Certain improvements of multi-beam generating and multi-beam deflecting units

A multi-beam raster unit configured to transmit beamlets of charged particles, the multi-beam raster unit comprising:

• a first multi-aperture plate comprising a beam exit side, a beam entrance side and a first membrane, the first membrane comprising a first thickness and a plurality of first apertures, the first membrane comprising a first segment having a first segment thickness and a plurality of cylindrical apertures having a first diameter at the beam entrance side of the first multi-aperture plate, the first membrane comprising a second segment having a plurality of apertures having a second diameter at the beam exit side of the first multi-aperture plate, the first membrane comprising a first electrode proximal to a first aperture at the beam exit side of the first multi-aperture plate;
• a second multi-aperture plate comprising a beam entrance side and a second membrane, the second membrane comprising a plurality of second apertures having a third diameter at the beam entrance side of the second multi-aperture plate, the first and second multi-aperture plates configured to have a gap therebetween;
• and
• a plurality of second electrodes proximal to the plurality of second apertures at the beam entrance side of the second multi-aperture plate,
• wherein:
• the second diameter is greater than the first diameter;
• a thickness of the gap is a distance from the beam exit side of the first multi-aperture plate to the beam entrance side of the second multi-aperture plate;
• the second diameter is in a range between the thickness of the gap and two times the thickness of the gap;
• the first segment thickness is less than 10 μm;
• and
• the first electrode and each of the plurality of second electrodes are configured to provide electrostatic elements to provide an electrostatic field between the first electrode and each of the plurality of second electrodes to influence the beamlets of charged particles.