Low resistance contacts fabricated in high aspect ratio openings by resputtering

Abstract

A method of producing a low resistance contact in an opening carried in a substrate is comprised of the steps of forming a first layer of conductive material along a portion of the walls of the opening. A portion of the conductive material is resputtered from the walls of the opening to form a thin layer at the bottom of the opening. A second layer of conductive material is deposited on the substrate in a manner to fill the opening. A contact thus formed is also disclosed.

Description

[0001] 1. Field of the Invention[0002] The present invention is directed to methods used in the fabrication of solid state devices and, more particularly, to methods of producing metal contacts.[0003] 2. Description of the Background[0004] During the fabrication of solid state devices, it is necessary to use various types of interconnect structures such as contacts and vias. A via is an electrical connection between two metal layers and a contact is an electrical connection between anything other than two metal layers, such as between metal and silicon. Vias and contacts are used extensively in very large scale integrated (VLSI) circuits. An average VLSI circuit may contain 16 million vias and contacts.[0005] It is desirable to completely fill vias and contact openings with metal or some other suitable electrically conductive material. However, when coating the surface of a substrate with a metal film by such processes as evaporation, ion beam deposition, or sputtering, self-shadowi...

AI Technical Summary

Benefits of technology

This approach reduces shadowing issues, achieves low resistance contacts, and is more efficient in equipment and material usage, leading to contacts with improved electrical properties and reduced failure rates.

Problems solved by technology

However, when coating the surface of a substrate with a metal film by such processes as evaporation, ion beam deposition, or sputtering, self-shadowing may arise.

Shadowing results in poor contact at the bottom of the opening, which results in high contact resistance, and the problems associated therewith, and can result in an open circuit.

Another problem associated with shadowing is that with the contact opening pinched-off, debris, chemicals used in the fabrication process, or other foreign materials become trapped.

When that occurs, the resulting contact has poor electrical properties and may ultimately fail.

As circuit complexity rises, submicron contact openings result which have severe aspect ratios which exacerbate the aforementioned shadowing problems.

A problem associated with the method of U.S. Pat. No. 4,874,493 is that processes such as ion beam milling and resputtering tend to be slow and inefficient.

To completely fill a contact or via opening through resputtering or ion beam milling substantially reduces the throughput of equipment.

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