# Presentation: 801756

## ATLAS SCT BARREL MODULE PARCOMPONENTS AND PRODUCTION OVERVIEWJanet Carter, Cambridge

**TOPICS:**
**1.****	**** Barrel Module Requirements**
**2.****	****Module Component Production**
**3.****	****Module Assembly Clusters**
**4.****	****Module Specifications and Categories**
**Module QA Steps and Common Issues**
**Production Schedule**
**Summary**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## The Barrel Module

**2112 Identical ****Barrel Modules**** required for SCT mounted on**
**     ****4 Barrels**** (B3, B4, B5, B6) **

**Bridged wrap-around hybrid** –
**copper-polyimide flex glued**** ****on carbon-carbon substrate**

**4 single-sided** ***p*****-in-*****n *****ac-coupled***** ***
**silicon microstrip sensors****, 80 ****μm pitch,**
**mounted back-to-back, 40 mrad**
**stereo rotation angle**

**12 128-channel ****ABCD3TA**
**binary readout ASICs**

**Thermo-mechanical baseboard -**
**encapsulated thermalised pyrolitic**
**graphite with fused BeO facings**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Module Requirements

**Detailed in Barrel Module FDR, May 2001:  SCT-BM-FDR-4**** ****(**_**[http://atlas.web.cern.ch/Atlas/GROUPS/INNER_DETECTOR/SCT/module/SCTbarrelmod.html](http://atlas.web.cern.ch/Atlas/GROUPS/INNER_DETECTOR/SCT/module/SCTbarrelmod.html)**_**)**
**Summary of Principal Module Requirements:**
**MIP Detection efficiency >99% with noise occupancy ≤ 5****×****10****-4**
**Intrinsic r-****φ**** point resolution per single-side measurement of 23 ****μm (80 μm  pitch sensor strip)**
**Giving 17 ****μm precision in ****r-****φ**** co-ordinate and 500 ****μm in z from back-to-back sensor pair with stereo rotation angle of 40 mrad**
**Precise mechanical assembly to simplify digitisation and alignment in ATLAS **
**Low mass - <1.2% X****0 ****per module, averaged over sensor area **
**1.17% X****0 ****achieved**
**Electrical performance maintained up to radiation levels of 2****×****10****14 ****n****eq****cm****-2 ****(barrel 3 with safety factor)**
**Verified through proton (CERN PS) and neutron (Llublyana) irradiation and lab and test beam studies (sensors, ASICs, modules)**
**	**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Summary of Principal Module Requirements (continued):

Cold operation in ATLAS (cooling pipes ~ -20oC) – module must routinely withstand thermal cycling between -25oC and +30oC
Tested by thermal cycling in module QA
Module safe against thermal runaway of sensors after irradiation in ATLAS
Thermal designs of baseboard, hybrid and cooling block – thermal simulations and tests with irradiated modules

**Cold operation in ATLAS (cooling pipes ~ -20****o****C) – module must routinely withstand thermal cycling between -25****o****C and +30****o****C**
**Tested by thermal cycling in module QA**
**Module safe against thermal runaway of sensors after irradiation in ATLAS**
**Thermal designs of baseboard, hybrid and cooling block – thermal simulations and tests with irradiated modules**
**	**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Module Component Production

**Hybrids**** – in production in Japanese industry – talk by S. Terada**
**Baseboards ****– in production by collaboration at CERN – talk by A. Carter**
**Glues ****– purchased centrally and distributed to module assembly sites**
**Silicon Sensors and ASICs**** – status briefly summarised here:**
**All SCT barrel sensors manufactured by Hamamatsu Photonics, Japan**
**Identical detectors for all modules:  64mm****×63.6mm×285 μm thick**
**Single-sided, ac-coupled, 768 readout strips at 80 ****μm pitch**
**Milestones – all achieved, on schedule:**
**Sensor FDR:**** April 1999**
**Sensor PRR following evaluation of pre-series:**** August 2000**
**Start of series deliveries:**** January 2001**
**Delivery (including purchase options) completed:**** May 2003**
**QA completed by collaboration (pre-irradiation and sampling after 3****×10****14**** p.cm****-2 **** 24 GeV/c proton irradiation at CERN PS)**
**Sensor quality is excellent**

**Silicon Microstrip Sensors**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Series Deliveries (Barrel + Endcap)

**Series ****Deliveries**** (Barrel + Endcap)**

**Purchase options**
**added**

|  
Contract  | Ordered (including purchase options) | 
Delivered |
| --- | --- | --- |
| Japan | 6000 | 5913 |
| Norway | 1950 | 1950 |
| UK | 2750 | 2750 |
| Total | 10,700 | 10,613 |

**Barrel 99% Complete on 1****st**** May 2003**

**  ****Pre-Irradiation:**
**All quantities within specification**
**Very low leakage currents**
**     ****Typically <200 nA at 500V bias at 20****o****C**
**>99.9% good readout strips**

