Carlos Eduardo Viana, Ana Neilde R. da Silva, Nilton Itiro Morimoto, LSI-DMI-EPUSP.
Plasma Enhanced Chemical Vapor Deposition (PECVD) by using TEOS as silicon source is now a well-known technique to deposit silicon oxide thin films. The advantage of this technique is to deposit silicon oxide at low temperature that is compatible with a large range of applications. Indeed, as well in very large integrated circuit process with very thin junction as in large area electronics using glass substrates, a temperature lower than 600°C is required. A high deposition rate is also needed for industrial point of view, and some additional studies in this way are in progress. A way to modify the deposition rate is to use a mixture of argon and TEOS in the plasma. In this work, we analyze the influence of the argon flow on the silicon oxide thin films deposited by PECVD onto silicon substrate. The presence of argon modifies the deposition rate but also can affect the plasma composition and thus can create some defects more especially at the Si/SiO2 interface. After a presentation of the experimental conditions of the developed process, several explanations of the observed phenomena are proposed on the base of physical analyses.
The substrate, in single wafer PECVD reactors, is in direct contact with the plasma, thus the sample is in constant ions, electrons and photons bombardment. Ions bombardment on silicon oxide films during the deposition process results in poor electronic properties. However, the ions bombardment also activates the surface sites which promotes the film growth and densifies the film. In rf diode discharges, where the ion energy can exceed hundreds of eV, the substrate has higher probability to be damaged.
We observed that adding argon in the gas mixture in the PETEOS silicon oxide deposition process the quality of the film is drastically improved. In order to understand the physical and chemical mechanisms of the influence of the argon in the deposition process, we are developing this work which the first results are present below.
The silicon oxide deposition process was carried out in the following basic conditions: process pressure (P) of 1 Torr; temperature (T) of 375°C; TEOS flow (FTEOS) of 7.0 sccm oxygen flow (FO2) of 450 sccm and RF power (Wrf) of 400 W.
We can conclude that adding an argon flow in the gas mixture in the PECVD silicon oxide deposition process cause a high influence in the deposition rate and uniformity of the deposited layer. However, the physical and chemical mechanisms is not well understood.
XXI CONGRESSO BRASILEIRO DE APLICAÇÕES DE VÁCUO NA INDÚSTRIA E NA CIÊNCIA - XXI CBRAVIC.
28 A 30 DE JULHO DE 1998 - ITA - São José dos Campos - SP.