Silicon Wafers for Spin Coating

university wafer substrates

What Silicon Wafer Should I use for Sping Coating?

University Researcher:

I have received the order of silicon wafer #478. I use the silicon wafers for spin coating and they works well. The silicon wafer is easy to be cut into smaller pieces and suitable for being coated with ultrathin film upon it. Thanks for your products and your nice help :) !

Buy Item #478 for Spin Coating!

The Spin coating process uniformly deposits thin layers on a substrate, such as silicon wafers, flat surface. Normally, a small amount of coating material is applied to the middle of the substrate, which rotates at low speed and does not rotate at all. The substrate is then rotated with centrifugal force distributed by the coating materials and rotation continues until the liquid turns around the edges of a substrate or reaches the desired thickness of the film.

So, what wafer spec should a researcher use for their spin coating?

A scientist asked us the following:

Could I have a quotation for the following please? - 10 boxes of 25 4-inch Si wafers, basic quality (for spin coating, but not electronics), 500µm thick and 1mm thick (both please) doping not important, orientation not important. 

Researchers have used the following inexpensive but high-quality substrate.

Si Item #452
100mm P(100) 0-100 ohm-cm SSP 500um Test Grade

Get Your Quote FAST!


Spin Coating Explained!

Video: Spin Coating meaning, definition, explanation

Important Spin Coating Terms

  • film coatings
  • polymer solutions
  • force microscopy
  • casting solvents
  • nanoscale stretching
  • solvent viscosity
  • surface treatmen
  • spin coating
  • solvent molecules
  • surface properties 
  • cofacial polymer
  • polymer concentration
  • polymer films
  • surface effects
  • solution viscosity    

Video: Learn About Spin Coating

How University Researchers Use Spin Coating

Phd candidate requested the following quote:

"I am using your wafers as a substrate to make a nanoimprint sample in UCSD's clean room facility.I do have a question for you. I wanted to confirm with you: The product I ordered should be clean wafers, right? In other words, are the wafers contaminated with any oil, particles, etc? Or are they clean fused silica? Is it necessary for me to do some sort of cleaning procedure prior to spin coating a PMMA layer?"

Please reference #45334 for the answer.

"We are interested in Si wafer n+Si/SiO2 with 300 nm thick SiO2 in 4 inch diameter.  Actually we would like to use the wafer as substrate for bottom gate top contact (BGTC) field-effect transistor fabrication. So do you have any recommendation?

My plan is making a field-effect transistor: spin coating a solution of conjugated polymer onto wafer first, then deposit gold onto the wafer by thermal evaporating. So the gold work as electrode.

Could you please provide us a quote for 10 pieces of 2373?"

Please reference #213688 for specs and pricing.

Substrates Used for Spin-Coating PDMS Layer

A Phd candidate requested the following quote:

"I would like to purchase 30mm diameter silicon wafers with one side polished. I want it undoped, and I am not picky about the orientation.  These will be used for spin-coating a PDMS layer on. I would like to order about 50 of them if possible.

Here are some more specs I would like if possible:

Diameter: 30mm
Type: Silicon Wafer
Doping: Undoped
Resistivity: 1-100 ohm/cm
Thickness: 500-550 micron
Polish: SSP
Quantity: 50

Everything else I don't care much about. These wafers are going to be used to spin coat PDMS."

Please reference #222076 for specs and pricing.

2 Inch Silicon Wafers for Neutron Reflectivity Experiments

"I'm after some 2" wafers, at least 675 um thick, ideally 1 mm thick, SSP, bare (no thermal oxide). Doping type and level not important though would prefer not Boron doped if possible. Polishing quality and flatness most important consideration as they will be used for neutron reflectivity experiments. Looking to purchase 25 or 50 wafers depending on price.

I looked on your website but you don’t seem to have any 2” Si wafers available thicker than 500 um. One concern is flatness - < 5 nm seems a bit high? These are for neutron reflectivity experiments so need to be as flat as possible. The need for 1 mm wafers is to prevent bowing during spin-coating of the polymer layer on top that we wish to interrogate. Our remaining issue is regarding flatness. We need an RMS roughness of < 5 Å but don’t know how this compares to your quoted flatness figure.

