J. Breibach, W. Karpinski, K. Lübelsmeyer, G. Pierschel  
I. Physikalisches Institut RWTH Aachen,  D-52056 Aachen, Germany
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Experiments at the forthcoming LHC will place stringent requirements on electronics used in 
the tracking detectors of charged particles, especially for those components which will be 
installed close to the beamline. Devices will be exposed to irradiation levels around 50 Mrad 
and 10exp14 particles/cm2 over their life time . Nevertheless, low noise operation must be 
preserved, timing resolution must remain adequate and power consumption per channel must 
be kept to a tolerable level. The technology used determines the quality of the whole readout 
system. To make the best choice and to prepare alternatives for the mass production the CMS 
Pixel Collaboration is investigating two radiation hard processes: DMILL and RICMOSIV.
In our laboratory we have tested the applicability of enhanced RICMOSIV (0,8 um SOI 
CMOS) technology for pixel detector front-end electronics. To this purpose we have 
measured the DC, AC and noise parameters of NMOS and PMOS transistors built in this 
technology before and after irradiation with gammas from Co60 to a total dose of 50 Mrad. 
All devices remained functional after irradiation and showed no anomalous behaviour. The 
threshold voltage shifts of the top channel were less than 140 mV for PMOS and 200 mV for 
NMOS transistors. The transconductance decreases only by 10% for PMOS and 20% for 
NMOS transistors. No radiation induced leakage current was observed over the entire range 
of the test. The devices exhibit low noise characteristics. After 30 Mrad the white serial noise 
increases by 10% for PMOS and 30% for NMOS. 
A pixel detector readout chip has been successfully implemented in both the DMILL and 
RICMOSIV processes. The prototypes include a number of functional blocks that are crucial 
for the final front-end. The chips consist of 704 pixel cells organized in 11 double columns 
with 32 pixels in each column. The pixels have a 125um x 125um square shape. Each pixel 
cell contains a preamplifier, shaper, comparator, analogue memory, flag register, and shift 
register controlling the readout . The gain of the preamplifier as well as the peaking time of 
the shaper are adjustable. The threshold of the comparator is controlled by a 3 bit DAC to 
accommodate variations of the parameters of the transistors. The double column periphery is 
equipped with control logic, which recognizes a hit in a pixel, a twelve-bit buffer for time 
stamping , and readout logic controlling the data transfer from pixel to periphery. The 
architecture of both chips is identical but we have changed the layout of the Honeywell chip 
to benefit from the advantages of the RICMOSIV process: high transistor density and three 
metal layers. Two of these layers are used for interconnections while the third is used entirely 
to shield the pixel detector against the transients on digital lines. The comparison between 
layouts of the chips shows that to implement the same functions we consume up to a factor of 
two less area in RICMOSIV than in DMILL technology.
Results from tests of the Honeywell prototype without detector show that the chip is fully 
functional before and after irradiation. (up to 30 Mrad of Co60 photons). Up to now we have 
observed only no significant changes due to the irradiation. Detailed measurements of the 
RICMOSIV and the DMILL chips in the same test setup are in progress and will be presented 
at time of the workshop.


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The CMS Pixel Collaboration is investigating two radiation hard processes, DMILL (Temic/MHS) 
and RICMOSIV-SOI (Honeywell), for the production of the front-end electronics. To 
evaluate the applicability of the technologies to this project a readout chip for a 22x32 pixel 
detector array has been developed. Chips were fabricated first in DMILL process (PSI32) and 
then we translated this architecture to the RICMOSIV technology. 
For both implementations detailed measurements are presented of the pulse shape, threshold 
dispersion, time walk, noise, and power consumption following irradiations up to 30 Mrad. 
For NMOS and PMOS transistors built in RICMOSIV process we summarise also the DC and 
noise parameters measured before and after irradiation with gammas from Co60 for a total 
dose of 50 Mrad. 
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