Specific Process Knowledge/Characterization/XPS: Difference between revisions
No edit summary |
No edit summary |
||
| Line 4: | Line 4: | ||
A X-ray | A X-ray Photoelectron Spectroscopy (XPS) system can be used at Danchip. The system is a Thermo K-Alpha system, and is found in LabManager under the name XPS-ThermoScientific. | ||
==Elemental analysis== | ==Elemental analysis== | ||
The XPS technique can be used to do elemental analysis. A | The XPS technique can be used to do elemental analysis. A comparison about techniques and instruments used for elemental analysis at Danchip can be found on the page [[Specific Process Knowledge/Characterization/Element analysis|Element analysis]]. | ||
==XPS technique== | ==XPS technique== | ||
| Line 13: | Line 13: | ||
XPS is a surface sensitive and non destructive technique used for analysis of the elemental composition. | XPS is a surface sensitive and non destructive technique used for analysis of the elemental composition. | ||
Only the outermost atomic layers (some nanometers) are probed, but with an ion gun etch it is | Only the outermost atomic layers (some nanometers) are probed, but with an ion gun etch it is possible to probe deeper laying layers. | ||
In the XPS spectrometer system the probed samples are irradiated by photons with a specific energy, and the photoelectrons that leaves the sample are detected. The energy levels of the electrons are elemental specific, and by measuring the energy of the outgoing electrons, it is possible to detect which elements that are present in a sample. | In the XPS spectrometer system the probed samples are irradiated by photons with a specific energy, and the photoelectrons that leaves the sample are detected. The energy levels of the electrons are elemental specific, and by measuring the energy of the outgoing electrons, it is possible to detect which elements that are present in a sample. | ||
You can read | You can read further about the technique here: [http://en.wikipedia.org/wiki/X-ray_photoelectron_spectroscopy] | ||
| Line 59: | Line 59: | ||
The figure to the left gives an illustration of the effect. An XPS Si2p spectrum of a Si reference sample and a Si sample that was treated in HF shortly before the measurement, is clearly showing two different curves. The untreated spectrum has a clear feature at about 103 eV due to Si atoms bonded to oxygen. In the spectrum from the HF treated sample, only the feature steaming from Si-Si interaction is present. Note that both curves only shows the Si signal, but with an clear indication of the chemical state of the Si atoms in the samples. | The figure to the left gives an illustration of the effect. An XPS Si2p spectrum of a Si reference sample and a Si sample that was treated in HF shortly before the measurement, is clearly showing two different curves. The untreated spectrum has a clear feature at about 103 eV due to Si atoms bonded to oxygen. In the spectrum from the HF treated sample, only the feature steaming from Si-Si interaction is present. Note that both curves only shows the Si signal, but with an clear indication of the chemical state of the Si atoms in the samples. | ||
If you study polymers, you can detect the | If you study polymers, you can detect the presence of different chemical groups, for example (C-C),(C-OH),(C=O),(CF3) or (CF2-CH2) in the polymeric layer. And after surface treatments, you may examine differences in the polymeric layer. | ||
Note that binding energies for different chemical states often can be found in the literature. | Note that binding energies for different chemical states often can be found in the literature. | ||
| Line 76: | Line 76: | ||
[[Image:Stochiometry 20110510.JPG|425x425px|left|thumb|The composition of a NiCr as a function of film depth (etch time). The relationship between Cr and Ni is quite constant through the 70nm thick film. Measurements done with XPS-ThermoScientific. ]] | [[Image:Stochiometry 20110510.JPG|425x425px|left|thumb|The composition of a NiCr as a function of film depth (etch time). The relationship between Cr and Ni is quite constant through the 70nm thick film. Measurements done with XPS-ThermoScientific. ]] | ||
The analysis is made on a chosen spot on the sample surface ( | The analysis is made on a chosen spot on the sample surface (chosen with the system camera). The technique is, as written above, very surface sensitive and probes only the top nanometers of the sample. | ||
With the ion beam gun on the system an etch of the sample can be done. The system measures the desired spectrum, does an etch step and measures again. A series of etch cycles can be set up, measuring the composition of the sample at different depths (for example at different depth of a film). | With the ion beam gun on the system an etch of the sample can be done. The system measures the desired spectrum, does an etch step and measures again. A series of etch cycles can be set up, measuring the composition of the sample at different depths (for example at different depth of a film). | ||