Site: Omron Corporation
Central R&D Laboratory
45, Wadai, Tsukuba City
Ibaraki 300-42, Japan

Date Visited: September 28, 1993

Report Author: R.S. Muller

ATTENDEES

JTEC:

S. Jacobsen
R.S. Muller
L. Salmon

HOSTS:

Hiroshi Goto
Minoru Sakata
Tsuneji Yada

The Omron spokesperson for most of the technical exchange was Minoru Sakata, who earlier had been a guest researcher for one year in the MIT laboratory headed by Professors J. Lang and M. Schmidt.

BACKGROUND

The Omron research facility is situated in a rural, park-like area, and has spacious grounds and facilities. The JTEC panel's meeting with Omron began with an overview given by Dr. Tsuneji Yada.

Omron's business in 1991 totaled 483 billion, of which ~60 percent was in control components, ~17 percent in electronic fund-handling systems, ~8 percent in office automation, and 6.5 percent in health-care equipment. The panel's hosts provided a company brochure that described the business aspects of Omron. The company has many overseas manufacturing and marketing affiliates. It began operations in 1933, producing switch gear. Omron's goal for 1993 is to develop small, smart control components. Omron has two R&D laboratories. The one in Kyoto focuses on optomechatronics, that is, microlens arrays (thirty-five researchers); the one in Tsukuba focuses on micromechanical sensors (fifty researchers -- roughly twenty-five for MEMS and twenty-five for circuits/systems).

Omron sees its mission served by developing expertise in: (1) fuzzy logic (FL) -- the company has developed controls with FL; (2) life science (this was a bit tenuous in relevance); (3) microcomponents; and (4) computers, controllers, and communications.

A typical Omron system is shown in Figure Omron.1. A concise statement of Omron's plan was presented as: In the longer term, integrate and reduce in size, and in the shorter term, use hybrids and reduce in size.


Figure Omron.1. View of typical Omron system.

RESEARCH AND DEVELOPMENT ACTIVITIES

Omron representatives with whom the JTEC panel spoke were participants in the national micromachine technology research program. Their company is one of three (Olympus, Omron, and Terumo) focusing on medical applications. In this program, the Omron team has responsibility for an MMI super-miniature recognition system. Omron showed the panelists a research project for this system in the form of an optical microactuated lens system. Figure Omron.2 shows a concept system of recognition sensor of less than 1 mm OD. Optical elements such as a microlens and a laser diode are mounted on a silicon cantilevered system. Resolution is expected to be -0.5 mm.


Figure Omron.2. Concept system with a Fresnel lens.

With photodiode readout, this system could function as an accelerometer with optical readout of the position of the cantilevered-seismic mass, which also contains the lens system. Actuation of cantilever is achieved by piezoelectric force. Again, the system fabrication is planned using silicon bulk micromachining with hybrid assembly of the lens. The lens is made of resin that is pressed and cured in a mold made by E-beam exposure of lithography resist into which Ni is deposited.

SUMMARY

Mr. Sakata said that Omron took some time to decide that an MMC project would interest the company. The company ultimately undertook an MMC project to compare and evaluate microtechnologies.

Omron has found bulk Si micromachining more troublesome than expected; difficulties have arisen in the fragility of structures and in the total cost of fabrication and assembly. Mr. Sakata estimated that the Si-based MEMS content of MEMS in Japan is likely to be reduced after three to five years from its present ~10 to 20 percent of total expenditures among all participating companies. It is still Omron's philosophy to pursue silicon processing wherever possible. The company is just now beginning a focus on surface micromachining. Omron sees its biggest advantage in its know-how in batch processing and in its IC experience.

Omron is interested in LIGA development, but no activity is taking place at this time; LIGA's main advantage would be high-aspect ratios. Omron is using anodic bonding for packaging now, but is looking at silicon/silicon bonding as a possible solution to problems with strain. The company is looking toward piezoelectric actuation using PZT thin films, and is collaborating with a Penn State group (Newham) in this area.