Is this something you can help with?"

UniversityWafer, Inc. Replied with Specs/Pricing

The offered Monocrystalline Silicon wafers are polished by the Semiconductor Industry Standard CMP (Chemical-Mechanical Planerization) process than normally yields Surface Roughness <1.0nm rms as measured by AFB/AFM. However this measurement is only done occasionally and it is not a standard QC measurement done on each batch of wafers, and so it is not reported in the Certificate of Conformance.

Reference #220131 for specs/pricing.

Gallium Nitride (GaN) Substrates for the Deposition of Nanostructures Precursors

A researcher from an international university requested the following quote:

What we need is one wafer of GaN substrate (diameter 2"). We need it to use it as a substrate for the deposition of nanostructures precursors on the substrate using the spin coating.
We need only one wafer. How much will it cost? Would you please send me a quotation?"

Reference #223914 for specs/pricing.

Removing Native Oxide on Silicon Substrates for Spin Coating

I want to coat them using a spin coater in my lab using. But to avoid an oxide layer, I would like the native oxide layer removed. I guess I need to know how fast does an oxide layer grow if they are kept at room temp? The wafer sizes are to be 1" - 2" dia. and n-type.

UniversityWafer, Inc. Replied:

"Silicon wafers after polishing do acquire a "Native Oxide" layer, perhaps one or two atoms thick within about 2 or 3 days. However, this layer is so thin that it does not affect uses of silicon wafers and does not interfere with spin-coating The only way it is noticed is that the wafer surface after SC1, SC2 cleaning is hydrophobic and after 2 or 3 days it turns hydrophylic. The way to restore it to hydrophobic condition is to rinse the wafers in dilute HF acid, dry them (in dry nitrogen or in dry air), and use them right away. We cannot pack and deliver wafers by a commercial carrier and guarantee that their surface will be hydrophobic.

You can buy semiconductor grade HF acid from any Laboratory Supply firm. However, HF is a dangerous chemical and you must use in accordance with good laboratory practice. We do use HF acid at our facility, but we cannot sell and ship it to you.

As we wrote, we do keep silicon wafers for years after polishing without other than "Native Oxide" forming, and such wafers remain excellent for electronic purposes and for spin-coating of photo-resist or other chemicals."

Reference #226164 for specs and pricing.

Helping Researchers Solve Their Spin Coating Problems

A Physics Researcher had a problem.

"I purchased low cost mechanical grade Si Wafer great for spin coating from another company. When measuring GISAXS on blank untreated wafer we do no not observe typical reflections which are well known for blank Si wafer with native oxide. Instead, we see an electron density difference on the 10- 100 nm length scale - i.e. not atomic structure, but an overlayer on the substrate of something else with nm periodicity. Could it be that the wafers are contaminated with some inorganic salt giving rise to unusual reflections? What type of contaminations are to be expected on as received wafers? Do you recommend to clean wafers prior to their use with Piranha or anything similar?"

UniversityWafer, Inc. Replied:

"You need a higher quality Substrates of test grade or even better prime grade. Send us the diameter, and other specs for a quote."

Reference #45258163 for specs/pricing.

How We Help Lab Managers With Substrates Needed for Volume Processing

An Asian university lab manager needed help sourcing high-quality, low cost silicon wafers for their many processes.

We want to use this wafers for chamber cleaning process and possibly buy 200 wafers where backside roughness matters.

Silicon 100mm N/P <100>, FZ 4.4-5.6 ohm-cm, 725um SSP MECH Grade, WITH: 530nm LPCVD TEOS Oxide.

Could you supply full specification like backside roughness, TTV & bending etc.,

"We have huge amount of wafer required for dummy process runs.

  1. Reactive Ion Etching systems
  2. Photoresist Spin coating & Lithography process
  3. Reactive Ion Etching Units : If we do one hour etching process then we perform one hour cleaning process, first one being the actual and later is the dummy process which does not require the prime wafer. but The wafer is cooled by Helium & Helium leak should be minimal and this depends upon the wafer backside surface roughness 2. We stick GaN & GaAs wafer pieces to the full wafer and do the sniping o photo-resist and Lithography.

