General Archives - Allresist EN https://www.allresist.com/category/resist-wiki/resist-wiki-e-beam-resist/resist-wiki-e-beam-resist-general/ ALLRESIST GmbH - Strausberg, Germany Mon, 13 Jun 2022 11:15:07 +0000 en-GB hourly 1 https://wordpress.org/?v=6.5.2 Electron beam resists https://www.allresist.com/electron-beam-resists/ Mon, 13 Jun 2022 10:15:17 +0000 https://www.allresist.com/?p=17544 Among the first resists used (since about 1980) and still applied in many cases are short-chain (50.000 g/mol (50k)) as well as long-chain (950.000 g/mol (950k)) poly(methyl methacrylate) (PMMA resist, sensitivity at 100 keV approximately 250 – 500 µC/cm2).

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Electron beam resists

Significant components of electron beam lithography systems are the electron source, the electro-optical system and the focusing system (deflection or respectively projection unit). Hot cathodes are used for equipment with lower resolution, devices with higher resolution, however, preferably need thermic field emission sources. In order to focus and concentrate the electron beams, special equipment is needed, which, analogical to optics, is refered to as lens systems. Both magnetic and electrostatic lenses are used for the direction of the electron beam, however, the latter ones are not suitable for fine focusing because they show greater aberration. For a very accurate focusing, electron beams with extremely narrow energy dispersion are prerequisite. Very little deflections of the electron beam are usually achieved by electrostatic systems, greater beam deflections by electromagnetic systems. Due to inaccuracies and the limited number of exposure steps, the exposure area is very small and only 100 to 1000 µm. For writing greater patterns, a moveable substrate plating is prerequisite and must fulfil particularly high requirements with regard to exact positioning for the pattern sequence.

Overview E-beam Other Resists



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]]> Electron beam lithography systems https://www.allresist.com/electron-beam-lithography-systems/ Thu, 09 Jun 2022 11:55:36 +0000 https://www.allresist.com/?p=17540 Significant components of electron beam lithography systems are the electron source, the electro-optical system and the focusing system (deflection or respectively projection unit). Hot cathodes are used for equipment with lower resolution, devices with higher resolution, however, preferably need thermic field emission sources.

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Electron beam lithography systems

Significant components of electron beam lithography systems are the electron source, the electro-optical system and the focusing system (deflection or respectively projection unit). Hot cathodes are used for equipment with lower resolution, devices with higher resolution, however, preferably need thermic field emission sources. In order to focus and concentrate the electron beams, special equipment is needed, which, analogical to optics, is refered to as lens systems. Both magnetic and electrostatic lenses are used for the direction of the electron beam, however, the latter ones are not suitable for fine focusing because they show greater aberration. For a very accurate focusing, electron beams with extremely narrow energy dispersion are prerequisite. Very little deflections of the electron beam are usually achieved by electrostatic systems, greater beam deflections by electromagnetic systems. Due to inaccuracies and the limited number of exposure steps, the exposure area is very small and only 100 to 1000 µm. For writing greater patterns, a moveable substrate plating is prerequisite and must fulfil particularly high requirements with regard to exact positioning for the pattern sequence.

Overview E-beam Other Resists



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]]> Generation of secondary electrons https://www.allresist.com/generation-of-secondary-electrons/ Thu, 09 Jun 2022 11:16:32 +0000 https://www.allresist.com/?p=17536 Alongside the occuring elastic scattering effects at a collision with other electrons or atoms, incoming primary electrons can also be scattered inelastically when entering or traversing resist layers.

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Generation of secondary electrons

Alongside the occuring elastic scattering effects at a collision with other electrons or atoms, incoming primary electrons can also be scattered inelastically when entering or traversing resist layers. In this process, primary electrons transfer a part of their energy or respectively their impulse onto other electrons. The released secondary electrons, which may have another wavelength, e.g. Auger electrons, are likewise able to  break down chemical bonds and release further elctrons of less energy in the material. This results in the formation of an electron cascade.

Overview E-beam Other Resists



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]]> E-beam resist: Procedures https://www.allresist.com/e-beam-resist-procedures/ Thu, 09 Jun 2022 10:48:25 +0000 https://www.allresist.com/?p=17532 There are both mask-based and maskless writing procedures in electron beam lithography. More up-to-date systems use defined beams with, by the application of masks, selectively adjusted geometrical cross sections or respectively profiles, which are deflected upon the various positions (vector scan mode).

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E-beam resist: Procedures

E-beam lithographic procedures

There are both mask-based and maskless writing procedures in electron beam lithography. For direct, maskless writing, older systems use electron beams with Gaussian energy distribution, which are directed over the substrate in the grid. More up-to-date systems use defined beams with, by the application of masks, selectively adjusted geometrical cross sections or respectively profiles, which are deflected upon the various positions (vector scan mode). The deflection of the electron beam is achieved by electrostatic interdependence of the electrons.

The used, variously shaped electron beams differ with regard to their energy distribution in the beam cross section in fixed shape beams on one hand (round, Gauss beams, square shape, round spot with steady energy distribution) and, on the other hand, beams of variable shape (mostly triangles or quadrangles of various sizes and form. The shape of the beam is generated by an aperture or respectively a structured aperture plate.

Similar to photolithography, there are specific proximity exposure techniques in mask-based procedures, such as 1:1 projection or also other projections in which the structures of the mask are downsized.

