Choosing the Right Chemical Delivery System for Your Application

Choosing the Right Chemical Delivery System for Your ApplicationSemiconductor manufacturers and research labs have extensive chemical handling requirements and need a safe way to supply chemicals to the points where they are used. Key factors for choosing chemical delivery systems are the storage options that are available, the system performance in terms of precision and reliability and the software that can be used to ensure safe and accurate operation.

The chemical delivery systems have to be able to receive the chemicals in bulk, store them safely and conveniently, supply them to the point of use in the required quantities, neutralize them as needed and dispose of them appropriately. Custom configurations, fast chemical change and control options may also be important. Suppliers have to be able to evaluate customer needs and make recommendations based on their experience with chemical delivery systems.

Chemical Delivery System Features

An ideal chemical delivery system improves facility or manufacturing line performance by increasing throughput and producing better quality output. It accomplishes this by reducing manual interventions that can slow down the process and introduce errors. When chemicals are supplied to the point of use exactly as they are needed and with the exact composition required by the process, the facility can operate at optimal efficiency.

A key component of a chemical delivery system is chemical storage. Storage space near the process is often limited but adequate storage to avoid frequent container changes is needed. Ideally the chemical delivery system can continue to operate with integrated storage while a main storage container is being changed.

The mixing and delivery of chemicals to the point of use has to be safe, precise and reliable. Software can calculate the precise amounts needed while monitoring sensors can show chemical paths, levels and other process variables. Extensive and flexible control configurations let customers choose exactly how the chemical delivery system will operate. High quality materials ensure reliable operation and long-term safety. Facility managers and engineers choosing a chemical delivery system have to evaluate such features and check which suppliers have the expertise to recommend a good fit for their needs.

Modutek’s Chemical Delivery Systems
Modutek’s advanced chemical delivery systems provide all the required features and functionality mentioned above. Large tote chemical containers with load cell interfaces can eliminate the need for frequent drum changes when large volumes of chemicals are used. For smaller quantities, a 55-gallon drum system is available and both storage systems are designed for quick chemical changes. Systems have all-Teflon fluid paths with leak detection and sensing of up to four levels. The automated chemical deliveries are displayed on a touch screen that also shows the status of key components such as valves, pumps and alarms. Modutek’s SolidWorks Flow Simulation and SolidWorks Simulation Professional provide accurate chemical delivery calculations and the Modutek systems can be integrated with the company’s own wet processing equipment or adapted for each customer.

Modutek’s chemical delivery systems use software and components that are designed and manufactured at the company’s San Jose, California facility. As a result, Modutek can offer unparalleled service for all its equipment and can prepare custom designs for specialized requests. In addition to providing chemical delivery systems for wet process stations, Modutek systems are suitable for tech benches, plating stations, fume hoods, cleaning stations and acid exhaust hoods. By eliminating manual operator interfaces and ensuring accurate chemical concentrations and mixtures, the Modutek chemical delivery systems can help with increasing facility efficiency and reducing failure rates. If you need a reliable chemical delivery system for your application, contact Modutek for a free quote or consultation.

Using KOH Etching for Batch Processing

Using KOH Etching for Batch ProcessingEtching baths with varying concentrations of potassium hydroxide (KOH) and controlled temperatures are used in creating microscopic structures on silicon wafers. Modutek can supply equipment such as PFA Teflon tanks, circulation and filtering systems and cassette handling equipment that supports KOH etching. The company designs and builds individualized systems for customers who want to use KOH etching and the resulting systems deliver accurate control, high repeatability, consistent performance and superior output quality.

The KOH Etching Process
The KOH etching process is well understood and is a preferred method for creating silicon wafer nano structures for semiconductor manufacturing and in research facilities. The process delivers controlled and uniform results with high precision and it is relatively safe.

