PECVD SiNx via CHF3 + O2

Goal

The purpose of this document is to examine the etch properties of the Oxford 80 Plus RIE system and to find the etch rate of SiNx and S1818 MicroChem positive resist.

Materials

• Microchem S1818 Photoresist
• Microchem MF-319 Developer
• 4 inch Silicon Wafers

Equipment

• Torrey Pines Scientific hotplate
• ReynoldsTech spinner
• Oxford PlasmaLab 100 PECVD
• Oxford 80 Plus RIE
• SUSS MicroTec MA6 Gen3 Mask Aligner

Units

• Gas flow rate: standard cubic centimeters per minute (sccm)
• Pressure: milliTorr (mT)
• Temperature: degrees Celsius (C)
• High frequency (RF) power: Watts (W)

Protocol

Coat

1. Mount wafer and ensure that it is centered.

2. Deposit 7 milliliters of S1818 photoresist in the center of the wafer.

3. Spin on photoresist at 4500 RPM for 60 Seconds.

Soft Bake

1. Bake wafer at 115 °C for 60 seconds.

Expose

1. Use the photomask to expose the wafer at 150 mJ/cm2 Develop

1. Dispense approximately 150 milliliters of AZ300 MIF developer into a six inch cylindrical container.

2. Fully submerge the exposed wafer.

3. Agitate and develop the wafer for 60 seconds.

Etch

1. Pump to 5e-04 Torr, “Pump to Pressure” checked.

2. Etch Step

• Trifluoromethane (CHF3) flow rate: 100 sccm Oxygen (O2) flow rate: 4 sccm
• Pressure: 50 mT
• RF Power: 150 W
• Capacitor starting points: Capacitor #1: 60 %, Capacitor #2: 80 %

Results

etch rate ~ 60 nm/min