US 9,383,646  B2  2  1  TWO-STEP PHOTORESIST COMPOSITIONS  AND METHODS  REFERENCE TO PRIOR FILED APPLICATIONS  FIELD OF INVENTION  BACKGROUND  SUMMARY OF THE DISCLOSURE  DESCRIPTION OF THE FIGURES  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  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: 