Satoshi Kakunai

Actinic mask metrology for extreme ultraviolet lithography

A new actinic mask inspection system has been developed, and simulations were carried out on its imaging performance. Preliminary experiments using the extreme ultraviolet (EUV) microscope developed at NTT have shown that it can resolve 250- and 350-nm-wide lines (on a mask). Furthermore, the type of absorber material used in a mask was found to have some effect on the contrast of mask images taken by EUVM. Our results demonstrate that an at-wavelength microscope is a powerful and useful tool for evaluating mask fabrication processes for EUVL.

Effect of acetabular component anteversion on dislocation mechanisms in total hip arthroplasty

Quantifying soft-tissue tension around the hip joint during total hip arthroplasty remains difficult. In this study, a three-dimensional computer-aided design model was developed to clarify how component position in total hip arthroplasty contributes to the primary cause of posterior dislocation in cases of flexion, adduction and internal rotation. To better understand the influences of anteversion angle of the acetabular component, its effects on the primary causes of dislocations and the range of motion were investigated. Three different primary dislocation mechanisms were noted: impingement of the prosthetic femoral neck on the cup liner; impingement of the osseous femur on the osseous pelvis; and spontaneous dislocation caused by soft-tissue traction without impingement. Spontaneous dislocation could be detected by calculating hip forces at any thigh position using the computer-aided design model developed. In computer analysis, a transition from prosthetic impingement rate to osseous impingement rate occurred with increasing anteversion angle of the acetabular component. Spontaneous dislocation was detected at angles > 10° of anteversion of the acetabular component when flexion occurred with extreme adduction and internal rotation. This study demonstrated the possibility of spontaneous dislocation that results not from prosthetic or bony impingement but from muscle traction with increased range of motion.

Profile Measurement by Projecting Two Gratings with Different Pitches

A new method for measuring objects with steps is proposed in which two gratings with different pitches are projected on the object surLace. The method is demonstrated with sinusoidal gratings made of laser interference fringes and also sinusoidal gratings formed by liquid crystal controlled by computer. An object with step height of 20 mm is measured with standard variation below 3%.

In Situ Measurement of Internal Stress in Electrolessly Deposited Copper Film by Television Holographic Interferometry

With a measurement technique called television holographic interferometry, we investigated the internal stress generated at the initial deposition stage in electrolessly deposited Cu films on silicon substrates. In a region of film thickness less than 100 nm, two inflection points, at which the direction of stress was reversed, were observed on the film thickness-stress curve. From cross-sectional transmission electron microscopy observation of these films, it was found that the films grew in the Volmer-Weber mode and that the above inflection points related to specific stages observed, such as islands growth, islands coalescence, the formation of continuous film, and grain growth.

In Situ Measurement of Internal Stress in Electroless Plating by Television Holographic Interferometry

Electroless plating can uniformly plate a material on irregular and non-conducting surfaces. Consequently, it has been utilized widely for printed circuit boards in the electronics industry. During the plating process, internal stress is frequently incorporated into the film and this often results in detachment from the substrate. In order to investigate the origins of stress in the films, measurements of film stress are required during the early stages of growth. In this study, TV holography, which can capture holographic images at TV frame rates, was used to sensitively measure the deflection of the cantilever beam during deposition. By substituting the deformation data in Stoney’s equation, it is possible to calculate internal stresses in-situ. The internal stress created by electroless plating from a Cu plating solution on a Be-Cu substrate is discussed. It is assumed that the internal stress is generated in the initial stage in which the plating grains with a thickness of about 0.01µm deposit. This paper shows that the present method can be very useful for in-situ measurement of initial internal stress.

Pattern inspection of EUV mask using an EUV microscope

It is proposed that at-wavelength EUV mask inspection system based on EUV microscope, which is the best way to observe the mask directly. Using this system, preliminary experiments to examine the pattern inspection of EUVL mask is carried out. EUV microscope has a capability to resolve 50 nm lithographic node finished EUVL mask. We confirmed that at-wavelength microscope rather than SEM is both powerful and useful for evaluating the mask fabrication process for EUVL. Furthermore, it is find out that the contrast of the mask images observed by EUVM influenced by the absorber material. As the result, important information of the finished EUVL mask can be obtained utilizing EUVM, which is very important tool for the finished EUVL mask inspection.

Effects of Adduction, Internal Rotation, and Flexion Angles on Dislocation for Total Hip Arthroplasty

Passive muscle tension around the hip joint following total hip arthroplasty (THA) plays an important role in post-surgery dislocation mechanisms, especially posterior dislocation. To analyze dislocation objectively and to clarify the distinction between implant-to-implant impingement and dislocation, three-dimensional finite element (FE) models of hybrid THA components were generated. An acetabular component was implanted into the acetabulum in 20 degrees of anteversion and 45 degrees of inclination. The bearing surface had 26 mm hemispherical plus 1 mm flat depth and a chamfered edge. In this study, posterior dislocation-prone movements such as flexion, adduction, internal rotation, and their combinations were analyzed, starting with the femoral component oriented in a manner corresponding to the hip being flexed to impingement with 0°, 10°, 20°, and 30° of internal rotation and 0°, 10°, 20°, and 30° of adduction. The nonlinear explicit FE simulations were driven by inputting a series of incremental flexion moments and hip joint forces concurrently. The angles of internal rotation and adduction affected both impingement and dislocation angles of flexion. The flexion angles both at impingement and dislocation decreased by increasing the internal rotation angles. Although the peak flexion moment to make the hip joint dislocate increased by increasing the internal rotation angle, it didn’t always increase with an increase in the adduction angle. The highest value of the peak flexion moment to dislocation was observed at 30° of internal rotation. Conversely, the lowest value of the peak flexion moment was observed at 10° of adduction. This lowest value means that the hip joint is easy to dislocate at this adduction angle.

Mechanical Characteristics of Spectacles

In order to wear spectacles comfortably, the lens power should be optimized and the spectacles should be secured at an appropriate position on the head so as to minimize any sensation of discomfort. For smooth fitting, the frame must be designed by taking in account the mechanical characteristics. However, the design and manufacture of spectacle frames often rely on the experience of engineers. This is partly because spectacle frames have complex forms and complex materials. Measuring and analysis technologies are currently making remarkable progress and consequently they can now be applied to industrial products comparatively easily[l-3]. In this study, we investigated the mechanical characteristics of three types of spectacles that are on the market: a titanium frame of a full-rim model that is popular because of its good lens protection, a gum-metal frame made from a recently developed material, and a rimless frame in which each lens is secured using two screws that allows very flexible lens design.