Prevent & Troubleshoot Defects in 200mm & 300mm Lithography Modules

Defects in 200mm & 300mm litho modules are a common, yet costly issue.

A major source of defects in lithography modules are fibers & particulates including resist particles that have been left in the track. Contamination that migrates to the scanner or stepper can result in serious defects including difficult to remedy hot spot and defocus issues.

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Above: wafer handler End-Effector with hanging lint fiber will cause scratch signature on production wafer.

Reduce Defects at the Start

Foamtec International WCC has created a cleaning BKM/SOP that enables much more thorough cleaning so that Track equipment have higher first pass QUAL rates. As a result, backside wafer contamination is greatly reduced minimizing cross contamination on scanner wafer table.

The SOP is production proven to reduce the need for and harsh wafer table polishing (stoning) PM’s, where a round abrasive stone is used to recondition the surface of the wafer table to help prevent hot spots and defocus issues.  A frequent stoning procedure will reduce the lifetime of the expensive wafer table.

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Above: Track oven with Foamtec ergonomic cleaning tool

Foamtec’s Track cleaning SOP helps eliminate hot spots, reduce resist and the need to stone the scanner wafer table, resulting in improved uptime greatly reducing defects and cost.

Below, the defect reduction measured with a surface particle counter is evident.

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For more information on Foamtec International’s BKM/SOP that will deliver a decrease in litho hot spots, fewer defocus issues, and longer time between stoning and cleaning of the table/chuck in the scanner email us at contact@foamtecintlwcc.com or visit our website at www.foamtecintlwcc.com

Prevent & Troubleshoot Defects in 200mm & 300mm Lithography Modules

Safer, Cleaner & Less Costly Ion Implant PM

Now, more than ever, with advances in Moore’s Law becoming ever more expensive, wafer fabs are looking at all areas for cost reductions.
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One area ripe for review are the costs associated with waste streams from Ion Implant tools in the form of toxic arsenic wastes.
 
Ion Implanters require frequent manual wet cleans to remove process residues from the Source, Beam line and process chamber sections of the tool. Each PM can require 200-400 clean room wipers and disposal costs can easily amount to $40 per pound given that the spent wipes contain both solvent and arsenic residues.
 
To enable safer, cleaner and less costly Ion Implant PM’s many fabs employ the UltraSOLV Chamber cleaning system that dramatically reduces the amount of scrubbing pads, wipers and the associated toxic waste.
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To learn more about the UltraSOLV Chamber Cleaning System visit: www.foamtecintlwcc.com

 

 

Safer, Cleaner & Less Costly Ion Implant PM

Understanding how clean room operators and quality engineers manage fiber and particulate contamination in the manufacturing of Medical Devices

At medical device manufacturing facilities, controlling particles and fibers is a critical task as foreign material (FM) is a leading cause of reject and rework. Moreover, the inspection, cleaning and rework process are major drags on productivity.

Because FM is and always will be present, devices are most often assembled in ISO 7 and 8 clean rooms. These room classifications dictate a controlled level of contamination, but even when airborne counts are within specification, operators frequently come in contact with devices contaminated with fibers 100-500 micron in size.

Lets understand what happens at the workstation when inspection reveals that fibers are present on the device.

To begin with, the inspection process carried out by the operators and Quality Control staff is labor-intensive and by no means fool proof.

QC staff has designated three categories of FM contamination:

(1) Fully Embedded Fibers
Devices with fibers that are fully embedded in the coating or the component. These devices can either be immediately disregarded as scrap or may pass the quality requirements and manufacturing may proceed. Both conclusions are entirely based on the specific product and the FM requirements in place. Either way, it is out of the operator’s control.

(2) Loose Fibers
Loose fibers on the surface of the device may be removed with wipers, swabs or hand tools. Especially when hand tools are required this is very labor intensive and expensive process. It is not uncommon for operators to use wipers , swabs and hand tools to rework devices. Especially when hand tools are required this is very labor intensive and expensive process.

