User Manual - The University of Texas at Dallas
Contents
1. Na OH a Calculate the number of grams of Na OH in one liter of solution from the density and concentration percentage PNaOH 1 53 x io Solution Density Since the concentration is only 50 Na OH the number of gms of Na OH in one liter is pwa 0 5 IL 765 gm Mass of sodium hydroxide in 1 Liter DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 28 of 32 Now to find the number of equiv wts of Na OH in one liter the Normality of the solution we divide the above number of gms in one liter by the equiv wt PNaOH 05 gm equiv wtin 1 L Norm Na O H Norm 19 125 gt Normality of Na OH solution Units are in mass equivalents per Liter H2 SO 4 a Calculate the number of grams of b SO in one liter of solution from the density and concentration percentage 3 gm PH2so4 1 84 x 10 ES Solution Density Since the concentration is only 96 KKSO 4 the number of gms of H SO in one liter is PH2504 0 96 IL 1 766 x 10 gm Mass of Sulfuric Acid in 1 Liter b Now to find the number of equiv wts of 4S0 in one liter the Normality of the solution we divide the above number of gms in one liter by the equiv wt 2p H2804 0 96 gm equiv wt in 1 L Norm eat aan EE Re Po 2 H S 4 0 98gm Norm 36 049 2 Normality of H2 SO 4 solution Units are in mass equivalents per Liter DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Rog2. Gram Equivalent Weight siciiscssetioniscontixasnzancttcdotaniarseiece tran rankvsatg gege bie EE egeg 26 N rmality sce cstdevaasttacevexnaraiia geesde geseent 26 RE 27 Concentrato wisecinctieds ccaatesavtesacaadieasnadsacdactedidesrsalevneaseaasiassddasnestacdine eaten subs ARENE 27 Theoretical Background E 28 APPENA b E 31 Practical Neutralization Calculations cece eens eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees 31 Chemical Calculations cccccccccccccccccceecceceeeeeeeeeceeeenecceeeeeeseneceeeseeesesaeesaeseaeenaes 31 elen Let 32 Detailed RCA Process Setup Procedure c cceeeceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeneeeees 32 Introd ctons nere tener rer errr EE EE 32 RECIPES vessvcsscavvecevanavevenvavwevacveadevendecvedswueanyconuaed eins deed E a a EEE a Ea a 32 DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 3 of 32 RCA Cleanup Hood Operations Roger Robbins 2 15 2006 Arnold Duenes C Mydocuments CleanRoomGeneral Equipment Hoods RCA RCAcleanupHoodOperation doc Introduction This document describes the Clean Room s new 8 foot RCA Cleanup Acid Hood from Leatherwood Plastics Inc of Lewisville Texas This hood is intended to be our special purpose starting semiconductor substrate cleanup acid hood It is anticipated that this process will use a significant amount of chemical resource therefore it will be set up to run on day per week We fondly call it the RC
3. This is where the acid dump catch tank is monitored and dilution and neutralization parameters and timer values are set This will be discussed in the Operating Software section later in the document Figure 4 Touch Screen DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 7 of 32 Process Features DI Water Sink The DI water is delivered to the sink through a gooseneck faucet that has recirculating DI water all the way to the valve This insures that the water will not have a stagnant line that can grow microorganisms which may contaminate your substrate As mentioned above this sink cannot accept any waste acid because the drain empties into the standard building sewer system Rinsing glassware in this sink is allowed however use plenty of water to dilute any acid residue Figure 5 This DI water sink cannot accept waste acids for neutralization N Gun and DI Water Spray The hood has the standard Nitrogen blow off gun and DI water spray hose to facilitate drying and water rinsing of substrates Note that the DI water hose is made of coaxial Teflon tubing and is somewhat stiff to stretch and it will spring back with considerable force if it slips out of your hands be careful and get a good grip Figure 5 shows the recessed location of both of these hood tools DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 8 of 32 Ch
4. i e 3 parts Sulfuric Acid to one part Hydrogen Peroxide This is generally the first step in the RCA cleanup process and is intended to remove any organic contaminants from the surface of starting semiconductor wafers Piranha solutions are usually operated at high temperatures of around 120 140 C which is why the tank is made of quartz with a wrap around heater Note however that at this temperature the Hydrogen Peroxide will decompose very quickly and will necessitate spiking the solution with fresh Hydrogen Peroxide after several wafer batches have been run This tank is sized to handle up to 6 inch diameter wafers so the volume of acid required to satisfy the level trip point is exactly 2 gallons Normally at UTD we process 3 to 4 inch wafers This tank would therefore waste a large proportion of the chemical mixture for these small diameter wafers so we have chosen the conservative approach and just use one gallon of liquid just enough to cover the 4 inch wafers and since the freshly mixed Pirahana heats itself up to about 100 C we do not use the heater just monitor the temperature with the tank thermocouple thermometer and add Hydrogen Peroxide when the temperature falls below acceptable levels SC 1 Clean Up Tank SC 1 is the abbreviation for Standard Clean 1 derived from the original RCA Cleanup process developed in the RCA Laboratories in 1970 and has been used ever since by the semiconductor industry to cle
