AVS 50th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuA

Paper PS-TuA5
Bilayer Mask Process for sub-90 nm Patterning using a New 100MHz CCP RIE

Tuesday, November 4, 2003, 3:20 pm, Room 315

Session: Dielectric Etch
Presenter: H. Hayashi, TOSHIBA Corporation Semiconductor Company, Japan
Authors: H. Hayashi, TOSHIBA Corporation Semiconductor Company, Japan
J. Abe, TOSHIBA Corporation Semiconductor Company, Japan
A. Kojima, TOSHIBA Corporation Semiconductor Company, Japan
J. Nishiwaki, TOSHIBA Corporation Semiconductor Company, Japan
A. Takase, TOSHIBA Corporation Semiconductor Company, Japan
K. Sho, TOSHIBA Corporation Semiconductor Company, Japan
E. Shiobara, TOSHIBA Corporation Semiconductor Company, Japan
I. Sakai, TOSHIBA Corporation Semiconductor Company, Japan
E. Shinomiya, TOSHIBA Corporation Semiconductor Company, Japan
T. Ohiwa, TOSHIBA Corporation Semiconductor Company, Japan
Correspondent: Click to Email
Shrinkage of LSI design rule, especially to sub-90 nm nodes, necessitates the reduction of photoresist thickness to maintain the process window in deep UV lithography. However, thinning the resist layer leads to critical dimension (CD) loss in the subsequent etch process due to resist erosion. A bilayer mask process, in which patterns formed at the Si-containing resist layer are transferred to spun-on-carbon film having anti-reflective property, is a promising candidate for sub-90 nm patterning. However, this process can be used only if carbon film etching with high selectivity to the thin Si-containing ArF resist is realized. In this paper, a new reactive ion etching (RIE) employing 100 MHz capacitive coupled plasma (CCP) where the wafer is placed on the cathode, is proposed. By introducing the high frequency of 100 MHz, low ion energy and high selectivity could be expected. Self-bias voltages (Vdc) generated in the 100 MHz Ar plasma at 40 mTorr were 20 to 90 V depending on RF power, less than 1/3 those of the 13.56 MHz plasma which were 290 to 540 V under the same conditions. As a result, the carbon film etch process using the 100 MHz plasma in hydrogen based gas chemistry showed great improvement of selectivity, to more than 8. Etch rates of the carbon film were 200 to 300 nm/min at the pressures of 5 to 100 mTorr. Finally, the etch profile of a pattern with a resist thickness of 150 nm and carbon 300 nm thick was examined, and it was found that a vertical carbon etch profile was obtained, with less faceting of the Si-containing resist mask. The ArF bilayer mask process combined with the new 100 MHz CCP proves to be the most effective patterning process for devices of 90 nm and below.