Acid  PEB  Polymer  generator  Quencher  Carboxylic acid  Organic solvent temp. Sensitivity CDU  (pbw)  (pbw)  (pbw)  (pbw)  (pbw)  (" c.)  (mJ/cm 2 )  (nm)  2 Comparative  PAG-1  Q-1  PGMEA (2,000) 95  38  4.7  Polymer 1  (25.0)  (3.00)  DAA (500)  (100)  3 Comparative  Q-1  PGMEA (2,000) 95  35  3.9  Polymer 2  (3.00)  DAA (500)  (100)  TABLE I-continued  Feb.4,2021  120  US 2021/0033971 Al  [0215]  It  is demonstrated in Table 1 that positive resist  compositions comprising a polymer comprising recurring  units having the structure of an ammonium salt of a car› boxylic acid having an iodized or brominated hydrocarbyl  group ( exclusive of iodized or brominated aromatic ring)  offer a high sensitivity and improved CDU.  [0216]  Japanese Patent Application No. 2019-142916 is  incorporated herein by reference.  [0217]  Although some preferred embodiments have been  described, many modifications and variations may be made  thereto in light of the above teachings.  It  is therefore to be  understood that the invention may be practiced otherwise  than as specifically described without departing from the  scope of the appended claims.  1.  A positive resist composition comprising a base poly› mer comprising recurring units (a) having the structure of an  ammonium salt of a carboxylic acid having an iodine or  bromine-substituted hydrocarbyl group which does not con› tain an iodine or bromine-substituted aromatic ring and  recurring units of at least one type selected from recurring  units (bl) having a carboxyl group substituted with an acid  labile group and recurring units (b2) having a phenolic  hydroxyl group substituted with an acid labile group.  2.  The resist composition of claim  1  wherein the recurring  units (a) have the formula (a):  3.  The resist composition of claim  1  wherein the recurring  units (bl) have the formula (bl) and the recurring units (b2)  have the formula (b2):  wherein  RA  is hydrogen or methyl,  wherein  RA  is each independently hydrogen or methyl, Y$^{1 }$is  a single bond, phenylene group, naphthylene group, or  C$_{1 }$-C$_{12 }$linking group containing an ester bond, ether bond or  lactone ring, Y 2  is a single bond, ester bond or amide bond,  Y 3  is a single bond, ether bond or ester bond, R 11  and R 12  each are an acid labile group, R $^{13 }$is fluorine, trifluoromethyl,  cyano or a C$_{1}$-C$_{6 }$ saturatedhydrocarbyl group, R$^{14 }$is a single  bond or C$_{1 }$-C$_{6 }$ alkanediyl group, a is 1 or 2, and b is an  integer of O to 4.  4.  The resist composition of claim  1  wherein the base  polymer further comprises recurring units ( c) having an  adhesive group selected from the group consisting of  hydroxyl, carboxyl, lactone ring, carbonate, thiocarbonate,  (bl)  (b2)  (a)  [[ cxB4_  ...-x2J  TI  ]  m’  R4  C---x3Ao_  ml  n  X 1 A  is a single bond, ester bond or amide bond,  X 1 B  is a single bond or a C$_{1 }$-C$_{20 }$ di- or trivalent hydro› carbon group which may contain an ether bond, car› bonyl moiety, ester bond, amide bond, sultone ring,  lactam ring, carbonate moiety, halogen, hydroxyl moi› ety or carboxyl moiety,  R 1 , R $^{2 }$and R3 are each independently hydrogen, a C$_{1 }$-C$_{12 }$ alkyl group,  C$_{2}$ -C$_{12 }$ alkenyl group,  CcC$_{12 }$ aryl group,  or C$_{7}$-C$_{12 }$aralkyl group, R$^{1 }$and R 2 , or R $^{1 }$and X1 B may  bond together to form a ring with the nitrogen atom to  which they are attached, the ring optionally containing  oxygen, sulfur, nitrogen, or a double bond,  XBI  is iodine or bromine,  X 2  is a single bond, ether bond, ester bond, amide bond,  carbonyl group or carbonate group,  X 3  is a single bond or a C$_{1}$-C$_{20 }$ (m$^{1}$+1)-valent hydrocar› bon group which may contain a heteroatom exclusive  of iodine and bromine,  R 4  is a  C$_{1 }$-C$_{20 }$ (m$^{2 }$+ 1 )-valent aliphatic hydrocarbon group  which may contain at least one moiety selected from  fluorine, chlorine, hydroxyl, carboxyl,  CcC$_{12 }$ aryl,  ether bond, ester bond, carbonyl, amide bond, carbon› ate, urethane bond, and urea bond,  m 1  and m 2  are each independently an integer of 1 to 3, n  is 1 or 2. 