(3) Semi-Embedded Fibers
Fibers that are semi-embedded comprise the most difficult category of contamination. These are most frequently removed with tweezers and the removal process may lead to expensive scrap or rework, especially if coatings are involved.

It is easy to see that for many facilities, the steps taken to remove large fibers can  significantly impact the cost of the device and the productivity of the facility. Please stay tuned for future articles that discuss root cause solutions or contact us if you would like more information to reduce contamination related defects and rework

Understanding how clean room operators and quality engineers manage fiber and particulate contamination in the manufacturing of Medical Devices

Greener Cleaner Clean Rooms

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A Major Source of VOC’s are IPA-Soaked Wipers.

Despite initiatives that target sustainability and Environmental Health and Safety (EH&S) performance improvements, companies that operate cleanrooms struggle to reduce Volatile Organic Compounds (VOC’s). Additionally, much of the VOC emissions are from spent wipers that are sitting in hazardous waste cans.

While the EH&S issues associated with Isopropyl Alcohol (IPA) are well understood, finding a suitable replacement has eluded the best efforts of cleanroom professionals. The surface tension and vapor pressure properties of IPA which make it so desirable as cleaning agent are directly tied to the EH&S risks that have so challenged cleanroom operators.

In addition to  acute flammability and VOC issues, users also face health risks from long term exposure to IPA fumes.

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Is it possible to Replace IPA-Soaked Wipers?

Deionized (DI) water as the universal solvent is the ideal substitute for IPA but existing polyester cleanroom wipers do not possess the absorbency or particle removal properties to enable its use. This is especially the case in microelectronics where much of the wiping is carried out on high vacuum chambers that require clean, dry surfaces to minimize pump down times.

In large part, wafer fabs and other microelectronic cleanrooms are forced to use IPA due to the poor absorption and pick-up properties of polyester cleanroom wipers.

Polyester’s circular shaped, adsorbent fiber offers very limited particle dislodgement and liquid pickup which necessitates the use of IPA to achieve clean, dry surfaces.

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VOC Free Wiping.

To enable microelectronic manufacturing facilities to replace IPA with DI water, Foamtec has developed MiraWIPE® Wipers, a unique microfiber fabric designed to produce ultra clean and dry surfaces. MiraWIPE® is already production proven to replace IPA-soaked cleanroom wipers at the most advanced 300mm wafers fabs running 14nm processes, even on Hi-Vac chambers and photolithography equipment.

MiraWIPE’s interstitial, star shaped fiber contains variegated edges that enable particles, residues and liquids to be easily dislodged, entrapped and removed from critical cleanroom surfaces. This combination enables operators to use the MiraWIPE® Wiper with DI water, eliminating the need for IPA.

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The Greener, Cleaner Cleanroom.

MiraWIPE® and DI water used together are an environmentally friendly, easy to implement, and cost-efficient green solution to the vexing EH&S issues plaguing cleanroom professionals.

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Play Video

Greener Cleaner Clean Rooms

Particles Are a Sticky Subject

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Due to the high manual labor content and the availability of terminal sterilization steps, medical devices are manufactured primarily in ISO Class 6-8 clean rooms. While these clean rooms are designed to control particles, fibers, and bio burden, the numerous contact points between operators and the device mandates that robust cleaning procedures be in place.

For example, it is often standard practice that work stations are wiped down each time an operator approaches or leaves the station.

In addition to work stations, gowning rooms are routinely mopped before and after shift changes and breaks.

It is also known that, despite rooms passing airborne particle checks, large surface fibers and particles are ever present sources of contamination.

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It is well recognized that an outside-in approach is the best way to keep work stations and devices free of contamination. Simply stated, keeping contamination out of the clean room is far easier than dealing with it at the workstation.

But we know in medical device clean rooms, several factors mitigate against this ideal situation.

Let’s focus on two: high traffic and the use of disinfectants.

