Why High Temperature Quartz Baths Are Required for Silicon Wafer Cleaning

Silicon wafers undergo many process steps during the manufacture of semiconductor components and cleaning the wafers properly is an important factor in successful fabrication. Process steps include etching and diffusion, both of which involve coating the wafer with masking material to guide the etching chemicals or diffusion targets. Once a step is completed, the masking chemicals have to be completely removed. If traces remain or if other impurities are introduced, the quality of the final semiconductor product will be affected.

Silicon wafers are cleaned with aggressive chemicals to remove organic masking material and other possible contaminants. As a result, the cleaning solution container has to be able to resist the action of corrosive chemicals while remaining inert without becoming a source of contamination itself. Baths made of quartz are highly stable, resist corrosion and can be designed and built to avoid contamination. Quartz baths are an ideal solution to the challenges of silicon wafer cleaning and the maintaining of high levels of wafer cleanliness.

How Quartz Baths Clean Silicon Wafers

Quartz baths provide a clean and safe container for the chemical reactions that are used in silicon wafer cleaning. Depending on the materials used, the quartz bath may simply hold the wafers and the cleaning chemicals, but some processes require heating, circulating the solution or the addition of chemicals. In each case, the control actions must be accurate, reliable and easily duplicated.

For example, materials such as hydrochloric acid, sulfuric acid and hydrogen peroxide may be used for cleaning the silicon wafers. Quartz is impervious to these strong chemicals and the quartz tanks remain unaffected while the acids clean the silicon wafers. With SPM clean, sulfuric acid and hydrogen peroxide are mixed and maintained at a constant temperature of about 130 degrees centigrade. Periodic spiking with hydrogen peroxide is necessary because it decomposes in the solution. The mixture cleans wafers rapidly but can’t attack the quartz bath container.

Using bath containers that are inert and don’t contaminate is important because the electrical and physical structures making up modern semiconductor components are extremely sensitive to contaminating particles. As these structures become smaller and more tightly packed on a wafer, even a single particle can interfere with the etching or the diffusion process. Such interference from particles reduces the yield of semiconductor components and affects the productivity of the semiconductor manufacturing facility.

The Benefits of Using Modutek’s Quartz Baths

Modutek has over 30 years experience in quartz bath design and manufacture so that the company’s baths fulfill all the basic requirements for semiconductor processing and deliver additional benefits. Modutek can provide standard units where they satisfy customer requirements but can also design and build custom systems for special applications.

Modutek’s QFa series high temperature re-circulating quartz baths are safe and reliable with a low total cost of ownership. The semiconductor grade quartz of the baths is flame polished to reduce contamination and the vessels are designed for an especially long service life. Particle addition from re-circulating flow is kept to a minimum and remote control is available. Tank sizes range from an inner measurement of 7.75 x 7.75 inches and 9 inches high to 21.5 x 11.5 inches and 10.5 inches high. Custom sizes are available as well.

The QFa baths have an integrated heater that provides an operating range of 30 to 180 degrees centigrade. The heaters produce a temperature rise of 2 degrees per minute and control accuracy is plus/minus 1 degree centigrade, these variables depending on the operating conditions. The wide temperature range, fast thermal response and accurate temperature control make the Modutek quartz baths ideal for silicon wafer cleaning. The high precision guarantees excellent repeatability of the process between batches and the fast heating rate reduces process times. Overall, Modutek’s quartz baths can help improve the semiconductor production performance of manufacturing facilities and research labs. For a free quote or consultation on selecting the right equipment for your manufacturing process contact Modutek at 866-803-1533.

Reviewed and Approved by Douglas Wagner
President & CEO, Modutek Corporation

Improving Silicon Wafer Cleaning with the Piranha Etch Process

The Piranha etch process removes organic material from silicon wafers rapidly and completely. Semiconductor manufacturing involves the repeated etching and cleaning of the silicon wafers and the Piranha mixture is a favorite method for the resist strip of wafers to prepare them for further processing. Modutek can provide high temperature re-circulating and constant temperature quartz baths and the company has developed a new “bleed and feed” control method to improve the silicon wafer cleaning process.

