Specific Process Knowledge/Characterization/SIMS: Secondary Ion Mass Spectrometry

Feedback to this page: click here

Atomika SIMS

The Atomika SIMS analyses the composition of a sample by secondary ion mass spectroscopy. By using either oxygen or cesium ions accelerated by a high tension the surface of the sample is sputtered off as ions. These ions are analysed in a mass spectrometer and one can determine the elemental composition as a function of depth. If compared to signals from reference materials one can quantify the atomic composition - in certain cases down to extremely low concentrations (ppm). Doping levels and impurities may be determined.

Please note that no user will be instructed on the SIMS. Danchip staff will run your samples.

The user manual and technical information and contact information can be found in LabManager:

The Atomika SIMS in Labmanager

An overview of the performance of the SIMS

Purpose	Determination of atomic composition	Doping level Sample contamination
Performance	Measurement accuracy depends on	Which atoms to be analysed The sample morphology (flat samples are much more suited than particles)
Process parameters	Ion gun parameters	Acceleration voltages and focusing lens parameters Gas inlet pressures and apertures
	Mass spectrometer parameters	Detector biases and range Scan parameters such as raster size, speeds and pattern
	Sample position	Angle towards spectrometer For non-conducting samples: Flood gun parameters
Sample requirements	Substrate material allowed	In principle all materials
	Substrate size	The samples must be cut into 5x5 or 7x7 mm pieces Other types of samples must be mounted onto appropriately sized carriers
	Batch size	The sample holder carries up to 6 samples at the time

Secondary Ion Mass Spectrometry (SIMS)

In the Atomika SIMS the samples are bombarded with a beam of either oxygen or caesium ions. When accelerated to high energy and rastered across the sample these ions will be able to gradually sputter off the surface atoms in a small area defined by the raster pattern. Some of the surface atoms are emitted as ionized particles. In this way one layer after another is peeled off the sample.

These charged species are led through a mass spectrometer where a magnetic field is used to deflect them. The deflection increases with charge and decreases with mass and we are therefore able detect and count them according to their mass. This technique is called Secondary Ion Mass Spectrometry or SIMS.

Typical application of SIMS

SIMS is the most sensitive technique for elemental composition. It is therefore ideal if you want to check doping profiles or for contaminations.

A typical application would be to check the concentration profile of boron doping in silicon. In that case one would put two samples into the SIMS.

A reference sample with a known boron profile
A sample