Specific Process Knowledge/Characterization/SEM: Scanning Electron Microscopy

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The Leo SEM

The Jeol SEM is located outside the cleanroom in the basement

Scanning electron microscopy at Danchip

The SEM's at Danchip cover a wide range of needs both in the cleanroom and outside: From the fast in-process verification of different process parameters such as etch rates, step coverages or lift-off quality to the ultra high resolution images on any type of sample intended for publication.

The 'workhorse' SEM that will cover most users needs is the Leo SEM. It is a very reliable and rugged instrument that provides high quality images of most samples. Excellent images on a large variety of materials such as semiconductors, semiconductor oxides or nitrides, metals, thin films and some polymers may be acquired on the Leo SEM. As such, we prefer that new users that have no prior SEM experience get trained on the Leo SEM before they start using the other SEM's.

The Zeiss SEM and the Supra 60 VP SEM are both 'Supra VP' models from Carl Zeiss (a 40 and 60 respectively). As such they share a lot of similaritites but they also differ in some respects. The SmartSEM operator software installed on both these SEM's is also running on the Leo. This is very convenient as it allows the users to shift between instruments quite easily.

The Zeiss SEM was installed in the cleanroom in 2010 and quickly became the 'Weapon of choice' for many SEM users. It's a state-of-the-art SEM that will produce excellent images on any sample. The possibility of operating at higher chamber pressures in the VP mode makes imaging of bulk non-conducting samples possible.

The Supra 60 VP SEM is basically the same as the Zeiss SEM but with some additional features such as an airlock and an EDX detector.

Outside the cleanroom in the basement of building 346, the Jeol SEM provides a possibilty of imaging samples that do not go into the cleanroom.

The user manuals, quality control procedures and results, user APVs, technical information and contact information can be found in LabManager:

• The SEM Leo page in LabManager,
• The SEM Zeiss page in LabManager,
• The SEM Supra 60 VP page in LabManager,
• The SEM Jeol page in LabManager,

Process information

Instrument specific

• The Leo SEM
• The Zeiss SEM
• The Supra 60 VP SEM
• The Jeol SEM

Common challenges in scanning electron microscopy

• Sample mounting
• Image optimisation
• Problems related to sample charging

Equipment performance and process related parameters

Equipment		SEM Leo	SEM Zeiss	SEM Supra 60VP	SEM Jeol
Model		Leo 1550 SEM	Zeiss Supra 40 VP	Zeiss Supra 60 VP	Jeol JSM 5500 LV
Purpose	Imaging and measurement of	Any (semi)conducting sample that may have thin (> ~ 5 µm) layers of non-conducting materials on top	Any sample except bulk insulators such as polymers, glass or quartz wafers	Any sample except bulk insulators such as polymers, glass or quartz wafers	Samples from the 'real' world outside the lab
Performance	Resolution	The resolution of a SEM is strongly dependent on the type of sample and the skills of the operator. The highest resolution is probably only achieved on special samples
		~ 5 nanometers (limited by vibrations)	1-2 nm (limited by vibrations)	1-2 nm (limited by vibrations)	20 nm (limited by instrument)
Instrument specifics	Detectors	Secondary electron (Se2) Inlens secondary electron (Inlens) Backscatter electron (BSD)	Secondary electron (Se2) Inlens secondary electron (Inlens) 4 Quadrant Backscatter electron (QBSD) (out of order) Variable pressure secondary electron (VPSE)	Secondary electron (Se2) Inlens secondary electron (Inlens) 4 Quadrant Backscatter electron (QBSD) Variable pressure secondary electron (VPSE)	Secondary electron (SEI) Backscatter electron (BEI)
	Stage	X, Y: 125 × 100 mm T: 0 to 90o R: 360o Z: 48 mm	X, Y: 130 × 130 mm T: -4 to 70o R: 360o Z: 50 mm	X, Y: 150 × 150 mm T: -10 to 70o R: 360o Z: XXX mm	X, Y: 73 × 40 mm T: -10 to 90o R: 360o Z: 38 mm
	Electron source	FEG (Field Emission Gun) source	FEG (Field Emission Gun) source	FEG (Field Emission Gun) source	Tungsten filament
	Operating pressures	Fixed at High vacuum (2 × 10-5mbar - 10-6mbar)	Fixed at High vacuum (2 × 10-4mbar - 10-6mbar) Variable at Low vacuum (0.1 mbar-2 mbar)	Fixed at High vacuum (2 × 10-4mbar - 10-6mbar) Variable at Low vacuum (0.1 mbar-2 mbar)	Fixed at High vacuum
	Options	Raith Elphy Quantum E-Beam Litography system	All software options available	Antivibration platform Fjeld M-200 airlock taking up to 8" wafers Oxford Instruments X-MaxN 50 mm2 SDD EDX detector and AZtec software package
Substrates	Sample sizes	Wafers up to 6" (only full view up to 4")	Up to 6" wafer with full view	Up to 8" wafer with 6" view	Up to 4" wafer
	Allowed materials	Any standard cleanroom material except graphene or CNT samples	Any standard cleanroom material except graphene or CNT samples	Any standard cleanroom material except graphene or CNT samples	Any standard cleanroom material including graphene or CNT samples Biological samples