The development of p-type silicon detectors for the high radiation regions of the LHC

This thesis describes the production and characterisation of silicon microstrip detectors and test structures on p-type substrates. An account is given of the production and full parameterisation of a p-type microstrip detector, incorporating the ATLAS-A geometry in a beam test. This detector is an AC coupled device incorporating a continuous p-stop isolation frame and polysilicon biasing and is typical of n-strip devices proposed for operation at the LHC. It was successfully read out using the FELix-128 analogue pipeline chip and a signal to noise (s/n) of 17+-1 is reported, along with a spatial resolution of 14.6+-0.2 mu m. Diode test structures were fabricated on both high resistivity float zone material and on epitaxial material and subsequently irradiated with 24 GeV protons at the CERN PS up to a dose of (8.22+-0.23) x 10 sup 1 sup 4 per cm sup 2. An account of the measurement program is presented along with results on the changes in the effective doping concentration (N sub e sub f sub f) with irradiation and the changes in bulk current. Changes in the effective doping concentration and leakage current for high resistivity p-type material under irradiation were found to be similar to to that of n-type material. Values of alpha=(3.30+-0.08) x 10 sup - sup 1 sup 7 A cm sup - sup 1 for the leakage current parameter and g sub c =(1.20+-0.05)x10 sup - sup 2 cm sup - sup 1 for the effective dopant introduction rate were found for this material. The epitaxial material did not perform better than the float zone material for the range of doses studied. Surprising results were obtained for highly irradiated p-type diodes illuminated on the ohmic side with an alpha-source, in that signals were observed well below the full depletion voltage. The processing that had been used to fabricate the test structures and the initial prototype that was studied in the test beam was based on the process used to fabricate devices on n-type material. Presented in this thesis are the modifications that were made to the process, which centred on the oxidation and ion implantation methods and the modifications to the mask which were made to try and improve device performance and yield during processing. 6 prototypes were successfully fabricated using the new process and subsequently evaluated electrically. Results are shown for the pre-irradiation leakage currents and coupling capacitor oxide integrity.