Variable Shaped Electron Beam Lithography Research Articles

Fabricating a high-resolution mask with improved line-edge roughness by using a nonchemically amplified resist and a postexposure bake.

The authors have developed a high-resolution technique for fabricating photomasks at the 10-nm half-pitch logic nodes and beyond. Current mask-manufacturing techniques use a chemically amplified resist (CAR) that has a complex mechanism of acid generation, complicating the criteria for selecting the polymer and the quencher for industrial purposes. Thus, it is important to study fabricating masks with non-CARs. The authors exposed a non-CAR, diluted ZEP520A, to variable-shaped electron-beam lithography and used a postexposure bake (PEB) to modify the resist. Studying how the PEB temperature affected the non-CAR and resultant masks, the authors demonstrate that their technique can produce high-resolution structures. By measuring the critical dimensions (CDs), the authors show that the PEB shrunk, enlarged, and retained the size of 1:1 line-and-space, isolated space, and isolated line patterns, respectively. By optimizing the PEB temperature, the authors improved the line-edge roughness (LER) of the 1:1 line-and-space and isolated space CDs by ∼40%. To understand how the PEB affected the resultant structures, the authors measured the hardness of cured resists with and without a PEB at various temperatures. Optimizing the PEB temperature of the non-CAR increased the resist contrast, annealing the resist and improving the LER. As such, their technique is capable of high resolutions on the order of 20 nm. The insights the authors gained from optimizing the PEB might be useful when fabricating next-generation masks.

Fabrication of a high-resolution mask by using variable-shaped electron beam lithography with a non-chemically amplified resist and a post-exposure bake

A high-resolution technique was developed for fabrication of photomasks for 10-nm-technology nodes and beyond. Current mask manufacturing techniques use a chemically amplified resist (CAR) photoresist material that has a complex mechanism of acid generation that obscures the criteria for selecting the polymer, quencher, and crosslinker for industrial purposes. It is therefore important to validate non-CAR materials as alternative solutions for mask fabrication. In this research, diluted ZEP520A was used as a non-CAR material in conjunction with a JBX9000 electron-beam lithography (EBL) tool. Additionally, a post-exposure bake (PEB) is normally used in mask fabrication. The PEB method was also used in this research, and we investigated its temperature dependence. Critical dimensions (CDs) of 1:1 line-and-space, isolated space, and isolated line patterns on a diluted ZEP520A resist were measured and showed CD shrinkage, an extension effect, and retention of the integrity of the shape after the PEB process. A resolution of the order of 20nm was attained and the insights gained from optimization of the PEB process might be usefully applied in advanced methods for fabricating masks of the next generation.

Plasmonic properties of aluminum nanorings generated by double patterning

In this Letter we evaluate a technique for the efficient and flexible generation of aluminum nanorings based on double patterning and variable shaped electron beam lithography. The process is demonstrated by realizing nanorings with diameters down to 90 nm and feature sizes of 30 nm utilizing a writing speed of one ring per microsecond. Because of redepositions caused by involved etching processes, the material of the rings and, therefore, the impact on the plasmonic properties, are unknown. This issue, which is commonly encountered when metals are nanostructured, is solved by adapting a realistic simulation model that accounts for geometry details and effective material properties. Based on this model, the redepositions are quantified, the plasmonic properties are investigated, and a design tool for the very general class of nanofabrication techniques involving the etching of metals is provided.

Variable Shaped Electron Beam Lithography for Fabrication of Very Large-Scale Integrated Circuits : An Example of Research and Development in the Information Science Laboratory, The Institute of Physical and Chemical Research

Variable Shaped Electron Beam Lithography for Fabrication of Very Large-Scale Integrated Circuits : An Example of Research and Development in the Information Science Laboratory, The Institute of Physical and Chemical Research

Advantageous Exposure of X Architecture Patterns when Using a Variable-Shaped Beam Tool

The concept of introducing diagonal interconnects in chip manufacturing offers several advantages and is known as X architecture. We investigated the fabrication of such patterns for high-resolution direct writing applications using variable-shaped electron beam lithography. The variable-shaped beam offers throughput advantages for Manhattan patterns. These advantages apply also to X architecture patterns, provided slanted rectangular and triangular shots can be used for pattern generation. This specific shot generation method has already been incorporated in Leica SB350 electron beam writing tools, so that it has become possible to significantly reduce the number of shots required for exposing X architecture layouts. The resolution is not affected by the pattern orientation. 130 nm pitch lines and spaces with axis-parallel and slanted orientations were successfully exposed in a 250-nm-thick NEB-33 resist.

Data preparation and fabrication of DOE using electron-beam lithography

The application of electron-beam lithography to the generation of diffractive optical elements topology is examined. The formula for the estimation of exposure data volume for variable-shaped electron-beam lithography is presented as a function of diffractive optical element parameters and approximation accuracy. A special software dedicated to preparing exposure data for fabrication of diffractive optical elements is developed. Diffractive optical elements with an artificial refractive index are manufactured with a feature size much less than the wavelength. Design and experimental results on photomasks fabrication for an optical element focusing radiation into a ring with pregiven parameters are presented. The photomask set is manufactured for a reflecting optical element focusing the high power CO 2 laser beam into two points with required parameters for laser welding.

