BCB etching Process using High Density Plasma

I.Toledo, R.Adler, Y. Knafo, O.Kalis , J.Kaplun
Gal-El (MMIC), P.O.B. 330, Ashdod 77102, Israel, Tel. +972-8-8572739
*Corresponding author email: itoledo@elta.co.il

Keywords: BCB (Bisbenzocyclotene), High Density Plasma, CF4, CHF3, Process

Abstract
BCB (Bisbenzocyclotene) material is widely used throughout semiconductors industry as interconnect structure filler or chip capsulate, mainly because it is a low-K dielectric material which causes low tangent loss at high frequency. This work presents systematic research based on the design of experiment (DoE) approach for BCB etching and integration in to the process flow in order to decrease the number of process steps and time. DoE parameters were ICP power, RIE power and two different gas mixtures CF4+8.5%O2/O2/Ar and CHF3/O2/Ar. Empirical models constructed from the DoE results permit to evaluate the impact of the process parameter on the etching rate of the BCB. Etching rate as high as ~1 um/min BCB on 3” GaAs was achieved.
Cleaning process after etching step is important for chip assemble bonding and reliability. Deferent chemical strippers EKC 830,505 and NMP were tested to achieve optimized cleaning process, the success criteria for this step was no side wall residue and clean surface.
The improved process decreased wafer etching cycle time by 75%, reduced total process steps and left clean open areas. The new process did not change the device performances.
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