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) Level 3 : major improvements requiring Su-field analysis (18% of all the patents) Level 4 : radical change / new concept, requires ARIZ (4% of all the patents)
      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,
      1. Life cycle of birth, growth, maturity and death.
      2. Trend of increasing ideality.
      3. Uneven development of sub-systems resulting in contradictions.
      4. First to match parts and later mismatch parts (to gain advantage).
      5. Increasing complexity followed by simplicity through integration.
      6. Transition from macro-system to micro-system.
      7. Technology follows increasing dynamism and controllability.
      8. 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,
          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

          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
      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:
        1. Trend of increasing Ideality
        2. Increasing complexity followed by simplicity through integration
        3. Transition from MACRO to micro (nano) system
        4. Increasing dynamism and controllability
        5. 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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