Fiji Thermal and Plasma Atomic Layer Deposition System (ALD) By Ultratech (Cambridge) PREPARED BY: You-Sheng (Wilson) Lin, Nanolab Staff 7-30-2013 Superusers: Steve Franz You-Sheng Lin Max Ho X68923 X68923 X49329 1
1.0 SAFETY RULES To avoid a fire or explosion, follow these instructions. Do not place flammable materials underneath, on or near the unit. Do not place paperwork, wipes etc. on or near the unit. Do not run the system unattended; do not run the system overnight. Do not heat materials to temperatures above those recommended by the manufacturer. Make sure heat monitoring and limiting devices are working properly. Note the maximum temperature settings for different parts. ALD pulse valves are rated to 150 o C and should not be heated above that temperature. Center heater maximum temperature is 400 o C, while outer heater should not be set higher then 250 o C because of the O-ring. The tee and flexible bellows of pumping line should not be heated above 150 o C. Temperature of the precursors should not exceed safety or decomposition temperature of the chemical used. Maximum for the precursor heater jacket is 200 o C. 2
2.0 OVERVIEW Principle of Al 2 O 3 formation Atomic Layer Deposition (ALD) is a technique that allows growth of thin films, atomic layer by layer. Deposition of Al 2 O 3 from water and trimethylaluminum (TMA) precursors will be used to illustrate the principle of ALD. Recipes for other materials can be found in the literature. The chemical principle of Al 2 O 3 growth from water and TMA is outlined in 5 steps shown in Figure 1. Step. 1: Put in a sample which is hydroxylated from exposure to air, oxygen or ozone (Figure 1A). Step 2: Pulse the TMA precursor; TMA will react with the OH groups on the surface. TMA does not react with itself and the monolayer formed passivates the surface (Figure 1B, 1C). Step 3: Remove unreacted TMA molecules by evacuation and/or purging with nitrogen (Figure 1D). Step 4: Pulse water (H 2 O) into the reactor. This will remove the CH 3 groups, create Al- O-Al bridges, and passivate surface with Al-OH. CH4 (methane) is formed as a gaseous byproduct (Figure 1E, 1F). Step 5: Remove unreacted H 2 O and CH 4 molecules by evacuation and/or purging with nitrogen (Figure 1G). Steps (1)-(5) form a cycle. Each cycle produces a maximum of 1.1 Å of Al 2 O 3 depending on temperature.thus, 100 cycles produces 11 nm of Al 2 O 3. 3
Similar reaction can be expected for HfO 2 by using Tetrakis(dimethylamido)hafnium (IV). WARNING: Trimethylaluminum (TMA) is a liquid at room temperature and is pyrophoric. This means that it burns upon exposure to air. 4
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3.0 SYSTEM INFORMATION The ALD system in the is a ULTRATECH (Cambridge NanoTech Fiji F200) equipped with a heated process chamber, remote plasma source, turbomolecular pump, and automated load lock for transferring substrates. The system is primarily intended for the deposition of a variety of thin films, including metals, oxides, and nitrides. Typical film thicknesses are monolayers up to tens of nanometers. Thicker films may be deposited but due to the low deposition rates (~ 3 20 nm/h) these films would required deposition times of several hours. Some key features are as follows. Highly conformable, well controlled layer by layer film deposition. Multi-layer film stacks possible. Aspect ratios of up to 450:1 in thermal mode or 20:1 in plasma mode are possible. Substrates up to 200 mm in diameter and 6 mm thick can be accommodated. Substrates may be heated up to 400 C, but most recipes only required up to 300 C. Process chamber turbomolecular pump provides a base pressure ~ 2 x 10-5 Torr. Load lock chamber with automated transfer of substrates into the process chamber. All depositions are performed from recipes. There are two main modes of operation: 1. Continuously flowing nitrogen carrier gas while pulsing (adding) precursor and pumping continuously 2. Pulsing precursors with stop valve closed and pumping in between pulses. 6
