RU2392685C1 - Sprayed targets of highly pure alloys on basis of transition metals and method of their production - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to the field of production of sprayed metal targets for microelectronics. Method for production of sprayed target on the basis of highly pure transition metal from the following range: titanium, vanadium, cobalt, includes serial deep vacuum refining of highly pure metal-ceramic stock by electronic beam drop remelting to produce bar of highly pure transition metal, formation of target stock in the form of bar by arc vacuum remelting with simultaneous alloying with silicon within the limits of 0.0005-0.15 wt % in vertical crystalliser in process of intense electromagnet mixing of hardening melt, and further produced stock is mechanically treated. Sprayed target of highly pure alloy on the basis of transition metal from the following range: titanium, vanadium, cobalt, contains transition metal and silicon, at the following ratio of specified components, wt %: silicon - 0.005-1.0 and metal from the following range: titanium, vanadium, cobalt - the rest.

EFFECT: improved quality and reliability of barrier and conducting films of disilicides of refractory metals.

3 cl, 1 tbl

Description

The invention relates to the field of production of sprayable metal targets for microelectronics. Stoichiometric silicide films of transition metals are of considerable interest as a material of low-resistance contacts, gate electrodes, interconnects, and diffusion barriers between a silicon substrate and metallization in integrated circuits.

Currently, two main industrial technologies for producing silicide films are used. The first is magnetron sputtering of targets made of silicides. For the manufacture of such targets, powder metallurgy technology is usually used, as a result of which uncontrolled contamination of the sprayed targets and the deterioration of the electrophysical properties of the resulting films are possible. The use of cast silicide targets proved to be a more progressive way of producing stoichiometric films, since a disilicide layer with previously known electrophysical parameters was immediately applied [RF Patent No. 2356964, 08/16/07]. The second technology is the deposition of pure metal films on a silicon surface with subsequent high-temperature annealing (up to 1000 ° C), resulting in silicide layers. When using this technology in the production of ultra-large integrated circuits with submicron sizes, problems may arise associated with the degradation of shallow pn junctions due to diffusion of impurity atoms into the silicide film during annealing and, as a result, an increase in contact resistance. Nevertheless, in the technology for the production of integrated circuits for the selective deposition of a silicide film, the method of applying thin layers of metal to silicon is used, and subsequent heat treatment leads to the production of a stoichiometric disilicide layer. In these cases, the use of disilicidal targets obtained in accordance with the aforementioned invention is low-tech.

The technical task is to improve the quality and stability of the electrophysical and adhesive properties of transition metal silicides obtained by burning.

This is achieved by using a method for producing a sputtered target from an alloy based on high-purity transition metal of high purity from the following series: titanium, vanadium, cobalt, including sequential deep vacuum refining by electron beam drip remelting of a high-purity workpiece to obtain a high-purity transition metal ingot, forming from arc vacuum remelting with simultaneous alloying with silicon in the range of 0.0005-0.15 m.% in a vertical mold of the target blank in the form of an ingot and machining of the obtained workpiece.

This is achieved by the fact that the sprayed target is made of a high-purity alloy based on a transition metal from the following series: titanium, vanadium, cobalt, is obtained by this method.

This is achieved by the fact that the sprayed target is made of a high-purity alloy based on a transition metal from the series: titanium, vanadium, cobalt contains a transition metal and silicon, in the following ratio of these components, m.%: Silicon - 0.005-1.0 and a metal from the series: titanium, vanadium, cobalt - the rest.

The lower limit of the selected ratio is limited by the low resistance of the proposed material to oxidation during heat treatment and chemical treatment, when the silicon content in the high-purity alloy is less than 0.0005 m.%. The upper limit of the silicon content in the alloys is limited by the need to have a low electrical resistivity of the proposed material, as well as the possibility of reproducibly producing thin-film elements during photolithographic processing.

The method is as follows.

The initial blanks are placed in a melting vacuum chamber of an electron beam furnace and gradually melted, bringing the blanks under the electron beam generated by the axial gun. Then, a silicon strip is fastened along the obtained high-purity transition metal ingot and a second remelting is performed in an electric arc vacuum installation with intensive electromagnetic mixing of the melt. The rotation of the melt contributes to the reduction, averaging of the chemical composition over silicon, the elimination of temperature gradients, and the formation of a fine-grained cast structure due to the destruction of crystallites and the appearance of additional crystallization centers.

An example implementation of the method.

The implementation of the method was carried out in the manufacture of cast targets of high-purity alloys based on transition metals (titanium, vanadium, cobalt). The source material was refined by electron beam melting in high vacuum using an EMO-250 unit in a vertical crystallizer to produce polycrystalline ingots. Further along each ingot of high-purity transition metal, strips of monocrystalline silicon were fastened every 90-100 mm. The mass of fixed silicon bands depended on a given concentration of silicon in the alloy in the range of 0.0005-0.15 m.%. The second vacuum remelting of the transition metal ingot with fixed silicon bands was carried out in a DDV electric arc vacuum unit equipped with a device for electromagnetic mixing of the solidified melt. As a result, an alloy ingot based on high-purity molybdenum with a given silicon content was obtained. The diameter of the ingot is up to 200 mm with a length of 500 mm. The ingot was cut on a tape electrospark machine into flat blanks of targets. Then, the workpieces of the sprayed targets were machined. The silicon content in the samples was determined by mass spectrometry.

