US 5,174,875 A · Method of enhancing the performance of a magnetron sputtering target

Abstract

A plasma confining magnetic field is generated over the sputtering region of a sputtering target with a critical field line which determines the shape of the plasma. The critical field line is progressively flattened over the course of the life of the target as the target erodes. Preferably, the magnet is configured with poles spaced around the portion of the target below the sputtering region to provide a magnetic field that flattens as its strength decreases. A regulated power supply maintains a regulated power level that is increased as the target erodes to maintain a constant deposition rate. The voltage delivered by the power supply is maintained at or above a constant level by progressively decreasing the current to an electromagnet to progressively reduce the field strength and flatten the field. As a result of the invention, the erosion groove of the target is broadened and the number of wafers coated by the target during its life is increased.

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Claims12

Dependent claims

A method of enhancing the performance of a generally concave magnetron sputtering target having at least one annular sputtering region thereon to increase the number of substrates coated from the target over the course of the life of the target as the target erodes, said method comprising the steps of:

providing an electromagnet having exterior pole structure generally surrounding the sputtering region of the target, and having interior pole structure of an opposite polarity opposite that of the exterior pole structure and spaced inward thereof, and positioning the external and internal pole structures such that, as the target erodes, the sputtering surface thereof progressively recedes within and between the pole structures of the electromagnet;
supplying current to the electromagnet to generate therewith a plasma confining magnetic field having magnetic lines of force extending radially over said region of the target between the interior and exterior pole structures of the electromagnet;
energizing the target by supplying electric power thereto to cause material to be sputtered from the sputtering region thereof and deposited at a predetermined rate onto a substrate that faces the sputtering region of the target;
sensing voltage supplied to the target and producing a control signal in response thereto;
progressively increasing the power supplied to the target over substantially the entire useful life of the target as the target erodes;
and
progressively reducing the current supplied to the electro magnet in response to the control signal to maintain the voltage at a generally constant level.

4 more elements

A method of enhancing the performance of a magnetron sputtering target having at least one sputtering region thereon to increase the number of substrates coated from the target over the course of the life of the target by maintaining a broad erosion profile at the sputtering region as the target erodes, said method comprising the steps of:

providing an electro magnet to produce a plasma confining magnetic field having magnetic lines of force extending over the sputtering region of the target, the filed having lines of force representing different strengths of the magnetic field, the lines of force including a critical field line which determines the shape of a plasma formed over the sputtering region;
positioning the electro magnet with respect to the target such that the lines of force have initial positions above the sputtering region and through the target, and such that, as the target erodes, the sputtering region thereof progressively recedes through different ones of the positions;
energizing the target by supplying electric power thereto to cause material to be sputtered from the sputtering region thereof and deposited at a predetermined rate onto a substrate that faces the sputtering region of the target;
sensing voltage supplied to the target and producing a control signal in response thereto;
progressively increasing the power supplied to the target over substantially the entire useful life of the target as the target erodes;
and
over the useful life of the target, progressively reducing the strength of the field and progressively flattening the critical field line over the sputtering region of the target in response to the control signal to maintain the voltage, as the power increases and the target erodes, at a level that is significantly greater than that which would result if electro magnet current and target power were to remain constant and significantly less than that which would result if target impedance were to remain constant as the power to the target is increased.

4 more elements

A method of enhancing the performance of a generally concave magnetron sputtering target, which is formed of a single piece of sputtering material having a plurality of sputtering regions thereon, including a first sputtering region and a second sputtering region, to increase the number of substrates coated from the target over the course of the life of the target as the target erodes, said method comprising the steps of:

