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NanoMaker Functions

NanoMaker functions

The main functions of lithographic system are:

Design of structure and data preparation for exposure


Design of a new structure.
Enlarge (in new window, 27.7 kb)
    Design
    A significant software part of the NanoMaker is the graphical database editor. Any structure can be designed and exposed within the same software platform without preparing intermediate data files and switching between different application to fulfil the tasks. NanoMaker allows one to design a structure of almost any size and any complexity, using a few simple geometric figures (points, lines and polygons), just like it happens in any system of computer-aided design (CAD). In contrast to CAD, these geometric shapes - elements are inherent additional attributes specific to lithographic structures - exposure dose, 3D attribute, layer, etc. In addition to simple there are a set of more specific elements, which simplify the designing of kinoform optics objects, holograms, etc. By inserting references to structures (or even arrays of references), one can create a very complex hierarchical structure, while maintaining relatively small data file.

    Proximity Correction
    Unlike CAD NanoMaker also includes the special subsystem for processing of the designed structures, which allows to achieve maximum resolution at electron beam exposure. For example, this subsystem performs the proximity effect correction (PEC), in which the original structure is cut into smaller elements and each element is assigned its own time of exposure (dose). This is especially important for densely packed, different size pattern elements. This function gives advantages of accurate pattern exposure at once without waste of time and resources on guessing attempts.


    Presenting the results of proximity effect correction. Enlarge (in new window, 32.3 kb)

    Import / Export
    The results of the design are stored in a special Graphic Database format (with GDB file name extension). To ensure compatibility with other CAD and / or with other lithographic systems NanoMaker provides import / export structures in GDSII, CSF, DXF (AutoCAD), DC2 and ELM (ASCII text) formats.

    Special transformations in postprocessing
    For best results in preparing the data for other lithographic systems NanoMaker includes additional operations for the whole structure or its selected part, such as leveling of the exposure doses (Union), search and removal of overlapped parts of elements (Overlaps Out), inversion of exposure field at transition from negative to positive resists (Negative), etc.

    The system of choosing parameters for exposure, proximity correction and simulation of resist development
    NanoMaker includes the reference table of recommended parameters, which essentially help to choose regimes of proximity effect correction, exposure and resist development simulation. Data obtained from a large number of experiments for several types of resists and substrates allow to approximate the parameters of the proximity function for a wide range of accelerating voltages, resist thicknesses and primary e-beam diameters. One can add the table with own data. Furthermore, data for selecting the parameters of exposure, correction and development simulation can be calculated using the Monte Carlo sub, which is integrated into NanoMaker.

Exposure, including exposure with stage displacements

    Exposure, exposure modeling, estimation of time
    One of the main NanoMaker functions is exposure at which the electron beam is deflected by pattern generator to certain point and is held a given time. With all this going on NanoMaker automatically performs the movement of the stage, if the structure exceeds the scanning field. Special procedure allows to assess in advance an exposure time, as well as to show on the PC screen the trajectory of the beam.

    Alignment for successive lithographies, including fields stitching by means of automatic markers detection
    Typically, lithography involves several sequential exposures, and therefore NanoMaker provides (automatic) search for and correct orientation of the exposed structure with respect to already existing structures on the substrate due to the search and recognition of markers.

    Special interrupts to compensate for drift
    In the case of long exposures (half an hour and longer), when accurate stage displacements are used, the special interrupts are provided (with storage of the position where termination of exposure happened), during which the NanoMaker moves one of markers to the scan field, measures shift of its position, introduces the necessary amendments to the beam deflection system to compensate for drift and returns to the place of exposure.

    Resist development simulation
    NanoMaker allows to predict the shape of resist after exposure and development. In addition resist contrast parameter or dose curve as a whole are used for the simulation of positive and negative resists development. Simulation of resist development is useful for lithography training and for choosing of optimal technological conditions, because very quickly, without executing the real exposure and development, allows to predict results of lithography and make improvements in the design.

    Controlling of SEM, stage, beam blanker et al
    NanoMaker allows to control the stage movement in most scanning systems with focused beam equipped with a motorized or laser controlled stages. If microscope is equipped with beam blanker, NanoMaker can control the blanking of the electron beam in the column. For some modern models of SEMs NanoMaker makes it possible to control the microscope, which includes, for example, controlling of working distance, magnification, accelerating voltage, beam current, etc.

Image acquisitions for measurements and multi-layer exposure alignments

    Image acquiring from a list of windows with graphics processing
    When connecting to analogue SEMs the NanoMaker can be used for high-resolution image recording, which can be saved in TIFF format files. Graphic processing is available (filtering, contrast optimization, adding of scalier and comments, etc.). There is a possibility of image acquisition with signal accumulation and averaging.

    Automatic and manual search and recognition of the markers
    NanoMaker has a procedure where one can specify a system of windows (with a variation of the size and resolution), which corresponds to position of markers on a substrate, and also provides a flexible controlling procedure for image acquisitions and automatic markers recognition to determine their positions. This feature is widely used in NanoMaker for calibration of a scan field, for alignment of coordinate systems, for matching layers in multi layer lithography, for drift compensation, etc.

    Measurement of static and dynamic distortions. Software compensation for errors in beam positioning
    NanoMaker contains special subsystem for fast and convenient measurement of static and dynamic distortions of deflection system of a SEM. The measured data then is used for software "on the fly" compensation of errors in positioning of the beam. These are an extremely important functions. They can significantly reduce the exposure time (6-10 times) by avoiding blanking and waiting of the beam settling after jumps through the active compensation of dynamic distortions, as well as to increase the writing field due to its linearization.

    Alignment of coordinate systems
    During exposure it is often necessary to align multiple coordinate systems, for example, coordinates of projected structure, coordinates of substrate, coordinates of the beam deflection system, stage coordinates and others. NanoMaker makes it possible to choose the one as master and to lead all the rest to it. For example, in presence of an accurate laser stage all the coordinate systems can be aligned to an exact stage movement.

Unique Features

The following unique features distinguish NanoMaker among of similar systems on a market:
  • Proximity effect correction for 2D-and 3D-structures.
  • Simulation of the proximity effect and resist development.
  • Measurement and active compensation of dynamic distortions of a beam deflecting system, which significantly reduces the total time of exposure.
  • The possibility of exposure without blanking the beam because of active compensation of dynamic distortions.
  • The compensation of static errors (distortion) deflecting system for exposure in a large field.
  • Special options for the design of hologram and kinoform applications.
  • Calculation of data for exposure on multilayered substrates with an integrated Monte Carlo module.

None of the companies on the market involved in the development of similar systems offers such feature set.
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
 
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