<title>Investigation into the origin of microbridging in chemically amplified negative-tone photoresists</title>

Abstract

Microbridge formation in a CAlViN photoresist we have developed is dependent on the ratio of dose to print ( DiP ) to dose to gel ( DTG ) as well as resist contrast. Photoresists formulated with poly(p-hydroxystyrene) (PHS) have a very high tendency to form microbridges when developed in 2.38 wt% TMAH due to high contrast and high a DTP/DTG ratio. When photoresists formulated from PHS were developed in 1 .2 wt% TMAH contrast and DTP/DTG ratio were reduced resulting in microbridging being nearly eliminated. Using this observation we developed an I-line CAMN photoresist with PHS type thermal stability and high resolution capabilities which can be developed in industry standard 2.38 wt% TMAH.

Optimization of DUV Negative Resists for 0.15 .MU.m Lithography.

“…The low molecular weight fraction is assumed to inhibit the formation of insoluble resist segments. Linehan et al have reported that a diluted developer (1.2% TMAH) reduces microbridging [12]. We suppose the reason for their result is that the concentration of the developer is too low to isolate the resist segments, and the microbridges are not observed.…”

Factors Controlling Pattern Formation in Chemically Amplified Resists at Sub-100 nm Dimensions.

“…In our results, the onset of nano-edge roughness and microbridging occur at different polymer molecular weights suggesting that they are independent phenomena. Microbridging has been identified in similar negative-tone CA resist chemistries [19] [20] where its severity was shown to increase with higher polymer molecular weights and/or with stronger developer hydroxide concentration. We are unable to distinguish between these two possibilities with the CGR data now at hand.…”

IBM-JSR 193-nm negative tone resist: polymer design, material properties, and lithographic performance

“…Resolution of chemically amplified, negative-tone resists have been historically plagued by microbridging across narrow trenches. A study by Linehan et al suggests microbridging may be related to high resist contrast and a high ratio of dose-to-print to dose-to-gel 5 when the molecular weight was reduced 6 . Others have suggested that penetration of developer into the exposed, insoluble polymer matrix resulting in swelling may be to blame 7 .…”