RU2091501C1 - Method of manufacturing target for magnetron spraying from special- purity aluminium - Google Patents

Abstract

FIELD: microelectronics. SUBSTANCE: in a method of manufacturing special-purity aluminium target involving press forming, target is cooled, e.g. in liquid nitrogen with temperature gradient at least 100 C/cm, and baked at 450-640 C. What is claimed is that, in the process of cooling target, uneven temperature deformations first occur in target structure leading to stresses which manifest themselves in baking process facilitating recrystallization and thus stabilization of structure. EFFECT: improved performance characteristics due to stabilized structure. 2 tbl

Description

 The invention relates to microelectronics, in particular, to the creation of targets for magnetron sputtering with improved operational characteristics, and can be used in metallurgy to create thermally stabilized profiles of aluminum of high purity.

 A known solution for the manufacture of a sputtering target with improved performance characteristics [1] The method includes the thermal shock of a heated pre-mounted target on a copper substrate by cooling in liquid nitrogen, which leads to cracking of the target, and then no new cracks are formed during operation, and the spraying process is stable.

 A disadvantage of the known solution is that the method is applicable only to targets with a stressed structure of brittle material, prone to cracking.

Closer in technical essence is the manufacturing method adopted for the prototype, including heating to a temperature of 450 ^o C and stamping [2]
The practice of operating targets manufactured according to this method showed that during operation the target is heated to a temperature of 450 ^o C for 9 hours. At the same time, collective recrystallization occurs, accompanied by reorientation of the grains, which leads to a change in the aluminum flux during deposition.

 The disadvantage of this method is the low performance due to the instability of the structure.

 The aim of the invention is to improve performance by stabilizing the structure.

This goal is achieved by the fact that in the method of manufacturing a target of high purity aluminum, including heating, stamping, the target is cooled, for example, in liquid nitrogen with a temperature gradient of at least 100 ^o C / cm and annealed at 450-640 ^o C.

The essence of the invention lies in the fact that in the process of cooling a target with a temperature gradient of at least 100 ^o C / cm followed by annealing at 450-640 ^o C in the structure of the target initially uneven temperature deformations occur, and stresses that occur during firing are realized, contributing to recrystallization and stabilization of the structure.

 A search by sources of scientific, technical and patent literature showed that such a combination of features is unknown, thus, the claimed solution meets the criterion of "significant differences".

где G вес изделия, кг;
F поверхность, м²;
t_мн и t_мк начальная и конечная температура металла, ^oС;
t_вс температура внешней среды, ^oС;
С средняя теплоемкость металла, ккал/кг•град;
α коэффициент теплоотдачи, ккал/м²•ч•град.The stress level in the target is proportional to the temperature gradient, which varies over time and depending on the duration of cooling is determined by the dependence [3]

where G is the weight of the product, kg;
F surface, m ² ;
t _mn and t _mk initial and final temperature of the metal, ^o С;
t _sun ambient temperature, ^o С;
With the average heat capacity of the metal, kcal / kg • deg;
α heat transfer coefficient, kcal / m ² • h • deg.

The upper limit of the annealing temperature should be 15-20 ^o C lower than the melting temperature due to the possible loss of geometry during annealing. The lower limit of 450 ^o With is the beginning of intense collective crystallization.

 Example. A hot stamped target 1 × 1 × 1 cm in size was cooled by dipping in liquid nitrogen for 2 minutes.

 The change in the temperature gradient between the target surface and its center depending on the duration of cooling in liquid nitrogen, as well as the calculated level of stresses that arise in the target, are presented in Table 1.

As can be seen from the data presented in Table 1, the largest temperature gradient and, correspondingly, the highest level of stresses occur when holding ≈ 0.5 min. However, in practice it is difficult to provide such a short-term treatment; therefore, cooling duration of 1-4 minutes was chosen. When cooling for more than 4 minutes, the temperature of the target will equalize, the temperature gradient will drop, it will reach less than 100 ^o C / cm and the stress level will be insufficient to promote recrystallization during further annealing.

 The influence of the annealing regime on the recrystallization of a target cooled in liquid nitrogen was evaluated by the change in grain size (Table 2).

 Thus, the proposed method of manufacturing a target, allowed to obtain a thermostabilized structure, which ensures the constancy of structural characteristics in the process of magnetron sputtering, and, thus, to increase the stability of operational characteristics.

LITERATURE
1. Japan, application N 62-278261, MKI C 23 C 14/34.

 2. Report on the topic: to develop a pilot industrial technology for the manufacture of “targets” for installing Magna 2H from lanthanide-containing alloys based on high-purity aluminum (AOCH) of the A5M grade topic 5-89-377, N, city of register. 01900060696, Leningrad, 1990.

 3. Shlichkov A.A. Thermist reference. M. 1961, p. 392.

Claims (1)

A method of manufacturing a target for magnetron sputtering from high purity aluminum, including heating the workpiece and forming the target by stamping, characterized in that, in order to improve performance by stabilizing the structure of the target, after stamping, the target is cooled with a temperature gradient of at least 100 ^o C / cm and annealed in the range of 450 640 ^o C.

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