Modutek Quartz Baths for Piranha Etch

Modutek quartz baths are based on extensive experience and the use of the highest quality materials. The baths themselves are made of virgin boron-free fused quartz in a flame-retardant polypropylene housing. The QFa series is a high temperature re-circulating bath with a temperature range of 30 to 180 degrees centigrade while the Qa series is a constant temperature bath with the same temperature range.

Both bath series are temperature controlled to plus/minus 1 degree centigrade with a heat-up rate of 2 degrees centigrade per minute. Process control can be fully automated, semi-automatic or manual. The baths are available in a variety of sizes and Modutek will construct custom units as required. The units are ideal for Piranha etch applications because of their quick and even heating, accurate temperature control and extended vessel life.

Improving Piranha Process Control

The Piranha process uses an aggressive mixture of sulfuric acid and hydrogen peroxide to dissolve organic residue on the silicon wafers. The mixture is heated to about 130 degrees centigrade to improve the strip speed. Control of the cleaning is difficult because mixing sulfuric acid and hydrogen peroxide is exothermic and heats up the solution when the mixture is first prepared. As the mixture cools, it has to be heated to maintain its temperature and the strip rate.

The hydrogen peroxide in the mixture is unstable and decomposes to form water, diluting the mixture and slowing the strip rate. Heating the mixture increases the rate of decomposition of the hydrogen peroxide. To keep the concentration and the strip rate constant, the sulfuric acid and hydrogen peroxide mixture is periodically spiked with extra hydrogen peroxide. This addition keeps the strip rate elevated but the overall process is hard to control and the mixture has to be replaced completely about once per day. To improve the Piranha process and silicon wafer cleaning, the concentration and temperature variation issues have to be addressed.

The Modutek “Bleed and Feed” Process Control Method

Modutek has developed a method of improving control of the Piranha process by using a two tank system with a clean and a dirty tank. When the concentration of hydrogen peroxide goes down, a small amount of mixture from the dirty tank is drained and discarded. The drained amount is replaced from the clean tank. The stripping process can continue and the concentration is maintained at the desired level. The clean tank has its sulfuric acid and hydrogen peroxide replenished. All “feed and bleed” amounts are programmable to match specific process variables.

Benefits of the Process Change

The “bleed and feed” control method can be fully automated and the frequent addition of small amounts of sulfuric acid and hydrogen peroxide mixture keeps the strip rate constant and allows for continuous use of the mixture over an extended period of time. The benefits include:

  • Savings of chemicals can reach 75 percent while chemical purchase and disposal costs are correspondingly lower.
  • Process efficiency is increased due to less downtime for replacement of the chemicals.
  • Process results are improved due to a more constant strip rate.

As a leading semiconductor equipment manufacturer, Modutek provides customers with high quality equipment that offers the highest degree of process control. Modutek supports the new “bleed and feed” process change for Piranha strip in the company’s new wet bench stations. Call for a free consultation to discuss your specific process requirements.

Reviewed and Approved by Douglas Wagner
President & CEO, Modutek Corporation

Why Pre-Diffusion Cleans Are Important for Silicon Wafer Cleaning

Why Pre-Diffusion Cleans Are Important for Silicon Wafer CleaningPre-diffusion cleans are carried out several times during the semiconductor manufacturing process, and each time the chemical residues and particles on the wafers have to be removed as completely as possible. If silicon wafers still have surface contamination when they are placed in the diffusion oven, diffusion may be uneven and the resulting semiconductor products may be defective.

The several methods available for wafer cleaning either use chemical baths or Megasonic cleaners to remove surface contaminants from the silicon wafers. Modutek offers a complete line of wet bench stations that support pre-diffusion wafer cleaning as well as other semiconductor fabrication processes.

