Silicon Wafers for Spin Coating

university wafer substrates

What Silicon Wafer Should I use for Sping 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!

Please watch the video below.

 

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]

Sources:

[0]: https://www.intechopen.com/books/new-research-on-silicon-structure-properties-technology/non-vacuum-process-for-production-of-crystalline-silicon-solar-cells

[1]: http://www.google.com/patents/US20110076858

[2]: https://www.scitek.com.au/applications/wafer-processing

[3]: https://www.eesemi.com/resist-processing.htm

[4]: https://www.osapublishing.org/oe/abstract.cfm?uri=oe-19-S5-A1109

[5]: https://www.hindawi.com/journals/jnm/2014/439212/

[6]: https://openwetware.org/wiki/Spin_Coating_-_Yizhuo_Chen

[7]: https://www.s-cubed.com/spin-coater-equipment-and-processes/

[8]: https://www.spincoating.com/en/applications/spin-coating-theory-process/68/

[9]: https://www.ossila.com/pages/spin-coating

[10]: http://www.google.com.pg/patents/US5952045