Sensor design and

mass test system development

Y. Kwon(Yonsei Univ.)

First real scale prototype chip from CERN

Our involvement

• Participation in chip design • Preparation of mass test system

CHIP DESIGN

Chip design opportunities

• Interesting approach based on CIS technology • Joint efforts with Prof. M. K. Song @ Dongguk Univ.• 2013-2014 : two master degree course students • 2014-2015 : two doctorate degree course students

– Student 1 : Daehyeok Kim• Continuation from 2013• Involvement in front end development

– Student 2 : Sungjoo Lee• New involvement• Past experiences in analog/digital circuits.

Front end under study

Interesting features

MASS TEST SYSTEM

Issue for the mass test system

• 50k delicate pixel sensors– Test configuration

• Probe card• Chuck• Test definition : Laser, readout

– Automation (machine vision + robot, commer-cial solution available)• To pick chips from tray, • load them on chuck, • test them according to the test configuration, • and return to the holder.

Minimum system to do custom chip test.

Probe-card

PAD layoutTotal 103 pads to make contact

Task 1, probe card

FPGA

CPU

ETH

ER

NET

Specification

1. 103 x 2 = 206 pins.

3. 8 LEDs to check probe card position by eye.

4. Contact status check at every 10 ms.

5. Contact status report by ethernet.

0. Dual pins for each pad Pin A for external connection (power/ground/IO), Pin B to check pin contact with the pad

2. 14 + 3 relays as switches when we decouple pin A and pin B

PAD sizeWe want dual pin contact for each pad.

Probe needle layout

Invisible

Chip

Programming option

• Computer + ethernet– Slow, but flexible

• On-board CPU– In-between

• FPGA– Fast, but limited

Pin A

Pin B

Input

Algorithm to check contact

1. Disconnect power/input using relay.2. Send 1.8(V) logic pulse to each digital input pad via

pin A and read pin B.

If no pair read back, raise chuck via .If any pair reads back, 3. Start careful adjustment ’. 4. Send 1.8(V) sequential logic pulse to other digital input

pad via pin A and read pin B.

5. Raise ’ up until all input pad pairs read back.6. Send 1.8(V) sequential logic pulse to digital input pads

via pin A and read pin B. (We will skip step 6 if we worry damage by electrical shock).

7. Raise ’ up until all input pad pairs read back.8. FPGA pull down for power pin B, FPGA pull up for ground pin B. 9. Disconnect FPGA output for pin A.10. Connect power.11. Check FPGA pin status12. Raise ’ up until all pin B status is OK.13. Disconnect pin B for analog input.

Use LED to display current status properly.

FPGA flexibility enables variation of algorithm.

Chuck

Transparent chuck?

Suction control

One hole

Would sensor be flat on the chuck?

Problem

ChuckVacuum holeChuck

Sensor

Solution

More small holes, air-tight chuck

Chucks in preparation

We are evaluating the optimal configuration.

Test definition : Laser, readout

Test definition?

• Basic elements are ready.• Open chuck in page 24– Laser (1000-1100 nm)?– X-Y stage with optical mask

• Requires further communication with CERN

Status

• Optimization in progress with the de-livery of proto type sensor.

• R&D in coordination with CERN --- We exchange experiences.