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.

How Quick Dump Rinsers Improve Silicon Wet Etching Processes

How Quick Dump Rinsers Improve Silicon Wet Etching ProcessesWhen silicon wafers in a wet etching process need rinsing, quick dump rinsers provide fast and effective rinsing of chemicals and particles. In semiconductor fabrication lines such as those of semiconductor manufacturers and research labs, silicon wafers are etched with chemicals. Once the required structures and current paths have been etched into the silicon, the chemicals have to be rinsed off to prevent continued etching. Modutek’s quick dump rinser uses de-ionized water to wash away all traces of chemicals while introducing no new sources of particle contamination. When rinsing is complete, the quick dump rinser drains rapidly. It combines excellent rinsing performance with fast processing and reduced particle counts.

What Makes a Quick Dump Rinser is Efficient and Effective?

Modutek has applied state-of-the-art engineering techniques to design a quick dump rinser that reduces de-ionized water consumption while featuring a short rinsing time and particle reduction. The large trap door and the contoured rinsing vessel shorten dump times and promote laminar flow to rinse away contaminants. The machined dump door has no seals or gaskets that could entrap particles and the smooth polypropylene construction of the tank ensures that it is not a source of new particle contamination.

When the silicon wafers are placed in the rinser, de-ionized water jets rinse the chemicals from the wafer surfaces. The tank fills, bringing the rinsed contaminants to the surface where they leave the tank through the overflow weir. A nitrogen bubbler generates gas bubbles that rise through the water, removing additional contaminants and particles. At the end of the rinse cycle, the trap door at the bottom of the tank opens to quickly drain the water. The whole process is fast and rinsing is complete without added contamination.

Quick Dump Rinsers Provide Substantial Benefits

The use of quick dump rinsers can improve production line performance and output quality. Modutek has designed its quick dump rinser to address wet process manufacturing concerns, including water use, rinsing effectiveness, particle counts and timing. When quick dump rinsers work rapidly, effectively removing chemicals and particles, throughput can increase and the product rejection rate can go down.

Fast rinsing reduces de-ionized water use. Modutek’s 360-degree overflow weir lets contaminated water exit the tank easily and reduces particle entrapment. Dual overhead spray manifolds and low misting nozzles improve rinsing performance with an even distribution of the spray. The nitrogen gas bubbler and tank design promote an even flow around the wafers and the large dump door drains the tank completely in seconds.

Key benefits include reduced costs, fewer product defects and faster production line operation. Reduced de-ionized water use lowers costs and an optional reclaim system can result in additional savings.

The tight packing of semiconductor structures and their decreasing size makes the process more and more sensitive to particle contamination. Even the tiniest particle can cause defects in the final product. Modutek’s quick dump rinser is designed to reduce particle counts and the product failure rate can decrease as a result.

Rinsing is required after many of the wet process production steps and any time saved with a quick dump rinser is multiplied by the number of times rinsing takes place in the semiconductor fabrication production line. The Modutek quick dump rinser delivers these benefits by addressing overall semiconductor manufacturing requirements.

Modutek Works to Improve the Silicon Wet Etching Process for Customers

In addition to quick dump rinsers, Modutek is committed to helping its customers with standard and custom silicon wet etching equipment. The company’s complete wet process product line includes quartz tanks, Teflon tanks and silicon nitride etch baths. Modutek offers free consultation and can ensure that the delivered systems fulfill the needs of its customers.

How Chemical Carts Support Chemical Disposal

How Chemical Carts Support Chemical DisposalWhen difficulties associated with chemical disposal and regulatory compliance increase, it’s time to think about either removing used chemicals for off-site disposal or using dedicated equipment for disposal according to official guidelines. Chemical carts can be rolled over to process stations and can pump used chemicals from the process tanks to a container on the cart. The used chemicals can then be turned over to a disposal company or can be neutralized and treated in an onsite facility. The manufacturing process can continue with a fresh batch of chemicals while documentation and handling of the used chemicals can be carried out according to local regulations.

Chemical Carts Remove Chemicals Quickly and Safely

Once the chemicals for a process step have fulfilled their function and the process step is complete, the used chemicals have to be drained from the process tank so that the next process batch can begin. The use of chemical handling equipment such as pump carts is a flexible solution allowing operators to remove used chemicals from the process tanks for different process steps.

An operator can roll the chemical pump cart to the tank that contains the used chemicals. A suction wand allows the operator to pump the chemicals out of the process tank. The used chemicals are pumped into a dedicated storage tank on the chemical pump cart and the cart can then be rolled out to a designated disposal area.

