PECVD SiNx via CHF3 + O2

Process description

This process is performed to measure the etch rate of PECVD SiNx using an Oxford 80 plus RIE tool. Lithography equipment and material used in this study can be substituted by others that would result in a similar pattern.

Materials

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

Equipment

• Oxford PlasmaLab 100 PECVD
• Oxford 80 Plus RIE

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 - measured on a 4" wafer on July 29th, 2024

Side SEM of a two step SiNx etch, totaling ~ 12 minutes