Acetone is good for removing substance that is greasy or oily for example wax on the surface of a silicon substrate or silicon dioxide (glass) substrate or a marker pen ink.

IPA (Isopropanol Alcohol) on the other hand, is good for removing particles.

To wash silicon or silicon dioxide substrate, as I work in a wafer fab, in our lab, we use DI (Deionised) water, as DI water has all or almost all of the ions removed from the water. This will prevent ionic contamination that may affect the proper operation of a transistor. Normal tap water usually contains a certain amount of ions that can cause ionic contamination. When you say water affect the dielectric layer (Ta2O5) what kind of effects do you observe? Ionic contamination, surface damage or what else? It would help if you describe the problem more precisely.

I hope my suggestion helps.

Glass is hydrophylic, so most hydrophylic solvent will do a good job washing it, e.g. methanol, ethanol, propanol....................

Acetone is good for removing substance that is greasy or oily for example wax on the surface of a silicon substrate or silicon dioxide (glass) substrate or a marker pen ink.

IPA (Isopropanol Alcohol) on the other hand, is good for removing particles.

To wash silicon or silicon dioxide substrate, as I work in a wafer fab, in our lab, we use DI (Deionised) water, as DI water has all or almost all of the ions removed from the water. This will prevent ionic contamination that may affect the proper operation of a transistor. Normal tap water usually contains a certain amount of ions that can cause ionic contamination. When you say water affect the dielectric layer (Ta2O5) what kind of effects do you observe? Ionic contamination, surface damage or what else? It would help if you describe the problem more precisely.

I hope my suggestion helps.

Hi ,try ethanol, propanol. also tell me what kind of problem you have faced during water cleaning?

If you don't want to use water, you can use ultrasonic cleaning using Acetone followed by Methanol or Ethanol. For good adhesion on glass you can do preheating of glass in vacuum up to 2 hour with slowly increase in temperature.

For more information go through the paper attached here.

May I know what do you mean by Pure Water?

What is your definition of Pure Water?

Are you talking about water that is 100% without impurities (consisting of only H2 and O?

Or are you talking about water that has gone through a Purification process?

Or are you talking about water that is very close to the neutral pH level of 7?

pH value of normal tap water we use daily is slightly alkaline at a vallue of about

7 to 8.

In the real natural world, you cannot get water that is 100% without impurities.

If you are talking about 90% to 99% without impurities, there is still a possibility.

Thanks.

For your info, the water we drink every day is NOT water without any impurities.

Usually, it contains small amounts of minerals and some other impurities beneficial for our health.

Drinking water totally without any impurities is actually NOT so beneficial for our health.

That is why some people prefer to drink mineral water.

However, too much minerals is also bad for our health.

Thanks to all for providing useful information.

I wash glass substrate first by Acetone and than using Purified water deionized (DI) water by ultrasonically and than using air Gun i dry the glass substrate.

I use Tantalum as gate electrode having resistance of 100-200 Ω . on tantalum i use Ta2O5 as dielectric.after creating contact hole for gate the resistance i checked is same around 100-200 Ω but after 2 days i checked the resistance goes on increasing upto 20KΩ . The substrate with out Ta2O5 dielectric layer the resistance remain same for many days.After etching Ta2O5 i wash the substrate with acetone and last by Purified water. some one told me that may be water is the reason. but i don't think that water cause any problem for resistance. if any body have any information regarding this please tell me. my transistor not operating because of high gate resistance......

Hi, i think that you should wash with the pure water at first then use the acetone,and instead of pure water you can use ethanol,propanol.

Ultrasonic cleaning with heat is the better way to clean the glass substrate.....U can use acetone followed by methenol for cleaning. If heating option is available then heat during the cleaning.....

If you use Ultrasonic cleaning or Megasonic cleaning, you have to be very careful and control the temperature, the sonic frequency, the power generated, and duration very well, otherwise surface damages may be induced relatively easily.

At high temperature, if the temperature exceeds a certain limit, surface damages start to appear. If you don't believe, you can try to boil a material, and check the surface before and after boiling.

