Mitsuo Sakurai

A study of applications scribe frame data verifications using design rule check

In semiconductor manufacturing, scribe frame data generally is generated for each LSI product according to its specific process design. Scribe frame data is designed based on definition tables of scanner alignment, wafer inspection and customers specified marks. We check that scribe frame design is conforming to specification of alignment and inspection marks at the end. Recently, in COT (customer owned tooling) business or new technology development, there is no effective verification method for the scribe frame data, and we take a lot of time to work on verification. Therefore, we tried to establish new verification method of scribe frame data by applying pattern matching and DRC (Design Rule Check) which is used in device verification. We would like to show scheme of the scribe frame data verification using DRC which we tried to apply. First, verification rules are created based on specifications of scanner, inspection and others, and a mark library is also created for pattern matching. Next, DRC verification is performed to scribe frame data. Then the DRC verification includes pattern matching using mark library. As a result, our experiments demonstrated that by use of pattern matching and DRC verification our new method can yield speed improvements of more than 12 percent compared to the conventional mark checks by visual inspection and the inspection time can be reduced to less than 5 percent if multi-CPU processing is used. Our method delivers both short processing time and excellent accuracy when checking many marks. It is easy to maintain and provides an easy way for COT customers to use original marks. We believe that our new DRC verification method for scribe frame data is indispensable and mutually beneficial.

Effectiveness of Mask data process using OASIS format

OASIS(Open Artwork System Interchange Standard) format was investigated for various logic device datas. In this investigation, the change in the processing time of the confirmation of the content of compression in OASIS and the mask data processing were confirmed. OASIS format has higher data compressibility than other methods, and its compressibility is independent on the data size. It is very effective in a advanced technology device according to the above-nentioned investigations. In data storage and data handling, applying after OPC processing is quite effective.

Study of hotspot repair using cellular automata method

In advanced semiconductor manufacturing, model-based optical proximity correction is commonly used to compensate for image errors. The final pattern is generated using correction values determined by lithography simulation. Image errors such as patterns with insufficient correction or patterns with excessive correction can be generated. These patterns with errors are called hotspots. Such errors are conventionally detected by lithography simulation of OPC patterns. When a hotspot is detected by lithography simulation, it has to be repaired manually or by repeated use of OPC tool. However, it is difficult to obtain correct pattern for a complicated shape, and the correction procedure may require a significant amount of additional processing. In order to solve this issue, we examine application of cellular automata (CA) method for hotspot correction. It is known that CA method can be used for weather or traffic analysis and prediction. In this report, we studied the CA method for deriving simple hotspot repair rule based on lattice cell-like models for light intensity distribution and OPC patterns. We will report on the results of hotspot correction technique with the OPC pattern using CA method.

Study of influence to transistor properties on the change of OPC pattern

Slight change of OPC pattern shape may influence transistor characteristics. So inputting the result of Litho- Simulation, Contour, to SPICE-simulator, we investigated the change of the transistor characteristic. First of all, we investigated the sensitivity of the transistor characteristics to OPC pattern change. We found that the difference of shape with Isolated, Dense pattern, and a different OPC tool caused difference after SPICE-simulation. In this investigation, we report focusing on the transient and DC analysis of transistor characteristics. Contour data was measured and averaged before input to SPICE and a change of transistor characteristic was able to be detected. We came to the conclusion that this investigation method is effective to check the influence of the transistor characteristics due to OPC pattern change. And we can adopt this method as one technique for deciding the applicability of the OPC tool and its upgrade, which were issues for MASK data processing.

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.

Simulation method using the image filter method

We conducted an experiment to determine if the use of image filter method for simulation that calculates the distribution of light intensity on a wafer can reduce processing time in comparison to the use of the Fourier transform. The image filter table value is set by changing the value of Gaussian distribution. The image filter method was approximated with the light intensity of optical simulation that keeps accuracy within the range of the allowance. In this experiment, we examined the differences between the distributions calculated using the Fourier transform and the calculation time by varying the sizes of the image filter tables. For the experiment, we used pattern data having a line width that used in the most advanced technology. When the area of pattern data was wide, the experiment revealed that use of the image filter method reduced calculation time by approximately 50 percent or more in comparison to a simulation that used the Fourier transform. As we decreased the size of the image filter tables, the calculation time became shorter, but the differences from the distribution calculated using the Fourier transform became larger. We intend to study the possibility of simulation by expanding the area of pattern data and using the image filter method for simulation-based OPC.