Status of the Planar Edgeless Silicon Detectors

Gennaro Ruggiero

TOTEM Collaboration Meeting 09/11/2005

Results AchievedThe Device Electric characterisations and test beams have shown the reliability

of our development of planar edgeless detector employing the Current Terminating Structure (CTS)

The characterisation of the edge is on the way (see Hubert’s talk on Thursday)

The cut at the sensitive edges has been the limit of our development …but has never compromised it!!!

We do not have a clear idea on the limit of this development and how We do not have a clear idea on the limit of this development and how close to the physical edge we could still go.close to the physical edge we could still go.

The Assembly of the Detector The assembly of detectors on the module has been very poor:

Almost 50% of the sensors employed in the test beam of last year have been found partially or totally unglued or even broken

Plan

Very optimistic and tight! Does not take into account possible Very optimistic and tight! Does not take into account possible delays rising for instance from bureaucracy etc…delays rising for instance from bureaucracy etc…

Pre-Series Run (I)The detectors of the pre-series will have the same sensitive area, pitch adaptation on the device, alignment marks and identificationpads of the detectors foreseen for the mass production and can beemployed in the experiment.

Of the 4 detectors (per wafer) in this pre-series run 1 of them will have a thinner insensitive volume at the edge (34um or 27um) still keeping the same principles of the CTS development

Double bonding pads

Finding the limit of the CTS

The volume of this production is of ~60 devices

Insensitive edge of 47um

Pre-Series Run (II)

If this test is satisfactory (in terms of yield and performance) we could still adopt this technique for the mass production

Line of the Cut

DiamondDiamond sawDry etching Dry etching

(CNM Barcelona)(CNM Barcelona)

“Precise” diamond saw VS dry etchingA fraction of this production will be sent to the CNM of Barcelona

for the dicing with dry etching

10um5u

m

Pre- Series, Mass production & QA testsYield definition & Optimisation of the QA Tests Strategy on the

Pre-Series runAlthough the acceptance tests on the pre-series leading to the design aimed

for the final mass production will be short, further test on these pre-production run will continue leading to the optimal definition of the QA tests that will be employed for the devices from the mass production.

QA tests will have to include: Visual Inspection

Rings/Electrodes/Strips Integrity Electric Tests

IVs from CTR, CR and BE and their stability Single Channel test: Strip current/ oxide quality/ inters trip capacitance

Part of these tests require equipments that we are missing so far. The investigation on outsourcing these tests is ongoing. Ian Bohm (Prague) has shown interest

Other tests will have to follow once the detector is assemble on the module

Sensor’s Passport

Identification

History in a Production Database Data from QA tests need to be stored The history has to be updated also in the following steps

with information on the assembly and following tests with detector bonded to the chips

The information have to be retrieved during the experiment run-time and re-updated if needed

Binary Coding

Detector on the module: Alignment StrategyStill missing.. time has come to face this problem Mechanical

Simple procedure but requires precise cuts Optical

Aligning marks on detectors matching marks on the card and on the frame

Might require a complicate machine and/or a very careful operator

Other Urgent Matter: storage space for the detectors and modules!!!

In parallel…

The “planar edgeless detector” is a very young development and requires furthers studies to ensure us the full understanding.

The simulations made so far on these devices have been always assuming a “guessed” boundary condition at the edge. The data so far obtained have clarified many points but not all. Elias, has started a deeper study with more advanced simulation tools. Me and Vladimir are continuously discussing with him the progress of this work.

We have submitted an INTAS project to develop radiation hard edgeless detectors. If the project is approved , will allow us to pursue these studies by delegating a good part of them to other institutes who have the facilities for specific measurements that should set a final word on this learning process.