The Importance of the Pre-Diffusion Wafer Cleaning Process

The contamination with particles on silicon wafer surfaces prior to diffusion is a key factor in reducing the yield of electronic components in semiconductor fabrication plants and research facilities. Particles may be diffused into the silicon and create electric defects or they may block diffusion behind the particle. After diffusion, particles may affect etching and interfere with microscopic conductors. The resulting electronic components may have to be scrapped.

As microscopic structures in silicon become smaller and more detailed, large particles become more disruptive on both an electrical and the physical scale. Even tiny particles that were previously considered unimportant can affect the smallest silicon structures. When electronic products are defective, it affects facility productivity and reduces throughput. Performance is lower and profitability is reduced. In some cases, the products are not defective but their life expectancy may be reduced and the manufacturer’s reputation is affected. An effective pre-diffusion wafer cleaning process results in fewer defects and a higher quality output.

How Pre-Diffusion Cleaning is Carried Out

Before being placed in the diffusion oven, silicon wafers are immersed in chemical or Megasonic baths. Surface impurities are dislodged, dissolved or chemically neutralized. Complete cleaning may take more than one process and the following methods are commonly used.

RCA cleaning is a popular method consisting of two components, SC1 and SC2, where the SC stands for standard clean. For SC1, the wafers are immersed in a solution of ammonium hydroxide and hydrogen peroxide. The aggressive chemicals remove all organic compounds from the wafer surfaces but may leave traces of metallic contamination. As a result, during SC2, the wafers are placed in a mixture of hydrochloric acid and hydrogen peroxide that removes any remaining metal ions.

An alternative to the RCA standard clean methods is the Piranha clean, especially useful for applications with heavy wafer contamination. It consists of a sulfuric and hydrogen peroxide mixture that rapidly removes material such as photo resist. A further feature of Piranha clean is the hydroxylation of the silicon wafer surface, making it hydrophilic or attractive to water, a characteristic useful for some subsequent process steps.

Megasonic cleaning uses high-frequency sound waves in a cleaning solution to dislodge contaminants from the surface of the silicon wafer. This cleaning method does not use harsh chemicals, and a generator is used to produce a signal in the MHz range at a specified power level. A transducer in the cleaning tank converts the signal to sound waves in water. The sound waves create microscopic cavitation bubbles with a strong scrubbing action that removes particles. Depending on the manufacturing process, semiconductor manufacturing facilities use one of these methods for pre-diffusion cleaning.

Modutek Pre-Diffusion Cleaning Equipment

Modutek’s wet bench chemical stations provide a complete range of pre-diffusion cleaning solutions. The company can offer equipment that supports each of the above cleaning methods as well as other semiconductor fabrication processes. All of Modutek’s pre-diffusion cleaning baths produce silicon wafers with extremely low particle counts while all of the company’s equipment is designed for high quality output, fast processing and efficient operation resulting in superior manufacturing facility performance. Contact Modutek for a free consultation or quote on equipment designed to meet specific manufacturing requirements.

Reviewed and Approved by Douglas Wagner
President & CEO, Modutek Corporation

 

How Customized Equipment Has Improved the Silicon Wafer Cleaning Process

Different customized systems or custom components may improve silicon wafer cleaning processes because customers have special requirements or because the process characteristics are unusual. Suppliers taking on such projects must have extensive in-house experience and expertise together with a board line of silicon wafer cleaning equipment to provide custom solutions. When customization is required, effective solutions can improve throughput, lower costs, and result in higher output quality and yield. Modutek has both the experience and in-house expertise required to offer such customized equipment.

Customized Software

Modutek’s SolidWorks Simulation Professional and SolidWorks Flow Simulation software allows customers to calculate chemical doses accurately as well as track chemical usage. Such calculations are especially important for custom installations because the inputs and the values obtained may be non-standard. Modutek develops and writes all its own software so the company can make adjustments and implement software customization whenever it’s required by a customer. This means that customers can rely on software that corresponds to their customized systems rather than trying to operate a custom system with standard software. Modutek’s software can tailored to precisely control and monitor even the most customized installations.

