Jens Janssen Diploma Thesis - Prof. Dr. Norbert Wermes ...

Figure 3.3: The ATLAS hybrid pixel module. The module readout electronicsis mounted on a polyimide printed circuit board (flex-hybrid). The flex-hybridis attached with an adhesive to the bare module (sensor bump bonded to 16FE-I3 chips). The flex-hybrid also provides high-voltage and low-voltage to theattached components. The sensor is wire bonded through a hole in the flexhybridexposing the sensor backplane (p-side). Wire bonds are also used toelectrically interconnect the FE-I3 readout chip to the flex-hybrid.of irradiated sensor material (see section 3.4.2). The use of lightweight materialsis crucial to reduce multiple scattering. The contribution of the pixel detectorto the total inner detector material budged is of the order of 10% X 0 (radiationlength) and 0.05% ⁄ (interaction length) at ÷ =0[6].There are two types of local support structures: staves and sectors. A staveholds 13 pixel modules while a sector holds eight pixel modules. Each barrellayer consists of di erent numbers of staves (22 staves for the b-layer, 38 forthe second and 52 for the third layer) and each end-cap disc is made of eightsectors. This leads to a total number of 1744 pixel modules for the entire pixeldetector.3.3 FE-I3 Pixel Readout ChipThe ATLAS FE-I3 pixel readout chip is implemented in a 0.25 µm CMOS fabricationprocess. The die has a size of 5.4mm◊ 11 mm. 3.5 million transistorsare fabricated on silicon using radiation tolerant design rules 2 to withstand the2 On transistor level: the NMOS transistors are separated by p + guard rings. Also a deepsub-micron technology is beneficial for radiation hardening. Due to the small MOS gate oxidethickness the upcharge is reduced significantly. On design level: single event upset (SEU)tolerant redundant structures/blocks/registers and parity checking. For more information see14