Mathies:RIE in BNC

RIE silicon etch in BNC (for thin Si films)

General

Si etching is usually done with SF6 plasma in the RIE system. RIE in the BNC is controlled by its attached computer. This computer should only be used for RIE processes. All valves and settings are controlled by the RIE program. “O” indicates opened and “X” indicates closed. Ptherm in the microlab works similarly. Please refer to microfabrication in microlab for more information.

Wafer preparation

• If the wafers have not already been marked with a # for identification, do this before taking the wafers to etching. The standard numbering system is *date* - *wafer #*, plus your initials. Carefully carve the ID # into the photoresist on the front of the wafer with the edge of a razor blade, then blow off the cracked PR debris with the nitrogen gun.

Before Silicon etch

The standby state of the RIE system should be:

• Chamber under vacuum
• Vacuum valve switched OFF
• RF Power Supply should be OFF.

Chamber cleaning and Silicon Etching

It's a good idea to do a chamber clean before etching, especially before stripping the Si layers off of the wafers prior to drilling and bonding. Otherwise, a thin-film residue will sometimes remain on the wafer surface.

1. Enter the service room and turn on the master valve for O2 and SF6 tanks.

2. The RIE chamber should be under vacuum in standby mode. Turn on the power supply if it’s not ready on. Before clicking open the “Vent” valve, make sure the “Vacuum” valve is off.

3. Open the chamber slowly. When the chamber is fully vented, place your substrate near the center of the stage. Close the chamber.

4. Turn off “Vent” and turn on “Vacuum”. Base pressure should set at 500 or below. Wait until pressure stabilizes around 0 torr.

5. Pull the slide bar down to zero at the O2 channel. Then turn on the valve. If the valve automatically pops closed, the base pressure is higher then the base set point. Repeat until the valve remains open.

6. Slowly increase the O2 set point to 10.

7. Pull the slide bar down to zero at the RF Supply. Then turn on the power icon.

8. Slowly increase the power to 17% (100W) and time for 90sec. Check that the plasma is ignited through the small glass window. Click to turn off the plasma.

9. Pull the slide bar down to zero at the O2 channel. Then turn off the valve. We don’t want to build up a pressure in the gas line.

10. Pull the slide bar down to zero at the SF6 channel. Then turn on the valve.

11. Slowly increase the SF6 set point to 10.

12. Pull the slide bar down to zero at the RF Supply. Then turn on the power icon.

13. Slowly increase the power to 25% (150W) and time for 2min30sec. Check that the plasma is ignited through the small glass window. Click to turn off the plasma.

14. Pull the slide bar down to zero at the SF6 channel. Then turn off the valve.

15. Click the “Vacuum” valve off and then “Vent” open.

16. You can remove your substrate when the chamber is fully vented. Close the chamber.

17. Close the “Vent” valve and open the “Vacuum” valve. Turn off the “Vacuum” valve when the chamber goes below base set point.

18. Turn off the power supply, and the gas tanks in the service room.

Note: Sometimes the plasma is not stable and does not etch at certain rate. Adjust the time from your previous test results.

Note: Information can be written on a bare Si surface (backside of the wafer only) with Sharpie, and if the etch times are shortened, (to ~20 sec for the O2 and ~1 min 15 sec for the SF6) the Si under the ink will remain.

Contact

• Eric Chu 10:30 12 June 2009 (PDT):

or instead, discuss this protocol.