Standard Operating Procedures for Process Gas Handling

Transcription

1 Standard Operating Procedures for Process Gas Handling A supplement to the SOP for Laboratory for Advanced Materials Processing JM Patterson Bldg., Room 2225 University of Maryland Revision 1.1 DRAFT April 13, 2000 Prepared by Laurent Henn-Lecordier, Institute for Systems Research and John N. Kidder, Department of Materials and Nuclear Engineering Standard Operating Procedures for Process Gas Handling Page 1 of 18

2 1 SAFETY SYSTEMS To optimize the safety in LAMP (Laboratory for Advanced Materials Processing) several safety sensors have been installed in order to generate a single alarm response in case of an emergency. These sensors and alarm devices are specially aimed at the detection of pyrophoric silane, used in the ULVAC CVD reactor (for more details about silane cf. Silane MSDS included in this report). This report will list the different sensors and the procedures to respect in case of an alarm within this laboratory. A section regarding the maintenance of this alarm system is also included. 1.1 Alarm Systems CSS E0883 MDA alarm unit The core of the alarm system is the MDA alarm unit located above the System 16 gas monitor. This system generates 24 V signals to the different sensor relays (MDA silane gas detector, smoke detectors, photohelic gauges, EPO button at the entrance of the lab, silane pressure switch and silane excess flow switch). If an alarm condition is detected by one of these sensors, their internal Normally Open relays will be closed and the 24 V signal will be returned to the MDA alarm interface. An appropriate response will be triggered in function of the origin (sensor) of the alarm. In all alarm cases (Level 1 or 2), the ULVAC gas interlock system will be shutdown (Alarm level 1). The silane bottle equipped with a pneumatic valve will be closed as well as all the other process gases delivered to the ULVAC tool. If the presence of silane or smoke is detected in the cleanroom or pre-cleanroom, or if the EPO button at the entrance of the lab is pushed (Alarm Level 2), a visual and audible alarm (remote alarm enunciators 1 and 2) will be triggered in both rooms (cleanroom and pre-cleanroom), in addition to the gas interlock shutdown. The MDA alarm unit is also connected to a 24 hour monitoring station that will notify UMPD and trigger an additional enunciator in the hallway (see next page). The building alarm will also be activated. Notice: the monitoring station and building alarm are activated via signal from MDA interface to ESL fire panel (see section ESL fire panel for additional information) If the MDA alarm unit stops functioning (power shortage, breakdown ), a Normally Open relay will open and shutdown the gas interlock system. In case of a power shortage, the MDA alarm unit and the System 16 gas detector are backed up by a Stabiline SL 1500 uninterruptible power supply whose 1440 max VA will provide power to these systems for 5 to 10 minutes. Standard Operating Procedures for Process Gas Handling Page 2 of 18

3 1.1.2 Remote alarm enunciators 1 and 2 Two visual (red flashlight) and aural remote alarms are connected to the MDA alarm interface and will respond to an Alarm level 2. One is located next to the MDA alarm interface above the System 16, the other on top of the ULVAC system. The 24V power supply to these units is provided by the MDA alarm unit which means that in the case of a building power shortage, these alarms will continue to function for a few minutes via the UPS. These alarms can only be shut down by deactivating the internal relays of the MDA alarm unit DSC power hour supervisory unit A 24-hour supervisory unit is connected to the University of Maryland Police Department. UMPD will immediately notify the fire department. This unit reports any alarm Level 2 from the MDA alarm unit. This system must be armed prior to utilization. A blue flash-light is installed in the hallway on top of the LAMP main entrance door. In addition to the visual signal, a prerecorded warning message will be annunciated. This speaker/light warning system is connected to the DSC supervisory unit. To stop the siren or rearm the system, enter on the keypad: The UMPD phone number to call or to cancel an accidental alarm is ext. # The manual related to the operation of this unit is included in this report. 1.2 Safety Sensors and Activators MDA / Zellweger Analytics System 16 gas detector ALARM LEVEL 2 This system is currently configured for the detection of silane and analyses sequentially the gas samples in four different locations (silane gas cabinet, ATM gas scrubber, Ulvac gas delivery system on the roof of the Ulvac cluster tool, cleanroom). If a silane concentration above 5 ppm (TLV) is detected at any of these locations, it will activate the MDA alarm interface (Alarm Level 2) The front panel of the System 16 can be read from the hallway through the glass window. Thus, in case of an alarm, the printed emergency report can be read without entering the lab. This system is backed up by a UPS station. A set of 3 green and 3 red LED s has been wired on the back panel of the System 16 gas detector. These LED s report the following fault detection: Standard Operating Procedures for Process Gas Handling Page 3 of 18

