The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10× tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.

Improving resolution in photolithography with a phase-shifting mask

A lithographic apparatus configured to project a patterned beam of radiation onto a target portion of a substrate is disclosed. The apparatus includes a first radiation dose detector and a second radiation dose detector, each detector comprising a secondary electron emission surface configured to receive a radiation flux and to emit secondary electrons due to the receipt of the radiation flux, the first radiation dose detector located upstream with respect to the second radiation dose detector viewed with respect to a direction of radiation transmission, and a meter, connected to each detector, to detect a current or voltage resulting from the secondary electron emission from the respective electron emission surface.

Lithographic apparatus, and device manufacturing method

A method of etching a substrate is provided. The method of etching a substrate includes transferring a pattern into the substrate using a double patterned amorphous carbon layer on the substrate as a hardmask. Optionally, a non-carbon based layer is deposited on the amorphous carbon layer as a capping layer before the pattern is transferred into the substrate.

Techniques for the use of amorphous carbon (APF) for various etch and litho integration scheme

In one aspect, the present invention is directed to a technique of, and system for simulating, verifying, inspecting, characterizing, determining and/or evaluating the lithographic designs, techniques and/or systems, and/or individual functions performed thereby or components used therein. In one embodiment, the present invention is a system and method that accelerates lithography simulation, inspection, characterization and/or evaluation of the optical characteristics and/or properties, as well as the effects and/or interactions of lithographic systems and processing techniques.

System and method for lithography simulation

Techniques are provided for extending the use of phase shift techniques to implementation of masks used for complex layouts in the layers of integrated circuits, beyond selected critical dimension features. The method includes identifying features for which phase shifting can be applied, automatically mapping the phase shifting regions for implementation of such features, resolving phase conflicts which might occur according to a given design rule, and application of assist features and proximity correction features. The method includes applying an adjustment to a phase shift mask pattern including a first and a second phase shift window, and a control chrome with a control width, and/or to a trim mask pattern having a trim shape with a trim width based upon one or both of a rule based correction and a model based correction to improve a match between a resulting exposure pattern and a target feature.

Phase shift masking for complex patterns with proximity adjustments

We present results looking into the feasibility of 100-nm Node imaging using KrF, 248-nm, exposure technology. This possibility is not currently envisioned by the 1999 ITRS Roadmap which lists 5 possible options for this 2005 Node, not including KrF. We show that double-exposure strong phase- shift, combined with two mask OPC, is capable of correcting the significant proximity effects present for 100-nm Node imaging at these low k1 factors. We also introduce a new PSM Paradigm, dubbed 'GRATEFUL,' that can image aggressive 100-nm Node features without using OPC. This is achieved by utilizing an optimized 'dense-only' imaging approach. The method also allows the re-use of a single PSM for multiple levels and designs, thus addressing the mask cost and turnaround time issues of concern in PSM technology.

100-nm node lithography with KrF?

The present invention generally relates to improved binary half tone (“BHT”) photomasks and microscopic three-dimensional structures (e.g., MEMS, micro-optics, photonics, micro-structures and other three-dimensional, microscopic devices) made from such BHT photomasks. More particularly, the present invention provides a method for designing a BHT photomask layout, transferring the layout to a BHT photomask and fabricating three-dimensional microscopic structures using the BHT photomask designed by the method of the present invention. In this regard, the method of designing a BHT photomask layout comprises the steps of generating at least two pixels, dividing each of the pixels into sub-pixels having a variable length in a first axis and fixed length in a second axis, and arraying the pixels to form a pattern for transmitting light through the pixels so as to form a continuous tone, aerial light image. The sub-pixels' area should be smaller than the minimum resolution of an optical system of an exposure tool with which the binary half tone photomask is intended to be used. By using this method, it is possible to design a BHT photomask to have continuous gray levels such that the change in light intensity between each gray level is both finite and linear. As a result, when this BHT photomask is used to make a three-dimensional microscopic structure, it is possible to produce a smoother and more linear profile on the object being made.

Binary half tone photomasks and microscopic three-dimensional devices and method of fabricating the same

This article presents the results of a collaborative effort between Molecular Imprints, Inc. (MII) and Photronics, Inc. to develop a baseline process for fabricating Step and Flash Imprint Lithography (S-FIL) templates that are compatible with lithography tools being developed by MII. S-FIL is a replication technique with sub-50nm resolution capability that has the potential to lead to a low cost, high throughput process. Template fabrication results and S-FIL patterning results on 200mm wafers are presented.

Fabrication of Step and Flash imprint lithography templates using commercial mask processes

The rise of low-k 1 optical lithography in integrated circuit manufacturing has introduced new questions concerning the physical and practical limits of particular subwavelength resolution-enhanced im- aging approaches. For a given application, trade-offs between mask complexity, design cycle time, process latitude and process throughput must be well understood. It has recently been shown that a dense-only phase shifting mask (PSM) approach can be applied to technology nodes approaching the physical limits of strong PSM with no proximity effects. Such an approach offers the benefits of reduced mask complex- ity and design cycle time, at the expense of decreased process through- put and limited design flexibility. In particular, dense-only methods offer k 1,0.3, thus enabling 90 nm node lithography with high-numerical ap- erture 248 nm exposure systems. We present the results of experiments, simulations, and analysis designed to explore the trade-offs inherent in dense-only phase shift lithography. Gate and contact patterns corre- sponding to various fully scaled circuits are presented, and the relation- ship between process complexity and design latitude is discussed. Par- ticular attention is given to approaches for obtaining gate features in both the horizontal and vertical orientation. Since semiconductor investment is dependent on cost amortization, the applicability of these methods is also considered in terms of production volume. © 2002 Society of Photo-

Investigation of the physical and practical limits of dense-only phase shift lithography for circuit feature definition

The steady move towards feature sizes ever deeper in the subwavelength regime has necessitated the increased use of aggressive resolution enhancement techniques (RET) in optical lithography. The use of ever more complex RET methods including strong phase shift masks and complex OPC has led to an alarming increase in the cost of photomasks, which cannot be amortized by many types of semiconductor applications. This paper reviews an alternative RET approach, dense template phase shift lithography, that can substantially reduce the cost of optical RET. The use of simple dense grating templates can also eliminate serious problems encountered in subwavelength lithography including optical proximity and spatial frequency effects. We show that, despite additional design rule restrictions and the use of multiple exposures per critical level, this type of lithography approach can make economic sense depending on the number of wafers produced per critical photomask.

Peter D. Rhyins

Papers

100-nm node lithography with KrF?

Binary half tone photomasks and microscopic three-dimensional devices and method of fabricating the same

Fabrication of Step and Flash imprint lithography templates using commercial mask processes

Investigation of the physical and practical limits of dense-only phase shift lithography for circuit feature definition

Dense only phase-shift template lithography