Custom-Fit Equipment

A lot of the equipment that goes into a silicon wafer cleaning installation has to fit into an existing space or fit other limiting installation parameters. Such custom-fit equipment may include:

  • Megasonic systems
  • Teflon tanks
  • Quartz baths
  • or other custom equipment

Modutek can build custom versions of these components to fit any existing or new wet process system to optimize the silicon wafer cleaning process. Megasonic cleaning systems can be customized for frequency and power while tanks can be sized according to custom requirements and can be fitted with heaters or re-circulating pumps as required. In each case, Modutek can analyze the silicon wafer cleaning application and recommend the most appropriate solution.

Custom Wet Bench Station Design

When preparing a custom wet bench station design, Modutek first looks at the process specifications. The software, chemical delivery systems, baths and wafer handling must all fit together to satisfy the process requirements. Sometimes customized components can be used in a standard configuration but at other times specially designed components may be arranged in a custom system.

This approach provides end-user flexibility while respecting customer specifications and ensuring that the equipment performs as expected. All systems are designed and built at Modutek’s company facilities based on their own in-house expertise and experience.

Customized Wet Process Systems

Wet process systems can be customized at the component or system level, but they can also feature customized levels of automation. Standard systems are manual, semi-automatic or fully automatic but special solutions are always possible. Customers may want a manual system but also want certain process sub-steps to run automatically. A customer may want the handling of hazardous chemicals to be fully automated for safety reasons but want the rest of the process to be manual. On the other hand, a fully automatic system may have a requirement for operator intervention at a specific point. Because Modutek designs these systems in-house, such customization is seamless and problem-free.

Customized wet process systems can find application in many research and industrial fields. A customized system is often needed for prototype development and testing since the prototype can have unusual or unique features. Cutting-edge research and development in industry or at universities may also require the special characteristics available from customized systems. Even full production manufacturing facilities may need customization if they want to try special cost-cutting or quality-enhancing production methods. In each case Modutek can analyze the requirements and propose solutions.

With over 35 years of experience in wet process technology, Modutek has pioneered customization as a tool for improving silicon wafer cleaning processes and continues to develop unique customized solutions for its customers. If you need a customized solution for your application contact Modutek for a free consultation or quote.

Why Particle Removal is Essential in Silicon Wafer Cleaning

During silicon wafer processing, impurities and particles are deposited on wafer surfaces or are left over from previous process steps. Such particles can cause defects in the final semiconductor product. With the reduced size of today’s silicon wafer microstructures, even the tiniest particles can block etching and affect the diffusion processes. The result appears in the final semiconductor circuit as either as a defect or reduce quality and life expectancy of the product. As a result, the focus of many wafer cleaning operations is to leave the silicon wafer surface intact but free of contaminating particles.

How Particles are Removed from Silicon Wafer Surfaces

The removal of particles can be difficult because they often have a chemical or electrostatic affinity for the silicon surface. They are attracted to the silicon wafer because of electrostatic charges and specific mechanisms have to be used to dislodge and remove them. The smaller the particle, the more such attraction may play a role and the harder it is to remove every particle from the wafer.

Mechanisms to remove particles include silicon wafer cleaning with a chemical that reacts with the particles, cleaning with a solution that dissolves the particles or washing the particles from the wafer surface. In each case, a specific type of equipment is required and traditional standard processes can be used together with new technologies aimed at removing even the smallest particles.

Cleaning Processes

Many chemical processes used to clean silicon wafers have remained unchanged since they were first used 30 years ago. These methods use aggressive chemicals to remove contamination from the wafers, which are then rinsed with de-ionized water and dried. These methods remove most of the contaminants but are less effective in removing the smallest particles. Refined older methods and new technologies such as megasonic cleaning are now often used to complete the cleaning process.

