Micro strip detector development. Li Long and Ralf Röder. CiS Institut für Mikrosensorik GmbH Konrad-Zuse-Str.14 D-99099, Erfurt [email protected] 10th CBM Collaboration Meeting: Dresden, September 25 -28, 2007. Outline. The design of CBM detector. The process of CBM detector.
The design of CBM detector
The process of CBM detector
Results: IV, CV of detectors
The analysis of test structures
The layout for second iteration
The first run of CBM detector manufacture:
We have started 2 bathes of CBM detector manufacture.
50% of the first batch are finished and detectors are delivered.
The rest of the wafers are processed to implantation step and waiting for
the feedback of final test of the finished chips.
2. Punch through biasing
3. Junction side: 15° stereo angle, double metallization, Multi guard.
4. Ohmic side: 90° stereo angle, P-spray isolation.
5. Three different types of detector, unit in µm
1. Punch through (7, 10, 13, 16µ)
2. Field plate (2, 0, -2µ)
n-Si <111> 4~6kOhmcm, 285µm
Double side polished
Double side metallization is developed and introduced to the
The other process steps are standard for irradiation detector.
1. CBM_01 Detector front side
2. CBM_01 Detector back side
The IV curves of detectors form Wafer #7
(The dark current of bias ring with guard rings floating)
Active area: SD=27.5cm2, SB1=4.2cm2, SB2~B5=1.7cm2
Dark current of D at operation bias ~10nA/cm2, at 300V < 1µA.
The C-2 ~v curve of full detector from Wafer #7
(The capacitance of bias ring with guard rings floating is measured)
Full depletion voltage 53.8V
Flat band voltage:
Vfb -> qox qox=CiVfb
Surface generation current
The leakage current vs gate voltage at different bias can be measured.
We can obtain the flat band voltage and surface generation current.
From these we can calculate the oxide charge, interface recombination velocity.
The effect of dicing edge
This group of test structure has 6 resistors with different width
s = A + B*x
Conductance as a function of resistance path width
In frame of INNOWATT project “SPID “, we are planning the second
run of manufacture to test more possibilities.
Status: simulation & layout finished.
Punch through, Poly-silicon
Charge, Micro discharge
pspray , pstop, field plate
The effect of dicing edge
Width=5µ, 235 Square.
Bias resistance 1MOhm->4.3k Ohm /Sq
For double side strip detector, one side of coupling capacitance
must sustain the operation voltage.
Since large coupling capacitance is preferred, thin oxide will be
used, which may breakdown before the pn-junction breakdown.
300V breakdown voltage is enough.
Poly silicon resistor
Field distribution of junction side
Field distribution ofOhmic side
A baby detector with pstop
resistance for p front 66kOhm/cm
resistance for n back 44kOhm/cm
coupling capacitance front 21pF/cm
coupling capacitance back 15pF/cm
resistance for front metal 25Ohm/cm
resistance for back metal 16Ohm/cm
resistance for cross connection 28Ohm/cm