Mask inspection

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

Setting MRC rules: balancing inspection capabilities, defect sensitivity, and OPC

Abstract: One of the challenges associated with shrinking design dimensions is finding photomask inspection settings which achieve sufficient defect detection capabilities while supporting aggressive Optical Proximity Correction (OPC). The most recent technology nodes require very aggressive and advanced Resolution Enhancement Techniques (RETs) which involve printing small features that are challenging for mask inspection tools. We examine the problems associated with constraining Models-Based OPC with mask inspection driven rules. We give examples of a 45nm technology node contact layer design which will receive sub-optimal OPC treatment due to mask inspection constraints. We then take the mask defect specification typically used for this mask layer, and use Monte Carlo simulation methods to place minimum sized simulated defects in various locations in close proximity to these sensitive layouts. Simulations of the optimal OPC are compared to optimal OPC with defects, and to the sub-optimal constrained OPC. Using knowledge about the frequency of small defects on masks, one can compare the risks associated with small mask defects to the risks associated with sub-optimal OPC. This exercise demonstrates that there are some instances where mask rules based on inspection capabilities and defect sensitivity alone can be problematic, and that OPC requirements need to be taken into account when choosing a defect specification and an inspection strategy. We conclude by proposing a strategy for balancing these requirements in a practical manner.

MTO-like reference mask modeling for advanced inverse lithography technology patterns

Abstract: Advanced Inverse Lithography Technology (ILT) can result in mask post-OPC databases with very small address units, all-angle figures, and very high vertex counts. This creates mask inspection issues for existing mask inspection database rendering. These issues include: large data volumes, low transfer rate, long data preparation times, slow inspection throughput, and marginal rendering accuracy leading to high false detections. This paper demonstrates the application of a new rendering method including a new OASIS-like mask inspection format, new high-speed rendering algorithms, and related hardware to meet the inspection challenges posed by Advanced ILT masks.

Compact excimer laser light source for optical (mask) inspection systems

Abstract: The discharge pumped excimer laser is a gas laser providing ultra violet (UV) radiation with well defined spectral, temporal and spatial properties. The fast development of excimer lasers in recent years has succeeded in designing very compact, turn-key systems delivering up to 10 W of radiation at 248 nm (5 W at 193 nm and 1 W at 157 nm) with repetition rates up to 1000 Hz [1]. Experimental data on important beam properties of excimer lasers in the field of mask inspection are being presented and discussed. Relevant parameters are spectral bandwidth, energetic pulse-to-pulse stability, pulse duration, beam pointing stability, beam direction stability, beam dimension, beam profile and coherence. We will compare the excimer laser with lamp sources and continuous wave (CW) lasers in the framework of these parameters. The discussion will show future opportunities of compact excimer lasers in optical inspection as well as in mask writing systems, improving resolution and throughput.

Practical mask inspection system with printability and pattern priority verification

Abstract: Through the four years of study in Association of Super-Advanced Electronics Technologies (ASET) on reducing mask manufacturing Turn Around Time (TAT) and cost, we have been able to establish a technology to improve the efficiency of the review process by applying a printability verification function that utilizes computational lithography simulations to analyze defects detected by a high-resolution mask inspection system. With the advent of Source-Mask Optimization (SMO) and other technologies that extend the life of existing optical lithography, it is becoming extremely difficult to judge a defect only by the shape of a mask pattern, while avoiding pseudo-defects. Thus, printability verification is indispensable for filtering out nuisance defects from high-resolution mask inspection results. When using computational lithography simulations to verify printability with high precision, the image captured by the inspection system must be prepared with extensive care. However, for practical applications, this preparation process needs to be simplified. In addition, utilizing Mask Data Rank (MDR) to vary the defect detection sensitivity according to the patterns is also useful for simultaneously inspecting minute patterns and avoiding pseudo-defects. Combining these two technologies, we believe practical mask inspection for next generation lithography is achievable. We have been improving the estimation accuracy of the printability verification function through discussion with several customers and evaluation of their masks. In this report, we will describe the progress of these practical mask verification functions developed through customers' evaluations.

Method for manufacturing photomask, depicting device, method for inspecting photomask, mask inspection device, and method for manufacturing display device

Abstract: The present invention provides a method for manufacturing a photomask, which is capable of improving coordinate accuracy of a pattern formed on a transfer-printed body. The method for manufacturing a photomask according to the present invention includes the following steps: preparing pattern design data A; obtaining transfer surface correction data D, which represent deformation of a main surface caused by holding the photomask in an exposing device, namely the deformation excluding bending caused by it own weight; obtaining height distribution data E in depicting, which represents height distribution of the main surface under the circumstances that a carrying table of a depicting device carries a photomask blank; obtaining depicting difference data F according to the height distribution data E in depicting and the transfer surface correction data D; estimating coordinate offsets corresponding to the depicting difference data F so as to obtain coordinate offset data G for depicting; and a step of depicting, which is to depict on the photomask blank by using the coordinate offset data G for depicting and the pattern design data A.