4375/5375 ECEN - Spring 2005 - Microstructures Laboratory
EXPERIMENT # 1: REVERSE ENGINEERING OF INTEGRATED CIRCUITS
Week of 1/17/05 Experiment #1: Reading: Reverse engineering of integrated circuits Jaeger 9.2: MOS transistor layout and design rules HP4145 basics: ece-www.colorado.edu/~bart/ecen4375/hp4145.htm
The purpose of this experiment is to familiarize the students with actual circuits and the testing of such circuits using the HP4145 parameter analyzer. Circuits previously fabricated by students as well as commercial integrated circuits are examined using a reverse engineering approach. 1.1 You receive a processed wafer containing several single devices, test structures and circuits. Identify the aluminum metal, the field oxide, diffusion oxide and gate oxide. Write down the observed color for each oxide. Identify a transistor and draw a top and crosssectional view like the one in Fig. 9.10 e). Make a picture of the layout to your report. Draw a stick diagram as well as a circuit diagram. Identify the input(s), output(s), power supply and ground. Is it an analog or digital circuit? Can you identify the function of this circuit?
1.2
Set up a program on the parameter analyzer to measure the I characteristics of a pMOS -V transistor. The intention is to obtain a set of characteristics as shown in figure 1. Keep in mind that we are measuring p-MOS devices, so that all voltages and currents will be negative.
Drain current (mA)
2.5 2 1.5 1 0.5 0 0 5 10 15
Drain voltage (V)
Figure 1: I-V characteristics of a n-MOSFET
Bart Van Zeghbroeck - 01/24/05 - LAB experiments ECEN4375 - page 3
ECEN 4375/5375 - Spring 2005 - Microstructures Laboratory
Pick a transistor with 10 m gate length and measure the W/L ratio. Apply initially a drain-source voltage from 0 to -5 V (using VAR1) and step the gate-source voltage from 0 to -5 V in steps of -1 V (using VAR2). Adjust the voltages if necessary to obtain reasonable I-V characteristics. Measure another transistor with identical layout and overlay the two I-V curves, using the STORE and RECALL feature of the instrument. (on the soft key menu) If the I-V curves differ substantially measure a third transistor. Add your initials to the plot as well as the W/L ratio by editing the comment line (COMMNT softkey). Measure the output conductance (gd = dID/dVDS) in saturation (i.e. VDS < VGS - VT). Plot the I-V curves using the PLOT button on the instrument: PLOT 200, 200, 8000, 6000 [EXECUTE]. You can save the program with the data on disk using SAVE Dxxx [EXECUTE], where D indicates that the data is stored with the program and xxx is a name of your choice. 1.3 Set up another program to measure the square root of the drain current as a function of the gatesource voltage (VAR1 ranging from 0 to -5V, increase the range if necessary). As example is shown in Figure 2.
(Drain Current)1/2 (A1/2)
0.05 0.04 0.03 0.02 0.01 0 0 2 4 6 Gate Voltage (V)
Figure 2: Square root of the drain current versus gate voltage Apply a large enough voltage at the drain to ensure that the transistor is in saturation. Fit a straight line to the measured curve using the CURSOR, SHORT MARKER and LINE softkeys on the extended (EXTN) softkey menus. (See also the HP4145 Basic commands file). Identify the threshold voltage of the device. Turn of the microscope light, measure the square root of I again, fit aline to the curve and D determine the threshold voltage of the device in the dark. Again add your initials and the W/L ratio of the transistor to the plot by editing the comment line.
Bart Van Zeghbroeck - 01/24/05 - LAB experiments ECEN4375 - page 4
ECEN 4375/5375 - Spring 2005 - Microstructures Laboratory
Plot the graph using the PLOT feature and save the program and the data. experiment(s): Additional 1.4 Modify the program of section 1.3 so that you vary the bulk-source voltage, VBS, (VAR2 ranging from 0 to 10 V is steps of 2.5 V). An example is shown in Figure 3.
0.05 0.04 0.03 0.02 0.01 0 0 2 4 6 Gate Voltage (V)
Figure 3: Square root of ID versus the gate-source voltage for different bulk souce voltage. Measure the threshold voltage at each bulk-source voltage as well as the slope. Since the slope is very similar, make sure you use the same procedure for each measurement. Add you initials and the W/L ratio on the comment line. Plot the graph and save the data.
Bart Van Zeghbroeck - 01/24/05 - LAB experiments ECEN4375 - page 5
(Drain Current)1/2 (A1/2 )
ECEN 4375/5375 - Spring 2005 - Microstructures Laboratory
Report # 1: Due Week of 1/24/05.
READ THIS BEFORE THE LAB AS WELL AS BEFORE LEAVING THE LAB TO ENSURE THAT YOU HAVE ALL DATA NEEDED TO COMPLETE THE REPORT The lab report consist of a brief summary, describing the experiment, its goal and purpose and the key results and conclusions. In addition answer the following questions in sequence. Place graphs, pictures and other material gathered during the lab period in the report with a caption. Do not attach it as an appendix. Report questions: a) List the color of all three oxides. Provide the top and cross-sectional view of the transistor you observed in the lab. Add a picture of the layout to your report. Draw a stick diagram as well as a circuit diagram. Identify the input(s), output(s), power supply and ground. Is it an analog or digital circuit? Can you identify the function of this circuit? What is the output conductance (gd = dID/dVDS) of the transistor you measured? Indicate the gate voltage at which you measured the output conductance. Include the I-V curve plot in your report. Add a figure caption. What is the threshold voltage of that same transistor as obtained from the curve? Attach the plot to your report. Fit the measured curve to the following expression: |ID| = /2 |VGS - VT| |ID| versus VGS
b)
c)
and extract the parameter ( = = p Cox W/L). From the parameter (= K) find the hole mobility p in the channel and compare it to the bulk hole mobility in the substrate. Assume the substrate is a 2 cm phosphorous-doped ...