Improving Standard Clean Particle Removal in a Wet Bench Process

When silicon wafer yields are not improved with the Standard Clean process, improved particle removal can be achieved with advanced processing equipment. Standard Clean or RCA clean was developed by the RCA company in 1965 and it has changed little since then. It has always been successful in cleaning wafers and removing most particles. However, with silicon circuits and structures decreasing in size and product density on wafers increasing, even the tiniest particles can cause device defects.

RCA clean works by first dissolving and removing organic materials from the surface of the wafers using powerful chemicals. In a second step, metallic impurities are removed and the wafer is rinsed clean. The two-step process and the rinsing remove most particles but the smallest particles often remain attached to the wafer with surface tension and electrostatic charges. Such particles can affect diffusion in wafers or block the etching of electronic structures or circuit paths.

The submicron particles are hard to remove completely with chemicals or by rinsing. The use of megasonic cleaning technology to generate very high-frequency sound waves in the wafer bath provides the capability to dislodge all remaining particles, allowing them to be rinsed away. Megasonic cleaning improves Standard Clean particle removal process and helps ensure defect-free production of microscopic structures on the silicon wafer.

How Megasonic Cleaning Works to Improve Standard Clean Particle Removal

The two steps making up the RCA wafer cleaning process are SC1, using a mixture of ammonium hydroxide and hydrogen peroxide, and SC2, using a mixture of hydrochloric acid and hydrogen peroxide. The SC1 process removes most of the contamination from the silicon wafer surface, but introduces metallic ion contaminants that can influence subsequent wafer processing steps. The SC2 process dissolves the remaining contaminants, allowing impurities to be rinsed away as they float to the surface of the cleaning mixture.

Standard Clean takes place in heated inert tanks such as quartz baths that are carefully designed to limit additional contamination. The chemical mixtures are heated to about 80 degrees centigrade and processing takes about 10 minutes for each step. After rinsing, the silicon wafers are clean but may still have an unacceptable number of submicron particles adhering to the wafer surfaces.

Megasonic cleaning can remove the majority of these particles while also dislodging the few larger particles that may still be present. The process involves adding a megasonic transducer to the tank holding the wafers. The transducer converts very high-frequency signals from a megasonic generator into sound waves that travel through the rinsing water to strike the wafer surfaces. Sound wave frequencies are typically at or above 1 MHz but may range as low as 200 kHz depending on the specific cleaning application.

As the sound waves travel through water, they create microscopic cavitation bubbles that form and burst in tune with the sound wave frequency. When the bubbles burst, they produce tiny but intense jets of water. The jets from the bubbles near the wafer surfaces dislodge any remaining particles, leaving them to be rinsed away at the surface of the bath, for example via an overflow weir. The additional Megasonic Cleaning step is very effective in particle removal because the tiny jets break any bonds that make the particles adhere to the wafer. The result is extremely low particle counts on wafers that undergo both the RCA wafer cleaning process and Megasonic Cleaning.

Modutek Designs and Builds Specialized Equipment to Improve Wet Bench Processes

Megasonic Cleaning is one example of Modutek’s implementation of designs and technologies that improve wet process performance for their customers. For over forty years Modutek has been providing specialized semiconductor manufacturing equipment to meet unique industry needs. As a leading semiconductor equipment manufacturer, the company offers free consulting and can provide recommendations on equipment from its complete product lines. When Modutek supplies wet bench equipment to customers, the company follows a well-defined process to ensure their equipment performance meets customer requirements.

The Importance of Pre-Diffusion Cleans in Silicon Wafer Cleaning

The Importance of Pre-Diffusion Cleans in Silicon Wafer CleaningWhen wafer cleaning immediately prior to diffusion is effective, semiconductor manufacturing output is of high quality and the defect rate is reduced. A major pre-occupation of pre-diffusion cleaning is the removal of microscopic particles from the surface of the silicon wafer. Particles can prevent even diffusion and may themselves be diffused into the silicon, causing defects.

