Maintenance of photoresist adhesion and activity on the surface of dielectric ARCS for 90 nm feature sizes

Abstract

We have traced the detachment of photoresist during development of patterned features in the range of about 90 nm and smaller to a combination of the reduced “foot print” of the pattern on the underlying substrate and to the contact angle between the underlying substrate surface and the developing reagent. By maintaining a contact angle of about 30 degrees or greater, the detachment of the photoresist from the underlying substrate can be avoided for photoresists including feature sizes in the range of about 90 nm. We have achieved an increased contact angle between the DARC surface and a water-based CAR photoresist developer while simultaneously reducing CAR poisoning by treating the surface of the DARC after film formation.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to the fabrication of semiconductor devices having feature sizes in the range of 90 nm and smaller. In particular, the invention relates to a method of maintaining the adhesion of a photoresist to a surface during development of a pattern in the photoresist and to maintenance of the functionality of a chemically amplified photoresist on the surface of a dielectric anti-reflection coating (DARC). [0003] 2. Description of the Background Art [0004] As semiconductor devices are becoming ever smaller, the device features necessarily become smaller. To produce feature sizes in the range of about 124 nm, for example, a chemically amplified photoresist (CAR) is pattern imaged using a DUV wavelength in the range of about 248 nm. To produce the next generation of feature sizes, in the range of 90 nm, the CAR will be pattern imaged using a radiation wavelength in the range of about 193-198 nm. The...

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Benefits of technology

[0017] We have traced the detachment of photoresist during development of patterned features in the range of about 90 m and smaller to a combination of the reduced “foot print” of the pattern on the underlying substrate and to the contact angle between the underlying substrate surface and the developing reagent used to develop a pattern in the photoresist. We have determined that by maintaining a contact angle of about 20 degrees or greater, and preferably 35 degrees or greater, the detachment of the photoresist from the underlying substrate can be avoided for photoresists including feature sizes in the range of about 90 nm. As feature sizes grow even smaller, it may be necessary to continually increase the contact angle to maintain adhesion of the photoresist to the underlying substrate during development of the photoresist. The key is to reduce the force exerted against the photoresist wall as the feature size becomes smaller, with the concurrent reduction in foot print of the photoresist on the underlying substrate surface.

[0018] The contact or wetting angle of the substrate depends on the composition of both the substrate and the developer used for photoresist development. The embodiments described below pertain to a DARC, and in particular a DARC comprised of SiOxHy:C, where x ranges from greater than 1 to about 2.0, and H ranges from about 0.1 to about 0.3, and the carbon content ranges from 0% up to 5.0% (typically less than about 3.0%). The reagents used to produce the DARC by PECVD are typically SiH4, and CO2, with helium added as a diluent plasma source gas, which also provides species for surface bombardment of the depositing film. For a silane-based PECVD film deposition process, where the silicon-containing precursor is SiH4, the carbon content in the polymeric film structure is typically less than about 3%, which is contributed by CO2 used in the firm formation process. We have discovered that an increase in carbon content of the DARC produces a higher contact angle, which is beneficial in terms of reducing the potential for detachment of the photoresist from the DARC surface during development of the photoresist using a water based developer of the kind commonly used in the semiconductor industry. To achieve a higher carbon content in the DARC, the amount of CO2 used in the SiH4/CO2 process may be increased to some extent; in an alternative, the silane-based precursor used in the PECVD deposition of the DARC may contain carbon, such as trimethyl silane ((CH3)3HSi) or tetramethyl silane ((CH3)4 Si), for example, but not by way of limitation.

[0019] Other Group IV elements such as silicon, germanium, tin and lead, by way of example and not by way of limitation, which are present in the DARC film may be increased in concentration, in a manner similar to the carbon content, to increase the contact angle between the DARC surface and the fluid photoresist developer.

[0020] While an increased carbon content in the DARC increases the contact angle and has a beneficial effect in terms of r

Problems solved by technology

While an increased carbon content in the DARC increases the contact angle and has a beneficial effect in terms of reducing photoresist detachment from the DARC surface during development, a higher carbon content in a silane precursor for PECVD film formation is generally more exp

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