RU2377330C1 - Method to produce high-purity nickel for dispersed targets and device to this end - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metallurgy. Proposed method comprises zone chlorination of nickel metal in gaseous chlorine flow at 940 to 970°C to produce nickel chloride powder. Then, one-stage sublimation of nickel chlorides powder in atmosphere of humid argon at 940 to 970°C is carried out to produce nickel chloride vapors. After sublimation, homogeneous recovery of nickel chloride vapors is performed in dehydrated hydrogen flow at 950 to 980°C and hydrogen-to-argon-flow rate ratio of 1:2-1:3 to produce foil and recovered nickel crystals. Now, said foil and crystals are pressed and vacuum zone re-crystallization is effected to produce ingots. The latter are remelted in cooled flat crystalliser in vacuum to produce flat ingot to be remelted on both sides for complete depth, at least, two times. Invention covers also device to produce nickel chloride powder for dispersed targets and device for sublimation and homogeneous recovery of nickel chloride.

EFFECT: sharp increase in nickel purity.

4 cl, 2 dwg, 1 tbl, 1 ex

Description

The invention relates to the field of metallurgy of non-ferrous metals and can be used in the production of sputtered magnetron targets in the production technology of silicon integrated circuits in microelectronics.

The prior art method for producing high-purity nickel, taken as a prototype, according to which nickel is produced by the chloride method with hydrogen reduction (WO 02102191 C1 A1, 12/27/2002). A device for producing nickel by reducing nickel chloride with hydrogen is known.

A disadvantage of the known method is that in the chloride process, the removal of impurities strongly depends on the choice of material and capacity of the reaction vessel, the ratio of chlorine to the starting metal, the selection of temperature for precipitation and the purity of the starting product. In addition, in the initial product, for example in carbonyl nickel, there are gas impurities that negatively affect the efficiency of the process, and impurities that are close in their chemical properties to nickel, such as cobalt and iron, are removed extremely inefficiently. The use of vacuum melting and purification of the initial nickel chloride powders obtained by the chloride technology often does not give the desired result, since the ingots at the final stage have a poor macrostructure, and the growth of single crystals is greatly complicated by the presence of impurities.

The technical problem is a sharp increase in the purity of nickel to obtain single crystals and sputtering targets used for thin-film metallization by various spraying methods, since the purity of nickel largely determines the electrophysical parameters of the applied thin layers.

This is achieved by using a method for producing high-purity nickel for sputtering targets, including zone chlorination of metallic nickel in a stream of chlorine gas at a temperature of 940–970 ° С to obtain nickel chloride powder, its single-stage sublimation in wet argon at a temperature of 940–970 ° С obtaining nickel chloride vapors, homogeneous reduction of nickel chloride vapors in a stream of dried hydrogen at a temperature of 950-980 ° C and a ratio of hydrogen and argon flow rates of 1: 2-1: 3 to obtain foil and crystals of reduced nickel, pressing the foil and the reduced nickel crystals, vacuum band recrystallization to obtain ingots are melted in the cooled crystallizer plane in vacuo to give a flat ingot and penetration on either side of its full depth at least twice. This is achieved by using a device for producing nickel chloride powder for producing high-purity nickel for sputtering targets, including a reactor made of refractory material - fused silica, a heater configured to move from top to bottom at a given speed along the processed material when it is heated to a temperature 940-970 ° С in countercurrent of chlorine, and systems of supply of liquid chlorine and supply of wet argon. This is achieved by the use of a device for the sublimation and homogeneous reduction of nickel chloride to produce high-purity nickel for sputtering targets, including a reactor made of refractory material, divided by a quartz diaphragm with a diameter of 1 mm into two zones: a reduction zone and a sublimation zone designed to evaporate nickel chloride and for feeding moist argon into it, which serves as a carrier of nickel chloride vapors from the sublimation zone to the reduction zone, a gradient heater installed in the zone formation of a quartz tube and reduced nickel deposition tube with a calibrated nozzle with a diameter of 1-3 mm for feeding the dried hydrogen.

Figure 1 and Figure 2 presents a device for implementing the proposed method. Figure 1 shows a laboratory device for zone chlorination: 1 - processed material; 2 - reactor; 3 - movable zone; 4 - heater; 5 - a system for supplying liquid chlorine; 6 - wet argon feed system. Figure 2 presents a laboratory device for sublimation and homogeneous recovery of Nickel chloride: 8 - zone of sublimation; 9 - recovery zone; 10 - aperture; 11 - pipe for deposition; 12 - tube with a calibrated nozzle; 13 - precipitated nickel; 14 - reactor; 15 - heater.

The method of producing high-purity nickel to obtain crystals and targets is as follows. The processed material 1 in the form of a metal nickel powder is placed in a reactor 2, heated to a temperature of 940-970 ° C using a heater 4, chlorine gas supplied from a container with liquid chlorine 5 is passed through a reactor 2, and the heater 4 is moved vertically down along the reactor 2 s processed material 1, moving the heating zone 3 and producing chlorination, fill the reactor 2 with wet argon, quickly move the heater 4 to its original upper position and repeat zone chlorination until the metal nickel is completely transferred in nickel chloride. To remove carbon impurities and use the differences in the ability to high-temperature hydrolysis of nickel chlorides and impurity elements, nickel chloride is evaporated in the sublimation zone 8 (Figure 2) at a temperature of 950-980 ° C in a gradient heater 15 in a slightly oxidizing atmosphere created by a stream of wet argon . In the reactor 14, the sublimation zone 8 and the homogeneous reduction zone 9 are separated by a quartz diaphragm 10 with a diameter of 1 mm and are heated separately, and the presence of the diaphragm is due to the need to prevent heterogeneous recovery of chloride in the sublimation zone. Chloride vapor recovery is carried out using dried hydrogen supplied to the reduction zone using a tube with a nozzle 12 with a diameter of 1-3 mm, reduced nickel 13 is deposited on the inner surface of the quartz tube 11 installed in the reduction zone 9. The reduced nickel in the form of foil and crystals is pressed and subjected to vacuum zone recrystallization. To obtain a target, the processed material in the form of nickel rods is placed in a cooled flat mold and vacuum remelted to produce a flat ingot, melting it from each side to full depth.