5. level to receive the next batch of acid for neutralization This is a programmable parameter e The caustic reservoir icon will always show green full unless it is empty i There is only one float level sensor at the bottom of the caustic reservoir ii Wear appropriate Personal Protective Equipment when refilling the caustic reservoir with Sodium Hydroxide NaOH because splash back is common because of the viscosity of the solution f The NEUTRALIZE AT nn TANK LEVEL box shows the programmed tank level at which neutralization will begin This value will likely be edited at least once during neutralization of all acids 4 Currently users of this bench are given one day per week to do RCA cleaning Because 3 of the 4 baths have heated solutions the tanks are left alone at the end of the day so the solutions can cool overnight There is no cooling method other than turning OFF the heaters and not adding anymore H O to the Piranha bath 5 The following morning the tanks will be drained by Clean Room Staff Understanding all the process parameters is key to understanding how the neutralization cycle works Neutralization Parameters 6 Explanation of Neutralization Parameters a Normally the hood is set to level 1 access OPERATOR LOGGED IN b To access the menus where all programmable parameters are found you must log in to level 5 access LEATHERWOOD LOGGED IN i To accomplish this you must first log out ii
6. Log in using the tool s manufacturer serial number DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 20 of 32 1 for security reasons this number is not included in this document 2 Your training will show you where to find this number c Looking at the main menu the tab menus labeled Process Monitor Setup and Tool Setup Parameters are where all neutralization parameters are found CHILLER OFF len f TH SW d s BATH S BA A DRAIN DRAIN ach g v 4 L ASPIRATOR i CS T WASTE L BATH ai BATH DRAIN ZO T v2 V1 1 i DRAIN TEMP i RECIRC V1 2 26 NEUTRALIZE AT TANK A WATER FILL TO TANK LEVEL CAUSTIC NEUTRALIZATION RESERVOIR TANK Figure A2 Process Setup Screen where 3 parameters are set up i Process Monitor Setup menu 1 pH Minimum Target a Selecting this box will bring up an overlay keypad to enable one to enter the minimum pH value that must be achieved during neutralization This number is currently set at 6 0 2 Neutralize at nn Tank Level a Selecting this box will bring up a keypad where you can enter the level at which neutralization will begin This number is currently set at 85 3 Water Fill to nn of Tank Level a Selecting this box will bring up a keypad where you can enter the level to which DI Water will be supplied after tank contents have been pumped to drain this number is currently set at 65 ii T
7. draining and begin adding DI water to the tank until the level reaches 65 of capacity 19 5 gallons Neutralization Preliminaries 1 Log out and then log back in under the Leatherwood Logged in top Level password 2 Select Neutralization Process from the main menu This will bring up the following screen DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 18 of 32 BATH Z BATH Sa BATH me BA Hf DRAIN H oran FH DRAN besi Sa ve a va D ASPIRATOR 1 v9 1 od WASTE Foie e Lesser NEUTRALIZE AT RECIRC TANK V1 2 LEYEL 6 8 pH SP 6 0pH FILL SP 55 CAUSTIC NEUTRALIZATION RESERVOIR TANK FNP WATER Bone ee Ememn Figure A1 Active Neutralization screen Note the red STOP NEUTRALIZATION button at the center left this must be present to enable neutralization a If the tab is highlighted in green and reads ENABLE NEUTRALIZATION you will need to press the tab to enable the neutralization i If this is the case please try to determine why it was disabled 1 Users are not allowed to disable neutralization 2 It might be possible that it was intentionally disabled by a clean room staff member because of a tool problem However staff should leave a note if this change is necessary ii A machine shutdown by the EMO emergency off button will also disable the neutralization b When neutralization is first enabled the recirculation
8. it take care in filling Wafers up to 6 inches can be immersed in the tank insert as shown in the photo To drain the tank one would drain the water out of the large tank and then open the manual drain of the tank insert and all liquid will drain into the neutralization tank under the work bench Figure 6 Filling the tank with DI water from spray gun left and 6 inch wafers immersed in tank insert right Cascade DI Water Rinse Tanks The cascade DI Water rinse tanks are designed to rinse away any residue that may accompany the wafer out of any of the RCA process tanks This step will isolate the process from each other so that chemicals and contaminants from one RCA step will not contaminate the next chemical bath The rinse tank system consists of two tanks each entitled First Rinse and Final Rinse The tanks are arranged so that the Final Rinse tank receives fresh DI Water by filling from the bottom This water fills the tank and overflows to a conveyance pan and then fills the First Rinse tank from the bottom The overflow from the First Rinse tank then overflows into the Industrial Waste sewer system This scheme is designed so that the wafers fresh from an acid process can be rough rinsed in the downstream tank first to remove droplets of acid solution and then be set in the Final Rinse tank for rinsing off any tiny amounts of contaminants that survived the first rinse Rinse times are on the order of 2 10 minute
9. pump will turn on for 5 minutes This is a default action to stir the tank contents however the stir time is programmable Plumbing Diagram Screen 3 Familiarize yourself with the plumbing diagram as displayed on the screen Figure A1 a Air operated valve names Note Red Closed Green Open i V1 1 Piranha bath drain valve ii V1 2 Recirculation valve for neutralization tank DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 19 of 32 iii V1 3 Waste valve open when pumping neutralization tank contents to building acid drain iv V2 1 SC 1 bath drain valve v V3 1 SC 2 bath drain valve vi V4 1 Oxide Etch bath drain valve vii V9 1 Deionized Water Supply valve for Neutralization tank viii V9 6 Aspirator drive valve b Actual and set point values of pH are displayed next to the neutralization tank i The top pH reading is the actual pH in the neutralization tank ii The bottom reading SP is the set point pH and is currently set to 6 0 It is programmable however c There are 2 pumps in the diagram i Recirculation pump next to the neutralization tank ii Caustic Supply pump next to the caustic reservoir d The neutralization tank icon displays a real time liquid level via the animated tank icon i Important tank levels to remember 1 At5 or less the system will switch from drain to filling the tank with DI water 2 The tank fills to a 65
