Ims Nanofabrication Gmbh

Wolf Naetar

Christoph Spengler

Elmar Platzgummer

Gottfried Hochleitner

Johannes Leitner

In order to compensate for undesired effects of varying elevation of a target with respect to a nominal target plane, during writing a desired pattern on the target in a charged-particle beam apparatus, the pattern is re-calculated in each of a number of segments of the target plane by: determining an elevation of the target in the segment from the nominal target plane; determining a local blur value which represents the actual value of blur corresponding to the elevation, with regard to a dependence of the blur upon the elevation of the target; calculating a convolution kernel which represents a point spreading function realizing a local blur value; and re-calculating a nominal exposure pattern by applying the kernel to the pattern. The convolution kernel corresponds to introducing an additional blur into the pattern in the segment, increasing the blur to a given target blur value which is uniform to all segments.

Correction of blur variation in a multi-beam writer

A method for irradiating a target with a beam of energetic electrically charged particles, wherein the target comprises an exposure region where an exposure by said beam is to be performed, and the exposure of a desired pattern is done employing a multitude of exposure positions on the target. Each exposure position represents the location of one of a multitude of exposure spots of uniform size and shape, with each exposure spot covering at least one pattern pixel of the desired pattern. The exposure positions are located within a number of mutually separate cluster areas which are defined at respective fixed locations on the target. In each cluster area the exposure position are within a given neighboring distance to a next neighboring exposure position, while the cluster areas are separated from each other by spaces free of exposure positions, which space has a width, which is at least the double of the neighboring distance.

Method for irradiating a target using restricted placement grids

In a charged-particle lithography apparatus, during writing a desired pattern, the duration of exposure slots is adapted to compensate for fluctuations of the particle beam. In the writing process the aperture images are mutually overlapping on the target so each pixel is exposed through a number of aperture images overlapping at the respective pixel, which results in an exposure of the respective pixel through an effective pixel exposure time, i.e., the sum of durations of contributing exposure slots, and the exposure slot durations are adjusted by: The durations in step (iii) are calculated in accordance with a predetermined set of allowed durations, wherein at least one of the durations thus calculated is different from the other durations selected for said set of exposure slots.

Adapting the duration of exposure slots in multi-beam writers

A rasterized exposure method implementing a position correction for edge positions to correct for a non-linear relationship between the position of a feature edge (dCD) of a pattern element boundary and the nominal position of the boundary as expressed through the dose of exposure (d) of the edge pixel is provided. The position correction includes: determining a position value of the edge position, determining a corrected position value based on the position value using a predefined non linear function, and modifying the pattern to effectively shift the pattern element boundary in accordance with the corrected position value. The non linear function describes the inverse of the relationship between a nominal position value (d), which is used as input value during exposure of the pattern, and a resulting position (dCD) of the pattern element boundary generated when exposed with the nominal position value.

Non-linear dose- and blur-dependent edge placement correction

A method for re-calculating a pattern to be exposed on a target by means of a charged-particle multi-beam writing apparatus is presented. The pattern elements of a pattern, initially associated with a respective assigned dose, are recalculated in view of obtaining reshaped pattern elements which have a nominal dose as assigned dose. The nominal dose represents a predefined standard value of exposure dose to be exposed for pixels during a scanning stripe exposure within the multi-beam apparatus. For the pattern elements associated with an assigned dose deviating from the nominal dose, the pattern element is reshaped by determining a reshape distance from the value of the assigned dose using a predefined dose slope function forming a reshaped pattern element, whose boundary is offset with regard to boundary of the initial pattern element by an offset distance equaling said reshape distance, assigning the nominal dose to the reshaped pattern element, and replacing the pattern element by the reshaped pattern element.

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Vienna, Austria

Wolf Naetar