Evaluation method for semiconductor device

An evaluation method for determining a surface potential distribution of a semiconductor device having a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type, the first semiconductor region formed at a surface of the semiconductor device and the second semiconductor region formed at a surface of the first semiconductor region contiguous said surface of the semiconductor device and surrounded by the first semiconductor region, the first and second semiconductor regions forming a junction, comprising the steps of:

• applying a reverse bias voltage between the first and second semiconductor regions to form a depletion layer in the first semiconductor region along the junction;
• scanning said surface of the semiconductor device in a lateral direction along said surface with a light beam forming a scanning line, said light beam having a wavelength with a penetration length less than a depth dimension of the second semiconductor region substantially perpendicular to said lateral scanning direction to cause an optical beam induced current to flow across said junction;
• measuring an optical beam induced current intensity profile on the scanning line extending throughout the lateral extent thereof corresponding to the depletion layer;
• integrating the optical beam induced current intensity profile over said lateral extent corresponding to the depletion layer;
• and
• normalizing the integrated optical beam induced current intensity profile in reference to the reverse bias voltage to determine the surface potential distribution of the semiconductor device.