4 Maintenance Warning: the instrument needs attention but the instrument is still able to monitor and operate as programmed. (e.g. chemcassette needs to be changed) Loss of Coverage: the monitoring capability is reduced, but not completely absent (failure of one or more points module) Loss of Monitoring: it indicates a complete absence of monitoring. The bottom line is that these LED s are easily visible either from the precleanroom or from the cleanroom. The operators of the ULVAC should systematically make sure that all three green LED s are ON before processing with silane. (for more details concerning the System 16, cf. Section 3 of this memo) Three-zone ESL Fire Alarm Control unit ALARM LEVEL 2 3 smoke detectors are located near the silane gas cabinet, the ATM scrubber and the ULVAC CVD cluster tool. They are connected to the three-zone ESL Fire Alarm control unit, located next to the System 16 and visible from the middle door in the hallway. If the presence of smoke is detected at any of these three locations: An internal audible alarm (from the ESL fire control unit) will go off. A double throw relay will activate the MDA alarm interface (Alarm Level 2). This system is backed up by a 24 V battery. The building alarm is tied to the ESL Fire panel. In order to have the building alarm activated in case of a level 2 alarm, a fourth zone has been installed by Physical Plant. This zone is an input from the MDA alarm interface. If an alarm Level 2 is generated, the A1 NO-relay from the MDA alarm interface will close. A 24 V signal is consequently received to the Zone 4 terminal triggering the Fire alarm and the building alarm Red Mushroom push-button ALARM LEVEL 2 Located at the entrance of the lab (on the left side of the door), it can be manually activated. It is connected to a 120 V relay in the mechanical room. The closure of this relay by pushing on the button will return a 24V signal to the MDA alarm interface (Alarm level 2). An internal flash light and an aural alarm are also activated (they are located above the entrance door in the pre-cleanroom. The 120V signal is provided by the building power supply Dwyer hi/low-setpoints photohelic gages ALARM LEVEL 1 3 photohelic gauges monitor the proper functioning of the duct exhaust system at the three following locations: silane gas cabinet exhaust, mechanical pumps and scrubber exhaust, ULVAC cluster tool exhaust. If the pressure in the exhaust is below 0.2 WG (normal pressure is between 0.5 and 1 ), it will activate the MDA alarm unit that will shutdown the gas interlock panel (the remote alarm enunciators will not be activated). Standard Operating Procedures for Process Gas Handling Page 4 of 18

5 1.2.5 Amtek overpressure switch ALARM LEVEL 1 On the high pressure side of the silane regulator (in the gas cabinet), an AMTEK high pressure switch is connected to the MDA alarm unit. If the silane pressure reaches 80 Torrs, the N.O. relay of the sensor will be closed and the MDA alarm unit will shut down the gas interlock panel (Alarm level 1) Silane excess flow switch ALARM LEVEL 1 The silane bottle outlet is equipped with an excess flow switch. An excess flow will trigger an alarm Level 1 (gas interlock shutdown). 1.3 Zellweger Analytics System 16 Gas Detector The System 16 is equipped with one 4-point module analyzer that can detect one gas at 4 different locations. This analyzer has a chemcassette formulated to react with silane: the target gas in the sample reacts with the tape, the reaction produces a stain with a density proportional to the gas concentration, the stain is measured is optically measured. This chemcassette and optical sensor must be maintained monthly (cf. Section 3-2). This system can be programmed either in Sequential Mode (System 16 monitors the sample from only one point at a time) or in Parallel Mode (the System 16 monitors simultaneously samples from the 4 points) System configuration This section is a descriptive list of the current configuration and the different steps followed by the System 16 in case of silane detection. For more details, cf. System 16 Technical Handbook. System 16 is configured in Sequential Mode. Alarm levels for the point group (i.e. 4 points): TLV1 = 5 ppm Æ early detection of silane TLV2 = 10 ppm Æ for critical levels which may require evacuation TLV: Threshold Limit Value Based on the alarm level of the point in the point group with the lowest programmed alarm level (in our case, each point has the same alarm level) In our case, all alarms are triggered at TLV1 and will require immediate evacuation. - If the gas concentration for one point exceeds 5 ppm: Standard Operating Procedures for Process Gas Handling Page 5 of 18

