A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

The theory of image formation is formulated in terms of the coherence function in the object plane, the diffraction distribution function of the image-forming system and a function describing the structure of the object. There results a four-fold integral involving these functions, and the complex conjugate functions of the latter two. This integral is evaluated in terms of the Fourier transforms of the coherence function, the diffraction distribution function and its complex conjugate. In fact, these transforms are respectively the distribution of intensity in an 'effective source', and the complex transmission of the optical system-they are the data initially known and are generally of simple form. A generalized 'transmission factor' is found which reduces to the known results in the simple cases of perfect coherence and complete incoherence. The procedure may be varied in a manner more suited to non-periodic objects. The theory is applied to study inter alia the influence of the method of illumination on the images of simple periodic structures and of an isolated line.

On the diffraction theory of optical images

A lithographic apparatus configured to project a patterned beam of radiation onto a target portion of a substrate is disclosed. The apparatus includes a first radiation dose detector and a second radiation dose detector, each detector comprising a secondary electron emission surface configured to receive a radiation flux and to emit secondary electrons due to the receipt of the radiation flux, the first radiation dose detector located upstream with respect to the second radiation dose detector viewed with respect to a direction of radiation transmission, and a meter, connected to each detector, to detect a current or voltage resulting from the secondary electron emission from the respective electron emission surface.

Lithographic apparatus, and device manufacturing method

A resist composition is provided comprising a silicone resin, a photoacid generator, a nitrogen-containing organic compound, and a solvent. The silicone resin is obtained through cohydrolytic condensation of a mixture of three silane monomers containing an organic group having a hydroxyl group and having at least 3 fluorine atoms, in total, on a proximate carbon atom, an organic group having a carboxyl group protected with an acid labile group, and a lactone ring-bearing organic group, respectively. The resist composition has satisfactory resolution and overcomes the problem of a low selective etching ratio between resist film and organic film during oxygen reactive etching.

Resist composition and patterning process

After forming a resist film including a hygroscopic compound, pattern exposure is performed by selectively irradiating the resist film with exposing light while supplying water onto the resist film. After the pattern exposure, the resist film is developed so as to form a resist pattern.

Pattern formation method

A newly developed sub-resolution assist feature (SRAF) placement technique with two-dimensional
transmission cross coefficient (2D-TCC) is described in this paper. In SRAF placement with 2D-TCC, Hopkins'
aerial image equation with four-dimensional TCC is decomposed into the sum of Fourier transforms of diffracted
light weighted by 2D-TCC, introducing an approximated aerial image so as to place SRAFs into a given reticle
layout. SRAFs are placed at peak positions of the approximated aerial image for enhanced resolution. Since the
approximated aerial image can handle the full optical model, SRAFs can be automatically optimized to the given
optical condition to generate the optimized reticle. The validity of this technique was confirmed by experiment
using a Canon FPA6000-ES6a, 248 nm with a numerical aperture (NA) of 0.86. A binary reticle optimized by this
technique with mild off-axis illumination was used in the experiment. Both isolated and dense 100 nm contacts (k 1 
= 0.35) were simultaneously resolved with the aid of this technique.

Resolution enhancement by aerial image approximation with 2D-TCC

In this paper, a new resolution enhancement technique named 2D-TCC technique is proposed. This method can enhance resolution of line patterns as well as that of contact hole patterns by the use of an approximate aerial image. The aerial image, which is obtained by 2D-TCC calculation, expresses the degree of coherence at the image plane of a projection optic considering mask transmission at the object plane. OPC of desired patterns and placement of assist patterns can be simultaneously performed according to an approximate aerial image called a 2D-TCC map. Fast calculation due to truncation of a series in calculating an aerial image is another advantage. Results of mask optimization for various line patterns and the validity of the 2D-TCC technique by simulations and experiments are reported.

Mask optimization for arbitrary patterns with 2D-TCC resolution enhancement technique

The extendibility of 2D-TCC technique to an isolated line of 45 nm width is investigated in this paper. The 2D-TCC
technique optimizes mask patterns placing assist pattern automatically. For 45 nm line patterns, the assist pattern width
generally becomes much smaller than the exposure wavelength of 193 nm. Thus, the impact of the topography of a mask
is examined using an electro-magnetic field (EMF) simulation. This simulation indicates that unwanted assist pattern
printings are brought about by assist patterns with a smaller size than expected by the Kirchhoff's approximation. The
difference, however, can be easily solved by giving a bias to the main pattern in the optimized mask. The main pattern
bias decreases DOF very little. Furthermore, DOF simulated with a thick mask model is roughly the same as that
simulated with a thin mask model. Therefore the topography of the optimized mask does not have an influence on the
assist pattern position of the optimized mask. From these results, we have confirmed that the 2D-TCC technique can be
extended to the optimization of 45 nm line patterns. As one of the notable features, the optimized aperiodic assist pattern
greatly reduces MEEF compared with the conventional periodic assist pattern. To verify the feasibility of the 2D-TCC
technique for 45 nm line, we performed experiment with an optimized mask. Experimental results showed that DOF
increased with the number of assist pattern as simulation indicated. In addition, a defect whose length was twice that of
the assist pattern did not have an influence on CD. From these results we have confirmed that the 2D-TCC technique can
enhance the resolution of 45 nm line and has practical feasibility.

Extension of the 2D-TCC technique to optimize mask pattern layouts

A photoactive medium has a complex format grating written thereon, the complex format grating including at least three component gratings, each of the component gratings characterized by a unique grating vector. Methods for writing the complex format grating include the steps of providing a photoactive medium; and focussing a plurality of pairs of mutually coherent light beams into a focal plane in the medium.

Volumetric track definition for data storage media used to record data by selective alteration of a format hologram

An optical channel monitoring device uses a linear variable filter (LVF) disposed in the path of a beam of light for selectively transmitting light in a variable manner along a length of the filter, a photodetector array positioned in the path of light transmitted through the LVF for measuring spectral characteristics of the transmitted light, and collimating means disposed between the input port and the LVF for collimating said beam of light. The device is a low-cost, compact and rugged high-resolution spectrometer for various uses.

Tokuyuki Honda

Papers

Resolution enhancement by aerial image approximation with 2D-TCC

Mask optimization for arbitrary patterns with 2D-TCC resolution enhancement technique

Extension of the 2D-TCC technique to optimize mask pattern layouts

Volumetric track definition for data storage media used to record data by selective alteration of a format hologram

Optical channel monitoring device