WaferSense® Airborne Particle Sensor(APS) FAQ
CyberOptics Semiconductor provides answers to the most commonly asked questions about WaferSense APS.
We are constantly adding questions and answers to our product FAQ section. If you don't find your product question/answer, please contact us.
Principles of Operation
- What is APS used for?
- What benefits does APS provide over such traditional particle measurement methods as monitor wafers and handheld or bench-top particle counters?
- How does APS count particles?
- Can APS be used to replace particle monitor wafers?
- What is the difference between how I use APS and how I currently use particle monitor wafers?
- What minimizes cross-contamination while APS travels from chamber to chamber inside the tool?
Product Uses and Features
- What is the smallest size particle that APS will detect?
- What range of particles will APS measure?
- What is the APS airflow rate?
- What is the APS operating temperature range?
- Is APS vacuum compatible?
- What types of chamber atmospheres will APS operate in?
- How is APS calibrated?
- What is APS Counting Efficiency?
- Can APS data be exported to other applications such as Matlab, LabView, or Excel?
Maintenance and Repairs
- Will APS need to be calibrated or serviced on a periodic basis?
- Is there a recommended field accuracy test?
- How long will the APS battery last?
ParticleView™ and ParticleReview™ Software
- Does APS software support data logging?
- What is the difference between Particle Density and Particle Frequency counting mode?
- What is the difference between Cumulative and Differential Particle counting mode?
- What is a Coincidence Alarm?
Principles of Operation
What is APS used for?
- WaferSense APS is a waferl-like, wireless sensing system sesigned to move through semiconductor process equipment and automated material handling systems to monitor and count airborne particles inside the system.
- Airborne Particle sensor monitors airborne particles inside process tools ... in real-time
- FOUP's, EFEM's, robots, spinners, plates ... almost anywhere wafers go
- Quality tools quicker ... to improve productivity
What benefits does APS provide over such traditional particle measurement methods as monitor wafers and handheld or bench-top particle counters?
- Wafer-like form factor helps shorten equipment maintenance cycles
- Complete Tool Qualifications Faster
- Partitioning and Troubleshooting time reduced
- Use fewer monitor wafers Advantages over “In Situ” systems because APS is not fixed and can travel to multiple areas of the tool and not isolated to the process chamber
- Find particles when and where they occur in “real-time”
- Wireless particle measurement speeds equipment qualification
- Objective and reproducible data helps lower maintenance expense maintenance plans
- When the “Start” button is pressed in ParticleView, a fan in the APS moves air through an internal chamber past a laser and detector.
- APS uses light scattering techniques to detect particles in the gas or air stream. As the laser light strikes the particles, some light is scattered into the detector, which counts the particle signals and sorts them into channels.
- The particle data is sent wirelessly to ParticleView application software running on a laptop or system console where the particle size and count information is processed, displayed and stored.
- The APS Concept:
Can APS be used to replace particle monitor wafers?
- APS is not intended to replace particle monitor wafers.
- The APS sensor enables the user to see where in a tool airborne particles may contaminate a wafer.
- A baseline from a qualified clean tool can be used to decide if a qualification tool is in fact “good enough” to run the monitor wafer thereby saving tool time at both the particle scanner and the qualification tool.
- APS can be used to identify bad situations that can be addressed immediately without sending a monitor wafer for scanning, thus saving significant time and money.
Back to the Top
What is the difference between how I use APS and how I currently use particle monitor wafers?
- Traditional monitor wafers provide information about the size and location of particles on a wafer, but they cannot directly give information about where in the tool particles fell on the wafer
- The WaferSense APS sensor can be transported through and positioned at most stations in process equipment. Particle counts at each station and along the connecting paths help equipment engineers quickly locate WHEN and WHERE the source of particles originated as well as WHAT was happing at the time!
What minimizes cross-contamination while APS travels from chamber to chamber inside the tool?
APS employs several methods and techniques to prevent cross-contamination, which includes but is not limited to the following:
- During the APS manufacturing process, the APS housing is cleaned to semiconductor industry standards. An IPA wipe of the APS exterior is recommended before each use.
