Tungsten Titanium Alloy by Plasma Sintering Preparation

Tungsten titanium alloy prepared by plasma sintering as a sputtering target for copper wiring diffusion barrier layer has many requirements in structure and properties. A large number of experimental results show that the grain size and Ti-rich phase content of WTi alloy structure are the main factors affecting the performance of the barrier layer.

In fact, the smaller the grain size of sputtering target and the less the content of Ti-rich phase, the better the properties of the prepared tungsten-titanium films. The finer and more uniform the grain size of the target, the less the rich phase content, the faster the sputtering rate, the better the thickness uniformity of the sputtering deposited film, and the less the number of contaminated particles. Therefore, controlling the grain size and phase composition of tungsten titanium alloy target is the key factor to obtain excellent films.

The preparation method and process parameters are the key factors affecting the structure and properties of tungsten titanium alloy target. The commonly used sintering methods are hot pressing sintering and hot isostatic pressing. In this paper, a new process, plasma sintering (SPS), is introduced.

The preparation of tungsten titanium alloy by plasma sintering requires the following steps:

Step 1: Put tungsten powder with particle size of 6-8 micron into the tank of planetary high-energy ball mill, add 5% alcohol as dispersant, add WC ball according to the ball-to-ball ratio of 15:1, then fill the ball-to-ball mill tank with nitrogen after pre-vacuumizing. The speed of ball mill is 400 r/min, and the milling time is 6-15 H.

Step 2: The tungsten powder and Ti powder after ball milling are mixed evenly on the V-type mixer.

Step 3: Put the mixed powders into the spark plasma sintering furnace and start heating when vacuum is pumped to 6Pa. The fine-grained tungsten titanium alloy can be obtained in a short time after cooling in the furnace at the heating rate of 100 C/s to 1300-1500 ℃ for 3-10 min.

Compared with the traditional sintering method, the grain size of tungsten titanium alloy prepared by plasma sintering method decreases, the proportion of Ti-rich phase in the area decreases, the voids in the structure decreases, the density increases, and the films with good blocking effect can be easily obtained during sputtering process.

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