1. MALTA Investigator I-V Measurements
Shiyu Wang (Boston University), Enrico Schioppa (CERN), Carlos Solans(University of Oxford)
CERN, Project Update 4

2. Recap: Motivation for IV Measurements
To observe and validate possible “punch-through” effect.
Sudden current spike between
Substrate (depleted zone) and pwell.
Caused by potential difference between pwell and sub overcoming isolation layer in between (depletion layer).
Expected to occur at large potential differences
between pwell and sub (also expected to see a intersection between the variable Pwell voltage and the sub voltage)
Modified Process
(Source from ATLAS Readout Meeting)

3. Setup, updated
Malta Readout Meeting
Measurements carried out in building 28/2-017 (Laser Telescope Lab)
Using probe station setup.(Bad decision, we keep having needles broken and bad resolution of the chip, probe station now retired)
Room kept at constant 21oC and stable humidity. (Again bad, we could use a fridge for the chip instead, may be expensive, but we are using fridge now)

4. Setup - Pwell/Sub GNDs Common
Malta Readout Meeting
Pwell and deep Pwell
SUB V+
VRESET

5. Results – Pwell/Sub GNDs Common
Malta Readout Meeting
First two measurements, problems encountered:
W12 sector example
W4 sector example
104
104
Substrate Current [A]
Substrate Current [A]
Pwell 0.00V Pwell 1.00V Pwell 2.00V Pwell 3.00V
Pwell 0.00V Pwell 1.00V Pwell 2.00V Pwell 3.00V Pwell 4.00V 10 3 10 3
Pwell 4.00V
102
Pwell 5.00V
Pwell 6.00V
102
Pwell 5.00V
Pwell 6.00V 10 10 1 1
101
101 5 10
15 20
Substrate Voltage [V]
Behavior does not make sense, as compared with the modified CMOS process, likely due to broken chip or flawed probe station or…
Breakdown voltage inversely proportional to Pwell voltage. (too strange to accept, let’s just change the setup and test again)

6. Setup - Pwell GND reference
Malta Readout Meeting
Deep Pwell
(Sub-Pwell) Δ V+
VRESET
All PSU GNDs are common / shorted

7. Results - Pwell GND reference
Malta Readout Meeting
W12 – E
(Sub-Pwell) Δ [V]
Currents observed by ΔV PSU. Breakdown voltage occurring following similar pattern to previous measurements (inversely proportional to pwell voltage). Negative currents between substrate and pwell in negative Δ regions.
Punch-through defined by difference in currents observed between pwell PSU and Δ PSU (we need more example of this).

8. Results - Pwell GND reference
Malta Readout Meeting
W4-A (MALTA have 12 different sectors)
Punch-through observed
at lowest pwell voltages
104
Punch-Through Current [A]
Punch-Through Current [A]
6000
Pwell 0.00V Pwell 1.00V
Pwell 0.00V Pwell 1.00V
10 Pwell 2.00V 3
Pwell 2.00V
4000
Pwell 3.00V Pwell 4.00V
Pwell 5.00V
Pwell 3.00V Pwell 4.00V
2000
102
Pwell 5.00V Pwell 6.00V
Pwell 6.00V
2000
4000
6000 10 1
101 5 5 10
15 20
 Voltage [V] 5 5 10
15 20
 Voltage [V]
Current difference between Pwell PSU and ΔV PSU, which could be evidence for the punch through current. (Punch through effect proved at W4 sector)

9. Results – Something more
Malta Readout Meeting
W12 – E
No punch-through observed
for W12.
104
Punch-Through Current [A]
Punch-Through Current [A]
Pwell 0.00V
2000
Pwell 0.00V
Pwell 1.00V Pwell 2.00V
Pwell 1.00V Pwell 2.00V 10 3
Pwell 3.00V Pwell 4.00V
Pwell 4.00V
Pwell 5.00V
Pwell 3.00V
102
Pwell 5.00V
Pwell 6.00V
Pwell 6.00V
2000 10
4000 1
6000
101 5 5 10
15 20
 Voltage [V] 5 5 10
15 20
 Voltage [V]
Current difference between Pwell PSU and ΔV PSU. (Punch through current)

10. TJ-Monopix pixel matrix
Pixel size: 36.4 μm x 36.4 μm, use standard process
the 64x16 pixel matrix includes 8 different sectors,
we use them to reset mechanism and process of the original MALTA chip
8x2 special pixels in the top corners to monitor the analogue signals on the
collection electrode and front-end output for different splits
1800 µm
5000 µm
TJ-Monopix with synchronization and fixes for improved charge collection

11. MALTA Telescope System
6 MALTA and Monopix sensor-based planes connected to 6 FPGAS
Centralized powering
Simulation estimates yield
3.9 um resolution (much efficient than 6 single MALTA sensors)
Plan to install at CERN SPS first before apply them on ATLAS ITK
Expected Beam Location