Papers

Guillermo Castro, Kiril Ivanov, Miguel Jiménez,Juan M. Trujillo-Sevilla, Juan Manuel Ramos-Rodríguez, Jan O. Gaudestad

Wafer overlay errors due to non-flatness and thickness variations of a mask need to be minimized to achieve a very accurate on-product-overlay (OPO). Due to the impact of overlay errors inherent in all reflective lithography systems, EUV reticles will need to adhere to flatness specifications below 10nm, which metric is not possible to achieve using current tooling infrastructure…

Miguel Jiménez, Kiril Ivanov Kurtev, Juan M. Trujillo-Sevilla, Rubén Abrante, Jose Manuel Ramos-Rodríguez, Jan O. Gaudestad

Wave Front Phase Imaging (WFPI), a new wafer geometry technique, is presented, that acquires 16.3 million data points in 12 seconds on a full 300mm wafer, providing lateral resolution of 65μm while holding the wafer vertically. The flatness of the silicon wafers used to manufacture integrated circuits (IC) is controlled to tight tolerances to help ensure that the full wafer is sufficiently flat for lithographic processing. Advanced lithographic patterning processes require a detailed map of the free, non-gravitational wafer shape to avoid overlay errors caused by depth-of-focus issues. For a wafer shape system to perform in a high-volume manufacturing environment, repeatability is a critical measure that needs to be tested. We present WFPI as a…

Kiril Ivanov Kurteva, Guillermo Castro Luis, Juan M. Trujillo-Sevilla, Jan O. Gaudestad, Richard van Haren, Leon van Dijk, Ronald Otten

On product overlay (OPO) is one of the most critical parameters for continued scaling according to Moore’s law. Besides the lithography scanner, also non-lithography processes contribute to the OPO performance. For example, processes like etching and thin film deposition can introduce stress, or stress changes, in the thin films on top of the silicon wafers. In general, the scanner Higher Order Wafer Alignment model up to 3rd order (HOWA3) has proven to be adequate to correct for most process-induced wafer distortions. This model is typically used with 28 wafer alignment marks placed across the wafer to correct for more global stress-induced distortions…

Kiril Ivanov Kurtev, Juan M. Trujillo-Sevilla, Guillermo Castro Luis, Miguel Jiménez, Rubén Abrante, José Manuel Ramos-Rodríguez, Jan O. Gaudestad

On-product overlay (OPO), with its continually shrinking overlay budget, remains a constraint in the continued effort at increasing device yield. Overlay metrology capability currently lags the need for improved overlay control, especially for multi-patterning applications. The free form shape of the silicon wafer is critical for process monitoring and is usually controlled through bow and warp measurements during the process flow. As the OPO budget shrinks, non-lithography process induced stress causing in plane distortions (IPD) becomes a…

Juan M. Trujillo-Sevilla, Rubén Abrante, Miguel Jiménez, Kiril Ivanov Kurtev, Guillermo Castro Luis, Jan O. Gaudestad

The shrinking depth of focus of high numerical aperture immersion microlithography optics requires a tight wafer flatness budget. Bare wafer surface topography variation is a significant part of the focus budget for microlithography. Thus, as the wafer surface quality becomes increasingly important, the metrology to control the surface quality is increasingly challenged1. Advanced lithographic patterning processes require a detailed map of the free, non-gravitational, wafer shape, to avoid overlay errors caused by depth-of-focus issues2. The semiconductor industry has been using interferometry-based techniques for measuring the free form wafer shape of blank silicon wafers for several years1. In this paper we introduce a…

Juan M. Trujillo-Sevilla, Óscar Casanova-González, Alex Roqué-Velasco, Miguel Jesús Sicilia, Javier González Pardo, José Manuel Ramos-Rodríguez, Jan O. Gaudestad

