Extendibility of synchrotron radiation lithography to the sub-100 nm region

Abstract

Studies on correction accuracy of proximity effect for the pattern area density method in electron beam direct writing J.This article discusses the resolution of synchrotron radiation lithography in the sub-100 nm region, taking into consideration the mass production of large-scale integrated circuits, under attainable conditions for the x-ray mask, proximity gap, and resist processes. Resolution and exposure latitude for line-and-space patterns are markedly improved by using a mask with a contrast of only 2.5. Resolutions of 90, 80, 70, and 60 nm can be achieved with proximity gaps of 30, 20, 15, and 10 m if a high-contrast resist and a low-surface tension developer are used. The latitude will be 10% for pattern sizes as small as 70 nm when the proximity gap is narrower than 15 m. The effects of mask duty ͓which is defined to be the ratio of the absorber ͑line͒ width to the pattern pitch, i.e., duty cycle͔ on the optimum exposure dose and mask linearity are also evaluated.

Printing characteristics of proximity x-ray lithography and comparison with optical lithography at 100 and 70 nm technology nodes

“…The extendibility of this technology to the sub-100 nm region has been investigated by carrying out exposure tests for line-and-space patterns, isolated lines, and dynamic random access memory ͑DRAM͒-like and static random access memory-like patterns. [4][5][6] These results indicate that performance of PXL for the mass-fabrication of ULSIs at advanced technology nodes has improved appreciably.…”

Micromachining of inorganic materials using plasma soft x‐rays

“…In addition, one can expect to obtain patterns with higher resolution by means of X-ray lithography [25]. However, the high photon cost and the need for heating or reactive gas are problems to be solved for practical use.…”

Current status and issues of X-ray mask

“…The most critical issue involving the X-ray mask is considered by many researchers to be image placement accuracy. Although the required image placement accuracy is 12 nm in 30 for the 100-nm design rule, the one achieved now is about 50 nm at NTT and the one reported is about 30 nm [5]. To improve this, much efforts are required to find methods reducing mask distortion.…”

“…Deguchi demonstrated that a 70 nm line-and-space pattern can be replicated with a gap of less than 15 pm as Fig. 9(a) shows [5]. The good depth-of-focus allows us to fabricate the high aspect ratio pattern in Fig.…”

“…Since a strong X-ray flux can easily be obtained from compact storage rings [2], generally througlh the use of super conducting magnets, the study of X-ray Jithography has accelerated in many ,absorber <---membrane ~ Si wafer frame companies both in Japan [3] and the U.S.A. [4]. Recently, resolution using X-ray lithography has been demonstrated at dimensions down to 70 nm and even below that [5].…”