Mask inspection

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

Fiber amplifier based light source for semiconductor inspection

Abstract: A laser illuminator for use in an inspection system, such as a semiconductor wafer inspection system or photomask inspection system is provided. The gain medium in the illuminator comprises optical fiber, and amplification, beam splitting, frequency and/or bandwidth conversion, peak power reduction, and q-switching or mode locking may be employed. Certain constructs including doped fiber, gratings, saturable absorbers, and laser diodes are disclosed to provide enhanced illumination.

Requirements and performance of an electron‐beam column designed for x‐ray mask inspection

Abstract: Production viable inspection of x‐ray masks requires the resolution of a scanning electron microscope (SEM) at an imaging rate approximately 1000 times that of commercially available systems. This article analyzes the inspection task for x‐ray masks and compares the requirements for beam‐current density and imaging efficiency necessary to achieve reasonable throughput with technologies available on current SEM and electron‐beam lithography systems. The resulting specifications have been translated into an electron‐optical column with many novel features. The gun, which contains six thermal field‐emission sources mounted on a turret, produces a Gaussian profile beam that is scanned over a continuously moving substrate. Dual electrostatic icosapole deflectors provide high speed telecentric deflection. Secondary electrons are separated from the primary beam by a Wien filter and accelerated into a semiconductor electron detector. An analog optical‐fiber link is used to transmit the signal to the image compute...

Method for mask inspection for mask design and mask production

Abstract: The invention relates to a mask inspection method that can be used for the design and production of masks, in order to detect relevant weak points early on and to correct the same. According to said method for mask inspection, an aerial image simulation, preferably an all-over aerial image simulation, is carried out on the basis of the mask design converted into a mask layout, in order to determine a list of hot spots. The mask/test mask is analysed by means of an AIMS tool, whereby real aerial images are produced and compared with the simulated aerial images. The determined differences between the aerial images are used to improve the mask design. The inventive arrangement enables a method to be carried out for mask inspection for mask design and mask production. The use of the AIMS tool directly in the mask production process essentially accelerates the mask production, while reducing the error rate and cost.

Enhanced optical inspectability of patterned EUVL mask

Abstract: For optical inspection of Extreme Ultraviolet Lithography (EUVL) masks using Deep Ultraviolet (DUV) light, contrast from reflected light is used to form the image of the mask and detect the defects. The inspectability of a patterned mask depends on the optical properties, surface conditions and thickness of absorber and buffer layer. The issue in EUVL mask inspection is the relatively low image contrast in the inspection tool because both the EUV-reflective and EUV-absorbing regions reflect DUV light. The need of a buffer layer to protect the multilayer (ML) reflector during mask processing and defect repair necessitates two inspections for a patterned mask: one with the buffer layer on to find the defect for repair and one with the buffer layer removed to qualify a final mask. Since the ML appears bright at DUV inspection wavelengths, the buffer layer is also chosen to give high reflectivity. Therefore, the absorber reflectivity must be low enough to provide high image contrast and to avoid the edge interference effect. Recently, we have developed a surface treatment process to reduce the reflectivity of absorber layer and result in a DUV contrast approaching 90 percent. This greatly improves the optical inspectability of EUVL mask to a level similar to conventional transmission mask. In this paper, we describe the overall EUVL mask inspection strategy and present a comprehensive discussion on mask optimization in materials selection and modification for high inspectability. We report the reflectivity of Mo-Si multilayer, buffer layers using SiO2 and Ru, and absorber layers of Cr and TaN. We will demonstrate with DUV inspection images of the optimized EUVL masks that the image contrast and quality from reflected light are close to those of conventional photo-masks with transmitted light. This greatly enhanced EUVL mask inspectability will increase defect detectability for inspection tools and simplify image rendering in die-to-database inspection.

Reference image generation from subject image for photolithography mask analysis

Abstract: A reference image is generated from a subject image of at least a portion of a photolithography mask to enable a photolithography mask inspection and analysis system that otherwise cannot generate a reference image from a reference die or digitized design data, for example, to perform a mask analysis using the reference image. A mask inspection and analysis system may then be enhanced to perform one or more additional mask analyses to analyze the mask. The reference image is generated by identifying a defect or contaminant of the mask in the subject image and modifying the subject image to remove the defect or contaminant from the mask to generate the reference image. For one embodiment, a system using a STARlight inspection tool that captures transmitted and reflected images of a portion of a mask may then be enhanced to perform one or more mask analyses that use a reference image.