It has been generally mentioned that EPL(Electron beam Projection Lithography) system has theoretically enough resolution of wafer processing because an energized electron beam might be finely controlled by multi electric lenses, however the system is very sensitive to outside disturbances, gas molecule, particles and electromagnetic field. The former two issues could be solved by exposing the system into a vacuum environment. On the other hand, since the latter will potentially be a peculiar problem for this lithography system, some concepts for AC and DC magnetic compensation are discussed in this paper. Especially, an electromagnetic linear motor which is almost a defacto standard in commercial base lithography tools should be also adopted to Nikon's EPL wafer stage in order to establish a common platform, so a magnetic flux leak from motors, eddy current excited and magnetized materials must are protected against an electron beam axis. First, a magnetic affect from wafer stage components are estimated, then DC/AC magnetic shielding and canceling methods of motor are introduced, furthermore the concepts are verified by manufacturing a full-scale Nikon's EPL tool and experimented. The studies, magnetic analyses and test results of magnetically conformed stage for Nikon's EPL are reported in this paper.
We have developed a stitching wavefront measurement system using a Shack-Hartmann sensor for a lens of a pupil larger than the CCD camera fields. This system has the following features; (a) algorithms for the stitching error compensation using the stage position data obtained with the laser interferometers, and (b) calibration for the lens array errors of the sensor. Experiments confirmed that the difference of the root-mean-square value of wavefronts measured with 1 shot and 3X3 shots is 0.0013 of a wavelength (355nm). We evaluated the stability of the wavefront measurement against the point source mis-adjustment from 0 to 1μm in the direction of the optical axis. The fluctuation of the wavefront rms is found to be 0.0086 (2σ). Finally, a Fourier transform lens of a pupil diameter of 40mm is measured using the stitching technique. It is confirmed that the stitched boundaries are smoothly connected.
Deep-holes can be bored by using deep-hole drilling machines as well as by using large lathes, machining centers, boring machines, etc. Even in the case of holes with a relatively small L/D ratio, which are machined using machines such as lathes, it is difficult to precisely evaluate their accuracy. We developed an on-machine measurement system on a lathe and evaluated the performance of the measurement system. The system consists of a laser interferometer set behind a head stock, and a measurement unit with the pentaprism and corner cube prism. It was observed it takes 25 min to evaluate the accuracy of a hole with a diameter of 63 mm and a length of 250 mm. If the system is used for the feed-back control of NC machines, the evaluation time should be shortened. In this study, the influence of the rotational speed and feed speed on the measurement accuracy was observed using three workpieces with holes of different shapes. Through the experiments, it was confirmed that the hole accuracy can be measured within 17 s at a high feed speed of 900 mm/min.
It is important for a continuous path control to identify the machine parameters, such as inertia and dominant nonlinear friction. This paper presents a practical identification method for the inertia and Coulomb friction by using steepest descent method and low-pass filtered M-sequence, in which the model in the inverse transfer-function quickly approaches to the true machine parameters. It is shown in the experimentation using real machine that the steepest descent method with a dead band is very effective in order to reduce estimation error and from the practical point of view.
It has been reported that heat accumulation enables the ablation threshold of the material lower and ablation rate higher in laser drilling. In this paper, the influence of the heat accumulation on high-aspect-ratio hole drilling with the fourth harmonic wave of Nd : YVO4 laser was investigated. Repetition rate caused the much difference of the depth, for example, the depths of the holes were changed from 1200 μm to 3000 μm, by changing the repetition rate from 1 kHz to 10 kHz, when the laser energy was set at 100 μJ/pulse. The repetition rates which the deepest holes were obtained at were dependent on the pulse energies. Temperature rise with 10 kHz pulses was calculated to be 20 times higher than that with 1 kHz pulses, when the successive pulse illuminated. The reasons that the repetition rate caused the different of the depths, were the diameters at the entrance of the holes, the heat accumulation effect and shielding effect by ablated particles.
This present paper is intended to show some experiments and discussion about autonomously motion of droplet on hydrophilic/hydrophobic-patterned substrate. An array of triangular PTFE works as specific pattern to have gradient wettability on a glass substrate. Water micro droplet can autonomously moved from hydrophobic region to hydrophilic region along the pattern. Both of pattern geometry and droplet size become the difference between success and failure of the droplet motion. Contact line geometries of water droplet allow us to estimate driving force and necessary condition for autonomously droplet motion. The obtained value is well consistent with the experimental results. The authors also apply multi-step motion by sandwiching in droplet between two patterned substrates. Another substrate changes in direction of droplet after initial motion on a substrate. The droplet position can be controlled with mm-scale resolution.
This paper presents a sensor-less process monitoring method to detect chatter vibration in square end milling. The method of monitoring cutting forces and detecting chatter vibration using external sensors such as accelerometer and force sensor has been proposed. However, using external sensors increases the cost of manufacturing systems and additional structures for sensor implementation often decrease the stiffness of workpiece fixturing, and it results in another chatter vibration. Therefore, a novel method without using any external sensors is developed to detect high-frequency vibration. Concretely, disturbance torque acting on the spindle is estimated by using disturbance observer and used simultaneously for spectrum analysis. From the experimental results, it is confirmed that the proposed method enables to estimate high-frequency disturbance. Certain peaks which are considered as a peak frequency of chatter vibration can be detected.
This study aimed to achieve the high-aspect-ratio microdrilling in L/D=20 by the reduction in cutting force. Effect of rake angle of a chisel edge by thinning on thrust force was examined. A strong correlation between rake angle of the chisel edge and the thrust force was obtained. The thinning of the microdrill with a diameter of 0.2mm resulted in a reduction in the thrust force by up to 70%. It has been found that optimal rake angle of the chisel edge in tool life was in the range from -10 to 0 degree. Furthermore, the rake angle of the chisel is able to be changed by changing the grinding wheel shape used for thinning.