Reinhard Springer

Comparative evaluation of chemically amplified resists for electron‐beeam top surface imaging use

The ultimate lithographic performance of e‐beam direct writing can only be achieved if the proximity effect is reduced by a top surface imaging resist technology. The capability of some commercial and experimental chemically amplified resists for an e‐beam‐sensitive top surface imaging process were evaluated. Analogous to the resist contrast, a silicon contrast was defined, which characterizes the silylation property of the resists very well and enables a comparison of the evaluated resists. The influence of bake and silylation conditions on the silicon contrast was investigated. The patterning results prove that the proximity effect was reduced dramatically. One of the evaluated resists was applied to structuring the metal layers of a 0.8‐μm‐CMOS technology.

Comparative evaluation of electron-beam sensitive single layer top surface imaging and bilayer chemical amplification of resist lines process for stencil mask making

Hardmask-less stencil mask making requires resist masks with a high aspect ratio. Single layer top surface imaging (TSI) and bilayer chemical amplification of resist lines (CARL) were evaluated and compared, with respect of generating irregular resist features below 180 nm in a film thickness of 850 nm. Special methods for eliminating the resolution-limiting effect of the glass transition temperature (Tg) drop are described. Optimized plasma etching conditions for both thin layer imaging (TLI) techniques were developed. Finally, results of a deep silicon etching process using the TLI resist masks are presented.

Top surface imaging process at and below quarter-micron resolution and pattern transfer into metal

The use of top surface imaging processes pushes the limits of both deep ultraviolet lithography and e-beam direct writing. However, the flow effect due to silylation with monofunctional aminosilanes prevents the creation of a faithful resist mask of a high resolution. The application of mixed mono- and bifunctional agents causes crosslinking of the silylated resist and eliminates the flow. We investigated details of the silylation of novolak-based chemically amplified resists with a mixture of bis(dimethylamino)methylsilane and dimethylsilydiethylamine. After mixing, new materials evolved until a stable ratio of all components was reached. During silylation the ratio changes again and requires a continuous adaptation of the silylation parameters. The optimized process enables the realization of a 0.15 μm pattern in 0.7 μm thick resist. An inductively coupled plasma etcher was evaluated for transferring of the resulting resist structures into typical aluminium alloys. The developed process enables the etch...

Systems of fiber-coupled diode lasers as versatile sources of high-brightness radiation

Incoherent superpositioning of radiation from a single-mode fiber bundle with 200 mW output power per fiber allows to realize power densities of 2 MW/cm2. The total power being directly scalable with the number of fibers. With special optics for imaging the fiber-bundle endface onto the target instead of simply focusing it is possible to control the power density within that spot. Coherent superpositioning allows to further increase the power density and to direct the beam to a spot within the field of the incoherent superposition. Such systems could be useful for all kinds of applications requiring high-brightness radiation like cutting and welding or laser projection, printing plates, lithography, etc.

High-performance TSI process for e-beam using vapor-applied crosslinking silylating agents

The use of the SAHR (silylated acid hardened resist)-process for e-beam direct writing enables a high resolution in thick resists because the resolution-limiting effect of the forward scattering is eliminated. However, the volume expansion combined with the drop in glass transition temperature during silylation by monofunctional agents prevents, in spite of using the flow- effect reducing pre silylation development (PSD), the faithful preparation of irregular subquarter-micron patterns. In order to eliminate the flow problem and ensure high silicon contrast as well as low swelling of the silylated resist region, we evaluated mixtures of dimethylsilydiethylamine (DMSDEA) and bis(dimethylamino)methylsilane [B(DMA)MS] as silylating agents. A bifunctional agent share of 30% restrains the flow effect without decreasing the silicon concentration in contrast to the use of pure DMSDEA. A short, dilute alkaline development before silylation increases the dependence of silicon depth on exposure dose and reduces as a consequence the CD-deviations of irregular pattern elements due to the pattern-related backscattering. The realization of a 0.15 micrometer pattern in 0.7 micrometer thick resist has been demonstrated.

Multiconcens: An exposure method for submicron contact‐hole layers, using variable‐shape electron‐beam direct‐write and single‐layer resist

With Multiconcens (multiple concentric shots), a novel exposure method is presented, which is especially tailored for variable‐shape electron‐beam lithography of submicron contact‐hole layers, exposed into single‐layer positive resist. The goal is to provide a critical dimension‐accurate, technological processable resist mask with minimum effort in order to generate functioning contact and via holes. Typical experiments demonstrate, after comparison with results from conventional uncorrected single‐shot exposure, the advantage of the method, which guarantees better stability with respect to process fluctuations, for the desired resist profile. Together with a convenient data preparation, the Multiconcens exposure principle can correct topography influences occuring with planarization effects of single layer resist. The feasabilty of contact holes with dimensions required for submicron technologies using thick single‐layer resist is also shown.