Introduction to ic manufacturing technology

It would probably be interesting to spend a little time seeing how integrated circuits are made. This chapter will be long ondescription, and rather short on equations (yay!). This is not to say that there is not a lot of analytical work in the ICfabrication process. It's just that things get very complicated in a hurry, and so we probably are better off just looking at most processes from a qualitative point ofview.

Let's start out by taking a look at the state of the industry, and remark on a few trends. is a plot of IC sales in the United States over the past 30 years. This mightnot be a bad field to get into! Maybe there will be a job or two out there when you are ready to graduate.

There has been a steady shift away from bipolar technology to MOS as is shown in . Currently, about 90% of the market is composed of MOS devices, and only about 10% ofbipolar. This is likely to be the case for some time to come. The change in slope, where MOS starts taking over frombipolar at a more rapid rate about 1987 is when CMOS technology really started to come into heavy use. At that point, bipolarTTL logic essentially faded to zero.

As you probably are aware, devices have been getting smaller and smaller, and chips have been getting bigger and bigger withtime. A most impressive plot is one which shows the number of components/chip as a function of time.

One of the main drivers for this has been feature size, which shows the same nearly exponential behavior ascomponents/chip. This is plotted in for your education. What is interesting to note about this is thatcertain "doom sayers" have been predicting an abrupt halt to this curve for some time now. It stands to reason that you cannot image something which is finer than $$ , the wavelength of the light you use to project it with. However, by going to theultraviolet, and using a variety of image enhancing techniques, lithographic engineers continue to be able to make finer andfiner structures.