Here we required less bending the wafer to get good Lithography patterns

Both of the above process requires TTV & Bow close to the prime wafers. Plz suggest which are the best wafers ( Test or Mech grade) and optimized price I joined as Lab Manager recently here: Our lab uses around 600-800 silicon wafers per year and future purchase we would like to contact you."

Please reference #246095 for specs and pricing.

Silicon Wafers Used as Masters for Porous PDMS Membrane Fabrication via Spin Coating

A university postdoc requested the folloiwng quote:

"I'm looking to get some silicon wafers made and I wanted to know if your company might be able to help with this. The wafers would be used as masters for porous PDMS membrane fabrication via spin coating. Since I'm trying to make my PDMS porous, I would need the silicon wafers to have micropillars consisting of 3 um diameters and a density of 8e5 pillars per cm2.

If making the wafers with the micropillars is possible, I'd love to try two iterations of wafers. One that would be ~50 mm in diameter and another that would be 40x 20 mm (if custom dimensions could be used).

Do you know if these wafers could be fabricated? If so, could you give me a rough estimate on the cost and time it would take to make these? I realize some of that might depend additional specs I haven't outline, but an estimate would be great as I have no clue how long it would take to make these. If you have any questions I'm happy to answer them. Thanks for your help with this!"

Please reference #249350 for specs and pricing.

What N-type Silicon Wafers are used for Spin Coating of Thin Films?

Posdoc request:

"I use silicon wafers for spin coating of thin films with thicknesses around 10-30 microns. I know the size i want is 150mm and 100 mm and they should be single-sided. But I do not know about other specs, such as grade, type. What would be your suggestion?"

Please reference # for specs and pricing.

What Thin Silicon Wafers Can Be Used for Spin Coating?

A company scientist requested the following quote:

"Ive been redirected to this email by the website. I am interested in thin (ideally <10um) 4" Si wafers. Id need them to be as thin as possible, but of course enabling handling and processing (i.e. spin coating of polymers on top). For a first test, Id need a small number (5 to 20 depending on specs and price). Could you send me a quotation? Do you have instructions on how these wafers should be handled?

UniversityWafer, Inc. Quoted:

4" 10um one side polished
Package: Tape attached for the protection

Reference #251144 for specs/and pricing.

Biomedical Engineering Spin Coating for Mold Fabrication

A biomedical engineering student requested help for their research:

"What Silicon Wafer Grade should I used for microfluidic device mold fabrication and training? What I need to do is some spin coating test and microfluidic device mold fabrication."

Reference #251363  for specs and pricing.

Wafers That Work Well for Thin-Film Experiments

UniversityWafer, Inc. Always follows up with our clients to see how well their wafers are working.

Postdoc response:

"They (the wafers) are working really well for our thin-film experiments, we use the wafers for spin-coating and flow-coating of polymers."

Reference #68426 for specs and pricing.

Substrates Used for Spin Coating Polyimide Polymers

Im interested in substrates for spin coating polyimide polymers. We are seeing that the selection of substrate makes a difference on our polymer properties after thermal curing. We see color differences between Corning Eagle XG, Corning Lotus NXT, Si Wafer, Fused Silica, etc. Cleaning (solution-based, UVO, plasma, etc) options dont seem to make a difference. We thought that the composition of the glass itself could be causing problems (mobile ions like K, Na, Li, etc) and we know that soda-lime is terrible for color. This is why we purchased some fused silica and this turned out not to be the best for color. This is from memory, but in order of good to bad for substrates and color: Lotus NXT (best), Si wafer, NEG AO11, Fused silica, Schott D263, Eagle XG, soda-lime glass. We have tried some other substrates, but we dont have great data for this and they aren’t included. Do you have any suggestions at what could be causing this interaction? Do you have any other substrates that you would suggest? I believe we just ordered some Borofloat33 from you to test next. 

