Objectives: Familiarize the students with often used instruments in the laboratory:

These two pieces of equipment will be useful in inspecting and characterizing the microstructures that you will  fabricate throughout the course.

None

II. Lab Work:

Warning: Laboratory equipment is delicate, so be careful when you use it. Take your time to setup and do the measurement, keep good notes of what you have done, and when in doubt consult the manuals or the instructors.

Samples: The test samples are in three wafer containers and they are color coded.

The "blue" coded wafer holder contains a "left-over" wafer from last year’s lab. This wafer had problems with open circuited piezo-resistors.

The "green" coded holder contains a wafer from an old run of the project that we are doing this year. Gold is used for metallization.

The "white" coded holder contains a tiny CMOS chip mounted on a glass wafer. This is how we will prepare small samples for inspection and characterization. The chip is fabricated in a commercial foundry in a 1.2 micron CMOS double metal, double polysilicon process.

Use the optical microscope to visually inspect the three samples. Use different magnification to obtain different views. Become familiar with the focus and position adjustment knobs.

Use the calibrated eyepiece to measure the distance between the fingers in one of the structures (interdigitated sensors ) on the "green" sample.

Measure the dimensions of the in the green sample.

Make a simple drawing for one of the structures on the "green" sample and mark the importantt dimensions.

Measure the depth of the etched wells in the backside of the pressure sensor on the "blue" sample.

Take a picture of the die ("white") sample. Make sure we can see the whole chip.

Task #2: Taking a profile of the surface using the profilometer.

The profilometer is a very delicate instrument so use extra caution when working with it. In particular, the lever must be forward when loading and unloading the samples. Scans are from left to right and they are 3mm in length. The Y position of the sample is adjusted using the knob on the left, the X position using the knob on the front (this is not very useful). The Z position is controlled by both the lever on the right side and the knob in front. CW rotation of the front knob raises the stage.

a) Use the profilometer to measure the thickness of the gold layer on the "green" sample and of the aluminium on the "blue" sample.

First initiate a baseline scan on the wafer next to the desired location by setting the instrument into manual mode and then pressing start. Use up or down arrows on the instrument to level the base so that the baseline doesn’t drift off the paper. Repeat until you get a good baseline -multiple scans may be necessary-, deposit the tip over the desired area and do an automatic scan.

b) Repeat the procedure to measure a stair like structure in the middle of the die on the "white" sample. Get a scan from one side to the chip to the other. Warning! You may have to do more than one scan.