CLEANLINESS STANDARD NCPRE tool contamination classification

Transcription

1 Tool Identifier NCPRE Phosphorous diffusion furnace Document version th May 2013 Documented by Karthick Murukesan CONTENTS I. CLEANLINESS STANDARD 1 II. PERFOMANCE OF THE TOOL 1 III. WAFER PRE REQUISITE 1 IV. STANDARD OPERATING PROCEDURE 2 a) Before entering clean room 2 b) After entering clean room 2 V. SAFETY PRECAUTIONS 4 VI. EMERGENCY RESPONSE 4 VII. CONTACT LIST AND HOW TO BECOME A USER 5 VIII. APPENDIX 6 CLEANLINESS STANDARD NCPRE tool contamination classification 1. PVCLEAN - Wafers should be RCA cleaned. Wafer should not contain any deposited metal or organic coatings. RCA cleaning (or) RCA cleaning + texturing should have been the immediate process proceeding the diffusion process. PERFOMANCE OF THE TOOL What the tool can do 1. The tool is capable of doing phosphorous diffusion in the silicon substrates using POCL3 liquid diffusion sources. The three zones of the furnace can reach to the temperature of 1200 o C. Recipes can be tuned to get the desired sheet resistance. WAFER PRE REQUISITE Cleanliness and dimensions 1. Wafer should be RCA cleaned and can be textured or planar. 2. Wafers can be 5inch Pseudo square or square wafers, 6inch Pseudo square or square wafers, 4inch circular wafers (Based on the present availability of the quartz wafer carriers). KNOW HOW & OPERATE DOCUMENT Page 1

2 STANDARD OPERATING PROCEDURE a) Before entering clean room: 1. Switch on the MAIN MCB corresponding to the protemp diffusion furnace from the power panel in the NCPRE fab lab corridor. 2. Switch on the TOOL EXHAUST (press green switch) in the NCPRE fab lab facility corridor (Being a common exhaust for several other tools it may be on already, which could be confirmed by the LEDs glowing ). 3. In the CYLINDER CABINET corresponding to the protemp diffusion furnace at the NCPRE fab lab facility corridor open the N 2 ( any one cylinder of the 2 connected to the manifold) and the O 2 cylinder. cylinder pressure: Cylinder pressure of N 2 should be >100bar. Cylinder pressure of O 2 should be >100bar. line pressure : Set the N 2 line pressure to 1 Bar (1kg/cm2 or 14.5 Psi) Set the O 2 line pressure to 4 Bar (1kg/cm2 or 14.5 Psi) 4. We should ensure the availability of facility staff to turn on the water supply to the SCRUBBER just before running the diffusion recipe. b) After entering clean room: 1. Flip the Furnace control system power (marked as 120V service). 2. Switch on the PC. Enter the username and password. 3. In the 3 stack furnace the top furnace corresponds to the Phosphorous diffusion furnace. Flip the power switch marked as top to power the Phosphorous diffusion furnace 4. Double click on the Tymplex shortcut to start the process, Click the download tab and standard recipes can be downloaded for 50 ohm per square, 100 ohm per square target sheet resistance. 5. IMPORTANT PRECHECKS BEFORE STARTING THE RECIPE i. Check the parameters in the recipe if it matches the desired. ii. Check the pressure meter showing the tool exhaust pressure. It should be between 55-60mm of mercury.this implies the tool exhaust is on and provides required suction (CFM). iii. Ask the facility staff to recheck the cylinder pressure, respective line pressure, tool exhaust status. KNOW HOW & OPERATE DOCUMENT Page 2

3 iv. Check whether the valve in the bubbler corresponding to the lo N 2 line is open appropriately so that the lo N 2 bubbles through the POCl3 and enters the tube. If not ask the facility staff to do the required [Please refer appendix for reference]. 6. Start the recipe. If any of the gas flow is below the critical limit instrument alarm strikes. If the alarm strikes then abort the process readjust the gas pressure and start the process again. 7. To understand the overall process flow a common recipe has been given below. TABLE 1- Baseline POCl 3 Recipe for 50 ohms/ cm 2 Step # Name Time Temp Gas Flow in SLPM 0 Idle C N2@8.15L 1 Boat In C N2@8.15L, O2@0.45L 2 Oxide 5 860C N2@8.15L, O2@0.45L 3 Stabilize C N2@8.15L 4 POCl 3 Deposition C N2@8.15L, O2@0.45L, POCL3@0.45L 5 Purge 5 860C N2@8.15L, O2@0.45L 6 Drive In C N2@8.15L, O2@0.45L 7 Boat Out C N2@8.15L 8 Idle 750C N2@8.15L 7a) Ramping Up, Loading and Unloading the wafer i. The ramping up time is set in the recipe accordingly it ramps up and at the boat in temperature the loading station comes out. Change the mode of the loading station from program to manual and Carefully load the wafers with a Teflon tweezer or gloved hands (if the wafers are 180 u thick). Then change the loading station to program mode and it loads in the wafer automatically. Ask the facility staff to open the water supply to the scrubber once the sample is loaded ii. Once the deposition is done and boat out temperature is reached the loading station automatically comes out (wear goggle and facemask). KNOW HOW & OPERATE DOCUMENT Page 3

