P5000 RIE/Processes/POLY PAT BKM

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About this Process
Process Details
Equipment P5000 RIE
Technology RIE
Material Polysilicon
Mask Materials PR, SiO2
Gases Used HBr, Cl2
Date Modified 4/10/2014
Authored By AMAT, Kevin Owen

The POLY PAT BKM recipe is a general recipe for etching polysilicon and amorphous silicon films on the P5000 RIE/Processes. It has a fast etch rate (3800 Å/min) and reasonable selectivity to photoresist and silicon dioxide. It can also be used for shallow etches (< 4 μm) in silicon substrates. This recipe can be run in chamber Chamber C on CMOS Clean samples.


  1. Review the material restrictions for each chamber and choose the appropriate one for the application.
  2. Follow the procedure outlined in the SOP.
  3. Open the POLY PAT BKM Process Program.
  4. Edit the time in the MAIN ETCH.
  5. Select POLYPATBKM from Wafer Lot Names.


The POLY PAT BKM etch has three main steps: breakthrough, main etch, and over etch.

  1. The breakthrough step is designed to etch through any native oxide or photoresist residue on the surface of the polysilicon. It is rarely modified.
  2. The main etch is a fast etch with reasonable selectivity and is used to etch through a polysilicon film.
  3. The over etch is a slower, very high selectivity etch that can be used for the final portion of a polysilicon film when stopping on a thin or sensitive film underneath. This is rarely used for normal processing circumstances.

All of the characterization data below is for the main etch.

Etch rate

Bulk etch rates for various oxides, nitrides, and masking materials are shown below. High aspect ratio (narrow) trenches will etch slower.

Material Etch rate
Polysilicon 3800 Å/min
Si (22% open area, SPR mask) 2480 Å/min
Thermal oxide 350 Å/min
HTO unknown
LTO unknown
PECVD oxide unknown
Stoichiometric nitride unknown
Low stress nitride unknown
SPR 220 1300 Å/min


  • Within-wafer uniformity: <4% (3 mm edge exclusion)
    • Etch rate is faster at the edge
  • Wafer-to-wafer uniformity: <2%

Mask selectivity

Mask selectivity of polysilicon to a selection of materials is shown below. Selectivity for your material can be calculated using the etch rates listed above.

Mask selectivity is based on bulk material etch rates (above). Selectivity will vary slightly with feature size.
Material Etch rate
SPR 220 3:1
Thermal oxide 10.9:1
Stoichiometric nitride unknown
Low stress nitride unknown

Sidewall profile

Warning Warning: not verified
  • 88 degrees


Parameters are shown below for the recipe. The first STAB, STRIKE, and BT are for the breakthrough step (BT being the etching portion). The second STAB and MAIN ETCH are for the main etch step. The OVER ETCH step has not been tested, please contact a tool engineer if you wish to test this step.

Chamber Selection C Only
Step end control By Time
Maximum step time 20 s 1 s 10 s 20 s 0 s
Endpoint selection No Endpoint
Pressure Servo 20 mTorr Servo 10 mTorr Servo 125 mTorr Servo 100 mTorr
Pressure ramp rate 0 mTorr/Second
RF Power 0 W 300 W 0 W 400 W 150 W
RF match, mode Auto, B-to-B Auto, RF Off
RF tune setpoint 0.0 V
DC Bias Limit -1000 to 0 V
Magnetic field 0 G 30 G
Argon Flow 120 sccm 50 sccm
HBr Flow 40 sccm 60 sccm
Cl2 Flow 40 sccm 20 sccm
O2He Flow 12 sccm


Etch time

Etch rate is very linear, tested down to 5 seconds. Maximum etch time is mask dependent, have demonstrated up to 4 µm etch depth.


This etch is not significantly load dependent.

Passivation removal

This etch deposits a bromine-based passivation layer to achieve anisotropy. Removal has been shown using a series of alternating BHF and Nanostrip processes.


The bulk etch rate of polysilicon is verified occasionally by running the recipe for 1 minute.