The Signatone Low Current System, combined with a suitable parametric instrument such as the HP4156A, allows measurements of current to the femtoamp (1 x 10 -
The components of the Triaxial Package are 1) a triaxially driven room temperature chuck or hot chuck, 2) triaxially driven probe tip holders engineered to operate with a 300°C chuck temperature, 3) a suitable electronically shielded dark box, and 4) appropriate cabling.
Triaxial measurements use a 3 conductor system with a driven guard between the source-sense (conductor to be measured) and the signal ground to enable measurements of very low currents. The results are: 1) A low noise floor which is a measure of the effective noise protection of the probe holder or chuck, shielded box, and the HP4156A or equivlaent meter, 2) A high equivalent resistance devinde by 1/Re=dI/dV where Re is the equivalent resistance and dI/dV is the change of current with voltage, and 3) A low residual capacitance defined by I=CrdV/dT. Where I is the forcing current, Cr is the residual capacitance and dV/dT is the change of voltage over time.
The Signatone Triaxial Package exhibits a typical noise floor of 2 fA and an effective resistance greater than 1 x 10^
Most parameters may be measured through a top-side contact. If the actual curent flowing through the chuck to ground must be measured, the porperties of the chuck become important. The Triaxial Hot Chuck System has a typical effective noise floor of less than 100fA and an effective resistance of approximately 1x10^
|Electrical Characteristics*||Noise Floor||Effective Resistance ohms||@ Chuck Temp.|
|Probe tip holder & tip|
Note: Measurements made on an HP4156A under long integration with a 10 second hold time and a 1 second delay time after temperature stabilization and zeroing the SMU.
6" & 8" both @ Ambient & 200°C.....................4 pf typical
Note: Measured on an HP4156A by recording the voltage change versus time while forcing current with the guard enabled.
|Temperature Parameters||6" chuck||8" Chuck|
|Ambient to 200°C typical|
|200°C to Ambient|
|Uniformity at 200°C|
|Max Operating Temp.|
|Physical Parameters||Diameter||Thickness or Length||Cable Length|
|Probe tip holder|
|Room Temp. Chuck|
|High Temp. Chuck|
Applications Notes for low current analysis.