CS259353B1 - Method of microelectronics quality sulphuric acid production - Google Patents

Abstract

Sulfur trioxide obtained by thermal displacement from olea is absorbed in sulfuric acid for microelectronics and / or water purity for microelectronics, while increasing the concentration of absorbent sulfuric acid. Careful dilution with water Purity for microelectronics is edited to desired concentration. Sulfur trioxide used for absorption in sulfuric acid and / or Water purity for microelectronics is purified filtering devices. The solution is can be used in the electrical industry.

Description

The invention relates to the production of sulfuric acid for microelectronics, which is particularly suitable for use in planar integrated circuit technology.

The production of sulfuric acid is one of the most widespread production in the chemical industry. Currently, the most widely used method of preparing high-quality sulfuric acid is by thermal oxidation of sulfur to sulfur dioxide, which is catalytically oxidized to sulfur trioxide, and this is absorbed in about 98% sulfuric acid by contact. However, the acid thus prepared does not yet meet the purity requirements necessary for use in planar technology in the production of integrated circuits.

Sulfuric acid is currently being prepared for this purpose by purification from chemical impurities by rectification and subsequently from heteroparticles by microfiltration through sophisticated devices containing filter candles with a mesh size of 0.2 to 0.45 μΐη.

Since the currently prepared sulfuric acid contains orders of magnitude of 10 ⁶ to 10 ⁷ heteroparticles per liter greater than 0.5 µm, their removal by microfiltration from sulfuric acid is very expensive.

The rectification of sulfuric acid itself is a very energy-intensive process.

These findings have been drawn from the following works and materials: E.O. Stepun et al. - Metody polučenija osobo čistých neorganičeskich veščestv. Moscow - 1969; Catalog of Sartórius 1984; Millipore 1983; Merck catalog - Selectlpur MOS 1983 and Carlo Erba Montedizon 1983 catalog.

At the same time, attempts have been made to partially purify concentrated sulfuric acid produced from flue gases obtained from melting and fusing sulphide ores. However, these acids contain a large number of heavy metals, mainly mercury. Their removal is described in English patent 6 215 of 1884 as well as in US patents 314 548 (1885) 1891294 (1932) and 3,145,080 (1964), which describe methods of their removal by means of soluble sulfides responsive to insoluble sulfides of these metals which are subsequently filtered off. Similarly, Orlando and Larzon, U.S. Patent 3,826,819 (1974) discloses a method for purifying sulfuric acid with hydrogen sulfide. In all these processes described above, besides dustiness, the difficulty of filtering the insoluble residue is the greatest.

Generally, in the preparation of sulfuric acid by converting SO2 to SO3 through a V2O5 bed, the catalytic oxidation efficiency is about 97% so that sulfuric acid contains a significant amount of SO2 (about 80 to 1260 ppm) which is laboriously removed by bubbling dry air through its volume.

The above-mentioned drawbacks have been eliminated by the method of production of sulfuric acid for microelectronics, the essence of which is that the high-purity sulfuric acid for microelectronics and the like is added to the process. In the initial phase, microelectronics grade water (with parameters of 18 MQcm ¹ and filtered through a 0.2 µm filter device) absorbs the filtered sulfuric oxide obtained by displacement from the oleum and at the same time concentrates the concentrated sulfuric acid obtained to the desired concentration again. water purity for microelectronics.

The invention is applicable to the production of sulfuric acid for microelectronics, which will find use mainly in the production of integrated circuits and other electrical components in the electrical industry.

Example 1

23% wt. The olea was displaced by heating SO3, which was fed through a filter device to an absorption flask, where 98.4 wt. quality sulfuric acid for microelectronics. During the circulation of absorbing sulfuric acid, its concentration increased to 99.5% by weight. This acid was subsequently set up with a water of purity for microelectronics to a concentration of 96.2% by weight, and had the following parameters: residue 3. . 10 ⁴ % by weight, sulphates 4. 10 ⁴ % by weight, heavy metals 3. 10 ⁵ % by weight, chlorides 3. 10 ⁶ pere. wt., lithium, less than 16 ⁶ wt., Mg up to 3. 15 ⁶ wt.

Number of particles per size range:

to 5 μΐη was 9 670 to 25 / tm was 350 above 25 μτη was 36

Example 2

The procedure was the same as in the first case, but during the absorption of SO 2, microelectronics grade water was continuously added to maintain a constant concentration of the absorbing acid in the range of 98.3 to 98.6% by weight. At the same time, the acid was collected and graded to a concentration of 96.3% by weight. while cooling the device with water. The sulfuric acid thus obtained had the following parameters: residue 2. 10 ⁴ % by weight, sulphates 2. 10 ⁴ % by weight, heavy metals 3. 10 ⁵ % by weight, sodium 4. 10 ⁵ pere. wt., potassium 2. 10 ⁶ % by weight, calcium 16 ⁶ % by weight, magnesium less than 3%. ^_O 10% by weight.

WITH

Number of particles vilo size interval: 1 to 5 μϊα was 6 354 to 25 μτη was 937 over 25 μία was 84

Claims (2)

Method for producing microelectronics-quality sulfuric acid, characterized in that sulfuric oxide thermally displaced from the oleo is introduced into water and / or microelectronic-grade diluted sulfuric acid. We claim: 2. The method of claim 1, wherein any impurities entrained in sulfur trioxide gas are collected by a filter.