Y. Jourlin

Direct nanopatterning of 100 nm metal oxide periodic structures by Deep-UV immersion lithography

Deep-UV lithography using high-efficiency phase mask has been developed to print 100 nm period grating on sol-gel based thin layer. High efficiency phase mask has been designed to produce a high-contrast interferogram (periodic fringes) under water immersion conditions for 244 nm laser. The demonstration has been applied to a new developed immersion-compatible sol-gel layer. A sol-gel photoresist prepared from zirconium alkoxides caped with methacrylic acids was developed to achieve 50 nm resolution in a single step exposure. The nanostructures can be thermally annealed into ZrO(2). Such route considerably simplifies the process for elaborating nanopatterned surfaces of transition metal oxides, and opens new routes for integrating materials of interest for applications in the field of photocatalysis, photovoltaic, optics, photonics or microelectronics.

Low-loss plasmon-triggered switching between reflected free-space diffraction orders

Surface plasmon coupling of a TM polarized free space incident beam by means of the + 1st or the -2nd order of a smooth corrugation grating at a metal surface causes the cancellation of the diffracted -1st order free space beam and a maximum of the 0th order Fresnel reflection whereas the converse occurs midway between these two conditions. This implies that angular tilting of the element or wavelength scanning provokes the switching between the -1st and 0th reflected orders. This plasmon-mediated effect on propagating free-space beams exhibits remarkably low absorption losses.

A new wireless and miniaturized high-resolution optical displacement sensor

A wireless displacement sensor is proposed which is composed of a fixed active head and a passive head which moves relatively to a grating scale. The passive head comprises a grating and two mirrors. It can be so small as to be inserted non-obtrusively where the displacement must be measured without spoiling the system optimum by undesirable size and structural compromises. It is insensitive to electromagnetic perturbations. The key characteristics of the sensor are high resolution and a very small size. The encoder uses a fixed grating scale as in standard designs, a passive-optical read head on the moving element and a stationary, opto-electronic source/detector module. Communication between the moving head and the detector module is done without cables using a free-space optical interconnection.

Monolithic diffractive interference detector on silicon

The presented interference detector comprises a standard pn junction in a silicon substrate and a corrugation grating engraved at its surface. Two beams with unknown phase difference impinge onto the detector under the Littrow condition for some diffraction order of the grating. The detected power exhibits a non-zero AC component as the relative phase between the incident beams changes. The present paper describes the operation principle and brings the evidence of non-zero interference contrast in the application case of a displacement sensor.

Low loss polarizing beam splitter using the long range plasmon mode along a continuous metal film

A sinusoidally weakly undulated continuous thin gold film embedded between a polymer substrate and a thin cover of the same polymer, the metal film thickness, the period and the wavelength being such that a normally incident wave excites the long range plasmon mode of the metal film, is shown to exhibit strong resonant transmission for the local TM polarization and strong reflection of the TE polarization. Such structure represents a very simple, average performance polarization beam splitter for white light processing.

Microelectronics planar technologies for the manufacturing of high spatial frequency gratings: sub-angstroem assessment of spatial coherence

The spatial coherence of optical gratings fabricated by means of a step & repeat camera is characterized by a diffractive interferometric displacement sensor using the grating under test as the grating scale. The displacement sensor head comprises two readout gratings at a definite distance from each other which allows the determination of the local deviation of the grating period with a resolution of 0.001 nanometer.

Verification and application of multi-source focus quantification

The concept of the multi-source focus correlation method was presented in 2015 [1, 2]. A more accurate understanding of real on-product focus can be obtained by gathering information from different sectors: design, scanner short loop monitoring, scanner leveling, on-product focus and topography. This work will show that chip topography can be predicted from reticle density and perimeter density data, including experimental proof. Different pixel sizes are used to perform the correlation in-line with the minimum resolution, correlation length of CMP effects and the spot size of the scanner level sensor. Potential applications of the topography determination will be evaluated, including optimizing scanner leveling by ignoring non-critical parts of the field, and without the need for time-consuming offline topography measurements.

Fast integral rigorous modeling applied to wafer topography effect prediction on 2x nm bulk technologies

Reflection by wafer topography and underlying layers during optical lithography can cause unwanted overexposure in the resist [1]. In most cases, the use of bottom anti reflective coating limits this effect. However, this solution is not always suitable because of process complexity, cost and cycle time penalty, as for ionic implantation lithography process in 28nm bulk technology. As a consequence, computational lithography solutions are currently under development to simulate and correct wafer topographical effects [2], [3]. For ionic implantation source drain (SD) photolithography step, wafer topography influences resulting in implant pattern variation are various: active silicon areas, Poly patterns, Shallow Trench Isolation (STI) and topographical transitions between these areas. In 28nm bulk SD process step, the large number of wafer stack variations involved in implant pattern modulation implies a complex modeling of optical proximity effects. Furthermore, those topography effects are expected to increase with wafer stack complexity through technology node downscaling evolution. In this context, rigorous simulation can bring significant value for wafer topography modeling evolution in R and D process development environment. Unfortunately, classical rigorous simulation engines are rapidly run time and memory limited with pattern complexity for multiple under layer wafer topography simulation. A presentation of a fast rigorous Maxwell’s equation solving algorithm integrated into a photolithography proximity effects simulation flow is detailed in this paper. Accuracy, run time and memory consumption of this fast rigorous modeling engine is presented through the simulation of wafer topography effects during ionic implantation SD lithography step in 28nm bulk technology. Also, run time and memory consumption comparison is shown between presented fast rigorous modeling and classical rigorous RCWA method through simulation of design of interest. Finally, integration opportunity of such fast rigorous modeling method into OPC flow is discussed in this paper.

Wide band, wide angular width wire-grid polarizer using galvanic growth technology

Functional demonstration of a wide band, wide angular width “wire-grid polarizer” has been made in the framework of a User Project of the European project ACTMOST (Access To Micro-Optics Expertise, Services and Technologies). The polarization function relies upon linear polarizers using the “wire-grid” polarizer principle by means of a metal grating of unusually large period, exhibiting a large extinction of the transmission of the TE polarization in the 850 nm wavelength range. This grating achieves a broadband and especially high angular aperture reflection with low loss and permits resorting to very low cost incoherent light sources of the transmitted TM polarization. The paper will describe the design, the modeling optimization, and the complete technological process chain which has been used: from the photoresist grating printing using phasemask UV-based lithography to the uniform galvanic growth of very shallow gold grating on transparent conductive layer deposited on a glass substrate. Transmission curves for both polarizations on the first demonstrators will be presented.

New low-cost high-efficiency solar module: diffracting deflector module

TiO2 based sol-gel microstructuring layer is applied to increase efficiency of solar cells modules or the so-called PV planar concentrators, by reducing the amount of solar cells (silicon based solar cells) while increasing the amount of solar energy trapped into the modules. The proposed solution is based on linear grating whose role is to trap and diffract the incident beam to solar cells. The design of the module and the optimized gratings, to be angularly and spectrally tolerant, are presented. The paper also deals with the fabrication of large and long gratings (m2 area), using the unique direct photopatterning sol-gel solution, based on the dynamic and continuous gratings writing using phase mask lithograghy.