Compensation of spacing between magnetron and sputter target

Abstract

A lift mechanism for and a corresponding use of a magnetron in a plasma sputter reactor. A magnetron rotating about the target axis is controllably lifted away from the back of the target to compensate for sputter erosion, thereby maintaining a constant magnetic field and resultant plasma density at the sputtered surface, which is particularly important for stable operation with a small magnetron, for example, one executing circular or planetary motion about the target axis. The lift mechanism can include a lead screw axially fixed to the magnetron support shaft and a lead nut engaged therewith to raise the magnetron as the lead nut is turned. Alternatively, the support shaft is axially fixed to a vertically moving slider. The amount of lift may be controlled according a recipe based on accumulated power applied to the target or by monitoring electrical characteristics of the target.

Description

RELATED APPLICATIONS [0001] This application claims benefit of U.S. provisional application Ser. No. 60 / 529,209, filed Dec. 12, 2003. It also is related to concurrently filed U.S. patent application entitled MECHANISM FOR VARYING THE SPACING BETWEEN SPUTTER MAGNETRON AND TARGET.FIELD OF THE INVENTION [0002] The invention relates generally to sputter deposition of materials. In particular, the invention relates to a movable magnetron that creates a magnetic field to enhance sputtering. BACKGROUND ART [0003] Sputtering, alternatively called physical vapor deposition (PVD), is the most prevalent method of depositing layers of metals and related materials in the fabrication of integrated circuits. The more conventional type of sputtering, as originally applied to integrated circuits as well as to other applications, deposits upon a workpiece a planar layer of the material of the target. However, the emphasis has recently changed in the use of sputtering for the fabrication of integrated...

AI Technical Summary

Benefits of technology

[0019] The invention includes the method and apparatus for compensating erosion of a plasma sputtering target by moving the magnetron away from the back of the target as the front of the target is eroded. The compensation provides a more constant magnetic field and plasma density at the surface of the target being sputtered and results in a more stable sputtering process.

Problems solved by technology

However, the emphasis has recently changed in the use of sputtering for the fabrication of integrated circuits because vertical interconnects through inter-level dielectrics having the high aspect ratios now being used present a much greater challenge than the horizontal interconnects.

The target erosion presents several problems if the lifetime of the target 12 is to be maximized.

These approaches do not address how the erosion affects the magnetic enhancement of sputtering.

Secondly, the concentrated magnetic field of the small magnetron increases the plasma density adjacent the portion of the target being sputtered, thereby increasing the ionization fraction of the target atoms being sputtered.

However, the target erosion affects the effective magnetic field at the target face being sputtered, thereby changing the sputtering rate and the ionization fraction.

Thirdly, the small magnetron makes uniform target sputtering that much more difficult.

Various magnetron shapes, e.g., triangular have been used to increase the uniformity of sputtering, but their uniformity is not complete.

Secondly, the non-uniformity of sputtering reduces the lifetime of the target to a number N1 at which the erosion trough maximum approaches the target backing plate or, in the case of an integral target, a minimum thickness of the target.

As a result, only a small area of the target 34 is subject to an increased target power density and resultant intensive sputtering.

That is, the sputtering at any instant of time is highly non-uniform.

However, as has been described with respect to the reactor of Fu et al., the resultant annular troughs in the target may produce significant radial non-uniformity in the sputtering.

Although the fall off in the simple rotary chamber is not as great in the planetary chamber, it is still significant.

As a result, the changing magnetic field and plasma density destabilizes the process causing variation in bottom and sidewall coverages across the lifetime of the target.

There is a significant rise in the target voltage and the magnitude of the bias voltage with increased sputtering.

The change of sputtering rate can be compensated by increasing the sputtering duration, but this does not address the sidewall coverage.

Such power compensation however involves an ad hoc relationship which needs to be determined for each set of conditions and also reduces the ability to maximize plasma densities and sputtering rates with limited power supplies.

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