After etching and rinsing, an IPA (isopropyl alcohol) vapor dryer can produce dry silicon wafers without watermarks and limited particle adders. In IPA drying, also known as Marangoni drying, the Marangoni effect relies on the low surface tension of IPA compared to water. When IPA vapor is introduced into the drying chamber, a surface tension gradient is established between the IPA and water on the surfaces of the silicon wafers. The surface tension gradient causes the water to flow off the wafers, leaving them clean and dry. The slow drain water feature also helps reduce particles contaminating the wafer surfaces. As a result, IPA vapor drying can be used to produce especially clean, wafers after a final etch and before the next semiconductor manufacturing step.
IPA Vapor Drying is Safe for Thin Silicon Wafers
IPA vapor dryers are especially suitable for drying thin, delicate silicon wafers. In other drying methods, the wafers are placed in a drying chamber and rotated or spun to remove the rinsing water, but handling and moving these wafers can result in damage. With the IPA vapor dryers, the Marangoni effect dries the wafers without moving them. Delicate wafers are not subjected to any stress and damage is minimized while drying performance is excellent.
IPA Vapor Dryers Improve Wafer Processing After HF Last Etching
As the final process in a silicon wafer fabrication step, the silicon oxide layer on the wafer has to be removed with hydrofluoric acid (HF) etching. The wafer is then rinsed with de-ionized water and dried before passing on to the next step in manufacturing the final semiconductor component. Providing a clean wafer with a low particle count is critical at this point because subsequent process steps are affected by the presence of contamination or particles. For high-density semiconductor components, a particle or film on the silicon wafer can prevent the correct etching of a structure or the deposit of a conductor. Because IPA vapor dryers remove water from the wafer surface and reduce particle counts with their Marangoni effect, IPA vapor dryers improve wafer processing results and ensure higher quality output.
Modutek Single Chamber Processing Delivers Further Improvements
At the end of a wet process wafer fabrication step, the wafers are etched with hydrofluoric acid in an etching chamber and then transferred to a dryer. The transfer exposes the wafers to particle contamination that can lead to elevated wafer surface particle counts, even after Marangoni drying. Modutek has eliminated this source of contamination by developing a method that allows etching and drying in a single chamber.
With the Modutek etching and drying station, hydrofluoric acid is injected into the chamber at a controlled ratio to etch the oxide layer down to the bare silicon. The wafers are then rinsed with de-ionized water to a set pH level. When the pH level is reached rinsing is complete and drying can begin.
IPA vapor is generated from a standard one-gallon bottle and introduced at the top of the drying chamber. The drying cycle takes about 10 to 15 minutes and the dry wafers are ready for their next fabrication step. The wafers are not moved during the whole etching, rinsing and drying process, reducing wafer breakage, especially for thin, delicate wafers. Since the wafers stay in the chamber from etching to drying, particle contamination is significantly reduced.
Modutek’s extensive experience in the semiconductor manufacturing industry allows it to support customers in integrating the new single chamber IPA vapor dryer in any new or existing wet processing equipment. Modutek designs and builds their own semiconductor manufacturing equipment and can therefore offer customized versions to meet the requirements of any application. The company’s staff work with a customer’s engineering team to make sure the equipment meets the customer’s process requirements. Contact Modutek for a free quote or consultation to discuss your manufacturing equipment requirements.
