According to the road map shown in ITRS , the EUV mask requirement for defect inspection is to detect the defect
size of sub- 20 nm in the near future. EB (Electron Beam) inspection with high resolution is one of the promising
candidates to meet such severe defect inspection requirements. However, conventional EB inspection using the SEM
method has the problem of low throughput. Therefore, we have developed an EB inspection tool, named Model EBEYE
M※. The tool has the PEM (Projection Electron Microscope) technique and the image acquisition technique with TDI
(Time Delay Integration) sensor while moving the stage continuously to achieve high throughput .
In our previous study, we showed the performance of the tool applied for the half pitch (hp) 2X nm node in a production
phase for particle inspection on an EUV blank. In the study, the sensitivity of 20 nm with capture rate of 100 % and the
throughput of 1 hour per 100 mm square were achieved, which was higher than the conventional optical inspection tool
for EUV mask inspection -.
Such particle inspection is called for not only on the EUV blank but also on the patterned EUV mask. It is required after
defect repair and final cleaning for EUV mask fabrication. Moreover, it is useful as a particle monitoring tool between a
certain numbers of exposures for wafer fabrication because EUV pellicle has not been ready yet. However, since the
patterned EUV mask consists of 3D structure, it is more difficult than that on the EUV blank.
In this paper, we evaluated that the particle inspection on the EUV blank using the tool which was applied for the
patterned EUV mask. Moreover, the capability of the particle inspection on the patterned EUV mask for the hp 2X nm
node, whose target is 25 nm of the sensitivity, was confirmed. As a result, the inspection and SEM review results of the
patterned EUV masks revealed that the sensitivity of the hp 100 nm Line/Space (LS) was 25 nm and that of the hp 140-
160 nm Contact Hole (CH) was 21 nm. Therefore, we confirmed that particle inspection on the patterned EUV mask
using Model EBEYE M could be available for the EUV mask of the hp 2X nm node. In the future, we will try to inspect
the production mask of the hp 2X nm node, and try to confirm the performance for the EUV mask of the hp 1X nm node.
According to the ITRS Roadmap , within a few years the EUV mask requirement for defect will be detection of defect
size of less than 25 nm. Electron Beam (EB) inspection is one of the candidates to meet such a severe defect requirement.
EB inspection system, Model EBEYE M※1, has been developed for EUV mask inspection. Model EBEYE M employs
Projection Electron Microscope (PEM) technique and image acquisition technique to acquire image with Time Delay
Integration (TDI) sensor while the stage moves continuously . Therefore, Model EBEYE M has high performance in
terms of sensitivity, throughput and cost.
In a previous study, we showed the performance of Model EBEYE M for 2X nm in a development phase whose
sensitivity in pattern inspection was around 20 nm and in particle inspection was 20 nm with throughput of 2 hours in
100 mm square , . With regard to pattern inspection, Model EBEYE M for High Volume Manufacturing (HVM) is
currently under development in the production phase. With regard to particle inspection, Model EBEYE M for 2X nm is
currently progressing from the development phase to the production phase.
In this paper, the particle inspection performance of Model EBEYE M for 2X nm in the production phase was evaluated.
Capture rate and repeatability were used for evaluating productivity. The target set was 100% capture rate of 20 nm.
100% repeatability of 20 nm with 3 inspection runs was also set as a target. Moreover, throughput of 1 hour in 100 mm
square, which was higher than for Model EBEYE M for 2X nm in the development phase, was set as a target. To meet
these targets, electron optical conditions were optimized by evaluating the Signal-to-Noise Ratio (SNR). As a result,
SNR of 30 nm PSL was improved 2.5 times. And the capture rate of 20 nm was improved from 21% with throughput of
2 hours to 100% with throughput of 1 hour. Moreover, the repeatability of 20 nm with 3 inspection runs was 100% with
throughput of 1 hour. From these results, we confirmed that Model EBEYE M particle inspection mode could be
available for EUV mask production.
According to the ITRS Roadmap, the EUV mask requirement for 2X nm technology node is detection of defect size of
20 nm. The history of optical mask inspection tools involves continuous efforts to realize higher resolution and higher
throughput. In terms of productivity, considering resolution, throughput and cost, we studied the capability of EUV light
inspection and Electron Beam (EB) inspection, using Scanning Electron Microscope (SEM), including prolongation of
the conventional optical inspection. As a result of our study, the solution we propose is EB inspection using Projection
Electron Microscope (PEM) technique and an image acquisition technique to acquire inspection images with Time Delay
Integration (TDI) sensor while the stage is continually moving. We have developed an EUV mask inspection tool,
EBeyeM, whole design concept includes these techniques. EBeyeM for 2X nm technology node has the following targets,
for inspection sensitivity, defects whose size is 20 nm must be detected and, for throughput, inspection time for particle
and pattern inspection mode must be less than 2 hours and 13 hours in 100 mm square, respectively. Performance of the
proto-type EBeyeM was reported. EBeyeM for 2X nm technology node was remodeled in light of the correlation
between Signal to Noise Ratio (SNR) and defect sensitivity for the proto-type EBeyeM. The principal remodeling points
were increase of the number of incident electrons to TDI sensor by increasing beam current for illuminating optics and
realization of smaller pixel size for imaging optics.
