Process proximity correction using an automated software tool

Maurer, Wilhelm; Dolainsky, Christoph; Thiele, Joerg; Friedrich, Christoph; Karakatsanis, Paul

doi:10.1117/12.310754

Cited by 11 publications

(5 citation statements)

References 3 publications

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“…5751 The deformation observed on the mask can be seen to of transferred to the images in resist as can be seen in figures 5 and 6. What is interesting to note is that any mask error transfer to the mask is not magnified in the out of focus case as it is for optical lithographies at these dimensions [9]. Photoresists used for e-beam lithography have a very long history and do not suffer the same etch resistance problems as were encountered during the introduction of 248nm and then 193nm lithography.…”

Section: Imaging Resultsmentioning

confidence: 98%

Device based evaluation of electron projection lithography

et al. 2005

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As we move technology further and further down the geometry scale we are coming upon imaging situations where our use of existing optical lithography is being questioned due to the lack of process margin in manufacturing lines. This is especially apparent in the imaging of contacts where memory devices, that generally have the densest arrays of these features, may no longer be able to print the desired features. To overcome this it is necessary to either modify the design, a very expensive and time consuming process, or find an imaging process capable of printing the desired features. Electron Projection Lithography (EPL) provides an option to print very small features with a large process margin.In this paper we detail the performance of both memory and logic based designs in an EPL process. We detail the manufacture and results of stencil mask manufacture. Data is also presented showing the imaging results (DOF, exposure latitude, pattern transfer) of features down to 50nm imaged on Nikon's EB1A tool.

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Section: Imaging Resultsmentioning

confidence: 98%

Device based evaluation of electron projection lithography

et al. 2005

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“…We will also highlight the changes in Mask Error Factor (MEF) [1] in EUV imaging as sigma is changed and through focus, for different CD sizes and densities. Data from line and space patterns will be analysed along with data for contact holes.…”

Section: ) Introductionmentioning

confidence: 99%

Compensation for imaging errors in EUV lithography

Harris

McCallum

2004

SPIE Proceedings

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In this paper we will examine some of the fundamental imaging effects that must be considered with the intended implementation of Extreme Ultraviolet Lithography (EUVL). The paper will show how simulation can be used to examine issues such as image placement and the effect of mask dimension errors. We will show how the exact structure of an EUV mask need not be simulated, but the use of Fourier boundary conditions may be used as an accurate substitute, considerably speeding up computation time. Further, this technique is used to show the positional error that is inherent in an off-axis reflective optic design such as that proposed for EUV exposure tools. Any dimension error that is produced on the mask will not linearly transfer to the printed wafer, this is known as Mask Error Factor (MEF). We will present simulation data showing that the off-axis nature of the incident light leads to different rates of change of printed CD, at defocus, for features orientated perpendicular to each other. These effects must then be taken into account when we consider reticle error budget for EUVL technology. 1) INTRODUCTIONIn the Extreme Ultraviolet (EUV) portion of the electromagnetic spectrum it is almost impossible to create highly transmissive materials, so in an optical system all optical elements must be reflective. The same principles must therefore be applied to the construction of the photomask, where we use a combination of an absorber and a multilayer stack to project an image from the mask. As a result in an EUV exposure tool, due to this requirement for reflectivity, the incident light onto the photomask is off-axis thus a shadow effect is created at the edge of the absorber on the mask. This 'shadow' then propagates through the imaging system to produce a non-ideal image on the wafer.In this paper we will use simulation based data to present how this shadow phenomenon effects both image placement and measured CD when comparing similar geometry's in both x and y directions. We will also highlight the changes in Mask Error Factor (MEF) [1] in EUV imaging as sigma is changed and through focus, for different CD sizes and densities. Data from line and space patterns will be analysed along with data for contact holes. 2) METHODToday we are at a relatively immature stage of tool development for EUV lithography. Our imaging capability is still at a developmental stage and so it is very difficult to accurately perform experiments to determine any effects that we wish to investigate. Simulation allows us to quickly and inexpensively conduct these types of experiments with a very good degree of accuracy, allowing us to better prepare for actual implementation of a technology. The software and models used for these simulations are, however, very complicated and require a great deal of computing power. In EUV lithography the mask is composed of a series of very thin layers that together form a highly reflective surface, effectively a multilayer 'mirror'. A buffer layer and absorber are then patterned on top of this to produce t...

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“…The main factors driving resolution are the following: 1 . ITRS roadmap 2. Introduction of OPC features 3 . Mask error enhancement factor (MEEF) [1] Along the ITRS roadmap features get smaller by 1 0% -1 5% each year. As an example, contact sizes decrease from 150 nm in the year 2001 to 100 nm in 2004.…”

Section: Introductionmentioning

confidence: 99%

Towards systematic CD process control for e-beam lithography

Kalus

2004

SPIE Proceedings

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The paper proposes a method to mitigate the ever tighter requirements for mask CD uniformity. The basic idea is simple. As the mask error enhancement factor (MEEF) soars at low ki values with pitches getting smaller it should be possible to alleviate the problem given there is a way to increase the pitch. For highly repetitive layouts like cell fields of DRAMs the solution is rather straightforward. One has to find the next larger pitch in the layout and divide the layout into sublayers. Those sub-layers are written into separate reticles for subsequent exposure. In consequence, the method will lead to double exposure in case two reticles have been generated. The simplest example is an array of lines and spaces with equal pitch. An almost trivial example, a regular square contact array, results in two equal checkerboards. The diagonal (1 , 1) in the square array is the second smallest pitch in a square array. To fully cover a square array requires two checkerboards separated by the base vector (1,0) of the original lattice. These two checkerboards will subsequently be printed by a double exposure. It is obvious that the pitch can be increased by choosing larger displacements at the cost of more sub-layers. Doubling the pitch, which makes manufacturing ofmasks a lot easier, would require four reticles, hence four exposures.The edges and corners of regular arrays print significantly different as the MEEF is position dependent. It can be expected that increasing the pitch is also beneficial in the sense that it levels off the MEEF variance. It will be investigated how much the common process window increases. The applicability of said method is obvious for memory layouts. It can, however, be extended to semi-periodic or even random layouts. It's value depends primarily on the density of the layout and on the ki value. It's potential use comes in only at the leading edge of lithography where the MEEF starts to become a real pain for the mask maker. Simulation results will be shown as well as calculations of the process latitude before and after dividing the layout.

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Process proximity correction using an automated software tool

Cited by 11 publications

References 3 publications

Device based evaluation of electron projection lithography

Device based evaluation of electron projection lithography

Compensation for imaging errors in EUV lithography

Towards systematic CD process control for e-beam lithography

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