Presented and published
Proc. of SPIE,
vol. 3903, pp 42-47
TRIZ in MEMS
P.R. Apte
Solid State Electronics Group
Tata Institute of Fundamental Research
Homi Bhabha Road
Colaba, BOMBAY - 400 005, India
e-mail : apte@tifr.res.in
Fax: +91-22-215 2110 or +91-22-215 2181
ABSTRACT
TRIZ is a Russian abbreviation for Teorijz
Rezhenija
Izobretatel’skich
Zadach.
Genrich Altshuller developed it fifty years ago in the former Soviet Union.
He examined thousands of inventions made in different technological systems
and formulated a "Theory of Inventive problem solving"(TRIZ). Altshuller’s
research of over fifty years on Creativity and Inventive Problem Solving
has led to many different classifications, methods and tools of invention.
Some of these are, Contradiction table, Level of inventions, Patterns in
evolution of technological systems, ARIZ-Algorithm for Inventive Problem
Solving, Diagnostic problem solving and Anticipatory Failure Determination.
MEMS research consists of conceptual design,
process technology and inclusion of various Mechanical, Electrical, Thermal,
Magnetic, Acoustic and other effects. MEMS systems are now rapidly growing
in complexity. Each system will thus follow one or more "patterns of evolution"
as given by Altshuller. This paper attempts to indicate how various TRIZ
tools can be used in MEMS research activities.
Keywords : TRIZ, MEMS, ARIZ, 40 Principles,
Contradiction, Su-Field analysis, Levels of Invention, Patterns of Evolution
of Technical systems, Diagnostic problem solving, Anticipatory Failure
Determination (AFD)
1. What is TRIZ ?
TRIZ is a Russian abbreviation for Teorijz Rezhenija
Izobretatel’skich
Zadach
which in English stands for Theory of Inventive Problem Solving. It was
developed and practiced for last fifty years in the former Soviet Union
by Genrich Altshuller1,2,3 and his disciples. He analyzed thousands
of worldwide patents from leading engineering fields. He found that each
of the most inventive patents primarily solved an ‘inventive’ problem.
Altshuller defined inventive problems as those which contain conflicting
requirements, which he called ‘contradictions’. Further he found that the
same fundamental solutions were used over and over again, often separated
by many years. He reasoned that if latter inventors had the knowledge of
earlier solutions their task would have been simpler. He, therefore, set
about extracting, compiling, and organizing such knowledge. He defined
39 basic properties and 40 principles for solving problems containing contradiction
in any two-of-39 properties. This he gave in the form of a contradiction
table of size 39 x 39 with each cell giving up to 4 principles (and examples
from patent data base), that may be used to eliminate the contradiction.
Altshuller also laid the foundation for development of an analytical
approach to solving inventive problems with an axiom – "The evolution of
all technical systems is governed by objective laws". Improvement of any
part of a system which has already reached the highest level of functional
performance will lead to conflict with another part. This will lead to
eventual improvement of the less evolved part(s). Such a continuing and
self-sustaining process will bring the system closer to its ‘ideal’ state.
Su-field analysis ("two substances and one field")1,2
is used whenever a new function is introduced or modified (either inadvertently
or intentionally) and inventive "standard solutions" (and examples from
patent database) are available to find an analogous solution. ARIZ – ‘Algorithm
for Inventive Problem Solving’ 1,4 is used when systems mature
and become complex thus making it difficult to modify or improve them in
an incremental fashion.
Altshuller’s research of over fifty years on Creativity and
Inventive Problem Solving has led to many different classifications, methods
and tools of invention. Some of these are,
1.1 Contradiction table 39 x 39
Contradiction appears while trying to improve one desirable property
another desirable property deteriorates! Conventional problem solving generally
leads to a ‘compromise’ solution. As mentioned before, the most ‘inventive’
solution is obtained when a technical problem containing a ‘contradiction’
is solved by completely eliminating the contradiction. Altshuller constructed
a "Contradiction Table" from his research over 40,000 most inventive patents
wherein he found that only 39 properties ( which improve or degrade) and
40 inventive Principles are used. This table is a straightforward look-up
table to find which principles can be used for solving an isolated single
contradiction between an improving property and a degrading property.
