Operation Manual
Contents
1. CO The PURGE time depends on the 6 cpd Chapter 2 14 setting of the timer knob the user set before the process starts See Section 8 for important notes on PURGE time settings 9 2 18 Upon Completion at the PURGE mode the unit will advance into a POST PURGE FILL mode in which the chamber fills with LCOs for an additional 4 minutes This will be indicated by illumination of both the FILL and PURGE LEDs 9 2 19 The unit will then switch to the HEAT mode The HEAT LED will be on 9 2 20 When the pressure reaches around 1350 psi and the temperature is above 31 C the Tousimis Equilibrium cycle starts At this point the HEAT LED will be blinking for 4 minutes 9 2 21 Atthe end of the Tousimis Equilibrium the unit switches to BLEED cycle and the BLEED LED will be on The Bleed flow should be around 40 50 SCFH for pressures between 1 300 and 400 psi This setting should yield an average of approximately 100 150 psi min reduction in pressure The temperature should be above 31 C 9 2 22 There may be a hissing or cracking sound in the BLEED cycle It is normal because gaseous COs or dry ice may be coming out the unit 9 2 23 When the pressure drops below 300 psi the unit switches to VENT mode The VENT LED will be on Do not try to loosen the nuts until the chamber is completely vented it will damage the threads on the nuts and the chamber After 3 to 4 minutes the chamber will come to atmospheric pressure NOW the chamb2. during the purge process but the LCO2 level stays constant and the chamber remains almost completely full of LCO2 The most convenient way to verify that these valves are properly set is to allow a minimum head space in the chamber just below the viewing window The minimum head space enables viewing of just a few mm size bubbles through the chamber window Track these bubbles by eye during the purge process so that the flow through the chamber enables a bubble travel speed of about 1inch second Once the valves have been properly set staff use the small allen set screws to lock the needle valves in position Though there is a chamber inlet and exit filter these valves sometimes become partially blocked and the needle valves need to be readjusted If you need to readjust the needle valves be sure to loosen the allen set screws prior to attempting to turn the needle valve Otherwise you will strip the needle valve handle Then follow the procedure above to set the needle valves and re tighten the needle valve set screws T cpd Chapter 2 14 10 3 If you enable cpd and find the vent LED not lit on check the main power of cpd It might be OFF by accident 11 0 Qualification Procedures 11 1 Potential new users should arrange ahead of time to have an existing user review cpd operation Casual questioning e g Hey can you review this with me for a moment is not to be considered an official review period 11 2 The first question t
3. Marvell Nanofabrication Laboratory Liniversity of California Berkerey Berkeley Microfabrication Laboratory ae Lab Manual HE Marvell Nanolab Member login Lab Manual Index Mercury Web Berkeley Microlab Tousimis 915B Critical Point Dryer cpd 1 0 Title Tousimis Model 915B Automegasamdri CO critical point drying system i criti re ery nT L913 z e E Pe fr SS all d ge i a l Af Figure 1 Tousimis 915B Critical Point Drying System 2 0 Purpose This document has specific information about the capabilities configuration and proper operation of the Model 915B critical point drying system cpd 3 0 4 0 5 0 6 0 7 0 8 0 Chapter 2 14 Scope 3 1 The Automegasamdri 915B cpd is a fully automatic COs critical point drying apparatus Figure 1 Its front panel consists of a pressure gauge a temperature gauge a purge timer knob and six process push buttons COOL FILL PURGE HEAT BLEED and VENT with green LEDs Only COOL and FILL buttons need to be pushed for a complete process The unit can also operate under semi automatic mode but it is not recommended for the inexperienced users The sample holders for cpd are available for 2 inch through 6 inch wafers Holders for the Tousimis 815 cpd2 can also be used in cpd 3 2 On the flat panel of the unit there are four micrometer valves that control the COOL BLEED FILL and PURGE VENT flows They are set during the inst
4. all and should not need readjustment DO NOT ADJUST THE VALVES Applicable Documents Revision History Automegasamadri 915B User Manual Serial Number 1257 Tousimis Inc Tousimis 915B Operating Manual 24 MB PDF file Pressure vs Temperature Graph for CPD Process Verified Temperature Pressure Graph of Microlab CPD Process Definitions Process Terminology Nomenclature 5 1 CPD critical point drying dryer 5 2 LCObz liquid carbon dioxide Safety 6 1 The CPD system normally operates under very high chamber pressures DO NOT DEVIATE FROM THE CORRECT PROCEDURE FOR LOADING THE SAMPLE AND SECURING THE CHAMBER LID personal injury is quite possible otherwise 6 2 An uncontrolled release of CO can cause personal injury due to frostbite Again DO NOT DEVIATE from the correct procedures Make very sure that persons near the system are always wearing protective eyeware Statistical Process Data Available Processes Process Notes 8 1 CPD uses copious amounts of LCO Requests for LCOs cylinder changes are the primary CPD problem report and result in decreased tool availability for all lab members Review the following Process Notes and attempt to minimize your LCO usage 8 2 Extra long purge time does NOT increase the effectiveness of your critical point drying process it just wastes LCOs 8 3 Minimize the amount of alcohol you add to the chamber You only need enough alcohol to just cover your parts 8 4 Maximize the volum
