This is an adaptation from an invited talk given at the tenth Annual International Workshop on "Micro Electro Mechanical Systems" in Nagoya, Japan, Proceedings IEEE Catalog Number 97CH36021, pages 9 to 13,

ABSTRACT

The field of micromechanics (also called MEMS or Micro System Technology or Micro Machines) describes a whole new realm of human endeavor.  This paper discusses:  Why has human interest in the small taken so long to develop?  What are the prospects?  What can we do to ensure the health of this emerging field?  Do small things have a grand future?
 

MANUSCRIPT

Perhaps things normally start small, and grow.  Man's habitats have grown from houses, to buildings, to skyscrapers.  Our ability to travel has increased from a few miles on foot, to horses, to trains, and now we can encircle the world in a few days.  Individually we work to make large accomplishments in hopes of enormous success.  We are enthralled with the big and significant and substantial.

The insignificant, insubstantial, and minuscule is usually beneath our concern.

And yet.

A dozen years ago, I was trying to persuade a machinist to build a very small structure.  He listened patiently for awhile, and then said 'Why do you want something small, a toy?  I can make you something that is big and good.'  In his mind, most people's mind, small things were cheap, and no more than a toy.  When H. A. Rowland (1848 to 1901, professor of physics at the Johns Hopkins University, Baltimore) went to make very small and accurate grooves for diffraction gratings, he used large machines, and buried them in even larger vaults for thermal stability.  Ten years ago, an eminent colleague at Bell Laboratories looked me in the eye, and said 'Your micro things will never amount to anything.  Large objects will always do a better job at a lower cost.'  This was very strongly the feeling at this time.

Even Feynman responded with good natured jesting to critics of small machines.  In his famous talk, There's Plenty of Room at the Bottom, [1] given at the American Physical Society meeting in 1959 he says "What would be the utility of such machines?  Who knows?  Of course, a small automobile would only be useful for the mites to drive around in, and I suppose our Christian interests don't go that far."  And in his 1983 talk, Infinitesimal Machinery,  [2] at the Jet Propulsion Laboratory he says "I also talked in the 1960 lecture about small machinery, and was able to suggest no particular use for the small machines.  You will see there has been no progress in that respect."

And yet.  There is something special about this field of small mechanical systems.

Most advances represent a specific technology.  The Scanning Tunneling Microscope for example, gives us the ability to detect and perhaps manipulate atoms.   High temperature superconductors hold the promise of efficient power transmission, and novel electronic circuits.  The diesel engine gives us a source of mechanical power.  Each of these is an important advance of a single thing.

The field we are contemplating here today is vast beyond our normal concerns.  It is the science and engineering and development and commercialization of a whole new realm of human enterprise.  I defy you to think of a large scale, macro, discipline in science or engineering that does not have a small scale, micro, equivalent.  Your challenge, should you decide to accept it, is the imaging of the macro into the micro.

You are the pioneers.  How you behave, how you interact with your colleagues, what areas you pursue, your understanding of how to develop a new science, the clarity of your vision, will define how this field explodes forth.

One thing giving me confidence in our future is the broad range of tools and techniques available.  We are not dependent upon a single tool solving a problem, there are many ways to make micro devices.  The designer has a host of fabrication techniques, actuators, and sensors at his command; and he should be free to choose the best for his purposes.  To define this field as a single technology is limiting it.

It is the richness of this field, and hopefully the collaboration between its practitioners, that will bear the sweetest fruit.

The original ingenious and intelligent systems were mechanical, things such as clocks that chimed and displayed dancing figures on the hour.  Electronics is now doing a superb job of providing this intelligence.  Complex calculations and decisions have now become inexpensive.  It is now the mechanical devices needed to interface electronics to the world that are expensive.  Fortunately micromechanical devices integrate well with electronics: one providing the intelligence and one providing the hands.  Electronics has lead much of the development of micromechanical devices by providing many of the tools and techniques, making the rapid advances possible.  This partnership is to great advantage.

Yet how did things insignificant in size gain a purpose?

Perhaps Johann Gutenberg gave an indication of the usefulness of small mechanical devices.  Gutenberg means good mountain, and indeed, in 1456 he set in motion a mountain of small mechanical devices (individual movable type) for the good of mankind.

