TMAH soak process optimization with DNQ positive resist for lift-off applications

Toukhy, Medhat A.; Lu, Peng-Han; Dixit, Sunit S.; Sellers, P.

doi:10.1117/12.485198

Cited by 5 publications

(4 citation statements)

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“…Taking λ = 365.4 nm as the principal wavelength absorbed by the AZ MiR 703 photoresist (corresponding to the i-line of the mercury vapor light source), the theoretical resolution limits for the 5×, 10×, and 20× lenses are ∼1.4, ∼0.7, and ∼0.4 μm, respectively. Minimum reproducible feature sizes as small as ∼0.5 μm have been demonstrated for AZ MiR 703, though the work herein did not obtain features smaller than ∼0.9 μm . The experimentally obtained feature sizes were slightly larger than expected, which could have been a result of the limitations from the minimum resolution of the objective lenses (e.g., due to the manufacturing aberrations therein).…”

Section: Resultsmentioning

confidence: 99%

“…Minimum reproducible feature sizes as small as ∼0.5 μm have been demonstrated for AZ MiR 703, though the work herein did not obtain features smaller than ∼0.9 μm. 41 The experimentally obtained feature sizes were slightly larger than expected, which could have been a result of the limitations from the minimum resolution of the objective lenses (e.g., due to the manufacturing aberrations therein). Optimal exposure times for the creation of the projected pattern of crossed bars using the 5×, 10×, and 20× objective lenses were 58, 20, and 20 s, respectively.…”

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confidence: 79%

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Microscale Contacts for Nanowire Characterization Using Microscope Projection Photolithography

Rea,

Zhang,

Mobrhan-Shafiee

et al. 2024

ACS Appl. Nano Mater.

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Microscope projection photolithography (MPP) offers a versatile method of prototyping microscale devices. The benefits of MPP include the ability to create features at a variety of dimensions, the ability to work outside of a clean room, and the ability to use robotic microscope stage controls to adjust the positions of features easily and accurately. This makes MPP a precise, yet flexible technique ideal for manufacturing contact pads that can be used to investigate the properties of individual nanowires. An enormous breadth of research has been dedicated to the synthesis and characterization of nanowires. The properties of individual nanowires can, however, vary greatly between syntheses or within a batch. Characterization of individual nanowires remains an important step in the scale-up of these materials. Their characterization does, however, often require complex and highly sensitive self-assembly techniques to arrange nanowires on substrates with proper placement of electrical contacts. Some work has been done on techniques for the selective characterization of individual nanowires, but those methods rely on using focused electron-beam writing techniques to connect nanowires to pre-existing electrical contacts. The study of nanowires would benefit from a rapid, flexible approach to fabricating contacts for individual nanowires. This study demonstrates a system for fabricating electrical contacts with minimum feature sizes of ∼0.9 μm on individual nanowires (e.g., diameters from <75 to >125 nm) that are positioned randomly on a small substrate (e.g., <1 cm2). Designs for double and quadruple contact pads have been shown to enable the effective measurement of the electrical properties of individual nanowires. The techniques provided herein can provide a rapid, simple, and customizable method of studying individual nanowires.

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 79%

Microscale Contacts for Nanowire Characterization Using Microscope Projection Photolithography

Rea,

Zhang,

Mobrhan-Shafiee

et al. 2024

ACS Appl. Nano Mater.

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“…This step leaves the film which was deposited directly on the substrate into the phoresist cavity. So far liftoff has been performed in three ways: the single-layer method 5 , the multi-layer method 6 and the surface-modified method 7,8 . The single-layer method, involve a negative tone photoresist.…”

Section: Introductionmentioning

confidence: 99%

Taguchi Design of Experiment Enabling the Reduction of Spikes on the Sides of Patterned Thin Films for Tunnel Junction Fabrication

et al. 2017

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Sputter thin film deposition after photolithography often produces unwanted spikes along the side edges. These spikes are a significant issue for the development of magnetic tunnel junction (MTJ)-based memory and molecular spintronics devices, microelectronics, and microelectro-mechanical systems because they influence the properties of the other films deposited on the top. Our molecular spintronics devices that utilizes MTJ as the testbed are almost short-lived and encountered high background current that masked the effect of molecular transport channels placed along the sides of MTJs. Therefore, tapered thin film edges are critically needed in devices. Here, we report a very cost efficient and fast way of creating an optimum photoresist profile for the production of 'spike-free' patterned films. This approach is based on performing a soaking in the photoresist developer after baking and before the UV exposure. However, the success of this method depends on multiple factors accounted for during photolithographyphotoresist thickness (spin speed), baking temperature, soaking time and exposure time. Our recent experiments systematically studied the effect of these factors by following the L9 experimental scheme of the Taguchi Design of experiment (TDOE). The L9 experimental scheme effectively accommodated the study of four photolithography factors, each with three levels. After performing photolithography as per L9 TDOE, we conducted sputtering thin film deposition of 20 nm Tantalum. Then we conducted an atomic force microscope (AFM) study of thin film patterns and measured the spikes along the edges of the deposited Tantalum. We utilized spike height as the desired property and chose "smaller the better" criteria for TDOE analysis. TDOE enabled us to understand the relative importance of the parameters, relationship amongst the parameters, and impact of the various levels of the parameters on the edge profile of the thin film patterns. We discovered that baking temperature was the most influential parameter; presoak time and photoresist thickness were two other influential factors; exposure time was the least effective factor. We also found that 4000 rpm, 100 C soft baking, 60 s soaking and 15 s UV exposure yielded the best results. Finally, the paper also discusses the interdependence of selected factors, and impact of the individual levels of each factor. This study is expected to benefit MEMS and micro/nanoelectronics device researchers because it attempts at finding a cheaper and faster alternative to creating an optimum photoresist profile.

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“…During lift-off, the sacrificial layer under the film is removed with a solvent, taking off the film on the sacrificial layer, leaving only the film which was deposited directly on the substrate. Historically, there were three basic ways in which lift-off could be performed: the single-layer method [1][2][3], the multi-layer method [2][3][4][5][6][7][8][9] and the surface-modified method [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

A simple and effective lift-off with positive photoresist

Lee

Yoon

2005

J. Micromech. Microeng.

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This paper describes a simple and effective lift-off method which relies upon a single layer of positive photoresist and the insertion of a diffuser in the conventional lithography. The inserted diffuser randomizes the paths of incident ultraviolet light, which creates the re-entrant photoresist profile necessary for proper metal lift-off. This method was applied to photoresists, with different thicknesses from 1.3 µm to 10 µm, showing a uniform undercut of 0.3 µm to 2.0 µm, depending upon the photoresist thickness. The gold lift-off test was performed to show the suitability of the photoresist profile generated by the proposed method. We could obtain very neat gold sidewall patterns after evaporation onto the fabricated photoresist pattern. The simplicity and versatility of the proposed method will provide wider options for meeting the strong demands for a simple and effective lift-off method.

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TMAH soak process optimization with DNQ positive resist for lift-off applications

Cited by 5 publications

References 0 publications

Microscale Contacts for Nanowire Characterization Using Microscope Projection Photolithography

Microscale Contacts for Nanowire Characterization Using Microscope Projection Photolithography

Taguchi Design of Experiment Enabling the Reduction of Spikes on the Sides of Patterned Thin Films for Tunnel Junction Fabrication

A simple and effective lift-off with positive photoresist

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