Ion implanter
The ion implanter consists of 5 parts: ion source, ion extraction and mass analyzer, acceleration tube, scanning system, and process chamber.
source of ion
The ion implanter uses the hot electrons generated by the filament in the ion source to bombard gas molecules under the action of an electric field to ionize them. If the impurity source to be implanted is in a gaseous state, it can be directly introduced into the electric field of the ion source. If it is in a solid state, it needs to be heated and evaporated, and then introduced into the electric field after it becomes a gaseous phase. Impurity sources in the gas phase become ions (ie, charged atoms or molecules) after being ionized in an electric field.
Ion extraction and mass analyzer
All positively charged ions are extracted from a slit by the positive pressure repelling of the anode of the ion source, and the electrons in the plasma are repelled by the cathode and are blocked, thus forming an ion beam composed of positive ions. Thermionic bombardment of impurity source gas molecules will produce a variety of ions, such as boron trifluoride gas source, in the ion source will form a variety of ions, such as , , , and , and the mass-to-charge ratio of each ion is different. When the analysis magnet is used, the ion trajectory will be different, and the mass analyzer of the ion implanter can separate the desired impurity ions from the mixed ion beam.
accelerator tube
To enable the ions to obtain greater energy, the positive ions must obtain the required velocity through the high pressure of the accelerating tube after they come out of the mass analyzer. The accelerating tube consists of a series of electrodes separated by a medium, and the negative voltage on the electrodes increases sequentially. When the positive ions enter the accelerating tube, each negative electrode accelerates the ions, and the moving speed of the ions is the superposition of the acceleration at all levels. The higher the total voltage, the faster the moving speed of the ions, that is, the greater the kinetic energy.
scan system
The scanning system of the ion implanter constitutes the relative motion between the ion beam and the silicon wafer. In order to make the impurities on the silicon wafer evenly distributed, to avoid the local overheating caused by the bombardment of ions for a long time, causing irreversible damage, the ions of the silicon wafer are The injection is done by scanning. There are two basic scanning methods: mechanical scanning and electromagnetic scanning. The mechanical scanning adopts the method of moving the silicon wafer, that is, the target disk drives the silicon wafer to move. Electromagnetic scanning is the use of electromagnetic fields to deflect the ion beam to achieve scanning. Some injectors also use a hybrid method, that is, a combination of mechanical and electromagnetic methods.
process chamber
The process chamber includes a target plate for placing silicon wafers, a scanning system, a wafer loading and unloading terminal table with a vacuum lock, a wafer transport system and a computer control system.