10. so that the operator will know when all the temperatures reach spec values DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 15 of 32 CHILLER OFF d ngt E BATH i T BATH T BATH H DRAIN H DRAIN HH DRAIN i V3 1 T v 1 WASTE NEUTRALIZE AT PUMP WATER el FILL SP 55 Ki Gel CAUSTIC NEUTRALIZATION MAIN RESERVOIR TANK 3 Figure 13 Neutralization process screen showing the hood s drain plumbing and valving configuration along with the neutralization tank and pumping plumbing DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 16 of 32 Rules of Operation For safety sake we have generated a set of rules to apply to operators of this hood They are listed below When first approaching the hood to start work please notice the conditions in the hood and note any situational dangers Either correct them or notify Clean Room Staff Assume any liquid on the work surface is acid This hood is off limits to any substrate or object containing metals Reduce the possibility of contaminating baths with metals which damage active semiconductor device parameters Do not place tools or glass ware next to quartz baths Reduce the possibility of breaking the quartz bath which is extremely expensive to replace Never dump acids into the DI water sink You can rinse glassware Work with a BUDDY Stay by the hood when heating m
11. takes a long time Note that the reaction of Sodium Hydroxide and Sulfuric acid is quite exothermic creating a nicely warm solution in the tank Thus the long cycle time a Note you will likely have to refill the caustic reservoir at least once during the Piranha neutralization 9 When all acids have been neutralized clean up any mess left on the work deck and replace all covers and then you re done DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 25 of 32 Appendix B Theoretical Neutralization Chemistry Neutralization Chemistry This section will be a short exposition of simple neutralization chemistry The purpose is to understand how the acids are neutralized and how much Sodium Hydroxide NaOH is required to neutralize a given quantity of acid This is somewhat complicated because in this RCA cleanup hood we will be neutralizing a number of different acids with different initial concentrations The amount of base NaOH is our choice required to neutralize the acid depends on what type of acid and how concentrated it is compared to the base concentration The concept of neutralization states that the base has to supply OH ions to the solution in such numbers as to match the number of H ions that the acid has added to the solution This means that we need to know what the reaction equation looks like and what the oxidation number is for the reactants In fact we need to re
12. A Hood but it actually has a real name HRO1 Description The RCA hood is constructed of a chemical and fire resistant white plastic PVCC with a 5 5 by 2 6 foot perforated work surface Features of the hood include at the work deck level a De lonized water sink with a recirculating gooseneck faucet Note that this sink drains into the normal sewer lines so absolutely no acid can be disposed of in this sink Other features include the 3 main RCA cleanup process chemical baths a temperature controlled etch bath and two cascade DI water rinse tank systems The cascade DI water rinse tanks consist of two tanks for each system where fresh DI water is supplied to the Final rinse tank and then overflowed into the First Rinse tank and finally drained away This allows a two stage rinse operation after exiting the acid baths Temperatures of all the acid baths can be read on the touch screen control panel The acid baths drain into a 30 gallon dilution and neutralization tank under the hood deck This has an active pH monitor and a caustic chemical Sodium Hydroxide supply for automatic neutralization The tank is initially filled to 55 of capacity with DI water to dilute the acids and when neutralization is complete the contents are pumped into the building acid drain system The hood is controlled by a solid state controller with a touch screen control panel user interface located on the right side of the hood There are 4 proce
13. RCA Cleanup Hood Operations Roger Robbins 2 15 2006 Arnold Duenes The University of Texas at Dallas ERIK JONSSON SCHOOL OF ENGINEERING DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 1 of 32 RCA Cleanup Hood Operations Roger Robbins 2 15 2006 Arnold Duenes Table of Contents RCA Cleanup Hood Operations enessseeseeeseeeeseeeeeertterttetttrrterrtttrrttrrtrerteertesrrterrrereene ent 4 ite CUO DNs ssc ioe ceces este te oe it ae cee eee ieee ee ee 4 Description iivscisvcsi davsideveisvetde er iecustvenearnarvieran inset ARENE ERAEN NEARE 4 Feature Detail Ss oeis ccs c 2s innzecc tances atte eeng SSES ENEE SEA 5 COMMON ANG iscezcsctcct cect czactescekesageescceasates acentactestnccusssaneesnqnasesanencensvecianuiasaethanattansthens 5 RRE TEE 5 e Au Get oO EC 6 Machine Gtart Gtop rneer neenneerneernnen naear nen nnn anneanne nannan nnana 7 EMO BUOM EE 7 Audio Enunciator enn nrk na kien kk nn kk ennnen Aunn An nnan rE e nanenane nannat 7 Be te e RE 7 Process EE 8 DI Water le 8 N2 Gun and DI Water Spray cccccccccccceecccaeeeaeceaeeeaeeeaeeeaeeeaaeeaaeeaaeeaaeeaaeaaaeeaes 8 Chemical Process Tanks nnn 9 Pirahana Acid Tank 9 SC 1 Clean Up Tank ENNEN 9 SC 2 Clean Up Tank meriiri oreiro a aaa aE eE aa eaaa ier enii 10 Buffered Oxide Etch Tank 10 Cascade DI Water Rinse Tanks 11 HF Acid Antidote 0c cccccccecccceeccceecesueeesueeseuueseuuaseuuesee
