Process Chemicals Archives - Allresist EN https://www.allresist.com/category/resist-wiki/resist-wiki-process-chemicals/ ALLRESIST GmbH - Strausberg, Germany Thu, 19 May 2022 11:04:37 +0000 en-GB hourly 1 https://wordpress.org/?v=6.5.2 New solvent remover https://www.allresist.com/new-solvent-remover/ Thu, 19 May 2022 11:04:03 +0000 https://www.allresist.com/?p=17363 A new strong solvent remover is able to solve resist layers tempered at room temperature. It is remarkable that the remover takes the same effect on novolak based as well as PMMA based resists and thus is suited for versatile applications. It must be pointed out, however, that the flash point of the remover is below 21 °C and therefore needs to be handled with care.

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New solvent remover

A new strong solvent remover AR 600-71 consisting of 1.3-dioxolane and 1-methoxy-2-propanol is able to solve resist layers tempered at room temperature. It is remarkable that the remover takes the same effect on novolak based as well as PMMA based resists and thus is suited for versatile applications. It must be pointed out, however, that the flash point of the remover is below 21 °C and therefore needs to be handled with care.

Overview Remover



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]]> Aqueous-alkaline removers https://www.allresist.com/aqueous-alkaline-removers/ Mon, 25 Apr 2022 08:49:55 +0000 https://www.allresist.com/?p=17102 The simplest but nevertheless highly effective removers are sodium hydroxide (NaOH) and potassium hydroxide (KOH) solutions. Already a 4 % KOH solution will remove basically all novolac-based photo- and e-beam resists within a few seconds.

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Aqueous-alkaline removers

The simplest but nevertheless highly effective removers are sodium hydroxide (NaOH) and potassium hydroxide (KOH) solutions. Already a 4 % KOH solution will remove basically all novolac-based photo- and e-beam resists within a few seconds. Exceptions are only resists particularly designed as alkali-stable resists (see Alkali-stabile and solvent-stable negative resist). Increasing the concentration of NaOH or KOH up to 40 % is possible. These strongly alkaline solutions are also suitable for difficult, particularly hard-baked resist films. Alkaline solutions are often not able to remove resist residuals entirely, but will in this case creep under the film. Residuals are then more or less lifted and subsequently completely removed. It should however be taken into account that highly concentrated alkaline solutions may also attack the silicon of the wafer and thus destroy the surface. An alternative to the above-mentioned alkaline solutions is the concentrated developer AR 300-26 which is based on buffered alkaline salts. The undiluted developer will also quickly remove most resist films.

Tetramethyl ammonium hydroxide (TMAH) solutions are also used as remover, with a maximum concentration of 25 %. At this concentration, TMAH is comparable with highly concentrated NaOH- and KOH-solutions. TMAH will also attack silicon and caution is likewise required during usage. The fourfold less concentrated TMAH-based remover AR 300-73 is considerably easier (i.e. safer) to be handled and also more environmentally friendly due to the lower consumption of TMAH. Aqueous-alkaline removers are not suitable for all polymers (PMMA, polystyrene, carbon hydrogens). This feature however can be specifically used in two-layer systems (PMMA/photoresist; carbon hydrogens/photoresist) for a selective development of the upper photoresist layer.

Overview Remover



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]]> Types of developers https://www.allresist.com/types-of-developers/ Thu, 14 Apr 2022 10:05:02 +0000 https://www.allresist.com/?p=17080 There are two main groups of developers: solvent-based and aqueous-alkaline developers. The solvent-based ones are intended mainly for PMMA e-beam resists, for CSAR 62 and also for special polymer based products. In this process, solvents such as methylisobutylketone (MIBK), IPA (partly with water) for PMMA, amyl acetate, MIBK, DEK, DEM, xylol for CSAR 62 and ethylbenzene as well as hexane are used for the protective coating.

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Types of developers

There are two main groups of developers: solvent-based and aqueous-alkaline developers. The solvent-based ones are intended mainly for PMMA e-beam resists (→ see process procedure e-beam resists), for CSAR 62 (→ CSAR 62 developers) and also for special polymer based products (e.g. SX AR-N 4800/16 (PMMA)) and accordingly SX AR-PC 5000/40 (KOH and HF protective coating). In this process, solvents such as methylisobutylketone (MIBK), IPA (partly with water) for PMMA, amyl acetate, MIBK, DEK, DEM, xylol for CSAR 62 and ethylbenzene as well as hexane are used for the protective coating.

