The AFM-tip characterizer contains patterns for an in-situ determination of the AFM-tip shape.

The AFM-tip characterizer offers a series of very smooth and sharp-edged line-space structures in silicon with vertical side-walls.

Each calibration chip has a size of 8×8 mm². In the centre of the calibration chip, where the two-stage finding structure ends, 3 groups of 5 line-space structures with different nominal widths (300, 500 and 800 nm) are arranged.

The space between the lines is about 1 μm. Each group is nominally 20 μm long.

The structures are sharp-edged with edge radii of less than 2 nm. The edge roughness is well below 5 nm (3σ).
 

Specification
Substrate	Material: <110> Si Chip dimension: 8×8 mm² Surface roughness: <1 nm
Finding structures	Grooves in the Si-substrate Depth (in general): 1 µm
Types of grating	1-dim
Size of grating	Normally 10×10 µm²
Linewidths (CD)	Nominal: 300 nm, 500 nm, 800 nm Linewidth variation along the lines (measuring within a central part of ca. 10 µm): <5 nm 1σ
Pitches	1 µm + CD value Uncertainty of mean pitch: 3 nm 1σ
Structure depth	in general: 1 µm
Edge radius	<2 nm
Edge roughness	± 4 nm (3σ)
Sidewall angle	89°
Traceability	CD, pitch and depth-calibration made by the PTB Braunschweig on request.

Structure details

Principle of detection of the AFM-tip shape and tip radius

The method of the in-situ characterization is based on the AFM-measurement of a well-known line-space structure and the calculation of the tip shape from the measurement result (see figure).

The sidewalls of the calibration structures are steeper than the half-cone angle of the tip. Therefore, the measured sidewalls reflect the shape of the tip. If, in addition to that, the edge radius of the calibration structures can be neglected, compared to the tip radius, then the measured radii also represent the tip radius.

By means of these standards the shape and the radius of the tip can be quickly quantified before and after the AFM measuring process.