Excimer laser lithography

New Negative Deep-UV Resist for KrF Excimer Laser Lithography... 

A photosensitive composition, consisting of an aromatic azide compound (4,4 -diazidodi-phenyl methane) and a resin matrix (poly (styrene-co-maleic acid half ester)), has been developed and evaluated as a negative deep UV resist for high resolution KrF excimer laser lithography. Solubility of this resist in aqueous alkaline developer decreases upon exposure to KrF excimer laser irradiation. The alkaline developer removes the unexposed areas of this resist. 

KrF excimer laser lithography that utilizes shorter wavelength has become of great interest as a means of fabricating 0.3-0.5 micron patterns in semiconductors (1-3). ... 

Azide-phenolic resin photoresists have been reported by workers at Hitachi. They are used for i-line (12) or for deep UV light (13), and the applications to KrF excimer laser lithography have not been demonstrated. 

In this paper, the material characteristics and lithographic evaluation of this new resist are demonstrated. The resist meets the requirements for KrF excimer laser lithography, which exhibits high sensitivity, high resolution and high aspect ratio pattern profiles. 

A negative deep UV resist, consisting of a photosensitive 4,4 -diazidodiphenyl methane and a poly-(styrene-co-maleic acid half ester) resin, has been found to meet the requirements needed for KrF excimer laser lithography. 

We achieved high aspect ratio sub-half-micron pattern fabrication in 1.0 micron film thickness using this new resist. We are convinced that this new resist could make possible simple and efficient single-layer-resist system for KrF excimer laser lithography. 

It is confirmed that the polymer matrix around ablated area was also affected strongly by laser ablation. The change of the matrix properties are brought about over a few tens of pin. This type of information is basically important and indispensable for practical applications such as excimer laser lithography. The time-resolved fluorescence spectroscopy is one of the powerful characterization methods for ablated polymer matrix. 

Chemical amplification type positive resist compositions provided in Table 1 were prepared by Takemoto [4] and were suitable for excimer laser lithography using ArF and KrF lasers. 

An important and interesting aspect of excimer laser lithography is the effect of the large instantaneous power density on the resist sensitivity. One might... 

The absorption characteristics of resist films at the exposure wavelength of an excimer laser are important. For example, an application of conventional positive resists to 248-nm KrF excimer laser lithography is limited by ex-... 

Although high photosensitivity may not be a major factor in the design of resists for excimer laser lithography, matching of the spectral characteristics of the resist and the exposure source continues to be an important challenge. 

A copolymer approach can provide more flexibility to the resist design because all the necessary functions do not have to reside on one component. Today s advanced positive deep UV resists are exclusively based on this concept with 4-hydroxystyrene as one component. However, early copolymer systems and some of the 193-nm resists consisted of lipophilic components only. Incorporation of 4-acetoxystyrene to poly(4- er -butoxycarbonyloxystyrene sulfone) has already been mentioned. This section deals with copolymer resists composed of lipophilic comonomers first and then the currently dominant hydroxystyrene copolymers. Co- and terpolymers for ArF excimer laser lithography will be described in a separate section. 

Another interesting acrylate polymer for 193 nm lithography is a terpolymer of tricyclo[5.2.1.02 6]decanyl acrylate, tetrahydropyranyl methacrylate, and methacrylic acid (Fig. 58) [237]. In conjunction, new alkylsulfonium salts for use in ArF excimer laser lithography have been synthesized [238]. Methyl-(cyclohexyl)(2-oxocyclohexyl)sulfonium and methyl(2-norbonyl)(2-oxocy-clohexyl)sulfonium triflates are highly transparent with their absorption coefficients of 1125 and 1650 L/mofrcm at 193 nm in sharp contrast with... 

With F2 excimer laser lithography at 157 nm, even polymers based on aerylates and norbonenes are too opaque to be of any useful value in resist appheations. Therefore, fluorocarbons and silanol polymers are the two main classes of polymers that have reasonable transparency at this wavelength. Again, like their 193-nm and 248-nm counterparts, the 157-nm resists employ chemical amplification in their imaging mechanism, for quite similar reasons. 

Ogawa, A. Sekiguchi, and N. Yoshizawa, Advantages of a SiO NyiH anti reflective layer for ArF excimer laser lithography, Jpn. J. Appl. Phys. 35 6360 (1996). 

K. Jain, C.G. WiUson, and B.J. Lin, Ultrafast deep UV lithography with excimer lasers, IEEE Electron Device Lett. EDL-3, 53 (1982) S. Rice and K. Jain, Reciprocity behavior of photoresists in excimer laser lithography, IEEE Trans. Electron Dev. ED-31, 1 (1984). 

K. Jain, Excimer Laser Lithography, p. 9. SPIE Press, Bellingham, WA (1990). 

Jain, Excimer Laser Lithography, p. 93, SPIE Press, Bellingham, WA (1990) J. Ewing, Rare gas halide lasers, Phys. Today 31(5), 32 (1978) A. Reiser, Photoreactive Polymers The Science and Technology of Resists, pp. 254 255, John Wiley Sons, Hoboken, NJ (1989). 

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