Hideo Tsuchiya

Die-to-database mask inspection with variable sensitivity

The cost of mask is increasing dramatically along with the continuous semiconductor scaling. ASET started a 4-year project to reduce mask manufacturing cost and TAT by optimizing Mask Data Preparation (MDP), mask writing, and mask inspection in 2006, with the support from the New Energy and Industrial Technology Development Organization (NEDO). We report on the development of a new low cost mask inspection technology with short Turn Around Time (TAT), as a result of adopting a method of selecting defect detection sensitivity level for every local area, defined by such factors as defect judgment algorithm and defect judgment threshold, as one of the pseudo-defect-reduction technique necessary to shorten mask inspection TAT. Those factors are extracted from the database of Mask Data Rank (MDR) and converted on the basis of pattern prioritization determined at device design stage, using parallel computation.

Development of advanced reticle inspection apparatus for hp 65 nm node device and beyond

The usage of ArF immersion lithography for hp 65nm node and beyond leads to the increase of mask error enhancement factor in the exposure process. Wavelength of inspection tool is required to consistent with wavelength of lithography tool. Wavelength consistency becomes more important by the introduction of phase shift mask such as Tri-tone mask and alternating phase shift mask. Therefore, mask inspection system, whose inspection light wavelength is 199nm, has been developed. This system has transmission and reflection inspection mode, and throughput, using 70 nm pixel size, were designed within 2hours per mask. The experimental results show expected advantages for Die-to-Die and Die-to-Database inspection compared with the system using 257nm inspection optics. Shorter wavelength effect makes transmission inspection sensitivity increase, and realizes 40nm size particle inspection. As for the phase shift mask, the difference of gray value between the area with phase defect and without phase defect was clear relatively. In this paper, specifications and design, experimental results are described.

Flexible Sensitivity Inspection with TK-CMI Software for Criticality-Awareness

In this paper we present the method that NuFlare photomask inspection systems can use to strongly reduce pseudo detections by use of TK-CMI software. The NuFlare inspection system is capable to detect the smallest defects in the 45 and 32-nm nodes and has recently been introduced to production. It links up with a compute cluster with Takumis Criticality-Marker Information software (TK-CMI). TK-CMI quickly analyzes the ~200GB post-OPC layout or multi-layer pre-OPC layout and assigns various types of criticality regions. The basic set of criticalities is made to address the challenges that typical maskmakers experience. The TKCMI system also supports design-intent-based criticalities. The NuFlare inspection system uses this full-mask criticality information and generates flexible inspection recipes that inspect low-criticality areas with relaxed sensitivity resulting in reduction of pseudo detections in such regions.

Mask defect inspection method by database comparison with 0.25-0.35 μm sensitivity

Photomasks used in the fabrication of ultra-LSI (ULSI) circuits must be inspected for defects. For 256 Mbit dynamic random access read write memory (DRAM), it is necessary to inspect defects as small as 0.15 µ m. Moreover, inspection of defects of phase-shift masks is becoming an important task of an inspection system. This paper describes an automated mask inspection system (MC-100) based on die-to-database comparison, and a defect inspection method with 0.15 µ m sensitivity for edge and pindot defects. System configuration and the defect inspection method are discussed in detail, including the difficulties of defect detection in an attenuated phase-shift mask.

Advanced mask inspection optical system (AMOS) using 198.5-nm wavelength for 65-nm (hp) node and beyond: system development and initial state D/D inspection performance

A novel high-resolution mask inspection platform using DUV wavelength has been developed. This platform is designed to enable the defect inspection of high quality masks for 65nm node used in 193nm lithography. In this paper, newly developed optical system and its performance are reported. The system is operated at wavelength of 198.5nm, which wavelength is nearly equal to 193nm-ArF laser exposure tool. Some defect image data and defect inspection sensitivity due to simulation-base die-to-die (D/D) inspection are shown on standard programmed defect test mask. As an initial state D/D inspection performance, 20-60 nm defects are certified. System capabilities for 65nm node inspection and beyond are also discussed.