6 1) The appropriate alarm LEDs lights (Level 2 and/or 1) 2) The point Relay contact activates and triggers the LAMP alarm Level 2 via the MDA alarm interface. 3) The printer module prints the alarm information with time, alarm levels and concentrations MDA System 16 Scheduled Maintenance Changing the Chemcassette (i.e. every month): Clean with alcohol everywhere the tape is in contact (especially the tape guides) Use the optic verification card to check the optics system (see Section 10 of Syst. 16 Handbook). Balance the flow (see Section 9) If problem with the flow balance, check the Acid Scrubber filter. MDA Service Mode (not in the manual) Password: #### Select Subfunction: Real CC Transducer 140 < S < 205 (operating range) Adjusting S will probably change the flow meter value (e.g. from 42 to 45 mm). This does not matter. The transducer data S is the most accurate and is the one that will be processed by the computer (not the flow meter value) Bi-annual Maintenance Optics Calibration Enter Service Submenu, and subfunction 9 (Read Raw Optics) Raw reading should be: /- 200 Lower limit 2000 (a lower value will give an Instrument failure) To clean the optics, remove the 2 screws of the optics block, pull the pipe straight back at the rear of the panel, remove the black plastic block with the LED s and clean with alcohol. When dirty, you can see a white stuff from the band. Also in case of false alarm, the optics should be always checked) Filter Maintenance (see section 12 of System 16 Technical Handbook) Acid Scrubber Filter (manufactured by Bolston, PN ) Standard Operating Procedures for Process Gas Handling Page 6 of 18

7 If ¾ or more of the acid scrubber turns blue, or the vacuum increases, replace it. Replacement frequency: 6 months. Primary Flow Module Filter (Replacement frequency 6-12 months) Standard Operating Procedures for Process Gas Handling Page 7 of 18

8 Alarm System Maintenance and Check-Up Only the System 16 gas detector requires a monthly maintenance (cf. Section 3.2, p 8). Nevertheless each sensor should be checked regularly. If running a full alarm test, notify first the UMPD station at *53333 or deactivate the monitoring station MDA System 16 Gas Detector The alarm LED s and alarm relays should be tested every month: - Press the service function key on the System 16 control module. - Select Subfunction Alarm Test by pressing key 2 twice. - Press 0, to select a full-system test or 1 if you want to check each point individually. - Remote Alarm 1 and 2 should go off and gas interlock should be shutdown. - Press Service on control module to turn off the alarm ESL Fire Alarm Control Unit The three smoke detectors should be tested individually and every month. - To test the smoke detectors, use the Smoke Detector Tester. Aim the spray for 2 seconds at detector. - The related zone relay should be activated: the internal audible alarm will go off as well as remote alarm 1 and 2. Gas interlock should be shutdown. - To disactivate the alarm, switch to Reset in the ESL system control unit Photohelic gauges The three photohelic gauges should be tested individually and every month. - For each photohelic gauges, increase the low setpoint till it reaches the current pressure in the duct system: Gas interlock should be shutdown. - To turn off alarm, reset the setpoint to its original value. Standard Operating Procedures for Process Gas Handling Page 8 of 18

