Specific Process Knowledge/Etch/DRIE-Pegasus/System-description: Difference between revisions
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== Description of the Bosch process at the DRIE-Pegasus == | == Description of the Bosch process at the DRIE-Pegasus == | ||
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{{Author-jmli1}} | |||
This section applies to all Pegasus tools. For Pegasus 4, however, it is less important as dielectrics etches are continuous. | |||
The DRIE-Pegasus tools take the well established Bosch process known from the [[Specific_Process_Knowledge/Etch/ASE_(Advanced_Silicon_Etch)|ASE]] a significant step further. In the ASE the Bosch process has two cycles, etch and passivation. During each cycle the process parameters are kept constant: | The DRIE-Pegasus tools take the well established Bosch process known from the [[Specific_Process_Knowledge/Etch/ASE_(Advanced_Silicon_Etch)|ASE]] a significant step further. In the ASE the Bosch process has two cycles, etch and passivation. During each cycle the process parameters are kept constant: | ||
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**the ion bombardment driven by the platen power ''first'' removes the passivation layer on the surfaces directly exposed to the ions (i.e. horizontal surfaces) | **the ion bombardment driven by the platen power ''first'' removes the passivation layer on the surfaces directly exposed to the ions (i.e. horizontal surfaces) | ||
**''then'' as the bottom of the structures are opened the etch of silicon itself starts. | **''then'' as the bottom of the structures are opened the etch of silicon itself starts. | ||
[[Image:boostdelay4b.jpg |400x400px|thumb|The etch cycle may be split into three parts, Boost, Delay and Main, where process parameters such as pressure, gas flows or RF powers have different values. The red curve shows the possible characteristics of the platen power.]] | [[Image:boostdelay4b.jpg |400x400px|thumb|The etch cycle may be split into three parts, Boost, Delay and Main, where process parameters such as pressure, gas flows or RF powers have different values. The red curve shows the possible characteristics of the platen power. {{image1}}]] | ||
Here, it is clear that one can distinguish two phases of the etch cycle; one where the ion bombardment removes the polymer and one where the actual etching of silicon takes place. Considering what process conditions are favorable we realize that | Here, it is clear that one can distinguish two phases of the etch cycle; one where the ion bombardment removes the polymer and one where the actual etching of silicon takes place. Considering what process conditions are favorable we realize that | ||
#the ion bombardment requires a low pressure in order for the ions to have a long mean free path and hence good directionality. Also, a high platen power is required to drive the ion bombardment. | #the ion bombardment requires a low pressure in order for the ions to have a long mean free path and hence good directionality. Also, a high platen power is required to drive the ion bombardment. | ||
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== Processing options on the Pegasus == | == Processing options on the Pegasus == | ||
This section applies to all Pegasus tools. | |||
The Pegasus has a lot of advanced processing options. | The Pegasus has a lot of advanced processing options. | ||
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== Modification of the showerhead== | == Modification of the showerhead== | ||
This section applies to all Pegasus tools. | |||
It is clear that optimizing the Bosch processes on the Pegasus can be done in countless ways. Reducing the cycle time is a very convenient way of getting rid of, or at least reducing, scallops. The faster the process switches the smaller the scallops will be. However, at some point the hardware (MFS's, RF generators, APC valve) cannot keep up with the demand and the process will essentially be continuous causing the Bosch process to break down. In its original setup, the Pegasus had standard processes with cycle durations down to 2 seconds. The hardware on the Pegasus is indeed very fast and allows faster switching. The limiting factor in the Bosch process was identified by Henri Jansen - and we have taken steps to improve this as described below. | It is clear that optimizing the Bosch processes on the Pegasus can be done in countless ways. Reducing the cycle time is a very convenient way of getting rid of, or at least reducing, scallops. The faster the process switches the smaller the scallops will be. However, at some point the hardware (MFS's, RF generators, APC valve) cannot keep up with the demand and the process will essentially be continuous causing the Bosch process to break down. In its original setup, the Pegasus had standard processes with cycle durations down to 2 seconds. The hardware on the Pegasus is indeed very fast and allows faster switching. The limiting factor in the Bosch process was identified by Henri Jansen - and we have taken steps to improve this as described below. | ||
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As stated, we believe that only switched processes will be affected by this change. Continuous processes such as [[Specific Process Knowledge/Etch/DRIE-Pegasus/processC|Process C]], [[Specific Process Knowledge/Etch/DRIE-Pegasus/nanoetch/nano142|Nano1.42]], isotropic etches, barc etches or the black silicon recipes are not believed to be noticeably affected. | As stated, we believe that only switched processes will be affected by this change. Continuous processes such as [[Specific Process Knowledge/Etch/DRIE-Pegasus/processC|Process C]], [[Specific Process Knowledge/Etch/DRIE-Pegasus/nanoetch/nano142|Nano1.42]], isotropic etches, barc etches or the black silicon recipes are not believed to be noticeably affected. | ||
Click [[Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange|HERE]] to see a comparison of some the etches before and after the change of the showerhead. | Click [[Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange|'''HERE''']] to see a comparison of some the etches before and after the change of the showerhead. | ||
== RF Matching == | == RF Matching == | ||
=== RF matching in general === | === RF matching in general === | ||
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* the RF powers | * the RF powers | ||
are changed every few seconds - hence requiring the capacitors to adjust to an entirely new situation. In other words, if not carefully tuned, the Bosch process will spend most of the time stabilizing the plasma. | are changed every few seconds - hence requiring the capacitors to adjust to an entirely new situation. In other words, if not carefully tuned, the Bosch process will spend most of the time stabilizing the plasma. | ||
== The Picoscope == | |||
The process monitoring on Pegasus 1, 2 and 3 has been dramatically improved with the installation of the Picoscope. Click [[Specific Process Knowledge/Etch/DRIE-Pegasus/picoscope|'''HERE''']] to access a page on the Picoscope only. | |||
== The Claritas endpoint system == | |||
This section applies to Pegasus 1. Too bad that it is empty so far... | |||