Tsutomu Murakawa

A study of phase defect measurement on EUV mask by multiple detectors CD-SEM

We have studied MVM (Multi Vision Metrology) -SEM® E3630 to measure 3D shape of defects. The four detectors (Detector A, B, C and D) are independently set up in symmetry for the primary electron beam axis. Signal processing of four direction images enables not only 2D (width) measurement but also 3D (height) measurement. At last PMJ, we have investigated the relation between the E3630’s signal of programmed defect on MoSi-HT and defect height measured by AFM (Atomic Force Microscope). It was confirmed that height of integral profile by this tool is correlated with AFM. It was tested that E3630 has capability of observing multilayer defect on EUV. We have investigated correlation with AFM of width and depth or height of multilayer defect. As the result of observing programmed defects, it was confirmed that measurement result by E3630 is well correlated with AFM. And the function of 3D view image enables to show nm order defect.

Novel three dimensional (3D) CD-SEM profile measurements

A new SEM technology, Advantests Wafer MVM-SEM E3310, is becoming available that allows quantitative, image-based 3D profile metrology of nanoscale features. CD-AFM is generally employed for 3D profile information, but this technique has its own limitations for 1Xnm node production due to tip size constraints in the tightest spaces, and due to finite tip lifetime which can influence measurement stability. Using the patented multi-channel detector technology, this system can acquire information of surface concave and convex features and relative side wall angle (SWA) and height, quickly and non-destructively for nanoscale structures [1] [2]. Here we evaluate this new technology and demonstrate its applicability to contemporary advanced structures.

Three dimensional profile measurement using multi-channel detector MVM-SEM

In next generation lithography (NGL) for the 1x nm node and beyond, the three dimensional (3D) shape measurements such as side wall angle (SWA) and height of feature on photomask become more critical for the process control. Until today, AFM (Atomic Force Microscope), X-SEM (cross-section Scanning Electron Microscope) and TEM (Transmission Electron Microscope) tools are normally used for 3D measurements, however, these techniques require time-consuming preparation and observation. And both X-SEM and TEM are destructive measurement techniques. This paper presents a technology for quick and non-destructive 3D shape analysis using multi-channel detector MVM-SEM (Multi Vision Metrology SEM), and also reports its accuracy and precision.

New CD-SEM metrology method for the side wall angle measurement using multiple detectors

A new metrology method for CD-SEM has been developed to measure the side wall angle of a pattern on photomask. The height and edge width of pattern can be measured by the analysis of the signal intensity profile of each channel from multiple detectors in CD-SEM. The edge width is measured by the peak width of the signal intensity profile. But it is not possible to measure the accurate edge width of the pattern, if the edge width is smaller than the primary electron beam diameter. Using four detectors, the edge width can be measured by the peak width which appears on the subtracting signal profile of two detectors in opposition to each other. Therefore, the side wall angle can be calculated if the pattern height is known. The shadow of the side wall appears in the signal profile from the detector of the opposite side of the side wall. Furthermore, we found that there was the proportional relation between pattern height and the shadow length of the signal on one side. This paper describes a method of measuring the side wall width of a pattern and experimental results of the side wall angle measurements.

The capability of lithography simulation based on MVM-SEM system

The 1Xnm technology node lithography is using SMO-ILT, NTD or more complex pattern. Therefore in mask defect inspection, defect verification becomes more difficult because many nuisance defects are detected in aggressive mask feature. One key Technology of mask manufacture is defect verification to use aerial image simulator or other printability simulation. AIMS™ Technology is excellent correlation for the wafer and standards tool for defect verification however it is difficult for verification over hundred numbers or more. We reported capability of defect verification based on lithography simulation with a SEM system that architecture and software is excellent correlation for simple line and space.[1] In this paper, we use a SEM system for the next generation combined with a lithography simulation tool for SMO-ILT, NTD and other complex pattern lithography. Furthermore we will use three dimension (3D) lithography simulation based on Multi Vision Metrology SEM system. Finally, we will confirm the performance of the 2D and 3D lithography simulation based on SEM system for a photomask verification.

Study of defect verification based on lithography simulation with a SEM system

In a Photomask manufacturing process, mask defect inspection is an increasingly important topic for 193nm optical lithography. Further extension of 193nm optical lithography to the next technology nodes, staying at a maximum numerical aperture (NA) of 1.35, pushes lithography to its utmost limits. This extension from technologies like ILT and SMO requires more complex mask patterns. In mask defect inspection, defect verification becomes more difficult because many nuisance defects are detected in aggressive mask features. One of the solutions is lithography simulation like AIMS. An issue with AIMS, however, is the low throughput of measurement, analysis etc.

Study of the three-dimensional shape measurement for mask patterns using Multiple Detector CD-SEM

The Multiple Detector CD-SEM acquires the secondary electron from pattern surface at each detector. The 3D shape and height of mask patterns are generated by adding or subtracting signal profile of each detector. In signal profile of the differential image formed in difference between left and right detector signal, including concavo-convex information of mask patterns. Therefore, the 3D shape of mask patterns can be obtained by integrating differential signal profile. This time, we found that proportional relation between pattern height and shadow length on one side of pattern edge. In this paper, we will report experimental results of pattern height measurement. The accuracy of measurement and side wall angle dependency are studied. The proposal method is applied to OMOG masks.

Addressing 3D metrology challenges by using a multiple detector CDSEM

In next generation lithography (NGL) for the 22nm node and beyond, the three dimensional (3D) shape measurements of side wall angle (SWA) and height of the photomask pattern will become critical for controlling the exposure characteristics and wafer printability. Until today, cross-section SEM (X-SEM) and Atomic Force Microscope (AFM) methods are used to make 3D measurements, however, these techniques require time consuming preparation and observation. This paper presents an innovative technology for 3D measurement using a multiple detector CDSEM and reports its accuracy and precision.

The large contour data generation from divided image of photomask pattern of 32 nm and beyond

The application of Mask CD-SEM for process management of photomask using two dimensional measurements as photomask patterns become smaller and more complex, [1]. Also, WPI technology application using an optical Mask inspection tool simulates wafer plane images using photomask images [2]. In order to simulate the MEEF influence for aggressive OPC and High-end photomask patterns in 32nm node and beyond, a requirement exists for wide Field of View (FOV) GDS data and tone information generated from high precision SEM images. In light of these requirements, we developed a GDS data extraction algorithm with sub-nanometer accuracy using wide FOV images, for example, greater than 10um square. As a result, we over come the difficulty of generating large contour data without the distortion that is normally associated with acquired SEM images. Also, it will be shown that the evaluation result can be effective for 32 nm applications and beyond using Mask CD-SEM E3620 manufactured by Advantest. On the other hand, we investigate the application example of the wide FOV GDS data. In order to easily compare the acquired GDS data with design data, we explain the separate algorithm with three layer structures for Tri-tone (Ternary) photomask pattern, consisting of an outer pattern and another pattern.