The Resist Wiki is a knowledge platform covering current technologies of micro electronics which is permanently updated to add further information from our research and development activities.
We have broken it down into the six topics “basics, e-beam resist, photoresist, protective resist, bottom resist and process chemicals” so that you can quickly find what you are looking for.
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Aluminium structures developed directly
Chemical dry etching
Composition of photoresists
Cross linker
Determining the conductivity of Electra 92 layers on glass
Exposure
Forays through the lithography of microelectronics (Matthias Schirmer)
Interference lithography
Other resist components
Photosensitive components
Polymers (film formers)
Principle and functioning
Process conditions
Process procedure e-beam resist
Development of PMMA films PMMA films can only be developed with solvent-based developers. Aqueous-alkaline PMMA developers will not attack PMMA - PMMA is even used as protective coating in the presence of strongly alkaline solutions.
Process procedure photoresists
Stabilisation/ hardening of resist films
Storage and ageing
UV-curing
Wet chemical etching
Wet-chemical etching procedures thus place very high demands on the protective resist layer. Decisive process parameters are, in addition to the choice of a suitable resist, the etching medium itself, the duration of the etching step and the etching temperature (which determines the reaction speed). Another important aspect concerns the adhesion properties of the resist on the substrate to be etched. An insufficient adhesion of the resist to the substrate may result in the detachment of the resist layer which renders the substrates unusable for any further applications. Adhesion problems and cracks in the resist layer frequently often appear at first at resist edges, since local heat and gas development lead to an additional mechanical load in these areas. Especially in the case of HF-containing etchings, additional large-area detachments of the resist are possible due to the diffusion of fluoride ions through the resist layer; the substrate surface is consequently attacked. Resist adhesion can generally be improved by a suitable pre-treatment of the substrate (adhesion promoter) and an optimised process management (sufficiently high resist thickness, adapted soft-bake and PEB, possible final final-hard bake).
Distinguished are anisotropic etching (rate-limited etching in which the activation energies are different for each crystal plane as in the case of Si etching with concentrated, hot KOH) and isotropic etching which occurs with amorphous materials (glasses, metals). In the case of isotropic etching, an under-etching of the resist layer cannot be avoided even if resist adhesion is optimal. If mass transport (diffusion of active components and etched products) does not limit the etch rate, a lateral under-etching occurs in proximity to the substrate surface which is comparable to the etching depth.
Specific etching mixtures are used for each material/substrate, and resists have to be selected with regard to their compatibility with the etching solution. After wet-chemical etching, intensive and multi-stage rinsing with DI water is required. These rinsing steps completely remove any etching solution which penetrated into the resist layer and prevents possible later resist damages. Insufficient rinsing may lead to a concentration of the etching solution during the final drying step, which then results in crack formation and altered/poor removing properties.
Novolac-based resists generally show a good stability against non-oxidizing acids and corrosive iodine solutions (KI*I2). Concentrated hydrochloric acid is thus generally no problem, while concentrated nitric acid or concentrated sulphuric acid solutions strongly attack the resist layers.
Diluted hydrofluoric acid (concentration < 6 %) is well tolerated, but more concentrated HF solutions causes problem with respect to the adhesion properties of the resist which are due to a diffusion of F– ions. The concentration of „free“ F– ions can however be reduced if NH4F-buffered HF etch is used (BOE process). At the same time, the formation of highly reactive HF2– ions induces a considerable increase of the etch rate and a more controllable, more homogeneous etching process. Novolac-based resists show a significantly higher stability against buffered HF solutions.
Novolac-based resists are quickly attacked in strongly alkaline etching solutions. PMMA (resist AR-PC 503) is well suited for a use as backside protection, e.g. for etchings with hot, concentrated KOH. The substrates (also the edges!) must however be coated without any defects in order to avoid a rapid detachment of the protective layer due to under-etching.
1. What are photoresists composed of, and how do they work?
10. Which developers are optimal for photoresist, and how do factors like developer concentration and temperature influence the result?
11. How can resist coatings be removed again?
12. What is the application range of protective coatings?
13. How do image reversal resists work?
14. How can undercut patterns (lift-off structures) be produced in one- or two layer systems?
15. How can thick films of > 10 µm be processed in an optimal way?
16. Which resolution and which contrast can be obtained with photoresists?
17. How high is the plasma etch resistance of photoresists?
18. How high is the etch resistance of photoresist in the presence of strong acids?
19. Which photoresists are suitable for hydrofluoric acid (HF) etching?
2. For how long are photoresists stable, and what are the optimal storage conditions?
20. How high is the solvent resistance of photoresist films?
3. How may age-related changes influence the quality of a photoresist?
4.What is the optimal pre-treatment of substrates for photoresists?
