LAM 9400/Processes/POLY ETCH 2

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About this Process
Process Details
Equipment LAM 9400
Technology RIE
Material Poly
Mask Materials PR
Gases Used HBr, He
Date Created 2008

POLY_ETCH_2 is a recipe designed for etching polysilicon in the LAM 9400. It works well for etching polysilicon and N-type single crystal silicon, where as with P-type wafers it can cause micro-pitting. This recipe first has a more aggressive Cl2 breakthrough to get through native oxide layers, then the main etch is HBr which produces a very straight sidewall and is useful for stopping on oxide.

Due to the nature of this recipe a significant amount of Si must be exposed during the etch in order for it to run, therefore it is recommended to us a plain Si carrier wafer when etching 100 mm wafers


Parameter Breakthrough Etch
Pressure 100 mTorr 12 mTorr
TCP Power 300 W 500 W
Bias Power 50 W 30 W
Cl2 Flow 100 sccm 0 sccm
C4F8 Flow 0 sccm 100 sccm
He Flow 0 sccm 100 sccm
HBr 0 sccm 100 sccm


Etch Rate

  • Blanket Si Etch: 1350 Å/min
    • Wafers with a small % open area may etch faster

Mask Selectivity

Sidewall Profile


The recipe is known to fail if there isn't enough exposed silicon to etch. It is highly recommended to use a plain Si carrier wafer for that reason. Also the recipe has difficulty stabilizing, so very short etches (under 10 seconds) may be unreliable.

P-Type Pitting

When the poly etch is run with a P-Type Si wafer micro-pitting can be seen. The two images below show a P and N type wafer after 5 minutes of etching. A similar affect can be seen when wet etching P-Type wafers with bromine when a voltage is applied to the wafer as per this paper.


Temporary Testing

Increase Pressure TCP Bias CF4
Oxide Etch Rate Down arrow.svg Up arrow.svg Up arrow.svg Up up arrow.svg
Uniformity No change arrow.svg Down arrow.svg Down arrow.svg No change arrow.svg
Poly to Oxide Sel. Down arrow.svg Down arrow.svg Up arrow.svg Up arrow.svg
Poly Etch Rate No change arrow.svg No change arrow.svg Down arrow.svg Down down arrow.svg