An example implementation of the method.

As a starting material, OCPh grade carbonyl metal nickel powder was used. Zone chlorination of metallic nickel was carried out in a vertical container of fused silica in a stream of chlorine. The zone heated to a temperature of 940–970 ° C was moved from top to bottom at a speed of 50 mm / h; chlorine gas was passed through the backfill material (nickel powder, PNA LA 11 grade) in the opposite direction to the zone heater. The height of the zone is 50 mm. The result of zone chlorination of metallic nickel was the production of stoichiometric nickel chloride powder, while chlorination occurred without sintering. Zone chlorination of carbonyl nickel followed by sublimation was carried out in 2–3 passes of the heated zone; as a result, nickel metal completely turned into nickel chloride powder. The duration of chlorination was 8-10 hours per 1 kg of chloride, the yield of pure product was 90-95% (the remaining 5-10% - distillation and metal residue). The high chloride yield and high chlorination rate are due to the fact that when the zone heater was moved onto the metal layer, the latter was first subjected to low-temperature chlorination. In this case, the particles were enveloped in a layer of chloride, which, under the influence of the high-temperature zone of the heater, evaporated, partially transferred, and at the same time protected the spongy metal from high-temperature sintering. Homogeneous chloride reduction was performed on the installation schematically depicted in Figure 2, the feature of which is the combination of two processes in one reactor: sublimation of nickel chloride in the initial part of the reactor (along the carrier gas) and hydrogen recovery of chloride vapor in the final part of the reactor, and the zone separated by a calibrated diaphragm. Optimum conditions for heating nickel chloride: in the sublimation zone 940–970 ° С, in the reduction zone 950–980 ° С; the ratio of hydrogen to argon consumption is from 1: 2 to 1: 3. Under these conditions, the yield of purified nickel was 80%. It was found that a higher temperature in the sublimation zone is undesirable due to a noticeable contamination of the final product with silicon. A study of the behavior of impurities (Table 1) showed that the proposed process is a highly efficient, one-step method for purification of impurities of alkali, alkaline earth and heavy metals, which allows to obtain a metal with a content of controlled impurities at the level of 0.1-1.0 ppm. Humidification of the carrier gas to a level of 2.4.10 ^-2 atm led to a deeper purification of nickel from some metal impurities (Table 1), and the carbon content fell below the sensitivity of the coulometric analysis method (4 ppm).

Thus, the proposed method for producing high-purity nickel allows high-purity purification of starting materials of reduced purity, which is extremely important for the preparation of magnetron targets, since it becomes possible to use a nickel product of record purity.

Table 1.
Impurity content in nickel obtained by homogeneous reduction of nickel chloride (ppm) Items Original Ni OSH Sample 1 Sample 2 (obtained with humidification Ar) Na 30.00 1.00 <0.1 TO 100.00 1.00 0.3 Mg 10.00 0.3 0.3 Al 30.00 0.1 0.1 Ca 10.00 1.00 1.00 Mn 300.00 0.1 <0.1 Fe 40.00 1.00 0.1 Cu 3.00 1.00 0.3 Wa 50.00 1.00 1.00 Cl 1000,00 10.00 3.00 With 30.00 0.1 0.1 Br - <0.1 <0.1 Si 1000,00 1.00 0.1 Cr 1.00 0,03 <0.1 As 3.00 0.3 0.3

Claims (3)

1. A method of producing high-purity nickel for sputtering targets, including zone chlorination of metallic nickel in a stream of chlorine gas at a temperature of 940-970 ° C to produce nickel chloride powder, one-step sublimation in wet argon at a temperature of 940-970 ° C of nickel chloride powder to produce vapors nickel chlorides, homogeneous recovery of nickel chloride vapors in a stream of dried hydrogen at a temperature of 950-980 ° C and a ratio of the flow rates of hydrogen and argon 1: 2-1: 3 to obtain foil and crystals of reduced nickel, press Contents of the foil and the reduced nickel crystals, vacuum band recrystallization to obtain ingots are melted in the cooled crystallizer plane in vacuo to give a flat ingot and its penetration from each side of the full depth of not less than two times. 2. A device for producing powder of nickel chloride intended to produce high-purity nickel for sputtering targets, including a reactor made of refractory material, for example fused silica, a heater configured to move from top to bottom at a given speed along the nickel metal being processed while heating it to temperatures of 940-970 ° С in countercurrent of chlorine, and systems for supplying liquid chlorine and supplying wet argon. 3. A device for the sublimation and homogeneous reduction of nickel chloride, designed to produce high-purity nickel for sputtering targets, comprising a reactor made of refractory material, separated by a 1 mm quartz diaphragm into a nickel chloride reduction zone and a sublimation zone, intended for evaporation of nickel chloride and for feeding it contains wet argon, which serves as a carrier of nickel chloride vapors from the sublimation zone to the reduction zone, a gradient heater installed in the reduction zone quartz tube to precipitate the nickel and the reduced tube with a calibrated nozzle with a diameter of 1-3 mm for feeding the dried hydrogen.

Images