3.1. System Overview: Precursor bottles Chamber Computer Drawer EMO Load Lock Mechanical Pump Chiller 3.2. System Control: All controls for processing recipes, system startup/shutdown, configuration, and the settings are performed via the supplied Windows platform laptop computer. The computer is stored in a computer drawer in the electronics cabinet located below the gas box: 7
3.3. Software Overview: 3.4. Process Tab: The Process Tab displays all the settings used to create/save/load and run recipes to perform ALD. The user interface allows manual operations of basic functions such as pumping down the system, turning on the heaters, setting gas flows and opening/closing valves. These features are described next. 8
Program Switch Stops the Fiji software and turns off all outputs. Typically this button is not used except to exit the system software prior to shutting down the system. For systems equipped with a turbo, stopping the program will automatically decelerate the turbo before exiting. Pump/Vent Toggle Switch (Radials display next-state rather than current state): This button is disabled on systems with load/locks. Refer to the Vacuum System tab. PUMP - pumps the system down to base pressure VENT - vents the process chamber to atmospheric pressure Closes the main stop valve to isolate the process chamber from the vacuum pump and then opens the main chamber vent valve. A window prompts the user to click OK to close the main chamber vent valve once atmospheric pressure is achieved. Heaters Toggle Switch (Radials display next-state rather than current state): ON - turns heaters ON (to default setpoints) OFF - turns heaters OFF (all temperature setpoints are set to C) Run Toggle Switch (Radials display next-state rather than current state): START - runs the recipe program ABORT - aborts a current recipe run When a process is running, Program, Pump/Vent and Heaters buttons are grey and not clickable. To abort a run, simply click on Run ABORT button. 9
4.0 OPERATING PROCEDURE 4.1. System Check: 1. Log into Labrunner to disable the interlock. 2. Check the logbook to make sure previous runs were OK. 3. Check the Water Chiller s temperature at 70F. 4. Check the mechanical pump and make sure it is ok ( POWER OK and RUNNING green lights are on). Step stool for access to load lock (Watch your step) Mechanical Pump POWER OK and RUNNING green light 10
5. Start filling out the logbook NOW (Date, Name, Badge Number, Film. Etc). 6. Make sure all the precursor valves are completely closed, if not, please report to Nanolab staff or superuser. Al Precursor Hf Precursor Water 4.2 Wafer Loading: 1 From the Vacuum System tab, press LL VENT to vent the load lock chamber. 11
ALD System 2 Wait 3 to 5 minutes until the load lock is completely vented. (Check the gap at load lock door). Under Vacuum Vented to Atmosphere 3 Once the chamber is completely vented, Press OK on the software popup screen to turn off the load lock vent valve. 4 Lift the load lock door up when atmospheric pressure is reached. 12
5 Load your wafer. Use the step stool to help reach the load lock door (Watch your steps when on the step stool) 6 After loading your sample, close the door down. To pump down LL and transfer wafer into the chamber: 7 From the Vacuum System screen, select Transfer Sample. Follow the system prompts. (The system will automatically pump down the load lock. After the pressure in the load lock and the process chamber is equilibrated, the main gate valve separating the two chambers will automatically open; the substrate carrier will then be loaded onto the heated chuck in the process chamber.) 8 At the end of transfer, follow the system prompts to visually verify the main gate is clear, and then click Gate Clear to close the gate valve. 4.3 Load Recipe: ***You are NOT allowed to create or edit any recipe. Please contact Nanolab staff if you have any special requirements*** Go to Process Window 1. Make sure that the system is pumped down. 2. Right click in the recipe steps table. This will bring up an options menu. 13