14. an up new wafers before starting the semiconductor manufacturing process This step consists of a mixture of Ammonium DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 9 of 32 Hydroxide NH OH Hydrogen Peroxide H202 and De lonized Water H20 The typical concentration ratio is 1 1 5 one part Ammonium Hydroxide to one part Hydrogen Peroxide to 5 parts Di Water NH OH H202 H20 This process is designed to remove particles organic contaminants and some metallic contaminants from the surface of the wafer It accomplishes this by continually oxidizing and then etching the oxides off the wafer surface thus dissolving the contaminants into solution This process is normally executed at a temperature range of 50 90 C In order to control this temperature the tank must be filled with 2 gallons of chemical solution SC 2 Clean Up Tank SC 2 in similarity to the previous step is the abbreviation for Standard Clean 2 in the RCA clean up process This solution follows the SC 1 step and generally consists of a mixture of Hydrochloric Acid HCL Hydrogen Peroxide H202 and De lonized Water H20 The typical concentration for this mix is a ratio of 1 1 5 that is one part Hydrochloric Acid one part Hydrogen Peroxide and 5 parts De lonized Water HCL H202 H20 This process is designed to remove metal contaminants from the wafer surface This chemistry also accompl
15. aterial in this hood Wear appropriate Personal Protective Equipment o Double gloves standard CR gloves with acid gloves over them o Safety glasses o Acid apron o Face shield o Solid top shoes Only one experiment at a time is allowed Never place a chemical container on the floor return it to the cabinet Acid Hood glassware is stored on the cart to the left of the acid hood Rinse your acid containers thoroughly with DI water Wet wipe and dry off the work surface so the following person will not be harmed by liquid acid spills When you are finished clean up your work area and return all the tools and PPE you have been using to their proper place especially papers and rags Conclusion This document has attempted to describe the RCA hood and its features in a manner to give some understanding of how it works and what it is intended to do Itisa top quality hood exceeding that in many universities Let us tend to it to keep it shining as a prized possession This is not only a matter of pride but also a necessity for safety This hood uses rather dangerous chemicals and you must be thoroughly trained in its operation before achieving qualification as an operator of this tool DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 17 of 32 Appendix A Neutralization Staff Procedure Arnold Duenes Purpose This appendix is intended as a refresher to trained Clean Room Staff abou
16. ations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 6 of 32 Machine Start Stop The green HOOD START button on the control panel turns on the electricity to the hood functions The Red MACHINE STOP button turns off most of the electricity to the hood The hood is generally left ON all the time This control is used when service or problem diagnostic is required EMO Button The EMergency Off button is used if the hood is having an electrical problem that portends of immediate emergency If there is smoke coming from the insides or the chemical baths are overheating etc Please don t hesitate to use this button If you have had to push the EMO button please notify Clean Room Staff immediately Audio Enunciator The audio enunciator is a piezoelectric beeper that announces either a non emergency fault or the completion of a timed event There is a convenient yellow alarm silencer button which you can use to cause immediate cessation of the annoying beeps However please make sure that the cause of this alarm is corrected before leaving the hood The identity of an alarm can be found by looking at the Alarms log screen chosen from the Main touch screen page Notify Clean Room staff if necessary Touch Screen The Touch Screen is the user interface for the microprocessor controller for the hood This controller has a password and multiple display screens for monitoring and controlling the hood
17. austic pump will use these ON OFF times to cycle pump Sodium Hydroxide into the neutralization tank until the contents reach a pH of 6 0 c Stage 3 Parameters i The parameter name pH Stabilize Time after Reaching pH Setpoint prior to Waste Dump is currently set at 3 min 0 sec This parameter means that once a pH of 6 0 or higher is achieved the system will wait for this amount of time before starting the pump to drain cycle to empty the tank d Other Parameters in this menu i The parameter name Recirculation Pump is used when the neutralization is enabled during normal operatin of the hood The current parameters are 3 min ON and 17 min OFF This is the neutralization tank stirring cycle definition ii The actual and setpoint pH values are displayed in as monitor parameters in this screen not adjustable DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 23 of 32 Neutralization Procedure 7 Before beginning the neutralization procedure you will need to be aware of several things prior to draining the process baths into the neutralization tank a You cannot drain a bath if its solution temperature is above 49 C b Initially there should be a DI water level of 65 in the neutralization tank c As described earlier NEUTRALIZATION PROCESS must be ENABLED 8 Draining the Process Baths a The Process Manual Control sub menu allows manual operation of
18. call a number of chemical definitions to be able to calculate the volumes of the constituents involved in the neutralization Chemical Definitions Mole One Mole of a substance is its collective molecular weight expressed in grams formula weight EX H2SO 4 2x1 1x32 4x16 gt 98gm Red numbers are atomic masses and multipliers are the number of times the atom appears in the molecule Gram Equivalent Weight One gram equivalent weight E of a substance is its gram atomic weight divided by its oxidation number EX H2SO0 2x1 1x32 4x16 2 gt E 49gm eq Red numbers are atomic masses multipliers are the number of times the atom appears in the molecule and the Blue 2 is the oxidation number of the sulfate ion SO in the sulfuric acid molecule reacting with NaOH Normality In order to calculate the quantities involved in a chemical solution reaction we need some measure of the concentration of the chemical in its solvent water The most convenient expression of this for calculating neutralization reactions is the Normality value DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 26 of 32 Normality N is defined as the number of gram equivalent weights of a substance per liter of solution N gram equivalent weights liters of solution gt N E V where E gt of gram equivalent weights Note that since this definition involves the oxidation numb