Higher temperature means higher chance of surface damage.

If the Ultrasonic (kHz) or Megasonic (MHz) cleaner generates more power (with more power consumption), this implies that the sonic force will also be greater.

Thus, the chance of surface damage will be greater also.

The same goes for frequency. Higher frequency means larger power, thus larger sonic force, and more chance for surface damage.

As Megasonic cleaners have higher frequency and larger power consumption, chances of surface damage will be definitely higher than that of an Ultrasonic cleaner.

Lastly, the duration of cleaning also matters.

Longer duration also means longer exposure to heat and the sonic force, and thus a higher chance of surface damage.

However, if the duration is too short, the surface may not be clean enough.

So, trial and error should be done to determine the optimized timing, temperature, frequency and power to use for Ultrasonic cleaning.

Hope this helps, if you want to consider Ultrasonic Cleaning.

Hi Mir,

It is still all right to do Ultrasonic cleaning if you know what is your acceptable level of surface damage. You may have to determine what is your acceptance criteria.

You may have to answer to yourself questions like:

1) Is a rough surface (usually due to some surface damage) acceptable to my application

2) Is a bit of roughness acceptable? How many percent (%) of damage is acceptable?

3) Do I need a surface that is extremely smooth (totally without any surface damage) and totally clean at the same time? This is usually the ideal case, but may be very difficult to achieve in practical situation.

4) Is my application extremely critical? How clean must it be?

5) Can I afford to use extremely costly and extremely purified water?

6) Would a less-costly deionized water be good enough for my application?

Thanks.

Hi Mir,

Please kindly take note that Deionized Water and Purified Water can mean two totally different type of water.

Deionized water, as its name implies, have almost all of its ions removed.

Purified water, on the other hand, MAY or MAY NOT be deionized.

The Deionization process, normally used in industry, is the ion-exchange method.

Here, filtered tap water is allowed to flow through a mixed-bed column of resins.

Ion-exchange happens between the resins and water and unwanted ions becomes attached to the resins and are thus removed from the water.

Then, this deionized water is flowed through a few more filters to get rid of further sediments and particles which may exists in the resins before it is released for use in the laboratories.

Depending on the needs of your application and purpose, and how purified is the water you need and the size of the purification plant, your purified water MAY or MAY NOT have gone through all of the following processes:

1) Pre-treatment to get rid of large debris and pre-chlorination to prevent the growth of fouling organisms.

2) pH adjustment to adjust the pH value of water to be as close to the value of 7 (neutral) as much as possible.

3) Coagulation and Flocculation that involves the addition of chemicals to assist in the removal of particles suspended in water. This particles may be organic or inorganic.

4) Sedimentation to allow the floc to settle to the bottom of the basin.

5) Sludge (due to settlement of particles) storage and removal. Most critical and expensive step.

6) Dissolved Air Flotation (DAF): Air bubbles attach to floc creating a floating mass of concentrated floc which is removed and the water withdrawn from the bottom of the DAF tank.

7) Filtration: Rapid Sand Filters and Slow Sand Filters.

8) Membrane Filtration: Filter all particles > 0.2um. Filtration for drinking water and sewage.

9) Deionization - removal of ions.

10) Disinfection to kill pathogens:

a) Chorine Dioxide disinfection

b) Chloramine disinfection

c) Ozone disinfection

d) Ultraviolet disinfection

e) various portable methods of disinfection

f) Solar water disinfection.

11) Additional treatment options:

a) Water Fluoridation

b) Plumbosolvency

c) Radium removal

d) Fluoride Removal

12) Other Water Purification Techniques:

a) Boiling to kill micro-organisms.

b) Granulated Activated Carbon Filtering to absorb toxic compounds.

c) Distillation - can produce 99.9% pure water.