Cleaning methods used at different stages of the silicon wafer fabrication process include the following:

  • The RCA clean process, often carried out in two steps called SC1 and SC2, prepares a wafer for further processing. SC1 cleans wafers with a mixture of ammonium hydroxide and hydrogen peroxide to remove organic residue. SC2 uses hydrochloric acid and hydrogen peroxide to remove metallic residues and particles.
  • The Piranha cleaning process removes large amounts of organic residue such as photoresist. It uses sulfuric acid and hydrogen peroxide in a particularly corrosive mixture that acts quickly but must be handled with care.
  • Megasonic cleaning dislodges particles and other contaminants using microscopic cavitation bubbles generated by a megasonic cleaning system. The bubbles form and collapse in time with the MHz sound waves, delivering a scrubbing action that overcomes particle attraction to the silicon wafer surface.
  • The Ozone cleaning process uses ozone to convert organic particles and contaminants to carbon dioxide. All organic traces on a wafer surface are completely removed, leaving the silicon wafer free from particles.

One of the most critical processes for silicon wafer cleaning is the pre-diffusion clean process that takes place just before the wafers are placed in the diffusion oven. Any of the above methods or a combination of cleaning methods can be used to ensure that wafers are free of particles and the diffusion will be even and consistent.

Equipment Used for Wafer Cleaning

Modutek’s wet bench technology supports all the above cleaning methods and can be provided within their manual, semi-automated or fully automatic systems. The company can offer equipment for traditional cleaning and for the new megasonic and ozone methods as well. All cleaning equipment is available in standard configurations but Modutek can also design custom products to meet the needs of any of their customers’ silicon wafer cleaning requirements. If you need highly reliable equipment to support your semiconductor manufacturing processes call Modutek for a free consultation or quote at 866-803-1533 or email [email protected].

 

Modutek Named Among Top Suppliers in Global Semiconductor Wafer Cleaning System Market

Modutek is a supplier of wet bench technology, wet processing and chemical handling stations to the semiconductor fabrication industry. The company was recently named as one of the top suppliers in the semiconductor wafer cleaning equipment market global opportunity Analysis and Industry Forecast (2017-2023) report published on alliedmarketresearch.com. Modutek emphasizes in house development of its software and equipment and focuses on a high level of customer support, leveraging the expertise of its own engineers to offer both standard and customized systems. At the forefront of innovative development, the company offers complete solutions to improve semiconductor fabrication facility performance and output quality.

The Characteristics of a Top Supplier

To become a top supplier in any industry a company has to supply high quality equipment that meets the needs of customers over an extended period of time. In the case of semiconductor equipment manufacturers, it means offering silicon wafer processing stations that execute the customer’s processes precisely with high output quality at a reasonable total cost of ownership. Top suppliers will know the details of the different etching, stripping and cleaning processes and will have developed equipment and software that handles them safely and effectively.

Modutek has been supplying the semiconductor equipment industry for over 35 years, building a reputation for high levels of competence and innovation. The company’s wet bench stations support all the common chemical processes for wafer fabrication and Modutek has developed innovative software and process steps that help reduce customer costs while increasing throughput and minimizing defective or low-quality semiconductor products. Modutek’s in house expertise resulting from designing, building and testing its own equipment allows the company to offer customized systems that exactly meet the needs of each customer. A high level of customer service completes the focus on customer satisfaction.

Innovation and Customer Focus

Modutek has become a top supplier to the global semiconductor wafer cleaning system market by introducing innovative solutions to address customer concerns in a changing technical and commercial environment. In general, the company introduces new systems that increase productivity while reducing costs. More specifically, new products allow for maintaining or even increasing yield in the face of challenges from denser component packing and more complex microstructures on the silicon wafer.