Depending on whether the company handles chemical neutralization and disposal in house or not, the chemicals can be transferred to a disposal system or turned over to an external chemical disposal specialist. In either case, documentation for the handling of chemicals according to local laws and regulations can be prepared before final disposal.

Modutek’s Chemical Carts Feature Ease of Use and Enhanced Safety

At 36″ long x 18″ wide x 42″ tall, Modutek’s chemical pump carts are compact and easy to roll out. Made of white polypropylene, the carts run on swivel casters with brakes and feature independent suction and discharge tubes. Pumping is with a 3/8th inch pneumatic pump. The five gallon chemical tank on the cart has a double containment system and is DOT (Department of Transportation) approved. A high level sensor on the tank is interlocked with the pump for additional safety. The plumbing is all Teflon and each cart can handle multiple applications.

As an option, chemical carts can be delivered in a stainless steel design for solvent applications. Other options include a pressure interlock safety switch, a large capacity tank and a double dump design. Modutek can help customers decide on the options they need and make sure that the chemical pump carts meet their requirements.

Modutek’s Chemical Handling Products Fulfill Manufacturing and Research Facility Needs

Modutek manufactures a complete line of chemical handling equipment to meet the needs of manufacturing plants and research facilities. In addition to chemical carts, Modutek’s chemical handling systems include chemical delivery systems, chemical collection systems and chemical lift stations. The systems can store chemicals, deliver them to process stations and remove them to neutralization areas. The chemical handling equipment is designed to interface with existing or new manufacturing lines and can be customized for almost any application. For example, storage in large tote containers with a load cell interface reduces drum changes and the lift station functions can be incorporated into a process station in a space-saving design. Throughout the design process, Modutek works closely with customers to identify production line issues and develop effective solutions. The company prioritizes customer satisfaction and delivers equipment of the highest quality with low operating costs and a low total cost of ownership. Contact Modutek for a free consultation or quote on selecting the right chemical handling equipment to meet your specific requirements.

How Customized Equipment Improves Silicon Wafer Processing

How Customized Equipment Improves Silicon Wafer ProcessingBecause semiconductor manufacturing is made up of a large number of steps, silicon wafer processing often includes unique requirements. Standard equipment may be suitable to some extent, but using custom equipment adapted to the particular process can improve production line performance. Customization of the physical characteristics of the system, the software, the degree of automation and the process components can impact how well the silicon wafer processing equipment works. An experienced supplier of wet processing equipment can advise customers regarding possible customization and follow up with specific equipment suggestions.

Physical Customization of Wet Process Equipment

Semiconductor manufacturing equipment often has to fit into a defined space or is retrofitted into an existing production line. In either case, the dimensions have to be customized to fit the available space. Modutek can build processing stations and tanks with special dimensions to fit and can arrange components for less depth or less length as required. Because Modutek designs and builds all its own equipment, the company is capable of changing the dimensions of its standard products to fit customer requirements.

Customized Software for Special Calculations

The Modutek SolidWorks Flow Simulation and Simulation Professional software allows customers to accurately calculate chemical dosages and to track chemical usage. Custom installations may require special calculations and the software may have to be adapted to calculate and track custom chemical use. Modutek writes all its own software and can therefore customize and adapt the program code. Customers can rely on Modutek to maintain and support the non-standard software and make sure it works the way the customer wants.

Automation With Customized Characteristics

Modutek’s standard wet processing equipment is available in fully automated, semi-automated or manual versions but customers may require some automated functions while other functions remain manual or semi-automatic. Prototypes often rely on manual controls to define basic process parameters. Then the process is optimized in semi-automatic operation while eventually running in fully automatic mode when in full production. Existing product manufacturing may require only full automation but the manufacturing process may need operators to execute some manual functions.

Depending on the customer’s manufacturing needs, Modutek can design automation combining manual and automatic controls as specified by the customer. The automatic process may run until operator intervention is required to execute a command or check a specific condition. Modutek can adapt its systems to meet such special automation needs.

Customized Process Components and Subsystems

Process components and subsystems may include chemical delivery, baths or tanks, wafer handling and wafer drying. Modutek can integrate some of these functions into a single unit or place separate units into a custom arrangement. For example, a chemical delivery station can have local or remote tanks and can be placed behind the processing stations to save space. An IPA vapor dryer can include de-ionized water rinsing and vapor drying in one unit. With the company’s experience as a leading wet bench manufacturer, Modutek can design custom arrangements that carry out the required wet process functions within the parameters set by the customer.

Modutek’s Customizations Improve Process Performance

Modutek has a complete line of standard wet process stations, all designed and built in house. For new customized projects, the custom system is evaluated for special requirements and possible solutions. Modutek then works closely with the customer to ensure that the chosen customizations reflect the special process requirements and will produce the expected results.

When Modutek builds such custom systems, they choose customization over standard systems because the customization will improve overall performance. Improvements can include higher throughput, better output quality and lower costs. Working transparently with the customer, Modutek can demonstrate how its proposals will produce better results and ensure that the finished system meets expectations.

How High Temperature Quartz Tanks Improve Silicon Wafer Processing

How High Temperature Quartz Tanks Improve Silicon Wafer ProcessingThe silicon wafer processing steps that include etching or cleaning the wafers with aggressive chemicals require tanks to hold the chemical process. Quartz tanks are impervious to the acids and bases used in wet process stations and the high temperature tanks can include heating and re-circulating. Modutek is a leader in the design and manufacture of high temperature quartz tanks and has over 30 years of experience in this field. As a result, Modutek quartz tanks are designed specifically for wet process etching and cleaning applications and reduce contamination to a minimum while ensuring precise heating for accurate process control.

Key Quartz Tank Characteristics for Silicon Wafer Processing

Silicon wafer processing involves etching the wafers to produce microscopic structures and cleaning the wafers in preparation for further process steps. Corrosive chemicals such as hydrochloric acid, sulfuric acid and hydrogen peroxide are used for the etching and cleaning process. Tanks made of quartz are not affected by these aggressive chemicals because quartz is a crystalline material made up of silicon and oxygen atoms held tightly in a crystal lattice. Semiconductor-grade quartz such as used in the Modutek quartz tanks is especially pure, reducing the possibility of contamination.

In addition to resisting corrosion by aggressive chemicals, quartz tanks are stable at high temperatures. Some etching processes work better at temperatures up to 180 degrees centigrade and the quartz crystal lattice remains intact at much higher temperatures. Modutek quartz tanks are designed to take advantage of the chemical and temperature stability of the quartz tanks to provide an ideal vessel for containing the silicon wafer etching and cleaning processes.

The Importance of Reduced Contamination

The use of high-purity flame-polished quartz in silicon wafer processing tanks ensures that there are few non-quartz substances in the crystal lattice and on the polished surface of the tanks. The possibility of contamination by the tanks is reduced to a minimum. Such contamination of the silicon wafers can affect the semiconductor products made from the wafers.

The functionality of semiconductor components relies of microscopic structures and current paths created on the silicon wafer. When a tiny particle or other contaminant interferes with the etching of these structures, the final semiconductor product may be defective or of inferior quality. The rejection rate for finished semiconductor products is heavily influenced by the presence of particles or other contaminants. Reducing the particle count by using high-quality quartz tanks reduces the number of defective components and increases output quality.

Why Precise Temperature Control Gives Improved Process Results

Depending on the chemicals used, a higher temperature may increase the etch rate and reduce processing times. While a high etch rate may be desirable, the amount of etching that takes place still has to be tightly controlled because the amount of etching determines the size and shape of the microscopic structures in the silicon. On the one hand, exactly the right amount of etching has to take place before the process finishes, and on the other hand, if the same process is run again, the amount of etching has to be the same.

The two main factors influencing the etch rate are chemical concentration and temperature. Modutek’s process controls ensure that the right chemical concentration is maintained and the quartz tank temperature controls keep the process at exactly the right temperature. Modutek’s quartz tank temperature controller can keep the temperature constant within plus/minus 1 degree centigrade for precise etching control and excellent repeatability from one batch to the next.

For improved silicon wafer processing, process tanks have to be free of contamination and have to accurately reproduce process conditions. With Modutek’s high temperature quartz tanks, reduced contamination during etching and cleaning of silicon wafers is ensured and the temperature controls of the tanks provide precise settings during the process and for subsequent batches.

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.

Improving Wafer Manufacturing Processes with Automated Equipment

Improving Wafer Manufacturing Processes with Automated EquipmentAutomated wafer fabrication equipment can improve semiconductor manufacturing facility performance, but all the associated process settings must be programmed properly. Before the manufacturing process can be implemented on a fully automated wet bench station, the settings, timing and other parameters have to be fine tuned. As circuit geometries and micro-structures become smaller and more tightly packed, the chemical concentrations, temperature levels and timed intervals affecting the etch rate become more and more critical. Fully automated equipment can precisely and reliably run a semiconductor manufacturing process once the correct variables are determined and programmed.

