The semiconductor industry has an irreplaceable position in the development of global science technology and economy. Semiconductor wafer handling equipment is one of the most important equipment in the semiconductor industry processing process. When transferring wafers, ceramic robotic arms are used to grab and clamp semiconductor wafers. Advanced ceramic materials are widely used to prepare ceramic arms (also called handling arms) for the pan-semiconductor field due to their excellent wear resistance, corrosion resistance, low expansion coefficient, and other properties.
There are tens of millions of chip manufacturing processes, and the “handling process” is naturally indispensable. In the process of moving wafers from process A to process B, how to repeatedly carry and process wafers at high speed and cleanly has a huge impact on the quality of the finished wafers.
“High speed” and “cleanliness” are the core characteristics of semiconductor wafer handling equipment. To meet these characteristics, the equipment has extremely demanding performance requirements for the components used. Since most processes are carried out in a vacuum, high-temperature, and corrosive gas environment, the handling arm used in the equipment must have excellent physical properties, such as high mechanical strength, corrosion resistance, high-temperature resistance, wear resistance, high hardness, insulation, etc.
During the operation of semiconductor equipment, ceramic arms are needed to transport wafers. Because the silicon wafers cannot be contaminated, they are generally carried out in a vacuum-clean environment. In a vacuum environment, most robotic arms made of other materials cannot meet the requirements. At this time, ceramic arms with high-temperature resistance, wear resistance, and high hardness are needed to complete the work.
Advantages of ceramic robotic arms:
1 Ceramic robotic arms are more resistant to acid corrosion and alkali corrosion. They have a longer service life during various semiconductor processing;
2 Ceramic robotic arms do not easy to react with other substances, will not leave contaminated fine particles and charged charges on contact objects, will not produce metal ions, and will not contaminate semiconductor parts;
3 When the semiconductor is heat treated, the ceramic robotic arm is less deformed by heat, reducing the deformation of semiconductor parts during heat treatment.
Materials of ceramic arms for semiconductor equipment
People usually use high-purity alumina and silicon carbide to prepare ceramic arms. Both raw materials have physical properties such as high hardness, good wear resistance, and high-temperature resistance, and are excellent materials for preparing ceramic arms.
– Alumina can be used to prepare most semiconductor ceramic parts. Depending on its content, the performance of the prepared products is also different. Alumina ceramic parts with a purity of 95% are light yellow, and alumina ceramic products with a purity of 99% are white. It has excellent rigidity, strength, and durability, and is resistant to high temperature, corrosion, and plasma erosion.
-Silicon carbide ceramics are black, have high thermal conductivity, high strength, and high hardness, are not easy to deform, have good shock resistance, and are also resistant to high temperature and corrosion; compared with alumina ceramics, it is light in weight.
Compared with these two materials, the performance of the ceramic arm made of silicon carbide is better than that of the alumina ceramic arm. However, compared with the material price and processing difficulty, the ceramic arm made of alumina is more cost-effective, and alumina ceramic arms are usually used more.
The technical barriers of ceramic robotic arms are relatively high.
The ceramic robotic arm adopts the Bernoulli principle: the gas introduced by the supply port will be ejected at high speed from the nozzle on the inner cylindrical side of the suction cup, and a rotating airflow will be formed in the cylindrical space inside the suction cup, and a negative pressure will be formed. The airflow is finally released to the outside space through the gap between the mechanical finger adsorption surface and the wafer surface. The airflow forms a stable laminar flow in the space between the cyclone suction cup and the wafer, causes a pressure difference between the upper and lower surfaces of the wafer, and finally forms an upward adsorption force on the wafer.
There are pores and ventilation grooves inside the ceramic arm. The grasping and placing actions of the ceramic arm are generally achieved through vacuum adsorption and release. When the air is pumped, a vacuum can be formed to adsorb the wafer. It must be fast and gentle, and no impact or vibration can be generated. The suction device will not damage the wafer during the process of grabbing the sheet, and it cannot bring any pollution to the entire production operation room. There are two main methods for preparing ceramic arms at present: one is to first fine-process the ceramic plates, and then rely on the combination of ceramic plates to form an airway. The ceramic plates are usually fixed with an adhesive, but the adhesive will gradually age with the increase of use time and is difficult to use in harsh environments such as high temperature and corrosion, resulting in short service life of the ceramic arm. The other is to introduce an inner model core for co-molding to prepare a ceramic blank, and then remove the core by physical or chemical methods, and finally sinter to obtain a ceramic arm with a closed airway. The manufacturing technology of ceramic arms is difficult and needs to meet indicators such as processing accuracy, corrosion resistance, sealing, cleanliness, and vacuum. It is necessary to ensure that the ceramic arm has zero pores, zero cracks, and zero defects, and to ensure the product performance and service life of the ceramic arm, so as to ultimately achieve the stability of the semiconductor equipment process in a vacuum environment.