Diffusion/Anneal SOP Page 1 of 12 Revision

Transcription

1 Diffusion/Anneal SOP Diffusion/Anneal SOP Page 1 of 12 1 Scope 1.1 This document provides the procedures and requirements to introduce and/or drive dopants into silicon using the Canary furnace. 2 Table of Contents 1 Scope Table of Contents Reference Documents Referenced within this Document External Documents Equipment and/or Materials Safety Setup Procedures Enable Furnace Remove Boat Select Program and Temperature Set Gas Flows Load Program Set Diffusion/Anneal Time Load Sample Wafers General Procedures Load Furnace Start the Program Unload Process Measurement Place System in Standby Disable Furnace Process Notes and Characterization Solid Source Wafer Cure Gas Flow Setpoint Conversions Auto-Sequencer Input Assignments Temperature Controller Recipes Auto-Sequencer Programs Revision History Figure 1, Diffusion/Anneal Gas Controller... 4 Figure 2, Anneal Boat Loading Diagram... 5 Figure 3, Diffusion Boat Loading Diagram... 5 Figure 4, Push Rod Alignment... 6 Table 1, Diffusion/Anneal Programs... 3 Table 2, Solid Source Cure Loop Counter... 8 Table 3, Diffusion/Anneal Gas Flow Setpoint Conversions... 8

2 Diffusion/Anneal SOP Page 2 of 12 Table 4, Diffusion/Anneal Auto-Sequencer Output Assignments... 8 Table 5, Diffusion/Anneal Temperature Controller Setup... 9 Table 6, Diffusion/Anneal Auto-Sequence Controller Setup Reference Documents 3.1 Referenced within this Document Canary Furnace SOP 3.2 External Documents None 4 Equipment and/or Materials 4.1 Oxygen (O 2 ) 4.2 Hydrogen (H 2 ) 4.3 House Nitrogen (N 2 ) 4.4 Canary Diffusion Furnace 4.5 Quartz boats 4.6 Quartz push rod with mark at 26 from hook 4.7 Solid Source Wafers, BoronPlus GS245 (Techneglas) 4.8 Solid Source Wafers, PhosPlus TP470 (Techneglas) 4.9 Heat-resistant gloves 4.10 Monitor wafers (bare silicon <100>, n and p-type) 5 Safety 5.1 Follow all Nanofab safety procedures. 5.2 Do NOT open the element door (danger of high voltage). 5.3 This system uses hazardous gases. Refer to MSDS for more detail Do NOT adjust any regulators or valves for any gases. 5.4 Do NOT store flammable solvents (e.g., squeeze bottles, etc.) near the furnace or loading station. 5.5 Do NOT touch quartz boats with your hands. They may be hot. Use only a clean quartz boat holder or high temperature gloves. 5.6 Do NOT touch quartz or wafers with wipes, gloves, teflon, plastic, etc. 5.7 Place quartz only on dedicated quartz carriers, quartz surfaces, or stainless steel surfaces. 6 Setup Procedures All new, unused solid source wafers (BoronPlus or PhosPlus) must be cured before use. Follow the procedures in section 8.1 Solid Source Wafer Cure to cure the wafers.

3 6.1 Enable Furnace Diffusion/Anneal SOP Page 3 of In Coral, enable the furnace and complete all required data entry. 6.2 Remove Boat Enabling the furnace will release the interlock and provide access to the keypad Verify the furnace is in step If the furnace is NOT in step 69, contact Lab Staff before proceeding Open the furnace door Using the high temperature gloves, remove the end cap Using the high temperature gloves or the quartz handle, remove the boat from the furnace and place on the quartzware rack Using the high temperature gloves, replace the end cap Close the furnace door Allow the boat and wafers to cool at least 5 minutes. 6.3 Select Program and Temperature Review the pre-defined programs shown in Table 1, Diffusion/Anneal Programs. Table 1, Diffusion/Anneal Programs Loop Counter Step for Diff/Anneal Setpoint (V) Approx. Run Time (min) Program Description Time N2 O2 Pre Diff/Anneal Post 0 Dope without LTO (1050 C) n/a 50 User defined 80 1 Dope with LTO (1050 C) User defined 92 2 Custom Dope Program n/a n/a n/a 3 Anneal (1050 C) User defined Custom Anneal Program n/a n/a n/a 5 Solid Source Cure (1050 C) BoronPlus: 799 (13:19) PhosPlus: 1279 (21:19) Identify the desired program If the desired conditions (temperature and gas flows) are NOT shown in Table 1, Diffusion/Anneal Programs, contact the Lab Staff before proceeding. The Lab Staff can create custom programs, as needed. 6.4 Set Gas Flows Using Table 1, Diffusion/Anneal Programs, find the voltage setpoints for each of the gases On the Anneal Dry Oxidation controller located in the gas jungle (see Figure 1, Anneal Dry Oxidation Gas Controller), rotate the selection knob on the gas controller to select the desired gas.