Aqueous-alkaline developers are divided into metal ion free (MIF) and anorganic metal salts. MIF developers contain tetramethylammonium hydroxide (TMAH) as active component. The commercial 25 % solution is diluted  to 2,38 % for the production of a 0,26 n solution (n = normality) verdünnt. This is the standard concentration used for developing most resists worldwide. For some resists, however, particularly Allresist resists, developers with lower concentration are necessary. In this case, the normality of  less than 0,26 n is adjusted down to 0,1 n. The 0,1 n developers are the thinnest recommended solutions, because due to the low TMAH concentration, small amounts of CO2 from the air are sufficient to change the normality in a few hours. For a better wetting, MIF developers contain tensides which optimize the surface tension.

The developers based on metal salts consist of metasilicates, phosphates, borates, caustic soda (NaOH) and caustic potash (KOH). The monovalent salts NaOH and KOH are very strong developers, they develop speedily and are used for high coating thickness. The disadvantages are a possible attack on the unexposed areas (dark erosion) and a low contrast.

Due to their polyvalency, the polyvalent silicates, phosphates and borates act as buffer systems. Thus, a gentler development is possible, there is virtually no dark erosion at the recommended concentrations. With regard to service life, they are more efficient than die MIF developers and can be diluted more easily and accordingly more precisely. Unlike TMAH developers, their development strength barely reacts to slight deviations of the concentration. Nonetheless, the use of a scale is recommended for all diluted developers if possible. Due to the higher accuracy when subject to a scale or beaker (volume measurements are, in addition, dependent on temperature) an optimum development result is ensured.

Overview Developer



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]]> Solvents and workplace safety https://www.allresist.com/solvents-and-workplace-safety/ Thu, 14 Apr 2022 08:21:27 +0000 https://www.allresist.com/?p=17073 All resists we offer as well as a large number of process chemicals contain organic solvents. When handling these products, provisions of the Ordinance on Hazardous Substances are to be complied with. The safety data sheets of our products are intended to provide required data and handling recommendations for the user to take effective measures for health protection, workplace safety and environmental protection.

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Solvents and workplace safety

All resists we offer as well as a large number of process chemicals contain organic solvents. When handling these products, provisions of the Ordinance on Hazardous Substances are to be complied with. The safety data sheets of our products are intended to provide required data and handling recommendations for the user to take effective measures for health protection, workplace safety and environmental protection.

The most important criterion for the rating and classification as hazardous substance is the flashpoint. The flashpoint is the lowest temperature at which under previousl y described experimental conditions at normal pressure a substance may give rise to an ignitable air-gas mixture formed above this substance.

The ignition temperature is the minimum temperature to which a substance has to be heated to spontaneously ignite in the presence of air without any external source of ignition, i.e. a flame or a spark, solely as the result of being heated. The ignition temperature does not correlate with the boiling point or the flash point of a flammable substance. The ignition temperature is a measure for the sensitivity to oxidation of a substance and exceeds for most organic solvents a temperature of 200°C.

The flammable range is the concentration at which combustible gases, mist or vapours will form a flammable mixture with air. The flammable range is defined by the explosion limits, i.e. the lower and upper limit concentration at which a mixture can be ignited by heating.

Selected properties of solvents:

Lösemittel

Siedepunkt

Flammpunkt

untere Explosionsgrenze

obere Explosionsgrenze

Zündtemp.

[°C]

[°C]

[Vol.%]

[Vol.%]

[°C]

Aceton

56

-18

2,5

13

540

i-Propanol

82,4

12

2

12

425

PGMEA

146

42

1,5

7

314

NEP

212,5

91

1,3

7,7

245

When handling organic solvents, the respective working place limit strictly has to be observed which is defined according to the German Ordinance on Hazardous Substances as the the li mit of the time-weighted average concentration of a substance in the air within the breathing zone of a worker in relation to a specified reference period. This value indicates the concentration of a substance up to which no acute or chronic harmful effects on the workers’ health in general are to be expected.

