Polymer blend and associated methods of preparation and use

A process for generating a resist image on a substrate, comprising:

• (a) coating a substrate with a film of a photoresist comprised of a radiation-sensitive acid generator and substantially homogeneous polymer blend comprising:
• (i) a first monomer unit having the structure of formula (II)
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• wherein
• R3 is H, F, CN, CF2H, CFH2, CF3, or CH3, R4a and R4b are H or F,
• R5 is CN or COOR, wherein R is selected from the group consisting of H, C1-12 alkyl and C1-12 fluoroalkyl, or is selected so as to render R5 acid-cleavable;
• and
• a second monomer unit selected from the group consisting of
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• wherein
• R1 is C1-12 alkyl or C1-12 fluoroalkyl,
• R2 is C1-12 fluoroalkyl,
• R6 is H, C1-12 alkyl, or C3-15 alicyclic,
• R7 is C1-12 alkyl, C1-12 alkyl substituted with 1-12 fluorine atoms and 0-2 hydroxyl groups, or C3-15 alicyclic, or R6 and R7 together form a five-, six-, or seven-membered ring,
• R8 is H, C1-12 alkyl, or C1-12 fluoroalkyl, or R6 and R8 together form a five-, six-, or seven-membered ring,
• R9 is H, C1-12 alkyl, or C1-12 fluoroalkyl, or R7 and R9 together represent —X—(CR10R11)n—, in which case R6 and R8 are H, X is O or CH2, n is 1 or 2,
• R10 and R11 are H, C1-12 alkyl, or C1-12 fluoroalkyl, or together form an oxo moiety (═O), with the proviso that when R8 and R11 together form ═O, n is 1, and
• L is C1-6 alkylene;
• and
• (ii) a second polymer comprised of monomer units have the structure (I);
• (b) exposing the film selectively to a predetermined pattern of radiation so as to form a latent, patterned image in the film;
• and
• (c) developing the latent image with a developer.

A method of improving the aqueous base development of a lithographic photoresist composition, comprising:

• providing a polymer transparent to deep ultraviolet radiation and a radiation-sensitive acid generator;
• and incorporating into the lithographic photoresist composition an additional polymer comprised of a monomer unit having the structure of formula
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• wherein R1 is C1-12 alkyl or C1-12 fluoroalkyl, R2 is C1-12 fluoroalkyl, and L is C1-6 alkylene.

A method of reducing the optical absorption in the vacuum ultraviolet region of a lithographic photoresist composition comprising:

• providing a polymer transparent to deep ultraviolet radiation and a radiation-sensitive acid generator;
• and incorporating into the lithographic photoresist composition an additional polymer including a monomer unit having the structure (I)
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• wherein R1 is C1-12 alkyl or C1-12 fluoroalkyl, R2 is C1-12 fluoroalkyl, and L is C1-6 alkylene.

A method for preparing a copolymer comprised of monomer units having the structure (I)

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• and monomer units having the structure (II)
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• comprising copolymerizing, via direct free radical polymerization in the presence of a free radical initiator, a first monomer having the structure of formula (V)
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• wherein
• R3 is H, F, CN, CF2H, CFH2, CF3, or CH3, R4a and R4b are H or F,
• R5 is CN or COOR, wherein R is selected from the group consisting of H, C1-12 alkyl and fluorinated C1-12 alkyl, or is selected so as to render R5 acid-cleavable;
• and
• a second monomer having the structure (VI)
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• wherein R1 is C1-12 alkyl or C1-12 fluoroalkyl, R2 is C1-12 fluoroalkyl, and L is C1-6 alkylene.