Update of CMS Process Quality Control

Sensor Meeting, CMS TK Week, 9.4.2003, CERN

FlorenceAnna Macchiolo

Carlo Civinini

Mirko Brianzi

StrasbourgJean-Charles Fontaine

Jean-Laurent Agram

ViennaThomas Bergauer

Margit Oberegger

Anna Macchiolo, Sensor Meeting, 9th April 2003 3

Inter-calibration

Results: Good agreement in all the measurements except • Aluminum resistivity• Inter-strip resistance

Circulation of 15 Test-structures

Vienna Strasbourg FlorenceStrasbourg Florence ViennaFlorence Vienna Strasbourg

Anna Macchiolo, Sensor Meeting, 9th April 2003 4

Aluminum resistivity

Florence Vienna Strasbourg30210415061610 29.9 25.5 35.630210421850314 27 24.5 31.730210421738304 26.8 25.2 32.530220126124234 24.3 21 27.530220126124237 21.8 21.8 27.4

•Differences in the measured aluminum resistivity in the three labs are of the order of 20-25 %

•The corrections we have to apply to take into account additional resistive contributions (from the probe-card, cables, switching matrix) are of the same order of the Al resistances

•Further investigations are going on

Al in m per square

Anna Macchiolo, Sensor Meeting, 9th April 2003 5

Inter-strip resistance

•Since we are measuring currents of few pA the spurious currents introduced by the probe-card make a big difference.

• Our measurements must be intended as lower limits on the real resistance

• We are able to detect the cases where the specification

Rint > 1 G

is not respected

OBJECT_ID VIENNA SBG FLR30210321847706 22975 136541 5277430210421174025 14602 152151 5702830210921054623 33915 185462 45326130220621600117 22344 234265 26346430220822000117 16473 238639 160180

Rint in M

Anna Macchiolo, Sensor Meeting, 9th April 2003 6

Software update

The acquisition software has been made faster by:

Decreasing the LCR meter integration time for the CV on diode and on MOS, where we do not need extreme precision

Optimization of the LCR driver, cutting useless initialization and configuration at every step

The time needed for the full analysis of a standard moon has decreased (for example in Florence it takes now 23 minutes

instead of 48).

The analysis VIs have changed to remove infinite loops in the cases where the fit fails

Anna Macchiolo, Sensor Meeting, 9th April 2003 7

Results from last STM sets measured

are of good quality

• low metal resistivity

• low V fb

All the PQC measurements are inside specifications with the exceptions shown in the following …

Perugia 22-24-25-26-27

Vienna 8-9

Anna Macchiolo, Sensor Meeting, 9th April 2003 8

Perugia 24 (STM): defects on the surface of many structures

Early breakdown of one mini-sensor with the surface heavily damaged

Anna Macchiolo, Sensor Meeting, 9th April 2003 9

Perugia 25 (STM)

3 structures from Perugia 25 have low depletion voltage

Wafer resistivity around 10 K per cm

Our request is

3.5 < <7.5 K per cm

The surface current measured on the GCD is very high for one structure but Vfb is inside limit.

First time we don’t see the correlation between the two problems. Only one sensor has been shipped from this batch.

We suggested to reject the corresponding sensor.

Anna Macchiolo, Sensor Meeting, 9th April 2003 10

Perugia 15-16-17-18-19-23

Pisa 61-62-63

Karlsruhe 05

Vienna 11-12-13

Results from last HPK batches

100 < Vdepl < 250 V

Almost perfect for the PQC qualification. The only notable problem is the depletion voltage, much lower than our specification

Anna Macchiolo, Sensor Meeting, 9th April 2003 11

HPK bulk resistivity

• … but last HPK batches have a substrate resistivity over 4 Kper cm

•Our original request on wafer resistivity is

1.5 < < 3.0 K per cm

• HPK has asked to enlarge the range to

1.25 < < 3.25 K per cm

since the wafer supplier cannot assure narrower specifications

Depletion voltage

measured on the diode

Compiled will all data in DB

Series production

Anna Macchiolo, Sensor Meeting, 9th April 2003 12

STM bulk resistivity

Depletion voltage

measured on the diode Inside our specifications

3.5 < < 7.5 K per cm

Anna Macchiolo, Sensor Meeting, 9th April 2003 13

Dependence of PQC variables upon production time (1)

All the Vfb values outside our limits come from production weeks 209 and 210

Compiled with all the data inserted in the DB up to now

STM

HPK

Anna Macchiolo, Sensor Meeting, 9th April 2003 14

0

500

1000

1500

2000

2500

3000

Before week 220: resistivity around 27 m per square . Strip width at the mask nominal value of 10 m

After week 220: resistivity in the range 15-23 m per square.

From the strip profile it’s difficult to disentangle the contribution to the strip height of the passivation oxide and of the metal layer but we can clearly observe:

Increase of 1 m in the strip height

Decrease of about 2 m in the strip width

Sheet Structure: Al strip profile measured with

a Scanning Near-field Optical Microscope (SNOM)

at LENS - european laboratory for non-linear spectroscopy

Fluctuations in the Al resistivity probably due to the fact that the numbers of squares used in the calculation was not correct (STM communicated the new numbers in October 2002).

10 m

7.7 m 2.7 m 1.6

mMetal resistivity in STM

Anna Macchiolo, Sensor Meeting, 9th April 2003 15

0

500

1000

1500

2000

2500

3000

10 m

7.7 m 2.7 m 1.6

m

2.7 m

1.6 m20 m

18 m

Metal strips in the Sheet Structure (STM)

302 104 203 870 17 : = 26.5 mper square

302 104 238 602 09 : = 20 mper square

Anna Macchiolo, Sensor Meeting, 9th April 2003 16

Dependence of PQC variables upon production time (2)

0.5 < Cint < 1.3 pF

0.5 < Cint < 1.3 pF

Cac > 16 pF

Cac > 18 pF

STM STM

HPK

HPK