Influence of base additives on the reaction-diffusion front of model chemically amplified photoresists

Abstract

The effects of amine base quencher on the photoacid catalyzed deprotection reaction-diffusion front in model photoresists were measured by combination of neutron reflectivity and Fourier transform infrared spectroscopy. Modulation in the location of the base with respect to the diffusing photoacid catalyst changes the spatial reaction extent and illuminates the complex role of the base on the shape of the reaction-diffusion front. Despite similar total extents of reaction, a comparison between uniform base and model photodegradable base distributions demonstrates distinct reaction time and base concentration effects on the deprotection profile shape. These differences arise from the modification of the initial deprotection extent due to both the neutralization of the photoacid and the influence of the changing photoresist composition on the reaction-diffusion process. The use of the model photodegradable base results in a sharper front due to these effects. Lastly, aqueous hydroxide development of these latent images demonstrates a limit to the improvement in feature quality obtained from sharpening of the deprotection profile with base additives.

Photoresist Latent and Developer Images as Probed by Neutron Reflectivity Methods

“…[ 35 ] A single 130 ° C PEB temperature for 15 s is highlighted in Figure 14a . A series of concentrations of the base trioctylamine (TOA) was added at PAG to base molar ratios of 31:1, 15:1 and 10:1, or equivalently 0.1%, 0.2%, and 0.3% mass fractions of TOA.…”

“…These two cases were quantitatively measured by neutron refl ectivity, along with a third case of amines blended with the photoacid generator called coupled acid-base. [ 35 ] The mechanism of how an amine reacts with an acidic proton in a solid thin fi lm will be dependent upon the mobility and reactivity. Proportional neutralization [ 40 , 42 ] is an ideal case whereby the acid is eliminated from the reaction and the concentration of effective acids is reduced by the stoichiometry.…”

“…With this approach the composition profi les of PMAdMA, MA, and MAA were resolved. [34][35][36] Figure 7 a shows neutron refl ectivity data for PHOSt/ PMAdMA bilayers containing di-tert -butylphenyl iodonium perfl uorooctane sulfonate (DTBPI-PFOS) PAG in the acid-feeder layer offset as a function of PEB times at 130 ° C. The periodicity of the refl ectivity fringe wavelength and amplitude indicates the bilayer structure is composed of layers with distinct scattering length densities. The refl ectivity data fi ts are shown by the solid lines.…”

Radiation Chemistry in Chemically Amplified Resists

“…Quenchers (basic compounds), which act as a proton trap site or a buffer in resists, are added to a resist formula to control acid diffusion, 207) sharpen the image slope (reduce LER), [208][209][210][211] and improve the environmental stability of resist materials. 212,213) Because the reaction of acids with quenchers is essential for pattern formation, many studies on it have been carried out.…”

Direct measurement of the spatial extent of the in situ developed latent image by neutron reflectivity

“…[12][13][14] This swollen layer must approach the nominally unreacted and unexposed areas as the bulk development ceases. [16][17][18][19] The mechanism of how the advancing swelling dissolution front faces the transition of soluble to insoluble species ͑solubility switch͒ is crucial to understand resist resolution limits. [16][17][18][19] The mechanism of how the advancing swelling dissolution front faces the transition of soluble to insoluble species ͑solubility switch͒ is crucial to understand resist resolution limits.…”