Probable value of the resistance offered by substrate

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satishgra

Joined: 29 Mar 2008
Posts: 23
Location: Bangalore

26 Oct 2009 6:11 Probable value of the resistance offered by substrate

Hi,

I am working on a mems device and need to model the equivalent lumped model

I wud like to know what is the probable value of the resistance offered by the substrate

Regards,
satish

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kspalla

Joined: 19 Aug 2008
Posts: 848
Helped: 140

30 Oct 2009 5:54 Probable value of the resistance offered by substrate

Check for the conductivity of the material by the Vendor.

satishgra

Joined: 29 Mar 2008
Posts: 23
Location: Bangalore

30 Oct 2009 5:58 Re: Probable value of the resistance offered by substrate

Hi,

I am using "silicon" as substrate...I know that the conductivity of silicon is ~0 (from pozar)...how am i going to calculate it from this value given the dimensions of substrate as 350*300*5 (um) ??

Any formula ??

timof

Joined: 21 Feb 2008
Posts: 86
Helped: 6

30 Oct 2009 7:36 Re: Probable value of the resistance offered by substrate

satishgra wrote:

Ask your wafer vendor about substrate resistivity, or conductivity, or doping level - silicon substrate are never absolutely pure from impurities, so they have a finite (non-zero) resistivity.

satishgra

Joined: 29 Mar 2008
Posts: 23
Location: Bangalore

30 Oct 2009 7:45 Re: Probable value of the resistance offered by substrate

Hey thanks,

what you mean to say is Ideally SI should give you a zero resistivity...but, due to impurities, it can be slightly more

Regards,
satish

timof

Joined: 21 Feb 2008
Posts: 86
Helped: 6

30 Oct 2009 18:36 Re: Probable value of the resistance offered by substrate

satishgra wrote:

Hey thanks,

what you mean to say is Ideally SI should give you a zero resistivity...but, due to impurities, it can be slightly more

Regards,
satish

No. Ideally pure Si (called intrinsic) has a very high resistivity (at room temperature). Pure silicon is very hard to produce. Silicon wafers are usually doped to a certain level (e.g. 1e14cm-3, 1e15cm-3, or higher), and this doping level (and corresponding conductivity or resistivity) are very tightly controlled by wafer vendors.