Abstract:
A micro-electromechancial system has a moveable element supported by a flexure, the flexure being formed of a substitutionally alloyed intermetallic compound. The substitutionally alloyed intermetallic compound includes a base intermetallic compound having a major component and a minor component; and at least one of a first substituent and a second substituent. The first and second substituents are substituted coherently for the major and minor components of the base intermetallic compound, respectively, in amounts sufficient to reduce creep in the resulting substitutionally alloyed intermetallic compound without substantially modifying the crystalline structure of the base intermetallic compound.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Micro-electromechanical systems (MEMS) are electrically operated mechanical devices of a size suited for use with and incorporation into integrated circuit devices. Examples of common MEMS include rotatable mirrors, actuators, resonators, motors, and the like. Many of these devices include moving parts whose movements are facilitated by a hinge or flexure that connects the moving part to the remainder of the MEMS. Ideally, the flexures of MEMS will deform in a perfectly elastic manner, i.e. they will twist or bend between known positions. Unfortunately, flexures are subject to a phenomenon known as ‘creep’ wherein the crystalline structure from which the flexures are made is permanently modified, typically through the action of slip between the crystalline planes of the material. Where creep occurs, the flexures no longer move between their predetermined positions. Where creep is extensive, the MEMS will no longer function as intended.  
         [0002]     Some manufactures have tried to reduce creep in MEMS flexures by using binary intermetallic compounds in the fabrication of MEMS flexures in place of unalloyed materials. One approach is the use of electrically conductive intermetallic binary compounds that all include aluminum and mixtures of various electrically conductive binary intermetallic compounds that all include aluminum. These binary compounds of aluminum and mixtures of binary compounds of aluminum impart strain to the crystalline structure of MEMS that can resist, to a degree, the dislocations that result in creep. However, the reduction in creep realized as a result of the use of binary compounds is limited. What is more, the use of incoherent mixtures of different binary intermetallic compounds may, in some instances, actually introduce additional creep between the boundary layers of crystals having distinct phases.  
         [0003]     Other manufacturers have attempted to limit creep in MEMS flexures by modifying the physical structure of the flexures to reduce stresses therein. While helpful, such structures are relatively complex and may make the fabrication of MEMS devices and their associated circuitry more difficult and more expensive. Accordingly, there is a need for other ways of limiting creep  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0004]      FIG. 1  is an exemplary MEMs that includes a flexure structure with substitutionally alloyed intermetallic compounds;  
         [0005]      FIG. 2  is an exemplary embodiment of the substitutionally alloyed intermetallic compounds;  
         [0006]      FIG. 3  is an exemplary embodiment of the substitutionally alloyed intermetallic compounds;  
         [0007]      FIG. 4  is a schematic view of a sputtering mechanism for depositing substitutionally alloyed intermetallic compounds having a single target; and,  
         [0008]      FIG. 5  is a schematic view of a sputtering mechanism for depositing substitutionally alloyed intermetallic compounds having multiple targets. 
     
    
     DETAILED DESCRIPTION  
       [0009]     In the following detailed description of the invention, reference is made to the accompanying drawings that form a part hereof and in which is shown, by way of illustration, specific embodiments in which the invention may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims and equivalents thereof.  
         [0010]      FIG. 1  is an exemplary MEMs  10  that includes a flexure structure with substitutionally alloyed intermetallic compounds that comprises a substrate  12  to which are attached a pair of supports  14 . Flexures  16  extend from supports  14  to structure  18 . When a voltage is applied to the structure  18 , an electromagnetic field is created between the structure  18  and capacitive plate structure  19 . The electromagnetic field formed between the structure  18  and structure  19  causes the structure  18  to move, thereby inducing bending and/or torsional stresses in the flexures  16 . These stresses may give rise to creep, especially in the presence of elevated temperatures, in the flexures  16 . As is understood by those skilled in the art, creep is a plastic deformation of a material generally resulting from a relative shift between the planes of a crystalline structure, particularly between the respective crystalline grains that make up the overall structure.  