On product overlay (OPO) is one of the most critical parameters for the continued scaling according to Moore’s law. Without good overlay between the mask and the silicon wafer inside the lithography tool, yield will suffer1. As the OPO budget shrinks, non-lithography process induced stress causing in plane distortions (IPD) becomes a more dominant contributor to the shrinking overlay budget2. To estimate the process induced in-plane wafer distortion after cucking…

Juan M. Trujillo-Sevilla, Alex Roqué-Velasco, Miguel Jesús Sicilia, Óscar Casanova-González, José Manuel Rodríguez-Ramos, Jan O. Gaudestad

Wave Front Phase Imaging (WFPI) is a new wafer shape measurement technique that acquires millions of data points in just seconds or less, on a full 300mm silicon wafer. This provides lateral resolution well below 100μm with the possibility of reaching the lens’ optical resolution limitation between 3-4μm…

Juan M. Trujillo-Sevilla, Miriam Velasco-Ocaña, Sergio Bonaque-González, Carolina Belda-Para, and José M. Rodríguez-Ramos

We present a method for evaluating the quality of optical glass using a high-resolution wavefront sensor, the wavefront phase imaging (WFPI) sensor. As shadowgraphy is a widely used method for inspecting striae in optical glass, it does not provide a quantitative metric that represents the potential optical quality of the glass and should be based on the operator’s experience. We compare the proposed method in two experiments…

Ricardo Oliva-García, Sabato Ceruso, José G. Marichal-Hernández and José M. Rodriguez-Ramos

This work introduces a real-time full-resolution depth estimation device, which allows integral displays to be fed with a real-time light-field. The core principle of the technique is a high-speed focal stack acquisition method combined with an efficient implementation of the depth estimation algorithm, …

Juan Trujillo, Álvaro Pérez, Óscar Casanova, Miriam Velasco, Sabato Ceruso, Ricardo Oliva, Óscar Gómez, Javier Martín, Alex Roqué, José Manuel Rodríguez, Jan O. Gaudestad

Wave Front Phase Imaging (WFPI), a new wafer geometry technique, is presented, that acquires 7.65 million data points in 5 seconds on a full 300mm wafer providing lateral resolution of 96µm.

Wooptix’ team with the collaboration of Damien Gatinel & Jack T. Holladay

In this work, we characterize the in vivo ocular optics of the human eye with a lateral resolution of 8.6 microns, which implies roughly 1 million measurement points for a pupil diameter of 9 mm. The results suggest that the normal human eye presents a series of hitherto unknown optical patterns. This discovery could have a great impact on the way we understand some fundamental mechanisms of human vision.

Juan M. Trujillo-Sevilla, Oscar Casanova-González, Miriam Velasco-Ocaña, Sabato Ceruso, Ricardo Oliva-García, Óscar Gómez-Cárdenes, Javier Martín-Hernández, Alex Roqué-Velasco, Alvaro Pérez-García, José Manuel Rodríguez-Ramos, Jan O. Gaudestad

Wave Front Phase Imaging (WFPI) is used to measure the stria on an artificial, transparent plate made of Schott N-BK7® glass material by accurately measuring the Optical Path Difference (OPD) map. WFPI is a new technique capable of reconstructing an accurate high resolution wave front phase map by capturing two intensity images at different propagation distances. An incoherent light source generated by a light emitting diode (LED) is collimated and transmitted through the sample…

Álvaro Pérez-García, Juan M. Trujillo-Sevilla, Óscar Casanova-González, Miriam Velasco- Ocaña, Sabato Ceruso, Ricardo Oliva-García, Óscar Gómez-Cárdenes, Javier Martín-Hernández, Alex Roqué-Velasco, Álvaro Pérez-García, Jose Manuel Ramos-Rodríguez, Jan O. Gaudestad

