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Drytek2 Model 100, drytek2

The Drytek plasma etchers at SNF all use chlorine and fluorine-based chemistry for etching various Si, polysilicon, nitride, tungsten, tungsten silicide films. Drytek4 (contaminated) also has additional capabilities for oxide etching and argon sputter etching.

Picture and Location


Drytek2 wafers and electrodes:

Electrodes and Wafers



Drytek2 is a plasma etcher for etching nitride, poly, Ti, W, and Si. It is also used for resist hardening O2 descum of patterned resist, and polymer stripping. Drytek2 has six etch electrodes and uses SF6, CHClF2, CF4, and oxygen. See the process and etch rate chart for the processes allowed in this machine. Any process not listed, must be approved by SpecMat.


  • Low energy etching for minimal substrate damage.
  • Excellent selectivity, e.g., 20:1 poly Si:SiO2
  • Laser interferometer for etch rate determination and end-point detection.


Process Capabilities

Cleanliness Standard

 Drytek2 is considered clean, semi-clean and contaminated.  The bottom two of six electrodes have been converted for contaminated work, while the top four are clean/semi-clean.


Performance of the Tool

What the Tool CAN do

  • Standard recipes for nitride, poly, Ti, W, and Si, resist hardening, O2 descum of patterened resist, and polymer stripping.

What the Tool CANNOT do

  • Drytek2 is not a resist stripper because of it's low power.  An alternative for semi-clean resist stripping is gasonics.
  • It should not be considered for oxide etching either.  Alternatives for semi-clean oxide etching are amtetcher and p5000etch.


Special Notes or Restrictions

Non-metals and standard metals (Al, Ti, and W) are allowed in Drytek2, the top two electrodes. (See the MATERIALS section for material and equipment compatibility).


Contact List and How to Become a User

Contact List

The following people make up the Drytek2 Team:

  • Process and Training Staff: Usha Raghuram
  • Maintenance:  Elmer, Mike Dickey


Training to Become a Tool User

We do not have a staff member assigned to training on it at this time.  What we suggest is that labmembers wanting training on the tool contact a trained research group co-worker or other trained labmember for training and/or shadowing.  Once the 'trainee' is comfortable in the use of the tool they contact the responsible Process Staff member for badger qualification.  This is done with the understanding that the newly trained labmember may be approached for training eventually.

If you cannot find someone to train you after looking at history in badger please contact the responsible Process Staff member and a trainer will be identified.

The labmember is responsible for having read and understood any and all documentation related to the tool. A Training Check List is included in these Operating Instructions. It can be a good tool to make sure everything has been covered in the shadowing session.

Please print and fill out this Shadowing Form. After the session give the form to the responsible staff member for qualification.

Drytek2 Etcher Training Check list

This check list represents the basic knowledge of the tool that new users should have. 

  • Know the contamination level of the specific drytek etch system.
  • Know stand-by conditions.
  • Know the functions of the various buttons.
  • Understand gas manifold and be able to turn on desired gases.
  • Know how to turn on RF power supply.
  • Know how to set and readout process timer.
  • Know how to select correct gases to flow into chamber using dip switches.
  • Know how to adjust gas flows.
  • Know how to adjust chamber pressure.
  • Know how to set RF power level and be able to read out power.
  • Know how to tune RF matching network.
  • Know how to stop an etch before it has timed out.
  • Know how to drain a gas if you are using a shared line.
  • Know how to put the system back into stand-by mode.


Operating Procedures

 Before you use drytek2 please read the new operating instructions located in the blue book and on the wiki.  They contain a new, as of 9/8/2011, RF tuning procedure.  The changes have been underlined or italicized to highlight them. In addition, there is a log form for you to fill out at the end of the etch.  You will be asked for the coil and cap settings.  They can be found by looking on the coil and cap tuning pots (the black knobs used to tune the RF).  We want to collect this information so that users of the tool can refer back to the last settings used for a given recipe and plug them in to ease the RF tuning procedure.

Lastly, we are requiring the labmembers turn the RF power level to zero after using the tool.  This will limit wear and tear on the RF power supply.  We also ask that users tune the RF at a much lower power (40W) before turning the RF to the full power desired.  This procedure is covered in the new operating instructions.