However, it does not produce 100% pure water due to contaminants with

similar boiling points and droplets of unvapourised liquid carried with the

steam.

d) Reverse Osmosis; Theoretically, the most thorough method of large scale

water purification, but perfect semi-permeable membranes are difficult to

create and maintain. Algae and other life-forms can colonise the

membranes.

e) Use of Iron to remove Arsenic from water - prevent Arsenic poisoning.

f) Direct Contact Membrane Distilation (DCMD).

g) Desalination - to remove the salt from water especially for sea water.

h) Gas Hydrate Crystals Centrifuge Method - Water released from hydrate

crystals by heating.

i) In Situ Chemical Oxidation - to destroy chemical contaminants.

So, you can clearly see that purification of water is definitely a much thorough and much more expensive process, but it does NOT imply that the water is definitely De-ionized.

For purified water, you will NOT know whether it is deionized or not unless you measure its resistivity.

If the resistivity is very high in the range of 16 to 18Mohms.cm, most probably, it has been deionized.

If the resistivity is much lower, then, definitely it is not de-ionized.

I hope these are useful information.

Sorry for the long answer.

Thanks.

A word of caution about Distilled Water and Reverse Osmosis (RO) water.

Distillation removes all minerals from the water.

The Reverse Osmosis (RO) and nanofiltration methods using membrane removes most to all minerals.

So, the product of both methods is demineralized water.

Note that Demineralized water is NOT ideal drinking water.

Studies done by WHO (World Health Organization), have shown that demineralized water increases diuresis (fluid loss) and the elimination of electrolytes, with decreased blood serum potassium concentration.

Electrolytes (from salt) are essential for normal human heart and circulation function.Too little electrolytes in our body or too rapid a loss of electrolytes can be fatal.

Demineralization also increases our risk from toxic metals that can be leeched from metal pipings like lead and cadmium which is normally prevented by minerals such as calcium and magnesium.

Cases have been reported of lead poisoning in infants due to the use of low-mineral water.

Normal tap water (non-distilled, non RO) does not have this problem and has all the necessary small amounts of minerals we need.

Recommendations for magnesium is a minimum of 10mg/L with an optimum level of 20 to 30mg/L.

Recommendations for calcium is a minimum of 20mg/L with an optimum level of 40 to 80mg/L.

It is also recommended that we have a total water hardness (adding magnesium and calcium) of 2 to 4 mmol/L for drinking water.

More magnesium and calcium means more water hardness.

However, be cautioned that at a water hardness of above 5mmol/L,

higher incidence of gallstones, kidney stones, urinary stones, arthrosis and arthropathies have been observed.

Therefore, this shows that too much minerals is BAD also.

This proves the saying that "Too much of anything is NOT Good!"

Thus, our common sense still prevails.

Hope this is good general knowledge for everyone.

Thank you very much.

Hi Mir,

When you heat a structure, the heat always reaches the surface of the structure first. Then this heat is slowly propagated towards the centre of the structure, causing changes to the internal structure.

So, any damage on the structure due to heat, usually starts from the surface.

This is called surface damage due to heat.

This type of heat propagation is called: "Heat by Conduction".

I believe this is common knowledge from our Secondary School days.

I mention this just to refresh our memories.

Thanks.

Hi Mir,

As much as possible, we should try our best NOT to heat up something unless really necessary or unless we want to do it to intentionally modify the surface: for example in RTA (Rapid Thermal Annealing) where we want to re-crystallize the surface and activate the dopants.

Even for RTA it is done for a very short period of time (may be 4 to 5 secs) although the temperature can be as high as 1000degC.

Heating will tend to change or damage the structure of the material we are heating, whereas cooling a material tends to allow it to maintain its structure.

This is one of the reason why superconductivity works very well at extremely low temperature.

Research has been carried out to make superconductivity feasible at room temperature with some promising results. However, it may take at least a few more years before this can be realized for real electronic devices which we can use in our everyday lives.

Superconductivity will mean hardly any resistance drop as current flows through a circuit which also means signals and data can travel at superb speed.

This may mean extremely fast microprocessors and computers in the near future.

Something we can only dream about previously looks so real and achievable nowadays all thanks to science, research and technology development.

Science really revolutionize mankind.

We may be leading a very different kind of life 10 years down the road.

Our children will be reaping the benefits of inventions in the near future.

May all our dreams come true!

