Paper PS-TuP12
Critical Dimension Shrink and Control with Different Frequency Source Powers in Dielectric Etch Chamber for 45nm Technology and Beyond

Tuesday, October 16, 2007, 6:00 pm, Room 4C

The Critical Dimension (CD) shrink from BARC was invested by using the capacitive coupled plasma etcher with high frequency source due to BARC open step is the most critical in dielectric etch. Two frequencies (<100MHz vs >100 MHz) source power with different plasma densities were compared. It was found that the CD shrink was related to the CF2 species that were excited from source and>100 MHz source power showed the strong control knob on CD shrink comparing to <100MHz. Chemistry selection and process control knobs have been evaluated and it was found that the CD shrink was basically controlled by pressure, polymer gas, and source power. And a maximum >60nm CD shrink bias was obtained when profile and final CD range was maintained in the spec. (1) CD bias comparison on the BARC open with and without source power indicated source power strong effect on CD shrink. The CF2 radical emission in etching plasma were collected by the optical emission spectroscopy (OES) as shown to evaluate the difference on the CD shrink when other process parameters changed . It was found that the >100 MHz source provided the efficient generation of CF2 radical density that resulted in more CD shrink. The CD shrink varied with different source power for both frequencies and it showed the more CD shrinks with high source power. The CF2 species density without source power showed lowest signal and the strongest emission with the high source power, which was pretty much consistent with the wafer results. (2) CHF3 flow on BARC open was tested at different pressure and the high CHF3 gas flow and low pressure were showing strong knobs on CD shrink control with source power. It was known that CF2 was one of many species from CHF3 dissociation during the plasma etch and more CF2 has been generated with high frequency power, which deposited on the sidewall to protect the isotropic etch and therefore made the top CD shrink. With the low CHF3, the CD shrink range was much bigger than high CHF3 flow with pressure change. The CF2 species density explained why high source power and low pressure as the knobs on CD shrink control. (3) The production-like runs on customerâ?Ts wafers were tested with two source powers and both showed CD shrink consistently repeatable. The high frequency source power provided the high plasma density as the strong knob for CD shrink and meantime allowed the high efficiency wafer-less dry clean, which benefited APF etch clean mode requirement.