         [0011]     It is known in the metallurgical arts to introduce alloying materials to interrupt the otherwise regular crystalline structure of a material. Regular crystalline structures have a more pronounced susceptibility to creep as the regular structure of the crystal lattice more readily defines a glide plane along which creep may occur. Where an alloying material is added to a material, the crystalline structure of the material is disrupted and glide planes are not so readily defined.  FIG. 2  is an exemplary embodiment of the substitutionally alloyed intermetallic compounds. The larger atom of the alloying material introduces an irregularity or strain into the crystalline structure of the material that acts to prevent dislocation motion along the plane  28 . The use of an alloying material having a generally smaller atomic size than the atoms of the base material as shown in  FIG. 3 , similarly introduces an irregularity or strain into the crystalline structure of the base material and also prevents dislocation motion along plane  28 . One embodiment of the present invention introduces alloying materials to preexisting binary intermetallic compounds to form compounds having three or more components in a manner that substantially preserves the preexisting crystalline structure, while at the same time introducing disruptions there into to interrupt glide planes along which creep may occur. In this manner, the physical properties of the base material are substantially unchanged and yet the resistance to creep is greatly enhanced. The resulting alloyed material is a ternary, quartemary or multi-component intermetallic compound having a generally coherent crystalline structure.  
         [0012]     Where a binary intermetallic compound (base material) is represented by the generic chemical formula A x B y  in which A and B are elements from the periodic table and x and y are the respective proportions of each element, the suitable substitutional alloy according to some embodiments will have formulas such as A x (B (y-s) C s ), (A (x-s) C s )B y  or (A (x-s) C s )(B (y-t) D t ), where C and D are elemental alloying materials from the periodic table and s, t are the respective proportions (or fractions) of each of these elements. For one embodiment the fraction “s” is in the range of 0 to 50%, and for another embodiment, the fraction “s” is in the range of 1% to 20%. For some embodiments, the fraction “t” is in the range of 0 to 50%, while for other embodiments, the fraction “t” is in the range of 1% to 20%. In certain preferred embodiments, the substituted alloying element(s) will form substantially the same crystal structure with the components of the base material as did the element the alloying materials are replacing. By way of example, in an embodiment involving the binary intermetallic compound Nb 3 Sn, it is possible to substitute Ta for a portion of the Nb. Both Ta and Nb form an intermetallic compound with Sn with the A15 crystal structure. The formula for the resulting ternary substitutional intermetallic compound is (Nb (3-s) Ta s )Sn. It should be noted that while the preceding example was of a ternary compound, quaternary compounds and compounds having five (5) or more components are also contemplated.  
         [0013]     In one embodiment, alloying materials for use in forming MEMS are chosen such that in the resulting ternary or quarternary substitutionally alloyed materials the substitutes are incorporated coherently into the crystal lattice. In order to facilitate the specification of a particular crystalline structure, it is has been found useful to select as a base material binary intermetallic compounds that may exist over a broad range of compositions as opposed to those compounds that exist over a relatively narrow range of compositions such as, for example, stoichiometric or line compounds. It has been found that crystalline structures including, but not limited to structures designated as A15, B2, C14, C15, L1 0 , and L1 2  accommodate a useful breadth of compositional variance.  
         [0014]     In one embodiment, some examples of binary intermetallic compounds in the Al 5  crystalline system and having a useful compositional breadth may include, but are not limited to: Ti 3 Ir, Mo 3 Ir, Nb 3 OS, Cr 3 Ge, AlMo 3 , Cr 3 Os, Cr 3 Pt, V 3 Si, Nb 3 Al, Nb 3 Ir, Ti 3 Pt, Nb 3 Pt, Nb 3 Au, Cr 3 Ir, V 3 Ga, Nb 3 In, V 3 Ir, V 3 Pt, and V 3 Rh. In this embodiment, some examples of substitutes for the major component include, but are not limited to: Cr, Mo, Nb, Os, Re, Ta, Ti, V and Zr. In this embodiment, some examples of substitutes for the minor component include, but are not limited to: Al, As, Au, Co, Ga, Ge, Hg, In, Ir, Ni, Os, Pd, Pt, Rh, Ru, Sb, Si, Sn and V. One example of a substitutionally alloyed intermetallic compound having an A15 crystalline structure is V 3 (Pt (1-s) Rh s ). In this case, Rh is substituted for Pt in the compound V 3 Pt. Another example is (Nb (3-s) Mo x )Al y , where Mo is substituted for Nb.  
         [0015]     In another embodiment, some examples of binary intermetallic compounds in the B2 system having a useful degree of breadth may include, but are not limited to: BeCo, BeCu, AlIr, DyIn, TiCo, MgPd, NiGa, OsHf, HfRh, HoIn, CuPd, AuCd, TiOs, InPd, MgSc, PdZn, OsV, HgLi, AgLi, AlCo, AgMg, RuV, FeAl, CoGa, FeRh and CoFe. In this embodiment, some examples of substitutes for the components of these binary compounds may include, but are not limited to: Ag, Al, Au, Ba, Be, Bi, Ca, Cd, Ce, Co, Cs, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, In, Ir, La, Li, Lu, Mg, Mn, Nb, Nd, Ni, Os, Pb, Pd, Pr, Pt, Rb, Rh, Ru, Sc, Si, Sm, Sr, Ta, Th, Te, Th, Ti, Tm, V, Y, Yb, Zn and Zr.  
