Tungsten Targets Preparation with Large Size by Powder Metallurgy

Large-scale integrated circuits often use tungsten target for vacuum sputtering, especially large-size tungsten target. In the current semiconductor field, large-size tungsten target has a diameter of 300 mm-450 mm and a thickness of 6 mm-15 mm. However, with the development of semiconductor industry, larger tungsten targets are needed.

Sputtering is one of the main technologies for preparing thin film materials. Atomics emitted by high-speed moving ions bombarding the target accumulate on the surface of the substrate to form a coating. The bombarded solid is the raw material for deposition of thin film by sputtering, which is called sputtering target. The films deposited by target sputtering have the advantages of high density and good adhesion.

As tungsten is a refractory metal, powder metallurgy is used to process tungsten target in the industry. The powder metallurgy process is to form metal powder into materials or products. In the specific process of powder metallurgy, the prepared powder is packed in a special die and then hot-pressed in a vacuum hot-pressing furnace. It is necessary to design matching dies and vacuum hot pressing furnaces according to the size of target materials.

For the manufacture of large-sized tungsten target, it is difficult to make large-sized tungsten target by powder metallurgy because of the limitation of die size and the use temperature of hot pressing furnace. It is necessary to pre-form tungsten powder to form a large-sized tungsten target blank, and then extend the large-sized tungsten target blank by rolling process. The rolling process is to use rolling mill to make tungsten target. The rolling of billet is usually divided into hot rolling and cold rolling to meet the size requirements, that is, to form tungsten target products with qualified size.

By controlling the parameters of extrusion forming process and heat treatment, the grain size of tungsten target can be well controlled only by controlling the extrusion ratio of extrusion forming and the heating temperature of heat treatment.

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