9 1.3.3 Electrical diagram of the MDA alarm interface and peripherals Standard Operating Procedures for Process Gas Handling Page 9 of 18

10 1.3.4 MDA Interface unit: relay connections Power ON No alarm P1 and P3 normally close => V P 2 = 24V => P2 relay closed (gas interlock OK) If alarm level 2 conditions (System 16, ESL fire panel, EPO) V P 1 = 24V => P1 opens => P3 is still closed => V P 2 = 0V => P2 opens (gas interlock shutdown) V P 1 = V A 1 = V Q = 24 V => A1 closes (Alarm level 2), Q opens (monitoring station, hallway enunciator) If alarm level 1 condition (photohelic gages, overpressure switch) V P 3 = 24 V =>P3 opens => V P 2 = OV => P2 opens (gas interlock shutdown) Power OFF P2 opens => gas interlock shuts down Standard Operating Procedures for Process Gas Handling Page 10 of 18

11 1.3.5 Floor plan of LAMP and positioning of sensor and alarm units MDA alarm unit Remote alarm 1 enunciator Silane Cabinet with purge pannel Overpressure sensor 100 g Silane bottle and N2 purge bottle Gas interlock pannel Smoke detectors Silane sampling points Pressure sampling Silane jacketed line Zellw. Syst 16 ESL Fire Remote alarm 2 enunciator HALLWAY UMPD unit PRE CLEANROOM Ulvac system Photohelic gauges ESL Fire flashlight EPO flashlight EPO CLEANROOM Dry gas scrubber Floor plan of LAMP and locations of sensor and alarm units Standard Operating Procedures for Process Gas Handling Page 11 of 18

12 1.3.6 Building Security Systems Unit SECURITY SYSTEM OPERATION 1). TO ARM THE SYSTEM: a). VERIFY THAT THE GREEN READY LIGHT IS ON. b). ENTER YOUR 4-DIGIT CODE OR PRESS THE AWAY BUTTON UNTIL THE SYSTEM ARMS. c). EXIT THE BUILDING AND CLOSE THE DOOR WITHIN 45 SECONDS. THE SYSTEM IS NOW ON!! 2). TO DISARM THE SYSTEM: a). UPON ENTERINGTHE BUILDING YOU WILL HEAR A PRE-ALARM SOUND FROM THE KEYPAD. b). ENTER YOUR 4-DIGIT CODE INTO THE KEYPAD. c). THE SOUNDER AND THE ALARM WILL TURN OFF. d). THE SYSTEM IS NOW OFF!!! 3) WHAT DO I DO IF THE KEYPAD SOUNDER ACTIVATES? a). CHECK THE MESSAGE READ WHAT IS SAYS AND FOLLOW DIRECTION ON THE SCREEN. b). TO SILENCE THE KEYPAD OR ALARM JUST ENTER YOUR CODE. c). IF ALL ELSE FAILS CALL (301) OR (301) AND ASK FOR BUILDING SECURITY. 4) How do I set the system to arm itself at night? a). Press the * button then press the number 6. b). Enter your MASTER CODE. c). Press the right > arrow until the screen says ENTER AUTO ARM TIME d). Enter the time (Military time) that you want the system to turn on. e). Then press the right > arrow until the system says AUTO ARM CONTROL. f). Press the * button to have the system auto arm. The screen will confirm that the feature is either on or off. Please read what the system says. Often people will think they have turned on the auto arm function when in fact they have actually turned it off. Standard Operating Procedures for Process Gas Handling Page 12 of 18