3. Click on Load recipe in the drop down menu. 4. Load the recipe you would like to use. (Here are the current recipes) a. Al2O3.thermal.200C b. Al2O3.plasma.200C c. HfO2.thermal.200C d. HfO2.plasma.200C 5. Select the appropriate processing conditions required for your run. (Please see appendix to choose the appropriate setting) a. Select the number of cycles at GOTO step (Ex: 100 cycles, then you will input 100). b. Heater temperature (#12, #13, #14, #15) Typically at 200 C unless you are changing your process temperature. 14
c. Precursor Delivery line (#16 at 150 C) and precursor manifold (#17 at 150 C). d. Precursor bottle temperature (TMA #18 @ room temperature set at 0) and (Hf 19 @ 65 C). e. Purge time and wait time (Please see appendix). f. Set APC at 9%. 6. Double check all the steps with the appendix. 7. Do not overwrite the standard recipe. If you want to save any recipe, please create a new folder (make sure to discuss your process with nanolab staff). 8. Wait 10 minutes for the substrate/chamber to stabilize the temperature. (Depending on process temperature and precursor) 9. Open the appropriate precursor valve. 10. Press Start to run the recipe. 11. Click Yes in the recipe start confirmation window. 12. Monitor the system to make sure your process is going well. 13. Record processing temperature and observe pulse time/process pressure. 14. Once complete, close precursor valve. 15
4.4 Unload the wafer after deposition: 1. From the Vacuum System screen, select Transfer Sample. The substrate carrier should be automatically transferred to the Load Lock. 2. Wait for your substrate to cool to near room temperature (Ex: for substrates which were heated to 200 C, allow at least 20 minutes). Go to Vacuum System screen, press LL Vent. 3. Wait 2-3 minutes for the LL to vent. During this interval, the load lock pressure should rise to 760 Torr and a dialogue box will appear requesting acknowledgement that the LL is at atmospheric pressure. DO NOT acknowledge yet. 4. Gently try to lift the LL door. If it will not lift easily, wait another minute and try again. Repeat until it lifts easily. 5. Once the LL door can be opened easily, press OK in the dialogue box to acknowledge that the LL is at atmospheric pressure. 6. Fully open the LL door. 7. Approach the substrate carrier carefully in case it is hot. If it is, allow it to cool. 8. Remove your wafer from the substrate carrier. 9. Close the LL door. 10. From the Vacuum System screen, select PumpChamber & LL without Turbo in order to pump down both the chamber and load lock. 4.5 Cleaning the ALD valve and manifold recipe (approximate 2 minutes) 1. Make sure all precursor valves are close. 16
2. Go to Process Window and right click in the recipe steps table. 3. Select Al_Headpurge or Hf_Headpurge recipe depending on which precursor you used. 4. Double check to make sure all precursor valves are close. 5. Make sure both Door Purge and Main Turbo Purge are on by clicking on them (Should be light green). 6. Press Start to run recipe. 7. After your run is completed, make sure the following settings are as follows: a. Heater temperature setting i. All precursor bottle temperature = 0 ii. Heater Temperature (#12, #13, #14, #15) = 200 C iii. Precursor Delivery line (#16 at 150 C) iv. Precursor manifold (#17 at 150 C) b. Argon idle flows: i. MFC0 Ar Carrier = 5 sccm ii. MFC1 Ar Plasma = 10 sccm c. Turn off all 2 purges; make sure they are dark green (on the Vacuum System screen). i. Door Purge ii. Main Turbo Purge 17
4.6. Logbook and Interlock 1. Fill in all the information in the logbook. a. User name and usage time b. All temperatures and process times c. Use ellipsometer to measure the film thickness and Index of reflection 2. Log out from the labrunner 18