Omron "has an impression" that the mechanical properties of polyimide are hard to control, and is not using this material at present. The company is evaluating use of MIT MEMCAD; the panel's hosts stated that "perhaps [they will] begin use next year."

Mr. Sakata explained that the MITI medical application program is very small (~$1 million per year spread among three participants: Olympus in the lead, followed by Omron and then by Terumo).

QUESTIONNAIRE

The following are answers to questions submitted to Omron Corporation before the JTEC panel's visit.

A. Advanced Materials and Process Technology

1. What materials and fabrication techniques are most likely to be used in production for MEMS? Will MEMS continue to be based primarily on silicon IC technology?

Since batch fabrication and characteristics control are key issues in real production line and at least IC process fulfill these requirements, Si-based materials and IC technology must be used in MEMS production.

2. What, in your opinion, is the most important new process or material needed for extending the capabilities of MEMS?

There exist several new materials [that] seem to be important to MEMS. Porous silicon, which has a high oxidation rate, [has] low permittivity, and emits light under suitable conditions, can be applicable to many types of MEMS in many ways.

Piezoelectric thin film like PZT, PSSZT, [and] ZnO are not new, but [are] very attractive, especially for actuators and radiation sensors. Therefore processes to form these films are very important.

3. Are there plans to use X-ray lithography for micromechanics?

We do not have any plan to use X-ray lithography for MEMS.

4. How attractive is the LIGA process for commercial use in MEMS at the present time? How attractive do you expect it to be in five years? Ten years?

Though we do not have any plan to use the LIGA process, it is surely attractive for commercial use now and in the future.

5. If you are pursuing LIGA and LIGA-like high-aspect-ratio structures, what materials are being investigated and why? To what extent do you feel that structures produced using high-aspect etching will be competitive with those formed by plating?

We are not pursuing the LIGA process.

6. What are the prospects for a low-temperature wafer-scale bonding process for MEMS? How low in temperature can we go? Do you feel metal-metal, silicon-glass, or other interfaces are most promising?

Field-assisted room temperature bonding can be realized in five years by adjusting the contents of glass and modifying wafer surface mechanically and chemically. Silicon-glass bonding is better than other combinations, especially sensors and actuators [that] use electrostatic fields.

7. To what extent will silicon fusion play a role in MEMS? Is the area coverage sufficiently high? How much of a real problem is the high bonding temperature?

High bonding temperature is not a big problem because fusion bonding can be done at an early step in the process. Silicon fusion must be a promising process for MEMS, which does not make use of electrostatic fields.

8. What polymeric materials are being explored as photomasks for high-aspect-ratio structures? Is the use of conformal coating processes practical?

We use a conventional AZ1350J resist dipping process for patterning A1 on holes of glass wafer to get interconnection, and it works.

9. Polymers for thick photoresist applications are required by MEMS. Are Japanese photoresist suppliers responsive to this need?

[We have] no idea.

10. Do you feel that nested/stacked wafer-level microstructures based on multiple bonding and/or etch-back operations will be feasible within the next five years? Are they important for MEMS?

It seems that nested structure is too complicated to be feasible enough to be used for a commercial-based product.

11. It appears that precision injection molding could play a major role in MEMS. Would you comment on this, please.

[We have] no idea.

12. Are room-temperature superconductors being explored, and if so, what materials and processing techniques are being used?

We are not working on it. We have no idea.

13. Do you expect major advances in micromachining curing the coming decade? Will photo-assist etching or new etch-stops emerge to play a major role? What other technology additions do you consider promising?

[We are] not sure about promising techniques. But the best system partitioning in each application will be made clear during the coming decade, and it will be one of the major advances of MEMS.

14. What are the most important attributes you would insist on for a MEMS processing tool?

Process stability.

B. Sensors and Sensing Microstructures

1. For which sensed variables and types of sensors will MEMS technology have the greatest importance? What are the key advantages of MEMS technology for these sensors?

MEMS technology will still have the greatest importance for mechanical variables like shear force, pressure, and acceleration. The key advantage of MEMS technology is to realize precise sensor dimensions by batch fabrication in fairly small size.

2. Approximately when will the new sensors under development today based on MEMS technology first appear in the marketplace?

It takes at least four years to launch in the marketplace.

3. How can MEMS technology be used to improve existing sensors? What sensor types are likely to be improved the most?

[The cost of] mechanical sensors can be [lowered significantly as a result of] size reduction using MEMS technology.

4. What new sensors can only be developed using MEMS technology? How does MEMS make these new sensors feasible?

[We have] no idea.

5. To what degree is self-testing likely to be possible with sensors? Will this be a major role for MEMS technology?

Adding a self-testing function to a sensor is possible for almost all sensors. This is one of the major factors [for selling] microsensors, but will not be a major role for MEMS technology.

6. After pressure sensors and accelerometers, what is the next major sensor based on MEMS that will be mass-produced in high volume?

Though there are several candidates, like the flow rate sensor and tactile sensor, we are not sure about it.

7. To what degree are feedback readout schemes likely to be important in sensors? Will these feedback schemes involve MEMS?

Only in case of capacitance-type sensors, limited to applications where high sensitivity is necessary, [are] feedback read schemes important. Except for [these] cases, [the] open read scheme should be adopted for simplifying sensors.

8. What are the principal problems in the use of scanning surface probes (e.g., tunneling current) as an approach to high-sensitivity sensor readout? Is this approach likely to find wide application?

The narrow dynamic range may be a problem. This sort of very high sensitivity sensor has only very limited applications.

C. Microactuators and Actuation Mechanisms

1. Can designs using arrays of microactuators achieve large and useful forces? Are there other devices similar to the large optical projection displays that have been reported that can be realized using MEMS technology?

I do not think arrays of microactuators fabricated by MEMS technology have enough force to move something on the same order of size as microactuators efficiently. [However,] biologically-fabricated, much smaller-size actuators may be able to move some biological unit like a cell. Besides, usual MEMS dimensions are not very suitable for microactuators in terms of actuation control because [they are] not under one dominant force regime, that is, large surface force and considerable mass force. Thus, commercial microactuators must be restricted to the application where force is not extracted from the actuator directly, like projection mirror arrays and microgyros. Several arrays of microactuators are presented by Professor Fujita of Tokyo University.

2. Considering their importance to MEMS, in what order of importance would you place the following microactuation mechanisms: shape-memory alloys, electromagnetics, electrostatics, thermal bimorphs, piezoelectric bimorphs, piezoelectrics, electrostriction devices, and phase-change devices? How many of these do you expect will find commercial applications in high-volume products?

Electrostatics, electrostriction and piezoelectric bimorphs are the most important microactuation mechanisms. These three have the possibility [of being] applied to commercial applications.

3. What are the most reasonable candidates for prime movers for microactuation?

Prime movers are optical applications like projection mirror.

4. To what extent can sticking problems due to surface forces be suppressed in microactuators? Will these problems seriously constrain the practical application of microactuators based on narrow gaps?

In [the] fabrication process, [the] sticking problem is a major problem [that] we have to solve. In actuation, a stick-prevent[ion] approach can be adopted. Therefore, [the] sticking problem will not limit practical application of microactuators.

5. What is the most promising candidate for a microrelay? Where are such devices most likely to be used?

The most promising candidate for a microrelay might be an electrostatic force. We once tried to develop an electrostatic microrelay and quit because of its poor characteristics. I am really not sure if we should use MEMS technology to develop microrelays rather than taking an approach of reducing the size of conventional electromagnetic relays. This kind of relay is likely to be used as a small signal relay for telephone switchboards.

6. What are the main design issues in microfluidic systems? Where will such systems find their primary application?

I suppose the most important design issue is dimension and charge control of channel surface.

