Endpoint detection in plasma etching

Abstract

Plasma etching is a main stream technology in integrated circuit fabrication. The general trend towards fine linewidths and decreasing thickness of underlying layers (etch stops) results in an increasing dependence on highly controlled plasma etch processes. Such tight control requires in situ process monitoring, particularly, for determination of the etch endpoint. This paper reviews the various methods for endpoint detection. A novel application of interferometric principles for very precise etch endpoint determination in high density circuits is described. A comparison of several methods used simultaneously in a plasma planarization process is presented. The etch endpoint can also be determined by monitoring the pressure change in the chamber upon completion of the etch. An application of this method to dielectric etching is demonstrated.

Fabrication of spintronic devices: etching endpoint detection by resistance measurement for magnetic tunnel junctions

“…Various techniques such as ion milling probe, optical emission spectroscopy, secondary ion mass spectroscopy, laser interferometry, atomic force microscopy and x-ray photoemission spectroscopy are used to serve this purpose [4][5][6][7][8][9][10][11][12]; however, they require expensive equipment and time-consuming, which can be a big obstacle for researchers wishing to optimize thin MTJs quickly. This ion milling step is critical; it should not stop before reaching M1 but it should not etch too much further after reaching M1.…”

Applying RF current harmonics for end-point detection during etching multi-layered substrates and cleaning discharge chambers with NF3 discharge

“…The time variation of the reflection coefficient of the film under etching is registered. Here, laser interferometry [27,30,31] as well as ellipsometry [32] may be used.…”

“…Another method consists in monitoring the discharge impedance [31,45] which varies due to variations in the chemical composition of the discharge at the end point of the process (and, as a consequence, variations in physical characteristics: plasma density, electron temperature, plasma potential, etc. ).…”

“…Gas pressure monitoring during etching and cleaning is maybe the simplest method of end-point detection [31,46]. During etching in chemically active gases, a solid material transforms into volatile species, this contributes to a change in gas pressure.…”

Neural network modeling of reactive ion etching using principal component analysis of optical emission spectroscopy data

“…This technique offers the unique capability of monitoring plasma chemistry directly in real time [3]. Currently, OES is widely used for endpoint detection [4]. OES has the advantage of non-invasiveness over other monitoring methods, but it provides a huge amount of information, and the analysis of such voluminous data is challenging.…”