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We have developed a novolak-based chemical-amplification resist for 0. 13-rim or later reticle fabrication. Forthe 0. 13.jim or later design-rule reticle-fabrication with OPC patterns, the resist resolution is required under 0.2-.tm on the mask substrate. To improve the chemical-amplification resist resolution, it is necessary to control theacid-diffusion in the resist film. We have developed the technique of the acid-diffusion control with neutral-saltadditives. By use of the resist with this technique, we could fabricate 0. 14-jim I/s patterns on a CrOx substrate ata dose of 9.3-iC/cm2 (50kV). The resist has a good margin of doses.Keywords: novolak-based chemical-amplification resist, resist resolution, acid-diffusion control, neutral-saltadditives 1. INTRODUCTION A novolak resin-based chemical amplification (CA) positive resist has been developed for 0. 13-j.tm design-rule reticle-fabrication using 50-kY e-beam reticle writer HL-800M. Novolak-resin-based resists have good process stability such asPost-Exposure Delay (PED) and Post-Coated Delay (PCD) and a good dry and wet etching durability. To achieve the next-generation reticle fabrication with OPC patterns, better critical-dimension (CD) control and cross-sectional pattern controlare necessary.It is well-known problems that CA positive resists form footing and/or T-top profiles due to the loss of photo-generated acidmolecules at the resistisubstrate interface and/or resists surface [1,2]. In a previous paper [1], we reported that the CA resistshows "footing" round corners at the bottom of the profile in the cross-sectional resist profiles on a mask (a chromium-oxide (CrOx) substrate). In addition, acid-diffusion in CA resists during post exposure baking (PEB) is the critical issue. Toperform next-generation reticle fabrication, these problems must be suppressed.To improve the resist profiles, substrate treatments [3,4] or the addition of bases to the resist solution [5-7] have beeninvestigated. On the other hand, there have been many studies on acid-diffusion suppression methods using basic orphotodecomposable basic additives [6,7]. However, substrate treatment may increase the number of defects and the processsteps in the photomask fabrication. The addition of bases, on the other hand, may lower resist sensitivity.To reduce the footing and/or T-top profiles, therefore, we investigated a new resist composition. The use of a matrix resinwhose molecular-weight distribution (MWD) can be controlled - for example, a tandem-type resin - is an effective methodto improve the performance of a conventional novolak resin-based positive photoresist [8]. In a previous paper [9], wereported a performance of the CA resist with the MWD-controfled (MWDC) matrix resin. The MWDC was very effectiveto enhance the resist resolution. For 0. 13-mm or later reticle fabrication, however, the resist performance is still moreimproved. Therefore, the acid-diffusion control is applied to the MWDC novolak based resist. We have been also proposed* |