Overview Process Chemicals- Thinner



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]]> Solvent removers https://www.allresist.com/solvent-remover/ Thu, 14 Apr 2022 08:05:25 +0000 https://www.allresist.com/?p=17069 The classical remover is acetone which is, together with isopropanol, used as cleaning agent in probably every lab worldwide. The dissolving power of acetone for non- or only low-baked films (up to 120 °C) is excellent.

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Solvent removers

The classical remover is acetone which is, together with isopropanol, used as cleaning agent in probably every lab worldwide. The dissolving power of acetone for non- or only low-baked films (up to 120 °C) is excellent. Care must however be taken with respect to the low boiling point (56 °C) and a flashpoint of only -20 °C. Under unfortunate circumstances, already electrostatic charge may cause an explosion. This problem does not occur with NEP (N-ethyl pyrrolidone) or NMP. Both removers have a boiling point of more than 200 °C. The dissolving power is comparable to the power of acetone and may be further enhanced by heating to max. 80 °C (which is harmless with respect to safety concerns, but at this temperature disturbing vapors begin to develop). In principle also other solvents are suitable as removers: IPA, PGMEA (PMA), methyl ethyl ketone (MEK) or thinners (see Thinners) dissolve residuals of not too hard-baked resists. In most cases however considerably more time will be needed if these solvents are used. Solvent removers are equally suitable for novolac-based resists as well as for all polymer resists (e.g. PMMA).

Overview Remover



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]]> Development cascade https://www.allresist.com/resist-wiki-development-cascade-2/ Tue, 11 Jul 2017 15:14:56 +0000 https://www.allresist.de/?p=6477 The use of a cascade is recommended for optimum performance of the developer and for the highest cleanliness during immersion development. The development often takes place in only one container.

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Development cascade

The use of a cascade is recommended for optimum performance of the developer and for the highest cleanliness during immersion development. The development often takes place in only one container. Exposed resist areas are completely dissolved, remain in the developer and thus also consume the developer successively. If the developed wafers usually present in one carrier are rinsed with DI water, the solids of the contaminated developer residues may precipitate and slightly pollute the wafer surface. Even though effect can be prevented by intense rinsing with water, a cascade should be used to be on the safe side.

For this purpose, two or even three developer containers are placed in a row. In the first container, wafers are fully developed. After completion of the development, the wafers are immersed briefly in the fresh developer of the second container (5 seconds). The process can then be completed with a third bath. The subsequent rinse is carried out in DI water. Contaminations are excluded with this development regime.

If the developer is consumed in the first bath (see “Developer ageing”), it is replaced by a second container, and, if necessary, the third container is used to replace the second one. By this process, the developer is optimally exploited and the highest cleanliness is obtained.

Overview Developer



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]]> New AR 300-80 and contact angle measurement https://www.allresist.com/resist-wiki-new-ar-300-80-and-contact-angle-measurement/ Tue, 11 Jul 2017 15:07:14 +0000 https://www.allresist.de/?p=6465 In addition to the established adhesion promoter AR 300-80 (which is based on diphenylsilanediol), also other silicone-containing compounds may be used to render hydrophilic surfaces more hydrophobic.

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New AR 300-80 and contact angle measurement

In addition to the established adhesion promoter AR 300-80 (which is based on diphenylsilanediol), also other silicone-containing compounds may be used to render hydrophilic surfaces more hydrophobic. Prerequisite for this to occur is that the silanes used for this purpose possess one or two reactive leaving groups which are able to react with the surface.

Reactive groups are for example chlorides, alcoholates or hydroxy groups, so that HCl, the free alcohols, or water are formed during the condensation reaction. Reactive groups however show marked differences with respect to their reactivity.

It is generally recommended to thoroughly clean all substrates before use. Frequently, just intensive rinsing with acetone and DI water is sufficient for this purpose. For more strongly contaminated surfaces, the use of O2 plasma, hot basic or acidic piranha solution is required. The subsequent thorough rinse with DI water is mandatory. Any direct contact of acidic piranha solution with acetone must be avoided since explosive acetone peroxides may be formed!

