Mask inspection

About: Mask inspection is a research topic. Over the lifetime, 1072 publications have been published within this topic receiving 8696 citations.

System and method for verifying appearance of photomask

Abstract: PROBLEM TO BE SOLVED: To provide a photomask appearance verification system for converting a coordinate value detected by a wafer inspection into a coordinate value to be used in a photomask inspection and for performing defect analysis of a photomask in an early stage. SOLUTION: The coordinate value of a defective place which is detected by a wafer inspecting device 4 and wafer inspection information are transmitted to a coordinate transformation computer 6 by using an inspection data management computer 5, the coordinate value detected by the wafer inspection is transformed into the coordinate value on the photomask based on the wafer inspection information and photomask inspection information and the defective place of the photomask is analyzed. COPYRIGHT: (C)2003,JPO

Mask defect inspection by detecting polarization variations

Abstract: State-of-the-art lithography is often severely influenced by defects that are smaller than the resolution limit of the mask inspection system. However, the mask inspection suffers from noises comparable to signal of the small defect, due to illumination nonuniformity, laser speckle, and fluctuation of the sensor signal. In order to overcome these issues, we propose a novel mask defect inspection method that uses detection optics for polarization variation. This inspection method uses the variation of polarization states which are caused by form birefringence in the mask feature. Thus the defect signals in the polarization-variation image can be obtained with sufficient intensity for much smaller defects than the wavelength. However since pattern edges are especially emphasized in the polarization-variation images, the images can not faithfully be acquired the mask pattern. To avoid these problems, we simultaneously use both conventional transmitted inspection images and the polarization variation images. By using numerical simulation, this paper discusses the validity of the mask inspection method that detects the polarization variation. The simulated results show that this new inspection method is quite effective for 20-nm-size defect and smaller ones.

A New Algorithm for Die-to-Wafer-like Image Mask Inspection in Real Time

Abstract: The effect of variations in defect printability must be considered in order to correctly evaluate mask defect inspection procedures. Because of nonlinear transfer effects and strong dependence of printability on defect types, it is difficult to define the boundary between real defect and false defect. To overcome this problem we developed a new algorithm for die-to-wafer-like image (D-to-WI) inspection in real time. This inspection method compares the die (wafer image calculated from CAD data) with the wafer-like image (WI) calculated from the mask image detected by the mask inspection system. To precisely calculate WI in real time, we developed a new simulation-based software. Since the phase of a mask inspection image cannot be measured, we introduce some assumptions regarding its phase. Moreover, we introduce some corrections for WI such as adding a DC component and multiplying by a proper value. To calculate the die which realizes the desired image with sufficient accuracy in real time, we also introduce a perturbation approach. We demonstrate numerically the possibility of a new algorithm for D-to-WI inspection. We confirm that this technique of generating WI from a measured mask pattern is well suited for attenuated phase shift masks (PSMs) and Cr binary masks.

Extending DUV mask inspection tool for inspecting 2xnm HP and beyond

Abstract: Advanced 193nm DUV optical inspection tools that can cover 2Xnm HP node become more important and they are being tested to estimate their extendibility. We report DUV based inspection results evaluated and compared to wafer prints, as well as mask CD-SEM images in order to determine the size of printable defects that must be detected in each device node. Applied Materials® advanced Aera™ optical mask inspection tool that adapted a new optical technology enhancement was utilized to evaluate its inspection capability. The illumination conditions and pixel size were optimized to increase inspection sensitivity and reach detection requirements for not only critical defects that print on the wafer but also non-printing defects that indicate to a mask issue. Simulation was used to study suitable optical illumination conditions analyzing results to achieve the best performance for high-end EUV mask inspection toward next generation lithography.

Inspection device for flaw of mask

Abstract: PURPOSE:To detect only such a flaw as is larger than desired by providing a scattering unit like ground glass on a main surface side in a device to detect luminous parts generated on the main surface of a photomask by irradiating a beam to the end of a light-transmissive substrate of the photomask. CONSTITUTION:A mask inspection device comprises a control box 1, a stage 3 to provide a photomask 2 thereon, a tubular cover 4 to prevent the ambient beam from coming onto the top of the photomask on the stage, and a lamp house 5 enclosing a lamp. A tungsten lamp 7 in the lamp house feeds a white beam to the photomask 2 through a projection port 16. There is arranged a ground glass 16 closely and in parallel over the stage 3. By arranging so, a luminous part relating to such a small flaw which to exerts no influence on the mask function is gradated by the ground glass, therefore only such luminous part which should be checked by the inspection can easily be observed through scattering and enlarging.