Lasertec has commercialized a new mask process monitoring system "M2351" that has pattern inspection capability based on the conventional mask blank inspection system "M3250" known as "MAGICS" and will start to accept order for this new product on December 1st. "M2351" is designed to be applicable to incoming inspection of Photomask blanks and to development of mask processes for the semiconductor devices with 90 nm design rule and onwards.
Lasertec counts on this new product as one of the flagship products from 2004 and onwards and is planning to receive orders for about 4 units in the first year.
* "MAGICS" is an abbreviation for Multiple image Acquisition for Giga-bit Inspection with Confocal System.
Overview
Along with the pursuit for ever-finer design rule, the demand for higher quality Photomask is heightening stronger and stronger.At the same time, the influence of mask process yield on the cost of high end masks is becoming very large. Under such circumstances, mask blank makers have started using M1320 for mask blank outgoing inspection and mask shops have started using M2350 for mask blank incoming inspection, both tools being based on laser confocal optics, in the aim to improve mask blank quality that greatly affects the mask production yield.
At the same time, in addition to the issue of mask blank quality, controlling of defects in the mask manufacturing process is becoming the most important issue because the improvement of yield in the patterning process is fundamental requirement for the cost reduction of mask manufacturing. For this reason, the resist pattern inspection after resist pattering has recently been recognized as an effective means and been utilized. However, it has been difficult for the conventional mask pattern inspection systems to realize high defect detection sensitivity, due to the influence of layer thickness distribution and such. Furthermore, it has been difficult to operate enough number of the inspection systems in the mask development processes because such systems operate only at low throughput and are very expensive. Unlike the conventional high sensitivity and very expensive systems, M2351 is a very innovative system that realizes defect inspection capability on chrome patterns and resist patterns based on the utilization of line and space monitor patterns, while maintaining the mask blank inspection function, the sensitivity and the price range of M2350. M2351 has the following features.
Features
- The first mask process monitor system that is applicable to Photomasks for semiconductor devices with 90 nm and below design rule, in the industry
- There is no cost increase because the mask blanks that have been found to be no good at the incoming inspection can be utilized as monitor masks.
- Writing cost can be kept low because line and space patters are used as test patterns and EB writing time is accordingly short.
- Very high pattern detection sensitivity is realized based on the usage of line and space monitor patterns, while maintaining the same high throughput of the conventional M2350.
- Inspection of chrome pattern, half tone mask pattern, resist pattern and such are available.
- Because the system employs bright-field method, sensitivities for pinhole and pattern defects are high, not only for foreign particles.
- Foreign particle/pinhole determination is easy because the system is equipped with detection optics in transmittance mode.
- Laser confocal optics provides observation of not only 2 dimensional shape but also 3 dimensional shape of the detected defects.
- Image recognition provides automatic verification of the type of defect detected.
- Tracing of defects through the progression of process is available because the sensitivity is very high. As a result, it is easy to find out the process condition in which defect generation is low.
Lineup of other features
- Mask blank shipping box, open cassette and RSP can be mounted and a mask blank can be , taken out of shipping box, inspected and stored in RSP.
- High Operationality
Features from technical viewpoint
- High speed scan of 33 multi laser beams
- Utilization of laser confocal optics that realizes high resolution, no flare and high S/N ratio
- Employment of high powered Ar Laser as the light source
- The maximum image processing speed of 3.1 billion pixels per second is established by simultaneously driving 31 channels of high speed image processing circuits.
Applications
Inspection of mask blanks and mask patterns
- Laser confocal optics shows high sensitivity not only to foreign particles but also to shallow scratches and pits because the system simultaneously illuminates the wafer from various angles.
- This system is indispensable to technical development due to its capability of observing 3 dimensional defect shape with its high review function.
- This system can be applied to developments aiming at the improvement of yield in patterning processes, new materials and new processes by performing inspection at various stages such as "after EB writing", "after resist image development", "after etching" and "after resist stripping", in addition to the mask blanks incoming inspection, at mask shops.
Configuration
Main body and control unit