The silicon surface is masked to allow etching and cavity creation in specific areas according to the layout of the final semiconductor product. The etch rate can be controlled by varying the concentration of KOH and the bath temperature. KOH etching is also impacted by the following:

  • The lattice planes of the crystalline silicon
  • Boron doping of the silicon
  • The presence of atomic defects in the silicon crystal
  • Natural impurities

Orienting the lattice planes in a particular direction can influence and control the direction of the etching and the shape of the cavities created in the silicon. Similarly, boron doping can be used to stop etching in a particular direction. Together with the mask, these factors permit the creation of cavities of the required shapes and orientations. Defects in the silicon crystal or natural impurities may reduce the quality of the final product and can result in defective items.

Advantages of KOH Etching
KOH etching provides excellent results and is used extensively because of the following advantages:

  • Safe and easy to handle
  • Rapid etching
  • Excellent reproducibility
  • Low cost
  • High precision when process variables are tightly controlled

Modutek can supply equipment that builds on the listed advantages to deliver corresponding benefits to the customer.

Modutek’s KOH Etching Process Equipment
Modutek’s wet bench technology supports KOH processing, and Modutek examines each request in detail before building the equipment for a particular application. This includes the KOH processing tank, the recirculating system and the silicon wafer handling. Sizes, capacities and control characteristics are adjusted for the customer’s requirements.

The systems supplied by Modutek use the latest technology to provide high accuracy and excellent output quality. Etch rates can be controlled precisely and etch uniformity is guaranteed. Even long etch times, such as up to 3 days, can be handled reliably and safely.

Modutek’s KOH processing tanks are PFA Teflon with all-Teflon fluid paths. The tanks are manufactured onsite using advanced PFA sheet welding techniques designed to minimize impurities and unwanted by-products. The tanks are available as static or as recirculating baths.

The static baths can be ambient temperature baths or temperature controlled from 30 to 100 degrees centigrade. The recirculating temperature controlled baths feature heat-up rates of 2 to 3 degrees centigrade per minute and a temperature control accuracy of plus/minus 0.5 degrees centigrade. The available semi automatic cassette handling reduces costs and increases reliability.

In each case Modutek makes sure that the equipment supplied fits into the existing or a new installation and is compatible with any other wet processing systems. Modutek’s specialists work to ensure the supplied equipment satisfies the customer’s requirements and meets or exceeds performance expectations.

Wet Processing Systems for Solar Cell Manufacturing

Wet Processing Systems for Solar Cell ManufacturingSolar cell manufacturing facilities and research labs use wet processing equipment to etch and clean solar cell silicon wafers. Efficient removal of wafer saw damage, adding of texture, chemical polishing and cleaning of the wafers with reliable, safe wet processing systems is a key factor for increased facility productivity and high quality output. Modutek offers the latest wet bench and ozone cleaning technology to meet customer requirements either with standard systems or customized solutions.

Silicon Wafer Saw Damage Removal

Solar cell silicon wafers are cut from silicon bricks with wire saws, leaving a damaged surface with irregular crystal structure and a damaged crystal lattice. The wafers are placed in an etching bath that removes a thin layer of damaged crystal and leaves a smooth and uniform surface. Modutek wet processing equipment delivers high throughput with accurate controls and consistent results for this process.

Silicon Wafer Texturing

Silicon wafers used for solar cells absorb more light and convert light to electricity more efficiently when their front surface is etched with a microscopic texture. The texture reduces reflection of light from the solar cell surface and promotes internal reflection. For monocrystaline silicon, an etching bath removes small pyramid shapes from the surface of the silicon, leaving an even, consistent texture. For multi crystal silicon, the surface can be etched the same way, but the result is uneven and less effective due to the different orientations of the crystals. Alternative solutions with ion-etching and masks are available.

Chemical Polishing

After the front of the wafer is textured, the rear side remains comparatively rough. Such roughness can reduce the life span of the solar cell and impacts performance. By polishing the rear side of the cell and the edges in an etching bath, internal light reflection is improved and a higher efficiency cell can be manufactured.

Ozone Pre-Cleaning

The cutting of silicon wafers with a wire saw uses a slurry applied to the wires. The cut wafers are contaminated with the slurry and have to be cleaned before they can be etched, textured and polished. The Modutek Ozone Cleaning Process uses ozone dissolved in a mild acid bath to deliver high-performance cleaning at low cost.

