The UHV NANOPROBE stage carries four individual SPM probe modules with 3D coarse positioning and a sample stage with 2D coarse positioning, a system with overall 14 degrees of freedom. A reliable UHV coarse positioning technology is therefore fundamental for efficient operation.

Omicron's patented remote-controlled piezo-electric inertia drives ensure independent and orthogonal axis movement for efficient navigation and step sizes from a few tens of nm up to several hundred nm. Although SEM navigation alone is usually sufficient for small research samples, an optical position read-out system with ± 50 nm nominal resolution is indispensable for rapid localisation and re-localisation of a single nanodevice among billions within large integrated circuits.

The UHV NANOPROBE is compatible with Omicron's standard fl at sample plates with a maximum sample size of 10 mm x 10 mm. For the investigation of temperature-dependent behavior of samples or devices, the UHV NANOPROBE allows sample temperatures up to 500 K by using an integrated solid state heater and a Pt100 sensor for temperature measurement. Sample cooling down to 50 K is achieved with a LHe flow cryostat which is thermally connected by a copper braid. This fine braid also ensures mechanical de-coupling from vibrational noise.

The sample stage is electrically isolated and can alternatively be connected to ground (for STM approach), to an external potential or be free floating to avoid current flow through the substrate during transport measurements. Alternatively, four spring-loaded electrical contacts provide electrical access to the sample to drive active devices.

Each probe module uses a single-tube piezo for STM-based tip approach and is capable of atomic-scale STM imaging. STM imaging is required for final precise positioning of the probe tip when its apex shadows nanometer-sized structures in the SEM navigation or if the structures are even smaller than accessible by SEM. The available STM functionalities depend only on the electronics used and range from simple electronics for manual control to a fully equipped Omicron MATRIX SPM control unit.

A dedicated pre-amplifier technology enables pA STM current detection for imaging and tip approach even on low-conducting samples. The external I/V converter features two ranges (3nA/330nA) and offset compensation for low currents.

Furthermore, probe modules can be equipped with optical fibres, thereby opening up a new field in SEM-navigated local optical illumination or light collection studies.

STM technology is the key to approaching and positioning probe tips with precision on the nanometer scale. Probe-to-sample distance control is based on the tunnelling current as the feedback signal and therefore requires a dedicated low-noise I/V converter. When the tunnelling contact is established, the probe-sample distance is well controlled in the nanometer range. To make an electrical contact and to control its resistance, the STM feedback loop is de-activated and the probe is manually approached by controlling the piezo scanner z-offset.

Since a permanently connected I/V converter in the signal line prevents transport measurements in four-point configuration, a dedicated pA STM compatible switching technology with an isolation resistance in the TΩ range is applied to route signals of the four probes to external BNC connectors. Remote or TTL trigger control of the switch allow for the integration into complex measurement procedures with third-party measurement equipment.

The open design and the accessibility for additional surface analysis techniques make the UHV NANOPROBE a very versatile nano-tool. With the UHV Gemini as the core unit and ultimate UHV scanning electron microscope, various techniques are available on an impressive performance level.

• Scanning Electron Microscopy (SEM)
• Scanning Auger Microscopy (AES/SAM)
• Scanning Electron Microscopy with polarisation analysis (SEMPA)
• Focussed Ion Beam (FIB)
• Electron Lithography (EBL)
• Cathodo-Luminescence (CL)
• Optical Fibre Probes
• High Frequency Probes