Thin Silicon Wafers | The Process of Creating Thin Silicon Wafers


May 3, 2019

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As gadgets become thinner and handier, the rise in demand for thin silicon wafers has pushed silicon manufacturers to refine their wafer manufacturing processes to achieve the desired thinness. If you’re wondering how ultra-thin silicon wafer is made possible despite its fragility, here are the processes involved in creating thin silicon wafers:

Back Grinding

This conventional approach is fast, creates low variation, and generates a good surface finish. The size of wafers is reduced to a dimension fitting for final packaging of die after dicing.

Grinding Damage Removal Processes

There are three methods commonly used to get rid of damage from grinding and boost final surface appearance at the same time:

  • Dry Plasma Etching: This method presents the advantage of removing surface damage, rounding the pointy edges, and controlling the surface roughness through atmospheric dry plasma etching.
  • Wet Etching: This method is a common thinning technique that uses wet-etching processes to remove exterior damage.
  • Traditional Loose-Abrasive Polishing: This method integrates polishing into the grinder. So, it thins the wafer while smoothening it. The disadvantage of this method, however, is that it has low removal rates and it bolsters the surface profile.

Wafer Handling

It’s almost impossible to handle fragile thin wafers without breaking it. But through bonding the thin wafers to a stiff carrier substrate before the back-thinning process, thin wafers are able to go through further processing without breaking.

Brief Bonding and Debonding with Waxes

Uniform wax coating is essential to endure rough mechanical processes. Wax is then removed through the heating or dissolving the wax in a solvent.

where are the best thin silicon wafers?

(I) Grinding of Thin Silicon WafersBack grinding is a well-known method to obtain a thin wafer. It involves two steps: coarse grinding and then fine grinding. In this process, protective tapes play a crucial role in deciding the total thickness variation as the wafers become thin. This method is faster than other techniques.(II) Dry EtchingThere are two types of dry etching: physical-ion etching (PIE) and reactive-ion etching (RIE).PIE removes the atoms from the substrate's back by bombarding it with energetic ions. Several factors, like scanning style, determines the etch rate.RIE involves using chemically-reactive plasma for removing the atoms. It offers high anisotropic behavior and a low level of surface damage.(III) Layer Transfer ProcessesThis process involves exfoliation or removal of the top processed layer. Based on this technique, there are two processes: controlled spalling and proton-induced exfoliation.Controlled spalling uses strained conditions for obtaining a thin Si layer. Proton-induced exfoliation involves exposing the wafer to a beam of hydrogen ions.Upon heating, the ions expand as microscopic hydrogen bubbles. Moreover, the thin Si layer detaches itself from the surface.(IV) Anisotropic Wet EtchingThis technology realizes ultra-thin chips by following several steps. It includes depositing suitable mask layers, LPCVD nitrate, and thermal oxide on each wafer side. After that, etching takes place from the backside of the wafer. The commonly-used etchants are EDP, TMAH, hydrazine, and KOH.Speak with us to learn more about Thin Silicon Wafers.Ultra-Thinning

  1. Grinding

The back grinding method reduces the thickness of the wafer to the desired level. A fast process gives an excellent surface finish. Nowadays, many new applications require an ultra-thin die. For them, grinding is commonly used for thinning.

  1. Grinding Rate

The grinding rate is precisely controlled to get the desired thickness of the wafer. For this purpose, the grinding wheels use diamond abrasive in binders on the wheel edge.At present, grinding can reduce the thickness of the wafer from 750 μm to 150 μm. Further thinning has become difficult due to possible yield loss due to grinding.

  1. Surface Polishing

Three methods are available to polish the surface of the wafers. These processes also eliminate the damages caused by grinding. They are traditional loose-abrasive polishing, dry plasma etching, and wet etching.

  1. Wafer Handling

Even before the back-thinning process, steps involving the handling of thin wafers begin. These include attaching device wafers to carrier substrates using adhesives.After the completion of the thinning process and subsequent steps, the carrier wafer releases the thin wafer. It paves the way for the packaging in the final stages.Get in touch with us to learn more about Thin Silicon Wafers.

Looking for Thin Silicon Wafers?

Thanks to the processes mentioned above ultra-thin silicon wafers are made possible and the world is now able to enjoy sleek, handy, and durable gadgets! Get high-quality thin silicon wafers for your business needs at Wafer World. Our 20 years of experience in the wafer industry assures that you get quality wafers at the best price possible! Contact us today for any inquiries or purchase wafers online!

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