- APS has a filter before the air exit-port to trap particles that enter APS before they exit. The exit filter can be replaced at the CyberOptics factory.
- APS can use its Field Cleaning Unit charging and storage case to monitor its own exhaust and verify that the APS exhaust is clean.
Product Uses and Features
What is the smallest size particle that APS will detect?
- APS200C0105 detects and counts particles down to 100 nm, (0.1 micron)
- APS200C0310 detects and counts particles down to 300 nm, (0.3 micron)
What range of particles will APS measure?
-
APS is available in the following two model options;
- 0105 option: two channels of 100nm to 500nm and 500nm & larger
- 0310 option: two channels of 300nm to 1,000nm and 1,00nm & larger
- APS airflow is 0.1 cubic foot per minute at 1 atmosphere
- APS pulls 1 cubic foot of air every 10 minutes at 1 atmosphere
- 6 cubic feet per hour
What is the APS operating temperature range?
- Internal operating temperature is 20c to 60c for extended periods of time
- APS is vacuum compatible in that it will not be damaged when exposed to chambers under vacuum. However, in order to count particles, APS will need a pressure of at least 0.4 atmosphere for the fan to move particles through the APS detector region.
- When vacuum chambers are partially or fully vented with clean dry N2, APS can do its work and the chamber can remain sealed and clean.
What types of chamber atmospheres will APS operate in?
- APS works at pressures of 0.4 to 1.6 atmospheres of air or inert gas.
- APS is NOT specified to be operated in toxic or corrosive gas.
- APS is calibrated using NIST traceable Poly Styrene Latex Spheres according to ISO 21501-4:2007(E), which defines the parameters and methods used to calibrate and verify airborne particle counters.
What is the APS Counting Efficiency?
- Counting Efficiency is defined by ISO 21501-4 as a test instrument’s count divided by a reference instrument’s count.
- APS counting efficiency for the smallest channel will be 30% to 70% per ISO 21501-4
- APS counting efficiency for larger channels will be 70% to 130% per ISO 21501-4
Can APS data be exported to other applications such as Matlab, LabView or Excel?
- In addition to the data that APS records for playback by the ParticleReview reader, it also can create a .CSV file when can be exported to any application which supports the .CVS file format.
Maintenance and Repairs
Will APS need to be calibrated or serviced on a periodic basis?
- APS should be factory calibrated on an annual basis to assure that the unit is performing to specification
- A battery replacement is included in annual factory calibrations
- If more than 12 months have passed since your sensor was last calibrated, we recommend you contact technical support to make arrangements to return your APS device for factory calibration verification.
Is there a recommended field accuracy test?
- When placed in a known particle free area such as ISO class 2 or better, APS cumulative particle count rate should be less than the APS false counting rate.
- When APS and a reference instrument are sampling the same air flow, the APS Counting Efficiency will be as specified in the datasheet.
How long will the APS battery last?
- APS will typically run from 1 to 1.5 hours on a full charge in measurement mode (i.e. fan and lasers on) an up to 12 hours in standby mode (i.e. unit on, but fan and laser off)
ParticleView™ and ParticleReview™ Software
Does APS software support data logging?
- Yes. Whenever you record particles measurements, you simply click on ‘Start.’
What is the difference between Particle Density and Particle Frequency counting mode?
- Particle Density mode sorts particle signals into bins and displays the counts per a user selectable volume.
- Particle Frequency mode sorts particle signals into bins and displays the raw counts per minute.
What is the difference between Cumulative and Differential Particle counting mode?
- Cumulative counts are the number of particles counted with sizes greater or equal to the channel size.
- Differential counts are the number of particles counted within a particular channel.
- The sum of all the differential channel counts will equal the cumulative counts of the smallest channel.
- When two or more particles pass through the laser beam at the same time, only one will be counted. ParticleView illuminates the Coincidence indicator when this happens.
- Coincidence will occur when APS is used to count particles in ordinary room air. APS is optimized for use in clean environments.