3-Dimensional X-Ray Diffraction Imaging Study of Damage to Silicon Wafers by Plasma Arcing.

J. Stopford1, D. Allen1, O. Aldrien1, M. Morshed1, J. Wittge2, A.N. Danilewsky2,

P.J. McNally1.

1. Research Institute for Networks and Communications Engineering (RINCE), School of Electronic Engineering, Dublin City University, Dublin 9, Ireland. 2. Kristallographisches Institut, Hermann-Herder-Strasse 5, 79104 Freiburg i. Br, Germany.

Plasma charging damage, and in particular damage caused by wafer arcing is one of the important plasma process induced damage phenomena and can result in pits and non-uniformities on the wafer surface [1-5]. In this study two different types of arcing damage were simulated on a silicon wafer in a plasma chamber under varying process conditions. Both samples were generated in the same plasma chamber, which consisted of a parallel plate design with the wafer on the grounded electrode, and was filled with Ar gas at approximately 3 mbar (2.25 torr). In the first damage regime a high current of ~200 mA, resulted in a single damage site (Figure 1). The second damage regime was caused by a low current of about 60 mA, and resulted in multiple arc damage sites (Figure 2).

Figure 1: SEM image of Damage Regime 1 showing approx. 1000 µm x 800 µm area of arcing damage on Si substrate.

Figure 2: SEM image of Damage Regime 2 showing 100 µm – 250 µm islands of arcing damage on Si substrate.

3-dimensional X-Ray Diffraction Imaging (3D-XRDI) is a high-resolution synchrotron based (1 µm X-Y spatial) imaging technique based on x-ray diffraction. 3D-XRDI provides an improvement over conventional Synchrotron X-Ray Topography (SXRT) in that it makes it easier to distinguish damage sites, identify stress/strain regions both above and below the surface, and gives a 3D analysis of defects in semiconductor wafers. 3D-XRDI uses images obtained in Transmission Section Topography (ST) geometry [6]. Topographs were generated at the HASYLAB-DESY F1 topography beamline on high-resolution Slavich VRP-M films with typical sample-to-film distances of 60 mm. The sample was mounted on a high precision X-Y stage which enabled the user to step across the sample in ~15 µm steps and thus obtain a series of ‘slices’ across the damage site. The raw data consisted of a series of, typically, 25 ST images. Each stach of section topographs was then rendered into a 3D image using topographic algorithms from the ImageJ software suite (Figures 3 & 6). Regions of interest were highlighted using k-means clustering.

Figure 3: 3D-XRDI of Damage Regime 1.

3D-XRDI for damage regime 1 shows a black cluster on the surface directly at the damage site, indicated by the white arrow in Figure 4. This region appears to experience the largest imposed strains, and measures approximately 850 of the wafer. The imaged strain fields propagating from the surface spread out toof ~1800 µm half way through the substrate, small indication of the extent of the da

Figure 5: 3D-XRDI of Damage Regime 2.

The 3D-XRDI in Figure 6 is rendered form a stack2, the raised grey regions at the surface of the sample can be attributed to amorphous silicon regions which are evident in the corresponding Large Area Back Reflection (damage regime 1, K-means clustering has been effectively used to levels present within the sample (Figure 600 µm x 350 µm, and penetrates almost completely through the 450 References [1] Sychyi Fang, James P. McVit 347. [2] K. Koski , J. Ho lsa, P. Juliet, [3] S. Ma, N. Hanabusa, S. Shoji, M. Kutney, T. Detrick, B. Patada and R. Straube, Int. Symp. on Process and Plasma [4] Liou, Y.H.; Chen, Y.S.; Wu, C.S.; Tsai, C.S.; Chi, MProcess-Induced Damage, p 33-35[5] Y Yin, D R McKenzie, M M M Bilek,[6] J. Kanatharana et al., Microelectronic Engineering

XRDI of Damage Regime 1. Figure 4: 3D-XRDI of Damage Regime

1 with K-means clustering applied.XRDI for damage regime 1 shows a black cluster on the surface directly at the damage site,

arrow in Figure 4. This region appears to experience the largest imposed strains, and measures approximately 850 µm wide and penetrates through 600 µm

strain fields propagating from the surface spread out toy through the substrate, illustrating that the surface condition gives only a

small indication of the extent of the damage.

XRDI of Damage Regime 2. Figure 6: 3D-XRDI of Damage Regime 2 with K-means clustering applied.

rendered form a stack of 12 ST images. In the case of damage regime he raised grey regions at the surface of the sample can be attributed to amorphous silicon regions

corresponding Large Area Back Reflection (LABRmeans clustering has been effectively used to highlight the different strain

(Figure 6). The largest strain field present measures approximately m, and penetrates almost completely through the 450 µm substrate.

James P. McVittie, IEEE Electron Device Letters, Vol. 13

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XRDI of Damage Regime

means clustering applied. XRDI for damage regime 1 shows a black cluster on the surface directly at the damage site,

arrow in Figure 4. This region appears to experience the largest imposed ugh 600 µm to the backside

strain fields propagating from the surface spread out to reach a maximum illustrating that the surface condition gives only a

XRDI of Damage Regime 2 means clustering applied.

In the case of damage regime he raised grey regions at the surface of the sample can be attributed to amorphous silicon regions

LABR) topograph. As with highlight the different strain

). The largest strain field present measures approximately m substrate.

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