Jan.  28,  2021  8  US 2021/0026244 Al  (In general formula (a),  Ra  is an unsubstituted alkyl group,  R 6  to  Rd  are each a fluorine atom or a fluorine atom› substituted alkyl group, and at least one of  Ra  to  Rd  includes  a fluorine atom.) Note that the compound represented by  general formula (a) is a fluorine-containing compound, and  a solvent that comprises this fluorine-containing compound  is a fluorine-containing solvent.  [0106]  Examples of unsubstituted alkyl groups that can  constitute  Ra  in general formula (a) include unsubstituted  alkyl groups having a carbon number of not less than 1 and  not more than 5, of which, a methyl group or an ethyl group  is preferable.  [0107]  Moreover, the fluorine atom-substituted alkyl  group that can constitute any ofR $^{6 }$to  Rd  in general formula  (a) is preferably a fluorine atom-substituted alkyl group  having a carbon number of not less than 1 and not more than  5, and more preferably a 1,1,2,2,3,3,3-heptafluoropropyl  group or a 1,1,2,2,2-pentafluoroethyl group.  [0108]  Although the rinsing liquid can contain one com› pound represented by general formula (a) or can contain a  plurality of compounds represented by general formula ( a),  it is preferable that the rinsing liquid contains only one  compound represented by general formula (a) from a view› point of ease of collection and re-use of the rinsing liquid.  Note that it is preferable that the rinsing liquid does not  substantially contain, in addition to a compound represented  by general formula (a), any of the compounds previously  described as the "developer" or any other solvent that can  typically be used in a pattern formation method using a main  chain scission-type positive resist composition. The phrase  "does not substantially contain" refers to an extremely low  ratio relative to the overall rinsing liquid, such as less than  0.1 volume %.  [0109]  In particular, preferable examples of compounds  that can be represented by general formula (a) and can be  contained in the rinsing liquid include methyl nonafluo› robutyl ether (surface tension: 13.6 mN/m; SP value: 6.5  (cal/cm 3 ) 112 ;  freezing point: -135°  C.; boiling point: 61 °  C.)  represented by general formula (a-1), shown below, ethyl  nonafluorobutyl ether (surface tension: 13.6 mN/m; SP  value: 6.3 (cal/cm 3 ) 112 ;  freezing point: -138°  C.; boiling  point: 76°  C.) represented by general formula (a-2), shown  below, and 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(tri› fluoromethyl)pentane (surface tension: 15.0 mN/m; SP  value: 6.2 ( cal/cm 3 ) 112 ;  freezing point (pour point): -38°  C.;  boiling point: 98°  C.) represented by general formula (a-3),  shown below, with methyl nonafluorobutyl ether represented  by general formula (a-1) and ethyl nonafluorobutyl ether  represented by general formula (a-2) being more preferable  from a viewpoint of even more effectively inhibiting the  presence of residues in an obtained resist pattern.  [0115]  The weight-average molecular weight (Mw) and  the number-average molecular weight (Mn) of a copolymer  obtained in each example or comparative example were  measured by gel permeation chromatography, and then the  molecular weight distribution (Mw/Mn) of the copolymer  was calculated. Specifically, the weight-average molecular  weight (Mw) and the number-average molecular weight  (Mn) of the copolymer were determined as values in terms  of standard polystyrene using a gel permeation chromato› graph (HLC-8220 produced by Tosoh Corporation) with  [0114]  <Weight-Average Molecular Weight, Number-Av› erage Molecular Weight, and Molecular Weight Distribu› tion>  [0113]  In the examples and comparative examples, the  following methods were used to measure and evaluate the  weight-average molecular weight, number-average molecu› lar weight, and molecular weight distribution of a copoly› mer, and the density and sensitivity to extreme ultraviolet  light of a resist film. Note that the SP value of a developer  and the SP value of a rinsing liquid were calculated by the  group contribution method of Hoy. Moreover, the surface  tension of a developer and the surface tension of a rinsing  liquid were measured by the ring method at 25°  C.  [0112]  The following provides a more specific description  of the present disclosure based on examples. However, the  present disclosure is not limited to the following examples.  In the following description,  "%" and "parts" used in  expressing quantities are by mass, unless otherwise speci› fied.  [0111]  The temperature of the rinsing liquid is not spe› cifically limited and can be set as not lower than 21 °  C. and  not higher than 25°  C., for example. Moreover, the rinsing  time can be set as not less than 5 seconds and not more than  3 minutes, for example.  [0110]  The solubility parameter (SP value) of the rinsing  liquid is preferably 11.0 ( cal/cm 3 ) $^{112 }$or less, more preferably  less than 6.8 (cal/cm 3 ) 112 ,  and even more preferably 6.5  ( cal/cm 3 ) 112  or less from a viewpoint of even more effec› tively inhibiting the presence of residues in an obtained  resist pattern. Note that the SP value of the rinsing liquid  can, for example, be 2.0 (cal/cm 3 ) $^{112 }$or more. The freezing  point of the rinsing liquid is preferably -30°  C. or lower, and  may be -100°  C. or lower. The boiling point of the rinsing  liquid is preferably 100°  C. or lower, and more preferably  80° C. or lower. Note that the "freezing point" and the  "boiling point" of the rinsing liquid are values at 1 atm  (absolute pressure).  EXAMPLES  (a)  (a-2)  F--+--+-1  j --+--+--1  j  o-c,H,  F  F  F  F  F  F  F  F  I I I  C3F7  F  F  O"’-.  CH3  (a-3)  -continued  F  F  F  F  (a-1)  F  I I I I  O-CH3  F  F  F  F 