US 10 394 127 B2  4  3  In a case where Re is the substituent and L$_{1 }$ is the linking  group  Re and L$_{1 }$may be bonded to each other to form a ring.  X represents a group capable of leaving by the action of  an acid.  <4> The pattern forming method as described in <3>  in  which the group represented by X in General Formula (1-1)  has a total number of carbon atoms and oxygen atoms of 4  or less.  <5> The pattern forming method as described in any one  of <l> to <4>  in which the content of the repeating unit  capable of decomposing by the action of an acid to generate  an acid having a pKa of3.0 or less is 55% to 100% by mole  with respect to all the repeating units of the resin.  <6> The pattern forming method as described in any one  of <l > to <5>  in which the resin further has a repeating unit  represented by General Formula (2).  In citations for a group ( atomic group) in the present  specification  in a case where the group is denoted without  specifying whether it is substituted or unsubstituted  the  group includes both a group not having a substituent and a  group having a substituent. For example  an "alkyl group"  includes not only an alkyl group not having a substituent  (unsubstituted alkyl group)  but also an alkyl group having  a substituent (substituted alkyl group).  "Actinic rays" or "radiation" in the present specification  means  for example  a bright line spectrum of a mercury  lamp  far ultraviolet rays represented by an excimer laser   extreme ultraviolet rays  X-rays  electron beams (EB)  or the  like. In addition  in the present invention  light means actinic  rays or radiation.  Unless otherwise specified  "exposure" in the present  specification includes not only exposure by a bright line  spectrum of a mercury lamp  far ultraviolet rays represented  by an excimer laser  extreme ultraviolet rays  X-rays   extreme ultraviolet rays  or the like  but also writing by  particle rays such as electron beams and ion beams.  In the present specification  a "(meth)acrylic monomer"  means at least one of monomers having a structure of  "CH$_{2}$=CH-CO-" or "CH$_{2}$=C(CH$_{3}$)----CO-". Simi› larly  "(meth)acrylate" and "(meth)acrylic acid" means "at  least one of acrylate or methacrylate" and "at least one of  acrylic acid or methacrylic acid".  In the present specification  the weight-average molecular  weight of the resin is a value measured in terms of poly› styrene by a GPC method. GPC follows a method using  HLC-8120 (manufactured by Tosoh Corporation)  TSK gel  Multipore HXL-M (manufactured by Tosoh Corporation   7.8 mmIDx30.0 cm) as a column  and tetrahydrofuran  (THF) or N-methyl-2-pyrrolidone (NMP) as an eluent.  Hereafter  the pattern forming method of the present  invention will be described in detail.  <Pattern Forming Method>  The pattern forming method of the present invention  includes:  a step (1) of forming a film using an actinic ray-sensitive  or radiation-sensitive resin composition (hereinafter also  referred to as a "composition") including a resin (hereinafter  also referred to as a "resin (A)") having an acid-decompos› able repeating unit capable of decomposing by the action of  an acid to generate an acid having a pKa of 3.0 or less   a step (2) of exposing the film using actinic rays or  radiation  and  a step (3) of carrying out development using a developer  including an organic solvent after the exposure to form a  negative tone pattern.  According to the present invention  it is possible to  provide a pattern forming method having excellent perfor› mance of resolution and line width roughness as well as  reduction in film shrinkage (PEB shrinkage) in a PEB  process  particularly in the formation of an ultrafine pattern  (for example  a pattern having a line width of 20 nm hp or  less).  The reason thereof is not clear  but presumed as follows   for example.  For example  it is thought that in a case where a film is  formed using a composition including a resin having an  acid-decomposable repeating unit capable of decomposing  by the action of an acid to generate methacrylic acid  and is  developed using a developer including an organic solvent  after the exposure to form a negative tone pattern  the  developer including an organic solvent permeates into the  pattern part  and thus  performance of resolution perfor› mance and line width roughness is deteriorated. In contrast   Hereafter  embodiments of the present invention will be  described in detail.  According to the present invention  it is possible to  provide a pattern forming method having excellent perfor› mance of resolution and line width roughness as well as  reduction in film shrinkage (PEB shrinkage) in a PEB  process  particularly in the formation of an ultrafine pattern  (for example  a pattern having a line width of 20 nm hp or  less). In addition  according to the present invention  it is  possible to provide a method for manufacturing an elec› tronic device  including the pattern forming method.  DESCRIPTION OF THE PREFERRED  EMBODIMENTS  the pattern forming method as described in any one of  <l> to <10>.  <11> A method for manufacturing an electronic device   comprising:  <10> The pattern forming method as described in any one  of <l> to <9>  in which the step (2) is a step of exposing the  film using electron beams  X-rays  or extreme ultraviolet  rays.  <9> The pattern forming method as described in any one  of <l> to <8>  in which the organic solvent includes an  ester-based solvent.  <8> The pattern forming method as described in any one  of <l> to <7>  in which the actinic ray-sensitive or radia› tion-sensitive resin composition contains a compound  capable of generating an acid with actinic rays or radiation.  <7> The pattern forming method as described in any one  of <l> to <6>  in which the resin does not contain a fluorine  atom.  In the formula   R$_{11 }$ and R$_{12 }$ each independently represent a hydrogen  atom  an alkyl group  a cycloalkyl group  a halogen atom  a  cyano group  or an alkoxycarbonyl group. R$_{13 }$represents a  hydrogen atom  an alkyl group  a cycloalkyl group  a halo› gen atom  a cyano group  or an alkoxycarbonyl group  or is  bonded to Ar below to form a ring structure. Ar represents  an aromatic cyclic group. n represents an integer of 1 to 4.  (2) 