In an initiative to reduce wafer particle counts by eliminating particles added during the move from the last etch to the drying chamber, Modutek has introduced a single chamber process. Instead of exposing wafers to contamination during additional handling, the HF acid last etch and IPA drying are performed in the same chamber, eliminating a transfer step. In recent tests, Modutek has been able to demonstrate that the single chamber process is effective in achieving very low particle counts and higher quality outputs.

In addition to such specific innovations, Modutek has developed comprehensive automation solutions that help reduce error and waste. The fully automated Modutek wet process stations deliver accurate chemical dosages and precise process times to ensure exact execution of programmed process steps. Such automation is cost-effective and provides the tight process control required for the latest wafer fabrication tasks.

The Benefits of Choosing Modutek as a Supplier

In addition to the company’s lengthy experience as a semiconductor equipment manufacturer in a field that has a high turnover of suppliers, Modutek distinguishes itself through its in house expertise. All software and equipment design is carried out by Modutek engineers and all equipment is assembled and tested in house. As a result, Modutek can offer unparalleled service and support without having to call on third parties to help out. As a top supplier to its market, Modutek can propose the right solutions to particular customer’s requirements deliver the needed equipment from its extensive range and offer seamless support as needed.

Single Wafer Processing Spurs Demand for Wafer Cleaning Equipment

Wafer cleaning equipment suppliers have to invest heavily in research and development to keep abreast of rapidly changing technologies and changing market conditions. Single wafer processing is one such change factor, spurring demand for wafer cleaning equipment and promising a rapid increase in market size. The wet process equipment supplier market is characterized by high barriers to entry since it requires substantial initial investment with high continuing costs. On the other hand, single wafer processing in mini-fab operations is very attractive due to flexibility and the speed with which a single wafer can be processed. As a result, the market may see additional entrants while existing suppliers try to keep up with the anticipated growth.

Wafer Cleaning Equipment Market Details

The global wafer cleaning equipment market size was about US $ 4 billion in 2016 and it is expected to grow to over US $ 7 billion by 2024. While semiconductor demand generally is fueling this growth, the use of single wafer processing is one of the factors that is behind the increasing demand for semiconductor cleaning equipment. Mini-fab facilities feature short cycle times and production lines that allow semiconductor manufacturers to quickly meet changing market conditions.

Single wafer processing uses ozonized water and hydrofluoric acid in single spin technology to reduce cycle times and increase output flexibility. As increasing numbers of operators jump into this segment of the semiconductor manufacturing industry, the demand for wafer cleaning equipment is skyrocketing.

Another factor in cleaning equipment market growth is the market for printed electronics. The technology creates electronic devices by printing on substrates and requires clean wafers as an input. Its primary advantage is low cost for high volume and the outputs are inexpensive, low-performance items such as RFID tags and smart labels.

The combination of single wafer processing and the high volume expected for printed electronics means that the almost doubling of market size over the next seven years is realistic. When electronic tags proliferate in transportation and retail and processors from single wafer mini-fabs become common in many industries that are not high users of electronics at present, the need for wafer cleaning equipment as an input for these market segments becomes clear.

Single Wafer Cleaning Techniques

Single wafer processing is only competitive when the cycle times for individual wafers are low and the output quality is at least comparable to wet batch processing. Single wafer spin processing can be used to etch silicon and provide a wet process for mini-fab single wafer cleaning. Spin processing can limit etching to one side of the wafer and can be used for wafer thinning. Single wafer cleaning is often carried out with megasonic cleaning because this method dislodges the tiniest particles and results in a low particle count for the finished substrate. As semiconductor manufacturers embrace single wafer processing, single wafer cleaning equipment is being brought out in the market.

Some single wafer processes are attractive because they deliver better results than traditional processes. Megasonic cleaning in particular can reduce particle counts for the smallest particles. The cleaning method uses megasonic sound waves in the cleaning solution to generate cavitation bubbles. When the bubbles collapse due to changing sound pressure they release energy that can free tiny particles from the substrate surface. Particle counts are often lower than with chemical cleaning methods.