         [0016]     In yet another embodiment, some examples of binary intermetallic compounds in the C14 system having a useful degree of breadth may include, but are not limited to: HfRe 2 , Fe 2 Ti, YbMg 2 , Be 2 W, Fe 2 Ta, Os 2 Hf, TiMn 2 , Fe 2 Nb, NbMn 2 , Mn 2 Hf, BeFe 2  and ZrMn 2 . In this embodiment, some substitutes for the major component in these exemplary binary intermetallic compounds in the C14 system may include, but are not limited to: Al, Be, Co, Cr, Fe, Li, Mg, Mn, Os, Re, Rh, Ru and Zn. Some substitutes for the minor component in the exemplary intermetallic binary compounds C14 crystalline system may include: Am, Ba, Be, Ca, Cr, Dy, Er, Eu, Fe, Gd, Hf, Ho, La, Lu, Mg, Mo, Nb, Nd, Np, Os, Pr, Ru, Sc, Sm, Ta, Th, Th, Ti, Tm, V, W, Y, Yb and Zr.  
         [0017]     In another embodiment, some examples of binary intermetallic compounds in the C  15  system having a useful degree of breadth may include, but are not limited to: Au 2 Na, CeIr 2 , CePt 2 , Co 2 Hf, Co 2 Ta, Co 2 Zr, Cu 2 Be, LaPt 2 , LiPt 2 , NdPt 2 , PrPt 2 , Pt 2 Eu, Pt 2 Gd, Rh 2 Er, ScNi 2 , SmPt 2 , ThIr 2  and ZrMo 2 . Some substitutes for the major components in the exemplary intermetallic compounds in the C15 crystalline system may include, but are not limited to: Ag, Al, Au, Be, Bi, Co, Cr, Cu, Fe, Ir, Mg, Mn, Mo, Ni, Os, Pd, Pt, Rh, Ru, V, W and Zn. Some substitutes for the minor components in the exemplary intermetallic compounds in the C15 crystalline system may include, but are not limited to: Ag, Am, Ba, Be, Bi, Ca, Ce, Cs, Dy, Er, Eu, Fe, Gd, Hf, Ho, K, La, Li, Lu, Mg, Na, Nb, Nd, Np, Pb, Pm, Pr, Rb, Sc, Sm, Sr, Ta, Th, Th, Ti, Tm, Y, Yb and Zr.  
         [0018]     In another embodiment, some examples of binary intermetallic compounds in the L1 0  crystalline system having a useful degree of breadth may include, but are not limited to: CoPt, HgPb, VRh, IrV, AuCu, PtZn, FePt and CdPd. Some substitutes for the components of these exemplary intermetallic compounds in the L1 0  crystalline system may include, but are not limited to: Al, Au, Bi, Ca, Cd, Co, Cr, Cu, Eu, Fe, Ga, Hf, Hg, In, Ir, Mg, Mn, Na, Nb, Ni, Pb, Pd, Pt, Rh, Ru, Sn, Ta, Ti, V, Yb, Zn and Zr.  
         [0019]     In yet another embodiment, some examples of binary intermetallic compounds in the L1 2  crystalline system having a useful degree of breadth may include, but are not limited to: CoPt 3 , FePd 3 , GeNi 3 , CrIr 3 , GaFe 3 , TaIr 3 , ZrIr 3 , PbPd 3 , YPd 3 , ErPd 3 , TiRh 3 , TiPt 3 , ZnPt 3 , GaNi 3 , NbRh 3 , GaPt 3 , TiPd 3 , TaRh 3 , CrPt 3 , HfRh 3 , VRh 3 , AuCu 3 , MnNi 3 , PdCu 3 , NbIr 3 , VIr 3 , Co 3 V, Fe 3 Pt, PtFe 3 , Au 3 Pd, Cr 2 Pd 3 , PtCu 3 , IrMn 3 , AuPd 3 , FeNi 3  and Au 3 Cu. Some substitutes for the major component in these exemplary binary intermetallic compounds in the L1 2  crystalline system may include, but are not limited to: Ag, Al, Au, Bi, Cd, Ce, Co, Cu, Fe, Ga, Hg, In, Ir, La, Lu, Mg, Mn, Nd, Ni, Np, Pb, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Zn and Zr. Some substitutes for the minor component in these exemplary binary intermetallic compounds in the L1 2  crystalline system may include, but are not limited to: Al, Am, Au, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Ho, In, Ir, La, Li, Lu, Mg, Mn, Na, Nb, Nd, Np, Pa, Pb, Pd, Pr, Pt, Rh, Sb, Sc, Si, Sm, Sn, Sr, Ta, Th, Th, Ti, Tm, V, Y, Yb, Zn and Zr.  
