1,1,3,3,3-hexamethyldisiloxane. At the first stage, in the known method, they are cleaned on a batch rectification column with a packing part filled with single-turn quartz rings at reflux numbers from 1 to 50 and a pressure of 0.2-1.5 ati. After distillation purification, organosilicon compounds in the prototype method are subjected to microfiltration for purification from heterogeneous impurities. For this, membranes made of fluoroplastic (MFF), polyvinyl chloride (PVC) and polyamide (SPA) with a pore size of 0.25 μm are used. As stated in the above article, as a result of filtering through one membrane, the content of heterogeneous particles with a diameter of 0.3 μm or more decreases to 10-30 parts. cm-3, and the content of the main substance after two stages of purification is at the level of 99.99 wt.%. The main disadvantage of the prototype method is that filtration membranes with micropores of the indicated size have low productivity, are prone to rapid clogging of pores and do not provide the currently required purity for the content of smaller impurities.

To obtain high-purity liquid volatile organosilicon compounds from the group of alkylsiloxanes and alkylsilazanes with a basic substance content of 99.99 wt.% And heterogeneous impurities of less than 10 ppm cm3 at a level of 0.1-0.5 microns in the new method of liquid purification, volatile alkylsiloxanes and alkylsilazanes are carried out in a combined way, including rectification, filtration on microporous polymer filters, evaporation and condensation in the bubble-free boiling mode, while filtration is carried out sequentially in liquid and oic phases on microporous polymeric filter with a pore size of 0.1-0.2 micron, and then purify the product is subjected to vaporization and condensation with a specific evaporation rate of 0.01-0.2 cm3 / chas.sm2 in boiling Bubble free mode.

The new method differs from the prototype method by the presence of an additional stage — evaporation and condensation in the bubbleless boiling mode, as well as by the modes of the filtration stage.

The introduction of an additional purification step increases the efficiency of purification from heterogeneous impurities, since in the process of evaporation and condensation in the bubbleless boiling mode, suspended ultrafine particles are retained in the liquid due to its surface tension and do not pass into the evaporated phase. An essential feature of this stage of the process is the specific bubbleless boiling rate of 0.01-0.2 cm3 / h.cm2, since it is within these limits that the most effective cleaning is achieved. Studies have shown that when this speed is exceeded, the entrainment of submicron particles with the evaporating substance is observed, and when the limit is lower than the declared limit, the efficiency of this cleaning step is nullified due to a decrease in productivity and the need to sharply increase the evaporation surface, which complicates the design of the element and reduces the reliability his works.

The conditions for carrying out the filtration stage in the new method also differ from the conditions for carrying out this stage in the prototype method. In the new method, the filtration is carried out sequentially first in the liquid and then in the vapor phases, which reduces the requirements for the pore sizes of the filters in the first stage and improves the performance of the liquids filtered on them.

The filtration stage in the new method is carried out on microporous polymer filters with pore sizes of 0.1-0.2 μm, which ensures maximum cleaning efficiency from heterogeneous impurities. An integral part of the new method is a certain sequence of all stages of purification of volatile liquid organosilicon compounds, namely, first rectification, then filtration and then evaporation and condensation from the surface in the mode of bubbleless boiling. At the same time, at the first stage, micro-impurities of metals, sulfur, and chlorine are purified, and at subsequent stages, heterogeneous impurities of suspended particles are purified.

The rectification process is carried out similarly to the process described in the prototype method.

As can be seen from the examples below, in the process of implementing the new method, high-purity alkylsiloxanes and alkylsilazanes are obtained containing a basic substance at a level of 99.99 wt.% And heterogeneous impurities with a size at a level of 0.1-0.5 microns less than 10 per cm -3.

The invention is illustrated by the following examples, which do not limit the possibility of implementing this purification method for other volatile, liquid alkylsiloxanes and alkylsilazanes.

Example 1

Liquid 1,1,1,3,3,3-hexametidlisilazane (HMDSA) (250 g), previously purified on a batch distillation column and containing solid microparticles with a size of 0.1-0.3 microns over 100 cm-3, is passed through a fluoroplastic filter with a pore size of 0.2 μm, then the liquid is transferred to the evaporator and the resulting vapor phase is passed through a fluoroplastic filter with a pore size of 0.2 μm, condensed and loaded into a bubble-free boiling apparatus, turned on, heated and evaporated from the surface at an evaporation rate 0.01 cm3 / h.sm2 at those temperature of 105 ° C and atmospheric pressure and condense into the receiver. Get GMDSA (248 g) containing 99.9 wt.% The main substance, metal impurities at the level of 10-5-10-6 wt.% Each and solid microparticles with a pore size of 0.1-0.3 microns - 9 cm 3.