1. Five ingots of a high-purity titanium-based alloy with a silicon content of 0.0004, 0.0005, 0.01, 0.15 and 0.16 m.%, As well as one ingot of high-purity titanium without alloying with silicon, are smelted. 1 target was made from each ingot - 6 round sprayed targets for the Oratorio-5 installation.

2. Five ingots of a high-purity vanadium-based alloy with a silicon content of 0.0004, 0.0005, 0.01, 0.15 and 0.16 m.%, As well as one ingot of high-purity vanadium with high purity without doping with silicon, are smelted. 1 target was made from each ingot - 6 round sprayed targets for the Oratorio-5 installation.

3. Five ingots of a high-purity cobalt-based alloy with a silicon content of 0.0004, 0.0005, 0.01, 0.15 and 0.16 m.%, As well as one high-purity cobalt ingot without alloying with silicon, are smelted. 1 target was made from each ingot - 6 round sprayed targets for the Oratorio-5 installation.

A comprehensive study of the processes of magnetron sputtering of targets from all three alloys, as well as structural and electrophysical parameters of thin films obtained by sputtering targets of all three alloys, was carried out. Silicon wafers of (100) p-type conductivity were thermally oxidized, resulting in a masking film of silicon dioxide with a thickness of 0.3 μm (in some areas - a thickness of 50 nm) and subsequent photolithography of a bus made of polycrystalline silicon with a thickness of 0.4 μm. Then, on a silicon wafer with photolithographically formed film elements, in accordance with the topological pattern of the test structures, the windows in the protective film of silicon dioxide were opened and created by ion doping at an energy of phosphorus ions of 30 keV and a dose of 400 μC / cm ² (followed by annealing at 950 ° C) n-type conductivity. Then, an open etching in 1% HF was used to remove a thin oxide film in the open windows and in the Oratorio-5 magnetron setup in pure argon at a pressure of 0.26 Pa, metallization was applied under the following conditions for targets based on titanium and vanadium: voltage at the anode 450 ± 50 V, current 5.5 A. For a cobalt-based target, the voltage at the anode is 420 ± 30 V, current 4.5 A. The temperature of the substrates when applying films of these metals doped with silicon to a thickness of 0.12 μm was 543 ± 10 K. Subsequent heat treatment was carried out in argon at temperatures e alloy films based on titanium 993 K, based on vanadium 1023 K, and based on cobalt 893 K, and the process duration was determined by the formation of disilicide on the entire thickness of the deposited initial film. On each plate, there were up to 180 test crystals with the same type of elements, which made it possible to evaluate the reproducibility of the formation of disilicide films using statistical methods. On the fabricated test samples during testing, we determined (1) the scatter of the resistance value of polycide structures; (2) the resistance of films and contacts from disilicides to electromigration when current flows with a density of 8 · 10 ⁵ A / cm ² along the cross section along the film and 3 · 10 ⁵ A / cm ² along the contact cross section; as well as the percentage of short-circuited shallow pn junctions on the plate. The experimental results are shown in the table.

Table Test Structure Test Results No. p / p The composition of the material, m.% Relates. the deviation of the resistance of polycide structures on the plate,% The uptime of the conductive elements (a) and contacts (b), h The number of structures with short-circuited pn junctions on the plate but b one Ti-Si (0.0004) 7 52 68 10 2 Ti-Si (0.0005) 3 88 116 2 3 Ti-Si (0.01) 2 96 120 - four Ti-Si (0.15) 2 94 112 2 5 Ti-Si (0.160) 6 48 72 fourteen 6 Ti 12 36 48 25 7 V-Si (0,0004) 5 48 72 eighteen 8 V-Si (0,0005) 2 96 120 5 9 V-Si (0.012) one 102 124 2 10 V-Si (0.15) 2 98 118 6 eleven V-Si (0.160) 5 48 78 21 12 V 10 42 52 37 13 Co-Si (0,0004) 6 46 72 12 fourteen Co-Si (0,0005) 3 84 106 2 fifteen Co-Si (0.01) 2 98 120 - 16 Co-Si (0.15) 3 86 112 3 17 Co-Si (0.16) 8 48 76 17 eighteen Co fourteen 36 48 28

The test results of test structures made of films of high-purity alloys based on titanium, vanadium and cobalt clearly indicate that magnetron sputtering of these alloys makes it possible to obtain films of disilicides of the highest quality with high reproducibility of the process of their formation.

Claims (3)

1. A method for the production of a spray target from an alloy based on high-purity transition metal of high purity from the series: titanium, vanadium, cobalt, including sequential deep vacuum refining by electron-beam drop remelting of a high-purity metal-ceramic billet to produce a high-purity transition metal ingot, forming from it an arc vacuum remelting with simultaneous doping with silicon in the range of 0.0005-0.15 m.% in a vertical crystallizer with intense electromagnetic stirring and solidifying the melt of the billet of the target in the form of an ingot and machining the obtained billet. 2. A spray target from an alloy based on a high-purity transition metal from the series: titanium, vanadium, cobalt, obtained by the method according to claim 1. 3. The sprayed target of a high-purity alloy based on a transition metal from the series: titanium, vanadium, cobalt containing a transition metal and silicon, in the following ratio of these components, m.%: Silicon 0.005-1.0 and a metal from the series: titanium, vanadium cobalt rest.