Chlorosilanes generally react readily even far below room temperature with the substrate, thereby cleaving off HCl. Alcoholates of silanes react considerably more slowly with surfaces at temperatures not below 30 °C, but higher temperatures accelerate the condensation reaction. In contrast, hydroxy silanes require much higher temperatures, for example about 170 – 180 °C for AR 300-80. These high SB temperatures are however unfavourable for many substrates. The use of Si alcoholates with soft-bake temperatures in a range of only about 70 °C – 90 °C thus provides a very good alternative. And, in contrast to chlorosilanes, no corrosive HCl is released. It also became apparent that the new variant of our adhesion promoter AR 300-80new which is based on these Si alcoholates is equally suitable as adhesion promoter as the previous variant. The comparable good effectiveness of AR 300-80 (new) was evaluated in detail by means of contact angle measurements.

In the following, we will briefly present a contact angle measurement (according to the sessile droplet method), taking a paraffin surface with different solvents as an example.

Contact angle measurements fall into two categories, either static or dynamic measurements. If a static contact angle is used, the liquid droplet to be analysed is deposited on a surface of a solid. The droplet diameter should amount to 2 to 6 mm, since the measured contact angle is in this case independent of the diameter of the drop. Dynamic contact angles in contrast describe processes at a liquid-solid interface during wetting and de-wetting processes. In this case, the advancing (enlargement of the droplet volume) and the receding angle (reduction of the droplet volume) are determined and the contact angle hysteresis is evaluated.

Static contact angles can be determined using the tangent method. The entire profile of the lying drop is here adapted to a general conic section equation. The derivation of this equation at the base line yields the slope at the three-phase boundary and thus the contact angle.

Young equation (Source: Wikipedia)

σL = Surface tension of the liquid

σS = Surface tension of the solid

σLS = Interfacial energy between liquid and solid

ϴ = Contact angle

The following figures show video recordings of drops of different solvents on paraffin for the measurement of the static contact angle q. The individual images illustrate how drop shape and thus also the contact angle changes as a function of the surface properties of the solvent. The static contact angle is 109 ° for water, 88 ° for ethylene glycol, and becomes substantially smaller (37 °) for long-chain alcohols. The difference between the contact angle of water and ethylene glycol becomes clearly apparent in the different drop shape and thus a different wetting behavior (difference of about 20 °).

Water on paraffin, q = 109 °

Ethylene glycol on paraffin, q = 88 °

Octanol on paraffin, q = 37 °

Overview Process Chemicals- Adhesion Promoter



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]]> Additional new experimental developers for AR-P 617 https://www.allresist.com/resist-wiki-additional-new-experimental-developers-for-ar-p-617/ Thu, 29 Sep 2016 12:15:33 +0000 https://www.allresist.de?p=6164 For some applications are universal developers of advantage, i.e. developers which are simultaneously well suited for a variety of resist families. Multilayer systems can in this case be developed in one step, and no change of the developer in between is required.

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Additional new experimental developers for AR-P 617

For some applications are universal developers of advantage, i.e. developers which are simultaneously well suited for a variety of resist families. Multilayer systems can in this case be developed in one step, and no change of the developer in between is required.

ar-p617_schichtdicke_1um_3

AR-P 617, film thickness: ~1 µm, SB 10 minutes at 200 °C, 50 kV, dose variations, dependence of the sensitivity on the developer system and the development time at 21.5°; stopper: IPA.

Experimental special developer X AR 600-50/4 is equally suited for the development of AR-P 617, CSAR 62, and 950K PMMA and can thus be used as universal developer for two- or three-layer processes (e.g. especially) for the manufacture of T-gates. The sensitivity is again adjusted via changing the development time. The dark erosion, offering advantages for the generation of undercut structures, is moderate and well controllable. After three minutes of development time, the dose to clear is only about 30 µC/cm2. X AR 600-50/4 is significantly more sensitive in comparison to the standard developer AR 600-50 (dose to clear ~ 50 µC/cm2). The special developer X AR 600-50/3 is also significantly more sensitive than the standard developer AR 600-50; the dose to clear is about 36 µC/cm2. The occurring dark erosion of almost 10 % can be exploited to produce a particularly pronounced undercut. Especially in the case of an irradiation at 100 kV, the production of undercut structures is often difficult because the required electron backscattering (proximity effect) barely occurs. Even though developer X AR 600-50/3 not at all or only weakly develops irradiated areas, the production of lift-off structures is nevertheless easily possible (see right image):

2-lagensystem_ar-p617

Two-layer system AR-P 617 (bottom, SB 200 °C) / CSAR 62 (top, SB 180 °C), 100 kV, developer 1. AR 600-546 (CSAR 62) and 2. AR 600-50 for AR-P 617 (bottom layer, left) or X AR 600-50/3 (bottom layer, right). Source: Tine Greibe, DTU Danship, Denmark.

