Why do the manufacturing stages of some semiconductor components have to be done in a vacuum?
The manufacture of semiconductor components and the need for an ultra-clean environment have some sequence of steps that need to be carried out in a vacuum. There are large amounts of nitrogen, oxygen, and other types of gas molecules in the atmosphere we live in. These gas molecules are always in a state of motion. When they move to the object’s surface, there will be a part sticking to that surface. In everyday life, that wouldn’t make much of an impact. But for the production sequence of semiconductor components with extremely high requirements on the surrounding environment, that small change is enough to cause trouble for production.
Each semiconductor component is composed of many material layers of many types. If there are mixed gas molecules between the layers of different materials, the component’s optical or electrical performance will be damaged. For example, suppose you want to grow one more crystal layer on the crystal layer (called the outer layer). In that case, the gas molecule is attracted by the bottom layer crystal surface, which will prevent the atom above to arrange orderly according to the lattice structure. The result is many defects in the peripheral layer, more importantly, not even growing crystalline, but an only polycrystalline or non-crystalline disordered arrangement both.
Under one atmosphere’s condition, every second is subjected to several hundred million gases molecular impacts on every crystal surface point. Therefore, to obtain a clean, crystalline surface, it is usually necessary to bring the molecular gas density down to a few hundredths of a million atmospheric density, that is to say, a vacuum environment. To do that, people make sealed boxes of all kinds, and invented all kinds of vacuum pumps, which draw the air out of them, making the inside of the box a true environment. are not. Lots of semiconductor components, such as laser discs (CDs, VCDs, and DVDs) and semiconductor lasers in fiber-optic communications, microwave integrated circuits in radar or satellite communications equipment, even multiple circuits Ordinary electronics, there are many processing steps, many parts must be done in the vacuum box—the higher the vacuum level, the better the performance of the manufactured semiconductor components. Today, many high-performance semiconductor components are made in ultra-high vacuum environments. To get the so-called super-high vacuum, the molecular gas density is only a few hundred billion to a few hundred trillion of the atmosphere! The ultra-high vacuum environment requires an extremely complex air extraction system that is very expensive.
Besides, in the processing of semiconductor components, it is necessary to use particles such as electron beams, ion beams, molecular beams, etc., to conduct irradiation and shelling of the material. In the atmosphere, gas molecules can collide with these particles, greatly shortening their paths, resulting in the vast majority of particles failing to reach the material surface. Placing these machining processes in a vacuum can avoid the problem.