US 5,605,637 AGranted

Adjustable dc bias control in a plasma reactor

AssigneeApplied Materials, Inc.

InventorsHongching Shan, Evans Lee, Robert Wu

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Abstract

A plasma chamber, and a related method for its use, in which the direct current (dc) bias on a wafer-supporting cathode is reduced by including a plasma shield that blocks plasma from reaching a region of the chamber and thereby reduces the effective surface area of a grounded anode electrode. The plasma shield has a number of narrow slits through it, small enough to preclude the passage of plasma through the shield, but large enough to permit pumping of process gases through the shield. The dc bias is further controllable by installing a chamber liner of dielectric or other material to cover a selected portion of the inside walls of the chamber. The liner also facilitates cleaning of the chamber walls to remove deposits resulting from plasma polymerization.

Claims21

Dependent claims

A plasma reactor with selectable direct current (dc) bias control, comprising:

a grounded reactor chamber having conductive walls;
a grounded first electrode located in the chamber;
a second electrode spaced apart from the first electrode, for supporting a workpiece to be processed in the reactor chamber;
at least one inlet port for supplying process gases to the reactor chamber;
at least one outlet port for evacuating gases from the chamber;
a high-frequency power source connected between the second electrode and ground, to generate and sustain a plasma in the reactor chamber;
and
a plasma shield installed in the reactor chamber to prevent the plasma from reaching a portion of the reactor chamber;
wherein the plasma shield has a plurality of narrow slits through it to permit the flow of process gases but not the plasma, the slits each having a cross-sectional area defined by a slit length dimension that is long relative to a slit width dimension, and the slits each having a length in the direction of gas flow that is also long relative to the slit width;
and wherein the effective area of the grounded first electrode is reduced because the plasma is prevented from contacting the full extent of the chamber walls, and the reduced effective area results in a reduced dc bias on the second electrode.

7 more elements

A plasma substrate processor for use with a high frequency power supply, comprising:

a substrate support including a first electrode;
a vacuum enclosure containing said support and defining an evacuable substrate processing environment about said substrate support;
a process gas inlet provided in a wall of said enclosure;
a gas evacuation output provided in a wall of said enclosure;
a second electrode within said enclosure spaced from said first electrode, one of said electrodes being adapted to be connected to a high frequency power supply, the other being adapted to be connected to ground, so as to sustain a plasma within said enclosure based on the processing gases within said enclosure;
and
a plasma shield overlaying a significant portion of the walls of said enclosure;
wherein any portion of the plasma shield which overlies one of said gas inlet and said gas evacuation outlet is provided with apertures small enough to prevent plasma from penetrating said apertures, yet large enough to allow passage of gas therethrough, each aperture having a cross-sectional area defined by a width dimension and a length dimension that is long relative to the width dimension, and each aperture having an axial length, measured in the direction of gas flow, that is also long relative the width dimension;
whereby the effective area of the chamber walls capable of contacting the plasma is reduced and self-bias on any substrate supported on the substrate support is reduced.

6 more elements

Dependencies are inferred from the claim text.