UniversityWafer, Inc. Replied:

Surface color of your polymers' surfaces can be affected by the chemicals that react with it or by the nano-scale morphology that is imparted to it by the substrate.

I have no knowledge of Corning Lotus NXT glass other than that it was designed to be a substrate or an encapsulant for OLED and other optoelectronic devices.

I can be of help with Silicon substrates and we can provide a variety of Silicon substrates that you can experiment with.

Monocrystalline silicon wafers made of ultra-pure Silicon {better than 5N pure even if you consider Oxygen as an impurity} are perfectly uniform on atomic scale. The other substances that you list are either amorphous glasses or polycrystalline powders fused by other compounds (fused quartz), hence inherently non-uniform on atomic scale. Glasses and fused quartz are polished with diamond or other abrasives which limit surface roughness, Monocrystalline Silicon is polished by Chemical-Mechanical Planerization (CMP) which relies on the properties of a crystal to create a smooth surface on the atomic scale (perfectly flat terraces with steps of only one crystal lattice spacing). In Silicon this process routinely produces surface roughness of <5 Angstrom units.

We can provide Monocrystalline Silicon substrates of different crystallographic orientations, such as (100), (111), (110) or (510). We can provide substrates with different resistivities, from 0.002 Ohmcm to 20,000 Ohmcm and corresponding levels of purity. We can provide Silicon surfaces made either hydrophobic or hydrophylic. We can provide Silicon substrates with surfaces passivated by Thermal Silicon Oxide or Silicon Nitride.

All of above variations you may find interesting in how they form polymer surfaces that you study.

Reference #253313 for specs and pricing.

What Supportive Substrate Specs are Used for for PI Spin Coating?

I would need the quotation for 25pcs 4inch Silicon wafers. Specification: - orientation <100> - Single polished wafer - intrinsic doping - 525µm thickness - without flats - no coating Application: supportive substrate for PI spin coating.  I would need 525µm thickness and resistivity >10000Ohm.

UniversityWafer, Inc. Quoted:

Pls see below for the offer on required pure round wafer 525µm thickness and resistivity >10000Ohm

Pure Round Intrinsic Wafer
25pcs 4inch Silicon wafers. Specification:
- orientation <100>
- Single polished wafer
- intrinsic doping resistivity >10000Ohm
- 525µm thickness
- without flats
- no coating

Reference #267292 for pricing and lead times.

A company engineer requested the following:

" Could I get a quote for some options of your low-cost 2” Si wafers? Preferably with the specs as close to those listed below, with multiple options, if possible. We are aiming to use them to deposit an oxide sticking layer coating on top, and then do some spin-coating tests with a solution, so they only need to be a good base for this purpose. - 2" P/B (1-0-0) 10-20 ohm-cm, -- or similar low-doped - 279±25μm – the standard thickness, only! - PRIME SILICON WAFER – not expensive FZ! - SSP – and quote for DSP as well Please let me know a list of the quoted options soon, as we’d like to decide and place an order today to get them shipped out for the coating deposition."

Reference #270219 for specs and pricing.

Silicon Wafers with Smooth Surface for Nanoparticle Research

I’m looking for some 1x1 wafers that are single side polished. I’m using these for nanoparticle research and don’t have any concerns about the electronic properties of the wafers, but do need a smooth surface for spin coating. I noticed there are generally a few options for wafers that are like less pristine, but I’m not sure which category I should look to for a cost effective option. Should I just be looking at slides that say bad quality? Would you have suggestions on which might be best?

Please reference #270734 for specs and pricing.

What is Silicon Wafer Spin Coating?

