STS Pegasus 4/Processes/LNF Si Thinning 2

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

LNF Si Thinning 2 (previously known as LNF si thinning etch - slow 1) is an SF₆ based process intended for isotropic thinning of Si wafers for device release.

Procedure

Follow the standard operating procedure.

Parameters

Parameter	Units	Setpoint
ICP Power	W	600
Bias Power (HF)	W	30
Pressure	mTorr	15
SF6 Flow	sccm	300
Ar Flow	sccm	100
Chuck Temperature	°C	10

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	3.5 µm/min	3.6%

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	240 Å/min	7%
Silicon nitride	700 Å/min	2%
Low stress nitride	590 Å/min	2%
SPR 220	860 Å/min	2%

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 therefore 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.