Differences

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--- e-beam_evaporator [2025/06/13 13:54] – wigbout
+++ e-beam_evaporator [2025/12/03 16:13] (current) – [Common errors] fabian
@@ Line 182: / Line 182: @@
    * Open the Ar-valve.
    * Wait until the chamber pressure is stable.
-   * Set your desired Argon flow (e.g. 2.5 sccm)
+   * Set your desired Argon flow (e.g. 3.0 sccm)
    * Check all the settings from the ion beam (voltages, etc.)
    * Press ''discharge''
@@ Line 195: / Line 195: @@
    * Close Ar-valve.
    * Put back the sampleholder to the original position, facing downwards.
+=== Etch rate ===
+The etch rate in theory is about half of the etch speed of the ion beam etcher in the clean room. Beam diameter of the clean room IBG is approx. 4 cm, beam diameter of the e-beam IBG is a little below 10 cm. Beam current of the clean room IBG is ~7.5 mA, beam current in the e-beam IBG is ~15 mA.
+The intensity is given as beam current divided by beam area (I/r^2π) where r is the radius of the beam (half the beam diameter).
+In practice, however, the etch rate is about 1/3 the etch rate of the clean room ion beam etcher (tested 02/12/2025 with 60 nm of Nb, capped with 5 nm Pt).
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@@ Line 235: / Line 243: @@
   - The conditioning of the Nb.
-== Conditioning the chamber: ==
+=== Conditioning the chamber: ===
 Evaporate a getter-material, such as Nb or Ti. These materials bond with dirt and oxygen in the chamber and end up sticking to the walls, improving pressure after pumping down again. The aim is to achieve e-9 to 1e-8 chamber base pressure..
@@ Line 241: / Line 249: @@
 By evaporating 5 - 10 nm of getter-material, and waiting for one hour, the chamber pressure will decrease. The aim is to achieve ~1e-8 or ~5e-9 mbar. In the first step, after some time, the getter will stop working as efficiently as in the beginning. So, when the pressure is stabilized, one can evaporate more.
-== Conditioning Nb: ==
+=== Conditioning Nb: ===
 There is still a lot of dirt in Nb after melting. This can be seen if there is a good base pressure but a very bad Nb evaporation pressure. To solve this, we evaporate a lot of Nb the get rid of the impurities. This has the double effect of also conditioning the chamber.
@@ Line 251: / Line 259: @@
-==== Common errors ====
+===== Common errors =====
+   * **IBG discharge failure.** If the ion beam gun power source shows the HLP26 or HLP27 error, reset the power source by pressing the button the says ''Discharge Enable / Standby'' with the label ''Reset'' next to it. A common cause for a discharge error is insufficient Ar pressure. A pressure of 3.8e-4 mbar is the lower boundary for a stable emission. At 3.7e-4 mbar to 3.6e-4 mbar there are insufficient Ar atoms for the IBG to maintain a stable discharge. An Ar flow rate of 3.0 sccm is sufficient, 2.5 sccm is on the lower end and might not be enough. **Note:** Pressure typically drops by 0.1e-4 mbar to 0.2e-4 mbar during etching over a scale of 1 to 3 minutes. Keep this in mind when selecting flow rate.
-   * Discharge failure? If the power source shows the HLP26 or HLP27 error, reset the power source by pressing the button the says ''Discharge Enable / Standby''