Reducing twisting in ultra-high aspect ratio dielectric etch

Abstract

An apparatus for etching a dielectric layer contained by a substrate is provided. An etch reactor comprises a top electrode and a bottom electrode. An etch gas source supplies an etch gas into the etch reactor. A first Radio Frequency (RF) source generates a first RF power with a first frequency and supplies the first RF power into the etch reactor, whereas the first frequency is between 100 kilo Hertz (kHz) and 600 kHz. A second RF source generates a second RF power with a second frequency and supplies the second RF power into the etch reactor, whereas the second frequency is at least 10 mega Hertz (MHz).

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to the fabrication of semiconductor devices.[0002]Plasma-etching processes are commonly used in the fabrication of semiconductor devices. Generally, photoresist material forms feature patterns on the surface of the wafer to be etched, and features are then etched into the wafer by exposing the wafer to a particular type of etching gas. One of the challenges faced in plasma etching is the ever-increasing aspect ratio needed to meet design requirements, especially for ultra-high density structures. When etching features on semiconductor wafers, the aspect ratio of an etched feature is defined as the ratio between the feature's depth (d) and the feature's width (w) or diameter. As more features are packed on a single piece of wafer to create higher density structures, the width (w) or diameter of each individual feature necessarily decreases, while the depth of the features remains unchanged. Thus, the aspect ratio of each ...

AI Technical Summary

Benefits of technology

[0007]To achieve the foregoing and in accordance with the purpose of the present invention, an apparatus for etching a dielectric layer over a substrate is provided. An etch reactor comprises a top electrode and a bottom electrode. An etch gas source supplies etch gas into the etch reactor. A first Radio Frequency (RF) source generates a first RF power with a first frequency and supplies the first RF power into the etch reactor, whereas the first frequency is between 100 kilo Hertz (kHz) and 600 kHz. A second RF source generates a second RF power with a second frequency and supplies the second RF power into the etch reactor, whereas the second frequency is at least 10 mega Hertz (MHz).

Problems solved by technology

One of the challenges faced in plasma etching is the ever-increasing aspect ratio needed to meet design requirements, especially for ultra-high density structures.

A new difficulty emerged recently during ultra-high aspect ratio (UHAR) etch is twisting, which is generally defined as deviations of location, orientation, shape, and size near the bottom of a feature from the pattern defined by the mask on the top of the feature.

When twisting occurs, the oval-shaped cross-section is not perfect in size, position, orientation, shape, or a combination thereof.

All forms of twisting result in defects and device failures.

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