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# Metal thickness in ie3D

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#### Narich

##### Newbie level 4
Hello,
Does anyone know the minimum metal thickness that can be modeled in ie3D?
I simulated a CPW filter with gold as the metal and got two very different results for 1 micron thickness and 0.2 microns. The manual say this thickness is only used to calculate the losses but I have a feeling that there is a problem with 0.2 microns
Richard

#### jian

Hi, Narich:

I would like to make a few comments:

1. Thickness may have significant effect to the performance of a structure espeically for filters. At the resonances, the S11 and S21 are strongly affected by metallic loss. Reducing the strip thickness from 1 um to 0.2 um may increase the loss significantly. That should be the reason why you see significant difference in your CPW filter.

2. On IE3D, there are 2 ways of modeling thickness. The thin model or the standard model assume the strips are infinitely thin in the structure modeling. However, it will include the loss effect using surface impedance concept. This loss effect is related to the thickness. Therefore, the loss effect of the thickness is included in the simulation while the structure effect of the thickness is not included. This model is accurate and fast for thin sheet structure. Many traditional microwave circuits, MMIC circuits and patch antennas can be modeled accurately and efficiently using this standard model.

3. Modern circuits (MMIC and RFIC) and antennas are getting smaller and smaller in size. When the strip width is not much larger than strip thickness, the structure effect of thickness will be critical. In such a case, users should try to use the thickness models using the "Grow Thickness..." command on IE3D. The thickness model will include both the loss and structure effects precisely. Certainly, it will slow down the simulation. Also, the explicit thickness model on IE3D layout editor (MGRID) will cause editing more difficult. For this reason, we have implemented the Automatic Run-Time Thickness (ARTT) feature. The ARTT feature allows users to edit the structure as thin model for simplicity while it automatically converts the structure to thickness model in run-time. ARTT is defined in Basic Parameters dialog.

Regards.

V
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