4 6.4.3 While holding the toggle switch on SET, adjust the setpoint dial until the MFC Voltage Display shows the correct voltage value Repeat through for each process gas. 6.5 Load Program Following the procedures in Canary Furnace SOP, load the desired program. The controller will change to the first step of the program and immediately go on hold with 10 seconds on the time display. The READY light will be on Verify the number of the desired program is shown in the Program Display field of the Auto-Sequence Controller If the correct number is NOT displayed, repeat through Diffusion/Anneal SOP Page 4 of 12 Setpoint Dials Set/Read Switch Selection Knob Following the procedures in Canary Furnace SOP, release the hold. MFC Voltage Display Figure 1, Anneal Dry Oxidation Gas Controller The RUN light will be on. The program will count down to 0 on the time display and go on hold. The READY light will be on again. 6.6 Set Diffusion/Anneal Time Following the procedures in Canary Furnace SOP, set the value of the applicable loop counter step to the desired number. (Refer to Table 1, Diffusion/Anneal Programs to find the correct loop counter step for the program being used.) One loop is one minute of diffusion/anneal. For example, to get 45 minutes of diffusion/anneal, set the loop counter to If you need a diffusion/anneal step longer than 600 minutes, contact lab staff for approval before proceeding. 6.7 Load Sample Wafers Ensure all sample wafers are completely clean, dry, and free of any surface contamination.!! WARNING!! No photoresist, kapton tape, metals, or other foreign material are allowed in the furnace. Only quartz, silicon, oxide, nitride, and/or Polysilicon are allowed without lab staff approval.!! WARNING!! Using the vacuum wand, load the wafers as shown in Figure 2, Anneal Boat Loading Diagram or Figure 3, Diffusion Boat Loading Diagram.

5 Diffusion/Anneal SOP Page 5 of 12 Monitor Wafer Sample Wafer \ \ / / Test Run Polished Side Handle \ \ / / With Sample Wafers Figure 2, Anneal Boat Loading Diagram Monitor Wafer Dummy or Sample Wafer Solid Source Wafer Handle \ \ / / Figure 3, Diffusion Boat Loading Diagram Include a monitor wafer at the center of the boat Boron doping and anneal require an n-type wafer Phosphorous doping requires a p-type wafer Monitor wafers are provided in a labeled box located on the storage rack For Anneal: Wafer spacing may be every slot The polished side of all wafers must face the handle end of the boat (door of the furnace) For Diffusion: 7 General Procedures For Diffusion, the solid source wafers should always have a dummy wafer or sample wafer in adjacent slots even when stored. Remove the necessary dummy wafers (adjacent to the solid source wafers) and place them in empty slots at either end of the boat. Load sample and monitor wafers in the slot next to a solid source The polished side of all wafers must face the solid source 7.1 Load Furnace Open the furnace door Using the high temperature gloves, remove the end cap Place the boat at the end of the furnace tube Using the quartz push rod, push the boat into the furnace at 1 inch every 5 seconds (12 inches per minute) Align the mark on the push rod to the front face of the furnace scavenger (see Figure 4, Push Rod Alignment).