19. cribed in detail in Appendix A for staff guidance However for your general information the neutralization process is as follows When fluids drain out of the sink they drain directly into a 30 gallon catch tank under the hood This tank is initially filled to the 65 level with DI water to act as a dilution bath to prevent strong acid base reactions The tank has an active neutralization system that measures the pH and supplies a 50 concentrated Sodium Hydroxide solution to the tank in a programmed cycle to neutralize the acid When the tank is full the dilute neutralized solution is pumped into the building acid drain At the conclusion of this step the tank is again filled with DI water to the 65 mark There are two pumps involved with this system 1 a recirculating pump used to stir the fluid in the tank and 2 a caustic pump to deliver the Sodium Hydroxide Both of these pumps are diaphragm pumps that make a noticeable clacking sound from behind the hood this is normal Figure 8 Used acid catch tank Left and Caustic Reservoir Right under the RCA hood Operating Software Overview The active hood functions are controlled by a microprocessor whose interface with the operator is the aforementioned touch screen on the control panel The control processor is concerned with two significant hood functions 1 Neutralization of the collected acid in the catch tank under the work surface and 2 general DOCUMENT TITLE RCA Clea
20. dd acid to water to avoid rapid boiling of the acid from its heat of reaction and resulting liquid splattering Piranha 3 parts 96 Sulfuric Acid 1 part Hydrogen Peroxide 3 H2SO4 1 H202 3 78L 1gal bottle 1260ml SC 1 5 parts DIW 1 part Ammonium Hydroxide 1 part Hydrogen Peroxide 5 H20 1 NH4OH 1 H202 5 40L 1 0L 1 0L SC 6 parts DIW 1 part Hydrochloric Acid 1 part Hydrogen Peroxide 6 H20 1 HCI 1 H202 5 68L 950ml 950ml N Oxide Etch 1 Hydrofluoric Acid 7 57L two 1gal bottles of 1 HF 2 bottles is enough to cover a 4 wafer boat DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 32 of 32
21. emical Process Tanks There are three quartz chemical process tanks with bonded wrap around blanket heaters for temperature control intended to facilitate the RCA wafer clean up process The temperatures are controlled by the system microprocessor using a Teflon sheathed thermocouple thermometer hanging over the edge and reaching about the way down into the tank There is also a liquid level sensor bubbler tube set to trigger an alarm if the level falls below the tube setting If this alarm triggers the heater will be turned off an audio alarm will sound and the touch screen will indicate a visual alarm Note that these are very expensive tanks and we must take extra care not to drop anything into them that might crack or break them Note that each of the four processing tanks has a stirring bar in a recess in the floor of the tank It is driven by a similar magnetic bar under the quartz floor by an air turbine drive This air flow sets the spin speed and is controlled by a knob along the front edge of the work surface The knobs are distinguished by a dark circle in the handle as illustrated in Figure 6 The RCA cleanup setup procedure will be outlined in detail in Appendix D so the process tank discussion below will be somewhat generic in nature Pirahana Acid Tank Piranha is a trade name for a chemical mixture consisting of Sulfuric Acid H2SO and Hydrogen Peroxide H202 It is typically mixed in concentration ratios of about 3 1
22. er Robbins and Arnold Duenes Page 29 of 32 Step 3 Calculate the amount of Na OH required to neutralize a given amount of Sulfuric acic The law of neutralization claims that the number of gm equivalent weights of base neutralize same number of gram equivalents of acid Stated in different form the Neutralization rule claims Ho SO 4 2Na OH gt Na SO 4 2HpO Norm Na Norm Ni Claim Norm is the Normality of the acid Therefore to calculate the volume of sodium hydroxide required to neutralize say liters of sulfuric acid V gt 4L Norm V K Claim equation rearranged Norm V 754L ANSWER The volume of sodium hydroxide required to neutralize 4 Liters of sulfuric acid is 7 54 Liters takng into account the solution concentrations specified DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 30 of 32 Appendix C Practical Neutralization Calculations Chemical Calculations Calculating how much sodium hydroxide one needs to neutralize some amount of acid is explained in detail in Appendix B However to make things a bit easier have included an imbedded EXCEL table with the formulas already included so that you can find the answer to the above question by inputting the starting parameters in a table and puff the answers appear in the last column Table C1 below includes the standard chemicals used in the acid hood and calculates the amount of NaOH re
23. er of a substance N can vary depending on the exact chemical reaction it is involved in Density This is defined as the simple physical quantity of weight per volume gm ml P M V Mass Volume Concentration Concentration of a chemical in a water solution is expressed as the percentage by mass of a substance per mass of the total solution i e 49 HF in water EX 49 by wt of HF in 1000gm solution gt 49x1000gm 490 gm of HF in 1000 gm of solution DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 27 of 32 Theoretical Background Acid Base Neutralization Reactions 1 11 20 RR How much 50 Sodium Hydroxide solution is needed to neutralize n liters of 96 Sulfuric Acid Solution Step 1 Calculate the gram equivalent weights of the reactants The gram equivalent wt of lt element is the gram atomic weight divided by the oxidation number of the reacting element in the compound of interest Given gm o DN OH 1 53 50 NaOH by wt Solution Densities a mL from bottle PH2S04 bg 96 Ho SO q by wt Atomic Mases Na OH Na 23gm O l6gm H lgm Gm Eq Wt of Na OH Na O H 40gm Equiv Wt of Sulfuric Acid H2 SO q H lem Si 32gm O 16gm GmEqWt of H S0 ZE 4ES 40 _ 07em Equiv Wt of Sulfuric Acid 2 Step 2 Calculate the Normality of each solution The normality is the number of gram equivalents per liter a chemical concentration unit