         [0020]     In substitutionally alloying binary or other intermetallic compounds to form ternary, quarternary, or other compounds having five or more components, other considerations that should be taken into consideration are the toxicity, reactivity, and usefulness of the constituent materials. While in some embodiments materials such as thallium, americium, arsenic, cadmium, beryllium, mercury, neptunium, promethium, protactinium, lead, tellurium, or thorium may be successfully alloyed for use in MEMS, it may be desirable in some circumstances to omit such toxic materials. Similarly, where materials are highly reactive, these materials may complicate the manufacture of MEMS and accordingly in some embodiments, it may be desirable to omit these materials. It is to be understood however, that many reactive materials may be successfully alloyed for use in MEMS. Examples of some reactive materials that may be omitted in favor of more stable constituents include barium, calcium, cesium, potassium, lithium, magnesium, rubidium, sodium, and strontium. What is more, some materials, such as gold, are readily attacked by standard etching materials and other chemicals commonly used in the manufacture of MEMS and other devices. In addition, some materials, such as gold, present contamination issues in some fabrication processes. Accordingly, while gold and other similarly situated materials may be successfully used in alloying materials for use in MEMS, it may simplify the manufacture of MEMS to omit this material  
         [0021]     Some examples of embodiments of substitutionally alloyed intermetallic compounds having an A15 crystalline structure that have been optimized with respect to toxicity, reactivity, and susceptibility to commonly used fabrication materials and which have a desirable breadth may include, but are not limited to Ti 3 Ir, Mo 3 Ir, Nb 3 OS, Cr 3 Ge, AlMo 3 , Cr 3 Os, Cr 3 Pt, V 3 Si, Nb 3 Al, Nb 3 Ir, Ti 3 Pt, Nb 3 Pt, Cr 3 Ir, V 3 Ga, Nb 3 In, V 3 Ir, V 3 Pt, and V 3 Rh. Some exemplary substitutes for the major components of these substitutionally alloyed intermetallic compounds having an A15 crystalline structure may include, but are not limited to Cr, Mo, Nb, Os, Re, Ta, Ti, V and Zr. Some exemplary substitutes for the minor components of these substitutionally alloyed intermetallic compounds having an A15 crystalline structure may include, but are not limited to Al, Co, Ga, Ge, In, Ir, Ni, Os, Pd, Pt, Rh, Ru, Sb, Si, Sn and V.  
         [0022]     Some examples of optimized intermetallic compounds having a B2 crystalline structure and which have a desirable breadth may include, but are not limited to AlIr, DyIn, TiCo, NiGa, OsHf, HfRh, HoIn, CuPd, TiOs, InPd, PdZn, OsV, AlCo, RuV, FeAl, CoGa, FeRh and CoFe. Some exemplary substitutes for the components of these substitutionally alloyed intermetallic compounds having the B2 crystalline structure may include, but are not limited to Ag, Al, Bi, Ce, Co, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Ho, In, Ir, La, Lu, Mn, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Sc, Si, Sm, Ta, Th, Ti, Tm, V, Y, Yb, Zn and Zr.  
         [0023]     Some examples of optimized intermetallic compounds having a C14 crystalline structure and which have a desirable breadth may include, but are not limited to HfRe 2 , Fe 2 Ti, Fe 2 Ta, Os 2 Hf, TiMn 2 , Fe 2 Nb, NbMn 2 , Mn 2 Hf and ZrMn 2 . Some exemplary substitutes for the major components of these substitutionally alloyed intermetallic compounds having the C14 crystalline structure may include, but are not limited to Al, Co, Cr, Fe, Mn, Os, Re, Rh, Ru and Zn. Some exemplary substitutes for the minor components of these substitutionally alloyed intermetallic compounds having the C14 crystalline structure may include, but are not limited to Cr, Dy, Er, Eu, Fe, Gd, Hf, Ho, La, Lu, Mo, Nb, Nd, Os, Pr, Ru, Sc, Sm, Ta, Th, Ti, Tm, V, W, Y, Yb and Zr.  