For decades, spin coating has been used to coat silicon wafers with a resistance film to produce high-yield, cost-effective, ultra-thin, high-performance and cost-effective silicon wafers. Spin coating usually involves coating or casting a solution of the desired material so that it can be easily coated or poured while it is being turned. [Sources: 7, 9]

In the traditional spin coating process, the coating material is deposited in the middle or back of the wafer and spun for a certain time until the remaining solvent evaporates and the thin film reaches from a few nanometers to a few micrometers thick. When the spinning layer is finished, a plate is placed on a hot plate, which is heated to about 100 oC, so that the solvent initially evaporates and solidifies in the plate. After the solvents have evaporated, it is put in a cold water bath for about 10 minutes until it solidifies. [Sources: 1, 8, 9]

Due to the influence of centrifugal forces on the spin coating process, the layer thickness and uniformity achieved by using the process solution in a spin coating process depends on both the size and shape of a wafer. Spin coating results in full coverage of wafers, but it suffers from the same problem of wasted coating as the traditional spinning process: it is too thin, too thick and not uniform enough. About 20% of the use is wasted because the excess solution is thrown away from the wafer substrate. [Sources: 1, 10]

This video shows poor uniformity of the coating caused by the capping of the spinning spreads on the dry surface of the substrate. In most cases, the two-stage spinning method involves drying the medium substrate before coating and removing the edge beads after coating to improve the uniformity of the spinning layer. Using a spin-coating spray jacket is much more efficient than coating the wafer with chemical vapor separation (CVD). [Sources: 9, 10]

As shown in examples, it is not necessary to coat the entire back of a semiconductor wafer with just one method. This video demonstrates the method of static dispensing coating using a 45 degree angle to avoid touching the edges of the substrate when moving the paint. It shows both static dispensing and spin coating methods, including touching substrate edges and inactive areas for applying paint. [Sources: 1, 9]

With spin coating at very low speeds, it is possible to produce higher nanorows than with drip casting. This provides a significant increase in uniformity compared to drip castings, although we cannot really describe the spin coatings because there are still centripetal forces. The repeatability is based on the fact that the parameters defined in the spinning process can lead to drastic fluctuations in coated films. [Sources: 2, 9]

In short, the properties of the film depend on its physical properties, such as thickness and uniformity. In most applications, the thickness of the films produced with spin coating is the most important consideration. [Sources: 9]

A resistance solution is dosed onto the surface of the wafer and spun quickly until it dries. After coating the resistance, a soft beacon is applied, in which the solvent is pushed away from the spinning resistance, improving the adhesion of the resistance to the wafer and exerting shear stress on it. Spin Coating normally performs the same task as Resist Coatings in the production of a thin layer of silicon wafers as they are produced for the production of high-performance electronics and other electronic components, but with a different purpose. [Sources: 3]

In most common spin coating techniques, the aim is to spin the substrate until the film is completely dry. The substrate is applied to a coating material that naturally covers the entire substrate well and then slowly rotates until it spreads well enough to cover it. However, if it rotates at all in silicon wafers, it does not rotate as quickly as in resist coating, but rotates so that the coating materials are well distributed over the entire substrate. [Sources: 6, 9]

A common defect in spin coating for beginners is dust, which can be seen both on the surface of silicon wafers and in the coating material itself. In spin coatings, the solution of the polymer solvent must be filtered through a 0.45 micron filter to remove dust (typically with a 1 / 4 micron filter). In addition, a solvent wash at the bottom of the wafer can eliminate the edge beads that form during the spinning process. [Sources: 8, 9, 10]

On the experimental side of the investigation, the textured silicon surface was first coated and then the reflection on the surface was measured. Figure 2 shows that the PS beads form a uniform monolayer and the etching direction is identical to the crystallographic orientation of silicon wafers with a chemical instability of 100%. When annealed experimentally at 125 degrees Celsius for 5 min, good surface uniformity is shown and surface reflection is significantly reduced. [Sources: 0, 4, 5]













What Silicon Wafers are used for Spin Coating on Polymers?

Scientists have used the following thin silicon wafers with tight Total Thickness Variation (TTV) for their research.

"I hope you are doing well. Just wondering if you would have single crystal, B-doped type silicon (100) wafers (native oxide layer) with thickness of 1 μm? Could you send me a quote for the #7 ultra thin wafers (5mm square, thickness 2 μm). I see there are 4 units in stock, right? By any chance, could you provide 5? If not, 4 wafers are fine."

