S.A. Pahlovy

Ion beam sharpening of diamond tools having small apex angle without facet and ripple formations

The sharpening of diamond tools with small apex angles by low energy (1.0 keV) ion beam faces great challenges because of facet formation at the cutting edge of the tools. Adding to the problem is the formation of ripple, also appearing at the cutting edge of the tools that occurs when the ion beam bombardment is done at some off-normal angle of incidence. In this work, the authors investigated the dependence of the facet angles on the ion beam energy. They also studied the phenomenon of ripple formation as influenced by ion dose, ion beam energy, and ion incidence angles. Based on the experimental results they then developed a method for sharpening the tool with 45° apex without facet formation. They also studied ripple formation using 1.0 keV Ar+ ion beam at a tilt angle β of 30°. The work also used simulations to predict the changes in the profile of diamond tools during ion beam machining at a fixed tilt angle β. They found that simulation results on the profile of the diamond knife matched quite well...

Nanosmoothing of single crystal diamond chips by 1 keV Ar+ ion bombardment

In this article the authors have studied the smoothing of diamond chips by irradiating them with 1 keV Ar ion beam at ion incident angles of 0°, 30°, 45°, 60°, and 80° with ion doses from 3.4×1018 to 6.8×1018 ions/cm2. They found that using ion dose of 6.8×1018 ions/cm2 at incident angles from 0° to 45°, the unprocessed surface (rms=0.14–1.2 nm) turned into ultrasmooth processed surface (rms=0.1 nm). Their results also confirmed the formation of ripples on diamond surface when the surface was irradiated with 1 keV Ar+ ion at incident angles of 60°–80°. They have also discussed the mechanism of smoothing and roughening of the surface by employing Bradley and Harper model and equations. These studies led to the understanding of the role of induced viscous flow in the smoothing process. Therefore, by choosing right conditions, 1.0 keV Ar+ ion beam machining can be employed to make diamond tools with nanofinished surface without any ripple effect.

CHANGES OF RIPPLE MORPHOLOGY OF CLEAVED Si SURFACE BY LOW-ENERGY Ar+ ION BEAM SPUTTERING

We have investigated the changes of ripple morphology of an atomically flat cleaved Si surface due to Ar+ ion bombardment. The cleaved atomically flat and smooth plane of Si wafer was obtained by cutting vertically against the orientation flat of a Si (100) wafer. Then, the cleaved surface was bombarded by 1 keV Ar+ ion beam at ion incidence angle of 0°, 50°, 60°, 70°, and 80°. The ripples structure were depends on ion dose and angle formed on atomically flat surface at ion incidence angle of 50°, 60°, 70°, and 80°. Ripples were unclear and small at ion doses of 1.0 × 1018 ions/cm2 but pronounced at ion dose of 8.0 × 1018 ions/cm2. The wave lengths of ripples were measured and the maximum wave length is 425 nm at ion incidence angle of 70° and ion dose of 8.0 × 1018 ions/cm2. Results show that the wave length of ripple depends on ion doses and angle of ion incidence. It was also observed that the wave vector of ripple changes with changing the angle of ion incidence. This research is concluded by discussing the wave vector changing mechanism with the help of BH model.

Two stage ion beam figuring and smoothening method for shape error correction of ULE® substrates of extreme ultraviolet lithography projection optics: Evaluation of high-spatial frequency roughness

The ULE® substrates used in projection optics of extreme ultraviolet lithography (EUVL) tools are mechanically prefinished with shape accuracy of several nanometer rms (specification: under 0.15 nm rms) with high-spatial frequency roughness (HSFR) (spatial wavelength: under 1 μm) of 0.06 nm rms. The ion beam figuring is used for the final shape error correction of the substrates at low spatial wavelength of greater than 1 mm using high energy (5–10 keV) Ar+ ion beam with 1 mm beam diameter. However, the surface roughness values of the ULE® substrates when machined by 5 and 10 keV Ar+ ion beams result in 0.15 and 0.17 nm rms, respectively; also it is to be noted that these values are greater than the required 0.15 nm rms specification of HFSR. Therefore, the authors developed a method where low energy (0.3 and 0.5 keV) ion beams are used for smoothening the surface of ULE® substrates, previously treated with high energy (5 and 10 keV) ion beams for figuring. By this two-stage operation of ion beam figuring...

Low energy Ar+ ion beam machining of Si thin layer deposited on a Zerodur® substrate for extreme ultraviolet lithography projection optics

For the final correction of the surface figure error of aspherical substrates used in the optics of extreme ultraviolet lithography, ion beam figuring (IBF), which is essentially a machining technique, is regarded as the most promising technique for the job. However, one problem with this technique is that it leaves the surface rougher after the IBF treatment than the surface was before the treatment. Moreover, the machined surface becomes positively charged due to the impact of Ar+ ions that constitute the beam for the IBF processing. Therefore, in this research a Si layer was deposited on a Zerodur® substrate by an ion beam sputtering process, following this process, the deposited substrate was machined by an Ar+ ion beam with energies in the range of 0.3–3keV. The high-spatial-frequency roughnesses (HSFR) of the Zerodur® substrate and of the deposited Si layer were found to be 0.11 and 0.08nm rms, respectively. However, the HSFR of the machined Si layer reaching to a depth of 50nm can be made to go bel...

Etching effects on machined surface characteristics of single crystal Si

This paper demonstrates the wet etching effects on machined surface of single crystal Si. The machined surface was prepared by irradiating sample with low energy (~ 2keV) ECR sourced Ar+ ion beam. Then we performed etching process by HF(2.4%) at 20min,40min and 60min respectively. We analyzed surface of sample (before and after etching) by AFM and white light interferometer to measure surface roughness and machined depth. Finally we compared the etching effects on machining depth and surface roughness and result shows HF etching has remarkable effect i.e. increases both machining depth and surface roughness. Result also confirmed that etching effect can be controlled by etching time.