Improving dry etch control for contact plugs in advanced DRAM manufacturing

Tianming Bao; Yuval Bar; David Fong; Mukund Godbole

doi:10.1117/12.770789

25 March 2008 Improving dry etch control for contact plugs in advanced DRAM manufacturing

Tianming Bao, Yuval Bar, David Fong, Mukund Godbole

Proceedings Volume 6922, Metrology, Inspection, and Process Control for Microlithography XXII; 69223G (2008) https://doi.org/10.1117/12.770789
Event: SPIE Advanced Lithography, 2008, San Jose, California, United States

Abstract

In advanced DRAM manufacturing, the process scaling to increase memory cell density creates a difficult challenge for conventional optical or SEM metrology tools to characterize wafer surface profiles after plasma etching. Dry plasma etch processes are used to form critical contact plugs within a stacked capacitor DRAM cell, two of which will be discussed in this article. One contact plug connects a buried digit line to an active area in array, while another contact plug connects a capacitor container to an active area through the first plug. In both cases, the etched surface structure features a complex three-dimensional (3D) topography with a minimum space at ~50nm (see Figure 1). Etch profiles are directly related to the DRAM yield and must be monitored inline. Scanning probe based atomic force microscopy (AFM) is particularly beneficial for this type of dimension measurements. This article presents the methodology and recent results of applying AFM as inline metrology for contact etch control at 70nm node and below. AFM is an advanced, high-resolution 3D imaging tool. It provides nondestructive and direct in-die measurements of the active circuit region on product wafers at the contact etch steps and other critical process layers. Calculated automatically from AFM images, the dry etch depth is used as inline metrology for process control and is a critical metric for process optimization.

Citation Download Citation

Tianming Bao, Yuval Bar, David Fong, and Mukund Godbole "Improving dry etch control for contact plugs in advanced DRAM manufacturing", Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 69223G (25 March 2008); https://doi.org/10.1117/12.770789

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