This report presents the performance of the remodeled EBeyeM (=EBeyeM for 2X nm) and compares it with that of the
proto-type EBeyeM. Performances of image quality, inspection sensitivity and throughput reveal that the EBeyeM for
2X nm is improved. The current performance of the EBeyeM for 2X nm is inspection sensitivity of 20 nm order for both
pattern and particle inspection mode, and throughput is 2 hours in 100 mm square for particle inspection mode.
We are developing new electron beam inspection system, named EBeyeM, which features high speed and high
resolution inspection for EUV mask. Because EBeyeM has the projection electron microscope technique, the scan time
of EBeyeM is much faster than that of conventional SEM inspection system.
We developed prototype of EBeyeM. The aim of prototype system is to prove the concept of EBeyeM and to estimate
the specification of system for 2Xnm and 1Xnm EUV mask.
In this paper, we describe outline of EBeyeM and performance results of the prototype system. This system has two
inspection mode. One is particle inspection and the other is pattern defect inspection. As to the sensitivity of EBeyeM
prototype system, the development target is 30nm for the particle inspection mode and 50nm for pattern defect
inspection mode. The performance of this system was evaluated. We confirmed the particle inspection mode of the
prototype system could detect 30nm PSL(Polystyrene Latex) and the sensitivity was much higher than conventional
optical blank inspection system. And we confirmed that the pattern defect sensitivity of the prototype system was
around 45nm. It was recognized that both particle inspection mode and pattern defect inspection mode met the
development target. It was estimated by the performance results of the prototype system that the specification of
EBeyeM would be able to achieve for 2Xnm EUV mask. As to 1Xnm EUV mask, we are considering tool concept to
meet the specification.
A 65 nm node mask is required to have total alignment accuracy of 20 nm (3σ) or less for 1st and 2nd layers, including the positional accuracy of each layer. We have developed a new electron beam mask lithography process using “alignment-and-height” marks to minimize the displacement between two layers resulting from additional bowing and contraction on the blank surface after the 1st layer exposure. The new process consists of the following steps: 1. Write “alignment-and-height” marks on the edge of a mask simultaneously with the pattern of the 1st layer. 2. Measure the position and height of “alignment-and-height” marks before writing the 2nd layer. 3. Create a position/height correction map to write the 2nd layer. 4. Write the 2nd layer with reference to the correction map. Basic system attributes, such as beam origin and positional drift of mask blank, are monitored and adjusted throughout the process. We tested the process and achieved an alignment accuracy of 20 nm (3σ) between 1st and 2nd layers regardless of the density of the pattern area ratio, confirming that the process is effective for 65 nm node phase shift mask exposure.
We have developed a high alignment-accuracy electron beam (EB) mask writing processes of phase shift layer using alignment-and-height marks. The new process consists of (1) First layer writing with “alignment-and-height” marks on peripheral area of the mask patterns; (2) Development of resist, Cr etching of the first layer pattern and coating of new resist; (3) Measurement of position, height and rotation of “alignment-and-height” marks with electron beams; (4) Create alignment map, scanning distortion correction map for the second layer writing; (5) Second layer pattern writing
using these correction maps. We performed a set of evaluation test of the processes and confirmed that an overlay alignment accuracy of within 16nm (3 sigma) between first and second layer is attainable, and thus, practically effective for phase shift image writing of 65nm node masks.
Results of conceptual design study of a solar occultation infrared sensor, improved limb atmospheric spectrometer-II (ILAS-II) which will be onboard ADEOS-II spacecraft, is discussed. The ILAS-II will have four grating spectrometers for solar occultation measurement: two are identical to the spectrometers of the ILAS onboard ADEOS to be launched in 1996. To observe ClONO<SUB>2</SUB>, which is a key species that controls catalytic destruction of ozone, an echelle grating spectrometer with 0.14 cm<SUP>-1</SUP> resolution for the 780.2 +/- 1 cm<SUP>-1</SUP> region will be added to the ILAS-II. Another new spectrometer will cover the 3 to 5.7 micrometers region to characterize the aerosols such as sulfuric acid aerosols and PSCs as well as to observe the chemical species.
Program overview, scientific targets and instrument design of the Improved Limb Atmospheric Spectrometer (ILAS) is described. The ILAS has two grating spectrometers for solar occultation measurement: one is for measurement of infrared band (850-1610 cm<sup>-1</sup>, 11.76 micrometers - 6.21 micrometers ) for O<SUB>3</SUB>, HNO<SUB>3</SUB>, NO<SUB>2</SUB>, N<SUB>2</SUB>O, H<SUB>2</SUB>O, CH<SUB>4</SUB> and CFC11, and the other is for visible band (753-784 nm, O<SUB>2</SUB> A band) for aerosols, temperature and air density measurement. ILAS will be onboard the ADEOS spacecraft and will observe high-latitude (N55-70, S63-87) ozone layer after February 1996 over 3 years with high vertical resolution (less than or equal to 2 km).