Chapter 8.03
I-V
Probe Station
(iv)
1.
Introduction
The Signatone S-1150 Analytical Prober, with Bausch & Lomb
MicroZoom microscope and the following equipment is available for device testing.
This manual describes only the operation of the probe station.
2.
Description and
Operational Overview
The probe station consists of the following:
► Bausch & Lomb MicroZoom Microscope
with 3 objectives: 2.25X (blue), 8X (green), 25X (gray)
► 5" Vacuum Chuck Stage with X, Y, Z
and Θ motion
► 4 Micromanipulators
► Z-Motion Adjustable Platen
► HP 4145A Semiconductor Parameter Analyzer
► Tektronics 576 Curve Tracer
► HP 34401A Digital Multimeter
► HP 6237B Power Supply
► HP 3312A Function Generator
► Tektronics 475 Oscilloscope
The light source for the B&L MicroZoom microscope is located
on the table, left of the station, and has three intensity settings. Please be
sure to turn the light off when you are through using the system.
Instrumentation
►
HP 4145A manual is on top of the equipment
►
HP 4145A BNC connectors are marked for SMU connections
The microscope can be displaced independently from the chuck in X,
Y and Z (focus) directions
The platen is the metallic shelf to which three micromanipulators
are held by vacuum. The large handle on the left side of the system raises and
lowers the platen and the probes. This handle should always be in the up
(rearmost) position when you leave the system.
A micromanipulator is moved by pressing the button at its base to
release the vacuum, and gently sliding it to the desired position. Be careful!
The micromanipulators have a tendency to "stick" and may move very
suddenly from their position if you exert too much force, causing the probe or
the micromanipulator itself to jam into another part of the system and damage
it.
The various chuck motion controls are located as described here:
X Motion: Crank at right
front of station.
Y Motion: Crank at left
front of station.
Z Motion: Knob to left at
base of chuck.
Θ Motion: Knob in front
at base of chuck.
The chuck vacuum used to secure the sample on the chuck is
controlled by a toggle switch on the left hand side of the station.
The strategy used to set up a sample for testing is first to set
the probes up correctly, and then to bring the probes and the sample into the
same focus plane. This will get you to a position from which it will be easy to
make the minor adjustments necessary to probe the devices without damaging
either the probe tips or the sample.
3.
Operating
Procedure
Use the following procedures to set up a sample for probing. Take
extreme caution at all times not to jam the probes into each other or into the
sample, as this will cause the probe tips to be bent into a hook, at which
point they must be changed. Changing the probes is tedious, so the care you
take in handling them is well worth the effort. If the probes hook, it is the
user's responsibility to change them.
New probes are available at the front desk in 406 Cory to replenish your
personal probe supply.
Before beginning,
check that the system is in standby condition as follows:
Light off;
Platen elevated (handle in rearmost
position);
Vacuum off;
Probes raised well above chuck.
1. Make sure that the chuck is
sufficiently low that when the platen is lowered, the probe tips to not bottom
out on the wafer (it should have been left this way by the previous user). Make sure that the microscope is
reasonably well centered.
2. Put the wafer on the chuck and turn
on the vacuum.
3. Rotate the chuck theta adjustment as
needed to "square" the wafer.
Be careful not to rotate the chuck so far that the vacuum tube gets
wrapped around the shaft driving the chuck.
4. Turn on the lamp. Move the X and Y
of the chuck to place the area of interest under the microscope. The 2.25X
magnification is recommended, as is the widest field of view for the alignment
procedure.
5. Raise the probes' Z adjustment all
the way up. Put the X and Y adjustments near the middle of their ranges.
6. Lower the platen.
7. Holding the vacuum switch on the
micromanipulator in, move each micromanipulator so that its probe is under the
microscope and a few millimeters above the wafer. Look at the probe tip from the side, not through the
microscope.
8. If needed, adjust the height of the
probe tip as follows.
a) Move the micromanipulator so that the
probe is away from the chuck and accessible to you.
b) Gently retract the sleeve away from the
probe while holding onto the top of the probe with flat-tipped. This will allow you to move the
probe. Use the tweezers to slide
the probe up or down as necessary. If the probe is too long on top and
threatens to hit the objective, you can either cut the top with the wire
cutters or bend it over using the tweezers. Wire cutters are available in the “IV Probe Station” drawer
located below the station.
c) Allow the sleeve to return to its normal
position. It will hold the probe
in place. Move the probe back over the chuck and check that it is nearly level
with the other probes.
d) The used probe tips should be placed in a
"Sharps Box" (not the regular trash) to avoid injuring the custodian.
9. Lower each probe
until it comes into focus. Move
the probes to the spot to be probed. Finally, lower them onto the wafer. You
will know that the tips are on the sample when they appear to "slide"
in the direction they are angled.
10. Devices with the same bond-pad pattern can
be probed by simply raising the platen, moving the chuck to so that the new
device is in view, and lowering the platen.
When switching wafers, the probes only need to rise slightly using
the micromanipulators; they can be raised up the rest of the way using the
platen.
The microscope can be moved independently from the chuck in order
to inspect the entire device at high magnification while the probe tips stay in
position.
11. Make sure that the cable connections are
correct. Because poor or missing
connections occur frequently on the probe station, it is worth doing a
"sanity check" by gently touching pairs of probes together and
checking that the wires you have connected to the probes are indeed shorted
together.
Attention: Do not connect
HP 4145A and the curve tracer together.
Check and make sure that they are not already both connected to the
probe station.
12. When you are finished, return the system
to standby by raising the probe tips so that they will not touch a wafer when
the platen is lowered, raising the platen all the way, turning off the lamp and
all the equipment you used, turning off the vacuum, moving the chuck out from
under the microscope, and removing your sample. If used, make sure that the
curve tracer is left on the lowest voltage scale. Disable the system.
13. To reiterate, when you are done with the
probe station, raise both the probe tips AND the platen so that the next user
doesn't jam the probe tips into his wafer, damaging both.
14. Users are required to maintain a supply of
replacement probe tips. During
qualification, users must show their probe-tip supply (minimum of two) to the
Superuser.
One way to store spare probe tips is to put a piece of thick
two-sided tape in a plastic dish. Probes are placed on the tape with their tips
hanging over the side of the tape, in free space. The dish is kept in the
user's storage space with the lid on.
