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SDD Implantation Type
Standard implantation type
The basic technology for the fabrication of highest quality silicon radiation detectors has been developed and introduced by J. Kemmer (see: publications). It makes use of a high purity planar process in combination with ion implantation doping. The principle process flow is briefly described in the following:
In a first step the high purity silicon wafers are passivated by an oxide layer with extremely low interface state density and low oxide charge necessary to minimize surface leakage current. This oxide growth is one of the basic key technologies for detector device fabrication.
Subsequently oxide windows are opened by photo lithography and wet chemical etching on the anode side to define the highly doped drift rings and anode region.
During the next steps the drift rings and anode as well as the voltage divider (not visible in the drawing), defining the lateral electrical drift field, are fabricated by three implantations.
Now the other side of the wafer is processed analogue: Opening of the oxide to define the entrance window, followed by the fabrication of the n-p+-contact by implantation technique.
Finally the metallization is deposited and structured on both wafer sides to enable wire bonding for the packaging of the chip. In addition to this basic process flow a high transconductance FET can be integrated within the anode area using the same technology (not shown in the picture).
The described technology enables the realization of large area silicon detectors with a low capacitance anode and low leakage currents. Hence a typical SDD can even be operated at room temperature with good performance. In our standard product line different detector layouts are offered.
The active areas of the first generation of SDDs were hexagonal shaped. In this way, the detectors can be easily combined to large area multi-channel detector arrays. Now the active areas of the standard SDDs are circular shaped, because the collimators are circular, and thus one can take advantage of the complete active area.