Triangular-variable-shaped beams using the cell projection method

A triangular variable shaped electron beam lithography method using the cell projection method is proposed. The shaped beams are formed by a conventional rectangular beam method and variable triangular apertures. This method has three significant characteristics: The plural kind of triangles can be made. This increases the pattern flexibility and decreases the number of shots. The position of one corner of the triangles is automatically determined. Therefore, there is no fluctuation of the triangular beam position and the size of the triangle can be varied with high precision. The triangular apertures are located such as to minimize the deflection distance. This realizes high speed and high precision beam formation. With these characteristics, this method is expected to be used for high speed and high precision mask fabrication.

Accuracy of exposure during continuous stage movement in a variable shaped vector scanning EB lithography system

We have developed a variable shaped electron beam lithography system “NOWEL-2” [1,2]. Continuously moving stage exposure mode, which we call CM exposure mode, is used in the system. To achieve high butting and overlay accuracy in CM exposure mode, we measured the beam positioning error using the continuously moving mark detection method. Up to a stage velocity of 10 mm/sec, beam positioning error caused by eddy current and system vibration was less than 0.04 μm. Total beam positioning drift during exposure was decreased to about 0.08 μm by keeping the temperature of the electromagnetic deflectors and lenses constant.

`NOWEL-2' Variable-Shaped Electron Beam Lithography System for 0.1 µm Patterns with Refocusing and Eddy Current Compensation

We have developed a variable-shaped electron beam (EB) lithography system which we call NOWEL-2. The system has the following features: (1) a short objective lens and a four-stage major deflection system; the landing angle at the corner of the 1.6 mm square major field is less than 2 mrad, and patterns from 0.1 to 3.0 µm are well resolved over the whole deflection field, (2) 20-bit digital-to-analog converter and high-precision current output amplifier, in which the least significant bit (LSB) corresponds to 0.0025 µm; linearity error is less than 1/4 LSB at 23±5°C, (3) refocusing and refocus-flyback; the edge sharpness of a 3 µm square beam was improved from 0.5 µm to 0.25 µm, (4) eddy current compensation; for a 100 µm electromagnetic jump, the waiting time is less than 50 µs, (5) continuously moving stage mode exposure; beam position accuracy is about 0.05 µm (3σ).

Investigation of the charging effect on thin SiO2 layers with the electron beam lithography system

The charging problem of a dielectric layer during direct exposure with an electron beam lithography system is investigated. Electron beam irradiation on a wafer with a dielectric layer such as SiO2 often causes charge buildup. This excessive accumulation of charge on the sample disturbs placement accuracy, and results in overlay errors. In order to analyze this charging problem, a metrology software package is used to measure the placement error of the exposed patterns on a target plane. Tested sample wafers are deposited with 0.2–1.5 μm SiO2, and then coated with 1 μm resist for exposure. To evaluate the charging dependence on electron beam current, a variable-shaped electron beam lithography system which can easily change beam current is used. The results indicate that nongrounding 0.2 and 0.5 μm SiO2 do not show charge-induced placement errors while 1 and 1.5 μm SiO2 show a definite placement error due to charging. On 1.5 μm Sio2 results indicate an electrostatic breakdown of SiO2, and no charging error is observed after breakdown. These pattern distortions due to charging are evaluated by a statistical analysis, and they are approximated by a simplified equation. To prevent charging, a mechanical contact with the substrate has proven to be effective. This grounding method, using a conductive diamond tip, shows excellent grounding ability.

6149. An experimental variable shaped electron beam lithography system

6149. An experimental variable shaped electron beam lithography system

High throughput variable shaped electron beam lithography: B. P. Piwczyk and A. E. Williams Solid St. Technol. 145 (September 1983)

High throughput variable shaped electron beam lithography: B. P. Piwczyk and A. E. Williams Solid St. Technol. 145 (September 1983)

An experimental variable shaped electron beam lithography system

An experimental variable shaped electron beam lithography system has been built to verify the theoretical design considerations and fundamental control method. The electron beam column consists of four magnetic lenses, two square apertures, two aligners, an angular aperture, a set of blanking plates, and a position deflection yoke. The size of the beam spot is varied by a set of electrostatic deflection plates. In order to maintain the current density in the spot constant, as the size of the beam spot varies, the center of the shaped deflection plates is placed to coincide with the image of the gun crossover, and the shaped deflection plates position can be electrically adjusted. The acceleration voltage is 20 kV. The field size is 2.5 mm square. The maximum spot size is 10 μm2. The maximum current density is 1 A/cm2. The system is controlled by an EG 3003 computer. The beam blanking switching time is 50 nS.

High throughput variable shaped electron beam lithography : B. P. Piwczyk and A. E. Williams. Solid St. Technol. 145 (September 1983)

It has been found that preferential sputtering of P from InP(110) is pronounced at low Ar ion energies (500 eV) but that for higher ion energies (ca 3 keV) no departure from the stoichiometric surface composition is observed. Annealing of the disordered surface produced by bombardment causes agglomeration of In atoms into microdroplets accompanied by a reordering of the remaining surface regions which, after the loss of In to the droplets, have a near stoichiometric composition. Reordering involves the formation of randomly oriented crystallites which at higher temperatures align with the underlying InP crystal structure to form flat ordered surface regions. These regions give rise to LEED and RHEED patterns essentially similar to those from the (110) cleavage surface despite the non-stoichiometric large-area composition.