Silicon wafer cleaning can be carried out in chemical baths or with megasonic cleaning systems. Several cleaning steps using different processes are sometimes required to get a specific level of cleanliness. The goal is to obtain wafers free from metallic or organic contamination and with as few surface particles as possible. As silicon microstructures are designed with smaller elements and with a higher component density, adequate wafer cleaning becomes more and more critical.

RCA Clean Uses Two Steps to Remove Organic and Metallic Contamination

RCA clean uses ammonium hydroxide, hydrogen peroxide and hydrochloric acid to remove surface contaminants from the silicon wafer. In the Standard Clean 1 (SC1) process, the wafers are placed in a mixture of ammonium hydroxide and hydrogen peroxide. The corrosive mixture removes organic matter but may leave metal ions behind.

In the Standard Clean 2 (SC2) process, the remaining metallic traces are removed by immersing the wafers in a mixture of hydrochloric acid and hydrogen peroxide. At the end of the RCA wafer cleaning process, organic and metallic contamination has been removed while as many remaining particles as possible are rinsed away as well.

Piranha Clean Removes Heavy Organic Contamination

When wafers are heavily contaminated with organic materials such as photo resist, the Piranha process cleans more quickly than RCA clean. The wafers are immersed in a mixture of sulfuric acid and hydrogen peroxide and the mixture may be heated to speed up the reaction. The piranha clean process hydroxilates the wafer surface, making it hydrophilic. This affinity for water is sometimes a useful feature for additional cleaning measures.

Megasonic Cleaning Removes Contaminants and Particles

Megasonic cleaning avoids the use of corrosive chemicals and is especially effective for dislodging microscopic particles from the wafer surface. The Megasonic process works by generating high-frequency sound waves in the cleaning bath. An ultrasonic generator produces the high-frequency electronic signal and a transducer converts the signal into sound waves that travel through the cleaning solution. The sound waves create tiny cavitation bubbles that produce a scrubbing action against the wafer surface. The action of the bubbles cleans the wafer.

Microscopic contaminating particles adhere to the wafer and are difficult to remove. With integrated circuits featuring increasingly smaller geometries, even the tiniest particles can cause defects. Megasonic silicon wafer cleaning operates in the frequency range near or above 1 MHz and the cavitation bubbles agitate the cleaning solution at the operating frequency. Such agitation breaks the bond holding the particle on the wafer surface and the floating particles can be rinsed away.

Modutek Wet Bench Equipment Supports Pre-Diffusion Cleaning Methods

RCA, Piranha and Megasonic cleans are commonly used in pre-diffusion clean, but each fabrication facility optimizes for its own sequence of semiconductor manufacturing processes. A production line may use one or several cleaning methods, and may have special requirements for production parameters such as size, temperature or timing.

Modutek designs and builds its own complete line of wet bench equipment and can advise customers on choosing the best processing stations for their applications. Ideal solutions often require extensive customization to optimize yield and reduce costs to a minimum. Modutek can provide custom solutions including pre-diffusion cleans, and can design new equipment for integration into the customer’s manufacturing line to meet specific wafer processing requirements.

How Process Controls Improve KOH Etching Results

How Process Controls Improve KOH Etching ResultsWhile potassium hydroxide (KOH) etching is a versatile process for creating silicon microstructures, precise and responsive controls are required to get superior results. The KOH wet bench process is popular because KOH etches quickly and it is less hazardous than some other processes. Combined with accurate chemical delivery and reliable process controls, KOH etching can deliver exact etching dimensions and reproducible results for batch processing.

KOH Etching Can Create Complex Shapes

The KOH process is used widely because, in addition to etching quickly, it can be set up to etch at different speeds in different directions. For example, technicians may want to etch downward, into the silicon wafer, more quickly than etching in a horizontal direction. They may want to create a rectangular shape, where the long side has a different etch rate than the short side.

