Chemical amplifying type positive resist compositions

A chemical amplifying type positive resist composition having resolution and sensitivity that are well balanced, undergoing a minimum of shrinkage due to the irradiation with electron rays of SEM, and comprising a resin that has a polymerization unit derived from an unsaturated monomer expressed by the following formula (1) and that itself is insoluble in an alkali but becomes alkali-soluble due to the action of an acid; and an acid generating agent: 1 wherein R 1 and R 2 each independently represents hydrogen or a methyl group, is provided.

RESIN SYNTHESIS EXAMPLE 1 
 Synthesis of Resin A1 2-ethyl-2-adamantyl-methacrylate, 3-hydroxy-1-adamantyl acrylate, 2-norbornen, and 2(5H)franone were mixed at a ratio of 2:2:3:3 (20.0 g:17.9 g:11.4 g:10.2 g), and 2-ethylhexyl 3-mercaptopropionate, equivalent to 3 mol % of all the monomers of the foregoing mixture, was added thereto. Then, methyl isobutyl ketone, equivalent to 2 times all the monomers by weight, was added thereto so as to obtain a solution. Furthermore, azo-bisisobutyronitrile, equivalent to 1 mol % of all the monomers, was added thereto as an initiator. Thereafter, it was heated to 80° C., and was stirred for 15 hours. After the reaction mass was cooled, an operation of precipitation with a massive amount of methanol was carried out three times for purification, and a copolymer having a weight average molecular weight of approximately 6000 was obtained. This copolymer is hereinafter referred to as resin A1. 
 RESIN SYNTHESIS EXAMPLE 2 
 Synthesis of Resin AX 2-ethyl-2-adamantyl-methacrylate, 3-hydroxy-1-adamantyl methacrylate, and &agr;-methacryloyloxy-&ggr;-butyrolactone were mixed at a ratio of 2:1:1 (20.0 g:9.5 g:6.8 g), and methyl isobutyl ketone, equivalent to 2 times all the monomers by weight, was added thereto so as to obtain a solution. Furthermore, azobis isobutyronitrile, equivalent to 2 mol % of all the monomers, was added thereto as an initiator. Thereafter, it was heated to 85° C., and was stirred for 5 hours. After the reaction mass was cooled, an operation of precipitation with a massive amount of methanol was carried out three times for purification, and a copolymer having a weight average molecular weight of approximately 10000 was obtained. This copolymer is hereinafter referred to as resin AX. Next, resist compositions were prepared using acid generating agents and quenchers shown below in addition to the respective resins obtained in the foregoing resin synthesis examples. The results of evaluation of the same are shown below. 
 EXAMPLE 1 AND COMPARATIVE EXAMPLE 1 The following components were mixed and dissolved, and faltered through a fluorine resin filter having a pore diameter of 0.2 &mgr;m to prepare a resin solution. 1 Resin (as to type, see Table 1) 10 parts Acid generating agent: p-tolyldiphenyl sulfonium 0.2 part perfluorooctane sulfonate Quencher: 2,6-diisopropile aniline 0.0075 parts Solvent: In Example 1, Propylene glycol monomethyl ether acetate 9 parts &ggr;-butyrolactone 3 parts 2-heptanone 48 parts In Comparative Example 1, Propylene glycol monomethyl ether acetate 57 parts &ggr;-butyrolactone 3 parts An organic anti-reflective coating composition, ARC-25-8, manufactured by Brewer was coated on a silicon wafer and was baked at 215° C. for 60 seconds, so that a 780 &angst;-thick organic anti-reflective coating was formed. The resist solution prepared as described above was applied thereon by spin coating so as to have a thickness of 0.39 &mgr;m. After the application of the resist, it was prebaked at temperatures shown in the column “PB” in Table 1 for 60 seconds on a direct hot plate. The wafer on which a resist film was thus provide was exposed using an ArF eximer stepper (“NSR ArF” manufactured by NICON, NAT&equals;0.55, &sgr;&equals;0.6), so that a line-and-space pattern was formed by varying an exposure light quantity stepwisely. After the exposure, it was subjected to post-exposure baking on a hot plate at a temperature shown in the column “PEB” in Table 1 for 60 seconds, and further, subjected to paddle development for 60 seconds by using 2.38 wt % aqueous solution of tetramethylammonium hydroxide. The line-and-space pattern on the organic anti-reflective film substrate after the development was observed with a scanning-type electron microscope, and effective sensitivity, resolution, and variation in sizes due to SEM were measured by the following method. The results are shown in Table 1. Effective sensitivity: expressed by exposure amount causing line-and-space pattern of 0.18 &mgr;m to be 1:1. Resolution: expressed by a minimum size of a line-and-space pattern resolved with the light exposure of the effective sensitivity. Variation in size due to SEM: A line pattern of 0.22 &mgr;m was measured with the light exposure of the effective sensitivity. In one portion, length measurement under conditions of an acceleration voltage of 800 V and a current of 12 pA by a normal method was carried out every 10 seconds repeatedly using a length-measuring SEM (KLA-8100XP) manufactured by KLA-Tencor Corporation. The variation in size due to SEM was expressed by a difference between a value measured in the first measurement and a value measured in the 20th measurement. 2 TABLE 1 Effective Resolu- SEM PB PEB Sensitivity tion Shrinkage Example No. Resin ° C. ° C. (mJ/cm 2 ) (&mgr;m) (&mgr;m) Example 1 A1 120 120 12 0.15 0.006 Comparative AX 130 130 22 0.15 0.01 Example 1 As seen in Table 1, the resist of Example 1 had sensitivity and resolution that are excellently balanced, and underwent smaller shrinkage due to the irradiation with electron beams of SEM. The chemical amplifying type positive resist composition of the present invention has resolution and sensitivity that are well balanced, and undergoes a minimum of shrinkage due to the irradiation with electron rays of SEM. Therefore, the composition is suitable for the exposure in which KrF eximer laser or ArF eximer laser. Hence it provides a resist pattern with high performance, and ensures size measurement with high accuracy.