RU2036832C1 - Method for production of gas mixture containing arsine or phosphine and device for its realization - Google Patents

Abstract

FIELD: microelectronics. SUBSTANCE: compound of arsenic with metals in form of granules is filled into reaction column through which carrier gas (e.g., hydrogen) is passed. Carrier gas is preliminary saturated with steam in thermostat with moistening vessel. Carrier gas is saturated with steam up to concentration corresponding to equilibrium state. Concentration of arsenic hydride in mixture with carrier gas is preset by concentration of saturated steam. EFFECT: higher efficiency. 5 cl, 1 dwg

Description

 The invention relates to the field of producing highly pure substances for microelectronics and specifically relates to a method for producing mixtures of high-purity arsine (phosphine) with carrier gases (hydrogen, argon, helium, etc.).

 The most common methods for producing arsine (phosphine) are the reduction of arsenic (phosphate) compounds with hydrogen or the decomposition of metal arsenides (phosphides) with water or acids.

 The closest technical solution to the proposed one is a method of producing arsine by hydrolysis of magnesium arsenide (phosphide) with water, which is used in the USSR on an industrial scale (arsenic concentrate TU 6-02-7-178-84, phosphine concentrate TU-6-02- 7-177-84) (1).

 The disadvantages of this method is the low purity of the obtained arsine, in particular the content of water vapor and other volatile impurities.

 A device is known for producing a gas mixture containing arsine or phosphine, consisting of a column filled with a powder of a starting substance, means for supplying a source gas and a carrier gas and outputting the resulting arsine or phosphine product (2).

 The disadvantage of this device is the need for an accurate dosage of the source gas and carrier gas to maintain a given concentration of arsine or phosphine in the product.

 However, these methods do not provide for any purification of arsine directly in the process of obtaining it. Currently, the urgent task is to develop environmentally friendly methods and devices for producing gas mixtures of arsine (phosphine) directly in the place of its consumption with the mass flow rate and concentration required by the consumer.

The main requirements for such a method and device are the maximum possible purity of the resulting arsine (phosphine) in order to eliminate or reduce subsequent cleaning operations; the minimum amount of poisonous arsine (phosphine) that is simultaneously in the device; high stability of the concentration of arsine (phosphine) in the gas mixture is not worse than 0.25%
In fact, we are talking about creating an environmentally friendly functional analogue, the usual 40 L cylinder containing a gas mixture of arsine, which consumers are currently using. If a 40 liter cylinder contains, depending on the pressure, several cubic meters of toxic gas, then its environmental safety is obvious.

 To eliminate the disadvantages of the known methods and devices in a known method, including the hydrolysis of metal arsenides (phosphides) in a protective gas (gas carrier), the hydrolysis reaction is carried out by passing gas saturated with water vapor through a layer of arsenide (phosphide) powder, sufficient for the required degree of removal of water vapor and other impurities, moreover, the gas may be saturated with water vapor at a selected temperature.

 A known device comprising a reactor for the hydrolysis of metal arsenides (phosphides) is additionally equipped with a thermostatically controlled water evaporator, and the reactor is made in the form of a column filled with arsenide (phosphide) powder larger than 0.1 mm, and the column can be made sectional with the number of individual sections not less than two with the possibility of their switching countercurrent to the direction of gas flow, and the height of the arsenide (phosphide) layer in each section should provide the required absorption of water vapor and is selected from the condition I H> nh, where h is the height of the layer, providing a decrease in the content of water vapor in the gas by 2 times (n> 1).

 The device operates as follows.

 The carrier gas of the required purity from the cylinder 1 (see the drawing) through the supply means (valves, pressure regulator, etc.) 2 enters the evaporator 3 located in the thermostat 4. From the evaporator 3 through the heated tubes 5 the gas saturated with water vapor enters sequentially into columns 6 and 7 with magnesium arsenide or phosphide, and then to sorption column 8, where the gas mixture is deeply refined. The gas mixture is supplied to the consumer through outlet means 9 (valves, flow regulator, pressure gauge, etc.).

The large contact surface of the water-gas in the evaporator and its design provide an accuracy of 0.2% equilibrium gas saturation with water vapor. The gas flow is passed through 2 sections of the column until the metal arsenide in the first section is hydrolyzed by 95-98%, while the height of the arsenide layer in the second section reduces the vapor concentration in the arsine gas mixture to the desired dew point (≈ 70 ^о С) . Then the process stops, the first column is turned off, the second column takes the place of the first, and the second column is connected to a new column filled with freshly loaded metal arsenide (phosphide).

