Abstract
The difficulty in the use of spin-on-glass (SOG) for multilevel interconnections leads to the requirement of higher-temperature (800~850℃) curing of the material, since the low-temperature annealed SOG may result in a significant amount of moisture during subsequent heat cycles leading to reliability problems.However, the application of an ion implantation method can improve the outgassing behavior of SOG annealed at 425℃. The temperature of the ion implantation treatment is made lower so as to be compatible with aluminum which is used as the conductive material. Ion implantation treatment using P (phosphorous) and As+ (arsenic) which are applied to the siloxane-type SOG is proposed in this research. The thermal desorption analysis from experiments shows that the implanted SOG has a much lower water content and does not have a moisture desorption peak up to 600℃ for both P+ and As+ implantations. The combination of the thermal curing and ion implantation treatment is beneficial for reducing the residual moisture content and promoting the thermal stability of SOG films. In addition, the results show that the implanted SOG is less sensitive to moisture absorption than the unimplanted SOG under the condition of 48-h air exposure. This implies that both water reabsorption and desorption performances of SOG can be further improved by ion implantation. Furthermore, the alkyl radicals in the organic SOG film are drastically reduced by this application. The deterioration caused by 02 ashing is also improved due to the previous decomposition of alkyl groups by ion bombardment. The results show that these degradations can be successfully improved through this approach. These improvements result from that the implanted region is physically densified by filling incident ions to form a blocking layer. Through this application, it is useful in both modifying the siloxane SOG and lowering the thermal budget in Si-LSI process.