Current status of optical maskless lithography

Martinsson, H.; Sandstrom, Tor; Bleeker, Arno J.; Hintersteiner, Jason D.

doi:10.1117/1.1862649

Cited by 34 publications

(34 citation statements)

References 14 publications

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“…As a result, a Fraunhofer IPMS MMA featuring one million individually and analog deflectable tilt mirrors is employed as a pattern generator in a novel lithographic deep ultraviolet ͑DUV͒ laser mask writer, capable of producing state-ofthe-art masks for the 65-nm and 45-nm technology nodes at higher speeds than conventional mask writers. [3][4][5] Furthermore, at IPMS piston-type mirror arrays for applications in adaptive optics are under development. 6,7 The large-scale integration of analog-operable micromirror arrays onto active CMOS address circuitry in one production line requires the development of a compatible mirror fabrication technology that ensures the vital properties of an SLM device: a high reflectance, smoothness and planarity of the micromirror surface, a high optical fill factor, and a stable deflection versus voltage characteristics of the actuators.…”

Section: Introductionmentioning

confidence: 99%

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Amorphous <inline-formula><math display="inline" overflow="scroll"><mrow><mi>TiAl</mi></mrow></math></inline-formula> films for micromirror arrays with stable analog deflection integrated on complementary metal oxide semiconductors

Schmidt

2008

J. Micro/Nanolith. MEMS MOEMS

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Large micromechanical mirror arrays ͑MMA͒ with analog pixel deflection integrated onto active CMOS address circuitry require both high-quality planar reflective optical surfaces and a stable deflection versus voltage characteristic. However, for implementing a CMOScompatible surface-micromachining process, certain obstacles such as a restricted thermal budget and a limited selection of suitable materials must be overcome. Amorphous TiAl is presented as a new actuator material for monolithical MEMS integration onto CMOS circuitry. TiAl films may be sputter deposited at room temperature, have an x-ray amorphous structure, and a low stress gradient. The glassy structure and high melting point make TiAl less vulnerable to stress relaxation, which makes TiAl an ideal spring material. One-level actuators with TiAl or Al-TiAl-Al structural layers and two-level actuators with separate TiAl spring and Al-alloy mirror layers were fabricated and tested with respect to their drift stability. The stability of TiAl-based actuators was found to be superior in comparison to one-level Al-alloy actuators. Two-level actuators with TiAl hinges emerge as the most promising design.

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Section: Introductionmentioning

confidence: 99%

“…So far, MEMS/MOEMS devices on top of active CMOS circuitry have been fabricated using polycrystalline SiGe, 8 amorphous silicon, 9 monocrystalline Si ͑layer transfer bonding͒, 10,11 and polycrystalline near-Al alloys. 3 The two latter technologies are pursued at the Fraunhofer IPMS.…”

Section: Introductionmentioning

confidence: 99%

Amorphous <inline-formula><math display="inline" overflow="scroll"><mrow><mi>TiAl</mi></mrow></math></inline-formula> films for micromirror arrays with stable analog deflection integrated on complementary metal oxide semiconductors

Schmidt

2008

J. Micro/Nanolith. MEMS MOEMS

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“…Using maskless lithography has become hot research projects of lithography. In fact, the cost of a mask set could double for each new technology node, resulting in an amazing $3 to $4 million for a state of the art 65-nm mask set in 2005 [1][2][3][4] , This will have a detrimental impact on foundries and application specific integrated circuit (ASIC) fabrications that are finding reticles to be an increasing dominating part of their manufacturing costs, especially for small series production. IMS nanofabrication GmbH developed PLM-2, which can manufacture less than 45 nm.…”

Section: Introductionmentioning

confidence: 99%

Design of maskless lithography system based on DMD

Liu

2007

SPIE Proceedings

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An experiment system of maskless lithography has been presented using the characteristics of digital micro-mirror device (DMD) and principle of light refraction and diffraction. The experiment system contains a worked lamp-house, a DMD controlled by computer and an imaging system. The main parameter of devices, such as the incident and reflected light on DMD by selection of optimal optical devices and realizes process of exposure have been designed. In this paper, the particular characteristics of this system were described and some preliminary experimental results were discussed in finally. With this system, the realizable rate of reduction projecting is 14; the minimum precision is 1.3µm. It avoids the process of replacement mask and subsequent problems, and simplifies operation process, improves overlay accuracy, shortens production cycle of IC, and greatly decreases production cost. It is convenient to actualize the process of exposal and optional to replace the digital mask. These can provide possibility for maskless lithography being further improved.

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“…Optical maskless lithography (ML2), using MEMS micromirror arrays or spatial light modulators (SLMs) as programmable masks, is a promising and potentially cost saving solution to the increasing mask costs of conventional lithography [1,2]. To fulfill the throughput requirement, typically millions of micromirrors are needed in the programmable mask.…”

Section: Introductionmentioning

confidence: 99%

High-sensitivity interferometric schemes for ML2 micromirror calibrations

2006

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This paper presents an interferometric method with high sensitivity and good linearity for calibration of micromirror arrays used in maskless lithography. An analytic model based on electric-field perturbation is developed to quantify the influences of mirror configuration and defocus on calibration sensitivity. With the analytic model, two optimization strategies to achieve the highest sensitivity are developed. For a 5-by-5 subarray with a pixel size of 0.5λ/NA, the sensitivity is improved from 0.0078 I/° when the surrounding pixels are not actuated, to 0.02286 I/° and 0.0347 I/° when the pixels are arranged in optimized schemes at defocus of 0.0RU and 1.5RU, respectively. The typical improvement is about 3X to 4X when the optimized calibration schemes are used.

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Current status of optical maskless lithography

Cited by 34 publications

References 14 publications

Amorphous <inline-formula><math display="inline" overflow="scroll"><mrow><mi>TiAl</mi></mrow></math></inline-formula> films for micromirror arrays with stable analog deflection integrated on complementary metal oxide semiconductors

Amorphous <inline-formula><math display="inline" overflow="scroll"><mrow><mi>TiAl</mi></mrow></math></inline-formula> films for micromirror arrays with stable analog deflection integrated on complementary metal oxide semiconductors

Design of maskless lithography system based on DMD

High-sensitivity interferometric schemes for ML2 micromirror calibrations

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