Novel EUV Resists Materials for 16nm HP and beyond

Abstract

Extreme ultraviolet (EUV) lithography is a candidate for the manufacturing of semiconductor devices at the 22 nm half pitch node and below. EUV lithography requires high performance resist with limited outgassing property. The key challenge for EUV resist is the simultaneous requirement of ultrahigh resolution (R), low line edge roughness (L) and high sensitivity (S) for lines and spaces (LS) features. To achieve high sensitivity, containing fluorine atom is one of the popular methods because the fluorine atom absorbs EUV light strongly. However, when the resist polymer has fluorine atom, the contact angle (CA) of the resist becomes high. It is difficult to rinse high CA resist so the containing fluorine atom have a problem of defects. In this paper, we will report the relationship of line edge roughness and acid diffusion length and the method to diminish defects caused by high CA. We achieved good resolution and LER improvement by controlling acid diffusion length. Moreover, we found the relationship of the number of defects and the structure of the monomers containing fluorine units.Keywords: EUV 16nm HP, Fluorine resin, Short acid diffusion length PAG, Rinse, Defect 1.IntroductionExtreme ultraviolet (EUV) lithography that extends photolithography to extreme shorter wavelength (13.5 nm) is capable to achieve sub 20 nm half pitch resolution by single exposure [1]. Therefore, EUV lithography is the leading candidate to succeed 193 nm immersion lithography. However EUV lithography presents new challenges in nature of the EUV radiation and requires development of new infrastructure which is different from traditional optical lithography system. EUV exposure will be performed under vacuum condition with reflective type photo mask instead of transmitting type photo mask since most of the materials absorb 13.5 nm radiation light. The source power of EUV light is still low. So EUV resist materials with ultrahigh resolution (sub-20nm HP) and high sensitivity is required for EUVL applications. To improve EUV resist lithography performance, many research groups were focused on the development of EUV resist with new and novel materials [2][3][4]. We have developed new resist materials such as short acid diffusion length PAG, silicon type under layer, nd molecular resist and etc [5,6]. To achieve minimum resolution, acid diffusion length (ADL) must be controlled. We have already demonstrated the relation between ADL and resist lithography performance. To achieve high sensitivity EUV resist absorption should be improved. Incorporating atoms which have high EUV absorption to EUV resist is one of the most attractive methods to improve EUV resist absorbance. Fluorine chemistry is one of the well-known and relatively simple process to be introduced to the resist material. However, resist containing resin with fluorine atom also shows hydrophobicity and the contact angle of these resist become high. Rinsing high contact angle resist is difficult during development step and causes defects. In this paper, we will discuss combinat...

Recent EUV Resists toward High Volume Manufacturing

“…Combined with photoradical initiator or PAG, these NP gave both positive and negative tone patterns. The best result was obtained from methacryl acid (MAA) or trans-2, 3-dimethylacrylic acid (DMA) ligated ZrO 2 -NP with PAG enabling sub 30 nm line patterns at an EUV dose below 5 mJ/cm 2 , showing one of the best EUV sensitivity results ever reported. It was assumed that ligand exchange from weaker acid (MAA, DMA) to stronger acid from PAG (benzoic acid, sulfonic acid etc.)…”

“…It is believed that higher Tg polymer is favorable to suppress acid diffusion which deteriorates resolution and LWR. Sakai et al reported that 13% increase of polymer Tg lead LWR improvement from 5.9 nm to 3.9 nm in 22 nm HP [2]. While sensitivity became slightly worse, the total resist performance turned out improved, judged from the Z-factor [3].…”

“…Saccharose cored star block copolymers by Wieberger et al consisted of GBLMA/ MAMA turned out better sensitivity than its star random polymer analogues [9], and an acid cleavable core based star polymer with polyhydroxystyrene (PHS) arms by Iwashita et al showed better EUV resist performance than its linear polymer in sensitivity and LWR for 30 nm LS [10]. Copolymers of tetrafluoroethylene(TFE)-norbornene derivative by Yamashita et al [11] and those of trifluoromethacrylate-vinyl ether by Christianson et al [12] were also reported aiming for high EUV light absorption by fluorine atoms, demonstrating 10 mJ/cm 2 [14]. From the electron affinity point of view, linear correlation between the reduction potential of PAG and the acid generation efficiency was found by Tsubaki et al [15].…”

Resist material options for extreme ultraviolet lithography

“…A significant improvement in the resolution has been expected for EUV lithography because of the reduction in the wavelength. The resolution of EUV lithography with chemically amplified resist processes has already reached the sub-16-nm region [5,6]. The focus of the resist development is shifting to the 11-nm half-pitch node.…”

Feasibility study of sub-10-nm-half-pitch fabrication by chemically amplified resist processes of extreme ultraviolet lithography: II. Stochastic effects

“…3) The development of chemically amplified resists capable of 11-nm-half-pitch fabrication is ongoing. 4,5) Also, high NA exposure tools have recently attracted much attention. 6) The resolution of the optical image will be significantly improved.…”