Homework Assignment #2

EE 477 Spring 2012 Professor Parker

Hardcopies due in the course boxes on the third floor of EEB 5 PM 2/7/12

Ecopies due 11:59 PM 2/7/12 using the "Assignment" Function on DEN

To ensure academic privacy, please use a cover page on your homework hard copies that does not contain any work.

1. (35%) Design a new type of binary counter that continuously counts down the even numbers from 6 to 0 skipping number 2 and then counts up the odd numbers from 1 to 7. So the sequence should be 6,4,0,1,3,5,7 and then repeat itself. The current number will change when the clock falls. If reset is asserted asynchronously, the current number will become 0 and should stay zero until the next negative clock edge, even if reset is subsequently unasserted. Reset is an asynchronous signal. Each bit of storage should be a negative edge-triggered flip flop. Each flip flop should contain two latches, as described in class. The data loaded into the flip flop will depend on the data currently in the flip flop along with data in the other flip flops.

Your counter should be designed at the gate level. Use NAND gates to build the multiplexer at the input to each latch.

Show your solution for the counter as a gate-level diagram.

2. (15%) Draw a transistor (circuit) level diagram for a compound gate that implements the following Boolean function

H = /[A * (B + C) *E + (/B) * D *F + B * (C + /D) * G +(/A)(/F)C +(/A)B(/G)+BC(/F)]

without simplifying the Boolean function.

You can assume that A,B,C,D,E,F,G as well as their complementary inputs are available. Label the sources and drains of all the transistors.

3. (10%) Sketch the side view (slice down into the silicon) of a staggered contact that connects metal2 to metal5 using colored pens or pencils.

4. (5%) In a positive photolithographic process, why do we expose the photoresist to UV light?

5. (5%) When and where do MOS parasistic transistors form?

6. (5%) In the fabrication video, what color was the silicon crystal that was sliced into wafers?

7. (15%) In the figure below for an N-well process, show the cross-section along the horizontal green line.

8. (10 %) Sketch the steps in the photolithographic process necessary to create and pattern the M1 to M2 via.