Manual Operation Can Determine the Settings for the Process Variables

Once wafer fabrication processes such as KOH etching are chosen, the process variables can be selected. Etching can be either isotropic or anisotropic and etching speed or precision can vary. Other factors may come into play as well. Initially it makes sense to run the new process on a manual station so that the process results for rough settings of basic variables such a concentrations, temperature and timing can be determined. These variables can then be adjusted to get an initial and acceptable process result.

Semi-Automatic Operation Can Fine Tune the Process

After determining the rough settings of the basic variables in manual operation, transferring to semi-automatic operation to optimize the process steps can save time. Those variables that will no longer change can be programmed into the semi-automatic software control while the others can be adjusted manually to get the best process result. In this way, as each process step is optimized, it can be programmed so that when optimization is complete, the process is ready to run on fully automated wafer processing equipment.

Fully Automated Operation Improves Semiconductor Manufacturing Facility Performance

Fully automated wet process stations for which the process has been optimized in manual and semi-automated operation can help improve overall production facility performance in the following ways:

  • Programmed settings ensure that the process is repeatable for different batches
  • Use of wet processing simulation software during optimization helps ensure accurate process parameters
  • Full automation eliminates human error
  • Precise dosages of chemicals and accurate timing results in fewer defective products
  • Throughput and wafer yields are increased

The programmed settings can be used again to get an identical result and they can be used for similar applications with minor adjustments. Instead of relying on operators to prepare etching baths, the fully automated station mixes the required chemicals quickly, safely and reliably, always the same way and without waste or spillage. The result is precise control over the process steps, fast execution without delays and high output quality.

Improved Output Relies on Optimized Software and Fully Automated Stations

Using an optimization strategy with manual and semi-automatic operation and running the optimized process on fully automated wafer fabrication equipment can lead to continuous improvement in semiconductor manufacturing operations. As new processes are brought online and optimized, they replace older versions that may not use chemicals as efficiently, may rely on some manual input or may not have the same precise and reliable execution as the fully automated stations. Tailor-made software working with fully automated wet process equipment can result in such continuous improvements.

With 40 years of experience in wet process technology and extensive in house expertise from manufacturing its own equipment, Modutek is ideally situated to supply fully automated equipment that improves semiconductor manufacturing output. The company has a complete line of standard and custom-built wet process equipment and the SolidWorks software used to calculate process parameters is programmed in house. Working closely with its customers, Modutek designs and builds its fully automated stations and programs the corresponding software to help them meet their goals for continuous improvement. Contact Modutek for a free quote or consultation on selecting equipment that supports your specific manufacturing process requirements.

How Specialized Wet Bench Equipment Improves the RCA Clean Process

How Specialized Wet Bench Equipment Improves the RCA Clean ProcessThe RCA clean process removes contaminants from the surface of silicon wafers so that additional wet process semiconductor manufacturing steps can take place. The process consists of two steps, with the SC1 step removing organic compounds and the SC2 step dislodging any remaining metallic residues or particles. Specialized wet benches ensure that contaminant and particle removal is as complete as possible and the silicon wafers remain clean. To accomplish this, the equipment carefully rinses away contaminants and minimizes the handling of the wafers. Automation can be used to replicate process parameters reliably and consistently. Modutek can supply both standard and customized specialized equipment to carry out the RCA clean process.

RCA Clean SC1 Removes Most of the Wafer Surface Contamination

The SC1 cleaning step uses chemicals to dissolve impurities while leaving the underlying silicon surface unaffected. The wafers are placed in a solution containing equal parts of NH4OH (ammonium hydroxide) and H2O2 (hydrogen peroxide) in five parts of de-ionized water. The solution is heated to about 75 degrees centigrade and the wafers are left in the solution for ten to fifteen minutes. Organic residues are dissolved and particles are removed. A thin layer of silicon oxide forms on the wafer and there is some contamination with metallic ions and particles.

RCA Clean SC2 Removes Metallic Impurities

For SC2, the newly cleaned wafers are placed in a bath containing equal parts of hydrochloric acid and hydrogen peroxide in five parts of de-ionized water. The exact ratio may vary depending on the application. The bath is heated to about 75 degrees centigrade with the wafers soaking for about ten minutes. The solution specifically eliminates alkali residues, metal hydroxides and other metallic particles. The wafers are now completely clean and free of all types of particles.

Wafer Cleaning Equipment Has to Fulfill Specialized Functions

Specialized equipment is needed to carry out RCA clean process steps effectively. The required chemicals have to be delivered in the right quantities to the cleaning baths and then, when the chemicals are no longer needed, they have to be neutralized and disposed of safely. The concentration of the chemicals, the bath temperature and the timing are all important for being able to subsequently reproduce the desired cleaning performance. Contaminants and particles have to be rinsed away and filtered out. Key features of effective cleaning are a low particle count on the wafer surface and a resulting low rejection rate for fabricated wafers.