5mm Square 2 micron TTV: 1 micron P/B 1-20 ohm-cm
Cz (100) Wafer Ring

Reference #2612548 for pricing.

What is Spin Coating on Polymers?

This article focuses on the technique and process of spin coating on polymers. We will examine the effects, problems, and other relevant information. To get started, we will first define what spin coating is. Then we will discuss the characteristics of the coating solvents used for spin coating on polymers. We will also review the different polymer classes used for spin coating. After that, we will discuss the effect of spin coating on polymers on the properties of the coatings.


Non-uniform film thickness is the most common problem associated with spin coating. To avoid this, lower the temperature of the spin coating solution. In addition, lowering the temperature will prevent the solution from evaporating too quickly. However, lowering the temperature of the spin coating solution will not completely eliminate the problems associated with non-uniform film thickness. Below are some common problems associated with spin coating on polymers.

The most significant disadvantage of spin coating on polymers is its low material efficiency. The final film thickness from this process is not proportional to o(-1/2), which is why larger substrates need a slower spin rate and thinner films. Another problem is that spin coating involves high-viscosity solutions, which tend to be less thinning than polymer films. Because of this, a larger film thickness requires a higher solution concentration to achieve the desired effect.

In addition to low throughput, spin coating on polymers is also problematic because it is a batch process. The solution used to coat the substrate is less than ten percent of the total material. Moreover, the solvent used during spin coating is not stable, which will change the surface properties and may damage other layers. If wetness problems are a concern, adjusting the volume will solve these issues. The video below shows a dynamic dispense spin coating procedure on PEDOT:PSS.


The spin coating technique is one of the most effective ways to deposit thin layers of materials. This technique can deposit high-quality layers of materials in a short amount of time. The high-speed spin coating process is particularly beneficial for industrial applications because it helps to achieve the most uniformity possible. In addition, spin coating speeds of over 1000 rpm help to achieve excellent uniformity, while those below 200 rpm may allow the polymer to dry slowly, allowing it to self-assemble.

The spin coating technique is an excellent choice for thin films, which are typically used for flat substrates. The coating solution is applied to the substrate, then spun off at high speed, ranging from 1000 to 8000 rpm. The spin speed and solvent concentration are crucial factors in determining the ultimate film thickness, as this can vary the thickness of the film. While this method works well for small substrates, it's not ideal for large scale applications because the film is thin and the process is expensive.

A significant challenge when using spin coating technique is using highly viscous solutions. The viscous solution is more resistant to deformation due to shear forces. As a result, the film formed may be very thick and not uniform. For this reason, it may be necessary to reduce the concentration of the solution before applying the film. However, this process can be a worthwhile investment if the desired film quality is sought. But be aware of the risks involved.


The videomicroscopy images show the various stages of the spin coating process. The solution contains P3HT with a concentration of 1 wt% in chlorobenzene. The spin rate determines the film thickness. The initial film thickness h0 is proportional to the angular velocity o. If the spin speed is four times higher than o, the film thickness will be half the initial value. The spin curve can be derived by using this equation.

In this equation, C is the volume fraction of solute dissolved in the substrate. h0 is the thickness of the film at the transition between the film-thinning regimes. The coating solvent, k, is a constant that controls the film thickness. The k of typical spin coating solvents is approximately one centimeter per second. hf o (-1/2) is equivalent to Equation 1. The k of spin coating solvents is dependent on several assumptions. If any of them is wrong, the equation will fail.

The speed of the spin coater is critical. The higher the speed, the faster the film dries. The higher the airflow, the more consistent the film is. Spin coating reduces the need for post-desposition heat treatments. The process of spin coating is also highly cost-effective. Other batch-processing methods require expensive equipment and high energy. These processes are ideal for low-volume production. In addition, spin coating can be used on a variety of polymers, including silicone.


To understand the effects of spin coating, we must first understand the relationship between angular velocity and thickness. In general, angular velocity equals the spin speed, so the lower the spin speed, the thinner the film. In addition, spin coating processes at lower speeds allow more time for self-assembly. Pseudo-spinning can be a powerful tool for investigating order.