7. What designs are most likely to be adopted for practical microvalves and micropumps? What is holding up the practical realization of these devices?

Professor Esashi's microvalve and micropump design (hybrid type) is a strong candidate. Packaging is the issue that may be the biggest problem in fabricating practical devices.

D. Sensor-Circuit Integration and System Partitioning

1. Will MEMS technology lead to complete microminiature "instruments on a chip?" For what types of instruments?

yes, there will be many types of "instruments on a chip" led by mems. an example is the flow measurement system developed at michigan university.

2. Will MEMS technology combine sensors and actuators into complete control systems? If so, what types of control systems will be most affected?

MEMS will be likely to combine these two in special cases such as a system of optical sensors (or CCD devices) and optical scanning mirrors.

3. Are systems involving sensors, actuators, and embedded microcontrollers likely to be realized in monolithic form or will they be hybrid? What factors are driving for monolithic integration for what types of products?

Those will be hybrid at first, and after integration techniques [for] sensors and other devices become solid, those will be realized in monolithic form. Parasitic capacitance reduction is a major motivation for realizing monolithic surface micromachined capacitance-type pressure sensors and accelerometers.

4. What levels of integration (transistor count) are we likely to see on MEMS chips by 1995? By the year 2000? Are full microprocessors needed or realistic?

By 1995, we can see at least around 300 transistors, and 1,000 transistors by 2000. Because integration of many devices makes its yield go down drastically, [we are] not sure if full microprocessor integration is realistic.

5. To what extent will embedded microcontrollers be used in (possibly hybrid) integrated sensing nodes -- high-end devices only, or will they eventually become pervasive in even low-end products?

The embedded microcontrollers will be used in only high-end devices. Application to low-end devices may not fulfill cost requirements.

6. What are the prospects for adopting sensor bus standards, at least in specific industries (automotive, process control, HVAC)? How important is the evolution of such standards to the development of MEMS?

We do not consider adopting sensor bus standards so much now. Our sensors have their own input/output specifications. They are adjusted to each application.

7. Will sensor calibration continue to be done in hardware (laser-trimming or EPROM), or will it evolve to digital compensation in software? Is this an important issue in MEMS development?

In the future, calibration will be carried out by software rather than hardware. It is also an important issue considering system partitioning.

8. Will a few standard processes emerge to dominate sensor-actuator-circuit integration, or will widely divergent processes continue to be the norm in MEMS? What issues will determine the answer to this question?

[The] system partitioning issue will lead [to] its answer.

E. Advanced Packaging, Microassembly, and Testing Technology

1. What are the general directions for progress in packaging MEMS? What are the principal challenges here?

There are two principal challenges. One is to obtain the reliable interconnections. The other is not to effect MEMS mechanically, electrically, and chemically.

2. What will be the application and impact of MEMS on the packaging of sensors?

MEMS will improve interconnection between chips and devices.

3. How much of a problem is die separation for surface micromachined devices? Is this optimally performed after release?

We are not working on surface micromachined devices now.

4. How important are the chip-level packaging schemes now under development to MEMS devices and systems? Is the increased process complexity worth it?

Chip-level packaging is the most important technical issue in MEMS packaging. It is worth pursuing this technique.

5. Are common packaging approaches across many types of devices feasible or will packaging continue to be very application specific?

Packaging will keep having significantly large application-dependency unless a chip-level packaging technique is developed.

6. What viable techniques exist for coupling force from integrated microactuators while protecting the device from hostile environments? Can mechanical microactuators only be used inside hermetic packages?

Possibilities are electrostatic or magnetic coupling. Using these kinds of noncontact coupling, microactuators can be inside of hermetic packages.

7. To what degree should MEMS continue to focus on monolithic silicon microstructures, and to what degree do you think it is really better suited to milliscale integration with components combined using microassembly techniques?

