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We will start XPS presentation with title that Advantages of Vertical Argon Ion Etching in XPS Depth Profiling, JPS-9030 Case Study. Today's content is this: first is overview of JEOL's XPS instruments, JPS-9030. Next is introduction of JPS-9030's ion etching system. After introduction of JPS-9030, we will explain about excellent point of JPS-9030's etching system. We will introduce two points. One is vertical argon ion irradiation system. Another is Kaufman-type ion source. At last, we will show actual analysis data measured by JPS-9030. This time, we measured thick multilayer film. Data one is comparison between different ion beam irradiation angle. Data two is comparison between different accelerating voltage of argon ion. Let's start introduction of JPS-9030 overview. Left figure is JPS-9030. Feature of JPS-9030 is shown in right table. First is X-ray source. JPS-9030 can be attached two types of X-ray source.
One is magnesium and aluminum twin anode X-ray source. Another one is monochromatic aluminum X-ray source. Next feature is analysis area. Analysis area of JPS-9030 is over 5 mm. Next feature is argon ion source. JPS-9030 has Kaufman-type ion source, and that ion source is mounted vertical direction of sample. Next is attachment. Various attachment, such as UPS, GCIB, heating system, and so on, can be attached to JPS-9030. Among these features, the analysis area is one of JPS-9030's unique features. Due to large analysis area, it is possible to analyze average composition of the sample. Next feature is about argon ion source. JPS-9030 has vertically mounted Kaufman-type argon ion source. Due to this system, JPS-9030 enables good depth profiling. We will explain the detail of argon ion etching system. This is figure of argon ion source attached to JPS-9030. In JPS-9030 system, Kaufman-type ion source is used.
Furthermore, that ion source is attached to the preparation chamber, not analysis chamber. This system is several good point. We will introduce that good point. This is a schematic diagram of ion etching system with JPS-9030. From below figure, sample preparation chamber and measurement chamber is separated by valve. In XPS analysis, HSA analyzer is used for detecting photoelectron. That analyzer is mounted vertical direction to the sample for detecting photoelectron with high sensitivity. For this reason, some XPS instruments do not enable the ion source to be mounted vertically on the sample. On the other hand, in JPS-9030, the ion source is mounted in the preparation chamber. Therefore, it can be mounted in the vertical direction of the sample. Due to irradiating argon ion beam from vertical direction, it is possible to suppress the surface roughness after ion beam irradiation. JPS-9030 has another features.
JPS-9030 uses a Kaufman-type ion source. Ion current of Kaufman-type ion source is high. Therefore, practical etching is possible even at lower accelerating voltage. Due to low accelerating voltage, it is possible to suppress atomic mixing. Next content is detail of advantage of vertical argon ion irradiation and Kaufman-type ion source for depth profiling analysis. Firstly, I will explain about importance of incident angle of ion beam. Left figure is schematic diagram of ion beam irradiation with tilted direction of ion beam or vertical direction of ion beam. As shown in this figure, when irradiating argon ion beam to rough sample, shadow area cannot be etched by tilted ion beam. Therefore, some XPS instrument requires sample rotation. In case of JPS-9030, argon ion beam is irradiated from vertical direction, so there is no shadow area, and entire sample surface can be etched uniformly without sample rotation.
This is a figure of the JPS-9030's etching system. The argon ion source is mounted in the vertical direction to the sample. Therefore, sample rotation is not required, and it is possible to analyze multiple samples at once, shown in the right figure. From the right figure, by simply setting the sample in the sample holder, the operator can perform depth analysis on multiple samples with minimal roughness effects. The next important point is about the accelerating voltage of the argon ion beam. When irradiating argon ion to the sample, argon ion penetrates into the sample. Argon ion penetrating into the sample mixes inside the solids. When atoms at the interface are mixed, depth profiling data become worse. Furthermore, in the case of high accelerating voltage of argon ion, penetrating depth is deep and influence of mixing is large. However, the JPS-9030 uses a Kaufman-type ion source with high ion current, enabling etching with lower accelerating voltage and less atomic mixing.