**Initial**
**current at**
**350V bias**
** ****(20****o****C)**

**Number of**
**Strip defects**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Post-Irradiation:
Within specification for operation at ~400V bias after 10 years of LHC

Points to note for module construction concerning high bias voltages:
The edges of the sensors are at the back-plane voltage
Great care must be taken to avoid conducting debris shorting to grounded areas – eg bond wires, openings in sensor passivation in guard rings, bond pads etc
Module production and assembly to barrels must be a clean process

On Barrels 3 and 4, modules must be tested to 500V bias during assembly and commissioning at CERN to ensure there are no HV shorts that would prevent final post-irradiation HV operation
So I-V of modules are tested up to 500V in assembly QA (even though initial modules will operate at <200V bias)

**Within specification for operation at ~400V bias after 10 years of LHC**
**Points to note for module construction concerning high bias voltages:**
**The edges of the sensors are at the back-plane voltage**
**Great care must be taken to avoid conducting debris shorting to grounded areas – eg bond wires, openings in sensor passivation in guard rings, bond pads etc**
**Module production and assembly to barrels must be a clean process**
**On Barrels 3 and 4, modules must be tested to 500V bias during assembly and commissioning at CERN to ensure there are no HV shorts that would prevent final post-irradiation HV operation**
**So I-V of modules are tested up to 500V in assembly QA (even though initial modules will operate at <200V bias)**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Pre-irradiation sensor ‘microdischarge’
A small fraction ( ≤ 2%) of sensors show ‘microdischarge’ (impact ionisation) pre-irradiation between 350V and 500V bias
Rapid current rise with bias voltage, but falls to normal levels with short time-constant (~30 mins) if bias maintained 
Not a problem for module operation in ATLAS:
Disappears after irradiation and type-inversion - field configuration changed:	

But will not use ‘mirodischarge’ modules for the inner barrels 3 and 4 as they complicate initial HV tests up to 500V during macro-assembly and commissioning

**A small fraction ( ≤ 2%) of sensors show ‘microdischarge’ (impact ionisation) pre-irradiation between 350V and 500V bias**
**Rapid current rise with bias voltage, but falls to normal levels with short time-constant (~30 mins) if bias maintained **
**Not a problem for module operation in ATLAS:**
**Disappears after irradiation and type-inversion - field configuration changed:****	**
**But will not use ‘mirodischarge’ modules for the inner barrels 3 and 4 as they complicate initial HV tests up to 500V during macro-assembly and commissioning**

**Example of smooth, normal I-V curves**
** ****of ‘microdischarge’ detectors up to **
**500 V bias after irradiation to **
**3****×10****14**** p cm****-2**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Front-End ASICs

**ABCD3TA ASIC **
**DMILL technology, fabricated by Atmel**
**Single-strip threshold binary readout**
**Threshold trimming for each channel**
**Performance meets requirements both **
**     ****pre- and post-irradiation, with ~1fC binary threshold**
**Series production released in July 2001 following PRR**
**~87% of SCT requirement for perfect ASICs now delivered and die identified after wafer testing **
**But Atmel may not deliver any more before the DMILL line is stopped**
**The SCT will use an ASIC with 1 bad channel on each module as necessary to make up the shortfall**
**Should have a negligible effect on barrel performance**

**Deliveries**
**stopped**

**ASIC Statistics**

| Lots delivered | 50 |
| --- | --- |
| Accepted wafers | 795 |
| Accepted wafer yield | 25.9% |
| Tested wafers rejected | 24.0% |
| Accepted perfect chips | 52,695 |
| % of total requirement | 87.5% |
| Wafers left to test | 0 |

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Module Assembly Clusters

**4 Barrel Clusters for module assembly:**
**Japan, Scandinavia, UK, US – reports from each on progress to-date**
**Clusters have developed different jigging and assembly techniques**
**Each builds to the same module specification**
**Site qualification process following FDR/PRR in May 2001 with documented requirements and module exchange before series module assembly can get fully underway**

| 
Cluster | 
Site Qualification Date | Number of modules to deliver to macro-assembly sites (Oxford, KEK) |
| --- | --- | --- |
| Japan | December 2001 | 800 |
| Scandinavia | Not yet | 400 |
| UK | June 2002 | 550 |
| US | April 2003 | 480 |

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Summary of Principal Module Build Specifications:
Detailed in Barrel Module FDR, May 2001:  SCT-BM-FDR-7 (http://atlas.web.cern.ch/Atlas/GROUPS/INNER_DETECTOR/SCT/module/SCTbarrelmod.html)
Electrical Performance
 <1% bad readout strips at 1fC binary threshold (noisy, dead, part-bonded, untrimmed, pipeline errors etc).  
Verified through a Characterisation Sequence test using custom SCT VME readout, prototype SCT voltage supplies and standardised DAQ and analysis code (SCTDAQ)
Module sensor leakage current < (sum of individual sensors + 4 μA) up to 500V bias at 20oC
Stable performance during 24 hour cold operation (hybrid at ~0oC)