The final film thickness hf o is calculated by a similarity boundary-layer analysis. This result is consistent with limited experimental data. The constants k, initial polymer concentration, kinematic viscosity, solute diffusivity, and spin speed all affect the film thickness. The ratio of total spin time O-1 to O-1 is consistent with the data from experiments. The ratio between the film thickness and solvent evaporation is proportional to K, with a high correlation between kinematic viscosity and spin speed.

The physical mechanism governing spin coating is discussed. It consists of several components, including centrifugal and viscous forces, solute diffusion, and solvent evaporation. Solvent evaporation makes the solution viscous and reduces the flow of solution. Diffusion boundary layer thickness is directly related to the final solid film thickness. This relationship is essential for understanding spin coating thin-film formation.


Monitoring spin coating on polymers is a challenging problem due to the high speeds of the process and the non-equilibrium nature of the resulting film. Most studies of the process have relied on inferring the structure development from the final morphology, which is not always accurate. Therefore, in situ monitoring of spin coating on polymers is vital for the development of new materials. Here we discuss the challenges and the potential of in situ monitoring in spin coating.

The evaporation of the main solvent can be slowed by saturating the solution. However, this is not a practical method because of solvent waste and health and safety issues. Furthermore, the Marangoni defects are not always visible in high-volatility solutions, because viscous forces tend to dominate the Marangoni flow. Therefore, slowing the evaporation rate may result in films with improved crystallinity.

The process can be improved by using a non-standard pipettor. The normal pipettor technique involves pipetting the solution to the second stop, where the excess is sucked back into the tip. The second step causes additional drops on the surface, whereas the first method reduces bubbles. In addition to reducing bubbles, non-standard pipettor use can reduce the amount of solution on the surface.


Spin coating can be used to create thin, uniform films. During the spin coating process, fluid is spun off the edges of the polymer substrate and evaporates at the same time. The thinner the film, the higher the angular spinning speed. The solvent and viscosity of the solution influence the thickness of the film. Studies have shown that spin coating at low speeds can produce good results, but they are limited by poor uniformity and inconsistency.

High-speed spin coating is a batch process, which is very easy to scale. The spin process is relatively low-cost, making it an ideal coating method for large-scale industrial applications. In addition to being cheaper than batch dip coating, spin coating also has better thinness and uniformity. Unlike other, more exotic coating methods, spin coating has been widely used in high-volume production of high-end electronic devices. As far back as the 1950s, spin coating was used to deposit phosphor onto the glass surfaces of color television tubes.

The drying time of spin coating is directly related to the film's properties, and ambient conditions can have significant effects on this. Professional cleanrooms have well-controlled humidity and temperature. Glove boxes typically contain a nitrogen atmosphere to ensure sterility. Research labs, on the other hand, are not well-controlled environments. Extreme conditions can affect the consistency of the spin coating and can cause defects. This is why the solvents used to spin coat polymers are critical.

Video: What is Spin Coating?

3 Inch Silicon Wafers for Spin Coating on a Vicinal Surface

A corporate researcher requested a quote on for the following:

I am looking for a 3 inch wafer that I can use as a substrate for a spin coating process. Ideally I would want something that I can dissolve away, leaving me just
the film. Do you possibly have any recommendations on a wafer option I can use, and if so, do you sell these wafers and what would they cost?

A while back we discussed the ability to dissolve the wafers I purchased from you after coating onto them. Thus far I have tried hydrochloric acid and it appears to have very little effect on the wafer, if any. We are discussing the use of Aqua Regia instead, but due to the dangers of the material, we are looking into other options as well. One of our scientists suggested a dichromate cleaning solution.

