Reactive-ion-etching (RIE) process in CF4 plasma as a method of fluorine implantation

We have investigated the concentration of fluorine in a newly formed film, which is located on the etched surface during modification of thermal silicon dioxide layer in reactive-ion-etching (RIE) system in CF4 plasma. We try to find the correlation between parameters of the RIE process, depth and concentration of implanted fluorine ions, and finally, the thermal stability of fluorine ions incorporated into etched layer.During the RIE of silicon dioxide in fluorine plasma, on the etched surface a layer containing fluorine atoms is formed. This layer is very thin (about 1.5 nm) and has high concentration of fluorine ions. This concentration can be changed with r.f. power, CF4 gas pressure and CF4 flow. The suitable selection of etching parameters makes inspection of concentration and of the depth of fluorine ions incorporated into silicon possible, during the etching process. Unfortunately, ultra-shallow junction formed in this way does not show resistance to high temperature. So it is recommended only for low-budget technologies.