The Modutek Ozone Cleaning Process reduces the use of expensive and environmentally harmful chemicals while improving throughput and producing wafer output with fewer defects. The equipment itself is less expensive than other cleaning solutions and there are lower costs due to reduced use of water and for disposal of waste.

Modutek Wet Processing Systems for the Solar Industry

Modutek has been providing wet processing equipment for semiconductor manufacturing for over 35 years and has the experience to examine customer applications and recommend the best solutions. For solar cell manufacturers, Modutek can offer the right equipment for cleaning, etching, polishing and texturing the silicon wafers and can make recommendations on the processes to be used.

In some cases it may make sense to combine saw damage removal with texturing or with polishing and different chemical baths may be appropriate for different customer needs. Modutek can advise customers which wet processing systems they need and can customize equipment if required. Modutek supplies wet processing systems and related equipment to solar cell manufacturers in the United States as well as around the world. Contact Modutek for a free quote or consultation to discuss which equipment to use for your application requirements.

Upgrading Used Semiconductor Manufacturing Equipment and Wet Benches

Upgrading Used Semiconductor Manufacturing Equipment and Wet BenchesSometimes it makes more sense to upgrade existing equipment than to buy complete new systems. Equipment may not be near the end of its useful life and new technology can often increase yield and output quality. Customers can address ongoing safety issues and reduce frequent unscheduled downtime. Upgrades can provide higher levels of automation and improved robotics can be installed.

When equipment breaks down, it may be an opportunity to replace key components while whole subsystems can be upgraded during scheduled maintenance to avoid additional downtime. By addressing known weaknesses in a production line, the overall reliability of operations can be increased. Upgrading wet bench stations and other semiconductor manufacturing equipment in this way can be a cost-effective means of improving productivity.

Specific Reasons for Upgrading Equipment

Retrofitting new components, upgrading existing equipment and repairing defective parts can often extend the life of your semiconductor manufacturing systems. Reasons for upgrading include the following:

  • Install improved technology to increase throughput
  • Upgrade components to obtain higher yield
  • Refurbish or replace equipment that is no longer supported
  • Save money by extending equipment life span
  • Accommodate larger wafers
  • Update the automatic and robotic systems and controls
  • Improve ventilation and safety
  • Upgrade electrical systems to the latest standards
  • Improve ergonomics and ease of operation
  • Improve chemical delivery system performance

Such upgrades depend on a supplier’s ability to evaluate a system’s specific requirements and implement a customized approach to install and repair components. Extensive experience with development and assembly of semiconductor fabrication equipment is a prerequisite for carrying out upgrades effectively.

Types of Upgrades Carried Out by Modutek

Modutek relies on their experience with in house development and manufacturing of wet bench and related equipment to carry out all types of upgrades, both on their own equipment and that of other manufacturers. Such upgrades can include:

  • Identifying and replacing failing parts
  • Replacing defective parts with new or retro-fitted components
  • Replacing obsolete components
  • Updating robotics, baths and wet etching components
  • Upgrading motion controls and software
  • Re-designing and improving systems within an existing footprint
  • Reconditioning existing systems to improve performance

Modutek can visit a customer’s site and perform system evaluations to develop possible upgrade, repair and retrofit scenarios. Customers can then decide how they want to proceed and Modutek can carry out the selected work.

Specific Benefits of Upgrading

Many upgrades have specific benefits associated with them and customers can rely on Modutek to carry out the work so that the expected advantages are realized. For example, upgrading controls is an effective way of improving performance. Customers can upgrade from manual or semi-automatic operation to semi-automatic or fully automatic systems to improve consistency and reduce operator errors. Upgraded controls can also reduce waste and ensure that chemical formulas are followed accurately.

Safety upgrades are often required and always reduce operator risk. Adding robotics can result in more accurate control and improved safety. When electrical systems are brought up to code, reliability often improves as well as making the systems safer. Adding ventilation, fire suppression, tank lids and fume control can improve operator comfort as well as increase safety.

Adding heaters, chillers and temperature controls can reduce process times and result in better performance. Level sensors give more accurate system feedback and adding pumps, valves and switches can result in better overall process control.