5. amples carefully Photoresist residue may re deposit on the dried samples or the chamber walls 9 1 3 Make sure your samples are sufficiently rinsed after a wet process that involves HF and or other acid treatments before entering the cod chamber 9 1 4 The user should also decide on the purge time beforehand and set the purge timer knob accordingly A setting of 1 indicates 5 minutes a setting of 2 indicates 10 minutes and so on to a maximum of 45 minutes See Section 8 for Process Notes regarding appropriate Purge times Operation 9 2 1 Check for reservations on the WAND for cpd or cpd2 The two systems share one CO tank therefore they cannot be used simultaneously Likewise if either of the systems is enabled already the ON indicator above the system on the front of the hood will be illuminated 9 2 2 Enable cod on the WAND Note the ON indicator at the front of the hood lights up Figure 3 The green LED on the VENT button on the cpd console will go on This means the unit is in the vent mode Figure 3 CPD Enable Indicator 9 2 3 Ensure that the three way manual valve Figure 4 on the front of the hood points toward CPD If not rotate the handle 180 until it does Figure 4 CO Selection Valve 4 cpd 9 2 4 9 2 5 9 2 6 9 2 7 9 2 8 9 2 9 9 2 10 Chapter 2 14 Verify that the cylinder valves of both liquid CO2 cylinders are open Check the weights of the cylinders Both liquid CO cyli
6. e of the CPD chamber filled with Teflon inserts The more Teflon in the chamber the less alcohol in the chamber and the less LCO needed 8 5 Most of the LCO2 is consumed during the PURGE process Each number of the PURGE dial indicator corresponds to 5 minutes of flowing LCO2 i e setting 1 5 min Setting 2 10 min Setting 4 20 min etc The goal of the purge process is to replace essentially all the methanol IPA in the chamber with LCOs Since methanol and IPA are especially soluble in 20 cpd 9 0 Chapter 2 14 LCO there is NOT a linear relationship between purge time and alcohol removal Most alcohol is removed from the chamber after only one LCO volume exchange Once the alcohol has been removed the LCO can be heated to supercritical conditions and a phase change from liquid to vapor can take place without crossing a liquid vapor equilibrium line and generating the surface tension forces that result in adhesion of released MEMS parts See Section 4 Pressure vs Temperature Graph for CPD Process 8 6 Process staff has verified that there was no remaining alcohol and therefore a completely effective CPD process was performed with the following samples and volumes of alcohol Number of wafers Amount of Methanol Purge Setting Cool CO Chamber CO Number of wafers Amount of Methanol Purge Setting Cool CO Chamber CO 8 7 For a single 4 or 6 wafer there is never a need for a purge setting greate
7. e the rings into the chamber wipe them down with a Techni cloth and IPA methanol Note that when all four rings are in the chamber the available sample size is the same as for cpd2 Place only enough Methanol or IPA into the chamber to cover your sample s More alcohol requires a longer purge time see 9 1 3 and thus more COs _5 cpd 9 2 11 9 2 12 9 2 13 9 2 14 9 2 15 9 2 16 9 2 17 Chapter 2 14 Place your sample s in the chamber There are five Teflon sample holders available 6 4 3 2 and pieces parts basket The sample holders are stored in a drawer below the cpd systems Alternatively some users have custom sample holders and in fact the system can be used without any sample holder at all by placing the sample on the bottom of the chamber Sample holders from cpd2 can also be used Be careful to keep the surface of the sample wet while transferring it into the chamber Practice and experience are very helpful here Place the lid on the chamber Take great care to avoid allowing the bottom of the lid to make contact with the top of the steel studs Once the bolt holes in the lid line up with the studs as viewed from directly above carefully lower the lid into place Press the COOL button The LED on the button will go on VENT LED will go off The unit will go on cooling by itself until slightly below 0 C If it takes more than 2 minutes to reach 0 C the COOL LCOsz cylinder may be depl
8. er lid may be removed by alternatively and evenly loosening all of the steel nuts using the spanning wrench Remove the nuts the bronze washers the lid carefully and the dry sample 9 2 24 Clean and blow dry the chamber and lid with methanol IPA if you see any residue Replace ALL of the Teflon spacer rings Close the lid to keep the chamber clean and moisture free Replace the flat washers and the steel nuts but do not tighten them 9 2 25 Leave the cylinder valves of both liquid CO cylinders open Report the initial and final cylinder weights on the WAND comment when disabling cpd If either of the final cylinder weights is below 20 Ib of the full weight report a fault on the WAND also 10 0 Troubleshooting Guidelines 10 1 10 2 A backing ring has been added to the chamber o ring groove which is supposed to extend the life of the Teflon o ring greatly The backing ring looks like a thin somewhat flat o ring with a triangular cross section It is located under the normal o ring and should not be removed during o ring changes If it comes out with the o ring it should be re installed just as it came out Care should be taken to ensure this as it can be installed upside down A spare o ring is in the cod drawer beneath the tool More spares are available from the stockroom There should be no reason to adjust the Fill or Bleed needle valves These valves have been adjusted and set so that there is slow flow through the chamber