Appendix: 1. Standard Thermal Al 2 O 3 Recipe Precursor: Trimethylaluminum, TMA, Al(CH 3 ) 3 CAS #: 75-24-1 Chemistry: Thermal ALD (Water, H 2 O) Process condition o Trimethylaluminum (TMA): 0.06 second and unheated o H 2 O: 0.06 second and unheated Temperature (C) TMA Pulse TMA Purge (Wait) H 2 O Pulse H 2 O Purge (Wait) 300 0.06 5 0.06 5 250 0.06 8 0.06 8 200 0.06 10 0.06 10 150 0.06 20 0.06 20 100 0.06 30 0.06 30 75 0.06 60 0.06 60 50 0.06 120 0.06 120 25 0.06 180 0.06 180 Door purge = 50sccm 0.06s room temperature TMA pulse 1.2mg 19
Standard Thermal Al 2 O 3 Recipe at 200 C Instruction # Value 0 flow 0 20 Set precursor manifold stand-by Ar flow rate 1 flow 1 40 Set plasma source stand-by Ar flow rate 2 heater 12 200 Set trap/cone temperature 3 heater 13 200 Set reactor zone 1 temperature 4 heater 14 200 Set reactor zone 2 temperature 5 heater 15 200 Set chuck temperature 6 heater 16 150 Set precursor delivery line to 150 C 7 heater 17 150 Set precursor manifold to 150 C 8 stabilize 12 Wait for trap/cone temperature to stabilize 9 stabilize 13 Wait for reactor zone 1 temperature to stabilize 10 stabilize 14 Wait for reactor zone 2 temperature to stabilize 11 stabilize 15 Wait for chuck temperature to stabilize 12 wait 600 Wait for substrate temperature to stabilize 13 flow 0 30 Set precursor manifold Ar for expo step 14 flow 1 100 Set plasma source Ar for expo step 15 APC 9 Set throttle valve. 16 wait 10 Wait for Ar MFCs to stabilize 17 pulse 1 0.06 Begin loop. Pulse TMA. TMA = TMA ALD valve number 18 wait 10 Purge TMA and reaction by-products 19 pulse 0 0.06 Pulse H 2 O. H 2 O = H 2 O ALD valve number 20 wait 10 Purge H 2 O and reaction by-products 21 goto 17 X Input # of cycles, number, x = cycles, GPC ~ 1A/cycle 22 flow 0 5 Set precursor manifold stand-by Ar flow rate 23 flow 1 10 Set plasma source stand-by Ar flow rate 24 APC 100 Open throttle valve. If no throttle valve, remove this line 25 Turbopurge 0 26 Doorpurge 0 20
2. Standard Plasma Al 2 O 3 Recipe Temperature (C) Precursor: Trimethylaluminum, TMA, Al(CH 3 ) 3 CAS #: 75-24-1 Chemistry: Plasma ALD (Oxygen, O 2 ) Process condition o Trimethylaluminum (TMA): 0.06 second and unheated o O 2 : 20 seconds TMA Pulse TMA Purge (Wait) O 2 Pulse O 2 Purge (Wait) 300 0.06 5 20 5 250 0.06 8 20 5 200 0.06 10 20 5 150 0.06 20 20 5 100 0.06 30 20 5 75 0.06 60 20 5 50 0.06 120 20 5 25 0.06 180 20 5 Door purge = 50sccm 0.06s room temperature TMA pulse 1.2mg 21
Standard Plasma Al 2 O 3 Recipe at 200 C Instruction # Value 0 flow 0 20 Set precursor manifold stand-by Ar flow rate 1 flow 1 40 Set plasma source stand-by Ar flow rate 2 heater 12 200 Set trap/cone temperature 3 heater 13 200 Set reactor zone 1 temperature 4 heater 14 200 Set reactor zone 2 temperature 5 heater 15 200 Set chuck temperature 6 heater 16 150 Set precursor delivery line to 150 C 7 heater 17 150 Set precursor manifold to 150 C 8 stabilize 12 Wait for trap/cone temperature to stabilize 9 stabilize 13 Wait for reactor zone 1 temperature to stabilize 10 stabilize 14 Wait for reactor zone 2 temperature to stabilize 11 stabilize 15 Wait for chuck temperature to stabilize 12 wait 600 Wait for substrate temperature to stabilize 13 flow 0 30 14 flow 1 100 15 APC 9 Set throttle valve 16 wait 10 Wait for Ar MFCs to stabilize 17 MFCvalve 3 1 Set precursor manifold Ar for expo step 18 wait 20 19 pulse 1 0.06 Begin loop. Pulse TMA. TMA = TMA ALD Valve number 20 wait 10 Purge TMA and reaction by-products 21 flow 3 50 Start O 2 flow 20 plasma 300 Turn on plasma. 23 wait 20 24 plasma 0 0 Turn off plasma. 25 flow 3 0 Start O 2 flow. 26 wait 5 Purge O 2 and reaction by-products 27 goto 19 X Input # of cycles, number, x = cycles, GPC ~ 1A/cycle 28 flow 0 5 29 flow 1 10 30 flow 3 0 Turn off O 2 31 APC 100 Open throttle valve. If no throttle valve, remove this line 32 turbopurge 0 33 doorpurge 0 22