UniveristyWafer, Replied:

It is common to take a CMP polished silicon wafer and spin coat it with a thin polymer. Then you dissolve the silicon wafer in strong acid (HCl or Aqua Regia or some other concoction which does not attack your polymer). You can use silicon wafers 2" to 6" in diameter or even larger. You want the wafers Prime grade CMP polished. It is preferable that they be thin (typically 300um thick) but other electronic characteristics are immaterial. For example, you would use wafers described as P/E 4"Ø×300±25µm, p-type Si:B[100], Ro=(1-100)Ohmcm. Silicon wafers are polished extremely smooth {rms Surface Roughness <1nm}, Silicon is inert with respect to most polymers and it is so pure that there is no contamination. You can also use metal wafer (eg Al or Cu or Ni), or glass or Quartz or Sapphire. But for the degree of purity and surface smoothness, silicon is least expensive.

Client replies:

Coating Silicon Surface with Polymer Film

I need to coat the wafer with a very thin polymer film and ideally have nothing but the film by the end of the process. I was told by a colleague that there are some wafers that you can coat on, treat with a solvent, and the wafer dissolves leaving just the film. I am unfamiliar with the process so this may not be possible, but I thought I would at least investigate the possibility. If you know anything about this, that would be helpful. Otherwise, we will probably buy the lower quality wafers you mentioned. I am somewhat unfamiliar with the different grades of wafers. Would the mech grade dissolve away after use, and if so, what would I have to use to dissolve it? Could you possibly provide some details on the use of these wafers?  Thank you.

UniversityWafer, Inc. Replied:

HCl will work but perhaps at higher temperature than you want to use.
Aqua Regia should work safely.
Nitric acid should work.
HF acid works very slowly (dissolves SiO2 quickly but Si slowly)

Common etchants are:

C Anisotropic KOH Etching  
KOH is one the most commonly used silicon etch chemistry for micromachining silicon wafers.  
1. Anisotropic KOH Etching Rates vs. Orientation  
 The KOH etch rate is strongly effected by the crystallographic orientation of the 
silicon (anisotropic).  Table 1 relates silicon orientation-dependent etch rates (µm/min) of KOH to crystal orientation with an etching temperature of 70°C. (values in () are normalized with respect to (110)

Crystallographic  Rates at different KOH Concentration 
Orientation    30%      40%              50% 
(100)  0.797 (0.548)  0.599 (0.463)  0.539 (0.619) 
(110)  1.455 (1.000)  1.294 (1.000)  0.870 (1.000) 
(210)  1.561 (1.072)  1.233 (0.953)  0.959 (1.103) 
(211)  1.319 (0.906)  0.950 (0.734)  0.621 (0.714) 
(221)  0.714 (0.491)  0.544 (0.420)  0.322 (0.371) 
(310)  1.456 (1.000)  1.088 (0.841)  0.757 (0.871) 
(311)  1.436 (0.987)  1.067 (0.824)  0.746 (0.858) 
(320)  1.543 (1.060)  1.287 (0.995)  1.013 (1.165) 
(331)  1.160 (0.797)  0.800 (0.619)  0.489 (0.563) 
(530)  1.556 (1.069)  1.280 (0.989)  1.033 (1.188) 
(540)  1.512 (1.039)  1.287 (0.994)  0.914 (1.051) 
(111)  0.005 (0.004)  0.009 (0.007)  0.009 (0.010) 
The (110) plane is the fastest etching primary surface.  The ideal (110) surface has 
a more corrugated atomic structure than the (100) and (111) primary surfaces.  
The (111) plane is an extremely slow etching plane that is tightly packed, has a 
single dangling-bond per atom, and is overall atomically flat.  As shown above, 
the strongly stepped and vicinal surfaces to the primary planes are typically fast 
etching surfaces. 

F Isotropic Silicon Etches
Isotropic etchants have dissolution rates independant of orientation.
These chemical mixtures tend to uniformly remove material, and are limited by the mass 
transport of  chemical species to the crystal surface.  The actual surface reaction rates are 
so great that variations to atomic structure do not alter the reaction speed relative to 
chemical transport.  

Formula                                                                  Comments 
HF, HNO3                                                               Fast acid etch
HF, HNO3, H20 or CH3COOH  {ethanol}                    Various combinations give different etch rates
900ml HNO3, 95 ml HF, 5ml CH3COOH, 14g NaClO2 15 µm/min etch rate (much quicker if you stir well)

Reference #119285 for specs/pricing.