All Modules classed for use in ATLAS satisfy the full electrical specification

**Detailed in Barrel Module FDR, May 2001:  SCT-BM-FDR-7 ****(**_**[http://atlas.web.cern.ch/Atlas/GROUPS/INNER_DETECTOR/SCT/module/SCTbarrelmod.html](http://atlas.web.cern.ch/Atlas/GROUPS/INNER_DETECTOR/SCT/module/SCTbarrelmod.html)**_**)**
**Electrical Performance**
** ****<1% bad readout strips at 1fC binary threshold (noisy, dead, part-bonded, untrimmed, pipeline errors etc).  **
**Verified through a *****Characterisation Sequence *****test using custom SCT VME readout, prototype SCT voltage supplies and standardised DAQ and analysis code (SCTDAQ)**
**Module sensor leakage current < (sum of individual sensors + 4 ****μA) up to 500V bias at 20****o****C**
**Stable performance during 24 hour cold operation (hybrid at ~0****o****C)**
**All Modules classed for use in ATLAS satisfy the full electrical specification**

**Module Specifications and Categories**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Mechanical Specifications
Principal in-plane parameters
    (further parameters define the hybrid position and angle)
    (y is perpendicular to the sensor strips to within half the stereo angle)		

**Principal in-plane parameters**
**    ****(further parameters define the hybrid position and angle)**
**    ****(****y is perpendicular to the sensor strips to within half the stereo angle)****	****	**

| 
In-Plane Parameter | Design Value | ‘Good’
Module
Tolerance | ‘Pass’
Module
Tolerance |
| --- | --- | --- | --- |
| Baseboard dowel mounting hole in x, mhx [μm]  | -6500 | ±30 | ±40 |
| Baseboard dowel mounting hole in y, mhy [μm] | -37500 | ±30 | ±40 |
| Baseboard dowel mounting slot in x, msx [μm]  | 38500 | ±100 | ±140 |
| Baseboard dowel mounting slot in y, msy [μm]  | -37500 | ±30 | ±40 |
| Mid-point of pair of front sensors in x, midxf [μm]  | 0 | ±10 | ±10 |
| Mid-point of pair of back sensors in y, midyf [μm]  | 0 | ±5 | ±8 |
| Separation of centres of sensors; front pair, sepf; back pair sepb [μm]  | 64090 | ±10 | ±20 |
| Rotation angles of the 4 sensors, a1, a3, a3, a4 [mrad]  | 0 | ±0.13 | ±0.13 |
| Half stereo angle between the front and back sensor pairs, stereo [mrad]  | -20 | ±0.13 | ±0.13 |
|  |  |  |  |

** ****The category ‘Good’ satisfies the agreed specification**
** ****The category ‘Pass’ is an extension to cover measurement error and the tails of  **
**    ****the observed distributions**
** ****Both ‘Good’ and ‘Pass’ modules will be used in ATLAS**

- SCT Barrel Module PAR - Overview

- 14th May 2003

##  Principal out-of-plane Parameters

| 
Out-of-Plane Parameter | Design Value | ‘Good’
Module
Tolerance | ‘Pass’
Module
Tolerance |
| --- | --- | --- | --- |
| Maximum deviation of lower sensor from module plane, maxZlower [mm]  | 0 | -0.2 | -0.2 |
| Maximum deviation of upper sensor from module plane, maxZupper [mm] | 0 | 0.2 | 0.2 |
| Module thickness [mm]  | 1.15 | ±0.1 | ±0.1 |
| Maximum deviation of lower sensor from common module profile, optimalmaxZerrorlower [mm]  | 0 | 0.05 | 0.07 |
| Maximum deviation of upper sensor from common module profile, optimalmaxZerrorupper [mm]  | 0 | 0.05 | 0.07 |
| RMS deviation of lower sensor from common module profile, optimalRMSZerrorlower [mm]  | 0 | 0.025 | 0.025 |
| RMS deviation of upper sensor from common module profile, optimalRMSZerrorupper [mm]  | 0 | 0.025 | 0.025 |
| Lower BeO cooling facing angle perpendicular to mounting line, b [mrad]  
(module cooling contact issue) | 0 | ±3 | ±5 |
| Lower BeO cooling facing angle parallel to mounting line, a [mrad]  | 0 | ±0.5 | ±0.5  |
| Lower BeO cooling facing concavity along the mounting line, 
loCoolingFacingConcavity [mm] | 0 | ±0.03 | ±0.03 |
| Maximum thickness of module at surface of large capacitors on hybrid,
capMaxThickness [mm]  (clearance issue) | 5.78 | 6.44 | 6.44 |

