Method for nondestructive measurement of dopant concentrations and profiles in the drift region of certain semiconductor devices

A method for determining a profile of impurity concentration (ND) along the length of a semiconductor device, the method comprising the steps of:

• reverse biasing the device with a voltage V which can be varied over a wide range;
• scanning along a length of the device with a beam of radiant energy to produce in the device a beam induced current signal;
• using the induced signal versus scanned length to measure a depletion width W in the device for a respective voltage V;
• repeating the above steps with different bias voltages to establish a series of such voltages V and respective widths W;
• and determining from a mathematical relationship amongst voltage V, width W, and concentration ND a profile of dopant impurity concentration ND along the length of the device.

A method for determining dopant impurity concentrations (ND) at points along the length of a semiconductor device which has internal capacitance (C), the method comprising the steps of:

• reverse biasing the device with a voltage V which can be varied over a wide range until the onset of avalanche breakdown of the device;
• scanning along a length of the device with a beam of radiant energy to produce in the device a beam induced current signal;
• using the induced signal versus scanned length to measure a depletion width W in the device for a respective voltage V;
• repeating the above steps with different bias voltages to establish a series of such voltages V and respective widths W;
• and determining from interrelationships of voltage V, width W, capacitance C and dopant concentration ND, the respective dopant concentrations ND at points along the length of the device.

A method for determining dopant impurity concentrations (ND) at points along the length of a semiconductor device such as a high voltage lateral double diffused metal oxide semiconductor (HV LDMOS) transistor which has internal capacitance (C), the method comprising the steps of:

• reverse biasing the device with a voltage V which can be varied over a wide range;
• scanning along a length of the device with a beam of radiant energy to produce in the device a beam induced current signal;
• using the induced signal to measure a depletion width W in the device for a respective voltage V, the induced current signal having a high generally constant value within a region of the depletion width W and decaying generally to zero outside the region, the depletion width W increasing as bias voltage V in increased;
• repeating the above steps with different bias voltages to establish a series of such voltages V and respective widths W;
• and determining from interrelationships of voltage V, width W, capacitance (C) and dopant concentration ND, the respective dopant concentrations ND at points along the length of the device.