Modutek can determine whether such upgrades and retrofits make sense and then carry out the appropriate work. The company can evaluate the performance of its own older systems as well as semiconductor fabrication equipment from other manufacturers on a case by case basis that includes MEI, Amerimade, Micro Tech Process, JST Manufacturing and others. With its in house expertise, Modutek can reliably upgrade semiconductor manufacturing equipment to provide optimal performance and guarantee the results.

How to Select a Supplier from Your List of Semiconductor Equipment Manufacturers

How to Select a Supplier from Your List of Semiconductor Equipment ManufacturersWhen choosing a supplier from a list of semiconductor equipment manufacturers you have to look at a wide variety of factors. Key points to evaluate include the following:

  • Customization capabilities to meet customer requirements
  • Equipment reliability
  • Company experience and expertise
  • Warranties
  • Service and customer support

Only after you have determined which manufacturers can actually supply the equipment you want can you look at cost of ownership and pricing to make your final decision.

Specifying What You Need

Semiconductor fabrication lines and research labs are different and have specific requirements when they want to upgrade lines, replace components or buy new equipment. Sometimes the purchased equipment has to interface with existing systems, sometimes space is a factor and sometimes the physical set-up of the production facilities limit what can be installed. A supplier has to be able to evaluate these constraints and suggest solutions. The equipment proposed often has to be customized to some extent and the supplier has to have the experience and the capability to adapt his standard solutions to particular situations.

Equipment Reliability

Once you have purchased your equipment, it has to keep working with a minimum of downtime. The best way to evaluate the reliability of a supplier’s equipment is to ask for references and reliability statistics. Suppliers should submit normal hours of scheduled downtime, estimates of unexpected downtime and the records of actual installations. Once you have narrowed down the list of suppliers, it’s a good idea to check with some of the references who are not direct competitors of your company and verify what the supplier has submitted.

Warranties, Service and Support

Before you sign a contract with a selected supplier, check on his equipment warranties and his service and support capabilities. Warranties should be simple, comprehensive and of sufficient length. Check on whether the supplier has enough service personnel. Also important is whether he can rely on his own personnel to carry out service or whether he has to call in third parties. If a supplier subcontracts a lot of his equipment manufacturing, he is less likely to have competent service personnel on staff to deal with that equipment. Call support to see how they respond to support requests. Often calling a supplier’s customer support line with an equipment question rather than going through your contacts in sales will give you an idea how well a supplier responds to support requests.

Conclusion

The selection of the right semiconductor manufacturing equipment supplier for additions to a fabrication line or a research lab affects future productivity and output quality. You have to make sure you buy the equipment you need and select a supplier who will keep it working optimally.

Modutek has the experience required and the expertise to advise customers and to support their installations. The company has been in operation for over 35 years and carries out assembly of its equipment and creation of associated software in house. As a result, Modutek can offer expert service and support for all of a customer’s needs. With its commitment to total customer satisfaction and its record of in house development and manufacturing, the company is an excellent choice and a leading supplier among semiconductor equipment manufacturers. If you have any questions about Modutek’s products and support services, take a minute to call and discuss your concerns with one of their customer service representatives.

Tips on Selecting Wafer Processing Equipment for Your Application

Tips on Selecting Wafer Processing Equipment for Your ApplicationSemiconductor manufacturing and research facilities use wet bench technology to produce silicon wafers that require many cleaning and etching process steps. The wet bench equipment needs to be flexible and configured for the particular manufacturing process. Ideally equipment should be suitable for both acid and solvent applications with designs based on extensive experience using high quality materials and meeting or exceeding all applicable safety standards. Typical processes used for wafer processing equipment include KOH Etching, BOE (Buffered Oxide Etching), RCA Clean, plating and Megasonic cleaning. For special applications, custom designs to meet specific process requirements may be needed. Depending on the budget framework and the process, wet benches can be fully automated, semi-automated or designed for manual operation.

Fully Automated Stations

Wafer fabrication equipment with full automation offers excellent consistency of process steps and improved output quality. Precise control of chemicals and process times allows for minimization of waste and a reduction of operator errors. A reduced use of chemicals due to exact dosages can save money and effective neutralization of discharges means compliance with environmental regulations is easier. Software calculates the chemical dosages and each process is completely repeatable in a consistent process environment.

