Today in class I did two activities. First we did a flow chart showing how we go from a pile of sand to a silicon wafer. The second activity was a CMOS sandwich which is shown in the picture. I used the image from figures 3.22 and 3.23 in "Semiconductor Manufacturing Technology" by Michael Quirk as a guide and the students made CMOS sandwiches according to the following guidelines:

1. Bread is the silicon substrate.
2. Ketchup is P-doped silicon
3. Mustard is N-doped silicon
4. Cheese is oxide
5. Meat is metal or polysilicon

They need to remember to put the gate oxide under the gate polysilicon where it contacts the silicon substrate. Also we forgot to put in the interlayer oxide with contact holes. Here is an example of a finished sandwich.

This was a fun activity and makes you really think about the three dimensional structure of the CMOS device. Since our class is near supper time this makes a good activity.

Here is a generic CMOS layout: