US 9,804,493 B2  14  13  Comparative Example 401 and Examples 401 to  409  A substrate was spin-coated with a resist composition in  a thickness of 50 nm. The resist composition was AZfi  AX2110 (manufactured by AZ Electronic Materials (Japan)  K.K. ). After the resist composition was cast on the substrate,  the resist was heated at 120°  C. for 60 seconds to form a  resist layer. Thickness of each of the resist layer thus formed  was measured.  light. A fine pattern may be intended to be formed according  to a lithographic process by use of extreme UV light, and a  light source emitting less of such deep UV light may be  used. The method of generating extreme UV light may be  controlled, and deep UV light may be removed from radia› tion emitted by exposure apparatuses. For example, optical  systems in the apparatuses may be regulated so as to remove  deep UV light from emission of light sources.  It  may be  difficult to remove deep UV light completely from emission  of conventional light sources, e.g., to reduce the ratio of deep  UV light down to 3% or less in exposure light. Deep UV  light contained in emission from extreme UV light sources  may cause impairment of resist patterns in view of rough- ness and pattern shape.  Further, each of the compositions for forming a topcoat  layer as shown in Table 4 was cast thereon by spin-coating  in a thickness of30 nm. The layered compositions were then  heated at 120°  C. for 60 seconds to obtain a resist layer  covered with a topcoat layer. The resist layer thus obtained  was subject to development with a 2.38 wt % TMAH  aqueous solution to remove the topcoat layer. Thereafter,  thickness of the layer left was measured.  The above measurement was repeated twice to thereby  evaluate the loss of thickness caused by development. The  results are shown in Table 4.  The top surface of a resist layer may be coated with a  topcoat layer that transmits extreme UV light and absorbs  deep UV light. Consideration has been given to polymers  that may absorb deep UV light enough to be usable for the  topcoat layer. The polymers may include benzene, naphtha- lene or anthracene skeletons.  Provided is a composition for forming a topcoat layer  containing a graphene derivative having a hydrophilic  group, and a solvent, the topcoat layer absorbing deep UV  light. The topcoat layer may reduce unfavorable effects of  deep UV light, may help protect a resist pattern from  impairment in roughness and in pattern shape, and may help  prevent a resist layer from releasing gases in a photolitho› graphic process for pattern formation including exposure to  extreme UV light. The composition may be provided on a  resist layer before the resist layer is exposed to extreme UV  light for producing a resist pattern in a photolithographic  process. The topcoat layer may achieve a greater deep UV  light absorbance. A minute pattern may be produced accu› rately. The composition for forming a topcoat layer may  reduce residue remaining after development on the surface  of a resist pattern and may contribute to excellent pattern  formation. Also provided is a pattern formation method  using the composition for forming a topcoat layer.  Although loss of thickness was somewhat higher in  examples with a topcoat layer than in the example without  a topcoat layer, such loss is not deemed to impede practi› cality.  Example embodiments has been disclosed herein, and  although specific terms are employed, they are used and are  to be interpreted in a generic and descriptive sense only and  not for purpose of limitation. In some instances, as would be  apparent to one of skill in the art as of the filing of the  present application, features, characteristics, and/or ele- ments described in connection with a particular embodiment  may be used singly or in combination with features, char› acteristics, and/or elements described in connection with  other embodiments unless otherwise specifically indicated.  Accordingly, it will be understood by those of skill in the art  that various changes in form and details may be made  without departing from the spirit and scope of the present  invention as set forth in the following claims.  By way of summation and review, resist compositions  sensitive to light in various wavelength ranges have been  developed. Commercially available chemically amplified  resist compositions have been considered for use in a  photo-lithographic process with extreme UV light. For  example, resist compositions for KrF or ArF laser exposure  have been considered for use in a lithographic process  including exposure to extreme UV light. However, resolu› tion, sensitivity, and roughness such as line width roughness  (LWR) and line edge roughness (LER) may merit attention.  Further, light sources and masks in exposure apparatuses  may merit attention. As such, lithography techniques with  extreme UV light have not yet been widely employed in  practice.  It  has been thought that resist pattern shapes are  impaired by longer wavelength light, for example, deep UV  light of, for example, 193 nm or 248 nm, contained in  emission from extreme UV light sources. When resist com- positions for KrF or ArF laser exposure are used as described  above in a lithographic process with extreme UV light, they  are made to sensitively react not only to extreme UV light,  but also to deep UV light in a longer wavelength range than  extreme UV light.  Extreme UV light sources may emit extreme UV light  together with longer wavelength light, such as deep UV  What is claimed is:  1.  A composition for forming a topcoat layer, the com- position comprising:  wherein:  a graphene derivative including a hydrophilic group;  a solvent; and  a binder including a deep-ultraviolet absorbing group,  the graphene derivative is present in an amount of about  0.5 to about 10 wt % based on a total weight of the  composition,  the binder is present in an amount about 0.01 to about 10  wt % based on a total weight of the composition,  the graphene derivative and the binder are present in a  weight ratio of about 30:70 to about 50:50 in the  composition, and  TABLE 4  Contents (wt%)  Loss of  Graphene  Binder  Thickness  Examples  oxide  Pl  P2  P4  (nm)  Comparative  No Binder  -1.6  Ex. 401  Ex. 401  50  50  -2.1  Ex. 402  30  70  -2.3  Ex. 403  10  90  -2.2  Ex. 404  50  50  -1.5  Ex. 405  30  70  -1.8  Ex. 406  10  90  -1.7  Ex. 407  50  50  -2.0  Ex. 408  30  70  -1.9  Ex. 409  10  90  -2.2 