How to improve the density and purity of sputtering targets?

In semiconductor manufacturing, flat panel display, solar cells and other fields, the quality of the sputtering target directly affects the performance of the final product. Therefore, improving the density and purity of sputtering targets is a goal that materials scientists and engineers are constantly pursuing. This paper will discuss several effective methods to improve these two key performance indicators of sputtering targets.

First, the use of high purity raw materials

The first step to improve the purity of the sputtering target is to select high purity raw materials. Impurities in the raw material can be introduced into the target during the subsequent preparation process, thus affecting its performance. Therefore, the use of high purity metals or alloys as raw materials is crucial. For example, for aluminum targets, high purity aluminum ingots above 99.99%(4N) should be selected as raw materials.

Second, optimize the sintering process

Sintering is one of the key steps in preparing high density sputtering targets. By optimizing sintering process parameters such as temperature, time and pressure, the density of the target can be significantly increased. Common sintering methods include hot press sintering, atmosphere sintering and discharge plasma sintering (SPS).

Hot press sintering: Sintering at high temperature and pressure can promote the bonding between particles, thereby increasing the density.

Atmosphere sintering: Sintering in a specific atmosphere, such as hydrogen or inert gases, can reduce oxidation and other chemical reactions and maintain a high purity of the material.

Discharge plasma sintering (SPS) : The use of pulsed current plasma to rapidly heat powders, achieving rapid densification while maintaining a high purity of the material.

Three, multiple rounds of purification technology

In order to further improve the purity of the sputtering target, the purification technology of multiple rounds can be used. These techniques include electron beam melting, zone melting and vacuum distillation.

Electron beam melting: The use of high-energy electron beams to melt raw materials can effectively remove volatile and non-volatile impurities.

Zone melting: The impurities are concentrated in the melt zone by local heating, and then the pure material is separated by moving the melt zone.

Vacuum distillation: Distillation in a high vacuum environment, using the difference in the boiling point of different elements to separate, resulting in a higher purity of the material.

Fourth, surface treatment technology

Even if high purity is achieved inside the target, surface contamination can affect its performance. Therefore, surface treatment technology is equally important. Common surface treatment techniques include mechanical polishing, chemical polishing and electrolytic polishing.

Mechanical polishing: Physical grinding removes oxides and other contaminants from the surface.

Chemical polishing: The use of specific chemical agents to dissolve the surface of the impurity, obtain a smooth surface.

Electrolytic polishing: The small bumps and impurities on the surface are removed by electrochemical reaction in the electrolyte to obtain a flat surface.

5. Control the production environment

In the entire production process, strict control of environmental conditions is also the key to improve the density and purity of the sputtering target. This includes measures such as the construction of dust-free workshops, the use of high vacuum systems and inert gas protection.

Dust-free workshop: reduce dust and microbial pollution in the air.

High vacuum systems: Reduce the content of oxygen and other active gases, reducing oxidation and other chemical reactions.

Inert gas protection: The use of inert gases such as argon or nitrogen during high-temperature treatment prevents the material from reacting with oxygen in the air.

Improving the density and purity of the sputtering target is a comprehensive process involving the selection of raw materials, the optimization of the production process, the application of surface treatment technology and the strict control of the production environment. Through the comprehensive application of the above methods, the performance of sputtering targets can be significantly improved to meet the needs of modern high-tech industry for high-quality sputtering targets. With the continuous development of new materials and new processes, the density and purity of sputtering targets will be further improved in the future.