The hardest question for a TCAD applications engineer is: "When will the new release be available"? The second hardest question is: "How predictive is TCAD"? The reason the second question is so difficult is that there is no simple answer. Some things can be predicted well, others things cannot. Recently, I heard that a CEO asked "Is TCAD predictive yet"? Here is my answer. You're welcome to use this in your TCAD marketing.

TCAD: Yesterday's problems solved tomorrow!

Being able to "predict" yesterday's problems is actually a significant accomplishment.

What does "predictive" mean?

Accuracy versus New Technology

Accuracy

One definition of "predictive" is accurate simulation of known technologies.

Semi-empirical approach.

New Technology

Another definition of "predictive" is the ability to simulate new technologies.

Requires fundamental physical understanding.

Problems with Prediction Accuracy

Difficult to define a single "accuracy" metric
that applies to an entire technology.

There are always some aspects that are simulated well,
and others that are not (half empty/half full).

Problems with Predicting New Technology

Elusive goal.

Technology is always changing (new materials),
as is the level of physics required (how fine is an atom?)

Notes on Accuracy Requirements

There is value in semi-accurate (non-predictive?) results,
if you know where the weak links are.

Trends can be as insightful as absolute results.

Metrology Analogy

Can we measure linewidths yet?

We can measure 1 um rather well.

There is significant noise at 0.3 um.

Summary

"Predictive" is a relative term.

Predictiveness changes as technology changes.

Our ability to be "predictive" is limited by our physical understanding, which in turn is limited by our metrology.

Michael Duane
June 1996