AVS 53rd International Symposium
    Plasma Science and Technology Friday Sessions
       Session PS1-FrM

Paper PS1-FrM9
An In-situ Diagnostic to Detect Charging During Plasma Etching

Friday, November 17, 2006, 10:40 am, Room 2009

Session: Plasma-Surface Interactions III
Presenter: E. Ritz, University of Illinois at Urbana-Champaign
Authors: E. Ritz, University of Illinois at Urbana-Champaign
D. Ruzic, University of Illinois at Urbana-Champaign
Correspondent: Click to Email
In plasma etching processes, especially those with high aspect ratios, it is known that defects can occur such as trenching, bowing, and twisting. These defects are particularly noteworthy in the manufacture of DRAM deep-trench capacitors. In order to investigate the role of charging on these phenomena an in-situ diagnostic was fabricated using photolithographic and deposition techniques. The device consists of a base layer of tungsten with alternating layers of silica and tungsten. During the construction of the device, vias are integrated into the layout, extending all the way from the top surface to the substrate. The silica layers act as insulators to create discrete measurement layers, provided by the tungsten layers. The tungsten layers are attached to voltage measurement leads and can then be used to measure the build up of sidewall charging at different heights along the via when exposed to a plasma. To determine the effect of geometry, if any, on charging, several aspect ratios were used by maintaining the same device thickness but varying the diameter of the vias. The entire stack is 30 microns thick, with vias ranging in diameter from 30 microns to only 1 micron, thereby producing aspect ratios of 1:1 to 30:1. Results from the diagnostic will be shown for various etching recipes.