General Operating Information


  • No pre-treatment is required.
  • However, if the sample backsides cannot be exposed to the plasma (etched), the backside(s) must be coated with the standard svgcoat program (1 um of resist).



  • No post-treatment is required.


Gas Information:

Gas Switch #

Chemical Symbol

Chemical Name

Maximum Flow



Freon 14

84 sccm



Sulfur Hexafluoride

280 sccm



Freon 22

240 sccm




200 sccm

  •  The Main system electronics are ON at all times.
  • The Vacuum pumps are located in the basement and are ON.


Button Information


  • Resets the microprocessor memory. Always push before pushing CYCLE START. Do not push MICRO RESET at any other time. Push (the blue light comes on) and release the button. MICRO RESET does not work unless the button pops back out (the blue light goes out).


  • Starts the microprocessor program. Always check the error message panel before pressing CYCLE START. If the LED's are red, the machine is not ready to start.


  • Holds the microprocessor at the current step in the program.
  • If the program is running, the timer continues timing, the plasma continues etching.
  • Press a second time to end the CYCLE HOLD. If the time is up the etch ends

To end a process before the timer has timed out:

  • When press a CLEAR WAFER, the plasma will stop, gases will be pumped out of the chamber, and the chamber will be vented.
  • CLEAR WAFER also allows you to end one process before the time is up and advance to the next process. 

  • Introduces N2 at the back of the chamber to prevent oil back-streaming.
  • To use STAND BY the drytek2 must be enabled.


Operating Procedure

Check Standby Conditions:

  • Check the Reservation page and the machine status (problems, shutdowns) on the computer lab management system.
  • Enable “Drytek2”.
  • Check the top panels.
  • White PROCESS select buttons (1, 2, 3) – OFF.
  • Pressure ~200 mT.
  • Green STANDBY light - ON.
  • Pull lightly on the Chamber door (it should not open).
  • Check the lower left panels.
  • Machine button – ON.
  • System button – ON.
  • Mechanical Pump button – ON.
  • Blower button – ON.
  • If any of these 4 buttons are not on, DO NOT proceed. Notify the maintenance technician via coral.
  • RF Power Supply toggle – OFF.
  • RF power level pots (the black knobs above the timers) should all be set to Zero.
  • Cooling water flow should be ~ 1 GPM
  • Check behind the machine: Gas Whitey valves - OFF.


Setup and system check:

Always run a test process before loading your wafers. There are two reasons for this. First, you need to set up the matching network so the rf generator does not see excessive reflective power, which will shorten it life. The second reason to “season” the chamber is that seasoning brings the chamber surface chemistry to equilibrium with the process being run so your process stabilizes quickly after the plasma is turned on. Seasoning leads more repeatable etching results.