For years the watch makers art has represented the limits of our micro excursion.  And the practitioners of the watch making art have succeeded admirably.  For example, the motor on a wrist watch has high efficiency, runs for years (even after being dropped), and cost less than a cup of coffee.  Yet, when I was talking with a gentleman who had designed many of the watches we wear, he said 'I have spent my life trying to make smaller mechanisms, and when you show me something really smaller, I do not know what to do with it.'  This is a common response to motors the diameter of a human hair.

Much that has happened in micromechanics was presaged by Feynman's remarkable talk, There's Plenty of Room at the Bottom.  [1]    Later Feynman gave a version of this talk to my college, and he is responsible for igniting my interest in the possibilities for the small.  If you have not, you should read the transcript of his presentation.

Yet making things too small to manipulate with human hands was one serious barrier to the exploration of the micro.  A number of techniques now make micro devices inexpensive to manufacture.

In 1967 the paper, The Resonant Gate Transistor,  [3]  described a structural-sacrificial fabrication technique.  In these initial experiments gold was used as the structural material and photoresist was the sacrificial material.  This is an extremely powerful technique that allows complete micro structures to be built without having to assemble components, a great advantage when dealing with components too small to see with the eye, or manipulate with the hand.  The 1983 paper, Polycrystalline Silicon Micromechanical Beams, [4] extended this work to the polysilicon-silicon dioxide, structural-sacrificial, material we now normally describe as surface micromachining.

A second powerful fabrication technique for making small things was discussed in the 1978 paper Anisotropic Etching of Silicon. [5]  A year later the paper Fabrication of Hemispherical Structures Using Semiconductor Technology for Use in Thermonuclear Fusion Research [6] describes how to make micro spheres filled with deuterium-tritium using isotropic etching.  These anisotropic and isotropic etching techniques in silicon and related materials are now commonly referred to as bulk micromachining.

The 1982 paper Production of Separation Nozzle Systems for Uranium Enrichment by a Combination of X-Ray Lithography and Galvano-plastics  [7] also presents an early application for microfabrication techniques in the nuclear power generation industry.  This technique is now called LIGA (in German Lithographie, Galvanoformung, Abformung), and makes plastic and metal parts with spectacular accuracy.

The above techniques demonstrate novel approaches to the manufacturing of micro parts:
v Surface micromachining makes parts without assembly.  It is as if an automobile was made by putting down alternate layers of steel and flour, and the last fabrication step was washing away the flour, leaving a completely assembled automobile, engine and all.
v In most manufacturing, the metric (measurement system) is defined by the tools used.  In contrast, bulk micromachining relies upon the metric in the material's crystalline structure to define the part.  The part helps define itself.
v LIGA, bulk micromachining, and surface micromachining use photons to shape the micro devices.

Other micromachining techniques are clever extensions of macro manufacturing techniques.  A nice description of these techniques is given in the paper Micro Machining by Machine Tools.  [8]

Extensions of single point diamond machining can make micro parts with spectacular accuracy of less than 0.01 microns (10E-8 meters or 100 Angstroms ! )  Diamond machining works well on most materials, except a few materials like steel.

Extensions of electro discharge machining, EDM, allows minute turbines, power generators, and orifices to be manufactured.  Sacrificial techniques, similar to surface micromachining, enable complex interior and exterior shapes.

Many other methods of making micro things are possible.  One example is Stereo Lithography.  A scanning laser beam writes the micro parts directly onto ultra violet curable epoxy, as discussed in the papers Real Three Dimensional Micro Fabrication using Stereo Lithography and Metal Molding [9] and Photoforming Applied to Fine Machining.  [10]

The race to more clever ways to machine micro parts has just begun.

The earlier disdain for the small and insignificant is gone.  Now I sense a growing excitement about the micro.

My fears are gone that the micro field would grow on 'isn't that neat' and then die when no purpose was found.  Enough people now recognize the importance of micro science and engineering and product development to ensure the field.

Things insignificant in size do have a grand purpose.

Yet, how to proceed?

First, we should work as a community, and profit from other's insights.

This  workshop (MEMS '97) is an excellent place to bring together disparate disciplines and ideas.  The hosting of this workshop by many different countries in the different regions of the world is strongly encouraged.  Also having only one session at a time helps bring people with different ideas into the same room.  And the support of students and their presentations help bring new ideas and people into the field.

Publishing excellent articles in archival journals is critical to the orderly development of the field.  Well written articles filled with new material help the authors and the field.  Poorly written material slapped together with one or two incrementally new results has the unfortunate effect of risking the reputations of the authors, and clogging the literature.