The experimental special developer X AR 600-55/1 is well suited for the development of both AR-P 617 and PMMA. This developer can thus be used as universal developer for two- or three-layer processes, especially e.g. for the fabrication of T-Gates. The sensitivity is again adjustable via the development time. Within a development time of 3 minutes, no significant dark erosion was observed. The forming of the undercut can thus easily be controlled via the exposure dose.

Overview Developer



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]]> New developers for PMMAcoMA (AR-P 617, 50 kV) https://www.allresist.com/resist-wiki-new-developers-for-pmmacoma-ar-p-617-50-kv/ Thu, 29 Sep 2016 12:00:00 +0000 https://www.allresist.de?p=6158 X AR 600-50/2 is a new, very sensitive and highly selective developer for AR-P 617. The dark erosion is very low even at longer development times. Layers of PMMA or CSAR 62 are not attacked, which is especially important for multi-layer processes.

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New developers for PMMAcoMA (AR-P 617, 50 kV)

X AR 600-50/2 is a new, very sensitive and highly selective developer for AR-P 617. The dark erosion is very low even at longer development times. Layers of PMMA or CSAR 62 are not attacked, which is especially important for multi-layer processes. The sensitivity can be well adjusted via the development time.

ar-p617_schichtdicke_1um

AR-P 617, Film thickness: ~1µm, SB 10 minutes at 200 °C, 50 kV, dose variations, dependence of the sensitivity on the development time in developer X AR 600-50/2 at room temperature, stopper: IPA.

At a development time of 60 s, the dose to clear is approx. 70 µC/cm2, after development for 3 minutes about 40 µC/cm2, after 6 minutes still 25 µC/cm2, and after 10 minutes only 20 µC/cm2! The dark erosion thus remains at moderate < 5%. Developer X AR 600-50/2 shows a pronounced temperature dependence.

ar-p617_schichtdicke_1um_2

AR-P 617, film thickness: ~1 µm, SB 10 minutes at 200 °C, 50 kV, dose variations, dependence of the sensitivity on the development temperature, development time: 3 minutes, stopper: IPA.

The sensitivity considerably increases with raising temperatures. The dose to clear is approximately 48 µC/cm2 at 19 °C, but just about 30 µC/cm2 at 23.5 °C. Enhancing the development temperature results in low dark erosion values of approximately 5 %.

Overview Developer



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]]> Evaluation of various developers for e-beam exposed CSAR 62 layers (100 kV) https://www.allresist.com/resist-wiki-evaluation-of-various-developers-for-e-beam-exposed-csar-62-layers-100-kv-2/ Thu, 29 Sep 2016 10:15:07 +0000 https://www.allresist.de?p=6139 To evaluate the suitability of various developers for CSAR 62, Dr. Lothar Hahn (Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology) kindly provided various substrates which had previously been exposed to 100 kV e-beam irradiation (dose variations).

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Evaluation of various developers for e-beam exposed CSAR 62 layers (100 kV)

To evaluate the suitability of various developers for CSAR 62, Dr. Lothar Hahn (Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology) kindly provided various substrates which had previously been exposed to 100 kV e-beam irradiation (dose variations). The substrates were developed for 60 s in different standard developers and other solvents (indicated is in each case only the main solvent as e.g. MIBK, but not minor additions of other solvents), developed, and the development was stopped in IPA. The layer thickness was scanned using a Dektak 150. If the measured layer thickness divided by the respective initial layer thickness (D/D0) is plotted against the radiation dose, characteristic gradation curves for each developer are obtained. The steeper the curve, the higher is the contrast of the developer used. Weaker, high-contrast developer cause no or only low dark erosion (development of unexposed areas). In the case of AR 600-546 (amyl acetate) and X AR 600-546/1 (hexyl acetate), an additional rinsing step for 10 s with pure MIBK was conducted after development prior to the stopping with IPA to ensure a complete, particle-free development.

dosisstaffel_fuer_csar-62

Dose variations for CSAR 62 (AR-P 6200); gradation curves of selected, high-contrast developers, SB 180 °C, film thickness: ~240 nm, 100 kV, development time 60 s each at 21.5 °C, stopper IPA.

