AVS 45th International Symposium
    Plasma Science and Technology Division Monday Sessions
       Session PS-MoM

Paper PS-MoM1
The Independence of Feature Profile Evolution on Mask Charging During Chlorine Plasma Etching of Si (100)

Monday, November 2, 1998, 8:20 am, Room 318/319/320

Session: Feature Evolution
Presenter: J.T.C. Lee, Bell Laboratories, Lucent Technologies
Authors: K.H.A. Bogart, Bell Laboratories, Lucent Technologies
F.P. Klemens, Bell Laboratories, Lucent Technologies
V.M. Donnelly, Bell Laboratories, Lucent Technologies
J.T.C. Lee, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
Non-ideal feature profiles including sidewall undercutting or bowing and microtrench formation at the feature bottom are often observed for crystalline (100) silicon (Si) with silicon dioxide (SiO@sub 2@) masks etched in pure chlorine (Cl@sub 2@) plasmas. Localized charging of the mask with respect to the underlying Si has been suggested as one possible cause for flawed profiles. Cl@sub 2@ plasma etching of Si (100) wafers (150 mm p-type, 4-200 @OMEGA@cm) with an insulating SiO@sub 2@ mask and patterned Si (100) wafers without a mask were compared directly to determine the effect of mask charging on the resulting feature profile. Etching was performed in a TCP plasma reactor (250 and 500 W rf source and 150 W rf bias power) at 2 and 10 mTorr Cl@sub 2@ . The pattern (nested and isolated lines and trenches) was transferred into the no-mask Si wafers by etching through a SiO@sub 2@ mask with a hydrogen bromide plasma, producing trenches with nearly vertical sidewalls and flat trench bottoms. The SiO@sub 2@ mask was removed in aqueous hydrofluoric acid, and the line and trench pattern was further propagated into the Si wafer by etching in Cl@sub 2@ plasmas under various conditions. In the latter case, the pattern through which etching proceeded was composed only of Si and was not insulating, but conductive. Therefore, localized charging of the patterned Si did not occur. Cross sectional scanning electron micrographs were used to compare feature profiles. In general, wafers etched with the insulating SiO@sub 2@ mask had line and trench profiles with bowed or tapered sidewalls and pronounced microtrenches. Wafers etched in the absence of the insulating SiO@sub 2@ mask showed nearly identical feature profiles. Therefore, localized charging of the insulating SiO@sub 2@2 mask is not a primary cause of sidewall bowing or microtrenching for Cl@sub 2@ plasma etching of Si under these conditions.