Isao Shimizu

An improved electron scattering simulation at the mask in a projection lithography system

There are two major critical issues to be solved in the technology of the electron beam projection lithography. One of them is the Coulomb interaction among electrons in the shaped beam. The other is the influence of the scattered electrons, which are produced at the mask. It is known that the scattered electrons hardly expose the wafer surface directly. However, the scattered electrons may exert the Coulomb interaction on the shaped beam along their trajectories to the wafer. In order to estimate their influences quantitatively, it is necessary to know the electron scattering behavior at the mask precisely. In the present study we propose a new simulation model, which expresses the electron scattering phenomena in the mask material, and we estimate the effect of the Coulomb interaction effect between the scattered electrons and electrons in the shaped beam.

A technique for making holograms easily and for measuring simultaneously the behaviour of particles of different sizes and/or shapes

A new technique for rapidly discriminating shapes and/or sizes of micrometre size particles which are spatially distributed on a large scale has been developed. The technique is based on multiplexed matched spatial filtering, which is a kind of Fourier holographic filtering technique. Using the technique, large view visualization of the spatial distribution and the spatial behaviour of specific particles (e.g. aerosols, allergen particles, red blood cells, etc) can be realized. To make the multiplexed matched spatial filter (MMSF), a new material for hologram recording has been applied. The material is a photoconductor plastic which is processed by a solvent vapour and a corona discharge. The method of hologram recording is a dry process, which processes the material in several minutes at the initial settings of the device. Therefore, the MMSF can be made very easily in a short time. In the research, the discrimination of spatial behaviour of moving particles of different shape and/or size has been carried out by the MMSF made by the photoconductor plastic material.

Shot number analysis on character projection e-beam lithography for random logic device fabrication at 70-nm node

A reduction efficiency of shot numbers in character projection (CP) electron-beam (EB) lithography with memory device application depends on a design rule (cell size) and a pattern complexity within a memory cell. Many researchers reported that it was approximately 1/10 to 1/100 compared with conventional variable-shaped beam (VSB) method. The reduction of shot numbers in memory devices mainly comes from allowance to place multiple cells in one CP-cell area and simplicity of the cells placement (regular pitch with adjacent allocation). On the other hand, there are few reports concerning reduction efficiency of shot numbers with logic specific application in CP EB lithography due to the complexity of logic cells allocation to CP-cell area. To analyze this, logic device layout data in 70nm node was prepared by shringking actual functional device data of 350 nm node in the ratio of 1/5 and extracting random logic region. The size of this region was 1,094 x 283 micrometers . The height of logic cell was 2.64micrometers and it was smaller than typical one CP-cell size in second aperture (5 x 5micrometers ). The pattern data in GDS-II stream format was converted into EB exposure data: divided figures (rectangles). By this procedure, numbers of figures and cells were obtained. The total number of referred logic cell was 26,812. Among 26,812 cells, only 111 common (unique) logic cells were used for the logic region. The sum of figures in gate layer was 412,251 and this value was assumed to be equal to a total number of shots in conventional VSB method. Among the 111 common cells, only 6 cells in the gate layer showed width more than 5micrometers (maximum CP-cell size). Most frequently referred cell was an inverter and the number of reference was 5,395. The referred frequency of each cell exponentially decreased when the cells were arranged in descending order of reference. Among the total figures, top cell showed 66,120 accumulated number of figures (referred number=2,204, figures in cell=30). The cumulative number of total shots also exponentially decreased when cells were arranged in descending order of total shots. So it is necessary to decide the appropriate maximum number of CP- cell for futur CP EB exposure systems considering the reductoin efficiency of the shot numbers. For the current CP EB exposure tool of Hitachi (HL system), allowed number of CP-cell is 21 which means only 5 different (frequently referred) logic cells can be allocated in CP aperture with typical placement in 4 orientations. But even in this case, total required shot numbers of this logic region for EB Exposure can be reduced to approximately ½. For the ADVANEST CP EB system (allowed number of CP-cell = 100), reduction ratio of shot numbers is 1/4. For the pseudo CP EB system with 500 CP-cells in second aperture, reduction ratio of shot numbers would be 1/15. So, CP EB lithography is one of the promising candidates for small or medium volume production technology especially memory with logic device application after 70 nm node if the maximum number of CP-cell is appropriately increased.

