As the dimension of transisters shrinks below the 0.5 ㎛ level, their speed will be limited by the delays in the existing interconnect materials, Al-Cu-Si alloy(ρ~3μΩ cm). So it will be necessary to construct interconnection materials that possess lower resistivites, strong resistance to electromigration, stress-migration, and hillock formation. Of all possible materials, copper is considered as the most probable interconnection material. But, plasma dry etching of copper have not been met with successful results. Plasma etching of photoresist masked copper films of this study was carried out by an electron cyclotron resonance apparatus. Etching gas was chlorine. Copper film was deposited on W or TiN films which were deposited on silicon substrate. Base pressure of chamber was $8\times10^{-6}$ Torr. Flow rate of chlorine was 10 sccm, and at that chlorine flow rate the operational pressure of chamber was 3.5 mTorr. Etching time was set to 3 minutes. After etching experiment the specimens were investigated by X-ray diffraction and scanning electron microscopy to see how the conditions of specimens were changed. Copper was not etched up to substrate temperature of 205℃ when substrate self-bias was not applied. But copper was reacted with chlorine, and has changed to copper(I) chloride(CuCl). Because CuCl has a very low vapor pressure, it is assumed that CuCl cannot be desorbed just by raising substrate temperature. But copper film was etched even at room temperature when self-bias of substrate was applied above 25 V. When self-bias was applied above 50 V to the substrate, not also barrier metals(W or TiN), but also Si substrate were etched, and photoresist mask was hardened by collision of chlorine ions. These results can be explained that energetic chlorine ions collide on CuCl, and CuCl is desorbed by the incoming chlorine ions. So etching of copper depends more on physical effect than on thermal effect in this study using electron cyclotron resonance plasma system. Important result of this study is that copper was etched by chlorine plasma at room temperature using electron cyclotron resonance apparatus.
