Barriers to Best Practice

BARRIERS TO BEST PRACTICE

The Interplay of Technological, Social, Economic, and Political Impediments

Massachusetts Institute of Technology

Leaders for Manufacturing Program

TEACHING GUIDE

“Barriers to Best Practice” is a case about making technology choices in a semiconductor manufacturing firm. The case offers both engineering and managerial content from which to focus class discussions. As the title implies, technology, social, economic, and political factors are discussed with respect to proposing and implementing a technological change. Environmental issues are given high coverage in this case. The primary lessons to teach with the case include:

the importance of defining critical performance metrics for a process technology;
the importance of weighing the multitude of factors that play a role in making technology decisions;
and the importance of considering the environment and industry trends at the time a change will be made.

Potential Questions for Class Discussion

What are the technological advantages of the methanol-iodine solution? What are the critical performance metrics for the wafer cleaning process?

Is it possible to place a value on workplace safety? Is there a social cost involved in disposing the inert calcium fluoride cakes in landfills? To what extent should these factors play a role in technology decision making?

How cost-effective is the methanol-iodine solution relative to the HF solution? What would make the methanol-iodine solution a more economically desirable substitute? What other factors should be included in a cost-benefit analysis of the two alternatives?

The chart shows that the costs of disposal are approaching the materials costs. What ratio can be anticipated for five years hence?

What is the real economic cost of disposal in terms of plant equipment, people, scavenger fees, and the greater society? Will the total economic value change in five years?

What trends in chemical recycling does the industry expect? What impact on cost can be forecast? What features must a solvent recovery system have in order to be feasible for the semiconductor industry?

Would you propose that Semicon take on the risk of developing the methanol-iodine solution at this time? Why or why not? Water usage is increasingly a limit to factory volume throughput. How would this trend influence your decision?

What other groups might you expect to resist this change? How would one best address the conflicting interests of the vested parties?

Partial Answers to Questions

Question 1

Technical advantages: smother and more stable wafer surfaces, larger processing windows
Critical performance metrics: gate oxide integrity

Question 2

Not easy to quantify the benefits of increased safety
Social cost involved in disposing inert cakes could become evident in the future.
To what extend safety and social factors are considered depends on the ethics and social responsibility of the firm (as well as governmental requirements).

Question 3

Considering only the cost of chemicals, the methanol-iodine solution is at least 8 times as expensive as the dilute HF solution.
It would be more economically desirable if methanol could be recycled efficiently. Alternatively, if the cost of DI water increased sharply, then the methanol-iodine solution would become a more economically viable alternative.
Other factors besides material costs that are important to consider in the cost-benefit or return-on-investment (ROI):
cost of building and operating a closed-loop recycling system for the methanol-

iodine solution (the cost of the system depends on the volume of solvent to be

recycled, the level of emission control necessary, and purity)

savings involved in eliminating the HF treatments and landfill disposal
savings on water (especially in places where water conservation is of concern)
savings involved in eliminating the extra clean and oxidation step in the manufacturing process (has implications for capital savings, material savings, as well as intangibles such as throughput time)
product yield savings (from the increase in oxide integrity and the increased stability of the surface)
costs to design and produce wafer cleaning stations specifically for methanol and iodine solutions
the cost of requalifying products (which could be substantial for large, high-volume semiconductor manufacturers)

Question 4

The ratio of disposal cost to material cost will most likely increase as more and more environmental controls are put in place.
The ratio could reach one or greater than one (disposal cost equals the material cost, possibly even more).

Question 5

Real economic cost will grow.
In five years, the effects of chemical disposal on the landscape will become more apparent, and thus resistance to disposal will grow.

Question 6

Trend is towards more and more recycling, especially in-house recycling
As recycling becomes more common, the costs should decline.
Solvent recovery features: high purity, high HAP and VOC control

Question 7

Students can argue both sides; the answer is not clear.
Increasing water usage and cost would make the methanol-iodine solution more attractive.

Question 8

The EPA and other environmental groups— They strongly discourage high-volume use of solvents, especially without HAP and VOC control measures.
Possibly customers— They would have to requalify the process technology (a time-consuming and costly procedure); new direct materials usually require customer notification and approval.