Control of patterned etching in semiconductor features

Abstract

Copper can be pattern etched in a manner which provides the desired feature dimension and integrity, at acceptable rates, and with selectivity over adjacent materials. To provide for feature integrity, the portion of the copper feature surface which has been etched to the desired dimensions and shape must be protected during the etching of adjacent feature surfaces. To avoid the trapping of reactive species interior of the etched copper surface, hydrogen is applied to that surface. Hydrogen is adsorbed on the copper exterior surface and may be absorbed into the exterior surface of the copper, so that it is available to react with species which would otherwise penetrate that exterior surface and react with the copper interior to that surface. Sufficient hydrogen must be applied to the exterior surface of the etched portion of the copper feature to prevent incident reactive species present due to etching of adjacent feature surfaces from penetrating the previously etched feature exterior surface. The most preferred embodiment of the invention provides for the use of hydrogen chloride (HCl) and/or hydrogen bromide (HBr) as the sole or principal source of the reactive species used in etching copper. Dissociation of the HCl and/or HBr provides the large amounts of hydrogen necessary to protect the copper feature etched surfaces from penetration by reactive species adjacent the etched surface. Additional hydrogen gas may be added to the plasma feed gas which comprises the HCl and/or HBr when the reactive species density in the etch process chamber is particularly high. Although the HCl or HBr may be used as an additive in combination with other plasma feed gases, preferably HCl or HBr or a combination thereof accounts for at least 40%, and more preferably at least 50%, of the reactive species generated by the plasma. Most preferably, HCl or HBr should account for at least 80% of the reactive species generated by the plasma.