The etching direction is influenced by the crystal lattice orientation of the silicon wafer and possible doping of the wafer with boron. The etching speed depends on the KOH mixture concentration and temperature. To obtain improved KOH etching results, the etching process has to be set up to include all these factors and produce the desired result every time the process runs.

When the microstructures to be etched into the wafer require different etching speeds, the process uses the fact that the crystal lattice can be denser in one direction than another. Because there are more atoms to etch away in the denser direction, etching progresses more slowly. Boron doping is a way to stop etching in a particular direction. KOH will not etch areas with boron impurities, so etching stops at the doped silicon.

Once the wafer with the correct crystal orientation and doping is ready for etching, a basic etch speed can be determined with the KOH concentration. The etch speed is controlled by the KOH mixture temperature but the concentration has to be high enough for the desired etch speed.

Typical KOH concentrations can vary from 10 percent to 50 percent with 30 percent KOH by weight representing a common value. The mixture is heated to between 60 and 80 degrees centigrade and held steady at the temperature that gives the desired etch speed. With right wafer crystal orientation, doping in the right places and the correct etch speed, the microstructures will be completed in a given time.

Teflon Tanks with Precise Controls Produce Improved Output

The Teflon tanks designed and manufactured by Modutek feature the precise temperature controls and accurate support equipment that an effective KOH process requires. To etch the silicon wafer with a high degree of accuracy, operators have to make sure the concentration of KOH is at exactly the right value and have to be able to control the temperature within narrow limits.

Modutek’s wet bench equipment can deliver the KOH mixture to the Teflon tanks at the right concentration. The tank temperature controls can produce a heating rate of 2 to 3 degrees centigrade per minute, leading to rapid correction of temperature deviations. The controller accuracy is plus/minus 0.5 degrees centigrade, precise enough for excellent etching speed control.

The precise controls mean that the etch rate remains exactly at the desired level. The dimensions of the silicon microstructures are etched exactly as planned and the KOH process delivers high-quality output. Equally important is that the next time a batch is run with identical requirements and settings, the output is reproducible and the silicon microstructures are the same.

Modutek offers a complete line of wet bench processing equipment and can adapt the KOH etching tanks as well as other processing stations to meet the needs of its customers. All equipment is designed and built-in house, allowing for extensive customization and unparalleled customer support and service.

How the IPA Vapor Dryer Further Improves Wafer Processing

The Advantages of Using Modutek's Quartz Tube Cleaning StationsWhen silicon wafers are dried after rinsing, the wafer surface has to be free of water marks and contaminating particles. This is especially true after hydrofluoric acid removes the silicon oxide layer during the last etching before further processing. The wafers are subsequently exposed to diffusion or vapor deposition and surface contamination will result in defective components.

During the IPA vapor dryer process, water flows off the surfaces of the wafers without evaporating and leaving water marks. Particle contamination is minimized and the wafers remain clean. The Modutek IPA vapor dryer is a space-saving way of ensuring high-quality semiconductor output for wet process manufacturing facilities and research labs.

Modutek’s IPA Vapor Dryer Delivers Clean Wafers While Reducing Costs

Modutek’s IPA vapor dryer incorporates rinsing and drying in a single station to reduce costs, save space, and minimize the handling of the silicon wafers. The station first rinses the wafers with de-ionized water and then introduces IPA vapor into the drying cabinet. The vapor is generated in a one-gallon bottle situated in the exhaust compartment for easy changing.

The IPA vapor is introduced into the drying chamber from the top to ensure even distribution, reducing the amount of IPA required and further reducing costs. When the IPA vapor condenses on the wafers, a surface tension gradient develops between the IPA and the remaining water. The water flows off the wafer surfaces, taking contaminating particles with it. The dry wafer surface doesn’t have any water marks and is practically particle-free.

Advantages and Benefits of Modutek’s IPA Dryer

Modutek’s IPA dryer lets operators transfer the silicon wafers from the last etch processing station to the dryer chamber without any further movement of the wafers. Wafers are fragile and can easily pick up particles when moved. With the single rinsing and drying chamber, wafers avoid damage and remain as particle-free as possible.

