## 3 Results and Discussion
### X-ray Photoelectron Spectroscopy (XPS) Surface Characterization  
#### 3.2.1 X-ray Photoelectron Spectroscopy (XPS) Spectra Analysis  
Four chemical states of C 1s, O 1s, F 1s, and Si 2p were selected to perform XPS analysis. For surface characterization, the advantage of XPS over AES is that the chemical state of FDTS SAM can be obtained due to the lower incident X-ray energy compared to incident Auger electron energy. Once the incident X-ray bombarded the FDTS SAM pattern surface, induced photoelectrons related to chemical state information could be gathered and analyzed. However, the disadvantage of XPS is its relatively large spatial resolution, which was about 7.5 um with the tool we used (PHI 5000 Versa Probe III spectrometer, ULVAC, Japan). For AES analysis, the spatial resolution with the tool we used could be as small as 7.0 nm. For XPS characterization, XPS spectra could be obtained from regions in an induced secondary electron image (SXI) as shown in Figure 4, which was not as sharp as the secondary electron SEM image from AES shown in Figure 3a. Additionally, the XPS spatial resolution was determined by the beam size of the incident X-ray. The smaller the beam size, the larger the spatial resolution. For instance, two points were selected from the SXI image induced from the incident X-ray shown in Figure 4, one in the silicon dioxide pattern area (Point 1) and the other in the FDTS SAM film pattern area (Point 2). As shown in Figure 5a, the amplitude of the F 1s peak increased gradually with the X-ray beam, increasing from 10 um to 200 um, respectively. As shown in Figure 5b,c, for X-ray beam sizes of 10 um and 20 um, the ratios between the amplitude of the F 1s peaks in Point 1 and Point 2 were 1.50:24.88 and 2.16:22.80, respectively. Therefore, the two kinds of areas could be differentiated readily. As the beam size increased, it became more difficult to differentiate these two points, as illustrated in Figure 5d. For beam sizes of 100 and 200 um shown in Figure 5e,f, the ratio between the amplitude of F 1s peaks in Point 1 and Point 2 was 27.39:34.92 and 30.73:28.54, respectively, which made it impossible to differentiate these two kinds of areas. Therefore, the selected X-ray beam size must be smaller than  
Figure 3: Reconstructed mapping image of KLL Auger electrons in two areas, fluorine Auger electrons, F1, oxygen Auger electrons, O1, carbon Auger electrons, C1, silicon Auger electrons, Si2. (**a**) The same area is shown in Figure 3a. (**b**) The area with a line width of 10 μm. the FDTS pattern feature size to obtain appropriate surface information. For FDTS pattern feature sizes on the silicon wafer as small as 2 microns, the surface information could not be extracted with this XPS tool at its spatial resolution of 7.5 \(\upmu\)m. For the following XPS characterization, we used an X-ray with a beam size of 10 \(\upmu\)m for further investigation. Once the X-ray beam size was determined as 10 \(\upmu\)m, XPS spectra with high resolutions could be obtained in Point 1 and Point 2. As shown in Figure 6 for Point 1, the chemical state of C 1s was from the C-C bond /C-H bond, C=O bond, and CF2 bond collectively. Each bond had binding energy (B.E.) of 284.80 eV, 288.11 eV, and 290.52 eV, with an atomic concentration (AC%) of 10.81%, 0.55%, and 1.04%. The chemical state of O 1s was from the C=O bond/Si-O bond, and the bonding energy (B.E.) was 532.84 eV with an atomic concentration (AC%) of 59.77%. The chemical state of Si 2p was from the Si-O bond, and the bonding energy (B.E.) was 103.18 eV with an atomic concentration (AC%) of 26.67%. The chemical state of F 1s was from the C-F bond, and the bonding energy (B.E.) was 687.44 eV with an atomic concentration (AC%) of 1.16%. The total atomic concentration (AC%) of these chemical states was 100%. The chemical state of C 1s is produced by the C-C bond/C-H bond, C=O bond, CF2 bond and CF3 bond collectively, as shown in Figure 7 for Point 2.