6 7.1.6 Remove the push rod and place in the storage cylinder Using the high temperature gloves, replace the end cap Close the furnace door. 7.2 Start the Program Following the procedures in Canary Furnace SOP, release the hold. The READY light will turn off and the RUN light will turn on. The controller will automatically execute the necessary steps to complete the diffusion/anneal process. A summary of the programs, steps, and outputs is given in Table 6, Diffusion/Anneal Auto-Sequence Controller Setup Wait until the controller is in step Unload Verify the program is complete. The controller will be on step Open the furnace door Using the high temperature gloves, remove the end cap. Diffusion/Anneal SOP Page 6 of Using the quartz push rod, pull the boat to the door of the furnace at 1 inch every 5 seconds (12 inches per minute) Place the push rod in the storage cylinder Allow the boat to cool a minimum of 2 minutes at the door of the furnace Using the high temperature gloves or the quartz handle, remove the boat from the furnace and place on the quartzware rack Using the high temperature gloves, replace the end cap Close the furnace door Allow the boat and wafers to cool at least 5 minutes Using the vacuum wand, remove the samples and monitor wafers from the quartz boat. 7.4 Process Measurement For Anneal, measure the oxide thickness of the monitor wafer. Figure 4, Push Rod Alignment Push Rod Mark Align Mark to Scavenger Face Scavenger Face For Diffusion without LTO, measure the oxide thickness and the resistivity of the monitor wafer.

7 Diffusion/Anneal SOP Page 7 of For Diffusion with LTO, do the following with the monitor wafer: Measure the oxide thickness Remove the oxide Measure the resistivity Place used monitor wafers in the labeled storage box located on the storage rack. 7.5 Place System in Standby This section is only necessary if the furnace will be idle for more than 1 hour Verify the furnace is in step If the furnace is NOT in step 69, contact Lab Staff before proceeding On the quartz boat, ensure each solid source wafer has a dummy wafer in the adjacent slots Open the furnace door Using the high temperature gloves, remove the end cap Place the boat at the end of the furnace tube Using the high temperature gloves, replace the end cap Close the furnace door Using the procedures in 6.4 Set Gas Flows, set the N2 flow at 1V (2 slpm). 7.6 Disable Furnace In Coral, disable the furnace and complete all data entry, including process measurement data. Disabling the furnace will activate the interlock and prevent access to the keypad. 8 Process Notes and Characterization 8.1 Solid Source Wafer Cure Load the solid source wafers into consecutive large slots in the quartz boat Load bare silicon wafers into all slots adjacent to the solid source wafers The polished side of the wafers must face the solid source wafer Set the gas flows per section 6.4 Set Gas Flows Set the cure time as per Table 2, Solid Source Cure Loop Counter and Canary Furnace SOP. One loop is equivalent to 10 minutes.

8 8.1.5 Run the cure recipe per sections Diffusion/Anneal SOP Page 8 of Gas Flow Setpoint Conversions Table 2, Solid Source Cure Loop Counter Source Wafer Type Loop Counter Value BoronPlus 60 PhosPlus Table 3, Diffusion/Anneal Gas Flow Setpoint Conversions shows the gas flow setpoints and corresponding voltage values for the MFC Voltage Display. 8.3 Auto-Sequencer Input Assignments Table 3, Diffusion/Anneal Gas Flow Setpoint Conversions Setpoint Display Setpoint Display N2 (slpm) O2 (slpm) Volts (V) N2 (slpm) O2 (slpm) Volts (V) Max Flow N 2 or O 2 : V = slpm/ Table 4, Diffusion/Anneal Auto-Sequencer Output Assignments shows the assignments of the input connections for the auto-sequencer. Table 4, Diffusion/Anneal Auto-Sequencer Output Assignments Output Description Output Description 1 N2 Upstream Valve 9 Temperature Control Bit1 2 O2 Upstream Valve 10 Temperature Control Bit2 3 Not used 11 Temperature Control Bit3 4 Not used 12 Temperature Control Bit4 5 Not used 13 Not used 6 Not used 14 Not used 7 Not used 15 Not used 8 Not used 16 Not used