13 2 EMERGENCY RESPONSE PROCEDURE In case of an alarm in LAMP resulting from a leak of silane and/or fire detection, the following actions are automatically taken by the LAMP safety system: - Activation of 2 red flash lights in pre-cleanroom and cleanroom with audible alarms plus a blue flash light above hallway door with audible evacuation call - Enunciation to UM Police Department via supervisory unit - Activation of building alarm Anyone present in the lab must: 1. Evacuate the facility immediately 2. If main building alarm is not already sounding, pull manual station in hallway for general evacuation of the building 3. Call 911 to confirm they have been notified by automated supervisory unit (JM Patterson building (083), second floor, room 2225) 4. Call the Lab manager (John ) and Laurent Henn ). In any case, it should not be attempted by any students to evaluate the source and gravity of the alarms. For any questions regarding this notice or safety issues in LAMP, contact John or refer to Lab SOP. 3 Fire Department General Notice The alarm from LAMP in JM Patterson results from the potential leak of pyrophoric silane. The pure 100g silane bottle is located in the first room of the lab (pre-clean-room), in the gas cabinet along the left-side wall. The silane gas bottle and the silane line are automatically closed via pneumatic valves connected to the gas interlock panel. The lab also contain a pure tungsten hexafluoride WF6 bottle (15 lbs max in a gas cabinet in the mechanical room) and an pure hydrogen bottle (8.2 m3 in preclean-room) This facility is monitored with a Zellweger system 16 to detect silane leaks. The position of the three sensors is shown on the diagram next page. The front panel of the system 16 silane detector and of the ESL Fire panel is visible from the lab middle window in the hallway. The printout menu or the LEDs will indicate the location of the potential leak. Standard Operating Procedures for Process Gas Handling Page 13 of 18

14 To shutdown the alarm in the lab: If ESL fire alarm is on, push Reset button on ESL panel If Systems 16 alarm is on, press Reset on keypad The whole alarm system can be powered down by switching off the switch located inside the MDA alarm interface box (located on top of the system 16) Standard Operating Procedures for Process Gas Handling Page 14 of 18

15 4 PROCESS GAS CYLINDER HANDLING PROCEDURES Full face shields and Nomex cover-all suits required for handling SiH 4 cylinders Breathing protection is required for changing WF Gas cylinder receiving Delivery of SiH 4 and WF 6 cylinders will be coordinated with the supplier (Air Products) and received at the rear entrance of the JM Patterson Building. Before entering the building the cylinder will be inspected for signs of a leak (discoloring or residue) and then will be transported to the LAMP facility and placed in a cabinet until installation. 4.2 First time installation of new cylinder This procedure is for installaion of a new cylinder on to gas system which has not been previously used with process gases Cycle purge and leak check process line Pump out the line upstream of the regulator using through the process tool. a) Set the ULVAC so that the chamber is being pumped by the turbo and monitored by the ion gauge. b) Close VS4 c) Open the process valves (PVs) and set the MFC to full open. d) Pump on the reactor chamber using the turbo pump. e) After reaching a base pressure (pump for at least 15 minutes) at the ion gauge, close the process valve immediately down stream of the MFC. f) After approximately 30 sec open this valve and monitor the effect at the ion gauge. A significant pressure jump MAY signify be a leak in the process plumbing. If this is observed, repeat the test after pumping on the chamber for another 15 minutes Installing and activation new cylinder Step 1: Connect the cylinder to the gas panel a) Secure cylinder in place in the gas cabinet b) Remove cylinder cap c) With the main cylinder valve closed (i.e., pneumatic air line NOT attached) SLOWLY remove the DISS connection cap and remove the gasket. Check for signs of a significant leak through the cylinder valve (white powder, smoke) d) Using a new DISS gasket, attach the pigtail fitting to the cylinder. Step 2: Cycle purge the gas panel Starting with all valves closed. a) Open VS5 to start N2 flow through the venturi element to generate a vacuum at VS2. b) Open VS3 and set the regulator open to near full pressure delivery. c) Open VS1 fill the panel with purge N2 and then close VS1. Standard Operating Procedures for Process Gas Handling Page 15 of 18

