One of the key process steps in all semiconductor manufacturing is the etching of the wafer. Etching refers to the process of removing materials in specified areas which leaves minute and intricate patterns on the wafer thereby making a semiconductor. The chemical predominately used in this industry for etching is Hydrofluoric Acid (HF). HF is a very hazardous waste and requires a great deal of care to manage and dispose of it property. In 1992 Motorola generated over 680 tons of HF waste which in the past was disposed of by deep well injection. In June of 1992 the Motorola Oak Hill facility installed a Fluoride Waste Treatment System on site to completely neutralize this very hazardous stream. The treatment method for our system is a one step chemical reaction of mixing the HF waste and Calcium Hydroxide, or Lime as it is commonly known, together which neutralizes the acid and balances the pH at the same time. It forms calcium fluoride, a stable, non hazardous, and very harmless material.
In 1993, Motorola expanded the FWTS to keep up with increased HF usage. The expansion increased our neutralization time and equipment efficiency by allowing us to filter one of our two reaction tanks while we are doing a reaction in the other. It also has almost doubled our capacity to treat HF waste.
The benefits for the Flouride Waste Treatment are:1. The on site treatment system keeps this very hazardous waste from traveling on our public highways to disposal sites in different areas. It is completely contained in covered tanks and continuously monitored for correct operation. All of these benefits represent an extensive reduction of potential impact to human health and the environment.
2. The FWTS also represents a real waste minimization effort which will account for a 46% reduction of Motorola's TOTAL hazardous waste generation and a 99% reduction of our HF waste generation.
3. THis sytem could be used industry wide for semiconductor plants.
Details of Reductions
Additional Information :
Motorola spent $378,00 for the initial unit and an additional $160,000 on the expansion to keep up with increases in production. A cost savings of over $24,000 for 1992 was determined by comparing the $0.44/gal cost to deepwell with the $0.29/gal cost to operate the FWTS.