Choosing an Acid Neutralization System to Safely Handle Chemical Disposal

Choosing an Acid Neutralization System to Safely Handle Chemical DisposalWet process semiconductor manufacturing lines use aggressive chemicals to clean and etch silicon wafers. When a cleaning or etching step is complete, the remaining chemicals have to be disposed of safely. Low pH acids such as hydrochloric acid have to be neutralized with high pH chemicals so that the pH of the mixture approaches the neutral value of seven. The acid neutralization can be carried out continuously or in batches and either process can be fully automated. Ideally an acid neutralization system acts reliably with a minimum of supervision and keeps records of chemical use and discharge to demonstrate compliance with environmental regulations.

Continuous Flow and Batch Neutralization Systems Fulfill Different Requirements

The choice of an acid neutralization system reflects the type of semiconductor manufacturing that takes place. Large scale continuous manufacturing lines produce a continuous flow of waste chemicals. The composition of the flow and its volume changes little and can be analyzed in detail. A continuous flow acid neutralization system can then be designed to automatically and reliably neutralize the out flow. Because small changes can easily be detected and the dosages of neutralizing chemicals can be automatically adjusted, the automation required for such a system is easily set up. The automated continuous flow acid neutralization system can keep records of its neutralization activity and the volume and pH of the waste flow.

The neutralization of waste chemicals used in batch manufacturing is usually more complicated. Batch manufacturing is used for prototypes, one-of-a-king components and small quantities of special parts. Each batch can be different and it makes sense to use a batch acid neutralization system for these processes.

Instead of adjusting chemical dosages of an established process as in the continuous flow systems, batch neutralization systems have to measure the pH of the waste chemicals and add specific neutralizers. Several stages of neutralization may be required before the discharge is acceptable. Once the neutralization process is finalized, the sequence can be fully automated and can run as the batch is processed.

Other Considerations When Choosing an Acid Neutralization System

Once the choice of continuous flow or batch system is made, the acid neutralization system has to fulfill a few basic requirements. The system capacity has to be sufficient for the proposed application, with capacities ranging from a few gallons to hundreds of gallons per minute. The system can be located indoors if there is space but it can also be designed for outdoor operation. If automated, the exact automatic functions have to be programmed and set up. Finally the monitoring and record-keeping functions have to be determined.

Operational characteristics have to be considered as well. If the system is fully automated, it may run without supervision but alarms will be required for situations such as low chemical supply or a pH level outside permissible limits. Recording of neutralization process parameters can be digital, with a log, or on a chart recorder. Containment of spills is important and depends on whether the installation is indoors or outdoors. Spill detection has to be incorporated into the alarm system and the whole operation has to comply with environmental regulations.

Modutek Can Supply Acid Neutralization Systems to Meet Customer Needs

Included in Modutek’s complete line of wet process equipment are compact acid neutralization systems that can be customized to meet specific needs. Systems can be designed to fit into the space available at a customer’s facility and Modutek can help select suitable automation and operating characteristics. The Modutek acid neutralization systems operate reliably to keep waste discharge parameters close to specified values and a digital chart recorder documents compliance with discharge regulations.

5 Important Things to Know Before Buying a Wet Bench Station

5 Important Things to Know Before Buying a Wet Bench StationWet bench semiconductor manufacturing has many variations and applications often have unique features. Before buying a wet bench station, there are several main things to look at before deciding what equipment is best suited for a specific manufacturing task. Options include the type of station, how it operates, how it receives its chemicals and what specialized or custom features are required. When a prospective supplier has extensive experience and the required expertise as well as offering a complete line of wet bench equipment and customization as required, the selection becomes easier. Five main things influence which of the available wet benches to buy. Knowing these five things helps determine which station satisfies the manufacturing application requirements.

1. Different Types of Wet Process Stations Have Different Advantages

Types of wet benches include a standard white polypropylene construction for acid and base process applications such as KOH and RCA clean. Solvent application wet benches for processes such as acetone, IPA and photo resist stripping have a stainless steel construction. Stations are available with a dry-to-dry process and can include a chemical fume hood. An experienced supplier can advise on the different options and the customization possibilities.

2. The Degree of Automation Depends on the Application

Manual stations are best suited for initial development work when the main process parameters are not yet known. Manual stations can be used to develop a process framework. Once the overall process is set, semi-automatic stations can be used to program the fixed parameters to run automatically while operators retain manual control of some variables for optimization purposes. Once the process is fully developed, fully automated stations can be used to run the productions line and increase throughput.

3. Chemical Delivery Systems Improve Process Control

Chemical delivery systems run and monitor chemical storage, delivery to the process and disposal of chemical discharge. They minimize waste and reduce spills. Chemical delivery systems are recommended for applications that rely on highly accurate dosages of specific chemicals during the manufacturing process.

4. Rinsing and Drying are Critical for Avoiding Particle Contamination

Reduced particle counts on wafers improve process yields because particles can cause product defects. Special configurations such as the combined rinsing and drying station and the quick dump rinser improve process efficiency and reduce the particle count. Depending on the wet process application, such rinsing and drying configurations may improve overall facility performance.

5. Special Custom Functionality Can Be Built Into Standard Stations

Semiconductor equipment manufacturers that build their own wet process stations in house can add custom functionality when an application requires it. For example, an application may include etching of aluminum layers on a wafer and a special vacuum metal etcher may have to be incorporated in the wet bench process. Some applications require an especially low particle count and wafers may have to be cleaned with Megasonic equipment to dislodge and remove the tiniest particles. Such specialized custom functions work best when a custom design integrates them into the rest of the wet bench process.

Once customers are aware of these five pieces of information, they can proceed to select a supplier that can satisfy them on all five points. They will then be able to specify the kind of performance they want to achieve and help make sure that they get the equipment they need.

Modutek Builds Their Own Equipment to the Highest Standards

Modutek design and build their own equipment in house and can customize wet process stations as required. Their specialized modules include the combined rinsing and drying IPA dryer, the quick dump rinser and the Megasonic cleaner. The company can help customers with all five of the listed points and ensure the purchased wet benches meet their needs.