1.2 Level of inventions
Altshuller partitioned problem solutions into 5 levels.
Level 1 : apparent solution (32% of all the patents)
A simple improvement of a technical system.
Use examples from the same field.
Altshuller felt that Level 1 is not really innovative as it provides only
some improvement to an existing system without solving any problem.
Level 2 : minor improvements, removing some contradictions (45%
of all the patents)
-
Use 40 Principles to separate and solve technical contradictions.
-
Requires knowledge from different areas within the same field.
Level 3 : major improvements requiring Su-field analysis (18% of
all the patents)
-
Use the 76 Standard Solutions to solve Physical contradictions.
-
Use effects – physical, chemical and geometrical.
-
Requires knowledge from other fields.
Level 4 : radical change / new concept, requires ARIZ (4% of all
the patents)
-
Use ARIZ to fully describe the ‘real’ problem and possible ‘new’ solutions.
-
This level improves a technical system, but without solving an existing
technical contradiction. It simply replaces the original technology with
a new technology so as to move towards ideality!
Level 5 : discovery-previously unknown (1% of all the patents).
Altshuller proposed to exclude the two extreme levels viz. Level 1
and Level 5 from his inventive problem solving tools. As one can see, the
tools become progressively more powerful as we move from Level 2 to Level
3 and to Level 4. Each level has its own defined problems and its own problem
solving tools. The aim is to move towards ideality. In this sense the level
4 is not better than Level 3 if Level 3 solution brings it closer to ideality.
Each higher level also requires more detailed analysis and resources.
1.3 Patterns in evolution of technological systems
Altshuller was able to determine 8 patterns of how technological systems
develop over time.
Technology follows,
-
Life cycle of birth, growth, maturity and death.
-
Trend of increasing ideality.
-
Uneven development of sub-systems resulting in contradictions.
-
First to match parts and later mismatch parts (to gain advantage).
-
Increasing complexity followed by simplicity through integration.
-
Transition from macro-system to micro-system.
-
Technology follows increasing dynamism and controllability.
-
Decreasing human involvement with increasing automation.
1.4 SU-Field Analysis and Standard Solutions
Altshuller’s main premise was that every technical system could
be thought of as a network of subsystems each of which performs some specific
function. Thus every system has subsystems and every subsystem is said
to belong to a supersystem. Subsystems can be progressively sub divided,
ultimately reaching microlevels like particles, molecules, atoms, electrons
etc. Supersystems are the result of growth of a technical system from simple
to more complex system. Finally, every supersystem will have environment
as its supersystem.
A technical system, in its smallest unit, performs a function. Altshuller
defined a function as the interaction between two substances and a field
acting between the two substances. The S-field (or energy) acts on substance
S2 to improve or modify interaction with the substance S1.
