Specific Process Knowledge/Etch/IBE⁄IBSD Ionfab 300/IBE process trends: Difference between revisions
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=General tips for finding etching parameters (given by Oxford Instruments)= | |||
One thing to remember is that the etch rate varies linearly with beam current while it varies exponentially with beam voltage. | |||
*Beam voltage – depends on application, 200-800eV. | |||
*Always have neutraliser current 20% extra of the beam current value. | |||
*Accelerator voltage between 100V –500V, adjust to get Ia < 10% Ib ('''it helps protect electronics and power supplies'''). | |||
*The real beam current is effectively the beam current minus accelerator current. | |||
*Varying Ar flow for source gas as well as beam current will have an effect on the accelerator current. | |||
*Arm Tilt affects: | |||
#Etch uniformity—the steeper the angle, the better the uniformity. However the etch rate reduces.<br> | |||
#Wall angle profile (Argon IBE) theoretical ideal is 11 degrees from vertical. Actual value depends on the design of the grids, i.e. beam divergence etc.<br> | |||
Typical arm angle is 0-12 degrees. The sample is usually rotated to cater for any non-uniformity in the beam profile. | |||
*A guide to optimize etch uniformity is as follows: | |||
#Set beam energy —a rough guide is, the higher the energy the rougher the surface as seen on an SEM. 500eV is considered medium energy.<br> | |||
#Then starting with beam current of 300mA increase the value until you reach the value where the PR is getting burnt.<br> | |||
#Adjust beam current to give optimum etch rate without overheating the sample.<brA> | |||
#Adjust Accelerator voltage to get uniformity. Note that as this will change beam divergence, the sample temperature will change. | |||
*Sample temperature is important because:<br> | |||
#Need to keep any resist cool<br> | |||
#Temperature can affect chemical processes | |||