The flatness of the silicon wafers used to manufacture integrated circuits (IC) is controlled to tight tolerances to help ensure that the full wafer is sufficiently flat for lithographic processing. Advanced lithographic patterning processes require a detailed map of the wafer shape to avoid overlay errors caused by depth-of-focus issues1. A large variety of new materials are being introduced in Back-End of Lines (BEOL) to ensure innovative architecture for new applications. The standard in-line control plan for the BEOL layer deposition steps is based on film thickness and global stress measurements which can be performed on blanket wafers to check the process equipment performance. However, the challenge remains to ensure high performance…

Sabato Ceruso, Sergio Bonaque-González, Ricardo Oliva-García, José Manuel Rodríguez-Ramos

The problem of reconstructing a depth map from a sequence of differently focused images (focal stack) is called Depth from focus. The core idea of this method is to analyze the sharpness of each pixel and compare it along the axis of the focal stack to estimate the true depth value. This approach has two main drawbacks: it depends on the optics of the camera and on the focus measure operator…

José G. Marichal-Hernández, Ricardo Oliva-García, Óscar Gómez-Cárdenes, Iván Rodríguez-Méndez, José M. Rodríguez-Ramos

The Radon transform is a valuable tool in inverse problems such as the ones present in electromagnetic imaging. Up to now the inversion of the multiscale discrete Radon transform has been only possible by iterative numerical methods while the continuous Radon transform is usually tackled…

Juan Manuel Trujillo-Sevilla, José Manuel Rodríguez-Ramos, Jan Olaf Gaudestad

In this paper we introduce a new metrology technique for measuring wafer geometry on silicon wafers. Wave Front Phase Imaging (WFPI) has high lateral resolution and is sensitive enough to measure roughness on a silicon wafer by simply acquiring a single image snapshot of the entire wafer.

Sergio Bonaque, Juan Manuel Trujillo, Oscar Casanova, David Carmona, Miguel Sicilia, Sabato Ceruso, Jan Gaudestad, José Manuel Rodríguez-Ramos

We present a new wave front sensing technique based on detecting the propagating light waves. This allows the user to acquire millions of data points within the pupil of the human eye; …

Juan Manuel Trujillo-Sevilla, Jose Manuel Ramos-Rodríguez, Jan Gaudestad

Wavefront phase imaging (WFPI) is a new technique to measure wafer geometry on a full wafer in a single image snapshot providing depth information for every pixel. The number of topography data points for the entire wafer will be proportional to the number of pixels in the image sensor, allowing for millions of data points to be acquired in less than a second.

Juan Manuel Trujillo, Jose Manuel Ramos-Rodríguez, Jan Gaudestad

In this paper we show that Wave Front Phase Imaging (WFPI) has high lateral resolution and high sensitivity enabling it to measure nanotopography and roughness on a silicon wafer by simply acquiring a single image of the entire wafer. WFPI is achieved by measuring the reflected light intensity from monochromatic…

Óscar Gómez, Ricardo Oliva, Gabriel A. Rodríguez, José G. Marichal

Discrete Radon Transform, DRT, is an integral transform that computes the complete set, in terms of slope and intercepts, of line integrals through a two-dimensional domain. It exhibits linearithmic computational complexity and avoids the usage of real numbers thanks to a divide and conquer, or multiscale, approach with a loose definition of discrete lines.

José Manuel Rodríguez-Ramos, Jan Gaudestad, Juan Manuel Trujillo

In this paper we show that Wave Front Phase Imaging (WFPI) has good enough lateral resolution and is sensitive enough to measure roughness on a silicon wafer by simply acquiring a simple image of the entire wafer. WFPI is achieved by measuring the reflected light intensity from monochromatic uncoherent light at two different planes along the optical path with the same field of view.

José Manuel Rodríguez-Ramos, Alex Roqué, David Carmona, Jan Gaudestad

We will discuss here the applications of the Wavefront Phase Imaging sensor (WFPI) on Adaptive Optics (AO) for Astronomy. The WFPI sensor is based on registering the intensity distribution at two different optical planes by a conventional imaging sensor. In the geometrical approximation, the light can be considered as a collection of light rays which bends according to Snellen’s law.

