To detect X-rays directly, we conducted research on the fabrication of array-type pixel sensors. To improve the detection efficiency of incident particles, we use a Positive-Intrinsic-Negative (PIN) structure to expand the area of the deficiency. To reduce the number of channels and read signal separately, we put the JFET structure into each sensor. When only one row of gate is opened and read all of the signal from the same row sensors finished, the gate voltage is applied to next row to read the signal from the NxN array sensors. A pixel silicon sensor integrated with the JFET was manufactured using a 650 µm thick, 5 kΩcm n-type high-resistance silicon wafer. Various variables have been set to find sensors that shows good switching effects in the JFET structure. Electrical characteristics were measured to find the variable of the sensor with good switching effect. When A space 0.5 µm, B space more than 1.8 µm shows good switching effect. However, C space and D space were not significantly affected. By selecting one of the sensors that shows good switching effect, we measured changes in electrical characteristics by expanding the width of LED pulses. As the pulse width of LED light increased, the measured current in the drain shows good linearity, and the result show that the sensor responded well to LED light. The reverse voltage was applied to the back to create depletion layer, and the change in electrical characteristics was measured with the X-ray generator inserted. As a result, we found that X-ray signal were detected through peaks in the measured drain current graph. Additionally, to see the switching effect of the array sensor, the 2x2 sensor was measured. We expected the sum of drain current when only one gate was opened and drain current when both of gates were opened would be same. However, since the drain voltage was 2.4 V or higher, the sum of only one gate opened were more measured than both gates opened. To solve the problem of isolation between array sensors, the simulation was carried out by changing the process conditions of the fieldshaper.
Thesis Advisor: Prof. Hwanbae Park