Instructions for Amtetcher Oxide Etch Process Qualification

 

Purpose: to provide verification and trend of the oxide program including etch rates of poly and photoresist, selectivity of those materials, and wafer-to-wafer and within-a-wafer uniformity of etch.

 

Frequency of the test: to be completed after major maintenance such as cleaning or gas line replacement or on a set schedule to be determined or as needed based on user feedback.

 

Documentation of results: to be posted on the log sheet located in the assigned book at the tool, posted in the equipment archive for amtetcher on the SNF website and in a file or webpage available to users in data or chart format.

 

Procedure:

 

  1. Use wafers with at least 900A thermal oxide, no pattern.  Patterned wafers may be used to measure photoresist etch rates, too.
  2. Season the chamber for 10 minutes using Program 3.  Be sure to check the program parameters before starting.
  3. Measure oxide and photoresist thickness using one of the Nanospecs.  Be sure to use reference wafer before testing to calibrate the tool.  Take readings for the Center, Top, Flat, Right and Left positions of the wafer.  Readings should be taken about 15mm from the edge.  See Fig. 2.
  4. Place two wafers into tray #1 in positions 2 and 3.  See Fig. 1.
  5. Etch for 2 minutes.  Monitor gas flows, RF power and bias and record on Monitor Log Form.
  6. Measure oxide and photoresist thickness using the same Nanospec.  Be sure to use reference wafer before testing to calibrate the tool.  Take readings for the Center, Top, Flat, Right and Left positions of the wafer.  Readings should be taken in roughly the same place as the first measurements.  See Fig. 2.
  7. Record results on the Monitor Log.  Record results in data file to get wafer-to-wafer and within-a-wafer
    1. Subtract the second average reading from the first average reading for oxide and for photoresist to get total material etched
    2. To get the etch rate per minute divide the average total material etched measurements by 2. 
    3. To get the selectivity for oxide vs photoresist divide the oxide etch rate by the photoresist etch rate

 

Figure 1:  Tray #1 with wafers

 

 

Figure 2: Reading placement.  Note that the “flat” is down.