S054102 Resist Removal by Steam-Water Mixed Spray
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In the manufacturing process of semiconductor device, MEMS, and so on, lithography which uses photo-resist is a key process to fabricate micro or nano-scale structures, and unnecessary resist should be removed after the process. Typically SPM is used for the resist removal. In this study, we apply the method of steam-water mixed spray that can remove resist without chemicals. In order to clarify the detail mechanism of resist removal, we performed resist removal experiment. In the experiment, spray is traversed over a resist-coated wafer and the removal area is evaluated. The resist-coated conditions such as bake temperature, rotating speed are changed to evaluate the effects of mechanical properties of resist. In addition, removal force is measured to estimate the mechanical properties of resist by using SAICAS. As a result, it is shown that thicker or harder resist tends to be difficult to remove and the results suggest that this method mainly utilizes the physical force of high-speed droplets impact.In this paper, we describe a lithographic technique of exposing complex patterns with an advanced resist processing that connects the high resolution of electron beam lithography and the fast exposure of optical i-line stepper lithography via an Intra Level Mix and Match (ILM&M) approach. The key element of our approach is that we use two successive exposures on one single resist layer directly followed by a single resist development. Process and resist characterization of negative tone resist ma-N 1402 as well as a resolution study for each lithographic tools involved. Lithographic performance of negative tone resist ma-N 1402 has shown structures with dimensions of 55 nm with 300 nm pitch for ebeam lithography (VISTEC SB254, shaped beam) and 350 nm structures for i-line stepper (Nikon NSR 2205i11D). Resist footing problem in structures exposed by i-line stepper is solved by introducing a 200 nm thick bottom antireflective coating AZ BARLI II in ILM&M resist processing sequence. A general processing recipe for electron beam/i-line stepper ILM&M with negative tone resist ma-N 1402 is successfully developed and patterns with different dimensions ranging from sub 100 nm to μm scale were reproducibly fabricated on the same resist layer.
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Extreme Ultraviolet Lithography
Next-generation lithography
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Resists are radiation-sensitive materials used in the fabrication of integrated circuits (VLSI) for imaging the desired pattern onto the silicon wafer. Most resists in use today consist of polymeric solutions that are spin-coated onto the silicon wafer, exposed in a lithographic tool, developed, and completely removed after the pattern has been transferred to the substrate. This paper presents a historical development of resist materials, present uses of resists, and future requirements, dictated primarily by developments in lithographic tools.
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Resist profile shapes become important for 22nm node and beyond as the process window shrinks. Degraded profile shapes for example may induce etching failures. Rigorous resist simulators can simulate a 3D resist profile accurately but they are not fast enough for correction or verification on a full chip. Compact resist models are fast but have traditionally modeled the resist in two dimensions. They provide no information on the resist loss and sidewall angle. However, they can be extended to predict resist profiles by proper setting of optical parameters and by accounting for vertical effects. Large resist shrinkages in NTD resists can also be included in the compact model. This article shows how a compact resist model in Calibre can be used to predict resist profiles and resist contours at arbitrary heights.
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This paper describes some of the basic physicochemical considerations necessary to design a resist for use in 193 nm lithography. Of fundamental importance are the photoreaction which generates the photoacid, the reactivity of the photoacid the dissolution of the resist in the developer, and the adhesion of the images to the substrate. These phenomena are discussed and we show results that demonstrate progress in these areas. In addition, we show preliminary etch resistance of our polymer system and selected lithographic results.
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Abstract An introduction to lithographic resists is presented. The principles of lithography are described and the essential attributes resist materials must possess are enumerated. The chemical and physical properties of resists of current technological importance are discussed within this framework, with an emphasis on how functional performance is related to these properties. Finally, examples are provided of how resist materials are being tailored for future lithographic imaging technologies.
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Laser linewidth
Characterization
Extreme Ultraviolet Lithography
Photoresist
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Synchrotron x-ray lithography of a new environmentally stable chemically amplified positive resist (ESCAP) is described. The resist consists of a thermally and hydrolytically stable resin and acid generator and employs high temperature bake processes to achieve resistance to airborne contamination. The resist is environmentally stable due to reduction of the free volume by annealing and affords true single layer x-ray lithography, eliminating a need for a protective overcoat. Its design concept and x-ray lithographic performance are discussed.
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Resist designing for mask-making has been carried out basically using Si-wafers or chrome-coated Si-wafers, and its baking has been done for 60 to 90 seconds which was used for the wafers generally. There is a definite difference that 6025 mask-substrates (6025s) require 7.5 minutes or over to achieve 150deg.C and such, depending on a baking system configuration though, while the wafers require only 30 seconds or less, due to differences in thermal properties and in thickness between the two substrates. Resist baking conversion, by the way, is generally accomplished by adjusting the 6025s surface temperature to the wafers. Meanwhile, resist baking conversion in time, including ramping up and cooling down speed (or slope), seems not to be considered carefully between the two substrates so far. Recently, we experienced a difficulty that an essential performance of a newly designed trial resist of a low activation energy type CAR, which had been designed and developed using the wafers as usual, was not shown on the 6025s due to deteriorating in contrast, i.e. gamma value as well as remaining resist thickness in un-exposed area (dark erosion). This seemed to be due to a particular long baking for 10min. This report describes a trial and its results to convert the baking condition from the wafers to the 6025 mask-substrates, and also brings up some issues found in the resist baking conversion or adjustment.
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The thickness dependence of resist performance has been investigated. It has been reported that principal properties such as resist sensitivity show strong dependence on resist film thickness. In current standard resist called chemically amplified resist, acids play the most important role in resist pattern formation. However, the dependence of acid concentration on resist thickness has not been reported. Better understanding of acid related issues is important for the development of high performance resists and the precise simulation of resist pattern profiles. In this work, the acid density in poly(4-hydroxystyrene), which is a widely-used backbone polymer for chemically amplified resists, was measured quantitatively by spectroscopic experiments. The average acid concentration nonlinearly increased by 14% with the increase of resist thickness from 65 to 4000 nm.
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Several chemically-amplified resists, positive and negative, have been evaluated for synchrotron x-ray lithography. Some have shown sensitivities as low as 10.1 mJ/cm2. Linewidths of 0.3 micron have been achieved in 1 micron thick single-layer resist with vertical sidewalls and good process latitude, at an x-ray dose of below 50 mJ/cm2. The chemically amplified resists are processed similarly to conventional resists using metal ion free aqueous base developers. Data re presented for resists from Shipley, Rohm and Haas, and Hoechst AG. Lithographic exposures were performed with the University of Wisconsin's Aladdin synchrotron, using the ES-1 beamline of the Center for X-ray Lithography.
Photoresist
Extreme Ultraviolet Lithography
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