Main performance requirements of the target
Purity is one of the main performance indicators of the target, because the purity of the target has a great influence on the performance of the film. However, in practical applications, the purity requirements of the target are not the same. For example, with the rapid development of the microelectronics industry, the silicon wafer size has been developed from 6”, 8” to 12”, and the wiring width has been reduced from 0.5um to 0.25um, 0.18um or even 0.13um, and the previous 99.995% target purity. It can meet the process requirements of 0.35umIC, while the preparation of 0.18um line requires 99.999% or even 99.9999% for target purity.
(2) Impurity content
Impurities in the target solids and oxygen and moisture in the pores are the main sources of contamination of the deposited film. Targets for different purposes have different requirements for different impurity levels. For example, pure aluminum and aluminum alloy targets for the semiconductor industry have special requirements for alkali metal content and radioactive element content.
In order to reduce pores in the solids of the target and improve the properties of the sputtered film, the target is usually required to have a higher density. The density of the target not only affects the sputtering rate, but also affects the electrical and optical properties of the film. The higher the target density, the better the performance of the film. In addition, increasing the density and strength of the target allows the target to better withstand the thermal stresses during sputtering. Density is also one of the key performance indicators of the target.
Grain size and grain size distribution
Typically the target is a polycrystalline structure with a grain size on the order of microns to millimeters. For the same target, the sputtering rate of the fine-grained target is faster than that of the coarse-grained target; and the thickness of the target sputter-deposited film with a smaller crystal grain size (smooth distribution) is more uniform. .
Tungsten-titanium targets have recently been developed as photovoltaic cell coating materials, and are the best choice as a barrier to third-generation solar cells.
Due to the excellent performance of W-Ti series films, the application volume has increased sharply in recent years. In 2008, the world consumption of W-Ti targets has reached 400t. With the development of photovoltaic industry, the demand for such targets will increase. The bigger. According to industry forecasts, there will be a big increase in its usage. The international solar cell market is growing at a rate of 100%. At present, many companies in the world are participating in the further development of the solar market and have already entered the market, such as Wverthsurlfulcell in Germany, Global solar Energy in the US, Honda showa Solar shell in Japan, Hitachi Metals. Company, etc.
The ultra-large size, high-density, high-purity W-Ti target developed in China is a new type of ion sputtering coating target material. It can be widely used in the barrier layer or toning layer of the display screen, the decorative layer of the notebook computer, the packaging of the battery, and the barrier layer of the solar (photovoltaic) battery, which has good market prospect and economic benefit. On the other hand, it can drive the upgrading of China’s tungsten industry products and obtain higher added value.