Modutek’s Silicon Wafer Cleaning Equipment

Modutek has over 35 years of experience in providing the latest state-of-the-art silicon wafer cleaning and processing equipment. The company can help customers with advice on semiconductor manufacturing equipment and offers a complete line of wet processing systems. Modutek is ideally situated to benefit from the increased demand for silicon wafer cleaning equipment.

 

 

How Megasonic Cleaning Improves the Silicon Wafer Cleaning Process

How Megasonic Cleaning Improves the Silicon Wafer Cleaning ProcessAs silicon microscopic circuits and structures shrink in size, the elimination of contaminants from becomes increasingly important. When silicon wafer cleaning is effective, it removes particles as small as 0.1 µm to prevent them from affecting the silicon fabrication process. Traditional wafer cleaning with chemicals may leave some of the smallest particles in place and production line output quality can suffer. The semiconductor components produced may be of inferior quality or fail completely. Megasonic cleaning with sound waves in the MHz range generated in a water cleaning solution can remove particles down to 0.1 µm in size and improve cleaning performance.

How the Megasonic Process Cleans

The Megasonic Cleaning System consists of a high-frequency generator, transducers that convert the electric signal from the generator to sound waves in the water, and a cleaning tank to hold the cleaning solution and the silicon wafers. Sound waves in the MHz frequency range travel through the cleaning liquid and generate microscopic cavitation bubbles in the low-pressure wave troughs. When the bubbles collapse in the high-pressure wave peaks, they produce tiny jets of water.

When the bubbles collapse near a wafer, the resulting jets hit the silicon and dislodge any particles adhering to the surface. The particles are carried away by the water currents and the microscopic bubbles are so numerous that all surfaces are cleaned. The bubbles and the cleaning effect are present throughout the liquid and they penetrate into holes, crevices and microscopic structures, cleaning completely.

Megasonic Cleaning Benefits

In addition to cleaning silicon wafers and removing microscopic particles more effectively than traditional cleaning methods, Megasonic Cleaning provides several other benefits over the use of chemicals. The rise in output quality is accompanied by lower costs, a safer process environment and shorter process times.

When a semiconductor fabrication facility uses fewer chemicals for cleaning wafers, costs decrease. The facility has to purchase smaller amounts of chemicals, storage costs are lower and costs for disposal are less. Depending on the process, Megasonic Cleaning may allow a facility to eliminate certain chemicals completely, resulting in even higher savings.

The Megasonic Cleaning process is safe and environmentally friendly. The megasonic waves and the cleaning solution do not present any danger to equipment or operators who can set a timer and come back when the cleaning process is finished. The water-based solution is not toxic and does not require special disposal. Compared to chemical cleaning, the storage and handling of Megasonic cleaning materials is safe and easy, power consumption is lower and less water is required.

Modutek’s Megasonic Cleaning System

The Modutek Megasonic Cleaning System was developed together with ultrasonic technology leader Kaijo Corporation to reflect the specific demands of silicon wafer cleaning. The high operating frequency in the MHz range ensures gentle but effective cleaning of delicate materials without pitting the silicon surface or damaging the silicon wafer structures.

Modutek’s partnership with Kaijo lets the company offer an integrated system that features the Quava Megasonic generator and transducer within Modutek’s cleaning baths. Megasonic’s baths are available in the indirect heating MSI series that can heat the cleaning solution up to 140 degrees centigrade while the direct heating MSD series can heat the cleaning solution up to 70 degrees centigrade. Both baths are ideal for submicron particle removal with a high power density and high efficiency.

The Megasonic System is available with 600 W, 900 W and 1200 W power ratings at the standard 950 kHz frequency. Frequencies of 200 kHz, 430 kHz, 750 kHz and 2 MHz are also available for applications that require the more robust cleaning action from the lower frequencies or for very delicate components at the higher frequency. In any case, Modutek can advise customers to make sure they select the ideal Megasonic Cleaning configuration for their specific 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.