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Since operators are a large source of contamination, airborne particle counts are widely used to measure room cleanliness while in operation.  Despite room counts being in control operators spend a great deal of time inspecting and cleaning large (50-150micron) fibers from devices.  In addition, there are excursion events where for days it seems no device is in spec for cleanliness; this necessitates extra inspection, device cleaning, and in some cases non-conformity reports and CAPA’s (which are often closed by triple cleaning the room).

Device firms that have investigated the excursions find the FM population diverse in the extreme which make root cause analysis very difficult.

So what is happening and what can be done?

Let’s go back to the triple cleaning of the room. Given that this often gets the room back in control this suggests that more robust cleaning of the large floor, wall, and ceiling surfaces could be a starting point.

This has, in fact, been validated at several device manufacturing facilities. It turns out that the disinfectants, applied daily to floors and weekly to walls and ceilings, tack down particles and fibers turning these large surfaces into FM storage containers.

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What is needed is a cleaning solution that allows these surfaces to be stripped free of the disinfectant residues so that the entrapped contaminants can be removed from the room. This is easier said than done as typical mops and wipers do not scrub free the built up residues.

To solve this issue Foamtec has developed the Sahara + mop system. This mop is constructed with a uniquely tough, resilient foam that will not scratch even the softest surfaces but that will dislodge fibers and particles entrapped in the disinfectant residues. The other component to the mop head is a ribbed microfiber fabric that entraps and removes the soils dislodged from the surface. Each material is optimized to clean different types of particles. The Sahara foam is ideal for large fibers and hairs while the microfiber and polyester fabric remove hydrophilic and hydrophobic soils and particles.

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The following video shows how cleaning can easily upgrade the cleanliness levels in clean rooms where medical devices are manufactured.

For more information about the Sahara+ System visit our website: www.foamtecintlwcc.com 

Particles Are a Sticky Subject

Food and Drug Administration Safety and Innovation Act (FDASIA) and Facility Appearance

Click here for: Foamtec Sahara Plus Cleaning Video

Improving Productivity in Pharmaceutical & Biotech Facilities:
Pharmaceutical and Biotech manufacturing facilities face ever more demanding regulatory and productivity challenges. With the passing of FDASIA legislation, regulatory expectations have increased further making it ever more imperative for facilities to review current practices.
Cleaning SOP’s are an area ripe for review as current practices are typically reactive rather than proactive. Moreover due the FDA’s Lifecycle approach
emphasis the fact that most cleaning and disinfection procedures due to not take into account facility wear increase audit failure and frequency risks. The chart below characterizes the Facility Appearance Cycle and reactive shutdown cleaning that is dictated by current cleaning and remediation practices.
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Because rinsing protocols are largely ineffective, facility and maintenance engineers can only deal with the buildup of residue, rouge and rust with hazardous chemicals that can only be used during shutdowns (insert link about facility shutdowns). In order to prepare the facility for audits, monthly, quarterly, semiannual and annual shutdowns are built into the calendar. Contract manufacturers often will have monthly shutdowns in place due to the high frequency of customer visits.
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While the ratios vary from plant to plant, the above chart fairly captures the low plant utilization rates that have characterized the manufacturing of Pharmaceutical products.
How do these current practices impede the overall productivity of the facility?
Plants must be shutdown due to the need to bring hazardous passivation chemicals onsite to recondition or re-passivate the stainless steel. Because surface cleanliness and appearance degrade over time until shutdowns, audits, inspections and routine cleanings can be prolonged and made more complicated than is necessary. Which is to say, in addition to productivity shortfalls facilities face severe risks in using current practices. These risks involve the use of hazardous passivation chemicals, which are poisonous to the product and degrading surface cleanliness that can lead to EM excursions.
The Sahara + System™
 
Up until now proactive cleaning has not been feasible due to the inability of Clean Room Mops and Wipers to remove residues from surface using WFI and 70%  Alcohol. To enable proactive cleaning Foamtec has introduced the Sahara + line (insert link to product page) of Clean Room Wipers, Sponges, Mops and Pads that enable technicians to quickly and easily remove disinfectant residues using only DI Water, WFI water, or 70% Alcohol.
Surface Condition Typical with Current Cleaning Practices / Sahara Enables Audit Ready Everyday