Semi-Automated Stations

Semi-automated stations offer the robotics of the fully automated wafer processing equipment without the automation and at a lower cost. The servo-controlled robots with three degrees of freedom produce a uniform process and allow operators to precisely control chemical dosages and process times. Controls are user friendly via a touch screen and software for simulations and dosage calculations is available.

Manual Stations

Stations without automation offer the same high quality process equipment as the automated stations but without the cost of automation. The manual wet benches include all the process and safety features of the automated equipment minus the cost of the robotics. The standard models and customized versions can be adapted for any wet bench processing application and the units are especially attractive due to the low cost of ownership.

Whether they are manual or automated, the process equipment features white polypropylene construction with wiring to NFPA 70 and 79. Safety features include an emergency power off button, safety interlocks and PVC safety shields. Process tanks have a one-inch lip exhaust and the units have a continuous flow DI water manifold along with a Teflon N2 gun and DI water hand spray. Third party certification for NEC and NFPA is available.

All of the wet benches and chemical stations can be ordered as standard units that can process semiconductor wafers up to 12” (300 mm) as well as glass substrates in a variety of sizes up to 30″ x 60″ solar panels. The units can be customized to fulfill any processing, etching or cleaning application. At Modutek, all design, assembly and testing is carried out in house including the writing of the SolidWorks Simulation software.

Modutek’s Wafer Processing Equipment

The Modutek fully automated, semi-automated and manual wet benches meet the highest standards of material quality and safety. All orders are reviewed by Modutek mechanical and electrical engineers and produced based on over 35 years of experience in the industry. The company uses its internal expertise to advise customers on the best equipment to meet their requirements.

Because Modutek writes its own software and builds the wafer processing equipment in house, the company can offer complete customer assistance without going to outside suppliers. Problems are handled internally and customers receive seamless technical support. Modutek’s technical staff can help customers during the ordering process, while manufacturing and assembly is taking place, during factory testing with de-ionized water and with on-site service after delivery. Call Modutek for a free quote and recommendations on using the right wafer processing equipment for your application.

How Marangoni Drying Produces Superior Surface Conditioning for Wafer Processing

How Marangoni Drying Produces Superior Surface Conditioning for Wafer ProcessingAt the end of a particular step in silicon wafer processing, wafers often have to be cleaned, rinsed and dried. The resulting wafer surfaces must be free of water, watermarks, particles and organic residues. Older technologies such as spinning the wafers rapidly or heat drying can no longer fulfill the requirements of high density electronic devices on today’s silicon wafers. Water is hard to remove completely from complicated geometries and drying can leave contaminating watermarks and particles.

Such contamination can lead to product defects in subsequent processing steps or to high failure rates as the contamination impacts quality. IPA (isopropyl alcohol) drying using the Marangoni drying effect leads to dry silicon wafer surfaces without watermarks or particles. Modutek’s IPA vapor dryer is cost effective and can be integrated in a wet bench process without adding drying transfer steps.

How it Works

In Modutek’ IPA drying process, IPA vapor is introduced at the top of the drying tank to ensure even vapor distribution. Because the IPA has a lower surface tension than water, it introduces a surface tension gradient where it interfaces with the water on the wafer surface. As a result of the Marangoni drying effect, water flows off the surface of the silicon wafer and leaves it dry and clean.

The departing water also takes along any impurities or particles suspended within it. No watermarks are present because the water does not dry on the wafer surface and ozone can be introduced into the drying tank to eliminate trace organic contamination. There are no moving parts inside the chamber so physical wafer damage is eliminated and drying cycles typically last ten to fifteen minutes.

Modutek’s Design

The stand-alone Modutek IPA dryer is a 30″ wide cabinet of polypropylene construction. It features wiring to NFPA 70 & 79 and has all Teflon fitting, valves and tubes. A touch screen controls operation with a graphic user interface and the dryer has a multiple recipe function.

The unit has an N2 head case purge with an interlock, a hot N2 dry feature, a continuous flow DI water manifold and an auto lid with foot switch open. PVC side shields are removable and there is DI water degassing function using a membrane contactor. Third party certification for NEC and NFPA is available.