The IPA drying method is a gentler alternative to heat drying or rotating the wafers to spin off excess water. Heating leaves particles in place and thin wafers can break when spun rapidly. Instead, the IPA dryer has no moving parts, eliminating sources of potential damage to the wafers. A drying cycle typically takes around 15 minutes.

IPA dryer cabinets are a compact 30 inches wide and made of white polypropylene. The graphic user interface operates via a touch screen and features multiple recipes. The SolidWorks Simulation Professional and SolidWorks Flow Simulation software calculates process flow characteristics and often reduces the required drying time. The Modutek IPA vapor dryer is a customizable unit that can be designed to fit into customer wet process lines and meet customer requirements.

Modutek Designs and Builds Their IPA Dryer Systems in House

Modutek’s IPA dryer is designed, built and tested at the company’s San Jose, California facility. Modutek does not outsource any of this work and even develops its own software, the SolidWorks Simulation Professional and SolidWorks Flow Simulation programs. As a result, Modutek can offer highly customized versions of its IPA dryer. Modutek engineers can work with customers to integrate the IPA vapor dryer in an existing wet process line or design a custom free-standing unit to meet the requirements of the customer application.

With more than 40 years of experience in wet process semiconductor manufacturing equipment, Modutek can analyze the needs of its customers with a free consultation. The company can then recommend equipment from its complete wet process equipment line and from associated equipment such as tanks, chemical handling equipment and lift stations. In each case, Modutek can offer customized systems and equipment to meet the needs of its customers.

The Advantages of Using Modutek’s Quartz Tube Cleaning Stations

The Advantages of Using Modutek's Quartz Tube Cleaning StationsAfter a quartz tube is used in a high-temperature semiconductor manufacturing process, it has to be cleaned thoroughly to remove contamination. Process steps such as diffusion leave traces of diffused material on the tube and the high-temperature furnace leaves contaminants. A Quartz tube cleaning station removes the surface contaminants and leaves the quartz tube clean and free of particles, ready for its next use.

Effective Quartz Tube Cleaning Is Critical for Output Quality

Quartz tubes are used as an inert container for semiconductor manufacturing processes such as vapor deposition and diffusion. The wafers inside the quartz tube are inserted into a furnace that can reach 1000 degrees centigrade. The semiconductor characteristics and the circuit paths of semiconductor components are created during these process steps. After use, the quartz tube surface has deposits from the furnace and from the process. Before it can be used again, the deposits have to be removed and the quartz tube has to be cleaned in a way that minimizes the particle count on its surfaces.

In a quartz tube cleaner, an acid spray dissolves the surface contaminants and washes them away. The clean tube is then rinsed with de-ionized water and dried carefully without introducing any new contaminating particles. Because quartz tubes are fragile and because handling them introduces new contamination, a degree of automation for quartz tube cleaning can be beneficial.

Minimizing the particle count is especially important for subsequent semiconductor manufacturing steps such as masking or etching. When micro-structures are etched into the wafers or current paths are created on masked wafers, even a single particle can affect a microstructure or block a current path. Such effects can lead to defective or poor quality semiconductor components. Manufacturing facility throughput is reduced by large numbers of rejected products and output quality can suffer.

Modutek’s Quartz Tube Cleaners Deliver Substantial Benefits

Quartz tube furnaces are typically placed in several locations along a semiconductor production line and each requires reliable cleaning. The benefits of Modutek’s quartz tube cleaning stations include the following:

  • Customization. Modutek designs and builds its quartz tube cleaning stations in house. As a result, the company can easily customize each station to exactly meet specific requirements.
  • Rugged, reliable construction. Made from white polypropylene, the cleaners feature a rugged tube roller system and powerful cleaning nozzles that ensure complete coverage.
  • Safe operation. Operators are protected with PVC safety shields and safety interlocks. The systems include emergency off mushroom buttons.
  • Variety of Options. Modutek offers many options, including hot N2 drying, acid holding tanks and acid mixing, lift stations and onboard bottle washers.
  • Automation. The cleaners can be operated manually or fully automatic. If required, different steps can be automated while others can be carried out manually. Manual operation can test out the cleaning process and then run it fully automated.

