Compensation of imaging deviations in a particle-beam writer using a convolution kernel

Charged-particle multi-beam processing apparatus for exposure of a target by means of a structured beam of electrically charged particles, comprising:

• an illumination system,
• a pattern definition device and
• a projection optics system,
• the illumination system being configured to produce a beam of said electrically charged particles and form it into a wide beam illuminating the pattern definition device, the pattern definition device being configured to form the shape of the illuminating beam into a structured beam composed of a multitude of sub-beams, and the projection optics system being configured to project an image of the beam shape defined in the pattern definition device onto the target, thus exposing a multitude of pixels within an image area on the target,
• wherein the pattern definition device comprises an aperture array composed of a plurality of blanking apertures forming said sub-beams, said plurality of blanking apertures being arranged in a predetermined arrangement defining mutual positions of the blanking apertures, each blanking aperture being selectively adjustable with regard to a dose value to be exposed through the respective blanking aperture onto a corresponding aperture image generated on the target during a respective exposure interval, said dose value taking a respective value selected from a discrete gray scale,
• configured such that wherein during a writing process of a desired pattern, a sequence of exposure intervals is made, wherein in each exposure interval the blanking apertures are imaged onto the target, thus generating a corresponding plurality of aperture images,
• said processing apparatus being configured for performing a writing process for a desired pattern using a method comprising:
• i) providing the desired pattern as a graphical representation on the image area on the target, said graphical representation having a predetermined width of resolution, said width being larger than a nominal distance between neighboring positions of the pixels within said image area,
• ii) providing a convolution kernel, said kernel describing a mapping from an element of the graphical representation to a group of pixels, said group of pixels being centered around a nominal position of said element, and
• iii) calculating a nominal exposure pattern as a pixel raster graphics defined on the multitude of pixels, by convolution of the graphical representation with the convolution kernel, said nominal exposure pattern being suitable to create a nominal dose distribution on the target,
• the method operating to convert the desired pattern into a nominal exposure pattern writable with the processing apparatus, wherein the convolution kernel is configured to compensate a deviation of the imaging from the pattern definition device to the target, said deviation concerning a desired value of critical dimension along at least one direction in the image area on the target.