24. eutralization tank has surpassed the 85 full level the system will close all valves and begin the neutralization operation Wait When it completes the process you can continue your drain rinse operations ii If you finish with all the draining and rinsing and the tank level is still under 85 full you can do either of two things 1 Continue dumping DI water down any of the three empty process baths until an 85 tank level is reached or 2 Access the Process Monitor Setup menu from the main menu and change the Neutralize at 85 Tank level to whatever the current level is in the tank a For example if the current level is 78 when you enter 78 and hit the RETURN key the data will be fed back to the PLC and neutralization will start immediately Remember to reset the value to 85 when the operation is complete iii It will take something like 2 hours to neutralize the chemicals from the 3 chemical baths iv Drain the Piranha Bath 1 Quartz 1 At the conclusion of the previous neutralization cycle the Neutralization tank will refill to its set point level 65 2 Drain the Piranha Bath and rinse the quartz tank 3 You will notice that the neutralization tank level has not increased much Again you can either dump DI water into the tank to achieve a level of at least 80 full and then change the setpoint to whatever the actual level is as described in ii 2 above 4 Neutralization of this particular process bath
25. ishes the clean up by continually oxidizing the surface and then etching it away so as to dissolve the contaminants away from the surface into the solution This solution temperature range is also set to 50 90 C In order to control this temperature the tank must also be filled with 2 gallons of solution to meet the heater level requirements Buffered Oxide Etch Tank This tank is designed for general oxide removal outside the RCA process flow It consists of a large Quartz tank with a corrugated Teflon coolant line wrapped around the inside of the tank This coolant line is attached to a heater chiller system in the chase behind the hood The temperature can be set above or below room temperature according to the value set in the controller window Nominally the temperature range expected for this tank is between 30 C above and 15 C below room temperature This is a 5 gallon tank but we again being conservative have cleverly designed a tank insert to hold a small volume of acid immersed in the tank To keep the acid at a constant settable temperature we fill the large tank with DI water to conduct thermal energy to or DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 10 of 32 from the insert tank The little tank can hold about 1 gallon of liquid thus saving 4 gallons if the full size tank were to be used Note that the little tank will float if there is not enough acid in
26. nup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 13 of 32 security timer temperature alarm data presentation These functions will be discussed in detail below Login From the Main screen on the touch screen there will be a soft button at the very top center of the screen entitled Log In Please as shown in Figure 9 The login level enables various portions of the controller capability to the operator Normally the hood will be logged in under the operator level The password for this level is currently set at UTD This level enables complete availability of all features of the hood in normal operation Figure 9 Main Screen with initial option buttons Higher levels of the login tree enable operating parameter changes reserved for staff If you need a parameter changed please see the staff person in charge of the hood If you have to login touch the thin top rectangle button that says Login Figure 9 shows a screen with that button reading Log Out since the hood was already logged in for this photo The resulting screen will look like that in Figure 10 Press the central button entitled Log In Please This brings up the keypad screen shown in Figure 11 Figure 10 Log in Screen Figure 11 Log In Keypad Note the Return key in the lower right corner for entering the password Since the operator password is UTD simply enter those letters and press the Ret
27. ody If a large spill gets on you then remove clothing and do a 15 minute shower in the emergency shower at the entrance to the bay Call for help immediately contact with this much HF could be life threatening If you get a lot of HF acid on your body your buddy must call 911 to get paramedic help and have you checked out by a doctor quickly More information on this situation is contained in the Clean Room Safety Handbook Calcium Glaconate Get 25 0 emm ka 41118 Docent Nev 2006 Hocadan b19 275 2016 o 7 Tube of Calcium Gluconate Gel HF Antidote DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 12 of 32 Acid Neutralization Tank The hood has an active acid neutralization system that disposes of the used chemicals Clean Room Management has set up a standard operation philosophy that reserves the major chemical mixing and tank filling to the Clean Room Staff Staff will fill the tanks on a designated day or days of the week and leave the process active in the hood all day When the day is over the Clean Room Staff will turn off the heaters and allow the tanks to cool to room temperature over night The next morning a trained staff member will drain the tanks and start the neutralization process Thus when you have finished your processes all you need to do is clean up the work surface inform staff that you are done and then leave The neutralization process will be des