Modutek horizontal quartz tube cleaners deliver reliable cleaning with the degree of automation ideal for the specific process application. Handling of the tubes is minimized and an extremely high degree of cleanliness is achieved consistently.

Modutek Designs, Builds and Supports the Equipment Needed for an Application

With its in house expertise and extensive experience in semiconductor manufacturing equipment, Modutek can analyze a manufacturing process and provide equipment to fulfill the process requirements. The complete line of Modutek wet processing equipment is developed in house so that the design and manufacturing knowledge stays in the company. As a result, Modutek can design and build equipment to meet specific needs. Customers can ask for a free consultation and select standard stations from the Modutek wet process line or receive customized equipment that fulfills their requirements.

Using the Advanced Ozone Cleaning Process to Improve Wafer Yields

Using the Advanced Ozone Cleaning Process to Improve Wafer YieldsTwo key goals for semiconductor manufacturers are to increase process yields and to reduce chemical usage. Wet process semiconductor manufacturing is sensitive to wafer contamination by microscopic particles that increase final product rejection rates and reduce output quality. The ozone cleaning process can reduce particle counts and improve wafer yields by reducing the number of defective products. At the same time, cleaning organic contaminants from the wafer with ozone reduces the use of expensive and toxic chemicals. Modutek’s Advanced Ozone Cleaning Process allows semiconductor manufacturing facilities to increase throughput and output quality while reducing operating costs.

How Advanced Ozone Cleaning Improves Wet Process Line Performance

Modutek’s Advanced Ozone Cleaning Process uses ozone to remove organic contaminants from the surfaces of silicon wafers during wet bench processing. Ozone is used with either room temperature acidic acid or chilled DI water to clean wafers without aggressive chemicals. In addition to saving money due to reduced use of chemicals, ozone cleaning takes less space and is faster than many chemical-based wet bench processes.

Ozone cleaning takes place in Modutek’s DryZone System. Modutek has developed the Coldstrip sub ambient process and the Organostrip process that operates at room temperature. Both ozone cleaning processes deliver reduced particle counts and increased yields.

The Coldstrip process operates at four to ten degrees centigrade and introduces ozone into the ozone chamber after the wafers have been rinsed with de-ionized water. The rinsing removes non-organic contamination while the ozone combines with the carbon of the organic contaminants to produce carbon dioxide. After completion of the Coldstrip process, the wafers are clean and almost particle-free.

In the Organostrip process, the wafers are rinsed with acidic acid containing ozone. The acidic acid used has extremely high ozone solubility and the high ozone level producing produces rapid decomposition and oxidation. The ambient temperature process eliminates the use of toxic chemicals and the process waste products are harmless.

The Modutek Advanced Ozone Cleaning Process Improves Performance While Saving Money

Modutek developed the Advanced Ozone Cleaning Process to achieve low particle counts and to reduce the use of harmful chemicals. Reduced particle counts are needed for the more compact architecture of modern semiconductors where a single particle can cause defects or lower component quality. Reduced use of chemicals is mandated by increasingly strict environmental regulations while chemical purchase, storage and disposal costs continue to rise. The patented Modutek Advanced Ozone Cleaning Process successfully addresses these issues.

Specific benefits from using the ozone cleaning process include the following:

  • Better wafer yields due to lower particle count
  • Savings from reduced use of chemicals
  • Compatibility with metal films
  • Safer work environment due to absence of toxic substances
  • More environmentally friendly operations
  • Space saving due to more compact equipment
  • No toxic waste disposal issues

Modutek’s Advanced Ozone Cleaning Process increases throughput due to shorter cleaning times and higher yields while cost savings due to reduced use of chemicals are substantial. Semiconductor manufacturers can improve the overall performance of their facility by incorporating Modutek’s DryZone cleaning stations in their wet process lines.

