Thin film apertures are frequently used in the objective lenses of high resolution and electron beam lithography instruments.
These apertures have the advantage that they heat up in the beam and are effectively self-cleaning.

This minimises astigmatism caused by a build-up of carbon contamination. The small amount of contamination that deposits after a lengthy operation may be removed by heating the aperture strongly for a short time with the focused electron beam. The benefits of using this type of aperture are particularly apparent when operating at low accelerating voltages or with small probe sizes.

Thin film apertures should not be used in the condenser lens as they may melt. They are, of course, more fragile to handle and can be irreparably damaged by abrasion or by a sudden rush of air in the vacuum system. Normal tolerance on hole diameter is 10%.

Agar apertures are made to exceptionally high standards and are only accepted after individual inspection to check the perfection of the edge of the hole, its roundness and absence of pinholes in the vicinity.

Other specific apertures and diameters can also be manufactured, please enquire with details of your application.