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e-beam_evaporator

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e-beam_evaporator [2025/06/13 13:51] – [Chamber Conditioning] wigboute-beam_evaporator [2025/12/03 16:13] (current) – [Common errors] fabian
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    * Open the Ar-valve.    * Open the Ar-valve.
    * Wait until the chamber pressure is stable.    * 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.)    * Check all the settings from the ion beam (voltages, etc.)
    * Press ''discharge''    * Press ''discharge''
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    * Put back the sampleholder to the original position, facing downwards.    * Put back the sampleholder to the original position, facing downwards.
  
----- +=== Etch rate ===
-===== Maintaining High Quality Materials =====+
  
-Because the system is used by a lot of users, we strongly urge every user to be aware of others' needs. After a bake-out, the system can be booked to condition the chamber. In that case, Nb will be evaporated without a sample, but for the sake of obtaining a ultra-high vacuum.+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.
  
-==== Melting Guide ====+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).
  
-After the materials are refilled or replaced, or the quartz crystal has been replaced, the chamber needs to be pumped down. Typically, this type of maintenance is done on a Friday, so that the system can be baked out for (at least) 48 hours during the weekend. After the bake-out, the pressure will be around 8e-8 mbar.+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).
  
-=== Motivation ===+---- 
 +===== Maintaining High Quality Materials =====
  
-Why do you want to melt materials loaded into the e-beam evaporator? +Because the system is used by a lot of users, we strongly urge every user to be aware of others' needs. After a bake-out, the pressure will be around 8e-8 mbar. After opening, the chamber always needs to be conditioned in order to obtain high quality Nb. 
-The metals are loaded in the form of tiny pellets.+ 
 +When materials are refilled, they need to be molten. Why do you want to melt materials loaded into the e-beam evaporator? The metals are loaded in the form of tiny pellets.
 These are often: These are often:
   * Oxidized   * Oxidized
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-=== Melting === +==== Melting ==== 
  
 Different materials have different melting points, so it is important to start with a low emission current and increase it gradually depending on the targeted metal. Melting must be done homogeneously over the entire area of the liner filled with pellets, which avoids the trapping of impurities and ensures that all pellets can be combined into a single amalgamation. So the steps are: Different materials have different melting points, so it is important to start with a low emission current and increase it gradually depending on the targeted metal. Melting must be done homogeneously over the entire area of the liner filled with pellets, which avoids the trapping of impurities and ensures that all pellets can be combined into a single amalgamation. So the steps are:
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   * Throughout the melting process, the chamber pressure should never reach the ~e-5 regime. If it does, you’re either using too high of a current or melting too fast.    * Throughout the melting process, the chamber pressure should never reach the ~e-5 regime. If it does, you’re either using too high of a current or melting too fast. 
  
-=== Aftermath ===+==== Aftermath ====
  
 After melting, there are two important things to do:  After melting, there are two important things to do: 
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   - The conditioning of the Nb.   - 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.. 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..
  
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 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. 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. 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.
  
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-==== 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'' 
  
  
e-beam_evaporator.1749822687.txt.gz · Last modified: 2025/06/13 13:51 by wigbout
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