I work on X-ray mirrors made of thin glass foils, and of course we are scared of surface roughness, including impurities and dust. We usually wash the glass with amberclean solution and rinse with tap water. But, before the glass dries out, we rinse it again in bi-distilled water to remove any trace of mineral salts. Finally, we dry the glass with a purified nitrogen flow. We prefer to avoid acetone because it may leave a residue.

Hope this helps.

Yes. It is always advisable to wash wash with the pure water followed by Ultrasonic cleaning.

We usually use isopropanol after acetone

Normally we use pure water after acetone followed by ultrasonic cleaning.

Hi,

I've just read your question, and I think this might help you.

In the liquid phase deposition (LPD) process for making metal oxide thin film on glass substrate, we usually use an alkaline solution made of 30 g Na4SiO4 and 10 g NaOH in 1 L water to clean up the surface of the glass substrate before dipping into the LPD reaction solution.

Once your alkaline solution is prepared,

- heat it up to 80oC,

- then immerse your glass substrate for 3 min.

- After that, remove the substrate and wash it with the tap water for 10 min,

- then use ultrasonic for 5 min,

- and again tap water for 10 min.

- Finally, use deionized water or ion exchange water to rinse the substrate.

You are done.

You may keep your alkaline solution for a while and reuse it as many time as you want. It lasts for several months. We have been using this technique for at least 2 decades.

Good luck

@alexis beleke how could one use tap water as it contains lots of ions,impurity, ??

@urmila... Plese check my above comments . I explained completely there

@Alexis thanks. but i think using tap water is not goood . it contain lot of impurites

@mir, hmm i i did not see it before. I see it now, piau ke kuch ans thik the par kuch to out of topic lage

@mir, Sach me,ans ke siva sub kuch likh dala he usne, vese kuch chiz achi thi jese unnecessary heat mat karo, Surface ko effect hoga, Rapid thermal annealing karo.

If you are concerned about residual water on the surface, you may want to consider using an IPA rinse after the water. IPA is typically used in hi-vac systems to aid in surface water removal.

Hi Mir and Urmila,

I think one of the reason Alexis is able to use tap water is that in the end he finally rinse the substrate with Deionized (DI) water.

As Deionized water is literally void of ions, when you use it to rinse a material, it will tend to attract the ions that are located on the material.

So, in a way, washing a material with DI water also removes the ions on the material.

But the only problem is that since it was previously rinsed with tap water which may contain ionic impurities, more ions may be added to the material that may already have unwanted ions by itself due to the fabrication process.

Therefore, by doing a final rinse with DI water, the question is whether all the unwanted ions can be removed effectively? Will there be anymore stubborn unwanted ions left on the material, since more unwanted ionic impurities may have been added previously by the use of tap water.

How well the DI water can attract all the unwanted ions from the substrate is something that is quite subjective unless there is a way to measure it.

This may also depends on how deionized the DI water is in the first place.

A higher resistivity means the water is more deionized and a lower resistivity means less deionized.

A more deionized water will be able to attract more unwanted ions from a material or substrate or anything that it comes in contact with.

I hope this is useful information.

Thanks.

Hi everyone,

In fact, we use double ion exchange water for rinsing the glass substrate at the end of the cleaning process. The most effective step is the cleaning with the alkaline solution. As I wrote before, we have been using this cleaning technique for decades and our films never suffered for any impurity nor adhesion problem.

But if you have enough ion exchange water to use for cleaning, I think there is no problem with that.

It's just a suggestion.

@Alexis thanks for ur useful suggestion . i will try that method..

@Mir. You are right. Some parts of what I wrote on the purification of water is copied and pasted from Wikipedia. But it is done to show you that there can be a great difference between Purified water and DI (Deionized) water.

I am very clear about how a De-ionizer works, as I was previously in-charge of a De-ionizer at a semiconductor company.

I think it would be better if all conversations are in English so that everyone can understand, otherwise people may think you are hiding something and writing bad things about them. As we are sharing things here, we should be hiding things.

If you have something personal to write, perhaps it is better to send personal messages.

Sorry. I mean we should not be hiding things.