A New Inspection Method for Phase-Shift Mask (PSM) on Deep-UV Inspection Light Source

As the mask pattern becomes smaller and more complex, the demand for a highly precise mask inspection system with high detection sensitivity and few false defects increases. In regard to inspection systems using a deep-UV wavelength, some issues have been encountered concerning inspection of an ArF-halftone (ArF-HT) mask, which is now entering practically used. In this paper, we report the defect detection sensitivity of Cr and KrF-HT masks, and discuss the issues concerning ArF-HT mask inspection and countermeasures to deal with them.

High-resolution DUV inspection system for 150-nm generation masks

In order to perform mask inspection with the high reliability for 150 nm-rule and below devices, the inspection system with high resolution is indispensable. The phase shift masks like DUV HT masks must also be inspected with high sensitivity. A next generation mask inspection system MC-3000 which used DUV optics has been developed, in order to achieve these requirement. The wavelength of this optics is 257 nm that is shorter than that of current UV inspection systems, and is nearly equal to that of current DUV lithography systems. Short wavelength light and high NA optics obtain high resolution, so the defect detection of 130 nm or less is attained. The special issues for the DUV optics were solved by several new techniques. This paper reports the system configuration, basic characteristics for defect detection and inspection performances.

DUV inspection tool application for beyond optical resolution limit pattern

Mask inspection tool with DUV laser source has been used for Photo-mask production in many years due to its high sensitivity, high throughput, and good CoO. Due to the advance of NGL technology such as EUVL and Nano-imprint lithography (NIL), there is a demand for extending inspection capability for DUV mask inspection tool for the minute pattern such as hp4xnm or less. But current DUV inspection tool has sensitivity constrain for the minute pattern since inspection optics has the resolution limit determined by the inspection wavelength and optics NA. Based on the unresolved pattern inspection capability study using DUV mask inspection tool NPI-7000 for 14nm/10nm technology nodes, we developed a new optical imaging method and tested its inspection capability for the minute pattern smaller than the optical resolution. We confirmed the excellent defect detection capability and the expendability of DUV optics inspection using the new inspection method. Here, the inspection result of unresolved hp26/20nm pattern obtained by NPI-7000 with the new inspection method is descried.

Mask inspection system with variable sensitivity and printability verification function

We report on the development of a new mask inspection technology that makes total inspection faster and less costly. The new technology adopts a method of selecting a defect detection sensitivity level for every local area, defined by factors such as defect judgment algorithm and defect judgment threshold. This approach results in a reduction of pseudodefect count leading to shorter inspection and review time. Selected defect detection sensitivity levels for every local area are extracted from a database of Mask Data Rank (MDR) that is based on the design intent from the design stage, and/or on a pre-analysis of inspection pattern data. The proposed system also executes a printability verification function, not only for the mask defect regions but also for specific portions where high Mask Error Enhancement Factor (MEEF) is determined. It is necessary to ascertain suppression of pseudo-defect detection for extremely complicated masks such as masks with Source-Mask Optimization (SMO). This work reports on the new mask inspection system.

Defect printability analysis by lithographic simulation from high resolution mask images

We report the development of Mask-LMC for defect printability evaluation from sub-200nm wavelength mask inspection images. Both transmitted and reflected images are utilized, and both die-to-die and die-to-database inspection modes are supported. The first step of the process is to recover the patterns on the mask from high resolution T and R images by de-convolving inspection optical effects. This step uses a mask reconstruction model, which is based on rigorous Hopkins-modeling of the inspection optics, and is pre-determined before the full mask inspection. After mask reconstruction, wafer scanner optics and wafer resist simulations are performed on the reconstructed mask, with a wafer lithography model. This step leverages Brions industry-proven, hardware-accelerated LMC (Lithography Manufacturability Check) technology1. Existing litho process models that are in use for Brions OPC+ and verification products may be used for this simulation. In the final step, special detectors are used to compare simulation results on the reference and defect dice. We have developed detectors for contact CD, contact area, line and space CD, and edge placement errors. The detection results on test and production reticles have been validated with AIMSTM.