Patrick Schiavone

Application of alternating-type phase shift mask to polysilicon level for random logic circuits

Of all phase shift mask techniques, the alternating type is both the best for improving resolution and the most difficult to use. The problems in its use include complicated design modifications, unwanted phase-transitionprinting and very challenging mask fabrication. This paper is the first report of a solution using an automatic shifter arrangement and a three-step phase-transition technique on etched-quartz alternating-type phase shift mask (PSM). The lithographic results as well as the electrical results presented demonstrate the feasibility of the technique for application to complex circuits and show the capabilities of this kind of mask in printing smaller dimension lines.

Flare impact on the intrafield CD control for sub-0.25-μm patterning

The aim of this paper is to investigate the intrafield flare distribution and its link with the intrafield CD variation for various ASML lithographic tools. Flare is measured as the required dose to clear a 100micrometers -large positive resist pattern and comparing it with dose-to-clear Eo. The reticle layout used is compared of a repetitive cell which allows for 77 measurements within a single 22 X 22 mm2 field. Experimental results show that in the field of a stepper, flare decreases almost linearly form center to edge. In the field of a scanner, the flare distribution result from the distribution inside the illumination slit which is ellipsoidal. Comparing the intrafield flare distribution to the intrafield CD uniformity , it appears that flare is responsible for a part of the across field CD variation. We will see in this paper how it is possible, using a method based on statistical considerations, to decorrelate both the contributions of mask CD errors and flare variation to the intrafield CD dispersion for dense lines and 1/3 for isolated lines. The intrafield flare variation is also found to contribute a lot to the signature of the CD uniformity and to the 3 sigma dispersion.

SiON-based antireflective coating for 193-nm lithography

Silicon oxynitride has been shown to be an efficient antireflective materials at 365 and 248 nm. In this paper, we confirm that SiON can be used successfully at 193nm. SiON is deposited at low substrate temperature in a Plasma Enhanced Chemical Vapor Deposition reactor using silane and nitrous oxide as precursor gases. Compatibility of the silicon oxynitride underlayer with sensitive chemically amplified resist is examined. A simple surface treatment is shown to give very good results and almost completely suppresses any contamination of the chemically amplified resist.

Process optimization of a negative-tone CVD photoresist for 193-nm lithography applications

New photoresists and processes are required for sub 0.15 micrometers design rules and currently an important effort is on- going for single layer resists optimization at 193 nm. Top surface imaging can be an interesting alternative approach. An all dry chemical vapor deposition (CVD) process based on plasma polymerized methylsilane (PPMS) or plasma polymerized dimethylsilane (PP2MS) provides a thin conformal and photosensitive layer at 193 nm. A thin amorphous film of Si- Si bonded material is deposited using plasma enhanced chemical vapor deposition with methylsilane or dimethylsilane as the gas precursor. Upon 193 nm exposure under air, photo-induced oxidation of the CVD resist occurs, generating a latent image. The image is then developed in a chlorine-based plasma, providing a negative tone process. This mask can be used to pattern a thick organic underlayer to provide a general bilevel process. Lithographic results on both a 193 microstepper as well as a full field production stepper are presented: resolution down to 0.10 micrometers equal L/S was obtained. A preliminary comparison between PPMS and PP2MS materials is presented, including FTIR results, stability of the films in air and lithographic performance including line edge roughness.

Inorganic bottom ARC SiOxNy for interconnection levels on 0.18-μm technology

BARC technology, originally developed for gate level has now to be applied to interconnection ones. Requirements for dielectric interconnection levels are different from gate level. In the case of gate level ARC has to minimize reflectivity at resist/substrate interface due to notching and resist swing curve effects. Whereas ARC for interconnections has to minimize reflectivity variation at resist/substrate interface due to swing curve effect in the dielectric layer. For interconnection, ARC must be as absorbent as possible at stepper exposure wavelength, and two ways are foreseen: ARC layer with high k value at 248 nm, and ARC layer with high thickness. For a reflectivity variation minimum criteria, we can find a couple values (k, minimum thickness). Experiments give us for a reflectivity variation below 5% the following couples: (k equals 0.7, 1200 angstroms thickness) and (k equals 1.1, 850 angstroms). In this paper we describe different applications of SiOxNy for interconnection levels: via, contact and damascene line level. Improvements depending of the SiOxNy thickness are seen in CD dispersion. To conclude SiOxNy ARC can be used for interconnection levels, and its performance depends on ARC couple values (k, thickness).