Miriam Velasco, Sergio Bonaque, Juan Manuel Trujillo, Jose Manuel Rodríguez Ramos

In this work we present a new method for optical characterization of glass samples. It is based on a new wavefront sensor method developed by the image processing specialist company Wooptix. With this novel wavefront phase sensor and a simple optical arrangement we have performed an objective optical characterization of glass specimens…

Ricardo Oliva, Óscar Gómez, David Carmona, José G. Marichal, José M Rodríguez-Ramos

Discrete Radon transform is a technique that allows to detect lines in images. It is much lighter to compute than Radon transforms based on Fourier slice theorem that use FFT as basis computing block. Even then, it is not that prone to optimal fine grain parallelization due to the need of running 4 passes to mirrored and flipped versions of the input…

David Carmona, Viana L. Guadalupe, Juan Manuel Trujillo, Sergio Bonaque, Ricardo Oliva, Jose G. Marichal, Miguel J. Sicilia, Lara Díaz, José Manuel Rodríguez-Ramos

We present our latest advances in the design and implementation of a tunable automultiscopic display based on the tensor display model. A design comprising a three-layer display was introduced. In such design, front and rear layers were enabled to be controlled in a six-degree of freedom manner related to the central layer of the system.

José Manuel Rodríguez-Ramos, Jan Gaudestad, Juan Manuel Trujillo

We present a new wafer metrology technique, Wave Front Phase Imaging (WFPI), for high speed measurement of wafer geometry including shape, flatness, nanotopography and even sub nm features found in roughness. WFPI acquires data of the entire wafer using a single image snapshot that provides depth data for every single pixel.

David Carmona, Juan Manuel Trujillo, Sabato Ceruso, Oscar Casanova

In this work we present a novel application in the field of shoulder-surfing prevention by using a light-field display consisting of a multilayered structure of LC screens. By controlling the directionally displayed content, we can discriminate between authorized and unauthorized observers. Optimizations regarding different parameters were assessed, i.e, number of unauthorized/authorized observers, quality and complexity of the contents, and physical limitations. Tests were made in simulations and a real model implementation.

Sergio Bonaque

Wavefront metrology is a key step in the manufacturing of high performance optical components and systems. We present a new wavefront sensor based in a deterministic approach for the propagation of light fields, able to recover the wavefront with the same resolution of the camera used from two intensity images recorded at two different planes…

Juan Manuel Trujillo, Oscar Casanova, Sergio Bonaque, Jan Gaudestad, José Manuel Rodríguez-Ramos

In this work we present a novel wave front phase sensing technique developed by Wooptix. This new wave front phase sensor uses only standard imaging sensor, and does not need any specialized optical hardware to sample the optical field. In addition, the wave front phase recovery is zonal, thus, the obtained wave front phase map provides as much height data points…

Jose Manuel Ramos Rodrigues, Juan Manuel Trujillo

We present a new wafer metrology technique called Wave Front Phase Imaging (WFPI) for high speed measurement of wafer warpage and nanotopography. This is accomplished by acquiring a single image snapshot using that provides depth data for every single pixel. The number of topography data points for the entire wafer will be proportional to the number of pixels in the image sensor.

Dailos Guerra, Lara Díaz, Juan Manuel Trujillo, Jose Manuel Rodríguez-Ramos

Most of the methods used today for the alignment of segmented mirrors are based on Shack-Hartman wavefront sensors. Other proposed methods are based on curvature sensors. These can be used to cross-check the measurements given by the primary method. We investigate a different approach which employs convolutional neural networks.

David Carmona, Juan Manuel Trujillo, Lara Díaz, Daniel Walo, Ángela Hernández, Juan J. Fernández, Óscar Casanova, Óscar Gómez, José Manuel Rodríguez-Ramos

In this work we have presented a brief insight into the capabilities of multilayer displays as to selectively display information in relation to the observers. We labeled the views of a light-field as blocked and non-blocked, and then a predefined text was assigned accordingly, modifying it to achieve a privacy criterion in the blocked case.

