Zeiss GeminiSEM Series, Instruction Manual

Page: 35 / 164

ZEISS 3 Product and Functional Description | 3.2 Main Components
Apertures
The electron beam passes through the anode aperture
3
first, afterwards through the multi-
hole aperture
5
.
The anode aperture defines the maximum possible probe current.
The multihole aperture is the final beam limiting aperture. It is decisive for the probe current. The
standard is the 30 μm aperture hole that is the central aperture. Other aperture sizes are se-
lectable to meet the requirements of a wide range of applications.
For the Gemini 1 column, two types of multihole aperture are available:
§
20 nA high resolution configuration
Multihole aperture type Probe current Typical application
7 hole aperture 3 pA to 20 nA High resolution
§
100 nA high current configuration
Multihole aperture type Probe current Typical application
6 hole aperture 6 pA to 100 nA High current
Condenser
The condenser
4
is used for aperture matching of the objective lens in order to guarantee op-
timum resolution at each probe current and EHT setting.
Together with the multihole aperture, the condenser allows to regulate the probe current.
Stigmator The stigmator is located inside the condenser and compensates for astigmatism so that the elec-
tron beam becomes rotationally symmetrical.
Deflection System
The electron beam is focused by the objective lens
7
onto the specimen
9
while being de-
flected in a point-by-point scan over the specimen surface by the scanning coils
8
.
Before the electron beam exits the objective lens, the electrostatic lens creates an opposing field
which reduces the potential of the electrons by +8 kV. The energy of the electrons reaching the
specimen surface therefore corresponds to the set acceleration voltage (EHT).
Signal Detection When the primary electron beam hits the specimen, certain interaction products are released,
which can be recorded by specific detectors, e.g. the InLens SE detector
6
. For more informa-
tion refer to Principle of Signal Detection [
}
40] .
Instruction Manual ZEISS GeminiSEM series | en-US | Rev. 2 | 349500-8138-000 35