Dryer options include PVC construction, a manual lid and a quick dump feature. Data logging and online support are available. Other options include a static eliminator, resistivity monitoring, HEPA fan filter units and a fire suppression system. Modutek can customize any dryer to customer specifications.

IPA Dryer Operation

The Modutek MVD series IPA dryer is a competitive solution with a single drying chamber for DI water rinsing and IPA vapor drying. The IPA vapor is generated in a one gallon bottle installed at deck level for easy changing. Introducing the vapor at the top of the tank is an efficient way of achieving even distribution of the vapor and reduces IPA consumption. The dryer can handle all wafer sizes and glass substrates and Modutek can integrate the IPA drying function into wet bench stations to eliminate a transfer step.

Benefits of Modutek’s IPA Vapor Dryer

Modutek’s specialists work with customer engineering teams to design a dryer that best matches the process application. Modutek’s design and software implementations are all carried out in house and acceptance testing with de-ionized water is available. The company’s extensive experience in the semiconductor manufacturing industry lets it provide first class customer support at all stages of a contract and after delivery. If you need to improve your wafer processing quality and want a free consultation or quote on using an IPA Vapor Dryer, call Modutek or email Modutek@modutek.com.

Why Pre-Diffusion Cleans Are Critical in Wafer Cleaning Processing

Why Pre-Diffusion Cleans Are Critical in Wafer Cleaning ProcessingBefore silicon wafers are placed in a diffusion furnace, they must be cleaned to remove impurities and particles from their surfaces. Such pre-diffusion cleaning takes place several times during semiconductor manufacturing as microscopic structures are fabricated in the silicon. Various wafer cleaning process methods include the use of different chemical baths, ozone treatment or megasonic cleaning for ensuring that wafers are clean and free from contamination. Modutek offers a complete range of equipment that supports the various cleaning methods and helps ensure the highest quality output from semiconductor manufacturing facilities.

Cleaning Methods

Standard cleaning methods involve immersing the silicon wafers in baths of powerful chemicals that remove contaminants and particles from the surface of the wafers. Silicon is relatively inert to reactions with the chemicals used but organic and metallic impurities on the wafer surfaces are oxidized and dissolved.

In the RCA wafer cleaning process silicon wafers are placed into a solution containing ammonium hydroxide and hydrogen peroxide. This bath removes organic contaminants but may leave metallic traces. As a result, the RCA clean process is often carried out in two parts called SC1 (standard clean 1) and SC2. After the ammonium hydroxide/hydrogen peroxide (APM) bath, the SC2 step consists of a bath containing hydrochloric acid and hydrogen peroxide (HPM). SC2 removes metal ions and leaves the wafer clean and ready for further processing.

Piranha etch clean is used to remove large amounts of organic residue from silicon wafers. It consists of a bath containing sulfuric acid and hydrogen peroxide and can dissolve hard to remove organic material such as photoresist. The solution’s strong oxidizing properties hydroxilate the surfaces of the silicon wafers, making them hydrophilic or attractive to water. This property may be an advantage for subsequent cleaning steps.

Megasonic cleaning is another method for obtaining clean, particle-free silicon wafers for diffusion. The method uses cavitation bubbles produced by megasonic waves in a cleaning solution to remove particles and contaminants from wafers. The bubbles produce a scrubbing action that cleans wafer surfaces without the use of expensive and corrosive chemicals.

In some cleaning applications, ozone may be used to obtain clean, particle-free silicon wafers. The wafers are first rinsed with deionized water to remove water-miscible contaminants and are then exposed to ozone in an ozone chamber.  All organic contaminants and particles are converted to carbon dioxide leaving the wafer surface clean and particle-free.

The Importance of Effective Cleaning

The presence of particles on the silicon wafer surface affects the subsequent diffusion steps and impacts the quality of the final product. Particles may be diffused into the silicon along with the doping substances and produce unknown electrical anomalies. They may remain on the surface and block subsequent etching processes to change microscopic structures. They may interfere with the creation of tiny conductor paths on the surface of the silicon and they can create chemical patches that don’t react as expected.

