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STS Pegasus 4/Processes/LNF Si Thinning 1

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LNF Si Thinning 1 (previously known as LNF Si Thinning Etch) is an SF6 based process intended for isotropic thinning of Si wafers for device release. It does not have high uniformity, but has good selectivity to other materials.

About this Process
Process Details
Equipment STS Pegasus 4
Technology RIE
Material Silicon
Mask Materials not typical
Gases Used SF6, O2


Contents

Procedure

Follow the standard operating procedure.

Parameters

Parameter Dep* Etch
ICP Power 0 W 2800 W
Bias Power (HF) 0 W 5 W
Pressure 100 mTorr
SF6 Flow 0 sccm 450 sccm
O2 Flow 0 sccm 45 sccm
Ar Flow 200 sccm
Time 40 s 20 s
Chuck Temperature 20°C

* Dep step is used as a cooldown (no plasma) for temperature control.

Capabilities

Etch rate

This recipe is only characterized for blanket etching (no mask, 100% loading) on a 100 mm wafer. Etch rate will change for different loading areas or sample sizes.

Material Etch Rate Uniformity
Silicon 3.2 µm/min 2.1%

Mask selectivity

This recipe is intended for blanket etching, however a few common materials are included, as they may be used as an etch stop or for certain unusual processes.

Material Etch Rate Uniformity
Silicon dioxide 38 Å/min 9%
Silicon nitride 150 Å/min 11%
Low stress nitride 120 Å/min 10%
SPR 220 130 Å/min 26%

Etch profile

The etch profile is not characterized, as it is intended as a blanket etch. However, the process is considered isotropic.

Limitations

Etch length

This etch is designed to generate minimal heat and includes a cooldown cycle, therefore it is capable of running for long periods of time without risking damage to samples. However, the standard operating procedure should be followed: in particular, for etches longer than 60 min, you must create a helpdesk to work with a tool engineer. It is not sufficient to simnply split the etch into multiple segments.

Etch depth

For any etches that require a carrier wafer per the guidelines in the SOP, it is required that 100 mm samples are mounted to a 150 mm wafer and processed in the STS Pegasus 6 to prevent particulate from falling onto the chuck.