9. eted Note that we could easily have begun the cool down cycle before placing the lid on the chamber Why might this be a bad thing If we were to cool down the chamber before installing the lid we run the risk of condensing moisture from the lab air By cooling the chamber after placing the lid in place we minimize that risk The cool down takes only a couple of minutes anyway so time savings is not an issue Replace the eight bronze flat washers then replace the eight steel nuts but do not tighten past gentle contact Using the spanner wrench and working in a star crossing pattern begin tightening the nuts one at a time It is critically important to tighten the bolts evenly to avoid leakage and damage to the lid or the chamber See Figure 6 Make two passes around the lid in the star pattern Proper tightening does not require a lot of force don t try to kill it Eg rtousimis ik Figure 6 Lid Tightening Sequence Verify that the chamber temperature has reached 0 C and then press the FILL button The unit will start filling the chamber with liquid CO The user can see a visible liquid flow through the fill port If not the CHAMBER LCO cylinder may be depleted Now the unit is in the AUTOMATIC mode It is not necessary to push any more buttons until the process has completed After 8 minutes the unit switches to PURGE Mode automatically The PURGE LED will be on The Methanol IPA is exchanged with liquid
10. hat should be asked is whether Section 2 8 Tousimis Critical Point Dryer of the WAND has been thoroughly reviewed If not insist that it be reviewed before the meeting 11 3 The meeting between the current and new user should be scheduled for enough time to explain equipment operation load amp unload sequence etc Equipment time can be recharged to new user s account if necessary 11 4 Step 3 should be done at least twice by two different current users 11 5 Superusers will first ask Who trained you of the new user Training implies adequately following Steps 11 1 11 4 above The users identified as being the ones who did the training will be responsible for the information conveyed by the new user during the qualification Teflon is a registered trademark of DuPont
11. nders are located behind the tools on the other side of the 432B wall One is labeled CHAMBER CO2 and the other COOL CO2 Report a fault on the WAND if the weight is 20 lbs or more below its full weight Record the weight of both CO2 cylinders see 9 2 25 below Remove the eight steel nuts and eight bronze washers from the chamber lid Place a clean Techni cloth or two on the table top Using the index fingers of both hands insert your fingers into the loops on the lid and lift the lid from the chamber and place it onto the Techni cloths The lid is heavy do this slowly and carefully Do not allow the lid bottom to contact the top of the steel bolts the bolts will scratch the lid sealing surface and cause it to leak Remove the four Teflon spacer rings from the chamber Figure 5 Remember to wear poly gloves clear when you are handling Teflon spacer rings Figure 5 Teflon Spacer Rings 4 Clean the chamber using methanol IPA and dry with No gun Repeat several times if necessary Do not use the handi wipes from the 432B hood they shed lint and the lint will end up all over your sample as well as the chamber This has been experimentally verified Use only Techni cloth cleanroom wipes Refit the appropriate Teflon spacer rings back into the chamber Sample Ringstouse 6 wafer None 4 wafer One the largest 3 wafer Two largest 2 wafer Three largest Something smaller All four As you replac
12. r than 2 8 8 CPD is often one of the last steps of a lengthy MEMS process Users are wary to risk their parts to an ineffective CPD process If you would like to verify that a lower purge time is suitable for your process run a dummy process one time Add a non critical sample and just enough alcohol to cover the sample Use the recommended minimum purge time Verify that the chamber is absolutely dry no residual alcohol at the end of the process If the chamber is dry you have performed a fully effective CPD process 8 9 If you ever observe residual alcohol in the chamber using the minimum recommended times report itas a CPD problem on the wand Important Note Any residual HF remaining on your samples from previous steps can easily damage the High Pressure Sensor on the cpd tool Therefore extra care must be taken to thoroughly rinse off your part s before entering the cod chamber Operation 9 1 Preparation 9 1 1 Before starting to use cpd the user should check the liquid CO cylinder weights See Figure 2 If either of the weights is 25 lbs or more below their full weights report a fault on the WAND This will give the staff adequate time to change the tank s A full tank provides 30 lbs of COs according to the vendor Therefore the cylinder has to be changed before 30 Ib has been used up cpd 9 2 Chapter 2 14 4 Ghamber Cool tank L tank Figure 2 CPD and CPD2 Cylinder Scale Readouts 9 1 2 Clean s
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