With the trend to smaller size geometries in silicon wafer structures, the potential damage that a single particle can cause has increased. Particles may affect the performance of a semiconductor product or its reliability. The product lifetime may be reduced or its functionality impaired. Defective products reduce plant performance while low quality products hurt the facility’s reputation. Ideally semiconductor manufacturers need equipment that will help them produce high quality semiconductors with low reject rates by emphasizing effective wafer cleaning methods with a maximum reduction in the presence of particle contamination.

Modutek Wafer Cleaning Solutions

Modutek offers a complete line of chemical baths and wet processing equipment that supports RCA clean with SC1 and SC2, piranha clean, megasonic cleaning and ozone clean. Each wafer cleaning process is designed to provide effective pre-diffusion cleaning to produce silicon wafers with a minimum of particle contamination.

In addition to traditional chemical cleaning, Modutek has pioneered advanced ozone cleaning and is using megasonic cleaning for additional particle removal for smaller device geometries. The company can help semiconductor manufacturing facilities increase their throughput, improve their performance and reduce their costs by drawing on the extensive experience they have developed in the various silicon wafer cleaning applications.

How the Advanced Ozone Cleaning Process Improves Wafer Yields and Reduces Costs

How-the-Advanced-Ozone-Cleaning-Process-Improves-Wafer-Yields-and-Reduces-CostsModutek’s advanced ozone cleaning process offers two methods that can improve silicon wafer cleaning and reduce chemical use. The main part of the process uses ozone to convert organic residue on wafers into carbon dioxide through oxidation. The wafers coming out of this process have reduced levels of particle contamination when compared to traditional cleaning methods using chemical baths. The improved cleaning performance of the patented advanced ozone cleaning process can increase facility throughput and improve semiconductor quality while reducing chemical use.

 

How Advanced Ozone Cleaning Works

With ozone cleaning in Modutek’s DryZone gradient dryer, wafers are first rinsed with deionized water to remove inorganic impurities before being exposed to ozone in an ozone chamber. The Coldstrip ozone cleaning method operates at sub ambient temperatures while Organostrip cleans at room temperature.

The ozone’s powerful oxidizing action converts the carbon of organic residue to carbon dioxide and leaves wafers clean and particle-free. The ozone is dissolved in either plain water or in a mild solvent solution and substrates receive a stable hydrophilic surface.. No harsh chemicals are required and the exhausts and waste products of the process are harmless.

 

Advantages and Benefits

The advantages of Modutek’s advanced ozone cleaning process in comparison to traditional chemical cleaning methods derive from the more compact process equipment, the absence of harsh chemicals and better cleaning performance. Benefits include lower costs, higher quality products due to lower particle counts and an environmentally-friendly cleaning process that doesn’t require compliance with onerous regulations.

Where Piranha cleaning requires as many as six processing tanks and traditional solvent cleaning five tanks, the Organostrip ozone cleaning method requires only three tanks while the Coldstrip method requires two. As a result, equipment costs and space required will be less.

One of the main issues with chemical bath cleaning is the short lifetime of the cleaning solution. The Piranha clean mixture deteriorates immediately and cleans effectively for only a few hours. Other solvents have a solution life span measured in days, after which the solution has to be replaced. Because the ozone cleaning methods do not rely on solution components that react chemically with each other, the lifetime of an ozone solution is at minimum greater than a week.

Other advantages of the ozone cleaning method are its compatibility with metal films, the absence of water stains and the low particle count. Where a typical particle count for ozone cleaning is less than 15, cleaning with Piranha solution or solvents produces particle counts in the thousands.

The resulting benefits for a semiconductor manufacturing facility can be substantial. The process costs for Coldstrip are estimated at $21,000 per year while Organostrip runs to $104,000. These amounts compare to approximately $300,000 for Piranha strip and $200,000 for other solvent methods.

In addition to saving money on process costs, the costs of chemical storage, handling and disposal must be factored in. All of these have a component for regulatory compliance that can be very costly, depending on the jurisdiction in which the facility is operating. The ozone cleaning process has no such costs.

