P5000 RIE/Processes/POLY PAT BKM
|Warning:||This page has not been released yet.|
|About this Process|
|Mask Materials||PR, SiO2|
|Gases Used||HBr, Cl2|
|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.
- Review the material restrictions for each chamber and choose the appropriate one for the application.
- Follow the procedure outlined in the SOP.
- Open the
POLY PAT BKMProcess Program.
- Edit the time in the
POLYPATBKMfrom Wafer Lot Names.
The POLY PAT BKM etch has three main steps: breakthrough, main etch, and over etch.
- The breakthrough step is designed to etch through any native oxide or photoresist residue on the surface of the polysilicon. It is rarely modified.
- The main etch is a fast etch with reasonable selectivity and is used to etch through a polysilicon film.
- 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.
Bulk etch rates for various oxides, nitrides, and masking materials are shown below. High aspect ratio (narrow) trenches will etch slower.
|Thermal oxide||350 Å/min|
|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 of polysilicon to a selection of materials is shown below. Selectivity for your material can be calculated using the etch rates listed above.
|Low stress nitride||unknown|
This process has incomplete or incorrect characterization data.
- 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.
|Parameter||STAB||STRIKE||BT||STAB||MAIN ETCH||OVER ETCH|
|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 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.
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.