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As apparent from the results in Table 7, with respect to electron beam exposure (irradiation) of the negative resist composition, in Comparative Examples IE and 2E using Comparative Compounds 1 and 2 (both are compounds described in Patent Document 2 (JP-A-2011-16746)) as the acid generator, the sensitivity, resolution and LER were poor, the variation of sensitivity after aging was large, and the outgassing was frequently generated. 

The reason why in Comparative Examples IE and 2E, the sensitivity was poor, particularly, as to the aging stability, the variation of sensitivity after aging was large, is considered to be the same as the reason described above in Example A. 

On the other hand, in Examples 1 E to 9E using, as the acid generator, (Al) a compound represented by formula (Zl) where when -L$_{1 }$-R$_{1 }$-A$_{1 }$ is substituted at the para-position relative to s+, L$_{1 }$ is not an oxygen atom, the sensitivity, reso› lution and LER were excellent, the variation of sensitivity after aging was small, and the outgassing was little generated, revealing that the composition is suitable also as a negative resist composition. 

The reason why in Examples IE to 9E using the compound (Al) according to the present invention, the sensitivity and LER were excellent, is not clearly known but is considered that the compound (Al) represented by formula (Zl) is con› figured to have a specific betaine structure of not allowing L $_{1 }$ to be an oxygen atom when -L$_{1 }$-R$_{1 }$-A$_{1 }$ is substituted at the para-position relative to s+, whereby the decomposition effi› ciency (acid generation efficiency) of the compound (Al) during exposure can be enhanced, the solubility of the com- pound (Al) for the solvent in the composition can be increased, the compound (Al) can be prevented from precipi› tating in the resist composition during storage and exhibit excellent aging stability (little variation of sensitivity after aging), and because of high acid generation efficiency, a large amount of acid can be generated, resulting in high sensitivity andlowLER. 

-continued 

## Examples IF to SF and Comparative Examples IF and2F 

<Preparation of Resist> 

The components shown in Table 8 below were dissolved in the solvent, and the obtained solution was filtered through a polytetrafluoroethylene filter having a pore size of0.1 µm to prepare a positive resist solution having a solid content con› centration of 4 mass %. 

<Evaluation of Resist> 

The positive resist solution prepared was uniformly coated on a hexamethyldisilazane-treated silicon substrate by using a spin coater and heated/dried on a hot plate at 120° C. for 60 seconds to form a resist film having a thickness of0.12 µm. 

This resist film was irradiated using an EUV exposure apparatus (wavelength: 13 nm) and immediately after the irradiation, baked on a hot plate at 110° C. for 90 seconds. Thereafter, the resist film was developed with an aqueous 2.38 mass % tetramethylammonium hydroxide solution at 23 ° C. for 60 seconds, rinsed with pure water for 30 seconds and then dried to form a line-and-space pattern (line: space= 1 : 1) with a line width of 50 nm. The obtained pattern was evaluated by the following methods. 

[Sensitivity] 

The obtained patterns was observed using a scanning elec› tron microscope (model S-9220 manufactured by Hitachi, Ltd.). The electron beam irradiation dose when resolving a line width of 50 nm (line: space= 1: 1) was taken as the sensi› tivity (E$_{0}$ ). 

[Resolution] 

The limiting resolution for 1:1 line-and-space (the mini› mum line width below which the line and the space were not separated and resolved) at the irradiation dose giving the sensitivity above was taken as the resolution. 

[LER (Line Edge Roughness)] 

A line pattern (L/S=l/1) with a line width of 50 nm was formed at the irradiation dose giving the sensitivity above, and the distances from the reference line where the edge should be present was measured using a scanning electron microscope (S-9220, manufactured by Hitachi, Ltd.) at arbi› trary 30 points included in the longitudinal range of 50 µm of the line pattern. The standard deviation of the distance was determined, and 3a was computed. 

[Aging Stability (Variation of Sensitivity after Aging)] 

The resist composition (resist solution) was refrigerated at 5° C. for 2 weeks and then measured for the sensitivity in the same manner as above to evaluate the aging stability. A smaller variation from the sensitivity when not aged is better. [Outgassing Performance: Percentage Variation in Film Thickness by Exposure] 

Irradiation with EUV at an exposure dose of 2.0 times the exposure dose giving the sensitivity above was performed, and the film thickness after exposure but before post-baking was measured. The percentage variation from the film thick› ness when not exposed was determined by the following formula: 

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## These measurement results are shown in Table 8 below. 

## ExampleF 

