Vacuum pumps should be turned on and both air bottles should be open.

At the moment, we are using straight 7A needles. We’ll try ones that are pre-bent by the manufacturer at some future date.

Old needles can be pulled out with tweezers. They should be put in the old needle box.

New ones should be cut off to shorten them by about 1 cm and bent down at about a 30-45° angle.

Push them into the probe station rod and rotate so that the section angled down is in line with the rod.

Cover must be down and lights off for all tests.

Turn on all three meters and supplies before you start so they can settle.

Vacuum control should be on Auto.

Light has a separate control box with Off/On and intensity controls.

CHECK the needle heights before hitting controls to move the chuck.

LOAD on control panel moves out chuck and turns off vacuum automatically.

HOME on control panel turns on vacuum and moves probe station to "chuck up" position.

STOP turns off external control.

Plugs on outside of hood set according to test performed.

Wiring inside the hood is never changed.

Probe needle height adjustment turns clockwise to move needle down, counter-clockwise for up.

Watch out that microscope lens doesn’t hit probe needles.

The Voltage plug (yellow) connects to the back contact bias supply and the high level input of the capacitance meter.

The Capacitor plug (green) connects to the low level input of the capacitance meter.

The Bias plug (red) connects to the sensitive ammeter.

The Guard plug (blue) connects to the insensitive ammeter.

The bias supply and meters are grounded through the Ground plug (black).

The needles holders are labelled Current (left) and Capacitance (right) but these labels don’t mean anything.

This test checks for full depletion voltage using testkeys on the cut-away section.

Look for testkey with PN etched label. These are in the shape of a solid circle surrounded by a circular guard ring. Use the largest one.

The test requires bias on the backplane, the capacitor probe on top of the circle, and the guard ring grounded.

Plug the current probe into the green socket and the capacitor probe into the green socket???

Place the right needle in the center of the solid circle (capacitor) and the left needle on the guard ring (the separated, outermost ring). Ignore the sublines.

Connect the Voltage plug into the Chuck socket, the Ground plug into the Left Needle socket, and the Capacitor plug into the Right Needle socket.

Labview program is PN_SOG_ONO_tester.

Program had input to specify testkey type.

Use the default voltage step of 2, Vmin of 0, and 51 steps.

Record temperature and humidity and press Start.

Check warnings and press Continue. The program asks about starting point and whether coordinates are OK, just say Yes.

The program cycles through the voltage steps, measuring capacitance.

For the database, use user sitester and password phobos.

The results are best viewed on the Si sensor web page under PN key. The bottom panel on the page shows the log plot and line fit that the program uses to calculate the full depletion voltage (Vfd).

This test checks the insulating layer thicknesses by measuring capacitance on testkeys on the section of the wafer cut away from the sensor.

It is typically done for only one sensor per batch.

Use testkeys labeled ONO or SOG. These are solid circles surrounded by a circular ring. These circles connect to conductors on opposite sides of the appropriate insulating layer.

Labview program is PN_SOG_ONO_tester.

The right needle goes in the center of the pad and the left needle goes on the guard ring.

Connect the Ground plug into the Chuck socket, the Voltage plug into the Right Needle socket, and the Capacitor plug into the Left Needle socket.

Follow instructions for PN testkey, except use only one voltage.

This test checks the value of the polysilicon resistors used in the bias voltage isolation circuit. It uses a special test structure on the cut away section.

There is a long row of pads labeled "poly". The two needles probe adjacent pads which connect to a progressively increasing resistance. There are 23 pads but the last pad is skipped so it takes 11 steps.

To start, put one needle on the first pad and the second needle on the next pad.

Connect the Voltage plug to the socket for one needle and the Bias plug to the socket for the other needle.

Labview program is PolySI_tester.

The program prompts you for the first location (needles on the first two pads) and then the final location which has one needle on the next to last (22nd) pad and the other needle on the 21st pad. The chuck should be down but you will need to turn brake off to move needles. Use the lowest magnification to see the pads and needles. Note that when you move to the final location, you do NOT put the needles down or change their height, just their position. After one more prompt confirming that the coordinates are OK, the program starts.

This test measures the guard and active area currents of the sensor as a function of bias voltage.

Place one needle on a bias pad and the other needle on a guard pad. Pads are near the readout side of the sensor, clearly labeled B & G.

Connect the Voltage plug to the Chuck socket, the Bias plug to the socket for the appropriate needle and the Guard plug to the other needle socket.

Labview program is IV_test.

Don’t forget to enter the temperature and humidity. Use the default of 0 to 150 in 5 volt steps.

For database writing, the datasource is phobos_mit. Click on Logon to Oracle, username is Sitester, password (entered twice) is phobos.

Guard typically breaks down around 120 volts. Bias current should rise, plateau, and then rise again.

This test checks the capacitance versus voltage characteristic of every readout pad on the sensor to look for broken readout lines or shorted pads.

This test requires a temporary bond connecting the bias and guard ring lines.

The sensor should be oriented so that the readout bonding pad row runs from front to back. For sensors with readout on only one edge, that edge should be to the right. For double readout sensors, bond pattern 0 goes on the right.

Don’t put the needles down until the program prompts you to do so. You will start with the right needle on the readout bonding pad (which will be on the left) and the left needle on the bias line (which will be on the right). Having the needles cross in this way allows you to see both needles so you avoid accidents from raising or lowering the wrong one.

The right needle should contact near the right edge of the readout pad.

Connect the Voltage plug to the Chuck socket, the Bias plug to the left needle (bias line) socket, and the Capacitance plug to the right needle (readout pad) socket.

Labview program is CV_scan.

Start the program, fill in the information (everything with a green label), and hit RUN. Use the default of 0 to 100 volts in 2 steps of 50. Following the directions in the program, put the right needle on the first readout pad (at the back right of the sensor) and lift it. You will then be prompted to move the needles so that the right needle is on the last readout pad in the pattern (front right) and the left needle is on the guard ring. Leaving the needles down, start the program running.

One option is to check the current with the lights on first. An overflow in the current meter verifies that you are making good contact. The real test should be run with the cover down and the lights off.

The program reads out about 700 pads in an hour.

For double readout sensors, you will later need to put the needles on the pads on the other edge of the sensor. You start by lifting both needles (the program says to lift only one). The chuck moves automatically to the approximate location of the readout pads at the back left of the sensor (readout pattern #7). Fine tune both needle positions. The left needle is still put on the bias line so the needles don’t cross each other anymore. The right needle should again be on the right edge of the readout pad. Use the microscope movement control (NOT the chuck or needle movements) to see the two needles. Leaving the needles down, start the program running again.

This test checks for shorts within the pad itself (in the insulating layers that form the coupling capacitor).

The needle setup is the same as for the CV test except that the right needle should contact the left edge of the readout pad. This way, you don’t keep digging up the same pad location, the center of the pad is left undamaged for later bonding, and you can check visually what tests have been performed.

Connect the Voltage plug to the left needle (bias line) socket, the Bias plug to the right needle (readout pads) socket, and the Ground plug to the Chuck socket.

Labview program is PINhole_scan.

Follow the instructions from the program (see CV Scan instructions for details).

In this case, there is no easy way to read a current to get information about the quality of the contact since the normal reading for a good pad is no current which is the same thing you get with bad contact.