  • In the process logbook find a recent listing of the setup parameters for the process you want to run. The parameters you want are the process step number ( 1, 2 or 3), the gas flow settings, the pressure, the coil and cap setting and the rf power. If you are developing  a new process, find a similar process listing so you have initial valves for the coil and cap settings.
  • Push the STANDBY button to vent the chamber. (Green light off)
  • Look at the DRYTEK2 PROCESSES WITH ETCH RATES sheet in the binder or on the website and choose the appropriate process.
  • Select the appropriate white PROCESS button(s).
  • Select the gases to be used for each process.
  • Push the DIP rocker switches (located in the center of the control panel), for each gas needed; to the right (OPEN) (Left = Process 1; Middle = Process 2; Right = Process 3).
  • Turn the desired gases ON at the wall behind drytek2. Rotate the gas Whitey valve of the desired gas from the OFF position toward the chosen gas label.
  • Set the mode toggle switches to "time."
  • Set the time in minutes (left two digits) and seconds (right two digits).
  • Unlatch the chamber door. Make sure inside the chamber is clean.
  • Turn on the RF power supply (the black box on the load station will light up).
  • Set RF power level pot to 0.40 (40w) for each process step to be used. 
  • Check that the sensing element for the Bird meter (located above the tuning pots) is turned to the correct direction to measure reflected power and that the element is the correct size, which is 50W.
  • There is a RF Network Matching Box located at the lower right panel. Make sure the Toggle switch in manual mode. The purpose of the matching box is to transform the plasma impedence to 50 ohms so we get the maximum power transferred efficiency from the rf generator to the plasma.
  • Run a system check with no wafers in the chamber to verify that gas flow(s), pressure, power, and RF tuning are correct.
  • Make sure CYCLE HOLD, CLEAR WAFER, and STANDBY buttons are off.
  • Make sure the door is latched.
  • Check for stabilization of gas flows and chamber pressure. Adjust as necessary.
  • The plasma should light when the timer counter starts. If the turning/matching is way off, the plasma may not light, which is ok at this point.
  • Use the bird meter (located above the tuning pots) to monitor the reflected power.
  • Start the turning process by first very very slowly adjusting the coil pot for the process step being run.  Slowly move the pot in the direction that lowers the reflected power. If you turn the pot too fast, the coil rotation will not keep up and you will overshoot the minimum.  You actually want to go slightly past the minimum so you will not end up at a local minimum.  If you can get below 5 w of reflected power,  you can increase the forward power level using the power level pot  for the the process step you are in.  You can monitor the power level using the top readout on the black box. When increasing the power keep the reflected power below 15w on the Birdmeter.
  • After the first adjustment of the coil pot go to the cap pot for your process step. Again move the pot in the direction which reduces the reflected power. Again you want to go slightly pass the minimum to avoid ending upm at a local tuning minimum.
  • Continue going back and forth between the coil and cap pots to lower reflected power. Everytime to go below 5w you can increase the forward power until you get the power level needed for your process.
  • Note the final RF pot set points on the logsheet.
  • If more than one process is to be used, adjust the flows and pressure and power during those steps. Push "CLEAR WAFER" while RF is on to advance to the next process or to end a process before the time is up.
  • Check that plasma color is correct for gas flowing.
    • a) O2 - silver
    • b) Freon 14 (CF4) and O2 - light blue
    • c) Freon 22 (CHClF2) and O2 - light blue
    • d) Freon 22 (CHClF2) and SF6 - light blue
    • e) N2 - pink (indicates a possible leak)
    • f) SF6 - deep purple


Etch Procedure:

  • Push CLEAR WAFER to abort the process.
  • Open the chamber door and place the samples on the electrode plate(s). The 4 pins should prevent the samples from sliding off the plate.
  • Close and latch the chamber door.
  • Set the desire process time.
  • Monitor the gas flows, pressure, and RF power during the etching process.
  • When the process is complete, the system will evacuate the gases and purge the N2 to vent the chamber. The door will pop out once it’s vented. Open the door and remove the sample.
  • Repeat the etch procedure until all samples are etched.


Shutdown Procedure:

  • Turn all the rf power level pots to zero.
  • Turn all white PROCESS buttons OFF.
  • Push STAND BY button (green light goes on; you will hear no sound).
  • Push CYCLE START (you will hear a hissing sound).
  • Pull lightly on the chamber door (it should not open).
  • Turn off whitey gas select valves in the back of the system.
  • Turn the RF Power OFF (white toggle down; the red light goes OFF).
  • This leaves the system in the standby condition.
  • Close all three doors.
  • Disable "drytek2"


Drytek2 Recipes and Etch Rates

 Standard Recipes and Etch Rates for Drytek2

Additional Information About Recipes 

  • ASML First Layer Targets- Use the Poly Etch for 30 seconds to create ASML targets (1200A)


Process Monitoring and Machine Qualification

Each month, tool qualification runs are performed on most tools in the SNF to monitor variations in each tool’s performance. The purpose of the Drytek2 qual is to monitor poly program trends such as etch rates of poly and photoresist, selectivity of those materials, and wafer-to-wafer and within-a-wafer uniformity of etch. The qual is performed by SUMO members, but users may perform the specified qual process before tool use if more recent qual data is desired for reference.

For more information on the SNF tool performance monitoring system and SUMO, please see the Monthly Tool Monitoring page under the Equipment tab on the SNF wiki.


Qual Process Overview

The Drytek2 qual runs three wafers through the poly-etch program, testing both the gold electrode and the clean electrode. First, two wafers with a 1.6um 3612 Photoresist pattern are etched for two minutes (one on the gold electrode, the other on the clean electrode) to obtain the photoresist etch rate. Then one wafer with 10,000A SiO2 coating is etched on the gold electrode for one minute. Nanospec measurements are taken before and after etching to calculate the PR and SiO2 etch rate respectively. To calculate the Si:PR selectivity, the two wafers coated in photoresist are then stripped of resist so that the Silicon step height may be measured via Alphastep.