Example 2

1,1,1,3,3.3-Hexamethyldisiloxane (HMDSO) (250 g) containing, after the rectification stage, 99.99 wt.% Of the basic substance and solid impurities with a size of 0.5 μm> 1000 cm-3 and a size of 0.3 μm >> 1000 cm-3, they are cleaned of heterogeneous impurities by passing in a liquid and then vapor phase through a polyvinyl filter with a pore size of 0.1 μm and then evaporate in the bubble-free boiling mode at a rate of 0.2 cm3 / h.cm2. Get GMDSO (240 g) containing 99.99 wt.% Of the basic substance and solid microparticles with a size of 0.5 μm - 4 cm-3 and a size of 0.3 μm - 4 cm-3.

Example 3

Purification of 1,1,3,3-tetramethyldisilazane (250 g), containing after the preliminary stage of rectification 99.99 wt.% Of the basic substance and> 1000 cm-3 solid microparticles with a size of 0.5 μm, is carried out similarly to the method described in the example 1, changing only the following parameters: filtration is carried out on a polyamide filter with a pore size of 0.2 μm, and evaporation in the bubbleless boiling mode is carried out at a speed of 0.1 cm3 / h.cm2. 1,1,3,3-tetramethyldisilazane (245 g) is obtained, containing 99.99 wt.% Of the basic substance and solid microimpurities with a size of 0.5 μm - 6 cm-3.

Example 4

1,1,3,3-Tetramethyldisiloxane (250 g), previously purified on a distillation column containing 99.99 wt.% Of the basic substance and solid microparticles with a size of 0.5 μm> 1000 cm-3, is purified similarly to the method described in the example 1, changing only the following process parameters: microfiltration is carried out on a polyvinyl chloride filter with a pore size of 0.1 μm, and evaporation in the bubbleless boiling mode is carried out at a speed of 0.05 cm3 / h.cm2. Obtain 1,1,3,3-tetramethyldisiloxane (246 g) containing 99.99 wt.% Of the basic substance and solid microparticles with a size of 0.5 μm - 7 cm-3.

Example 5

1,1,3,3,5,5-Hexamethylcyclotrisilazane (250 g), previously purified on a distillation column, containing 99.99 wt.% Of the basic substance and solid impurities with a size of 0.5 μm> 100 cm-3, 0.3 μm >> 100 cm-3, it is cleaned on a fluoroplastic filter with a pore size of 0.2 μm, and evaporation in the bubbleless boiling mode is carried out at a rate of 0.05 cm3 / h.sm2. Get 1,1,3,3,5,5-hexamethylcyclotrisilazane (240 g), containing the main substance 99.99 wt.% And solid microparticles with a size of 0.5 μm - 2 cm-3 and 0.3 μm - 7 cm 3.

Example 6

1,1,3,3.5,5-Hexamethyltrisilazane (250 g), previously purified on a distillation column, containing 99.99 wt.% Of the basic substance and solid microparticles with a size of 0.3 μm >> 1000 cm-3 is purified analogously to example 1, only the microfiltration stage is carried out on a polyamide filter with a pore size of 0.1 μm, and evaporation in the bubbleless boiling mode is carried out at a speed of 0.15 cm3 / h.cm2. Get 1,1,3,3,5,5-hexamethyltrisilazane with a basic substance content of 99.99 wt.% And solid microparticles with a size of 0.3 μm - 7 cm-3.

Claims (1)

The method of purification of liquid, volatile alkylsiloxanes and alkylsilazanes, including rectification and subsequent filtration on microporous polymer filters, characterized in that it further comprises the stage of evaporation and condensation in the bubble free boiling mode, moreover, the filtration is carried out sequentially in the liquid and vapor phases on filters with pore size 0, 1-0.2 μm, and evaporation and condensation in the bubbleless mode is carried out after the filtration stage and with a specific evaporation rate equal to 0.01-0.2 cm ³ / h · cm ² .