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Comparison standard and graded substrate,

simulation with ISE-TCAD

Andrei Dorokhov,May 14 , 2007

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Doping profiles and the geometry

Standard (uniformly doped) substrate

Andrei.Dorokhov@IReS.in2p3.fr 3

Doping profiles and the geometry

Graded (linearly doped) substrate

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Particle energy loss distribution and one pixel geometry

Pwell

Nwell

Nepi

Pepi

Electron, 2keV

SiO2, 1nm

Backplane

Backplane One pixel layout

TOX

Energy deposition

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Electrons collection

Electrons density (saturated color scale, in the n-well the actual density much larger)

Standard and Graded

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Resultscce %,standard

cce %, graded

90% collection time ns, standard

90% collection time ns, graded

hit pixel 5.8 26 143 16

cluster 2x2 13 32 192 20

cluster 3x3 24 40 206 22

cluster 5x5 49 41 227 23

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Conclusions

1.Charge collection in the graded substrate much faster (~10 times), and in the order of 16-23 ns

2.In the graded substrate the charge collection in 5x5 cluster smaller by 20% but in the seed pixel ~5 times larger -> much smaller spread