4 iii. UNLOADING (?): Once the loading station has come out wait for 5 to 10 minutes for the wafers to reach the room temperature, check the temperature of the wafer using the IR gun and once it reaches the room temperature unload the wafers (use a stool if required) be careful not to touch the quartz carrier. (Else check the temperature of the wafer as well as the quartz carrier using the IR gun and wait for both of them to reach the room temperature. Then remove the carrier (?) along with the wafers put it over the stainless steel bench and unload the wafers carefully ). iv. In case you have touched any of the hot component and a stain has been developed don t put the quartz back into the tube. Inform the system owner about it and a 2% HF dip has to be given to the quartz and then used. 8. Instrument Shut Down i. Add an additional recipe step where only Hi flow N 2 flows through the tube for approx 3 hours during which the furnace naturally cools down. ii. Once the centre, left and right zones of the temperature is below 100 o C. Abort the recipe. Close the Tymplex window. iii. Shut down the PC, flip off the furnace control system power, flip off the furnace main power. iv. After coming out of the clean room ensure that the nitrogen and oxygen cylinders are closed and main MCB is switched off SAFETY PRECAUTIONS 1. During loading and unloading the wafers, wear goggles and facemasks. The loading and unloading temperatures are quite higher of the order of degree Celsius. Never touch the hot furnace components and the wafers with gloves when they are at high temperatures. 2. If you are not confident of any step or any procedure never guess feel free to call system owner or authorised users. EMERGENCY RESPONSE a) Power shut down: 1. If you have some time remaining before the power shut down follow the following steps 1a) Abort the process running in the TYMPLEX. 1b)Switch off the furnace power (switch marked as top corresponding to the phosphorous diffusion tube ). 1c) If the temperature of the tube is high > 800 o C and your samples are inside. Since we cannot wait for the temperature to reach the unloading temperature leave the sample inside itself. Else if the temperature of the tube is the unloading KNOW HOW & OPERATE DOCUMENT Page 4

5 temperature and power is available for the time to unload the samples, unload and close the loading station. 1d)Shut down the PC. 1e)Switch off the furnace control unit power (labelled as 120V service) 2. If the power to the furnace is suddenly not available. 2a) switch off the furnace power and the control unit power wait for the power to come to unload the wafer or plan a new process b) Gas detector Alarm triggered: 1. It automatically shuts off the lo nitrogen flow through the bubbler once the alarm is triggered. 2. Immediately get out of the clean room and alert the facility staff Sandeep Kumbare, Lab manager Dr. Diksha about it. c) If Alerted to go out of the lab immediately: 1. Abort the process running in the PC. 3. Switch off the furnace power (switch marked as top corresponding to the phosphorous diffusion tube ) 4. Run the recipe named as emergency recipe (on desktop) which will facilitate the flow of high flow N 2 during the ramping down. 5. Leave the lab (all the above processes can be done within a minute. If its taking a long time please mind to leave the lab without taking care of all this). d) System malfunction: 1. Contact the system owner, other authorised users for help. CONTACT LIST AND HOW TO BECOME A USER System owner/au Karthick Murukesan NCPRE, Department of Electrical Engineering karthick31388@gmail.com Mobile: Authorised user for Phosphorus diffusion furnace Bandana singha NCPRE, Department of Energy Science Amrutha NCPRE,Department of Energy science Materials allowed Silicon (for other materials you can contact Professor BM Arora, Professor Anil Kottanttharayil for contamination clearance). KNOW HOW & OPERATE DOCUMENT Page 5

6 Training For training please contact system owner.send an to system owner, lab manager NCPRE. (?) - lines marked with this requires a discussion to decide. APPENDIX A) Bubbler operation: Fig 1 Showing the POCl3 bubbler in off condition (with bypass on). Turning the respective T s as shown in figure makes it in on as required before the process of diffusion. KNOW HOW & OPERATE DOCUMENT Page 6

7 B) Pressure meter showing tool exhaust suction Fig 2 Pressure meter showing the tool exhaust suction ( The reading should be between 50 and 25 ). This ensures there is a sufficient CFM suction provided by the tool exhaust. KNOW HOW & OPERATE DOCUMENT Page 7