Wafers for Processing

SUMO Wafer #
(all Si 4" wafers)
Coating Pattern
(using SUMO mask)
Electrode to be Tested
45   10,000A SiO2 - gold
 86  -  1.6um 3612 PR pattern, 1min bake @ 110C  clean
 87  -  1.6um 3612 PR pattern, 1min bake @ 110C   gold



Pre-Etch Wafer Measurements

All pre-etch measurements are taken on Nanospec. Reference the SUMO Characterization How-To's for Nanospec operating procedure.

For Wafer 45, use the Oxide on Silicon Recipe (#1). For Wafers 86 and 87, use the Positive Resist on Silicon Recipe (#10). Use 10x magnification for all measurements (Objective 1 on Nanospec).

  1.  Use the reference wafer to calibrate before measuring.
  2. Take readings for the Center, Top, Flat, Right and Left positions of the wafer. Readings should be taken about 15mm from the wafer edge.
        a.  For Wafers 86 and 86, measure the PR thickness, which is darker in color than the Si. Accidentally measuring the Si will result in a <100A reading.
  3. Calculate the average.
  4. Record results on the SUMO Qualification Log Sheet. 


Etch Process

Before loading the wafers,  season the chamber so that the chamber surface chemistry is brought to equilibrium with the process being run. This enables the actual process to stabilize quickly after the plasma is turned on. This seasoning also leads to more repeatable etching result.

  1. Season the chamber for 10 minutes using the poly etch program (Process 2).  Follow the standard operating procedure as outlined above, or on the procedure print out at the tool. Be sure to check the program parameters while seasoning and adjust the resistor/capacitor settings as necessary.
  2. For Wafers 86 and 87 (1.6um 3612 PR pattern), set the etch time for 2 minutes.
             a.  Remember to bake the wafers at 110C for 1 min before the etch.
             b.  Run the poly-etch recipe.
             c.  Monitor gas flow rate, RF power, and reverse power.
   3.   For Wafer 45 (10,000A SiO2), set the etch time for 1 minute.
             a.   Run the poly-etch recipe.
             b.   Monitor gas flow rate, RF power, and reverse power. 

   4.    Record process settings on the Drytek2 process log.


Post-Etch Wafer Measurements

  1. Measure post-etch thickness for all wafers using the same Nanospec as before and the same respective Nanospec analysis recipes.
  2. Take readings for the Center, Top, Flat, Right and Left positions of the wafer. Readings should be taken about 15mm from the wafer edge.
  3. Calculate the etch-rate for PR and SiO2 by subtracting the post-etch thickness from the pre-etch thickness and then dividing by etch time.
  4. To calculate selectivity, measure the Silicon step height of wafers 86 and 87.
  5.              a.   Strip the wafers of PR using the Strip.rcp recipe on Matrix. A 2 minute (120sec) run should be sufficient.
                 b.   Measure the step height at each of the 5 points via Alphastep. Readings should be taken about 15mm from the wafer edge.
                 c.   Calculate the average step height.
                 d.   Calculate the amount of Si lost and divide by etch time to determine the Si etch rate.
  6.  Calculate the selectivities by dividing the PR etch rate by the Si etch rate for the Clean chamber and Gold chamber, and then the SiO2 etch rate by the Si etch rate for the Gold chamber.

Reported Data

Qual data may also be found on the Badger comment log. The following data is reported for the Drytek2 qual:

Clean Chamber

  • PR Etch Rate (3612)
  • Si Etch Rate
  • PR:Si Selectivity
Gold Chamber
  • PR Etch Rate (3612)
  • Si Etch Rate
  • PR:Si Selectivity
  • SiO2 Etch Rate
  • SiO2:PR Selectivity


Qualification Results

Machine Status States

  • Red: A major sub-system of the tool (RF power supply, mass flow controller, vacuum pump, etc.) is not functioning up to standard.
  • Yellow: A sub-system of the tool not common to all recipes is not up to standard. For example, RF tuning for Process 2 is down, or a specific gas is being replaced.
  • Green: System is up to standard.

 For recent process qualification results click here.

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