Photoconductive Plastic Holography Employing White-Light Laser.

We have succeeded in quasi real-time holography engineering by using a photoconductive plastic (PCP) plate and in full-color holography engineering by employing a hollow-cathode type, He?Cd+, white-light laser. We have also succeeded in eliminating ghost images, which are inherent in holograms reconstructed from multiwavelength light, using diffused reference illumination.

Influence of electron density distribution at the electron source in a projection exposure system

The exposure characteristics are largely influenced by the size of the electron source. The characteristics are also influenced by the electron density distribution at the source. In order to discuss these effects quantitatively, individual electron trajectory is traced in a realistic projection exposure optical system in the present study. Based on the results obtained above, the most preferable conditions on the electron source are clarified for the projection exposure system.

Developmental research on simultaneous discrimination of shapes by a photoconductor plastic hologram automatically processed by solvent vapor

A new technique has been developed to simultaneously and instantaneously discriminate the shapes of objects by using a Multiplexed Matched Spatial Filter (MMSF). In order to make a hologram automatically, rapidly and efficiently and to process the hologram on the initially setting place, the techniques processing a photoconductor-plastic plate by solvent vapor and cutting off tremor using optical system composed on a rail base have been developed by authors. The diffraction patterns generated from objects at the frontal focal plane of the convex lens in the parallel coherent laser beam are superimposed at the back focal plane of the lens and the information of these shapes are filtered by a hologram (MMSF). In a consequence of mention above, the grope of auto-correlation peaks discriminating the shapes of objects appear in each measuring field skew-symmetrically to the location of input objects. The spatial distributions of objects in each shape or size could be measured simultaneously and instantaneously using the technique.

Multiple Matched Spatial Filtering with Corresponding Symbols by the Hybrid System

A system for multiple pattern recognition without observing peak autocorrelation signals is described. A multiplexed matched spatial filter is used for multiple operations. The reconstructed peak signals are not directly used for recognition. They are first fed into a frame buffer memory via a CCD camera to be processed by a microcomputer. Unknown inputs are finally recognized by taking a glance at symbols, which are displayed on a CRT screen and are deduced from the peak signals by the microcomputer. The system presents easier recognition for observers who are not expert in matched filtering.

Experimental study of electron beam projection lithography mask defect printability

Mask defect printability of electron beam projection lithography (EPL) was investigated. We fabricated EPL chip reticles including programmed defects. The design of these programmed defects was based on semiconductor equipment and materials international (SEMI) standards, but we modified it from the original to a new design for the 100–70 nm node. In our defect printability experiment, Nikon’s electron beam (EB) projection experimental column was used as an exposure tool with those chip reticles. The acceleration voltage of the electron beam was 100 kV. In the case of the “size shift” defects, the correlation between the defect size on the reticle (×1/4) and the critical dimension (CD) change on the wafer is linear and the defect down to 40 nm was printed. Furthermore mask error enhancement factor is nearly equal to 1. This is the advantage of the EPL over the optical lithography. On the other hand, in the case of “dot” defects, defects smaller than 100 nm on the reticle has a small impact on the CD chang...

Simultaneous Visualization of Moving Human Body by Means of DVR and Infrared Radiometer

Digital Video Recorder is widely used to visualize the dynamic image of moving body. In the field of motion science, DVR is often applied to study two and three-dimensional moving images of the human body under walking, running and jumping by means of several tracer markers on the body surface. In this study, the high-speed infrared radiometer IR simultaneously visualized the visual and thermal image of the moving human body using thermal marker and thermal footmarks. Characteristics of single- and multi-flash imaging methods were evaluated using the dynamic motion recorder.

Developmental research on the system for making holograms easily and rapidly in real-time holographic interferometry

A new system for making hologram easily and/or rapidly has been developed, by using solvent vapor for automatic development of photo-conductor plastic hologram (PPH) at initial setting place of the photosensitive plate in an open room, and by aligning all optical units on an optical rail base for reducing vibrational effect. The new optical system is compact and easy to operate and can be used as an adequate device for real time holographic interferometry. In experiments, interferometric frames of rapid variation of air density distributions by temperature distributions in flame and the vibration mode of surface of radio-speaker have been taken in the photography as the real time holographic interferometry. It is recognized that the new system for making hologram easily and rapidly can be used effectively in the real time interferometric measurement.