9 8.4 Temperature Controller Recipes Diffusion/Anneal SOP Page 9 of Table 5, Diffusion/Anneal Temperature Controller Setup shows the setup of the temperature controller. Table 5, Diffusion/Anneal Temperature Controller Setup Recipe Setpoint Auto-Sequencer Outputs variable 1 variable variable 12 9 variable n/a n/a n/a n/a n/a n/a *Maximum Allowed Temperature: 1050 C Ramp Rate (Slope) for all recipes and zones: 7.00

10 Diffusion/Anneal SOP Page 10 of Auto-Sequencer Programs Table 6, Diffusion/Anneal Auto-Sequence Controller Setup shows the defined program steps. Table 6, Diffusion/Anneal Auto-Sequence Controller Setup Output LED s Program Step Instruction Program Alarm Change Branch Temp # Function # Description Start Enable Enable Step ( C) Time Push Load 6 HOLD AT END YES Ramp Up and Stabilize 4 HOLD WITH OUTPUTS none 0 No operation none 0 No operation Start Loop 1 SET LOOP Counter YES *** 0 5 Doping Cycle 4 HOLD WITH OUTPUTS End Loop 2 LOOP BACK Ramp Down 7 BRANCH AT END none 0 No operation none 0 No operation Push Load 6 HOLD AT END YES Ramp Up and Stabilize 4 HOLD WITH OUTPUTS none 0 No operation none 0 No operation Start Loop 1 SET LOOP Counter YES *** 1 15 Doping Cycle 4 HOLD WITH OUTPUTS End Loop 2 LOOP BACK Ramp Down/LTO 7 BRANCH AT END none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation Push Load 6 HOLD AT END YES Ramp Up and Stabilize 4 HOLD WITH OUTPUTS Skin Oxidation 4 HOLD WITH OUTPUTS Ramp Up and Stabilize 4 HOLD WITH OUTPUTS Start Loop 1 SET LOOP Counter YES *** 3 35 Anneal 4 HOLD WITH OUTPUTS End Loop 2 LOOP BACK Ramp Down 7 BRANCH AT END none 0 No operation none 0 No operation 0.0

11 Diffusion/Anneal SOP Page 11 of 12 Table 6, Diffusion/Anneal Auto-Sequence Controller Setup Output LED s Program Step Instruction Program Alarm Change Branch Temp # Function # Description Start Enable Enable Step ( C) Time none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation Push Load 6 HOLD AT END YES Ramp Up and Stabilize 4 HOLD WITH OUTPUTS none 0 No operation none 0 No operation Start Loop 1 SET LOOP Counter YES *** 5 55 Cure Sources 4 HOLD WITH OUTPUTS End Loop 2 LOOP BACK Ramp Down 7 BRANCH AT END none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation none 0 No operation Power out Program 0 6 HOLD AT END YES Power out Program 1 6 HOLD AT END YES Power out Program 2 6 HOLD AT END YES Power out Program HOLD AT END YES Abort 6 HOLD AT END YES Idle 6 HOLD AT END *** This value is adjusted as necessary between Time values with a decimal are in minutes; values without a decimal are in seconds.

12 Diffusion/Anneal SOP Page 12 of 12 9 Revision History Rev Date Orginator Description of Changes 5 12 May 2011 T. Olsen Update gas flow setting instructions (section 6.4) to reflect the replacement of portable multi-meters with a permanently mounted voltage display, including Figure 1 and Table Mar 2011 T. Olsen Replace references to log sheets with Enable/Disable in Coral and required data entry. Clarify use and availability of monitor wafers Jul 2010 T. Olsen Change length of push rod mark from 30 to 26. Update Table 2, Diffusion/Anneal Programs to include gas flows (move table to Table 1). Update Loading Diagram and instructions to keep dummy wafers next to solid source wafers. Updated Table 1, Diffusion/Anneal Programs and Table 6, Diffusion/Anneal Auto-Sequence Controller Setup to remove unused programs. Update Table 5 due to nonfunctioning outputs 9 and Mar 2010 T. Olsen Changed time of first step of each program from 0.1 minutes to 10 seconds. Updated/clarified procedures for program processing and loop counter usage. Added Handle and Polished Side to anneal wafer loading diagram. Added Pre and Post times to Table Feb 2010 T. Olsen Initial Release.