Capacitively coupled plasma reactor with magnetic plasma control

Abstract

A plasma reactor includes a vacuum enclosure including a side wall and a ceiling defining a vacuum chamber, and a workpiece support within the chamber and facing the ceiling for supporting a planar workpiece, the workpiece support and the ceiling together defining a processing region between the workpiece support and the ceiling. Process gas inlets furnish a process gas into the chamber. A plasma source power electrode is connected to an RF power generator for capacitively coupling plasma source power into the chamber for maintaining a plasma within the chamber. The reactor further includes at least a first overhead solenoidal electromagnet adjacent the ceiling, the overhead solenoidal electromagnet, the ceiling, the side wall and the workpiece support being located along a common axis of symmetry. A current source is connected to the first solenoidal electromagnet and furnishes a first electric current in the first solenoidal electromagnet whereby to generate within the chamber a magnetic field which is a function of the first electric current, the first electric current having a value such that the magnetic field increases uniformity of plasma ion density radial distribution about the axis of symmetry near a surface of the workpiece support.

Description

BACKGROUND Capacitively coupled plasma reactors are used in fabricating semiconductor microelectronic structures with high aspect ratios. Such structures typically have narrow, deep openings through one or more thin films formed on a semiconductor substrate. Capacitively coupled plasma reactors are used in various types of processes in fabricating such devices, including dielectric etch processes, metal etch processes, chemical vapor deposition and others. Such reactors are also employed in fabricating photolithographic masks and in fabricating semiconductor flat panel displays. Such applications depend upon plasma ions to enhance or enable desired processes. The density of the plasma ions over the surface of the semiconductor workpiece affects the process parameters, and is particularly critical in the fabrication of high aspect ratio microelectronic structures. In fact, a problem in fabricating high aspect ratio microelectronic integrated circuits is that non-uniformities in the ...

AI Technical Summary

Benefits of technology

A plasma reactor includes a vacuum enclosure including a side wall and a ceiling defining a vacuum chamber, and a workpiece support within the chamber and facing the ceiling for supporting a planar workpiece, the workpiece support and the ceiling together defining a processing region between the workpiece support and the ceiling. Process gas inlets furnish a process gas into the chamber. A plasma source power electrode is connected to an RF power generator for capacitively coupling plasma source power into the chamber for maintaining a plasma within the chamber. The reactor further includes at least a first overhead solenoidal electromagnet adjacent the ceiling, the overhead solenoidal electromagnet, the ceiling, the side wall and the workpiece support being located along a common axis of symmetry. A current source is connected to the first solenoidal electromagnet and furnishes a first electric current in the first solenoidal electromagnet whereby to generate within the chamber a magnetic field which is a function of the first electric current, the first electric current having a value such that the magnetic field increases uniformity of plasma ion density radial distribution about the axis of symmetry near a surface of the workpiece support.

Problems solved by technology

In fact, a problem in fabricating high aspect ratio microelectronic integrated circuits is that non-uniformities in the plasma ion density across the workpiece surface can lead to process failure due to non-uniform etch rates or deposition rates.

Nevertheless, such reactors have non-uniform plasma density distributions.

Typically, the radial density distribution of plasma ions is high over the center of the wafer support and low near the periphery, a significant problem.

In particular, the strength of the magnetic field may need to be limited in order to avoid device damage to microelectronic structures on the semiconductor workpiece associated with the strength of the magnetic field.

As a result, the total MERIE magnetic field may need to be substantially reduced and therefore may face substantial limitations in plasma ion density uniformity control.

This approach is vulnerable to chamber or wafer arcing problems due to the abrupt switching of the CMF magnetic fields, and therefore the magnetic field strength must be limited.

As a result, in some applications the magnetic field cannot be sufficient to compensate for plasma ion density non-uniformities produced by the reactor.

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