28. ool Setup Parameter menu DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 21 of 32 1 From the Process Setup Screen Figure A3 touch TOOL SETUP PARAMETERS This will bring up a screen to set up the Heater parameters Now in the lower left corner is a tab entitled CAUSTIC PUMP SETUP Figure A3 Software tree screens to find Caustic Pump Setup parameters Figure A4 Caustic Pump Setup screen for editing the pump parameters DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 22 of 32 Caustic Pump Setup a Stage 1 Parameter i The parameter by the name Caustic Pump RUN Constantly Below is currently set at 3 0 pH This means that the caustic pump will supply Sodium Hydroxide continuously if the actual pH of the tank contents is less than 3 0 b Stage 2 Parameters i The parameter name pH Stabilize Time after Reaching Stage 1 Prior to pH Setpoint is currently set at 2 0 minutes After reaching a pH of 2 0 or higher the system will wait for this amount of time before moving on to stage 3 If in this time period the pH falls below 2 0 again it will pump Sodium Hydroxide into the neutralization tank until the pH reaches 2 0 or higher ii The parameter Caustic Pump Cycle after Reaching Stage 1 Setpoint is currently set at 5 sec ON and 25 sec OFF After the 2 min stabilization time expires the c
29. quired to neutralize the acids If you have a mix of acids then calculate the volume of NaOH required for one acid and add the NaOH amount from the next independent acid reaction Table C1 Acid Neutralization Calculation Chart Sodium Hydroxide Acid Neutralization Calculator 11 17 2006 RAR Calculator instructions Input numbers in Blue Read answers in Red Nominally this calculator is designed to tell how much sodium hydroxide is required to neutralize a given volume of acid Thus just fill in the volume of the acid and the chart will fill in the required sodium hydroxide volume in red Units are Liters 1 Gal 3 7854 Liters 1 Liter 0 264 Gal Liq Wt NaOH Vol Oxidation Formula Volume Density Concen L req for Reactants a Wt gm mL SH Normality ae Meo 1 Be 125 a EE HPO 3 1 17 e EECHER mme 60 1 1 048 Tse Double click in the chart Excel will open and allow input and auto calculation DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 31 of 32 Appendix D Detailed RCA Process Setup Procedure Arnold Duenes Introduction This procedure is intended as a quick reference outline principally for the Clean Room Staff to set up the RCA clean up procedure It will list the chemicals required and the mixing steps in order with the exact amount of ingredient required for each tank Recipes RCA Clean Solution Volumes NOTE Always a
30. s each for these rinses The water fill valve is at the front edge of the hood s work surface as shown in the photo The water flow should be set to minimum via the following procedure First open the valve and quickly fill both tanks Then completely shut off the valve and finally re open the valve by turning the handle 180 degrees 1 2 turn This will set the DI water flow to a minimum flow so we can conserve the DI water but still be effective in rinsing the wafers DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 11 of 32 CHEMICAL BATH 1 CHEMICAL BATH 2 FINAL RINSE TANK 1 FIRST RINSE TANK 1 S peers DN UPFLOW Shaner ores Figure 7 Cascade DI Water rinse tanks with controls The center front knob in this photo is the DI water control valve The ringed knobs are the air flow controls for setting the stirrer spin speeds in the rear chemical tanks The gray knobs in the rinse tanks are the drain plugs HF Acid Antidote There should always be a supply of Hydrofluoric Acid HF antidote in plastic tubes in the back of the hood work surface If you accidentally get HF on your skin wash it off with DI water for about 10 minutes and then apply the antidote cream by rubbing it into the skin for about 5 minutes This Calcium Gluconate antidote will react with the HF to create benign Calcium Fluoride salt thus capturing the E ions that can do serious damage to the b
31. sistivity of the water in meg ohms The nominal value of gocd DI water is 18 1 meg ohms or better If the value has slipped below the 17 meg ohm level an alarm will DOCUMENT TITLE RCa Cieanup Hood Operations 6 2 2006 AUTHORS Roger Robhins and Arnold Duenes Page 5 of 32 sound Please notify the clean room staff and if this would impact your work discontinue processing your work in this hood DI Water Condition Meter Meg Ohms Loss of Exhaust Indicator Light Hood Start Button Audio Alarm Enunciator Emergency OFF Button Alarm Silence Button Hood Power off Button Figure 2 Hood Control Panel details Figure 3 Photohelic Exhaust pressure gauge left and alarm horn right Exhaust The photohelic pressure gauge Figure 3 measures the exhaust pressure in the exhaust line above the hood and if the pressure falls out of the acceptable range it will trigger the alarm horn Figure 3 which will then complain very loudly and light up the red alarm light on the control panel Figure 2 If this happens quickly bring your work to a safe conclusion and discontinue the use of the hood Also immediately notify clean room staff There may be a general loss of exhaust requiring clean room evacuation Follow staff direction By the way the exhaust alarm cannot be silenced except by shutting off the main power to the hood Do not attempt to change the photohelic pressure gauge set points DOCUMENT TITLE RCA Cleanup Hood Oper
32. ss timers on the front panel below the work surface Alarms are handled by the upper portion of the right hand side control panel The Big Red emergency off button is also located prominently on this panel Exhaust is monitored by a Photohelic differential pressure gauge on the left side of the front panel below deck level An alarm will go off if the hood exhaust is out of spec this would be the time to notify clean room staff and leave clean room since any acid vapors will drift back out into the clean room air and recirculate throughout the clean room DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 4 of 32 DI water faucet and Sink Touch Screen Process n Timers Exhaust Photohelic d Neutralization system Figure 1 RCA Cleanup Hood identifying the principal operating features Feature Details Control Panel The control panel is shown in Figure 2 with labels This panel is composed of two segments 1 a section of actuator buttons and indicator lights and 2 a touch screen linked to a microprocessor for controlling the operation of the hood These will be described in detail in the following sections DI Water The hood has a recirculating de ionized water plumbing system to prevent stagnani water from growing microorganisms and contaminating the purity of the water There is a monitor readout of this condition at the top of the conirol panel that displays the re