5. What are the adhesion features of photoresists on different wafers?
6. What are the optimum coating parameters for photoresists in order to achieve good film images?
7. Why may air bubbles develop in photoresist films, and how can they be avoided?
8. What is the function of the softbake of photoresist films after the coating?
9. How are photo resists exposed, and how can the optimum exposure dose be determined? How long can coated and exposed substrates be stored prior to exposure?
Adaptable two-layer resist AR-BR 5460 for variable lift-off structures
Adhesive strength
Alkali-stable and solvent-stable negative resist
Alkali-stable positive resist obtained after treatment with HMDS
Alkali-stable, easily structurable positive resist SX AR-P 5900/8
Aqueous negative resist based on gelatine
Atlas 46 for nanoimprint lithography
ATLAS 46 in general
Black resist
Bleachable resists
CAR 44 on copper
Chemically enhanced negative resist (Process parameters and resolution)
Chemically enhanced negative resist without cross-linking
Coloured negative photoresists
Development of thick negative resist layer
Dilution of resists
Dose-dependent structure size with negative resists
Ethanol and toluene-resistant photoresist AR-U 4060
Fabrication of vertical flanks with CAR 44
Fluorescent resist structures with photoresists
General: Resist composition
Image reversal resists are positive resists with an additional amine. Depending on the manufacturing process, positive or negative images can be generated.
Generation of undercut structures with negative resists
Laser ablation of PPA (Phoenix 81)
Laser direct exposure with AR-P 3540
Lift off (one layer – two layer)
Negative CAR PMMA resist SX AR-N 4810/1
Negative poly(hydroxystyrene) and (hydroxystyrene-co-MMA) photoresist with high-temperature stability
Negative polyimide photoresist
Negative two- layer lift-off system
New procedure for the spray coating of deep topologies with SX AR-P 1250/20
NIR-laser structurable photoresists
One-layer and two-layer lift-off
Photoresist coatings on Teflon substrates
Polyimide two-layer systems
Positive polyimide one-layer resist
Positive resist for temperature sensitive substrates
Positive two- layer lift-off system
Ready-to-use spray resists with EVG devices (positive and negative)
Resist for 488 nm exposure wavelength
Resist for near infrared (NIR)
Sensitive negative PMMA resist (CAR)
Sensitive negative resist for 405 nm laser direct exposure
Spray resists for different topologies (negative)
Spray resists for different topologies (positive and negative)
Structuring by ablation of the resist materials
Structuring of polyphthalaldehydes with photolithography
Surface imaging resist system SX AR-N 7100 – silylable photoresist
Temperature-stable negative resist
Thermally stable two-layer lift-off systems
Thermostable photoresists
Top surface imaging (TSI) photoresist – principles
Two-layer photoresist system for water-sensitive substrates
Two-layer resist system for hydrofluoric acid etching
UV-structuring of PMMA resists
Water-based resists
Waterfree developable special resist SX AR-N 4810/1
1. What are e-beam resists composed of, and how do they work?
10. How high is the etch resistance of e-beam resists in the presence of strong acids?
11. How high is the solvent resistance of e-beam resist films?
2. For how long are e-beam resists stable, and what are the optimal storage conditions?
3. What is the optimal pre-treatment of substrates for e-beam resist application?
4. How high is the adhesion strength of e-beam resists to different wafers?
5. How are e-beam resists exposed? How can the optimum exposure dose be determined?
6. Which developers are optimal for e-beam resists, and how do factors like developer concentration and temperature influence the result?
