Method for measuring source and drain junction depth in silicon on insulator technology

A method for determining a source/drain junction depth of an inspected semiconductor device formed on a substrate, the substrate comprising a bottom semiconductor layer, an insulating layer on the bottom semiconductor layer, and an upper semiconductor layer, the inspected device having a source region and a drain region formed in the upper semiconductor layer, the method comprising:

• measuring a threshold voltage of a bottom transistor comprising the source region, the drain region and the substrate by:
• grounding the source and applying a low voltage to the drain;
• and
• applying a test voltage varing from about zero to at least the threshold voltage, wherein the threshold voltage comprises a voltage that corresponds to formation of a depletion region between the source and drain regions;
• determining threshold voltages of bottom transistors of a plurality of reference devices, the reference devices each having a different known source/drain junction depth and having physical characteristics corresponding to those of the inspected device;
• comparing the threshold voltage of the inspected device bottom transistor to the threshold voltages of the reference device bottom transistors;
• and
• determining that the source/drain junction depth of the inspected device is about the same as the source/drain junction depth of one of the reference devices when the threshold voltage of the inspected device bottom transistor is about equal to the threshold voltage of the one of the reference devices bottom transistor.