providing an electromagnetic for each sputtering region of the target, including a first electromagnet having a first pole structure extending into the target between the first and second sputtering regions and a second pole structure of opposite polarity located opposite the first sputtering region from the first pole structure such that sputtering material beneath the first sputtering region lies directly between the first and second pole structure, the first and second pole structures being positioned with respect to the target such that, when current is supplied to the first electromagnet at a given level, a magnetic field is produced having lines of force representing different strengths of the magnetic field at respective different positions above the first sputtering region and through the sputtering material between the first and second pole structures, the positions being located such that, as the target erodes at the firs sputtering region, the first sputtering region progressively recedes between the first and second pole structure through different ones of the positions at which the lines of force progressively flatten;
supplying electromagnet current to the first electromagnet sufficient to generate therewith a plasma confining magnetic field over the target, the field having magnetic lines of force extending over the first sputtering region of the target;
while current is being supplied to the first electromagnet, energizing the target by supplying electric power thereto to cause material to be sputtered from the first sputtering region and deposited onto a substrate that faces the target;
sensing voltage supplied to the target, when the target is energized and current is being supplied to the first electromagnet, and producing a control signal in response to the voltage sensed;
and
progressively reducing the current supplied to the first electromagnet throughout the useful life of the target in response to the control signal.

3 more elements

Dependencies are inferred from the claim text.

Description8,625 words

Summary3,648 words

#The present invention relates to methods for extending the use of cathode sputtering targets and more particularly to methods for controlling the energization of a cathode sputtering target over the course of its life to broaden the erosion area of the target and thereby increase the utilization of target material.

#Sputter coating is a process carried out in a vacuum chamber, filled with a generally chemically inert gas, in which a substrate to be coated is mounted facing a target formed of the coating material. In the chamber, the target is subjected to an electrical potential negative with respect to the chamber wall or some other anode within the chamber. The potential gradient adjacent the target surface causes electrons to be emitted from the target. As they are attracted toward the chamber anode, the emitted electrons strike and ionize some of the atoms of the inert gas by stripping electrons from them. Positive ions of the gas are thereby formed and attracted toward the negative target which they strike, transferring momentum to the target material, and ejecting particles of the material from the target surface. The substrate to be coated, which is positioned in the chamber usually with its surface facing the target so as to intercept the moving particles of coating material sputtered from the target, receives some of the ejected particles, which adhere to and coat the substrate surface.

#In magnetron enhanced sputtering processes, a magnetic field is formed over the target surface with magnetic field lines having components extending parallel to the target surface. In many applications, the field lines arch over the target surface and form a closed magnetic tunnel. The magnetic field causes the electrons moving from the target to curve in spiral paths over regions of the target surface enclosed by the field, thereby increasing the electron density in the enclosed space, and resulting in an increase in the rate of electron collisions with gas atoms over the enclosed regions of the target surface. The increased collision rate in turn increases the ionization of the gas in the enclosed space and thus increases the efficiency of the sputtering process at the underlying target region. Where the magnetic field lines equal or exceed a critical field strength over the target surface, a glowing ion cloud or plasma is seen trapped within the field over the region of the target surface.

Brief description of the drawings4 figures

#FIG. 1 is a cross-sectional view of a processing chamber of the sputter coating apparatus embodying principles of the present invention;

#FIG. 2 is a diagram illustrating an electrical circuit arrangement according to principles of the present invention;

#FIG. 3 is a graph illustrating the variation of various electrical values of the circuit of FIG. 2 as a function of time over the operative life of the target; and

Detailed description4,881 words

#Magnetron sputtering devices of the type to which the present invention relates are described in the following commonly assigned U.S. patents and copending patent applications which are hereby expressly incorporated in their entirety into this application by reference:

#U.S. Pat. No. 4,853,033 for "Cathode Target Design for a Sputter Coating Apparatus";

#U.S. Pat. No. 4,871,433 for "Apparatus for Improving the Uniformity of Ion Bombardment In a Magnetron Sputtering System";

Facts

Application

07/814,320Filed 23 Dec 1991 · continuation

Priority

29 Aug 1990

Granted

29 Dec 1992

Term ended

29 Aug 2010

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification5 codes

C23C 14/345
Applying energy to the substrate during sputtering: using substrate bias
C23C 14/35
Sputtering: by application of a magnetic field, e.g. magnetron sputtering
H01J 37/3405
Using supplementary magnetic fields: magnetron sputtering
C23C
Coating metallic material

Method of enhancing the performance of a magnetron sputtering target

Life of this patent

Method of enhancing the performance of a magnetron sputtering target

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims12

Description8,625 words

Drawings

Classification5 codes

Life of this patent

Description8,625 words