Satoshi Akutagawa

Reticle inspection using an image filter method

This paper reports a technique of reticle inspection incorporating the use of an image filter. In this technique, optical intensity distribution is calculated by optical simulation of electron beam lithography (EB) data or an image file obtained from a SEM photograph to evaluate the printability of defects on a reticle. When an image file is compared with the EB data, the image file has differences at the rounded corners as well as at the areas with defects because the image file is obtained from the reticle pattern. To reduce the differences, an image filter (or reticle filter), which simulates the pattern creation process on a reticle, was applied to the EB data. The simulated EB data is defined as the non-defect reference pattern. The optical intensity and critical dimension (CD) were then obtained. Image files of defects were obtained from the SEM photographs of reticle patterns having various sizes of defects. By applying optical simulation to patterns obtained from the image files, the optical intensity and CD were calculated and compared with those of the reference pattern, and the differences are evaluated. The evaluation results showed that optical intensity and CD changes fluctuate regardless of the size or type of defect. Correlation was confirmed between the differences in optical intensity and the CD changes in the defect area. It was thus concluded that defect printability can be evaluated by the differences in optical intensity obtained from image files.

Parallel photomask pattern data conversion and verification system

This system is designed to convert and to verify different types of LSI layout design data and EB writer data, such as GDS-II, MEBES, and JEOL, with the help of its original internal format. The internal format data can be processed not only by a single workstation sequentially but also by network-linked workstations or a single workstation having two or more processing units concurrently. This parallel processing mechanism enables the system to reduce total processing time when handling large volume of data. The resultant internal format data produced by the conversion processes including logical operations, magnifications, and re-sizing operations can be immediately verified by built-in DRC program that is driven by a series of user commands, which consequently yields highly reliable output EB writer data. The built-in pattern viewer can graphically visualize any combination of the layout design data, the EB writer data, and the results of each conversion and verification in the same display window to provide users with an intuitive and easy method for verification. The features of the system and the parallel processing performance are described in this paper.

Mask-/reticle-making control system

The mask making is the first step in the semiconductor device manufacturing. It depends entirely upon mask delivery time whether it will take a short time or not to develop and produce the new devices. It is required to construct the system which can manage mask making and delivery quickly. It is very important to control the much various information on the many kinds of the mask for ASIC use quickly. It is also important to control the many various masks processing parameters, that is, to memorize the parameters and to use the appropriate parameters when the masks for general purpose device like a memory use are revised. The data base system to control the various information and parameters is requested from many mask makers and device ones. We have made a unitary data base including a large amount of information on the various ASIC devices and the various processing parameters of the memory devices, and information on the mask making progress, whereabouts of the masks. And we have constructed the new mask/reticle making control system using with the database.