33. t how to run a neutralization operation on Leatherwood Plastic s 6 ft RCA Cleanup Hood 187 This hood is named HR01 in the Clean Room Equipment list Notes e This procedure is intended for Clean Room Staff use only e Proper Personal Protective Equipment is required when operating this bench or during maintenance operations e Neutralization Process must be ENABLED in order to run the Neutralization Process Neutralization Procedure Details Introduction The neutralization procedure follows the general outline described below At the conclusion of a day of RCA cleanup the chemical baths are allowed to cool to room temperature and then the neutralization process can be started by trained Clean Room Staff Spent acids from the four process baths are manually drained into a 30 gallon neutralization tank located under the bench Although acid neutralization on this hood is automatic several manual steps must be performed by clean room staff to insure that acids are properly neutralized Once the baths are drained tank contents with a pH lower than 6 0 will require Sodium Hydroxide 50 concentration in DI water to be pumped into the neutralization tank from a 2 gallon caustic reservoir until the pH is equal to or greater than 6 0 The contents of the tank will continue to recirculate for a programmed time period and then pumped into the building acid drain When the tank liquid level drops to 5 or less the system will automatically stop
34. uaeesuuaseuaaeeeaaeeeuaueeanasess 12 Acid Neutralization Tank isicccscsccdsdaccaccccacsceaaceeecateseadvessanersaacndaatneadedlaiieessaacasadectaact 13 Operating OV E 13 ENEE ee A A 13 e e GE 14 Timer Operation cc cece cccccececeeee cece sete cece ceeeceeeceeeeegeeeseeeseeeseeesesesseeeeeeeseeneeeeseeess 14 Neutralization System EE 15 Rules Of Operation 17 ele ele NEE 17 PADD CNIGIX EE 18 Neutralization Staff Drocedure 18 PURDOSE vs deene eg eeh ee 18 INQUGS AANA T ETS csateoss dee cstcecs E A TT TTT 18 Neutralization Procedure Details ccc ccccccccceesseeeseeeeseeeeeeeeueeeaeeeeueueeeeueeeaeeeaeeeeaes 18 tee e ee WEE 18 Neutralization Preliminaries ccccccccccccceccceeccseeccseeceseeuseueecsuueceseeueeuuessuuaeeueaeeaeanes 18 Plumbing Diagram Screen cecccdscaincedenctotensercenad enue vhcvesseiva EECHER EE EEGEN 19 Neutralization PDarameterzs ana ananr innnan nne 20 Caustic Pump Setup cccccccccceccceecccececeeeceeeeeeeeeeeeeceneecceeeceeeeaeeceeeeeesesaeesneseneeaaes 23 Neutralization Procedure 24 FANG OY 1 Tel oi EE 26 DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 2 of 32 Theoretical Neutralization Chemistry eee eeeceeeeeeee cere eeeeeeeeaaeeeeeeeeeeeeenaaaeeeeeeeeneenaea 26 Neutralization Chemistry eege ee eet ees 26 Chemical Definitions ccccccccccccccccceccceecceeeeeeeeeeeceeesaeeeeeeceeeeeeeeeeseeeseeaeesaeseneenas 26 le 26
35. urn key in the lower right corner of the keypad This will enable the hood software and bring up the Main screen as shown in Figure 9 Timer Operation The two buttons on the Main screen important to hood operators are the ones entitled Cycle Timers and Neutralization Process Pressing the Cycle Timers button produces a new screen as in Figure 12 and shows the timer indicators DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 14 of 32 Figure 12 Cycle Timer screen Enter time by pressing the appropriate numeral block until the desired number appears The clocks can be started from the touch screen or from the front panel on the front surface under the work area When you need to access other functions press Main and the system will return to the Main screen for additional action The timers can be started and stopped from either the front panel below the work surface as indicated in Figure 1 or from the touch screen itself This screen also shows the thermocouple thermometer temperature along with its temperature alarm limits Neutralization System The screen most useful for starting the chemical processes is the Neutralization screen This is a somewhat complicated depiction of the hood s drain plumbing and neutralization pumping and valving system Figure 13 shows this screen This overview screen shows at a glance the hood parameters in real time
36. valves and pumps Access levels 4 and 5 grant operation permission to this sub menu but you are already logged in the highest level 5 Leatherwood logged in 2 D 3 QUARTZ HF ETCH 1 m Si es 8 Ei q NEUTRALIZE AT ap TANK sl LEVEL CAUSTIC RESERVOIR Figure A5 Pressing the PROCESS MANUAL CONTROL button on the main screen Left brings up the NEUTRALIZATION MANUAL CONTROL screen Right from which the drain valves can be manually opened b The valves in the large image in Figure A5 show a green outline implying that if your finger pushes on the button inside the green outline the valve will change state However YOU CAN ONLY DRAIN ONE TANK AT A TIME This prevents any possible violent chemical cross reaction in the drain lines from interaction of chemicals from different tanks c Begin draining the following chemical tanks manually 2 Quartz 3 Quartz and HF Etch tank Wait until the entire solution is fully drained and then you MUST rinse out the sink with the DI water sprayer It is highly recommended that you spend at least 3 to 5 minutes rinsing out each tank Once rinsed close the drain valve and move on to the next tank d After draining and rinsing all the chemical baths the neutralization tank level should read something like 80 full DOCUMENT TITLE RCA Cleanup Hood Operations 6 2 2006 AUTHORS Roger Robbins and Arnold Duenes Page 24 of 32 i If during your draining and rinsing operation the n
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