ELSEVIER Microelectronie Engineering 30 (1996) 295-299 MICROELECTRONIC ENGINEERING Determination of acid diffusion and energy deposition parameters by point e-beam exposure in chemically amplified resists I.Raptis, L.Grella a, P.Argitis, M.Gentili a, N.Glezos, G.Petrocco a Institute of Microelectronics (IMEL) -NCSR "DEMOKRITOS" 15310 Ag. Paraskevi, Greece aIstituto di Elettronica dello Stato Solido (IESS) -CNR Via Cineto Romano 42 1-00156 Rome, Italy ABSTRACT A new method for the measurement of acid diffusion in chemically amplified resists is introduced. It is based on the measurement of the diameter of lithographic features (pillars for negative resists) obtained from single pixei e-beam exposures to determine the proximity function in a wide range of doses and PEB times. The method is applied in the measurement of the diffusion coefficients of two negative chemically amplified resists, the commercial resist SAL-601 (Shipley) and a prototype epoxy novolac based resist (EPR) developed at IMEL. The method directly provides proximity effect correction parameters for chemically amplified resists. 1. INTRODUCTION In recent years chemically amplified resists, CARs, have been increasingly used in microlithography due to their high sensitivity and high resolution capabilities. Negative resists of this class have been successfully applied in sub quarter micron e-beam lithography (e.g. [1]). Nevertheless, their process complexity poses limitations to their use. In these resists acid is generated by the sensitizer during exposure (optical, e-beam, or X-ray) which catalyses the necessary for solubility change reactions during Post Exposure Bake (PEB). The acid diffuses during exposure - PEB delay time and especially during PEB time, thus changing the after exposure latent resist image. Therefore, PEB conditions strongly affect the lithographic characteristics of the examined resist. Several models have been applied for the measurement of acid diffusion and its influence on lithography. Fedynyshyn et.al [2] have used the threshold acid density model on 1.0 p,m lines/ spaces exposed by excimer laser radiation. Yoshimura-et.al [3] used single line patterning with SEM (beam diameter 2 nm at 5 KeV) on 20 nm SAL-601. Nakamura-et.al [4,5] used a mask replication method based on X-ray exposure and measuring the undercut beneath a X-ray absorber layer. Methods for physicochemical measurement of acid diffusion coefficients, eg conductivity measurements [5, 6] have been also developed. In this paper, a new method for the determination of acid diffusion parameters and the lithographic performance of CARs is proposed. It is related to other lithography based methods but it is especially developed for e-beam lithography. This method is based on single pixel exposures and it has been applied on two different negative resists. 2. EXPERIMENTAL SET-UP The patterning in all cases was performed by a Leica Cambridge EBMF 10cs/120 vector scan e- beam. The system was calibrated at an accelerating voltage of 40 KV and delivered e- beam spot sizes (Full Width Half Maximum : FWHM) were in the range of 45 - 55 nm for 0.3 - 0.5 nA current. The method used, is based on single electron beam exposures [7] in a wide range of doses (5-6 orders of magnitude incident charge with logarithmic scale). After development, resist pillars are remaining with increasing diameter as incident charge increases (Figure 1). Inspection and metrology of resist pillars was performed by a calibrated Leica Stereoscan 360 SEM equipped with a LaB 6 cathode. In order to improve resolution and therefore reduce uncertainty, measurements were performed by 0167-9317/96/$15.00 © 1996 - Elsevier Science B.V. All fights reserved. SSDI 0167-9317(95)00249-9