         [0024]     Some examples of optimized intermetallic compounds having a C15 crystalline structure and which have a desirable breadth may include, but are not limited to CeIr 2 , CePt 2 , Co 2 Hf, Co 2 Ta, Co 2 Zr, LaPt 2 , NdPt 2 , PrPt 2 , Pt 2 Eu, Pt 2 Gd, Rh 2 Er, ScNi 2 , SmPt 2  and ZrMo 2 . The substitutes for the major component in the C15 system are: Ag, Al, Bi, Co, Cr, Cu, Fe, Ir, Mn, Mo, Ni, Os, Pd, Pt, Rh, Ru, V, W and Zn. Some exemplary substitutes for the minor components of these substitutionally alloyed intermetallic compounds having the C15 crystalline structure may include, but are not limited to system are Ag, Bi, Ce, Dy, Er, Eu, Fe, Gd, Hf, Ho, La, Lu, Nb, Nd, Pr, Sc, Sm, Ta, Th, Ti, Tm, Y, Yb and Zr.  
         [0025]     Some examples of optimized intermetallic compounds having a L1 0  crystalline structure and which have a desirable breadth may include, but are not limited to CoPt, VRh, IrV, PtZn and FePt. Some exemplary substitutes for the components of these substitutionally alloyed intermetallic compounds having the L1 0  crystalline structure may include, but are not limited to Al, Bi, Co, Cr, Cu, Eu, Fe, Ga, Hf, In, Ir, Mn, Nb, Ni, Pd, Pt, Rh, Ru, Sn, Ta, Ti, V, Yb, Zn and Zr.  
         [0026]     Some examples of optimized intermetallic compounds having a L1 2  crystalline structure and which have a desirable breadth may include, but are not limited to CoPt 3 , FePd 3 , GeNi 3 , CrIr 3 , GaFe 3 , TaIr 3 , ZrIr 3 , YPd 3 , ErPd 3 , TiRh 3 , TiPt 3 , ZnPt 3 , GaNi 3 , NbRh 3 , GaPt 3 , TiPd 3 , TaRh 3 , CrPt 3 , HfRh 3 , VRh 3 , MnNi 3 , PdCu 3 , NbIr 3 , VIr 3 , Co 3 V, Fe 3 Pt, PtFe 3 , Cr 2 Pd 3 , PtCu 3 , IrMn 3  and FeNi 3 . Some exemplary substitutes for the major components of these substitutionally alloyed intermetallic compounds having the L1 2  crystalline structure may include, but are not limited to Ag, Al, Bi, Ce, Co, Cu, Fe, Ga, In, Ir, La, Lu, Mn, Nd, Ni, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Zn and Zr. Some exemplary substitutes for the minor components of these substitutionally alloyed intermetallic compounds having the L1 2  crystalline structure may include, but are not limited to Al, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Ho, In, Ir, La, Lu, Mn, Nb, Nd, Np, Pd, Pr, Pt, Rh, Sb, Sc, Si, Sm, Sn, Ta, Th, Ti, Tm, V, Y, Yb, Zn and Zr.  
         [0027]     Substitutionally alloyed intermetallic compounds used in the formation of MEMS may be applied or formed using any of a number of known methodologies including, but not limited to physical or chemical vapor deposition, ion beam assisted deposition, ion beam sputtering deposition, thermal evaporation deposition, electron-beam evaporation deposition, atomic layer deposition, ion plating and reactive sputtering, cathodic arc deposition, atomic layer epitaxy, molecular beam epitaxy, and successive ionic layer adsorption and reaction. In one embodiment illustrated in  FIG. 4 , substitutionally alloyed intermetallic compounds are applied to a substrate during the fabrication process using a physical deposition or sputtering process in which the constituent parts of the chosen substitutionally alloyed intermetallic compound are sintered to form a target. Source or target  50  is shown in use in a typical sputtering or physical deposition chamber  40  wherein material  52  from the source  50  is deposited on a substrate  54 .  
         [0028]     In another embodiment, the constituent parts of the chosen substitutionally alloyed intermetallic compound are combined, melted and cast to form target  50  for use in a physical deposition process. See  FIG. 4 .  
         [0029]     As seen in  FIG. 5 , in yet another embodiment, elemental targets are used to form a multi-layer, film or object that is later annealed to yield a suitably substitutionally alloyed ternary, quarternary, or other intermetallic compound having five or more components. In this embodiment, multiple targets or sources  51  are used to transfer materials  52  to the substrate  54 . In the latter embodiment, where the energy levels and properties of the materials in question are suitable, annealing may be omitted.  
       CONCLUSION  
       [0030]     Although specific embodiments have been illustrated and described herein, it is manifestly intended that this invention be limited only by the following claims and equivalents thereof.