Targets and wafers are essential materials in the preparation of microelectronic semiconductor integrated circuits. In the optical disk, liquid crystal flat display, LCD and other technical fields, the requirements of targets are different and targets with a variety of performance are needed. Wafers are the basic raw materials for making semiconductor devices. Wafers are obtained by pulling and slicing of extremely high purity semiconductors. Furthermore, after a series of semiconductor manufacturing processes, extremely tiny circuit structures could be formed and then they will turn into chips through cutting, packaging and testing, which are widely used in various kinds of electronic equipment.
- Information storage field: Targets with high quality, special crystallization and components are widely used in information storage fields, including hard disk, optical disk, magnetic disk and the others.
- Optical devices field: Wafers are widely used in optical devices field, including LED light-emitting diodes, LD laser diodes, PD optical receivers, and the others. Among them, LED light-emitting diodes takes the largest proportion.
- Electronic devices field: The electronic devices used wafers include PA power amplifiers, LNA low noise amplifiers, RF switches, digital-to-analog converters, power semiconductor devices and the others.
- The others: Wafers can also be used in many fields, such as smart phones, satellite communications, mobile communications, optical communications, GPS navigation and the others.
According to the composition, the targets can be divided into pure metal, alloy and compound targets.
- Pure metal targets: Pure metal targets mainly include Al, Au, Cr, Co, Ni, Cu, Mo and the others.
- Alloy metal targets: Alloy metal targets include Ni - Cr, Co - Ni, Co - Cr, Tb – Fe - Co, Gd – Fe - Co, and the others.
- Compound targets: Compound targets can be classified into oxides, silicides, carbides, sulfides and the others.
Wafers can be divided into first, second, and third generations according to the order in which they developed.
- First - generation wafers: First - generation wafers are germanium (Ge) and silicon (Si). Silicon has the advantages of abundant reserves, mature purification and crystallization process, and the silicon dioxide (SiO2) thin film formed by oxidation has good insulation performance, which can greatly improve the stability and reliability of devices. Therefore, silicon has become the most widely used wafers materials.
Figure 1. A picture of silicon wafer.
- Second - generation wafers: Gallium arsenide (GaAs) and indium phosphide (InP) are the representatives of second-generation wafer, which are mainly used to make light-emitting electronic devices that are high-speed, high-frequency and high-power. However, GaAs and InP wafers are scarce, expensive and toxic, which can pollute the environment. InP is even considered as a suspected carcinogen.
- Third - generation wafers: The third - generation wafers with wide band gap width mainly include SiC, GaN and the others. Compared with the first - generation and second - generation wafers, the third - generation wafers with high heat conductivity, high breakdown voltage, high saturated electron drift velocity and high bonding energy, can meet the demands of the modern electronic technology.