The essential features of the proposed method and device are
high purity of the obtained arsine (phosphine), which is ensured by the absorption of water vapor by a layer of metal arsenide (phosphide) to the extent required by the consumer, for example, to a dew point of no worse than 70 ^° C, as well as by chemical and physical sorption of impurities as in a layer of metal hydrate formed as a result of hydrolysis, and in a layer of unreacted metal arsenide (phosphide).

The height of the metal arsenide (phosphide) layer is H ≥ 3h, where h is the layer height, which provides a 2-fold reduction in water vapor, according to experimental data, provides the required arsine purity both in the concentration of water vapor and in the content of other impurities and hydrocarbons. The concentration of arsine (phosphine) in the gas mixture is determined only by the concentration of water vapor, which is easily maintained by an ultra-thermostat with an accuracy of ± 0.05-0.1 ^о С, which ensures high stability of the concentration of arsine (phosphine) during the process.

 The amount of arsine (phosphine) in the device at a time is minimal, since arsine (phosphine) is only in the layer of metal arsenide (phosphide).

 It was experimentally found that when the particle size of the metal arsenide (phosphide) is more than 0.1 mm, the layer does not clog the column in the formation of metal hydrate, and the sectional design of the column with the number of separate sections of at least two provides a more economical use of metal arsenide (phosphide) while maintaining the required purity of the obtained arsine (phosphine).

PRI me R. To obtain arsine, a device was mounted containing a 40 liter hydrogen cylinder equipped with a pressure regulator, ODV-4 diffusion gas purification of hydrogen, an electronic gas flow regulator of the RRG type, an evaporator made of stainless steel with a water surface area of 0.2 m ² , which was heated with using an ultra-thermostat, and two sectional columns, also made of stainless steel. Each section had a diameter of 40 mm and a total height of 0.6 m with a height of a layer of magnesium arsenide of 0.5 m.

 Magnesium arsenide powder was 0.5-2 mm in size. The gas system was assembled from welded stainless steel tubes with a diameter of 6 mm and equipped with bellows shut-off and control valves (valves, valves, etc.).

After three times washing the hydrogen-vacuum system (not evaporator) yielded arsine at a temperature of the evaporator 32 + (± 0,1) ^{° C} and a gas flow rate of 50 (± 0,02) cm ³ / s. In the resulting gas mixture, the uniformity of the mass flow rate of arsine for 6 hours of continuous operation was ± 0.5 rel. The moisture content corresponded to a dew point of 85 ^° C, the concentration of the main impurities was at. sulfur, selenium and tellurium (in total) 10 ^-5 ; silicon 2 ˙ 10 ^-5 ; heavy metals (in total) 5 ˙ 10 ^-6 , iron 3 ˙ 10 ^-5 . Arsenic gas mixtures of the indicated quality are suitable for direct use in gallium arsenide gas epitaxy units. The calculated one-time volume of the arsine mixture in the installation did not exceed 0.5 l.

 A similar device was used to produce phosphine, but instead of magnesium arsenide, magnesium phosphide was loaded into the columns.

The phosphine production regimen was also similar; as a result, a gas mixture of arsine was obtained with a dew point of 82 ^° C, with a total chalcogen content of 6 ˙ 10 ^-6 at. heavy metals 8 10 ^-6 at. and hydrocarbons 5 ˙ 10 ^-4 at.

Claims (4)

 1. A method of producing a gas mixture containing arsine or phosphine, comprising hydrolysis of a metal arsenide or phosphide, characterized in that the hydrolysis is carried out by passing a carrier gas pre-saturated with water vapor to the equilibrium state of the carrier gas through layers of a metal arsenide or phosphide powder.  2. The method according to claim 1, characterized in that the thickness H of the arsenide or metal phosphide powder layer is selected from the condition H> nh, where n is a coefficient> 1, h is the thickness of the arsenide or metal phosphide powder layer, which reduces the concentration of water vapor in arsine or phosphine twice.  3. The method according to claim 1, characterized in that the particle size of the powder of arsenide or metal phosphide is selected more than 0.1 mm  4. A device for producing a gas mixture containing arsine or phosphine, including a column for hydrolysis, means for supplying a carrier gas and withdrawing the obtained product, characterized in that it is additionally equipped with a thermostatic water evaporator, and the column is made in the form of at least two separate sections.