Modutek Can Help Customers with Innovative Solutions

The Advanced Ozone Cleaning Process is one example of Modutek’s initiatives to improve the performance of wet process technology stations and help customers address common problems. The patented process solves issues with current semiconductor manufacturing and helps customers with product quality and with their bottom line.

With Modutek’s emphasis on customer service and on working with customers to improve wet process technology, the company continues to be a leader among semiconductor equipment manufacturers. Customers can rely on Modutek to supply the equipment they need and to provide the support ensuring the equipment meets or exceeds performance expectations.

Achieving Optimum Particle Removal in a Wet Bench Process

Achieving Optimum Particle Removal in a Wet Bench ProcessAs component packing is tighter and circuit geometries trend towards smaller structures, the reduction of submicron particle contamination during the wet bench process steps becomes more important for output quality. When circuit paths are reduced in size, a single submicron particle can block the path and render the final semiconductor component defective. Even when the presence of particles doesn’t cause defects, their influence on semiconductor performance can reduce the quality and lifespan of the final products.

Semiconductor manufacturing facilities and research labs using typical wet bench equipment face challenges when trying to reduce submicron particle contamination to acceptable levels. Innovative solutions such as the use of Megasonic Cleaning and the reduction of wafer handling with a single chamber IPA dryer can help bring down the particle count. When such solutions are integrated directly into the wet bench processing line, throughput and yields can increase. The process may require fewer chemicals and overall facility performance can improve.

How Megasonic Cleaning Reduces Particle Contamination

The use of high-frequency sound waves in cleaning systems is common in many industries but the delicate silicon wafer structures and surfaces require extra-high frequencies to make sure wafers are not damaged. Megasonic cleaners use frequencies of 950 kHz and higher, in the megahertz range, to deliver the soft cleaning action required.

The sound waves from lower frequency systems create microscopic but comparatively large cavitation bubbles in the cleaning bath. The bubbles produce intense scrubbing against the surfaces of the parts to be cleaned, dislodging contaminants and delivering a powerful cleaning action. For the soft surfaces, delicate structures and thin metallic deposits of silicon wafers, such intense cleaning can result in the pitting of surfaces and damage to silicon structures.

In Megasonic cleaning systems, the high-frequency sound waves produce smaller bubbles and more gentle scrubbing. The cleaning action is soft enough to preserve silicon surfaces and structures but strong enough to dislodge contaminating particles. The particles often adhere to the wafer surfaces and are difficult to dislodge with normal rinsing. Megasonic Cleaning breaks the adhesion and creates currents that wash the particles away.

The Megasonic Cleaning action is especially important for submicron particles where the adhesion to the wafer surface inside a boundary layer makes rinsing less effective. The soft scrubbing of tiny bubbles against the wafer dislodges submicron particles effectively and reduces particle contamination.

How the Single Chamber IPA Dryer Reduces Particle Contamination

One of the ways silicon wafers pick up contaminating particles is during the transfer from etching to drying stations. This transfer is especially critical for HF last etching. During the final etching in a wafer fabrication step, the silicon oxide layer is removed through etching with hydrofluoric acid. The wafer is then rinsed and dried before moving on to the next fabrication step. Particles remaining on the wafer surface can interfere with the subsequent fabrication process.

In an innovative development that eliminates this source of particle contamination, a single chamber handles HF last etching and IPA vapor drying. First, hydrofluoric acid is injected into the station chamber to etch the wafer. When etching is complete, the wafer is rinsed with de-ionized water until the acid is neutralized to a safe pH. IPA vapor is then introduced into the station chamber, and after about 15 minutes, the wafers are dry and ready for the next fabrication step. The particle count remains low because the wafers have not been moved throughout the etching and drying process.