Sergio Bonaque, Oscar Casanova, Juan Manuel Trujillo, J.J. Fernández Valdivia, A. Hernández-Delgado, David Carmona

Optical organic materials, or optical plastics, are raising interest in recent decades thanks to advances in manufacturing processes. It is already common for these materials to be in optical systems, for example in the field of medicine or computer science.

David Carmona, Juan Manuel Trujillo, Sergio Bonaque, Óscar Gómez, José Manuel Rodríguez-Ramos

Context. Increasing the area on the sky over which atmospheric turbulences can be corrected is a matter of wide interest in astrophysics, especially when a new generation of extremely large telescopes (ELT) is to come in the near future. Aims. In this study we tested if a method for visual representation in three-dimensional displays, the weighted nonnegative tensor factorization (WNTF)…

David Carmona, Juan Manuel Trujillo, Sergio Bonaque, Ángela Hernández, José M Rodríguez-Ramos

Tensor display is an option in glasses-free three-dimensional (3-D) display technology. An initial solution has to be set to decompose the light-field information to be represented by the system. We have analyzed the impact of the initial guess on the multiplicative update rules in terms of peak signal-to-noise ratio, and proposed a method based on depth map estimation from an input light field.

Óscar Gómez, José G. Marichal, Juan Manuel Trujillo, David Carmona, José Manuel Rodríguez-Ramos

The discrete Radon transform, DRT, calculates, with linearithmic complexity, the sum of pixels through a set of discrete lines covering all possible slopes and intercepts in an image. In 2006, a method was proposed to compute the inverse DRT that remains exact and fast, in spite of being iterative. In this work the DRT pair is used to propose a Ridgelet and a Curvelet transform that perform focus measurement of an image.

Sergio Bonaque, J.J. Fernández-Valdivia, Juan Manuel Trujillo, Oscar Gomez

In this work we propose the use of a new full definition wave front sensing technique for aberration measurement in optical elements. The technique apparatus doesn’t need additional optics elements and wave front map resolution is only limited by the resolution of the imaging sensor being used. We outline some of the analitical details and the advantages of this method compared with classic wave front sensors.

J.J. Fernández, Juan Trujillo, Oscar Casanova, R. L. López, S. Velasco, C. Colodro, M. Puga, A. Oscoz, R. Rebolo, C. Mackay, A. Pérez, L.F. Rodríguez, D. King, L. Labadie, B. Muthusubramanian, G. Rodríguez-Coira, José M Rodríguez-Ramos

This paper presents a method to recover the wavefront phase at the telescope pupil, distorted because of the atmosphere action, and its use to command a deformable mirror…

Juan Manuel Trujillo, Vladimir Katkovnik, Bahram Javidi, José Manuel Rodríguez-Ramos

This paper contains an original development of the compressed sensing technique for restoring integral images from a number of observed 2D images. The proposed data acquisition uses a conventional camera equipped with a horizontal 1D mask placed in the pupil plane of the lens. The compressed sensing style algorithm developed is based on a sparsity hypothesis imposed on 2D cross sections of the light field.

Juan Manuel Trujillo, Juan J. Fernández, Luis F. Rodríguez, Óscar G. Cárdenes, José G. Marichal, Bahram Javidi, José Manuel Rodríguez-Ramos

In this paper, we use information from the light field to obtain a distribution map of the wavefront phase. This distribution is associated with changes in refractive index which are relevant in the propagation of light through a heterogeneous or turbulent medium. Through the measurement of the wavefront phase from a single shot, it is possible to make the deconvolution of blurred images affected by the turbulence.

Juan Manuel Trujillo, J. J. Fernández-Valdivia, J. G. Marichal-Hernández, José Manuel Rodríguez-Ramos, L. F. Rodríguez-Ramos, I. Mantilla

The deconvolution applied to plenoptic sensors has only been studied in the area of light intensity, including no treatment for the possible path changes that optical rays suffer due to the refraction index changes in the medium.

