AVS 45th International Symposium
    Plasma Science and Technology Division Tuesday Sessions
       Session PS2-TuM

Invited Paper PS2-TuM5
Analysis of C@sub 4@F@sub 8@/Ar/O@sub 2@ Plasma for High-aspect Contact Hole Etching using Narrow-gap RIE

Tuesday, November 3, 1998, 9:40 am, Room 318/319/320

Session: Oxide Etching
Presenter: T. Tatsumi, Association of Super-Advanced Electronics Technologies (ASET), Japan
Authors: T. Tatsumi, Association of Super-Advanced Electronics Technologies (ASET), Japan
H. Hayashi, Association of Super-Advanced Electronics Technologies (ASET), Japan
S. Morishita, Association of Super-Advanced Electronics Technologies (ASET), Japan
S. Noda, Association of Super-Advanced Electronics Technologies (ASET), Japan
Y. Hikosaka, Association of Super-Advanced Electronics Technologies (ASET), Japan
M. Okigawa, Association of Super-Advanced Electronics Technologies (ASET), Japan
M. Inoue, Association of Super-Advanced Electronics Technologies (ASET), Japan
M. Sekine, Association of Super-Advanced Electronics Technologies (ASET), Japan
Correspondent: Click to Email
Plasma characteristics and radical species in a dual-frequency (27/0.8MHz) parallel plate system were measured using various in-situ measurement tools, such as infrared laser absorption spectroscopy (IRLAS), appearance mass spectroscopy (AMS), and optical emission spectroscopy (OES). In particular, the densities of key radical species, C@sub x@F@sub y@, CF@sub x@, F, C, SiF@sub x@ and O were analyzed in conjunction with SiO@sub 2@ etch performance. We found that the radical composition could be controlled by limiting the number of collisions with electrons and the interaction with the wall materials, besides the composition of the inlet gases. The number of collisions with electrons can be described as @tau@N@sub e@<@sigma@v>, where @tau@ is residence time, N@sub e@ is electron density, @sigma@ is collision cross section of dissociation, and v is electron velocity. <@sigma@v> means integrated value of @sigma@v multiplied by normalized electron energy distribution function.@footnote 1@ When @tau@N@sub e@<@sigma@v> was large, C@sub 4@F@sub 8@ was dissociated excessively and the relative density of F radical increased. Under long-residence-time conditions, large molecules, such as C@sub x@F@sub y@ and SiF@sub x@, were also observed that were released from the top electrode surface made of Si. The etch rate and the selectivities to photoresist and underlying Si were affected by not only the [F]/[CF@sub x@] (x=1,2,3) ratio but also these depositive species, i.e., the large molecules. It was possible to suppress both the excessive dissociation of C@sub 4@F@sub 8@ and the excessive deposition of the large species under the short-residence-time condition. We achieved a 0.09 µm@phi@ contact hole with an aspect ratio of 11, under low [F]/[CF@sub x@] ratio plasma conditions established by a short residence time (6 ms), and under an optimized radical/ion flux ratio controlled by the Ar diluted process. @FootnoteText@ This work was supported by NEDO. @footnote 1@T.Tatsumi et al., Jpn. J. Appl. Phys., 37 (1998); to be published.