Modutek Provides Innovative Semiconductor Manufacturing Equipment for Excellent Results

Modutek works closely with customers to develop innovative wet bench stations that meet their requirements. Attention to customer needs and finding new solutions to common problems allow the company to remain one of the leading wet bench manufacturers.

For Megasonic Cleaning applications, Modutek has partnered with Kaijo Corporation, a world leader in high sound frequency cleaning technology. Modutek’s integration of the Kaijo Megasonic cleaners into the wet bench product line has produced low particle counts that are difficult to obtain with other methods.

Because Modutek designs and builds its own etching and IPA drying stations in house, the company was able to develop its innovative single chamber station and integrate it into its comprehensive wet process product line. In parallel with Megasonic Cleaning, the single chamber station further reduces particle counts, improves yields and reduces costs. On these and other wet process questions, Modutek offers free consultations to ensure customers get the best equipment for their needs.

Solvent Processing Using Stainless Steel Stations

Solvent Processing Using Stainless Steel StationsManufacturing processes using volatile solvents have to be specially designed to minimize the risk of explosions or fire. Solvents such as acetone or alcohol are used to clean parts, dissolve materials and extract substances. Modutek’s stainless steel stations meet strict safety regulations that reduce the risk of ignition of the solvents or their vapors and they have additional features and interlocks in an integrated approach to operator safety. As a result, the stainless steel stations can be installed safely in both new and existing facilities for solvent processing.

Special Design Measures Ensure Safe Solvent Station Operation

Safe stainless steel solvent station operation depends on specific design measures that reduce the risk of fire or explosion. Modutek’s stations satisfy safety regulations and include design features that improve safety based on extensive experience in wet bench processing. Special safety design measures can include the following:

  • Electrical equipment runs on low voltages and weak currents to reduce the risk from sparks.
  • Electric wiring satisfies fire protection standards NFPA 70 and 79.
  • Overall station design satisfies hazardous location standards and is certified for Class 1, Division 2 environments.
  • The manufacturing process is monitored to detect dangerous conditions such as high temperature.
  • Liquid solvent waste is collected in carboys for controlled disposal.
  • Safety interlocks eliminate unsafe operation and shut down the process for unsafe conditions.
  • Automatic lid operation can seal off chemical containers.
  • Operators are trained for safe operation.
  • Access controls limit equipment operation to trained personnel.

How Stainless Steel Solvent Processing Stations Operate Safely and Reliably

Modutek’s Series SFa and Sa Stainless Steel Stations for solvent processes meet all the safety requirements of the applicable regulations. Made of electropolished stainless steel, the stations satisfy the National Electrical Code Class 1 Division 2 Group D standard for hazardous locations. The baths feature PVC safety shields, N2 head case purge and an auto lid option. They are designed for operator safety and prioritize safe containment and disposal of volatile solvents.

The SFa series station uses a temperature controlled re-circulating bath while the Sa series is constant temperature. The baths have a temperature control precision of plus/minus 1 degree centigrade, a heat-up rate of 2 degrees centigrade per minute and an operating temperature range of 30 to 100 degrees centigrade. Bath heaters are rated from 2 to 6 kW depending on the tank size. With precise temperature control and a fast heating rate, the baths can improve yield and produce high-quality process output.

In addition to the safety features and temperature control characteristics, the baths have multi-sided heating elements, a 360 degree overflow weir, operating interlocks, process control thermocouples and liquid level sensors. The tanks are available in standard sizes from about 8 inches to 24 inches a side. Custom sizes are also available.

Modutek’s Can Provide Solvent Processing Stations to Satisfy Customer Requirements

With 40 years experience in designing wet benches for semiconductor manufacturing, Modutek supplies stations made with high-quality materials designed for safety, ease of use and reliable operation. As a leading wet bench manufacturer, Modutek is constantly innovating to incorporate the latest advancements in its wet process equipment including its solvent processing stations.