** ****Principal out-of-plane Parameters**
** ****Detector surfaces compared with a standard shape**
** ‘****Good’ and ‘Pass’ categories again defined**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Barrel Module Categories
Each produced module is assigned to one of the following categories:

From component availability and schedule requirements, ~90% of modules started in assembly need to be suitable for use in ATLAS

**Each produced module is assigned to one of the following categories:**
**	****	****	**
**From component availability and schedule requirements, ~90% of modules started in assembly need to be suitable for use in ATLAS**

| Category | Description |
| --- | --- |
| Good | Satisfies all electrical and ‘good’ mechanical specifications. |
| Pass | In ‘pass’ grade for 1 or more mechanical parameters.
Satisfies all electrical specifications. |
| Hold | Outside ‘pass’ grade for 1 or more mechanical parameters
and/or does not satisfy all electrical specifications.
Such a module is stopped in production and stored. |
| Fail | Could never be used in ATLAS (damage, gross errors). |
| Rework | Rework is needed before the module could be usable. |

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Module QA Steps and Common Issues

**Basic steps in module assembly (with small variations between Clusters):**

| Step | QA  after step |
| --- | --- |
| 1. Load 12 ASICs on hybrid | Electrical tests warm and cold |
| 2. Glue 4 sensors to baseboard | In-plane metrology |
| 3. Wrap hybrid around and glue to baseboard-sensor sandwich |  |
| 4. Wire-bond module | Metrology (in-plane and out-of-plane) following thermal cycling
Electrical characterisation warm
Long-term (24 hr) electrical test cold
Visual inspection |

- SCT Barrel Module PAR - Overview

- 14th May 2003

## A Common Electrical Issue: s-curves

**Noise-occupancy s-curves are part of module electrical characterisation**
**These are occupancy vs threshold for no injected charge**
**Normally they are smooth curves:**
**                               ****picture here**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## But coherent effects can build up between ASICs when digital activity is high and produce s-curve distortions at thresholds << 1fC
A severe example:

				picture here

**A severe example:**
**	****	****	****	****picture here**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Barrel Clusters have recently been studying all their available data because a high fraction (of the small number) of series modules completed by Scandinavia have severely distorted s-curves
Has caused a delay in Scand site qualification, in case of any association with the hybrid mounting technique used by Scand – they are now proceeding cautiously with a new method
But s-curve distortions are seen in varying degrees by all Clusters
An on-going study to look for correlations and differences between Clusters
Does it matter?
We think not, provided the distortions are well below (<0.3 fC) the operating threshold of 1fC – which they are
Noise Occupancy of module at 1fC is not affected
Effect reduces with irradiation 
Has not to-date caused problems in system test operation
The properties after irradiation and system operation will be further tested this summer using modules with the most severely distorted s-curves

**Has caused a delay in Scand site qualification, in case of any association with the hybrid mounting technique used by Scand – they are now proceeding cautiously with a new method**
**But s-curve distortions are seen in varying degrees by all Clusters**
**An on-going study to look for correlations and differences between Clusters**
**Does it matter?**
**We think not, provided the distortions are well below (<0.3 fC) the operating threshold of 1fC – which they are**
**Noise Occupancy of module at 1fC is not affected**
**Effect reduces with irradiation **
**Has not to-date caused problems in system test operation**
**The properties after irradiation and system operation will be further tested this summer using modules with the most severely distorted s-curves**

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Production Schedule 

**SCT Schedule requirements for macro-assembly imply:**
********I have made up these dates, which are later than the schedule*********
**There are further constraints on selecting the modules with the most robust high bias voltage characteristics for barrels 3 and 4**
**Nevertheless, sufficient modules should be available in time for the required completion of the first barrel - B3  **

| Barrel | Number of Modules to deliver | From Clusters | Delivery to be completed by |
| --- | --- | --- | --- |
| B3 | 404 | All | December 2003 |
| B6 | 706 | All | March 2004 |
| B5 | 605 | All | May 2004 |
| B4 | 504 | Japan | June 2004 |

- SCT Barrel Module PAR - Overview

- 14th May 2003

## Summary

**Sensors are in-hand and of very good quality**
**Problems with the end of ASIC delivery, but 1-bad channel chips can be used to make up the difference**
**Module assembly underway – now x% of total ‘Good’ + ‘ Pass’ requirement completed**
**Site qualification of the Scandinavian cluster is an urgent priority**
**Integrated assembly yield is still lower than the 90% target for all but the Japanese cluster (to be seen from the Cluster presentations)**
**Overall quality of modules is good – s-curves need careful monitoring and some more study**

- SCT Barrel Module PAR - Overview

- 14th May 2003