3. Standard Thermal HfO 2 Recipe Precursors: Tetrakis(Dimethylamido)Hafnium (Hf(NMe 2 ) 4 ) CAS#: 19962-11-9 Chemistry: Thermal ALD (Hf(NMe 2 ) 4 ), H 2 O Process condition: o Tetrakis(Dimethylamido)Hafnium (Hf(NMe 2 ) 4 ): 0.25 second and heated to 75 C o H 2 O: 0.06 second and unheated Temperature (C) Hf(NMe 2 ) 4 Pulse Hf(NMe 2 ) 4 Purge (Wait) H 2 O Pulse H 2 O Purge (Wait) 200 0.25 15 0.06 15 90 0.25 120 0.06 120 23
Standard Thermal HfO 2 Recipe at 200 C Instruction # Value 0 flow 0 20 Set precursor manifold stand-by Ar flow rate 1 flow 1 40 Set plasma source stand-by Ar flow rate 2 heater 12 200 Set trap/cone temperature 3 heater 13 200 Set reactor zone 1 temperature 4 heater 14 200 Set reactor zone 2 temperature 5 heater 15 200 Set chuck temperature 6 heater 16 150 Set precursor delivery line to 150 C 7 heater 17 150 Set precursor manifold to 150 C 8 heater 19 75 Set precursor bottle to 75 C 9 stabilize 12 Wait for trap/cone temperature to stabilize 10 stabilize 13 Wait for reactor zone 1 temperature to stabilize 11 stabilize 14 Wait for reactor zone 2 temperature to stabilize 12 stabilize 15 Wait for chuck temperature to stabilize 13 Stabilize 19 Wait for precursor bottle to stabilize 14 wait 600 Wait for substrate temperature to stabilize 15 flow 0 60 Set precursor manifold Ar for expo step 16 flow 1 200 Set plasma source Ar for expo step 17 APC 9 Set throttle valve. 18 wait 20 Wait for Ar MFCs to stabilize 19 pulse 0 0.06 Begin loop. Pulse H 2 O. H 2 O = H 2 O ALD valve number 20 wait 10 Purge TMA and reaction by-products 21 pulse 2 0.25 Pulse Hf. Hf=Hf ALD valve number 22 wait 10 Purge H 2 O and reaction by-products 23 goto 19 X Input # of cycles, number, x = cycles, GPC ~ 1A/cycle 24 flow 0 5 Set precursor manifold stand-by Ar flow rate 25 flow 1 10 Set plasma source stand-by Ar flow rate 26 APC 100 Open throttle valve. If no throttle valve, remove this line 27 Turbopurge 0 28 Doorpurge 0 24
4. Standard Plasma HfO 2 Recipe Precursors: Tetrakis(Dimethylamido)Hafnium (Hf(NMe 2 ) 4 ) CAS#: 19962-11-9 Chemistry: Thermal ALD (Hf(NMe 2 ) 4 ), O 2 Process condition: Temperature (C) o Tetrakis(Dimethylamido)Hafnium (Hf(NMe 2 ) 4 ): 0.25 second and heated to 75 C o O 2 : 20 second and unheated Hf(NMe 2 ) 4 Pulse Hf(NMe 2 ) 4 Purge (Wait) O 2 Puluse O 2 Purge (Wait) 250 0.25 5 20 5 200 0.25 5 20 5 150 0.25 30 20 5 90 0.25 120 120 20 25
Standard Plasma HfO 2 Recipe at 200 C Instruction # Value 0 flow 0 20 Set precursor manifold stand-by Ar flow rate 1 flow 1 40 Set plasma source stand-by Ar flow rate 2 heater 12 200 Set trap/cone temperature 3 heater 13 200 Set reactor zone 1 temperature 4 heater 14 200 Set reactor zone 2 temperature 5 heater 15 200 Set chuck temperature 6 heater 16 150 Set precursor delivery line to 150 C 7 heater 17 150 Set precursor manifold to 150 C 8 Heater 19 75 Set precursor bottle to 75 C 9 stabilize 12 Wait for trap/cone temperature to stabilize 10 stabilize 13 Wait for reactor zone 1 temperature to stabilize 11 stabilize 14 Wait for reactor zone 2 temperature to stabilize 12 stabilize 15 Wait for chuck temperature to stabilize 13 stabilize 19 Wait for precursor bottle to stabilize 14 wait 600 Wait for substrate temperature to stabilize 15 MFCvalve 3 1 Set precursor manifold Ar for expo step 16 flow 0 60 17 flow 1 200 18 APC 9 Set throttle valve 19 wait 20 Wait for Ar MFCs to stabilize 20 pulse 2 0.25 Begin loop. Pulse Hf. Hf = Hf ALD Valve number 21 wait 5 Purge Hf and reaction by-products 22 flow 3 20 Start O 2 flow 23 wait 5 24 plasma 300 Turn on plasma. 25 wait 20 26 plasma 0 0 Turn off plasma. 27 flow 3 0 Start O 2 flow. 28 wait 5 Purge O 2 and reaction by-products 29 goto 19 X Input # of cycles, number, x = cycles, GPC ~ 1A/cycle 30 flow 0 5 31 flow 1 10 32 flow 3 0 Turn off O 2 33 APC 100 Open throttle valve. If no throttle valve, remove this line 34 turbopurge 0 35 doorpurge 0 26