## TWO-STEP PHOTORESIST COMPOSITIONS AND METHODS 

## REFERENCE TO PRIOR FILED APPLICATIONS 

This application is a divisional of, and claims the benefit of, U.S. patent application Ser. No. 14/187,649 filed Feb. 24, 2014 under 35 U.S.C.§120. 

The present invention relates to novel methanofullerene derivatives, negative-type photoresist compositions prepared therefrom and methods of using them. The invention further relates to 2-step resist processes which allow for improve› ments in contrast, resolution and/or line edge roughness. The invention also relates to dual resist processes including fullerenes and/or chemically amplified materials. The deriva› tives, their photoresist compositions and/or the methods are ideal for fine pattern processing using, for example, ultravio- let radiation, extreme ultraviolet radiation, beyond extreme ultraviolet radiation, X-rays and charged particle rays. 

As is well known, the manufacturing process of various kinds of electronic or semiconductor devices such as ICs, LS Is and the like involves a fine patterning of a resist layer on the surface of a substrate material such as a semiconductor silicon wafer. This fine patterning process has traditionally been conducted by the photo lithographic method in which the substrate surface is uniformly coated with a positive or nega› tive tone photoresist composition to form a thin layer of the photoresist composition and selectively irradiating with actinic rays (such as ultraviolet light) through a photomask followed by a development treatment to selectively dissolve away the photoresist layer in the areas exposed or unexposed, respectively, to the actinic rays leaving a patterned resist layer on the substrate surface. The thus obtained patterned resist layer is utilized as a mask in the subsequent treatment on the substrate surface such as etching. The fabrication of struc› tures with dimensions of the order of nanometers is an area of considerable interest since it enables the realization of elec› tronic and optical devices which exploit novel phenomena such as quantum confinement effects and also allows greater component packing density. As a result, the resist layer is required to have an ever increasing fineness which can by accomplished only by using actinic rays having a shorter wavelength than the conventional ultraviolet light. Accord› ingly, it is now the case that, in place of the conventional ultraviolet light, electron beams (e-beams), excimer laser beams, EUV, BEUV and X-rays are used as the short wave› length actinic rays. Needless to say the minimum size obtain› able is primarily determined by the performance of the resist material and the wavelength of the actinic rays. Various mate- rials have been proposed as suitable resist materials. In the case of negative tone resists based on polymer crosslinking, there is an inherent resolution limit of about 10 nm, which is the approximate radius of a single polymer molecule. 

It is also known to apply a technique called "chemical 60 amplification" to the polymeric resist materials. A chemically amplified resist material is generally a multi-component for› mulation in which there is a main polymeric component, such as a novolac resin which contributes towards properties such as resistance of the material to etching and its mechanical 65 stability and one or more additional components which impart desired properties to the resist and a sensitizer. By 

## FIELD OF INVENTION 

## BACKGROUND 

definition, the chemical amplification occurs through a cata› lytic process involving the sensitizer which results in a single irradiation event causing exposure of multiple resist mol› ecules. In a typical example the resist comprises a polymer and a photoacid generator (PAG) as sensitizer. The PAG releases a proton in the presence of radiation (light or e-beam). This proton then reacts with the polymer to cause it to lose a functional group. In the process, a second proton is generated which can then react with a further molecule. The speed of the reaction can be controlled, for example, by heating the resist film to drive the reaction. After heating, the reacted polymer molecules are free to react with remaining components of the formulation, as would be suitable for a negative-tone resist. In this way the sensitivity of the material to actinic radiation is greatly increased, as small numbers of irradiation events give rise to a large number of exposure events. 

In such chemical amplification schemes, irradiation results in cross-linking of the exposed resist material; thereby creat› ing a negative tone resist. The polymeric resist material may be self cross-linking or a cross linking molecule may be included. Chemical amplification of polymeric-based resists is disclosed in U.S. Pat. Nos. 5,968,712, 5,529,885, 5,981, 139 and 6,607,870. 

Various methanofullerene derivatives have been shown to be useful e-beam resist materials by the present inventors, Appl. Phys. Lett. Volume 72, page 1302 (1998), Appl. Phys. Lett. Volume 312, page 469 (1999), Mat. Res. Soc. Symp. Proc. volume 546, page 219 (1999) and U.S. Pat. No. 6,117, 617. 

As can be seen there is an ongoing desire to obtain finer and finer resolution of photoresists that will allow for the manu› facture of smaller and smaller semiconductor devices in order to meet the requirements of current and further needs. It is also desirable to create materials which can be used in con› junction with these photoresists which will be more robust to the processes used to create current semiconductor devices, such as, for example, etching resistance. 

FIG. 1: shows an SEM showing the resolution obtained from example 1. 

FIG. 2: shows an SEM showing the resolution obtained from example 2. 

FIG. 3: shows an SEM showing the resolution obtained from example 3. 

FIG. 4: shows an SEM showing the resolution obtained from example 4. 

FIG. 5: shows an SEM showing the resolution obtained from example 5. 

FIG. 6: shows an SEM showing the resolution obtained from example 6. 

FIG. 7: shows an SEM showing the resolution obtained from example 7. 

FIG. 8: shows an SEM showing the resolution obtained from example 8. 

FIG. 9: shows an SEM showing the resolution obtained from example 9. 

FIG. 10: shows an SEM showing the resolution obtained from example 10. 

In a first embodiment, a methanofullerene comprising the general formula: 

## DESCRIPTION OF THE FIGURES 

## SUMMARY OF THE DISCLOSURE 