Finally there is a key benefit to the reduced particle counts obtained with the ozone process. Subsequent diffusion and etching will result in fewer defective components and a higher quality final product. Overall, ozone cleaning allows a semiconductor manufacturing facility to improve production line performance and substantially reduce costs.

 

Modutek Can Help

Modutek offers the equipment for applying the patented ozone cleaning process to semiconductor manufacturing and can help in determining the ideal configuration for a particular application. The company also delivers equipment for traditional chemical bath cleaning methods and is therefore ideally placed to advise how the new ozone cleaning methods can improve production. Semiconductor manufacturers can take advantage of this capability to cut costs and increase productivity in their plant.

How Piranha Etch is Used in Silicon Wafer Cleaning

How Piranha Etch is Used in Silicon Wafer CleaningThe fabrication of silicon wafers is carried out with repeated etching and cleaning steps to produce the micro-structures required for the final silicon semiconductor products. Piranha or SPM (sulfuric peroxide mix) solutions can clean organic material from wafers and oxidize most metals. The powerful chemical action that makes it a favorite for resist strip and for the cleaning of wafers with organic residue also makes it difficult to use. High quality silicon wafer cleaning equipment designed to handle the corrosive chemicals safely is required for carrying out piranha etch safely and effectively.

What is Piranha Etch and How is it Used

A piranha solution is made up of a mixture of sulfuric acid and hydrogen peroxide. The most common ratio is approximately three parts acid to one part peroxide but solutions of up to seven parts acid to one part peroxide are sometimes used. The solution is highly exothermic and is prepared by slowly adding the peroxide to the acid. The mixture heats up rapidly and is often used at temperatures of around 130 degrees C. Once operating temperature and the desired concentration are reached, the wet bench equipment has to heat the solution to maintain the temperature and keep the etch rate constant.

When a facility wants to re-use a piranha solution for an extended period of time, the solution must be spiked with extra hydrogen peroxide. Hydrogen peroxide is unstable in the solution and decomposes, reducing the etching power of the bath. Spiking with additional hydrogen peroxide lets a facility use a piranha solution for up to eight hours rather than having to replace it every two hours. Spiking saves money by conserving sulfuric acid but it requires wet bench equipment that can handle the process and the spiking.

Semiconductor fabrication facilities and research labs use piranha etching to clean residue from silicon wafers and glass. The solution removes trace organic contaminants and strip residue while oxidizing metals. The underlying surfaces are hydroxilated making them hydrophilic or attractive to water, a characteristic that can be used in subsequent silicon semiconductor manufacturing process steps.

Modutek’s Silicon Wafer Cleaning Solutions

Modutek specializes in semiconductor manufacturing equipment and wet bench technology that includes solutions for wafer cleaning. The company can supply standard equipment or can customize wet bench solutions to fit specific customer requirements. Priorities are high quality materials, excellent designs, low cost of ownership and high quality results. Piranha wafer cleaning is supported by Modutek’s QFa quartz recirculating tanks and the QA constant temperature baths. Both can be installed in a wet bench station and the process can be controlled automatically, semi-automatically or manually.

The QFa series high temperature re-circulating baths provide fast even heating over a temperature range of 30 to 180 degrees C. The heat up rate can be up to 2 degrees C. per minute and the temperature control is up to plus/minus 1 degree C. The quartz bath is made of flame-polished semiconductor-grade quartz insulated with silica fiber rated up to 1260 degrees C.

The QA series constant temperature quartz baths are made from the same materials with the same control characteristics as the QFa series but they feature a magnetic stirrer, an aspirator valve system, gravity drain and a quartz bubbler. Both baths are available in standard sizes or can be custom made to fit customer requirements.

Modutek can provide a complete range of wet bench and silicon wafer cleaning equipment that includes baths suitable for piranha cleaning applications. The equipment is designed with safe and reliable operation in mind and the cleaning equipment eliminates contaminants and impurities to the greatest extent possible. Modutek wet bench equipment allows operators to use piranha cleaning methods safely to increase facility throughput while maintaining or improving output quality. Call or email Modutek for a free quote or recommendations on using the right equipment for your wafer cleaning application.