KrF 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. 

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-... 

The first laser lithography for mass production is KrF excimer laser lithography. Since the middle of 1990s, it is used for mass production of 256-Mb DRAM with a feature size of 0.25 /xm. The linewidth of 0.6 pm with spectral narrowing technique is widely used. The KrF laser operates at several kHz, with an average output power of several tens watts, and a gas lifetime of over 1x10 shots. 

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. 

As mentioned in Section 3.1.2, attractive UV sources for lithography are those that produce high power and poor spatial and temporal coherence. Jain and co-workers (13-15) demonstrated that excimer lasers provide excellent quality, speckle-free images with resolution to 0.5 xm in a contact mode. The images were obtained in l- xm-thick diazoquinone photoresists such as AZ2400 with a XeCl laser at 308 nm and a KrF laser at 248 nm... 

Excimer laser projection lithography was attempted by Dubroeucq and Zahorsky (212). The image projection system having a KrF laser and a lOx microscope objective lens is shown in Figure 3.63. The low divergence of... 

The key operational parameters of exciplex and excimer lasers used in optical lithographic applications include exposure-dose-related parameters comprising average power, pulse energy, repetition rate, and pulse width temporal coherence spatial coherence including beam dimensions, beam divergence, and beam uniformity and maintenance and reliability. Table 13.2 lists some of the key operational parameters of KrF, ArF, and F2 laser systems used in optical lithography. 

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