Of all investigated high-contrast developers, MIBK turned out to be the strongest developer with a dose to clear of about 150 µC/cm2. The developers o-xylene and AR 600-546 (standard developer) yield comparable sensitivities of about 230 µC/cm2, whereby amyl acetate leads to a higher contrast than o-xylene. The solvents methyl trimethylacetate and octyl acetate also provide a high-contrast development, are however significantly less sensitive than the standard developer. Developer AR 600-55 which is generally used for PMMA films is not suitable for CSAR 62, since even at a dose of 600 µC/cm2 no complete development was observed.

Higher sensitivity values can generally be obtained if the development time is extended to 3 minutes. The contrast is in this case slightly reduced since the development process begins already at lower exposure doses (earlier onset).

dosisstaffel_fuer_csar-62_2

Dose variations for CSAR 62 (AR-P 6200); gradation curves of selected, high-contrast developers, SB 180°C, film thickness: ~240 nm, 100 kV, development times 60 s each at 21.5 °C, stopper IPA.

If strong developers are used for the development of CSAR 62, the resulting contrast is lower, but at the same time the sensitivity increases. The writing times can thus be reduced in particular for larger exposed areas, but a considerable amount of dark erosion has to be taken into account.

dosisstaffel_fuer_csar-62_3

Dose variations for CSAR 62 (AR-P 6200); gradation curves of selected strong developers (reference MIBK), SB 180 °C, film thickness: ~240 nm, 100 kV, development times 60 s each at 21.5 °C, stopper IPA.

AR 600-548 showed the highest sensitivity of 50 µC/cm2, and the dark erosion can substantially be reduced if shorter development times are chosen. The strong special developer X AR 300-12/21 (containing PGMEA) causes a lower dark erosion as compared to AR 600-548 and is approximately as sensitive as the standard developer AR 600-549 (dose to clear of about 125 µC/cm2). Also the ethylbenzene-based developer X AR 300-74/1 is well suited for a sensitive development of CSAR 62 (dose to clear < 125 µC/cm2). Generally are higher sensitivities observed if the development time is extended to 3 minutes; the dose to clear is significantly reduced.

dosisstaffel_fuer_csar-62_4

Dose variations for CSAR 62 (AR-P 6200); gradation curves of different strong developers, SB 180 °C, film thickness: ~240 nm, 100 kV, development times 60 s and 180 s in comparison (21.5 °C), stopper IPA.

If developer X AR 300-12/21 is used, a low dark erosion of about 5 % is observed at a development time of 3 minutes. The influence of the development time on the sensitivity was investigated in more detail for the standard developer AR 600-549.

dosisstaffel_fuer_csar-62_5

Dose variations for CSAR 62 (AR-P 6200); gradation curves for AR 600-549, SB 180 °C, film thickness: ~240 nm, 100 kV, development times 60 s – 360 s each at 21.5 °C, stopper IPA.

If the development time is extended from 1 minute to 6 minutes, the dose to clear can be reduced by more than half from 125 µC/cm2 to approximately 50 µC/cm2. Despite the very sensitive development, the dark erosion of about 7 % is comparatively moderate. Within 3 minutes of development time, no significant dark erosion occurs.

Especially in the case of thin resist layers, the process window is small if strong developers are used. Even only moderate dark erosion has a much greater impact in percentage terms when thin layers as compared to thicker layers are concerned. The dark erosion can be significantly reduced by lowering the developer temperature by a few degrees, as shown in the following for AR 600-548 as example.

dosisstaffel_fuer_csar-62_6

Dose variations for CSAR 62 (AR-P 6200); gradation curves for AR 600-548 in dependence on the developer temperature, SB 180 °C, film thickness: ~240 nm, 100 kV, stopper IPA.

While at room temperature a dark erosion of just below 15 % is observed within 60 s, this rate is reduced to only 5 % if the development step is carried out at 15 °C. At the same time, the dose to clear is reduced from 50 µC/cm2 to approximately 75 µC/cm2, and the contrast increases slightly.

Overview Process chemicals



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