Ox-RIE - Operating Instructions

Thanks to Yunhan Chen and Monica Hew for the operating instructions. Oxford-rie is a capacitively coupled plasma (ccp) etch equipment with fluorine based etch gases and oxygen. It belongs to the "Flexible" group.

Operating Instructions- Ox-RIE

Picture and Location

Background

Process Capabilities

Cleanliness Standard

Performance of the Tool

Contact List and How to Become a User

Contact List

Training to Become a Tool User

Operating Procedures

Recipe management

Step Library

Create a New Recipe

Edit an Existing Recipe

Process Characterization Data

Process Monitoring and Machine Qualification

Reported Data

Machine Status States

Process Monitoring Results

Picture and Location

 The tool is located at D section of the lab, right across the non-metal wet bench.

Oxford-RIE - Picture

OxfordRIE Location Map

Background

 The OX-RIE Oxford etcher is a reactive ion etcher (RIE), designed for etching various materials as shown in the performance of the tool section. The OX-RIE is currently approved to etch silicon and carbon based materials only. Please contact Jim McVittie (mcvittie@stanford.edu) for approval to etch other substrates. The system is gold contaminated.

There are several important points regarding usage of this etcher:

  1. Only 4” wafers can be etched using this machine. Any smaller chips must be mounted on a carrier wafer for etching. Any carrier wafers that are not etched by the chemistry can be used; Si and SiO2-on-Si wafers are acceptable with most chemistries.
  2. 5mm EBR (edge-bead removal) is required on all wafers due to the wafer clamp. The backside of the wafer must also be clean.
  3. Never run the etcher without a wafer in the chamber. The plasma will damage the wafer clamp if it is exposed.
  4. Never place a wafer back into the etch chamber after running a process without physically resetting it! The wafer may shift, leading to breakage.
  5. The measured bias voltage may drift significantly if an oxide carrier wafer is used, but this is not indicative of actual process variations.

Process Capabilities

Cleanliness Standard

Performance of the Tool

What the Tool CAN do

  1. Types of materials to be etched
  1. List of Available Gasses

What the Tool CANNOT do

Process Monitoring

Contact List and How to Become a User

Contact List

The following people make up the Tool Quality Circle:

Training to Become a Tool User

        Contact process staff to set up a training session.

Operating Procedures

Pumping Screen

Process Screen

Recipe management

Recipe management screen can be accessed by pressing Process→Recipe located at the top left of the screen. The left side of the screen shows the recipe that is currently loaded to the program. The panel on the right side is the Step Library.

REcipe Management Screen

               

Step Library

Step Library stores process steps that can be used to compose a recipe. Several standard steps are stored here.

Process Step Editor               

Create a New Recipe

  1. Click on an empty step and press “Repeat Step”.
  2. Enter the number of times that the loop will repeat.
  3. Close the loop by insert a loop step by pressing “Loop Step”.
  4. Any steps between Repeat Step and Loop Step will be repeated the number of times that has been set in the Repeat Step.

Recipe Editing Commands

 

Edit an Existing Recipe

               

               

Process Characterization Data

CHF3/CF4 process characterization - Data Collected by Ken Leedle and summarized by Yunhan Chen

SiO2Etch_Characterization

Process Monitoring and Machine Qualification 

Frequency

The Ox-RIE qual runs two wafers through the CHF3/CH4/Ar etch process. We use the Oxide ER test recipe in the library. One wafer with a 1.6um 3612 Photoresist pattern and one wafer with a 10,000A SiO2 coating are etched separately for 10 minutes and 2 minutes respectively. Nanospec measurements are taken before and after etching to calculate the PR and SiO2 etch rate respectively. To calculate the PR:Si selectivity, the two wafers coated in photoresist are then stripped of resist so that the Silicon step height may be measured via Alphastep.

Procedure

SUMO Wafer #

(all Si 4" wafers)

Coating

Pattern

(using SUMO mask)

-

 10,000A SiO2

gold

 -

 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 the SiO2 wafer, use the Oxide on Silicon Recipe (#1). For Wafer 88, 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.
  3.     a.  For PR wafer, measure the PR thickness, which is darker in color than the Si. Accidentally measuring the Si will result in a <100A reading.
  4. Calculate the averages.
  5. 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 15 minutes using the Oxide etch CF4 / CHF3. 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. Run a separate etch for each of the two wafers. Each etch is 10 minutes for the PR wafer and 2 minutes for the SiO2 wafer.

Recipe = Oxide_ER_Test : Oxide etch CF4 / CHF3

 

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 PR wafer.

             a.   Strip the wafers of PR using the Strip.rcp recipe on Matrix.

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.

  1.  Calculate the selectivity by dividing the PR etch rate by the Si etch rate.

Reported Data

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

Machine Status States

Process Monitoring Results