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]]> Basics https://www.allresist.com/basics/ Wed, 08 Jun 2022 09:23:16 +0000 https://www.allresist.com/?p=17503 Information on:

Polymer resists (layer builders)
Photosensitive components
Cross linker
Other resist components (adhesion promoter, tenside, solvent, colorant)
Process information such as: Cleaning of substrates, adhesive strength, dilution of resists, yellow light, softbake, rehydration, exposure and storage
Process procedures such as:   Lift-off procedures, wet-chemical etching, dry-chemical etching, UV-curing, lithographic procedures and stabilization/curing of resist layers

See Photo resists: General

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Basics

Information on:

  • Polymere resists (layer builder)
  • Photosensitive components
  • Cross linker
  • Other resist components (adhesion promoter, tenside, solvent, colorant)
  • Process information such as: Cleaning of substrates, adhesive strength, dilution of resists, yellow light, softbake, rehydration, exposure and storage
  • Process procedures such as:   Lift-off procedures, wet-chemical etching, dry-chemical etching, UV-curing, lithographic procedures and stabilization/curing of resist layers

See Photo resists: General

Overview E-beam Other Resists



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]]> E-beam resists: General https://www.allresist.com/e-beam-resists-general/ Wed, 08 Jun 2022 08:14:08 +0000 https://www.allresist.com/?p=17497 Electron beam lithography is a special procedure for the structuring of electron beam sensitive resist layers in order to produce microelectronic circuits and photomasks used in photolithography.

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E-beam resists: General

Electron beam lithography is a special procedure for the structuring of electron beam sensitive resist layers in order to produce microelectronic circuits and photomasks used in photolithography. Electron beam lithography is a promising technology for the 32-nm structures aimed for in the near future with the potential to generate structures with even smaller resolution and in mass production later. The competing extreme deep UV lithography, which is likewise predestined for solving this ambitious task, is not analyzed in this Wiki because these resists are not focal for us.

By exposure to accelerated electron beams, the polymers in the e-beam resist are chemically modified in such a way that their dissolving behavior changes in the developers used (mostly organic solvent mixtures in the case of positive resists) and the resist layer thus can be structured systematically up to the nanometer range. The developed structures can subsequently be transferred to other materials, either by metal deposition or by etching of the substrate beneath.

Overview E-beam Other Resists



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]]> Scattering https://www.allresist.com/scattering/ Wed, 08 Jun 2022 07:22:27 +0000 https://www.allresist.com/?p=17493 If an electron beam with high energy is channeled onto a resist layer (5- 100 keV), forward scattering ( 90° in direction of arrival). The deflection causes the electron beam to widen, thus reducing resolution.

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Scattering

If an electron beam with high energy is channeled onto a resist layer (5- 100 keV), forward scattering (< 90° in direction of arrival) occurs as well as backward scattering (> 90° in direction of arrival). The deflection causes the electron beam to widen, thus reducing resolution. The backward scattered primary electrons, given a sufficient dose, cause a complete exposure of a resist volume which is significantly bigger than the original beamwidth. This effect can be systematically put to use in order to generate undercut resist structures. The electrons are scattered backward on the substrate and cause an increased exposure of the lower resist areas (proximity effect). The forming of the undercut can be specifically controlled by adjusting a suitable dose.

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]]> Writing time https://www.allresist.com/writing-time/ Wed, 08 Jun 2022 06:44:56 +0000 https://www.allresist.com/?p=17487 The minimum necessary exposure time for a certain area, at a given exposure dose, can be calculated by the following correlation: Area * dose = Duration of exposure * beam current.

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Writing time

The minimum necessary exposure time for a certain area, at a given exposure dose, can be calculated by the following correlation:

Area * dose = Duration of exposure * beam current

In the minimum writing time, the time expenditure for movements of the substrate mount (fade-out times) and respectively corrections and adjustments during writing are not taken into consideration. Due to the required time expenditure (writing a sample with sub-100nm solution on a wafer using a not particularly sensitive resist (PMMA) already takes several days), direct writing procedures with one beam only are not suited for mass production. For a significant reduction of writing times and thus a more economic performance, there is research/ development of facilities which allow the parallel application of several electron beams (multiple beam writers, mappers).

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]]> SCALPEL https://www.allresist.com/scalpel/ Tue, 07 Jun 2022 11:13:31 +0000 https://www.allresist.com/?p=17478 A further mask-based technology is SCALPEL (Scattering with Angular Limitation Projection Electron-beam Lithography). Due to the interposed mask, certain parts of the electron beam are shadowed. The scattering layer strongly deflects incident electrons. A great advantage of this procedure as compared to electron absorption is less loading and less heating of the mask.

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SCALPEL

A further mask-based technology is SCALPEL (Scattering with Angular Limitation Projection Electron-beam Lithography). This procedure uses scattering masks with a sheet that is partly transparent for electrons. Due to the interposed mask, certain parts of the electron beam are shadowed. The scattering layer strongly deflects incident electrons. A great advantage of this procedure as compared to electron absorption is less loading and less heating of the mask.

Overview E-beam Other Resists



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]]> Raster and vector scan principle https://www.allresist.com/raster-and-vector-scan-principle/ Tue, 07 Jun 2022 10:57:32 +0000 https://www.allresist.com/?p=17474 Raster scan principle is a procedure in which the electron beam is led line by line over the exposure area, comparable to the beam guidance in an electron microscope. The structures are exposed by switching the electron beam on and off while continuously moving the substrate (XY regulation).

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Raster and vector scan principle

Raster scan principle is a procedure in which the electron beam is led line by line over the exposure area, comparable to the beam guidance in an electron microscope. The structures are exposed by switching the electron beam on and off while continuously moving the substrate (XY regulation).

The vector scan principle needs shorter process times and, in contrast to the raster scan method, the electron beam is systematically led onto the areas meant to be exposed and writing in a waved or spiral movement. After exposure in the deflecting field, the X-Y-table moves on to the next defined position.

Overview E-beam Other Resists



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