AVS 57th International Symposium & Exhibition
    Plasma Science and Technology Wednesday Sessions
       Session PS+MN-WeM

Paper PS+MN-WeM1
High Etch Rate of TSV using by Ultra Self-Confined VHF-CCP

Wednesday, October 20, 2010, 8:00 am, Room Galisteo

Session: Plasma Processing for 3D Integration, TSV, and MEMS
Presenter: Y. Morikawa, ULVAC, Inc., Japan
Authors: Y. Morikawa, ULVAC, Inc., Japan
M. Yoshii, ULVAC, Inc., Japan
N. Mizutani, ULVAC, Inc., Japan
K. Suu, ULVAC, Inc., Japan
Correspondent: Click to Email
Thru silicon via (TSV) etch process for deep and high-aspect ratio structure has been studied thoroughly for applications such as MEMS devices. Recently, TSV used in 3D-LSI devices, the via diameter and depth would be several tens of microns, and, the package for CMOS image sensors using TSV may have via diameters and depths up to 100 microns. A diameter of above 50um account for 50 % of TSVs. Therefore, development of high etch rate about 50um via is very important for realizing these applications. In this study, a large via size of 50 um etching in a low-pressure process was focused by using very high frequency capacitive coupled plasma (VHF –CCP) with an ultra self-confined system. This plasma system is simple parallel plate CCP. And the cathode has a structure designed to minimize the stray capacitance (Cs) and impedance (L) to get a low-pressure process of about 100Pa or more. Low-pressure process was carried out on the plasma confined, because mean free pass is very short. And, ion energy distribution (IED) is also controllable by low-presser process with VHF bias. The bimodal IED changes under low-pressure. The peak of high-energy side is reduced, and a charge exchange peak appears. It is considered that the charge exchange is important to anisotropic Si etching with VHF bias. Finally, an etch rate of more than 60 μm/min was realized. It was found that the Si etch rate depended on fluorine radical density and ion energy distribution, so, the high rate was obtained by creating a high fluorine radical density condition by using a high pressure condition of 100Pa using a VHF-CCP reactor with an ultra confined system and SF6 gas chemistry.