7. How can e-beam resist films be removed again?
8. Which resolutions do e-beam resists achieve?
9. How high is the plasma etch resistance of e-beam resists?
AR-N 7700, 4 µm thick, proximity effect
AR-P 617 Two layer lift-off system
Atlas 46 for e-beam lithography
Basics
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
BOE etching of SiO2 with CSAR 62 mask
CAR 44 for e-beam lithography
Chemically amplified, highly sensitive negative e-beam resist SX AR-N 7730/37
Collapse of extreme high-resolution e-beam resist structures
Conductivity under the application conditions of e-beam lithography
CSAR 62 Avoidance of particles during large-area exposures
CSAR 62 for EUV applications
CSAR 62 for thick films
CSAR 62 lift-off for thick layers
CSAR 62 nanostructures written at 100 kV
CSAR 62 single layer lift-off system
CSAR 62 thick layers
CSAR 62 – Development at low temperatures
CSAR 62 – Experimental studies on new, sensitive developers
CSAR 62 – Mechanism of action
CSAR structures on glass
Diffractive optics with the “analogous“ e-beam resist
E-beam resist: Procedures
E-beam resists: General
Electra 92 variant optimised for applications on novolac-based resists
Electron beam lithography systems
Electron beam resists
Evaluation of various developers for e-beam exposed CSAR 62 layers (100 kV)
Fluorescent resist structures
Generation of secondary electrons
HF etching of GaAs with CSAR 62 masks
High resolution on quartz with Electra 92 on HSQ resists
High-resolution negative e-beam resist
High-resolution negative e-beam resist AR-N 7520.17new for etching application
High-resolution PMMA one layer resist
Highly sensitive e-beam resist AR-P 617 (PMMA-copolymer)
Loading
Long-term stability of Electra 92
Manufacture of plasmonic nanostructures with CSAR 62
Medusa 82 for EUV applications
Medusa 82 with photoacid generator (PAG)
Medusa 82 – the alternative to HSQ-resists, storage stability
Medusa 82: Influence of post exposure bake (PEB)
Patterning of the conductive protective coating Electra 92
Phoenix 81 – Storage conditions and dispatch
PMMA e-beam resist with flat gradation for three-dimensional structures
PMMA e-beam resist, positive and negative in the case of overexposure, suitable for bridge structures
PMMA lift-off structures on semi-precious stone substrates using Electra 92
Poly(phthalaldehyde)-based electron beam resists
Poly(phthalaldehyde)-based electron beam resists, University of Tübingen
Positive polyimide resist for e-beam-lithography
PPA for two layer applications
Proximity effect
Raster and vector scan principle
Ratio resolution and dose, exemplarily shown for e-beam resist SX AR-N 7530/1
Resists for novel applications in lithography – thermally structurable polymers
SCALPEL
Scattering
Sensitive, etch-stable negative e-beam resist for processes without yellow light
Solution
Solvents in e-beam resists
T-gates with three-layer system CSAR/PMMAcoMA/PMMA
Temperature resistance of e-beam polymers
Thick CSAR 62
Three-layer system CSAR/PMMAcoMA/PMMA
Top Surface Imaging E-Beamresist
Two-layer PMMA e-beam resist system for high-resolution lift-off
Use of CSAR 62 for the manufacture of nanostructures on GaAs substrates
Utilising Electra 92 for SEM applications
Writing time
Black-Protect – stable protective coating for HF and KOH etchings
Improved protective coating SX AR-PC 5000/31
PMMA protective coating: reduction of cotton candy effect
Protective coating as spray resist for the smoothing of surfaces
Protective coating for KOH-etching
Protective coating to prevent mechanical damage
Safer solvent PMMA protective coating
SX AR-PC 5060 F-Protect (replacement for Cytop)
2L-Lift-off system AR-P 617 – AR-P 8100
Manufacture of undercut structures for T-gates in three-layer processes
Two-layer e-beam resist system with novolacs as bottom resist
Use of PPA in multilayer processes
Additional new experimental developers for AR-P 617
Adhesion promoter HMDS and diphenylsilanediol (AR 300-80)
Adhesive strength of AR 300-80
Ageing of developer
Alkaline developers for aluminium substrates
Alternatives for NMP-based removers
Aqueous-alkaline removers
Developer AR 300-35 for alkali-sensitive substrates
Developer for CSAR 62 (AR-P 6200)
Development cascade
Development procedures
Evaluation of various developers for e-beam exposed CSAR 62 layers (100 kV)
New AR 300-80 and contact angle measurement
New developer for AR-P 5320
New developers for AR-P 617
New developers for PMMAcoMA (AR-P 617, 50 kV)
New safer solvent remover AR 300-76
New solvent remover
Removers in general
Solvent removers
Solvents and workplace safety
Stopper
Thinner
Types of developers
Quality Promise
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Contact
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