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The Sahara + System™ is a production proven process that enables
cleaning staff to remove the disinfectant residues that lead to rust and rouge and which necessitate the expensive and reactive shut down cycle that is the current norm.
The Proactive cleaning enabled by Sahara + Cleaning System leads to less workdays devoted to audits and shutdowns.
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Optimally Facilities would be in audit ready conditions every day. If this were the case, facility appearance would be represented by the below chart.
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In Conclusion…
The Sahara Cleaning System Enables improvements in the following areas:
 
Productivity- Shutdowns can be shorter as rust busting is no longer necessary.
 
Safety/Product Purity- Acid based passivation chemistry is no longer required.
 
Risk Reduction- Audits are smoother and particle excursion incidents are reduced as a result of cleaner surfaces.
 
Cost Reduction- Expensive stainless steel equipment need not be replaced or repaired due to corrosion damage.
Food and Drug Administration Safety and Innovation Act (FDASIA) and Facility Appearance

Trouble Shooting Particle and Fiber Excursions in Advanced 300MM Wafer Fabs

With the advent of sub 20nm device geometries, wafer fabs face daunting challenges scaling these new nodes to yields that earn acceptable ROI. Ramping production at acceptable yields is imperative due to the much higher equipment costs, especially lithography and metrology that are required for sub 20nm nodes. Among the many impediments to yield are particle defects including scratch defects.

While fabs have invested heavily in metrology in order to stay ahead of such defects, particle excursions are a significant source of yield loss. Fiber related scratch defects are especially difficult to manage as metrology tools often do not catch the defect immediately, causing huge yield loss events to occur more frequently. Furthermore, the time to uncover the root cause failure mechanism is a significant strain on engineering resources. Scratch defects are a perfect example of a problem that resists root cause understanding, even when modern metrology tools are available. The reason is while scratch defects are caused by particle, or more exactly fibers, these fibers often do not remain on test wafers giving the engineer a false sense of confidence.

Ironically, scratch defects are most frequently associated with fibers that are released by clean room wipers which suffer snags and abrasion damage during wet cleans of transfer robots and other wafer contact surfaces. In the wrong place these fibers drag across wafers creating scratch defects in the pattern. And, as mentioned above, these defects are very hard to track down as the fibers or particles do not transfer to the wafer lending identification by test wafers.

* The pictures below are examples of how lint fibers cause scratch defects:

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Lint fiber hanging from end effector / Scratch defect shown on wafer map, caused by hanging lint fiber dragging across wafer on every wafer transfer

The following link is a video showing the effects of electrostatic charge on hanging lint fibers, making it extremely difficult to locate the culprit when troubleshooting fiber excursions

Scratch defects are a very specific fiber related defect; however, clean room polyester wipers, due to very low resistance to abrasion damage, release high quantities of particles and fibers on wafer contact surfaces and especially in wafer transfer robots as pictured below:

To aid wafer fab engineers in understanding the root cause of scratch defects, Foamtec has developed a fiber inspection kit. This kit enables equipment engineers to quickly inspect vacuum chambers, wafer transfer robots, and other wafer contact surfaces to ensure they are clean enough to process production wafers. By using Foamtec’s fiber inspection kit, equipment engineers will be able to reduce particle and fiber contamination that lead to reduced wafer fab yields.

* The pictures below show a step-by-step process how to use the fiber inspection kit to troubleshoot a suspected tool that had resulted in scratch defect related yield loss:

Foamtec Fiber Inspection Kit

Step 1:  Inspect end effector using LED magnifier


Step 2:  Inspect end effector using digital microscope to take picture and document findings




Step 3:  Picture of stuck fibers under end effector   


Step 4:  Stuck fibers being pulled from under end effector showing risk to loss of yield 

  

Trouble Shooting Particle and Fiber Excursions in Advanced 300MM Wafer Fabs