Controlled multi-step magnetron sputtering process

Abstract

A multi-step sputtering process in plasma sputter reactor having target and magnetron operable in two modes, for example, in a substrate sputter etch and a substrate sputter deposition. The target has an annular vault facing the wafer to be sputter coated. Various types of magnetic means positioned around the vault create a magnetic field supporting a plasma extending over a large volume of the vault. An integrated copper via filling process with the inventive reactor or other reactor includes a first step of highly ionized sputter deposition of copper, which can optionally be used to remove the barrier layer at the bottom of the via, a second step of more neutral, lower-energy sputter deposition of copper to complete the seed layer, and a third step of electroplating copper into the hole to complete the metallization. The first two steps can be also used with barrier metals.

Description

RELATED APPLICATIONS [0001] This application is a division of Ser. No. 10 / 934,231, filed Sep. 3, 2004, which is a division of Ser. No. 10 / 197,680, filed Jul. 16, 2002, now issued as U.S. Pat. No. 6,787,006, which is a division of Ser. No. 09 / 703,601, filed Nov. 1, 2000, now issued as U.S. Pat. No. 6,451,177, which is a continuation in part of Ser. No. 09 / 518,180, filed Mar. 2, 2000, now issued as U.S. Pat. No. 6,277,249, which is a continuation in part of Ser. No. 09 / 490,026, filed Jan. 21, 2000, now issued as U.S. Pat. No. 6,251,242. The application is also related to Ser. No. 09 / 703,738, filed Nov. 1, 2000, now issued as U.S. Pat. No. 6,406,599.FIELD OF THE INVENTION [0002] The invention relates generally to plasma sputtering. In particular, the invention relates to the sputter target and associated magnetron used in a sputter reactor and to an integrated via filling process using sputtering. BACKGROUND ART [0003] A semiconductor integrated circuit contains many layers of differen...

AI Technical Summary

Benefits of technology

"The invention is about a method and apparatus for sputtering a plasma using a magnetron. The apparatus includes a target with a central well and outer annular space, which can be filled with a magnetic pole of one polarity and an inner magnetic pole of the other polarity. The target also has a vault on its front side. The invention allows for controlled ionization of sputtering atoms, resulting in a high-energy plasma. The two-step sputtering process produces high-energy ionized copper sputter ions and a more neutral, lower-energy sputter flux. The simultaneous clean-deposition step removes material on flat areas of a wafer and reinforces the thickness of a copper seed layer on the sidewall. The invention also includes a self-clean deposition step using high-energy ions to remove material from the barrier layer at the bottom of a contact / via feature."

Problems solved by technology

However, some materials such as barrier materials, for example, TiN, are not so easily classified.

However, sputtering has an inherent disadvantage when a material needs to be filled into a deep narrow hole, that is, one having a high aspect ratio.

The same disadvantage obtains when a thin layer of the material needs to be coated onto the sides of the hole, which is often required for barrier materials.

Contacts to the underlying silicon present a larger problem, but may still be accomplished with either aluminum or copper.

Due to continued downward scaling of the critical dimensions of microcircuits, critical electrical parameters of integrated circuits, such as contact and via resistances, have become more difficult to achieve.

HDP sputter reactors, however, have disadvantages.

They involve a somewhat new technology and are relatively expensive.

Furthermore, the quality of the sputtered films they produce is often not the best, typically having an undulatory surface.

Also, high-energy ions, particularly the argon ions which are also attracted to the wafer, tend to damage the material already deposited.

The small area of the magnetron may require circumferential scanning of the magnetron in a rotary motion at the back of the target to achieve even a minimal level of uniformity, and even with rotary scanning, radial uniformity is difficult to achieve.

High-capacity power supplies are expensive and necessitate complicated target cooling.

The facing pair geometry has the disadvantage that the magnets are stationary and create a horizontally extending field that is inherently non-uniform with respect to the wafer.

This structure has the disadvantage that the soft magnetic material forming the two poles, particularly the central spindle, are exposed to the plasma during sputtering and inevitably contaminate the sputtered layer.

Furthermore, the coil drive provides a substantially cylindrical geometry, which may not be desired in some situations.

Also, the disclosure illustrates a relatively shallow geometry for the target vault, which does not take advantage of some possible beneficial effects for a concavely shaped target.

However, Helmer et al. admit that uniformity of deposition with this magnetic configuration is not good.

Furthermore, the process deleteriously also removes the barrier at the bottom of the trench in a dual-damascene structure.

With shrinking dimension of the integrated circuits, the efficacy of the pre-clean step, as well as sidewall coverage of the seed layer within the contact / via feature, become more problematical.

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