Challenge

A very large Japanese-based semiconductor fabricator (fab) located in the US introduced a new product consisting of Flash memory with a smaller geometry. The customer’s upgrade in technology called for an upgrade in water treatment. The previous memory technology used water treatment equipment provided by Siemens Water Technologies, formerly USFilter. The treatment was successfully meeting water specifications for the old memory technology, but was having difficulty meeting water quality requirements for the new smaller Flash product line.

The initial water purification system contained EPDM (ethylene propylene diene monomer) rubber gaskets and butterfly valve linings which were suitable for the intended product at that time. Part of the process uses a Hot UPW Loop incorporating a plate and frame heat exchanger which also incorporated the EPDM gaskets. The hot water is heated from 75 degrees Fahrenheit to approximately 170 degrees and is used to clean the Flash product in between manufacturing processes. This aggressive hot DI water deteriorates the lining of the gaskets causing for a higher metal particle count in the water. This higher metal particle count signaled the issuing of more stringent water quality requirements which intern meant that the customer would have to find a way to continue production of their new Flash memory line while meeting tighter water quality requirements.

Solution

Since Siemens Water Technologies provided and operated the initial system, it seemed only fitting to step in once again, diagnose the problem and find the most efficient and cost effective solution. A competitor’s suggestion was to have the customer completely replace the water treatment polishing system. However, after Siemens provided a detailed audit they found that the lining of the gaskets, primarily in the heat exchanger, were the primary culprits of the increase in metal particles and NVRs (Non-Volatile Residue) in the water.

Siemens was requested to make the recommend upgrades on the EPDM gaskets along with other system upgrades (materials of construction, instrumentation, final polishing PPQ resin, method of operation, etc.). These upgrades were retrofitted into the existing system not only making this the quickest solution for the customer, but also the most cost effective while at the same time meeting water requirements. The system upgrades were carefully planned starting 4 months before an annual holiday shut down to minimize any impact to the manufacturing process. Those upgrades that could be done before shut down without impacting the fab were performed.

Another significant modification made by Siemens Water Technologies was the relocation of the UF (ultrafiltration) membrane from upstream of the heat exchangers to down stream after the heat exchangers to provide more complete final filtration for improved water quality. Since Siemens was already operating the UPW facility, this work was performed at no additional engineering cost to the customer.

Results

The customer, in using Siemens Water Technologies, not only had the benefit of working with a company they were already familiar with and had aided them in reaching water quality requirements in the past, but also received the most effective and economical solution. This allowed the customer to continue fabricating their new Flash memory product line without fear of not meeting tightened water requirements. The Non-Volatile Residue level was reduced from over 200 ppt to below 50 ppt with the end result of the customer having improved product yield with minimal impact to production and minimal upgrade cost.