Juan Manuel Trujillo, L. F. Rodríguez-Ramos, I. Montilla, José Manuel Rodríguez-Ramos

Plenoptic imaging systems are becoming more common since they provide capabilities unattainable in conventional imaging systems, but one of their main limitations is the poor bidimensional resolution. Combining the wavefront phase measurement and the plenoptic image deconvolution, we propose a system capable of improving the resolution when a wavefront aberration is present and the image is blurred.

Juan Manuel Trujillo, L. F. Rodríguez-Ramos, Juan J. Fernández-Valdivia, José G. Marichal, José Manuel Rodríguez-Ramos

Modern astronomic telescopes take advantage of multi-conjugate adaptive optics, in which wavefront sensors play a key role. A single sensor capable of measuring wavefront phases at any angle of observation would be helpful when improving atmospheric tomographic reconstruction.

Luis F. Rodríguez-Ramos, Icíar Montilla, Juan Manuel Trujillo, José Manuel Rodríguez-Ramos

The use of the plenoptic camera as a wavefront sensor has been proposed and demonstrated in the past by our group, as especially adequate for extended objects, within the context of the design of the European Solar Telescope (EST), and also may be used with point sources and even with elongated objects like laser guide stars.

Juan Manuel Trujillo, José Manuel Rodríguez-Ramos, L. F. Rodríguez-Ramos, B. Javidi

Plenoptic sensors have been developed as passive method for 3D scanning of a scene by the intensity of the light. In this work a new method to measure 3D, not by its intensity but its wavefront phase, is presented. Microscopy on translucent or fluorescent samples, can take advantage of this technique. Preliminary studies and simulations are presented to show the feasibility of the technique.

M. G. Thomas, I. Montilla, J. G. Marichal, J. J. Fernández-Valdivia, Juan Manuel Trujillo, José Manuel Rodríguez-Ramos

The CAFADIS plenoptic camera was mounted onto a Leica M205A stereomicroscope and used as a prototype light field microscope. The ability to generate image stacks focused at different focal planes from a single plenoptic image was demonstrated. The focal stacks were used to create a composite extended focus image and depth map.

L. F. Rodríguez-Ramos, I. Montilla, J. J. Fernández-Valdivia, Juan Manuel Trujillo, José Manuel Rodríguez-Ramos

The plenoptic camera has been proposed as an alternative wavefront sensor adequate for extended objects within the context of the design of the European Solar Telescope (EST), but it can also be used with point sources. Originated in the field of the Electronic Photography…

L. F. Rodríguez-Ramos, I. Montilla, J. P. Lüke, R. López, J. G. Marichal, Juan Manuel Trujillo, B. Femenía, M. López, J. J. Fernández, M. Puga, F. Rosa, José Manuel Rodríguez-Ramos

Plenoptic cameras have been developed the last years as a passive method for 3d scanning, allowing focal stack capture from a single shot.

José Manuel Rodríguez-Ramos, J. G. Marichal, J. P. Lüke, Juan Manuel Trujillo, M. Puga, M. López, J. J. Fernández, C. Dominguez, J. C. Sanluis, F. Rosa, V. Guadalupe, H. Quintero, C. Militello, L. F. Rodríguez-Ramos, R. López, I. Montilla, B. Femenía

The CAFADIS camera project has consisted in building a camera to measure wave-front phases and distances under different scenarios (from microns to kilometres).

Juan Manuel Trujillo, M. R. Valido, L. F. Rodríguez, E. Boemo, F. Rosa, José Manuel Rodríguez-Ramos

ELT laser guide star wavefront sensors are planned to handle an expected amount of data to be overwhelmingly large (1600×1600 pixels at 700 fps). According to the calculations involved, the solutions must consider to run on specialized hardware as Graphical Processing Units (GPUs) or Field Programmable Gate Arrays (FPGAs), among others.