0.12 µm Optical Lithography Performances Using an Alternating Deep UV Phase Shift Mask

Manufacturing the next generation of devices will demand lithographic capability in the sub-0.18 µm range. The phase shift mask (PSM) is a key emerging technology which is thought to extend 248 nm optical lithography. Using the Levenson PSM technique allows us to improve resolution by as much as 50% at gate level. This paper describes the lithographic performances of the Shipley UV5 photoresist on SiOxNy bottom antireflective coating (BARC), using alternating PSM and an ASM/90 Deep UV stepper. Critical dimension (CD) measurement was done on an OPAL 7830i metrology scanning electron microscope (SEM). Results on sub-0.18 µm design rules are presented as follows. –The first part concerns experimental conditions: masks, process conditions, anti-reflective substrates, etching and metrology are discussed. –The second part concerns lithographic performances: process linearity from 0.12 µm to 0.18 µm, 0.12 µm isolated line process latitudes of 7% energy latitude for 0.8 µm depth of focus (DOF) have been exhibited. Finally we try to evaluate the proximity effect and the ultimate resolution of this technology.

Prediction of lithographic performance of resist/BARC bilayers in topographic situations: application to organic and inorganic BARCs

Due to inherent planarization effects when coating on topography, both the resist and organic bottom anti reflective coating (BARC) thicknesses vary, as do the final reflectivity and critical dimensions (CD). As a consequence, determination of the optimal BARC thicknesses and prediction of the lithographic performance, taking into account topography effects over the whole chip, are not easy. Lithographic performances are thus usually measured or calculated using modeling over plane wafers. In this paper, we propose a practical representation of the lithographic performance of the BARC/resist bilayer and a simulation algorithm allowing determination of both the optimal BARC thicknesses and the lithographic performance window over the whole chip. Practical examples are given demonstrating the role of such a simulation.

0.18-μm optical lithography performances using an alternating DUV phase-shift mask

The phase shift mask (PSM) is a key emerging technology thought to be extending 248 nm lithography. In this paper, we describe the lithographic performances of Shipley UV5 photoresist on SiOxNy Bottom Anti Reflective coating (BARC), using alternating PSM and ASM/90 Deep-UV stepper. Results on 0.18 micrometer design rules are presented: lithographic performances, comparison between PSM and binary mask, sub 0.18 micrometer performances ({1}) and the ultimate resolution of this technology are reported. To conclude we demonstrated the 0.18 micrometer lithography feasibility with alternating mask and KrF stepper, and showed that all the necessary tools are today available to achieve such goals.

0.12 mm optical lithography performances using an alternating DUV phase shift mask

Abstract Manufacturing the next generation of devices will demand lithographic capability in the sub 0.18 μm range. The phase shift mask (PSM) is a key emerging technology thought to be extending 248 nm optical lithography. Using the Levenson PSM technique allows us to improve resolution by as much as 50% at gate level. This paper describes the lithographic performances of Shipley UV5 photoresist on SiOxNy BARC, using alternating PSM and an ASM/90 Deep UV stepper. CD measurement was done on OPAL 7830i metrology SEM. Results on sub 0.18 μm design rules are presented: • - The first part concerns experimental conditions: masks, process conditions, anti-reflective substrates, etching and metrology are discussed. • - The second part concerns lithographic performances: process linearity from 0.12 μm to 0.18 μm, 0.12 μm isolated line process latitudes of 7% Energy Latitude for 0.8 μm DOF have been exhibited. Finally we try to evaluate proximity effect and the ultimate resolution of this technology.

New method of determination of the photoresist Dill parameters using reflectivity measurements

In this paper, we describe a new methodology for the determination of Dill parameters based on reflectivity measurements. In opposition to previous methods, samples are produced using the usual process steps. Silicon wafers and standard photoresist coating procedures are used. Moreover, reflectivity measurements can be performed on any reflectometer, a piece of equipment universally present in an industrial environment. A fitting procedure is performed on the reflectivity data in order to extract the ABC parameters. The delicate steps of the methods are described in the paper. Comparison with other exposure parameter extraction methods on I line resist shows good agreement. Dependence between exposure parameters and development parameter extraction is also discussed. It is shown that several empirical parameter sets can be equivalent, at least from the simulation point of view.