[We have] no idea. It really depends on the purpose of individual MEMS R&D. In case the purpose is to figure out what MEMS should be in the future, also monolithic types should be investigated. On the contrary, if the project aims to develop commercial MEMS, the microassembly approach must be taken.

8. Are there microassembly techniques that can be sufficiently automated to make millielectromechanical devices in high volume at moderate or low cost? What are the generic barriers to such devices and techniques?

[We have] no idea.

9. What techniques are available for testing MEMS structures after encapsulation/packaging? What happens when they are no longer viewable?

Now we are testing sensors only electrically after [they are] packaged. Therefore, we can get only secondary information of sensor structure through its response. We do not have any other method now.

F. MEMS Design Techniques, Applications, and Infrastructure

1. The term "MEMS" has many meanings. Could you tell us your interpretation?

MEMS means components that include critical parts that are micron order-of-size and/or fabricated with micron-order preciseness.

2. Is there a MEMS technology driver equivalent to the DRAM in the IC industry? If so, what is it?

[We have] no idea.

3. Is the integrated-circuit industry the principal application driver for MEMS? If so, what are the alternative drivers during the next decade, if any?

[We have] no idea.

4. In what sensor application areas do you see MEMS technology having the greatest importance? (Examples might be: automotive, medical, robotics, consumer products, etc.) What are the key advantages of MEMS technology for these applications?

Automotive and medical areas. Key advantages are size reduction and dimension control.

5. What will be the application and impact of MEMS on the interfacing of sensors to the environment?

Because MEMS are usually very small, [they do] not affect the environment so much, and we can measure variables without giving effective disturbance to [the] environment.

6. Looking ahead five years, what new MEMS-based sensors and sensor applications do you anticipate?

[We have] no idea.

7. In what time frame do you anticipate MEMS technology having the most impact on sensor products (for example, three years, five years, ten years, etc.).

Three years.

8. What is the prognosis for MEMS foundries? Are they needed? What technologies would need to be present in a MEMS foundry?

[We have] no idea. But microassembly technology will be essential for MEMS foundries.

9. What is the state of the art in MEMS reliability? Where are the principal problems?

Reliability is still not good. The principal problem we have to solve is durability.

10. What is the "state of the art" in MEMS designability? How important are CAD tools for MEMS? Do you have an active CAD effort for MEMS in your organization?

MEMS designability now is very low. Therefore CAD tools are very important, and we have a project on it.

11. What priority would you place on the creation of a central MEMS database of material and design parameters? Does your organization have an active project in this area?

The priority is very high. We also have a project on it.

12. How much funding is being directed into MEMS research and development in your organization? What percentage is this amount of the total R&D budget?

[We] cannot comment on it.

13. In your view, is enough funding available to support MEMS research in Japan? In the world? Are the principal bottlenecks to more rapid progress money or ideas?

There is not enough funding to support MEMS R&D in Japan. I have no idea as to [whether there is enough] world funding. Ideas for application are very critical and [are] a major bottleneck.

14. What portions of your R&D funding for MEMS comes from internal, government or other sources? Has increased government funding had a major impact in your organization?

[We] cannot comment on the portion. Increased government funding had an impact in our organization.

15. What percentage of your research is directed toward specific products? Toward basic research?

The percentage of basic research is around 5 percent.

16. What emerging technologies do you see as having the largest influence on MEMS and why (i.e., LIGA, superconductors, submicron ICs, piezoelectrics, thin-film magnetics, etc.)?

Piezoelectric thin films [will] have [an] influence on MEMS, especially for actuators.

17. What are the principal barriers to the success of MEMS?

Difficulties in finding good applications for MEMS is the principal barrier.

18. What do you believe to be the major competitive technology alternative to MEMS?

[We have] no idea.

19. Are patents a key to commercial success or are base technology skills more critical?

Both are key factors to commercial success.

20. The first generation of university graduates who specialized in MEMS are now finishing their degrees. Are employment opportunities for these students plentiful in Japan?

Yes.


Published: September 1994; WTEC Hyper-Librarian