Semiconductor detectors for detecting electromagnetic radiation are based on the measurement of free charge carriers which are generated by the radiation in a semiconductor component. The charge carriers produce an electrical signal, which is conducted over at least one connecting conductor to a measuring device. The design of the connecting conductor represents a general problem in the production of semiconductors. The detector together with the connecting conductor must be practicable to manufacture and easy to handle, but must also not impair the detector function via the connecting conductor.
There are, for example, semiconductor detectors for locally resolved radiation detection which have multiple semiconductor electrodes situated in a semiconductor substrate (known as strip or track detectors). In these detectors, insulated connecting conductors are guided directly over the semiconductor electrodes to a substrate edge. However, such a conductor crossover is possible only when there is no interfering difference of potential between the connecting conductor and the semiconductor electrodes.
Drift detectors are known for high-resolution radiation detection in the field of X-ray spectroscopy (see L. Strüder in “Nuclear Instruments and Methods in Physics Research A,” Vol. 454, 2000, pp. 73-113, and DE 34 27 476 A1, for example). A drift detector comprises, for example, a semiconductor substrate made of weakly n-doped silicon which has a strongly n-doped, centrally located anode on one surface (top side), and has a reverse contact made of a strongly p-doped semiconductor material on the opposite surface (bottom side). Annular semiconductor electrodes made of a strongly p-doped semiconductor material, concentrically arranged about the anode are also provided on the top side. The semiconductor electrodes are each kept at a fixed electrical potential which becomes increasingly negative as the distance from the anode increases. In the effective region of the electrodes this results in total depletion of the semiconductor substrate, and also produces an electrical drift field in the semiconductor substrate. Radiation interactions cause free electrons to be generated in the semiconductor substrate which are driven through the drift field to the anode, so that the electrical signal at the anode is a measure of the energy and/or intensity of the radiation.
The design of the connecting conductor to the anode has thus far represented a significant problem in the drift detectors. On account of the large differences in potential between the connecting conductor and the semiconductor substrate together with the semiconductor electrodes, the above-referenced guiding of the connecting conductor over the semiconductor electrodes would lead to erroneous signals caused by undesired charge carrier amplification, and/or to electrical breakthroughs. The known silicon drift detectors are thus characterized by a freely guided contacting of the anode from the top side of the semiconductor substrate to the outside. Electrical connecting conductors are guided from the anode to a spatially separate connector unit or measuring device through the half-space adjoining the top side.
The free guiding of connecting conductors has several disadvantages. The electrical contacting is difficult since the connecting conductors are typically attached by ultrasound bonding, whereby the semiconductor substrate tends to undergo undesired mechanical vibrations. As a result, faulty contacting may occur. Damage in the sensitive region of the semiconductor substrate upon bonding may cause the detector to fail. Furthermore, the free guiding of connecting conductors has disadvantages with regard to the stability of the contacting and the combination of drift detectors in groups.