Method and apparatus for nitride spacer etch process implementing in situ interferometry endpoint detection and non-interferometry endpoint monitoring

Abstract

An in situ dual-stage etch endpoint detection system is disclosed. The system includes an etch chamber, an interferometry endpoint monitoring system, and a non-IEP endpoint monitoring system. The etch chamber includes an electrostatic chuck (ESC), a top electrode, and a bottom electrode. The ESC is designed to support a wafer having a spacer layer formed over a gate structure. The interferometry endpoint (IEP) monitoring system is designed to monitor an interference photon beam reflected by the top of spacer layer and the reflection beam on interface of bottom of spacer during a first etch operation. The non-IEP endpoint monitoring system monitors a second etch operation by monitoring an etch time. A first etch operation implementing the IEP monitoring system is discontinued, leaving a thin spacer layer to be etched during the second etch operation.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a of U.S. patent application Ser. No. 09 / 998,858, filed on Oct. 31, 2001, from which priority under 35 U.S.C. § 120 is claimed. The disclosure of this application is incorporated herein by reference in its entirety.BACKGROUND [0002] The present invention relates generally to the fabrication of semiconductor devices and, more particularly, to improving the fabrication of spacers by enhancing the etch endpoint detection of a nitride layer. DESCRIPTION OF THE RELATED ART [0003] As is well known, the semiconductor manufacturing process involves several stages during which millions of transistors including source / drain diffusion regions, a conductive polysilicon gate, and a dielectric gate oxide are fabricated on a single semiconductor chip. One of such fabrication stages is the silicon nitride spacer etch process during which a conformal layer of silicon nitride is deposited on a surface of the substrate having fabricate...

AI Technical Summary

Benefits of technology

The present invention provides an apparatus and method for fabricating nitride spacers using an in-situ two-step etch process that can precisely control the etch process and shape of the nitride spacers. The two-step in situ spacer etch process can accurately etch spacer layers having different thicknesses, reducing defects in wafers and increasing throughput. The process also increases tool reliability and production yield.

Problems solved by technology

However, this need is specifically more pronounced during the one step silicon nitride spacer etch process as the aggressive nature of the etch chemistry implemented inevitably results in gate oxide punch through leading to changes in gate oxide dimensions.

As is well known, changes to the gate oxide are disfavored since they modify the electrical conductivity of the gate oxide and thus the transistor.

Thus far, however, the OES method has proven to be less than reliable and efficient etch endpoint detection as it causes the overetching or underetching of the silicon nitride layer, rendering the outcome of the one-step etch process unpredictable.

Unfortunately, the unreliability and unpredictability associated with the OES method has a severe negative impact on fabrication stages and thus semiconductor manufacturing.

Among others, the unpredictability mandates the close monitoring of the one-step etch process, multiple inspections of the semiconductor substrate during the one-step etching operation, necessity to recalibrate the tools for each substrate within the same lot as well as different lots, thus needlessly wasting valuable time, slowing down the production, yield loss, and ultimately semiconductor substrate throughput.

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