What is titanium target in sputtering?

Titanium metal and titanium sputtering target are basically the same, and both are composed of titanium element. The difference is that titanium metal is more like raw materials, while titanium targets are more like titanium products. Titanium as a raw material can be made into titanium sputtering targets by several methods, and they are widely used in high-tech fields such as electronics, information industry, home decoration, and automotive glass manufacturing. In these industries, titanium targets are mainly used for surface panel displays of coated integrated circuits, flat panels and other components, or as decoration and glass coating.

Performance requirements of titanium target

Magnetron sputtering-Ti targets are mainly used in electronics and information industries, such as integrated circuits, flat-panel displays, and decorative coatings in the home improvement and automotive industries, such as glass decorative coatings and wheel hub decorative coatings. There are also great requirements for Ti targets in different industries. The differences mainly include: purity, microstructure, welding performance, and dimensional accuracy. The specific index requirements are as follows:

1) Purity: for non-integrated circuits: 99.9%; for integrated circuits: 99.995%, 99.99%

2) Microstructure: for non-integrated circuits: the average grain size is less than 100 μm; for integrated circuits: the average grain size is less than 30 μm, and for ultra-fine grains, the average grain size is less than 10 μm

3) Welding performance: for non-integrated circuits: brazing, monomer; for integrated circuits: monomer, brazing, diffusion welding

4) Dimensional accuracy: non-integrated circuit: 0.1mm; non-integrated circuit: 0.01mm

Magnetron sputtering Ti target preparation technology

According to the production process, the raw material preparation technology of Ti target can be divided into electron beam melting billet and vacuum consumable electric arc furnace melting billet (two categories, in the process of target material preparation, in addition to strict control of material purity, density, grain In addition to the degree and crystallographic orientation, the heat treatment process conditions and the subsequent molding process also need to be strictly controlled to ensure the quality of the target.

For high-purity Ti raw materials, the impurity elements with high melting point in the Ti matrix are usually removed by melting electrolysis, and then further purified by vacuum electron beam melting. Vacuum electron beam melting is to use high-energy electron beams to bombard the metal surface, and then the temperature gradually Raise until the metal melts, the elements with high vapor pressure will be volatilized first, and the elements with low vapor pressure will remain in the melt. The greater the difference between the vapor pressure of impurity elements and the matrix, the better the purification effect. And the vacuum refining after melting, Its advantage is that it removes the impurity elements in the Ti matrix without introducing other impurities. Therefore, when the electron beam is smelting 99.99% electrolytic Ti in a high-vacuum environment, the impurity whose saturated vapor pressure in the raw material is higher than the saturated vapor pressure of the Ti element itself Elements (iron, cobalt, copper) will be volatilized preferentially to reduce the impurity content in the matrix and achieve the purpose of purification. The combination of the two methods can obtain high-purity metal titanium with a purity of 99.995 or more.

Technical requirements for Ti targets In order to ensure the quality of the deposited film, the quality of the target must be strictly controlled. After a lot of practice, the main factors affecting the quality of the Ti target include purity, average grain size, crystal orientation and structural uniformity, geometry and size, etc.

The use of high-purity titanium targets mainly includes the following points

1. Biomaterials

Titanium is a non-magnetic metal, and it will not be magnetized in a strong magnetic field. It has good compatibility with the human body and has no toxic side effects. It can be used to manufacture human implants. General medical titanium does not reach the level of high-purity titanium, but considering the dissolution of impurities in titanium, the purity of titanium for implants should be as high as possible. It is mentioned in the literature that high-purity titanium wire can be used as a biological binding material. In addition, the titanium injection needle embedded in the catheter has also reached the high-purity titanium grade.

2. Decorative materials

High-purity titanium has excellent atmospheric corrosion resistance, and it will not change color after long-term use in the atmosphere, ensuring the original color of titanium. Therefore, high-purity titanium can also be used as building decoration materials. In addition, in recent years, some high-end decorations and some wearing objects, such as bracelets, watches and spectacle frames, are made of titanium, which takes advantage of the characteristics of titanium, such as corrosion resistance, no discoloration, long-term maintenance of good luster, and non-allergic contact with human skin. The purity of titanium used for some decorations has now reached the 5N level.

3. Getter material

As a chemically very active metal, titanium can react with many elements and compounds at high temperature. High-purity titanium has a strong adsorption capacity for active gases (such as O2, N2, CO, CO2, and water vapor above 650 ° C). The Ti film evaporated on the pump wall can form a surface with high adsorption capacity. This property makes Ti is widely used as a getter in ultra-high vacuum pumping systems. If used in sublimation pumps, sputtering ion pumps, etc., the limit working pressure of the sputtering ion pump can be reduced to a certain extent.

4. Electronic information materials

In recent years, with the rapid development of high-tech fields such as semiconductor technology and information technology, the amount of high-purity titanium used in sputtering targets, integrated circuits, DRAMs and flat-panel displays has increased, and the purity requirements for titanium materials have become higher and higher. come higher. In the semiconductor VLSI industry, the control electrodes use titanium silicon compounds, titanium nitrogen compounds, tungsten titanium compounds, etc. as diffusion barriers and wiring materials. The sputtering method is used to make these materials, and the titanium target material used in the sputtering method has high requirements on purity, especially the extremely low content of alkali metal elements and radioactive elements.