Among many possibilities that exist the most important ones are the ‘useful
interaction’ and the ‘harmful interaction’. Altshuller divided the standard
solutions into five classes:
Class #1 : Build or destroy a S-field
Usually, a ‘useful interaction’ is intentionally built up while
a ‘harmful interaction’ is intended to be destroyed through the S-field
Class #2 : Develop (or bring into existence) an S-field
Class #3 : Transition from a base system to a supersystem or
To a subsystem (all the way ) to the micro-level
Class #4 : Measure or detect anything within a technical
system
Class #5 : Describe how to introduce substances or fields into
the technical system
1.5 Law of Ideality
Law of ideality states that any technical system, throughout its lifetime,
tends to become more reliable, simple, effective – more ideal. Ideality
always reflects the maximum utilization of existing resources – within
subsystems themselves or within supersytems including environment’s free
resources like gravity, air, heat, magnetic field, light etc. Altshuller
stated that "art of inventing is the ability to remove barriers to Ideality
in order to qualitatively improve a technical system". There are several
ways to make the system more ideal:
1.5.1 Increase amount of functions of the system - make it multi-function
1.5.2 Transfer as many functions as possible to that working element
which produces the system’s final action
1.5.3 Transfer some of the functions of the system to a supersystem
or to the outside environment
1.6 Utilize internal and external resources
that already exist and are available
1.7 ARIZ: Algorithm for Inventive Problem Solving 4
ARIZ is the central analytical tool of TRIZ. It is a systematic procedure
for identifying solutions, without apparent contradictions, to the very
complex problems. This is achieved by a step by step analysis which inevitably
leads even to reformulation of the problem, that should be solved, and
the solutions to the right problem. The most recent version, ARIZ-85C contains
nine steps:
Step #1: Analysis of the problem
Step #2: Analysis of the problem’s (functional) model
Step #3: Formulation of the Ideal Final Result (IFR)
Step #4: Utilization of outside substances and resources
Step #5: Utilization of (patent) informational data bank
Step #6: Change or reformulate the problem
Step #7: Analysis of the method that removed the Physical contradiction
Step #8: Utilization of found solution
Step #9: Analysis of steps that lead to the solution
1.8 Diagnostic problem solving and Anticipatory Failure
Determination
Diagnostic problem solving attempts to find the ‘root cause of failure’
(in answer to the question "Why has the system failed?"). The Anticipatory
Failure Determination (AFD) is a tool for systematically identifying and
eliminating system failure before these occurs. (in answer to the question
"How can we make the system fail ?").
2. Use of TRIZ tools in MEMS Research
MEMS research consists of conceptual design, process technology and inclusion
of various Mechanical, Electrical, Thermal, Magnetic, Acoustic and other
effects. Various TRIZ tools 5 can be used in MEMS research activities
mentioned above:
2.1 Minor improvements by removing some contradictions (Level
2 inventions)
As miniaturization is the main thrust of MEMS activity, which includes
sensors and actuators, process technology is continuously modified and
new materials are integrated in the existing structures. Each new step
aimed at improving a desired property invariably leads to degradation of
another property. A statement of this conflict is termed as "Technical
Contradiction". This contradiction is referred to the "Contradiction Matrix"
and upto 4 inventive principles are identified which have helped earlier
inventors to get rid of these contradictions. Knowledge database gives
a few examples each for these Principles. Using analogous thinking, a feasible
solution to eliminate the problem (contradiction) is found.
2.2 Major improvements by using Su-field analysis (Level
3 inventions)
Main stay of Altshuller’s TRIZ is that every function can be represented
by "two substances and one field" and is thus known as "Su-field
analysis". In MEMS whenever a new function is introduced or modified (either
inadvertently or intentionally), we can look at examples from patent database
to find an analogous solution. These examples are further classified as
standard solutions, physical, chemical or geometrical effects. Standard
solutions point out how the substances or fields are modified and the effects
give definite ways to implement the solutions.
2.3 Radical change or New concept requiring ARIZ (Level
4 inventions)
When systems mature and become complex, it becomes difficult
to modify or improve them in an incremental fashion. If it is still difficult
to arrive at proper solution by using the "Technical Contradiction removal"
or "S-Field analysis" then a detailed analysis of the conflict is done.
The analysis points to a single physical parameter which must have opposing
values at the same time and at the same space! This statement is called
"Physical Contradiction" and forms the basis for applying ARIZ and related
TRIZ tools. ARIZ allows one to develop a function model and suggest concepts
for,
-
Improving efficiency of useful actions:
A function, whose useful action is either deficient or excessive, is
first identified. The Su-field model clearly shows which of the Standard
solutions (or any other solution) is to be utilized for correcting the
deficient or excessive action. Effects can then be used to implement these
solutions.
and/or
-
Avoiding or eliminating harmful actions:
Components which essentially create harmful effects are TRIMMED (eliminated
) and their useful actions are absorbed either by reconnecting components
differently or by adding a substance or field at appropriate component.