Modutek can examine solvent processing needs and recommend stations for specific applications. A complete line of standard baths and the ability to customize as required means the company can build solvent processing stations to meet special customer needs. Modutek builds all its own equipment and designs and writes its own software in-house. As a result, Modutek can give expert guidance on what is required and follow up with complete customer support and service for all its products. For a free quote or consultation to discuss your specific requirements contact Modutek at 866-803-1533 or email [email protected].

Selecting Chemical Handling Equipment for Solvents and Acids

When chemicals are used in a manufacturing process, chemical handling systems are Selecting Chemical Handling Equipment for Solvents and Acidscritical for accurate chemical delivery to the process equipment and the safe disposal of the chemical waste. Effective chemical handling systems are especially important for solvents and acids because of the corrosive nature and the dangers of unsafe handling of these chemicals. Finding the right chemical handling system for a manufacturing facility is often challenging because the applicable regulations have to be followed and worker safety has to be guaranteed. A competent manufacturer with extensive experience in chemical handling and a proven track record in chemical handling equipment can advise customers of the most appropriate system for their specific application.

Chemical Handling Equipment Functions and Features

Chemical handling equipment ensures the safe acquisition, use and disposal of hazardous chemicals used in manufacturing. Essential functions include the following:

  • Delivery: Chemicals have to be delivered to the process equipment in the quantities, mixtures and concentrations required. This requires accurate repeatability. We build all our delivery systems around your chemical drums. This includes single or double drums requirements.
  • Collection: Collection of hazardous chemicals takes place in a specially secured cabinet with containment and leak detection capabilities. Modutek’s systems are designed for use with Department of Transportation (DOT) approved drums for direct shipment for disposal.
  • Neutralization: This option is also available if chemical disposal becomes too expensive. Once chemical is neutralized properly chemicals can than drain directly to your main drain.

In addition to chemical handling equipment functionality, specific manufacturing applications may benefit from features that increase operational safety, reduce costs or improve manufacturing operations. For expensive chemicals, features that reduce chemical waste are important. Chemical handling equipment dealing with dangerous chemicals may have to include extra operator safety protections. Dangerous chemical waste is best neutralized next to the manufacturing process, but if that’s not possible, chemical collection systems can safely hold chemicals that will later be transported for off-site treatment. Chemical handling equipment often has to be customized to address the functions needed and make sure the required features are in place.

Modutek’s Line of Chemical Handling Equipment Can Meet Manufacturing Needs

Modutek can offer a complete line of chemical handling equipment that can customized for specific manufacturing needs. Modutek’s equipment line includes the following:

  • Acid neutralization systems. These compact systems add neutralizing chemicals to acid or alkaline waste. They feature low operating costs and either batch or continuous operation.
  • Chemical delivery systems. Chemicals are delivered to the process in exact quantities and at the right times. These systems reduce chemical waste and eliminate operator errors that cause spills.
  • Chemical lift stations. These stations pump chemicals directly from the process to the neutralization area. They can be incorporated into the process line and feature flow capacity adapted to process requirements.
  • Chemical collection systems. Chemicals are collected and stored locally near the process or remotely in large collection tanks. In the absence of neutralization, storage can be sized to process requirements and designed to permit transportation of the containers for off-site treatment.

Modutek’s chemical handling equipment is designed to ensure safe and precise handling of hazardous chemicals. Chemical use is lower due to reduced waste and workplace safety is increased. Neutralization and disposal of hazardous chemicals can be carried out in accordance with regulations and can be documented to demonstrate compliance. Modutek can offer solutions for the chemical handling needs of varied manufacturing operations and the company’s experience in the field and its in-house expertise lets it customize the equipment exactly as needed. Contact Modutek for a free consultation or quote on equipment for your specific manufacturing requirements.

How Innovative Changes to the SPM Process Improves Results

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

How the SPM Process Cleans Wafers

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

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

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

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

Benefits from “Bleed and Feed” Process Change

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

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