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Integrated Circuits

Designing integrated circuits depends onunderstanding the electronic properties of thematerials used in the manufacture of thedevices. In order to create devices such astransistors, diodes, and capacitors there has tobe patterning on the silicon which is achievedby doping or by depositing an amorphous layerand by coating with dielectric and metal films.As well as engineering the electronicproperties of the materials, there are importantmaterials compatibility issues which can beaddressed with Raman spectroscopy.

Raman spectroscopy is often the technique ofchoice for studying the materials in anintegrated circuit. It provides information oninteratomic bonding, crystallographic phase,and strain, and it does all this with better than 1m spatial resolution.

In this note, we illustrate these capabilities bycreating a detailed map of a feature on anintegrated circuit with feature sizes between 3and 10 m.

Image of Device Feature Composed ofAmorphous Silicon

The LabRAMs patented line-scanningcapabilities were used to collect spectra fromthe area of the device illustrated in the videoimage.

In this case, the Raman Map will show areas ofthe crystalline silicon substrate and amorphoussilicon deposited on it.

Raman spectra of the crystal and amorphousphases are quite easy to distinguish. Thisfigure shows spectra acquired from thesubstrate (the darker material in the videoimage, top spectral trace), from the amorphousfeature (the bright 15 m square and L-shapedconnector, bottom spectral trace), and from thedark line between the two (middle trace). Thespectrum of the amorphous layer shows asmall residual signal from crystalline silicon at521 cm

-1because the amorphous layer is

semi-transparent to 633 nm excitation, thewavelength used in this study. The spectrumfrom the dark line has a highercrystalline-to-amorphous intensity implying athinner amorphous layer. The dotted red andblue lines span the wavenumber regions thatwere bracketed to reconstruct the Raman map.

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This figure is the Raman map where the samecolour-coding was employed. The red area isthe deposited amorphous material; the bluebackground is the crystalline substrate. At theedge of the amorphous region the pink/purple

colour corresponds to the narrow edge wherethe contributions from the two phases aresomewhat different than in the centre. Theoverlap of the red and blue creates thedifferent colour.

In order to illustrate more clearly the variationin the relative intensities of the two bands, wehave also mapped the intensity ratio. In thisfigure the map is shown as a

three-dimensional intensity projection in orderto be more sensitive to differences in relativeintensities at the edge.

What is apparent is that the intensity ratio doespeak at the edge - however this peaking is notequivalent on all edges. This phenomenoncould be a result of the manner in which thefeature was manufactured.

Conclusion

The simple measurement made here illustratesthe facility with which one can map species onintegrated circuits. Note that no opticalresolution is lost in the map; it is determinedonly by the spacing between the points on thesample from which Raman signals arecollected. The flexible capabilities of the

mapping software provide information on thesample treatment that might not be apparentbefore data processing.

France : HORIBA Jobin Yvon S.A.S., 231 rue de Lille, 59650 Villeneuve dAscq. Tel : +33 (0)3 20 59 18 00,Fax : +33 (0)3 20 59 18 08. Email : raman@jobinyvon.fr www.jobinyvon.fr

USA : HORIBA Jobin Yvon Inc., 3880 Park Avenue, Edison, NJ 08820-3012. Tel : +1-732-494-8660,Fax : +1-732-549-2571. Email : raman@jobinyvon.com www.jobinyvon.com

Japan : HORIBA Ltd., JY Optical Sales Dept., 1-7-8 Higashi-kanda, Chiyoda-ku, Tokyo 101-0031.Tel: +81 (0)3 3861 8231, Fax: +81 (0)3 3861 8259. Email: raman@horiba.com

Germany: +49 (0) 6251 84 75-0 Italy: +39 02 57603050 UK: +44 (0)20 8204 8142China: +86 (0) 10 6849 2216

(All HORIBA Jobin Yvon companies were formerly known as Jobin Yvon)