How Innovative Changes to the SPM Process Improves Results

How Innovative Changes to the SPM Process Improves ResultsWhen the SPM process requires frequent spiking with hydrogen peroxide, precise control is difficult and the useful lifetime of the mixture is reduced. The SPM process, using a mixture of sulfuric acid and hydrogen peroxide, is a popular wafer cleaning process because it quickly removes large amounts of organic material from the surface of silicon wafers. It is ideally suited for stripping photoresist and it hydroxylates surfaces making them hydrophilic (having an affinity for water) in preparation for subsequent wafer processing steps. Spiking with hydrogen peroxide keeps the process going but it means the mixture has to be replaced about once a day. Modutek has developed an innovative way to control the process, resulting in significant cost savings and improved results.

How the SPM Process Cleans Wafers

The mixture of sulfuric acid and hydrogen peroxide removes organic material very quickly because it is highly corrosive, but it is also unstable. The hydrogen peroxide decays to form water that reduces the mixture concentration and slows down cleaning. To keep the process going, the mixture is periodically spiked with hydrogen peroxide, bringing the concentration back up. At the same time, adding hydrogen peroxide to sulfuric acid is exothermic, raising the temperature of the mixture. Cleaning takes place more quickly at higher temperatures, but the hydrogen peroxide decays more quickly as well, influencing control accuracy. Repeated spiking limits the useful life of the mixture to about one day. Daily replacement of the chemicals is expensive and results in delays for the processing line.

“Bleed and Feed” Process Change Saves Money and Improves Output

Modutek has developed an innovative SPM control strategy that prolongs the life of the SPM mixture while precisely controlling mixture temperature and concentration. In the “bleed and feed” method, Modutek uses a two tank system with a clean tank and a dirty tank. Small programmable amounts are regularly drained from the dirty tank and replaced with mixture from the clean tank. To restore the mixture in both tanks, sulfuric acid is added to the clean tank to replace the amount drained and small amounts of hydrogen peroxide are added to both tanks to maintain the required concentration. This semi-continuous process keeps the mixture concentration within narrow limits without spiking and without the temperature changes caused by spiking.

The “bleed and feed” method is PLC-controlled and the amounts to be drained, the replacement amounts and the frequency of operation can all be adjusted for optimal process results. The concentration and temperature of the mixture remain within tight limits and the process control is more accurate. The useful life of the mixture can be extended to as much as a week and the more precise process control gives improved results.

Benefits from “Bleed and Feed” Process Change

Modutek’s “bleed and feed” method means that chemical use and disposal is reduced substantially. When the wafer cleaning process performance is precise and predictable, better repeatability and consistent cleaning times result in better process line performance. When mixture life is stretched from one day to a week, the cost of chemicals is greatly reduced while the process equipment can stay in service longer since it doesn’t have to be shut down as often for changing the mixture. Downtime is lower and throughput increases.

As a leading semiconductor equipment manufacturer, Modutek continues to work closely with customers to develop innovations that can improve process results. The “bleed and feed” control method increases productivity and reduces costs while the decreased use of chemicals is environmentally friendly. The new process control method could be of interest to manufacturing and research facility managers who can use it to lower production costs, improve output quality and decrease the plant’s environmental footprint. Modutek offers free consultation can discuss details on how the new SPM control method can improve the process for your application.

Systems That Support Chemical Delivery and Disposal Requirements

Systems that Support Chemical Delivery and Disposal RequirementsWhen corrosive chemicals are used by manufacturers and research centers, they have to be stored safely, delivered to the process in precise quantities and neutralized prior to disposal. Chemical delivery systems that manage the use and disposal of chemicals have to be designed for high reliability and for compliance with local environmental regulations. Even for chemicals that are not hazardous, these systems can reduce waste and improve productivity. The varied requirements for chemical handling systems that fulfill these functions mean that a high degree of customization is necessary. Modutek offers a complete line of chemical handling products that support chemical delivery and disposal with extensive customization.

How Chemical Delivery Systems Improve Manufacturing Facility Performance

Effective chemical delivery systems make sure that chemicals are tracked from reception through storage to use in the manufacturing process. Low storage volume alarms let operators place orders to ensure a continuous supply. Bulk storage can take place in a separate storage area while smaller quantities can be stored close to the process. Sometimes chemicals have to be mixed or different chemicals added to the process at different times. Both storage and delivery to the process can be automated to varying degrees. Double containment and leak detection may be required. Such chemical delivery systems provide the following benefits:

  • Better process flow. Tracking chemical use and making sure there is enough supply lets the manufacturing process run more smoothly with a constant chemical consumption.
  • Higher output quality. Precise dosage and excellent repeatability results in reliable product quality over time.
  • Reduced waste. Chemical tracking, leak detection and reduced operator error mean there is less chemical waste.
  • Improved workplace safety. When operators don’t have to handle chemicals directly, they are less exposed to hazardous substances and the workplace becomes safer.

As a result of these benefits, chemical delivery systems can reduce costs and improve overall manufacturing and research facility performance.

How Chemical Disposal Systems Ensure Safety and Regulatory Compliance

When chemical disposal systems work properly, they ensure that all chemical waste is collected and disposed of safely in accordance with environmental regulations. Chemical disposal requires the use of Department of Transportation (DOT) approved containers. DOT approved containers provide added safety to prevent leaks during handling and transportation.

Modutek offers different chemical collection and disposal systems which include mobile chemical carts as well as larger volume chemical collection systems. Chemical carts (sometimes called chemical pump carts, chemical collection carts or chemical disposal carts) are units that can be easily rolled up to a process station to pump used chemicals into the DOT approved container within the cart. Modutek also provides chemical collection systems from 5 gallon carboy DOT approved containers to larger collection tanks and collection tank farms to support higher volume requirements. These systems incorporate the use of software controls to monitor chemical disposal levels, leak detection and data logging to keep your facility in continuous operation. With Modutek’s chemical collection systems and software interface there is no down time due to the “fill/empty” control system. Since Modutek designs all their Chemical Collection and Disposal Systems in house all the software and equipment is engineered and manufactured to meet a customer’s specific requirements.

Reliable Systems Customized for Volume, Process and Facility

Modutek has the experience and in-house expertise to customize all chemical handling systems for chemical delivery and disposal as needed. Factors such as chemical volumes used, types of chemical processes and facility layout all influence the system design. The degree of automation desired and the local regulatory environment are always different. Chemical delivery and disposal systems have to be adapted to meet these different requirements. Since Modutek builds its own systems, the company can adapt standard designs and automation to satisfy the unique needs of its customers. Contact Modutek for a free consultation to determine the right chemical delivery and disposal equipment that is needed to meet your requirements.