Therefore, we calculated the penetration depth with changing accelerating voltage of argon ion. This time, we used SRIM simulation, and, as a result of simulation, it was revealed that penetration depth become shallower by decreasing accelerating voltage. In case of JPS-9030, due to Kaufman-type ion source, etching rate is high, even at low acceleration voltage below 500 volt. Next is application data. This time, we measured thick multilayer sample. Data one is comparison between different incident angle. This time, we compared 90 degree and 45 degree. This time, we measured silicon and aluminum multilayer sample. This film is formed by alternating layers of silicon and aluminum of about 50 nanometer, for a total structure of 8 layers. The thicker the sample is etched, the greater the roughness of the sample surface.
Therefore, this sample was used to evaluate how different etching condition after the result of depth profiling analysis. This is surface roughness of etched sample. After etching silicon and aluminum layer and exposing silicon substrate, we observed the sample by AFM. Before ion beam irradiation, roughness of sample surface is 2.4 nanometer. Right figure is the surface after ion etching. Above sample is etched by vertical direction. In case of vertical direction, sample roughness was suppressed. Below sample is etched by tilted direction. In case of tilted direction, sample surface become rough after etching. As shown in this data, incident angle of argon beam affects surface roughness. It was revealed that tilted ion beam makes sample surface rough. We checked the relationship between sample roughness and depth profile data.
This profile was taken under two conditions: 90-degree ion beam irradiation and 45-degree ion beam irradiation, and accelerating voltage of 1,000 V. In the left profile, alternating layers of silicon and aluminum can be verified from the profile. Furthermore, the interface area between silicon and aluminum is steep, and it can be determined the thin film has high degree of flatness. In contrast, steepness of right profile become worse in deeper region. This is due to sample roughness by argon ion beam irradiation. In case of obtaining this profile, operator cannot distinguish whether the sample really has poor steepness at the interface, or whether the equipment is causing poor steepness. We quantitatively evaluated the interface steepness from this profile. Firstly, we enlarged specific range of profile. This is enlarged profile.
This enlarged area is the interface region, where the peak intensity of aluminum decreases and peak intensity of silicon increases. The profile of this interface was used to evaluate the steepness. This time, steepness was defined as the thickness of 84% and 16% intensity. As a result of steepness evaluation, steepness of 90 degree was 12.9 nanometer, and that of 45 degree was 17.0 nanometer. Furthermore, this is the result of evaluating steepness at all interfaces. For both 90 degree and 45 degree incidence, steepness of the interface decreased with etching. On the other hand, vertical irradiation was able to maintain a higher steepness than tilted irradiation. From this data, it was revealed that sample steepness can be evaluated by vertical direction argon ion beam. Next is other comparison result. Data two is comparison between different accelerating voltage.
This time, we compared 500, 700, and 1,000 volt. This is analysis data obtained by JPS-9030 with changing the accelerating voltage. Left profile is obtained with accelerating voltage of 500 volt. Right profile is obtained by 1,000 volt. Both profiles are steep enough to reveal the layered structure of the sample. Since it was difficult to determine steepness from appearance, steepness was quantitatively calculated from the profile. This is evaluation result of steepness. This result showed lower accelerating voltage gives better steepness. Changing accelerating voltage from 1,000 to 500 volt, steepness improves by a few nanometers. And by using lower accelerating voltage, it is possible to evaluate the slight steepness of a sample without worsening the steepness during measurement. This is summary. This time, we introduced JPS-9030 and its ion etching system.
Compared with 45-degree incident, vertical argon ion incident eliminates shadowing and minimize surface roughing, enabling uniform etching and stable depth profiling. Furthermore, low acceleration voltage argon ion etching reduces atomic mixing, achieving high depth resolution, even in multilayer structures. Thank you for attending this presentation. That's all.
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