16 d) Open VS2 to evacuate the panel, checking for a pressure drop to near 30" Hg at the regulator low P side. e) Close VS2. f) Repeat steps c and d AT LEAST 10 times. g) Complete this procedure with with step d. h) Leave the system for approximately 1 hour noting the pressure at the regulator gauge. i) If after 1 hour the pressure does not rise, close VS3 and proceed to the next step. Step 3: Cycle purge the process line. Deliver N2 to the process line from the purge cylinder. a) Open VS1 to apply pressure to the panel. b) Open VS3 and set pressure at regulator to ~ 10 psi. c) Open VS4 to pressurize the process line with the purge N2. d) Close VS4. e) Put the SiH 4 MFCs in full open and open the upstream PV. f) Open the By-Pass PV to evacuate process line back to the cylinder valve VS4. g) Close the By-Pass PV. h) Open VS4 to fill the process line, then close VS4 i) Repeat steps f through h at least 10 times. j) End the process with step g, evacuating the process line. k) Cycle Purge the panel (see above Step 2) and leave in evacuated state Switching cylinders Removal of used cylinder Verify that the gas cylinder main valve is closed. Disconnect the air line to the pneumatically operated main cylinder valve. Step 1 Cycle purge the panel. Starting with all valves closed. a) Open VS5 to start N2 flow through the venturi element to generate a vacuum at VS2. b) Set the regulator open to near full pressure delivery. c) Open VS2 to evacuate the panel, checking for a pressure drop to near 30" Hg at the regulator low P side. d) Close VS2. e) Open VS1 to fill the panel with purge N2. f) Close VS1. g) Repeat steps c and d AT LEAST 10 times. h) Open VS1 and pressurize the panel with purge gas to provide outward purge flow when the pigtail connection is disconnected. Step 2 Disconnect and remove the used cylinder a) VERIFY that the pneumatic air line to the main cylinder valve is disconnected. b) Slowly loosen DISS cylinder fitting and disconnect. c) Place cap over cylinder valve. d) Remove cylinder and store for pick-up. Standard Operating Procedures for Process Gas Handling Page 16 of 18

17 Installation of new cylinder Step 1: Connect the cylinder to the gas panel e) Secure cylinder in place in the gas cabinet f) Remove cylinder cap g) With the main cylinder valve closed (i.e., pneumatic air line NOT attached) SLOWLY remove the DISS connection cap and remove the gasket. Check for signs of a significant leak through the cylinder valve (white powder, smoke) h) Using a new DISS fitting gasket, attach the pigtail fitting to the cylinder. Step 2: Cycle purge the gas panel Start with VS1 open, all other valves closed. a) Open VS5 to start N2 flow through the venturi element to generate a vacuum at VS2. b) Open VS3 and set the regulator open to near full pressure delivery. c) Close VS1 d) Open VS2 to evacuate the panel, checking for a pressure drop to near 30" Hg at the regulator low P side. e) Close VS2. f) Open VS1 g) Repeat steps c and d AT LEAST 10 times. h) Complete this procedure with step e (panel evacuated). i) Leave the system for approximately 1 hour noting the pressure at the regulator gauge. [A pressure rise is associated with a leak in the panel or the DISS connection.] j) If no signs of a leak is detected, proceed to step 3. Step 3: Open the cylinder Start with all valves closed. Verify that dowstream process valves are closed. a) Verify that the electronic switch for the main cylinder valve is OFF. b) Connect the pneumatic air line for the cylinder main valve. c) Open the SiH 4 main cylinder valve using the switch at the remote panel. d) Open VS3 and check pressure at the panel regulator. e) Open VS4. f) Adjust panel regulator to 30 psi to deliver SiH 4 pressure to the ULVAC. Standard Operating Procedures for Process Gas Handling Page 17 of 18

18 4.3 Silane Usage Policy Silane check-list This check list must be filled out before any utilization of silane. Blank copies are in a log book located at the control module. No less than two knowledgeable operators must be present at any time when using the silane gas in a deposition experiment. Is the ATM gas scrubber on? Is the scrubber line < 400 Torr? Is the System 16 Monitor on? Are the three status LEDs all green? Is SiH 4 line jacket purge flow on? YES? Operators Name 1 Name 2 Date Hour Date Hour Standard Operating Procedures for Process Gas Handling Page 18 of 18