  We are developing position sensitive silicon detectors (PSDs) which have an
electrode at each of four corners so that incident position of a charged
particle can be obtained with signal from the electrodes. It is expected that
the position resolution of the electromagnetic calorimeter (ECAL) of the ILD
detector will be improved by introducing PSDs to detection layers. We have been
developing the PSDs for several years. In the previous production we found that
the charge separation is not optimally done due to the readout impedance. To
solve the issue, we produced new PSDs with higher surface resistance with an
additional resistive layer on the surface. We also implemented several
techniques to decrease position distortion and increase signal-to-noise ratio
which are essential for the optimal position resolution. The measurements on
the prototype sensors are ongoing, including radiation source measurement and
laser measurement using an ASIC for silicon pad detectors.