Modutek’s Wet Process Equipment Provides Specialized Features

Modutek’s wet benches and chemical stations support both of the RCA cleaning steps. Chemical delivery systems ensure that the right amounts of chemicals are supplied to the process safely and that waste chemicals are neutralized before disposal. The FM4910 material of construction keeps particle contamination low and is safe to use with the acid and base processes of RCA clean. All baths include a continuous flow de-ionized water chamber with chemical circulation and filtration to rinse away and remove contaminants. The SolidWorks flow simulation software lets operators calibrate dosages precisely and store settings for future use.

As well as fulfilling customer needs from its extensive line of wet process equipment, Modutek can build custom systems for specific applications. Customers who wish to incorporate drying, etching or stripping functions as well as RCA clean in their process lines can rely on Modutek to design and build exactly what they need.

With 40 years of experience in the wet process and technology sector and one of the leading semiconductor equipment manufacturers, Modutek has the expertise in house to provide specialized equipment for the RCA clean process and other semiconductor manufacturing applications. Customers can count on Modutek to help them find effective solutions and supply the corresponding equipment. Contact Modutek for a free quote or consultation to discuss your process equipment requirements.

How Are Isotropic and Anisotropic Processes Used to Improve Silicon Wet Etching?

How Are Isotropic and Anisotropic Processes Used to Improve Silicon Wet EtchingThe microscopic structures produced by silicon wet etching can be created with a high degree of precision by using both isotropic and anisotropic processes. Isotropic etching is faster but may etch under masks to create rounded shapes. Anisotropic etching can be controlled more precisely and can produce straight sides with exact dimensions. In each case, controlling the etch bath temperature and the etchant concentration is critical for successful micro-structure creation and for repeatability for subsequent batches.

How Isotropic and Anisotropic Etching Differ

Silicon wafers have a mono-crystalline lattice structure that repeats in all directions but is not equally dense in all directions. Vertical planes contain a different number of silicon atoms than diagonal planes. This means that etching with certain etchants is slower in the directions with more atoms while it progresses faster in the directions with fewer atoms.

Etchants used for isotropic etching, such as hydrofluoric acid, etch at the same speed in all directions, independently of silicon atom density. For etchants used for anisotropic etching, such as potassium hydroxide (KOH), the etching speed depends on the number of silicon atoms in a crystal lattice plane and therefore depends on the direction of the different planes.

The difference in anisotropic etching speeds allows a better control of shapes etched into the silicon wafers. With a corresponding orientation of the silicon wafer, etching can be timed to produce straight or angled sides and sharp corners. Etching under masks can be reduced.

How Isotropic and Anisotropic Etching Are Used in Semiconductor Manufacturing

Isotropic etching is harder to control than anisotropic etching but it is faster. In the initial stages of silicon wafer fabrication, large features are etched into the silicon. At this stage of manufacturing, etching speed is important for facility throughput. Isotropic etching is used to quickly create these large shapes with rounded sides and corners. Although process engineers and operators have less control over the shape of the feature being etched, accurate temperature and concentration control are still important to ensure that the rounded shapes being created are the same on wafers processed in different batches.

After the large shapes are etched with an isotropic process, the micro-structures and metal paths require better control of the details. Anisotropic etching provides this control as long as the lattice structure of the silicon wafer is oriented correctly. Anisotropic KOH etching is reliable and easily controlled. It can be used to create the precise, straight-sided shapes that are required in the final semiconductor product. Accurate control of the temperature and etchant concentration is even more important for anisotropic etching because these process parameters strongly influence the etching speeds in the various directions and therefore influence the final shapes that are etched.

Modutek Teflon Tanks Support Both Isotropic and Anisotropic Etching

For silicon wet etching processes in which the etch speed is temperature dependent, Modutek’s heated Teflon tanks provide rapid heating and tight temperature control. The tanks are either recirculating or static and they can be built into any new wet bench configuration. The tanks feature 360-degree overflow filtration and uniform heating throughout the bath. The heat-up rate is 2 to 3 degrees centigrade per minute and the temperature control accuracy is plus/minus 0.5 degree centigrade. The temperature controls of these tanks are ideally suited for both isotropic and anisotropic etching.

In terms of control of etchant concentration, Modutek can provide for the injection of de-ionized water into the tanks. Because etchant concentration affects the etch speed, accurate concentration control is important for final product quality and repeatability. Modutek can analyze customer requirements, find and build custom solutions and ensure that process control is precise enough to deliver the required results, both for isotropic and for anisotropic etching.