And finally
-
Anticipatory Failure Determination (AFD):
AFD can be applied to a function model of a MEMS system to determine
how the system may fail and prevent the same. This is very useful in a
well-developed MEMS technology with many constraints coming from guaranteeing
compatibility with the microelectronics VLSI technology. The process technology
is so very complex already that making a change (even if it is meant as
an improvement) may cause some problem which will make the system fail.
The AFD assures that such ‘problems’ that may crop up are identified with
appropriate ranking parameter so that a decision can be made as to what
needs to be done for ‘preventing’ failure of the function(s).
2.4 Stages in life of MEMS
There are 4-stages in life of a system,
Stage #1 : Selection of Parts
Stage #2 : Improvement of Parts
Stage #3 : Dynamization of Parts (movement and control)
Stage #4 : Self-development of System (adaptive control – sense, measure,
control)
In any MEMS activity, one can determine in which ‘life stage’ the particular
MEMS system is and from this move to activity in the next stage of life.
This way one can "INVENT THAT DOES NOT EXIST YET!" As an example, we take
the micromachined structure of a micro-torsion resonator with double suspension.
Stage #1 design selects various dimensions to achieve a high Q torsion
resonator action. In stage #2 activity the suspensions, the torsion wire
and the torque are individually improved by selecting compatible materials
and technologies. The torsion wire is made of pure Silicon dioxide (quartz-like
properties) and the suspensions are made of single crystal silicon and/or
silicon nitride. In Stage #3 the movements of the torsion vibrator are
sensed through the stresses developed in suspensions. This can be achieved
by including piezoresistors (boron-diffused resistors) in the suspensions.
In Stage #4, a feedback system comprising of sensors and actuators is conceived
to give adaptive (self-) control system.
2.5 Pattern of MEMS Evolution
MEMS systems are now rapidly growing in complexity. Each system
will thus follow one or more "patterns of evolution" as given by Altshuller.
Most appropriate trends of evolution are:
-
Trend of increasing Ideality
-
Increasing complexity followed by simplicity through integration
-
Transition from MACRO to micro (nano) system
-
Increasing dynamism and controllability
-
Decreasing human involvement with increasing automation
2.6 SUMMARY of how to use TRIZ tools in MEMS Development
The developer of a micro-system (using MEMS) must first decide
on what is the ultimate or ‘ideal’ goal. The patterns of evolution then
act as main guidelines for reaching this ideal system. The TRIZ tools like
Contradiction Matrix, Su-field analysis, Standard solutions, Effects, ARIZ,
AFD are used to improve the system with a Step-by-Step approach. This paper
has attempted to indicate how the TRIZ tools can be applied to development
of MEMS.
3. References
(1) Lev Shulyak, Introduction to TRIZ,
Technical Innovation
Center, Massachusetts, 1998
(2) H. Altov, (Pseudonym of Altshuller), translated by Lev Shulyak
And Suddenly the Inventor Appeared,
Technical Innovation Center, Massachusetts, 1996
(3) G.S. Altshuller, Translated by Lev Shulyak
40 principles : TRIZ keys to Technical Innovation,
Technical Innovation Center, Massachusetts, 1998
(4) Janice Marconi, "ARIZ : The Algorithm for Inventive Problem
Solving",
TRIZ Journal, April 1998,
http://www.triz-journal.com/archives/98apr/98apr-article4/98apr-article4.htm
(5) Kowalick, James, "Tutorial: Use of Functional Analysis
and Pruning, with TRIZ and ARIZ",
TRIZ Journal,
December 1996
http://www.triz-journal.com/archives/96dec/article4/tutorial.html
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