Many excellent research programs and developments have resulted from the collaborations between people with diverse backgrounds.  I especially encourage people new to this field to form collaborations with established groups.  The behavior of micro systems is substantially different from our normal macro experiences.

Second, a science grows by the unfettered competition of ideas, not people.

People should be free to suggest and work on the new.  Unfortunately it is easy to disdain the unfamiliar.

Scholarship requires an unbiased and careful evaluation of one's own and others work, an understanding of the previous literature, and honesty.

Journal articles must be fairly refereed, with a special tolerance given to new approaches.

Science is driven by people's excitement about  learning.

Third, we should build infrastructures that facilitate the growth of the field.

Much work is needed developing the basic science and metrology of this new field.  As the field prospers and grows, more resources should be devoted to a fundamental understanding.

Multi-user runs, where many projects share a fabrication run, help give access and capabilities to groups far removed from the fabricators.

Efficient use of journals, books, and the world wide web for the free exchange of information, ideas, experimental results, and computer modeling tools speeds the development of the field.

Fourth, we should not forget our purpose.

As a child, I read about the great scientists.  Men and women who have structured our understanding of the universe by their discoveries.  I wished I could have been with these great scientists, and shared in their adventure.

We are fortunate.

Though our work from day to day may seem insignificant in size, together our work is grand in purpose.

I wish you well.
 

REFERENCES

[1] R. Feynman, "There's Plenty of Room at the Bottom," Caltech's Engineering & Science magazine, February, 1960.  (Reprinted in Micromechanics and Mems: Classic and Seminal Papers to 1990, Edited by W. Trimmer, the IEEE Press PC4390-QCL, ISBN 0-7803-1085-3, January 1997, page 3.)

[2] R. Feynman, "Infinitesimal Machinery," Journal of Microelectromechanical Systems, Volume 2, Number 1, pages 4 to 14, March, 1993. (Reprinted in Micromechanics and MEMS,  page 10.)

[3] H. C. Nathanson, W. E. Newell, R. A. Wickstrom, and J. R. Davis, Jr., "The Resonant Gate Transistor," IEEE Transactions on Electron Devices, March, 1967.  (Reprinted in Micromechanics and MEMS,  page 21.)

[4] R. T. Howe and R. S. Muller, "Polycrystalline Silicon Micromechanical Beams," Journal of the Electrochemical Society: Solid State Science and Technology, June, 1983. (Reprinted in Micromechanics and MEMS,  page 505.)

[5] K. E. Beam, "Anisotropic Etching of Silicon," IEEE Transactions on Electron Devices, October, 1978. (Reprinted in Micromechanics and MEMS,  page 50.)

[6] K. D. Wise, T. N. Jackson, N. A. Masnari, M. B. Robinson, D. E. Solomon, G. H. Wuttke, and W. B. Rensel, "Fabrication of Hemispherical Structures Using Semiconductor Technology for Use in Thermonuclear Fusion Research," Journal of Vacuum Science Technology, May/June, 1979.  (Reprinted in Micromechanics and MEMS,  page 551.)

[7] E. W. Becker, H. Betz, W. Ehrfeld, W. Glashauser, A. Heuberger, H. J. Michel, D. Munchmeyer, S. Pongratz, and R.v. Siemens, "Production of Separation Nozzle Systems for Uranium Enrichment by a Combination of X-Ray Lithography and Galvano-plastics," Naturwissenschaften, 69, (1982), pages 520 to 523.

[8] T. Higuchi and Y. Yamagata, "Micro Machining by Machine Tools," MEMS 1993 Workshop on Micro Electro Mechanical Systems, Fort lauderdale, FL, USA, February, 1993, pages 1 to 6.

[9] K. Ikuta and K. Hirowatari, "Real Three Dimensional Micro Fabrication using Stereo Lithography and Metal Molding,"  MEMS 1993 Workshop on Micro Electro Mechanical Systems, Fort lauderdale, FL, USA, February, 1993, page 42.

[10] T. Takagi and N. Nakajima, "Photoforming Applied to Fine Machining,"  MEMS 1993 Workshop on Micro Electro Mechanical Systems, Fort lauderdale, FL, USA, February, 1993, page 173.

Keywords:  micromechanics field, history of micromachines, prospects for MEMS, opportunities for microelectromechanical systems, development of microsystem technology